Experimental study on the thermal-dependent nonlinear dynamics of a bi-metallic beam

This study investigates the nonlinear dynamics of a bi-metallic beam composed of aluminum alloy and copper layers joined through an explosive welding technique, with emphasis on the effect of temperature on its stability and vibrational characteristics. Although thermal buckling and vibration of the beams have been extensively investigated through analytical and numerical methods, experimental studies capturing the combined effects of thermal loading, material heterogeneity, geometric nonlinearity, and damping evolution across buckling are still scarce. To address this gap, various experimental tests-impact, random control, and stepped-sine-are conducted to investigate the dynamics of the system. Experimental vibration tests were performed within a climate chamber, where the bi-metallic beam was excited at its base using a shaking table to evaluate large-amplitude vibrations across a temperature range from 5 degrees C to 70 degrees C. The results reveal a pronounced non-monotonic evolution of the fundamental frequency, decreasing by nearly 32% as the temperature approaches the critical buckling temperature at about 30 degrees C, followed by a significant recovery in the post-buckling regime. The damping ratio exhibits an inverse trend, peaking at approximately 3.5% at 35 degrees C. The uniform aluminum beam tested under different thermal conditions conducted to delve into the dynamics of the bi-metallic beam. At the buckling threshold, the dynamic frequency-response curves display a softening-to-hardening transition. The results contribute new insights into the thermal dependence of nonlinear vibrations in layered metallic structures, offering valuable guidelines for the design, reliability, and performance optimization of thermally loaded components.