不良・失敗
residual stress
Japanese: 残留応力
Stress trapped inside the material due to rapid cooling. This occurs when the material is not cooled slowly enough and can lead to spontaneous cracking at a later date. / Note: This can be visualized using a polarizing filter.
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Residual stress is strain that becomes locked within the glass during the cooling process. It occurs when there is a difference in cooling rates near the slow-cooling point, and if the glass is rapidly cooled below the strain point, the residual stress remains unreleased.
Insufficient cooling can cause spontaneous cracking (annealing cracks) at a later date. This can be visualized as interference colors using a polarizing filter.
This entry is written in Japanese by Rei Chikaoka and translated for readers outside Japan. If something reads oddly, the original is the source of truth.