Key Engineering Materials Vols. 589-590

Abstract: Titanium matrix composites (TMCs) possess many outstanding properties and have increasing and potential application in aerospace, automobile and other industries. However, TMCs are typical difficult-to-machining material due to the rapid tool wear rate and excessive machining induced defects. In this paper, tool wear, cutting forces, cutting temperature and surface roughness were investigated when milling TMCs with Polycrystalline Diamond (PCD) and carbide tools. The results showed that the values of surface roughness obtained by carbide tools were higher than that of PCD tools under the same cutting conditions. The value of cutting temperature for PCD tool was about 75% of the carbide tools, and the main cutting force value of PCD tool was about 85% of the carbide tool. Abrasive and adhesive wear were the main wear mechanisms of PCD and carbide tools. In all, PCD tools had a better cutting performance than carbide tools during finishing milling titanium matrix composites.

Abstract: Carbon fiber reinforced plastics (CFRP) has increasing applications in aerospace and other fields, due to low density, high strength, high stiffness, great resistance to corrosion, etc. Although, delamination damages in drilling holes for assembly influence the final characteristics of CFRP components. This paper presents an experimental investigation to analyze delamination damage, in which acoustic emission and thrust force are monitored during drilling CFRP laminates to clarify the relationship between AE signals and delamination damages. The results show that delamination damage has close correlation with thrust force and acoustic emission energy. AE root mean square (rms) is recommended to be selected as AE signal parameter. Abrupt peak feature of AE rms can be used as a dependable trigger for delamination monitoring. The number of abrupt pulses of AE rms can be counted online to predict the degree of delamination damages, based on which delaminations can be monitored and controlled online.

Abstract: This study describes the theoretical basis of ultra-high-speed grinding. In addition, a new grinding machine tool whose maximum grinding speed can reach 450m/s has been recently developed, particularly, some of main components are basically discussed. Finally, this paper concludes with a presentation of current work and some future desirable plans in the area of ultra-high-speed grinding by means of the developed grinding machine tool.

Abstract: With the development of modern aircraft, complex titanium alloy aircraft structural parts are widely used. As a kind of difficult machining material, it’s easy to burn the tools and the parts during machining the titanium alloy structural parts because of the gathering heat. The article studies the technology to prevent burning the titanium structural parts during the machining process. The burnt problem can be effectively solved by using proper tools, proper machining parameters and fully cooling environment.

Abstract: TiB₂/WC/h-BN micro-nano composite gradient self-lubricating ceramic tool material was prepared by vacuum hot-pressing technique. The mechanical properties were tested and compared. The best flexural strength, fracture toughness and Vickers hardness of the tool material were 678MPa, 4.75MPa·m^1/2 and 15.1GPa, respectively. The microstructure was analyzed by thermal field emission scanning electron microscope (SEM). TiB₂ nanoparticles were obviously observed in the ceramic matrix. It suggested that the developed TiB₂/WC/h-BN micro-nano composite gradient self-lubricating ceramic tool materials will have potential application in dry machining.

Abstract: To achieve the components of the highest quality in terms of shape, dimension, surface integrity and high efficiency in the course of processing difficult-to-cut material, the concept of self-sharpening fine super-hard abrasive tool as machining tool is put forward, this method not only improves the dressing performance of the abrasive tool, but also ensures the accuracy and durability of the abrasive tool, self-sharpening fine super-hard abrasive tool lapping technology is developed by using Zn as abrasive fillers and using FeCl₃ solution as lapping liquid, the wear form of the self-sharpening fine super-hard abrasive tool and the influence of abrasive wear on the material removal form is studied, research shows that the wear of the self-sharpening fine super-hard abrasive tool is mainly in breakage wear, which has a good self-sharpening performance, and the material removal form is mainly in two-body material removal mode., which means this method has good holding force of abrasives.

Abstract: In the present research, a model of the cryogenic oil mist flow field of milling cutters with different interior oil channels was conducted to determine the effects of rotational speed, temperature and flow of cold air. For the milling cutters with single direct hole and double direct holes, the increase of the rotational speed has little effect on the velocity and temperature of the measuring points at different distances along the milling cutters. For the milling cutter with double direct holes the separated streamlines of double direct holes are nearer with the rise of the distance because of the viscidity of cutting fluid. When the distance exceeds 5mm, the separated streamlines combine with each other. For the milling cutter with double helical holes the streamlines of cold air present irregularly. At last, some of the simulated results were validated.

Abstract: Tool wear is a problem in machining nickel-based superalloy Inconel 718, and it is thus of great importance to understand and quantitatively predict tool wear. The experiments of machining Inconel 718 with cemented carbide tools (uncoated and coated) were carried out. Some new observations and analysis of tool wear through CCD, SEM and EDS were done. The results showed that at low cutting speed, the built up edge (BUE) formed easily and dropped at last which caused severe cutting tool breakage. When cutting speed came to 30m/min, the main reason that caused cutting tool wear was that the tool material fell off from the tool body at the form of wear debris. What’s more, the element diffusion between tool and workpiece and oxidation reaction all accelerate the formation and the cast of the wear debris.

Abstract: In this paper, the machinability of surface is introduced, and it is obtained from the analysis that the main macroscopic factors of tool premature failure are forging defects. Through research on the mechanism and rule of heavy-duty turning tool fracture failure, the conclusion is obtained that dynamic load leads to tool fracture and breakage finally. The tool working state under dynamic load is analyzed similarly by finite element software, and the simulate result verifies accuracy of the conclusion. Finally, the critical time model of tool fracture under dynamic load is established and the prevention measures of tool premature failure are formulated, which provide reference for the improvement of production efficiency and tool breakage prediction.

Abstract: A systematic cutting test was conducted turning normalized AISI1045 carbon steel with two kinds of Ti (C, N)-based cermet cutters, which were made with micron and nanometer TiC powders. And the cutting performance and abrasion mechanism was discussed in the article. The effect of tool orthogonal clearance on tool life was also researched in this paper. Results showed that: The tool life was affected seriously by tool orthogonal clearance angle, and the optimum tool orthogonal clearance angle of Ti (C, N)-based cermet cutter was 5°when cutting normalized AISI1045 steel. The cutting Performance of Ti (C, N)-based cermet cutters which were made with nanoTiC powders was better than the ones which were made with micron TiC powders obviously. And the primary wear behaviors were wear.