激光超声复合精密切削硬质合金材料的机理研究

发布时间：2018-05-24 15:10

本文选题：硬质合金 + 激光超声复合切削　；参考：《河南理工大学》2016年博士论文

【摘要】：采用单晶金刚石刀具,普通切削加工硬质合金材料时,因连续切削且金刚石刀具红硬性差,影响刀具使用寿命,加工表面容易出现脆性裂纹,质量难以保证;采用金刚石砂轮对硬质合金进行磨削加工时,为了进一步提高工件精度并减轻磨削痕迹,需进行多次超精加工,制造成本高昂,且难以达到现代工业对加工效率、复杂度和精度的要求。为改善硬质合金材料的切削加工性能,实现高效延性精密加工,本文提出一种新型复合切削技术—激光加热与超声振动辅助复合切削(简称激光超声复合切削)来精密加工硬质合金。首先,建立激光超声复合下的硬质合金材料的非局部损伤模型,描述振动参数、温度参数与非局部核函数中的内部特征参数的联系,仿真一维杆在超声激励下的应变局部化,进行激光超声复合下的试件轴向拉伸有限元仿真。其次,分析变幅杆上所开斜槽的结构参数对变幅杆振幅与谐振频率的影响,依据影响规律设计变幅杆,进行切削实验,基于获得的切削力和工件表面质量,选出合适的变幅杆,完成激光超声复合切削实验平台的搭建。接着,建立激光超声复合下的硬质合金的脆性—延性转变临界切削深度模型,分析加工模式、切削参数、加热温度、硬质合金材料性能对临界切深的影响,并研究材料去除方式的转变对表面质量的影响。最后,建立复合切削硬质合金时的切削力理论模型,分析激光超声复合精密切削硬质合金时的切削力特性,研究激光超声复合精密切削硬质合金时的刀具磨损及其对表面质量的影响。研究结果表明:超声激励与材料温度的提升会加剧应变局部化现象,材料局部软化程度更加明显,使得激光超声复合精密切削模式下的硬质合金脆性—延性转变临界切深远大于超声椭圆振动精密切削模式与传统加工模式,切削力显著降低。超声波振幅与频率越大,加热的温度越高,刀具刃口半径越小与材料中的Co含量越高,脆性—延性转变临界切深值越大,切削力越小,刀具磨损程度越轻,加工表面质量越好,表面粗糙度值越小。当超声椭圆振动的共振频率f为35KHz与纵向振幅为2.1μm时,硬质合金的脆性—延性转变临界切深在切削速度v=10m/min附近达到峰值。激光超声复合切削可以增加延性域切削,提高硬质合金的切削加工性能,切削过程更稳定,实现精密加工硬质合金的目的。
[Abstract]:When single crystal diamond tool is used, when cutting cemented carbide material, it is difficult to guarantee the quality because of the continuous cutting and poor red hardness of diamond tool, which affects the tool service life and the brittle crack on the machined surface. In order to further improve the precision of the workpiece and reduce the trace of grinding, it is necessary to carry out several super-finishing machining when grinding cemented carbide with diamond grinding wheel. The manufacturing cost is high, and it is difficult to achieve the efficiency of modern industrial machining. Complexity and accuracy requirements. In order to improve the cutting performance of cemented carbide material and realize high efficiency ductility precision machining, In this paper, a new type of compound cutting technology, laser heating and ultrasonic vibration assisted composite cutting (LASC), is proposed for precision machining of cemented carbides. Firstly, the nonlocal damage model of cemented carbide materials under laser ultrasonic recombination is established, the vibration parameters, the relationship between temperature parameters and internal characteristic parameters in nonlocal kernel function are described, and the strain localization of one-dimensional bar under ultrasonic excitation is simulated. The axial tensile finite element simulation of the specimen under laser ultrasonic composite is carried out. Secondly, the influence of structural parameters of sloping slot on amplitude change rod and resonant frequency is analyzed. According to the law of influence, the variable amplitude rod is designed and cutting experiment is carried out. Based on the obtained cutting force and the surface quality of workpiece, the appropriate amplitude change rod is selected. The experimental platform of laser ultrasonic combined cutting is built. Then, the critical cutting depth model of brittle ductility transition of cemented carbide under laser ultrasonic recombination is established, and the effects of machining mode, cutting parameters, heating temperature and cemented carbide material properties on critical cutting depth are analyzed. The influence of the change of material removal mode on the surface quality was also studied. Finally, a theoretical model of cutting force in composite cutting of cemented carbide is established, and the cutting force characteristics of laser ultrasonic combined precision cutting of cemented carbide are analyzed. The tool wear and its influence on the surface quality of cemented carbide were studied. The results show that the phenomenon of strain localization will be aggravated by ultrasonic excitation and the increase of material temperature, and the local softening degree of the material will be more obvious. The critical shear of brittle ductility transition of cemented carbide under laser ultrasonic combined precision cutting mode is more profound than that of ultrasonic elliptical vibration precision cutting mode and traditional machining mode, and the cutting force is obviously reduced. The larger the amplitude and frequency of ultrasonic wave, the higher the heating temperature, the smaller the cutting edge radius and the higher the Co content in the material, the greater the critical cutting depth of brittleness and ductility transition, the smaller the cutting force, the lighter the wear degree of the tool and the better the quality of the machined surface. The surface roughness value is smaller. When the resonance frequency f of ultrasonic elliptic vibration is 35KHz and the longitudinal amplitude is 2.1 渭 m, the critical shear depth of brittleness ductility transition of cemented carbide reaches its peak near the cutting speed v=10m/min. Laser ultrasonic combined cutting can increase the ductility of cutting, improve the cutting performance of cemented carbide, and the cutting process is more stable, so the purpose of precision machining of cemented carbide can be realized.
【学位授予单位】：河南理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG506.7;TG66

【相似文献】