Changes In Temperature Field Research Articles

Развитие вибротермографии как метода неразрушающего контроля изделий из полимерных конструкционных материалов с использованием принудительных механических вибраций

The method of vibrothermography may be considered as one of the promising thermal non-destructive testing techniques, which can be applied for the detection of internal damage in composite structures. The thermal excitation of the structure in case of vibrothermography is caused by the mechanical oscillations on the sonic or ultrasonic frequency, and the change in temperature field of the object is controlled by thermography methods. The present paper considers the method of vibration testing and presents the results of thermography studies focused on the behavior of composite structure with impact damage subjected to vibration loading.

Research and Analysis on hydration heat effect of mass concrete for main tower cap of long-span self anchored suspension bridge

The self anchored suspension bridge on Jiancai North Road in Xi’an city is a typical cable structure. According to the force transmission characteristics of the cable, the main tower bearing platform is planned to adopt the construction method of laying embedded parts in the bottom layer and pouring the upper layer at one time, which is very different from the traditional layered and phased pouring of the bearing platform. In this paper, the finite element analysis software is used to carry out the fine modeling analysis of the foundation cap and its foundation temperature diffusion area, and the actual simulation of temperature and stress is carried out, and the “temperature stress asynchronous” effect caused by the bottom layer embedded parts and the upper layer pouring construction is studied; by analyzing the asynchronous difference of stress and temperature peak, the transfer law of temperature core area and the temperature field change caused by surface temperature control effect, the construction and monitoring measurement scheme is optimized.

Investigation on dynamic behaviour of shape memory alloy (SMA) wire embedded composite

Smart Material are responsive and intelligent materials. Shape memory alloy (SMA) are subset of a broad class of smart material. The functionalities arise from their underlying microstructural changes when subjected to external non-mechanical stimuli like temperature or magnetic field changes. The study of SMA uses and applications has been done because recently use of shape memory alloy used in the field of the automobile, robotics, medical, Aerospace, Biomedical domain etc. Shape memory alloy can be used for an actuator, sensor, stiffness changer, and damper. The extensive literature survey has been conducted to explore the potential and research scope in this project. This research will help industry to use SMA embedded composite for vibration isolation and damping.

Curing parameters’ influences of early-age temperature field in concrete continuous rigid frame bridge

The unstable change of early temperature field during concrete curing of box girder could lead to the thermal deformation and autogenous shrinkage deformation of concrete, make the concrete crack early, and even affect the subsequent mechanical performance. In order to study the variation law of the early-age temperature field of the box girder concrete and to seek the method to control the variation of the temperature field of the box girder concrete, the No.0 box segment with the most complex structure and the largest volume in the bridge was selected as the research object. The early-age temperature field of No.0 box segment after pouring was simulated by Midas/FEA and the correctness of the simulation was verified by field measurement. Then the time-history law of early-age temperature field of the box girder under the coupling effect of hydration heat and ambient temperature was studied, and the time-history law of the early-age temperature field of the box girder was investigated by changing different concrete curing parameters. The results show that the larger the local size is, the larger the temperature difference is. The selection of formwork's material and thickness should integrate the factors of formwork bearing capacity and thermal insulation performance. The reasonable selection of formwork can effectively control the core temperature and the temperature difference between the inside and outside of the box girder. Formwork installation temperature and wind velocity have a great influence on the temperature difference between the inside and outside of the box girder. The research results can provide technical support for controlling the early-age temperature field changes of box girder concrete, be used to provide a theoretical basis for the best selection of formwork and the selection of the best concrete curing conditions, and help to improve efficiencies in the uses of human capital, energy, and building materials in engineering construction.

