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Linear Motors are potential candidates for replacing traditional rotary motors in high-speed transit systems. Linear Switched Reluctance Motor (LSRM) is the widely researched motor for such applications. This paper presents a design for linear switched reluctance motor (LSRM) with an improved propulsion force profile. The proposed motor consists of moving translator for direct drive transmission, without the use of mechanical gears. The stator contains a split-teethed stator structure. The proposed motor has more translator teeth than stator teeth. This paper includes a new design methodology for the proposed combination of stator and translator. The motor is designed and analyzed using 3-D finite-element method (FEM). The proposed motor has been optimized using a parameter-based cumulative deterministic optimization algorithm (PBCDOA) for further improving the force profile. The FEM results demonstrate the effectiveness of the design procedure and better force performance of the proposed topology. [ABSTRACT FROM AUTHOR]

Thin-walled structures have been widely adopted in engineering projects because of the advantages of good load-bearing capacity, light weight and low cost. In this paper, a refined finite element method (FEM) based on the Carrera Unified Formula (CUF) is performed to analyze the free vibration of thin-walled beams with the variables cross-section, length and boundary. The low-dimensional FEM method could improve the efficiency of numerical analysis and reduce the time consumption. The one-dimensional (1D) CUF is employed in which the models are assumed to be a beam-like axis-oriented structures. In this case, the geometry of the thin-walled beam can be discretized as a limited number of 1D beam elements along the axis, while the Lagrange polynomial expansion may be used to approximate the displacement field on the cross-beam surface. Thus, FEM matrices and vectors can be written in terms of fundamental nuclei whose forms are independent of beam theories. The validity and capabilities of the method presented are examined in some numerical examples, and a comparative study is carried out between the method proposed and the three-dimensional element method with and without warping solutions. The results obtained by CUF 1D models are in close agreement with the reference solutions. In addition, it has been argued that the innovative approach presented in this paper can be used as a precise tool for structural analysis for complex cross-section thin-walled beams to reduce computational costs. [ABSTRACT FROM AUTHOR]

This paper focuses on effective elastic properties, and thermal conductivity of materials constituted by an isotropic homogeneous solid matrix containing both ellipsoidal and non-ellipsoidal pores. In the frame of Effective Media Theory (EMT), property contribution tensor approach extended to non-ellipsoidal inhomogeneities are used to estimate effective elastic properties and thermal conductivity. On the basis of recent results obtained by the authors, a reference 3D shape is considered: supersphere characterised by a concavity parameter and being convex or concave. Related compliance contribution tensors verifying cubic symmetry have been characterised thanks to 3 D finite element modelling and analytical approximation formula have been derived and are used in this paper. Analysis is focussed on the effect of the parameter characterising concavity on both effective elastic coefficients and thermal conductivity. Application to isotropic porous rock with two separated classes of pores, such as oolitic limestones, is considered. Numerical results are presented for a reference oolitic rock, Lavoux limestone. Maxwell, Self-Consistent and Differential schemes are compared. It is shown that concavity parameter is of major importance as may be aspect ratio of spheroidal pores, and that the three reference schemes may conduce to comparable results for the particular investigated microstructure, characterised by a high volume fraction of porous grains (oolites) [ABSTRACT FROM AUTHOR]

The vibration reduction characteristics of the flexible blade with a dovetail joint and underplatform damper are studied in this paper. Considering the influence of the platform mass on the inherent characteristics of the blade, this paper regards the underplatform as a particle with mass. Moreover, two types of friction models are introduced on the contact interfaces of the blade. Meanwhile, the normal pressure of the contact interfaces will change with the rotating speed of the blade. Also, the dynamical equation for the rotating blade is established based on the finite element method. The nonlinear friction force on the contact interface is brought into the dynamical equation, and the vibration response of the blade is solved. The effects of the rotating speed, the initial preload, and the contact angle of the underplatform on the vibration reduction characteristic of the blade are investigated. [ABSTRACT FROM AUTHOR]

The effect of temperature on the meso-mechanical properties of each structural layer of the pavement was studied in this paper. Fitting standard indoor uniaxial compression tests, meso-scale parameters of the material were obtained. With the mesoscopic parameters of each structural layer, a two-dimensional discrete element model of the pavement was constructed. This discrete element model of the road surface was coupled with the 2 DOF 1/4 vehicle model, and the unevenness of the road surface provided incentives for vehicles. At different temperatures, the meso-mechanical response of each structural layer of the road surface was solved under the action of vehicle loads. The movement of particles at different temperatures was analysed. The results show: compared with the finite element model, the vertical displacement produced by the discrete element model is 4.8% larger than the finite element model. That shows that the discrete element model data has certain credibility. The vertical displacement decreases as the depth of the structural layer increases and increases as the road surface temperature increases. And the vertical stress decreases as the depth of the structural layer increases, and increases as the road surface temperature increases. The horizontal stress of the upper layer is compressed, the horizontal stress of the lower layer is stretched, and the horizontal stress of the remaining structural layers does not change significantly. The horizontal stress decreases as the road surface temperature increases. The tangential stress of each structural layer is in anti-symmetric state, both tensile state and compressed state. Tangential stress decreases with increasing road surface temperature. The higher the temperature, the smaller the tangential stress. The effect of temperature on the velocity of particles in the early stage is greater than that in the late stage. [ABSTRACT FROM AUTHOR]

The adhesive bonding strength of the membrane layers between the asphalt concrete surface layers and the decks of steel bridges has a strong influence on the fatigue life of orthotropic steel deck bridges (OSDBs). The interfacial properties between the membrane and the layers bonded to it have not been extensively studied in the current orthotropic steel deck bridge system. For the adequate characterisation of the adhesive-bonding strength of various membranes and surrounding materials on OSDBs and for the collection of the necessary parameters for finite element model, details of the membrane adhesion test (MAT) are introduced and simulated by using the adhesive traction-separation interface element which was developed in a companion paper to this contribution (Liu, X., Kasbergen, C., Li, J., & Scarpas, A. (2019). Modelling of membrane bonding response: part 1 development of an adhesive contact interface element. International Journal of Pavement Engineering). Parametric studies of the adhesive contact element utilised for modelling the membrane bonding layer in the MAT test have been performed on the basis of the combination of different critical strain energy release rates and the characteristic opening length in the constitutive model. Comparison of membrane deformation profiles and the in-time debonding force distribution between experimental observations and finite element simulations have been presented. [ABSTRACT FROM AUTHOR]

