Hybrid Ball Research Articles

Mechanical properties and chemical microscopic characteristics of all-solid-waste composite cementitious materials prepared from phosphogypsum and granulated blast furnace slag

Industrial wastes, such as phosphogypsum, are characterized by high production and accumulation volumes, and significant pollution. A high-performance, all-solid waste, phosphogypsum-based composite cementitious material (PCCM) was developed by using a hybrid ball milling method and thermal activation to stimulate various industrial wastes. Optimization of rationing was analyzed using extreme variance, standard variance, and multiple regression models. The macro-engineering parameters of PCCM were evaluated through flexural and compressive tests. The mineralogical composition, functional groups, micro-morphology, and molecular structure of PCCM were examined through micro-testing. When the mass ratio of Ball milled calcined phosphogypsum (BCPG) to granulated blast furnace slag (GGBS) is 1.2:1, with a 4 % addition of calcium oxide and a water-cement ratio of 0.4, the 28-day flexural and compressive strengths, as well as the softening coefficients, of PCCM can reach 7.27 MPa, 40.1 MPa, and 0.922, respectively, closely matching the performance of C42.5 cement. Under the synergistic effects of the hydration reaction and an alkaline environment, the CaSO4 in the PCCM system hydrated and crystallized to produce gypsum-phase crystals, enhancing early strength properties by 60–174 %. As hydration continued, SO42- reacted with silicon and aluminum oxides, prompting secondary hydration of GGBS, and increasing AFt and C-(A)-S-H in the system. This research offers a new approach for the co-disposal and resource utilization of various solid wastes while identifying a cementitious material that can replace traditional cement in practical engineering applications.

Experience in using ceramics (Si3N4) as a material for rolling bearings of high-speed machines

To analyse the influence of the material of the rolling elements (steel and ceramics) of a high-speed ball bearing on the stresses in the contact zone of the rolling elements and rings and on friction losses in the contact zone.The study considers the outer ring of an angular contact ball bearing, which is loaded with additional centrifugal force. A nonstationary nonlinear volumetric interaction problem between the ball and the raceway was solved to determine the contact angle using the “DYNA” application package. The values of contact stresses for ceramic and steel rolling elements of a hybrid ball bearing are determined, as well as the value of deformations of balls and raceways based on Hertz's theory. The specific friction power deals with the differential slipping of the rolling elements relative to the raceway was estimated.Analysis of the behaviour of the bearings at different rotation speeds showed that at rotational speeds of more than 7000 rad/s, bearings with ceramic rolling elements of the considered standard size have advantages in contact strength. In addition, it was found out that at high rotational speeds, the friction power of the ceramic rolling elements is almost two times less than the friction power of the steel rolling elements.The research results relate to rolling ball bearings operating at a speed parameter dn of up to 4∙106 mm∙rpm and the analysis of friction losses is limited to losses from differential slip, which suggests further research of other components of losses.The study can justify the choice of bearing type (steel or ceramic rolling elements) depending on the operating speed and the lubrication and cooling system, which depends on the level of heat generation in the bearing.The work obtained original results of contact stresses and friction loss components for a certain type of bearing in a wide range of rotation speeds.

Vibration behavior of a 3D-printed hybrid polymer bearing with outer race defect

PurposeIn industry applications, polymer hybrid bearings have become widespread in recent years owing to the lack of lubricant requirements, particularly in areas requiring hygiene. The additive manufacturing method gives significant advantages to have complex machinery parts, and it has become popular in the industry in recent years. However, it has some inherent disadvantages caused by layered deposition/addition of the materials, and the probability of the localized defect is much higher than in the conventional manufacturing methods. This study aims to investigate the effect of the outer race defect on the characteristics of vibration and service lifetime of hybrid polymer ball bearings produced with the stereolithography (SLA) additive manufacturing method.Design/methodology/approachIn this study, polymer bearings’ races were produced with the additive manufacturing SLA method, and the outer race defect was analyzed with measured vibrations.FindingsThe results show that the additive manufacturing method suggests a practical solution for producing a polymer hybrid ball bearing. On the other hand, the hybrid three-dimensional-printed bearing, which has an outer race defect, worked for approximately 8 h without any problems under a 1 kg load and a shaft speed of around 1,000 rpm. In addition, when there is a defect in the outer and/or inner race of the ball bearing, the crest factor and kurtosis of the vibration are higher than faultless ball bearing, as expected.Originality/valueThis paper provides valuable information on the lifetime and vibration characteristics of polymer hybrid ball bearing produced by means of additive manufacturing.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-06-2023-0183/

