Thermo-mechanical Stress Analysis Research Articles

Detailed modeling and numerical analysis of thermo mechanical stresses in the crystalline silicon and thin film PV modules under varying climatic conditions

The present manuscript provides an in-depth analysis of the modeling and simulation of thermo-mechanical stresses in photovoltaic panels using finite element (FEM) analysis. It covers important aspects such as the choice of the model, including governing equations, boundary conditions, and simplifying assumptions. The study mainly focuses on evaluating the impact of environmental conditions on the thermo-mechanical stresses of first-generation c-Si and second-generation thin-film CdTe and a-Si PV panels in five different climatic zones in Algeria. The proposed transient 3D numerical model is validated against experimental measurements by other researchers and the tabulated values of the nominal operating temperature of the cell (NOCT). The obtained results indicate that the first principle stress for the c-Si cell is lower compared to CdTe and a-Si cells; this can be explained by looking at the thickness, as well as the Young modulus of the solar cell. Consequently, in regions or countries with hot climatic conditions or large temperature gradients, it is recommended to use PV panels based on first-generation c-Si cells with glass-glass as the front and back covers.

Thermomechanical Stress Analysis, Characterization, and Optimization for Double-Side Cooled Power Modules With Ceramic Substrate

Thermomechanical Stress Analysis, Characterization, and Optimization for Double-Side Cooled Power Modules With Ceramic Substrate

Research and Analysis of Thermomechanical Stresses in the Structure of a Wafer with Embedded ICs with Consideration of Temperature Effects in Manufacturing Process Route

Research and Analysis of Thermomechanical Stresses in the Structure of a Wafer with Embedded ICs with Consideration of Temperature Effects in Manufacturing Process Route

Thermomechanical stress analysis of popliteal artery in various configurations during vitrification

Thermomechanical stress analysis of popliteal artery in various configurations during vitrification

Thermomechanical stress analysis and fatigue lifetime evaluation of coal-fired boiler components during peak shaving transient processes: Effects of load cycling rate

The operational flexibility of coal-fired power plants has become a critical concern, but it leads to heightened fatigue damage and reduced operational lifetime as the load cycling rate increases. This study mainly focuses on the fatigue lifetime evaluation of main components within the boiler. Based on the dynamic model of the coal-fired power plants via GSE software, the dynamic characteristics of main thermodynamic parameters within the boiler under different load cycling rates are obtained. Additionally, the equivalent thermomechanical stresses by using the finite difference method are calculated and the fatigue lifetimes in accordance with the ASME design fatigue evaluation code of main components within the boiler are evaluated. It turns out that the maximum load cycling rate is 3.0 % Pe min−1 for the loading up and down processes between 50 % THA and 75 % THA. Moreover, during the loading up process, the panel superheater exhibits the highest equivalent thermomechanical stress, peaking at 171.22 MPa, and is the component with the lowest allowable number of cycles, merely reaching 19458 at a 3.0 % Pe min−1 load cycling rate. Conversely, during the loading down process, the high temperature superheater exhibits the highest equivalent thermomechanical stress at 145.74 MPa and is also the component with the fewest allowable cycles, amounting to 20182 at a 3.0 % Pe min−1 load cycling rate.

Transient Thermomechanical Stress Analysis of Hot Surface Ignition Device Using Sequentially Coupled Computational Fluid Dynamics–Finite Element Analysis Approach

Abstract Energy addition using a hot surface ignition device is required for reliable ignition of aircraft compression ignition engines running on fuel variations and at altitude conditions. Thus, durability of the hot surface ignition device is crucial for application in these engines. Thermomechanical stress is one of the key parameters that determine durability, which requires an accurate prediction of the transient temperature field based on well-defined boundary conditions representing the dynamic and complex fluid flow inside engines. To meet this requirement, the present study focuses on transient thermomechanical stress analysis using a sequentially coupled computational fluid dynamics (CFD)–finite element analysis (FEA) approach to understand transient thermomechanical responses of the hot surface ignition device. A three-dimensional transient reacting flow simulation was conducted first using converge software, the results of which were exported to map thermal and pressure boundary conditions onto a structural finite element mesh. Transient thermomechanical stress analysis was performed sequentially using abaqus software utilizing the mapped boundary conditions. The results such as transient temperature history, resultant thermomechanical stress, displacement, potential failure modes, etc., were critically reviewed, which can provide helpful information for further design improvement.

