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Fe-Si/MnO-SiO2 soft magnetic composites (SMCs) are prepared by sintering ball milled Fe-Si/MnO2 core–shell structured composites. The correlation between the coating uniformity and electromagnetic properties have been investigated via adjusting ball milling parameters in detail. The results indicate that uniform MnO2 coating can be transformed into MnO-SiO2 composite coatings with high insulation due to the high temperature reaction between MnO2 and Si. Agate ball is more effective than stainless steel ball to improve the uniformity of MnO2 coating as well as the electromagnetic properties such as significantly higher resistivity, lower core loss and better frequency stability of permeability. Moreover, increasing the ball milling time from 4 h to 24 h can obviously improve the coating uniformity and thus result in the remarkable increase of the resistivity from 2.4 mΩ·cm to 356.9 mΩ·cm. And the core loss and dynamic loss decrease rapidly while the Ms shows a slight decline. When the ball milling time reaches 24 h, the Fe-Si SMCs exhibits superior magnetic properties such as high Ms (181.0 emu/g), very low core loss (361.5 kW/m3 at 100 kHz) and good frequency stability of permeability (65) from 50 Hz to 1000 kHz.

When dealing with post-processing steps of additively manufactured parts, the issue of the surface finishing of freeform surfaces has to be addressed. The flexibility of ball end milling makes this machining operation particularly suitable to finish such parts. However, literature records dealing with this kind of cutting operation on additively manufactured alloys are very scarce. The microstructural anisotropy induced by the additive manufacturing process may influence the machinability of a metal alloy such produced, distinguishing it from the same alloy conventionally fabricated. At present, there is no thorough understanding of the influence of additively built component anisotropy on ball end milling operations, resulting in the unpredictability of the part behavior once machined. In this work, ball end milling was carried out on both additively and conventionally manufactured Ti6Al4V alloy workpieces characterized by an inclination angle of 15°, 45°, and 75°. For the first time, the impact of the peculiar microstructural features induced by additive manufacturing was studied in ball end milling operations with different tool paths orientations. The interpretation of the results was helped by the comparison with the wrought alloy. The machinability was assessed in terms of cutting forces, surface topography, surface defects, and chip morphology. The results demonstrated that the additively manufactured alloy allowed for better machinability than the wrought one only when the cutting edge was parallel to the α phase colonies within the prior β grains, thus favoring the material removal by locally decreasing the material resistance to cutting.

A novel desulphurization technology has been put forward using a dispersed in-situ phases induced by an explosive reaction of a composite ball. A composite ball with this function has been designed...

This experimental study deals with the effect of modifying an Si-rich LM6 cast alloy by ball milling with Si/Al powder particulates in which alloying was conducted via semi-solid liquid processing....

Highly transparent leafhopper (Thaia rubiginosa) wings are self-decorated with embroidered ball-shaped proteinaceous brochosmoes as distinct anti-predator defenses. The non-sticky brochosomal coating serves as antireflective structures for camouflage in vegetated environments. Inspired by the leafhopper wings, this study reports a new type of reversible antireflection coating enabled by integrating self-assembly methodologies using a shape memory polymer. The resulting embroidered ball-like structure array establishes a refractive index transition on surface, and thereby behaves omnidirectional antireflective characteristics in a broadband visible light region. Interestingly, the highly transparent appearance can be instantly erased and recovered by submerging in common liquids, such as water and ethanol, or by applying contact pressures at ambient conditions. Furthermore, the reversibility and structure-shape effect on the antireflective characteristics are systematically evaluated in this study.

Compressive residual stress is the major aspect in the extension of the fatigue life of aeroengine components. In this study, a modified burnishing surface treatment and conventional shot peening process was used was proposed to improve surface integrity characteristics such as surface finish, hardness, and stable, advantageous compressive residual stress in turned Cylindrical Aluminum 2024Specimen. In burnishing process, a rolling rigid spherical HSS ball is pressed across an Aluminum 2024Specimen under definite fluid pressure generated by the hydraulic unit and also shot peening was carried out at a shot velocity of 300 m/s. This research examined the effect of burnishing treatment and shot peening process on beneficial compressive residual stresses.

Materials with high hardness are usually difficult to machine, and accomplishing precise and economical machining depends on all the cutting conditions. Appropriate tool geometry is one important aspect for the cutting process that can be optimized based on the machining parameters. In this study, the finite element simulation method was applied to analyze the effects of tool geometry on the cutting forces and tool temperature during the ball end milling of tool steel (AISI H13). Multi-objective optimization of the geometrical parameters was performed using the grey relational method, which gave a set of input parameters to obtain the minimum cutting forces and temperature. The findings of this work could be used as a basis for tool design. Experiments were conducted with mono-objective and multi-objective optimal geometries to validate the finite element analysis. The finite element and experimental results were both congruous with an error limit of 5%.

