Thermographic NDT Using Temperature-Limited Modulation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current thermographic non-destructive testing systems face challenges in detecting deeper subsurface features due to decreasing temperature differences and interference from noise and convection, which limits the detection of anomalies, especially in composite materials.
Innovation Solution
The method involves applying an intermittent sequence of excitation pulses to maintain a stable surface temperature, using thermal excitation devices and imaging devices to capture iso-time frames, and adjusting pulse duration, amplitude, or spacing to enhance the detection of subsurface discontinuities without significant temperature fluctuations, allowing for real-time inspection and reduced convection effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If continuous or modulated heating is applied to increase surface temperature, then the temperature difference for detection is improved, but convection effects increase and impede detection of subsurface features
Solution Approach 1:
The patent applies periodic heating pulses instead of continuous heating, creating a modulated thermal excitation that allows the surface temperature to oscillate within a controlled range. This periodic action maintains sufficient temperature differential for detection while limiting the average temperature rise that drives convection, thereby resolving the contradiction between detection sensitivity and convection interference.
2Measurement precision
If excitation energy is increased to increase temperature difference, then detection sensitivity is improved, but convection and energy loss increase
Solution Approach 1:
By using periodic heating pulses with optimized duty cycle and amplitude, the system achieves sufficient temperature differential for sensitive detection while limiting the total energy input. The intermittent nature of the heating allows thermal diffusion to dominate over convection, reducing energy loss while maintaining detection precision.
Solution Approach 2:
The patent optimizes multiple parameters including pulse duration, amplitude, frequency, and spacing to achieve the maximum temperature difference for detection while minimizing convection. By carefully adjusting these parameters, the system finds the optimal balance between detection sensitivity and energy efficiency.
3Length of stationary object
If transient pulse heating is used to detect deeper features, then detection depth is improved, but temperature difference decreases over time
Solution Approach 1:
The patent employs a sequence of repeated heating pulses rather than a single transient pulse. Each pulse rejuvenates the thermal signal, allowing continuous monitoring of temperature evolution at different depths. This continuous thermal excitation maintains sufficient temperature differential over extended measurement periods, enabling detection of deeper features that would otherwise be undetectable as the temperature difference diminishes.
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 approach increases the depth range and sensitivity to deeper defects, reduces reflection artifacts and convection interference, and provides quantitative measurements of depth and thermal properties without requiring a defect-free reference, enabling more accurate detection of subsurface features.
Implementation Method 1
Thermal energy uniformly deposited at the surface of the sample will diffuse into the volume of the sample
Implementation Method 2
the temperature of the surface is monitored using an infrared camera
Implementation Method 3
energy transfer by convection may become comparable or greater than thermal diffusion
Data Source
AI summary
A method for performing non-destructive testing using active thermography includes applying, using at least one thermal excitation device, a first excitation pulse to a workpiece; capturing, using an imaging device, a first iso-time frame of the workpiece; and determining a second excitation pulse by modifying one or more of a duration D of the first excitation pulse, an amplitude A of the first excitation pulse, or a spacing W between the first excitation pulse and the second excitation pulse. The method also includes applying, using the at least one of the thermal excitation device, the second excitation pulse to the workpiece; capturing, using the imaging device, a second iso-time frame of the workpiece; and determining a numerical fit of the first iso-time frame and the second iso-time frame.