Research on 3D temperature field and thermal-stress field numerical simulation of dry-type transformer curing process

Comsol 2D Simulation of Heavy Oil and Bitumen Recovery by SAGD

In order to control the thermal stress of forming process,based on "element birth and death" technology of finite element method,a numerical simulation of three-dimensional temperature field and stress field during multi-track and multi-layer laser metal deposition shaping(LMDS) process is developed with ANSYS parametric design language(APDL).The dynamic variances of temperature field and stress field of forming process are calculated with the energy compensation of interaction between molten pool-powder and laser-powder.The temperature field,temperature gradient,thermal stress field and distribution of residual stress are obtained.The results indicate that although the nodes on different layers are activated at different time,their temperature variations are similar.The temperature gradients of samples are larger near the molten pool area and mainly along z-direction.The transient thermal stress has concentrated in large temperature gradient area,which is in accordance with thermal stress forming theory.Through analyzing the residual stress of the as-formed samples in different directions,distribution rule of residual stress is achieved from temperature gradient perspective.And formation mechanism of residual stress is verified with an indirect way.Finally,it's verified that the analysis results are consistent with actual situation by the experiments with same process parameters.

Laser induced morphological damage have been observed in silicon-based positive-intrinsic-negative photodiode. This paper adopted the methods of the theoretical calculation and finite element numerical simulation to model, then solved the temperature field and thermal stress field in silicon-based positive-intrinsic-negative photodiode irradiated by multipulsed millisecond laser, and researched the features and laws of the temperature field and thermal stress field. As for the thermal-mechanical problem of multipulsed millisecond laser irradiating silicon-based positive-intrinsic-negative photodiode, based on Fourier heat conduction and thermoelasticity theories, we established a two-dimensional axisymmetric mathematical model .Then adopted finite element method to simulate the transient temperature field and thermal stress field. The temperature dependences of the material parameters and the absorption coefficient were taken into account in the calculation. The results indicated that there was the heat accumulation effect when multipulsed millisecond laser irradiating silicon-based positive-intrinsic-negative photodiode. The morphological damage threshold were obtained numerically. The evolution of temperature at the central point of the top surface, the temperature distribution along the radial direction in the end of laser irradiation and the temperature distribution along the axial direction in the end of laser irradiation were considered. Meanwhile, the radial stress, hoop stress, axial stress on the top surface and the R=500μm axis were also considered. The results showed that the morphological damage threshold decreased with the increased of the pulse number. The results of this study have reference significance of researching the thermal and thermal stress effect evolution’s features when multipulsed millisecond laser irradiating silicon-based positive-intrinsic-negative photodiode, then revealing the mechanism of interactions between millisecond laser and photodiode.

The temperature field and thermal stress field of cast-hot-working-die (CHWD) steel under high density electropulsing were investigated by finite element analysis method. The simulation analysis showed that, during the electropulsing discharging process, the existence of specimen notch resulted in the concentration effect of electric current, namely that the increase of current density in local position. The electric current with high density induced the concentration release of Joule heat and the formation of heat affected zone (HAZ) ahead of specimen notch tip. Because the expanding of HAZ with high temperature was restricted by the neighboring matrix with low temperature, the thermal compressive stress formed in the former during electropulsing discharging. The metallurgy process, under the condition of high temperature and pressure and accompanying thermal compressive stress, was regarded as being beneficial for enhancing mechanical properties and thermal fatigue resistance of CHWD steel and prolonging service lifetime of die in extremely high temperature condition.

Based on Von Mises yield criterion and elasto-plastic constitutive equations, an axisymmetric finite element model of a Gaussian laser beam irradiating a metal substrate was established. In the model of finite element, the finite difference hybrid algorithm is used to solve the problem of transient temperature field and stress field. Taking nonlinear thermal and mechanical properties into account, transient distributions of temperature field and stress fields generated by the pulse train of long-pulse laser in a piece of aluminium alloy plate were computed by the model. Moreover,distributions as well as histories of temperature and stress fields were obtained. Finite element analysis software COMSOL is used to simulate the Temperature and thermal stress fields during the pulse train of long-pulse laser irradiating 7A04 aluminium alloy plate. By the analysis of the results, it is found that Mises equivalent stress on the target surface distribute within the scope of the center of a certain radius. However, the stress is becoming smaller where far away from the center. Futhermore, the Mises equivalent stress almost does not effect on stress damage while the Mises equivalent stress is far less than the yield strength of aluminum alloy targets. Because of the good thermal conductivity of 7A04 aluminum alloy, thermal diffusion is extremely quick after laser irradiate. As a result, for the multi-pulsed laser, 7A04 aluminum alloy will not produce obvious temperature accumulation when the laser frequency is less than or equal to 10 Hz. The result of this paper provides theoretical foundation not only for research of theories of 7A04 aluminium alloy and its numerical simulation under laser radiation but also for long-pulse laser technology and widening its application scope.

In order to control the thermal stress of forming process, based on “element birth and death” technology of finite element method, a numerical simulation of three-dimensional temperature field and stress field during multi-track & multi-layer laser metal deposition shaping(LMDS) process is developed with ANSYS parametric design language (APDL). The dynamic variances of temperature field and stress field of forming process are calculated with the energy compensation of interaction between molten pool-powder and laser-powder. The temperature field, temperature gradient, thermal stress field and distribution of residual stress are obtained. The results indicate that although the nodes on different layers are activated at different time, their temperature variations are similar. The temperature gradients of samples are larger near the molten pool area and mainly along z-direction. Finally, it’s verified that the analysis results are consistent with actual situation by the experiments with same process parameters.

