A Study on the Bending Test (1)

Abstract

The authors carried out the bending test of 13 Cr steel with different sizes. The process of the bending test studied was divided into the following four steps:
[] (1) The elastic bending: (2) Inner radius of the specimen contacts with the jig radius: (3) The bending angle moves up to 150°: (4) After 150°, the loading direction changes to right angle to before and bending to 180°: The experimental results showed that the bending rate of angle proportionates with the partial maximum elongation in the second period, and after the 3rd period, theoretically the following equation has been found, de_smax⁄dx=0. Inotherwords, the partial maximum elongation shows to be constant during this step. And furthere testing has been found to be useless.
The critical value of e_s is obtained by the following term, h⁄(r_j+h), where h is half thickness of specimen and r_j is jig’s radius. For this purpose we must use a specimen with suitable thickness and decide the proper length of jig’s radius corresponding to the specimen being hard or soft, and the length of supporting rollers also.