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The purpose of this paper is to find out how to model the effect of mechanical stresses on the magnetic properties of electrical steel used in electromagnetic devices and especially in electrical machines. Further, the effect of these stresses on the operation of the machines should be studied.

The constitutive equation of the electrical steel is usually modeled as a non linear relation between the magnetic flux density and the magnetic field strength. In this research, this constitutive equation is developed to account for the mechanical stresses through a parametric relationship, the parameters of which are estimated from measurements. Further, the constitutive equation is used in a magnetomechanically coupled numerical simulation of an induction machine.

The mechanical stresses degrade the properties of the electrical steel and increase the magnetization current in electrical machines. This leads to a decrease in the efficiency of these machines.

The effect of mechanical stresses is studied from the point of view of magnetization properties. This work does not model the effect of stresses on the specific losses of the material. Such a research is still going on.

The effect of mechanical stress on the magnetic properties of the materials used in electrical machines is modeled in an easy and original way, which allow for its application in numerical simulation and analysis of these machines.

The electric stress profiles of a needle‐plane electrode system used in the laboratory for investigation of tree initiation and growth have been studied. Results from analytical solution based on a hyperboloid shaped needle tend to differ from those from experiments. One reason is that in practice it is difficult to produce a needle of such a shape. Moreover, researchers have used various shaped needles for their tests. Presents the effects of these needle parameters on the electric stress profile. To simulate the presence of space charge, examines two models, i.e. spherical and cylindrical regions around the tip. For simplicity, the space charge was assumed to be uniformly distributed in the confined region. Results show that space charges can enhance or reduce the electric stress adjacent to the needle tip depending on the nature of the applied voltage.

The purpose is to implement and compare different approaches for modelling the magnetostriction phenomenon in iron sheet used in rotating electrical machines.

In the force-based approach, the magnetostriction is modelled as a set of equivalent forces, which produce the same deformation of the material as the magnetostriction strains. These forces among other magnetic forces are computed from the solution of the finite element (FE) field computation and used as loads for the displacement-based mechanical FE analysis. In the strain-based approach, the equivalent magnetostrictive forces are not needed and an energy-based model is used to define magnetomechanically coupled constitutive equations of the material. These equations are then space-discretised and solved with the FE method for the magnetic field and the displacements.

It is found that the equivalent forces method can reproduce the displacements and strains of the structure but it results in erroneous stress states. The energy-based method has the ability to reproduce both the stress and strains correctly; thus enabling the analysis of stress-dependent quantities such as the iron losses and the magnetostriction itself.

The investigated methods do not account for hysteresis and other dynamic effects. They also require long computation times. With the available computing resources, the computation time does not present any problem as far as they are not used in everyday design procedures but the modelling of dynamic effect needs to be elaborated.

The developed and implemented methods are verified with measurements and simulation experiments and applied to as complex structure as an electrical machine. The problems related to the different approaches are investigated and explained through simulations.

Magnetic properties of electrical steel are affected by mechanical stress. In electrical machines, influences because of manufacturing and assembling and because of operation cause a mechanical stress distribution inside the steel lamination. The purpose of this study is to analyse the local mechanical stress distribution and its consequences for the magnetic properties which must be considered when designing electrical machines.

In this paper, an approach for modelling stress-dependent magnetic material properties such as magnetic flux density using a continuous local material model is presented.

The presented model shows a good approximation to measurement results for mechanical tensile stress up to 100 MPa for the studied material.

The presented model allows a simple determination of model parameters by using stress-dependent magnetic material measurements. The model can also be used to determine a scalar mechanical stress distribution by using a known magnetic flux density distribution.

Conventional wear models cannot satisfy the requirements of electrical contact wear simulation. Therefore, this study aims to establish a novel wear simulation model that considered the influence of thermal-stress-wear interaction to achieve high accuracy under various current conditions, especially high current.

The proposed electrical contact wear model was established by combining oxidation theory and the modified Archard wear model. The wear subroutine was written in FORTRAN, and adaptive mesh technology was used to update the wear depth. The simulation results were compared with the experimental results and the typically used stress-wear model. The temperature of the contact surface, distribution of the wear depth and evolution of the wear rate were analyzed.

With the increase in the current flow, the linear relationship between the wear depth and time changed to the parabola. Electrical contact wear occurred in two stages, namely, acceleration and stability stages. In the acceleration stage, the wear rate increased continuously because of the influence of material hardness reduction and oxidation loss.

In previous wear simulation models, the influence of multiple physical fields in friction and wear has been typically ignored. In this study, the oxidation loss during electrical contact wear was considered, and the thermo-stress-wear complete coupling method was used to analyze the wear process.

