A method for calculating elasto-plastic notch tip strains and stresses in bodies subjected to proportional multiaxial loading is presented. Notch tip strains and stresses are estimated using the generalized Neuber's rule and equivalent strain energy density method. These estimates form upper and lower bounds of the exact solution. All necessary relationships in the form of five simultaneous algebraic equations are derived for a general multiaxial stress state. An efficient solution method is proposed enabling fast calculation of numerical values and the choice of the appropriate solution. This method may be particularly useful for fatigue analysis of notched components.

The assessment of steam generator tubes with defects is of great importance for the life extension of steam generators. Circumferential through-wall cracks are the most severe of all tube circumferential defects, and usually require plugging of the affected tubes. The assessment of the tubes with through-wall circumferential cracks or cracks projected to become through-wall can be conducted using the failure assessment diagram (FAD) approach. This approach requires the calculation of the stress intensity factor and the limit load. The available stress intensity factor and limit load solutions for cracked tubes do not include the constraining effect of the tube supports. In the present paper, it is shown that this can be overly conservative. Solutions for stress intensity factors and limit loads are presented for tubes with circumferential through-wall cracks including the effect from the tube support plates. Different values of support spacing are considered. Based on these solutions, the assessment of a typical steam generator tube is demonstrated.

Fatigue cracks in shot-peened and case-hardened notched machine components are subjected to stress fields induced by the external load and residual stresses resulting from the surface treatment. Both stress fields are characterized by nonuniform distributions, and handbook stress intensity factor solutions are in such cases unavailable, especially in the case of planar nonelliptical cracks. The method presented here is based on the generalized weight function technique enabling the stress intensity factors to be calculated for any Mode I loading applied to arbitrary planar convex and embedded crack. The stress intensity factor can be determined at any point on the crack contour by using one general weight function discussed in the paper. The weight function, mA, can be sufficiently well described by two quantities, i.e., the distance, ρ, from the load point, P(x, y), on the crack surface to the point, A, on the crack front where the stress intensity is to be calculated and the length, Γc, of the inverted crack contour. The stress intensity factors are calculated by integrating the product of the stress field and the weight function over the entire crack area. The general weight function and calculated stress intensity factors are validated against arious numerical and analytical data. The numerical procedure for calculating stress intensity factors for arbitrary nonlinear stress distributions is briefly discussed as well. Several examples of typical input data and stress intensity factor results are presented including embedded and edge cracks subjected to two-dimensional stress fields. The method is particularly suitable for modeling fatigue crack growth in the presence of complex stress fields.

An ASME Section III Task Group (TG) was formed in 2012 to develop alternate rules for the design assessment of Section III Class 1 nuclear components subject to fatigue service with environmental effects. Specifically, a flaw tolerance approach is being investigated based on similar methodology to that found in ASME Section XI Nonmandatory Appendix L. A key initial task of the TG (which reports to the Section III Working Group on Environmental Fatigue Evaluation Methods) was to develop and solve a detailed sample problem. The intent of the sample problem was to illustrate application of proposed rules, which will be documented as a Section III Code Case with a supporting technical basis document. Insights gained from round robin solution of the sample problem are presented and discussed in this paper. The objective of documenting the findings from the sample problem are to highlight the observed benefits and limitations of the proposed procedures, particularly how rules typically associated with in-service experience might be adapted into design methods. The sample problem is based on a heavy-walled stainless steel nozzle that meets cumulative fatigue usage requirements in air (i.e., usage factor, U, without reactor water environment effects less than unity), but fails to meet usage factor requirements when environmental fatigue effects are applied. The sample problem demonstrates that there is a class of problems dominated by severe thermal transients where fatigue initiation is predicted based on elastic methods including environmental effects, but fatigue crack propagation results are acceptable. Preliminary conclusions are drawn based on the results of the sample problem, and the next steps are also identified.

The current fatigue assessment method of the ASME B&PV Code uses an elastic stress multiplier to determine the total stress in perforated plates with triangular pattern. This method contains several simplifications and shortcomings. The present paper shows that the perforation pattern symmetry imposes constraints on the total stress multipliers that can be used to simplify the elastic analysis, particularly of three-dimensional (non-axisymmetric) plates. For thin ligament conditions, the very conservative Code analysis can be replaced by a more accurate stress multiplier approach for which the stress concentration around the hole is derived from an elastic Finite Element analysis. This can result in a significant reduction of the calculated fatigue usage factor. Finally, the issue of strain concentration is addressed. When the total stress range at a location around the ligament exceeds 2Sy, the elastically predicted strain range is potentially unconservative. The elastic-plastic strain at this location can be estimated from the elastic result using simplified methods. The corresponding predictions are compared to elastic-plastic analysis results.