表面超声滚压处理工艺对高速列车车轴钢表面状态的影响

为提高高速列车车轴钢的疲劳性能,对车轴钢EA4T进行了表面超声滚压处理(SURP)。综合运用了粗糙度测量仪、扫描电子显微镜(SEM)、X射线衍射应力分析仪、显微硬度仪以及金相显微镜研究了表面超声滚压处理工艺参数中静压力和进给速度对高速列车车轴钢表面粗糙度、表面残余应力状态、表层显微硬度及微观组织的影响规律。结果表明:在试验参数范围内,静压力和进给速度越低,车轴钢的表面粗糙度越低;SURP后,试样表面轴向残余压应力得到大幅度提高,并且随着静压力的增加而增加,随着进给速度的增加而减小;表面硬度以及塑性变形层厚度随两参数的变化规律与残余应力的变化规律相似。     

RESIDENCE TIME DISTRIBUTION IN A SCREW EXTRUDER

It has been studied that the residence time distribution(RTD)function in a screw extruder in relation to that in thescrew and that in the die.For a complex flow field such as that between screw and die,it was supposed that the RTDfunction in the screw and that in the die were almost independent on each other.Therefore,a probabilistic method wasused to predict the RTD function in a complete extruder from that in the screw and that in the die.The experiments fordetermining the RTD were based on a stimulus-response technique.The results predicted,both in single-screw extruderand in twin-screw extruder,were in good agreement with those experimentally obtained.     

螺杆挤出机中的停留时间分布

物料在螺杆挤出机中的停留时间分布(简称RTD)对于挤出过程,尤其是对于带有反应的体系或热敏性物料的挤出过程来说,是一个极为重要的工艺参数.同时RTD又是一个很难确定也很难测定的参数.因此,国外相当多的学者对其进行了深入的研究.国内除郑柯等人曾作过一般性研究之外尚无人在这方面作深入研究.