This paper presents HALO3D, a CFD code simulating the wide range of Mach numbers a hypervelocity vehicle experiences. HALO3D is composed of (a) a RANS edge-based Finite Element (FE) solver modelling high-velocity thermo-chemical non-equilibrium flows, (b) an electromagnetic interactions solver, (c) an ablation module, (d) a Direct Simulation Monte Carlo (DSMC) solver for the rarefied regime, seamlessly linked to the continuum one, and (e) a powerful automatic mesh optimiser finely capturing the many singular hypersonic flow phenomena. Verification and validation simulations for two- and three-dimensional hypersonic flows over a flat plate, a cylinder, a blunt conical body, re-entry capsules, and a waverider geometry demonstrate accurate aerothermodynamic predictions in a wide range of Knudsen numbers, complex geometries and multiphysics. [ABSTRACT FROM AUTHOR]

In graphite/copper composites, the intrinsic non-wettability of graphite and copper makes it difficult for the copper melt to realize effective infiltration into the porous graphite matrix. The resulted void defects have reduced the final performance of the composites. It is of great significance to improve the saturation of copper melt in the graphite skeleton, which requires a well understanding of the infiltration behavior of copper melt. In this paper, a two-phase flow finite element model was developed, and verified by previous published experimental data. Effects of the external pressure on the infiltration behavior has been studied, and then an optimization method based on WC particle doping was proposed. Results indicated that effective transfer of displacement pressure at the liquid flow front can reduce the void defects of composite materials. WC doping has reduced the capillary resistance, and effectively improved the copper saturation in the infiltration process from 80.4% to 90.7%. This work provided a new method to reduce the void defects of composites, which may be helpful for the development of high performance copper/graphite composites. [ABSTRACT FROM AUTHOR]

AbstractCarbon fiber-reinforced polymer (CFRP) is prone to machining defects, including burrs and tearing, during milling. These defects are closely associated with interface delamination while milling force plays a crucial role in their occurrence. In this paper, a nonlinear explicit finite element (FE) model is developed to predict the milling force and analyze the delamination damage occurring during the milling of unidirectional CFRP (UD-CFRP). The proposed FE model is validated through numerical comparison with experimental data for milling force. Moreover, a detailed study is conducted to examine the influences of spindle speed, feed rate and depth-of-cut on the side-milling performance and damage response of UD-CFRP. This study provides valuable insights into the effects of machining parameters on milling force and delamination damage in CFRP, thereby supporting the optimization of machining technology for this composite material system. [ABSTRACT FROM AUTHOR]

In the quest to elevate the mechanical properties of cellulose nanofiber-reinforced poly (lactic acid) composite materials for robust industrial applications, we conducted multiscale nonlinear finite element analysis rooted in homogenization theory. Our study delved into the intricate web of mechanical mechanisms and their pivotal influencers. This paper zeroed in on three paramount factors: the distribution of fibers, the fiber–matrix interface, and the aspect ratio of the fibers. For fiber distribution, we assumed fiber orientation control in fused filament fabrication and clarified the limit of material improvement by setting one-dimensional orientation as the upper limit. Our analysis of the fiber–matrix interface proposed a comprehensive three-scale structure, encompassing microstructures featuring intricate interfacial phases around the fibers, sub-microstructures with myriad dispersed fibers, and macrostructures subjected to external loads. The profound impact of the fiber–matrix interface on material properties was unveiled through a meticulous two-step homogenization process. Furthermore, we examined the substantial influence of the fiber aspect ratio on material properties. By unraveling the complex interplay among these critical factors, this research provided new design guidelines for fiber morphology to the performance of cellulose composites. [ABSTRACT FROM AUTHOR]

Aiming at the mutual coupling of multiple physical fields in the microwave heating process and the generation of thermal runaway phenomenon, in this paper, a cooperative variable power heating strategy with multi-microwave source clusters under dynamic switching topology is proposed in order to improve the temperature uniformity. Firstly, an algebraic graph theory is used to establish a communication topology for complete information transfer, which is used to construct a distributed structure among multiple microwave source intelligences. Secondly, the dynamic topology switching algorithm under event triggering is introduced, and the real-time temperature distribution of the heated materials is considered to achieve the dynamic switching of the topology connection mode between microwave source clusters in order to synchronously coordinate the power consistency output between different clusters. On this basis, a numerical calculation model is constructed to solve the mixed optimization of integer and continuum variables by means of the finite element method. Finally, the effectiveness of the heating strategy to improve temperature uniformity is verified by microwave heating SiC media simulation calculation. The numerical calculation results show that the temperature uniformity indexes are improved by 34.1%–50.4% and 28.1%–55.2% in each horizontal and vertical section for single materials, and by 59.1%–59.7% and 46.5%–63.4% in each horizontal and vertical section for multi-materials, respectively, in comparison with the general heating method. This strategy effectively avoids the residence of hot and cold spots in the material, which in turn optimizes the temperature distribution. [ABSTRACT FROM AUTHOR]

AbstractThe automation and assembly lines of factories have faced the need for reliable handling of porous, fragile, and soft objects. Current soft grippers have difficulty robustly grasping flat, flexible surfaces without distorting them. This paper proposes a soft gripper based on annulus microwedge adhesive for grasping flat objects using negative pressure actuation mechanisms, which can achieve controllable adhesives to reliably grasp and easily release smooth flat objects. This is achieved through negative pressure actuation, which provides a centripetal load to the annular microwedge adhesives for strong attachment, by returning to normal pressure, the centripetal load is rapidly removed, allowing for easy detachment from the adhesive surface. Additionally, the relationship between the geometrical parameters of the deformation chamber and the contact area of annulus microwedges is investigated by using finite-element method models and experiments. The results show that the wall thickness is a key parameter in designing the deformation chamber. The results of the payload test have determined the geometrical and pressure parameters of the deformation chamber with the best adhesion performance. Finally, a demonstration shows that the gripper can handle various objects for potential applications, such as in clean environmental industries. [ABSTRACT FROM AUTHOR]