Thermal network model and experimental validation for a motorized spindle including thermal–mechanical coupling effect

Thermal deformation caused by temperature rise affects the contact status of bearings in motorized spindles. In turn, the change in the contact status will affect the temperature rise and thermal deformation of the system. However, the latter has been rarely focused on in the previous literature. Therefore, a thermal network model of motorized spindle is enhanced by considering the thermal–mechanical coupling effect. Then, an iterative method is presented to solve the coupled equations, and a temperature test rig of the motorized spindle is set up to verify the proposed model. The predicted results by the proposed model are compared with the experimental results and the predicted results by the previous model. The relative error between the predicted and experimental results at two test points decreases by 9.56% and 3.44%, respectively, after considering the thermal–mechanical coupling effect. The temperature changes the contact angle and contact load of the bearings, thereby causing changes in frictional heat and temperature field. Such changes cause the difference between the proposed and previous models. The comparison with the experimental results shows that the proposed model with thermal–mechanical coupling effect can obtain a more accurate temperature field than the previous model.

Temperature field and heat generation at the tip of a cutout in a viscoelastic solid body undergoing loading

Using the finite element method we quantitatively analyse temperature field evolution in a viscoelastic solid undergoing a loading–unloading process. In particular we investigate the temperature field inside a Kelvin–Voigt type viscoelastic body with a thin cutout. We find that the viscosity significantly contributes to the temperature field changes, and that the temperature field changes initiated by the loading–unloading process are strongly concentrated at the tip of the thin cutout. The predicted temperature field qualitatively corresponds to the temperature field observed in experiments focused on simultaneous heat and strain measurements at the crack tip inside materials such as the filled rubber.

Investigation on solidification structure and temperature field with novel processing of synchronous powder-feeding underwater laser cladding

Synchronous powder-feeding underwater laser cladding(SULC) has a great application prospect in underwater in-situ manufacturing/remanufacturing due to its advantages of small heat input to the substrate and adjustable of additive materials. In this study, the iron-based planar coating with no phase transformation and dilution zone less than 8 μm was prepared on A32 deck steel by SULC using self-designed powder-feeding nozzle and optimizing process parameters. The powder-feeding gas flow rate directly determines the size and stability of the local dry region above the deposition point, and the laser power and powder-feeding rate are the key factors to compensate the laser energy dissipation. Due to the influence of local temperature gradient in SULC, the coating has obvious solidification structure distribution. Columnar grains are mainly distributed upon the trough of fusion line, while dendrites and equiaxed grains are distributed on both sides caused by the temperature gradient becomes smaller and the direction of heat flow changes due to the external environment. In the upper region of SULC coating the equiaxed grains tend to grow up with the increase of laser power. To gain better scientific understanding on differences between atmospheric laser cladding and SULC, the numerical simulation was used to reveal the temperature field changes and coating formation under SULC working parameters. The results show that under the same laser power, due to the forced cooling of larger gas flow and external water environment in SULC process, there is a larger temperature gradient at the deposition point, and the temperature drop rate of the coating and the substrate is greater. In the microstructure, it is shown as columnar grains has a greater directional growth trend. With the increase of laser power, this phenomenon becomes more obvious.

Box Experiment Study of Thermally Enhanced SVE for Benzene.

In order to describe the changes of soil temperature field, air flow field and remediation situation with time during the process of thermally enhanced SVE (soil vapor extraction), a remediation experiment of benzene contaminated soil with single extraction pipe was carried out in a box device. The results showed that the whole temperature of the system was raised to 80 °C in 4 h. 43% of benzene were removed in the first 2% of the extraction time. After 24 h, the repair efficiency was close to 100%. The device can efficiently remove benzene from soil. By continuously monitoring the parameters in the operation process of the system, the spatial distribution of temperature and soil gas pollutant concentration with time was plotted. It showed the benzene concentration distribution in the soil gas was more consistent with the temperature distribution before the start of ventilation, and the concentration of benzene in the soil gas dropped rapidly after ventilation, while the temperature distribution was almost unaffected. In the treatment of soil with a benzene content of 17.8 mg∙kg−1, when the soil gas benzene concentration is the highest at 180 min, the peak value is 11,200 mg∙m−3, and the average concentration is 7629.4 mg∙m−3.

