While performing Rockwell hardness tests (HRC scale) on a steel rod, I noticed that the diamond indenter caused the surface of the rod to slightly bend downward during the test; however, this bending was less prominent when I raised the sample stage such that the rod firmly pressed against the indenter head; this is a cone-shaped chamber with a hole in the middle, from which the indenter goes in and out.
Through many tests, it has become evident that there is greater scatter when there is visible bending of the rod, but I haven't been able to identify the relationship between the degree of bending and measured hardness.
EDIT: I am already aware that bar deflection will scatter results. What I am trying to understand is how it does so. Looking at it from a logical standpoint, if the bar bends away from the indenter, this will trick the hardness tester into thinking the indenter penetrated a deeper distance, registering the measured hardness as systematically lower; however, this is not necessarily the case.
Thank you!
The bending during hardness may absolutely affect the hardness value and you have to use a wedge that the rod would be fixed and avoid bending of the rod.
And if the scatters has a usual trend you can calculate the deviation and modify your measurements by the calculation and it is clear that by increasing the distance between the fixtures that have fasten the rod would cause more bending in the rod and more scatter in the hardness measurements, so you can try to make relation between hardness scatter and distance between the fixtures that fastens the rod.
the sample needs to be supported during the measurement to avod deflection.
To avoid the bending of bar. It is necessary use Macro Vickers test.
- Badges
- Science topic