In the present study, experimental tests and finite element simulation were conducted in order to investigate chip formation and its effects on cutting force, tool temperature, tool stress, and cutting edge wear in high-and ultra-highspeed (v=200∼2000 m/min) milling. It was found that the serration of chip became more and more obvious as the cutting speed increased. Most of the saw-tooth chip was separated at the cutting speed of 2000 m/min. During the formation process of the separated saw-tooth, the high temperature in the shear band had substantial effect on the initiation of the crack in the chip. When the cutting speed increased, the formation frequency of the saw-tooth increased with decreasing growth rate and the tool-chip contact length exhibited a decreasing trend. At each cutting speed used in the present work, the fluctuation frequency of cutting force, tool temperature, and tool stress was consistent with that of the saw-tooth formation. The saw-tooth formation which led to periodically changing cutting thickness had great effects on the cyclical fluctuations of the cutting force, tool temperature, and tool stress. When the cutting speed increased from 650 to 2000 m/min, the amplitude of the cutting force and tool temperature grew 116 and 93 %, respectively. The higher degree of chip serration at higher cutting speed resulted in the substantial change of the cutting thickness, leading to greater mechanical and thermal impact. The tool temperature had greater effect on the tool stress than the cutting force did when the cutting speed was relatively high. Due to the small tool-chip contact length at cutting speeds of 1550 and 2000 m/min, no obvious wear appeared on the tool rake face. Because of the higher average value and the higher amplitude of tool stress at the cutting speed of 2000 m/min, chipping emerged on the tool cutting edge. This phenomenon was not found on the cutting edge when the cutting speed was 1550 m/min.
In this study, we propose a longitudinal-torsion ultrasonic-assisted milling (LTUM) machining method for difficult-to-cut materials—such as titanium alloy—in order to realize anti-fatigue manufacturing. In addition, a theoretical prediction model of cutting force is established. To achieve this, we used the cutting edge trajectory of LTUM to reveal the difference in trajectory between LTUM and traditional milling (TM). Then, an undeformed chip thickness (UCT) model of LTUM was constructed. From this, the cutting force model was able to be established. A series of experiments were subsequently carried out to verify this LTUM cutting force model. Based on the established model, the influence of several parameters on cutting force was analyzed. The results showed that the established theoretical model of cutting force was in agreement with the experimental results, and that, compared to TM, the cutting force was lower in LTUM. Specifically, the cutting force in the feed direction, Fx, decreased by 24.8%, while the cutting force in the width of cut direction Fy, decreased by 29.9%.
SUMMARYA boundary integral equation method is presented for the analysis of a thin cylindrical shell embedded in an elastic half-space under axisymmetric excitations. By virtue of a set of ring-load Green's functions for the shell and a group of dynamic fundamental solutions for the semi-infinite medium, the structure-medium interaction problem of wave propagation is shown to be reducible to a set of coupled boundary integral equations. Through the analysis of an auxiliary pair of Cauchy integral equations, the singularities of the contact stress distributions are rendered explicit. With a direct incorporation of such analytical features into the formulation, an effective computational procedure is developed which involves an interpolation of regular functions only.. Typical results for the dynamic contact load distributions, displacements, and complex compliance functions are included as illustrations. In addition to furnishing quantities of direct engineering interest, this treatment is apt to be useful as a foundation for further rigorous as well as approximate developments for various related physical problems and boundary integral methods.
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