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Strain-Rate Dependency of a Unidirectional Filament Wound Composite under Compression

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Computer modeling in Engineering & Sciences 2023年第12期137卷 2149-2161页

作者： Stepan Konev Victor A.Eremeyev hamid m.sedighi Leonid Igumnov Anatoly Bragov Aleksandr Konstantinov Ayaulym Kuanyshova Ivan Sergeichev Skolkovo Institute of Science and Technologies Center for Materials TechnologiesMoscowRussia National Research Lobachevsky State University of Nizhny Novgorod Nizhny NovgorodRussia Dipartimento di Ingegneria Civile Ambientale e Architettura(DICAAR)Universitàdegli Studi di CagliariCagliari(CA)Italy mechanical Engineering Department Faculty of EngineeringShahid Chamran University of AhvazAhvazIran Drilling Center of Excellence and Research Center Shahid Chamran University of AhvazAhvazIran

This article presents the results of experimental studies concerning the dynamic deformation and failure of a unidirectional carbon fiber reinforced plastic(T700/LY113)under compression.The test samples were manufactured through the filament winding of flat plates.To establish the strain rate dependencies of the strength and elastic modulus of the material,dynamic tests were carried out using a drop tower,the Split Hopkinson Pressure Bar method,and standard static tests.The samples were loaded both along and perpendicular to the direction of the reinforcing fiber.The applicability of the obtained samples for static and dynamic tests was confirmed through finite elementmodeling and the high-speed imaging of the deformation and failure of samples during testing.As a result of the conducted experimental studies,static and dynamic stress-strain curves,time dependencies of deformation and the stress and strain rates of the samples during compression were obtained.Based on these results,the strain rate dependencies of the strength and elasticity modulus in the strain rate range of 0.001-6001/s are constructed.It is shown that the strain rate significantly affects the strength and deformation characteristics of the unidirectional carbon fiber composites under compression.An increase in the strain rate by 5 orders of magnitude increased the strength and elastic modulus along the fiber direction by 42%and 50%,respectively.Perpendicular loading resulted in a strength and elastic modulus increase by 58%and 50%,respectively.The average strength along the fibers at the largest studied strain rate was about 1000mPa.The obtained results can be used to design structural elements made of polymer composite materials operating under dynamic shock loads,as well as to build models of mechanical behavior and failure criteria of such materials,taking into account the strain rate effects.

关键词： High strain rate composites filament winding dynamic strength Split Hopkinson Pressure Bar compression

DYNAmIC PULL-IN INSTABILITY OF DOUBLE-SIDED ACTUATED NANO-TORSIONAL SWITCHES

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Acta mechanica Solida Sinica 2015年第1期28卷 91-101页

作者： hamid m.sedighi Kourosh H.Shirazi Department of mechanical Engineering Shahid Chamran University

A nonlinear frequency-amplitude relation is developed to investigate the vibrational amplitude effect on the dynamic pull-in instability of double-sided-actuated nano-torsional switches. The governing equation of a nano-electro-mechanical system pre-deformed by an electric field contains the quintic nonlinear term. The influences of basic parameters on the pull-in instability and natural frequency are investigated using a powerful analytical approach called the homotopy perturbation method. It is demonstrated that two terms in series expansion are sufficient to produce an acceptable solution. The numerical results obtained have verified the soundness of the asymptotic procedure. The phase portraits of the double-sided nano-torsionalactuator exhibit periodic, homoclinic and heteroclinic orbits.

关键词： homotopy perturbation method frequency-amplitude relationship double-sidedactuated nano-switch dynamic pull-in instability homoclinic orbit heteroclinic orbit

Velocity gradient elasticity for nonlinear vibration of carbon nanotube resonators

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Frontiers of Structural and Civil Engineering 2020年第6期14卷 1520-1530页

作者： hamid msedighi Hassen mOUAKAD mechanical Engineering Deparment Faculty of Engineering Shahid Chamran University of AhvazAhvaz ***Iran Driling Center of Exellence and Research Center Shahid Chamran University of AhvazAhvaz ***Iran mechanical and Industrial Engineering Department Collge of EngineeringSultan Qaboos UniversitMuscalOMAN

In this study,for the first time,we investigate the nonlocality superimposed to the size effects on the nonlinear dynamics of an electrically actuated single-walled carbon-nanotube-based resonator.We undertake two models to capture the nanostructure nonlocal size effects:the strain and the velocity gradient theories.We use a reduced-order model based on the differential quadrature method(DQm)to discretize the goverming nonlinear equation of motion and acquire a discretized-parameter nonlinear model of the system.The structural nonlinear behavior of the system assuming both strain and velocity gradient theories is investigated using the discretized model.The results suggest that nonlocal and size effects should not be neglected because they improve the prediction of corresponding dynamic amplitudes and,most importantly,the critical resonant frequencies of such nanoresonators.Neglcting these effects may impose a considerable source of error,which can be amended using more accurate modeling techniques.

