Papers by Keyword: Static

Abstract: A novel substrate of 4H-SiC bonded substrate is expected to solve issues such as decreasing the on-resistance, which has attracted much attention. Therefore, several studies have been conducted on the use of bonded substrates. In this study, we fabricated a DMOSFET on a bonded substrate and compared its static and dynamic characteristics with those on a single-crystal substrate. Consequently, the on-resistance of the DMOSFET fabricated on a bonded substrate was lower than that on a single-crystal substrate owing to the low resistivity of the polycrystalline substrate. Also, reverse recovery loss of the DMOSFET fabricated on a bonded substrate was lower than that on single-crystal substrate at high temperature due to low carrier lifetime in a drift layer. Additionally, we observed that the DMOSFET fabricated on a bonded substrate did not generate bipolar degradation despite the application of a forward-current stress of over 1500 A cm^-2. According to these results, we expected that the carrier lifetime in both drift layer and transfer layer was decreased on a bonded substrate.

Abstract: The article deals with the creation of a mathematical model that can be applied in the testing of various materials. These are testing cases where the measurement and subsequent evaluation of the value of the coefficient of friction in various tribological measurements is considered. The mathematical model considers the static and dynamic coefficient of friction. It started with the creation of a simpler mathematical model, which was subsequently modified to a more sophisticated one, considering the real situation, which is closer to the real case. With the mathematical model created in this way, various simulations were performed and evaluated for cases of (constant) permanent load, but also repetitive (periodic) load. In another case, an improvement of the mathematical model was carried out, which represented the addition of an option that allows considering the degradation of the investigated material. Degradation of the material represents only part of the surface of the material, which during testing is exposed to contact with another material with a higher hardness than the tested material.

Abstract: Beam-column joint is the most vulnerable location of a moment-resisting reinforced concrete frame structure. The joint region experiences the maximum shear stress both in vertically and horizontally which is generated due to the shear transfer mechanism from the adjoining beams and columns. The shear capacity and bond stress capacity are the two major factors affecting the strength of a joint core in RC structure. An important discovery recently is the ductile behaviour of the whole structure under repeated loading. The behaviour of the concrete beyond elastic limit which is in the concrete hardening zone can drastically influence the ductility of the concrete. The non-linear stress-strain behaviour after the onset of the initial crack and up to ultimate compressive strength plays an important role in improving ductility. Beyond the ultimate compressive strength, concrete will undergo softening which is neglected in this study as once concrete reaches ultimate stress it is unsafe for service. This material ductility can be fulfilled with the application of high-strength fibres with ductile behaviour. However, the hybridization of two or more fibres can incorporate two different characteristics of the fibre used. The use of ordinary-grade of concrete moreover reduces the shear-resisting capacity of the joint. A hybrid mix of hooked-end steel fibre with basalt fibre and crimpled steel fibre with polypropylene fibre are used with a volume fraction of 1% to 1.4% of the concrete. In this study, ordinary M25 grade concrete and fibre mixed M25 grade concrete is employed under static and cyclic loading. The laboratory tests are also conducted to evaluate the compressive strength, split-tensile strength, and flexural strength of the hybrid mix fibre-reinforced concrete at the age of 28^th days. Five full-scale models of the beam-column joint are designed as per the Bureau of Indian Standards. Numerical models of concrete and steel reinforcement are developed. Numerical analysis is carried out using finite element software ANSYS-v21. The behaviours of the beam-column joint are observed under static as well as cyclic loading. Crack patterns, first crack load, initial displacement, ultimate load, and ultimate displacement are observed under static conditions. And under cyclic loading, hysteresis load vs displacement, energy dissipation, and stiffness degradation are observed. The hybridization of hooked steel with basalt fibre gives better results in mechanical strengths and the hybrid effect of crimpled steel with polypropylene fibre gives better results in mechanical strengths. And also under numerical study, the above specimens show an improvement in energy dissipation capacity. Keywords beam-column joint, hybrid fibre reinforced concrete, numerical concrete model, ANSYS, static, reverse cyclic, energy dissipation, stiffness, crack

Abstract: The numerical analysis using finite difference method to study static and dynamic performance of embankment dams is a complex process, in which the materials behavior, soil-dam foundation interaction, hydraulic conditions and saturation effects, should be taken into account. In this study, static and dynamic analysis of Keddara earth dam, located in Boumerdes region (Algeria), is conducted by a numerical analysis using finite difference method (FLAC 3D), with the objective to define its behavior in terms of settlement, strain and pore pressure variation, during its construction and operation. Two stages are considered; the dam construction stage and water filling stage. In this way, two mathematical models are considered for the static analysis; the elastic model and Mohr-Coulomb model. To conduct a coupled dynamic analysis a real earthquake record is used and the interaction between the fluid and solid phases is taken into account.

