开坑 meaning in Chinese

spud in

When the projectile velocity reaches to the normal projectile velocity , the projectiles fracture crushingly , the penetration process is similar to the process penetrated by long rod projectile and can be divided into three processes that is crater process , steady penetration process and plugging process
当弹速达到常规弹速后，弹体发生粉碎性破坏，此时侵彻过程类似于长杆弹侵彻，侵彻过程可分为开坑阶段、定常侵彻阶段和剪切冲塞阶段。