8.8级M24高强螺栓的常幅疲劳性能试验研究

EXPERIMENTAL RESEARCH ON CONSTANT-AMPLITUDE FATIGUE CHARACTERISTICS OF 8.8 GRADE M24 HIGH-STRENGTH BOLTS

为研究8.8级高强螺栓“轴心拉-拉”常幅疲劳性能,对材质为35K的M24高强螺栓进行了3个试件静力拉伸试验和15个试件(应力比为0.3)的常幅疲劳试验,拟合了S-N曲线,对代表性试件疲劳断口进行宏观和微观分析,并与基于GB 50017—2017《钢结构设计标准》相关公式的计算结果进行了对比。结果表明:疲劳试验数据总体较为离散,但均在95%置信区间内,拟合的S-N曲线基本反映不同应力幅下试件的疲劳寿命;试件缺口效应明显,尤其在螺栓螺纹齿根处,应力集中程度严重,点状疲劳源易扩展形成线状疲劳源,断口韧窝特征明显;相比标准建议值,试验所得2×106次对应疲劳强度为其1.61倍。

In order to study the constant-amplitude fatigue performance of 8.8 grade high-strength bolts under axial tension-tension condition,3 static tensile tests and 15 M24 bolts with 35K material were carried out.S-N curves were fitted and the fatigue fracture surfaces of representative specimens were analyzed macroscopically and microscopically.In addition,all the test results were compared with those calculated based on the relevant formula of Standard for Classification of Steel Structures(GB 50017—2017).The conclusions are as follows:The fatigue test data were generally discrete,but all within 95%confidence interval;The S-N curves could basically reflect the fatigue life of specimens under different stress amplitudes;At the root of the screw thread,the stress concentration was especially serious,punctiform fatigue source was easy to expand to form linear fatigue source,the notch effect of the specimen was evident;Comparing the test results with the recommended values of allowable fatigue strength stipulated in the national standards,the corresponding fatigue strength of 2×106 times was 1.61 times of the recommended value.