Sheet metal forming simulation for automotive applications · Hydro-forming of the close-ended part Prof. Dr.-Ing. K. Roll Sheet metal forming simulation for automotive applications

1

Sheet metal forming simulation for

automotive applications Prof. Dr.-Ing. K. Roll

Summer School Dortmund, 7. September 2012

Sheet metal forming simulation for automotive applications Prof. Dr.-Ing. K. Roll Sommerschool Dortmund 2012; Slide 2

Outline

• Introduction

• History of sheet metal simulation Examples (Springback, Compensation etc.)

Stochastic Simulation

• Necessary Developments in Forming Simulation – Refinement of Materials Models

– Influence of Anisotropy

– Effect of Yield Loci and the Hardening Model

– Failure Models

– Influence of Temperature

– Elastic Tools

– Influence of the Press

– Metamodels

• Simulation of the process chain sheet metal forming – Hemming Simulation

– Rollhemming Simulation

– Metamodels

– Mechanical Joining Simulation

– Welding Simulation

• Simulation of the part properties (Static, Crash, Fatigue..) – Forming to Crash

– Forming to Fatigue

• Outlook

2


Sheet Metal Forming Knights Armor (15. Century a. d.)

Source: Prof. Voelkner; TU Dresden

History of sheet metal forming


Sheet rolling mill (mid of 19. Century a. d.)


History of sheet metal forming

3


Sheet Metal Forming - History

Production of a front fender



Sheet Metal Forming - today

Production of an engine hood outer

Coil Store Blanking Line Stacking Line

Pressline Destacking Line

4


Chronological development of plasticity theory

computational procedures History of sheet metal forming simulation


Possible simulation techniques in metal forming

- Smooth Particle Hydrodynamics - Element Free Galerkin Method - Moving Least Square Method Approx. - Reproducing Kernel Particle Method

Upper / Lower Bound Methods

Finite Difference Methods

Finite Element Methods

Boundary Element Methods

Finite Volume Methods

Meshless Methods

- Static Implicit - Static Explicit - Dynamic Explicit

History of sheet metal forming simulation

5


Chronological development of plasticity theory

computational FE-procedures History of sheet metal forming simulation


Progress simulation sheet metal forming

B-Column without

Remeshing (1987)

ca. 1400 Elements

(Source: Hora et.al., 1st NUMIFORM)

Deformierte Platine am Ende des Ziehvorganges

Front Fender (2001)

ca. 3500 Elements

Source: M. Gröber, 1st NumiSheet, Zürich)


6


Progress simulation sheet metal forming

Sidewall with Remeshing

(6 000 000 Elements; 2005)



History of sheet metal forming simulation at Daimler

Year Parts Set-uptime Trial runs

1992 5 3 – 4 weeks 6 - 8

1993 8 2 weeks 5

1995 20 1 week 3

1998 >100 < 2 days 1 - 2

2012 >350 < 1.5 days 1 - 2

Model Size: Die: up to 400.000 Elements

Blank: up to 6.000.000 Elements

Computing Time: from days (1992) to hours on Workstations

or Linux-Clusters

Simulation engineers: 2 in 1992 to 52 in 2011


7


Simulation chain of the complete forming process

Examples of forming simulation


Virtual “Die - Making”: Engine Hood Examples of forming simulation

8


Finite element model

Punch

Blank

Die

Binder

PunchPunch

BlankBlank

DieDie

BinderBinder



Simulation deep drawing process of an Engine Hood

Initial Position Gravity Holding

25 mm to

home

Final

position

Initial PositionInitial Position GravityGravity HoldingHolding

25 mm to

home

25 mm to

home

Final

position

Final

position


9


Simulation of sheet forming processes - examples Examples of forming simulation


Hydroforming of sheet metal pairs - Failure modes Examples of forming simulation

10


Surface defects - door handle

Distribution of Thickness [mm]

( 3 %)

two different forming geometries



Surface defects - door handle - Detail

Minor stress [GPa]Minor stress [GPa]

Danger:

compression stress - 0.05 GPa

Better:

only tensile stress + 0.15 GPa

Minor stress [GPa]Minor stress [GPa]Minor stress [GPa]Minor stress [GPa]

Danger:


Danger:


Better:

only tensile stress + 0.15 GPa

Minor stress [GPa]Minor stress [GPa]


11


Variables influencing springback

Numerical

Time Discretisation

Space Discretisation

type and size of element

Material Model

Convergence Tolerance

Damping, ...

