Showing papers in "International Journal of Mechanics and Materials in Design in 2012"
TL;DR: In this article, the authors used element free Galerkin method (EFGM) and extended finite element method (XFEM) under mode-I and mixed mode loading conditions.
Abstract: In this paper, bi-material interfacial cracks have been simulated using element free Galerkin method (EFGM) and extended finite element method (XFEM) under mode-I and mixed mode loading conditions. Few crack interaction problems of dissimilar layered materials are also simulated using extrinsic partition of unity enriched approach. Material discontinuity has been modeled by a signed distance function whereas strong discontinuity has been modeled by two functions i.e. Heaviside and asymptotic crack tip enrichment functions. The stress intensity factors for bi-material interface cracks are numerically evaluated using the modified domain form of interaction integral. The results obtained by EFGM and XFEM for bi-material edge and center cracks are compared with those available in literature. In order to check the validity of simulations, the results have been obtained for two different ratio of Young’s modulus.
71 citations
TL;DR: In this article, a new reliability analysis method is developed for uncertain structures with mixed uncertainty, where the uncertain parameters with sufficient information are treated by random distributions, while some ones with limited information can only be given variation intervals.
Abstract: In this paper, a new reliability analysis method is developed for uncertain structures with mixed uncertainty. In our problem, the uncertain parameters with sufficient information are treated by random distributions, while some ones with limited information can only be given variation intervals. A complex nesting optimization will be involved when using the existing methods to compute such a hybrid reliability, which will lead to extremely low efficiency or instable convergence performance. In this paper, an equivalent model is firstly created for the hybrid reliability, which is a conventional reliability analysis problem with only random variables. Thus only through computing the reliability of the equivalent model the original hybrid reliability can be easily evaluated. Based on the above equivalent model, an algorithm with high efficiency and robust convergence performance is then constructed for computation of the above hybrid reliability with both random and interval variables. Two numerical examples are provided to demonstrate the effectiveness of the present method.
69 citations
TL;DR: In this article, the transient thermoelastic response of a hollow cylinder made of functionally graded material under thermal loading is studied, where the thermal and mechanical properties of the material are varied in the radial direction according to a power law variation as a function of the volume fractions of the constituents.
Abstract: The transient thermoelastic response of a thick hollow cylinder made of functionally graded material under thermal loading is studied. The generalized theory of thermoelasticity based on Green–Lindsay model is used in this paper. The thermal and mechanical properties of the functionally graded material are assumed to be varied in the radial direction according to a power law variation as a function of the volume fractions of the constituents. The heat conduction equation and the equation of motion are solved by using Galerkin finite element method. All the finite element calculations were done by using commercial finite element program FlexPDE. The transient temperature, radial displacement, and thermal stresses distribution through the radial direction of the cylinder are plotted. The material composition effect on temperature, radial displacement and thermal stresses is shown.
36 citations
TL;DR: In this paper, the kinematics and inverse dynamic analysis of a 6-SPS parallel mechanism based on the principle of Kane is presented, where the gravity and inertial forces of all links and moving platform are considered in the mathematical model of inverse dynamics.
Abstract: This paper presents the kinematics and inverse dynamic analysis of a 6-SPS parallel mechanism based on the principle of Kane. The parameters of orientation and Euler angles of the moving platform are adopted as generalized coordinate. The gravity and inertial forces of all links and moving platform are considered in the mathematical model of inverse dynamics. Both kinematics and inverse dynamics equations are derived. Driving forces–time relation is derived form inverse dynamics model. The approach is verified by simulation results, which are consistent with the planned trajectory and kinematics parameters.
34 citations
TL;DR: In this article, the authors have developed aircraft wings that imitate the amazing flight of birds using shape memory alloys as actuators in an antagonistic fashion, which achieved a high degree of flight adaptability, enhanced manoeuvrability and improved performance with a limited added weight.
