Design optimization using multiple strain gauges in regions of high strain gradients

Many of those concerned with the design of engineering components or the re-design of spare parts in Tanzania industry are not familiar with the stress analysis and design optimization techniques available to them, and even those who are practiced in the art may not be fully cognizant of the attributes or deficiencies of different techniques and so be unable to select the best methods to apply to their own problems. Broadly, the design engineer encounters two basic kinds of problems. The first is urgent and requires a more or less on-the-spot solution and the second is more routine and can be dealt with at leisure. In cases of structural failure however, a rapid diagnostic analysis is frequently required to access peak stresses in order to establish the cause of failure and a suitable remedy. The majority of fractures of machine components in service can be attributed to the presence of high stress concentration at re-entrant corners and points of sharp variation of cross-sectional dimensions. Optimization of the design or shapes of the machine components to minimize stress concentration effects without compromise to the basic design features becomes necessary to ensure a better fatigue behaviour. How this is achieved constitute the main objective of this research. A plate with circular fillets under uniform tension is investigated as a known case of a component with high strain gradient in those regions of the plate which are in the neighbourhood of the fillets. Optimization is carried out by varying the size of the fillets. Stress levels are then obtained experimentally by using multiple strain gauges and analytically by using finite element computer software for advanced stress analysis. Analysis of the results shows that optimization of fillet designs in regions of high strain gradient using multiple stain gauges is possible and generally the results are in agreement with the results obtained using the computer simulation method, and those obtained by other researchers who employed other methods such as photo elasticity. It has also been found that the accuracy of the method of using multiple strain gauges can be further increased by employing strain gauges of much smaller length. The method also has the added advantage of its simplicity in application especially on actual components. Limitations of the method employed in this research are discussed and suggestions made for further investigation