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thermal stresses in two-and three-component anisotropic materials

第五届国际材料与热加工物理模拟及数值模拟学术会议

作者： Ziliang LI1,a, Heming CHENG2,b, Junruo CHEN3,c and Meihong LIU4,d 1,2,3,4Kunming University of Science & Technology, Kunming, 650093, China

In this paper, based on the analysis of coupled action of temperature, phase transformation and stress, the phase transformation condition and equation related to the thermal physical properties are discussed, and the transient temperature distribution of a Cr12 steel cylinder workpiece during gas quenching was obtained by solving the governing equations with a nonlinear boundary. According to the theories of thermal non-elasticity, computational mechanics and phase transformation, a new constitutive equation considering effects of phase transformation with a nonlinear surface heat transfer coefficient is proposed and is solved by means of finite element method (FEM). The thermal stress field is obtained and a way of simulating the technology of the heat treatment by computer is explored.

关键词： Numerical simulation thermal stress Gas quenching FEM

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Acta Mechanica Sinica 2010年第5期26卷 695-709页

作者： Ladislav Ceniga Institute of Materials Research Slovak Academy of Sciences

This paper deals with an analytical model of thermal stresses which originate during a cooling process of an anisotropic solid continuum with uniaxial or triaxial anisotropy. The anisotropic solid continuum consists of anisotropic spherical particles periodically distributed in an anisotropic infinite matrix. The particles are or are not embedded in an anisotropic spherical envelope, and the infinite matrix is imaginarily divided into identical cubic cells with central particles. The thermal stresses are thus investigated within the cubic cell. This mulfi-particle-（envelope）-matrix system based on the cell model is applicable to two- and three-component materials of precipitate-matrix and precipitate-envelope-matrix types, respectively. Finally, an analysis of the determination of the thermal stresses in the multi-par- ticle-（envelope）-matrix system which consists of isotropic as well as uniaxial- and/or triaxial-anisotropic components is presented. Additionally, the thermal-stress induced elastic energy density for the anisotropic components is also derived. These analytical models which are valid for isotropic, anisotropic and isotropic-anisotropic multi-particle- （envelope）-matrix systems represent the determination of important material characteristics. This analytical determination includes：（1） the determination of a critical particle radius which defines a limit state regarding the crack initiation in an elastic, elastic-plastic and plastic components; （2） the determination of dimensions and a shape of a crack propagated in a ceramic components; （3） the determination of an energy barrier and micro-/macro-strengthening in a component; and （4） analytical-（experimental）-computational methods of the lifetime prediction. The determination of the thermal stresses in the anisotropic components presented in this paper can be used to determine these material characteristics of real two- and three-component materials with anisotropic components or with anisotropic and isotropic components.

关键词： thermal stress Component material Anisotropic solid continuum Analytical modelling Cell model

thermal stresses in infinite circular cylinder subjected to rotation

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Applied Mathematics and Mechanics(English Edition) 2012年第8期33卷 1059-1078页

作者： A.M.ABD-ALLA G.A.YAHYA Department of Mathematics Faculty of ScienceTaif UniversitySaudi Arabia Department of Physics Faculty of ScienceTaif UniversitySaudi Arabia Department of Physics Faculty of ScienceAswan UniversityAswan 81528AswanEgypt

The present investigation is concerned with the effect of rotation on an infi- nite circular cylinder subjected to certain boundary conditions. An analytical procedure for evaluation of thermal stresses, displacements, and temperature in rotating cylinder subjected to thermal load along the radius is presented. The dynamic thermal stresses in an infinite elastic cylinder of radius a due to a constant temperature applied to a variable portion of the curved surface while the rest of surface is maintained at zero temperature are discussed. Such situation can arise due to melting of insulating material deposited on the surface cylinder. A solution and numerical results are obtained for the stress components, displacement components, and temperature. The results obtained from the present semi-analytical method are in good agreement with those obtained by using the previously developed methods.

关键词： wave propagation thermoelasticity isotropic material rotating cylinder Lam’e potential thermal stress

Numerical simulation investigation on hydration heat temperature and early cracking risk of concrete box girder in cold regions

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Journal of Traffic and Transportation Engineering(English Edition) 2023年第4期10卷 697-720页

作者： Shi Han Yongjian Liu Yi Lyu Jiang Liu Ning Zhang School of Highway Chang'an UniversityXian 710064China Qinghai Transportation Engineering Technical Service Center Xining 810008China School of Civil Engineering Chongqing UniversityChongqing 400045China College of Water Resources and Architectural Engineering Northwest A&F UniversityYangling 712100China

