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Hardness Testing of Materials

Hardness Testing of Materials. Elizabeth Merten University of Washington, Seattle Department of Materials Science & Engineering. Key Concepts. Hardness is measurement of a material’s ability to withstand permanent deformation under an applied (known) force.

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Hardness Testing of Materials

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  1. Hardness Testing of Materials Elizabeth Merten University of Washington, Seattle Department of Materials Science & Engineering

  2. Key Concepts • Hardness is measurement of a material’s ability to withstand permanent deformation under an applied (known) force. • It’s important to have standardized techniques in measuring a materials hardness in order to obtain accurate measurements for comparison • Three typical hardness testers • Brinell • Rockwell • Vickers

  3. Typical Machines and Indentors Coarse Focus/Positioning Knob Eye Piece Fine Focus Horizontal Site Translator Indenter holder Platform/Stage Indent Button Dial Face Indenter Anvil/Platform Wheel Knurled Collar Crank Trip Lever Rockwell Hardness Tester Vickers Hardness Tester wilsoninstruments.com Typical Hardness Indenters

  4. Experimental Set-up • Carefully center sample onto the platform* • Slowly adjust the machine so that the indenter is in contact with the sample • Apply the load by using the trip lever • Record measurement on dial indicator • Be sure to take three hardness measurements on different locations on the sample and calculate the average • Remove the load and the sample • Rotate samples among groups and compare measurement values *Samples should be no less than ¼ inch in thickness for accurate measurements. (If the sample is too thin the indenter could penetrate through the sample possibly damaging the machine)

  5. Example of Indentation http://www.nhml.com/resources/2002/7/1/hardness-testing Vickers hardness testing on a brass sample* http://bruce.cs.cf.ac.uk/bruce/LVM/LA%20Method%20117/LA_117 Hardness values are obtained through the size and shape of the indentation And varies from each method

  6. Discussion & Questions • What if any differences in measurements were noted and what are the possible reasons they differed from one another? • Why is it important to have a standard way of measuring these samples? • Were the measurements what you expected to be? Why or Why not?

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