A cylindrical specimen of some metal alloy having an elastic modulus of 129 GPa and an original cross-sectional diameter of 4.4 mm will experience only elastic deformation when a tensile load of 1570 N is applied. Calculate the maximum length of the specimen before deformation if the maximum allowable elongation is 0.48 mm.

Respuesta :

Explanation:

The cross-sectional area of the specimen is calculated as follows.

         [tex]A_{o} = \frac{pi}{4} d^{2}[/tex]

                     = [tex]\frac{3.14}{4} \times (\frac{4.4}{1000})^{2}[/tex]

                     = [tex]1.5197 \times 10^{-5} m^{2}[/tex]

Equation of stress is as follows.

              [tex]\sigma = \frac{F}{A_{o}}[/tex]

And, the equation of strain is as follows.

             [tex]\epsilon = \frac{\Delta l}{l_{o}}[/tex]

Hence, the Hook's law is as follows.

              E = [tex]\frac{\sigma}{\epsilon}[/tex]

       E = [tex]\frac{\frac{F}{A_{o}}}{\frac{\Delta l}{l_{o}}}[/tex]

          = [tex]\frac{F \times l_{o}}{A_{o} \times \Delta l}[/tex]

or,    [tex]l_{o} = \frac{E \times \Delta l \times A_{o}}{F}[/tex]          

                   = [tex]\frac{129 \times 10^{9} \times \frac{0.48}{1000} \times 1.662 \times 10^{-5}}{1570}[/tex]

                  = 0.6554 m

or,         [tex]l_{o}[/tex] = 655.4 mm

Thus, we can conclude that the maximum length of the specimen before deformation if the maximum allowable elongation is 0.48 mm is 655.4 mm.

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