Thermomechanical Coupling Research Articles

The lightweight design of steel pistons for diesel engines based on thermo-mechanical characteristics

Traditional aluminum–silicon alloy pistons are gradually replaced by steel pistons, which has become the trend of future diesel engine development. However, the efficient design and broad application of steel pistons are limited by the higher density of steel. For this reason, a new lightweight design method for steel pistons in diesel engines was proposed in this paper. The progressive design of the cooling gallery cross-section and the topology optimization of the window region were carried out to meet the strength and deformation requirements. Ultimately, a lightweight steel piston (LSP) was obtained. The results of the study showed that the total mass of LSP could be reduced by 8.86% compared to the original steel piston (OSP). The thermal states of LSP are all superior to those of OSP. The highest temperature, maximum thermal stress, maximum longitudinal thermal deformation, and maximum transverse thermal deformation can be reduced by 0.96 °C, 3.03%, 11.65%, and 8.99%, respectively. LSP has a larger thermo-mechanical coupling stress manifestation compared to OSP. However, the maximum longitudinal and transverse thermo-mechanical coupling deformations can be obtained with a significant reduction of 8.33% and 42.19%, respectively.

Mechanical properties of rubber sealing material in lined rock cavern for compressed air energy storage considering thermo-mechanical coupling effect

Mechanical properties of rubber sealing material in lined rock cavern for compressed air energy storage considering thermo-mechanical coupling effect

Analytical Solutions for Thermo-Mechanical Coupling Bending of Cross-Laminated Timber Panels

This study presents analytical solutions grounded in three-dimensional (3D) thermo-elasticity theory to predict the bending behavior of cross-laminated timber (CLT) panels under thermo-mechanical conditions, incorporating the orthotropic and temperature-dependent properties of wood. The model initially utilizes Fourier series expansion based on heat transfer theory to address non-uniform temperature distributions. By restructuring the governing equations into eigenvalue equations, the general solutions for stresses and displacements in the CLT panel are derived, with coefficients determined through the transfer matrix method. A comparative analysis shows that the proposed solution aligns well with finite element results while offering superior computational efficiency. The solution based on the plane section assumption closely matches the proposed solution for thinner panels; however, discrepancies increase as panel thickness rises. Finally, this study explores the thermo-mechanical bending behavior of the CLT panel and proposes a modified superposition principle. The parameter study indicates that the normal stress is mainly affected by modulus and thermal expansion coefficients, while the deflection of the panel is largely dependent on thermal expansion coefficients but less affected by modulus.

Modeling the Dynamics of Quasi-Zero Stiffness Vibration Isolator of Shape Memory Alloy Spring Using Matlab Software

This study investigates the dynamic behavior of a quasi-zero stiffness (QZS) vibration isolator integrated with shape memory alloy (SMA) springs to achieve enhanced vibration isolation performance. QZS isolators are designed to mitigate vibrations effectively in low-frequency environments by combining linear and nonlinear stiffness elements to achieve a near-zero effective stiffness around the equilibrium position. The inclusion of SMA springs introduces unique properties such as shape memory effect and pseudoelasticity, enabling tunable stiffness and damping characteristics.. A comprehensive mathematical model of the isolator is developed, incorporating the nonlinear force-displacement behavior of the SMA spring based on thermomechanical coupling and constitutive relations. The dynamics of the system are analyzed under harmonic and random excitation, and key parameters influencing isolation performance, such as temperature, pre-compression of the SMA spring, and system damping, are systematically explored. Numerical simulations reveal that the SMA-based QZS isolator exhibits superior vibration attenuation compared to traditional isolators, with the added benefit of adaptability to changing operational conditions. It is demonstrated that the resonant frequency of the proposed isolation system is near zero. Numerical simulations are carried out, and the influence of the excitation amplitude and frequency on vibration isolation are studied. It is shown that a quasi-zero dynamic stiffness is achieved; hence the feasibility of the proposed system for low-frequency excitation isolation is validated.

Numerical Simulation Study on the Response of Ship Engine Room Structure Under Fire Based on Thermo-Mechanical Coupling Model

Ship structures may collapse or be severely deformed during a fire. To precisely assess the post-fire structural integrity of ships, in this study, a thermal–mechanical coupling data interface was created, employing a significant eddy simulation algorithm for fire dynamics and a technique to analyze the structural thermal–mechanical coupling reaction. PyroSim was utilized to build a fire scenario, exporting 3D data through the device’s own program, and then the ANSYS thermal–mechanical coupling model was employed to study the spatial temperature distribution under fire-induced conditions. Data from the three-dimensional spatial temperature field served as the boundary condition for the determination of the structural temperature burden. Building on this, an analysis was conducted on the structural response of the intricate two-story interior compartment under fire conditions. The results showed that the location of the fire source and the structural distribution of the mechanical equipment inside the cabin had a great influence on the temperature and combustion heat, followed by the ventilation conditions, while the temperature variations in the parallel dual fuel tanks were greatly influenced by the stack effect. By comparing the stress and strain of the two-layer cabin under normal and fire conditions, the damage and mechanisms associated with important positions in the cabin under fire conditions were revealed.

