Diamond Grinding Research Articles

Diamond grinding wheel wear characterization after finishing cemented tungsten carbide cutting inserts

Diamond grinding wheel wear characterization after finishing cemented tungsten carbide cutting inserts

Evaluation of chemical–mechanical polishing of processed WC-Co surface structure

The cutting edges of commercial cutting tools have severe surface irregularities caused by the diamond grinding wheels that are used to form the cutting edges, which result in the introduction of lattice defects to the interior of the tungsten carbide (WC) crystal. In this study, we applied semiconductor polishing technology to finish the tool edge using a chemical–mechanical polishing grinding wheel. Microstructural analysis by backscattered electron imaging and electron backscattered diffraction revealed that WC crystal structures without any processing strain were obtained at a depth of ∼ 50 nm from the surface. We believe that this study will lead to the development of improved tool polishing technology that will prevent machining strain, and therefore, increase tool life.

Dry grinding of Al-SiCP composite with patterned diamond wheel

Aluminium being soft and ductile in nature, is one of the challenging materials to grind in industrial practice. Furthermore, load-free grinding of Al-SiC composites has been the most daunting task for many of the researchers with the available tools. In the present work, the feasibility of grinding of Al-SiC particulate composite by an indigenously developed single-layered brazed diamond grinding tool having uniformly arranged abrasive grits has been investigated. The experiments were carried out in reciprocating surface grinding mode without providing any crossfeed. Dry grinding was performed with increasing order of downfeed up to 30 μm at two different grinding velocities of 30 and 40 m/s and table feed of 2 and 5 m/min. Cutting forces, specific grinding energy, and roughness of the ground surface at different cutting depths were studied to analyze the grindability of Al2124-17SiCP composite, which is, as such, known to be a sticky-abrasive material. There was no sign of wheel loading, but a hint of mechanical chip adherence on grit tips was noted at higher down feeds. Although such abrasive machining was realized without any trace of wheel loading, surface roughness was recorded to be unfavorably high due to fewer overlapping cuts and non-participation of passive grits. However, it was observed that roughness could be improved significantly with the application of suitable crossfeed.

Diamond Grinding of Ceramic Balls with a Circular Feed

Diamond Grinding of Ceramic Balls with a Circular Feed

Design of a High-Speed Rotary Ultrasonic Machining Machine Tool for Machining Microstructure of Brittle Materials.

Aiming at the problems of low machining accuracy and more serious tool wear in the traditional diamond grinding machining (DGM) microstructure of hard and brittle materials, this paper proposes high-speed rotary ultrasonic machining (HRUM) technology and develops a HRUM machine tool. The hardware part of the machine tool mainly includes the spindle module, micro-motion system module, ultrasonic machining tank module, and data acquisition (DAQ) system module. The LabView-based controlled machining control system, including motion selection, initialization, coarse tool setting, constant force tool setting, control machining, and coordinate display module, is developed. Comparative experimental research of the HRUM and DGM of small holes in Al2O3 ceramics is carried out in the developed HRUM machine tool. The results demonstrate that HRUM effectively reduces axial cutting forces, reduces binder adhesion, and suppresses slippage while improving tool-cutting ability and extending tool life compared to DGM under the same machining parameters. This technology has essential research significance for the high-precision and efficient machining of microstructures in hard and brittle materials.

INVESTIGATING THE MECHANISM OF DIAMOND GRINDING STONE DISCHARGE IN MIST ENVIRONMENT

The study investigates the mechanism of electrical discharge machining in a mist environment for grinding diamond stones. The mist-assisted diamond grinding technology shows great promise, with advantages such as environmental protection and high efficiency. Additionally, utilizing a mist environment for grinding diamond stones reduces the dependence on working fluids and allows for direct grinding in highly accurate grinding machines.

