1 Vibration Analysis of Laminated Composite Plates Carrying Rotating Circular Mass , R. Akbari Alashti, R. Alibakhshi*
In this paper, the free vibration response of a laminated composite rectangular plate supporting a rotating circular patch mass is studied. The two variables refined plate theory which has the number of unknown functions involved is only four, as against five in case of other simple shear deformation theories, is applied to define the third order displacement field of a composite rectangular plate. The plate is considered to have simply supported boundaries. The first variation of the Lagrangian (Hamilton’s principle) is used to obtain the equations of motion for the rectangular plate. Due to the significance of fundamental frequency of the plate, its variation with respect to the non-dimensional geometrical parameters such as aspect ratio of the plate, size, location and angular velocity of the rotating patch mass, is investigated. It will be shown herein that the proposed theory is simple in solving the free vibration problems of plates with patch masses.
2 Optimization of Suspension System of Sport Car in Three Dimensional Reactions Space , R. Kazemi*, M. Raf’at & H. Zolghadr
Suspension system as one of the most important key elements of vehicle has always been considered by research centres and auto makers over the world. This is of higher importance when it comes to sports cars which work within especially sensitive conditions and their performances may be affected adversely even by the smallest defects. This study investigates optimization of effective handling parameters of a sport car with three optimization indices covering racetrack at the shortest possible time. For this purpose, a sport car model simulated in ADAMS/Car software has been used and all test steps have been implemented in this environment. To reach optimum solution in different racetrack conditions, Pareto solution set optimization method was used in which optimization indices have been examined covering distance in standard constant radius test with three different radii. Implementing these experiments at different levels of optimization parameters, all solution sets were collected in a three dimensional diagram called performance space whose coordinates axes are optimization indices values; then using LP norm idea, possible optimum solutions were selected among other ones. In order to find optimum solution in a special racetrack, a new idea was proposed through which weighted coefficients related to optimization indices for a special racetrack were determined and optimum solutions appropriate for that track were selected from Pareto solution set.
3 Effects of Scan Direction and Orientation on Mechanical Properties of Laser Sintered Polyamide-12, J. A. Nelson, G. Galloway, A. E. W. Rennie*,T. N. Abram & G. R. Bennett
In order to understand the impact of layer-wise scanning direction in the Selective Laser Sintering process, test coupons were manufactured for mechanical testing from DuraForm™ Polyamide powder. The effects of laser energy density, varying between 0.003 and 0.024 J/mm2 were examined in test specimens rotated 90º through the Z axis. SLS machines do not always facilitate ‘cross-hatching’ of layers and therefore orientation has a major influence on part quality. When employed, the cross-hatching technique scans successive layers perpendicularly to the previous. Studying how parts perform with scan lines in a common direction, will assist in the understanding of how SLS parts behave in practice. Results showed that physical density, tensile strength and elongation rose with energy density up to 0.012 J/mm². This initial rise was due to a continued improvement in particle fusion with increasing energy density. Above 0.012 J/mm², these properties started to decline at different rates depending on their orientation (scan direction) on the part bed. Specimen’s oriented perpendicularly to the X axis exhibited a greater elongation at the expense of tensile strength, when compared to parallel specimens.
4 A Finite-Volume Method in General Curvilinear Coordinates for Simulation of Blood Flow past a Stenosed Artery, S. Pasha Zanous*, R. Shafaghat, Q. Esmaili
In this study, the ?ow characteristics through symmetric stenosis artery are investigated. The shape of eccentricity for stenotic ?ows is limited by circular-cross sections and plaques usually assumed to be oriented concentrically. The governing equations are the usual Navier-Stokes equations and are numerically solved by using finite volume method in arbitrary orthogonal curvilinear coordinates. In addition, three-dimensional (3D) elliptic grid is presented, which the generating system is based on the solution of a partial differential system. To prevent serious distortion or overlapping of mesh lines, grid regularity is verified by some controlling parameter like Skewness value and maximum grid aspect ratio (MAR). The main objective of the present study is to investigate different degrees of the stenosis (45%, 55%, 65%, and 75% by area reduction) and finding the critical one playing a significant role in the development of forming sediment in the vessel wall. It is shown that the magnitude of inlet Reynolds number has strong relationship with the velocity, pressure, and wall shear stress (WSS) distributions as expected. The most important conclusion obtained from this model is the high WSS, pressure drop, and formation of large recirculation regions found in the downstream of the stenosis, especially in the case of severe stenosis that could create various pathological diseases.
