Papers by Keyword: Material Removal

Abstract: This paper explores the application of Abrasive Flow Machining (AFM) as an innovative technique to enhance the finishing process of fracture plate implants. The study aims to deepen the understanding of AFM machining dynamics, optimize process parameters, and assess the effectiveness of AFM through advanced modeling and simulation. The major contributions include detailed simulation frameworks and validation through practical applications on SS316L implants, highlighting AFM’s effectiveness in achieving high-precision finishes essential for biomedical applications.

Abstract: Surface/subsurface processing damage on optical component can severely affect its surface mechanical properties and cause its resistance to external deformation to deteriorate. At the same time, the processing damage will also affect the surface quality. The surface processing defects are the main reasons leading to the decrease in the laser induced damage threshold in high-density laser system. In this paper, the damage formation mode and morphology of the traditional optical processing methods based on the mechanical removal in brittle and plastic modes are evaluated, then the traditional processing damage model is established accordingly. The polishing technology with material removal in elastic mode is proposed based on the damage generation mechanism. In the elastic mode, it is impossible to form the material removal by mechanical action due to the inability to overcome the yield limit of the material, thus it is necessary to introduce a weakening of the chemical reaction to reduce the bonding force of the surface layer of the optical element, using less force to form the material removal to ensure the disturbance of the basic material is controlled. The mechanism of material removal in elastic mode was analyzed. The polishing process was realized by elastic hydrodynamic ultra-smooth polishing and nano-particle jet polishing. The performance of the elastic polishing process was analyzed. The experimental results show that the elastic polishing processing method can effectively remove surface damage and achieve effective control of processing damage.

Abstract: The traditional finishing processes are incapable of producing required surface finish and other characteristics in difficult-to machine materials like Nickel based superalloys and also complex geometrical shapes of engineering components. Hence to achieve these goals non-traditional micro-machining processes have been developed. Extrusion honing (EH) is one of the non-traditional micro-machining process to debur, radius, polish, and remove recast layer of components in a wide range of applications. In this process material is removed from the work-piece by flowing abrasive laden medium under pressure through or past the work surface to be finished. Components made up of complex passages having surface/areas inaccessible to traditional methods can be finished to high quality and precision by this process. Hastelloy C22 offers resistance to both aqueous corrosion and attack at elevated temperatures and it is a difficult metal to machine using traditional techniques. In this study, micro finishing of internal surface of Hastelloy C22 material having predrilled passage diameters 7, 8, 9 and 10 mm have been performed in an indigenously built hydraulic operated one way extrusion honing setup. For the present EH process, patented polymer mixed with SiC abrasive at 35% volume concentration was used as carrier medium. The study was performed for 46, 54, and 60 grit sizes of SiC abrasive. The material removal in EH process varies with passage diameter and grit size of abrasives at each trial. A feed forward back propagation neural network model has been developed for the prediction of material removal and it has successfully predicted material removed in each trial of EH process.

Abstract: Abrasive flow machining (AFM) is one of the most promising technologies for internal finishing and de-burring for features with complex geometry. This study investigates the effect of media degradation on finishing characteristics achieved using the AFM process. A total of 50 experiments, using Inconel 718 cylindrical coupons machined by Wire-Electron Discharge Machining (WEDM), were conducted employing the same process conditions while using a single batch of AFM media. Experimental results indicate that media degradation has minor influence on surface roughness, but more significant influence on material removal and media flow rate. Material removal decreases exponentially with increasing cumulative media flow volume despite media flow rate increasing. There is a linear correlation between material removal and media flow rate. As a result, material removal can be estimated from media flow rate which can be monitored easily.

Abstract: The chip formation mechanisms during grinding are not yet fully understood. The abrupt interruption of the grinding process with a quick stop device is a suitable method to analyze the chip formation mechanisms during grinding. However, there is no device available that enables a reproducible interruption at cutting speeds above vc = 5 m/s. Therefore a new method for the interruption of face grinding processes in order to analyze the chip formation mechanisms is presented in this paper. A quick stop device is designed and constructed based on the advantages and disadvantages of former approaches of other researchers. Grinding experiments with different rotational speeds confirm the potential of this new device. Interruptions of the grinding process at cutting speeds of vc = 5 m/s, 15 m/s, 25 m/s and 35 m/s are successfully accomplished. A detailed analysis of the contact zone with the help of SEM pictures impressively shows the interaction of hundreds of cutting edges along the contact zone.

