Artykuły w czasopismach: „Coupled Thermomechanical Structures”

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Machairas, Theodoros T., Alexandros G. Solomou, Anargyros A. Karakalas i Dimitris A. Saravanos. "Effect of shape memory alloy actuator geometric non-linearity and thermomechanical coupling on the response of morphing structures". Journal of Intelligent Material Systems and Structures 30, nr 14 (10.07.2019): 2166–85. http://dx.doi.org/10.1177/1045389x19862362.

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The response of adaptive structures entailing shape memory alloy actuators is investigated both numerically and experimentally in this work. Emphasis is placed on the inclusion of large displacements and rotations, as well as thermomechanical coupling in the simulation of the shape memory alloy actuators. Reduced multi-field beam finite element models for shape memory alloy actuators, encompassing a co-rotational formulation for large displacements and capability to provide the thermomechanically coupled transient response, are briefly overviewed. Prototypes of two adaptive structure configurations are developed, experimentally characterized, and numerically modeled. The measured response of the two prototypes is correlated with respective numerical results that consider both the geometric non-linearity and the thermomechanical coupling of the shape memory alloy actuators. Hence, the influence of these two effects on the predicted response of both the actuator and the adaptive structure is demonstrated. The results quantify also the interactions between geometric non-linearity and thermomechanical coupling terms. As it is shown, better agreement with experimental data is obtained when considering both effects.

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Son, Myeong Jin, i Eui Sup Shin. "Thermomechanical Coupled Analysis of Carbon/phenolic Composite Structures in Reentry Environments". Journal of the Korean Society for Aeronautical & Space Sciences 47, nr 6 (30.06.2019): 414–21. http://dx.doi.org/10.5139/jksas.2019.47.6.414.

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Kundu, Animesh, i Atanu Banerjee. "Coupled thermomechanical modelling of shape memory alloy structures undergoing large deformation". International Journal of Mechanical Sciences 220 (kwiecień 2022): 107102. http://dx.doi.org/10.1016/j.ijmecsci.2022.107102.

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Baker, Graham, i René de Borst. "An anisotropic thermomechanical damage model for concrete at transient elevated temperatures". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 363, nr 1836 (10.10.2005): 2603–28. http://dx.doi.org/10.1098/rsta.2005.1589.

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The behaviour of concrete at elevated temperatures is important for an assessment of integrity (strength and durability) of structures exposed to a high-temperature environment, in applications such as fire exposure, smelting plants and nuclear installations. In modelling terms, a coupled thermomechanical analysis represents a generalization of the computational mechanics of fracture and damage. Here, we develop a fully coupled anisotropic thermomechanical damage model for concrete under high stress and transient temperature, with emphasis on the adherence of the model to the laws of thermodynamics. Specific analytical results are given, deduced from thermodynamics, of a novel interpretation on specific heat, evolution of entropy and the identification of the complete anisotropic, thermomechanical damage surface. The model is also shown to be stable in a computational sense, and to satisfy the laws of thermodynamics.

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Li, Zhenghong, Yuheng Liu, Yafei Wang, Haibao Lu, Ming Lei i Yong Qing Fu. "3D Printing of Auxetic Shape-Memory Metamaterial Towards Designable Buckling". International Journal of Applied Mechanics 13, nr 01 (styczeń 2021): 2150011. http://dx.doi.org/10.1142/s1758825121500113.

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As one of the most popular 3D printed metamaterials, the auxetic structure with its tunable Poisson’s ratio has attracted huge amount of attention recently. In this study, we designed an auxetic shape-memory metamaterial, which showed designable buckling responses by using the thermomechanically coupled in-plane instability. The influence of viscoelasticity on in-plane moduli and Poisson’s ratios of shape-memory auxetic metamaterial was experimentally investigated. Based on the generalized Maxwell model and finite-element method, the buckling behaviors and their main influence factors were studied. The analytical results and experimental ones showed a good agreement. Thermomechanical properties of the printed metamaterials govern the temperature and strain rate-dependent buckling, and a controllable transition from the negative to positive Poisson’s ratio in the metamaterials can be achieved. Based on the shape memory effect, the buckled state and the Poisson’s ratio of the metamaterials can be tuned by programmed thermomechanical processes. This study provides a simple and efficient way to generate morphing structures using the designable buckling effect.

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Ma, Zhu, Changzheng Shi, Hegao Wu i Songzi Liu. "Structural Behavior of Massive Reinforced Concrete Structures Exposed to Thermomechanical Loads". Energies 15, nr 7 (6.04.2022): 2671. http://dx.doi.org/10.3390/en15072671.

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Massive reinforced concrete (MRC) structures are utilized in a variety of applications where both mechanical and thermal properties are of concern. A 1:2 large-scale test model of the steel-lined reinforced concrete penstock (a kind of MRC) and a coupled thermomechanical numerical analysis are both implemented to investigate the thermomechanical effects on structural behavior. Three different temperature fields and eight temperature gradients are selected to explore how the temperature affects the crack width, steel stress, and deformation. The results show that the numerical simulation results are consistent with the experimental results and that this method can be applied to other similar MRC structure analysis. The thermal effect can cause 10−3~10−2 mm thermal crack width and ±45 MPa thermal stress and this may lead the total crack width to exceed the limited value and the reinforcement stress beyond the yield strength. Consequently, the influence of the thermomechanical loads cannot be ignored and the corresponding temperature control measures must be taken to ensure structural safety and durability.

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Xu, Chenglong, i Zhi Liu. "Coupled CFD-FEM Simulation of Steel Box Bridge Exposed to Fire". Advances in Civil Engineering 2022 (10.01.2022): 1–12. http://dx.doi.org/10.1155/2022/5889743.

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Increasing fire-induced bridge failures are demanding more precise behavior prediction for the bridges subjected to fires. However, current numerical methods are limited to temperature curves prescribed for building structures, which can misestimate the fire impact significantly. This paper developed a framework coupling the computational dynamics (CFD) method and finite element method (FEM) to predict the performance of fire-exposed bridges. The fire combustion was simulated in CFD software, Fire Dynamic Simulator, to calculate the thermal boundary required by the thermomechanical simulation. Then, the adiabatic surface temperatures and heat transfer coefficient were applied to the FEM model of the entire bridge girder. A sequential coupled thermomechanical FEM simulation was then carried out to evaluate the performance of the fire-exposed bridge, thermally and structurally. The methodology was then validated through a real fire experiment on a steel beam. The fire performance of a simply supported steel box bridge was simulated using the proposed coupled CFD-FEM methodology. Numerical results show that the presented method was able to replicate the inhomogeneous thermomechanical response of box bridges exposed to real fires. The girder failed due to the buckling of a central diaphragm after the ignition of the investigated tanker fire in no more than 10 min. The framework presented in this study is programmatic and friendly to researchers and can be applied for the estimation of bridges in different fire conditions.

