Internal Clearance Research Articles

Prescribing Exercise to Cancer Patients Suffering from Increased Bone Fracture Risk Due to Metastatic Bone Disease or Multiple Myeloma in Austria—An Inter- and Multidisciplinary Evaluation Measure

In the current absence of specific functional fracture risk assessment technology, the planning of physical exercise interventions for cancer patients suffering from increased bone fracture risk remains a serious clinical challenge. Until a reliable, solely technical solution is available for the clinician, fracture risk assessment remains an inter- and multidisciplinary decision to be made by various medical experts. The aim of this short paper is depicting how this challenge should be approached in the clinical reality according to Austrian experts in cancer rehabilitation, presenting the best-practice model in Austria. Following referral from the specialist responsible for the primary cancer treatment (oncologist, surgeon, etc.), the physiatrist takes on the role of rehabilitation case manager for each individual patient. Fracture risk assessment is then undertaken by specialists in radiology, orthopedics, oncology, and radiation therapy, with the result that the affected bone regions are classified as being at highly/slightly/not increased fracture risk. Following internal clearance, exercise planning is undertaken by a specialist in exercise therapy together with the physiatrist based on the individual's fracture risk assessment. In the case in which the patient shows exercise limitations due to additional musculoskeletal impairments, adjuvant physical modalities such as physiotherapy should be prescribed to increase exercisability. Exercise prescription for cancer patients suffering from increased fracture risk is an inter- and multidisciplinary team decision for each individual patient.

Effects of Axial Clearance on Surface Initiated Flaking in Tapered Roller Bearings

Abstract The calculating method for fatigue life of rolling bearings is based on the theory of Lundberg and Palmgren. The rated life is determined from the ratio of the dynamic load rating of the bearing to the dynamic equivalent load. However, in actual applications, flaking damage may occur earlier than this rated life. For example, surface initiated flaking may occur due to contamination in the lubricant. In addition, differences in the internal clearance of bearings are also thought to influence the occurrence of surface initiated flaking. This study aims to investigate the effect of different internal clearance on surface initiated flaking in tapered roller bearings. First, rotating tests were conducted on combination tapered roller bearings with dented raceways under several axial clearances different from the standard condition. Second, the surface profiles of the bearings before and after the tests were compared to investigate the relationship between the distribution of flaking area and the axial clearance. Furthermore, the effect of axial clearance on the surface initiated flaking life was clarified from the comparison between the results of the rotating tests. Finally, the theoretical and experimental lives were compared. As a result, it has been found that when the axial clearance is excessively large, the distribution of flaking is biased toward the large diameter side of the outer raceway. In addition, it has been demonstrated that the bearing life is substantially affected by the axial clearance, and that the bearing life shortens as the axial clearance increases.

Mechanical Behavior of Variable Nozzle Guide Vane Systems Based on Full-Scale Testing

Abstract A full-scale test bench for the analysis of frictional and modal behavior of nozzle guide vanes (NGV) is an advanced tool enabling high design accuracy for these components equipped with an increasing number of turbo-expanders. This subassembly is a key feature enabling operational flexibility for the expander. During the NGVs design, great attention must be paid to the natural frequencies of its kinematic chain, which are influenced by internal clearances and by friction. In this paper, the results of a testing campaign performed on an NGV assembly employing realistic blade geometry are presented together with details concerning the test bench commissioning and setup procedure. The testing campaign involves three different combinations of blade orientation and preload corresponding to typical design conditions of the expander. In addition, two bushing clearance values corresponding to different worn-out conditions were investigated. The measurements of the global friction coefficient based on actuator force detection are summarized. After that, the reconstruction of mode shapes based on experimental modal analysis is explained. The results highlight the importance of loading conditions on the actual value of friction force and their influence on blade natural frequencies. The testing campaign was used to properly validate finite element models to be used for further investigations.

