Different Degrees Of Wear Research Articles

Analysis of the Pulpal Blood Flow Microdynamics during Prosthetic Tooth Preparation Using Diamond Burs with Different Degrees of Wear.

Pulpal modifications taking place during prosthetic tooth preparation using worn-out burs may represent a risk for the vitality of the dental pulp. The aim of this in vivo study was to evaluate whether the wear of diamond burs has an influence on the vascular microdynamics at the level of the dental pulp, during vertical preparation for zirconia crowns. The study was performed with a split-mouth design and included 32 vital permanent monoradicular teeth (20 maxillary and 12 mandibular), from six subjects, aged between 20 and 50 years. The teeth were randomly assigned to two study groups of 16 teeth each. For prosthetic preparation, new burs were used in the first group, and burs at their 5th use were used in the second group. Four consecutive determinations of the pulpal blood flow by Laser Doppler flowmetry (LDF-laser Doppler MoorLab instrument VMS-LDF2, Moor Instruments Ltd., Axminster, UK) were taken for each tooth included in the study: before the preparation (control values), immediately, at 24 h, and at 7 days after the prosthetic preparation. A four-way ANOVA statistical analysis was applied to analyze the effect of four considered factors (bur wear degree, time of measurement, tooth number, and tooth location) on the pulpal blood flow (PBF). A significant increase in pulpal blood flow compared to the baseline was recorded immediately after preparation (p < 0.01), at 24 h (p < 0.01), and at 7 days (p < 0.05) in both groups, but more pronounced in the case of burs at the 5th use. The blood flow was significantly higher in upper jaw teeth, irrespective of the measurement time. In conclusion, the use of worn-out diamond burs produces lasting modifications in the pulpal blood flow of teeth that undergo prosthetic crown preparation. ISRCTN registry: ISRCTN49594720.

Fatigue Damage Assessment of Turbine Runner Blades Considering Sediment Wear

The wear phenomenon that occurs on the blades during operation has a significant impact on the fatigue life of the blades. To address the issue of fatigue life assessment for turbine runner blades subjected to increased dynamic stress due to sediment wear, taking a specific high-head hydropower unit’s mixed-flow turbine as the research subject, a hydraulic model of the turbine was established. The wear zones of the runner blades are determined based on the distribution of the flow field’s velocity and the sediment volume fraction. According to the wear rate formula for runner blade material, the amount of wear on the blades is determined, and the dynamic stress data for the dangerous areas of the blades under different degrees of wear are calculated using a unidirectional fluid–structure coupling method. The load spectrum of the time–stress history data for the dangerous area at different levels of wear was compiled using the rain-flow counting statistical method. The operating time ratios for the flood season and the non-flood season are combined. Based on the fatigue cumulative damage theory, the total fatigue damage at the maximum stress part of the runner blade was calculated for different stages of wear, providing a reference for the life calculation of mixed-flow hydraulic turbines.

Fatigue failure of high precision spindle bearing under extreme service conditions

Four sets of high precision spindle bearings (HPSB) had been in extreme service for 6040 h and 85,000 r/min. The service temperature, wear fatigue form, hardness, residual stress, retained austenite, metamorphic layer and element content of the bearing raceway were analyzed. The surface layer and inner layer of bearing raceway were analyzed by Electron Backscatter Diffraction (EBSD), Focused Ion Beam (FIB) and Transmission Electron Microscopy (TEM). The results show that the service temperature range of the four sets of bearings is from 17.5℃ to 74.7℃. With the increase of rotating speed, the bearing temperature can reach 65℃ at 85,000 r/min. The four sets of bearings have different degrees of wear, including fatigue shedding (FS), wear (W), corrosion (C), peristalsis (P), burn (B) and defect (D). In the extreme speed service, taking the bearing No.2 with the highest temperature as the research object, the maximum and minimum hardness differences of outer ring raceway, inner ring raceway and ball are 423.1 HV, 368.7 HV and 405 HV, respectively. The tangential residual stresses of the outer and inner ring raceways are found to be tensile stresses, which are 31.3 MPa and 110.8 MPa, respectively. The retained austenite in the outer and inner ring raceways of bearings are found to increase abnormally, reaching 36.7 % and 34.7 %, respectively. In addition to the highest Ion (Fe) element, the outer and inner ring raceways of bearings also contain higher Praseodymium (Pr) elements, reaching 35.5 % and 14.5 %, respectively. The maximum thickness of the “white layer” of the outer and inner ring raceways of the bearing is 15 μm and 17 μm, respectively. The surface layer of bearing outer and inner ring raceways contain nanocrystals of 200 nm and 100 nm, respectively. Certain nanocrystalline layer will prolong the service life of bearings. Nanocrystals mainly contain Phosphorus (P) and Copper (Cu) elements. The research findings of this study can provide theoretical and data support for enterprises and scholars in the engineering field.

