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NAFEMS Benchmark Challenges

In late 2014, ESRD began participating in the NAFEMS Benchmark Challenge series.  NAFEMS is the International Association for the Engineering Modelling, Analysis and Simulation Community (about NAFEMS).  The goal is to compare solutions from multiple FEA tools, and determine who is closest to the exact solution.

The NAFEMS Benchmark Challenges are presented below, as well as NAFEM's and ESRD's solutions to the benchmark problems:

 
 
CAE Handbooks As Benchmark Solutions

Users want to know: How well does your finite element analysis software predict the response of a physical system to an applied load?  A comparison is made to test data if available, or benchmark solutions (e.g. classical methods, text books).  

ESRD provides with the StressCheck software a Handbook Library of parametrically defined models for comparison to published solutions from Timenshenko, Peterson, Mura, Tada, Blevins, Roark, et al.  If there are differences, do they result from the mathematical model (in this case an approximation using the finite element method) or are they the result of errors in idealization (boundary conditions, material properties, etc.)?   

StressCheck is the only FEA software tool on the market that provides feedback to the user regarding the quality of the computed information.  This 'verification' process assesses the sensitivity of the computed data to changes in the mesh density, order of the element shape functions, and element mapping.  Verification is an important first step in validating the model.

  • Verification - Am I solving the equations right?
  • Validation - Am I solving the right equations?
It is clear that validation can only be achieved if verification of the data of interest has been completed.  For more information on CAE Handbook terminology, click here.

General guidelines pertaining to the use of mathematical models in solid mechanics were issued by the American Society of Mechanical Engineers (ASME) in 2006 and adopted by the American National Standards Institute. This document describes the importance of verification and validation.   


The Girkmann Challenge
 

In many cases, benchmark challenges are defined as problems involving significant resources to solve accurately using numerical methods.  We invite those who are users of FEA tools to solve one such problem, the classical Girkmann Problem:

  1. Stress resultants Qa (shearing force, kN/m) and Ma (bending moment, Nm/m)
  2. The location and magnitude of the maximum bending moment in the shell.
  3. Verify the results are accurate to within 5 percent.  Describe how accuracy was verified.
  4. Software used, what mesh and type of elements were used.

ESRD received responses to this exercise from 15 FEA experts using a range of different modeling techniques and FEA software tools.   

Click here to view a summary of the study results, and here to download a PDF of the proper approach to the solution of the problem.
 

 

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