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Power transmission covering long-distances has shifted from overhead high voltage cables to underground power cable systems due to numerous failures under severe weather conditions and electromagnetic pollution. The underground power cable systems are limited by the melting point of the insulator around the conductor, which depends on the surrounding soils’ heat transfer capacity or the thermal conductivity. In the past, numerical and theoretical studies have been conducted based on the mechanistic heat and mass transfer model. However, limited experimental evidence has been provided. Therefore, in this study, we performed a series of experiments for static and cyclic thermal loads with a cylindrical heater embedded in the sand. The results suggest thermal charging of the surrounding dry sand and natural convection within the wet sand. A comparison of heat transfer for dry, unsaturated and fully saturated sand is presented with graphs and colour maps which provide valuable information and insight of heat and mass transfer around an underground power cable. Furthermore, the measurements of thermal conductivity against density, moisture and temperature are presented showing positive nonlinear dependence.

The optimal operation of high-voltage underground power cables is crucial for powering our communities, and it hinges on the intricate dynamics of insulation temperature around the conductor, primarily influenced by joule heating. This temperature responsiveness is further molded by seasonal and diurnal fluctuations in power demand, as well as the moisture content in the surrounding soil. Past research concentrated on theoretical analyses and experiments under dry conditions, but our study expands this scope. Through extensive laboratory tests exploring static and cyclic thermal loads in both dry and saturated sand environments, we uncovered valuable insights. Cyclic thermal loads in dry sand demonstrated a significant thermal charging effect, especially with shorter relaxation times. In static thermal loading, utilizing saturated sand enhanced heat dissipation due to higher thermal conductivity. However, it also revealed a noteworthy observation: a robust convection cell formed after three days of continuous heating, presenting challenges for cables under crop fields despite facilitating efficient cooling. Highlighting the importance of high-voltage power cable infrastructure, our study delves into the critical intersection between infrastructure and the underground soil. Understanding these interactions becomes imperative for the sustainable development of clean energy initiatives. As the world transitions to cleaner energy practices, optimizing the performance of underground power cable systems becomes pivotal in realizing their full potential and aligning with broader clean energy goals. This research contributes essential knowledge to enhance the safety, efficiency, and sustainability of high-voltage underground power cable systems in support of a cleaner and more sustainable energy future.

Laboratory tests have been conducted to investigate the effects of rapid thermal cooling on various rock specimens including igneous, sedimentary, and metamorphic rocks. At first, various types of thermal loading were conducted: heating up to 100, 200, and 300 °C, followed by rapid cooling with a fan. In addition, multiple cyclic thermal cooling (10, 15 and 20 cycles) with a maximum temperature of only 100 °C was conducted. Experiments included edge notched disc (END) tests to determine the Mode I fracture toughness, Brazilian disc tests to determine tensile strength, seismic tests to determine P-wave velocity, and porosity tests leading to meaningful results. Even though only small changes of temperature (rapid cooling from 100 °C to room temperature) were applied, the results showed that crack growth occurred in some rock types (granite, diabase with ore veins, and KVS) while crack healing occurred in other rock types (diabase without ore veins, quartzite, and skarn). To better understand the results, 3D transient thermo-mechanical analysis was conducted using the ANSYS program. The results indicated that there was a thin region near the outside of the specimen where large tensile stresses occur and microcracking would be expected, and that there was a large area in the middle of the specimen where lower magnitude compressive stresses occur and crack closure would be expected. It was found that the more heterogeneous and more coarse-grained rock types are more likely to exhibit crack growth , while less heterogeneous and more fine-grained rocks are more likely to exhibit crack healing .

A modified numerical procedure for the shakedown analysis of structures under dual cyclic loadings, based on the Abdalla method, is proposed in this paper. Based on the proposed numerical procedure, the shakedown analysis of the thick cylindrical vessels with crossholes (TCVCs) under cyclic internal pressure and cyclic thermal loading was carried out. The effects of material parameters (elastic modulus and thermal expansion coefficient) and crosshole radius on the elastic shakedown limit of TCVCs are discussed and, finally, normalized and formularized. Furthermore, the obtained shakedown limit boundary formulation is compared with FEA results and is verified to evaluate the shakedown behavior of TCVCs under cyclic internal pressure and cyclic thermal loading.

In this study, marble specimens were used to investigate the effects of freezing and thermal cyclic loading on physical and mechanical properties. For this purpose, four types of loading were considered, including freezing-cooling (F–C), heating–cooling (H-C), freezing-cooling-heating (F–C-H) and heating–cooling-freezing (H-C-F). The changes observed in physical and mechanical properties of the marble were analyzed in temperature extend shifting from − 30 °C to 160 °C. To achieve this goal, two marble blocks with a dimension of 30 × 30 × 30 cm 3 were selected. Then, compressive and shear wave velocities, uniaxial compressive strength (UCS), Young’s modulus ( E ) and Brazilian tensile strength (BTS) were measured and compared in different loading conditions. Results showed that the number of freezing-cooling cycles influenced the mechanical properties of the marble. With an increase in the loading cycles, both compressional and shear wave velocities of the marble decreased. The highest reduction in tensile strength was observed in heating–cooling cycles. That is to say, the thermal loading of rock specimens caused weakening, thereby increasing the micro-crack density in the marble specimens by means of thermally shocks. It was observed that the increase in the number of loading cycles, brings about a huge decline in the marble dynamic modulus. The damage index ( D ) is introduced to reflect the variation of the mechanical properties and ultrasonic wave velocities of the samples before and after the thermal cyclic loading. In all freezing and thermal cyclic loading conditions, the main and predominant failure mechanism was shear failure.

