Search

The uncertainty of thermal protection system (TPS) is inevitable in practical engineering. In this article, the interval finite element model of TPS is established by taking the uncertainties of TPS in thermomechanical coupling analysis as interval parameters. The perturbed-based interval finite element method (PIFEM) and affine-based interval finite element method (AIFEM) are proposed to study the displacement response of uncertain TPS under thermomechanical coupling. Two numerical examples are given and compared with Monte Carlo method (MCM) to verify the effectiveness and accuracy of the PIFEM and AIFEM proposed in this article. The results show that compared with the MCM, the computational efficiency of PIFEM and AIFEM is improved by more than three orders of magnitude, and the computational efficiency of PIFEM and AIFEM is similar. In the case of considering uncertain parameters, the conservative AIFEM is more suitable for the thermomechanical coupled uncertainty analysis of TPS. The numerical results provide useful guidance for TPS design. [ABSTRACT FROM AUTHOR]

This study proposes a comprehensive, coupled thermomechanical model that replaces local spatial derivatives in classical differential thermomechanical equations with nonlocal integral forms derived from the peridynamic differential operator (PDDO), eliminating the need for calibration procedures. The model employs a multi-rate explicit time integration scheme to handle varying time scales in multi-physics systems. Through simulations conducted on granite and ceramic materials, this model demonstrates its effectiveness. It successfully simulates thermal damage behavior in granite arising from incompatible mineral expansion and accurately calculates thermal crack propagation in ceramic slabs during quenching. To account for material heterogeneity, the model utilizes the Shuffle algorithm andWeibull distribution, yielding results that align with numerical simulations and experimental observations. This coupled thermomechanical model shows great promise for analyzing intricate thermomechanical phenomena in brittle materials. [ABSTRACT FROM AUTHOR]

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.

The adaptation of traditional roads (tRoads) into electrified roads (eRoads) generally requires the inclusion of a charging unit (CU) in the pavement. In this study, the structural behaviour of a conductive eRoad is assessed using 2-D FEM simulations, and compared to the behaviour of a tRoad. Thermal and mechanical loadings representative of field configurations were applied and the relaxation response of the bituminous mixtures was calculated. Resulted strain and stress fields indicated a differential thermomechanical behaviour of the eRoad components. Strain and stress concentrations due to daily temperature fluctuations were pronounced near the interface with the CU. Traditional parameters obtained at the bottom of the bituminous layer were found similar for tRoad and eRoad. It is concluded that the development of new failure criteria is necessary to predict the service life of eRoads, in order to consider the thermally-induced strain and the impact of the volumetric rearrangement of the CU. [ABSTRACT FROM AUTHOR]

The global demand for energy is on the rise, accompanied by increasing requirements for low-carbon environmental protection. In recent years, China's "double carbon action" initiative has brought about new development opportunities across various sectors. The concept of energy pile foundation aims to harness geothermal energy, aligning well with green, low-carbon, and sustainable development principles, thus offering extensive application prospects in engineering. Drawing from existing research globally, this paper delves into four key aspects impacting the thermodynamic properties of energy piles: the design of buried pipes, pile structure, heat storage materials within the pipe core, and soil treatment around the pile using carbon fiber urease mineralization. Leveraging the innovative mineralization technique known as urease-induced carbonate mineralization precipitation (EICP), this study employs COMSOL Multiphysics simulation software to analyze heat transfer dynamics and establish twelve sets of numerical models for energy piles. The buried pipe design encompasses two types, U-shaped and spiral, while the pile structure includes concrete solid energy piles and tubular energy piles. Soil conditions around the pile are classified into undisturbed sand and carbon fiber-infused EICP mineralized sand. Different inner core heat storage materials such as air, water, unaltered sand, and carbon fiber-based EICP mineralized sand are examined within tubular piles. Key findings indicate that spiral buried pipes outperform U-shaped ones, especially when filled with liquid thermal energy storage (TES) materials, enhancing temperature control of energy piles. The carbon fiber urease mineralization technique significantly improves heat exchange between energy piles and surrounding soil, reducing soil porosity to 4.9%. With a carbon fiber content of 1.2%, the ultimate compressive strength reaches 1419.4 kPa. Tubular energy piles mitigate pile stress during summer temperature fluctuations. Pile stress distribution varies under load and temperature stresses, with downward and upward friction observed at different points along the pile length. Overall, this research underscores the efficacy of energy pile technologies in optimizing energy efficiency while aligning with sustainable development goals. [ABSTRACT FROM AUTHOR]

The friction contact state of the brake friction interface of high-speed trains in the braking process affects the braking efficiency, which in turn affects the braking safety and the service life of the components. This article focuses on the heat and stress distribution at the friction interface under the action of a floating brake pad structure. A floating brake pad structure comprising two sets of spherical joint structure is introduced. The multibody structure and rigid–flexible coupling effects of the floating brake pad are considered. Furthermore, a full reproduction flexible thermomechanical coupling braking model in the floating brake pad structure is constructed. The accuracy of the model is validated by conducting tests on a 1:1-scale high-speed train brake test bench. The temperature and stress distribution of the fixed/floating brake pad structure at 80 km/h are studied accordingly. The results show that in accordance with the temperature outcomes derived from the simulation model, the observed temperature variations in the test results demonstrate an average error of 8.93%. The action of the floating brake pad resulted in a significant reduction of 36.99% in the maximum surface temperature of the brake pad, as well as a reduction of 30.91% in the maximum stress. The temperature of the brake disk surface is decreased by 32.01%, while the maximum stress experienced a decrease of 30.65%. The contact area of the friction interface is increased by 100%. The floating brake pad demonstrates a more uniform distribution and consistent gradient of temperature and stress across its friction interface in comparison to the fixed brake pad. The thermomechanical coupling effect of friction interface and multibody interaction in the floating brake pad structure are considered. A full reproduction flexible thermomechanical coupling braking model with the floating brake pad structure is established. The connection between the movement changes of the components of the floating brake plate and the heat–force coupling state of the brake friction interface is established. The correlation between the dynamic behavior of different components of a floating brake pad structure during braking and the thermomechanical coupling state at the friction interface is established. The floating type brake pad is verified through simulation, confirming its effective enhancement of the contact area at the braking interface. Consequently, this improvement leads to enhanced braking performance and prolonged service life for both the brake pad and the disk. [ABSTRACT FROM AUTHOR]

