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Marc and Mentat 2014Release Guide

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C o n t e n t sMarc and Mentat 2014 Release Guide

Contents

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

CAD Technology in Mentat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Historical Evolution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7CAD to Mesh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Defeaturing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Meshing Technology in Mentat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Model Length Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Models Created by Mentat Versions Prior to 2014. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Import . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Merge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Segment-to-Segment Contact. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27Improved Convergence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Breaking Glue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Deactivating Glue Contact. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Pressure Cavity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Circuit Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Fracture Mechanics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Global Adaptive Meshing with Self Contact . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Composite Orientation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

Known Limitations and Defects with the New 2014 Capabilities. . . . . . . . . . . . . . . . . . . . . . . . . 43Marc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43Mentat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44List of Corrected Defects in the 2014 Release . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47Marc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47Mentat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Contents4List of Build and Supported Platforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57Marc Platforms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57Mentat Platforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57Mentat Graphic Card Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58Peripheral Devices. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58Capability Discontinuance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58Platform and Version to be Dropped . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

Security Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

6 Marc and Mentat Release Guide

OverviewThe Marc 2014 release is focused on a few key areas to improve engineering productivity. This includes:

New CAD import capabilities. New geometric defeaturing tools for CAD model clean-up. New Meshing technology leveraging the Parasolid geometry capabilities introduced in Marc 2013.1 and the

new CAD import technology introduced in this release. Improved robustness of the segment-to-segment contact capabilities to reduce the user interaction to find the

optimal parameters for contact problems involving physically or geometrically nonlinear behavior as well as frictional contact.

The breaking glue capability is now available using the segment-to-segment contact procedure. The perfect gas pressure cavity capability has been expanded to allow nearly incompressible liquid filled

cavity. Improved global adaptive meshing when bodies come into self contact. The crack propagation feature has been enhanced with high cycle fatigue count and better determination of the

shape of the crack front after growth. The magnetostatic, harmonic electromagnetic, and transient electromagnetic capabilities have been enriched

to allow the user to prescribe an applied voltage across the circuit as opposed to prescribing the current. This is characterized as the Circuit approach which is particularly useful for induction heating simulations.

CAD Technology in Mentat

Historical EvolutionPrior to the Marc 2011 release, the import of CAD models was limited to what were considered to be basic generic formats. The models were imported directly into the Mentat NURBS geometric format or STL representation.

The Marc 2011 release of the product extended the previously available CAD import by extending the capability to

more commercial CAD systems and providing a mechanism to either import the geometry as NURBS surfaces or as tessellated meshes. Unfortunately, the geometry did not go directly into the solid model (ACIS) representation which limited the ability of the user to edit the geometry from within Mentat. Furthermore, the tessellated surface often needed additional clean-up before it could be used to either generate a solid tetrahedral mesh or as a surface mesh.

The Marc 2013.1 release introduced the Parasolid geometric kernel which replaced the previous ACIS geometric engine. It is more robust and is the technology that is used in other MSC products including Patran and SimXpert. This insured that geometric models can be better shared between these products and provided synergy for new meshing technology.

The Marc 2014 release introduces a new CAD import tool which converts the CAD model directly into Parasolid geometry. This method is stronger than the previous capabilities because it allows better mesh clean-up, Boolean operations to be applied, is substantially faster, and incorporates improved meshing technology. In particular, the new process significantly reduces the time required to generate a finite element mesh, especially for CAD assemblies.

7CAD Technology in MentatTerminology

The Marc 2014 release does not remove any capability in the 2013.1 release of the product, but it is anticipated that the support of older CAD formats will be removed in subsequent releases. Please see Capability Discontinuance at the end of this document.

TerminologyOver the past 30 years the terminology of CAD and CAE/Finite elements has not always been aligned, and some of this differs from the terminology used in Marc (and MSC Nastran).

In CAD, the highest level is considered the assembly file, and this may point to multiple files which may each contain one or more parts. These assemblies may reference parts that, in fact, are identical to other parts, but have some sort of Transformation Operator applied to them. These copies of existing parts are generally known as instances, and the Transformation Operations are a combination of translation, scaling, rotating, and/or mirroring. Once the assembly is imported into Mentat, the process associated with building the CAD assembly is lost.

While some of this may be analogous to using INCLUDE files within one finite element model, and the use of super elements or model sections there is, in fact, only loose associativity.

In Parasolid terminology, the parts can be constructed of four types of geometric entities or bodies: solids, sheets, wires, and points.

A solid body is a 3-D body that will be meshed with volume elements such as tetrahedral elements.A sheet body is effectively a surface that will be meshed with triangular or quadrilateral shell or membrane elements. If the sheet fully lies in a plane, one can use plane strain, plane stress, or axisymmetric elements.A wire body is effectively a curve that can be meshed with truss or beam elements.A point is similar to a traditional Mentat point and can be converted to a node.

The concept of parts is really not exposed in Mentat in this release. Also, even more significantly the Parasolid concept of body does not correlate with the Marc concept of contact body. In Mentat, one will see the word body used in both of these contexts.

CAD to Mesh

There are three steps required to generate a finite element mesh from a CAD representation. The technique will be outlined here. For greater detail, see the Marc Users Guide, Chapter 2.37.

CAD ImportWhen using the FILE > Import command, one will observe two techniques General CAD as Solid and General CAD as Surfaces/Elements, where the former is the new procedure introduced in this release. This drop-down introduces a new pop-up that provides the tools to import the CAD model and perform some geometric clean-up during the import process.

First, let us review the different CAD formats that are supported through the three techniques along with the CAD version that is supported.


When requesting the CAD as Solid method, the following pop-up is displayed.

CAD FormatBasic no Geometry

Clean-up General CAD as SolidGeneral CAD as

Surfaces/ElementsWin 32/64 Linux Win 32 / 64 Linux Win 32/64 Linux

IGES 5.3 5.3 3 & 5 3 & 5 5.3 5.3VDAFS 2.0 2.0 N A N A 2.0 2.0Parasolid V 27 V 27 V 25 V 25 V 25 V 25STEP 203 & 214 203 & 214 203, 214, 242 203, 214, 242 203 & 214 203 & 214STL Yes Yes N A N A N A N AACIS R22 R22 R21 R21 R23 R23DXF Yes Yes N A N A Yes YesCatia V4 N A N A 4.XX 4.XX 4.1 4.2Catia V5 N A N A R10 to R24 R10 to R24 R22 N APro/Engineering Wildfire 3 to 5

N A N A 13 to Creo 2 13 to Creo 2 3 to 5 3 to 5

SolidWorks N A N A All to 2014 All to 2014 All to 2013 N AUnigraphics N A N A All to 9.0 All to 9.0 NX 8 NX 8Inventor N A N A All to 2014 All to 2014 All to 2013 N AJT N A N A 7.0 to 9.5 7.0 to 9.5 N A N A

LegendNA Not available in the Marc 2014 release.

There is an additional charge for this CAD-to-solid import and clean-up capability. It also requires as a prerequisite a Mentat_Geometry_Translators license.There is an additional charge for this CAD import and clean-up capability.The Type is the type of CAD model to be imported; the choices are:

ACIS Catia V4

9CAD Technology in MentatCAD to Mesh

Catia V5 IGES Inventor Parasolid Pro/ENGINEER SolidWorks Unigraphics JT

There are two methods to read in the CAD model, the Direct Approach and the Indirect Approach (default). In the Direct Approach, the CAD model is directly imported into the Mentat/Parasolid geometry and no clean-up occurs. Because the number of bodies remains the same, it is possible to associate the CAD model names with the Mentat Parasolid body names. The disadvantage is that one may need to do the defeaturing as a separate step.

In the Indirect Approach, the CAD model is first converted into Internal Geometry, and then a series of clean-up operations are performed. The improved model is saved as a Parasolid geometry.

