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This study presents a thermo-mechanical fracture analysis of porous functionally graded cracked plates using the extended finite element method. Three types of functionally graded cracked plates with two different types of porosity distributions, namely homogeneous and nonhomogeneous, are considered in this investigation. Specifically, edge and center-cracked porous functionally graded material plates are analyzed to determine the stress intensity factors. Thermo-mechanical loading conditions are considered to simulate the effects of temperature gradients and mechanical stresses on cracked plates. The analysis aims to investigate the influence of the crack length, crack location, porosity distribution, porosity volume fraction, crack angle, and material gradient on the SIF values. The results of the study provide valuable insights into the behavior of functionally graded cracked plates with different porosity distributions. The findings contribute to the understanding of the mechanical response of such plates under thermo-mechanical loading conditions and can aid in the design and optimization of structures made from functionally graded porous materials. [ABSTRACT FROM AUTHOR]

This research introduces the Stochastic Extended Isogeometric Analysis (XIGA) method to investigate fracture behavior of isotropic and orthotropic materials under mechanical, thermal, and thermomechanical loads. Employing knot spans from Isogeometric Analysis (IGA) for domain discretization, the study utilizes identical basis functions for geometry construction and solution discretization. Utilizing Extended Finite Element Method (XFEM) enrichment functions, accurate crack face displacement discontinuity and tip singularity within the stress field are characterized. Additionally, employing a second-order perturbation technique within XIGA framework, the research derives mean and coefficient of variance values for mixed-mode Stress Intensity Factors (SIF). Stochastic variations in material elastic properties, crack length, and crack angle are considered in this computation. Credibility and robustness of the study are confirmed through comparative analyses against available literatures and Monte Carlo Simulations (MCS). The observed exceptional agreement validates the precision and reliability of the proposed stochastic XIGA method for fracture analysis in orthotropic material systems under thermomechanical loading conditions.

This study included two aspects - an experimental study and a numerical study – to determine which type of composite materials is more efficient in repairing corroded and cracked aluminum plates that have been repaired by the composite material technique. In the numerical study, the adhesive damage area theory was used to analyze the effect of corrosion and inclined crack behavior of Al 2017 A aluminum plate under thermo-mechanical loading. The effects of crack inclination and temperature change were highlighted as well as the effects of patch shape and type. In the experimental study, we prepared corroded sheets, repaired them with several types of composite materials, and then subjected them to tensile strength until wear. The results obtained either through a numerical or experimental study, proved that the boron/epoxy type composite is the most efficient in rust repair compared to the other types used in this study. [ABSTRACT FROM AUTHOR]

AbstractReinforcement in composite and notched structures has long been the objective of many researchers. One of the commonly used solutions is hybrid composite. Other recently reemerged solutions are graded materials. These respond, according to their modes of solicitation, to the targeted resistance objectives. However, composites with UD (unidirectional) fiber quality limit the choice of structural grading solely based on their thickness. Using the finite element method and the ABAQUS calculation code, this work presents the embodiment through numerical prediction of an idea based on the concept of material grading by FGM function. The objective of this approach is to introduce the volumetric fraction of the FGM concept into the Fiber-Matrix mixing laws in UD composite. Thickness-graded composites are subjected to a volumetric fraction function raised to the power of a parameter called volumetric fraction index (n). These structures, according to the proposed concepts, are analyzed under thermomechanical loading. The proposed grading of these composites is based on the presence of fibers in the matrix, where the fiber is denser on one side, called the simple concept C-S. The other two symmetrical concepts, named C-2 and C-3, present denser fibers in the middle and on both sides of the plate, respectively. These proposed concepts aim to observe how damage is caused by different responses and levels. The results under the different analyzed parameters are evaluated and compared to the results of the two other non-graded composites, thus showing the limits of those that are graded in terms of properties. According to the thermomechanical loading, the proposed graded composite has demonstrated a resistance overcapacity by the grading index (n) or their locations by concept C1- and C-2 of fibers have played a role in optimizing this capacity. The results also show that damage is caused by deformation overcapacity. [ABSTRACT FROM AUTHOR]

The free vibration behavior of a bidirectional functionally graded rotating micro-disk that is subjected to uniform transverse pressure and high-temperature thermal loading has been studied. The micro-disk is functionally graded along the radial and thickness directions. The problem is mathematically formulated using two distinct but interrelated steps within the framework of Kirchhoff plate theory and modified couple stress theory. The first step determines the time-invariant deformed configuration of the micro-disk under centrifugal, pressure, and thermal loading using minimum potential energy principle. The second step determines the free vibration behavior of the micro-disk in the neighborhood of the deformed configuration using Hamilton's principle. The solutions of the governing equations for both these steps are obtained using the Ritz method. The mathematical model is successfully validated with various reduced problems. The numerical results for the first four axisymmetric bending vibration modes are presented to investigate the effects of wide range of parameters such as rotational speed, applied pressure, thermal loading, size-dependent thickness, volume fraction indices, and radius ratio. The mode shapes of vibration are illustrated through surface and contour plots. [ABSTRACT FROM AUTHOR]

