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对４种金属材料在Ⅱ型加载条件下的疲劳裂纹扩散行为进行的试验研究表明：在Ⅱ型加载条件下，裂纹可能仍沿Ⅱ型方向继续扩展，亦可能发生分支转变成Ⅰ型甚至Ⅰ＋Ⅱ型扩展，主要取决于材料本身的性质和它们的微观结构以及应力水平。当裂纹仍沿Ⅱ型方向扩展时，其扩展速率比相当应力水平的Ⅰ型裂纹扩展速率要大得多。
The experimental study on the fatigue crack propagation behavior of four kinds of metal under type Ⅱ loading shows that the crack may still continue to expand along type Ⅱ under type Ⅱ loading, and the branching may change to type Ⅰ or even type Ⅰ + Ⅱ Expansion depends mainly on the nature of the material itself and their microstructure and stress level. When the crack is still expanding along the direction of type Ⅱ, its propagation rate is much larger than that of the type Ⅰ crack at the equivalent stress level.