Behaviour and design of steel structures made by wire arc additive manufacturing

: (Alternative Format Thesis)

Abstract

The increasing interest in additive manufacturing, particularly wire arc additive manufacturing (WAAM), for fabricating more material-efficient stainless steel structures poses a challenge to current design codes, which are based on structures produced using conventional methods. This gap is addressed in the current study by investigating the stability of WAAM stainless steel sections through a comprehensive study involving 73 tensile coupon tests on both machined and as-built WAAM material to determine the material properties. The microstructure of the material has also been investigated, and comprehensive geometric analysis has been conducted to characterise the print accuracy. To assess the stability of outstand flanges and internal elements, 50 stub column tests have been carried out on equal angle sections and square hollow sections of different slendernesses and the results have been combined with the findings of the tensile coupon tests and the geometric characterisation to evaluate the applicability of the current design methods to WAAM structures. Based on the results, modifications to the current design methods to account for the undulating geometry of WAAM material have been proposed, thus making it easier to design and verify the safety of WAAM structures.

The results of the stub column tests also highlight the need for standardisation of the WAAM process for construction purposes as variations in manufacturing parameters hinder accurate predictions of WAAM’s structural behaviour. To facilitate standardisation, the effects of the deposition rate (a key parameter affecting the cost and environmental impact of WAAM) on the material properties, geometric accuracy and stability of WAAM structures has been investigated, leading to the identification of an optimal deposition rate.

Finally, the novel concept of strengthening sections by imposing sinusoidal waveforms on their geometries has been investigated via a series of stub column tests on WAAM specimens with varying waveforms. This concept aims to utilise WAAM’s full capabilities and demonstrates the potential to increase the strength of sections with minimal increases in mass.

Date of Award	26 Jun 2024
Original language	English
Awarding Institution	University of Bath
Supervisor	Jie Wang (Supervisor), Vimal Dhokia (Supervisor) & Tim Ibell (Supervisor)