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Geothermal power is being regarded as depending on techniques derived from hydrocarbon production in worldwide current strategy. However, it has artificially been developed far less than its natural potentials due to technical restrictions. This paper introduces the Enhanced Geothermal System based on Excavation (EGS-E), which is an innovative scheme of geothermal energy extraction. Then, based on cohesion-weakening-friction-strengthening model (CWFS) and literature investigation of granite test at high temperature, the initiation, propagation of excavation damaged zones (EDZs) under unloading and the EDZs scale in EGS-E closed to hydrostatic pressure state is studied. Finally, we have a discussion about the further evolution of surrounding rock stress and EDZs during ventilation is studied by thermal-mechanical coupling. The results show that the influence of high temperature damage on the mechanical parameters of granite should be considered; Lateral pressure coefficient affects the fracture morphology and scale of tunnel surrounding rock, and EDZs area is larger when the lateral pressure coefficient is 1.0 or 1.2; Ventilation of high temperature and high in-situ stress tunnel have a significant effect on the EDZs scale; Additional tensile stress is generated in the shallow of tunnel surrounding rock, and the compressive stress concentration transfers to the deep. EDZs experiences three expansion stages of slow, rapid and deceleration with cooling time, and the thermal insulation layer prolongs the slow growth stage.

Failures of multi-plate clutches must be reliably excluded due to safety-critical functionalities in the drive train. The main reason for failures of multi-plate clutches due to long-term and spontaneous damage is thermal damage. In this paper, a parameterizable two-dimensional finite element model is developed and validated for damage prevention and for analyzing the thermo-mechanical behavior of a clutch in transient operation. Both numerical verification and validation with experimental results are very good despite the simplifications in the model. Subsequently, the temperature and pressure distribution of the individual friction areas is determined. The results show that the maximum temperatures tend to occur at the outer diameter of the friction area. The pressure distribution is very homogeneous. In a parameter study, the influence of Young’s modulus of the friction lining, the thermal conductivity of the friction lining, and the steel plate thickness on the temperature and pressure behavior in the clutch is investigated. Although the Young’s modulus of the friction lining influences the pressure distribution in the friction contact, the temperature behavior is only slightly changed by the variation of the elastic modulus due to the load case. The thermal conductivity of the lining and steel plate thickness have a strong influence on the temperature level in the clutch. However, the distribution of pressures is still very homogeneous compared to the reference model.

This paper developed a statistical damage constitutive model for deep rock by considering the effects of external load and thermal treatment temperature based on the distortion energy. The model parameters were determined through the extremum features of stress – strain curve. Subsequently, the model predictions were compared with experimental results of marble samples. It is found that when the treatment temperature rises, the coupling damage evolution curve shows an S-shape and the slope of ascending branch gradually decreases during the coupling damage evolution process. At a constant temperature, confining pressure can suppress the expansion of micro-fractures. As the confining pressure increases the rock exhibits ductility characteristics, and the shape of coupling damage curve changes from an S-shape into a quasi-parabolic shape. This model can well characterize the influence of high temperature on the mechanical properties of deep rock and its brittleness-ductility transition characteristics under confining pressure. Also, it is suitable for sandstone and granite, especially in predicting the pre-peak stage and peak stress of stress – strain curve under the coupling action of confining pressure and high temperature. The relevant results can provide a reference for further research on the constitutive relationship of rock-like materials and their engineering applications.

Analyzing the nonlinear characteristics of dual-rotor systems under thermo-mechanical (TM) coupling situations is critical, as operational conditions should be accurately determined, to avoid potential thermally-induced failures. This paper proposes the coupled TM model of a dual-rotor system, which considers multiple nonlinearities and heat generation of four bearings that couple the mechanical and thermal fields. Heat dissipation controlled by lubricant flow rates is introduced into the model to simulate different TM coupling degrees. Nonlinear phenomena and stability evolution are analyzed by the modified incremental harmonic balance method (IHB) at primary resonance regions. An increase in TM coupling degrees can lead to more bifurcation points, resonance regions with lower frequencies, larger vibration responses, and unstable regions. It can also transform resonance hysteresis phenomena into more complex nonlinear phenomena and some saddle-node bifurcation points into Neimark–Sacker bifurcation points. The reason for these transformations is that the effective radial clearance (RC) of bearings changes with rotation speed and thermal expansion. Temperature nonlinearities are induced by the radial bearing loads and the lubricant viscosity, which are investigated by various generalized nonlinear thermal forces. These findings can help further understand nonlinear coupled TM problems of complex dual-rotor systems.

The increase of coal seam mining depth leads to the increase of ground temperature stress, which affects the fracture development and spontaneous combustion characteristics of coal samples. Taking anthracite as the research object, scanning electron microscopy, low-temperature N 2 adsorption, temperature- programmed experiments and infrared spectroscopy tests were carried out to analyze the mechanism of the influence of pore structure and the number of oxygen-containing functional groups on the spontaneous combustion characteristics of coal samples from the physical and chemical perspectives. The results show that the connection between pores and fractures is enhanced and the scale of micro-fractures is also increased after the thermal and mechanical coupling. After treatment, the oxidation of the coal sample was enhanced, and the overall production rate of the three iconic gases increased. The thermal and mechanical coupling results in the increase of the content of aromatic hydrocarbon, oxygen-containing functional group and aliphatic hydrocarbon in coal. The thermal and mechanical coupling effects promote the occurrence and development of coal spontaneous combustion by changing the structure, temperature and stress state of coal and affecting the reaction process of coal and oxygen. The research results have laid a theoretical foundation for the prevention and control of multi-field coupling CSC.

