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RESEARCH PRODUCT

Form defect influence on the shrinkage fit characteristics

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Abstract Today, manufacturing products must meet more and more severe specifications. The different parts composing the product often necessitate high dimensional precision, which increases the difficulties for a large series production. Then it it necessary to optimize dimensioning of the different components in an economic context. In the case of small dimensional fits, there is an influence of the micro-geometry (form of defect, roughness) and time of the process on the geometrical characteristics of the assembly. At the time of conception, it is necessary to obtain a good specification that relates the product functionalities with the best cost. The objective study of this is to simulate a shrinkage fit process and provide the fit characteristics according to the microgeometrical defects. Only the form of the defects are taken into account. In the first part, a method a solution of a three dimensional contact involving two cylindrical bodies is presented. The contact is closely conformed (non-Hertzian). The stress field and the strain field, in both bodies, are calculated with the hypothesis that the interface pressure is a sum of different concentrated loads superposing and depending locally on the defects after rendering the contact area discrete. The different basis loads are formulated by Fourier series and modified Bessel functions. Several cases are simualated for different types of defects that can show the influence of the microgeometry on the cylindrical characteristics fit. Finally, an experiment is presented which shows a good correspondence with theory and predicts the extract strength.