ENERGYMETHOD 2. Calculation of the strain energy of rods in torsion M(x) UEL 2GI dx or U m4 2G:/ i P Density of the strain energy. =ty 2 3. Calculation of strain energy of rods in bending M2(x) M-L edx or U=∑ 丿L2EⅠ 2E11 Density of the strain energy: u=OE2. Calculation of the strain energy of rods in torsion：  = L P n x GI M x U d 2 ( ) 2 = = n i i Pi ni i G I M L U 1 2 2  2 1 u = 3. Calculation of strain energy of rods in bending：  = L x EI M x U d 2 ( ) 2 = = n i i i i i E I M L U 1 2 2  2 1 u = or Density of the strain energy: or Density of the strain energy: