PSI - Issue 57

C2 - Confidential

Hayder Y Ahmad et al. / Procedia Structural Integrity 57 (2024) 478–486 Ahmad et al./ Structural Integrity Procedia 00 (2023) 000 – 000

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Centre of Starburst Feature Identified as probable location of crack initiation

Fixing bolt Counter bore

Figure 8: Starburst feature showing proximity to the fixing hole counter-bore

Indication of ‘Chevron’ marks the direction pointing to location of crack initiation position

Small inclusion at the centre of the Star Burst Feature, which was the nucleus of the fracture

Figure 9: Starburst feature showing position of inclusion

5.2. Fractography Examination An SEM investigation carried out confirmed that the housing casting had failed as a result of a brittle fracture and no indications of fatigue were visible on the fracture face. This is shown in figure 10 (a and b).

(a)

(b)

Figure 10 (a and b): SEM images of the fracture surface at different magnifications showing the brittle failure mode

Furthermore, figure 11 (a and b) shows the origin of the fracture could be traced to the inclusion that was at the centre of the ‘starburst’ feature and established that the inclusion was primarily composed of Magnesium and Silicon (confirmed by the EDX figure 11 b) which was identified as ‘reacted sand’ from the casting mould.