Abstract: Biologically inspired engineering or Biomimicry is the practice of developing designs and technologies inspired by nature. This conscious use of examples from nature is a form of applied case-based reasoning thus treating nature itself as a database of solutions that have survived for millions of years-survival of the fittest. Inspired by nature, we have developed aircraft wings that imitate the amazing flight of birds. This bio-inspired effort, which is the result of a collaborative research program with Defence Science Organisation National Laboratories of Singapore, is concerned with the design and development of a novel wing prototype for unmanned aerial vehicles (UAVs) that morphs seamlessly without the use of complex hydraulics and/or servo motors. The novel design, selected from a number of designs, is characterised by a high degree of flight adaptability, enhanced manoeuvrability and improved performance with a limited added weight. These characteristics were attained through the use of shape memory alloys as actuators in an antagonistic fashion. Unlike compliant actuators that require continued input of thermal energy, antagonistic setup does not suffer from this difficulty. This is because they require the thermal energy to deform the wing but not to maintain its morphed shape. Structural analysis based upon safety factors specified by FAR23 standards and aerodynamic analysis using FLUENT were conducted on the novel designs to validate their suitability as viable wings for UAVs. In addition, conditioning of the shape memory actuators was conducted using a specially designed circuitry that imposes the appropriate heating and cooling cycles at set periodic times. The outcome of this study is manifest in the new designs that satisfy the missions of different UAVs.
32 citations
TL;DR: In this paper, an equivalent continuum-structural mechanics approach is used to characterize the mechanical behavior of nanostructured graphene, and the in-plane elastic deformation of armchair graphene sheets is simulated by using finite element modeling.
Abstract: In this paper, an equivalent continuum- structural mechanics approach is used to characterize the mechanical behaviour of nanostructured graphene. The in-plane elastic deformation of armchair graphene sheets is simulated by using finite element modelling. The model is based on the assumption that force interaction among carbon atoms can be modelled by load-carrying beams in a representative two-dimen- sional honeycomb lattice structure. The elastic prop- erties of beam elements are determined by equating the energies of the molecular structure and the continuum beam model subjected to small strain deformation. Then an equivalent continuum technique is adopted to estimate effective elastic moduli from which elastic constants are extracted. A comparison of elastic constants obtained from current modelling concur with results reported in literature. With the multifunctional properties of graphene sheets as manifested in a broad range of industrial applications, determination of their elastic moduli will facilitate a better design of the corresponding materials at mac- roscopic level.
27 citations
TL;DR: In this paper, an analysis of active constrained layer damping (ACLD) of sandwich plate with laminated composite faces has been carried out and the effect of the ratio between the face sheet thickness and the core thickness of the sandwich plate on the frequency response has been studied.
Abstract: This paper deals with the analysis of active constrained layer damping (ACLD) of sandwich plate with laminated composite faces. The constraining layer of the ACLD treatment is composed of the vertically/obliquely reinforced 1–3 piezoelectric composites. Several honeycomb core materials like HEREX honeycomb and honeycomb with foam fill separated by different facing materials have been studied and a three-dimensional finite element model has been developed considering first order shear deformation theory individually for each layer of the sandwich plate. The effect of the ratio between the face sheet thickness and the core thickness of the sandwich plate on the frequency response has been studied. Particular emphasis has been placed on investigating the effect of the variation of piezoelectric fiber orientation angle on the performance of the ACLD treatment.
26 citations
TL;DR: In this paper, the nonlinear equation of dynamic motion of the FGM micro-beam is derived and the equilibrium positions of the microbeam are determined and shown in the state control space.
Abstract: The present article studies the mechanical behavior of a FGM micro-beam subjected to a nonlinear electrostatic pressure. The FGM micro-beam is made of metal and ceramic and material properties vary continuously along the beam thickness according to a power-law. The nonlinear equation of dynamic motion of the FGM micro-beam is derived. By solving the equation of the static deflection, equilibrium positions of the micro-beam are determined and shown in the state control space. To study the stability of the fixed points, the trajectories of the beam motion are illustrated in the phase plane for different initial conditions. In order to find the response of the micro-beam to a step DC applied voltage, the nonlinear equation of motion is solved using a Galerkin based reduced order model. Moreover, time histories and phase portraits for different applied voltages are illustrated. The effect of different power law exponent on the stability of the micro-beam is studied.
