International Journal of Abrasive Technology (12 papers in press)
Study on the Surface Micro-topography in Pre-stressed Dry Grinding Proces
by Yansheng Deng, Xiaoliang Shi, Shichao Xiu, Minghe Liu
Abstract: To study the surface micro-topography in pre-stressed dry grinding process, the single grain cutting simulations were carried out in DEFORM-3D, besides, dry grinding experiments were conducted. The residual stress, groove depth and pile-up height were analyzed in the simulations. The surface roughness was measured and micro-surface topography was observed by SEM in the experiments. The results indicated that the application of pre-stress is beneficial to generate more compressive stress, which is beneficial to restrain the generation of surface micro-cracks. Pre-stress can reduce the pile-up height. When pre-stress is within a lower range, the groove depth decreases with pre-stress increasing, however, once pre-stress overcomes a certain value, surface fold appears and surface roughness increases instead. The influence rules of the cutting depth and feeding speed on surface micro-topography in pre-stressed dry grinding process are consistent with them in the traditional grinding process.
Keywords: pre-stressed dry grinding; residual stress; groove depth; pile-up height; surface micro-topography; surface roughness.
Wheel lift-off in creep-feed grinding: thermal damage, power surge, chip thickness and optimization
by Radovan Drazumeric, Jeffrey Badger, Peter Krajnik
Abstract: An investigation is made into the phenomenon of early lift-off in creep-feed grinding, where the wheel lifts away from the workpiece before reaching the end of cut. In single-pass operations, early lift-off can result in thermal damage. In multi-pass operations, there is a surge in material-removal rate just before lift-off, which can result in thermal damage and excess wheel wear. This study examines the current inadequate methods of dealing with lift-off. It then develops a geometric and kinematic model for analyzing the lift-off phenomenon. It finally proposes a thermal-model-based optimization method for achieving a constant maximum surface temperature, resulting in shorter cycle times and less risk of thermal damage. The power-surge model is validated experimentally in diamond grinding of tungsten-carbide rotary tools.
Keywords: Grinding; Tooling; Thermal damage; Optimization.
Effects of grinding process parameters on the surface topography of PCBN cutting inserts
by Bahman Azarhoushang, Thomas Stehle, Heike Kitzig-Frank
Abstract: PCBN (polycrystalline cubic boron nitride) as cutting tool material is a proper choice for machining difficult-to-cut materials, such as hardened steels, superalloys and cast irons. This is mainly due to its high hardness, high chemical stability and toughness. Grinding with a diamond wheel is the most commonly used process to achieve dimensional accuracy and the required surface finish of PCBN tools. The surface quality of PCBN tools and hence their machining performance strongly depend on the grinding parameters. The induced cutting forces, temperature, loading and wear of the grinding wheel influence the quality of the ground PCBN surface. The effects of cutting parameters, i.e. cutting speed, axial feed speed and oversize, on the cutting forces, surface roughness and loading of the grinding wheel during plunge face grinding of PCBN inserts are studied in this work. The grinding process was divided into two stages, namely roughing and finishing. It was found that increasing the cutting speed from 20 m/s to 40 m/s can decrease the cutting forces and surface roughness up to 20% and 30% respectively. Additionally, the amount of oversize in roughing and the roughing parameters have a significant influence on the induced cutting forces in the finishing stage and the surface quality of the ground PCBN inserts.
Keywords: Face Grinding; PCBN Inserts; Cutting Speed; Roughing; Finishing.
The Effects of Temperature Curves on the Diamond/NiCr Interfacial Properties in Highfrequency Induction Brazing
by Guoqin Huang, Meiqin Zhang, Hua Guo, Xipeng Xu
Abstract: The present study alters the temperature characteristics during high-frequency induction brazing of diamond grits and investigates their effects on the properties of the diamond/brazing alloy interface. The high-frequency induction brazing was conducted in a vacuum using NiCr as active filler alloy. An active temperature range was identified for the brazing of high-quality diamond tools. This temperature range, coupled with long heating time, favours the wetting of filler alloy to diamonds, and the chemical reactions and element diffusion at the diamond/alloy interface, but reduces the static compressive strength of the diamonds. If the temperature is slowly raised, the protrusion height and location of brazed diamonds can be more precisely controlled. Brazed diamonds with 3050% protrusion are optimal for cutting.
