Magneto-thermally coupled field simulation of homogenized foil winding models

This paper presents a study on the buckling and vibration of initially stressed composite plates with temperature-dependent material properties in thermal environments. The effects of various parameters on the buckling and vibration behaviors of laminated plates with respective temperature-dependent and temperatureindependent material properties are investigated. The buckling load and natural frequency are sensitive to the thermal stresses and initial stresses.

In this paper, a novel overlapping approach between the copper foil windings and copper bar is presented. The electromagnetic field is computed and analyzed using three-dimensional (3-D) finite element method based on an actual SCB transformer with amorphous foil winding. The current density cloud of foil winding and copper bar is obtained using the magnetic vector potential method to visually observe the existence of skin effect. Then the current density of novel overlapping mode is computed and compared with the traditional one. The results show that the novel overlapping mode not only reduce maximum current density of foil winding, but also save material. The study of this paper is significant for practical manufacture and production.

A thermo-elastic contact problem of functionally graded materials (FGMs) rotating brake disk with different pure brake pad areas under temperature dependent material properties is solved by Finite Element Method (FEM). The properties of brake disk change gradually from metal to ceramic by power-law distribution along the radial direction from the inner to the outer surface. Areas of the pure pad are changing while the vertical force is constant. The ratio of brake pad thickness to FGMs brake disk thickness is assumed 0.66. Two sources of thermal loads are considered: (1) Heat generation between the pad and brake disk due to contact friction, and (2) External thermal load due to a constant temperature at inner and outer surfaces. Mechanical responses of FGMs disk are compared with several pad contact areas. The results for temperature-dependent and temperature-independent material properties are investigated and presented. The results show that the absolute value of the shear stress in temperature-dependent material can be greater than that for temperature-independent material. The radial stress for some specific grading index (n = 1.5) is compressive near the inner surface for double contact while it is tensile for a single contact. It is concluded that the radial strain for some specific value of grading index (n = 1) is lower than other FGMs and pure double side contact brake disks.

Effect of temperature dependent material properties on thermoelastic damping in thin beams

: A one-dimensional, dynamic, thermomechanical model, which includes nonlinear inelastic deformation, internal heat generation (strain-heating), temperature dependent material properties, thermal expansion and thermoelastic coupling, is considered for a uniform thin bar subjected to mechanical or thermal disturbances. A nonlinear Maxwell material is examined in this model and special attention is focused on the temperature change. By solving a nonlinear problem, it is found that a thermal instability, called thermal runaway, may result due to the mutual feedback between strain-heating and the temperature dependent inelastic material properties. Neglecting this important phenomenon may lead to unexpected material failure.

Molten Oxide Electrolysis (MOE) is a leading contender for processing extra-terrestrial minerals because it produces oxygen and liquid metal without the use of consumables. During electrolysis a gravitational field stratifies gas, electrolyte, and metal from each other by density. Processing on the moon, with ~1/6g, or Mars, with ~1/3g, will reduce the buoyancy force slowing bubble velocity and lowering convection intensity. Low thermal conductivity, (~1Wm-1K-1) and high viscosity, (~1Pa⋅s) of molten regolith contribute to thermal and chemical transport being dominated by convection, even as convection velocity decreases. We explore MOE system dynamics in Earth’s (1g), Mars’ (1/3g), and the Moon’s (1/6g) gravity through simulations that include composition and temperature dependent material properties and two phase flow. We implement the level set method to track the interface between the bubble laden flow near the anode and the bubble free flow far from the anode. By grouping bubble dynamics into the material properties of the fluid near the anode we relax the requirements for a fine mesh to track individual bubble-fluid interfaces, and are able to use a mesh that is finer than that required for a bubbly flow mixture model. Thus, all physics can be captured on one mesh. This is particularly relevant because bubble sizes for proposed systems are 1/10 to 1/100 of the system scale. While other simulations have been presented and experiments performed in micro and zero gravity for gas evolving electrolysis systems, none have investigated the downward facing electrode, heat transfer, or species diffusion. The focus of this work is to address this gap in the literature through simulation. Here, multiphysics simulation is supported by inspection of dimensionless groups and observations from other electrolysis systems. This work demonstrates that combining heat and mass transfer with temperature and composition dependent material properties is critical to designing MOE and other electrolysis systems for earth and beyond.

Coupled Electromagnetic and Thermal Analysis of Permanent Magnet Rectifier Generator Based on LPTN

An inverse method for real-time estimation of aerothermal heating for thermal protection systems of space vehicles

A thermo-mechanical model of drill margin-borehole surface interface contact conditions in dry drilling of thick CFRP laminates

This study presents an isogeometric analysis (IGA) for investigating the buckling behavior of functionally graded material (FGM) plates in thermal environments. The material properties of the FGM plate are considered to be graded across the thickness, and temperature dependency of the material properties is taken into account. A new nth-order shear deformation theory with the von Karman type of geometric nonlinearity, in which the optimum order number to best approximate the thermal buckling problem can be chosen, is developed. The principle of virtual work is used to derive the governing equations for the nonlinear thermal buckling analysis. The nth-order shear deformation theory is incorporated into the non-uniform rational B-spline-based IGA which fulfills the $$C^{1}$$ -continuity requirement of the proposed higher-order plate theory. The discrete nonlinear system equations are solved by utilizing the modified Newton–Raphson iterative technique. Parametric studies on the buckling behavior of FGM plates subjected to diverse through-thickness temperature variations are performed, and the influence of temperature dependency of the material properties is examined. Results validate the performance accuracy and effectiveness of the proposed IGA based on the nth-order shear deformation theory, and they demonstrate that temperature-dependent material properties should be included in the thermal buckling analysis.

A method is presented to determine the additional load losses in transformers caused by harmonic currents. Several blackbox short circuit tests at different harmonic frequencies have to be conducted on existing transformers or have to be simulated in the design stage. A 'K-factor'-related formula allowing for the estimation of the total augmented losses in the transformers is derived. This approach is also valid for transformers containing windings of the foil type. It is shown by means of measurements and simulations that the rise of the losses does not follow a squared dependency as it is the case with traditional wire winding transformers. An alternative K-factor definition to be used with these transformers seems to be necessary and is provided here.

Thermal postbuckling analysis is presented for graphene-reinforced composite (GRC) laminated cylindrical shells under a uniform temperature field. The GRC layers are arranged in a functionally graded (FG) graphene reinforcement pattern by varying the graphene volume fraction in each GRC layer. The GRCs possess temperature dependent and anisotropic material properties and the extended Halpin–Tsai model is employed to evaluate the GRC material properties. The governing equations are based on a higher order shear deformation shell theory and include the von Karman-type kinematic nonlinearity and the thermal effects. A singular perturbation method in conjunction with a two-step perturbation approach is applied to determine the thermal postbuckling equilibrium path for a GRC shell with or without geometric imperfection. An iterative scheme is developed to obtain numerical thermal buckling temperatures and thermal postbuckling load–deflection curves for the shells. The results reveal that the FG-X piece-wise FG graphene distribution can enhance the thermal postbuckling capacity of the shells when the shells are subjected to a uniform temperature loading.

Thermal buckling of cylindrical shell with temperature-dependent material properties: Conventional theoretical solution and new numerical method

Modeling of thermal and lattice misfit stresses within a thermal barrier coating

Thermo-mechanical buckling analysis of non-uniformly heated rectangular plates with temperature-dependent material properties