Advanced Materials Research Vol. 497

Abstract: With preplaced Ti-8Al-1Mo-1V + BN powder mixtures, the Ti-base composite coatings with in-suit synthesis nano particulates were obtained by laser cladding on titanium alloy substrate. The microstructures, fracture morphology, phase composition and mechanical property were studied by SEM, XRD and micro-hardness tests. The results show that, there are two kinds of typical nano particulates in the composites, i.e. the TiB with a diameter of ~400nm and the _Ti2N with a diameter of ~10 nm. Both the TiB and Ti2N reinforced particulates are uniformly distributed in the composites. As a result, the average hardness of the composites were ~360HV0.05 which is about 20% higher than the substrate. In the composites, the distribution of _Ti2N particulates shows a peculiar characteristic of dendrite-like morphologies. The analysis shows that the _Ti2N precipitates out from the solid state α-Ti(N) is the reason why Ti2N is only of a diameter of ~10nm and distributes in a certain way of dendrite-like morphologies.

Abstract: In this paper electrochemical machining of micro slots using a shaped electrode instead of the traditional cylindrical electrode is presented. By applying shaped electrode the flow state of processing can be improved. An electrochemical machining (ECM system for meeting the requirements of the ECM process was established and a shaped electrode was fabricated by BEDG (Block Electrical Discharge Grinding). A set of experiments were carried out to investigate the influence of shaped electrode on machining efficiency and shape precision. The results show that the side gap and frontal gap of the micro slots can be reduced and machining speed will be improved when the shaped electrode was used compare with cylindrical electrode.

Abstract: The fabrication of a micro air journal bearing for micro gas turbine engine is investigated based on CAD/CAE and CAM in this paper. Numerical simulation of the aerodynamic micro air bearing is conducted to investigate the bearing load capacity. Then, a removal analysis and contouring strategy of accurate micro-WEDM processing for the air bearing is conducted based on CAM postprocessor. The extended and trimmed tool path is adopted for micro-WEDM. The inner and outer diameter of the bearing is 1.068mm and 1.165mm, respectively. The radius of the bearing corner is 15.9µm, and the height is 53µm.The satisfactory workpiece shape illustrates that the CAD/CAM integrated system is accurate and useful in micro-structures machining.

Abstract: Vibration-assisted cutting (VAC) with polycrystalline diamond (PCD) tool refers to the cutting with certain amplitude and high frequency tool vibration, which can definitely reduce the cutting force and tool wear compared with conventional cutting (CC). In this paper, a plane strain orthogonal model for PCD tool cutting steel AISI 1045 is established by using the finite element software ABAQUS/explicit. Then the cutting force of VAC compared with CC is explained. The value and distribution of cutting force at different depths of cutting is analyzed. It is also studied the effects of vibration frequency and amplitude on cutting force and thrust force during the ultra-precision cutting process. Afterwards, optimum selection of process parameters is presented for VAC processing of steel AISI 1045.

Abstract: this paper relates to the following studies: The model of cutting depth distribution of grains of Multi-cell-disc was analyzed and established. The shape of the abrasive grit has been discussed and the abrasive grit shape model of unit-bold was simplified. The superficial characters of elastic elements were tested by Nano-indentation tests and the loading-displacement character of superficial abrasive particles during loading was gotten. By using probability and statistics, the model of cutting depth distribution of grains was obtained.

Abstract: The numerical simulation of squeeze casting to right motorcycle crankcase,as a object of study, has been performed ，based on finite element analysis software on casting and orthogonal test method.Firstly,the three feeding technology parameters, feeding pressure,feeding delay and dwell time, were confirmed by calculation and analysis after the forecast of shrinkage defects location,then,orthogonal test and test program optimization to the parameters were completed. The results show that the deeding effect was the best when the parameter values , respectively,were 190Mpa,7.5s and 12s.

Abstract: To study the temperature characteristics of multi-squeeze casting, a prototype model was developed in PROCAST by the help of PRO/E, a seamless interface program between the former two pieces of software. And then numerical simulations were carried out. The results of the simulations are consistent to the reality states that the model was created correctly and the simulations were reliable.

Abstract: In order to study the effect of freezing treatment on the mechanical properties of SiCp/Al composites, SiCp/Al composites were froze by liquid nitrogen for different time. The micro-area hardness, two-phase residual stress and interface combination status of were analyzed with micro hardness tester, x-ray diffractometer and SEM before and after freezing treatment. The results show that the hardness of Al matrix after freezing is higher than that of before freezing, while the hardness of SiC particles does not show much change. Low-temperature freezing makes the residual compressive stress of matrix phase and the residual tensile stress of reinforcing phase reduce. With the increasing of freezing time, the difference value between the measured residual stress and the primary residual stress of Al matrix and SiC particles both turn out to be greater. Freezing can not destroy the interface combination status between the matrix phase and the reinforcing phase.

Abstract: The software CFDesign was used for the analysis of flow field simulation of two different kinds of drilling bit. The results showed that, if the waterway design of drilling bit was unreasonable, it could result in the following phenomenon: the local position of drilling bit could get severe erode of drilling fluid; the return of flow and eddy currents could be observed in the bottom of drilling well; negative pressure could be detected and might result in cavitation corrosion; the direction vector of flow field were diffused and resulted in cross flow. The waterway structure of arc-bottom bit was more reasonable comparing that of flat-bottom bit.

Abstract: A three-layers assembled cavity die and its technological measures were designed for cold extrusion forming for the bevel gear. Numerical simulation of the cold extrusion forming process was applied using Deform-3D software, load curve, velocity field, stress field and temperature field were analyzed, thus obtain the basic knowledge of the law of the bevel gear deformation. Subsequent targets for optimization were introduced, aiming to solve the remaining problems of the current cold extrusion forming. The accomplished work shows some significance in guiding how to design a die and its technological measures.