• Steel and Composite Structures
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• v.14 no.3
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• pp.205-227
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• 2013

Current design standards do not provide adequate guidelines for the fire design of cold-formed steel compression members subject to flexural-torsional buckling. Eurocode 3 Part 1.2 (2005) recommends the same fire design guidelines for both hot-rolled and cold-formed steel compression members subject to flexural-torsional buckling although considerable behavioural differences exist between cold-formed and hot-rolled steel members. Past research has recommended the use of ambient temperature cold-formed steel design rules for the fire design of cold-formed steel compression members provided appropriately reduced mechanical properties are used at elevated temperatures. To assess the accuracy of flexural-torsional buckling design rules in both ambient temperature cold-formed steel design and fire design standards, an experimental study of slender cold-formed steel compression members was undertaken at both ambient and elevated temperatures. This paper presents the details of this experimental study, its results, and their comparison with the predictions from the current design rules. It was found that the current ambient temperature design rules are conservative while the fire design rules are overly conservative. Suitable recommendations have been made in relation to the currently available design rules for flexural-torsional buckling including methods of improvement. Most importantly, this paper has addressed the lack of experimental results for slender cold-formed steel columns at elevated temperatures.

• Journal of Korean Society of Steel Construction
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• v.16 no.4 s.71
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• pp.433-442
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• 2004

This paper discusses the development of a computer program to analyze elastic local buckling stress based on Eurocode 3 Part 1.3 for the flange and web of cold-formed channel columns under compression at elevated temperatures. The high-temperature, stress-strain relationships of the steel used in this paper were determined according to Eurocode 3 Part 1.2. The critical temperatures and the elastic local buckling stresses of cold-formed channel columns under compression at elevated temperatures were analyzed with the computer program developed in this study. Analysis examples were given to show the applicability of the computer program.

• 한국공간정보시스템학회:학술대회논문집
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• 2004.05a
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• pp.63-72
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• 2004

This paper is developed a computer program to analysis the elastic local and overall buckling stress based on Eurocode 3 Part 1.3 for the flange and web, and Euler equations for columns of cold-formed channel under compression at elevated temperatures. The high temperature stress-strain relationships of steel used this paper are determined according to Eurocode 3 Part 1.2. Critical temperatures and the elastic local buckling stresses of the cold-formed channel columns under compression at elevated temperatures are analysed by the computer program developed in this study. Analysis examples are given to show the applicability of the computer program developed in this study.

• Journal of Korean Society of Steel Construction
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• v.10 no.4 s.37
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• pp.677-689
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• 1998

In relation to concentrically loaded compression, this research is to describe, analyze, and evaluate the design strength in steel stud. The similarity and difference among load and resistance factor design specification for cold-formed steel structural members (AISI), cold-formed thin gauge members and sheeting (EC3 part 1.3), and German draft (DASt-Richtlinie 016) are introduced, discussed, and systematically evaluated. Especially, the effective width and global instability problems (flexural buckling and torsional flexural buckling) are here implied in this research. The design axial strength by dual standards (AISI and EC3) is calculated and compared using the example.

• Transactions of Materials Processing
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• v.24 no.3
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• pp.181-186
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• 2015

Many in the industrial world that consume high amounts of energy are trying to reduce energy when manufacturing their products. Energy saving during manufacturing is a cost reduction. Reduced cost is necessary for profit improvement. The Piston Under Drive Brake used in the current study is an automotive transmission part. The original machining after hot forging was changed to machining after cold forging of a plate in order to save energy and cost. Two extrusion shapes along the outer diameter caused decreased tool life because of the interrupted cut during turning. Therefore, a thickness reduction of two extrusion areas in the outer diameter was needed. The current study suggests an effective way to reduce the thickness of interrupted cut by using progressive blanking.

• Transactions of Materials Processing
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• v.6 no.3
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• pp.221-226
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• 1997

Chevron crack in cold extrusion has been studied in view of deformation conditions and material characteristics. There is V formed chevron crack is occasionally occurred in core part of shaft by multistage free extrusion. Although many research results were reported and theoretical analyses were accompanied, in this study we discussed practical method to prevent chevron crack in the field of working conditions and material characteristics. We have found that chevron crack is eliminated under condition of high hydrostatic state in deformation and decreased segregation, refinement of micro structure of materials.

