Experimental investigation of inconsistent ultrasonic measurements on a titanium turbine blade

• Main Author: Choo, Jia Wei
• Other Authors: Fan Zheng, David
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2021
• Subjects: Engineering::Aeronautical engineering; Engineering::Materials::Material testing and characterization
• Online Access: https://hdl.handle.net/10356/153516
• Institution: Nanyang Technological University

This study investigates inconsistent results from ultrasonic testing to detect and size defects of titanium alloy turbine blades. Specifically, for all intents and purposes, multiple identical specimens of titanium turbine blades will return different results undergoing ultrasonic testing. This is due to the inherent differences in microstructure of polycrystalline specimen where the local difference of acoustic impedance causing different ultrasonic wave attenuation and backscattering. Such anisotropy can reduce inspection reliability. Furthermore, an ability to predict and cope with anisotropy would be advantageous to prevent structural failure. Additionally, new complex alloys are constantly being designed and a better understanding of the material microstructure is beneficial. Such knowledge could be utilized in the design stage to aid the development of new materials. Accurately understanding the nuances of microstructure will allow for a higher level of assurance to newly manufactured parts or for overhauled parts to give an estimation of part degradation. In this paper, an experimental study on titanium turbine blades samples has been performed to study the ultrasonic parameters such as wave amplitude and attenuation as a function of the microstructural differences. The titanium turbine blades has undergone a variety of ultrasound testing in this study with different equipment and procedures listed in the appendix. This is presented in a largely descriptive manner to seek a better understanding of the factors which influence the ability of ultrasonic techniques to detect and size defects. The results show that extraneous factors have large effect to the results in this study. Depending on equipment, defects detection is dependent on the equipment used and is not translatable between equipment. And in many cases, smaller defects are the ones that is heavily affected by the material properties which is the interest of this study. The property of material is related to the path of the ultrasound and in some cases the material may be regarded as truly isotropic.