Understanding the thermal problem of variable gradient functionally graded plate based on hybrid numerical method under linear heat source

The thermal problem of functionally graded materials (FGM) under linear heat source is studied by a hybrid numerical method. The accuracy of the analytical method and the efficiency of the finite element method are taken into account. The volume fraction of FGM in the thickness direction can be changed by changing the gradient parameters. Based on the weighted residual method, the heat conduction equation under the third boundary condition is established. The temperature distribution of FGM under the action of linear heat source is obtained by Fourier transform. The results show that the closer to the heat source it is, the greater the influence of the heat source is and the influence of the heat source is local. The temperature change trend of the observation points is consistent with the heat source, showing a linear change. The results also show that the higher the value of gradient parameter is, the higher the temperature of location point is. The temperature distribution of observation points is positively correlated with gradient parameter. When the gradient parameter value exceeds a certain value, it has a little effect on the temperature change in the model and the heat conduction in the model tends to be pure metal heat conduction, the optimal gradient parameters combined the thermal insulation property of ceramics and the high strength toughness of metals are obtained.

Investigation of Heat Flux Propagation in Heat-Conducting Oxide Substrates with Different Heat Conductivity by the Linear Heat Source Method

Introduction. For controlled thermal management of power electronics devices, an important task is to increase the efficiency of heat removal from active components. Aim. To introduce a new approach to placing a linear contact-type heat source on the surface of thin samples in order to study the features of propagation of heat fluxes in oxide substrates from materials with different thermal conductivities. Methods and materials. The paper presents the results of studies of the propagation of heat fluxes in oxide substrates with different thermal conductivity (glassceramic and aluminum oxide ceramic - polycor). To generate the heat flux, a linear heat source was used, for which an electrically conductive carbon fiber was applied. Results. Thermograms and temperature distribution profiles were obtained at different periods of heating time on the surface of the substrate with a heating element and on its reverse side. It was shown that the placement of the linear heat source, implemented using an electrically conductive carbon filament, on the surface of the studied samples and time monitoring of thermograms from two opposite surfaces of the samples allowed to obtain data for evaluating the thermal properties of oxide substrates. The distribution of the heat flux in a homogeneous material near the generation point had the form of a cone of a heat pipe with a base on the surface with a heat source. The thermal cone for an aluminum oxide ceramic substrate had a larger angle of inclination than that in the case of glassceramic. Conclusion. The results obtained allowed to propose a method for reduction of thermal resistance of a heatconducting substrate by creating conditions for increasing the area of heat-conducting section.

Development of an Arbitrary Adaptive Volumetric Heat Source Model for Keyhole Mode Laser Welding Process

One of the anticipated objectives of laser welding is to produce deep penetration by forming a keyhole that entrains the energy over the depth without appreciable enlargement of weld width. The evolution of liquid/vapour interface over time considering the effect of interfacial phenomena like evaporation, homogeneous boiling, and multiple reflections makes the formation of keyhole geometry complex in nature. An analytical approach is developed explicitly to predict the keyhole geometry in the weldment during laser spot welding as well as linear welding. The model highly simplifies the heat transfer during the welding process by assuming an instantaneous linear heat source. The temperature field is then used to estimate the shape as well as the size of keyhole, which is arbitrary in shape in a discrete solution domain. This keyhole is considered as initial source of volumetric energy that is considered in a finite element-based Fourier heat conduction model. The distributed volumetric heat energy is adaptive in nature since it is mapped with the arbitrary volume of weld fusion zone at a time instant. The calculated results are validated with experimental results reported in independent literature.

СONTACT LOCAL HEATING OF AN ALUMINUM BASE WITH NANOPOROUS ALUMINA BY A LINEAR HEAT SOURCE FOR USE IN THERMOMETRY

The paper presents the results of thermal studies for a sample of aluminum with nanoporous alumina using thermal imaging measurements. As a heating element, a carbon thread based on a viscose technical thread was used. On the base of results, it was established that local heating of the sample surface by the contact method using a linear heat source can be used in thermometry to determine the thermal conductivity of solid multicomponent dielectric materials.