Thermal-mechanical Coupling Analysis Research Articles

Design, thermal-mechanical coupling analysis, and optimization of polymeric matrix composite sandwiches with a lattice core exposed to a high temperature

This study presents the design of a sandwich structure tailored for post-heat transfer applications subjected to out-of-plane compression. A three-dimensional finite element simulation model was developed to analyze the temperature distribution within the sandwich structure and investigate the effects of high-temperature exposure on its mechanical behaviors. The structure was subjected to a temperature of 300 °C for 400 s, and the temperature distribution at the upper connection point between the top face sheet and the struts of the core was determined. Subsequently, upon returning the sandwich to ambient temperature, a comprehensive calculation of its mechanical properties was conducted and then enhanced by applying different optimization techniques. The results demonstrate that filling the core with Saffil alumina fibers in the presence of a 1.5 mm a thermal barrier coating of Superwool 607 helps increase the mechanical properties of the sandwich structure by around 55%.

Thermal-mechanical coupling analysis of membrane surface failure of the air-supported membrane structure under fire considering weld seams

The membrane surface failure by developing a tear in air-supported membrane structures under fire conditions affects the deflation and collapse of the structure. However, in most existing studies, the failure is evaluated only according to whether the membrane surface temperature reaches the burn-through temperature of the membrane materials, without considering the effect of internal pressure variation caused by fire, and there have been even few studies on the impact of weld seams on membrane surface. This paper introduces the simplified constitutive models for PVC membranes and weld seams and a numerical simulation method to analyze the stress on the membrane surface of air-supported membrane structures during fire, taking into consideration the coupling effect of high temperature and internal pressure change. Numerical responses and the results of the full-scale fire test case by HIT (Harbin Institute of Technology) team are compared to demonstrate the effectiveness and applicability of the proposed material models and the simulation method. The study shows that the weld seams are the weak parts of the membrane surface under fire. The membrane surface failure may not first occur at the maximum temperature point of the membrane surface and the initial failure temperature is much less than the burn-through temperature of the membrane materials. Moreover, the initial failure of membrane surface should be attributed to the coevolutionary results of the stress field on the membrane surface and the degraded material properties at elevated temperatures. If the temperature is the only index to determine membrane surface failure in the air-supported membrane structure under fire, the common reference failure temperature should be reduced (approximately 120 ℃ for weld seams and 140 ℃ for membranes). The present study is valuable for fire risk assessment, performance-based fire protection design, and coupled analysis of fire and wind disasters in membrane structures.

Early-age cracking in mass concrete: Modeling and case study of an extra-large exhibition pool

Early-age cracking is one of the most common and challenging problems in the construction of mass concrete structures. This paper addresses the effects of factors such as temperature, hydration, creep, and shrinkage on the time-varying properties of concrete during construction by establishing an energy-based constitutive model for early-age concrete within the framework of continuous damage mechanics. The model comprehensively describes the damage of concrete due to the aging effect related to the degree of hydration, where the mechanical damage is driven by the work conjugated to the elastoplastic damage energy release rates. The thermal evolution during hydration is fitted with a large amount of experimental data, enabling the partial decoupling of multi-factor effects and facilitating the establishment of a sequential thermal-mechanical coupling analysis method. After preliminary verification through restrained ring cracking tests, the proposed model and method are applied to simulate the construction of an actual large-scale Orcinus orca exhibition pool. By predicting and analyzing the worst-case scenarios, the cracking risk, potential cracking mode, and cracking location of the large pool are determined, providing an important basis for practical construction control and optimization. Examples of these strategies include segmented schemes, reinforcement optimization, and the addition of tensile fibers, as well as selecting the best wind speed, environmental temperature, and casting temperature during construction. These efforts provided crucial guidance for the actual construction of the exhibition pool, and as a result, no visible cracks were found in the completed structure.

