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The main object of this research is to formulate the linear free vibration as well as static stability of embedded functionally graded carbon nanotube-reinforced composite microbeams in thermal environment. The nonlocal stress–strain gradient theory in conjunction with the unified higher-order beam theory by considering the temperature dependence of material properties and the initial thermal stresses...
In this article, linear and nonlinear transverse vibration of Euler–Bernoulli beams with multiple concentrated masses have been investigated using variational iteration method (VIM), and the effects of concentrated mass on natural frequencies and mode shapes have been taken into account as well. VIM is a powerful method with high convergence which gives analytical solution to linear problems and is...
In this paper, output power and voltage from piezoelectric materials for trapezoidal sandwich beams, considering proof mass on free end of the beam with base excitation, are formulated. The proposed analytic formulation has a general form and can be applied to rectangular and triangular beams. Using this formulation, geometrical dimensions of a trapezoidal beam with volume less than a cubic centimeter...
The free vibration behavior of isotropic and orthotropic composite plates under the hygrothermal environment is investigated in this article. The composite material properties are considered to be the function of temperature and moisture concentration, and the effective properties are evaluated using the micromechanics approach. The plate model is developed mathematically using refined nth-order shear...
It is known that atherosclerosis disease can lead to narrowing of human arteries over time. In this research, the flow field in the left external carotid artery is studied numerically considering fluid–structure interactions and effect of different activities on the risk of atherosclerosis disease is evaluated. In this research, it is studied as to whether having physical exercise can reduce the risk...
In this study, the low-velocity impact behavior of porous metal matrix composites (MMCs) has been investigated. The MMCs consisting of spheroidal cast iron chips (GGG-40) and bronze chips (CuSn10) were produced by hot isostatic pressing. The MMCs were produced with different CuSn10 contents as 90–80–70–60%. The hot isostatic pressing was performed under three different pressures and temperatures....
The flutter vibration of a functionally graded carbon nanotube-reinforced composite (FG-CNTRC) beam subjected to a follower force has been studied in this paper; in addition, by using an inverse dynamics controller, the flutter vibrations of the beam have been suppressed. The material properties of the composite beam which are graded in the thickness direction of it are estimated through the rule...
The current study presents an experimental analysis of a custom-designed heat exchanger (CDHX), for recovering the waste heat energy of the exhaust gas from a stationary diesel engine. It has triangular external finned tubular construction with its shell flue side fitted with segmental baffles sloped at 20°, to effectively extract heat to raise the tube side circulating thermal oil temperature for...
In this paper, flattening process of polyurethane foam-filled aluminum columns with rectangular and square cross-sections subjected to lateral compression load is investigated, theoretically and experimentally. For this purpose, some flattening tests were performed on the foam-filled rectangular columns using a DMG machine, model 7166. Based on a new theoretical plastic deformation model, a relation...
In this paper, free vibration of functionally graded (FG) microbeams under thermal environment based on modified couple stress theory is investigated. The internal length-scale parameter is considered to account for material size effect. The Rayleigh–Ritz method is employed, and the eigenvalue problem for obtaining the natural frequencies of FG microbeam is solved for different boundary conditions...
On the basis of a nonlocal shell model, the thermal buckling analysis of carbon nanocones (CNCs) is presented. Using Donnell’s strain–displacement relations and considering Eringen’s nonlocal elasticity theory, the stability equations of CNCs are derived. Employing the generalized differential quadrature method and trigonometric expansion in axial and circumferential directions of CNC, the stability...
An active preview control strategy is presented to suppress the vibration of hydrostatic guideway under dynamic machining force. A state space model of closed hydrostatic guideway system is built, and the predictability of machining force during cutting process is analyzed. Numerical simulation model of preview compensation control systems is established. The displacements of slide carriage are compared...
With growing concerns about air pollution, Human Powered Vehicle (HPV) offers a possible solution. With limited power available from human muscle, HPVs must be as efficient as possible because aerodynamic drag is the dominant retarding force at high speed. Two fairings for the use cases of pure speed and everyday use are conceived, designed, implemented and operated where the key parameters of frontal...
The pump structure may involve using fins on the impeller discs to reduce axial thrust. The fins are also used to reduce pressure acting on the discharge-side stuffing box, throw mechanical impurities away and protect the seal against mechanical impurities at the pump impeller inlet. Extensive laboratory tests were performed on finned discs at the water centrifugal flow for different fin widths and...
In this article, the vibrational behavior of beam-type microstructures made of carbon nanotube-reinforced composite is studied based on a finite element approach accounting for micro-/nanoscale effects. It is considered that the surface of microbeams is perfectly bonded with a piezoelectric actuator layer. First, the random distribution of CNTs into the polymer matrix is modeled using a three-phase...
The present study focuses on the detailed technical and cost-effective feasibility analyses of a 60 MWe steam power plant integrated with parabolic trough solar collectors. Aluminum oxide (Al2O3) nanoparticles are mixed with thermal oil to be used as a heat transfer fluid in the collector loops. The electric power is generated using steam Rankine cycle. For this purpose, the steam turbine of 60 MWe...
Stick–slip vibration (SSV) in oilwell drillstring presents one of the primary reasons of drilling performance deterioration as it reduces rate of penetration, aggravates tool failures, reduces wellbore quality, and increases drilling cost. Although a number of research works have focused on this subject, there is not a commonly accepted explanation of its cause yet. In our previous work, influences...
This research article is a numerical simulation study and experimental verification of the frictional behaviors of grease lubricated sliding contact under mixed lubrication conditions. The influences of surface texture parameters on the frictional properties were investigated. A numerical simulation model was specifically developed in MatLab which employs the average flow Reynolds equation established...
In this paper, a new, simple and cheap sensor is proposed to detect the multipoint contact of a typical robotic wheel. The new sensor empowers a wheeled robot to scan the surface and to find stability margins during real-time locomotion without camera or laser sensors. Furthermore, it enhances the ability of the real-time solution of the dynamic equations. The new sensor is based on the total resistance...
In this paper, two types of helical gear pairs are defined based on the relationship between the transverse contact ratio and overlap contact ratio. An improved analytical model using the slicing principle is proposed for the calculation of the single mesh stiffness of helical gears. The main improvement in this model against traditional models, that assume no coupling effects between neighbouring...
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