Prediction of Mechanical Properties based on Integrated Computational Materials Engineering: Application to Nanoindentation and Pipe Forming

DoctorIt is necessary to understand the materials and the manufacturing process to make a good final product. Recently, an individual researcher cannot figure out the entire picture of the product production because of the development, the specialization, and the subdivision of the technology. Integrated computational materials engineering (ICME) is invented to overcome the lack of understanding and to cooperate with the researchers among various fields. ICME is a concept which designs the materials, the manufacturing process, and the final product by combining of the material models with various length scales. It is required that the basic material properties with microscale, understanding about the manufacturing process with macroscopic point of view, and the consideration for the linking of the various length scales to apply ICME. The aim of this thesis is to investigate the several stages of ICME. Microscopic material properties were obtained from the nanoindentation test which can be implemented to the small size samples. These mechanical properties were combined with the representative volume element method, or unit cell model which is suitable to determine the mechanical properties of materials with complex structures, or parameterized for several constitutive equations to link into the researches with larger scales. And the mechanical properties of the final product after the manufacturing process based on the initial material properties before the process by the research for the production process with macroscale. A technique to obtain the microscale material properties and the link between the microscale and the mesoscale or macroscale were shown by the studies for the nanoindentation in this thesis. The technique extracting stress-strain curves from the load-displacement curves of the nanoindentation tests was developed and the technique was applied to various samples. The nanoindentation tests were implemented for high pressure torsion processed copper sample to investigate about the possibility of obtaining local mechanical properties and the accuracy of the nanoindentation test. Each phase of TRIP steel was tested by the nanoindentation to get the mechanical properties of a single phase from the multiphase material and it was shown that the extracted microscale properties can be linked into the bulk properties by combining the extracted properties and the representative volume element method. The mechanical properties of iron powder sample and AZ31 magnesium alloy were measured with the nanoindentation test, and the measured stress-strain curves were converted to parameters for constitutive equations. These results present the development possibility of the nanoindentation for the various types of materials. In this thesis, the prediction for the mechanical properties of the final product using the initial material properties and the understanding about the manufacturing process were shown by the research for the pipe forming process. Various process conditions were controlled and investigated to find the relationship between the process conditions and the mechanical properties of the final product