title: A method to estimate the absolute ultrasonic nonlinearity parameter from relative measurements.
abstract: The ultrasonic nonlinearity parameter (β) is determined from the particle displacement amplitudes of the fundamental and second-order harmonic components in an ultrasonic wave propagated through a material. This parameter is generally referred to as the absolute parameter. However, measuring the second harmonic component is especially difficult because its amplitude is usually much smaller than those of signals in typical ultrasonic measurements. For this reason, most studies use the relative parameter determined using the measured electric signal amplitudes of the fundamental and second harmonic ultrasonic waves. However, in many occasions, the absolute parameter is needed for a quantitative assessment of material degradation. This study proposes a method to estimate the absolute parameter from a measured relative parameter along with a proportionality constant between normalized absolute and relative parameters. This method is based on the observed fact that the ratio of between normalized relative and absolute parameters is identical after compensating proportionality constant. The method was experimentally validated for Al6061-T6 alloy specimens heat-treated for different aging times. The parameter determined through the proposed method were compared with the absolute parameters which were measured separately. The results show that these two parameters were close to each other within the measurement errors.
authors.affiliation: Department of Mechanical Convergence Engineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul 04736, Republic of Korea.
authors.forename: Jongbeom
authors.initials: J
authors.lastname: Kim
authors.affiliation: Department of Mechanical Convergence Engineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul 04736, Republic of Korea.
authors.forename: Dong-Gi
authors.initials: DG
authors.lastname: Song
authors.affiliation: School of Mechanical Engineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul 04736, Republic of Korea. Electronic address: kyjhang@hanyang.ac.kr.
authors.forename: Kyung-Young
authors.initials: KY
authors.lastname: Jhang
keywords: Absolute parameter; Al6061-T6 alloy; Relative parameter; Thermal aging; Ultrasonic nonlinearity parameter