硬质合金表面织构液相辅助激光制备及摩擦性能

采用激光加工技术在空气介质与辅助液相(无水乙醇与双氧水体积比为50:1)下对YT15硬质合金表面进行了交叉扫描织构加工,制备出了两组织构试样. 借助Quanta 200扫描电子显微镜及能谱对织构硬质合金表面形貌与元素含量进行了测量,并用SDC-100接触角测量仪表征了润湿性,最后在MWF-500往复式摩擦磨损试验机上进行了干摩擦、润滑油及润滑油与MoS₂颗粒润滑的摩擦和磨损对比试验. 研究结果表明:相比空气介质激光加工试样,液相辅助激光加工表面的微凹坑分布更加均匀,无明显的氧化及熔融物重铸现象,表面接触角最小(55°);三种工况下液相辅助激光加工表面织构的摩擦系数最小,磨损量有一定改善. 分析表明:辅助液体对激光加工表面起到了冷却及保护作用,固-液界面快速产生的气泡散射了激光光束,使激光光束的作用区域发生干涉,同时携带出加工熔融物. 因此,润滑介质更容易在界面间渗入及铺展,改善了界面摩擦学特性.      

On the Density of Transmission Eigenvalue for the Schrödinger Operator with the Robin Boundary Condition北大核心CSCD

In this paper, we study the transmission eigenvalue problem with the Robin boundary condition. Applying the related properties of entire function of exponential type, we show the relationship between the density of eigenvalues and the length of the support interval of the potential function. Meanwhile, we prove that the transmission eigenvalue problem is equivalent to a kind of Sturm–Liouville problem with spectral parameter in the boundary condition. © 2022 Chinese Academy of Sciences. All rights reserved.