Strengthened Glass Cladding via Low-Temperature Densification
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Solution Overview
Problem
Existing methods for strengthening glass articles, such as thermal tempering and chemical tempering, have limitations in achieving uniform compressive stress and are resource-intensive, particularly for thinner sheets and glass laminates, leading to challenges in machining and fracture risks.
Innovation Solution
A method involving low-temperature heat-treatment of glass-to-glass laminates below the annealing range to increase compressive stress by altering the density of the glass portion, allowing for controlled stress imparting and machining before stress elevation, using glasses with different thermal histories and compositions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If thermal tempering is used to strengthen glass, then compressive stress is achieved, but the process is difficult to apply to thinner sheets and requires high energy input
Solution Approach 1:
The patent changes the temperature parameter from conventional high-temperature tempering to low-temperature heat treatment (below annealing range), fundamentally altering the strengthening mechanism while reducing energy input requirements and enabling application to thinner glass sheets
Solution Approach 2:
The patent replaces the conventional thermal tempering mechanism with a density-altering heat treatment process that occurs below the annealing range, substituting a different physical mechanism to achieve compressive stress with lower energy consumption
2Strength
If chemical tempering is used to strengthen glass, then compressive stress is achieved, but the process is time-consuming and resource-intensive
Solution Approach 1:
The patent replaces chemical tempering (ion exchange in salt bath) with a thermal heat treatment process occurring below the annealing range, substituting a chemical mechanism with a thermal one that achieves compressive stress more efficiently with shorter process times
Solution Approach 2:
The patent changes the treatment temperature parameter to below the annealing range, which fundamentally alters the process kinetics and reduces the time required to achieve compressive stress compared to conventional chemical tempering
3Strength
If glass-to-glass laminate is used with different thermal expansion characteristics, then compressive stress is achieved, but the laminate becomes difficult to machine due to internal stresses
Solution Approach 1:
The patent applies heat treatment below the annealing range as a preliminary action to alter glass density and induce compressive stress in the cladding layer before machining operations, enabling easier manufacturing while maintaining structural integrity
Solution Approach 2:
The patent changes the thermal treatment parameter to below the annealing range, which alters the stress distribution and material properties to improve machinability while maintaining the compressive stress benefits of glass-to-glass laminates
4Reliability
If compressive stress is applied to cladding, then fracture resistance is improved, but the stress state during processing creates risk of catastrophic failure
Solution Approach 1:
The patent applies heat treatment below the annealing range as a preliminary action to induce compressive stress in the cladding layer before any machining or handling operations, establishing fracture resistance early while avoiding the creation of harmful stress states during processing
Solution Approach 2:
The patent changes the thermal treatment parameter to below the annealing range, which creates compressive stress in a controlled manner that improves fracture resistance without generating the harmful stress states that would lead to catastrophic failure during processing
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 controlled strengthening of glass articles with increased compressive stress in the cladding, facilitating easier processing and reducing fracture risks, while maintaining a lower stress state during manufacturing and machining.
Implementation Method 1
heating the glass to a temperature greater than 100° C. and below a softening temperature of the glass, whereby the compacted glass pulls the cladding into compression
Implementation Method 2
compacting the glass from a first density to a second density at least 10 mg/cm3 greater than the first density
Data Source
AI summary
A method of making a strengthened glass-based article includes compressing a cladding bonded to a glass at least in part by compacting the glass from a first density to a second density at least 10 mg/cm3 greater than the first density, where the compacting occurs when heating the glass to a temperature greater than 100° C. and below a softening temperature of the glass, whereby the compacted glass pulls the cladding into compression, thereby strengthening the glass-based article.