5 Analytical Investigation of Rupture Phenomena in Sheet Hydroforming Process by Hemispherical Punch, A. Naddaf Oskouei*, M. R. Elhami & I. Karami Fath
Rupture and wrinkling are two prevalent phenomena that happen in hydroforming process. Many efforts have been made to achieve the upper and lower bounds for the pressure related to rupture and wrinkling of sheet, respectively. The aim of this investigation is to improve the upper bound of fluid pressure in hydroforming process by hemispherical punch. In this article, analytical study of the upper bound of fluid pressure based on new assumption of Hill theory is presented. Next, governing equations of the process is derived, and numerical methods are used to solve these equations. In this process, the effect of material and geometric properties on the upper bound pressure is investigated. The results are compared with experimental and theoretical based on Tresca criterion. The study on the effect of geometry and material shows that increasing the sheet thickness raises the upper bound pressure. Moreover, the reduction of sheet to punch diameter ratio leads to increase of the upper bound pressure. On the other hand, decreasing the friction force as well as increasing the anisotropic coefficient both causes the rise of upper bound pressure. Finally, the increase of work hardening parameter leads to the rise of rupture point.
6 Faults Diagnosis of a Girth Gear using Discrete Wavelet Transform and Artificial Neural Networks , M. Akbari, H. Homaei & M. Heidari*
In this paper, a fault diagnosis system based on discrete wavelet transform (DWT) and artificial neural networks (ANNs) was designed to diagnose different types of faults in gears. DWT is an advanced signal-processing technique for fault detection and identification. Five features of wavelet transform RMS, crest factor, kurtosis, standard deviation and skewness of discrete wavelet coefficients of normalized vibration signals have been selected. These features are considered as the feature vector for training purpose of the ANN. A wavelet selection criteria, namely Maximum Energy to Shannon Entropy ratio, was used to select an appropriate mother wavelet and discrete level, for feature extraction. To ameliorate the algorithm, various ANNs were exploited to optimize the algorithm so as to determine the best values for “number of neurons in hidden layer” resulted in a high-speed, meticulous three-layer ANN with a small-sized structure. The diagnosis success rate of this ANN was 100% for experimental data set. An experimental set of data has been used to verify the effectiveness and accuracy of the proposed method. To develop this method in general fault diagnosis application, an example was investigated in cement industry. At first, a MLP network with well-formed and optimized structure (20:12:3) and remarkable accuracy was presented providing the capability to identify different faults of gears. Then this neural network with optimized structure was presented to diagnose different faults of gears. The performance of the neural networks in learning, classifying and general fault diagnosis were found encouraging and can be concluded that neural networks have high potentiality in condition monitoring of the gears with various faults.
7 Engineering Design of Guidance System of 6R Tele-robot based on DTMF, M. H. Korayem*, S. R. Nekoo & A. H. Korayem
In this article, the advantages of navigation based on dual tone multiple frequencies (DTMF) technique through telecommunication lines is studied. First, the calculations of direct and inverse kinematics of the manipulator in computer are transferred to the PIC microprocessors center. Next, each PIC is required to control and automate the relevant link separately. The main purpose of this work is making it possible to control the robot via a telephone line without a modem. In order to apply this idea, computer has analyzed the data received from the operator and inserts the necessary instructions through the serial port using AVR microcontroller in the embedded hardware at the phone line and sending them to the robot hardware. Then the robot performed the processes as a closed loop design and provided the necessary feedback for the computer. Real-time control, low volume of software and hardware computations and the possibility of using the phone lines with low and medium bandwidth in addition to ADSL lines simultaneously, are the special features of this method. In the proposed method, control data and the corresponding feedbacks are transmitted as the remote closed loop control, which can be combined in the developing stages with other control methods such as neural networks which results the maximum productivity. At the end of this work, examination of the time delay of tele-controller system and experimenting according to the ISO9283 standard, specific to the accuracy of the robot, is carried out.
