Date of Award


Document Type

Open Access Master's Report

Degree Name

Master of Science in Mechanical Engineering (MS)

Administrative Home Department

Department of Mechanical Engineering-Engineering Mechanics

Advisor 1

Dr. Gregory Odegard

Committee Member 1

Dr. Paul Sanders

Committee Member 2

Dr. Timothy Hilditch


Automotive emission standards are getting more stringent day by day and governments worldwide are moving to reduce emissions from automobiles. In this scenario reducing the weight of automobile components becomes an important design objective to reduce emissions. A 10% reduction of weight in the complete automobile leads to 6-8 percent improvement in mileage (Mhapankar 2015). Also, powertrain components make up for approximately 27% of the total automobile weight and thus optimizing the design of components in the powertrain is an important task (Mhapankar 2015). Statistics show that 26% of component failures in automobiles are part of powertrain and 21% of overall failures are due to design and manufacturing defects (Heyes 1998). Furthermore, more than 90% of design failures are due to fatigue loading rather than static stress failure. The differential design was already optimized using the high Si ductile iron for static stresses by the work done by Mr. Parag Deshpande (Deshpande 2016) and Mr. Pankaj Kalan (Kalan 2016) in this project.

Thus, in this study the new differential design is evaluated for fatigue stresses using a stress life approach. The loading and boundary conditions have been modified from the previous works to better estimate the working condition of the differential case. Time integration of static load cases has been done to obtain fatigue results by running a linear static analysis. FEA models using a quasi-static analysis and transient analysis are compared as a part of the study to select the best possible approach in future applications. The model to use static load cases for fatigue analysis has been compared to standard fatigue solver of Optistruct.

In the second part of the project a flexural fatigue test is designed to study the effects of casting skin and its properties on fatigue life of ductile iron. Sample geometry for the test is designed and updated based on test results. The effects of thickness on the sample behavior and flexural testing is studied. A fracture mechanics approach is proposed to model the crack propagation in ductile iron for crack initiation at the nodules. A preliminary literature study for initiation at other casting defects is done which needs to be expanded and incorporated in the crack growth model.