Journal of Emerging Trends in Engineering and Applied Sciences: Research Areas

Abstract:
This paper shows the fracture behaviour of AISI 8630 keel block casting subjected to fatigue. The purpose is to study how repeated loading initiates cracks, which grow slowly until failure occurs affects the structural rigidity, durability and life of the entire structures of keel block casting in order determines its safety and structural reliability. The AISI 8630 steel was heated and poured at a temperature of 1593oC with a die temperature of 204oC.The casting used in this research was subjected to heat treatment. Fatigue experiment was performed using the Rotating Beam Fatigue Testing Machine using frequencies 25 Hz and 50 Hz .The graph of cyclic stress was plotted against the number of cycles to failure. Fractographic analysis for fatigue specimens was conducted on the fracture surface using a Scanning Electron Microscope (SEM) after testing was completed by cutting the fractured sample and viewing under the Scanning Electron Microscope. The results shows that as the cyclic stress increases, the life of the material decreases and as the frequency increases, the number of cycles to failure decreases. Results also show that gradients decrease with increase in frequencies and smaller frequencies give higher intercepts on y-axis. The fractography of the fractured specimen also revealed that the failure begins with crack initiations at the external surface and propagates slowly into the material till final fracture occurred

Keywords: fatigue experiment, cyclic stress, fractography, frequency, fracture behaviour, fatigue crack growth.

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