Optical Seal Integrity Detection via Pressure Excitation
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Solution Overview
Problem
Current methods lack an automated and effective way to verify the integrity of seal features, such as caps and sealants, in aircraft composite fuel tanks, especially under changing air pressure conditions, which can compromise their protective function.
Innovation Solution
The use of optical metrology techniques like electrical shearography and speckle shearing interferometry, combined with a diode laser and shearing optics, to detect deformations in seal features when air pressure is altered, allowing for the determination of seal integrity by comparing pre- and post-excitation images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If visual inspection by human inspectors is used to verify seal feature integrity, then the inspection method is simple and requires no complex equipment, but the process is manual, time-consuming, and cannot effectively detect deformations under changing air pressure conditions
Solution Approach 1:
The patent replaces manual visual inspection with an automated optical metrology system using shearography. The mechanical/manual process of human inspectors visually examining seals is substituted with an optical system that uses laser illumination and digital image processing to automatically detect seal deformations, achieving automation while managing complexity through non-contact measurement
Solution Approach 2:
The patent creates optical copies (digital images) of the seal features under different pressure conditions. By capturing and comparing digital images of the seal at reference and excited pressure states, the system analyzes deformations through image processing rather than direct physical measurement, enabling automated integrity assessment
2Reliability
If no inspection method is used other than visual inspection, then the equipment required is minimal, but the ability to detect compromised seals, especially in operational situations, is severely limited
Solution Approach 1:
The patent replaces inadequate visual inspection with shearography, an optical non-contact measurement technique. The system uses laser light and shearing optics to detect microscopic deformations in seal features that are invisible to the human eye, dramatically improving detection reliability for both manufacturing and operational inspections
Solution Approach 2:
The patent applies pressure excitation (analogous to vibration in dynamic systems) to the seal features by changing air pressure within a chamber. This excitation causes deformations in compromised seals that can be detected by the optical system, enabling reliable differentiation between intact and damaged seals through their differential response to pressure changes
3Productivity
If manual visual inspection is used, then the equipment cost is low, but the time required for inspection is excessive and productivity is reduced
Solution Approach 1:
The patent enables continuous inspection by automating the measurement process. The optical system can rapidly capture multiple images under different pressure conditions and process them through algorithms, eliminating the sequential, discrete nature of manual inspection and enabling higher throughput with reduced assessment time
Solution Approach 2:
The patent uses digital image copying and comparison to rapidly assess seal integrity. By capturing digital images at different pressure states and using automated image processing algorithms to compare them, the system achieves rapid analysis without the time-consuming nature of manual visual examination
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 method automates the assessment of seal feature integrity, enabling the detection of compromised seals by identifying deformations caused by pressure changes, thereby ensuring the protective integrity of the seal features.
Implementation Method 1
electrical shearography or speckle shearing interferometry to determine whether a change in air pressure, such as a reduction in air pressure, causes a deformation of seal features
Implementation Method 2
electrical shearography or speckle shearing interferometry to determine whether a change in air pressure, such as a reduction in air pressure, causes a deformation of seal features
Implementation Method 3
shearing optics disposed within the chamber and adapted to convey light from the interior of the chamber to an imaging system
Implementation Method 4
a camera having shearing optics comprised of either birefringence materials or two 45 degree beam splitters
Data Source
AI summary
Optical metrology methods, apparatuses, and systems for detecting seal integrity. These comprise changing an air pressure inside a chamber to an excitation pressure level when the chamber is placed over a segment of a surface of a structure having one or more seal features and determining whether the integrity of any of the one or more seal features has been compromised by determining, using an optical system, whether any of the one or more seal features have been deformed by the changing of the air pressure.