How to determine the influence of geometric deviations on elastic deformations and the structural performance?

Abstract

Geometric deviations are observable on every manufactured part since manufacturing processes are inherently imprecise and measuring processes always involve uncertainties. These geometric deviations have influences on the function and the quality of the product. Therefore, allowable limits for these geometric deviations, depicted as geometric tolerances, have to be set. They define the allowable geometric deviations of a part for which the product function is guaranteed. In this context, elastic deformations and the structural performance are key aspects. However, the manufacturing-caused geometric deviations have an influence on the elastic deformations during use and the structural performance of the parts. In other words, there are interdependencies between geometric deviations and elastic deformations which affect the dimensional accuracy of a loaded part in an assembly. Therefore, this article proposes an approach for determining the impact of geometric deviations on the structural performance. This approach employs techniques such as sensitivity analysis, analysis of robustness and evaluation of reliability, and aims at providing information about the expectable elastic deformations and structural performance to geometric tolerancing. It can be concluded that geometric deviations can have a big impact on the structural performance, and thus, not only parametric deviations but also geometric deviations regarding the form and shape of a part itself should be taken into account within the structural performance analysis and tolerance simulations. KeywordsStructural performance, computer-aided tolerancing, geometric deviations Date received: 11 July 2012; accepted: 1 November 2012 Structural performance evaluation in computer-aided tolerancing Since every manufacturing process is inherently imprecise and every measuring process involves uncertainties, geometric deviations are generally observable on every manufactured and measured part.1 These geometric imperfections can have huge influences on the function and the customer-perceived quality of the product. Hence, geometric dimensioning and tolerancing is an important step in the product development process since it is the step where the limits of allowable geometric deviations are defined. However, it is difficult to set these limits since geometric deviations influence the functional behaviour of the part in many ways. The structural performance, however, is a key aspect. Therefore, an approach is proposed that helps to determine the effects of geometric deviations on the structural performance.By connecting different methods of computer-aided design (CAD), computer-aided tolerancing and tools for computer-aided simulations such as the finiteelement (FE) method and assembly simulations, the product developer can be supported in setting the tolerance requirements. In this respect, the main goal is to draw a realistic virtual image of the geometry, function and behaviour of the real part or assembly group with geometric deviations during product dev...

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