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1
RAHMAN, S. M. MUJIBUR, e SAMIRA SALEK. "THERMOMECHANICAL PROPERTIES OF CERTAIN ELEMENTAL CRYSTALS". International Journal of Modern Physics B 06, n. 18 (20 settembre 1992): 3069–77. http://dx.doi.org/10.1142/s0217979292002371.
Testo completoAbstract (sommario):
We have investigated the temperature variation of the Einstein temperatures and elastic constants of various metallic crystals. In this respect we have employed the interatomic pair potential involving pseudopotential and an appropriate exchange and correlation function. The temperature dependence of the properties concerned is taken into account through changes in the number densities. The systematic compilation of these thermomechanical properties may prove to be useful for various metallurgical purposes.
2
KARAOGLU, B., e S. M. MUJIBUR RAHMAN. "THERMOMECHANICAL PROPERTIES OF 3d TRANSITION METALS". International Journal of Modern Physics B 08, n. 11n12 (30 maggio 1994): 1639–54. http://dx.doi.org/10.1142/s0217979294000701.
Testo completoAbstract (sommario):
We have investigated the density variation of the Einstein temperatures and elastic constants of the 3d transition metals. In this respect we have employed the transition metal (TM) pair potentials involving the sp contribution with an appropriate exchange and correlation function, the d-band broadening contribution and the d-band hybridization term. These calculations are aimed at testing the TM pair potentials in generating the aforesaid quasilocal and local thermomechanical properties.
3
Zhang, Zhong, Wenjie Zhao, Ying Sun, Zhenyuan Gu, Wangping Qian e Hai Gong. "Thermoelastic Behaviors of Temperature-Dependent Multilayer Arches under Thermomechanical Loadings". Buildings 13, n. 10 (16 ottobre 2023): 2607. http://dx.doi.org/10.3390/buildings13102607.
Testo completoAbstract (sommario):
This work presents analytical solutions for thermoelastic behaviors of multilayer arches with temperature-dependent (TD) thermomechanical properties under thermomechanical loadings. The temperature is varied across the thickness of the arch. Firstly, an arched-slice model is developed, which divides every layer of the arch into numerous hypothetical arched slices with uniform thermomechanical properties. Based on the model, the nonlinear heat conduction equations across the thickness of the arch are solved using the iteration approach, and then the thermoelastic equations obtained from the two-dimensional thermoelasticity theory are solved using the state-space approach and transfer-matrix approach. The present solutions are compared with those obtained using the finite element method and the Euler–Bernoulli theory (EBT). It is found that the error of the EBT increases when the angle of the arch increases or the length-to-thickness ratio decreases. Finally, numerical examples are conducted to analyze the effects of surface temperature and TD thermomechanical properties on the temperature, displacement, and stress distributions of a sandwich arch. The results show that the temperature dependency of thermomechanical properties is a key parameter in predicting the thermoelastic behaviors of the arch in a high-temperature environment.
4
Zhang, Tao, Qiang Li, Jia-Jia Mao e Chunqing Zha. "Nonlinear Thermomechanical Low-Velocity Impact Behaviors of Geometrically Imperfect GRC Beams". Materials 17, n. 24 (11 dicembre 2024): 6062. https://doi.org/10.3390/ma17246062.
Testo completoAbstract (sommario):
This paper studies the thermomechanical low-velocity impact behaviors of geometrically imperfect nanoplatelet-reinforced composite (GRC) beams considering the von Kármán nonlinear geometric relationship. The graphene nanoplatelets (GPLs) are assumed to have a functionally graded (FG) distribution in the matrix beam along its thickness, following the X-pattern. The Halpin–Tsai model and the rule of mixture are employed to predict the effective Young modulus and other material properties. Dividing the impact process into two stages, the corresponding impact forces are calculated using the modified nonlinear Hertz contact law. The nonlinear governing equations are obtained by introducing the von Kármán nonlinear displacement–strain relationship into the first-order shear deformation theory and dispersed via the differential quadrature (DQ) method. Combining the governing equation of the impactor’s motion, they are further parametrically solved by the Newmark-β method associated with the Newton–Raphson iterative process. The influence of different types of geometrical imperfections on the nonlinear thermomechanical low-velocity impact behaviors of GRC beams with varying weight fractions of GPLs, subjected to different initial impact velocities, are studied in detail.
5
LIM, SHEAU HOOI, KAIYANG ZENG e CHAOBIN HE. "PREPARATION, MORPHOLOGY AND MECHANICAL PROPERTIES OF EPOXY NANOCOMPOSITES WITH ALUMINA FILLERS". International Journal of Modern Physics B 24, n. 01n02 (20 gennaio 2010): 136–47. http://dx.doi.org/10.1142/s021797921006406x.
Testo completoAbstract (sommario):
This paper presents recent studies on the processing and characterization of epoxy-alumina nanocomposites. Nano-sized alumina particles are incorporated into epoxy resin via solvent-assisted method, so that the particles are dispersed homogeneously in the epoxy matrix. The morphologies, mechanical and thermomechanical properties of the resulting nanocomposites are studied using transmission electron microscope (TEM), conventional tensile testing and thermomechanical testing methods. TEM results show that the alumina nano-particles with a higher specific surface area tend to agglomerate. Furthermore platelet shape particles shows a better dispersion homogeneity as well as better improvement in the mechanical properties of the composites compared to the rod shape particles.
6
Hadi, Abbas, Hamid Reza Ovesy, Saeed Shakhesi e Jamshid Fazilati. "Large Amplitude Dynamic Analysis of FGM Cylindrical Shells on Nonlinear Elastic Foundation Under Thermomechanical Loads". International Journal of Applied Mechanics 09, n. 07 (ottobre 2017): 1750105. http://dx.doi.org/10.1142/s1758825117501058.
Testo completoAbstract (sommario):
Nonlinear dynamic characteristics of functionally graded material (FGM) cylindrical shells surrounded by nonlinear elastic foundation under axial static and lateral dynamic loads in thermal environment are investigated in the current paper. The main emphasis is on the simulation of the elastic foundation model and thermal loads. Nonlinear tri-parametric elastic foundation including linear and nonlinear parameters is used to model the reaction of the elastic foundation on the cylindrical shell. Different thermal loading scenarios are applied to the system to study the effects of thermal environment, including uniform, linear and nonlinear temperature distribution across the shell thickness. Governing equations are derived based on the Donnell’s thin shell theory. Material properties of the FGM are assumed to be variable through the shell thickness according to a power law function. Discretization of the obtained governing equations is performed using the Galerkin’s method. An averaging method and the Runge–Kutta method are applied to obtain the frequency–amplitude relation and time–deflection relation, respectively. Comprehensive numerical results are given for investigating the effects of thermo-mechanical loads, material and geometrical properties and nonlinear elastic foundation parameters on nonlinear dynamic characteristics of the functionally graded cylindrical shells (FGCSs). Present formulations are validated by comparing the results with the published data for some specific cases.
7
Khorshidvand, A. R., e M. Jabbari. "Thermomechanical Analysis in FG Rotating Hollow Disk". Applied Mechanics and Materials 110-116 (ottobre 2011): 148–54. http://dx.doi.org/10.4028/www.scientific.net/amm.110-116.148.
Testo completoAbstract (sommario):
In this paper, mechanical and thermal stresses of rotating hollow disks composed of functionally graded materials (FGMs) is presented. The material properties for FG are expressed as nonlinear exponential functions through the radius of disk and Poisson’s ratio is taken to be constant. The temperature distribution is derived from first law thermodynamics by solving energy equation, general thermal and mechanical boundary conditions are assumed on the inside and outside surfaces of the disk. Heat conduction and Navier equations of a FGM disk are expressed in elliptic cylinder coordinates system and solved analytically. The results are shown for displacement and stresses components along the radial direction.
8
Dasgupta, A., e S. M. Bhandarkar. "Effective Thermomechanical Behavior of Plain-Weave Fabric-Reinforced Composites Using Homogenization Theory". Journal of Engineering Materials and Technology 116, n. 1 (1 gennaio 1994): 99–105. http://dx.doi.org/10.1115/1.2904262.
