Issue 37

D. Angelova et alii, Frattura ed Integrità Strutturale, 37 (2016) 265-271; DOI: 10.3221/IGF-ESIS.37.35 270 Figure 5 : Energy-Stress-Elongation Constructions-Space MVZQQ 1 M 1 V 1 Z 1 , expressing mechanical behaviour, including plasticity, of 30 mm plates/sheets C ONCLUSION he technological process of obtaining hot-rolled steel plates/sheets of steel S355J2 + N has been investigated aiming at improving mechanical characteristics of the final product. Two different regimes of normalization rolling have been studied (carrying out 20 experiments per regime) – the basic Regime A and a newly designed Regime B (including automatic application optimization procedure) – and Regime B is found and proved to be the more efficient one. Using standard test data characterizing mechanical (tensile strength, yield strength) and plastic (elongation) behaviour of the final product, as well as impact energy providing information about impact strength, some Energy-Stress and Energy- Stress-Elongation Constructions-Spaces have been built. These spaces can be used as an instrument for general evaluation of the applied rolling technology and for prediction of steel-sheet mechanical behaviour under exploitation conditions. Transition from one space to the other can be done through a specific stress-elongation area, including the elongation after fracture. A CKNOWLEDGEMENTS his paper has been produced with the financial assistance of the European Social Fund, projects number BG051PO001-3.3.06-0014 and BG051PO001-3.3.06-0038. The authors are responsible for the content of this material, and under no circumstances can be considered as an official position of the European Union and the Ministry of Education and Science of Bulgaria. R EFERENCES [1] Dieter, E. G., Mechanical Metallurgy, McGraw-Hill Book Company (1988). [2] Angelova, D., Kolarov, D., Philipov, К. , Yordanova, R., Metal Science and Metal Forming Handbook, Part 5, Sofia, Bulgaria: Academic publishing house “М. Drinov”, (2009) (in Bulgarian) T T