Abstract

Angle Beam Ultrasonic Spectroscopy to Evaluate Adhesive Layers: Linear and Nonlinear Methods

L.Adler (Adler Cosultants Inc./ Ohio State University, Belleair Beach, Florida, USA); S.I.Rokhlin (Department of Industrial, Welding and System Engineering, Ohio State University, Columbus, USA); J.H.Cantrell (NASA Langley Research Center, Hampton, VA, USA)

e-mail: ladler1@aol.com

We have developed a new technique for quantitative evaluation of adhesive bond integrity of metals and composites using Angle Beam Ultrasonic Spectroscopy (ABUS). The novelty of our approach is that it utilizes both normal and obliquely incident ultrasonic beams on the bond line simultaneously and measures the frequency response of the reflected ultrasonic signals. The oblique wave introduces shear stress on the bond line and allows discrimination of kissing or poor bonds from good bonds. The bond line thickness is determined from the normal incidence ultrasonic signature and thus the thickness variation is accounted for in data analysis. The method was further enhanced to utilize Angle Beam Ultrasonic Spectroscopy for weak bond evaluation by combining it with a low frequency dynamic load acting as a nonlinear (parametric) enhancement. The low frequency excitation parameters are set to make the maximum stress distribution coincide with the bond line. The bond layer properties are evaluated using Angle Beam Ultrasonic Spectroscopy for different states of stress of the bondline. Calculations of chemical bonding contributions to the adhesive strength of adhesive/adherent interfaces have been also performed which predicts an upper bound to the interfacial properties measured by these techniques.

Section : 3