Grinding Depths Research Articles

Study on influence of grinding depth and grain shape on grinding damage of K9 glass by SPH simulation

This work use the SPH method to study the relationship between grinding depth and grinding force of K9 glass in ultra-precision grinding, and the effect of grain shape on material removal. The relationship between the force and the depth in the stable scratching stage is FR = 0.55078ap1.15356, which provides a basis for controlling the grinding depth by force. The material removal modes at different grinding depths were obtained, that is, plastic removal occurs below 0.2 μm, brittle transition occurs between 0.2 and 0.4 μm, and brittle removal occurs at more than 0.5 μm. It is found that the cutting resultant force of sharp grains is smaller and the normal force is smaller than the tangential force. By analyzing the plastic deformation depth and residual stress depth, it is found that the material removal mode with small deformation and little removal has the lowest cutting force fluctuation and the highest grinding quality. It provides a reference for the choosing of grain shape in rough grinding and ultra-precision grinding. The correctness and reliability of the simulation results were verified by the comparison of the simulation findings with the results obtained from varied-depth scratching experiments and the multi-shape indenter scratch experiments.

Grinding force modelling for ductile-brittle transition in laser macro-micro-structured grinding of zirconia ceramics

Laser ablation accomplishes high geometrical adaptability by the use of pulsing lasers and permits the manufacture of macro-micro-structures. In this paper, a systematic approach with a laser structuring technology was devised and utilized to generate macro-micro-structured patterns on the diamond wheel surface. An experiment on zirconia ceramic grinding was performed by the macro-micro-structured wheel. The grinding force and the surface morphology were investigated. The forming mechanism of the three grinding stages was analyzed, including ductile-stage grinding, ductile-to-brittle-transition-stage grinding and brittle-stage grinding. A theoretical grinding force model was presented by taking into account the three grinding stages in laser macro-micro-structured grinding (LMMSG). In addition, the mean grinding depths were defined in grinding force modelling for the ductile area, the ductile-to-brittle-transition area and the brittle area, separately. The amount of effective diamond grains was proposed for the final grinding force model. The model revealed the connection between the grinding force and the grinding parameters. Finally, the model was verified by experiments, and the experimental results were coincided with model predictions. It was obvious that the theoretical grinding force model may be available to predict the grinding force of zirconia ceramics under the LMMSG condition. Meanwhile, the influence between the grinding parameters and the surface morphology were discussed. The experimental results verify that the three grinding stages were existed and the theoretical model was proved to be reliable.

Research on dynamic hardening effect on workpiece’s hardness distribution with depth of cut

Grinding hardening is a kind of attractive processing technology, which utilizes grinding heat to generate the hardening layers. Previous studies have attached the importance on generation mechanism in experiments and simulations. However, grinding hardening is a dynamic hardness improvement process due to the system’s dynamic characteristics, whose hardness becomes different during the dynamic process. To this end, this paper presents a new hybrid model to investigate the dynamic hardness distribution with the system’s dynamic characteristics. When the effect of cutting, rubbing, and plowing is considered, the dynamic grinding force is calculated firstly. Afterwards, coupled with the dynamic grinding force, the dynamic grinding temperature distribution is obtained accordingly. Moreover, in terms of the hardness superposition rule, the dynamic hardness model is established based on the calculated dynamic grinding force and the dynamic temperature distribution. Finally, the model is validated by the measurement of the ground workpiece’s hardness via grinding experiments under different grinding depths. It can be concluded that the system’s dynamic characteristics can result in the time delay of the hardness temporal distribution and the inhomogeneity of the hardness spatial distribution. Consequently, the model is anticipated to be meaningful for both the manufacturing industries and the research fields.

