Roller Race Research Articles

Measuring the Roller Skew Angle in the Loading Zone of a Cylindrical Roller Bearing With Strain Gauges for Long-Term Monitoring

Abstract Roller skew in roller bearings can cause heat generation in roller–race and roller–rib contacts, thus reducing bearing life. It is significant to obtain the roller skew angle in situ for guiding the bearing design and adjusting the operating conditions. In this study, a method for measuring the roller skew angle in the loading zone of a cylindrical roller bearing with strain gauges is presented. The measurement principle is that the roller skew angle is related to the movement of the contact line between the roller and raceway. The strain gauge array on the outer surface of the outer ring shows temporally separated responses when roller skew occurs. An experimental system is developed to validate the effectiveness of the proposed method for cylindrical roller bearing measurements. A laser measurement system is incorporated into the experimental system to detect the horizontal displacement of the reflected spot using a high-speed camera, which is then converted into the roller skew angle. The calculated roller skew angle from the time shift of the strain response agrees well with the value of a specially modified roller independently measured with the laser detection system. Compared with other measurement methods, the proposed method provides a potential way to achieve the nondestructive measurement of the roller skew angle in actual service for long-term purposes.

Tribodynamic Modelling of High-Speed Rolling Element Bearings in Flexible Multi-Body Environments

This study presents a new flexible dynamic model for drive systems comprising lubricated bearings operating under conditions representative of electrified vehicle powertrains. The multi-physics approach importantly accounts for the tribological phenomena at the roller–race conjunction and models their effect on shaft-bearing system dynamics. This is achieved by embedding a non-linear lubricated bearing model within a flexible system level model; this is something which has not, to the authors’ knowledge, been reported on hitherto. The elastohydrodynamic (EHL) film is shown to increase contact deflection, leading to increased contact forces and total bearing stiffness as rotational speeds increase. Results show that for a 68 Nm hub motor operating up to 21,000 rpm, the input bearing EHL film reaches a thickness of 4.15 μm. The lubricant entrainment increases the roller–race contact deflection, causing the contact stiffness to increase non-linearly with speed. The contribution of the lubricant film leads to a 16.6% greater bearing stiffness at 21,000 rpm when compared to conventional dry-bearing modelling methods used in current multi-body dynamic software. This new methodology leads to more accurate dynamic response of high-speed systems necessary for the next generation of electrified vehicles.

Analytical Investigation of Roller Skew and Tilt in a Spherical Roller Bearing

Abstract The objective of this investigation was to analytically investigate the performance of a spherical roller bearing (SRB) operating under various loading and speed combinations. In order to achieve the objective, a full six degrees-of-freedom SRB dynamic model was developed. The model was corroborated with results in the open literature. An adaptive slicing method was developed to optimize the accuracy and computational effort of the roller force, skew, and tilt calculations. A comprehensive roller–race contact analysis in terms of slip velocity and contact area was then carried out to identify how bearing load and inner race (IR) speed variations change slip velocity and skew at the roller–race contact. The results from this investigation demonstrate that roller skew increases with IR speed, while the roller tilt remains relatively constant. The IR speed and roller slip velocity correlate well, which causes the traction force to increase and therefore produce greater skew. Skew and tilt angles also increase with applied axial load. However, at a certain load, the skew angle begins to decrease.

Ectoparasite Habrobracon Hebetor Say Is an Efficient Biological Control Agent of Lepidopteran Pests

