thermal stress analysis using finite element method in area

ACTA TECHNICA CORVINIENSIS – BULLETIN of ENGINEERINGIn Figure 5 we gave the ensemble of the rollcross section, as well as the magnitudes of theVon Mises strains for the following knots(schematically pointed out on the surface of theupper roll): 35126, 35129, 35132, 35135, 35138,35141, 35144, 35147, 35150, 35153 and 35156.The diagram shows a decrease in the thermalstrains away from the rolling area, knot 35126having a Von Mises strain of 930.77N/mm 2 andknot 35156 of about 246 N/mm 2 . In this case, thecalculated length is 185.1947mm.Fig. 7. The variation of Sigma Von Mises strainsSimilarly, in Figure 6 we gave the ensemble ofthe roll cross section, as well as the magnitudesof the Von Mises strains for the following knots(schematically pointed out on the surface of theupper roll): 4277, 4281, 4285, 4289, 4293, 4297,4301, 4305, 4309, 4313, 4317 and 4321. In theplan given in Figure 6 one can notice a decreasein the thermal strain away from the rolling area.Thus, for knot 4277 Von Mises strain is of902,51N/mm 2 and for knot 4321 of 173.26N/mm 2(in this case, the calculated length is 185.1947mm). In Figure 7 we gave the ensemble of theroll cross section, as well as the magnitudes ofthe Von Mises strains for the following knots(schematically pointed out on the surface of theupper roll): 4423, 4427, 4431, 4435, 4439, 4443,4447, 4451, 4455, 4459, 4463 and 4467. Figure 7shows that for knot 4467 Von Mises strain is of822.58 N/mm 2 and for knot 4423 of 99.203 N/mm 2(the calculated length is 185.1947 mm).CONCLUSIONAs a result of simulating the rolling process bymeans of the finite element method in view ofquantitatively and qualitatively determiningthermal strains, we came to the followingconclusions:• thermal strains are the basic cause of fissuringthe rolling surface of rolls as a result of thermalfatigue, caused by the high values in the areasneighboring the contact area with theincandescent semi-finished part; the graphsshow that the values of the thermal strains inthe area under consideration rank within121,73 and 930.77 N/mm 2 for the upper rolland 99.303 and 902.51 N/mm 2 for the lowerroll;• thermal strains have significantly higher valuesas compared to the mechanical ones and actat relatively short intervals of time (withinfractions of a second);• the rolling rolls break during the rollingprocess because of thermal fatigue;• a most precise knowledge of the character ofthe strains generated by the complex stressesthe hot rolling rolls undergo, allows thedetermination of the duration in exploitationunder safe conditions, by their comparison tocertain limit values imposed from the verybeginning;• strains in the rolling rolls have a cyclicalcharacter and the strain state is mainly theresult of the action of the fields of symmetricaland asymmetrical temperatures that causethermal fatigue on their surface and superficiallayer.Engineering is concerned with the design of asolution to a practical problem. A scientist mayask why a problem arises, and proceed toresearch the answer to the question or actuallysolve the problem in his first try, perhapscreating a mathematical model of hisobservations. By contrast, engineers want toknow how to solve a problem, and how toimplement that solution. In other words,scientists attempt to explain phenomena,682010/Fascicule 1/January‐March/Tome III