One-dimensional Lumped-Circuit for Transient Thermal Study of an Induction Electric Motor

Electrical machines lifetime and performances could be improved when along the design process both electromagnetic and thermal behaviors are taken into account. Moreover, real time information about the device thermal state is necessary to an appropriate control with minimized losses. Models based on lumped parameter thermal circuits are: generic, rapid, accurate and qualified as a convenient solution for power systems. The purpose of the present paper is to validate a simulation platform intended for the prediction of the thermal state of an induction motor covering all operation regimes.  To do so, in steady state, the proposed model is validated using finite element calculation and experimental records. Then, in an overload situation, obtained temperatures are compared to finite element’s ones. It has been found that, in both regimes, simulation results are with closed proximity to finite element’s ones and experimental records

Factors Correlated with Communication Confidence in Persons with Aphasia: A Synthetic Cohort Analysis

Aphasia is an acquired language disorder that affects a person's communication abilities. Consequently, aphasia can have a profound impact on how persons with aphasia (PWA) experience their personal life. Recently, approaches to aphasia management have taken a turn from the medical model of deficit to the functional and social model of deficit, which places emphasis on functional communication, social participation, and communication efficacy. In line with this approach, the construct of communication confidence was introduced. Communication confidence is a psychosocial construct related to the constructs of life participation, autonomy and self-determination, and self-efficacy. Communication confidence in PWA has received little attention, although confidence levels have been shown to be related to lifestyle changes in PWA. The purpose of this study was to determine the factors that correlate with communication confidence in PWA and contribute to broadening the general understanding of this construct. Fifteen participants with with aphasia as the result of a left hemisphere cerebrovascular accident (CVA) participated in the investigation. In a single session at East Carolina University in the Communication Equity and Outcomes Laboratory, the participants provided their medical and demographic information and were administered an objective impairment-level language measure as well as subjective measures. The former was the Western Aphasia Battery - Revised (WAB-R) to assess their language performance and the latter were the American Speech-Language-Hearing Association (ASHA) Quality of Communication Life Scale (ASHA-QCL) and the Communication Confidence Rating Scale for Aphasia (CCRSA) to capture their perception of their communication impairment from the quality of communication life standpoint and a communication confidence point of view, respectively. Synthetic data analysis utilized the distributional properties of the original data to interpolate statistically robust estimates of the relationship between communication confidence and demographic, objective measure, and subjective measure variables. The synthetic cohort analyses simulated results using a probabilistically constructed simulation of 5000 participants. This synthesized data were closely similar to that collected across all included variables. Regression analyses indicated that a statistically significant positive correlation of ASHA-QCL (p = 0.03) and ASHA-Q18 (p = 0.04) with the CCRSA existed. Demographic variables and objective measures were not correlated with the CCRSA. The constructs of quality of life, quality of communication life, and communication of confidence, therefore, seem strongly interrelated and are important factors that may contribute to better adaptation and living successfully with aphasia

Scalar-based strain gradient plasticity theory to model size-dependent kinematic hardening effects

A common belief in phenomenological strain gradient plasticity modeling is that including the gradient of scalar variables in the constitutive setting leads to size-dependent isotropic hardening, whereas the gradient of second-order tensors induces size-dependent kinematic hardening. The present paper shows that it is also possible to produce size-dependent kinematic hardening using scalar-based gradient theory. For this purpose, a new model involving the gradient of the equivalent plastic strain is developed and compared with two reference scalar-based and tensor-based theories. Theoretical investigations using simple monotonic loading conditions are first presented to assess the ability of the proposed model to solve some issues related to existing scalar-based gradient theories. Simulations under cyclic loading conditions are then provided to investigate the nature of the resulting hardening. These simulations show that the proposed model is capable of producing size-dependent kinematic hardening effects at more affordable costs, compared to existing tensor-based strain gradient plasticity theories

Congrès français de mécanique (21; 2013; Bordeaux (Gironde))

The indentation response of glasses can be classified into three classes : normal, anomalous and intermediate depending on the deformation mechanism and the cracking response. Silica glass, as a typical anomalous glass, deforms primarily by densification and has a strong tendency to form cone cracks that can accompany median, radial and lateral cracks when indented with a Vickers tip. This is due to its propensity to deform elastically by resisting plastic flow. Several investigations of this anomalous behavior can be found in the literature. The present paper serves to corroborate these results numerically using the discrete element method. A new pressure-densification model involving the discrete element method (DEM) is developed that allows for a quantitative estimate of the densification under very high pressure. This model is then used to simulate the Vickers indentation response of silica glass under various indentation forces. The numerical results obtained compare favorably with past experimental results

A multi-scale coupling method to simulate the silica glass behavior under high pressures

