Acoustic Interface Device Shear Wave Attenuation
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Solution Overview
Problem
Ultrasonic techniques for non-destructive testing in harsh environments, such as underground or undersea hydrocarbon exploration, face challenges due to spurious echoes caused by mode conversion at buffer rod boundaries, which are exacerbated by the need for smaller, more compact designs suitable for downhole tools.
Innovation Solution
An acoustic interface device with a material composition having a shear wave attenuation coefficient of at least 5 dB/cm at frequencies between 200 to 500 kHz, formed from materials like polytetrafluoroethylene (Teflon), perfluoroalkoxy alkane (PFA), or polycarbonate (Lexan), is used to couple with transducers and specimens, reducing spurious echoes and accommodating smaller tool sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a buffer rod is used to protect the transducer from adverse conditions, then the transducer is protected from high temperature, pressure, and corrosion, but spurious echoes are generated due to mode conversion at the buffer rod boundaries
Solution Approach 1:
The patent removes the buffer rod component entirely and replaces it with an acoustic matching layer that performs the essential function of interface coupling without generating spurious echoes. This extraction eliminates the source of mode conversion problems while maintaining transducer protection through the matching layer design.
Solution Approach 2:
The patent changes the material parameters of the interface device by selecting materials with specific acoustic impedance values that match both the transducer and the specimen. This parameter optimization reduces reflections and mode conversions at boundaries, eliminating spurious echoes while maintaining reliable operation in harsh environments.
2Measurement precision
If the buffer rod is made large, tapered, or grooved to mitigate spurious echoes, then the accuracy of ultrasonic measurement is improved, but the device becomes too large for accommodation in a downhole tool
Solution Approach 1:
The patent extracts the problematic buffer rod structure and replaces it with a thin acoustic matching layer that achieves high measurement precision without requiring large dimensions, tapering, or grooving. This layer is sufficiently thin to fit within downhole tool constraints while maintaining measurement accuracy.
Solution Approach 2:
The patent employs composite material structures in the acoustic matching layer, combining materials with different acoustic properties to achieve optimal impedance matching. This composite approach enables high measurement precision in a compact form factor suitable for downhole applications.
3Volume of moving object
If a thin acoustic matching layer is used instead of a buffer rod, then the device size is reduced for downhole tool accommodation, but the ability to protect the transducer from adverse conditions may be compromised
Solution Approach 1:
The patent introduces an acoustic matching layer as an intermediary between the transducer and the harsh environment. This thin layer serves as a mediator that provides necessary acoustic impedance matching while the transducer remains protected within the downhole tool housing, eliminating the need for a thick buffer rod.
Solution Approach 2:
The patent replaces the mechanical protection approach (thick buffer rod) with an acoustic approach (thin matching layer with optimized impedance). This substitution allows the thin layer to perform both acoustic matching and environmental isolation functions, maintaining transducer protection while minimizing device size.
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
This solution enhances the accuracy and sensitivity of ultrasonic measurements by minimizing noise and spurious echoes, allowing for more reliable determination of acoustic properties and physical features in challenging environments, while fitting within the constraints of downhole tools.
Implementation Method 1
The acoustic interface device has a material composition having a shear wave attenuation coefficient αS of at least about 5 dB/cm when subjected to an acoustic signal at a frequency between about 200 to 500 kHz
Data Source
AI summary
A system is provided including an acoustic interface device, configured for coupling to a transducer and to a specimen, the acoustic interface device comprising a material composition having a shear wave attenuation coefficient αS of at least about 5 dB/cm when subjected to an acoustic signal at a frequency between about 200 to 500 kHz. The acoustic interface device may be formed of polytetrafluoroethylene (Teflon®), a perfluoroalkoxy alkane (PFA), polycarbonate (Lexan®), or polyether ether ketone (PEEK). Methods of using the acoustic interface device with a transducer for ultrasonic measurement of a specimen are also disclosed.