Numerical and experimental investigation on grinding-induced exit burr formation

Exit burrs are easily generated on workpiece edges. In grinding process, particularly, exit burrs could deteriorate the highly required precision and even affect the functionality of components. Therefore, to understand the burr formation mechanism and control it in grinding process is of great significance. To this end, this paper investigates the features and mechanism of exit burr formation, as well as the influence of grinding conditions including grinding speed, grinding depth, wheel granularity, and grinding pass sequences on the exit burr formation of 12CrMoV stainless steel using the Al2O3 grinding wheels. A 3D finite element (FE) model of single-grit scratching process was developed for explaining the exit burr formation procedures. The effects of different grinding conditions on the exit burr sizes were analyzed, and the characteristics of the exit burr sizes and hardness were observed via experiments. It was found that the whole procedure of exit burr formation during grinding could be divided into six stages: steady-state grinding, pre-initiation, appearance of the fourth deformation zone, formation of plastic deformation band, burr development, and finish of burr formation. The burr sizes were strongly determined by the wheel granularity and grinding depth, rather than the grinding speed. For the same required grinding depths, using whether single pass or multiple passes of the grit has a very small impact on the exit burr sizes. The hardness of the burr root part is relatively stronger than that of the burr rollover part, while the burr hardness would increase when decreasing the grinding depth.

Study on force and temperature characteristics of micro-grinding nickel-based single-crystal superalloy

Aiming at the status of fewer researches on the anisotropy of single-crystal superalloy and micro-grinding temperature field, micro-grinding using the tool of < 1 mm in diameter to remove material is the final procedure of machining micro-parts. This paper firstly analyzes the anisotropy of surface-centered cubic structural material and establishes the theoretical model of elastic modulus and shearing modulus of single-crystal superalloy in the (001), (110) and (111) crystal plane. Afterward, it builds the three-dimensional simulation model of grinding temperature based on the Hill model, adopts any Lagrangian–Euler method to realize the simulation of micro-grinding temperature, gets the distribution of temperature field and changing situation during the micro-grinding through single-factor experiment and simulation analysis, and makes a study on the laws of different grinding depths, feeding rates, grinding velocities, different crystal planes {(001), (110) and (111)} and different crystal orientations in (001) crystal plane that affect the micro-grinding temperature, thus obtaining the crystal orientation which produces low grinding force and temperature. The result indicates that the grinding temperature increases with the increase in spindle speed, feeding rate and grinding depth; the grinding force and temperature are proportional to the elastic modulus and shearing modulus of the single-crystal material; the grinding temperature along (111) crystal plane is the highest, that of the (110) crystal plane is at the middle, and that along (001) is the lowest. When grinding in the (001) crystal plane, the normal grinding force and temperature along [110], $$ [\bar{1}10] $$ , $$ [\bar{1}\bar{1}0] $$ , $$ [1\bar{1}0] $$ crystal orientations are the highest, and those along [100], [010], $$ [\bar{1}00] $$ , $$ [0\bar{1}0] $$ crystal orientations are the lowest. And along with the aggravating of wear of abrasives on the grinding tool, the normal grinding force, tangential grinding force and grinding temperature all increase and the wear state of grinding tool can be judged online according to the signal of grinding force and temperature. These results provide an important evidence to do further research on the surface integrity of grinding single-crystal superalloy.

Study of subsurface damage of monocrystalline nickel in nanometric grinding with spherical abrasive grain

In this paper, molecular dynamics is used to analyze monocrystalline nickel by spherical abrasive grinding. The effects of different grinding speeds, different grinding depths and different sizes of abrasive grains on subsurface defects are compared. According to the X-direction and Z-direction displacement of the some workpiece atoms, the subsurface formation mechanism is obtained. The subsurface defects under different grinding conditions are studied according to the Common Neighbor Analysis (CNA) technique. According to the deformation criterion, subsurface deformation depth of the workpiece under different grinding conditions is quantitatively calculated, by analyzing the potential energy curve of the atom. It is concluded that within a certain range, increased grinding speed results in reduced subsurface defects, and grinding depth is proportional to subsurface defects.

Effects of cooling conditions and grinding depth on sustainable surface grinding of Ti-6Al-4V: Taguchi approach

