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Tutorial:Engineering metrology Topic: Hardness measuring Prepared by: Ing. Pavel Roek Projekt Anglicky v odbornch pedmtech, CZ.1.07/1.3.09/04.0002 je spolufinancovn Evropskm socilnm fondem a sttnm rozpotem esk republiky.

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Hardness measuring

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Material hardness is mechanical quality defined as resistance which is put up by material against foreign element penetration. Main point of methods hardness measuring is based on pressing a small body (indenter) into tested material surface by specific force in defined conditions. Trace size is hardness criterion which results by suitably shaped body pressing (small ball, cone, pyramid) of hard enough material (quenched steel, sintered carbide, diamond).

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Hardness tests divide into: scratch penetrating reflective Up to loading force: Static Dynamic

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They are the most common and the most famous. Indentation is made by slow pressing of penetrating body continuously with increasing force vertically to tested surface. Basic tests are: Brinell Rockwell Vickers

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Made by SN EN ISO 6506 standard. Measuring made on Brinell durometer. Steel quenched ball with diameter D is pressed into tested material by force F. Indentation diameter is measured in 2 perpendicular directions. Brinell tests are suitable only for hardness testing of medium hard and light materials.

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Marking Hardness up to Brinell is marked by measured value and by H letters at standard force and ball size H. Third letter marks ball material, HBS marks Brinell test with steel ball and HBW with tungsten ball. 228 HBW 2,5/187,5/30 228 -Hardness value HBW -Brinell and ball material 2,5ball diameter in mm 187,5force in kp 187,5 x 9,81 = 1839 N 30exposure time in seconds

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Made up to SN EN ISO 6507 standard. Measuring made on Vickers durometer. Regular diamond four-walled pyramid is pressed with apex angle 136. Hardness is determined after measuring of mean length of both diagonal indentation. Vickers hardness tests are used for soft and hard materials of the same tested body.

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Marking Hardness up to Vickers is marked by numeral hardness value, abbreviation HV, by testing force ratio value and force 9,81 N and by exposure force time in seconds. 210 HV/50/30 210 hardness value HV tests up to Vickers 50 testing force F = 50 x 9,81 N = 490,3 N 30 exposure force time in seconds

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Made up to SN EN ISO 6508 standard. Made on Rockwell durometer. Penetrating body is diamond cone with apex angle 120 or quenched steel ball with 1/16 or 1/8 diameter. Indentation depth reached by penetrating body pressing is measured in defined conditions.

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Marking Hardness up to Rockwell is marked by measured value, by letters HR and by measuring scale letter. Diamond cone with apex angle 120 is used to hardness measuring of hard materials (e.g. At HRB and HRA process). Quenched steel ball with 1,59 mm or 3,175 mm diameter is used to measuring soft materials (e.g. at HRB and HRF process). 58 HRC 56 hardness value HRC Rockwell test C

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Used to hardness testing of big components or difficult to reach components spaces. Manual durometer is pressed to material and it is switched on by button. Measured hardness value is displayed. Ultrasound durometer evaluates reflected ultrasound signal and it determines material hardness by sound decay (hard material absorbs little energy). Reflective durometer evaluates reflected steel ball speed (hard material absorbs little energy).

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What materials are appropriate to be measured by Brinell or Vickers methods? Question Question 2: Explain the example of Vickers hardness designation: 220HV/50/30

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BUMBLEK, Leo. Kontrola a men. 1. Praha: Informatorium, 2009. 205 s. ISBN 978-80-7333-072-9 Modern strojrenstv pro kolu i praxi. 55. Praha: EUROPA - SOBOTLES cz., 2007. ISBN 978-80-86706-19-1. Translation: www.seznam.cz www.seznam.cz www.slovnik.cz www.slovnik.cz JANATA, Petr. Handy slovnk technick anglicko-esk a esko-anglick. Plze: Nakladatelstv Fraus, 2000. ISBN 80-7238-075-3 Lingea LEXIKON 5, Technick slovnk anglicko-esk a esko-anglick. 2010.