26 citations
TL;DR: By increasing the modulus of the implant, the bone becomes susceptible to stress shielding, therefore, it is important to optimize implants for both stress shielding and micromotion.
Abstract: One of the most vital criteria for hip implant longevity is bony ingrowth that would anchor the implant to the bone. However, motion between the implant and surrounding bone (called micromotion) can hamper this, eventually leading to pain, loss of motion, damage to the bone, and eventual revision of the surgery. The objective of this research was to determine how mechanical properties; namely Young’s modulus, affects micromotion and failure in the surrounding bone. Mathematical models were used, along with finite element analysis, to determine if elastic modulus played a role in both micromotion and bone failure. However, by increasing the modulus of the implant, the bone becomes susceptible to stress shielding. Therefore, it is important to optimize implants for both stress shielding and micromotion.
24 citations
TL;DR: In this article, a study for two-unequal-collinear cracks in a 2D finite piezoelectric specimen is carried out using a new set of six crack-tip enrichment functions proposed here for piezolectric media in the X-FEM framework, where intensity factors and energy release rate are calculated using interaction integral in conjugation with the near tip behavior given by the Stroh formalism.
Abstract: A study for two-unequal-collinear cracks in a 2-D finite piezoelectric specimen is carried out using a new set of six crack-tip enrichment functions proposed here for piezoelectric media in the X-FEM framework. The intensity factors and energy release rate are calculated using interaction integral in conjugation with the near tip behavior given by the Stroh formalism. Effect of finite size of the specimen is analyzed with respect to offset distances of the cracks from the specimen boundaries. ERR variations are investigated with respect to inter- crack space, crack lengths and electrical/mechanical loadings. Hence, two-unequal-collinear cracks in an infinite domain problem is simulated, analyzed and validated using X-FEM. Further, ERR at the crack tips for the asymmetric case of two collinear equal and unequal cracks, is also computed. It is concluded through this investigation that the proposed enrichment functions could be used to handle the problems of fracture mechanics in 2-D piezoelectric media within a good accuracy.
21 citations
TL;DR: Simulation results for several difficult test functions indicate that the present method has higher efficiency and better convergence near the globally Pareto-optimal set for all test functions, and a better spread of solutions for some test functions compared to NSGAII.
Abstract: In this paper, an efficient multi-objective optimization approach based on the micro genetic algorithm is suggested to solving the multi-objective optimization problems. An external elite archive is used to store Pareto-optimal solutions found in the evolutionary process. A non-dominated sorting is employed to classify the combinational population of the evolutionary population and the external elite population into several different non-dominated levels. Once the evolutionary population converges, an exploratory operator will be performed to explore more non-dominated solutions, and a restart strategy will be subsequently adopted. Simulation results for several difficult test functions indicate that the present method has higher efficiency and better convergence near the globally Pareto-optimal set for all test functions, and a better spread of solutions for some test functions compared to NSGAII. Eventually, this approach is applied to the structural optimization of a composite laminated plate for maximum stiffness in thickness direction and minimum mass.
TL;DR: In this paper, an analysis of active constrained layer damping (ACLD) of geometrically nonlinear vibrations of sandwich plate with orthotropic laminated composite faces separated by a flexible core is presented.
Abstract: This paper deals with the analysis of active constrained layer damping (ACLD) of geometrically nonlinear vibrations of sandwich plate with orthotropic laminated composite faces separated by a flexible core. The constraining layer of the ACLD treatment is composed of the vertically/obliquely reinforced 1–3 piezoelectric composites. The Golla–Hughes–McTavish method has been implemented to model the constrained viscoelastic layer of the ACLD treatment in time domain. The first-order shear deformation theory and the Von Karman type nonlinear strain displacement relations are used for analyzing this coupled electro-elastic problem. A three dimensional finite element model of smart laminated composite sandwich plate integrated with ACLD patches has been developed to investigate the performance of these patches for controlling the geometrically nonlinear vibrations of the plates. The numerical results indicate that the ACLD patches significantly improve the damping characteristics of the sandwich plates with laminated cross-ply and angle-ply facings for suppressing their geometrically nonlinear vibrations. Particular emphasis has been placed on investigating the effect of the variation of piezoelectric fiber orientation angle on the performance of the ACLD treatment.