In this research, the effects of coolant types, cooling techniques, and grinding depth on the surface properties of the Ti-6Al-4V after surface grinding with white alumina wheel were investigated. Three coolant types namely sunflower oil, formulated sunflower oil-based emulsions and soluble cutting oil were applied to the grinding zone using two cooling techniques: wet cooling and minimum quantity lubrication. The grinding was undertaken at grinding depths of 0.005, 0.010 and 0.015 mm. An L 9 orthogonal array was used to design the experiments and undertaken the evaluation of the variable interrelationships. Surface hardness and surface morphology of the ground surfaces were determined using Vickers Macro-hardness tester and <i>Zeiss Axio Zoom V16</i> optical microscope, respectively.<br />Results from the signal-to-noise ratio analysis revealed that cooling technique has the most influence while the grinding depth has the least influence on the surface hardness of ground Ti-6Al-4V. The optimal parametric setting which gives the highest surface hardness of Ti-6Al-4V was identified from the main effect plots and were sunflower oil (SO), MQL 2 at a flow rate of 0.65 L/h and a grinding depth of 0.015 mm. Analysis of variance demonstrated that the individual<br />contributions of coolant types, cooling techniques and grinding depths to surface hardness were 24.11%, 52.47% and 14.15%, respectively. The morphological investigations established that better surface finish was achieved through the application of sunflower oil-based emulsions in MQL cooling technique at a grinding depth of 0.005 mm.

Effect of grinding depth on surface topography by considering vibrations and a force prediction model

Little consideration has been given to vibrations when the effect of grinding process parameters on the surface morphology is studied. Taking a grinding force as the intermediate variable, influences of grinding depths on the surface topography are investigated with considering vibrations in this paper. Firstly, a novel grinding force prediction model is proposed through amending the Malkin model by integrating with contact arc length and abrasive grain contact angle. Secondly, vibrations of the feed platform and the grinding wheel shaft are analysed. Vibration displacement in the x-direction of wheel axis remains substantially between 140-150 nm, while in the y-direction, it increases with the grinding depth. Finally, three-dimensional surface topographies with different grinding depths are investigated. It is observed that the pronounced defects and a coarse texture are generated as the grinding depth increases. Parameters like Sa, Sq, Sku, Ssk are more suitable to represent the real grinding quality of workpiece surface.

Effect of grinding depth on surface topography by considering vibrations and a force prediction model

Little consideration has been given to vibrations when the effect of grinding process parameters on the surface morphology is studied. Taking a grinding force as the intermediate variable, influences of grinding depths on the surface topography are investigated with considering vibrations in this paper. Firstly, a novel grinding force prediction model is proposed through amending the Malkin model by integrating with contact arc length and abrasive grain contact angle. Secondly, vibrations of the feed platform and the grinding wheel shaft are analysed. Vibration displacement in the x-direction of wheel axis remains substantially between 140-150 nm, while in the y-direction, it increases with the grinding depth. Finally, three-dimensional surface topographies with different grinding depths are investigated. It is observed that the pronounced defects and a coarse texture are generated as the grinding depth increases. Parameters like Sa, Sq, Sku, Ssk are more suitable to represent the real grinding quality of workpiece surface.

Wpływ parametrów szlifowania wgłębnego na nanotwardość i chropowatość powierzchni stali C45

The paper presents the results of investigations on the effect of the depth of concurrent grinding of flat surfaces on the roughness and nano-hardness of the surface layer of C45 steel with a ferritic-pearlitic structure and average grain size of 20 μm. A significant increase in the hardness of the surface layer of the workpiece was obtained for all grinding depths.

Study on the surface topography in consideration of the dynamic grinding hardening process

The workpiece’s surface topography is always a key factor to measure the quality of the workpiece’s finish. However, most previous studies on modeling of the workpiece’s surface topography neglect the dynamic hardening effect, which derives from the workpiece’s material microstructure transformation. In this paper, a new coupling model is established to investigate the influence of dynamic hardening effect on the workpiece’s surface topography. Coupled with the analytical and the numerical method, the dynamic grinding force is obtained firstly. Then, the dynamic grinding force is utilized to calculate the dynamic temperature in finite difference method (FDM). Afterwards, the model of the dynamic hardness is established according to the corresponding temperature distribution. Furthermore, coupled with the calculated dynamic hardness, the wheel’s and the workpiece’s surface topography is set up on the basis of the grits’ Gaussian distribution and the grits’ movement trajectory respectively. Finally, the proposed model is further validated by the experiments in different grinding depths. From the comparison, it can be found that the grinding hardening effect should be taken into consideration in analyzing the workpiece’s surface topography. Moreover, the surface roughness of the workpiece can be reduced by decreasing the larger grinding depth, which can result in a stronger hardening effect.