Material

Young´s Modulus

Yield Strength

Hardening

Pre-Treatment

Plastic Strain

Anisotropy

Geometry

Sheet Thickness

Sheet Dimensions

Radius

Forming Depth

Process Conditions

Forming Process

Tool

Force

Tribology

Forming Velocity

TemperatureVariables

influencing

SpringbackNumerical

Time Discretisation



Material Model


Damping, ...

Numerical

Time Discretisation



Material Model


Damping, ...

Material

Young´s Modulus

Yield Strength

Hardening

Pre-Treatment

Plastic Strain

Anisotropy

Material

Young´s Modulus

Yield Strength

Hardening

Pre-Treatment

Plastic Strain

Anisotropy

Geometry

Sheet Thickness

Sheet Dimensions

Radius

Forming Depth

Geometry

Sheet Thickness

Sheet Dimensions

Radius

Forming Depth

Process Conditions

Forming Process

Tool

Force

Tribology

Forming Velocity

Temperature

Process Conditions

Forming Process

Tool

Force

Tribology

Forming Velocity

TemperatureVariables

influencing

Springback

Variables

influencing

Springback

springback simulation


Springback - It’s not a new Phenomena

Springback of materials

with constant conditions

TRIP 700 ZE

DP 500 ZE

THM 280 Z

ZE 340 ZE

ZStE180 BK ZE

Source:

