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首页> 外文期刊>Journal of the Mechanics and Physics of Solids >Mode Ⅱ fracture behavior of a Zr-based bulk metallic glass
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Mode Ⅱ fracture behavior of a Zr-based bulk metallic glass

机译：Zr基块状金属玻璃的Ⅱ型断裂行为

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摘要

Shear band formation and fracture are characterized during mode Ⅱ loading of a Zr-based bulk metallic glass. The measured mode Ⅱ fracture toughness, K_(Ⅱc) = 75±4 MPa√m, exceeds the reported mode Ⅰ fracture toughness by ～4 times, suggesting that normal or mean stresses play a significant role in the deformation process at the crack tip. This effect is explained in light of a mean stress modified free volume model for shear localization in metallic glasses. Thermal imaging of deformation at the mode Ⅱ crack tip further reveals that shear bands initiate, arrest, and reactivate along the same path, indicating that flow in the shear band leads to permanent changes in the glass structure that retain a memory of the shear band path. The measured temperature increase within the shear band is a fraction of a degree. However, heat dissipation models indicate that the temperature could have exceeded the glass transition temperature for less than 1 ms immediately after the shear band formed. It is shown that this time scale is sufficient for mechanical relaxation slightly above the glass transition temperature.
机译：Zr基块状金属玻璃在Ⅱ型加载过程中表征了剪切带的形成和断裂。测得的Ⅱ型断裂韧度K_（Ⅱc）= 75±4MPa√m，比报道的Ⅰ型断裂韧度高出〜4倍，表明正应力或平均应力在裂纹尖端的变形过程中起着重要作用。根据用于金属玻璃中剪切局部化的平均应力修正自由体积模型来解释此效应。对Ⅱ型裂纹尖端变形的热成像进一步揭示，剪切带沿着相同的路径引发，停止并重新激活，这表明剪切带中的流动导致玻璃结构的永久性变化，从而保留了剪切带路径的记忆。 。剪切带内测得的温度升高为度的几分之一。但是，散热模型表明，剪切带形成后，温度可能超过玻璃化转变温度的时间不到1 ms。结果表明，该时间尺度足以使机械弛豫略高于玻璃化转变温度。

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