Distribution Law Of Temperature Field Research Articles

Analysis on Effects of Material Parameters on Thermoelastic Instability of Separate Plate in Wet Clutch

Abstract The working characteristics of wet clutches have an important impact on the safety performance of vehicles. In order to obtain the thermoelastic instability characteristics of wet clutch separate plate, a finite element modeling method is proposed. The temperature field calculation model of separate plate and its thermo-hydro-mechanical coupling relationship are constructed. The distribution law of high-temperature hot spots on the surface of separate plate is obtained and the thermoelastic instability mechanism is revealed. Effectiveness of the simulation model is verified by road test, and surface topography of separate plate is observed by scanning electron microscope. A thermoelastic instability calculation model considering different material parameters is established. The temperature field distribution law is reviewed under different elastic moduli, specific heat capacities, thermal conductivities, and thermal expansion coefficients. Results show that increasing the specific heat capacity and thermal conductivity of the separate plate, decreasing the elastic modulus and thermal expansion coefficient can improve the stability of the system. The thermal conductivity and thermal expansion coefficient have important effects on the thermoelastic instability. The specific heat capacity has a certain effect, and the elastic modulus’ effect is the least. The research results of this paper can provide theoretical support for optimizing the structure of wet clutch and improving the stability of the system.

Study on Temperature Field Distribution Law and Mechanical Properties of Hydraulic Tunnel-Surrounding Rock under the Action of Large Temperature Differences

This study aims to explore the temperature field and mechanical characteristics of hydraulic tunnels during operation in an area with large temperature differences throughout a year. By relying on the measured displacement field change results of a water transmission tunnel in Xinjiang, a finite element calculation model applicable to the hydraulic tunnel-surrounding rock under the action of large temperature differences was established. Then, the FEM model was used to analyze the temperature field distribution and stress field variation of hydraulic tunnel-surrounding rock under the effect of large temperature differences. The results showed that, under the action of large temperature differences, the displacement of the cave top was the largest, followed by the cave bottom, and finally the cave waist. The obtained displacement field data using the calculation model in this study were basically consistent with the on-site measured data, and the displacement field change law was the same, indicating that the established finite element calculation model is reliable. When the ambient temperature was below zero, the freezing front gradually expanded to the depth of the surrounding rock along the tunnel radial direction, while the frozen rock at the intersection of the lining and the surrounding rock melted first when the ambient temperature was above zero. The stress in various parts of the surrounding rock of the hydraulic tunnel increased continuously. To be specific, the growth rate of the tensile stress at the cave bottom, the tensile stress at the cave top, and the compressive stress at the cave waist of the tunnel reached 0.052 MPa/year, 0.053 MPa/year, and 0.096 MPa/year, respectively, in the first year, but the increasing rate subsequently tended to slow down continuously. Therefore, in actual projects, attention should be focused on the effect of large temperature differences on the stress growth of tunnel-surrounding rocks at an early stage, especially the growth of compressive stress at the cave waist. Notably, there are a large number of symmetrical and asymmetric phenomena related to engineering in this study.

Mixed Heat Transfer in a Double Barrel with Differential Velocity based on CFD-DEM and Experiment

Abstract A double barrel with differential velocity (DBDV) was proposed to improve the mixture quality. Temperature is one of the indexes to evaluate the mixture quality. At present, there are few studies on the heat transfer of DBDV. The heat transfer of particles in DBDV was studied by CFD-DEM to deeply understand the proposed DBDV. The heat transfer process in DBDV was analyzed. The distribution law of temperature field under the coupling effect of particles and fluid was obtained. The influence of fluid speed on particle temperature and the regeneration proportion in DBDV were analyzed and compared with the existing double barrel. And the main heat transfer mode of particles in DBDV was to be obtained. The results show that the mixture temperature in the proposed DBDV is generally higher than that in the existing DB. And the mixture produced by DBDV is not only friendly to the environment, but also the mixture temperature can meet the construction requirements even if more than half of the RAP materials are added to the mixture. Compared with DB, the addition proportion of DBDV is increased by 9.38% - 20.70%. And the reliability of the simulation work was verified by the indoor experiment platform, which lays a foundation for the application of DBDV.

Analytical solution for the temperature field of an elliptical tunnel in cold regions