voestalpine Desired

Shape

Springback is ALWAYS existing

arises from stored elastic

forming energy

can be reduced

is depending on • material

• process parameters

• evenly distributed

hardening


12


After

springback

+ -

After

forming

+ -

elastic

plastic

plastic

Elastic bending stresses

through sheet thickness

Different membrane

stresses in flanges

Original blank

shape

Formed blank

Relaxed blank

After

forming

After

springback

Two Principle Mechanisms of Springback springback simulation


Complex Testing Part for the Investigation of

Springback Deviations

AA5182

AA6016

DC06

H320 LA

DP600


13


Possible Forming Processes Using the Testing Tool

Deep drawing

of the open-ended part

Deep drawing

of the close-ended part

Hydro-forming

of the close-ended part


Computed Springback Results - Material Influence

DC06 H320 LA

AA5182 AA6016

Displacement

in mm

max. 7,42 mm max. 9,73 mm

max. 15,67 mm max. 19,02 mm


14


Computed Springback Results – Effect of Forming Technologies

max. 6,3 mm max. 4,3 mm max. 0,8 mm

Deep Drawing

Open-Ended

Deep Drawing

Close-Ended

Hydro-Forming

> >>

Material: DC06



Simulation Sidewall Examples of forming simulation

15


Sidewall – Steps of Simulation: Deep Drawing Examples of forming simulation


Sidewall – Steps of Simulation: Springback Examples of forming simulation

16


Compensation Program

Die with compensated Geometry

CAD-Geometry

Real-Geometry

Die

Compensation: Changing the

Die - Geometry

Part after Compensation Part after springback

Software based compensation

Source: INPRO



Engine Hood Inner - Simulated Springback

Front of part deviates

upwards along bending line

Springback nearly

symmetrical to Y

Deviation

mm

5.0

3.0

1.0

3.0 mm

3.4 mm

Maximum: 4.8 mm

Material: AA 6181 A, Thickness: 1.15 mm

Springback

Deviations from

desired shape


17


Compensation of springback - Hood Inner



One recut of tool set

for compensation

of shape deviations

OP40 to

OP60

5 weeks*

5 weeks*

OP20 and

OP30

Savings by simulation-supported Compensation Overall Cycle Time

Each avoided tool recut can

save between 5 and 10 weeks

in overall cycle time

Time period of die process

engineering is constant, due

to parallel run of simulation

and die process engineering

Tool building

SWF

Engineering

Today

10 weeks*

Future

* example: Engine Hood Inner


18


SWF

Today

Tool building

Engineering

One recut of tool set

for compensation

of shape deviations

OP40 to

OP60

70 T€*

80 T€*

OP20 and

OP30

125 T€*

Future

25 T€

Savings by simulation-supported Compensation

Costs

Each avoided tool recut can

saved up to 125 T€

Additional costs of

25 T€ per tool set during die

process engineering due to

additional human and

computational resources

* example: Engine Hood Inner



2. Compensation

Deviation from CAD-Model

mm 1.0 0.5 0.0

Without Compensation

Modifications locally applied on mesh of tools

Several iterations reduce shape deviations from

CAD-Model (desired shape)

KDS

1. Compensation

Material: TRIP 700

Thickness: 1.4 mm

Semi-Automatic Iterative Compensation Examples of forming simulation

19



Source: Autoform



20


Stochastic Simulation – Variation of Parameters

Basic simulation:

AutoForm Final Validation – Setup

Blank: original

Lube: 0.15

BHkraft: 145t (half)

New Simulation:

AutoForm Final Validation – Setup

Blank: smaller

Lube: 0.11; BHkraft: 145t (half)

Failure Failure


Predictable Variables Using Sheet Metal Forming

Simulation State of the art in sheet forming simulation

21


Simulation vs. Reality

Factor Reality Simulation

Production stroke rate Not constant Not in the model

Machine Elastic Not in the model

Tool Elastic Rigid

Characteristics of the direction of draw Not constant Not in the model

Coefficient of Friction Not constant Constant

Temperature Not constant (Not) in the model

Topology of blankholder surface Not constant Not in the model

Material Complex Simple models

Material characteristics Not constant (Not) constant

Necessary Developments in Simulation Engineering


Components of material modeling for sheet metal

forming

zzyzxz

zyyyxy

zxyxxx

zzyzxz

zyyyxy

zxyxxx

Plastic

hardening

Yield locus

Flow rule

Definition of in-plane transition for elastic

to plastic material response

Definition of material work

hardening based on plastic flow

Defines the correlation of

stress and strain state

x

y

Refinement of Materials Models

22


Yield Curves - Method of Extrapolation

DP600

0

0,2

0,4

0,6

0,8

1

1,2

0 0,2 0,4 0,6 0,8 1 j

GPa

DP600_Voce

DP600_Swift

DP600_Gosh

DP600_Hocket_Sherby

DP600_Ludwik

DP600_Tensile test

DP600_Layered compression test



Effect of flow-curve approximation on the

simulation result

Section length [mm]

thic

kn

ess

red

ucti

on

[%

]

Section length [mm]

thic

kn

ess

red

ucti

on

[%

]


23


Yield loci models for sheet in-plane anisotropy

Barlat2000

Hill48

Barlat89

xx

yy

Hill48(Barlat89_M2)

Barlat89_M8

MATFEM_A8

A chosen yield locus

defines the correlation

of yield stress

depending on the

actual stress state and

rolling direction in the

sheet plane. Recent developments

concentrated on more

and more complex

functions to describe a

constant anisotropy.

Influence of Anisotropy


Todays choice for material model and failure

prediction

Source: Dr. Kessler; TKS

Numisheet 2008


24


Yield locus models for sheet metal forming

Source: Dr. Kessler; TKS

Numisheet 2008



Yield locus calibration – parameters to be determined


25


Yield Surface DP600

Hill 1948 Barlat-Lian 1989 Barlat-Lian 1996

Biaxial Stress Factor

Hill 1979

Hill 1990

= Combination Hill 48 + Hill 79

Simulation

Experiment

Hill 1948 Barlat-Lian 1989 Barlat-Lian 1996

Biaxial Stress Factor

Hill 1979

Hill 1990

= Combination Hill 48 + Hill 79

Simulation

Experiment



Influence of Yield-Loci Model to Failure Description

Source: Heinl, BMW; Dr. Kessler, TKSE; SFU 2010


26


The assumption of isotropic material hardening

x

y

Monotonic expansion of the

yield locus

Isotropic material hardening:

All directions gain the same

hardening

The hardening rule specifies the expansion

of the yield locus in case of plastic

deformation.

