摘要
本文对40C_r 的断裂韧性试样断口进行了扫描电子显微镜观察分析.结果表明:断裂韧性试样预制疲劳裂纹区之后有一个较平坦的延伸区,延伸区后就接着是有一定宽度的韧窝区,它们的出现与否及宽窄程度与材料的断裂韧性 K_(IC)值有密切关系.延伸区宽度 W 越大,材料 K_(IC)值越高.W 与裂纹尖端张开位移量2V_C 成正比,关系为:W≈1/2(2V_c),从而使 K_(IC)~2=2Eσ_s(2V_c)≈4Eσ_sW,则只要在电镜下测出延伸区的宽度 W 就可得到40C_r 材料的断裂韧性值,该值同其它测试方法所得的结果相比较为接近,所以可把电镜法作为估算材料的断裂韧性的一种途径.
This paper observes and analyses the crash section of fracture toughness specimen with scanning electron microscope.The results show that there is a smooth stretch zone after prefabricated fatigue crack zone of fracture toughness specimen,and there is a certain width tough hollow zone after the stretch zone.Their appearance and width have a close relation the fracture toughness K_(IC) of materal. The wider the width w of the stretch zone,the higher the fracture tdughness K_(IC) of material.The width w of stretch zone is directly proportional to the opening displacement 2Vc on crack top.The formula is:W≈1/2(2Vc),and K_(IC)~2=2Eσ_S(2V_c)≈4Eσ_s W.Pro- vided we measure the width w of strech zone with electron microscope,we will gain the fracture toughness value of 40Cr material.The value is very close to that of other methods. Thus,Electron Microscope Method is regarded as way of estimating the value of material fracture toughness.
关键词
断裂韧性
扫描电镜
钢
40CR钢
Fracture toughness
Scanning electron microscope
Crack opening displacement
Stretch zone width
