剪切失效是强动载荷作用下结构失效的重要模式。着重研究了自由梁在中点受到质量块撞击后的剪切效应 ,给出了发生剪切失效的无量纲判据。分析表明 ,在初始速度的间断界面上是否发生剪切失效取决于质量块无量纲初始动能、质量比及梁的无量纲厚度 Shear failure is an important mode of structural failure under strong dynamic load. The shear effect of the free beam after being hit by the mass at the midpoint is studied emphatically, and the dimensionless criterion of shear failure is given. Analysis shows that shear failure at the discontinuous interface of the initial velocity depends on the massless initial initial kinetic energy, the mass ratio, and the dimensionless thickness of the beam