Thesis. 1977. Ph.D.--Massachusetts Institute of Technology. Dept. of Materials Science and Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Includes bibliographical references. / Ph.D.

The structural behaviour of single shear bolted connections and double shear bolted connections of cold-formed stainless steel at elevated temperatures and post-fire condition has been investigated in this study. The current design rules on bolted connections of cold-formed stainless steel are mainly based on those of carbon steel, and are applicable for room (ambient) temperature condition only. These design rules may not be applicable for elevated temperatures. Therefore, design guidelines should be prepared for bolted connections of cold-formed stainless steel structures at elevated temperatures. The key findings of the investigation are described in the following paragraphs. A total of 25 tensile coupon tests were conducted to investigate the material deterioration of three different grades of stainless steel at elevated temperatures. The stainless steels are austenitic stainless steel EN 1.4301 (AISI 304) and EN 1.4571 (AISI 316Ti having small amount of titanium) as well as lean duplex stainless steel EN 1.4162 (AISI S32101). Totally 434 tests on bolted connections of stainless steel were performed in the temperature ranged from 22 to 950 ºC using both steady state and transient state test methods. The test results were compared with the nominal strengths calculated from the American Specification, Australian/New Zealand Standard and European codes for stainless steel structures. In calculating the nominal strengths of the connections, the material properties at elevated temperatures were used in the design equations for room temperature. It is shown that the nominal strengths predicted by these specifications are generally conservative at elevated temperatures. A total of 78 cold-formed stainless steel single shear and double shear bolted connections were tested in post-fire condition. The test results were compared with those tested at room temperature. Generally, it is found that the bolted connection strengths in post-fire condition cooling down from 350 and 650 ºC are higher than those tested at room temperature for all three grades of stainless steel. Finite element models for single shear and double shear bolted connections were developed and verified against the experimental results. Static analysis technique was used in the numerical analyses. Extensive parametric studies that included 450 specimens were performed using the verified finite element models to evaluate the bearing resistances of bolted connections of stainless steel at elevated temperatures. Design equations for bearing resistances of cold-formed stainless steel single shear and double shear bolted connections were proposed based on both the experimental and numerical results in the temperature ranged from 22 to 950 ºC. The bearing resistances of bolted connections obtained from the tests and the finite element analyses were compared with the nominal strengths calculated using the current design rules and also compared with the predicted strengths calculated using the proposed design equations. It is shown that the proposed design equations are generally more accurate and reliable in predicting the bearing resistances of bolted connections at elevated temperatures than the current design rules. The reliability of the current and proposed design rules was evaluated using reliability analysis. The proposed design equations are recommended for bolted connections assembled using cold-formed stainless steels. / published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

Thesis (M.App.Sc.) - Carleton University, 2007. / Includes bibliographical references (p. 134-142). Also available in electronic format on the Internet.

M.Ing. / Because cold-formed stainless steel is a new type of light steel material and dose not have a long history of utilisation in structures, there are many issues that need to be researched and discussed. Making a more thorough investigation and study of cold-formed stainless steels is essential. As a numerical analysis tool, the finite element method proves to be useful in structural analysis. The buckling modes of cold-formed stainless steel members, such as local, flexural, torsional and torsional-flexural buckling, are well known and well documented in design specifications. Distortional buckling is a special kind of buckling mode, which is less well known. Researchers have recently paid more attention to this problem. For stainless steel structures, it is necessary to investigate their behaviour when distortional buckling occurs. In this project, the distortional buckling of cold-formed stainless steel columns under axial compression is investigated. The finite element method is used to analyse and calculate different buckling modes, especially distortional buckling. This is compared to experimental results and other theoretical predictions. The ABAQUS finite element code is used throughout. Finite element modelling is very important prior to processing and analysis. ABAQUS models are created to study distortional buckling. The initial imperfection of structural members is taken into account with these models, using specific sine wave descriptions with respect to different structural parameters. A dynamic processing approach is chosen in the finite element analysis. The effectiveness and accuracy of these models have been verified by both experimental tests and theoretical calculations. Buckling mode and behaviour are predicted and analysed in terms of the finite element models and processes. Suggestions are made for buckling analysis and design based on the research results.

