Moharam Habibnejad korayem; A. Tajik; H. Tourajizadeh
Volume 6, Issue 2 , June 2013
Abstract
In this paper, a new approach to modify cable tension measuring mechanism is described; furthermore, the constructed boards which amplify load cell output are introduced. This approach has some advantages including of providing feedback for motors, evaluating the robot’s ultimate load carrying capacity, ...
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In this paper, a new approach to modify cable tension measuring mechanism is described; furthermore, the constructed boards which amplify load cell output are introduced. This approach has some advantages including of providing feedback for motors, evaluating the robot’s ultimate load carrying capacity, improving the motor control system and estimating the vibrating deflections of the end effecter final position. Close loop control of the robot and improvement its accuracy are of the objectives of this work. In addition, a new approach to transfer data from load cell to PC for a six Degree of Freedom (DOF) cable robot called ICaSbot is investigated. With neglecting cable mass, the value of cable length variation is estimated using cable tension theory in the specific path. The mechanism, the designed board and the sensors’ output and calibration equation are validated by the aid of a comparison study with simulation results of MATLAB for two different predefined paths
Suresh Babu Valeru; Tarasasanka Cherukuri
Volume 6, Issue 2 , June 2013
Abstract
In this study, behavior of pin-loaded glass fiber reinforced with polyethylene laminated composites with different stacking sequence and different dimensions has been observed experimentally and stress analysis was performed using ANSYS software. The aim is to investigate stresses, failure strength and ...
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In this study, behavior of pin-loaded glass fiber reinforced with polyethylene laminated composites with different stacking sequence and different dimensions has been observed experimentally and stress analysis was performed using ANSYS software. The aim is to investigate stresses, failure strength and failure mode of composite laminates containing a pin loaded hole when the material exhibits linear elastic behavior. The logical methodology for modeling the joint problem uses the two major steps:, failure analysis and stress analysis. Failure analysis is done experimentally and stress analysis is done by using ANSYS software. To investigate and verify to the analytical predictions of mechanical behavior, and to observe the failure characteristics of the pin-loaded composites, a series of experiments was performed with eight different material configurations, in all, over 36 specimens. The edge distance-to-hole diameter ratios and width-to-hole diameter ratios of plate were changed. For this part of study, layered composite materials were manufactured in our Institute. The stress distribution around the hole in pin-loaded glass-fiber with polyethylene laminate was performed, and In addition, ANSYS was performed to compare effects of different boundary conditions used to simulate the pin load on stress distributions around the hole.
Mohammad Akhondzadeh; Mehrdad Vahdati
Volume 6, Issue 2 , June 2013
Abstract
Air spindles are one of the main elements of precise machine tools. Vibration of these spindles is one of the vital issues necessary for investigation. Among parameters which influence air spindle vibrations are rotational speed, compression air method, input nozzle diameter, air gap pressure. In this ...
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Air spindles are one of the main elements of precise machine tools. Vibration of these spindles is one of the vital issues necessary for investigation. Among parameters which influence air spindle vibrations are rotational speed, compression air method, input nozzle diameter, air gap pressure. In this study using ANSYS, the effects of air gap thickness on air spindle vibrations have been investigated. In this simulation the air gap is modelled by numbers of linear springs. Then the effect of air gap thickness on air spindle vibrations has been investigated. Rotor externally rotates around stator. Simulation results indicate that for static and transient analysis the values of radial displacements of rotor reduce by decreasing spring length (i.e. rotor and stator gap), and its minimum value are equal to 3.634 µm and 15.6 nm, respectively. Because of constant spring stiffness, in modal and harmonic analysis, results for different spring length haven’t any variation and are equal to 1.053 mm and 23.7 nm, respectively.
seyed mehdi hoseini
Volume 6, Issue 2 , June 2013
Abstract
Engineering ceramics due to high-strength-to-weight ratio, wear and corrosion resistance, and high strength temperatures, in the industries especially in aerospace, automobile, electronics and computers are used widely. In attention to the increasingly usage process of these material, applying of conventional ...
