For a tensile test, it can be demonstrated that necking begins when dσTdεT=σT. Using Equation σT=K(εT)n, determine an expression for the value of true strain at this onset of necking.

Complete Question

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The value of the true strain at the onset of the necking is proved as,

Explanation:

From the question we see that necking begins when

Now we are told that

So substituting this into equation 1

But  we are told in the question that   So,

Dividing both sides with

  We have

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