【作者】 刘春；

【导师】 孙杰；

【作者基本信息】 山东大学 ， 机械工程（专业学位）， 2018， 硕士

【摘要】 钛合金薄壁件因其质量轻、结构强度高等优点而被广泛用于航空航天领域。为了减轻质量并确保相应的强度和刚度,钛合金薄壁件在加工过程中具有较大的材料去除率,导致相对刚度低。因此,在夹紧力和切削力等多种因素的影响下,钛合金薄壁件在切削时容易发生加工变形和颤振,使得刀具磨损严重、工件表面质量恶化,难以有效保证加工质量和加工精度。切削力的不稳定是高速切削中钛合金薄壁件剧烈振动的主要原因。因此,通过研究减小加工过程中钛合金薄壁件切削力和切削振动的新方法,提高钛合金薄壁件的加工质量和加工精度,对实现高质量、高效率加工具有重要意义。本文研究了气射流辅助支撑对钛合金薄壁件铣削加工性能的影响。首先基于流体有限元分析相关理论,进行喷嘴内外气射流流场仿真,通过研究压力场、速度场,分析了喷嘴内外流场特性;设计单因素试验和正交试验,分析了不同气射流对钛合金薄壁件所受冲击力及变形的影响规律,比较了有、无气射流辅助支撑的钛合金薄壁件铣削试验,对比研究了有、无气射流冲击对钛合金薄壁件侧壁加工稳定性、加工质量和加工精度的影响。喷嘴内外气射流流场仿真是通过Ansys Fluent进行模拟的,通过分析喷嘴结构几何参数对喷嘴内压力场、速度场和喷嘴出口流体径向速度的影响规律,以及入口压力对喷嘴内、外压力场、速度场的影响规律,为优化喷嘴结构几何参数提供合理的依据。气射流冲击钛合金薄壁件动态特性试验是利用已获得的Fluent流体仿真求解结果,应用ANSYS Workbench协调仿真平台进行流体力学分析的,通过研究喷嘴结构几何参数及外部参数对钛合金薄壁件所受的气射流冲击力及变形的影响规律,并基于射流冲击力,对喷嘴结构几何参数、入口压力和靶距进行了优化。有、无气射流辅助支撑的钛合金薄壁件铣削试验对比分析了铣削过程中的振动加速度、切削力以及加工完成后侧壁厚度误差和表面粗糙度,最后验证了气射流辅助支撑确实可以提高钛合金薄壁件的加工精度和加工质量。更多还原

【Abstract】 In the aerospace industry,titanium alloy thin-walled parts are extensively used due to their excellent characteristics,such as light weight and high structural strength.A titanium alloy thin-walled part needs to remove large amounts of material from a single billet because of the titanium alloy component’s design to reduce its weight as much as possible while maintain the necessary strength and rigidity.But one disadvantage of the titanium alloy component is that its relative rigidity will be low.Therefore,titanium alloy thin-walled parts are difficult to machine as a fact of easy deformation and vibration during the cutting process,which will lead to aggravated tool wear and degradation of the machined surface,because of the comprehensive influence of different factors like clamping force,cutting force and cutting heat,etc.Finaly,it will difficult to effectively guarantee the machining quality and precision.The instability of cutting force is the main reason for severe vibrations during high-speed cutting of titanium alloy thin-walled parts.Therefore,it is of great significance to reduce the cutting force and suppress the vibration while machining the titanium alloy thin-walled parts by exploring new methods.Because it will also make sense to improve the machining quality and precision,thus realizing the high quality and high efficiency machining of the titanium alloy thin-walled parts.In this paper,the influence of air jet assistance on milling performance of titanium alloy thin-walled parts is studied.Firstly,the simulation of flow field of air jet inside and outside the nozzle is carried out based on the relevant theory of fluid finite element analysis.So the flow field characteristics inside and outside the nozzle could be investigated by studying the pressure field and velocity field.Secondly,single factor tests and orthogonal experiment were designed to analyze the influence of different air jets on the impact force and deformation of titanium alloy thin-walled parts.Thirdly,milling experiments of titanium alloy thin-walled parts with and without air jet assistance were carried out and the influence of the impingement on processing stability,machining quality and precision of the side wall of the titanium alloy thin-walled parts were compared and investigated.The air jet flow field inside and outside nozzle is simulated by the use of Ansys Fluent software.The influences of geometric parameters of the nozzle structure on the pressure field,the velocity field and the radial velocity of the nozzle outlet,as well as the influence of the inlet pressure on the inner and outer pressure fields and the velocity field of the nozzle,are all analyzed to provide a reasonable basis for optimizing the geometric parameters of the nozzle structure.The ANSYS Workbench coordinated simulation platform is applied for the fluid mechanics analysis by using the obtained Fluent fluid simulation results.The influences of the geometric parameters of the nozzle structure and external parameters on the impact force and deformation of the titanium alloy thin-walled parts by air jet are studied.The nozzle structure parameters are optimized based on the air jet impact force.inlet pressure and target distance.The experiments on the milling of titanium alloy thin-walled parts with and without air jet assistance were carried out.The vibration acceleration,cutting force,the thickness error and surface roughness of the finished side wall are all compared and analyzed.It is proved that the machining quality and precision of the side wall can be improved by the auxiliary support of the air jet.更多还原