The material removal mechanism in mechanical lapping of diamond cutting tools

In order to reveal the surface layer removal nature and explain the anisotropy of material removal rate in mechanical lapping single crystal diamond cutting tools, a brittle-ductile transition lapping mechanism is proposed. And then, the dynamic critical depths of cut for brittle-ductile transition in different directions on different planes can be calculated. The lapped surface layer of diamond cutting tool will be removed in plastic mode as long as the embedding depth of diamond grit into the lapped surface is less than the corresponding critical depth of cut. Lapping experiments on the named (110) plane and (100) plane are carried out and the lapped surfaces are measured with atomic force microscope (AFM). The results show that all the lapped surfaces of diamond cutting tools consist of plastic grooves in nanometric scale and the maximal groove depths have prominent anisotropy in different orientations and on different planes, which are consistent with the critical depths of cut well. Therefore, the material removal rate anisotropy of lapped surface layer can be analyzed by comparing the critical depths of cut on different crystallographic planes and in different orientations of the identical plane quantitatively.     

Multiscale simulation of nanometric cutting of single crystal copper —— effect of different cutting speeds

A multiscale simulation has been performed to determine the effect of the cutting speed on the deformation mechanism and cutting forces in nanometric cutting of single crystal copper. The multiscale simulation model, which links the finite element method and the molecular dynamics method, captures the atomistic mechanisms during nanometric cutting from the free surface without the computational cost of full atomistic simulations. Simulation results show the material deformation mechanism of single crystal copper greatly changes when the cutting speed exceeds the material static propagation speed of plastic wave. At such a high cutting speed, the average magnitudes of tangential and normal forces increase rapidly. In addition, the variation of strain energy of work material atoms in different cutting speeds is investigated.     

Prediction of cutting forces in the micro-machining of silicon using a “hybrid molecular dynamic-finite element analysis” force model

The study and development of micro-machining technology has been an area of ongoing focus for numerous researchers. Interest in this topic has been increasing over the past decade due to the trend towards higher accuracy, smaller-sized components. Linking material property acquisition and modelling in the nanometric scale with those on the micro-scale is a considerable challenge in material science in general and in micro-machining in particular. Due to computational limitations it is presently extremely difficult to inflate atomic level models and simulations to the micro-sized component dimensions. This detailed knowledge of material behaviour will provide the necessary insight to support process development, modelling and the optimization of critical ultra-precision machining processes. This paper presents a new methodology of providing a finite element model of the micro-cutting process with relevant material properties acquired from a newly developed molecular dynamics simulation model of a uniaxial tension test performed on silicon. Material properties such as yield stress, ultimate stress and modulus of elasticity are extracted from the stress–strain curve produced by the molecular dynamics model and automatically fed to the finite element model to evaluate the cutting forces required to machine a silicon wafer using different cutting parameters.     

Nanometric cutting mechanism of silicon carbide

Ductile to brittle transition is critical to achieve nanometric surfaces in the ultraprecision diamond cutting of silicon carbide. Although atomic simulations have long been used to better understand this mechanism, the extremely small model scale limits its capability in matching the actual cutting process. To overcome this serious issue, an enhanced molecular dynamics method is proposed in this study, which successfully predicts and clarifies the onset of brittle regime machining, and indicates the essential roles of dislocation and the shear band. The experimental results validate the effectiveness of this modelling approach.     

Experiments and computer simulation analysis of impact behaviors of micro-sized abrasive in waterjet cutting of thin multiple layered materials

The abrasive waterjet (AWJ) is now widely used in the advanced cutting processes of polymers,metals,glass,ceramics and composite materials like thin multiple-layered material (TMM).Various research and development efforts have recently been made to understand the science of AWJ.However,the interaction mechanism between a workpiece and high-velocity abrasive particles still remains a complicated problem.In this work,the material removal mechanisms of AWJ such as micro penetration and micro dent were experimentally investigated.In addition,a new computer simulation model considering high strain rate effect was proposed to understand the micro impact behavior of high-velocity micro-sized abrasives in AWJ cutting.     

Experimental investigation of the process behaviour in Mechano-Electrochemical Milling

The increasing demand for high-performance materials, in for example aerospace and biomedical industries, calls for more efficient and capable technologies. This paper describes a new technology, namely Mechano-Electrochemical Milling (MECM), which combines electrochemical machining (ECM) with a mechanical cutting process. The process behaviour has been investigated experimentally based on the machining of two Titanium alloys, Titanium grade 2 and Titanium grade 5. The material removal mechanism was investigated through analysis of the machined surface and removed material. Besides the slightly higher material removal rate in MECM compared to ECM, the MECM process results in more stable process conditions.     

Modeling and simulation of cylindrical electro-chemical magnetic abrasive machining of AISI-420 magnetic steel

The objective of the present research is to simulate cylindrical electro-chemical magnetic abrasive machining (C-EMAM) process for magnetic stainless steel (AISI-420). C-EMAM is a new hybrid machining process used for high efficiency finishing of cylindrical jobs made of advanced engineering materials. The material is removed from the workpiece surface due to simultaneous effect of abrasion and electrochemical dissolution. Finite element method is used to calculate the distribution of magnetic field between the magnetic poles in which cylindrical shaped workpiece is placed. The cutting forces responsible for abrasion are calculated from the magnetic forces due to gradient of magnetic field in the working gap. The effect of electrochemical dissolution and abrasion-assisted dissolution are incorporated into the C-EMAM process model using empirical relation for average anodic current. The empirical relation is correlated with the input parameters in the present system based on experimental results. Finally a surface roughness model is developed by considering total volume of material removed with the assumption of triangular surface profile. The simulation results for material removal and surface roughness are validated using experimental results. The simulated results agree with experimental observations.     

Influence of the ploughing effect on the dynamic behaviour of the self-vibratory drilling head

The vibratory drilling process enables the chip to be split into small elements thanks to axial vibrations of the drill self-maintained by the cutting energy. The vibrations should remain stable when machining, and damping be removed or very limited—particularly the ploughing force induced by the chisel edge and the flank face. To predict the behaviour of the self-vibratory drilling head, a new ploughing model has been developed. In this model, the interaction of the tool flank face with the machined material can be perceived as a virtual cutting edge that produces an additional thrust force and an additional removal of material. This model improves the cutting force models and is integrated into a numerical vibratory drilling simulator. The model shows a good correlation with experimental results.     

Modelling of Abrasive Waterjet Machining: A New Approach

Abrasive waterjet (AWJ) machining is one of the recent non-traditional methods starting to be used widely in industry for material removal of different materials. The cutting performance of AWJ is achieved by a very high speed, small-scale erosion process. In this paper, a modified form of Finnie's model for erosion is developed for application to AWJ. This modified form is able to deal with curved surfaces rather than flat surfaces only. Furthermore, the new modelling approach is capable of simulating multiple particle erosion. This approach uses standard material properties and requires no calibration constants. The modelled results agreed well with both experimental and analytical data.     

A Model for Surface Roughness in Ultraprecision Hard Turning

Numerical modelling procedures to predict surface roughness in turning processes have been in use for more than forty years. However, the procedures available to date do not correlate well with hard turning. A novel numerical model is presented which incorporates process disturbances such as tool cutting edge defects and machine vibration in hard turning and thus their effect on the achievable surface roughness. It includes a material partition equation to address the behaviour of chip removal and deformations during the cutting process; it also allows additional information to be derived about the mechanism of generation involved at a given point on the surface. Experimental results show good correlation of calculated with measured roughness parameters even at low feed rates.