Testo completoAbstract (sommario):
A micromechanical analysis is presented to obtain the effective macroscale orthotropic thermomechanical behavior of plain-weave fabric reinforced laminated composites based on a two-scale asymptotic homogenization theory. The model is based on the properties of the constituents and an accurate, three-dimensional simulation of the weave microarchitecture, and is used for predicting the thermomechanical behavior of glass-epoxy (FR-4) woven-fabric laminates typically used by the electronics industry in Multilayered Printed Wiring Boards (MLBs). Parametric studies are conducted to examine the effect of varying fiber volume fractions on constitutive properties. Nonlinear constitutive behavior due to matrix nonlinearity and post-damage behavior due to transverse yarn failure under in-plane uniaxial loads is then investigated. Numerical results obtained from the model show good agreement with experimental values and with data from the literature. This model may be utilized by material designers to design and manufacture fabric reinforced composites with tailored effective properties such as elastic moduli, shear moduli, Poisson’s ratio, and coefficients of thermal expansion.
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Tabouret, V., B. Viana e J. Petit. "ZnGa2Se4, a nonlinear material with wide mid infrared transparency and good thermomechanical properties". Optical Materials: X 1 (gennaio 2019): 100007. http://dx.doi.org/10.1016/j.omx.2019.100007.
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Chamis, C. C., P. L. N. Murthy, S. N. Singhal e J. J. Lackney. "HITCAN for Actively Cooled Hot-Composite Thermostructural Analysis". Journal of Engineering for Gas Turbines and Power 114, n. 2 (1 aprile 1992): 315–20. http://dx.doi.org/10.1115/1.2906589.
Testo completoAbstract (sommario):
A computer code, HITCAN (High Temperature Composite Analyzer) has been developed to analyze/design hot metal matrix composite structures. HITCAN is a general purpose code for predicting the global structural and local stress-strain response of multilayered (arbitrarily oriented) metal matrix structures both at the constituent (fiber, matrix, and interphase) and the structure level and including the fabrication process effects. The thermomechanical properties of the constituents are considered to be nonlinearly dependent on several parameters, including temperature, stress, and stress rate. The computational procedure employs an incremental iterative nonlinear approach utilizing a multifactor-interaction material behavior model, i.e., the material properties are expressed in terms of a product of several factors that affect the properties. HITCAN structural analysis capabilities (static, load stepping—a multistep static analysis with material properties updated at each step, modal, and buckling) for cooled hot structures are demonstrated through a specific example problem.
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Shi, Hui Ji, Ya-Xiong Zheng, Ran Guo e Gerard Mesmacque. "Characterization of High Temperature Thermomechanical Fatigue Properties for Particle Reinforced Composites". Key Engineering Materials 297-300 (novembre 2005): 1495–502. http://dx.doi.org/10.4028/www.scientific.net/kem.297-300.1495.
Testo completoAbstract (sommario):
Voronoi cell finite element method (VCFEM) is introduced in this paper to describe the elastic-plastic-creep behavior of particle reinforced composites. The interfacial damage is simulated by partly debonding between Matrix and inclusion. A validation of the nonlinear behavior of the cell element has been carry out by comparing VCFEM results with those calculated by the general finite element package MARC and ABAQUS, and good agreements are found. A microstructure with five inclusions is taken as an example to describe the cyclic stress-strain behavior under different particulate orientation condition, and it shows the influence of the topological microstructure of inclusions. Thermomechanical fatigue properties are also investigated and the loops of stress-strain show the great differences of fatigue behavior between the in-phase case and out-of-case.
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Yavari, B., W. W. Tworzydlo e J. M. Bass. "A Thermomechanical Model to Predict the Temperature Distribution of Steady State Rolling Tires". Tire Science and Technology 21, n. 3 (1 luglio 1993): 163–78. http://dx.doi.org/10.2346/1.2139527.
Testo completoAbstract (sommario):
Abstract The thermomechanical behavior of pneumatic tires is a highly complex transient phenomenon that, in general, requires the solution of a dynamic nonlinear coupled thermoviscoelasticity problem with heat sources resulting from internal dissipation and contact and friction. This highly complex and nonlinear system requires indepth knowledge of the geometry, material properties, friction coefficients, dissipation mechanisms, convective heat transfer coefficients, and many other aspects of tire design that are not fully understood at the present time. In this paper, a simplified approach to modeling this system that couples all of these phenomena in a straightforward manner is presented in order to predict temperature distributions in static and rolling tires. The model is based on a one-way coupling approach, wherein the solution of a mechanical rolling contact problem (with friction and viscoelastic material properties) provides heat source terms for the solution of a thermal problem. The thermal solution is based on the thermodynamics of irreversible processes and is performed on the deformed tire configuration. Several numerical examples are provided to illustrate the performance of the method.
13
Alshammari, Yousef, Fei Yang e Leandro Bolzoni. "Thermomechanical powder processing of beta-eutectoid bearing near-alpha Ti alloys". International Journal of Modern Physics B 34, n. 01n03 (20 dicembre 2019): 2040030. http://dx.doi.org/10.1142/s0217979220400305.
Testo completoAbstract (sommario):
This work focuses on developing near-alpha Ti alloys via the selective addition of small concentrations of low-cost eutectoid [Formula: see text]-stabilizers like Cu and Mn. In particular, these newly designed near-alpha Ti alloys are manufactured via the cheapest powder metallurgy route of cold pressing plus sintering. Moreover, thermomechanical deformation of the sintered alloys via hot forging in the [Formula: see text] and [Formula: see text] field was also investigated aiming to enhance the mechanical properties through reduction of the residual porosity and microstructural control. It is found that the initial addition of a small amount of eutectoid [Formula: see text]-stabilizers leads to higher tensile properties with comprision to pure Ti produced by powder metallurgy, and this is due to the formation of a coarse lamellar structure due to the presence of [Formula: see text]-stabilizers. Further enhancement of the strength is achieved by means of hot thermomechanical processing thanks to sealing of the residual pores, texturing, and refinement of the microstructural features.
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JAGANNATHAN, N., e R. PALANINATHAN. "THERMOMECHANICAL MODELING OF ELECTRONIC PACKAGES". International Journal of Modeling, Simulation, and Scientific Computing 02, n. 01 (marzo 2011): 45–66. http://dx.doi.org/10.1142/s1793962311000384.
Testo completoAbstract (sommario):
This paper is concerned with an integrated thermomechanical modeling and analysis of electronic packages. As the technology advances in terms of speed and density of circuit within a chip, the power dissipation increases exponentially. The packages are subjected to heating during fabrication, testing, and service. Due to the heterogeneous construction with wide mismatch of material properties, thermal stresses are induced which would result in mechanical failures such as cracking and delamination. It is essential to analyze the packages for thermal and stress fields and check their compliance with the design requirements. Earlier investigations were mostly based on approximate models such as plane-stress, plane-strain, and axisymmetric conditions. In reality, none of the packages satisfies the conditions associated with these models. In this work, 3D solid finite element with variable nodes, 8–21 nodes per element is employed. Software has been developed with the following features: sequentially coupled thermomechanical modeling, nonlinear transient solution capability, incompatible mode option when 8-node brick element is used, better estimation of nodal stresses by transformation from gauss point stresses, and quadratic criterion for delamination failure. A flipchip has been analyzed using the software developed for their thermal and stress fields. Numerical results indicate: the junction temperatures exceed the specification limits for higher heat dissipation, if appropriate cooling is not applied. The stresses in the die corner and at the solder balls are critical. Three-dimensional modeling is necessary for estimation of the same. Appropriate failure criterion was used in the failure prediction.
15
Shojaei, Amir, e Guoqiang Li. "Thermomechanical constitutive modelling of shape memory polymer including continuum functional and mechanical damage effects". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 470, n. 2170 (8 ottobre 2014): 20140199. http://dx.doi.org/10.1098/rspa.2014.0199.
