1Cr11Ni2W2MoV钢疲劳裂纹闭合与试样类型的相关性

Dependency of fatigue crack closure in 1Cr11Ni2W2MoV steel on specimen type

压力容器材料的疲劳裂纹扩展门槛值在预测服役寿命方面具有重要意义,而门槛值的准确测定常受到裂纹闭合的影响。为了验证采用角裂纹(CC)试样测定疲劳裂纹扩展门槛值时是否受裂纹闭合影响,采用1Cr11Ni2W2MoV钢加工了角裂纹试样和紧凑拉伸(C(T))试样,在室温下开展了疲劳裂纹扩展门槛值试验,并测定了门槛值对应的载荷-裂纹张开位移曲线。通过扫描电子显微镜对断口形貌中由裂纹闭合产生的磨损痕迹进行了观察。结合试验结果分析了两种试样类型的裂纹闭合程度及成因。通过CC试样测定的门槛值与C(T)试样相近或更小。在所测试4个CC试样中,仅有一个出现了足以影响裂纹扩展驱动力的裂纹闭合现象,而在所有测试的C(T)试样中均观察到了裂纹闭合。CC试样可用于疲劳裂纹扩展门槛值试验,并在当前试验条件下获得了接近理想门槛值的结果。

Fatigue crack growth threshold of pressure vessel materials is of great significance in predicting service life.However,the determination of threshold value is often affected by crack closure.In order to verify whether the result of fatigue crack growth threshold measured with corner crack(CC)specimen is affected by crack closure,corner crack specimens and compact tensile(C(T))specimens were machined with 1Cr11Ni2W2MoV steel.Fatigue crack growth threshold tests were carried out at room temperature,and the load-crack opening displacement curves corresponding to the threshold values were measured.The abrasions caused by crack closure in fracture morphology were observed by scanning electron microscopy.The degree and cause of crack closure in the two specimen types were analyzed in combination with the test results.The threshold value measured by CC specimen is similar to or smaller than that of C(T)specimen.Among the four CC specimens tested,only one shows crack closure sufficient to influence crack growth driving force,while crack closure is observed in all the C(T)specimens tested.CC specimens can be used in fatigue crack growth threshold test,and the results close to the ideal threshold value have been obtained under the current test conditions.