Coating Adhesion Testing Apparatus Without Adhesive Contamination
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Solution Overview
Problem
Current methods for testing the adhesion and cohesive strength of coatings, such as thermally sprayed coatings, are limited as they do not accurately differentiate between adhesive and cohesive failures, and can be contaminated by adhesives used in bonding fixtures, while also neglecting residual stresses that affect the coating's toughness and resistance to cracking.
Innovation Solution
An apparatus comprising a first member with an aperture, a second member that can be located within, temperature and strain gauges to measure thermal and residual stresses, and a device to apply a tensile load, allowing for the measurement of adhesive and cohesive strength without adhesive contamination, while analyzing the relationship between temperature, strain, and strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an adhesive is used to bond the fixture to the coating for testing, then the coating can be securely held during testing, but the adhesive may diffuse into the coating and contaminate the test results by increasing the coating strength
Solution Approach 1:
The invention extracts and removes the adhesive from the testing system entirely. Instead of using an adhesive to bond the fixture to the coating, the fixture is mechanically attached to the substrate without any adhesive layer, thereby eliminating the contamination source and allowing accurate measurement of coating adhesion strength.
Solution Approach 2:
The invention introduces the substrate as an intermediary element between the fixture and the coating. The fixture is bonded to the substrate (not directly to the coating), and the coating is deposited on the substrate surface. This intermediary arrangement allows mechanical bonding while preventing adhesive contamination of the coating.
2Ease of operation
If a weak coating is tested using adhesive bonding, then the test can proceed, but the coating may fail cohesively prior to fully testing the adhesive strength between the coating and substrate
Solution Approach 1:
The invention removes the adhesive layer that was causing the test to measure cohesive strength rather than adhesive strength. By eliminating the adhesive and directly bonding the fixture to the substrate, the test can now properly assess the adhesion strength of weak coatings without premature cohesive failure.
3Productivity
If current adhesive testing methods are used, then the test can be performed, but the residual stress generated in the coating during deposition is not taken into account
Solution Approach 1:
The invention merges the adhesion strength testing function with the residual stress measurement function into a single integrated apparatus. Strain gauges are incorporated into the fixture to simultaneously measure residual stresses in the coating during the same test that measures adhesion strength, eliminating the need for separate testing procedures.
4Ease of manufacture
If the coating is thermally sprayed, then the coating can be deposited, but residual stress is generated which affects toughness and resistance to cracking
Solution Approach 1:
The invention implements feedback by using strain gauges to measure residual stresses in the coating during deposition, and using this information to adjust deposition parameters. The system provides real-time data on coating stress states, allowing operators to modify spraying conditions to optimize both deposition efficiency and coating mechanical properties.
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 solution enables accurate assessment of both adhesive and cohesive strengths, allowing for the determination of the coating's toughness and resistance to cracking, and the optimization of deposition parameters to enhance the coating's strength, without relying on adhesives and accounting for residual stresses.
Implementation Method 1
a temperature sensor arranged to measure the temperature of the first member
Implementation Method 2
a first strain gauge to measure the strain in a first direction, a second strain gauge to measure the strain in a second direction perpendicular to the first direction
Implementation Method 3
a load sensor to measure the adhesive strength and/or cohesive strength of a coating deposited on the surfaces of the first and second members
Data Source
AI summary
An apparatus (10) to test the adhesion strength and/or cohesive strength of a coating (12) comprises a first member (14) having an aperture (16) and a second member (18) locatable in the aperture (16) in the first member (14). A temperature sensor (20) is arranged to measure the temperature of the first member (14). A third member (22) and a fourth member (24) are mounted on the first member (14). The third member (22) has a first strain gauge (26) to measure the strain in a first direction and the fourth member (24) has a second strain gauge (28) to measure the strain in a second direction perpendicular to the first direction. A device (30) is arranged to apply a tensile load to move the second member (18) from a first position where the second member (18) is located in the aperture (16) in the first member (14) and the surfaces (15, 19) of the first and second members (14, 18) are substantially flush to a second position where the surfaces (15, 19) of the first and second members (14, 18) are not flush and a load sensor (32) is arranged to measure the adhesive strength and/or cohesive strength of a coating (12) deposited on the surfaces (15, 19) of the first and second members (14, 18).