Under service conditions, apart from the harsh temperature environment, mechanical loading also seriously affects the life of thermal barrier coatings (TBCs). A comprehensive understanding of the combined effects of thermo-mechanical loads can help to further reveal the failure mechanism of TBCs. In this work, a portion of a thin-walled circular pipe is intercepted for numerical analysis, and the interface is simplified as a sinusoidal curve. The dynamic growth of thermally grown oxide (TGO) is included into the model. A cohesive model is used for interfacial cracking analysis. The results show that the effects of tensile and compressive loads on the normal stress of the coating are not significant, while the effect on the shear stress of the coating is more obvious. In addition, the in-phase load will delay the occurrence of interfacial failure behavior, while an out-of-phase load can promote the failure. These results will help to better understand the effects of the coupling of mechanical and temperature loads and to provide support and guidance for the design of new TBCs structures in the future. [ABSTRACT FROM AUTHOR]

The fibre reinforced composites are widely used materials in transportation sector. The parameters like the fibre orientation angle, laminate thickness, fibre volume fraction influence the properties of the composite structure. To reduce the experimentation cost, mathematical modelling is used to obtain optimal parameters. In the present study, the effect of the fibre orientation angle on the stresses in a composite plate with a circular cutout and a virtual crack under the thermo-mechanical loads. To impart thermo-mechanical load, a constant pressure of 5 MPa and four different temperatures (30–180 °C) are used simultaneously. The crack propagation in the laminate is quantified by the stresses at the particular location. The normal stress ( σ zz ) and shear stresses ( τ xz , τ yz ) were calculated and reported as a function of the location on the circular cut-out. The location with the higher stresses has higher probability of crack formation. It is observed that the increase in the temperature increases the stress in the composite laminate. The change in angle-ply orientation has significant effect on the optimum fibre orientation angle. [ABSTRACT FROM AUTHOR]

Rock wool insulation slabs are produced in special curing ovens, where molten rock wool fibres coated with binder are compressed between two slat conveyors and blown with hot air for vitrification. Often, the cross-section of the final slabs is slightly convex, which is undesirable. The degree of convexity depends on the deformation of the steel crossbars of the slat conveyors, which are subjected to combined pressure and nonlinear temperature loadings. Due to this complex loading state, it is difficult to determine the contribution of individual load to the total deformation. The main aim of the study was to determine these contributions. Temperature and stress measurements of the crossbars were performed during rock wool production. Upon collecting these measurements, a finite element (FE) model of a crossbar was established for the identification of the pressure loading acting on the crossbars, and finally for determination of their deformations. As a main result of the study, an inverse problem-based methodology for the identification of the deflection of a structure due to unknown temperature and pressure loadings was established and applied on the specific case. The deviations between the deformations of the FE crossbars and the final shape of the rock wool slabs were below 10%, which validates the novel methodology. [ABSTRACT FROM AUTHOR]

Apart from mechanical actions, structural components in the construction industry may be subjected to a thermal gradient, causing (internally) restrained thermal expansion. These thermal loads can alter the mechanical response of components in a structural topology optimization procedure. Therefore, the influence of thermal loading should be considered in the sensitivity analysis to efficiently update the structural layout of material. In this paper, a density-based topology optimization procedure is developed for compliance minimization of structural components subjected to thermo-mechanical loads considering steady-state heat conduction and weak thermo-mechanical coupling. The adjoint method is employed to obtain the analytical sensitivities, taking into account the influence of the design-dependent temperature field and thermal properties. The proposed topology optimization procedure is demonstrated on the MBB problem, extended with thermal loading, to investigate the influence of the proposed sensitivities on the optimized results. Furthermore, the thermo-mechanical load ratio is quantitatively defined and its effect on the resulting topologies is studied. The results show that the thermo-mechanical load ratio significantly changes the topology of the optimized results. Finally, the topology optimization procedure is presented in an efficient 138-line MATLAB code and provided as supplementary material, serving as a basis for further research. [ABSTRACT FROM AUTHOR]