Skiving has potential for gear machining, but its cutting force fluctuates greatly, its cutting temperature is high during processing, and it has the characteristics of thermomechanical coupling. It is difficult for traditional methods to dynamically predict the thermomechanical coupling during the skiving process, whose efficiency and stability cannot be guaranteed. Aiming to solve these problems, a digital twin (DT)-based dynamic method is proposed to predict thermomechanical coupling in the skiving process. Considering the time-varying characteristics and coupling of the cutting force and temperature, a multi-physical modeling method dual-driven by mechanism and data is proposed to establish a thermomechanical coupling DT (TMDT) model of the skiving process. The dynamic consistency of the skiving process between the digital and physical spaces is realized. Principal component analysis (PCA) and an extreme learning machine (ELM) are used to reduce the order of the TMDT, the reduced-order model is trained using the skiving big data, and a relationship mapping model of the cutting parameters and the cutting force and temperature is established to realize the dynamic prediction of the cutting force and temperature. The effectiveness of the proposed method is verified through gear skiving experiments. This research has important theoretical guiding significance to realize efficient and stable skiving processing. [ABSTRACT FROM AUTHOR]

This paper reports a method to construct the complete constitutive model of carbon fiber‐reinforced plastic (CFRP) by distinguishing the strain rate state and modifying the material stiffness. In quasistatic (low strain rate) compression, the initial nonlinear effect caused by the material defects was described by introducing an nonlinear increasing factor. In dynamic (high strain rate) impact, the nonlinear strengthening effect was described by introducing the dynamic amplification factors of stress and strain based on the reference state. Considering the instantaneous temperature rise obtained from the impact work–temperature generation equation and the influence of temperature on modulus and strength, the coupled thermomechanical constitutive models combining the strain rate effect and the temperature effect were established. The user‐defined material subroutines (VUMAT) were developed, and then these constitutive models were verified by finite element analysis (FEA). Finally, the developed material subroutine was applied to predict the impact penetration of CFRP laminates, and the results show that the opening holes, damage and energy dissipation are in good agreement with the reference experiment. This work comprehensively analyzed the construction method of CFRP constitutive models, which would provide a guidance for the coupled thermomechanical behavior under dynamic impact. Highlights: An anisotropic continuum mechanical constitutive behavior considering strain rate effect and damage evolution behavior was established.A macroscopic anisotropic constitutive model including the coupled impact temperature generation‐mechanical behavior was established.Combined with the incremental finite element method, the three‐dimensional user‐defined material subroutines (VUMAT) were developed and verified.The thermomechanical impact penetration behaviors of CFRP laminates was predicted, and the stress field, temperature field and failure characteristics were visualized. [ABSTRACT FROM AUTHOR]

Severe heat generated by the hysteresis loss can be accumulated inside of the aircraft tire during the free rolling stage, which affects the performance and safety of aircraft. In this paper, verifying a thermomechanical coupling simulation method through experiments to predict the temperature field evolution and internal temperature distribution of natural rubber during high-speed rolling. The high-speed rolling performance of the aircraft tire can be reflected by the disc-shaped specimen based on the similar working and contact conditions, which provides theoretical basis for the further application in aircraft tire. The cyclic tensile test is conducted on dumbbell rubber specimen, and the results show that the temperature increases with the strain. The simulated temperature field distribution corresponds well with the test results, and the maximum error of the temperature rise data is within 4%. Rolling test is conducted on solid rubber wheels, the error between the simulated temperature rise curve and the test is within 1.2%, which proves that this method accurately predicts the temperature evolution process of the disc rubber wheel, and provides a basis for the study of aircraft tire heat generation under different conditions. [ABSTRACT FROM AUTHOR]

Liquid crystal elastomers (LCEs) are made of liquid crystal molecules integrated with rubber-like polymer networks. An LCE exhibits both the thermotropic property of liquid crystals and the large deformation of elastomers. It can be monodomain or polydomain in the nematic phase and transforms to an isotropic phase at elevated temperature. These features have enabled various new applications of LCEs in robotics and other fields. However, despite substantial research and development in recent years, thermomechanical coupling in polydomain LCEs remains poorly studied, such as their temperature-dependent mechanical response and stretch-influenced isotropic-nematic phase transition. This knowledge gap severely limits the fundamental understanding of the structure-property relationship, as well as future developments of LCEs with precisely controlled material behaviors. Here, we construct a theoretical model to investigate the thermomechanical coupling in polydomain LCEs. The model includes a quasi-convex elastic energy of the polymer network and a free energy of mesogens. We study the working conditions where a polydomain LCE is subjected to various prescribed planar stretches and temperatures. The quasi-convex elastic energy enables a "mechanical phase diagram" that describes the macroscopic effective mechanical response of the material, and the free energy of mesogens governs their first-order nematic-isotropic phase transition. The evolution of the mechanical phase diagram and the order parameter with temperature is predicted and discussed. Unique temperature-dependent mechanical behaviors of the polydomain LCE that have never been reported before are shown in their stress-stretch curves. These results are hoped to motivate future fundamental studies and new applications of thermomechanical LCEs. [ABSTRACT FROM AUTHOR]

Abstract As nonlinear thermal devices, thermal regulators can intelligently respond to temperature and control heat flow through changes in heat transfer capacities, which allows them to reduce energy consumption without external intervention. However, current thermal regulators generally based on high‐quality crystalline‐structure transitions are intrinsically rigid, which may cause structural damage and functional failure under mechanical strain; moreover, they are difficult to integrate into emerging soft electronic platforms. In this study, we develop a flexible, elastic thermal regulator based on the reversible thermally induced deformation of a liquid crystal elastomer/liquid metal (LCE/LM) composite foam. By adjusting the crosslinking densities, the LCE foam exhibits a high actuation strain of 121% with flexibility below the nematic–isotropic phase transition temperature (TNI) and hyperelasticity above TNI. The incorporation of LM results in a high thermal resistance switching ratio of 3.8 over a wide working temperature window of 60°C with good cycling stability. This feature originates from the synergistic effect of fragmentation and recombination of the internal LM network and lengthening and shortening of the bond line thickness. Furthermore, we fabricate a “grid window” utilizing photic‐thermal integrated thermal control, achieving a superior heat supply of 13.7°C at a light intensity of 180 mW/cm2 and a thermal protection of 43.4°C at 1200 mW/cm2. The proposed method meets the mechanical softness requirements of thermal regulator materials with multimode intelligent temperature control.

