Abrasive Instrument Research Articles

Силовой анализ процесса резания единичным зерном сферокорунда при шлифовании древесины

The productivity of the wood grinding process can be increased by using abrasive wheels with spherical corundum grains. They also expand the area of application of rigid abrasive instruments by reducing soiling and eliminating burns on the treated surface. The studies revealed several advantages of the abrasive wheels over sanding paper: very precise processing, achievement of the desired grade of the treated surface, high durability of the instrument, and low cost. A force analysis of a grinding surface with micro-cuttings made of spherical corundum grains was performed depending on the degree of its wear. The results revealed that chip removal by the spherical corundum grains was possible only under certain conditions when the cutting edges of the grains were exposed. Besides, the theoretical dependencies of forces in micro-cutting were obtained from every principal condition for the process of grinding wood and wooden materials: properties of the spheres, treatment modes, and material-related factors. The special properties were analyzed by the chip formation process and self-sharpening conditions of the spherical corundum wheels. The grain size had the greatest influence on the thickness of chips which were cut by one grain. The grain content and bonding, like other properties of the internal volumetric structure, had a less substantial impact. The abrasive tool characteristics must complement the processed material, such as grain size, hardness, and structure. On the other hand, spherical corundum has optimal physical and mechanical properties for grinding, particularly the thickness of the grain’s edges, which primarily determine the material’s tensile strength. The grinding depth and feed rate mostly define the parameters of the grinding performance of wood and wood-based materials. An increase in those leads to a rise in cutting forces, roughness of the ground surface, a reduction in the grinding length over the period of the wheel’s durability, and the grinding coefficient. If the grinding depth and feed rate are constant, the performance can be improved by increasing the cutting rate. For citation: Sergeevichev A.V., Sokolova V.A., Mikhailova A.E., Ovcharova E.O., Voinash S.A. Force Analysis of a Single Grain Cutting Process in Wood Grinding Using Spherical Corundum. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 3, pp. 140–154. (In Russ.). https://doi.org/10.37482/0536-1036-2023-3-140-154

Landmarks in the Traumatic Brain Injury A Retrospective Study

As one might expect, prehistoric brain surgery lacked knowledge of the anatomy, concept recognition of the disease, and comprehension of the disease’s origin. Unfortunately, failure to deeply understand these important principles delayed the progression of medical and surgical practice. Trepanation may be one of the oldest surgical interventions for which archaeological evidence is present. In the 1990s, standardized guidelines were developed and established for the management of traumatic brain injury. They included protocols regarding the pharmaceutical therapy and the management of increased ICP. Since then, research has improved TBI survival. Evidence of trepanation practice and other techniques in pre-Columbian Mesoamerica is demonstrated by the cranial remains in pre-Columbian burials, iconographic artworks, and post-colonial reports. The intellectual understanding of neurosurgery developed during the golden age of ancient Greece where no surgeon restricted oneself in strict to neurosurgery. Head injuries on the other hand appear to have been abundant; an expected result of wars and internecine conflict, as recorded by Herodotus, Thucydides, and Homer. Then and now, war remains the primary source of study material for the improvement of knowledge regarding head injuries. Surgical procedures for the management of even minimal lesions of the theca cranica, continued throughout the 16 th and 17 th Century. The surgical technique, with cross-shaped skin incision and the instruments used (trephine, lever, scalpel, gouge, protector of the meninx, etc.) would remain unchanged with respect to the past, but one should take notice at the improved quality of the materials and the ameliorated precision with which the instruments were made. Some instruments appeared to be real work of art, as shown by the findings now displayed in museums and in illustrations of the times. The most ancient technique of craniotomy involved using abrasive instruments to thin down the bony wall. Subsequently, circular incisions were progressively made deeper, or a series of small holes were made in a circular fashion. The remaining bony bridges between these small holes would be broken down. The two latter methods that continued to be used for a very long period depended on using metal instruments.

