Applied Mechanics and Materials Vol. 392

Abstract: We improved the piezoelectric property of poly (vinylidene fluoride) (PVDF) by employing multi-walled carbon nanotube (MWCNT) as nanofillers. The MWCNT/PVDF nanocomposite was prepared by the solution casting method with MWCNT contents ranging from 0.0 wt.% to 0.3 wt.%. To induce the piezoelectric β-phase crystal structure, the nanocomposite films were drawn lengthwise with a ratio of 4 ~ 5 and polarized by step-wise poling method. To evaluate the piezoelectric property, the output voltages of the nanocomposite films were measured through extensive experimental vibration tests. The experimental results show that the nanocomposite films with 0.05 wt.% MWCNT possess the highest output voltage, i.e., around 2 times as that of pure PVDF films. The main reason is that more β-crystalline phase can be formed at this content, as confirmed by X-ray diffraction.

Abstract: Using ring friction testing machine and metallographic and SEM on three formula of carbon fiber reinforced PFFE composite materials (CFRP) and stainless steel under water lubrication tribological properties were studied, and analyses the influence of load, grinding time on friction coefficient and wear quantity. It was found that CFRP with carbon-fiber content of 15% mass fraction and the high temperature nitride treated OCr17Ni14Cu4Nb got a friction coefficient of 0.0ll under 200N load, sliding speed of 5 m/s , which is the lowest one between all of the similar materials in domestic reporting.15 min before testing, the friction coefficient decreased with the increase of load. After 15 min, the friction coefficient basically was stabilized at around 0.011-0.014, Main wear mechanism of the CFRP material containing carbon fiber is fatigue wear, the higher the carbon fiber content, the lower the friction coefficient; the applied load increases from100N to 250N, the wear quantity increases with load decrease, starting from250 N wear increases with load increase.

Abstract: A Finite Element Modeling (FEM) and Simulation was Used to Investigate the Effect of Tool Rake Angle, Cutting Speed and Feed Rate on the Cutting Temperature of Tial6v4 Alloy. the Purpose of this Study was to Find Proper Cutting Parameters for Machining of Titanium Alloy where Cutting Temperature was Lowest. A FEM Based on ABAQUS Software which Involves Jonson-Cook Material Model and Coulomb’s Friction Law was Applied to Simulate an Orthogonal Cutting Process. in this Simulation Work, a Range of Tool Rake Angle from 0° to 10°, a Range of Cutting Speed from 300 m/min to 600 m/min and a Range of Feed Rate between 0.1 Rev/mm and 0.25 Rev/mm were Investigated. the Simulation Results Indicated that Increase in Rake Angle Reduces Cutting Temperature while Increasing Cutting Speed and Feed Rate Increase the Cutting Temperature.

Abstract: In this study, core-shell rubber (CSR) and liquid rubber (LR) were used to modify the matrix toughness of unidirectional carbon fibre/epoxy composites. Double cantilever beam (DCB) and end notched flexure (END) tests were performed to evaluate the interlaminar fracture toughness. It was found that LR was identified to be more effective than CSR in improving G_IC and G_IIC of the composites, although fracture toughness of the CSR-modified epoxy was better than that of the LR-modified epoxy. SEM observation of post-fracture surfaces of the specimens shows that the degree of plastic deformation of matrix is well related to the rating of fracture toughness of composites for these unmodified and modified composite laminates, and is the key factor controlling the interlaminar fracture toughness of composite laminates. Further, it was confirmed that rigid fibres constrain growth of plastic zone in composites laminates, comparing with toughened bulk epoxy matrix. However, plastic zone is not limited to a single resin layer and it is capable of developing across rigid fibre layers.

Abstract: It is generally believed that raw materials for the manufacture of welding electrodes are not available in Nigeria. As a result, completely manufactured electrodes are imported and where they are produced locally, all the components are imported from the home countries of the technical partners. The aim of this research therefore is to produce a welding flux formulation from local materials. Various minerals were beneficiated, pulverized and mixed in various ratios using sodium silicate as binder. The welding flux developed yielded results comparable with ISO2560: E432R11

Abstract: In HDD air flow simulation, the well known LES turbulent model requires large computing times and resources, including CPU, RAM and storage intensive which is not appropriate when using various variables. The effect of an air damper is studied by the k-e model with a reduced boundary due to the lower number of equations, computing time and computer resources. Firstly the RMS velocities of a partial model are compared between LES and k-e and then the reduced boundary models are compared with the partial model. The RMS velocity errors of the partial model compared with LES and k-e are less than 6 %. The mean RMS velocity errors compared with the reduced boundary model and the partial model are 3.93% at ID and 2.12% at MD position while the OD position increased to 26.5% because there is no effect from a return flow from the flex bracket and voice coil zone. Computing time of the reduced boundary and k-e model is reduced by 68.4%. In primary HDD air flow analysis, the k-e method together with a reduced model can be used to predict the effect of an air damper.

Abstract: The ice amount accreting on the rotating multi-cylinders can be used to obtain the liquid water content (LWC) and the median volume diameter of water droplet (MVD) based on cylindrical icing model. In this model, the overall collision efficiency is usually calculated by Finstads (φ100) and Langmuirs formulations (φ<100). But this combined expression doesnt agree well with the numerical calculation in some case. This paper gives a new expression based on a large number of numerical calculation results, and this expression agrees better with the numerical computation than existing expression.

Abstract: In order to reduce Shigetai coal mine ventilation resistance of mine ventilation system, using balanced ventilation principle Shigetai coal mine ventilation resistance of mine ventilation system was analysed and balanced, and the balanced ventilation resistance measure mine ventilation resistance in 2014-2015 simulation calculation. Results suggest that balanced ventilation measures implemented in mine ventilation resistance, coal mine ventilation resistance in the next two years not only with increased ventilation line length increases, but lower. Visible, balanced ventilation of mine has better technical and economic results are obvious, merits promotion.

Abstract: In this paper we present a robust, high order method for numerical solution of multidimensional compressible inviscid flow equations. Our scheme is based on Nodal Discontinuous Galerkin Finite Element Method (NDG-FEM). This method utilizes the favorable features of Finite Volume Method (FVM) and Finite Element Method (FEM). In this method, space discretization is carried out by finite element discontinuous approximations. The resulting semi discrete differential equations were solved using explicit Runge-Kutta (ERK) method. In order to compute fluxes at element interfaces, we have used Roe Approximate scheme. In this article, we demonstrate the use of exponential filter to remove Gibbs oscillations near the shock waves. Numerical predictions for two dimensional compressible fluid flows are presented here. The solution was obtained with overall order of accuracy of 3. The numerical results obtained are compared with experimental and finite volume method results.

Abstract: The study focuses on using fracture mechanics to evaluate mixed-mode fracture properties of adhesively bonded aerospace material systems. As a part of experimental efforts, mixed-mode fracture tests were performed using modified Arcan specimens consisting of several combinations of adhesive, composite and metallic adherends using a special loading device. Experimental and numerical studies of mixed-mode fracture behaviour of adhesively bonded aluminum and steel were also performed using an adhesive in the aerospace industry. Finite element analyses were carried out on specimens with different adherends. Based on those analyses, many fundamental numerical results were obtained.