Numerical Study of the Effects of Residual Stress in Welded Pipe Joints

In general, welding processes can be understood as the establishment of the union of parts, generally metallic, using a heat source to promote the fusion of materials, with or without the presence of pressure efforts. Studies related to the distributions and levels of residual resistance arising from the thermal cycles involved in welding processes are of vital importance for evaluating and guaranteeing the integrity of welded pipes. This work proposes the implementation of a routine in PYTHON language to automate the production of thermomechanical coupling welding models using the ABAQUS® CAE finite element tool, considering the heat distribution model of the welding source according to Goldak et al. (1984), better known as the double ellipsoid model. The studies are produced considering an ambient temperature of 20 °C and another with preheating of the tubes to 300 °C. The results achieved by this study are related solely to analyzes of the residual stress fields in a thin walled tube joint manufactured in AISI 304 stainless steel, welded using TIG (Tungsten Inert Gas) processes in a single pass. Thus, this study seeks to analyze the hoop and axial residual stress distributions on the internal or external walls of post-welded tubes in angular positions 0°, 90°, 180° and 270°, whether or not there is uniform preheating of the pre-welding pipes. The results show that, in general, residual stresses differ slightly with the angular position, being relatively high when compared to the yield stress of the steel, and therefore have a considerable impact on reducing the mechanical strength of the welded joint. It should also be noted that when considering the preheating of the pipes there is a significant decrease in the peak temperatures reached in the transfer process, in the cooling rates and in the residual stress levels of the joints, especially in the most critical regions, located in the proximity from the center of the weld beads.

Effect of considering thermoplasticity of gun steel on thermomechanical coupling response of barrel

Abstract To explore the effect of considering thermoplasticity of gun steel on the thermomechanical coupling of the barrel during artillery firing, the thermoplastic coupling behavior of the barrel under transient thermal and mechanical loads is investigated. A thermomechanical coupling finite element model of the barrel was established. The transient temperature field and stress field of the barrel during the gun firing process were analyzed. By comparing the results of the thermoelastic model with that of thermoplasticity model, the effect of considering thermoplastic of gun steel on thermomechanical coupling response of barrel was investigated. The results show that the peak of Mises stress evolution considering thermoplasticity of material in the bore of the barrel is significantly reduced during the gun firing process, and the hoop stress evolution appears double-peak phenomenon. In addition, at the peak moment of bore pressure, the peak values that the hoop and Mises stress distributions along the radial direction at the midpoint of the land are reduced by 14.5 % and 20.9 %, respectively. This paper can provide a reference for the design of a large-caliber barrel.

Study on the dynamic characteristics of the revolver cannon under high-speed impact

Abstract Aiming at the problems of discontinuous mechanism action, excessive energy consumption and poor matching with the chainless feeding system under the harsh working conditions of high-speed strong impact, a certain revolver cannon has the problems of discontinuous mechanism action, excessive energy consumption and poor matching with the chainless feeding system. In order to further study the dynamic characteristics of the gas-operated revolver cannon under high-speed impact load, solve the matching problem between the revolver cannon and the chainless feeding system, and improve the firing rate of the revolver cannon, based on the principle of the revolver cannon, the multi-body dynamics and gas dynamics theory are used to couple the thermomechanical coupling calculation model of the revolver cannon gas chamber and the transmission efficiency and impact numerical calculation method between the key parts into the ADAMS dynamic simulation model, and the dynamic analysis and calculation of the whole cannon of the revolver cannon are carried out. The motion characteristic curves of the key parts of the revolver cannon are obtained by simulation, the motion matching between the key parts is analyzed, and the simulation results are verified by experiments. The results show that the error of the motion characteristic parameters such as the active slide displacement and the gun box recoil displacement obtained by simulation and experiment is very small, which verifies the correctness of the calculation model. The simulation calculation method can provide technical support for the matching research between the revolver cannon and the chainless feeding system and the design and structural optimization of the revolver cannon.

