应力集中系数对转向架用16MnR钢对接接头疲劳寿命的影响

Effect of Stress Concentration Coefficient on Fatigue Life of 16MnR Steel Butt Joint of Bogie

分别采用线切割和磨削方法加工转向架用16MnR钢对接接头的焊趾区域,制成有咬边缺陷和无缺陷的接头试件,并利用EHF-EM200K2-070-1A疲劳试验机,在应力比为0.1、载荷频率为10Hz的条件下,对接头试件进行疲劳寿命对比试验。结果表明:加工前接头试件的应力集中系数Kt为2.24;而分别经线切割和磨削2种方法加工后,接头试件的Kt分别降至1.29和1.00;与加工前相比,用线切割和磨削方法加工的无缺陷接头试件的平均疲劳寿命分别提高5.8和8.9倍左右;当接头试件焊趾处存在严重咬边缺陷时,即使经过线切割或磨削加工,也不能提高接头的疲劳寿命;应力集中系数对转向架用16MnR钢对接接头的疲劳寿命具有非常大的影响,因此对接头焊趾区域进行机加工处理,可有效降低接头的应力集中系数,从而提高其疲劳寿命和运行可靠性。

16MnR butt joint specimens of bogie with and without undercut defect were obtained by process- ing weld toe area with wire-electrode cutting and grinding method. Under the condition that stress ratio was 0. 1 and load frequency was 10 Hz, the fatigue life contrast tests were performed on butt joints specimen by using EHF-EM200K2-070-1A type fatigue tester. The results indicate that the stress concentration coefficient Kt of butt joint specimen before processing is 2.24. While after wire-electrode cutting and grinding, Kt is decreased to 1.29 and 1.00 respectively. Compared with the butt joint before processing, after wire-electrode cutting and grinding, the average fatigue life of butt joint without undercut defect is in- creased about 5.8 and 8.9 times respectively. Even using the wire-electrode cutting and grinding method, the fatigue life of butt joint can not be increased when weld toe has serious undercut defect. Stress concen- tration coefficient has great effect on the fatigue life of 16MnR steel butt joint of bogie. It can effectively reduce the stress concentration coefficient of butt joint as well as increase the fatigue life and reliability of the welded bogie frame by machining or grinding the weld toe area.