Thermomechanical Coupling Research Articles

Theoretical and numerical study of the thermo-mechanical coupling effect on the fluid viscous damper

The fluid viscous damper (FVD) is a typical passive energy dissipation device applied to civil engineering structures for vibration control. However, the heat generated during its operation will alter the properties of the fluid, thereby affecting the damping force. This study explores the thermo-mechanical coupling effect on the performance of the FVD. A theoretical model is developed based on fluid dynamics and thermodynamics to reflect the interaction between the real-time damping force and temperature of the FVD. Computational fluid dynamics (CFD) simulations are performed to investigate the impact of the thermo-mechanical coupling effect on the hysteresis performance of the damper and validate the proposed calculation method. The dynamic behavior and vibration mitigation effectiveness of the FVD considering the thermo-mechanical coupling effect are examined based on time history analysis on a single-degree-of-freedom and a multi-degree-of-freedom system. The results indicate that the increased temperature will lead to a reduction in the damping force, while the degraded force will in turn slow the temperature rise. Long-duration and high-intensity excitations can significantly amplify the impact of the thermo-mechanical coupling effect, thus it is essential to be considered in designing dampers for loads in the service stage and major earthquakes. The thermo-mechanical coupling effect on the supplemental damping ratio of the damper is greater than that on structural response control effectiveness, thereby it cannot be neglected when the damping ratio is used as the design criterion for FVDs.

Wear characteristics evolution of corundum wheel and its influence on performance in creep feed grinding of nickel-based superalloy

Wheel wear is an unavoidable occurrence in the process of creep feed grinding nickel-based superalloys, leading to reduced geometric accuracy, productivity, and surface integrity. Therefore, quantifying wheel wear forms and grinding performance is essential to minimize adverse impacts and optimize grinding processes. This study investigates the evolution of wheel wear and its consequences on grinding loads, chip formation, and surface quality. The results indicate that as the material removal volume (MRV) increases in the life cycle of the grinding wheel, the accumulation of timing damage leads to various forms of wear, mainly including grain fractures, material adhesion, attritious wear, and wheel clogging. The macro effects of the grinding ratio exhibit an initial increase followed by a subsequent decrease. At the micro level, the height of grain protrusions decrease, causing deviation from the normal distribution. Upon reaching the steady wear stage with an MRV of 9990 mm3, the wear flat rate and wheel clogging rate increase to approximately 10 % and 16.7 %, respectively. This indicates a significant rise in grinding thermo-mechanical load, serving as key indicators for evaluating the durability of grinding wheel. The presence of dull grains and material adhesion exacerbates the rubbing and ploughing effects, causing a transition of chip morphology from continuous flow to shear deformation, while heightened plastic pile-up contributes to elevated surface roughness. The intense thermo-mechanical coupling results in the formation of redeposited material and burn defects on the surface.

A thermo-mechanical coupling load model for high-frequency piezoelectric ultrasonic transducer

The ultrasonic micromachining systems significantly improve machining efficiency and quality, which are increasingly being applied in the manufacturing of microstructures and micro parts. However, the mechanical and thermal loads of the high-frequency piezoelectric ultrasonic transducer (HPUT) of ultrasonic micromachining systems have serious interference with the precise control of resonance frequency tracking, which further causes uncontrollable processing quality and precision. To improve the controllability of resonance frequency tracking, a thermo-mechanical coupling load model for HPUTs is proposed to establish the relationship between the resonance frequency and thermo-mechanical coupling load by introducing the force load constants and thermal load constants into the 6-terminal network electromechanical equivalent circuit. The experimental results show that the proposed thermo-mechanical coupling load model can accurately predict the trend of the resonance frequency when the thermo-mechanical coupling load is under the axial force range of 0–10 N and temperature range of 35–60°C.

Design optimization of continuous fiber composites with thermo-mechanical coupling and load uncertainties

This paper introduces a theoretical framework for the design optimization of continuous fiber composites reinforced with continuous fiber trajectories subject to thermo-mechanical coupling and load uncertainties. Different uniform temperature variations are applied in the structure to investigate the influence of ambient temperature change on the structural performance. To consider the external load uncertainties, a robust design optimization model is proposed where the loads are modeled as hybrid variables, namely magnitudes as random variables and directions as interval variables, with the robust objective determined through a hybrid orthogonal polynomial expansion method. Furthermore, we use a level-set function to represent the structural boundary, with its evolution driven by shape derivatives calculated based on uncertainty analysis. The continuous fiber paths are subsequently determined by the level-set isoline extracted from the structural boundary, which in turn influences the structural mechanical performance due to the material anisotropy of composites. The continuity of continuous fiber and the equal space between adjacent trajectories largely ensure the additive manufacturability of the composites. Three numerical examples are presented to demonstrate the effectiveness of the developed framework. The results show that the ambient temperature variations and load uncertainties largely impact the optimized topology and fiber infill patterns of composites, thus are important to be considered in the design stage. Moreover, the optimized structure can have a 5-fold stiffness per unit mass compared with the initial design thus largely increasing the material efficiency in carrying external uncertain loads.