The Study on Grinding Ratio in Form Grinding with White Fused Alumina (WA) Grinding Wheels

The study is carried out based on an experiment of form grinding spur rack with white fused alumina (WA) grinding wheels. In the experiment, SOV-3020A type tri-axial image mapper is utilized to measure the profile of the tooth space in the rack, and the curve equations between the sectional area of the tooth space and the tooth sequence under different grinding depths are established by nonlinear curve regress using software of origin8.0. Then, it deduces the prediction equations for current grinding ratio and cumulative grinding ratio under different grinding depths. The result shows that the grinding ratio is exponential decline relationship with the increase of the number of the tooth to be ground under the same grinding depth, and the decline speed is fast in the initial stage. With the increase of grinding depth, the grinding ratio increases gradually. The cumulative grinding ratio is about twice as high as the current grinding ratio. Thus, large grinding depth is generally used in rough grinding to improve grinding efficiency.

Influence of application of hybrid MQL-CCA method of applying coolant during hob cutter sharpening on cutting blade surface condition

Abrasive machining processes are aimed at the complete removal of the coolant which is designed mainly to cool and lubricate the machining zone. This results from economic reasons, which require a decrease in the general production costs, as well as environmental reasons and the necessity to adjust production processes to ever-stricter environmental protection regulations. Complete coolant elimination is difficult to achieve in grinding processes. The heat and high temperature that appear in the area of contact between the tool and the workpiece cause an unacceptable deterioration of the quality of the machined surfaces. The research presented here concerns the determination of the influence of the application of the MQL-CCA hybrid method that decreases the amount of the coolant applied during sharpening of the hob cutters on the condition of the cutting blades' surface layer. The MQL-CCA method consists of the simultaneous introduction into the grinding area of both a minimal amount of the lubricating agent using the minimum quantity lubrication (MQL) method and the coolant in the form of compressed cooled air (CCA). For comparison, the tests were also carried out by applying the coolant with the flood method (WET) and with MQL, as well as by providing CCA. The research results show that (in the described range of changes in grinding parameters) solely applying the MQL-CCA method does not cause considerable changes in surface layer microhardness as compared to “wet” processing. The differences in microhardness values (on the Vickers' scale – HV) obtained closest to the grinding surface are 3–5 units. At the same time, for both of the applied grinding depths (0.01 and 0.03 mm) changes in microhardness were observed up to approximately 40 μm from the cutter dressing surface. In the case of the MQL and CCA methods being applied separately, the drop in microhardness was observed up to approximately 60–70 μm from the grinding surface, while microhardness at a depth of 10 μm was smaller by approximately 70–100HV for each grinding depth. Moreover, the surface roughness obtained when using the MQL-CCA method is comparable to that obtained during grinding with the flood method. For a grinding depth of 0.01 mm, the difference in the Rz parameter values is 4.6%, while for a grinding depth of 0.03 mm it was only 2.5%. In the case of applying the MQL method, the obtained surface roughness with a grinding depth 0.01 mm is approximately 30% larger in relation to WET and approximately 47% larger for a grinding depth of 0.03 mm. As far as the CCA method is concerned, the roughness is approximately 135% greater as compared to WET for both grinding depths. The SEM images for the MQL-CCA and WET method did not reveal any typical defects in the form of feather edges or chips on the edges of the ground surfaces. Simultaneously, burrs occurred on edges that were ground using minimal lubrication with the MQL method or by applying cooled compressed air (CCA). The research results indicate that it is possible to considerably limit the traditional cooling coolant flow rate by applying the hybrid MQL-CCA method without considerable deterioration of the quality of the surface layer of the ground surfaces. Therefore, grinding cutting hobs using the hybrid MQL-CCA method in the described range of grinding conditions may be an alternative to using the conventional flood method (WET).

