Local Ratcheting by Elastic-Plastic FEA: Criteria and Code Based Approaches

Abstract

Emanating from a discussion of local ratcheting effects and appropriate limiting criteria this paper examines existing ratcheting rules based on local (or material) response that are currently in Section III of the ASME B&PV Code, German KTA rules, and other design codes. The objective is to offer clarification of the rules that may be useful to the designer, their bases and practical application. Among these rules, different ratcheting checks are required that use different ratcheting measures. The paper considers only the rules for which the ratcheting checks can be evaluated by a direct cycle-by-cycle elastic-plastic FEA. Examples are provided to illustrate the procedures.Note that Section III of the ASME B&PV Code and the German KTA rule 3201.2 both address Local Ratcheting within the elastic-plastic ratcheting check. Furthermore, the code based ratcheting check is closely related to the fatigue check.Further rules are given in EN 13445-3 4 .

Towards reliable design-by-analysis for divertor plasma facing components – Guidelines for inelastic assessment (part 1: Unirradiated)

“…The ratcheting rule exposes the potential for the progressive growth of strain or deformation leading to component failure or loss of function. Its detection in PFC design is important, because it potentially causes two forms of failure (following the distinction defined by Rudolph et al [12]). Firstly, ratcheting can cause thinning of the cooling pipe wall until eventually failure occurs due to plastic collapse.…”

Study the Cyclic Plasticity Behavior of 508 LAS under Constant, Variable and Grid-Load-Following Loading Cycles for Fatigue Evaluation of PWR Components

“…Hence, for better accuracy, it is essential to estimate the fatigue and ratcheting damage of reactor components based on the results of elastic-plastic stress analysis rather than pure elastic stress analysis alone. Recently, elasticplastic analysis and fatigue life estimation based on flaw tolerance [17][18][19][20][21][22] have increasingly become an active research area by infusing more mechanics-based prediction capability into the overall fatigue evaluation methodology. Since elastic-plastic ratcheting is a phenomenon closely related to the transient plastic deformation behavior, its accurate description requires the calculation of material hardening stressstrain states as a function of fatigue cycles or time.…”

“…21 Von-Mises stress contour at a typical full power condition[29]. Arrow showing a typical nodal location, where stress states are used as fatigue test loading input for grid-load-following fatigue tests (ET-F3 and EN-F34).…”

Tensile and Fatigue Testing and Material Hardening Model Development for 508 LAS Base Metal and 316 SS Similar Metal Weld under In-air and PWR Primary Loop Water Conditions

“…Most of the presently available fatigue modeling literature has focused on improving the stress-life data set and related empirical fatigue design curves [5][6][7] for estimating fatigue life given the stress/strain state of a component. A few studies [8][9][10][11][12][13][14] have given emphasis to the more mechanistic aspects of fatigue life prediction, such as through-ratcheting or shakedown analysis of reactor component by means of FE models based on nonlinear kinematic hardening. Most of the models discussed in these studies are based on the monotonic stress-strain curve obtained from a tension specimen.…”