Thermal-mechanical Coupling Analysis Research Articles

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.

Numerical Fracture Analysis of a Reactor Pressure Vessel based on Abaqus-FRANC3D Co-simulation Method

The reactor pressure vessel (RPV) is subjected to many cyclic loadings critical of which is the integrity risk posed by pressurized thermal shock (PTS) loadings induced by one of the most frequent anticipated operational occurrences - inadvertent operation of the safety injection system (SIS). In this paper, the fracture mechanics analysis for an ageing pressurized water reactor subjected to PTS induced by inadvertent actuation of the SIS is performed using a proposed simplified Abaqus-FRANC3D co-simulation method. A three-dimensional (3-D) finite element half-symmetric model of a typical pressured water reactor RPV is used to perform thermal-mechanical stress coupling analysis. 3-D fracture mechanic submodel with an assumed surface crack is created for the computation of the transient integrity parameter-stress intensity factor (SIF), using M-integral approach coupled in the proposed co-simulation method. Subsequently ASME method is used to evaluate the vessel’s material fracture toughness. Finally, the SIFs obtained with the simplified co-simulation method is compared with the conventional virtual crack-closure technique (VCCT), and the result show good agreement. This work serves as a useful reference for fast crack propagation and life prediction analysis of ageing PWR RPVs.

Study on thermal-mechanical coupling of the ceramic layer in diesel engine piston with thermal barrier coating

Piston performance has an important on vehicle reliability, efficiency, and exhaust emissions. Application of the thermal barrier coating is an effective method for preventing heat transfer from combustion chamber to the substrate. The numerical model of thermal barrier coating piston is established by using finite element method, and a comprehensive thermal-mechanical result is given to determine the influence of ceramic thickness on ceramic layer and substrate. Compared with uncoated piston, the maximum temperature of substrate decreased by 3.34%, 4.09%, 5.19%, 5.95%, and 6.69%, corresponding to ceramic thicknesses of 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, and 0.35 mm. The maximum thermal stress decreases from 78 MPa to 73 MPa. For ceramic layer of the thermal barrier coating piston, the maximum temperature appears at the top surface of the ceramic layer, while the maximum thermal stress occurs at the bottom of the ceramic layer. As the ceramics thickness increases from 0.15 mm to 0.35 mm, the maximum temperature of the ceramic layer increases from 322 ?C to 377 ?C, while the maximum thermal stress decreases from 95 MPa to 89 MPa. Thermal-mechanical coupled stress analysis shows that the maximum coupling stress occurs at the pinhole and its value does not change significantly. The thickness of the ceramic layer has little effect on the pinhole, but has a great influence on the ceramic layer.

Design, fabrication and testing of a coated conductor magnet for electrodynamic suspension

The coated conductor magnet, as the onboard magnet of the electrodynamic suspension (EDS) train, is deemed promising due to its relatively high operating temperature, low cooling cost, and good mechanical tolerance, making the liquid-helium-free high-temperature superconducting (HTS) EDS train possible. In order to promote the progress of the HTS EDS train, this work aims at designing, fabricating and testing a coated conductor magnet as the onboard magnet of EDS train. The HTS magnet is designed with the comprehensive considerations of the electromagnetic calculation, thermal–mechanical coupling analysis, as well as the heat load estimation. The magnet is conduction-cooled without any coolant. A radiation shield was used to reduce the heat leakage, enabling the cryogenic system to provide a better low-temperature environment for the magnet. Through a deliberate design, the magnet was fabricated, including two HTS coils and the tailored cryogenic system. Afterwards, the electromagnetic and thermal performances of this magnet were tested and analysed in detail. It was proven that the magnet can be cooled to below 15 K; besides, the magnet has been successfully charged to 240 A. Further increase in the current is possible because of the high safe margin of the critical currents for both the HTS magnet and its current lead, although a slight performance degradation was observed on two double-pancake coils inside the magnet. The present study will provide useful implications for the design and application of onboard HTS magnets in EDS train.

