ZG20SiMn铸钢的高周疲劳行为

针对不同应力比下ZG20SiMn铸钢的高周疲劳行为进行了研究,确定了应力比对ZG20SiMn铸钢的高周疲劳寿命和疲劳极限等的影响。研究结果表明,在R=0.5的高应力比下,ZG20SiMn铸钢的疲劳极限明显高于R=0.1下的疲劳极限;在相同的外加应力幅下,当R=0.1时,ZG20SiMn铸钢的疲劳寿命明显高于R=0.5时的疲劳寿命。疲劳断口形貌的扫描电子显微分析结果表明,在不同的疲劳加载条件下,裂纹均以穿晶方式萌生于ZG20SiMn铸钢试样表面,并以穿晶方式扩展。此外,钢中的鱼骨状硫化物夹杂或者呈链状分布的含钼和锰的球状化合物相会显著降低ZG20SiMn铸钢的疲劳寿命。

ZG20SiMn铸钢的应变疲劳行为研究

为了深入理解ZG20SiMn铸钢在应变疲劳期间的循环变形及断裂行为,在应变控制模式下针对ZG20SiMn铸钢的疲劳行为进行了研究.结果表明,在应变控制的加载模式下,ZG20SiMn铸钢可表现为循环硬化和循环稳定特征,主要取决于外加总应变幅的高低,且其弹性应变幅、塑性应变幅与疲劳断裂时的载荷反向周次之间表现为单斜率线性行为.透射电镜分析结果表明,ZG20SiMn的疲劳变形机制主要为波状滑移机制.扫描电镜分析结果表明,在不同的外加总应变幅下,疲劳裂纹均以穿晶方式萌生于ZG20SiMn铸钢试样表面,并以穿晶方式扩展.

EFFECTS OF STRESS RATIO AND FREQUENCY ON CORROSION FATIGUE CRACK GROWTH MECHANISM IN LOW ALLOY STEELS

Based on theoretical analysis about local strain,strain rate and dissolving rate at crack tip, the corrosion fatigue crack growth rate of steels ZG20SiMn and SM50B-Zc in fresh water and 3.5% NaCl solution were measured experimentally,and the PH and electrode potential within crack were also measured continuously along with crack propagating.It showed that the increase of crack growth rate,caused by both decreasing frequency and raising stress ratio,was mainly accelerated by hydrogen embrittlement.

应力比和频率对低合金钢腐蚀疲劳裂纹扩展机理的影响

在理论分析裂尖局部应变、应变速率及溶解速度的基础上、实验测定了低合金钢ZG20SiMn,SM50B—Zc的腐蚀疲劳裂纹扩展速率,并随着裂纹的扩展测定了裂纹内和裂纹尖端的pH值和金属电极电位。