The Method of Influence Coefficients is widely used for predicting part deformation during the assembly process of thin flat flexible parts such as automotive body parts. It predicts the dimensional variations on the assembly as linear functions of those on the parts before assembly. This linear relationship is expressed as the sensitivity matrix, and it is obtained by a few FEA runs.
This tolerance analysis method is very efficient because it would require hundreds and thousands of FEA runs (called Direct Monte Carlo simulation) considering each random case of variations. As such, it is widely used in the automotive industry. Yet, it is based on several assumptions; for example, planar shapes of the parts to be assembled.
This paper studies the application limitations of the Method of Influence Coefficients, particularly in terms of the non-planar form of parts. As a result of this study, the applicability of the method will become clear for each problem at hand. Also, the reliability of the method for moderately non-planar parts will be clarified.