JOURNAL OF SIMULATION AND ANALYSIS OF NOVEL TECHNOLOGIES IN MECHANICAL ENGINEERING (JOURNAL OF SOLID MECHANICS IN ENGINEERING)
Year:2016 | Volume:9 | Issue:3 |Papers Count:15

This paper numerically examines the laminar forced convection of a water–Al2O3 nanofluid flowing through a horizontal rib-microchannel. The middle section of the down wall microchannel is Affected by cold temperatures with a constant and uniform tempreture Tc. The middle section is also influenced by a transverse rib array. The effects of height rib in a two dimensional rib-microchannel on flow and heat transfer parameters of laminar water- Al2O3 nanofluid are investigated. The characteristics of this research are numerically investigated by the commercial software Fluent 6.3 in a Reynolds number as Re=10 and Re=100. Four different states of hight rib are analyzed. Higher conventional internal ribs or increasing the turbulators can significantly improve the performances of the convective heat transfer within a microchannel. It is seen that larger height rib and volume fraction of nanoparticles corresponds more heat transfer rate; however the added high ribs can cause a larger friction factor than that in the corresponding microchannel by constant height rib. At present article the effect of height rib on the fluid flow parameters are also studied for all different states of it. The results show that the microchannel performs better heat transfers at higher values of the Reynolds numbers. For all values of the Reynolds numbers and volume fraction of nanoparticles considered in this study, the average Nusselt number on the middle section surface of the microchannel increases as the solid volume fraction increases. Variations of the solid volume fraction result in changes to the dimensionless temperature along the centreline and the temperature profile at different cross-sections of the microchannel. For all values of the Reynolds and height rib, s, the average Nusselt number on the middle section increases as the solid volume fraction increases. The Results are shown as velocity, temperature and Nusselt number profiles and isotherms and contours of streamlines.

The use of aluminum alloys in various industries, especially the automotive industries, to have less structural weight, is on the rise. The use of semi-solid forming process in addition to changes in the microstructure which improves the mechanical properties can reduce the volume of production and ultimately lead to the improvement of the structural weight. In this paper, optimization of the governing parameters is investigated in one method of the semisolid forming named the mechanical vibration. A380 grade aluminum alloy is cast in our study. The initial parameters that investigated here are the pouring temperature, frequency and holding vibration time. The output result is investigated on the hardness. As the result showed the hardness value of 80 is the best result. Also results showed that the temperature of the melt is the important parameter in this method. Also the hardness will be increased when the frequency and holding vibration time increases.

In this numerical study the heat transfer and laminar nanofluid flow in the three-dimensional microchannels with triangular cross-section is simulated. For increase the heat transfer from the walls of the channel, semiattached & offset mid- truncated rib, s Placed in the canal, and the tooth geometry and the impact is studied. In this study, the water is base fluid, and the influence of the volume fraction of nanoparticles of titanium oxide on the the heat transfer and the fluid flow physics is studied. The presented results include the distribution of Nusselt number in the channel, The coefficient of friction and the thermal-fluid performance for each of the different states. The results show the existence of is the tooth on the effective flow physics. And their efficacy is highly dependent on Reynolds number. Use indentation in the microchannels, increase the heat transfer rate and the reduce the temperature gradient between the layers of the cooling fluid. Also, the presence of nanoparticles in the fluid cooling is effective and the pain increase the heat transfer by increasing the Reynolds number, the effect of nanoparticles also increase the heat transfer increases.

In recent decade, the new advanced nanofluids, composed from various particles, have attracted the attention of researchers. This class of nanofluids, which can be prepared by suspending several types (two or more than two) of nanoparticles in base fluid, is termed as hybrid nanofluids. In this work, an experimental investigation on the effects of temperature and concentration of nanoparticles on the thermal conductivity of MgO-MWCNT/EG hybrid nanofluid is presented. The experiments performed at temperatures ranging from 25oC to 50oC and solid volume fraction range of 0 to 0.6%. The measurements revealed that the thermal conductivity of nanofluids enhances up to 23.3% with increase in concentration of nanoparticles and temperature. Moreover, efforts were made to provide an accurate correlation for estimating the thermal conductivity at various temperatures and concentrations. Deviation analysis of the thermal conductivity ratio was performed. The comparison between experimental results and correlations outputs showed a maximum deviation margin of 0.95%, which is an acceptable accuracy for an empirical correlation.

In the present study, vibration of cylindrical laminates with different layers and angles were studied. In order to actuate and polarize in radial direction, a piezoelectric layer was located at outer surface of composite shell. Laminates were assumed long enough so that plane strain state analysis in 2D can be used properly. In order to satisfy the boundary conditions, variables in terms of Fourier series were obtained. The governing equations reduced to ordinary differential equations at thickness direction and by power series method, the exact solution equations were obtained, unknown coefficient were calculated with rapid convergence. By using the matrix transfer method, vibration response of composite shell was obtained. Finally, results for the first seven modes of natural frequency of multi-layer cylindrical shells were obtained. In addition, for both state of one single piezoelectric layer and five layer shell at the end, some responses such as displacement, principal stress and strain were achieved.

