LS-Dyna at CAE Associates
Overview Experience with LS-Dyna for Dynamics Modeling CAE Associates engineers have nearly 30 years of experience using explicit dynamics finite element codes for complex design and analysis applications. Their experience with these codes began in 1975 at Pratt and Whitney Aircraft when the WHAM code was first used to model jet engine foreign object damage and containment. At that time, WHAM only supported shell elements and did not have any contact capabilities. Dr. Kenneth Brown, currently working with CAE Associates, developed and implemented contact capabilities for WHAM, as well as adding a membrane element for analysis of Kevlar containment designs. In the early 1990 s DYNA3D superseded WHAM as the impact software of choice for these applications, due to its more complete library of elements and contact capabilities. Dr. Brown was one of several developers nationwide to use the public domain, Lawrence-Livermore version of DYNA. He continued to provide code improvements, including development of a PC version of DYNA and a fabric constitutive model for Kevlar containment applications. This model was included in the Livermore version of Dyna (LS-Dyna) as Material Type 41 (Fabric with Damage). He also calculated numerous material coefficients from test data using regression fitting techniques for a variety of applications, including: Bammann model coefficients for Titanium containment applications, including strain rate and thermal softening effects. Johnson-Cook models for ballistic impact applications. Mooney-Rivlin models for soft-body ballistic impact simulations. Mooney-Rivlin and Ogden models for sporting goods applications. 2
Overview CAE Associates has considerable experience in preprocessing models in ANSYS for use with LS-Dyna. Particular areas of expertise include brickonly meshing techniques,mesh distribution methods considering accuracy versus time step size, contact algorithm selection and definition, element type selection, load curve application,and hourglass control methods. Other strengths include the ability to identify and correct several common problems associated with high speed impact analysis in LS-Dyna, including the following: Over-penetration of one body into another Excessive run times High hourglass energies Initial contact penetration Solution instabilities often associated with out-of-range velocities errors CAE Associates has also provided consulting and training in explicit dynamics finite element methods for many years. 3
Overview Training in LS-Dyna, Finite Element Analysis, Dynamics, and other Mechanical Engineering Topics CAE Associates provides training classes in the following areas: ANSYS/LS-Dyna for Explicit Dynamics Analysis ANSYS Dynamics Modal, Harmonic, Transient, and Random Vibration Methods Finite Element Best Practices Introduction to ANSYS Advanced ANSYS Nonlinear Analysis, Contact, and Bolt Pretension ANSYS Parametric Design Language (APDL) ANSYS Heat Transfer CAE Associates engineers have received training i from the developers of LS-Dyna (Livermore Software Technology Corporation) in the application of ALE (Arbitrary Lagrangian Eulerian), SPH (Smooth Particle Hydrodynamics), and manufacturing simulation methods. CAEA engineers have also received training in the use of LS-Dyna for general transient modeling applications, including impact analyses. All CAE Associates engineers have M.S. and/or Ph.D. degrees in Mechanical Engineering. They have received training in general materials science, dynamics, and finite element analysis through a range of undergraduate and graduate level courses, including the following: Materials Science Fatigue and Fracture of Materials Advanced Mechanics of Materials Advanced Dynamics Finite Element Methods Solid Mechanics and Elasticity Plasticity Advanced Fluid Mechanics 4
Overview Partial List of Consulting Projects Utilizing LS-Dyna Developed numerous projectile impact models for the U.S. Army using lagrangian, multimaterial ALE, and SPH modeling methods. Numerous material models were investigated for the projectiles, soft targets, and hard targets. Performed LS-Dyna analyses of a helicopter clutch assembly to predict the potential for slipping during torque application. Provided drop test simulations of a nuclear spent fuel cask using ANSYS/LS-Dyna to predict the potential for loss of containment at several different drop orientations and heights. Results were compared to experimental data to validate the model, and they were reviewed and approved by the NRC. Developed LS-Dyna models for Pratt & Whitney Aircraft to simulate fan blade loss,containment, and bird ingestion. These included pre-stress, complex contact definitions, iti and high h strain rate material models. These models were used to predict failure in existing and proposed containment case, blade, and disk designs. Provided sporting goods design analyses of golf balls, basketballs, soccer balls, golf clubs, and softball bats. These allowed for predictions of dynamic behavior of existing and proposed designs to reduce prototype testing. Predicted knuckle pullout strength of concrete decking in support of NIST s World Trade Center investigation. Developed LS-Dyna models of battery deep drawing processes, arterial stent insertion, drop-testing of surgical devices, accident simulations. 5
