S11.2 Strain Energy 259 work done =x load x extension =5P+pgA的P+pgAd AE P2 2AEdsE = 2E .∴，total strain energy or work done P2 ds+ P sds+ 2AE E 片(p9PAg2as 2E 0 0 P2L PpgL2 (pg)2AL 2AE 2E+ 6E (11.4) The last two terms are therefore the modifying terms to eqn.(11.1)to account for the body-weight effect of the bar. 11.2.Strain energy-shear Consider the elemental bar now subjected to a shear load o at one end causing deformation through the angle y(the shear strain)and a shear deflection as shown in Fg.11.3. ds Fig.11.3.Shear. Strain energy U work done =108=Qyds Now G- shear stress t shear strain y yA y= AG Q2 shear strain energy =x Gx ds =ds$1 1.2 Strain Energy 259 .. work done = 3 x load x extension :. total strain energy or work done L L L -- p2 ds+ jFsds+ {ws2ds 2AE 2E 0 0 0 (1 1.4) PzL PpgL’ + (pg)’AL3 2AE 2E 6E +--- - -- The last two terms are therefore the modifying terms to eqn. (1 1.1) to account for the body-weight effect of the bar. 11.2. Strain energy-shear Consider the elemental bar now subjected to a shear load Q at one end causing deformation through the angle y (the shear strain) and a shear deflection 6, as shown in Fig. 11.3. Now .. tQ Fig. 11.3. Shear. Strain energy U = work done = 3QS = 3Qyds shear stress t Q shear strain y yA G= =-=- Q y=- AG Q shear strain energy = 3Q x - x ds = ds AG 2AG