The generation mechanism of cutting force in ultrasonic vibration assisted turning (UAT), with the composition and decomposition of cutting force is discussed in this paper, and the model of cutting force in UAT is established based on the mechanism of UAT. The force measuring test system is designed on the basis of the established machining system of UAT. The contrast experiments for turning the workpiece of 304 austenitic stainless steel are conducted with and without ultrasonic vibration under different technological parameters. Furthermore, the relational model and correlation between technological parameters and cutting force is obtained by regression analysis and variance analysis. Thereby, the mutual relation among these technological parameters is effectively controlled, which contributes to achieving the high quality and high efficient processing. Simultaneously, the influences of single technological parameter with the interaction between technological parameters on cutting force are researched and analyzed. The results prove that the cutting force is reduced significantly with the aid of ultrasonic vibration in turning and the choice of the proper ultrasonic amplitude, there is an optimal range of ultrasonic amplitudes as well. Meanwhile, the cutting parameters have great influence on cutting force, among which depth of cut has the superior influence, then the cutting speed, and feed rate has the minimal influence. Moreover, cutting parameters should not be too large, UAT is mainly used for semi-finishing or finishing at medium-low speed. UAT will get more ideal machining effect if cutting parameters are chosen properly.
There are many problems and physical phenomena in turning process, like machined surface quality, cutting force, tool wear, and so on. These factors and the chip shape of workpiece materials, which is an important aspect to study the mechanism of ultrasonic vibration–assisted turning, go hand in hand. This article first introduces the types and changes of chip, meanwhile the chip formation mechanism of ultrasonic vibration–assisted turning is studied and analyzed, and the turning experiments of 304 austenitic stainless steel with and without ultrasonic vibration are carried out. The difference of chip morphology between ultrasonic vibration–assisted turning and conventional turning is contrasted and analyzed from the macroscopic and microscopic point of view. The influence of process parameters on chip shape and the impact of chip shape on machining effect are also analyzed. Results indicate that when process parameters (vibration frequency, ultrasonic amplitude, and cutting parameters) are suitably selected, ultrasonic vibration–assisted turning can gain access to better chip shape and chip breaking effect than conventional turning. By contrast with conventional turning, phenomenon of serrated burr on the chip edge and the surface defects of chip in ultrasonic vibration–assisted turning have improved significantly. Moreover, it is found that superior chip morphology in ultrasonic vibration–assisted turning can be acquired under the circumstance of comparatively small cutting parameters (cutting speed, depth of cut, and feed rate); at the same time, preferable chips can also obtain ranking machining effect.
Water-assisted injection molding (WAIM) is a promising molding process developed based on conventional injection molding (CIM). It has been a research hotspot in recent years and is still receiving extensive attention from many scholars and industries because of its significant potential advantages in practical applications. However, compared with CIM, since the additional water-related parameters are involved, the process moldability of thermoplastics is significantly reduced, especially for fiber-reinforced thermoplastics, which stunts the development of WAIM process. In this work, short-shot WAIM with an overflow cavity (OSSWAIM) was developed to address the problems and broaden the application scope of WAIMs. The results showed that compared with overflow WAIM (OWAIM) and short-shot WAIM (SSWAIM), OSSWAIM could significantly improve the process moldability and part quality of fiber-reinforced thermoplastics, especially for thermoplastic composites with a high fiber weight fraction. Besides, it was also found that water penetration had a slight influence on the fiber orientation near the water inlet, but had a significant influence on the fiber orientation near the end of mold cavity. Finally, three processing parameters affecting the water penetration, i.e., water pressure, melt temperature, and water injection delay time were investigated in terms of their influences on the fiber orientation within OSSWAIM.
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