TL;DR: In this article, the stochastic nonlinear bending response of functionally graded materials (FGMs) plate with uncertain system properties subjected to transverse uniformly distributed load in thermal environments is investigated.
Abstract: This study deals with the stochastic nonlinear bending response of functionally graded materials (FGMs) plate with uncertain system properties subjected to transverse uniformly distributed load in thermal environments. The system properties such as material properties of each constituent’s material, volume fraction index and transverse load are taken as independent random input variables. The material properties are assumed to be temperature independent (TID) and temperature dependent (TD). The basic formulation is based on higher order shear deformation theory with von-Karman nonlinear strain kinematics using modified C0 continuity. A direct iterative based nonlinear finite element method in conjunction with first-order perturbation technique developed by last two authors for the composite plate is extended for the FGM plate to compute the second order statistics (mean and standard deviation) of the nonlinear bending response of the FGM plates. Effects of TD, TID material properties, aspect ratios, volume fraction index and boundary conditions, uniform temperature and non-uniform temperature distribution on the nonlinear bending are presented in detail through parametric studies. The present outlined approach has been validated with the results available in the literature and independent Monte Carlo simulation.
TL;DR: In this article, mixed semi-analytical and analytical solutions for a rectangular plate made of functionally graded (FG) material are presented for a two-point boundary value problem governed by a set of first-order ordinary differential equations in the plate thickness direction.
Abstract: In this article mixed semi-analytical and analytical solutions are presented for a rectangular plate made of functionally graded (FG) material. All edges of a plate are under simply supported (diaphragm) end conditions and general stress boundary conditions can be applied on both top and bottom surface of a plate during solution. A mixed semi-analytical model consists in defining a two-point boundary value problem governed by a set of first-order ordinary differential equations in the plate thickness direction. Analytical solutions based on shear-normal deformation theories are also established to show the accuracy, simplicity and effectiveness of mixed semi-analytical model. The FG material is assumed to be exponential in the thickness direction and Poisson’s ratio is assumed to be constant.
TL;DR: In this article, a group of unique flexure-based parallel micromanipulators with/without symmetrical design based on a multi-level displacement amplifier was developed and a comprehensive finite-element modeling including the strain and total deformation, modal and frequency response is undertaken.
Abstract: Conventional flexure-based parallel micromanipulators (FPM) usually suffer from a small stroke. The performance of a FPM is highly related to the stroke of each actuated limb and the associated constraints, including non-actuated joints. To conquer the drawbacks of the small workspace of conventional FPMs, a device for displacement amplification could improve motion ranges when incorporated into the design of the actuated limbs. This research is focused on the development of a group of unique FPMs with/without symmetrical design based on a multi-level displacement amplifier. Firstly, structural modeling based on a compact and modular design is introduced. Then a macro/micro analysis of the displacement amplifier is conducted. Subsequently, a comprehensive finite-element modeling including the strain and total deformation, modal and frequency response is undertaken to examine the mechanical behavior of the proposed mechanism. The developed method and technology provide a promising solution to enhance the performance of generic FPMs.
TL;DR: In this article, a single-layer cable assembly is modeled under axial tensile load and an axial twisting moment and the effect of the friction and the associated slip of the wires have been included.