Numerical simulation study on the matching of third-generation explosives and large-caliber reactive shaped charge

Abstract In order to further study the matching problem between the third-generation explosives and the large-diameter active shaped jet charge, the jet forming characteristics and thermo-mechanical coupling characteristics were studied based on the AUTODYN-2D finite element analysis platform. The evolution behavior and distribution law of pressure field, velocity field and temperature field during the active jet forming process were analyzed, and the active jet forming law under different charge structures was analyzed. The numerical simulation results show that the large-diameter active energy-gathering structure under the condition of the third-generation explosive charge can form a stable active jet. With the extension of the jet forming time, the high-pressure zone and the high-temperature zone have obvious movement and diffusion phenomena. The high-speed zone moves from the middle of the axis to the head of the jet, resulting in a velocity difference between the head and tail of the jet. In addition, the penetration ability parameters of PTFE / AL active jet, such as head velocity and effective jet length, are significantly improved by the third generation explosives, especially CL-20 explosives, and are significantly affected by the charge type, the thickness of the active liner and the cone angle of the liner.

Study on the Thermo-mechanical Coupling Behavior of Phase Change Backfill Materials and Its Influence on the Borehole and Surrounding Ground

Study on the Thermo-mechanical Coupling Behavior of Phase Change Backfill Materials and Its Influence on the Borehole and Surrounding Ground

Review on the mechanism of failure mode based on mechanical performance analysis of brake disc

The reliability and efficiency of brake discs are crucial for ensuring the safe operation of vehicles. With the growing demands of industrial applications and technological advancements, the mechanical performance and failure issues of brake discs have garnered extensive attention. To better understand the mechanisms affecting the mechanical performance and failure modes of brake discs, a comprehensive review of the influencing factors on their mechanical properties is presented. This includes an examination of the impact of brake disc structure, materials, and working conditions from both numerical simulation and experimental perspectives. Furthermore, the effects of temperature distribution and stress distribution on different failure modes of brake discs are summarized. Based on thermomechanical coupling theory, the failure modes under varying temperature and stress conditions are analyzed. Finally, considering the current research status of brake discs, in-depth mechanical performance analysis and failure mode studies can provide significant theoretical and practical guidance for designing more durable and safer brake discs.

Study on ablation behavior and mechanism for accurate determination of rare earth elements in CaF2 crystals by UV-LA-ICP-MS

Catastrophic ablation of CaF2 crystals is often observed in ultraviolet-laser ablation-inductively coupled plasma-mass spectrometry (UV-LA-ICP-MS) analysis, leading to variations in the volume of ablated material and resulting analytical errors in LA-ICP-MS microanalysis. Therefore, it is essential to understand the ablation behavior and the interaction mechanisms between the laser and CaF2 crystals. In this study, we examined the effects of crystal surface roughness and laser fluence on ablation behavior. The CaF2 crystal polished with 1500 mesh abrasive paper exhibited a stable signal profile, a regular ablation crater, and the formation of nanoparticles, which align with predictions from the thermo-mechanical coupling model. Both higher and lower roughness resulted in either unstable ablation or uncontrolled ejection of fragments; the latter occurred when the thermal stress from accumulated light energy significantly exceeded the compressive strength of CaF2. Consequently, a roughness of 1500 mesh at the bottom of the ablation craters was deduced. We also identified a laser fluence of 14 J·cm−2 as the threshold for effective LA-ICP-MS analysis of CaF2 crystals, based on consistent signal profiles, elemental fractionation index (EFI), and crater morphology as revealed by LA-ICP-MS and scanning electron microscope (SEM) analyses, along with theoretical calculations from the thermo-mechanical coupling model. The optimal roughness (1500 mesh) and fluence (14 J·cm−2), together with the thermo-mechanical coupling model, can serve as guidelines for UV-LA-ICP-MS settings in further quantitative analyses of CaF2 crystals.

Time dependent thermal behavior of geothermal energy pile (GEP) for summer and winter periods using CFD analysis

This study investigates the thermomechanical behavior of geothermal energy piles, which serve the dual function of providing structural support and facilitating heat exchange with the surrounding ground. The thermal energy transfer is achieved by circulating a working fluid through U-shaped heat exchanger pipes embedded in the pile, enabling cooling during summer and heating in winter. Unlike conventional piles, the thermomechanical coupling in energy piles alters their load transfer mechanisms, with distinct responses during summer (cooling) and winter (heating) periods that require separate evaluation. While energy pile modeling is relatively new compared to borehole systems, both share operational similarities. To explore this, a numerical simulation was conducted using ANSYS Fluent, incorporating a polyethylene tube, concrete, and surrounding soil. The analysis was performed under various Reynolds numbers (500, 1000, 1500, and 2000) and time intervals (60 min, 360 min, and 720 min) to capture the time-dependent thermal behavior for both cooling and heating periods. The simulations demonstrated satisfactory outcomes, suggesting promising potential for geothermal energy applications in Algerian residential buildings.