关键词： velocity gradient elasticity theory nanotube resonators differential-quadrature method nonlinear vibration

Experimental and theoretical investigations of the lateral vibrations of an unbalanced Jeffcott rotor

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Frontiers of Structural and Civil Engineering 2020年第4期14卷 1024-1032页

作者： Ali ALSALEH hamid msedighi Hassen mOUAKAD Saudi Arabian Oil Company(ARAmCO) Dhahran 31311Saudi Arabia mechanical Engineering Deparment Faculty of EngineeringShahid Chamran University of AhvazAhvaz 61357-43337Iran Drilling Center of Excellence and Research Shahid Chamran University of AhvazAhvaz 61357-43337Iran mechanical and Industrial Engineering Deparment Sultan Qaboos UniversinAI Khoudh MuscatOman

The current work experimentally explores and then theoretically examines the lateral vibrations of an unbalanced Jeffcott rotor-system working at several unbalance conditions.To this end,three conditions of eccentric masses are considered by using a Bently Nevada RK-4 rotor kit.measurements of the steady-state as well as the startup data at rigid and flexible rotor states are captured by conducting a setup that mimics the vibration monitoring industrial practices.The linear governing equation of the considered rotor is extracted by adopting the Lagrange method on the basis of rigid rotor assumptions to theoretically predict the lateral vibrations.The dynamic features of the rotor system such as the linearized bearing induced stiffness are exclusively acquired from startup data.It is demonstrated that,with an error of less than 5%,the proposed two-degrees-of-freedom model can predict the flexural vibrations at rigid condition.While at flexible condition,it fails to accurately predict the dynamic response.In contrast to the other works where nonlinear mathematical models with some complexities are proposed to mathematically model the real systems,the present study illustrates the applicability of employing simple models to predict the dynamic response of a real rotor-system with an acceptable accuracy.

关键词： rotor-dynamics Jeffcott rotor lateral vibrations Lagrange method system-equivalent stfess sleeve bearings il film induced stiffness

PCL/HA静电纺丝纤维涂层对可降解mg/HA复合材料的表面改性:力学性能、腐蚀和生物相容性

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Transactions of Nonferrous metals Society of China 2024年第5期34卷 1470-1486页

作者： m.SHAmSI m.sedighi A.BAGHERI School of mechanical Engineering Iran University of Science and TechnologyTehranIran

采用搅拌铸造和挤压法制备mg/HA复合材料,并在其表面采用静电纺丝法涂覆聚己内酯/羟基磷灰石(PCL/HA)纤维(2.5%和5%HA,质量分数),以提高其耐腐蚀性。力学性能测试结果表明,复合材料的压缩屈服强度从73mPa(纯镁)提高到151mPa,提高了107%... 详细信息

采用搅拌铸造和挤压法制备mg/HA复合材料,并在其表面采用静电纺丝法涂覆聚己内酯/羟基磷灰石(PCL/HA)纤维(2.5%和5%HA,质量分数),以提高其耐腐蚀性。力学性能测试结果表明,复合材料的压缩屈服强度从73mPa(纯镁)提高到151mPa,提高了107%。SEm、EDS和XRD分析表明,HA颗粒分布在多孔涂层中。极化曲线结果表明,涂层试样的耐腐蚀性能均优于未涂覆试样。PCL涂层使样品的腐蚀电流密度降低了两个数量级。通过极化和体外腐蚀试验证明了HA在涂层中的有效性。涂层和随后形成的Ca-P层阻碍了模拟体液与基体的接触和渗透,从而起到保护表面的作用。PCL/2.5%HA涂层样品的腐蚀速率最低,其平均值为0.98mm/a,与未涂层样品相比,在14天内减少了81%。根据3天mTT结果,使用PCL/2.5%HA涂层可使细胞活性从43%提高到121%。综上,涂覆PCL/2.5%HA纤维的mg/HA复合材料在生物可吸收植入物方面具有广阔的应用前景。

关键词：镁基复合材料复合涂层生物可降解羟基磷灰石聚己内酯纤维

Static and Dynamic Pull-In Instability of Nano-Beams Resting on Elastic Foundation Based on the Nonlocal Elasticity Theory

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Chinese Journal of mechanical Engineering 2017年第2期30卷 385-397页

作者： hamid m.sedighi ASHKAN Sheikhanzadeh mechanical Engineering Department Faculty of EngineeringShahid Chamran University of Ahvaz Departmentof mechanical Engineering Najafabad BranchIslamic Azad Univesity

This paper provides the static and dynamic pullin behavior of nano-beams resting on the elastic foundation based on the nonlocal theory which is able to capture the size effects for structures in micron and sub-micron scales. For this purpose, the governing equation of motion and the boundary conditions are driven using a variational approach. This formulation includes the influences of fringing field and intermolecular forces such as Casimir and van der Waals forces. The differential quadrature （DQ） method is employed as a high-order approximation to discretize the governing nonlinear differential equation, yielding more accurate results with a Considerably smaller number of grid points. In addition, a powerful analytical method called parameter expansion method （PEm） is utilized to compute the dynamic solution and frequency-amplitude relationship. It is illustrated that the first two terms in series expansions are sufficient to produce an acceptable solution of the mentioned structure. Finally, the effects of basic parameters on static and dynamic pull-in insta- bility and natural frequency are studied.