The temperature change caused by hydration leads to early-age cracking in concrete box girder.The early-age cracking risk is further improved with low air temperature and large daily temperature difference,especially in Northwest China.To fill this gap,a temperature experiment and numerical simulation were performed on an actual concrete box girder segment in Northwest China.The temperature field,thermal stress and cracking risk were analyzed using evolution curves,distribution curves and contours.The key parameters that influence the hydration heat temperature,including the cement hydration heat release,cement content,height-width ratio of web,initial temperature,convective coefficient of top plate surface,were analyzed.An anti-cracking case based on parameters analysis was put forward.The results indicated that the temperature evolution can be divided into three stages:warming,cooling and environment significantly impacting.Along the thickness of each plate,temperature distributed is single peak in the center.Along the width or height,temperature distributed is double peaks at axillary position for the top and bottom plates,and single peak in center for the web.The axillary position and web have high thermal stress and significant cracking risks.The temperature difference of each plate,and the early-age cracking risk can be reduced by effectively adjusting the key parameters.Among these,the former two parameters are the most significant factors.The maximum cracking risk can be decreased by 15.7%for every 50 kJ/kg hydration heat reduction.The maximum cracking risk can be decreased by 13.1%for every 50 kg/m^(3)cement content reduction.

关键词： Bridge engineering Concrete boxgirder Hydration heat Cold region Temperature action thermal stress

Mechanical stress in high-temperature superconducting ring-shaped bulk during the pulsed-field magnetization

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Science China(Technological Sciences) 2023年第2期66卷 574-585页

作者： WANG Lan WU HaoWei YONG HuaDong Key Laboratory of Mechanics on Disaster and Environment in Western China Ministry of EducationLanzhou UniversityLanzhou 730000China Department of Mechanics and Engineering Sciences College of Civil Engineering and MechanicsLanzhou UniversityLanzhou 730000China School of Science Lanzhou University of TechnologyLanzhou 730050China

The high-temperature superconducting(HTS)bulk has a higher critical current density and can trap the larger magnetic field.When the high-temperature superconducting bulk is magnetized by the pulsed-field,it will be subjected to electromagnetic stress and thermal stress.Furthermore,the bulk may be damaged under larger mechanical stress or strain during the pulsed-field magnetization.In this paper,the electromagnetic field,the temperature and the mechanical response of the ring-shaped bulk are simulated based on the electromagnetic and mechanical governing equations,and the simulated trapped field is consistent with the experimental results given in the reference.The stress distribution on the top surface of the ring-shaped bulk during pulsedfield magnetization is opposite to the case of field cold magnetization.Moreover,the inner edge on the middle plane of the bulk may be broken more easily than the outer edge during the pulsed-field magnetization.Afterward,the influences of the size of the inner radius,ambient temperature and rise time of the applied field are presented.Finally,the mechanical stress of the bulk with the cooling process is investigated,and the tensile stress on the surface can be enhanced by the cooling process.

关键词： ring-shaped superconducting bulk cooling process trapped field thermal stress electromagnetic stress

Multiphysics Design of a High-Speed Permanent Magnet Machine for a Micro Gas Turbine Application

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Journal of thermal Science 2022年第1期31卷 251-260页

作者： ZHENG Mengzi HUANG Weiguang GAO Chuang WU Fuxian Shanghai Advanced Research Institute Chinese Academy of SciencesShanghai 201210China School of Chemical Engineering University of Chinese Academy of SciencesBeijing 100049China Innovation Academy for Light-duty Gas Turbine Chinese Academy of SciencesBeijing 100190China Helan Turbines Co. LtdShanghai 210815China

This paper presents a detailed and comprehensive multiphysics design process of an 80 kW, 60 000 r/min high-speed permanent magnet machine (HSPMM) for a micro gas turbine application. First, the preliminary design of the HSPMM is carried out according to the mechanical and electromagnetic theory. Afterwards, the influence of carbon fiber sleeve (CFS) thickness, rotor diameter and core length on rotor stress and rotor dynamics is carefully analyzed to obtain the optimal range of rotor diameter and core length. On this basis, the electromagnetic and power loss characteristics are analyzed in detail to obtain the final design scheme. Fluid-solid coupling model is used to calculate the temperature field of the HSPMM to verify the rationality of the scheme. The rotor thermal stress analysis considering the multi-layer and multi-angle winding of CFS is carried out to obtain the rotor models suitable for prototype and mass production, respectively. Finally, the prototypes are manufactured and tested to verify the reliability of the multiphysics design process.

