Material Removal Behavior Research Articles

Effect of amplitude on material removal behavior and surface formation in ultrasonic elliptical vibration cutting of tungsten heavy alloys

Effect of amplitude on material removal behavior and surface formation in ultrasonic elliptical vibration cutting of tungsten heavy alloys

Influence of cold plasma on material removal behavior during diamond grit scratching single crystal silicon

As a typical brittle crystal material, single crystal silicon has high hardness and brittleness, which makes the machined surface prone to microscopic cracks and other subsurface damage. In addition, the anisotropic crystal structure may cause large differences in the material removal behavior along different crystal orientations. To solve these problems, researchers have proposed the methods of machining along the easy-to-cut direction and inducing external energy fields assisted machining, but there remain problems like cracks and surface thermal damage. In this study, we propose to modulate the deformation process of single crystal silicon by atmospheric pressure cold plasma and elucidate the influence of plasma on the material removal behavior based on diamond grit scratching experiments along different directions. The results show that before plasma treatment, the toughness along <110> direction is higher than that along <100> direction, and plasma has significant improvement effects on the plastic deformability in both directions. The critical load for plastic-brittle transition along <110> direction can be increased from 76.2 mN to 107.1 mN, and from 69.6 mN to 109.8 mN along <100> direction. The plasticity regulation mechanism is that the interaction of multiple shear bands dissipates the energy of crack propagation and inhibits the premature generation of cracks. Compared with the conventional scratching along <110> direction, the material removal rate of plasma-assisted scratching under normal loads of 20 mN, 40 mN and 80 mN can be increased by 30.2%, 24.2% and 21.9%, respectively; while that along <100> direction can also be increased by 33.7% and 19.5% under 20 mN and 40 mN, respectively. This study may provide a novel approach for realizing high-quality and efficient processing of hard and brittle materials.

The ablation behavior of diamond/Cu composites by infrared nanosecond pulsed laser

This paper investigates the material removal behavior of diamond/Cu composites by multi-passes infrared nanosecond pulsed laser ablation, focusing on the formed surface cracks, periodic ripples, profile evolution and deposition. Combining nanosecond laser ablation experiments with simulations based on thermophysical properties is then undertaken to effectively reduce the maximum thermal stress and inhibit crack initiation and propagation. Three types of cracks were identified in nanosecond laser ablation, which were influenced by the diverse thermophysical properties of the material and the temperature gradient. The periodic ripples of 300–1800 nm on the sidewalls of the machined groove on diamond grains were induced when the laser fluence approached the ablation threshold, which did not even appear on the copper matrix as the thermal effects dominate. The groove profile showed a limited change as the ablation passes further increase to be over 40 due to the plasma shielding effect inside the groove, the laser defocusing phenomenon and the increased difficulty of sputtering the molten material. In addition, the different ablation mechanisms of diamond and copper resulted in the formation of overlapping deposition layers with changed surface characteristics at varying laser energy densities. The uneven island-like recast layer affected the uniformity of the ablated grooves, which was dependent on the material microstructure and accumulated laser energy.

Analysis of the process behaviour of diamond-coated foams in finishing of ground hardened steel

To broaden the process understanding with regard to a tool concept for finishing operations based on soft foams coated with diamonds, the application behaviour with respect to the surface preparation of a ground hardened steel surface is considered. By analysing the surface on the basis of established roughness parameters, the material removal behaviour is investigated in dependence on the process parameters and tool specifications. Furthermore, the influence on the micro roughness superimposed on the roughness profile can be analysed. The recorded process forces serve as a basis for understanding the underlying mechanisms and for interpreting the results.

