PSI - Issue 14

Premkumar Manda et al. / Procedia Structural Integrity 14 (2019) 467–474 Author name / Structural Integrity Procedia 00 (2018) 000–000

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4.3. Hardness Bulk Vickers hardness values are measured on the damaged cooling duct in different locations (encircled area in Fig. 1b) and these are shown in Table 3. It is clear from the Table 3 that the hardness values of damaged cooling duct are nearly same at different locations of the damaged area.

Table 3. Vickers hardness values of damaged cooling duct .

Sample designation

Vickers Hardness Number (HV 2 )

Cooling duct

35, 36, 35, 36, 36

4.4. Fractography The fracture surfaces of the damaged cooling duct of the fighter aircraft are shown in Figs. 7 and 8. The fracture surfaces portray the several micro-cracks and flat features. In addition, shallow dimples area present in some locations. The encircled areas in Fig. 7 (a and b) indicate the fatigue type features. The fracture surfaces taken from other locations of the cooling duct also display the rubbed and/or brittle features (Fig. 8 (a and b)), mud cracks (Fig. 8c) and featureless features (Fig.8d).

Fig. 7: The fracture surfaces of the damaged cooling duct taken from different locations. Encircled areas indicate fatigue type features.

5. Discussion The analyzed chemical composition of the damaged cooling duct of fighter aircraft indicates that it is manufactured from aluminium based alloy (AA 3003). The microstructure of the cooling duct displays the presence of two phases, namely, matrix and insoluble particles. The insoluble particles are large and small with dark contrast.