A Theoretical and Experimental Study on the Critical Clamping Force for Suppressing Buckling in In-Plane Tension–Compression Testing of Sheet Metals

Accurate characterization of the Bauschinger effect is essential for improving springback prediction in simulations of complex sheet-metal components. However, in-plane tension–compression tests are prone to compressive instability and wrinkling during reverse loading, and the selection of clamping force still lacks a theoretical basis. In this study, a critical clamping force prediction model was developed based on energy conservation and the Cao–Boyce instability criterion. The model establishes the relationship between the critical clamping force, material strength coefficient, strain-hardening exponent, specimen geometry, and effective support area. Finite element simulations and experiments were conducted to investigate the contact state, local support effect, and instability-mode transition of Q890 high-strength steel, 2A14 aluminum alloy, and 304 stainless steel under different clamping forces. For Q890 steel, the critical clamping force interval was 900–1000 N, within which the compressive instability strain increased from nearly 0 to 0.085 and the instability mode changed from single-wave to double-wave buckling. After calibrating the boundary correction coefficient using Q890 steel, the predicted critical clamping forces for 2A14 aluminum alloy and 304 stainless steel were 594 N and 278 N, respectively. The optimized clamping forces enabled smooth cyclic tension–compression curves.