Effect of Yield Loci and the Hardening Model


Industrial aspects of material modeling for steel

grades - Simplification procedure in daily practice

So

urc

e:

Dr.

Kessle

r, T

hyssen

Kru

pp

Ste

el

N

um

ish

eet

2008

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

IYL

No

rmaliz

ed

str

ess

2

2

SYL

Material hardening

Normalized stress 11

Assuming isotropic hardening

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

Barlat m=8 SYL

Normalized stress 11

No

rmaliz

ed

str

ess

2

2

► Industrial simulation is mostly based on isotropic hardening!


27


Drawback of the actual modeling method

Modern high strength steel grades may show a stress state dependent

hardening – this is hardly to fit with conventional model assumptions

• Reasons can be found in phase

transformations or micro-structure

The up to now used approach with

constant yield locus and one single

hardening curve can definitely not cover

these effects!

Do we have alternative modeling options

for industrial simulation tasks? 0.0

0.5

1.0

1.5

2.0

0.0 0.1 0.2 0.3 0.4

Equivalent strain / -

Eq

uiv

ale

nt

str

ess /

GP

a

U-Tension

Stack compression

Hydraulic Bulge

Shear



Alternative ways for hardening with the

Gen_Yld* model

xx

yy


28


Yield curve comparison for different load paths

3.0 Isotropic hardening

Barlat 2000

0.0

0.5

1.0

1.5

2.0

2.5

0 0.25 0.5 0.75 1


Eq

uiv

ale

nt

str

ess /

GP

a

uniaxial tension compression biaxial tension shear

3.0


Anisotropic hardening

Hill ´48

0.0

0.5

1.0

1.5

2.0

2.5

0 0.25 0.5 0.75 1

Eq

uiv

ale

nt

str

ess

/ G

Pa



0

100

200

300

0 10 20 30 40 50 60 70

drawing depth / mm

pu

nch

fo

rce / k

N

experimental Hill48 anisotropic

Yld89 isotropic Yld2000 isotropic

Results in comparison – punch force prediction

• anisotropic hardening approach leads to a better punch force prediction


29


Results in comparison - distribution of major strain

0.0

0.1

0.2

0.3

0 50 100 150

section length / mm

ma

jor

str

ain

/ -

Experimental

Hill48 anisotropic

Yld89 isotropic

Yld2000 isotropic

better prediction

with anisotropic

model



Material failure due to cracking Experiment – Simulation comparison

Failure Models

30


Prediction of Failure – Cross Die (TRIP 700)

Experiment Simulation

Failure predicted by FLC

Thinning [%] Failure predicted by „numerical thinning“

Failure Models


A new Model for Failure Prediction and Damage

Dynamic Models with Damage

Models: von Mises, Gurson, Gurson-JC

Anisotropic Yield Locus

Models: Barlat89, Barlat2000, Hill48, Mat_TRIP

Plastic Strain

Thickness

Damage

Transfer of Variables

Crash Simulation

Forming Simulation

•Energy absorption

•Prediction of structural folding patterns

•Correct description of yield locus

•Anisotropy

Failure Models

31


Concept:

Coupling of a damage model to an unaltered material model for forming simulations

Damage

model

Forming material model

Crash material model with

damage

p ,

tp ,,

Damage

Mapping

Forming simulation Crash simulation


Failure Models


Gurson

BarlatGurson

p ,

thicknessp ,,

Damage f

Mapping


extended

Johnson-

Cook

(GISSMO)

Barlat Mat_024

p ,

thicknessp ,,

Damage D

p ,

extended

Johnson-

Cook

(GISSMO)

Mapping

Mapping


1.) Using the Gurson

model

2.) Using an extended

Johnson-Cook model

(GISSMO)

