Glazing Quench Mark Sensitivity Evaluation for Coated Glass
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Solution Overview
Problem
Existing methods for thermally toughening glass do not guarantee uniform cooling, leading to nonuniform stress distribution and visible quench marks or 'strain patterns' on the glass, which can be complicated by coatings such as low-E layers.
Innovation Solution
A method to evaluate the sensitivity of glass to forming quench marks by computing a parameter σv, which measures the color difference between regions with and without optical phase shifts, allowing for simulation and prediction of how coatings affect quench marks before production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If air jets are used for cooling during thermal toughening, then the glass can be rapidly cooled to generate stress field, but uniform cooling cannot be guaranteed leading to quench marks
Solution Approach 1:
The glass surface is divided into multiple zones with different cooling requirements. The method segments the cooling process by applying different cooling intensities to different regions (edges vs center, or different quadrants) to achieve uniform overall cooling and prevent quench marks while maintaining the necessary stress field generation.
2Adaptability or versatility
If coatings such as low-E layers are applied to glass, then functional properties are improved, but quench marks become more complex and difficult to control
Solution Approach 1:
The patent applies preliminary actions by pre-heating or pre-cooling specific regions of the glass before the main thermal toughening process. This preliminary treatment prepares the glass to accommodate coatings without excessive quench marks, allowing functional coatings to be applied while maintaining aesthetic quality.
3Strength
If strong air jets are used to cool thick glass, then stress field generation is effective, but quench marks increase due to nonuniform cooling
Solution Approach 1:
The cooling process is customized for local regions of the glass. Different cooling intensities are applied to different areas based on their thickness, position, and thermal properties. This local quality approach ensures that each region receives appropriate cooling to generate necessary stress fields while minimizing quench marks in each specific area.
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 the prediction and evaluation of how coatings influence quench marks, allowing for the selection of coatings that either conceal or emphasize these marks, thereby improving the uniformity and appearance of thermally toughened glass.
Implementation Method 1
heating above 600° C. followed by rapid cooling with air jets. To this end, the glass is heated in a furnace, in particular a radiative or convective furnace
Implementation Method 2
cooled using a cooling device generally comprising quench chambers that administer, to the glass, a plurality of air jets
Implementation Method 3
This stress field is due to the differential in cooling rate between the surfaces of the main faces of the glass and its core, as the glass sets
Implementation Method 4
because of the photo-elastic properties of the glass, this may result, under polarized light, in the appearance of iridescence
Data Source
AI summary
A method for evaluating the sensitivity of a glazing to forming quench marks depending on its anisotropy, the sensitivity being evaluated by computing parameter σv, the quench marks resulting from different optical phase shifts in different regions of the glazing for a vision in transmission or reflection and from either side of the glazing, the method including computing a transmission parameter T1, T2 through face 1 or 2 or a reflection parameter R1, R2 from face 1 or 2, this computation being done for a region of the glazing without optical phase shift and for a region of the glazing inducing an optical phase shift δ; computing a parameter ΔE(δ) corresponding to the color difference between said regions, based on at least one of T1, T2, R1, R2, and computing σv by applying a function G dependent on computed ΔE(δ) and where appropriate on the one or more corresponding δ.