But in the forming process, equator of the shell tends to withdraw inwards and therefore creates wrinkles here, which badly affects the quality of the vessel.

但在成形过程中，壳体赤道环焊缝处极易向内收缩，从而引发该处的失稳起皱，严重影响了球形容器的质量。

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A round draw bead can prevent the forming of inner wrinkles.

环形拉深筋经常用来内皱。

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