The bending test is used for determining the bending ability of material by bending material to specific bending radius or angle. The cross section of testing sample might be any shape such as square, sphere etc.
The bending test is necessary to apply load with stable direction and slowly to prevent side slipping of material. After testing as specification, tester should check cracking at outer surface of testing sample which is received tension stress during testing by using visual check or microscope (not over than 20X, normally use by visual check). In case of testing material has width/thickness ratio greater than 8 times, if we found cracking at testing material edge, we can eliminating this crack and test it again.
Minimum bend radius is minimum radius applied to material without cracking on surface of testing sample. Normally it will be ratio with thickness then bending ability is flavor to present as ratio of thickness i.e. 3t; it means that this material can be bended with minimum bend radius at 3 times of thickness without cracking.
In case of hot rolled strip, bending test will refer to testing standard of each grade which is difference in dimension and rolling direction of sample including bending radius.
Resource: Iron and Steel Institute of Thailand