International Journal of Advanced Design and Manufacturing Technology
Volume:7 Issue: 4, Dec 2014

Intermetallic phase formation and oxidation reaction during combustion synthesis (CS) of Ni-Ti equiatomic mixture are affected by mechanical activation (MA) and pre-heating conditions. Important parameters are ignition time, reaction duration, temperature rise, microstructural change, titanium oxidation and intermetallic phase formation. Superelasticity and shape memory effects are influenced by two-stage austenite-rhombohedral and rhombohedral-martensite transformations detected by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) of the combusted samples. Tension tests indicated superelastic behavior after 1 h, production of Ni3Ti after ½ h and delayed superelastic/thermoelastic behavior after 2 h MA. Results indicate that pre-combustion heating fosters mono-phase formation and titanium oxidation; while mechanical activation lowers ignition-start-time, synthesis-duration and Ni3Ti formation.

Sewing is one of the most commonly used manufacturing processes in the world. In the textile industry, development of sewing machines with optimal mechanical performance is very important. Obviously, the quality of sewing, the increase of the needle transmission force and the optimal mechanical advantage are greatly dependent on the design criteria of the needle driving mechanism. Unfortunately, despite the importance of this topic, very limited number of researches has been carried out in this regard. Therefore, in this paper, first a newly developed needle driving mechanism of a sewing machine is introduced. Then, the concepts of transmission angle and mechanical advantage are described. Next, the multiobjective constrained optimization process of this mechanism using the genetic algorithm is explained. For this purpose, some objective functions are presented to reduce the needle generated heat by minimizing the needle velocity in the penetration zone, to reduce undesirable vibrations by minimizing the needle jerk, and to increase the mechanical performance by maximizing the mechanical advantage and minimizing deviations of the transmission angle from its ideal value. Results confirm improvement of the required design criteria of the newly developed mechanism in this study

Owing to elastic and viscous characteristics embedded rubber compounds, the dissipated energy from periodic deformation is converted into heat generation and consequently, the tire may have different body temperatures for different operating conditions. In most performed investigations, just temperature distribution is considered and the mechanical behaviour of rubber parts which are highly temperature-dependent is ignored. In this study a 3D finite element model is used for evaluating the effects of loading conditions and rubber temperature on mechanical behaviour of tire. Comparing with related published works, the results of presented study have a great accuracy and can provide a comprehensive analysis to avoid the temperature related failure.

The object of this work is to present a study of the thermomechanical behavior of the automobile disc brake for the prediction of their resistance to fatigue. Then, a study of purely mechanical dry contact between the disc and pads is developed with a good prediction becomes a major stake for the industrialists while modeling the loading and the boundary conditions around the disc.We used the same computer code to visualize displacements, total deformations in the disc, shear stresses, Von Mises stresses and, the tools of contact pads. We also studied the case of thermoelasticity while interpreting the various exits results during this simulation.

This work reports the effect of nanotube aspect ratio and waviness index on stress and displacement distributions of functionally graded nanocomposite cylinders reinforced by wavy single walled carbon nanotubes based on a mesh-free method. The mechanical properties of these composites are assumed to be graded along radial direction and estimate by a micro mechanical model. In the mesh-free analysis, moving least squares shape functions are used for approximation of displacement field in the weak form of motion equation and the transformation method is used for the imposition of essential boundary conditions. Effects of CNT waviness and aspect ratio, kind of distribution and volume fraction of carbon nanotubes and also boundary conditions and thickness of cylinder are investigated on the static responses of these cylinders. It is observed that CNT waviness has a significant effect on the effective reinforcement of the nanocomposites.

Dynamic analysis and study of Atomic force microscope in liquid environment is the main goal of this research. Hydrodynamic and squeeze forces act on Cantilever of Atomic force microscope which works in liquid environment, so. In this paper the effect of different environmental and physical factors had studied on frequency response diagrams. The importance of frequency response analysis is studying the possibility of occur a phenomenon which causes disturbance and decreases accuracy of imaging. Timoshenko beam model and finite element method had been used in order to simulation. Meanwhile interaction forces between sample and tip point in gas and liquid environment were also considered in simulations. Achieved results had showed that in comparison with gas, resonance frequency has decreased considerably in liquid environment which is due to additional mass of liquid and also amplitude is decreased in liquid environment that’s because of additional damping due to presence of liquid. Meanwhile several studies in repulsion and attraction area with more and less distance from equilibrium distance, had showed that in repulsion state, stimulation frequency is more than attraction area, that the reason is related to more hardness in repulsion area, and also the presence of interaction forces had caused that in zero excitation frequency, amplitude isn’t zero.

