Phased Array Calibration for Anisotropic Rotor Blade Defect Detection
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Solution Overview
Problem
Existing phased array ultrasonic systems struggle to accurately detect defects in anisotropic rotor blades due to material anisotropy causing ghost echoes and poor signal-to-noise ratios, making it difficult to inspect narrow and convoluted cooling passages in turbine blades.
Innovation Solution
A phased array ultrasonic system that accounts for the anisotropic tilt angle by using geometric fiducial markers and adjusting the position of the probe or rotor blade to ensure accurate scanning, employing time delays and phase shifts to steer acoustic waves effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phased array ultrasonic scanning is performed on anisotropic rotor blades, then defect detection capability is improved, but material anisotropy causes ghost echoes and poor signal-to-noise ratio
Solution Approach 1:
The method performs preliminary calibration by scanning geometric fiducial markers embedded in the rotor blade before actual defect detection. This preliminary action establishes reference data about the anisotropic material's acoustic properties, including sound velocity variations and wave propagation characteristics. The calibration process creates a baseline that enables subsequent compensation for anisotropy effects during defect inspection, thereby reducing ghost echoes and improving signal-to-noise ratio.
Solution Approach 2:
The system dynamically adjusts ultrasonic scanning parameters based on the calibrated anisotropic characteristics of the specific rotor blade. This includes modifying sound velocity values, probe positioning, and scanning angles to account for the material's directional properties. By changing these parameters according to the measured anisotropy, the system compensates for ghost echoes and enhances defect detection accuracy.
2Area of stationary object
If conventional ultrasonic probes are used to inspect cooling passages, then inspection coverage is improved, but narrow and convoluted passages make reliable inspection difficult
Solution Approach 1:
The method replaces physical probe insertion into cooling passages with external phased array ultrasonic scanning. Instead of mechanically navigating probes through narrow and convoluted passages, the system uses phased array transducers positioned on the rotor blade exterior to generate ultrasonic waves that propagate through the blade material to detect defects in cooling passages. This substitution eliminates the mechanical accessibility problem while maintaining inspection coverage.
Solution Approach 2:
The inspection approach transitions from one-dimensional probe insertion to three-dimensional phased array scanning. By positioning the probe on the external surface and utilizing phased array technology to steer and focus ultrasonic beams in multiple directions, the system achieves comprehensive coverage of internal cooling passages without physical access to them. This dimensional change enables inspection of convoluted passages from the exterior.
3Device complexity
If single element immersion ultrasonic technique is used, then simplicity is improved, but signal to noise ratio becomes extremely poor for detecting small cracks
Solution Approach 1:
The ultrasonic transducer is divided into multiple independent elements within the phased array, replacing the single element approach. Each element can be individually controlled to transmit and receive ultrasonic waves. This segmentation enables beam steering, focusing, and synthetic aperture techniques that significantly improve signal-to-noise ratio for detecting small cracks while maintaining manageable system complexity through electronic control.
Solution Approach 2:
The phased array system combines the signals from multiple transducer elements through coherent summation and signal processing techniques. By merging the weak signals from individual elements constructively, the system achieves high signal-to-noise ratio for detecting small cracks. The calibration process further enhances this by combining reference data from fiducial markers with defect signals to improve detection precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method enables precise detection of defects such as cracks, corrosion, and voids in anisotropic rotor blades without ghost echoes, improving inspection accuracy and reliability.
Implementation Method 1
A phased array ultrasonic system scans a sector of an anisotropic rotor blade with a probe. The system transmits ultrasonic waves into the rotor blade and receives reflected echoes to detect defects such as cracks, corrosion, and voids.
Implementation Method 2
As the ultrasonic waves pass into the test object, various reflections, called echoes, occur as the ultrasonic waves interact with anomalies and other physical characteristics in the test object.
Implementation Method 3
By varying the timing of the electrical pulses applied to the ultrasonic transducers using delay criteria, a phased linear array ultrasonic probe can generate ultrasonic waves passing into the test object at different angles (e.g., from zero to one hundred eighty degrees).
Implementation Method 4
when the reflected ultrasonic waves are received by the piezoelectric surface of the ultrasonic transducers, it causes the transducers to vibrate which generates a voltage difference across the transducer electrodes that is detected as an electrical signal
Implementation Method 5
the present disclosure is directed to calibrating a phased array ultrasound system based on geometric fiducial markers within the anisotropic rotor blade
Data Source
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AI summary
The method includes positioning a probe of the phased array ultrasound system on the mounting portion of the anisotropic rotor blade at the axial centerline. The method further includes scanning a sector of the anisotropic rotor blade along the axial centerline with the probe of the phased array ultrasound system. The method further includes determining a magnitude and a time delay of an echo signal corresponding with a geometric fiducial marker. The method further includes adjusting a position of one of the anisotropic rotor blade or the probe based on the magnitude and/or the time delay of the echo signal corresponding with the geometric fiducial marker. The method further includes repeating the scanning, determining, and adjusting steps until the magnitude and the time delay of the echo signal corresponding with the geometric fiducial marker is within a predetermined maximum echo range. The method further includes scanning the anisotropic rotor blade for defects.