【導讀】通過整合VAC的核心因素，包括網絡BRE. 分析，研制成功預測的切削力可靠的力學模型流程。進行有關的實驗表明，該模。形變，促進有利科幻BRE骨折在切割界面，并在很大程度上提高加工表面的質量。存在切口的臨界深度，超過該音響B(tài)RE矩陣剝離深度由施加在刀。尖的振動不再影響。這大大阻礙了EVA切削技術的優(yōu)化與應用。切削所用到的原理并建立必要的基礎。用于先進結構中。斷裂、基體開裂、纖維與基體脫粘和分層等。目前為止，大多數對FRP材料加。為了獲得高質量表面的FRP產品，普遍認為磨削較為合適，因。為在磨削時，單刃磨的切削深度比纖維直徑要小得多。他們的調查顯示，EVA切削可顯著降低切削力。與表面缺陷，即使是用普通的切削刀具。有利于降低切削力，而法向更有利于排屑。時在XZ平面上以超聲頻率微幅振動。在每個周期中，發(fā)生在刀尖擠入工件

　　

【正文】 r normal direction can significantly decrease cutting forces, minimise fibre deformation, facilitate favourable fibre fracture at the cutting interface, and largely improve the quality of a machined surface. When the vibrations are applied to both the cutting and normal directions, the elliptic vibration trajectory of the tool tip can bring about an optimal cutting process. There exists a critical depth of cut, beyond which the fibrematrix debonding depth is no longer infl uenced by the vibration applied on the tool tip. Keywords: Fibrereinforced polymer posites。Vibrationassisted cutting。Cutting mechanics。Material removal m echanism。Fibrematrix debonding 1. Introduction Fibrereinforced polymer (FRP) posites have been widely used in advanced structural applications due to their high strength and stiffness to weight ratio. However, the machining of FRP posite products is difficult because of the significant difference in the mechanical properties of the fibres and matrix. As a result, a machined FRP posite usually contains various damages, such as fibre pullout, fibre fragmentation, matrix cracking, fibrematrix debonding and delamination . To 32 date, most experimental investigations on the machining of FRP posites are on the following issues: effect of fibre or matrix types , influence of fibre volume fraction and orientations , role of tool materials and geometries , contribution of the depth of cut , and selection of processing parameters . These studies, however, are limited to the traditional machining methods, such as turning,milling and drilling, and are still facing the poor surface integrity problems highlighted above. To acplish a high quality surface of FRP posites, the mon understanding is that grinding is more appropriate , because the instant depth of cut of a single cutting edge in grinding is much smaller than the diameter of a fibre . Nevertheless, grinding is inefficient in many cases. On the other hand, vibrationassisted cutting, which adds a displacement of microscale amplitude at an ultrasonic frequency to the tip motion of a cutting tool, has been experimentally evidenced to be an effective method to cut many single phase materials such as metals and ceramics . In order to machine FRP posites effectively, the authors have developed a vibrationassisted cutting technique . This technique applies ultrasonic vibrations to the tool tip and based on the directions of the vibrations, the tool tip trajectories can be controlled to follow, ., an elliptic path named as an elliptic vibrationassisted (EVA) cutting. Their investigation has shown that the EVA can significantly reduce cutting forces and subsurface damages in a workpiece even by using a simple cutting tool. The effects of vibrations in cutting and normal directions on machining characteristics have also been studied using the novel vibrator developed. They found that the vibration in the cutting direction is more effective in reducing the cutting force, but that normal to the cutting direction facilitates the chip removal. When the vibration is applied to both the directions in an EVA cutting, the cutting force can be greatly reduced, the surface integrity of an FRP workpiece can be much improved, and the tool life can be largely extended. However, the mechanics and mechanisms of the EVA in the material removal process are still unclear. This has significantly hindered the optimisation and practical application of the EVA technique. The objective of this paper is to remove the above barrier through a detailed mechanics analysis to understand the science behind the EVA cutting of unidirectional FRP posites and thus to establish he essential fundamentals . The most imp ortant factors, such as cutting forces, fibre deformation, fibre fragmentation, and fibrematrix debonding, will be prehensively integrated in experiments will be carried out to examine the model established. 33 2. Mechanics modelling . The principle Fig. 1 illustrates the principle of an EVA cutting process, in which the cutting tool feeds at a feed rate, v, while it vibrates elliptically at an ultrasonic frequency with a microscale amplitude in the xzplane. The feed rate is smaller than the maximum vibration speed in xdirection, such that an intermittent cutting is generated in each vibration cycle of the tool. In a cycle, cutting takes place only when the tip wedges into the workpiece at time instant tb, and finishes when the tangential cutting direction is parallel to the fibre orientation at time instant te. Thus, if a fibre/matrix breakage happens during this process, chips form and are pulled out by the tool. To facilitate the breakage of the fibres and matrix, the cutting distance within a cycle of the tool vibration, Δ, is set to be smaller than the fibre diameter, D, so as to improve the surface quality as explored in the previous work . Assume that a and b are the vibration amplitudes in x and zdirections, respectively, f is the vibration frequency, ψ is the phase difference,r e is the radius of the cutting edge, ap is the set depth of cut, and δ is the bouncing back of the workpiece in the contact zone of the tool with the finished surface. The relative elliptic motions of the tool in xdirection, x(t), and zdirection, z(t), can be described by the equations shown in Table 1 . Based on the motion of the tool vibration relative to the feed direction, one can define three types of vibrationassisted cutting: (1) cuttingdirectional Fig. 1. A schematic illustration of an elliptic vibrationassisted cutting of an FRP posite 34 vibrationassisted (CDVA) cutting where the tool vibrates in the cutting direction only (., a≠0 but b=0)。 (2) normaldirectional vibrationassisted (NDVA) cutting where the tool vibrates in th