I want to determine approximate plateau stress from Stress Vs Strain curve (Fig 1) where the stress is not almost constant in plateau region. I have obtained the densification strain using energy efficiency-based approach.
Is it appropriate to use the formula mentioned in figure 2 to find plateau stress.
where, εa is nominal strain . If yes, then what shall I consider the value of εa ?
Or any other alternative ?
Regards,
You may use integral approximation according to formula attached for determination of plateau stress. The alternative formula of more simple linear approximation in the range ecr...ea may be used also. It is interesting to compare the results of both approximations. Best regards
@Serge V. Shik'ko : Thank you for you kind reply. I have calculated the plateau stress using the integral formula provided. But the major concern is what should be the limit for ea. Because, if I count the plateau stress from ecr to ea where ea=ed (densification strain), then plateau stress will be much more than ecr.
Example : ecr is 10 MPa, ea=ed=0.48.Then by integral formula I have plateau stress = 19 MPa which is much higher than ecr
Can such high value be accepted ? Or should there be any limit for ea ?
If it is porous or cellular metal, you could use the definition of plateau stress in ISO 13314:2011 standard (see enclosed abstract). Then at first view your computed plateau stress value = 19 MPa could be OK (strain interval 20-30%). See definition 3.4. And the corresponding plateau end at 24.7 MPa (1.3 x 19 MPa, as indicated in definition 3.5) couldindeed match.
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