Abstract: Abrasive flow machining is a suitable technique for surface polishing due to its rheological characteristics, however, it's difficult to achieve uniform roughness for polished surfaces as the material removal mechanism is still ambiguous. In this paper the viscoelastic properties of abrasive flow media are incorporated to explore the phenomena of inconsistent material removal in the AFM polishing process, where the material removal near the edges is obviously higher than that in the middle along the flow direction. The rheological parameters of the viscoelastic constitutive model adopted are varied to study the polishing effectiveness under different process conditions. The results of numerical analysis reveal that there exist distinct differences of viscoelastic stress fields between the edges and the middle regions, which leads to the material removal near the edges is higher than that in the middle. It could be concluded that the viscoelastic properties of abrasive media play the dominant role for the inconsistent material removal in abrasive flow machining process.

Abstract: Oxygen-free copper (OFC) is a popular material used for molds/dies in injection molding of plastic lens because of its high ductility, strong impact strength and good thermal conductivity. nanoprecision polishing is essential as the final process in its fabrication. For this purpose, a novel polishing method using magnetic compound fluid (MCF) slurry was proposed. In this article, the construction of an experimental rig to realize the proposed method was described at first. Then the effects of process parameters including MCF slurry composition, workpiece oscillation parameter f/A_p-p and clearance Δ between workpiece and MCF carrier on work-surface roughness and material removal were experimentally investigated. As a result, nanoprecision surface finish of OFC was successfully attained by polishing with MCF slurry and the optimum process parameters (f/A_p-p=30 Hz/4mm, Δ=0.6 mm with an MCF slurry (45wt.% of CIP, 12 wt.% of Al₂O₃ grain, 3 wt.% of α-cellulose, 40 wt.% of MF) for obtaining the smoothest work-surface were determined.

Abstract: The first step to predict the milling stability is to identify the dynamic characteristics of cutting process. And the mass loading effects of removal material play an important role on the dynamic characteristics of milling process for thin-walled parts, such as impeller, turbine blades and automobile components, which is changing with cutting time or tool position. Therefore, how to identify the instantaneous dynamic characteristics of milling process is one of the most significant problems. In the paper, a structural dynamic modification method with variable mass to predict the instantaneous dynamic characteristics of multi-axis milling thin-walled workpiece with complex curved surface is proposed. The proposed method takes into account the variations of dynamics characteristics of workpiece with the tool position and material removal. And the material cutting process is regarded as the structural dynamic modifications of cutting system, the instantaneous dynamic characteristics of which can be estimated by the extended Sherman-Morrison-Woodbury formula to obtain the corrected frequency response function (FRF). Experiments were carried out to obtain the instantaneous dynamics of a thin-walled workpiece and the results were verified by finite element method (FEM).

Abstract: To understand the thermal effects on material removal at atomic level, molecular dynamics (MD) simulation and optimization method are performed with the aid of Morse, EAM and Tersoff potential. The heat distribution is showed in 3D images under various parameters. The simulation results reveal that the heat distribution is roughly concentric around the tool edge and a steep temperature gradient is observed between diamond tool and chip. During material removal process, there is a narrow region with high temperature in shear zone where most of heat generated due to plastic deformation of workpiece material, the high temperature extends from here to chip, diamond tool and workpiece, but the highest temperature lies in chip. Compared with low speed, a higher temperature region below the tool edge implied a larger shear stress is built up in a local region and a rougher machined surface is generated at high cutting speed.

Abstract: Molecular dynamics (MD) simulations of nanomachining of monocrystalline silicon were performed with the aid of Tersoff potential. The effects of machining conditions on the nature of heat distribution and corresponding phase transformation during nanomachining were investigated. It is clearly demonstrated that heat distribution shows a roughly concentric shape around the shear zone. A steep temperature gradient is observed in diamond tool and the highest temperature lies in chip. Stress distribution presents dual annular shapes, the highest compressive stress and tensile stress lay in shear zone and machined surface, respectively. Phase transformation mainly occurred in chips, shear zone and machined surface. Additionally, atoms in the machined surface are transformed from diamond cubic structure (Si-I) to β-tin structure (Si-II) and bct5-Si.