Surface integrity and acoustic emission characteristics during slot milling 3D carbon/carbon composites using superabrasive diamond grinding point

This study mainly investigated the effect of machining parameters on surface morphology and defects in three-dimensional carbon/carbon ceramic matrix composites during slotting with superabrasive diamond grinding points. Specifically, it discussed the mechanisms of burr and uncut fiber formation based on the relationship between grinding and fiber directions. The experimental work was conducted under different spindle speeds and feed speeds, revealing that the poor machining surfaces and severe defects occurred at the minimum spindle speed (2000 rpm) with maximum feed speed (160 mm/min), and most uncut fiber defects occurred when the fiber cutting angle exceeded 90°. Acoustic emission (AE) signals were analyzed via signal processing techniques to capture the energy and frequency characteristics of slotting process under various machining parameters. Results indicated that spindle speed had a significant impact on the frequency band distribution of AE signals, while feed speed primarily influenced the stability of signal profiles. The material removal and tool wear mechanisms were examined through SEM micrographs of machined surfaces and grinding points, revealing that fiber debonding and fracture were the primary material removal mechanisms, and were highly dependent on the fiber cutting angle. Abrasive particles with relatively lower cutting velocity at the center of the grinding tool suffered severe damage/wear.

Improved grinding performance of SiC using an innovative bionic vein-like structured grinding wheel optimized by hydrodynamics

Diamond grinding wheel grinding has gradually become the main method for processing hard and brittle materials such as silicon carbide. Surface-structured grinding wheel prepared by laser ablation is a key technology to enhance grinding performance. A novel laser ablation vein-like structured grinding wheel (VLSGW) is suggested in this paper. The vein structure can effectively reduce the flow resistance. Four kinds of bionic vein structure flow channels were ablated on grinding wheels by picosecond pulse laser. The influence of the VLSGW on the air backflow and air pressure on the workpiece surface was analyzed by simulation. The grinding performance of VLSGW and unstructured grinding wheel (USGW) grinding SiC were compared. Compared with USGW, VLSGW can reduce normal and tangential grinding forces by up to 47.37 % and 41.06 %. At the same time VLSGW has a better workpiece surface topology and wear resistance than USGW.

Grain wear properties and grinding performance of porous diamond grinding wheels

Conventional diamond grinding wheels present challenges such as poor self-sharpening and difficulties in achieving ductile domain machining when processing hard and brittle materials, reducing machining quality and efficiency. This paper introduces a novel grinding wheel composed of porous diamond abrasive grains for better ultra-precision machining. Thermochemical etching is used to produce porous diamond grains of varying corrosion levels, and the cutting and wear mechanisms of these grains are investigated through molecular dynamics simulations and single-grain scratch tests. Compared to conventional diamond grains, the increased "micro-edge" and "multi-edge" features of porous diamond grains effectively reduce cutting force and heat. Notably, corrosion pore sizes ranging from 2 μm to 5 μm reduce cutting damage. Conventional diamond abrasive grains primarily incur damage through crystal surface dissociation and block crushing, whereas porous diamond abrasive grains experience damage mainly due to micro-crushing and micro-fracture. Ultra-precision grinding tests on 4H–SiC revealed that conventional abrasives produced cracks and pits on the grinding surface. In contrast, abrasives with a 2 μm eroded aperture exhibited predominantly ductile removal with minimal cracks and pits present. Abrasives with a 5 μm eroded aperture displayed desirable characteristics. This research offers valuable technical insights for enhancing the grinding performance of diamond wheels.

Influence of pulsed laser mode on ablation and modification processes of Si3N4‒ТiC ceramics surface layer

The influence of pulsed laser treatment mode parameters on ablation and modification processes of Si3N4‒ТiС ceramics is determined. Using the revealed interrelations a mode of pulsed laser processing after diamond grinding of Si3N4‒TiC ceramic parts is established and recommended for practical use, which ensures the defective layer removal and defectfree structure formation in the surface layer. Ill. 5. Ref. 31.

