Finite element modelling of back-to-back built-up cold-formed stainless-steel lipped channels under axial compression

Krishanu Roy,Hieng Ho Lau,James B.P. Lim 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.33 No.1

In cold-formed steel structures, such as trusses, wall frames and portal frames, the use of back-to-back built-up cold-formed stainless-steel lipped channels as compression members are becoming increasingly popular. The advantages of using stainless-steel as structural members are corrosion resistance and durability, compared with carbon steel. The AISI/ASCE Standard, SEI/ASCE-8-02 and AS/NZS do not include the design of stainless-steel built-up channels and very few experimental tests or finite element analyses have been reported in the literature for such back-to back cold-formed stainless-steel channels. Current guidance by the American Iron and Steel Institute (AISI) and the Australian and New Zealand (AS/NZS) standards for built-up carbon steel sections only describe a modified slenderness approach, to consider the spacing of the intermediate fasteners. Thus, this paper presents a numerical investigation on the behavior of back-to-back cold-formed stainless-steel built-up lipped channels. Three different grades of stainless steel i.e., duplex EN1.4462, ferritic EN1.4003 and austenitic EN1.4404 have been considered. Effect of screw spacing on the axial strength of such built-up channels was investigated. As expected, most of the short and intermediate columns failed by either local-global or local-distortional buckling interactions, whereas the long columns, failed by global buckling. All three grades of stainless-steel stub columns failed by local buckling. A comprehensive parametric study was then carried out covering a wide range of slenderness and different cross-sectional geometries to assess the performance of the current design guidelines by AISI and AS/NZS. In total, 647 finite element models were analyzed. From the results of the parametric study, it was found that the AISI & AS/NZS are conservative by around 10 to 20% for cold-formed stainless-steel built-up lipped channels failed through overall buckling, irrespective of the stainless-steel grades. However, the AISI and AS/NZS can be un-conservative by around 6% for all three grades of stainless-steel built-up channels, which failed by local buckling.

철을 소재로 한 친환경조형물 제작 연구

변건호(Byun, kun-ho) 한국조형디자인학회 2006 조형디자인연구 Vol.9 No.2

The Environmental formations are stand between nature and human being. Nature and the human create new space where they could interchange to each other. The iron is one of the material which is able to recycle and refine again and again as like as the nature circulates and born again and again. An author has concluded the iron is best for the environmental-friendly material which feels and breaths with the time and space by becoming one with nature. The iron has been using in the facilities like a road, harbors, and the buildings in town for a long time because, it is durable and formative even it cost relatively inexpensive. During the investigation, we have made progress meaningfully about application method and utilization in the environmental formations of stainless steel, one of the iron material that basis of our society. We had mainly used stainless steel, but we have found limits in formational expression from limited colour senses. Therefore we have applied black stainless steel while we were looking for the material which is able to try various colour senses and also it is durable.We have investigate various methods of representation by harmonized arrangement of individually painted closing stainless steel(stabled stainless steel which keeps from rust, rusted stainless-steel and creating black film on the surface stainless steel from inverse conception). Therefore we could have result of durabilities and abundant effects of representation. And it corresponds to aim of creation from the beginning that the way of wise harmonization between nature and the human being. Also the result of inverse conception that rusted stabled stainless steel which keeps from rust, gave us enough pleasure while we were working on this investigation. Finally we have realized creating black film on the surface stainless steel has much room for consideration to be element of formation for the environmental formations or the structures. Because it breaths with environment when it has born even it looks like upward suddenly and spontaneously from the earth which goes against a natural law.

철을 소재로 한 친환경조형물 제작 연구 : 제작과정을 중심으로

변건호(Byun, kun-ho) 한국조형디자인학회 2008 조형디자인연구 Vol.11 No.2

The Environmental formations are stand between nature and human being. Nature and the human create new space where they could interchange to each other. The iron is one of the material which is able to recycle and refine again and again as like as the nature circulates and born again and again. An author has concluded the iron is best for the environmental-friendly material which feels and breaths with the time and space by becoming one with nature. The iron has been using in the facilities like a road, harbors, and the buildings in town for a long time because, it is durable and formative even it cost relatively inexpensive. During the investigation, we have made progress meaningfully about application method and utilization in the environmental formations of stainless steel, one of the iron material that basis of our society. We had mainly used stainless steel, but we have found limits in formational expression from limited colour senses. Therefore we have applied black stainless steel while we were looking for the material which is able to try various colour senses and also it is durable.We have investigate various methods of representation by harmonized arrangement of individually painted closing stainless steel(stabled stainless steel which keeps from rust, rusted stainless-steel and creating black film on the surface stainless steel from inverse conception). Therefore we could have result of durabilities and abundant effects of representation. And it corresponds to aim of creation from the beginning that the way of wise harmonization between nature and the human being. Also the result of inverse conception that rusted stabled stainless steel which keeps from rust, gave us enough pleasure while we were working on this investigation. Finally we have realized creating black film on the surface stainless steel has much room for consideration to be element of formation for the environmental formations or the structures. Because it breaths with environment when it has born even it looks like upward suddenly and spontaneously from the earth which goes against a natural law.

