Abstract: | Through this work, it is proposed the study of the increase rate of the crack da/dN, for a solicitation to fatigue through eccentric monoaxial straightening, in a sample made of steel for boilers and recipients mark R 520. There are analyzed variants for the cracking rate: the standardized polynomial method, the method of Paris’ formula, the secant method and the simple polynomial method. The samples have been solicited with the asymmetry coefficient R=0.3, for the following temperatures: 293 K, 253 K and 293 K. The equipment used was a hydraulic installation with one pulsator, with the possibility of regulating the asymmetry coefficient R. For low temperatures was mounted on the machine a frigorific precincts cooled with liquid nitrogen. During the attempt we have noted the variation of the crack’s length ai and the numbers of solicitation cycles Ni with the data obtained and the solicitation tasks we have calculated the stress intensity factor ?K and the tension ? at the top of the crack. With the parameters calculated above we passed to tracing some graphics for the cracking rate in report to SIF ?K, V(?K), the rate in report to the durability N, V(N), respectively, in report to the tension ?, V(?). We have drawn these curbs for the three attempt temperatures. |