Flatness Enhancement of Metal-Supported Solid Oxide Fuel Cells with Additional Compensation Layer

Solid oxide fuel cells are high-temperature fuel cells which offer several advantages: high efficiency, fuel flexibility, high-quality waste heat, and the use of non-noble metal catalysts. Metal-supported solid oxide fuel cells, in which the ceramic mechanical support layer is replaced with the metal support, are considered as next-generation solid oxide fuel cells because of their enhanced mechanical/thermal ruggedness compared to conventional ceramic-supported solid oxide fuel cells. However, different thermomechanical behavior of metal support and ceramic layers during sintering makes metal-supported cells vulnerable to warping. Cell warpage must be minimized because it reduces not only uniformity of wet-chemical coating, but also actual contact area between electrode and interconnect, increasing the contact resistance.In this study, causes of metal-supported cell warpage are identified, and the design that can minimize cell warpage is suggested for successful scale-up of metal-supported solid oxide fuel cells. Through thermomechanical and residual stress analyses, it is found that residual stress derived from coefficient of thermal expansion mismatch between electrode layers and the metal substrate is the main cause of the warpage of metal-supported solid oxide fuel cells. Based on these results, a novel design that has thicker metal protection layer on the opposite side of the electrolyte is proposed for minimizing cell warpage due to residual stress. Through the design modification, vertical deformation of 2-inch metal-supported solid oxide fuel cell can be successfully controlled to 17.36% of the previous design. Furthermore, electrochemical evaluation showed a 21% decrease in ohmic ASR and a 25% increase in peak power density after the design modification, implicating reduction of contact resistance as a result of increased contact area by enhanced flatness.

Thermomechanical Stress Analysis of Hydrated Vital Gluten with Large Amplitude Oscillatory Shear Rheology.

Vital gluten is increasingly researched as a non-food product for biodegradable materials. During processing, the protein network is confronted with increased thermal and mechanical stress, altering the network characteristics. With the prospect of using the protein for materials beyond food, it is important to understand the mechanical properties at various processing temperatures. To achieve this, the study investigates hydrated vital gluten under thermomechanical stress based on large amplitude oscillatory shear (LAOS) rheology. LAOS rheology was conducted at increasing shear strains (0.01-100%), various frequencies (5-20 rad/s) and temperatures of 25, 45, 55, 65, 70 and 85 °C. With elevating temperatures up to 55 °C, the linear viscoelastic moduli decrease, indicating material softening. Then, protein polymerization and the formation of new cross-links due to thermal denaturation cause more network connectivity, resulting in significantly higher elastic moduli. Beyond the linear viscoelastic regime, the strain-stiffening ratio rises disproportionately. This effect becomes even more evident at higher temperatures. Lacking a viscous contribution, the highly elastic but also stiff network shows less mechanical resilience. Additionally, at these elevated temperatures, structural changes during the protein's denaturation and network shrinkage due to water evaporation could be visualized with confocal laser scanning microscopy (CLSM).

Thermomechanical stress analyses of nanowarming-assisted recovery from cryopreservation by vitrification in human heart and rat heart models.

This study investigates thermomechanical stress in cryopreservation by vitrification of the heart, while exploring the effects of nanowarming-assisted recovery from cryogenic storage. This study expands upon a recently published study, combining experimental investigation and thermal analysis of cryopreservation on a rat heart model. Specifically, this study focuses on scenarios with variable concentrations of silica-coated iron-oxide nanoparticles (sIONPs), while accounting for loading limitations associated with the heart physiology, as well as the properties of cryoprotective agent (CPA) solution and the geometry of the container. Results of this study suggest that variable sIONP concentration based on the heart physiology will elevate mechanical stresses when compared with the mathematically simplified, uniform distribution case. The most dangerous part of rewarming is below glass transition and at the onset of nanowarming past the glass transition temperature on the way for organ recovery from cryogenic storage. Throughout rewarming, regions that rewarm faster, such as the chambers of the heart (higher sIONP concentration), undergo compressive stresses, while the slower rewarming regions, such as the heart myocardium (low sIONP concentration), undergo tension. Being a brittle material, the vitrified organ is expected to fail under tension in lower stresses than in compression. Unfortunately, the location and magnitude of the maximum stress in the investigated cases varied, while general rules were not identified. This investigation demonstrates the need to tailor the thermal protocol of heart cryopreservation on a case-by-case basis, since the location, orientation, magnitude, and instant at which the maximum mechanical stress is found cannot be predicted a priori. While thermomechanical stress poses a significant risk to organ integrity, careful design of the thermal protocol can be instrumental in reducing the likelihood of structural damage, while taking full advantage of the benefits of nanowarming.

