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Thin-walled tubular deployable composite boom (DCB) has gained significant attention due to its lightweight, simple structure and high packaging efficiency. The experimental and numerical simulation methods were employed in this paper to investigate the folding behavior of the DCB. Using T700/epoxy unidirectional reinforced prepreg as raw material, DCB specimens were prepared by the vacuum bag method. To complete the folding experiments of DCB specimens, a folding mechanism was designed and manufactured. Folding experiments of DCB specimens were conducted and folding moment versus rotational displacement curves were measured. In addition, a Finite Element Model (FEM) was established to predict the folding behavior of the DCB. Different failure criteria were considered in the numerical analysis, including the Tsai‐Hill criterion and maximum stress criterion. Prediction results using the FEM were compared with experimental results, and both sets of results were in good agreement. It is shown that the DCB can achieve the folding function without failure. The research results in this paper are of great significance to the practical engineering application of the DCB. [Display omitted] • Six tubular deployable composite boom specimens and a precise folding mechanism were designed and prepared. • Folding experiments were conducted to measure the folding moment and rotational displacement curves. • A finite element model for predicting the folding behavior of the tubular deployable composite boom was established. [ABSTRACT FROM AUTHOR]

The purpose of the paper was to design geometric models of the movable connection made of brass for three different attachment options and three different loads. The numerical analysis of the mechanical properties, stresses, strains and displacements using the finite element method was carried out in SolidWorks 2020 and their comparative analysis was performed. The computer simulations performed will allow the boundary conditions that directly affect the mechanical properties of the engineering materials to be optimised [ABSTRACT FROM AUTHOR]

Recently, hydroforming has paid dividends in composite forming due to its uniform pressure distribution, which helps in reducing the delamination defects. Considering the need to develop an appropriate criterion for evaluating the formability of FMLs, inspired by sheet metal forming and testing, the uniform pressure loading test was adopted to characterize the formability of semi-cured FMLs by forming limit curve (FLC). In this paper, both theoretical analysis models considering and ignoring the tangential cohesive effect were established, and the stress expression of the critical zone was given. The results show that the tangential cohesive stress demonstrates a non-negligible influence on the FLC. A new form of comprehensive FLC was given by defining global equivalent strain and global strain ratio and analyzed by the finite element method. In addition, the numerical simulation model and the experimental parameters were verified. A simplified Hashin criterion was proposed and developed into the numerical simulation as a subroutine based on theoretical analysis. Parameters such as blank holder pressure, pressure rate, and temperature were considered both in experiments and simulation. Only fiber stretching damage was distinguished in the cross, single, and arc crack but no wrinkling. As predicted theoretically, a lower forming limit is expected when FMLs are subjected to greater tangential cohesive stress. Finally, with the help of numerical simulation, the influence of different boundary conditions on the comprehensive FLC was studied. Instead of a simple evaluation of FMLs, this comprehensive FLC could be used directly to optimize hydroforming processes in the engineering field. [ABSTRACT FROM AUTHOR]

• Proper quantification of joint rotational stiffness (JRS) of a flight intersection joint (FIJ) influences the dynamic characteristics of a flight vehicle. • JRS of an FIJ is often determined experimentally due to the lack of a right predictive model. • An analytical model is proposed to evaluate the JRS of a radial-type FIJ when subjected to an external bending moment. • Numerical analyses and experiments are performed on six different FIJ configurations. • JRS and moment-rotation behavior predicted by the proposed model are correlated with both experimental and numerical analyses. • Further, the effect of joint clearances on the behavior of FIJ is investigated through the present model. Joint rotational stiffness (JRS) of a flight intersection joint (FIJ) and its accurate quantification play an essential role in studying the dynamic modal characteristics of a flight vehicle. This JRS of a FIJ is mostly determined through elaborate experiments due to the non-availability of a reliable predictive model. Therefore, in this paper, an analytical model is proposed to evaluate JRS of a radial type FIJ when subjected to external bending moment. In this model, at first, the tensile and compressive part of the FIJ section is identified by determining the neutral axis position. The respective part's contributing stiffness is then estimated by employing a spring-mass model. Later, the JRS expression is derived from the moment equilibrium condition and expressed as a function of the stiffness of the tensile and compressive part and neutral axis position. Subsequently, finite element analysis (FEA) is conducted with different numbers of screws, followed by detailed experimental investigations. The proposed analytical model is validated with the results from FEA and experiments for different screw configurations of FIJ. Further, the proposed model is extended to account for the effect of joint clearances on the JRS and the corresponding moment-rotation characteristics of the FIJ. [Display omitted] [ABSTRACT FROM AUTHOR]

Numerical simulations are used in this work to investigate aspects of microstructure and microsegregation during rapid solidification of a Ni-based superalloy in a laser powder bed fusion additive manufacturing process. Thermal modeling by finite element analysis simulates the laser melt pool, with surface temperatures in agreement with in situ thermographic measurements on Inconel 625. Geometric and thermal features of the simulated melt pools are extracted and used in subsequent mesoscale simulations. Solidification in the melt pool is simulated on two length scales. For the multicomponent alloy Inconel 625, microsegregation between dendrite arms is calculated using the Scheil-Gulliver solidification model and DICTRA software. Phase-field simulations, using Ni–Nb as a binary analogue to Inconel 625, produced microstructures with primary cellular/dendritic arm spacings in agreement with measured spacings in experimentally observed microstructures and a lesser extent of microsegregation than predicted by DICTRA simulations. The composition profiles are used to compare thermodynamic driving forces for nucleation against experimentally observed precipitates identified by electron and X-ray diffraction analyses. Our analysis lists the precipitates that may form from FCC phase of enriched interdendritic compositions and compares these against experimentally observed phases from 1 h heat treatments at two temperatures: stress relief at 1143 K (870 °C) or homogenization at 1423 K (1150 °C). [ABSTRACT FROM AUTHOR]