Axial capacity of back-to-back built-up cold-formed stainless steel unlipped channels-Numerical investigation and parametric study

Krishanu Roy,Hieng Ho Lau,Zhiyuan Fang,Abdeliazim Mustafa Mohamed Ahmed,James B.P. Lim 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.40 No.5

In cold-formed steel structures, such as trusses, wall frames and portal frames, the use of back-to-back built-up cold-formed stainless steel unlipped channels as compression members are becoming popular. The advantages of using stainless steel as structural members are corrosion resistance and durability, compared with carbon steel. Current guidance by the American Iron and Steel Institute (AISI) and the Australian and New Zealand (AS/NZS) standards for built-up carbon steel sections describes a modified slenderness approach, to consider the spacing of the intermediate fasteners. The AISI and AS/NZS do not include the design of stainless-steel built-up channels and very few experimental tests or finite element (FE) analyses have been reported in the literature for such back-to-back cold-formed stainless steel unlipped channel section columns. This paper presents a numerical investigation on the behavior of back-to-back built-up cold-formed stainless steel unlipped channel section columns. Three different grades of stainless steel i.e., duplex EN1.4462, ferritic EN1.4003 and austenitic EN1.4404, were considered. The effects of screw spacing on the axial strength of such built-up unlipped channels were investigated. As expected, most of the short and intermediate columns failed by either local-global or local-distortional buckling interactions, whereas the long columns failed by global buckling. All three grades of stainless-steel stub columns failed by local buckling. A comprehensive parametric study was then carried out covering a wide range of slenderness and different cross-sectional geometries to assess the performance of the current design guidelines of carbon steel built-up sections in accordance with the AISI and AS/NZS. In total, 647 FE models were analyzed. From the results of the parametric study, it was found that the AISI and AS/NZS are conservative by around 14 to 20% for all three grades of stainless steel built-up unlipped channel section columns failed through global buckling. However, the AISI and AS/NZS carbon steel design rules can be un-conservative by around 8 to 13%, when they are used to calculate the axial capacity of those stainless steel built-up unlipped channels which are failed in local buckling.

스테인레스 스틸 테이블웨어의 프레싱 기법 연구

임효정(Lim, Hyo-Jung),추원교(Choo, Won-Gyo) 한국조형디자인학회 2008 조형디자인연구 Vol.11 No.3

스테인레스 스틸은 현재 사용되고 있는 테이블웨어 중에 가장 실용성 있는 재료다. 그리고 대부분의 스테인레스 스틸 테이블웨어는 프레스 기법을 통해 완성된다. 스테인레스 스틸을 위한프레스 기법은 외부에 의례되어 가공되어 지는데, 그만큼 디자이너들이 가지고 있는 기법의 이해가 중요하다. 기법의 이해가 있어야 실현 가능한 디자인, 기법을 활용할 수 있는 디자인을 할수 있기 때문이다.스테인레스 스틸 테이블웨어에 가장 많이 쓰이는 기법은 프레스 기법 중 드로잉 가공과 부풀림가공을 들 수 있다. 드로잉가공은 금형을 가지고 원통, 각통, 반구 등의 형상을 만드는 가공법이고 부풀림 가공법은 드로잉 가공된 원통을 기본으로 구의 형태를 만드는 가공법이다. 드로잉 가공과 부풀림 가공에는 드로잉력, 블랭크 크기, 드로잉율, 드로잉비, 재료의 두께 등이 알맞게 측정 되어져야 원하는 형상을 제작할 수 있다. 스테인레스 스틸 테이블웨어에 가장 자주 쓰이는가공방법이 프레스 기법이지만 모든 디자인에 다 적합하지는 않기 때문에 프레스 기법의 한계점도 알아두어야 한다.이 연구에서는 스테인레스 스틸 테이블웨어의 가공방법 중 프레스 기법의 드로잉 가공법과 부풀림 가공법을 집중적으로 다루지만 이 연구가 스테인레스 스틸의 다른 가공법의 연구를 위한 좋은 시작이 되었으면 한다. Stainless steel is the most practicable material among table wares, which are being used now. And, most of stainless-steel table wares are completed through the press technique. The press technique for stainless steel is entrusted to the outside, and is processed However, designers need to perform the design work with understanding about the technique, which will complete their design. That is because only when understanding technique leads to possibly doing the realizable design, and the design of being able to use technique. The technique, which is used the most in stainless-steel tableware, can be said to be drawing processing and bulging processing out of the press technique. The drawing processing is the processing method that makes the shape in cylinder, square tube, and dome with a mold. And, the bulging processing is the processing method that makes the shape of a globe by having the basis as the cylinder, which was performed the drawing processing. The desired shape in the drawing processing and the bulging processing can be manufactured only when being suitably measured the drawing force, blank size, drawing rate, drawing ratio, and the thickness of materials. However, it is not that all designs can be processed, thereby being very important to design with having knowledge of the manufacturing process. This study intensively addresses only the drawing and bulging processing method in the press technique, which is often used out of stainless-steel tablewares. However, this study is desired to be a good beginning for a research of other processing method in stainless-steel.