Ball-end milling is widely used in industrial applications, such as mold manufacturing and aerospace industries. One of many difficulties in milling research is the milling force, which is often cr...

The special features of thick combined electrospark coatings (СESC) formed on cylindrical 12Kh18N10T stainless steel samples are analyzed. The samples were carbonized with the help of combined electrospark alloying (CЕSA) using an Elitron-52A device and aluminized with the help of electrospark alloying (ESA) using an EIL-9 automated device at a discharge energy of Wd = 3.4 J. The coatings were deposited on the aluminized surfaces with the help of the T15K6 hard alloy using the same device at Wd = 0.9 and 3.4 J. The СESC roughness was reduced by means of ball rolling and applying a metal–polymer material (MPM) reinforced with the VK6 hard-alloy powder. A new technology to recover parts, such as rotation bodies, has been proposed for practical applications. It made it possible to form the СESC on 12Kh18N10T steel in the following sequence: CЕSA → ESA Al → ESA T15K6 → MPM (reinforced with VK6), with a thickness up to 1.5 mm, a continuity of 100%, a microhardness of ∼10 100–9500 MPa, and a roughness of Ra = 1.2 μm.

In present paper we show results of ball-on-disk wear experiment of MoS2 film deposited on Ti6Al4V substrate. The ball materials is aluminum oxide. The tests are performed for different surrounding temperature conditions: 20 oC, 200 oC and 350 oC. It is shown that depth of the wear groove increases with increasing surrounding temperature. A finite element modeling approach is next developed to mimic the experimental observations of ball-on-disk wear process. It is based on the assumption of steady state condition developed during short time scale at contact region. The steady state results can next be applied to long time scale in which wear process is numerically simulated. Model results are compared with experimentally obtained wear groove and show satisfactory agreement.

Textured surfaces offer the potential to promote friction and wear reduction by increasing the hydrodynamic pressure, fluid uptake, or acting as oil or debris reservoirs. However, texturing techniques often require additional manufacturing steps and costs, thus frequently being not economically feasible for real engineering applications. This experimental study aims at applying a fast laser texturing technique on curved surfaces for obtaining superior tribological performances. A femtosecond pulsed laser (Ti:Sapphire) and direct laser interference patterning (with a solid-state Nd:YAG laser) were used for manufacturing dimple and groove patterns on curved steel surfaces (ball samples). Tribological tests were carried out under elasto-hydrodynamic lubricated contact conditions varying slide-roll ratio using a ball-on-disk configuration. Furthermore, a specific interferometry technique for rough surfaces was used to measure the film thickness of smooth and textured surfaces. Smooth steel samples were used to obtain data for the reference surface. The results showed that dimples promoted friction reduction (up to 20%) compared to the reference smooth specimens, whereas grooves generally caused less beneficial or detrimental effects. In addition, dimples promoted the formation of full film lubrication conditions at lower speeds. This study demonstrates how fast texturing techniques could potentially be used for improving the tribological performance of bearings as well as other mechanical components utilised in several engineering applications.

The wet grinding of iron ore powder was investigated using a stirred media mill. In this study, the fitting degree of four cumulative undersize distribution functions was compared and the parameters of the four functions were discussed. It was concluded that the particle size distribution (PSD) of grinding products followed well with the Rosin Rammler Benne (RRB) function. In addition, operational parameters such as ball filling rates, stirrer tip speeds and grinding time have been investigated in terms of the width of PSD and specific energy input. The results indicated that slight differences in the width of PSD could be observed at different ball filling rates and stirrer tip speeds. It was also found that increasing the ball filling rate and stirrer tip speed could improve energy efficiency. Furthermore, an equation was established to predict PSD based on the characteristic particle size of the RRB function and size-energy model, which provided a sound fit to the grinding products under various grinding conditions

Stencil printing using solder paste material is one of the challenging processes in semiconductor assembly manufacturing. During evaluation of a semiconductor device, off-centered ball issue was encountered. The study aimed to mitigate the off-centered ball issue at stencil printing process by exploring the effect of different solder paste materials. Both solder paste materials were cured using the same reflow condition. However, solder paste material 1 (S1) resulted to cold solder joints while material 2 (S2) showed cured solder paste characteristic. With S2 material used in stencil printing, the off-centered ball occurrence was eventually eliminated. For future works, the solder paste material and configuration could be used for devices with similar requirement.

