建筑结构钢材Q390GJD的疲劳性能试验研究

为研究结构钢的疲劳性能,促进GB 50017—2003《钢结构设计规范》关于结构钢设计条文的进一步完善和结构钢材的更广泛应用,并为今后的相关研究提供参考。通过常规试验方法对Q390GJD钢材光滑板试件进行轴向拉伸疲劳试验,测绘出能够描述其疲劳性能的S-N曲线,并用电子显微镜观测到试件疲劳破坏后的断面特征。试验结果表明:对于所研究的该批次Q390GJD钢,其疲劳性能相对于疲劳荷载非常敏感,根据试验得出的S-N曲线,该批试件在N为2×10~6次疲劳破坏时的最大应力为258.75MPa。根据试验得出的S-N曲线取95%的保证率,相应的最大应力值应为218.68MPa,高于根据GB 50017-2003计算出的相应值154.88 MPa。Q390GJD疲劳试验试件在较高应力幅下的疲劳裂纹起源于试样表面的某种缺陷,在较低应力幅下的疲劳裂纹起源于大尺寸的夹杂物;疲劳扩展区断口微观形貌可观测到疲劳辉纹和微孔空穴,瞬断区断口形貌具有典型的韧窝特征。

FATIGUE TEST OF STRUCTURAL STEEL Q390GJD

In order to study the fatigue performance of structural steel Q390GJD, and promote the complement of GB 50017-2003 Steel Structures Design Code in terms of fatigue performance and the wider application of steel in civil engineering and also provide useful data for following up research, a number of axial tensile fatigue tests by conventional test methods using Q390GJD＇s smooth plate specimens were conducted and the S- N curve was plot. The specimens＇ cross-section failure characteristics was observed by electronic microscope. The test results showed that for these Q390GJD steel specimens, the fatigue performance was very sensitive to the fatigue load, the measured maximum stress was 258.75 MPa when the specimens failed with load cycle number N equals to 2 X 106 , the corresponding values taking 95% guarantee ratio was 218.68 MPa which was greater than the corresponding value 154.88 MPa proposed by GB 50017- 2003. It was observed by electronic microscopy experiments that the fatigue cracks originated from the sample surface defect at higher stress amplitude loading, while at the lower stress amplitude loading, the fatigue crack originated from the large size of inclusions, fatigue fracture morphology of expansion area has the fatigue striation and micro-pit, the surface of fast fracture zone has typical dimple features.