3D experimental investigation on enhanced oil recovery by flue gas assisted steam assisted gravity drainage

Flue gas assisted steam assisted gravity drainage (SAGD) is a frontier technology to enhance oil recovery for heavy oil reservoirs. The carbon dioxide generated from the thermal recovery of heavy oil can be utilized and consumed to mitigate climate warming for the world. However, most studies are limited to merely use numerical simulation or small physical simulation device and hardly focus on large scale three-dimensions experiment, which cannot fully investigate the enhanced oil recovery (EOR) mechanism of flue gas assisted SAGD, thus the effect of flue gas on SAGD production performance is still not very clear. In this paper, large-scaled and high temperature and pressure resistant 3D physical simulation experiment was conducted, where simulated the real reservoir to a maximum extent, and systematically explored the EOR mechanisms of the flue gas assisted SAGD. Furthermore, the differences between the steam huff and puff, SAGD and flue gas assisted SAGD are discussed. The experimental result showed that the production effect of SAGD was improved by injecting flue gas, with the oil recovery was increased by 5.7%. With the help of thermocouple temperature measuring sensors, changes of temperature field display that flue gas can promote lateral re-development of the steam chamber, and the degree of reservoir exploitation around the horizontal wells has been increased particularly. What’s more, the addition of flue gas further increased the content of light components and decreased the content of heavy by comparing the content of heavy oil components produced in different production times.

Research on microstructure and hardness of AISI1050 disk based on FDM and FEM methods during quenching process

Microstructures of AISI1050 disk during quenching were simulated by DEFORM-HT, and corresponding parameters of mechanical properties were investigated by applying the algorithm of finite difference method (FDM). Above all, thermo-physical parameters and diagrams of CCT curve were calculated by JMATPRO. Besides, the simulation of multi-phase microstructure considering initial thermo-physical parameters was realized by DEFORM-HT. The volume fraction of single phase were obtained by the FDM method, and then a weight function considering carbon equivalent of phases was introduced to predict the final hardness of multi-phase and according to the quenched microstructure and independent single phase hardness simulated. Temperature field, stress field and microstructure change of an AISI1050 disk under different quenching processes were studied by using the DEFORM-HT software numerical simulation calculation, combined with the continuous cooling transition curve ( CCT curve) of AISI1050 steel. The martensite transformation of the disk tread during the quenching process can increase the wear resistance. According to the actual working conditions combined with the CCT curve of AISI1050 steel, the hardness of the disk rim surface is 54.8 HRC, which can meet the requirements of 51-56 HRC. It is concluded that the maximum equivalent stress of the disk( the equivalent stress after unloading is the residual stress) is distributed near the disk inner layer in the inside of the plate to hand over the location. The microstructure of the specimen is observed and compared with the simulation results, which prove that the simulation results are reliable. The simulated hardness by using both JMATPRO and DEFORM-HT can provide some basis to predict the hardness on certain degree.

Analysis and evaluation of temperature field and experiment for magnetorheological fluid testing devices

When a large amount of heat is produced during the operation of a MRF (magnetorheological fluid) testing device, the temperature of the device will increase, which will in turn affect the characteristics of the MRF. Exploring the temperature field characteristics of the MRF yield stress testing device is necessary to improve the accuracy of the device. In this study, first, the yield stress testing device is designed, and then its temperature field model, including enameled wire and assembly gap, is established. Second, simulation software is used to simulate the temperature field change. Finally, a test platform is developed to test the simulation results, especially for two factors, namely, thermal conductivity of the coil winding and assembly gap, which demonstrate considerable influence. Comprehensive thermal conductivity and assembly clearance are determined, and the optimum temperature field of the device for measuring yield stress is resulted.

