20 kHz频率下高强度钢超高周疲劳研究

应用超声疲劳试验技术，对两种高强度钢在20kHz频率下10^5～10^10循环周次的疲劳性能进行了测试分析。结果表明：应力比R=-1时，D38MSV5S钢与100C6钢在10^5～10^10循环周次之间，试样仍会发生疲劳断裂，疲劳强度随循环次数的增加而下降；R=0．1时，D38MSV5S钢在10^6～10^7循环周次之问会出现疲劳强度。与30Hz频率下常规疲劳试验数据比较发现，频率对100C6钢的疲劳性能影响不大；R=-1时，D38MSV5S钢20kHz频率下的SN曲线略低于30Hz频率下的SN曲线，当R=0．1时，频率对D38MSV5S钢疲劳性能的影响更为明显。在超高周疲劳循环下，疲劳破坏主要起源于试样内部夹杂物。

Super High Cycle Fatigue of High Strength Steels at a Frequency of 20 kHz

Super high cycle fatigue behavior of 100C6 and D38MSV5S high strength steels, were investigated using ultrasonic fatigue testing equipment at a frequency of 20 kHz up to 1010 cycles. The S-N curve at room temperature with different stress ratios CR=-1 and R=0. 1) was determined The experimental results show that fatigue strength decreased with increasing number of cycles between 105 and 1010 cycles for R= - 1, there was no fatigue limit; however, fatigue limit of D38MSV5S was found between 106 and 107 cycles for R=0. 1. S-N curves show that the results for 20 kHz testing agreed quite well with those for conventional 30 Hz testing in the 105-107 cycle range for 100C6; frequency effects were found in the testing of D38MSV5S, specially, frequency effect was very obvious for the testing with R = 0. 1. SEM examination of fracture surfaces reveals that fatigue damage was governed by the formation of cracks, and subsurface crack initiation was dominant in the very long-life range.