ansys_ls-dyna multi material

ANSYS/LS-Dyna Multi-Material ALE Modeling

Presented By: Steven Hale, M.S.M.E.Computer Aided Engineering Associates, Inc.

Computer Aided Engineering Associates, Inc. APDL - 2

Multi-Material ALE Basics

What is the Multi-Material ALE method (MMALE)— MMALE stands for Multi-Material Arbitrary Lagrangian Eulerian

— Combines Lagrangian and Eulerian methods• Lagrangian step – mesh moves with the material in the first part of the step

• Eulerian step – the mesh is smoothed out to minimize element distortion and material flows between elements. This is also known as the advection step.

• ADVANTAGE over a pure Eulerian method – Elements are allowed to move and distort which minimizes advection. This minimizes energy dissipation and speeds up run time.


Multi-Material ALE Basics

MMALE requires a domain mesh with some elements that contain solid or fluid materials.

• The outer elements of the domain mesh typically contain a vacuum or fluid material.

• Solid materials are then assigned to elements within the domain mesh.— *INITIAL_VOLUME_FRACTION can be used to assign volume fractions of different

materials in each element of the domain


Support for MMALE in ANSYS

The ANSYS pre-processor does not support inputs for the MMALE method

The following model features can be assigned in ANSYS:— Geometry— Mesh— Material properties— Hourglass controls— Boundary constraints— Initial velocities— Time and output controls— All inputs specific to lagrangian parts

The following model features must be added directly to the LS-Dyna input file:

— Contact definitions— MMALE control settings: advection control, mesh smoothing, movement, and

expansion control— MMALE group definitions – used to define discrete MMALE parts


MMALE Input

Element formulation — *SECTION_SOLID— SECID, ELFORM

• ELFORM = 5 (single-material ALE)

• ELFORM = 6 (pure Eulerian)

• ELFORM = 11 (multi-material ALE) *


MMALE Input

*CONTROL_ALE: MMALE control settings— DCT,NADV,METH,AFAC,BFAC,CFAC,DFAC,EFAC

• DCT (ignored)

• NADV: Number of time steps between mesh smoothing and advection cycles— Can speed up run time but reduce stability

• METH: Advection method— Meth = 1 (1st order advecton – fast, valid for fluids only)

— Meth = 2 (2nd order advection – slower, minimizes energy loss)

• AFAC,BFAC,CFAC,DFAC: Mesh smoothing parameters— AFAC = -1 (no smoothing), 1 (simple average smoothing)

• -1 does not allow element distortion, only expansion and contraction

• 1 simple average method – commonly used

— BFAC = 1 (volume-weighted smoothing)

— CFAC = 1 (isoparametric smoothing)

— DFAC = 1 (equipotential smoothing) - commonly used

— EFAC = 1 (equilibrium smoothing)


MMALE Input


MMALE Input

*ALE_MULTI-MATERIAL_GROUP— Defines MMALE groups

— Part/Set ID list


MMALE Input

*ALE_REFERENCE_SYSTEM_GROUP— Defines the motion of the ALE mesh


MMALE Input


MMALE Input

*CONSTRAINED_LAGRANGE_IN_SOLID— Defines contact between MMALE groups and Lagrangian elements

Slave part must be lagrangian, Master part is MMALE

CTYPE = 2 (constrained acel and vel (default). Cannot be used with rigid bodies. Does not conserve energy)

CTYPE = 4 (penalty coupling without erosion)

CTYPE = 5 (penalty coupling wih erosion in Lagrangian part)

DIREC = 1 (glued together in tension and compression)

DIREC = 2 (compression only)


MMALE Input


Example: Lagrange Sphere – MMALE Block

MMALE Input— Defines contact between MMALE groups and Lagrangian elements

$$ 2nd order advection, No smoothing*CONTROL_ALE,1,2,-1.,

*ALE_MULTI-MATERIAL_GROUP2, 13, 1$$ ALE mesh motion/expansion control$ 7 = no rotations*ALE_REFERENCE_SYSTEM_GROUP4,0,4,0,5,3,7,0,0,0,,$$ Define coupling between Part 1 (ALE) and Part 3 (Lagrangian)$ Use 2 x 2 quadrature*CONSTRAINED_LAGRANGE_IN_SOLID1,4,1,0,-2,4,2,1, ,

$*SET_PART_LIST4,2,3,

ansys_ls-dyna multi material

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