Analytical and Experimental Investigation on Cutting Force in Longitudinal-Torsional Coupled Rotary Ultrasonic Machining Zirconia Ceramics

Ceramics and other hard-and-brittle materials are very effectively processed by longitudinal-torsional coupled rotary ultrasonic machining (LTC-RUM). However, the cutting force evolution and the effects of processing parameters on the material removal mechanism in LTC-RUM need to be clarified for machining optimization. This paper proposes a cutting force model of the LTC-RUM of zirconia ceramics via the brittle material removal mechanism. Firstly, the kinematic analysis of a single abrasive grain was performed, with further consideration of the material removal volume, the effective contact time, and the impact force per one ultrasonic vibration cycle. Then, the longitudinal-torsional coupled vibration of the core tool was analyzed from the standpoint of wave energy conversion. The analytical model was finalized and experimentally verified by LTC-RUM tests. The cutting force curves predicted via the proposed model were in good agreement with the experimental results. The results obtained are considered instrumental in predicting the effects of processing parameters on cutting force during LTC-RUM of ceramics and their further optimization.

Investigation on the Effect of Dynamic Fracture Toughness to Zirconia Ceramic Grinding Performance with Different Grain Sizes

To reveal the material removal mechanism of zirconia ceramics, an improved prediction models of the critical grinding force and maximum subsurface damage depth models are developed based on the dynamic fracture toughness. The effects of three different grain sizes on the material removal mechanism during brittle- ductile transition process of zirconia ceramics is analyzed through grinding experiments. And the influence of grain size on grinding force, workpiece surface roughness, surface fragmentation rate and subsurface damage depth in grinding are discussed. The results of the experiment results indicated that the value of dynamic fracture toughness tends to decrease with an increase in equivalent grinding thickness, and the ductile removal range of zirconia ceramics expands for the reason that the critical grinding force considering dynamic fracture toughness is higher than the static grinding force considering static fracture toughness, and the maximum subsurface damage depth is closer to actual maximum subsurface damage depth. Besides the smaller the grain size of zirconia ceramics, the higher the surface quality of grinding.

Experimental Research on Material Removal Mechanism and Grinding Force of FeCoNiCrMo0.1 High Entropy Alloy (HEA)

High entropy alloy (HEA) is an advanced alloy material, which has a wide application prospect due to its excellent properties. However, the material removal mechanism and change rule of grinding force of HEA in the grinding process have seldom been studied. The main work of this paper is that the material removal mechanism of the FeCoNiCrMo0.1 HEA is obtained by analyzing grinding debris and subsurface microstructure after grinding, the theoretical grinding force model of HEAs in plane grinding process is established on the basis of the force of a single abrasive grain, and the experimental verification is performed. According to the experimental results, the influences of different grinding parameters on grinding force are discussed, the influences of different types of grinding wheels on grinding force are analyzed, and the grinding forces generated by grinding different FeCoNiCr HEAs are compared. The results indicate that the material removal mechanism of FeCoNiCrMo0.1 HEA is the plastic removal. With the increase of grinding speed and the decrease of grinding depth and feed speed, both normal and tangential grinding forces decrease. Under the same grinding parameters, the grinding force produced by electroplated CBN grinding wheel is greater, followed by resin-bonded CBN grinding wheel and vitrified CBN grinding wheel. The grinding force produced by grinding FeCoNiCrAl0.1 HEA is lower than that produced by grinding FeCoNiCrMo0.1 HEA under the same grinding conditions. The calculated value of grinding force model is consistent with the experimental value, which can scientifically reflect the variation law of HEA grinding force.