Investigation of cryogenic friction and wear properties of Invar 36 alloy against Si3N4 ceramic balls

The existing materials for liquefied natural gas (LNG) cryogenic submersible pump bearings are very susceptible to wear and failure in LNG environments where oil lubricants and greases are ineffective, posing a major hazard to the safety of LNG storage and transportation. Therefore, searching for a type of material with excellent cryogenic tribological properties for improving the life of LNG bearings has become a huge challenge for researchers. Invar 36 alloy, as a low expansion nickel-titanium alloy, is used in control instruments, moulds, laser control equipment, and materials of LNG transport hull at temperatures below −162 °C. However, there is a lack of research data in the field of bearings. Currently, the Si3N4 ceramic balls are widely used in ceramic hybrid ball bearings and exhibit excellent tribological properties. In this work, the tribological performance of Invar 36 alloy is mainly investigated against Si3N4 ceramic ball under extremely cryogenic and dry conditions using the modified ball-on-disk tribometer with a cryogenic module, with temperatures as low as −196 °C. All experiments are performed at loads of 0.5 N, 1 N, 1.5 N, and 2 N, and at temperatures of 20 °C, 0 °C, −78 °C, and −196 °C, respectively. The experimental results show that the coefficient of friction (COF) and wear rate decrease with temperature and load, with a minimum value of −196 °C. The Invar 36 alloy exhibits excellent tribological properties, whose COF decreases gradually from 20 °C to −78 °C. However, as the temperature drops to −196 °C, the COF decreases abruptly, reaching a minimum value at −196 °C. On the contrary, the COF gradually increases with load. In addition, a commercial bearing grade material (G95Cr18 steel) is tested and compared under the same conditions, proving that Invar 36 alloy exhibits better tribological properties than G95Cr18 steel, with a wear rate 55.43% lower than G95Cr18 steel at −196 °C. Further simulation comparisons demonstrate that, due to its extremely low coefficient of thermal expansion, Invar 36 alloy exhibits higher toughness and strength than G95Cr18 steel under cryogenic conditions. This study complements the tribological data of Invar 36 alloy and G95Cr18 steel against Si3N4 ceramic balls under different temperatures and loads and provides important theoretical guidance and technical support for the bearings’ future development of LNG cryogenic submersible pump.

Impact of low inner ring waviness orders on hybrid ball bearing under high speeds

Deep groove ball bearings (DGBB) are widely used in rotating equipment in many fields among which we have electric vehicle Powerpack, so very demanding in terms of noise and vibration. Geometrical design, clearance, component material, and lubricant properties influence vibratory behavior and bearing life cycle. In rotating machines, bearings are acting as friction reducers to allow a smooth rotation but are also exciters inducing vibrations due to the rotation of ball set, even in the case of a theoretical perfect bearing. Bearing performance depends highly on contact surface quality (ring races and balls surface). In a ball bearing, contact surface quality results from several manufacturing processes (heat treatment, turning, grinding, honing and assembly) and directly affects the noise and vibration levels generated by the bearing in the application. Also, component materials and hardness will affect the contact forces between balls and rings path on rotating bearings. Hybrid bearings are known for their performance when operating under high rotation speeds. In this article, inner and outer ring low waviness orders are studied on Hybrid Deep Groove Ball Bearings (DGBB). Both numerical model and, experimental tests were carried out to study the effect of rings waviness on hybrid bearing under high rotation speed.

Temperature and Vibration Condition Monitoring of a Polymer Hybrid Ball Bearing

Temperature and Vibration Condition Monitoring of a Polymer Hybrid Ball Bearing

Analysis of the effect of friction of hybrid ball bearings on grease evaporation in cold compressors

Bearings are the essential part of the cold compressor rotor system, which has a great influence on the operation of cold compressor. Hybrid ball bearing has been successfully applied in cold compressors with the lubrication of grease. With the high-speed rotation of the cold compressor, the bearing will be affected by the axial thrust of the impeller, which will cause friction, and the grease will be impacted by the frictional heat. To understand the influence of frictional heat on grease evaporation, it is important to study the bearing heat generation. In this article, the application of grease-lubricated hybrid ball bearings in cold compressors was introduced. Based on the parameters of a successfully applied impeller and a ball bearing of the cold compressor, the axial thrust of impeller was calculated, and a bearing frictional heat generation model was proposed, which considered the dynamic change of the axial thrust of the cold compressor impeller. The heat generation and temperature of the bearing was analyzed and calculated using the proposed model. According to the results of the calculation and practical experience, a test was performed on high-speed greases, and the adding amount of grease was estimated with reference to the bearing temperature.