Testo completoAbstract (sommario):
A multi-mechanism-based phenomenological model is developed within the finite deformation kinematics framework for capturing the thermomechanical behaviour of shape memory polymers (SMPs) both during programming and in service. Particularly, the damage mechanisms in SMPs are studied within the continuum damage mechanics (CDMs) framework in which they are classified into mechanical or physical damage, induced during service condition, e.g. fatigue and functional damage induced during thermomechanical cycles, e.g. shape recovery loss. Statistical mechanics is incorporated to describe the initiation and saturation of these deformation mechanisms. The main advantage of the presented viscoplastic model, comparing to the existing counterparts, is its simplicity by minimizing the need for curve fitting, and capability in simulating the nonlinear stress–strain behaviour of amorphous, crystalline or semicrystalline SMPs. The developed viscoplastic CDM model takes into account several distinctive deformation mechanisms involved in the thermomechanical cycle of SMPs, including glass transition loss events, temperature-dependent material properties, stress relaxation, shape recovery transient events and damage effects. The established model correlates well with the experimental results and its computational capabilities provide material designers with a powerful design tool for future SMP applications.
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Kumar, G. Ramesh, S. Gokul Raj, Thenneti Raghavalu, V. Mathivanan, M. Kovendhan, R. Mohan e R. Jayavel. "Effect of pH, thermal, electrical and thermomechanical properties of nonlinear optical l-threonine single crystals". Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 68, n. 2 (ottobre 2007): 300–304. http://dx.doi.org/10.1016/j.saa.2006.11.033.
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Mehditabar, Aref, e Gholam H. Rahimi. "Numerical prediction of the elastoplastic response of FG tubes using nonlinear kinematic hardening rule with power-law function model under thermomechanical loadings". Engineering Computations 36, n. 1 (29 novembre 2018): 103–25. http://dx.doi.org/10.1108/ec-02-2018-0102.
Testo completoAbstract (sommario):
PurposeThis study aims to explain the characterization of cyclic behavior of a tube made of functionally graded material (FGM) under different combinations of internal pressure and cyclic through-thickness temperature gradients.Design/methodology/approachThe normality rule, nonlinear kinematic hardening Chaboche model and Von Mises yield criterion were used to model the constitutive behavior of an FG tube in the incremental form. The material properties and hardening parameters of the Chaboche model vary according to the power-law function in the radial direction. The backward Euler integration scheme combined with return mapping algorithm which relies on the solution of a nonlinear equation performs the numerical procedure. The algorithm is implemented within the user subroutine UMAT in ABAQUS/standard.FindingsThe published works on FG components considering only the mechanical and physical properties as a function of spatial coordinate and nonlinear kinematic hardening parameters have not been considered to be changed continuously from one surface to another. Motivated by this, the present paper has deliberately been targeted to tackle this kind of problem to simulate the cyclic behavior of an FG tube as accurately as possible. In addition, to classify various behaviors the FG tube under cyclic thermomechanical loadings, Bree’s interaction diagram as an essential tool in designing of the FG pressure vessels in many engineering sectors is presented.Originality/valueProvides a detailed description of the FG parameters of Chaboche kinematic hardening parameters in the adopted constitutive equations. In this paper, the significant effects of internal pressure values, kinematic hardening models and also FG inhomogeneity index related to the hardening rule parameters on plastic deformation of the FG tube are illustrated. Finally, the various cyclic behaviors of the FG tube under different combinations of thermomechanical loading are fully explored.
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Ebrahimi, Farzad, e Ali Jafari. "A Higher-Order Thermomechanical Vibration Analysis of Temperature-Dependent FGM Beams with Porosities". Journal of Engineering 2016 (2016): 1–20. http://dx.doi.org/10.1155/2016/9561504.
Testo completoAbstract (sommario):
In the present paper, thermomechanical vibration characteristics of functionally graded (FG) Reddy beams made of porous material subjected to various thermal loadings are investigated by utilizing a Navier solution method for the first time. Four types of thermal loadings, namely, uniform, linear, nonlinear, and sinusoidal temperature rises, through the thickness direction are considered. Thermomechanical material properties of FG beam are assumed to be temperature-dependent and supposed to vary through thickness direction of the constituents according to power-law distribution (P-FGM) which is modified to approximate the porous material properties with even and uneven distributions of porosities phases. The governing differential equations of motion are derived based on higher order shear deformation beam theory. Hamilton’s principle is applied to obtain the governing differential equations of motion which are solved by employing an analytical technique called the Navier type solution method. Influences of several important parameters such as power-law exponents, porosity distributions, porosity volume fractions, thermal effects, and slenderness ratios on natural frequencies of the temperature-dependent FG beams with porosities are investigated and discussed in detail. It is concluded that these effects play significant role in the thermodynamic behavior of porous FG beams.
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Romero, Carlos, Fei Yang e Leandro Bolzoni. "Influence of microstructure on the fatigue behavior of blended elemental Ti-6AL-4V alloy post-consolidated by extrusion". International Journal of Modern Physics B 34, n. 01n03 (11 novembre 2019): 2040025. http://dx.doi.org/10.1142/s0217979220400251.
Testo completoAbstract (sommario):
The blended elemental (BE) route is currently the main way for obtaining cost-affordable titanium alloys. Via post-consolidation processes like hot isostatic pressing (HIP) or thermomechanical processing, the material can improve its mechanical properties. In this work, a titanium alloy is processed via the BE approach, combined with thermomechanical processing of the sintered billets and subsequently heat treated. The tensile behavior of the sintered, extruded and heat-treated Ti-6Al-4V alloy was studied, finding an overall improvement of the properties after extrusion and a considerable increase in strength without compromising ductility after heat treatment. The high cycle fatigue behavior of the as-extruded alloy was studied by means of axial testing. There is a strong dependence between the location of the initiation of failure of the alloy and its fatigue life, but the defects that initiated failure were facets, not pores. The fatigue life of the as-extruded alloy is comparable to that of other fully-dense powder metallurgy (PM) and wrought Ti-6Al-4V alloys. These findings encourage the use of this route of processing as a balanced approach between low-cost and high-performance titanium alloys.
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Van Tung, Hoang. "Nonlinear thermomechanical response of pressure-loaded doubly curved functionally graded material sandwich panels in thermal environments including tangential edge constraints". Journal of Sandwich Structures & Materials 20, n. 8 (2 gennaio 2017): 974–1008. http://dx.doi.org/10.1177/1099636216684312.
Testo completoAbstract (sommario):
This paper investigates the nonlinear response of doubly curved functionally graded material sandwich panels resting on elastic foundations, exposed to thermal environments and subjected to uniform external pressure. The material properties of both face sheets and core layer are assumed to be temperature dependent, and effective material properties of functionally graded material layers are assumed to be graded in the thickness direction according to a simple power law distribution in terms of the volume fractions of the constituents. Formulations are based on first-order shear deformation shell theory taking geometrical nonlinearity, initial geometrical imperfection, Pasternak type elastic foundations, and tangential edge constraints into consideration. Approximate solutions are assumed to satisfy simply supported boundary conditions and Galerkin procedure is applied to derive expressions of buckling loads and nonlinear load–deflection relation. The effects of material, geometry and foundation parameters, face sheet thickness ratio, initial geometrical imperfection, thermal environments and degree of tangential restraint of edges on the snap-through instability, and nonlinear response of spherical and cylindrical functionally graded material sandwich panels are analyzed and discussed in detail.
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Trang, Le Thi Nhu, e Hoang Van Tung. "Nonlinear stability of CNT-reinforced composite cylindrical panels with elastically restrained straight edges under combined thermomechanical loading conditions". Journal of Thermoplastic Composite Materials 33, n. 2 (10 ottobre 2018): 153–79. http://dx.doi.org/10.1177/0892705718805134.
