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GATE 2017 ME (ME2) – Question 60

Casting, Forming and Joining Processes · Casting: patterns, moulds, cores, solidification, riser and gating design, defects · 2 marks · Multiple choice

A 20 mm rod is stretched to 40 mm, then compressed to 10 mm. With tensile longitudinal strain positive and compressive strain negative, its total true strain is ______.

  1. −0.5
  2. −0.69
  3. −0.75
  4. −1.0

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Show answer and explanation

Correct answer: (B) −0.69

Explanation

True strains add logarithmically: ln(40/20)+ln(10/40)=ln(10/20)=ln0.5=−0.69315. Therefore **−0.69, B**. The result depends only on final/original length; adding engineering strains from successive reference lengths would be incorrect.