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Song, Ying, Renwei Liu, Shaofan Li, Zhuang Kang i Feng Zhang. "Peridynamic modeling and simulation of coupled thermomechanical removal of ice from frozen structures". Meccanica 55, nr 4 (19.12.2019): 961–76. http://dx.doi.org/10.1007/s11012-019-01106-z.

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Wang, Lixiang, Shihai Li, Guoxin Zhang, Zhaosong Ma i Lei Zhang. "A GPU-Based Parallel Procedure for Nonlinear Analysis of Complex Structures Using a Coupled FEM/DEM Approach". Mathematical Problems in Engineering 2013 (2013): 1–15. http://dx.doi.org/10.1155/2013/618980.

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This study reports the GPU parallelization of complex three-dimensional software for nonlinear analysis of concrete structures. It focuses on coupled thermomechanical analysis of complex structures. A coupled FEM/DEM approach (CDEM) is given from a fundamental theoretical viewpoint. As the modeling of a large structure by means of FEM/DEM may lead to prohibitive computation times, a parallelization strategy is required. With the substantial development of computer science, a GPU-based parallel procedure is implemented. A comparative study between the GPU and CPU computation results is presented, and the runtimes and speedups are analyzed. The results show that dramatic performance improvements are gained from GPU parallelization.

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Tong, Fujuan, Wenxuan Gou, Lei Li, Wenjing Gao i Zhu Feng Yue. "Thermomechanical stress analysis for gas turbine blade with cooling structures". Multidiscipline Modeling in Materials and Structures 14, nr 4 (3.12.2018): 722–34. http://dx.doi.org/10.1108/mmms-08-2017-0081.

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Purpose Blade tip clearance has always been a concern for the gas turbine design and control. The numerical analysis of tip clearance is based on the turbine components displacement. The purpose of this paper is to investigate the thermal and mechanical effects on a real cooling blade rather than the simplified model. Design/methodology/approach The coupled fluid-solid method is used. The thermal analysis involves solid and fluid domains. The distributions of blade temperature, stress and displacement have been calculated numerically under real turbine operating conditions. Findings Temperature contour can provide a reference for stress analysis. The results show that temperature gradient is the main source of solid stress and radial displacement. Compared with thermal or mechanical effect, there is a great change of stress magnitude for the thermomechanical effect. Large stress gradients are found between the leading and trailing edge of turbine cooling blade. Also, the blade radial displacement is mainly attributed to the thermal load rather than the centrifugal force. The analysis of the practical three-dimensional model has achieved the more precise results. Originality/value It is significant for clearance design and life prediction.

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Darcourt, C., J. M. Roelandt, M. Rachik, D. Deloison i B. Journet. "Thermomechanical analysis applied to the laser beam welding simulation of aeronautical structures". Journal de Physique IV 120 (grudzień 2004): 785–92. http://dx.doi.org/10.1051/jp4:2004120091.

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The present work is being done in the framework of a national program about the lightening of aeronautical structures and describes a three-dimensional finite element simulation of the laser beam welding process. The targeted aeronautical structures are stiffened panels in aluminum alloys, which tend to replace riveted assemblies. Semi-coupled thermomechanical finite element analyses have been carried out to evaluate the magnitude and distribution of welding-induced residual stresses in order to take them into account for fatigue sizing. The finite element code MSC.Marc is used for the different calculations. Specific welding features have been added to the code through the implementation of a moving heat source or an elastoviscoplastic law. Experimental tests have been carried out in order to provide mechanical and thermal databases to the model. Monitored experimental welding have been made for comparisons with the simulation. In particular, results of thermocouple measurements have permitted to improve the thermal model.

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Benelfellah, Abdelkibir, Damien Halm, Denis Bertheau, Pascal Boulet, Zoubir Acem, Damien Brissinger i Thomas Rogaume. "Effect of a coupled thermomechanical loading on the residual mechanical strength and on the surface temperature of wound carbon/epoxy composite". Journal of Composite Materials 51, nr 22 (11.01.2017): 3137–47. http://dx.doi.org/10.1177/0021998316688339.

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Wound composite structures such as hyperbaric hydrogen tanks may experience accidental situations, for example in case of a fire. The FCH-JU project FireComp aims at better characterizing the conditions that need to be achieved in order to avoid a failure of a composite pressure vessel. This research program involves specific experiments to improve the understanding of loss of strength of composite high-pressure vessels in fire conditions. The present study investigates the effect of a coupled thermomechanical loading (cone calorimeter exposure and, simultaneously, mechanical stress) on the residual strength of a composite material. A specific device combining a cone and a four-point bending bench has been designed. The influence of the coupled aggression is addressed by comparing the temperature on the front and the rear sides, the mass loss, and the residual tensile strength of a set of samples subjected to a heat flux only and a set subjected to a heat flux and a four-point bending. The results do not exhibit a clear effect of the mechanical load: the thermomechanical properties of both sets of samples are similar.

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Katunin, Andrzej. "Analysis of influence of fibre type and orientation on dynamic properties of polymer laminates for evaluation of their damping and self-heating". Science and Engineering of Composite Materials 24, nr 3 (1.05.2017): 387–99. http://dx.doi.org/10.1515/secm-2014-0415.

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AbstractIn the following study, the dynamic behaviour of polymer laminates reinforced by glass and carbon fibres with different orientations was considered for several excitation frequencies and elevated temperatures. The obtained dynamic moduli, loss factors and glass-transition temperatures were used for the evaluation of damping capabilities and the self-heating phenomenon. In order to evaluate the influence of a fibre type, additional studies for a pure matrix were carried out and used in the analysis as the reference. The obtained results show significant differences both in thermal and dynamic mechanical properties with respect to a fibre type and its orientation, which has a direct influence on the analysed self-heating and damping phenomena. The results of the present study could be used for the design of composite properties with respect to thermal degradation resulting from coupled thermomechanical loading conditions. Several hypotheses on the influence of a heating rate on estimation of the thermomechanical properties as well as structural degradation of composites in such conditions were presented with appropriate discussion and argumentation. The present study has a preliminary character. Furthermore, it is planned to perform such tests for specimens with a low cross-linking degree in order to analyse its influence on the resulting thermomechanical response of fibre-reinforced composite structures.

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Apalowo, RK, D. Chronopoulos, M. Ichchou, Y. Essa i F. Martin De La Escalera. "The impact of temperature on wave interaction with damage in composite structures". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 231, nr 16 (sierpień 2017): 3042–56. http://dx.doi.org/10.1177/0954406217718217.

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The increased use of composite materials in modern aerospace and automotive structures, and the broad range of launch vehicles’ operating temperature imply a great temperature range for which the structures has to be frequently and thoroughly inspected. A thermal mechanical analysis is used to experimentally measure the temperature-dependent mechanical properties of a composite layered panel in the range of −100 ℃ to 150 ℃. A hybrid wave finite element/finite element computational scheme is developed to calculate the temperature-dependent wave propagation and interaction properties of a system of two structural waveguides connected through a coupling joint. Calculations are made using the measured thermomechanical properties. Temperature-dependent wave propagation constants of each structural waveguide are obtained by the wave finite element approach and then coupled to the fully finite element described coupling joint, on which damage is modelled, in order to calculate the scattering magnitudes of the waves interaction with damage across the coupling joint. The significance of the panel’s glass transition range on the measured and calculated properties is emphasised. Numerical results are presented as illustration of the work.

