Three-dimensional Thermal Analysis Research Articles

Three-dimensional thermal stress analysis using the indirect BEM in conjunction with the radial integration method

Thermal stress analysis is one of key aspects in mechanical design. Based on the indirect boundary integral equation (BIE) and the radial integration method (RIM), this paper develops a boundary-only element method for the boundary stress analysis of three-dimensional (3D) static thermoelastic problems. A transformation system constructed with the normal and two special tangential vectors is used to regularize the singularity in the indirect BIE. The RIM is then employed to transform the domain integrals arising in both displacement and its derivative integral equations into the equivalent boundary integrals, which results in a pure boundary discretized algorithm. Several numerical experiments are provided to verify the accuracy and convergence of the present approach.

Thermal hydraulic and stress coupling analysis for AP1000 Pressurized Thermal Shock (PTS) study under SBLOCA scenario

Pressurized Thermal Shock (PTS) analysis for AP1000 under Small Break Loss of Coolant Accident (SBLOCA) was performed in this paper. The three-dimensional models of Direct Vessel Injection (DVI) line, Reactor Pressure Vessel (RPV) nozzles and downcomer were established. The mathematic models of three-dimensional thermal hydraulic and stress analysis were introduced. The numerical simulation of thermal-hydraulic mixing was carried out using Computational Fluid Dynamics (CFD) method under SBLOCA scenario. It was found that the temperature distribution in RPV downcomer depended on the injection velocity relative to cross-flow greatly. The RPV cooling center region was moving up with the increase of injection velocity. The temperature distribution was non-uniform along the circumferential orientation on RPV wall and the great temperature gradient was generated between the cooling center and other regions. The AP1000 RPV stress analysis was performed using Finite Element Analysis (FEA) method following thermal-hydraulic mixing study. Results show that the most critical zone was located in the DVI nozzle chamfering under SBLOCA transient. The stress was mainly induced by high temperature gradient and the maximum stress occured when the wall temperature has the largest reduce rate. This work is meaningful for the structure integrity study of AP1000 nuclear power plant.

Three-Dimensional FEM Thermal and Electrical Analysis of Copper Electrowining Intercell Bars

Intercell bars for copper electrowining collect and transfer the dc current from one cell to the next adjacent cell in a series configuration. Equipotential intercell bars are made of a large continuous copper busbar conductor to receive the cathode currents from one cell, rebalance the potential of the electrodes, and split the current to the next cell anodes. The potential balance by the bar itself produces undesirable side circulating currents with respective extra power losses at electrode contacts and throughout the copper busbar. This Joule heating collateral effect increases the busbar temperatures, the corrosion rates, and the electrical resistivity when copper annealed. This phenomenon is present on industrial sites. Using 3-D multiphysics finite-element methods tuned with industrial parameters, this study produces a scientific answer for this phenomenon. For describing the side effects of the potential reset, the concept of circulating current is developed and presented. This concept resembles reactive currents and its effects in power systems. In short, it explains why equipotential busbars exhibit and suffer higher overheating and accelerated corrosion rates. By contrast, its current source counterpart's bars are free of circulating currents and overheating. Finally, industrial measurements are included to support the results.

Thermal buckling of FGEM plates integrated with surface-bonded piezoelectric layers and temperature-dependent material properties

ABSTRACTBased on Reissner’s mixed variational theorem (RMVT), a unified formulation of finite layer methods (FLMs) is developed for the quasi three-dimensional (3-D) thermal buckling analysis of simply-supported, sandwich piezoelectric plates embedded with a functionally graded elastic material (FGEM) core, the material properties of which are considered to be thickness- and temperature-dependent. The plate is subjected to a uniform temperature change and with open-/closed-circuit boundary conditions on the lateral surfaces. A 3-D linear buckling theory is used, in which a set of membrane stresses is assumed to exist just before buckling occurs, and these membrane stresses are determined using a set of predefined 3-D deformations for the pre-buckling state. The material properties of the FGEM core are assumed to obey the power-law distributions varying through the thickness coordinate of the core according to the volume fractions of the constituents. The effective material properties are estimated using the rule of mixtures and Mori-Tanaka’s model. The accuracies and convergence rates of the FLMs with various orders, as used for expanding the elastic and electric variables in the thickness direction, are assessed by comparing their solutions with the exact 3D and accurate two-dimensional ones available in the literature.

