A Novel Compliant Assembly Variation Analysis with Consideration of Initial Deviation and Welding Shrinkage

Welding, as the most common joining technique, causes welding deformations that reduce the geometrical accuracy of hull structures. In conventional variation analysis, welding distortion is not taken into account. In this paper, a compliant assembly variation modeling and analysis method is presented to investigate the impact of local weld-induced shrinkage on the propagation relation from the initial deviation to the final assembly deviation in thin plate assembly. First, welding deformations in the form of inherent strains are incorporated into variation analysis model based on Kirchhoff plate model. Additionally, part deviations are also introduced via equivalent forces in order to consider the effects of geometrical variation on compliant assembly. Then, other variation sources, such as fixture locating errors, are modeled as equality constraints of the mechanical variation model, which are then transformed into boundary conditions with Lagrange multiplier method. With an additional stiffness matrix, we describe concisely the coupling relationship between initial deviations and welding deformations caused by gaps and misalignments. In order to validate the effectiveness of the proposed method, numerical simulations and experimental verifications are carried out for two assembly cases, and the results show that the present method has high prediction accuracy and efficiency. This study provides a potential application for improving assembly dimensions considering the inevitable manufacturing deviations and welding deformations.