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.
ASME V&V 10-2006Model Development
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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
ASME V&V 10-2006Model Development
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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
ASME V&V 10-2006Model Development
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ASME V&V 10-2006V&V Process
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Verification
ASME V&V 10-2006V&V Process
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Validation
Verification
ASME V&V 10-2006V&V Process
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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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Hierarchical Modelling
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Hierarchical Modelling
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Hierarchical Modelling