After a loss of coolant accident (LOCA) in the prestressed concrete containment vessels (PCCVs) of nuclear power plants, the coupling of temperature and pressure can significantly affect the mechanical properties of the PCCVs. However, there is no consensus on how this coupling affects the failure mechanism of PCCVs. In this paper, a simplified finite element modeling method is proposed to study the effect of temperature and pressure coupling on PCCVs. The experiment results of a 1:4 scale PCCV model tested at Sandia National Laboratory (SNL) are compared with the results obtained from the proposed modeling approach. Seven working conditions are set up by varying the internal and external temperatures to investigate the failure mechanism of the PCCV model under the coupling effect of temperature and pressure. The results of this paper demonstrate that the finite element model established by the simplified finite element method proposed in this paper is highly consistent with the experimental results. Furthermore, the stress-displacement curve of the PCCV during loading can be divided into four stages, each of which corresponds to the damage to the concrete, steel liner, steel rebar, and prestressing tendon. Finally, the failure mechanism of the PCCV is significantly affected by temperature.

The performance of Lithium-ion batteries (LIBs) is seriously affected by temperature rise and mechanical degradation during the charge or discharge. In this work, a fully coupled thermomechanical model with the total heat generation rate is developed to analyze the mechanism of the temperature rise and stress distribution. Then numerical simulations are performed to show the evolution of temperature and stress for 18650 LIBs. The comparisons of the surface temperature evolution between the present model and experimental results, and the temperature variation with radius between the present model and the pure thermal model are made, respectively. Finally, the influences of some design parameters upon the Li-ions concentration and the stress are discussed. The numerical results show that the present model is more validated against the pure thermal model, and the temperature and stress will be reduced if the positive electrode particle radius, the volume fraction of the positive active material and the initial electrolyte salt concentration are decreased, or the positive electrode thickness is increased which will provide some guides for the design of LIBs. [ABSTRACT FROM AUTHOR]

The development of thermomechanical coupled simulations for rolling contacts is challenging when the adjacent material is temperature-dependent or when there are cracks or other discontinuities on the contact surface. This paper proposes a novel thermomechanical coupled modeling method for rolling contacts using a nonlocal peridynamic (PD) approach. Fully coupled, ordinary state-based PD thermomechanical equations for the plane strain and plane stress cases are derived based on the strain-energy density, including thermal coupling terms, and detailed information on each parameter is provided. Subsequently, an algorithm for rolling thermal contacts in PD is proposed based on the penalty method. This study further provides a detailed modeling process and an algorithm for the proposed method based on a multi-rate time-integration scheme for numerical implementation. A typical two-dimensional (2D) wheel–rail rolling contact model is established to evaluate the performance of the proposed contact modeling method in wheel–rail thermal contact and to analyze the influence of temperature-dependent material and rail-surface cracks on the thermomechanical response. It is found that the contact stress and rail-surface temperature rise in the case of small creepages and temperature-independent materials are in good agreement with the analytical solution. In the case of large creepages, the mechanical and temperature results of using temperature-dependent materials and temperature-independent materials are quite different, and the frictional heat generated can cause martensitic transformation of adjacent materials. Rail-surface cracks cause a sharp increase in the contact stress and temperature rise near the cracks, and the high temperature also promotes crack growth. • A nonlocal thermomechanical coupled modeling method for rolling contacts using peridynamic is proposed. • Fully coupled, ordinary state-based PD thermomechanical equations are derived. • An algorithm for rolling thermal contacts in PD is proposed based on the penalty method. • A typical 2D wheel–rail rolling contact model is established for a case study. [ABSTRACT FROM AUTHOR]

As nonlinear thermal devices, thermal regulators can intelligently respond to temperature and control heat flow through changes in heat transfer capacities, which allows them to reduce energy consumption without external intervention. However, current thermal regulators generally based on high‐quality crystalline‐structure transitions are intrinsically rigid, which may cause structural damage and functional failure under mechanical strain; moreover, they are difficult to integrate into emerging soft electronic platforms. In this study, we develop a flexible, elastic thermal regulator based on the reversible thermally induced deformation of a liquid crystal elastomer/liquid metal (LCE/LM) composite foam. By adjusting the crosslinking densities, the LCE foam exhibits a high actuation strain of 121% with flexibility below the nematic–isotropic phase transition temperature (TNI) and hyperelasticity above TNI. The incorporation of LM results in a high thermal resistance switching ratio of 3.8 over a wide working temperature window of 60°C with good cycling stability. This feature originates from the synergistic effect of fragmentation and recombination of the internal LM network and lengthening and shortening of the bond line thickness. Furthermore, we fabricate a "grid window" utilizing photic‐thermal integrated thermal control, achieving a superior heat supply of 13.7°C at a light intensity of 180 mW/cm2 and a thermal protection of 43.4°C at 1200 mW/cm2. The proposed method meets the mechanical softness requirements of thermal regulator materials with multimode intelligent temperature control. [ABSTRACT FROM AUTHOR]