Empirical correlation of heat generation in hybrid ball bearings, depending on the operational conditions in the aero-engine rotor supports

Modern gas turbine bearings operate at high rotational speeds. Their speed index reaches dmn=3…3, 5-106 mmrpm, where dm = bearing mean diameter, and n = rotational speed. At high speeds, significant heat is generated in conventional steel bearings, and substantial cooling oil consumption may be required. A promising solution to this problem is using hybrid bearings with steel rings and ceramic rolling elements. Due to ceramic’s relatively small coefficient of thermal expansion, hybrid bearings retain radial clearance in a wide temperature range. Hybrid ball bearings, with an inner diameter of 130mm and 150mm, were tested in the bearings test rigs at the Central Institute of Aviation Motors (CIAM). From these tests, an empirical method for determining the thermal state of the bearings was developed. The calculated values correspond well with the experimental data presented in the extant literature.

Real-Time Dynamics Modeling of Cryogenic Ball Bearings With Thermal Coupling

Abstract Real-time dynamic modeling of cryogenic ball bearings, where the rotating inner race accelerates to the operating speed, is based on integration of classical differential equations of motion of bearing elements, when experimentally measured ball/race traction behavior is used to compute the imposed acceleration on the rolling elements. The dynamic performance simulation provides a realistic coupling between traction behavior in the ball-to-race contacts and dynamics of bearing element motion as the bearing goes through the transient speed variation. However, due to vastly different mechanical and thermal time scales, heat generation in the bearing is time-averaged over a relatively large thermal time-step to model temperature fields as a step change, while the bearing motion is simulated in real-time. The emphasis is on dynamic modeling with thermal coupling in a static sense. Under stable conditions, the step change in temperature field converges to operating value as the bearing approaches a dynamic steady-state condition, which demonstrates acceptable significance of the dynamic simulation with coupled thermal interactions. Both all steel and hybrid ball bearings for liquid oxygen (LOX) turbo pump applications are modeled. Bearing performance simulations are closely modeled over experimental time cycles in both transient and steady-state domains. Steady-state solutions are shown to be independent of initial conditions to demonstrate acceptable convergence of time domain integrations. Model predictions of heat transferred to circulating LOX is within the range of variation in experimental data. Parametric evaluation of bearing performance as a function of operating conditions demonstrate that while the ball/race contact stress is higher in a hybrid bearing, contact heat generation is significantly lower in comparison with that in the all steel bearings.

Rolling Friction of Hybrid Ceramic–Steel Pairs under Different Lubrication Conditions

We present the results of a study of a model rolling tribosystem with ceramic balls making a point “ceramic–steel” contact with a flat movable thrust ring under dry rolling friction and under lubrication. The results of laboratory tribotechnical tests enabled a comparative assessment of the wear rate of hybrid “steel–ceramics–steel” model rolling tribosystems with balls made of different ceramic materials. We ranked the studied material in terms of efficiency and improved the technology of rolling elements for hybrid ball bearings. We manufactured prototype hybrid bearings that undergo bench durability tests.

Life Model Enhancement for Hybrid Ball Bearings

Based on experimental life data on silicon nitride balls, the stress-life exponent and life constant in the generalized ball life equation, developed earlier, are modified to better simulate the fatigue life of silicon nitride balls in hybrid ball bearings. The modified ball life equation is then integrated with generalized life equations for the outer and inner races to model the life of a complete hybrid ball bearing. It is found that in view of the relatively high stress-life exponent for silicon nitride balls, computation of hybrid bearing life with infinite ball life may not be unreasonable. Model predictions are in good agreement with limited available experimental life data on hybrid ball bearings.

Experimental and Numerical Investigation of the Outer Ring Cooling Concept in a Hybrid and in an All-Steel Ball Bearing Used in Aero-Engines by the Introduction of a Helical Duct

