Verification of Osakada’s method to calculate stress-strain curves from upset test load-stroke curves under various work hardening conditions
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Osakada and his coworkers have suggested a method to calculate the true stress—true strain curves from the load—stroke curves obtained in the upset test which is carried out with sticking friction. The friction effect is corrected using the modification factors obtained by the finite element method (FEM). Since Osakada and his coworkers assumed no work hardening, this investigation was carried out to verify this method under various work hardening behaviors using the ALPID FEM code. It is observed that different work hardening behaviors do not affect the modification factors significantly, and thus, only one set of values can be used. A comparison with experimental results obtained with a minimum amount of friction reveals that the stress—strain curves calculated with the modification factors obtained in this investigation agree with experimental results better than those with the values Osakada suggested. Overall, it can be concluded that this modification technique is useful because it enables the analyses of the two aspects of cold forgeability, workability limit and strength, simultaneously in one upset test set-up.
KeywordsEffective Strain Modification Factor Finite Element Method Simulation Slow Strain Rate Average Effective Stress
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