Mechanical properties of ZrB2 ceramics determined by two laboratories

AbstractThe mechanical properties for zirconium diboride (ZrB2) were measured at two laboratories and compared. Two billets of ZrB2 were prepared by hot‐pressing commercial powder. The relative densities of the billets were >99% and with an average grain size of 5.9 ± 4.5 µm. Both laboratories prepared American Society for Testing and Materials (ASTM) C1161 B‐bars for strength and ASTM C1421 bars with notch configuration A for fracture toughness. Specimens were machined by diamond grinding at the Army Research Laboratory (ARL) and electrical discharge machining (EDM) at Missouri S&T. Strength bars tested at Missouri S&T were polished to a .25 μm finish while the bars were tested as‐ground at ARL. Strengths were 473 ± 79 MPa for the Missouri S&T bars and 438 ± 68 for the ARL bars while the fracture toughness values were 3.9 ± .7 MPa•m1/2 for the Missouri S&T bars and 4.4 ± .6 MPa•m1/2 for the ARL bars. Vickers hardness was measured by both laboratories over a range of indentation loads. The resulting hardness values were on the low end of previously reported values and were quite different from each other especially at indentation loads ≤20N. The study demonstrated that the properties of materials tested to ASTM standards at different laboratories can be compared directly. In addition, strength and fracture toughness were nearly identical for bars prepared by conventional diamond grinding or EDM.

TRANSITION FROM THE PLASTIC MODE OF DIAMOND GRINDING OF CERAMICS TO MELTING AND FEATURES OF THE MELTING OF INSTRUMENTAL CERAMICS

It is shown that the traditional method of estimating the specific energy capacity based on the ratio of grinding power to processing productivity does not provide an adequate solution, since with it the specific heat capacity of processing exceeds the specific heat capacity of melting ceramics by almost an order of magnitude, and therefore, any diamond processing of ceramics should immediately enter the plasticity regime, which is not really the case. Therefore, it is the application of a new approach to the assessment of the specific energy intensity of diamond grinding, taking into account the wear of the working layer of the diamond wheel, that makes it possible to assess the possibility of achieving the energy conditions for the transition of ceramic processing to the plastic mode.
 It is shown that the plastic mode occurs precisely when the specific energy capacity of grinding becomes close to the specific heat capacity of melting ceramics.
 It was found that similar to the processes during the thermal melting of ceramics, melting crusts are also formed in the discharge hole during electroerosion grinding. Quantitative analysis of melting products shows that a structure close to the fracture of the sample is formed in the discharge holes after melting, in which there is no oxygen.

Permeability design and assessment of the additively manufactured metal-bonded diamond grinding wheel based on TPMS structures

The development of porous metal-bonded diamond grinding wheel with excellent permeability and satisfying mechanical properties is a huge challenge for traditional manufacturing process. In this paper, a novel design and fabrication method of metal-bonded diamond grinding wheel with human-designed open porous structure is proposed based on triply periodic minimal surfaces (TPMS) and additive manufacturing (AM) process. Darcy’ law and Kozeny-Carman equation are used to calculate the permeability coefficient for the porous grinding wheel. The optimal design method of grinding wheel porous structure is proposed comprehensively considering the geometric characteristic, permeability and mechanical properties. The grinding performance of AM porous grinding wheel is evaluated by BK7 glass grinding experiment. The permeability test result proves the effectiveness of permeability design method for the novel diamond grinding wheel. The grinding test result proves the advantages of the novel diamond grinding wheel.

Microscale viscous sintering model application to the preparation of metal bonded diamond grinding wheels

During sintering, with the interfacial free energy decreasing, particles bond to each other and the dense density increases, which are familiar phenomena in the preparation of metal bond diamond wheels and affect the mechanical properties of the grinding wheel. Herein, a sintering model of metal bond diamond wheels at a microscopic scale was constructed based on the computational fluid dynamics (CFD) and discrete element method (DEM), which was carried out to reveal the flow field, pressure field, and kinetic properties of the metal material in the heating process. Meanwhile, the finite element method (FEM) was used to analyze the thermal stress of diamond particles. The results show that with the increase in temperature, the viscous flow of particles intensifies. In the middle and late stages of sintering, the porosity of the particles changes significantly, and the densification rate is accelerated. Under the same temperature conditions, compared with the dodecahedral diamond, the octahedron produces less thermal stress and has better mechanical properties.

