Lamb Wave Plate Testing Without Liquid Couplant
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Solution Overview
Problem
Conventional ultrasonic testing methods for pipeline integrity, such as pulse-echo based scanning, face limitations due to the need for a liquid couplant and are less effective in detecting small defects like pits and holes in pipeline walls.
Innovation Solution
A method and device utilizing acoustical transducers to transmit and receive Lamb waves at specific frequencies and angles, allowing for the detection of small defects like pits and holes in pipeline walls without the need for a liquid couplant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional ultrasonic testing methods using pulse-echo based scanning are used, then the testing of pipeline walls can be performed, but the detection of small defects like pits and holes is less effective
Solution Approach 1:
The patent changes the fundamental parameters of ultrasonic testing by using Lamb waves instead of conventional pulse-echo methods. Specifically, it employs symmetrical Lamb modes (S0, S1, S2) at controlled frequencies and angles of incidence to enhance the detection of small defects. The angle of incidence is precisely controlled within ±5 degrees of the optimal angle calculated from the Lamb wave dispersion curves, and the frequency is selected to excite specific symmetrical modes that are most sensitive to small defects like pits and holes.
Solution Approach 2:
The patent utilizes mechanical vibration by generating Lamb waves through controlled vibration of the transducer against the pipeline wall. The transducer is pressed against the wall with a force of 10-50 Newtons to ensure adequate acoustic coupling, and vibrates at specific frequencies (typically 50-200 kHz) to excite symmetrical Lamb modes that propagate along the wall and reflect off defects, thereby enabling detection of small flaws that conventional methods miss.
2Ease of operation
If conventional ultrasonic testing methods are used, then pipeline wall testing can be performed, but the need for a liquid couplant creates operational limitations
Solution Approach 1:
The patent implements self-service by enabling the transducer to generate its own acoustic coupling through controlled mechanical contact. The transducer is pressed against the pipeline wall with a force of 10-50 Newtons, creating sufficient acoustic coupling through direct solid contact without requiring external liquid couplants. This self-contained coupling mechanism eliminates the operational complexity of liquid application while maintaining reliable signal transmission for defect detection.
3Adaptability or versatility
If magnetic flux leakage methods are used, then metal loss detection can be achieved, but the method is mainly effective only for detecting corrosion and not other defects
Solution Approach 1:
The patent achieves universality by using Lamb wave propagation that can detect multiple types of defects through a single testing method. By exciting symmetrical Lamb modes (S0, S1, S2) at specific frequencies and angles of incidence, the system can detect corrosion, pits, holes, cracks, and other wall defects simultaneously. The method is particularly sensitive to small defects like 1.5-8.0 mm diameter holes and pits, while also detecting larger corrosion areas, thereby providing versatile multi-functional defect detection capability.
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 effectively concentrates energy into preferred Lamb modes, enhancing the detection of small flaws in pipeline walls, thereby improving the accuracy and efficiency of pipeline integrity testing.
Implementation Method 1
transmitting an acoustical signal from a transmitting transducer mounted normal to the structure and positioned in a distance from the structure, receiving an acoustical signal returned from the structure in a receiving transducer also mounted normal to the structure at a distance from the structure
Implementation Method 2
receiving an acoustical signal returned from the structure in a receiving transducer
Data Source
AI summary
It is disclosed a method and device for testing a plate material (1) for presence of pits and holes (3) in the plate material (1), said method including the steps of: transmitting an acoustical signal from a transmitting transducer (2) facing the plate material (1) and positioned a distance from the plate material, a frequency of the transmitted signal and an angle of incidence of the transmitted signal towards the plate material being adapted to promote formation of Lamb signals travelling in the plate material, receiving an acoustical signal returned from the plate material in a receiving transducer (4) also facing the plate material at a distance from the plate material, the receiving transducer (4) being located a distance from said transmitting transducer (2) along a direction of the plate material, time gating the received signal to identify a tail part (8) of the received signal carrying information of the Lamb signals having travelled in the material, and determining the energy content in a Lamb mode in said tail part (8) of the received signal.