Experimental-Analytical Method for Temperature Determination in the Cutting Zone during Orthogonal Turning of GRADE 2 Titanium Alloy

The paper presents an experimental-analytical method for determination of temperature in the cutting zone during the orthogonal turning of GRADE 2 titanium alloy. A cutting insert with a complex rake geometry was used in the experiments. The experimental part of the method involved orthogonal turning tests during which the cutting forces and the chip forming process were recorded for two different insert rake faces. The analytical part used a relationship between the cutting forces and the temperature in the Primary Shear Zone (PSZ) and the Secondary Shear Zone (SSZ), which are described by the Johnson-Cook (J-C) constitutive model and the chip forming model according to the Oxley’s theory. The temperature in the PSZ and SSZ was determined by finding the minimum difference between the shear flow stress determined in the J-C model and the Oxley’s model. Finally, using the described method, the relationship between the temperature in the PSZ and SSZ and the rake face geometry was determined. In addition, the temperature in the cutting zone was measured during the experimental tests with the use of a thermovision camera. The temperature distribution results determined experimentally with a thermovision camera were compared with the results obtained with the described method.

Effect of Minimum Quantity Lubrication to Prediction of Cutting Temperature Distribution in Turning Material AISI-1045

This paper presents a prediction of cutting temperature in turning process, using a continuous cutting model of Johnson-Cook (J-C). An method to predict the temperature distribution in orthogonal cutting is based on the constituent model of various material and the mechanics of their cutting process. In this method, the average temperature at the primary shear zone (PSZ) and the secondary shear zone (SSZ) were determined for various materials, based on a constitutive model and a chip-formation model using measurements of cutting force and chip thicknes. The J-C model constants were taken from Hopkinson pressure bar tests. Cutting conditions, cutting forces and chip thickness were used to predict shear stress. Experimental cutting heat results with the same cutting parameters using the minimum lubrication method (MQL) were recorded through the Testo-871 thermal camera. The thermal distribution results between the two methods has a difference in value, as well as distribution. From the difference, we have analyzed some of the causes, finding the effect of the minimum quantity lubrication parameters on the difference.

Methodology for the Measurement of the Heat Partitioning by Thermal Imaging in the Orthogonal Cutting Process

The thermal conditions like temperature distribution and heat fluxes during metal cutting have a major influence on the machinability, the tool life time, and the metallurgical structure of the work piece material. Though numerous analytical and experimental efforts have been developed in order to understand the thermal conditions in metal cutting, many questions still prevail. So, the exact form, distribution, and intensity of heat sources in the primary and secondary shear zone, which may describe the observed temperature distributions, are not explored to a satisfactory extend. On the other hand, the influence of the material properties like friction coefficient, heat conductivity, and shear strength is not yet fully understood. Another essential question is the heat flux partition among chip, work piece, and tool depending on process parameters and material. The particular novelty of the current investigation is a new methodological approach using modern thermal measurement system and postprocessing methods in order not only to measure the entire temperature field in the orthogonal cutting zone but also to calculate the affiliated heat flow distribution in the cutting process. Thus, the cutting process is treated as energy conversation process of the governing mechanical power into sensible heat. This point of view offers compatibility across process parameters and materials, thus new possibilities for process design.

Insights into Machining of a β Titanium Biomedical Alloy from Chip Microstructures

New metastable β titanium alloys are receiving increasing attention due to their excellent biomechanical properties and machinability is critical to their uptake. In this study, machining chip microstructure has been investigated to gain an understanding of strain and temperature fields during cutting. For higher cutting speeds, ≥60 m/min, the chips have segmented morphologies characterised by a serrated appearance. High levels of strain in the primary shear zone promote formation of expanded shear band regions between segments which exhibit intensive refinement of the β phase down to grain sizes below 100 nm. The presence of both α and β phases across the expanded shear band suggests that temperatures during cutting are in the range of 400–600 °C. For the secondary shear zone, very large strains at the cutting interface result in heavily refined and approximately equiaxed nanocrystalline β grains with sizes around 20–50 nm, while further from the interface the β grains become highly elongated in the shear direction. An absence of the α phase in the region immediately adjacent to the cutting interface indicates recrystallization during cutting and temperatures in excess of the 720 °C β transus temperature.