Testo completoAbstract (sommario):
This article investigates the nonlinear stability of composite cylindrical panels (CPs) reinforced by carbon nanotubes (CNTs), resting on elastic foundations and subjected to combined thermomechanical loading conditions. CNTs are embedded into matrix phase through uniform distribution or functionally graded distribution. Material properties of constituents are assumed to be temperature dependent and effective elastic moduli of carbon nanotube–reinforced composite are estimated by the extended rule of mixture. Nonlinear governing equations of geometrically imperfect panels are based on first-order shear deformation theory accounting for elastic foundations and tangential constraint of straight edges. Analytical solutions are assumed to satisfy simply supported boundary conditions and closed-form expressions relating load and deflection are derived through Galerkin method. Numerical examples show the effects of preexisting nondestabilizing loads, distribution patterns, panel curvature, in-plane condition of unloaded edges, thermal environments, initial imperfection, and elastic foundations on the nonlinear stability of nanocomposite CPs under combined loading conditions.
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Liao, L. L., e K. N. Chiang. "Nonlinear and Temperature-Dependent Material Properties of AU/SN Alloy for Power Module". Journal of Mechanics 33, n. 5 (15 maggio 2017): 663–72. http://dx.doi.org/10.1017/jmech.2017.21.
Testo completoAbstract (sommario):
AbstractIn recent years, the material Au-20Sn eutectic solder, which is resistant to high temperatures, is used for electric interconnections in high-power modules, the material properties such as temperature and strain rate dependent stress-strain curve are critically needed for reliability assessment of Au-20Sn solder joint. Thus, this study was performed to determine the material properties of Au-20Sn eutectic solder under various strain rates and temperature loads. Many researches using shear test to determine the shear resistance of solder joint, however, the mechanical strength as measured by the shear test is the maximum shear strength of the package joint, but this measurement does not represent the stress-strain behavior of Au-20Sn material. To identify the material properties of Au-20Sn eutectic solder, the tensile test was performed to measure its mechanical strength and nonlinear material properties. The strain rate effect was examined in terms of the influence of the mechanical strength on the Au-20Sn eutectic solder at different tensile rates. The temperature-dependent material properties of Au-20Sn solder were also measured under various thermal loadings, and material properties of Au-20Sn obtained in this research can be applied to the simulation model, the thermomechanical behavior and reliability of the power module can be further analyzed and evaluated.
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Monsorno, D., C. Varsakelis e M. V. Papalexandris. "A two-phase thermomechanical theory for granular suspensions". Journal of Fluid Mechanics 808 (2 novembre 2016): 410–40. http://dx.doi.org/10.1017/jfm.2016.649.
Testo completoAbstract (sommario):
In this paper, a two-phase thermomechanical theory for granular suspensions is presented. Our approach is based on a mixture-theoretic formalism and is coupled with a nonlinear representation for the granular viscous stresses so as to capture the complex non-Newtonian behaviour of the suspensions of interest. This representation has a number of interesting properties: it is thermodynamically consistent, it is non-singular and vanishes at equilibrium and it predicts non-zero granular bulk viscosity and shear-rate-dependent normal viscous stresses. Another feature of the theory is that the resulting model incorporates a rate equation for the evolution of the volume fraction of the granular phase. As a result, the velocity fields of both the granular material and the carrier fluid are divergent even for constant-density flows. Further, in this article we present the incompressible limit of our model which is derived via low-Mach-number asymptotics. The reduced equations for the important special case of constant-density flows are also presented and discussed. Finally, we apply the proposed model to two test cases, namely, steady shear flow of a homogeneous suspension and fully developed pressure-driven channel flow, and compare its predictions with available experimental and numerical results.
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Trang, Le Thi Nhu, e Hoang Van Tung. "Thermomechanical nonlinear stability of pressure-loaded CNT-reinforced composite doubly curved panels resting on elastic foundations". Nonlinear Engineering 8, n. 1 (28 gennaio 2019): 582–96. http://dx.doi.org/10.1515/nleng-2018-0077.
Testo completoAbstract (sommario):
Abstract Nonlinear stability of nanocomposite spherical and cylindrical panels reinforced by carbon nanotubes (CNTs), resting on elastic foundations and subjected to uniform external pressure in thermal environments is investigated in this paper. CNTs are embedded into matrix phase through uniform distribution (UD) or functionally graded (FG) distribution, and effective properties of CNT-reinforced composite are estimated through an extended rule of mixture. Governing equations are based on classical shell theory taking geometrical nonlinearity, initial geometrical imperfection and panel-foundation interaction into consideration. Approximate solutions of deflection and stress functions are assumed to satisfy simply supported boundary conditions and Galerkin method is applied to obtain nonlinear load-deflection relation. Numerical examples show the effects of volume fraction and distribution type of CNTs, in-plane condition of edges, curvature of panel, thermal environments, elastic foundations and imperfection size on the nonlinear response and snap-through instability of the curved panels. The present study reveals that efficiency of CNT distribution type depends on curvature of panel and in-plane behavior of boundary edges, and bifurcation type buckling response of pressure-loaded panels may occur at elevated temperature.
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Liu, Yuhong. "Polymerization-induced phase separation and resulting thermomechanical properties of thermosetting/reactive nonlinear polymer blends: A review". Journal of Applied Polymer Science 127, n. 5 (4 novembre 2012): 3279–92. http://dx.doi.org/10.1002/app.38721.
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Yaleu, T. B. Djuitchou, E. R. Fankem e B. R. Nana Nbendjo. "On the Nonlinear Thermomechanical Analysis of a Stayed-Beam Having Fractional Viscoelastic Properties in Complex Environment". Journal of Applied Nonlinear Dynamics 13, n. 2 (giugno 2024): 351–71. http://dx.doi.org/10.5890/jand.2024.06.012.
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Trang, Le Thi Nhu, e Hoang Van Tung. "Thermomechanical nonlinear stability of pressure-loaded functionally graded carbon nanotube-reinforced composite doubly curved panels with tangentially restrained edges". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 233, n. 16 (11 giugno 2019): 5848–59. http://dx.doi.org/10.1177/0954406219856374.
Testo completoAbstract (sommario):
Geometrically nonlinear response of doubly curved panels reinforced by carbon nanotubes exposed to thermal environments and subjected to uniform external pressure are presented in this paper. Carbon nanotubes are reinforced into isotropic matrix through uniform and functionally graded distributions. Material properties of constituents are assumed to be temperature dependent, and effective elastic moduli of carbon nanotube-reinforced composite are determined according to an extended rule of mixture. Basic equations for carbon nanotube-reinforced composite doubly curved panels are established within the framework of first-order shear deformation theory. Analytical solutions are assumed, and Galerkin method is used to derive closed-form expressions of nonlinear load–deflection relation. Separate and combined effects of carbon nanotube distribution and volume fraction, elasticity of in-plane constraint, elevated temperature, initial imperfection, geometrical ratios and stiffness of elastic foundations on the nonlinear stability of nanocomposite doubly curved panels are analyzed through numerical examples.
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Yang, Jian, Li-Yun Fu, Bo-Ye Fu, Zhiwei Wang e Wanting Hou. "High-temperature effect on the material constants and elastic moduli for solid rocks". Journal of Geophysics and Engineering 18, n. 4 (agosto 2021): 583–93. http://dx.doi.org/10.1093/jge/gxab037.
Testo completoAbstract (sommario):
Abstract Thermally coupled constitutive relations are generally used to determine material constants and elastic moduli (Young's modulus and shear modulus) of solid media. Conventional studies on this issue are mainly based on the linear temperature dependence of elastic moduli, whereas analytical difficulties are often encountered in theoretical studies on nonlinear temperature dependence, particularly at high temperatures. This study investigates the thermally coupled constitutive relations for elastic moduli and material constants using the assumption of axisymmetric fields, with applications to geologic materials (marble, limestone and granite). The Taylor power series of the Helmholtz free energy function within dimensionless temperatures could be used to develop the thermally coupled constitutive relations. The thermoelastic equivalent constitutive equations were formulated under the generalized Hooke's law. The material constants of solid rocks were determined by fitting experimental data using axisymmetric stress and strain fields at different temperatures, based on their thermomechanical properties. For these geologic materials, the resultant equivalent elastic moduli and deformations were in good agreement with those from the experimental measurements. Thermal stresses, internal moisture evaporation and internal rock compositions significantly affected the experimental results. This study provides a profound understanding of the thermally coupled constitutive relations that are associated with the thermomechanical properties of solid rocks exposed to high temperatures.