Numerical simulation research on heat transfer characteristics of a Chinese kang

In order to obtain the thermal physical parameters of heat transfer in Chinese kang, the fluid-solid coupling heat transfer is analyzed through the Fluent and Static Structural modules in ANSYS. The indoor temperature field changes under different external influences are obtained, and the distribution characteristics of the severity of the thermal damage area of the kang body are basically grasped. The temperature distribution in the heated area of the Chinese kang is not uniform, and the temperature of the kang body changes more slowly than air. One hour after the heating is stopped, the temperature of the kang body can still continue to rise. The equivalent elastic strain value near the smoke heating area is higher, and the value is between 1.2752 × 10−12–1.5939 × 10−12 m/m. This area has a higher risk of thermal damage and structural deformation. The traditional Chinese kang has good thermal inertia and has a 5 h warmth retention effect after heating is stopped.

Study on dynamic flashover characteristics of iced insulators

In this paper, based on fxbw4-10/100 insulators, the flashover dynamic characteristics of iced insulators are studied. The insulators are artificially iced and flashover experiments are carried out with water of different conductivity in the laboratory, and different flashover voltages are obtained. The dynamic changes of insulator temperature field, electric field and potential are simulated by using finite element software. Finally, the influence of different physical parameters on insulator flashover characteristics is studied.

Numerical Simulation and Experimental Study on Flow Forming of Laser Concave–Convex Microtexture of Cr12 Steel Surface

In this paper, Cr12 steel was taken as the research object, and laser micro melting model was established in comsol software based on physical equations such as laser heat source, convection heat transfer, evaporation mobility, recoil pressure, Marangoni effect. The forming mechanism and evolution law of concave–convex microtexture morphology were studied by numerical simulation. The research reveals the changing process of the velocity of the flow field inside the material during the surface deformation. In addition, it can be found from the temperature field changes under different power that the higher the power is, the faster the surface temperature of Cr12 material increases in the process of thermal deformation. And the hardness of the microtexture was greatly improved after the material experienced sudden heat and cold in a very short time. By comparing the numerical simulation results and the experimental results, it can be found that with the increase of power, the height, depth and diameter of the concave–convex microtexture morphology all show an increasing trend, and the surface geometry obtained through numerical simulation matches well with the experimental results. It indicates that the numerical simulation has high feasibility and can effectively reflect the forming process and morphology of concave-convex microtexture.

The destruction of pure metal cathodes during the initiation of direct current arc

In this work, the behavior of cathodes made from pure tungsten and pure hafnium in the direct current electric arc at 200 A and in atmospheric pressured argon medium was investigated. The research was focused on the processes happening with the cathodes during the arc initiation phase (first 100 ms after the power input). The processes of rapid cathode destruction were registered, and can be characterized as the destruction of the cathode in liquid phase due to electro-magnetic forces. Characteristic times of the whole process were recorded, as well as the changes in temperature fields on the cathodes surfaces and the rate of mass loss for both types of cathodes. It has been shown that the initial destruction of the cathode plays a major role in the cathodes resource life.

The study of the possibility of X-ray inspection of fiber-optic sensors embedded into the structure of a polymer composite material

Annotation. Currently, during the operation of structures, it is important to use the so-called systems for monitoring the state of structures, which in real time allow you to monitor changes in temperature and deformation fields. To diagnose the condition in such systems, various sensors are used, for example, strain gauges, fiber-optic, piezoluminescent. Most modern monitoring systems use fiberoptic sensors because they have more advantages and fewer disadvantages than other sensors. When monitoring the state of a structure, fiber sensors are mounted on the surface of the structure, however, when monitoring structures made of composite materials, it is possible to introduce fiber lines directly into the structure of the composite material at the stage of manufacturing the structure. When fiber lines are introduced into the structure of a composite material, a number of difficulties arise, namely, due to the fragility of fiber lines, breaks are possible both at the exit from the structure and inside. When considering polymer composite materials, the problem of the location of fiber sensors arises due to the resin flow during the process of forming structures. The solution to the problems described above can be the creation of the so-called Smart-layer, in which the fiber lines will be rigidly fixed, which will protect the fiber from breaking, and limit the movement of the fiber during the formation of structures. Thus, within the framework of this work, we investigate the issue associated with the assessment of the location of fiber sensors in the Smart layer after the formation mode. The location of the sensors after the structure is formed is investigated by radiation methods of non-destructive testing.

