Increasing Wheel Speed Research Articles

Precision grinding of bearing steel based on active control of oxide layer state with electrolytic interval dressing

The oxide layer state directly relates to machining quality in electrolytic in-process dressing (ELID) grinding. In this paper, intermittent grinding control strategy was used to monitor and control the state of the oxide layer in interval ELID (ELID II) grinding. Some experiments were implemented based on active control of the oxide layer state. The influence of dressing current, wheel speeds, and grit size on surface roughness and waviness has been discussed in detail with ELID II grinding for bearing steel. The experimental results illustrate that the ELID II method can realize a stable grinding process based on active control of the oxide layer state. The surface roughness (Ra) and waviness (Wa) increase with increase of the dressing current. When the dressing current is constant, Ra and Wa reduce as wheel speed increases and decrease as grain size of wheel decreases. The experimental results also show that sufficient abrasive protrusion can be ensured in ELID II grinding, especially for grinding with a W2.5 super-abrasive wheel which may produce a very smooth surface quality, Ra 0.0166 μm and Wa 0.018 μm.

Effects of Cr3C2 content and wheel speed on amorphization behavior of melt-spun SmCo7-x(Cr3C2)x alloys

The effects of the Cr3C2 content and wheel speed on the amorphization behavior of the melt-spun SmCo7-x(Cr3C2)x (x=0.10-0.25) alloys were studied systematically by X-ray diffraction analysis (XRD), differential scanning calorimetry (DSC) and magnetic measurements. The ribbon melt-spun at lower wheel speed (20 m/s) has composite structure composed of mostly SmCo7 and a small amount of Sm2Co17R. The grain size of SmCo7 phase decreases with the increase of Cr3C2 content. With the increase of wheel speed, the XRD peaks become lower and accompanied with a broad increase in backgrounds, indicating a considerable decrease in the grain size of the SmCo7 phase. When the wheel speed increases to 40 m/s, SmCo7-x(Cr3C2)x alloys can be obtained in the amorphous state for 0.15≤x≤0.25 with intrinsic coercive Hci of 0.004-0.007 T. The DSC analysis reveals that SmCo7 phase firstly precipitates from the amorphous matrix at 650 °C, followed by the crystallization of Sm2Co17 phase at 770 °C.

Investigation of Material Removal Rate in Mill-Grinding SiC Particle Reinforced Aluminum Matrix Composites

Particle reinforced metal matrix composites (SiCp/Al composites) have proved to be extremely difficult to machine with traditional cutting processes due to serious tool-wear and high machining cost, which lead to the low machining efficiency. This paper presents the results of an experimental research on mill-grinding of SiC particle reinforced aluminum matrix composites. Based on the Taguchi experimental design method, study on the material removal rate was carried out to gain the optimal processing parameters combination by using the analysis of S/N ratio. The detailed effect of wheel speed on material removal rate through single factor experiment was also studied. Though analysis of S/N ratio and variance, the depth of cut has greatest effect on the material removal rate, followed by feed rate. And grinding wheel speed has least effect on it. But the depth of cut and feed rate affect on the material removal rate nonlinearly. In the range of machining parameters applied, the optimal processing parameters combination gained is A2B3C3, namely, vs=11.77m/s, vw=100mm/min, ap=0.8mm. Material removal rate increased at first and then there was a decreasing trend with increasing wheel speed.

Experimental Study of Material Removal Rate for Rotary Curved Surface Workpieces of Si<sub>3</sub>N<sub>4</sub> in Chemical-Mechanical Polishing Using Taguchi Technique

By applying chemical-mechanical polishing (CMP) technique to high precision processing of rotary surface workpieces of silicon nitride (Si3N4) ceramic, a CMP experimental device was established on a numerical control (NC) jig grinder. The polyurethane wheel and nonwoven cloth wheel was adoped. The CeO2abrasive was applied to configure the water base polishing solution. Using Taguchi robust design method, through S/N ratios and analysis of variance, the influence of slurry concentration, polishing wheel speed and polishing wheel feed rate on material removal rate (MRR) were analyzed. With the increase of polishing wheel speed and polishing wheel feed rate, the MRR decreased. There was a balance concentration leading to the largest MRR. The best process parameters were selected: the slurry concentration of 20%, polishing wheel speed of 6000r/min, polishing wheel feed rate of 2.29mm/min, The result showed the descending order of selected process parameters impacting on MRR was polishing wheel speed, polishing wheel feed rate and slurry concentration.

