短寿命区采用四级恒定应力水平的成组试验法，长寿命区采用应力升降试验法。

The grouping test method at four constant stress levels was applied for short life span areas while the stress up and down test method were used for long life span areas.

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短寿命区采用四级恒定应力水平的成组试验法，长寿命区采用应力升降试验法。

K... the grouping test method at four classes of constant stress levels was applied for short life-span areas while the stress up-and-down test method was used for long life-span areas.

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