扭转 (△qm △ △- 1 ml Tl U7=W=m·△q==m 2 G 2G1 2G/ U T2(x) 2G1(x) CL12TU2二、扭转 U = W    m m CL12TU2 =  1 2 m  = = = 1 2 2 2 2 2 m ml G I m l G I T l G I p p p U T x G I x x p l =  2 2 ( ) ( ) d