Pulsed Laser Layer Adhesion Quality Assessment
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Solution Overview
Problem
Existing methods for determining the quality of layers on substrates, such as the Rockwell hardness test, shearography, and thermography, are limited by their inability to perform non-destructive, large-area measurements of adhesion quality, often resulting in random and time-consuming local assessments that are not suitable for comprehensive quality control in series production.
Innovation Solution
A method utilizing a pulsed laser to scan the layer, where the laser parameters are optimized based on the layer's refractive index and thermal expansion coefficients, allowing for spatially resolved adhesion evaluation by detecting shear stresses and reflection changes across the layer's surface, enabling automatic and non-destructive assessment of adhesion quality over a large area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional mechanical test methods like Rockwell hardness test are used, then adhesion strength can be measured on individual components, but the method causes plastic deformation and material bulge that damages the layer
Solution Approach 1:
The patent replaces mechanical testing methods (Rockwell hardness test with conical diamond tip) with an optical measurement system using laser beams. The laser measures adhesion quality through optical properties (reflectivity, absorption) without physical contact, eliminating plastic deformation and material bulge that damage the layer.
Solution Approach 2:
The patent introduces an optical intermediary (laser beam) to measure adhesion strength indirectly through optical properties rather than direct mechanical contact. The laser interacts with the layer's optical characteristics to determine adhesion quality without applying mechanical stress that would damage the layer.
2Measurement precision
If random local measurements on individual components are performed, then adhesion quality can be assessed at selected points, but the method is time-consuming and only suitable for limited quality control
Solution Approach 1:
The patent implements continuous scanning measurement where the laser beam systematically scans across the entire layer surface without interruption. This continuous measurement approach covers large areas efficiently, replacing random point measurements with comprehensive systematic inspection, thereby improving productivity while maintaining measurement precision.
Solution Approach 2:
The patent transitions from one-dimensional point measurements to two-dimensional surface scanning. The laser beam scans across the entire layer surface, providing spatially resolved adhesion quality data over large areas, effectively adding the dimension of comprehensive surface coverage to the measurement process.
3Measurement precision
If shearography is used to detect near-surface deformations, then interferometric measurement can be performed, but insufficient energy coupling prevents detection in the boundary layer area between carbon layer and substrate
Solution Approach 1:
The patent changes the energy parameters of the measurement beam by using laser radiation with specific wavelengths and intensities optimized for deep penetration into the layer structure. This allows sufficient energy coupling into the boundary layer area between the carbon layer and substrate, enabling detection of adhesion quality at the interface rather than only near-surface deformations.
4Temperature
If thermography with amplitude-modulated light beam is applied, then thermal wave heating can be generated, but measurement results are not clearly correlated with adhesion fluctuations
Solution Approach 1:
The patent replaces thermal wave-based thermography with direct optical measurement using laser beams. Instead of using amplitude-modulated light to generate thermal waves and measure temperature changes, the laser directly measures optical properties (reflectivity, absorption) that are clearly correlated with adhesion quality, providing more precise and directly interpretable results.
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 allows for comprehensive, non-destructive evaluation of adhesion quality across a large area, reducing the risk of damage and enabling efficient quality control in series production by detecting adhesion differences through cyclic heating and cooling of the layer interface, providing a more reliable assessment of layer adhesion compared to traditional methods.
Implementation Method 1
the laser beam pulsed in this way causes a cyclic heating and at least partial cooling of this layer segment
Implementation Method 2
a temperature increase is briefly generated over a pulse length in the interface layer between substrate 3 and layer 4, which leads to thermal expansion of substrate 3 and layer 4. Due to the different thermal linear expansion coefficients of substrate 3 and layer 4
Implementation Method 3
the intensity profile, possibly also the phase and polarization of the beam of rays 6 reflected by the layer 4 is indicated
Implementation Method 4
the layer 4 applied to the substrate 3 is at least partially optically transparent to the incident electromagnetic radiation 1 of the laser in order to ensure that the electromagnetic radiation has a penetration depth into the layer 4
Data Source
Figure 1
Figure 2~3
AI summary
The invention relates to a method for determining the quality of layers (4) deposited on substrates (3), in particular of layers (4) deposited on substrates (3) for wear protection, corrosion protection, decoration, photovoltaics, and/or paints and laminates, wherein pulsed light is generated, by means of which the surface of the layer to be examined (4) is scanned in a spatially resolved manner, and a beam (6) reflected by the layer (4) is detected and evaluated in respect of intensity and/or phase and/or polarisation, the laser light being pulsed such that a particular layer section (10) that has been irradiated therewith is heated in a cyclically alternating manner and is cooled at least partially. To this end, the pulse duration of the laser light is selected such that temperature increases at least temporarily in the layer (4) as far as the boundary layer between the layer (4) and the substrate (3) arranged therebelow. The pulse spacing is adjusted such that the layer in the irradiated layer section (10) can cool. The emission wave length of the laser light is selected such that the layer behaves at least partially optically transparently for the incident laser light.