This work presents a comprehensive study consisting of two aspects: a numerical analytical aspect and a laboratory experimental aspect. The numerical study was a three-dimensional finite element numerical analysis of performance of corroded and horizontally cracked aluminium plates, which were repaired by composite patching. The effect of the composite types on the variance of the damaged area of the adhesive (FM-73) and their efficiency on the stress intensity factor were studied. In the experimental study, corroded aluminium plates were prepared and repaired them using technology of the composite. The results showed that the panels that were repaired with composite (boron/epoxy) give values of stress intensity factor (KI) and damaged area ratio (DR) less than the other two studied composites (glass/epoxy and graphite/epoxy), and increase the ultimate strength of plates damage, and this leads to the conclusion that (Boron/epoxy) increases the performance and durability of (Al 2017-A) plates. [ABSTRACT FROM AUTHOR]

Under service conditions, apart from the harsh temperature environment, mechanical loading also seriously affects the life of thermal barrier coatings (TBCs). A comprehensive understanding of the combined effects of thermo-mechanical loads can help to further reveal the failure mechanism of TBCs. In this work, a portion of a thin-walled circular pipe is intercepted for numerical analysis, and the interface is simplified as a sinusoidal curve. The dynamic growth of thermally grown oxide (TGO) is included into the model. A cohesive model is used for interfacial cracking analysis. The results show that the effects of tensile and compressive loads on the normal stress of the coating are not significant, while the effect on the shear stress of the coating is more obvious. In addition, the in-phase load will delay the occurrence of interfacial failure behavior, while an out-of-phase load can promote the failure. These results will help to better understand the effects of the coupling of mechanical and temperature loads and to provide support and guidance for the design of new TBCs structures in the future.

A high-temperature multi-axial test is carried out to characterize the thermo-mechanical behaviour of a 3D-woven SiC/SiC composite aeronautical part under loads representative of operating conditions. The sample is L-shaped and cut out from the part. It is subjected to severe thermal gradients and a superimposed mechanical load that progressively increases up to the first damage. The sample shape and its associated microstructure, the heterogeneity of the stress field and the limited accessibility to regions susceptible to damage require non-contact imaging modalities. An in situ experiment, conducted with a dedicated testing machine at the SOLEIL synchrotron facility, provides the sample microstructure from computed micro-tomographic imaging and thermal loads from infrared thermography. Experimental constraints lead to non-ideal acquisition conditions for both measurement modalities. This article details the procedure of correcting artefacts to use the volumes for quantitative exploitation (i.e. full-field measurement, model validation and identification). After proper processing, despite its complexity, the in situ experiment provides high-quality data about a part under realistic operating conditions. The influence of the mesostructure on fracture phenomena can be inferred from the tomography in the damaged state. Experiments show that the localization of damage initiation is driven by the geometry, while the woven structure moderates the crack propagation. This study widens the scope of in situ thermo-mechanical experiments to more complex loading states, closer to in-service conditions.

This article presents crack repair in the structure by piezoelectric material and predict the fatigue life of the structure. The extended finite element method is applied to model the crack discontinuity. Heaviside function is used for modeling the crack surface while branch functions are used for modeling the crack front. Effects of active and passive repair on structural integrity are investigated under a thermo-mechanical loading environment at zero R-ratio. Paris law is applied to predict life in terms of fatigue cycles. The efficacy of the repair is measured in terms of fatigue life and stress intensity factor. [ABSTRACT FROM AUTHOR]

This paper presents an extension of the existing phase kinetics model of shape memory alloy (SMA) wire on a SMA spring actuator. The phenomenological modeling of an SMA spring under two different bias conditions – SMA spring with (A) normal spring (B) SMA wire along with the computing algorithm is addressed. The results of Case A are found in close agreement with the published literature. Whereas, the results of Case B are reported for the first time and outperform the results of Case A in terms of equal deflection, more controllability, and degrees of freedom as compared with Case A. [ABSTRACT FROM AUTHOR]

In a thermal environment, using the formulations of the refined shear deformation theory, the flexion of the functionally graduated rectangular plates (P-FGM) based on nonuniform elastic foundations is presented. The layers resting on nonuniform elastic foundation are subjected to symmetrical distributed loads. Nonlinear variations in the in-plane displacements through the thickness of the plate are based on the choice of the displacement field of the present theory. Without including shear correction factor, the present theory satisfies the free transverse shear stress conditions on the top and bottom surfaces of the plate. The present refined shear deformation theory contains only four unknowns. According to a power law of the volume fraction, the properties of the materials of this plate vary continuously across the thickness. Comparisons with other results have been made nonuniform foundation. The effects of the index and the dimensions of the P-FGM plate and of the elastic foundation parameters on the thermomechanical behavior are studied. Numerical results show accuracy comparable to other theories in the literature.

