在結構物、机器零件等設計問題中,常常会遇到一些“平板”,像房屋的楼板、輪船的甲板等等都是平板。这种物体的特点是構成物体的三个尺寸——長、寬、高中有一个尺寸(假如是高)比其他二个尺寸要小得很多。固体受到外力的作用的时候,总要發生形狀和体积的变化,这种变化叫做形变。这种外力,我們称它为載荷(或負載)。載荷引起固体变形而在固体的內部發生的附加內力,叫做应力(或胁强)。应力的大小是用截面积除內力来表示的。力学上研 In the design problems of structures, machine parts, etc., there are often “flat panels”, such as the floor of a house, the deck of a ship, and so on. This object is characterized by the three dimensions that make up an object—long, wide, and high school have one size (if high) that is much smaller than the other two sizes. When solids are subjected to external forces, changes in shape and volume always occur. This change is called deformation. This external force, we call it the load (or load). The additional internal forces that occur as a result of the load deforming the solid and occur inside the solid are called stress (or stress). The size of the stress is represented by the internal force divided by the cross-sectional area. Mechanical research