Research of thermal energy processes during silicon carbide production in the resistance furnace

Thegoal. Silicon carbide is one of the most essential artificial inorganic materials widely used to produce abrasive instruments, high-temperature heaters, fireclay ceramics, and metallurgy. The most amount of silicon carbide produces in the resistance furnaces. One of the issues of the silicon carbide production process is the lack of supervisory of thermal state in the furnace working space, which does not always allow for select rational electrical modes and accordingly get the material of appropriate quality. One of the methods to solve this issue is computer modeling the thermal state of the resistance furnace. Therefore, the goal of this research is the development of a computer model of the thermal state in the reaction zone of the resistance furnace, that further allows the development of technological recommendations concerning modes of conducting the process of obtaining silicon carbide. In addition, the development of a mathematical model of the dynamics of the thermal state of the resistance furnace opens up new opportunities for improving the existing automated control systems, which is very important from the point of view of the implementation of the Industry 4.0 paradigm at the enterprises of the mining and metallurgical complex of Ukraine. Methodology. The thermophysical model of the silicon carbide production process in the resistance furnace was developed. By finite difference method, the dynamics of the thermal state of the reaction zone in the furnace are computed. Resultsandscientificnovelty. Zones of the existence of products of carbothermic reduction of silica due to the heat generated when an electric current is passed through the furnace core are sized up by results of modeling, and the temperature front of the progress of the reductive reactions was detected. Practical value. The developed model allows for evaluating the influence of supplied power dynamics on the reduction products size zones, obtaining the analytical dependences of changes in the thermal state of the reaction furnace zone, and thereafter developing the technological recommendations concerning silicon carbide production process performance and improvements for the furnace automated control system. The structure of control of the thermal modes of the resistance furnace and the control computer complex based on Siemens technology is proposed.

Theory of Formation of Edge’s Surface Roughness Finished by Radial Polymer-Abrasive Brushes

Formation of roughness during treatment by polymer-abrasive brushes occurred as a result of interaction of cutting micro-relief with processed surface. The cutting micro-relief of abrasive instrument is described in the form of random process with normal distributional law. When calculation of roughness, the depths of penetration of cutting lugs in processed material as well as regularity of changing of radial radius of rounding of peaks of cutting lugs from modes of treatment are taken into consideration. Set are relations of roughness of processed edge from modes of treatment (deformations of instrument, cutting velocities, feeding) as well as from constituent cutting force. It is proved that usage of polymer-abrasive brushes for rounding of edges faces all requirements of aviation industry on roughness of processed edges.

БАЛАНС ТЕПЛА В ЗОНІ РІЗАННЯ ПРИ ВІБРОМАГНІТНОАБРАЗИВНОЇ ОБРОБЦІ НАДТВЕРДОЇ КЕРАМІКИ

In the process of cutting, at any type of treatment plenty of heat is distinguished. An appearing heat spreads from the hearths of thermogenesis to more cold areas, redistributed between shaving, detail, instrument and environment. Greater part of the warmth distinguished inplane cutting goes to heating of shaving and speeds away by her from the zone of cutting. Part of the warmth distinguished on an abrasive instrument accumulates on cutting part of instrument and gradually spreads on all volume. An abrasive instrument is the explorer of the second stream of the taken warmth. Part of the warmth distinguished in area of treatment, some part of the warmth distinguished on the surface of abrasive instrument, gets to the processed material of purveyance and heats her. Part of general amount of warmth is taken from the zone of treatment in an environment. At cutting without the use OCL this warmth is taken in an air environment by a radiation. But, as it is already marked, part of heat passes to the purveyance, and this fact is negative. In case with super hard ceramics a negative is conditioned yet and by that ceramics must not overheat at treatment. Using the process of oscillation magnetic abrasive treatment for work with super hard ceramics this problem becomes yet more actual because a process takes place in the closed working chamber without admission OCL. In the article an analysis is given distribution of thermal streams at oscillation magnetic abrasive treatment. It is shown through a mathematical model that thermal streams practically do not influence on heating of purveyance from super hard ceramics. The amount of heat is shown that arises up in process it is confirmed abrasive treatment, that heating of super hard nitride of ceramics does not exceed possible norms. Thus, there was attempt to showthat oscillation magnetic abrasive treatment is able to process super hard ceramics not violating her internal structure and change of geometrical form.