Elastic disordered microcellular metal rubber (EDMMR) is a lightweight metal material widely employed for damping or support in high‐temperature environments, addressing the limitations of traditional polymer rubbers. Herein, three sets of solid finite element models of EDMMR with different relative densities are developed using virtual manufacturing technology (VMT). Thermal–mechanical coupled finite element simulations explore the dynamic evolution of two typical spatial topological structures in the material's microstructure: unit contact characteristics and angle distribution under temperature variations. Results indicate that the mechanical performance of the material under high‐temperature loads exhibits distinct spatial topological structures compared to those at room temperature. At 100, 200, and 300 °C, the material experiences internal stress distributions of up to 0.5, 1.2, and 1.8 MPa, respectively, due to expansion. Additionally, during the initial loading stage, stress differentials of approximately 0.4 MPa are observed between different temperatures due to boundary effects. Furthermore, the study investigates the probability density distribution of typical microstructural combinations of EDMMR along the forming direction based on VMT, enhancing the generality of the constitutive model. Finally, three groups of EDMMR samples with different relative densities are prepared using standardized processes, and the model is validated through high‐temperature quasistatic compression experiments. [ABSTRACT FROM AUTHOR]

In this study, the fire safety of a ship structure is evaluated using a fire dynamics algorithm for large eddy simulations and a structural-thermal coupling method. Taking a two-story cabin as an example, a typical I-channel is adopted and the fire-thermal-structure coupling calculation of the cabin is realised through a thermal-mechanical coupling data interface. On this basis, the failure characteristics, stress distribution, and deformation modes of the cabin under different heat release rate (0–8 MW) and fire locations (side and middle chambers) are studied. The results show that an increase in the heat release rate in the side chamber causes the failure path of the cabin to gradually expand from the fire-source side to the sagging plane. This differs from the failure mode of the cabin in the sagging plane at ambient temperature. When a high-power fire occurs in the middle chamber of the cabin, its spatial layout significantly influences the damage location. Moreover, the residual strength of the cabin at different fire positions in a heat release rate range of 0–8 MW is predicted. [ABSTRACT FROM AUTHOR]

Residual martensite and plastic deformation are the culprits of functional degradation in NiTi alloys. However, their roles in thermomechanically coupled functional degradation of nanocrystalline superelastic NiTi alloys have not been investigated systematically and quantitatively. In this paper, the origins of thermomechanically coupled functional degradation of nanocrystalline superelastic NiTi alloys are subdivided into (i) plastic deformation including dislocation slipping in nanocrystals and shearing of amorphous phase, (ii) Type A residual martensite (RMA) originating from the incomplete reverse transformation during non-isothermal deformation, and (iii) Type B residual martensite (RMB) stabilized by the internal stress owing to inconsistent plastic strains among neighboring grains. For the first time, the inverse relation between fRMA and strain rate in NiTi with GS of 6 nm (a crystalline-amorphous nanocomposite) is determined experimentally. We find that the residual strain is mainly caused by plastic deformation except when RMA accumulates drastically. It is substantiated that plastic deformation lowers both forward and reverse transformation stresses significantly. Residual martensite plays an important role in the decrement of forward transformation stress, while has little impact on reverse transformation stress.

The global demand for energy is on the rise, accompanied by increasing requirements for low-carbon environmental protection. In recent years, China’s “double carbon action” initiative has brought about new development opportunities across various sectors. The concept of energy pile foundation aims to harness geothermal energy, aligning well with green, low-carbon, and sustainable development principles, thus offering extensive application prospects in engineering. Drawing from existing research globally, this paper delves into four key aspects impacting the thermodynamic properties of energy piles: the design of buried pipes, pile structure, heat storage materials within the pipe core, and soil treatment around the pile using carbon fiber urease mineralization. Leveraging the innovative mineralization technique known as urease-induced carbonate mineralization precipitation (EICP), this study employs COMSOL Multiphysics simulation software to analyze heat transfer dynamics and establish twelve sets of numerical models for energy piles. The buried pipe design encompasses two types, U-shaped and spiral, while the pile structure includes concrete solid energy piles and tubular energy piles. Soil conditions around the pile are classified into undisturbed sand and carbon fiber-infused EICP mineralized sand. Different inner core heat storage materials such as air, water, unaltered sand, and carbon fiber-based EICP mineralized sand are examined within tubular piles. Key findings indicate that spiral buried pipes outperform U-shaped ones, especially when filled with liquid thermal energy storage (TES) materials, enhancing temperature control of energy piles. The carbon fiber urease mineralization technique significantly improves heat exchange between energy piles and surrounding soil, reducing soil porosity to 4.9%. With a carbon fiber content of 1.2%, the ultimate compressive strength reaches 1419.4 kPa. Tubular energy piles mitigate pile stress during summer temperature fluctuations. Pile stress distribution varies under load and temperature stresses, with downward and upward friction observed at different points along the pile length. Overall, this research underscores the efficacy of energy pile technologies in optimizing energy efficiency while aligning with sustainable development goals.

Elastomeric materials are well-known for their ability to dissipate mechanical energy into heat. Under cyclic loading, this dissipated energy, combined with the low thermal conductivity of these materials causes heat storage in the sample resulting in a rise of the material temperature. As this phenomenon induces negative effects on fatigue life, this heat build-up has been widely studied in recent years but a few for multiaxial loadings. In this paper, we propose to investigate the self-heating induced by multiaxial mechanical loading of Natural Rubber (NR). The goal of this research work is to find a suitable modeling to predict the heat build-up of elastomers under multiaxial cyclic loadings. The proposed model, based upon a weak coupling approach and which only requires an estimation of the energy dissipation during a cycle of loading, is used to predict the heat build-up evolution of 3 different specimen geometries under multiaxial cyclic mechanical loading for 2 materials: a natural rubber (NR) experimentally investigated in this work allowing to develop the model and a styrene-butadiene rubber (SBR) which heat build-up data are taken from the literature for further model validation. A satisfactory agreement between simulations and experiments is found, making this approach a useful tool for temperature evolution estimates during fatigue loading.

