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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]

Single rigid body models are often used for fast simulation of tracked vehicle dynamics on soft soils. Modeling of soil-track interaction forces is the key modeling aspect here. Accuracy of the soil-track interaction model depends on calculation of soil deformation in track contact patch and modeling of soil resistive response to this deformation. An algorithmic method to calculate soft soil deformation at points in track contact patch, during spatial motion simulation using single body models of tracked vehicles, is discussed here. Improved calculations of shear displacement distribution in the track contact patch compared to existing methods, and realistically modeling plastically deformable nature of soil in the sinkage direction in single body modeling of tracked vehicle, are the novel contributions of this paper. Results of spatial motion simulation from a single body model using the proposed method and from a higher degree of freedom multibody model are compared for motion over flat and uneven terrains. Single body modeling of tracked vehicle using the proposed method affords quicker results with sufficient accuracy when compared to those obtained from the multibody model. [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]

In this paper, the recent development of extended consecutive-interpolation 4-node quadrilateral element (XCQ4), which goes beyond certain limitations of conventional methods, is further employed to study dynamic and static thermoelastic fracture problems. In particular, static stress intensity factors (SIFs) and transient dynamic responses of two-dimensional (2-D) stationary cracks in elastic solids under thermal and thermal-mechanical loadings are investigated. In addition, simulation of quasi-static crack propagation under thermal-mechanical loading condition is also performed. To precisely capture the singularity and discontinuity of temperature, heat flux, and displacements due to the presence of crack, the unknown field variables of mechanical displacements and temperature are approximated in terms of the XCQ4 framework by different enrichment strategies, which include either the use of the conventional branch functions or the new ramp function associated with Heaviside function. Only adiabatic condition is considered on the crack surfaces. For quasi-static crack growth analysis, the maximum hoop stress criterion, which is also valid for thermo-elastic fracture mechanics, is adopted. For transient crack analyses, the inertial effect is taken into account for the interaction integral in the consideration of DSIFs. Through eight numerical examples for thermoelastic fracture problems, the validity of the XCQ4 is confirmed by a comparison of the obtained results to those derived from different approaches in previous studies. In addition, the accuracy, performance, and superior advantages of the XCQ4 over standard extended finite element approach are also demonstrated. [ABSTRACT FROM AUTHOR]

Abstract: Previous studies of pounding responses of bridge structures to seismic loadings are usually based on the point to point pounding assumption by using the simplified lumped mass model or beam–column element model. It has been found these simplified models can be used to calculate bridge pounding response with consideration of only the longitudinal excitation. In a real bridge structure under seismic loading, pounding could take place along the entire or part of surfaces of the adjacent segments. Moreover, torsional response of the adjacent decks owing to the asymmetric deck or induced by spatially varying transverse ground motions at multiple bridge supports may result in eccentric poundings between adjacent bridge decks. A detailed 3D finite element model is necessary to consider the surface to surface and torsional response induced eccentric poundings and the corresponding damage. This paper performs numerical simulations of pounding damage between bridge girders and between bridge girder and the corresponding abutment of a two-span simply-supported bridge to spatially varying ground motions based on a detailed 3D finite element model by using the explicit finite element code LS-DYNA. The dislocation and unseating potentials of the bridge are also modelled. The bridge components including the bridge girders, abutments, pier, bearings, longitudinal reinforcement bars and stirrups are included in the model. The non-linear material behaviour including the strain rate effects of concrete and steel rebar are considered. The spatially varying ground motions are stochastically simulated. The damage mechanism of the bridge under spatially varying seismic loadings is examined. Numerical results show that the method adopted in the present paper can realistically capture the seismic induced damage of bridge structures. [Copyright &y& Elsevier]

In this paper, the gas tungsten-arc welding (GTAW) process of a thin cylinder made of Al6061-T6 alloy was simulated using 3-D finite element model in the ABAQUS code and the induced distribution of residual stress was obtained. Temperature dependent thermo-mechanical properties were considered for the aluminum alloy and for simulating the heat source of tungsten arc welding; Goldak's double ellipsoid model was employed. The numerical simulation method employed for the GTAW process of investigated aluminum material was validated experimentally using the hole drilling method as well. High residual stresses were found around the weld line and HAZ area which can increase the risk of crack initiation and propagation in this region of welded aluminum cylinder. Hence in the second part of this research, a longitudinal semi-elliptical crack was considered in the wall of aluminum cylinder subjected to combined internal pressure and torsional loads and its mixed mode I/II fracture parameters (i.e. K I , K II and T ) were determined numerically along the crack front and for different crack geometries. Finally the influence of obtained residual stress field on the computed fracture parameters was reanalyzed using the coupled residual stress/mechanical loading applied to the cylinder. The residual stress field had no effect on the mode II fracture component but the most influence of this factor was observed for mode I stress intensity factor ( K I ) and the deepest point of 3D elliptical crack. [ABSTRACT FROM AUTHOR]