Modeling and analysis of surface integrity transition in cutting of Sip/Al composites based on coordination deformation effect of particle-matrix

With the wide application of Sip/Al composites in key fields, it is critical to understand the material removal behavior and surface integrity evolution mechanism of Sip/Al composites. In this paper, based on the nanoindentation and scratching experiments, the coordination deformation behavior of Si particles and the Al matrix were investigated at the micro-scale, and the mechanism and conditions of surface integrity transition (SIT) of Sip/Al composites were elucidated. Then, taking into account the feature of particle fragmentation and detachment caused by interfacial failure, an analytical model of specific cutting energy for Sip/Al composites cutting under different material removal modes was established. The competitive relationship between ductile deformation and surface defect formation was investigated, and a quantitative prediction model for the critical depth of SIT was proposed. The results show that the evolution of the material removal behavior of Sip/Al composites is a consequence of the coordination deformation the Al matrix and Si particles. The material removal mode of Sip/Al composites transitions from ductile removal to quasi-brittle removal with particle fragmentation and detachment, and there is an obvious SIT characteristic. The prediction results of critical depth are in agreement with the experimental results, with an average error of less than 9.8 %. Moreover, an appropriate increase in cutting speed can effectively enhance the surface integrity of Sip/Al composites. This research contributes to a deeper understanding of the low-damage machining mechanism of Sip/Al composites.

Multi-Step Two-Dimensional Ultrasonic-Assisted Grinding of Silicon Carbide: An Experimental Study on Surface Topography and Roughness.

Two-dimensional ultrasonic-assisted grinding (2D-UAG) has exhibited advantages in improving the machining quality of hard and brittle materials. However, the grinding mechanism in this process has not been thoroughly revealed due to the complicated material removal behaviors. In this study, multi-step 2D-UAG experiments of silicon carbide are conducted to investigate the effects of machining parameters on surface quality. The experimental results demonstrate that the tool amplitude and the workpiece amplitude have similar effects on surface roughness. In the rough grinding stage, the surface roughness decreases continuously with increasing ultrasonic amplitudes and the material is mainly removed by brittle fracture with different surface defects. Under semi-finishing and finishing grinding steps, the surface roughness first declines and then increases as the tool amplitude or workpiece amplitude grows from 0 μm to 8 μm and the inflection point appears around 4 μm. The surface damage contains small-sized pits with band-like distribution and localized grooves. Furthermore, the influences of cutting parameters on surface quality are similar to those in conventional grinding. Discussions of the underlying mechanisms for the experimental phenomena are also provided based on kinematic analysis. The conclusions gained in this study can provide references for the optimization of machining parameters in 2D-UAG of hard and brittle materials.

Anisotropy Dependence of Material Deformation Mechanisms in Nanoscratching Monocrystalline BaF2: Experiments and Atomic Simulations.

Monocrystalline barium fluoride (BaF2), known for its exceptional optical properties in the infrared spectrum, exhibits anisotropy that influences surface quality and material removal efficiency during ultraprecision machining. This research explores the impact of anisotropy on the deformation and removal mechanisms of monocrystalline BaF2 by integrating nanoscratch tests with molecular dynamics (MD) simulations. Nanoscratch tests conducted on variously oriented monocrystalline BaF2 surfaces using a ramp loading mode facilitated the identification of surface cracks and a systematic description of material removal behaviors. This study elucidates the effect of crystal orientation on the ductile-brittle transition (DBT) of monocrystalline BaF2, further developing a critical depth prediction model for DBT on the (111) crystal plane to reveal the underlying anisotropy mechanisms. Moreover, nanofriction and wear behaviors in monocrystalline BaF2 are found to be predominantly influenced by scratch direction, crystal surface, and applied load, with the (110) and (100) planes showing pronounced frictional and wear anisotropy. A coefficient of friction model, accounting for the material's elastic recovery, establishes the intrinsic relationship between anisotropic friction and wear behaviors, the size effect, and scratch direction. Lastly, MD modeling of nanoscratched monocrystalline BaF2 reveals the diversity of dislocations and strain distributions along the (111) [-110] and [-1-12] crystal directions, offering atomic scale insights into the origins of BaF2 anisotropy. Thus, this study provides a theoretical foundation for the efficient processing of fluorine-based infrared optic materials exhibiting anisotropy.