Ectoparasite Habrobracon hebetor Say is one of the most widely used biological controllers in biological plant protection against a number of harmful lepidopterans, including especially dangerous pests of corn, soy, fruit and vegetable crops. As a result of research conducted in 2017, food specialization and parasitic activity of three different populations of H.hebetor were studied. Two races have been identified for mass rearing and application: pyralid and leaf roller (against corn moth, bean pod borer, apple and plum moths), and pyralid owl-moth (against cotton moth, corn borer, bean pod borer and boxwood moth). As a result of studies of biological features and trophic needs, it has been determined that caterpillars of mill moth (Ephestia cuhniellia Zella) should be used as a host insect for laboratory cultivation of the stock population of the Habrobracon pyralid and leaf roller race (race No. 1). For the introduced from South Kazakhstan the H.hebetor pyralid and noctuid race the most productive rearing is on the caterpillars of large bee moth (Galleria mellonela L.). Optimal temperature for rearing of both races is 26-28 ° C, relative air humidity is 70% and photoperiod is not less than 16 hours. It has been noticed that before laying eggs on the host’s caterpillars, the Habrobracon female preliminarily paralyzes the victim, piercing the sheath with ovipositor. As a result, the caterpillar stops eating and is immobilized. In 3-4 days larvae hatch out of the laid on the caterpillar eggs. The larvae feed on the contents of the caterpillars for 4-5 days, then pupate and after 6-8 days an adult insect leaves the cocoon. The development of one generation lasts 13-16 days, one cocoon includes one parasite. 1,000 large bee moth caterpillars used for infection provide on average 5.8-6.0 thousand cocoons, of which an average of 4.5-4.7 thousand parasites fly out.

Influence of roller defect and coupled roller–inner–outer race defects on the performance of cylindrical roller bearing

In the present study, a novel mathematical model is developed for the deformation between roller and races of cylindrical roller bearing using the effect of tilting and skewing of roller due to thrust load, radial deflection due to normal load, radial internal gap, and individual defect on roller as well as coupled defect on all races and roller. Also, novel roller defect function is proposed for the preparation of simultaneous nonlinear equations. MATLAB is used to solve nonlinear equations for equilibrium conditions of deflection, radial load, thrust load, moment in plane, and total roller loading. However, waviness due to surface irregularity on both races as well as out-of-balance assembly is not considered in this analysis. The bearing is analyzed for individual roller defect as well as coupled races–roller defects to identify the behavior of bearing under speed-varying conditions. The equation of motion is solved through Newmark-β technique. Defect segment of roller consecutively in contact with both races results in higher acceleration. Time-to-impact concept is utilized for the analysis. The acceleration during roller–race defect interaction with intermittent connection is applied in the model for observation. The outcomes are shown in the time domain, orbit, and envelope analysis, which describe the complexity of the system with speed variation for roller defect and coupled roller–inner–outer race defects. The periodic, quasi-periodic, and chaotic phenomena are observed for roller and coupled defects. Simulated frequencies for all defects are compared with theoretical frequencies to validate the model.

Dynamic model of a cylindrical roller on a rough surface, with applications to wind turbine gearbox planetary bearings

Wind turbines of larger power ratings have become increasingly prevalent in recent years, improving the viability of wind energy as a sustainable energy source. However, these large wind turbines have been subjected to higher rates of failure of the wind turbine gearbox, resulting in larger downtime of operation and an increase in cost due to repairs. These failures most frequently initiate in the gearbox’s bearings, especially in the planetary bearings of the planetary stage and high-speed bearings. Currently, most of the research on the detection of planetary bearing faults only addresses the case of localised faults in the outer bearing race, while fewer research considering the detection of distributed bearing faults. The research that does consider distributed bearing faults relies on techniques – such as machine learning for the identification of faulty bearings – that do not account much for the underlying physics of the bearing. In this paper, a model is developed to simulate and analyse the dynamic interaction of a planetary bearing in the presence of surface roughness, which can be used to represent a distributed fault. The model presented uses random vibration theory for simulating the response of the planet bearing induced by distributed faults. The input of the model considers statistical expressions of the roughness geometry using multiple parallel tracks. Numerical simulation of the random vibration of the model is performed using 16 tracks, and the power spectral density of the radial deflection of the roller and the roller–race contact force is determined. The results of the simulation with the multi-track model show that a single-track model significantly overestimates the power spectral densities, and also suggests the stiffness of the bearing race is too high to have an effect on the roller dynamics for a planet bearing.