This paper presents a quasistatic problem of an elastic body in frictional contact with a moving foundation. The model takes into account wear of the contact surface of the body caused by the friction. We recall existence and uniqueness results obtained in Sofonea et al. (2017). The main aim of this paper is to present a fully discrete scheme for numerical approximation together with an error estimation of a solution to this problem. Finally, computational simulations are performed to illustrate the mathematical model. [ABSTRACT FROM AUTHOR]

Abstract In this paper, compressive material tests on unconfined/confined resin and steel reinforced resin were experimentally evaluated in order to validate the numerical results. The uniaxial model which combines damage mechanics and Ramberg-Osgood relationship is proposed in this paper to describe the uniaxial compressive behaviour of resin and steel reinforced resin. Numerical homogenization is conducted to predict the tensile and shear behaviour of steel reinforced resin after validated by compressive material test results. The friction angle β , the ratio of the yield stress in triaxial tension to the yield stress in triaxial compression K, and the dilation angle ψ of the linear drucker-prager plastic model are obtained based on experiments and numerical homogenization simulation. The confinement effects on resin and steel reinforced resin could be effectively simulated by combing above parameters and uniaxial compressive model. Finite element simulations on unconfined/ confined resin and steel reinforced resin material tests were conducted to validate the material parameters proposed in this paper. A good agreement is observed, indicating the model and parameters proposed in this paper could be effectively used in the finite element simulation of injected bolts. [ABSTRACT FROM AUTHOR]

Abstract As part of the LEAP-GWU-2015 exercise, a dynamic centrifuge test was conducted at the University of Cambridge on a 5° slope of medium dense Ottawa F-65 sand. The model preparation and saturation details are presented in this paper. This paper presents the experimental data recorded during small and large magnitude sinusoidal ground motions. After the experiment, numerical simulations of the experiment were performed using the finite element code Swandyne. The results from these numerical analyses are compared with the centrifuge test data and the deformations observed during the post-test investigations. The numerical analyses replicated many of the salient features of the test, such as the overall generation of excess pore pressures and attenuation of accelerations in the liquefying ground. More subtle results, such as the de-liquefaction shocks and the asymmetric response due to differences in upslope and downslope accelerations were less well captured in terms of the expected spikes in the dynamic excess pore pressures and accelerations. Overall, the combination of centrifuge testing and numerical analysis were found to complement each other well. Highlights • The effect of shaker translation on the model is explored in terms of accelerations and excess pore pressure generation. • Relative performance between the numerical analysis and experimental data are discussed for each earthquake loading. • The influence of high frequency components in the acceleration input were assessed using an additional numerical analysis. • Interpretation of the numerical analyses were guided by the discrepancies between predicted and measured pore pressures. [ABSTRACT FROM AUTHOR]

This paper presents the results of an analysis of the linear wear of the inside of a pipe transporting loose materials. The aim is to present a mathematical model simulating the abrasive wear of individual elements of a transport pipe, depending on the volume of transported material. The model presented in this paper was developed based on the measurement data obtained from a dismantled transport system used in a railway handling terminal. [ABSTRACT FROM AUTHOR]

A solid rocket motor is one of the critical components of solid missiles, and its life and reliability mostly depend on the mechanical behavior of a composite solid propellant (CSP). Effective mechanical properties are critical material constants to analyze the structural integrity of propellant grain. They are estimated by a numerical method that combines the Voronoi cell finite element method (VCFEM) and the homogenization method in the present paper. The correctness of this combined method has been validated by comparing with a standard finite element method and conventional theoretical models. The effective modulus and the effective Poisson’s ratio of a CSP varying with volume fraction and component material properties are estimated. The result indicates that the variations of the volume fraction of inclusions and the properties of the matrix have obvious influences on the effective mechanical properties of a CSP. The microscopic numerical analysis method proposed in this paper can also be used to provide references for the design and the analysis of other large volume fraction composite materials. [ABSTRACT FROM AUTHOR]

The paper presents results of numerical analyses of the collision of various bird models (dummies) with a helicopter windshield. Three different numerical bird models were elaborated. According to the subject literature, applying an appropriate equation of state has an influence on impact parameters. The author used the LS_DYNA software package. This is a computational code designed to analyse fast-changing phenomena by means of the finite-element method. SPH method has been used for bird strike simulations. In the research, three different equations of state have been used: Grüneisen's, polynomial and tabulated. [ABSTRACT FROM AUTHOR]

This paper provides the result of the geometrical optimisation of a wing strut joint of an aircraft. The objective of the geometrical optimisation was to modify the geometry of the wing strut joint components to meet an optimisation criterion defined as yield strength determined by static tensile testing. The geometrical optimisation was processed on a computer model of the wing strut joint using FEM (finite element method). The design variables assumed in this geometrical optimisation were the load option and boundary conditions of interaction between the wing strut joint components. An analysis carried out as part of the geometrical optimisation was based on proposing modifications to the geometry of the joint features at their maximum stress levels. The geometry optimisation results will be applied in the preparation and performance of validation strength testing of the wing strut joint assembly. [ABSTRACT FROM AUTHOR]

This paper presents the blast responses of ultrahigh-performance concrete (UHPC) structural members obtained using finite element (FE) modelling. The FE model was developed using LS-DYNA with an explicit solver. In the FE simulation, the concrete damage model, which is a plasticity-based constitutive material model, was employed for the concrete material. The simulation results were verified against previous experimental results available in the literature and were shown to be in good agreement with the experimental results. In addition, the developed FE model was implemented in a parametric study by varying the blast weight charges. The numerical results for UHPC members were compared with those for conventional reinforced concrete (RC) members. The numerical responses, such as the maximum deflections, deflected shapes, and damage patterns, of the UHPC members subjected to blast loading were significantly better performance than those of the RC members as a result of the high strength and ductile capacity of UHPC. [ABSTRACT FROM AUTHOR]