Studying mechanism of anisotropic crack generation on C-, R-, A-, and M-planes of sapphire during ultra-precision orthogonal cutting using a visualized slip/fracture activation model

With the growing demand for the fabrication of microminiaturized components, a comprehensive understanding of material removal behavior during ultra-precision cutting has become increasingly significant. Single-crystal sapphire stands out as a promising material for microelectronic components, ultra-precision lenses, and semiconductor structures owing to its exceptional characteristics, such as high hardness, chemical stability, and optical properties. This paper focuses on understanding the mechanism responsible for generating anisotropic crack morphologies along various cutting orientations on four crystal planes (C-, R-, A-, and M-planes) of sapphire during ultra-precision orthogonal cutting. By employing a scanning electric microscope to examine the machined surfaces, the crack morphologies can be categorized into three distinct types on the basis of their distinctive features: layered, sculptured, and lateral. To understand the mechanism determining crack morphology, visualized parameters related to the plastic deformation and cleavage fracture parameters are utilized. These parameters provide insight into both the likelihood and direction of plastic deformation and fracture system activations. Analysis of the results shows that the formation of crack morphology is predominantly influenced by the directionality of crystallographic fracture system activation and by the interplay between fracture and plastic deformation system activations.

Effect of laser-assisted heat treatment on material removal behavior of sapphire in indentation and scratching

Sapphire is widely used in aerospace, microelectronics and defense applications. Due to its high hardness and low fracture toughness, it is difficult to achieve high efficiency and low damage machining. Laser-assisted machining is an effective method for machining hard and brittle materials and has been explored in many experimental and theoretical studies. In this paper, the mechanical property of sapphire and the variation of the coefficient of friction assisted by different laser powers are investigated in detail. Meanwhile, Raman spectroscopy was employed to reveal the residual stress characteristics in the deformation zone of the scratch grooves, and to analyse the changes in the depth of plastic-brittle transition of sapphire after heat treatment with different laser powers. Comparing the material removal behavior of sapphire in indentation and scratching experiments with and without laser-assisted heat treatment (LAHT), and exploring their material removal mechanisms. Experimental results show that LAHT can improve the ductility and workability of sapphire by reducing the hardness and improving the fracture behavior of the material. Hardness and elasticity modulus decrease with increasing power, and the distribution of residual stress changes from compressive to tensile with increasing power. Laser treated surface was found to possess shorter crack length, no significant localized chipping and spalling in indentation, and its scratch grooves were deeper with no radial cracks observed, the scratching force ratio was higher, the critical load for brittle-plastic transition became larger, and plastic flow lines and lumpy spalling debris appeared in the scratch areas. Nearly zero cracks were observed in material subsurface under the LAHT. With LAHT, the material is removed at a higher rate and in a more plastic way, fracture behavior of the material is improved, surface and subsurface damage is reduced, and the machining efficiency is enhanced. This study has important implications and benefits for the machining of sapphire in ensuring surface quality and achieving high efficiency.

Effect of Grain Size on Nanometric Cutting of Polycrystalline Silicon via Molecular Dynamics Simulation.

The grain size effect is an important factor in determining the material removal behavior of polycrystalline silicon (p-Si). In the present study, to improve the understanding of nanoscale machining of p-Si, we performed molecular dynamics simulation of nanometric cutting on a p-Si workpiece and discussed the grain size effect on material removal behavior and subsurface damage formation. The simulation results indicate that when cutting on the polycrystal workpiece, the material removal process becomes unstable compared with single crystals. Higher removal efficiency, less elastic recovery and higher frictional coefficient are observed as the average grain size decreases. In the subsurface workpiece, when the grain size decreases, slip along grain boundaries merges as a nonnegligible process of the plastic deformation and suppresses the elastic deformation ahead of the cutting tool. It is also revealed that when cutting on a polycrystal workpiece with smaller grains, the average stress decreases while the workpiece temperature increases due to the impediment of heat transfer by grain boundaries. These results could provide a fundamental understanding in the material deformation mechanism of p-Si during nanoscale machining.

