1 Functionally Gradient Ceramic Tools 3-dimensional Machinery Tension Calculation Model
Functionally gradient ceramic tools because of its composition changes in the distribution of a certain gradient, so under the situations of high speed cutting potential of the anti breakage than ordinary ceramic tools has improved drastically. But in low speed cutting, functionally gradient ceramic tool capacity and resistance to breakage than ordinary ceramic tool is not a lot benefit. Low-speed cutting smaller sized thermal pressure, mechanical anxiety is the primary tool breakage. Finite element technique by cutting the time of the evaluation of functionally gradient ceramic tools can be obtained and the mechanical pressure.
Figure 1 shows the calculation model for the mechanical anxiety. Location knife blade slot, knife blade bottom surface binding damaging z-axis displacement of blade rake face of the plate bound z-axis optimistic displacement blade, knife blade slot of the two side constraints of x and y to the displacement, surface and bottom knife blade around the plate also restricted x-axis and y-axis spin, knife blade about the slot limit the sides of z axis. In this way, the blades 6 degrees of freedom are all bound.
In the cutting process, the tool has to withstand the cutting forces Fr FZ, Fy and Fx 3 elements. As a result of the finite element method calculation of cutting force to be applied at all nodes, it assumes that the cutting force along the knife? Chip contacting length of the triangular distribution, while along the primary and auxiliary cutting edge direction is uniformly distributed. By a document identified, SG-4 ceramic cutting tools in machining hardened high-carbon Tool Steel cutting force when the empirical formula for the Fz = 34444ap0.88f0.65v-.12 (1)
Assume that FY = .5Fz (2) FX = .8Fz (3) Table 1, two kinds of ceramic cutting tools in a variety of cutting speeds of 3-dimensional cutting force element worth v (m / min) 50100150Fz (N) 74.968.965.4FX (N) 59.955.152.3FY (N) 37.534.532.7
Table 1 for the FG-two functionally gradient ceramic tool (assuming equation (1) ~ (3) also applies to the FG-two) and SG-4 ordinary ceramic cutting tools in a range of cutting speeds of three-dimensional cutting force component value. Among them, the cutting speed have been taken v = 50m/min, v = 100m/min, v = 150m/min, feed rate f = .05mm / r, back knife to eat the quantity ap = .2mm, the workpiece material for the T10A (hardness 59.five HRC). FG-two levels in the physical properties of Table 2 (SG-four of the physical properties of the 1st layer of FG-two the exact same).
Far as clamping tip dot pitch, the clamping force on the tension state near the tip has small impact, so from time to contemplate the impact of clamping force very same time, due to the fact the surface of ceramic blade is smooth, the friction coefficient is modest, so clamping the friction effect can not be considered. Measure of material harm theory of maximum tensile tension (Principal) theory, the maximum shear anxiety (Tresca) theory, the maximum distortion power (Mises) theory, the Mohr theory. Fatigue failure for brittle materials the maximum stress theory ought to be adopted and the maximum shear anxiety theory for brittle material ductile failure ought to adopt the maximum distortion power theory. Functionally gradient ceramic tools for high-speed cutting, the current fatigue damage, but also the plastic tip temperature is also higher causing damage, it should be calculated inside the functionally gradient ceramic tool maximum anxiety, maximum shear pressure and the maximum shape adjust power (Mises) anxiety. Table 2FG-2 levels the proportion of the physical properties of layer quantity r
(G? Cm-3) thermal conductivity k (20 )
[W? (MK) -1] the specific heat C (20 )
[Cal? (GK) -1] thermal expansion coefficient a (20 )
( 106/K-1) elastic modulus E
(GPa) Poisson’s ratio v45.66635.160.1277.660424.70.2423/55.9434.350.1217.522432.60.2392/66.2233.550.1157.386440.70.2351/76.5032.770.1107.251448.90.232