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Uncertainty propagation in dynamics of composite plates: A semi-analytical non-sampling-based approach

Frontiers of Structural and Civil Engineering 2020年第6期14卷 1359-1371页

作者： mahdi fakoor Hadi PARVIZ Faculty of New Sciences and Technologies University o f TehranTehran 14395-1561Iran

In this study,the influences of spatially varying stochastic properties on free vibration analysis of composite plates were investigated via development of a new approach named the deterministic-stochastic Galerkin-based semi-analytical *** material properties including tensile modulus,shear modulus,and density of the plate were assumed to be spatially varying and *** fields with first-order Markov kernels were utilized to define the aforementioned material *** stochastic fields were decomposed via application of the K arhunen-Loeve theorem.A first-order shear deformation theory was assumed,following which the displacement field was defined using admissible trigonometric modes to derive the potential and kinetic *** stochastic equations of motion of the plate were obtained using the variational *** deterministic-stochastic Galerkin-based method was utilized to find the probability space of natural frequencies,and the corresponding mode shapes of the plate were determined using a polynomial chaos *** proposed method significantly reduced the size of the mathematical models of the structure,which is very useful for enhancing the computational efficiency of stochastic *** methodology was verifed using a stochastic finite element method and the available results in *** sensitivity of natural frequencies and corresponding mode shapes due to the uncertainty of material properties was investigated,and the results indicated that the higher-order modes are more sensitive to uncertainty propagation in spatially varying properties.

关键词： composite plate spatially varying stochastic properties Galerkin method polynomial chaos approach semi-analytical approach

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Long-term effects of main-body's obliquity on satellite formation perturbed by third-body gravity in elliptical and inclined orbit

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Research in Astronomy and Astrophysics 2017年第4期17卷 81-96页

作者： Majid Bakhtiari Kamran Daneshjou mahdi fakoor Department of Mechanical Engineering Iran University of Science and Technology Department of Aerospace Engineering Faculty of New Sciences and TechnologiesUniversity of Tehran

A new non-simplified model of formation flying is derived in the presence of an oblate main- body and third-body perturbation. In the proposed model, considering the perturbation of the third- body in an inclined orbit, the effect of obliquity （axial tilt） of the main-body is becoming important and has been propounded in the absolute motion of a reference satellite and the relative motion of a follower satellite. From a new point of view, J2 perturbed relative motion equations and considering a disturbing body in an elliptic inclined three dimensional orbit, are derived using Lagrangian mechanics based on accurate introduced perturbed reference satellite motion. To validate the accuracy of the model presented in this study, an auxiliary model was constructed as the Main-body Center based Relative Motion （MCRM） model. Finally, the importance of the main-body＇s obliquity is demonstrated by several examples related to the Earth-Moon system in relative motion and lunar satellite formation keeping. The main-body＇s obliquity has a remarkable effect on formation keeping in the examined in-track and projected circular orbit （PCO） formations.

关键词： space vehicles - celestial mechanics - Moon - planets and satellites - formation -obliquity

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Progressive failure analysis of notched composite plate by utilizing macro mechanics approach

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Frontiers of Structural and Civil Engineering 2021年第3期15卷 623-642页

作者： Seyed M.N.GHOREISHI mahdi fakoor Ahmad AZIZI Faculty of New Sciences and Technologies University of TehranTehran***Iran Department of Mechanical Engineering Science and Research BranchIslamic Azad UniversityTehran***Iran

In this study,gradual and sudden reduction methods were combined to simulate a progressive failure in notched composite plates using a macro mechanics *** the presented method,a progressive failure is simulated based on a linear softening law prior to a catastrophic failure,and thereafter,sudden reduction methods are employed for modeling a progressive *** combination method significantly reduces the computational cost and is also capable of simultaneously predicting the first and last ply failures(LPFs)in composite *** proposed method is intended to predict the first ply failure(FPF),LPF,and dominant failure modes of carbon/epoxy and glass/epoxy notched composite *** addition,the effects of mechanical properties and different stacking sequences on the propagation of damage in notched composite plates were *** results of the presented method were compared with experimental data previously reported in the *** comparing the numerical and experimental data,it is revealed that the proposed method can accurately simulate the failure propagation in notched composite plates at a low computational cost.

关键词： progressive failure notched composite plate Hashin failure criterion macro mechanics approach finite element method

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Conceptual Design Process for LEO Satellite Constellations Based on System Engineering Disciplines

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Computer Modeling in Engineering & Sciences 2022年第5期131卷 599-618页

作者： Ali Salehi mahdi fakoor Amirreza Kosari Seyed Mohammad Navid Ghoreishi Faculty of New Sciences and Technologies University of TehranTehranIran

Satellite design process is an interdisciplinary subject in which the need for collaboration among various science and engineering disciplines is ***,finding an optimal process for conceptual design of a satellite,which can optimize time and cost,is still an important *** this paper,based on system engineering approach,an optimal design process is proposed for LEO satellite *** the proposed method,design process,design sequences,and data flow are *** this regard,the conceptual design process is divided into two levels of mission(or constellation)and system(or satellite)as well as 15 main activities based on the mission profile,previous experiences of the authors,and existing ***,the relationships between these activities have been determined by considering the importance of relationships according to their ***,these relations are optimized based on design structure matrix(DSM).By utilizing this approach,system design process of a telecommunication satellite constellation in LEO is formulated in conceptual design *** and capability of the proposed approach in optimal design process of the satellite constellation are investigated by comparing the outcome with existing results in the literature.

关键词： Satellite constellation system engineering design structure matrix conceptual design

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