Thermal Shock Loading Research Articles

Numerical Fracture Analysis of a Reactor Pressure Vessel based on Abaqus-FRANC3D Co-simulation Method

The reactor pressure vessel (RPV) is subjected to many cyclic loadings critical of which is the integrity risk posed by pressurized thermal shock (PTS) loadings induced by one of the most frequent anticipated operational occurrences - inadvertent operation of the safety injection system (SIS). In this paper, the fracture mechanics analysis for an ageing pressurized water reactor subjected to PTS induced by inadvertent actuation of the SIS is performed using a proposed simplified Abaqus-FRANC3D co-simulation method. A three-dimensional (3-D) finite element half-symmetric model of a typical pressured water reactor RPV is used to perform thermal-mechanical stress coupling analysis. 3-D fracture mechanic submodel with an assumed surface crack is created for the computation of the transient integrity parameter-stress intensity factor (SIF), using M-integral approach coupled in the proposed co-simulation method. Subsequently ASME method is used to evaluate the vessel’s material fracture toughness. Finally, the SIFs obtained with the simplified co-simulation method is compared with the conventional virtual crack-closure technique (VCCT), and the result show good agreement. This work serves as a useful reference for fast crack propagation and life prediction analysis of ageing PWR RPVs.

Magnetic-electric composite coating with oriented segregated structure for enhanced electromagnetic shielding

Manipulation of the internal architecture is essential for electromagnetic interference (EMI) shielding performance of metal-based coatings, which can address the electromagnetic pollution in large-size, complex geometries, and harsh environments. In this work, oriented segregated structure with conductive networks embedded in magnetic matrix was achieved in Fe-based amorphous coatings via Ni–Cu–P functionalization of (Fe0.76Si0.09B0.1P0.05)99Nb1 amorphous powder precursors and then thermal spraying them onto aluminum (Al) substrate. Benefiting from the unique magnetic-electric structure, the [email protected] composite delivered prominent EMI shielding performance. The EMI shielding effectiveness (SE) of modified [email protected] composite is ~41 dB at 8–12 GHz, doubling the value of Al substrate and is 15 dB greater than that of Ni–Cu–P-free [email protected] composite. Microstructure analysis showed that the introduced Ni−Cu−P insertions forcefully suppress the serious oxidation of the magnetic precursors during thermal spraying and form a dense conductive network in the magnetic matrix. Electron holography observation and electromagnetism simulation clarified that the modified coating can effectively trap and attenuate the incident radiations because of the electric loss from Ni−Cu−P conductive network, magnetic loss from Fe-based amorphous coating, and the electromagnetic interactions in the oriented segregated architectures. Moreover, the optimized thermal isolation and mechanical properties brought by structural improvement enable the coating to shield complex parts in thermal shock and mechanical loading environments. Our work gives an insight on the design strategies for metal-based EMI shielding materials and enriches the fundamental understanding of EMI shielding mechanisms.

Dynamic response of a cracked thermopiezoelectric strip under thermoelectric loading using fractional heat conduction

This study is concerned with the dynamic behavior of a piezoelectric material strip with a parallel crack under thermal shock and transient electric loading. The governing thermal and electromechanical equations are exactly reduced to a system of Cauchy-type singular integral equations by applying Laplace and Fourier transforms and the dislocation density functions. Numerical examples are discussed in detail to show the effects of the applied heat conduction model, cracked strip configuration, and electrical load variables on the dynamic thermal results and the stress-electric displacement intensity factors. The results reveal that the overshooting phenomenon would be more evident with the longer relaxation time and higher fractional order, while the wave behavior becomes weaker and stronger, respectively. There are apparent inflection points on the dynamic stress intensity factors (DSIFs) and the dynamic electric displacement intensity factor (DEDF) curves for different configurations of the strip and the coefficients of the heat conduction model. In addition, the stress intensity factors are insensitive to the electric load which has a dominant influence on the electric displacement intensity factor.