In this study, a new method for joining aluminum tubes in subsurface structures using steel converting and aluminum welding are presented and reviewed. But near the weld area is under high thermal cycle and will cause residual stresses in heat affected zone. Therefore for assessment of proposed connection from the perspective of residual stress by using the finite element method welding of tubes has been modeled in three dimensions. Thermal history is determined from thermal analysis and then the residual stresses due to welding are calculated. Because of the sensitivity of subject, the simulation process and properties are validated. The mechanical and thermal properties have been considered as a function of temperature. According to current, voltage and speed electrode, heat flux is applied by Goldak's heat source model. The modeling results were good agreement with experimental results and show that the initiative plan can be used to connect aluminum tubes of subsurface structures.

After the invention of the automobile, people soon realized the relationship between air resistance and the movement of cars. Over time, the improved performance of the cars from different directions, aerodynamically improvement also became the fundamental question. The researchers found that attention to aerodynamics not only achieve higher speeds, but also appropriate to reduce fuel consumption and vehicle stability. This article will examine the effect of surface roughness underside of the vehicle at some points. In this method procedure we study on two zones which have maximum probability of separation flow. These zones find on rear of wheels on floor of vehicle that air flow leaves the automobile that rough sheets was attached And the results of these rough sheets compare with case of drag and lift test in wind tunnel. Results show that between speeds 15m/s to 35m/s drag force decreases about 6 percent.

Nowadays, Titanium-based alloys are among the most attractive metallic materials for biomedical applications (as implants) due to their non-biodegradability, low density, good mechanical properties as well as their good biocompatibility. Hydroxyapatite (Ca10 (PO4) 6 (OH) 2, HA) has been widely used for biomedical applications due to its bioactive, biocompatible and osteoconductive properties. Firstly, Ti-6Al-4V alloy was synthesized by mechanical alloy method with high energy ball milling plantery, HEBM. And then in this work began with preparing hydroxyapatite, HA, from bovine bones and continued with composite in Nano clay powder.At the end a hydroxyapatite–clay (HA/Clay) Nano composite ceramic, 80 wt.% of HA and 20 wt.% nano clay powder, was synthesized through a mechanical method, HEBM. The ability of apatite formation on the produced nanocomposite samples, as a yardstick for evaluation of the bioactivity, was estimated by using simulated body fluid. According to the results obtained mechanical and density values and bioactivity behavior, the sample containing 20 wt. % HA/Clay indicated the optimal properties in mechanical and bioactivity behavior. In fact, this Nano composite sample, Ti-6Al-4V/20 HA-clay, is good candidate for medical purposes, bone tissue applications.

Since the composite materials, especially with polymer matrix composite is vulnerable structures to injuries in the form of cracks and fractures Since the composite materials, especially. In recent years, new scientific efforts have been made to create an internal control unit, to be able to act autonomously in composite restorations. The theory is resilient Biologicallymatched resilient theory of shows, just as the deepest wounds cuts to heal itself, can claim to be all natural substances have the ability to repair its structure. In this paper, the study on the healing properties of the microcapsules contained in the composite capsular base is examined and to investigate the interaction between carbon nanotubes and energy from urea formaldehyde polymer as the base matrix resilient material base in the microcapsules contained in the capsule, the method theory density function. At first the effect of chirality and diameter of the nanotubes was investigated. After that different functional groups are placed on the nanotubes. Finally, the Young's modulus that is based on the strain energy in the elastic deformation range, was calculated.

Nowadays, light weight and high strength metals are being used in various industries such as automotive and aerospace. Using aluminum-magnesium alloys is an efficient way to reduce the weight of a specific part. These alloys have poor formability in room temperature thus they should be formed at elevated temperature. Warm hydroforming and hot metal gas forming are conventional methods to form aforementioned alloys. It is proven that using hammering pressure is an efficient way in order to optimize hydroforming process that it improves formability and thickness distribution. In this paper, the effect of hammering pressure on hot free bulging of an Al6063 tube is investigated numerically and the results are compared with the results of constant pressure path. Results show that reduction of thickness is greater for peak constant pressure while using hammering pressure, due to gradual thickness reduction, could improve formability and thickness distribution. Results also show that axial feeding, increase the effect of formability caused by hammering pressure.

In this article, failure and fracture mechanisms in an aluminum alloy (which has been used in diesel internal combustion engines), with and without ceramic thermal barrier coatings, have been investigated under isothermal and non-isothermal fatigue loadings. In this research, the base material is an aluminum-silicon-magnesium alloy and the thermal barrier coating includes a metallic bond coat layer with 150 mm thickness and a top coat layer, made of zirconia stabilized 8%wt. yttria with 350 mm thickness, which is applied on the substrate by the plasma thermal spray method. In order to study the failure and the sensitivity analysis, isothermal fatigue tests (or low-cycle fatigue tests at constant temperatures) and non-isothermal fatigue tests (or out-of-phase thermo-mechanical fatigue tests) were performed on test specimens. Then, fracture mechanisms in the aluminum alloy, were investigated by the scanning electron microscopy. After checking the fatigue damage and the failure analysis, the sensitivity of the material lifetime was studied based on different parameters (the temperature and the strain). Based on obtained results, the fracture surface of the aluminum alloy had dimples and therefore, its fracture was ductile. In thermal barrier coating, the damage mechanism was the separation between the substrate and the bond coat layer. The highest sensitivity was related to the strain parameter in fatigue tests of the aluminum alloy (with and without coating).