Several studies have examined the geotechnical behaviour of energy piles; however, the behaviour of piled-raft foundations containing thermal piles is not fully understood. Because piled-raft foundations are optimally designed to bear mechanical loading from the top structure, the energy piles induce extra stress and bending moments on the raft foundation (slab) from the thermal loads, which may cause structural failure. The present study evaluated the thermo-mechanical behaviour of the energy piled-raft foundations using 3D FEM to simulate the geometrical and mechanical parameters of the pile group with an emphasis on slab stiffness. The interaction between the adjacent piles in a group as well as the bending moment induced through the slab have been evaluated. The results showed that, under thermo-mechanical loads, the stiffness of the slab prevented the free expansion and contraction of the energy pile. Increasing in slab thickness from 0.2 to 0.5 m reduced the energy-pile displacement about 50%. It also was observed that a heating load induced more stress than a cooling load along the longer piles. Cooling mechanical loads caused negative skin friction in the longer piles. It was shown that the equivalent pier method is generally applicable for a group of energy piles. [ABSTRACT FROM AUTHOR]

A high‐temperature multi‐axial test is carried out to characterize the thermo‐mechanical behaviour of a 3D‐woven SiC/SiC composite aeronautical part under loads representative of operating conditions. The sample is L‐shaped and cut out from the part. It is subjected to severe thermal gradients and a superimposed mechanical load that progressively increases up to the first damage. The sample shape and its associated microstructure, the heterogeneity of the stress field and the limited accessibility to regions susceptible to damage require non‐contact imaging modalities. An in situ experiment, conducted with a dedicated testing machine at the SOLEIL synchrotron facility, provides the sample microstructure from computed micro‐tomographic imaging and thermal loads from infrared thermography. Experimental constraints lead to non‐ideal acquisition conditions for both measurement modalities. This article details the procedure of correcting artefacts to use the volumes for quantitative exploitation (i.e. full‐field measurement, model validation and identification). After proper processing, despite its complexity, the in situ experiment provides high‐quality data about a part under realistic operating conditions. The influence of the mesostructure on fracture phenomena can be inferred from the tomography in the damaged state. Experiments show that the localization of damage initiation is driven by the geometry, while the woven structure moderates the crack propagation. This study widens the scope of in situ thermo‐mechanical experiments to more complex loading states, closer to in‐service conditions. [ABSTRACT FROM AUTHOR]

In a thermal environment, using the formulations of the refined shear deformation theory, the flexion of the functionally graduated rectangular plates (P-FGM) based on nonuniform elastic foundations is presented. The layers resting on nonuniform elastic foundation are subjected to symmetrical distributed loads. Nonlinear variations in the in-plane displacements through the thickness of the plate are based on the choice of the displacement field of the present theory. Without including shear correction factor, the present theory satisfies the free transverse shear stress conditions on the top and bottom surfaces of the plate. The present refined shear deformation theory contains only four unknowns. According to a power law of the volume fraction, the properties of the materials of this plate vary continuously across the thickness. Comparisons with other results have been made nonuniform foundation. The effects of the index and the dimensions of the P-FGM plate and of the elastic foundation parameters on the thermomechanical behavior are studied. Numerical results show accuracy comparable to other theories in the literature. [ABSTRACT FROM AUTHOR]

Amaç: Mine-sement sınırının altında hazırlanan kavitelerde mikrosızıntı ile mücadele edebilmek oldukça güçtür. Bu nedenle çalışmanın amacı derin class II kavitelerdeki stres ve marginal bölgedeki kapanma problemlerinin çözümüne yönelik son yıllarda sağlanan teknolojik ilerlemelerle geliştirilen nano dolduruculu kompozitlerin akışkan formlarının açık sandviç tekniği ile restore edilen derin kavitelerdeki etkinliğinin incelenmesidir. Yöntem: 60 adet dişe standart meziyo-okluzal (MO), aproksimal kutu (box) şeklinde kaviteler, oklüzo-gingival derinliği mine-sement sınırının 1 mm altında olacak şekilde ve aproksimal kutunun ebatları 2x4x6 mm olacak şekilde açılmıştır. Restorasyonları bitirilen dişler rastgele seçilerek 3 gruba ayrılmıştır (n=20). Grup 1 kontrol grubudur ve kaviteler direkt kompozit (Filtek Z250) uygulaması ile bitirilmiştir. Grup 2 de basamakta Supreme XT Flow, Grup 3 te basamakta Grandio Flow kullanılmış olup, her 3 grubun üst yapıları mikrohibrit kompozit rezin (Filtek Z250) ile restore edilmiştir. Tüm örnekler termo-mekanik yüklemeye maruz bırakılarak yaşlandırılmıştır. Mikrosızıntı tayini bazik fuksin boyasının penetrasyon miktarının stereomikroskop (X40) altında incelenmesi ile yapılarak istatistiksel analize tabi tutulmuştur. Bulgular: Sonuçların değerlendirilmesinde Mann Whitney U Test kullanılmıştır. Her iki nano dolduruculu akışkan kompozitler Supreme XT Flow ve Grandio Flow kontrol grubunda yer alan mikrohibrit rezine istatistiksel olarak anlamlı bir üstünlük sağlayamamışlardır (p>0,05). Ayrıca Supreme ve Grandio materyallerinin mikrosızıntı dereceleri arasında istatistiksel olarak anlamlı bir farklılık bulunamamıştır (p>0,05). Sonuç: Nanohibrit akışkan kompozitler kendilerinden beklenen derin class II kavitelerdeki mikrosızıntıyı azaltma konusunda daha üstün özellikler sergileyememiştir.

