Narrow Results

The temperature field distribution uniformity has a crucial influence on growing high-quality diamond grains by hot-filament chemical vapor deposition (HFCVD). In this paper, we explored the effect of the temperature of the tungsten wire on the temperature field distribution on the surface of the polycrystalline diamond compact (PDC) substrate using the finite element method and found that, with the temperature of tungsten wire being 2200^∘C, it is suitable for the growth of diamond grains and the temperature distribution is more uniform. Meanwhile, the HFCVD method has been used to probe the effect of the parameters of the hot wire power on the diamond grains filling hole and the quality of the diamond film on the PDC surface, analyzed by various characterizations including SEM, XRD, Image J, and Raman. It turned out that both the size of the diamond grains and the acceleration of the deposition increase, as the hot wire power is increased. The size of the diamond grains decreases when the hot wire power is increased to 4.00kW, while the uniform and cauliflower-like nanodiamond films are formed. However, the hot wire power continued to increase and the deposition focused on the growing graphite phase rather than the diamond phase, resulting in a decrease in the quality and properties of the diamond film. The study was able to achieve good tenacity and wearability of the PDC for applications in oil drilling and ultra-hard coating tools.

The dynamic analysis of a functionally gradient material (FGM) beam undergoing large overall motion based on meshless methods is studied in the variable temperature field environment. Considering the high-order terms of nonlinear coupling deformation which were often ignored in previous studies, the high-order rigid–flexible coupled (HOC) dynamic model of a rotating FGM beam with a lumped mass in a temperature field is established by employing Lagrange’s equations of the second kind. Compared with the first-order approximate coupled (FOAC) dynamic model, the HOC dynamic model is more accurate and has a wider scope of application. The validity of the point interpolation (PIM) method and radial point interpolation method (RPIM) in this paper is verified by comparison with simulation results of the assumed mode method (AMM) and the finite element method (FEM). On this basis, the factors affecting the dynamic characteristics of the FGM beam such as the form of temperature field, the functionally gradient index, and the location of added lumped mass are discussed. In this paper, the meshless method with higher computational efficiency and the HOC dynamic model with more accurate results are adopted. This study will provide guidance and reference for dealing with problems in engineering, machinery, aerospace, and other fields in complex environment.

In this paper, a three-dimensional (3D) randomly packed bed model is established to research the filtration combustion process. 3D numerical simulation of premixed combustion in the randomly packed bed is carried out, and the temperature distributions and flame propagation characteristics are predicted and discussed. Simulation results show that the change rules of the temperature field and the flame surface in the random model are consistent with the classical theory, and the stochastic packed model is more promising for numerical simulation of filtration combustion in comparison with the traditional regular structures.

A closed cylindrical shell with circular cross-section having constant stiffness and density and subjected to sign changeable loading and embedded into a temperature field is analyzed. Both Bubnov–Galerkin (with a higher approximation) and Fourier methods are applied to solve the derived nonlinear nondimensional partial differential equations. Among others, the novel scenario of transition from shell harmonic to chaotic vibrations via the collapse of quasi-periodic vibrations with one independent frequency and Hopf bifurcation is detected, illustrated and discussed. In addition, it is shown how for various intensities of the temperature field (including its absence) the increase of the loading yields qualitative changes in the investigated shell dynamics, and how chaotic zones are transmitted into periodic ones and vice versa.

Diamond-coated tools have extremely extraordinary physical and chemical properties and have become ideal tools for machining the emerging materials that are hard to machine. In mass production of diamond-coated milling tools, the homogeneity of diamond coatings has always been sought for and is highly influenced by the uniformity of temperature field near the tool substrate. In order to further improve the uniformity of the temperature field and deposit diamond coatings with uniform thickness, a novel hot filament chemical vapor deposition (HFCVD) device with separated worktables and plates for mass production of diamond-coated milling tools is proposed. First, the simulation models of previous device with integrated worktable versus new device with separated worktables are established using finite volume method. The simulation results shows that the temperature distribution is more uniform in the device with separated worktables. Second, temperature measurement experiments are conducted, which prove the correctness of simulation model. Subsequently, experiments involving the deposition of diamond coatings on milling tools are conducted using two kinds of worktables, utilizing the same parameters as in the simulation. Finally, high-speed milling experiments are conducted to test the diamond-coated milling tools. According to the results of SEM, Raman and high-speed milling experiments, it can be concluded that the homogeneity of coating thickness and cutting performance of the milling tools produced by HFCVD device with separated worktables and plates are better.

