*Squeak and rattle are annoying sounds that often are counted as the indicators for defects and quality issues by the automotive customers. By the emergence of a quieter environment inside the passenger cars, there exists a growing demand among the automakers to prevent or eliminate these sounds. To avoid extra product development costs, these activities have to be shifted towards the pre-design-freeze phases in product development. Among the major causes for the generation of squeak and rattle sounds, geometric variation and tolerance stack-up is a key contributor. Hence, the focus of this work is to prevent squeak and rattle by introducing a geometric variation management approach to be used in the design phase in the automotive industry. The dimensional variation of parts can be minimised by improving the part manufacturing processes. However, in the assembly process, the dimensional variation in critical interfaces for generating squeak and rattle events can be magnified due to tolerance stack-up. One provision to manage the tolerance stack-up in these critical interfaces is to optimise the location of connectors between parts in an assembly. The objective is to identify connection configurations that result in minimum variation and deviation in selected measure points from the critical interfaces for squeak and rattle. In this study, a two-stage evolutionary optimisation scheme is introduced to fine-tune the connectors’ configuration in an assembly to minimise the risk for the generation of squeak and rattle events. The design space was discretised into equidistant connection candidates in the design plane. The measurements were done in the defined measure point in the normal direction between the two parts and the in-plane direction. The objective function was defined as a linear weighted sum of the 6-sigma value of the variation and the mean-shift of the tolerance propagation. In the first stage, the location of one-dimensional normal connectors was opted by minimising the objective function in the normal direction. In the second stage, the best combination of some of the connectors from the first stage was found to define planar fasteners to optimise the objective function both in the normal direction and the in-plane measures. The optimisation algorithm was based on the genetic algorithm employing the elitism pool. The variation analysis was done using flexible bodies and a Monte-Carlo variation simulation. The results of the optimisation for two different subassemblies from the car interior parts were compared to the baseline designs. It was shown that by using the proposed two-stage optimisation scheme, the variation and deviation results in critical interfaces for squeak and rattle improved compared to the baseline results. Indeed, by automatically managing the geometric variation in the selected interfaces, the most robust design can be identified. The resultant optimised configuration of the connectors is the least sensitive design against the assembly tolerances. Therefore, the static gap values in normal and in-plane directions in critical interfaces are least varied as a result of tolerance stack-up.*


Squeak and Rattle Prevention by Geometric Variation Management Using a Two-Stage Evolutionary Optimisation Approach

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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