In the present study, the fracture analysis of functionally graded materials (FGMs) of various material distributions with discontinuities (crack and inclusion) under localized loadings is carried out by the extended finite element method (XFEM). In the present work, the effect of discontinuities and material distributions like exponential, power law, Mori–Tanaka, and sigmoidal in FGMs is also presented, where the different material distributions are compared for the fracture analysis of FGM plates and beams. This present work will be helpful for the researchers to understand the effect of different material distributions on FGMs under localized ladings. The XFEM-based numerical analysis is carried out to find stress intensity factors (SIFs) and stress distributions. The MATLAB code is developed for this analysis and is validated with a previously published research paper. [ABSTRACT FROM AUTHOR]

Present study develops the experimental and finite element analysis of an auxetic piezoelectric energy harvester consisting of a cantilever, auxetic substrate, and piezoelectric layer. Firstly, five auxetic models with 1, 4, 9, 16, and 25 honeycomb auxetic cells are presented. Harvested power and stress distribution of the piezoelectric layer for these models are compared with plain piezoelectric energy harvester. All the analysis has been performed using the experimental tests and finite element method. Mesh size sensitivity analysis of the finite element model is presented, and it is verified by previous experimental studies. The model with 25 auxetic cells harvests more power than other models. Furthermore, comparing stress distribution on the piezoelectric layer of these models indicates that increasing the number of auxetic cells leads to increasing the average stress on the piezoelectric layer. The present investigation illustrates that harvested power of an auxetic energy harvester in resonant frequency could improve to twenty times more than a plain harvester. Besides, the new auxetic model with trapezoidal geometry is presented in the present paper. Utilizing this model as the substrate in a piezoelectric energy harvester leads to increasing the efficiency of the energy harvester by 82.5%. The damping ratio of the auxetic energy harvester has been measured by experimental investigation. Also, experimental analysis has been performed to find the optimum energy harvester circuit resistor. The density of the harvested power for the trapezoidal energy harvester with an optimum circuit resistor is 107% more than the rectangular energy harvester. [ABSTRACT FROM AUTHOR]

In this paper, the spoke structure of a non-pneumatic tire is optimized. The finite element model of the spoke structure is created and structural dynamic analysis is made using ABAQUS. The optimization goal is to simultaneously reduce three characteristics of the spoke structure, the mass, vertical displacement and acceleration. Simulations are performed according to the center composite design table, and the objective function is estimated using response surface analysis (RSA), random forest regression (RFR), gradient boosting regression (GBR) and artificial neural network (ANN). The genetic algorithm is used for minimization, and the optimization results of each objective function are analyzed through verification simulation. As a result of the optimization, the error between the predicted value and the actual value is 18.6% for RSA 3.1% for RFR, 1.7% for GBR, and 15.0% for the ANN. The ANN proposes the optimum design variables which derive output values smaller than the current minimum value because the ANN properly represents the nonlinear characteristics of the spoke model generated in this study. Highlights Simulation based optimization of the spoke structure of a non-pneumatic tire Various regression models are used and their accuracy is compared A two-step genetic algorithm is used for optimization [ABSTRACT FROM AUTHOR]

This paper presents an analysis of stress developed in flex-gear (FG) cup with conventional strain wave generating (SWG) cam and split-cam SWG in strain wave gear/harmonic drive (HD), using initial load distribution by tooth pairs as a boundary condition in finite element method (FEM). The initial load distribution by tooth pairs is achieved with the assembly of ring gear (RG) and deformed FG before the application of any external load. A closed-form solution to the analytical method describes the exact initial load distribution by tooth pairs in the presence of secondary contacts. However, with spit-cam SWG the phenomenon of secondary contact is completely eradicated. Therefore, the load is distributed by contacting tooth pairs that lie only in the line of action and the tooth pair that lies along the major axis of split-cam SWG experiences maximum load compared to conventional SWG. The strain developed in FG cup based on the load distribution with both SWG cams obtained from FEM is verified with the experiment. The comparison shows a rise of 44 microns in circumferential strain around the major axis of deformed FG, when RG is assembled. This testifies the presence of initial load, which is distributed among all interfering tooth pairs before applying external load. [ABSTRACT FROM AUTHOR]

In this paper, the transverse low-velocity impact behavior of uniaxial and biaxial braided composite tubes is investigated to improve the impact resistance of tubular composite structures and to reveal their energy absorption mechanism. Based on the nonlinear progressive damage model, the finite element method is used for experimental verification and numerical analysis. The composite tubes with different stacking sequences and stacking angles were simulated, and their impact responses were evaluated by the peak load Fmax, the maximum indentation depth αmax and the energy absorption EA. The results show that the numerical simulation results are in good agreement with the experimental data, and can accurately capture the failure behavior in the actual scene. The damage mode of the braided composite circular tube under low-velocity impact load is mainly manifested as matrix cracking and interlayer separation, and the expansion direction of the damaged area is basically consistent with the fiber orientation. The impact resistance depends more on the stacking sequence, while the stacking angle is the main factor affecting the energy absorption. Under reasonable design, the uniaxial/biaxial hybrid braided tube can obtain the best low-velocity impact characteristics. [ABSTRACT FROM AUTHOR]

Achieving a correct cooling in glass manufacturing is very important to obtain the desired level of stresses and to avoid breakage. Numerical simulations can be used to optimize the cooling parameters. Such simulations have to be multiphysical coupling thermics and mechanics. Moreover, since glass is a semitransparent material, radiative effects inside the glass have to be taken into account. The present paper is devoted to numerical study of the cooling of a glass square plate on a metallic frame. To this end, the commercial software Abaqus was used to model the thermomechanical behavior of glass using adapted subroutines and was combined with an in-house C++ tool developed to solve the Radiative Transfer Equation. During and at the end of the cooling, weak areas in the glass plate are revealed by the simulation. Depending on the case studied, taking accurately the radiative effects into account leads to difference of residual stresses which can reach 10 MPa in certain cases. [ABSTRACT FROM AUTHOR]