For the existing tunnels, only few of them are circular sections, the most of them are approximately elliptical sections. Correspondingly, the existing analytical solution researches basically focus on the circular tunnels. To study the distribution law of temperature field of an elliptical section tunnel in cold region, the conformal mapping method is adopted in this paper. Through the conformal mapping method function, a circular function in complex variable space is transformed into an elliptic function in Euclidean space, and then the analytical solution of variation law of temperature field of elliptic section tunnel is derived based on the analytical solution of temperature field of a circular tunnel in complex variable space. An analytical solution example for the temperature field distribution of an elliptical section tunnel in cold region is derived, the calculation results show that: (1) Sizes and variation rates of elliptic freezing surface are greatly affected by freezing time. At the outset, the elliptic freezing surface changes relatively quickly with the increase of freezing time, but the elliptic freezing surface changes relatively slowly when the freezing time is relatively long. (2) The temperature values on a certain elliptic cross section surface decrease with the increase of freezing time. (3) The ratio of the major semidiameter to minor semidiameter of elliptic freezing surfaces is getting closer to 1 with the increase of freezing time. It is also said that the elliptic freezing surface changes from ellipse to circle with the freezing time increasing. By comparing the analytical solution with the numerical solution, it is found that the analytical solution proposed in this paper has high accuracy. This study can provide important theoretical and engineering guidance for the evaluation, design, construction and maintenance of tunnel engineering in seasonally frozen soil regions and permafrost regions, and this study also has important scientific value.

Ultrasonic welding of AZ31B magnesium alloy and pure copper: microstructure, mechanical properties and finite element analysis

Magnesium alloy, copper and other light alloys are widely used in aerospace, new energy vehicles, lightweight manufacturing and other fields due to their excellent mechanical properties, but the connection between light alloys has always been a challenge. Ultrasonic welding is an advanced manufacturing technology that can realize high-strength connection between heterogeneous light alloys. In this study, ultrasonic welding between AZ31B magnesium and pure copper are carried out. The fracture, microstructure and tensile properties of the joint are studied, and its connection mechanism is analyzed. The finite element analysis model of magnesium-copper ultrasonic welding process is established. The fracture mode of magnesium-copper ultrasonic welded joint is interface-type fracture. The joint strength reaches the maximum value of 3798 N. The ultrasonic connection between magnesium alloy and copper is mainly realized by the interface diffusion layer formed in the welding process. The main component of the interface diffusion layer is Mg2Cu. The growth trend of interface diffusion layer is revealed. During welding, heat is generated in the central area of the solder joint, and then transferred around. The maximum temperature at the interface can reach 550 °C. The distribution law of temperature field and plastic deformation field of joint are revealed.

Analysis and test of conductive shaft of large horizontal NC ECM machine tool

In order to solve the problems of serious heating and easy ablation of conductive shaft in electrochemical machining of special-shaped deep hole with large aspect ratio, the two schemes of single-sided copper bar and symmetrical copper bar of conductive shaft are studied by ANSYS software. By establishing the thermoelectric coupling model of the conductive shaft, the distribution law of temperature field and thermal deformation of conductive shaft under different working conditions is analyzed. The conductive shaft structure based on symmetrical copper bar scheme is determined. Monitoring points are set at the key parts of the conductive shaft, and the temperature field distribution is verified by using the data acquisition card. The temperature acquisition results are consistent with the simulation results. Through the machining test of special-shaped inner spiral deep hole parts with large aspect ratio, the results show that under the conditions of working current of 15 000 A, feed rate of 5 mm/min, and continuous machining for 14 h, the forming accuracy of the workpiece is ± 0.15 mm and the surface roughness is better than Ra0.8 μm. The performance of the conductive shaft is stable and meets the actual processing requirements. The heat dissipation performance of the conductive shaft is optimized by providing air flow on the upper surface and side at the same time.

Temperature Field Distribution and Thermal Stability of Roadbed in Permafrost Regions

Many highways and railways in western China are built on permafrost roadbed. Frost heave and thaw settlement might cause diseases to frozen soil roadbed, such as deformation and cracking. For long-term operation, frozen soil roadbed should be kept stable and durable. Therefore, this paper analyzes the distribution law of temperature field of roadbed in permafrost regions, under the effect of thermal stability. Based on the thermodynamic properties of permafrost, the authors analyzed the influence of engineering geological factors, roadbed structural factors, and natural environmental factors on the thermal stability of frozen soil roadbed. Next, the antifreeze mechanism of frozen soil roadbed was described, together with the calculation methods for the relevant parameters. Afterwards, the temperature field of the roadbed with low thermal conductivity insulation material was analyzed by two methods, namely, steady-state thermal analysis and transient thermal analysis, and the solving process of roadbed temperature field was explained in details. The proposed analysis method and solving algorithm were proved valid through experiments. The research results provide a reference for the reasonable design of frozen soil roadbed.

Analysis of rock cracking characteristics during pyrolysis drilling

Thermal jet rock breaking technology refers to the use of high temperature medium such as supercritical water for a rapid local heating of rocks to break the rocks. Because of the low thermal conductivity of the rock matrix, thermal stress will only form on the rock surface. When the temperature stress exceeds the strength of the rock, micro-cracks will appear in the rock, and continue to expand, resulting in the thermal cracking on the rock surface, which will cause the rock surface to fall off from the body and break the rock. Based on thermal-solid coupling theory, a pyrolysis drilling model was established, and the distribution law of temperature field and temperature stress of bottom hole rock during pyrolysis was obtained by using a finite element method. The results show that during the pyrolysis drilling process, the temperature of the heated part of the rock increases rapidly, producing temperature gradients in radial and axial directions. The expansion of the heated volume is affected by compressive stress in the radial direction, buckling in the axial direction and shear stress. This is very important to the field application of pyrolysis drilling.