Thermohydraulic Design Analysis of the Target Assembly in the Material Plasma Exposure eXperiment Facility

The Material Plasma Exposure eXperiment (MPEX) project seeks to design a steady-state linear plasma facility at Oak Ridge National Laboratory that will be used to study plasma-material interactions (PMIs) at fusion prototypic levels, supporting the evaluation and development of materials for the next generation of fusion devices. This study is focused on PMI exposure of small-size neutron-irradiated specimens, which are clamped onto an actively cooled component. A thermohydraulic evaluation of a new MPEX target assembly design to assess the appropriate operation during MPEX operation is presented. To further guide the design and assess the structural integrity of the components under expected loads, preliminary thermomechanical stress analyses were also conducted. To ensure good thermal contact between the components, thermal interface materials, such as silver flexible graphite, were used in the assembly. It was found that the maximum target temperatures of 1572, 1463, and 1315 K were obtained for Grafoil thicknesses of 0.61, 0.38, and 0.25 mm, respectively. The distribution of the axial deformation at high heat fluxes showed that there are no gaps between components, indicating good contact at material interfaces. Moreover, the contact pressure between the target and other components indicated that very good contact was established at these interfaces. The stress-strain conditions for the target will be further used to assess the appropriate operation during MPEX experiments and gain insight into materials science phenomena during PMI experiments.

Thermal-elastic analysis of laminated plates based on the incompatible generalized partial mixed method

Based on the generalized Hellinger-Reissner (H-R) mixed variational principle, the incompatible generalized partial mixed finite element method (IGPMFEM) is proposed in this paper for the thermomechanical stress analysis of laminated composites and sandwich plates. This method inherits the advantages of the generalized mixed element method, allowing for the simultaneous introduction of displacement and stress boundary conditions, and satisfies the discontinuity of the in-plane stresses at the material interface. Introduction of incompatible displacement mode adds higher-order terms in the polynomial expansion of the exact displacements, effectively improving the bending performance and the element accuracy. Although adding stress components would normally increase the computational effort, we address this issue by the elimination method, considering only the out-of-plane stress variables to reduce the matrix dimensions. The accuracy and effectiveness of the proposed method are evaluated by comparing the numerical results of this method with existing elasticity solutions, while the effect of stress boundary conditions is also investigated.

Analysis of Thermomechanical Stresses in Silicon During Heating of Aluminum Interconnects on its Surface by a Pulse Current

Analysis of Thermomechanical Stresses in Silicon During Heating of Aluminum Interconnects on its Surface by a Pulse Current

Thermo-mechanical deformation and stress analysis of a rotating FG hollow cylindrical body

PurposeThe purpose of this study was to perform thermo-mechanical deformation and stress analysis in a functionally graded (FG) hollow cylinder considering steady-state temperature distribution under the effect of rotation, gravity and constant heat generation.Design/methodology/approachNavier's equation was used to solve the problem, and the obtained results were validated with benchmarks found to be in excellent agreement. The variation of temperature and other material properties such as Young's modulus, density, thermal expansion coefficient and thermal conductivity varied radially as per power-law variation.FindingsThe effect of rotation was found to be vital compared to gravity and heat generation when compared individually and in combination. The results of displacement and stresses were presented for varying grading indices.Practical implicationsFG cylinders have huge industrial applications as it opens the possibility of developing structures with a high strength/weight ratio. The present study will benefit industries in identifying the effective grading index that can be used by industries for fabricating FG structures.Originality/valueThe effect of rotation, body force and heat generation on a cylindrical body has not been studied before. Furthermore, the combined effect of rotation, body force and heat generation has been studied to understand the behaviour of cylinders operating under similar conditions.

(Invited, Digital Presentation) Advanced Methodology for Assessing Chip Package Interaction Induced Stress Effects on Chip Performance and Reliability