Transient response analysis of FG-CNTRC curved composite panel under multi-directional initially stresses resting on nonpolonomial elastic foundation

Due to importance of exploring novel ways to protect systems from detrimental influences of thermal shock phenomenon, this study aims at analyzing the transient coupled poro/thermoelasticity response of functionally graded CNT reinforced (FG-CNTR) nanocomposite panels surrounded by non-polynomial kind of elastic foundation. In addition to thermal shock, the mentioned nanocomposite structure is subjected to initial mechanical loads in different orientations. As the accuracy of the results is of high prominence to guarantee reliability of the practical designs, the governing equations are developed on the basis of the exact type of elasticity theory known as three-dimensional form. Also, analytical solution is determined by applying Navier approach to solve the governing differential equations for simply-supported boundaries. Energy balance equation is utilized to determine the temperature gradient of the cylindrical panel considering the assumptions that the internal surface is fully isolated and the external one is subjected to thermal shock loading. Modified type of Dunber and Abate’s approach is implemented to inverse the Laplace transform in order to map the response of the system from Laplace into time domain. Convergence of the determined deflection, shear stresses, and temperature versus passing time is analyzed and confirmed. The acquired numerical results elucidate the role of different factors such as mid-radius to thickness ratio, volume-fraction, and scattering pattern of CNT in the transient coupled poro/thermoelasticity response of the FG-CNTR nanocomposite cylindrical panel. As a valuable result, it is found that increasing the volume-fraction of CNT applies negative impacts on the variation of the transverse shear stress.

Microwave-enhanced consolidation of zirconia/titanium functionally graded materials

This study aims to fabricate ZrO2/Ti functionally graded materials (FGMs) using microwave-enhanced sintering techniques with a domestic microwave oven. The compositional gradient is expected to make temperature gradient in the materials due to increases in dielectric losses of ZrO2 at high temperatures during consolidation processes. The fabricated ZrO2/Ti FGMs demonstrated the sound microstructures and thermo-mechanical properties under cyclic thermal shock loading conditions. Finite element analysis (FEA) with mean-field micromechanics was conducted to examine the experimental results.

A deep learning approach based on a data-driven tool for classification and prediction of thermoelastic wave’s band structures for phononic crystals

This article deals with the data-driven prediction of the band structures of thermoelastic waves in the nano-scale phononic crystal beams considering nano-size effects. The computational intelligence methods are developed using a data-driven tool to discover the design space of phononic crystals, which are subjected to thermal shock loading. For this purpose, a rich dataset is created utilizing an analytical solution, which was previously proposed for the nonlocal coupled thermoelasticity analysis in a nano-sized phononic crystal beam. The preprocessing methods, hyperparameters optimization, and shallow and deep neural networks are used to classify and predict the bandgaps. Also, according to the created dataset and the data-driven method, the phononic crystal feature importance and behavior based on the design parameters are assessed in detail. The detailed investigation reveals the importance of the design parameters according to the deep neural network’s results. It is demonstrated by numerical results that the proposed final data-driven model can predict the characteristics of the phononic crystals pretty well. Also, the results show that the deep neural network outperforms the shallow neural network for the classification and prediction of the band structures. The final results can be a helpful tool to have a fast numerical framework for the prediction of photonic crystals’ bandgaps before the application of time-consuming accurate frameworks.

Physiological Predictors for the Audio-Motor Synchronization Ability

The meshless local Petrov–Galerkin (MLPG) method is employed for anisotropic transient thermoelasticity analysis of 2D decagonal quasicrystals (QCs) subjected to transient thermal and mechanical shock loadings. The wave type model and the elasto-hydrodynamic model are applied to derive the phonon and phason governing equations, respectively. The temperature affects only the phonon field. To find the temperature distributions on the assumed 2D domain, the anisotropic heat conduction problem is solved using the MLPG method. Also, the MLPG method is successfully employed to obtain the transient behaviors of both phonon and phason displacements by solving the governing equations in local integral equations (LIEs) forms. Making use a unit step function as the test functions in the local weak-form of governing equations, we derived the local integral equations (LIEs) considered on small subdomains identical with support domains of test functions around each node. The radial basis functions are used for approximation of the spatial variation of field variables. The Laplace-transform technique is utilized to discretize the time variations.

