A Geometric Approach to Modeling Microstructurally Small Fatigue Crack Formation

The objective of this paper is to develop further a framework for computationally modeling microstructurally small fatigue crack growth in AA 7075-T651 [1]. The focus is on the nucleation event, when a crack extends from within a second-phase particle into a surrounding grain, since this has been observed to be an initiating mechanism for fatigue crack growth in this alloy. It is hypothesized that nucleation can be predicted by computing a non-local nucleation metric near the crack front. The hypothesis is tested by employing a combination of experimentation and nite element modeling in which various slip-based and energy-based nucleation metrics are tested for validity, where each metric is derived from a continuum crystal plasticity formulation. To investigate each metric, a non-local procedure is developed for the calculation of nucleation metrics in the neighborhood of a crack front. Initially, an idealized baseline model consisting of a single grain containing a semi-ellipsoidal surface particle is studied to investigate the dependence of each nucleation metric on lattice orientation, number of load cycles, and non-local regularization method. This is followed by a comparison of experimental observations and computational results for microstructural models constructed by replicating the observed microstructural geometry near second-phase particles in fatigue specimens. It is found that orientation strongly influences the direction of slip localization and, as a result, in uences the nucleation mechanism. Also, the baseline models, replication models, and past experimental observation consistently suggest that a set of particular grain orientations is most likely to nucleate fatigue cracks. It is found that a continuum crystal plasticity model and a non-local nucleation metric can be used to predict the nucleation event in AA 7075-T651. However, nucleation metric threshold values that correspond to various nucleation governing mechanisms must be calibrated

Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine

[This corrects the article DOI: 10.1186/s13054-016-1208-6.]

Alcohol Outlet Density and Young Women’s Perpetration of Violence Toward Male Intimate Partners

This paper examines the relationships between alcohol outlet density, alcohol use, and perpetration of intimate partner violence (IPV) among young adult women in the US. Data were from Wave III of the National Longitudinal Study of Adolescent Health (Add Health; N = 4,430 in present analyses). Multinomial logistic regression was used to examine occurrence of past year IPV perpetration toward a male partner based on tract-level on-premise and off-premise alcohol outlet density, controlling for individuals’ demographic, alcohol use, and childhood abuse characteristics and neighborhood socio-demographic factors. Higher off-premise alcohol outlet density was found to be associated with young women’s perpetration of physical only IPV, controlling for individual-level and ecological factors. Alcohol use had an independent association with IPV perpetration but was not a mediator of the outlet density-IPV relationship. Findings suggest that considering alcohol-related environmental factors may help efforts aimed at preventing young women’s use of physical violence toward partners