Extension of the Slip Band Area under Magnetization during Steel Machining
12 Sep 2012-Materials and Manufacturing Processes (Taylor & Francis Group)-Vol. 27, Iss: 10, pp 1073-1077
TL;DR: In this paper, the machinability of AISI-1045 steel in a magnetically assisted environment was discussed, and the changes were manifested through an enhancement in steel plasticity, resulting in a widened slip band area within the primary shear zone (PSZ) and improved plastic flow at tool-steel interfaces along the SZ.
Abstract: This work discusses the machinability of AISI–1045 steel in a magnetically assisted environment. Physically, magnetization causes suppression of Bloch walls in ferromagnetics, which enhances the dislocation paths within the Weiss domains of the matrix material. From a material point of view, the changes were manifested through an enhancement in steel plasticity, resulting in (i) a widened slip band area within the primary shear zone (PSZ) and (ii) improved plastic flow at tool-steel interfaces along the secondary shear zone (SSZ). From a mechanical point of view, the modifications can be summarized as a neat drop of the thrust force component due to the magnetic action generated by the external source, i.e., the current coil. The changes observed in the local diagram of forces cause alterations in the tribological properties at the tool-material interfaces. These alterations act to accelerate formation of the chip and lead to save energy because of the decrease in the cutting period, which should signific...
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TL;DR: In this paper, the influence of modified tool (tool with texturing) on the process of orthogonal turning of Ti-6Al-4V work material was investigated.
Abstract: Importance of this present investigation is to identify the influence of modified tool (tool with texturing) on the process of orthogonal turning of Ti–6Al–4V work material. To achieve the enhanced...
76 citations
Cites background from "Extension of the Slip Band Area und..."
...It was observed from exploration that the slip bands become wider with the increase in magnetic intensity and the BUE formation increased in secondary deformation zone([20])....
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...was observed in the range of 13–20% during machining with textured tools than the conventional tool.([20,21]) Figure 6b illustrates the rate of shear strain for the different type of inserts at different cutting speeds....
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TL;DR: In this article , a coupled analysis of magneto-plasticity and crystal plasticity is developed to demonstrate the susceptibility of non-magnetic single-crystal calcium fluoride (CaF 2 ) to the magnetoplastic effect.
Abstract: • A weak magnetic field can enhance ductile-mode cutting of CaF 2 single crystal. • Magnetic field direction shows anisotropy in affecting ductile–brittle transition. • A coupled analysis of magneto-plasticity and crystal plasticity is developed. • Dislocation behaviour and fracture toughness are revealed under magnetic field. • DFT computation corroborates the magnetic-induced dislocation depinning theory. Magneto-plasticity occurs when a weak magnetic field alters material plasticity and offers a viable solution to enhance ductile-mode cutting of brittle materials. This study demonstrates the susceptibility of non-magnetic single-crystal calcium fluoride (CaF 2 ) to the magneto-plastic effect. The influence of magneto-plasticity on CaF 2 was confirmed in micro-deformation tests under a weak magnetic field of 20 mT. The surface pile-up effect was weakened by 10–15 nm along with an enlarged plastic zone and suppressed crack propagation under the influence of the magnetic field. Micro-cutting tests along different crystal orientations on the ( 111 ) plane of CaF 2 revealed an increase in the ductile–brittle transition of the machined surface with the aid of magneto-plasticity where the largest increase in ductile–brittle transition occurred along the [ 11 2 ¯ ] orientation from 512 nm to a range of 664–806 nm. Meanwhile, the subsurface damage layer was concurrently thinner under magnetic influence. An anisotropic influence of the magnetic field relative to the single-crystal orientation and the cutting direction was also observed. An analytical model was derived to determine an orientation factor M that successfully describes the anisotropy while considering the single-crystal dislocation behaviour, material fracture toughness, and the orientation of the magnetic field. Previously suggested theoretical mechanism of magneto-plasticity via formation of non-singlet electronic states in defected configurations was confirmed with density functional theory calculations. The successful findings on the influence of a weak magnetic field on plasticity present an opportunity for the adoption of magnetic-assisted micro-cutting of non-magnetic materials.
7 citations
TL;DR: In this article, the reliability of a novel constitutive approach to model the magnetically assisted dry cutting of steel was discussed, where the magnetic force combined with the mechanical force components, was found to be responsible for the perturbation observed in the primary shear angle.
