فهرست مطالب

  • Volume:13 Issue: 2, 2020
  • تاریخ انتشار: 1399/03/12
  • تعداد عناوین: 13
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  • Vahid Pourmostaghimi, Mohammad Zadshakoyan * Pages 1-12
    In this paper, a real-time intelligent adaptive control with optimization methodology is proposed to produce parts with uniform surface roughness in finish turning of hardened AISI D2. Unlike traditional optimization approaches, the proposed methodology considers cutting tool real condition. Wavelet packet transform of cutting tool vibration signals followed by neural network was used to estimate tool flank wear. Intelligent models (artificial neural networks and genetic programming) were utilized to predict surface roughness and tool wear during machining process. Particle swarm optimization algorithm determined optimum feed rate that resulted in desired surface roughness. Performed confirmatory experiments indicated that the proposed adaptive control method not only resulted in parts with acceptable uniform quality, but also decreased the machining cost up to 8.8% and increased material removal rate up to 20% in comparison with those of traditional CNC turning systems.
    Keywords: Adaptive control, Artificial Neural Networks, Genetic Programming, Hard Turning, Optimization, particle swarm optimization
  • Mahmoud Jeddi, Ahmad Khoogar *, Ali Mehdipoor Omrani Pages 13-21
    A robot detects its surroundings through camera information and its response requires a high-speed image process. Due to the increasing application of vision systems, various algorithms have been developed to increase speed of image processing. This paper proposes a double density Discrete Wavelet-based Neural Network to enhance feature extraction and classification of parts in each picture. The Discrete Wavelet-based Neural Network combines multi-scale analysis ability of the wavelet transform and the classification capability of the artificial neural network by setting the wavelet function as the transfer function of the neural network. The automatic assembly process needs to capture the image in an online process in order to recognize the parts in the image and identify the location and orientation of the parts. In this part, the two dimensional double density discrete wavelet transform have been applied to compress and remove noise from the captured Image. By applying a value for the threshold, the coefficients of the wavelet transform function are obtained using these coefficients and the characteristics of the wavelet coefficients are calculated. Subsequently, a multilayer perceptron is trained using these extracted features of the images. To find the best vector characteristics, various combinations of extracted properties have been investigated. This method has succeeded in object detection and results show that the Neural Networks and the training algorithm based on the wavelet transform function have exquisite accuracy in classification. Thus, the developed method is considered effective as compared to other state-of-the-art techniques.
    Keywords: Feature extraction, Image compression, Neural network, Object Detection, Wavelet Transform
  • Reza Abdi Behnagh *, Peyman Esmaeilzadeh, Mohsen Agha Mohammad Pour Pages 23-31
    Ultrasonic welding is gaining popularity for joining of thin and dissimilar materials and foils in the fabrication of automotive Li-ion battery packs because of excellent efficiency, high production rate, high welding quality, etc. Precise control of the parameters of the welding process plays an important role in achieving good joint quality. Numerical simulation can greatly help control the main input parameters such as frequency, clamping pressure, friction coefficient, and vibration amplitude. In this present work, a three-dimensional thermo-mechanical Finite Element (FE) model is proposed using ABAQUS/EXPLICIT for the dissimilar Al to Cu weld to predict the deformation and temperature as output parameters during welding process by varying input parameters. The simulation results showed that the clamping pressure, vibration frequency and friction coefficient have a great influence on heat production during the process which was critical to determine the final quality of the welded joint. Studies also showed that increased clamping force and welding frequency led to increased deformation.
    Keywords: Ultrasonic welding, Finite element model, Aluminum, Copper, Li-ion battery
  • Abolghasem Mokhtari, Sayedali Mousavi * Pages 33-40
    Surgeries, such as orthopedic surgeries, are always performed with the use of a free hand with the aid of a fluoroscopic device to drill and place the screw in the bone position. However, such surgeries are of high risk and radioactive contamination, and have long surgery duration. Since the drilling process is very important and usually depends on the skill of the surgeon, a teleoperation system is provided to perform this task. In order to gain better control over the patient's body by the surgeon, an impedance control algorithm that incorporates the robot's position and velocity signal along with the surgeon's hand force and bone response force is provided in order for the surgeon to have proper control over the surgical process. Finally, drilling operation is performed on a cow bone to evaluate the teleoperation system presented. The results of the teleoperation system show that the desired system is acceptable under the proposed control algorithm. The results show that the drilling tool on the cow bone correctly follows the surgeon's hand position and the surgeon correctly feels the force applied to the tool by the cow bone.
    Keywords: Orthopedic Surgery, Teleoperation Systems, Impedance Control, Time delay
  • Afshin Ahmadi Nadooshan *, Afshin Shiriny, Morteza Bayareh Pages 41-49