Experimental study on fire resistance of high strength Q960 steel columns under axial compression

In order to obtain the mechanical behavior of H-shaped high-strength Q960 steel column under axial compression in fire, the bearing capacity tests of two Q960 steel columns at ambient temperature and fire resistance tests of six Q960 steel columns at elevated temperature were carried out. By considering different slenderness ratios, load ratios, and heating rates of the test columns, the furnace temperature, column temperature, lateral displacement, and axial displacement were measured and recorded. Then, critical temperature, fire resistance, and failure mode of the columns were obtained. The thermal-mechanical coupling analysis model for the Q960 steel column was established by using ABAQUS finite element analysis software. After verifying the accuracy of the model, parameter analysis was carried out to investigate the effects of load ratio, slenderness ratio, geometric imperfection, thermal creep, residual stress, and steel strength on the fire resistance of steel columns. Based on the test data and analysis results, a fire resistance design method for high-strength Q960 steel columns under axial compression is proposed.

Thermal-mechanical coupling analysis of the ribbed channels in regenerative cooling

Regenerative cooling plays a critical role in the thermal management for scramjet combustors, and the design of cooling channels is of utmost importance. To comprehensively analyze the performance of cooling channels, a validated thermal-mechanical coupling model was utilized in this study. The thermal and mechanical performance of both smooth and ribbed channels in regenerative cooling was investigated using Finite Volume Method and Finite Element Method. The findings indicate that the ribbed wall has a notable effect on enhancing the overall thermal performance of the channel. Moreover, the presence of ribs weakens the influence of buoyancy in the flow field, which can be one of the contributing factors in inhibiting heat transfer deterioration. Additionally, the design of ribs significantly reduces the average thermal stress experienced by the channel. However, it should be noted that the non-uniform heat transfer in the axial direction leads to a significant increase in local thermal stress. The triangular ribbed channel proves to be an effective approach in reducing thermal stress. Compared to rectangular ribbed ribs, the utilization of triangular ribs can result in a reduction of thermal stress by up to 30%. This observation highlights the advantage of triangular ribs in enhancing system life and safety by minimizing thermal stress.

Numerical simulation of fatigue crack growth in an engine heat shield

In order to prevent the body from overheating, a corresponding thermal protection device is usually designed on the inner wall of the combustion chamber. The working environment of this thermal protection device is very harsh, and it needs to withstand internal and external pressure loads and thermal radiation loads of the combustion chamber, especially at the connection between the cylinder and the support parts, the force is harsher. In order to avoid engine damage, causing unnecessary losses. In this article, the thermal–mechanical coupling analysis of the heat shield is carried out by finite element method to analyze the thermal stress and mechanical stress. According to the finite element simulation results, the initial cracks are inserted, respectively, at the stress concentration. Using linear elastic fracture mechanics and Forman–Newman–de Koning models, the crack growth lifetimes of cracks at different locations were calculated. The results of the study show that comparing the initial cracks at different locations, the cracks on the side near the edge of the heat shield have the largest reduction in crack growth life of 64.4% and the critical crack length of 52.0%. The linear superposition of thermal and mechanical stresses under different working conditions has different degrees of nonlinear effects on the crack growth life and critical crack length. The research work in this article can provide a basis for the evaluation of fatigue crack growth life of heat shield and can also provide a reference for engine maintenance.

Structural Uncertainty Analysis of High-Temperature Strain Gauge Based on Monte Carlo Stochastic Finite Element Method.

The high-temperature strain gauge is a sensor for strain measurement in high-temperature environments. The measurement results often have a certain divergence, so the uncertainty of the high-temperature strain gauge system is analyzed theoretically. Firstly, in the conducted research, a deterministic finite element analysis of the temperature field of the strain gauge is carried out using MATLAB software. Then, the primary sub-model method is used to model the system; an equivalent thermal load and force are loaded onto the model. The thermal response of the grid wire is calculated by the finite element method (FEM). Thermal-mechanical coupling analysis is carried out by ANSYS, and the MATLAB program is verified. Finally, the stochastic finite element method (SFEM) combined with the Monte Carlo method (MCM) is used to analyze the effects of the physical parameters, geometric parameters, and load uncertainties on the thermal response of the grid wire. The results show that the difference of temperature and strain calculated by ANSYS and MATLAB is 1.34% and 0.64%, respectively. The calculation program is accurate and effective. The primary sub-model method is suitable for the finite element modeling of strain gauge systems, and the number of elements is reduced effectively. The stochastic uncertainty analysis of the thermal response on the grid wire of a high-temperature strain gauge provides a theoretical basis for the dispersion of the measurement results of the strain gauge.