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Woods, Bruce W., Stephen A. Payne, John E. Marion, Robert S. Hughes e Laura E. Davis. "Thermomechanical and thermo-optical properties of the LiCaAlF_6:Cr^3+ laser material". Journal of the Optical Society of America B 8, n. 5 (1 maggio 1991): 970. http://dx.doi.org/10.1364/josab.8.000970.
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Gaval, Vivek Ramdas, M. Divekar, A. Wonisch e G. Jadhav. "Increase in Warpage Prediction Accuracy for Glass Filled Polyamide Material (PA66) through Integrative Simulation Approach". ASM Science Journal 15 (17 maggio 2021): 1–9. http://dx.doi.org/10.32802/asmscj.2021.697.
Testo completoAbstract (sommario):
The warpage prediction accuracy of the simulation software depends on part geometry, material model and methodology. However, the material model in the existing simulation software’s does not consider factors such as nonlinear mechanical properties, temperature dependent behaviour, viscoelastic behaviour and transient description of warpage leading to less accuracy. Using an integrative simulation approach, BASF has developed Ultrasim® tool to overcome limitations in the material model of existing simulation software. In the new material model thermomechanical properties, stress relaxation behaviour and nonlinear mechanical properties were considered and this new material model is added to Ultrasim® tool. The model also considers time dependent descriptions of the warpage starting from packing phase of the moulding process, followed by actual ejection and cooling. In this paper warpage results predicted through new integrative simulation approach and existing simulation approach are compared with actual experimental results for 50% glass filled polyamide material (Ultramid®A3WG10). The results revealed that warpage values predicted by integrative simulation based Ultrasim® tool are closer to actual experimental results compared to values predicted by existing simulation technologies. Therefore an integrative simulation approach can be used prior to making real parts to reduce manufacturing cost.
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Song, Chengli, Tim Frank e Alfred Cuschieri. "Shape Memory Alloy Clip for Compression Colonic Anastomosis". Journal of Biomechanical Engineering 127, n. 2 (8 novembre 2004): 351–54. http://dx.doi.org/10.1115/1.1871195.
Testo completoAbstract (sommario):
This study was setup to investigate the design and performance of a shape memory alloy clip for colonic anastomosis. The thermomechanical properties of the shape memory alloy material were studied and the data were used to derive a nonlinear material model. This enabled the development of computer computer aided design models and finite element analysis of the clip and tissue compression. The maximum strain of the anastomosis clip was within the recoverable range, and it exerted parallel compression of the colonic walls with a uniform pressure distribution. The design of the anastomosis clip was optimized for safe, simple, and effective use in colon surgery.
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Zivkovic, Dragoljub, Dragan Milcic, Milan Banic e Pedja Milosavljevic. "Thermomechanical finite element analysis of hot water boiler structure". Thermal Science 16, suppl. 2 (2012): 387–98. http://dx.doi.org/10.2298/tsci120503177z.
Testo completoAbstract (sommario):
The paper presents an application of the Finite Elements Method for stress and strain analysis of the hot water boiler structure. The aim of the research was to investigate the influence of the boiler scale on the thermal stresses and strains of the structure of hot water boilers. Results show that maximum thermal stresses appear in the zone of the pipe carrying wall of the first reversing chamber. This indicates that the most critical part of the boiler are weld spots of the smoke pipes and pipe carrying plate, which in the case of significant scale deposits can lead to cracks in the welds and water leakage from the boiler. The nonlinear effects were taken into account by defining the bilinear isotropic hardening model for all boiler elements. Temperature dependency was defined for all relevant material properties, i. e. isotropic coefficient of thermal expansion, Young?s modulus, and isotropic thermal conductivity. The verification of the FEA model was performed by comparing the measured deformations of the hot water boiler with the simulation results. As a reference object, a Viessmann - Vitomax 200 HW boiler was used, with the installed power of 18.2 MW. CAD modeling was done within the Autodesk Inventor, and stress and strain analysis was performed in the ANSYS Software.
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ТРЕЩЕВ, А. А., e М. Ю. ДЕЛЯГИН. "COUPLED THERMOMECHANICAL CALCULATION OF A GRAPHITE-PLASTIC SHELL TAKING INTO CONSIDERATION SIGNIFICANTLY NONLINEAR MULTIMODULUS BEHAVIOUR". ВЕСТНИК ПОВОЛЖСКОГО ГОСУДАРСТВЕННОГО ТЕХНОЛОГИЧЕСКОГО УНИВЕРСИТЕТА. СЕРИЯ: МАТЕРИАЛЫ. КОНСТРУКЦИИ. ТЕХНОЛОГИИ, n. 3(11) (6 settembre 2019): 101–10. http://dx.doi.org/10.25686/2542-114x.2019.3.101.
Testo completoAbstract (sommario):
В работе поставлена проблема зависимости жёсткостных и температурных свойств материалов от вида реализуемого в точке напряжённого состояния. Приведены ссылки на экспериментальные исследования, подтверждающие существование этих зависимостей. Подчёркнута особая важность учёта возможного изменения температурного режима эксплуатации конструкций для сооружений повышенного уровня ответственности, в том числе при аварийных ситуациях. Рассмотрен термодинамический потенциал Гиббса для изначально изотропных существенно нелинейных разносопротивляющихся материалов, находящихся в температурном поле. Форма потенциала содержит квазилинейную механическую часть, нелинейную механическую часть, отличающуюся от квазилинейной константой материала в показателе степени, и термомеханическую часть, предназначенную для учёта связанности напряжений и температур. Проанализированы свойства потенциала при различных частных случаях напряжённодеформированного состояния и сделаны выводы. Дана оценка адекватности выявленных свойств имеющимся материалам экспериментальных исследований, в том числе отмечен эффект дилатации при отсутствии гидростатических напряжений и отсутствие изменения формы при нулевых касательных напряжениях. Разработана модель связанного термомеханического расчёта конструкций методом конечных элементов с применением пошагового итерационного процесса с пересчётом координат узлов конечноэлементной модели на каждом этапе нагружения. Модифицирован объёмный конечный элемент в виде тетраэдра с целью учёта зависимости свойств материала от вида реализуемого в точке напряжённодеформированного состояния и взаимного влияния полей механических напряжений и температур. Рассмотрена задача о расчёте пологой оболочки двоякой гауссовой кривизны, квадратной в плане и нагруженной равномерной нагрузкой на части верхней поверхности, несимметрично относительно центра, и перепадом температур между верхней и нижней поверхностями. Приведены результаты расчета оболочки, основанные на модификации объёмного конечного элемента. Проведен анализ отдельных количественных и качественных результатов расчёта напряжённодеформированного состояния оболочки, выполненной из графитокомпозита АРВ. Отмечено влияние связанности перепада температур и распределения напряжений с учетом нелинейной разносопротивляемости графита АРВ и деформируемости конечноэлементной структуры. Уточнение законов деформирования материалов с усложнёнными свойствами может значительно увеличить эффективность использования ресурсов и дать надёжную базу для внедрения в строительство и машиностроение прогрессивных материалов. The paper deals with the problem of stiffness and temperature dependence on the type of stress state at the point. The authors refer to the experimental studies confirming the existence of these dependencies and emphasize the importance of taking into account possible changes in the temperature regime of building structures operation, particularly when it concerns those with the increased level of responsibility or emergency situations. The paper considers thermodynamic potential of Gibbs for initially isotropic essentially nonlinear resistive materials located in the temperature field. The form of the potential contains quasilinear mechanical part, nonlinear mechanical part different from the quasilinear constant of the material in the exponent, and thermomechanical part designated for consideration of voltage and temperatures connectedness. The authors analyze the properties of the potential in a variety of stressstrain states and draw conclusions. The adequacy of the identified properties to the available materials of experimental studies is assessed, including the effect of dilation in the absence of hydrostatic stresses and the absence of shape change at zero shear stresses. The authors have developed the model of coupled thermomechanical calculation for structures by finite element method using a stepbystep iterative process with recalculation of the coordinates of the nodes of the finite element model at each stage of loading. The volumetric finite element in the form of a tetrahedron was modified for the purpose of taking into account the dependence of the material properties on the type of stressstrain state at a certain point and examination of mutual influence of mechanical stress and temperature field. The problem of calculating the flat shell of a double Gaussian curvature, square in plan and loaded with uniform load on the part of the upper surface, asymmetrically relative to the center, and the temperature difference between the upper and lower surfaces is considered. The authors also provide the results of shell calculation based on the modification of the bulk finite element. The analysis of some quantitative and qualitative results of the calculation of the stressstrain state of the shell made of ARV graphite composite is carried out. The influence of temperature drop and stress distribution connectivity is emphasized, taking into account the nonlinear resistivity of ARV graphite and the deformation of the finite element structure. Clarification of the laws of deformation of materials with complicated properties can significantly enhance the effectiveness of resource use and provide a reliable basis for the introduction of advanced materials in construction and engineering.