Retraction Notice: Thermal mechanical coupling analysis of two-dimensional decagonal quasicrystals with elastic elliptical inclusion

Retraction Notice: Thermal mechanical coupling analysis of two-dimensional decagonal quasicrystals with elastic elliptical inclusion

Comment: “Thermal mechanical coupling analysis of two-dimensional decagonal quasicrystals with elastic elliptical inclusion” (Yuan-Yuan Ma, Xue-Fen Zhao, Ting Zhai, Sheng-Hu Ding. Mathematics and Mechanics of Solids (Online First) First Published Online: August 16 2021)

Comment: “Thermal mechanical coupling analysis of two-dimensional decagonal quasicrystals with elastic elliptical inclusion” (Yuan-Yuan Ma, Xue-Fen Zhao, Ting Zhai, Sheng-Hu Ding. Mathematics and Mechanics of Solids (Online First) First Published Online: August 16 2021)

Integrity Evaluation of a Reactor Pressure Vessel Based on a Sequential Abaqus-FRANC3D Simulation Method

The safety-risk pressurized thermal shock (PTS) have on a reactor pressure vessel (RPV) is one of the most important studies for the lifetime ageing management of a reactor. Several studies have investigated PTS induced by postulated accidents and other anticipated transients. However, there is no study that analyzes the effect of PTS induced by one of the most frequent anticipated operational occurrences—inadvertent operation of the safety injection system. In this paper, a sequential Abaqus-FRANC3D simulation method is proposed to study the integrity status of an ageing pressurized water reactor subjected to PTS induced by inadvertent actuation of the safety injection system. A sequential thermal-mechanical coupling analysis is first performed using a three-dimensional reactor pressure vessel finite element model (3D-FEM). A linear elastic fracture mechanics submodel with a postulated semielliptical surface crack is then created from the 3D-FEM. Subsequently, the submodel is used to evaluate the stress intensity factors based on the M-integral approach coupled within the proposed simulation method. Finally, the stress intensity factors (SIFs) obtained using the proposed method are compared with the conventional extended finite element method approach, and the result shows a good agreement. The maximal thermomechanical stress concentration was observed at the inlet nozzle-inner wall intersection. In addition, The ASME fracture toughness of the reactor vessel’s steel compared with SIFs show that the PTS event and crack configuration analysed may not pose a risk to the integrity of the RPV. This work serves as a critical reference for the ageing management and fatigue life prediction of reactor pressure vessels.

RETRACTED: Thermal mechanical coupling analysis of two-dimensional decagonal quasicrystals with elastic elliptical inclusion

In this paper, the thermal mechanical coupling problem of an infinite two-dimensional decagonal quasicrystal matrix containing elastic elliptic inclusion is studied under remote uniform loading and linear temperature variation. Combining with the theory of the sectional holomorphic function, conformal transformation, singularity analysis, Cauchy-type integral and Riemann boundary value problem, the analytic relations among the sectional functions are obtained, and the problem is transformed into a basic complex potential function equation. The closed form solutions of the temperature field and thermo-elastic field in the matrix and inclusion are obtained. The solutions demonstrate that the uniform temperature and remote uniform stresses will induce an internal uniform stress field. Numerical examples show the effects of the thermal conductivity coefficient ratio, the heat flow direction angle and the elastic modulus on the interface stresses. The results provide a valuable reference for the design and application of reinforced quasicrystal materials.

Fire behavior and design of steel columns reinforced by prestressed CFRP strips

This study analyzes the behavior of steel columns reinforced by prestressed (PS) carbon fiber reinforced polymer (CFRP) strips exposed to fire. First, tests are performed to study the CFRP material degradation under high temperatures. The elastic modulus and strength of the CFRP decrease with increasing temperature. Second, a thermal–mechanical coupling analysis is conducted with finite element method (FEM) to study the behavior of composite members exposed to fire. Under compressive preloading, the columns are exposed to the ISO 834 standard fire curve. The fire exposure time of columns with different initial CFRP prestressing forces is obtained. All the specimens fail because of global buckling either due to the slacking of the concave side of the CFRP or the plastic deformation of the steel. Subsequently, parametric studies are performed considering different initial CFRP prestressing forces, preloadings and column slenderness values. Finally, a design method is proposed for steel columns with PS CFRP that are exposed to fire, followed by a design example. Columns with protections can achieve high buckling capacities at room temperature and long fire exposure time.

