Rotary ultrasonic machining of difficult-to-machine materials: experimental and theoretical investigations

Doctor of PhilosophyDepartment of Industrial & Manufacturing Systems EngineeringZhijian PeiMeng (Peter) ZhangHigh-performance materials such as composite materials, metal alloys, and advanced ceramics are attractive to engineering applications in aerospace, automobile and sport industries. Materials with superior properties are often difficult-to-machine due to their high strength, high hardness, and high toughness, which make the cutting force and temperature at the cutting interface very high and result to a short tool life. This limits their market expansion due to the high cost of machining with current machining procedures. However, the demand for high-performance materials is increasing in certain industries such as aerospace and automotive. In addition to machining of high performance materials, some of the conventional materials such as rocks also can be categorized into difficult-to-machine materials. Some causes which made rock drilling complicated are expose to several rock types in a single drilling, an infinite variability of rock properties, relatively high hardness and high abrasiveness of rocks, friction between rock and tool, severe wear and damage to tools etc. Therefore, it is crucial to develop more cost-effective machining processes for difficult-to-machine materials. Rotary ultrasonic machining (RUM), a hybrid non-traditional machining process combining the material removal mechanisms of abrasive grinding and ultrasonic machining, has the potential for low-cost and high quality machining of difficult-to-machine materials. Researchers have shown that RUM can attain a higher material removal rate than both ultrasonic machining (USM) and grinding. RUM can also drill deep holes with high accuracy, improved surface finish, and low cutting force and torque. The objectives of this research are to investigate the relationships between input variables and output variables of RUM of difficult-to-machine materials, to study the measurement methods of ultrasonic vibration amplitude and the effects of tool natural frequency on ultrasonic vibration amplitude, and to model RUM of rocks. In this dissertation, research has been conducted by experimental, numerical, and theoretical investigations on output variables including cutting force, torque, surface roughness, edge chipping, and delamination. The goal of this research is to provide new knowledge based on machining difficult-to-machine materials on RUM in order to improve the quality of the machined holes while decreasing the machining cost and to study the effects of machining variables (feedrate, tool rotation speed, and ultrasonic power) and tool variables (abrasive size and concentration, tool diameter, and tool geometry) on output variables. This dissertation firstly provides the introduction to difficult-to-machine materials and rotary ultrasonic machining. After that Chapter 2 investigates the effects of input variables on cutting force, torque, and surface roughness, and study the effects of machining variables, tool end angle, and the use of a backing plate on the delamination of RUM of CFRP. Chapter 3 studies the comparison between intermittent RUM and continuous RUM when machining K9 glass from the perspectives of cutting force, surface roughness, and chipping size. Chapter 4 investigates the effects of input variables on cutting force, torque, surface roughness, and edge chipping of the RUM of basalt, travertine, and marble, and development of a mechanistic predictive cutting force model for RUM of rocks based on the ductile mode removal and brittle fracture mode removal of rock under the indentation of a single abrasive particle. Chapter 5 discusses the effects of tool natural frequency on ultrasonic vibration amplitude. Finally, conclusions and contributions on RUM drilling are discussed in Chapter 6

การศึกษาแรงสั่นสะเทือนอัลตร้าโซนิคช่วยในการตัดอะลูมิเนียมหล่อ

บทคัดย่อ การประยุกต์ใช้แรงสั่นสะเทือนอัลตร้าโซนิคในงานกัดสามารถช่วยในการปรับปรุงลักษณะเฉพาะในการขึ้นรูปหลายๆ ด้าน เช่น แรงในการตัดเฉือน ความหยาบผิวของชิ้นงาน และอายุการใช้งานของเครื่องมือตัด อย่างไรก็ตาม จำนวนงานวิจัยในด้านนี้ยังมีอยู่ไม่มากและส่วนใหญ่เป็นการศึกษาวัสดุประเภทแข็งเปราะ ดังนั้น งานวิจัยนี้ได้ขยายขอบเขตการศึกษาในงานกัดอะลูมิเนียมหล่อเกรด A356 ซึ่งมีสมบัติอ่อนเหนียว โดยสร้างแรงสั่นสะเทือนความถี่ 19.74 กิโลเฮิรตซ์ ขนาดแอมพลิจูด 12 ไมโครเมตร ส่งผ่านให้กับชิ้นงานในทิศทางการเคลื่อนที่ของเครื่องมือตัด งานกัดถูกทำขึ้นภายใต้เครื่องกัดซีเอ็นซีและดอกเอ็นมิลคาร์ไบด์ขนาดเส้นผ่านศูนย์กลาง 6 มิลลิเมตร กัดแบบร่องปราศจากการหล่อเย็น ผลการทดลองพบว่า อัตราการป้อนสูงขึ้นส่งผลให้ค่าเฉลี่ยแรงตัดเฉือนในแนวระนาบของการใช้แรงสั่นสะเทือนอัลตร้าโซนิคมีค่าน้อยกว่ากระบวนการกัดแบบทั่วไปถึงร้อยละ 13.9 ลักษณะโครงสร้างจุลภาคของพื้นผิวงานหลังประยุกต์แรงสั่นสะเทือนอัลตร้าโซนิคมีการก่อตัวที่เป็นแบบแผนและแตกต่างจากกระบวนการกัดแบบทั่วไป เมื่อความเร็วในการตัดเฉือนเพิ่มสูงขึ้นค่าความหยาบผิวลดลงร้อยละ 21.4 สรุปได้ว่าแรงสั่นสะเทือนอัลตร้าโซนิคสามารถก่อให้เกิดผลกระทบเชิงบวกต่อค่าเฉลี่ยแรงตัดเฉือนและค่าความหยาบผิวโดยขึ้นอยู่กับอัตราการป้อนต่อฟันและความเร็วในการตัดเฉือน - - - Study of Ultrasonic Vibration Assisted Milling of Casted Aluminum  ABSTRACT Ultrasonic vibration-assisted milling (UAM) has been proven to improve machining characteristics such as cutting force, surface roughness quality, and cutting tool life. However, the number of research studies in the field of UAM is very small and mainly focused on hard-brittle material machining processes. Accordingly, to expand UAM research into a wider variety of materials, a study of UAM on a ductile material, A356 Cast aluminum is presented in this research. In the experiment, ultrasonic vibration of 19.74 kHz with an amplitude of 12 µm was applied to the workpiece along cutting feed direction. Besides, CNC machining center and carbide end mill with a diameter of 6 millimeters were used for slot milling under dry cutting condition. Characteristics of cutting force magnitude in end mill revolution, surface topography, and surface roughness were compared between UAM and conventional milling (CM). Experimental results showed that the average horizontal force in cutting direction of UAM was lower than CM at large feed per tooth value by 13.9%. UAM surface topography was different when comparing to CM because ultrasonic vibration assistance enables the generation of a uniformed pattern on the workpiece. Surface roughness was improved by 21.4% when cutting speed increases. It was concluded that UAM application on A356 Cast aluminum material has positive effects on cutting force and surface roughness depending on feed per tooth and cutting speed.