    In this study, forced convection heat transfer of water/alumina Nano fluid in a rectangular microchannel with cross-flow injection is studied. The Nano fluid enters the microchannel with a temperature of 293 K and cools its walls. The upper wall of the microchannel is at constant temperature of 303 K. On the lower wall, there are two holes for injection of Nano fluid flow. Other parts of the microchannel wall are insulated. Slip velocity boundary condition is used for the walls of the microchannel. Simulations are performed for different injection velocities and the results are presented as velocity and temperature fields, and variation of the Nusselt number. The results show that the slip velocity on the channel wall and the Nusselt number increase by increasing the injection velocity. It is revealed that the Nusselt number is maximum at the channel entrance and decreases along the channel. After each injection, local Nusselt number increases due to the increase of the temperature gradient in the microchannel. Moreover, an optimal value for the ratio of the injection velocity to the inlet velocity is achieved using performance evaluation criteria (PEC). It is concluded that  is an optimal value of the injection velocity, leading to maximum PEC.
    Keywords: Forced Convection, Microchannel, Nano fluid, Slip Velocity, Vertical Injection
  • Venkatratnam Dirisala *, KESAVA RAO V.V.S Pages 51-64
    In the present work dissimilar joints of AISI 202 and AISI 316steels are produced using Metal Inert Gas (MIG) welding.  Welding current, wire feed rate, flow rate of gas and edge included angle are considered as input parameters and tensile strength, Impact strength and Maximum bending load are considered as output responses. Response Surface Method (RSM) is adopted using Central Composite Design (CCD) and 31 experiments were performed for 4 factors and 5 levels. Analysis of Variance (ANOVA) is carried out at 95% confidence level and coefficient of determination (R2) of 0.94 is obtained for all the output responses. Effect of welding parameters on output responses are studied by drawing main effect plots. Dominating parameters are identified using contour plots and surface plots are drawn to find the optimal solution. Optimal weld parameters are identified using Response optimizer.
    Keywords: AISI 202, AISI 316, Dissimilar Welds, MIG Welding, Response Surface Method, Steels
  • Ali Hossein Zadeh *, Mohammad Reza Maraki, Mohsen Sadidi Pages 65-72
    In the present study Charpy impact tests on a 7075-T651 aluminium alloy with full size (55×10×10 mm) with different notch tip radius (range of 0.19 to 0.40 mm) were conducted and the fracture energy was measured. The experimental results showed that the relationship between the fracture energy (E) and the notch tip radius of the Charpy samples (r) for the tested Aluminium is E=18.052r+1.741. Using this relationship, the Charpy energy can be determined for this Aluminium for any notch tip radius. Fracture surfaces revealed an intergranular failure for base metal in longitudinal direction, that a predominately brittle failure (cleavage) with some insights of ductile characteristics was observed. Moreover, with increasing notch tip radius, cracked particles were observed and some microvoids were nucleated, i.e., ductile fracture. Changes in the primary crack notch cause a change in the stress intensity factor adjacent to the crack tip, where the fracture energy in the Charpy Impact Test is subjected to the primary crack notch.
    Keywords: Aluminum Alloy 7075, Charpy Impact Test, Notch Tip Radius Effect, V-Notch
  • Hamed Vahabi, Mohammad Esmaeil Golmakani *, Ismaeil Mobasher Pages 73-90
    In this study, axisymmetric buckling of annular orthotropic graphene sheet embedded in a Winkler–Pasternak elastic medium is scrutinized for different boundary conditions based on non-local elasticity theory. With the aid of principle of virtual work, the non-local governing equations are derived based on First-order Shear Deformation Theory (FSDT). Differential Quadrature Method (DQM) is also used to solve equilibrium equations. Edges of Nano-plate might be restrained by different combinations of free, simply supported or clamped boundary conditions. To confirm results, comparison of studies is made between results obtained and available solutions in the literature. Finally, a detailed parametric study is conducted to investigate the impact of small scale effects, surrounding elastic medium, boundary conditions and geometrical parameters on critical buckling load. The main goal of this work is to study the effect of various non-local parameters on the buckling load of annular Nano-plate for different boundary conditions, Winkler and shear foundation parameters, annularity and thickness-to-radius ratios. It is seen that for Nano-plates without an elastic foundation, the impact of thickness on buckling load does not depend on values of non-local parameter and annularity. Results also show that impact of elastic basis on the buckling load is independent of small scale effects.
    Keywords: Buckling, DQ Method, Elastic medium, Graphene sheet, Non-Local Elasticity
  • Ali Mohammad Rousta, Peyman Beiranvand *, Farzad Akbarinia, Mehdi Hooshmand Pages 91-97
    Sometimes, suddenly or gradually structural or nonstructural damages are created in structure’s members due to natural or unnatural reasons like earthquake or corrosion. One of the methods used from the early in last decade to recognize damage is wavelet transform method. In this method, instead of examination of natural frequencies and the rate of its changes, vibration response or static response of a structure in various points of a structure is recorded at the same time, which in fact is a place-domain signal. In this paper, some factors have been investigated on a plate such as the effect of crack depth reduction, effect of changing support conditions, and the effect of approaching two rectangular cracks; and the responses obtained from finite element analysis, have been studied and the following results are gained: the ability of wavelet method to recognize the locality and severity of cracks, identification of tiny cracks up to 0.5mm depth and increasing the intensification of cracks’ effect on plate by reducing their distance from each other.
    Keywords: Crack, Damage, Plate, Wavelet Transform
  • Abbas Heydari * Pages 99-108

