Numerical Simulation of Waveform Adjustment in high G Accelerometer Calibration System Using Hopkinson Bar

Abstract

High-G accelerometer impact excitation using Hopkinson pressure bar was introduced. The impact excitation course was simulated on ANSYS/LS-DYNA using Lagrange's method and Johnson-Cook constitutive model. The effects of projectile nose shape, nose length, and adjustment pad material on acceleration waveforms were studied. The simulated results are in good agreement with the experimental results. The results show that projectiles with small nose taper or with large nose length will impact and produce acceleration waveform pulses with long rising time, low amplitude, and large pulse width. For adjustment pad material with small yield stress, the pulses of corresponding acceleration waveforms have long rise time, low amplitude, and large pulse width. Along with the rapid development of silicon microtechnology, high-G accelerometers as an important measuring element are widely applied in load measurement during high-speed impacting. In particular, high-G accelerometers are used in study of penetration, anti-penetration, and target panel goal characteristics in the field of weapons (e.g. measurement of deceleration for armor piercing projectiles during penetration and breakthrough). High-G acceleration transducers are also widely used in civil industry, such as in anti-crash design of civil aviation aircraft, and in measurement of overload produced when plane structure drops on the ground. A high-G accelerometer's sensitivity coefficient directly affects its measurement accuracy. After repeated use, its sensitivity coefficient will change because of overload and thus it should be frequently calibrated. In calibration of high-G accelerometers, Hopkinson bar is commonly used as a loading means, since it has high repeatability and convenient operation, and its acceleration amplitude can reach