Gradient damage vs phase-field approaches for fracture: Similarities and differences

Gradient-enhanced damage models and phase-field models are seemingly very disparate approaches to fracture. Whereas gradient-enhanced damage models find their roots in damage mechanics, which is a smeared approach from the onset, and gradients were added to restore well-posedness beyond a critical strain level, the phase-field approach to brittle fracture departs from a discontinuous description of failure, where the distribution function is regularised, leading to the inclusion of spatial gradients as well. Herein, we will consider both approaches, and discuss their similarities and differences. The averaging (diffusion) equations for the averaging field and the phase-field will be compared, and it is shown that the diffusion equation for the phase-field can be conceived as a special case of the averaging equation of a gradient-damage model where the damage is averaged. Further, the role of the driving force is examined, and it is shown that subtle differences in the degradation functions commonly adopted in damage and phase-field approaches are key to the observation that, different from damage mechanics, the fracture process zone does not broaden in the wake of the crack tip

Research of working area development parameters in conditions of deep steep deposit finalizing

Отримано формули розрахунку об’єму запасів корисних копалин в приконтурній та глибинній зоні. Встановлено характер впливу параметрів доробки глибоких крутоспадних родовищ відкритим способом на доцільне положення поточних та проектних контурів кар’єру. Встановлено, що найменший середній коефіцієнт розкриву досягається при мінімальному значенні суми обсягів корисної копалини приконтурної зони лежачого і висячого боків покладу в проектному положенні. Найменший поточний коефіцієнт розкриву досягається при мінімальному значенні суми обсягів корисної копалини приконтурної зони лежачого і висячого боків покладу, а також робочого борту кар'єру в поточному положенні

Improved image quality for x-ray CT imaging of gel dosimeters

Purpose: This study provides a simple method for improving precision of x-ray computed tomography (CT) scans of irradiated polymer gel dosimetry. The noise affecting CT scans of irradiated gels has been an impediment to the use of clinical CT scanners for gel dosimetry studies. Method: In this study, it is shown that multiple scans of a single PAGAT gel dosimeter can be used to extrapolate a ‘zero-scan’ image which displays a similar level of precision to an image obtained by averaging multiple CT images, without the compromised dose measurement resulting from the exposure of the gel to radiation from the CT scanner. Results: When extrapolating the zero-scan image, it is shown that exponential and simple linear fits to the relationship between Hounsfield unit and scan number, for each pixel in the image, provides an accurate indication of gel density. Conclusions: It is expected that this work will be utilised in the analysis of three-dimensional gel volumes irradiated using complex radiotherapy treatments

A methodology for dynamic material characterizations via terahertz time-domain spectroscopy.

In this work, the challenges of terahertz (THz) time-domain spectroscopy on complex (multilayer) samples with time-varying (dynamic) characteristics are addressed. The challenges appear in characterizations of the refractive index and extinction coefficient, as etalon artifacts due to internal reflections, and are accentuated in multilayer structures having dynamic and low-loss materials, such as biomolecular materials. This is because nonidealities may form as airgaps at the interfaces and as inhomogeneity in the bulk. The proposed methodology addresses the challenges by introducing a generalized model that accommodates dynamic formation of airgaps and inhomogeneity. It is shown that the generality of the model allows it to mitigate etalon artifacts and yield a highly accurate representation of the material characteristics, with low systematic error, even for low-loss materials. The methodology is applied to characterizations of quartz and glucose in the THz spectrum to see fine detail in the characteristics of quartz and the crystallization of glucose.Applied Science, Faculty ofArts and Social Sciences, Irving K. Barber Faculty of (Okanagan)Engineering, School of (Okanagan)ReviewedFacult

Reseni integralnich rovnic pro dvouatomove molekuly

The aim of this work is the solution of the Ornstein-Zernike integral equation and its application to the model system of two-centre square-well fluid. This relation between the total and direct molecular correlation function enables, after the completion of the so-called closure, the approximate relation between the direct and total correlation function , to observe both the structure and the thermodynamic properties of the chosen model systemAvailable from STL Prague, CZ / NTK - National Technical LibrarySIGLECZCzech Republi

Inelastic analysis of structures.

Available from STL Prague, CZ / NTK - National Technical LibrarySIGLECZCzech Republi