Research on the Rotary Ultrasonic Facing Milling of Ceramic Matrix Composites

AbstractCeramic matrix composites (CMC) has got increasing importance in many fields of industry, especially in the aerospace. However, due to the special properties, the conventional machining methods are generally very challenging for CMC. The rotary ultrasonic machining (RUM) is a high efficiency processing technology for these advanced materials. This paper carried out research on the rotary ultrasonic facing milling of C/SiC and developed the cutting force simulation software to optimize the cutting parameters. Verification experiments were conducted showing that the efficiency improved by RUM is 5.8 times while the surface quality is improved by 54.4% compared with the conventional milling

A cutting force model based on kinematics analysis for C/SiC in rotary ultrasonic face machining

Ceramic matrix composites (CMC) superior properties and are used in the harsh conditions of high temperature and pressure, in aerospace and other industries. However, due to inhomogeneous and anisotropic properties of the composites, the machining is still challenging to achieve desired efficiency and quality. For advanced materials, Rotary ultrasonic machining is considered as a process with high efficiency technology. The cutting force is a critical factor required to be effectively predicted and controlled to reduce processing defects in composites. In this research, the rotary ultrasonic machining was used for face machining of carbon reinforced silicon carbide matrix composites (C/SiC), with a conical shaped tool. The kinematics between individual diamond abrasive and the workpiece material was analyzed to illustrate the separation characteristics in the cutting area. The condition for the intermittent machining during RUFM was obtained by establishing the mathematical relation between cutting parameters and vibration parameters. The indentation fracture theory was adopted to calculate the penetration depth into the workpiece by diamond abrasives in the RUFM. The relationship of cutting force and processing parameters including spindle speed, feed rate, and cutting depth were investigated. The comparison of the experimental and simulation data of the cutting force, showed that most of the tests, the errors were below 15 %. It is therefore stipulated that the cutting force model developed in this paper can be applied to predict cutting forces and optimize the process in the RUFM of C/SiC

Grinding of TiC particle-reinforced steel-matrix composite GT35 with small diameter grinding rods

Side milling experiments with small diameter grinding rods were carried out on TiC particle-reinforced steel-matrix composite to investigate the reasonable machining parameters and the cooling and lubrication conditions for this material, and to understand the influence of machining parameters on cutting forces, surface quality and tool wear. The results show that dry cutting and water-based synthetic grinding fluids lubrication are not as effective as extreme pressure grinding oil lubrication, especially that dry cutting causes tool burn. With extreme pressure grinding oil lubrication, the tool wear is stable after 12 minutes of continuous grinding, the main wear forms of which are fracture of abrasive grain wear, abrasive grain breakage and abrasive grain shedding. It is also found that the influence of spindle speed on cutting force is greater than that of feed speed, namely higher spindle speed leading to smaller cutting force, and that the machined surface roughness is mainly related to the level of tool abrasive grain but less affected by spindle speed and feed speed. In conclusion, when grinding TiC particle-reinforced steel-matrix composites, the conditions of extreme pressure grinding oil lubrication, high spindle speed and medium feed rate are recommended to obtain good tool life, surface quality and appropriate processing efficiency

An Eight-Zonal Piezoelectric Tube-Type Threaded Ultrasonic Motor Based on Second-Order Bending Mode

In order to reduce the driving voltage and gain better output characteristics of piezoelectric actuators, an eight-zonal piezoelectric tube-type threaded ultrasonic motor based on two second-order bending modes was analyzed using the method of finite element analysis (FEA), and a prototype was fabricated and experimentally studied in this research. This piezoelectric motor was designed to be excited by four electrical sources applied simultaneously to four groups of electrodes on the customized lead zirconate titanate (PZT) tubular stator (inside diameter 5.35 mm, outside diameter 6.35 mm, length 30 mm), with ±90° phase shifts between adjacent electrodes. Experimental results show that the threaded motor could output a stall force (stall force means the output pull or thrust force when the linear speed is set to be zero) of about 5.0 N and a linear velocity of 4.9 mm/s with no load at the driving voltage of 40 Vpp (Vpp means the peak-to-peak value of the voltage volts). This piezoelectric motor with a compact structure and screw drive mechanism shows relatively fine velocity controllability and has huge superiority in micro-positioning systems

