Propagation of part tolerances through the assembly process affects the quality and overall performance of the products. Therefore, it is crucial to have a comprehensive model in order to analyse the relationship between part tolerances and final assembly errors. Assembly processes are often complex and nonlinear in nature. In sheet metal assemblies, the most important factor that makes the process nonlinear is contact interaction between mating parts during the assembly process. Another important feature in sheet metal variation analysis is the effect of geometric covariance. In sheet metal components, covariance always occurs since the surface continuity conditions force the deformation of the neighbouring points to be correlated. This paper aims to develop a new methodology for variation analysis of compliant sheet metal assemblies focusing on nonlinear contact analysis and including the effect of geometric covariance. The proposed methodology integrates a nonlinear finite element analysis with an improved sensitivityfree probability analysis in order to predict the final assembly variation. The efficiency of the developed approach is evaluated by an experimental case study as well as Monte Carlo simulation.

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