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This book presents an in-depth study and elucidation on the mechanisms of the micro-cutting process, with particular emphasis and a novel viewpoint on materials characterization and its influences on ultra-precision machining. Ultra-precision single point diamond turning is a key technology in the manufacture of mechanical, optical and opto-electronics components with a surface roughness of a few nanometers and form accuracy in the sub-micrometric range.

In the context of subtractive manufacturing, ultra-precision diamond turning is based on the pillars of materials science, machine tools, modeling and simulation technologies, etc., making the study of such machining processes intrinsically interdisciplinary. However, in contrast to the substantial advances that have been achieved in machine design, laser metrology and control systems, relatively little research has been conducted on the material behavior and its effects on surface finish, such as the material anisotropy of crystalline materials. The feature of the significantly reduced depth of cut on the order of a few micrometers or less, which is much smaller than the average grain size of work-piece materials, unavoidably means that conventional metal cutting theories can only be of limited value in the investigation of the mechanisms at work in micro-cutting processes in ultra-precision diamond turning.

Inhaltsverzeichnis

Frontmatter

Fundamentals

Frontmatter

Chapter 1. Single Point Diamond Turning Technology

Abstract
Manufacturing with high precision is a development which has been gathering momentum over the last 200 years and accelerating over the last 30 years in terms of research, development and applications in product innovation. It has been driven by demands for much higher performance of products, higher reliability, longer life and miniaturisation. This development is widely known as precision engineering and today is generally understood as manufacturing to tolerances smaller than one part in 104 or perhaps one part in 105. This chapter profiles the categorisation of machining processes with a highlight on the ultra-precision single point diamond turning technology.
Sandy Suet To, Victor Hao Wang, Wing Bun Lee

Chapter 2. Factors Influencing Machined Surface Quality

Abstract
Ultra-precision diamond turning aims at producing advanced components with not only a high-dimensional accuracy but also a good surface roughness and form accuracy. Since the achievable machining accuracy is governed by the accuracy of the relative motion between the cutting edge and the workpiece, the performance of machine tools is of prime importance. Optimum conditions of factors such as machine tools, cutting tools, workpiece materials, cutting variables, cutting fluid, working environment, etc., need to be chosen to achieve a good result in diamond turning. This chapter elaborates all these key factors influencing the machined surface finish.
Sandy Suet To, Victor Hao Wang, Wing Bun Lee

Chapter 3. Modelling and Simulation for Ultra-Precision Machining

Abstract
This chapter thoroughly reviews the modelling and simulation of ultra-precision machining. The analytical and numerical methods and their applications are summarised, including the Slip-line Field Modelling, Molecular Dynamics Simulation, Quasicontinuum Method, Meshfree Method, Discrete Element Method, Finite Element Method, etc. The dedicated models for chip morphology and shear band theory are further explained in details.
Sandy Suet To, Victor Hao Wang, Wing Bun Lee

Materials Characterisation in Ultra-Precision Diamond Turning

Frontmatter

Chapter 4. Machinability of Single Crystals in Diamond Turning

Abstract
Machinability refers to the relative ease with which a material can be cut successfully. The criteria to measure a successful cut are plentiful. Some commonly accepted measures include the surface roughness, the ease of removal of the chip, the amount of tool wear, the cutting force and the power consumption. These factors are often related to one another. This chapter showcases the material characterisation methods and the in-depth study on the machinability of single crystal materials in a series of delicate diamond turning experiments undertaken by the authors and their colleagues.
Sandy Suet To, Victor Hao Wang, Wing Bun Lee

Chapter 5. Materials Deformation Behaviour and Characterisation

Abstract
Ultraprecision diamond turning can produce advanced components with not only a high-dimensional accuracy but also with a good surface integrity such as a small surface roughness and low-residual stress. In this chapter, an experimental study on diamond-turned surface layers was conducted by machining single crystals with different crystallographic planes. The influences of the depth of cut and the initial crystal orientation on the plastic properties were studied from the changes in dislocation density, the microstrain, the microhardness of the machined surface layer and the deformed structure. The block size, microstrain and dislocation density in the deformation layer were derived from the X-ray diffraction (XRD) line profile analysis method. The elastic modulus and the recovery behaviour were measured by nano-indenter testing. Transmission electron microscopy (TEM) was used to characterise the dislocation structure of the diamond-turned surface at various depths of cut.
Sandy Suet To, Victor Hao Wang, Wing Bun Lee