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Engineering ceramics due to high-strength-to-weight ratio, wear and corrosion resistance, and high strength temperatures, in the industries especially in aerospace, automobile, electronics and computers are used widely. In attention to the increasingly usage process of these material, applying of conventional machining methods for producing machined into complex and desired shapes or making hole with high production ratio and adequate accuracy, are not suitable and it commonly has not enough output. Ultrasonic machining is a modern mechanical machining method that is appropriate to create holes in hard and brittle materials by means of an ultrasonically vibrating properly-shaped tool that exciting vertically on the workpiece and abrasive slurry. In this article modal analysis is used to choose the best shape for wave amplitude magnification and concentration. A desktop CNC milling machine is used to create feed motion control on ultrasonic head on a ceramic sample. Effects of input factors: power, abrasive grit size, slurry concentration and feed rate are analyzed by Taguchi method on the material removal rate (MRR), tool wear rate (TWR) and hole over size (HOS). The results imply that among input parameters, power has the most effect on MRR, also grit size and feed rate have the most effects on TWR and HOS.
Surinder Kumar
Volume 6, Issue 2 , June 2013
Abstract
This work presents an experimental investigation of the influence of the six important machining parameters (tool nose radius, tool rake angle, feed rate, cutting speed, cutting environment (dry, wet and cooled) and depth of cut) on surface roughness & material removal rate in the machining unidirectional ...
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This work presents an experimental investigation of the influence of the six important machining parameters (tool nose radius, tool rake angle, feed rate, cutting speed, cutting environment (dry, wet and cooled) and depth of cut) on surface roughness & material removal rate in the machining unidirectional glass fiber reinforced plastics (UD-GFRP) composite using carbide (K10) cutting tool during turning operation. Orthogonal L18 array in Taguchi method was employed to carry out the experimental work. ANOVA is performed for significant parameter and later Regression model is developed for the significant parameters. Validation (confirmatory) results indicate that the model is suitable for surface roughness & material removal rate during the study
ardeshir karami mohammadi; nasim ale ali
Volume 6, Issue 2 , June 2013
Abstract
In this paper the effects of non-linearity of suspension on dynamic behavior of a railway wheelset has been studied. This wheelset has four degrees of freedom that with two constraints it has reduced to two degrees of freedom. Vermeulen-Johnson theory has been used to calculate contact forces between ...
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In this paper the effects of non-linearity of suspension on dynamic behavior of a railway wheelset has been studied. This wheelset has four degrees of freedom that with two constraints it has reduced to two degrees of freedom. Vermeulen-Johnson theory has been used to calculate contact forces between wheel and rail. In this study the creep coefficients have considered constant. Any linearization has not been used for obtaining motion equations. Lateral suspension for these wheelset is dry friction which has been modeled by using Kolesch theory. Runge-kutta method has been used for solving these equations and results have presented to obtain limit cycles due to hunting behavior of wheelset.
Amin Etminan
Volume 6, Issue 2 , June 2013
Abstract
Flow structure and heat transfer characteristics around two-equal in-tandem square cylinders in the two dimensional laminar and turbulent flow regimes are simulated numerically for Reynolds and Prandtl numbers, Re=1-1×105, Pr=0.71, respectively. The investigation is based on an implicit finite volume ...
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Flow structure and heat transfer characteristics around two-equal in-tandem square cylinders in the two dimensional laminar and turbulent flow regimes are simulated numerically for Reynolds and Prandtl numbers, Re=1-1×105, Pr=0.71, respectively. The investigation is based on an implicit finite volume scheme for integrating the unsteady Navier-Stokes equations and use of standard κ-ε model to Reynolds stresses and scalar fluxes terms modelling. In this study, the instantaneous and mean streamlines, vorticity and isotherm patterns for different Reynolds numbers and distance between the cylinders are presented and discussed. In addition, the global quantities such as drag coefficients, RMS lift and drag coefficients, Strouhal number and Nusselt number are determined. An interesting phenomenon has been observed in the flow patterns depending upon the Reynolds number and the distance between the cylinders. A switch over in the nature of the fluctuations of the lift and drag coefficients has been also observed with the increase of Reynolds number and the distance between the cylinders. The numerical results are in good agreement with the experimental and numerical data available in the literature
Hamid Jahedi Amlashi
Volume 6, Issue 2 , June 2013
Abstract
In this work, a thermal energy storage system was designed and equipped with measuring instruments to study heat transfer characteristics and energy storage and release. In this system, a cubic container which is made of plexiglass was filled with dodecanoic acid as a phase change material. In order ...
