Papers by Keyword: High Speed Cutting

Abstract: High-speed cutting (HSC) is frequently adopted to manufacture parts in many industries, including aerospace and automotive. To manufacture high-quality parts, adiabatic shear banding (ASB), often observed on serrated chips of various metallic materials during the HSC process, should be suppressed and studied. ASB is formed due to work hardening of metallic materials and work softening induced by adiabatic heating. The onset of ASB during the orthogonal cutting of Ti6Al4V is modeled based on the continuum mechanics, taking both work hardening and work softening into considerations. The model is validated by finite element method (FEM) and experiments. Moreover, the ASB onset process is simulated in FEM to reveal the ASB formation mechanism. The effect of the mechanical properties of Ti6Al4V on the onset of ASB is investigated based on the Johnson-Cook model. The investigation reveals the main factors that affect the onset of ASB during the HSC process. Future work includes characterizing the mechanical behavior of Ti6Al4V after the onset of ASB during a cutting process by coupling the continuum mechanics and micromechanics.

Abstract: Micro-milling offers high flexibility by producing complex 3D micro-scale products. Weight reduction are one of the optimizations of the product that can make it stronger and more efficient nowadays. Titanium are the most commonly used for micro-scale products especially in biomedical industries because of the biocompatibility properties. Titanium alloys offers high strength with low density and high corrosion resistance that is suitable for weight reduction. This study aims to investigate the influence of high speed cutting parameters to the surface roughness in micromilling of titanium alloy Ti-6Al-4V as high speed cutting offers more productivity since producing more cutting length in the same time. experiments are carried out by micromilling process with variations in high speed cutting parameters of spindle speed and feed rate with a constant depth of cut using a carbide cutting tool of with a diameter of 1 mm. The machining results in the form of a 4 mm slot with a depth as the same as depth of cut, which then measures its surface roughness. It was found that higher feed rate that is followed by higher spindle speed will produce better surface roughness.

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: This paper investigated the variation in a heat partition ratio of the cutting tool with the cutting speed ranging from 38 m/min to 6500 m/min. The orthogonal high-speed cutting experiment was performed utilizing an impact cutting tester developed. The cutting length in this study was 60 mm. The temperatures at the tool-chip interface were measured directly with three pairs of Cu/Ni micro thermocouples fabricated on the rake face. The temperature rises rapidly from the beginning of cutting, and then levels off when a cutting distance exceeds about 10 to 20 times the depth of cut. The distance depends on the cutting speed. Using the temperatures measured, a variation in the heat partition ratio with cutting time was estimated with the aid of a FEA. The heat partition ratio at the end of cutting estimated decreases approximately from 7 % to 1 % as the cutting speed increases from 38 m/min to 6500 m/min. The heat partition ratio estimated is quite higher than that calculated by employing an analysis assuming the steady state, particularly under the high speed cutting conditions.

Abstract: In this study, high speed milling of stainless steel was tried for purpose of high efficiency cutting of a steam turbine blade. In the experiment, cutting tool used TiAlN coating radius solid end mill made of cemented carbide. Diameter of end mill is 5mm. Corner radius is 0.2mm. Cutting speed carried out at 100m/s~600m/s. Work pieces was used in the experiment are four kinds of stainless steel which alloy elements differ. Mainly, content of chromium and nickel is different. There are many researches about high speed milling [1, 2].However, the researches which examined relationship between alloy elements of stainless steel and cutting characteristics on high speed milling using small diameter endmill are few.As the results, in the case of stainless steel containing much nickel, tool life becomes short in high speed cutting area. This reason is nickel has low thermal conductivity. Because the cutting point temperature becomes higher. If the coating removes, wear becomes large rapidly. In other words, maximum limit value of cutting speed was found to be dependent on heat resistance temperature of the coating.On the other hand, Chromium has the effect of improving the abrasion resistant of the workpiece. However, Flank wear was not increased in a low cutting speed area. In the range of this experimental condition, chromium didn't influence tool life. When cutting point temperature is below heat resistant temperature of the coating, it is thought that effect of the coating is maintained. Namely, it was found that appropriate cutting speed followed heat resistant temperature of the coating.

