JOURNAL OF SIMULATION AND ANALYSIS OF NOVEL TECHNOLOGIES IN MECHANICAL ENGINEERING (JOURNAL OF SOLID MECHANICS IN ENGINEERING)
Year:2016 | Volume:9 | Issue:1 |Papers Count:15

In this paper, an attempt is made for solution of free vibration analysis of annular plate reinforced with carbon nanotubes for Uniformly Distribution (UD), resting on an elastic foundation using a refined theory presented. In this theory, a parabolic distribution of shear stress and strain in the thickness direction and satisfies the boundary conditions of zero shear stress on the upper and lower crust cut without using a correction factor to be considered. The equations of motion are obtained using Hamilton's principle. And then these equations are solved by GDQ method.Factors affecting the frequency such large radius to small radius, the ratio of thickness to the radius of the annular plate, the length of the radius is obtained. To check the compatibility equations and solving method is used, a comparison between the present work has been done with papers.

The stress distribution on crack tips and the stress intensity factor on them are the main courses in the fracture mechanic. The stress intensity factor of the cracks with the different exited loads and geometries are listed in the tables of the standard book tables. In all of them, the cracks are located in the central position in the plates. In the case that, the exited load is concentrated the stress distributions is not uniform and vanish in the different point on the plate. Therefore, the stress intensity factor of the crack, changes with the displacement of the crack line from load. In this paper, the stress intensity factor calculated with the change of the crack displacement from load point. A new relation is introduced from the simulation results with the Abaqus. Also, the analytical solution was used from the linear fracture mechanic theory and Another function and relation were determined. These two relations from Abaqus and the analytical method were compared and finally more accurate relation was introduced as the relation of the stress intensity factor of the crack in term of the distance from point load.

Considering their suitable strength and ability to properly stabilize, metal screws are used to repair bone fractures. However, problems such as osteoporosis due to high elasticity of metals relative to bones, and local infections caused by releasing metallic ions have motivated research on replacing metallic screws with non metallic ones. Use of bioresorbable screws could eliminate disadvantages associated with metals such as removal operations, corrosion and stress shielding. In this study, the composite containing poly-l-lactic acid and bioactive glass fibers were considered for the design of the screw using ABAQUS software (V6.11). The elastic constants were first estimated in micro analysis then transferred to macro analysis for modeling in two-layer situations composed of unidirectional fibers and random fibers (UD/R) and also for modeling in three-layer situations composed of unidirectional fibers, fibers with an angle of ±20 degree in relation to force vector, and random fibers (UD /±20/R) with various percentages of layer thickness. Results show that in the analysis with %65 layers of unidirectional fibers, %10 layers by fibers with an angle of ±20 degree, and %25 of layers with random fibers, flexural modulus, flexural strength, and longitudinal elasticity coefficient were estimated about 22.7 GPa, 347 MPa, and 24.8 GPa respectively, the last one being slightly higher than that of cortical bone. Considering similar results for cortical bones, our designed composite screws are robust enough to replace metal screws for repairing orthopedic fractures.

Carbon / epoxy composite is one of the most useful polymer matrix composites that has special properties such as high strength-to-weight ratio, high hardness, high corrosion resistance.Resistance to nuclear radiation has high consumption in different industries such as aerospace industry and therefor monitoring of loading of this type of composite is important. In order to determine failure mechanisms, acoustic emission method has more performance than other non-destructive methods. In this research acoustic emission method was used to evaluate and monitoring of the carbon epoxy composite three point bending load. For this purpose bending behavior of composite and relationship between acoustic signals was studied. Using both fast Fourier transform and wavelet transform method in this research, which led to the same result. Using FFT maximum frequency 140 KHZ was determined, that wavelet transform was confirmed this result too. Time limits that events was occurred on the under load specimen, was monitored by online diagrams that obtained from acoustic system. Finally failure mechanisms of composite were confirmed by SEM pictures. Time limits and ascending progress of diagrams validates bending diagram.

In this paper, the nonlinear vibration analysis of a thin cylindrical shell made of Functionally Graded Material (FGM) resting on a nonlinear viscoelastic foundation under compressive axial and lateral loads is studied. Nonlinear governing coupled partial differential equations of motions (PDEs) for cylindrical shell are derived using improved Donnell shell theory. The equations of motions (EOMs) then are solved using the Galerkin method, Volmir’s assumption and the forth-order Runge-Kutta method to obtain dynamic response of the shell including nonlinear frequencies, frequency-amplitude curves and nonlinear radial deflection for the shell of revolution. Afterward, the effect of changing the value of different parameters on the nonlinear dynamic response of the FGM cylindrical shell considering compressive axial and lateral loads, geometric characteristics of the shell, FGM material distribution along direction of the thickness of the shell and coefficients of the viscoelastic foundation are all investigated.