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Apalowo, Rilwan Kayode, Dimitrios Chronopoulos i Muhammed Malik. "The influence of temperature on wave scattering of damaged segments within composite structures". MATEC Web of Conferences 211 (2018): 19005. http://dx.doi.org/10.1051/matecconf/201821119005.

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The increased use of composite materials in modern aerospace and automotive structures, and the broad range of launch vehicles’ operating temperature imply a great temperature range for which the structures has to be frequently and thoroughly inspected. A thermal mechanical analysis is used to experimentally measure the temperature-dependent mechanical properties of a composite layered panel in the range of -100°C to 150°C. A hybrid wave finite element/finite element computational scheme is developed to calculate the temperature-dependent wave propagation and interaction properties of a system of two structural waveguides connected through a coupling joint. Calculations are made using the measured thermomechanical properties. Temperaturedependent wave propagation constants of each structural waveguide are obtained by the wave finite element approach and then coupled to the fully finite element described coupling joint, on which damage is modelled, in order to calculate the scattering magnitudes of the waves interaction with damage across the coupling joint. The significance of the panel’s glass transition range on the measured and calculated properties is emphasised. Numerical results are presented as illustration of the work.

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Baqasah, Hamzah, Feiyang He, Behzad A. Zai, Muhammad Asif, Kamran A. Khan, Vijay K. Thakur i Muhammad A. Khan. "In-Situ Dynamic Response Measurement for Damage Quantification of 3D Printed ABS Cantilever Beam under Thermomechanical Load". Polymers 11, nr 12 (12.12.2019): 2079. http://dx.doi.org/10.3390/polym11122079.

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Acrylonitrile butadiene styrene (ABS) offers good mechanical properties and is effective in use to make polymeric structures for industrial applications. It is one of the most common raw material used for printing structures with fused deposition modeling (FDM). However, most of its properties and behavior are known under quasi-static loading conditions. These are suitable to design ABS structures for applications that are operated under static or dead loads. Still, comprehensive research is required to determine the properties and behavior of ABS structures under dynamic loads, especially in the presence of temperature more than the ambient. The presented research was an effort mainly to provide any evidence about the structural behavior and damage resistance of ABS material if operated under dynamic load conditions coupled with relatively high-temperature values. A non-prismatic fixed-free cantilever ABS beam was used in this study. The beam specimens were manufactured with a 3D printer based on FDM. A total of 190 specimens were tested with a combination of different temperatures, initial seeded damage or crack, and crack location values. The structural dynamic response, crack propagation, crack depth quantification, and their changes due to applied temperature were investigated by using analytical, numerical, and experimental approaches. In experiments, a combination of the modal exciter and heat mats was used to apply the dynamic loads on the beam structure with different temperature values. The response measurement and crack propagation behavior were monitored with the instrumentation, including a 200× microscope, accelerometer, and a laser vibrometer. The obtained findings could be used as an in-situ damage assessment tool to predict crack depth in an ABS beam as a function of dynamic response and applied temperature.

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Guillaume, Helbert, Dieng Lamine, Chirani Shabnam Arbab i Pilvin Philippe. "Influence of the thermomechanical behavior of NiTi wires embedded in a damper on its damping capacity: Application to a bridge cable". AIMS Materials Science 10, nr 1 (2022): 1–25. http://dx.doi.org/10.3934/matersci.2023001.

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<abstract><p>Thanks to high dissipation properties, embedding NiTi Shape Memory Alloys in passive damping devices is effective to mitigate vibrations in building and cable structures. These devices can inconceivably be tested directly on full-scale experimental structures or on structures in service. To predict their effectiveness and optimize the set-up parameters, numerical tools are more and more developed. Most of them consist of Finite Element models representing the structure equipped with the damping device, embedding parts associated with a superelastic behavior. Generally, the implemented behavior laws do not include all the phenomena at the origin of strain energy dissipation, but stress-induced martensitic transformation only. This article presents a thermomechanical behavior law including the following phenomena: (i) intermediate R-phase transformation, (ii) thermal effects and (iii) strain localization. This law was implemented in a commercial Finite Element code to study the dynamic response of a bridge cable equipped with a NiTi wire-based damping device. The numerical results were compared to full-scale experimental ones, by considering the above-mentioned phenomena taken coupled or isolated: it has been shown that it is necessary to take all of these phenomena into account in order to successfully predict the damping capacity of the device.</p></abstract>

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HUANG, HUI, JIAN CHEN, ZHILI FENG, HUI-PING WANG, WAYNE CAI i BLAIR E. CARLSON. "Large-Scale Welding Process Simulation by GPU Parallelized Computing". Welding Journal 100, nr 11 (1.11.2021): 359–70. http://dx.doi.org/10.29391/2022.101.032.

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The computational design of industrially relevant welded structures is extremely time consuming due to coupled physics and high nonlinearity. Previously, most welding distortion and residual stress simulations have been limited to small coupons and reduced order (from three-dimensional [3D] to two-dimensional [2D]), or inherent strain approximations were used for large structures. In this current study, an explicit finite element code based on a graphics processing unit was utilized to perform 3D transient thermomechanical simulation of structural components during welding. Laser brazing of aluminum alloy panels as representative of automotive manufacturing scenarios was simulated to predict out-of-plane distortion under different clamping conditions. The predicted deformation pattern and magnitude were validated by laser scanning data of physical assemblies. In addition, the code was used to investigate residual stresses developed during multipass arc welding of a nuclear industry pressurizer surge nozzle and subsequent welding repair where a 3D simulation was necessary. Taking the experimental data as reference, the 3D model predicted better residual stress distribution than a typical 2D asymmetrical model. Stress evolution in welding repair was also presented and discussed in this study. The efficient numerical model made it feasible to use integrated computational welding engineering to simulate welding processes for large-scale structures.

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Nguyen, Ngoc, Christopher Bowland, Peter Bonnesen, Kenneth Littrell, Jong Keum i Amit Naskar. "Fractionation of Lignin for Selective Shape Memory Effects at Elevated Temperatures". Materials 13, nr 8 (20.04.2020): 1940. http://dx.doi.org/10.3390/ma13081940.

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We report a facile approach to control the shape memory effects and thermomechanical characteristics of a lignin-based multiphase polymer. Solvent fractionation of a syringylpropane-rich technical organosolv lignin resulted in selective lignin structures having excellent thermal stability coupled with high stiffness and melt-flow resistance. The fractionated lignins were reacted with rubber in melt-phase to form partially networked elastomer enabling selective programmability of the material shape either at 70 °C, a temperature that is high enough for rubbery matrix materials, or at an extremely high temperature, 150 °C. Utilizing appropriate functionalities in fractionated lignins, tunable shape fixity with high strain and stress recovery, particularly high-stress tolerance were maintained. Detailed studies of lignin structures and chemistries were correlated to molecular rigidity, morphology, and stress relaxation, as well as shape memory effects of the materials. The fractionation of lignin enabled enrichment of specific lignin properties for efficient shape memory effects that broaden the materials’ application window. Electron microscopy, melt-rheology, dynamic mechanical analysis and ultra-small angle neutron scattering were conducted to establish morphology of acrylonitrile butadiene rubber (NBR)-lignin elastomers from solvent fractionated lignins.