Gurson

BarlatGurson

p ,

thicknessp ,,

Damage f

Mapping


Gurson

BarlatGurson

p ,

thicknessp ,,

Damage f

MappingMapping


extended

Johnson-

Cook

(GISSMO)

Barlat Mat_024

p ,

thicknessp ,,

Damage D

p ,

extended

Johnson-

Cook

(GISSMO)

Mapping

Mapping


extended

Johnson-

Cook

(GISSMO)

Barlat Mat_024

p ,

thicknessp ,,

Damage D

p ,

extended

Johnson-

Cook

(GISSMO)

MappingMapping

MappingMapping


1.) Using the Gurson

model

2.) Using an extended

Johnson-Cook model

(GISSMO)

A new Model for Failure Prediction and Damage Failure Models

32



Failure strain vs. Triaxiality (plane stress)

Modification for GISSMO:

Failure strain can be defined arbitrarily

Tabulated input of failure Strain vs. Triaxiality

0

0,2

0,4

0,6

0,8

1

1,2

1,4

1,6

1,8

2

2,2

-0,2 0 0,2 0,4 0,6 0,8

η

εf

Failure strain

curve can be

determined using

coupon tests of

several distinct

triaxialities

Failure Models



Simulation of Cross - die formability test using GISSMO coupled to Barlat :

• Failure spot predicted correctly at the

same position

• Less damage predicted in areas that are

not close to failure

Real failed part

Simulation of Cross - die formability test using GISSMO coupled to Barlat :

Linear accumulation GISSMO n=2 Linear accumulation Linear accumulation GISSMO n=2 GISSMO n=2


same position



Real failed part


same position



Real failed part Real failed part

Failure Models

33


Press Hardening - Process Modeling Subdivision into Partial Stages

more computational efficiency

use of different time scales

use of different tool models

use of different solvers

Handling Gravity & Waiting

Forming Quenching

temperature temperature

geometry

(stress, strain)

temperature

geometry

(stress, strain)

Influence of Temperature


Press Hardening of a roof frame Prediction of Die Temperature

Time after tool closing

1 s 4 s 8s


34


Press Hardening of a roof frame Prediction of Punch Temperature

Time after tool closing

1 s 4 s 8s



Press Hardening of a Roof Frame Temperature Change during Forming


35


Thermo-mechanical coupling of sheet forming

processes

Die

Punch

0,0

0,5

1,0

1,5

2,0

2,5

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8

X-IP

TRIP

H320LA

90 ... 80 ..ηΔTcρdVεσηw pV

eqeq

Forming of XIP-Steel in a cross-die

extrem strain hardening of X-IP-Steel




processes

Temperature after Forming - TRIP 700


36


Damaging of TRIP-steel within deep drawing Influence of Temperature


Cracks after the forming process


37


Forming of Magnesium sheets using a heated tool

Magnesium sheet at 200°C Final part: roof inner

Tool with heating system Heated blankholder



Sheet metal forming Application of different heat treatment methods Influence of Temperature

Without heat treatment With heat treatment

38


Sheet metal forming Application of different heat treatment methods

0

Ext. Subroutine

Forming simulation

External Subroutine to

introduce heat treatment

Calibration



We need for high-strength steel a thermo-mechanical coupled

simulation in order to respect the temperature distribution in the

sheet during the forming process

We have to respect the Influence of the Temperature in the Material

model

Temperature calculation give information about the thermal load of

the tool

Temperature dependence of the friction must be considered

Heating up of sheet and tool by frictional heat can be considered


processes Conclusion

39


Elastic tools in the simulation of sheet metal forming

Rigid model

Elastic model

• local deformations caused by sheet thickening

• Consideration of local load application

More accurate simulation of the draw in

Variations:

1. Models with elastic volume elements

2. Condensation of the tool stiffness on effective areas

Substructuring

3. Modal Analysis

Elastic Tools


Elastic tool: Example

binder

die

die

punch

elastic plate spacer

pressure pad

binder

die

die

punch

elastic plate spacer

pressure pad

Elastic Tools

40


Comparison between rigid and elastic

simulation models

ca. 6,6 mm ca. 6,6 mm

-0,1

Distance along the section [mm]

