During the experiment a constant tensile load was applied tothe sample, as described in Study session 17.1. This caused thesample to extend. You measured the change in length of the sampleover time, which enabled you to calculate the strain.
In Question 2a you are asked to calculate the stress acting onparts of a sample at the beginning and end of an experiment similarto that in Week 17. The load applied in the experiment was 5.1kN.
All your answers to Question 2a should be given to 3significant figures, in appropriate units.
a.
i.To calculate the stress on the sample due to the appliedtensile load you need to know the area over which this force isacting. Using information from Figure 2, show that the relevantcross-sectional area of the sample within the gauge length at thestart of the experiment is 50.3 mm2.
ii.Using the value for the cross-sectional area from Question2a(i), calculate the stress experienced by the test specimen withinits gauge length, at the start of the test.
iii.The applied load remains constant throughout the test. Atthe end of the test, the diameter of the test specimen shown inFigure 1 at the location where necking occurred was measured andthe cross-sectional area calculated to be 16.0 mm2. Based on thereduced cross-sectional area at the necking location, calculate thestress in the neck at the point of failure.
iv.Compare the value of stress at the beginning of the test(your answer to Question 2a(ii)) with the stress value at the pointof failure (your answer to Question 2a(iii)) and use these valuesto calculate the percentage increase in the value of stress due to‘necking’ of the test specimen from the start of the test to thepoint of failure