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Bencheikh, I., F. Bilteryst i M. Nouari. "Modelling of the thermomechanical behaviour of coated structures using single and multi-level-set techniques coupled with the eXtended Finite Element Method". Finite Elements in Analysis and Design 134 (październik 2017): 68–81. http://dx.doi.org/10.1016/j.finel.2017.06.001.

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Salem, Brahim, Ali Mkaddem, Sami Ghazali, Malek Habak, Bassem F. Felemban i Abdessalem Jarraya. "Towards an Advanced Modeling of Hybrid Composite Cutting: Heat Discontinuity at Interface Region". Polymers 15, nr 8 (20.04.2023): 1955. http://dx.doi.org/10.3390/polym15081955.

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In this study, a thermomechanical model is developed to simulate a finite drilling set of Carbon Fibre Reinforced Polymers (CFRP)/Titanium (Ti) hybrid structures widely known for their energy saving performance. The model applies different heat fluxes at the trim plane of the two phases of the composite, owing to cutting forces, in order to simulate the temperature evolution at the workpiece during the cutting step. A user-defined subroutine VDFLUX was implemented to address the temperature-coupled displacement approach. A user-material subroutine VUMAT was developed to describe Hashin damage-coupled elasticity model for the CFRP phase while Johnson–Cook damage criteria was considered for describing the behavior of titanium phase. The two subroutines coordinate to evaluate sensitively the heat effects at the CFRP/Ti interface and within the subsurface of the structure at each increment. The proposed model has been first calibrated based on tensile standard tests. The material removal process was then investigated versus cutting conditions. Predictions show discontinuity in temperature field at interface that should further favor damage to localize especially at CFRP phase. The obtained results highlight the significant effects of fibre orientation in dominating cutting temperature and thermal effects over the whole hybrid structure.

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Waltz, Laurent, Delphine Retraint i Arjen Roos. "Semi-Massive Nanocrystallised Composites: From the Process to Mechanical and Microstructural Investigations". Materials Science Forum 762 (lipiec 2013): 487–92. http://dx.doi.org/10.4028/www.scientific.net/msf.762.487.

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The aim of the present study is first to describe an original process, the so called duplex process, whose feature is the coupling between the well-known SMAT (Surface Mechanical Attrition Treatment) and the traditional co-rolling. The first step of this process consists of SMA-Treatment of 316L stainless steel sheets to generate nanocrystalline layers on their top surfaces according to the grain refinement mechanism of austenitic steels which is well described in the literature. During the second step, three treated sheets are co-rolled at 550°C to obtain a semi-massive nanocrystallised multilayer structure with improved mechanical strength alternating nanocrystalline, transition and coarse grain layers. The second part of this work deals with the mechanical and the microstructural characterization of the as-obtained structures. Thus, sharp nanoindentation tests performed over the cross section of the laminates coupled with Transmission Electron Microscopy (TEM) confirm the presence of nanograins after the thermomechanical treatment. In addition, the enhanced yield strength demonstrated by tensile tests correlate well with the theoretical volume fractions of nanoand transition layers. The interface cohesion between the sheets is tested by three-point bending tests and the interface bonding is evaluated by microstructural observations.

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Holanda, Samuell A., Antonio A. Silva, Carlos J. de Araújo i Alberdan S. de Aquino. "Study of the Complex Stiffness of a Vibratory Mechanical System with Shape Memory Alloy Coil Spring Actuator". Shock and Vibration 2014 (2014): 1–11. http://dx.doi.org/10.1155/2014/162781.

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The vibration control is an important area in the dynamic of structures that seeks to reduce the amplitude of structural responses in certain critical frequency ranges. Currently, the scientific development leads to the application of some actuators and sensors technologically superior comparing to the same features available on the market. For developing these advanced sensors and actuators, smart materials that can change their mechanical properties when subjected to certain thermomechanical loads can be employed. In this context, Shape memory alloys (SMAs) may be used for developing dynamic vibration dampers which are capable of acting on the system providing proper tuning of the excitation frequency and the natural frequency. This paper aims to analyze the behavior of the stiffness and damping of a SMA helical coil spring actuator coupled to a mechanical system of one degree of freedom (1 DOF) subjected to an unbalanced excitement force and a temperature control system. By analyzing the effect of these parameters on the structural response and considering the concept of complex stiffness, it can be possible to predict the system's behavior within certain acceptable ranges of vibration, already in the design phase.

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M. Abdullah, Fawaz, Saqib Anwar i Abdulrahman Al-Ahmari. "Thermomechanical Simulations of Residual Stresses and Distortion in Electron Beam Melting with Experimental Validation for Ti-6Al-4V". Metals 10, nr 9 (25.08.2020): 1151. http://dx.doi.org/10.3390/met10091151.

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Electron beam melting (EBM) is a relatively new process in three-dimensional (3D) printing to enable rapid manufacturing. EBM can manufacture metallic parts with thin walls, multi-layers, and complex internal structures that could not otherwise be produced for applications in aerospace, medicine, and other fields. A 3D transient coupled thermomechanical finite element (FE) model was built to simulate the temperature distribution, distortion, and residual stresses in electron beam additive manufactured Ti-6Al-4V parts. This research enhances the understanding of the EBM-based 3D printing process to achieve parts with lower levels of residual stress and distortion and hence improved quality. The model used a fine mesh in the layer deposition zone, and the mesh size was gradually increased with distance away from the deposits. Then, elements are activated layer by layer during deposition according to the desired material properties. On the top surface, a Gaussian distributed heat flux is used to model the heat source, and the temperature-dependent properties of the powder and solid are also included to improve accuracy. The current simulation has been validated by comparing the FE distortion and temperature results with the experimental results and other reported simulation studies. The residual stress results calculated by the FE analysis were also compared with the previously reported simulation studies on the EBM process. The results showed that the finite element approach can efficiently and accurately predict the temperature field of a part during the EBM process and can easily be extended to other powder bed fusion processes.

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Kang, Peng, Peng Wu, Yan Jin, Shengpeng Shi, Dali Gao, Guangxin Chen i Qifang Li. "Formation and Emissions of Volatile Organic Compounds from Homo-PP and Co-PP Resins during Manufacturing Process and Accelerated Photoaging Degradation". Molecules 25, nr 12 (15.06.2020): 2761. http://dx.doi.org/10.3390/molecules25122761.

