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박문식 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.9
A simple estimation method of equivalent porosity and strength of scrapped aluminum die-casting floor panel is suggested in which various defects like pores can be allowed. During shop practice of processing die-casting parts, equivalent porosity is evaluated by the ratio of linear stiffness from the simple test to the analytical stiffness value. Porosity equation is derived from the inclusion theory. Then using Mori-Tanaka method the porosity value is used to find an elasto-plastic stress-strain curve for the porous material. In this paper Hollomon equation is used to describe the strain hardening effect of the die-casting material. Finally, the stress-strain curve for the porous material is used to calculate strength of die-casting part that captures the nonlinearity of the porous material. A facility die-casting floor panel is chosen to verify the proposed method. The result is accurate and adequate to the test result.
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박문식,서영성 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.2
A plastic strain gradient theory incorporating the geometrically necessary dislocation density based on the low order displacement finite element method is proposed for calculation of the hardness value by Berkovich indentation. The obtained analysis results by this work are found to be in good agreement with the experimental data. Three-dimensional modeling technique of Berkovich indentation is also suggested. An empirical coefficient that includes the strain gradient effect into the yield stress formula is introduced and determined by reviewing area factors and hardness curves generated from the analyses. As pile-up occurs, classical plasticity theory gives a higher area factor and lower hardness value than those from experiment. However the strain gradient plasticity theory used in this work gives corrected area factor and hardness values. Dislocation density plots are generated that can explain the size effect during indentation and the availability of the three-dimensional modeling of Berkovich indentation.
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박문식,JongPilPark,So-Hee Yun,Jae-Un Lee,Joong-Keun Kim,Na-Eun Lee,Ji-Eun Song,Shin-Eun Lee,Sung-Hee John,JiHyunLim,Jay-Young Rhew 대한심장학회 2012 Korean Circulation Journal Vol.42 No.12
A paradoxical embolism is defined as a systemic arterial embolism requiring the passage of a venous thrombus into the arterial circulato -ry system through a right-to-left shunt, and is commonly related to patent foramen ovale (PFO). However, coexisting pulmonary embo-lisms, deep vein thromboses (DVT), and multipe systemic arterial embolisms, associated with PFO, are rare. Here, we report a patient who had a cryptogenic ischemic stroke, associated with PFO, which is complicated with a massive pulmonary thromboembolism, DVT, and re-nal infarctions, and subsequently, the patient was treated using a thrombolytic therapy.
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박문식,Park, Mun-Sik 대한기계학회 2000 大韓機械學會論文集A Vol.24 No.4
In design and manufacturing airframe structures which are composed of a lot of sub-assemblies and large complex profile shapes it is difficult to reduce so called hardware variations. Accordingly cost increasing factors for manufacturing airframe parts are much more than other machine parts because of the variability of fabricated details and assemlies. To improve cost and quality, accurate assembly methods and DPD techniques are proposed in this paper which are based upon using CAD/CAM techniques, the concept of KC's and the coordinated datum and index throughout the design, tooling, manufacturing and inspection. The proposed methods are applied to produce fuselage frame assemblies and related engineering aspects are described regarding the design of parts and tools in the context of concurrent digital definition. First articles and consequent mass production of frame assemblies shows a great improvement of the process capability ratio from 0.7 by the past processes to 1.0 by the proposed methods in addition to the cost reduction due to the less number of tools, reduced total assembly times and the space compaction needed by massive inventory. The need to achieve better Cpk, however, and future studies to be investigated will be addressed briefly.
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