Key Engineering Materials Vols. 407-408

Abstract: Thin-walled workpiece is prone to produce deformation in the process of machining because of cutting and clamping forces. In this paper, a model of cutting parameters optimization is proposed to control the deflection. The influence of deflection on nominal milling depth is taken into account and the machining deflection is computed by iterative method. Based on the optimization model, a prototype system is developed to optimize the cutting parameters for a thin-walled workpiece with the genetic algorithm and finite element method. Finally, a simulation example is used to demonstrate the feasibility of the cutting parameters optimization method. The simulation result can be further employed into practical machining situation.

Abstract: In contrast to microscale method (molecular dynamics) or macroscale method (FEM), multiscale modeling is a new, fast developing and challenging scientific field with contributions from many scientific disciplines in an effort to assure materials simulation across length/time scale. In this paper we propose MPM/MD handshaking method to establish multiscale modeling of thin film formation/nanocutting. First, the detailed handshaking method is presented for large scale simulation along with basic principles of the multiscale approach. Then, quantitative items: flatness, cutting force, adhesion between cluster and substrate, etc. are provided to avoid drawbacks of current qualitative manner. Finally, simulations are carried out to clarify the efficiency of system.

Abstract: This paper presents the results of a series of experiments performed to examine the validity of a theoretical analysis for evaluation of machining error in ball end milling of spherical surface. In the analysis, the trochoidal paths of cutting edges are considered in the evaluation of chip geometry. The cutting forces are evaluated based on the theory of oblique cutting. The machining errors resulting from cutting force induced tool deflections are calculated at various parts of the machined surface. The experiments are carried out at various cutting conditions for convex spherical surface, and the influences of cutting mode and milling position angle on machining error are examined.

Abstract: The material removal mechanisms of sapphire substrate in double-side lapping process were studied. The concepts of brittle vs. ductile machining and two-body vs. three-body abrasion were used to classify the processing mechanisms. The material removal models of double-side lapping process in different mechanisms were analyzed and researched. The experiment showed that the material removal model can describe double-side lapping process of sapphire qualitatively.

Abstract: A Lagrange finite element model is presented that simulates cutting forces and temperature distributions when orthogonal turning aluminum alloy. The effect of the large strain, strain-rate and temperature associated with cutting on the material properties is taken into account. The model predicts chip geometry, stress, strain and temperature distribution in the workpiece, chip, and tool. Cutting experiments were performed to validate the model.

Abstract: A new method for evaluation of adhesion in cutting is proposed. Adhesion of chip induces fluctuation in chip flow or stick-slip movement of chip, so that dynamic component of cutting forces depends on the cutting conditions and properties of the work materials. In this investigation continuous turning of a medium carbon steel was carried out and dynamic components of cutting forces are measured by piezoelectric dynamometer. Fluctuation in dynamic force on rake face of the tool is considered at a range of cutting speeds under dry condition and oil-mist lubrication. Surface profiles of machined surfaces and sticking of chip on tool face were also investigated. In cutting of medium carbon steel, the dynamic components below 500Hz increased under the condition of build-up edge (BUE) formation, and gradually decreased as increase of cutting speed. Tool-edge geometry well transferred onto the machined surface when the dynamic components were low level. Smoothness of chip flow on rake face is strongly associated with good surface finish.

Abstract: Chip control is a major problem to be solved in automated machining system. It involves a total system to produce chips that can be evacuated easily and reliably from the working zone and can be disposed of efficiently. In order to realize those, prediction of chip-breaking in machining is one of effective methods. In this paper, to predict the chip breakage systematically, the equivalent parameters concept is used. Through presenting a study of the effect of complicated groove insert equivalent parameters on chip formation and breaking, a predictive model of chip-breaking is constructed. Finally, chip-breaking experiments are made and the tested results show that differential chip-breaking point’s ratio is fewer than five percent, so it proves that the chip-breaking predictive model is reasonable.

Abstract: The Movable Cellular Automata (MCA) method is introduced into the analysis of cutting process, and is employed to build the discretised MCA tool-chip model of orthogonal cutting. The chip breaking and curling rule are proposed to determine the MCA local rule. The simple local rule and discretised method are presented to describe the continuous process of chip’s formation and breaking. The states’ rule of a cell and its neighbors can be used to predict and calculate the chips’ breaking and curling. The numerical calculation and a numerical example in the process of chip breaking and curling are proposed.

Abstract: In plane lapping, workpiece material removal and lapping wheel wear has been influenced each other and should be evenly distributed. Only required a flat lapping wheel, it could be obtained with flat workpieces and small thickness deviations. Therefore, the choice of the truing operation has an important effect on the quality of the lapping wheel and on the flatness of product. This is a way that using truing ring to true lapping wheel in certain eccentricity plane lapping system　to acquire the flatness. The kinematics of certain eccentricity plane lapping for uniformity of processing is analyzed in this paper firstly. Then different sizes and locations of truing ring that influences truing on the flatness of lapping wheel has evaluated and simulated. Lastly, a suitable truing operation of certain eccentricity plane lapping is proposed.

Abstract: A better understanding of friction modeling is really important for producing more realistic finite element models of machining processes. This paper presents a methodology to determine the friction at the tool-chip interface. By matching the measured values of the cutting forces with the predicted results from finite element simulations (FEM), a revised friction model on the tool-chip interface is developed. Reasonable distribution of the stress, strain and strain-rate, as well as the temperature fields at the tool-chip interface could be achieved by using this approach. An attempt is made by FEM to obtain a full understanding of relationships between the complex physical behavior and friction at the tool-chip interface. It is found that the sticking-sliding separated area is located at the points with the greatest temperature. And the corresponding relationship between cutting parameters and sticking-sliding friction separated area is found.