MODEL OF TRANSFORMATION TOUGHENING IN BRITTLE MATERIALS
MODEL OF TRANSFORMATION TOUGHENING IN BRITTLE MATERIALS
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DOI：
10.1111/j.1151-2916.1991.tb06800.x
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发表时间：
1991-10-01
影响因子：
3.9
通讯作者：
CHEN, IW
中科院分区：
文献类型：
--
作者：
CHEN, IW
假设能量耗散与距裂纹尖端的距离成反比，相变增韧陶瓷的稳态韧性的增加估计为Δ J =（Δ-J（o）/omega）ln（1 + ω），其中（i）Δ-J（o）表示在给定区域高度h（o）下所预期的韧性增量，假设整个区域完全转变，和（ii）ω是无量纲参数，给出非弹性转变应变（对于完全转变）与转变开始时的初始弹性应变的比率。 这一估计在两个重要方面扩展了McMeeking和Evans（1982）的早期结果：（i）相变应变可能包括剪切分量，而不是纯粹的剪切分量;（ii）Ω的范围现在不受限制，而McMeeking和Evans的方法仅严格适用于弱相变极限，Ω < < 1。 内部区域的高度h（i）估计为h（i）= h（o）/（1 + Ω），在该内部区域内，转化已经进行到完成（或饱和）。 该近似模型可以定量地解释Mg-PSZ和Ce-TZP的实验数据，与Budiansky、哈钦森和Lambropoulos在亚临界相变特殊情况下的严格有限元结果也非常吻合。
Assuming that the energy dissipation decreases inversely with distance from the crack tip, the increase in steady-state toughness of a transformation-toughened ceramic is estimated to be DELTA-J = (DELTA-J(o)/omega) ln (1 + omega), where (i) DELTA-J(o) denotes the toughness increment which would be expected for a given zone height h(o) assuming full transformation throughout the zone, and (ii) omega is a nondimensional parameter giving the ratio of the inelastic transformation strain (for full transformation) to the initial elastic strain at the onset of transformation. This estimate extends the earlier result of McMeeking and Evans (1982) in two significant respects: (i) the transformation strain may include a shear component, instead of being purely dilatational, and (ii) the range of omega is now unrestricted, whereas the McMeeking and Evans approach strictly applies only in the weak transformation limit, omega < < 1. The height of the inner zone h(i) within which transformation has proceeded to completion (or saturation) is estimated to be h(i) = h(o)/(1 + omega). Experimental data of Mg-PSZ and Ce-TZP can be quantitatively accounted for using this approximate model, which is also in very good agreement with the rigorous finite-element results of Budiansky, Hutchinson, and Lambropoulos in the special case of subcritical dilatational transformation.