فهرست مطالب

  • Volume:21 Issue: 2, 2020
  • تاریخ انتشار: 1399/07/23
  • تعداد عناوین: 7
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  • MohammadAmir Bayatinezhad, Arash Mohammadi *, Ali Davood Abadi Pages 6-13

    In this paper, the temperature feature was employed to track down the degradation trend of rolling element bearings. The remaining useful life(RUL) of the rolling element bearing was predicted byassuming root mean square growth (RMS) of the acceleration signal to exponential function form and extraction of two other features. Then, the performance of these features was investigated in the prediction using a recurrent neural network(RNN). The experimental data of the accelerated life test on the rolling element bearing have been extracted from the prognostic. Contrary to the previous works, this paper considers the temperature feature instead of the time feature and also assuming the RMS of the acceleration signal to the exponential function form and using a RNN which causes a newmodel more applicable than previous models.

    Keywords: Rolling element bearing, Remaining useful life, Recurrent Neural Network, Degradation, Condition monitoring
  • Mohammad Nadjafi *, Fatollah Ommi, MohammadAli Farsi Pages 14-32

    Injection process and its parameters are the most important factors in the combustion process that depends on some factors in operation. In this paper, initially, injection parameters from viewpoint of macroscopic and microscopic in a manufactured model scale liquid fuel micro-motor that are measured experimentally in Cold-Test and Phase Doppler Analyzer (PDA) laboratories, are evaluated. And then, Uncertainty Analysis (UA) methodologies for experimental uncertainty assessment are implemented to drive the respective block diagram. The sources of uncertainty associated with the techniques are presented, and where such data were available, quantitative estimates of their magnitude are given. Uncertainty analysis results that are taken to spraying parameters show the high accuracy of experimental test results. This framework is a comprehensive and complete technique that could be implemented and executed over any set to analyze uncertainty value, with difference that each set or case study has its respective parameters.

    Keywords: Uncertainty Analysis, Injection parameters, Spray Parameters, Injector, Injector plate, PDA
  • An Analytical Study for Nonlinear Vibration Analysis of Two-directional Functionally Graded Rectangular Plate
    Soheil Hashemi *, AliAsghar Jafari Pages 33-56

    In this study, an analytical solution is presented for investigating the nonlinear vibration analysis of two-directional functionally graded rectangular plate for the first time. On the basis of first order shear deformation theory (FSDT) and Galerkin procedure, the equations of motion are developed. The nonlinear equation of motion is then solved analytically by modified Lindstedt-Poincare method. Thevolume fraction distribution is assumed to be symmetrical for characterizing the in-plane material inhomogeneity. Finally, the effects of some system parameters such as non-dimensional vibration amplitude, volume fraction indexes and aspect ratio on the nonlinear to linear frequency ratio are discussed in detail. To validate the analysis, the results of this paper are compared with the published data and good agreements are found.

    Keywords: Nonlinear vibration, Rectangular plate, bi-directional functionally graded material, first order shear deformation theory, modified Lindstedt-Poincare method
  • Wind Farm Layout Optimization using a Reynolds-averaged Navier–Stokes Model and a Genetic Algorithm
    Abolfazl Pourrajabian *, Reza Ebrahimi, Morteza Rahmanpour, Saeed Rahgozar, Maziar Dehghan Pages 57-74
    The placement of wind turbines in a wind farm can considerably affect the total output power. Using computational fluid dynamics and genetic algorithm, the optimal arrangement of turbines in a given wind farm was determined. A three-dimensional Reynolds-averaged Navier-Stokes simulation was conducted on a 660 kW three-bladed horizontal axis turbine. The airflow was assumed to be steady state and a pressure-based approach was adopted to solve the governing equations. By employing the characteristics of the wake propagation, the appropriate distances between the adjacent turbines were calculated. To find the optimal placement of the turbines, a purpose-built genetic algorithm was employed. The results show that the final configuration is in line with the outcomes of the previous study. The sensitivity analysis of the genetic algorithm with respect to its parameters was also performed to guarantee that the final layout is an optimal one.
    Keywords: Wind farm layout, Optimization, RANS, Genetic Algorithms
  • The Effect of Repeated Impact Loading on Reservoir Rock Properties
    Marzieh Naderan Tahan, Khosro Naderan Tahan *, Seyed Saied Bahrainian Pages 75-95
    The objective of this paper is to present the results of a research program launched to investigate the mechanism and amount of changes of reservoir rock properties due to pulse stress waves. These waves are induced in cylindrical samples by applying repeated impact loading along the sample axes in a falling weight testing apparatus. After each step of loading, permeability, effective porosity, wave velocities are measured by standard methods and CT images are prepared. Results show that if the amplitude of dynamic stress exceeds the dynamic fracture strength and spall strength of the samples, micro fracture will emerge and permeability will increase significantly while the effective porosity decreases at first steps of loading but, recovers during the subsequent steps. Emerging and growth of new fractures are visible in CT images, too. Total energy consumption prior to complete breakage, and the strain rate of incident wave, affect the results.
    Keywords: dynamic fracture strength, effective porosity, impact loading, Permeability, Reservoir rock, spallation
  • Free and Forced Vibration Behavior of Cylinders Made of Two Dimensional Functionally Graded Materials using Meshless Method
    Habib Mirzaie *, Ali Roknizadeh Pages 96-110
    In this article, a meshless method is developed to analyze free and forced vibration behavior of axisymmetric cylinders made of two dimensional functionally graded materials (2D-FGMs). The meshless method is the based on weak form of motion equations using the moving least square (MLS) shape functions. The 2D-FGM cylinders are made of a mixture of a ceramic and a metal. The volume fraction of each component is assumed to be functionally varied along both radial and axial directions of cylinders. The effects of profile of material distributions, cylinder dimensions, boundary conditions and loading on the vibrational characteristics of the proposed 2D-FGM cylinders are investigated. The results of investigating the vibrations of the cylinders made of 2D-FGM confirmed that in the engineering design applications, the radial vibrations can be attenuated by adjusting the power coefficients along the radius and length of the cylinder.
    Keywords: Free, forced vibrations, meshless method, Functionally graded materials
  • Robust Sliding Mode Control of Nonlinear Ship Autopilot System
    Farzan Rashidi *, Abbas Harifi Pages 111-126
    Designing of ship autopilot is a challenging problem because of high nonlinearity of ship dynamics and various acting disturbances. The goal of this research work is to design a robust and efficient sliding mode control for ship autopilot system. The main contribution is to employ a nonlinear dynamic model bound of uncertainties for controller design. In order to reduce the side effects of chattering phenomenon, integral switching variable is used to modify the proposed control technique. Simulation results in the rough wave condition show that the proposed sliding mode control method is able to cope with nonlinearity, uncertainty, and disturbances in the system. Moreover, the controller significantly reduces the chattering in comparison with a previous similar research.
    Keywords: sliding mode control, Integral Switching Variable, nonlinear controller, Ship Autopilot