Sphere impacts into gelatin Lagrange and multi-material ALE gelatin block models Many different gelatin material models were investigated: Mooney-Rivlin Strain-rate dependent plasticity Fluid Simplified rubber (Ogden hyperelastic) Piecewise linear plasticity 6
Bullet impact into a gelatin block Lagrange gelatin block and bullet Eroding gelatin elements Bullet spin and precession included 7
High speed impact of a copper block into a gelatin block A Multi-material Arbitrary Lagrange-Eulerian (ALE) method was used for the copper block. This allows the copper to flow at impact. A Johnson-Cook material model was used for the copper. 8
Lead projectile impact into gelatin A Multi-material ALE method was used for the projectile. A Johnson-Cook material model was used for the lead 9
SPH cylinder impact models High velocity impact of a copper cylinder onto a lagrange steel plate. A Johnson-Cook material model was used for the copper. The cylinder was modeled with SPH particles (smooth particle hydrodynamics) to evaluate the ability of this method for predicting fragmentation. 10
Bullet travel through a rifle barrel with rifling grooves CAE Associates developed a LS-Dyna model to simulate the dynamics of a bullet traveling through a barrel. Meshing methods were developed to generate rifling grooves in the barrel. Pressure curves were applied to the base of the bullet and to the interior of the barrel. The copper jacket of the bullet was modeled with a plasticity material law to allow for the formation of grooves as it enters the barrel. 11
Differentiation of time-history t results to obtain bullet velocities 12
Copper rod impacts (Taylor bar impact tests) Johnson-Cook and Bamman material models were investigated. This model was used to calibrate the material laws and showed the correct gross deformation and failure behavior. 13
Elevator frame Buffer strike with plasticity 14
Inflatable packaging inflation using airbag elements 15
Arterial vessel expansion using airbag elements and a plaque failure model 16
Nitinol stent insertion into a flexible artery A shape memory material model was used for the Nitinol 17
Impact models of hyperelastic golf balls Looking at backspin and sidespin for a toe hit Multilayer molded golf ball models were generated using Mooney-Rivlin and Ogden hyperelastic material laws. LS-Dyna models of golf balls and clubs were developed to predict their dynamic behavior with the goal of reducing prototype testing. 18
Nuclear spent fuel cask drop analysis Spent fuel shipping and storage casks must go through a detailed analytical evaluation to gain certification. CAE Associates has performed drop test analyses of nuclear spent fuel casks using ANSYS/LS-DYNA explicit dynamics software. The analyses include a simulation of the slapdown effect with material models that include crushing of the concrete pad. Experimental data was used to validate the finite element models. The analyses performed by CAE Associates for their client were reviewed by the NRC and approved without any follow-up required. 19
Nuclear spent fuel cask drop analysis Cask Model for End Drop Soil Concrete Pad 20
Nuclear spent fuel cask drop analysis End cask drop: Displacements after impact 21
Nuclear spent fuel cask drop analysis Side impact with slapdown 22
Nuclear spent fuel cask drop analysis Stress results after impact: Simplified model of internals 23
Spring clutch analysis Quasi-static analysis using critical damping to minimize dynamic effects Alpha damping applied to minimize local oscillations in the flexible spring (some Beta damping also added) Mass scaling used to speed up the run time Torque applied as pressures to the spline faces Cylinder pushed over the spring with a ½ sine wave velocity curve 24
Battery deep drawing analysis Quasi-static analysis Plasticity material model with considerable strain 25
Simulation of knuckle pull-out in concrete blocks Quasi-static analyses Material models included cracking and crushing in the concrete, and plasticity in the steel 26
Blast load on a concrete wall Modeled walls both with and without rebar. An air blast load was applied based on an equivalent weight of TNT. A concrete material model with an unconfined compression strength was used. 27