Residual shear behaviour of steel-concrete composite girders after fire exposure: Experimental and numerical study

Steel-concrete composite girders are widely used for their superior mechanical performance. However, research on the shear behaviour of composite girders after fire exposure is limited. This study attempts to reveal the effects of high temperatures and cooling methods on the shear behaviour of composite girders. With heating temperatures (200 °C, 400 °C and 600 °C) and cooling methods (natural cooling and water cooling) as variables, 7 composite girders were designed. First, the composite girders were placed in the fire furnace and heated to simulate fire exposure. Subsequently, the residual shear performance of the cooled composite girders was tested and discussed. The test results show that there is a significant temperature gradient along the height of the girders during heating. High temperatures of no more than 600 °C have a more pronounced effect on the properties of concrete than steel, resulting in a progressive deterioration in the synergistic working property of the concrete slab and steel beam as the temperature increases. The deterioration of the shear performance of composite girders with natural cooling is similar to those with water cooling, probably due to the neutralization of the positive effect of water on the hydration reaction of concrete and the negative effect of the rapid reduction in temperature of the structure caused by water cooling. Further, finite element models of the composite girders were developed and thermal-mechanical coupling analysis was performed to simulate the effects of fire exposure. The parametric analysis conducted show that the steel beam web thickness is highly effective in enhancing the residual shear performance of the composite girders after fire, while the effect of the concrete slab width is relatively minor.

Thermal-mechanical coupling characteristics and heat pipe failure analysis of heat pipe cooled space reactor

Heat pipe cooled reactor has wide application prospects in space environment because of the advantages of high reliability and small mass. Heat Pipe-Segmented Thermoelectric Module Converters (HP–STMCs) is a typical design of space heat pipe cooled reactor. In this paper, a new thermal–mechanical coupling analysis method for the reactor was proposed. A two-dimensional heat pipe code for multiphase heat transfer was developed, with simplification of the wick as a purely conductive process and consideration of the flow of compressible vapor. A thermal stress computational model of the core was established using COMSOL Multiphysics, with the heat pipes divided into six channels. Based on various power distribution conditions, different heating powers were employed to simulate the heat pipe operation within each channel. Normal and accident operating characteristics were analyzed by the model. Under normal operation, the maximum temperature is 1641.9 K, located in the center of the core, and heat pipes in the fifth channel have the highest heat transfer power, reaching 13.674 kW. During accidents, thermal stress emerges as the main threat to the reactor's safety. A single heat pipe failure at any location poses no safety risk, but the thermal stress exceeds the safety limit if two heat pipes fail at the reactor core's edge, reaching 269.92Mpa. With three failed heat pipes, stress exceeds limits even at the well-cooled middle position and raises the local maximum temperature to 1959.8 K. This research provides valuable experience for local effects assessment and safety analysis of heat pipe cooled reactors.