8 Developments in Conventional Machining of Aluminium Matrix Composite Material: A Review, V. K. Saini*, Z. A. Khan, A. N. Siddiquee
Aluminium matrix composites (AMCs) materials are continuously displacing traditional engineering materials because of their advantages of high stiffness and strength over homogeneous material formulations. Properties of AMCs can be tailored to the demands of different industrial applications by suitable combinations of matrix, reinforcement and processing route. Presently, several grades of AMCs are manufactured by different methods. The hard ceramic component that increases the mechanical characteristics of AMCs causes quick tool wear and premature tool failure in the machining operations. Therefore, the solution of the machining problems is one of the prerequisites for a widespread industrial application of AMCs. This paper provides a review of various research activities and various developments in the field of conventional machining of AMCs. Researchers have explored a number of ways to improve machining efficiency by traditional methods. This paper presents an overview of AMC material that reveals the role of the reinforcement particles on the machinability of AMCs and provides a valuable guide for a better control of their machining processes.
9 Design of an Artificial Foot using Series Elastic Actuator, H. Kheirollahi, A. M. Goudarzi*, M. Fazeli & M. Imani
Investigation of natural foot behaviour shows that it’s kinetic and kinematics functions can be compared to mechanisms containing simple mechanical elements such as springs, dampers and actuators. Hence, appropriate design of this mechanism may give rise to an artificial foot that might help amputees properly. Studies show that whatever the biomechanical behavior of an artificial foot is similar to that of natural foot, where it might be utilized consuming less energy. In this study, required parameters for design of an artificial foot including spring and electromechanical actuator were examined by investigating biomechanical behavior of natural foot in walking level. Moreover, an algorithm was suggested for design of foot prosthesis and according to this algorithm, a prototype was designed and fabricated.
10 Intermetallic Phase Formation during Combustion Synthesis of Mechanically Activated Ni-Ti Alloy, S. K. Sadrnezhaad*, Sh. Katiraei and A. Ghasemi
Both mechanical activation (MA) and pre-heating conditions affect intermetallic phase formation during combustion synthesis (CS) of Ni-Ti equiatomic alloy. Input parameters are pre-heating temperature, activation duration and compaction pressure. Output variables are ignition time, temperature rise, reaction duration, product microstructure, constituent oxidation and intermetallic phase formation. Superelasticity and shape memory behaviors depend on austenite-rhombohedral and rhombohedral-martensite transformation temperatures. These temperatures were detected by differential scanning calorimetry (DSC) measurements. The phase changes were studied by scanning electron microscopy (SEM) and x-ray diffraction (XRD) analysis. Production of Ni3Ti was detected when CS was performed on 1800 s milled sample pre-heated to 400°C. Compression tests indicated appearance of superelastic and superelastic/thermoelastic behaviors after CS of (a) 3600 s activated and (b) 7200 s activated samples at 400°C pre-heating, respectively. It was concluded that pre-combustion heating fostered mono-phase formation and titanium oxidation; while mechanical activation lowered ignition-start-time, duration of synthesis and Ni3Ti formation.
11 Multiobjective Constrained Optimization of a Newly Developed Needle Driving Mechanism in Sewing Machine for Performance Improvement , S. Ebrahimi*, I.Hajizadeh & P. Payvandy
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, increase of the needle transmission force and the optimal mechanical advantage are greatly dependent on the design criteria of the needle driving mechanism. 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 of this mechanism using the genetic algorithm is explained. The objective functions of the optimization problem are considered in such a way to fulfil some of the most important design criteria such as reducing the needle generated heat, reducing undesirable vibrations and increasing the mechanical performance. The obtained results confirm improvement of the required design criteria of the newly developed mechanism in this study. It is also concluded that improving the mechanical advantage of about 14% causes an increase in the value of the needle jerk about 30%. This clearly states that higher mechanical advantage, is achieved by the cost of increasing the needle jerk.
12 Investigating Temperature Effects on Mechanical Behavior of Rubber Compounds Embedded in Composite Structure of Pneumatic Tires, H. Golbakhshi, M. Namjoo*
Owing to elastic and viscous characteristics of embedded rubber compounds, some of the supplied mechanical energy to composite structure of a rolling tire is dissipated as heat. As a result, the tire may have different body temperatures for different operating conditions. In most performed studies, just temperature distribution is investigated and the mechanical behaviour of tire structure, which is highly temperature-dependent, is ignored. In this study a 3D finite element model is developed for evaluating the effects of loading conditions and the body temperature on mechanical behaviour of the tire. The obtained results are compared with related published works to evaluate the accuracy of the analysis.