Grinding Patterns Research Articles

Optimisation of rail profile and grinding pattern in the curve section of a subway

During routine rail maintenance, rail grinding of sharp curves is challenging. In particular, setting up the grinding pattern is essential. A rail-grinding pattern optimisation method is proposed based on the mathematical relationship between the grinding pattern parameters and geometric parameters of the rail grinding profile. In this method, the design variables and constraints are reasonably selected, and a multi-objective optimisation function considering the wheel-rail contact stress, wheel-rail lateral force, and rail grinding amount is established. The optimisation model is solved using a chaotic microvariation adaptive genetic algorithm. The optimisation method is applied to the repairable grinding of a worn rail in a metro curve section. The results demonstrate that using this method can realise an ideal grinding pattern with the expected grinding effect in addition to high accuracy and high optimisation speed. The wheel-rail contact characteristics, wear characteristics, and train dynamic performance are significantly improved after rail grinding; this is significant for conducting grinding operations and improving the train’s curve-passing ability. Therefore, this study provides theoretical guidance for formulating rail-grinding patterns.

Technological Properties of Orange Sweet Potato Flour Intended for Functional Food Products as Affected by Conventional Drying and Milling Methods

The aim of this study was to evaluate the effect of drying temperature and grinding pattern on physicochemical, hydration, thermal, and pasting properties of orange sweet potato flour (OSPF) and to define its potential application in functional food products. Air convection drying temperatures (50 and 80 °C) and grinding patterns (shear and consecutive shear–impact) were evaluated. Hydration and pasting properties were influenced by the two factors and their interaction. Particle size and damaged starch content are significantly related to technological properties. The results indicated that drying at 80 °C and consecutive shear–impact grinding can produce thickening flours, while drying at 50 or 80 °C and shear grinding can produce flours with water retention suitable for gluten-free bread-type products with good antioxidant capacity. Additional knowledge provided by these findings is the importance of the combination of drying temperature and grinding pattern in the technological properties of OSPF.

Development of dispersion layers for dental drills with reduced nickel release

ObjectivesWithout rotating instruments, for example diamond-coated drills with a core made of stainless steel, the dental routine would be unimaginable, since these are used in almost every dental activity and are thus indispensable for the professional practice. Unfortunately, such drills release Nickel particles to a high content into the cooling water of the drill. Values up to 1.3 mg/l Nickel were found by ICP – OES in the cooling water of the drillers which is of course also transferred into the patient's oral cavity with possible severe negative effects. Therefore, novel plating procedures have to be developed to increase the patients (and dentists) safety during treatment. MethodsDispersion layers with the hard metal Tungsten carbide (WC) particles on stainless steel blanks were deposited following two synthesis routines (i) Plasma-Electrolytic Oxidation (PEO) and (ii) galvanic plating out of a Watts bath. Both were accomplished using water-based electrolytes. ResultsIn order to verify the dental applicability of the developed coatings, tests-drills were accomplished under defined conditions on plastic teeth for the sake of reproducibility.Commercially produced drills were compared with the newly plated ones by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and the drilling cooling water was examined for heavy metal residues using Inductively Coupled Plasma (ICP) analytics. The resulting grinding patterns in the plastic teeth were investigated by light microscopy and SEM.It could be shown that dispersion layers plated by a galvanic procedure showed a reduced Nickel release compared to a commercial driller by factor 7.6 and 13.4 compared to PEO plated ones during dental treatments. ConclusionsFollowing the clinical significance the Watts bath plated drillers showed a better WC particle distribution on the surface and better abrasive properties during the drilling experiments compared to PEO plated drillers. In addition the Nickel release during dental use is much less from the galvanic treated ones. By optimising the plating condition from the Watts dispersion bath further novel drilling devices with significantly reduced release of Nickel particles can be developed for the benefit of the patients.

Influence of masticating cycles and chewing patterns on inadvertent enamel wear caused by zirconia brackets.

Little information is available about enamel wear caused by zirconia brackets, an inadvertent side effect of orthodontic treatment. The purpose of this study was to examine potential enamel damage induced by contact with zirconia brackets. Sliding and impact wear simulations were performed using bovine enamel specimens positioned at a 25° slant to a zirconium ball to determine wear behaviour. Different chewing patterns, tapping and grinding, were simulated. Specimens were profiled using confocal laser scanning microscopy, and the mean maximum depth and surface roughness were measured. Scanning electron microscopy was also performed. The mean maximum depth of wear values differed according to the number of mastication cycles, with a higher number of cycles producing higher depths of wear. The facet wear depth was significantly greater with the tapping pattern than with the grinding pattern. Scanning electron microscopic observation of the wear facets revealed that surface textures at the edges were rougher than those at the centre of all facets. The results of this study indicated that enamel wear was induced by contact with zirconia brackets during the early period of mastication, and that the patterns and number of cycles of mastication affected the wear progression of enamel.

Simulation research on temperature field and stress field during rail grinding

The rail grinding process generates a large amount of heat, which could lead to heat damage on the ground rails. But, the whole temperature field of rail ground by the grinding train has not been explored in detail. In the present study, finite element models of a rail and grinding wheel were established to simulate the rail grinding process. The temperature field and the thermo-mechanical coupling stress during rail grinding, and the residual stress after grinding were studied. Furthermore, through simplifying grinding wheels into heat sources, the temperature field of rail ground by a whole grinding train was investigated as well. The results indicated that the grinding temperature and the residual stress increased with the grinding depth and rotational speed, but decreased with the feed speed and radius of rail head. The thermo-mechanical coupling stress increased with the radius of rail head and grinding depth, and decreased with the rotational speed and feed speed. When ground by the whole grinding train, the increase in the number of grinding wheels at the same grinding angle and adjacent angles could lead to a rise in temperature on the rail surface. The speeds of grinding train and the rail head radius also have an influence on the temperature. The optimal feed speed of the grinding train should be below 12 km/h for R300, 16 km/h for R80, and 18 km/h for R13. The results could be used to optimize the grinding parameters and grinding pattern in the field.

Wear of a Diamond Wheel during Grinding of Ceramic Balls Made of Silicon Carbide

The results of an experimental study of the effect of the mode of processing on the wear of the diamond wheel surface and on the accuracy of batch processing during diamond grinding of ceramic balls made of silicon carbide are discussed. The grinding pattern and the frequency of wheel strokes have a statistically significant effect on the maintaining of the original flat shape of the wheel, while the discrete feeding of the wheel has no direct effect on its uneven wear. The condition for minimizing the difference in the diameter of the balls within a batch and maintaining the original flat shape of the wheel will be the choice of grinding pattern with the trajectory of the balls tangent from the inside to the outer edge of the wheel, as well as minimizing the discrete feed of the wheel in the investigated range when grinding and a simultaneous increase in the wheel feed frequency to the maximum. However, the variance of the ball diameter within a batch under these conditions does not reach the minimum possible value.

A laboratory demonstration of rail grinding and analysis of running roughness and wear

Rail grinding has been widely used for rail maintenance to keep the performance of the rail track at satisfactory levels. However, there is a lack of knowledge on the relationship between different grinding parameters and the effect on the rails and the post-grinding evolution of roughness and wear. Rail undergoes significant levels of stress during grinding to remove any defects that appear during its life-cycle which can cause significant microstructural change. By developing a method of demonstrating rail grinding it will allow further investigation of the process and potentially the exploration of different grinding patterns. Moreover, an analysis of the roughness of wheel and rail is an input parameter in most modern simulation tools that could be associated with the coefficient of friction. This paper reports a laboratory demonstration of rail grinding followed by a series of tests to determine the wear of the rail and if there is a relationship between friction coefficient and roughness. The rail specimens that were ground have undergone a phase transformation and showed White Etching Layer (WEL) on the contact surface. This was found to initially act protectively for the rail disc reducing the wear rates, but then contributed to crack formation. No clear long-term correlation was identified between the coefficient of friction and roughness during the testing, however a relationship could be drawn when test periods were studied individually.

The elements of mathematical modelling of the bearing ring grinding

According to the calculation results, numerical values of the error of the shape along the profile of the inner surface of the ring are obtained. The largest error values were obtained with cartridge grinding of the inner surface of the ring. Smaller error values correspond to the grinding scheme on hard supports. In this paper, we propose a method for forming a volume finite element model of a bearing ring. Application of the model made it possible to assess the effect of the grinding pattern of the inner cylindrical surface on the error in the shape of the ring.

The Identification of a Steel Mold's Marks on Fake Drug Bottles.

Plastic bottles are commonly encountered in drug cases where they are used as packaging materials and produced with polymers. However, to the best of our knowledge, systematic studies on the evidential values of medicine bottles have not been carried out. Therefore, it is difficult practically to determine if it is possible to identify whether the plastic bottles are manufactured with the same steel mold by comparing the manufacturing marks on plastic bottles. This paper reports the successful attempt of the authors in establishing a definite relationship between three different medicine bottles with a steel mold recovered from suspects. Fourier transform infrared spectroscopy (FT-IR) was used to characterize the chemical composition of submitted medicine bottles, and then some physical characteristics (viz., total length, length, and diameter of different parts) and the manufactured marks on these bottles were examined. The results showed that the linkage of the medicine bottles to a steel mold was successfully established using the similarities in physical characteristics and manufacturing marks. In the process, the FT-IR was only complementary in the identification process. The individual characteristics of plastic medicine bottles included the imperfections and striated impressions that were produced by the grinding patterns on the inner surface of a steel mold.

Drying Kinetics, Grinding Characteristics, and Physicochemical Properties of Broccoli Sprouts

In this study, we studied the drying process, grinding characteristics and physicochemical characteristics of broccoli sprouts (BS). The seeds of broccoli were germinated at 20 °C for 3 and 6 days. Then, the seeds were air- and freeze-dried, and the Page model was used for prediction of drying kinetics of broccoli sprouts. It was observed that the drying time of BS decreased about twofold as the air-drying temperature increased from 40 to 80 °C. An increasing the air-drying temperature from 40 to 80 °C decreased the drying time by approximately twofold. Freeze-drying of sprouts took the longest drying time. Germination of seeds significantly decreased the value of grinding energy requirements, and the ground sprouts exhibited a different grinding pattern in comparison to ground non-germinated seeds. In terms of color parameters, the highest lightness and yellowness were found for freeze-dried sprouts. Redness and yellowness of sprouts increased with an increase in the air-drying temperature. The lowest total color difference was obtained for the freeze-dried sprouts. Higher drying temperature resulted in lower total phenolics content (TPC) and decreased antioxidant activity (AA). The highest TPC and AA were observed in air-dried sprouts (40 °C) and freeze-dried sprouts after 6 days of germination.

Determining the conditions for decreasing cutting force and temperature during machining

The theoretical approach to calculating and controlling the force and temperature parameters of edge cutting and abrasive machining processes taking into account the provision of the minimum possible power consumption of the cutting process is given. The conditions for reducing cutting force and temperature and improving the quality and rate of grinding and edge cutting machining are theoretically determined. They consist mainly in reducing the relative shear angle of the machined material and, accordingly, power consumption by increasing the cutting capacity of the tool. It is analytically found that in grinding, cutting force and temperature are greater than in edge cutting machining due to the intense friction of the grinding wheel bond with the machined material and the presence of negative rake angles of cutting grains. It is shown that cutting temperature during grinding can be reduced using the multipass grinding pattern, as well as patterns of high-velocity creep-feed wheel-face and double-disc grinding. On this basis, the approach to creating technologies of effective high-velocity defect-free edge cutting and abrasive machining of machine parts and carbide cutting tools is developed. The developed technology of form grinding on the modern HOFLER RAPID 1250 gear grinding machine using a special highly porous form abrasive wheel tapered on both sides received practical application. This wheel has a high cutting capacity in conditions of high-velocity creep-feed grinding. Compared to the conventional method of gear grinding by the generating process, carried out under conditions of multipass grinding, this allowed increasing machining rate up to 5 times. The technology of high-velocity creep-feed external grinding of multipoint carbide cutting tools (milling cutters, reamers) with high-strength metal-bonded diamond wheels using the electrical discharge dressing method is developed. This made it possible to increase the rate by 2–3 times and provide high-quality defect-free machining of carbide tools

Influence of Masticatory Behavior on Muscle Compensations During the Oral Phase of Swallowing of Smokers.

Introduction Chewing and swallowing are physiologically interconnected functions, which share motor structures and supranuclear regions of the central nervous system (CNS), involving a sensorimotor synchrony. Objective To analyze the influence of masticatory behavior on muscular compensations in the oral phase of swallowing in smokers compared with nonsmokers. Methods A cross-sectional study comparing smokers and nonsmokers composed of 24 participants in each group. The aspects of food crunching, masticatory pattern, masticatory speed, atypical muscular contractions, and lip closure were analyzed during mastication. In swallowing, aspects of contraction of the orbicular and mental muscles, head movement and presence of deglutition, mastication, smoking, and of stomatognathic system of residues after swallowing were characterized. Results Statistically significant differences were identified between the study groups related to food grinding pattern, masticatory velocity, and mental contraction during swallowing. There was no significant association between masticatory function and compensations during swallowing. Conclusion Differences were observed in the pattern of chewing and swallowing in smokers compared with nonsmokers, but no influence of masticatory performance was observed in the presence of muscle compensations during the oral phase of swallowing.

Efficiency and effectivity of high precision grinding manufacturing processes: An approach based on combined DEA and cluster analyses

The manufacturing reproducibility of high precision grinding patterns depends on many process influences and technology characteristics, like cutting speed, lining, grinding disc, cutting fluid and longitudinal feed. This paper outlines a combined approach for the detection of grinding parameter settings, which ensure on the one hand reproducibility and on the other hand guarantee economy. Cluster analytics is utilised to identify grinding parameter sets and grinding results with similar characteristics within a group. Data Envelopment Analysis (DEA) is applied to describe the efficiency of these grinding processes based on input and output parameters which are selected with regard to grinding patterns.

Segregation patterns and characteristics differences of superfine pulverized coal ground by three pulverizing systems

Comminution methods and segregation of coal powder are key factors affecting the characteristics of superfine pulverized coal. However, there are few articles available in this issue. In this paper, three representative pulverizing systems with diverse grinding patterns and gathering methods are selected to prepare superfine powder using the same raw coal. Afterwards, element analysis, approximate analysis, maceral determinations, surface area measurement and XPS tests are performed successively. The segregation tendencies and its influences on the coal powder are compared and discussed among three groups. Data of similar sizes in three groups receive special attentions. Based on the experiments, it is found that at the same conditions, vitrinite is easier to gain thorough crushing compared with inertinite. Due to the smaller sizes, vitrinite and ashes are prone to escape from the cyclone separator. Due to the high density, inertinite and ashes are apt to accumulate in the lower part of the coal pile. The maceral segregation imposes greater influences on the C-containing functional groups on the surfaces than the mechanochemical effects. The significances of this paper lie in figuring out the influences of grinding methods on properties and segregation patterns of superfine pulverized coal, which provide valuable references for industrial applications of this technology.

Surface property variations in flotation performance of calcite particles under different grinding patterns

Based on the working principles of particle bed comminution, particles produced by high-pressure grinding rolls (HPGR) have surface properties different from particles produced by other grinding patterns, which exert great influence on mineral flotation. Flotation performances of calcite particles under different grinding patterns involving the use of HPGR, a jaw crusher, a dry ball mill, a wet ball mill, and a wet rod mill were studied using single mineral flotation tests. The surface properties of the particles under different grinding patterns were characterized to determine the flotation performance variation in terms of specific surface area, particle size distribution, AFM, XPS, and zeta potential. The results show that particles ground by HPGR exhibited improved flotation performance within the lower range of grinding fineness in both NaOL and dodecyl amine flotation systems compared to the particles prepared using other grinding patterns. Specific surface area, particle size distribution, surface roughness, Fe(III) contamination, binding energy, and zeta potential are greatly influenced by grinding patterns, which is the main cause of the flotation performance variation.

Mechanical fragmentation of wheat and rice straw at different scales: Energy requirement in relation to microstructure properties and enzymatic hydrolysis

Mechanical fragmentation is an important pretreatment step in lignocellulosic biorefinery. In this study, we explored the energy requirement (ER) for mechanical fragmentation of wheat and rice straw at different scales in relation to modifications of microstructure properties and enzymatic hydrolysis. The ER showed a reciprocal relationship with mean particle size (MPZ), but a negative linear relationship with cellulose crystallinity (CrI). An exponential relationship was observed between the ER with a specific surface area (SSA) and the oxygen-to-carbon surface ratio (O/C). The results showed that modification of the cellulose crystallinity required the most energy consumption, whereas reduction of particle size consumed the lowest energy. The order of importance of modifications of different microstructure parameters on the ER was: CrI > O/C > pore volume (PV) > SSA > MPZ. Sugar yield showed a clear, positive linear relationship with ER, indicating that grinding patterns with a high ER could significantly enhance the enzymatic hydrolysis yield owing to the plant cell wall deconstruction. The energy efficiency declined with an increasing ER because of the markedly lower increase in sugar yield compared with the corresponding increase in ER.

Analytical modeling of grinding process in rail profile correction considering grinding pattern

An analytical introduction to rail grinding was presented in this paper where a newly-designed profile serves as the targeted ground profile to extend the rail's service life. A method for determining eliminated metal due to rail grinding is established as an initial consideration in the process of rail profile correction. The analytical model of material removal contains grinding wheel characteristics such as rotation speed, feeding speed, and applied pressure to the ground rail. The assumed coefficient in this model was fitted by a scratch test between a single abrasive grain and rail specimen. The sectional area s of removed metal can be used to estimate grinding capacity rather than the traditional grinding depth. An algorithm that generates personalized grinding patterns is proposed to arrange grinding wheel location and proper sequence. The whole procedure was indirectly validated in terms of grinding quality and rail profile error through rail grinding field data. A grinding pattern was generated by the proposed method that can effectively simulate the ground rail profile within a pre-determined tolerance. The area difference of predicted and target profiles was 13 mm2 (6.6%) and the experimental result was 12.2mm2 at rail cross-section.

Investigation into the anisotropy of cross-grinding surface quality in C- and M-planes of sapphire

Sapphire is an important material for optical applications, but the anisotropy of key properties makes it difficult to obtain uniform ground surface. In this work, cross-grinding experiments were first conducted on C- and M-planes of sapphire to investigate the dependence of the ground surface quality on crystal orientation. Then, scratching tests were performed along the specific crystal orientations to explain the formation mechanism of the anisotropic grinding patterns. The results showed that the surface roughness distribution on C-plane is of a threefold symmetry, while one axis of symmetry for M-plane. The damage pits on C-plane possess lower aspect ratio than that on M-plane. By combining the scratching-induced fracture features with the contact-induced deformation theory of sapphire, it was found that the propagation of the primary cracks in sapphire is accompanied by activating different deformation systems. The material removal on C-plane is dominated by the shallow lateral cracks, which propagate parallel to the ground surface and result in shallow and wide pits. However, the deep lateral cracks play an important role on M-plane, which intersect with the ground surface and cause deep and dense defects. The non-uniformity of the ground surface is attributed to the appearance of radial cracks for C-plane, while it is associated with the number of the available deformation systems for M-plane.

Optimal design of rail grinding patterns based on a rail grinding target profile

Based on the grinding target profile of the rail and the grinding capacity of a single grinding stone, a numerical calculation method for rail grinding patterns that includes grinding angle and grinding power of each grinding stone of the GMC96 rail grinding train was designed and established. By means of this numerical method, the grinding pattern of each grinding pass was optimized and the rail head profile after grinding was calculated. Furthermore, a method for the evaluation of the grinding quality is provided. The results indicate that in multipass rail grinding, a sequence of grinding passes – where the greatest grinding effort is applied on the earlier passes, with the last pass applying reducing levels of grinding effort – produces the highest conformance to the target grinding profile. For example, when rail grinding is planned for two passes, applying 60% of the total grinding effort on the first pass and 40% on the second pass decreases the final grinding error by 7.3%.

Mandibular condylar morphology for bruxers with different grinding patterns

Objectives: The purpose of this study was to investigate the mandibular condylar morphology for bruxers with different grinding patterns.Method: Condylar sectional morphology and condylar position of 30 subjects were determined by two viewers using cone beam computed tomography (CBCT) image data sets. The grinding patterns during sleep bruxism (SB) were determined objectively using a Brux-checker device.Chi-square tests were used for statistical analysis for the condylar morphology type between different tooth grinding patterns. Spearman’s rank correlation coefficient was used for correlation analysis between condylar position and the canine guidance area during SB.Results: Theincidence of condylarmorphologicaldivergence from idealwas35%.There isa significant difference in distribution of condylar morphology type between the group grinding (GG) and GG combined with mediotrusive side grinding (MG) (p < 0.05). There was no significant correlation between condylar position and canine guidance area during bruxism.Discussion: MG during SB is associated with condylar morphology that is considered not to be ideal.