EntitiesEnties define the types of bodies that are to be imported into Mentat. It should be noted that in the CAD model, there are often electrical wires, plumbing tubes, and hoses which do not have any structural value. So, while the default is to import wires; in many cases, they can be neglected. This can be done by suppressing them at import time or by selecting and deleting them later.

HealHeal is the first stage to correct errors when importing CAD models. It is often used because the CAD system where the data is imported from is less precise than the Parasolid system. This is particularly true for models transferred using IGES. Healing must be performed carefully, because it may result in significant changes in shape.

Sew

Sew is used to close gaps between surfaces in an attempt to obtain a continuous surface. One of the objectives of sewing is to make the geometric representation water tight so that one can subsequently create an interior volumetric mesh.

As an example, the following IGES model was imported and recognized to be in error. It was then imported a second time with Heal and Sew activated.


Geometry Clean-up

With Heal and Sew ActivatedInitial Import of IGES GeometryThe options above allow one to remove small geometric details during the import phase. This can also be done using the Defeature option later. This gives one more options as one can observe which features are removed from the model. Normally the Minimum value remains at zero, and the Maximum value is something appropriate to the model. Note that Remove Small Surfaces is only appropriate for Sheet bodies. In a similar manner, Remove Small Bodies is only appropriate for Solid bodies.


When not using the Direct Approach, then, by default, all geometry from the CAD model is imported as is, and no conversion or simplification is performed. If desired, however, geometry from the CAD model can be converted or simplified upon import, by switching on the Geometry Simplification option in the Import CAD As Solids menu. In that case, the settings in the above menu define the conversion rules. These options are only required for an advanced user.

This is an important set of commands when complex geometries are imported. For many models, the Heal And Sew option is preferred over the Knitting option.

The following figure shows the importing of an assembly made of six solids which is reflected in the model browser.


Identify Solid

ModelBrowserOne can use the Select Menu to activate different geometric entities including selecting the Solids by the type shown as follows.


DefeaturingAfter the CAD model is imported into Mentat, additional clean-up can occur using the Defeature menu on the GEOMETRY and MESH tab. The following menu appears:

Feature types are:

Holes/Pockets Fillets/Blends Chamfers Small Surfaces Small Bodies Faults

Similar to earlier, one can specify a geometric range over which the program will look for a particular feature. Additionally, the feature will be highlighted in the model, appear in the model tree, and be included in the Select list.

After a feature has been found, depending on the feature type, one has the choice of: Remove Change Radius or Width Move

Offset will move the feature normal to its existing geometry.

Move allows you additional options to determine the direction to move the feature. For a surface of a part-way through hole, a positive offset will offset the surface inward, making the hole shallower while a negative offset will increase the hole depth.

As an example, in the following figures, the holes are identified in the model. Note that they are highlighted in blue and added to the model tree.

15CAD Technology in MentatDefeaturing

The one hole is selected for deletion by using the right mouse button over the model tree.


The hole is then deleted.

17CAD Technology in MentatDefeaturing

Finally, the housing is meshed, demonstrating that the hole has been eliminated.


Meshing Technology in MentatThe Automesh capabilities under the Geometry and Mesh tab have been expanded to support the three types (Wires, Sheets, and Volumes) of Parasolid bodies in a consistent manner. Additionally, either fully automatic meshing can be used, or you have the option to define additional seed points.

WiresThere is only one way to convert a wire to a finite element beam or truss mesh.

Use Automesh Curves

If you toggle Description to Wire, the following menu pops up.Note that one can mesh either one wire at a time or a selected group of wires. The elements are either lower-order 2-node linear elements or higher-order 3-node elements. Also, you can either let Mentat automatically control the finite element length along the wire, or you can set a target length. When higher order elements are used, the mid-side nodes are placed exactly on the wire.

19Meshing Technology in MentatDefeaturing

SheetsThere is only one way to convert a sheet to a finite element shell or membrane mesh.

Use Auto Mesh Surfaces.

If you toggle Description to Sheets, the following menu pops up.Note that one can mesh either one sheet at a time or a selected group of sheets. The elements are either lower-order 3-node triangular or 4-node quadrilateral elements or higher-order 6-node triangular or 8-node quadrilateral elements. Also, you can either let Mentat automatically control the finite element length over the sheet, or you can set a target length. When higher order elements are used, the mid-side nodes are placed exactly on the sheet. Note that the Curvature Check is very important to capture the sheet geometry.


CAD Model of SheetGenerated Quadrilateral Mesh Generated Triangular Mesh


VolumesThere are multiple ways to mesh a solid, but the easiest is to use the direct approach shown in the following menu.

Note that one can mesh either one solid at a time or a selected group of solids. The elements are either lower-order 4-node linear tetrahedral or higher-order 10-node quadratic tetrahedral elements. Also, you can either let Mentat automatically control the finite element mesh size, or you can set a target length. When higher-order elements are used the mid-side nodes are places exactly on the surface. Note for nonlinear analysis, when using the 4-node tetrahedral element, it is strongly recommended that one use element type 157 to obtain accurate results.

Mesh Control

A simple example will be used to demonstrate a different mesh quality and mesh density controls. In the first example, Mentat will compute a background element size. Additionally, the user will select a target element length along the edges. The yellow lines with circles give an indication of this target element size along the edges as shown in the following figure.


The resultant mesh is seen as follows.


One can observe that there is a large gradient in element size and the curvature of blend on the leading edge is not nicely preserved. To improve the curvature, the curvature check feature is activated (this is normally the default).


To further improve the mesh, a seed distance is applied to the blended leading edge and the top surface using the following menu which results in the following mesh.

The following figure shows the meshing of an assembly where smaller elements are automatically placed on smaller parts or parts that have a higher curvature.Finite Element Mesh for Assembly Model Shown Earlier

25Model Length UnitModels Created by Mentat Versions Prior to 2014

Model Length UnitThe Length Unit option sets the unit of length for the current model. The coordinates of the nodes and points, as well as all other geometrical data, are stored in the model in this length unit and are written to the Marc input file also in the unit when the job is submitted (i.e., no unit conversion is performed). The unit of length is stored in the model file (.mud or .mfd) if the model is saved in the default style.The Length Unit should preferably be set once when a new model is created. The default unit for new models is in millimeters.

If the length unit of a model is changed (i.e., from millimeter to meter), then all geometrical data associated with the geometry and the mesh in the model are converted to the new length unit. All other data in the model, such as material properties, geometric properties, boundary conditions, contact data, etc., is not converted to the new unit and has to be changed manually. More specifically, only the following data is converted.

Coordinated of nodes, points, and solid vertices Curve divisions applied to the curves (target length, minimum and maximum lengths, and the L1 and L2

lengths for biased seed points) Target lengths of solid mesh seeds

Models Created by Mentat Versions Prior to 2014For models created by Mentat prior to 2014, the length unit is not known. These models have been created in a particular unit system, but this information has not been saved in the model file. If such a model is opened in the 2014 Mentat version, then the unit of length in which the model has been created must be specified. By default, the length unit is set to the default unit (millimeter). However, if the model has been created in a different unit system, then the appropriate length unit for the file can be set in the Tools Program Settings menu. This must be done prior to opening the model file. Note that this is a one time operation. If the model is subsequently saved in the default style, then the unit of length is saved in that model file as well.

Import

CAD models are converted upon import from the length unit in which they have been created to the model length unit. This applies to the following options in the File Import menu:

Import of Parasolid, ACIS, and IGES models via the respective Parasolid, ACIS, and IGES options Import of general CAD models as solids via the General CAD as Solids option Import of general CAD models as surfaces or elements via the General CAD as Surfaces/Elements menu

The length unit of files imported vias one of the other import options File Import menu is not known. If such a file is imported, then it is assumed that the file is defined in the same length unit as the current model. If this is not the case, then the appropriate length unit for the file can be selected in the Tools Program Settings menu. This must be done prior to importing the file. The data in the file is then converted to length unit of the current model upon import.


