magna steyr india limited 10/05/2012...super element (dmig model) for trim body excluding steering...

NVH Performance Refinement and Weight Optimization o f a Light Weight Car using CAE.

10/05/2012

Vaibhav Salunkhe, Rahul Sawant , Vishal Guttal, Rakesh Nagrani

Magna Steyr India Limited .

Magna Steyr India Engineering Centre (MSIA)

• Located in Pune

• Office area 2800 m2,

• Operate in 2-shift pattern

• World-class IT facilities

• Current Headcount - 252

ISO 9001:2008

Certified

Date Author 2Disclosure or duplication without consent is prohib ited

MSIA(Complete Vehicle Engineering Solution)

Body & TrimEngine

& Drive train

Electrical/

ElectronicsCAE

Sourcing

and SQA

MSIA – Capability Overview

Seating FD


Design and Dvlpmnt

of Design and

Development of

BIW structures

plastic Interiors and

Exteriors trim parts

Simulation

for Durability,

NVH, Crash,

MBS and

other

aspects.

Design, Development

& testing of engine,

engine components

Drivetrain, and

suspension

component

Design,

Dvlpmnt &

Testing of SW

and HW of

Electronics in

Automotive

Global

Sourcing, SQA,

Logistics,

Localization

&Homologation

support

Design ,

Dvlpmnt

and Testing

of complete

Seating

Systems

Concepts &

specifications

of

Mechatronics

Systems

Structural Durability

NVH Vehicle Crash and Occupant Safety

MSIA – CAE Capability Overview


Capabilities mentioned above are the ones currently available at Pune office. We can of course work on all other areas with the support and / or g uidance from our worldwide offices.

Introduction:

• Indian and worldwide automotive markets are moving towards low cost, compact, light weight and fuel efficient cars.

• The trend of automotive OEMs currently is to reduce weight of BIW and at the same time to do downsizing of engines.

• Focus on downsizing of engines has lead to some of the automotive OEMs even introducing vehicles having twocylinder engines.

Current Trend:

BIW Power Train Vehicle Feature

Weight Downsizing Price

Target :160 to 180 Kg No. of Cylinders: 4 3 2 Price: $ 3000


Target :160 to 180 Kg No. of Cylinders: 4 3 2 Price: $ 3000

Performance Target: Good Vehicle comfort/ NVH performance/ Vehicle “feel”

Customer

Requirement: Innovative/Modified CAE approach is required to meet NVH refinement targets for this new classof vehicle.

Generic Problem of low cost / light weight / downsi zed engine car

Attachment stiffness plot at Engine mount showing drop in attachment stiffness at global modes

Problem Definition:


Attachment stiffness plot at Engine mount showing drop in attachment stiffness at global modes

• A downsized engine will excite the global modes more frequently than the engine with more number of cylinders.

• Reduced isolation for vibrations due to poor dynamic stiffness at these global modes.

• Increased strong impulsive forcing from downsized power train.

This problem most often translates to low frequency “ Boom Noise ” & tactile vibrations.

Requirement : This problem has to be considered in early stages of CAE analysis.

NVH Performance Parameters for BIW Structural devel opment

Structure Borne Noise:


Tactile Vibrations:

• These performance parameters have been used as a me asure of NVH performance in traditional CAE process of BIW development .

Type of Analysis / Activity Category Vehicledevelopmentstage

Preparation of modal alignment chart Target setting Pre concept

BIW structure analysis for joint & pillar stiffnessStructural Performance ConceptBIW static bending & torsion stiffness analysis

BIW Modal analysis: front end, lateral, rear end bending, global bending & torsion

BIW Attachment Stiffness analysis

Steering system modal performance analysisAlpha, BetaClosure modal analysis –Doors & Tailgate

BIW development Process –Structure Borne Noise

Optimization 1 : Joint StiffnessOptimization 2 : Pillar Stiffness


Closure modal analysis –Doors & Tailgate

Seats modal performance analysis

Suspension component modal performance analysis

Trimmed body attachment stiffness performance

Trimmed body Attachment point mobility

Trimmed body Vibration transfer function performance

Passenger compartment acoustic cavity analysis Acoustic Performance

Trimmed body Noise transfer function analysis Vibra –acousticPerformanceFull vehicle Structure borne road & power train induced noise

Weight optimization of BIW Optimization Beta

(Note: a) This list is not exhaustive considering all CAE analysis for BIW development.b) This list covers some non BIW related components as they have an influence on BIW design)

Optimization 3: Suspension component modalperformance

Optimization 4: Topology optimization of criticalcomponents (e.g. sub frame).Optimization 5: Equivalent Radiated Power analysis

Optimization 6: Weight optimization of BIW

Joint Stiffness Optimization

Objective: To improve low frequency attachment stiffness by identifying & improving critical joints.

Input: Concept CAD data of BIW skeleton.

