焊缝冷却后,在焊缝区域内产生什么?而使焊体内产生什么力?
焊缝冷却后,在焊缝区域内产生收缩,而使焊体内产生内应力。
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
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