The Influence of the Assembly Gaps and Tightening Operations on the Stress Distribution during the Assembly Process

Abstract

In the manufacturing process of the large-scale wing boxes of the airplane, the assembly gaps of the bolts play a significant role in the safety assessment of the whole plane. Moreover, unreasonable tightening operations can also affect the assembly quality. In this paper, some experiments about the different tightening sequences and torques applied on the gap-existing bolts are executed for the influence on stress distribution. The recording of the surface profile is based on the trilinear coordinates measuring instrument, while the deformations of the surface can be measured by the strain gauges. Both the tightening sequence and torques can cause the local stress concentrations, especially in the places where the gaps appear firstly. The residual gaps of this place is of nearly 30% of the maximum clearance, which cannot be eliminated without shimming.