role of crack tip shielding in the initiation and growth of long and small fatigue cracks in composite microstructures
role of crack tip shielding in the initiation and growth of long and small fatigue cracks in composite microstructures
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裂纹尖端屏蔽在复合材料微结构中长小疲劳裂纹的萌生和扩展中的作用
DOI：
10.1007/bf02646145
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发表时间：
1987
期刊：
影响因子：
--
通讯作者：
Mr. Tzou
中科院分区：
文献类型：
--
作者：
Jian Ku;J.;R. Ritchie;Ji an;Ku Shang;Mr. Tzou
以获得最大的疲劳抗力为目标，研究了裂纹尖端屏蔽在金属复合材料组织(由硬相和软相组成)中抑制疲劳裂纹萌生和扩展的作用。具体地说，在AISI1008和1015低碳钢中开发了双相铁素体-马氏体组织，以在不损失强度的情况下促进屏蔽。屏蔽主要是从裂纹偏转和由此产生的裂纹闭合发展而来的，从而获得了异常高的长裂纹扩展阻力。研究发现，在不牺牲强度的情况下，AISI1008的疲劳门槛ΔKTH值可提高100%以上，达到20 Mpa以上，这是迄今报道的金属合金最高的环境温度门槛值。AISI 1015指数也出现了类似但幅度较小的增长。然而，双相组织对裂纹萌生和小裂纹(10~1000ώm)扩展的影响是明显不同的，其行为特征受到内在和外部(屏蔽)“增韧”机制相互作用的影响。相应地，复合材料组织对长裂纹扩展的阻力最高，对裂纹萌生和小裂纹扩展的阻力最低。一般来说，双相钢具有显著的疲劳性能，疲劳极限高达抗拉强度的58%，疲劳阈值在13到20 MPaVm之间。
The role of crack tip shielding in retarding the initiation and growth of fatigue cracks has been examined in metallic composite microstructures (consisting of hard and soft phases), with the objective of achieving maximum resistance to fatigue. Specifically, duplex ferritic-martensitic structures have been developed in AISI 1008 and 1015 mild steels to promote shielding without loss in strength. The shielding is developed primarily from crack deflection and resultant crack closure, such that unusually high long crack propagation resistance is obtained. It is found that the fatigue threshold ΔKTHin AISI 1008 can be increased by more than 100 Pct to over 20 MPa Vm, without sacrifice in strength, representing the highest ambient temperature threshold reported for a metallic alloy to date. Similar but smaller increases are found in AISI 1015. The effect of the dual-phase microstructures on crack initiation and small crack (10 to 1000 ώm) growth, however, is markedly different, characteristic of behavior influenced by the mutual comPctition of intrinsic and extrinsic (shielding) “toughening” mechanisms. Accordingly, the composite microstructures which appear to show the highest resistance to the growth of long cracks, show the lowest resistance to crack initiation and small crack growth. In general, dual-phase steels are found to display remarkable fatigue properties, with fatigue limits as high as 58 Pct of the tensile strengths and fatigue thresholds in the range of 13 to 20 MPaVm.
影响因子：
5.4
作者：
NEWMAN, JC;RAJU, IS
通讯作者：
RAJU, IS