• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.403-407
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• 2009

In this work, finite element investigations were carried out to manufacture a seamless aluminum liner without crack generation using four-stage deep drawing followed by two-stage ironing process. In order to predict the crack generation during the liner manufacturing process, the Normalize Cockroft-Latham(NCL) which is one of ductile fracture criteria was adopted. In addition, the tensile tests were carried out to obtain the critical value of NCL by comparing the experimental and FE simulation results. From this, various case studies based on FE simulation were carried to obtain the optimum die designs which can prevent the crack generation during ironing processes. Finally, the aluminum liner was successfully made using obtained die designs so that requirements were met in terms of thickness and height of the liner.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.05a
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• pp.85-88
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• 2001

Examination of the die design is carried out for a multi-stage rectangular cup drawing process with the large aspect ratio with the aid of the finite element analysis. The analysis considers the deep drawing process with the ironing process for the thickness control in the cup wall. Simulation is performed to investigate the deformation mechanism in the initial design and the modified design. The analysis clarifies that the irregular cross section and the irregular contact condition produces unfavorable deformation. The analysis results show that the modified design improves the quality of a deep-drawn product with the low possibility of failure. The analysis result also shows good agreement with the experimental one.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.9
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• pp.2234-2244
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• 1994

A process sequence of multi-operation cold forging for actual application in industry is designed with the rigid-plastic finite element method to form a constant velocity joint housing(CVJ housing). The material flow during the CVJ housing forming is axisymmetric until the final forging process for forming of ball grooves. This study treats the deformation as an axisymmetric case. The main objective of the process sequence design is to obtain preforms which satisfy the design criteria of near-net-shape product requiring less machining after forming. The process sequence design also investigates velocity distributions, effective strain distributions and forging loads, which are useful information in the real process design.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.630-634
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• 1997

In this paper,we will discuss in the forming process design of the making engine pulleys for automobiles. These pulleys are required to be made by precision deep drawing process because these are to be combined with bearings and engine timing belts. These pulleys are used of cold rolled steel plates starting with the initial blanking size of 115.2mm and the initial thickness of 1.2mm. Our deep drawing process is designed the continuous 5-steps process, that is, 1'st deep drawing, 2'nd reverse redrawing, 3'rd trimming, 4'th drawing-ironing and 5'yh piercing. This process need no in-process annealing.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.6
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• pp.629-637
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• 2013

In this study, a theoretical analysis method was suggested for predicting forming loads of continuous deep drawing and ironing processes (D.D.I. processes) by considering back tension and continuity equation, and FEA for D.D.I. processes was performed. Dimensions of a punch and a mold on the basis of design rules for a CNG storage vessel were applied for the analysis. To verify the suggested theoretical analysis, the results of theoretical analysis were compared with both those of FEA and experiments of previous studies. As the result of analysis, the values and tendencies of the loads predicted by the theoretical analysis were in agreement with those of FEA and the experiments. So, it is considered that the analysis suggested has reliability for predicting the forming loads of the continuous processes(deep drawing+ironing(1)+ironing(2)).

• Journal of the Korean Society for Precision Engineering
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• v.20 no.8
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• pp.21-29
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• 2003

This paper describes a research work on the development of computer-aided design system for deep drawing & ironing of a high pressure vessel. An approach to the system is based on the knowledge-based rules. Knowledge for the system is formulated from plasticity theories, handbook, experimental results and empirical knowledge of field experts. An attempt is made to link programs incorporating a number of expert design rules with the process variables obtained by commercial FEM software, DEFORM and ANSYS, to form a useful package. It is composed of five main modules, which are calculation of product thickness, input, production feasibility check, process planning, and autofrettage process modules and two submodules, which are folding check and process variable verification submodules. Programs for the system have been written in AutoLISP on the AutoCAD 2000 using personal computer. The developed system makes it possible to design and manufacture large high pressure vessel requiring D.D.I. process more efficiently.

• Journal of the Korean institute of surface engineering
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• v.30 no.3
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• pp.191-201
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• 1997

Non-passivated electrolytic tinplates withour conventinal chemical treatment self-oxidize in ambient atmosphere to from yellow stain on the outermost surface during the long-term storage. The degree of yellowness of the stain increased linerly with the oxide thickness due to the interfeefence color of the $SnO_2$ Even though the thickness of the oxide layer was very thin, less than 100$\AA$ , it exerts an undesirable influence on the can-making processes, particularly the stripping behavior after ironing. Investigations were carried out on the morphologies of the coating layer, the changes in oxide thickness during successive can-making processes and the averge friction coefficients with the different oxide thinkness. These oxide layers were broken up and distributed within the bulk tin coating during the ironing process. This redistribution of the oxide layer prvented smooth pressing-aside of the tin coating layer, resulting in an increase in the ironing friction coefficient. As the friction was increased, the residual stress along the can wall thinkness(i.e., the hoop stress) was also increased. Due to both the oxibe layer accumulation, which increased the friction coefficient, and the hoop stress, can stripping efficiency without roll-back is reduced.

