A calculation model for a tube-sheet under thermal shock loading with the finite element code ANSYS is established in this paper. A three-dimensional finite element model is established to simulate thermal shock process in order to obtain temperature and stress distributions of the structure. The duration time of the thermal shock is taken as about ten seconds and thermal cycling numbers are more than 1000 times for the whole service life of the structure. In order to capture accurate temperature and stress profile of this structure, thermo-mechanical coupling approach and transient thermal analysis is used. Temperature and stress distribution are obtained under the given thermal boundary conditions at different time points and it is also easy to get the stress amplitude of the other points in this structure between any two time points. According to the numerical results, the stress induced by thermal shock changes with time and its magnitude and amplitude cannot be ignored. Strength and fatigue evaluations are also performed according to ASME VIII-2 to ensure its safety.

In the past, shakedown evaluation was usually based on the elastic method that the sum of the primary and secondary stress should be limited to 3Sm or the simplified elastic-plastic analysis method. The elastic method is just an approximate analysis, and the rigorous evaluation of shakedown normally requires an elastic-plastic analysis. In this paper, using an elastic perfectly plastic material model, the shakedown analysis was performed by a series of elastic-plastic analyses. Taking a shell with a nozzle subjected to parameterized temperature loads as an example, the impact of temperature change on the shakedown load was discussed and the shakedown loads of this structure at different temperature change rates were also obtained. This study can provide helpful references for engineering design.

The thermal load is one of important design condition that should be considered carefully in engineering practice. In most instances, the heat source is located inside the vessel, which causes a temperature gradient along the thickness, especially when the thickness is large. In this case, secondary stress should be considered and thermal ratcheting should be checked. In this paper, a thin-walled ellipsoidal head with heating spiral was studied. In this structure, temperature is uniformly distributed along the thickness but changes alternately between hot and cold along the meridional direction. This has a significant effect not only on the head itself but also on the nozzle. For the nozzle, its elastic support condition has been changed and then its stress distribution will also be changed. In this paper, several cases have been calculated and some laws are established. Finally, some useful conclusions and suggestions are proposed for engineering design.

Thermal load is one of the most important design conditions that should be considered carefully in engineering practice. Most inner-pressure vessels suffer thermo-mechanical ratcheting or unacceptable plastic deformation under cyclic thermal stress produced by inside heat source and pressure-induced primary stress. However, thermal load is also a crucial factor for external-pressure vessels where the failure model of buckling should not be ignored. The effect of thermal load on buckling is not only thermal stress itself but also shape distortion due to thermal load. In some cases, the latter is more important. In this paper, an external-pressure thin-walled ellipsoidal head with heating jackets has been studied. The temperature of this structure is uniformly distributed along the thickness direction but changes alternately between hot and cold along the meridional direction, which will have a significant effect on buckling behavior of this typical structure. Buckling load is sensitive to initial defect and small deformation. Several comparative calculations based on nonlinear buckling analysis have been conducted and some laws are established. Finally, some useful conclusions and suggestions are proposed for engineering design.