Presented the analysis of the deposition features of thick-layer combined electrospark coatings (CEC), which are formed on stainless steel 12X18H10T parts flat and curved surfaces. The coatings were applied to the surface of the samples in the form of a thick-walled cylindrical tube. The samples were carburized by the method of electrospark alloying (ESAC) on the Elitron-52A equipment and aluminized by the ESA method on the mechanized equipment EIL-9 at a discharge energy of Wp = 3.4 J. The aluminized surface was coated with electrodes made of T15K6 hard alloy at Wp = 0.9 and 3.4 J. The CEC roughness was reduced by rolling with a ball and applying a metal polymer material (MPM) reinforced with a VK6 hard alloy powder. In the next step, a ring was cut from the coated pipe, which was then cut into separate segments. Then, by surfaces plastic deformation (SPD), the segment was unbent on a press to the required size and mechanically attached to the parts subject to wear. A new technology for restoring flat and curved surfaces of parts has been proposed for practical application, which makes it possible to form a CEC on steel 12X18H10T with a thickness of up to 1.3 mm, a continuity of 100%, a microhardness of the order of 10500 - 11000 MPa and a roughness of Ra ~ 1.0 μm in the sequence: ESAC + ESA Al + ESA T15K6 + SPD + MPM (reinforced VK6) + PD. The developed technology has passed industrial testing during the repair of the stainless steel screw of the OGSh-631K-02 centrifuge, which is used at treatment facilities for the treatment of industrial and domestic wastewater.

Burnishing, a plastic deformation process, becomes more popular in satisfying the increasing demands of machine component performance and reliability. Thus, investigating the burnishing parameters in order to improve the product quality is especially crucial. The objective of this research is 10 studies on the effect of the burnishing process on fatigue life. Experimental work was carried out on a CNC lathe to study the effect of burnishing parameters, such as, burnishing feed and burnishing force, on some surface characteristics such as; surface roughness, microhardness, and reduction in diameter. Then the effects of the burnishing parameters on the fatigue life are investigated through a fatigue test. Burnishing force and burnishing feed play an important role in controlling the values of all surface characteristics and fatigue life. Optimum burnishing parameters are established to minimize roughness and/or maximize surface hardening and fatigue life. It is found that it is possible to get longer fatigue life for machined parts than the virgin material by setting the proper burnishing conditions. Longer fatigue life is achieved using burnishing force of 210 N and feed rate of 0.12inm/rev. In general the microhardness at the burnished surface increases as the force and feed rate increase. The distribution of microhardness along the depth below the burnished surface and its affected depth are directly proportional with the burnishing force. It is also clearly shown that the fatigue life of burnished materials cannot be determined or explained solely by surface roughness or microhardness.

It is importance to understand the accurate material mechanical property of local area with flaws in the structure integrity evaluation, and the plastic hardening induced by the welding or other processing would induce the change of the mechanical property of the local area in structures. To understand and obtain heterogeneous material mechanical properties in the welded joint or other local region in the core structure of nuclear power plants, a group tests of tensile work hardening and continuous ball indentation, combining with inversion analysis by using the finite element method, are used to obtain the local mechanical properties of nuclear grade 316L austenitic stainless steel, and an approach to obtain the stress–strain relationship of the stainless steel material during the plastic deformation stage under different elongations is developed based on the representative stress–strain method in this paper. The investigated results indicates that the related mechanical parameters of 316L austenitic stainless steel increase with different elongations, and the deviations of the yield strength and the tensile strength values are both within 6%. It provides a reasonable and effective method to obtain the actual material mechanical property of the local area in important structures.

The elastic compliance of the instrument (hardness tester) should be taken into account when determining the mechanical properties of materials by means of instrumented indentation with registration of indentation diagrams. The values of Young’s modulus of the tested materials significantly depend on the method for evaluating and accounting for elastic compliance. Therefore, the methods should be verified during instrumented indentation of materials with known but very different Young’s moduli. Successful experience in evaluating and accounting for elastic compliance of the instrument during the instrumented indentation of materials with a diamond pyramid has already been accumulated to date. This is reflected in the relevant standards. However, this experience cannot be applied to instrumented indentation with a steel ball or hard-metal ball without additional research and experimental verification. We propose a method for evaluating the elastic compliance of the hardness tester using the instrumented diagram of ball indentation based on the Hertz equation in the case of elastic contact of the ball with the plane. It is found that additional elastic deformations of the links of instrument are directly proportional to the indentation load; this dependence is typical of each instrument and the diameter of the ball does not affect it. This dependence allows one to take into account the elastic compliance of the instrument using software when registering and processing diagrams of ball indentation. Experiments to determine Young’s modulus and hardness by instrumented ball indentation of various materials (steel, aluminum alloy, magnesium alloy, and titanium alloy) using the known and proposed methods to account for the elastic compliance of the instrument are performed. The main criterion confirming the reliability of the method is the coincidence or proximity of the values ​​of Young’s modulus of the same material determined from the diagram of ball indentation and the diagram of tension of the sample. The advantages and disadvantages of the known and proposed methods are described. Practical recommendations for use of these methods are given.

