ANSYS/LS-Dyna M lti M t i l ALEMulti-Material ALE

Modeling

Prepared bySteven Hale M S M ESteven Hale, M.S.M.E.

Senior Engineering Manager

Multi-Material ALE Basics

What is the Multi-Material ALE method (MMALE)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• 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

d h h d h d ddistort which minimizes advection. This minimizes energy dissipation and speeds up run time.

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Multi-Material ALE Basics

MMALE requires a domain mesh with some elements that containMMALE 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.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

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Support for MMALE in ANSYS

Th ANSYS d t t i t f th MMALE th dThe ANSYS pre-processor does not support inputs for the MMALE methodThe following model features can be assigned in ANSYS:

— GeometryMesh— Mesh

— Material properties— Hourglass controls— Boundary constraintsy— 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

i t lexpansion control— MMALE group definitions – used to define discrete MMALE parts

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MMALE Input

Element formulationElement formulation — *SECTION_SOLID— SECID, ELFORM

• ELFORM = 5 (single-material ALE)• ELFORM = 5 (single-material ALE)• ELFORM = 6 (pure Eulerian)• ELFORM = 11 (multi-material ALE) *

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MMALE Input

*CONTROL ALE: MMALE control settingsCONTROL_ALE: MMALE control settings— DCT,NADV,METH,AFAC,BFAC,CFAC,DFAC,EFAC

• DCT (ignored)• NADV: Number of time steps between mesh smoothing and advection cyclesNADV: 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)

M th 2 (2nd d d ti l i i i l )— 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( q p g) y— EFAC = 1 (equilibrium smoothing)

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MMALE Input

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MMALE Input

*ALE MULTI-MATERIAL GROUPALE_MULTI-MATERIAL_GROUP— Defines MMALE groups— Part/Set ID list

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MMALE Input

*ALE REFERENCE SYSTEM GROUPALE_REFERENCE_SYSTEM_GROUP— Defines the motion of the ALE mesh

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MMALE Input

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MMALE Input

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MMALE Input

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MMALE Input

*CONSTRAINED LAGRANGE IN SOLIDCONSTRAINED_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)g gy)

CTYPE = 4 (penalty coupling without erosion)

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

DIREC = 1 (glued together in tension and compression)

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DIREC = 2 (compression only)

MMALE Input

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MMALE Input

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MMALE Input

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MMALE Input

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Example: Lagrange Sphere – MMALE Block

MMALE Input— Defines contact between MMALE groups and Lagrangian elements

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

*ALE_MULTI-MATERIAL_GROUP2, 13, 1$$ ALE mesh motion/expansion control$ 7 = no rotations*ALE_REFERENCE_SYSTEM_GROUP4,0,4,0,5,3,7,0 0 00,0,0,,$$ Define coupling between Part 1 (ALE) and Part 3 (Lagrangian)$ Use 2 x 2 quadrature*CONSTRAINED_LAGRANGE_IN_SOLID1,4,1,0,-2,4,2,11,4,1,0, 2,4,2,1, ,

$*SET_PART_LIST4,

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2,3,