MergeIf the model file created by Mentat 2014 or newer is merged into the current model via the File Merge option and the length unit of the model file differs from the length unit of the current model, then all geometrical data from the model file associated with the geometry and the mesh are converted to the length unit of the current model before adding the model to the current model. All other data in the model, such as material properties, geometric properties, boundary conditions, or contact data are not converted.

As the unit of length is not known for models created by Mentat versions prior to 2014. If such a model is merged into the current model, then it is assumed that the model is defined in the same unit of length as the current model. If this is not the case, then the appropriate length unit can be selected in the Tools Program Settings menu. This must be done prior to merging the file. All geometrical data from the model file associated with the geometry and the mesh are then converted to the length unit of the current model before adding the model to the current model.

An example of using the new CAD and meshing technologies is given in the Marc Users Guide, Chapter 2.37.

27Segment-to-Segment ContactImproved Convergence

Segment-to-Segment ContactThe segment-to-segment method continues to be enhanced to both improve the performance and broaden the capabilities. The Marc 2014 release builds on the capabilities that have been developed in prior releases. The goal is to provide an accurate easy-to-use method that can span engineering requirements. The current enhancements are focused on improving convergence and allowing the breaking glue option to be used with this method.

Improved ConvergencePreviously, the segment-to-segment procedure required more iterations than the node-to-segment method, which leads to higher computational costs. There are several reasons for this, and some of the issues have been alleviated in this release.

Using the node-to-segment method, the nodes which are in contact are not checked for residual convergence; while using the segment-to-segment approach, all nodes are tested. This results in a fundamentally tighter requirement on the equilibrium accuracy. This has not been changed in the Marc 2014 release, and there is no plan on doing so in the future.

In the Marc 2014 release, you may activate a flag that activates a different method to determine the defaults for the segment-to-segment method that will be outlined here.Version 1 indicates the method used in 2013 or earlier releases, while Version 2 indicates the 2014 method.

1. The segment-to-segment uses a penalty approach to fulfill the no penetration constraint. You may either define the penalty, or the program calculates the penalty. If one activates the flag to obtain the Marc 2014 defaults, the consequences are as follows: a. In the case where a deformable body contacts a rigid body, there is no change in the procedure.b. In the case of deformable to deformable contact where the bodies have the same stiffness, a lower value of

the penalty is used than in previous releases.c. In the case of deformable to deformable contact and the bodies have different stiffness, the penalty is based

upon the lower stiffness.2. To improve the accuracy and the convergence, Marc also uses an augmentation method. This augmentation is

activated as soon as and remains active as long as the penetration exceeds a certain value and the maximum

number of iterations has not been reached. Previously, the value was 1/1000 of the characteristic length. It has been found that this is too small a value, which led to excessive number of iterations. The default value has been increased.

3. In the case of friction, there is also a value of the Augmented Lagrange penalty value for sticking. In the past, this value was a constant for the whole model, or at least for each contact pair. In Marc 2014, activating the new procedure results in a value that is dependent on the normal pressure. Effectively, this results in, at low normal stresses, the bodies are more likely to slip than at high normal stresses.

4. If separation occurs and the convergence is based upon displacement control only, then residual testing is invoked with a default tolerance of 0.1 to ensure that the equilibrium is satisfied. While this may increase computational costs, it should result in a more stable solution:

5. Unlike the Node-to-Segment algorithm, the Segment-to-Segment algorithm already performs a check on separation if the solution is not completely converged. The effect of separating polyline/polygon points on the


solution is then reflected in the global equilibrium check. In some cases, there are many points that separate during an increment, which results in a failure to converge. Instead of increasing the maximum number of iterations, Version 2 allows resetting the iteration count to 1 upon separation. The maximum number of times such a reset of the iteration count can be applied during an increment is by default 9999, but can be user-defined in the Advanced Contact Control menu.

To activate the new set of defaults use:As a first example, a ship bumper will come into contact with a rigid surface and self-contact as shown in the following figures. The number of iterations is given in the following table.

Method Number of IterationsNode-to-Segment 276Segment-to-Segment Standard Augmentation 246Segment-to-Segment Modified 2014 71

29Segment-to-Segment ContactImproved Convergence

The computational cost would be approximately one-third of the node-to-segment method.

Original MeshDeformed Mesh with Self Contact Stress Distribution


In the next example, we see a 3-D contact model that demonstrates that the segment-to-segment method provides better results and the new augmentation method provides a stable solution.

Method Analysis BehaviorNode-to-Segment Mesh penetrationSegment-to-Segment Standard Augmentation Fails to convergeSegment-to-Segment Modified 2014 Successful analysis

Original Mesh

31Breaking GlueImproved Convergence

A similar example, including friction, is provided in the Marc Users Guide, Chapter 2.31.

Breaking GlueThe breaking glue option allows one to indicate that bodies which are initially glued together may separate if a stress limit is reached. The separation is based upon

Penetration Using Node-to-Segment Method Successful Analysis Segment-to-Segment Method

nSn------

m tSt-----

n+ 1This capability is now available for segment-to-segment contact. In such cases rather than testing at the nodal points, the testing occurs at the auxiliary points. Geometrically, one will not observe the separation until multiple points separate.

Because of differences in convergence techniques, the results between node-to-segment and segment-to segment procedure will not be identical but the engineering trends should be similar.

An example of the use of breaking glue may be found in Marc Volume E: Demonstration Problems, Chapter 8.30.


Deactivating Glue ContactIt is now possible to utilize the DEACT GLUE option with segment-to-segment contact. Rather than defining a list of nodes, one would specify a list of element IDs with the edge or face number depending on whether a 2-D or 3-D contact simulation is being performed.

Pressure CavityThe pressure cavity capability which is available for planar, axisymmetric and 3-D has been expanded so that it not only supports a perfect gas law, but also supports a nearly incompressible liquid. In either case, the cavity region is assumed to be filled.

For a fluid filled cavity, one needs to enter the bulk modulus of the fluid.

In previous versions of Marc, the volume of the cavity was determined at the beginning of the increment and then held constant. In the 2014 release, it is possible for the program to use the latest iteration volume. This may allow the user to take larger increments. This is activated through the JOB>JOB PARAMETER> CAVITY menu shown as follows.

CavityDefinitionforPerfectGasModel CavityDefinitionforLiquidModel

33Pressure CavityImproved Convergence

As an example, a rubber seal with three cavities is compressed (shown in the following figure). The first and second cavity with water. The time history of the volume shows that the air filled cavities collapse (with associated increase in pressure) while the fluid filled cavity volume is almost constant.

User Selection of Incremental or Iterative Control Over Cavity Volume CalculationThis example may be found in Marc Volume E: Demonstration Problems, Chapter 4.27.Geometry showing Three Cavities Time History of Cavity Volume


Circuit AnalysisAlmost all magnetic devices are excited by voltage or current sources. These sources are applied to the two terminals of a single wound coil or a number of such wound coils connected in series. A wound coil will have one or more turns. The voltage or a current source is applied as a single value on the two terminals. The source, the coils, and any externally connected components like resistance, inductance, or capacitance are connected in series and form a single loop called a circuit. The series connection of the coils in this single circuit is sometimes referred to as a winding. A magnetic device may have one or more circuits depending upon its application. In general, most magnetic devices are excited by voltage sources, and the remaining are excited by injected current sources. Due to magnetic nonlinearity and skin effect that may exist in a device, the electric current in a conductor is usually unknown. Conventional finite element formulation for magnetostatic and magnetodynamic field computation, which requires current density as input, is modified and supplemented with electric circuit equations to allow a magnetic-circuit coupled analysis. With this feature, the magnetic device can be converted to an equivalent circuit device and a circuit analysis carried out to analyze the actual practical problem. Both types of sources are handled by the circuit approach.

