Finite Element Analysis of Mechanical Properties of 3D Four-directional Rectangular Braided Composites—Part 2: Validation of the 3D Finite Element Model

In the first part of the work, we have established a new parameterized three-dimensional (3D) finite element model (FEM) which precisely simulated the spatial configuration of the braiding yarns and considered the cross-section deformation as well as the surface contact relationship between the yarns. This paper presents a prediction of the effective elastic properties and the meso-scale mechanical response of 3D braided composites to verify the validation of the FEM. The effects of the braiding parameters on the mechanical properties are investigated in detail. By analyzing the deformation and stress nephogram of the model, a reasonable overall stress field is provided and the results well support the strength prediction. The results indicate it is convenient to predict all the elastic constants of 3D braided composites with different parameters simultaneously using the FEM. Moreover, the FEM can successfully predict the meso-scale mechanical response of 3D braided composites containing periodical structures.     

Ball Impact and Crack Propagation – Simulations of Particle Compound Material

Particle compounds are the combination of various sized particles with non-uniform properties and can be considered as one of the most complicated engineering materials. The properties of the particle compounds vary in large range depending upon applications, methods of manufacturing and ratios of its compositions. Even if the method of manufacturing is same, the properties may be different because of the arrangements of ingredients. The different types of engineering agglomerates and building materials, like concretes, are some examples of the particle compounds. Similarly, the proper recycling of particle compound is very important in order to utilize the valuable aggregates from the cheaper fine matrixes. The aim of this research is to study the crack initiation and propagation in the building materials of spherically shaped concrete structures under impact loadings. A 2 Dimensional Finite Element Analysis is carried out with central impact loading condition to understand the stress pattern distributions before cracking. The Discrete Element Method (DEM) is adopted for further analysis to study the crack propagation in particle compound. Concrete spheres of diameter 150 mm with properties of B35 (35 N/mm² compressive strength) are chosen for the representation. A sphere is geometrically easier for the analysis. The assumption can be made that after some stages of loading the cube shaped concrete will be similar to sphere after losing its edges. This paper discusses the continuum and discrete approach for the analysis of crack propagation in particle compound with reference to the concrete ball. The analysis is done with central impact loading conditions in different velocities ranges between 7.7 m/s to 39 m/s. The correlations between theoretical simulations and practical experiments are also discussed.KeywordsFracture pattern, Crack propagation, Crack simulation, Air cannon, Numerical simulationThe authors would like to acknowledge German Research Foundation for the financial support.     

Two Dimension Finite Element Simulations on the Electromagnetic Containment in Twin-Roll Strip Casting

Distribution of magnetic field and electromagnetic force in twin-roll casting of steels was studied by the metod of numerical simulation in this paper,Two-dimension finite element model ,which includes the regions of melt ,stainless collar ,coil and magnetic core ,has been constructed,By solving magnetic vector potential formulations of quasi-static electromagnetic field,distribution of magnetic flux density and magnetic force at different molten heigh is determined,Calculated results showed that intensity of the distribution of magnetic flux density increased linearly with the increased coil current ;and the magnetic force in the melt increased as a quadratic cure with creased coil current ,More attention was given to the distribution of eddy current and magnetic force in the melt ,the confine effect at different molten height was also discussed.     

Analysis of Equivalent Oxygen Diffusivity of Particle Dispersed Composites

This paper presents a new method to determine the equivalent oxygen diffusivities of particle dispersed composites.This method can be used to design FGM thermal barrier systems with the function of oxygen barrier.A qualitative explanation of the oxidation of nickel with the increment of zirconia contents in the composite samples can be accepted by this method.The values of equivalent oxygen diffusivities obtained with this method are in excellent agreement with those from the EMT method for the composites with ZrO2 particle dispersed phase when the volume fractions of dispersed phase are lower than 25%.     

Nonlinear Finite Element Analysis of Paper Movement in Air

1IntroductionWitl1thedevelopInentofsciencetuldtechnology,officeequipment,suchascopiersal1dpril1ters,havebeenbecomingindispensablet()olsinthepeople'sdailylifC.Butcoonol1lyencounteredfaultinrunningofficcequipment,paPerjaIn,isbringingaboutmuchtroubletotheusersandthelnakersofofficeequiplnent.AnalyzingtheworkprocessofofficeequipInent,wecanfil1dtliatthepaperalwaysbetransportedalongacomPlexpath-Duringthetransportatiol1,thepaPerisloadedonmanydifferentpositionswitl1diffeentfeedingforces.Ifthepathco…     

Failure Analysis and Finite Element Simulation of Above Ground Oil–Gas Pipeline Impacted by Rockfall

