Papers by Keyword: Chip Formation

Abstract: The present study describes the impact of various protective process agents on chip forming processes. The research was conducted on NiCr20TiAl and 34NiCrMoV14-5 nickel-chromium alloys. New lubricant-cooling process agents with carbon nanopowder additives are studied. The optimal composition of the nanopowder additive and its effect during alloy cutting is examined. Experiments reveal the dependence of shrinkage ratio on cutting speed and various protective process agents. The values of H50 microhardness are also defined when cutting these alloys using protective process agents. Experimental studies found the positive effect of developed agents with nanopowder additives on the processes of NiCr20TiAl and 34NiCrMoV14-5 alloys chip formation.

Abstract: Aluminum alloy 7050-T7451 is widely used in aeronautical large structural parts, and high speed cutting is often used in machining. The serrated chip is a critical state for chip formation in high speed cutting, and its formation and control mechanism are of great significance for actual machining. To study the chip formation of high speed cutting aluminum alloy 7050-T7451, the chips at different cutting speeds are obtained by high speed cutting experiments. Combined with microscopic observation, the chip shape evolution, chip localization fracture process and mechanism of different cutting speeds are analyzed. The morphological evolution of chips and the mechanism of chip breaking during high speed cutting of aluminum alloy are revealed. According to the machined surface of the chip root and the angle of the chip, the formation mechanism of the curl radius formed by the chip is analyzed. The critical cutting speed of plastic-brittle transformation of aluminum alloy 7050-T7451 in high speed cutting is obtained by studying the critical condition for strip-to-serration transition of chip morphology.

Abstract: The aim of this work is to develop a methodology for graphically analytical calculation of angles of chip formation process for the case when the initial data are reliable empirical dependencies for the cutting forces’ components and value of shearing angle are obtained experimentally. The research method is based on the application of the elements of cutting theory with respect to flow chip formation scheme and the model of plastic deformation of metal with one slip surface with free cutting without a build-up on the front surface of the blade. Academic novelty is characterized by the developed algorithmic model which is based on the interrelation of shearing angles, external friction-slip chips on the front surface of the blade, internal friction-shear in the plane of shear and the front angle of the blade. The algorithmic model is implemented programmatically in the NI LabVIEW environment and graphically analytical in the KOMPAS-3D program. There were carried out computer experiments and identified the dependencies of chip formation angles on cutting speed and the front angle of the blade. The practical significance consists in the possibility to carry out an engineering analysis of the metal cutting mechanics without carrying out some valuable complex experiments.

Abstract: The results of experimental studies of a new method for turning billets from thermoplastic polymers such as caprolon and fluoroplastic are presented. The technical essence of the method is in workpiece advanced processing by ultrasonic vibrations using preliminary machining. Experimental studies were carried out on a lathe which is equipped with an ultrasonic oscillatory system. Roughness level profilograms of the caprolon and fluoroplastic treated surfaces are used for visual and operational control of the turning process. The results of the experimental verification of the developed method confirmed the expediency of its implementation since the use of advanced ultrasonic treatment during turning of thermoplastics leads to a decrease in the roughness level of the treated surface of the part as evidenced by the values ​​of roughness parameters and the type of chips obtained.

Abstract: The potential of a recently developed technique that uses a clean supercritical High Pressure Cryogenic Nitrogen Jet (HPCryoN2Jet) for surface ablation and cleaning is depicted. In contrast to existent coating-removal techniques (chemical stripping, hydro-blast, water jet cleaning...), as nitrogen is naturally recycled in the air, this process has a high potential for surface treatment without any chemical and physical effluents or sewage disposal. The treatment consists in impacting the surface with a high pressure (up to 3500 bar) cryogenic nitrogen jet (down to-160°C). The pressurized cryogenic nitrogen exits from a nozzle - having generally a 0.2 to 0.5 mm diameter outlet - to form the high velocity (supersonic) nitrogen jet. In this contribution, the ability of the process to remove polymeric (PA) coatings is evaluated on different types of metallic substrates (Cu, Al, E24, 316L stainless steel). The mechanisms of chip formation have been visualized using a high speed camera. Coating failure is shown experimentally to occur downstream of the jet and the influence of the substrate thermal properties on the stripping efficiency of the PA coating is highlighted.

Abstract: Aluminum based metal matrix composites (AMMC) have found its applications in the automobile, aerospace, medical, and metal industries due to their superior mechanical properties. Fabricated Aluminum based metal matrix composites require machining to improve the surface finish and dimensional tolerance. Machining should be accomplished by good surface finish by consuming lowest energy and less tool wear. This paper reviews the machining of Aluminum based metal matrix composites to investigate the effect of process parameters such as tool geometry, tool wear, surface roughness, chip formation and also process parameters.

Abstract: In the paper it is pointed out that machining of titanium alloys is the most difficult problem in metal cutting. The leading world companies are dealing with this problem, as titanium alloys are the basis of the aerospace industry. In the paper high-speed cutters with wavelike teeth edges used for titanium alloys processing are investigated. Every subsequent tooth is displaced at half-space distance. This reduces power load on the hardening of the machined surface. On the basis of power and wear-resistance studies, the advantage of wavy milling cutters in comparison with standard ones is established; it is proved that wavy cutters have a lower specific power load, greater wear resistance and less surface hardening.

Abstract: This paper studied chip morphology in end milling of aluminium alloy 6061 by various cutting parameter such as feed rate, cutting speed and depth of cut. Slot milling operation were conducted. The analysis consists of chip morphology, chip weight, chip thickness and chip length. Scanning Electron Microscope (SEM) were used to obtain and examine the chips. Result shows that, end milling with higher cutting speed, feed rate and depth of cut generated short, small and light weigh of chips.

Abstract: Independent research studies have shown notable dissimilarity in the machining behaviour of aluminum alloys AA6061−T6 and AA7075−T651 commonly used in automotive and aeronautical applications. The present work attempts to investigate this dissimilarity based on experimental and numerical data with a focus on chip formation and generated residual stresses under similar high−speed machining (HSM) conditions. The numerical data were calculated by a finite element modeling (FEM) developed using Deform^TM 2D software. The results showed that both studied alloys exhibit different chip formation mechanisms and residual stress states at the machined surfaces. On one hand, the AA6061−T6 alloy generates continuous chips and tensile residual stresses whereas the AA7075−T651 alloy produces segmented chips and compressive residual stresses. FEM results showed that the AA6061−T6 alloy generates lower cutting temperature at the tool−chip interface along with higher equivalent total strains at the machined surface as compared to the AA7075−T651 alloy. Based on the experimental and numerical results, it was pointed out that the differences in terms of thermal conductivity and initial yield stress are the main reasons explaining the dissimilarity observed.

Abstract: The research aim is to study and analyze the shear zone by application of merchant circle during machining of titanium alloy (Ti6Al4V). The thermo-mechanical reaction during machining plays an important role in defining machinability of titanium alloys. The scientific community is concerned about machining of titanium alloy due to problems occurring in the shear zone that affect tool life. Studying the cutting action contributes to understanding and addressing these problems effectively. For this purpose, an experimental setup, utilizing a high speed camera will be used to study the shear zone. The shear zone characteristics are studied by analyzing the images captured by a high speed camera placed near to the shear zone during machining. The experimental design consists of conducting a series of turning trials using combination of cutting parameters namely constant spindle speed (n) 770 rpm; feed rate (f) of 2 and 4 mm/rev; and depth of cut (d) of 1 and 2 mm. The length of cut (L) of 10 mm remains constant and no coolant is used for all trials. The images obtained from the camera are analyzed against the theory of orthogonal cutting using merchants circle.