“…In order to study penetration dynamics, a number of researchers ( [19], [22], [15], [28], [8], and [32]) have attempted to measure penetration depth, velocity, and deceleration time history during penetration. The measurement methods employed include: High-speed photography to measure penetration depth-time history ([19], [22] and [32]); Laser Doppler anemometry to determine projectile velocity-time history ( [31]); On-board accelerometers to record deceleration time history ( [15], [28], and [8]); and Reversed experiments to measure strain, stress and particle velocity in projectile materials ( [5]). The understanding of rigid penetration into various soft materials (soils, clays, sands and soft rocks like tuff) has been improved using on-board instrument measurements combined with numerical simulation ( [4], and [13]) because of low resistance force and no crack generation during penetration.…”