Abstract
Geometrical and dimensional errors are basic factors for the satisfaction of the functional requirements of a mechanical assembly. In order to put under control the effects of parts variations it is possible to use dedicated software tools which are capable of performing tolerance analysis both for a single mechanical part and for a complete assembly. There are many commercial software dedicated to Statistical Tolerance Analysis (STA), however all of them are based on the assumption of perfectly rigid parts. It is evident that such an assumption is not acceptable for many industrial cases; quite often, actually, the assembling procedure causes an amount of deformation in the parts making up the assembly, which cannot be neglected. As a result, assembling simulations, carried out by current STA software tools, lead to a final assembly geometry which is considerably different from the actual one.
A typical example is provided by the automotive industry, in which low thickness panels (therefore flexible) are widely used in complex assemblies (e.g. the car doors). In such a situation deformations may be induced by several causes that can take effect either individually or at the same time (e.g. flexibility, assembly method, etc.).
This paper describes a method for performing tolerance analysis for assemblies made up of flexible parts. The presented approach couples the results provided by a commercial STA software tool with a Finite Element based technique. The final goal of the work is to perform an assembling simulation, based on Geometrical Dimensioning and Tolerancing (GD&T) specifications, taking into account the main causes for deformation in mechanical assemblies. The results obtained according to the developed numerical procedures are presented with reference to a simple practical application. A comparison with the results obtainable with the assumption of rigid parts is also provided.