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Ватульян, Александр Ованесович, e Сергей Анатольевич Нестеров. "Об особенностях идентификации переменных термомеханических характеристик функционально-градиентного прямоугольника". Computational Continuum Mechanics 16, n. 4 (4 gennaio 2024): 504–16. http://dx.doi.org/10.7242/1999-6691/2023.16.4.42.
Testo completoAbstract (sommario):
The inverse thermoelastic problem of identification of the variable properties of a functionally graded rectangle is studied. Unsteady vibrations are excited by applying mechanical and thermal loads to the upper side of the rectangle. To solve the direct problem in Laplace transforms, the method of separation of variables and the shooting method for harmonics are used. Transformants are inverted by expanding the origin in terms of shifted Legendre polynomials. The method proposed for solving the direct problem is verified by comparison with a finite element solution. The influence of the laws of change of variable characteristics on the boundary physical fields is analyzed. The displacement components give additional information on the mechanical loading, and the temperature measured on the upper side of the rectangle over a certain time interval – on the thermal loading. Assuming that the additional information admits expansion in Fourier series, the two-dimensional inverse problem is reduced to one-dimensional problems for various harmonics. The solution of the obtained nonlinear inverse problems is carried out on the basis of an iterative process, at each stage of which, in order to find corrections for thermomechanical characteristics, systems of Fredholm integral equations of the 1st kind are solved. The possibility of simultaneous reconstruction of several characteristics is investigated. The results of computational experiments on the phased reconstruction of thermomechanical characteristics are presented. The influence of the thermomechanical coupling parameter on the results of the thermal stress coefficient reconstruction was clarified.
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Emel yanov, I. G., e A. N. Kislov. "THE LIMITING STATE OF A STEEL STRUCTURE UNDER EXTREME THERMOMECHANICAL LOADINGS". PNRPU Mechanics Bulletin, n. 2 (15 dicembre 2024): 59–68. http://dx.doi.org/10.15593/perm.mech/2024.2.07.
Testo completoAbstract (sommario):
Using numerical methods, the problem of determining the strength and limiting state of a steel shell structure under thermomechanical loading is solved. The operating stresses are determined by solving a physically nonlinear boundary value problem for a shell of revolution. The classical theory of shells, based on the Kirchhoff – Love hypotheses, and the method of integrating shell equations with discrete S.K. Godunov orthogonalization are used. By integrating a system of ordinary differential equations at each point of the shell, the meridional and circumferential stresses and the corresponding deformations are calculated. When taking into account the plastic deformation of the material, the boundary value problem becomes nonlinear. The relationship between stress and strain is linearized by the method of additional strains. A limiting state criterion for thin-walled structures is proposed. In the absence of the necessary parameters for the material of construction, interpolation and extrapolation of the experimental data based on neural networks is used. The method uses the example of a muffle, which is a revolution shell structure loaded with an internal excess pressure of a hydrogen-containing gas and a non-stationary thermal field. The muffle is designed for high-temperature annealing of the electrolytic steel, and is made of non-heat-resistant St3 steel, its mechanical properties have not been sufficiently studied at temperatures above 500 °C. However, the operating temperature of the muffle can reach more than 1000 °C. Under the influence of such a thermal load, noticeable residual deformations are formed in the muffle structure and the muffle may lose its load-bearing capacity. For thermomechanical loads, a maximum temperature of 1000 °C is determined at which the limit state occurs and the operation of the muffle is not permissible. A satisfactory agreement was obtained with the actual muffle temperature during operations of 1100 °C, at which the muffle loses its load-bearing capacity.
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Ghahfarokhi, Zahra Matin, Mehdi Salmani-Tehrani e Mahdi Moghimi Zand. "Nonlinear Thermohyperviscoelastic Constitutive Model for Soft Materials with Strain Rate and Temperature Dependency". International Journal of Applied Mechanics 12, n. 06 (luglio 2020): 2050059. http://dx.doi.org/10.1142/s1758825120500593.
Testo completoAbstract (sommario):
Soft materials, such as polymeric materials and biological tissues, often exhibit strain rate and temperature-dependent behavior when subjected to external loads. To characterize the thermomechanical behavior of isotropic soft material, a thermohyperviscoelastic constitutive model has been developed through an additive decomposition of strain energy function into elastic and viscous parts. A three-term generalized Rivlin strain energy function is utilized to formulate the hyperelastic part of the model, while a new viscous potential function is proposed to describe the effect of strain rate and temperature on material behavior. Toward this end, a new procedure has been proposed to determine the viscous mechanical properties as a function of strain-rate and temperature. Comparing with the previously published experimental data for linear low-density polyethylene reveals that the proposed model can sufficiently capture the nonlinearity, rate- and temperature-dependent behavior of the soft materials.
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Park, H. C., S.-K. Youn, T. S. Song e N.-J. Kim. "Analysis of Temperature Distribution in a Rolling Tire Due to Strain Energy Dissipation". Tire Science and Technology 25, n. 3 (1 luglio 1997): 214–28. http://dx.doi.org/10.2346/1.2137541.
Testo completoAbstract (sommario):
Abstract This paper addresses a systematic procedure using a sequential approach for the analysis of the coupled thermomechanical behavior of a steady state rolling tire. Not only knowledge of mechanical stresses but also knowledge of the temperature loading in a rolling tire are very important because material damage and material properties are affected significantly by the temperature. In general, the thermomechanical behavior of a pneumatic tire is a highly complex transient phenomenon that requires the solution of a dynamic nonlinear coupled thermoviscoelasticity problem with heat sources resulting from internal dissipation and friction. In this paper, a sequential approach, with effective calculation schemes, to modeling this system is presented to predict the temperature distribution with reasonable accuracy in a steady state rolling tire. This approach has three major analysis modules: deformation, dissipation, and thermal modules. In the dissipation module, an analytic method for the calculation of the heat source in a rolling tire is established using viscoelastic theory. For the verification of the calculated temperature profiles and rolling resistance at different velocities, they are compared with measured ones. Also, discussed are the accuracies of the linear and quadratic finite element models used in the analysis.
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Thosago, Kgomotshwana Frans, Lazarus Rundora e Samuel Olumide Adesanya. "Thermodynamic Analysis of Magnetohydrodynamic Third Grade Fluid Flow with Variable Properties". International Journal of Engineering Research in Africa 55 (10 agosto 2021): 28–46. http://dx.doi.org/10.4028/www.scientific.net/jera.55.28.
