• Structural Engineering and Mechanics
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• v.69 no.6
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• pp.667-676
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• 2019

Minimizing the stress concentration around hypotrochoid hole in finite metallic plates under in-plane loading is an important consideration in engineering design. In the analysis of finite metallic plate, the effective factors on stress distribution around holes include curvature radius of the corner of the hole, hole orientation, plate's aspect ratio, and hole size. This paper aims to investigate the impact of these factors on stress analysis of finite metallic plate with central hypotrochoid hole. To obtain the lowest value of stress around a hypotrochoid hole, a swarm intelligence optimization method named ant lion optimizer is used. In this study, with the hypothesis of plane stress circumstances, analytical solution of Muskhelishvili's complex variable method and conformal mapping is employed. The plate is taken into account to be finite, isotropic and linearly elastic. By applying suitable boundary conditions and least square boundary collocation technique, undefined coefficients of stress function are found. The results revealed that by choosing the above-mentioned factor correctly, the lowest value of stress would be obtained around the hole allowing to an increment in load-bearing capacity of the structure.

• Metals and materials international
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• v.24 no.6
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• pp.1333-1345
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• 2018

The effect of manganese sulfide (MnS) inclusions on the machinability of free-cutting steel is based on their morphology, size and distribution. Furthermore, the plasticity of MnS is high during the hot working caused different characterization of MnS. In this study, the deformation behavior of MnS in 1215MS steel after a thermomechanical process was investigated at 1323 K. The microstructures of MnS inclusions were characterized by optical microscopy, scanning electron microscopy, energy-dispersive spectrometry, and electron backscattering diffraction (EBSD). As the thickness reduction of the inclusions increased from 10 to 70%, their average aspect ratio increased from 1.20 to 2.39. In addition, the deformability of MnS inclusions was lower than that of the matrix. The possible slip systems of A, B, C, and D plane traces were (${\bar{1}}0{\bar{1}}$)[${\bar{1}}01$], ($10{\bar{1}}$)[101], (011)[$01{\bar{1}}$], and (110)[$1{\bar{1}}0$]. Furthermore, the EBSD measurements suggested that slip planes in MnS inclusions occur on {110} planes.

• Advances in nano research
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• v.6 no.4
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• pp.377-397
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• 2018

In the present investigation, thermal buckling and free vibration characteristics of functionally graded (FG) Timoshenko nanobeams subjected to nonlinear thermal loading are carried out by presenting a Navier type solution. The thermal load is assumed to be nonlinear distribution through the thickness of FG nanobeam. Thermo-mechanical properties of FG nanobeam are supposed to vary smoothly and continuously throughout the thickness based on power-law model and the material properties are assumed to be temperature-dependent. Eringen's nonlocal elasticity theory is exploited to describe the size dependency of nanobeam. Using Hamilton's principle, the nonlocal equations of motion together with corresponding boundary conditions based on Timoshenko beam theory are obtained for the thermal buckling and vibration analysis of graded nanobeams including size effect. Moreover, in following a parametric study is accompanied to examine the effects of the several parameters such as nonlocal parameter, thermal effect, power law index and aspect ratio on the critical buckling temperatures and natural frequencies of the size-dependent FG nanobeams in detail. According to the numerical results, it is revealed that the proposed modeling can provide accurate frequency results of the FG nanobeams as compared some cases in the literature. Also, it is found that the small scale effects and nonlinear thermal loading have a significant effect on thermal stability and vibration characteristics of FG nanobeams.

• Coupled systems mechanics
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• v.12 no.4
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• pp.391-407
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• 2023

This paper presents a static study of a rectangular functional graded material (FGM) plate, simply supported on its four edges, adopting a refined higher order theory that looks for, only,four unknowns,without taking into account any corrective factor of the deformation energy with the satisfaction of the zero shear stress conditions on the upper and lower faces of the plate. We will have determined the contribution of these stresses in the transverse deflection of the plate, as well as their effects on the axial stress within the interfaces between the layers(to avoid any problem of imperfections such as delamination) and on the top and bottom edges of the plate in order to take into account the fatigue phenomenon when choosing the distribution law of the properties used during the design of the plate. A numerical statement, in percentage, of the contribution of the shear effect is made in order to show the reliability of the adopted theory. We will also have demonstrated the need to add the shear effect when the aspect ratio is small or large. Code routines are programmed to obtain numerical results illustrating the validity of the model proposed in the theory compared to those available in the literature.

• Advances in nano research
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• v.12 no.3
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• pp.253-261
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• 2022

Numerical modelling of an integrated Carbon NanoTube (CNT) membrane is only achievable if probable deformations and realistic alterations from a perfect CNT membrane are taken into account. Considering the possible forms of CNTs, bending is one of the most probable deformations in these high aspect ratio nanostructures. Hence, investigation of effect associated with bent CNTs are of great interest. In the present study, molecular dynamics simulation is utilized to investigate fluid flow dynamics in deformed CNT membranes, specifically when the tube cross section is not affected. Bending in armchair (5,5) CNT was simulated using Tersoff potential, prior to flow rate investigation. Also, to study effect of inclined entry of the CNT to the membrane wall, argon flow through generated inclined CNT membranes is examined. The results show significant variation in both cases, which can be interpreted as counter-intuitive, since the cross section of the CNT was not deformed in either case. The distribution of fluid-fluid and fluid-wall interaction potential is investigated to explain the anomalous behavior of the flow rate versus bending angle.