The circuit approach is built upon the coil option (earlier called winding). Coils are defined by the coil feature and a circuit is defined by the new circuit option. This option defines a single closed loop circuit containing coils, external components like resistance, inductance, or capacitance and an extra control node. For a circuit, the voltage or current source is applied by the new terminal voltage or current boundary condition. This boundary condition is applied on the extra control node.

The following examples show the application of the circuit approach to magnetostatic and harmonic magnetodynamic analysis. Coupled thermal or structural analysis is also shown.

Example 1: Plunger solenoid arrangementThe plunger solenoid problem: The magnetic induction plot and displacement of the plunger in the X direction. Applied terminal voltage is 100 volts, externally connected resistance is 0.1 ohm, and calculated circuit current is 125 Amperes and coil resistance is 0.7 ohms.

35Circuit AnalysisImproved Convergence

Example 2: Circuit analysis of a circular inductance for different harmonic frequencies ranging from 1 to 100 KHz. Terminal voltage is 10 volts.

Distribution of the real and imaginary magnetic induction and variation of the inductance with frequency is shown as follows.Example 3: Induction Heating

Induction Tube heating with coil motion: A sheet is folded to form a tube and the contacting edges of the sheet is heated and welded to form a cylindrical tube. The motion of the coil is adjusted to facilitate proper heating and temperature at the welded edges.


Temperature distribution during welding process. The coil is excited by a terminal voltage of 5 volts at 5 KHz.

In summary, the Marc 2014 release supports the following features:

1. Magnetostatic Circuit analysis works with all the previous features in magnetostatic analysis.2. Magnetodynamic circuit analysis: The following is supported:

a. Harmonic magnetodynamic circuit analysis and coupled thermal and structural analysis including induction heating.

b. Transient magnetodynamic circuit analysis.c. Inductance matrix computation for harmonic magnetodynamic circuit analysis.

LimitationsThe known limitations are:

1. In magnetodynamic circuit analysis, circuit coils cannot be massive conductors, and it is assumed that there is no skin effect in circuit coils. This means that the cross-section of a single coil must be less than the skin depth for a given conductor material and operation frequency.

2. Inductance matrix computation is not supported for transient magnetodynamic circuit analysis.

3. In 3-D problems, there can be issues with the identification of elements that belong to a coil:

a. Some integration points inside coil geometry may be missed or an integration point outside coil geometry may be selected. Both will produce inaccuracies. Inaccuracy depends on the ratio incorrect integration points divided by total number of integration points in the coil.

b. A non-conductor element may get included in a coil. Marc writes a warning message for this in the .out file.The remedy is:a. The coil path and coil orientation path segments should be similar in size as the element edges of the coil. It

is best to have the coil path and the coil orientation path not in the same plane. When there is abrupt change in angle of coil path and coil orientation, replace both by a proper fillet. This ensures smaller volumes of search and reduces chances of incorrect integration points being chosen.

37Fracture MechanicsImproved Convergence

b. Ensure that the elements lie fully inside or outside the coil geometry. All elements in coil geometry must have a single conductor material.

Examples of the circuit method may be found in Marc Volume E: Demonstration Problems, Chapter 12.55, Marc Users Guide, Chapter 5.5, and Marc 104 training class.

Fracture MechanicsMarc has a low cycle fatigue capability for a number of releases. It is limited to a small number of cycles since every single fatigue cycle has to be modeled explicitly. Hence, it is not well suited to cases where there are thousands or millions of load cycles. The Marc 2014 release offers a new capability for high cycle fatigue. A small number of representative cycles are modeled in Marc, and it uses Paris law to calculate the true number of cycles from the data collected during the fatigue cycles. It is also possible to use a user subroutine to define the fatigue law and to include a general load spectrum. The 2014 release also offers an improved method for scaling the crack growth along a crack front and between separate cracks. In previous releases, the growth was either prescribed (constant along the crack front and independently between cracks) or calculated using Paris law. With the new method, the user specifies a maximum crack growth increment, and this growth increment is scaled between cracks and along the crack front using the local value of the stress intensity factor.

The scaling between cracks and the cycle count are illustrated by a simple shell example. A flat plate has two holes with a crack at each hole. The plate is stretched and unloaded; this is repeated 25 times. After each loading/unloading event, the cracks grow.As can be seen from the figure above, the cracks do not grow the same amount. The maximum stress intensity factor is higher for the lower crack, and the growth rate of the other crack is scaled by the quotient between the respective stress intensity factor. In this example, we use Paris law with an exponent of 2.1. This exponent is used when scaling

InitialModel FinalMeshafter25FatigueCycles


the growth increment. With denoting the growth increment, the largest stress intensity factor, m the Paris law exponent, and the user specified growth increment, we have

After each fatigue cycle, we accumulate the number of real cycles by integrating Paris law. Since we scale the growth using the Paris law exponent, we obtain the same cycle count for both cracks, as seen in the results for Global Post Variables.

The following example shows a block with a through hole. A crack is initiated at the hole and two rigid bodies are used to give it a pulsating load. The motion of one of the rigid bodies is given by the load table shown below.

a Kmaxa0

a a0 KKmax------------

m=

39Fracture MechanicsImproved Convergence

The analysis is done in two loadcases. In the first loadcase, the crack is initiated and the load (shown in red below) is ramped up to a value of 0.2 times the maximum. Then in the second loadcase, the load is oscillating between 1.0 and 0.2.This loading illustrates another new feature in 2014. The fatigue time period as defined in Marc is specified as 1.0. The time of the first loadcase is set to 0.5, which is smaller than the fatigue time period. The new capability in 2014 is the

Time

Load


fatigue time period which is reset after each loadcase. The effect here is that the fatigue period is in sync for the second loadcase.

The example is done with three different definitions on how to update the crack front in fatigue.

1. Constant growth long the front,2. Linear scaling along the front,3. Exponential scaling with a Paris law exponent of 2.0.

The pictures below show the shape of the crack front after a number of growth steps.

1.ConstantGrowth 2.LinearScalingIt is clearly seen that the scaling gives a higher growth rate through the thickness, and more pronounced for the exponential scaling.

Two new user subroutines have been added for use with the new fatigue procedure. UCRACK_FATIGUE_LAW allows the specification of a user defined fatigue law as an alternative to the standard Paris law. This routine is used for two purposes: to provide the scaling of the growth increments and for the integration of Paris law to obtain the cycle count. The integration is done cycle by cycle and the routine is called in this cycle. This also allows the usage of a general load spectrum, where scale factors of the loads are used in the subroutine. The second new user subroutine is called UCRACK_FATIGUE_CYCLES and allows for a general integration of the fatigue law.

3.ExponentialScaling

41Global Adaptive Meshing with Self ContactImproved Convergence

Another Marc 2014 enhancement for fracture mechanics is a new option for loadcase termination:

This option is used in conjunction with the Delamination option. The loadcase is terminated when a crack initiated through the DELAMIN option is created. This facilates an analysis where the load to reach the first crack is unknown. The loadcase (hence, the loading) is terminated when the crack starts, and one can start a fatigue calculation in the following loadcase.

Examples of the new fracture mechanics capabilities may be found in the Marc Users Guide, Chapters 2.35 and 2.36.

Global Adaptive Meshing with Self ContactA large challenge in previous releases was the use of global adaptive meshing when a body came into self contact. The problem was that if the surface curves (2-D) or polygons (3-D) intersected one another, the mesher would fail, and the result would be MARC Exit 5059. These intersections were the result of minute penetration or due to the fact that the numerical discretization was based upon piece-wise linear representation.While often these penetrations were of the

order of 1.e-4 of a typical geometry, they still had significant negative consequences. In the Marc 2014 release, we have introduced a method to alleviate this problem. The four common engineering problems where this occurs are:

1. Compressing of rubber seals which have internal cavities.2. Closing of seals which fold on one another.3. Manufacturing problems where a lap is formed.4. Cyclic loading of cracked structures where the crack closes.

