Thermal Stress Distribution Research Articles

Direct Growth of Patterned Vertical Graphene Using Thermal Stress Mismatch between Barrier Layer and Substrate

Vertical graphene (VG) combines the excellent properties of conventional graphene with a unique vertical nanosheet structure, and has shown tremendous promise in the field of electronics and composites. However, its complex surface morphology brings great difficulties to micro-nano fabrication, especially regarding photolithography induced nanosheet collapse and remaining chemical residues. Here, we demonstrate an innovative method for directly growing patterned VG on a SiO2/Si substrate. A patterned Cr film was deposited on the substrate as a barrier layer. The VG was synthesized by PECVD on both the patterned Cr film and the exposed SiO2/Si substrate. During the cooling process, the patterned Cr film covered by VG naturally peeled off from the substrate due to the thermal stress mismatch, while the VG directly grown on the SiO2/Si substrate was remained. The temperature-dependent thermal stress distribution in each layer was analyzed using finite element simulations, and the separation mechanism of the Cr film from the substrate was explained. This method avoids the contamination and damage caused by the VG photolithography process. Our work is expected to provide a convenient and reliable solution for the manufacture of VG-based electronic devices.

Investigation of temperature field for the in-situ fabrication of particle-reinforced alumina ceramics coating via laser induction

Laser-induced aluminum thermal reaction was used to prepare a new iron particle reinforced alumina ceramic coating on the surface of TC4 titanium alloy. The aluminum thermal reaction heat generation in the on-line laser melting and coating process is fast and not easy to control, and its effect on the coating quality is unknown and usually neglected in the preparation process. In this paper, a numerical simulation model of a dual heat source containing the reaction heat is established. The temperature field of the new Al2O3-Fe composite coating and the thermal stress distribution pattern of the components were investigated. The effects of different laser parameters on the maximum molten pool temperature, thermal deformation and coating morphology of TC4 titanium alloy substrates were also discussed. The accuracy of the model is verified by the joint temperature acquisition experiment, which provides a reference for the selection of laser cladding process parameters. The simulation results show that the maximum temperature and volume of the melt pool increase significantly due to the coupling of the induced reaction heat, and the maximum temperature is not inversely proportional to the laser scanning speed, but directly proportional. The residual stress analysis shows that the residual stress on the coating is mainly the tensile stress along the laser cladding direction, which is the main reason for the transverse crack of the single layer coating after laser cladding.

The microstructure and mechanical properties of 316L austenitic stainless steel prepared by forge and laser melting deposition

In this study, the 316L austenitic stainless steel blocks were prepared by forge and laser melting deposition (LMD). To clarify the effect of deposition strategy on microstructure and mechanical properties of 316L samples, three different deposition strategies (30°, 67° and 90°) are selected. The results showed that the molten pool of LMDed sample consists of a large number of coarse columnar grains and a few irregular equiaxed grains, which contains plentiful cellular and fiber sub-structures with an average size of ∼4 μm. The LMD process can significantly improve the comprehensive mechanical properties perpendicular to the build direction of 316L austenitic stainless steel, which was mainly attributed to sub-structural strengthening, but also slightly due to the local misorientation and texture distribution. The yield strength and ultimate tensile strength of R90 sample increased to 484.0 MPa and 627.6 MPa from 305.3 MPa to 601.4 MPa of as-forged 316L, and its elongation has a negligible reduction. The sub-structures produced during solidification have the same fine grain strengthening effect as the high-angle grain boundary, and the yield strength and average size of sub-structures conform to the Hall-Petch relationship. The deterioration of the plastic deformation capacity of the R67 sample is attributed to the larger thermal stress and texture distribution with a certain hard orientation. The plastic deformation of as-forged sample is mainly coordinated by multi-system slip, while twinning and slip are activated together during deformation of LMDed 316L austenitic stainless steel. The grain boundary map indicated that the strain location preferentially appears along cell wall of sub-structures, which promotes the formation of sub-grain boundaries during deformation of LMDed samples.

