Thermo-mechanical Coupling Characteristics Research Articles

Thermo-mechanical coupling characteristics of the shearer’s guiding shoe during the friction

The reliability and longevity of the guiding shoe are crucial for the proper functioning of coal mining machines. The heavy wear of the sliding surface under thermal stress coupling is the primary factor influencing the service life of the guiding shoe. To reveal the heat flow distribution patterns and the thermo-stress coupling mechanisms of the guiding surface, a thermo-mechanical coupling model of the guiding shoe and the pin row is established. The transient thermodynamic behavior of the guiding shoe under different load and speed conditions is studied using the coupled temp-displacement analysis method in Abaqus. The results indicate that the overall temperature of the guiding shoe friction surface experiences a rapid increase during the initial running-in phase, followed by a progressively slower temperature increase over time. Temperature and stress concentration regions on the friction surface primarily localize at the corners of the shoe groove, and the distribution of temperature and stress shows a strong coupling. Furthermore, elevated traction speed and mechanical load exacerbate the thermo-elastic instability of the guiding shoe, consequently augmenting thermal stress on the friction surface. The increase in support load results in significant thermal shock on the lower area of the left side of the guiding shoe. The research provides a reference for exploring the fatigue failure and wear mechanisms of the guiding shoe while considering thermal effects.

Analysis of thermo-mechanical coupling characteristics of feed system of woodworking center based on fuzzy control algorithm

With the rapid development of science and technology, automatic control systems have been applied in more and more fields. At the same time, the requirements for the stability, accuracy, response speed, and self-regulation ability of the system are also increasing. In the wood processing industry, the heating system of factories is an important link to ensure normal production. Therefore, in order to further improve the production efficiency of the wood processing industry and enhance the stability and controllability of the heating system in wood processing production, this article takes into account the delay and coupling effects in the rapid heating process, and combines fuzzy control with temperature control to study and establish a woodworking thermal mechanical coupling model based on fuzzy control algorithm. The results show that compared with traditional PID control, fuzzy control has advantages such as short response time, small overshoot, high steady-state accuracy, fast steady-state recovery, and good dynamic and static performance. Under the condition of rapid heating, the existence of delay effect weakens the effect of Thermal shock, while the coupling effect not only affects the propagation of thermoelastic waves in the elastic body, but also weakens the weakening effect of delay effect on Thermal shock to a certain extent.

Thermo-mechanical coupling analysis of edge-cracked rubber specimen focusing on the crack tip: Experimental observation and numerical simulation

The fatigue performance of rubber composite cannot be ignored in the field of engineering. Fatigue crack growth rate (FCGR) test by using a planar tensile specimen with a crack or cracks is often used for rubber fatigue characterization. Thermo-mechanical coupling characteristics of rubber composite under dynamic loading are significant and need to be considered. In our work, an interesting experimental phenomenon was observed during rubber FCGR test. The temperature around crack tip region is the highest at the beginning, and then the high temperature region shifts from the crack tip to the central region of the planar tensile specimen, and finally a steady-state temperature distribution is achieved. To explain such observation, a thermo-mechanical coupling method based on finite element analysis (FEA) for the edge-cracked rubber specimen was established. The simulation result was consistent with the experimental observation, and can explain the heat build-up phenomenon of the edge-cracked rubber well.

Study on Thermo-Mechanical Coupling Characteristics of Surrounding Rock of HLW Disposal Repository in Clay Rock

With the long-term decay, releasing a large amount of heat is one of the main characteristics of high-level radioactive waste. Safe operation of high-level radioactive waste repository must consider the effect of thermo-mechanical coupling on repository stability. In this paper, core drilling samples and in-situ stress tests were performed systematically on clay rock in Tamusu area. Thermal conductivity and triaxial tests were operated on samples near the depth of target layer of repository, to obtain the thermal and mechanical characteristics parameters. According to these parameters, a repository model was established in FLAC 3D to simulate excavation of repository and thermo-mechanical coupling of surrounding rock within 100 years after it closed. Results reveal that thermo-mechanical coupling effect has a significant impact on stability of repository. Thermal field reaches a steady state when high-level radioactive waste releases for 20 years, and the temperature in surrounding rock decrease as negative exponential with the distance from the gallery increases of. Due the temperature of the surrounding rock increases, thermal stress is generated, and the stress level in the near field of repository is growing as a whole, thus, strain increases. After heating without support for 100 years, there is the possibility of shear failure at the top and bottom of the chamber. It is necessary to reinforce the chamber lining to ensure the safe and stable operation of the repository.