It is also recommended to used the segment-to-segment procedure when self contact occurs.

As an example, a rubber body with initially a twisted cut through the section is shown in the following figure, and the final configuration after six adaptive meshing steps.


The defaults in Marc 2014 usually resolve these problems. If Exit 5059 still occurs, increasing the Self Contact Shift Factor may resolve the problem.

Initial Mesh Closed Cut using Segment-to-Segment Contactand Adaptive MeshingComposite OrientationAn option is provided to consistently project material orientations onto the element plane for solid composite and solid shell elements. This addresses a requirement that most users would want the specified orientation system to be projected onto the ply so that the properties in the plane of the ply and perpendicular to the ply are clearly defined.

Previously, various material orientation options were used to define local systems for solid composites and solid shells in different ways. With the new option, all material orientation options allow a consistent projection onto the ply plane to define the local system.

43Known Limitations and Defects with the New 2014 CapabilitiesMarc

Known Limitations and Defects with the New 2014 Capabilities

Marc

Contact

Global remeshing and local adaptivity

1. Stress-free initial contact may not work correctly in a large rotation segment-to-segment contact analysis.

1. Retaining the mesh density upon global remeshing by specifying the scale factor as unity (mesh density control 'Full'), may not work correctly. Instead, the finite element mesh tends to get denser.Materials

Multi-physics

2. 3-D global remeshing may fail in case of self-contact. Using a Self Contact Shift Factor greater than one may resolve this.

1. Table driven density input is currently not supported for the Exponential Cap Powder model.

1. In rare cases, too many elements are found to be part of a winding or coil path as defined by the EMWINDING option.


Mentat

General

1. On Red Hat 6.3 Linux when Compiz effects are on, Mentat Classic appears to be transparent. The solution is to either use the new Mentat version or to disable the desktop effects; i.e., use Desktop Effects standard.

2. If existing Mentat procedure files do not have a program version (set via a command like *prog_option compatibility:prog_version:ment2013.1), it is strongly recommended to add this at the top of a procedure file.

3. If surfaces are plotted in solid mode and the Lines option in the View Plot Control Surface Settings menu is switched off, then some surfaces may not be displayed properly. In rare cases, Mentat may even crash or hang when drawing these surfaces. The same problem exists for the Identify Backfaces and Identify Contact options.

4. If surfaces are plotted in solid mode and the Lines option in the View Plot Control Surface Settings menu is switched on (the default), then some trimmed surfaces may not be displayed correctly. For such surfaces, the area outside the trimming curves is also drawn.

5. On Linux console, the check boxes in the First and Second Level filters of the List tab of the Model Navigator may not be visible.

6. If the new Mentat runs on a Linux machine and the display is set to a VNC or NX server that runs on a Red Hat 5 Linux machine, then the X that marks the X-direction of the triad in the lower left corner of the graphics window is displayed twice. The same problem exists for the OpenGL version of classic Mentat.

7. The VMRL option in the Tools menu to export the model to VMRL is not working properly. The command executed by this option is incorrect and results in a "Bad Float!" message. The workaround is the enter the following command in the Dialog:

*export_vrml 1 "filename.wrl" yes

Here, the integer is the view number to create the VRML file from.8. The cross hairs option, which is available in classic Mentat to provide guidance when picking items from the

graphics window and which can be activated by clicking the SHIFT key on the graphics window, is not supported in the new Mentat.9. No options exist to set the window size at startup of the new Mentat.10. If a model file or a post file is opened while the graphics window shows a table, a history plot, or a path plot (in

general, anything other than the model) from another model file or post file, then the filename displayed in the title bar of the Mentat window is potentially incorrect.

11. Animations created by the Mentat 2014 release are not compatible with older Mentat versions. Animations created by older Mentat versions cannot be played by Mentat 2014 and vice versa.

45Known Limitations and Defects with the New 2014 CapabilitiesMentat

Preprocessing

1. The Bergstrm-Boyce viscoelastic material cannot be selected for the Anisotropic Hyperelastic model in Mentat, although this is supported in Marc.

2. For some CAD models, the automatic feature removal options in the File Import General CAD As Solid menu may fail. Workaround is to remove the features after import via the Defeature menu on the Geometry & Mesh tab of the main menu.

3. Solid mesh seeds of type # Divisions defined on edges of a solid body may not always be obeyed, in particular if they have been defined on edges of a hole.

4. Graphics updates are slow if many elements in the model have an orientation of type Curves (i.e. the first direction of the material coordinate system of the element is defined by the tangent to curve at the point of the curves closest to the element centroid).

5. When searching for holes in solid bodies using the Defeature menu, a non-circular hole (for example, a square or a hexagonal hole) that has been detected may show up in the Defeature menu and in the model tree as multiple holes and it may not be possible to remove such a hole.

6. When importing ACIS models with multiple bodies, the bodies may appear in a different order and with different names each time the model is imported. Procedure files that import such a model may fail because of this and if a Mentat session is replayed (by running the mentat.proc file), the results may be different. The workaround is to import the model, save it to a Mentat model file (.mud or .mfd) and open the model file in the procedure file instead of the ACIS file.

7. Mentat does not support Geometric Properties for Electrostatic analyses to define for example, the thickness of a shell. The workaround is to temporarily change the Analysis class to Thermal, create a Thermal Geometric Property of the appropriate type for these elements and then change the Analysis Class back to Electrostatic.

8. The Zero Volume command in the Check menu fails to find elements whose volume is not exactly zero, but for all practical purposes can be considered to be zero.

9. Mentat allows creating materials with identical names. This can be confusing when selecting a material.10. Mentat does not support the Marc option to choose magnitude/phase or real/imaginary nodal output in

harmonics for the PRINT NODE option.11. Multiple axes of rotation for Centrifugal loads are not supported within Mentat.Marc Input File Writer

12. The General Traction distributed load type 21 is not supported within Mentat.13. Mentat does not support the Foundation option for 2-node line elements.14. Mentat is unable to control the prescribed displacement boundary conditions in a Modal Dynamics Load case.

This may results in problems with Design Optimization in a modal dynamics simulation.15. When subdividing elements in a Cylindrical or Spherical coordinate system, some nodes may get a wrong

position if a node of the subdivided elements is at the origin of the coordinate system.

1. Table driven density input is currently not supported for the Exponential Cap Powder model.2. Mentat does not write a correct Marc input file if two node, element, edge, face, point, curve, or surface sets

exist with the same name.


Postprocessing

3. Mentat fails to generate an error message when checking the job writing a Marc input file if both I-DEAS and Hypermesh results are requested.

4. Mentat does not write a correct Marc input file when element type 95 (axisymmetric with bending) is used. The SHELL SECT parameter is not written.

5. When preparing a DDM analysis in Mentat, there is no check for elements which have not been assigned to any domains. In such cases, the resulting Marc input is incorrect.

1. In the new Mentat, it is not possible to interrupt the creation of an animated GIF, MPEG or AVI movie.2. The Select Post Increments menu to select the increments to be when creating an animated GIF, MPEG or AVI

movie using the List method, is confusing. It shows two columns with check boxes to select the increments. The first column shows the increments that have been selected and that will be used to create the movie from. The second column is only visible initially and if the Range Select or Range Clear has been clicked. In that case, a range of increments can be selected or cleared by clicking the check boxes in the second column corresponding to the first and last increment of the range. Once the range has been entered, the second column disappears again and changes are reflected in the first column. The same problem occurs when selecting a list of increments for the Report Writer.

