Download - Single model Multi Attribute Analysis and Optimization · 2018-10-18 · Automated Multi-level Sub-structuring Approximate eigen value solvers can be used instead of Lanczos to reduce

Single model Multi Attribute Analysis and Optimization

Amar Ourchane, Ford Motor Company

Abhilash Patel, Altair

27 September 2018 1

Goal

“Establish a single model to assess Stiffness, Strength and Fatigue on an

automotive rear subframe model for both parent metal and weldments.”

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Benefits of single model approach

1. Drives the use of common model practice for modeling efficiencies and

elimination of modeling inconsistencies due to multiple model build and

analysis processes for Stiffness, Strength and Fatigue load cases (i.e. model

counts, non-uniform material definitions, ID management, etc)

2. Offers a better way to efficiently perform and assess design iterations and

improvements, and enables possibilities for Design Exploration with direct

optimization ready format

3. Common model for Strength and Fatigue assessment, enables simpler

automation and ensures efficient attributes tracking across CAE groups for

quicker design progression 3

Traditional process :

Optimization

Cost

Efficient

NVH & Global Stiffness –

Nastran AMLS

OptiStruct AMLS/AMSES

Strength – Abaqus

Fatigue Durability : Parent and welds– internal Solver

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objective

Optimization Ready

Single CAE model

NVH & Global Stiffness

Strength

Fatigue Durability

Altair OptiStruct™

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Process flexibility

Stiffness

❑Solver A/B

✓ OptiStruct

Strength✓ OptiStruct

Fatigue✓ OptiStruct

Pre Processing

▪ Fatigue set up

Solver

▪ DAC,RPC,RSP file channel handling

within solver

Post Processing:

▪ Dynamic Stiffness population

Optimization Set up:

▪ Design Variable and linking

▪ Response and Constraint set up

Automation for Single Model and Optimization

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Process flexibility

Concept and Fine tuning Optimization

Optimization Ready

Stiffness

❑Solver A/B model

✓ OptiStruct model

Strength


Fatigue


+

+

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Loadcase Review

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SCOPE

Durability Model (Abaqus)

Sources of Nonlinearity:

• Nonlinear Material

• Permanent Set due to Load/Unload

Response:

• Displacement & Plastic Strain (O/P)

Fatigue Subcases (Internal Solvers)

• Parent metal Fatigue

• Seam weld Fatigue

NVH Model (Nastran)

• Modal Frequency Response

Response:

• Dynamic Stiffness (42 subcases) 9

Stiffness

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NVH loadcase

▪ Dynamic stiffness results at 2 Hz (Nastran run with CQUAD4 vs modern

CQUAD4 in OS)

▪ Less than 2 % variation

Showing only above 1% variation 11

Automated Multi-level Sub-structuring

▪Approximate eigen value solvers can be used instead of Lanczos to reduce the

cost of frequency response and eigenvalue analysis for large finite element

models

▪AMSES is a multi-threaded application and can use any number of processors.

▪FASTFRS and FASTFR are available within OptiStruct

▪ AMSES, Automated Multi-level Sub-structuring Eigen Value Solver is built into

OptiStruct and it kicks in automatically when EIGRA is used instead of EIGRL.

▪

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Strength

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Strength loadcase – Permanent Set

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PLASTIC STRAINS

▪ Loading / Un-loading : Permanent Set problem solved in Abaqus was

converted to OptiStruct

• ABAQUSOPTISTRUCT Plastic Strain Results

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Strength loadcase

▪ Loading / Un-loading : Permanent Set problem solved in Solver A was


LoadingABAQUSOPTISTRUCT Displacement Results

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Durability loadcase

▪ Loading / Un-loading : Permanent Set problem solved in Solver A was


UnloadingDisplacement Results

ABAQUSOPTISTRUCT

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Conversion process

▪ OptiStruct converters within HyperMesh used

▪ 99% conversion rate of existing load cases

▪ OptiStruct check runs and elaborate error/warning messages help

identify and fix any formatting concerns

▪ No need for null skin mesh. OptiStruct has direct output requests for membrane of solid

▪ Modify negative or zero slope terms on material stress strain curve

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Other strength simulations requirements

Nonlinear MaterialNonlinear Contact Small and Large Displacement Analysis

Large Scale Computing & Parallelization

20 40 80 160 320

Cores

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Fatigue

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Fatigue loadcase

▪ Direct support of RSP/DAC files in OptiStruct enable ease in set up

▪ Solver pick up channels directly from rsp files

▪ Both parent metal and seam weld fatigue run in a single model set up

▪ Parent metal : Strain-Life (E-N) Approach

▪ SWT Model

▪ Seam weld : (not addressed in this study)

▪ VOLVO method 21

InternalSolver_____OptiStruct Fatigue

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Simulation Run times

Single Attribute model run times Single

model

Multi

AttributeDurability NVH

Parent

metal

Seam Weld

Fatigue

SMP 4 cpus

(available @ Ford)00:13:14 00:03:50 00:28:38 00:34:00 01:43:11

DDM 48 cpus

(available @ Ford)00:05:41 00:01:00 00:03:36 00:05:00 00:11:00

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Permanent Set @ LH Hardpoints

▪ Analysis can be done using small and large displacement theory

▪ Optimization process assumes only small displacement theory for now

▪ Results between both large and small are comparable

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Neuber corrected stress / strain responses

www.efatigue.com

Neuber correction responses are

used in both linear and nonlinear

static (small displacement)

optimization subcases

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GAUGE optimization

Gauge Design Variables for parent metal and weldments

Design variable links with weldment thickness as a function of parent metal gauge

Life / Damage as a response

5 Hard points Permanent set – 2 mm

Neuber Corrected Stress/Strain response – 2%

42 Dynamic Stiffness constraints 5 % degradation

Minimize Mass

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Iteration History

• Design freedom provided – 0.65 to 4.5 mm

• Initial starting point : 4.5 mm – Very liberal

Objective:Mass

Dynamic Stiffness

(KN/mm)

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Other possible Optimization opportunities

1. Topology(Blow holes) and Topography(Add beads) on parent metal to

improve stiffness.

2. 2D Topology on seam weld PSHELLS – Objective / Constraints = Mass /

weld Life.

3. Freeshape parent metal – Objective / Constraints = Mass /Life/ Neuber

Stress/ disp

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