AbstractIn this article, an analytical method for predicting the thermal expansion coefficient of 2D composite fabrics is established. First of all, different from the traditional prediction of thermal expansion coefficient by classical laminate theory, this paper extends the self-consistent method of micromechanics to 2D composite fabrics to improve the accuracy of thickness direction prediction. Analytical Prediction method of Thermal expansion coefficient of 2D Composite fabric (APTC)was established. In the x section of Representative Volume Element(RVE) model, the stress balance equation and deformation coordination equation are applied to derive the internal thermal expansion coefficient. In the z section, the coefficient of thermal expansion is derived from the Poisson effect. Secondly, the formula of thermal expansion coefficient is derived for plain fabric, twill fabric and satin fabric respectively, which is consistent with the APTC method, indicating that the method is representative. Finally, RVE finite element model is established according to the braided structure parameters of 5284/T800 composite fabric. Comparing analytical solution, numerical solution and experimental solution, the α1 and α2 of the numerical and experimental solutions is close enough to be considered equal, which is consistent with the transverse isotropy of the composite fabric in xOy plane predicted by theoretical analysis.When predicting α1 and α2, the maximum error between numerical solution and analytical solution is 1.79%, the maximum error between numerical solution and experimental solution is 22.29%, and the error remains at about 4% during predicting α3.In general, the APTC method for predicting the thermal expansion coefficient of composite fabrics is accurate and effective, and the simplified formula is more convenient to popularize and apply. [ABSTRACT FROM AUTHOR]

AbstractThis paper presents the results of numerical predictions for an instrumented piled raft foundation of a tall building in tropical soil. The analysis was performed using 3D finite element analysis and included a comparison of foundation settlements, pile loads, skin friction mobilisation, and raft-soil contact pressure. Initially, the geotechnical model was defined based on field and laboratory test data to conduct a Class A geotechnical prediction. Subsequently, the soil parameters used in the numerical model were re-evaluated to match the measured settlements, aiming for a Class C prediction. The study discusses the main factors that affect the accuracy of the computed settlements, providing valuable insights for foundation designers. Additionally, it highlights the significance of considering the pile-soil-pile and raft-soil-pile interactions in the design of the piles beneath the raft, as these interactions impact the mobilisation of the pile skin friction at different depths. [ABSTRACT FROM AUTHOR]

Previously, we developed an adaptive method in angle that is based on solving in Haar wavelet space with a matrix-free multigrid for Boltzmann transport problems. This method scalably mapped to the underlying P0 space during every matrix-free matrix-vector product; however, the multigrid method itself was not scalable in the streaming limit. To tackle this, we recently built an iterative method based on using an Approximate Ideal Restriction multigrid with GMRES polynomials (AIRG) for Boltzmann transport that showed scalable work with uniform P0 angle in the streaming and scattering limits. This paper details the practical requirements of using this new iterative method with angular adaptivity. Hence, we modify our angular adaptivity to occur directly in P0 space rather than the Haar space. We then develop a modified stabilization term for our Finite Element Method that results in scalable growth in the number of nonzeros in the streaming operator with P0 adaptivity. We can therefore combine the use of this iterative method with P0 angular adaptivity to solve problems in both the scattering and the streaming limits, with close to fixed work and memory use.We also present a coarse-fine splitting for multigrid methods based on element agglomeration combined with angular adaptivity, which can produce a semicoarsening in the streaming limit without access to the matrix entries. The equivalence between our adapted P0 and Haar wavelet spaces also allows us to introduce a robust convergence test for our iterative method when using regular adaptivity. This allows the early termination of the solve in each adapt step, reducing the cost of producing an adapted angular discretization. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the use of a graphene oxide (GO)-coated planar inductor as a transducer for gas sensing applications in alternating current (AC) mode. The GO is synthesized using the Hummers method and coated as a functional layer on a square-shaped planar inductor with an area of 16 × 16 mm2 printed on a circuit board (PCB). Preliminary finite element analysis showed that the magnetic field around the inductor was tightened and amplified due to the presence of the GO layer. This result was confirmed by electrical measurements using a vector network analyzer (VNA), revealing that the GO led to an increase in the self-inductance due to its paramagnetic character. In fact, for a frequency of 1 MHz, the series resistance increased significantly by 32% compared to the initial value obtained without GO, while the inductance increased only by 0.18%. After CO2 injection, a frequency screen ranging from 1 MHz to 200 MHz demonstrated that the effect of CO2 is more relevant at low frequencies. Hence, measurements show that for 1 MHz, the series inductance and resistance decrease by about 9.33% and 31%, respectively, from their values measured after GO coating. Accordingly, this work highlights the relevance of the GO-coated inductor as a transducer for CO2 detection working in AC regime. [ABSTRACT FROM AUTHOR]

This paper aimed to investigate the biomechanical changes during the talus impact with the calcaneus at varying velocities. Various three-dimensional reconstruction software was utilized to construct a finite element model that consisted of the talus, calcaneus, and ligaments. The explicit dynamics method was used to explore the process of the talus impacting on the calcaneus. The velocity of impact was altered from 5 m/s to 10 m/s with a 1 m/s interval. Stress readings were collected from the posterior, intermediate, and anterior subtalar articular (PSA, ISA, ASA), calcaneocubic articular (CA), Gissane Angle (GA), calcaneal base (BC), medial wall (MW), and lateral wall (LW) of the calcaneus. The changes in the amount and distribution of stress in the different regions of the calcaneus that varied with velocity were analysed. The model was validated through comparison with findings from the existing literature. During the process of impact between the talus and calcaneus, the stress in the PSA reached its peak first. Notably, stress was concentrated mainly in the PSA, ASA, MW, and LW of the calcaneus. At varying impact velocities of the talus, the mean maximum stress of the PSA, LW, CA, BA, and MW exhibited statistically significant differences (P values were 0.024, 0.004, <0.001, <0.001, and 0.001, respectively). However, the mean maximum stress of the ISA, ASA, and GA was not statistically significant (P values were 0.289, 0.213, and 0.087, respectively). In comparison with the velocity at 5 m/s, the mean maximum stress increases in each region of the calcaneus at a velocity of 10 m/s were as follows: PSA 73.81%, ISA 7.11%, ASA 63.57%, GA 89.10%, LW 140.16%, CA 140.58%, BC 137.67%, MW 135.99%. The regions of stress concentration were altered, and the magnitude and sequence of peak stress in the calcaneus also varied according to the velocity of the talus during impact. In conclusion, the velocity of the talus during impact had a significant influence on the magnitude and distribution of stress within the calcaneus, which was a crucial factor in the development of calcaneal fractures. It was possible that the magnitude and sequence of stress peaks played a vital role in determining the emergence of fracture patterns. [ABSTRACT FROM AUTHOR]

