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Technical Paper

Experimental and Hybrid Modeling of the Medium Frequency Behaviour of Car Panels

This paper discusses an approach to identify critical car panels and to derive detailed experimental models for these critical panels. The research was conducted in the framework of the Brite/Euram project SALOME and the EUREKA project HOLOMODAL. The panel identification method is based on a numerical or experimental contribution analysis, assessing the partial noise contributions of individual panels to the interior noise. The second step in the approach consists of the derivation of detailed modal analysis models for the critical panels. A novel Electronic Speckle Pattern Interferometry (ESPI) system was developed, and integrated in a classical CAE system. The components of this system are briefly reviewed, and their application to several industrial cases is shown.
Technical Paper

Application of a Modular Vehicle Noise and Vibration Development Approach

The paper addresses the problem of NVH development of vehicles. An approach for the specification and assessment of subsystem performance as well as of the early part of the integration process is presented hereto. The basic technologies applied are those of Transfer Path Analysis and System Synthesis. Various applications to industrial problems are discussed.
Technical Paper

Structural Modelling of Car Panels Using Holographic Modal Analysis

In order to optimise the vibro-acoustic behaviour of panel-like structures in a more systematic way, accurate structural models are needed. However, at the frequencies of relevance to the vibro-acoustic problem, the mode shapes are very complex, requiring a high spatial resolution in the measurement procedure. The large number of required transducers and their mass loading effects limit the applicability of accelerometer testing. In recent years, optical measuring methods have been proposed. Direct electronic (ESPI) imaging, using strobed continuous laser illumination, or more recently, pulsed laser illumination, have lately created the possibility to bring the holographic testing approach to the level of industrial applicability for modal analysis procedures. The present paper discusses the various critical elements of a holographic ESPI modal testing system.
Technical Paper

Transfer Path Analysis in the Critical Path of Vehicle Refinement: The Role of Fast, Hybrid and Operational Path Analysis

15 years of NVH applications make Transfer Path Analysis appear a commodity tool. This is however not the case. Required insight in the application constraints makes TPA remain an expert approach. This paper reviews past progress in TPA methodology and its limitations. It then introduces a number of innovative approaches addressing these, opening new application fields. This includes speed improvement (Fast TPA), structural modeling integration (Modal Contribution Analysis), CAE integration (Hybrid TPA), sound quality interpretation (TPA-sound synthesis) and supporting better exploitation of operational data (Operational Path Analysis). An outlook is given to the next challenge, the application to transient problems.
Technical Paper

Vibro-Acoustic CAE from an Industrial Application Perspective

Vibro-acoustic simulation methods such as FEM and BEM have made an enormous progress for modelling and describing the acoustic and vibro-acoustic behaviour of mechanical systems. In order to make these techniques truly become part of the “virtual” industrial design process however, the specific challenges related to industrial-sized problems must be overcome. The paper reviews the critical issues to building and solving large-scale problems and discusses practical aspects such as the correct load definition and simulation performance requirements and improvements. Some breakthrough solutions like Acoustic Transfer Vectors and parallel computing are discussed. Specific attention is devoted to the potential of hybrid methods combining virtual models with experimental data. The discussed are illustrated by means of powertrain noise and vibration case studies.
Technical Paper

Reducing Body Development Time by Integrating NVH and Durability Analysis from the Start

Due to the trend to build more vehicle models on a common platform, body development is very often on the critical path in the automotive development process. While the virtual assessment of attributes like crash, structural rigidity or production feasibility is common practice today, it is done less systematically for NVH and durability. They are traditionally only considered close to the availability of prototypes. Performance issues discovered at this stage will lead to additional design cycles which conflicts with the need to further shorten the total development time. The process proposed in this paper results in a better initial design by doing more NVH analysis in the pre-CAD phase and a reduced number of iteration cycles required for NVH and durability engineering by iterating much faster to the final design. Mesh morphing and beam concept analysis make it possible to evaluate and optimize functional performance characteristics based upon predecessor FE models.
Technical Paper

Experimental and Numerical Modelling of Friction Induced Noise in Disc Brakes

Friction-induced vibration is a serious problem in many industrial applications containing systems with rotating and/or sliding parts. Brake noise is a typical example. The critical element in the noise generation process is the combination of friction-induced loads with the dynamics of the braking system. In the present paper, a detailed experimental and numerical study of a specific low-frequency brake squeal problem is made on a simplified brake noise test rig. First, the signal and spatial characteristics of the noise were analyzed by spectral and acoustic holography techniques. A parametric study of influence factors as brake pressure, rotation speed, etc. was made. Operational deformation analysis during squeal confirms the dominant modal behavior of the components, implying the critical role of the assembly structural dynamics.