To explore the effects of cutter path orientations on milling force, temperature, and surface integrity, end ball milling experiments of TC17 titanium alloy were accomplished derived from different cutter path orientations. The experiment results of milling force and temperature were obtained. Combining with the thermo-mechanical coupling, this paper analyzes the impact of the cutter path orientations on the surface roughness, surface topography, in-depth residual stress, microhardness distributions, and microstructure. The results indicate that the maximum milling force is 224.24 N and the temperature is 672°C under vertical downward milling path, while horizontal downward orientation provides the lowest cutting force of 81.12 N and temperature of 493°C. The surface topography of the four cutter path orientations is basin-like shape, and the minimum surface roughness of 1.128 µm is achieved under vertical upward mode. Moreover, the maximum compressive residual stress of −491.8 MPa and the maximum residual stress layer depth of 45 µm are acquired under vertical downward milling. The maximum microhardness can arrive at 390 HV0.025 under the vertical path. Additionally, the transformation of the material microstructure remains elongated, bent, and fractured. The maximum plastic deformation layer depth is 44 µm under vertical downward milling path.

application/pdf, Chemical Engineering Research and Design. 2020, 163, P.241-247

The effect of sub-zero treatments on dry sliding wear performance of Vanadis 6 tool steel was investigated by pin-ondisc tests against three counterpart types: alumina, 100Cr6 ball bearing steel, and CuSn6 bronze. The microstructure of the examined steel consists of tempered martensitic matrix with very small amounts of retained austenite, and three carbide types. Sub-zero treatments increase the carbides count. The hardness of the steel increases with increasing the austenitizing temperature but slightly decreases with the application of sub-zero treatments. Sub-zero treatments affect the wear performance of the Vanadis 6 steel when tempered at the secondary hardening peak as follows: almost no effect of this kind of treatment was detected when alumina was used as a counterpart but moderate amelioration was recorded when either 100Cr6 steel or CuSn6 bronze was used in the sliding couple. This behaviour is attributed to the combined effect of hardness variations and changes in population density of carbides, due to application of sub-zero treatment.

Sports engineering uses mathematics and physics to develop solutions to sporting problems. It involves the design and manufacture of sports equipment and facilities that can help maximise athletic performance. In order to develop fit-for-purpose products, it is necessary to consider the motions and movements of athletes. Professor Shinobu Sakai, Production Systems Engineering and Sciences, Komatsu University, Japan, is combining AI and neural networks (NN) to develop multifunctional and high-performance sports equipment and training machines that can benefit athletes and people across the globe who play sports. Believing that machines are subordinate to human beings, a key goal for Sakai is to augment the performance of sports players through the development of tools and machines. Some of the state-of-the-art tools and methodologies he uses in his work are high-resolution sensors, laser-speed sensors, MATLAB and general finite element method analysis software (ANSYS/LS-DYNA). He has developed a shuttlecock launching machine for badminton that can launch at high speed, a high-performance baseball pitching machine that is able to generate an efficient and objective gyro spin and has a high throwing performance and a pitching control method that uses AI.

In this study, the changes in the specific rate of breakage and breakage distribution function of the nepheline syenite sample were investigated by using alloy steel ball in five different sizes. Specific rate of breakage and breakage distribution function values were obtained from the particle size distributions acquired after the grinding periods. As a result of grinding tests, an increase in rate of breakage is observed due to the increase in ball diameter.

A new set of half-Heusler high-entropy alloys Ti2NiCoSn1-xSb1+x (x = 0.5, 1), with a valence electron count higher than 18, were investigated for thermoelectric applications. Vacuum arc melting was employed for synthesis. Atom probe analysis confirmed single-phase at atomic level. The alloys were subsequently ball milled for 1 h followed by spark plasma sintering for consolidation. In 1 h BM cases, the alloy with x = 0.5 exhibited a low lattice thermal conductivity of 2.48 Wm−1K−1, and a ZT of 0.29 at 873 K.

Cemented tungsten carbide balls (hereafter abbreviated as WC balls) are commonly applied in grinding of wasted tool steel for reuse owing to their extraordinary surface hardness (89.5 HRA) and high density (14.5 –14.9 g/cm3). In this study, grinding tests were conducted with WC balls on quartz ore to estimate comminution kinetics. Compared with steel balls, they provided high breakage rates, lower energy-specific breakage rates, and finer breakage distributions due to their high density. Simulations were conducted using an energy-based population balance model. The simulated results demonstrated that WC balls had higher throughput for coarse particles and lower energy efficiency for fine particles. Subsequently, a preliminary criterion for ball selection was established and indicated that WC balls could be substituted for steel balls to certain particle size ranges.