Abstract: The mechanical behaviour of cables and ropes used in engineering applications, though studied for the past three decades, varies widely depending on the numerical models adopted. Though these models predict the global response reasonably well, they differ widely in modelling the local contact conditions, the frictional effects at the interfaces and predicting the loss of stiffness of the cable assemblies. Three modes of contact can exist among the wires in a stranded cable assembly, i.e. the contact among the wires in the same layer (known as hoop or lateral contact), the contact among the wires in adjoining layers (radial contact) and the combined contact of all the wires (combined lateral and radial contact). The cables are hitherto modelled on the assumption of the presence of one of the contact modes only, though in reality the contact of modes change from one to the other, depending on the loading and the nature of contraction of the wires. The behaviour of the cable can be well understood if the appropriate mode of contact prevalent at every stage of loading is adopted in the model. This paper analyses the contact modes present in a single layer cable assembly and considers its response under an axial tensile load and an axial twisting moment. Based on the initial geometry, the contact mode is determined and depending on successive loading, the contraction of all the wires in the radial and lateral directions are ascertained and the threshold limits at which the contact modes change from one to the other are established. The overall response of the cables under the cascading effects of the presence of different contact modes, is compared with the works of the other authors who have adopted one type of contact mode only during their study. This has resulted in an overall reduction in the stiffness of the cable assembly, compared to the existing models. The force and moments in the individual wires are studied and the contact forces and the resulting contact stresses are established as a function of applied loads. The effect of the friction and the associated slip of the wires have been included. Apart from consideration of the radial contraction of the wires due to the Poisson effect, as accounted by few authors, this paper considers the radial deformation due to contact forces, as a special feature. This has resulted in refined expressions for the curvatures and twist of the wire and the associated forces in the normal and binormal directions. The predictions with these inclusions are compared with the existing works and the importance of the refinements to the cable designers are highlighted.
TL;DR: In this paper, a simplified and accurate analytical cum numerical model is presented to investigate the behavior of functionally graded (FG) cylinders of finite length subjected to thermal load, which is considered as a 2D plane strain problem of thermoelasticity in (r, z) direction.
Abstract: A simplified and accurate analytical cum numerical model is presented here to investigate the behavior of functionally graded (FG) cylinders of finite length subjected to thermal load. A diaphragm supported FG cylinder under symmetric thermal load which is considered as a two dimensional (2D) plane strain problem of thermoelasticity in (r, z) direction. The boundary conditions are satisfied exactly in axial direction (z) by taking an analytical expression in terms of Fourier series expansion. Fundamental (basic) dependent variables are chosen in the radial coordinate of the cylinder. First order simultaneous ordinary differential equations are obtained as mathematical model which are integrated through an effective numerical integration technique by first transforming the boundary value problem into a set of initial value problems. For FG cylinders, the material properties have power law dependence in the radial coordinate. Effect of non homogeneity parameters and orthotropy of the materials on the stresses and displacements of FG cylinder are studied. The numerical results obtained are also first validated with existing literature for their accuracy. Stresses and displacements in axial and radial directions in cylinders having various l/ri and ro/ri ratios parameter are presented for future reference.
TL;DR: In this article, the isotropic softening effect in non-homogeneous deformation resulting from combined effect of torsion, extension and inflation of cylindrical rubber tube is discussed.
Abstract: The isotropic softening effect in non-homogeneous deformation resulting from combined effect of torsion, extension and inflation of cylindrical rubber tube is discussed. The effects of deformation induced anisotropy, permanent set and hysteresis are neglected. A general neo-Hookean parent material model is illustrated and subsequently the stress-softening effect on the same hyperelastic material is analyzed. Simple torsion of cylindrical tube with neo-Hookean material model is analyzed and the results obtained are shown in various plots. Analytical results are compared with the experimental results of Rivlin and Saunders. Universal relations are also established for incompressible, isotropic, hyperelastic material for non-homogeneous deformation with isotropic damage function in both virgin and stress-softened cases.
TL;DR: In this article, an ultrasonic-based Lamb wave propagation method for identifying and measuring the damage location in a material as a basis for structural health monitoring (SHM) is presented.
Abstract: We present an ultrasonic-based Lamb wave propagation method for identifying and measuring the damage location in a material as a basis for structural health monitoring (SHM). Lamb waves can propagate in a structure via mode conversion and reflection from the surfaces of the structure, and can lead to interference patterns as a resulting wave vector propagates along the structure. We determined the experimental and analytical effects of various parameters on the sensitivity of damage detection. A methodology is proposed for estimating and measuring the location of damage in test specimens. An experimental setup is used for generating Ao− Lamb waves by calibrating ultrasonic pulse generation for optimal values of parameters. Materials with different damage levels are tested in their undamaged and damaged conditions, and the effects of the parameters on the generated waves in test specimens are observed experimentally.