• Advances in nano research
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• v.12 no.3
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• pp.231-251
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• 2022

Dynamic behavior of temperature-dependent Reddy functionally graded (RFG) nanobeam subjected to thermomagnetic effects under the action of moving point load is carried out in the present work. Both symmetric and sigmoid functionally graded material distributions throughout the beam thickness are considered. To consider the significance of strain-stress gradient field, a material length scale parameter (LSP) is introduced while the significance of nonlocal elastic stress field is considered by introducing a nonlocal parameter (NP). In the framework of the nonlocal strain gradient theory (NSGT), the dynamic equations of motion are derived through Hamilton's principle. Navier approach is employed to solve the resulting equations of motion of the functionally graded (FG) nanoscale beam. The developed model is verified and compared with the available previous results and good agreement is observed. Effects of through-thickness variation of FG material distribution, beam aspect ratio, temperature variation, and magnetic field as well as the size-dependent parameters on the dynamic behavior are investigated. Introduction of the magnetic effect creates a hardening effect; therefore, higher values of natural frequencies are obtained while smaller values of the transverse deflections are produced. The obtained results can be useful as reference solutions for future dynamic and control analysis of FG nanobeams reinforced nanocomposites under thermomagnetic effects.

• Steel and Composite Structures
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• v.49 no.6
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• pp.603-614
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• 2023

In this paper, frequency analysis of curved functionally graded (FG) nanobeam by consideration of deepness effect has been studied. Differential transform method (DTM) has been used to obtain frequency responses. The nonlocal theory of Eringen has been applied to consider nanoscales. Material properties are supposed to vary in radial direction according to power-law distribution. Differential equations and related boundary conditions have been derived using Hamilton's principle. Finally, by consideration of nonlocal theory, the governing equations have been derived. Natural frequencies have been obtained using semi analytical method (DTM) for different boundary conditions. In order to study the effect of deepness, the deepness term is considered in strain field. The effects of the gradient index, radius of curvature, the aspect ratio, the nonlocal parameter and interaction of aforementioned parameters on frequency value for different boundary conditions such as clamped-clamped (C-C), clamped-hinged (C-H), and clamped-free (C-F) have been investigated. In addition, the obtained results are compared with the results in previous literature in order to validate present study, a good agreement was observed in the present results.

• Design & Manufacturing
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• v.18 no.2
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• pp.29-34
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• 2024

This study intends to reduce forming load by adding die rotation to flange-upsetting process. Materials arc formed by the compression and rotational torque which are accrued from rotation of the lower die accompanied by axial compression of the punch. For the theoretic analysis of flange-upsetting process using rotation die, slab method was used. Furthermore, for the verification of the theoretic analysis results, FEM simulation using DEFORM 3D a commercial software was done, and through the model material experiment using Prasticine, the results were compared and reviewed. Flange-upsetting process using rotation die shows reduced forming load compared with process without die rotation and demonstrates uniform distribution of strain. And as for the effect of the reduction of forming load, the less the aspect ratio(h₀/d₀) and the greater friction coefficient, the greater effect is. With increase in die rotation velocity, the effect of forming load reduction also increases little by little, but its effect on forming load reduction is very negligible compared with other forming parameters. Theoretic analysis results and simulation results coincided pretty well. The flange-upsetting process using die rotation are evaluated as useful process that can produce reduction of forming load and uniform strain.

• Journal of Korean Society of Steel Construction
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• v.22 no.1
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• pp.43-53
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• 2010

Seismic isolation is one of the most widely implemented and accepted seismic protection systems to limit or avoid damages from unforeseeable earthquakes. As an energy absorption device, however, the supplemental lead itself tends to pollute the environment. Consequently, it is predicted that the use of lead would be controlled. Considering the pollution caused by lead, several researchers are interested in the viability of using steel in place of lead. In this study, first, based on the results of a non-linear finite element analysis, the excellent deformation capacity of a very tough steel damper was demonstrated by comparing it with that of the SS400 damper and determining the effects of main parameters (the aspect ratio, thickness, and width) on the deformation capacity. Second, an optimum shape and design equation for a U-shaped damper with an opening based on stress distribution was suggested.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.66 no.4
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• pp.242-246
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• 2017

In this study, it was investigated about optical simulation in high brightness and high uniformity general lighting using glass light guide plate. And we adopt edge-light emission type light plate. Edge-light type lighting has been used LCD application, especially note PC or smart phone backlight unit. Because it had the good properties such as slim shape and light weight. We thought this type was suitable for general lighting application such as wall attached type or ceiling mount type. But many of edge-light type lighting had problems. It called slanted output light rays. That was main key parameter how could control the direction of output light rays. We investigated the solution of this problems, using ray tracing method, we recognized the major fact of the solution relied on the geometric structure of diffusing dot shape. We set the conditions of aspect ratio in diffusing dot shape such as 0.5 to 1. And, at first, we designed diffusing dots shape based on the results of optical simulation and made specimen. as above condition, and acquired good result in confirming dots shape such as the value of the output rays's peak angle was around 75 degrees. And good light distribution characteristics were measured by slated spectro-radiometer. It was shown that the effective ways of designing light distribution characteristics using optical simulation such as ray tracing linear method for making general lighting using glass light guide plate.