A process has been developed to press fuel briquettes from autumn leaves. It has been shown that a spherical shape of a briquette is optimal since even dense packing of balls provides air access to each individual ball. This is especially important in the initial phase of burning when briquettes touch each other and gain a certain temperature, because of the quality of burning increases. The technology of briquette pressing has been devised. We studied dispersion of particles of dry leaves of nutwood, maple, and oak after grinding and found that particle size distribution of powders of different leaves is not the same, and their bulk density is proportional to size with the highest content. A new method for pressing briquettes in a round closed matrix has been proposed. The difference of the method is in the fact that the process takes place at the creation of a scheme of all-embracing uniform compression with a spherical application of force and obtaining of a ball-shaped briquette in the final phase. The method makes it possible to compress ground leaves radially and evenly and thereby to ensure equal burning conditions for a briquette in a radial direction from any point on the periphery. We derived a mathematical model of the dependence of the density of dry briquettes on the bulk density of ground leaves and the degree of compression of a briquette. It has been shown that the bulk density of ground leaves (65%) has the greatest influence on the density of dry briquettes. An increase in the bulk density of ground leaves leads to an increase in the density of dry briquettes. The influence of the degree of compression of a briquette is much smaller (35%) but it is significant. Its increase leads to an increase in the density of dry briquettes. The density of dry briquettes was from 0.67 to 1.07g/cm3during studies. We proposed a design of a round closed matrix with a variable wall thickness, which makes it possible to reduce its metal consumption and cost by 20‒30%. It has been shown that it is expedient to use spherical briquettes of leaves as an alternative environmentally friendly fuel

Magnesium and magnesium-based alloys are considered ideal materials for implants in orthopedic treatment because their stiffness is close to that of human bones, and they can be absorbed gradually in the human organism. However, a major issue in their actual application is that the corrosion speed of Mg alloys is very high in aggressive environments such as the human fluids. In previous studies, many approaches have been attempted to enhance the corrosion resistance of Mg alloys. In this research, ball burnishing, a mechanical surface finishing process, is applied to improve the corrosion resistance of Mg alloys by changing its surface properties. The influence of the burnishing parameters on the corrosion resistance is investigated, and the corrosion of a treated and non-treated sample are compared. The test material used is the AZ31 Mg alloy. Firstly, a comprehensive review of the effect of burnishing on the final microstructures is reported. The influence of burnishing on grain size, work-hardened layer thickness, crystal orientation, and residual stress of the sample is discussed. Secondly, by conducting an especially designed long-term immersion test, the mass loss and surface evolution of each sample are evaluated. The experimental results indicate that, under proper processing conditions, the mass loss of the treated sample (8.8 mg) can be reduced to 36% of the non-treated one (24.2 mg). To elucidate the mechanism behind corrosion resistance enhancement by burnishing, the samples treated with the optimal processing parameters found are immersed in an aggressive solution for 1, 3, 5, and 7 days. From the results of mass loss measurement and surface structure characterization, it was found that, among pitting, general, and intergranular corrosion, pitting corrosion is the dominant corrosion mechanism. The holes enlarge because pits combine together, representing the greatest portion of mass loss. The main mechanism enhancing corrosion resistance is the size reduction of the grains on the surface induced by ball burnishing, causing a denser distribution of corrosion products in the immersion test. These corrosion products protect the material underneath accelerated corrosion.

Two floating object interact each other in a certain time when the initial separation distance of them is not greather than the radius. This interaction is caused by asymmetric deformation in the liquid-air boundary plane due to contact with spherical particles. Asymmetric deformation plane of the liquid-air boundary between the two spheres and outside the sphere results an attractive force. This force is experienced by two balls that interact in a certain period of time until they come close to each other and after contact they will bond and difficult to escape. The position of each ball is observed using a video camera with 25 fps specifications and processed using Python and OpenCV and obtained data on the position of the center of mass of the system at any time until both are in contact. From the equation of position to time, the acceleration value of the ball is obtained, so that the magnitude of the attractive force can be known. The attractive force of the object is varied with the density of the object.

Cutting tool material has a significant effect on the temperature of the tool during machining that determines the tool life and machining performance. The objective of this study is to analyze the effect of reducing the grain size of tool material on tool life and cutting performance in terms of tool temperature and cutting forces during ball end milling of tool steel AISI H13. Tool material was prepared from three different sizes of tungsten carbide (WC) powder mixed with cobalt binder and sintered to fabricate ball end mills. The thermo-mechanical properties of the tool material were determined to investigate the effect of grain size. Machining tests were conducted to evaluate the performance of the tool in terms of tool temperature, cutting forces, and tool wear. Results showing a decrease in tooltip temperature with the reduction in grain size of the tool are the main and novel findings of this paper. The same trend was followed in the case of cutting forces and wear.

Sintered tungsten carbide which has high hardness and high heat resistance, has been widely used in molds and dies. Research on the development of a cutting technology for sintered tungsten carbide (sintered WC-Co alloy) has been pursued mainly with the use of a turning process. We focused on building an efficient milling method for sintered tungsten carbide by using diamond-coated ball end tools, and have investigated their basic properties under specific cutting conditions. This study extends our previous work by enhancing cutting distance in the milling of sintered tungsten carbide, especially that with a “fine” WC grain. The surface roughness of cut workpieces is evaluated from the point of view of the quality of surface roughness. A series of cutting experiments under different cutting conditions were carried out, and the possibility of deriving a suitable cutting condition for the ball end milling of sintered tungsten carbide is discussed.