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

Mechanism of crack propagation for K9 glass

In order to study the mechanism of crack propagation, the varied cutting-depth scratch experiment is carried out and smoothed particle hydrodynamics (SPH) simulation method is used to assistant the investigation. The SPH simulation results reveal that crack will propagate in the direction where stress concentration exceeds the fracture toughness of K9 glass. The initial crack length in critical transition depth is calculated by combining the critical stress of fracture and the fracture toughness of K9 glass. Based on the effective plastic strain, the relation between scratching depth and crack depth is obtained. The recovery of crack tip is found and explained from the relationship between cutting depth and crack depth. Using the energy balance theory of Griffith, the variation of material internal energy is revealed. Comparing the scratching forces obtained from experiment and simulation, the validity of simulation results is verified. The phenomenon of crack delayed propagation is found in both experiment and simulation. The explanation of mechanism is given

Experimental investigations on core drilling by ultrasonic-vibration-assisted grinding for hard-to-machine materials - A review

Citation: Qin, N., Lei, J., & Pei, Z. J. (2016). Experimental investigations on core drilling by ultrasonic-vibration-assisted grinding for hard-to-machine materials - A review. International Journal of Manufacturing Research, 11(1), 28-52. doi:10.1504/IJMR.2016.076976Ultrasonic-vibration-assisted grinding (UVAG), a hybrid machining process combining material removal mechanisms of diamond grinding and ultrasonic machining, has been used to machine various hard-to-machine materials. Large amount of research work on UVAG has been carried out since it is invented. However there are few review papers to cover the current literature on UVAG. The emphasis of this literature review is the experimental investigations of the drilling process with ultrasonic vibration using a core drill with metal-bonded diamond abrasives. Experimental results are summarised and compared. The inconsistent results and their reasons are discussed. Furthermore, directions of future research on UVAG are also presented. © 2016 Inderscience Enterprises Ltd

Advances in Micro and Nano Manufacturing: Process Modeling and Applications

Micro- and nanomanufacturing technologies have been researched and developed in the industrial environment with the goal of supporting product miniaturization and the integration of new functionalities. The technological development of new materials and processing methods needs to be supported by predictive models which can simulate the interactions between materials, process states, and product properties. In comparison with the conventional manufacturing scale, micro- and nanoscale technologies require the study of different mechanical, thermal, and fluid dynamics, phenomena which need to be assessed and modeled.This Special Issue is dedicated to advances in the modeling of micro- and nanomanufacturing processes. The development of new models, validation of state-of-the-art modeling strategies, and approaches to material model calibration are presented. The goal is to provide state-of-the-art examples of the use of modeling and simulation in micro- and nanomanufacturing processes, promoting the diffusion and development of these technologies

Investigation on the Machinability in the Micro-Milling of Amorphous Materials

Amorphous materials have been widely used in various industrial areas such as optics, aerospace, sports, and biomedical applications. The fundamental mechanism in machining amorphous materials is different from that in machining metallic materials due to their unique microstructure and mechanical properties. This thesis presents experimental investigations on the machinability in the micro-milling of two typical amorphous materials: Zirconium based bulk metallic glass (Zr-BMG) and BK-7 glass.A three-axis micro-milling machine is developed to perform the machining experiments on Zr-BMG with a spindle speed of up to 105,000 rpm. The effect of cutting conditions on light emission and surface melting in the micro-milling of Zr-BMG is investigated. The microstructure and crystallization of machined surface are characterized using scanning electron microscopy, metalloscope, X-ray diffraction and Energy Dispersive Spectroscopy. The critical cutting conditions that correspond to the onset of surface crystallization are determined. Progressive tool flank wear with respect to the cutting distance with and without coolant is also analyzed. A resonance based two dimensional vibration stage with thin-wall design is developed to perform the vibration assisted micro-milling of brittle BK-7 glass. The dynamic property of the vibration stage is analyzed using the finite element method and experimental identification. The effects of vibration direction, vibration amplitude and frequency on the surface roughness and surface damage are investigated. It is concluded that the vibration applied in the normal direction has a major effect on the improvement of surface quality by enhancing the brittle-ductile transition of the material in the micro-milling process.Mechanical & Aerospace Engineerin

Aspheric geodesic lenses for an integrated optical spectrum analyser

Abstract available p. xiii-xi