In order to further improve the crack resistance of concrete engineering, a numerical simulation method is constructed to study the effect of temperature on the fission of concrete. Based on the finite element method, the mathematical model is constructed, and the numerical calculation and image display are used to simulate and analyze the engineering problems. The temperature sensor is used to observe the whole variation law of typical temperature field, and the temperature of concrete entering and pouring is obtained. Thus, the temperature control real-time automatic acquisition system is set up. According to the temperature field and temperature stress distribution rules, the ideal temperature control curve model of concrete is proposed. Finally, the numerical calculation and experiment of the model are carried out. The results show that the maximum surface stress level decreases in varying degrees after different surface insulation measures are taken, and if the thermal insulation material's β = 10 kJ/m²h °C, the maximum surface stress of concrete can be reduced to 0.06~0.14 MPa. In this paper, it is shown that the negative effect of the large diurnal temperature difference on concrete surface insulation can be controlled. [ABSTRACT FROM AUTHOR]

A numerical method is employed to investigate the fluid flowing dynamics in fractured reservoirs in this paper. Owing to the multi-scales and strong heterogeneity, description of fracture network systems plays a significant role for a successful fractured reservoir simulation model. Comparing to previous works, this paper proposes a combination of dual continuum and discrete fracture network (DFN) model, which is used to simulate the flow in reservoirs with multi-scale fractures and proved feasible. In the first part of the paper, implicit flow equations of oil and water phase in fractured reservoirs are established to consider the nonlinearity properties. And then the control volume finite element method based on the unstructured grid system and N-R iteration are used to obtain the numerical solution. Moreover, the accuracy of this simulator is proved to be reasonable by field data; Sensitivity analysis shows that the existences of complex multi-scale fracture networks have great impacts on water flooding. Compared with the homogeneous reservoir, natural fracture (micro and large scale) networks can change the direction and velocity of the waterfront, which finally leads to the more serious water breakthrough, higher water cut and less recovery. The research and the numerical results obtained in this paper can provide theoretical guidance for efficient and scale development of natural fractured reservoirs. [ABSTRACT FROM AUTHOR]

• A numerical simulation method for the multifactor coupling of stress field and temperature field is developed. • The numerical simulation method is in good agreement with the experiment results at elevated temperatures. • The numerical simulative description of the grout material failure and fracture of a steel bar. • Prediction of the yield point and the ultimate point of FGSC from 25 °C to 1000 °C. Fire is one of the main objects of study at the cutting edge of the research on disaster prevention and mitigation in structures. In the event of a fire, the mechanical properties of the structural material will be significantly reduced, resulting in serious consequences. This paper simulates the tensile properties of sleeve grouting members at five different temperatures, to contribute to the research here. The simulated member stress-strain curves fit well with the corresponding experimental results. The paper introduces constitutive models of concrete, steel, and sleeve. Beyond that, a feasible finite element model of the grouted sleeve is proposed. Two special points' (yield point, ultimate point) coordinate formulas which are related to different temperatures (25–1000 °C) are presented. It indicates the regularity of fully-grouted sleeve tensile force-displacement curves in various temperatures. Meanwhile, the research content provides the basis for further research on reinforcing bars spliced by grout-filled coupling sleeves. [ABSTRACT FROM AUTHOR]

Currently, surgical continuum robots (CRs) are predominantly used as telemanipulators where modeling errors are overcome by the user. Such errors preclude their use for autonomous tasks. In this paper, we investigate the calibration of CRs with specific focus on capturing joint space errors due to homing offsets, assembly errors causing twist about the robot's backbone, and uncertainty in the equilibrium bending shapes of segments of these robots. A kinematic framework focusing on multibackbone CR is presented with emphasis on deriving calibration identification Jacobians. This framework captures the coupling between twist and the equilibrium shapes of a continuum segment as a function of its bending angle. To capture equilibrium shape variations as a function of bending, a homotopy of curves is defined and represented by respective modal coefficients. The estimation of the calibration parameters is cast as a nonlinear least-squares problem. The framework is validated by simulations and experimentally using a single-port access surgery robot. We believe this calibration framework will facilitate semiautomation of surgical tasks carried out by CRs. [ABSTRACT FROM AUTHOR]

Abstract This paper was dealt with buckling and post-buckling behavior of short thin-walled Z-columns made of a carbon-epoxy laminate, subjected to eccentric compressive load. The buckling mode and the buckling load of real structures versus load eccentricity were discussed. The study involved both experimental tests were carried out on real laminated structures and numerical simulations by the finite element method. The buckling load of real structures was determined by approximation methods on the basis of experimental and numerical post-buckling equilibrium paths of the structure. Additionally, in numerical simulations, the bifurcation load value was determined by solving an eigen problem. In all cases, experimental findings and numerical results show high agreement. The study determined the quantitative influence of the direction and value of compressive load eccentricity on the buckling load and rigidity of the structure in the post-buckling state. [ABSTRACT FROM AUTHOR]