The response of glasses subjected to high pressures can be classified into three classes : normal, anomalous and intermediate depending on the deformation mechanism and the cracking pattern. The silica glass which is the scope of this work is a typical anomalous glass. The numerical study of this behavior with continuum methods (e.g. FEM, CNEM) presents several difficulties and drawbacks. Because, this requires a very small scale analysis. The discrete methods (e.g. MD, DEM) represent a good choice to simulate this behavior. However, these methods are very time consuming (CPU-wise). In this work, a discrete-continuum coupling method is proposed to study the behavior of this brittle material subjected to high pressures. The coupling results, obtained in this work, compare favorably with past experimental results

Bioactive Gelatin-based Date By-Product for Packaging Applications: Physico-Chemical and Biological Characterization

 Biodegradable films from gelatin (Gn) with various date by-product (DBP) concentrations (1, 2, 3 and 4 wt %) were prepared. Elaborated films were examined in terms of physical properties (thickness, density, water solubility, water content, degree of swelling, color), and antimicrobial properties (Escherichia coli and Staphylcoccus aureus). Adding the highest concentration of DBP (4%), resulted an increase in the WHC of film as compared with control film. Moreover, the incorporation of 1% DBP reduced the moisture level of Gn based composite films as compared with the control film. Furthermore, Film with 4% of DBP had the lowest solubility which reached 39.39%. Incorporation of DBP from 1 to 4% showed decrease of L- and a-values. The active Gn-DBP 1% showed less lightness as compared to Gn-DBP 3%. The incorporation of DBP into film-forming solutions led to increased opaqueness for all gelatin-based composite films. The calculated opacity value was inversely proportional to transparency. Moreover, the Active Gn-DBP 1% and 2% film presented effective antibacterial activity against bacteria such as Staphylococcus aureus and Escherichia coli. The results showed an enhancement in the biodegradability of Gn-DBP films in moist soil. The results reveal the benefits of date by-products incorporated into gelatin based films as a potential material for active food packaging.&nbsp

Uncoupled dissipation assumption to control elastic gaps in Gurtin-type strain gradient models

Thanks to their capabilities in capturing size effects, strain gradient plasticity theories have received a strong scientific interest in the last two decades. However, despite the great scientific effort on these theories, several challenging issues related to them remain to be addressed. One of these issues is concerned with the description of the dissipative processes due to plastic strains and plastic strain gradients. In almost all existing strain gradient works, such processes are described using generalized effective plastic strain measures, which imply plastic strains and their gradients in a coupled manner. This kind of (coupled) measures makes the issue of proposing robust and flexible dissipation formulations and the control of important dissipative effects difficult. Using such measures, it is not easy to control, for example, the elastic gaps at initial yield or under non-proportional loading. However, in most cases, the coupling between dissipative processes is only used by assumption. Its consistency with the current understanding of small scale plasticity is not confirmed in the literature. In spirit of multi-criterion approaches available in the literature, the present work proposes a flexible uncoupled dissipation assumption to describe dissipative processes. These processes are assumed to be derived from a pseudo-potential that is a sum of two independent functions of plastic strains and plastic strain gradients. Using this assumption, a new Gurtin-type strain gradient crystal plasticity (SGCP) model is developed and applied to simulate various two-dimensional plane-strain tests under proportional and non-proportional loading conditions. Results associated with these tests show the great flexibility of the proposed model in controlling some major dissipative effects, such as elastic gaps. A simple way to remove these gaps under certain non-proportional loading conditions is provided. Application of the proposed uncoupling assumption to simulate the mechanical response of a sheared strip has led to accurate prediction of the plastic strain distributions, which compare very favorably with those predicted using discrete dislocation mechanics

Strain Localization Modes within Single Crystals Using Finite Deformation Strain Gradient Crystal Plasticity

The present paper aims at providing a comprehensive investigation of the abilities and limitations of strain gradient crystal plasticity (SGCP) theories in capturing different kinds of localization modes in single crystals. To this end, the small deformation Gurtin-type SGCP model recently proposed by the authors, based on non-quadratic defect energy and the uncoupled dissipation assumption, is extended to finite deformation. The extended model is then applied to simulate several single crystal localization problems with different slip system configurations. These configurations are chosen in such a way as to obtain idealized slip and kink bands as well as general localization bands, i.e., with no particular orientation with respect to the initial crystallographic directions. The obtained results show the good abilities of the applied model in regularizing various kinds of localization bands, except for idealized slip bands. Finally, the model is applied to reproduce the complex localization behavior of single crystals undergoing single slip, where competition between kink and slip bands can take place. Both higher-order energetic and dissipative effects are considered in this investigation. For both effects, mesh-independent results are obtained, proving the good capabilities of SGCP theories in regularizing complex localization behaviors. The results associated with higher-order energetic effects are in close agreement with those obtained using a micromorphic crystal plasticity approach. Higher-order dissipative effects led to different results with dominant slip banding