Laser Bond Testing Dissimilar Materials Acoustic Impedance
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Solution Overview
Problem
Current non-destructive testing methods for bond strength between dissimilar materials are inadequate, as they fail to generate sufficient tension waves to evaluate the strength of bonds between materials with different acoustic impedances, leading to costly and time-consuming physical testing.
Innovation Solution
A method involving directing laser energy at a first surface of a material with higher acoustic impedance, using a tailored pulse width and peak irradiance to generate mechanical waves that create rarefaction at the bond interface, allowing for non-destructive inspection of bond strength between dissimilar materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional non-destructive testing methods (ultrasonics, x-rays, acoustics) are used to detect inconsistencies in bond interfaces, then the presence of voids or disbond can be detected, but these methods cannot evaluate the actual strength of the bond between dissimilar materials
Solution Approach 1:
The patent replaces conventional mechanical or acoustic testing methods with a laser-based optical system. A laser generates stress waves in the first material that travel through the bond interface, and the reflected or transmitted waves are detected optically, eliminating the need for direct mechanical contact or acoustic coupling required by traditional methods
Solution Approach 2:
The patent changes the physical parameters of the testing approach by using laser energy to generate stress waves with specific characteristics (amplitude, frequency, duration) that are optimized for testing bonds between dissimilar materials with different acoustic impedances, rather than using conventional acoustic waves
2Measurement precision
If physical testing to failure is performed using witness coupons to verify bond strength, then accurate strength verification is achieved, but manufacturing time and cost increase significantly
Solution Approach 1:
The patent replaces destructive mechanical testing with a non-destructive laser-based stress wave method, allowing bond strength verification without physical failure of test specimens, thereby eliminating the time-consuming witness coupon process
Solution Approach 2:
The patent uses stress wave propagation and reflection patterns as a proxy or copy of the actual bond strength characteristics, allowing indirect measurement of bond strength without requiring physical failure or direct mechanical loading to failure
3Force
If laser energy is directed at the surface of the material with lower acoustic impedance to generate compression waves, then waves can be generated, but the reflected waves from the back surface do not create sufficient tension to evaluate bonds between dissimilar materials
Solution Approach 1:
The patent inverts the conventional approach by directing laser energy at the surface of the material with higher acoustic impedance rather than lower acoustic impedance. This reversal changes the wave generation and reflection characteristics, creating sufficient tension waves at the bond interface for reliable evaluation of dissimilar material bonds
Solution Approach 2:
The patent changes the material selection parameter for laser application, using the material with higher acoustic impedance as the laser entry point, which fundamentally alters the stress wave generation mechanism and enables sufficient tension wave creation at the bond interface
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 effective non-destructive testing of bond strength between dissimilar materials, reducing manufacturing time and costs by generating sufficient tension to evaluate bond integrity without damaging the composite material.
Implementation Method 1
depositing laser energy onto the front surface of a bonded article and generating compression stress waves
Implementation Method 2
generating compression stress waves that reflect off the back surface of the bonded article as tensile stress waves
Implementation Method 3
A first acoustic impedance of the first material is greater than a second acoustic impedance of the second material
Implementation Method 4
The tensile waves predominantly provide the stresses that test the bond between similar materials
Data Source
AI summary
A method and apparatus for testing a bond interface is provided. The method comprises directing laser energy at a first surface of a first material connected to a second material by an adhesive at a bond interface. The first surface is opposite the bond interface. A first acoustic impedance of the first material is greater than a second acoustic impedance of the second material. The method also determines whether an inconsistency is present in the bond interface after directing the laser energy.