Peripheral arterial occlusive disease is a chronic pathology affecting at least 8-12 million people in the USA, typically treated with a vein graft bypass or through the deployment of a stent in order to restore the physiological circulation. Failure of peripheral endovascular interventions occurs at the intersection of vascular biology, biomechanics, and clinical decision making. It is our hypothesis that the majority of endovascular treatment approaches share the same driving mechanisms and that a deep understanding of the adaptation process is pivotal in order to improve the current outcome of the procedure. The postsurgical adaptation of vein graft bypasses offers the perfect example of how the balance between intimal hyperplasia and wall remodeling determines the failure or the success of the intervention. Accordingly, this work presents a versatile computational model able to capture the feedback loop that describes the interaction between events at cellular/tissue level and mechano-environmental conditions. The work here presented is a generalization and an improvement of a previous work by our group of investigators, where an agent-based model uses a cellular automata principle on a fixed hexagonal grid to reproduce the leading events of the graft's restenosis. The new hybrid model here presented allows a more realistic simulation both of the biological laws that drive the cellular behavior and of the active role of the membranes that separate the various layers of the vein. The novel feature is to use an immersed boundary implementation of a highly viscous flow to represent SMC motility and matrix reorganization in response to graft adaptation. Our implementation is modular, and this makes us able to choose the right compromise between closeness to the physiological reality and complexity of the model. The focus of this paper is to offer a new modular implementation that combines the best features of an agent-based model, continuum mechanics, and particle-tracking methods to cope with the multiscale nature of the adaptation phenomena. This hybrid method allows us to quickly test various hypotheses with a particular attention to cellular motility, a process that we demonstrated should be driven by mechanical homeostasis in order to maintain the right balance between cells and extracellular matrix in order to reproduce a distribution similar to histological experimental data from vein grafts. [ABSTRACT FROM AUTHOR]

Numerical models for vibro-acoustic analyses of complex mechanical systems are becoming more and more popular, in particular in the field of virtual product development. Therefore, reliable, comprehensive, and validated modeling methodologies remain crucial. However, system characteristics such as elasticities of the drive train components and nonlinear characteristics can lead to complex, and costly numerical models with a huge number of degrees of freedom. This may raise not only the need for novel and reasonable modeling strategies, but also exacerbates validation process, due to the wide scope in terms of operating conditions. In practice, structure-borne noise signals, for example, from accelerometers, are often used for the validation of mechanical systems. By choice of a sufficient number of measurement points, the interpretation becomes more complex. A lot of vibration response curves then need to be compared and interpreted over a wide operating range. In general, the interpretation focuses on deviations in quality and quantity. In this paper, to overcome these mentioned challenges, a validation methodology is proposed allowing a fast and transparent check of a number of captured signals. Therefore, it is shown how the original information can be reduced in a meaningful manner, making it possible to run a fast and accurate validation. The method is demonstrated on a real application with high mechanical complexity and it is shown that the chosen parameters are reliable. [ABSTRACT FROM AUTHOR]

This paper describes the beneficial effects of multiple layers of rubber-sand mixture (RSM). The plate load tests, using circular plate of 300 mm diameter, were performed at an outdoor test pit, dug in natural ground with dimensions of 2000 × 2000 mm in plan and 720 mm in depth to facilitate realistic test conditions. The rubber used in the RSM layers was granulated rubber, produced from waste tires. The optimum thickness of the RSM layer was determined to be approximately 0.4 times the footing diameter. By increasing the number of RSM layers, the bearing capacity of the foundation can be increased and the footing settlement reduced. The influence of the number of RSM layers on bearing capacity and settlement become almost insignificant beyond three layers of RSM, particularly at low settlement ratios. At a ratio of settlement to plate diameter of 4%, the values of bearing pressure for the installation with one, two, three and four layers of RSM were about 1.26, 1.47, 1.52 and 1.54 times greater, respectively, than that for the unreinforced installation. Layers of the RSM reduced the vertical stress transferred through the foundation depth by distributing the load over a wider area. For example, at an applied footing pressure of 560 kPa, the transferred pressure at a depth of 570 mm was about 58, 45 and 35% for one, two and three layers of RSM, respectively, compared to the transferred stress in the unreinforced bed. By numerical analysis, it was found that the presence of soil-rubber layers resulted in expansion of passive zones in the foundation due to the effectiveness of the confinement provided by the rubber inclusions, and this tends to make the bed deflect less. On the basis of this study, the concept of using multiple RSM layers has not only been shown to improve the performance of foundations under heavy loading, but also, the environmental impacts of waste tires are attenuated by re-using their rubber as part of a composite soil material in civil engineering works. [ABSTRACT FROM AUTHOR]

Abstract Downburst produces strong winds near the ground and causes severe damage to buildings and people. The non-stationarity of downburst is characterized by moving downdraft and pulsed jet to the ground. In practice, both characteristics have often been observed simultaneously. These characteristics significantly affect the wind loads on buildings, particularly on low-rise buildings. However, the previous experimental studies of downbursts focused on each of these characteristics separately. No study has been made of their coupled effect. Therefore, we have developed a downburst simulator, which can generate a pulsed jet and a moving downdraft either separately or simultaneously. In the present paper, we have experimentally investigated the effects of non-stationary characteristics of downbursts on the wind field and wind loads on a flat-roofed low-rise building using this downburst simulator. The results may become a useful database for validating numerical simulation models of downbursts. Highlights • Effects of movement and impinging jet on the flow field of downburst is investigated. • Non-stationary flow fields of moving and pulsed jet are experimentally reproduced. • Downburst-induced pressure on a building is measured with a downburst simulator. • Downburst-induced wind forces are different from those by turbulent boundary layers. [ABSTRACT FROM AUTHOR]

To respond to changes in the requirements of the information and control system, it is necessary to rebuild the system with new functions and/or systems with a different architecture. In this paper, we propose a method that enables on-site technicians to perform step-wise migration from a legacy system to a target system without having to stop the whole system and without requiring advance preparation or support from a system engineer who is an expert in system design and development. Accordingly, we aimed to develop a technology for the coexistence of and cooperation between with target and legacy systems and cooperation test between heterogeneous systems. We implemented this method and evaluated its effectiveness by applying it for rebuilding a production line management system. [ABSTRACT FROM AUTHOR]