Phase composition, microstructures and magnetic properties of melt-spun Nd1.2Fe10.5Mo1.5 ribbons and their nitrides

The effect of wheel speed on the phase compositions and microstructures of melt-spun Nd1.2Fe10.5Mo1.5 ribbon was investigated. It is found that the Nd(Fe,Mo)12 phase can be obtained at the wheel speed of 10m/s, and TbCu7-type Nd(Fe,Mo)7 phase is formed with the wheel speed higher than 10m/s. The amorphous phase is achieved at 65m/s. The average grain size of phases decreases linearly with increasing wheel speed. The Nd(Fe,Mo)12N1.0 nitride obtained from annealed ribbons quenched at 65m/s shows a coercivity much higher than that from the ribbons quenched at 10m/s, which is due to the smaller grain size in the former ribbons.

Research on Heat Transfer and Calculation Method of Workpiece Surface Temperature in High Speed Grinding

The surface quality of workpiece depends largely on workpiece surface temperature in grinding. The key parameters on workpiece surface temperature calculation model have been researched and the calculation model constructed in this paper, including the convective heat transfer coefficient (CHTC) (hf), heat flux (qch) and the grain contact half-width (r0) which are assumed to be constant in workpiece surface temperature model given by Rowe. And the improved Rowe model has been proposed (Rowe/Li model) which not only involves the grinding process parameters such as the speed of wheel and workpiece, but also the geometric parameters of workpiece, grinding wheel and abrasive. The experimental results of the surface temperature in high-speed grinding are very close to the results by Rowe / Li model. Relative to the Rowe model, the obtained surface temperature by Rowe / Li model has decreased by about 35-40%. Under the conditions of the same material removal rate, high-speed grinding, namely, increasing wheel speed can effectively reduce the surface temperature and improve the grinding quality.

Study on Residual Stress Distribution in Surface Grinding

The grinding process is currently used for most of the parts requiring good precision. However, the apparition of some damage related to this process is still uncontrolled. The major deterioration is from residual stress. In order to investigate the residual stresses caused by mechanical plastic deformation, thermal plastic deformation and phase transformation in ground components, a feasible numerical method was developed to accommodate appropriately thermal stress and phase transformation in a workpiece experiencing critical temperature variation during grinding. The change of the material properties was modeled as function of temperature history. The wheel velocityVsis a key factor in determining the distribution of residual stress; both the surface residual stress and the depth of residual stress are induced with the increase of the wheel speed.

Crystallographic alignment and magnetic anisotropy in melt-spun Nd-Fe-B/α-Fe composite ribbons with different neodymium contents

Crystallographic alignment and magnetic anisotropy were studied for Nd xFe 94- x B 6 ( x=8, 9, 10, 11) ribbons prepared via melt-spinning. Effect of Nd content and wheel speed on the crystal structure and magnetic properties of the ribbons was investigated. Both the free and wheel side of the ribbons could obtain strong c-axis crystal texture of Nd 2Fe 14B phase perpendicular to the ribbons surface at low wheel speed, but the texture weakened gradually with the increase of the wheel speed. Increase of Nd content led to better formation of crystal texture in the ribbons, indicating that the α-Fe phase might undermine the formation of crystal texture. Magnetic measurement results showed that the magnetic anisotropy of the ribbons exhibited corresponding behavior with the invariance of the c-axis crystal texture of Nd 2Fe 14B phase in the ribbons, and the coercivity of the ribbons rose with the increase of both Nd content and wheel speed during melt-spun process.

Study on the Simulation Model and High-Speed Characteristics of Cylindrical Grinding

The existing research shows that high-speed grinding is the main way to machining the common materials and difficult-to-machine materials efficiently and critically. However, the research on mechanism and high-speed characteristics of high-speed cylindrical grinding is few searched. Based on three-dimensional simulation software DEFORM-3D, the simulation model of high speed cylindrical grinding with single grit was established, and the relevant experiment of 3D simulation for high speed cylindrical grinding process was processed. In this paper, the impact of the grinding parameters, such as wheel speed and depth of cut on the grinding force and grinding temperature is explored through analyzing the variation of strain rate, grinding force and temperature, and found that the increasing strain rate can lead to the increase in grinding force and temperature. According to the simulation experiment results, the control model of grinding temperature for prediction of grinding temperature and optimization of grinding parameters, is analyzed and developed in the end. The engineering experiment, conducted on the high speed cylindrical grinder and measured grinding temperature with thermal infrared imager, has been carried out in this study. Engineering and simulation experiments results show good match, for grinding temperature would decline with the increasing wheel speed when the grinding depth keeps constant, and thus can reduce grinding burn, improve the surface quality of workpiece.

