Index of content:
Volume 120, Issue 3, September 2006
- NONLINEAR ACOUSTICS 
120(2006); http://dx.doi.org/10.1121/1.2216560View Description Hide Description
The stability of inkjet printers is a major requirement for high-quality-printing. However, in piezo-driven inkjet printheads, air entrapment can lead to malfunctioning of the jet formation. The piezoactuator is employed to actively monitor the channel acoustics and to identify distortions at an early stage. Modifications of the response of the piezoactuator indicate entrapped air bubbles and these allow us to investigate them. When we employ the signal as a trigger for high-speed imaging, we can visualize the consequences of the entrained bubbles on the dropletformation. Two mechanisms are found to cause air entrapment: First, a distorted dropletformation caused by small particles, and, second, an accumulation of ink on the nozzle plate, which favors void formation once the meniscus is pulled back.
Experimental characterization of fatigue damage in a nickel-base superalloy using nonlinear ultrasonic waves120(2006); http://dx.doi.org/10.1121/1.2221557View Description Hide Description
This research develops a robust experimental procedure to track the evolution of fatigue damage in a nickel-base superalloy with the acoustic nonlinearity parameter,, and demonstrates its effectiveness by making repeatable measurements of in multiple specimens, subjected to both high- and low-cycle fatigue. The measurement procedure developed in this research is robust in that it is based on conventional piezoelectric contact transducers, which are readily available off the shelf, and it offers the potential for field applications. In addition, the measurement procedure enables the user to isolate sample nonlinearity from measurement system nonlinearity. The experimental results show that there is a significant increase in linked to the high plasticity of low-cycle fatigue, and illustrate how these nonlinear ultrasonicmeasurements quantitatively characterize the damage state of a specimen in the early stages of fatigue. The high-cycle fatigue results are less definitive (the increase in is not as substantial) due to increased uncertainties involved in the high-cycle fatigue tests, but still show a clear relationship between and remaining fatigue life. One application of the measured versus fatigue-life data is to potentially serve as a master curve for life prediction based on nonlinear ultrasonicmeasurements.