Thermal–Mechanical Coupling Analysis of Wheel–Rail Sliding Friction under Two-Point Contact Conditions

The generation of wheel–rail-sliding frictional heat is often accompanied by transverse displacement of a wheel. To study the thermal problem of wheel–rail sliding friction at two-point contact, this paper uses an LM tread wheel and a 60 kg·m−1 rail as examples. A thermal–mechanical-coupled finite-element model of equal proportion wheel–rail sliding is established. A direct-coupling method is used to analyze the thermal–mechanical coupling of the wheel–rail interface under sliding contact. This model considers the temperature-dependent material properties and boundary conditions, such as thermal convection and thermal dissipation, in the process of nonstationary frictional-heat conduction. Firstly, the effects of different sliding speeds, axle loads, and contact modes on the temperature and stress fields of the contact area are analyzed. Then, the lubrication and cooling effects of friction modifiers on the rail top and rail gauge angle are compared. The results show that, at a sliding speed of 2 m/s and an axle load of 30 t under a sliding condition of 200 mm, on the top and side of the rail, the temperatures at the contact patch centers are 813 °C and 547.7 °C, respectively. Under different operating conditions, the rail-side temperature is 55–75% of that of the temperature at the rail top, and the rail-side contact and friction stress values are 76–96% of those at the rail top. This indicates that frictional thermal damage on the rail side cannot be ignored. With a lower sliding speed, the thermal response of the two contact patches is closer. The impact of axle load on the frictional temperature and stress on the rail side is more critical than the sliding speed. The optimal lubrication choice is overall lubrication, which can decrease the rail top temperature by 47.2% and frictional stress by 56.2%, as well as decreasing the rail side temperature by 70.3% and frictional stress by 77.4%.

Failure analysis and structural optimization for rotary mechanism of large sling based on thermal–mechanical coupling analysis

Rotary mechanism is the core part of the multi-functional sling for turning over and erecting the castings and forgings. The mechanical performance of a nail plate inside the structure determines the working safety. In this paper, the dangerous working condition of the rotary mechanism is first introduced when the castings and forgings with different diameters are clamped by the sling. Then, the temperature field and the thermal–mechanical coupling model for the nail plate are established, and the failure mode is analyzed. Next, the layout and shape of the nails on the nail plate are studied to improve the load-bearing performance. A mathematical model, taking the height and draft angle of the nail as the design variables, is established, and a new nail plate model is given. The comparison is carried out through simulation and experiment. The results show that the mechanical performances of the nail plate are significantly improved, and the failure problem of the rotary mechanism is solved.

Thermal-Mechanical Coupling Analysis of Track Concrete and Study on Thermal Damage at Initial Stage of Construction

Thermal-Mechanical Coupling Analysis of Track Concrete and Study on Thermal Damage at Initial Stage of Construction

Finite Element Modeling, Thermal–Mechanical Coupling Analysis, and Demonstration of Multibusbar Half-Cell Double-Glass Overlapping Photovoltaic Module During Lamination

The gap-free interconnect using structural round ribbons in overlapping photovoltaic modules is an effective measure to improve module efficiency. Cells in the overlapping module are interconnected by round ribbons with local flattened parts rather than conductive adhesive. The structure of overlapping modules has a crucial effect on the thermal–mechanical stress of crystalline silicon cells during the laminating process of modules. Excessive stress will produce microcracks in the cells, which will adversely affect the long-term reliability of the modules. In this article, the coupled temperature–displacement is used to simulate the stress evolution of the double-glass multibusbar overlapping modules during lamination and comparative experiments were carried out. The results show that in the overlapping area, the cell near the solder band will be subjected to more concentrated stress than other regions, resulting in local bending of the cell. Large stress concentration may induce the generation and propagation of microcracks. The cell stress is sensitive to the dosage of encapsulating agent and the thickness of the flattened ribbon. Increasing the amount of encapsulating agent and reducing the thickness of the flattened section will help to relieve stress concentration. Finally, we demonstrate the overlapping process with modules interconnected by 0.12-mm flattened round ribbons and encapsulated by 0.65-mm ethylene vinyl acetate. The overlapping modules pass 200 thermal cycles and 3600-Pa mechanical load without cracks.

Research on Mechanical Behavior of the Steel-Concrete-Steel Composite Structures Subjected to High Temperature of Fire.

