A steel bar having (45 mm x 45 mm) c/s and 5m long is subjected to an axial pull of 170 kN. Find the strain energy stored in the bar. Also, determine the extension of the bar. Take E=200GPa

Data:

Area of c/s=$A=45*45$ $mm^2$ $P=170KN$

$L=5m, E=200 GPa=200*10^3 N/mm^2, P=170*10^3 N$

L=5000mm

$Stress=p=\frac{P}{A}=\frac{170*10^3}{45*45}=83.95 N/mm^2$

Strain energy:

$U=\frac{p^2}{2E}*AL=\frac{53.95^2}{2*200*10^3}*(45*45)*5000$

$U=178.39*10^3 Nmm$

and Extension of bar=$\delta L=\frac{p*L}{E}=\frac{83.95*5000}{200*1000}$

$\delta l=2.098mm$