Abstract: This paper discusses the reliability of a novel constitutive approach to model the magnetically assisted dry cutting of steel. The magnetic force combined with the mechanical force components, was found to be responsible for the perturbation observed in the primary shear angle. This perturbation is considered the basis of the analytical development. Quick-Stop Trials (QST) were first performed on AISI-1045 steel to investigate the shear angle evolution during the chip formation process. Both the Merchant and the Lee–Shaffer models were used to develop the coupled magnetic–mechanical approach. Magnetically free and magnetically assisted orthogonal cutting tests were then conducted to validate the analytical predictions. The shear angle showed a sensitive increase with the magnetic intensity until the steel magnetic saturation limit was reached. A magnetic field seems to be capable of altering the plastic shear, resulting in modification of the chip formation mechanisms. The neat drop observed in contact length proves the ability of the magnetic field to enhance the material flow along the secondary shear zone. The changes at the tool–steel interface, i.e., friction, are found to correlate strongly with the force magnitude change due to the magnetic component. The good agreement between the measurements and predictions demonstrates the efficiency of the proposed approach.
7 citations
TL;DR: In this paper , the effect of magneto-plasticity on the micro-cutting of a single-crystal copper was investigated under a weak magnetic field and the influence of the phenomenon on the cutting forces and machined surface quality was reported.
Abstract: • Magneto-plasticity can be induced by a weak magnetic field in micro-cutting. • Cutting force, chip and machined surface are affected by magneto-plasticity. • Magneto-plasticity shows anisotropy with magnetic field direction. • Directional dislocation flow results in anisotropic magneto-plasticity. The plasticity of metals can be significantly affected by the application of a magnetic field, otherwise known as the magneto-plastic effect. This paper investigates the magneto-plastic effect in the micro-cutting of a non-magnetic ductile material, single-crystal copper, under a weak magnetic field and reports the influence of the phenomenon on the cutting forces and machined surface quality. A softening effect was observed from the large reduction in cutting forces from 3.2 N to 1.5 N under the magnetic field. As compared to the magnetic field intensity and polarity, the variation in magnetic field orientations with respect to the cutting direction exhibited a stronger influence on the cutting force, chip morphology, machined surface texture, subsurface microstructure, surface roughness, and machined surface microhardness of the copper sample. An analytical model was developed based on the geometry of the cutting chips to correlate the orientation-dependent influence of the magnetic field on the cutting forces. On the surface quality, excessive folds with four different types of morphology produced under magnetic-free cutting were suppressed after applying the magnetic field with the most significant improvement achieved with the 90° magnetic field direction. The magnetic-assisted changes in machined surface morphology also led to the reduction in machined surface roughness and microhardness. The optimistic micro-cutting outcomes in this work establish a greater understanding of the magneto-plastic effect and demonstrate the applicability of magneto-plasticity in ultraprecision manufacturing.
4 citations
References
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TL;DR: In this paper, the analysis of the orthogonal cutting with a type 2 chip is extended by introducing those physical properties of the work material which control its plastic behavior, and a simple additional plasticity condition is obtained by application of the principle of minimum energy.
Abstract: The analysis of the mechanics of orthogonal cutting with a type 2 chip as presented in the first paper of this series can be extended by introducing those physical properties of the work material which control its plastic behavior. One evident plasticity condition is the equality of the shear stress on the plane of shear to the shear strength of the metal. If it is also assumed that the shear strength of the work material is a constant and is the only quantity controlling its plastic behavior, then a very simple additional plasticity condition is obtained by application of the principle of minimum energy. This condition is 2φ+τ−α=90°, where φ is the shear angle, τ the friction angle, and α the rake angle. This condition, however, is found by experiment to be a poor approximation in the case of polycrystalline metals. A very good approximation is obtained, though, if use is made of the fact that the shear strength of the polycrystalline metal is actually a function of the compressive stress on the shear pl...
725 citations
"Extension of the Slip Band Area und..." refers background in this paper
...The discontinuity of the local field of the tangential velocity [14, 15] within the shear zone describes the typical angle....
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TL;DR: In this paper, it was shown that in the region where the chip is separated from the workpiece (i.e., the primary shear zone) the work piece material is sheared considerably to equivalent strains in the order of 1-2.
Abstract: A major problem in finding the flow stress in metal cutting is the intense circumstances under which deformation takes place in the chip root. Large deformations are imposed on the workpiece material at high speed in a very small area. This results in mechanical material behaviour far removed from that encountered in conventional material tests. Therefore, to determine the flow stress in cutting it is necessary to determine the conditions under which the material is being deformed. This paper describes how the strains, strain rates and temperatures have been determined in orthogonal cutting tests of steel AISI 1045 and aluminium AA 6082-T6. It appears that in the region where the chip is separated from the workpiece (i.e. the primary shear zone) the workpiece material is sheared considerably to equivalent strains in the order of 1–2. Also, the strain rate in the primary shear zone is found to be very large: in the order of 2.0×104 s−1. To find the temperatures in metal cutting an IR camera is used. It appears that the feed rate and cutting speed hardly influence the shear plane temperature. The measured shear plane temperature is approximately 290 °C in the case of the steel and approximately 190 °C in the case of the aluminium alloy.