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Volatile organic compounds (VOCs) from polypropylene (PP) seriously restricts the application of PP in an automotive field. Herein, the traceability of VOCs from PP resins during manufacturing process and accelerated photoaging degradation was clarified on basis of an accurate characterization method of key VOCs. The influence of PP structures on changing the accelerated photoaging degradation on the VOCs was systematic. The VOCs were identified by means of Gas chromatography (GC) coupled with both a hydrogen flame ion detector (FID) and a mass spectrometry detector (MSD). Results showed that both the molecular structure of PP and the manufacturing process affected the species and contents of VOCs. In addition, the photoaging degradation of PP resulted in a large number of new emerged volatile carbonyl compounds. Our work proposed a possible VOC formation mechanism during the manufacturing and photoaging process. VOCs from PP resins were originated from oligomers and chain random scission during thermomechanical degradation. However, β scission of alkoxy radical and Norrish tape I reactions of ketones via intermediate transition were probably the main VOCs formation routes towards PP during photoaging degradation. This work could provide scientific knowledge on both the accurate traceability of VOCs emissions and new technology for development of low-VOCs PP composites for vehicle.

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Nguyen Tien, Duong. "Numerical simulation for determination of temperature field and residual stress of stainless steel butt joints with and without clamping". Vietnam Journal of Science and Technology 60, nr 4 (31.08.2022): 713–25. http://dx.doi.org/10.15625/2525-2518/16486.

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Many welded structures are fabricated from stainless steels because these steels have good mechanical properties and good corrosion resistance. It is necessary to predict the residual stress after welding in order to evaluate the performance of the welded joint. In this paper, the butt welded joint of AISI 316L stainless steel plates is studied. The Metal Inert Gas (MIG) welding process is selected for this material. A SYSWELD software based on the Finite Element Method (FEM) is used to determine the temperature field and residual stresses of two stainless steel plates. The welding simulation includes a sequential coupled thermomechanical analysis. The elemental generation and death technique is utilized to simulate metal deposition in welding. The double ellipsoidal heat source model is used for the heat input of the MIG welding process. The temperature distribution for various time steps at some important points is presented. Cooling times and cooling rates over a temperature range of 800 oC to 500 oC at these points are determined. The residual stress distribution in the longitudinal and transverse direction in two cases with and without clamping is obtained and compared. Obtained results show that: the temperature field in the case of clamping is the same as in the case of no clamping; only the longitudinal stress and transverse stress components are important, the other stress components are not important; the longitudinal stress at the middle of weld line is very high; the transverse stress in the case of clamping is greatly increased, so it is necessary to limit clamping to reduce residual stress after welding

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Edmonds, D. V. "Advanced Bainitic and Martensitic Steels with Carbide-Free Microstructures Containing Retained Austenite". Materials Science Forum 638-642 (styczeń 2010): 110–17. http://dx.doi.org/10.4028/www.scientific.net/msf.638-642.110.

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Recent decades have witnessed some remarkable advances in engineering steels driven by the need to respond to challenges posed, for example, by recovery and transmission of oil and gas, or enhanced vehicle safety and fuel economy. Foremost amongst these must surely be the extended application of carbon steels, achieved principally through ferrite grain refinement by the practice of microalloying coupled with controlled thermomechanical processing. Limitations to strengthening ferrite/pearlite structures further by grain refinement or precipitation, however, has focused attention back to acicular forms of microstructure. One of the most interesting advances in this area has been the development of bainitic steels, which have been almost dormant since the mid-20th century. This resurgence may partly be attributed to a better appreciation of the bainite transformation mechanism, and the experimental work for this which unexpectedly spawned some interesting bainitic microstructures which have seen further development and application. These are the so-called ‘carbide-free’ bainites, which employ alloying to replace carbides, principally cementite, with carbon-stabilized retained austenite. Particularly noteworthy has been the emergence of the transformation induced plasticity (TRIP) sheet steels with enhanced properties principally targeted for automotive use. It is worth mentioning also that a parallel development has produced similar microstructure in austempered ductile irons (ADI), another important ferrous alloy which has seen recent expanding interest in its application. Even more recently, as we proceed into the 21st century, the concept of employing steel microstructures containing carbon-enriched retained austenite, has been developed further by combining both alloying and novel heat treatment procedures to exchange ‘bainitic’ ferrite with ‘martensitic’ ferrite. Interestingly, this non-equilibrium ‘quenching and partitioning’ process route also offers the possibility to increase the retained austenite carbon concentration to very high levels, potentially revealing new and previously unobtainable properties.

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Yankovskii, A. P. "MODELING OF THERMO-ELASTIC-VISCO-PLASTIC DEFORMATION OF SHALLOW METAL-COMPOSITE SHELLS USING THE REFINED THEORY OF BENDING". Problems of Strength and Plasticity 85, nr 1 (2023): 45–62. http://dx.doi.org/10.32326/1814-9146-2023-85-1-45-62.

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The dynamic problem of thermo-elastic-viscous-plastic deformation of shallow composite shells is formulated using the refined theory of bending. In this case, tangential displacements along the thickness of constructions are approximated by polynomials of the third and higher orders, and the deflection does not depend on the transverse coordinate. Normal transverse stresses in the composition have a linear distribution over the thickness. The temperature over the thickness of the curved panels is approximated by a 7th order polynomial. The geometric nonlinearity of the problem is taken into account in the Karman approximation. The constructions are multidirectionally reinforced with continuous fibres. The composition materials are isotropic; their plastic deformation is described by the flow theory with isotropic hardening, and the loading function depends on temperature and strain rate. The numerical solution of the coupled nonlinear two-dimensional initial-boundary value problem is obtained using an explicit scheme. Elastic-viscous-plastic, thermo-elastic-plastic and thermo-elastic-viscous-plastic response of a metal-composite cylindrical shallow shell of a rectangular shape with an orthogonal 2D-reinforcement structure has been studied. The construction is frontally loaded with an air blast wave. It has been demonstrated that curved metal-composite panels under such loading must be calculated, taking into account the temperature response that occurs in them and the sensitivity of the plastic properties of the composite materials to the rate of their deformation. In this case, it is necessary to apply the refined theory of bending of shallow shells, and not its simplest version, the Ambartsumian theory. A more intense thermomechanical response of a curved panel is observed when it is dynamically loaded from the convex front surface. In this case, at individual points of the construction, the temperature can briefly increase by 200 °C. It has been found that under dynamic loading of shallow shells from the side of any face-surface, they snapping towards the concavity of thin-walled structures.

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Xiao, Li, Chao Zhang, Yang Liu, Mingrui Zhao, Guangzhe Zhang, Fenglei Du, Xiangyu Li i Dongjian Yu. "Field-Scale Experimental Study on Thermomechanical Behaviors of Super-Long and Large-Diameter Energy Piles under Liquefied Natural Gas Tank". Advances in Civil Engineering 2023 (3.08.2023): 1–13. http://dx.doi.org/10.1155/2023/2427773.