Boiler feed water pumps: techniques for improvement in design and balance of the drum

Boiler Feed Water Pumps (BFWP) are considered a critical part of boilers in power plant operations. The performance of the pump in a system is estimated by one of these quantifiers in pump performance (power, efficiency, head, and flow). The design and balance of the drum in the boiler feed pump are critical for the smooth flow and optimum efficiency of the pump. The wearing tolerance limits of the drum are correlated with the type of pump and the characteristics of the system in which it is installed. A study was conducted to evaluate the drum design at Saudi Aramco Jazan Integrated Gasification Combined Cycle (IGCC) Power Block Project. The study provided a mechanism for improvement in the design issues associated with the internal clearance of balance drums related to the BFWPs. Furthermore, gradual design improvements were also implemented. Successful performance testing of Boiler Feed Water Pumps (BFWPs) fitted with upgraded balance drums was also performed. This study provides a better understanding of drum design and techniques to improve the balance of the drum.

Modal balancing for ball bearing-rotor system using nonlinear normal modes

Rotor dynamic balancing procedure relies on the linearisation hypothesis of the rotor system. However, some mechanical elements constituting a rotor system behave in various nonlinearities, such as the contact force and radial internal clearance between rolling balls and races for a rotor-bearing system. To balance a nonlinear rotor system, the traditional modal balancing method must be extended. This paper investigates the modal balancing method for a rotor-bearing system based on nonlinear normal modes (NNMs). The proposed algorithm includes three main steps. First, compute the NNMs and express nonlinear modal shapes using complex Fourier series. Second, describe the unbalance response as a complex amplitude containing higher harmonics. Third, estimate the correction coefficient of each harmonic, then compute the unbalance correction of each mode of interest until the total unbalance corrections are obtained. Hertz contact force and two different sizes of radial internal clearances of the ball bearings are considered during the balancing simulation. The responses after balancing with NNMs are present and compared with the linear modal method to demonstrate the accuracy and effectiveness of the proposed method.

A New Approach for the Load Calculation of the Most-Loaded Rolling Element of the Rolling Bearing with Internal Radial Clearance—A Case Study

One of the most important factors influencing the study of the tribological behaviour of a rolling bearing is the calculation of the loads transmitted by individual rolling elements of the bearing. However, the calculation of the internal load distribution of rolling bearings is quite complicated. It is a nonlinear, statically indeterminate problem, which can only be solved numerically, through a number of iterations. This is often a problem in analysis because it complicates the mathematical model. This paper is presenting a case study with the goal to show the benefits of the application of a new approach for the calculation of the load of the most-loaded rolling element in the rolling bearing with the internal radial clearance. The calculation is based on the so-called load factors. By multiplying the load factors with the value of the external radial load, the load that is transferred by the most-loaded rolling element of the bearing is obtained. The accuracy of the results largely depends on the correct choice of the load factor. The case study aims to define guidelines for the correct choice of load factors. The case study is made for two types of bearings: the ball bearing and the roller bearing. Obtained results were compared with the results obtained based on the calculation using some of the most commonly used methods so far. The analysis showed greater precision of the considered model with the same or much simpler use. For this reason, the proposed model is considered very suitable for practical application.

Preclinical study of pharmacokinetic ADME processes of phenosanic acid <i>in vitro</i> and <i>in vivo</i>

BACKGROUND: Phenosanic acid is a synthetic antioxidant, the active ingredient of the original domestic drug recommended for the treatment of epilepsy. To improve the effectiveness and safety of the use of phenosanoic acid, additional study of its pharmacokinetic properties is necessary.
 AIM: To study the pharmacokinetic parameters of the active ingredient of the drug Dibufelon, capsule 200 mg (LLC Piq-Pharma, Russia) in vitro and in vivo systems in rats after single administration in one dose.
 MATERIALS AND METHODS: Phenosanic acid binding to blood plasma proteins, microsomal stability and permeability through the monolayer of Caco-2 cells were evaluated in in vitro tests. The pharmacokinetics parameters were studied after a single intragastric administration in Wistar rats in dose of 80 mg/kg. The samples were analyzed by HPLC-UV.
 RESULTS: A high variability in the degree of binding of phenosanic acid to blood plasma proteins by 2065% depending on the concentration was revealed, relatively high microsomal stability (half-life 1106 789 min, internal clearance 2.05 0.86 l/min/mg protein of liver microsome; residual content after 60 min incubation 87.9 7.8%) and the ability to penetrate through the monolayer of cells Caco-2. The rapid absorbtion of the substance into the systemic bloodstream was established its maximum concentration in blood plasma was observed already 3.6 1.2 hours after administration, and its slow removal from the systemic bloodstream the half-life was about 19 h, the average retention time was about 29 h. Phenosanic acid with different degrees of intensity was distributed to all the examined organs and tissues: kidneys liver brain omentum muscle, and invariably excreted in a small amount with urine and feces, about 0.04% and 5.5%, respectively.
 CONCLUSIONS: As a result of the study, it was found that phenosanic acid is characterized by rapid absorbtion into the systemic bloodstream and a long stay in it invariably, which may be due to the peculiarities of its binding to blood plasma proteins and relatively high metabolic stability, revealed during the corresponding in vitro tests. The study of the permeability and transport of phenosanic acid showed that it can presumably be attributed to compounds with medium permeability and is not a substrate for the transport protein P-glycoprotein (P-gp). The study of tissue availability of phenosanic acid confirmed its entry into peripheral tissues, including the brain, which is the area of implementation of the anticonvulsant effect.