Sharpening of graded diamond grinding wheels

Grinding the flutes of cemented carbide end mill cutters results in high and uneven radial wear of the grinding wheel. This is a consequence of the varying geometrical contact conditions over the grinding wheel width. Decreased manufacturing accuracy regarding the tool target geometry is the consequence. To compensate for this, the dressing intervals must be shortened. High non-productive times and an additionally reduction of the grinding layer results from this. The higher non-productive times reduce the productivity of the grinding process and, in conjunction with the shorter lifetime of the grinding tool, thus increase the costs per work piece. It has already been shown that load-adapted grinding wheels can reduce uneven radial wear up to 50%. The adaptation of the wear behaviour to non-uniform engagement conditions causes non-uniform radial wear to occur again under uniform engagement conditions. Uniform engagement conditions occur during grinding wheel sharpening. Therefore, the present study investigates the influence of sharpening on the grinding tool topography. For this purpose, sharpening tests are carried out on four differently graded grinding wheels. For comparability, the tests are also carried out on two non-graded grinding wheels. In the present work, the surface parameters are evaluated with regard to their suitability for analysing the sharpening condition of graded grinding wheels. The grain protrusion derived from this is subsequently used for evaluation. For this, a dependency on the grain concentration is proven and the grain protrusions are shown over the grinding wheel widths. From this, sharpening parameters are determined that enable reproducible sharpening of graded grinding wheels.

Grinding performance evaluation of SiC ceramic by bird feather-like structure diamond grinding wheel

In recent years, the diamond grinding wheel has become the primary tool to process hard and brittle materials. A promising technology for enhancing grinding performance is surface-structured grinding wheels. A novel laser simulation bird feather-structured bronze bond diamond grinding wheel is suggested in this paper. It provides outstanding drag reduction and diversion effects since it is based on the structure of bird feathers. The bionic swallows' secondary feathers prototype was ablated on the bronze-bonded diamond grinding wheel by the pulse laser. The grinding processing mechanism of silicon carbide ceramics with a feather-like structured grinding wheel (FLSGW) was analyzed. The grinding performance of FLSGW, V-shaped structured grinding wheel (VSSGW), and a traditional grinding wheel (TGW) grinding silicon carbide ceramics were compared. The effect of FLSGW on the grinding force, workpiece surface quality, and wheel wear were investigated. The results show that FLSGW can reduce normal and tangential grinding forces by up to 56.3 % and 47.7 %, respectively, when compared to TGW. Furthermore, FLSGW has a higher workpiece surface quality than TGW and VSSGW. The FLSGW has significantly less abrasive wear than the of VSSGW and TGW.

An experimental investigation of sapphire grinding by porous and vitrified M0.5/1.5 diamond grinding wheel

Monocrystalline sapphire is known to be difficult to machine. Sapphire generally is machined with chemical mechanical polishing technology. However, low material removal rate (MRR) in machining gives rise to several limitations on mass manufacture of sapphire. Fixed ultrafine abrasive grinding is a promising technology for precision grinding of sapphire substrate and offers the possibility of improving manufacture efficiency. In this study, a novel porous and vitrified M0.5/1.5 diamond grinding wheel and preparation equipment are fabricated in an innovative way to precisely grinding sapphire. The experimental results demonstrate the recommended technological parameters for the grinding wheel, speed for which is below 1200 rpm, pressure below 15 N, and sapphire spindle speed lower than 30 rpm. Meanwhile, the removal mechanism of sapphire under the recommended technological parameters is in ductile grinding mode. Besides, in this study, the MRR of sapphire is 10.2 µm / h when the recommended technological parameters are adopted, the Sa of the sapphire after grinding is 0.03 µm and no depth of subface damage layer is observed.

