Loading rates:
In general, increasing the speed at which a load is applied tends to make the material respond in a more brittle fashion. This is most easily seen in silly putty. Im assuming most of you have been in contact with silly putty at some point. When you pull silly putty really fast, it breaks cleanly. However, if you pull it slowly, it will deform and end up strung out.
This happens to varying degrees in all materials I can think of. Unfortunately I dont have any equations associated with this effect, but ASTM does specify loading (and/or strain) rates when testing materials.
This is a difficult to really change much in the bend test.
Hardness:
In general, hardness increases the yield strength, but significantly reduces the ductility of the material. This means that the material can take less deformation but it takes more force to deform it that far.
So essentially, increased hardness will almost always make the bend test more difficult, but depending on the cross sectional properties it may not be impossible.
I guess this installation didnt have any equations or definite relationships between material properties. Hopefully it gives you at least a vague idea of how these factors affect performance in the bend test.