Keywords: Diamond; Ni–Cr alloy; High-frequency induction brazing; Interface.
An experimental study of the particle velocities in abrasive waterjets
by Kunlapat Thongkaew, Jun Wang
Abstract: Abstract: An experimental study using particle image velocimetry (PIV) and laser induced fluorescence (LIF) techniques is presented to examine the particle flow characteristics inside the high velocity abrasive waterjet (AWJ) and assess the capability of this measurement technique. Although the particle velocity is found to increase with an increase in water pressure, the velocity of particles on the jet centreline decreases while that at the jet edge increases as the jet flows downstream within 40 mm distance from the nozzle exit considered in this study. It is also shown that particles rotate while moving downstream from the nozzle exit. While these particle flow characteristics may be anticipated from theoretical understanding, it confirms that the capability of this technique is not only able to measure the particle velocities, but also observe the particle trajectory in high velocity flows. The measured particle velocity data are then used to assess the applicability of a previously developed particle velocity model for low water pressures. It is found that the model can equally give adequate predictions of particles velocities in AWJ for relatively low water pressures of within 20 MPa.
Keywords: Keywords: Abrasive waterjet; Particle image velocimetry; Laser induced fluorescence; Particle velocity; Particle distribution.
Modeling of the micro-grinding process considering the grinding tool topography
by Mohammadali Kadivar, Ali Zahedi, Bahman Azarhoushang, Peter Krajnik
Abstract: The micro topography of the grinding tool has a considerable influence on the cutting forces and temperature as well as the tool wear. This paper addresses an analytical modeling of the micro-grinding process based on the real tool topography and kinematic modeling of the cutting-edge-workpiece interactions. An approximate shape of the abrasive grains and their distribution is obtained from the confocal images, which are taken from the tool surface – determining the grain height protrusion and the probability density function of the grains. To determine the grinding forces, a transient kinematic approach is developed. In this method, the individual grit interaction with the workpiece is extended to the whole cutting zone in the peripheral flank grinding operation. Hence a predictive model of cutting forces and surface roughness in micro grinding of titanium grade 5 is developed. Finally, the simulated forces and surface roughness are validated by the experimental results.
Keywords: Single-grain interaction; micro grinding, Diamond grinding pin; grinding pin topology
Effect of small quantity lubrication on grindability of hardened AISI 4340 steel
by Sirsendu Mahata, Joydip Roy, Ankesh Samanta, Bijoy Mandal, Santanu Das
Abstract: The process of grinding is normally associated with generation of considerable amount of heat. To reduce thermal damages, grinding zone is often flooded with liquid coolant, most of which is wasted and may cause severe environmental pollution. In the present work, grindability of hardened AISI 4340 steel is assessed at various infeeds, using an eco-friendly vegetable oil applied by small quantity lubrication (SQL) technique, so as to reduce the quantity of coolant. At the same infeed, grinding is also performed by applying a uniform layer of semi-solid lubricant (grease) on the work surface. Comparison is made between the two methods in terms of force, surface roughness, specific grinding energy and observed chip forms. Results prove that SQL technique using vegetable oil is better than grease as a lubricant in terms of force requirement, while surface quality shows improvement with grease layer lapped on the work surface than with SQL technique.
Keywords: grinding; grindability; cooling; lubrication; SQL; roughness; force; eco-friendly manufacturing
Experimental investigations on super-smooth polishing of strontium titanate based ceramics substrates
by Qiusheng Yan, Xiaobei Cao, Jisheng Pan
Abstract: Strontium titanate (SrTiO3) is a new type of multi-function electronic ceramic material. SrTiO3 ceramic substrates with a high dielectric constant can be obtained by non-pressurised sintering using ultrathin blanks, which result in the characteristics of thin, soft, brittle and warped. So that SrTiO3 ceramics substrates need to be polished to improve surface quality and dimensional precision before application. In this research, polish experiments with various processing parameters on the surface roughness, the material removal rate and the surface morphologies of SrTiO3 ceramic substrates were conducted. The results show that the SrTiO3 ceramic substrate with a highest quality surface was obtained in the condition: employing a brown polyurethane pad to polish the substrates at a polishing velocity of 45 r/min. Meanwhile, the slurry flow rate, the concentration of the polishing slurry and the polishing pressure were 20 ml/min, 4 wt% and 15.043 kPa, respectively, which rates with an overall and a partial surface roughness of Ra 0.01 µm and Ra 4 nm, respectively. While some new micro-scratches were generated on the surface of the SrTiO3 ceramics substrate in the polishing process because the embedding and scratching of abrasive particle led to expose the inherent pores and grain boundaries.
