• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.10
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• pp.1411-1417
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• 2010

CFRP (Carbon Fiber Reinforced Plastic) has received considerable attention in various fields as a structural material, because of its high specific strength, high specific stiffness, excellent design flexibility, favorable chemical properties, etc. Most products consisting of several parts are generally assembled by mechanical joining methods (using rivets, bolts, pins, etc.). Holes must be drilled in the parts to be joined, and the strength of the components subjected to static and fatigue loads caused by stress concentration must be decreased. In this study, we experimentally evaluated the variation in the residual strength of a holenotched CFRP plate subjected to fatigue load. We repeatedly subjected the hole-notched specimen to fatigue load for a certain number of cycles, and then we investigated the residual strength of the hole-notched specimen by performing the fracture test. From the results of the test, we can observe the initiation of a directional crack caused by the applied fatigue load. Further, we observed that the residual strength increases with a decrease in the notch effect due to this crack. It was evaluated that the residual strength increases to a certain level and subsequently decreases. This variation in the residual strength was represented by a simple equation by using a model of the decrease in residual strength for plain plate, which was developed by Reifsnider and a stress redistribution model for hole-notched plate, which was developed by Yip.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.7
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• pp.735-742
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• 2014

A self-piercing rivet (SPR) is a mechanical component for joining dissimilar material sheets such as those of aluminum alloy and steel. Unlike conventional rivets, the SPR directly pierces sheets without the need for drilling them beforehand. However, the regular SPR can undergo buckling when it pierces a high-strength steel sheet, warranting the design of a helical SPR. In this study, the joining and forging processes using the helical SPR were simulated using the commercial FEM code, DEFORM-3D. High-tensile-strength steel sheets of different strengths were joined with aluminum alloy sheets using the designed helical SPR. The simulation results were found to agree with the experimental results, validating the optimal design of a helical SPR that can pierce high-strength steel sheets.

• Conservation Science in Museum
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• v.3
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• pp.65-69
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• 2001

Scientific analysis are carried on gilded ornamental shoes, which have been excavated from tomb No 1. and No 4. in Beopcheon-ri, Wonju dated from Baekje Period. This object is a very important because it provides valuable information on the development of metal-making techniques of that period. Thus, this article illustrates the investigation conducted to reveal how the object was created using what materials and techniques. Instead of the spikes-attached to the bottom plate of the object-that couldn't be sampled, a sample of a decorative rivet showing a similar structure to the spikes-attached to the other parts of the shoes-was prepared for a cross-section examination. Using radiography and microscopes, it was found that the head of a spike was placed and then punched to the gilded plate, so it can be held to the shoes. Under the SEM-EDS, the cross-section of the rivet shows that the gilding layer was applied before the attachment of the rivets. It also shows that the gilding layer is distributed unevenly and there are empty spaces indicating amalgam gilding was employed. This was confirmed as Mercury was detected on the SEM-EDS analysis of the object. The examination of the microstructure of the plate using the SEM-EDS revealed that the object is made of a single copper alloy plate with recrystallized twining and non-metallic white inclusions, which found to be lead in this case.

• Korean Journal of Heritage: History & Science
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• v.56 no.4
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• pp.24-37
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• 2023

This study analyzes the materials and external characteristics of the Angbu-ilgu, a kind of scaphe sundial, which was newly designated as a Korean Treasure in 2022. The Angbu-ilgu Treasure is owned by three institutions - the National Palace Museum Of Korea, Gyeongju National Museum, and Sungshin Women's University Museum - and is similar as a twin in its material, size, outward appearance, as well as production techniques that include casting, silver inlays, and metal joints. The Three-Treasure Angbu-ilgu is made of brass in the ratio of 90.6: 6.0: 1.8 with Cu: Zn: Pb. This composition clearly differs from Treasure No. 845, an Angbuilgu which has a composition ratio of 82.2: 3.7: 11.8 with Cu: Zn: Pb. In this new Angbu-ilgu Treasure, the hemisphere's stand has four vertical pillars sculpted in a dragon pattern and bilateral wings carved in a cloud pattern on the pillars, which are joined to the hemisphere's horizontal ring with rivets and silver solders, respectively. The dragon-in-clouds pillar (雲龍柱) shows the most outstanding formative beauty of the various Angbu-ilgu pillars produced in the late Joseon Dynasty. It can be seen that the altitude of the north pole engraved on the Angbu-ilgu was made after 1713. Production is, however, actually estimated to have occurred close to the 19th century, the era of the Jinju Kang family, who were professional Angbuilgu makers. Hopefully, this study will lead to a historical science and technology review with modern scientific instruments analyzing the materials and external characteristics of the three Angbu-ilgus designated as a Korean Treasure in 2022.

• Korean Journal of Heritage: History & Science
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• v.54 no.3
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• pp.4-23
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• 2021

The purpose of this study was to classify the types of tweezers used across time and to examine the social culture of periods through the use of tweezers. Chapter II summarized the terms for tweezers and looked at the use of tweezers in two cases related to the social culture and politics of a period. The first is the use of tweezers for beauty purposes. Men used tweezers as a kind of self-management to maintain their social status and power, and thus they helped develop a wide range of tweezers cultures. People with gray hair are usually old. The perception that we should step down from politics when we are aged has become strong. Therefore, politicians pulled out gray hairs with tweezers to maintain only black hair and show youth, which indicates that their social influence is still strong. The second is the use of tweezers for first aid. Chapter III classified tweezers by type during the Goryeo and Joseon periods. The tweezers are largely divided into basic and composite types. The basic type of tweezers is a form that has been continued since the Three Kingdoms Period and consists of tongs and handles, and a fixed type of tweezers with a fixed ring appeared. Composite tweezers are made by grafting earpick or multipurpose knives. Composite tweezers are all-in-one tweezers with an earpick and an all-in-one knife. Tweezers are usually all-in-one. Among the composite tweezers, rivet separation and ring separation are characterized by separation, unlike the all-in-one tweezers. The method of connecting is divided into rivets and connection rings. The all-in-one tweezers appear only during the Goryeo Dynasty and are characterized by the lifestyle that provides a glimpse of the tastes of contemporary users. The manufacturing takes shape after making a thin metal plate. Decorative techniques are carved on soft metal tweezers, such as silver and bronze with a line, point, and a pressed angle. These tweezers are presumed to have been used by the royal family or aristocrats. However, most tweezers are made of strong bronze or iron. Therefore, the majority of simple X-shaped patterns are sampled or without patterns. The biggest reason why there are such diverse types of tweezers is that the culture of tweezers was widespread regardless of the times. In addition, the basic type of tweezers has been used since the Three Kingdoms Period and has been modified and used together as necessary because the shape of tweezers is a practical daily tool. Study of metal crafts have been limited to royal objects and Buddhist crafts. We hope that research on everyday tools such as tweezers will continue to serve as an opportunity to examine the social and cultural aspects of the times in various ways.