Reducing Cf/SiC composite damages through collaborative control of laser ablating depth and grinding modes

Cf/SiC composites are regarded as difficult-to-machine aerospace materials. A low-damage surface machining of Cf/SiC composite by laser-ablating assisted grinding (LAAG) was conducted, and investigated the effects of laser-ablating depth and grinding modes on surface/subsurface damages. The results showed that ablated material depth reached 420 μm after 1200 times scanning, while the effective ablating rate was inhibited by the depth. Compared with down grinding, the grinding forces and temperatures were substantially higher in up grinding, with a maximum increase of 123.5 % and 140 % in normal and tangential grinding forces, respectively; however, micro brittle fracture and ductile removal were remarkably enhanced in normal and transverse fibers, and surface macroscopic damage has been suppressed; subsurface damage remained insignificant, mainly exhibited in internal micro cracks and minor interfacial debonding. It was attributed to cutting characteristics of up grinding. Furthermore, as grinding depth increased, the material removal behavior underwent a brittle-ductile transition and the surface roughness grew accordingly. Moreover, a laser scanning angle of 0° and up grinding facilitated the occurrence of longitudinal fiber debonding, producing larger sized fiber bundle chips. Combining up grinding with 90° scanning angle at low grinding depth was an effective method to improve the surface quality of Cf/SiC composite.

Influence of mechanical properties on material deformation behavior of different ceramics in scratching

To understand the differences in material removal behavior during grinding for different ceramics, scratching of Al2O3, AlN, Si3N4 and ZrO2 (3Y-TZP) ceramics by a cube-corner diamond indenter was investigated in this paper. Scratching characteristics, including material deformation, scratching force, coefficient of friction (COF) and scratching damage of different ceramics were compared and analyzed. Elastic recovery rate model and stress field model were built to analyze the mechanism of material deformation and scratching damage during scratching on different ceramics. The results demonstrated that material deformation behaviors vary significantly, and depend on mechanical properties of the ceramics. Ceramics with higher hardness exhibit shallower penetration depth of scratching, while higher fracture toughness results in shorter maximum surface damage distance. Elastic recovery rate model can predict the extent of material deformation. The ceramic with the highest elastic recovery rate is Al2O3, followed by Si3N4, ZrO2, and finally AlN. Elastic recovery rate decreases with increase in force. In stress field model, AlN exhibits the highest maximum principal stress, followed by Al2O3 and Si3N4, with ZrO2 displaying the lowest stress. These distribution patterns are consistent with the results of scratching damage pattern.

Investigating micro-cutting mechanism of glow discharge polymer based on material properties and removal behaviors analysis

Glow discharge polymer (GDP) is the unique artificial material for the target balls in Inertial Confinement Fusion tests, while its practical micromachining such as the fabrication of microstructure on material surfaces keeps challenging due to its unclear micro-cutting mechanism. Hence, this paper seeks to investigate the micro-cutting mechanism of GDP from the perspective of the material flow and cutting energy. To achieve it, the energy conservation equation of three cutting modes triggered by different ratios of uncut chip thickness to the tool cutting edge radius (RTS) was established based on cutting deformation behaviors. Meanwhile, the diamond cutting tests and the FEM simulation at different RTS were developed. The experimental observation of cutting forces and specific cutting forces verified the evolution of three cutting modes, including shearing, shearing-ploughing and ploughing in the micro-cutting of GDP with the decrease of RTS. Next, from the change of the node displacement vector observed from the simulated results, it can be seen that the real-time material flow behavior during micro-cutting of GDP varies obviously with the evolution of cutting modes. Besides, the fracture toughness Gc, and the energy dissipation of different cutting modes were analyzed. The proportion of the energy spent on material fracture (Gc=9.95 N/mm) is the largest one in shearing and shearing-ploughing modes, while in ploughing mode, the material plastic deformation consumed the most energy. The above results reveal the specific material properties and removal behaviors of GDP and contribute to optimizing the machining strategies for the practical micromachining of microstructures on material surfaces.

