Thermal stress analysis for fatigue damage evaluation at a mixing tee

Abstract Fatigue cracks have been found at mixing tees where fluids of different temperature flow in. In this study, the thermal stress at a mixing tee was calculated by the finite element method using temperature transients obtained by a fluid dynamics simulation. The simulation target was an experiment for a mixing tee, in which cold water flowed into the main pipe from a branch pipe. The cold water flowed along the main pipe wall and caused a cold spot, at which the membrane stress was relatively large. Based on the evaluated thermal stress, the magnitude of the fatigue damage was assessed according to the linear damage accumulation rule and the rain-flow procedure. Precise distributions of the thermal stress and fatigue damage could be identified. Relatively large axial stress occurred downstream from the branch pipe due to the cold spot. The variation ranges of thermal stress and fatigue damage became large near the position 20° from the symmetry line in the circumferential direction. The position of the cold spot changed slowly in the circumferential direction, and this was the main cause of the fatigue damage. The fatigue damage was investigated for various differences in the temperature between the main and branch pipes. Since the magnitude of accumulated damage increased abruptly when the temperature difference exceeded the value corresponding to the fatigue limit, it was suggested that the stress amplitude should be suppressed less than the fatigue limit. In the thermal stress analysis for fatigue damage assessment, it was found that the detailed three-dimensional structural analysis was not required. Namely, for the current case, a one-dimensional simplified analysis could be used for evaluating the fatigue damage without adopting the stress enhancement factor K t quoted in the JSME guideline. The results also suggested that, for a precise assessment of the fatigue damage at a mixing tee, the effect of multi-axial stress on the fatigue life together with the mean stress effect should be taken into account.

[1]  C. Amzallag,et al.  Influence of Mean Stress on the Fatigue Behavior of 304L SS in Air and PWR Water , 2005 .

[2]  Olivier Berder,et al.  An Advanced Mixing Tee Mock-Up Called “The Skin of the Fluid” Designed to Qualify the Numerical LES Analyses Applied to the Thermal Evaluation , 2006 .

[3]  Stéphane Chapuliot,et al.  Experimental and numerical study of crack initiation and propagation under a 3D thermal fatigue loading in a welded structure , 2008 .

[4]  Hideki Kamide,et al.  Study on mixing behavior in a tee piping and numerical analyses for evaluation of thermal striping , 2009 .

[5]  Naoto Kasahara,et al.  Structural response function approach for evaluation of thermal striping phenomena , 2002 .

[6]  J. L. Roux,et al.  CYCLIC DEFORMATION AND FATIGUE BEHAVIORS OF STAINLESS STEEL 304L INCLUDING MEAN STRESS AND PRE-STRAINING EFFECTS , 2008 .

[7]  P. Coste,et al.  Large Eddy Simulation of Highly Fluctuational Temperature and Velocity Fields Observed in a Mixing-Tee Experiment , 2008 .

[8]  O. Braillard,et al.  High-Cycle Thermal Fatigue in Mixing Zones: Investigations on Heat Transfer Coefficient and Temperature Fields in PWR Mixing Configurations , 2010 .

[9]  S. Quilici,et al.  Fatigue Evaluation in Mixing Zones: Comparison of Different Criteria of Fatigue , 2008 .

[10]  M. Strelets,et al.  Al A A 2001-0879 Detached Eddy Simulation of Massively Separated Flows , 2001 .

[11]  Ian Jones,et al.  THE EFFECT OF VARIOUS CONSTRAINT CONDITIONS IN THE FREQUENCY RESPONSE MODEL OF THERMAL STRIPING , 1995 .

[12]  C. E. Jaske,et al.  Fatigue Design Criteria for Pressure Vessel Alloys , 1977 .

[13]  Y. Takahashi,et al.  High-cycle fatigue behavior of type 316 stainless steel at 288 °C including mean stress effect , 2006 .

[14]  E. Paffumi,et al.  Simulation of thermal fatigue damage in a 316L model pipe component , 2008 .

[15]  Florian Menter,et al.  The SST Turbulence Model with Improved Wall Treatment for Heat Transfer Predictions in Gas Turbines , 2003 .

[16]  S. Taheri.  Some Advances on Understanding of High Cycle Thermal Fatigue Crazing , 2007 .

[17]  Naoto Kasahara,et al.  Advanced creep-fatigue evaluation rule for fast breeder reactor components: generalization of elastic follow-up model☆ , 1995 .