PSI - Issue 46

6

Alok Gupta et al. / Structural Integrity Procedia 00 (2021) 000–000

Alok Gupta et al. / Procedia Structural Integrity 46 (2023) 35–41

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(b)

(c)

Lack of Fusion Void

Initiation Site (b)

(a)

Propagation

Lack of Fusion Voids

Lip

Initiation Site

Beach Marks

400  m

400  m

2 mm

Fig. 5. SEM micrographs of fracture surface of location 1: (a) Fracture surface identifying zones of initiation and propagation and fast fracture (lip) zone, (b) identification of initiation site and beach marks, and (c) lack of fusion void in the final fracture (lip) zone.

3.3. Appraisal on design and SLM process The weight optimized bracket in a ‘struts & connectors’ shape was built using the SLM process to test its LCF performance at 200  C. The bracket was successfully tested against the targeted 3000 cycles without failure for the upper bound of LCF load conditions. Additionally, it has been demonstrated that the failure of bracket at higher loading levels, causing elasto-plastic strain levels, is sequential and the bracket does not lose its full load carrying capability suddenly due to its particular design, with multiple load carrying struts. This feature of the bracket design provides a good option to build confidence for the practicing engineers. Further component tests of LCF and LCF nature shall be required in the future to prove maturity of component designs and understand possible scatter in fatigue performance of SLM components. Furthermore, it is recommended that the crack life prediction methods proposed by Jones et al. (2020) and Gupta et al. (2020) are used to predict the crack growth life of small cracks in AM Ti-6Al 4V components. 4. Conclusions The key findings from this study are summarized as below:  The SLM Ti-6Al-4V bracket was found to have been designed successfully to operate under the expected thermo-mechanical normal operating loading environment.  The aero-engine bracket in a ‘struts & connectors’ shape completed the target cycles at the upper bound of the LCF load condition.  The sequential failures in the bracket at higher loading levels, causing elasto-plastic strain, exhibit a distinct design feature of the bracket where it demonstrates redundancies in the load path due to its particular design, with multiple load-carrying struts.  The successful outcome of the elevated temperature LCF testing of the bracket is a significant forward step towards adopting the SLM technology for safety critical load bearing applications. Acknowledgements We thank Rolls-Royce plc and the EPSRC for the support under the Prosperity Partnership Grant \ Cornerstone: Mechanical Engineering Science to Enable Aero Propulsion Futures, Grant Ref: EP/R004951/1. Also, our sincere thanks to Mr. Daniel Cousins (Rolls-Royce Plc.) for his contribution on the development of bracket design. We also extend our sincere thanks to the Materials Solutions Limited, UK for their support in manufacturing the SLM brackets.