3. Postprocessing models with a large number of rigid surfaces is slow.4. When postprocessing jobs in which VCCT cracks are initiated during the analysis (i.e. not all cracks already

exist at the start of the analysis), then history plots involving crack related quantities, such as Energy Release Rate, Accumulated Crack Growth and the Number of Fatigue Cycles, may be incorrect if the data is collected in a range of increments in which a new crack has been initiated. The workaround is to collect data from the increment in which the crack has been initiated to the last increment before the next crack is initiated.

5. In rare cases, if sample points have been created during postprocessing of a job with global remeshing, the program may not be able to map a sample point from the current mesh to the mesh corresponding to another increment when skipping to or past that increment. In that case, the message WARNING: Could not update sample point is printed.

6. The automatically computed range of the current scalar or vector quantity, as shown in the Scalar Plot Settings and Vector Plot Settings menus, respectively, is not updated automatically if one skips to a different increment. Marc Reader

The legend on the graphics window shows the correct range though. The menus can be updated by pressing the Enter key once in the Command box of the Dialog, i.e. by entering an empty command string.

7. The automatically computed value range for a vector plot of 3-D continuum elements may be wrong when only the Edges on the Surface are being drawn.

8. In rare cases, an non-symmetric contour plot is shown for a symmetric problem.

1. The ABLATION parameter is not imported by the Marc input file reader.2. If a Marc input file is imported, then the Analysis Dimension in the Job Properties menu is not set to the

dimension of the Marc input file (3-D, Axisymmetric, Plane Strain, Plane Stress or 2-D).

47List of Corrected Defects in the 2014 ReleaseMarc

List of Corrected Defects in the 2014 Release

Marc

Contact

1. Cyclic symmetry with a cyclic angle of 180 and multiple connected areas within one contact body did not work correctly.

2. In a thermal/diffusion analysis, the automatic discontinuity detection activated on the SPLINE option was not executed during increment zero. As a result, immediate remeshing could cause the analysis to stop prematurely with exit number 1005.

3. In a segment-to-segment contact analysis, the friction force contribution to the reported reaction forces due to contact (in the log file and output file) was incorrect. This could have a (usually) minor impact on the residual convergence check. The contact normal and friction forces as well as the reaction forces on the post file were correct.

4. If post code 73 (Glue Deactivation Status) is activated for an analysis with segment-to-segment contact, Marc could crash.

5. In a segment-to-segment contact analysis, the EXCLUDE option did not work for thickness segments of shell elements.

6. Reaction forces reported on the post file and the output were wrong if the Near Contact Distance (nodal post code 65) is used in combination with the option to write iterative results on the post file.

7. Variable TEMP(1) in user subroutine UFRIC could only be used for friction based on nodal stresses.8. An analysis with AUTO INCREMENT and segment-to-segment contact stopped with a data error.9. A temperature dependent friction coefficient did not work correctly in a segment-to-segment contact analysis

(the temperatures were always assumed to be zero).10. Using the Near Contact Distance (nodal post code 65) could slow down an analysis significantly. 11. In rare cases, an analysis with beam-to-beam contact using the node-to-segment algorithm could result in a

memory overwrite while creating new beam-to-beam contact tyings; this could cause Marc to crash.

12. The EXCLUDE option for element faces/edges defined via sets did not work when used as a model definition

option. It also did not work with tetrahedral and higher order elements.13. Reaction forces reported on the post file and the output were wrong if the Near Contact Distance (nodal post

code 65) is used in combination with the option to write iterative results on the post file.14. In rare cases, in a structural analysis with rigid contact bodies using the node-to-segment algorithm, nodes in a

concave corner could lose contact (this occurred if at concave corners a NURBS surface has a zero area).15. If in a structural analysis a breaking glue stress is defined as a function of temperature, the analysis could stop

with data errors.16. A friction coefficient could not be defined as a function of stress (equivalent stress; table independent variable

type 20).


17. The Contact Normal Stress, Contact Normal Force, Contact Friction Stress and Contact Friction Force were incorrect for nodes using a changing coordinate system via the COORD SYSTEM option.

18. In a segment-to-segment contact analysis, the Contact Normal Stress and Contact Friction Stress for generalized plane strain elements were calculated incorrectly.

19. If incremental nodal displacements are large compared to the dimensions of a NURBS surface, in rare cases contact detection with a rigid contact body containing such a NURBS surface could fail.

20. A coupled analysis with frictional heat generation could crash in the following rare cases:

DDM is combined with global remeshing and the deformable contact bodies used have common nodes; elements are deactivated in such a way that at least one deformable contact body does not contain any

element.21. Distributed loads entered via the DIST LOADS option did not work for user elements if table driven input is

used.22. If shells are glued to solids with segment-to-segment contact and large rotations occur, then spurious stresses

could be introduced.23. In rare cases, in a 2-D segment-to-segment contact analysis a segment could come into contact with multiple

segments, such that effectively slightly more than 100% of its length was considered to be in contact. This could lead to convergence problems if friction is included.

24. A node-to -segment contact analysis could cause Marc to crash under one of the following circumstances:

there are more than 166 meshed contact bodies and friction is included; dynamics is included, the analysis is forced to continue if convergence has not been reached within the

maximum number of iterations and during the last iteration of an increment the Iterative Penetration Checking procedure scales the iterative displacement vector.

25. The RIGID NODE option did not work correctly if the number of degrees of freedom per node is larger than the dimension of the problem, so e.g. if shell/beam elements are included in the model.

26. When polygons are re-created in a segment-to-segment contact analysis with non-flat faces, contact could get lost in the corner areas.Elements

27. In rare cases, nodes lying not exactly in a contact symmetry plane, but within the error tolerance zone, could lose contact after global remeshing, especially if the element size decreases upon remeshing.

28. Global remeshing in a 3-D analysis in combination with analytical rigid contact bodies could lead to loss of contact upon remeshing.

29. The two features breaking glue and crack propagation by releasing glued contact did not work correctly if the contact option to suppress or delay separation is used.

1. Temperature dependent elastic foundation did not work if this dependency is described using a table.2. For shell elements, the back stress tensor data per layer written to the post file was incorrect. Note that this did

not affect the overall analysis.


Fracture Mechanics

3. If adaptive load stepping with the AUTO STEP option is used and if an incremental distributed load on a cable element (type 51) is zero, the analysis aborted erroneously with exit number 3015.

4. If the thickness direction is not defined for solid composite elements, then Marc and Mentat did not behave consistently. Where Mentat gives a relevant error message, Marc used a default thickness direction and continued the analysis. Now Marc stops with a data error.

5. For reduced integration elements, mass matrix, gravity load and centrifugal load calculations were incorrect.6. For elements with less than three direct strain components (like truss and plane stress elements), the Equivalent

Plastic Strain (post code 27) and the Equivalent Creep Strain (post code 37) could be non-zero even if all components of the plastic and creep strain tensor are zero. This was only a post processing issue; it did not affect the overall analysis.

7. The Herrmann element formulation for ORTHOTROPIC materials was not identical to that for ISOTROPIC materials with respect to the hydrostatic stress definition.

8. User subroutine FILM/UFILM did not work correctly for linear and quadratic pentahedral elements.

1. Direct crack growth by global remeshing could have problems if growth occurred at single scattered front nodes. Now a method is used which involves growing at segments connected to such front nodes and scaling using a smoothed value of the energy release rate.

2. For an analysis involving multiple cracks and non-consecutive numbering, not all cracks were properly initiated. The mesh was split up properly but not all cracks were generated. This was true for both 2-D and 3-D analyses.

3. In crack growth simulations with a curved crack, if the user wants to grow the crack in the same plane using remeshing based growth, it would not remain in plane.

