Key Engineering Materials Vol. 693

Abstract: The cutting performance, failure mechanisms and reliability of Al₂O₃/TiC micro-nanocomposite ceramic tools with different geometry parameters in continuous machining of austenitic stainless steel were studied. The results showed that the largest metal removal amount was got at the cutting speed of 80 m/min, the feed rate of 0.15 mm/r and the cutting depth of 0.1 mm. The failure modes of the tool with small chamfering width and corner radius were mainly cutting edge fracture and tool materials peeling off, which was due to the subcritical crack growth. The life of the tool with small chamfering width and corner radius well followed the Gamma distribution.

Abstract: Dental ceramics has become dominant materials used in dental restorations. Dental ceramics have several advantages, such as stable performance, good bio-compatibility, little possibility to attach plaque, and similarity to the color of permanent tooth. However complex surface characteristics and hard and brittle properties of dental ceramic materials caused difficulties in the processing and subsequent grinding. The complicated craft and high failure rate of dental ceramics greatly limit its wide application in clinical. Thus, fully understanding the special cutting tools grinding performance and researching the material damage process caused by grinding temperature and grinding force are of great significance. Research on dental ceramic grinding was reviewed in this paper. The removal mechanism of dental ceramic materials and the influence of parameters settings on the grinding force, grinding temperature, and the surface quality have been studied. Besides the existing problems in dental ceramic grinding technology were pointed out.

Abstract: Ti-6Al-4V alloy has been tapped with the HSS/Co-M35 by the orthogonal test method. The empirical relationship between the cutting force and four type parameters are given. Also, factors such as hook angle, relief angle, passivation edge radius and main spindle speed collected from the AdvantEdge FEM software are examined by using both statistical analysis and regression analysis. The impact of tapping performance under the multiple type parameters of tap which contain hook angle, relief angle, passivation edge radius and main spindle speed are studied by extreme difference analysis. Three tapping performance indexes which are maximum torque, axial cutting force and cutting temperature have been converted into a single composite indicator y_i^* by using the comprehensive evaluation method. The optimal process parameters in test are that rake of tap is 11°, relief angle is 12°, and passivation edge radius is 0.015mm, while main spindle speed is 250r/min.

Abstract: laser shock forming, which combines the metal forming and material modification, is a non-mode, flexible forming new technology using laser-induced force effect of high amplitude shock waves to obtain the plastic deformation of sheet metal. in this paper, the simulation of laser shock forming process of tc4 sheet metal was carried out through the commercial finite element analysis software abaqus. the influence of the sheet thickness, laser energy, constraints aperture and laser spot spacing on the sheet metal deformation are investigated. the results show that: with the increase of sheet thickness, the deformation range of sheet decreases, and the amplitude of deformation decreases firstly and then increases. the deformation increases linearly with the increase of laser energy. the larger boundary constraint aperture leads to the larger deformation of sheet metal. there are no obvious influence on the forming accuracy when an opposite laser spot spacing is adopted. therefore, under the condition of meeting the accuracy requirement, for improving the efficiency, adopting a certain laser spot spacing to finish the forming should be considered.

Abstract: A series of research on the interactions among tool wear, cutting force and cutting vibration were conducted through high speed milling experiment in this paper, which objected the titanium alloy as difficult-to-cut materials. The results showed that the increasing of tool wear led to enlarging the cutting force and cutting vibration; and vice versa, the increasing of cutting force and cutting vibration aggravated the tool wear in the process of machining. Besides, the variation trend of tool wear with cutting was similar to the trend of cutting force, while the variation trend between cutting vibration and tool wear was different. Especially in the sharply cutting tool wear stage, the influence of tool wear on cutting vibration became more complicated.

Abstract: A Si₃N₄ ceramic tool material with high mechanical properties was fabricated by hot-pressing sintering process. The high speed machining of Inconel 718 tests were carried out with round ceramic inserts. The failure surface and microstructure were analyzed by scanning electron microscopy (SEM) to reveal the ceramic tool failure mechanisms. The results showed that the main failure mechanisms of the Si₃N₄ ceramic tool were flaking, micro-chipping, abrasive wear and adhesive wear in the turning process. On the other hand, chipping, flaking and adhesive wear were the main failure reasons in the milling process. Meanwhile, some small flaking along the cutting edge and step-shaped flaking on the rake face closed to the cutting edge were found on the failure surfaces, which was a typical self-sharpening failure characteristic of the ceramic tool in the high-speed cutting process. This tool failure evolution characteristic of the ceramic tool can be attributed to its higher flexural strength and fracture toughness, which was beneficial to improve the tool life and was constrained by cutting conditions.

Abstract: To increase the utility rate of machine, the sculptured surface machining method was researched to use in the spiral bevel gear tooth surface manufacturing with the industrial CNC milling machine. The three dimentional tooth surface points are required to design tool path planning in the SSM method. For obtaining the arbitrary point of tooth surface, the uniform bicubic B-spline tooth surface was reconstructed by cutting simulation and fitting programs. The discrepancies between fitted and theoretical points of tooth surface were provided with CAD/CAM platform. According to the results, the tool path planning of sculptured tooth surface machining can be designed and realized further.

Abstract: In this work, two kinds of Al₂O₃-TiC-TiN ceramic cutting tools (AC2U and AC2UN2) were developed by hot-pressing sintering techniques. The mechanical properties were measured and the cutting performance was investigated. The workpiece used in the cutting experiment was quenched carbon tool steel T10A, and the tool material for comparison was LT55. The wear resistance and the main wear patterns of the ceramic tools were analyzed at the high speed of 300m/min. The results indicated that the novel Al₂O₃-TiC-TiN ceramic cutting tools showed better cutting performance than LT55, and AC2UN2 was better suitable for machining quenched T10A. When the cutting condition was v=300m/min, f=0.1mm/r and a_p=0.1mm, the adhesion wear and abrasive wear of the novel ceramic tools were slighter than those of LT55, the diffusion wear resistance of AC2U was better and the oxidation resistance of AC2UN2 was better.

Abstract: Related researches of bionic tribology indicate that reasonable bionic micro-texture’s surface has a good effect on tool’s anti-friction property. In order to study bionic micro-texture effects on tools’ cutting performance further, in this paper groove and scallop micro-texture are made out on the surface of carbide tool with laser processing technology. Then orthogonal cutting tests are made to cut steel 45 in dry or wet cutting with different feedings. The results show that cutting forces can be effectively reduced by the cutting tool with micro-texture’s surface. Especially, the micro-texture’s tool has the best effect when the direction of grooves is vertical to the direction of chip’s motion, and the wear degree of its rake face is also slighter. All of those will be helpful to guide the design of cutting tool.

Abstract: This paper introduces an optimization algorithm for rapid prototyping. In the optimization algorithm, several important influencing factors are considered, such as the molding direction, the extrusion speed, and layer thickness, etc. And the velocity and effectiveness of the method are validated experimentally. The algorithm can get the best molding direction and maximum hierarchical layer thickness. The method is comprehensive, overcoming the problems of current optimization methods for one-side shortcomings, and can make guidance for the adaptive slicing and path planning.