In this paper, transmitted surface waves are used to quantitatively detect the length and angle of inclined surface cracks based on laser ultrasonic technique. The interaction between laser-generated surface waves and inclined surface cracks is analysed, and the propagation path and mode conversion process of the transmitted surface waves are considered. Then, the propagation paths of some peaks and troughs of the transmitted surface waves are obtained. Based on the obtained path and modal conversion information, a quantitative detection method for the length and angle of inclined surface cracks is proposed. The finite element method is used to verify the propagation paths and proposed method, and the results show that the arrival time of the theoretical path is consistent with that of the simulation. The relative measurement errors of the surface crack length and angle are less than 15% and 10%, respectively, which verifies the rationality and correctness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper is aimed to validate the trend between thermal-related parameters and field-measured thermal cracking. Field thermal cracking is collected from four projects with twelve pavement sections. The material properties include creep compliance m-value and tensile strength of mixture, and asphalt low-temperature performance grade (PG). A lower value of m-value and tensile strength leads to a higher thermal cracking, while the low-temperature PG has the contrary trend. One or even several material properties cannot fully characterize field thermal cracking for all projects. Then the change of material properties, pavement structures, and climatic conditions are considered in three-dimensional finite element models (FEM). The aging effect of material properties attributes to the increase of thermal stress. The placement of chip seal could greatly reduce the aging rate, and the thicker pavement result in less thermal stress. Both material property and thickness are important design factors for thermal cracking resistance. [ABSTRACT FROM AUTHOR]

In order to realize the visual identification of the three-dimensional geometric characteristics of rail corrugation, the three-dimensional reconstruction method of rail corrugation based on vision detection is developed in the present paper. The acquisition equipment is designed to acquire the images of rail corrugation and corresponding depth information. Then, the image preprocessing method is proposed to achieve the automatic segmentation of rail corrugation images. The fitting equation between the image and depth of rail corrugation is obtained, which allows the three-dimensional reconstruction of rail corrugation. Furthermore, based on the finite element model of the wheel-rail system and the wear calculation model, the practicality and effectiveness of the three-dimensional reconstruction method are verified. Results show that the depth-grayscale correlation equation is well fitted with the coefficient of determination of 0.94 and the root mean square error of 0.02. The three-dimensional reconstruction method has an error of 2.63% at the maximum wear depth. When the three-dimensional reconstruction method is applied to the wear prediction of rail corrugation, the wear prediction of rail corrugation with the three-dimensional reconstruction is approximately the same as the actual wear distribution, which has an error of 5.02% at the maximum wear depth. The aforementioned results demonstrate the effectiveness of the three-dimensional reconstruction method of rail corrugation based on the vision detection. [ABSTRACT FROM AUTHOR]

This paper discusses and presents an example of fire risk analysis for a case study of an existing heritage building: the Duomo of Modena Cathedral, located in Italy. The main issues related to the application of the fire risk analysis to heritage buildings are discussed in detail, and an ad-hoc procedure is proposed to manage them for the case study. In order to assess the performances of the building in probabilistic terms, the fire risk analysis is conducted by the event-tree method, the fire dynamics are analyzed by numerical thermo-fluid dynamics models, while the structural behavior is investigated by advanced nonlinear thermomechanical finite element models. Results are expressed in terms of risk curves related to a fixed return period, which quantify the occurrence probability of different damage levels induced by fire in the wooden roof of the case study building. This kind of result is fully compatible with probabilistic performance-based engineering frameworks commonly accepted for other hazards (i.e., earthquakes). [ABSTRACT FROM AUTHOR]

To explore the dynamic crack propagation behaviour in the fracture zone and the damage characteristics of the rock mass around the blasthole during eccentric uncoupled blasting of a deep-level rock mass, theoretical analysis, model experiments and numerical simulation studies have been described in this paper. Firstly, the stress state of the crack and the stress distribution state and failure mechanism of the rock mass around the blasthole under the influence of the in-situ stress, and the pressure distribution of blast shock wave on the blasthole were analysed. Secondly, with the help of a new digital laser caustics experimental system, the eccentric uncoupled blasting model experiment under the action of the in-situ stress was carried out. The fractal damage theory is used to quantitatively evaluate the damage degree of the rock mass in different areas around the blasthole, and the blast-induced crack propagation mechanical behaviour characteristics in the fracture zone are analyzed from the perspective of dynamics. Then, based on the LS-DYNA software, a numerical simulation study was conducted on the eccentric blasting of deep rock mass. Finally, some discussions and suggestions are provided for the analysis of blasting mechanisms in a deep-level rock mass. [ABSTRACT FROM AUTHOR]