In this paper, the finite element simulation of laser drilling process has been carried out for the nickel alloy DD6. Both the transient temperature field and thermal stress field were computed via the commercial software package ANSYS. Based on the method of dimensional analysis, the dependence of various non-dimensional parameters on both fields was specified and demonstrated in graphical forms.

A typical 3D-BGA packaging model was set up and numerical simulation method was used to study its thermal field and thermal stress field distribution when chip works on a given power. Different heat convection coefficients and packaging materials had been applied to study their effects on the temperature and stress field. The results show that the influence on the temperature and stress field decreases with the increasing heat convection coefficients. On the study of the thermal stress and strain field, the maximum strain occurs at the edges region of the packaging, but the maximum stress appears on the top surface of sub-center ball because of the structural design with a cover shell, and it limits the occurrence of large deformation in some extent. This paper shows the general rules when BGA packaging model works, and helps to design advanced and reliable packaging structure.

A typical 3D-BGA packaging model was set up and numerical simulation method was used to study its thermal field and thermal stress field distribution when chip works on a given power. Different heat convection coefficients and packaging materials had been applied to study their effects on the temperature and stress field. The results show that the influence on the temperature and stress field decreases with the increasing heat convection coefficients. On the study of the thermal stress and strain field, the maximum strain occurs at the edges region of the packaging, but the maximum stress appears on the top surface of sub-center ball because of the structural design with a cover shell, and it limits the occurrence of large deformation in some extent. This paper shows the general rules when BGA packaging model works, and helps to design advanced and reliable packaging structure.

Two-dimensional (2D) transient coupled finite element model was developed to compute the temperature and stress field in cast billets, so as to predict the defects of the I-type billets made from AZ31 magnesium alloy and find the causes and solutions for surface cracks and shrinkages during direct-chill (DC) casting process. Method of equivalent specific heat was used in the heat conduction equation. The boundary and initial conditions used for primary and secondary cooling were elucidated on the basis of the heat transfer during the solidification of the billet. The temperature and the thermal-stress fields were simulated with the thermal-structural coupled module of ANSYS software. The influences of casting parameters on the distributions of temperature and stress were studied, which helped optimize the parameters (at pouring temperature of 680 °C, casting speed of 2 mm/s, heat-transfer coefficient of the second cooling equals to 5 000 W/m2·°C−1). The simulation results of thermal stress and strain fields reveal the formation mechanism of some casting defects, which is favourable for optimizing the casting parameters and obtain high quality billets. Some measures of controlling processes were taken to prevent the defects for direct-chill casting billets.

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Mild steel welded products are widely used for their excellent ductility. Tungsten inert gas (TIG) welding is a high-quality, pollution-free welding process suitable for a base part thickness greater than 3 mm. Fabricating mild steel products with an optimized welding process, material properties, and parameters is important to achieve better weld quality and minimum stresses/distortion. This study uses the finite element method to analyze the temperature and thermal stress fields during TIG welding for optimum bead geometry. The bead geometry was optimized using grey relational analysis by considering the flow rate, welding current, and gap distance. The welding current was the most influential factor affecting the performance measures, followed by the gas flow rate. The effect of welding parameters, such as welding voltage, efficiency, and speed on the temperature field and thermal stress were also numerically investigated. The maximum temperature and thermal stress induced in the weld part were 2083.63 °C and 424 MPa, respectively, for the given heat flux of 0.62 × 106 W/m2. Results showed that the temperature increases with the voltage and efficiency of the weld joint but decreases with an increase in welding speed.

Through numerical simulation, this study explores the effect of vibration-impact composite electric spark (VIES) surface treatment technology on the temperature and thermal stress fields of 2024-T3 aluminum alloy surfaces. The depth of the molten pool and residual stress are evaluated using orthogonal experiments to score different experimental schemes, resulting in three experimental parameters categorized as good, medium, and poor. The study then examines the temperature and thermal stress fields for these three sets of parameters during the strengthening process. The results indicate that, considering the temperature field, the distance between the heat source and the work piece directly affects the heating efficiency and temperature distribution. An appropriate distance and sufficient dwell time are essential for creating the ideal molten pool thickness. Analysis of the stress field results shows that in the early stage of strengthening, the inertia force of the small spheres is dominant, while in the later stage, the stress field created by the electric current becomes decisively dominant. This indicates that the electric current is the core of the three influencing factors in the orthogonal experiment.

FEA simulation and RSM based parametric optimisation of vibrating transmission gearbox housing

Based on finite element method(FEM), with general simulation software ANSYS FLOTRAN-CFD module as the platform, using three-dimensional SOLA-VOF method, set the velocity, pressure and temperature boundary conditions and initial conditions reasonably, simulate temperature field, flow field and free surface of Mold Filling process. To simulate the flow of molten metal more factually, mesh dividing method that suited the Liquid simulation was studied, and important thermophysical properties of viscosity and density used the form of function change with temperature. The least square method was used to fit viscosity and density function and these functions were given to boundary conditions. Analyzed the relationship between temperature field and flow field according to simulation result, and get the conclusion that the node temperature depends on filled state of elements attached. At the same time, Get the temperature field at the end of mold filling process, which provides accurate initial temperature field for temperature field and thermal stress field simulation of solidification process. Also provide valuable reference for numerical simulation of Mold Filling process and solidification process of similar part.