TL;DR: In this article, a mathematical correlation of the change in density of breast tissue with change in collagen content and the corresponding change in the bio-mechanical characteristics of the breast tissue was developed.
Abstract: Various clinical studies have established the influence of breast tissue density on the onset and formation of breast tumor. In this paper we develop a mathematical correlation of the change in density with the change in collagen content and the corresponding change in the bio-mechanical characteristics of the breast tissue. The developed computational model is used in understanding the mechanical response of the breast tissue using multiscale mathematical homogenization techniques. The mathematical modeling is carried out using hyperelastic material formulations for the macro-scale finite element simulations and small strain material models for the lower order homogenization.
TL;DR: In this paper, an efficient inverse analysis to detect corrosion in concrete structures including multilayered rebar using the observation accuracy as prior information was proposed, including factors such as the number, shape, and location of multiple corroded areas from a potential distribution on a concrete surface using the boundary element method and a genetic algorithm.
Abstract: The present paper proposes an efficient inverse analysis to detect corrosion in concrete structures including multilayered rebar using the observation accuracy as prior information. The proposed method can efficiently detect the corrosion profile, including factors such as the number, shape, and location of multiple corroded areas from a potential distribution on a concrete surface using the boundary element method and a genetic algorithm. The detectable are of rebar corrosion is estimated for each rebar layer. The estimation can effectively limit a solution space to detect corrosion. Numerical simulations are performed in order to demonstrate the validity and efficiency of the proposed method.
TL;DR: In this article, the authors used the tools of stochastic theory given by Random Marked Point Field to propose models for the temporal and thermal evolutions of the statistics of the random cumulative features on grains in nanomaterials under different grain growth mechanisms.
Abstract: Each nanomaterial grain has some number of features, such as faces or triple junctions, on it. The sum of all the features on all grains in nanomaterials, herein called cumulative feature, can be obtained. During grain growth both the number of features per grain and the cumulative features on all grain in nanomaterials evolve randomly with time. Different mechanisms are responsible for grain growth in nanomaterials. This includes Grain Boundary Migration, Grain Rotation-Coalescence, T1 and T2 events. Evolution models for number of features per grain are known already, and not model for evolution of cumulative features. The present paper uses the tools of stochastic theory given by Random Marked Point Field to propose models for the temporal and thermal evolutions of the statistics of the random cumulative features on grains in nanomaterials under different grain growth mechanisms. The resulting differential equations are solved simultaneously using data from nanocrystalline aluminium. It is observed that the mean number of features per grain increases and density of grains in nanomaterials decreases during grain growth. It is revealed that grain growth results in decrease in moments of the cumulative features. It is shown that an increase in annealing temperature results in relatively higher increase in mean number of features per grain, further decrease in grain density, relative increase in mean cumulative features on grain and variable dispersions of cumulative features. It is also observed that the evolution of the statistics of the cumulative features depends on the nature of Galzier-diffusion term, the form of the critical number of faces per grain and the type of grain growth mechanisms. For some choices of the Glazier diffusion term, the dispersion of the cumulative feature evolves in a manner similar to that of the nanomaterials mechanical properties given by the Hall–Petch to Reversed-Hall–Petch Relationship. The variables results are explained to be consequences of different grain growth mechanisms, temperature and the diffusion termed. Thus, it can be concluded that processing route, processing conditions and the nature of evolution of the constituents of nanomaterials are simultaneously vital when designing or characterising nanomaterials.
TL;DR: In this article, a hybrid finite element method based on a numerical procedure is proposed to compute singular field near V-shaped notch corners in an anisotropic material containing polygonal holes.
