SiC p /Al composite is a rigid particle reinforced metal matrix composite because it has high specific strength and specific stiffness, small linear expansion coefficient, good dimensional stability, good wear resistance and heat resistance, and good remeltable property. It is widely used in the aerospace, aerospace and automotive industries due to its low price and low price. Due to the addition of high-strength hard-brittle SiC ceramic particles, the mechanical properties of the matrix material are greatly improved, and the macroscopic isotropy of the composite material is also obtained. On the other hand, it is precisely because of the addition of SiC reinforcing particles that the machinability of the composite material is deteriorated, and the tool wear is severe during processing, and it is difficult to ensure the processing accuracy and the quality of the machined surface. Studies have shown that high-speed steel tools and carbide tools expose more and more defects in the cutting of SiC p /Al composites, so many scholars are committed to research and development of new tool materials suitable for processing SiC p /Al composites.
Polycrystalline diamond (PCD) is a new type of superhard tool material. The PCD tool is made of selected synthetic diamond microcrystals sintered at high temperature and high pressure. Due to the addition of additives during the sintering process, diamond crystals are formed. TiC, SiC, Fe, Co, Ni, etc. are the main components of the bonding bridge. The diamond crystals are firmly embedded in the solid skeleton formed by the bonding bridge in the form of covalent bonds, so that the hardness and toughness of the PCD are greatly improved. Therefore, the PCD tool has both high hardness of diamond and high toughness of single crystal diamond, and the blade base also has high bending strength. The machining of metal-based silicon carbide particle reinforced composites with PCD tools is a sophisticated and efficient new processing method. Many scholars have studied this, but most of them are limited to ordinary cutting with PCD tools. In recent years, the application of ultrasonic vibration cutting method to process difficult-to-machine materials has shown the advantages of high processing precision and good quality. Its good processing performance has attracted great attention. Ultrasonic vibration processing is becoming an important means of precision and ultra-precision machining. One. Based on PCD tool machining of SiC p /Al composites, the general turning and ultrasonic vibration turning tests are carried out. The processing technology of ultrasonic vibration cutting of metal-based silicon carbide particle reinforced composites by PCD tools is discussed. The cutting speed and feed are analyzed and compared. The influence of cutting parameters such as the amount and depth of cut on the cutting force, the test and discussion results have certain guiding significance for the cutting of metal matrix composites (especially for the processing of thin-walled and slender shaft parts).2 cutting test conditions
Machine tool: CA6140 ordinary lathe; tool: PCD welding turning tool; workpiece material: metal matrix composite material SiC p / Al bar material, casting, weight percentage 12%, particle size W14, bar material diameter Ø42mm, length 150mm.
Vibrating device: Self-made longitudinal vibration device (amplitude 15 μm, frequency 20 kHz). Figure 1 Cutting force measuring device |
3 Single factor relationship test and analysis of cutting force and cutting parameters
Effect of cutting speed on cutting forceTest and measurement
| Machine speed n (r/min) | 60 | 90 | 180 | 305 |
|---|---|---|---|---|
| Vibration cutting force F c (N) | 12.27 | 13.16 | 16.91 | 25.25 |
| Ordinary cutting force F c (N) | 33.9 | 33.25 | 30.27 | 33.26 |
In order to study the influence of the change of cutting speed on the ultrasonic vibration cutting force, in the cutting test, the feed rate f=0.08mm and the depth of cut a p =0.3mm are kept unchanged, only the cutting speed is changed, and the machine speed is measured respectively n=60r The cutting force F c during ultrasonic vibration cutting and ordinary cutting at /min, 90r/min, 180r/min, 305r/min, the test results are shown in Table 1.
results and analysis
 Figure 2 Relationship between cutting speed and cutting force |
The relationship between the cutting speed and the cutting force obtained in the test is shown in Fig. 2. It can be seen from the figure that during normal cutting, as the machine speed increases, the cutting force does not change much. During vibration cutting, due to its pulse cutting effect, cutting is only performed at t c time in one vibration period T, so the average cutting force F c is the t c /T of the peak value of the pulse cutting force, and the effective cutting time increases as the cutting speed increases. When t c becomes longer, the average cutting force F c also gradually increases. When the cutting speed approaches the critical cutting speed (ie, t c /T≈1), F c =F c (this is the normal cutting state). It can be seen from the figure that the cutting force gradually increases with the increase of the rotational speed: when the rotational speed is 60r/min, the cutting force of the vibration cutting is only 1/3 of that of ordinary cutting; as the rotational speed increases, the effective cutting time follows. Increasing, when the rotational speed is increased to 180r/min, the average cutting force of the vibration cutting increases to about 1/2 of that of ordinary cutting; when the rotational speed is close to the critical rotational speed, the vibration cutting is converted into ordinary cutting. It can be seen that the test results are basically consistent with the theoretical analysis.
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 Figure 3 Relationship between feed rate and cutting force |
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