【作者】 郑伟；

【导师】 周明；

【作者基本信息】 哈尔滨工业大学 ， 航空宇航制造工程， 2017， 博士

【摘要】 碳化硅颗粒增强铝基复合材料(SiCp/Al复合材料)由于其优异的力学性能广泛应用在国防工业和国民经济领域中。然而硬质碳化硅颗粒使得SiCp/Al复合材料具有一系列优异性能的同时,也削弱了SiCp/Al复合材料的塑性、韧性和机械加工性,使其成为典型的难加工材料。采用常规磨削方法加工,加工表面质量差,严重影响了该材料的实际应用。超声振动磨削技术(Ultrasonic Vibration Grinding,UVG)是一种将传统磨削加工与超声振动加工结合在一起的新方法,具有切削力小、切削温度低等技术优势,适宜于难加工材料的加工。开展SiCp/Al复合材料超声振动磨削加工机理及表面质量的研究,对推动该类复合材料的进一步应用具有十分重要的意义。SiCp/Al复合材料超声振动磨削加工时材料的去除是铝合金基体、碳化硅颗粒和两相界面协同变形的结果,由材料本身固有的多相非均质特性所导致的微观力学性能的非均一性将直接影响SiCp/Al复合材料的去除机制和加工表面质量。为研究SiCp/Al复合材料的非均质特性对其微观力学性能的影响,本文基于纳米压痕实验,对SiCp/Al复合材料的微观力学性能进行了测试,分析了压痕变形行为。在此基础上,进行了单颗粒普通刻划实验和超声振动刻划实验。基于刻划力、摩擦系数和刻划表面形貌的分析,研究了在超声振动作用下SiCp/Al复合材料的去除机制,为分析超声振动作用对加工表面质量的影响提供了依据。为研究SiCp/Al复合材料的非均质特性以及两相界面变形行为对加工表面缺陷的影响,本文在SiCp/Al复合材料去除机制研究的基础上,建立了考虑材料非均质特性及两相界面变形行为的SiCp/Al复合材料的微观力学仿真模型,利用ABAQUS软件,结合脚本语言python编程,仿真分析了复合材料已加工表面缺陷的形成机理和超声振动作用对碳化硅颗粒去除的影响。结果表明,碳化硅颗粒的去除形式主要包括翻滚压入、破碎断裂和脱粘拔出三种,碳化硅颗粒的破碎断裂和脱粘拔出形成的凹坑是加工表面的主要缺陷形式。利用扫描电子显微镜对刻划实验加工表面缺陷进行了检测,验证了仿真模型的有效性。研究结果为探索提高SiCp/Al复合材料加工表面质量的技术措施、优选工艺参数提供了依据。磨削力对材料去除过程和加工表面质量有着至关重要的影响。本文基于超声振动磨削加工中磨粒的运动学分析,考虑两相材料的切屑成形特点,分别建立了超声振动磨削SiCp/Al复合材料侧磨磨削力和端磨磨削力的预测模型,并进行了SiCp/Al复合材料超声振动磨削力实验,验证了所建立的磨削力模型的正确性。在此基础上,研究了工艺参数对磨削力的影响规律,为加工表面质量的实验研究中工艺参数的选择提供了依据。在以上研究的基础上,进行了SiCp/Al复合材料超声振动磨削加工表面质量的实验研究。采用三维粗糙度和分形维数综合评价了SiCp/Al复合材料已加工表面形貌,探讨了表面粗糙度、表面缺陷与分形维数之间的关系,以及工艺参数对表面形貌的影响规律。在此基础上,以综合反映SiCp/Al复合材料已加工表面形貌特点的特征参数Scr为优化目标,采用非支配排序遗传算法(NSGA-II)获得了SiCp/Al复合材料超声振动磨削加工的优化工艺参数,并通过加工实验对工艺参数优化方法的有效性进行了验证。研究结果为实现SiCp/Al复合材料超声振动精密磨削加工工艺参数的选择提供了依据。更多还原

【Abstract】 Superior properties make silicon carbide particle reinforced aluminum matrix composites(SiCp/Al composites)being widely used in defense industry and national economic field.However,the addition of SiC particles makes SiCp/Al composites hard to be manufactured due to its extreme abrasive properties.Ultrasonic vibration assisted grinding is a combination of two ordinary material remove processes,i.e.grinding and ultrasonic machining.Compared with other traditional machining methods,this machining method has many advantages,such as lower grinding force and temperature and is suitable for machining of difficult-to-machine materials.Thus,fundamental research on the material removal mechanism and surface finish of SiCp/Al composites in ultrasonic vibration assisted grinding process is of great significance to the further application of this kind of composite materials.The material removal process of SiCp/Al composites is a result of synergetic deformation and interactions among Al matrix,SiC particles and interface under a certain process condition.The non-homogeneity of microscopic mechanical properties due to the inherent polyphase heterogeneity of SiCp/Al composites will directly affect the removal mechanism and surface finish in the machining process.In order to investigate the influence of non-homogeneity of SiCp/Al composites on the microscopic mechanical properties,based on the nanoindentation test,the micromechanical properties of the SiCp/Al composite materials were tested and the deformation behavior was analyzed.On the basis of this,the tradit ional scratch and ultrasonic vibration assisted scratch tests were carried out to analyz scratch force,friction coefficient and curve surface morphology,and investigate the effect of ultrasonic vibration on the material removal mechanism of SiCp/Al compo sites.All of these provide the basis for subsequent research on the influence of the ultrasonic vibration on surface finish.In order to study the heterogeneity properties and the influence of the deformation behavior on the surface defects of SiCp/Al com posites,based on the research of material removal mechanism of SiCp/Al composites,a micromechanics finite element model of SiCp/Al composites was established,in which Al matrix,SiC particles and interface were modeled respectively by using ABAQUS softw are and python language.The formatin mechanism of defects on machined surface and the influence of ultrasonic vibration on the material removal process of SiC particles were simulated by the use of this model.The simulation results show that there were three kinds of material removal modes for SiC particles,including rolled and pulled in Al matrix,fractured and pulled out.As a result of SiC particles being fractured and pulled out,the pit was the main defect on the machined surface.The defects of the machining surface in the scratch tests were analyzed by scanning electron microscopy,and the validity of the simulation model was verified.The results provide a basis for the subsequent evaluation and optimization of the surface finish of SiCp/Al composites.The results provide a basis for the exploration of technical measures to improve the surface finish of SiCp/Al compositesGrinding force has a great effect on the material removal process and machined surface finish.Based on the research of material removal mechanism of SiCp/Al composites and kinematics analysis of ultrasonic vibration assisted grinding,considering the chip forming characteristics of two phase materials,predictive force model in ultrasonic vibration assisted grinding of SiCp/Al com posites is established and verified,which is consist of side grinding force model and end grinding force model.And then,the influence of process parameters on grinding force are investigated,which provides evidence for the selection of process paramete rs in the research on the surface finish.On the basis of above research,the machined surface finish is experimental studied in ultrasonic vibration assisted grinding of SiCp/Al composites.The machined surface topography is evaluated by three dimensional surface roughness and fractal dimension.The relationship between surface roughness,surface defect and fractal dimension,and the influence of process parameters on machined surface are investigated.Finally,setting a new parameter which reflects the ch aracteristics of the machined surface of SiCp/Al composites as the optimization objective,process parameters are optimizated by using nondominated sorting genetic algorithm(NSGA-II),and the experimental results agree well with optimization results.The results of the study provide evidence for the selection of process parameters in ultrasonic vibration grinding of SiCp/Al composites.更多还原