Testo completoAbstract (sommario):
This article aims to computationally study entropy generation in a magnetohydrodynamic (MHD) third grade fluid flow in a horizontal channel with impermeable walls. The fluids viscosity and thermal conductivity are assumed to be dependent on temperature. The flow is driven by an applied uniform axial pressure gradient between infinite parallel plates and is considered to be incompressible, steady and fully developed. Adomian decomposition method (ADM) is used to obtain series solutions of the nonlinear governing equations. Thermodynamic analysis is done by computing the entropy generation rate and the irreversibility ratio (Bejan number). The effects of the various pertinent embedded parameters on the velocity field, temperature field, entropy generation rate and Bejan number are analysed through vivid graphical manipulations. The analysis shows that an appropriate combination of thermophysical parameters efficiently achieves entropy generation minimization in the thermomechanical system. The analysis shows that entropy generation minimization is achieved by increasing the magnetic field and the third grade material parameters, and therefore designs and processes incorporating MHD third grade fluid flow systems are far more likely to give optimum and efficient performance.
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Behnke, Ronny, e Michael Kaliske. "Finite Element Based Analysis of Reinforcing Cords in Rolling Tires: Influence of Mechanical and Thermal Cord Properties on Tire Response". Tire Science and Technology 46, n. 4 (1 ottobre 2018): 294–327. http://dx.doi.org/10.2346/tire.18.4604010.
Testo completoAbstract (sommario):
ABSTRACT Tires of passenger cars and other special tires are made of rubber compounds and reinforcing cords of different type to form a composite with distinct mechanical and thermal properties. One of the major load cases is the steady state rolling operation during the tire's service. In this contribution, attention is paid to the strain and force state as well as the temperature distribution in the carcass cord layer of a steady state rolling tire. A simple benchmark tire geometry is considered, which is made of one rubber compound, one carcass cord layer (textile), and two belt cord layers (steel). From the given geometry, two tire designs are derived by using two distinct types of reinforcing cords (polyester and rayon) for the carcass cord layer. Subsequently, the two tire designs are subjected to three load cases with different inner pressure, vertical force, and translational velocity. The strain and the force state as well as the temperature distribution in the cords are computed via a thermomechanically coupled finite element simulation approach for each tire design and load case. To realistically capture the thermomechanical behavior of the cords, a temperature- and deformation-dependent nonlinear elastic cord model is proposed. The cord model parameters can be directly derived from data of cord tensile tests at different temperatures. Finally, cord design parameters (minimum and maximum strains and forces in the cords, maximum strain and force range per cycle, and maximum cord temperature) are summarized and compared. Additionally, the global vertical stiffness and the rolling resistance for each tire design are addressed.
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Tung, Hoang Van. "Nonlinear thermomechanical stability of shear deformable FGM shallow spherical shells resting on elastic foundations with temperature dependent properties". Composite Structures 114 (agosto 2014): 107–16. http://dx.doi.org/10.1016/j.compstruct.2014.04.004.
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Krupke, W. F., M. D. Shinn, J. E. Marion, J. A. Caird e S. E. Stokowski. "Spectroscopic, optical, and thermomechanical properties of neodymium- and chromium-doped gadolinium scandium gallium garnet". Journal of the Optical Society of America B 3, n. 1 (1 gennaio 1986): 102. http://dx.doi.org/10.1364/josab.3.000102.
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Glerum, Anne, Cedric Thieulot, Menno Fraters, Constantijn Blom e Wim Spakman. "Nonlinear viscoplasticity in ASPECT: benchmarking and applications to subduction". Solid Earth 9, n. 2 (19 marzo 2018): 267–94. http://dx.doi.org/10.5194/se-9-267-2018.
Testo completoAbstract (sommario):
Abstract. ASPECT (Advanced Solver for Problems in Earth's ConvecTion) is a massively parallel finite element code originally designed for modeling thermal convection in the mantle with a Newtonian rheology. The code is characterized by modern numerical methods, high-performance parallelism and extensibility. This last characteristic is illustrated in this work: we have extended the use of ASPECT from global thermal convection modeling to upper-mantle-scale applications of subduction.Subduction modeling generally requires the tracking of multiple materials with different properties and with nonlinear viscous and viscoplastic rheologies. To this end, we implemented a frictional plasticity criterion that is combined with a viscous diffusion and dislocation creep rheology. Because ASPECT uses compositional fields to represent different materials, all material parameters are made dependent on a user-specified number of fields.The goal of this paper is primarily to describe and verify our implementations of complex, multi-material rheology by reproducing the results of four well-known two-dimensional benchmarks: the indentor benchmark, the brick experiment, the sandbox experiment and the slab detachment benchmark. Furthermore, we aim to provide hands-on examples for prospective users by demonstrating the use of multi-material viscoplasticity with three-dimensional, thermomechanical models of oceanic subduction, putting ASPECT on the map as a community code for high-resolution, nonlinear rheology subduction modeling.
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Granell, Ignacio, Abel Ramos e Alberto Carnicero. "A Geometry-Based Welding Distortion Prediction Tool". Materials 14, n. 17 (24 agosto 2021): 4789. http://dx.doi.org/10.3390/ma14174789.
Testo completoAbstract (sommario):
The prediction of welding distortion requires expertise in computer simulation programs, a clear definition of the nonlinear material properties, and mesh settings together with the nonlinear solution settings of a coupled thermal–structural analysis. The purpose of this paper is to present the validation of an automatic simulation tool implemented in Ansys using Python scripting. This tool allows users to automate the preparation of the simulation model with a reduced number of inputs. The goal was, based on some assumptions, to provide an automated simulation setup that enables users to predict accurate distortion during the welding manufacturing process. Any geometry prepared in a CAD software can be used as the input, which gave us much geometrical flexibility in the shapes and sizes to be modeled. A thermomechanical loosely coupled analysis approach together with element birth and death technology was used to predict the distortions. The automation of the setup enables both simulation and manufacturing engineers to perform welding-induced distortion prediction. The results showed that the method proposed predicts distortion with 80–98% accuracy.
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Hieu, Pham Thanh, e Hoang Van Tung. "Thermomechanical nonlinear buckling of pressure-loaded carbon nanotube reinforced composite toroidal shell segment surrounded by an elastic medium with tangentially restrained edges". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 233, n. 9 (30 settembre 2018): 3193–207. http://dx.doi.org/10.1177/0954406218802942.
Testo completoAbstract (sommario):
Buckling and postbuckling behaviors of toroidal shell segment reinforced by single-walled carbon nanotubes, surrounded by an elastic medium, exposed to a thermal environment and subjected to uniform external pressure are investigated in this paper. Carbon nanotubes are reinforced into matrix phase by uniform distribution or functionally graded distribution along the thickness direction. Material properties of constituents are assumed to be temperature dependent, and the effective properties of carbon nanotube reinforced composite are estimated by extended mixture rule through a micromechanical model. Governing equations for toroidal shell segments are based on the classical thin shell theory taking into account geometrical nonlinearity, surrounding elastic medium, and varying degree of tangential constraints of edges. Three-term solution of deflection and stress function are assumed to satisfy simply supported boundary condition, and Galerkin method is applied to derive nonlinear load–deflection relation from which buckling loads and postbuckling equilibrium paths are determined. Analysis shows that tangential edge restraints have significant effects on nonlinear buckling of carbon nanotube reinforced composite toroidal shell segments. In addition, the effects of carbon nanotube volume fraction, distribution types, geometrical ratios, elastic foundation, and thermal environments on the buckling and postbuckling behaviors of carbon nanotube reinforced composite toroidal shell segments are analyzed and discussed.
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den Toonder, J. M. J., Y. Ramone, A. R. van Dijken, J. G. J. Beijer e G. Q. Zhang. "Viscoelastic Characterization of Low-Dielectric Constant SiLK Films Using Nanoindentation in Combination With Finite Element Modeling". Journal of Electronic Packaging 127, n. 3 (12 agosto 2004): 276–85. http://dx.doi.org/10.1115/1.1938990.
Testo completoAbstract (sommario):
SiLK is a polymer material developed for use as a thin-film dielectric in the interconnect structure of high-density integrated circuits. Among others, its thermomechanical properties play a dominant role for the integrity and reliability of the interconnect during processing, testing, and use. Being a polymer, SiLK may show viscoelastic (time-dependent) behavior. In this paper, we use nanoindentation techniques in combination with analytical and finite element modeling (FEM) to determine the viscoelastic properties of a thin SiLK film on a silicon substrate. Indentation-creep experiments show that this SiLK film indeed responds in a viscoelastic way. This may be caused by the non fully cross-linked test samples prepared using nonstandard processing. Using the FEM simulation, we find that the behavior of this thin SiLK film can be described with a linear viscoelastic model up to the characteristic stress and strain levels of approximately 200MPa and 3%, respectively. For higher stress and strain levels, the response becomes nonlinear. The results are validated with independent indentation load-unload measurements.