A new type of steel–concrete–steel composite structure was adopted and widely used in the immersed tunnel of the Shenzhen–Zhongshan access. The research on the mechanical behavior of the new composite structure under a high temperature of fire is of great engineering significance to the fire protection design of the structure. Both the model test and a numerical simulation were adopted to study the mechanical behavior and damage characteristics of the new composite structure under fire. The RABT standard temperature rise curve was used to simulate the temperature rising law under fire (it reflects the characteristics of temperature rise in case of fire in an enclosed environment: rapidly raised to 1200 °C within 5 min, maintained at 1200 °C for 120 min, then it is cooled to normal temperature after 110 min). The temperature distribution law inside the structure, the deformation development law of the roof and the crack distribution were analyzed based on the thermal–mechanical coupling analysis method. The results showed that the internal part of the composite structure close to the fire surface was directly affected by the high temperature, and the temperature presented a step distribution law, while the part far from the fire surface was affected by the lag effect of the temperature transfer, and the temperature presented a continuous growth law. The roof deformation presented a three-stage model of “rapid growth-deformation stability-deformation recovery” with time. The overall cracks of the composite structure showed a symmetrical distribution under fire. The composite structure presented a shear failure mode as a whole. The results could provide a reference for the study of fire resistance for the new composite structure and support the structural fire protection design of the immersed tunnel of the Shenzhen–Zhongshan access.

Thermal-mechanical coupling analysis and optimization of mine hoist brake disc

Based on heat conduction theory and energy conversion, the theoretical model of brake disc temperature field was established. The temperature field and equivalent Von Mises stress field distribution of brake disc during braking were investigated by using the finite element (FE) analysis. According to the thermal-mechanical coupling analysis, orthogonal optimization and analysis of variance (ANOVA) were used to optimize brake for reducing Von Mises stress on the brake disc. Results show that the temperature of a friction surface is high in the middle and low on both sides, with a large temperature gradient. In addition, the temperature and Von Mises stress form two extreme points in a direction of the friction surface circumference. Temperature and stress values decrease slowly along the direction of a brake disc rotation from an extreme value point, and decrease faster in the opposite direction. The maximum temperature of the optimized brake during braking is 473 K and the maximum equivalent Von Mises stress is 264 MPa. The main objective of this work is to reveal the influence of brake shoes structure and material on thermal-mechanical coupling of the brake disc to ensure famous strength that guarantees a longer life.

Waterproof Performance of Sealing Gasket in Shield Tunnel: A Review

Rubber gaskets are commonly adopted as the waterproof component in shield tunnels for their outstanding sealing performance. The contact pressure between surfaces generated by the assembly stress ensures that the gaskets resist certain water pressure without leaking. However, with the continuous occurrence of leakage accidents, attention has been drawn to the topic of the waterproof performance of gasketed joint shield tunnels. In this article, prominent contributions to the waterproof performance of sealing gasket in shield tunnels are listed and sorted into four sections: (1) structural behavior of lining and joint; (2) material constitutive model and durability; (3) numerical simulation methods; (4) thermal-mechanical coupling analysis. First, examples of leakage are discussed and tests on gaskets are elucidated, which is followed by a summary of the progress on material mechanical properties and durability. Then, the development of the simulation methods is presented. Finally, the existing research on the thermal-mechanical coupling analysis is summarized. It is found that the contributions to gaskets’ waterproof performance are fruitful, however, with stringent construction conditions, such as the material constitutive model and aging mechanism under special conditions, such as high temperature, numerical simulation, and laboratory test methods, which need to be further explored.

Effects of gear structural parameters on unsteady-state temperature field of large transmission ratio gear and tooth root thermal stress

A calculation method of tooth root stress for large transmission ratio gear and rack is proposed using a broken-line section model and thermal-mechanical coupling analysis. To describe the transient meshing dynamics between the gear and the rack, a contact deformation model between the gear and the rack is fitted by using the least square method, and the meshing temperature field is calculated using the Blok flash temperature theory. The method of the broken-line section is modified based on the fatigue crack growth path at the tooth root. A new broken-line section model to calculate the tooth root stress is established, and a stress permeability factor is introduced to identify the width of the broken line. Using the meshing temperature field of gear and rack, the calculation formulas of root bending stress and root compression stress are derived by the integral-iterative method under thermal-mechanical coupling, and the correctness of the maximum tooth root stress model is validated by the finite element method (FEM). Compared with other methods for analyzing the thermal strength of gear roots, the proposed novel broken-line section method has simpler calculations and higher accuracy, and it can systematically analyze the effect of structural parameters on the dynamic strength of gear transmission mechanisms under actual working conditions.

