摘要
测试了中碳高强度弹簧钢NHS1的超高周(10~9 cyc)疲劳破坏行为,并利用FESEM对疲劳断口进行了观察.NHS1钢的S-N曲线呈台阶型,在10~9 cyc内疲劳极限消失.疲劳断口分析表明,在高应力幅区,实验钢的疲劳破坏主要起源于基体表面;而在低应力幅长寿命区,疲劳破坏主要起裂于试样内部的夹杂物,形成"鱼眼"型断裂.在夹杂物周围存在一个粗糙的粒状亮区(GBF).GBF区边界的应力场强度因子为3.6 MPa.m^(1/2),与疲劳寿命无关,该值与疲劳裂纹扩展的门槛值相等;"鱼眼"边界的应力场强度因子同样与疲劳寿命无关,约为10.6 MPa.m^(1/2).
Ultra high cycle fatigue behavior of a new kind of medium-carbon high strength spring steel （NHS1） was investigated and its fractographs were analyzed by means of field emission SEM （FESEM）. It was found that the S-N curve of NHS1 steel is a step-wise curve, and the fatigue limit eliminated to be in 109 cyc regime. Analysis of fractographs showed that surface fracture occurred in the region of short fatigue life at high stress amplitude level and interior inclusion-induced fracture in the region of long fatigue life at low stress amplitude level. Fish-eye marks were always observed around the interior inclusions on the fracture surfaces and a granular bright facet （GBF） was observed in the vicinity around the inclusion. The stress intensity factor range at GBF boundary △KGBF is a constant of 3.6 MPa.m^1/2, which is just equal to the threshold stress intensity range △Kth. The stress intensity factor range at fish-eye boundary △KFE is also a constant, 10.6 MPa.m^1/2.
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2007年第10期1031-1036,共6页
Acta Metallurgica Sinica
基金
国家重点基础研究发展计划资助项目2004CB619104
关键词
中碳高强度弹簧钢
超高周疲劳
鱼眼型断裂
疲劳裂纹扩展
medium-carbon high strength spring steel, ultra high cycle fatigue, fish-eye fracture, fatigue crack growth