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In this work, field-scale experiments were carried out on two energy piles to investigate the mechanical behavior of the piles when subjected to thermomechanical loads under a liquefied natural gas tank. The results showed that the super-long and large-diameter energy pile exhibited a better heat transfer performance. After pile heating or cooling, the temperature in the mid-depth of the pile increased or decreased rapidly, and at the two ends, the temperature varied relatively slowly. Regarding the observed axial strain, energy pile 1 exhibited predominately compressive deformation during the coupled heating–loading process, while a certain tensile deformation was found near the pile toe of energy pile 2 during the coupled cooling–loading process. Moreover, for both energy piles, positive shaft resistances appeared predominately under both the pure mechanical and coupled thermomechanical conditions, and occasional and local occurrences of negative resistances could be related to the ground conditions on site. The settlement and bearing capacity values of the two energy piles were not significantly affected by the coupled thermomechanical loads, and thus, the serviceability of the gas tank would not diminish.

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Dimitrienko, Yuriy, Andrey Zakharov i Mikhail Koryakov. "Coupled problems of high-speed aerodynamics and thermomechanics of heat-shielding structures". Journal of Physics: Conference Series 1141 (grudzień 2018): 012094. http://dx.doi.org/10.1088/1742-6596/1141/1/012094.

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Angelov, T. A. "A thermomechanically coupled rolling problem with damage". Mechanics Research Communications 26, nr 3 (maj 1999): 287–93. http://dx.doi.org/10.1016/s0093-6413(99)00026-9.

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Lu, Weimiao, Cedric D’Mello i Ashraf Ayoub. "Coupled Thermomechanical Damage Modeling for Structural Steel in Fire Conditions". Journal of Structural Engineering 146, nr 7 (lipiec 2020): 04020127. http://dx.doi.org/10.1061/(asce)st.1943-541x.0002652.

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Bréthous, R., V. Nassiet i B. Hassoune-Rhabbour. "Models of Adhesive Bonding of Hybrid Structures". Key Engineering Materials 550 (kwiecień 2013): 143–55. http://dx.doi.org/10.4028/www.scientific.net/kem.550.143.

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Adhesives are often based on polymers materials. They are good candidates in order to manufacture adhesives joint because of their thermomechanical properties and their processing which is easier than other materials. Epoxy resins are widely used as adhesives joint. We can meet them in various industrial areas like car, spatial and aerospace domains. Because of numerous combinations between epoxy and amine chemical functions, these joints may be efficient at high or at low temperature. Indeed, close to their glassy transition temperature (Tg), exists an elastic modulus / ductility couple for which, shear stress is optimum: the Optimum Stress Zone (OSZ)[ which is restricted on limited temperatures range. Our study consists in formulating an epoxy amine joint able to be efficient on an extended temperatures rangei.e.a joint able to ensure a stress continuity over a large range of temperatures, for example-50°C to 100°C. To reach this objective, we propose an evolution of the Multi Adhesive Joints (MAJ): an adhesive joint presenting a gradient of mechanical properties. To make this adhesive joint formulation possible, its necessary to control kinetics diffusion at the adhesive scale (200μm to 500μm) between the low temperature adhesive (LTA) and the high temperature adhesive (HTA). The diffusion study will be carried out by using a rheometer. For such adhesive thickness, the rheometer compliance may have an influence on the results. Therefore, this present work proposes to identify and to set up the key parameters, which allow following kinetics diffusion in a rheometer for dimensions similar to those of bonding assembly, by checking the measurements are performed in the linear viscoelastic domain. In a first part, the morphological, mechanical and thermomechanical properties of the nanostructured thermosets versus time are performed. And, the second part will deal with the optimization of the key parameters by performing dynamic shear tests versus time on HTA and LTA samples in sight of kinetics diffusion study.

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Rega, Giuseppe, Eduardo Saetta i Valeria Settimi. "Modeling and nonlinear dynamics of thermomechanically coupled composite plates". International Journal of Mechanical Sciences 187 (grudzień 2020): 106106. http://dx.doi.org/10.1016/j.ijmecsci.2020.106106.

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Sato, Taijiro, i James J. Beaudoin. "Coupled AC impedance and thermomechanical analysis of freezing phenomena in cement paste". Materials and Structures 44, nr 2 (20.06.2010): 405–14. http://dx.doi.org/10.1617/s11527-010-9635-3.

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Wu, JiWei, XueGang Wang, Lin Song, ShouMing Zhong i WenFeng Yin. "Microannulus Formation Mechanism at the Cementing Interface of a Thermal Recovery Well during Cyclic Steam Injection". Advances in Civil Engineering 2020 (22.02.2020): 1–11. http://dx.doi.org/10.1155/2020/8217013.

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During the thermal recovery of heavy oil when using cyclic steam injection technology, a microannulus tends to form at the cementing interface subjected to high temperature and pressure during steam injection, and large temperature and pressure differences after injection can lead to wellbore integrity failure. In this study, a thermomechanical coupled finite element casing-cement-formation model of a thermal recovery wellbore is established. The deformation of the wellbore during both the steam injection stage and the steam shutdown stage is analyzed. The microannulus formation mechanism at the cementing interface of the wellbore is studied. During steam injection, under the large thermomechanical coupling load, the wellbore generates a high stress that leads to elastic-plastic deformation. In the steam shutdown stage, with the load on the wellbore decreasing, elastic deformation recovers mostly, while plastic deformation continues. If the plastic deformation is large enough, a microannulus will form at the cementing interface. Increasing the elastic moduli of the casing, cement, and the formation can enlarge their plastic deformation during steam injection. The increase of plastic deformation of the cement or formation can enlarge the microannulus of the casing-cement interface or the cement-formation interface correspondingly in the steam shutdown stage.

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Gao, Yan, i Selda Oterkus. "Fully coupled thermomechanical analysis of laminated composites by using ordinary state based peridynamic theory". Composite Structures 207 (styczeń 2019): 397–424. http://dx.doi.org/10.1016/j.compstruct.2018.09.034.

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Borzabadi Farahani, E., B. Sobhani Aragh, A. Sarhadi i D. Juhre. "A framework to model thermomechanical coupled of fracture and martensite transformation in austenitic microstructures". Thin-Walled Structures 183 (luty 2023): 110435. http://dx.doi.org/10.1016/j.tws.2022.110435.

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Du, Cong, Yiren Sun, Jingyun Chen, Changjun Zhou, Pengfei Liu, Dawei Wang i Markus Oeser. "Coupled Thermomechanical Damage Behavior Analysis of Asphalt Pavements Using a 2D Mesostructure-Based Finite-Element Method". Journal of Transportation Engineering, Part B: Pavements 147, nr 2 (czerwiec 2021): 04021012. http://dx.doi.org/10.1061/jpeodx.0000263.

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Belhocine, Ali, i Oday Ibraheem Abdullah. "Modeling and simulation of frictional disc/pad interface considering the effects of thermo-mechanical coupling". World Journal of Engineering 17, nr 6 (11.08.2020): 761–84. http://dx.doi.org/10.1108/wje-04-2020-0124.

