Tempered Glass Edge Strength via Rounded Corners
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Solution Overview
Problem
Tempered glass sheets with sharp edges exhibit a shallower compressive layer depth and higher local tension at corners, leading to a lower breaking strength at the edges compared to the surfaces, making them vulnerable to damage and crack propagation.
Innovation Solution
Rounding the edge-to-surface and inner-edge corners of the glass sheet before tempering to achieve a surface compression of at least 78% of the compression at the center, ensuring a more uniform distribution of compressive and tensile stresses, thereby increasing the breaking strength of the edges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the glass sheet is tempered with sharp edges, then the tempering process can be completed efficiently, but the edge breaking strength becomes significantly lower than the surface breaking strength
Solution Approach 1:
The glass sheet edges are rounded before the tempering process is applied. This preliminary geometric modification ensures that when compression is applied during tempering, the stress distributes more uniformly across the edge geometry, preventing the formation of high-stress concentration zones that would otherwise occur at sharp corners and lead to edge failure.
Solution Approach 2:
The sharp edges of the glass sheet are replaced with rounded edges having a specific radius of curvature. This curvature modification eliminates the geometric discontinuity at the edges, allowing compressive stresses to distribute more evenly throughout the edge region during tempering, thereby significantly improving edge breaking strength while maintaining manufacturing efficiency.
2Ease of manufacture
If the corners are left sharp, then the manufacturing process is simpler, but the local tension at corners increases and compressive layer depth decreases
Solution Approach 1:
Corners are rounded before tempering to prevent the formation of high-tension zones. This preliminary geometric adjustment ensures that when compression is applied during tempering, it distributes uniformly across the corner regions, eliminating the shallow compressive layer and high local tension that would otherwise occur at sharp corners.
Solution Approach 2:
Sharp corners are replaced with rounded corners having a controlled radius. This curvature eliminates the geometric stress concentrators that cause high local tension and shallow compressive layer depth, thereby improving reliability and resistance to crack formation without significantly complicating the manufacturing process.
3Strength
If edge protection is applied, then edge breaking strength increases, but the edge cannot be exposed for application requirements
Solution Approach 1:
Instead of applying protective coatings or treatments to the edges after manufacturing, the edges are rounded before tempering. This preliminary geometric modification inherently strengthens the edges through improved stress distribution, eliminating the need for additional protective measures and allowing the edges to remain exposed for various applications.
Solution Approach 2:
The geometric parameter of the edge (sharp vs. rounded) is changed to improve strength characteristics. By modifying the edge radius parameter before tempering, the stress distribution pattern changes fundamentally, allowing the edge to achieve high breaking strength in its exposed state without requiring additional protective treatments.
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
The rounded corners result in a more uniform distribution of compressive and tensile stresses, significantly enhancing the breaking strength of the edges to match that of the surfaces, reducing the likelihood of cracks forming and propagating, and improving the overall durability of the tempered glass sheet.
Implementation Method 1
ion-exchange, or chemical, tempering
Implementation Method 2
result in a more uniform distribution of compressive and tensile stresses
Data Source
AI summary
A tempered glass sheet article includes a glass sheet having a thickness t, at least one edge, and at least one surface. The at least one edge is connected to the at least one surface by an edge-to-surface corner. The edge-to-surface corner is rounded with a radius r and has a surface compression that is at least 78% of a surface compression measured at or near a center of the at least one surface.