The objective of this project was to develop a technology platform for structural dynamic analysis that integrates fatigue analysis and acoustic radiation prediction with vibration analysis.
Acoustic radiation, dynamic fatigue and vibrations are frequently interrelated aspects in the structural dynamics optimization of cars. Realistic assessment of these phenomena is only possible after development of first prototypes at a stage where large design modifications are only implemented at considerable expense. For acoustic radiation prediction, techniques based on the boundary element method (BEM) are promising but several aspects remain to be improved: the solution to the coupled fluid structure problem, modelling of specific boundary conditions and proper simulation of excitation. Methodology for traditional fatigue analysis is well developed for predictions based on crack initiation, but less for the crack growth case. The methodology is applied at the stage when first prototypes are available. The underlying relation between fatigue and structural vibrations is rarely developed at all, even in the prototype optimization phase. As a consequence, the effect of structural dynamics modifications on the fatigue behaviour is not understood. The project develops improved methods for acoustic radiation prediction and fatigue analysis, including the relation with structure vibration models. The technology is implemented in a computer assisted engineering (CAE) software architecture that is designed for UNIX computer workstations. Progress was made in each of the addressed technology domains: improved crack initiation and crack growth based fatigue analysers; extended element types, boundary conditions and acoustic sources for acoustic radiation prediction and improved operating vibration data analysis techniques. The basic methodology for integratingstructural modelling with both fatigue analysis and noise prediction was spelled out and the development initiated. For fatigue analysis, this mainly involves the modelling and quantification of the effect of resonance induced strains on the lifetime, enabling the prediction of appropriate design modifications. For a coustic radiation, this involves the coupling of the structural models with the acoustic BEM models. A prototype integration, including all required interfaces, was realised. An extensive test program, to relate modelling with experimental results for a set of laboratory systems was defined and initiated. The definition of the required open system architecture, based on a standardised user interface approach was completed and the development of the necessary platform building blocks started.
The prototype of the platform software is targeted at engineering workstations, using advanced user interfaces and data management techniques, with interfaces to existing CAD and FEM systems and to experimental analysis programs for vibration analysis data. The integrated platform allows interaction between designers and experimenters at an early stage in the design process. The project aimed to achieve:
- the extension of fatigue life estimation methods and their integration with vibration analysis and test
- the extension of acoustic radiation prediction techniques and their integration with vibration analysis and test
- the development of technical modelling techniques with respect to fatigue analysis and acoustic radiation prediction and their integration with geometric modelling
- the enhancement of vibration analysis techniques in view of specific requirements for fatigue analysis and acoustic radiation prediction.
Developments have been validated in conjunction with major manufacturers in the automotive industry.
The methodology and tools developed will have important applications in the automotive and aerospace industries and in the mechanical engineering industry in general. The following benefits are expected:
- superior products in terms of improved dynamic characteristics (reduced vibration and noise emission, improved fatigue life)
- shortened design cycles, since products with improved dynamic characteristics will require less prototype testing and trouble shooting in later phases of the design process
- higher degree of flexibility, as an improved understanding of the dynamics of the product will enable the prediction of the effects of design changes and the forecasting of the performance of variations of a new product (eg cars with different engines, gear transmissions, etc).
The results of the development will be made available as commercial products by the IT project partners.
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S9 3OQ Sheffield
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