Technological conditions of abrasive tool operation

. An abrasive instrument with every day finds all greater application at implementation of operations from finish abrasive treatment of details of machines, cleaning of metallic and non-metal surfaces from paints and varnishes coverages, blight and contaminations. Polymeric-abrasive brushes in most cases apply in combination with the hand angular grinding machines of small power.The basic task of work are determinations of power charges and their distribution with the aim of minimization of heating of polymeric matrix and increase of part of energy, that is spent on the output of material that is subject to moving away.At determination of power charges the next indexes of power were taken into account, namely: power, that is passed from abrasive grain that gap-filling fiber, at a contact with the processed surface; power of destruction of surface that is processed; power of thermal losses of energy is at the friction of fiber at the surface of material that is processed. Taking into account the enumerated indexes of power the condition of balance of energy is made. It allowed to define an output-input of abrasive instrument ratio and set, what factors result in his increase. And also, to get dependence, that describes the general overfall of temperatures on that the fiber of brush is heated for all the time of her work.For determination of probability of faultless work of machines with polymeric-abrasive brushes a flow diagram that includes two criteria was made: probability of destruction of fiber from a tiredness and probability of destruction of fiber from the pin loading. The made chart was examined with authenticity of faultless work of instrument on each of these criteria. The decision of the system of probability of faultless work of brush is dependence, that allows to define tenure of employment of brush. Thus, possibility to expect the number of polymeric-abrasive brushes for providing of trouble-free implementation of works appears on a site or assembling area.An increase to the output-input ratio is provided by next indexes, namely, diminishing of specific heat capacity, mass of fiber and overfall of temperatures of fiber for one turn of brush. And also increase of amount of abrasive, border of durability and crossing of fiber and length of arc of contact.Determination of probability of faultless work of hand and portable machines with polymeric-abrasive brushes the resource of their work allows to determine.

Surface Topography, Gloss and Flexural Strength of Pressable Ceramic After Finishing-Polishing Protocols.

This study evaluated the effect of different finishing-polishing protocols on surface roughness, gloss, morphology and biaxial flexural strength of pressable fluorapatite glass ceramic. Thirty ceramic discs (12x1 mm) were produced and divided into five groups (n=6): CT: control (glaze); DA: fine grit diamond bur; DG: DA + new glaze layer; DP: DA + felt disk with fine grit diamond paste; DK: DA+ sequential polishing with silicon abrasive instruments, goat hair brush and cotton wheel. The specimens were analyzed for surface roughness (Ra) under profilometry and atomic force microscopy (AFM). Gloss was measured with spectrophotometry and micromorphology with scanning electron microscopy (SEM). Flexural strength was assessed by biaxial flexural strength test. Data were analyzed using one-way ANOVA and Tukey's post hoc test (a=0.05). DK showed the lowest surface roughness values and DA presented the highest in the perfilometer analysis. No significant differences were observed in the AFM for the CT, DG and DK groups, which presented the lower surface roughness; DA and DP had the higher Ra values. The DA, DP and CT showed the lowest surface gloss values, and the reflectance was significantly different from those observed for DK and DG groups. SEM analysis revealed the smoothest surface for DK group, followed by DG and CT groups; DA and DP groups exhibited variable degrees of surface irregularities. No significant differences were observed among groups for the biaxial flexural strength. The polishing protocol used in DK group can be a good alternative for chairside finishing of adjusted pressable fluorapatite glass ceramic surfaces.

Особливості загострювання ножів лущильних і шпоностругальних верстатів

Розглянуто проблему загострювання ножів лущильних та шпоностругальних верстатів, яка є на підприємствах, що спеціалізуються з виготовлення струганого та лущеного шпону. Особливістю загострювання цих ножів є те, що вони мають широку задню поверхню, малі кути загострення та велику довжину. Велика зона контакту абразивного круга з поверхнею ножа призводить до утворення високих температур на поверхні ножа. Внаслідок цього змінюються початкові властивості леза, відбувається його припалювання, виникають великі завусениці, мікротріщини та інші дефекти. Наявні рекомендації щодо раціональних режимів загострення та доводіння дереворізальних інструментів, зокрема лущильних і шпоностругальних ножів, частково вирішують цю проблему, але істотно зменшують продуктивність процесу загострення. Оцінено та проаналізовано конструкції абразивних кругів, які застосовуються для загострення цих ножів. З'ясовано, що для загострення ножів з широкою задньою поверхнею потрібно удосконалювати та розробляти новий спеціальний абразивний інструмент, який повною мірою забезпечить якісне загострювання та високу продуктивність процесу. Цей інструмент не повинен потребувати значних змін у конструкції верстата для загострення дереворізальних ножів, повинен бути дешевим і надійним в експлуатації.