Study on nickel-based single crystal superalloy DD6 subsurface damage of belt grinding with a large cutting depth of one pass

Single crystal superalloy has been widely utilized as a crucial manufacturing material for aeroengine turbine blades due to its excellent properties. However, machining this alloy is easy to cause subsurface damage, resulting in the engineering failure of blades. To explore a large cutting depth and low damage processing method, this paper established a grinding depth analytical model for the abrasive belt. The model provides insights into the material removal behavior mechanism during belt grinding and predicts the impact of process parameters on the grinding depth. Subsequently, the grinding experiments of this alloy with different abrasive belts were conducted. The experimental results showed that grinding depth increased as normal force amplified and exhibited a nonlinear growth pattern with the reduction of feed velocity. This preliminary verified the prediction model of grinding depth. The material removal properties of the pyramid, diamond, and hollow-sphere belts were analyzed, and the ratio of material removal capacity for the three was found to be 12:8:5. Based on the analysis of the topography and roughness of the grinding surface, the study examined the influence mechanism of grinding force, feed velocity and abrasive grain morphology on grinding depth and surface quality. The subsurface damage behavior mechanism and recrystallization depth change law of belt grinding were revealed. The grinding depth of the pyramid and diamond belts could exceed 160 μm and the recrystallization depth was less than 5 μm. To achieve efficient and low-damage machining, it is recommended to reduce the feed velocity rather than increase the grinding normal force. It is important to note that the feed velocity should not exceed 10 mm/s. This study is to furnish a theoretical groundwork and offer engineering technical recommendations for achieving large grinding depth and low damage machining of single crystal superalloy.

Research on the influence of cutting thickness on CFRP material removal behavior considering tool wear

Small cutting thicknesses are commonly employed to minimize surface damage during the CFRP finishing process. However, reducing cutting thickness is not always beneficial to surface quality and the cutting process, particularly in cases involving tool wear. In this paper, the influence of cutting thicknesses on CFRP material removal behavior is studied, considering different stages of tool wear, through finite element simulations and orthogonal cutting experiments. The results show that tool wear exerts a more pronounced impact on the chip formation mechanism at smaller cutting thicknesses. When the fiber cutting angle θ = 0°, machining quality is minimally influenced by the cutting thickness but is primarily affected by tool wear. When θ = 45°/90°, it becomes challenging to form cutting chips when using worn tools at small cutting thicknesses (≤10 μm), but appropriately increasing the cutting thickness is conducive to fiber removal and enhancing machining quality. When θ = 135°, the chip formation mechanism remains relatively unchanged with tool wear, but the increase in cutting thickness results in a substantial rise in subsurface damage. This research illuminates the complex relationship between cutting thickness, tool wear and machining quality of CFRP, offering valuable insights for the CFRP cutting process.

Introducing transversal vibration in twist drilling: Material removal mechanisms and surface integrity

In twist drilling, severe extrusion is unavoidable at the chisel edge zone and results in high thrust force and poor surface integrity. Traditional axial vibration-assisted twist drilling only modifies the material removed from the continuous extrusion to the interrupted extrusion for the chisel edge centre, and must satisfy the chip-breaking conditions to ensure that the cutting edge is periodically separated from the workpiece. Hence, transversal vibration, has been introduced in twist drilling to overcome the severe extrusion behaviour of the chisel edges of the twist drills, referred to as ultrasonic transversal vibration-assisted drilling (UTVD). Theoretical models revealed that the material removal behaviour of the chisel edge centre changed from extrusion in CD to cutting in UTVD. Experiments were performed on UTVD of Ti-6Al-4V to confirm the feasibility with this novel method. The results indicated that transverse vibration significantly affected the thrust force and torque, and the maximum decline was 29.4% and 31.5%, respectively, compared with CD. Generated chips verified the material removal behaviour of the chisel edge centre zone changed from extrusion in CD to cutting in UTVD. Therefore, the hole quality and surface integrity were improved significantly by UTVD. Deeper plastic deformation (∼2.5 times), higher surface microhardness and compressive residual stress were realised using UTVD. This study enhanced the understanding of material removal and formation mechanisms of the surface and subsurface in UTVD, thereby providing a novel method and theoretical basis for the high-performance twist drilling of difficult-to-cut alloys.