In order to solve the problem of uneven distribution of air conditioning temperature and air velocity in the ward, it is easy to produce the uncomfortable feeling of cold and hot and wind blowing. Taking the standard double room general ward of a newly built hospital as the research object, a mathematical model was established, and CFD software was used to numerically simulate the temperature field and velocity field of the air in the ward, optimize the location of the air outlet, and put forward the suggestion of the optimal installation location of the hospital bed. The results show that when the fan coiler air supply outlet is close to the west wall and the fresh air outlet is far away from the west wall, the inhomogeneity of the distribution of the temperature field and velocity field in the ward is reduced, and at this time, the temperature and velocity distribution of the air in the ward is more uniform, so that the patients’ overall feeling in the ward is more comfortable, and at this time, the installation position of the air outlet is more reasonable; and it is determined that the optimal placement of the beds in the room is at the locations of $x$ = 2 m, $y$ = 2.5 m and $x$ = 2 m, $y$ = 4.5 m, and at this time the two beds are at the same time, which is more reasonable. When $y$ = 4.5 m, the temperature difference between the two beds is less than 0.5 K, the wind speed difference is not more than 0.08 m/s, and the velocity gradient direction is the same.

The numerical simulation and experiment method for temperature field research in the laser quenching process is proposed. First, several assumptions of the laser quenching process are discussed for the research convenience. The simulation process is analyzed by the Laser Heat-Treatment-2 software, which is developed in FORTRAN. A discrete simulation process and results are given through the setting of different parameters in the laser quenching process. Finally, the experimental study is carried out to demonstrate the validity of the simulation results.

The paper is devoted to simulating the impact of a thermal shock on a thin homogeneous plate in the ANSYS package. The assessment of the stress–strain state is carried out and the dynamics of changes in the temperature field of the plate is determined. The obtained results were compared with the data of other authors and can be used when taking into account the thermal shock of large elastic elements of spacecraft.

The problem of overheating is the main factor to limit the serviceable range of permanent magnet governor, in order to find out the reason of overheating and its influencing factors, the numerical simulation of the cylindrical permanent magnet governor is carried out by using the computational fluid dynamics method. Results show that the internal high temperature fluid in the rotor of the Permanent magnet governor cannot flow is the main factor causing the overheating of the permanent magnet governor, opened air convection holes, and equipped with cooling fins in conductor rotor and permanent magnet rotor's outer circumference direction of the permanent magnet governor. The results of the study show that the internal air flow of the optimized permanent magnet governor is effective and the air flow rate is increased, the heat transfer effect is enhanced, the maximum temperature of the permanent magnet governor is decreased from 120.2 to 72.6, so the cooling effect is obvious.

Based on the rigid-plastic finite element method, the extrusion process of AZ31 magnesium alloy cylindrical shell was simulated numerically in this paper. Concurrently, the distributions of equivalent strain field, equivalent force field and temperature field in the extrusion process were analyzed. In addition, the influence of the blank temperature and preheating temperature of the die on extrusion pressure and the quality of the test pieces were analyzed. The results demonstrate that the deformation of the blank bottom and lug part is the most severe in the whole extrusion process and it exhibits a higher temperature than the other parts. The contact area between the edge of male die head and the blank; the area of deformation in the cylinder wall; the contact area between the bottom of the blank and the female die; and the area of deformation of the lug are all areas prone to cracks, due to the larger stress caused by the changing speed of flowing metal and compounded by poor lubrication. Under experimental conditions, the optimal deformation parameters of AZ31 magnesium alloy are as follows: the preheating temperature of the blank should be controlled at 350°C and the preheating temperature of die should be controlled between 260°C to 320°C. The precision of the of hot extrusion process for AZ31 magnesium alloy cylindrical shell is verified by numerical analysis and therefore this paper provides a theoretical basis for the optimization of die design and production guidance.

Aiming at the difficulties such as unreasonable cold insulation structure of Liquefied natural gas (LNG) pipe, bad effect of cold insulation, high cold loss, complicated and difficult construction, long-time installation and etc., this paper studies the types and performance characteristics of cold insulation material of LNG pipe. In the paper, finite-element method is used to analyze cold insulation structure and distribution regularities of temperature field of thickness, and the rationality of cold insulation structure is verified. Carrying out construction according to the requirements for cold insulation construction technology in the paper will provide reference for cold insulation construction of LNG pipe.

Analysis on the temperature field and the temperature stress field of mass concrete at early age under different curing conditions was conducted by utilizing ANSYS software, in consideration of hydration heat of concrete, tensile strength, Young’s modulus and bond strength which change with time. The impact of different curing conditions on the crack resistance of mass concrete at early age was also analyzed. In the analysis, five curing conditions were simulated by changing the convection heat transfer coefficient. The results demonstrate that, curing condition has significant impact on the temperature field and the temperature stress field of mass concrete at early age. Under the condition of full insulation, concrete temperature distribution is even, which leads to a much smaller temperature stress.

