International Journal of Advanced Design and Manufacturing Technology
Volume:8 Issue: 1, Mar 2015

A plain strain analysis of frictional rolling contact on an elastic graded coating is presented in this paper. Finite element method is applied to gain an understanding of the stresses and contact zone properties caused during rolling contact. The effects of friction, material stiffness ratio and coating thickness on stresses in contact zone and coating/substrate interface are studied. Shear modulus of softening and stiffening graded coatings change with exponential, power law and linear functions. The substrate is homogenous and the rigid cylindrical roller moves in a steady state condition with constant velocity. The coating is modeled in multi layers and a 2-D hard contact of rolling surfaces is considered. The analytical results verify the present method and show a good agreement. It is shown that thinner thicknesses have more effects on stresses and energy density, but these effects are not seen for thicknesses larger than a specific limit.

Ultrasonic Vibration assisted Single Point Incremental Forming (UVaSPIF) process is an attractive and adaptive method in which a sheet metal is gradually and locally formed by a vibrating hemispherical-head tool. The ultrasonic excitation of forming tool reduces the average of vertical component of forming force and spring-back rate of the formed sample. The spring-back phenomenon is one of the most important geometrical errors in SPIF process, which appear in the formed sample after the process execution. In the present article, a statistical analysis and optimization of effective factors on this phenomenon is performed in the UVaSPIF process based on DOE (Design of Experiments) principles. For this purpose, RSM (Response Surface Methodology) is selected as the experiment design technique. The controllable factors such as vertical step size, sheet thickness, tool diameter, wall inclination angle, and feed rate is specified as input variables of the process. The obtained results from ANOVA (Analysis of Variance) and regression analysis of experimental data, confirm the accuracy of mathematical model. Furthermore, it is shown that the linear, quadratic, and interactional terms of the variables are effective on the spring-back phenomenon. To optimize the spring-back phenomenon, the finest conditions of the experiment are determined using desirability method, and statistical optimization is subsequently verified by conducting the confirmation test.

In this paper, a simple and efficient method for modeling and solving the equations of a rotor with any number of disks, bearings and mass unbalances is presented using the assumed modes method. This model consists of a continuous shaft, arbitrary number of mass unbalances in any axial location and phase angle, and any number of rigid disks and bearings. This arrangement is extensively used in diverse applications. In this study, final governing differential equations are not derived because the assumed modes method is directly inserted to solving process. Some examples in both cases of free and forced vibration are performed. The results show the accuracy of this modeling and the ability of it to predicting the vibration behavior of the rotor in a complex combination of shaft, disk and bearing. This study also shows that the present approach can give the results as accurate as the most popular approach, i.e. the Finite Element Method.

This paper presents a hybrid method for the optimization of forging process of an aerofoil blade. Preform shape and die parting-line angle are optimized in order to minimize the volume of the unfilled die cavity, material waste, forging forces. The overall optimization scheme used in this research work includes a multi-objective approach that is combination of response surface and finite element methods. The results show that the proposed approach is a suitable method for optimization of the forging process of aerofoil blades.

This paper describes a modified structural dynamics model for aeroelastic analysis of high-aspect-ratio wings undergoing large deformation behavior. To gain this aim, a moderate deflection beam model is modified with some important large deflection terms and then coupled with a state space unsteady aerodynamics model. Finite element method is used to discretize the equations of motion. A dynamic perturbation equation about a nonlinear static equilibrium is applied to determine the flutter boundary. The obtained results show good agreement in comparison with the other existing data such as high-altitude long-endurance (HALE) wing and Goland wing. It is found that the present aeroelastic tool have a good agreement in comparison with valid researches and also considering the effect of the geometric structural nonlinearity and higher order nonlinear terms on the flutter boundary determination is very significant.

