A B S T R A C TA modification of the Morrow and the Smith, Watson and Topper (SWT) mean stress correction models is proposed to account for the mean stress effect on fatigue life. The capability and accuracy of the proposed model are compared to those of the original Morrow and the SWT model using published mean stress fatigue test data. The proposed mean stress correction model was found to be superior to both the SWT and the Morrow model in the case of the Incoloy 901 superalloy and the ASTM A723 steel. On the other hand both the proposed and the original SWT model provided equally good correlation with experimental data in the case of 7075-T561 aluminium alloy and 1045 HRC 55 steel. The Morrow model was found to give the least accurate predictions for all four materials analysed.

No abstract

No abstract

A new mean stress fatigue model based on the distortional strain energy is proposed to account for the mean stress effects on fatigue life. The proposed model is compared with the Morrow and the Smith‐Watson‐Topper (SWT) mean stress correction models using a number of experimental data sets for one cast iron, two steels and two aluminium alloys under tensile and compressive mean stress loadings. It is found that both the proposed mean stress correction model and the SWT model yield similar results and provide very good correlation for positive mean stress data and moderate negative mean stress data. For high compressive mean stresses, the proposed model shows reasonably good correlations, while the SWT model fails to correlate the fatigue data. The Morrow model was found to give poor correlations for all fatigue data analysed by yielding conservative results for compressive mean stresses and non‐conservative results for tensile mean stresses.

Through characterizing the interaction of normal/shear stress–strain behavior on material planes of TC4 alloys, a new strain energy critical plane model describing mean stress effects is proposed for life prediction under tension–compression, pure torsion, and tension–torsion loadings. Moreover, a modified Ince–Glinka model is elaborated through considering crack surface close to the maximum shear strain plane. Three simple solutions are presented to determine cracking failure mode using the concepts of life, damage, and strain. Comparing with lifing models of Liu, Smith–Watson–Topper, and modified Ince–Glinka, the proposed model provides more accurate life predictions for TC4 and a compressor turbine disc by full-scale fatigue testing.

No abstract

In this paper, recent fatigue tests conducted on welded specimens subjected to high frequency mechanical impact (HFMI) treatment are described, geometry measurements and metallurgical analyses of the tested specimens are presented, and efforts to estimate the test results using a nonlinear fracture mechanics model are discussed. The specimens were fabricated from 9.5-mm-thick (3/8 in.) aluminum (5083-H321) and high-strength steel (ASTM A514) plate. The specimen geometry and preparation followed procedures used in previous studies on mild steel (CSA 350W). Fatigue tests were performed on the as-welded and impact-treated specimens under two loading histories (constant amplitude with and without periodic under-loads) at several equivalent stress ranges. Residual stress distributions were determined by x-ray diffraction. In addition, weld toe geometry measurements were obtained using silicon impressions and microhardness distributions were obtained on polished weld samples for each material type. This information was used to establish parameter values for a nonlinear fracture mechanics analysis. The employed fracture mechanics model is reviewed in this paper, and its benefits as a tool for modelling the fatigue behavior of impact-treated welds are discussed. Following this, the effectiveness of the model in estimating the test results for the three materials is assessed.

Additive manufacturing (AM) process has extensively been used to fabricate metal parts for large variety of applications. Residual stresses are inevitable in the AM process since material experiences heating and cooling cycles. Implementing finite element (FE) analysis tool to predict residual stress distributions could be of great importance in many applications. Developing an FE‐based modeling framework to accurately simulate residual stresses in a reasonably reduced computational time is highly needed. The FE‐based modeling approach presented here to simulate direct metal deposition (DMD) of AISI 304 L aims to significantly reduce computation cost by implementing an adaptive mesh coarsening algorithm integrated with the FE method. Simulations were performed by the proposed approach, and the results were found in good agreement with conventional fine mesh configuration. The proposed modeling framework offers a potential solution to substantially reduce the computational time for simulating the AM process.