Denoising graph neural network based hydraulic component fault diagnosis method

Accurately identifying faults in hydraulic components is essential for improving the reliability and safety of hydraulic systems. Since the hydraulic components of heavy-duty equipment usually work in complex and variable environments and are subject to interference from multiple sources of noise. As a result, fault diagnosis of hydraulic components is challenging, leading to the development of various fault diagnosis models. However, current hydraulic component fault diagnosis models have the following limitations: (1) only able to handle Euclidean space data and ignore the topological relationships within the signals that could provide additional useful information for fault diagnosis, (2) only diagnose faults using single-dimensional acceleration data and fail to incorporate more equipment working conditions. This study focuses on the hydraulic directional valve and proposes a fault diagnosis method based on denoising graph neural network. Firstly, computational fluid dynamics(CFD) is used to analyze the flow field of the spool and sleeve of the valve under different wear states and working conditions. It is found that different degrees of wear have similarities under different working conditions, and there is a regular correlation between the acceleration signal of the valve body and the fault mode under the same working condition. Therefore, acceleration and working condition information are selected as the raw information for fault diagnosis. Then, horizontal visibility graph(HVG) was utilized to transform acceleration signal to graph, and the graph nodes, which can incorporate multidimensional information, were set to be the equipment working conditions and acceleration values. However, the noise in the raw signal could seriously affect the quality of the HVG. To solve this problem, an adaptive threshold denoising algorithm was proposed to reduce the interference noise in the acceleration signal. The denoising threshold parameter was learned directly from the raw data. Finally, graph neural network(GNN) is applied to fault diagnosis of hydraulic components from non-Euclidean multidimensional information. Experimental results demonstrate the superior robustness and accuracy of this method in handling strong noise and multiple working conditions compared to several classical fault diagnosis methods. This research provides an effective approach for hydraulic component fault diagnosis.

Primeras tendencias del registro de raspadores líticos en el curso medio del arroyo Salado, provincia de Río Negro (Argentina)

This paper presents research on a sample of scrapers recovered from the Paredón de los Grabados archaeological area in the Río Negro province (Argentina). The site, a wall with petroglyphs, is located near the Somuncurá plateau, 40 km from the Atlantic coast, where there are small, seasonal tributaries of the Salado stream. Distributional studies show a high-density concentration of the archaeological record in areas circumscribed by canyons and gullies formed by river erosion. The spatial distribution of the archaeological material suggests accumulation through fluvial action (traction or washing), with high visibility in open spaces among the vegetation. The recovered scrapers were noteworthy in quantity and variability. Preliminary analyses indicate they were manufactured from various raw materials, primarily siliceous rock and obsidian. The great difference in size could indicate they are from different moments in the area’s occupation. The artifacts also show different degrees of wear and even reactivation. Taphonomic studies have identified middle stages of abrasion with slightly rounded edges.

Evaluation of the Pulp Chamber Temperature during Tooth Veneer Preparation Using Burs with Different Degrees of Wear-A Preliminary In Vitro Study.

The heat produced during tooth preparation could be a source of damage for dental pulp, and many variables are involved in this process. The aim of this in vitro study was to evaluate whether the different degrees of wear of the diamond burs significantly influenced the temperature changes in the pulp chamber during tangential veneer preparation. The sample comprised 30 intact permanent monoradicular teeth, randomly assigned to three study groups of 10 teeth each, of which 5 had the pulp tissue preserved and 5 had thermoconductive paste in the pulp chamber. For prosthetic preparation, we used new burs in the first group, burs at their fifth use in the second group, and burs at their eighth use for the third group. The pulp chamber temperature was evaluated at the start, after one minute, and after three minutes of preparation, using a k-type thermocouple. The results of the three-way ANOVA and Tukey post hoc comparisons showed a highly significant effect of the time of measurement, while the pulp condition and the degree of wear of the burs had no effect. In conclusion, the different degrees of wear of conventional diamond burs do not produce statistically significant different changes in the pulp chamber temperature.