This paper deals with the investigation of a numerical simulation method to appropriately represent relevant failure mechanisms of carbon fiber reinforced plastic (CFRP) components subjected to dynamic crash loads. The presented work considers the stacked shell approach, using a stack of continuum shell elements and cohesive elements, and focuses on the calibration of simulation input parameters. Furthermore, modeling aspects are discussed to reduce mesh-dependencies for the simulation of progressive crushing. The validation of the numerical approach is performed on the basis of an extensive test program of CFRP crush absorbers on the structural level. The capability of current state-of-the-art technologies for the simulation of progressive crushing is identified. The simulations capture general failure effects and force-displacement characteristics for different designs and loading conditions. Drawbacks are identified in the definition of cohesive input parameters to obtain numerical stability for complex loading conditions. The numerical simulations were performed using the commercial finite element software Abaqus/Explicit. [ABSTRACT FROM AUTHOR]

This paper presents a detailed investigation about the geometric non-linear stiffness behavior of corrugated laminates in six different load cases. The considered tensile, bending, and shear load cases allow the modeling with a unit-cell approach assuming a generalized plane strain state. The torsional load case is more complex. There the mechanical response depends on the number of unit-cells and the width of the samples in case of geometric non-linearities. We first identify the load cases that show a non-linear stiffness response under large deformation. Then the non-linear behavior is analyzed in detail using numerical simulation and we aim for mechanical explanations to describe the non-linear behavior. The FE simulations of the torsional load case are validated using experiments with 3D printed samples. [ABSTRACT FROM AUTHOR]

Abstract: One of the key components in a mining dump truck is the drive axle housing. Failure of this component during normal use is unacceptable. Recently, early fatigue fracture became a problem during the normal working process of these machines. However, it is difficult to calculate exactly the fatigue failure life of the drive axle housing based on bench testing or pure computer simulation due to the differences between practical road conditions (such as slope and roughness) and simplified boundary conditions. To increase the reliability of analysis results a new analysis method based on dynamic strain measurement from practical mine road surface conditions combined with finite element analysis is proposed in this paper. The dynamic strain and stress on the drive axle housing is obtained by strain measurements while the truck travels over normal mine road surface conditions. The dynamic stress was analyzed using the rain-flow counting method, which can determine the amplitudes and mean values of counted cycles. The influence of the stress mean value was taken into consideration with the Morrow’s model. According to the assumption of a linear Palmgren–Miner hypothesis of damage accumulation and using typical fatigue characteristics of the material, the fatigue failure life was calculated. Analysis of the measurements showed that the dynamic stress experienced by the axle housing was far greater than expected. In order to find the factors affecting the dynamic stress of the drive axle housing, the slope of the road surface, any uneven loading and eccentricities were analyzed using the finite element method. This paper shows that the new analysis methods described are valuable tools for analyzing the reasons behind the failure of these truck axle housings. [Copyright &y& Elsevier]

Ground overload is one of the most important factors that threaten the safe operations of oil and gas pipelines. The mechanical behaviour of a buried pipeline under ground overload was investigated using the finite element method in this paper. The effects of the overload parameters, pipeline parameters and surrounding soil parameters on the stress–strain response of the buried pipeline were discussed. The results show that the maximum von Mises stress appears on the top of the buried pipeline under the loading area when the ground load is small, and the stress distribution is oval. As the ground load increases, the maximum stress increases, and the high stress area extends. The von Mises stress, plastic strain, plastic area size, settlement and ovality of the buried pipeline increase as the ground load and loading area increase. The buckling phenomenon of the no-pressure buried pipeline is more serious than the pressure pipeline. As the internal pressure increases, the high stress area and the maximum plastic strain of the buried pipeline first decrease and then increase, the settlement of the buried pipeline increases, and the ovality decreases. The von Mises stress, maximum plastic strain, settlement and ovality of the buried pipeline decrease with increasing buried depth, the surrounding soil's elasticity modulus, Poisson's ratio and cohesion. The maximum von Mises stress, high stress area, the maximum plastic strain, plastic area and ovality increase as the diameter–thickness ratio increases. The critical diameter–thickness ratio is 60, and the settlement of the buried pipeline first increases and then decreases as the diameter–thickness ratio increases. Finally, a protective device of the buried pipeline is designed for preventing ground overload. It can be repaired in a timely manner without stopping the transmission of oil and gas and widely used in different locations because of its simple structure and convenient installation. [ABSTRACT FROM AUTHOR]