关键词： high-speed permanent magnet machine multiphysics design carbon fiber sleeve thermal stress

Thermo-Mechanical Calculation of Printed Circuit Heat Exchanger Using Homogenization

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Journal of thermal Science 2022年第6期31卷 2309-2328页

作者： GARNIER Christophe VINCENT Sébastien LAMAGNERE Pierre LEJEAIL Yves CACHON Lionel CEA DESIRESNENuclear Technology DepartmentCadarache F-13108 Saint-Paul-Lez-DuranceFrance

The Finite-Element Method(FEM) is mainly used to design Compact Heat Exchanger structures. However, the narrow channel structures require fine mesh to accurately compute stress and strain. Combined with the dimensions of the overall component, this leads to an excessively large numerical model and therefore long computing time. This is especially true for transient thermal analyses, which require taking into account the full geometry. It is therefore interesting to reduce the size of the mesh. Periodic homogenization is an efficient method for achieving this goal. It can be applied to the core of the structure when periodic patterns(identified on basis of the arrangement of the channels) exist. A method based on this technique, with some improvements, is proposed in this paper for thermal loading without internal pressure. In addition to the Equivalent Homogenous Medium(EHM) replacing the periodic patterns, some explicit channels are interposed between the EHM and the cover plates. This has two advantages. The first is to smooth the transition of stiffness between the cover plates and the homogenized medium. The second one is to be able to directly compute stress and strain on the most critical channels located in this area. This paper assesses the method’s effectiveness for thermal loadings in order to conduct thermal stress analyses. First, the equivalent elastic constants of the EHM are obtained with a numerical Finite Elements Method. Then, two 2D cases using EHM are compared against a 2D explicit model(i.e. explicit geometry for the core channels). These cases are chosen to validate the EHM itself and its effectiveness for a real section of the heat exchanger. Results show very good agreement with a relative difference lower than 1%. In addition, the sensitivity to the number of layers added between the EHM and the cover plates is analysed. It is recommended interposing at least two layers of patterns to obtain converged results for the considered configuration. Finally, a triangular mesh is considered to re

关键词： compact heat exchanger thermal stress finite element method homogenization

Enhance liquid nitrogen fracturing performance on hot dry rock by cyclic injection

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Petroleum Science 2023年第2期20卷 951-972页

作者： Chun-Yang Hong Rui-Yue Yang Zhong-Wei Huang Xiao-Ying Zhuang Hai-Tao Wen Xiao-Li Hu State Key Laboratory of Petroleum Resources and Prospecting China University of PetroleumBeijing102249China Chair of Computational Science and Simulation Technology Faculty of Mathematics and PhysicsLeibniz Universität HannoverHannover30167Germany

Producing complex fracture networks in a safe way plays a critical role in the hot dry rock (HDR) geothermal energy exploitation. However, conventional hydraulic fracturing (HF) generally produces high breakdown pressure and results only in single main fracture morphology. Furthermore, HF has also other problems such as the increased risk of seismic events and consuption of large amount of water. In this work, a new stimulation method based on cyclic soft stimulation (CSS) and liquid nitrogen (LN2) fracturing, known as cyclic LN2 fracturing is explored, which we believe has the potential to solve the above issues related to HF. The fracturing performances including breakdown pressure and fracture morphology on granites under true-triaxial stresses are investigated and compared with cyclic water fracturing. Cryo-scanning electron microscopy (Cryo-SEM) tests and X-ray computed tomography (CT) scanning tests were used for quantitative characterization of fracture parameters and to evaluate the cyclic LN2 fracturing performances. The results demonstrate that the cyclic LN2 fracturing results in reduced breakdown pressure, with between 21% and 67% lower pressure compared with using cyclic water fracturing. Cyclic LN2 fracturing tends to produce more complex and branched fractures, whereas cyclic water fracturing usually produces a single main fracture under a low number of cycles and pressure levels. thermally-induced fractures mostly occur around the interfaces of different particles. This study shows the potential benefits of cyclic LN2 fracturing on HDR. It is expected to provide theoretical guidance for the cyclic LN2 fracturing application in HDR reservoirs.

关键词： Hot dry rock Liquid nitrogen fracturing Cyclic injection thermal stress Fatigue damage

thermal stresses in a Cylinder Block Casting Due to Coupled thermal and Mechanical Effects

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Tsinghua Science and Technology 2008年第2期13卷 132-136页

作者：徐艳康进武黄天佑胡永沂 Key Laboratory for Advanced Materials Processing Technology of the Ministry of Education Department of Mechanical Engineering Tsinghua University

thermal stress in castings results from nonuniform cooling. The thermal stress and the deformation can change the casting and mold contact conditions which then alter the heat transfer between the casting and the mold. The contact element method was used to study the interaction between a sand mold and a casting. The contact status was then fed back to the heat transfer analysis between the sand mold and the casting to re-evaluate the heat transfer coefficient based on the gap size or pressure between surfaces. The thermal and mechanical phenomena are then coupled in two directions. The method was applied to analyze stress in a stress frame specimen casting and a cylinder block. The results are more accurate than without consideration of the contact effects on the heat transfer.

关键词： cylinder block casting/mold （core） interaction thermal stress contact element method