Dry friction dampers in turbomachinery not only decrease the vibration level, but also generate frictional heat. This thermal process may cause a significant temperature rise at the contact interface, producing thermal expansion and altering tribological properties subsequently. These effects in turn can change structural dynamics. Besides, the temperature rise may also cause the material melting and ablation, leading to damper failure. Hence, the structural dynamics and the thermal process in dry friction systems are interacting. The thermomechanical coupling should be included in analyses. In this paper, a novel numerical method, namely Dry Friction Thermo-Mechanical Coupling Response Prediction (DFTMCP), is proposed. Based on the multi-harmonic balance method, the DFTMCP can synchronously predict the nonlinear forced response and interface temperature in the steady state. This method is under the framework of steady heat transfer assumption, and a dimensionless number is proposed to determine the rationality of the assumption. To guarantee efficiency and convergence, an ad hoc model reduction technique for the nonlinear thermomechanical coupling problem and the corresponding analytical Jacobian matrix, which are also the highlights of the work, are implemented. The former reduces the dimension of the governing equations by over 98.6% while the latter makes the time cost drop over 37 times. By using the proposed numerical method, two essential coupling factors, the thermoelastic deformation and the friction coefficient variation at the interface, are considered and discussed quantitatively for the influence on the forced response through the finite element model of a blade with a flat underplatform damper in engineering. A convergence analysis has been performed to validate the correctness of the simulation results. Results show that under the specific rotational speed, the average temperature at the contact surface rises by 415 °C, and the maximum local temperature increases to 1229 °C, which is close to the melting point. Ignoring the thermomechanical coupling effect leads to a 19.0% misprediction of the optimal centrifugal force and a 21.4% underestimation of the resonant peak. [ABSTRACT FROM AUTHOR]

Based on the L-S generalized thermoelastic theory and in view of the specific heat capacity change of material with temperature, the control equations for the thermoelastic coupling system with internal heating source were established. The thermomechanical responses of yttrium tetragonal zirconia (YSZ) under the action of ultrashort pulse laser were studied by means of the finite element method. The effects of the specific heat capacity change with temperature, and the pulse width of the laser on the thermomechanical responses and the mechanical wave reflections in material were obtained. The results show that, under repeated pulse laser actions, the stress and displacement of the material will undergo fluctuations, and the mechanical response will be more sensitive to heating than the thermal response. The specific heat capacity change with temperature will result in the decrease of the thermal response. The study provides an important guidance for improving the ultrashort pulse laser machining quality. [ABSTRACT FROM AUTHOR]

This paper is devoted to the numerical and experimental study of ductile fracture in bulk metal forming of the 2017A-T4 aluminum alloy. From an experimental standpoint, the ductile fracture of the2017A-T4aluminum alloy is investigated under compressive load. Two cross-sections of solid and hollow specimens are considered. The mechanical behavior and the microstructure of the 2017A-T4 aluminum alloy were characterized. It is found that the well-known barrel shape is obtained when a compressive load is applied. Analyses of fracture topographies show a ductile fracture with dimples under tension and coexistence of ductile fracture with dimples and slant under compression. The classical physically-based Gurson-Tvergaard-Needleman (GTN) model and its extension to incorporateshear mechanisms to predict failure at low-stress triaxiality are considered. These two models have been extended to take into account the thermal heating effect induced by the mechanical dissipation within the material during the metal forming process. The two models have been implemented into the finite element code Abaqus/Explicit using a Vectorized User MATerial (VUMAT) subroutine. Numerical simulations of the forging process made for hollow and solid cylindrical specimens show good agreement with experimental results. In contrast with the GTN model, the modified GTN model incorporating shear mechanisms can capture the final material failure.

Advances in the field of processing and characterization of material behaviors are driving innovations in materials design at a nanoscale. Thus, it is demanding to develop physics-based computational methods that can advance the understanding of material Multiphysics behaviors from a bottom-up manner at a higher level of precision. Traditional computational modeling techniques such as finite element analysis (FE) and molecular dynamics (MD) fail to fully explain experimental observations at the nanoscale because of the inherent nature of each method. Concurrently coupled atomic to the continuum (AtC) multi-scale material models have the potential to meet the needs of nano-scale engineering. With the goal of representing atomistic details without explicitly treating every atom, the AtC coupling provides a framework to ensure that full atomistic detail is retained in regions of the problem while continuum assumptions reduce the computational demand. This review is intended to provide an on-demand review of the AtC methods for simulating thermo-mechanical behavior. Emphasis is given to the fundamental concepts necessary to understand several coupling methods that have been developed. Three methods that couple mechanical behavior, three methods that couple thermal behavior, and three methods that couple thermo-mechanical behavior is reviewed to provide an evolutionary perspective of the thermo-mechanical coupling methods.

The nonlinear dynamics of composite plates with thermomechanical coupling is analytically addressed in order to describe the main bifurcation phenomena triggering the involved pre- and post-buckling response scenario. The static buckling occurrence and two resonance conditions around the unbuckled and buckled equilibria are investigated by means of the asymptotic multiple scale method, together with the double-zero bifurcation marking the occurrence of dynamical buckling. The resulting modulation equations and the steady-state mechanical and thermal responses are determined and compared with the numerical outcomes in order to verify the adequacy and effectiveness of the refined scalings adopted in the multiple scale analyses to describe the various bifurcation scenarios. [ABSTRACT FROM AUTHOR]

The preparation of Cu-Ti alloys with homogenous elemental distribution is related to the engineering applications. Considering the thickness ratio and crosssectional geometry of components change with the increase in cumulative equivalent strain in accumulative roll bonding-deformation diffusion (ARB-DD) process, an elemental diffusion model is established based on different solute concentration fields. The accuracy of the model is verified by preparing Cu-Ti alloys in different states. The morphology of Ti layers evolve from a flat to a shuttle-shaped structure due to the strong shear effect as cumulative equivalent strain increases. The diffusion heat treatment time for homogenization is predicted based on the model, and the results show that the model basically matches with the experimental results. The absolute error of prediction is within 9%, and the average error is about 4.4%. It indicates that the synergistic control of elemental diffusion behavior in ARB-DD process can be achieved. Besides, it demonstrates that the effective diffusion activation plays a key role in determining the accuracy of the model. The difference of deformation energy storage in various cumulative equivalent strain states causes a significant change in effective diffusion activation energy, thereby producing a great influence on elemental diffusion behavior of Cu/Ti alloys. [ABSTRACT FROM AUTHOR]