Experimental Verification of the Impact of Radial Internal Clearance on a Bearing’s Dynamics

This paper focuses on the influence of radial internal clearance on the dynamics of a rolling-element bearing. In the beginning, the 2—Degree of Freedom (DOF) model was studied, in which the clearance was treated as a bifurcation parameter. The derived nonlinear mathematical model is based on Hertzian contact theory and takes into consideration shape errors of rolling surfaces and eccentricity reflecting real operating conditions. The analysis showed characteristic dynamical behavior by specific clearance range, which reflects others in a low or high amplitude and can refer to the optimal clearance. The experimental validation was conducted with the use of a double row self-aligning ball bearing (SABB) NTN 2309SK in which the acceleration response was measured by various rotational velocities. The time series obtained from the mathematical model and the experiment were analyzed with the recurrence quantification analysis.

Experimental Verification and Nonlinear Dynamic Response Analysis of a Rolling Element Bearing with Localized Defects

In this paper, the dynamic behavior of rolling element bearings with localized faults on the inner and outer rings is investigated. A nonlinear mathematical model is developed with five degrees of freedom considering rotor unbalance. In this bearing model, the nonlinearity is caused by the Hertzian contact forces and the radial internal clearance. The fourth-order Runge–Kutta technique is used to solve the coupled nonlinear equations of motion numerically. Nonlinear vibration response of the rotor and bearing housing can be obtained in both time and frequency domains. An experimental verification of the numerical model is presented where experimental measurements for defective ball bearings are compared with the numerical results. Envelope spectra of the numerical results show similar behavior to that of the measured experimental signals. A parametric analysis is conducted to investigate the effect of system parameters on the nonlinear dynamic response using time waveforms, orbit plots, frequency spectra and bifurcation diagrams. The presented results demonstrate that the dynamic response shows periodic, quasi-periodic and chaotic motions because of varying rotational speeds and defect width. The proposed model contributes toward improved design and better health monitoring of bearings in practice.

Research on the influence of thermal expansion of steel shaft on dynamic characteristics of full ceramic bearing-rotor system

Bearing as the core components of high-grade CNC machine tools, with the constant change of internal clearance of bearing wear increasingly aggravated, spindle rotation accuracy reduced. In this paper, the idea of control variable method is used to explore the dynamic change of bearing clearance from different speeds and different radial loads. Starting with the dynamic model of bearing vibration, the theoretical model of rolling bearing with five degrees of freedom is established in this paper. The interaction force between steel shaft and ceramic bearing inner ring is calculated by Runge-Kutta method with elastic wall thickness ring theory, and the reduction of radial clearance of bearing is obtained. Therefore, a dynamic model of ceramic bearing considering the extrusion force of ceramic bearing inner ring is proposed. At the same time, the vibration test of steel shaft-all-ceramic bearing is designed and carried out. The test results show that under the same load, the higher the rotating speed, the shorter the time for the bearing-rotor system to reach temperature stability, and the root mean square of ceramic bearing-rotor system is obviously reduced. At the same speed, the greater the load, the more obvious the root mean square increase of the bearing-rotor system.