Electrical discharge machining process is one of the most Applicable methods in Non-traditional machining for Machining chip in Conduct electricity Piece that reaching to the Pieces that have good quality and high rate of machining chip is very important. Due to the rapid and widespread use of alloy DIN1.2080 in different industry such as Molding, lathe tools, reamer, broaching, cutting guillotine, etc. Reaching to optimum condition of machining is very important. Therefore the main aim in this article is to consider the effect of input parameter such voltage, Current strength, on-time pulse and off-time pulse on the machining chip rate and optimizing this in the electrical discharge machining for alloy DIN1.2080. So to reach better result after doing some experiments to predict and optimize the rate of removing chip, neural network method and genetic algorithm are used. Then optimizing input parameters to maximize the rate of removing chip are performed. In this condition, by decreasing time, the product cost is decreased. Optimum parameters in this experiment in this condition are obtained under Current strength 20 ampere, 160 volt, on-time pulse 100 micro second and off-time pulse 12 micro second that is obtained 0.063 cm3/min as rate of machining chip. After doing experiment, surveying the level of error and its accuracy are evaluated. According to the obtained error value that is about 5.18%, used method is evaluated for genetic algorithm.

Structural health monitoring is a developing research field which is multifunctional and can estimate the health condition of the structure by data analyzing and also can prognosticate the structural damages. Illuminating the damages by using piezoelectric sensors is one of the most effective techniques in structural health monitoring. Pressurized equipments are very important components in process industries such as oil, gas, petrochemical and power plants, that their health monitoring is vital. The aim of this research is to introduce a technique to illuminate the damages in these equipments by using guided waves. Thereby, two different specimens were used as pressurized vessels at different conditions: pristine and corroded. Different internal pressures were also studied. Piezoelectric transducers were electromechanically coupled to the vessels and the guided waves were propagated by using pitch-catch method. The outcomes indicated that damage parameters in vessels such as corrosion and pressure changes have considerable effect on the signals that piezoelectric sensors receive. Corrosion, the most common damage in pressurized vessels, reduce the signal domain in frequency field to 11%. Also increasing pressure reduce the signal domain. We can used these outcomes to innovate a technique for structural health monitoring of pressure equipments.

Loading conditions and complex geometry have led the cylinder heads to become the most challenging parts of diesel engines. One of the most important durability problems in diesel engines is due to the cracks valves bridge area. The purpose of this study is a thermo-mechanical analysis of cylinder heads of diesel engines using a two-layer viscoplasticity model. The results of the thermo-mechanical analysis indicate that the maximum temperature and stress exist in the valves bridge. The results of the finite element analysis correspond with the experimental tests, carried out in references, and illustrate the cylinder heads cracked in this region. The results of the thermo-mechanical analysis show that when the engine is running the stress in the region is compressive caused by the thermal loading and combustion pressure. When the engine shuts off the compressive stress turns into the tensile stress because of assembly loads. The valves bridge is under the cyclic tensile and compressive stress and then is under low-cycle fatigue. After several cycles the fatigue cracks will appear in this region. The lifetime of this part can be determined through finite element analysis instead of experimental tests. Viscous strain is more than the plastic strain which is not negligible.

In this paper, a discontinuity in beams whose intensity is adjusted by the spring stiffness factor is modeled using a torsional spring. Adapting two analyses in strong and weak forms for discontinuous beams, the improved governing differential equations and the modified stiffness matrix are derived respectively. In the strong form, two different solution methods have been presented to make an analogy between the formulation of the Euler-Bernoulli and Timoshenko theories that indicates the influence of the shear deformation in discontinuous beams. The flexural stiffness of discontinuous beams is corrected by using theDirac’s delta function. In the weak form, the reduced stiffness matrix is derived from the strain energy equation established by the continuity, kinematics and constitutive equations. The linearity assumption of the geometry and material is considered to construct the kinematics and constitutive equations respectively. The continuity conditions mathematically connect two divided parts of the Euler-Bernoulli beam for which an improved Hermitian shape function is employed to interpolate displacement field. An application shows the comparison and validation of the results of the strong and weak forms, and also the static behavior of discontinuous beams.

