engleski

Flow Stress Curves Using Modified Bulging Test

In this study the original method has been derived from well known hydraulic bulging test, with a purpose of recording the true stress – strain curves. New method allows more accurate determination of membrane stress in the deforming material. Assumption on the bulk geometry is no longer needed since modification, using sphere as an obstacle, determines the radius of curvature needed in acquisition of membrane stress. Performing modified hydraulic bulging upon just one test specimen yields three points of stress-strain curve. Two different sheet thickness and two different sphere diameters have been researched in attempt to establish whether the assumption of membrane stress can be somewhat neglected. The modified method has proved to be adequate for checking the numerical model, because it enables direct experimental measurement of the true stresses in the material, which cannot be obtained when classical hydraulic bulging test is performed.

modified hydraulic bulging ; hydroforming ; flow curves ; FE simulation

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