Question

Tensile testing

can someone tell me how to calcualte the true strain, engineering strain, true stress and engineering stress of the following data o got from tensile testing machine. I assumed area to be constant during the test

i need to draw the curves of the true and engineeing in excel please

TESTNUM	POINTNUM	TIME	POSIT	FORCE	EXT	Area
5368	1	0.156	-5E-05	347.6111	-0.00138	0.0628
5368	2	0.58	-5E-05	348.3641	0	0.0628
5368	3	0.777	0.0007	363.0201	0.021787	0.0628
5368	4	0.875	0.001375	398.4846	0.041394	0.0628
5368	5	0.975	0.002025	438.6508	0.060276	0.0628
5368	6	1.086	0.002675	477.715	0.079158	0.0628
5368	7	1.175	0.00335	515.8242	0.098766	0.0628
5368	8	1.276	0.004	552.9417	0.117647	0.0628
5368	9	1.374	0.00465	590.1509	0.136529	0.0628
5368	10	1.483	0.0053	625.4869	0.155411	0.0628
5368	11	1.579	0.00595	659.7577	0.174292	0.0628
5368	12	1.678	0.006575	693.257	0.192448	0.0628

Answer 1

Engineering stress: The formula for finding engineering stress = P/A; whrere P is the reading from load dial and A is the initial area. For eg, at time 0.777, the engineering stress = 363.0201/0,0628 = 5780.57

True stress: The formula for finding engineering stress = P/A; whrere P is the reading from load dial and A is the area.at that particular time instant. Since the area is same at all times, Engineering stress = True stress

True strain: The formula for true stain = ln(L2/L1); where L2 is the length at a particular instant of time and L1 length is at the previous instant of time

Engineerig Strain: Engineering Strain is calculated as dL/L1 where L1: initial length of specimen. And final length=L1+dL