Study on thermomechanical coupling characteristics of embedded sensor lithium batteries under low‐temperature environment

AbstractAircraft usually undergoes a low temperature during flight. It is crucial to understand the strain generation mechanism within lithium‐ion batteries in low temperature to prevent electrode rupture caused by uneven strain of the cell. As such, LFP pouch cell was chosen as experimental objects and the sensors were embedded inside the battery to get the internal parameters directly. Battery cycle experiments were conducted in a 2 m × 2 m × 2 m cabin in, respectively, 25°C, 10°C, −10°C, −20°C ambient temperatures with high C rates of 3C during the charge‐discharge process, which is to simulate the aircraft flying process in low temperatures at different altitudes. Parameters such as voltage, internal temperature, and strain were measured. The results revealed the significant impact on thermomechanical coupling characteristics of LFP battery caused by low temperature. As the ambient temperature decreases, the maximum strain increases. The strain is positively correlated with the temperature of the battery, and as the ambient temperature decreases, battery temperature would have more effects on strain. Besides, it was also found that in a low‐temperature environment, the heat generated by the battery itself is beneficial to its performance recovery.

Thermo-mechanical coupling numerical simulation method under high temperature heterogeneous rock and application in underground coal gasification

The heterogeneity of a rock mass under high temperature and its thermo-mechanical coupling characteristics are difficult problems to investigate. This situation brings considerable difficulties to the study of underground coal gasification under thermo-mechanical coupling. The development of a numerical simulation method for the thermo-mechanical coupling of heterogeneity rock mass under high-temperature burnt conditions can provide an important foundation for related research. On the basis of the variation of mechanical properties of rock mass with temperature, a thermo-mechanical coupling simulation method, which considers the heterogeneity of a rock mass under high temperature, is proposed in this study. A test block experiment is implemented and then applied to the strata movement and failure of underground coal gasification. The results are as follows: (1) The proposed method can truly reflect the heterogeneity of a rock mass under high-temperature environment, providing an effective method for the numerical simulation of geotechnical engineering in high-temperature conditions. (2) The variation of mechanical properties of rock mass after an increase in temperature is the main reason for the change law of strata movement and failure of underground coal gasification. These factors should be considered in the investigation of underground gasification strata movement and failure. The present study can provide an important means for the research on geotechnical engineering in high-temperature environments.

Study on thermo-mechanical coupling characteristics of angle contact ball bearing with fix-position preload

PurposeUnder fix-position preload, the high rotation speed of the angular contact ball bearing exacerbates the frictional heat generation, which causes the increase of the bearing temperature and the thermal expansion. The high rotation speed also leads to the centrifugal expansion of the bearing. Under the thermal and centrifugal effect, the structural parameters of the bearing change, affecting the mechanical properties of the bearing. The mechanical properties of the bearing determine its heat generation mechanism and thermal boundary conditions. The purpose of this paper is to study the effect of centrifugal and thermal effects on the thermo-mechanical characteristics of an angular contact ball bearing with fix-position preload.Design/methodology/approachBecause of operating conditions, elastic deformation occurs between the ball and the raceway. Assuming that the surfaces of the ball and channel are absolutely smooth and the material is isotropic, quasi-static theory and thermal network method are used to establish the thermo-mechanical coupling model of the bearing, which is solved by Newton–Raphson iterative method.FindingsThe higher the rotation speed, the greater the influence of centrifugal and thermal effects on the bearing dynamic parameters, temperature rise and actual axial force. The calculation results show that the effects of thermal field on bearing dynamic parameters are more significant than the centrifugal effect. The temperature rise and actual axial force of the bearing are measured. Comparing the calculation and the experimental results, it is found that the temperature rise and the actual axial force of the bearing are closer to reality considering thermal and centrifugal effects.Originality/valueIn the past studies, the thermo-mechanical coupling characteristics research and experimental verification of angular contact ball bearing with fix-position preload are not concerned. Research findings of this paper provide theoretical guidance for spindle design.

Thermoelastic analysis of friction pairs in hydro-viscous drive combined thermal and mechanical loads under soft startup condition

Thermo-mechanical characteristics significantly impact the operating performance of the friction pairs in hydro-viscous drive. A three-dimensional transient thermo-mechanical coupling model was established for investigation of the distributions and coupling relationships of the temperature, stress, and displacement generated by the combination of the thermal and mechanical loads under soft startup condition. Then, the time-dependent contact pressure and velocity were extensively examined, as well as their effects on the thermo-mechanical coupling characteristics. Finally, the effects of the material and structural parameters were analyzed by the one-factor-at-a-time method. The observations confirmed plastic deformation of the steel disc will occur when the steel disc and friction disc are, respectively, restrained at the outer and inner diameters. However, there is a low likelihood of plastic deformation of the friction lining occurring. The thermal load and constraint locations were also found to crucially affect the stress and displacement distributions. Moreover, the circumferential stress was determined to be the most important stress component, and can thus be used as a basis for judging whether plastic deformation will occur. The results provide theoretical reference for predicting the thermal characteristics of the friction pairs, as well as a foundation for selecting the material and structural parameters.

