铣削加工参数对SiCp/Al复合材料表面粗糙度的影响

文摘SiC_p/Al复合材料在切削加工中存在严重的表面质量问题。本文设计单因素试验,采用硬质合金涂层刀具对SiC_p/Al复合材料进行铣削加工,研究了加工参数对表面粗糙度的影响。结果表明:表面粗糙度随切削速度的增大先增大后减小,随进给量、径向切深、轴向切深的增大而增大;使用较大的切削速度、较小的进给量和不大于4 mm的径向切深能获得较好的加工表面质量。     

SiCp/Al复合材料切削仿真研究

文摘针对SiC_p/Al复合材料的难加工性,建立了二维有限元切削模型,利用ABAQUS完成复合材料正交切削的动态物理仿真。通过仿真与实验结果的比较,验证模型的准确性。同时,利用该切削模型分析颗粒分布形式、直径及刀尖圆弧半径对切削力的影响。结果表明,SiC颗粒的分布形式对切屑形态和切削力具有明显的影响,颗粒形成团簇不利于复合材料加工。切削力随颗粒直径的增大而减小,随刀尖圆弧半径的增大而增大。     

金刚石涂层刀具钻削高比分SiC_p/Al复合材料试验研究

SiC_p/Al复合材料与传统的金属材料相比,具有优异的物理和热学性能。但在孔加工中,棱边加工缺陷成为影响其在高端产品中使用的主要问题之一。开展金刚石涂层刀具钻削SiC_p/Al复合材料的试验研究,对试验力学信号进行分析,对出入口棱边缺陷形成机理及形貌特征做出了解释。结果表明:使用金刚石涂层刀具钻削SiC_p/Al复合材料时,每步钻削深度、进给速度和主轴转速对轴向力的作用依次减弱;出口处质量明显优于入口处,入口缺陷形成机理主要是Al基体的断裂和SiC颗粒脱落;金刚石涂层钻头适合用于加工SiC_p/Al复合材料。对于SiC_p/Al复合材料的实际加工应用有一定的参考价值。     

切削参数对SiCp/Al复合材料铣削棱边形貌的影响

针对20vol%的SiC_p/Al复合材料的棱边缺陷问题,利用单因素实验对其进行面铣,研究了切削参数对出口棱边形貌的影响。研究结果表明:出口棱边形貌受铣削速度变化的影响较大,在低速(40和80 m/min)和高速(200 m/min)时棱边形貌均较好;当进给量为0.02和0.04 mm/r时,出口棱边主要存在毛刺。随着进给量的不断增大,棱边出现了严重的缺陷和表层剥落,之后棱边又以少量的毛刺和缺陷为主。当只改变轴向切深时,出口棱边均会出现严重的缺陷,只改变轴向切深对改善棱边形貌质量效果不显著。因此,当铣削速度为低速或高速、进给量较小且轴向切深适中时,SiC_p/Al才能获得较好的出口棱边形貌。     

SiC_p/Al复合材料内螺纹螺旋磨削加工方法研究

铝基碳化硅颗粒增强型复合材料(SiC_p/Al复合材料)切削加工性能较差,其内螺纹的切削加工难度更大。在研究SiC_p/Al复合材料磨削加工性能的基础上,提出利用电镀超硬磨料成形砂轮进行SiC_p/Al复合材料内螺纹螺旋磨削加工的工艺方法,并研制了电镀CBN成形砂轮,进行了具体的内螺纹磨削试验。试验结果验证了SiC_p/Al复合材料内螺纹螺旋磨削加工方法的可行性和灵活性。在砂轮线速度v_s=5.86m/s、进给速度v_f=80mm/min的条件下,CBN成形砂轮对SiC_p/Al复合材料展现出较好的磨削能力,单个砂轮可以完成17个M8螺纹孔的螺旋磨削加工,其内螺纹的加工尺寸精度均满足6H塞规的检测要求。同时,电镀CBN砂轮的磨损形式以磨粒磨损为主,砂轮表面未出现大面积脱落的现象。这说明,利用超硬磨料成形砂轮可以实现SiC_p/Al复合材料内螺纹的高效高质量加工,此工艺方法具有较高的工程应用价值,适于在实际生产中推广应用。     

SiCp/Al复合材料低损伤表面切削加工研究与进展

SiC_p/Al复合材料属于典型的难加工材料,其SiC颗粒增强相的存在使得切削加工时材料已加工表面极易出现基体撕裂、微裂纹、微空穴等缺陷。为了实现SiC_p/Al复合材料的高效低损伤加工,从切屑形成机制、表面完整性和刀具磨损等方面总结SiC_p/Al复合材料切削加工性能及其影响因素,研究表明,该材料增强相颗粒去除方式和去除机理对表面形成过程影响显著;探讨了SiC_p/Al复合材料塑性域加工机理和塑脆转换临界条件获取方面的研究进展,综述了表征SiC_p/Al动态力学性能的宏微观建模方法,分析了多尺度多相耦合切削加工有限元仿真的热点和难点问题;指出了低温微切削、超声辅助微切削、激光辅助微切削等是实现SiC_p/Al复合材料协调变形和塑性域加工工艺条件的发展方向。     

