Non-contact Thermo-elastic Imaging for Composite Damage Detection
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Solution Overview
Problem
Existing nondestructive evaluation techniques for detecting heat damage in composite materials are not sensitive to incipient damage and often require direct contact, which can cause additional damage and are limited to revealing gross damage only.
Innovation Solution
A non-contact thermo-elastic property measurement and imaging system that uses a sound source to emit pulses of increasing intensity and a thermal camera to generate images of temperature changes caused by acoustic wave interaction with the material, allowing for quantitative detection and imaging of defects without physical contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If direct contact methods (piezoelectric transducer or ultrasonic horn) are used to excite acoustic waves in the material, then sufficient acoustic wave energy can be launched into the material for NDE testing, but the contact excitation may cause additional damage to the specimen and complicate the vibration modes
Solution Approach 1:
The patent replaces the mechanical contact excitation system (piezoelectric transducer or ultrasonic horn) with an optical excitation system (pulsed laser). The laser beam delivers acoustic wave energy to the material surface without physical contact, eliminating mechanical damage while maintaining sufficient excitation energy for NDE testing.
Solution Approach 2:
The patent introduces light (laser beam) as an intermediary carrier to transfer energy to the material. The optical energy is converted to mechanical vibration through photoelastic or photothermal effects, serving as a non-contact intermediary that delivers acoustic excitation without direct mechanical contact.
2Reliability
If conventional NDE techniques (acoustic wave propagation or IR thermography) are used to detect heat damage, then gross damage can be identified, but incipient damage cannot be detected due to lack of sensitivity to early-stage changes
Solution Approach 1:
The patent changes the measurement parameter from thermal properties (IR thermography) or elastic wave propagation (acoustic NDE) to thermo-elastic temperature changes. By measuring the subtle temperature variations that occur during cyclic loading using high-resolution infrared thermography, the system can detect incipient damage before gross structural changes occur.
Solution Approach 2:
The patent applies periodic cyclic loading to the specimen and synchronizes the infrared camera measurements with the loading cycles. This periodic excitation amplifies the thermo-elastic signal from incipient damage, allowing detection through lock-in detection techniques that filter out background thermal noise.
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
Enables sensitive detection and imaging of heat damage in composite materials, including incipient damage, through non-contact acoustic excitation and thermal imaging, providing a more reliable and non-destructive evaluation method.
Implementation Method 1
The testing and evaluation of a material by the system is based on measuring and imaging heat generation and increase of temperature due to interaction of acoustic waves with the material
Implementation Method 2
A thermal camera is directed towards the structure and generating thermal images of the structure when the sound source emits the at least one pulse of the sound signal
Data Source
AI summary
A non-contact thermo-elastic property measurement and imaging system and method thereof are described. Acoustic energy is incident on a first surface of a specimen under test. The acoustic energy is converted partially into heat by the specimen, causing a slight increase in the temperature in a region of interaction. The temperature increase is imaged using a high sensitivity infrared camera. Presence of defects (surface and subsurface) in the material modifies the distribution of temperature. An image of temperature distribution can be used for nondestructive testing and evaluation of materials. The temperature change in the specimen caused by acoustic excitation is related to thermal and elastic properties of the material. A measurement of the change in the temperature as a function of the amplitude of incident excitation can be used for direct measurement of thermo-elastic property of the specimen.