Modern approaches dedicated to controlling the operation of gas foil bearings require advanced measurement techniques to comprehensively investigate the bearings' thermal and thermomechanical properties. Their successful long-term maintenance with constant operational characteristics may be feasible only when the allowed thermal and mechanical regimes are rigorously kept. Hence, an adequate acquisition of experimental readings for the critical physical quantities should be conducted to track the actual condition of the bearing. The above-stated demand has motivated the authors of this present work to perform the thermomechanical characterization of the prototype installation of a gas foil bearing, applying a specialized sensing foil. This so-called top foil is a component of the structural part of the bearing's supporting layer and composed of a superalloy, Inconel 625. The strain and temperature distributions were identified based on the readings from the strain gauges and integrated thermocouples mounted on the top foil. The measurements' results were obtained for the experiments that represent the arbitrarily selected operational conditions of the tested bearing. Specifically, the considered measurement scenario relates to the operation at a nominal rotational speed, i.e., during the stable process, as well as to the run-up and run-out stages. The main objectives of the work are: (a) experimental proof for the described functionalities of the designed and manufactured specialized sensing foil that allow for the application of a novel approach to the bearing's characterization, and (b) qualitative investigation of the relation between the mechanical and thermal properties of the tested bearing, using the measurements conducted with the newly proposed technical solution. [ABSTRACT FROM AUTHOR]

Background: The conversion of plastic work to heat and its efficiency (the Taylor-Quinney coefficient - TQC), are traditionally measured using infrared single-detectors (named detectors from here on) which measure the temperature at a single point on the surface. Lately, fast infrared cameras (focal plane array of detectors that measures a 2-dimensional field of view on the surface) have been increasingly used for that purpose too, but no systematic study has been carried out yet to compare the respective performance of each monitoring system for impact loading conditions. Objective: A comparison between the two techniques (infrared detector and infrared fast camera) is reported for commercial 316L stainless steel under dynamic loading in the Kolsky bar. The respective merits and limitations of each setup are compared and discussed. Methods: Cylindrical specimens were loaded at a strain rate of about 3000 [1/s] in a split Hopkinson pressure bar (Kolsky bar) apparatus. The transient temperature change was monitored in two separate series of experiments: In the first, we used a liquid N2 cooled Mercury-Cadmium-Telluride (MCT) detector made by InfraRed Associates (USA) with a 1.5 MHz sampling rate, and in the second, a Telops FAST M2K high-speed infrared camera made by Telops (Canada) based on Indium Antimonide (InSb) array-detector and with a sampling rate of up to 90 kHz. Results: Temperature changes under impact were successfully measured and compared using the two distinct techniques. In addition, the IR camera rendered a satisfactory thermal and visual recording of dynamic shear failure of various specimens. Conclusions: The integral Taylor-Quinney coefficient ( β int ) can be assessed using either infrared detector or fast infrared camera alike, under dynamic loading conditions. However, the evaluation of the differential TQC ( β diff ) necessitates high sampling rates such as those enabled by infrared single detectors as compared to infrared high-speed cameras. [ABSTRACT FROM AUTHOR]

Two-scale modeling is adopted to investigate the thermo-mechanical behavior of 3D four-directional (3D4D), 3D five-directional (3D5D), and 3D full five-directional (3DF5D) braided composites. Based on the stress-strain relationship considering thermal expansion and the periodic boundary conditions, the elastic constants and the coefficients of thermal expansion (CTE) of the three types of braided composites are predicted by a two-scale homogenization method. The micro stress under free expansion and thermo-mechanical coupling is also simulated. The calculated results are in good agreement with experimental results from relevant references. The numerical results show that the longitudinal elastic and thermal expansion properties are gradually improved with the increase of axial yarn content from 3D4D to 3D5D and then to 3DF5D braided composites. The braiding angle corresponding to the zero longitudinal CTE of each braided structure is basically about 40°. Furthermore, with the increase of temperature, the longitudinal micro-stress in yarns increases gradually, but that in matrix drops. These conclusions will provide a reliable basis for the structural optimization design and safety evaluation of 3D multi-directional braided composites in a thermal environment. [ABSTRACT FROM AUTHOR]

Achieving process stability in the thermoforming of fiber reinforced polymer materials (FRPs) for aerospace or automotive manufacturing is usually associated with a costly trial-and-error process, where experimental boundary conditions and other influencing factors, such as, for example, material composition, need to be adjusted over time. This is especially true when material phenomena on the microlevel, such as the crystallization kinetics of the polymer matrix or resulting stresses from temperature gradients, are the cause of the process instability. To reduce the experimental effort and reliably predict the material behavior during thermoforming, finite element simulation tools on multiple scales are a useful solution. Hereby, incorporating micromechanical phenomena into the model approaches is crucial for an accurate prediction by further reducing the deviation between simulation and experiment, in particular with regard to the underlying nonlinear material behavior. In this work, unit cell simulations on the microscale of a unidirectional glass fiber reinforced polymer (UD GFRP) are conducted to predict effective thermomechanical properties of a single material ply and ascertain the effect of individual ply constituents on the homogenized material behavior. The polymeric matrix material model used was identified in a prior publication with experimental data at various temperatures for polyamide 6 blends with varying degrees of crystallinities. Various randomization methods are tested to generate the unit cells and replicate the composites' random fiber distribution, with a focus on process automation. The simulative results are successfully compared to an experimental study on glass fiber reinforced polyamide 6 tested at various temperatures, demonstrating the potential of the approach to reduce both time and cost required for material characterization. Finally, the unit cells are used to generate a database to predict untested load cases that will be used in future work to characterize a homogenized macroscopic material model. • Tensile and compression tests with different loading procedures for varying fiber angles, temperatures, and strain rates. • Thermal analysis of glass fiber reinforced polyamide 6 in different material directions. • Investigation of different randomization methods, automatic generation of repeating unit cells and successful comparison to experimental results. • Mechanical and thermal micromechanical analysis of glass fiber reinforced polyamide 6. • Finite strain thermo-mechanically coupled material model for polyamide 6, valid over a wide range of degrees of crystallinity. [ABSTRACT FROM AUTHOR]