Strain gradient and Green–Naghdi-based thermoelastic wave propagation with energy dissipation in a Love–Bishop nanorod resonator under thermal shock loading

The thermoelastic wave propagation analysis is developed in a Love–Bishop nanorod resonator employing the strain gradient elasticity and Green–Naghdi theories with energy dissipation for the first time. The assumed nanorod resonator is subjected to thermal shock loading. The variational principle is applied to derive the coupled system of partial differential equations for temperature and displacement fields in a Love–Bishop nanorod. An analytical solution is proposed to solve the governing equations in Laplace domain. To obtain the temporal variation of fields’ variables, a proper Laplace inversion technique is employed in the problem. The size effects in the nano-sized Love–Bishop rods are taken into account with five small-scale parameters including three higher-order materials length parameters, the micro-length inertia and thermal parameters. Two types of thermal shock loadings such as laser pulse-induced suddenly increasing temperature are utilized in this work, and the laser shock-induced thermoelastic wave propagations in both temperature and displacement fields are illustrated. The effects of the higher-order materials length parameters and the micro-length inertia and thermal parameters on the propagation of thermal and elastic waves are studied in detail.

Evaluation of plastic deformation and prediction of thermal mechanical fatigue life of an Al–Si alloy piston for diesel engines

AbstractIn this study, a three‐step prediction method was developed to predict the thermal mechanical fatigue (TMF) life of an Al–Si alloy piston: (1) establishing a relation between the plastic deformation and fatigue life under the temperature cycle of 100–350°C via a series of TMF tests of the aluminum alloy specimens; (2) computing the dangerous plastic deformation of the piston under the thermal shock condition of interest by numerical simulation; (3) estimating the life of the piston through taking the computed plastic deformation into the established relation. The effectiveness of the proposed prediction method was verified by thermal shock tests of the piston, and the prediction error is no more than 25%. The mechanism of piston cracking can be summarized as follows: the inhomogeneous plastic deformation induced higher tensile stress around primary Si particles and protrusions at the rim and then microcracks were produced at the protrusions under the dangerous tensile stress, and finally, macrocracks occurred. The life of the piston under the thermal shock load and combustion pressure is speculated to be shorter than that under the thermal shock load. Considering the effect of stress relaxation on plastic deformation, the long full‐load operation of the engine contributes to the piston cracking in T direction, while the long idling operation reduces the piston cracking tendency in T direction and increases the piston cracking tendency in F and R directions.

Coupled thermoelasticity of FG-GPLRC multi-curved composite panel under thermal shock loading

This study is dedicated to explore the transient coupled thermoelasticity solution of the FG-GPLRC multi-curved composite panel subjected to thermal shock for the first time. Time dependent equations of motion within the context of theory of elasticity are formulated and analytically solved by means of Navier approach. The temperature gradient is acquaried by employing the energy balance equation for the composite cylindrical panel subjected to thermal shock at its outer surface and thermally isolated at its inner surface. The time history of deflections, stresses and temperature are acquired by applying modified format of Dubner’s and Abate’s technique to inverse the Laplace transform. The effective thermoelastic properties of the composite are calculated according to correlations presented by modified form of Halpin-Tsai micromechanics. The numerical results of this study are compared with those recorded in the associated high-quality sources to verify their accuracy. The thorough parametric exploration is executed to analyze the role of various items like mid-radius to thickness ratio, distribution patterns and weight fraction of GPL in the transient coupled thermoelasticity response of FG-GPLRC multi-curved composite panel.