Rolling element bearings for aero engine applications have to withstand very challenging operating conditions because of the high thermal impact due to elevated rotational speeds and loads. The high rate of heat generation in the bearing has to be sustained by the materials, and in the absence of lubrication these will fail within seconds. For this reason, aero engine bearings have to be lubricated and cooled by a continuous oil stream. When the oil has reached the outer ring it has already been heated up, thus its capability to remove extra heat from the outer ring is considerably reduced. Increasing the mass flow of oil to the bearing is not a solution since excess oil quantity would cause high parasitic losses (churning) in the bearing chamber and also increase the demands in the oil system for oil storage, scavenging, cooling, hardware weight, etc. A method has been developed for actively cooling the outer ring of the bearing. The idea behind the outer ring cooling concept was adopted from fins that are used for cooling electronic devices. A spiral groove engraved in the outer ring material of the bearing would function as a fin body with oil instead of air as the cooling medium. The method was first evaluated in an all steel ball bearing and the results were a 50% reduction in the lubricating oil flow with an additional reduction in heat generation by more than 25%. It was then applied on a Hybrid ball bearing of the same size and the former results were reconfirmed. Hybrid bearings are a combination of steel made parts, like the outer ring, the inner ring, and the cage and of ceramic rolling elements. This paper describes the work done to-date as a follow up of the work described in, and demonstrates the potential of the outer ring cooling for a bearing. Friction loss coefficient, Nusselt number, and efficiency correlations have been developed on the basis of the test results and have been compared to correlations from other authors. Computational Fluid Dynamics (CFD) analysis with ANSYS CFX has been used to verify test results and also for parametric studies.

Vibration based diagnostic of cracks in hybrid ball bearings

The paper presents a vibration based diagnostic system to detect cracks in balls of hybrid ball bearings. The diagnostic system based on a Bayesian Classifier. It is shown that it is able to separate healthy bearings from damaged balls and races. The system is tested with measurement data from a bearing test bench in different operating points of the bearing. Moreover, a novelty detection approach based on a support vector machine is presented.

Identification of Bearing Defects in Hybrid Thrust Ball Bearings by Vibration Analysis

Hybrid ball bearings, consisting of metallic washers in combination with ceramic bearing balls, feature a variety of significant advantages in comparison to standard steel bearings, including mechanical properties and reduced friction during operation. Key aspects for a successful operation are a prevention of defects of both balls and washers, as well as the knowledge of critical and optimal operation parameters. This relevant information can be obtained through test rig trials, where vibration analysis has found to be a versatile and efficient tool for the characterization of the operational status. In this contribution, hybrid thrust ball bearings with Si3N4 balls are investigated. After an introduction of defined damages in different parts of the bearing, test rig trials were conducted, and the vibration behavior during operation was compared to new, unused bearings. The characteristic vibrational frequencies, obtained through a variety of software-based filter and analysis algorithms, were correlated with materialographic investigations of failed bearings. The proposed method was shown to yield valuable information about damage morphologies and, subsequently, about the status of the bearing during operation.

Friction Torque Measurement in Partial Hybrid S-C Angular Contact Ball Bearings

To monitor the friction torque evolution in tandems of angular contact ball bearings, a new testing device is developed. New partial hybrid bearings from 7206C series are obtained by combining 8 steel balls with 4 silicon nitride balls of the same diameter equally spaced in the cage, these bearings being denoted hereafter as 8S-4C type. For comparison, tests are carried-out also on conventional all-steel bearings and hybrid bearings with all the steel balls replaced by silicon nitride balls. The equilibrium temperature of the all-steel, hybrid and 8S-4C ball bearings is determined by tests. At high speed and light axial load, the 8S-4C ball bearings withstand to an oil shut-off test of one minute, while the similar all-steel bearings seized. The 8S-4C partial hybrid ball bearings can be an advantageous solution comparative to more expensive all hybrid bearings, avoiding the scuffing due to the self-healing effect induced by the higher hardness of the silicon nitride balls.

Monitoring of distributed defects on HSM spindle bearings

The High Speed Machining (HSM) spindle is one of the most critical bearing applications, because it requires both high speed and high power in order to obtain high quality and productivity. Therefore, bearing condition monitoring is important. Firstly, this paper presents a real and typical spindle life example. The vibration signals and their evolution are discussed in relation to the bearing failures that have been observed after the spindle disassembly. Cleavage notably occurred on the ceramic balls of the hybrid ball bearing. Damaged balls and their chippings then damaged uniformly the rings raceways on the whole circumference. As a consequence, a noise component increases in vibration signal due to the worsening of the ball-race contact during the rolling process. In a second section, the noise component produced by bearing condition is studied and characterized. The frequency spectrum distribution is briefly discussed in relation to a signal model. It is demonstrated by Pearson’s test that the distribution follows a Gaussian law all along the spindle life. Besides, it evolves with bearing condition. Thus, a new criterion, called SBN (Spindle Bearing Noise), is proposed for the monitoring of the uniformly distributed defect. A specific monitoring device was also developed in order to collect real industrial data during the spindle lifetime. Vibration signals are used in order to evaluate the criterion relevancy by comparison with the current best practices. The analyses through three required conditions for bearing condition monitoring and based on three spindles signals, have shown some good results.

