sw2.2 (10 pts) Estimate the following values using the figure provided based on

Question

sw2.2 (10 pts) Estimate the following values using the figure provided based on a standard uni-axial tensile test. Label the figure accordingly a) Modulus of Elasticity. (3 pts) b) The approximate 0.2% offset yield strength (3 pts) c) The permanent off set if the specimen is loaded to 60 ksi and then allowed to relax. (4 pts) (Hint: what is the ( ksi ) 70 60 50 40 30 20 10 nominal gauge length used for the test?) 0 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.2 0 00025 00050.0075 001 001250.01500175 002 00255025 CEEN3311.XXX EX4/FEX Sum 1 2018 Page 6 of 8

Explanation / Answer

1. Modulus of elasticity:

Modulus of elasticity = stress / strain , for the linear region only and also know as slope of straight line of stress strain curve.

Consider starting triangle portion upto stress 50 ksi,

Height of triangle= stress upto which graph is linear = 50 ksi

Width of triangle = base of triangle upto linear region = 0.005

Modulus of elasticity = 50/0.005

Moduls of elasticity = 10000 ksi

B) 0.2 % yield stress :

To get 0.2% yield stress, draw a line with origin from 0.2% strain (0.002 in/in) and parallel to initial linear straight line until it interests the graph. Then project that Interested point to y axis to get yield stress.

If you draw a line as per above conditions for our case it will intersects the curve near to 50ksi value because with given figure, it will be very difficult to precisely select a point.

Therefore 0.2% yield stress ~50 ksi

C) permanent set:

Assume gauge length as "L"

Strain coresponding to 60 ksi = 0.04

Strain corresponding to yield strength of 50 ksi = 0.005

Permanent set strain = 0.04 - 0.005 = 0.0035

Permanent set= 0.0035 x L

= 0.0035L

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