3D打印钢结构的进展与机遇

报告人：

Leroy Gardner教授（结构工程教授、伦敦帝国理工学院、英国皇家工程院院士）

报告摘要：

增材制造或3D打印金属材料在结构工程领域的应用前景广阔。目前，增材制造技术在结构工程领域取得了一系列新进展，主要表现在科学研究、其他领域经验借鉴、工程实践等诸多方面。本报告基于建筑工程领域的要求，针对当前最有应用前景的“电弧增材制造技术〞(WAAM)，介绍WAAM薄壁型钢、不锈钢结构的材料力学性能，以及其截面、构件、连接、体系的结构性能。围绕WAAM金属材料的固有几何变异性、潜在各向异性，探讨其研究与应用方面的挑战。考虑增材制造技术对结构优化的推动作用，以及二者协同发展为结构优化带来的机遇，讨论近期采用增材制造技术开展结构优化的案例。

报告人简介：

Leroy Gardner，伦敦帝国理工学院土木与环境工程系教授，英国皇家工程院院士。主要从事结构工程教学、科研与工程咨询工作，其带领的研究团队长期活跃于国际研究领域。Gardner教授是国际钢结构领域的著名学者，其研究涵盖了钢结构试验、模拟、分析、设计、建造等诸多方面。现已累计出版4部著作、7篇专著章节，发表论文500余篇。Gardner教授是两本国际期刊的主编，多部《欧洲规范》《美国规范》的编写委员会成员。Gardner教授于2017年荣获，国际桥梁与结构工程协会国际结构工程功勋奖〞（IABSE），并于2021年荣获美国土木工程师学会 ( ASCE) Shortridge Hardesty奖〞

Digital Image Correlation (DIC)

Speckle patterns were applied to coupons (and other tested elements) to provide features for DIC system to capture to allow us to obtain full field strain measurements

Stress-strain curves of machined carbon steel coupons

Carbon steel σ-ɛ response was found to be largely isotropic, with similar mechanical properties to conventionally formed material

stress-strain curves of machined stainless steel coupons

Microstructural analysis of WAAM carbon steel

Microstructural analysis of WAAM stainless steel

From the WAAM stainless steel (FCC), EBSD revealed a strong crystallographic texture, arising from solidification of the printed material under a thermal gradient. This explained the strong anisotropy.

Influence of as-built geometry on key mechanical property

Key 'effective' mechanical properties of as-built (AB) carbon steel below machined (M) coupons typically by between about 0% an larger reduction for stainless steel coupons owing to lower print quality. Ductility more sensitive.

Ductility of as-built material - coupons before and after loading

Fatigue behaviour of WAAM carbon steel

High-cycle fatigue testing performed on θ= 90° machined and as-built coupons performed, covering various stress ranges and stress ratios (R = min/0.1, 0.2, 0.3 and 0.4).

Comparisons with steel butt welds and S355 structural steel

Fatigue crack growth (FCG) behaviour of WAAM steels

FCG tests on machined compact tension (CT) specimens were conducted, extracted at different directions to the print layer orientation (θ = 0°, 45° and 90°).

Analysis of geometry

Scan data used to determine volume, mean cross-sectional area, variation in thickness etc

Comparison with AISC 370 provisions

When weakening effect of geometric undulations is included in material properties (i.e. provided as-built 'effective' material properties are used), local buckling behaviour of 3D printed stub columns similar to that of conventional sections and well predicted by existing design provisions

Column buckling

Comparison with code predictions for columns