International Journal of Mechanical and Materials Engineering最新文献

This study was conducted to investigate the synergistic effects of cutting parameters on surface roughness in ball end milling of oxygen-free high conductivity (OFHC) copper and to determine a statistical model that can suitably correlate the experimental results. Firstly, an experimental plan based on a full factorial rotatable central composite design with variable parameters, the cutting feed rate or feed per tooth, axial depth of cut, radial depth of cut, and the cutting speed, was developed. The range for each variable was varied through five different levels. Secondly, a mathematical model was formulated based on the response surface methodology (RSM) for roughness components (R_a and R_z micron). The predicted values from the model were found to be close to the actual experimental values. Finally, for checking the adequacy of the models, analysis of variance (ANOVA) was used to examine the dependence of the process parameters and their interactions. The developed model would assist in selecting the cutting variables for optimization of ball end milling process for a particular material. Based on the results from this study, it is concluded that the step over or radial depth of cut have a higher contribution (45.81%) and thus has a significant influence on the surface roughness of the milled OFHC copper.

This paper aimed to study the influence of zirconium phosphate (ZrP) nanoparticles on reducing the diameter of nanofibres during electrospinning. Addition of metal oxide such as zirconium phosphate decreases the diameter and smooths on the polyacrylonitrile (PAN) nanofibres as observed by the SEM techniques. Furthermore, this work investigated the effect of zirconium phosphate on the morphology and conductivity of modified PAN nanofibres under SEM, XRD and electrochemical cells. The PAN/zirconium phosphate nanofibres were obtained with the diameter ranges between 100 and 200?nm, which mean that the nanofibres morphology significantly changed with the addition of the zirconium phosphate nanoparticles. The conductivity of PAN and PAN-Nafion zirconium phosphate nanofibres was more improved when compared to that of the plain PAN nanofibres as observed under electrochemical measurements. The plain PAN nanofibres show the total degradation on thermal gravimetric analysis results when compared to the modified PAN with zirconium phosphate nanoparticles. The thermal properties and proton conductivity make the PAN/ZrP nanofibres as promising nanofillers for fuel cell electrolytes.

In the machining operations, final surface finish and dimensional accuracy are the most specified customer requirements. Hard turning machining operation using cubic boron nitride tool as an alternative of grinding process is a type of turning operation in which hardened steel are machined with the hardness greater than 45 HRc. During the hard turning operation because of the hard condition, the variations of surface finish and dimensional accuracy are completely different from that of the traditional turning operation. Thus, the variation of surface finish and dimensional accuracy under various cutting parameters has been investigated in the hard turning with cubic boron nitride tools.?The extracted knolwdge can be used for developing a knowledged base expert system. In order to have a comprehensive study, the variation of vibration, cutting forces, and tool wear has also been considered. The obtained results showed that depth of cut and spindle speed have the greatest effect on the dimensional accuracy, while feed rate is the most important factor affecting the surface roughness. The analysis of the vibration and tool wear proved that the flank wear has insignificant influence on the dimensional accuracy, whereas the vibration effect is considerable. The experimental results showed that when the feed rate is gradually increased from 0.08 to 0.32, the dimensional deviation first decreases unexpectedly until the lowest value is achieved at 0.16?mm/rev, then by further increasing the feed from 0.16 to 0.32?mm/rev, the dimensional deviation increases significantly. It was also seen that the best dimensional accuracy is achieved at the lowest level of the cutting depth, the medium level of the feed rate, and the spindle speed lower than its moderate level. The best surface roughness of 0.312?μm was obtained at 0.08?mm/rev feed rate, 0.5?mm depth of cut, 2000-rpm speed, and 1.2?mm insert nose radius, which is comparable with the surface finish obtained by the grinding operation.

The primary function of a suspension system is to isolate the vehicle body from road irregularities thus providing the ride comfort and to support the vehicle and provide stability. The suspension system has to perform conflicting requirements; hence, a passive suspension system is replaced by the active suspension system which can supply force to the system. Active suspension supplies energy to respond dynamically and achieve relative motion between body and wheel and thus improves the performance of suspension system.

This study presents modelling and control optimization of a nonlinear quarter car suspension system. A mathematical model of nonlinear quarter car is developed and simulated for control and optimization in Matlab/Simulink? environment. Class C road is selected as input road condition with the vehicle traveling at 80?kmph. Active control of the suspension system is achieved using FLC and PID control actions. Instead of guessing and or trial and error method, genetic algorithm (GA)-based optimization algorithm is implemented to tune PID parameters and FLC membership functions’ range and scaling factors. The optimization function is modeled as a multi-objective problem comprising of frequency weighted RMS seat acceleration, Vibration dose value (VDV), RMS suspension space, and RMS tyre deflection. ISO 2631-1 standard is adopted to assess the ride and health criterion.

The nonlinear quarter model along with the controller is modeled and simulated and optimized in a Matlab/Simulink environment. It is observed that GA-optimized FLC gives better control as compared to PID and passive suspension system. Further simulations are validated on suspension system with seat and human model. Parameters under observation are frequency-weighted RMS head acceleration, VDV at the head, crest factor, and amplitude ratios at the head and upper torso?(AR_h and AR_ut). Simulation results are presented in time and frequency domain.

Simulation results show that GA-based FLC and PID controller gives better ride comfort and health criterion by reducing RMS head acceleration, VDV at the head, CF, and AR_h and AR_ut over passive suspension system.

The theoretical investigation of the rapid sintering mechanism under pulse electric current sintering has no unified understanding. Especially for non-conductive powder, since there is no current flowing directly through the powder materials, the driving force in the neck growth mechanism becomes a key problem and needs to make progress.

The sintering driving force of nonconductive Al₂O₃ powders at the initial stage of pulse electric current sintering is investigated under the thermoelastic diffusion coupling transmission with the consideration of non-Fourier and non-Fick effect.

