超声激励复频加工机理分析及实验研究

发布时间：2018-05-26 07:39

本文选题：陶瓷材料 + 超声激励复频加工　；参考：《太原理工大学》2017年硕士论文

【摘要】：陶瓷等硬脆材料以其高熔点、高硬度、高耐磨性、耐氧化、密度小等优点,广泛应用于各个领域,但也使得其加工变得十分困难。为解决传统加工方法中效率低、成本高、表面损伤、精度低、导电性要求较高和加工质量差的缺点,本文将超声激励复频加工技术应用于陶瓷加工中,提出了超声激励复频加工方法,该加工方法是在传统超声加工的基础上,引入自由质量,自由质量作低频振动,高、低频振动共同驱使钻头完成切削。本文首先介绍了超声激励复频加工的运动规律和特点,在此基础上分析了自由质量、变幅杆输出端和钻头三者在碰撞过程中位移和速度的变化情况,得出自由质量通过碰撞可以改变变幅杆和钻头的振幅,从而使振动能量更加有效地传递到钻头;建立了加工系统的数学模型,根据一维纵向振动方程和冲击振动理论,推导了钻头的动应力方程,即自由质量的厚度与钻头的动应力有关,并且两者呈正相关;利用压痕断裂力学模型,探究了材料去除机制,发现随着钻头动应力的增加,裂纹的生成速度、数目和扩展速度也随着增加。通过分析自由质量的运动形式,得到了自由质量的振动频率公式,发现其振动频率与厚度有关,而且当振动范围不变时,厚度越大振动频率越高;并根据能量守恒得出,钻头的平均振动功率能够达到3310 W,较换能器的机械功率高出15倍,结果说明自由质量可以将高频振动转换为低频、高功率的机械冲击运动;利用频率测量设备,分别测得不同自由质量的振动频率,发现自由质量同时以多种频率在振动,并且振动频率随着厚度的增加而增加;厚度4.5 mm自由质量的平均振动频率约为6311.4 Hz,为厚度3.5 mm自由质量的3倍,与理论分析结果相一致。基于弹簧质量模型,分析了自由质量的运动过程,发现自由质量能够极大地提高钻头的振动能量;为验证自由质量对加工效果的影响,开展了超声激励复频加工陶瓷实验,测得不同自由质量厚度条件下的材料去除率,发现相对于传统超声加工,4.5 mm的自由质量能够使材料去除率提高5倍,并且避免了表面损伤;此外,随着厚度的增加,材料去除率呈增长趋势,且增长速度越来越快,其平均增长速度达到91(mg/min)/mm。为研究材料去除率的变化规律及影响因素,对自由质量厚度、外径和加工时间三因素进行了正交实验,发现自由质量厚度的极差最大,为77.7mg/min,说明自由质量厚度对材料去除率的影响最为显著,并且厚度越大材料去除率越高;材料去除率随外径的增加,其近似成线性增长;加工时间越长,材料去除率越高,并且增长速度越来越快。
[Abstract]:Ceramics and other hard brittle materials are widely used in various fields because of their advantages of high melting point, high hardness, high wear resistance, oxidation resistance and low density, but also make it very difficult to process. In order to solve the disadvantages of low efficiency, high cost, surface damage, low precision, high electrical conductivity and poor machining quality in traditional machining methods, this paper applies ultrasonic excitation complex frequency machining technology to ceramic machining. The ultrasonic excitation complex frequency machining method is put forward. The machining method is based on the traditional ultrasonic machining. The free mass and free mass are introduced for low frequency vibration. The high and low frequency vibration together drive the bit to complete the cutting. In this paper, the motion law and characteristics of ultrasonic excited complex frequency machining are introduced, and the displacement and velocity of free mass, output end of amplitude lever and bit during collision are analyzed. It is concluded that the free mass can change the amplitude of the horn and bit by collision, so that the vibration energy can be transferred to the drill more effectively, and the mathematical model of the machining system is established, which is based on the one-dimensional longitudinal vibration equation and the shock vibration theory. The dynamic stress equation of the bit is derived, that is, the thickness of the free mass is related to the dynamic stress of the bit, and there is a positive correlation between them, and the mechanism of material removal is explored by using the indentation fracture mechanics model, and it is found that with the increase of the dynamic stress of the bit, The rate of crack formation, the number of cracks and the propagation rate also increase. By analyzing the motion form of free mass, the formula of vibration frequency of free mass is obtained. It is found that the vibration frequency is related to thickness, and when the vibration range is constant, the greater the thickness of vibration is, the higher the vibration frequency is, and according to the conservation of energy, The average vibration power of the bit can reach 3310 Ws, which is 15 times higher than the mechanical power of the transducer. The result shows that the free mass can convert the high frequency vibration into the low frequency and high power mechanical impact motion. The vibration frequencies of different free masses are measured, and it is found that the free mass vibrates simultaneously with a variety of frequencies, and the vibration frequency increases with the increase of the thickness. The average vibration frequency of 4.5mm free mass is about 6311.4 Hz, which is 3 times of the thickness of 3.5mm free mass, which is consistent with the theoretical analysis. Based on the spring mass model, the movement process of free mass is analyzed, and it is found that free mass can greatly improve the vibration energy of drill bit. It is found that the free mass of 4.5 mm in ultrasonic machining can increase the material removal rate by 5 times and avoid the surface damage with the increase of the thickness, and the material removal rate under different free mass thickness can be increased by 5 times, in addition, with the increase of the thickness, the material removal rate can be increased by 5 times, and the surface damage can be avoided. The material removal rate showed an increasing trend, and the growth rate was faster and faster. The average growth rate of the material removal rate was 91 mg / min / m ~ (-1) 路min ~ (-1) 路m ~ (-1). In order to study the change law of material removal rate and its influencing factors, the orthogonal experiments were carried out on three factors, free mass thickness, outer diameter and processing time, and it was found that the maximum difference of free mass thickness was found. It is 77.7 mg / min, which shows that the free mass thickness has the most significant effect on the material removal rate, and the larger the material thickness is, the higher the material removal rate is, and the material removal rate increases linearly with the increase of external diameter, and the longer the processing time, the higher the material removal rate. And growing faster and faster.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ174.6

【参考文献】