Browsing by Author "Nwafor, O. M. I."

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    The effect of surface finish on the low cycle fatigue of medium carbon steel
    (Federal University of Technology, Owerri, 2024-10) Obiukwu, O. O.; Nwafor, O. M. I.; Okafor, B.; Osueke, G.
    As fatigue cracks initiate predominantly at the free surface of a material, the condition of the surface can be assumed to be critical with regards to fatigue strength. The features of a mechanically prepared surface which are considered to be major factors affecting fatigue strength fatigue are stress concentration (a shape factor), dimension (a scale factor), and surface finish (a technological factor). This paper investigates the effect of surface finish on the fatigue life of AISI/ SAE 1040 (medium carbon steels). A compositional analysis was performed to ascertain the percentage of carbon in the materials. The specimens were machined to a precise gauge length and diameter and exposed to various surface finishes mainly; polishing and grinding machining surface conditions. A fatigue test was performed with the use of Avery Dennison and bending stress was obtained using the curve supplied with the machine. The results from the machine were converted to Mega Pascal (MPa) and the values used to plot S-N curves. The fatigue resistance for the specimens at various surface finishes of the different carbon steels was thus established. The results show that the polished surface with surface roughness (Ra = 0.20microns) has the longest fatigue life.
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    The optimum mesophilic temperature of batch process biogas production from animal-based wastes
    (Federal University of Technology, Owerri, 2010-05) Obiukwu, O. O.; Nwafor, O. M. I.
    The optimum temperature of biogas production from blends of animal-based wastes was determined under controlled heat supply to the digester in a batch digestion process. Cow Dung (CD) and Poultry Droppings (PD) were blended in the ratio of CD: PD::1:3. The digester was operated at average ambient temperature of 30°C as baseline. Biogas production from the waste blends was monitored under the temperatures of 32°C to 45°C. Results obtained indicate maximum cumulative gas yield was observed at the temperature of 40°C.The 40°C temperature gave the highest biogas yield of 2685 ml followed by the 35°C temperature with the cumulative yield of 2535 ml. The ambient temperature of 30°C had the least cumulative biogas yield of 185 ml. These results indicate that increased and steady biogas production can be achieved under the optimum mesophilic temperature of 40°C when these animal-based wastes are digested in batch digestion process.