Advanced Materials Research Vol. 500

Abstract: Considering cold-welding repaired layer is rough and microstructure contains hard phases, firstly, the two-factor three-level orthogonal milling experiment was conducted in remanufacturing cold-welding repaired area, then the influences of different parameters on Ni-base cold-welding repaired layer milling were studied. At the end, cutting force and surface roughness were used as objectives to optimize the milling parameters. Cutting force and surface roughness were processed by range analysis, and their influence sequences were obtained. The empirical formula of milling force and surface roughness can be obtained through linear regression method, which provided theoretical base for the prediction. The influences on cutting force and surface roughness of different parameters were studied to further optimization, which can provide technical support for high efficiency and precision cutting in cold-welding area.

Abstract: In order to improve the machining efficiency and tool life in manufacturing process of hydrogenation reactor shell components, the cutting performance of quadrate GC4235 coated carbide tool in intermittent turning 2.25Cr-1Mo-0.25V steel was investigated, the optimal cutting parameters were obtained. The empirical mathematical models of relationships among the amount of metal removal, tool life, cutting force and cutting parameters were established. The failure mechanism of the GC4235 carbide coated tools for turning 2.25Cr-1Mo-0.25V steel at lower speed intermittent turning was abrasive wear and the coating peeling; however coating peeling and substrate adhesive wear were the main failure forms at the higher speed.

Abstract: In this paper, the effects of the variational combinations of cutter inclination angle in feed direction and the feed per tooth on the machined surface hardness were mainly concerned. The cutting forces transformed from the measured cutting forces in OXYZ and the SEM microstructures of the surface layer were analyzed to explore the generation condition of the hardness. Variations of the surface hardness are not apparent with the increment of feed per tooth with the identical other cutting parameters. Inclination angles in feed direction of approximately ranging from 10° to 15° and from 25° to 30°, which correspond to high surface hardness, are suggested to be applied in cutting process when high abrasive resistance is expected. While values of inclination angle approximately equal to 0° and 45° are prior to be chosen when high shock resistance performance is firstly expected. Optimization of the cutting parameters, which could offer guidance to the machining of sculptured surface concerning cutter inclination angle, was presented.

Abstract: Cryogenic cooling is a new emerging cooling application in machining processes. Quantitative understanding of the effects of cryogenic cooling on the machining performance is important for continued applications. This study focuses on cryogenic machining of hard-to-machine material, AISI 52100, particularly with an analysis of cooling-induced chip morphology, chip hardness and the effect of workpiece hardness, etc., as these measures reflect the material`s thermo-mechanical behavior during the plastic deformation. AISI 52100 steel, with different initial hardness values, is selected as the work material for orthogonal cutting under dry and cryogenic cooling conditions, and the results are compared. The findings of this study show that cryogenic cooling affects the chip formation process, and the associated hardness produced on the machined surface.

Abstract: In this paper, a finite element method was used to dynamically simulate the process of the edge defects formation during orthogonal cutting SiCp/Al composites. The influence of the cutting speed, cutting depth and rake angle of the PCD insert on the size of the edge defects have been investigated by using scanning electron. According to the simulated results, it can be provided that the cutting layer material has an effect on transfer stress and hinder the chip formation in the critical transition stage, and the critical transition point and distance are defined in this stage. The negative shear phenomenon is found when the chip transit to the edge defects in the flexure deformation stage, so the process of the chip formation is the basis of the edge defects formation. In addition, the relationship between the nucleation and propagation direction of the crack and the variation of the edge defect shape on the workpiece was investigated by theory, and it found that the negative shear angle formation is the primary cause of the edge defect formation. A mixed mode crack is found in the crack propagation stage. The sizes of edge defects were measured by the experiment and simulation, and the edge defect size decrease with the increasing of tool rake angle, while increase with increasing cutting depth and cutting speed.

Abstract: A finite element model of a two dimensional orthogonal cutting process is developed. The simulation uses standard finite software is able to solve complex thermo-mechanical problems. A thermo-visco-plastic model for the machined material and a rigid cutting tool were assumed. One of the main characteristic of titanium alloy is serrated shape for a wide range of cutting conditions. In order to understand the influence of cutting parameters on the chip formation when machining titanium alloy Ti-6Al-4V. The influence of the cutting speed,the cutting depth and the feed on the chip shape giving rise to segmented chips by strain localisation is respectively discussed.

Abstract: Due to the complex structures of aviation products made of titanium alloy TC4, residual stress can be generated by the high speed cutting process at their surface which has an important influence on their fatigue strength and also service life. Therefore, in this paper, a 3D finite element model is built to analyze the cutting process with different tool parameters and to investigate the residual stress inside the processed surface. By the numerical study, when the cutting speed is 140 m/min, the residual tensile stress can be generated in the inner cutting surface, while the compressive residual stress in the outer cutting surface. Residual compressive stress can be enhanced by choosing the smaller tool rake angle, the bigger tool relief angle and the bigger cutting edge radius properly.

Abstract: Considering the problems of the current cutting tools, such as wide varieties, low management efficiency, high cost and selection difficulty, this paper builds a cutting tools total life cycle management system model, by using the total life cycle management concept the total life cycle management of the milling cutters from purchasing to the use and discarding is realized. In this paper, through researching on cutters selection law, rules for milling cutters selection is made and intelligent cutters selection system is established with rule reasoning method.

Abstract: This paper explains and demonstrates the machinability of dry and wet machining of SiC particle-reinforced aluminum metal matrix composites based on the experiments. The plunge surface experiments with mill-grinding method under wheel peripheral speed of up to 14.13m/s, feed rate 80mm/min and depth of cutting 50μm were carried out on a vertical CNC milling machine. The comparisons of dry and wet machining on the force composites and surface roughness (Ra) versus material removal volume were studied. The material removal volume was gained with the same machining parameters after an equal period of time. In most cases, the tangential mill-grinding force values are greater in wet machining condition than that in dry condition. But for normal mill-grinding force, the Fn values are much greater in dry machining condition than that in wet condition. And the normal mill-grinding force in wet machining increased quickly with increasing material removal volume. A better surface finish can be produced in dry machining than that produced by wet machining. The surface roughness decreased slowly with the increasing material removal volume and the surface roughness shows an insignificant decreasing trend in wet machining.

Abstract: In this paper, for turning the inner ring groove of a large nuclear cylindrical shell, based on requirements of machining condition, the matching tool assembled are designed. Based on the platform of finite element simulation analysis, the deformation and stress analysis of the tools overall structures are carried out, this provides a theoretical basis for the static strength evaluation of the tools. Through the dynamics modal analysis of the tools, natural frequencies and modal shapes of the tools are obtained, this provides a theoretical basis to evaluate the dynamic characteristics of the tools, in particularly, the resonance characteristics. Through static and dynamic analysis, the reasonableness of structural design of the tools is evaluated theoretically.