The concentration diffusion flux, which is caused by the local concentration gradient, and the thermal diffusion flux act as additional driving forces for the surface curvature driving.

Equal-sized particles model reveals that these fluxes exert the dominant influence on sintering driving force for volume and simultaneous surface and volume diffusion mechanisms. In particular, the sintering driving force is remarkably increased at the postperiod of the initial stage of sintering.

Analytical method for studying stress concentration around arbitrary shape cavity is proposed.

The method is based on the assumption that it is possible to simulate the influence of cavity on the redistribution of internal forces by including fictitious forces in the solution. To determine the stress-strain state, additional forces acting on cavity surface are used. The magnitude of these forces is chosen on the basis of the value of stress tensor flow through the examined surfaces limiting cavity volume.

Research of stress-strain state for the most general three-dimensional case is done: an elastic half-space with a cubic shape cavity under action of a concentrated force applied to a free surface. The obtained results are comprehensively compared with the solution of a similar problem by the finite element method. Distributions of the stress tensor components in the vicinity of these cavities are constructed. The estimation of accuracy and efficiency of the proposed calculation model is made; the boundary of applicability of the proposed solution is determined.

It seems promising to use the resource of structural materials advantageously, namely, creating in the bodies of the cavity system the required shape and size, to obtain stress reduction at critical points, thereby increasing the strength of the product.

The aim of this study is to propose a method for studying the free transverse vibration of the human lumbar spine using Timoshenko and Euler–Bernoulli beam theories.

The cross section of the lumber spine is assumed to be uniform, and the material properties are different for the vertebral bodies, endplates, and intervertebral discs. To derive equations with biomedical approach, they were developed with n segments of the lumbar spine including vertebrae, intervertebral discs, and endplates.

Three first natural frequencies and mode shapes of system were computed and then validated with a finite element analyzer.

Due to good agreements between the results, it was concluded that the proposed method offered acceptable results; therefore, it can be applied to the entire spine from the neck region to the tailbone and pelvis ones.

Applying nanofluid made by adding alumina nanoparticles to industrial oil may reduce the cutting force, friction, and cutting temperature and, from that, improve the tool life in the hobbing process. However, it is difficult to set up the experiment for the actual gear hobbing process, because measuring the cutting force and temperature in the hobbing process is very complicated and expensive. Therefore, a fly hobbing test on the horizontal milling machine was performed to simulate the actual hobbing process.

In this research, the fuzzy theory was combined with the Taguchi method in order to optimize multi-responses of the fly hobbing process as the total cutting force, the force ratio F_z/F_y, the cutting temperature, and the surface roughness.

The optimal condition—A1B1C3 (the cutting speed 38?mpm, the nanoparticle size 20?nm, and concentration 0.5%)—was determined by analyzing the performance index (FRTS) of the fuzzy model. Furthermore, this condition was applied to the actual hobbing process in the FUTU1 Company and compared with the actual conditions of this company and other conditions using the nanolubricant with 0.3% Al₂O₃, 20?nm. The results show that it can reduce a maximum 39.3% of the flank wear and 59.4% of the crater wear on the hob when using the optimal conditions.

The study indicates that the optimal condition determined by using Taguchi-Fuzzy method can be applied in the FUTU1 company with the high efficiency.

Measurement of the ductility like elongation and reduction of area of the fine metal wire is important because of the progress for the weight reduction and miniaturization of various products. This study established a simple and reliable method of measuring the ductility of a fine metal wire.

Tensile and loading-unloading tests were performed with applying initial load to high-carbon steel wire (diameters of 0.06–0.296 mm) through capstan-type grippers for non-metal fiber. The wire fastened with the grippers was separated into three parts: the fastened part, the contact part, and the non-contact part. Scanning electron microscope (SEM) images were used to measure the wire radius under uniform deformation and agreed well with the radius calculated using the radius before tensile testing and uniform elongation.

The following conditions were clarified: non-slippage at the fastening between gripper and wire, a longitudinally uniform elongation, negligible cross-head bending, and the stroke calculation accuracy of elongated length by the initial load. Thus, uniform elongations were calculated as the ratio of the stroke at 0 N subtracted from the stroke at maximum tensile load to the additional initial chuck distance and the stroke at 0 N. The maximum error of uniform elongation was 0.21%. The reduction of area could be calculated by using the radius at uniform deformation portion, while the radius at the most constricted point was measured using SEM image of one fractured piece and uniform elongation. The measurement error of reduction of area was 1.9%.

This measurement method can be applied to other metal wires less than 1 mm in diameter.

In this paper, the heat and mass transfer of MHD nanofluid squeezing flow between two parallel plates are investigated. In squeezing flows, a material is compressed between two parallel plates and then squeezed out radially. The significance of this study is the hydrothermal investigation of MHD nanofluid during squeezing flow. The affecting parameters on the flow and heat transfer are Brownian motion, Thermophoresis parameter, Squeezing parameter and the magnetic field.

By applying the proper similarity parameters, the governing equations of the problem are converted to nondimensional forms and are solved analytically using the Homotopy Perturbation Method (HPM) and the Collocation Method (CM). Moreover, the analytical solution is compared with numerical Finite Element Method (FEM) and a good agreement is obtained.

The results indicated that increasing the Brownian motion parameter causes an increase in the temperature profile, while an inverse treatment is observed for the concentration profile. Also, it was found that enhancing the thermophoresis parameter results in decreasing the temperature profile and augmenting the concentration profile.

Effects of active parameters have been considered for the flow, heat and mass transfer. The results indicated that temperature boundary layer thickness will increases by augmentation of Brownian motion parameter and Thermophoresis parameter, while it decreases by raising the other active parameters.