Gope, P.C.Tiwari, Saurabh2022-01-252022-01-252021-12https://krishikosh.egranth.ac.in/handle/1/5810181195Aluminium alloy 7075 and 2024 are some of the widely used materials in the aerospace industry. In the present investigation, the effect of SiC nanoparticles on fatigue crack growth and mechanical properties were tested on friction stir welded specimens and compared with as-welded specimens. Fatigue test is performed on different loading angles i.e., 0°, 30°, 45°, 60° and 90° with Pmax= 2 kN, Pmin= 0.2 kN and frequency of 5 Hz with R=0.1 and cracks length is measured using a digital camera fitted on travelling tripod and then compared them with numerically calculated values. All specimens were solution annealed at 460 °C for 2 h and then the ageing heat treatment procedure was done at 170 °C for 16 hours. The experimental data obtained was used to plot stress-strain curve, a-N and da/dN vs. 􀀧Keq curve and various fatigue crack growth parameters such as Paris crack growth constants, crack opening stress intensity factor, etc. were determined. The fatigue life was found to be 37000, 36500, 33000, 30000 and 28000 cycles for friction stir welded CTS specimen at 90°, 60°, 45°, 30° and 0° respectively in as-weld condition. It was observed that there is a significant variation in the variances of crack length increment after the incorporation of SiC nanoparticles. The fatigue life after SiC incorporation was found to be 48200, 39000, 36000, 34500 and 30000 cycles at 90°, 60°, 45°, 30° and 0° respectively. The values of material constants C and m are calculated through a single Paris Curve fit. Scanning electron microscope (SEM) study of fracture surface at different locations was carried out to investigate the different modes of fracture that occurred at different loading conditions and morphology test is used to investigate the grain size distribution at different welding zones.EnglishThesis