A cylindrical specimen of a metal alloy is stressed elastically in tension. The original diameter was 8 mm and a force of 15,700 N produces a reduction in diameter of 5x10-3 mm (magnitude). Compute Poisson's ratio for this alloy if its modulus of elasticity is 140 GPa.

Respuesta :

Answer:

The value of poisson's ratio of the material = 0.28

Explanation:

Given data

Force F = 15700 N

Diameter D = 8 mm

Change in diameter ΔD = 0.005 mm

Modulus of elasticity E = 140 × [tex]10^{3}[/tex] M Pa.

Stress induced in the shaft due to applied force

[tex]\sigma = \frac{F}{A}[/tex]

Area  A = [tex]\frac{\pi}{4} d^{2}[/tex]

⇒ A = [tex]\frac{\pi}{4} 8^{2}[/tex] = 50.24 [tex]mm^{2}[/tex]

Now stress [tex]\sigma = \frac{15700}{50.24}[/tex]

⇒ Stress [tex]\sigma[/tex] = 312.5 M pa ------  (1)

Now strain in the element is given by

∈ [tex]= \frac{\sigma}{E}[/tex]

⇒ ∈ = [tex]\frac{312.5}{140000}[/tex]

⇒ Strain ∈ = 2.232 × [tex]10^{-3}[/tex]

We know that poisson's ratio is given by

⇒ [tex]\mu =[/tex] [tex]\frac{\frac{change in diameter}{original diameter} }{strain}[/tex]

Change in diameter ΔD = 0.005 mm

Diameter D = 8 mm

Strain ∈ = 2.232 × [tex]10^{-3}[/tex]

⇒ [tex]\mu = \frac{\frac{0.005}{8} }{0.002232}[/tex]

[tex]\mu =[/tex] 0.28

This is the value of poisson's ratio of the material.