The Center for NDE has extensive research capabilities that were developed primarily under FAA funding to enable the quantitative assessment of fluorescent penetrant inspection (FPI). Given that a typical commercial air carrier will have over 30,000 parts in its inventory that require FPI, the aviation industry is quite interested in understanding the efficacy of this method. In addition to work with the aviation industry, CNDE staff also use both Type 1 – Fluorescent Penetrants and Type 2 – Visible Penetrants in their research efforts with a variety of companies, particularly Iowa-based companies as part of the Iowa Companies Assistance Program (http://www.iprt.iastate.edu/nde/).
Included among the tools that CNDE staff have used for assessing FPI performance are brightness measurements, digital recording of UVa indications, and formal probability of detection studies. Brightness measurements are made using a Photo Research PR-880 Photometer. The photometer measures indication luminence in ft-lamberts. The instrument is shown in the top figure while the view through the eyepiece is shown in the lower figure. By measuring brightness of the actual indications, comparative studies can be completed which enable an assessment of the factors that impact detectability
CNDE also has extensive experience in the fabrication of fatigue samples for use in FPI and other crack detection studies. Two mechanical testing systems are available with loads up to 22 KIP. The typical sample fabrication approach involves the use of an EDM starter notch which is used to initiate crack growth in 3-point bending. Once the crack has initiated, the starter notch is machined away and the crack is grown to the desired length. A typical crack aspect ratio is shown in the lower right figure.
In addition to brightness measurements, UVa images are captured acquired using a Leica MZFL III wide field tilting binocular stereo microscope (12.80 – 160 X magnification) combined with a Retiga 1300C digital camera with a 3.34 Megapixel interlace scan CCD digital camera. The software used in image acquisition is ImagePro software. Ultraviolet (UVA) light is provided by means of an ebq 100 isolated power supply connected to an ultraviolet light source.
CNDE staff are available to answer questions related to prior research efforts and welcome the opportunity to support additional R&D needs of the industry.