Phased Array Probe Flexible Delay Line Spot Weld Testing
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Solution Overview
Problem
Conventional ultrasonic systems for non-destructive testing of spot-welds face challenges in reliably determining the minimal nugget diameter and reproducibly identifying defects like stick-welds due to limited coupling and non-reproducible inspection results, especially with hard rexolite delay lines, which hinder accurate measurement of the 2-dimensional area of fusion.
Innovation Solution
A phased array probe system with a flexible delay line and advanced signal processing algorithms, such as the Total Focusing Method (TFM), is used to optimize probe positioning and alignment, enabling high-resolution determination of the minimal spot-weld nugget diameter and 2-dimensional area of fusion, while detecting defects like stick-welds, burned, and loose welds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional matrix phased array systems with hard rexolite delay line are used, then spot weld diameter can be imaged, but coupling to the area of interest is limited due to indent and non-flat coupling surface
Solution Approach 1:
The patent employs a flexible membrane as the coupling interface between the transducer array and the spot weld surface. This flexible membrane can conform to non-flat and indented surfaces, ensuring consistent acoustic coupling across the inspection area. The flexibility allows the membrane to adapt to surface irregularities while maintaining intimate contact, thereby enabling reliable ultrasonic signal transmission and reception without requiring a perfectly flat surface.
Solution Approach 2:
The flexible membrane acts as an intermediary layer between the rigid transducer array and the workpiece surface. It mediates the acoustic energy transfer by conforming to surface irregularities and maintaining consistent coupling, thus enabling the hard transducer array to effectively inspect non-flat surfaces without direct mechanical contact requirements.
2Reliability
If conventional single element probes are used, then flaws like stick-welds and burned spot-welds can be detected, but direct measurement of minimal nugget diameter cannot be achieved
Solution Approach 1:
The patent divides the single ultrasonic beam into multiple beams by using a phased array of transducer elements. Each element can be independently controlled to generate and receive ultrasonic signals at different angles and positions. This segmentation of the beam allows simultaneous detection of flaws and precise measurement of nugget diameter by analyzing reflections from multiple locations within the weld zone.
Solution Approach 2:
The phased array system transitions from single-point measurement to multi-point spatial mapping by controlling the phase and amplitude of each transducer element. This enables two-dimensional imaging of the weld cross-section, providing both qualitative flaw detection and quantitative diameter measurement through spatial distribution of reflected signals.
3Productivity
If interpolation algorithms are used to determine minimal valid nugget diameter, then C-scan imaging can be performed, but reconstruction resolution is insufficient (typically 0.2 mm)
Solution Approach 1:
The system uses feedback from the received ultrasonic signals to iteratively optimize the reconstruction of the weld geometry. By analyzing the amplitude and time-of-flight of reflected signals from multiple transducer elements, the system continuously refines its estimate of the nugget boundary, achieving sub-0.2mm resolution through signal processing feedback loops that enhance the raw measurement data.
Solution Approach 2:
The patent changes the processing parameters by using full matrix capture data and advanced reconstruction algorithms that utilize phase information and amplitude variations across all transducer elements. This parameter optimization in the signal processing domain enables resolution beyond the physical limits of the transducer array spacing, achieving super-resolution measurements.
4Stability of the object's composition
If hard rexolite delay line is used, then phased array probe structure is maintained, but reproducible coupling leads to non-reproducible inspection results
Solution Approach 1:
The flexible membrane provides a compliant coupling interface that absorbs variations in surface topology and probe positioning. While the rigid transducer array maintains structural stability, the flexible membrane ensures consistent acoustic coupling by conforming to surface irregularities, thereby making inspection results reproducible even when probe placement varies slightly.
Solution Approach 2:
The flexible membrane acts as a cushioning layer that compensates for potential misalignments and surface irregularities before they affect the ultrasonic signal transmission. This pre-compensation ensures that variations in coupling conditions do not translate into variations in measurement results.
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 system achieves high-resolution and reproducible inspection results for spot-welds, reducing processing time and allowing for both manual and automated inspection, providing accurate pass/fail criteria and improved detection of weld defects.
Implementation Method 1
a phased array transducer - comprises a plurality of electrically and acoustically independent transducer elements that incorporate piezoelectric ceramics. During operation, electrical waveform pulses are applied to the electrodes of the phased array transducer elements of the probe causing a mechanical change in the condition of the piezoelectric ceramics and generating ultrasonic signals
Implementation Method 2
By varying the timing of the electrical waveform pulses applied to the phased array transducer elements, the phased array transducer can generate ultrasonic beams at different angles, allowing the phased array transducer to steer the ultrasonic beam at different angles through the test object
Implementation Method 3
When an ultrasonic beam reflected from the material under inspection contacts the surface of the piezoelectric ceramic of a phased array transducer element, it generates a voltage difference across the electrodes that is detected as a receive signal by signal processing electronics
Implementation Method 4
As the ultrasonic beams pass through the object, various pulse reflections called echoes occur as the ultrasonic beams interact with internal structures (e.g., anomalies) within the test object
Data Source
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AI summary
A phased array probe system and method for testing a spot- weld on a structure. The phased array probe includes a plurality of transducers and may include a flexible delay Sine. The phased array probe is positioned at a first position on the structure relative to the spot- weld. First ultrasonic signals are generated to and received from the spot-weld using at least one first transducer of the phased array probe. The first received ultrasonic signals are processed to determine a second optimized position on the structure relative to the spot-weld. Second ultrasonic signals are generated at the second optimized position to and received from the spot-weld using second transducers of the phased array probe. The second received ultrasonic signals are processed to determine a feature dimension of the spot-weld.