摘要
研究了ＴｉＢ２颗粒增强锌基合金及其基体材料中由缺口起始的疲劳短、长裂纹的扩展行为。通过精抛光试样表面跟踪裂纹路径，在同一试样上采用降低施加负荷的方法，测定了短、长疲劳裂纹的扩展速率，并沿裂纹路径观察了增强粒子与裂纹尖端的作用。研究结果表明：在该复合材料及基体材料中均存在小裂纹扩展延迟现象，此现象与缺口塑性有关，复合材料中还与粒子与裂纹尖端的作用有关，两种材料在相同的△Ｋ水平下，短、长疲劳裂纹具有不同的扩展速率，这起因于不同的裂纹闭合效应。当用有限应力强度因子代替名义应力强度因子后，两者趋于一致。
The propagation behavior of short and long fatigue cracks emanating from notches in specimens of a TiB_2 particulate reinforced ZA-8 Zn metal matrix composite(MMC) and the corresponding constituent matrix material was studied.By using well-polished specimens and monitoring the development of fatigue crack path,the growth rate of short and long fatigue cracks was measured through a load-reducing program.The interaction between particles and crack tip was observed along the crack path as well.Results of this study revealed the arresting phenomenon of short cracks in the MMC specimens as well as in the constituent matrix material. This arresting behavior is attributed to the notch plasticity in both materials,and also to the interaction between particles and crack in the MMC,It was also found that short and long fatigue cracks in the two materials demonstrated clearly the different growth rates at same △K levels,resulting from different closure effects as the crack length increased.However,through subtracting out the effect of closure behavior so as to demonstrate the characteristics of crack growth rate in terms of △Keff,the difference in crack growth rate between short and long cracks has become minimal.
出处
《材料工程》
EI
CAS
CSCD
北大核心
1996年第3期9-13,共5页
Journal of Materials Engineering
