International Journal of Mechanical and Materials Engineering最新文献

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.

Structure and properties of welded joints of low-alloy thermomechanically processed (09G2FB) and quenched and tempered shipbuilding steels (10XN2MD, 08XN3MD, and 12XN3MF), welded with manual metal arc welding (MMA) and submerged arc welding (SAW), were studied.

Effects of specific energy input on the microstructure, mechanical properties, and impact energy of the heat-affected zone (HAZ) have been investigated, and probable reasons for crack formation in welded joints have been found.

It was found that welding heat input increase leads to a significant increase in grain size near the fusion boundary and the formation of martensite with high hardness. Therefore, the heat input is recommended to be limited to 2.5–3.5?kJ/mm for these specific steel grades.

The study indicates that microalloying elements can be used to limit the grain growth when the steel is subjected to high temperatures during welding thermal cycle. Carbon content and alloying level reduction tend to increase the steel ductility and lower the HAZ toughness.

This paper explores the impact of thermal radiation on boundary layer flow of dusty hyperbolic tangent fluid over a stretching sheet in the presence of magnetic field. The flow is generated by the action of two equal and opposite. A uniform magnetic field is imposed along the y-axis and the sheet being stretched with the velocity along the x-axis. The number density is assumed to be constant and volume fraction of dust particles is neglected. The fluid and dust particles motions are coupled only through drag and heat transfer between them.

The method of solution involves similarity transformation which reduces the partial differential equations into a non-linear ordinary differential equation. These non-linear ordinary differential equations have been solved by applying Runge-Kutta-Fehlberg forth-fifth order method (RKF45 Method) with help of shooting technique.

The velocity and temperature profile for each fluid and dust phase are aforethought to research the influence of assorted flow dominant parameters. The numerical values for skin friction coefficient and Nusselt number are maintained in Tables 3 and 4. The numerical results of a present investigation are compared with previous published results and located to be sensible agreement as shown in Tables 1 and 2.

It is scrutinized that, the temperature profile and corresponding boundary layer thickness was depressed by uplifting the Prandtl number. Further, an increase in the thermal boundary layer thickness and decrease in momentum boundary layer thickness was observed for the increasing values of the magnetic parameter.

Metal forming has played a significant role in manufacturing development, thus investigations in the field of metal forming to improve the quality of the forming process are necessary. In the present study, the experimental and numerical analysis of airfoil contour forming of 301 austenitic stainless steel is examined in order to reduce the spring reversible ability under preheat temperature.

Considering the stress-strain properties of the preheat temperature; the body forming is simulated in ABAQUS software according to the theory of increasing the blank holder force during forming.

The obtained results of the spring-back for simulating the austenitic stainless steel airfoil are compared and investigated with the manufactured experimental sample results using deep tensile forming.

By comparing the results it can be seen that the control of blank holder force during forming cause to minimize the spring-back effects.

Renewable energy resources are becoming more important to meet growing energy demands while reducing pollutants in the environment. In the current market, wind turbines are primarily restricted to rural use due to the large size, noise creation, and physical appearance. However, wind turbines possess the ability to run at any time of the day. Horizontal axis wind turbines remain the most widely used, but there is significant room for improvement in vertical axis wind turbines.

While vertical axis wind turbines are not reaching the same level of efficiency of horizontal axis wind turbines, there are significant benefits to researching improvements. One of the main benefits is to make use of vertical axis wind turbines in urban settings. In order to improve the efficiency of the vertical axis wind turbine, a biological approach was taken to design blades that mimic the shape of maple seeds and triplaris samara seeds. This approach was taken because due to its geometrical properties, typically extra lift is generated.

The results obtained through FEA simulations were consistent with the expected results for the application that was considered. The results obtained provide valuable insight for engineers to iterate and design optimum wind turbine blades taking advantage of biological phenomena applied to conventional airfoils.

The purpose of this paper is to provide structural analysis details into the design of a vertical axis wind turbine blades that mimic the geometry of maple and triplaris samaras seeds.

The present exploration deliberates the effect of nonlinear thermal radiation on double diffusive free convective boundary layer flow of a viscoelastic nanofluid over a stretching sheet. Fluid is assumed to be electrically conducting in the presence of applied magnetic field. In this model, the Brownian motion and thermophoresis are classified as the main mechanisms which are responsible for the enhancement of convection features of the nanofluid. Entire different concept of nonlinear thermal radiation is utilized in the heat transfer process.

Appropriate similarity transformations reduce the nonlinear partial differential system to ordinary differential system which is then solved numerically by using the Runge–Kutta–Fehlberg method with the help of shooting technique. Validation of the current method is proved by having compared with the preexisting results with limiting solution.

The effect of pertinent parameters on the velocity, temperature, solute concentration and nano particles concentration profiles are depicted graphically with some relevant discussion and tabulated result.

It is found that the effect of nanoparticle volume fraction and nonlinear thermal radiation stabilizes the thermal boundary layer growth. Also it was found that as the Brownian motion parameter increases, the local Nusselt number decreases, while the local friction factor coefficient and local Sherwood number increase.

In this study, a quasi-analytical solution for longitudinal fin and pin heat conduction problems is investigated.

The differential transform method, which is based on the Taylor series expansion, is adapted for the development of the solution. The proposed differential transform solution uses a set of mathematical operations to transform the heat conduction equation together with the fin profile in order to yield a closeform series of homogeneous extended surface heat diffusion equation.

The application of the proposed differential transform method solution to longitudinal fins of rectangular and triangular profiles and pins of cylindrical and conical profiles heat conduction problems showed an excellent agreement on both fin temperature and efficiencies when compared to exact results. Therefore, the proposed differential transform method can be useful for optimal design of practical extended surfaces with suitable profile for temperature response.