A dvanced Simulation Techniques for the coupled Fatigue and NVH Optimization of Engines

Advanced Simulation Techniques for the

coupled Fatigue and NVH Optimization of Engines.

K+P Software, Schönbrunngasse 24, A - 8043 Graz / Austria

Tel.: 0043/316/328251, Fax: 0043/316/328351

E-Mail: office@kplusp.com

Environmental Pollutionincreasing government regulations concerning the emissions of vehicles

Limited Ressourcesoil and raw material consumption ...

(air pollution and noise ...)

Customer Requirementsoil consumption, sound engineering ...

Tasks for the Automotive Industry reduce vehicle weights and oil consumption

optimize NVH Behaviour and create specific sounds

convenient numerical simulation tools (FEM ...) can help to- analyze and optimize structures in the very first development stage

- avoid numerous test series- reduce time and costs required for prototyping

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Introduction

State-of-the-Art

Linear static finite element analyses of

Loading cases, maximum gas load‘, single crank throws

,maximum mass force‘ and ,maximumtorque‘

Nonlinear dynamic analysis

Linear static analyses however do not enable the consideration of actual dynamic effects, such as

the statically undetermined supporting of the rotating crankshaft gyroscopic effects (flywheel wobbling ...)

the nonlinearities (time dependencies) of mass-, stiffness- and damping matrices

hydrodynamic conditions in the bearings ...

Fatigue analysis of crankshafts

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Flow Chart Flow Chart

Nonlinear dynamic analysis of crankshafts

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Beam-Mass-Model, perfect correlationbetween analysis and measurement results

Solid-Element-Model, time dependent stress distribution due to the 3-dimensional vibration behaviour of the powertrain, momentary views

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Example: ,Nonlinear fatigue analysis of a 4-cylinder-inline crankshaft‘

Time dependent stress distribution,momentary view

Safety factors versus engine speed, influenced by a resonanceeffect caused by flywheel wobbling

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Example: ,Nonlinear fatigue analysis of a 6-cylinder-boxer crankshaft‘

Flywheel wobbling, momentary view

Time dependent stressdistribution in the transfer mechanism due to flywheelwobbling, momentary views

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Example: ,Nonlinear fatigue analysis of a Two-Mass-Flywheel‘

CSG-Stator Crankshaft with Flywheel/CSG-Rotor

Finite-Element-Models

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Example: ‚Nonlinear dynamic analysis of a Crankshaft-Starter-Generator‘

3.000 RPM ,Full Load‘, Operating temperature 90°Air gap distribution and electromotive forces between Rotor and Stator versus circumference and crank angle, influenced by flywheel wobbling

Air gap distribution Electromotive forces

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Example: ‚Nonlinear dynamic analysis of a Crankshaft-Starter-Generator‘

State-of-the-art

Fatigue assessments of engines usually are done based on the linear static analysis of subdomains (deformation behaviour of single main bearing walls ...)

Furthermore linear analysis in the frequency domain are state-of-the-art for NVH assessments (determination of transfer functions ...)

Nonlinear dynamic analyses

Actual dynamic effects and excitation mechanisms however can have a dominant influence on both the fatigue and the NVH behaviour of engines

the nonlinearities (time dependencies) of mass-, stiffness- and damping

statically undetermined supported, rotating shafts (crankshaft, balancing

gyroscopic effects (flywheel wobbling ...) misalignment and excentric pressure distributions in the bearings

Nonlinear analyses in the time domain are unavoidable to enable a convenient consideration of those effects, such as

matrices

shafts ...)

resonance effects nonlinearities in toothings ...

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Fatigue and NVH analyses of engines

Flow Chart

Nonlinear fatigue and NVH analysis of engines

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Example: ,FE-Models for fatigue and NVH analyses‘

Nonlinear fatigue and NVH analysis of engines

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Normal mode analysis

knowledge about the basic dynamic behaviour (identification of resonance effects, explanation of phenomena occuring at forced vibration analysis ...)

Nonlinear NVH analysis of engines

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Flow chart for the iterationprocedure between shaft dynamics and tooth backlashes / tooth forces

Example: ,Nonlinear NVH analysis of an4-cyl.-inline engine with balancing shafts‘

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Equivalent System for the nonlinear analysis of the gear drive dynamics

Example: ‚Nonlinear NVH analysis of an 4-cyl.-inline engine with balancing shafts‘

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3.000 RPM ,Full Load‘, Operating temperature 90° Tooth forces in the primary toothing

Example: ‚Nonlinear NVH analysis of an 4-cyl.-inline engine withbalancing shafts‘

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3.000 RPM ,Full Load‘, Operating temperature 90° Reaction forces in the axial thrust bearing of the primary balancing shaft

Example: ‚Nonlinear NVH analysis of an 4-cyl.-inline engine with balancing shafts‘

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,Room temperatur‘ 25°

3.000 RPM ,Full Load‘, Influence of different operating temperatures Integral velocity levels influenced by gear drive dynamics

Operating temperature 90°

Example: ,Nonlinear NVH analysis of an 4-cyl.-inline engine with balancing shafts‘

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Basic design

3.000 RPM ,Full Load‘, Operating temperature 90° Integral Velocity Levels for the basic design and a design modification

Design modification

Example: ‚Nonlinear NVH analysis of an 4-cyl.-inline engine withbalancing shafts‘

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Finite-Element-Model

Example: ‚Nonlinear NVH analysis of an 4-cyl.-inline engine with mechatronic actuators for a fully variable electromechanical valve train‘

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Time dependent vibration behaviour of an actuator, momentary views

Example: ‚Nonlinear NVH analysis of an 4-cyl.-inline engine with mechatronic actuators for a fully variable electromechanical valve train‘

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Design modification

3.000 RPM ,Full Load‘, Integral velocity levels before/after an

Basic design

optimization

Example: ‚Nonlinear NVH analysis of an 4-cyl.-inline engine with mechatronic actuators for a fully variable electromechanical valve train‘

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Further examples for actual excitation mechanisms

Piston

Piston side forces Piston slap

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Nonlinear NVH analysis of engines

5.000 RPM ,Full Load‘, time dependent stress distribution influenced by flywheel wobbling, momentary views

Example: ‚Nonlinear fatigue analysis of an 4-cyl.-inline engine‘

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Linear static and dynamic finite element analysis can be a usable tool to achieve a basic knowledge about the fatigue behaviour of engine componentsand the NVH behaviour of complete power units

Both the stress distributions and the NVH behaviour however can be highly influenced by actual dynamic effects and excitation mechanisms (flywheel wobbling, clearances, resonance effects ...)

Therefore nonlinear transient analysis are unavoidable to enable the simulation results to be close to reality. Furthermore temperature dependencies (oil viscosity and clearances at different operating temperatures...) also haveto be considered.

K+P‘s highly advanced simulation techniques (nonlinear dynamics ...) and enhanced algorithms for pre- and post-processing (automized mesh modification, advanced fatigue assessment ...) provide a powerful framework for analyses of ultimate quality and efficiency.

Conclusion

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