Co-vulcanization of natural rubber and Eucommia ulmoides gum for mediation of the nonlinear rheology behaviors

Co-vulcanization of natural rubber (NR) and high-moduli Eucommia ulmoides gum (EUG) is promising while the reduction in crystallinity of crosslinked EUG is adverse for developing high-performance materials. Proposed herein is a novel method to prepare high-strength and high-stretchability NR/EUG vulcanizates with rapid vulcanization of EUG into slightly crosslinked particles, followed by further vulcanization of NR to form crosslinked matrix network. Deep eutectic solvents (DESs) are employed to facilitate the vulcanization of EUG during its blending with NR. The two-step vulcanization results in vulcanizates exhibiting superior mechanical properties under shear, tensile, and compressive conditions, significantly exceeding those of vulcanizates prepared by traditional processing methods. The reinforcement mechanism is elucidated by controlling thermomechanical coupling conditions and is supported by comprehensive structural characterizations. It is suggested that the EUG crystalline regions, maintained through the special processing method, work in conjunction with the stress-induced crystallization of the matrix to enhance the vulcanizates, nearly doubling the deformation stress at 800 % strain. The crystalline regions can mediate the deformation stress during shear and compression and weaken nonlinear rheological behavior. The established structure-performance relationship is guidable for preparing high-performance NR/EUG blend vulcanizates.

Adiabatic Shear Localization in Metallic Materials: Review.

In advanced engineering applications, there has been an increasing demand for the service performance of materials under high-strain-rate conditions where a key phenomenon of adiabatic shear instability is inevitably involved. The presence of adiabatic shear instability is typically associated with large shear strains, high strain rates, and elevated temperatures. Significant plastic deformation that concentrates within a adiabatic shear band (ASB) often results in catastrophic failure, and it is necessary to avoid the occurrence of such a phenomenon in most areas. However, in certain areas, such as high-speed machining and self-sharpening projectile penetration, this phenomenon can be exploited. The thermal softening effect and microstructural softening effect are widely recognized as the foundational theories for the formation of ASB. Thus, elucidating various complex deformation mechanisms under thermomechanical coupling along with changes in temperatures in the shear instability process has become a focal point of research. This review highlights these two important aspects and examines the development of relevant theories and experimental results, identifying key challenges faced in this field of study. Furthermore, advancements in modern experimental characterization and computational technologies, which lead to a deeper understanding of the adiabatic shear instability phenomenon, have also been summarized.

Cyclic functional degradation of NiTi shape memory alloy wires in wide ranges of strain rate and ambient temperature

Shape memory alloy (SMA) dampers frequently experience cyclic loading over a broad spectrum of strain rates and ambient temperatures, resulting in a significant thermo-mechanical coupling effect during cyclic deformation. Nevertheless, the impact of this coupling effect on the functional degradation of SMAs has not been thoroughly examined, particularly in scenarios involving severe deformation. In this study, a series of strain-controlled cyclic loading–unloading tests were conducted on NiTi SMA wires utilizing various combinations of strain rates ranging from 5 × 10−4 to 6 × 10−2/s and different ambient temperatures (313–393 K). The functional degradation was exacerbated by increasing ambient temperature and loading rate due to the complex interactions among the inelastic deformation mechanisms and thermo-mechanical coupling effects. Furthermore, although the cyclic deformation behavior of NiTi SMA wires varied with the loading rate, this rate dependence diminished with increasing ambient temperature. The synergistic effect of elevated strain rates and high temperatures markedly accelerated the fatigue failure of NiTi SMA wires and substantially altered the underlying microstructural morphology. These findings can provide valuable support for evaluating the service performance of NiTi SMA dampers under various engineering conditions and contribute to developing a cyclic constitutive model for NiTi SMAs.

