Orthotropic Material Properties Research Articles

Finite Element Thrust Line Analysis (FETLA) of Axisymmetric Masonry Dome with Meridian Cracks

Many masonry domes in their lower portion are subjected to hoop tensile forces which mostly lead to vertical cracks appearing along the dome's meridian planes. A close inspection of any such dome reveals these hoop tension cracks. The dome stands as a series of arches with common key stone, with cracks as a matter of non-structural consequences. Different strategies have been considered historically to arrest these cracks. The provision of tension ring mechanism adds to the stability of these domes, and hence many masonry domes are retrofitted with the provision of the tension rings using steel and FRP rings. The challenge in such retrofitting will remain to analyze its effect on stability of these masonry domes, more specifically in absence of reliable mechanical properties of such masonry domes. This paper presents a simplified analysis procedure combining thrust line analysis with the finite element analysis called here as Finite Element Thrust Line Analysis (FETLA). The development of a new element suitable for masonry dome analysis to include the effect of hoop tension cracks is demonstrated. The orthotropic material properties are utilized for penalty approach to allow redistribution of the forces from meridian direction to the hooping rings, with thrust line approaching the extrados or intrados of the dome. The analysis results of FETLA are validated with the previously available results. The analysis method proposed in this paper gives the rational estimates for the failure load without utilizing inelastic properties of the material to model the hoop tension cracks and its propagation.

Identification of the flexural stiffness parameters of an orthotropic plate from the local dynamic equilibrium without a priori knowledge of the principal directions

This paper proposes an inverse method to characterize orthotropic material properties from vibratory measurements on plate-like structures. The method is an adaptation of the Force Analysis Technique (FAT), which was originally developed to identify the external force distribution acting on a structure using its local discretized equation of motion. This method was recently adapted to the identification of elastic and damping properties of isotropic plates. In the present approach, the equation of motion of an orthotropic plate with respect to an arbitrary set of orthogonal axes is considered. The angle between the axes of the measurement mesh and the principal directions of orthotropy therefore explicitly appears in the equation and constitutes an unknown. A procedure to identify this angle together with the flexural stiffness parameters is proposed, as well as an automatic regularization procedure to overcome the high sensitivity of the inverse problem to measurement noise. The method is illustrated using simulated data. Experimental results shown on various structures demonstrate the ability of the method to simultaneously identify the principal orthotropy directions and the flexural stiffness parameters.

Numerical Determination of Orthotropic Material Properties of Textile Composite Layers and their Validation by Measurement

Numerical Determination of Orthotropic Material Properties of Textile Composite Layers and their Validation by Measurement

Vibrating nonlocal multi-nanoplate system under inplane magnetic field

The recent development in nanotechnology resulted in growing of various nanoplate like structures. High attention was devoted to graphene sheet nanostructure, which enforced the scientist to start developing various theoretical models to investigate its physical properties. Magnetic field effects on nanoplates, especially graphene sheets, have also attracted a considerable attention of the scientific community. Here, by using the nonlocal theory, we examine the influence of in-plane magnetic field on the viscoelastic orthotropic multi-nanoplate system (VOMNPS) embedded in a viscoelastic medium. We derive the system of m partial differential equations describing the free transverse vibration of VOMNPS under the uniaxial in-plane magnetic field using the Eringen's nonlocal elasticity and Kirchhoff's plate theory considering the viscoelastic and orthotropic material properties of nanoplates. Closed form solutions for complex natural frequencies are derived by applying the Navier's and trigonometric method for the case of simply supported nanoplates. The results obtained with analytical method are validated with the results obtained by using the numerical method. In addition, numerical examples are given to show the effects of nonlocal parameter, internal damping, damping and stiffness of viscoelastic medium, rotary inertia and uniaxial in-plane magnetic force on the real and the imaginary parts of complex natural frequencies of VOMNPS. This study can be useful as a starting point for the research and design of nanoelectromechanical devices based on graphene sheets.

