Serrated Chips Formation in Micro Orthogonal Cutting of Ti6Al4V Alloys with Equiaxial and Martensitic Microstructures

The formation of serrated chips is an important feature during machining of difficult-to-cut materials, such as titanium alloy, nickel based alloy, and some steels. In this study, Ti6Al4V alloys with equiaxial and acicular martensitic microstructures were adopted to analyze the effects of material structures on the formation of serrated chips in straight line micro orthogonal machining. The martensitic alloy was obtained using highly efficient electropulsing treatment (EPT) followed by water quenching. The results showed that serrated chips could be formed on both Ti6Al4V alloys, however the chip features varied with material microstructures. The number of chip segments per unit length of the alloy with martensite was more than that of the equiaxial alloy due to poor ductility. Besides, the average cutting and thrust forces were about 8.41 and 4.53 N, respectively, for the equiaxed Ti6Al4V alloys, which were consistently lower than those with a martensitic structure. The high cutting force of martensitic alloy is because of the large yield stress required to overcome plastic deformation, and this force is also significantly affected by the orientations of the martensite. Power spectral density (PSD) analyses indicated that the characteristic frequency of cutting force variation of the equiaxed alloy ranged from 100 to 200 Hz, while it ranged from 200 to 400 Hz for workpieces with martensites, which was supposedly due to the formation of serrated chips during the machining process.

High Speed Machining of Hardened AISI 1045 Steel

Hardened AISI 1045 steel implemented in machine tool spindle was previously ground using grinding operation. This research aims to address the feasibility of hard turning AISI 1045 using PCBN tool with chip breaker under dry condition. Chip morphology, cutting force and temperature were measured, analyzed and correlated with machining parameters. Experimental results demonstrate that serrated chips are generated at high speeds, high feed rate is an assistant to promote serrated chips, and chip breaker can help break chip into acceptable lengths. Cutting forces were characterized with periodic fluctuation along three directions as chips are serrated. Temperature at machined zone can reach as high as 1200°C, which indicates that adiabatic shear bands can be successfully achieved during the machining of hardened AISI 1045 steel without applying lubricants.

Experimental Study on the Formation Mechanism of Serrated Chip of TC11 Titanium Alloy

Serrated chips were a universal phenomenon and it had a significant effect on cutting process. In this paper, single tooth dry cutting of TC11 titanium alloy were conducted on a five-axis CNC machine using Stellram milling cutter with a diameter of 32 mm. Both chip macroscopic morphology and microcosmic morphology of TC11 titanium alloy were studied in-depth examining the impact of cutting speed and feed rate to the serrated chips. The results showed that: with the increase of cutting speed, the chip morphology of titanium alloy TC4 experienced a change process from the hair bar to a “C” shape and then become a long strip. The critical cutting speed of TC11 for serrated chips was found at 80 m/min and the critical feed rate to form serrated chip was defined as 0.05mm/z. With the increasing of cutting speed, the extent of chip serration was significantly enhanced. Increasing cutting speed can decrease the feed rate to form serrated chips.

Machining Mechanism of Fresnel Lens Mold

This paper analyzed the large diameter Fresnel lens mold machining mechanism based on modal test methods .The design and mold machining principle of Fresnel lens were introduced . Explored the cutting speed and feed on chip formation process. The results show that: the material strength and plastic brittle have significant impact on chip morphology in the H62 brass mold processing, an improvement of material strength with the increase of strain rate and the evolution process of the chip can be divided into: ribbon cuttings, serrated chips, cell chips.

Finite Element Method Simulation Study of High-Temperature Alloy Serrated Chip

High-temperature alloy can easily produce jagged chips in high-speed cutting conditions. The serrated chips will lead to the volatility of cutting force and impact the processing efficiency and quality. The formation mechanism of serrated chip has important significance to improve processing quality and efficiency. As the serrated chips have very short generation time, it is very hard to measure the changes of the stress, strain and temperature during the formation of serrated chips in experimental method. And it is more difficult to carry out quantitative and qualitative analysis. So it has been the research priorities and difficulties in the field of metal cutting. In this paper, both the finite element method simulation and experimental method are used to study the formation mechanism of serrated chip, deformation of material and the degree of variation of jagged. It has an important reference value to select cutting parameters for high-temperature alloy cutting.

Changing Boundaries of Serrated Chip in Hard Cutting GCr15 Steel

Hard cutting process is easy to produce serrated chip. Hardened steel GCr15 as the object for the study, chip morphology was studied on hard cutting test and chip cross-sectional microscopic analysis methods. The boundaries of ribbon cuttings to serrated chips cutting was determined, under certain conditions of PCBN cutting tool cutting precision hardened steel GCr15, and form a quantitative description of the chip. With the increase in the amount of cutting, serrated chips have the degree of improved trend, in which the most significant impact of cutting speed, while the hardness increases, the degree of sawtooth also increases. Hard cutting research will enrich the theory provides a theoretical basis for the choice of cutting parameters.