Studying the Effect of Thermal Fatigue on Multiple Cracks Propagating in an SS316L Thin Flange on a Shaft Specimen Using a Multi-Physics Numerical Simulation Model

Abstract

After more than a decade of research on thermal fatigue cracking in nuclear reactor components, the science remains incomplete. It is essential to understand the crack propagation behaviour and the influence of multiple cracks on the fatigue life of a component due to thermal fatigue load. Accurate numerical simulation modelling can help in better understanding the influence of different factors on failure propagation. In this research, a finite element-based numerical simulation model has been developed using ABAQUS commercial software to obtain insight into crack propagation and crack arrest in an SS316L thin flange on shaft specimen; the assembly is cooled internally, and cyclic thermal loading is applied on the flange rim. The experiment was carried out on a specially designed rig using an induction coil for heating the outer rim. Thermocouples were attached radially on the rim to collect detailed temperature profiles. Real-time temperature-dependent elastic-plastic material data was used for modelling. The boundary conditions and thermal profile used for the numerical model were matched with experimental data. The stresses responsible for crack initiation, the effect of crack number and crack lengths on stresses, energy absorbed at the crack tip after every thermal cycle and the threshold values of cracks are evaluated in the current work. The obtained simulation results were validated by comparing experimental observations. The developed simulation model helps in better understanding the evolution of stresses and strains in uncracked and cracked SS316L discs mounted on a flange due to thermal cycling. It also helped in better understanding the crack propagation behaviour and the evolution of energy release at crack tips. Such a model can help future researchers in designing components undergoing thermal fatigue loading, for example, in nuclear power plants.

Influence of microstructural evolution and localized delta ferrite number on high-cycle fatigue crack opening and propagation rate

“…Resultantly, a large plastically deformed zone forms at the crack tip, which is not only responsible for large COD but also for faster crack propagation rate, this has also been reported by earlier researchers. 39,40 From Figure 17, it is observed that occasionally the FZ of W1 shows less cyclic fragility and COD, especially when the propagation rate approaches 1 Â 10 À4 to 1 Â 10 À3 . It is perhaps due to observed variations in ferrite morphology at the surface and root of the weld zone.…”

Transformation of 2D RVE Local Stress and Strain Distributions to 3D Observations in Full Phase Crystal Plasticity Simulations of Dual-Phase Steels

“…Repeatedly, through the least square method, the linear equation for the second iteration condition can be calculated by Equations ( 7) and (8). Through a 2 and b 2 , the first revised stress/strain result ( f r1i ) will forcibly be modified with a corresponding value of a linear equation and become the second revised stress/strain result ( f r2i ) in Equation (9).…”

“…The effect of these attributes is interdependent and plays a key role in defining the deformation and damage behavior under varying loading conditions [5,6], i.e., strain rate, temperature, and loading direction. Numerical simulation models provide an interesting outlook for targeted material development by avoiding the expensive and time-consuming experimentation of every iterative modification in the material microstructure [7][8][9].…”

Size effects on spheroidal voids by Finite Fracture Mechanics and application to corrosion pits

“…All in all, these features enable FFM to provide reliable failure estimations for plain, cracked, and notched elements: In comparison, LEFM only works for geometries with a sufficiently large crack 7,8 . Indeed, FFM is able to catch the transition from strength to toughness‐governed failure regimes as the characteristic size of the stress‐raiser varies.…”