Detecting small flaws in two-phase Ti-6Al-4V with rough surfaces

Xiongbing Li; Yingdong Fu; Feng Zhang; Yanni Rao

doi:10.1016/j.ultras.2020.106128

Detecting small flaws in two-phase Ti-6Al-4V with rough surfaces

Ultrasonics. 2020 Aug:106:106128. doi: 10.1016/j.ultras.2020.106128. Epub 2020 Mar 10.

Authors

Xiongbing Li¹, Yingdong Fu², Feng Zhang³, Yanni Rao⁴

Affiliations

¹ School of Traffic and Transportation Engineering, Central South University, Changsha 410075, China; Joint International Research Laboratory of Key Technology for Rail Traffic Safety, Changsha 410075, China; National & Local Joint Engineering Research Center of Safety Technology for Rail Vehicle, Changsha 410075, China.
² School of Traffic and Transportation Engineering, Central South University, Changsha 410075, China; Joint International Research Laboratory of Key Technology for Rail Traffic Safety, Changsha 410075, China.
³ School of Traffic and Transportation Engineering, Central South University, Changsha 410075, China.
⁴ School of Traffic and Transportation Engineering, Central South University, Changsha 410075, China; Joint International Research Laboratory of Key Technology for Rail Traffic Safety, Changsha 410075, China. Electronic address: raoyn1@csu.edu.cn.

PMID: 32283418
DOI: 10.1016/j.ultras.2020.106128

Abstract

Surface roughness degrades the performance of ultrasonic methods when detecting sub-wavelength flaws. In this work, a roughness-modified doubly-scattered response (DSR) model is developed to enhance the flaw detection method for two-phase Ti-6Al-4V with rough surfaces. Extreme value statistics are used to calculate the confidence bounds of grain noise, then the bounds are treated as a time-dependent threshold for segmenting flaws in C-scan images of two-phase Ti-6Al-4V with rough surfaces. Three Ti-6Al-4V samples with different surface roughness are designed and manufactured for validating the present method; ultrasonic C-scan results show that it can distinguish sub-wavelength flaws (about 1/3 wavelength) in two-phase Ti-6Al-4V with rough surfaces, which can be extended to industry applications.

Keywords: Double scattering; Rough surfaces; Sub-wavelength flaws; Two-phase Ti-6Al-4V; Ultrasonic testing.