高体分SiCp/Al复合材料表面吸附氦气特性

针对高体分SiC_p/Al复合材料气密性问题,系统研究了镀覆、原材料方向性对表面氦气吸附性能影响规律。研究发现该材料经镀覆处理后,其表面氦气吸附合格率提高20%,且随着镀层厚度的增加合格率逐渐提高;不同的机械加工方式对表面氦气吸附合格率影响较小;原材料存在方向各异性,横向切削下料方式下氦气吸附合格率高达91%,纵向切削下料方式下合格率仅为68%。     

使役条件下SiC_p/Al复合材料的建模拟实

基于有限元方法,通过Python语言开发了SiC_p/Al复合材料的参数化建模程序,利用ABAQUS图形用户界面(GUI)完成了建模过程的可视化,搭建了颗粒的大小、形状、体积含量和分布可控的快速建模拟实平台。利用此平台建立了SiC_p/Al复合材料基于微细观的代表性体积单元(RVE)有限元模型,并先后引入了颗粒的弹脆性断裂行为、基体的弹塑性断裂损伤行为和界面的拉伸-开裂行为,实现了SiC_p/Al复合材料的变形和断裂的全过程模拟。为研究使役条件下SiC_p/Al复合材料的构效关系,建立了颗粒体积含量为7%和14%的复合材料有限元模型,首先研究了拉伸过程中颗粒体积含量对复合材料变形和损伤行为的影响;然后将体积含量为7%的复合材料模拟压缩过程与拉伸过程进行对比,分析了在不同载荷条件下复合材料的变形和损伤机理。实践证明,所建立的SiC_p/Al复合材料参数化建模平台可用于颗粒增强金属基复合材料基于微细观的有限元建模,对复合材料强韧化机理分析和构效关系研究具有重要的价值。     

原位自生TiB2/Al基复合材料的制备及性能

在合金的基础上进一步引入纳米陶瓷颗粒,从而制备出颗粒增强金属基复合材料,是提高金属材料综合性能的重要手段。本文从原位自生TiB_2/Al基复合材料的制备方法、不同加工工艺下复合材料的微观组织、复合材料的力学性能三个方面总结了其研究现状,同时展望了原位自生TiB_2/Al基复合材料的发展方向。通过原位自生方法制备出的TiB_2颗粒增强铝基复合材料具有颗粒尺寸小、与基体界面结合良好等优点。通过合金化设计、热加工塑性变形、快速凝固工艺可进一步改善纳米陶瓷颗粒的分散性。相对于外加法制备的金属基复合材料,原位自生TiB_2/Al基复合材料具有更加优异的力学性能,如弹性模量、强度、抗疲劳性能、抗蠕变性能等。     

基于高体积分数SiC/Al复合材料的零件加工质量提升实践

对某机载光电产品中典型零件,从加工刀具、切削参数、工装设计等方面进行了SiC/Al复合材料的加工工艺研究,得出了一套SiC/Al复合材料的加工工艺方法,提高了SiC/Al复合材料的加工质量,为航空新材料应用做出有效探索。     

Simulation of temperature distribution and discharge crater of SiCp/Al composites in a single-pulsed arc discharge

SiC_p/Al composites are difficult-to-cut materials. In recent years, electrical arc discharge machining has been developed to improve the machinability of these materials. However, there is a big challenge to build a satisfactory heat transfer model of SiC_p/Al composites in the arc machining. This is not only because of the material property difference between the reinforcement and matrix material but also because of the micro-dimension SiC reinforcements. This paper established a new heat conduction simulation model considering the SiC particle-Al matrix interface and the phase change effects in a single-pulsed arc discharge of SiC_p/Al composites. A novel SiC particle-Al matrix cell geometric model was designed firstly. Then, the temperature distribution at a different depth from the workpiece surface was analyzed, the influence of sic volume fraction on temperature field was studied, and the contribution of the interface thermal resistance and latent heat were explained. To demonstrate the validity of the new numerical model, comparisons and verifications were employed. Finally, the method of improving the model was proposed and the machining mechanism of arc discharge of SiC_p/Al matrix materials was discussed. It was found that high temperature is prone to concentrate on the surface layers of the workpiece especially when the SiC fraction is high, also, the temperature fluctuates respectively at the evaporation point of aluminum and SiC, and the SiC-Al resistance has less influence on temperature distribution compared to latent heat, etc. The model build in this work improves the simulation accuracy observably compared to the previous model, and the simulation work will help to acquire a detailed mechanism of material removal of SiC_p/Al composites in the arc discharge machining.     