The aim of this paper is to develop an unconditionally stable Euler implicit/explicit scheme for the natural convection equations based on an introduced exponential scalar auxiliary variable. Our numerical scheme involves treating the linear terms in the implicit scheme and nonlinear terms in the explicit scheme. Then, the considered problem is decoupled into a series of linearized subproblems, and these algebraic systems with constant coefficient matrixes can be solved efficiently. Compared with the existing theoretical findings of the implicit/explicit scheme for the incompressible flow [He YN. The Euler implicit/explicit scheme for the 2D time-dependent Navier-Stokes equations with smooth or nonsmooth initial data. Math Comput. 2008;77(264):2097–2124.; He YN, Huang PZ, Feng XL. H2-stability of first order fully discrete schemes for the time-dependent Navier-Stokes equations. J Sci Comput. 2015;62:230–264; He YN, Li J. A penalty finite element method based on the Euler implicit/explicit scheme for the time-dependent Navier-Stokes equations. J Comput Appl Math. 2010;235(3):708–725; Jin JJ, Zhang T, Li J. H2 stability of the first order Galerkin method for the Boussinesq equations with smooth and nonsmooth initial data. Comput Math Appl. 2018;75(1):248–288; Su J, He YN. The almost unconditional convergence of the Euler implicit/explicit scheme for the three dimensional nonstationary Navier-Stokes equations. Discrete Continuous Dyn Syst Ser B. 2017;22(9):3421–3438], our analysis removes the restriction on time step Δ t ≤ C , and obtains the unconditional stability and convergence theoretical findings. Some numerical results are also provided to verify the established theoretical analysis and show the performances of the considered numerical scheme. [ABSTRACT FROM AUTHOR]

The long-term quality assurance of bridges demands an adequate quality control plan detailing the main required activities and assessment tools. This paper presents the application of a quality control plan on two existing reinforced concrete bridges located in Portugal and North Macedonia. Based on the available results from visual inspections and non-destructive tests, defects and corresponding damage processes were identified. The structural safety of the case studies was assessed by means of a reliability index considering the identified damages. The reliability index computation was supported by a nonlinear finite element analysis. The computed reliability index that reflects the actual ('today') bridge condition was used as the base information in the preparation of possible maintenance scenarios. Three different maintenance scenarios were considered, namely, the improvement (corrective scenario), reduction (do nothing and rebuilt scenario), or delay in the reduction (preventative scenario) of the performance of the structure. By comparison of normalised net present values of the key performance indicators (reliability, safety, availability and costs), the most appropriate scenarios are found. [ABSTRACT FROM AUTHOR]

This paper investigates the influence of multi-components strong motion duration on seismic performance of high concrete-faced rockfill dams (CFRDs) by fragility analysis based on the method of incremental dynamic analysis (IDA). The contributions of all compositions of earthquake excitations are considered by the definition of integrated duration based on the concept of significant duration. The nonlinear finite element model of a 2D 200-m-high CFRD is established as a case study and the vertical and horizontal displacements are selected as damage measures. Fragility curves and probabilities of two sets of 23 and 25 spectrally equivalent as-recorded bi-directional long-duration and short-duration motions are determined under different failure grades and intensities. The results show that the duration of vertical component has a certain effect on correction between strong motion duration and deformation of the dam and fragility analysis indicates that the ground motions with long duration can make more risk of failure of high CFRDs than short duration motions. Therefore, the seismic performance of high CFRDs will be reformed by taking the effect of ground motion duration into seismic design and risk assessment consideration. [ABSTRACT FROM AUTHOR]

Argillaceous rocks are candidate host and/or cap formations for the geological disposal of nuclear wastes in many countries, including Canada, France and Switzerland. The understanding of the long term mechanical behaviour of such rocks is an essential requirement for the assessment of their performance as a barrier against radionuclide migration. Due to the existence of bedding, argillaceous rocks are inherently anisotropic and the development of stress-strain models for their mechanical behaviour needs to take this anisotropy into account. This paper presents two examples of the practical implementation of stress-strain relationships in finite element models to simulate the excavation damage zones (EDZ) in bedded argillaceous rocks. The first example concerns the EDZ around a micro-tunnel in Opalinus Clay, in Switzerland. The second example relates to the EDZ around the century-old tunnel in Tournemire shale, in France. Both examples show the importance of developing robust stress-strain models that can replicate inherent anisotropy of the rock, and of calibrating and validating the models with a comprehensive set of laboratory experiments. The second example shows the additional influence of dessication and fault zone on the extent and shape of the EDZ. [ABSTRACT FROM AUTHOR]

Single point incremental forming has no support on the back of the sheet, which leads to the defects such as sheet instability and poor forming accuracy. In this paper, isostatic pressing technology is introduced into single point incremental forming process to provide effective support for the back of sheet metal. Taking cone parts with 1060 aluminum as the research object, the forming force under different static pressure parameters was analyzed by finite element analysis and experimental study. The results show that the horizontal forces Fx and Fy increase slightly under static pressure. The axial force Fz has a relatively large change, and with the static pressure increasing, the axial force increases significantly. The experimental equipment of isostatic pressing single point incremental forming was designed to obtain the forming force variation under different static pressing conditions. Compared with the simulation results, the accuracy of the finite element model was verified. [ABSTRACT FROM AUTHOR]

In this paper, a multi-cell design method with built-in stiffeners is proposed to improve the crashworthiness of metal circular tubes. In the study, multi-cell circular tubes with three different stiffeners (Line, Waved, Polyline) were subjected to compression tests under quasi-static load. The finite element model of the metal circular tube was validated by ABAQUS/EXPLICIT, and the geometry of the stiffener was designed on this basis. The results showed that the energy absorption of the multi-cell tube was significantly better than that of the initial tube. Further, 'Waved' and 'Polyline' are more conducive to improving the crashworthiness of the multi-cell tube from the geometric design of the stiffeners. Through the analysis of load-displacement responses and crashworthiness indexs, it was found that the more the number of 'Waved' or 'Polyline' (from 2 to 8), the better the energy absorption of the multi-cell tubes and the smaller the load fluctuation. In addition the effect of the number of stiffeners on energy absorption was also revealed. [ABSTRACT FROM AUTHOR]

In this paper, the seismic stability number of unsupported excavations in cohesive-frictional soil under the influence of pseudo-static seismic body forces is examined. Three-dimensional finite element limit analysis is employed to numerically solve the upper and lower bounded models of unsupported excavations. The results are represented by a dimensionless stability number which is a function of four dimensionless parameters including the excavation aspect ratio, the excavated depth ratio, the soil's effective friction angle, and the coefficient of horizontal earthquake acceleration. For the first time in literature, the influences of a soil's effective friction angle and the coefficient of horizontal earthquake acceleration on the mechanisms of excavation failures are examined and discussed. Also presented is a case study to demonstrate the use of the proposed seismic stability number in studying unsupported excavations in seismic risk areas. [ABSTRACT FROM AUTHOR]