Prediction of fatigue damage due to fretting is complex due to the number of influential factors and the competitive interaction between wear and fatigue. The majority of current fretting damage modeling approaches are limited to narrow ranges of conditions where little competition between damage mechanisms occurs. Recent models which account for damage interaction are largely phenomenological in nature and are still limited to a narrow range of applicability. A method to characterize and model the level of fatigue damage due to fretting was developed in this work to address the shortcomings of the current methods available by extending the range of conditions captured and enhancing the physical basis of the damage model. Baseline material properties for thin sheets of AISI 301 stainless steel in the full hard condition were determined as a function of temperature through tensile tests, fatigue tests, and metallography. Fretting experiments were performed for contact between 301 stainless steel and each ANSI A356 aluminum and AISI 52100 steel. Fretting experiments were performed over a range of material combinations, normal forces, displacement amplitudes, atmospheres, and temperatures. Subsequent characterization of the damage due to fretting was performed to determine the level of wear and fatigue damage incurred for each condition tested. A finite element model of the experiment was created to determine the cyclic stress-strain behavior and local frictional energy dissipation for each condition. Fatigue damage metrics were evaluated to determine the effects of the contact conditions on the driver for fatigue damage. A new model for fatigue damage due to fretting was developed which incorporates the wear behavior to describe the effect of wear on the level of fatigue damage caused by fretting. The level of fatigue damage is influenced using a function of frictional energy dissipation and wear rate to account for differences in wear mechanisms and changes in the severity of wear caused by changes in oxidation behavior and mechanical properties which result from changes in temperature or contacting materials.

No description available.

Influence of China¡¦s Trade Protective Policies on Export of Taiwan¡¦s Flat Stainless Steel and the Response Strategies Abstract The export of Taiwan¡¦s flat stainless steel has been highly concentrated in China. However, China has expanded its domestic production capacity of flat stainless steel and reduced import volumes in recent years. Under such a background, this paper probes into the influence of China¡¦s trade protective measures on the competitive ability of Taiwan¡¦s products in Chinese market and submits some response strategies. Survey data from both the flat stainless steel industry (including upstream factories, midstream export agents, and downstream factories) in Taiwan and China were collected and analyzed. Interviews with experts, analysis of practical experiences, and literature on the subject were also adopted to induce the results as follows: 1. The four major variables included in this study are background, trade protective policy (consisting of two factors: the past temporary protective measures during 2002~2004 and the potential trade protective policy in the future), market influence (in pure domestic market and proceed and reexport) and competitiveness index. 2. The following variables show statistically significant correlation (influence) between them: (1) ¡§background¡¨ and ¡§trade protective policy (of the past safeguard and in the future)¡¨; ¡§background¡¨ and ¡§market influence in pure domestic market¡¨. (2) ¡§trade protective policy of the past safeguard¡¨ and ¡§market influence in pure domestic market¡¨. (3) ¡§trade protective policy in the future¡¨ and ¡§pure domestic market¡¨; ¡§trade protective policy in the future¡¨ and ¡§competitiveness index¡¨. (4) ¡§market influence in proceed and reexport¡¨ and ¡§competitiveness index¡¨ The following variables don¡¦t have any statistically significant correlation (influence) between them: (1) ¡§background¡¨ and ¡§competitiveness index¡¨. (2) ¡§trade protective policy of the past safeguard¡¨ and ¡§market influence in proceed and reexport¡¨; ¡§trade protective policy of the past safeguard¡¨ and ¡§competitiveness index¡¨. (3) ¡§trade protective policy in the future¡¨ and ¡§market influence in proceed and reexport.¡¨ (4) ¡§pure domestic market¡¨ and ¡§competitiveness index¡¨. 3. Different industries, structure, capital and operation revenue show no significant difference in the study results. 4. Competitiveness index = - 0.498 x trade protective policy in the future ¡V 0.404 x market influence in proceed and reexport. 5. According to the evaluation of the influence of China¡¦s ¡§trade protective policy of the past safeguard¡¨ and ¡§trade protective policy in the future¡¨ on Taiwan¡¦s competitiveness index, the results show that the total evaluation indexes are 0.078 and ¡V 0.619 respectively. 6. In general, most people feel that Taiwan¡¦s export of flat stainless steel to China will be significantly affected commencing from 2006. 7. In response to China¡¦s protective policy of the past safeguard (temporary protective measures), Taiwan business community took the following strategies in order: (1) Shift and export to other areas (2) Increase selling inside the Taiwan market (3) Increase stocks in warehouses or quays in Taiwan, Hong Kong or China. (4) Drop in production To cope with the trade protective policies to be adopted by China in the future, some measures should be taken as follows in order: (1) Shift and export to other areas (2) Shift partial production to China (3) Increase investments in China and adopt effective competitive strategies. (4) Drop in production 8. The upper stream may increase vertical integration and investments; the middle and down stream may increase logistic path investment. As for diversification of export markets, the stainless steel industry should focus on increasing their markets in Asia, Europe, North America, and especially the areas with big potential demand for nickel. Keywords: stainless steel, background, trade protective policy, market influence, competitiveness index, response strategy

