ls-dyna at cae associatescae associates · pdf fileoverview zexperience with ls-dyna for...

LS-Dyna yat

CAE AssociatesCAE Associates

Overview

Experience with LS-Dyna for Dynamics Modelingh l f l d— 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 h i l d h ll l d did hthat 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— In the early 1990’s DYNA3D superseded WHAM as the impact software of choice for these applications, due to its more complete library of elements and contact capabilities.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

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• Mooney-Rivlin models for soft-body ballistic impact simulations.• Mooney-Rivlin and Ogden models for sporting goods applications.

Overview

CAE Associates has considerable experience in preprocessing models inCAE Associates has considerable experience in preprocessing models in ANSYS for use with LS-Dyna. Particular areas of expertise include brick-only meshing techniques,mesh distribution methods considering accuracy versus time step size, contact algorithm selection andaccuracy 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 y gspeed 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.

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OverviewTraining in LS-Dyna, Finite Element Analysis, Dynamics, and other Mechanical Engineering TopicsMechanical 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 A i t i h i d t i i f th d l f LS D (Li— CAE Associates engineers have received training 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.g p y

— 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

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• Solid Mechanics and Elasticity• Plasticity• Advanced Fluid Mechanics

Overview

Partial List of Consulting Projects Utilizing LS-DynaD l d j til i t d l f th U S A i l i— 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 y y p y p pfor 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 modeland 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 d fi iti d hi h t i t t i l d l Th d l d tdefinitions, and high 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 p yexisting and proposed designs to reduce prototype testing.

— Predicted knuckle pullout strength of concrete decking in support of NIST’s World Trade Center investigation.

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— Developed LS-Dyna models of battery deep drawing processes, arterial stent insertion, drop-testing of surgical devices, accident simulations.

LS-Dyna Analyses at CAE Associates

Sphere impacts into gelatinSphere impacts into gelatin— Lagrange and multi-material ALE gelatin block models— Many different gelatin material models were investigated:

• Mooney-Rivlin• Mooney-Rivlin• Strain-rate dependent plasticity• Fluid• Simplified rubber (Ogden hyperelastic)p g yp• Piecewise linear plasticity

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Bullet impact into a gelatin blockBullet impact into a gelatin block— Lagrange gelatin block and bullet— Eroding gelatin elements

Bullet spin and precession included— Bullet spin and precession included

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High speed impact of a copper block into a gelatin blockHigh 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 copperA Johnson Cook material model was used for the copper.

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Lead projectile impact into gelatinLead projectile impact into gelatin— A Multi-material ALE method was used for the projectile. — A Johnson-Cook material model was used for the lead

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SPH cylinder impact modelsSPH 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— The cylinder was modeled with SPH particles (smooth particle hydrodynamics) to evaluate the ability of this method for predicting fragmentation.

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Bullet travel through a rifle barrel with rifling groovesBullet 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 g g g ppbase 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.

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Diff ti ti f ti hi t lt t bt i b ll t l itiDifferentiation of time-history results to obtain bullet velocities

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Copper rod impacts (Taylor bar impact tests)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 behaviorgross deformation and failure behavior.

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Elevator frame – Buffer strike with plasticityElevator frame – Buffer strike with plasticity

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Inflatable packaging inflation using airbag elementsInflatable packaging inflation using airbag elements

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Arterial vessel expansion using airbag elements and a plaque failureArterial vessel expansion using airbag elements and a plaque failure model

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Nitinol stent insertion into a flexible arteryNitinol stent insertion into a flexible artery— A shape memory material model was used for the Nitinol

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Impact models of hyperelastic golf ballsImpact 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 andand 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.

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Nuclear spent fuel cask drop analysisNuclear 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 fuelCAE 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.

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Nuclear spent fuel cask drop analysisNuclear spent fuel cask drop analysis

Cask Model for End Drop

Soil

Concrete Pad

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Nuclear spent fuel cask drop analysisNuclear spent fuel cask drop analysis — End cask drop: Displacements after impact

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Nuclear spent fuel cask drop analysisNuclear spent fuel cask drop analysis — Side impact with slapdown

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Nuclear spent fuel cask drop analysisNuclear spent fuel cask drop analysis — Stress results after impact: Simplified model of internals

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Spring clutch analysisSpring 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)( p g )

• 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

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Battery deep drawing analysisBattery deep drawing analysis— Quasi-static analysis— Plasticity material model with considerable strain

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Simulation of knuckle pull-out in concrete blocksSimulation of knuckle pull-out in concrete blocks— Quasi-static analyses— Material models included cracking and crushing in the concrete, and

plasticity in the steelplasticity in the steel

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Blast load on a concrete wallBlast 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— A concrete material model with an unconfined compression strength was used.

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ls-dyna at cae associatescae associates · pdf fileoverview zexperience with ls-dyna for...

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