Insights into Machining of a β Titanium Biomedical Alloy from Chip Microstructures

New metastable β titanium alloys are receiving increasing attention due to their excellent biomechanical properties and machinability is critical to their uptake. In this study machining chip microstructure have been investigated to gain an understanding of strain and temperature fields during cutting. For higher cutting speeds, ≥60 m/min, the chips have segmented morphologies characterised by a serrated appearance. High levels of strain in the primary shear zone promote formation of expanded shear band regions between segments which exhibit intensive refinement of the β phase down to grain sizes below 100 nm. The presence of both α and β phases across the expanded shear band suggests that temperatures during cutting are in the range of 400–600 °C. For the secondary shear zone, very large strains at the cutting interface result in heavily refined and approximately equiaxed nanocrystalline β grains with sizes around 20–50 nm, while further from the interface the β grains become highly elongated in the shear direction. An absence of the α phase in the region immediately adjacent to the cutting interface indicates recrystallization during cutting and temperatures in excess of the 720 °C β transus temperature.

Insights Into Machining of a β Titanium Biomedical Alloy from Chip Microstructures

New metastable β titanium alloys are receiving increasing attention due to their excellent biomechanical properties and machinability is critical to their uptake. In this study machining chip microstructure have been investigated to gain an understanding of strain and temperature fields during cutting. For higher cutting speeds, ≥60 m/min, the chips have segmented morphologies characterised by a serrated appearance. High levels of strain in the primary shear zone promote formation of expanded shear band regions between segments which exhibit intensive refinement of the β phase down to grain sizes below 100 nm. The presence of both α and β phases across the expanded shear band suggests that temperatures during cutting are in the range of 400-600°C. For the secondary shear zone, very large strains at the cutting interface result in heavily refined and approximately equiaxed nanocrystalline β grains with sizes around 20-50 nm, while further from the interface the β grains become highly elongated in the shear direction. An absence of the α phase in the region immediately adjacent to the cutting interface indicates recrystallization during cutting and temperatures in excess of the 720°C β transus temperature.

Analytical Modelling of Friction Along Tool Chip Interface for Inconel 718

Inconel 718 is gaining its importance in the aerospace and power plant industries because of its high strength to weight ratio. The lack of understanding of the tool chip interface for Inconel 718 restricts the prediction of the apparent coefficient of friction and thus the cutting forces, thereby the machining efficiency. In the present study an analytical model has been developed accounting the actual variation of stresses over the rake face. The model focuses on the variation of shear stresses in the sticking region and has been considered to be increasing exponentially with distance from tool tip. The primary shear zone is assumed to be a thin layer with constant thickness and has been modelled using Johnson Cook material model. The shear stresses at the entry and exit of the primary shear zone has been calculated using iterative techniques proposed in the literature. The secondary shear zone has been analyzed dividing the contact length into two distinct regions and each region has been dealt separately. The ratio of real area of contact to the apparent area of contact has been given consideration and dealt with at macroscopic level. Experimental values have been extracted from previous studies on Inconel 718. The predictions of the analytical model was found to be in good agreement with experimental results. The experimental apparent coefficient of friction was obtained as 0.5119 against 0.4733 from the developed model at a velocity of 70 mm/min, depth of cut of 1mm, nose radius of 0.8mm and with negative rake angle (−6°) with CNMG0812 tool. The predicted and the experimental friction coefficient showed a variation of 7.07% – 10% and thus can serve as reliable model for Inconel 718.

Friction Modeling and Experimental Research of Tool-Chip in Turning Titanium Alloy Ti6Al4V

Cutting force, cutting heat and tool wear are closely related to the friction characteristics of tool-chip interface in the process of metal cutting. The variation of the cutting speed and temperature have been analyzed by the distribution of stress and strain in the primary and the secondary shear zone. A new friction model has been established to analyze the contact length between cutting tool and chip and local friction coefficient at the sliding zone. Cutting experiments have been performed in the process of carbide tools cutting the titaniumTi6Al4V, the contact length of sticking zone and sliding zone and friction coefficient have been analyzed by measured cutting force. The simulation of cutting process has been carried out based on Deform software, then the simulation results have been compared with the test ones, which verifies the accuracy of the established model.