Pipeline is the most important transmission way of oil and gas. Rockfall impact is one of the factors that result in above ground oil–gas pipelines accidents. Deformation of oil–gas pipeline caused by rockfall impacts were investigated using finite element method. Pipeline deformation caused by spherical and cube rockfalls were discussed under radial impact, inclined impact, and eccentric impact. The results show that crater depth of spherical rockfall impact is bigger than the cube rockfall with the same volume. The smaller curvature radius of rockfall’s contact zone has a greater harm to oil–gas pipeline. Angle part impact of irregular rockfall is very harmful for oil–gas pipeline. Under inclined impact, the maximum plastic strain of spherical rockfall impact crater appears when incidence angle α is 45°. Pipeline is prone to rupture when α is small under cube rockfall impact. The plastic strain distribution of the impact crater is more uneven with the increasing of the incidence angle. Plastic strain zone of pipeline decreases with the increasing of eccentricity k under eccentric impact.     

Application of Wavelet Finite Element Method to Simulation of the Temperature Field of Copier Paper

Simulation of the temperature field of copier paper in copier fusing is very important for im-proving the fusing property of reprography.The temperature field of copier paper varies with a high gradient when the copier paper is moving through the fusing rollers.By means of conventional shaft elements,the high gradient temperature variety causes the oscillation of the numerical solution.Based on the Daubechies scaling functions,a kind of wavelet-based element is comstructed for the above prob-lem.The temperature field of the copier paper moving through the fusing rollers is simulated using the two methods.Comparison of the results shows the advantages of the wavelet finite element method,which provides a new method for improving the copier properties.     

Analytical Formulation of (0°, ± α°) Braided Composites and Its Application In Crashworthiness Simulations

New types of tridimensional composite materials have been developed during the last few years. These new materials consist of braided, weft or warp knitted, and 3D woven composites preforms, and they present excellent out-of-plane mechanical properties. In this article, tubular energy absorbers, constituted of carbon-glass hybrid braided composites, are analyzed by means of the finite-element method, with explicit time integration of the equations of motion. A new material model for (0°, - f °) braided composites is introduced in a commercial finite-element code by means of user-developed subroutines. Braided materials with carbon fiber in the 0° direction and glass fibers in the - f ° directions are studied. Moreover, different fiber orientations and geometry of the triggering devices are analyzed in order to obtain the optimum configuration in terms of specific energy absorption.     

Research on Pantograph and Overhead Contact System′s Simulation of High Speed Railway and Comparison of Three Calculation Methods by Finite Element Method

This study relies on the project about Jining to Tongliao railway electrification reconstruction project. The dynamic simulation model of the pantograph-OCS(overhead contact system) suitable for Jitong project is designed, according to the corresponding numerical calculation method and workflow. Firstly, We establish the pantograph and catenary′s BIM models, and the parameters related to the dynamic simulation of the pantograph system are attached to the BIM model. Then, the BIM model is transformed into a mechanical analysis model, which is input into the dynamic simulation software of pantograph-OCS. The rationality of the design scheme of the pantograph system is verified through simulation.     

Progressive damage and failure of mechanically fastened joints in CFRP laminates – Part I: Refined Finite Element modelling of single-fastener joints

This paper presents a refined Finite Element modelling for strength prediction, and especially bearing strength prediction, of mechanically fastened joints in CFRP laminates. Although the importance of delamination on the bearing strength of the joint is well established in the literature, only rarely has it been introduced into the models. In the present work, delamination onset and propagation are explicitly taken into account in the model by means of cohesive elements. The ply behaviour is described through a viscoelastic model combined with a progressive damage approach. A multi-model calculation strategy is developed to reduce the calculation costs. Prediction of the proposed model are compared to both bearing tests and open-hole tests results. For further validation, numerical predictions are also compared to filled-hole tensile tests and bearing/bypass interaction tests. Bearing, open-hole, and filled-hole tests are performed in this study. An original pin-bearing test configuration is proposed. Predicted strengths and experimental results turn out to be in good agreement. The obtained results are promising and demonstrate the capability of the proposed model to capture the material and stacking sequence effects on the joint behaviour and strength, as well as the influence of the geometrical dimensions of the joint.     

Finite element modelling of rubber-like materials — a comparison between simulation and experiment

In this work finite element simulations are used based on the micro structure of polymers in order to transfer the information of the micro level to the macro level. The microscopic structure of polymers is characterized by a three-dimensional network consisting of randomly oriented chain-like macromolecules linked together at certain points. Different techniques are used to simulate the rubber-like material behaviour of such networks. These techniques range from molecular dynamics to the finite element method.The proposed approach is based on a so-called unit cell. This unit cell consists of one tetrahedral element and six truss elements. To each edge of the tetrahedron one truss element is attached which models the force-stretch behaviour of a bundle of polymer chains. The proposed method provides the possibility to observe how changes at the microscopic level influence the macroscopic material behaviour. Such observations were carried out in [1]. The main focus of this work is the validation of the proposed approach. Therefore the model is compared to different experimental data and other statistically-based network models describing rubber-like material behaviour.     

