Photothermal Material Testing for Precise Near-Surface Property Measurement
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Solution Overview
Problem
Existing methods for determining material properties in near-surface regions of test specimens are limited in their reliability and precision, particularly for applications like automotive paint layer thickness and quality assurance, and do not effectively handle structural changes due to processes like carburization or nitriding.
Innovation Solution
A device and method utilizing an evaluation device to compare reference and measurement signals, combined with frequency and intensity modulation of electromagnetic radiation, and a matrix-shaped sensor array, allows for precise determination of material properties by analyzing thermal radiation emitted from the surface region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional photothermal methods are used to determine material properties, then the measurement can be performed non-destructively, but the reliability and precision are insufficient for near-surface regions
Solution Approach 1:
The patent applies periodic modulation of the excitation radiation intensity at a defined modulation frequency to heat the surface region. This periodic heating creates a time-dependent thermal field that generates characteristic thermal radiation signals. By analyzing the phase shift and amplitude of these periodic thermal signals relative to the excitation signal, the evaluation device can precisely determine material properties in near-surface regions, resolving the contradiction between reliability and measurement precision.
Solution Approach 2:
The patent changes the parameter of excitation radiation by modulating its intensity at a defined frequency. This parameter change creates a dynamic thermal excitation that produces measurable thermal radiation responses. The evaluation device analyzes these responses to determine material properties with high precision, transforming a static measurement problem into a dynamic one that can be solved with greater reliability.
2Measurement precision
If electromagnetic radiation is used to heat and detect thermal radiation, then non-destructive testing is achieved, but the determination of specific material properties like layer thickness and roughness lacks sufficient precision
Solution Approach 1:
The patent implements feedback by comparing the detected thermal radiation signal with a reference signal in the evaluation device. The evaluation device processes the thermal radiation signal to extract information about material properties such as layer thickness and roughness. This feedback mechanism allows precise determination of material properties by analyzing the relationship between the excitation signal and the thermal response, achieving high measurement precision without excessive device complexity.
Solution Approach 2:
The patent replaces complex mechanical measurement systems with an optical-thermal measurement system. Instead of using mechanical contact methods to measure layer thickness and roughness, the system uses electromagnetic radiation for excitation and detection of thermal radiation. This substitution simplifies the device structure while achieving high measurement precision for material properties.
3Adaptability or versatility
If existing methods are used for quality assurance, then the process can be performed non-destructively, but the ability to detect structural changes from carburization or nitriding is insufficient
Solution Approach 1:
The patent creates a universal measurement system that can detect multiple material properties including layer thickness, surface roughness, and structural changes from heat treatment processes like carburization and nitriding. The evaluation device analyzes thermal radiation signals to determine various material properties simultaneously, making the system adaptable to different quality assurance requirements while maintaining high reliability through consistent non-destructive measurement principles.
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 reliable and non-destructive determination of material properties, including layer thickness, roughness, and defect detection, with high precision and flexibility for various test specimen shapes, suitable for quality assurance in the automotive industry.
Implementation Method 1
a radiation source for heating a surface region (4) of a test specimen (5) with electromagnetic radiation
Implementation Method 2
a detection device for detecting thermal radiation (9) emitted by the surface region (4)
Data Source
Figure 1
Figure 2
Figure 3a
AI summary
The invention relates to an apparatus (1; 1a; 1b; 1c) and a method for determining a material property of a test specimen (5; 5a; 5b; 5c) in a test specimen region (6; 6a; 6b; 6c) near the surface, said apparatus comprising at least one electromagnetic radiation source (2; 2a; 2b; 2c) for irradiating at least one surface region (4; 4a; 4b; 4c) of the test specimen, and a detection device (8; 8a; 8b; 8c) for detecting thermal radiation (9; 9a; 9b) emitted by the surface region and/or for detecting radiation (31) reflected from the surface region (4; 4a; 4b; 4c) of the test specimen. An evaluation device (13; 13a; 13b; 13c) for ascertaining the material property to be determined on the basis of the emitted thermal radiation (9; 9a; 9b) and/or the reflected radiation (31) is expediently provided. Advantageously, it is possible for the material property to be determined particularly reliably and nondestructively.