Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Mechanical measurement system
Reexamination Certificate
2003-09-08
2004-12-28
Hoff, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Mechanical measurement system
C703S014000
Reexamination Certificate
active
06836735
ABSTRACT:
BACKGROUND OF INVENTION
The invention relates generally to nondestructive methods for determining the integrity of components and structures. More particularly, the invention is a method and circuit used in a system for nondestructive test method qualification and probability of detection determination, for establishing and maintaining nondestructive testing proficiency of inspectors, for periodically presenting flaw signals to inspectors during routine inspections, and for ensuring sufficient scan coverage for detection of material defects in a test piece. The invention enables the injection of a virtual flaw signal into an NDT system that makes use of eddy current testing (ECT) to detect the presence of flaws in components and structures.
Nondestructive testing (NOT) is used in many industries to detect the presence of flaws so that the integrity of components and structures may be determined. NDT involves using various test methods, such as eddy current and ultrasonics. Applications include military and civilian aircraft, fossil and nuclear electrical power generation equipment, petrochemical plants, etc. There are several needs within the NDT environment that, if satisfied, would significantly reduce inspection costs and improve the reliability and quality of inspections.
NDT method qualification and probability of detection (POD) determination is one area of need. Demonstration of the capability and reliability of new NDT techniques must often be done in a short period of time and at minimal cost. The present approach is to perform a POD study. These studies involve producing many test specimens with realistic flaws, training multiple NDT technicians, and conducting blind tests. Fabrication of the flawed specimens is very expensive and time consuming. As a result, a POD study is usually performed only for the most critical applications. A system and method to reduce costs and time required to implement POD studies is needed.
NDT inspectors must be trained to ensure proficiency in new and existing NDT procedures. Training is also required periodically in order to maintain proficiency of the inspectors. Although specimens with realistic flaws are needed for training, they are often not available. Video-based training courses are available, but they do not provide “hands-on” experience with real flaws. Therefore, better training methods are another area of need.
Monitoring existing inspections when flaws are infrequent presents another area of need. In some routine inspections, flaws are encountered very infrequently, sometimes less than once per year. Inspectors may become conditioned to not expecting flaws, resulting in a loss of proficiency. A method is needed to periodically present simulated flaws to inspectors during routine inspections.
Ensuring that a thorough scan is conducted over an entire test piece in another area of need. Some inspections are performed by hand scanning, and the scanning coverage of the appropriate area is dependent on the skill and attention of the operator. A method is needed to monitor scan position so that proper coverage is obtained.
The purpose of the present invention is to enable virtual flaw signal injection into a NDT system that relies on eddy current testing (ECT) to inspect a test piece. This enables reliability testing and training to be performed without the need for actual flaws. The method and circuit disclosed herein is used with a simulator to inject virtual flaw signals into a probe input terminal of ECT instrumentation. The signal injection is performed without interfering with normal ECT instrument probe operation or with signals from the probe. The invention is able to inject virtual flaw signals while allowing the ECT instrumentation to be responsive to existing flaws and geometry features of a work piece, as well as variations in the probe's distance from or orientation to the work piece.
SUMMARY OF INVENTION
The present invention provides for a method and circuit that enables ECT instrumentation to satisfy the needs for reducing costs and time required to implement POD studies, providing improved realistic training methods, presenting simulated flaws to inspectors during routine inspections, and for monitoring scan position to ensure proper coverage of test pieces. This invention enables a simulation system to perform the functions of an NDT inspection simulator analogous to flight simulators used to train aircraft pilots. The operations of the NDT simulator using the present invention are transparent to the inspector using the system when realistic, virtual flaw signals are presented at preprogrammed locations on the actual test piece. The virtual flaw signals may be premeasured or generated from a model. This method of presenting virtual flaws provides the equivalent of real flaws to an inspector without the requirement for having actual flaws in a test piece. The inspector may use the same probes and instrumentation of a conventional ECT instrument that are normally used in the inspection process. The injection circuit comprising the present invention may be connected between the probe and ECT instrument so that flaw responses will be injected into the instrument, and the operator may view a response on the actual ECT instrument display. The probe and instrument may remain “live”, so that the interaction between the probe and the test piece remain active as well. The simulator may track the probe position so that responses from flaws can be injected at a selected location on the test piece.
The present invention enables POD tests to be accomplished without the need for manufacturing a large number of actually flawed test pieces. A training mode may be implemented in which the inspector receives instructions from the system and can practice with the equivalent of actual flawed test pieces. The system may be used with routine inspections to inject virtual flaw signals to keep inspectors alert, and may be used to monitor probe position in manual test scans to ensure proper coverage.
An embodiment of the present invention is a method for injecting virtual flaw signals into a nondestructive test system, comprising the steps for moving a test probe over a test piece by an inspector, providing an excitation signal from the nondestructive test system to the test probe and a virtual flaw injection circuit, determining virtual flaw parameter signals from test probe position signals and a stored virtual flaw map for the test piece, sending the virtual flaw parameter signals and an output signal from the test probe to the virtual flaw injection circuit, processing the excitation signal and the test probe output signal using the virtual flaw parameter signals for generating a virtual flaw response signal by the virtual flaw injection circuit, transmitting the virtual flaw response signal to a test probe input of the nondestructive test system, and displaying actual and virtual flaws to the inspector from the nondestructive test system. The step for determining virtual flaw parameter signals may further comprise the steps for reading test probe position signals for indicating test probe positions relative to a test piece, reading test probe liftoff measurement signals for indicating test probe liftoff from the test piece, reading a virtual flaw map for the test piece stored in a memory for determining uncorrected virtual flaw parameter signals based on the test probe position signals, and applying a liftoff correction based on the lest probe liftoff measurement signals to the uncorrected virtual flaw parameter signals for determining corrected virtual flaw parameter signals. The step for processing may further comprise the steps for modulating an amplitude of the excitation signal by the virtual flaw parameter signals, shifting a phase of the amplitude modulated excitation signal by the virtual flaw parameter signals, and summing the amplitude modulated and phase shifted excitation signal with the test probe output signal for generating a virtual flaw response signal by the virtual flaw injection circuit. The step for modula
Burkhardt Gary L.
Fisher Jay L.
Peterson Ronald H.
Hoff Marc S.
Raymond Edward
Southwest Research Institute
Taylor Russell & Russell, PC
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