치과용 단층촬영을 이용한 Stainless-Steel File과 MFile-System^® 전동식 기구의 근관 성형 능력에 대한 비교 연구

서동진,윤미란,이린,유미경,Seo, Dong-Jin,Yoon, Mi-Ran,Lee, Rin,Yu, Mi-Kyoung 대한턱관절교합학회 2006 구강회복응용과학지 Vol.22 No.2

Objectives The aim of this study is to compare the quality of root canal preparation completed using MFile-$System^{(R)}$ instrument ( Komet, Gebr.Brsaseler, Germany) and conventional stainless steel file in the canals of Maxillary molar teeth that had a canal curvature between $25^{\circ}$ or more Materials & Methods Buccal canals of 24 first and second maxillary molar teeth, extracted for periodontal and prosthetic reasons were used. Tissue fragments and calcified debris were removed from teeth by scaling and the teeth were stored in 10% formalin solution for 24 hour. Then, teeth were stored in saline until used. To be included the roots had to have completed formed apices and angle of curvature ranging between $25^{\circ}$ or more according to the criteria described by Schneider(1971). Palatal and Second mesiobuccal canals were not included. Teeth were embedded into transparent acrylic. The teeth were randomly divided into two experimental groups. All teeth were scanned by Dental CT (PSR9000N, Asahi, Japan) to determine the root canal shape before instrumentation. Image slices were prepared from the apical end point to the pulp chamber. The first two sections were 2 mm from the apical end of root and 2 mm below the orifice. Further section was recorded, dividing the distance between the sections of apical and coronal levels into two equal lengths. 12 teeth were instrumented using stainless steel fileand another 12 teeth were instrumented using MFile-$System^{(R)}$. Following the completion of the instrumentation, the teeth were again scanned and compared with the cross sectional images taken prior to canal preparation. Amount of transportation and centering ability was assessed. Student's t-test was used for statistical analysis. Result Less transportation occurred with MFile-$System^{(R)}$ rotary instrumentation than stainless steel instrument. MFile-$System^{(R)}$ had better centering ability than stainless steel instrument. Conclusion MFile-$System^{(R)}$ rotary instrumentation transported canals less and had good centering ability.

Buckling of axially loaded shell structures made of stainless steel

Özer Zeybek,Ali İhsan Çelik,Yasin Onuralp Özkılıç 국제구조공학회 2023 Steel and Composite Structures, An International J Vol.48 No.6

Stainless steels are commonly employed in engineering applications since they have superior properties such as low maintenance cost, and high temperature and corrosion resistance. These features allow them to be preferred in cylindrical shell structures as well. The behavior of a cylindrical shell structure made of stainless steel can be quite different from that made of carbon steel, as the material properties differ from each other. This paper deals with buckling behavior of axially loaded cylindrical shells made of stainless-steel. For this purpose, a combined experimental and numerical study was carried out. The experimental study comprised of testing of 18 cylindrical specimens. Following the experimental study, a numerical study was first conducted to validate test results. The comparisons show that finite element models provide good agreement with test results. Then, a numerical parametric study consisting of 450 models was performed to develop more generalized design recommendations for axially compressed cylindrical shell structures made of stainless steel. A simple formula was proposed for the practical design purposes. In other words, buckling strength curve equation is developed for three different fabrication quality.

Characteristics of a Stack Separator Prepared from Composites of Stainless Steel and TiNx for Fuel Cells

Farkhod R. Turaev,Sung Bum Park,Taeho Bahn,Sung Jin Kim,Jung-Ho Ahn,홍태환 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.3