Subcritical vibrations of a large flexible rotor efficiently reduced by modifying the bearing inner ring roundness profile

Abstract Undesired vibration of a rotor is harmful for industrial processes and decreases the machine lifetime. In industrial processes, large rotors are commonly operated below the critical speed. In the subcritical speed range, the bearings are an important excitation source of vibration. The bearing inner ring based excitation is observed at a frequency, which is the rotor rotating frequency multiplied by the number of undulations in the roundness profile of the roller race of the bearing inner ring. Subcritical resonance occurs, when the bearing excitation frequency equals the natural frequency of the rotor system. The present study investigates the effect of the bearing inner ring roundness profile on the subcritical vibrations of a flexible rotor. The roundness profile of the bearing inner ring was measured, while installed on the rotor shaft. The roundness profile was modified to five different geometries to investigate different excitation cases. Finally, the roundness error of the inner ring was minimized. The rotor subcritical vibration was measured with each bearing inner ring geometry in the horizontal and vertical directions. The analysis was focused on the 2nd, 3rd and 4th harmonic vibration components, occurring at 1/2, 1/3 and 1/4 of the critical rotational speed. The results clearly suggest that the roundness profile of the roller race of the bearing inner ring affects the rotor subcritical vibration significantly. The increased waviness components of the bearing inner ring roundness profile increased the corresponding subcritical vibration amplitude. Minimizing the roundness error decreased the subcritical vibration substantially.

Nonlinear vibration prediction of cylindrical roller bearing rotor system modeling for localized defect at inner race with finite element approach

In this paper, an analytical model is proposed to study the behavior of defective bearing and rotor system. An overhung rotor system and defective roller bearing are considered for the study. Rotor is considered with unbalanced mass and bearing is taken as the cylindrical roller bearing having localized surface defect. To analyze all the system components’ effect at one node, finite element method is used to predict exact system vibrations. Euler–Bernoulli’s beam element is used to discretize the shaft. Gyroscopic effect of overhung rotor is also taken into account and governing equations of motion have been modified according to our system. Hertz contact stress theory is used for every roller–race contact to calculate the overall nonlinear bearing force. Governing differential equation is solved by Newmark-β time integration method. Nonlinear matrix equation, which is generated at each time-step in Newmark’s method, is solved by Broyden’s method. Results for defective bearing are obtained and plotted in the time and frequency domain. Poincare map has been plotted to view the system’s minimum stability time. An experiment has been carried out to validate the proposed analysis work. In this paper, it has been shown how rotor dynamic analysis can be achieved numerically with minimum calculations.

Nonlinear Dynamic Response of Cylindrical Roller Bearing–Rotor System with 9 Degree of Freedom Model Having a Combined Localized Defect at Inner–Outer Races of Bearing

ABSTRACTThis article presents a nonlinear dynamic model for a cylindrical roller bearing–rotor system with interaction forces between the inner race, outer race, and roller. Roller–race contacts are modeled predicting nonlinear stiffness (Hertz contact theory) and nonlinear damping for a rotor–cylindrical roller bearing system. Here a shaft–rotor bearing system is modeled with 9 degrees of freedom with one defect on the inner race and one defect on the outer race for a case of combined localized defects. In the mathematical formulation, contacts between rolling elements and inner and outer races are considered as nonlinear springs and nonlinear damping is taken into consideration. Contact force calculations with nonlinearity are solved using the Newton-Raphson method for n unknown nonlinear simultaneous equation. The Newmark-β implicit integration technique coupled with the Newton-Raphson method is used to solve the differential equations. The results are obtained in the form of a time domain plot, frequency domain plot, and phase plot/Poincare map. The validity of the proposed model is compared with experimental results. A bifurcation graph of speed versus peak amplitude predicts the behavior of the system.

New strategy for testing new high nitrogen bearing steel for offshore wind turbines

This article presents some results obtained during the first stage of the European Union project titled “STEELWIND,” a part of which has been dedicated to roller–race contact dynamics. Contact has been modeled qualitatively using viscous-elastic friction, in the sliding regions, and hysteresis-modified Hertzian pressure in the whole contact zone. Slip and stick areas are detected within the contact area where the sliding velocity may have both opposite directions parallel to the entraining velocity. Considering the complexity of the hybrid rolling–sliding–sticking conditions, the developed model, although simplified, can be helpful to develop a sliding–rolling test by means of a standard reciprocator stand, where nonsymmetrical and mobile configurations of the testing race samples are introduced.

