• Title/Summary/Keyword: Non-material Factors

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Experimental Study on Characteristics of Dry Wire Electrical Discharge Machining (EDM) Process (건성 와이어방전가공 프로세스 특성에 관한 실험적 연구)

  • Lee, Sang-Won;Kim, Hong-Seok
    • Journal of the Korean Society for Precision Engineering
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    • v.27 no.1
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    • pp.11-17
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    • 2010
  • This study investigates the non-traditional manufacturing process of dry wire electrical discharge machining (EDM) in which liquid dielectric is replaced by a gaseous medium. Wire EDM experiments of thin workpieces were conducted both in wet and dry EDM conditions to examine the effects of spark cycle (T), spark on-time ($T_{on}$), thickness of work pieces, and work material on machining performance. The material removal rate (MRR) in the dry wire EDM case was much lower than that in the wet wire EDM case. In addition, the thickness of workpiece and work-material were found to be critical factors influencing the MRR for dry EDM process. The relative ratios of spark, arc and short circuit were also calculated and compared to examine the effectiveness of processes of dry and wet wire EDM.

The Possibilities to use the Non- Destructive Testing on Diagnosing Wears of Wagon Chassis

  • Munkhtsetseg, T.
    • International Journal of Railway
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    • v.5 no.1
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    • pp.22-28
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    • 2012
  • This report is devoted to the problems of Mongolian Railway Transportation Safety such as high length of wagon service life, defects due to the more factors of exploitation, idle time, increase of faults, poor condition of repairing shops and more hand and mechanical operations and these conditions are quite difficult to meet the safety and reliability of increasing transportation from day to day. The paper discusses that the most optimum solution is diagnosing before occurring wear, breakdown, and defects on the basis of studying characteristics of structural material breakdown, residual methods of voltage, effects of material hardness and linear defects of a crystal net and the reform of machines is very important to implement it. It focuses the structures, characteristics of the material transportation and tests and analyses of the wagon cart which has to meet the traffic safety of wagons and slow and soft movement. The study is done on the wagon chassis which has to meet the traffic safety of luggage wagons.

A four-variable plate theory for thermal vibration of embedded FG nanoplates under non-uniform temperature distributions with different boundary conditions

  • Barati, Mohammad Reza;Shahverdi, Hossein
    • Structural Engineering and Mechanics
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    • v.60 no.4
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    • pp.707-727
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    • 2016
  • In this paper, thermal vibration of a nonlocal functionally graded (FG) plates with arbitrary boundary conditions under linear and non-linear temperature fields is explored by developing a refined shear deformation plate theory with an inverse cotangential function in which shear deformation effect was involved without the need for shear correction factors. The material properties of FG nanoplate are considered to be temperature-dependent and graded in the thickness direction according to the Mori-Tanaka model. On the basis of non-classical higher order plate model and Eringen's nonlocal elasticity theory, the small size influence was captured. Numerical examples show the importance of non-uniform thermal loadings, boundary conditions, gradient index, nonlocal parameter and aspect and side-to-thickness ratio on vibrational responses of size-dependent FG nanoplates.

Nonlocal vibration analysis of FG nano beams with different boundary conditions

  • Ehyaei, Javad;Ebrahimi, Farzad;Salari, Erfan
    • Advances in nano research
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    • v.4 no.2
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    • pp.85-111
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    • 2016
  • In this paper, the classical and non-classical boundary conditions effect on free vibration characteristics of functionally graded (FG) size-dependent nanobeams are investigated by presenting a semi analytical differential transform method (DTM) for the first time. Three kinds of mathematical models, namely; power law (P-FGM), sigmoid (S-FGM) and Mori-Tanaka (MT-FGM) distribution are considered to describe the material properties in the thickness direction. The nonlocal Eringen theory takes into account the effect of small size, which enables the present model to become effective in the analysis and design of nanosensors and nanoactuators. Governing equations are derived through Hamilton's principle and they are solved applying semi analytical differential transform method. The good agreement between the results of this article and those available in literature validated the presented approach. The detailed mathematical derivations are presented and numerical investigations are performed while the emphasis is placed on investigating the effect of the several parameters such as small scale effects, spring constant factors, various material compositions and mode number on the normalized natural frequencies of the FG nanobeams in detail. It is explicitly shown that the vibration of FG nanobeams is significantly influenced by these effects. Numerical results are presented to serve as benchmarks for future analyses of FG nanobeams.

