A coupled fluid-solid-piezoelectric model has been developed by finite element method to study and improve the performance of a micro piezoelectric transducer designed for fluid flow energy harvesting. In this harvester, when the... more
A coupled fluid-solid-piezoelectric model has been developed by finite element method to study and improve the performance of a micro piezoelectric transducer designed for fluid flow energy harvesting. In this harvester, when the turbulence flow of water passes over a bluff body, the vortex shedding phenomenon occurs and applies a periodical lift force to a piezoelectric beam placed in the downstream region. The resulting oscillations in the piezoelectric beam lead to electrical power generation. Navier-Stokes equations and large-eddy simulation method have been used to describe the fluid turbulence flow, and equations of conservation of linear momentum along with piezoelectric constitutive relations have been employed to obtain solid deformation and electric field intensity. Numerical experiments designed by Taguchi’s method have been used to study the effect of different parameters on the harvester performance. The results have shown that using a triangular or D-shape bluff body, ...
Stenting is considered to be the favoured tool for therapy of coronary stenosis disease. However, despite the many advantages of this treatment strategy, its outcome may be undermined by the restenosis occurrence in the stent deployment... more
Stenting is considered to be the favoured tool for therapy of coronary stenosis disease. However, despite the many advantages of this treatment strategy, its outcome may be undermined by the restenosis occurrence in the stent deployment site. Observations have shown that stent deployment in the artery alters the hemodynamic parameters such as wall shear stress and vortice size and prepares the conditions for in-stent restenosis development. Considering this fact, in this paper, the effect of some geometrical parameters such as the shape and the size of the stent strut on the wall shear stress distribution and vortice size is investigated. Furthermore, employment of a stent with partial flexible strut is suggested to decrease the restenosis risk, and the effect of the flexible part stiffness is explored. For this purpose, the interaction between the blood flow and the flexible part is simulated by arbitrary Lagrangian-Eulerian approach in the framework of the finite element method. T...
Tolerance analysis of flexible assemblies with contact effects based on modified influence coefficients method, Modares Mechanical Engineering, ABSTRACT In sheet metal structures, due to high flexibility of the sheets, the dimensional and... more
Tolerance analysis of flexible assemblies with contact effects based on modified influence coefficients method, Modares Mechanical Engineering, ABSTRACT In sheet metal structures, due to high flexibility of the sheets, the dimensional and geometrical errors do considerably influence the assembly tolerances. n one hand, various stages of design, manufacturing and assembly of mechanical sets are involved in various factors such as dimensional, geometrical and material uncertainties. As a result, presenting a comprehensive model based on which propagation of the changes resulted from the uncertainties of the manufacturing processes and their relations with assembly tolerances could be approximated with a high accuracy seems necessary. In normal influence coefficients method, neglecting the contact effects between the components not only causes the diffusion of contact surfaces, but also leads to errors in predicting assembly tolerances. In this paper, an applicative method for toleranc...
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Radial forging is an open die forging process used for reducing the diameters of shafts, tubes, stepped shafts and axels, and for creating internal profiles in tubes. In this study, the effect of the workpiece rotation (the... more
Radial forging is an open die forging process used for reducing the diameters of shafts, tubes, stepped shafts and axels, and for creating internal profiles in tubes. In this study, the effect of the workpiece rotation (the circumferential feed) on the strain and residual stress distribution in the inner surface of the tube in the cold radial forging process is investigated using nonlinear three dimensional finite element modeling. To verify the model, the predicted radial forging load is compared with the published experimental data which shows a good agreement. It is shown that for achieving a more favorable residual stress distribution in the workpiece inner surface, the rotation angle associated with each stroke should be reduced. Furthermore, a total rotation angle of 90° seems to be sufficient for finalizing the strain and residual stress distribution in the workpiece inner surface and using additional rotation is just a waste of time and energy in this respect.
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Radial forging is an open die forging process used for reducing the diameters of shafts, tubes, stepped shafts and axels, and for creating internal profiles in tubes. Among parameters affecting process variables, the die geometry is of... more
Radial forging is an open die forging process used for reducing the diameters of shafts, tubes, stepped shafts and axels, and for creating internal profiles in tubes. Among parameters affecting process variables, the die geometry is of fundamental importance and greatly influences variables such as forging load, stress distribution on the dies, metal flow during deformation, and surface finish of the forged product. In this paper a generalized slab method analysis of radial forging process is presented which can handle this process with curved shape dies. Results for dies with various curves are presented and it is shown that the analysis reduces to that of Lahoti and Altan [2] when the die has a linear profile.