In this study, changes in speed and turbulence intensity in the wake of a Peugeot model and the drag coefficient changes with increases vehicle speed in Unsteady Flow Measured and evaluated. The blow open circuit wind tunnel to simulate fluid flow is used. Disturbances and nominal maximum speed of the device, respectively is, 30 m / s and 0.01%. Has been continuously increasing speed by an inverter Causing changes in rotational speed of the electric motor, wind tunnels. The results showed three different regimes in the velocity profile of the wake model and the location near the model with increasing distance from the model and with increasing Speed, three regimes in the wake are close to each other. Turbulence intensity is measured in the wake and drag coefficient by increasing the flow Speed decreased and reached a minimum value and then increases.

Strip tearing during cold rolling process has always been considered among the main concerns for steel companies. Several works have been done so far regarding the examination of the issue. In this paper, experimental data from cold rolling tandem mill is used for detecting strip tearing. Sensors are placed across the cold rolling tandem mill. They receive information on parameters (such as angular velocity of the rolls, voltage and the electrical current of electrical motors driving rolls, roll gap, and strip tension force between rolls) directly from the cold rolling tandem mill and save as files. The information included two modes: perfect rolling and ruptured rolling. A neural network was designed by means of MATLAB software and, then, trained using the information from files. Finally, the neural network was examined by new data. It was concluded that neural network has high accuracy in distinguishing between perfect and defected rolling.

The occurrence of chatter vibrations in boring operation has a great influence in improving workpiece dimensional accuracy, surface quality and production efficiency. In this paper instability analysis of machining process is presented by dynamic model of boring machine. This model, which consists of machine tool’s structure, is provided by finite element method and ANSYS software. The model is evaluated and corrected with experimental results by modal testing on boring machine in which the natural frequencies and the shape of vibration modes are analyzed. The natural frequencies of this modal testing are extracted through Pulse Labshop and ME’scope modal analysis software.Finally, the stability lobes obtained from this model are plotted and compared with experimental results.

In this research, the compositing of the surface of AZ31B magnesium alloy with CNT was studied by FSP. The parameters under study were rotational speed (500-1500 rpm), transverse speed (12-44 mm/min), number of passes (1-4), and CNT weight fraction (0-2%). Microhardness testing, optical metallography, FESEM, and EDS analysis were employed for the characterization of the samples. The suitable limits for the transverse speed and rotational speed were 12-24mm/min and 870-1140 rpm, respectively. The highest hardness in the FSP without compositing was assigned to the transverse speed of 24 mm/min and rotational speed of 870 rpm with a hardness of about 60 Vickers and the stir region grain size of less than 5 microns. The Zener-Holman parameter was calculated for computation and the least value was related to the conditions of the transverse speed of 12-24 mm/min and rotational speed of 870 rpm; as a result, the samples with the finest grain size were theoretically and experimentally specified. The most homogenous structure with the highest hardness was related to the three-pass state with a hardness of 69 Vickers. The best rate was the CNT weight percentage with a %2 weight enjoying the highest hardness. The FESEM images confirmed the suitable distribution of CNTs in the background after the performance of the three-pass processing.

In this paper the effect of block shape Vortex Generators (VGs) on an air-water fin-tube heat exchanger has been studied experimentally using exergy analysis method. Also the effect of these VGs on increasing heat transfer rate has been simulated numerically and the Results show a good agreement with the experiments. In this research we used a wind tunnel to produce wind flow over heat exchanger in the range of 0.054 kg/s to 0.069 kg/s. Hot water was circulating with the steady volume flow rate of 240 L/h and the temperature of 44 to 68 centigrade in the system. These experiments have been repeated with and without VGs on the heat exchanger. Results show using the VGs has reduced Air Side Irreversibility to Heat transfer Ratio (ASIHR). To reveal the effect of VGs on heat exchanger performance with respect to reducing ASIHR, a quantity is used namely Performance of Vortex Generator (PVG). The results represent that PVG values are in the range of less than 15% to over 35% which represents the good effects of VGs on the heat exchanger performance.