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Purpose This study aims to investigate numerically a thermomechanical behavior of disc brake using ANSYS 11.0 which applies the finite element method (FEM) to solve the transient thermal analysis and the static structural sequentially with the coupled method. Computational fluid dynamics analysis will help the authors in the calculation of the values of the heat transfer (h) that will be exploited in the transient evolution of the brake disc temperatures. Finally, the model resolution allows the authors to visualize other important results of this research such as the deformations and the Von Mises stress on the disc, as well as the contact pressure of the brake pads. Design/methodology/approach A transient finite element analysis (FEA) model was developed to calculate the temperature distribution of the brake rotor with respect to time. A steady-state CFD model was created to obtain convective heat transfer coefficients (HTC) that were used in the FE model. Because HTCs are dependent on temperature, it was necessary to couple the CFD and FEA solutions. A comparison was made between the temperature of full and ventilated brake disc showing the importance of cooling mode in the design of automobile discs. Findings These results are quite in good agreement with those found in reality in the brake discs in service and those that may be encountered before in literature research investigations of which these will be very useful for engineers and in the design field in the vehicle brake system industry. These are then compared to experimental results obtained from literatures that measured ventilated discs surface temperatures to validate the accuracy of the results from this simulation model. Originality/value The novelty of the work is the application of the FEM to solve the thermomechanical problem in which the results of this analysis are in accordance with the realized and in the current life of the braking phenomenon and in the brake discs in service thus with the thermal gradients and the phenomena of damage observed on used discs brake.

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Noll, Isabelle, Thorsten Bartel i Andreas Menzel. "A computational phase transformation model for selective laser melting processes". Computational Mechanics 66, nr 6 (2.09.2020): 1321–42. http://dx.doi.org/10.1007/s00466-020-01903-4.

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AbstractSelective laser melting (SLM) has gained large interest due to advanced manufacturing possibilities. However, the growing potential also necessitates reliable predictions of structures in particular regarding their long-term behaviour. The constitutive and structural response is thereby challenging to reproduce, due to the complex material behaviour. This motivates the aims of this contribution: To establish a material model that accounts for the behaviour of the different phases occurring during SLM but that still allows the use of (basic) process simulations. In particular, the present modelling framework explicitly takes into account the mass fractions of the different phases, their mass densities, and specific inelastic strain contributions. The thermomechanically fully coupled framework is implemented into the software Abaqus. The numerical examples emphasise the capabilities of the framework to predict, e.g., the residual stresses occurring in the final part. Furthermore, a postprocessing of averaged inelastic strains is presented yielding a micromechanics-based motivation for inherent strains.

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Arshid, Ehsan, i Saeed Amir. "Size-dependent vibration analysis of fluid-infiltrated porous curved microbeams integrated with reinforced functionally graded graphene platelets face sheets considering thickness stretching effect". Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications 235, nr 5 (28.01.2021): 1077–99. http://dx.doi.org/10.1177/1464420720985556.

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Size-dependent vibration analysis of three-layered fluid-infiltrated porous curved microbeams, which are integrated with nanocomposite face sheets, is provided in this work. The effect of the fluids within the pores of the core is taken into consideration and the core’s thermomechanical properties vary across the thickness based on three different patterns. Also, the face sheets are made from epoxy, which are reinforced by graphene platelets as lightweight and high-stiffness reinforcements. Graphene platelets dispersion patterns are also considered, which obey three different functions, namely parabolic, linear, and uniform. Moreover, effective thermomechanical properties of the face sheets are determined with the aid of ERM and Halpin–Tsai micromechanical models. The microstructure is under thermal load and it is rested on Pasternak elastic foundation. In the polar coordinate system, the strains are determined for deep curved beams that lead to more accurate results. Based on a refined higher-order shear deformation theory, which includes four variables and considers the thickness stretching effect, and employing the modified couple stress theory for accounting the size effect, the differential motion equations are derived and via an analytical method, they are solved. A verification study is conducted by neglecting some parameters and after that, the results are presented and discussed in detail. It is seen that the porous core and nanocomposite face sheets material properties have significant effects on the vibrational response of the under consideration model. Up to now, no similar work in the available literature has been found, therefore, the results of this study can be considered as a benchmark for future ones. The outcomes of this study may help to design more efficient structures with the desired properties.

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43

Zeng, Hao, Zhimin Xie, Jianping Gu i Huiyu Sun. "A 1D thermomechanical network transition constitutive model coupled with multiple structural relaxation for shape memory polymers". Smart Materials and Structures 27, nr 3 (23.02.2018): 035024. http://dx.doi.org/10.1088/1361-665x/aaae29.

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Gu, Xiaojun, Weihong Zhang, Wael Zaki i Ziad Moumni. "An extended thermomechanically coupled 3D rate-dependent model for pseudoelastic SMAs under cyclic loading". Smart Materials and Structures 26, nr 9 (15.08.2017): 095047. http://dx.doi.org/10.1088/1361-665x/aa7c36.

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Xu, Rui, Céline Bouby, Hamid Zahrouni, Tarak Ben Zineb, Heng Hu i Michel Potier-Ferry. "A Multiscale Analysis on the Superelasticity Behavior of Architected Shape Memory Alloy Materials". Materials 11, nr 9 (17.09.2018): 1746. http://dx.doi.org/10.3390/ma11091746.

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In this paper, the superelasticity effects of architected shape memory alloys (SMAs) are focused on by using a multiscale approach. Firstly, a parametric analysis at the cellular level with a series of representative volume elements (RVEs) is carried out to predict the relations between the void fraction, the total stiffness, the hysteresis effect and the mass of the SMAs. The superelasticity effects of the architected SMAs are modeled by the thermomechanical constitutive model proposed by Chemisky et al. 2011. Secondly, the structural responses of the architected SMAs are studied by the multilevel finite element method (FE 2 ), which uses the effective constitutive behavior of the RVE to represent the behavior of the macroscopic structure. This approach can truly couple the responses of both the RVE level and structural level by the real-time information interactions between two levels. Through a three point bending test, it is observed that the structure inherits the strong nonlinear responses—both the hysteresis effect and the superelasticity—of the architected SMAs at the cellular level. Furthermore, the influence of the void fraction at the RVE level to the materials’ structural responses can be more specifically and directly described, instead of using an RVE to predict at the microscopic level. Thus, this work could be referred to for optimizing the stiffness, the hysteresis effect and the mass of architected SMA structures and extended for possible advanced applications.

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CHEN, HUI, i WENBIN YU. "SECONDARY INSTABILITY AND MODE JUMPING OF DEEP THERMOELASTICALLY BUCKLED COMPOSITE LAMINATES". International Journal of Structural Stability and Dynamics 07, nr 03 (wrzesień 2007): 457–86. http://dx.doi.org/10.1142/s021945540700237x.