This paper investigates the torsional dynamic response of a single pile with a circular cross-section embedded in multi-layered soils. The energy principles and variational approach are employed to establish the governing equations of the pile-soil system subjected to dynamic torque applied at the pile head in the frequency domain. The proposed solution is based on the finite element method for a bar on an elastic foundation to provide the torsional dynamic subgrade reaction, angle of twist, torque along the pile and the torsional impedance at the pile head. The accuracy of the proposed method is verified by comparing the analysis results with those of existing analytical solutions. Parametric studies are also performed to investigate the influence of the soil properties and the excitation frequencies on the stiffness and radiation damping of the pile-soil system. [ABSTRACT FROM AUTHOR]

The load and resistance factor design (LRFD) approach employed in geotechnical design codes is often calibrated using the reliability-based design (RBD) method. However, the LRFD may not achieve the target safety level exactly. This paper makes comparisons between the LRFD and RBD by considering the ultimate and serviceability limit state design of strip foundations. The RBD is carried out via the Random Finite Element Method. It is found that the failure probability and the resulting foundation width for ULS obtained using the RBD increase with the soil spatial correlation length, gradually reaching a plateau. The comparison between the LRFD and RBD results for ULS suggests that the LRFD is conservative for low to medium soil variability, particularly at smaller correlation lengths. The reliability-based SLS design is less dependent on the soil correlation length, particularly for lower coefficients of variation of the soil elastic modulus. However, a resistance factor of 1.0 for SLS is unconservative, and resistance factors of 0.65, 0.7 and 0.8 are better aligned with the RBD when the target failure probabilities are 1×10−3, 1×10−2 and 1×10−1. The current study can be used to guide the design of shallow foundations and the calibration of the LRFD approach. [ABSTRACT FROM AUTHOR]

This paper investigates the influence of three forms of uncertainty on the probabilistic stability of an idealised 3D embankment slope. These are: 1D spatial variability in the external geometry of the slope along its length, 2D spatial variability in the depth of the boundary between the embankment material and the foundation layer, and 3D spatial variability in the shear strength properties of the slope and foundation materials. The relative influence of each uncertainty has been investigated using the random finite element method, based on statistics consistent with a Dutch regional dyke. The results indicate that, for such a structure, the soil spatial variability has a much greater influence than uncertainties relating to embankment geometry and inter-layer boundary. In particular, it is demonstrated that the spatial correlation of material properties along the length of the embankment has a greater influence on the probabilistic characteristics of the embankment slope stability and failure consequence than the spatial correlation of properties perpendicular to it. A worst case scale of fluctuation for the material properties is identified. [ABSTRACT FROM AUTHOR]

Safety assessment of vehicles crossing highway interchanges during earthquakes by reliability-based numerical simulations is presented in this paper. The assessment was performed for two limit states: vehicle rollover and sideslipping accidents. Simulations were conducted using three-dimensional finite element models of two existing highway interchanges consisting of straight and curved bridges under site-specific earthquakes. Effects of curved bridges radii, levels of earthquake, vehicle type, driving velocity, and road surface conditions on the safety limit states of five types of vehicles, namely, sedan-type, SUV, small-box truck, bus, and large truck, were investigated and clarified in the Monte Carlo simulation. [ABSTRACT FROM AUTHOR]

To simulate the indoor air distribution accurately and quickly, this paper proposed a turbulence calculation model based on the zero-equation model and the SUPG finite element method. The optimal calculation parameters were investigated. The effects of air outlet positions, Reynolds numbers, and obstacle positions on indoor air distribution were studied. The results show that the ranges of Reynolds numbers which satisfy the summer and winter demands of indoor air velocity as the outlet at the right down position are larger than those when the outlet locates left down. When the air outlet locates at the left down position, the velocity non-uniformity coefficients are less than those under the other two conditions. Regardless of whether the air outlet is at the left or right position, the obstacle in the middle of a room can lead to worse velocity uniformity when air velocities in the working zone can meet the velocity demand. [ABSTRACT FROM AUTHOR]

The aim of this paper is to study the T-stress and its effect on crack propagation in FGM materials with adiabatic cracks subjected to thermo-mechanical loading based on the J-integral formulation and the extended finite element method (XFEM). Path-independent J-integral responses of T-stress for adiabatic cracks and the effects of incompatible terms for FGMs are discussed. Having examined the T-stress parameter, the effect of fracture characteristic/process length on crack propagation angle in adiabatic cracks is studied. The results show that the initial crack propagation angle deviates from the standard propagation angle by increasing the size of the fracture process zone. [ABSTRACT FROM AUTHOR]

In this paper, three types of hybrid monopiles are proposed for 3MW OWTs in offshore areas where the batholith is shallowly buried. Three-dimensional FE models are established considering the soil-structure-interaction (SSI) to calculate the bearing performances of these monopiles. Model verification is conducted through comparisons with existing numerical results. The static bearing performance and dynamic character under the serviceability limit state (SLS) in silty sand and normally consolidated (NC) clay are investigated. In the static analysis, we focus on the lateral deflection and the rotation at the mudline, whereas in the modal analysis, we focus on the natural frequencies of the OWTs. Results show that the circular skirt performs better than square fins in improving the bearing performance of traditional monopiles, and the improving effect increases with the length of the additional components. In addition, the improving effect is more obvious in NC clay than in silty sand. [ABSTRACT FROM AUTHOR]

Nonlinear finite-element model updating (FEMU) is a promising approach for post-event damage assessment of civil structures. This paper conducted FEMU for a full-scale reinforced concrete bridge column tested under a sequence of earthquakes and examined the evolution of seismic damage across different earthquake ground motions. It was found that using experimental data, FEMU can be applied to identify unknown key model parameters (e.g. bond-slip and core concrete parameters) and damage of the columns as represented by the change of the key parameters. In addition, the updated models demonstrated their ability to better predict the system response for future earthquakes. [ABSTRACT FROM AUTHOR]

