Crack Growth Detection via Digital Image Correlation
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Solution Overview
Problem
Current methods for detecting crack growth in test specimens are inaccurate due to limited X-ray image capture and manual measurement of cracks, leading to potential premature failure of materials in service.
Innovation Solution
A system and method that utilize a camera to acquire multiple photographic images of a test specimen under stress load, with an image processing program to detect pixel characteristics and calculate crack length and strain energy release rate, providing more accurate material characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If X-ray imaging equipment is used to detect cracks, then crack detection is possible, but the image capture rate is limited (one image per three seconds)
Solution Approach 1:
The patent replaces X-ray imaging equipment with a digital camera system that captures photographic images at much higher rates. The digital camera with image processing program substitutes the mechanical X-ray imaging system, enabling capture of multiple images during crack propagation while maintaining measurement capability through automated pixel analysis.
Solution Approach 2:
The patent changes the detection parameter from X-ray absorption imaging to optical reflection/imaging. By using a digital camera to capture reflected light from the specimen surface, the system achieves higher frame rates while the image processing program analyzes pixel characteristics to detect crack length, transforming the detection approach to overcome the capture rate limitation.
2Measurement precision
If manual measurement of cracks using a ruler is performed, then measurement is possible, but measurement accuracy is insufficient due to unclear crack boundaries in averaged frames
Solution Approach 1:
The patent replaces manual measurement with an automated image processing program that analyzes photographic images. The program detects pixel characteristics, identifies crack boundaries through image processing algorithms, and calculates crack length automatically, eliminating the need for manual ruler measurement and providing superior accuracy by clearly defining crack boundaries through digital analysis.
Solution Approach 2:
The patent creates a digital copy of the crack through photographic imaging and processes this copy using image analysis algorithms. The image processing program generates a digital representation of the crack from the photographic image, allowing precise measurement of crack length without physical contact or manual intervention, thereby achieving high measurement accuracy.
3Quantity of substance
If a limited number of X-ray images are obtained during crack propagation, then radiation exposure is reduced, but the data on crack formation and propagation is insufficient
Solution Approach 1:
The patent substitutes X-ray imaging with optical photography using a digital camera. This replacement eliminates radiation exposure entirely while capturing numerous images during crack propagation. The digital camera system records crack formation and propagation at high frame rates without the harmful radiation effects associated with X-ray imaging.
Data Source
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AI summary
A system and method for detecting crack propagation in a material test specimen may include color contrasting a surface of a test specimen, acquiring a plurality of photographic images of the specimen during application of a stress load, processing the plurality of images to detect characteristics of pixels that are outside a baseline range of pixel characteristics indicative of a contrast between a crack in the test specimen and the color contrasted surface of the test specimen, and generating an output of a strain energy release rate based on changes in detected crack length over time.