This paper studies the influence of diverse friction models on the numerical analysis of an industrial skew rolling mill using FORGE®. The originality of the present contribution is the analysis of the effect of the friction model on important parameters, namely, consumed power, plastic deformation and surface temperature. The aim is to evaluate which of these friction models is appropriate for simulating these industrial processes. The high values of temperature, pressure and sliding velocity at the contacts make the assessment of the friction model incidence on the deformation and temperature evolution fundamental, given its importance on the thermomechanical processing of materials. As a conclusion, IFUM is not valid because of its sliding velocity approach. On the other hand, Neumaier presents the highest deviations in terms of experimental power. It is concluded that Tresca is valid for this sort of processes and Norton model gives the most accurate results for friction power, related to the high sliding conditions at the contact. [ABSTRACT FROM AUTHOR]

This paper presents a novel hybrid observer structure to estimate the lateral tire forces and road grip potential without using any tire-road friction model. The observer consists of an Extended Kalman Filter structure, which incorporates the available prior knowledge about the vehicle dynamics, a feedforward Neural Network structure, which is used to estimate the highly nonlinear tire behavior, and a Recursive Least Squares block, which predicts the road grip potential. The proposed observer was evaluated under a wide range of aggressive maneuvers and different road grip conditions using a validated vehicle model, validated tire model, and sensor models in the simulation environment IPG CarMaker®. The results confirm its good and robust performance. [ABSTRACT FROM AUTHOR]

When a railway track presents an abrupt discontinuity of vertical stiffness (e.g., due to the presence of a structure), an amplification of the dynamic forces acting on both the vehicle and the track may be expected. Therefore, diverse solutions—generally known as track transitions—have been proposed in the literature to provide a smoother stiffness change between different track sections. An extensive research has been performed in recent years in order to better understand the dynamics of track transitions as well as the processes involved. However, to the best of the authors’ knowledge, no research has fully studied the effect of vehicle speed and only one value is generally used instead of considering a wider range. Hence, this paper explicitly analyzes the effect of train speed on the vibrational performance of four transition typologies: a concrete wedge; a hot mixed asphalt wedge; a geogrid; and a soil reinforcement. The results show that mitigation capacity of all the alternatives increases with train speed, the concrete wedge being the most effective solution. Moreover, the effects on vertical vibrations of the abrupt stiffness change are found to be significant only for high train speeds (220–300 km/h). Finally, an amplification effect due to resonance has been found for the concrete transition when a vehicle speed of 100 km/h is considered. [ABSTRACT FROM AUTHOR]

In this paper, an enriched FEM technique is employed for thermo-mechanical contact problem based on the extended finite element method. A fully coupled thermo-mechanical contact formulation is presented in the framework of X-FEM technique that takes into account the deformable continuum mechanics and the transient heat transfer analysis. The Coulomb frictional law is applied for the mechanical contact problem and a pressure dependent thermal contact model is employed through an explicit formulation in the weak form of X-FEM method. The equilibrium equations are discretized by the Newmark time splitting method and the final set of non-linear equations are solved based on the Newton-Raphson method using a staggered algorithm. Finally, in order to illustrate the capability of the proposed computational model several numerical examples are solved and the results are compared with those reported in literature. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this paper is to propose a new three-node triangular element in the framework of the numerical manifold method (NMM), which is designated by Trig3-MLScns.Design/methodology/approach The formulation uses the improved parametric shape functions of classical triangular elements (Trig3-0) to construct the partition of unity (PU) and the moving least square (MLS) interpolation method to construct the local approximation function.Findings Compared with the classical three-node element (Trig3-0), the Trig3-MLScns element has a higher order of approximations, much better accuracy and continuous nodal stress. Moreover, the linear dependence problem associated with many PU-based methods with high-order approximations is eliminated in the present element. A number of numerical examples indicate the high accuracy and robustness of the Trig3-MLScns element.Originality/value The proposed element inherits the individual merits of the NMM and the MLS. [ABSTRACT FROM AUTHOR]

Purpose The velocity head is usually neglected in the energy equation for a pipeline junction when one-dimensional (1D) hydraulic transient flow is solved by method of characteristics. The purpose of this paper is to investigate the effect of velocity head on filling transients in a branched pipeline by an energy equation considering velocity head.Design/methodology/approach An interface tracking method is used to locate the air–water interface during pipeline filling. The pressured pipe flow is solved by a method of characteristics. A discrete gas cavity model is included to permit the occurrence of column separation. A universal energy equation is built by considering the velocity head. The numerical method is provisionally verified in a series pipeline and the numerical results and experimental data accord well with each other.Findings The numerical results show that some differences in filling velocity and piezometric head occur in the branched pipeline. These differences arise because the velocity head in the energy equation can become an important contributor to the hydraulic response of the system. It is also confirmed that a local high point in the profile is apt to experience column separation during rapid filling. Significantly, the magnitude of overpressure and cavity volume induced by filling transients at the local high point is predicted to increase with the velocity in the pipes.Originality/value The velocity head in the energy equation for a pipeline junction could play an important role in the prediction of filling velocity, piezometric head and column separation phenomenon, which should be given more attention in 1D hydraulic transient analysis. [ABSTRACT FROM AUTHOR]

