A new virtual functional element method for deviation prediction of assembled structures with parallel connection chain

Abstract

The assembly precision prediction of industrial products with numerous tolerance information and complex assembly relations is a challenge for existing deviation analysis methods since their dimensional chains usually form parallel connections. The parallel connection chain is often transformed into a serial connection chain by discarding some tolerance information and physical constraints in practical application, which leads to amplifying the range of predicted results and reducing the predicted accuracy. In this paper, a virtual functional element method is proposed to simplify the parallel connection chain by integrating the tolerance information into the torsor parameters of specified virtual functional elements. A general Jacobian-Torsor model is developed to solve the simplified parallel connection chain, in which the Boolean intersection operation on torsor parameters is used to obtain comprehensive deviation results for multiple branches in a parallel connection chain. Meanwhile, the locking effect and leverage activation effect are proposed to characterize the effect of the invariant degree in parallel connection chain. Finally, an assembly case of a power plant is applied to validate the proposed method, and the results show that it has a high potential to improve the prediction accuracy of assembly deviation compared to three conventional methods.