Papers by Keyword: Cutting Mechanism

Abstract: Latest research clearly demonstrates the excellent capability of the gear power skiving technology. For further improvement of the skiving process and enhancement of the process reliability the fundamental research on the cutting mechanism of cylindrical gear power skiving was conducted. First the kinematic model of power skiving and mathematical equations of cutter were established according to the engagement principle of crossed helical gears. Then, based on the proposed model, we investigated the simulation process, chip deformation mechanism and the cutter top relief angle. The results support the skiving cutter design and process optimization and are an important basis for the implementation of the advanced gear process.

Abstract: In order to study the physical phenomena and mechanical properties of cutters when cutting rock, a test apparatus for cutting performance of cutters of large excavation equipment is established. The test apparatus is composed of a vertical loading system, a rotary loading system, a control system and a test system. Tests of different cut penetrations and spacings were carried out using the test apparatus. Meanwhile, the real-time images of the cutting process and forces acting on the cutters were obtained. The result shows that the test apparatus has good practicality and reliability, and it provides a laboratory test method to study the cutter-rock coupling mechanism and cutting performance of cutters.

Abstract: The orthogonal cutting tests of oxygen free copper with a cutting speed of from 1 m/s to 210 m/s were performed. The effect of the high-speed cutting on the improvement over the quality of the machined surface, which was evaluated by the thickness of the plastic flow layer and the surface roughness, was examined. By employing the simple shear plane model, the cutting mechanism was analyzed. The results were compared with the results for cutting of aluminum alloy obtained previously. For oxygen free copper, the resultant cutting force does not increase in high-speed cutting. However, the friction angle on the tool-chip interface rises clearly in high-speed cutting. This paper discusses the reason for the increase in the friction angle at the tool-chip interface by investigating the stress and temperature fields on the shear plane and the tool-chip interface.

Abstract: The cutting mechanism in different position on the cutting edge of flat drill is researched in low-frequency vibration drilling. Experiments are carried on to measure the temperature on the bottom and locate the highest temperature position. And also, the variation of temperature resulting from different amplitudes is analyzed. Experiment results show that low-frequency vibration drilling can reduce the highest temperature relative to normal drilling and temperature reduces by 37% with the 0.18mm amplitude.

Abstract: High-speed orthogonal cutting experiments with cutting speeds of up to 200 m/s with a high-speed impact cutting tester of air-gun type are attempted. In this tester, a light projectile with a small built-in cutting tool is loaded into a tube, being accelerated by a compressed gas. The projectile captures the chip that is indispensable to analyze the cutting mechanism. The projectile holding the chip is decelerated by another compressed gas just after finishing the cutting, being stopped without damage in the tube. Successful experiment can be accomplished by setting adequate values of the operation parameters for the experiment, which are the pressure of each gas and the opening and shutting time of the solenoid-controlled valve for each compressed gas. In order to determine the adequate values of these parameters, a ballistic simulator that simulates the velocity and position of the projectile traveling in the tube is developed. By setting the values of these parameters obtained by the simulator, the cutting speed of 200 m/s is achieved when the ambient pressure is set to be a vacuum and helium is used for each compressed gas. This paper describes the ballistic simulator developed and shows the experimental results of the high-speed cutting of aluminum alloy A2017.

Abstract: Orthogonal cutting experiment of powder metallurgy steel was performed in cutting speeds ranging from 1 m/s to 150 m/s. High-speed cutting experiment was carried out with a high-speed impact-cutting tester. This study focuses on the change in the effects of free-cutting of manganese sulfide with cutting speed. The principal force and thrust force were measured. The cross sections of the chip and of the machined surface were observed. Color mapping analysis of the tool-chip contact region on the rake face with EPMA was done. Although the serrated type of chip formed in all experiments, the cutting mechanism was analyzed by employing a shear plane model. This paper discusses how the effect that MnS promotes the ductile fracture and the effect that MnS improves the friction property at the tool-chip interface change as the cutting speed increases.

Abstract: This document explained and demonstrated the crack growth of unidirectional glass fiber-reinforced composites (UD-GFRP) using the fracture mechanics theory during the process of machining. The models of fracture mechanics were established at antidromic cutting and direct cutting. The result is obtained that mode-I crack and mode-II crack transform each other during cutting and the complex crack is come into being. The propagation of complex crack makes the material fracture. The quality of machined surface at direct cutting is better than the quality at antidromic cutting.

Abstract: Raising a cutting speed to above speed of a plastic wave of a workpiece material induces the high levels of the hydrostatic stresses in the shear zone, because a plastic wave traveling there becomes a shock wave. In order to ascertain the cutting phenomena occurring under the ultra high-speed cutting condition, the cutting experiments of a pure lead with cutting speeds of up to 140 m/s are performed with a high-speed impact cutting tester developed. The experimental result reveals that the cutting mechanism, especially chip formation, changes remarkably and the friction angle at the tool-chip interface rises in the ultra high-speed cutting. It can be explained that these phenomena arise from the plastic shock wave in the shear zone.

Abstract: The present paper proposes a methodology to optimize process parameters for trimming applications with diamond abrasive cutters. This methodology is based on the study of quality of trimmed surface, through material integrity and surface roughness, and on the study of cutting mechanisms. Their evolutions according to tool parameters and cutting conditions have been analysed. Results show that diamond grits size must be chosen according to the required surface roughness. Feedrate must respect cutting limitations due to CFRP removal mechanisms with abrasive cutters, which have been identify through analyses of specific cutting energy. Finally, a protocol in two steps is proposed to determine the optimum process parameters according to the application. Firstly, constraint functions due to respect of quality and to limiting cutting phenomena are defined. Thus, limiting values of process parameters are determined. Then, process parameters are selected in order to optimize productivity.

Abstract: The objective of this paper is to understand the abrasive wear mechanism for producing a nano scale groove on a bulk material through nano machining. A nano indenter equipped with a nano scratching attachment was used for nano machining operation and in situ observation of the machined surfaces. Two different tools (Berkovich and Conical) with the same tip radius (100nm) but different edge geometries were used to machine both Copper and Nickel coatings. It was found that the percentage of elastic recovery was lower for Cu than Ni during this nano machining operations. Hence, the deformation mechanism in nano machining operation was identified as elasto-plastic in nature as opposed to the well established completely plastic mode of conventional machining operations. The pile up volume due to plastic deformation was utilized to distinguish between the ploughing and cutting modes of abrasive wear mechanisms. The results reveal that the ploughing mechanism was dominant for Cu and the cutting mechanism was dominant for Ni machining. Moreover, both mechanisms ploughing and cutting were the dominant modes of abrasive wear using the Berkovich tip compared to the Conical tip for producing a nano scale groove through nano machining.