2.65 In a standard tensile test a steel rod of 22-mm diameter is subjected to a tension force of 75 kN. Knowing that n 5 0.30 and E 5 200 GPa, determine (a) the elongation of the rod in a 200-mm gage length, (b) the change in diameter of the rod.

Respuesta :

To solve this problem it is necessary to apply the concepts related to uniaxial deflection for which the training variable is applied, determined as

[tex]\delta = \frac{Pl}{AE}[/tex]

Where,

P = Tensile Force

L= Length

A = Cross sectional Area

E = Young's modulus

PART A) The elongation of the bar in a length of 200 mm caliber, could be determined through the previous equation, then

[tex]\delta = \frac{Pl}{AE}[/tex]

[tex]\delta = \frac{(75*10^3)(200)}{(\pi/4*22^2)(200*10^3)}[/tex]

[tex]\delta = 0.1973mm[/tex]

Therefore the elongaton of the rod in a 200mm gage length is [tex]0.1973mm[/tex]

PART B) To know the change in the diameter, we apply the similar ratio of the change in length for which,

[tex]\upsilon = \frac{l_{a}}{l_{s}}[/tex]

Where,

[tex]\upsilon =[/tex]Poission's ratio

[tex]l_{a}[/tex]= Lateral strain

[tex]l_{s}[/tex]= Linear strain

[tex]\upsilon = \frac{\delta/d}{\delta/l}[/tex]

[tex]0.3 = \frac{\delta/22}{0.1973/200}[/tex]

[tex]0.3(\frac{0.1973}{200}) = \frac{\delta}{22}[/tex]

[tex]\delta = 6.5109*10^{-3}mm[/tex]

Therefore the change in diameter of the rod is [tex]6.5109*10^{-3}mm[/tex]