• 한국벤처창업학회:학술대회논문집
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• 2020.11a
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• pp.103-108
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• 2020

본 연구는 미청구공사의 테마감리 지정으로 인해 해당 기업의 보수주의 성향이 증가하였는지 검증한다. 미청구공사에 대한 테마감리 대상지정 배경은 공사 진행률 과대산정 및 평가의 적정성 문제로 회계적 의혹의 적정성에서부터 출발하였다. 미청구공사 금액 계산 시 밀접하게 연관되는 공사진행률은 경영자의 재량적 판단이 반영될 수 있다. 만약 경영자가 이익을 상향할 목적으로 진행률을 부풀린다면 미청구공사가 과다하게 인식되는 문제가 발생한다. 이러한 문제점은 2013년 일부 건설업계의 어닝쇼크를 비롯하여 수주산업에서의 회계부실 문제가 사회적으로 큰 이슈가 되었다. 특히 조선업과 건설업의 잇달은 부실과 함께 미청구공사와 관련된 회계 불투명성이 크게 드러나는 등 회계자료에 대한 불신이 증가되었다. 이로 인해 미청구공사 과대계상 이슈는 금융감독원의 테마감리 대상으로 지정되었다. 본 연구의 실증분석 방법은 2012년부터 2017년까지 Basu(1997)의 보수주의 측정 모형을 이용하여 미청구공사 금액을 반영하기 전과 후를 비교하여 동 기업의 보수주의 회계처리에 미치는 영향을 분석하였다. 중요분석 결과로는 테마감리 지정 이후에 미청구공사에 대한 보수적 회계처리가 유의하게 증가되었다. 이를 통해 테마감리 지정 목적인 미청구공사금액의 과대계상 금지와 공시 강화라는 측면에서 그 실효성을 확인하였다.

• KIEAE Journal
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• v.17 no.3
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• pp.5-13
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• 2017

Purpose: Various studies have been performed to address the issue of increased energy use by buildings. In particular, research on complex envelopes that combines diverse envelope element techniques is currently in progress in the building sector. The present study aimed to develop an awning system using a light shelf, and to verify its validity through performance evaluation. Method: In the present study, a testbed was established for the performance evaluation of the awning system using a light shelf, and the uniformity ratio and lighting energy consumption were compared and analyzed relative to those with no awning and light shelf installation (Case 1), awning installation (Case 2), and light shelf installation (Case 3). Result: 1) In the present study, an awning system using a light shelf (Case 4) where an opening is made on the awning screen and natural light can be introduced through the light shelf located at the bottom was developed. 2) The optimum standard for Case 4 obtained through the performance evaluation was a 0.6m lighting length and a 2m extension length at a light shelf angle of $30^{\circ}$. 3) Case 4 with the optimum standard had a 5.5% lower uniformity ratio than Case 2, but had a higher uniformity ratio than Case 1 and Case 3. 4) Case 4 with the optimum standard showed 13.3%, 44.6%, and 0%~8.7% lighting energy reductions compared to Case 1, Case 2, and Case 3, respectively. 5) Based on the above results, Case 4 suggested in the present study was found to be effective for indoor light environment improvement and lighting energy reduction.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.16 no.2
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• pp.177-188
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• 2021

On December 2015, Financial Supervisory Service(FSS) announced the four key thematic audit review areas, one of them is an appropriation of unbilled revenue. Accounting of unbilled revenue is intertwined with a percentage of completion, that is concerned about discretionary decision by manager. Therefore, if manager motivated by income-increasing manipulation is exaggerating percentage of completion, unbilled revenue is excessively recognized. This problem is caused the serious accounting issues(e.g., shock at a loss for 2013 fiscal year by some construction firms, malpractice of accounting in order-made production industry). Distrust of accounting was grown because the shipbuilding and construction industries successively went poor management and bad accounting of them is revealed. Those accounting issues were the trigger for problem recognition of unbilled revenue, they were background for the designation of appropriation unbilled revenue as thematic audit review areas by FSS. Therefore, this study verified effectiveness of thematic audit review by empirically analyzing whether designation of thematic audit review makes the firm increases conservative behavior. Conservative accounting is estimated by using Basu(1997) model. We analyzed the effect of the thematic audit review on conservative accounting of unbilled revenue by comparing with reflecting unbilled revenue or not. The sample for test consists of firm-years the manufacturing and construction industries from 2012 to 2017. The test results of this study suggested that the conservative accounting of unbilled revenue after designation of the thematic audit review was significantly increased. We also tested again by classifying whether or not it is construction industry. We found that construction industry is more conservative than the other industry only for the designated year of the thematic audit review, otherwise there was not any evidence for significantly increasing conservatism. This study contributes to the literature by empirically analysing relationship of the unbilled revenue to the thematic audit review from the perspective of the conservatism and verifying effectiveness of the thematic audit review.