Advanced Materials Research Vol. 426

Abstract: To study effects of nano-Al2O3p (nanometric Al2O3 particles) on high temperature frictional wear behaviors of the NiCoCrAlY coating (a high temperature protective coating), three NiCoCrAlY coatings strengthened by different contents of nano-Al2O3p were prepared on a Ni-based super alloy by using laser cladding technology and their dry frictional wear behaviors at 500 °C in static air were investigated. The comparison was made with the coating without nano-particles. The results show that the frictional coefficient of the coatings increased with the hardness after adding nano-Al2O3p and the wear resistance of the coatings was enhanced. Among nano-Al2O3p-added coatings, the coating added with 1.0 wt% nano-Al2O3p performs best. The wear rate of the coating is only 58% of the coating without nano-particles. Moreover, the improvement of the oxidation behavior plays an important role in improving the high temperature wear resistance.

Abstract: This paper introduces the electrical discharging characteristics of PCD based on experimental studies. The relationship between gap voltage, peak current and electrical resistance of various PCD materials is presented. The influence of peak current on the discharge waveforms is analyzed. The conclusion provides important information for the development of new generators specifically designed for the machining of PCD tools.

Abstract: It is difficult to study the chip deformation due to the complexity of the chip formation process in drilling. The chip deformation has a direct effect on the drilling forces, drilling temperature and surface quality. The austenitic stainless steel 1Cr18Ni9Ti belongs to the hard-to-cut material, so it is necessary to investigate the chip deformation of 1Cr18Ni9Ti in drilling. An experimental investigation of the chip transformation process on the cutting edges using quick-stop of the drilling processes is carried out. Results indicate that the chip deformation increases with the increment of drilling velocity and decreases with the increment of the distance to chisel edge on cutting edge and the feed rate in drilling 1Cr18Ni9Ti; the chip deformation decreases with the increment of drilling velocity, and decreases with the increment of the distance to chisel edge on cutting edge and the feed rate in drilling AISI 1045; the chip deformation in drilling 1Cr18Ni9Ti is larger than that in drilling AISI 1045.

Abstract: This paper investigates the machinability of TC4 and TC11 in conventional grinding using SiC abrasive. The experiment result indicated that TC11 is more difficult to grind than TC4 because of its higher strength and ductility. Ground surface was in a state of high tensile residual stress to each material, thermal cycling of surface layer had the greatest effect. The ground surface experienced microstructure alteration, a heat-affected zone (HAZ) and plastically deformed layer were observed.

Abstract: More and more attention is put on the machinability of printed circuit board (PCB) with the increasing demand of PCBs driven by the strong need of the market of the electronic products. In this paper, drill wear and burr size, as two main objects of experimental investigation, have been observed and analyzed in drilling PCB through-holes. The results of the drilling experiment conducted with normal drill and specialized drill, indicate that appropriate chisel edge thinning is in favor of decreasing flank wear of the drill, but has no apparent effect on reducing burr size for PCB through-holes drilling.

Abstract: Surface hardening plays an important role in the evaluation of surface quality and performance of wear-resisting of components. Surface hardening of aluminum alloy 7050 is researched in high speed milling by means of micro-hardness experiments and formula. It is greatly influenced by different cutting speed and material. The relationship between surface hardness and cutting parameters are obtained and studied. The surface hardening is particularly sensitive to cutting speed and slightly to the width of cut. The effect of depth variant of machined layer on micro-hardness is analyzed, and the equation between work hardening capacity and layer depth is established to predict the harden layer depth in different conditions. The experiment results show that the work hardening capacity and layer depth in high speed cutting is greater than that in conventional cutting.

Abstract: Precision metal sieve-sheets are one of the key components of several high-tech products. Fabrication of the precision sieve-sheets possessing high open area percentage, large thickness and good quality simultaneously has always been a tickler in micro-machining area. In this paper, aiming to manufacture micro-sieves with open areas of about 90% and good quality, micro-electroforming was taken as a major process means, and the technical points and technical difficulties of some key process steps in the preparation of micro-precision sieves were explored emphatically. Meanwhile, operational conditions were optimized and major technological parameters were selected optimally. Using the optimal conditions as well as the optimum parameters, two specifications of hexagon micromesh sieve-sheets whose side length, open-area percent and sheet-thickness was 210μm, 88%, (120±3)μm and 520μm, 92%, (100±2)μm, respectively, were successfully obtained. The electroformed sieves are characterized by flat and smooth surfaces of aperture walls, sharp edge definition, rigid and homogeneous structures and well-distributed mesh.

Abstract: This paper describes a synthesis method of designing flexible cam profiles by using quintic non-uniform rational B spline (NURBS) curves. The cam profile curve can be optimized by adjusting knot vector, control points and weight factors of NURBS curve. The multiobjective optimization for a cam curve was described to satisfy both kinematic and dynamic requirements. To solve the optimization model for NURBS cam curve, an improved genetic algorithm (GA) called INSGA in the paper was proposed. Application examples on the kinematical and dynamical optimization of cam curves are presented together with detailed discussions. These examples, especial the dynamic optimization to control the residual vibration for a cam curve used in an indexing cam mechanism, sufficiently illustrate the effectiveness of the proposed approach.

Abstract: Cutting direction burr/fracture is one of the important factors that influence the edge quality and performance of precision parts. A finite element model based on material failure mode is developed in this study to simulate the burr /fracture forming process. According to workpiece materials deformation and mechanical properties from the simulation results, the cutting direction burr/fracture formation process is analyzed. The cutting direction burr forms when there is a crack in the area near the tool tip and grow along the principal shear zone, the cutting direction fracture forms as the crack grow along negative zone.

Abstract: Monotonically decreasing sequence data for the traditional modeling method using the gray model accuracy is not high, using Accumulated Generating Operation in reciprocal number, utilize three gray derivative processing method is deduced and the parameters optimization grey derivative calculation formula, and then established GRM(1,1) based on accumulated generating operation in reciprocal number on the equidistance, Gray provides a new method of modeling. Data processing examples show that the model's practicality and reliability.