A New Method for Correcting the Stress-Strain Curves after Bulging in Metals

Document Type : Original Research Paper


1 Mechanical Engineering Department, Hamedan Branch, Islamic Azad University, Hamedan, Iran.

2 Department of Computer Science, South Tehran Branch, Islamic Azad University, Tehran, Iran.


True stress-strain curve has a basic role in the analysis of deformation in theoretical plasticity and numerical simulations. Because of the triaxial state of stresses in the necking or bulging zones, in tension and the compression tests respectively, the true stress-strain curves obtained from relationsare no longer valid and must be corrected. Various correction techniques have been proposed and can be found in literatures. In this study, a new semi-analytical approach 
for correction of the stress-strain curve in compression test for circular cross-section specimens was introduced and a relation for the correction factor was derived based on the theory of plasticity. This relation requires only a few experimental surface strain measurements which can easily be done using an image processing technique. The correction factor formula was obtained in terms of the initial radius of specimen, the bulge radius, and the surface strain on the bulge surface. The proposed approach in this study was compared with the results of the numerical simulations. Simulation was used to correct the stress-strain curve based on the optimization method with comparing the bulging profile of tested samples and ones simulated by using genetic algorithm. 


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