• Transactions of Materials Processing
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• v.30 no.5
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• pp.242-246
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• 2021

Aluminum alloy sheet is being applied to automobiles continuously for the purpose of reducing car body weight. However, due to low formability, there's a limit to application of products with a deep forming depth such as door inner parts. Therefore, the difficult-to-form parts are mainly segmented formed then joined together, which is also disadvantageous as it increases the cost of manufacturing. This study proposes a hybrid cold-hot stamping method for the 1-piece door inner part to reduce cost. To design the stamping process, numerical simulation method is established by using the temperature-dependent mechanical properties of AA6016. The formability according to the hybrid cold-hot stamping method is evaluated using numerical analysis. The suitability of the proposed stamping method is then verified through the stamping tryout.

• Transactions of Materials Processing
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• v.26 no.2
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• pp.101-107
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• 2017

Aluminum alloys are widely used in automotive industry because of their high strength-to-density ratio and excellent corrosion resistance. However, conventional cold stamping of aluminum alloys leads to low formability and excessive spring-back. To overcome these problems, Hot Forming Quenching (HFQ) is applied to manufacture automotive part using aluminum alloy. The purpose of this study is to investigate effect of forming temperature on spring-back in HFQ of T6 heat treated AA6061 sheet. In this study, hat shape forming test was adopted to evaluate spring-back characteristics according to various forming temperatures. In additions, the test was also performed with warm forming conditions in comparison with dimensional accuracy of HFQed part. The experimental results showed that dimensional accuracy of HFQed part was superior to warm formed part and amount of spring-back was decreased as forming temperature rise.

• The Journal of Korean Medical History
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• v.27 no.2
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• pp.99-120
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• 2014

Purpose : There are two types of sleep disturbance: inability to sleep (不眠) and somnolence (多眠). This study is to examine treatments of the two types of sleep disturbance in the Books of Cold Damage and how those theories were established and formed. Methods : 1. Verses including the words related to inability to sleep and somnolence were extracted from "Treatise on Cold Damage Diseases" (傷寒論). 2. Among the Books on Cold Damages that are classified according to the symptoms, 17 books with contents related to inability to sleep and somnolence were selected to collect and classify data in three perspectives: mechanism of disease (病機), method of treatment (治法) and disease pattern (病證). 3. Data collected through the above methods were compared and diagramed. Results & Conclusions : 1. On Cold Damage, inability to sleep is mostly rooted when human body lacks yin energy while having excessive yang energy (陽盛陰虛) due to fire and heat (火熱). The reason could be misuse of perspiration inducing method (汗法) or purgation (下法) on the doctors' part. 2. On Cold Damage, somnolence is rooted when pathogen (邪氣) is spread to yin meridians (陰經) and the human body lacks yang while having excessive yin energy (陰盛陽虛) or when heat (熱邪) is invaded into interior parts (裏部). 3. Many scholars of Cold Damage in later periods had copied the "Treatise on Cold Damage Diseases" for treatments of sleep disturbance but many others have applied the verses from "Treatise on Cold Damage Diseases" or added new treatments. Do jeol-am (陶節庵) and Wang Geung-dang (王肯堂) particularly had deep understanding on "Treatise on Cold Damage Diseases" and utilized the content freely or suggested new remedies because they had thorough knowledge on relating formula as well.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.43-46
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• 2004

Since Mg alloy has many attractive advantages among the practically used metals, many researchers have been studied to develop useful process and material. However, study for sheet forming has not been a few because of low formability on room temperature. Formability and springback for AZ31 alloy sheet have been studied to develop the cold forming technology. The experimental and FE analysis were performed to analyzed the springback amounts by using a model of our on. A different three materials were used to investigate the effects of material characteristics. The springback amounts of Mg-alloy sheet formed part were larger than that of the other material.