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Feed provided by ADMT Journal. Click to visit.Investigating the Performance of Coated Carbide Insert in Hard Steel Helical Milling
http://admt.iaumajlesi.ac.ir/article_543450_115254.html
Helical milling is an alternative hole-making machining process which presents several advantages when compared to conventional drilling. In the helical milling process, the tool proceeds a helical path while rotates around its own axis. Due to its flexible kinematics, low cutting forces, tool wear, and improved borehole quality may be achieved. In this study, a new helical milling process to create holes in hardened steel with a hardness of HRC 52 was used. Carbide inserts with PVD TiN coating were applied. Input parameters including cutting speed and feed rate were considered in 4 and 2 levels, respectively. In order to increase the reliability of the results, experiments were repeated 4 times and the total of 32 tests were performed. Other cutting parameters, such as axial and radial depth of cut were constant. Machining process was performed in dry state and without any lubricant. Output characteristics were tool wear, surface roughness, cutting force, machining time and material removal rate. Tool wear, surface roughness and forces, were measured by tool maker microscopy, roughness tester and dynamometer, respectively. The results showed that increasing the cutting speed on this type of hardened steel, decreases the surface roughness, machining forces and machining time. However, increasing the cutting speed and the feed rate enhances the tool wear and material removal rate considerably. Cutting speed and Feed rate of 50 m/min and 0.05 mm/tooth, offered the best mechanical properties of the Machining.Fri, 31 Aug 2018 19:30:00 +0100Nonlinear Vibration Analysis of FG Nano-Beams in Thermal Environment and Resting on Nonlinear ...
http://admt.iaumajlesi.ac.ir/article_543451_115254.html
In present research, nonlinear vibration of functionally graded nano-beams subjected to uniform temperature rise and resting on nonlinear foundation is comprehensively studied. The elastic center can be defined to remove stretching and bending couplings caused by the FG material variation. The small-size effect, playing essential role in the dynamical behavior of nano-beams, is considered here applying strain-inertia gradient and non-local elasticity theory. The governing partial differential equations have been derived based on the Euler-Bernoulli beam theory utilizing the von Karman strain-displacement relations. Subsequently, using the Galerkin method, the governing equations is reduced to a nonlinear ordinary differential equation. The closed form analytical solution of the nonlinear natural frequency is then established using the homotopy analysis method. Finally, the effects of different parameters such as length, nonlinear elastic foundation parameter, thermal loading, non-local parameter and gradient parameters are comprehensively investigated on the FG nano-beams vibration using the homotopy analysis method. As the main results, it is observed that by increasing the non-local parameter, the frequency ratio for strain-inertia gradient theory has an increasing trend while it has decreasing trend for non-local elasticity theory. Also, the nonlinear natural frequencies obtained using strain-inertia gradient theory are greater than the results of non-local elasticity and classical theory.Fri, 31 Aug 2018 19:30:00 +0100Geometrical Effects of Duct on the Entropy Generation in the Laminar Forced Convection ...
http://admt.iaumajlesi.ac.ir/article_543452_115254.html
In this research paper, irreversibility analysis of laminar forced convection flow in a duct with variable cross-section are numerically studied. Two-dimensional Cartesian coordinate system is used to solve the set of governing equations and also the blocked-off method is considered for simulation of the inclined surfaces. To obtain the velocity and temperature fields, the basic equations are numerically solved using the finite volume method and SIMPLE algorithm. To determine the flow irreversibility, the entropy generation number is calculated according to the thermodynamic second law. The geometrical effects of duct on the distributions of streamlines, friction coefficient, Nusselt number, entropy generation, and Bejan number are presented with details. The results show that the duct heights and inclination angle of surfaces have great effects on the flow irreversibility and the hydrodynamics and thermal behaviours. Also, comparison of the present numerical results with the available data published in the open literature shows an excellent consistency.Fri, 31 Aug 2018 19:30:00 +0100Sensitivity Analysis for Optimal Design of Multibody Systems with Clearance Joint
http://admt.iaumajlesi.ac.ir/article_543623_115254.html
This paper deals with the sensitivity analysis and optimization of system parameters for a classical slider-crank mechanism as a multibody system which includes a clearance between the joints of coupler and slider. Due to the nonlinearity involved in the dynamics of clearance joints, the base reaction force, exerted on the base from the crank, changes roughly and does not vary as smooth as the case of the mechanism with ideal joint. Variation of the base reaction force can be a measure of the undesired vibrations induced due to the effect of clearance joint. After deriving the equations of motion and modeling the clearance, the direct differentiation method is used to conduct a local sensitivity analysis to assess the sensitivity measure of the base reaction force on some kinematic and contact parameters. The results show that the reaction force is more sensitive to the variation of link lengths and link masses compared to the variation of contact surface characteristics such as Young’s modulus, restitution coefficient and contact generalized stiffness in most parts of the motion cycle. On the other hand, the sensitivity of the base reaction force to the clearance size is very higher than its sensitivity to the above-mentioned kinematic and contact properties. Finally, based on the results of the sensitivity analysis, an optimization procedure is used to reduce the amount of the maximum base reaction force by choosing the optimized link lengths.Fri, 31 Aug 2018 19:30:00 +0100Evaluating the Effect of Operating Conditions on Temperature Variation Rate of Inner Walls and ...
http://admt.iaumajlesi.ac.ir/article_544975_115254.html
For rolling pneumatic tires, the thermal induced effects are mainly resulted from the visco-elastic behaviour of rubber parts and dissipation of stores strain energy during the cyclic deformations. It is noted that the operating conditions crucially contribute to the rubber hysteresis effect and temperature development in a rolling tire. In the current study, an elaborated 3D FE model is worked up for simulating the certain inflation pressure, loading and velocity conditions for a specified radial tire. Special emphasis is given to transient temperature distribution of interior walls and tire cavities as critical zones. Compared with the experimental tests, the current study gives satisfactory results for the time rate of change in the temperature of tire walls and inside inflated air.Fri, 31 Aug 2018 19:30:00 +0100Thermal Optimization of an Array of Needle-Shaped using Constructal Theory
http://admt.iaumajlesi.ac.ir/article_544976_115254.html
In the present paper, the constructal theory is employed to determine the optimal configuration of three rows of needle-shaped fins. The heat transfer across the fins is due to laminar forced convection. Second order upwind scheme is used for discretization of the diffusion terms of governing equations. The pressure–velocity coupling is performed using the SIMPLE algorithm. The heat transfer is optimized subject to constant fin volume. The effect of Reynolds number and thermal conductivity on the optimal configuration is investigated. The results obtained from the present simulations are in good agreement with the numerical results. The results show that pin–fins flow structure leads to the best performance when the pin–fin diameters and heights are non-uniform. At Re = 100 and 200, the optimal value of is 1.3. It is revealed that at Re = 50, the optimal value for is approximately 1.1. The results demonstrate that heat transfer rate is an increasing function of the Reynolds number. Fri, 31 Aug 2018 19:30:00 +0100