【作者】 孙波；

【导师】 王玉魁；

【作者基本信息】 哈尔滨工业大学 ， 机械工程， 2022， 硕士

【摘要】 颗粒增强的金属基复合材料在航空航天航天、精密仪器的制造等领域有着广阔的发展前景,而在这些材料之中,SiCp/Al材料以其优异的性能受到了广泛的关注。由于SiCp/Al硬度大,耐磨损,加工困难,尤其是在微细加工领域,采取微铣削等常规的加工方式会导致刀具磨损严重,加工成本较高,因此要降低SiCp/Al的加工成本可以采取特种加工的方式,比如电火花加工。但由于电火花加工的表面质量较差,且加工过程中产生的重铸层会影响材料的力学性能,因此,为了高效且低成本的加工SiCp/Al,本文开展了针对SiCp/Al的微细电火花加工和表面重铸层去除工艺的研究。本文首先进行了针对SiCp/Al材料的单因素单脉冲实验仿真,利用生死单元法对高于熔点的单元进行去除,探究不同参数下材料的去除机理,发现模型中不同位置被去除的单元数量量会随着增强颗粒密度的不同而变化。为获得更准确的凹坑尺寸结果,对颗粒增强模型进行均质化处理,使用同样的放电参数对均质化的模型进行仿真,得到了更准确的凹坑理论尺寸。对SiCp/Al材料进行单脉冲电火花放电实验并用钛合金材料进行对照,实验数据与仿真结果之间的误差小于10%,验证了仿真结果,获得了不同参数对SiCp/Al材料加工过程的影响。对SiCp/Al进行了一系列连续脉冲的仿真,通过颗粒增强的模型对SiCp/Al在微细电火花加工过程中的材料蚀除机理进行仿真模拟,并通过均质模型对材料的去除率和表面质量进行模拟,再通过微细电火花铣削的实验对仿真参数进行验证。实验发现由于长脉宽大电流的参数下电极的积碳增加,因此可以减小电极相对损耗;在电镜下观察工件的加工侧面并确定重铸层的最大厚度小于20μm,为重铸层的去除确定了参数。采取微铣削的方式对电火花加工过的表面进行加工,通过三组单因素实验分别确定铣削深度、主轴的转速以及进给速度对SiCp/Al工件加工表面的粗糙度的影响。实验证明铣削深度对加工表面的粗糙度影响最明显,且当铣削深度超过重铸层厚度时粗糙度显著增加。通过微细电火花和微铣削组合的工艺加工SiCp/Al样件,大大提高了效率,证明该工艺可以在保证较高的加工效率的情况下得到较高表面质量的工件。更多还原

【Abstract】 Metal matrix particle reinforced composites have broad application prospects in aerospace,precision instruments,electronic packaging and other fields.Among them,SiCp/Al materials have attracted extensive attention because of their excellent properties.Because SiCp/Al is hard,wear-resistant and difficult to process,especially in the field of micro machining,conventional processing methods will lead to severe tool wear and high processing cost.Therefore,to reduce the processing cost of SiCp/Al,special processing methods can be adopted,such as spark processing.However,the surface quality of EDM is poor,and the recast layer produced in the machining process will affect the mechanical properties of the material.Therefore,in order to process SiCp/Al with high efficiency and low cost,the process of micro EDM and surface recast layer removal for SiCp/Al is studied in this paper.In this paper,the single factor single pulse experimental simulation for SiCp/Al material is carried out firstly.The elements above the melting point are removed by using the birth and death element method,and the removal mechanism of the material under different parameters is explored.It is found that the number of elements removed at different positions in the model will change with the density of reinforced particles.In order to obtain more accurate pit size results,the model is normalized,and the homogeneous model is simulated under the same parameters to obtain more accurate pit theoretical size.The single pulse EDM experiment of SiCp/Al material is carried out and compared with titanium alloy material.The simulation results are verified by the experimental data,and the effects of different parameters on the machining process of SiCp/Al material are obtained.Before the experiment of micro EDM milling,in order to reduce the number of experiments and save the cost,a series of continuous pulses were simulated for SiCp/Al.The material removal mechanism in the EDM process of SiCp/Al materials was simulated through the model of random particle distribution,and the material removal rate and surface quality were simulated through the homogeneous model.Then the simulation parameters were verified through the experiment of micro EDM milling.It is found that the relative electrode loss can be reduced due to the increase of carbon deposition at the electrode under the parameters of long pulse width and large current;Observe the machined side of the workpiece under the electron microscope and confirm that the maximum thickness of the recast layer is less than 20 μm.The parameters are determined for the removal of recast layer.The surface machined by EDM is machined by micro milling.The effects of milling depth,spindle speed and feed speed on the machined surface roughness of SiCp/Al workpiece are determined through three groups of single factor experiments.Experiments show that the milling depth has the most obvious effect on the roughness of the machined surface,and the roughness increases significantly when the milling depth exceeds the thickness of the recast layer.The efficiency of machining SiCp/Al samples by micro EDM and micro milling is greatly improved.It is proved that this process can obtain high surface quality workpieces under the condition of ensuring high machining efficiency.更多还原