In IC industry, the use of multiple die stack packaging has emerged to meet the increasing demand in miniaturization and improved functionality of mobile devices. During chip operation, transistor power dissipation raises temperature unevenly across a die. The generated thermal hotspots negatively impact reliability and degrade performance. In mechanical aspects, dies become thinner, and bumps and pitch become smaller, which makes heat dissipation more difficult, and lead to increase in mechanical stress. Such stress may cause carrier mobility degradation for transistors and could lead to parametric circuit failure. In the back-end-of-line (BEoL) interconnects, the employed ultra-low k materials prone to damage interconnects when mechanical stress is present, due to its brittle nature and poor adhesion to the barrier materials. These stresses originated at the die packaging step due to thermal mismatch between die and package materials, which is termed as chip package interaction (CPI). We call mechanical CPI (mCPI) when such stress affects reliability of the whole chip, i.e., BEoL, RDL (redistribution layer), bump, or TSVs (through silicon vias). When such stress affects device performance, we call electrical CPI (eCPI).To analyze CPI effects on a feature scale, i.e., in transistor channel or in the individual metal line or ILD (inter layer dielectric) /IMD (inter metal dielectric) gap, an analysis tool must generate accurate feature-scale stress variation across a die. Finite element analysis (FEA) is widely used for analyzing CPI induced problems. However, the traditional FEA cannot effectively handle feature-scale geometries due to huge memory consumption, and instead, treats a die as a uniform material block. Therefore, this approach cannot describe stress distribution caused by local non-uniformity of metal line distribution and fail to provide the needed accuracy for feature-scale analysis. [1]Here, we present an advanced physics-based EDA tool that overcomes the above-mentioned problems by introducing the novel methodology of extracting effective anisotropic thermal-mechanical properties (EMP), as well as employing FEA-based multi-scale simulation procedure. Prior to running FEA, the tool extracts EMP that accurately represent non-uniformities at different scales within a simulation domain. Here, each metal layer in a die is considered a binary system that consists of metal inclusions embedded in an insulator matrix. By dividing the die area into bins, metal density dependent effective properties for each bin are calculated according to theory of anisotropic composite materials. Anisotropy of properties can be obtained by taking routing direction of metal lines into account [2, 3]. EMP can adjust to multi-scale by varying bin size as shown in Fig.1. Here, Young’s modulus is extracted globally with coarse grid, and on sub-modeling region with very fine grid, which shows the corresponding property variation with much finer scale. Since EMP constructs no actual geometrical objects, the methodology can efficiently handle feature-scale objects on a large layout region. When a user selects a circuit block, or a region to be analyzed in detail, the automated tool flow enables two step stress simulation procedure, which is schematically shown in Fig. 2. First, the global-scale stress simulation is performed with coarse both the simulation mesh and EMP bin and extracts the boundary displacements for the circuit block. These boundary displacements are employed in the sub-modeling, with employed fine mesh and EMP bin.Figure 3 demonstrates the importance of EMP for accurate resolution of stress field. The 2D color maps show the x-component of stress distributions in a circuit block as a result of sub-modeling. Here, die BEoL is represented by EMP in (a), while in (b), the entire die including BEoL is represented by silicon, which is employed in traditional FEA. The stress pattern due to interconnect layout details are visible only when EMP is employed. The difference is even more pronounced when 1D stress profile is compared.By back annotating the obtained stress components in a SPICE netlist, the tool enables a user to perform accurate circuit simulation with accounted CPI effects. In eCPI analysis, the tool has been validated by employing measurements of different types of devices [4].The additional tool capabilities that will be presented are mCPI analysis and thermomechanical stress analysis during chip operating conditions.[1] R. Radojcic, More-than-Moore 2.5D and 3D SiP Integration, Springer, 2017.[2] V. Sukharev et al. J. Electron Test, vol. 28, pp. 63-72, 2012[3] V. Sukharev et al., Proc. Int. 3D Systems Integration Conference, 2019[4]. A. Kteyan, et al. Proc. ISPD 2022 Figure 1

Life prediction of C3X gas turbine Blade of CMSX-4 material

ABSTRACT Life prediction plays an important role in avoiding the catastrophic failure of a gas turbine blade subjected to simultaneous high thermal and mechanical load. The purpose of this paper is to predict the life of C3X blade of a nickel-based single crystal super alloy, CMSX-4 material under thermo-mechanical load at four different operating conditions. The blade was geometrically modelled and by using computational fluid dynamics approach with k-ε turbulence model the distribution of temperature, pressure and heat transfer coefficient on the surface of the blade was determined. Mechanical and thermal were determined by uncoupled heat transfer analysis and thermomechanical stresses by sequentially coupled thermo-mechanical stress analyses for a flight length of 5000 seconds. Finally, life of the blade was estimated considering fatigue-creep interaction by applying ductility exhaustion method and morrow mean stress correction. The results show that the critical damage occurred at trailing edge and fixed portion of the blade. In comparison to the mechanical or thermal load, there is a significant change in stress magnitude for the thermo-mechanical load. Also, the blade radial displacement is mainly ascribed to the thermal load rather than the mechanical load.

