Measurement Device for Crack Depth in Thick Structures
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Solution Overview
Problem
Existing methods struggle to accurately detect the depth of fatigue cracks in structures like bridges due to limitations in measuring elastic waves, particularly in determining the source depth within thick solid materials.
Innovation Solution
A measurement device comprising an ultrasonic sensor and an AE sensor, along with a signal processing unit, detects surface waves generated by elastic waves propagating through the structure, utilizing the arrival time difference and amplitude to calculate the depth of the source, employing principles of P-R conversion and Rayleigh waves to enhance detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional elastic wave detection methods are used, then detection coverage is achieved, but measurement precision of crack depth is insufficient
Solution Approach 1:
The patent segments the detection process into two distinct parts: detecting body waves (P-waves) to determine arrival time, and detecting surface waves (Rayleigh waves) to determine crack depth. This segmentation allows each wave type to be analyzed for its specific characteristics, with body waves providing timing information and surface waves providing depth information, thereby resolving the contradiction between measurement precision and reliability.
Solution Approach 2:
The patent introduces surface waves as an intermediary element that mediates between the body waves and the crack depth measurement. The surface waves are generated by the conversion of body waves at the structure surface, and their detection provides indirect but precise information about crack depth, improving measurement precision while maintaining detection reliability.
2Loss of information
If only body waves are detected, then arrival time measurement is simple, but depth information cannot be obtained
Solution Approach 1:
The patent makes the detection device multi-functional by enabling it to detect both body waves and surface waves using the same sensor system. The ultrasonic sensor can identify P-waves for arrival time measurement and Rayleigh waves for depth calculation, eliminating information loss about crack depth without requiring separate specialized devices, thus maintaining simplicity while gaining comprehensive measurement capability.
Solution Approach 2:
The patent transitions from one-dimensional body wave detection (providing only arrival time) to two-dimensional detection by incorporating surface wave detection (providing both arrival time and depth information). This dimensional expansion allows the system to extract depth information from the surface wave component generated by body wave conversion, recovering lost depth information without proportionally increasing device complexity.
3Measurement precision
If surface waves are selectively detected, then depth measurement accuracy improves, but detection system complexity increases
Solution Approach 1:
The patent implements feedback mechanisms in the signal processing unit that automatically identify and separate body wave and surface wave signals based on their characteristic properties. The system uses the arrival time of P-waves as feedback to trigger surface wave detection, and employs amplitude ratio feedback to distinguish Rayleigh waves from other signals, thereby improving depth measurement accuracy while automating the complex signal processing to minimize operational complexity.
Solution Approach 2:
The patent utilizes parameter changes in wave characteristics (arrival time, amplitude, wave velocity) to simplify the detection process. By monitoring changes in these parameters, the system can automatically differentiate between body waves and surface waves, extract depth information from Rayleigh wave amplitude, and calculate crack depth without requiring complex manual analysis, thus improving measurement precision while keeping the system relatively simple.
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 solution enables precise determination of crack depth within thick structures, improving detection accuracy and overcoming limitations of conventional methods by selectively detecting surface waves and body waves, facilitating early detection of structural deterioration.
Implementation Method 1
The first detector selectively detects surface waves that are excited when first elastic waves generated inside a structure formed of a solid material have reached a surface of the structure
Implementation Method 2
The information processing device obtains information about the depth of a source of the first elastic waves within the structure on the basis of information of at least one of an amplitude and a time of arrival of the surface waves detected by the first detector
Data Source
AI summary
A measurement device and a measurement method capable of measuring a depth of a damage source in a structure having a thickness of a predetermined value or more. According to an embodiment, a measurement device includes a first detector and a signal processing device. The first detector selectively detects surface waves that are excited when first elastic waves generated inside a structure formed of a solid material have reached a surface of the structure. The information processing device obtains information about a depth of a source of the first elastic waves within the structure on the basis of information of at least one of an amplitude and a time of arrival of the surface waves detected by the first detector.