Critical Flaw Size in Silicon Nitride Ball Bearings

Silicon nitride balls, used in hybrid ball bearings, are susceptible to failure from fatigue spalls emanating from preexisting partial cone cracks that can grow under rolling contact fatigue (RCF). We simulate the range of three-dimensional nonplanar surface flaw geometries subject to RCF to calculate mixed mode stress intensity factors to determine the critical flaw size (CFS) or the largest allowable flaw that does not grow under service conditions. The cost of nondestructive evaluation (NDE) methods for silicon nitride balls scales exponentially with decreasing CFS and increasing ball diameter and can become a significant fraction of the overall manufacturing cost. Stress intensity factor variability is analyzed for variations of the location and orientation of the load relative to the crack, the geometry of load, and full-slip traction. The modeling techniques utilized in the creation of a three-dimensional (3D) finite element analysis (FEA) model is discussed and the maximum tensile contact periphery stress is examined for effect on crack driving force under RCF. The CFS results are presented as a function of Hertzian contact stress, traction magnitude, and crack size.

Uncertainty analysis for rolling contact fatigue failure probability of silicon nitride ball bearings

Uncertainty analysis and parametric studies are presented for estimating the fatigue failure probability of surface cracks in silicon nitride ball bearings subjected to rolling contact fatigue. Uncertainty quantification of input parameters are presented first based on experimental data, inspection capability, and geometric reasoning. Surrogate models for equivalent stress intensity factors are then used for uncertainty propagation, which are built upon high fidelity finite element modeling with half-penny-shaped surface cracks. Instead of black-box type surrogate modeling, physical observations are employed to decompose the high dimensional surrogate model into multiple one-dimensional models. The cross-validation technique is used to find the best surrogate that has the smallest prediction variance. The probability of failure is estimated using Monte Carlo simulation and surrogate models. The parametric studies show that reducing the maximum crack size (by limiting inspection threshold) and increasing the fatigue threshold (by improving fracture toughness of a material) are the most effective ways of reducing the probability of failure. For example, decreasing the maximum crack size by 4.4% and increasing the lowest fracture threshold by 2.8% results in the reduction of probability of failure by 40%. Ball survivability increases with decreasing ball diameter, for a given peak Hertzian stress. In order to apply the current study to hybrid ball bearing design, the survivability results are generalized through non-dimensionalization.

Cutting force integration at the CAM stage in the high-speed milling of complex surfaces

High-speed milling (HSM) technology has been rapidly absorbed by the die and mould manufacturing industry and by the aeronautical sector. The new cutting tools can withstand much higher machining conditions than 10 years ago. Last-generation, high-speed machining centres are equipped with high-frequency spindles with hybrid ball bearings, leading to rotational speeds over 18 000 r/min. Multiaxis machining can be effectively carried out in five-axis machining centres of different architecture. These new and advanced machining processes are much more complex and provide the final component with a higher added value. However, the reliability of the whole process must be reconsidered, since collisions, tool breakage and dynamic problems can result in expensive machine repairs and some parts may be impossible to recover. In order both to minimize the above problems and increase machining performance, a new machining approach based on two ideas has been developed. First, virtual verification of the NC programs, avoiding collisions or tool – machine interferences that may arise during the machining of complex surfaces. Second, toolpath optimization in the machining of complex surfaces. For this purpose a utility to estimate the cutting forces before machining has been integrated in the computer-aided manufacturing (CAM) planning process stage. The estimation of cutting force uses a semi-empirical approach, in which the pair tool/material is characterized by six specific cutting force coefficients. The force model introduces the effect of part slope in calculations, just with tool geometry, cutting conditions, and material. The value of cutting force is used as an estimator for selecting the best cutting toolpaths for a complex surface. In this way a more accurate, better-finished surface is machined, and a reduced tool wear is withstood. The global CAM process is applied to three examples that are discussed. They are representative of a highly efficient high-speed process, without any risks of tool collisions, surface machined errors and low cutting forces.

Materials failure mechanisms of hybrid ball bearings with silicon nitride balls

A modified Shell four-ball apparatus was used to determine failure mechanisms and estimate time to failure of hybrid ball bearings using silicon nitride and zirconia balls. The machine was set up to hold a hybrid bearing containing three ceramic balls, instead of the usual 14 in order to increase contact pressure. Five kinds of silicon nitride ceramics, which differed in terms of surface roughness, porosity as well as the amount and chemical composition of additives were investigated. The goal of this study was to establish a quality criterion for silicon nitride for industrial use in hybrid ball bearings. Lifetime and failure mechanisms varied between the five bearings with silicon nitride balls and a dependance was found on the porosity and chemical composition of the materials, whereas surface roughness did not seem to influence their performance.