2011 Volume 52 Issue 3 Pages 397-405
Acoustic emission is defined as the ultrasonic wave phenomenon due to rapid release of strain energy in the solid materials. This paper aims at the extension of acoustic emission method for certain and effective analysis that can adapt to material research field. The rise time of two kinds of martensitic transformation in Cu-Al-Ni shape memory alloy, the β1 to β1′ and the β1 to γ1′ phase transformation, were observed by acoustic emission monitoring and the analysis based on the simulation of acoustic emission wave utilizing finite element method. In the simulation on finite element method, we considered the acoustic emission wave with the effect of inclined source such as the martensitic habit plane, source location in thickness direction of the specimen and rise time of acoustic emission source as the dynamic behavior. We found that the particular frequency range of zeroth-order mode Lamb wave has the differences only due to rise time of acoustic emission source. Finally we analyzed the rise time of two kinds of martensitic transformation with reviewing the results of simulation. As the result, the β1 to β1′ phase transformation showed the longer rise time than the β1 to γ1′ phase transformation in the nucleation step. It is thought that there is the difference between 18R and 2H periodic stacking order structure of martensite.