Relationship between trace elements in synovial fluid and cartilage and severity of knee osteoarthritis

To investigate the relationship between trace elements in synovial fluid and cartilage and severity of knee osteoarthritis (KOA). Patients with KOA who underwent knee arthrocentesis or total knee arthroplasty (TKA) were recruited based on inclusion criteria between June 2021 and December 2021. Synovial fluid samples were obtained during knee arthrocentesis and TKA, and participants were divided into the mild group (grading Ⅰ/Ⅱ) and the severe group (grading Ⅲ/Ⅳ) according to the Kellgren-Lawrence grading (K-L grading). Cartilage samples with different degrees of wear were collected during the TKA from the same patient and were divided into mild wear (0-1 point) and severe wear (2-4 points) groups based on the Pelletier score. The contents of copper (Cu), zinc (Zn), and manganese (Mn) in synovial fluid and cartilage were evaluated by inductively coupled plasma mass spectrometry, and the differences between groups were compared. A total of 33 synovial fluid samples were collected, including 19 specimens from 14 patients who underwent knee arthrocentesis of mild group, with 5 bilateral sides knee arthrocentesis in them, and 14 specimens from 14 TKA patients of severe group. The patients were significantly younger in the mild group than in the severe group ( P<0.05), but there was no significant difference in gender or body mass index between the two groups ( P>0.05). Nineteen pairs of cartilage samples with mild and severe wear were collected from severe KOA patients (K-L grading Ⅲ and Ⅳ), including 9 males and 10 females, with an average age of 70.4 years (range, 58-80 years). The body mass index ranged from 21.2 to 30.7 kg/m 2, with an average of 25.6 kg/m 2. The content of Zn in synovial fluid and cartilage from KOA patients was the highest, followed by Cu, and Mn was the lowest. The Cu content in synovial fluid was significantly higher in the severe group than in the mild group ( P<0.05), and in the severe wear group than in the mild wear group ( P<0.05). There was no significant difference in Zn and Mn content between the two groups ( P>0.05). The Cu content increases with the severity of cartilage wear in patients with KOA.

Environmental control of the technical condition of electromagnetic nozzles of internal combustion engines

Harmful motor vehicle emissions are often the primary source of urban air pollution worldwide. Incorrectly serviced high-mileage motor vehicles emit significantly more harmful substances into the atmosphere than established by accepted standards. This paper presents an algorithm for the process of diagnostics and analysis of the technical condition of the fuel supply system elements for internal combustion engines (ICE) by means of selective sampling of exhaust gases. A gas analyzer system allows for the simultaneous monitoring of the 4 components of exhaust gases: CO, CH, O2 and CO2, assessment of the air-fuel ratio and internal combustion engine crankshaft rotation speed. Studies were carried out on an engine and a series of malfunctions were created artificially, by means of installing faulty elements and additional elements simulating different degrees of wear on the ICE systems. The study resulted in the development of a method and a hardware and software system. These allow for the test regimes to be established, in order to determine the failure of ICE systems which affect the composition of the exhaust gas.

APPLICATION OF CLOUD-BASED MACHINE LEARNING IN CUTTING TOOL CONDITION MONITORING

One of the primary technologies in the Industry 4.0 concept refers to Smart maintenance or predictive maintenance that includes continuous or periodic sensor monitoring of physical changes in the condition of manufacturing resources (Condition monitoring). In this way, production delays or failures are timely prevented or minimized. In this context, the paper present a developed cloud-based system for monitoring the condition of cutting tool wear by measuring vibration. This system applies a machine learning method that is integrated within the MS Azure cloud system. The verification was performed on the data of the calculated central moments during the turning process, for cutting tool inserts with different degrees of wear.