Abstract: The present study aims to carry out a parametric investigation on a pile made of different materials, and subjected to static and dynamic loading resulting from the weight of the structure and the shear force acting on the head of the pile. It is worth specifying that the pile is anchored in the ground on a Winkler-Pasternak elastic foundation that is made up of five different layers. In this study, the equilibrium equations were treated using the high-order theory with a new shear deformation shape function of a cylindrical pile made of an isotropic material and a sandwich functionally graded material.The results obtained with a numerical study based on the minimization of energies by the Rayleigh-Ritz method was carried out in order to highlight the influence of the geometric ratio, the volume fraction of the functionally graded material, and the type of loading on the vibration frequencies and the admissible stresses in order to determine the most appropriate material for the pile so that extreme stresses can be absorbed. The precision and the applicability of the method with new solution of the transverse shear deformation are demonstrated through this study with modeling of the layered property of the soil, were then compared with those reported in previous work available in the literature. It turned out that these results are in good agreement with each other, for the different materials of pile and for all boundary conditions considered. The results of pile with sandwich functionally graded material, it is revealed that the role of this material has an influence on the type of loading, especially, in the case statique of a pile subjected to a compound bending weight and the shear effect, in case dynamique the pile with vibration flexible or rigid .

Abstract: The article presents the technological scheme of the “stretching-over” hybrid technology, when the workpiece is simultaneously affected by two sources of loading: static and dynamic. It is proposed to use a pulsed magnetic field as a dynamic load. In this case, the tightening punch is equipped with an inductor connected to a magnetic-pulse unit. As a result of computer simulation, the distribution patterns of the stress-strain state in a tight-fitting workpiece were obtained both in the case of a conventional tight-fitting and with the proposed hybrid one. It was found that exposure to a pulsed magnetic field changes the stress-strain state, making it possible to intensify the stretching process.

Abstract: Static balancing of a mechanical system can be regarded as the total or partial cancellation of the mechanical effects (force or moment) of static loads to the actuating system of it, in all configurations, respectively in a finite number of configurations, from functioning domain, under quasi-static conditions. Active balancing is taking into consideration the variation of static loads during the functioning of mechanical systems. As a consequence the active balancing requires an adaptive controlling system and a dynamic model of mechatronic system. In this article, some aspects of the active static balancing problem of mechanical systems are surveyed.

Abstract: The cryogenic performance of two commercially available SiC power MOSFETs are presented in this work. The devices are characterised in static and dynamic tests at 10 K intervals from 20-320 K. Static current-voltage characterisation indicates that at low temperatures threshold voltage, turn-on voltage, on-state resistance, transconductance, and the body diode turn-on voltage all increase while saturation current decreases. Dynamic, 60 V, 3A switching tests within the cryogenic chamber are also reported and the trends of switching speed, losses, and total power losses, which rise at low temperature, are presented. Overall, both MOSFETs are fully operable down to 30 K with both positive and negative changes in behaviour.

Abstract: Hemp fibres are using as reinforcement for compounds based on polymer in different industrial manufacturing (aerospace and automotive) for their interesting mechanical and ecological properties. The hemp fibres present a non-constant cross section and complex geometry that can have a high effect on their mechanical properties. In this study, a micro-traction test coupled with a numerical imaging treatment and a finite elements method are used. The mechanical tensile test allows to determinate the evolution of the traction load in function of the displacement until the fibre crack. The used fiber are incorporate in plastic material is order to obtained PP/hemp reinforcement composite part. Static and dynamic tests are proposed in order to study trhe behaviour of green material subjected to tensile load.

Abstract: A new model is introduced, for predicting the nonlinear behavior of the concrete until the rupture. The non-linear behavior of the concrete is taken into account under monotonic load verifying the principles of the mechanics damage [1] and the concepts of the mechanics of the fracture, using the foundations of the continuum mechanics of materials [2]. The nonlinear mechanical behavior of the concrete in unidirectional is described by two laws (Sargin [3] for the compression and Grelat [4] on the tension). By introducing two variables of damage applied in unidirectional respectively in tension and in compression (Y. Bouafia , R. Smahi, and al., (2014)) [5]. Their combination with the laws of the continuum mechanics of materials (Hooke’s low generalized) [2], and the theory of the mechanics damage (theory of the isotropy of the damage, and principle of the equivalent deformation), brings us to a law of variation of the damage in three-directional applied in bidirectional. In addition, if the variation of the Poisson’s ratio of concrete in unidirectional compression has attracted the interest of several researchers we can cites: (Sami, A., Klink, 1975 [6], Murray D.W. 1979 [7], Niels Saabye ottosen, (1980) [8], Atheel E. Allos., L.H.Martin, (1981) [9], Ramtani.S, Y. Berthaud , J. Mazars, (1992) [10] and Ferretti, E., (2004) [11]. For the three-dimensional, we can mention: Chen 1982 [12], Guo 1997 [13], Zhu 1998 [14], Hyuk-Chun Noh, Hyo-Gyoung Kwak 2006 [15] and Ding Faxing Yu Zhiwu 2006 [16]. Confrontations of the calculations with experimental results (behavior of the concrete in biaxial compression and tension) have allowed to describe and to follow the real behavior of the concrete.