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Ling, S., e A. Dasgupta. "A Nonlinear Multi-Domain Thermomechanical Stress Analysis Method for Surface-Mount Solder Joints—Part II: Viscoplastic Analysis". Journal of Electronic Packaging 119, n. 3 (1 settembre 1997): 177–82. http://dx.doi.org/10.1115/1.2792231.
Testo completoAbstract (sommario):
This is part II of a two-part paper presented by the authors for thermomechanical stress analysis of surface mount interconnects. A generalized multi-domain Rayleigh Ritz (MDRR) stress analysis technique has been developed to obtain the stress and strain fields in surface-mount solder joints under cyclic thermal loading conditions. The methodology was first proposed in Part I by the authors and results were presented for elastic-plastic loading (Ling et al., 1996). This paper extends the analysis for viscoplastic material properties. The solder joint domain is discretized selectively into colonies of nested sub-domains at locations where high stress concentrations are expected. Potential energy stored in the solder domain and in the attached lead and Printed Wiring Board (PWB) is calculated based on an assumed displacement field. Minimization of this potential energy provides a unique solution for the displacement field, consequently, stress and strain distribution. The MDRR technique was demonstrated to provide reasonable accuracy for elastic deformation (Ling and Dasgupta, 1995) and for time-independent elastic-plastic deformation (Ling and Dasgupta, 1996) for solder joints under cyclic thermal loading conditions. A piecewise linear incremental loading technique is used to solve the nonlinear elastic-plastic problem. The focus in the current paper is primarily on time-dependent viscoplastic deformation of the solder joints. Full field elastic, plastic, and viscoplastic analyses are performed, and the stress, strain hysteresis loops are obtained. Results are presented for a J-lead solder joint as an illustrative example.
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Fedorov, Viktor S., Valery E. Levitsky e Ekaterina A. Isaeva. "Basic principles in the theory of force and thermal force resistance of concrete". Structural Mechanics of Engineering Constructions and Buildings 18, n. 6 (15 dicembre 2022): 584–96. http://dx.doi.org/10.22363/1815-5235-2022-18-6-584-596.
Testo completoAbstract (sommario):
In the development of the ideas and approaches to the analysis of the force resistance of concrete of V.M. Bondarenko, the initial prerequisites for the model of the thermomechanical state of concrete under short-term sharp high-temperature exposure, characteristic of fire conditions, are formulated. The separation of force deformations into components is carried out on the basis of the connection with the accumulation of damage in the structure of the material, based on the principle of independence of the limiting structural stresses from temperature and the mode of force action, which makes it possible to establish basic thermomechanical relationships and determine the deformation parameters of concrete operating under conditions of unsteady heating in a loaded state. Based on the extension of the hypothesis of entropy damping of nonequilibrium processes to the area of action of an active destructive factor, the principle of normalization was formulated and a kinetic equation was proposed, from the solution of which exponential dependences having a single structure were obtained, which make it possible to describe the basic temperature parameters of concrete, the relationship of stresses with deformations, and other nonlinear characteristics. The application of the proposed principles creates a reliable theoretical basis for describing the mechanisms of thermal resistance of concrete and greatly simplifies the modeling of the effect of high temperature on the properties of concrete in the practical implementation of methods for the numerical calculation of reinforced concrete structures.
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Ahmad, Mohammad Ismail Ramadan, Inggar Septhia Irawati, Ali Awaludin e Suprapto Siswosukarto. "Thermomechanical Analysis of Cement Hydration Effects in Multi-layered Pier Head Concrete: Finite Element Approach". Journal of Engineering and Technological Sciences 56, n. 5 (30 settembre 2024): 625–38. http://dx.doi.org/10.5614/j.eng.technol.sci.2024.56.5.7.
Testo completoAbstract (sommario):
Mass concrete plays a crucial role in infrastructure development, yet its complex thermo-mechanical behavior poses challenges, especially in the construction of multi-layered structures like pier heads. This study investigated the thermo-mechanical behavior of a pier head during its concreting process in three stages, including the influence of temperature differences that impact the thermomechanical balance of the concrete. By utilizing the ABAQUS software, thermo-mechanical analysis was conducted to simulate temperature fluctuations during cement hydration. The model integrates thermal analysis to simulate temperature fluctuations during cement hydration and stress distribution during construction, validated through mesh convergence studies and field data comparison. The mechanical analysis considered concrete properties, temperature variations, and construction phase. Nonlinear material behavior and contact interactions between layers were incorporated to obtain a realistic simulation. The results indicated that a multi-layer system can balance temperatures, reducing thermal stress-induced cracking risks. Furthermore, specific test points within the pier head were assessed, revealing potential internal cracks by comparing thermal stresses to the concrete’s tensile strength. This research offers insight into pier head conditions during construction, highlighting critical stress zones, crack prediction, and construction sequence efficacy.
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Lee, Baik Woo, Jeung Hyun Jeong, Woosoon Jang, Ju Young Kim, Dong Won Kim, Dongil Kwon, Jae Woong Nah e Kyung Wook Paik. "Determination of Stress-Strain Curve for Microelectronic Solder Joint by ESPI Measurement and FE Analysis". International Journal of Modern Physics B 17, n. 08n09 (10 aprile 2003): 1983–88. http://dx.doi.org/10.1142/s0217979203019988.
Testo completoAbstract (sommario):
Many thermomechanical reliability studies on microelectronics and microsystems have relied upon computational analysis, since experimental work is rather difficult and very time-consuming. For computational analysis, it is essential to use as input accurate material properties; if not, the results of a reliability analysis may be very inaccurate. However, it is still quite difficult to arrive at unified material properties for modeling microelectronic assemblies because of the absence of standards for micro-material characterization, the difference between bulk and in-situ material properties, and so forth. The goal of this study was to determine the uniaxial stress-strain curve of a solder in a flip-chip assembly, using experimental measurements and finite-element analysis (FEA) of the solder's thermal deformation characteristics with increasing temperature. The thermal deformation of flip-chip solder joints was measured by electronic speckle pattern interferometry (ESPI). For the scale of evaluation required, the measurement magnification was modified to allow its application to micromaterials by using a long-working-distance microscope, iris and zoom lens. Local deformation of solder balls could be measured at submicrometer scale, and stress-strain curves could be determined using the measured thermal deformation as input data for finite-element analysis. The procedure was applied to an Sn-36Pb-2Ag flip-chip solder joint.
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Qian, Zhengming, Gaiqi Li, Dong Mi e Xin An. "Thermomechanical Fatigue Life Prediction Method of the Trailing Edge Holes in the Turbine Blade for Turboshaft Engine". Journal of Physics: Conference Series 2168, n. 1 (1 gennaio 2022): 012003. http://dx.doi.org/10.1088/1742-6596/2168/1/012003.
Testo completoAbstract (sommario):
Abstract In this paper, a thermomechanical fatigue (TMF) life analysis method considering stress relaxation was established for turbine blade in a turboshaft engine. The nonlinear creep deformation of a superalloy is predicted by coupling creep damage in the framework of viscoplastic theory. The results revealed that the calculation error of the model for the elastic-plastic stress-strain curve was less than 5%, while the simulation accuracy for the creep curve is within the dispersion range of the inherent properties of material creep deformation. Based on the elastic-plastic creep analysis of a turbine blade, the creep damage and its evolution law of the leading edge and trailing edge of the blade are clarified, and a new method is provided for determining the local dangerous points on the blade. With the help of the linear damage cumulative life theory, the fatigue creep life of the trailing edge hole of a turbine blade considering the stress relaxation is obtained, which provides a more reasonable and better engineering application method for the blade life evaluation.