Experimental investigations on the dynamic plastic buckling of a slender beam subject to axial impact

Experimental investigations on the dynamic plastic impact buckling of slender beams were conducted. A 10 kg free-fall impact hammer applied an axial impulsive load to aluminium (6061-T6) and cold rolled steel beams (CR1018) with a fixed-slide bearing boundary condition. Two rectangular cross-sections (50.8 mm×3.175 mm and 50.8 mm×4.7625 mm) with effective slenderness ratios ranging from 75 to 300 were considered. A total of 94 tests were conducted and the deformed buckled geometry for each impact event was profiled. A normalized response parameter was defined to characterize the observed dynamic buckling behaviour, which related the axial position and transverse amplitude of the peak buckle with respect to local stiffness and natural frequency characteristics. Simplified theoretical expressions defining the critical buckle wavelength provided a reasonable bound limit with respect to the experimental data.