Direct tension indicators are sometimes used instead of torque wrenches to ensure that a bolt has a prescribed tension when used for connections. If a nut on the bolt is tightened so that the six 3 - mm high heads of the indicator are strained 0.1 mm/mm

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Complete Question

The complete question is shown on the uploaded image

Answer:

The tension on the shank is  [tex]T =8391.6 N[/tex]

Explanation:

From the question we are told that

       The strain on the strain on the head is [tex]\Delta l = 0.1 mm/mm = \frac{0.1}{1000} = 0.1 *10^{-3} m/m[/tex]

         The contact area is  [tex]A = 2.8 mm^2 = 2.8* (\frac{1}{1000} )^2 = 2.8*10^{-6} m^2[/tex]  

Looking at the first diagram

           At  600 MPa of stress

               The strain is  [tex]0.3mm/mm[/tex]

          At   450 MPa of stress

                 The strain is   [tex]0.0015 mm/mm[/tex]

 To find the stress at  [tex]\Delta l[/tex] we use the interpolation method

            [tex]\frac{\sigma_{\Delta l} - \sigma_{0.0015} }{ \sigma _ {0.3} - \sigma_{0.0015} } = \frac{e_{\Delta l } - e_{0.0015}}{e_{0.3} - e_{ 0.0015}}[/tex]

Substituting values

              [tex]\frac{\sigma _{\Delta l} - 450}{600 - 450} = \frac{0.1 -0.0015}{0.3 - 0.0015}[/tex]

            [tex]\sigma _{\Delta l} -450 = 49.50[/tex]

             [tex]\sigma _{\Delta l} = 499.50 MPa[/tex]

Generally the force on each head is mathematically represented as

              [tex]F = \sigma_{\Delta l} * A[/tex]

Substituting values

             [tex]F = 499.50*10^{6} * 2.8*10^{-6}[/tex]

                [tex]=1398.6N[/tex]

Now the tension on the bolt shank is as a result of the force on the 6 head which is mathematically evaluated as

              [tex]T = 6 * F[/tex]

                  [tex]= 6* 1398.6[/tex]

              [tex]T =8391.6 N[/tex]

                 

     

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