Application of OptiStruct to Solution of Powertrain Problems

Innovation Intelligence®

Application of OptiStruct to Solution

of Powertrain Problems

Woytek Tworzydlo

AETC - April 24, 2013

Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.

Altair OptiStruct

• A comprehensive high-performance FE-solver and optimizer

• Solution sequences:

• Statics (small deformations)

• Non-linear contact

• Non-linear materials

• Heat Transfer

• Comprehensive NVH Solution

• Normal modes

• Frequency response

• Transient Analysis

• Acoustic Analysis

• Easy to use

• robust element formulations

• thorough model check, informative messages

• Seamlessly integrated with optimization


OptiStruct for Powertrain Applications

New advanced analysis and optimization capabilities have been added in

version 12.0 addressing specific needs of Powertrain modeling:

Gaskets

Fine details

Contact

Large models

Heat transfer

Vibrations

Second order

elements

Global - local

Bolt

tensioning

Moving parts

Thermal loads

Nonlinear

Pre-tensioning

Gaskets


Powertrain Modeling Requirements

Contact • Hertz contact conditions with friction

• Contact friendly 2nd order solid & 3D gasket elements

• Thermal contact – conductivity ƒ(gap, pressure)

• Coupled thermal and static analysis

3-dof Gaskets • Nonlinear behavior in thickness direction

• Optional 3D stiffness

• Pressure, Leakage status

Pretensioned bolts (1D & 3D)

Non-linear materials w/ plasticity • Isotropic, kinematic and mixed hardening

• Metals, gray cast iron


OptiStruct 12.0 – Pretensioned Bolts

• Pretensioning of bolted assemblies

• “Cut and Load” approach

• 1D bolts

• Surface cut on a 3D bold model

• Logical and general flow

• pretension Force

• pretension Adjustment

• arbitrary combinations and sequencing

• Available for use with

• Static analysis (linear and nonlinear)

• Preloaded normal modes

• Preloaded frequency response

• Optimization…

Surface

Pretension and Ignition


OptiStruct 12.0 – Gasket Elements

• Single material to model behavior

of complex gasket profiles

• FE Modeling

• Unique behavior in normal direction

• Highly nonlinear

• Large “strain” (closure)

• Based on experimental curves

• First and second-order elements

• CGASK6, … 8, 12, 16

• Contact-friendly version available

Complex structure

in real life

One ‘material’

in FE world


Gasket Elements – cont’d

• Result types

• closure, stress, pressure, sealing status

• Robust behavior

• normal compression only, or full 3D stiffness

• works over cutouts, etc.

Displacements (to scale) Gasket pressure


OptiStruct 12.0 Plasticity Enhancements

• Von Mises plasticity. Isotropic, kinematic and mixed hardening.

• solids and shells

• good nonlinear convergence

• easy to use – automatically switch the element formulation for elasto-plastic

regions

Plastic

Strain

Residual Stress after unloading


OptiStruct 12.0 CONTACT/Friction Improvements

• Improved convergence with Friction

• nonsymmetric solver

• new friction model

• stabilized Expert System – prevents

fly-away of disconnected parts

• Improved contact on imperfect meshes

• CLEARANCE

• ADJUST – (12.220)

• smoother solution

P

F

CLEARANCE


STANDARD IMPROVED

OptiStruct 12.0 – Contact-Friendly Elements

• Contact-friendly second-order elements (solids, gaskets – all types)

• more realistic contact forces

• elasticity and elasto-plasticity

• Benefits

• better nonlinear convergence

• improved CONTACT pressure

• improved open/closed status


Thermal (Heat Transfer) in OptiStruct 12.0

• Available thermal solutions (12.0 - linear)

• Conduction, surface convection & heat

generation

• Coupled thermal / structural analysis

• Transient thermal, coupled transient thermal /

structural

• Surface heating from fluid - Acusolve

• Heat transfer across CONTACTs

• gap-dependent conductivity

• pressure-dependent (in 12.210)

• Optimization for coupled thermal /

structural problems pressure gap


Powerful NVH Capabilities

• Core NVH Solutions

• Normal modes

• Frequency response

• Random Response

• Transient Analysis

• Acoustic Analysis

• AMSES fast eigenvalue solver

• Advanced Post-Processing

• TPA (Transfer Path Analysis)

• Modal Participation

• DSA (Design Sensitivity Analysis)

• Automatic filtering – PEAKOUT

F

r Ff

F

r F

f

F

t F

e


Setup in Hypermesh and SimLab - Pretension

• Hypermesh

• 12.0 - use Loads panel

• Pretension Manager (in 12.0.110)

• Simlab

• specialized pretension setup

page and tools


Contact Definition Tools

• HyperMesh

• Auto-Contact manager -

(in 12.110)

• SimLab

• Automated Contact manager


Example: Engine Assembly System Model

Subcase 1:

• Bolt Pretension in Head Bolts

Subcase 2:

• Lock Pre-tension Displacements

• Apply Temperature Loading

Subcase 3:


• Continue Temperature Loading

• Apply Combustion Pressure Loading

Thermo-structural Model


Gasket loading curve

Gasket un-loading curve

Model Features

• 3D pretension bolts

• Gasket material

• 2nd order modified

tetrahedral elements

• Contact with friction (0.1)

• Tied contacts

(total = 130)


• Apply Pre-tension Loading (41.25 KN) in Head Bolts

Subcase 1


Subcase 1: Stresses in Bolts


Subcase 1: Gasket Pressure and Sealing Status



• Apply Temperature Loading

Subcase 2


Cylinder Head

Subcase 2: Temperature Distribution Load Applied


Subcase 2: Stress Contour


Subcase 2: Contact Pressure Distribution



• Continue Temperature Loading

• Apply Combustion Pressure Loading

Subcase 3


Subcase 3: Combustion Pressure Load Application


Subcase 3: Stress Contour


The top and bottom edge

deformation of the bores are

shown in next slide

Top edge

Bottom edge

Subcase 3: Bore Deformations


Subcase 2

Scaled 300x

Subcase 1

Scaled 3000x

Subcase 3

Scaled 300x

Bore Deformations


Example – Connecting Rod Optimization

• Analysis setup

• interference fit

• bolt pretension

• contact with friction

• bearing pressure load

• Free shape optimization setup

• Design Constraints: Stresses

• Objective: Minimize Volume


Results of Free Shape Optimization


Results of Free Shape Optimization

• Weight – unchanged

• Stress constraint violation (by 50%) eliminated

Shape Change


OptiStruct for Powertrain - Summary

Courtesy PSA Peugeot Citroën

• Software of choice for Powertrain modeling

• sealing pressure with bolt pretension

• nonlinear structural analysis

• thermal solution (heat transfer)

• NVH

• Highly accurate

• Modeling errors detected*

• Some are fixed automatically

• Easy to use

• Best formulation picked automatically

• Integrated optimization


Upcoming Version 12.210

• Preprocessing

• pretension manager in HyperMesh

• auto-contact in HyperMesh

• improved import/translation of other solver’s decks

• CONTACT

• ADJUST

• more results (friction, contact status, …)

• Gasket

• temperature-dependent material properties

• Thermal - Nonlinear

• temperature-dependent materials

• pressure-dependent contact

• radiation

A complete package for Powertrain Analysis and Optimization

Technology

Application of OptiStruct to Solution of Powertrain Problems