Effects of Size of Microchannels on Thermo-Electrical Performance of an Internally Cooled Li-Ion Battery Cell

Thermal management of Li-ion batteries utilizing internal cooling method is the promising way to keep these batteries in an appropriate temperature range and to improve the temperature uniformity. In this study, three-dimensional transient thermal analysis was carried out to investigate the effects of size of embedded microchannels inside the electrodes on the thermal and electrical performances of a Li-ion battery cell. Based on the ratio of the width of microchannels to the width of the cell, different cases were designed; from the ratio of 0 (without any microchannels) to the ratio of 0.5. The results showed that increasing the size of the microchannels from the width ratio of 0 to the width ratio of 0.5 can reduce the maximum temperature inside the battery cell up to 11.22 K; it can also improve the temperature uniformity inside the battery cell. Increasing the electrolyte flow inlet temperature from 288.15 K to 308.15 K can enhance the temperature uniformity inside the battery and the cell voltage up to 33.20% and 2.79%, respectively. Increasing the electrolyte flow inlet velocity from 1 cm/s to 10 cm/s can reduce the maximum temperature inside the battery cell up to 8.09 K.

Three-dimensional thermal buckling analysis of functionally graded cylindrical panels using differential quadrature method (DQM)

Thermal buckling analysis of functionally graded cylindrical panels subjected to various conditions is discussed in this paper. Buckling governing equations are solved using the differential quadrature method. It is assumed that the mechanical properties of the panel are graded through thickness according to a power function of the thickness variable. The panel is assumed to be under the action of three types of thermal loading including uniform temperature rise and variable temperature rise in the axial and radial direction. In the present study, the effects of power law index, panel angle, different thermal load conditions and geometric parameters on the buckling behavior of functionally graded curved panels are studied. The results obtained through the present method are compared to the finite element solutions and the reported results in the literature. A desirable compatibility is concluded.

Optimization of a waste heat recovery system with thermoelectric generators by three-dimensional thermal resistance analysis

Three-dimensional (3D) thermal resistance analysis provides a rapid and simple method to estimate the power generated from a waste heat recovery system with thermoelectric generators (TEGs), and facilitates an optimization of the system. Such a system comprises three parts – a waste heat recovery chamber, TEG modules and a cooling system. A fin-structured duct serves as a waste heat recovery chamber, which is attached to the hot sides of the TEGs; the cold sides of the TEGs are attached to a cooling system. The waste heat recovery chamber harvests energy from exhaust heat that the TEGs convert into electricity. The estimation of generated power is an important part of the system design. Methods of Computational Fluid Dynamics (CFD) assist the analysis and improve the performance with great accuracy but great computational duration. The use of this method saves much time relative to such CFD methods. In 3D thermal resistance analysis, a node of unknown temperature is located at the centroid of each cell into which the system is divided. The relations of unknown temperatures at the cells are based on the energy conservation and the definition of thermal resistance. The temperatures of inlet waste hot gas and ambient fluid are known. With these boundary conditions, the unknown temperatures in the system are solved, enabling estimation of the power generated with TEGs. A 3D model of the system was simulated with FloTHERM; its numerical solution matched the solution of the 3D thermal resistance analysis within 6%. The power generated with the same system with TEGs (TMH400302055, Wise Life Technology, Taiwan) was measured; the experimental result is consistent with the result obtained from the 3D thermal resistance analysis; the relative deviation is approximately 10%. The power generated is affected by many variables; the positions of the TEGs, the uniformity of the internal flow of the velocity profile and the internal and external flow velocities are considered in our 3D thermal resistance analysis. According to the results, both the positions of the TEGs and the uniformity of the internal flow of the velocity profile should be taken into account to maximize the power generation. Under varied operational conditions, the power generated from the system might be more sensitive to the velocity of either the internal or external flow. Choosing an appropriate method makes increasing the power generation efficient. The relations between variables and power generation are readily revealed, even with varied parameters, yielding an optimal design of a waste heat recovery system.