On the Lubricating Mechanism of Roller Skew in Cylindrical Roller Bearings

Skewing is the motion of a roller as it turns about an axis normal to the roller–race interface in cylindrical roller bearings. With a special coordinate transformation technique, complete numerical solutions for the finite line elastohydrodynamic lubrication (EHL) contact formed between a roller and races were obtained to investigate the lubricating mechanism of roller skew. The effects of skew angle, rotational speed, applied load, length of the roller, and radius of the outer race on the lubricating performance of skewed roller contact in rolling bearings is discussed. In addition, in order to weaken the end concentration of the pressure due to the skewing effect, a parabolic profile modification for the roller's generatrix was carried out. A coupled solution combining skewing and tilting effects was achieved. The results showed that when the roller is skewed, the maximum pressure appears at the end parts of the roller for a roller–outer race contact but in the middle part of the roller for a roller–inner race contact. For the roller–outer race contact, a more serious skewing effect on the lubrication can be generated by a larger skew angle, higher speed, lighter load, longer roller length, and larger radius of the outer race. The skewing effect can be reduced through the profile modification for a roller's generatrix. In general, local lubricating failure may easily occur when roller skew is coupled with the tilting effect in cylindrical roller bearings.

Nonlinear dynamic analysis of cylindrical roller bearing with flexible rings

A nonlinear plan dynamic model for cylindrical bearings has been developed, predicting the interaction forces between the retainers and the rolling elements. Roller–race contacts are analyzed in detail and resulting forces and moments are determined. An elastohydrodynamic lubrication (EHL) model provides the traction components while a hydrodynamic formulation is used for the roller–cage interactions. Structural deformations of the rings are included in the geometrical equations linking the relative displacements between rings. The Newmark type implicit integration technique coupled with the Newton–Raphson method is used to solve the differential equation system iteratively. Time displacements and theirs FFT are used to illustrate and elucidate the diversity of the system response. Computations performed when considering the structural deformations of the rings show a low frequency shift, as higher harmonics are attenuated while the first are more pronounced. With an unbalanced rotor, the ball pass frequency (BPF) is modulated with this perturbation leading to an aperiodic response. This is particularly true for the counter-rotating bearing investigated. Finally, results for different cage materials show a significant influence only on the cage center location, whereas the inertia moment of the cage is of little impact on the global dynamics behavior.

Differences in displayed pump flow compared to measured flow under varying conditions during simulated cardiopulmonary bypass

Errors in blood flow delivery due to shunting have been reported to reduce flow by, potentially, up to 40-83% during cardiopulmonary bypass. The standard roller-pump measures revolutions per minute and a calibration factor for different tubing sizes calculates and displays flow accordingly. We compared displayed roller-pump flow with ultrasonically measured flow to ascertain if measured flow correlated with the heart-lung pump flow reading. Comparison of flows was measured under varying conditions of pump run duration, temperature, viscosity, varying arterial/venous loops, occlusiveness, outlet pressure, use of silicone or polyvinyl chloride (PVC) in the roller race, different tubing diameters, and use of a venous vacuum-drainage device.

OXYGEN PULSE PREDICTS STROKE VOLUME DURING WHEELCHAIR RACING IN TRAINED MALES WITH QUADRIPLEGIA 484

Oxygen pulse (O2 pulse), which is defined as the oxygen utilization per heart beat, is calculated as the product of cardiac stroke volume (SV) and mixed arteriovenous oxygen difference {(a-v)O2diff)}. The purpose of this study was to examine the inter-relationship among these variables during wheelchair racing in subjects with quadriplegia. Eight trained males (4 Class 1A, 2 Class 1B and 2 Class 1C, mean age = 31.8 ± 6.9 yr, peak VO2 = 19.8 ± 4.3 ml/kg/min) completed a 7.5km simulated wheelchair roller race in their personal racing wheelchairs. Cardiorespiratory and metabolic measurements were continuously monitored throughout the test. Cardiac output (Q) was measured by CO2 rebreathing at 3km and 6km of the race, from which SV and (a-v)O2diff were calculated. Reliability coefficients for the VO2, Q, HR, SV, and (a-v)O2diff between the two race stages were O.93, 0.91, 0.94, 0.92, and 0.87 respectively (p<.01). No significant differences (P>.05) were observed between the means for each of these variables at the two stages. At each stage of the race, O2 pulse was significantly related to the SV (0.84 and 0.88, P<.01) but not to the (a-v)O2diff (P>.05). As well, no significant correlations (-0.27 and -0.14 respectively, P>.05) were observed between SV and(a-v)O2diff. The regression equation for predicting SV from O2 pulse using the pooled means of the two race stages was: Y = 10.98X - 23.8, SEE = 12.1. These observations indicate that O2 pulse is a valid predictor of SV during wheelchair exercise in trained subjects with quadriplegia.