Section +0.30

+0.20

+0.10

0

-0.10

[mm]

Elastic Tools


Comparison between rigid and elastic

simulation models Elastic Tools

41


Blankholder Surface

Dimensions

2700 x 1660 x 550

Blankholder

pressure: 2,0 N/mm²

Real Die: Blankholder ca. 7 Mio. Elements Elastic Tools


Structural optimization of tools

Original structure Optimized structure (weight reduced)

Elastic Tools

42


Next Step: Forming simulation with elastic Tools and elastic Press (ca. 134.000 Volumelements)

Influence of the Machine


Simulation of a Forming Machine with different Loads

(0,5 and 0,92 x nominal Force) Influence of the Machine

43


From process simulation to press line simulation

Process simulation

Rigid die model

Elastic die model

Elastic machine model (static)

Dynamic machine model

Press line simulation


Forming simulation with elastic Tools and elastic Press

Conclusions:

Forming Simulation with elastic Tools increase the accuracy of the

simulation.

•Local deformations caused by sheet thickening

•Friction Forces are more accurate

•Consideration of local load application

•More accurate simulation of the draw in

•Better calculation of the stresses and deformations of the Tool

Problems:

How we can handle the elastic properties of Tool and Machine in an economic way?

44


Simulation chain of the complete forming process

Model

Setup

CAD Discretization Tool generation

Forming

Gravity Holding Stamping

Progressive

Processes

Trimming Flanging Hemming Springback


Workflow Sheet Metal Part Production Simulation of the process chain sheet metal forming

45


Problems:

• Each operating step (drawing, cutting, hemming etc.) need

a “own “ FE - Mesh

• Data must be mapped between the FE - Meshes statically and

kinematically compatibly

• Simulating the assembly process parts the different FE – Meshes

of the parts must be brought by best fit into the correct position.

How we can handle the springback of the assembled part?

• In which operation step we have to compensate the springback

of the assembled part?

• How can we simulate the influence of the adhesive bonding in the

hemming operation?

Simulation of the forming process chain

Solved Progress ?

Simulation of the process chain sheet metal forming


Trimming operation (OP30) Trimming Simulation

46


Scrap Flow Simulation Trimming Simulation


Simulation Hemming

hemming of

curved edges

Hemming Simulation

47


Front Fender – (Roll in) Experiment vs. Simulation

Hemming Simulation


Frontfender – Flange radius Experiment vs. Simulation

Hemming Simulation

48


Rollhemming

General procedure

Inner part

> 90°

~45°

Roller

After flanging

Pre-hemming

Final-hemming

Step 1

Step 2

• Incremental forming with a roller

•Application robotically manipulated

hemming roller

•Example:

Tangential compression

Tangential tension stress

Hemming roller

Flange

Hemming bed

Stress in Y [MPa]

Flange

Roller Hemming

Rollhemming Simulation


Rollhemming Simulation Rollhemming Simulation

49


•Identification of relevant factors by Design of Experiments

DEAEAC

AEFBEBDCDEF

ABCACE

BAFCFABA

ACDABD

FBC

ADFE

ADEACF

DFADBFCEDC

300025002000150010005000

Te

rm

Standardisierter Effekt

13

A Krümmung XY

B Krümmung Z

C Blechdicke

D Abkantradius

E Falzkanal

F Vordehnung

Faktor Name

Pareto-Diagramm der standardisierten Effekte

(Antwort ist REL, Alpha = ,05)