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Thesis (Ph. D.)--Brigham Young University. Department of Mechanical Engineering, 2004. / Includes bibliographical references (p. 49-50).

Cold-formed stainless steel sections have been increasingly used in architectural and structural applications. Yet the high price of stainless steel limits the application to construction projects. The lean duplex stainless steel (EN 1.4162) offers an opportunity for stainless steels to be used more widely due to its competitive in price, good mechanical properties and corrosion resistance. The lean duplex stainless steel is a relatively new material, and research on this material is limited. Currently, the lean duplex stainless steel is not covered in any design specification, and no design rules are available for such material. Therefore, the behaviour and design of cold-formed lean duplex stainless steel members are investigated in this study. The investigation focused on columns, beams and beam-columns of square and rectangular hollow sections. Both experimental and numerical investigations were performed and reported. Design rules for cold-form lean duplex stainless steel members are proposed. The experimental investigation included material tests, column tests, beam tests and beam-column tests at room and elevated temperatures ranged from 24 – 900 °C. The test specimens were cold-rolled from flat strips. The test program consists of two square hollow sections and four rectangular hollow sections. Coupon specimens were extracted from each hollow section, and their material properties were obtained from tensile coupon tests at room temperature and elevated temperatures. In this study, a modified design rule was proposed to predict the cold-formed lean duplex stainless steel material properties at elevated temperatures. The local and overall geometric imperfections were measured. A total of 38 column tests were conducted. The effective column length ranged from 75 to 1660 mm in order to obtain a column curve for each test series. The test program for beams included 10 pure bending tests, and the bending capacities of the specimens were determined. A total of 37 beam-column specimens were compressed between pinned ends at different eccentricities in order to obtain an interactive curve for each series of test. Numerical investigation on columns, beams and beam-columns at room temperature as well as elevated temperatures are also presented. Accurate finite element models were developed and verified against the experimental results for columns, beams and beam-columns at room temperature. The structural members at elevated temperatures were simulated by replacing the material properties with those obtained at elevated temperatures. Extensive parametric studies were carried out, including 150 columns, 126 beams and 150 beam-columns at room temperature, as well as 180 columns, 125 beams and 195 beam-columns at elevated temperatures. Column, beam and beam-column strengths obtained from the experimental and numerical investigations as well as available data were compared with the design strengths calculated using American, Australian/New Zealand, European specifications for stainless steel structures of duplex material, since lean duplex material is not covered by these specifications. In addition, direct strength method for carbon steel and stainless steel as well as continuous strength method for stainless steel were assessed for cold-formed lean duplex stainless steel. Modified design rules were proposed. The reliability of the current and modified design rules was evaluated using reliability analysis. / published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy