Grinding Quality Research Articles

A spatio-temporal data decoupling convolution network model for specific surface area prediction in cement grind process

The specific surface area is one of the important indicators for measuring the quality of cement products. Realizing accurate prediction for specific surface area is very important for the production scheduling of the cement industry, energy conservation and consumption reduction and improvement of cement performance. However, due to the non-linearity, uncertainty, multiple interference, dynamic time-varying delay and multi scales in cement grinding process, it is difficult to establish an accurate soft-sensing model for cement quality prediction. Aiming at the above problems, we proposed a spatio-temporal decoupling convolution neural network model (STG-DCNN) to predict specific surface area by extracting and fusing data features in temporal and spatial dimension. To complete the prediction of specific surface area, we established the temporal series map and spatial series map by the production variables data according to the mechanism of cement grinding process. Then, sliding window technique was utilized to match the time scale in temporal series map and construct variable coupling relationship in spatial series map. The prediction accuracy, robustness and superiority of the proposed method were demonstrated by experiments results implemented on the actual cement grinding quality management database in a cement production enterprise.

FCSNet: A quantitative explanation method for surface scratch defects during belt grinding based on deep learning

The presence of surface defects during abrasive belt grinding has a significant impact on the service performance of the parts, and the precise extraction of surface defect feature information helps to enhance grinding quality. However, in the face of abrasive belt grinding surfaces with complex texture features, it is a challenging task to effectively extract defect features and quantify the characterization. Therefore, this research suggests a quantitative explanation approach for surface scratch defects in abrasive belt grinding based on the deep learning theory. Facing challenging issues like complex texture background, defect size, area, and depth of grinding surface, the automatic segmentation model (FCSNet) concentrating on the multiscale channel and spatial attention information is proposed. To concentrate on the multiscale channel and spatial information and accurately detect the defect features, the residual atrous convolutional pyramid module with channel and spatial dual attention module (RAPCS) is constructed. To capture the global, long-range context characteristics and emphasize target regions, the convolutional block attention module (CBAM) concatenate block is included in the skip connections between the encoder path and the decoder path. To address the issue of foreground-background data imbalance caused by too small segmented target regions, the Focal Tversky hybrid loss function was adopted to guide the model to learn the difficult region of interest (ROI). At the end of the network structure, Grad-CAM is adopted and statistical knowledge is incorporated for a qualitative and quantitative visual explanation of the segmentation results. Finally, the dataset of surface scratch defects in abrasive belt grinding was established and numerous experiments were carried out based on this dataset. The results demonstrate that the proposed model has an excellent segmentation performance and defect quantitative explanation ability, achieving 98.80% in Accuracy, 81.72% in Recall, 81.81% in Precision, 81.42% in F1-score, and 81.87% in mIoU, respectively.

Material removal and surface damage in high-speed grinding of enamel

Although high-speed grinding of the enamel surface is often required in restorative dentistry, the knowledge of grinding mechanics, material removal, and fracture damage mechanism related to this process is still relatively limited; therefore, it is important to perform relevant scientific and theoretical research. As per the occlusal surface and the buccal/lingual surface of the teeth, the experimental scheme of high-speed grinding of the enamel surface using a diamond grinding bur was designed, and the grinding force, force ratio, grinding temperature, chips, surface morphology, surface damage, and other important characteristics were tested and analyzed. Furthermore, the grinding geometry model, grinding mechanics, material fracture, and removal mechanism associated with the high-speed grinding of an enamel surface were considered. The results show that the grinding force, friction coefficient, grinding temperature, and surface damage achieved through buccal/lingual surface grinding are considerably greater, and the grinding quality is worse than that obtained via occlusal surface grinding under the same grinding conditions. With the increase in the feed rate, grinding force, friction coefficient, grinding temperature, and surface damage obviously increase, and the surface quality decreases. The embrittlement effect and the ironing mechanism are present during the process of high-speed grinding of enamel. Regardless of the feed rate, the three types of material fracture modes of the buccal/lingual surface are more serious than those of the occlusal surface (making it more likely to produce unstable large chips or tearing chips); moreover, the brittle fracture and damage of the final machined surface are more obvious. The cutting mechanics and cutting mechanism identified in this study will provide scientific guidance for dental grinding operations.

Експериментальне дослідження впливу зернистості абразиву силікатної пасти на якість поверхонь тертя

Currently, many technological methods have been developed to change the structure and properties of surface layers of metal in the desired direction or to create layers with predefined properties. The use of these methods can increase wear resistance, resistance to fatigue and other performance properties of automotive parts. One such method is grinding with abrasive compounds. Grinding technology consists in applying abrasive compositions on the surface of the part and subsequent machining using special devices.The results of experimental research of influence of granularity of abrasive of silicate paste on quality of friction surfaces are resulted in work. Silicate compositions with electrocorundum abrasive of different grain size were made for the study. In order to compare the performance of silicate paste, the existing abrasive pastes «KT» with abrasive titanium carbide abrasive of similar grain size were selected. The research was performed on a special installation, which allows to reproduce with high accuracy the process of processing the abrasive composition in the laboratory. The evaluation was based on the duration of grinding, metal removal and surface quality. Stabilization of the coefficient of friction showed the completion of the grinding process.The study confirms that with increasing grain size of the abrasive silicate composition increases the time of formation of the surface layer and the amount of metal that is removed. It is proved that the high quality of the surface after treatment with silicate composition is due to the appearance in the grinding process of amorphous silica (SiO2), which enhances the work of abrasive grains and reduces the action of the scratching abrasive. Under the action of abrasive particles, SiO2 enters the depressions of the treated surface and adheres to the surface. It is established that the productivity of grinding with silicate composition is 1.5 times higher than when treating surfaces with «KT» paste. It was found that when treating surfaces with a silicate composition with electrocorundum abrasive, the removal of metal is 1.8 times less than when treating with «KT» paste. It is proposed to assign an allowance for treatment with silicate paste from 0.035 to 0.07 mm.

Wear mechanisms of abrasive wheel for rail facing grinding

Facing grinding by abrasive wheel is the most widely used method to maintain the rails. The wear of abrasive wheel is inevitable and influences the grinding performance significantly. Therefore, a deep understanding on the wear mechanisms of abrasive wheel is beneficial for the development of grinding wheels and optimization of grinding processes. In the present study, rail grinding experiments were conducted using whole abrasive wheels and a single abrasive grain. The wear mechanisms of abrasive wheel were revealed, including the attrition wear, fracture and pulling-out of abrasive grains, material adhesion, clogging, and chemical wear. With the degradation of abrasive grain, the attrition wear, micro-fracture, macro-fracture and pulling-out of grain successively became the primary wear mode as the function of service time. With the primary wear state changing from attrition wear to grain fracture and grain pulling-out, the grinding efficiency was improved, but the grinding quality was decreased. The grinding wheel in the wear state of grain fracture had the optimum grinding performance.

Regulating the grinding performance of grindstones via using basalt fibers

For adapting to the working condition of high-speed rail grinding with strong impact and heat, the basalt fibers reinforced grindstones (BFRGs) were prepared. Their performances were evaluated from three aspects, including the mechanical properties of grindstones themselves, grinding behavior and grinding quality. The results show that basalt fibers significantly improve the strength of grindstone, which has reached up to 78.3 MPa increased by 25.5%. The heat effect of BFRGs drops as low as 159 ℃. After grinding, the thickness of white etching layer is reduced to 0.5 µm. The content of basalt fiber at 6.7 wt% in resin can achieve the optimum comprehensive performance, mainly depending on the advantages in blocking effect and rolling bearing of basalt fibers.

Experimental study on the mechanism of strain rate on grinding damage of zirconia ceramics

To study the mechanism of strain rate on the grinding damage of zirconia ceramics (ZrO2), a ZrO2 surface grinding experiment was conducted to analyse the effect of strain rate on the grinding force, surface morphology and subsurface cracks. As the strain rate increased, the grinding force decreased significantly; the grinding scratches gradually became continuous and clear, and the grinding surface gradually became smooth. Increasing the strain rate can greatly reduce the length of subsurface cracks; however, the length of subsurface cracks drops slowly and tends to stabilise when the strain rate reaches a certain value. The direction of subsurface cracks is related to the internal defects of the material, and there is a trend of approaching the surrounding cracks and defects. When the internal defects were stimulated by the impact stress wave, the cracks started to grow and expand from the tip, and the expanding direction remained at approximately 125° in the direction of the defect length. The results show that an increase in the grinding strain rate can effectively improve the grinding quality of zirconia ceramics, which has guiding significance for practical production.

Grinding behavior of biomimetic fractal-branched silicon carbide ceramic inspired from leaf-vein structure

Silicon carbide ceramics are widely used in many industrial fields owing to their outstanding physical and chemical characteristics. However, their inherent hardness and brittleness make the grinding process very difficult compared to that involving ductile materials. In the present study, the effects of the biomimetic fractal-branched structure, inspired from the leaf-vein, on the grinding behavior of silicon carbide were investigated. Two biomimetic fractal-branched structures with different densities of micro-channels were designed and compared with the non-structured silicon carbide surface. The surface of the silicon carbide ceramic was textured through pulsed-laser ablation. Thereafter, the grinding experiment was conducted on the biomimetic fractal-branched and non-structured workpieces. The surface topography, subsurface damage, grinding force, grinding force ratio, surface roughness and grinding wheel wear were examined throughout the experiment. The experimental results indicated that the normal and tangential grinding forces for the fractal-branched structure surface are 7.61–18.21% and 8.34–26.13% lower than those for the non-structured surface. The grinding force ratio also increased significantly with an increase in the micro-channel density. In addition, a larger volume of coolant was transported through the grinding zone of the fractal-branched structure. The research results confirmed that the biomimetic fractal-branched structure on the silicon carbide surface enhanced the grinding performance and improved the grinding quality.

Development of a Grinding Tool with Contact-Force Control Capability

The grinding normal force is one of the main factors that affect grinding quality. We report on the development of a compact grinding tool which not only can rotate the grind wheel but also can actively control the wheel in the fore/aft direction to modulate the contact force. The two motion degrees of freedom are coupled in the sense of mechanism yet their motions are independent. The designed grinding tool was modeled and its parameters were systemically identified. A repetitive controller was designed to suppress periodic force variation, which was mainly caused by the rotational motion of the grinding wheel, and the results were compared with other control methods. The selection of the grinding parameters was conducted using the Taguchi method. Finally, the grinding tool and the repetitive controller were experimentally evaluated, and the experimental results confirm that the proposed control strategy can reduce the force disturbance and improve the surface quality of the flat and curvy workpieces.

Influence of the dynamic disc grinding wheel displacement on surface generation

Different from the general grinding process, the disc grinding quality varies with the part position due to the complicated abrasive removal. Based on the main shaft system dynamic-static characteristic, the work aims to study the disc grinding surface generation mechanism. The element deformation model on dynamic-static characteristic is established. Afterwards, based on the abrasive position and the size information, the three dimensional abrasive trajectory equation is built. The profile search method is applied to analyze the dynamic-static surface generation process of disc grinding material. Combined with the corresponding disc grinding experiment, the influence regulation of the system dynamic-static characteristic on machining surface waviness and surface roughness is investigated. The essence of the uneven machining effect on grinding surface is explained. It shows that the static deformation at the faraway position of the workpiece center is relatively larger than that at the nearby workpiece center. However, the difference of the dynamic vibration is relatively smaller. It can be concluded that the static characteristic is a key factor to influence the disc grinding surface waviness, and disc grinding surface roughness is controlled by the system dynamic-static characteristic. The findings can not only give an in-depth comprehending in disc grinding surface generation mechanism, but also give a parametric controllable measure for improving the machining surface quality characterization.

The influence of the moisture content of the stem mass on the quality of grinding at using a hammer crusher

Purpose. Experimentally determine the influence of the humidity of the stem raw material during its grinding for further pelletization. Methods. When conducting research, monographic, calculation and construction methods were used. Raw materials obtained as a result of grinding were analyzed using sieve analysis. Grinding quality was assessed by the weighted average size of the particles. The methods of statistics, graphic and regression analysis were used in the processing and analysis of the obtained results. Results. The features of the sieve analysis of crushed stem materials have been specified, the weighted average particle size after crushing with a hammer crusher of wheat straw, rape stalks and corn at different moisture levels has been determined. Conclusions 1. Carrying out a sieve analysis of crushed stem raw materials requires compliance with DSTU EN 15149-2:2013 and careful observance of the sieving time of individual samples. 2. The dependences of the influence of humidity (in the range of 8–30%) of wheat straw, rape stalks and corn on the size of the particles, the weighted average length of which varies from 1.6 to 2.4 mm, were obtained when they were crushed with a hammer crusher. Keywords: hammer grinder, weighted average length of grinding, stem materials, humidity, dependence.

Data-Driven Modeling and Prediction Analysis for Surface Roughness of Special-Shaped Stone by Robotic Grinding

This paper aims to accurately predict the surface quality of the special-shaped stone by robotic grinding and effectively guide the adjustment of process parameters to ensure stable grinding quality, applies a support vector machine model based on improved whale optimization algorithm (IWOA-SVR), so as to establish a prediction model of surface roughness of special-shaped stone and a selection method of process parameters. The proposed IWOA-SVR was used to improve the prediction accuracy of support vector machine regression model, and a prediction model of surface roughness (Ra) for stone was established. On this basis, the relationship between the output parameters (surface roughness) and inutput parameters (spindle speed, feed speed, cutting depth and cutting width)was explored to obtain more suitable process parameters. Combining the grinding experiment data of special-shaped stone, the comparison was carried out between IWOA-SVR and the SVR model optimized by the commonly used optimization algorithms (grid-search optimization algorithm (GS) and whale optimization algorithm (WOA)). Under the same sample condition, the prediction error of GS-SVR is the most large, and the average prediction error of IWOA-SVR is only 86.1% if that of WOA-SVR, the training time is shortened by 54.4%. The influence of process parameters on surface roughness obtained by IWOA-SVR can effectively guide the selection and adjustment of process parameters. It has good guiding significance for maintaining the excellent grinding quality of special-shaped stone.

Robotic Grinding Process Monitoring by Vibration Signal Based on LSTM Method

In robotic grinding, the trajectory deviation of the robot will change the grinding force and then affect the grinding material removal. Therefore, grinding force and material removal monitoring is important for the machining quality of robotic grinding. In this paper, force and material removal estimation methods are proposed based on the acceleration signal. The dynamic model of robotic grinding is studied and the vibration force relationship can be obtained. Based on the vibration force relationship, the framework of the grinding force and material removal monitoring is established. In this framework, the peak value of the acceleration is firstly extracted by the signal process, and the Long Short-Term Memory (LSTM) network is used to train the vibration-force mapping model. Then the grinding removal can be calculated by the empirical formula. The experiments of robotic grinding are carried out. The real grinding force and the material removal can be estimated in time, which proved the effectiveness and potential of our method.

Increasing performance of feed grinder in obtaining pelleted sunflower cake

One of the options for improving the protein feed (the feed in the form of sunflower cake) grinders, for which Russian Federation patent No. 2648392 was obtained, is the modernization of the working surface of knife packages. They include knives in the form of an Archimedes Arbelo curvilinear triangle with saw-edged teeth along the perimeter of its entire surface of cutting edges. This will reduce the energy intensity of the process and improve the grinding quality. In literary sources, the values of the performance quantities and the energy intensity of the grinder in obtaining pelleted sunflower cake are absent. As a result of mathematical modeling of the grinding process of sunflower cake in the pelleted form, the optimal parameters of the studied factors were determined. In the indicated ranges of factors changing, the obtaining of pelleted sunflower cake is provided, it meets the zootechnical requirements for cattle with a minimum energy intensity of the grinding process E = 1.03 kWh/t and its performance W = 2.3 t/h.

Experimental Data of Grinding Dried Fibrous Plant Materials

Introduction. Developing a method for energy-efficient grinding of fibrous vegetable raw materials to avoid the clogging of grids remains an urgent task. The aim of the research is to study the process of grinding dried fibrous plant materials and to estimate the influence of the device operating characteristics on the quality of grinding and the process energy intensity. Materials and Methods. The experimental apparatus is a rotor grinder. Its working bodies are alternate knives and hammers. When a hammer is in motion, its triangle side creates the reduced pressure area. There was studied the influence of the linear velocities of knife motion and of feed of raw materials on fractional composition of the grinded materials, grinder productivity, and grinding specific energy capacity. Results. It is found that the change in the fractional composition of the grinded product occurs when the speed of the rotor knives increases. Optimal range of knife speed for producing the product of the required fractional composition is 55‒75 m/s. The increase in the speed leads to increasing productivity, but is accompanied by the growth of specific power intensity. If the rotor speed is constant, the increase of raw material feed increases the grinder productivity, but only up to a certain value. After that, the productivity decreases because of excessive filling of the working chamber with raw materials and clogging of the grates. For each value of the knife speed, there is an optimal feed that ensures the maximum productivity. High values of knife speed lead to significant energy intensity of the process and overgrinding of raw materials. Therefore, the optimal range of knife speed is 55‒65 m/s. Discussion and Conclusion. Effective grinding of raw materials is achieved through lower energy capacity of grinding process and absence of grate clogs resulted from separating particles from the surface of plants to be grinded.

Constant force control for aluminum wheel hub grinding based on ESO + backstepping

PurposeThis paper aims to present a control method to realize the constant force grinding of automobile wheel hub.Design/methodology/approachA constant force control strategy combined by extended state observer (ESO) and backstepping control is proposed. ESO is used to estimate the total disturbance to improve the anti-interference and stability of the system and Backstepping control is used to improve the response speed of the system.FindingsThe simulation and grinding experimental results show that, compared with the proportional integral differential control and active disturbance rejection control, the designed controller can improve the dynamic response performance and anti-interference ability of the system and can quickly track the expected force and improve the grinding quality of the hub surface.Originality/valueThe main contribution of this paper lies in the proposed of a new constant force control strategy, which significantly improved the stability and precision of grinding force.

Real-time monitoring of silica ceramic composites grinding surface roughness based on signal spectrum analysis

Aiming at the difficulty of real-time ceramic surface roughness monitoring in the automatic grinding process, a time–spatial domain spectrum analysis method was proposed based on the monitored grinding force signal and grinding surface texture curve. Discrete Fourier Transform (DFT) was employed to acquire spectral responses of grinding force and surface texture. The mean and maximum values of grinding force signal and surface texture in their amplitude-frequency curve were found to be positively correlated. The chi-square distribution model was then developed to predict the amplitude-frequency response of surface texture by monitoring force signal. Subsequently, the Inverse Discrete Fourier Transform (IDFT) was performed to obtain the surface texture curve. The mathematical function of the surface texture curve was modelled by the grinding force signal, finally. The surface roughness (Ra) could be calculated from the surface texture curve. In this work, taking the surface grinding of silica ceramic composites as an example, 75 stochastic groups of grinding experiments were designed. The results show that the real-time monitoring of silica ceramic composites grinding surface roughness could be accurately predicted by the chi-square model. The correlation coefficient between the predicted Ra and the actual one has reached 0.9821. The proposed prediction model could be valuable for the online measurement of grinding quality towards intelligent manufacturing.

Characterization and formation mechanisms of rail chips from facing grinding by abrasive wheel

Rail grinding is a widely-used method to eliminate surface damages on railway tracks. The grinding chips are closely related to the grinding parameters and the grinding quality. Therefore, the investigation on the characteristics and the formation mechanism of chips from rail grinding is beneficial for the optimization of rail grinding process. In the present study, the grinding chips from the real rail grinding in the field and from the rail grinding experiments in the laboratory were analyzed in terms of their morphologies, microstructural evolution and chemical characteristics. The results showed that flowing, knife, slice and spherical chips were generated during rail grinding. The formation mechanism of flowing, knife and slice chips was plastic deformation by forces from abrasive grains with oxidation in air by grinding heat. Primary and secondary shear zones and central zones were generated. In the primary shear zone, cracks were generated in knife and slice chips. In the secondary shear zone, obvious plastic deformation was formed in knife and slice chips and a significant white etching layer (WEL) was generated in knife chips. The formation mechanism of spherical chips was melting of small powdery grinding debris by the high temperature and the subsequent solidification, accompanied with severe oxidization in air. The oxides produced in chips consisted of FeO, Fe3O4, Fe2O3 and AlFe2O4. The grinding quality could be predicted through observing the grinding debris. The larger percentage of flowing chips represented the better grinding quality (smaller surface roughness, slighter surface burn and thinner WEL on ground rail), which could be the goal for the grinding parameters choice.

Study on the Algorithm of Three-Dimensional Surface Residual Material Height of Nano-ZrO2 Ceramics under Ultra-Precision Grinding.

A large number of studies have shown that the height of a residual material is the key factor affecting the surface quality of ultra-precision grinding. However, the grinding process contains several random factors, such as the randomness of grinding particle size and the random distribution of grinding particles, which cause the complexity of the material removal process. In this study, taking the Nano-ZrO2 as an example, the removal process of surface materials in ultra-precision grinding of hard and brittle materials was analyzed by probability. A new calculation method for the height of surface residual materials in ultra-precision grinding of Nano-ZrO2 was proposed, and the prediction model of the three-dimensional roughness Sa and Sq were established by using this calculation method. The simulation and experimental results show that this calculation method can obtain the more accurate surface residual material height value which accords with the characteristics of three-dimensional roughness sampling, which provides a theoretical reference for the analysis of the material removal process and the surface quality evaluation of ultra-precision grinding of hard and brittle materials.

Surface integrity during rail grinding under wet conditions: Full-scale experiment and multi-grain grinding simulation

Rail grinding will cause poor surface integrity when the critical grinding temperature is exceeded. To improve the grinding quality and explore the feasibility of grinding operations in rainy days, this study first investigated the surface integrity during rail grinding under wet conditions, including surface roughness, grinding burn, phase transition, residual stress, etc. Moreover, a grinding wheel finite element model was established considering abrasive grains' actual geometry and distribution, providing a novel thermodynamic coupling analysis method. As a result, it is revealed that the surface integrity is significantly improved under wet conditions, especially the grinding burn and white etching layer can be avoided, and residual tensile stress can be reduced by up to 45% since the thermodynamic coupling becomes less apparent.