凸模受轴向力作用时,是在直线形状下维持平衡,因而凸模的破坏都是由于强度不足而引起。事实上当凸模受轴向压力大于一定数值时,凸模就变弯,就在原有直线形状下平衡变为不稳定。由于它维持不了直线形状下的平衡而不能正常工作。凸模在原直线形状下稳定过渡到不稳定,这种过渡压力的数值就称为临界力。 Punch by the axial force, is to maintain a balance in the shape of a straight line, so the destruction of the punch are due to lack of strength caused. In fact, when the punch by the axial pressure is greater than a certain value, the punch becomes curved, in the original shape of the linear balance becomes unstable. Because it can not maintain the balance of the straight shape and can not work properly. Punches in the original linear shape of a stable transition to unstable, the value of this transition pressure is called the critical force.