Thermal Shock Behaviour of Alumina—Iron Composites

Thermal shock behaviour was investigated for two morphologically different composites comprising an alumina matrix and 20 vol.pct Fe particles for a wide range of quenching temperature differences(ΔT=100-800℃)and compared to a monolithic alumina.The retained strength and critical quenching temperature difference,ΔTc,of the two composites were a significant improvement over the values for the respective monolithic alumina.Crack lengths and densities were shown to be greater for the alumina than for the two composites at all quenching temperature differences .The thermal shock resistance parameters for monolithic alumina and the two composites were calculated according to their mechanical and physical properties.The calculated results agree well with the experimental one and indicate possible explanations for the differences in thermal shock behaviour.     

Synthesis and Characterization of Aluminum–Zirconium Intermetallic Composites

The search for composite materials comes from a necessity of improving properties of conventional materials. The reaction synthesis process frequently gives products with some level of porosity that may be improved through the use of hot pressing routes. The combination of aluminum and zirconia in controlled conditions has led to a metal matrix composite with a dispersion of intermetallics, especially Al₃Zr. Temperature, pressure, and chemical composition were the main parameters varied during the production of the samples. The experimental procedures consisted initially of the mixing and homogenization of the powders in three proportions (5, 10, and 20 in zirconia wt. %). The powders were pressed for the production of green bodies, cylinders of 9 × 9 mm, with the application of three pressures (150, 250, and 300 MPa). Synthesis was carried out in a tubular furnace (1073, 1173, and 1273 K) using a helium atmosphere. Reactive hot pressing was carried out in a MTS machine. The densification process in the simultaneous hot pressing was observed with the use of mercury picnometry to measure the densities and confirmed with the help of an image analyzer. The temperatures were monitored by a thermocouple connected to an A/D interface. Determination of Vickers microhardness was carried out in the aluminum matrix and in the intermetallic particles; hardness was determined in all samples. The identification of the phases was obtained utilizing XRD, optical, and SEM microscopy.     

3D Finite Element Numerical Simulation of Residual Stresses on Electron Beam Welded BT20 Plates

A three-dimensional finite-element model (FEM) used for calculating electron beam (EB) welding temperature and stresses fields of thin plates of BT20 titanium has been developed in which the nonlinear thermophysical and thermo-mechanical properties of the material has been considered. The welding temperature field, the distributions of residual stresses in as-welded (AW) and electron beam local post-weld heat treatment (EBLPWHT) conditions have been successfully simulated. The results show that: (1) In the weld center, the maximum magnitude of residual tensile stresses of BT20 thin plates of Ti alloy is equal to 60%- 70% of its yield strength σs. (2) The residual tensile stresses in weld center can be even decreased after EBLPWHT and the longitudinal tensile stresses are decreased about 50% compared to joints in AW conditions. (3) The numerical calculating results of residual stresses by using FEM are basically in agreement with the experimental results. Combined with numerical calculating results, the     

Modeling and Optimization of Properties of Domestic Mullite–Corundum Composites

High Temperature - Mathematical modeling of spectral-kinetic, thermal, and electrophysical characteristics, which are difficult to determine experimentally, has been carried out based on the...     

Processing and Performance of Alumina Fiber Reinforced Alumina Composites

Processing of alumina fiber-reinforced alumina matrix composites by hot-pressing was described. The mechanical properties of the composites fabricated by different sintering conditions including temperature and pressure have been investigated. The results indicated that the higher sintering temperature and pressure corresponded to the higher bulk density and higher maximum strength of the composite, whereas the pseudo-ductility of the composite was lower. The preliminary results of the composite with monazite-coated fibers showed that maximum strength could be improved up to 35% compared with the noncoated fiber composite in the same sintering condition. Moreover, the fracture behavior of the composite changed from completely brittle fracture to non-brittle fracture under the suitable sintering conditions. SEM observation of the fracture surface indicated that the coating worked as a protective barrier and avoided sintering of the fibers together even at high temperature and pressure during densification process.     

Synthesis and Photoluminescence of Fluorinated Yttria–Alumina Composites

Inorganic Materials - Composites have been prepared via thermal decomposition of gel-like mixtures containing yttrium, aluminum, and europium(III) salts and ethyl acetate as a basic component....     

Element segregation and thermal stability of Ni–Pd nanoparticles

Journal of Materials Science - A new high-precision angular-dependent potential of the Ni–Pd system was obtained by fitting the experimental data and first-principles calculations. Then, the...