A strip of chicken skin was excised for mechanical testing in tension. The initial dimensions of the rectangular specimen were 3
0 mm long and 15 mm wide, with an average thickness of 3 mm. The mechanical testing was conducted at a rate of 5 mm/sec. The following data were obtained:a. Calculate the engineering stresses and strains from the information given and plot the engineering stress-strain curve. Assume that 5 mm of the specimen length is clamped by the testing grips at each end, such that the initial gauge length of the specimen is 20 mm.b. It was found that immediately before the last data point, the average width of the sample was 8 mm and the average thickness of the samples was 0.75 mm. considering this information, determine the true stress and true strain of the sample at the last data point.c. Compare the true stress and strain values for the final data point with the engineering stress and strain values for the final data point.
1 answer:
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Answer:
The principal stresses are σp1 = 27 ksi, σp2 = -37 ksi and the shear stress is zero
Explanation:
The expression for the maximum shear stress is given:
Where
σx = stress in vertical plane = 20 ksi
σy = stress in horizontal plane = -30 ksi
τM = 32 ksi
Replacing:
Solving for τxy:
τxy = ±19.98 ksi
The principal stress is:
Where
σp1 = 20 ksi
σp2 = -30 ksi
(equation 1)
equation 2
Solving both equations:
σp1 = 27 ksi
σp2 = -37 ksi
The shear stress on the vertical plane is zero