Hyuck-Moo Kwon

An economic selective assembly procedure for two mating components with equal variance

An economic procedure of selective assembly is proposed when a product is composed of two mating components. The major quality characteristic of the product is the clearance between the two components. The components are divided into several classes prior to assembly. The component characteristics are assumed to be independently and normally distributed with equal variance. The procedure is designed so that the proportions of both components in their corresponding classes are the same. A cost model is developed based on a quadratic loss function and methods of obtaining the optimal class limits as well as the optimal number of classes are provided. Formulas for obtaining the proportion of rejection and the unavailability of mating components are also provided. The proposed model is compared with the equal width and the equal area partitioning methods using a numerical example.

ECONOMIC SELECTION OF MEAN VALUE FOR A FILLING PROCESS UNDER QUADRATIC QUALITY LOSS

Consider a filling process where containers are filled with an important ingredient in a character. All containers are inspected, and the containers satisfying to meet the predetermined specification limits are sold in a regular market for a fixed price, and failing to meet them are emptied and refilled by the same filling process after some reprocessing. We assume that reprocessing cost is proportional to the quantity of the ingredients in a container that is not changed after reprocessing. An economic model is constructed on the basis of the selling price and the costs of production, inspection, reprocessing, and quality. We assume that the quality cost function is a quadratic function of the deviation from target and the quantity of the ingredients in a container is normally distributed with a known variance. Method for finding the optimum process mean is presented and a numerical example is given.

A process monitoring procedure based on a surrogate variable for dichotomous performance variable

A monitoring procedure using a surrogate variable is proposed for a process with a binary performance variable. Using the procedure, every item is inspected on a surrogate variable. When an item is rejected, the latest number of consecutively accepted items up to this point is compared with a predetermined number, r, to decide whether to stop the process for an investigation. The conditional distribution of the surrogate variable given the performance variable is assumed to be normal. A cost model is developed, which incorporates costs of inspection, misclassification, investigation, opportunity, and correction. We develop methods of finding the optimum r value and screening limit and analyze the effects of cost parameters on the optimal solution.

High electrical resistivity Nd-Fe-B die-upset magnet doped with eutectic DyF3–LiF salt mixture

Nd-Fe-B-type die-upset magnet with high electrical resistivity was prepared by doping of eutectic DyF3–LiF salt mixture. Mixture of melt-spun Nd-Fe-B flakes (MQU-F: Nd13.6Fe73.6Co6.6Ga0.6B5.6) and eutectic binary (DyF3–LiF) salt (25 mol% DyF3 – 75 mol% LiF) was hot-pressed and then die-upset. By adding the eutectic salt mixture (> 4 wt%), electrical resistivity of the die-upset magnet was enhanced to over 400 μΩ.cm compared to 190 μΩ.cm of the un-doped magnet. Remarkable enhancement of the electrical resistivity was attributed to homogeneous and continuous coverage of the interface between flakes by the easily melted eutectic salt dielectric mixture. It was revealed that active substitution of the Nd atoms in neighboring flakes by the Dy atoms from the added (DyF3–LiF) salt mixture had occurred during such a quick thermal processing of hot-pressing and die-upsetting. This Dy substitution led to coercivity enhancement in the die-upset magnet doped with the eutectic (DyF3–LiF) salt mixture. Coercivity and r...

Automotive Functional Safety-ISO 26262 and Its Countermeasures

Abstract Purpose : This paper is focused on introducing the Automotive Functional Safety International Standard - ISO 26262 and proposing effective countermeasures of ISO 26262.Methods : We studied collected data about ISO 26262 and analyzed the relationship between ISO 26262 and Quality 5 Star of Hyundai·Kia Motors for the integrated product development process.Results: Results showed the product development process for the integration plan between ISO 26262 and Quality 5 Star. In addition, we added an entry about the functional safety in the evaluation item of Quality 5 Star System.Conclusion : In order to introduce ISO 26262 effectively, we proposed ISO 26262 requirements and functional safety concept to be added to Quality 5 Star.Key Words : ISO 26262, Product Development Process, Quality 5 Star + 1. 서 론 최근에 출시되는 자동차에는 안전거리 감지, 헤드 업 디스플레이, 차선이탈 경보 시스템, 주차 조향 보조시스템 등과 같이 운전자 사용편의 및 안전성을 높이는 신기술들이 많이 탑재되고 있다. 이러한 자동차 ECU(Electronic ● Received 12 February 2013, 1st revised 15 May 20 13, 2nd revised 31 May 2013, accepted 31 May 2013† Corresponding Author(shhong@jbnu.ac.kr)ⓒ 2013, The Korean Society for Quality ManagementThis is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-Commercial use, distribution, and reproduction i n any medium, provided the original work is properly cited.

Feasibility study of electrophoresis deposition of DyF3 on Nd-Fe-B particles for coercivity enhancement

Feasibility of the electrophoresis deposition (EPD) technique for homogeneous and adhesive deposition of DyF3 particles on the Nd-Fe-B-type particles was studied, and coercivity enhancement in the diffusion-treated Nd-Fe-B-type particles deposited with DyF3 by EPD was investigated. HDDR-treated Nd12.5Fe80.6B6.4Ga0.3Nb0.2 particles were deposited with DyF3 particles by EPD. More homogeneous and adhesive deposition of DyF3 particles on the surface of Nd-Fe-B particles was made by the EPD with respect to conventional dip-coating, and this led to more active and homogeneous diffusion of Dy. More profound coercivity enhancement was achieved in the diffusion-treated Nd-Fe-B-type particles deposited with DyF3 by EPD compared to dip-coated particles.

Ceramics-bonded Nd-Fe-B-type magnet with high electrical resistivity

Ceramics-bonded magnet with remarkably high electrical resistivity was fabricated by hot-pressing the mixture of Nd13.6Fe73.6Co6.6Ga0.6B5.6 alloy melt-spun flakes and dielectric Bi2O3-SiO2-B2O3 ceramics powder with low melting point. Coercivity of the ceramics-bonded magnet decreased with increasing the addition of ceramics binder, and this was attributed to the increased demagnetizing factor. Thin oxidized layer on the flake surface formed by reaction between the flake and oxide binder also contributed to reducing coercivity in the ceramics-bonded magnet. Highly resistive ceramics-bonded magnet containing 30 vol% ceramics binder still had good magnetic performance and high mechanical strength at 175 oC: iHc = 5 kOe, Mr = 4.8 kG, (BH)max = 4.3 MGOe, and over 900 MPa.Ceramics-bonded magnet with remarkably high electrical resistivity was fabricated by hot-pressing the mixture of Nd13.6Fe73.6Co6.6Ga0.6B5.6 alloy melt-spun flakes and dielectric Bi2O3-SiO2-B2O3 ceramics powder with low melting point. Coercivity of the ceramics-bonded magnet decreased with increasing the addition of ceramics binder, and this was attributed to the increased demagnetizing factor. Thin oxidized layer on the flake surface formed by reaction between the flake and oxide binder also contributed to reducing coercivity in the ceramics-bonded magnet. Highly resistive ceramics-bonded magnet containing 30 vol% ceramics binder still had good magnetic performance and high mechanical strength at 175 oC: iHc = 5 kOe, Mr = 4.8 kG, (BH)max = 4.3 MGOe, and over 900 MPa.