关键词： Static and dynamic pull·in voltages Size dependent Nonlocal theory Euler·Bernoulli beam model Differential quadrature method Parameter Expansion method

Ensemble Wind Power Prediction Interval with Optimal Reserve Requirement

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Journal of modern Power Systems and Clean Energy 2024年第1期12卷 65-76页

作者： hamid Rezaie Cheuk Hei Chung Nima Safari the Saskatchewan Power Corporation(SaskPower) ReginaSaskatchewanCanada the Department of Electrical and Computer Engineering and Department of Human Biology University of TorontoTorontoON M5S 3G4Canada the Alberta Electric System Operator(AESO) CalgaryAlbertaCanada

Wind power prediction interval(WPPI)models in the literature have predominantly been developed for and tested on specific case studies.However,wind behavior and characteristics can vary significantly across regions.Thus,a prediction model that performs well in one case might underperform in another.To address this shortcoming,this paper proposes an ensemble WPPI framework that integrates multiple WPPI models with distinct characteristics to improve robustness.Another important and often overlooked factor is the role of probabilistic wind power prediction(WPP)in quantifying wind power uncertainty,which should be handled by operating reserve.Operating reserve in WPPI frameworks enhances the efficacy of WPP.In this regard,the proposed framework employs a novel bi-layer optimization approach that takes both WPPI quality and reserve requirements into account.Comprehensive analysis with different real-world datasets and various benchmark models validates the quality of the obtained WPPIs while resulting in more optimal reserve requirements.

关键词： Ensemble model linear programming operating reserve optimal reserve requirement prediction interval probabilistic prediction renewable integration uncertainty representation wind power prediction(WPP)

Severe plastic deformation (SPD) of biodegradable magnesium alloys and composites: A review of developments and prospects

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Journal of magnesium and Alloys 2022年第4期10卷 938-955页

作者： m.Kasaeian-Naeini m.sedighi R.Hashemi School of mechanical Engineering Iran University of Science and TechnologyTehranIran

The use of magnesium in orthopedic and cardiovascular applications has been widely attracted by diminishing the risk of abnormal interaction of the implant with the body tissue and eliminating the second surgery to remove it from the body.Nevertheless,the fast degradation rate and generally inhomogeneous corrosion subsequently caused a decline in the mechanical strength of mg during the healing period.Numerous researches have been conducted on the influences of various severe plastic deformation(SPD)processes on magnesium bioalloys and biocomposites.This paper strives to summarize the various SPD techniques used to achieve magnesium with an ultrafine-grained(UFG)structure.moreover,the effects of various severe plastic deformation methods on magnesium microstructure,mechanical properties,and corrosion behavior have been discussed.Overall,this review intends to clarify the different potentials of applying SPD processes to the magnesium alloys and composites to augment their usage in biomedical applications.

关键词： magnesium Severe plastic deformation Biodegradable implant mechanical properties Corrosion

Kaoline-based catalyst for a high stability desulfurization of sour heavy naphtha in a three-phase oscillatory baffled reactor

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Particuology 2024年第1期84卷 249-260页

作者： Hassan m.Hmood Saba A.Gheni Safaa m.R.Ahmed mudheher m.Ali hamid Yonis Saleh mohammed H.mohammed Awad E.mohammed marwan A.mahomood Hiba R.mohammed Ahmed A.Hassan Adam Harvey North Refineries Company Ministry of OilIraq Chemical Engineering Department Tikrit UniversityIraq ministry of Oil Iraq AL-Hawija Technical Institute Northern Technical UniversityMoselIraq School of Engineering Newcastle UniversityUK

To meet the rapidly increasing demand for energy and the dramatic depletion of conventional crude oil,it is imperative to utilize sour naphtha.With no coke being produced,oxidative desulfurization(ODS)of naphtha lowers its sulfur content and average molecular weight.In this article,we outline a method for heavy naphtha non-extractive ODS using a very stable catalyst.The technique involves the use of a solid catalyst with oxygen gas as the oxidant.This necessitated relatively high mixing intensities;hence a three-phase Oscillatory Baffled Reactor(OBR)was used.The catalyst was based on the zeolite ZSm-5,prepared from natural kaolin by a series of delamination and activation steps and impregnated with Fe.A TiO2 nanolayer was applied,using the sol-gel method,to prevent rapid deactivation.The reactor performance was evaluated to minimize the sulfur content in the naphtha fuel.Due to the protective coating,the sulfur conversion stabilized at 90%.The results of this work establish the use of natural clay-based catalysts in a continuous,three-phase ODS,particularly with regard to proving long-term stability.It also showed that modest ODS can be achieved using an environmentally friendly oxidant,at mild operating conditions,whilst maintaining stability.

关键词： Natural kaoline Desulfurization Three-phase Oscillatory baffled reactor