Radiuseinsatzlinie (REL)

konvexkonkav

2,34

2,28

2,22

2,16

2,10

HochpunktTiefpunkt 1,150,95

1,51,0

2,34

2,28

2,22

2,16

2,10

30 100

Krümmung XY

Mit

telw

ert

Krümmung Z Blechdicke

Abkantradius Falzkanal Vordehnung

Haupteffektediagramm für RELDatenmittelwerte

prestrain rolling direction flange length

Development of a metamodel Metamodel


Generation of response Surfaces

• for example, by a sum of weighted

Gauss bells, with the parameter you are

looking for using the method of least

squares

• Minimization through local search

Source: FCE Frankfurt Consulting Engineers GmbH

Metamodel

50


Meta model as a basis of a forecast tool for the

planning process of Rollhemming

•Result forecast based on FEM calculations of rollhemming

Metamodel


Joining: Simulation of Clinch - Process Mechanical Joining Simulation

51


Joining: Simulation of Riveting Mechanical Joining Simulation


Joining: Simulation Tack-setting Mechanical Joining Simulation

52


Joining: Simulation of Spot Welding

0.75 mm

1 Per. 3 Per.

6 Per. 10 Per.

Processing conditions: flat upper electrode, 2.8 kN, AC1

Processing time: 1, 3, 6,10 periods

Welding Simulation


Forming to Welding Distortion

Welding Lines

Welding Simulation

53


Forming to Welding Distortion Welding Simulation


Simulation of the part properties (Static, Crash,

Fatigue..)

Results of the forming

simulation are input for

• Crash - analysis

• Static analysis

• Fatigue analysis

• Static analysis

of the tool

Results of the forming

simulation are input for

• Crash - analysis

• Static analysis

• Fatigue analysis

• Static analysis

• Welding distortion

Simulation of the part properties

54


Simulation of the part properties (Static, Crash,

Fatigue..)

Problems:

• Each simulation method (static, crash, etc. ) needs a " own " FE - Program

(exception Forming - Crash with explicit codes)

• Each simulation method (static, crash, etc. ) needs a „own“ FE - Mesh

• Each simulation method has " own " material and failure models

• Data must be mapped between the programs statically and kinematically

compatibly.

• Today it is only possible to interpolate Scalars such as thickness, plastic

strain, etc.

• Which influence does the " damage " have by the mapping process on the

characteristics of the component?

• With the extrapolation of Tensors still many questions are open (e.g.: as

equilibrium can be achieved with mapping?)

Solved Progress ?

Simulation of the part properties


Coupling Crash - Forming Simulation

Crash - / Staticsimulation Formingsimulation

(Prototyp Dies)

Job No. 1

Today

Styling

Formingsimulation

(Hard Dies)

Formingsimulation

Crash - / Staticsimulation

Tomorrow

With Forming

History

Crash - / Staticsimulation Formingsimulation

(Prototyp Dies) Crash - / Staticsimulation Formingsimulation

(Prototyp Dies)

Job No.. 1

Today Today

Styling

Formingsimulation

(Hard Dies)

Formingsimulation


Tomorrow

With Forming

History

Formingsimulation

(Hard Dies)

Formingsimulation


Forming simulation

(Hard Dies)

Formingsimulation


Tomorrow

With Forming

History

Forming to Crash

55


Crash - Forming Simulation - Example

50285 Nodes

Crash Model:

10855 Elements

10759 Nodes

Forming Simulation Modell:

Thickness-Distribution after Mapping

49007 Elements (AUTOFORM)

50285

Crash Model:

10855 Elements

10759 Nodes

Forming to Crash


Crash-Forming Simulation

§

Forming properties from 64 parts are mapped to the Crash - Simulation

Forming to Crash

56


Crash-Forming Simulation

•Euro-NCAP-Test (deformable Wall): 64 km/h with 40% Overlapping

Standard

With Influence of Thickness &

plastic strain

-

Forming to Crash


Crash to Forming: Failure and Damage

Three Point Bending Test B-column

Forming to Crash

57


Crash to Forming: Failure and Damage

Three point Bending Test B-column

Experiment Simulation

with forming

simulation

Simulation

without forming

Simulation

Failure at 196 mm

Buckling at 82.1 mm

Barlat + Failure Source: FhG - IWM, Freiburg

Forming to Crash


Fatigue - Part of the Suspension System Forming to Fatigue

58


Fatigue - Stress Calculation

+15%

+16%

+16%

+9%

+16%

+16%

“Classical Simulation with

Constant Sheet Thickness

Simulation with Sheet Thickness

after the Forming Process

Forming to Fatigue


Fatigue - Failure

+52%

+47%

+15%

+55%

+108%

+108%

1.

