Angled Laser Bond Inspection with Compact Surface Motion Sensor
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Solution Overview
Problem
Conventional nondestructive evaluation techniques fail to adequately identify weak or 'kissing' bonds in composite structures, which can lead to structural failures, especially in aircraft construction where material defects and improper adhesive application are common.
Innovation Solution
A laser bond inspection system using a compact surface motion sensor and angled inspection head with a low-high-low pulse energy sequence is employed to non-destructively test bonded articles with angled or compact structures, utilizing off-axis EMAT sensors or optical interferometers to detect surface motion and evaluate bond strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional NDE techniques are used to inspect bonded materials, then the inspection process is simple and non-invasive, but weak bonds or kissing bonds cannot be adequately identified
Solution Approach 1:
The system uses periodic laser pulsing with specific timing sequences (e.g., 10 ns intervals) to generate stress waves at controlled intervals, allowing multiple measurements to be taken at different stress wave phases to detect weak bonds that static methods miss
Solution Approach 2:
The laser-generated stress waves create mechanical vibrations in the bonded structure, and the system detects these vibrations using interferometric sensors to identify bond deficiencies that conventional static NDE methods cannot detect
2Measurement precision
If laser energy is deposited at high intensity to generate stress waves, then bond defects can be detected, but surface damage may occur
Solution Approach 1:
Multiple low-energy laser pulses are delivered in periodic sequences rather than a single high-energy pulse, accumulating sufficient stress wave energy to detect bonds while keeping individual pulse energies below the surface damage threshold
Solution Approach 2:
The system uses multiple partial laser pulses that individually deliver sub-threshold energy, but collectively generate sufficient stress waves for bond detection without causing surface damage from any single pulse
3Adaptability or versatility
If standard inspection heads are used for laser bond inspection, then the system works for flat surfaces, but it cannot access angled structures or confined spaces
Solution Approach 1:
The inspection head is rotated to operate at angles up to 50 degrees relative to the surface normal, allowing access to angled structures and confined spaces that are inaccessible to conventional perpendicular inspection configurations
Solution Approach 2:
The inspection head incorporates movable or adjustable components that allow dynamic repositioning and angling to adapt to different geometric configurations of bonded structures, enabling inspection of diverse geometries with a single system
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 method effectively assesses the integrity of bonds in confined and angled composite structures without damaging them, allowing for the identification of weak bonds and improving the reliability of bonded materials in structural applications.
Implementation Method 1
LBI is a method that involves sending a precisely controlled dynamic stress wave through an adhesive bond of a composite structure. Generally speaking, and with reference to FIG. 1, LBI 100 involves the deposition of laser energy 102 at a first surface 106 of a bonded material 104, generating a compressive stress wave 108.
Implementation Method 2
Laser pulse 102 passes through transparent overlay 110 and is absorbed by opaque overlay 112. A plasma is created and as the plasma blows off, compressive stress wave 108 is induced into surface 106.
Implementation Method 3
U.S. Pat. Nos. 7,770,454 and 8,156,811 (LSP Technologies, Inc.), both of which are incorporated herein by reference in their entireties, teach LBI systems using VISAR probes, electromagnetic acoustic transducer (EMAT) coils, capacitance probes, and piezoelectric ultrasonic transducers (UT) as sensors.
Implementation Method 4
U.S. Pat. Nos. 7,770,454 and 8,156,811 (LSP Technologies, Inc.), both of which are incorporated herein by reference in their entireties, teach LBI systems using VISAR probes, electromagnetic acoustic transducer (EMAT) coils, capacitance probes, and piezoelectric ultrasonic transducers (UT) as sensors.
Implementation Method 5
Compressive stress wave 108 propagates through bonded material 104, through a bond of interest 114, to a second surface 116 of bonded material 104, where stress wave 108 is reflected as a tensile wave (not shown). The tensile wave propagates back through bonded material 104 and, when it reaches bond 114, stresses bond 114.
Data Source
AI summary
Methods, systems, and apparatuses are disclosed for laser bond inspection of an angled or compact bonded article.