Establishment of the thermo-mechanical coupling model of axle box bearings with track irregularity excitation and analysis of its temperature characteristics

Establishment of the thermo-mechanical coupling model of axle box bearings with track irregularity excitation and analysis of its temperature characteristics

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.

A new methodology to calculate interface thermal resistance between intumescent coating and steel substrate

Interface thermal resistance (ITR) plays a very important role in heat transfer and thermomechanical coupling response from intumescent coating to steel substrate in fire. However, the dynamic ITR between intumescent coating and steel substrate during burning is seldom reported. In this paper, a new methodology is presented to calculate dynamic ITR between intumescent coating and steel substrate under high incident heat flux based on the interface conservation equation. The new methodology focuses on measuring the temperature distribution and thermal conductivity of intumescent coating and steel substrate, with fewer variables. In this way, the calculation of ITR can be simplified. Firstly, the temperature variation function curves inside the intumescent coating and the steel substrate were fitted separately based on the temperature measurement data. Secondly, the interface temperatures (Tci,Tsi) were determined separately at the interface position by temperature variation function curves inside the intumescent coating or the steel substrate. Finally, the ITR calculation formula was deduced and the key parameters required for ITR calculation were obtained by cone calorimetry et al. An illustrative example was studied and validate the applicability of the new methodology.

Thermo-Mechanical Coupling Load Transfer Method of Energy Pile Based on Hyperbolic Tangent Model

By employing the hyperbolic tangent model of load transfer (LT), this paper establishes the thermo-mechanical (TM) coupling load transfer analysis approach for an energy pile (EP). By incorporating the control condition of the unbalance force at the null point, the method for determining the null point considering the temperature effect is enhanced. The viability of the presented method is validated through the measured outcomes from model experiments of energy piles. A parametric investigation is conducted to explore the impact of the soil shear strength parameters, upper load, temperature variation, head stiffness, and radial expansion on the axial force, strain, and displacement of the energy pile under thermo-mechanical coupling. The results suggest that the locations of the null point and the maximum axial force are dependent on the constraint boundary conditions of the pile side and the two ends. When the stiffness of the pile top increases, axial stress and displacement increase, while strain decreases. An increase in the drained friction angle leads to an increase in axial stress under thermal-load coupling, but strain and displacement decline. The radial expansion has a negligible influence on the thermo-mechanical interaction between the pile and the soil.

Evaluating predictive scheme for thermomechanical properties of Si-diamond composites.

A novel, parameter-independent multiscale correlational constitutive model has been devised to predict thermomechanical properties of Si-diamond-SiC and Si-diamond composites, including the effective elastic modulus, effective bulk modulus, effective shear modulus, effective Poisson's ratio, average coefficients of thermal expansion as well as thermal conductivity. Based on this model, the effective thermomechanical response of two kinds of composites was simulated, and the underlying mechanisms of thermomechanical coupling between constituents were also critically evaluated. The findings were shown that the effective elastic properties of composites, including effective elastic modulus, effective bulk modulus, effective shear modulus, increased with diamond and SiC, and that the introduction of dispersed diamond with highly thermal conductivity and lowly thermal expansion significantly enhanced thermophysical properties of Si-diamond-SiC composites. The thermomechanical coupling of these composites was influenced by the effective elastic properties of composites and the disparity in the intrinsic properties of constituents.

Investigation on the creep mechanism of PA6 films based on quasi point defect theory

Polyamide 6 (PA6) films with significant α relaxation process was selected as the model system. The creep behavior and rheological mechanism during deformation in the amorphous regions of semi-crystalline polymers are systematically investigated by carrying out creep experiments. Based on the quasi point defect (QPD) theory, the complete physical process of PA6 film creep behavior from elasticity to viscoelasticity and viscoplasticity was analyzed and modeled from the perspective of structural heterogeneity. The results demonstrate that the creep deformation of PA6 film is a typical thermo-mechanical coupling and nonlinear mechanics process, and potential creep mechanisms corresponds to stress-induced local shear deformation enhancement and thermal activation-induced particle flow diffusion. The elastic-plastic transition involved in the creep deformation process of semi-crystalline polymer originates from the activation of quasi-point defective sites in the amorphous region, the expansion of sheared micro-domains and irreversible fusion. The generalized fractional Kelvin (GFK) model is proposed, and the physical meaning of parameters is explained by combining the quasi point defect theory and creep delay spectrum(L(τ)). Finally, the effectiveness of the GFK model and the QPD theory in studying the deformation behavior of PA6 films was validated by comparing experimental data with theoretical results, which theoretically reveals the structural evolution of PA6 film during creep process.