Formation of metastable phases and nanocomposite structures in rapidly solidified Al–Fe alloys

In the present work the structure and morphology of the phases of nanocomposites formed in rapidly solidified Al–Fe alloys were investigated in details using analytical transmission electron microscopy and X-ray diffraction. Nanoquasicrystalline phases, amorphous phase and intermetallics like Al 5Fe 2, Al 13F 4 coexisted with α-Al in nanocomposites of the melt spun alloys. It was seen that the Fe supersaturation in α-Al diminished with the increase in Fe content and wheel speed indicating the dominant role of the thermodynamic driving force in the precipitation of Fe-rich phases. Nanoquasicrystalline phases were observed for the first time in the dilute Al alloys like Al–2.5Fe and Al–5Fe as confirmed by high resolution TEM. High hardness (3.57 GPa) was measured in nanocomposite of Al–10Fe alloy, which was attributed to synergistic effect of solid solution strengthening due to high solute content (9.17 at.% Fe), dispersion strengthening by high volume fraction of nanoquasicrystalline phase; and Hall–Petch strengthening from finer cell size (20–30 nm) of α-Al matrix.

콤바인 HST 전자제어시스템 개발 - 제어특성 실외시험 -

I/An electro-hydraulic transmission having advantages of convenience, safety, simple linking and high power, and an electronic control system were designed and fabricated. In this study, characteristics of the control system were investigated through outdoor tests for evaluation of installation of the system on a combine. Major findings were as followings. 1. Experiment for performance evaluation of the control system was conducted on concrete road. With steering lever in neutral position, driving HST swash plate and left/right wheel speed increased in proportion to driving lever angle. In case of steering control, steering swash plate angle changed in proportion to steering lever angle. This should cause increase in outer wheel speed, but it was observed that HST swash plate was controlled toward neutral to maintain the speed before steering. As a result, speed before steering was maintained despite the change in outer wheel speed by steering HST swash plate angle change. 2. It was observed that the HST system enabled steering with outer wheel maintained at constant speeds while inner wheel speed decreased, which was more stable than conventional mechanical links. In addition, for the selected 5 criteria, experiment showed satisfactory results and it was judged that installation on real vehicle would be feasible. 3. The control system showed response property of appropriate forward/reverse movement and lift/right steering, without causing any problems during experiment on concrete. Result of response property experiment on field operation also showed appropriate control over forward/reverse movement and left/right steering

Microstructure, phase evolution and magnetic properties of melt-spun SmCo 6.8− xSn xZr 0.2 ( x = 0, 0.1 and 0.3) ribbons

SmCo 6.8− x Sn x Zr 0.2 ( x = 0, 0.1 and 0.3) melt-spun ribbons have been produced from bulk as-cast samples by varying wheel speeds from 8 to 32 m/s. The microstructure, phase evolution and magnetic properties of as-spun ribbon samples were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM), respectively. The XRD results show that the addition of Sn to SmCo 6.8Zr 0.2 alloy has significant role to shift the TbCu 7-structure into Sm 2Co 17(H) and Sm 2Co 17(R) -phases for the Sn content of 0.1 and 0.3, respectively. The SEM analysis reveals that the grain size of the as-spun ribbon samples is gradually refined from several microns to 600−800 nm with the increase of wheel speed from 8 to 32 m/s. A wheel speed of 24 m/s has been found to be optimal in achieving reasonably good combination of coercivity ( H c) and magnetization ( M s) values in the as-spun SmCo 6.8- x Sn x Zr 0.2 ( x = 0, 0.1 and 0.3) ribbons. Maximum values of H c of 5.1 kOe and M s of 76.9 emu/g were achieved for the SmCo 6.5Sn 0.3Zr 0.2 ribbons spun at 24 m/s; upon annealing at 550 °C, the H c values of these ribbons were significantly improved (10.4 kOe) with not much destruction in the M s value.

Formation mechanism of layered microstructure and monotectic cell within rapidly solidified Fe62.1Sn27.9Si10 alloy

Ternary Fe62.1Sn27.9Si10 monotectic alloy is rapidly solidified in drop tube with the freely-falling-body techniqual and with melt spinning method separately. The phase separation, the microstructure characteristics, and the heat transfer of this alloy are investigated theoretically. Under free fall condition, the core-shell structure with two layers is formed because of Marangoni migration and surface segregation, where the Sn-rich phase is always located at droplet surface and the Fe-rich phase in the center. With the decrease of droplet diameter, both cooling rate and temperature gradient increase quickly, which facilitates the rapid growth of monotectic cell. With the increase of wheel speed, the cooling rate of alloy ribbon increases from 1.1107 to 6.5107 K/s, the fluid flow and the phase separation are suppressed to a great extent, and the nine layers two layers no layer structural transition occurs during the rapid solidification of Fe62.1Sn27.9Si10 alloy obtained by the melt spinning method. Meanwhile, the FeSn+L2FeSn2 peritectic transformation is also suppressed, thus resulting in different phase constitutions as compared with the case of free fall condition. The energy dispersive spectroscopy (EDS) analysis reveals that the Fe phase exhibits a conspicuous solute trapping effect during rapid solidification.