Modeling high-speed cutting of SiCp/Al composites using a semi-phenomenologically based damage model

In this paper, we attempts to investigate cutting mechanisms in high-speed cutting of Al6061/SiC_p/15p composites using a semi-phenomenologically based damage model in the equivalent homogeneous material (EHM) framework. By combining macroscale EHM modeling and underlying microscale physical mechanisms, a feasible semi-phenomenological plastic model is proposed for prediction of cutting forces and chip morphology during high-speed turning Al6061/SiC_p/15p composites. This model incorporates the modified Weibull weakest-link effect to represent the strain-based damage evolution in large deformations. This proposed semi-phenomenological constitutive model is implemented by compiling material subroutines into cutting finite element (FE) codes. The effects of the critical shear stresses on chip formation that depend on the tool-chip frictional coefficient are accounted for in the cutting FE model. The chip formation mechanism affecting material removal behaviors during high-speed turning is further investigated. The capabilities of the proposed constitutive model are evaluated by comparing cutting forces and chip morphologies between experiments and simulations at different cutting speeds associated with strain rates. The EHM-based and microstructure-based models are further compared in both computational efficiency and accuracy. The simulation results show that the developed semi-phenomenological constitutive formalism and cutting model are promising and efficient tools for further investigation of dynamic mechanical and cutting behaviors of particle-reinforced composites with different volume fraction and particle size.     

SiC_(f)/SiC复合材料铣削加工表面质量北大核心CSCD

使用PCD立式铣刀对聚合物浸渍裂解法(PIP)制备的SiC_(f)/SiC复合材料开展单因素铣削试验,通过对加工中产生的切削力和加工后的表面粗糙度进行测量,分析了铣削工艺参数对其的影响;对加工表面、纤维断口进行SEM分析,讨论了SiC_(f)/SiC复合材料加工表面的形成。研究结果表明,表面粗糙度与切削力的变化趋势相同,高主轴转速和小切削宽度有利于得到表面粗糙度较小的加工表面;近孔洞区域与远离孔洞区域的材料去除方式不同;材料中纤维发生面内偏移和层间屈曲,纤维存在多种去除方式。     

Study on the Fracture Behavior of SiCp/LD10 Composites by Means of In-situ SEM

With tensile loading under SEM, the nucleation, p ropagation of cracks to fracture of SiC_p/LD10 composites were observed dynamically. It was di scovered that cracks nucleated mainly at the interface of SiC_p/LD10, fractured p articles and original defects. The whole process of crack formation was that mic ro-cracks nucleated, propagated and linked each other in the stress concentrati on zone of the tip of the main crack, then combined in the perpendicular direction of main stress to from a macro-cr ack.     

SiCf/SiC陶瓷基复合材料制孔工艺

分别采用机械钻削制孔与激光制孔两种工艺对SiC_f/SiC陶瓷基复合材料进行制孔,对其质量以及工艺特点进行评价分析。结果表明,机械钻削制孔孔径精度较好但存在刀具磨损严重、出现毛刺崩边现象等问题;激光制孔效率较高,但孔存在锥度且因热影响区的存在导致孔的内壁表面出现分层、裂纹等缺陷。     

Analytical model of cutting force in axial ultrasonic vibration-assisted milling in-situ TiB2/7050Al PRMMCs

Ultrasonic vibration-assisted milling has been widely applied in machining the difficult-to-cut materials owing to the remarkable improvements in reducing the cutting force. However, analytical models to reveal the mechanism and predict the cutting force of ultrasonic vibration-assisted milling metal matrix composites are still needed to be developed. In this paper, an analytical model of cutting force was established for ultrasonic vibration-assisted milling in-situ TiB₂/7050Al metal matrix composites. During modeling, change of motion of the cutting tool, contact of tool-chip-workpiece and acceleration of the chip caused by ultrasonic vibration was considered based on equivalent oblique cutting model. Meanwhile, material properties, tool geometry, cutting parameters and vibration parameters were taken into consideration. Furthermore, the developed analytical force model was validated with and without ultrasonic vibration milling experiments on in-situ TiB₂/7050Al metal matrix composites. The predicted cutting forces show to be consistent well with the measured cutting forces. Besides, the relative error of instantaneous maximum forces between the predicted and measured data is from 0.4% to 15.1%. The analytical model is significant for cutting force prediction not only in ultrasonic-vibration assisted milling but also in conventional milling in-situ TiB₂/7050Al metal matrix composites, which was proved with general applicability.