With its advantages of lost circulation prevention, drilling speed improvement and reservoir protection, gas drilling technology has been widely applied in Sichuan and Xinjiang oilfields in China . However, drill collar failures have often occurred under high weight on bit (WOB) during gas drilling. These incidents have not only caused serious economic loss but hampered the development and application of gas drilling. Finite element analysis is used to determine the drill collar thread stress distribution and, using simulation of drill string dynamics, multi-axial fatigue life theory is used to calculate the life of a standard API drill collar connection. The computed results reveal the early drill collar fatigue failures in gas drilling. Then, the multi-axial fatigue life of drill collar with double shoulder thread is analyzed under the same loads. Analysis shows that the fatigue life of a double shoulder thread is some thirty times that of the API thread. So drill collar with double shoulder thread could be an efficient way to solve the fatigue failure problems of drill collar in gas drilling. The work presented in this paper can provide theoretical foundations for safe and efficient drilling with gas. [ABSTRACT FROM AUTHOR]

In this paper, the buckling response of glass panels linearly supported along the top and bottom edges, under the action of in-plane shear loads, is investigated by means of analytical and Finite-Element (FE) methods. The typical buckling behaviour is first assessed in the hypothesis of fully neglecting the possible deformability contribution of adhesive linear supports, while successively the effects of linear, flexible sealant joints on the overall structural response of the same panels are also properly taken into account and highlighted. Based on extended parametric FE linear buckling and nonlinear incremental simulations, the influence of initial geometrical imperfections with various shapes and amplitudes, adhesive stiffnesses and glass types is investigated, both for monolithic and laminated glass panels. In the latter case, the accuracy of an equivalent thickness approach derived from early contributions is also demonstrated. Analytical approximating curves are proposed for the fitting of numerically derived buckling coefficients, so that they could represent a practical tool in the calculation of the expected Euler’s critical load. A normalized buckling curve for ideally simply supported glass panels under in-plane shear loads is finally recalled from past research projects and proposed as a rational design method for the examined loading and boundary condition. [ABSTRACT FROM AUTHOR]

This paper is to develop a simple micromechanics-based model taking account of progressive damaging for carbon black (CB) filled rubbers. The present model constitutes of the instantaneous Young's modulus and Poisson's ratio characterizing rubber-like material, a double-inclusion (DI) configuration considering the absorption of rubber chains onto CB particles, and the incremental Mori-Tanaka formula to compute the effective stress–strain relations. The progressive damage in filled rubbers is described by the DI cracking, which is represented by the remaining load–carrying capacity. The present predictions are capable of embodying the well-known S -shaped response of filled rubbers, and also verified by the comparison with the experimental and analytical results. Moreover, strain localization effect is clearly demonstrated by finite element method (FEM) simulations, and reaches a decisive interpretation to the complicated synergic micro-mechanisms between hard fillers and soft phase in such flexible composites. [ABSTRACT FROM AUTHOR]

The present paper aims at investigating the homogenisation of cellular materials in view of the modelling of large but finite cellular structures. Indeed, computation costs associated with the complete modelling of such structures can be rapidly prohibitive if industrial applications are considered. The use of a homogeneous equivalent medium (HEM) for these cellular materials can be an efficient approach to address this issue, but it requires the calibration of relevant homogeneous equivalent laws (HELs). Here, the considered cellular materials are tube stackings. Various uni-axial and multi-axial loading cases have been simulated, through the finite element method, on representative volume elements of such periodic stackings. From these simulations, anisotropic compressible elasto-plastic constitutive equations have been identified for the HEL. The anisotropy of the yield surfaces is discussed depending on the pattern of the tube stacking (e.g. square or hexagonal). A validation of the identified laws is proposed by simulating uni-axial compression and simple shear tests on sandwich structures made of tube stackings for their cores. A systematic comparison, between the results obtained from the fully meshed structures and those obtained from the structures whose core has been replaced with its HEM, allows us to address the limitations of the HEM-based approach and the boundary layer effects observed on finite structures. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a discussion on the behaviour of non-confined and confined masonry walls with different types of horizontal reinforcement when subjected to in-plane horizontal loads, using advanced numerical simulations. An isotropic continuum nonlinear finite element macromodel, based on smeared crack total strain–stress models with scarce parameter input is used to represent previously tested masonry walls. The masonry units, the mortar and the bonding interfaces between the units and mortar have been lumped in continuum elements. The input data is based on experimental results or inverse fitting, with a clearly identification and justification. The results are presented and compared against experimental data, with an emphasis on force–displacement curves and failure modes. [Copyright &y& Elsevier]