Structural, thermal and magnetic properties of Fe–Si–B–P–Cu melt-spun ribbons: Application of non-isothermal kinetics and the amorphous random anisotropy model

The microstructural variation of Fe–Si–B–P–Cu melt-spun ribbons was analyzed on the basis of non-isothermal kinetics and the amorphous random anisotropy model. The magnitude of latent heat of the crystallization process obtained from DSC curves increases with the increase of quenching wheel speed. The apparent activation energies of the nucleation and growth of α-Fe nanocrystallites increase as the quenching wheel speed increases. Thermal analysis implies that the size of the local short-medium order (cluster) in melt-spun ribbons reduces with the increase of quenching wheel speed. Meanwhile, magnetic measurements display that the coercivity of the stress-released ribbons decreases with the increasing quenching wheel speed. This confirms the thermal analysis results on the basis of the amorphous random anisotropy model. Combing thermal analysis with magnetic measurements, it is believed that the cluster size of the melt-spun ribbons decreases with the increase of the cooling rate during melt-spinning process. Nanocrystalline alloy with desirable microstructure and soft magnetic properties is anticipated to be obtained from an amorphous alloy prepared at an appropriate cooling rate by adjusting the quenching wheel speed.

Influence of wheel speed during planar flow melt spinning on the microstructure and soft magnetic properties of Fe68.5Si18.5B9Nb3Cu1 ribbons

The structure and soft magnetic properties of Fe68.5Si18.5B9Nb3Cu1 (at.%) alloy ribbons produced through planar flow melt spinning at different wheel speeds viz. 34, 17 and 12 m/s have been investigated using X-ray diffraction, differential scanning calorimetry, transmission electron microscopy, vibrating sample magnetometer and positron lifetime spectroscopy. Amorphous ribbons formed with different wheel speeds manifested different enthalpy and activation energy of crystallization. The volume fraction of nanocrystalline phase, saturation magnetization and permeability are found to increase whereas coercivity is found to decrease with increasing wheel speed on annealing. A detailed analysis of positron lifetime spectra obtained from the as-spun ribbons has been used to rationalize the variation in microstructure and magnetic properties. The presence of larger number of defects at higher wheel speed increases the volume fraction of nanocrystalline phase on annealing which improves the soft magnetic properties.

Elliptical Ultrasonic Assisted Grinding (EUAG) of Monocrystal Sapphire – Surface Formation Characteristics

This study investigates surface formation characteristics in elliptical ultrasonic assisted grinding (EUAG) of monocrystal sapphire. During EUAG process, the workpiece is imposed to ultrasonically vibrate in two directions, i.e., vertical and parallel to work-surface, by using an elliptical ultrasonic vibrator. In our previous work, the vibrator has been produced by bonding a piezoelectric ceramic device (PZT) on a metal elastic body. When two alternating current voltages with a phase difference are applied to the PZT at the same frequency that is close to the resonant frequency of the longitudinal and bending mode of the vibrator, two dimensional ultrasonic vibrations are generated simultaneously, resulting in an elliptical motion on the end face of the vibrator. In this paper, to clarify the work-surface formation characteristics in EUAG of sapphire material, grinding experiments are carried out involving sapphire substrate. In experiments, work-surface roughness is measured, and the ground work-surface morphology is examined by scanning electron microscope (SEM). The experimental results are summarized as: (1) Compared with conventional grinding (CG), the elliptical vibration leads to a decrease of surface roughness up to 25% in EUAG; (2) The surface roughness has a monotonously increasing trend with the increasing wheel depth of cut in both EUAG and CG, but has little variation with the worktable feed rate. As the wheel speed increases, the surface roughness decreases until it reaches a minimum, and then increases in a monotonous trend in both EUAG and CG; (3) The surface quality in EUAG has a significant improvement, and it is prone to achieve the ductile regime grinding of sapphire compared with CG. These indicate that the elliptical ultrasonic assisted grinding is an efficient technique for high performance machining of monocrystal sapphire.

