Mohamad Palizvan; Mohammad Tahaie Abadi; Mohammad Homayoun Sadr
Abstract
This paper investigates the micromechanical damage behavior of composite materials on the transverse tensile response of representative volume elements (RVEs) with various fiber volume fractions. A new algorithm is developed to generate the random distribution of fibers in the RVE, and it is possible ...
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This paper investigates the micromechanical damage behavior of composite materials on the transverse tensile response of representative volume elements (RVEs) with various fiber volume fractions. A new algorithm is developed to generate the random distribution of fibers in the RVE, and it is possible to create a fiber distribution with high fiber volume fraction. The fibers and matrix are considered linear elastic and elastoplastic with Drucker–Prager's criterion, respectively. The fiber-matrix debonding is modeled by cohesive elements which lead to matrix cracking. To achieve a more realistic microstructure, the normal cohesive properties distribution is applied for interfaces between fibers and the matrix. To investigate the effect of the position of fibers with the weakest cohesive strength, sensitivity analysis concerning the different arrangements of specific normal cohesive properties on the RVE’s strength are performed. Moreover, the effects of different damage parameters such as fiber random distributions and various cohesive strengths on the overall damage behavior of the RVE are described in detail. It is revealed that the application of a normal cohesive distribution strongly reduces the maximum strength of the RVE and shifts the strain of damage initiation point and crack propagation path.
Farhad Fani saberi; Ali Kasiri
Abstract
This paper studies an output feedback second-order sliding mode control problem of spacecraft attitude control in the presence of the inertia tensor uncertainty and external disturbance. Mathematical modeling is presented based on spacecraft nonlinear equations of motion and quaternion parameters. Firstly, ...
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This paper studies an output feedback second-order sliding mode control problem of spacecraft attitude control in the presence of the inertia tensor uncertainty and external disturbance. Mathematical modeling is presented based on spacecraft nonlinear equations of motion and quaternion parameters. Firstly, a new sliding surface based on only attitude error is selected, then the standard second-order sliding mode control approach is followed. Finally, controller stability and tracking problem are guaranteed by choosing suitable auxiliary control input. The stability is proven by using concepts of a strong Lyapunov function and Lyapunov stability theory. Numerical simulations of attitude control of spacecraft equipped with 6 PWPF thrusters are given to demonstrate the performance of the proposed controller.
Mohammad Reza Hashemi; Farhad Salek; Alireza Naghavi Moghaddam
Abstract
Nowadays, Light aircrafts play key role in the aviation industry. Therefore, it is important to select the right equipment in airplane propulsion system. In this paper, at first, airplane propulsion system blades are designed in SOLIDWORKS software, then they are analyzed in ANSYS software using fluid-structure ...
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Nowadays, Light aircrafts play key role in the aviation industry. Therefore, it is important to select the right equipment in airplane propulsion system. In this paper, at first, airplane propulsion system blades are designed in SOLIDWORKS software, then they are analyzed in ANSYS software using fluid-structure interaction analysis (FSI) method. The blades pressure contours under various conditions obtained in ANSYS fluent software. After that, the output data of analysis in fluent software is transferred to ANSYS static structural to perform tension and deflection analysis of blades. The results demonstrate the sections which are near the blade tip are imposed by higher pressure than other sections. For determination of blade material, three materials such as stainless steel, copper and aluminum have been chosen as blade material. At next, deflection and stress applied to each blade with different material are compared with each other. The stress and deflection values were calculated based on van Mises criteria and maximum deflection. By comparing the values of stress and deflection of each blade made by mentioned materials, the blade made by stainless steel which has the lowest deflection was selected as the best material.
Alireza Moghaddasi; Mohammad Hassan Djavareshkian
Abstract
In this paper a comparison of Weighted Essentially Non-Oscillatory (WENO) scheme is presented and different kinds are compared. High resolution schemes are one of the best ways decreasing the cost of processes and also increasing the resolution as is clear. Different WENO’s influence on the weights ...
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In this paper a comparison of Weighted Essentially Non-Oscillatory (WENO) scheme is presented and different kinds are compared. High resolution schemes are one of the best ways decreasing the cost of processes and also increasing the resolution as is clear. Different WENO’s influence on the weights that applies on the neighborhood of the cells that is supposing to be calculated. Mentioned schemes, were tested on wave equation at first and in continued with the first and second dimension test cases. 3rd ,5th, 7th and 9th order of JS-WENO, MWENO, ZWENO and MZWENO are compared in Goethe tests. This scheme was applied in finite volume characteristic wise algorithm in order to reach much more accuracy. Buckley-Leverette, Sod shock tube, Shu-Osher, Lax test, Riley-Taylor instability and double Mach reflection test cases was compared. As the result, MZWENO in equal order with the other ones would report more accurate reply. But as a new research here we showed that e.g. although MZWENO 5th order could promote the accuracy of the scheme up to about two times higher, but the cost of computing will increase more than the JS 7th order one. So, it is concluded that employing 7th order of JSWENO leads to higher accuracy with less computational costs.
Mohammadreza Nozari; Sadegh Tabejamaat; Hasan Sadeghizade; Majid Aghayari
Abstract
The influence of fuel injector on the performance parameters of a can-type combustor were examined experimentally using LPG fuel and at atmospheric conditions. The first injector is a typical 45° conical injector with 6 holes on its curved surface, and the second injector is a swirl injector with ...
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The influence of fuel injector on the performance parameters of a can-type combustor were examined experimentally using LPG fuel and at atmospheric conditions. The first injector is a typical 45° conical injector with 6 holes on its curved surface, and the second injector is a swirl injector with 6 holes whose axes are not parallel with each other and are oriented at 19° in respect to the combustor’s axis. Three operating points were selected, and temperature distribution in the intermediate zone of the combustor and at the outlet section of the combustor was obtained using k-type thermocouples. Results reveal that the swirl injector provides better air-fuel mixing (due to the tangential motion forced on the fuel flow), more uniform temperature distribution in the combustor, lower liner temperature, higher combustion efficiency, and lower pattern factor. In addition, stability curve was also obtained for two configurations, and the results showed that the conical injector provides better stability for the combustor and is operable in a wider range of operating conditions. The results also show that the flame is generally shaped near the walls and the vicinity of the combustor’s liner and outlet walls are in contact with hot gases which reduces the combustor’s lifetime.
H. Chenarani; T. Binazadeh; M.H Shafiei
Abstract
This paper considers the problem of asymptotic stabilizing of velocity and body rates of a spacecraft in the presence of uncertainties and external disturbances. One of the important methods in controller design for nonlinear systems; is designing based on the passivity concept. This concept which provides ...
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This paper considers the problem of asymptotic stabilizing of velocity and body rates of a spacecraft in the presence of uncertainties and external disturbances. One of the important methods in controller design for nonlinear systems; is designing based on the passivity concept. This concept which provides a useful tool for analysis of nonlinear systems has been also used for asymptotic stabilizing of nonlinear dynamical systems especially mechanical systems. The passivity-based control law is a static output feedback and has valuable features. Because of existence of uncertainties and external disturbances in the state-space of equations of physical systems; first the robust version of passivity-based control method, which is recently developed in literature, is given and the control law for nonlinear uncertain systems with affine structure is presented. Then, this approach is used in controller design for a spacecraft. Since, this paper considers only the stabilization of velocity and body rates, therefore the reduced-order model is extracted from the state-space equation of a spacecraft with six degree of freedom and then the robust control law is designed. Computer simulations show the efficiency of the proposed controller in robust asymptotic stabilizing of the velocity and body rate vectors of the spacecraft in the presence of uncertainties and external disturbances.