Abstract: A new type of flexure hinge, called power-function-shaped flexure hinge, is presented in this paper. Based on the unit-load method, the closed-form compliance equations of the flexure hinge are derived, and the motion accuracy is investigated. These equations are verified through finite element analysis, which shows that the maximum error is less than 15%. Based on the compliance equations, numerical simulations are conducted to discuss the performance of the flexure hinge. The results indicate that, the stiffness of the power-function-shaped flexure hinge decreases as r increases, increases as β increases, and increases as t increases; the displacement along axis y is the dominant parasitic motion; and based on the same l, h and b, the power-function-shaped flexure hinge can rotate more accurately than circular flexure hinge with the same β and V-shaped flexure hinge with the same β and r. The equations obtained can be utilized to design the power-function-shaped flexure hinges, and can achieve higher motion accuracy than the commonly used circular flexure hinge and V-shaped flexure hinge. [Copyright &y& Elsevier]

Abstract: A new glass fibre reinforced polymer (GFRP) sandwich panel has been developed for flooring system. The new panel is made of modified phenolic core and E-CR glass skins. This paper presents the results of the experimental behaviour and the non-linear finite element analysis (FEA) of the GFRP sandwich panel. The experimental works investigate the behaviour of the GFRP sandwich panel, skin–core interaction, and core behaviour. A non-linear finite element model was developed to simulate the behaviour of the skin–core interaction, and the model was verified by comparing the results with those obtained from testing. The non-linear FE model was applied to a single span GFRP sandwich floor panel under point load test. The GFRP sandwich floor panel demonstrated a linear behaviour under point load. The results of the numerical simulations show a good agreement with the experimental results. [Copyright &y& Elsevier]

Abstract: The paper presents asymptotic modeling of reciprocating sliding wear with increasing contact zone under a prescribed constant normal load. The wear contact problem is formulated within the framework of the two-dimensional theory of elasticity in conjunction with Archard’s law of wear. It is shown that the asymptotic modeling approach, which maintains the experimentally-related feature of contact pressure in the steady-state regime, leads to simple but sufficiently accurate analytical approximations. In particular, simple closed-form approximations are derived for the planimetric wear, half-width of contact zone, and wear scar profiles. The obtained analytical results have been compared with finite-element simulation results published in the literature, and a good correlation was revealed between the analytically predicted and numerically simulated worn profiles in the case of fretting when there is no stick zone between the contacting surfaces. [Copyright &y& Elsevier]

Abstract: This paper deals with the investigation of the load carrying capacity of transmission steel pipelines in case of occurrence of corrosion defects on the outer surface of the pipe wall. Different including dimensions of the corrosion metal loss (length, width, depth) influence the burst pressure of the corroded pipelines to a different extent. The effects of the width to length ratios of the corrosion defects were investigated with numerical simulations included in this article. The calculations were performed with FEA (Finite Element Analysis) method and the results were verified based on measurement data. [Copyright &y& Elsevier]

Abstract: This paper presents the second part of an experimental investigation carried out on a construction system based on completed in-situ sandwich panels with non-shear connectors, concerning the study of floor sandwich panels. Four-point flexural tests were carried out on several full-scale panel specimens with different slenderness ratios in order to study the behaviour of panels under vertical loads. Additionally, wall–floor nodes with different connection details were tested to analyze the effective degree of the rotational restraint of different realistic nodes. Furthermore, a loading test on the floor of a full scale 3D mock-up entirely built with sandwich panels was carried out to investigate the service and ultimate behaviour of a real floor. The most significant load-displacement diagrams for increasing load are illustrated and the failure modalities are discussed. The semi-composite behaviour of the panels, guaranteed by the internal layer of polystyrene and the reinforced concrete beams at the panel ends, is highlighted. The effects of the wall–floor connection and the bi-dimensional behaviour of the floor are also evaluated. Finally, some numerical simulations are performed with non-linear finite element models and some useful design indications are given. [Copyright &y& Elsevier]

Abstract: The paper presents problems related to the assessment of historical objects, especially brick arch structures, in view of potential improvement of their strength using various technologies. We have presented the methodology and computer simulations used for assessment of present strain and load bearing capacity of brick arches along with a variety of reinforcement techniques. We also present arch deformation FEM analysis along with results of assessment of actual objects. [Copyright &y& Elsevier]

