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Title: Improvements in Design and Manufacturing of Camshafts for High HP Engines
Authors: Bansal, Rajnish
Batish, Ajay (Guide)
Keywords: Design;Manufacturing;Camshaft;High horse power engine
Issue Date: 8-Feb-2017
Abstract: While designing of components which are required to work under cyclic loading, fatigue life becomes an important parameter. It primarily depends on geometrical features like fillet radius and sharpness of the corners which creates stress concentrations zones. Besides this, surface finish, loading conditions, thermal stresses and metallurgical flaws also play a secondary role. Various studies have been conducted on S-N relationships for simple geometries but in practice these results cannot be used because of dimensional and geometrical constraints imposed by the assembly designs. Nowadays FE analysis is used in such situations. Though it helps in analysing a design but designers need firsthand knowledge about the effect of such constraints on the Stress Concentration to make the design process efficient. A real life problem faced by Indian Railways on pre-mature fatigue failures of engine camshafts used in upgraded high horsepower diesel locomotives has been taken for study. Reported failures have been analysed and existing design has also been reviewed. Various design options within given constraints have been explored to develop 3-D models on Creo Elements/Pro 5.0 3-D modelling software, followed by meshing on HyperMesh V09 and FE analysis using RADIOSS software. After thorough analysis, the suitability of each options for adoption was adjudged and a combination model was developed to arrive at an optimal solution. A comparative study of different manufacturing processes has also been carried out so that benefits can accrue over and above the improvement made in stress concentration factor by alternate geometry. The studies conducted through modelling and FEA has revealed that introduction of an undercut groove in the shaft, increase in thickness of the coupling flanges and above all, reduction in the depth of dowel holes can play significant role in reducing the maximum stress induced in the geometries and it can be adopted well in components where there is a space constraint in the assembly and operations. It has also been found that contrary to common belief, blended grooves to increase fillet radius in the flanges increases the induced stress whereas similar grooves in shaft tends to reduce the stress. Further, the studies made on adopting forging process for manufacturing of camshafts has revealed that not only it helps in improving the mechanical properties significantly, especially iv | P a g e the UTS and Yield Strength at the most vulnerable locations vis-à-vis components manufactured out of round bars, but it also reduces the cost of manufacturing considerably, though it primarily depends on the volume over which cost of forging dies can be amortised. In the current study an improvement of 22% and 26% was achieved in UTS and Yield Strength respectively over the shear plane where failures were occurring along with cost reduction of 21% in the manufacturing cost. This study can be of great use to designers to understand the effect of variations in common geometrical features on the maximum induced stress while designing various mechanical components transmitting torque. It has a direct correlation with the fatigue life of components during service and thus it can help in improving their reliability. Further, this thesis has established, how forgings can be adopted to strengthen the vulnerable locations and at the same time save upon the cost of manufacturing.
Description: Master of Engineering-Production
Appears in Collections:Masters Theses@MED

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