In this paper, efforts have devoted to developing heat conduction formulation to determine the exact temperature for power law varied functionally graded (FG) laminate. Further, the semi-analytical approach has re-invented for displacement and stress analysis of FG laminate. This way of analysis involves solving of two-point boundary value problem (BVP) ruled by first-order ordinary differential equations (ODE's). Here material properties such as modulus of elasticity, coefficient of thermal expansion, and heat conductivity have considered being varied as per power law, whereas Poisson’s ratio kept constant. The effect has undergone examination for applied transverse thermal loading and mechanical loading with the developed semi-analytical formulation. The observation of the effect of variation of volume fraction as per power law on through thickness temperature distribution along with consideration of exact temperature and with assumed power law temperature has carried out. Further corresponding thermal stress analysis and its comparison with numerical parametric studies lead to productive output in this area of research.

This work presents a three-dimensional finite element numerical analysis of the performance of plates repaired by composite patch. The effect of the geometric shapes of the composite patches on the damaged area variation of the adhesive (FM-73) of corroded and cracked Al 2024-T3 plates, the mechanical properties of different composites and the thermal loading on the ratio of the damaged area (DR) to the crack size were studied. The results show that glass/epoxy repaired sheets give lower KI and DR values than the other two composites studied, and this leads to the conclusion that glass/epoxy increases the performance and durability of Al 2024-T3 aircraft structures repaired by patch composite. [ABSTRACT FROM AUTHOR]

The aim of this paper is to propose a computation strategy for fatigue propagation simulation of a crack by taking into account the plasticity. Feulvarch et al. (Comput Methods Appl Mech Eng 361: 112805, 2020) recently proposed a first XFEM formulation capable of overcoming the volumetric locking phenomenon due to plastic incompressibility in 3D. This formulation is here applied to quadratic elements for the mode I propagation of a crack in a valve structure submitted to cyclic thermo-mechanical loading. A simulation strategy is proposed where it is not necessary to compute all the cycles and thus the complete plastic history. This is of great interest because it avoids the treatment of the possible closing of the crack and uses the conventional J-integral. The application reveals the interest of taking plasticity into account for the propagation accuracy. [ABSTRACT FROM AUTHOR]

This paper presents a thermodynamically consistent phase field formulation designed for investigating quasi-static brittle fracture under thermo-mechanical loading conditions in functionally graded materials. The governing equations for linear momentum and crack evolution are derived by minimizing the free energy functional, which includes elastic strain energy and surface energy, with respect to displacement field and the phase field variable, respectively. A thermodynamically consistent formulation is employed to establish the governing equation for heat conduction. The proposed formulation is converted into a set of finite element equations using the Ritz method and implemented in COMSOL Multiphysics, a commercial finite element software which allows for writing governing equations in their strong form. A segregated solver is utilized to solve iteratively the coupled problem. The proposed model is verified against existing mechanical and thermo-mechanical phase field models, demonstrating good agreement with the literature. To explore the model's capabilities, a graded layer composed of Zirconia and a Titanium alloy with a surface crack undergoing thermo-mechanical loading is considered as a case study for this investigation. Additionally, the model incorporates a thermal conductivity degradation proposed. A parametric study is performed to investigate the effect of varying parameters like volume fraction, thermal loading rate, and the thermal conductivity degradation on the load–displacement curve of the graded layer. These findings contribute to the understanding of thermo-mechanical behavior of surface graded layers and serve as a foundation for addressing more complex thermo-mechanical problems. [ABSTRACT FROM AUTHOR]