A stack separator made from carbon or carbon composites has many advantages, such as electrochemical stability, low density, low contact resistance and good corrosion resistance. However, it has some weak points, including higher thickness and low manufacturing reliability. Therefore, many attempts have been made to fabricate a stack separator from materials that have low-cost, high manufacturing reliability and corrosion resistance. It is very important to take into account that it is very difficult to achieve good corrosion resistance of a stack separator at high temperatures. Therefore, many researchers have tried to use expensive materials that are high temperature and corrosion resistant superalloys. In this paper, the fabrication of a stack separator made of low-price metal and TiNx is investigated. Stainless steel, which is a low-price, corrosion resistant metal and TiNx are used as a reinforcement support to reveal high heat resistance and corrosion resistance and to decrease the hydrogen permeability. We fabricated the plates for use as stack separators reinforced by TiNx by mixing stainless-steel powders with 2 % of nano-sized TiNx. Spark plasma sintering (SPS) was chosen for sintering the composites. The physical properties of the specimens were analyzed by performing hardness tests, biaxial strength tests and shear strength tests. The electrochemical properties, such as the corrosion resistance and the hydrogen permeability, were also investigated. The microstructures of the specimens were investigated by using eld-emission scanning electron microscopy and the proles of the chemical compositions were analyzed by using energy dispersive X-Ray analysis. A stack separator made from carbon or carbon composites has many advantages, such as electrochemical stability, low density, low contact resistance and good corrosion resistance. However, it has some weak points, including higher thickness and low manufacturing reliability. Therefore, many attempts have been made to fabricate a stack separator from materials that have low-cost, high manufacturing reliability and corrosion resistance. It is very important to take into account that it is very difficult to achieve good corrosion resistance of a stack separator at high temperatures. Therefore, many researchers have tried to use expensive materials that are high temperature and corrosion resistant superalloys. In this paper, the fabrication of a stack separator made of low-price metal and TiNx is investigated. Stainless steel, which is a low-price, corrosion resistant metal and TiNx are used as a reinforcement support to reveal high heat resistance and corrosion resistance and to decrease the hydrogen permeability. We fabricated the plates for use as stack separators reinforced by TiNx by mixing stainless-steel powders with 2 % of nano-sized TiNx. Spark plasma sintering (SPS) was chosen for sintering the composites. The physical properties of the specimens were analyzed by performing hardness tests, biaxial strength tests and shear strength tests. The electrochemical properties, such as the corrosion resistance and the hydrogen permeability, were also investigated. The microstructures of the specimens were investigated by using eld-emission scanning electron microscopy and the proles of the chemical compositions were analyzed by using energy dispersive X-Ray analysis.

A Comparative Test Study of the Impact Performances of Stainless-Steel Rebar Equal-Strength Replacement Piers

Xiwu Zhou,Wenchao Zhang,Yushen Gao,Guoxue Zhang,Ruisheng Xiong 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.1

It has been found that there are rebar instability and construction complexity phenomena associated with the replacements of ordinary pier rebars with stainless-steel rebars of equal piece numbers and strength. Therefore, this study explored the issues of the equal-strength replacements of stainless-steel pier rebars with diff erent distributions. The study utilized the most advanced domestic multi-function super-high heavy hammer impact test system available, and conducted a comparative test of the horizontal impact results of two groups of pier models with 1/5 contraction scales. The purpose of the testing was to analyze the impact force, impact displacement, strain time history curve, crack propagation and distribution, ultrasonic damages to the concrete, and so on. The test results showed the following: The original specimen displayed a consistent variation trend with the equal replacement specimen of the stainless-steel rebar of diff erent distributions from the aspects of the maximum impact force, strain of the rebar and concrete, displacement peak, and so on, under the conditions of continuous multiple impacts. The relative variation rate was found to be within the scope of ± 10% under equal impact energy. The quantity and distribution of the cracks, as well as the concrete damages, were also found to be approximately consistent under equal impact energy. Therefore, in this study, it was considered to be feasible for the solution of the problems related to rebar corrosion, strength surplus, resource waste, and so on, to replace ordinary pier rebars with stainless-steel rebars with equal-strength and diff erent distributions.

Electrochemical Study of Three Stainless Steel Alloys and Titanium Metal in Cola Soft Drinks

Peralta-Lopez, D.,Sotelo-Mazon, O.,Henao, J.,Porcayo-Calderon, J.,Valdez, S.,Salinas-Solano, G.,Martinez-Gomez, L. The Korean Electrochemical Society 2017 Journal of electrochemical science and technology Vol.8 No.4

Stainless steels and titanium alloys are widely used in the medical industry as replacement materials. These materials may be affected by the conditions and type of environment. In the same manner, soft drinks are widely consumed products. It is of interest for dental industry to know the behavior of medical-grade alloys when these are in contact with soft drinks, since any excessive ion release can suppose a risk for human health. In the present study, the electrochemical behavior of three stainless steel alloys and pure titanium was analyzed using three types of cola soft drinks as electrolyte. The objective of this study was to evaluate the response of these metallic materials in each type of solution (cola standard, light and zero). Different electrochemical techniques were used for the evaluation of the alloys, namely potentiodynamic polarization, linear polarization, and open-circuit potential measurements. The corrosion resistance of the stainless-steel alloys and titanium in the cola soft drinks was provided by the formation of a stable passive film formed by metal oxides. Scanning electron microscopy was used as a complementary technique to reveal corrosion phenomena at the surface of the materials evaluated.