1. THE HARDNESS ANALYSIS OF THE IF SHEET STEEL AFTER A PLASTIC DEFORMATION Mihaliková Mária – Ambriško Ľubomír – Pešek Ladislav Mihaliková Mária – Ambriško Ľubomír – Pešek Ladislav Department of Materials Science, Faculty of Metallurgy, Technical University of Košice, Slovak Republic Telč 2009

2. Introduction Behaviour of IF steel has been observed in this contribution. Steels were loaded by static tension by the loading rate 1.3 mm/min. Behaviour of IF steel has been observed in this contribution. Steels were loaded by static tension by the loading rate 1.3 mm/min. Videoextensometry method has been used for scanning of the distribution of deformation nearly before fracture. Videoextensometry method has been used for scanning of the distribution of deformation nearly before fracture.

3. Experimental material For tensile tests were applied specimens from IF cold rolled steel sheets. IF (interstitial free) steel, with thickness 1.8 mm. Microstructure Steel Mechanical properties R p 0.2 [MPa] R m [MPa] A 5 [%] IF18530045

4. Experimental methods CCD camera Computer Specimen Light 1 2 3 4 5 6 7 8 9

5. Principe of UCI V-Vickers diamond R-Resonant rod F-Fixing T-Transmitting

6. Relation between HV1 and y of steel IF 1 2 3 4 5 6 7 8 9

7. Conclusions Using the videoextensometry and hardness HV1 test enables to characterize the relation between the plastics deformation y and hardness. The power relation between the hardness HV1 and longitudal deformation was applied. UCI is practical, portable method appropriate to satisfactory determination of deformation state of materials.

8. Thank you for your attention This study was supported by the Grant Agency of Slovak Republic; grant project VEGA No. 1/4149/07 and APVV No. 0326-07.