超声冲击对高速列车转向架焊接十字接头超高周疲劳性能的影响

针对高速列车转向架在实际运用中出现的疲劳问题,利用HJ-Ⅲ型超声冲击处理装置,对高速列车转向架用SAM490BW钢十字接头焊趾进行超声冲击处理,并对处理后接头的超高周疲劳性能进行研究。结果表明,原始焊态试样和超声冲击态试样的S-N曲线均出现了传统意义上的水平段。超声冲击处理试样的疲劳强度相比于未处理试样提高了25%。经过超声冲击处理后,疲劳裂纹源的数量由多个变为单个,焊接接头焊趾处的应力集中系数下降了32.4%,降低了裂纹萌生概率;超声冲击降低了焊趾区域的残余拉应力,并诱发产生残余压应力,高达-255.5 MPa;焊趾表层晶粒得到细化,晶粒平均尺寸小于100nm;裂纹在塑性变形区扩展路径变长。

Influence of Ultrasonic Impact on the Very High Cycle Fatigue Properties of Welded Cross Joint for High-speed Train Bogie

To address the fatigue problem occurring to the bogie of high-speed train in the practical application,the weld toes were treated by H J-Ⅲ type ultrasonic impact treatment device at room temperature,in order to investigate the effect of ultrasonic impact treatment (UIT) on very high cycle fatigue (VHCF) behavior of welded SAM490BW cross joint of high-speed train bogie.The results indicated that the S-N curves of as-welded and UIT specimens exhibit a plateau beyond 107 cycles.Compared with the aswelded.joints,the degree of improvement of VHCF performance of SAM490BW steel cross welded joint treated was up to 25％.There were several crack initiation locations on the fracture surface for as-welded samples,whereas,there was only one crack source for UIT specimens.The concentration coefficient of the welded joints toes decreased by 32.4％ after UIT,the crack initiation probability was reduced.Residual tensile stress could be significantly reduced by UIT and residual compressive stress was induced on surface of welded joints toe,up to-255.5 MPa.A surface layer of nanocrystalline microstructure could be produced,the average grain size was less than 100 nm.Crack propagation path,in plastic deformation region,could get longer by implementing the UIT.