# No increase in temperature during bending?

Good day, I am a mechanical engineering student, we conducted three-point bending test for a metal specimen and I am wondering why the temperature of the specimen did not increase as the UTM certainly did work on the specimen, therefore some thermal energy increase should be present.

This is in comparison when we conducted tensile test to another specimen in which we realized that the metal became appreciably hot.

I think it was because bending involved tension and compression, reasoning that because they are opposite of the other, while tension releases thermal energy because of the pulling away (rupture) of interatomic bonds, compression accepts thermal energy because it needs for the compression of the bonds? Therefore no (or minimal) thermal energy increase could be observed after bending.

I can't research anything related to this phenomena on the internet. (Also we had never conducted yet a compressive test, so I don't know if compressing the metal reduces its temperature). I also know the physics of thermal expansion (metal expands with increase in temperature), I am not just sure if it applies the other way around.

I just want to know if you think my hypothesis is correct, or if not could you provide a link or explanation? Thank You

• How much temperature rise did you expect to see, based on the amount of work done and the mass + specific heat of the sample? Commented May 22, 2016 at 11:17
• I doubt the compression accepted enough (if any) thermal energy to negate the energy from the bending. It is not something I have ever heard of! Can you give some figures? Total mass, dimensions, bending energy input, bending force & distance, thermal conductivity, accuracy of temperature measurement, duration of vending, time between bending and temperature measurement? Commented May 22, 2016 at 11:25
• Length of specimen: 18.2 cm <br/> Weight of specimen: 0.369 kg <br/> Nominal Cross Section Area: 262.16 mm2 <br/> Degree of bend of neutral axis: (from 180) to 9 degrees <br/> Distance between support: 130mm <br/> Punch diameter: 30 mm <br/> Max Bending Load: 28.2016 kN <br/> Bending Stress: 1 530 880 kPa Commented May 22, 2016 at 12:14
• The specimen is reinforcing steel bar Commented May 22, 2016 at 12:20
• I expect to observe a temperature rise like in our experiment in tensile test, as it is the same kind of specimen and they both experience plastic deformation. So I am confused why there is no temperature increase. Commented May 22, 2016 at 12:26