Cyclic fatigue life characteristics of ceramic balls under variable thermal shock loadings

Ceramic balls made of silicon nitride (Si3N4) exhibited excellent mechanical properties are used in high-end components operating at ultra-high speeds, and high and low temperatures. Previously, studies have involved the cyclic mechanical and thermal fatigue tests of ceramic balls under a constant temperature. However, the thermal fatigue characteristics of brittle materials have not been theoretically or experimentally investigated under variable thermal shock loadings to date. Herein, cyclic thermal shock fatigue (CTSF) life characteristics of Si3N4 ceramic balls subjected to single- and two-stage cyclic thermal shock loadings were theoretically and experimentally investigated using a probabilistic model based on slow crack growth concept in conjunction with Weibull distribution. Consequently, the fracture criterion derived from the probabilistic model was related to the linear cumulative damage law (Miner’s rule). Thereafter, the predicted CTSF life of the ceramic balls was compared with the experimental results to validate the proposed probabilistic model. Therefore, the proposed model accurately reproduced the experimental results to a certain extent.

Gaussian thermal shock-induced thermoelastic wave propagation in an FG multilayer hybrid nanocomposite cylinder reinforced by GPLs and CNTs

In this paper, a new modified micromechanical model is proposed to obtain the mechanical and thermal properties of a reinforced functionally graded (FG) multilayer hybrid nanocomposite cylinder for thermoelastic wave propagation analysis with energy dissipation using Green–Naghdi theory. The FG multilayer hybrid nanocomposite cylinder is assumed to be under Gaussian thermal shock loading and also it is reinforced by graphene platelets (GPLs) and carbon nanotubes (CNTs). The cylinder is assumed to be made of multi-layers (sub-cylinders), and each layer is reinforced by a uniform distribution of GPLs and CNTs. A modified micromechanical model is proposed to calculate the thermo-mechanical properties with nonlinear grading patterns of the GPLs and CNTs along the radial direction of the cylinder. The nonlinear grading patterns of the GPLs and CNTs distributions along the radial direction of the whole cylinder can be created using a suitable arrangement of the layers (sub-cylinders). An effective meshless collocation method based on the generalized finite difference (GFD) method and the Newmark method are employed to solve the coupled governing equations of the GN-based coupled thermoelasticity analysis. The effects of the key parameters such as the weight fraction of the GPLs and CNTs and volume fraction index on the thermoelastic wave propagations and dynamic behaviors of the field variables are studied in detail. Also, the effects of the reinforcement by GPLs and/or CNTs in a hybrid nanocomposite on the transient behaviors of cylinder in both temperature and displacement fields are compared. The accuracy and stability of the presented meshless method and also the proposed new modified micromechanical model is verified by the published reference data.

Effect of hybrid thermal cycling and shock on flexural properties of nanoclay/glass/epoxy nanocomposites

In present research, the flexural properties of glass/epoxy composites reinforced by nanoclay particles (3, 5 and 7 wt.%) under various hybrid thermal cycling and shock loadings (15 and 30 thermal cycles at immediate −70°C and +100°C temperatures) have been investigated. It was found that the flexural strength of 5 wt.% nanoclay/glass/epoxy nanocomposites under 15 and 30 hybrid thermal loadings was enhanced by 19.35% and 20.78%, respectively. Also, after 15 hybrid thermal loadings, the flexural stiffness of 5 wt.% clay/glass/epoxy nanocomposites increased by 9.30% compared to static conditions. More importantly, after 30 hybrid thermal loadings, by adding more filler contents, the flexural stiffness was increased. For instance, at 7 wt.% clay/glass/epoxy nanocomposites, the flexural stiffness enhanced 17.97% compared to neat composite. FESEM morphology images confirmed that presence of optimum filler contents changed the composites inherent properties. Therefore, the outcome of this research can show various remarkable advantages for researchers to apply nanoclay as nanofillers to reinforce composites structures under hybrid thermal cycling and shock applications.