The dam piers undertake crucial tasks of structural support, surface overflow management, and dynamic gate operation under load. Any occurrence of cracks poses risks to their safe and efficient operation. Given the large‐volume characteristics of dam pier concrete, controlling cracks is challenging. The existing analytical methods for dam pier concrete still have certain limitations in revealing the causes of cracks under complex environmental conditions. In particular, when accounting for the coupled effects of early‐age temperature, humidity, and stress fields, further refinement of analytical models and methods is essential to develop more precise active crack control strategies. This study applied a hygro–thermo–mechanical coupling modeling method for early‐age dam pier concrete. Comprehensive physical and mechanical experiments were conducted to calibrate the coupling model parameters to align with actual conditions. An experiment was conducted in a real dam pier to optimize the construction process to control cracks proactively, rather than applying remedial measures postcrack occurrence. The results show that the proposed method effectively analyzes the causes of cracks, and the proactive control measures targeting these causes are proven to be effective. This study provides a reference for proactive crack control of mass concrete structures.

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.

This study develops a thermo-mechanical damage (TMD) model for predicting damage evolution in heterogeneous rock materials after heat treatment. The TMD model employs a Weibull distribution to characterize the spatial heterogeneity of the mechanical properties of rock materials and develops a framework that incorporates thermal effects into a nonlocal gradient damage model, thereby overcoming the mesh dependency issue inherent in homogeneous local damage models. The model is validated by numerical simulations of a notched cruciform specimen subjected to combined mechanical and thermal loading, confirming its capability in thermo-mechanical coupled scenarios. Sensitivity analysis shows increased material heterogeneity promotes localized, X-shaped shear-dominated failure patterns, while lower heterogeneity produces more diffuse, network-like damage distributions. Furthermore, the results demonstrate that thermal loading induces micro-damage that progressively spreads throughout the specimen, resulting in a significant reduction in both overall stiffness and critical strength; this effect becomes increasingly pronounced at higher heating temperatures. These findings demonstrate the model’s ability to predict the mechanical behavior of heterogeneous rock materials under thermal loading, offering valuable insights for safety assessments in high-temperature geotechnical engineering applications.

Addressing the issue of sealing failure in liquid hydrogen triple-offset butterfly valves within rocket fuel delivery systems under ultra-low temperature conditions due to insufficient cold shrinkage compensation capability, this paper first proposes a soft-sealing elastic compensation structure. Its sealing performance is evaluated using a thermo-mechanical coupling method. Secondly, sensitivity analysis using the Spearman method identifies key optimization variables: radial offset distance D e , third offset angle α , sealing surface width B , and sealing surface interference T . The optimization objectives are the maximum contact stress P 1max and average contact stress P 1ave during forward sealing, and the maximum contact stress P 2max and average contact stress P 2ave during reverse sealing. Finally, an optimal Latin hypercube sampling method is used to construct the sample space, and a high-precision RBF surrogate model combined with the NSGA-II algorithm is employed to find excellent Pareto front solutions. After optimization, the Maximum contact stress of the butterfly valve sealing structure during forward sealing decreased by 23.43%, and the average contact stress decreased by 22.41%; during reverse sealing, the Maximum contact stress increased by 51.07%, and the average contact stress increased by 48.83%. The optimized butterfly valve sealing structure achieves reliable bidirectional sealing under liquid hydrogen ultra-low temperature conditions.

Belt grinding is a common surface machining method for titanium alloy parts. However, belt grinding can result in poor surface integrity when grinding forces or temperatures exceed a certain threshold. This study systematically studied belt grinding force and temperature under different parameters (i.e., belt speed, feed speed and normal displacement), and analyzed the surface integrity of titanium alloy under corresponding conditions, including three-dimensional surface morphology, surface roughness and grinding scratch morphology. As a result, it is revealed that the decrease of the belt speed, the increase of the feed speed and the normal displacement will lead to the increase of the grinding force, the decrease of the feed speed, the increase of the belt speed and normal displacement will cause the temperature to rise. Among many grinding parameters, the normal displacement has the most significant effect on the grinding thermal–mechanical coupling characteristics. High grinding force and grinding temperature will cause the surface quality to deteriorate and even more serious defects. As the grinding force increases, the surface roughness and the depth of grinding scratches show an increasing trend. When the normal grinding force reaches 21.4 N, the tangential grinding force reaches 12.6 N and the grinding temperature reaches 341.9℃, the surface roughness increases sharply, and the grinding burn will be formed on the workpiece surface. This research is of significance for better understanding the belt grinding mechanism and improving the surface integrity of titanium alloy.