Experimental and analytical investigation of effects of refurbishing on rolling contact fatigue

In this study, the effects of refurbishing on rolling contact fatigue (RCF) in case carburized AISI 8620 steel were experimentally and analytically investigated. A thrust bearing test apparatus (TBTA) was designed and developed to simulate RCF. Initial RCF tests were conducted on AISI 8620 steel specimens to determine the baseline for pristine. Then new specimens were exposed to fatigue cycles equal to 90% of the L10 life of the pristine material. These specimens were then refurbished to the depths of 0.13b and 1.27b (b is the half width of Hertzian contact). The refurbished specimens were then subjected to RCF cycles in the TBTA until a spall appeared on the surface. The experimental results of refurbished specimens indicated a significant amount of fatigue life after refurbishing for both grinding depths. Moreover, it was observed that the remaining useful life of the refurbished test specimens was extended by increasing the depth of the regrinding.For the analytical investigation, a two-dimensional elastic-plastic finite element model was developed to estimate RCF life for pristine and refurbished specimens of case carburized steel. The characteristics of case carburized materials (e.g., variations in hardness and residual stresses) were incorporated in the 2D finite element model. In the present study, a continuum damage mechanics approach was employed to determine fatigue damage accumulation in original and refurbished domains. The results obtained from the experimental and FEA models for pristine and refurbished case carburized steel are in good agreement for both grinding depths.

Study on grinding surface deformation and subsurface damage mechanism of reaction-bonded SiC ceramics

In order to explore the grinding surface deformation and subsurface damage mechanism for reaction-bonded SiC ceramics, the grinding experiment for reaction-bonded SiC ceramics was carried out under the condition of different grinding depths using two different kinds of grain sizes of grinding wheel. The ground surface morphology of specimen was observed using the field emission scanning electron microscope (5000 ×), and the value of surface roughness Rz was measured by the confocal microscope, which found that there were the brittle removal region and the plastic removal region on the ground surface of reaction-bonded SiC ceramics and it could improve the ground surface quality and proportion of ductile region using the fine grinding wheel and reducing the grinding depth. The specimen was polished by the ion cross section polisher and the ground subsurface was analyzed by the field emission scanning electron microscope, which found that there were transgranular fracture, intergranular fracture, crack bifurcation, ladder-shaped crack and other phenomenon in the grinding process. And it could control the subsurface damage depth using the fine grinding wheel and reducing the grinding depth. The relationship between surface roughness and subsurface damage was analyzed based on the indentation theory, which found that the simulation results were close to the experiment results when the value of m is in the range of 1/8–1/4. When m is 0.2143 calculated by genetic algorithm, the simulation results are the best.

Modeling and analysis of dynamic cutting points density of the grinding wheel with an abrasive phyllotactic pattern

The model of dynamic cutting points density (Nd) using the grinding wheel with an abrasive phyllotactic pattern was established in this paper, which can be generalized to other engineered grinding wheels with orderly arrayed abrasive grains. The curves of Nd over time of a grinding wheel with the abrasive phyllotactic pattern and two kinds of engineered grinding wheels were figured out at different wheel speeds, workpiece velocities, and grinding depths. The mathematical expectation, amplitude, and period of Nd were compared and analyzed in different conditions based on the model. Results showed that Nd of these engineered grinding wheels vary regularly according to process parameters. Also, Nd of grinding wheel with the abrasive phyllotactic pattern has higher mathematical expectation and lower amplitude than that of the others. Finally, through analyzing the influence of the phyllotactic coefficient on Nd based on the model, the change rule of Nd is observed: Nd decreases when the phyllotactic coefficient increases, but the decreasing rate will slow down gradually. This research is not only indispensable and fundamental for subsequent researches including grinding force, grinding and surface quality of workpiece, but also provides important information for a better understanding of the mechanism of grinding using engineered grinding wheels.

Force characteristics in continuous path controlled crankpin grinding

Recent research on the grinding force involved in cylindrical plunge grinding has focused mainly on steady-state conditions. Unlike in conventional external cylindrical plunge grinding, the conditions between the grinding wheel and the crankpin change periodically in path controlled grinding because of the eccentricity of the crankpin and the constant rotational speed of the crankshaft. The objective of this study is to investigate the effects of various grinding conditions on the characteristics of the grinding force during continuous path controlled grinding. Path controlled plunge grinding is conducted at a constant rotational speed using a cubic boron nitride (CBN) wheel. The grinding force is determined by measuring the torque. The experimental results show that the force and torque vary sinusoidally during dry grinding and load grinding. The variations in the results reveal that the resultant grinding force and torque decrease with higher grinding speeds and increase with higher peripheral speeds of the pin and higher grinding depths. In path controlled grinding, unlike in conventional external cylindrical plunge grinding, the axial grinding force cannot be disregarded. The speeds and speed ratios of the workpiece and wheel are also analyzed, and the analysis results show that up-grinding and down-grinding occur during the grinding process. This paper proposes a method for describing the force behavior under varied process conditions during continuous path controlled grinding, which provides a beneficial reference for describing the material removal mechanism and for optimizing continuous controlled crankpin grinding.

