在整堂课的教学中，刘教师总是让学生带着问题来学习，而问题的设置具有一定的梯度，由浅入深，所提出的问题也很明确Translation The concepts of stress and strain can be illustrated in an elementary way by considering the extension of a prismatic bar. As shown in Fig. 1, a prismatic bar is one that has constant cross section throughout its length and a straight axis. In this illustration the bar is assumed to be loaded at its ends by axial forces P that produce a uniform stretching, or tension, of the bar. 应力和应变的概念可以通过考虑一根矩形梁的拉伸的简单方法来举例说明。如图1所示，这根矩形梁可以看作是由遍