Keywords: strontium titanate; ceramic substrate; polishing; surface roughness; material removal rate.
Experimental investigation of process parameters for conductive graphite abrasive mixed EDM of WC alloy
by Jagdeep Singh, Rajiv Kumar Sharma
Abstract: The aim of current experimental investigation is to perform and study the effect of input processing parameters for abrasive mixed electrical discharge machining (PM-EDM) of tungsten carbide alloy. Mainly, four input processing parameters have been studied, i.e., pulse duration, peak current, abrasive concentration and abrasive grain size for the machinability evaluation of material removal rate and tool wear rate. In this study, graphite (C) abrasive is suspended into the dielectric fluid to make the discharging process stable and uniform, which results in improvement of process mechanism and efficiency. However, this study highlights the mathematical modelling to express the inter relationship between input processing and performance characteristics with the help of response surface methodology (RSM). Results from the study shows the positive influence of graphite abrasive used for PM-EDM of WC alloy with reduction in tool wear rate (5.22%) along with the achievement of significant material removal rate (6.74%).
Keywords: abrasive; graphite; discharge; tungsten; alloy; ANOVA; response surface methodology; RSM; machining; material removal rate; MRR; tool wear rate; TWR.
Design of dimpled engineering surfaces for improving lubrication performance in rolling-sliding contacts
by Fukuo Hashimoto, Rao S. Zhou
Abstract: Functional performance depends largely on the surface characteristics of critical components. This paper describes the design of dimpled engineering surfaces and the fabrication of micro-patterns on steel samples. The designed engineering surfaces are analysed and evaluated in terms of their mixed EHL film thicknesses and pressure distributions in the elliptical Hertzian contact zone.
Keywords: surface engineering; surface structuring; surfaces; mixed EHL contact; film thickness; dimpled surfaces; finishing technology.
Study on hardening mechanism in GH and PSHG based on classical nucleation theory
by Xiaoliang Shi, Shichao Xiu, Xiuming Zhang
Abstract: Grinding hardening (GH) is a common processing method and pre-stressed hardening grinding (PSHG) is presented combined with the advantages of grinding hardening and pre-stress grinding. In order to study their hardening and transformation mechanism, the paper carried on the GH and PSHG experiments. According to the results, the hardening mechanism in GH was reanalysed through the point of classical nucleation theory. And the coupling relationship of stress, temperature and microstructure in PSHG is studied as well. The study shows: the dislocation in the grinding area compensates the negative factors of cooling speed during GH, so the hardening effect is remarkable. In PSHG, the parent-phase-hardening and strain-inducing-phase-changing due to applying pre-stress have comprehensive effect on the martensitic phase transformation in the grinding process. The characteristic of microstructure in hardening layer can be controlled by applying different pre-stress in PSHG.
Keywords: grinding; hardening; martensite; pre-stress; classical nucleation theory; 40Cr.
An analytical force and surface roughness model for cylindrical grinding of brittle materials
by Ali Zahedi, Bahman Azarhoushang
Abstract: In this paper, an analytical approach is proposed for the modelling of ground surface and grinding forces in cylindrical grinding of ceramic materials. The model incorporates the near-actual distribution of cutting grains over the grinding wheel surface and a kinematic approach for the engagement of the grains with the workpiece surface per grinding parameters and conditions. To interpret the stochastic engagement of arbitrary grains with the workpiece, and to distinguish the dominant material removal mechanism, fracture mechanics of single-grain indentation is applied. The approach based on the fracture mechanics accounts for grain size and geometry and material properties. The results of a previously performed research on single-grain scratch tests are taken for interpreting force and workpiece surface characteristics. Without losing generality, the model was applied to a cylindrical plunge grinding of an alumina ceramic. The experiments show qualitative agreement of model predictions with the experimental force and ground workpiece topography.
Keywords: cylindrical grinding; brittle ceramics; alumina; kinematic modelling; indentation mechanics; surface roughness; grinding force; ductile grinding.