0 应力状态的分类 三向（空间）应力状态 (Three-Dimensional State of Stresses xy XZ y ( Three-Dimensional State of Stresses ) 三向（空间）应力状态 x y z  x  y  z  xy yx yz  zy  zx xz 应力状态的分类           = z x z y z yx y yz x xy xz          σ