Thermal buckling Analysis of functionally graded plates using trigonometric shear deformation theory for temperature-dependent material properties

  • Lazreg Hadji;Royal Madan;Hassen Ait Atmane;Fabrice Bernard;Nafissa Zouatnia;Abdelkader Safa
    • Structural Engineering and Mechanics
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    • v.91 no.6
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    • pp.539-549
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    • 2024
  • In this paper, thermal buckling analysis was conducted using trigonometric shear deformation theory, which employs only four unknowns instead of five. This present theory is variationally consistent, and accounts for a trigonometric variation of the transverse shear strains across the thickness and satisfies the zero traction boundary conditions on the top and bottom surfaces of the plate without using shear correction factors. The grading is provided along the thickness of the plate as per power law volume fraction variation of metal-matrix ceramic reinforced composite. The non-linear governing equation problem was solved for simply supported boundary conditions. Three types of thermal loads are assumed in this work: uniform, linear and non-linear distribution through-the-thickness. It is well known that material properties change with temperature variations and so the analysis was performed for both the cases: temperature-dependent (TD) and temperature-independent (TID) material properties. The impact on thermal buckling for both linear and non-linear temperature variation was considered. The results were validated for the TID case with other theories and were found to be in good agreement. Furthermore, a comprehensive analysis was performed to study the impact of grading indices and geometrical parameters, such as aspect ratio (a/b) and side-to-thickness ratio (a/h), on the thermal buckling of the FG plate.

The Numerical Analysis of Non-Newtonian Flow through Branched and Stenotic Tube (CFD를 이용한 분지관.협착관의 비뉴턴 유체 해석)

  • Hwang, Do-Yeon;Ki, Min-Cheol;Han, Byeong-Yun;Park, Hyung-Koo
    • 한국전산유체공학회:학술대회논문집
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    • 2008.03b
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    • pp.385-388
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    • 2008
  • The objective of this paper is simulating blood flow through the branched and stenotic tube numerically. SC-Tetra, which is one of the commercial code using FVM method, was utilized for this analysis. The flow is assumed as an incompressible laminar flow with the additional condition of non-Newtonian fluid. As the constitutive equation for the fluid viscosity, the following models were solved with governing equations ; Cross Model, Modified Cross Model, Carreau Model and Carreau-Yasuda Model. Final goal was achieved to get analytic data about shear stress, at specific points, changing the geometry with various factors like the bifurcation angle, diameter of the branches, the ratio of stenosis, and etc. The material property of blood was referred from the related papers. Furthermore, to verify results they were compared with those of the published papers. There were some discrepancies based on the different solver and the different data post-processing method. However, many parameters like the location of low shear stress, which arised from bifurcation or stenosis, and the tendency of various factors were found to be very similar.

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A Study on Central Bursting Defects in Forward Extrusion by the Finite Element Method (유한요소법을 이용한 전방압출공정의 내부결함에 관한 연구)

  • Kim, T.H.;Lee, J.H.;Kwon, H.H.;Kim, B.M.;Kang, B.S.;Choi, J.C.
    • Transactions of Materials Processing
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    • v.1 no.1
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    • pp.66-74
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    • 1992
  • According to the variation of hydrostatic pressure on the central axis of deformable material, the V-shaped central bursting defect may be created in extrusion or drawing processes. The process factors which affect the generation of defects are semi-angle of die, reduction ratio of cross-sectional area, friction factor, material properties and so on. The combination of these factors can determine the possibility of defect creation and the shape of various round holes which have been created inside already. By the rigid plastic finite element method, this paper describes the observations of change in shape of round holes with process conditions such as semi-angle of die, reduction ratio of cross-sectional area and friction factor at the non-steady state of axisymmetrical extrusion process when the round hole is already existed inside the original billet. Also, the effects of process factors are investigated to prevent the possible defects.

