cylindrical specimen of this alloy 32 mm in diameter and 188 mm long is to be pulled in tension. Assume a value of 0.34 for Poisson's ratio. Calculate the stress (in MPa) necessary to cause a 0.0105 mm reduction in diameter.

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Answer:

The answer is below

Explanation:

The poison ratio is given by the formula:

[tex]v=-\frac{\epsilon_x}{\epsilon_z} =-\frac{\epsilon_y}{\epsilon_z} \\\\Where\ \epsilon_y=transverse\ strain, \epsilon_z=longitudinal\ strain,v=poison\ ratio\\ \\The\ transverse\ strain(\epsilon_x)=\epsilon_y=\frac{change\ in\ diameter}{initial\ diameter}=\frac{\Delta d}{d_o} =\frac{-0.0105\ mm}{32\ mm} \\=-0.000328\\\\v=-\frac{\epsilon_x}{\epsilon_z} \\\\\epsilon_z=\frac{-\epsilon_x}{v} =\frac{-(-0.000328)}{0.34}\\ \\\epsilon_z=9.65*10^{-4}[/tex]

We then locate the strain of 9.65 * 10⁻⁴ on the stress-strain curve, this gives a stress of 68.9 MPa

The stress required to cause a reduction of 0.0105mm on the alloy is 68.9MPa

Data Given;

  • d = 32mm
  • l = 188mm
  • v = 0.34
  • Δd = 0.0105mm

Transverse Strain

The transverse strain of the cylindrical alloy is the ratio between the reduction in diameter to the actual diameter

[tex]E^x = \frac{\delta d}{d}\\ E^x = \frac{-0.0105}{32}\\ E^x = -0.00033\\ E^x = -3.3*10^-^4[/tex]

Longitudinal Strain

The longitudinal strain is the ratio between the transverse strain to the Poisson's ratio.

[tex]E^y = \frac{-E^x}{v}\\ E^y = \frac{3.3*10^-^4}{0.34}\\ E^y = 0.00097 = 9.7 *10^-^4[/tex]

Using the strain-stress graph of a cylindrical alloy, we would find the strain of 0.00097 around the stress of 68.9MPa

Learn more on strain-stress here;

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