Occlusion failure analysis and optimization design for steel piston pin hole-pin friction pair

The focus of the present study was on the D25TCIF steel piston, and the underlying causes of pin hole occlusion failure were systematically analyzed. The investigation considered factors such as heat transfer, mechanics, lubrication, material properties, and forging processes. Additionally, an optimization strategy was introduced based on the cause of the failure to reduce the risk of occlusion failure of the pin hole. At the same time, the influence of the structural parameters of the connecting rod small head on the lubrication performance of the pin hole bearing was investigated, providing a theoretical basis for the matching design of the structural parameters of the double friction pair of the piston pin bearing. The findings indicate that the primary cause of pin hole occlusion failure in steel pistons is the concentration of thermo-mechanical coupling stresses and elevated temperatures within the pin hole. This condition results in the rupture of the lubricating oil film in the pin hole bearing, leading to dry friction between the piston pin and the bearing surface. The optimization method designed in the present study enhanced the minimum oil film thickness of the pin hole bearing from 0.354 μm to 0.377 μm, reflecting an increase of 6.50 %. Additionally, the minimum oil film thickness of the small head bearing was improved from 0.599 μm to 0.691 μm, corresponding to a 15.36 % increase compared to the original configuration. Meanwhile, the optimization method predicted a minimum oil film thickness of 0.382 μm for pin hole bearings and 0.693 μm for small-head bearings, with a relative error of less than 5 % from the simulated values. Such findings demonstrate that the optimization method has a good optimization effect and accurate prediction. This approach offers novel insights for the development of future solutions to address the failure of steel pistons in engineering applications.

Prediction of transient thermal stress distribution in SOFC based on coupled computational fluid dynamics and thermodynamics modeling

Long-term stability and safety are two key factors for the application of solid oxide fuel cell (SOFC) technology, with thermodynamics playing a central role in influencing this stability. Thus, understanding the thermodynamic behavior within SOFC and how it will depend on the stack structure are very important, especially at the start and stop stages. In this study, a 3D calculated fluid dynamics model and thermomechanical coupling model based on the actual component structures are established. We place emphasis on understanding how these factors evolve during dynamic phases, shedding light on the transient thermal stress behavior of the SOFC. The influence of different interconnect structures on the thermal stress distribution is studied. The coupling calculation results show that the first principal stress of the electrolyte is significantly affected by the specific interconnect structure. Adopting cylindrical ribs instead of rectangular ribs, the thermal stresses of the SOFC components can be reduced by 13–25 %, respectively.

On the multi-physics elastoplastic electrical contact of rough surfaces

Multi-physics coupling effect and elastoplastic deformation of rough surface asperities on contact interfaces are the two critical factors influencing the electrical contact properties. It is challenging to consider both factors in the modeling and efficient computation of rough surface electrical contact problems. To address this challenge, this study proposes a novel and efficient method for the behavior investigation of multi-physics elastoplastic electrical contact of rough surfaces. The electro-thermal and thermo-mechanical coupling equations are derived by incorporating the Joule heating and resultant expansion of material. The J2 plasticity criterion, with both the isotropic and kinematic hardening laws, describes the plastic deformation of contact components. The displacement field caused by the contact pressure of the asperities is calculated using the boundary integral method, while the stresses due to plastic and thermal strains are treated as bulk stresses, and their contribution is solved using the volume integral method. An iterative algorithm is applied to obtain the electrical contact results including electric potential, electrical contact resistance, temperature rise, contact area, contact pressure, displacement, stress, elastic and plastic strains. This method is validated compared with a finite element model. The influence of plastic deformation and multi-physics coupling on the behavior of rough surface electrical contact is investigated.

Design and Construction of Analog Water Heater Chamber (AWHC) for Sma Rod and Spring Tensile Testing

This study details the design and construction of an Analog Water Heater Chamber (AWHC) specifically tailored for tensile testing of Shape Memory Alloy (SMA) rods and springs. The AWHC is designed to simulate various temperature conditions, enabling precise control over the thermo-mechanical behavior of SMA specimens. Energy conversion from the electrical to heat form is achieved using an electrical heating element of 1000 watts. This heat is transferred to the SMA spring/wire using convection using a water medium, and phase transformation occurs. The chamber's unique design allows for real-time monitoring of deformation and recovery processes under controlled temperature and loading conditions. Different test results for both the SMA rod and SMA spring at various loading rates and constant temperature, and continuous loading rate and different temperatures showed a good thermo-mechanical coupling result The AWHC's performance was validated through tensile testing of SMA rods and springs, demonstrating its efficacy in evaluating the mechanical properties and phase transformation temperatures of these materials. The results show excellent correlation with theoretical predictions, confirming the AWHC's suitability for characterizing SMA behavior under diverse thermal and mechanical conditions. This research contributes to the development of efficient testing protocols for SMA components, paving the way for their enhanced integration into various engineering applications, thus the aim of which AWHC is designed for is achieved.

