Glass Surface Etching to Reduce Flaw Stress Concentration
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Solution Overview
Problem
Existing methods for improving the reliability of glass articles by reducing strength distribution variability are limited, as tempering processes like thermal quenching and ion exchange strengthening are ineffective for flaws extending beyond the depth of residual compressive stress, and coatings only maintain strength distribution without reducing variability.
Innovation Solution
A method involving selective chemical processing of glass articles to etch flaws, reducing the stress concentration factor at the flaw tips without completely removing the flaws, thereby increasing the uniaxial compressive strength to at least 90% of a flaw-free glass article's strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If thermal quenching or ion exchange strengthening is used to temper the glass article, then the surface compressive stress is improved, but the effectiveness is limited when flaws extend beyond the depth of residual compressive stress
Solution Approach 1:
The patent applies preliminary chemical etching to modify flaw geometry before the glass article is subjected to service loading. By etching flaws to reduce their stress concentration factors in advance, the glass article's strength distribution variability is reduced before tempering or during service, making subsequent tempering more effective at improving overall reliability.
Solution Approach 2:
The patent changes the physical-chemical parameters of surface flaws through controlled chemical etching. The etching process modifies flaw depth, width, and geometry, transforming high-stress-concentration sharp flaws into lower-stress-concentration blunted features, thereby improving strength distribution without requiring deeper compressive stress layers.
2Reliability
If coatings are applied to maintain strength distribution, then the strength distribution is preserved, but the variability is not reduced
Solution Approach 1:
The patent extracts harmful surface material containing deep flaws through controlled chemical etching. By removing a thin surface layer that contains the most severe flaw tips, the process eliminates the primary sources of strength distribution variability without requiring complex multi-layer coating systems.
3Strength
If flaws are completely removed by deep etching, then strength is improved, but excessive material is removed and manufacturing complexity increases
Solution Approach 1:
The patent applies partial etching action, removing only enough surface material to blunt flaw tips and reduce stress concentration factors, rather than completely removing all flaws. This partial action achieves sufficient strength improvement (≥90% of flaw-free strength) while minimizing material removal and maintaining manufacturing simplicity.
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 effectively mitigates mechanical failure and improves the reliability of glass articles by reducing the Weibull strength distribution variability, allowing for increased allowable loading without completely removing flaws, thus enhancing the glass articles' durability.
Implementation Method 1
The first surface of the glass body may be etched to a depth less than or equal to about 25% of the maximum initial flaw depth Ai of the flaw population present in the first surface
Data Source
AI summary
According to one embodiment, a glass article may include a glass body having a first surface and a second surface opposite the first surface. The first surface of the glass body may be etched to a depth less than or equal to about 25% of the maximum initial flaw depth Ai of a flaw population present in the first surface. The flaw population of the first surface is etched to selectively remove material adjacent to each flaw of the flaw population along the maximum initial flaw depth Ai. When the glass article is under uniaxial compressive loading, at least a portion of the first surface is in tension and a uniaxial compressive strength of the glass article is greater than or equal to 90% of a uniaxial compressive strength of a flaw-free glass article.