A FATIGUE CRACK CLOSURE MECHANISM IN TITANIUM
A FATIGUE CRACK CLOSURE MECHANISM IN TITANIUM
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DOI：
10.1111/j.1460-2695.1979.tb00372.x
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发表时间：
1979
影响因子：
3.7
通讯作者：
N. Walker;C. Beevers
中科院分区：
文献类型：
--
作者：
N. Walker;C. Beevers
摘要：通过使用两阶段复制技术检查裂纹轮廓和监测裂纹开口位移，研究了商业钛的疲劳裂纹闭合。复制品表明，当闭合发生时，裂纹不会从裂纹尖端闭合，而是在沿着裂纹面的离散接触点处闭合。因此，观察到的闭合机制与普遍接受的模型大不相同。假设接触点楔入裂纹张开，则最小载荷下的应力强度大于预期，并且应力强度的范围有效地减小。在0·05 ~ 0·7的范围内，裂纹扩展速率对参数Δθ的依赖性是奇异的，对于SEN试样，Δθ近似于裂纹面对向角的变化。因此，Δθ与有效应力强度幅值之间存在着直接的联系。
Abstract— Fatigue crack closure in commercial titanium has been investigated by examining the crack profile using a two-stage replica technique and by monitoring the crack raouth opening displacement. The replicas show that when closure occurs the crack does not close back from the crack tip but at discrete contact points along the crack faces. The observed closure mechanism is therefore quite different from the generally accepted model. Assuming that the contact points wedge the crack open, the stress intensity at the minimum load is greater than expected and the range of the stress intensity is effectively reduced. Also, it was found that the crack growth rates measured in the range 0·05 ≦R≦ 0·7 showed a singular dependence on the parameter Δθ which for SEN specimens approximates to the change in angle subtended by the crack faces. It is therefore suggested that there is a direct link between Δθ and the effective stress intensity amplitude.