A novel approach to analyzing thermoelastic behavior of brake disc under the combined action of thermal and mechanical loads

Friction hot spots have been troubling the industry and academia as the root cause of a series of brake NVH and thermal fatigue problems. Previous experimental and simulation studies on hot spots have focused only on the role of thermal load but lacks consideration of mechanical load. And there are few methods for transient simulation of brake hot spots under thermal and mechanical loads, leading to a lack of consensus on the mechanism. In this paper, the idea of ’combined but not coupled’ is adopted to investigate the thermoelastic behavior of a simplified brake disc under combined thermal and mechanical loads through both experiments and simulations. A new test method for the thermoelastic behavior of brake disc under thermal and mechanical loading has been designed, and the hot spots are successfully reproduced. The evolution process and spatial distribution of temperature and deformation fields are analyzed, revealing that the deformation field evolves earlier than the temperature field. To replicate the hot spots observed in the experiment, a novel finite element (FE) model based on a modified Riks algorithm and thermomechanical coupling is established. The simulation results align with the experimental results. The number of hot spots is found to correspond to the main order of the deformation, and their locations coincided with the peaks of the waviness distortion. The effects of heating method, rotation speed, initial distance (representing braking pressure), wrap angle, and phase difference between the thermal load and the mechanical load are analyzed. It is found that there is a critical rotation speed and a critical braking pressure for the emergence of hot spots. Finally, a new mechanism for the generation of brake hot spots is proposed. This study may provide a valuable reference for revealing the mechanism of brake hot spots and the theory of progressive waviness distortion. The research is also valuable for automotive brake design and safety.

Thermo-Mechanically Coupled Settlement and Temperature Response of a Composite Foundation in Complex Geological Conditions for Molten Salt Tank in Tower Solar Plants

The degradation of complex geological structures due to thermo-mechanical cycling results in a reduction in bearing capacity, which can readily induce engineering issues such as uneven settlement, cracking, and even the destabilization of the foundations of molten salt storage tanks. This study establishes a foundational model for a molten salt storage tank through the use of COMSOL Multiphysics and conducts a numerical simulation analysis to evaluate the settlement deformation and temperature distribution of the foundation under the influence of thermo-mechanical coupling. Concurrently, the research proposes two distinct design approaches for the tank’s foundational structure. A comparative analysis of the results indicates that the use of a pile raft foundation in conjunction with a traditional foundation mode results in a reduction of settlement at the center of the foundation’s top surface by 380.1 mm, while also decreasing the maximum effective stress in the steel ring wall by 240.7 MPa. The thermal effects impact a depth of 10 m in the foundation soil and an influence radius of 20 m. Additionally, the foundation soil exhibits optimal thermal insulation properties, resulting in minimal energy loss. These findings indicate that the pile raft foundation in conjunction with a traditional foundation mode displays remarkable adaptability to complex geological conditions, with both settlement and temperature distribution of the foundation maintained within acceptable limits.

Experimental Investigations on Thermo-mechanical Behavior and Failure Mechanisms of Hybrid Bonded-bolted Plain-woven Composite Joint

This paper focuses on the thermo-mechanical coupling behavior and failure mechanisms of single-lap bonded, bolted, and hybrid bonded-bolted plain-woven composite joints. Quasi-static tension tests were conducted on these three types of joints at -50 ℃, -20 ℃, +23 ℃, +70 ℃ and +120 ℃, respectively. Based on the experimental results, the failure mechanisms and hybridization effect of the hybrid joint under temperature impact were analyzed and discussed. It is shown that i) failure load in the bonding stage of the hybrid joint is significantly lower than that of the bonded joint. ii) The increasing temperature not only leads to the decreasing joint performances of joints but also the transition of failure modes for the bonded joint and hybrid joint. iii) Compared with the bonded joint and bolted joint, no significant improvement is observed in the joint strength and joint stiffness of the hybrid joint, which is due to the high stiffness of the adhesive and the thread embedment-induced adhesive failure. iv) Although the hybridization effect is not sensitive to the temperature of -50 ℃ and -20 ℃, it shows a strong relation with the temperature of +120 ℃, which is probably due to the premature adhesive failure.