Tungsten heavy alloys (WHAs) have been widely investigated due to their high density and strength, thus making them suitable candidates for defense applications, especially those involving high strain rates, such as Kinetic Energy Penetrators (KEP) for armour-piercing fin-stabilized discarding sabot (APFSDS) ammunition. Besides their mechanical properties, the extent of the thermomechanical coupling, i.e., the Taylor-Quinney coefficient (TQC), is relevant for producing accurate numerical models of high strain rate configurations. However, the TQC of WHAs has not been investigated yet. Four different WHA prototypes were evaluated. Changing the content of tungsten from 70 to 92.5 wt% had little effect on the TQC which had an average value of 0.24. Those low TQC values are accompanied by a significant strain-rate sensitivity with minimal strain hardening. Throughout the tests, dynamic shear localization was not observed. • Four types of tungsten alloys were tested for their Taylor-Quinney coefficient. • Different densities, chemical composition, manufacturing process were considered. • A synchronized experimental setup used for coupled thermo-mechanical study. • The ratio of mechanical to thermal energy remained constant controlled by tungsten. • A single value of the Taylor-Quinney coefficient of 0.24 fitted all materials. [ABSTRACT FROM AUTHOR]

Needle-punched composites are highly valued for their exceptional resistance to interlaminar properties, ablation, and design flexibility, making them increasingly popular in aerospace thermal protection systems. This work investigates the mesoscale structural characteristics and thermophysical properties of needle-punched composites in ablation process. Oxyacetylene ablation experiments were carried out at different temperatures, and a mesoscopic needle-punched structure model was established based on the results of CT characterization. Further, Abaqus custom subroutine was used to reveal the ablation evolution mechanism of carbon fiber reinforced phenolic resin-based needle-punched composites. The results show that, at mesoscopic scale, the acicular fiber bundle perpendicular to the ablative surface accelerates the heat conduction to the interior of the material and promotes the thermal damage and performance degradation of the composite. [Display omitted] [ABSTRACT FROM AUTHOR]

Thermally induced fractures in solids pose significant challenges in various fields, such as aerospace, deep underground, and civil engineering structures. Numerical methods are effective for addressing such problems, with recent advancements in phase-field and material point methods demonstrating notable advantages in crack simulation. This paper presents a computational approach within an explicit material point method framework for coupling the solutions of temperature, displacement, and phase (damage) fields. The displacement and phase fields are intricately linked through a history-dependent strain field and degradation function. The model incorporates temperature-induced strains from temperature gradients for coupling the temperature and displacement fields. In addition, the model accounts for the detrimental effects of cracks on heat conduction, ensuring a comprehensive representation of the coupled system. Two numerical examples involving thermomechanical coupling and dynamic crack branching were used to validate the effectiveness of the proposed method. Finally, the proposed method was applied to simulate the thermal shock and large deformations of thin circular ceramic specimens, successfully replicating the initiation and propagation of cracks observed during the experiment. The simulated thermally induced fractures exhibited periodic and hierarchical characteristics consistent with the experimental findings. [ABSTRACT FROM AUTHOR]

The present study aims at studying the influence of some parameters on the numerical results obtained from the simulation of the high-speed machining process using a commercial finite element computation code, namely Abaqus-Exp. Starting from models available by default in the computation code, comparisons are made between full and weak thermo-mechanical coupling, and the influence of the fracture strain and inelastic heat fraction values is studied. The high-strength Ti-6Al-4 V titanium alloy is taken as an example. Continuous, serrated and segmented chips are reproduced at low, moderate and high cutting speeds and the differences observed between experimental and numerical results are discussed. [ABSTRACT FROM AUTHOR]

Advances in the field of processing and characterization of material behaviors are driving innovations in materials design at a nanoscale. Thus, it is demanding to develop physics-based computational methods that can advance the understanding of material Multiphysics behaviors from a bottom-up manner at a higher level of precision. Traditional computational modeling techniques such as finite element analysis (FE) and molecular dynamics (MD) fail to fully explain experimental observations at the nanoscale because of the inherent nature of each method. Concurrently coupled atomic to the continuum (AtC) multi-scale material models have the potential to meet the needs of nano-scale engineering. With the goal of representing atomistic details without explicitly treating every atom, the AtC coupling provides a framework to ensure that full atomistic detail is retained in regions of the problem while continuum assumptions reduce the computational demand. This review is intended to provide an on-demand review of the AtC methods for simulating thermo-mechanical behavior. Emphasis is given to the fundamental concepts necessary to understand several coupling methods that have been developed. Three methods that couple mechanical behavior, three methods that couple thermal behavior, and three methods that couple thermo-mechanical behavior is reviewed to provide an evolutionary perspective of the thermo-mechanical coupling methods. [ABSTRACT FROM AUTHOR]

Abstract This article proposes a coupled thermomechanical finite element model tailored to the macroscale simulation of metal additive manufacturing processes such as selective laser melting. A first focus lies on the derivation of a consistent constitutive law on basis of a Voigt-type spatial homogenization procedure across the relevant phases, powder, melt and solid. The proposed constitutive law accounts for the irreversibility of phase change and consistently represents thermally induced residual stresses. In particular, the incorporation of a reference strain term, formulated in rate form, allows to consistently enforce a stress-free configuration for newly solidifying material at melt temperature. Application to elementary test cases demonstrates the validity of the proposed constitutive law and allows for a comparison with analytical and reference solutions. Moreover, these elementary solidification scenarios give detailed insights and foster understanding of basic mechanisms of residual stress generation in melting and solidification problems with localized, moving heat sources. As a second methodological aspect, dual mortar mesh tying strategies are proposed for the coupling of successively applied powder layers. This approach allows for very flexible mesh generation for complex geometries. As compared to collocation-type coupling schemes, e.g., based on hanging nodes, these mortar methods enforce the coupling conditions between non-matching meshes in an $$L^2$$ L 2 -optimal manner. The combination of the proposed constitutive law and mortar mesh tying approach is validated on realistic three-dimensional examples, representing a first step towards part-scale predictions.