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In this work, a thermal energy storage system was designed and equipped with measuring instruments to study heat transfer characteristics and energy storage and release. In this system, a cubic container which is made of plexiglass was filled with dodecanoic acid as a phase change material. In order to transfer heat to the storage container, a constant temperature heat exchanger was designed and mounted on the side of the container. Several experimental tests were conducted for both the melting process (energy charging) and solidification process (energy discharging) with setting the temperature at 60 and 70 degrees of Celsius for the former experiments and 15 and 10 degrees of Celsius for the latter ones. Result indicated that the maximum amount of stored energy was 209 kJ/kg in the charging process. Furthermore, the charging process time was reduced, at most, by 42% and the absorbed energy was increased 9% when the temperature of heat exchanger was increased 10°C. Also the discharging process time was decreased 9% as the temperature of heat exchanger reduced by 5°C.
S. Mohammad Reza Khalili; R. Eslami Farsani; V. Daghigh
Volume 6, Issue 2 , June 2013
Abstract
Changes in moisture content and temperature can perturb both stiffness and strength and as such the impact resistance of composite structures. In this paper, the pre-notched basalt fibre reinforced epoxy (BFRE) composite specimens are studied under Charpy impact loads in order to investigate the changes ...
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Changes in moisture content and temperature can perturb both stiffness and strength and as such the impact resistance of composite structures. In this paper, the pre-notched basalt fibre reinforced epoxy (BFRE) composite specimens are studied under Charpy impact loads in order to investigate the changes in impact energy absorption (fracture toughness) with different kinds of aging conditions. To create three types of aggressive environmental conditions, the specimens were frozen in dried air at T= -18 °C, frozen in tap water at T= -18 °C and kept in tap water at T= 30 °C and the results were compared with the specimen without aging influence (T= 25 °C). Water used for this examination has a high percentage of precipitation (70-80%) which causes high corrosion and consequent decrease in mechanical properties. The outcomes illustrated that the long-term exposure to tap water (T= 30 °C), dried air (T= -18 °C) and frozen in tap water (T= -18 °C) were all affected on energy absorption of BFRE composites, however, freezing effect in water was more intense. To study the nature of the failure mechanisms, all failed specimens were inspected by Scanning Electron Microscopy (SEM) photographs.
Hassan Farsijani; Mohsen Shafiei Nikabadi
Volume 6, Issue 2 , June 2013
Abstract
Machine-part family formation is one of major applications of group technology (GT). The machine cell formation problem in cellular manufacturing system (CMS) involves the decomposition of the manufacturing system into machine cells. Part families are identified such that they are fully processed within ...
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Machine-part family formation is one of major applications of group technology (GT). The machine cell formation problem in cellular manufacturing system (CMS) involves the decomposition of the manufacturing system into machine cells. Part families are identified such that they are fully processed within a machine cell. The problem of cell design is a very complex task with wide ranging implications for any organization. Cell design is generally understood as the problem of identifying a set of part types that are suitable for manufacturing on a group of machines. Among the many methods utilized in cell design, the distance or dissimilarity between two entries is fairly less used. In this study, a mathematical programming model based on the Minkowski distance measure to minimize the total distance between entries is introduced. Furthermore, a hypothetical manufacturing facility with 10 machines and 15 parts is used as a case. Finally, simulation models are developed for two manufacturing systems, a new cellular manufacturing and a conventional job shop manufacturing system. The main purpose of this paper is to combine different techniques such as the design and evaluation of a cellular manufacturing system.