A cylindrical bar of steel 10.1 mm (0.3976 in.) in diameter is to be deformed elastically by application of a force along the bar axis. Determine the force that will produce an elastic reduction of 2.7 ×10-3 mm (1.063 ×10-4 in.) in the diameter. For steel, values for the elastic modulus (E) and Poisson's ratio (ν) are, respectively, 207 GPa and 0.30.

Respuesta :

Answer:

14778.29 N

Explanation:

Diameter, d=10.1mm= [tex]10.1*10^{-3}m[/tex]

Since stress, [tex]\sigma= \frac {F}{A}[/tex] where F is force, A is area and since specimen is cylindrical,  

A= [tex]\pi *(d/2)^{2}[/tex]  Therefore, [tex]\sigma= \frac {F}{\pi*(0.5d)^{2}}[/tex]

Also strain [tex]\epsilon= \frac { \triangle L}{L}[/tex] where L is length

Poison’s ratio,v is the ratio of lateral strain to longitudinal strain hence

V= [tex]-\frac {\epsilon_{x}}{\epsilon_{z}}= \frac {\triangle dl_{o}}{d \triangle l}[/tex]

From Hooke’s law, [tex]\sigma=E \epsilon_{z}[/tex]

Conclusively, [tex]E* \epsilon_{z}=E* \frac {- \epsilon_{x}}{v}=\frac {F}{\pi*(0.5d)^{2}}[/tex]

[tex]\frac {4F}{ \pi *d^{2}}=- \frac {E \triangle d}{vd}[/tex]

F=[tex]- \frac {\pi *Ed \triangle d}{4v}[/tex]

F= [tex]- \frac {\pi *207*10^{9} *10.1*10^{-3}* (-2.7*10^{-6})}{4*0.3}[/tex]= 14778.29N

Therefore, required force F is 14778.29 N