Three dimensional chatter stability prediction based on the exponential cutting force model

International audienceChatter stability prediction is widely used to avoid chatter which restricts the machining quality and productivity. A lot of works have been done to predict the stability chart fast and accurately. However, most of them are based on the linear force model, and the chatter stability limits is formulated as independent on the feedrate, which does not conform to the reality well. This paper intends to investigate the chatter stability prediction based on the exponential force model, which is linearized by the Taylor equation when calculating the directional coefficients. Meanwhile, the stability model is extended to the three dimensional, which is especially applicable for the ballend mills, bull-nose end mills and inserted cutter where chatter may be brought up in Z direction. Simulation results show that the exponential force model agrees with the measurements as well as the linear force model in the cutting force prediction, and it is able to demonstrate the effect of the feedrate on the stability limit

Study on removal mechanism of steel bonded cemented carbide material GT35 in cutting process

Single particle diamond cutting experiments are designed to research the micro scratching process and material removal mechanism of GT35 steel bonded cemented carbide. The value of linear scale coefficient k is estimated as well. The exact value of k is further confirmed by equal depth cutting experiment. Furthermore, the material removal approaches at different cutting depths are discussed by microscopic observation and three-dimensional morphology modeling by SEM and laser confocal microscope. It is observed that there is a linear functional relationship between cutting force and groove cross-sectional area. k (Fx) is 0.026 29 N/μm2(R2=0.990 46) and k (Fz) is 0.046 42 N/μm2(R2=0.994 08) after fitting. The quenched and tempered GT35 material is mainly plastic removal under various cutting depths, in which the bottom surface of the groove shows an obvious plastic shear removal state, and the edge shows a certain brittle removal state. During the cutting process, there will form a material stacking dead zone at the tool tip, causing tool edge collapse and wear. The formation of the surface morphology is closely related to tool wear

Research on Rapid and Accurate Fixture Design for Non-Intervention Machining of Complex Parts

Aerospace parts have the characteristics of complex shape and high machining accuracy, the machining processes of which is complicated and diverse. Numerous special tooling fixtures need to be designed to ensure the smooth implementation of the machining process. In particular, the cabins of the aircraft have thin-walled, weakly rigid, complex, and special-shaped curved structures, the clamping alignment of which is difficult because of a great deal of human influence and poor versatility. In response to the above problems, off-machine clamping technology was investigated, which supports the non-intervention processing of flexible production lines. Then, a scheme suitable for accurate transmission of benchmarks was proposed. A cabin’s mathematical model of casting clamping force analysis was established. Immediately afterwards, the optimization of clamping project was realized by a finite element analysis method based on clamping force and deformation control. The off-machine clamping scheme was designed to realize rapid positioning and accurate datum transmission between flexible tooling and parts, flexible tooling, and equipment. Finally, the designed scheme was implemented through a case to verify its feasibility

Analysis and Experimental Research of a Multilayer Linear Piezoelectric Actuator

To lower the operating voltage and improve the output performance of piezoelectric actuators, a multilayer monolithic ultrasonic linear piezoelectric actuator was analyzed with the method of finite element analysis (FEA), and a prototype was fabricated and experimentally researched in this study. Experimental results show that the actuator with a multilayer piezoelectric lead zirconate titanate (PZT) structure (size: 30 × 7.5 × 3 mm3, mass: 5.49 g) can output a pulling force of 5.0 N maximum and a linear velocity up to 270 mm/s at the voltage of 100 Vpp (Vpp means the peak-to-peak value of the voltage volts), showing a relatively good velocity controllability at the same time. The temperature rise characteristic of the actuator at various voltages was studied. The results indicate that: the temperature of this actuator rises rapidly but tends to saturate at some value; applying an offsetting voltage or decreasing the amplitude of the voltage would reduce the heat production