Study on the evolution process of recast layer for fast EDM drilling based on observation experiment and a novel thermal-fluid coupling model

The existence of a recast layer of film cooling holes on turbine blades imposes a crucial problem that affects the quality of fast electrical discharge machining (EDM) drilling. This paper focuses on an evolution process from molten material generation to recast layer formation. Single pulse discharge observation experiments with a high speed camera and a self-built observation platform were carried out to observe the formation and movement of the molten material. A novel thermal-fluid coupling model is proposed to combine fast EDM drilling methods with special materials and geometric properties of film cooling hole machining. A heat transfer module, a turbulent flow computational fluid dynamics module, a phase change module and a level set method are combined in this model. The complete process of generation, flow and solidification of molten materials is investigated by simulation with a single pulse discharging. The simulation results agree well with the experimental observation results. A thermal-mechanical coupling analysis of a molten material evolution process is carried out based on the temperature, velocity and pressure fields from the thermal-fluid model. Simulation results show that the molten material is generated at 1 μs after the starting of a discharge, and solidifies within 20 μs after the ending of the discharge. Under the influence of a high-speed flushing fluid, molten materials will not splash into a gap channel along the radial directions. Most of the molten material enters the gap channel along the workpiece surface with a velocity of over 25 m s−1. The moving direction of the molten material is consistent with that of a flushing fluid. The thickness of a recast layer gradually increases from bottom to top in the fast EDM drilling.

Electro–Thermal–Mechanical Coupled Analysis on Two High-Current Composite Umbilical Cable Cross Sections

Abstract A new type of umbilical cable named “high-current composite umbilical cable” is composed of electronic cables, optical cables, steel tubes, and structural strengthening components. It can be regarded as a key piece of industrial equipment in subsea production systems that provide control functions, high electric current, and hydraulic remote transmission. When it is oriented at a power supply with a relatively high rated current, power transmission will produce a lot of heat. Then, the cross-sectional temperature increases, which affects the performances of its material and mechanical responses. Therefore, electro–thermal–mechanical coupled analysis is critical for the cross-sectional design of the high-current composite umbilical cable. Accordingly, a multi-physics coupled analysis was performed based on two typical umbilical cable cross sections. Finite element models were established and subjected to electro–thermal analysis to obtain a temperature distribution of the two sections at different current capacities. Based on results of temperature field analysis, the section models were subjected to thermo–mechanical analysis. The results of the two types of analyses are compared and differences are discussed, which illustrate the multi-physics coupled effect cannot be neglected. The armored layers will relatively reduce the heat dissipation performance, but compared with the umbilical cable model without the armored layers, the model with double-armored layers is less affected by temperature, so its capacity of resistance external pressure is relatively better. The proposed coupled analysis methodology provides a new guidance for the design of the high-current composite umbilical cables.

Thermal-mechanical Coupling Analysis of Rear Wheel Brake of Sightseeing Vehicle Based on Workbench

Taking the rear wheel brake of a certain brand of sightseeing vehicle as an example, floating caliper disc brakes and leading trailing shoe brake were simulated and compared for determining rear wheel brake types. The simplified model is established by UG software, imported into Workbench for thermal-mechanical coupling analysis under 10 braking conditions. The results show that the two brakes can meet the requirements of the vehicle, the former has better performance, and the latter has lower cost.

Study on Fracture Characteristics of Asphalt Pavement with Longitudinal and Transverse Cracks under the Influence of Real Temperature Field

In order to study the influence of the actual temperature field of asphalt pavement on the fracture characteristics of asphalt pavement structure, the finite element(FE) software ABAQUS is used to simulate the temperature field of asphalt pavement in summer and winter, and then the temperature field corresponding to specific time period is introduced into the thermal mechanical coupling analysis. The effects of different loading speeds (10, 20 m/s) and different loads sizes (0.7, 1.2 MPa) on the stress intensity factors (SIF) of top-down (longitudinal) and base reflective (transverse) cracks were studied, and the crack propagation characteristics were discussed. It is found that in summer, the top-down cracks in the surface layer mainly propagate in mode II, and the value increases with the increase of load. In winter, the low temperature promotes the propagation of mode I crack, and the sign of K? value in winter is opposite to that in summer. For the reflection crack of base course, the coupled field promotes the propagation of mode II crack at high temperature in summer. However, in winter, the base is prone to mode I expansion, and increases with the increase of load. When there is no coupling field, the speed has little effect on crack propagation, but the location of SIF peak value changes in time. In the coupled field, the SIF value increases with the decrease of speed. Therefore, considering the real temperature field, heavy load and slow speed have the greater damage to the pavement.