Description: The analysis steps for joint stiffness optimization are as follows:Step 1: Evaluation of dynamic stiffness at power train & suspension attachment points on 1D beam of BIW.Step 2: Identification of critical joints having maximum influence on attachment points in step 1 through nastran SOL 200 run. Here the target is to improve the attachment stiffness at global bending and torsion frequency by 20 %.


1D beam model with critical joints

Step 3: For critical joints identified in step 2, detailed FE model of joints are made and static stiffness of joints is improved as suggested by nastran SOL 200 run with in packaging constraints.

Benefit: Only Critical joints are improved which leads to minimal weight addition.

BIW Pillar\Section Stiffness Optimization:

Objective: Optimize BIW sections for torsional stiffness performance.

Input: Concept CAD data of BIW skeleton.

Description: This analysis finds out the point of inflection for dynamic stiffness variation along length\height of major BIW sections. Identification of point of inflection is important as it defines the locations on BIW which will make maximum influence on torsion stiffness.


concept of point of inflection

Identification of point on inflection on B pillar

The BIW was then reinforced at these inflection points to improve stiffness. Similar analysis was carried out for cant rail,sill, A pillar, B pillar, C pillar, long member etc.

Benefit: This analysis identifies critical locations on BIW structure having maximum effect on torsional performance.

Topology Optimization of Critical components

Objective: Through Transfer Path Analysis (TPA) the components and significant transfer paths of noise & vibration are identified for 3GWOT operating condition. Topology optimization was done for sub frame to find out the best design of sub frame having good attachment stiffness with in the current packaging and weight considerations.

Description:To identify the optimized material distribution, topology optimization of sub frame using modal frequency response was done. Following steps were carried out to design a new sub frame:Super element (DMIG model) for trim body excluding steering and sub frame system was created. Sub frame design region for optimization was defined based on packaging constraint.Topology optimization analysis for decreasing steering wheel acceleration (SWA) for engine roll mounts excitations using


Topology optimization analysis for decreasing steering wheel acceleration (SWA) for engine roll mounts excitations using Modal frequency response

Benefit: Optimum design of structural components /assemblies for performance & weight can be achieved .

DMIG model of BIW Vibration response at steering wheel

Sub frame Design suggestion by software

ERP Optimization

Objective: To identify panels contributing significantly to Vibra acoustic response in early design stage.

Input: Concept BIW structure.

Description: Calculation of ERP does not require a passenger acoustic cavity for calculation of sound power radiated by BIW. Use of ERP in concept/alpha stage of vehicle program helps to identify panels contributing significantly to acoustic response. Sincein concept/alpha stage of program scope for changes is more, the BIW sections, panel design etc can be changed to improve the acoustic response by avoiding additional reinforcements.


Benefit: Changes in concept CAD structure can avoid weight addition of reinforcements for NTF improvement

ERP contribution of BIW panels

BIW thickness Optimization

Objective: To optimize thickness of panels in 3GWOT for SBN & Vibration response.

Input : Complete BIW structure with 3GWOT excitation data.

Description: For 3GWOT operating condition structure borne noise and tactile point vibration simulations are done. For SBN , PACA analysis is done and panels not contributing significantly to sound pressure are found out. The thickness of these panelsIs then optimized using SOL 200 in nastran.


PACA plot for a frequency

Benefit: This analysis reduces panel thickness & thus reduces weight.

Performance improvement / Benefits with new approac h


Key Benefits:

• The low frequency boom noise seen with traditional approach is eliminated with proposed approach.

• The weight target for BIW are successfully met .

• Requirement of Late design changes in traditional approach are reduced with proposed approach.

• This BIW weight can be further optimized for higher upgraded engines.

Summary:

• Low cost, light weight cars with down sized engines seems to be the recent trend for automotive OEMs in Indian market.

• These vehicles are a challenge for NVH refinement.

• The proposed approach for BIW structure development for NVH using CAE will help to meet stringent weight targets.

• The proposed process in this paper will also cater to low frequency vibration and noise problems generic to this type ofvehicle in the earlier stages of BIW design process.

• The target weight of BIW can only be achieved if optimization of BIW performance & weight is done at each stage of


• The target weight of BIW can only be achieved if optimization of BIW performance & weight is done at each stage ofCAE analysis.

• The proposed approach has to be improved to cover other NVH performance parameters. For example optimization ofsuspension component design can improve road noise performance with optimization of un sprung mass weight.

Mr. Salunkhe VaibhavSenior Manager, Magna Steyr India LimitedPune, [email protected]: +91 20 6675 1161

Mr. Sawant RahulManager, Magna Steyr India LimitedPune, [email protected]: +91 20 6675 1161

Contact Information


Mr. Guttal VishalAsst. Manager, Magna Steyr India LimitedPune, [email protected]: +91 20 6675 1167

Mr. Nagrani RakeshHead CAE, Magna Steyr India LimitedPune, [email protected]: +91 20 6675 1165

Thank You


magna steyr india limited 10/05/2012...super element (dmig model) for trim body excluding steering...

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