Design of a diamond tool for laser in situ assistance

Laser in-situ auxiliary processing is an advanced hard and brittle material processing method. In order to improve the utilization rate of the laser in the processing process and better realize the thermal softening effect on hard and brittle materials, the transmission model of the laser and diamond tools was established by COMSOL, and the laser transmission through the rake face of the ordinary arc-edged diamond tool was analyzed. A diamond tool with laser incident surface parallel to the rake surface is designed. The laser incident surface of this diamond tool is parallel to the rake surface, so that the laser can penetrate the diamond rake surface perpendicularly, which is compared with the ordinary circle. The arc turning tool can significantly improve the beam quality, increase the power density of the laser penetrating the tool, and obtain the temperature field change of the diamond tool during laser irradiation and the rule of tool tip deformation. The research is to improve the laser in-situ assisted diamond tool Machining accuracy provides theoretical basis.

Investigations on axially compressed composite cylindrical shells with surface bonded PZT

Smart materials integrated with thin walled structures can be used to achieve the desired shape, stiffness, damping and other mechanical properties of structures in response to the induced changes in temperature, electric or magnetic field in these, without causing any significant change in the mass as is required in aerospace applications. In this paper, the effects of surface bonded piezo ceramic (PZT-Lead Zirconate Titanate) actuation patches to enhance the strength of thin composite cylindrical shells have been studied experimentally and numerically under the actuation of PZT. The study reveals that it is feasible to minimize the effects of the local imperfections and increase the strength closer to the theoretical buckling strength. However, it has been found that even with the currently available PZTs with minimum thickness, the strength of the tested shell increases owing to the added stiffness of the PZT than due to the actuation. Furthermore, with thinner PZTs of thickness of the order 0.01 times the thickness of the shell and with high actuation force, improvements in the shell capacity is possible by the application of voltage. In addition, the actuation of PZT can be used to decrease the radial buckling deformation for any given load. Importantly, the effect of PZT actuation would increase if the initial imperfections are large leading to larger reductions in the ultimate strength of the shell. Finally, a numerical procedure is established to corroborate the experimental results and also for arriving at an optimum PZT configuration.

Design of distributed temperature-measuring system based on 1-wire bus for ultra-kilometre frozen deep well

The temperature field of artificial freezing curtain is a transient temperature field changing with time. In order to ensure the safety of the project, improve the timeliness and accuracy of temperature measurement, and ensure the safety strength and effective water sealing of the curtain, it is necessary to implement the information temperature monitoring control for the freezing process. According to the application environment of the freezing monitoring for the long distance and multi measuring points in the construction of the coal mine over a kilometre, a monitoring system of the frozen deep wells which is developed by the 1-wire bus technology is proposed. By using high-performance single chip microcomputer, designing pull-up and level detection driving circuit, matching cable characteristic impedance and distributing digital temperature measurement cable, the 1-wire bus network monitoring points can reach 55 and the transmission distance is over 1000 m, which meets the current monitoring requirements of frozen deep wells.

Seebeck coefficient controlled by magnetic field based on the P3HT/PCBM heterojunction device

Abstract In this article, Magneto-Seebeck effect was studied by applying P3HT/PCBM bulk heterojunction devices. We found that illumination and magnetic field can improve the Seebeck coefficient of the pure P3HT device. Our magneto-photocurrent (MPC) effects indicate that the singlet and triplet ratios in these devices can be changed by external magnetic field. Furthermore, the Seebeck coefficient under light was measured as changing temperature and magnetic field. Based on the experimental results and theoretical models, we conclude that the change of singlet and triplet ratios caused by magnetic field influences carrier concentration, and affects the thermoelectric properties of organic semiconductor materials and devices. In addition, the impact of magnetic fields on Seebeck coefficient in our experiments differs from the traditional magnetic field effects, which becomes more conspicuous as temperatures rises at high temperature. Our study can further develop magnetic-thermoelectric effects, and contribute to presenting new strategies about magnetic-photo-thermoelectric coupling.