圆轴扭转时斜截面的应力° T A dA cos a dasin a T F.=0 证1a)osa=0 T o, dA+(ddaC a s ∑F;=0 t f t,dA-dA yos af ce eos een a)sin a=0T T 圆轴扭转时斜截面的应力 A τ τ τ A e τ f dAsin dAcos  dA   x n     e f  F = 0     dA+ (dAcos)sin  + (dAsin )cos = 0 F = 0   dA−(dAcos)cos + (dAsin )sin  = 0   = − sin 2   = cos2