Diamond face grinding of WC-Co composite with spark assistance: Experimental study and parameter optimization

Electro-discharge machining (EDM) characteristics of tungsten carbide-cobalt composite are accompanied by a number of problems such as the presence of resolidified layer, large tool wear rate and thermal cracks. Use of combination of conventional grinding and EDM (a new hybrid feature) has potential to overcome these problems. This article presents the face grinding of tungsten carbide-cobalt composite (WC-Co) with electrical spark discharge incorporated within face of wheel and flat surface of cylindrical workpiece. A face grinding setup for electro- discharge diamond grinding (EDDG) process is developed. The effect of input parameters such as wheel speed, current, pulse on-time and duty factor on output parameters such as material removal rate (MRR), wheel wear rate (WWR) and average surface roughness (ASR), are investigated. The present study shows that MRR increases with increase in current and wheel speed while it decreases with increase in pulse on-time for higher pulse on-time (above 100 µs). The most significant factor has been found as wheel speed affecting the robustness of electro- discharge diamond face grinding (EDDFG) process.

Microstructure and electrochemical properties of melt-spun Nd 0.8Mg 0.2(Ni 0.8Co 0.2) 3.8 hydrogen storage alloy

The effects of rapid solidification on the microstructure and electrochemical properties of Nd 0.8Mg 0.2(Ni 0.8Co 0.2) 3.8 alloy were systematically investigated. The microstructure of alloys was characterized by scanning electron microscopy (SEM), X-ray diffractometer (XRD) and transmission electron microscopy (TEM). It was found that the melt-spun Nd 0.8Mg 0.2(Ni 0.8Co 0.2) 3.8 ribbons became thinner and the average grain size of the ribbons became smaller with increasing wheel speed. A fraction of amorphous phase was observed for the ribbons melt-spun at high wheel speed (≥20 m/s). Microstructural characterization revealed that two phases: (Nd,Mg) 2(Ni,Co) 7 main phase (Ce 2Ni 7 type structure) and NdNi 5 second phase (CaCu 5 type structure), existed in the samples in cast state and melt-spun. The cycle stability of the melt-spun alloys was significantly enhanced as compared with cast alloy, and the sample prepared at wheel speed of 20 m/s exhibited good comprehensive electrochemical properties.

Microstructure and mechanical properties of rapidly solidified FeAlCr intermetallic compound

In this work results regarding microstructural characterization of a melt‐spun intermetallic compound Fe40Al5Cr (% at.) produced by rapid solidification employing the melt spinning technique at three different tangential wheel speeds (12, 16 and 20 ms‐1) are presented. Melt spun ribbons were characterized by optical and scanning electron microscopy (SEM) in order to observe morphology, grain size, ribbon thickness and also fracture surfaces after tensile tests. EDS coupled to SEM was employed to perform punctual and scan line chemical analyses on samples, x‐ray diffraction (XRD) was utilized to identify crystal structure and phases. Transmission electron microscopy (TEM) was employed to confirm crystal structure and also to characterize nanopores formed in the specimens by vacancy clustering. With regard to mechanical properties, micro hardness Vickers measurements as well as tensile tests at room temperature were applied to the rapidly solidified ribbons.The grain size of rapidly solidified Fe40Al5Cr ribbons suffered a drastic reduction as compared with alloys of the same composition produced by conventional melting and casting methods, and in melt‐spun ribbons it decreases as the wheel speed increases. Punctual and line‐scanning chemical analyses revealed that Cr enters in solid solution in FeAl matrix. Hardness measurements revealed a softening in rapidly solidified FeAlCr ribbons as compared with FeAl alloys and tensile test exhibited a (transgranular + intergranular) mode of fracture, reaching up to 3 % of elongation in FeAlCr alloys. The presence of porous (meso and nano) were also characterized.

Influence of quenching rate on the structural, soft magnetic and magnetoimpedance properties of melt-spun Co 69Fe 7Si 14B 10 alloy

Melt-spun ribbons of Co 69Fe 7Si 14B 10 alloy have been prepared at different wheel speeds viz. 47, 34 and 17 m/s and investigated for structural and magnetic properties. Degree of amorphicity in the as-spun ribbons is found to increase with wheel speed. Amorphous phase crystallizes in two stages producing Co 2Si, Co 2B and CoSi phases on annealing. Increase in wheel speed improves soft magnetic and magnetoimpedance properties due to decrease in perpendicular anisotropy which is associated with stripe domain formation. On annealing soft magnetic properties and magnetoimpedance deteriorate due to the formation of crystalline phases.