Metallurgical Principles and Practice of Engineering (PE) Study Guide: Question #46

It Is the Policy of The Minerals, Metals & Materials Society (TMS) to Encourage the Professional Registration of Metallurgical Engineers.
Your facility's metallography laboratory has Rockwell, Brinell, and Vickers hardness testers. There is often confusion among investigators regarding the proper kind of hardness test to choose. You have been asked to present a seminar on hardness testing and the capabilities of each kind of test. This is done in order to obtain maximum value from the testing machines and optimum use of people's time. Your research into the subject shows that it is necessary to carefully choose the kind of hardness test, and indeed, whether anything useful can be obtained from hardness testing. Which of the following statements is most correct?

(A)	Rockwell testing is limited to a very narrow range of materials hardness because the indenter and the applied load are fixed at diamond "Brale" indenter and 30 kg major load.
(B)	A good correlation can be made between Brinell hardness (hardened steel ball indenter and major load of 500 or 300 kg) and percent elongation in a tensile test.
(C)	Surface preparation is unimportant in hardness testing because the indenter will penetrate through the surface layer of the material.
(D)	Thickness of the specimen being tested must be considered when choosing a type of hardness test and the major load to apply.

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