基于超声空化与应变梯度塑性理论的功率超声珩磨磨削区微射流切削的基础研究

Power ultrasonic cylinder liners honing has a greater advantage than ordinary honing. The main processing of power ultrasonic honing is wet processing, which happens ultrasonic cavitation in the grinding zone. It is shown that the micro-jet produced by ultrasonic cavitation can change surface morphology of the liner wall, impact the storage and distribution, flow of the liner lubricating oil, further influence the performance and emissions of engine. However, it has not open research literature about the mechanism of micro-jet liner affect wall surface. The sound field and ultrasonic cavitation and the effect of ultrasonic bubble on the liner surface are deeply studied with bubble dynamics in this project. Based on the strain gradient plasticity theory, it primarily focuses on the microcutting mechanism that micro-jet produced by ultrasonic cavitation process the cylinder liner wall. The theoretical model of micro-cutting force and the constitutive equation of microcutting process which describe the case of micro-jet cutting the cylinder liner wall are established. The heat balance equation is established and the effect of micro-jet on power ultrasonic honing grinding heat is studied thermodynamically. The ultrasonic cavitation test by the special test apparatus designed and power ultrasonic honing surface test are made. The role of micro-jet of the microscopic surface of the cylinder liner wall is verified. Acoustics is organically combined with machining in this project. From the microscopic point of view, the positive role of the ultrasonic cavitation effect of power ultrasonic honing is explored, the essence mechanism of power ultrasonic honing is revealed on the basis of acoustics. The research results of this project will drive the development of precision and special machining.

功率超声珩磨以湿式加工为主,在磨削区产生的超声空化微射流能显著改变缸套壁微观结构，直接影响发动机的性能与排放，但目前关于微射流对缸套壁作用机理的相关研究很少，尚无公开研究文献。本项目借助空泡动力学理论从声场、超声空化机理、超声空泡作用于缸套壁等方面对功率超声珩磨中的空化效应进行深入研究；基于应变梯度塑性理论重点研究磨削区超声空化微射流对缸套壁的微切削加工机理，建立微射流对缸套壁切削的微切削力理论模型与微切削过程的材料本构方程；从热力学角度建立超声空化在内的宏观热力学平衡方程，研究微射流对功率超声珩磨磨削热的影响；设计专用试验装置进行超声空化微射流试验，进行功率超声珩磨加工表面试验，验证缸套壁微观表面的微射流切削作用。本项目将超声声学与机械加工有机结合，从微观角度探索超声空化效应对超声珩磨缸套的积极作用，从声学角度揭示功率超声珩磨加工机理。项目的研究成果将有助于推动精密与超精密加工学科发展。

功率超声珩磨以湿式加工为主,在磨削区产生的超声空化微射流能显著改变缸套壁微观结构，直接影响发动机的性能与排放。本项目从超声振动珩磨的工作原理出发，对其声振系统进行了多物理场耦合声场分析；考虑珩磨环境因素，基于气泡运动能量守恒，建立了磨削液单空化泡的动力学模型；应用实际气体绝热方程和范德瓦尔斯方程对其进行了修正；基于速度势叠加原理，建立了两空化泡的动力学模型；将空化泡泡内气体的膨胀视为等温过程，压缩视为绝热过程，修正了超声振动珩磨下单、双空化泡的动力学模型。利用镜像原理，建立了考虑刚性壁面作用的单、双空化泡动力学模型，数值对比了刚性界面与自由界面下单、双空化泡的运动特性，分析了不同参数对空化泡溃灭的影响。在此基础上，确立了空化泡溃灭速度和微射流的相互关系，研究证实通过控制空化泡溃灭速度可以达到间接判断和控制微射流的目的。推导了超声振动珩磨作用下不同界面附近单、双空化泡的共振频率、振动位移；研究了超声振动珩磨作用下刚性界面附近空化泡的速度场及压力场分布规律。为探究微射流对壁面的冲击作用，考虑壁面弹塑性变形、超声场及珩磨压力场，建立了空化微射流冲击模型。基于超声空化动力学和热力学基本定律，建立了超声振动珩磨单空化泡热力学方程；间接分析了各参数对单空化泡溃灭温度的影响。采用试纸法和功率声强测量仪测量方法分别从定性测量和定量测量角度对磨削区的空化声场进行了实验测量；提出了粗糙度法间接反映液体介质空化强度的方法；采用铝箔腐蚀法进行了空蚀试验；基于空化的记忆效应，对超声振动珩磨下磨削液的空化特征进行实验观察。本项目将超声声学与机械加工有机结合，从微观角度探索超声空化效应对超声珩磨缸套的积极作用，从声学角度揭示功率超声珩磨加工机理。项目的研究成果将有助于推动精密与超精密加工学科发展。