This study aims to obtain Bree's diagram for a Functionally Graded (FG) beam under cyclic thermal and constant mechanical loadings. For this purpose, the mapping algorithm is employed to specify the borders of ratcheting, shakedown, and elastic. Also, two parameters are considered to obtain Bree's diagram, and the iteration method is utilized to predict the beam's elastoplastic behavior uniaxially. Since the FG beam comprises two types of metal, namely 90% aluminum alloy (EN A W 6061 T4) and 10% carbon (S275), the procedure to develop Bree's diagram for FG structure is unique, and it can be implemented for other combinations. Bilinear isotropic hardening model and the FG beam with fixed-free boundary conditions are considered. The FG beam is constrained along the vertical direction to avoid any deflection in the horizontal directions. The analysis conducted in this study is geared toward the Finite Element Method (FEM). Ansys Parametric Design Language (APDL) in Ansys 16 is employed. A novel method based on the FEM is proposed, which is on par with the other state-of-the-art methods in this regard and is even able to outperform them in terms of accuracy and authenticity. Interestingly Bree's diagram present for the metal–metal FG beam can be generalized to other FG beams like ceramic–ceramic and metal–ceramic FG beams and so on, considering the analysis of this study. Notably, due to the available results in the literature, the Bree diagram obtained by the proposed numerical method is reliable.

Thermoelectric generators (TEGs) make use of the Seebeck effect in semiconductors for the direct conversion of heat to electrical energy. The possible use of a device consisting of numerous TEG modules for waste heat recovery from an internal combustion (IC) engine could considerably help worldwide efforts towards energy saving. However, commercially available TEGs operate at temperatures much lower than the actual operating temperature range in the exhaust pipe of an automobile, which could cause structural failure of the thermoelectric elements. Furthermore, continuous thermal cycling could lead to reduced efficiency and lifetime of the TEG. In this work we investigate the long-term performance and stability of a commercially available TEG under temperature and power cycling. The module was subjected to sequential hot-side heating (at 200°C) and cooling for long times (3000 h) in order to measure changes in the TEG’s performance. A reduction in Seebeck coefficient and an increase in resistivity were observed. Alternating-current (AC) impedance measurements and scanning electron microscope (SEM) observations were performed on the module, and results are presented and discussed.

In most practical cases, the free deformation tendency of energy piles is constrained by the cap and surrounding soil. As a result of these constrained thermal deformations, additional forces are introduced into the system and are balanced by transfer to the ground via soil-structure interfaces. Consequently, interface conditions and structural element constraints play crucial roles in the behavior of energy pile foundations, and their evaluation is essential. This study evaluates the effects of constraints on the response of a large-scale piled raft foundation in homogeneous stiff saturated clay to cyclic thermal loads using coupled Thermo-Hydro-Mechanical Finite Element modeling. Particularly, the effects of interface stiffness and mechanical load variations in the evolution of mechanical fields, including stresses, displacements, and load-sharing ratios, were investigated. Despite the magnitude independence of the initial stresses, the greater constraining effect of the stiffer soil-structure interface and stronger pile-raft connection led to substantial excess loads, especially at shallow depths. Nevertheless, due to the performance of floating piles, the thermal axial stress variations in deep regions were virtually identical. Moreover, the larger tendency of the soil than the piles to undergo thermal deformations was found to be the primary determinant of the resultant load redistribution, which led to the soil-raft interface being a significant factor in determining vertical raft displacements. In the most severe case, the thermal axial stress variation range and stabilized excess settlement of the foundation were approximately three times the mechanical stress and one-fifth of the mechanical settlement, respectively.

There is extensive data to show that heating and cooling produces irrecoverable deformations in clays under fully drained conditions. The effects are most pronounced for normally and lightly overconsolidated clays that undergo significant compression. Most constitutive models have key limitations for predicting the thermo-mechanical response of clays through long-term (seasonal) cycles of heating and cooling. The Tsinghua ThermoSoil model (TTS; Zhang and Cheng in Int J Numer Anal Methods Geomech 41(4):527–554, 2017) presents a novel theoretical framework for simulating the coupled thermo-mechanical response of clays. The model uses a double-entropy approach to capture effects of energy dissipation at the microscopic particulate contact level on continuum behavior. This paper proposes a simple procedure for calibrating input parameters and illustrates this process using recent laboratory data for Geneva Clay (Di Donna and Laloui in Eng Geol 190:65–76, 2015). We then investigate capabilities of the TTS model in simulating familiar aspects of thermal consolidation of clays as well as the long-term, progressive accumulation of strains associated with seasonal heating and cooling processes for shallow geothermal systems installed in clays. The model predicts the existence of a long-term steady-state condition where there is no further accumulation of strain. This state depends on the consolidation stress and stress history but is independent of the imposed range of temperature, Tcyc. However, the value of Tcyc does affect the rate of accumulation of strain with thermal cycles. Simulations for normally consolidated Geneva Clay find steady-state strain conditions ranged from 2.0 to 3.7% accumulating within N = 10–50 thermal cycles.

This paper describes computational analysis of the thermal ratcheting of solder-bonded layered plates subjected to cyclic thermal loading following solder-bonding. Finite element computations of Si/solder/Cu layered plates are performed by taking into account mechanical ratcheting of the copper as well as temperature-dependent creep of the solder. A sophisticated non-linear kinematic hardening model is used for appropriately representing mechanical ratcheting of the copper; a temperature-dependent power-law creep model is assumed for the solder. It is shown that the layered plates can exhibit either the cyclic recovery or the cyclic growth of deflection depending on the extent of plastic yielding in the copper layer, and that the cyclic recovery always occurs if the copper layer is elastic. It is also demonstrated that the cyclic recovery of deflection can be much greater than the static recovery of deflection at a constant temperature.