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- 검색키워드
- 저자 : Baofeng Jiang (검색결과 4 건)
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Study on Residual Stress Distributions in Press-Braked Stainless Steel Sections
Baofeng Zheng,Gan-Ping Shu,Qinglin Jiang 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.5
The distribution of residual stresses is one of the substantial issues in determining mechanical behaviors of stainless steel structural members. Proper residual stress distribution models are necessary to include the residual stress infl uence in the analysis and design. Currently, the existing residual stress distribution model for press-braked stainless steel sections is either relatively complicated for the application, or only focuses on the longitudinal residual stress. In this study, a simplifi ed residual stress distribution model was proposed based on the analysis of the key mechanisms in the press-braking process that was assumed as two-stage (bending and rebounding) plane strain pure bending process. The stress–strain relationship was represented as a simplifi ed three–stage material model, and all the minor eff ects like the coiling and uncoiling, the material anisotropy, and the shift of neutral axis, etc. were neglected. Compared with test data, the predicted results by the proposed simplifi ed model indicate good agreement for specimens within the commonly used ratio of internal corner radius over the thickness ( r i / t ). Finite element models for the press-braking process were then developed in ABAQUS and validated using the available data from literature. A series of models with varied ratios of r i / t were analyzed. Simulation results indicate that the center of the corner region in the press-braked sections has the largest equivalent plastic strain and residual stresses. From the center to the edge, the equivalent plastic strain and residual stresses declined signifi cantly. As the ratios of r i / t become smaller and smaller, the neutral axis moves towards to the compression side and the proposed simplifi ed model gradually loses its prediction accuracy. Based on the theoretical and fi nite element analysis, the proposed simplifi ed model is applicable for press-braked stainless steel sections with r i / t ratios higher than 2.0.
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Material Enhancement Model for Austenitic Stainless Steel Sheets Subjected to Pre-stretching
Baofeng Zheng,Gan-Ping Shu,Rui-Hua Lu,Qinglin Jiang 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.5
Austenitic stainless steel has considerable strain hardening property, which can be utilized in the design of cold-formed stainless steel structures to eff ectively reduce project costs. Pre-stretching is a simple and fundamental cold-forming process. Material enhancement model developed for pre-stretching lays a basis for characterizing material properties in more complicated cold-forming process(e.g. cold-rolling and press-braking). In this study, a series of material tensile tests were performed to develop material enhancement models for austenitic stainless steel sheets subjected to pre-stretching. Austenitic stainless steel sheets were tensioned in six diff erent levels to introduce cold working into the sheets. Material properties of the sheets in two directions (i.e. along and perpendicular to the pre-stretching direction) were obtained through coupon tensile tests. To facilitate the development of the material enhancement models, a simplifi ed three-stage material model with six independent parameters was proposed. Enhancement model for each material parameter was developed with the plastic strain experienced in the pre-stretching process as a key factor. Key material parameters and full-range stress–strain curves at diff erent levels of pre-stretching were generated based on the proposed and the available predictive models in literatures. Comparisons of the generated material parameters and the stress–strain curves with the test ones show good agreement.
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Pengjiao Jia,Baofeng Jiang,Wen Zhao,Yongping Guan,Jianyong Han,Cheng Cheng 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.4
Recently, the Steel Tube Slab (STS) curtain method has been successfully used in the construction of ultra-shallow metro stations in modern urban areas. By using the STS curtain method, the external surfaces of pipes are welded with flange slabs, and then the pipes are jacked into soils. However, the nature and extent of the influence of flange slabs on the calculation of jacking force is unclear. This paper presents the first combined theoretical and case study to calculate the increase of jacking forces for circular steel pipes with welded flange slabs during the entire jacking process. The increase of jacking forces was assumed to balance the friction at the soil-pipeline interface. Theoretical formulae were firstly developed to calculate earth pressure based on pressure arch theory and elastic foundation beam theory. A case study was then performed to verify the theoretical results with the field data from Olympic Metro Station on the Shenyang Metro Line 9 in China. Subsequently, factors influencing the calculation of jacking force were analyzed and discussed. Results show that the theoretical formulae produced good results with minor errors. The implications of these findings regarding the prediction of jacking force and selection of hydraulic jack are discussed.
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