Simulation of the Carton Erection for the Rubber Glove Packing Machine Using Finite Element Method

The rubber glove packing machine had been designed an important function which worked with folding carton. Each folded paper carton would be pulled to be erected by vacuum cups. Some carton could not completely form because of an unsuitable design of the erector. Cartons were collapsed or buckling while pulled by vacuum cups that cause to sudden stop the packing process and affect to number and cost of rubber glove production. This research aimed to use simulation method to erect the folded carton. Finite element (FE) model of the rubber glove carton was created with shell elements. The orthotropic material properties were employed to specify FE model for analysis erection behavior of the folding carton. Vacuum cups number, positions and rotation points were simulated until obtained a good situation of the folding carton erector. Subsequently, finite element analysis results will be used to fabricate erector of the rubber glove packing machine in a further work.

Limitation of the Lateral Angled Broadband Low Frequency Impact Excitation on the Non-Destructive Condition Assessment of the Timber Utility Poles

Timber utility poles play a significant role in the infrastructure of Australia as well as many other countries for power distribution and communication networks. Due to the advanced age of Australia’s timber pole infrastructure, substantial efforts are undertaken on maintenance and asset management to avoid any failures of the utility lines. Nevertheless, the lack of reliable tools for assessing the condition of in-service poles seriously jeopardizes the maintenance and asset management. For instance, each year approximately 300,000 poles are replaced in the Eastern States of Australia with up to 80% of them still being in a very good condition, resulting in major waste of natural resources and money. Non-destructive testing (NDT) methods based on stress wave propagation can potentially offer simple and cost-effective tools for identifying the in-service condition of timber poles. Nonetheless, most of the currently available methods are not appropriate for condition assessment of timber poles in-service due to presence of uncertainties such as complicated material properties, environmental conditions, interaction of soil and structure, and an impact excitation type. In order to address these complexities, advanced digital signal processing methodologies are needed to be employed. Deterministic signal separation, blind signal separation, and frequency-wavenumber velocity filtering are the three groups of methodologies, which could most probably provide solutions. In this paper applicability and effectiveness of the blind signal separation methods is investigated through a numerical data obtained from of a timber pole modelled with both isotropic and orthotropic material properties. Principal Component Analysis (PCA), Singular Value Decomposition (SVD), and K-means clustering algorithms are the blind signal separation methodologies that are employed in this research work.

Reduction possibility of residual stresses from additive manufacturing by photostress method

Additive manufacturing results usually orthotropic material properties. To examine this anisotropy it has to made tensile specimens in different directions. In case of some materials there is a possibility to print the parts from transparency material. This is suitable for optical photostress analysis. With this method during the tensile test it was observed the stress distribution in the specimen. However in unloaded state also can be seen stresses in the specimen which is refers residual stresses.

Analysis of stress concentration in isotropic and orthotropic plates with hole under uniformly distributed loading conditions

The Behaviour of Stress Concentration Factor in rectangular and circular plates of Isotropic (Magnesium alloy) and Orthotropic material (E-glass/Epoxy) under static loading in transverse direction (UDL) has been studied. Aim of this work was to analyse the effect of D/A (From 0.1 to 0.9) and D/t ratio (From 0 to 90) upon Stress Concentration Factor (SCF) for Isotropic and Orthotropic material under given boundary conditions. To solve this problem, Finite Element Method (i.e. FEM Software) ‘ANSYS’ was used. Element length of 2mm was adopted. For design, a quarter rectangular plate and a complete circular plate were considered. Orthotropic material of rectangular plate for given boundary conditions achieved more Stress Concentration Factor than Isotropic Material. In Orthotropic Material, circular plate, Stress concentration was observed less than Rectangular Plate, whereas in Isotropic circular plate, SCF is almost similar to rectangular plate. Material properties of Orthotropic material has vital role for this behaviour when compared with Isotropic material and Geometry of the plate was also a reason to get SCF for Rectangular plate.

Numerical Estimation Method of Orthotropic Material Properties of a Roving for Reinforcement of Composite Materials

Numerical Estimation Method of Orthotropic Material Properties of a Roving for Reinforcement of Composite Materials

A novel algorithm using an orthotropic material model for topology optimization

ABSTRACTThis article presents a novel algorithm for topology optimization using an orthotropic material model. Based on the virtual work principle, mathematical formulations for effective orthotropic material properties of an element containing two materials are derived. An algorithm is developed for structural topology optimization using four orthotropic material properties, instead of one density or area ratio, in each element as design variables. As an illustrative example, minimum compliance problems for linear and nonlinear structures are solved using the present algorithm in conjunction with the moving iso-surface threshold method. The present numerical results reveal that: (1) chequerboards and single-node connections are not present even without filtering; (2) final topologies do not contain large grey areas even using a unity penalty factor; and (3) the well-known numerical issues caused by low-density material when considering geometric nonlinearity are resolved by eliminating low-density elements in finite element analyses.

A unified analysis of isotropic and composite Belleville springs

This article discusses a method developed for predicting the deformation behavior of a Belleville spring under axial loading by using the minimum potential energy principle. Strain energy and work done of the Belleville spring are formulated based on the classical thin shell theory in a conical coordinate system. The von Kármán and Reissner approximations to the nonlinear strain-displacement relations take the geometrical effects of the moderately and very large axial deflection into consideration, respectively. The Ritz method is used to solve for the deformation and force characteristics of isotropic springs and the solutions are compared with the seminal equation of Almen and Laszlo, experiments, and finite element analyses. The present energy model can capture the effect of a geometric parameter that has been missing from the formulation of Almen and Laszo. The comparison shows that the developed method gives very good agreement with the results from the testing and finite-element method, whereas in most cases, owing to their limited assumptions, Almen and Laszlo's equation overpredicts the applied load at a given deflection. This energy model is also applicable for composite Belleville springs with orthotropic material properties. A load factor and a orthotropic factor are defined to readily analyze load-deflection relationship of the composite springs based on the existing relationship of the isotropic elastic spring.

Mechanical characterization and modeling of an innovative composite material for railway applications

The innovation in the railway industry is focused on the production of lightweight vehicles with high performance, in order to obtain an energy power saving and to satisfy the environmental and global community requests. To pursue this aim, new materials have been increasingly used for vehicle structures. The selection of innovative materials and the definition of the relative properties represent, however, one of the most critical aspects for the design. Several factors, such as technical requirements, strength- and stiffness-to-weight ratios, crash resistance, and cost, are involved in material selection for rail vehicles. In addition, materials have to be chosen in accordance with the reference standards concerning fire resistance. This paper describes the activity carried out in order to acquire the needed information about selected composite materials to be used in the design and validation phases for a structural rail vehicle end and a roof. The material under investigation has been manufactured in order to satisfy the strict railway light metro fire normative. Due to the novelty of the adopted composite materials, a full mechanical characterization of the lamina was needed. The orthotropic material properties were verified and tuned using further tests on laminate and sandwich configurations in order to take into account, also, the influence of manufacturing process parameters. Analytical and numerical approaches have been used to validate and optimize the structural layout. Results of the multistep material characterization, acquired during the above phases, have been used to perform computational analysis in order to further improve the component design.

The numerical assessment of a full-scale historical truss structure reconstructed with use of traditional all-wooden joints

Abstract This paper focuses on description of the mechanical behavior of the historical gothic truss of St. James's Church in Brno. The numerical approach using finite element analysis (FEA) provided virtual assessment of the truss with a prediction of its behavior after simulated restoration using joints at locations of possible failure. The historical truss was subsequently analyzed by both beam truss structure and detailed 3D solid lap scarf joint modeled by reduction technique using substructuring. Static analyses were carried out using the finite element method (FEM) in order to establish a reliable numerical model and assess the static risks. The finite element models in ANSYS software assume fully orthotropic material properties of wood (Norway spruce and European beech) with elastic behavior. Results portrayed very good design of the assessed truss in the global mechanical behavior despite the rigidity of joints varied in longitudinal and transverse directions of the frames. Changes in global truss behavior were observed, but the changes in objective vertical displacement were not high. The differences based on rigidity level were not more than 7% of maximum vertical displacement of beams. The minor differences were recognized in the global truss behavior owing to new positions of implemented joints in the truss. Analyses showed each member in the truss contributes to global truss rigidity and stability to different degree. Further, analyses showed areas in the truss where it was necessary to correct joints orientation.