Finite element analysis of deformation in early stage of multi-pass circumferential dissimilar welding of thick-walled pipes with narrow gap

Three-dimensional thermal elastic-plastic finite element analyses were conducted in order to reveal the mechanism of gap shrinkage in early stage of multi-pass narrow gap welding of thick-walled dissimilar pipes and thick plates. The gap shrinkage up to the 8th pass indicates that the shrinkage of plates becomes to be much larger than that of pipes with increasing the weld passes. In addition, through the decomposition of gap shrinkage to transverse shrinkage and angular distortion, it is found that the gap shrinkage of pipes is mainly governed by the transverse shrinkage, while the shrinkage of plates is influenced by both the transverse shrinkage and angular distortion. Moreover, the serial computational results with various groove shapes suggest that the transverse shrinkage of pipes almost linearly increases with increasing the weld pass, and its increment can be predicted by a linear approximation function obtained by the transverse shrinkage of plates regardless of the groove shape.

Thermal Analysis Simulation of Germanium Zone Refining Process Assuming a Constant Radio-Frequency Heating Source

Three-dimensional thermal analysis simulation of a horizontal zone refining system is conducted for germanium semiconductor materials. The considered geometry includes a graphite boat filled with germanium placed in a cylindrical quartz tube. A flow of Ar and H2 gas mixture is purged through the tube. A narrow section of the boat is assumed to be exposed to a constant heat rate produced by an rf coil located outside the quartz tube. The results of this analysis provide essential information about various parameters such as the shape of the molten zone, required power and temperature gradient in the system.

Examination using three-dimensional thermal conductivity-thermal stress analysis for prevention of galvanizing cracks during hot dip galvanizing of beam-to-column welded connection

Examination using three-dimensional thermal conductivity-thermal stress analysis for prevention of galvanizing cracks during hot dip galvanizing of beam-to-column welded connection

Sampling surfaces formulation for thermoelastic analysis of laminated functionally graded shells

This paper focuses on implementation of the sampling surfaces (SaS) method for the three-dimensional (3D) thermal stress analysis of steady-state thermoelasticity problems for laminated functionally graded (FG) shells. The SaS formulation is based on choosing inside the nth layer I n not equally spaced SaS parallel to the middle surface of the shell in order to introduce the temperatures and displacements of these surfaces as basic shell variables. Such choice of unknowns permits the presentation of the proposed thermoelastic FG shell formulation in a very compact form. The SaS are located inside each layer at Chebyshev polynomial nodes that improves the convergence of the SaS method significantly. As a result, the SaS formulation can be applied efficiently to analytical solutions for laminated FG shells, which asymptotically approach the 3D exact solutions of thermoelasticity as the number of SaS I n tends to infinity.

Numerical simulation and experimental validation of angular distortion and residual stresses in a T-joint

Abstract Welding is the most important method in modern industry. However, welding distortion and residual stress after welding are inevitable. In this paper, experiments were performed to obtain the angular distortion, temperature field and longitudinal residual stress in two T plate structures after welding and post-weld heat treatment, respectively. Then, a three-dimensional thermal elastic-plastic finite element analysis using internal heat generation was carried out to simulate the deformation and stress. The FE analysis results were in good agreement with the measurements. The results showed that both, the thickness of the plates and the heat treatment, could influence the angular distortion and residual stress distribution. Finally, the welding process at a bogie was also simulated by using the same heat source model as for the T-joint. The deformation and stresses were shown and explained.