Abstract: In this paper, as a typical example, a valve in a coal-fired thermal power plant with a semi-elliptic crack in its body is presented to illustrate an effective method to predict the surface crack shape under thermo-mechanical loading. The 3D finite element analysis (FEA) is employed to estimate the stress intensity factor (SIF) based on the 3D constraint effect at a set of points along the crack front, and then the evolution of the crack shape is studied according to the SIF. Some numerical techniques were well applied to simulate the real charge condition during the valve operation. It has been assumed that each point in the front of the crack advances in direction perpendicular to such a front, according to the Paris–Erdogan Law. Numerical results of the present method agree fairly well with detective results. [Copyright &y& Elsevier]

Abstract: In this paper a new method is presented to determine the crack-tip opening displacement (CTOD) for the center cracked plate with uniaxial uniform tension load. The maximum crack opening displacement (MCOD) is adopted to estimate CTOD. Based on the series of calculation results by elastic–plastic finite element simulation, an explicit function expression for the CTOD versus MCOD is determined, which enables to consider the influence effects of crack geometries, plate sizes, applied loads, plane state and material properties. Hence, the presented method of CTOD determined by MCOD is suitable to any center crack finite plate of any material under uniaxial tension. [Copyright &y& Elsevier]

Abstract: The load response of a rock-socketed steel H-pile can be strongly influenced by the nonlinear interfacial behavior between the grout and the steel H-pile, and between the pile and the rock mass. This paper focuses on the load-transfer mechanism of the former interface through experimental push-out tests and numerical simulation of the tests. The study is divided into two parts. In the first part, a series of push-out tests have been carried out on four types of specimens (with studs+confinement (Case I); no stud+confinement (Case II); no stud+no confinement (Case III); and studs+no confinement (Case IV)). The second part is a numerical study based on three-dimensional finite element technique, which takes into account possible damage and cracking in grout, as well as bond-slip along the interface. It is shown that the numerical predictions of the four cases compare favorably with the corresponding test results, including the load–displacement response and the development of cracks. Furthermore, parametric study has been carried out to investigate the influence of various factors, including the studs, the casing confinement, the grout fracture energy, and the dilation property of steel-grout interface. Lastly, some implications, based on the test and numerical results, on the design of socketed steel H-piles are discussed. [Copyright &y& Elsevier]

Abstract: This paper presents the numerical simulations of thin-walled square hollow steel beams subjected to a uniform transverse blast load. The objectives of the numerical simulations were to gain an insight into the temporal distribution of the global and local deformation and the adiabatic temperature rise in the beams as a result of impulsive loading. Additionally, the finite element predictions using Ls-Dyna are compared to the experimentally observed global and local deformations. The full lengths of the beams were modelled using three material models based on the linear piecewise plasticity material model which incorporated strain hardening, with and without strain-rate hardening and with strain-rate hardening and temperature softening. The blast wave was simulated as a rectangular pressure pulse distributed over the top surface of the beams. Ls-Dyna and the material model used were found to predict the global and local deformation of the beams reasonably well. Incorporating strain-rate hardening was found to be important to be able to predict the global and local deformation of the beams. Thermal softening was found to play a small but not negligible role. [Copyright &y& Elsevier]

Abstract: This paper deals with the shape generation of structural shells within the field of Conceptual Design. Both physical models and computational simulations are presented and discussed. The design is based on the biological principle of homeostasis which states the following: When an external agent attacks the structure, the latter defends itself “intelligently” to recover its bearing capacity. Here, heat is the external agent used to cause the model material degradation. Thus the model adopts a more appropriate structural shape in order to continue to resist loads. The physical experiment is carried out by introducing a Polymethyl Methacrylate (PMMA) plate in an oven with defined boundary conditions and loads. The virtual simulation is performed using a finite element software. A thermal elasto-plastic material model is included to represent the PMMA behavior. A comparison between the shapes found with both approaches is presented. Notwithstanding the diversity of the methods and uncertainties in the material characterization the match is more than acceptable. The numerical simulation may constitute a low cost complement to shell form-finding using the Homeostatic Model Technique. Additionally, the obtained shape is employed as the geometry of a structural shell and both, experimental and finite element stress analyses are performed, yielding a quasi-membranal behavior. [Copyright &y& Elsevier]

Abstract: This paper treats the dynamic response and energy absorption of aluminum foam-filled conical tubes under axial impact loading using non-linear finite element techniques. The influence of geometrical, material and loading parameters on the impact response is investigated using validated numerical models. Results are quantified in terms of important impact response parameters and indicate that the foam filler stabilizes the crushing process and thus improves the energy absorption capacity. The superior performance of foam-filled conical tubes as impact energy absorbers is evident from the results. The research information generated will be useful in developing guidance towards the design of these devices in impact applications. [Copyright &y& Elsevier]