    Functionally Graded Materials (FGMs) can be described by continuous variation in structure and composition over volume, resulting in corresponding changes in the properties of the material. These kinds of materials are designed to achieve specific properties for specific applications. For the first time, the effects of stepwise fractional axial material gradation pattern and axial compressive load with piecewise function on buckling behaviour of Euler-Bernoulli beam rested on semi-rigid restraints are studied. It is worth mentioning that the more computational efforts are required to solve current problem with respect to the buckling problem of transversely graded beam due to discontinues material gradation especially in the axial direction, axial span-load with piecewise function and natural conditions of rotational spring hinges. The deflection continuity, natural equations as well as boundary conditions are written in the matrix form. The beam discretizing and nontrivial solution are employed to obtain buckling characteristic equation and matrix operations are used to calculate corresponding first mode shapes. Compatibility with various conditions and eliminating convergence drawbacks of conventional numerical tools are advantages of the proposed method. It is observed that the buckling load is decreased by increasing lengths of beam parts and increased by increasing rotational stiffness at semi-rigid supports. In the case of homogeneous beam, the result validity is proved by observing an excellent agreement between results of current work and well-known data in literature.

    Keywords: Axial Span-Load, Buckling, Discontinues Axially Graded Beam, Fractional Gradation, Semi-Rigid Restraint
  • Hossein Rahmani *, Mohammad Ahmadi Balootaki Pages 109-117

    In analytical studies, step (Heaviside) function is used to simulate an impact load. However, in real behaviour of materials, loading and unloading take a short time. The present study discusses analytically the effects of pulse shape and rising time of an impact load on dynamic stress intensity factor. Firstly, a pulse load with positive slip (linear and non-linear) is applied on a cracked plate and the amount of dynamic stress intensity factor on the crack tip is obtained. Then the effects of pulse time are discussed. Results show that increasing the rise time decreases the stress intensity factor because of reduction of inertia effects. Moreover, the duration of rise time plays the main role in dynamic stress intensity factor changes and how the variations are not matter.

    Keywords: Dynamic Stress Intensity Factor, Fracture, Impact, Pulse Shape
  • Sajjad Dehghanpour, Keivan Hosseini Safari *, Farzan Barati, Mohammadmahdi Attar Pages 119-127

    Purpose of this study is to obtain failure modes and failure loads of two Parallel pin loaded holes in unidirectional glass fibre/epoxy by adding nanoclay in the absence of nanoclay composite laminates using finite element analysis; the results are validated through experiment. The geometrical parameters studies in this survey include the distance between the diameter of the hole (e/d) and the free edge of specimen, the distance between two holes-to-hole diameter (M/d). The samples were exposed to constant speed tensile loading. The results showed that by adding nanoclay, failure load increases and failure modes varies from shear out to bearing failure. Furthermore, increasing distance from the free edge of the pin centre’s increases load bearing capacity of two type of composite materials and changes the failure mode from shear to the bear, it increases and decreases the distance from canter’s of pin in layers with and without nanoclay particles, respectively and changes failure mode from shear to bear mode. In order to find morphology of specimens and dispersion quality, Scanning Electron Microscope (SEM) was used. For predicting failure load and differentiating failure modes, Tsai-hill failure criteria associated with material property degradation is used. Experimental and FEM results indicate importance of considering the impact of e/d and M/d ratios in the design of two Parallel pin joints. ANSYS was used to carry out numerical simulation and the results denote a good agreement between numerical and experimental results. In this study, by designing an experimental and numerical procedure to estimate the effect of nanoclay, on failure mode and failure load of typical composite material, glass-epoxy, we could illustrate that adding nanoclay brought with it improvement of shear and tensional strength of glass-epoxy about 10 %.

    Keywords: ANSYS Software, Failure Behaviour, Finite Element Analysis, Nano-Composite Material, Nanoclay, Parallel Pin-Joints, Polymer Nano Composites
  • Sajjad Pakzad *, Ebrahim Imani Pages 129-137

    The use of parallel mechanisms in the structure of 3D printers are developing. Parallel mechanisms have excellent capabilities in terms of accuracy, stiffness and high load-bearing capacity. This article studies a 3D printer with four degrees of freedom that has three degrees of linear freedom and one degree of rotational freedom. The advantages of this printer are greater than conventional Cartesian printers, including higher print speed and stiffness, and there are also higher degrees of freedom for manoeuvrability. In this paper, the Newton-Euler analytical method is used to analyse the inverse dynamics and identify the driving forces required by the 3D nozzle motion. By coding the inverse dynamic equations in the MATLAB software environment, the driving forces diagrams are extracted based on the printer's nozzle motion. To validate the inverse dynamics relationships, simulations with the Simmechanic model of MATLAB software have been performed. Through changing the speed of movement of the printer nozzle and also change of the velocity and acceleration of drives, the forces required for the drive also change. The effect of changes in print speed of a specific geometry on the driving forces is also studied. As well as, choosing the optimum print speed with regard to the motor driver power and the dynamics of the forces applied to the drivers and the less print time are the most important factors that are discussed in this article.

    Keywords: 3D Printer, Dynamic, Force Analysis, MATLAB