This paper proposes a novel semi-rigid rocking wall-floor connection. To study its seismic behavior, a preliminary study using finite element modeling (FEM) has been conducted to perceive the rocking wall response towards the precast plank before conducting a physical experimental testing in the laboratory. The finite element model was developed to investigate the lateral quasi-static-load response of the isolated rocking wall system. Subsequently, the rocking wall model was further extended by incorporating a precast concrete plank using the proposed connection. The finite element model of the rocking wall showed a good correlation with the analytical model. Furthermore, the study showed that a semi-rigid connection would result in an overstrength that should be considered when designing the rocking wall. [ABSTRACT FROM AUTHOR]

A resilient rocking steel column base (RRSCB) installed with composite combination disc spring (CCDS) is proposed in this paper. The restoring force model and energy calculation formulae of the RRSCB are derived by the theoretical analyses and energy conservation law, respectively. A refined finite element model validated by the cyclic loading tests is established with the aid of ABAQUS to investigate the seismic performance of the RRSCB. The results indicate that the RRSCB possesses satisfactory self-centering capability and desirable energy dissipation capacity for the design displacement. The established restoring force model and energy calculation formulae can reasonably predict the hysteretic behavior of RRSCB under cyclic loading. [ABSTRACT FROM AUTHOR]

This paper presents refined one-dimensional (1D) finite element models develop by an effective nodal kinematics optimization method. The refined models belong to Best Theory Diagrams, which are built by using the Carrera Unified Formulation (CUF), Axiomatic/Asymptotic method and a Genetic Algorithm (GA). The influence of different chromosome types on the refined models and GA performance have been investigated. It is shown that the proposed method can improve the accuracy of regular 1D-CUF finite element models. Furthermore, the results suggest that it is possible to built refined models for compound loads from the ones optimized for individual loads. [ABSTRACT FROM AUTHOR]

Conservation of the European-built heritage is nowadays closely related to interventions in masonry construction. Since a significant part of these structures are located in earthquake prone zones, designing protective measures that ensure their preservation requires the assessment of the associated seismic vulnerability and the understanding of their degradation mechanisms. However, due to the presence of discontinuities between its constituent elements, the numerical simulation of the non-linear response of masonry structures subjected to strong earthquakes is a cumbersome task, especially when performed using the traditional finite element method. As an alternative, the discrete element method is particularly suitable for the numerical analysis of such structures under large, damaging loads. By allowing discrete displacements/rotations of individual bodies, and by automatically recognising new contacts between bodies, while eliminating obsolete ones, this numerical approach can simulate the complete detachment of discrete bodies initially in contact. The present paper illustrates the use of the discrete element method to assess the seismic vulnerability of stone arches. A probabilistic approach allows to consider the variability of the seismic action and the uncertainties in the definition of the material properties. First, an un-reinforced masonry arch is considered. Based on non-linear multi-directional incremental dynamic analyses, five damage states are proposed and the respective fragility curves are elaborated. To improve the arch's seismic performance, two reinforcing solutions using steel elements are considered and analysed comparatively. [ABSTRACT FROM AUTHOR]

This paper reports a double-sided polished microstructured fiber based on the refractive index that simultaneously measures the refractive index and temperature. Two polished planes were introduced into the cladding. A gold film and polydimethylsiloxane are deposited on one side of the plane for temperature measurements, and graphene layers are coated on the surface of the silver film on the other side for refractive index measurements. The finite element method is used to characterize the sensing characteristics of the sensor. The results show that when the liquid refractive index is from 1.36 to 1.4 and the temperature from 70 °C to 110 °C, the maximum sensitivity of the sensor is 15,000 nm/RIU and 8.8 nm/°C, respectively. The double-sided polished structure facilitates the development of multi-parameter measurement sensors for various applications. [ABSTRACT FROM AUTHOR]

In this paper, a new approach for measurement of the fracture toughness of concrete using the edge cracked semi-cylinder disk (ECSD) specimens has been rendered. The critical stress intensity factor (fracture toughness) of concretes was determined by using the edge cracked semi-cylinder disk (ECSCD) type specimens. The normalized Mode I stress intensity factor of concrete was measured and estimated through a new formula. The versatile finite element method (FEM) was used to derive this appropriate formula and the Mode I fracture toughness of the specimens determined with a reasonable accuracy. In the laboratory, the notched Brazilian disks (NBD) were tested to evaluate the accuracy of the ECSCD method. A discrete element analysis of the ECSCD tests was also carried out to numerically simulate these experiments and validate the accuracy of the fracture toughness values. Finally, very good agreements gained by comparing the crack extension patterns obtained from the experimental tests with the numerical simulations' results. However, the toughness values obtained through ECSCD experiments were lower than those measured from the NBD tests. This is due to the smooth distribution of tensile stress around the notch in the ECSCD concrete specimens. [ABSTRACT FROM AUTHOR]

Recently, non-prismatic beams have been considered as perfect substitutes to replace uniform cantilever beam structures in harvester design. This is due to their tendencies to provide uniform strain distribution, which enhances piezoelectric (PZT) charge generation when coupled with the beams. As the voltage produced by the PZT depends largely on the geometrical shape of the substrate, thus there is need for formulations to analyze the behavior of the shim prior to practical implementation. In this paper, analytical and finite element models were developed to study deflection and strain distribution of a non-prismatic beam termed, wedge edged cantilever (WEC) for patch-like harvester application. The analyses offer possibility for maximum utilization of strain location along the beam span for efficient harvester design. Vibration energy harvesting characteristics of the WEC beam with partially covered PZT material forming three configurations namely: Config1, Config2 and Config3 were studied. Both numerical and experimental results show that Confg3 with macro fiber composite (MFC) as the PZT material covering the determined optimal strain position yielded 2 to 3 times more peak output voltage than Config1 and Config2 with the MFC bonded at non-optimal positions. [ABSTRACT FROM AUTHOR]