An experimental thermo-mechanical facility was developed with conditions towards that of the combustion environments experienced by the hot section components of a jet engine. Two different melt-infiltrated (MI) ceramic matrix composites (CMCs) were evaluated, one containing Hi-Nicalon Type S fibers and the other Tyranno SA fibers. Specimens considered in this study were subjected to fatigue loading with a stress ratio of 0.1, frequency of 1 Hz and a specimen surface temperature of 1200 ± 20 °C. Results indicate that fatigue life in the combustion environment was an order of magnitude lower compared to the furnace environment and is attributed to the hostile environment present with the burner rig. Post-test microscopy was conducted in order to understand the damage mechanisms and oxidation behavior. Polished longitudinal sections of the burner rig specimens revealed longitudinal cracking which could be attributed to the presence of thermal gradient stress. Electrical resistance (ER) was implemented to monitor the damage. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to analyze the repair of a straight and angular crack in the structure using a piezoelectric material under thermo-mechanical loading by the extended finite element method (XFEM) approach. This provides a general and simple solution for the modeling of crack in the structure to analyze the repair. Design/methodology/approach: The extended finite element method is used to model crack geometry. The crack surface is modeled by Heaviside enrichment function while the crack front is modeled by branch enrichment functions. Findings: The effectiveness of the repair is measured in terms of stress intensity factor and J-integral. The critical voltage at which patch repair is most effective is evaluated and presented. Optimal patch shape, location of patch, adhesive thickness and adhesive modulus are obtained for effective repair under thermo-mechanical loading environment. Originality/value: The presented numerical modeling and simulation by the XFEM approach are of great benefit to analyze crack repair in two-dimensional and three-dimensional structures using piezoelectric patch material under thermo-mechanical loading. [ABSTRACT FROM AUTHOR]

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This article presents an experimental investigation of repair of a crack in a structure using piezoelectric material under thermo-mechanical loading environment. The cyclic mechanical load is applied on a plate with a straight and angular crack under uniform temperature environment. Two cases have been considered for the repair of crack under (a) mechanical loading and (b) thermo-mechanical loading environment. A piezoelectric sensor is utilized to measure voltage. The measured voltage is used to calculate the stress intensity factor in passive and active modes. The effect of a single and double piezoelectric patch in the repair of the plate is investigated. The double piezoelectric patch is found to be more effective as compared to single patch when placed symmetrically offset from the crack. An optimal value of voltage and phase difference is evaluated for most effective crack repair. Location of the piezoelectric patch is varied with respect to crack location, and best-suited position for effective crack repair is proposed. The viability of piezoelectric used for repair under thermo-mechanical loading is discussed. The active mode of repair by piezoelectric is found to be effective under thermo-mechanical loading environment. [ABSTRACT FROM AUTHOR]

Multiple cracks subsist in functionally graded materials (FGMs) components. These cracks interact with each other and induce fracture phenomenon. The thermo-mechanical loading creates singular stress field at the crack tips, which causes the sudden failure of component and loss of human life. Therefore, the present work deals with the crack interaction study under mixed mode mechanical and thermal loading environment. The crack discontinuities have been modeled by extrinsically enrichment eXtended Finite Element (XFEM) approach. The heterogeneous functionally graded material property has been modeled by exponential law. [ABSTRACT FROM AUTHOR]

Energy piles are an emerging energy technology for both structural and thermal purposes. To support structure load, piles are always used in groups with raft; however, the cost and complexity of field tests and numerical modelling limits the research on the bearing characteristics of energy pile group. In this paper, exponential model was applied to simulate the thermo-mechanical soil-pile interaction of energy pile group. Axial load transfer (τ-z) analysis was first performed to calculate the shear stress distribution in the soil, then matrix displacement method was introduced to determine the thermo-mechanical response of energy pile group. The validity of the analytical model was tested against field tests and numerical results. A case study was further performed to analyze the influence of thermal cycles and arrangement of thermally active piles on the bearing response of the whole pile group. Test results show that with the thermally activated pile in pile group, (1) differential settlement increases with thermal cycle numbers; (2) the axial force of thermally active pile increases during heating process and decreases during cooling process, and this trend varies for the surrounding nonthermal piles; (3) induced load on thermal pile increases with thermal cycles, but decreases for nonthermal piles. The proposed analytical model is expected to serve as a simple and convenient alternative for the preliminary analysis on the bearing characteristics of energy group pile.

