Evaluation of SSY boundary using DIC results

In this work the boundaries of small-scale yielding (SSY) and large-scale yielding (LSY) have been experimentally evaluated from the analysis of crack tip opening displacement (CTOD) measured by Digital Image Correlation (DIC). The approach published in a previous numerical work [18] has been used to define the boundaries of SSY and LSY. According to this approach, CTOD must be resolved into its elastic and plastic components, analysing the ratio between the elastic CTOD range and the total CTOD range ( Δδ/ Δδ) to define the boundary where SSY conditions can be established. Three materials have been studied, commercially pure titanium and 2024-T3 and 7050-T6 aluminium alloys, tested at different stress ratio values (0.1 and 0.6 for titanium, and 0.1, 0.3 and 0.5 for the aluminium alloys). SSY conditions are shown to dominate when Δδ/ Δδ≥79% and ≥78% for titanium and the two aluminium alloys, respectively. In addition, LSY can be established when Δδ/ Δδ≤66.3% and ≤67.2% for titanium and for 2024-T3 and 7050-T6 aluminum alloys, respectively. Transition or LSY conditions are more probable in fatigue tests conducted at low R-ratio than in tests at high R-ratio. In addition, crack lengths above 40% with respect to the width of the specimen promote transition or LSY conditions. The results obtained in this work can assist to a better understanding of the mechanisms driving fatigue crack growth.

Mexican validation of the Sociocultural Attitudes Towards Appearance Questionnaire (SATAQ-3) in men undergraduate students / Validación mexicana del Cuestionario de Actitudes Socioculturales hacia la Apariencia (SATAQ-3) en estudiantes universitarios varones

The Sociocultural Attitudes Towards Appearance Questionnaire-3 (SATAQ-3) is one of the instruments used to measure the influence of mass media on adolescents, and is a useful instrument that has been widely applied in different countries and translated to many languages. The present study is the first validation of the Mexican version of the SATAQ-3 with a male college student sample. A total of 148 students participated in the study (M = 19.1, SD = 2.14). A principal axis factor analysis was used to evaluate the scale, yielding a poor result, due to the formation of an extra factor with reverse-keyed items. Therefore, reversed key items were removed and a second analysis was conducted. After removing reverse-key items, a four-factor structure was obtained: Pressures, Internalization-general, Internalization-athletic, and Information. The internal consistency obtained for SATAQ-3 was satisfactory (α = .81), however, it was slightly lower than the original. Regarding the concurrent validation, the SATAQ-3 presented significant correlations with body dissatisfaction, social perfectionism and psychological distress. SATAQ-3 is an appropriate instrument to measure the internalization of aesthetic ideals and acceptance, among male college students in Mexico.ResumenUno de los cuestionarios más utilizados para medir la influencia de los medios de comunicación es el Cuestionario de Actitudes Socioculturales hacia la Apariencia (SATAQ-3), el cual ha sido traducido a varias lenguas y aplicado en distintos países. El presente estudio constituye la primera validación mexicana del SATAQ-3 en varones. Participaron 148 estudiantes universitarios (M = 19.1, DE = 2.14). Para evaluar la escala se realizó un análisis factorial de ejes principales, obteniendo inicialmente un resultado pobre, dada la formación de un factor extra con los ítems con redacción inversa. Por esta razón dichos ítems fueron removidos y se condujo un segundo análisis que derivó una estructura de cuatro factores: Presión, Interiorización general, Interiorización atlética, e Información. La consistencia interna del SATAQ-3 fue satisfactoria (α = .81), sin embargo fue un poco menor a la obtenida de la escala original. Respecto a la validación concurrente, el SATAQ-3 presentó correlaciones significativas con la insatisfacción corporal, el perfeccionismo social y el malestar psicológico. El SATAQ-3 es un instrumento apropiado para medir la interiorización de los ideales estéticos y su aceptación en estudiantes universitarios varones mexicanos.

Probing atomic-scale symmetry breaking by rotationally invariant machine learning of multidimensional electron scattering

The 4D scanning transmission electron microscopy (STEM) method maps the structure and functionality of solids on the atomic scale, yielding information-rich data sets describing the interatomic electric and magnetic fields, structural and electronic order parameters, and other symmetry breaking distortions. A critical bottleneck is the dearth of analytical tools that can reduce complex 4D-STEM data to physically relevant descriptors. We propose an approach for the systematic exploration of 4D-STEM data using rotationally invariant variational autoencoders (rrVAE), which disentangle the general rotation of the object from other latent representations. The implementation of purely rotational rrVAE is discussed as are applications to simulated data for graphene and zincblende structures. The rrVAE analysis of experimental 4D-STEM data of defects in graphene is illustrated and compared to the classical center-of-mass analysis. This approach is universal for probing symmetry-breaking phenomena in complex systems and can be implemented for a broad range of diffraction methods.

Advantageous Description of Short Fatigue Crack Growth Rates in Austenitic Stainless Steels with Distinct Properties

In this work two approaches to the description of short fatigue crack growth rate under large-scale yielding condition were comprehensively tested: (i) plastic component of the J-integral and (ii) Polák model of crack propagation. The ability to predict residual fatigue life of bodies with short initial cracks was studied for stainless steels Sanicro 25 and 304L. Despite their coarse microstructure and very different cyclic stress–strain response, the employed continuum mechanics models were found to give satisfactory results. Finite element modeling was used to determine the J-integrals and to simulate the evolution of crack front shapes, which corresponded to the real cracks observed on the fracture surfaces of the specimens. Residual fatigue lives estimated by these models were in good agreement with the number of cycles to failure of individual test specimens strained at various total strain amplitudes. Moreover, the crack growth rates of both investigated materials fell onto the same curve that was previously obtained for other steels with different properties. Such a “master curve” was achieved using the plastic part of J-integral and it has the potential of being an advantageous tool to model the fatigue crack propagation under large-scale yielding regime without a need of any additional experimental data.