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Prediction of Etch Profile Uniformity Using Wavelet and Neural Network

  • Park, Won-Sun;Lim, Myo-Taeg;Kim, Byungwhan
    • International Journal of Control, Automation, and Systems
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    • v.2 no.2
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    • pp.256-262
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    • 2004
  • Conventionally, profile non-uniformity has been characterized by relying on approximated profile with angle or anisotropy. In this study, a new non-uniformity model for etch profile is presented by applying a discrete wavelet to the image obtained from a scanning electron microscopy (SEM). Prediction models for wavelet-transformed data are then constructed using a back-propagation neural network. The proposed method was applied to the data collected from the etching of tungsten material. Additionally, 7 experiments were conducted to obtain test data. Model performance was evaluated in terms of the average prediction accuracy (APA) and the best prediction accuracy (BPA). To take into account randomness in initial weights, two hundred models were generated for a given set of training factors. Behaviors of the APA and BPA were investigated as a function of training factors, including training tolerance, hidden neuron, initial weight distribution, and two slopes for bipolar sig-moid and linear function. For all variations in training factors, the APA was not consistent with the BPA. The prediction accuracy was optimized using three approaches, the best model based approach, the average model based approach and the combined model based approach. Despite the largest APA of the first approach, its BPA was smallest compared to the other two approaches.

Derivation of response spectrum compatible non-stationary stochastic processes relying on Monte Carlo-based peak factor estimation

  • Giaralis, Agathoklis;Spanos, Pol D.
    • Earthquakes and Structures
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    • v.3 no.5
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    • pp.719-747
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    • 2012
  • In this paper a novel approach is proposed to address the problem of deriving non-stationary stochastic processes which are compatible in the mean sense with a given (target) response (uniform hazard) spectrum (UHS) as commonly desired in the aseismic structural design regulated by contemporary codes of practice. The appealing feature of the approach is that it is non-iterative and "one-step". This is accomplished by solving a standard over-determined minimization problem in conjunction with appropriate median peak factors. These factors are determined by a plethora of reported new Monte Carlo studies which on their own possess considerable stochastic dynamics merit. In the proposed approach, generation and treatment of samples of the processes individually on a deterministic basis is not required as is the case with the various "two-step" approaches found in the literature addressing the herein considered task. The applicability and usefulness of the approach is demonstrated by furnishing extensive numerical data associated with the elastic design UHS of the current European (EC8) and the Chinese (GB 50011) aseismic code provisions. Purposely, simple and thus attractive from a practical viewpoint, uniformly modulated processes assuming either the Kanai-Tajimi (K-T) or the Clough-Penzien (C-P) spectral form are employed. The Monte Carlo studies yield damping and duration dependent median peak factor spectra, given in a polynomial form, associated with the first passage problem for UHS compatible K-T and C-P uniformly modulated stochastic processes. Hopefully, the herein derived stochastic processes and median peak factor spectra can be used to facilitate the aseismic design of structures regulated by contemporary code provisions in a Monte Carlo simulation-based or stochastic dynamics-based context of analysis.

Derivation of response spectrum compatible non-stationary stochastic processes relying on Monte Carlo-based peak factor estimation

  • Giaralis, Agathoklis;Spanos, Pol D.
    • Earthquakes and Structures
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    • v.3 no.3_4
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    • pp.581-609
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    • 2012
  • In this paper a novel non-iterative approach is proposed to address the problem of deriving non-stationary stochastic processes which are compatible in the mean sense with a given (target) response (uniform hazard) spectrum (UHS) as commonly desired in the aseismic structural design regulated by contemporary codes of practice. This is accomplished by solving a standard over-determined minimization problem in conjunction with appropriate median peak factors. These factors are determined by a plethora of reported new Monte Carlo studies which on their own possess considerable stochastic dynamics merit. In the proposed approach, generation and treatment of samples of the processes individually on a deterministic basis is not required as is the case with the various approaches found in the literature addressing the herein considered task. The applicability and usefulness of the approach is demonstrated by furnishing extensive numerical data associated with the elastic design UHS of the current European (EC8) and the Chinese (GB 50011) aseismic code provisions. Purposely, simple and thus attractive from a practical viewpoint, uniformly modulated processes assuming either the Kanai-Tajimi (K-T) or the Clough-Penzien (C-P) spectral form are employed. The Monte Carlo studies yield damping and duration dependent median peak factor spectra, given in a polynomial form, associated with the first passage problem for UHS compatible K-T and C-P uniformly modulated stochastic processes. Hopefully, the herein derived stochastic processes and median peak factor spectra can be used to facilitate the aseismic design of structures regulated by contemporary code provisions in a Monte Carlo simulation-based or stochastic dynamics-based context of analysis.