The R F first order second moment method will produce more error for calculating the reliability of welded engineering pipe structures when the failure function is seriously nonlinear and the random variables don...The R F first order second moment method will produce more error for calculating the reliability of welded engineering pipe structures when the failure function is seriously nonlinear and the random variables don′t serve as normal distribution. In order to increase the computing accuracy of reliability, an improved FOSM method is used for calculating the failure probability of welded pipes with flaws in this paper. Because of solving the problems of the linear expansion of failure function at the failure point and constructing equivalent normal variables, the new algorithm can greatly improve the calculating accuracy of probability of the welded pipes with cracks. The examples show that this method is simple, efficient and accurate for reliability safety assessment of the welded pipes with cracks. It can save more time than the Monte Carlo method does, so that the improved FOSM method is recommended for engineering reliability safety assessment of the welded pipes with flaws.展开更多
Secondary flow effects were discussed in numerous papers at the past ISAIF Symposia, mainly in connection with turbine or compressor cascades. This paper will complement these papers by looking at the problem from the...Secondary flow effects were discussed in numerous papers at the past ISAIF Symposia, mainly in connection with turbine or compressor cascades. This paper will complement these papers by looking at the problem from the channel (or blade passages) geometry point of view. If we describe as secondary flows any flows in planes perpendicular to the main flow direction, then there are at least three kinds of secondary flows in a typical turbine rotor cascade:-secondary flows of the 1st kind, generated by centrifugal forces in closed curved channels,-secondary flows of the 2nd kind, generated by interacting boundary layers, mainly in corners (this will include even the horseshoe vortices),-secondary flows due to mass inflow through the tip clearance.Quite often all the secondary flow vortices merge downstream into a passage vortex with a non-negligible contribution to the channel (cascade) losses, and it is worth investigating the individual contributions to these losses to take them into account in the design procedure.展开更多
文摘The R F first order second moment method will produce more error for calculating the reliability of welded engineering pipe structures when the failure function is seriously nonlinear and the random variables don′t serve as normal distribution. In order to increase the computing accuracy of reliability, an improved FOSM method is used for calculating the failure probability of welded pipes with flaws in this paper. Because of solving the problems of the linear expansion of failure function at the failure point and constructing equivalent normal variables, the new algorithm can greatly improve the calculating accuracy of probability of the welded pipes with cracks. The examples show that this method is simple, efficient and accurate for reliability safety assessment of the welded pipes with cracks. It can save more time than the Monte Carlo method does, so that the improved FOSM method is recommended for engineering reliability safety assessment of the welded pipes with flaws.
文摘Secondary flow effects were discussed in numerous papers at the past ISAIF Symposia, mainly in connection with turbine or compressor cascades. This paper will complement these papers by looking at the problem from the channel (or blade passages) geometry point of view. If we describe as secondary flows any flows in planes perpendicular to the main flow direction, then there are at least three kinds of secondary flows in a typical turbine rotor cascade:-secondary flows of the 1st kind, generated by centrifugal forces in closed curved channels,-secondary flows of the 2nd kind, generated by interacting boundary layers, mainly in corners (this will include even the horseshoe vortices),-secondary flows due to mass inflow through the tip clearance.Quite often all the secondary flow vortices merge downstream into a passage vortex with a non-negligible contribution to the channel (cascade) losses, and it is worth investigating the individual contributions to these losses to take them into account in the design procedure.
