Q235、Q345钢结构材料的低周疲劳性能

对Q235、Q345钢的低周疲劳性能进行了研究。采用轴向应变控制方法,在岛津电液伺服疲劳试验机上测定了2种钢低周疲劳过程中的循环应力响应特征、循环应力与应变的关系,通过拟合Basquin公式和Coffin-Manson公式得到了2种钢的疲劳寿命公式,据此计算了Nf=100周时的循环能量吸收率σa.Δεt值,并与别的钢筋进行了比较。通过断口扫描发现,Q235钢裂纹起源于试样表面,由于第二相质点和夹杂物的存在,形成微孔洞和微裂纹,互相连接形成疲劳断裂;Q345钢裂纹起源于表面,然后通过不断扩展形成微裂纹,再连接成宏观裂纹,最终导致材料断裂。

Low Cycle Fatigue Properties of Steel Structure Materials Q235 and Q345

Low cycle fatigue (LCF) properties of Q235 and Q345 steels were investigated. The fatigue tests were conducted on a Shimadzu servo-hydraulic testing machine. The tests were run under uniaxial tension-compression loading with total strain control. Cyclic stress response characteristics and the cyclic stress-strain relationships of the two kinds of test materials were investigated. The Coffin-Manson parameters were derived from the test results. The values of at the fatigue life of 100 cycles were obtained and compared with the results of other steel bars. The SEM micrographs revealed that fatigue crack initiated at the specimen surface. More cavities were observed on the fracture surface of Q235 steel than on that of Q345 steel. Due to the propagation and connection of the micro-cracks, the macro-cracks were formed and fracture occurred eventually.