Numerical Simulation Analysis of Unsteady Temperature in Thermal Insulation Supporting Roadway

High geothermal hazard is a basic problem that must be solved in deep mining; thereby the research on thermal insulation supporting for high temperature control of deep roadway is increasing. However, the quantitative analysis of its thermal insulation effect is yet to be carried out. By building the physical model and control equations of the thermal insulation supporting roadway and considering heat-humidity transfer at wall, the temperature field distribution of surrounding rock and airflow is numerically calculated. Based on numerical simulation results, the evolution law of temperature with ventilation time is analyzed at airflow inlet, outlet, and different sections, then the variation law of surface heat transfer coefficient with position and time is obtained. For heat insulation support structure, the results show that it is not obvious to change the distribution law of temperature field, but it is effective to weaken the convection heat transfer between surrounding rock and airflow. In the main airflow area, the rate of heat exchange gradually decreases with the heat exchange becoming more and more sufficient; in boundary layer, the airflow temperature quickly transits from the wall temperature to that of the main airflow area because of intense collisions of airflow masses, so the mechanism of temperature change is different. The surface heat transfer coefficient well reflected the unstable heat-humidity transfer, especially in the beginning of ventilation or at airflow inlet. Therefore, the heat insulation supporting structure is helpful to the auxiliary cooling of high temperature mine.

Thermal control for ion beam figuring of thin-layer unimorph deformable mirror

To improve the effective deformation of the unimorph deformable mirror (DM), ion beam figuring (IBF) is applied for manufacturing the initial surface figure. However, heat produced during IBF can cause comparable internal stress and thermal deformation on the adhesive layer, which causes the mirror’s figure to be unsatisfactory. Consequently, the whole manufacturing process, especially thermal distribution on the adhesive, should be monitored and controlled. A 19-unit thin-layer unimorph DM is adopted as the object to simulate and measure the distribution law of temperature field on the adhesive during the IBF process. IBF parameters are optimized according to the characteristics of the adhesive and the manufacturing simulation results. With a ϕ3-mm diaphragm integrated on IBF, the processing temperature is reduced below the adhesive’s glass transition temperature Tg. Actual figuring results report over 50% reduction on both peak-to-valley (PV) and root-mean-square (RMS) of DM with the value from 310 to 141 nm and from 38 to 17 nm, respectively. This precision has satisfied the self-corrected requirement of general unimorph DMs, which is usually <20 nm RMS. The voltage fitting coefficient of self-correcting for most electrodes is reduced to <0.05, which means the significant improvement in the effective deformation and correction ability.

Analysis of temperature field of embankment-CFG piles composite soft soil foundation system in cold regions

For the major projects built on the soft soil area in cold regions, the effective treatment of deep soft soil layer and the stable bearing capacity of foundation are of great importance. In this paper, the finite element model of embankment-CFG piles composite soft soil foundation for D3K629-D3K629+950 of Harbin-Dalian railway is established based on ABAQUS. The depth and regional distribution of freezing and thawing and distribution law of temperature field of CFG piles are studied. The results show that the horizontal position of 0-degree line is higher and the protective effect of embankment on the foundation is obvious when the embankment is higher. The embankment almost has no effect on the CFG piles near embankment foot. For the middle pile at the center of the embankment, the protection effect of the embankment is remarkable.

Temperature Field Simulation of Wood Powder/PES Composite Powder Material

In view of the physical process of the wood powder/PES composite powder material selective laser sintering forming ,this article establishes the plane moving Gaussian heat source as the input laser heat source model .Based on selective laser sintering wood powder/PES composite powder sintering theory and combined with thermal conductivity of composite powder, specific heat, density and other related theoretical analytical models .It establishes three dimensional finite element model of selective laser sintering process of wood powder/PES composite powder transient temperature field .The laser sintering simulation experiment of wood powder/PES composite powder under different laser power obtains temperature field distribution law of the wood powder/PES composite powder forming under different laser power distribution, and the influence of the forming parts forming quality of wood powder/PES composite powder materials caused by the temperature field. The simulation results also provide certain theoretical basis for the choice of laser power in the subsequent laser sintering experiment.

Study on Asphalt Pavement Temperature Field Distribution Law in Seasonally Frozen Regions

Based on the temperature field data collected from a self-developed pavement system, asphalt pavement temperature field distribution law in seasonally frozen regions was studied in detail. Test data illustrated that: The atmospheric and pavement temperature shows cycle sine rule; Minimum and maximum values of pavement temperature occur at surface, In winter, pavement temperature gradually increases with increasing depth, but has contrary result in summer; As the increase of depth, the fluctuation range of pavement temperature decreases gradually, which lead to the appearance of daily and annual constant temperature point; The max freezing depth appeared at 120cm and there will be freezing core in spring in seasonally frozen regions.