Papers by Keyword: Machining Damage

Abstract: Carbon fiber/epoxy resin composites (C/E composites) are wildly used in manufacture of aircraft fuselages and wings in aerospace industry, due to their excellent properties. However, hole making of C/E composites always results in machining damage, such as burr, tearing, delamination and so on. Milling tools with different shapes were used to conduct helical milling experiments on C/E composites. The influence of tool shape on machining damage was analyzed by measuring the damage area of burr, tearing and delamination. And then the feed speed, axial feed per orbital revolution and spindle speed was changed respectively to study the effect of processing parameters on machining damage. The machining damage can be reduced by choosing appropriate tool shape and processing parameters.

Abstract: In aerospace industry, chromic acid anodizing (CAA) has been traditionally used as a non-destructive testing (NDT) technique to detect flaws in aluminium alloys. However, with the increasing restriction on the use of chromic acid and the application of lithium-containing aluminium alloys to aircraft structures, the capability of anodizing as a NDT method is challenged. In this work, machining damage was deliberately introduced to an Al-Li-Cu alloy AA2099-T8. Then, the visibility of the machine damage after tartaric-sulphuric acid anodizing (TSAA), which is an environmentally friendly anodizing process, was studied. It is suggested that, with proper lighting condition, it is possible to replace CAA with TSAA for detecting machining damage on lithium-containing aluminium alloys during manufacturing.

Abstract: Based on the theory of metal pre-stressing machining, the method of pre-stressing suitable for ceramic materials machining was presented. Using the cluster method, the discrete element method (DEM) model of ceramic materials machining was established. The DEM simulations of cutting process of SiC ceramic under different machining parameters were carried out by orthogonal test design method, and the effects of machining parameters on the number of surface cracks and maximum crack depth after processing were also analyzed. The results showed that the tool edge radius influenced greatly on the number of surface cracks, while the pre-stress influenced greatly on the maximum crack depth.

Abstract: The objective of this study is to experimentally investigate the effect of reinforced SiC particles on the machining of Aluminum/SiC composite (15% volume ratio of SiC particles with average grain size 15m). Aluminum/SiC composite and aluminum metal were milled by a tungsten carbide endmill in this study. Based on the surface observation and surface roughness inspection, it is found that the machining parameters of Aluminum/SiC composite have optimum values, and that the surface roughness of aluminum/SiC composite is smaller than that of aluminum metal. when feedrate and depth of cut are smaller than limited values, satisfactory surface finish can be attainable, however, as the depth of cut and feedrate increases, the microcracks are first initiated at the interface of SiC particles and aluminum matrix, and then periodically macrocracks are formed on the machined surface, The damage mechanism during the machining of aluminum/SiC are discussed in this paper.

Abstract: Machining damage and its influence on strength was examined for alumina ceramics with various grain sizes, which were prepared by dry-pressing method with spray-dried granules, followed by sintering at 1350-1550°C for 2-27 hours. Grain sizes of the sintered bodies were 1-6μm. After machining at the same grinding force, specimens were placed in an alcohol solution of fluorescent dye and dried. The fracture strength was measured by 4 point bending. The machining flaws in the specimens were observed with a confocal scanning laser fluorescence microscope. Machining flaws appeared continuous, wide and deep in the specimen with small grain size, and discontinuous with large size. On ground surfaces, intra-grain fracture appeared on the surface, whereas inter-grain fracture dominates. The continuous, wide and deep flaws were attributed to the dissipation of stored energy associated with the cracks propagation. The result suggested that the stored energy on the machining process increased with decreasing grain size. The strength of the specimen with 1 μm grain size reduced from 500MPa to 250 MPa with machining damage. The strength depended remarkably on the depth of the machining damage.