Toughening produced by crack‐tip‐stress‐induced domain reorientation in ferroelectric and/or ferroelastic materials
Toughening produced by crack‐tip‐stress‐induced domain reorientation in ferroelectric and/or ferroelastic materials
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DOI：
10.1080/01418610110058301
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发表时间：
2002-01
期刊：
影响因子：
--
通讯作者：
M. Reece;F. Guiu
中科院分区：
文献类型：
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作者：
M. Reece;F. Guiu
本文计算了铁电和/或铁弹性材料中裂纹尖端应力引起的磁畴重新取向所产生的增韧。计算的基础是得到裂纹尖端周围并延伸到裂纹表面的区域的剪切相变产生的屏蔽应力强度因子。结果表明，相变的有效剪切应变γe在相变区内并不是均匀的，而是裂纹尖端剪切应力的函数，τ激活了磁区的重定向。结果表明，从材料的压应力-应变曲线可以实验得到γe与τ之间的关系。准确计算这种非均匀相变区产生的屏蔽应力强度因子需要解决一个没有尝试过的难题。然而，一个简单的高估表明，即使在最有利的条件下，铁电和/或铁弹性材料中由裂纹尖端应力引起的磁畴重新取向所能预期的增韧也不到10%。这一结果在物理上是合理的，并认为计算所预测的小韧化是因为驱动相变所需的裂纹尖端应力随着相变应变成比例增加而增加。这种情况与裂纹尖端应力引起的相变所期望的更大的增韧形成对比，后者主要是由相变的化学或体相自由能变化驱动的。
Abstract A calculation is carried out of the toughening produced by the crack-tip-stress-induced reorientation of domains in a ferroelectric and/or ferroelastic material. The calculation is based on obtaining the shielding stress intensity factor produced by the shear transformation of a zone surrounding the crack tip and extending over the crack surfaces. It is argued that the effective shear strain γe of the transformation is not uniform inside the transformation zone but is a function of the resolved shear stress of the crack tip, τ activating the domain reorientation. It is shown that the relation between γe and τ can be obtained experimentally from the compressive stress-strain curve of the material. An accurate calculation of the shielding stress intensity factor produced by such an inhomogeneous transformation zone requires the solution of a difficult problem which is not attempted. However, a simple overestimate is made, showing that the toughening which can be expected from the crack-tip-stress-induced reorientation of domains in a ferroelectric and/or ferroelastic material is less than 10% even in the most favourable conditions. This result is justified on physical grounds and it is argued that the small toughening predicted by the calculations arises because the crack tip stresses needed to drive the transformation increase proportionally with the transformation strain. This case is contrasted with the much greater toughening which is expected from the crack tip-stress-induced phase transformations which are largely driven by the chemical or bulk, free-energy change of the transformation.