Investigation on deformation of single-sided stringer parts based on fluctuant initial residual stress

Abstract

Deformation has a significant effect on the machining accuracy of the monolithic components. Fluctuant initial residual stress is one of the factors causing deformation. In this paper, initial residual stresses of six specimens of 7050-T7451 aluminum alloy plates with 65 mm thickness and 70 mm thickness are measured respectively. Fluctuant initial residual stresses are fitted by segmented polynomials of best uniform approximation. An analytical model in terms of the deformation and initial residual stress is established for single-sided stringer parts. The results show that the weight of web-induced deformation in the whole deformation of the part is about 74%–98.5% and the weight sidewall-induced deformation is about 1.5%–26%. Therefore, minimizing the web-induced deformation is the key to minimize the whole part deformation. The condition number calculated by coefficients matrix of initial residual stress inside the web is defined in the model. The value of condition number is determined by initial residual stress inside the web and its fluctuant degree, which is positively correlated with web-induced deformation when the structural stiffness is invariant. By selecting the blank with a small fluctuant amplitude of stress or changing the workpiece position, condition number will be decreased, and the deformation is minimized.