4. When a crack first reaches a 90 edge, and then hits a sharp edge, Marc could stop with exit number 5059.5. VCCT crack growth by remeshing at sharp corners or near the external surface could fail due to remeshing.6. The crack initiation feature with remeshing using faceted surfaces did not work correctly if multiple faceted

surfaces are used in the same crack initiation definition. A workaround was to use multiple crack initiation definitions with a single faceted surface in each.7. If the crack propagation option Cut Through Elements is used and there is crack growth in the first increment, then the analysis would stop after this increment.

8. There was a problem with the feature of crack propagation in a shell structure with new cracks being branched at shell intersections. If multiple cracks reach shell intersections at the same or adjacent increments, then the new cracks were not created correctly and Marc could crash.

9. Crack initiation with faceted surfaces and remeshing did not work correctly if the triangles defining the faceted surface did not have a consistent orientation of their normals.


Global Remeshing and Local Adaptivity

Materials

1. Using pressure cavities with global remeshing could yield wrong results, since the element numbers associated with a cavity were not updated upon remeshing.

2. It is not allowed to create a model section at the end of an analysis using global remeshing. However, there was no protection for this combination, so that a model section could be created which cannot be used in a subsequent analysis.

3. With the LARGE STRAIN,1 option, the reported Cauchy stresses in a trimming load case were incorrect.4. Local adaptive meshing in combination with shell/beam offsets and the ELSTO option gave slightly incorrect

results.5. An analysis with global remeshing could fail to run correctly if the model becomes too large for in-core element

storage after remeshing. Marc will automatically switch to out-of-core element storage, but this did not work correctly for this case.

6. In rare cases, in a 3-D analysis the TRIM option produced distorted slim elements near hard edges.7. When local adaptive meshing is used in a magnetodynamic/thermal analysis, it could cause Marc to crash.8. If, due to local adaptive criteria, an element gets subdivided and un-subdivided multiple times, this could lead

to excessive memory usage.9. Restarting an analysis with multiple global remeshing criteria would not work correctly. This only applied to

the procedure with mesh density control Full.

1. If a table reference is used in the CURE RATE or CURE SHRINKAGE model definition option, then the following warning message was erroneously printed in the output file: *** warning table ID has been defined but is not referenced, where ID is the table ID used.

2. Some material subroutines such as MD_UGENT and MD_UARRBO could not be called in a frequency domain analysis.

3. A model with phi-functions defined directly in the input file produced slightly incorrect results.4. Incorrect results were obtained if a zero was entered for the exponent psi in the Arrhenius-Rho pyrolysis model properties when the virgin density was equal to the charred density.5. The Arrhenius shift function was not supported in the frequency domain. Also, its time domain implementation

was based on shifting using 10-logarithm instead of natural logarithm.6. The table definitions for the N coefficient and K value of a CHABOCHE hardening model were ignored.7. The GASKET material properties could not be defined as a function of the state variables.8. Models using a non-symmetric stress-strain law (e.g. defined using HYPELA2) in combination with the updated

Lagrange procedure could show a slow convergence behavior.9. Viscoelasticity in the volumetric response for OGDEN materials was giving incorrect answers and it was not

supported for MOONEY and other materials based on strain energy formulations in terms of the strain invariants. It is now supported for all isotropic rubber materials (OGDEN, MOONEY, ARRUDA BOYCE, GENT and MARLOW) in the updated Lagrange framework. In the total Lagrange framework it is only supported for OGDEN materials, but this is not recommended.


Multi-physics

Parallel Processing

1. When using the streamline model (ATAS) together with the coking effect, the output file could contain NaNs.2. A thermal analysis using shell elements and involving radiation to space lead to incorrect results if the Monte

Carlo method is used for the view factor calculation.3. Fluid-structural pressure coupling did not work with table driven input.4. The weak thermal-fluid or thermal-fluid-structural coupling could be activated, but gave poor results. Now only

the strong coupling is allowed.5. When the MARLOW model is used with rubber damage, incorrect results were produced. Without damage,

everything was as expected.6. For a coupled diffusion/structural analysis using multi-physics input, an incorrect warning message about

diffusion properties was issued.7. If for the last layer of a composite shell a material is used without curing, the degree of cure was ignored across

all layers.8. The thermal curing computation was wrong for solid elements when the model also contains shell elements

which do not have curing properties.9. When user subroutine FORCDT is used to prescribe nodal temperatures rather than point fluxes, the total

temperature was not available in variable DU. This inconsistency was also true for other physics, such as joule heating and electrostatics.

10. Radiation boundary conditions via the FILMS option gave slightly inaccurate results.11. For a coupled magnetodynamic/thermal/structural analysis, temperatures were not included in the status file. 12. The resistance calculation for a conducting body in a current/thermal(/structural) analysis was wrong when a

non-default conversion factor was used.

1. If a DDM analysis with stress-free initial contact writes multiple post files, the results in these post files could not be accessed.

2. When using the -nte option for SMP assembly and stress recovery, too much information was written to the Various

output file.3. In complicated multi-body contact situations, a DDM Marc analysis could stop with exit 2011, where it ran

successfully without DDM.4. When DDM is used for data files with a space in their name, Marc stopped with exit number 26.5. For a thermal analysis using DDM, the time step determination at the end of an increment was incorrect when

the AUTO STEP option is used. This could lead to different results compared to a run without DDM.

1. If the FIXED ACCE option is used with old style input, Marc could crash.2. The OSET definition in DEFINE,,OSET,name did not work for the N1 to N2 input mode.


3. In rare cases, the algorithm used by the AUTO STEP option to determine the critical points to reach in a load curve, could fail, so that the applied load was incorrect. This typically could happen if the curve has a (near) discontinuity in time.

4. If a model is restarted and parameter or model definition options have been changed compared to the original model, then the analysis crashed if a restart file must be written at the end of the analysis.

5. In a buckling analysis, for a load case preceding the BUCKLE load case, if the assembly flag on the CONTROL option is set to 1, Marc could stop with exit number 1001.

6. If more than 2048 element post variables are defined, Marc could crash or hang.7. On Windows, it was not allowed to use Marc data file names containing a parenthesis.8. If a load case is terminated based on the TERMINATE option and the analysis continues with the next load case,

then applying boundary conditions as a function of time using table driven input went wrong in this next load case. An option has been added to update the analysis time upon terminating a load case.

9. If a coupled thermal-mechanical load case has to be terminated based on the TERMINATE option, though the output file mentioned that the load case will be terminated, the analysis actually continued with the next increment of this load case.

10. If a load case has to be terminated based on the TERMINATE option and the criterion chosen is based on a displacement or rotation magnitude, then the time of termination could be wrong.

11. For an analysis with the DIST LOAD but without the PRINT VMASS option, a change in volume caused a corresponding change in mass of the job.

12. TRACK file data could be incorrect for user-defined element variables (defined in user subroutine PLOTV) if the calculation of these variables involves a call to user subroutine ELMVAR for quantities requiring the determination of invariants of a strain or stress tensor.

13. For graphic cards with GPU capability 3.0 or more, the device information utility program returned negative values for the number of cores per multiprocessor and the total number of cores.

14. If a 3-D model with Herrmann elements (but without shell or beam elements) contains an unconnected node (i.e. a node not belonging to an element, a spring or an RBE) with a transformation, then the solution could be wrong. Such incorrect behavior was typically recognized by a non-converging solution.

15. The MACHINING option only worked with respect to the initial configuration. i.e. nodal displacements were not

taken into account.

16. The option to ramp a prescribed displacement from the current to a target value did not function correctly if the reference position is the position at the activation of the boundary condition.

17. If a scratch directory is specified for a Marc analysis using the CASI solver, only the *.t23 file was written to this scratch directory, but all the other temporary files were written to the current working directory.

18. Model Sections were not supported for analyses with creep (including the solder material).19. The rebar angles and rebar directions on the post file were wrong if the number of degrees of freedom per node

is larger than the dimension of the model, e.g. if shell or beam elements are included in the model. This did not affect the other results.