Experimental Study of Surface Roughness and Tool Flank Wear during Hybrid Milling

Two advanced machining methods such as thermally enhanced machining and ultrasonic-assisted machining are recently considered in many studies. In this article, a new hybrid milling process is presented by gathering the characteristics of these two methods. In order to determine the axial depth of cut and engagement in the process, three-dimensional thermal finite-element analysis is applied to determine the dimensions of softened materials. Finite-element modal analysis is used to determine the dimensions and clamping state of the workpiece while cutting area has the highest vibration amplitude. Full factorial experimental design is applied to investigate the effect of hybrid machining parameters on the surface roughness and tool wear. Tool flank wear was investigated under the condition of constant cutting speed during different period of times. Hybrid milling process with an amplitude of 6 µm and a temperature of 900°C creates a surface with 42% lower roughness in comparison to conventional milling in feed 0.08 mm/tooth. In a study of tool flank wear, the results show that application of TEUAM decreases flank wear at least 16% in comparison to all other processes.

Three-dimensional thermal stress analysis of laminated composite plates with general layups by a sampling surfaces method

Abstract A paper focuses on the application of the method of sampling surfaces (SaS) to three-dimensional (3D) steady-state thermoelasticity problems for orthotropic and anisotropic laminated plates subjected to thermal loading. This method is based on selecting inside the n th layer I n not equally spaced SaS parallel to the middle surface of the plate in order to choose temperatures and displacements of these surfaces as basic plate variables. Such an idea permits the presentation of the proposed thermoelastic laminated plate formulation in a very compact form. It is worth noting that the SaS are located inside each layer at Chebyshev polynomial nodes that leads to a uniform convergence of the SaS method. As a result, the SaS method can be applied efficiently to the 3D stress analysis of cross-ply and angle-ply composite plates with a specified accuracy utilizing the sufficient number of SaS.

Three-Dimensional Thermal Analysis of Three-Phase Enclosed GIS Bus Bars

The ampacity of GIS bus bars is limited by the maximum operation temperature of the contacts. This paper employs the coupled eddy current, fluid and thermal finite-element method (FEM) to solve the three-dimensional (3-D) heat transfer problem in a three-phase enclosed GIS bus bar. The contact resistance is considered and described as a resistor between the conductor and the contact finger. In order to avoid convective boundary condition on the tank surface which is not easy to apply, the ambient air is introduced into the solution region. The temperature dependent thermal properties of SF 6 gas and air are considered. The temperatures calculated by proposed model are found to be in good agreement with the experimental data of a 126 kV three-phase enclosed bus bar prototype.

Three-Dimensional Thermal Analysis of Three-Phase Enclosed GIS Bus Bars

Three-Dimensional Thermal Analysis of Three-Phase Enclosed GIS Bus Bars

3 차원 열전달/열응력 해석을 통한 STD61 열간 금형강의 하드페이싱 재료 및 두께 예측

The goal of this paper is to estimate proper hardfacing material and thickness of STD61 hot-working tool steel through three-dimensional heat transfer and thermal stress analyses. Stellite6, Stellite21 and 19-9DL superalloys are chosen as alternative hardfacing materials. The influence of hardfacing materials and thicknesses on temperature, thermal stress and thermal strain distributions of the hardfaced part are investigated using the results of the analyses. From the results of the investigation, it has been noted that a hardfacing material with a high conductivity and a thinner hardfaced layer are desired to create an effective hardfacing layer in terms of heat transfer characteristics. In addition, it has been revealed that the deviation of effective stress and principal strain in the vicinity of the joined region are minimized when the Stellite21 hardfaced layer with the thickness of 2 mm is created on the STD61. Based on the above results, a proper hardfacing material and thickness for STD61 tool steel have been estimated.

