Date of Graduation
Statler College of Engineering and Mineral Resources
Mechanical and Aerospace Engineering
Bruce S Kang
Since Tabor showed the application of the spherical indentation approach to obtain material post-yielding true stress-strain curves, the indentation technique has been investigated to determine mechanical properties besides hardness measurement. With the development of various thin film materials, depth-sensing indentation is often applied to evaluate mechanical properties of thin film materials. However, indentation testing is a complicated mechanical process and analytical solutions are difficult to obtain. As a result, much of the understanding of the indentation process has been acquired through experiments and finite element simulations. Thus accurate measurement of indentation parameters is critical in the determination of surface mechanical properties using indentation method.;In this research, a Transparent Indenter Measurement (TIM) method was developed for material inspection and mechanical property measurement. The TIM method is capable of on-site, in-situ, (i) mechanical property measurement (hardness, Young's modulus, yield strength and post-yielding stress strain data) of material samples/machined parts and (ii) qualitative inspection of material surface conditions. The residual surface deformation after spherical indentations was first investigated on IN783 superalloy samples using phase-shifting moire and Twyman-Green interferometry. The elastic-plastic boundary was identified based on the characteristic of the out-of-plane deformation fringe patterns. Then using the measured in-plane deformation, yield strength of the tested material was obtained. Using the TIM system, real-time in-situ measurement of indentation-induced out-of-plane deformation and contact radius are directly measured during an indentation process. Coupled with elastic recovery theories and 2D finite element analyses, a procedure was developed to determine the material stress-strain curve. It is also demonstrated that the TIM method is suitable for debonding inspection of thin film materials.
Feng, Chuanyu, "Development of a transparent indenter measurement system and indentation analysis for material mechanical property evaluation" (2005). Graduate Theses, Dissertations, and Problem Reports. 4147.