Rockwell, Vickers, or Brinell are some of the methods of testing. Of these tests, Rockwell is the one most frequently used. The basic principle used in the Rockwell test is that a hard material can penetrate a softer one. We then measure the amount of penetration and compare it to a scale. .
INTRODUCTION.
There are several tests to determine hardness. Rockwell is one of them. It is also possible to estimate other mechanical properties from hardness data. This report contains the results of an experiment to determine the Rockwell hardness values of 2 materials and calculation of another important material property which is called ultimate tensile strength. Procedures for the experiment, analysis of those results and discussion about three main types of hardness tests are also included.
THEORY.
When forces are applied to materials, they deform in reaction to those forces. The magnitude of the deformation for a constant force depends on the geometry of the materials. Likewise, the magnitude of the force required to cause a given deformation, depends on the geometry of the material. For these reasons, engineers define stress and strain. Stress (engineering definition) is given by: [1].
Equation 1 o = F A0.
Defined in this manner, the stress can be thought of as a normalized force. Strain (engineering definition) is given by: [1].
Equation 2 å = ∆l l0.
The strain can be thought of as a normalized deformation. While the relationship between the force and deformation depends on the geometry of the material, the relationship between the stress and strain is geometry independent. The relationship between stress and strain is given by a simplified form of Hooke's Law: [1].
Equation 3 oUTS = E å.
Deformation in which stress and strain are proportional is called elastic deformation.
