project1e. spring12

project1e. spring12 - ME 452: Machine Design II Spring...

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1 ME 452: Machine Design II Spring Semester 2012 Project 1. Stress Analysis of a Crankshaft. An initial design of a small, single-cylinder diesel engine is almost complete. The designer requires that you now perform a stress analysis of the crankshaft. To do this you will need to model the motion of the engine components to determine the loads on the crankshaft, from which you can determine the stresses, which will fluctuate with time. Combining these fluctuating stresses with the material properties of the crankshaft will allow you to predict the static and fatigue factors of safety for the crankshaft. You will also need to specify the material properties and the heat treatment. You may have studied stress analysis and static failure theories in previous courses in mechanics, for example, ME 323. In this course, ME 452, you will review some of the important concepts and then study fatigue failure theories. Fatigue is caused by time-varying stresses and strains in the material. These stresses can initiate at a crack, usually at a local surface imperfection such as a machining mark or a notch in the geometry. Therefore, the stress concentration effects are very important in fatigue. As the stresses are cycled, even at levels below the yield point of the material, the crack propagates through the material reducing its cross-sectional area. Eventually, the area of material holding the loads decreases sufficiently to push the stresses beyond the yield or even the ultimate strength of the material, in which case the part breaks. The key to a successful stress analysis of the crankshaft in this project is to estimate the stresses in the
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project1e. spring12 - ME 452: Machine Design II Spring...

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