Microstructure, mechanical properties and cross-sectional behaviour of additively manufactured stainless steel cylindrical shells
Ruizhi Zhang, Mohsen Amraei, Heidi Piili, Leroy Gardner
Abstract
• Coupon tests conducted to explore the material response of AM stainless steels and to correlate with observed microstructure. • Test investigation presented into cross-sectional behaviour of AM stainless steel cylindrical shells under axial compression. • Numerical models validated against test results for additively manufactured cylindrical shells under axial compression. • Validated numerical models used to perform parametric studies considering key parameters. • Applicability of existing design provisions in EN 1993-1-6 assessed using derived experimental and numerical data. Powder bed fusion is a rapidly developing method of metal additive manufacturing that offers an unprecedented ability to manufacture complex and flexible components with high accuracy. Stainless steel is a high value material that particularly lends itself to the emerging opportunities offered by metal additive manufacturing. There is, however, limited information related to the microstructure, mechanical properties and structural performance of thin-walled stainless steel elements additively manufactured by powder bed fusion; this is addressed in the present study in the context of thin-walled circular shells, which are investigated through a series of physical experiments and numerical simulations. The experimental programme consisted of material coupon tests, microstructural characterisation, geometric measurements and axial compression tests on stainless steel thin-walled cylindrical shells with large diameter-to-thickness ( D / t ) ratios produced by powder bed fusion. Advanced measurement techniques—3D-laser scanning and digital image correlation, were utilised to capture the geometric properties prior to testing and the distribution and development of the deformations and strains during testing, respectively. The measured geometric imperfections in the shells were such that most specimens met the Class A fabrication quality requirements set out in EC3-1-6; all tested shells buckled below their yield loads in an asymmetric chequerboard pattern, showing significant sensitivity to local imperfections. In parallel with the experimental investigation, a numerical modelling programme was carried out, aimed at first replicating the compression tests and then extending the current test data pool over a wider range of slenderness values. The experimental and numerical data were analysed and employed to assess the applicability of existing design methods for conventionally formed tubular sections to those manufactured by powder bed fusion. EC3-1-6 was found to give consistent and safe-sided buckling resistance predictions for the studied stainless steel cylindrical shells under axial compression.