Purpose Metal plates are usually used as protective shields of engineering structures, which probably undergo multiple projectile impacts resulting from gunshot and blast. Though a large number of studies have been conducted on the performance of metal plates under a single projectile impact, few studies have explored their performance under multiple projectile impacts. This paper aims to explore the performance of Weldox 460 E steel plates against multiple projectile impacts through numerical simulation.Design/methodology/approach A three-dimensional coupled finite element (FE) and smoothed particle hydrodynamics (SPH) model was developed to simulate the perforation of a 12-mm-thick Weldox 460 E steel plate by an ogival projectile. The model was verified by existing experimental data. Then, it was extended to investigate the same target plate subjected to impacts with multiple projectiles. Simultaneous impacts with different number of projectiles, as well as sequential impacts with two projectiles, were considered.Findings Effects of spacing between projectiles on residual velocity of projectile, ballistic limit and failure mode of target were revealed for simultaneous impacts. Effects of spacing and axial distance between projectiles on residual velocity of projectile were explored for sequential impacts.Originality/value This work developed an advanced FE–SPH model to simulate perforation of steel plates by multiple projectiles, and revealed the effects of multiple impacts on ballistic performance of steel plates. It provides guidance for the design of protective structures/shields in various engineering applications. [ABSTRACT FROM AUTHOR]

The article proposes the implementation of a novel method of plastic forming of internal toothing in flange spline sleeves. A method being the subject of Polish patent application P.416772 has been used for this purpose, which involves a combination of the scheme of the direct extrusion of a cone hollow with the die press forming of the wall to obtain a flange. The entire process takes place in a single technological sequence. The operations come one after another, so that there is no need for reheating the stock or carrying out intermediate soft annealing. The proposed method is assumed to be an alternative to the operation of press forming of internal spline sleeve toothing in a conical die [1] and to the operation of swaging on rotary swaging machines [2]. It is assumed that this method, too, is alternative to other technologies known from the literature and industrial practice, whose specifications and literature references will be indicated later on in this paper. Computer simulations of the flanged sleeve plastic forming process were performed using the commercial numerical program Forge®3D. During the numerical computations, the distributions of temperature fields were determined on the cross-section of the plastically formed product. The computations enabled also the visualization of the plastic flow of metal, especially in the toothing forming regions, and the determination of the energy and force parameters of the process. [ABSTRACT FROM AUTHOR]

The subject of the study are alumina foams produced by gelcasting method. The results of micro-computed tomography of the foam samples are used to create the numerical model reconstructing the real structure of the foam skeleton as well as the simplified periodic open-cell structure models. The aim of the paper is to present a new idea of the energy-based assessment of failure strength under uniaxial compression of real alumina foams of various porosity with use of the periodic structure model of the same porosity. Considering two kinds of cellular structures: the periodic one, for instance of fcc type, and the random structure of real alumina foam it is possible to justify the hypothesis, computationally and experimentally, that the same elastic energy density cumulated in the both structures of the same porosity allows to determine the close values of fracture strength under compression. Application of finite element computations for the analysis of deformation and failure processes in real ceramic foams is time consuming. Therefore, the use of simplified periodic cell structure models for the assessment of elastic moduli and failure strength appears very attractive from the point of view of practical applications. [ABSTRACT FROM AUTHOR]

Block pavements are an attractive alternative to asphalt and concrete pavements, especially in communal areas. Architects and urban planners would like to take advantage of various shapes, colours and textures of paving blocks in order to achieve a higher quality of urban space if the performance of block pavements could be better predicted to avoid large horizontal displacements of chipped stone corners and rutting. Unfortunately, the computational performance prediction of paving block structures is more complex than that for flexible pavements with homogeneous surface layers of asphalt concrete. The influence of the large number of vertical joints between paving blocks on the overall mechanical performance has not been considered sufficiently within computational tools yet. The proposed numerical simulation tool is able to take into account the complex mechanical behaviour of sand-filled joints as well as the non-linear mechanical behaviour of the underlying base courses. Joints are modelled using a Mohr-Coulomb-type friction model with the normal stresses non-linearly related with joint opening. Three different experimental set-ups were developed for the identification of the model parameters. The base behaviour was modelled using the Drucker-Prager cap model. The paper shows that the proposed tool predicts reasonable deformations and stresses in block pavements. The results of the simulations were compared with measured stresses from the full-scale accelerated pavement testing and a good agreement was observed. [ABSTRACT FROM AUTHOR]

The framework of this paper is to investigate the mitigation ability of an expanded rigid polyurethane foam against extremely fast (>106 s−1) and intense ( >10 GPa) dynamic loadings. Cyclic quasi-static tests and dynamic experiments (gas gun and low inductance generator) have been performed to investigate the foam behaviour for strain rates ranging from 10−3 to 105 s−1. Analysis of the experimental results shows that the foam has an elastic behaviour phase followed by a compaction phase with significant permanent sets. Compaction threshold is about 8 MPa under quasi-static loading, and 21 MPa for strain rates above 104 s−1. A porous compaction model is used to represent the macroscopic behaviour of the foam for the whole range of strain rates. The parameters are identified from dynamic experimental results. The model is validated by comparing calculated velocity profiles with an explicit hydrocode and velocity profiles measured during the experiments. [ABSTRACT FROM AUTHOR]

Numerical schemes provably preserving the positivity of density and pressure are highly desirable for ideal magnetohydrodynamics (MHD), but the rigorous positivity-preserving (PP) analysis remains challenging. The difficulties mainly arise from the intrinsic complexity of the MHD equations as well as the indeterminate relation between the PP property and the divergence-free condition on the magnetic field. This paper presents the first rigorous PP analysis of conservative schemes with the Lax--Friedrichs (LF) flux for 1D and multidimensional ideal MHD. The significant innovation is the discovery of the theoretical connection between the PP property and a discrete divergence-free (DDF) condition. This connection is established through the generalized LF splitting properties, which are alternatives to the usually expected LF splitting property that does not hold for ideal MHD. The generalized LF splitting properties involve a number of admissible states strongly coupled by the DDF condition, making their derivation very difficult. We derive these properties via a novel equivalent form of the admissible state set and an important inequality, which is skillfully constructed by technical estimates. Rigorous PP analysis is then presented for finite volume and discontinuous Galerkin schemes with the LF flux on uniform Cartesian meshes. In the 1D case, the PP property is proved for the first-order scheme with proper numerical viscosity, and also for arbitrarily high-order schemes under conditions accessible by a PP limiter. In the 2D case, we show that the DDF condition is necessary and crucial for achieving the PP property. It is observed that even slightly violating the proposed DDF condition may cause failure to preserve the positivity of pressure. We prove that the 2D LF type scheme with proper numerical viscosity preserves both the positivity and the DDF condition. Sufficient conditions are derived for 2D PP high-order schemes, and extension to 3D is discussed. Numerical examples provided in the supplementary material further confirm the theoretical findings. [ABSTRACT FROM AUTHOR]