This paper investigates the nonlinear bending behaviours of functionally graded trapezoidal nanocomposite plates reinforced with graphene platelets (GPLs) under thermo-mechanical loading by employing finite element method. The modified Halpin–Tsai model and rule of mixtures are adopted to determine the Young's modulus, Poisson's ratio and the thermal expansion coefficient of the nanocomposites. The influences of a number of factors, including the distribution pattern, concentration and size of GPLs, plate geometry and temperature, on the nonlinear bending of the nanocomposite plates are comprehensively investigated. Numerical results demonstrate that dispersing a small amount of GPLs into nanocomposites can significantly enhance the nonlinear bending performance of the trapezoidal plates. The trapezoidal plates with more GPLs dispersing close to the top and bottom surfaces has the minimum bending deflection and are less sensitive to the temperature increases. GPLs with fewer layers and larger surface area are better reinforcing fillers than their counterparts. Moreover, the plates with bigger bottom angles are found to have better bending performances. However, when the bottom angles are greater than 75°, the variation of the bottom angles will have limited effects on the bending behaviours of the trapezoidal plates. [ABSTRACT FROM AUTHOR]

In this paper, a refined quasi-three-dimensional shear deformation theory for thermo-mechanical analysis of functionally graded sandwich plates resting on a two-parameter (Pasternak model) elastic foundation is developed. Unlike the other higher-order theories the number of unknowns and governing equations of the present theory is only four against six or more unknown displacement functions used in the corresponding ones. Furthermore, this theory takes into account the stretching effect due to its quasi-three-dimensional nature. The boundary conditions in the top and bottoms surfaces of the sandwich functionally graded plate are satisfied and no correction factor is required. Various types of functionally graded material sandwich plates are considered. The governing equations and boundary conditions are derived using the principle of virtual displacements. Numerical examples, selected from the literature, are illustrated. A good agreement is obtained between numerical results of the refined theory and the reference solutions. A parametric study is presented to examine the effect of the material gradation and elastic foundation on the deflections and stresses of functionally graded sandwich plate resting on elastic foundation subjected to thermo-mechanical loading. [ABSTRACT FROM AUTHOR]

Abstract A cyclic cohesive zone model is developed which is capable of predicting fatigue driven delamination under thermo–mechanical loading conditions. The model is an extension of an exponential traction–separation law describing the quasi–static constitutive behavior of the interface. Mixed–mode loading conditions are accounted for using an interaction criterion based on the Benzeggagh and Kenane expression. Damage degradation under thermo–mechanical fatigue loading is accounted for by using a cycle–by–cycle analysis. A Paris' law type formulation is utilized to model fatigue damage which is based on physically interpretable interface properties, overcoming the need of any parameter fitting. Varying load amplitudes are captured by the model formulation. For constant amplitude loading a cycle jump technique is implemented to decrease the computational time. The cohesive zone parameters are assumed to be temperature dependent and the model formulation accounts for interface weakening at elevated temperatures. In addition, the effect of interface degradation onto the heat transfer across the damaged interface is modeled by linking the mechanical damage variable to the thermal conductance of the interface. The model is implemented within the framework of the nonlinear Finite Element Method and includes non–local evaluation of the cohesive zone length and the mode ratio. Finally, the proposed model is demonstrated on mode I, mode II, and mixed–mode delamination tests. [ABSTRACT FROM AUTHOR]

Highlights • The thermo-elastic nonlinear analysis of various Functionally Graded shell is studied. • The Voigt's model is adopted to define the Functionally Graded material properties. • A six-noded isoparanetric triangular shell element is presented. • The Euler-Rodrigues formulations and the first-order shear deformation theory are employed. • Thermo-mechanical buckling of FG shell is predicted. • Both the pre-buckling and post-buckling equilibrium paths are traced. Abstract In this paper, the thermo-elastic nonlinear analysis of various Functionally Graded (FG) shells under different loading conditions is studied. A second-order isoparametric triangular shell element is presented for this purpose. The element is six-noded, and each node has all six independent degrees of freedom in space. It should be added, the first-order shear deformation theory is induced. Furthermore, Voigt's model is adopted to define the FG material properties, which are considered to change gradually from one surface to another. The critical temperature is predicted. Both the pre-buckling and post-buckling equilibrium paths are traced. Since the linear eigenvalue analysis leads to wrong responses in the problems with strong nonlinearity, the suggested procedure is performed based on the FEM and more exact estimations are achieved using equilibrium path. [ABSTRACT FROM AUTHOR]

Abstract In this work, a formulation for buckling and geometrically nonlinear analysis of functionally graded plates under thermo-mechanical loading is presented. The influence of high temperature environment on deflections due to mechanical loading as well the deflections produced by thermal loads acting alone or combined with mechanical loads is analysed. The implemented finite element model is based on a non-conforming triangular flat plate/shell element, with three nodes and eight degrees of freedom per node, associated with a higher order shear deformation theory. The solutions of some illustrative examples are evaluated involving the variation of volume fractions of constituent materials, temperature range and material combinations, which have significant impact on the deflections of plates. The numerical results obtained with the present model are presented and compared with alternative solutions. [ABSTRACT FROM AUTHOR]

