Simulation of drop testing at extremely high accelerations

摘要

Advances in drop tower technology have extended the range of obtainable accelerations in drop testing from 5,000 Gs to as much as 100,000 Gs. To achieve excitations in excess of the conventional 5,000 Gs, a mechanical accelerator, called the Dual Mass Shock Amplifier (DMSA), is mounted on the drop table. This device produces extremely high, short duration shock amplitudes, by using secondary impacts. In this study, we use transient finite element analysis with nonlinear contact elements, to assess the DMSA table acceleration response profile (height and width) as a function of different system parameters like DMSA design parameters, programmer configuration, drop height, etc. DMSA design variables include table weight, height of the rebound travel rods, stiffness of rebound springs, and rebound damper materials. The programmer configuration includes: (i) height, diameter, material and surface shape of the programmer cylinder that is placed between the drop table and the shock table; (ii) thickness and damping coefficients of the programmer layers placed between the DMSA base and DMSA table; (iii) programmer tubes between the DMSA table and the DMSA rebound stopper bar. Contact elements in the finite element analysis (FEA) are introduced between the shock and drop tables and also between the DMSA base, DMSA table and DMSA rebound stopper bar. Specimen fixtures of different weights are introduced on the DMSA table to see the effect of the payload weight. The effect of these variables in the DMSA table acceleration profile are parametrically explored.