Shock response regulation effects and nonlinear dynamic model of lead-cone waveform generator

Abstract

Lead-cone waveform generator (LCWG) is one of the crucial components in shock tests to generate final-peak saw-tooth shock pulses which are widely used to evaluate the safety and reliability of structure/equipment under shock environment in laboratory. With aim to generate a desired final-peak saw-tooth waveform and develop its dynamic model, it is necessary to investigate the working mechanism of LCWG in impact conditions. In this work, a series of customized shock tests based on LCWGs were performed by using a drop test machine (DTM). Meanwhile, the regulation effects of several core characters, including the aspect ratio (h/2R) of LCWG, the impact velocity, and the impact mass, on the generated final-peak saw-tooth waveforms are studied systematically. Experimental results showed that the overall geometric shapes of LCWGs varied from cone to truncated cone during impact processes, accompanying with local non-uniform deformation near the contact position. The correlation analysis indicated that peak acceleration of the generated final-peak saw-tooth waveform increased linearly with the increasing impact velocity, the impact mass, but decreased exponentially with elevated aspect ratio of lead-cone; the pulse duration of the generated final-peak saw-tooth waveform exhibited nonlinear increase trend with the increase of aspect ratio, but was not sensitive to the changes of impact velocity and impact mass. Subsequently, a nonlinear dynamic model of LCWG to predict the final-peak saw-tooth waveform was established by incorporating the geometric deformation model of the lead-cone during impact process and the mechanical constitutive model of the lead. The proposed model considered main parameters of the LCWG in shock tests, including the impact mass, the impact velocity, the geometric dimensioning of the LCWG, and the mechanical properties of lead. The predicted waveforms based on the established model agreed well with the experimental shock pulses, which provided a basis design for shock test.

Keywords

• Lead-cone waveform generator
• Final-peak saw-tooth waveform
• Shock test
• Nonlinear dynamic model
• Shock pulse prediction