Increasing the sensitivity and expanding the functionality of bipolar analysis of rotary machine vibrations

Vibration-acoustic diagnostics of rotary machine defects is the most effective method for non-destructive testing of their technical condition. Practice shows that its successful use largely depends on a set of available methods for analyzing vibration processes. Gears are the most common and heavy-duty components that largely determine the overall vibratory condition of a machine. There is quite a variety of methods for vibration-based diagnostics of gear defects. They include an interesting method of bipolar analysis which consists in separate analysis of the positive and negative parts of a vibration signal with subsequent formation of the diagnostic indicator in the form of differences, ratios, etc. The method is aimed at assessing the quality of gearbox assembly by the position of the tooth contact pattern. Limited area of use and low sensitivity is a disadvantage of this method. The paper shows that the use of broadband vibration maxima in the application of bipolar analysis in vibration-based diagnostics of rotary machine defects significantly increases its efficiency. Using the example of wear of tooth flanks in the sun gear satellite gears pair and the value of the backlash in the differential gearbox of a turboprop engine, it was found to be ensured by increasing the sensitivity of the method and expanding its functionality. In our analysis, we used statistics of gearboxes with different degrees of wear of the tooth flanks and repaired gearboxes with different backlashes. In this case, a wide set of well-known diagnostic indicators can be used: intensity of n-dimensional vectors of informative series, parameters of individual harmonics, amplitude modulation depth, probabilistic characteristics in selected frequency bands, dimensionless discriminants, cepstra, etc. The paper presents some examples of these methods.

Research on Wear Characteristics and Experiment on Internal Through-Passage Components for a New Type of Deep-Sea Mining Pump

The conveyor electric pump for deep-sea mining is a key piece of equipment in deep-sea mineral transportation systems, as its flow capacity and wear resistance affect the reliability of the entire system. In this study, aimed at solving problems such as mining pumps being prone to clogging and wear, which could lead to performance degradation, a mining pump with wide flow paths and high performance was designed, and hydraulic performance tests were conducted on the new pump. The test results obtained were in good agreement with the numerical simulation results. Based on the reliability of the performance test results, using computational fluid dynamics (CFD) methods, and taking the wear model into consideration, a wear analysis was conducted on the internal through-passage components of the pump under different solid-phase particle parameters and operating conditions, and the average wear rate on the surface of the predominant through-passage components was calculated. The results showed that the hydraulic performance of the newly designed pump met the design requirements, with different particle parameters and operating conditions causing different degrees of wear on the through-passage components. The wear test was carried out with a test pump, and the comparison between the test results and the numerical calculation results showed that the numerical calculation of the wear of the deep-sea mining pump was accurate.

Nonlinear dynamic analysis of gear system in shearer cutting section under wear failure

Gear wear failure is one of the important failures of the gear system in the shearer cutting section. To reveal the influence mechanism of shearer cutting gear wear on the system dynamic characteristics, considering coupling factors such as time-varying meshing stiffness, dynamic gear clearance, internal error excitation, end load constraint and bearing radial clearance under wear failure, an improved dynamic model of shearer drive gear system is introduced to present an in-depth investigation of uniform wear of gear teeth effect. The dynamic meshing stiffness of gears under different degrees of wear is analysed. Furthermore, the bifurcation diagram is utilized to observe the motion state of the system experiencing different excitation frequencies, support damping as well as terminal loads. It is demonstrated that the gear surface wear could bring a change in gear dynamic transmission error, vibration impact state and amplitude, which is mainly manifested in increasing the unstable area and the vibration amplitude of the gear system, providing a method for monitoring and diagnosing of gear surface faults.

Influence of wear state of forward disc cutter in Ignimbrite on its mechanical characteristics

As the main rock-breaking tool, the disc cutter will directly affect the tunnelling efficiency of TBM. The research on the mechanical characteristics of cutter is the key to determine the TBM tunnelling parameters. The mechanical behaviour of disc cutter is still unclear at present, especially when taking wear state into consideration. Based on the above background, finite element method is used to study the rock-breaking characteristics of disc cutter under different working conditions, and the main research contents are: a numerical simulation model of disc cutter during rock-breaking was established by using ABAQUS. According to the characteristics of high compressive strength and high abrasiveness of the slightly weathered Ignimbrite in Fuzhou area, it is determined that the wear form of disc cutter in slightly weathered Ignimbrite is flat-edged wear. Based on this wear form, a study on the change rule of vertical, rolling and lateral forces, specific energy of rock breaking under different degrees of wear were carried on. Results indicate that vertical and rolling forces, specific energy of rock breaking generally increase with the degree of wear, reduce the tunneling efficiency of the disc cutter.

