I tested a 0.55% Carbon steel in UTM. The Yield strength is 409.8 MPa. THe machine gave me a load (N) vs Displacement (mm) curve. Gauge length is 50 mm. Displacement at Yield limit is 5 mm. Using elastic limit formula for Young's modulus , I calculated as (409.8/ 0.1) = 4098 MPa. Young's modulus is 4.098 GPa which is very less compared to 210 GPa we follow for any calculations. So help me to predict and calculate the Young's modulus correctly.
Dear Pradeep Samiappan,
I believe that you confused with displacement and strain. During monotonic tensile test, we put a mechanical extensometer on the gauge length region. then, from computer output, we obtain some sets of data: grip displacement, force, strain, time. Then, true strain and true stress can be obtained. you mentioned, YS=409.8MPa (0.2% offset strain + slope E0). No problem with that. E=YS/(strain@YS-0.2%). The question is, how do you obtain 0.1 in the equation? that is a wrong number. You need check it again. Hope it helps.
You can also use the impulse excitation technique (IET) to get the dynamic elastic properties nondestructively. The technique is described in several ASTM standards such as E1876 and C1259. Basically one excites a test piece mechanically by tapping it with a small hammer. The resulting natural vibrations are then used along with the size, shape and mass/density of the sample to obtain the Young's modulus, shear modulus and Poisson's ratio. My company has a commercial instrument also. Contact me if you are interested <firstname.lastname@example.org>.
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