True Stress - True Strain curve obtained from Uni-axial Tensile Testing of processed aluminium at strain rate 0.001/s is showing decreasing tendency after reaching the fracture point which is not commonly seen. Can possible dynamic recrystallization associated with the processing be the reason behind this?
Hi Akash!
This is due to the formation of the "neck" as a result of plastic deformation.
This may not be a property of the material, but a property of the sample as a construction.
In addition, micropores and microcracks in the neck can be formed.
Best regards,
Valery A.
This part of the tensile stress-strain plot is not concerned with the test result. It often happens with the ductile materials having good flowability with predomination over the crack propagation phenomenon of ductile fracture mechanism. Due to this the two parts of the test specimen do not get separated instantaneously after the basic fracture, as it happens with the material showing brittle nature of fracture, and maintain some fibrous link. Thus the specimen carriers some diminishing mode of stress till the final separation under tensile loading occurs.
This type of graph may be due to
1. Inherent discontinuities in the specimen
2. Instantaneous cross sectional area is incorrect
3. Load may not be true
4. Calculation or malfunction of testing Machine or unsymmetrical specimen
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