Abstract: The dynamic process of cracks initiation in brittle materials during high speed cutting is primary for the analysis of material fracture mode and finished surface. Cast iron was considered in this paper and discrete element method (DEM) was employed to create a density packed bonded-particle model for studying its machining cracks. The numerical tests of split Hopkinson pressure bar (SHPB) and oblique plane impact were conducted to calibrate the dynamic behaviour of the model. The cutting simulations were carried out for a range of rake angles and cutting speeds. The results showed that both the processes of cracks initiation and the cracks distribution were different greatly under different cutting conditions and the cracks number increased with the cutting speed. In addition, within the detection zone in the model, the duration of crack initiation decreased dramatically with the increase of cutting speed in the lower range. But for the high speed cutting, the duration tended to be stable and was not affected by cutting speed and it was very close to the time of stress wave produced by cutting arriving at the zone. Furthermore, the stress state of particles’ connectors under the action of stress wave was analysed, which suggests that the stress wave is the key factor causing cracks initiation of brittle materials during high speed cutting.

Abstract: High speed cutting (HSC) has been used widely in the metal machining industry. However, applications and investigations have shown that to optimize an HSC process, many issues need to be understood, such as the fluctuations of cutting forces and residual stresses. Extensive studies have found that these fluctuations are originated from the shear banding during chip formation and from the work-material properties influenced by the coupled attack of high strain rate and high temperature rise during cutting. Due to the complexity of the material deformation mechanisms during HSC, both experimental examination and theoretical analysis are essential. This keynote presentation reviews an integral approach of the author’s team to establishing the investigation chain of experimental analysis, constitutive modelling and numerical simulation to tackle the intricacy of HSC-induced deformation. It points out that while an experimental examination can provide insightful understanding of the deformation mechanisms, it is often limited to a narrow range of testing conditions. A numerical simulation can overcome such experimental difficulties through large-scale parametric studies, but can also bring about erroneous results if the constitutive behavior of a workpiece material is improperly described.

Abstract: Application prospect of the high volume fraction SiCp/Al composites becomes increasingly widespread, the study of cutting mechanism is important for achieving its high efficient and precision machining. In this paper, a three-dimensional beveled simulation model of high volume fraction SiCp/Al composites on high-speed milling is established by finite element software ABAQUS, the constitutive on model material, the tool-chip contact and the chip separation model is elected reasonably.The paper analyzes the effect of cutting speed on the chip formation and the stress distribution of the material. The results shows that: with the increasing of cutting speed, the chip is easily broken, cutting speed have little impact on the maximum stress of the material.

Abstract: Under the condition of cutting speed 10-300m/min, rake angle -10°、0°、10°and cutting depths 0.05mm、0.1mm and 0.2mm, the experiment study of adiabatic shear serrated chip and surface roughness are carried out. The influence of cutting condition on serrated chip is analyzed through the metallographic observation of obtained chip. By the measurement of finished surface, the influenc of cutting condition and adiabatic shear on surface roughness is also investigated. The rusults show that the reason lead to serrated chip in high speed cutting of Ti6Al4V is adiabatic shear, not the periodic fracture.The adiabatic shear serrated chip is easier appear and the degree of segment is more large under the condition of higher cutting speed, larger cutting depth and smaller rake angle. The surface roughness is smaller when the cutting speed is higher, cutting depth is larger, and rake angle is smaller.

Abstract: In view of the cutting speed reduced and cutting quality became poor because cutting front changes to flat and amount of lag changes to large, light-gas eccentrically cutting method was proposed. Through the experiment and analysis of the results, the conclusion can be obtained that when laser beam is before gas jet, cutting speed can be improved. While offset distance have impacts to cutting result. If the offset distance is too small, it has no difference with light - gas coaxial cutting; if the offset distance is too large, it weakens the gas jet at the cutting surface, which is not conducive to cutting. It can achieve the best results when the offset distance is 0.3mm.The cutting quality with 1.5mm diameter nozzle is better than that of 2mm. Therefore within the allowable range in the offset distance the nozzle aperture should be reduced.