Abstract: A novel hybrid finite element method based on a numerical procedure is proposed to compute singular field near V-shaped notch corners in an anisotropic material containing polygonal holes. The finite element method is established by the following three steps: (1) an ad hoc one-dimensional finite element formulation is employed to determined numerical eigensolutions of the singular field near an V-shaped notch corner; (2) a super corner tip element is constructed to determine the strength of the singular field, in which the independent assumed stress fields are extracted from the eigensolutions; (3) a novel hybrid finite element equation is obtained by coupling the super corner tip element with the conventional hybrid stress elements. In numerical examples, generalized stress intensity factors for interactions between two polygonal holes with various geometry, space position and material property are mainly discussed. All the numerical results show that present method yields satisfactory singular stress field solutions with fewer elements. Compared with the conventional finite element methods and integral equation methods, the present method is more suitable for dealing with micromechanics of anisotropic materials.
TL;DR: In this article, a novel approach for explicit analysis of transversely anisotropic 2D sheet metal forming using 6-component Barlat yield function is elaborated in detail in detail.
Abstract: In most FEM codes, the isotropic-elastic and transversely anisotropic-elastoplastic model using Hill’s yield function has been widely adopted in 3D shell elements (modified to meet the plane stress condition) and 3D solid elements However, when the 4-node quadrilateral plane strain or axisymmetric element is used for 2D sheet metal forming simulation, the above transversely anisotropic Hill model is not available in some FEM code like Ls-Dyna A novel approach for explicit analysis of transversely anisotropic 2D sheet metal forming using 6-component Barlat yield function is elaborated in detail in this paper, the related formula between the material anisotropic coefficients in Barlat yield function and the Lankford parameters are derived directly Numerical 2D results obtained from the novel approach fit well with the 3D solution
TL;DR: In this paper, the effect of various constrained layers [electro rheological fluid (ERF), magneto rheologically fluid (MRF), and viscoelastic layer (VEL)] over natural frequency and damping loss factor with five different fiber orientations (0, 30, 45, 60 and 90°) for a boron/epoxy (B/E), carbon/encoxy (C/E) and kevlar/eboxy (K/E)) shaft disc system was investigated.
Abstract: This paper focuses on investigating the effect of various constrained layers [electro rheological fluid (ERF), magneto rheological fluid (MRF) and viscoelastic layer (VEL)] over natural frequency and damping loss factor with five different fiber orientations (0, 30, 45, 60 and 90°) for a boron/epoxy (B/E), carbon/epoxy (C/E) and kevlar/epoxy (K/E) shaft disc system. Finite element technique is employed to evaluate the natural frequency and damping loss factor for various combinations. Also the vibrational characteristics of composite sandwich shaft disc system are compared for better damping capabilities. From the study VEL core shows excellent frequency and loss factor performances and the 90° fiber oriented composites is dominant in vibration damping. Also, it is evident that the damping performance of ERF and MRF core depends on applied electric and magnetic field.
TL;DR: In this article, the magnetic flux density in longitudinal x-direction is not affected by the electric displacement current for all the boundary conditions of the plate excited with time-harmonic mechanical excitation.
Abstract: Dynamic response of moderately thick magneto–electro-elastic plate using magnetic vector potential in finite element formulation is presented in this paper. Dynamic loading generate time varying electric and magnetic fields in magneto–electro-elastic continuum. Displacement current is associated with the generation of magnetic field due to time varying electric field. The non-conservative electric field is represented using electric scalar potential and magnetic vector potentials. Studies are carried out for CCCC, CCFC, CFFC and FCFC boundary conditions of the plate excited with time-harmonic mechanical excitation, the frequency range being chosen based on the critical frequency of the plate analyzed. The magnetic flux density in longitudinal x-direction is not affected by the electric displacement current for all the boundary conditions. The longitudinal y-direction and transverse direction components of magnetic flux density are showing variations for FCFC boundary condition when displacement current is accounted. The effect of displacement current is significant when two opposite edges of the plate are clamped.
TL;DR: In this article, an anthropomorphic test device has been made available and experimental tests have been worked out to obtain reliable data about the interaction of passengers, seat and seatbelt of a specific type.
