Isogeometric Analysis in LS-DYNA - Semantic Scholar

Isogeometric Analysis

in LS-DYNA

Liping Li, Attila P. Nagy, Dave J. Benson | Livermore Software Technology

Corporation

Stefan Hartmann | DYNAmore GmbH

Outline

Isogeometric Analysis – motivation

The importance of geometry

Analysis enhancements

Selected applications

Future developments and challenges

Isogeometric Analysis – motivation

The importance of geometry

Analysis enhancements

Selected applications

Future developments and challenges

2

Isogeometric Analysis – motivation

Reduce effort of geometry conversion from CAD into a suitable

mesh for FEA

Isogeometric

same description of the geometry in the design (CAD) and the analysis

CAD Geometry Design

FE Mesh

Analysis Optimization

CAD Geometry Design

NURBS

Analysis Optimization

3

Outline

Isogeometric Analysis – motivation

The importance of geometry

Analysis enhancements

Selected applications

Future developments and challanges

4

NURBS Shell

5

Shell formulations

Reissner-Mindlin - with and without rotational DOF

Kirchhoff-Love

Blended - selective addition of rotational DOFs

Consistent or lumped mass matrix

Integration schemes

Standard or uniformly reduced Gaussian quadrature

Patch-wise reduced Gaussian quadrature (quadratic NURBS only)

Designed quadrature rules (trimmed elements only)

Uniformly sized interpolation elements

Improved keyword format for trimmed shells

Trimming loops are represented by NURBS curves

Topology preserving - backward compatibility with CAD

Trimming is a generic capability - user defined Splines

*DEFINE_NURBS_CURVE

*ELEMENT_SHELL_NURBS_PATCH_TRIMMED_TITLE

NURBS Shell

6

Shell formulations

Reissner-Mindlin - with and without rotational DOF

Kirchhoff-Love

Blended - selective addition of rotational DOFs

Consistent or lumped mass matrix

Integration schemes

Standard or uniformly reduced Gaussian quadrature

Patch-wise reduced Gaussian quadrature (quadratic NURBS only)

Designed quadrature rules (trimmed elements only)

Uniformly sized interpolation elements

Improved keyword format for trimmed shells

Trimming loops are represented by NURBS curves

Topology preserving - backward compatibility with CAD

Trimming is a generic capability - user defined Splines

*DEFINE_NURBS_CURVE

*ELEMENT_SHELL_NURBS_PATCH_TRIMMED_TITLE

Trimmed NURBS Shell *ELEMENT_SHELL_NURBS_PATCH_TRIMMED

$# npeid pid npr pr nps ps 1 1 665 3 319 3

$# wfl form int nisr niss imass

0 0 0 -2. -2. 0 $# r1 r2 r3 r4 r5 r6 r7 r8

… trimming loop 1

$# c1 c2 c3 c4 c5 c6 c7 c8

1 2 3 4 ...

*DEFINE_NURBS_CURVE $# id n p peri type wfl

1 78 3 0 1 1

$# t1 t2 t3 t4 t5 t6 t7 t8 0.000000 0.000000 0.000000 0.000000 0.031701 0.039515 0.040491 ...

$# r s - w 0.000000 0.000000 0.875000

CAD

0

-2.

7 *ELEMENT_SOLID_NURBS_PATCH (no trimming capability)

Standard trivariate tensor product formulation

Lack of mesh generators is a limitation

Standard Gaussian quadrature

Interpolation elements

Contact, boundary conditions, and post-processing

NURBS Solid

8

Analysis suitable geometry (ASG) is unlikely to be prepared by the designer

Lack of support in the de facto industry standard CAD softwares

Plenty of work on the CAGD CAE interface

LSPrepost: import IGES file to create ASG.

CAD to ASG

9

Cross-field optimized or approximated trimmed NURBS Elysium Co., Ltd. . Honda Motor Co., Ltd.

~600 patches approximated by a single trimmed NURBS patch

LS-DYNA keyword output

CAD to ASG

10

T-splines, U-splines

Coreform LLC . Ford Motor Co., Inc.