In this paper we propose a new Eulerian model and related accurate and robust numerical methods, describing polydisperse evaporating sprays, based on high order moment methods in size. The main novelty of this model relies on the use of fractional droplet surface moments and their ability to predict some geometrical variables of the droplet-gas interface, by analogy with the liquid-gas interface in interfacial flows. Evaporation is evaluated by using a maximum entropy (ME) reconstruction. The use of fractional moments introduces some theoretical and numerical difficulties. First, relying on a study of the moment space, we extend the ME reconstruction to the case of fractional moments. Then we propose a new high order and robust algorithm to solve the moment evolution due to evaporation, which preserves the structure of the moment space. It involves some negative order fractional moments for which a novel treatment is introduced. The present model and numerical schemes yield an accurate and stable evaluation of the moment dynamics with a minimal number of variables, as well as minimal computational cost, but also provide an additional capacity of coupling with the diffuse interface model and the transport equation of averaged geometrical interface variables, which are essential in order to describe atomization. [ABSTRACT FROM AUTHOR]

This paper deals with numerical simulation of fluid-structure interaction as it occurs during aircraft ditching - an emergency condition where an aircraft is forced to land on water. The work is motivated by the requirement for aircraft manufactures to analyze ditching as part of the aircraft certification process requested by airworthiness authorities. The strong interaction of highly non-linear fluid flow phenomena and structural responses requires a coupled solution of this transient problem. Therefore, an approach coupling Smoothed Particle Hydrodynamics and the Finite Element method within the commercial, explicit software Virtual Performance Solutions has been pursued. In this paper, several innovative features are presented, which allow for accurate and efficient solution. Finally, exemplary numerical results are successfully compared to experimental data from a unique test campaign of guided ditching tests at quasi-full scale impact conditions. It may be concluded that through the application of state-of-the-art numerical techniques it has become possible to simulate the coupled fluidstructure interaction as occurring during ditching. Therefore, aircraft manufacturers may significantly benefit from numerical analysis for design and certification purposes. [ABSTRACT FROM AUTHOR]

Wang, C.; Ren, H.; Li, H., and Wang, J., 2015. A direct assessment method for structure strength of icebreaker based on numerical simulation. Considering the changes of ice stress caused by strain rate of ice, a finite element method is presented to assess structure strength of icebreaker and ice failure model is based on multi-surface criterion. This paper discusses both principle of ice and ship model and presents results of structure stress in ice environment. Secondary development technology of finite element software is applied to simulate ice failure. Phenomena such as ice failure model and velocity changes of icebreaker are shown in simulation results, which show that the simulated ice loads are in good agreement with the literature results. The method presented in this paper can reflect the stress distribution of the structure and the numerical model can be applied to predict ice load and structure strength. [ABSTRACT FROM AUTHOR]

In this paper, the stability problem of impulsive functional differential equations (IFDEs) is considered. Several criteria ensuring the uniform stability of IFDEs with finite or infinite delay are derived by establishing some new Razumikhin conditions. Different with the current existing ones, our development results can be applied to delay systems with persistent impulsive effects. Finally, an example and its computer simulation is given to show the effectiveness and advantages of the proposed method. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) enables the fabrication of parts of unprecedented complexity. Dedicated topology optimization approaches, that account for specific AM restrictions, are instrumental in fully exploiting this capability. In popular powder-bed-based AM processes, the critical overhang angle of downward facing surfaces limits printability of parts. This can be addressed by changing build orientation, part adaptation, or addition of sacrificial support structures. Thus far, each of these measures have been studied separately and applied sequentially, which leads to suboptimal solutions or excessive computation cost. This paper presents and studies, based on 2D test problems, an approach enabling simultaneous optimization of part geometry, support layout and build orientation. This allows designers to find a rational tradeoff between manufacturing cost and part performance. The relative computational cost of the approach is modest, and in numerical tests it consistently obtains high quality solutions. [ABSTRACT FROM AUTHOR]

The particle-in-cell (PIC) method has been widely used for plasma simulation, because of its noise-reduction capability and moderate computational cost. The immersed finite element (IFE) method is efficient for solving interface problems on Cartesian meshes, which is desirable for the PIC method. The combination of these two methods provides an effective tool for plasma simulation with complex interface/boundary. This paper introduces an improved IFE–PIC method that enhances the performance in both IFE and PIC aspects. For the electric field solver, we adopt the newly developed partially penalized IFE method with enhanced accuracy. For PIC implementation, we introduce a new interpolation technique to ensure the conservation of the charge. Numerical examples are provided to demonstrate the features of the improved IFE–PIC method. [ABSTRACT FROM AUTHOR]