1.

2.2.

Simulation with Sheet Thickness

after the Forming Process

“Classical” Simulation with

Constant Sheet Thickness

Ranking List of Failure

Forming to Fatigue

59


• Warm forming and hot forming

• Press hardening (22MnB5), hot stamping

• New lightweight materials (Al, Mg, Ti?)

• Hybrid composites (sheet metal / textiles, sheet metal / polymer,

sandwich sheets, sheet metal / fiber-reinforced polymers, …)

• Tailored (engineered) blanks, bonded blanks, patchwork blanks

special sheets for lightweight design

• Aluminum fusion alloys and cladded blanks

• Functionally graded materials

• Tailored heat treated blanks (Al, 22MnB5)

• Cold forming of HSS, AHSS, UHSS

• Mechanical joining processes

• Servo presses

• Special technologies (EMF, superplastic forming,..)

Trends in Metalforming I Outlook


This has the following consequences for the simulation

• Thermal-mechanical coupling will have to be the standard

• Heating methods (induction, conduction) will have to be simulated

• Tooling properties (thermal, elastic) will have to be considered

• Structural optimization of tools and dies will be required

• In the long term the system machine-tooling-process will have

to be simulated

• The real time has to be used and shown

• Development of new, sophisticated material models

• Joining technologies for new materials will have to be

simulated as well

• Adhesives in mechanical joining processes will have

to be simulated

Trends in Metalforming II Outlook

60


Vision: the future simulation environment

Source: Dr. Haufe, DynaMore

Rückfederung Kompensation

Walzen Mapping Crash - Umformen

; ; ; ; ; ; T

Mapping

Beurteilung des Gefüges

Anisotropie in Dickenrichtung

Oberflächenqualität etc.

Möglichst universales, durchgängiges Materialmodell oder größtmö gliche Kompatibilität!

Glühen Fügen

Beurteilung der Herstellbarkeit

Anisotropie in der Ebene

Umformbarkeit etc.

Energieaufnahme

Entwicklung Bauteilgeometrie

Div. Anforderungen aus Crash/Festigkeit/ Steifigkeit


Beurteilung der Wärmeeinflusszone

Rückfederung Kompensation

Springback Compensation

Rolling Annealing Mapping Crash-simulation - Forming


Anisotropie in Dickenrichtung

Oberflächenqualität etc.

• texture

• grain size

• strength

• transformation

• ductility

One description of the material for all simulations if possible

Joining

Beurteilung der Herstellbarkeit

Anisotropie in der Ebene

Umformbarkeit etc.

• yield locus

• hardening

• phase transformation

• damage

• accuracy

Energieaufnahme

Entwicklung Bauteilgeometrie

Div. Anforderungen aus Crash/Festigkeit/ Steifigkeit

•Energyconsumption

•Intrusion

•Stiffness

•Fatigue


Beurteilung der Wärmeeinflusszone

•depend on joining Technique

•thermal wakening

•mechanical

hardening

•Welding distortion

Mapping

Outlook


Vision of Digital Factory

Facility

Line

Cell

Operation

Specific

Process

Building

Worker Focus :

• technical processes

• facility components

• quality

• costs

• capacities

Focus :



• quality

• costs

• capacities

Not a single production facility

will

without having been completely

supported by digital planning

methods


will



methods

be planned

be built/

go into operation

be working

be planned

be built/

go into operation

be working

Facility

Line

Cell

Operation

Specific

Process

Building

Worker

Facility

Line

Cell

Operation

Specific

Process

Building

Worker Focus :



• quality

• costs

• capacities

Focus :



• quality

• costs

• capacities


will



methods


will



methods

be planned

be built/

go into operation

be working

be planned

be built/

go into operation

be working

Outlook

61


Thank you for your attention!

Documents

Sheet metal forming simulation for automotive applications · Hydro-forming of the close-ended part Prof. Dr.-Ing. K. Roll Sheet metal forming simulation for automotive applications