The Influence of Abrasive Instrument and Cutting Modes in Fine Grinding of Wear Resistance Composite Parts on the Parameters of Surface Roughness Friction of Printing Machines

Background. Study on the technological process of thin abrasive grinding of wear resistance composite parts, synthesized on the base of utilized and regenerated industrial wastes of nickel alloys XH55BMTKЮ, XH50BTФKЮ, ЭП975 with additions of hard lubricant CaF2 has been carried out.Objective. The purpose of the work is the experimental research of processes of thin abrasive grinding of friction parts made of new composite materials based on nickel and identification of influence on the parameters of part surface roughness of the abrasive instrument type, its granularity and cutting modes.Methods. Surface treatment of printing machines wear-resistant parts based on nickel by thin grinding on the plain-grinding, round-external-finishing and internal-grinding machines with grinding instruments made of chromium electrocorundum (33A) with granularity 14–28 µm on the glyphtal bond and application of thin cutting modes.Results. It was show, that granularity, the abrasive instrument bond material and parameters of thin abrasive grinding essentially influence the parameters of surface roughness machining Ra. The best performance Ra parameters satisfy the grinding chromium electrocorundum 33A discs with granularity 14–28 µm on the glyphtal bond and thin cutting modes that meet the high requirements at work surfaces of friction parts for printing machines. Advantage of the surface machining with grinding chromium electrocorundum discs was shown.Conclusions. Also it was demonstrated, that the formation of high quality parameters of details surface, made of new composite materials based on nickel essentially depends on the type of the abrasive instrument, cutting modes of composites and bond material. The recommendations on the production were developed.

Root canals decontamination by coherent photons initiated photoacustic streaming (PIPS) of irrigants: an ex-vivo study

The aim of this ex vivo study was to assess the antibacterial effectiveness of coherent photon initiated photoacoustic streaming (PIPS) of irrigants using an Er:YAG laser equipped with a newly designed, stripped and tapered, tip in extracted teeth with infected root canals. One hundred-forty-eight single-rooted extracted teeth were prepared using a rotary abrasive instrument providing a root channel with a suitable size. The samples were sterilized and all teeth except ten (negative control group) were inoculated with Enterococcus faecalis and incubated in a CO2 chamber at 37°C for 15 days in Eppendorff tubes filled with trypticase soy broth medium changed every 2 days. Infected teeth were then randomly divided into 4 test groups (n=32 for each): pulsed erbium:YAG laser at non-ablative settings for 30 seconds with sterile bi-distilled water (Group A) or 5% sodium hypochlorite (NaOCl) (Group B); without laser activated sterile bi-distilled water irrigation for 30 seconds (Group C) or 5% NaOCl irrigation for 30 seconds (Group D); the positive control group received no treatment in infected teeth (n=10). Colony-forming units (CFUs) were counted from bacteriologic samples taken before (S1) and after treatment (S2). Data were analyzed by Kruskal-Wallis and post hoc Dunn's multiple comparison tests. CFU counts were significantly lower in groups B and D than in group C (P<0.001). Moreover, there was a significant difference between Group A and C (P<0.001). Group B showed the highest CFU reduction, which was significantly greater than that evident in groups A or C (P<0.001). There were no statistically significant differences between group B and D (P>0.05). None of the four groups predictably generated negative samples. Under the conditions of this ex vivo study, statistically significant difference wasn't found in planktonic bacteria reduction between the laser and NaOCl or NaOCl alone groups.