The method of composite brazing induced by ultrasonic vibration is used in preparing Sn-58Bi-0.05Sm micro braze welding joint. Heat transfer experiments are carried out using a self-made multi-field coupling aging device. Temperature changes at the ends of the specimen and the ends of solder are detected by a thermocouple thermometer. ABAQUS, an finite element analysis software, is used to draw the three-dimensional model of the micro tensile specimen, bring into the parameters and the measured temperature value, simulate the temperature at both ends of the solder, and calculate the temperature gradient. The results of ABAQUS simulation show that: the cold end and hot end temperature of Cu/ Sn-58Bi-0.05Sm /Cu micro solder joint are 66.95,°C and 73.05°C, the temperature gradient being 305°C /cm. When the temperature of the hot end and cold end reaches 40°C and 180°C, the temperature gradient at the ends of the solder joint is as high as 1068°C / cm. Such a high temperature gradient can be sufficient to induce heat transfer of metal atoms and cause serious problems of reliability.

CATIA software is used to build two-dimensional and three-dimensional model of LNG storage tank, hexahedral meshes are generated in HYPERMESH software and ANSYS software is imported to analyze overall temperature field and thermal stress distribution of 30000m³ LNG storage tank. According to analysis result file, the distribution regularities of temperature and thermal stress of 30000 m³ LNG storage tank is concluded, key control points of cold insulation construction of LNG storage tank are highlighted, management of quality of cold insulation construction of LNG storage tank is tightened up and LNG construction level is upgraded.

Consisting of a CCD camera, a frame grabber and a computer, a system is developed to monitor the molten pool parameters in laser cladding. The molten pool images, grabbed by the CCD camera, are processed by the software, and then the geometry and temperature field distribution of molten pool are measured, which can show the changes in laser cladding. The relationship between the molten pool parameter and the visible defects is revealed, and the visible defects can be detected in-time by diagnosis of the molten pool parameters.

Cracks of concrete structure during construction are mainly caused by temperature load, but good effect of cracks prevention methods can be achieved if the timely and reasonable scheme of temperature control is selected. Research shows that the method of external heat preservation and internal cooling pipes can prevent cracks, while the type and thickness of the thermal insulating materials, cooling water temperature, cooling lasting days and cooling pipe arrangement influence the effect of temperature control by certain degree. In view of this problem, a case study is presented where the 3-D FEM including water-pipe cooling is adopted to simulate the thermal field and stress field of concrete under different combinations of measures. The result shows that good effect of temperature control and crack prevention is achieved. This research should have great reference signification to similar concrete projects in the future.

The temperature field of laser-MIG hybrid welding were investigated by the MSC. Marc software and experimental tests. The results showed that the calculated values were in good agreement with experimental measurements in the Macrophotograph of welding joint and temperature change of base. The deviation of comparison between computed temperature values and measured temperature values in the three points of the base are all controlled within 8%. That weld in bottom surface cooling from solid temperature to 300°C will spend more time than that in up surface.

The finite element model of radial-axial hot ring rolling of large-diameter, wide-width and thin-wall ring is established based on the finite element software ABAQUS. The strain field and temperature field have been analyzed. The results indicate that the maximum strain concentrate in the upper and lower surfaces of the ring, and the minimum strain is mainly distributed in the middle zone of the ring. The overall temperature shows a trend of decline. The temperature of ring middle area is higher than ring surface and the temperature of the four corner edge is lowest.

In this paper, the effect of acceleration on the airflow level posture sensor is explained using a finite element model with the temperature field and the stream field monitored by the sensor as independent variable. By using the finite element method, the temperature field and the stream field in sensing element has been obtained. The results are as follow: (1) The temperature field and the stream field in sensing element deform under the effect of acceleration. (2) The velocity difference of airflow at two point heat sources changes with the acceleration, with the increase in acceleration, the airflow rate difference of two detecting hot wires decreases, difference of current through the thermal resistance wire is increased, the bridge outputs a voltage signal corresponding to the acceleration. (3) Effect of acceleration on the airflow level posture sensor is similar to the solid and liquid pendulum tilt angle sensor, when the acceleration inputs, the sensor can't tell acceleration signal and angle signal. In dynamic use, the interference of acceleration on airflow level posture sensor must be suppressed in order to ensure the use of the precision.

The paper determines the optimal position of thermistors in sensitive components of gas pendulum omnibearing level posture sensor is d=900 μm (d is distance of two relatively detection thermistors). By using the finite element method, through the establishment of three-dimensional modeling of the thermistors of sensitive element in different positions, different tilting states, the distribution of temperature field and flow field inside the sensitive element are calculated. The results show that: (1) When the d is changed, the temperature field and flow field changes. (2) The relation curve, which is about the difference Δv of airflow velocity around the two relatively detection thermistors and tilt angle, changes with the d. This opens the effective approaches for the optimization design of the sensor.