Speed Clamp
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Speed Clamp
Ceramic cutting tool speed finite element analysis
A functionally gradient ceramic tool of three-dimensional calculation model of mechanical stress
Functionally gradient ceramic tools because of its composition changes in the distribution of a certain gradient, so under the conditions of high speed cutting ability of the anti breakage than ordinary ceramic tools has improved significantly. But in low speed cutting, functionally gradient ceramic tool capacity and resistance to breakage than ordinary ceramic tool is not much advantage. Small low-speed cutting thermal stress, mechanical stress is the main tool breakage. Finite element method by cutting the time of the analysis of functionally gradient ceramic tools can be obtained and the mechanical stress.
Figure 1 shows the calculation model for the mechanical stress. Place knife blade slot, knife blade bottom surface binding negative z-axis displacement of blade rake face of the plate bound z-axis positive 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 limited x-axis and y-axis spin, knife blade around 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 cutting forces Fr bear with FZ, Fy and Fx three components. 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 tool - chip contact length direction of the triangle, and along the main and auxiliary cutting edge direction is uniformly distributed. By a document known, SG-4 ceramic cutting tools in machining hardened high carbon tool steel cutting force when the empirical formula for the Fz = 34444ap0.88f0.65v-0.12 (1)
Assume that FY = 0.5Fz (2) FX = 0.8Fz (3) Table 1 of two ceramic cutting tools in a variety of cutting speeds of three-dimensional cutting force component value v (m / min) 50100150Fz (N) 74.968.965.4FX (N) 59.955.152.3FY (N) 37.534.532.7
Table 1 FG-2 functionally gradient ceramic tool (assuming equation (1) ~ (3) also applies to the FG-2) and SG-4 ordinary ceramic cutting tools in a variety of cutting speeds of three-dimensional cutting force component value. Among them, the cutting speed were taken v = 50m/min, v = 100m/min, v = 150m/min, feed rate f = 0.05mm / r, back knife to eat the amount ap = 0.2mm, the workpiece material for the T10A (hardness 59.5 HRC). FG-2 levels in the physical properties of Table 2 (SG-4 of the physical properties of the first layer of FG-2 the same).
As far tip clamp dot pitch, the clamping force on the stress state near the tip has little effect, so from time to consider the impact of clamping force; same time, because the surface of ceramic blade is smooth, the friction coefficient is small, so clamping friction effects can not be considered. Measure of material damage theory of maximum tensile stress (Principal) theory, the maximum shear stress (Tresca) theory, the maximum distortion energy (Mises) theory, the Mohr theory. Fatigue failure for brittle materials the maximum stress theory should be adopted and the maximum shear stress theory; for brittle material ductile failure should adopt the maximum distortion energy theory. Functionally gradient ceramic tools for high-speed cutting, the existing fatigue damage, but also the plastic tip temperature is too high causing damage, it should be calculated within the functionally gradient ceramic tool maximum stress, maximum shear stress and the maximum shape change energy (Mises) stress. Table 2FG-2 levels the proportion of the physical properties of layer number 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
2 Three-dimensional mechanical stress field results and analysis
Figure 2 for the FG-2 and SG-4 the maximum Mises stress of two knives and cutting speed curves. Figure 3 is the maximum shear stress of two knives and cutting speed curves. Figure 4 shows two kinds of maximum stress and the tool cutting speed curve. As can be seen from the figure, FG-2 and SG-4 of the maximum Mises stress, maximum shear stress and maximum tensile stress is almost identical, indicating that functionally gradient ceramic tool material against damage caused by mechanical stress with the normal ceramic tool materials there was no significant advantage. Finite element results show that: the three cutting speeds FG-2 of the rake face of the Mises stress field and SG-4 is basically the same, are the largest in the Corner Office Mises stress, plastic, therefore prone to damage here.
Figure 2FG-2 and SG-4 of the maximum Mises stress of the relationship between the curve and the cutting speed
Figure 3FG-2 and SG-4 of the maximum shear stress and the relationship between cutting speed curve
Figure 4FG-2 and SG-4 of the maximum tensile stress curve with the cutting speed
Figure 5v = 50m/min main FG-2 when the maximum tensile stress field flank
Figure 6v = 50m/min SG-4 when the maximum principal tensile stress field flank
Figure 5 and Figure 6 were FG-2 and SG-4 in v = 50m/min flank when the maximum principal tensile stress field. The figure shows the two main cutting tool flank is no difference between the maximum tensile stress field, the maximum tensile stress field in the vicinity from the rake face, can be deduced here shall be a breach of the location of the rake face flaking .
3 Conclusion
Functionally gradient ceramic tool ceramic cutting tools and general consistent with the mechanical stress field, both the maximum Mises stress within the tool, the maximum shear stress and maximum tensile stress is basically the same. As the low-speed cutting tool breakage ceramic mechanical stress is the main reason, therefore functionally gradient ceramic tool at low cutting ability and resistance to breakage than ordinary ceramic tool is not much advantage.
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is speed the killer or is it bad driving skills?
all you hear is about how speed kills and the police clamp down on it heavily but is speed the real problem or is it inexperienced and incapable drivers not knowing how to controll their vehicle correctly and not paying attention properly.
also how come you can get a driving license without ever having experienced driving on a motorway.
i uderstand that speed is dangerous and i hardly ever do it but i just dont understand while the police concentrate so much on speed and not on driver training.
When you pass your driving test and throw away your L plates
you are beginning the start of a long journey in how to drive.
You will spend many years learning and once you think you know it all you will crash.You will get another car and carry on
for a while learning from your past experiences and maybe
have another accident even though its not your fault.Driving
a car is a skill which will take up most of your life and you still
won`t be ready for whatever life throws at you.There are lots of people who think they know how to drive but, from what i have seen these days i think not.
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