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An analytic method is presented to study the secondary instability (bifurcation) and mode jumping of thermomechanically deep buckled composite laminates. Unlike most ad hoc approaches, the governing partial differential equations (PDEs) and constitutive relations are rigorously derived from an asymptotically correct, geometrically nonlinear theory. A novel and simpler solution approach is developed to solve the two coupled fourth-order PDEs, namely, the compatibility equation and the dynamic governing equation. The generalized Galerkin method is used to solve boundary value problems corresponding to antisymmetric angle-ply and cross-ply composite plates. The variety of possible modal interactions is expressed in an explicit and concise form by transforming the coupled nonlinear governing equations into a system of nonlinear ordinary differential equations (ODEs). The comparison between the present method and the finite element analysis (FEA) shows a pretty good match in their numerical results in the primary postbuckling region. While the FEA may lose its convergence when solution comes close the secondary bifurcation point, the analytic approach has the capability of exploring deeply into the post-secondary buckling realm and capture the mode jumping phenomenon for various combinations of plate configurations and in-plane boundary conditions. Qualitatively different propagations of buckling pattern are observed before and after mode jumping. Free vibration along the stable primary postbuckling and the jumped equilibrium paths are also studied.

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Skripnyak, Vladimir A., Kristina Iokhim, Evgeniya Skripnyak i Vladimir V. Skripnyak. "MODELING OF TITANIUM ALLOYS PLASTIC FLOW IN LINEAR FRICTION WELDING". Facta Universitatis, Series: Mechanical Engineering 19, nr 1 (1.04.2021): 091. http://dx.doi.org/10.22190/fume201225014s.

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The article presents the results of the analysis of the plastic flow of titanium alloys in the process of the Linear Friction Welding (LFW). LFW is a high-tech process for joining critical structural elements of aerospace engineering from light and high-temperature alloys. Experimental studies of LFW modes of such alloys are expensive and technically difficult. Numerical simulation was carried out for understanding the physics of the LFW process and the formation laws of a strong welded joint of titanium alloys. Simulation by the SPH method was performed using the LS DYNA software package (ANSYS WB 15.2) and the developed module for the constitutive equation. The new coupled thermomechanical 3D model of LFW process for joining structural elements from alpha and alpha + beta titanium alloys was proposed. It was shown that the formation of a welded joint occurs in a complex and unsteady stress-strain state. In the near-surface layers of the bodies being welded, titanium alloys can be deformed in the mode of severe plastic deformation. A deviation of the symmetry plane of the plastic deformation zone from the initial position of the contact plane of the bodies being welded occurs during a process of LFW. Extrusion of material from the welded joint zone in the transverse direction with respect to the movement of bodies is caused by a pressure gradient and a decrease in the alloy flow stress due to heating. The hcp-bcc phase transition of titanium alloys upon heating in the LFW process necessitates an increase in the cyclic loading time to obtain a welded joint.

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Goodpaster, Benjamin A., i Ryan L. Harne. "Analytical Modeling and Impedance Characterization of the Nonlinear Dynamics of Thermomechanically Coupled Structures". Journal of Applied Mechanics 85, nr 8 (4.06.2018). http://dx.doi.org/10.1115/1.4040243.

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In many applications, coupling between thermal and mechanical domains can significantly influence structural dynamics. Analytical approaches to study such problems have previously used assumptions such as a proscribed temperature distribution or one-way coupling to enable assessments. In contrast, time-stepping numerical simulations have captured more detailed aspects of multiphysics interactions at the expense of high computational demands and lack of insight of the underlying physics. To provide a new tool that closes the knowledge gap and broadens potential for analytical techniques, this research formulates and analytically solves a thermomechanical beam model considering a combination of thermal and mechanical excitations that result in extreme nonlinear behaviors. Validated by experimental evidence, the analytical framework facilitates the prediction of the nonlinear dynamics of multi-degree-of-freedom structures exhibiting two-way thermomechanical coupling. The analysis enables the investigation of mechanical and thermomechanical impedance metrics as a means to forecast future nonlinear dynamic behaviors such as extreme bifurcations. For the first time, characteristics of mechanical impedance previously reported to predict the onset of dynamic bifurcations in discrete systems are translated to illuminate the nearness of distributed parameter structures to bifurcations. In addition, fundamental connections are discovered in the thermomechanical evaluations between nonlinear low amplitude dynamics of the postbuckled beam and the energetic snap-through vibration that are otherwise hidden by studying displacement amplitudes alone.

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Mücke, Roland, i Klaus Rau. "Coupled Thermomechanical Fatigue Tests for Simulating Load Conditions in Cooled Turbine Parts". Journal of Engineering for Gas Turbines and Power 134, nr 5 (1.03.2012). http://dx.doi.org/10.1115/1.4004731.

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Modern heavy-duty gas turbines operate under hot gas temperatures that are much higher than the temperature capability of nickel superalloys. For that reason, advanced cooling technology is applied for reducing the metal temperature to an acceptable level. Highly cooled components, however, are characterized by large thermal gradients resulting in inhomogeneous temperature fields and complex thermomechanical load conditions. In particular, the different rates of stress relaxation due to the different metal temperatures on hot gas and cooling air exposed surfaces lead to load redistributions in cooled structures, which have to be considered in the lifetime prediction methodology. In this context, the paper describes coupled thermomechanical fatigue (CTMF) tests for simultaneously simulating load conditions on hot and cold surfaces of cooled turbine parts (Beck et al., 2001, “Experimental Analysis of the Interaction of Hot and Cold Volume Elements During Thermal Fatigue of Cooled Components Made From AISI 316 L Steel,” Z. Metallkunde, 92, pp. 875–881 and Rau et al., 2003, “Isothermal Thermo-mechanical and Complex Thermo-mechanical Fatigue Tests on AISI 316 L Steel—A Critical Evaluation,” Mater. Sci. Eng., A345, pp. 309–318). In contrary to standard thermomechanical fatigue (TMF) testing methods, CTMF tests involve the interaction between hot and cold regions of the parts and thus more closely simulates the material behavior in cooled gas turbine structures. The paper describes the methodology of CTMF tests and their application to typical load conditions in cooled gas turbine parts. Experimental results are compared with numerical predictions showing the advantages of the proposed testing method.

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Ji, Qingxiang, Johnny Moughames, Xueyan Chen, Guodong Fang, Juan J. Huaroto, Vincent Laude, Julio Andrés Iglesias Martínez i in. "4D Thermomechanical metamaterials for soft microrobotics". Communications Materials 2, nr 1 (9.09.2021). http://dx.doi.org/10.1038/s43246-021-00189-0.

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AbstractMetamaterials have attracted wide scientific interest to break fundamental bounds on materials properties. Recently, the field has been extending to coupled physical phenomena where one physics acts as the driving force for another. Stimuli-responsive or 4D metamaterials have been demonstrated for thermo-elasticity, magneto-optics or piezo-electricity. Herein, a soft, ultra-compact and accurate microrobot is described which can achieve controlled motion under thermal stimuli. The system consists of an organized assembly of two functional structures: a rotational and a translational element. Both elements are designed basing upon the principle of the thermoelastic bilayer plate that bends as temperature changes. Samples are fabricated using gray-tone lithography from a single polymer but with two different laser writing powers, making each part different in its thermal and mechanical behaviors. Excellent motion-controllable, reversible and stable features in a dry environment are verified by simulations and experiments, revealing broad application prospects for the designed soft micro actuators.

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