Eddy Current Inspection
In order to monitor on-line blade steel quality, MPI has developed high-speed, on-line process control eddy current capabilities to determine three major parameters: hardness, percentage of retained austenite, and impact (toughness) in its manufacturing lines.
New sensor development
Since commercial probes introduce a number of engineering problems, chief among them proximity effects and lift-off measurement errors, a special purpose sensor was developed to overcome these difficulties. A newly constructed encircling coil on a carbide former was found to be insensitive to small random motions of the steel blade due to the relative uniform field within the cross section. In addition, side effect and lift-off measurement errors were virtually eliminated, therefore enabling high-speed, on-line testing. Based on the industrial requirement of monitoring the ambient temperature, a thermocouple was also embedded in the coil former with a protective sheath.
Generic dynamic eddy current testing system
The system interface developed by MPI is completely automated. It is comprised of two eddy current sensors with integrated thermocouples. The thermocouples are directly connected to a standard data acquisition board that is connected to the PC via a serial interface. For the custom-built sensors, shielded cables are utilized to connect to impedance analyzers that in turn are connected to the PC via a fast GPIB interface. Within the PC an appropriate Graphical User Interface (GUI) will allow the operator to determine the impedance calibrated retained austenite value in conjunction with the coil temperature. In addition to the on-line display of the RA and temperature, a software algorithm stores the recorded information for further off-line data processing and statistical analysis.
Last modified: September 21, 2007 10:14:49