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ABSTRACT A new design for a valveless micropumping device has been proposed that integrates two existing pumping technologies, namely, the wall induced traveling wave and the obstacle-type valveless micropump. The liquid in the... more
ABSTRACT A new design for a valveless micropumping device has been proposed that integrates two existing pumping technologies, namely, the wall induced traveling wave and the obstacle-type valveless micropump. The liquid in the microchannel is transported by generating a traveling wave on the channel, while the placing of two asymmetric trapezoid obstacles, along the centerline of the channel inlet and outlet, leads to a significant (up to seven times) increase of the net flow rate of the device. The effectiveness of this innovative design has been proved through a verified three-dimensional finite element model. Fluid–Structure Interaction (FSI) analysis is performed in the framework of an Arbitrary Lagrangian–Eulerian (ALE) method.
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... Fluids (2011) Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/fld.2592 Fluidstructure interaction analysis in microfluidic devices: A dimensionless finite element approach Hamed Afrasiab, Mohammad R.... more
... Fluids (2011) Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/fld.2592 Fluidstructure interaction analysis in microfluidic devices: A dimensionless finite element approach Hamed Afrasiab, Mohammad R. Movahhedy*, and Ahmad Assempour ...
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دییامن هدافتسا لیذ ترابع زا هلاقم نیا هب عاجرا یارب : Please cite this article using: S. OmidDezyani, R. A. Jafari-Talookolaei, M. Abedi, H. Afrasiab, Vibration analysis of a microplate in contact with a fluid based on the modified couple... more
دییامن هدافتسا لیذ ترابع زا هلاقم نیا هب عاجرا یارب : Please cite this article using: S. OmidDezyani, R. A. Jafari-Talookolaei, M. Abedi, H. Afrasiab, Vibration analysis of a microplate in contact with a fluid based on the modified couple stress theory, Modares Mechanical Engineering, Vol. 17, No. 2, pp. 47-57, 2017 (in Persian) هدش حلاصا لپوک شنت یروئت سبسارب لبیس بب سبمت رد هحفص ورکیم یشبعترا لیلحت
ABSTRACT: Pathological studies have shown that coronary atherosclerotic plaques are more prone to rupture under physical exercise. In this paper, using a fully coupled fluid-structure interaction (FSI) analysis based on arbitrary... more
ABSTRACT: Pathological studies have shown that coronary atherosclerotic plaques are more prone to rupture under physical exercise. In this paper, using a fully coupled fluid-structure interaction (FSI) analysis based on arbitrary Lagrangian-Eulerian (ALE) finite element method, the effect of the coronary blood flow rate increase during physical exercise on the plaque rupture risk is investigated for different plaque types. It is proved that the increase in coronary blood flow rate during physical exercise considerably increases the maximum stress in the plaque fibrous cap which can potentially lead to the plaque rupture. The issue is investigated for different plaque shapes and their vulnerability to exercise condition is compared. It is observed that the diffused plaque type which experiences the maximum stress of 187.9 kPa at rest and 544 kPa at exercise is the most critical plaque type. Because it is subjected to the highest stress in both of these conditions. However, the descen...
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In sheet metal structures, due to high flexibility of the sheets, the dimensional and geometrical errors do considerably influence the assembly tolerances. On one hand, various stages of design, manufacturing and assembly of mechanical... more
In sheet metal structures, due to high flexibility of the sheets, the dimensional and geometrical errors do considerably influence the assembly tolerances. On one hand, various stages of design, manufacturing and assembly of mechanical sets are involved in various factors such as dimensional, geometrical and material uncertainties. As a result, presenting a comprehensive model based on which propagation of the changes resulted from the uncertainties of the manufacturing processes and their relations with assembly tolerances could be approximated with a high accuracy seems necessary. In normal influence coefficients method, neglecting the contact effects between the components not only causes the diffusion of contact surfaces, but also leads to errors in predicting assembly tolerances. In this paper, an applicative method for tolerance analysis of flexible sheet structures and precise prediction of abundant errors in assembly characteristics is presented by modifying the influence co...
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In this paper, the direct extrusion process of bimetallic rods in conical dies is analyzed by an improved upper bound method. The deformation zone is subdivided into six smaller zones and by considering a non-spherical entrance boundary... more
In this paper, the direct extrusion process of bimetallic rods in conical dies is analyzed by an improved upper bound method. The deformation zone is subdivided into six smaller zones and by considering a non-spherical entrance boundary to the deformation zone, a velocity field is presented which is different from velocity fields employed in previous studies. The total power consumption of the process including internal, shear and frictional powers is obtained using this velocity field, and then the forming force is calculated by employing the upper bound theory. The superior accuracy of the proposed analysis is demonstrated by comparing the computed force with available experimental data and results of an upper bound analysis in the literature. Finally, the developed model is employed to study the effect of some process parameters on the forming load. I t is observed that there is an optimal die angle that minimizes the extrusion force. The value of this optimum angle increases wit...