This paper is devoted to the numerical and experimental study of ductile fracture in bulk metal forming of the 2017A-T4 aluminum alloy. From an experimental standpoint, the ductile fracture of the 2017A-T4 aluminum alloy is investigated under compressive load. Two cross-sections of solid and hollow specimens are considered. The mechanical behavior and the microstructure of the 2017A-T4 aluminum alloy were characterized. It is found that the well-known barrel shape is obtained when a compressive load is applied. Analyses of fracture topographies show a ductile fracture with dimples under tension and coexistence of ductile fracture with dimples and slant under compression. The classical physically-based Gurson-Tvergaard-Needleman (GTN) model and its extension to incorporate shear mechanisms to predict failure at low-stress triaxiality are considered. These two models have been extended to take into account the thermal heating effect induced by the mechanical dissipation within the material during the metal forming process. The two models have been implemented into the finite element code Abaqus/Explicit using a Vectorized User MATerial (VUMAT) subroutine. Numerical simulations of the forging process made for hollow and solid cylindrical specimens show good agreement with experimental results. In contrast with the GTN model, the modified GTN model incorporating shear mechanisms can capture the final material failure.

Thermal barrier coating (TBC) systems have long been used in many engineering applications, such as jet engines and gas turbines. One pressing task is to evaluate their performance and integrity under long-term thermal cycles. This task requires an accurate and efficient time integration technique that is unconditionally stable, since large time steps are required to simulate TBC systems under long-term thermal effects. In this work, we present in detail several numerical methods to model the thermomechanically coupled responses of TBC systems, including a monolithic approach and two staggered approaches based on the isothermal split and the adiabatic split, respectively. We also demonstrate several finite element simulation techniques, such as the periodic boundary conditions and the adaptive mesh refinement, in the modeling of TBC systems. Through several numerical examples, we show that the staggered approach based on the adiabatic split preserves the unconditional stability of individual time integration techniques used for the mechanical phase and the thermal phase of the coupled problem. Moreover, the computational cost is significantly lower compared to the monolithic approach. This work provides an efficient time integration approach to model more complex behaviors of TBC systems under long-term thermal cycles. • Thermomechanically coupled responses of thermal barrier coating are investigated. • Time integration methods based on monolithic and staggered approaches are presented. • Staggered approach based on adiabatic split preserves unconditional stability. • Periodic boundary conditions and adaptive mesh refinement improve efficiency. • Stress concentration at interfaces inside thermal barrier coating is demonstrated. [ABSTRACT FROM AUTHOR]

Rock blasting is widely used in various engineering constructions. Local temperature rise in rock mass caused by the blasting load significantly influences the physical properties of rock materials. To simulate rock fracturing under blast loading, a fully coupled thermomechanical peridynamic (PD) model is presented and improved by volume correction, surface correction, and GPU parallel technique. An initial damage model is incorporated to consider the influence of the initial pore damage in rock mass on the fracture pattern under blast loading. Through three benchmark problems, the PD model is qualitatively and quantitatively validated against results obtained from FEM simulations. The initial damage induced by randomly distributed pores of rock mass is considered in the PD modeling of the granite fracture subjected different blast loads. The correlation between temperature distribution and crack pattern is analyzed, the results show that temperature influences both radial and circumferential crack expansion, and the initial pore damage can affect the crack and fracture patterns in granite specimen. [ABSTRACT FROM AUTHOR]

Due to the exponential growth in offshore renewable energies and structures such as floating offshore wind turbines and wave power converters, the research and engineering in this field is experiencing exceptional development. This emergence of offshore renewable energy requires power cables which are usually made up of copper to transport this energy ashore. These power cables are critical structures that must withstand harsh environmental conditions, handling, and shipping, at high seas which can cause copper wires to deform well above the limit of proportionality and consequently break. Copper, being an excellent electric conductor, has, however, very weak mechanical properties. If plasticity propagates inside copper not only will the mechanical properties be affected, but the electrical properties are also disrupted. Constantly monitoring such large-scale structures can be carried out by providing continuous strain using fiber-optic sensors (FOSs). The embedding of optical fibers within the cables (not within the phase) is practiced. Nevertheless, these optical fibers are first introduced into a cylinder of larger diameter than the optical fiber before this same fiber is embedded within the insulator surrounding the phases. Therefore, this type of embedding can in no way give a precise idea of the true deformation of the copper wires inside the phase. In this article, a set of numerical simulations are carried-out on a single phase (we are not yet working on the whole cable) with the aim of conceptualizing the placement of FOSs that will monitor strain and temperature within the conductor. It is well known that copper wire must never exceed temperatures above 90 °C, as this will result in shutdown of the whole system and therefore result in heavy maintenance, which would be a real catastrophe, economically speaking. This research explores the option of embedding sensors in several areas of the phase and how this can enable obtaining strain values that are representative of what really is happening in the conductor. It is, therefore, the primary objective of the current preliminary model to try to prove that the principle of embedding sensors in between copper wires can be envisaged, in particular to obtain an accurate idea about strain tensor of helical ones (multi-parameter strain sensing). The challenge is to ensure that they are not plastically deformed and hence able to transport electricity without exceeding or even becoming closer to 90 °C (fear of shutdown). The research solely focuses on mechanical aspects of the sensors. There are certainly some others, pertaining to sensors physics, instrumentation, and engineering, that are of prime importance, too. The upstream strategy of this research is to come up with a general concept that can be refined later by including, step by step, all the aspects listed above. [ABSTRACT FROM AUTHOR]

The mathematical model of thermomechanical coupling multi-objective topology optimization for anisotropic structures was established using the element-free Galerkin (EFG) method, and the weighted function of compliance and heat dissipation was defined as the objective function. The proposed model and procedure were verified by the topological results based on the finite element method. The multi-objective EFG optimal topological structures have clearer boundary profiles even without using the sensitivity filtering technique. The effects of the weight coefficient, thermal conductivity factor, Poisson's ratio factor, off-angle and volume fraction on the multi-objective EFG optimal topological structure and multi-objective function were evaluated in detail, and reasonable ranges of the above parameters were recommended to improve the heat dissipation and mechanical performance. The multi-objective optimal results of the anisotropic structure were 3D printed and compared with the isotropic material, and their temperature, displacement and stress were improved, which reflects the advantages of orthotropic structures. [ABSTRACT FROM AUTHOR]