Wear Estimation Using 3D Surface Roughness Parameters

The aim of this work is to propose a methodology of lifetime prediction of details by new approach for linear wear intensity determination using 3D surface roughness parameters. For qualitative evaluation of the wear process the linear wear intensity (Ih), which may be determined separately for the plastic and elastic contact, is commonly used. Since the elastic contact is mainly required in pairs of details in mechanical engineering in these paper this kind of contact was examined. In our research, the random surface model was used. The surface machined with abrasive instruments (grinding, polishing, honing, etc) has the irregular shape of surface roughness, which can be described with random function. Irregular surface is expressed by a random field h(x, y) of two variables x and y which are Cartesian coordinates of a surfaces point, where the height of roughness asperity h(x, y) has a normal probability distribution. In wear research the probability theory was used. Further in deformed volume calculation, as well as in determination of the length of the surface’s contact the 3D surface roughness parameters were used. The strong correlation between 3D roughness parameters Sa (arithmetic mean height) and Str=Rsm1/Rsm2 (texture aspect ratio of the surface) was revealed. As a result of research, the methodology of lifetime prediction of details by new approach for linear wear intensity determination using 3D surface roughness parameters was elaborated and proposed. After calculation of linear wear intensity Ih, it is possible to estimate lifetime of wearing details. So, at a first time in wear estimation the 3D surface roughness parameters were used. The results of this work have wide practical application, for example in design, texture specification on drawings etc.

Microtopography Model of Rough Surface

For perfect surface roughness description is not enough to know characteristics of surface profile. It is necessary to use topography methods, so called microtopography. Thereby, surface roughness in microtopographycal understanding must be described with three coordinates, whose in Cartesian coordinates system compose point under consideration height h, abscissa and ordinate, determines point position in the plane. Most efficient methods in irregular surface roughness research are random function theory methods. Therefore, microtopography, analogically to profile, may consider as random function, but two dimensional function, i.e. two variable x and y random field h(x,y). From analogy with random process, random field can be normal – ordinates are distributed by normal (Gaussian) distribution. Moreover, random field can be homogeneous and heterogeneous. Random field is deemed homogeneous if its mean value is discretionary and correlation function depends only from distance between surface points. Important characteristic of random field is correlation function, whose depends of two variables t1 and t2 – orthogonal Cartesian coordinates of vector t. Random field is homogeneous and isotropic when its characteristics are equivalent in any direction. There are three types of surface anisotropy: • General event of surface anisotropy. Characteristics of this event roughness parameters are depend of surface split direction. • Surface roughness with direct anisotropy. Those surfaces are with typical traces of tool and they proper two mutually perpendicular surface roughness directions. • Extended anisotropy area – special event of anisotropy roughness. Of analytical opinion, gainfully anisotropy roughness see as extended occasional isotropy area. This let easy cross from anisotropy surface to isotropy and contrariwise, thereby embrace amount class of surface roughness. Let’s formulate microtopography model of rough surface [1]. Surface roughness is described with homogeneous normal random field h(x,y) that has uninterrupted correlation function and uninterrupted deriviates. We may consider that E{h(x,y)}=0. The mean random field value is plane called mean plane. For describing random field we must know mathematical expectation and field correlation function, what in fact reduces on determining dispersion and rationed correlation function r(t1, t2). Homogeneous random field dispersion D{h} doesn’t depends of direction and can be founded in any surface split. Given model of rough surface let inspect surfaces produced by abrasive instruments and friction surfaces after wear-in period.

Factors affecting the surface quality of the ground WC-Co alloy

We study the influence of the interelectrode and anode voltages applied to the abrasive instrument, its pressure, and the sizes of abrasive particles and the rate of treatment on the surface roughness and topography of sintered WC-Co alloy after mechanical and electrochemical grinding. The optimal values of the parameters of treatment are determined.

Selection of the Binder Composition for Abrasive Electrocorundum Instruments

The properties of ceramic binders used in the production of electrocorundum abrasive instruments are discussed. The methods for studying the properties of ceramic binders are analyzed, including the methods making it possible to study the process of sintering of the binder components and the electrocorundum grains and the formation of the binder structure and the contact zone between the binder and the electrocorundum.

