Materials Science Forum Vols. 532-533

Abstract: The Finite Element Method (FEM) has proven to be an effective technique to investigate cutting process so as to improve cutting tool design and select optimum cutting conditions. The present work focuses on the FEM simulation of cutting forces in high speed cutting by using an orthogonal cutting model with variant undeformed chip thickness under plane-strain condition to mimic intermittent cutting process such as milling. High speed cutting of 45%C steel using uncoated carbide tools are simulated as the application of the proposed model. The updated Lagrangian formulation is adopted in the dynamic FEM simulation in which the normalized Cockroft and Latham damage criterion is used as the ductile fracture criterion. The simulation results of cutting force components under different cutting conditions show that both the thrust cutting force and the tangential cutting force increase with the increase in undeformed chip thickness or feed rate, whereas decrease with the increase in cutting speed. Some important aspects of modeling the high speed cutting are discussed as well to expect the future work in FEM simulation.

Abstract: Uneven distribution of the residual stress is the main factor causing the distortion of a workpiece. Different clamping scheme may cause different clamping stress. Clamping stress coupling with the residual stress inside the part induces different stress distribution, which affects components’ machining distortion and service life. To reflect the relationship between clamps and residual stress , finite element model with different clamping schemes were bulit and the clamping process was simulated. And the chip removal effect was taken into account using a material removal approach based on element death technique. Stress distribution in the workpiece is analyzed and compared under different clamping conditions. It is verified that clamping position has a significant effect on the residual stress. Otherwise the clamping sequence has a little effect on the stress redistribution.

Abstract: Many solution tools TRIZ provided, such as innovative principles, technology evolution, have been widely used for product innovative design in last decade. The key using TRIZ to improve design is the correct definition and solving of technical problems. However, it’s difficult for engineers to discover the inherent problems of product, especially for complex engineering systems. Therefore, this paper proposes a whole process model for product systematical innovation design, whose objective is to obtain ideal solution and whose technical method is to analyze and solve conflicts. This model integrates the definition, analysis of problems from top to bottom, with the resolving of problems from bottom to top, and will contribute to a systematic and operable process for problems definition, analysis, resolving. A practical application of this work is also presented.

Abstract: The constant flux blanking plug is a downhole flow control device used in the separate layer water injection system of oil-field, its flow characteristic and reliability are the most important matters that people care about. So these performances of the constant flux blanking plug are analyzed by numerical methods here. The dynamic model of the constant flux blanking plug is established by bond-graph, then the simulation is made by the 20-SIM software. The influence of local flow field is studied by CFD (computational fluid dynamics), with which some different valve spools and pockets are compared. The discrete particles’ trajectories are analyzed by the Lagrangian method, and the particle erosion rates of different materials are calculated with Bitter’s erosion model. All the simulation data show that the structure and material have great influence on the flow control precision and reliability which need to improve at present. The simulation results are verified through ground or field tests in the end.

Abstract: Approximate Double Circular Arc Interpolated Method (ADCAIM) has been proposed by the authors. It requires only the included angles in the normal directions of the adjacent arcs at intersection points to be less than specified value, but does not require the adjacent arcs to be tangent as in other circular arc interpolated methods. ADCAIM is an approximate method with better calculating speed because of its concise calculation, and its interpolated error can meet the requirement too. The problems in NC programming of aspheric curves have been solved by using ADCAIM. In this paper, to the plane profile including aspheric curves, using VB program language as the second development tool, auto-programming for NC machining of aspheric curve is also realized by using ADCAIM, as long as the curve’s profile graphics on the AutoCAD is known. The research result indicates: the method introduced in this paper can meet the needs of NC machining in both interpolated accuracy and calculating speed for the example.

Abstract: In ultrasonic vibration assisted grinding (UAG) along the axial direction, the machining process of an abrasive grit is introduced in this paper. During the internal UAG, the critical speed is determined by the amplitude and frequency of ultrasonic vibration. During the surface UAG, the cutting model of an abrasive grit is established and the cutting trace length of an abrasive grit and the grinding force making chips deformation is analyzed in theory. The analysis results show that the cutting trace length is longer by introducing ultrasonic vibration along the axial direction; the grinding force is decreased, the higher vibration amplitude and frequency is helpful to the decrease of the grinding force and the higher grinding wheel speed weakens the contributiveness of ultrasonic vibration to the decrease of the grinding force.

Abstract: The main function of the wheel side is to remove the material and the main function of the wheel edge is to finish the workpiece in quick-point grinding process. So the grinding layer model of conventional cylindrical grinding process is not fit for quick-point grinding process anymore. Based on the technical characters and the principle of the process, a new side contact layer model and the formulas to calculate the contact layer parameters are presented. It is basement to study the mechanism of materials removal and wheel wear in quick-point grinding process.

Abstract: The CAD/CAM software UGNX3 was used to implement tool positioning strategy in CNC milling. The Sturz strategy embedded in UG was replaced by curvature matching strategy using the interface of the UG/OPEN API. The feed direction was constrained along u direction of the machined surface. An extra angle was added to eliminate the interference between the cutter and the surface and some additional cutter locations were calculated to ensure the whole face to be machined. After the previous algorithms applied in computer program, an optimized tool path was generated. By the method of ZIG-ZAG mode, the efficiency was increased. The new strategy was verified by the simulation and machining experiment. It showed that combining the new strategy in UG was feasible. The precision and efficiency could thus be improved.

Abstract: Subdivision algorithms have emerged recently as a powerful and useful technique in modeling free-form surfaces. Subdivision algorithms exited at present however, being their disadvantages, can’t meet the demand of wide application in modeling surfaces and don’t still belong to a general theory. In this paper, a general subdivision algorithm is presented which is a general conclusion inferred from classical Catmull-Clark subdivision algorithm and can produce existing subdivision algorithm by selecting reasonable vertical weights and horizontal weights. The subdivision algorithm is an ideal resolution for keeping shape feature such as crease, corner and dart contrast to all existing subdivision algorithms, it also have the advantage of flexible weights selection, easily control of shape and high compute speed. Therefore, the algorithms are extensively applicable for shape modeling in computer aided geometric design, industrial prototype design and reverse engineering.