Effect of cutting speed on the material removal behaviour for sapphire

Sapphire optical components are widely used in various industrial sectors. However, they are currently not available through efficient and highly accurate ultra-precision cutting. Therefore, this paper investigates the effect of cutting speed, a key factor in ultra-precision cutting, on the removal behaviour of sapphire materials. The plunge-cuts tests at different cutting speeds (10, 20 and 30 mm/s) have been conducted. The groove surface morphology, critical cutting depth for ductile-brittle transition, cutting force and tool wear of each plunge-cuts test with various cutting speed test were analysed. The experimental results shown that increasing the cutting speed is beneficial to obtain less defective machined surfaces and increase the critical cutting depth for ductile-brittle transition. However, at the same time, the cutting force increases dramatically in the brittle removal mode during high-speed cutting, which leads to severe tool wear. Therefore, increasing the cutting speed to meet the requirements of ultra-precision cutting and machining within the critical cutting depth is a highly efficient measure for obtaining sapphire optical surfaces.

Knowledge-wrapping method for prediction and evaluation of material removal behavior in robotic belt grinding

Reliable prediction and evaluation of material removal (MR) is a continuing pursuit in the grinding process. Mechanistic and empirical MR models always suffer from inaccuracies and restricted applicability, whereas data-driven approaches remain deficient in sample dependence, generalization, and physical interpretability. This motivates us to develop a knowledge-wrapping method (KWM) to predict and characterize the material removal behavior in robotic belt grinding. A physical material removal profile model (PHY) that suits the robotic belt grinding is first presented by appealing to the Archard law and Hertzian theory. Next, the knowledge-wrapping matrix is designed to wrap the physical constraints into a form of design matrix by transforming the mechanistic and empirical models into a linear system. The knowledge-wrapping matrix and the experimental data are then connected via a likelihood function with the consideration of measuring noise, yielding a hybrid-driven learning process that preserves interpretability from PHY. Comparative experiments and MR mechanism interpretations are finally presented to demonstrate the effectiveness and superiority of the proposed method.

Towards understanding the material removal mechanism on the effect of ultrasonic vibration and anisotropy for unidirectional CFRP by scratching

Rotary Ultrasonic Machining (RUM) is a well-known non-traditional machining method for hole-making and surface grinding of Carbon Fiber Reinforced Plastics (CFRP). However, the complicated material removal behavior of CFRP is difficult to understand due to its heterogeneity and anisotropy resulting from components and the nature of laminated structures. In this concern, we conducted ultrasonic vibration-assisted scratching (UVAS) to understand the material removal mechanisms with the effect of ultrasonic vibration and fiber anisotropy. Based on scratching morphology, the removal behavior of unidirectional CFRP (UD-CFRP) varied in different scratching directions. Meanwhile, the addition of ultrasonic vibration could suppress machining damage generated by the scratching process. The motion trajectory analysis and experimental results show that the ultrasonic vibration-assisted scratching load is smaller under the same machining parameters. Discussions on the material removal mechanism of UD-CFRP during the effect of ultrasonic vibration and fiber anisotropy were also provided. This research will contribute towards an in-depth understanding of the material removal mechanism for fiber reinforced plastics composites in RUM, which will be useful in optimizing the application of ultrasonic vibration assisted processes for advanced composites machining.

Insight into crack propagation induced by fiber orientations during single grain scratching of SiCf/SiC composites using FEM

Due to the multiphase structure and anisotropy of ceramic matrix composites (CMCs), crack propagation is extremely complex during grinding. However, there is no full comprehension of the crack propagation law of CMCs in varying fiber directions, which limits high-quality CMCs machining. Based on experimental and numerical results, the effect of fiber directions on crack propagation of SiCf/SiC composites was analyzed. Results demonstrate that the change in crack propagation path is the primary reason why the removal behavior of CMCs is different from traditional ceramics. For CMCs, the interface is the priority path of crack propagation no matter along any fiber direction. Besides, the fiber orientation determines the propagation paths of radial and subsurface cracks, which affects material removal behavior. Comparing the scratched groove, the groove edge damage is the most severe when scratching along the fiber transverse direction, whereas the scratched groove surface quality is best in the perpendicular direction.