II. A rapid mechanical extraction method suitable for intensive sampling ofCostelytra zealandicaand other scarabaeids

Abstract A mechanical method has been developed for the rapid and large-scale extraction of the scarabaeid Costelytra zealandica (White) from soil samples (10 cm diameter × 25 cm). The method gives acceptable recovery rates for the egg, larvae, and teneral beetle stages of between 95 and 99%, without adversely affecting their viability. Cadavers of the species are recovered together with a wide range of soil macro-arthropods. The average extraction rate varies from 77 egg samples to 109 third-instar teneral adult samples per 8 hour man-day. This rapid rate has been accomplished by eliminating oil-water-interface separation and by using various labour-saving devices such as a recirculation system for aqueous magnesium sulphate, a conveyor belt to remove waste soil from the extraction unit, and roller races to move processed samples between operators. The method has been used successfully for two other soil-inhabiting scarabaeids. Herteronychus arator (Fabricius) and Pyronota jestiva (Fabricius).

Elastohydrodynamic Lubrication of Rollers

IT is now well known that the lubrication at such nominal line contacts as are found in roller races and between gear teeth is hydrodynamic in character. It is also known that this lubrication possesses peculiar features not found in journal bearings and which arise from the high pressure—a pressure, for example, of tens of tons per square inch as compared with 100 lb. in.−2. Because of the pressure the surfaces are deformed, in general elastically, and in addition within the pressure zone the oil acquires a much higher viscosity than it normally possesses; the viscosity might be greater by a thousand-fold. These circumstances have excited much inquiry as to the shape in cross-section of the hydrodynamic film. This communication reports an experimental measurement of that shape.

Tools for the Workshop

Fig. 1 shows a small tool which has been produced by Civitas Trading Corporation Ltd., Wigmorc House, 10 Duke Street, London, Wl, forthcremoval of ball bearings from shafts without damaging the race. A range of collets are provided to fit various types of bearings, and these are held in a self‐centring chuck which causes them to grip the inner race. The hollow body of the tool carries a thrust pin which is made in two parts separated by a ball bearing, to prevent the surface of the end of the shaft being damaged by the turning of the pin end. The threaded thrust pin is screwed home with a tommy bar and the race drawn offthc end of the shaft. It is claimed that no damage is caused to the race, and it can be used again if not otherwise due for replacement. Extension tubes are available to cater for bearings mounted at a distance along the shaft beyond the reach of the tool. The device is known as the Tracta ball and roller bearing extractor, collets being also provided which will fit roller races.

High-Pressure Gear Pumps

Gear pumps have been used in very large numbers for the various hydraulic services of war aircraft. For the higher pressures the main problems have been in connexion with the load on the journal bearings, with wear, and with the reduction in volumetric efficiency caused by internal leakage. The journal loads are affected by the number of teeth and by the ratio of width to diameter of the gears. With high pressures it is difficult to accommodate standard ball or roller races on account of their diameter: designs are illustrated using a combination of standard races and special needle roller bearings. Small amounts of wear cause comparatively large reductions in volumetric efficiency. Major causes of wear are rubbing on the gear end faces and solid matter in suspension in the liquid and methods of dealing with these are discussed. The percentage slip due to internal leakage varies inversely as the factor (r.p.m. × viscosity). At low speeds and with low-viscosity liquids, internal leakage often limits the pressure at which the pump can be used. Multistage pumps reduce the leakage and have been used extensively for undercarriage operation. Internal leakage becomes relatively less as the size of the pump is increased and the paper gives a graph, showing the relationship between the limit of pressure at which 80 per cent volumetric efficiency is possible, the capacity and rotational speed of the pump, and the viscosity of the liquid. Aircraft pumps generally use gears with involute teeth: ports in the end covers of the casing are used to prevent excessive pressure in the liquid trapped between the teeth. Low- and high-leakage conditions call for difficult arrangements of ports, and this involves differing displacements and variations in flow velocity.