Influence of Defects in Surface Layer of Al2O3/TiC and SiAlON Ceramics on Physical and Mechanical Characteristics

The paper studies the influence of diamond grinding, lapping, and polishing on the surface layer and defectiveness of the Al2O3/TiC and SiAlON ceramic samples. The index of defectiveness ID, which is the product of the defect density and the defective layer’s thickness (Rt), and a method for its evaluation are proposed to quantify the defectiveness of the ceramic surfaces. Lapping reduces the Rt parameter by 2.6–2.7 times when the density of defects was decreased by 2 times. After polishing, the Rt parameter decreases to 0.42 μm for Al2O3/TiC and 0.37 μm for SiAlON samples. The density of defects decreases many times after polishing: up to 0.005 and 0.004, respectively. The crack resistance of the polished samples increased by 5–7%. The volumetric wear of polished samples decreased by 1.5–1.9 times compared to the ground ones after 20 min of abrasion wear. The polished samples show a decrease in the coefficient of friction at 800 °C and a decrease in the volumetric wear by 1.5 and 1.3 times, respectively, compared to the ground ones after 200 m of friction distance. The volumetric wear at high-temperature friction of sliding for polished specimens was 55% and 42% less than for the ground ones, respectively.

Development of Pavement Performance and Remaining Service Life Prediction Tools for Iowa Jointed Plain Concrete Pavement Systems

Moving Ahead for Progress in the Twenty-First Century (MAP-21) requires US state highway agencies (SHA) to utilize performance-based approaches in their pavement management decision-making processes, and use of a remaining service life (RSL) model would be one of such performance-based approaches for facilitating the pavement management decision-making process for SHAs. In this study, statistical and artificial neural network (ANN)-based pavement performance and RSL models were developed for Iowa jointed plain concrete pavement systems (JPCP) using actual pavement structural, traffic, construction history, and pavement performance records obtained from the Iowa Department of Transportation pavement-management information system database. While both models were found to be potentially useful for project and network level performance and RSL predictions, statistical and ANN-based models were respectively found to be more suitable for project and network level analysis. Using these models, efficient Microsoft Excel-based automation tools were created to predict future performance of a JPCP section and estimate RSL values based on predicted future performance and threshold limits for the performance indicators. Consequence analysis was also conducted to investigate the impact of traffic and preservation treatment (diamond grinding) on the RSL of a JPCP. The tool, also capable of estimating realistic pavement pretreatment and posttreatment performance and RSL, could be successfully used as part of performance-based pavement management strategies and helping decision-makers make better-informed pavement management decisions to properly allocate agency resource expenditures. Moreover, this study provides a better understanding of RSL and the factors that influence both the project and network level RSL.

Molecular dynamics study of the repetitive friction mechanism of nickel-based single crystals in an aqueous environment

In this study, molecular dynamics simulations were used to simulate the iterative rotational friction of nickel-based single crystals using diamond grinding balls in both the presence and absence of water. First, the friction force, depth and morphology of wear marks, wear rate, and evolution of internal defects during the friction process of nickel-based single crystals were investigated. Second, a comparative study of the frictional wear of nickel-based single crystals in both the presence and absence of water was carried out in terms of temperature, water molecule distribution, atomic displacement vector, and wear scar depth during the friction process. Finally, the formation process of irregular grinding chips under aqueous conditions was elucidated. The following phenomena were observed: As the number of rubs increased, the single rub depth of the workpiece, the wear rate, and the rate of increase in the number of defective atoms produced all decreased. A comparison of friction under aqueous and water-free conditions showed that, in the presence of water, the force exerted by the grinding ball on the workpiece was shared by the water molecules. This resulted in a decrease in the roughness of the machined surface, a reduction in the number of internally generated layer errors, a lower overall friction temperature, and a nickel matrix that was protected by water molecules. Finally, when grinding under aqueous conditions, water molecules interfered with the normal chip removal process of the grinding balls, leading to the production of irregular grinding chips.