The increasing level of integration in PCB technology demands from the designer a new level of sensitivity to high electrical field problems and to the degradation processes that may be involved. High electrical fields interacting with thermal and mechanical stresses could lead to the growth of ‘latent defects’, not easily identifiable during final stage acceptance tests, that could lead the PCB's failure during service. The paper discusses degradation mechanisms which can lead to dielectric failure, together with first results relevant to a wider research project regarding identification of latent defects in PCBs and the development of new test procedures.

Underground cables can produce higher electromagnetic fields directly above them than an overhead line. The majority of cable failures on distribution system are caused by defects in the cable accessories. Nowadays, significant research has been carried out worldwide into examining whether electricity, and in particular, the presence of electric and magnetic fields have an adverse impact on health, especially the occurrence of cancer and childhood leukemia. The purpose of this paper is to optimize the electric field distribution in underground cable accessories. This reduces the impact of the harmful effects of the fields on living beings and humans.

Cable terminations and joints are designed to eliminate the stress concentration at the termination screen to avoid the breakdown of the cable and high values of electric field at these points. Any improvement in the cable termination and joints construction is of great interest. There are several methods for the solution of electric field distribution. These can be summarized as analytical, experimental, free-hand field mapping, analogue methods and numerical methods. In this paper cable accessories are modeled by using multilayer dielectric system and very thin deflector’s cones.

This model includes specific insulators design and smart choice of electrodes position. Stress-grading nonlinear materials in form of tapes and tubes were used with much success. In order to optimize the cable joint parameters, two criteria were monitored – total electric field magnitude and magnitude of the tangential component. More than 30 percent is reduced impact of cables on the environment.

In order to investigate the accuracy of the applied numerical model, various configurations of the cable accessories are studied. The first time is applied new Hybrid Boundary Elements Method on the protection of the environment.

The contact behaviors of droplets on confined surfaces influence significantly their dynamics and morphological transition induced by the electric field. This paper aims to delve into the electric stress, electric field distribution, flow field and evolution of droplet neck to understand the underlying mechanisms.

Electrohydrodynamics of droplets in confined environment is numerically analyzed based on finite volume method (FVM) combining with volume-of-fluid (VOF) method for two-phase interface capturing. Numerical solutions are obtained through solving electrohydrodynamics model coupling fluid dynamics with electrostatics.

It was found that the droplet neck with high interfacial curvature undergoes different transition depending on the contact angle. At large domain height, the droplets on the surfaces with the contact angle of θ < 90° tend to break up into smaller droplets adhered on top and bottom surfaces. The detachment of droplets is identified when the contact angle is much greater than 90°. Notably, the droplets at θ = 90° exhibit asymmetrical shape evolution, but for other cases there is symmetrical shape of droplets during transition process. With decreasing the domain height, no obvious deformation through driving the contraction of the droplet neck is observed.

It remains unclear how the electric field parallel to the surfaces affects the shape transition and electrohydrodynamics of confined droplets when changing the contact angle. In this paper, the authors study the electrohydrodynamics of droplets in confined space when the electric field is exerted parallel to contact surfaces. In particular, the authors consider the effect of the surface wettability on the droplet deformation. The problem is solved through FVM combining with the VOF method to implement the capturing of two-phase interfaces. The results indicate that the electrohydrodynamic behaviors of droplets are sensitive to the contact properties of droplets on the surfaces, which has not been reported in previous works.

The purpose of this paper is to investigate the effects of electric current stressing on damping properties of Sn5Sb solder.

Uniformly shaped Sn5Sb solders were prepared as samples. The length, width and thickness of the samples were 60.0, 5.0 and 0.5 mm, respectively. The damping properties of the samples were tested by dynamic mechanical analyzer with a cooling system to control the test temperature in the range of −100 to 100°C. Simultaneously, electric current was imposed to the tested samples using a direct current supply. After tests, the samples were characterized using scanning electron microscope, electron backscatter diffraction and transmission electron microscope, which was aimed to figure out the damping mechanism in terms of electric current stressing induced microstructure evolution.

It is confirmed experimentally that the increase in damping properties is due to Joule heating and athermal effects of current stressing, in which Joule heating should make a higher contribution. G–L theory can be used to explain the damping properties of strain amplitude under current stressing by quantitative description of geometrically necessary dislocation density. While the critical strain amplitude and high temperature activation energy decrease with increasing electric current.

These results provide a new method for vibration reliability evaluation of high-temperature lead-free solders in serving electronics. Notably, this method should be also inspiring for the mechanical performance evaluation and reliability assessment of conductive materials and structures serving under electric current stressing.

The paper discusses the aspect of probable stress induced embrittlement of 304 stainless steel stresses originating from thermal exposure, uniaxial tension, and reverse bending, which have been simulated on the surface of SS plates of 1mm thickness, using conventional techniques. The physical and electrochemical properties of the treated SS materials have been followed up as a function of the corroding medium and also the type and extent of the stress interaction.