This paper presents finite-time chaos synchronization of time-delay chaotic systems with uncertain parameters. According to the proposed method, a lot of coupled items can be treated as zero items. Thus, the whole system can be simplified greatly. Based on robust chaotic synchronization, secure communication can be realized with a wide range of parameter disturbance and time-delay. Numerical simulations are provided to illustrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The paper has considered the fractal flow in a dual media with fractal properties, where the media could be elastic, heterogeneous and visco-elastic. We argued that, the fractal flow within a geological formation with elastic property cannot be accurately described with the concept of differentiation with local operator, as this operator is unable to include into mathematical formulation the effect of elasticity. Thus to include into mathematical formula the observed facts, we have modified the model by replacing the local derivative with the non-local operator with power. A more complex problem was considered where the geological formation is considered to have visco-elastic and heterogeneity properties. We argued that, the flow within a matrix rock with these two properties cannot either be described with local derivative nor a non-local derivative with power law. In this case two non-local operators were considered, an operator with Mittag-Leffler kernel and Mittag-Leffler-Power law kernel [F. Ali et al., J. Magn. Magn. Mater. 423, 327 (2017); F. Ali et al., Eur. Phys. J. Plus 131, 310 (2016); F. Ali et al., Eur. Phys. J. Plus 131, 377 (2016); F. Ali et al., Nonlinear Sci. Lett. A 8, 101 (2017); N.A. Sheikh et al., Neural Comput. Appl. (2016) https://doi.org/10.1007/s00521-016-2815-5]. For each model, a detailed study of existence and uniqueness of the system solutions was presented using the fixed point theorem. We solved numerically each model using a more acculturate numerical scheme known as Upwind. Some numerical simulations are presented to underpin the effect of the suggested fractional differentiation. [ABSTRACT FROM AUTHOR]

In this paper, collapse properties of the capped-end cone tubes made from steel alloy 430 with circular holes under quasi-static axial loading have been studied experimentally and numerically. Simulations were performed using finite element LS-Dyna software and 11 types of cone with various number of holes (3, 4 and 5) and heights (20,40 and 60 mm relative to bottom base of cone) in four different thicknesses (0.2, 0.4, 0.6 and 1 mm), so, 44 different states were totally simulated and the collapse properties of them were extracted. The samples with the thickness of 0.2 mm were tested on an experimental basis in order to ensure the accuracy of the simulation results. Comparing the obtained results indicates good agreement between the experimental and numerical data. According to the obtained results, it was found that open end absorbers are more efficient compared to similar capped-end structures. Also, it was revealed that creating holes in the capped-end cone decreases the maximum force and increases crush force efficiency. In addition, it was found that creating hole farther away from the underlying base is more effective for improving the collapse properties. In the final section, the effects of thickness on the collapse properties were evaluated. The obtained results in this study can be a good guidance for investigation on the effect of discontinuity on collapse properties. [ABSTRACT FROM AUTHOR]

The ventilated disc brake of vehicles was selected as the objective of this study, which was built on 3D modeling technology. Through establishing thermo-structural coupling model, this study analyzed the transient temperature field of automobile brake under the condition of hard braking. Meanwhile, the test of hard braking was carried out on professional platform of vehicle test bench in this paper, and temperature curves of brake disc in radial and circumferential directions were obtained. By comparison, the experimental values and simulation values were basically equal. The rationality of the selected finite element analysis (FEA) was attributed, which provided a better theoretical basis for further experimental analysis. [ABSTRACT FROM AUTHOR]

Computer experiments often have inputs that are proportions/fractions of components in a mixture. In these mixture computer experiments, it can be of interest to perform robust and tolerance design on the mixture proportions since the proportions are subjected to noise variations. Traditionally, manufacturing of mixture products is controlled via interval tolerances for mixture amounts. In this paper, an optimal tolerance region for proportions, which gives optimal quality cost among all possible tolerance regions for mixture proportions with the same acceptance probability, is proposed for integrated parameter and tolerance design in mixture computer experiments. Real examples are given to demonstrate the improvements that can be achieved with the optimal tolerance region. [ABSTRACT FROM AUTHOR]

In this paper, we present a new multiscale model reduction technique for the Stokes flows in heterogeneous perforated domains. The challenge in the numerical simulations of this problem lies in the fact that the solution contains many multiscale features and requires a very fine mesh to resolve all details. In order to efficiently compute the solutions, some model reductions are necessary. To obtain a reduced model, we apply the generalized multiscale finite element approach, which is a framework allowing systematic construction of reduced models. Based on this general framework, we will first construct a local snapshot space, which contains many possible multiscale features of the solution. Using the snapshot space and a local spectral problem, we identify dominant modes in the snapshot space and use them as the multiscale basis functions. Our basis functions are constructed locally with non-overlapping supports, which enhances the sparsity of the resulting linear system. In order to enforce the mass conservation, we propose a hybridized technique, and uses a Lagrange multiplier to achieve mass conservation. We will mathematically analyze the stability and the convergence of the proposed method. In addition, we will present some numerical examples to show the performance of the scheme. We show that, with a few basis functions per coarse region, one can obtain a solution with excellent accuracy. [ABSTRACT FROM AUTHOR]

A thermo-hydro-mechanical-damage coupled model is developed in this paper for exploring the mechanism of thermo-hydro-mechanical-damage behaviors during enhanced oil recovery. The thermo-poroelastic deformation, two-phase flow and heat transport are all solved in finite element framework. Rock damage is determined by the tensile and shear failure criterions, and the contact problem for pre-existing fractures is based on the extended finite element method and augmented Lagrangian multipliers method. Then with the numerical framework, we simulated the damage evolution, fracture activation and rock properties damage caused by the thermo-poroelastic response during water injection in enhanced oil recovery. As the water injection and oil production are carried on, damage propagation and pre-existing fracture activation gradually appear around injection well. Complex fracture-damage network system and an enhanced permeability area are observed. The expansion of damage-enhanced permeability evolution to production well will greatly affect the oil recovery. And the fracture-damage network system and enhanced permeability area evolution is highly sensitive to the injection rate, injection viscosity and injection temperature difference. The simulations and discussions demonstrated that comprehensive modelling of thermo-hydro-mechanism-damage behaviors has important significance for enhanced oil recovery and other underground liquid injection engineerings. [ABSTRACT FROM AUTHOR]