A brittle model analysis of a diesel engine crankshaft

Walker, R. J (1969). A brittle model analysis of a diesel engine crankshaft Master's Thesis, School of Engineering, The University of Queensland.

       
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Author Walker, R. J
Thesis Title A brittle model analysis of a diesel engine crankshaft
School, Centre or Institute School of Engineering
Institution The University of Queensland
Publication date 1969
Thesis type Master's Thesis
Supervisor Mr. T. Leahy
Total pages 138
Language eng
Subjects 09 Engineering
Formatted abstract With continuing research the internal combustion engine has become one of the most reliable and efficient forms of motive power. For a given rated horsepower units of today show a marked decrease in overall size and weight when compared with engines manufactured just a decade ago. This has been achieved with the use of better materials operating at higher stress levels. High stress levels demand careful design and rigid adherence to high standards of manufacture, if reliability in service is to be attained. This thesis surveys the stress level operating in the crankshaft of a small diesel engine and develops a method whereby the strength to weight ratio may be optimised.

A comprehensive literature survey has been undertaken placing emphasis on those methods which are applicable to the smaller internal combustion engine crankshaft, A detailed description is given of studies undertaken to test the usefulness of the newer experimental stress analysis techniques for this investigation. The brittle model method using gypsum plaster was chosen. A brittle material fails in tension on a plane perpendicular to the direction of the maximum principal stress giving a unique solution to the problem being studied. A comparison between the design load and the gypsum plaster model rupture load checks the suitability of the component shape and size for both stress and strength.

For the small diesel engine crankshaft studied, three load conditions were tested and the shaft was found to have the least reserve strength when loaded in combined compression and torsion. This situation occurs Just after top dead centre of the firing stroke* The critical section is parallel and adjacent to the inner crankweb face, and failure begins in the fillet radius Joining the crankweb and the crankpin. A comparison between these findings and the failure of an actual fatigued crankshaft of the same dimensions as the model shows complete agreement.
Keyword Cranks and crankshafts
Diesel motor

 
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