• Transactions of Materials Processing
• /
• v.16 no.4 s.94
• /
• pp.276-281
• /
• 2007

The hardening and the constitutive equation based on the crystal plasticity are introduced for the numerical simulation of hemispherical sheet metal forming. For calculating the deformation and the stress of the crystal, Taylor's model of the crystalline aggregate is employed. The hardening is evaluated by using the Taylor factor, the critical resolved shear stress of the slip system, and the sum of the crystallographic shears. During the hemispherical forming process, the texture of the sheet metal is evolved by the plastic deformation of the crystal. By calculating the Euler angles of the BCC sheet, the texture evolution of the sheet is traced during the forming process. Deformation texture of the BCC sheet is represented by using the pole figure. The comparison of the strain distribution and punch force in the hemispherical forming process between the prediction using crystal plasticity and experiment shows the verification of the crystal plasticity-based formulation and the accuracy of the hardening and constitutive equation obtained from the crystal plasticity.

• Journal of Educational Research in Mathematics
• /
• v.12 no.2
• /
• pp.265-274
• /
• 2002

The purpose of the paper is to provide the importance of matacognition as a factor to correct the errors generated by the intuition. For this, first of all, we examine not only the role of metacognition in mathematics education but also the errors generated by the intuition in the mathematical problem solving process. Next, we research the possibility of using metacognition as a factor to correct the errors in the mathematical problem solving process via both the related theories about the metacognition and an example. In particular, we are able to acknowledge the importance of the role of metacognition throughout the example in the process of the problem solving It is not difficult to conclude from the study that emphasis on problem solving will enhance the development of problem solving ability via not only the activity of metacognition but also intuitive thinking. For this, it is essential to provide an environment that the students can experience intuitive thinking and metacognitive activity in mathematics education .

• International Journal of Reliability and Applications
• /
• v.14 no.2
• /
• pp.55-70
• /
• 2013

This paper deals with the Bayesian analysis of the failure data of a repairable mechanical system subject to minimal repairs and periodic overhauls. The effect of overhauls on the reliability of the system is modeled by a proportional age reduction model and the failure process between two successive overhauls is assumed to be 2-parameter Engelhardt-Bain process (2-EBP). Power Law Process (PLP) model has a disadvantage which 2-EBP can overcome. On the basis of the observed data and of a number of suitable prior densities, point and interval estimation of model parameters, as well as quantities of relevant interest are found. Also hypothesis tests on the effectiveness of performed overhauls have been developed using Bayes factor. Sensitivity analysis of improvement parameter is carried out. Finally, a numerical application is used to illustrate the proposed method.

• Journal of the Korean Society of Mechanical Technology
• /
• v.20 no.6
• /
• pp.796-802
• /
• 2018

In order to remove rust and impurities from surface of raw SUS circular bar, peeling machine is used to make lustrous and clean surface of SUS circular bar. Drawing process system is used to manufacture SUS hexagonal bar. SUS hexagonal bar have been widely used to make hexagonal bolt/nut, adapter and fittings and so on. The purpose of this study is to investigate the stabilities for guide bar of clamp in drawing process system. As the results, the guide bar showed structural stability in cases of below load of 50 Ton and over hook radius of 3.0mm. Further as the thickness of guide bar hooking with jaw was increased, minimum safety factor was decreased.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.30 no.4 s.247
• /
• pp.381-388
• /
• 2006

The objective of this study is to predict the etching characteristics using spray characteristics for the optimization on the etching process of Lead-Frame. The etching characteristics such as etching factor, uniformity were investigated on the actual operating conditions. The correlation between the etching characteristics and the spray ones obtained by measurement were analyzed to simulate the etching characteristics according to actual conditions of lead-frame etching process. These conditions of lead-frame process were spray pressure, distance from nozzle tip to substrate, pipe pitch, and nozzle pitch. To improve the etching characteristics in the lead-frame process, effects of the various operating conditions should be understood in detail. The spray characteristics obtained by experiment using PDA system were simulated by the Monte-Carlo method. The etching process model was coded by Java language. It was found that simulation results generally agreed well with the measured results of etching characteristics in lead-frame etching process. The optimal operating parameters were successfully found under variable conditions.

• Journal of the Korean Vacuum Society
• /
• v.1 no.1
• /
• pp.37-42
• /
• 1992

Abstract-The ECR(E1ectron Cyclotron Resonance) plasma etcher was developed for process of manufacturing 16M164' DRAM and applied to poly-Si etching process. The etching rate and selectivity of poly-Si were investigated by changing the process factor of pressure gas and microwave power. The increasing power of microwave will have the trend of increasing the etching rate and selectivity of Oxide, and have suitable value process pressure at 6 mTorr. The increasing value of process gas SFdSF6+ Clz will cause the decrease of etching rate and selectivity, this is because the best process factor is not found.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.18 no.8
• /
• pp.51-59
• /
• 2019

Flow forming is an eco-friendly and high-efficiency plastic deformation process with fewer chips during a process which is specifically used to manufacture seamless tubular products like tire wheels, rocket motor cases etc. On the development of mortar barrel using Inconel718 tube, some flow formed products had dimensional errors on their thickness. In this study, our purpose is to optimize the process conditions with the smallest dimensional error. In order to find an optimum process condition, 2D axisymmetric FEM simulation analyses with Taguchi method were conducted. Geometric variables (attack angle, flatting angle, roller nose radius) and operating parameters (depth of forming, feed rate) are considered as control factors. Forward flow forming with single roller was first analyzed to determine the effective factors using AFDEX software and attack angle of the roller was identified as the most influential factor. Also, the nose radius of the rollers was confirmed as a significant factor in multi-rollers flow forming system. The effect of rollers offset values are also studied and finally, we proposed optimal conditions to improve the accuracy of flow forming process with Inconel718 tube for mortar barrel manufacturing.

• 제어로봇시스템학회:학술대회논문집
• /
• 2000.10a
• /
• pp.177-177
• /
• 2000

In this paper, we propose a two-input two-output fuzzy controller to improve the performance of transient response and to eliminate the steady state error. The outputs of this controller are the control input calculated by position-type fuzzy controller and the accumulated error scaling factor. Here, the accumulated error scaling factor is adjusted on-line by fuzzy rules according to the current trend of the controlled process. To show the usefulness of the proposed controller, it is applied to several systems that are difficult to get satisfactory response by conventional PD controllers or PI controllers.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2007.10a
• /
• pp.296-299
• /
• 2007

The focus of this study is to estimate the stiffness factor of the separator plate of MCFC (Molten Carbonate Fuel Cell) at the elevated temperature. The process factors affecting the stiffness of the separator plate were chosen to determine the most important factor using the finite element analysis with the Taguchi method. The most influential factor, picked out by the ANOYA, turned out the pitch in the separator plate.

• Journal of Digital Convergence
• /
• v.16 no.6
• /
• pp.63-73
• /
• 2018

The purpose of this study is to investigate the influence of KMS(Knowledge Management System) on the performance of KMS by setting the factors affecting KMS 's management performance as knowledge information factor and management factor. And the moderating effect of evaluation and compensation on knowledge information factor, management factor and management performance. As a result of the analysis, it was analyzed that the knowledge information factor set by the knowledge adaptability, the reliability of knowledge information, and knowledge management process affects the definition of management performance. Among the management factors, organizationalization and cooperation factors influence definition Respectively. In the results of verifying whether assessment and compensation play a moderating role, it is found that knowledge compatibility of knowledge information factor, reliability of knowledge information, support of knowledge management process, knowledge sharing activity of management factor, cooperation has played a moderating role in business performance.