中文摘要：

根据刚性弹侵彻动力学的量纲一侵彻深度公式，分析了刚性弹侵彻过程中弹丸所受的靶板阻力，并从冲量角度讨论了常阻力假设适用的撞击速度阈值vc，得出统一的表达式，求出了针对不同弹靶系统的相应vc值。根据相关数值模拟结果，进一步验证了所求vc值的正确性，同时也检验了不同侵彻深度公式的适用范围。

英文摘要：

According to the dimensionless depth-of-penetration formula for different targets penetrated by rigid projectiles, the present paper theoretically analyses the resistive force which the target exerts on the projectile during penetration. In particular, the impact velocity threshold, which is applicable for the assumption of constant resistive force, is formulated by impulse analysis. The impact velocity thresholds are calculated for different projectile/target combinations by the proposed formula and the calculated velocity thresholds are in good agreement with the relative numerical results.