Surface morphology of grinding of Si&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;N&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt; with cup grinding wheel

Grinding parameters affect the morphology of a machined surface. Creep-feed face grinding with a cup wheel is a highly efficient and highly precise grinding method for the manufacturing of hard and brittle materials. There is a trade-off between the rate of material removal and machining precision because substantial material removal necessitates a deep grinding depth that usually results in poor surface quality. The problem of how to machine a high-quality surface while maintaining a high removal rate is therefore important in precision grinding. This paper first introduces this grinding method. Si3N4 is an important engineering ceramic widely used in many fields, and to improve its ground surface quality, an experimental design is established to investigate the relationship between the grinding depth in this method and the ground surface morphology. Making a non-contact optical measurement, the surface morphology is derived and then analyzed. First, surface roughness is investigated for different grinding depths, showing that depth does not affect the surface roughness because the end face of the cup wheel has a regrinding effect. Second, the power spectrum density is investigated, showing that the peaks and valleys of the surface morphology are distributed with increasing intensity as grinding depth increases. Third, the machined surfaces waviness is investigated, and is found to increase with the grinding depth. This is explained by the grinding force increasing with the depth, which intensifies the grinding machines vibration. This paper reveals an important characteristic of this method in that the grinding depth has little effect on the roughness of the ground surface.

Numerical and experimental studies on grind-hardening cylindrical surface

This study focused on the rules and effects of grind hardening a cylindrical surface. A compound heat transfer model of grinding, appropriate for cylindrical surfaces, was established to study the grinding mechanism, and the temperature distribution of grind-hardening cylindrical surfaces was analysed. Experiments were conducted to validate the theoretical model and study the effect of different materials, grinding depths, workpiece rotational speeds and wheel characteristics on grind hardening. The results indicated that the transition layer and strengthened layer of steel 41Cr4 were thicker than those of steel C45E4 and that there were more explicit boundaries between the steel 41Cr4’s matrix, transition layer and strengthened layer. The surface hardness and thickness of the hardened layer were affected primarily by grinding depth. The greatest surface hardness and hardened layer thickness were obtained at a grinding depth of 0.4 mm and a workpiece rotational speed of 0.2 m/min with grinding wheel model PA46L8V for both steel 41Cr4 and C45E4.

Combination of Grinding and Wet Welding to Repair Localized Cracking in T-Welded Connections

This paper presents experimental research work on the combination of grinding and wet welding techniques to repair T-welded connections employed in the construction of offshore structures. A longitudinal rectangular grinding profile was performed at the weld toe of T-welded connections for localized cracking material removal. Two different grinding depths of 6 mm and 10 mm were performed in the welded connections to eliminate two different level of damage depth. Subsequent wet welding was applied in the grinded region to repair the grinded material. The wet welding was performed in a hyperbaric chamber simulating three different water depths: 50 m, 70 m and 100 m (shallow water). Once the combined repair techniques were performed, further experimental work was done to characterize the mechanical behavior of the repaired structures. The mechanical characterization was done with tensile, Charpy tests and Vickers Hardness tests. The region of interest from the structures was the weld toes the grinded-wet welding repair of the T-welded connections. Subsequent scanning electron microscopy (SEM) was also performed to examine the developed microstructures in the T-welded connection. The results showed that the combination of the repair techniques can restore the mechanical properties of the damaged structures. This was demonstrated by the measurement of the ultimate tensile strength, which were similar to those measured with no repair applied techniques. But the Charpy energy values were quite lower to those previously measured. This behavior was attributed to the level of porosity formed by the high level of gases created during the welding process for the simulated water depths, which were more severe at the higher water depth resulting in pore formation