RESEARCH OF THE CUTTING MECHANISM AT ELECTRICAL DISCHARGE GRINDING

The paper presents the results of a study of the cutting mechanism during electrical discharge grinding of hard alloys. The cutting mechanism during electrical discharge grinding was studied using mathematical modeling. By means of geometric modeling, a method of grinding cup wear was developed. The functional dependence of the diamonds use factor in the Kw wheel on the technological parameters of processing, wear and tool characteristics were determined. Analysis of the results of the study shows that an increase in efficiency at electrical discharge grinding can be achieved by reducing the wear of S, and by corresponding variation in the concentration of diamonds and technological modes of processing.

Study On The Formation Mechanism of Cutting Surface of Carbon Fiber Reinforced Composites

Carbon fiber-reinforced plastic (CFRP) is used widely in aerospace. The cutting mechanism of CFRP is markedly different from that of metals due to anisotropic and non-homogeneous material structure. The cutting mechanisms are highly dependent on the fiber orientation. The quality of the machined surface can be affected by the fiber fracture models. In this paper, based on the elastic foundation beam theory and the Hertzian contact theory, the cutting mechanics are established. And the cutting model is simulated by the three-dimensional micro-scale numerical model. Then, the continuous varying cutting mechanism and the sub-damage are deeply studied in detail by combining the cutting mechanics model and the simulation model. The results indicate that the fiber orientation θ=80° and θ=150° is the transition critical point of the fracture form. When θ=0°, the fiber failure mode is buckling-dominated. When 0°<θ<80° and 150°<θ<180°, the fiber failure mode is dominated by contact fracture. When 80°<θ<150°, the fiber failure mode is bending-dominated. The cutting mechanics model and finite element model can effectively reflect the evolution law of CFRP machined surface.

Design of a stationary disc chipper project for dendromass chipping with stress analysis FEM methods

The design of a stationary disc wood chipping machine was considered, as well as the stress-strain analysis of a cutting knife with a flat and shaped cutting edge, which will produce a dimensional chip. The design consisted of the conceptual design of a cutting knife, a cutting mechanism, and an entire disc chipping machine, which includes cutting tools. The design solution is based on mathematical calculations of the individual parts of the cutting device. Calculations of the cutting mechanism and the cutting tool were performed using the finite element method. The results of the stress analysis found that the maximum stress acting on the edge of the knife during cutting corresponded to the permissible stresses of the knife material and subsequent use in practice. Based on the design and physical parameters of the wood cutting process, the design of the entire chipping machine was simulated and then was modeled using the PTC Creo parametric 5.0 program. Additional finite element analysis was performed using the Creo Simulate 5.0 software.

Cutting mechanism of straight-tooth milling process of titanium alloy TC21 based on simulation and experiment

Due to the characteristics of high strength, high chemical activity and low heat conduction, titanium alloy materials are generally difficult to machine. As a typical titanium alloy with higher strength and lower heat conductivity, the machinability of titanium alloy TC21 is very poor and its cutting process is companied with larger cutting force and rapid tool wear. Straight-tooth milling tool is often used to cut the groove and side surface in the titanium alloy parts. And the milling method can be used to investigate the cutting mechanism because the cutting force has only two components and the better chip morphology is obtained. To investigate the straight-tooth milling process of TC21 alloy, a series of milling force experiments have been done. In addition, a 3D finite element model (FEM) for the straight-tooth milling process of TC21 alloy is presented to simulate the milling process. In the model, the constitutive material model, the failure model, the friction model and the heat transfer model were adopted. Through the simulation, chip formation, stress distribution, cutting force and milling temperature were obtained. The cutting force reaches its maximum when the spindle speed reaches about 13000 rpm, and then decreases as the speed continues to increase. The results confirmed that the similar “Salomon” phenomenon existed in the cutting process of TC21 alloy.

Effect Mechanism of Plain Woven Structure of Carbon Fiber on CFRP Cutting

Carbon fiber-reinforced plastic (CFRP) is increasingly employed as structural components for aircrafts in aerospace. The plain woven CFRP is more commonly used than the UD-CFRP. The machining-induced damages are easy to occur. The influence of the plain-woven structure on the cutting mechanism and the defects occurrence mechanism are seldom studied in detail. In this paper, the three-dimensional FEM model of plain woven CFRP is established. The occurrence and propagation of the delamination are investigated. The results indicate that the stress concentrations are easy to occur at the junction of warp and fill bundles near the cutting position. The plain-woven structure can block the transfer of stress and the crack propagation. When θ=90°, the damages of the fill fibers and the crack of the interface are easy to occur. When θ=45°, the step-like fracture is formed in both of the warp and the fill bundles, especially in the fill bundles. Under the same cutting conditions, the exit delamination of the plain-woven CFRP is obviously less than that of the UD-CFRP. The delamination greatly increases with the increase of the feed speed. The delamination decreases with the increase of the cutting speed. The delamination is closely related to the instantaneous cutting position of the cutter.

Investigation on the Cutting Mechanism of Al/SiCp Composites in Ultrasonic Elliptical Vibration Machining

Aluminum (Al)-based silicon carbide (SiC) material composites are considered as difficult-to-machine materials because of the presence of hard reinforced SiC particles, which results in a greater cutting force and poor surface integrity during the machining process. This paper uses two finite element models to study the difference in the machining mechanism between ultrasonic elliptical vibration cutting (UEVC) and ordinary cutting (OC). Moreover, this paper mainly focuses on the influence of UEVC on cutting force, von Mises stress distribution, surface integrity, and chip formation. The models are validated by comparing chip shapes and machined surface features in OC machining Al/SiCp experience from the literature. Simulation results indicate that the cutting mechanism of Al/SiCp on UEVC is different from that of OC and has several good properties. At the same cutting parameters, high frequency vibration makes the cutting force of UEVC exhibit variable periodicity and reduces average cutting force. The instantaneous impact of tool and fast separation results in a more concentrated von Mises stress distribution, thereby resulting in the particles having a greater break degree than that obtained with OC. A comparison of the surface roughness values from the simulation result shows that UEVC obtains better surface integrity than OC does.