Blog

Temporary stress in glass bottles

admin 2022-04-07 10:04:3003 Comments
The external shrinkage rate of the glass bottle at a lower temperature during the cooling process should be greater than the shrinkage rate of the inner layer,glasscookware, but due to the hindrance of the inner layer, the shrinkage rate of the glass bottle cannot be reduced to the normal shrinkage rate, so the outer layer produces tensile stress, and the inner layer produces tensile stress. Layer compressive stress is generated in the compressive state. At this time, the stress distribution in the thickness direction of the glass is tensile stress, the inner layer is compressive stress, and the stress distribution is parabolic. In the layer in the middle of the glass, the compressive stress and the tensile stress are equal in magnitude, the stress directions are opposite to each other, and the layer stress is zero, which is called the neutral layer.
The glass bottle continues to cool, when the surface layer cools down to room temperature, the surface temperature doesn't drop anymore, its volume doesn't shrink, but the inner layer temperature is higher than the outer layer, it continues to cool, so the outer layer starts to receive the inner layer is pulled to produce compression stress, which will partially offset the tensile stress received at the onset of cooling, while the inner layer is stretched by the outer layer when stretched, which will partially offset the pressure at the onset of cooling. emphasize. As the temperature of the inner layer decreases, the tensile stress of the outer layer and the compressive stress of the inner layer continuously cancel each other out. When the temperature of the inner and outer layers is the same, there is no longer any stress in the glass. Conversely, if the glass sheet is heated from room temperature until it remains at a temperature below the strain point, the temperature and stress curves are reversed from the above.
Although the temporary stress disappears with the disappearance of the temperature gradient, the stress value should be strictly controlled. If the limit of the tensile strength of the glass is exceeded, the glass will break. This phenomenon is commonly used to cut glass articles, glass tubes, glass rods, etc. by quenching.

Leave a comment

Do you have any Projects ?

Whether you want to work with us or are interested in learning more about what we do,we’d love to hear from you.