Ductile iron crack prediction via finite element simulation

• Main Author: Wu, Gabriel Aoli
• Other Authors: School of Mechanical and Aerospace Engineering
• Format: Final Year Project
• Language: English
• Published: 2014
• Subjects: DRNTU::Engineering::Mechanical engineering
• Online Access: http://hdl.handle.net/10356/60151
• Institution: Nanyang Technological University

Ductile iron usage dates back some 5,000 years ago as forms of weapons and tools. During the industrial revolution, large machineries were built using ductile iron. However, it was not until recently when in depth studies on ductile iron fatigue life prediction were carried out. Currently, it seems like there is no generalized fatigue model available to predict the fatigue life of ductile iron. Thus, the objective of this project was to create a generalized ductile iron fatigue model using finite element analysis and utilize it to observe the microstructure changes in the ductile iron material. This was carried out using the finite element simulation software Abaqus version 6.13. A series of methodologies were carried out to develop the finite element model. The first step was to obtain the ductile iron microstructure through etching. After which, nano-indentation was done to acquire the material properties. Then, a 2-dimensional model was created to serve as a reference for further work. Progressing on, a 3-dimensional model was created SolidWorks and imported into Abaqus to perform explicit analysis. Moving on, a 3-dimensional submodel was created upon the basic 3-dimensional model to provide a detailed solution. Lastly, the 3-dimensional submodel was utilized to carry out crack initiation and propagation prediction via eXtended Finite Element Analysis (XFEM). Results of the 2-dimensional and 3-dimensional models coincide with past experimental studies, which state that stress is likely to concentrate around the graphite nodule. In addition, the XFEM analysis agree with past experimental studies which states that cracks normally initiate outward from graphite nodules in a perpendicular direction with respect to the load applied. From these results gathered, it can be concluded that a generalized ductile iron fatigue model has been created. Further mesh refinement can be carried out to improve the accuracy of the results if time and resources permit.