Thermal shock resistance and crack growth behavior of Aurivillius phase Bi4Ti3O12-based ferroelectric ceramics

A type of W/Cr co-doped Bi4Ti3O12 (ab. BTWC) ceramics were synthesized utilizing the traditional solid-state reaction process, and its thermal shock resistance (TSR) as well as the crack growth behavior was systematically investigated by water quenching technology. It can be found by the succeeded fractographic analysis that many edge thermal cracks began to appear in the samples subjected to thermal shock with ΔT ​= ​400 ​°C. According to an integrated TSR model, the critical thermal-shock temperature difference ΔTCwas calculated to be 356 ​°C. Moreover, it can be noticed that the indenter induced crack growth behaviors under thermal shock loads presented three stages, i.e. no growth, large growth, and moderate growth, along with ΔT increasing from 0 ​°C to 700 ​°C. Finally, the asymmetry of P-E hysteresis loops was observed and understood by the orientated polarization of defect dipoles after the sample was thermally shocked, while the water-quenching process above the Curie temperature of the ceramics could lead to a random orientation of the defect dipoles. This research can not only evaluate the service conditions of Bi4Ti3O12 high-temperature piezoceramics, but also understand the failure mechanism of bismuth layer structured ferroelectric ceramics in the case of thermal shock.

Modeling and studies of fracture in functionally graded materials under thermal shock loading using peridynamics

In this study, an extended ordinary state-based peridynamic (OSBPD) model was proposed and applied to study the thermal shock damage and fracture of functionally graded materials (FGM) and structures. A modified term including thermal expansion coefficient is introduced into the conventional peridynamic model for investigating the thermal deformation of materials, and an influence function reflecting the gradient change of material properties is introduced into the force vector state in peridynamic model. The model and algorithm are validated by analyzing the cracking of a plate quenching in water and comparing with experimental results and available literature data. Furthermore, the effects of gradient distribution of elastic modulus, thermal expansion coefficient and fracture toughness of FGM on thermal damage and crack propagation are investigated. Numerical results show that the proposed model can effectively describe the failure process of functionally gradient materials under thermal shock loading. The distribution of elastic modulus, coefficient of thermal expansion and fracture toughness in FGM have great influence on the initiation and propagation of cracks, and reasonable gradient change form of materials can improve the thermal resistance ability of the structure.

Thermal diffusion analysis by using dual horizon peridynamics

In this study, Dual Horizon Peridynamics formulation is presented for thermal diffusion analysis. Lagrangian formalism is utilized to derive the governing equations. The proposed formulation allows utilization of variable discretization and horizon sizes inside the solution domain which can result in significant benefits in terms of computational time. To demonstrate the capability of the Dual Horizon Peridynamics formulation, three different example problems are considered including a square plate with temperature and no flux boundary conditions, a square plate under thermal shock loading, and a square plate with an insulated crack. For all problems that are considered good agreement is obtained between peridynamics (PD) predictions and finite element method (FEM) results.

Generalized Thermoelastic Waves Propagation in Non-uniform Rational B-spline Rods Under Quadratic Thermal Shock Loading Using Isogeometric Approach

Generalized thermoelasticity based on Lord–Shulman theory that admits the second sound effect is developed for continuum-based modeling of the thermoelastic wave propagation in functionally graded material (FGM) rods with a variable cross-sectional area under quadratic thermal shock loading. The geometry of the problem, as well as the distribution of material properties, is defined continuously with Non-uniform rational B-spline. To assure the exact modeling of geometry, the problem is analyzed using the isogeometric approach. The effects of geometry and material distribution on thermoelastic waves are discussed in detail. Also, propagation, reflections, and propagation speed along the rod axis are investigated. It is shown that the amplitudes and speed of thermoelastic waves can be desirably controlled by the cross-sectional area and the material distribution of the rod, respectively.