144 citations
"Extension of the Slip Band Area und..." refers background in this paper
...It was demonstrated in the literature that this latter layer has a uniform thickness along the chip’s back that does not change with the cutting radius [16, 17]....
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TL;DR: In this article, the grain size dependence of the flow strength of polycrystals is analyzed using plane strain, discrete dislocation plasticity, and constitutive rules are used to model lattice resistance to dislocation motion, as well as dislocation nucleation, dislocation annihilation and the interaction with obstacles.
Abstract: The grain size dependence of the flow strength of polycrystals is analyzed using plane strain, discrete dislocation plasticity. Dislocations are modeled as line singularities in a linear elastic solid and plasticity occurs through the collective motion of large numbers of dislocations. Constitutive rules are used to model lattice resistance to dislocation motion, as well as dislocation nucleation, dislocation annihilation and the interaction with obstacles. The materials analyzed consist of micron scale grains having either one or three slip systems and two types of grain arrangements: either a checker-board pattern or randomly dispersed with a specified volume fraction. Calculations are carried out for materials with either a high density of dislocation sources or a low density of dislocation sources. In all cases, the grain boundaries are taken to be impenetrable to dislocations. A Hall–Petch type relation is predicted with Hall–Petch exponents ranging from ≈0.3 to ≈1.6 depending on the number of slip systems, the grain arrangement, the dislocation source density and the range of grain sizes to which a Hall–Petch expression is fit. The grain size dependence of the flow strength is obtained even when no slip incompatibility exists between grains suggesting that slip blocking/transmission governs the Hall–Petch effect in the simulations.
121 citations
"Extension of the Slip Band Area und..." refers background in this paper
...The rearrangements within the microstructure of metals ultimately affect the material plasticity that occurs through the collective motion of large numbers of dislocations [2]....
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TL;DR: In this paper, the microscopic changes in the surface texture resulting from interaction of abrasives with ground workpiece surface were investigated using X-ray diffraction and atomic force microscopy.
Abstract: Ultrasonic-assisted magnetic abrasive finishing (UAMAF) integrates the use of ultrasonic vibrations and magnetic abrasive finishing (MAF) processes to finish surfaces of nanometer order within a minute's time. The present study emphasizes the mechanism of surface finishing in UAMAF. This article reports the study of the microscopic changes in the surface texture resulting from interaction of abrasives with ground workpiece surface. In addition to the surface roughness measurement, scanning electron and atomic force microscopy were used to understand the material removal process and wear behavior during finishing and to provide a fundamental insight of the finishing in UAMAF. The observed surface texture showed that the process is an accumulation of the microscratches resulting from the interaction of abrasive cutting edges with the workpiece surface. The X-ray diffraction (XRD) analysis revealed that the SiC is induced in the workpiece surface, increasing the hardness of the workpiece up to 960 HV.
60 citations
"Extension of the Slip Band Area und..." refers background in this paper
...Henceforth, changes observed on the diagram of forces will inevitably manifest as mechanical transformations [13, 18] that the steel undergoes at the toolmaterial interfaces where friction mechanisms play a primary role in the formation of the chip and the definition of its morphology....
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TL;DR: In this article, the authors used the Taguchi method to evaluate surface roughness in magnetic finishing with gel abrasives (MFGA) process and found that the temperature of the gel abrasive on the workpiece exceeded 110°C within 30min.
Abstract: Magnetic finishing with gel abrasives (MFGA) created an excellent efficiency in the polishing process. They were not only easily produced but recycled after machining as well. The silicone gel, which was then chosen as the medium in this study, played a crucial role to locate the abrasion behavior and establish the mechanism of MFGA. In the article, polishing efficiencies with or without silicone gels were identified to finish cylindrical rod first. In addition, temperature in the working area was to verify the relation between the circulation and efficiency. Finally, the Taguchi method was used to elucidate optimal parameters in MFGA process. Results show that the temperature of the gel abrasive on the workpiece exceeded 110°C within 30 min. Such high temperatures will induce new abrasives due to the slow motion of gel in the working area. In the Taguchi method, the ‘the smaller the better’ role was employed to evaluate surface roughness in MFGA. The signal-to-noise (S/N) ratio shows that concentration o...
34 citations