Random process model of rough surfaces contact

This paper discusses rough surfaces contact phenomena and in particular examines surfaces machined with abrasive instruments. The nature of surface roughness obtained as a result of this type of mechanical treatment can be described by the random field of two variables. Attention is paid to three-dimensional surface roughness parameters whose statistical characteristics are determined by the simple rough surface model: for an anisotropic random field obtained by mathematical stretching of an isotropic random field. Consideration is given to surface contacts: rough and smooth surface interaction and the contact of two rough surfaces. Two types of asperities contact are examined: plastic and elastic. The criteria for contact type have been developed. Contact theory is used for the calculation of contact resistance in welding and of wear intensity. The equations obtained reveal that all of them contain one surface roughness height parameter and two spacing parameters.

Surface alterations on dental restorative materials subjected to an air-powder abrasive instrument

This study assessed the effect of an air-powder abrasive instrument (Prophy Jet) on the surface integrity of a series of restorative materials. Four types of amalgam alloys (Amalcap, Dispersalloy, Tytin, Ana 2000), three types of composite resins (Silux, Brilliant Lux, Adaptic II), a heat-cured resin (SR Vivadent), and porcelain (Vita VMK) fused to a Gr-Ni alloy at 1 mm and 2.5 mm thickness were subjected from 5 mm distance to the abrasive stream at 100 psi for 5 seconds. The resulting surface topography was studied under an electron probe microanalyzer. All of the amalgams presented increased surface roughness and alterations in the surface composition assigned to the destruction of the soluble gamma-2 and n phases. Composite resins showed excessive matrix disruption, exposure of the filler particles and pitting on the prepolymer surfaces. The crown and fixed partial denture resin was the most affected material. Porcelain at 2.5 mm thickness exhibited moderate stain pitting, whereas in 1 mm thickness severe glaze cracking was identified.

Effect of air-powder abrasive instrument on porcelain

The effects of an air-powder abrasive instrument on porcelain were evaluated. Sample disks made from two commercial porcelains and three porcelain stains were treated for 30 seconds with this instrument. Although there was no visible change in the stain or glaze of the samples, scanning electron microscopy revealed severe pitting of all of the Vita porcelain/Vita stain samples, moderate pitting of all of the Vita porcelain/Ceramco stain samples, and no pitting or effects on Willceram porcelain/Crystar stain samples. It is recommended that the air-powder abrasive instrument be used cautiously or not at all on porcelain restorations, especially those with staining and/or specific characterizations. Pitting of the surface could be a result of this treatment.

Effect of air-powder abrasive instrument on restorative materials

Effect of air-powder abrasive instrument on restorative materials

The effect of an air-powder abrasive instrument on composite resin

Three composite resins were subjected to applications of sodium bicarbonate with an air-powder abrasive instrument. Materials tested were a microfilled, a conventional, and a light-cured composite resin. Samples were tested for surface roughness before and during applications. The applications produced significant increases in roughness. It was concluded that the light-cured composite resin should be the material used for patients undergoing a recall maintenance program in which the instrument is used.

The surface of composite resin finished with instruments and matrices

I t is difficult to obtain a smooth surface on composite resin restorations.‘-” The problem is inherent in the composite resin. Some investigators have suggested that the difference in hardness between the filler particles and matrix contributes to a roughened surface.‘, *, I37 I4 Still others suggest that a rough surface is to be expected and results from wear factors. These include wear of the resin matrix, exposure of air bubbles and loss of the filler particles by shearing forces, bond failure, and cracking of the resin matrix.2* 3, 6, “3 “* I6 Various finishing and polishing procedures have been studied to produce a smooth composite resin surface. ‘, 6, ‘3 “v 13, ‘X ” Nonsmooth or irregular and rough surfaces can be irritating to the periodontal ligament and lead to increased adhesion of dental plaque, inviting recurrent caries.‘-+ ‘3 *, I3 With complex lesions and defects occurring in the gingival third of teeth, restorations with rough surface texture, adhesion of dental plaque, and irritation of the periodontal ligament induce pathoses. In the cervical area, access for finishing and polishing with abrasive instruments is limited. To minimize these problems, care in the insertion of the composite resin and proper matrix technique have been suggested.‘3s’8 In this manner it is possible that with minimal finishing, a smooth surface, recreating the natural contours of the tooth, is produced and decreases the potential for dental plaque to injure the periodontal ligament and also induce recurrent caries. The purpose of this study was to compare the surface finish ptoduced by various insertion and matrix techniques.