§12-2杆件变形能计算 轴向拉伸和压缩 1 Pl U=W=P·△=P EA P4 N-l 2EA 2EA P n(x)dx △- 2EA() CLI2TUI§12-2 杆件变形能计算 一、轴向拉伸和压缩 U = W P P l l CL12TU1 =  1 2 P l = 1 2 P Pl EA = = P l EA N l EA 2 2 2 2 U N x EA x x l =  2 2 ( ) ( ) d