Language
Country/Area
No result found
This is why glass cracks! Learn how thermal shock destroys materials
In our daily lives, the breakage of glassware is often surprising, and it often occurs at unexpected times. In such cases, the physical phenomenon of thermal shock is often the culprit. Thermal shock refers to the transient mechanical loading experienced by an object at rapidly changing temperatures, resulting from differences in expansion between different parts of the object due to temperature changes. When the strain caused by this change exceeds the tensile strength of the material, cracks may develop, ultimately leading to structural failure.
Thermal shock is usually defined as a temperature change that the material cannot adapt to in a short period of time. In this case, the relationship between strain and stress must be understood.
What is thermal shock?
Thermal shock is primarily defined as a rapid temperature change that causes uneven expansion and contraction between different parts of an object. Such changes not only cause stress but also cause local structural damage, which is a key cause of failure of many materials. Therefore, preventing thermal shock is an important factor to consider when designing and using various materials.
How does thermal shock affect materials?
For example, heat-resistant glass, such as borosilicate glass, is better able to withstand thermal shock due to its lower coefficient of expansion and greater strength. In contrast, fused quartz performs better in these aspects. Certain glass-ceramic materials, especially lithium aluminosilicate systems, control the proportion of negative expansion coefficients in the material so that the overall expansion coefficient drops to almost zero over a wide range of temperatures. This type of material exhibits superior thermomechanical properties.
Testing for thermal shock typically uses shock excitation techniques, a non-destructive measurement method.
Measures to prevent thermal shock
To effectively prevent thermal shock, the following measures can be taken during design:
- Minimize thermal gradients by gradually changing temperature.
- Improve the thermal conductivity of the material.
- Reduce the thermal expansion coefficient of the material.
- Enhance the strength of the material.
- Introducing compressive stress, such as using tempered glass.
Examples of thermal shock testing
In industrial applications, thermal shock testing is often used to ensure product stability under extreme temperature changes. For example, some glass containers may become brittle when exposed to brief cycles of high and low temperatures, and this testing method is often used to evaluate their durability. In these tests, samples are placed in an environment that rapidly switches between high and low temperatures, sometimes at speeds exceeding 15°C per minute.
Thermal shock failure of brittle materials
Brittle materials are often more susceptible to thermal shock, especially under rapid temperature changes. For example, old iron stoves can cause the material to crack if they are overheated and then coated with cold water. This is because the outside of the material cools rapidly while the inside remains high, resulting in uneven stress.
Thermal shock testing is used by many industries to improve the stability of products and ensure they maintain their integrity under extreme conditions.
Summary of the effects of thermal shock and its significance for material selection
The impact of thermal shock cannot be ignored, especially when designing and selecting materials. Choosing materials with high thermal shock resistance, such as certain glasses and ceramics, can significantly improve product performance and stability. As materials science advances, more innovative materials that can address thermal shock challenges may be developed in the future.
When we select materials, have we considered the potential impact of thermal shock on their performance?