A novel reconstruction method of temperature field for thermomechanical stress analysis of arch dams

Temperature distribution on the dam surface plays an important role in reliable thermomechanical stress analysis of arch dams. In this paper, a novel reconstruction method based on a convolutional neural network is proposed for the temperature field on the downstream surface of arch dams. The environmental variables, including solar radiation, mountain shadows, ambient temperature, and weather conditions, are considered in the reconstruction method. The temperature field of the Xiaowan dam is predicted using the proposed method and it agrees well with the monitoring data in the spatial and temporal scale. The results show that the environmental variables significantly affect the temperature on the downstream surface, and result in temporal-spatial variability of nonuniform temperature distribution. In addition, the proposed method solves the data sparseness and low-frequency acquisition problems that may miss the peak temperature values in the current monitoring system. The thermomechanical stress analysis based on the reconstructed method and finite element method is conducted, and its results illustrate that the proposed reconstructed method can give more realistic performance of the dam and predict possible thermal cracking on the dam surface.

Thermo-mechanical stress analysis of rotating fiber reinforced variable thickness disk

Circumferentially fiber reinforced composite disk, which has a variable thickness, is modeled via analytical approaches. The disk is subjected to rotation in traction free conditions and decreasing, constant, and increasing steady state radial temperature gradients along the disk radius. Limit angular velocities are calculated by operating Tsai-Wu and Norris failure indexes to the problem. Subsequently, these limit velocities are gradually decreased to examine the stress and displacement fields. Acquired results show that as the angular velocity drops, the effects of temperature gradients become more visible. At lower angular velocities, these gradients may even alter the stress field directions. Also, different failure criteria implementation may change the calculated limit velocities to a considerable degree. Therefore, the failure index should be chosen attentively to procure conservative results. In the investigation, the influence of disk geometry on the directional stresses is studied as well. Without further ado, it can be expressed that the geometry causes slight alterations in stresses and displacements.

Analysis of Thermomechanical Stresses of a Photovoltaic Panel Using a Passive System of Cooling

In this paper, the gradient temperature and the thermomechanical stresses of a photovoltaic panel has been studied with and without heatsink. For this purpose, a three-dimensional analysis was carried out. Accordingly, a heat transfer analysis was developed. The numerical results show a cooling close to 26.7% with the proposed triangle fins compared with the rectangular fins studied before by another author, and the temperature distribution was determined. With this information, the stress analysis was carried out in order to find the effect on the panel due to the thermomechanical stresses. The aluminium frame was restricted to move freely. The resulting stresses field established the magnitude of the alternative stresses, resulting in a 6.7% drop compared with a reference panel. The guidelines of IEC 61215 have to be take into account. Due to the results obtained, the use of this kind of system in desert conditions is desirable because of its high operational temperature and due to the increase in heat transfer by the fins.

Thermo-mechanical stress analysis of feed-water valves in nuclear power plants

Feed-water valves (FWVs) are used to regulate the flow rate of water entering steam generators, which are very important devices in nuclear power plants. Due to the working environment of relatively high pressure and temperature, there is strength failure problem of valve body in some cases. Based on the thermo-fluid-solid coupling model, the valve body stress of the feed-water valve in the opening process is investigated. The flow field characteristics inside the valve and temperature change of the valve body with time are studied. The stress analysis of the valve body is carried out considering mechanical stress and thermal stress comprehensively. The results show that the area with relatively high-velocity area moves gradually from the bottom of the cross section to the top of the cross section with the increase of the opening degree. The whole valve body reaches the same temperature of 250 °C at the time of 1894 s. The maximum stress of the valve body meets the design requirements by stress assessment. This work can be referred for the design of FWVs and other similar valves.

Displacement-function modeling of thermo-mechanical behavior of fiber-reinforced composite structures

A new modeling scheme has been developed for the analysis of thermo-mechanical stresses in structural problems of fiber-reinforced composite materials with mixed mode of physical conditions. In contrast with conventional approaches, the coupled thermal and mechanical problems of structural mechanics are integrated here using a single scalar function of space variables, which is defined in terms of the displacement components of plane elasticity. The displacement-function is governed by a single partial-differential equation of equilibrium that takes into account the two orthogonal gradients of the resulting non-uniform temperature field through two different versions of the formulation. The temperature-dependent elastic field is determined using a two-step solution scheme that utilizes the two versions of displacement-function formulations in two sequential steps. The scheme is developed in such a flexible fashion that even the solution of the corresponding isotropic problems can readily be obtained with thermal and/or mechanical loading as a limiting case of the formulation. The application of the proposed modeling scheme is demonstrated through the solution of a number of problems of structural mechanics, namely plates and beams subjected to thermal as well as thermo-mechanical loadings with both uniform and mixed mode of physical conditions. An attempt is also made to verify the soundness and accuracy of the resulting thermoelastic fields by comparing them with the corresponding analytical as well as computational solutions available in the literature. Moreover, the correspondence between the versions of the displacement-function formulation is also verified by solving identical problems using different versions or different combinations of the versions of the formulation.