Damage Severity Assessment in Ductile and Brittle Media Using Improved b Value Analysis of AE Data

Abstract

Non-destructive testing has evolved as one of the most preferred testing method for structural health monitoring. Structural health monitoring in the field of aerospace, mechanical, nuclear power, civil engineering, etc. requires techniques to detect damage at early stages of development. The early detection of damage helps to take appropriate action required for retrofitting. Risks to human lives can be decreased if the time of catastrophic failure is well known. AE is preferred over other NDT techniques for its in-situ examination and for its active nature. Damage quantification tools are used to analyse data to know the type, size and severity of damage. This report presents the use of improved b value analysis to differentiate Ib values for indication of failure mechanisms in ductile and brittle material. In the present study, mild steel specimens were used as ductile material and concrete cubes cured for different time period were used as brittle material. The mild steel specimens were tested in tensile loading at different loading rate. The R15α sensors were mounted with the help of tape using grease as couplant. In bending, a notch was deliberately machined on tension side in mild steel specimens. In case of concrete, cubes cured for different time period were tested under compressive load. The R3α sensors used for the study of brittle material were mounted with the help of grease and tape. The AE data captured for both ductile and brittle material was analysed using improved b value analysis. Amplitude, absolute energy, improved b value, load and other parameters were plotted with time to understand failure mechanisms in ductile and brittle materials. The Ib value for both ductile and brittle material was obtained.