Transient Finite-Speed Heat Transfer Influence on Deformation of a Nanoplate with Ultrafast Circular Ring Heating

The present study provides a theoretical estimate for the thermal stress distribution and the displacement vector inside a nano-thick infinite plate due to an exponentially temporal decaying boundary heating on the front surface of the elastic plate. The surface heating is in the form of a circular ring; therefore, the axisymmetric formulation is adopted. Three different hyperbolic models of thermal transport are considered: the Maxwell-Cattaneo-Vernotte (MCV), hyperbolic Dual-Phase-Lag (HDPL) and modified hyperbolic Dual-Phase-Lag (MHDPL), which coincides with the two-step model under certain constraints. A focus is directed to the main features of the corresponding hyperbolic thermoelastic models, e.g., finite-speed thermal waves, singular surfaces (wave fronts) and wave reflection on the rear surface of the plate. Explicit expressions for the thermal and mechanical wave speeds are derived and discussed. Exact solution for the temperature in the short-time domain is derived when the thermalization time on the front surface is very long. The temperature, hydrostatic stress and displacement vector are represented in the space-time domain, with concentrating attention on the thermal reflection phenomenon on the thermally insulated rear surface. We find that the mechanical wave speeds are approximately equal for the considered models, while the thermal wave speeds are entirely different such that the modified hyperbolic dual-phase-lag thermoelasticity has the faster thermal wave speed and the Lord-Shulman thermoelasticity has the slower thermal wave speed.

Cold plate performance enhancement based on parametric modeling of multiple structures

Power electronic equipment to miniaturization, high integration direction while facing the problem of high heat flow density and uneven temperature distribution. The large temperature fluctuations and uneven temperature distribution in the operation of power electronic equipment will lead to thermal stress, and excessive thermal stress or uneven distribution will cause fatigue failure of the packaging material, resulting in reduced reliability, module failure, and reduced life of power electronic equipment. In this paper, we propose two kinds of liquid-cooled flow channel non-linear reinforced heat transfer homogeneous liquid-cooled plate, which is theoretically derived to achieve the design requirement of uniform temperature on the heating side wall surface. The thermal design of the cold plate is carried out using ANSYS Workbench, and the indicators of various structures of the cold plate are analyzed and compared in terms of their ability to dissipate heat and maintain temperature uniformity. Based on the original runner structure, the heat dissipation performance of the rod structure and fin structure was evaluated, and the form of the internal heat dissipation structure of the runner was determined. The results show that the integrated liquid cooling plate temperature uniformity and flow resistance of both factors, the fin column heat sink is significantly better than the cylindrical fin column heat sink in the case of the same thermal resistance, the fin column heat sink flow resistance is significantly lower than the cylindrical fin column heat sink.

Distribution optimization of thermal through-silicon via for 3D chip based on thermal-mechanic coupling

This study establishes a unit cell model of thermal-mechanical coupling of 3D chip thermal through-silicon via (TTSV), and conducts optimization study under the constraints of the given ratio of total unit cell volume to TTSV volume. A single-degree-of-freedom optimization study with TTSV spacing as the design variable was first carried out to analyze the impact laws of heat flow density in the hot spot region, TTSV filling material and volume share on the optimal structure and maximum temperature. The results of the two-degree-of-freedom optimization with TTSV spacing and TTSV array rotation angle as design variables were further investigated to determine the distribution of thermal stresses. The maximum temperature of the cell decreases and then increases with the increase in the TTSV pitch, regardless of the rotation angle of the TTSV array, and there exists a minimum value. The higher the temperature, the higher the thermal stress. Thermal stress is always concentrated in the inner and edge regions of the TTSV.

Finite element simulation of residual stress distribution during selective laser melting of Mg-Y-Sm-Zn-Zr alloy

Selective laser melting (SLM) has been confirmed as a promising additive manufacturing technology for the formation of lightweight structural parts of magnesium alloy. However, it is noteworthy that residual stress is easily generated during the SLM process of magnesium alloy, and it will induce cracks to reduce the compactness of formed parts. In this study, a three-dimensional (3D) nonlinear transient thermodynamic coupled finite element model (FEM) was built to analyze the effects of the scanning strategy on the thermal stress evolution and residual stress distribution during the SLM process of Mg-Y-Sm-Zn-Zr alloy. Moreover, six groups of simulation tests were performed based on three different scanning strategies (i.e., successive scanning, island scanning, and orthogonal scanning). The stress values of equal scale specimens produced with the same process parameters were examined to verify the simulation results. The equivalent residual stress was the largest under the use of the successive scanning strategy, as indicated by the results. Using the island scanning, the stress distribution in the island was similar to that of successive scanning, whereas there was a high-stress island close to the interface. Besides, the average S11 and S22 residual stresses were 4.90% and 36.13% lower than that of the successive scanning, respectively. Orthogonal scanning was confirmed as the most effective scanning strategy to reduce residual stress. To be specific, the average S11 and S22 residual stresses were 25.19% and 43.12% lower than that of successive scanning when using the intralayer orthogonal scanning. The simulation and experimental verification results indicated that the maximum equivalent residual stress is the lowest (229 MPa), and the stress distribution was most uniform when orthogonal scanning was performed between 4 × 4 island.