Abstract: The research activities described in the present paper deal with the causes and the typologies of secondary impact injuries suffered by passengers of a railway vehicle during an assigned crash event; those considerations are to be a starting point to understand the degree in which those injuries can be absorbed and to propose useful ways to reduce or eliminate them. In particular, the seatbelt installation has been investigated as a suitable system to restrain the passengers. An anthropomorphic test device has been made available and experimental tests have been worked out to obtain reliable data about the interaction of passengers, seat and seatbelt of a specific type. By using the experimental data a multibody (MB) numerical model of the sled test has been examined, calibrated and validated and then the performances of restraining configurations, which could not be physically tested, have been simulated. Relevant overloads on the seat frame appear when seatbelts are installed, because of the inertial loads which are transferred from the passenger. Different structural analyses of the seat, by means of finite element simulations, have been undertaken to determine if a stiffening of the seat is required to sustain those overloads. The results showed in this paper refer to the case of a frontal impact and to real geometry, structural characteristics and lay-out of the seat, obtained by considering a specific test case. In the context of the presented study MADYMO® code has been adopted to perform the preliminary MB analyses which are required to calibrate and to evaluate the relevant parameters of dummy-seat contact surfaces and of seat-belt stiffness, while LS DYNA® code hasbeen used for the structural dynamic FE analyses.
TL;DR: In this article, the contact stresses between a tilted, shallow wedge and half-plane, under frictional sliding condition, are investigated analytically and the closed-form of contact law itself, together with the contact tractions and the size of the contact segments are explicitly found.
Abstract: The contact stresses between a tilted, shallow wedge and half-plane, under frictional sliding condition, are investigated analytically The closed-form of contact law itself, together with the contact tractions and the size of the contact segments are explicitly found The effects of tilt moment, material property, geometry variation and the applied loads on the contact pressure distributions are investigated By making use of the Muskhelishvili’s potential function and the Plemelj formulae, the analytically derived contact pressure is the same as that obtained based on the singular integral equations The result is verified by comparing with that in the literature The in-plane stress field is evaluated from the standpoint of fatigue It is shown that the Muskhelishvili’s potential function and the Plemelj formulae can be also used to solve this type of contact problem This study is helpful for understanding the mechanism of frictional sliding contact problem with singular point and designing better high precision instruments and devices
TL;DR: A Rayleigh-Ritz structural model, which uses Zernike polynomials directly to describe the displacements, is proposed in this paper, which produces a numerically inexpensive model that predicts deformations with remarkable accuracy.
Abstract: Piezoelectric bimorph- or unimorph-type deformable mirrors are commonly used in adaptive optics to correct for time-dependent phase aberrations. In the optics community, the surface deformations that deformable mirrors are required to achieve, are routinely and conveniently described using Zernike polynomials. A Rayleigh-Ritz structural model, which uses Zernike polynomials directly to describe the displacements, is proposed in this paper. The proposed formulation produces a numerically inexpensive model that predicts deformations with remarkable accuracy. Since design variables, such as electrode layout, material properties, and mirror dimensions, are represented analytically, the model is well suited to optimization or sensitivity analysis applications. Furthermore, since the numerical implementation is very efficient, it could be employed in closed-loop control applications. Results achieved with the proposed model compare well with results from a traditional finite element analysis as well as experimental results of a representative design.
TL;DR: In this article, a meshless element free Galerkin (EFG) method is used to simulate the multi-scale constitutive relation of concrete blocks and the scale separation is based on decomposition of the mesh free shape function into α and β scales, similar decomposition is also adopted for the constitutive equations.
Abstract: In this paper, a new multi-scale numerical model is presented using meshless element free Galerkin (EFG) method to simulate the multi-scale constitutive relation of concrete. The scale separation is based on the decomposition of the mesh free shape function into α and β scales, similar decomposition is also adopted for the constitutive equations. And the constitutive relations in different scales for concrete are established. The multi-scale EFG model is utilized for discretization of components of concrete block, which are aggregate, cement and transition region. The strengths of these components are adopted according to Weibull distribution. Consequently, the multi-scale EFG model is applied to describe the evolutionary processes of damage, the propagation of cracks and the characteristics of hysteresis of concrete. The plain static analysis of concrete block is performed by using this model and the calculated result is discussed.