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Prediction of machining process capability in the design stage plays a key role to reach the precision design and manufacturing of mechanical products. Inaccuracies in machining process lead to errors in position and orientation of... more
Prediction of machining process capability in the design stage plays a key role to reach the precision design and manufacturing of mechanical products. Inaccuracies in machining process lead to errors in position and orientation of machined features on the part, and strongly affect the process capability in the final quality of the product. In this paper, an efficient systematic approach is given to investigate the machining errors to predict the manufacturing errors of the parts and capability prediction of corresponding machining processes. A mathematical formulation of fixture locators modeling is presented to establish the relationship between the part errors and the related sources. Based on this method, the final machining errors of the part can be accurately estimated by relating them to the combined dimensional and geometric tolerances of the workpiece – fixture system. This method is developed for uncertainty analysis based on the Worst Case and statistical approaches. The ...
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This article investigates the interaction between a surface gravity wave that propagates over an elastic plate based on linear viscoelastic foundation. The plate is considered to be thin and infinite and is modeled based on the... more
This article investigates the interaction between a surface gravity wave that propagates over an elastic plate based on linear viscoelastic foundation. The plate is considered to be thin and infinite and is modeled based on the Euler–Bernoulli beam theory. Static and dynamic boundary conditions are applied to the Laplace equation of the fluid domain. The dispersion relation of the wave–plate system is derived and ratio of surface wave amplitude and plate deflection is proposed. Considering dimensionless dispersion relation, two modes of propagating wave are attained. Problem is analyzed for two cases of presence and absence of viscous damping coefficient in the foundation of the elastic plate. It is shown that flexural rigidity of the submerged plate has considerable effect on wave decay and plate vibration. It is illustrated that shallowness has noticeable effect on the wave propagation frequency and a critical shallowness demarcates damped or overdamped excitation of the elastic plate based on the viscoelastic foundation. Moreover, effects of flexural rigidity of the plate, foundation stiffness coefficient, and foundation viscous coefficient on phase and group velocities of wave are discussed in the present study.
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Abstract In this paper, the size-effect and fluid-structure interaction on the vibrational characteristics of a simply supported rectangular microplate is investigated. The influences of rotary inertia and transverse shear deformation... more
Abstract In this paper, the size-effect and fluid-structure interaction on the vibrational characteristics of a simply supported rectangular microplate is investigated. The influences of rotary inertia and transverse shear deformation which have the remarkable role in the analysis of moderately thick microplates are considered. The first order shear deformation theory along with the modified couple stress theory has been used to perform the free vibrational analysis of the considered problem. The Hamilton's principle is employed to derive the governing differential equations of motion and the corresponding boundary conditions. The fluid is assumed to be incompressible, inviscid and irrotational. The fluid velocity potential is obtained using the boundary and compatibility conditions. Then the Rayleigh-Ritz method has been applied to calculate the natural frequencies of the system. A convergence study is carried out. The obtained results are compared against available data in the published papers and very good agreements have been observed. Finally by referring to the numerical results, the effects of dimensionless thickness, side to thickness ratio, aspect ratio, material length scale parameter and fluid depth ratio on the natural frequencies are discussed in details.
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Abstract In this paper, the effect of hygrothermal conditions on elastic properties of polymeric composite materials is investigated by the finite element method . A micromechanical degradation model is developed based on Fick’s second... more
Abstract In this paper, the effect of hygrothermal conditions on elastic properties of polymeric composite materials is investigated by the finite element method . A micromechanical degradation model is developed based on Fick’s second law utilizing an ABAQUS python scripting micro modeling (APSMM) and an ABAQUS parallel finite element analysis (APFEA). The APSMM algorithm is used to study the degradation of elastic constants of a fiber-reinforced polymeric composite (AS/3501–5) under specific hygrothermal conditions, while, the APFEA scheme is employed to solve the problem under time-dependent (transient) hygrothermal conditions. The results are verified against available experimental data. The main advantage of the proposed methods is that by experimentally determining the composite material properties only at one particular temperature and humidity condition, these properties can be obtained after any time of exposure to constant or time-varying hygrothermal conditions. Furthermore, these methods can be extended to analyze different types of composites with any kind of material and/or construction.