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872 results on '"Gardner, Leroy"'

208. Topology optimisation of self-supporting structures based on the multi-directional additive manufacturing technique.

Author

Jun Ye, Qichen Guo, Hongjia Lu, Kyvelou, Pinelopi, Yang Zhao, Gardner, Leroy, and Yi Min Xie

Subjects
TOPOLOGY, SURFACE structure
Abstract

Although additive manufacturing (AM) continues to gain widespread adoption, the overhang problem remains a critical issue affecting printing quality. The design of self-supporting structures via topology optimisation approaches has been extensively studied. However, current optimisation research predominantly focuses on 3-axis AM machines, overlooking the more recently developed multi-axis machines. Moreover, the performance sacrifice due to overhang constraints in 3-axis AM can be significant, especially in structures with small volume fractions. To address this, we propose a two-step approach considering overhang constraints for multiaxis AM. This approach begins with a structure optimised using traditional topology optimisation. In the first step, a new optimisation problem determines printing surfaces for the given structure. If the proportion of unprintable elements isn't satisfactory, a second reoptimisation step is carried out to further reduce the unprintable proportion. Several examples demonstrate the effectiveness of the proposed approach. Notably, the significant performance sacrifice associated with the 3-axis AM approach becomes negligible when applying our multiaxis AM-based method. [ABSTRACT FROM AUTHOR]

Published
2023
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242. Structural stainless steel design: resistance based on deformation capacity

Author

Ashraf, Mahmud, Gardner, Leroy, and Nethercot, David A.

Subjects
Steel, Stainless -- Mechanical properties, Steel, Stainless -- Testing, Load factor design -- Analysis, Engineering and manufacturing industries, Science and technology
Abstract

Stainless steel structural sections possess several features that result in a significantly different response to that of equivalent carbon steel sections. To date these features have not been fully recognized in design codes, which have largely adapted rules devised for carbon steel in a rather simplistic fashion. Recently, a new approach for dealing with local buckling and the associated loss of effectiveness that does not utilize the concepts of either cross-sectional classification or effective cross-sectional properties has been developed for stainless steel and has also been applied to other nonlinear metallic materials. The method is based directly on the deformation capacities of cross sections and covers the behavior of stainless steel members subjected to flexural buckling and combined axial load plus bending. The proposed method has been verified using test results and its performance has been compared against the existing ASCE and Eurocode design guidance for structural stainless steel. Significantly improved and more consistent predictions have been obtained using the proposed method without any extra calculation effort. DOI: 10.1061/(ASCE)0733-9445(2008)134:3(402) CE Database subject headings: Column beams: Bending: Compression; Cross sections: Stainless steel: Structural design.

Published
2008

243. Behaviour and design of stainless steel columns in fire

Author

Kucukler, Merih, Xing , Zhe, and Gardner, Leroy

Subjects
TA, TH
Abstract

The flexural buckling behaviour and design of stainless steel I-section columns at elevated temperatures are investigated in this paper. Finite element models able to accurately replicate the response of structural stainless steel columns in fire are created and validated. The models are then utilised to carry out extensive numerical parametric studies considering a broad range of stainless steel grades, cross-section geometries, slendernesses and elevated temperature levels. Using the results from the parametric studies, the safety and accuracy of existing design rules provided in the European structural steel fire design code EN 1993-1-2 for stainless steel columns in fire are assessed. It is observed that the existing design rules provide rather scattered and inaccurate ultimate strength predictions for stainless steel columns at elevated temperatures. For the purpose of establishing an accurate and practical means of designing stainless steel columns in fire, a new design approach, compatible with existing design rules in EN 1993-1-2, is proposed. The safety, accuracy and reliability of the proposed approach are illustrated for a wide range of cases against the results obtained through nonlinear finite element modelling. The proposed stainless steel column fire design rules are due to be incorporated into the upcoming version of the European steel fire design standard EN 1993-1-2.

Published
2020

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