Thermal-Stress Coupling Optimization for Coaxial through Silicon Via

In this paper, a thermal-stress coupling optimization strategy for coaxial through silicon via (TSV) is developed based on the finite element method (FEM), artificial neural network (ANN) model and particle swarm optimization (PSO) algorithm. In order to analyze the effect of design parameters on the thermal-stress distribution of coaxial TSV, the FEM simulations of coaxial TSV are conducted by COMSOL Multiphysics. The structure of coaxial TSV is symmetric. The mapping relationships between the design parameters and performance indexes are described by ANN models based on the simulation data of FEM. In addition, the multi-objective optimization function is formulated based on the desired performance indexes, and then the design parameters are optimized by the modified PSO algorithm. Based on the optimized design parameters, the effectiveness of the developed method is validated by FEM simulations. The simulated performance indexes agree well with the desired ones, which implies that the design parameters of coaxial TSV can be optimized to control the thermal-stress distribution. Therefore, the thermal-stress coupling optimization of coaxial TSV can achieve thermal-stress management to improve its reliability.

Prediction of thermal and residual stress distributions in SS304 materials for nuclear application using finite element analysis

Prediction of thermal and residual stress distributions in SS304 materials for nuclear application using finite element analysis

Minimization of thermal stress in perforated composite plate using metaheuristic algorithms WOA, SCA and GA

In this study, an attempt is made to achieve optimal thermal stress distribution in symmetric composite plates with non-circular holes under uniform heat flux by using metaheuristic optimization algorithms. The analytical solution is based on the thermo-elastic theory and the complex variable method. In addition, the stress analysis of laminated composite plates with circular holes is extended to non-circular holes using the appropriate mapping function. To determine the optimum thermal stress, the whale optimization algorithm (WOA) which is inspired by the lifestyle of humpback whales in nature, the sine cosine algorithm (SCA) that is inspired by the calculation of sine and cosine functions and the genetic algorithm (GA) are utilized. The effect of hole orientation, stacking sequence of laminates, bluntness and hole shape as significant parameters on optimum thermal stress distribution around the holes are studied. The laminate is made of graphite/epoxy material with stacking sequences of [0/90] s , [45/-45] s and [30/0/–30] s . The cost function is considered as the maximum value of thermal stress surrounding the hole. The performance of optimization algorithms is examined. It is found out that the circular shape for hole may not necessarily be the optimum geometry for all stacking sequences.

3D Simulation Study on Thermal Behavior and Thermal Stress of Lithium‐Ion Battery

Temperature and thermal stress are crucial factors affecting the working performance and thermal safety of lithium‐ion batteries (LIBs). During the discharge process of the battery, the temperature increases. The thermal expansion stress caused by the entropy heat and the ohmic heat can lead to the battery's lifetime reduction and even thermal safety issues. Herein, based on the coupled electrochemical model, the LIB's thermal behavior and thermal stress distribution at a 1C discharge rate are simulated and analyzed. The results show that the temperature distribution inside the battery is mainly affected by the heat exchange surface and the position of the tabs during the discharging process, in which the localized high‐temperature region occurs in the positive tab. The thermal stress inside the battery enhances rapidly at both the beginning and end of the discharging process while increasing slowly in the middle.

Effects of voltage variation on heat and stress distributions in the electrochromic glass

Electrochromic glass has been used in many applications, such as the building envelope, because its light filtration can be adjusted in a controllable manner using low input energy. Electrochromic glass is a composite glass that consists of five layers. These five layers have two layers of glass, two layers of Indium Tin Oxide (ITO) and a layer of Poly (3-hexylthiophene), which is an electrochromic film. When a current passes through the glass, a voltage difference occurs, resulting in a redox reaction at an electrode layer. This causes the glass to change colour from transparent to opaque, resulting in a change in radiation absorption, which affects the heat transfer process. The study investigates temperature and thermal stress distributions in electrochromic glass by adjusting an input voltage in a range of 0–2.6 V. The spectral absorbance data at all light spectrum ranges were experimentally obtained. The averaged absorbance data were used for calculating the heat generation rate, and used as the input parameter for three-dimensional (3D) multiphysics simulations. The maximum temperature and thermal stress of the electrochromic glass are reached at 1.8 V according to the high rate of heat generation. The peak value of stress occurs at the interface between ITO and electrochromic layers. This study provides information regarding the heat transfer process and the stress induced in the electrochromic glass which varies with the applied voltages and can be applied to glass industries and many other related fields.

Significance of thermal stress in a convective-radiative annular fin with magnetic field and heat generation: application of DTM and MRPSM

The present paper explains the temperature attribute of a convective-radiative rectangular profiled annular fin with the impact of magnetic field. The effect of thermal radiation, convection, and magnetic field on thermal stress distribution is also studied in this investigation. The governing energy equation representing the steady-state heat conduction, convection, and radiation process is transformed into its dimensionless nonlinear ordinary differential equation (ODE) with corresponding boundary conditions using non-dimensional terms. The obtained ODE is then solved analytically by employing the Pade approximant-differential transform method (DTM) and modified residual power series method (MRPSM). Moreover, the important characteristics of the temperature field, the thermal stress, and the impact of some non-dimensional parameters are inspected graphically, and a physical explanation is provided to aid in comprehension. The significant findings of the investigation reveal that temperature distribution enhances with an increase in the magnitude of the heat generation parameter and thermal conductivity parameter, but it gradually decreases with an increment of convective-conductive parameter, Hartmann number, and radiative-conductive parameter. The thermal stress distribution of the fin varies considerably in the applied magnetic field effect.

Investigation of Electrical and Mechanical Reliability of Inkjet-Printed 4-Terminal Microelectromechanical Relays

We investigate the mechanical and electrical reliability of inkjet-printed 4-terminal (4T) microelectromechanical (MEM) relays in various failure modes. Since an inkjet-printed mechanical relay exhibits an extremely low on-resistance (~4 Ω), the endurance of MEM relays can be limited dominantly by Joule heating from the high current density at the contacting asperities, which eventually leads to welding-induced and electromigration failures. Therefore, high drain-source voltage can reduce the mean number of cycles to failure (MCTF). In addition, the endurance also depends on the structural fatigue of the floated beams, where the mechanical strain is concentrated near the junction area of the two floated beams. Thermal and mechanical stress distributions of the suggested printed 4T MEM relay are analyzed by 3-dimensional affected significantly by charging of the dielectric or oxidation of the contacting surface which can degrade a pull-in voltage and on-current, respectively.

Generalized Thermoelastic Interactions in an Infinite Viscothermoelastic Medium under the Nonlocal Thermoelastic Model

The wave propagation in viscothermoelastic materials is discussed in the present work using the nonlocal thermoelasticity model. This model was created using the Lord and Shulman generalized thermoelastic model due to the consequences of delay times in the formulations of heat conduction and the motion equations. This model was created using Eringen’s theory of the nonlocal continuum. The linear Kelvin–Voigt viscoelasticity model explains the viscoelastic properties of isotropic material. The analytical solutions for the displacement, temperature, and thermal stress distributions are obtained by the eigenvalues approach with the integral transforms in the Laplace transform techniques. The field functions, namely displacement, temperature, and stress, have been graphically depicted for local and nonlocal viscothermoelastic materials to assess the quality of wave propagation in various outcomes of interest. The results are displayed graphically to illustrate the effects of nonlocal thermoelasticity and viscoelasticity. Comparisons are made with and without thermal relaxation time. The outcomes show that Eringen’s nonlocal viscothemoelasticity theory is a promising criterion for analyzing nanostructures, considering the small size effects.

Numerical Investigation of Heat/Flow Transfer and Thermal Stress in an Anode-Supported Planar SOFC

To elucidate the thermofluid reacting environment and thermal stress inside a solid oxide fuel cell (SOFC), a three-dimensional SOFC model is implemented by using the finite element method in the commercial software COMSOL Multiphysics®, which contains both a geometric model of the full-cell structure and a mathematical model. The mathematical model describes heat and mass transfer, electrochemical reactions, internal reforming reactions, and mechanical behaviors that occur within the cell. A parameter study is performed focusing on the inlet fuel composition, where humidified hydrogen and methane syngas (the steam-to-carbon ratio is 3) as well as the local distribution of temperature, velocity, gas concentrations, and thermal stress are predicted and presented. The simulated results show that the fuel inlet composition has a significant effect on the temperature and gas concentration distributions. The high-temperature zone of the hydrogen-fueled SOFC is located at the central part of units 5, 6, and 7, and the maximum value is about 44 K higher than that of methane syngas-fueled SOFC. The methane-reforming and electrochemical reactions in the anode active layer result in a significant concentration gradient between the anode support layer and the active layer of the methane syngas-fueled SOFC. It is also found that the thermal stress distributions of different fuel inlet compositions are rather different. The maximum stress variation gradient between electrode layers of hydrogen SOFC is larger (44.2 MPa) than that of methanol syngas SOFC (14.1 MPa), but the remaining components have a more uniform stress distribution. In addition, the electrode layer of each fuel SOFC produces a significant stress gradient in the y-axis direction, and stress extremes appear in the corner regions where adjacent assembly components are in contact.

Determination of three-dimensional thermo-mechanical behavior of bidirectional functionally graded rectangular plates with the theory of elasticity

In this study, the thermo-mechanical behavior of rectangular plates functionally graded (FG) in two directions along the plane is investigated with three-dimensional (3D) elasticity equations. In numerical analysis, the finite difference method (FDM) is used and the directional variation of the derivatives of the material properties is taken into account. The thermo-mechanical behavior of the plates is investigated for different compositional gradient exponents and it is emphasized that the variation of the compositional gradient exponent in both directions significantly changed the thermal stress distribution and the results are confirmed.

Thermal stress analysis for a typical planar anode-supported fuel cell stack

Many stack designing and optimizing works are addressed basing on the single fuel cell unit or one-cell stack by experiment or 3D calculated fluid dynamics modeling. Whether these results are also suitable for a larger stack may require further investigation. In this paper, the electrochemical-multiphysical and mechanic coupling model for a typical solid oxide fuel cell (SOFC) stack is well established and verified by experiment result. Then, the performance and thermal stress distributions within the stacks with different layers are studied. The result shows that the electrochemical-multiphysics distributing characteristics within four different small-scale stacks are similar, while they are fed with similar fuel/air flow rates. The effects of the structure and parameters on the electrochemical-multiphysics performance obtained by single SOFC unit would be proved to be also suitable for the extended small-scale stacks. The stress magnitude and distributing zone over the piled SOFC units, however, are different from each other, even there are similar temperature distributions. The farther the cell unit from the bottom support the bigger of the high stress areas in those cells. The junction between the glass–ceramic and SOFC unit would suffer from high stress risk and is a potential failure location on the stack.

Heat Flow and Thermal Stress Analysis to Enhance the Temperature Distribution and Service Life of Stone Grill Plates in Barbecue Ovens

The causes of the fracturing of stone grills in barbecue ovens were analyzed using a coupled analysis model that combined combustion thermodynamics with heat conduction and the finite element method. The proportion of mixed air for combustion was simulated, and the stone grill plate temperature and thermal stress distribution were the two factors taken to enhance the design of stone grill plates. Moreover, thermal images were used to compare the performance of the original and the improved plates to quantify the improvements, and validate the accuracy of the simulations. The results showed that the temperature distribution was uniform across the stone grill plate. When comparing the simulation model and the actual experiment, the simulation model can generate an optimal design with fewer errors in a shorter period. The combustion tube is deemed to have considerable influence on the performance of the barbecue oven. The surface temperature distribution of the stone grill plate was improved by controlling the amount of fuel entering the combustion system and/or changing the material and shape of the stone grill. On the other hand, the analysis results of the improved stone grill plate in this study showed that we can correct the temperature difference and thermal stress difference caused by the opening of the upper cover of the oven. According to our study, the average thermal stress on the surface of the stone grill plate was effectively reduced by 45.3 MPa. The average temperature difference decreased by 91 °C. At the same time, by improving the intake position and method of the combustion tube, the air mass flow in the combustion tube increased by 12%, which effectively improved the combustion efficiency of the combustion tube. In particular, a more uniform distribution was achieved by decreasing the temperature of the mixed air entering the combustion tube, which in turn increased the flow rate and velocity of the air flowing through the top of the flame to the bottom surface of the stone grill plate. The strategies employed can prevent the thermal-stress-induced fracturing of stone grill plates and prolong their service life.

The Effect of a Nonlocal Thermoelastic Model on a Thermoelastic Material under Fractional Time Derivatives

This article develops a novel nonlocal theory of generalized thermoelastic material based on fractional time derivatives and Eringen’s nonlocal thermoelasticity. An ultra-short pulse laser heats the surface of the medium’s surrounding plane. Using the Laplace transform method, the basic equations and their accompanying boundary conditions were numerically solved. The distribution of thermal stress, temperature and displacement are physical variables for which the eigenvalues approach was employed to generate the analytical solution. Visual representations were used to examine the influence of the nonlocal parameters and fractional time derivative parameters on the wave propagation distributions of the physical fields for materials. The consideration of the nonlocal thermoelasticity theory (nonlocal elasticity and heat conduction) with fractional time derivatives may lead us to conclude that the variations in physical quantities are considerably impacted.