A multiscale and multiphysics model of strain development in a 1.5 T MRI magnet designed with 36 filament composite MgB2 superconducting wire

High temperature superconductors such as MgB2 focus on conduction cooling of electromagnets that eliminates the use of liquid helium. With the recent advances in the strain sustainability of MgB2, a full body 1.5 T conduction cooled magnetic resonance imaging (MRI) magnet shows promise. In this article, a 36 filament MgB2 superconducting wire is considered for a 1.5 T full-body MRI system and is analyzed in terms of strain development. In order to facilitate analysis, this composite wire is homogenized and the orthotropic wire material properties are employed to solve for strain development using a 2D-axisymmetric finite element analysis (FEA) model of the entire set of MRI magnet. The entire multiscale multiphysics analysis is considered from the wire to the magnet bundles addressing winding, cooling and electromagnetic excitation. The FEA solution is verified with proven analytical equations and acceptable agreement is reported. The results show a maximum mechanical strain development of 0.06% that is within the failure criteria of −0.6% to 0.4% (−0.3% to 0.2% for design) for the 36 filament MgB2 wire. Therefore, the study indicates the safe operation of the conduction cooled MgB2 based MRI magnet as far as strain development is concerned.

Relevance of inhomogeneous–anisotropic models of human cortical bone: a tibia study using the finite element method

ABSTRACTCortical bone is an inhomogeneous and anisotropic tissue subjected to large loads during typical daily activities. While studies assuming isotropic material properties are frequent, anisotropy and inhomogeneity of cortical bone have been rarely taken into account. Moreover, the question, whether an assumption of anisotropy and inhomogeneity has an impact in the mechanical analysis of cortical bone, has not been explored in the literature. This study explores the relevance of anisotropy in human cortical bone. The cortical bone model has been divided into six radial regions and a different set of orthotropic material properties has been assigned to each region. This inhomogeneous and anisotropic elastic tibia model has been compared with a corresponding isotropic model under various loading modes using the finite element method. In particular, the variation in the maximum von Mises stress and strain values has been observed along the bone axis. We have observed that the isotropic model may overestimate the maximum von Mises strain up to 15% under pure compression and underestimate up to 50% under pure torsion relative to the inhomogeneous–anisotropic model. Our results suggest that consideration of anisotropy and inhomogeneity of the bone may make a significant difference in the predicted maximum von Mises strain values, which can be important for strain-based damage accumulation studies and fracture risk evaluation.

制振CFRP積層板減衰特性に及ぼす積層構成の影響

Carbon fiber reinforced plastics (CFRP) have orthotropic material properties and are usually used as laminated structures. Therefore, their mechanical properties can be varied by changing their fiber orientation angles according to the purpose of their use. However, in the case of CFRP that has poor vibration damping, resonance problems become easily crucial and hence it is necessary to suppress the vibration occurred in the CFRP laminates. The present study proposes to improve the value of coefficient of mode loss by introducing so-called damping sheets. Fiber orientation angle and insert point of damping sheets are decided from numerical results (1280 patterns) in terms of a few lower natural frequencies, modal loss factors and mode shapes numerically obtained by the general purpose finite element method(FEM) code, ANSYS.

Development of Alpine Skis Using FE Simulations

The ski manufacturing industry is characterized by short product life cycles and high innovation pressure in order to meet customer's expectations of progressive improvements of skis. To reduce development time a FE model was developed and validated to simulate the influence of changes of the ski construction on its bending and torsional stiffness. Moreover, the study aimed to evaluate the feasibility of a novel ski sandwich construction with a load dependent bending stiffness. Therefore, the FE model was used to define required strain-stiffening of a single construction layer material to reach a perceptible change of the overall ski's bending stiffness. Two existing skis with identical geometry but distinctive differences of their torsional and bending stiffness were modelled using ANSYS Workbench. The sandwich construction was modelled by 18 solid bodies with bonded contacts: core, sidewalls, edges, upper and lower face with 13 layers including 3 additional resin interlayers. Orthotropic linear elastic material properties were taken from data sheets of suppliers and from material tests of the manufacturer. Sweep meshing was used to create an all-hex mesh of solid elements. Static structural simulations of a 3-point bending test and a torsion test were run in accordance to existing laboratory tests to validate the model. For both skis, the FE model showed good agreement with the experimental data for ski A and B. The simulated overall bending stiffness (center spring constant) was, respectively 2.8% and 3.2% higher compared to the experiments. The elastic curves revealed the model as slightly too stiff at the afterbody and too soft at the forebody. The simulated torsional stiffness (torsional spring constant) was, respectively 2.1% and 4.2% lower than found in the experiments. In the development process, for example, the model was then used to quantify the influence of edge profile heights on the ski's overall bending stiffness (3% per 0.1mm edge height). The application of strain-stiffening materials to realize a load depending ski stiffness turned as not feasible due to too small strains within the ski structure. A realistic representation of the different construction layers of an alpine ski is still challenging, especially due to the heterogeneity of the fibre compound layers and the resin distribution. Using bulk properties of the upper and lower face of the sandwich construction is not an alternative. To virtually test the influence of new materials and layups every single layer has to be represented. Using two skis for validation and additional resin interlayers for calibration appeared appropriate in order to achieve adequate model results.