Mixed convection of Cu-Water nanofluid is studied numerically in a shallow inclined enclosure by applying lattice Boltzmann method. The D2Q9 lattice and internal energy distribution function based on the BGK collision operator are used in order to develop the thermal flow field. The enclosure's hot lid has the constant velocity of U0 while its cold lower wall has no motion. Moreover, sidewalls are taken in to account as adiabatic ones. At 3 modes of convection heat transfer (free convection, force convection and mixed convection), the effects of volume fraction and inclination angle of enclosure are studied for different values of Reynolds number as equal to 10 and 100. Comparison of achieved results as like the streamlines, isotherms and profiles of velocity and temperature versus pervious available ones, implies the appropriate agreement. It is seen that more amount of volume fraction and enclosure inclination angle at the state of free convection would correspond to higher Nusselt number. The incomes of present work show the suitable performance of lattice Boltzmann method in order to simulate the nanofluid mixed convection in an inclined enclosure.

One of the recently considered applications of fiber optic, in their usage in building lighting systems. In this research, in order to reduce energy consumption, by transmission of sun light from the roof to the desired place (i.e. an office), the required standard luminance is produced. The main aims of this research are: 1. Reduction of energy consumption.2. Making the place compatible with the human favorable mental conditions and environment.3. Preparing the basics of mass production of the system and economical benefits for the university In this research besides concentrating the sun light to magnify its density, some investigations are made for light transmission by fiber optics, because, no mathematical model was found for this per pose, practical tests are made in addition to statistical analysis.Using different lenses and fiber optics and a position control system (which specially designed for this research), many experiences was made and iluminances were measured by a lux meter. After that by SPSS V.17 software, the results were analyzed. Finally the best Lenz and fiber were selected and a straight forward method was presented for designing a typical office in such manner.

In this research, effect of nanoparticles diameter on free convection of aluminum oxide-water was investigated in a cavity by single phase and two phase models. The range of Rayleigh number is considered 105-107 in volume fractions of 0.01 to 0.03 for nanoparticles with various diameters (25, 33, 50 and 100 nm). Given that the two phase nature of nanofluids, necessity of modeling by this method is increasing. Single phase approach (in contrary of two-phase modeling) for nanofluids is based on that the behaviors of each two solid phase (nanoparticles) and liquid phase (base fluid) are completely similar. In this study, Eulerian-Eulerian approach and mixture model was used given that Brownian motion and thermophoresis effects. Brownian motion and thermophoresis creates under influences of volume fraction gradient and temperature gradient, respectively that cause to creating slip between nanoparticles and base fluid; thus, kind of non-uniformity creates on behavior between nanoparticles and base fluid. This non-uniformity leads to significant effects on results of two phase modeling that creates better agreement to single phase modeling with experimental results. Results indicate that heat transfer decreases with increasing diameter and volume fraction of nanoparticles. Also, effect of nanoparticle diameter on flow and heat transfer is tangible.

Since the cutting tools used in machining process of super alloys are subjected to high cutting forces, accordingly tools life is reduced, therefore improvement in alloys machining and reducing cutting forces to achieve longer tools life is an essential necessity. In this research, the effect of changes in feed rate on cutting forces in machining process of nickel based super alloys is investigated. Cutting tools used in this experiment was a tungsten carbide material, model 890, geometry square shaped and specification of SNMG 120412. Also the tools has been coated using physical vapor deposition by chemical composition of TiN/TiCN/AlTiSiN in both micro and nano layer conditions. According to the results, as the feed rate is increased cutting forces mostly increases in both micro and nano layer coating conditions.. Generally in this research, application of micro layer coating results in less cutting forces compared to nano layer coating, so it can be said that micro layer coating has a better performance.

Today, the expansion of the Federation of Automobile racing car increases the competition of Go-kart. Go-kart is one of the best and safest car racing competitions. A history of nearly a century in the world. Go-karts are tiny car that can be controlled with good stability on the road and curved path for drivers bring excitement and exhilaration. Stability and control when crossing the road bend are the important parameters in designing Go-karts that the designer should always keep in mind. In this paper, the Go-kart vehicle is simulated in numerical software and then the simulation is versified with experimental test with a Go-kart that is developed in Islamic Azad university, Khomeinishahr Branch.

The purpose of this article is modal analysis of ionic polymer metal composite beams, then briefing the system to the unique parameters to help in up modeling of the actuator. In this paper at first using of Mathematical analysis andClosed form transfer function of cantilever beam dynamic response to the forces of different inputs (intensive and continuous) is calculated and for different types of systems resonance and anti-resonance points in frequency analysis are found, then with using modal analysis of system the entire response is briefed in the basic mode and parameters of un-damped natural frequency and damping coefficient in this mode is to introduced for the system, after the cantilever composite beam considered as an operator with the input voltage, displacement and produces a force on the free end, By observing the behavior of the system, analyzed responses to the inputs.