Three-dimensional thermal sensitivity analysis of cooling of a magma chamber in the Los Azufres geothermal field, Michoacán, Mexico

We present three-dimensional simulation of cooling of 63 models of a magma chamber in the Los Azufres geothermal field by varying the top of the chamber depth between 5 and 9 km (centroid from about 7 to 13 km) and its volume between 300 and 600 km3. Nineteen new best-fit cubic equations are presented to represent the temperature field in the geothermal reservoir in terms of the chamber centroid depth, its volume, or both. These equations clearly show that the thermal regime is much more sensitive to chamber depth than to its volume. These simulation results imply that, for a better estimation of the energy budget of a volcanic area, the depth parameter should be better constrained than the chamber volume. Geoscientists are, therefore, encouraged to obtain more reliable estimates of magma chamber depths for active volcanoes and potential geothermal areas. Furthermore, the smallest discretization time and mesh size should be used for solving the heat flow equations in three-dimensions.

Reduction of Welding Distortion for an Improved Assembly Process for Hatch Coaming Production

The alignment between the hatch coaming top surface and hatch cover is essential to maintain hatch cover water tightness and smooth mechanical operation. An improved assembly process for hatch coaming production is proposed, in which the complete hatch coaming is assembled on the shop floor and then lifted as one part, fitted, and welded to the deck. When this complete hatch coaming is assembled to a ship deck, an irregularly distributed gap is usually found between the lower side of the hatch coaming and the deck. Fitting and welding distortion, in particular longitudinal and transverse shrinkage, influence the dimensional accuracy and consequently the production schedule. In this research, welding pass sequence of a fillet welded joint is improved using thermal elastic plastic analysis and welding distortion of the hatch coaming top surface is predicted using elastic analysis. First, three specimens with different gaps that model the welded joint between the hatch coaming and deck were welded and the changed distance between the measuring equipment and the flange was measured. A three-dimensional thermal elastic plastic finite element analysis was carried out for the same specimens and the computed welding distortion was shown to have good agreement with the measurements. As a result of the possible significant influence of welding pass sequence on transverse shrinkage of a fillet welded joint, the influence of welding pass sequence is studied using the computational approach and improved welding pass sequences are proposed to reduce transverse shrinkage. Finally, elastic analysis using inherent longitudinal and transverse shrinkage deformations evaluated by thermal elastic plastic analysis is used to predict welding distortion of the hatch coaming. In this elastic analysis, the influence of different gaps at different locations between the hatch coaming and the deck is considered.

Reduction of Welding Distortion for an Improved Assembly Process for Hatch Coaming Production

The alignment between the hatch coaming top surface and hatch cover is essential to maintain hatch cover water tightness and smooth mechanical operation. An improved assembly process for hatch coaming production is proposed, in which the complete hatch coaming is assembled on the shop floor and then lifted as one part, fitted, and welded to the deck. When this complete hatch coaming is assembled to a ship deck, an irregularly distributed gap is usually found between the lower side of the hatch coaming and the deck. Fitting and welding distortion, in particular longitudinal and transverse shrinkage, influence the dimensional accuracy and consequently the production schedule. In this research, welding pass sequence of a fillet welded joint is improved using thermal elastic plastic analysis and welding distortion of the hatch coaming top surface is predicted using elastic analysis. First, three specimens with different gaps that model the welded joint between the hatch coaming and deck were welded and the changed distance between the measuring equipment and the flange was measured. A three-dimensional thermal elastic plastic finite element analysis was carried out for the same specimens and the computed welding distortion was shown to have good agreement with the measurements. As a result of the possible significant influence of welding pass sequence on transverse shrinkage of a fillet welded joint, the influence of welding pass sequence is studied using the computational approach and improved welding pass sequences are proposed to reduce transverse shrinkage. Finally, elastic analysis using inherent longitudinal and transverse shrinkage deformations evaluated by thermal elastic plastic analysis is used to predict welding distortion of the hatch coaming. In this elastic analysis, the influence of different gaps at different locations between the hatch coaming and the deck is considered.