Nowadays, atomic force microscopes are considered as useful tools in the determination of intermolecular forces and surface topography with the resolution of nanometers. In this kind of microscope, micro cantilever is considered as the heart of the microscope and is used as a measuring tool. Piezoelectric micro cantilevers are the new generation of the cantilevers among the common micro cantilevers that are used in atomic force microscopes. Having the ability to self-stimulate and self-measure, they have greater popularity among other cantilevers.This paper is aimed towards investigating the behavior of a piezoelectric micro cantilever with a triangular head, in self-measure mode and close proximity to the surface of a sample. Output charge from the piezoelectric layer and also the output current, in this mode, are considered as effective factors in themeasurement of the bending. The micro cantilever’s vibration behavior becomes nonlinear, as it approaches the surface of the sample. Surely the piezoelectric layer in the self-measure mode can be considered as a good measuring tool, only when it reflects the effects of the nonlinear interaction between the tip of the probe and the surface of the sample in its measurements. In order to investigate this matter, first the differential equations that are ruling over the vibrating movements of the piezoelectric micro cantilever with a triangular head are transformed into normal nonlinear differential equations using the Galerkin method. Then the resulting nonlinear differential equation is solved using the multiple scale method. After solving the governing differential equation of the problem, the micro cantilevers behavior in the proximity of the surface of the sample is simulated and the effect of factors such as balancing distance, oscillation modes and the substance of piezoelectric layer are investigated.

Magnesium and its alloys are light, biodegradable, biocompatible metals that have promising applications as biomaterials. Magnesium is potentially useful for orthopedic and cardiovascular applications. However, the corrosion rate of this metal is so high that its degradation occurs before the end of the healing process. One of the ways to improve the corrosion rate isto compose it’s with ceramic materials such as HA. In this study, at first the alloy with a nominal composition of Mg-3%Al-1%Zn (AZ31 alloy) was produced by high energy ball milling (HEBM) of Mg powder, Zn powder and Al powder under high purity argon. The ball milling parameters were chosen following: shaft rotation was 600 rpm, ratio of balls to powder was 20: 1 and milling time was 2, 4 and 6 h under argon atmosphere. The Mg alloy powders obtained were pressed with different amounts of HA-Zeolite nano composite powder, weight ratio HA (Hydroxyapatite) to Zeolite 4: 1, HZ, under 1000 MPa in steel die with 10 mm in diameter and 20 mm in height. The samples pressed were sintered for 1 h at 630 K in an inert atmosphere furnace. Microstructure characterization of as-milled powders and as-sintered alloys were carried out by SEM. An X-ray diffraction (XRD) was used for phase analysis. It means that powder obtained is nano structure. Mechanical strength and El. % improved up to approximately 50% and 40% by in AZ31/HZ bio- composite samples containing 20 wt. % HZ. So, this nano biocomposite is good candidate for orthopedic medical applications.

Ti-6Al-4V titanium alloy has great application in medicine and military industries due to its capabilities, namely high strength to weight ratio and corrosion resistance. In the current research, the effect of aging treatment on microstructure and wear behavior of Ti-6Al-4V titanium alloy was investigated. Pin on disk wear test was applied to assess the wear behavior. Specimens were first solution treated at 950oC and 1050oC and then were quenched and aged. Some specimens were annealed before aging at 700oC. The results showed that aging treatment resulted in the hardness increase and the wear resistance decrease. It was also observed that annealing treatment before aging, enhanced the martensite decomposition and the formation of a2 particles, and correspondingly resulted in more hardness and lower wear resistance. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses confirmed that presence of hard phase a2 particles within soft beta phase was the main reason for wear resistance decrease.

 “Comeld” is a novel technology which can be applied in connecting composites and metals by manufacture of an array of metal pins on the metal part and layup the composite layers on the pins to make an adhesive and mechanical Joint at the same time. The aim of this paper is an experimental, numerical and analytical investigation on strength of comeld joint system and also to calculate the stiffness properties of composite after comeld process. Experimental test were carried out with fabrication of 21 specimens of comeld and uncomeld joints with different geometry and arrays of pins. Samples were tested under pure tensile loading. For the numerical simulation and investigation, the commerical software ABAQUS has been used and the tensile test were carried out to model a 3D Simulation of the joints considering adhesive behaviour. The analytical investigation was focused on the calculation of laminate stiffness properties after comeld process and the results were calculated using MATLAB capabilities. The results of experimental tests showed a good agreement with those of numerical results. The results show that the comeld joint system has a high potential for effective joining of metal and composite.