Different types of ferrimagnetic spinel nanoferrites having the general formula Li0.5Fe2.5O4, NiFe2O4, ZnFe2O4 and MnFe2O4 were synthesized by chemical sol-gel method. The synthesized nanoferrites ...

The present study investigates the cutting performance of ball nose end mills in high-speed dry-milling of a specific mold steel grade Super Plast ® 300 (SP300). The cutting performance was evaluated in terms of cutting length and tool wear. However, the milling tests were performed at finishing cutting conditions with a two fluted solid carbide ball nose end mill (diameter d is 16 mm, TiCN coating). Nevertheless, this investigation focuses mainly on the flank wear of ball nose end mill. It was found from the results that, the dominant wear mechanism was abrasive wear. Further, the flanks wear increases brutally at a specific cutting length or time. This is made when the coating layer vanished.

Many mechanical components require mirror–like surface appearance. When the application concerns the manufacturing of steel dies and moulds, material removal processes are the preferential choice in order to achieve the wanted dimensions and surface topography. In particular, ball milling is used in all those cases that require the machining of free form surfaces. When mirror-like surface appearance is in focus in such components, the final machining operations consists in a very shallow cut. The theoretical surface roughness (kinematic surface topography) that can be achieved in a finishing operation by ball end milling is orders of magnitude below the actual surface roughness. Beside runout and machine tool positioning errors, the quality of the cutting tools is a key factor in determining the surface topography. The combination of shallow depth of cut together with the finite size of the cutting edge radius of the tool are responsible for the occurrence of material smearing phenomena. Smearing, consisting in the accumulation of plastically deformed material over the surface, is particularly detrimental for the aesthetic functionality of machined components because it is responsible of the “foggy” appearance. In order to minimize the occurrence of the smeared material it is necessary to have a good understanding of the causes of the smearing formation process. The aim of this paper is the description and quantification of the smearing phenomena for ball end milling operations. The location of the smeared material is determined through SEM image analysis and related with the direction of the cutting speed and milling strategy. Subsequently the volume of the smeared material is quantified through a combination of confocal microscopy and SEM image analysis. Based on the volumetric analysis of the smeared material a new method for determining the Minimum Uncut Chip Thickness for the material is proposed.

Introduction. The paper considers the efficiency of significant technical and tactical elements of the game (catching and passing the ball) in a competitive environment. The purpose of the study is to examine the performance of catching and passing by qualified handball teams using the HandballTraning computer program. Review of the literature. The coaches do not sufficiently focus on catching and passing techniques during training and competition. As a result, there are few scientific and methodological publications related to these elements. The paper reviews scientific publications by V.Ya. Ignatieva, V.V. Ampleeva, O.V. Romenskaya, I.Yu. Bliznova, Nguen Khyu Chung, and M.V. Zhiiyar. Material and methods. The study involved analyzing the games of the Belarusian Handball Championship among the women’s Top League teams. Seven teams participating in the Championship were analyzed, and 28 games were considered. The results of the study. Analysis of the games has indicated that the teams at the bottom of the championship table make a large number of errors in the considered game elements. It is also worth noting that more mistakes are made during important and crucial games, which determine the team tournament standings. Besides, outside and half-right and left players showed a low level of catching and passing the ball. Conclusion. The technique of catching and passing the ball makes a significant contribution to the victory of the team. This technique should be given more attention during the training of teams of different ages and levels of skills. Moreover, the level of general, special, and technical training of a player affects the performance and efficiency of catching and passing the ball, which is also worth paying attention to in the training process. Keywords: handball, technique, tactics, catching and passing the ball, information, and communication technologies.

Bearings and chains are important industrial machine components used in wide range of heavy cyclical load applications. Main aim of this research work is to conduct a metallurgical investigation of failure analysis in failed bearing and chain parts. The failure analysis is carried out by chemical analysis, optical metallography, hardness analysis and scanning electron microscopy (SEM) analysis. In failed bearing inner race ways ridged marks were perceived due to electrical pitting and outer race ball groove worn-out on one side due to axial thrust load. Bearing balls have surface spalling due to contact fatigue. In chain failed bush multiple crack fronts are observed in longitudinal and circumferential. Crack geometry and fracture surface indicates failure through impact fatigue mode. The fracture surface indicated quasi cleavage fracture mode near the crack origins. The results in both investigations suggest that the major common causes of failures are due to over load, fatigue, wear and unsuitable material selection. MoS2coating, thin dense chromium coating and thin hard titanium nitride coating in all bearing components has been suggested to further improve the wear resistance and fatigue strength. Material SAE 8620 alloy steel for chain bush has been suggested to further improve life to withstand in the impact load conditions.

