Study on mechanical hammer forming and surface layer properties of 7075 aluminum alloy thin-walled parts

This study systematically investigated the mechanical hammer forming of 7075 aluminum alloy driven by a voice coil motor through experiments and simulations, focusing on the effects of hammering force, offset distance, and thickness on forming behavior and surface quality. Parameter optimization, theoretical modeling of stress–deformation, stress relaxation analysis, and multi-contour plate forming were also explored. Results showed that increasing the force from 35 N to 65 N raised the maximum arc height by 53%, extending the offset distance from 1 mm to 1.6 mm increased it by 29%, and raising thickness from 2 mm to 5 mm yielded a 110% rise, identifying thickness as the dominant factor. Surface waviness and roughness were strongly influenced by force and offset distance but only slightly by thickness, with higher force and smaller offset distance leading to poorer quality. Offset distance most affected surface hardness, while thickness had the least influence. A BP neural network optimization identified optimal parameters (55 N, 1.2 mm, 3 mm) balancing deformation and surface quality. Furthermore, an arc height model was established to correlate residual stress redistribution with deformation, and stress relaxation was described using an exponential decay model with extracted relaxation time constants (τ). Finally, multi-contour plate forming was demonstrated through trajectory design, providing a reference for correcting deformed thin-walled parts.