Elastic-Plastic Thermal and Residual Stress Analysis of Adhesively Bonded Single Lap Joint

In this work, an elastic-plastic thermal and residual stress analysis were performed for adhesively bonded single lap joint. For this purpose, thermoplastic composite adherents were bonded to each other with epoxy adhesive. Thermoplastic composite material was reinforced by steel-fibres, unidirectionally. Finite element method (FEM) was preferred to obtain thermal elastic and elastic-plastic stress distributions on single lap joint. Accordingly, modelling and solution processes were achieved using ANSYS software. So as to determine effects of uniform temperature loadings on thermal and residual stresses, different values of it were loaded on the joint, uniformly. Briefly, both thermal and residual thermal stresses were calculated under uniform temperature loading which was selected from 40 °C to 80 °C. According to obtained results different thermal expansion coefficients of composite adherents and adhesive layer caused thermal and residual stresses on adhesively bonded single lap joint due to applied uniform temperature loadings. Thermal stress values for x and y-directions are very different from each other owing to orthotropic material properties of thermoplastic composite. The magnitudes of elastic analyses results are higher than elastic-plastic analysis results. Contrary to elastic analysis results, elastic-plastic analysis results were nonlinear. Thermal and residual stresses are increased by increasing uniform temperature values, so the highest values were calculated when 80 °C. The plastic yielding was firstly come into being for 50 °C loading and it is expanded related to raising thermal loadings as nonlinear.

Shear vibration and buckling of double-layer orthotropic nanoplates based on RPT resting on elastic foundations by DQM including surface effects

In this article, shear vibration and buckling of double-layer orthotropic nanoplates resting on elastic foundations are analyzed subjected to in-plane loadings including surface and nonlocal effects. These effects are considered by Gurtin---Murdoch's theory. Using the principle of virtual work, the governing equations for bulk and surface of double-layer orthotropic nanoplate are derived using refined plate theory. Differential quadrature method (DQM) is implemented. DQM solutions are validated by Navier's method and journal references. The influences of nonlocal parameter, van der Waals, Winkler, shear modulus, orthotropic material properties, boundary conditions, and in-plane biaxial, uniaxial, and shear loadings, are investigated on the surface effects of buckling and vibration modes of out-of-phase and in-phase. Results demonstrate that by augmenting nonlocal parameter, the surface effects on the vibration and buckling modes of both out-of-phase and in-phase increase. This result is in contrast with the works of other researchers in the field. Moreover, by enhancing in-plane loadings, the degree of surface effects on the vibration increase. On the other hand, the effects of nonlocal parameter on the vibration and buckling under in-plane shear load are more influential than those of biaxial and uniaxial, while the surface effects on the biaxial vibration and buckling are more remarkable than those of shear vibration and buckling.

Elastodynamic analysis of mode III multiple cracks in a functionally graded orthotropic half-plane

This paper presents a set of dynamic analyses of multiple parallel or perpendicular cracks to the boundary in a functionally graded orthotropic half-plane subjected to anti-plane shear stresses. The material properties are assumed to vary based on an exponential law. Integral transformations (Laplace and Fourier) and Green’s function method are applied to elastodynamic equations. The displacement discontinuous distribution method is used to model the crack problems which are solved by using a set of appropriate boundary conditions. As a result, a set of stress equations with both hypersingular and logarithm singular terms is obtained. Using Chebyshev series expansion and collocation points in Laplace domain, the solution of hypersingular integral equation for multiple cracks is achieved. Finally, different algorithms of numerical Laplace inversion are presented and the dynamic stress intensity factors (DSIFs) are obtained. The presented results are compared with the available published data and a very good agreement is observed. Moreover, it is also demonstrated that the present theoretical study is capable of modeling multiple cracks with different arrangements and variety of FG Orthotropic material properties. Furthermore, influence of FGM constant and shear modulus ratio on the dynamic overshoot of stress intensity is investigated.