Please send email to schwerdubois@yahoo.com to request Registration Form_2012 or for more information.
Class Title
Modeling & Simulation With LS-DYNA: Insights Into Modeling With a Goal of Providing Credible Predictive Simulations
Essentially, all models are wrong, but some are useful. - Professor George Box, May 1979
Abstract
Most applications of LS-DYNA are for complex, and often combined, physics where nonlinearities due to large deformations and material response, including failure, are the norm. Often the goal of such simulations are to provide predictions which will ultimately be used to guide product development and safety assessments. In very few cases, some limited experimental data is available to help guide the model development, and assess the accuracy of the results. When no experimental data are available, or the LS-DYNA predictions are intended to guide development of limited experiments, in addition to the predicted result, the analyst needs to provide, and convey to the customer, the degree of confidence in the results.
This two day class focuses on two critical aspects in the application of LS-DYNA: modeling and simulation. Here modeling is taken to mean the large number of decisions the analyst makes in constructing an LS-DYNA input file, which is intended to mimic the response of some physical event. Simulation refers to the results produced by LS-DYNA to an analyst’s input. The emphasis for simulation is how to assess the credibility, i.e. correctness and accuracy, of predictive simulation results. Hopefully, long gone are the days when the quip “It came from the computer, so it must be right.” may have been taken as a serious statement.
Insights into modeling and simulation are illustrated through examples. An emphasis is placed on modeling techniques, guidelines for which technique(s) to select, which techniques work well and when, and possible pitfalls in modeling choice selections. Simulation credibility is demonstrated through solution of multiple models, with associated multiple solvers, required checks of global and local energies, and mesh refinement strategies. In addition, strategies for recovering from unexpected termination error conditions are discussed.
Audience
This training class is intended for the LS-DYNA analyst possessing a comfortable command of the LS-DYNA keywords and options associated with typical Lagrangian analyses. The training class will attempt to provide the analyst with the additional tools and knowledge required to model the above described class of high energy events. The typical attendee is likely to have a background in defense applications, to include protective structures and vehicle vulnerability, Homeland Defense topics, and terrorist threat mitigation techniques. Because the class uses example problems to illustrate concepts and techniques, numerous modeling ‘tricks’ and options are discussed, and this knowledge would benefit any LS-DYNA user.
Instructors
The motivation to create this Modeling & Simulation class came from the numerous attendee interactions during the instructors’ popular Blast and Penetration classes. Some of the most interesting discussions were not about the details needed to create an LS-DYNA input file, but why certain selections and options were chosen. Both instructors always place a strong emphasis on assessing the credibility of results: from simple hand calculations to confirm ‘ballpark’ values, to more rigorous estimates of discretization error.
Over 55 years of LS-DYNA experience in a wide range of commercial and defense applications allows the instructors to provide insights into many aspects of modeling and simulation. In addition, their presentation style has often been complemented for being clear, concise, useful, interesting, and at times hopefully also entertaining.
Paul Du Bois - Consultant
Paul Du Bois has worked as an independent consultant in the field of industrial application of large scale numerical simulations since September 1987. He has specialized in the application of explicit integration techniques for crashworthiness and impact problems. Amongst Paul’s customers are most of the world’s automotive assemblers such as Daimler, GM, Ford, Opel, Fiat, Porsche, Volvo, PSA, Renault, Toyota, Nissan, Honda, Hyundai and many others including automotive suppliers and design and engineering companies. Paul’s more recent projects include a Daimler sponsored development of a generalized plasticity law for the simulation of plastics and the formulation of a tabulated hyper-elastic material law with damage for the simulation of rubber and foam. He was involved with the joint research organization of the German automotive industry, FAT, in the working groups: ‘side impact dummies’ from 1992 through 1997 and ‘Foam materials’ from 1996 until 2009. In 2003 Paul was asked by LSTC to perform a training mission at the Russian national laboratory in Snezinskh. Since 2004 he has also been a consultant to NASA and has worked on the space shuttle’s ‘return-to-flight’ program. In the field of defense applications, he is a consultant to Rafael in Haifa, Israel where he was involved with the simulation of mine blast problems and helicopter crash landings.
Paul Du Bois also teaches the LS-DYNA training class Advanced Impact Analysis & Polymeric Material Modeling, and co-teaches, with Len Schwer, the LS-DYNA Blast & Penetration classes. Paul’s Advanced Impact Analysis course notes were published as a book by LSTC in 2004 and the first revised edition will appear soon.
Len Schwer, Ph.D. - Schwer Engineering & Consulting Services
Len Schwer has worked in the area of defense applications where failure prediction is of primary interest, for the past 30 years; he had been a DYNA3D user since 1983 and an LSDYNA user since 1998. His early work at SRI International included modeling the collapse of deeply buried tunnels under very high pressure loadings. While at Lockheed Missile and Space Company he worked on high speed earth penetrators designed to penetrate reinforced concrete structures buried in soil. He is currently working with the US Navy to develop an analysis capability for predicting the penetration & perforation of metallic, concrete, and soil targets associated with improvised explosive devices (IED’s). He is currently consulting with NASA LARC on crew vehicle recover simulations. He has a strong interest in verification and validation in computational solid mechanics, and is the past Chair of the ASME Standards Committee on Verification and Validation in Computational Solid Mechanics. Dr. Schwer is a Fellow of the American Society of Mechanical; Engineers (ASME) and the United States Association of Computational Mechanics (USACM).
Len Schwer also teaches the LS-DYNA training class “Geomaterial Modeling with LS-DYNA,” and co-teaches, with Paul Du Bois, the LS-DYNA Blast & Penetration classes.
Contents
Day 1
- Opening Remarks (Len/Paul)
- Introduction to Modeling & Simulation - Verification &Validation (Len)
- Introduction to Constitutive Models – Basics of Plasticity Algorithms (Len)
- Overview of Lagrange Element Formulations- What is the ‘Right’ Element for an Analysis
- Beams – Numerical Cross Integration (Len)
- Shells & Solids – Hourglass Control (Paul)
- Time Integration – Explicit & Implicit - Choosing an Appropriate Time Integrator
Day 2
- Contact – Which Type to Use, When, and Why (Paul)
- Stress Initialization or Preloads
- Dynamic Relaxation and *STRESS_INITIALIZATION
- Causes & Curse for Common Termination Errors (Len/Paul
- “Abnormal Termination” investigation and determination of problems
- What are ‘NaN’s” and how to get rid of them
- Negative volumes: causes and remedies
- When implicit integration fails to converge
- The advantages and dangers of Mass Scaling
- Systematic Assessment of Results – “How do I know my results are correct?”
- Mesh Refinement