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The crank noise of a motorcycle often spoils the product value because of its annoying sound. Many approaches have been tried to cope with this troublesome issue. In recent years, a CAE-based method has been adopted to evaluate new designs for engines and to propose design changes that determine any identified issue. But it was a challenge to make an accurate CAE model due to the relatively high frequency characteristics of the noise generated by ball bearing-supported crankshafts. This paper presents the virtual modeling of a single-cylinder engine of a motorcycle that succeeds in identifying the mechanism behind the generation of annoying noise. Furthermore, different possible design changes were evaluated in order to determine the issue. A combined experimental and numerical approach was adopted to obtain the necessary accuracy. Experimental data were used to identify important parameters that determine the engine behavior and thus are critical to the modeling of such an engine.

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.

The DIANA project aims studying “Development & Integration of a Unified Approach for Structure Borne Noise Analysis”. The project was led by LMS Engineering (Belgium) which collaborated with the research centres of FIAT (CRF, Italy) and Renault (RNUR-DE, France). Other members in the consortium were MIRA (UK) and the Technical University of Bielefeld. Ford Germany acted as sponsor and provided testvehicles. The first objective of the project included the investigation of advantages, disadvantages, sensitivity to boundary conditions and limits of confidence of several classical techniques in the field of structure borne noise analysis. These techniques were amongst others: single input transfer path analysis, principal component analysis and mount testing. At the other hand new techniques have also been elaborated. They were related to algorithms for indirect force determination, tire domain principal component analysis and advanced mount testing.

As powertrain noise is better and better controlled, road inputs become more important. The trend to mount 6 cylinder engines in smaller cars also emphasizes the importance of road induced noise. A method to qualify and quantify the different contributions is presented and illustrated. This methodology is based on a novel combination of existing technology: transferpath analysis, traditionally used for ranking of powertrain inputs on one hand and principal component analysis, traditionally used for visualisation of operating shapes in a multiple uncorrelated input environment. As suspension inputs represent multiple incoherent sources, the classical vector summation used in noise path analysis is not applicable. On the other hand, root mean square summation of all contributions does not keep track of phase relations between suspension-body connections which are important in the understanding of the global picture.