Study of cylindrical brush wear effect on its elastic characteristics, on required pressing force and on pressure at the outlet of hydraulic pneumatic accumulator for controlling position of chipping working body

Introduction. The article is devoted to a current issue of improving the quality of road surface cleaning and increasing the resource of brush working equipment. Improving the quality of cleaning and the resource of the brush working equipment will reduce the cost of operating a communal machine. In the process of operation, the pile of the cylindrical brush is worns out, while its elastic characteristics change, which is reflected in the required pressing force to maintain the most favorable value of the width of the contact spot from the condition of ensuring high quality cleaning and minimal intensity of pile wear.Materials and methods. The results of studies of the interaction of the pile of a cylindrical brush with the surface to be cleaned are presented at various degrees of wear of the brush pile. The research results are presented in analytical and graphical forms. The calculations were carried out using the Microsoft Excel software product and the Mathkad software environment for mathematical calculations.Results. The paper shows the dependence of the degree of wear of the pile of the brush working equipment on the actual radius of the cylindrical brush. The relationship between the width of the contact spot and the deformation of the cylindrical brush at different degrees of wear and tear is shown as a graph.The influence of the degree of wear on the elastic characteristics of the brush working equipment is considered. The dependences of the average stiffness coefficient on the degree of wear of the pile of a cylindrical brush, as well as the required pressing force on the degree of wear at different values of the width of the contact patch of the cylindrical brush are given.

Influence of the charging pressure of the hydraulic pneumatic accumulator of the communal machine control device on the pressure force of the brushed working body

The article is devoted to the actual problem of increasing the efficiency of cleaning the roadway with a communal machine. To increase the cleaning efficiency, it is necessary to provide the required pressing force and thus the required area of the contact spot between the brush pile and the surface to be cleaned, which can be done by using a position control device for the brush working equipment.Research methods. In the process of research were used the following methods: analysis, synthesis, ascent from the abstract to the concrete. The results of the study of the influence of the parameters of the control device on the criterion of the efficiency of the working process of the communal machine are presented.Results. As a result of the analysis of the process of interaction of the brush working equipment with the surface being cleaned, the dependences connecting the standard deviation of the pressing force of the brush working equipment to the surface to be cleaned from the required value, taking into account the wear of the pile and the charging pressure of the hydraulic pneumatic accumulator, were revealed, their approximation was carried out, and the regression equation was obtained.Conclusions. The studies carried out made it possible to obtain regression equations which are used to determine the optimal value of the standard deviation of the pressing force from the required one for different degrees of wear of the pile, depending on the charging pressure of the hydraulic pneumatic accumulator. The research results can be applied in the design of automatic control systems for the position of the working bodies of construction and road machines.

Features of determining engagement line of traction gears with different degrees of wear of gear teeth

Calculations of strength, forecasting the residual operation life for repairing traction gears (TG) is carried out on the results of modeling their motion characteristic, which is based on the determined coordinates of the contact points of the gear and wheel profile for the period of engagement (engagement line). This article presents results of a study aimed at developing mathematical dependencies for a refined determination of TG engagement line with the established wear of gear teeth. Adequacy verification of proposed mathematical descriptions was carried out based on the results of the study of new TG of ER-2 electric train series. Their comparison with the coordinates of the engagement line, calculated by the traditional method, showed that modelling uncertainty does not exceed 0.06%. As an example of practical use of the received mathematical descriptions, results of research of motion characteristic of new TG of ER-2 electric train series with the established degrees of wear of gear and wheel teeth are presented.