The surface roughness of a part produced plays a critical role in influencing functional properties such as corrosion behavior, fatigue strength, and wear resistance. Therefore, it is very important to improve the surface roughness of Al 7075−T6 material, which is frequently used in the aerospace industry. For this reason, the finishing process, used to improve the surface quality of the parts in an easy, inexpensive and chipless manner, has recently become an interesting research topic. In this study, a ball burnishing apparatus was designed and experiments were carried out at different parameters (force, feed rate and number of passes) for the purpose of improving the surface quality of the parts. For the design of the experiments, the Taguchi method was used, thus saving time and cost savings and reducing the number of experiments required. Variance analysis (ANOVA) was performed and the effect contribution of the parameters on surface quality were obtained. As a result of the experiments, it was found that force, feed rate and the number of passes were important factors.

This article evaluates the frictional performance of different bearing grease formulations in full rolling bearings and a ball-on-disc rig and subsequently assesses whether the ball-on-disc test results can be used to predict the grease performance in actual bearings. A selection of custom-made greases with systematically varied formulations as well as their base oils were tested. Bearing torque was measured in two different cylindrical roller thrust bearings and a thrust ball bearing. The same lubricants were tested with ball-on-disc tribometers, a mini traction machine (MTM) to measure friction and an optical elastohydrodynamic (EHD) rig to measure film thickness. Both lithium complex and diurea greases were observed to produce lower friction than their base oils within the low speed, low nominal lambda ratio region, whereas the greases and oils had the same friction at high nominal lambda ratio values. These relative trends were the same in full bearing and single-contact MTM tests. The reduction in friction was seen to be related to the level of film thickness enhancement provided by greases at lower speeds, which leads to an increase in the effective lambda ratio and hence reduced friction. By extracting the sliding torque component from the overall measured bearing torque, a plot of the friction coefficient against the effective lambda ratio was produced encompassing all bearing and single-contact tests and all lubricants and test conditions. This plot was seen to follow a general shape of a master Stribeck curve, indicating that the numerical values of the friction coefficient from ball-on-disc and full bearing tests overlap and can be related to each other using this approach over the range of conditions employed here. Thus, single-contact ball-on-disc tests can provide a fast and economical way of establishing the frictional performance of bearing greases in full bearings in terms of both relative performance rankings and quantitative values of bearing frictional power losses.

When St. Louis Cardinals pitcher Jordan Hicks [below] takes to the mound, batters tremble. He has the same form as any other pitcher in Major League Baseball (MLB) as he throws the ball, but his results are extraordinary. In the windup, he steps back on one leg, lifting his other leg to raise his center of gravity. Then he strides forward, his hips swiveling, while his throwing arm extends back nearly parallel to the ground. As his arm comes forward, the muscles and ligaments in his elbow absorb over 100 newton meters of torque.

The studies on mechanical treatments of layered alkali metal oxides are limited despite their diverse compositions/structures and potential for property tuning. In this work, we vibratory mill Cs0....

River sand, a non-renewable resource, is used in concrete as a fine aggregate, which is called filler material that fills the voids in concrete. This paper provides outcomes of compressive strength of concrete by using the ceramic ball as substitutes of fine aggregate that is compared with nominal mix concrete. Here, the ceramic ball is a commercial waste product produced in industries. The report includes the chemical test of the substitute, and it is having 73% of silica and 0.7% of alumina. Zone I and Zone II are selected as fineness modulus of sand for calculation of nominal mix design and partial mix design. As per the 28th-day compressive strength result, 30% replacement of fine aggregate gives a good result in comparison with a nominal strength of concrete, and hence, this waste material can be used as fine aggregate in concrete production. The main objective of this project is to find ways of disposing of waste products and to reduce the use of sand in the production of concrete as a fine aggregate.

A sphere is "the set of all points in three-dimensional space lying the same distance (the radius) from a given point (the centre)" (Encyclopedia Britannica Online). In terms of robotics, a spherical structure can freely rotate in any direction and all positions are stable. The shape of a sphere provides complete symmetry and a soft, safe, and friendly look without any sharp corners or protrusions, which is advantageous when a robotic device is dealing with people. The principle of mobility for a ball-shaped robot is usually based on the movement of the robot’s centre of gravity (cog) inside the spherical shell. The further the cog is from the centre of the ball, the greater the driving torque. Naturally, the ball diameter defines the maximum distance and the total mass limits the unbalanced mass being moved inside the ball. Often the available torque is quite modest compared to the total weight of the robot. An alternative method to create torque is based on the inertia of a rotating mass; inside the ball a rotating mass is accelerated and generates a counter-torque that drives the ball in the opposite direction. As the torque is a result of acceleration, the speed limit of the rotating mass sets a time limit for the applied torque. Hence this method can be used only for short periods and it also requires a means to decelerate the rotating mass back to rest. Inertia can, however, be used for orienting the ball when selecting the desired rolling direction. A large diameter for the robot helps to generate greater driving torque and, at the same time, resistive torque from environmental objects such as stones or doorsteps remains lower. Hence large size is a benefit, while the overall mass then tends to increase. Technological developments with robotic balls aim to maximise the driving torque while minimising the mass, providing steering capability, modifying sphere surface texture to achieve the desired terrain interaction, and generating autonomous functions through sensors and added intelligence. The greatest technical challenges are the robot’s limited off-road capability and the challenge of controllability. Step-climbing capability is defined by the radius of the ball and the ratio of the masses of the cover and the unbalanced mass. Typically, the static step-climbing capability is less than 0.25 x R. The possibility of rotation in all directions makes the control of the ball challenging. Ball oscillation during movement is difficult to handle and the control system requires powerful actuators to compensate the oscillations. While the propulsion system is located inside the ball it can be hermetically sealed to provide the best possible shield for the interior parts. The spherical shape maximises the