In this study, the longitudinal shrinkage behavior of knitted fabrics during drying has been studied. In this context, a model is presented to predict the longitudinal shrinkage of plain knitted fabric during drying process. In order to model the shrinkage behavior, a 1DOF model consists of a mass, a linear spring and a linear damper have been used. In presented model the time-varying mass is considered due to fabric drying process. Nonlinear Equation of motion derived from the model have been solved using Three-order Straight Forward Expansion method. The results of the model were compared with the experimental results for five samples with different courses densities. The results shown that in high courses densities the presented model is capable enough to predict the longitudinal shrinkage of plain knitted fabric mass center during drying process. Error rate is 11.3 percent for the samples with high density. But with decrease in density, the error rate increases to 18 percent. Then the genetic algorithm is used to optimize the model. Using optimized model the simulated error rate fell into 5.7 percent for samples with high density and the rate fell to 6.1 percent with decrease in density.

In this paper, the effect of electric field on two-dimensional low Reynolds air flow around an airfoil and variation of the forces acting on the airfoil is numerically investigated. The electric current and Poisson’s equations are solved and the outcome is considered as a source term in the momentum equations. The energy equation is not considered due to its weak effect on the phenomena. The finite volume method is utilized to solve both the electrical and flow equations. The results demonstrate that the forces acting on the body can be altered and controlled by imposing high voltage electric field.

There exist simple theories to predict the strain of sandwich structures under a bending load and specific support conditions. Although theoretical predictions are highly effective, but the role of testing in validation of these theories and their progress is undeniable. The main goal of the present paper is to prepare a test instruction in order to minimize the error of data acquisition and their analysis. The effects of specimen thickness, place of strain gauge installation and kind of strain gauge was investigated. Characterization of mechanical properties of test specimens are another focus of the present study. Classic theories are used to validate the results of the tests. Based on the large number of tests conducted on the samples, the results show that an important source of error in between experimental and theoretical results may be incorrect installation of the strain gauge. A method to find this out, is to obtain the results of loading and unloading. The method of using the gauge factor of the strain gauge on the package gives better results. Using a circuit with three wires omits the error of wire resistance. The results of the tests on composite specimens obtained by TML Company strain gauges showed small differences with the results obtained by BLH Company strain gauges. The error between experimental and theoretical results in sandwich specimens increases by increasing the core thickness. The measurements obtained by strain gauge in compression is not reliable. An important result obtained was that a half-bridge installation of the strain gauge decreases the error so much.

In this paper, welding feasibility between AA1100, AA5050 and AA6082 aluminum alloys and A441 AISI steel by friction stir welding has been studied. Mathematical analysis of the heat generation during process showed that the maximum temperature produced in AA6082 aluminum alloy and A441 AISI joint but heat distribution in AA1100 aluminum alloy was higher than the other alloys. The investigation on joints windows concluded that the connecting link between AA1100 and A441 AISI steel was without any defect. Because of improper heat production and distribution in other joints, small tunnel was formed in the joints lower zones. Due to the softness of aluminums rather than steels, in tensile tests all joints were broken from the aluminum base metals. Strongest weld belonged to AA5050 aluminum alloy and A441 AISI steel joint that was about 84% of the aluminum base metal strength. Maximum joint efficacy based on A441 AISI has its place to AA6082 to A441 weld. Microhardness tests shows that welding line between AA1100 aluminum alloy and A441 AISI steel is harder that other joints.

A series of subsonic wind tunnel tests was conducted on an ogive-cylinder-flare configuration at zero angle of attack to study the effects of small helical protuberances on viscous drag reduction behavior. The experiments have been carried out on a smooth model and two wire-wrapped models with different spacing between the helical riblet rings, known as pitch length. In the present experiments, the pitch length to model diameter ratio for the wire-wrapped models were 0.5 and 1.0 and the velocity profiles at 19 streetwise locations as well as the pressure distribution on the model at the same positions have been measured and compared for the smooth model and the two wire-wrapped ones. The results show about %10 reduction in the local skin friction drag for the wire-wrapped model in comparison with the smooth one. The investigations also showed that depending on the boundary layer thickness, optimum values could be found for the riblet diameter and its pitch length for which, the maximum reduction would be achieved in the local friction drag.