Mechanism of initiation and propagation of surface cracks in gun bore under thermomechanical coupling impact

Surface cracks in gun bore may exacerbate rifling ablation and wear and in turn shorten barrel life. Thermomechanical coupling finite element (FE) models of bore are established and the dynamic responses of the bore under high-temperature and high-pressure are numerically simulated. The stress distribution characteristics on the inner surface are analyzed and the effects of autofrettage, number of firings and harden layer on the stress distribution are discussed. Based on the stress distribution characteristics, FE models with two initial cracks on the ledge of land surface are set up and the propagation, interaction and intersection of the cracks are numerically simulated, considering the effect of the distance between the two cracks. Based on simulation results, the initiation and propagation pattern and mechanism of the cracks on the inner surface are analyzed. An ablation test system was designed and produced, and used to experimentally verify the initiation and propagation mechanism of the cracks. The observed crack patterns on the inner surface of a real gun bore are also used to illustrate the mechanism obtained in this work. Understanding of the initiation and propagation mechanism of cracks in gun bore can be applied to improve and optimize the design of barrels.

Mechanical properties and damage constitutive model of concrete containing waste glass and rice husk ash in high-temperature environments

The application of waste glass and rice husk ash in concrete promotes sustainable development by reducing resource consumption and environmental pollution. This study evaluates the high-temperature performance of concrete containing glass sand, glass powder, and rice husk ash. Results show that waste glass increases mass loss, while rice husk ash reduces it and enhances concrete compactness. At ambient temperature, compressive strength is lower in rice husk ash samples compared to waste glass concrete, but higher at elevated temperatures. Particle size differences between glass sand and glass powder mainly influence high-temperature performance. Waste glass does not significantly mitigate cyclic loading damage, whereas rice husk ash reduces damage in glass sand concrete but not in glass powder concrete. A uniaxial compression thermo-mechanical coupling damage model and an improved Broutman-Hull cyclic compression damage model are established, providing a basis for the design and safety evaluation of concrete structures in high-temperature environments.

Size effect on CFST-column seismic performances at cryogenic temperature via mesoscale simulations

The macro-mechanical performances of CFST column at low temperatures can be significantly affected by three main factors: the change of meso-material properties, the filling and frost heave effects caused by pore ice, and the interaction between each meso-component. Therefore, a three-dimensional thermo-mechanical sequential coupling mesoscopic simulation method was established and verified by existing experimental results with the maximum errors within 10 %. The seismic performances of CFST columns with various cross-section sizes (200–800 mm) at different temperatures (20, −30, −60 and − 90 °C) were simulated and investigated, with focused on the damage mechanism and quantitative analysis of the low-temperature effect on various seismic performance indexes (i.e., hysteretic characteristic, nominal shear strength, ductility, energy dissipation and reparability) as well as the corresponding size effects. The results indicate that the low temperature can increase the nominal strengths (i.e., peak strength, yield strength and ultimate strength), but weaken ductility, energy dissipation capacity and reparability of CFST columns. With the increase of cross-section size, the reparability increases, while other seismic performance indexes decrease, showing the size effect, which tends to be more obvious at low temperatures. The size effect on peak strength at −90 °C is enhanced by 115.5 % than that at 20 °C, while 127.9 % for yield strength and 113.5 % for ultimate strength. Based on research results, a modified size effect formula for calculating shear strengths of CFST columns considering the influence of low temperature and structural size was developed, which can provide references for seismic design of large-sized CFST columns in extreme low temperature environments.

Thermo-mechanical coupling failure modeling of 3D four-directional braided composite I-beam under four-point flexure at room temperature, −50°C and 85°C

This paper aims to experimentally and numerically probe thermo-mechanical coupling behaviors of 3D4D (three-dimensional four-directional) braided composite I-beam under four-point flexure. An improved algorithm based on thermo-mechanical coupling constitution model, and mixed failure criterion are devised for modeling thermo-mechanical coupling failure process of 3D4D braided composite I-beam under four-point flexure. Quasi-static four-point flexure tests are, respectively, performed on 3D4D braided composite I-beam at RT (room temperature), −50 ° C and 85 ° C , and mechanical behaviors and failure mechanisms are analyzed and discussed from experiment results. To validate the aforementioned model and algorithm, novel global-local FE (finite element) model is generated and integrated with new algorithm for modeling failure process of 3D4D braided composite I-beam under four-point flexure at three temperatures, and numerical predictions agree well with experimental findings, demonstrating the effective and rational use of the proposed model in the paper.