Frost-Heave Deformation and Prevention Technology of Power Transmission and Transformation Foundation under Extreme Boundary Temperature

Freezing and thawing disasters in seasonal frozen soil areas seriously affect the safety of power transmission and transformation projects. Studying the distribution of soil temperature and deformation under thermal insulation foundations is an important basis for the analysis of foundation stability in seasonal frozen soil areas. The thermal protection structure is closely related to the thickness of the insulation layer and the external thermal field. This dissertation takes the typical tower foundation of the 750 kV Hexi Power Grid Project and the geological conditions of the Shule River area in Gansu as the research objects. The theoretical analysis and numerical simulation methods are used to consider the impact of different thermal protection structures on the tower foundation and surrounding soil under extreme boundary temperatures. The influence of body deformation, stress, and temperature changes was analyzed. Through comparative analysis, it is found that the optimized structural form can effectively increase the temperature of the soil in extreme environments, avoid frost heave, and meet the design requirements for bearing capacity. In addition, the thermal-mechanical coupling analysis of the foundations of the initial temperature fields of different boundaries is carried out, and the applicability of the insulation foundation under different boundary conditions is discussed.

Numerical Simulation Research on Multi-field Coupling of Underground Energy Pile

The bearing capacity of the pile foundation determines the safety and stability of the upper structure. However, during the thermal cycling of the energy pile, the stress of the pile will be changed due to temperature changes., which will affect the bearing capacity of the energy pile foundation. In order to analyze the mechanical properties of the energy pile under multi-field coupling, the finite element software COMSOL Multiphysics is used to establish the thermal-mechanical coupling analysis model of the energy pile. We apply thermal load on the pile body and vertical load on the top of the pile. The results show that: Under the multi-field coupling of temperature and mechanical load, the energy pile body expands when heated, and the displacement of the pile top decreases; this will cause uneven settlement between the energy pile foundation laying the heat exchange tube and other pile foundations, which will lead to the tilt and damage of the superstructure; the stress of the pile during the heating of the energy pile will increase.

Modeling and Thermal-Mechanical Coupling Analysis of Piston in Car Engines

In this paper, finite-element analysis (FEA) is carried out on the temperature field and stress field of automobile engine piston, as well as the thermal-mechanical load coupling stress field. Through the analysis, the authors grasped the thermal load and combined stress distribution of the piston, and thus optimized the piston design to improve its operational reliability. Specifically, a 1/4 solid model of the piston was constructed in the three-dimensional (3D) computer-aided design (CAD) software Pro/ENGINEER, and then converted into a finite-element model in Pro/Mechanica. Then, an alternating load was imposed on the piston model, and fatigue analysis was performed to identify the parts of the piston prone to fatigue failure, and judge whether the piston structure satisfies working requirements. Next, temperature field analysis was carried out on the piston model. The distribution of the steady-state temperature field as determined by applying temperatures and heat transfer coefficients as required by the boundary conditions of the third kind. Finally, the piston model was subject to thermal-mechanical coupling analysis. The stress and deformation distributions of the piston under the coupled stress field were ascertained under the boundary conditions of temperature field distribution and mechanical load. Through the above work, the authors obtained the basis for safety evaluation of piston, laying the foundation for further reducing the thermal load and optimizing the stress distribution of piston.

Random generation of asphalt mixture mesostructure and thermal–mechanical coupling analysis at low temperature

To further study the damage mechanism of asphalt mixture during ice crystal frost heaving force and to provide reference and suggestions for the prevention and research of frost damage of asphalt pavement in severe cold areas. Taking AC-13 asphalt mixture as an example, this study uses Matlab to establish a random delivery model of irregular aggregates and uses ANSYS to conduct a thermal–mechanical coupling analysis of asphalt mixtures with different porosity and temperatures. Results show that the numerical model can be used for the microstructure analysis of asphalt mixtures. Moreover, in a low temperature environment of −5 °C to −25 °C, the moisture in the void will freeze sharply within 60 s and eventually reach the same temperature value as the matrix. In the three-way constrained displacement field, the frost heave force generated by ice crystals causes the largest and most obvious deformation on the surface of the specimen. In addition, due to the interaction of the aggregate surface, the asphalt components are reorganized. Under the extreme condition of −25 °C, the stress value in the bonding surface reaches the maximum 33.07 MPa, which is three times that of asphalt mortar under the same conditions. It shows that under the same strain, the bonding surface reaches the allowable stress earlier than the asphalt mortar and fails. Therefore, this study not only provides a quantitative expression for the frost heave damage of ice crystals but also reveals the influence of ice crystals on the macroscopic properties of asphalt mixture from a meso level.