This study aims to explore the wear performance of maraging 18Ni-300 steel, fabricated via laser powder bed fusion (LPBF). The building direction dependence of wear resistance was investigated with various wear loads and in terms of ball-on-disk wear tests. The effect of direct aging heat treatment, i.e., aging without solution heat treatment, on the wear performance was investigated by comparing the wear rates of directly aged samples, followed by solution heat treatment. The effect of counterpart material on the wear performance of the maraging steel was studied using two counterpart materials of bearing steel and ZrO2 balls. When the bearing steel ball was used as the counterpart material, both the as-built and heat-treated maraging steel produced by the LPBF showed pronounced building direction dependence on their wear performance when the applied wear load was sufficiently high. However, when the ZrO2 ball was used as the counterpart material, isotropic wear resistance was reported. The maraging steel produced by the LPBF demonstrated excellent wear resistance, particularly when it was aging heat-treated and the counterpart material was ZrO2. The directly aged sample showed wear performance almost the same as the sample solution heat-treated and then aged, indicating that direct aging can be used as an alternative post heat treatment for tribological applications of the maraging steels produced by LPBF.

This paper presents the results of a study of the influence of preliminary heat treatment (pressure 10−3 MPa, temperature 390 K for 12 h) and ball milling (milling time 90 s, ball to powder ratio 160:30) of copper powder on the deposition process and coating properties (porosity and microhardness). It was shown that coatings sprayed from ball milled powders have increased porosity and microhardness compared to coatings obtained from the initial powders. Heat treatment of powders leads to an increase in the deposition efficiency of coating.

Burnishing is a surface finishing process, in which a very smooth surface finish is obtained by pressing a ball or roller against a machined workpiece. Additionally, owing to the surface plastic deformation caused by the movement of the hardened ball or roller, other surface properties such as hardness, fatigue life, and wear resistance can be improved. Burnishing force is one of the most important factors affecting the surface modification quality. However, methods for precisely monitoring and controlling the burnishing force are rarely investigated. In this research, a novel ball burnishing tool embedded with a load-cell and air-servo system was developed and fabricated for application to a CNC machining center. Using a specially designed control software, the burnishing force in the burnishing process was monitored in real time and controlled constantly and precisely by a force feedback system. Magnesium alloy AZ31 specimens were used to evaluate the performance of the developed system. The experiments were divided into two parts. In the first part, the effects of the processing parameters on the surface roughness were investigated. The results indicated that the surface roughness could be improved from Ra= 1.95 μm to Ra= 0.26 μm. In the second part, the effects of the burnishing parameters on the surface properties were investigated by conducting experiments using Taguchi’s orthogonal array. The results suggested that the burnishing force was the most significant factors affecting the surface hardness and grain size. The Vickers hardness could be increased from HV62 to HV149. The average grain size was reduced after the burnishing process, and a work-hardening layer thickness of 0.75 mm was achieved. X-ray diffraction results indicated that the crystal orientation was modified after burnishing, and the maximum measured compressed residual stress was 186.3 MPa in the tool feed direction and 87.8 MPa in the step over direction.

The ball vibroburnishing process of external cylindrical surfaces involves workpiece rotation, while a ball is being pressed and forced to roll on the cylindrical surface, simultaneously, achieving an axial vibration. Experimental research was designed in accordance with the principles of a full factorial experiment with six independent variables at two levels on the test pieces made of two distinct steels, the medium-carbon steel 1C45 and the low-carbon alloy steel 18CrMn4-4. The frequency and amplitude of the vibration motion, ball diameter, radial rolling force, workpiece peripheral speed, and feed rate were considered as process input factors. The process output parameters were the surface roughness parameter Ra, Vickers microhardness of the surface layer measured at a certain distance from the hardened surface, and the hardened layer thickness. Through mathematical processing of the experimental results, power type functions were determined as empirical models. Worth mentioning is the fact that significant influence is exerted by the vibration amplitude on the size of the surface roughness parameter Ra, as well as the vibration motion frequency on the surface layer Vickers microhardness. Keywords: Ball vibroburnishing, Asperity generation, Process input factors, Surface roughness, Surface layer Vickers microhardness, Hardened layer thickness