53List of Corrected Defects in the 2014 ReleaseMentat

Mentat

General

20. Thermal radiation with multiple radiation cavities in combination with multiple symmetry planes did not work correctly.

21. The active plastic strain (used by the Bonora damage model) was not available for post processing.

1. When launching a Marc analysis using the SUBMIT 3 option, Mentat could crash.2. In Mentat 2013.1 Classic, the SELECT ELEMENT BY CLASS menu did not allow to set the HEX20 and HEX27

element classes.3. In rare cases, Mentat could crash while drawing solids with complex edges.4. If a vector PostScript file was created from a xy-plot (i.e. a table, a history plot, a path plot, a generalized xy-

plot, an experimental data fit plot or a design plot), then the line width settings for the curves in the xy-plot were not reflected in the PostScript file.

5. The graphics performance has been improved in the following cases:

If large amounts of text are displayed (for example, when node or element labels are plotted or, during postprocessing, when numerics are plotted).

If Mentat is run over a network, in particular on Linux.6. On Linux, the option Run Saved Executable (to run a Marc analysis with a saved executable based on a user

subroutine) failed if the user subroutine had the extension .F.7. The filters on the List tab of the Model Navigator did not work properly for entity types that contained

parentheses such as the contact body types Meshed (Deformable) and Meshed (Rigid).8. When identifying element types or element classes, the legend would also show element types or classes of

elements which previously had been made invisible. This is inconsistent with identification of other entities like materials or geometric properties, in which only the materials or geometric properties of the visible elements are listed in the legend. This has been changed. Only the element types or element class of the visible elements are now shown in the legend.Preprocessing

1. When creating servo links via the N to N Servo Links menu, the coefficients for the terms in the servo links could not be set.

2. Enhanced transverse shear options could not be selected for coupled analyses such as thermal/structural and electrostatic/structural analyses.

3. Sweeping of coincident nodes failed if the nodes had identical IDs.4. When selecting Element Quantities for a tracking file in the new Mentat, the selected quantities were unreadable

because multiple text strings were displayed at the same location.


5. If the Contact Table command Add/Replace Entries was executed in Create or Copy mode, multiple contact interactions were created instead of a single one.

6. The constants tz (temperature offset), q (activation energy), sb (Stefan-Boltzman constant) and r (universal gas constant) were not supported in the formula of a table defined by this formula. These constants have been added. The values of tz, r and sb are taken from the current job and the value of q is taken from the current material. If no job or material exists, then default values are used for these constants.

7. No button existed to assign a table to the Poisson's Ratio for a Hypoelastic and Simplified Nonlinear Elastic material using the Stress model.

8. Mentat allowed entering anisotropic properties for electric permittivity, magnetic permeability and electric conductivity, but this is not supported in Marc, except for anisotropic electrical conductivity in analyses with a steady state current flow pass (analysis classes Current/Thermal and Current/Thermal/Structural). An error is now issued when performing a job check or writing a Marc input file.

9. The surface recession rate by mechanical erosion was not supported for surface energy boundary conditions in the thermal part of an analysis.

10. In models with VCCT cracks, the user subroutines UCRACKGROW and UCRACK_PARIS, which are automatically used if a VCCT crack exists in the model, showed up in the list of Selected User Subroutines in the Job Properties Run menu, even though these subroutines cannot be selected or deselected.

11. The calculated properties of a thin-walled beam section (area, moments of inertia and center of gravity) defined by an arc were incorrect. This did not affect the Marc data file written by Mentat.

12. If a job consists of multiple load cases of which the last one is a SUPERELEM load case, then for table driven input the number of active boundary conditions written for this SUPERELEM load case could be nonzero, causing the entries of the generated DMIG file to be incorrect.

13. If the Full Mesh Density Control option was used in a Global Remeshing criterion with a mesh density control of type Region and the region was defined by a cylinder, then the region was not always displayed correctly. This did not affect the Marc input written by Mentat nor the results of the analysis.

14. Converting relatively complicated trimmed surfaces to solid faces could cause Mentat to crash.15. In the new Mentat, the program would terminate if the Insert Interface Elements option was used in the

Delamination Properties menu and the Create And Set button was clicked. The workaround was to create the

Interface Material first, and then use the Set button in the Delamination Properties menu to associate the Material with the Delamination.

16. In the new Mentat, clicking the Create button in the Matching Boundaries menu to create Interface Elements between two matching boundaries failed to open the Matching Boundary Interface Elements menu.

17. Out-of-plane edge currents for 2-D and axisymmetric magnetodynamic analyses were not supported by Mentat.18. Edge loads on 3-D shell elements perpendicular to the mid-plane were plotted in the wrong direction.19. The active plastic strain of the Bonora damage model was not available for post processing.20. When fitting the parameters of the Bergstrm Boyce viscoelastic material model on experimental data, incorrect

values could be obtained for the network B parameters.21. Mentat could crash if the Advancing Front mesher was used to mesh a surface and the mesher failed to mesh

the surface. The problem did not occur if the mesher succeeded in meshing the surface.

55List of Corrected Defects in the 2014 ReleaseMentat

Marc Input File Writer

22. Solids stored in sets were not displayed in the color of the set if the Identify Sets option was used.23. After meshing a solid body (or a list of bodies) with tetrahedral elements, the command did not prompt for the

next body (or list of bodies) to be meshed. The Tet Mesh! button had to be clicked again.

1. The friction coefficient in the second slip direction was not written to the Marc input file even though it shows up correctly in Mentat.

2. If the Water Drying Model is used in thermal diffusion analyses involving pyrolysis, then a Liquid Water Material and a Water Vapor Material can be selected, but the Water Vapor Material was not written to the Marc input file.

3. When Multi-Physics Input Style is used, an incorrect input file was written for Acoustic-Structural analyses. The workaround was to edit the input file and replace the keyword isotropic, acoustic by acoustic.

4. If for the Rate Power Law plasticity model either the Coefficient A or the Minimum Yield Stress is zero (but not both) an error message is printed, but the text of the message was incorrect.

5. An incorrect input file was created if the model contained a thin-walled section beam with an open section (element type 79 or 77), and the option Open Section had been set for the related geometric property (in the Geometric Properties Element Types menu). In that case, the second field of the GEOMETRY option equalled zero. The latter now refers to the valid beam section. In addition, if for any line element the element type had not been set by the user, and for its geometric property one or more of the options in the Geometric Properties Element Types menu had been set to a non-default value, then the program would assign the default element type to the element instead of the element type corresponding to the options in the Geometric Properties Element Types menu. Finally, a warning is now issued for any inconsistency in element type and its geometric property.

6. If a material orientation is assigned to an element which is not consistent with the element type, then the Marc Input file writer failed to report this inconsistency. Moreover, Marc did not catch this correctly.

7. The adaptive load stepping option AUTO THERM CREEP was incorrectly written by Mentat, which caused an analysis to terminate prematurely with exit number 13.Postprocessing

1. Opening a results file with many transformations or sets was very slow. A workaround was to disable updates to the Model Navigator in the Tools Program Settings menu before opening the results file.

2. If an animation was played or an animated GIF, MPEG or AVI movie was created with the Mentat 2013.1 release, then the element edges and other line segments were not always displayed with the correct line width and the program might even hang or crash while playing the animation or creating the movie.

3. The Select-by-Scalar Value selection methods, which select nodes or elements based upon the values of the scalar quantity that is currently being postprocessed, did not honor the Delta option in the Model Plot menu. The nodes or elements were selected based upon the values for the scalar quantity in the current increment, rather than on the difference between the values in the current increment and in the previously visited increment.

4. Mentat could crash if a results file was opened that contained flow line data but no node or element data.


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MSC Marc 2013