Definitions Procedures

8/13/2019 Definitions Procedures

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Development of Verification and

Validation Procedures for Computer

Simulation use in Roadside Safety

Applications

NCHRP 22-24

DEFINITIONS AND PROCEDURES

Worcester Polytechnic Institute

Battelle Memorial Institute

Politecnico di Milano


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FEA IN ROADSIDE HARDWARE DESIGN

Specialty codes prior to 1990 (i.e.,NARD, Guard, BarrierVII, etc.)

Shift to DYNA/LSDYNA in mid-1990s

Today

Almost exclusively LSDYNA Used in nearly all new productdevelopments

Requests for approval now comingbased partly or entirely on LSDYNAresults.

Decision-makers need a way to judgegood from bad results. Who do youtrust? How do you make anacceptance decision based onsimulations?


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OBJECTIVE

to develop guidelines for verification and validationof detailed finite element analysis for crashsimulations of roadside safety features. The focus ofthese guidelines will be on establishing accuracy,credibility, and confidence in the results of crash testsimulations intended (1) to support policy decisionsand (2) to be used for approval of designmodifications to roadside safety devices that were

originally approved with full-scale crash testing.


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These are domain-specific guides

with more step-by-step

procedures and defined metrics.

These are general purpose, broad-

based guides that out-line general

procedures and provide

terminology definitions. They are

notstep-by-step guides.

Existing V&V Procedures

NASA

DoD

AIAA

Sandia Los Almos

LLNL

ASME

FHWA/NARD

FAA

FRA

Several organizations have developed V&V procedures in recent years.

ASME Guide draws on all the above guides in

developing its recommendations.

Lockhead

EU (rail)

Chrysler


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ASME V&V 10-2006

History

1999 An ad hoc verification & validation specialty

committee was formed under the auspices of

the United States Association for

Computational Mechanics (USACM).

2001 ASME approved the committees charter:

To develop standards for assessing the

correctness and credibility of modeling and

simulation in computational solid mechanics.

Committee was assigned the title and

designation of the ASME Committee forVerification & Validation in Computational

Solid Mechanics (PTC 60).

2006 ASME published the Guide for verification

and validation in computational solid

mechanics. ASME V&V 10-2006.

2007 Developing a series of best practicesguides


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ASME V&V 10-2006

Committee Members

M. C. Anderson, Los Alamos National Laboratory

J. A. Cafeo, General Motors Corporation

R. L. Crane, The American Society of Mechanical Engineers

S. W. Doebling, Los Alamos National Laboratory

J. H. Fortna,ANSYS

M. E. Giltrud, Defense Threat Deduction Agency

J. K. Gran, SRI International

T. K. Hasselman,Acta Inc.

H. M. Kim, Boeing

R. W. Logan, Lawrence Livermore National Laboratory

H. U. Mair, Institute for Defense Analyses

A. K. Noor, Old Dominion University

W. L. Oberkampf, Sandia National Laboratories

J. T. Oden, University of Texas

D. K. Pace, Consultant

T. Paez, Sandia National Laboratories

A. B. Pifko, Consultant

L. Proctor, MSC Software

J. N. Reddy, Texas A & M University

P. J. Roache, Consultant

L. E. Schwer, Schwer Engineering

P. E. Senseny, Consultant

M. S. Shephard, Rensselaer Polytechnic Institute

D. A. Simons, Northrop Grumman

B. H. Thacker, Southwest Research Institute

T. G. Trucano, Sandia National Laboratories

R. J. Yang, Ford Motor Company

Y. Zhao, St. Jude Medical

The committee derives its author i ty from thedivers i ty of its membership and consensus of opinion.


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ASME V&V 10-2006

The Guide doesprovide a:

Framework and process for V&V

activities.

Standard definitions for V&V terms.

The Guide does not provide:

A step-by-step procedure for V&V.

Specific recommendation for metrics.


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ASME V&V 10-2006

Some Definitions

Validation -- The process of determining the degree towhich a model is an accurate representation of the realworld from the perspective of the intended uses of themodel. Model results are compared to physical experiments.

Verification -- The process of determining that acomputational model accurately represents the underlyingmathematical model and its solution. Model results are compared to known mathematical solution.

Calibration -- The process of adjusting physical modelingparameters in the computational model to improveagreement with experimental data. Physical experiments used to estimate model parameters.


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ASME V&V 10-2006

Validation

The process of determining the degree to which amodel is an accurate representation of the real

worldfrom the perspective of the intended uses ofthe model.


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ASME V&V 10-2006

Verification

The process of determining that a computational

model accurately represents the underlying

mathematical model and its solution.


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ASME V&V 10-2006

Calibration

The process of adjusting physical modeling

parameters in the computational model to

improve agreement with experimental data.


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The airplane is manufactured by Karel Klenor - KLN, Choce, the firm

is one of the biggest producers of composites in the Czech Republic www.kln.cz

We need to know the wing tip deflection of the ABC experimental aircraft under

a distributed load of X Newtons/meter, in this case the reality of interest is the

aircraft wing.

Before we begin to develop a model, a reality of interestisidentified (i.e., what is the physical system to be modeled).

ASME V&V 10-2006Model Development


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Conceptual Modelthe collection ofassumptions and descriptions of physical

processesrepresenting the solid mechanics

behavior of the reality of interest from which the

mathematical model and validation experiments

can be constructed.



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Mathematical ModelThe mathematical

equations, boundary values, initial conditions, and

modeling data needed to describe the conceptual

model.

0

0 0 0

EI x y w x x L

y y y L y L



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Computational ModelThe numerical

implementation of the mathematical model,

usually in the form of numerical discretization,

solution algorithm, and convergence criteria.

Commercial Software



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ASME V&V 10-2006V&V Process


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Verification



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Validation

Verification



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The goal of the validation processis toassess thepredictive capability of the

model by comparing the predictive

results of the model with validation

experiments.

Three key elements of Validation:

1. Precision Testing2. Uncertainty Quantification

3. Comparative Metrics

ASME V&V 10-2006Validation Process


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ASME V&V 10-2006

Comments on the V&V Process

The V&V process diagram is valid not only forwhole models but for components,assemblies, parts, etc.

While most roadside safety work usesLSDYNA, this process and definitions areapplicable to any numerical simulationsoftware (e.g., MADYMO, BVII, HVOSM, HVE,etc.).

We can not usually do code verificationwedo not generally have access to the code. Counter example: Yvonne Murrays soil and

timber models for LSDYNA.

We cando calculation verificationthis isanother word for benchmarking. Example: do different versions of LSDYNA

produce the same result? Do differentcomputational platforms produce the sameresult?

Notice the comparison is quantitative. Qualitative validation is not really validation

because it is subjective.


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Recommendation

The project team recommends thatwe adopt the ASME V&V 10-2006Guide as a basis for the basic V&Vprocess and definition of termsbecause

The 22-24 panel definitions are more

or less consistent with the ASMEdefinitions and

The ASME definitions have beenadopted by a broad cross-section ofthe computational solid mechanicscommunity and ...

The ASME process includes all theessential pieces needed incomputation roadside safety.

Discussion?


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Hierarchical Modelling

The ultimate goal is to use a

validated model toextrapolateresults to an

untested situation.

We need to have confidence

in the model before we canuse it to predict untested

situations.


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Hierarchical ModellingVehicle assembly

Barrier assembly

Whole modellevel

Top Rail assembly

MiddleRail assembly

Rubrailpart

Post part AssemblyLevel

Guardrail part

Spacerpart

Blockoutpart Stiffner parts

Main-railpart

Postsparts

Part Level


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Documents

Definitions Procedures