Experimental and computational study on thermo‐mechanical fatigue life of aluminium alloy piston

AbstractTo assess the life of a new diesel aluminium alloy piston under thermal shock loads, thermo‐mechanical fatigue (TMF) testing was conducted to characterise the TMF properties of the piston alloy, and an empirical model based on the constraint ratio concept was proposed to predict the TMF life of the piston. Considering that the empirical model required expensive experimental support, a platform with high‐frequency induction heating was established to simulate the force on the piston under thermal shock loads to calculate the piston life using the thermal shock test. Additionally, a finite element method was developed to compute the distributions of temperature, strain, and stress during this process. The characteristics of crack initiation and propagation in TMF test rods and piston mock‐ups were also investigated. The results showed that the TMF test rod suffered brittle fracture with brittle quasi‐cleavage features. The microcracks mainly occurred in primary Si particles due to stress concentration around the primary Si particles induced by the difference between the thermal expansion coefficients of Si and Al. From a macro perspective, the piston initially cracked at the rim above the pinhole, where the stress is larger than that along other directions. From a micro perspective, the protrusions of various sizes on the piston rim were induced by the compression stresses at high temperature. The piston cracks usually initiate around primary Si particles, propagate along the edge of primary Si in a straight line, bifurcate and then stop at a certain depth. If the piston was only heated, cracks or plastic deformations were not produced. The piston life can be assessed using the proposed empirical model based on the constraint ratio concept or thermal shock testing based on the developed platform. The difference between the predicted and experimental life was not greater than 7%.

Nonlocal coupled photo-thermoelasticity analysis in a semiconducting micro/nano beam resonator subjected to plasma shock loading: A Green-Naghdi-based analytical solution

In this article, coupled photo-thermoelasticity analysis is carried out using an analytical method in a semiconducting micro/nano beam resonator, considering Green – Naghdi theory (with energy dissipation) and small scale effects. The governing equations for temperature and displacement fields are derived using Eringen nonlocal theory combined with Rayleigh beam theory. One end of the assumed semiconducting MEMS/NEMS is excited by three types of suddenly increasing carrier density and temperature as the plasma and thermal shock loading. The transient behaviours of carrier density field are studied and the effects of disturbances in plasma field on other fields including temperature and deflection are obtained using the proposed analytical solution. The presented analytical solution is based on Laplace transform. To find the dynamic and transient behaviours of fields’ variables in time domain, an inversion Laplace technique is utilized, which is called Talbot method. The effects of small scale parameter and dimensions of the semiconducting micro/nano beam on the dynamic behaviours of fields’ variables are discussed in detail. The axial wave propagation and the distribution of fields’ variables along axial direction are studied at various times.

Microstructure, oxidation behaviour and thermal shock resistance of self-passivating W-Cr-Y-Zr alloys

Abstract Self-passivating tungsten based alloys for the first wall armor of future fusion reactors are expected to provide an important safety advantage compare to pure tungsten in case of a loss-of-coolant accident with simultaneous air ingress, due to the formation of a stable protective scale at high temperatures in presence of oxygen preventing the formation of volatile and radioactive WO3. In this work, Zr is added to self-passivating W-10Cr-0.5Y alloy, manufactured by mechanical alloying and HIP, in view of improving its mechanical strength and thus, its thermal shock resistance. The as-HIPed W-10Cr-0.5Y-0.5Zr exhibits a nanocrystalline microstructure with the presence of an extremely fine nanoparticle dispersion. After heat treatment at 1555 °C for 1.5 h, the grain size growths from less than 100 nm to 620 nm and nanoparticles are present both at the grain boundaries and inside the grains. Oxidation tests at 1000 °C revealed that the alloy with Zr exhibits also a strong oxidation reduction compared to pure W. The long-term oxidation rate is similar to that of the alloy without Zr. Under thermal shock loading simulating 1000 ELM-like pulses at the divertor, the heat treated Zr-containing alloy did not present any damage.