Abstract We use pattern matching of experimental and dynamically simulated backscattered Kikuchi diffraction (BKD) patterns to increase the orientation precision of electron backscatter diffraction (EBSD) measurements. In order to quantify the improvement in orientation precision, we analyze the experimental distribution of the kernel average misorientation (KAM) angles. We find that for the same raw data, i.e. the same EBSD data acquisition time budget, the pattern matching approach improves the KAM resolution by an order of magnitude compared to orientation data delivered from the conventional Hough-transform based data analysis. This quantitative improvement enables us to interpret small orientation changes in plastically deformed materials which are hidden in noisy orientation data delivered from the reference EBSD system. As an application example, we analyze a ferritic-martensitic steel (P92) sample before and after low-cycle fatigue (LCF) loading (± 0.3 % strain) at 620 °C. Whereas the low precision of the EBSD orientation data from the manufacturer software does not allow a reliable discrimination of the gradually changing microstructure, we find very clear systematic differences of the local microstructure after the pattern matching orientation refinement of the initial, raw pattern data. For the investigated P92 sample, the KAM-angle histograms are well described by two log-normal distributions indicating the already tempered and the remaining and mostly untempered martensite. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Highlights • Thermo-mechanical cyclic experiments of 304SS were performed at large temperature ranges. • The saturated cyclic behavior observed was simulated using a cyclic viscoplastic model with a cyclic hardening parameter. • The saturated behavior was not simulated well by considering temperature dependence of the cyclic hardening parameter. • The saturated behavior was simulated well by assuming maximum temperature dependence of the cyclic hardening parameter. • The micro-structure evolution for cyclic hardening was suggested to be dependent on maximum temperature. Abstract Thermo-mechanical cyclic experiments on 304 stainless steel were performed at several temperature ranges with T min (minimum temperature) of 150 °C and T max (maximum temperature) ranging from 350 °C to 1000 °C. Corresponding isothermal cyclic experiments were also performed at several temperatures. Temperature-history dependent cyclic hardening was thus observed to significantly occur under thermo-mechanical cyclic loading when T max was around 600 °C. In contrast, almost no cyclic hardening occurred when T max was 1000 °C. The observed, thermo-mechanical cyclic hardening behavior was then simulated using a cyclic viscoplastic constitutive model with a cyclic hardening parameter. The simulation focused on the saturated state of cyclic hardening, leading to the following findings. The saturated thermo-mechanical cyclic hysteresis loops were not predicted well by simply taking into account temperature dependence in the cyclic hardening parameter. Then, by assuming the cyclic hardening parameter to be dependent on T max , the saturated thermo-mechanical hysteresis loops were simulated well. These mean that the cyclic hardening parameter of 304 stainless steel should not change with temperature but depend on T max in the saturated state of cyclic hardening under thermo-mechanical cyclic loading. Graphical abstract Image, graphical abstract [ABSTRACT FROM AUTHOR]

Carbon fibre-reinforced polymer (CFRP), a polymer matrix composite material, has been increasingly used in industry, science, daily use equipment and engineering in recent decades. In civil engineering, when a construction structure reinforced with external bonded CFRP is subjected to fire, both the structure and CFRP reinforcement are concurrently affected by the elevated temperature and mechanical load. In Eurocode, the evolution of the mechanical properties of concrete and steel are described as decreasing with increasing temperature, while the performance of CFRP has not been clearly mentioned. In civil engineering, there are two common types of CFRP: one that is fabricated in a factory before installation (pultruded CFRP) and one that is fabricated on site during the installation with hand lay-up methods. In the literature, several experimental datasets focus on the first type of CFRP considering different aspects, such as performance under different testing conditions, different temperature levels, etc. This paper focuses on the thermo-mechanical performance of the second type of CFRP with a fire application purpose. The material is tested for mechanical performance at temperature levels varying from 20 °C to 600 °C and for thermal resistance at different tensile stress ratios from 10% to 75% of the material's ultimate tensile stress at ambient temperatures. The results show that the mechanical performance of the tested material decreased as the temperature increased, the ultimate strength decreased by 50% at 350 °C, and the Young's modulus only decreased by 30% at 600 °C. The results also confirm that the mechanical status has an influence on the thermal performance of the material and vice versa. A new analytical model has been proposed for the thermo-mechanical performance of the tested material and fits well with other experimental data obtained from similar testing conditions. The outcome of the proposed analytical model is applicable to fire design in civil engineering. [ABSTRACT FROM AUTHOR]