Thermal Mechanical Coupling Analysis of a Flexible Spoke Non-pneumatic Tire

A new type of non-pneumatic tire with a flexible spoke structure is proposed to solve traditional pneumatic tire defects, such as easy bursting, the requirement of real-time maintenance to keep tire pressure, and a complex manufacturing process. The thermal mechanical coupling characteristics of the flexible spoke non-pneumatic tire are studied in detail to obtain the steady-state temperature field distribution pattern under different operating conditions. A unit configuration method is proposed to build the 3D model of the flexible spoke non-pneumatic tire. Then, the thermal-mechanical sequential coupling method is used to analyse the deformation, energy loss and heat conduction of the flexible spoke non-pneumatic tire. Finally, the steady-state temperature field distribution pattern under thermal-mechanical coupling is obtained. The results show that the high temperature region of the non-pneumatic tire is mainly distributed in the middle bending part of the flexible spoke unit, and the temperature gradually decreases from the centre of the flexible spoke to the surrounding parts. The influence of load on the temperature change of non-pneumatic tire is greater than that of the driving speed. This study provides a theoretical basis and method guidance for solving the failure problem of the non-pneumatic tires under the action of thermal-mechanical coupling.

Research on the thermal shock simulation of the super high speed aircraft

Ultra high temperature ceramics (UHTC) with good mechanical properties and thermal physical properties, including high melting point (>30000C), high conductivity, high thermal conductivity, high thermal shock resistance rate, provides a sharp leading edge and smooth surface of a new generation of aerospace vehicle design to the aerospace industry; Due to ultra-high temperature ceramic materials with high strength, oxidation resistance and thermal shock resistance, it can be applied to extreme environments such as hypersonic flight, atmospheric reentry and rocket propulsion system, and have been widely used in key components of aircraft front cone, engine, wing and engine hot end. Based on the application of ultra-high temperature superconducting materials in practical application, the solid modeling of ultra-high temperature superconducting front-end components of ultra-high speed aircraft wing is carried out by using ABAQUS software, the ultra-high temperature thermal field of loaded aircraft flying at ultra-high speed is simulated, the stress-strain field at the flange is obtained, and the thermal mechanical coupling analysis is carried out.

A safety assessment methodology for thermo-mechanical response of offshore jacket platform under fire

Fire accidents caused by the leakage of combustible gas pose a serious threat to the offshore platform, probably resulting in local damage and even progressive collapse of the platform structure. The aim of this paper is to systematically assess the structure safety of platform under fire accidents. The uniqueness of this study is the integration of fluid-thermal-structural coupling simulations with the advantage of considering an accidental fire scenario. The dispersion behavior of leaked gas is studied and the development of elevated temperature generated on the offshore platform during the combustion process is predicted based on Computational Fluid Dynamics (CFD)- Finite Element Analysis (FEA) coupling method. Then, the thermal-mechanical coupling analysis is performed to predict the responses of structure under high temperature. Eventually, the criteria of ultimate bearing capacity of the component and the overall offshore structure are utilized to evaluate the safety of the offshore platform. The results show that with the development of fire, the high temperature zone spreads to cover the space between two neighboring decks, and the maximum temperature in the platform reaches 877 °C. The structural strength of the platform is significantly affected by high temperature. Under the vertical load, the ultimate bearing capacity of the platform at high temperature is decreased by 78% compared to that at ambient temperature. The methodology proposed could be applied to the safety assessment of other similar offshore or marine facilities, so as to support to the process safety in fire accidents.