Chapter 6. Material Electropulsing Treatment and Characterisation of Machinability

Abstract
The machinability of metals and alloys is well known for being affected by the cutting conditions, cutting tools and material properties. A very high-quality surface finish can be obtained by the use of advanced machine tools based on single point diamond turning (SPDT). However, no matter how accurate the machining system is, the limit of performance is determined by the tool/workpiece interaction during the chip removal process at the micro- and nano-scales. In particular, the dimensional accuracy and stability of the machined surface depend on the metallurgical properties of the surface before and after machining, such as the plastic deformation, microstructural changes, phase transformation. This chapter introduces the electropulsing treatment (EPT), as an alternative to traditional thermal and mechanical processes, to enhance the machinability of the difficult-to-machine materials for ultraprecision machining.
Sandy Suet To, Victor Hao Wang, Wing Bun Lee

Chapter 7. Microplasticity Analysis for Materials Characterisation

Abstract
During the last few decades, much research work has been done to develop accurate tool force models for studying the characteristics of the cutting process in ultraprecision machining based on the concept of shear angles in the chip formation, the fluctuation of which leads to fluctuation of the deformed chip thickness and hence the cutting forces. A microplasticity model is developed in this chapter to analyse the variation of the shear angle and hence the cutting force in ultraprecision diamond turning. The model took into account the effect of material anisotropy due to the changing crystallographic orientation of the workpiece being cut and a spectrum analysis technique is deployed to reveal the features of the cutting force patterns. A series of cutting experiments was conducted on a single crystal with different crystallographic cutting plane normals. The complexity of the shear angle formation is further revealed by a microstructural analysis of the chip cross-sections showing plasticity by means of scanning electron micrographs.
Sandy Suet To, Victor Hao Wang, Wing Bun Lee

Theory and Mechanism of Ultra-Precision Diamond Turning

Frontmatter

Chapter 8. Shear Bands in Ultra-Precision Diamond Turning

Abstract
Shear bands are common phenomena reported in various metal-working processes, such as forming, forging, hot rolling, cold rolling and high-speed cutting. In the micro-cutting process, there is strong experimental evidence that the fluctuation in cutting force is related to the variation of chip thickness and is related to the shear plane angle of the metals being cut. This chapter investigates the mechanism of elastic strain-induced shear bands and regularly space shear bands with a generalised model for shear angle prediction.
Sandy Suet To, Victor Hao Wang, Wing Bun Lee

Chapter 9. Tool-Tip Vibration at High Frequencies

Abstract
This chapter presents a theoretical and experimental investigation of the influence of tool-tip vibration on surface generation in single-point diamond turning. Although it is well known that the relative vibration between the tool and the workpiece plays an important role in surface generation in single-point diamond turning, most of the previous work has focused on studying the relative tool-work vibration in the infeed (thrust force) direction while the significant contribution of the effect of the tool-tip vibration in the cutting force direction has been overlooked. In ultraprecision diamond turning, the characteristic twin peaks are identified and found to correspond to the tool-tip vibrations by power spectrum density analyses. The vibrations possess the features of small amplitude but high frequency. A theoretical physical model is proposed to describe and correlate the characteristic peaks in the frequency domain with the behaviour of the tool-tip vibration in the steady-state cutting process. The proposed model has the capability of capturing the dominant factors influencing the surface roughness of the machined surfaces.
Sandy Suet To, Victor Hao Wang, Wing Bun Lee

Chapter 10. Dynamic Modelling of Shear Band Formation and Tool-Tip Vibration in Ultra-Precision Diamond Turning

Abstract
Elastic strain induced shear bands and high-frequency tool-tip vibration are two important physical phenomena associated with the chip morphology and machining dynamics of the micro-cutting process. These phenomena and related topics have been studied separately and so far, there has been no model developed that can successfully link together these phenomena in different research areas of ultra-precision machining. This chapter is based on the system approach which includes the components of the machine tool and cutting process. The embedded system time manifests its function in the cyclic behaviour of the formation of serrated chips with elastic strain-induced shear bands, the dynamic response of high-frequency tool-tip vibration, and the previously proposed characterisation method of the machined surface.
Sandy Suet To, Victor Hao Wang, Wing Bun Lee
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