一、填空题在研究构件强度、刚度、稳定性问题时，为使问题简化，对材料的性质作了三个简化假设：________________________________、________________________________________________和各向同性假设。任意形状的物体在两个力作用下处于平衡，则这个物体被称为________________________。平面一般力系的平衡方程的基本形式：、、。根据工程力学的要求，对变形固体作了三种假设其内容是：、、。拉压杆的轴向拉伸与压缩变形，其轴力的正号规定是：。塑性材料在拉伸试验的过程中，其曲线可分为四个阶段，即：、、、。扭转是轴的主要变形形式，轴上的扭矩可以用截面法来求得，扭矩的符号规定为：。力学将两分为两大类：静定梁和超静定梁。根据约束情况的不同静定梁可分为：、、三种常见形式。图所示的受扭圆轴横截面上最大扭矩________________________________，若其横截面为实心圆，直径为，则最大切应力________________________________。图中的边长为的正方形截面悬臂梁，受均布荷载作用，梁的最大弯矩为________________________________。