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Lab02_Hardness_Test_DKSinha_ - (a San Francisco State...

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(a) (b) (c) Figure 2 . Hardness test specimens. (Left to right) copper, brass, aluminum, and steel. Use table on the wall to convert from HB to HRB Calculated using equation (1) San Francisco State University School of Engineering ENGR 200: Materials of Engineering Laboratory 2 Material Hardness Testing I. OBJECTIVES The purpose of this experiment is to familiarize the student with performing hardness tests and obtaining the hardness values of several common metals. II. INTRODUCTION Hardness is defined as the      ability of a material to resist plastic deformation     , and is a complex  property related to the strength of interatomic bonding and other variables. The hardness of a  machine or a structural element can be obtained without destroying the element and for this  reason hardness is classified as a non-destructive test.  In general, hardness tests are performed by pressing a hard indenter of known size and geometry  into the surface of the test specimen using a standard load. The depth of the resulting impression  is used to obtain an empirical hardness number. In this experiment, two common methods for  measuring hardness will be used: the Rockwell and the Brinell hardness tests. Test 1. The Rockwell Test : The load and the penetrator used depend on the expected hardness of  the material under investigation. For hard materials, a diamond cone (brale) indenter and a 150 kg  load are used. This combination is defined as the “C” scale (HRC). For metals with moderate  hardness, a hard steel ball (1/16 inch diameter) indenter and 100 kg load are used. This is known  as the “B” scale (HRB).  We will be using Rockwell “B” scale (HRB) for Rockwell hardness
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