2. Tutorial:Engineering metrology Topic: Hardness measuring Prepared by: Ing. Pavel Rožek Projekt Anglicky v odborných předmětech, CZ.1.07/1.3.09/04.0002 je spolufinancován Evropským sociálním fondem a státním rozpočtem České republiky.

3. Hardness measuring

4.  Material hardness is mechanical quality defined as resistance which is put up by material against foreign element penetration.  Main point of method’s 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).

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

6.  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

7.  Made by ČSN 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.

8. 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

9.  Made up to ČSN 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.

10. 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

11.  Made up to ČSN 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.

12. 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

13.  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).

14. 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

15.  BUMBÁLEK, Leoš. Kontrola a měření. 1. Praha: Informatorium, 2009. 205 s. ISBN 978-80-7333-072-9  Moderní strojírenství pro školu i praxi. 55. Praha: EUROPA - SOBOTÁLES cz., 2007. ISBN 978-80-86706-19-1. Translation:  www.seznam.cz www.seznam.cz  www.slovnik.cz www.slovnik.cz  JANATA, Petr. Handy slovník technický anglicko-český a česko-anglický. Plzeň: Nakladatelství Fraus, 2000. ISBN 80-7238-075-3  Lingea LEXIKON 5, Technický slovník anglicko-český a česko-anglický. 2010.