Establishment of unified parametric equation and performance analysis of screw motor stator and rotor linetype

Aiming at the screw motor stator and rotor linetype parameter equations are not uniform and the linetype characteristics have not been completely studied, resulting in the linetype design and selection method is not perfect and poor interchangeability and so on. In this paper, the unified parameter of linetype equation of the screw motor stator and rotor and the thermo-mechanical coupling model and the shell-bushing cohesive zone model of the 5/6 screw motor under the three linetypes of equidistant hypocycloid, equidistant epicycloid and hypocycloid and epicycloid are established. The relationship between the three linetypes of stator and rotor and the lagging heat generation of the bushing, drilling fluid pressure, downhole temperature and shell-bushing bonding performance is studied. The results show that the stator temperature rise of the equidistant epicycloid method is 22%–30% lower than that of the other two types of stator. The stator with equidistant epicycloid is less affected by drilling fluid pressure and is more conducive to forming conjugate sealing cavity in deep wells. The downhole temperature has a certain influence on the stator linetype, which needs to be considered in the design. The CSMAXSCRT value of the bonding interface of the screw motor using the equidistant epicycloid method is 6.1%–10.1% higher than that of the screw motor using the other two linetypes, which is prone to bonding failure. When the interference is small, the equidistant hypocycloid method and the hypocycloid and epicycloid method can be used, and the equidistant hypocycloid method is recommended when the interference is large. The research in this paper provides a theoretical basis for the design and selection of screw motor linetypes, and has important engineering practical significance for realizing product interchangeability.

A data-driven underground gas storage production system string failure prediction model for time-varying reliability analysis

In underground gas storage (UGS) systems, the production tubing string system undergoes complex thermo-mechanical loading conditions, leading to fatigue damage accumulation and potential failure risks. To accurately assess the fatigue reliability and mitigate risks, it is crucial to develop a data-driven physics-informed uncertainty modeling approach that captures the coupled thermo-mechanical effects and accounts for various uncertainties. This study proposes a data-driven physics-informed modeling method based on thermo-mechanical coupling for fatigue reliability assessment and risk mitigation in critical UGS systems. A quantitative analysis method is introduced, which relies on small-scale multi-stage loading experiments and combines the stochastic degradation process with time-series reliability theory. To analyze the fatigue life of joints under complex loading conditions, a modified S-N curve model is developed. This model takes into account the influences of the dimension coefficient, stress concentration factors, surface finish coefficients, and thermal load. It considers the uncertainties associated with different temperature loads and surface finish on fatigue life. By integrating physics-informed modeling, uncertainty quantification, and fatigue damage accumulation analysis, this approach provides a comprehensive framework for fatigue reliability assessment and risk mitigation in critical UGS systems. It enables informed decision-making for safe and reliable operations, as well as optimized maintenance strategies, ultimately enhancing the overall system performance and mitigating potential failures.

Quantum Effect Enables Large Elastocaloric Effect in Monolayer MoSi2N4${\rm MoSi}_2{\rm N}_4$ and Graphene

AbstractLow‐dimensional materials with outstanding heat conductivity and elastocaloric effect (eCE) are significant for environmentally friendly and energy‐efficient nano refrigerators. However, most of elastocaloric materials with first/second‐order phase transition suffer from hysteresis loss. Herein, an emerging monolayer is theoretically demonstrated as a promising candidate, which exhibits no hysteresis loss enabled by reversible elastic response, as well as large eCE and high eC strength enabled by quantum effect (QE). Considering the remarkable influence of QE and thermo‐mechanical coupling (TMC) in the monolayer limit, the adiabatic temperature change () is evaluate by incorporating QE and TMC. Molecular dynamics simulation significantly underestimates , whereas method with QE slightly overestimates when compared to method with QE+TMC. At 300 K, of is –(11–42) K under biaxial tensile forces of 26–84 nN. The elastocaloric coefficients are –(0.3–0.9) , comparable to that of armchair carbon nanotubes. A large eCE ( around 15 K under a biaxial tensile load of 35 nN) is also revealed for graphene by incorporating QE and TMC. This study proposes a more comprehensive method for quantitatively predicting eCE in 2D materials by including QE and TMC, offering a theoretical guideline for refrigerating materials in the monolayer limit.