*INCLUDE_TRANSFORM

Bézier Extraction Format - Shell

11

Truncated hierarchical T-splines

Carnegie Mellon University . Honda Motor Co., Ltd.

*INCLUDE_TRANSFORM

Bézier Extraction Format - Solid

12

Watertight CAD models B Urik, UT Austin LS-DYNA modal analysis

Novel CAD Solutions

Outline

Isogeometric Analysis – motivation

The importance of geometry

Analysis enhancements

Selected applications

Future developments and challanges

13

14 *CONSTRAINED_NODE_TO_NURBS_PATCH_SET

*LOAD_NURBS_SHELL_ID

Quadratic NURBS under vertical point load

Boundary conditions

Prescribed motions, e.g. spot welds - penalty formulation

Point, distributed, and pressure loads

Display of section forces

Shells and solids

Improved stable time step estimates

Trimmed and untrimmed elements

Consistency and performance

SMP, MPP, and hybrid

Recent Features and Improvements

15

*MAT_022 or *MAT_COMPOSITE_DAMAGE

*MAT_033 or *MAT_BARLAT_ANISOTROPIC_PLASTICITY

*MAT_USED_DEFINED_MATERIALS etc.

Directional dependent material models Anisotropic elasticity

Anisotropic plasticity

User defined materials

List of available materials is steadily increasing

Constitutive Models

Outline

Isogeometric Analysis – motivation

The importance of geometry

Analysis enhancements

Selected applications

Future developments and challanges

16

17

Aerospace

Jet engines and blades

Foreign object impact

Automotive

Crashworthiness

Metal stamping and other manufacturing processes

Noise, vibration, and harshness (NVH)

Fluid-structure interaction (FSI)

Biomedical

Cardiovascular modeling

Industrial Focus

18

IGA and combined FEA with IGA Ford Motor Co., Inc.

Front rigid barrier sled test

35 mph against 450 kg rigid fixture

Steel crash can

trimmed NURBS

Y Chen et al., LS-DYNA UC, 2016

regular mesh

Crashworthiness

19

Rigid upper die Blank

Rigid binder Rigid lower punch

Draw-bead radius: ~4mm

NUMISHEET 2005 benchmark in 2017

Average element size: ~4 mm (draw-bead driven)

Patch-wise reduced integration rule (biquadratic patch)

Al5182-0 - piecewise linear plasticity (*MAT_024)

Uniform initial blank thickness: 1.6 mm

Thickness update during analysis

No adaptive refinement

MPP

FEA baseline model Fully integrated shell with assumed strain formulation

Average element size ~2 mm

Metal Stamping

20

FEA 3h 41m

IGA 2h 12m

Comparison of Results

21

NURBS Shell Model

Full Guass integration rule

Piecewise linear plasticity (*MAT_024)

FEA baseline model Fully integrated shell with assumed strain formulation

Frequency Domain: SSD

22

IGA:1444 47s

Comparison of Results

FEA:1444 6s

FEA:5776 23s

FEA:12996 54s

23

IGA:1444 47s

Comparison of Results

FEA:1444 6s

FEA:5776 23s

FEA:12996 54s

FEA

IGA

24

Chevrolet Camaro

with Facundo del Pin

Fluid-Structure Interaction

Outline

Isogeometric Analysis – motivation

The importance of geometry

Analysis enhancements

Selected applications

Future developments and challenges

25

26

Pre-processing

Analysis suitable geometry (ASG) is unlikely to be prepared by the draftsmen/designer

Generating (an editable) ASG is essential and necessary - meshing is analysis dependent

Accommodate ASG in the new STEP standard

Analysis

Rethink and enable existing FEA capabilities for IGA - 9M+ lines of code in LS-DYNA

Coupling of patches/parts (shell to shell and shell to solid)

Adaptive mesh refinement

Further enhance support for geometric input

Increase efficiency - SMP, MPP, and hybrid

Continue coupling with different formulations, e.g. FEA (mostly done), acoustics, EM, ICFD,

meshless, etc.

Post-processing

Enhance field rendering capabilities in LS-PrePost

Future Challenges

Thank you!