Acoustic Emission Sensor for Structural Failure Detection
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Solution Overview
Problem
Current methods for predicting roof falls in underground mines and structural failures in bridges are unreliable due to variations in bolt materials and stress-strain relationships, leading to inadequate detection of impending failures and resulting in accidents and costly damages.
Innovation Solution
A self-managed sensing and alarm system using acoustic emission sensors placed on strategic infrastructure components, such as roof bolts and bridges, which detect critical changes in acoustic waves to trigger alarms before structural collapse, utilizing piezoelectric film sensors and electronic circuits to process signals and determine alarm thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If stress-strain measurement methods are used to predict bolt breakage, then bolt failure can be detected, but the prediction is unreliable due to material variations and stress history effects
Solution Approach 1:
The patent replaces mechanical stress-strain measurement systems with acoustic emission sensing. Instead of measuring mechanical parameters that are affected by material variations and stress history, the system uses acoustic sensors to detect elastic waves generated by micro-fractures and material degradation, providing a more reliable indication of impending failure that is independent of bolt-specific mechanical properties
Solution Approach 2:
The patent introduces acoustic waves as an intermediary parameter to detect structural integrity. Rather than directly measuring stress-strain which varies with material properties, the system uses acoustic emissions as a mediator that consistently indicate material degradation and impending failure across different bolts and loading histories
2Reliability
If traditional acoustic emission sensors are used, then structural weakening can be detected, but the system cost is high
Solution Approach 1:
The patent employs low-cost piezoelectric film sensors that can be manufactured economically and replaced if necessary. These thin-film sensors provide the required acoustic emission detection capability at a fraction of the cost of traditional acoustic sensors, making the system economically viable for widespread deployment
Solution Approach 2:
The patent changes the sensor technology parameter from traditional acoustic emission sensors to piezoelectric film sensors. This parameter change maintains the ability to detect acoustic waves and structural weakening while dramatically reducing system cost through the use of inexpensive piezoelectric materials and thin-film fabrication techniques
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 system effectively identifies weakening infrastructure before collapse, reducing the risk of accidents and damages by providing timely proactive alerts through visible, sonic, or communication-based warnings, offering a cost-effective solution compared to traditional sensor technologies.
Implementation Method 1
The sensor device (135) responds to acoustic emission, or AE pressure waves from the target metallic material, anchorage resin or overburden
Implementation Method 2
utilizing piezoelectric film sensors and electronic circuits to process signals
Data Source
AI summary
A detection and alarm system comprises a piezoelectric film sensor and associated circuitry. The sensor detects acoustic emission signals from metallic objects under stress upon which it is affixed. The associated circuitry receives electronic signals from the sensor, creates and evaluates a sensor output value including rate ratio and frequency content of such signals within preset time limits. This data allows the detection of impending failure, an alarm condition, of the metallic object by identifying significant changes in the rate of emission of such sensor signals. An alarm condition may then trigger an alarm signal to warn of such impending failure.