Thermo-mechanical coupling analysis of transient temperature and rolling resistance for solid rubber tire: Numerical simulation and experimental verification

The achievement of low rolling resistance and long-term durability of tires on various vehicles is of great challenge. Tire performances heavily depend on rubber properties; however, the thermo-mechanical coupling characteristics of rubber composites are complicated rendering the design of high-performance tires time-consuming and costly. In our research, the transient temperature and rolling resistance of a solid rubber tire were performed based on the thermo-mechanical coupling approach and nonlinear viscoelastic theory by using finite element method. Particular attention was paid to the strain cycles as the tire rolling on the road presents non-sinusoidal deformation. First, a static three dimensional tire-road contact analysis was conducted to obtain the principal strain cycles. Second, the 100th-order Fourier sine series was used to approximate the strain amplitude. Third, the heat generation rate proportional to the product of the loss modulus and the square of strain amplitude was calculated. The loss modulus was updated as a function of strain amplitude, temperature and frequency. Loss modulus softening effect was also considered. A practical method was proposed to compute the rolling resistance and transient temperature distributions by establishing a 2-D axisymmetric model. A rubber rolling tester was used to verify the numerical results. The comparison between numerical data and test data reveals that the proposed analytical method is a reliable approach to predict rolling resistance and transient temperature distribution for rubber tires. At last, the dependence of rolling resistance and heat build-up on thermal conductivity and loss factor were investigated by the parametric numerical experiments.

Thermo-mechanical coupling analysis of a high-speed actuating mechanism based on a new thermal contact resistance model

Present thermal models for analyzing the thermo or thermo-mechanical characteristics of machine tools either neglect the effect of thermal contact resistance (TCR) between rough solid surfaces or neglect the asperities’ long transition process from elastic deformation to plastic one in calculating TCR, which cannot reflect real engineering practice. To improve the simulation accuracy of the thermo-mechanical characteristics of a high-speed actuating mechanism, a new TCR model is proposed considering the multiple deformation states of asperities including elastic, elastic-plastic and plastic deformations. The formulae for calculating the heat generation powers at bearings and the convective heat transfer coefficients are also proposed. The validity of the proposed thermal model is verified by a comparison analysis of the simulated and measured transient temperatures at a series of measurement points. Finally, both the transient and steady thermo-mechanical coupling characteristics of the high-speed actuating mechanism are analyzed by integrating the force loads and the thermal loads obtained by the proposed thermal model, which provide a theoretical basis for the further optimization of the mechanism’s structural parameters and lubrication system.

Thermo-Mechanical Coupling Analysis of the Actuating Mechanism in a High Speed Press

In order to ensure the manufacturing precision of an ultra-precision high speed press, an integrated thermo-mechanical coupling model of its actuating mechanism is proposed, which includes the mechanical models of the slider and crankshaft, the thermal models for calculating the heat generation powers at different bearings as well as the heat transfer and heat dissipation in the actuating mechanism. The validity of the proposed thermo-mechanical coupling model is verified by a thermal equilibrium experiment when the press operates under the full load of 3000kN at 300 rpm. A sensitivity analysis is conducted to investigate the simulation errors resulting from the variation of the ambient temperature, the results of which demonstrate that the average ambient temperature should be applied for improving simulation accuracy. Then the thermal stiffness of the actuating mechanism and the thermo-mechanical coupling characteristics of different parts are analyzed by the proposed model with the average ambient temperature applied. The influences of the thermally induced loads on the thermal stiffness are discussed in detail. It is concluded that the temperature rise of the actuating mechanism in the stamping process of a high speed press should be fully considered in the design phase for ensuring its manufacturing precision.

Ultrafast thermomechanical responses of a copper film under femtosecond laser trains: a molecular dynamics study

Using molecular dynamics (MD) simulation, the ultrafast thermomechanical coupling responses of an immense homogeneous, isotropic copper film with the thickness of 1 μm, which is irradiated by various ultra-short laser pulse trains, are investigated. For the same energy injection, the effect of laser pulse trains is studied and it is observed from the numerical results that the pulse train technology may improve the ultrafast thermomechanical responses of the film significantly. By thoroughly analysing temperature, stress and displacement (strain) of the film, the thermomechanical coupling characteristics between stress, displacement (strain) and temperature are presented perfectly at the atomic scale. It is found that the lattice temperature of the region under tensile stress (or compressive stress) is lower (or higher) than the lattice temperature of the surrounding region, and the positive and negative strain (tensile or compressive) is related to tensile and compressive stress very well.