ПРИВАТНИЙ ТЯГОВИЙ РУХОМИЙ СКЛАД НА МАГІСТРАЛЬНИХ КОЛІЯХ. ОСОБЛИВОСТІ СЕРТИФІКАЦІЯ ПРИВАТНИХ ЛОКОМОТИВІВ

The article deals with the procedures for certification of private locomotives in order to grant authorization for their operation on certain public railway lines. The special feature of the certification is that, as a rule, locomotives belonging to departments, enterprises and organizations that are not within the management sphere of JSC "Ukrzaliznytsia" and were not previously used on public railway lines of Ukraine, but are now presented for participation in the project, can be of several types, different years of construction, have different diesel operating hours (SMU hours), different degrees of wear of the mechanical part of load-bearing structures, wheelsets, trolleys, couplings, braking equipment, different technical condition of measuring instruments, safety devices and air tanks, devices security, etc. Therefore, the article presents the provisions of certification schemes (models) that can be used by the certification body for the certification of single locomotives and batches of private locomotives, and their aspects. The paper also presents the basic normative documents according to which certification procedures are carried out. The key aspects of existing certification testing of locomotives are specified. The scope of work on technical diagnostics of locomotives for certification is described. The procedure and duration of the direct certification process are given taking into account the analysis of documentation, technical inspection, provision of expert evaluation, selection and identification of a sample (samples) of a representative item from the batch submitted for sampling, certification testing, processing and registration of test results, comprehensive conclusion on compliance of the locomotive with the requirements of regulatory and technical documents, decision-making on the possibility (or impossibility) of issuing a certificate.

Application progress of scour-abrasion resistant materials of hydraulic concrete

As the concrete surfaces of the sluice structure in the water conservancy and hydropower engineering would often suffer from the erosion of high speed sandy flow or water flow with bed load, there will often appear different degrees of wear and cavitations damages after a certain time of operation. Therefore, it is especially important to use the materials with high performance in resisting erosion and abrasion. Based on analyzing the abrasion damage mechanism and form of concrete, this paper mainly summarizes the research and application of scour-abrasion resistant materials, introduces the new development of scour-abrasion resistant materials, and finally provides an effective way of solving the impact of high silt-laden water erosion.

STRENGTHENING OF THE SURFACE OF STEEL (9XФМ) EXPOSED TO A HIGH-CURRENT ELECTRON BEAM

9ХФМ steel was irradiated with a high-current electron beam. The high-current electron beam was obtained in the TEMP-A accelerator. The irradiation was performed for various samples of the material of a ball mill drum. Part of the samples were taken from the surface of the balls, which had different degrees of wear. Samples taken from the depth of the balls, which is equal to half the diameter, were also irradiated. Microhardness measurements, metallographic, and fractographic analysis were used to study mechanical and microstructural changes. In all cases, a change in hardness was detected. The degree of change in hardness is different for different samples. Based on fractographic analysis, using SEM microscopy, one of the mechanisms that contribute to increasing the surface hardness is determined. This mechanism is the cleaning of the surface of samples from impurities of phosphorus and sulfur using a high-current electron beam.

Tearing of post-consumer cotton T-shirts and jeans of varying degree of wear

The demand for textile fibres is growing quickly. However, global cotton production has stabilized around 25 Mton/year. This is a sound development since cotton cultivation causes major sustainable development issues. Even if regenerated cellulose fibre production steadily grows, it is still only from a sixth to a fifth of cotton volumes. Hence, it is essential to find resource-efficient routes to generate alternatives to virgin cotton. There are many promising research initiatives that discover the possibility to utilize waste streams of neat cotton and cotton in fibre blends as raw materials for dissolving pulp for regeneration into, for example, viscose or Lyocell. However, there is a much simpler and energy-efficient route at hand. If fabrics are disintegrated mechanically, the separated fibres can be turned into yarn again. However, since fibre length is a key parameter to accomplish strong and durable textiles, fibre length loss upon tearing should be minimized. This study evaluates how fibre length distribution alters upon tearing of post-consumer cotton waste of two different constructions: denim and single jersey; and different degrees of wear, rendering four different fractions: (1) barely worn denim, (2) rather worn denim, (3) barely worn single-jersey and (4) rather worn single-jersey. Before tearing, the garments were dissembled, their yarns were characterized, fibre length distributions were manually determined for (1)–(4). Length analysis of the recovered fibres after tearing revealed that the length drop was most severe for (a) the finer single-jersey and (b) the barely worn fractions. The findings suggest that significant wear does not exclude from mechanical recycling.