Comparative experimental analysis of the effect of lubricant viscosity on the performance of a single-screw expander with different structures

Compressed air energy storage (CAES) is considered a promising energy storage technology because it promotes global energy saving, emission reduction, and the development of renewable energy. Improvement in the expander performance is a major concern in CAES systems. The addition of lubricant is beneficial for reducing leakage and friction losses, which can improve the expander performance and the CAES system efficiency. To clarify the influence of lubricant on the expander performance, a comparative experimental study was conducted. A single-screw expander (SSE) with different internal volume ratios and clearances was analyzed under different operating conditions with six different lubricant viscosities (viscosity from small to large: 10#, 22#, 32#, 46#, 68#, and 80#). The results show that increasing the kinematic viscosity of lubricant can effectively improve the volumetric efficiency. The volumetric efficiency of an SSE with a small clearance and a small internal volume ratio is higher, and it can approach 100% with 68# and 80# lubricants when the intake pressure is 0.5 MPa. Increasing the kinematic viscosity of the lubricant reduces the shaft power. The shaft power of an SSE with a large clearance and a small internal volume ratio is larger, and the maximum shaft power with 10# lubricant is 5.78 kW at 0.9 MPa and 3000 rpm. The kinematic viscosity of the lubricant significantly influences the shaft power of the SSE under high-speed conditions, and with the maximum variation being 11.9%. The shaft efficiency of an SSE with a small clearance and a small internal volume ratio is higher, and the gas consumption rate is lower. A low-viscosity lubricant should be used to avoid over-expansion when the intake pressure is lower than 0.6 MPa. The SSE with 46# lubricant has good comprehensive performance, where the maximum shaft efficiency and the minimum gas consumption rate obtained experimentally are 49.29% and 61.23 kg/(kW·h), respectively.

Beyond single host, single parasite interactions: Quantifying competence for complete multi‐host, multi‐parasite communities

Abstract Understanding parasite transmission in communities requires knowledge of each species' capacity to support transmission. This property, ‘competence’, is a critical currency for modelling transmission under community change and for testing diversity–disease theory. Despite the central role of competence in disease ecology, we lack a clear understanding of the factors that generate competence and drive its variation. We developed novel conceptual and quantitative approaches to systematically quantify competence for a multi‐host, multi‐parasite community. We applied our framework to an extensive dataset: five amphibian host species exposed to four parasitic trematode species across five ecologically realistic exposure doses. Together, this experimental design captured 20 host–parasite interactions while integrating important information on variation in parasite exposure. Using experimental infection assays, we measured multiple components of the infection process and combined them to produce competence estimates for each interaction. With directly estimated competence values, we asked which components of the infection process best explained variation in competence: barrier resistance (the initial fraction of administered parasites blocked from infecting a host), internal clearance (the fraction of established parasites lost over time) or pre‐transmission mortality (the probability of host death prior to transmission). We found that variation in competence among the 20 interactions was best explained by differences in barrier resistance and pre‐transmission mortality, underscoring the importance of host resistance and parasite pathogenicity in shaping competence. We also produced dose‐integrated estimates of competence that incorporated natural variation in exposure to address questions on the basis and extent of variation in competence. We found strong signals that host species identity shaped competence variation (as opposed to parasite species identity). While variation in infection outcomes across hosts, parasites, individuals and doses was considerable, individual heterogeneity was limited compared to among‐species differences. This finding highlights the robustness of our competence estimates and suggests that species‐level values may be strong predictors for community‐level transmission in natural systems. Competence emerges from distinct underlying processes and can have strong species‐level characteristics; thus, this property has great potential for linking mechanisms of infection to epidemiological patterns. Read the free Plain Language Summary for this article on the Journal blog.

Study of the feeding tube optimal diameter for enteral nutrition in a model experiment

Introduction. The question of selecting the optimal diameter of gastrostomic tubes for enteric feeding remains unresolved. The aim of the study is to justify the choice of tube diameter for enteric feeding by studying deposits on the inner wall. Materials and Methods. A model for the introduction of specialized enteric and blender food through a tube at a temperature ranging from 36° to 40 °C has been developed. Polyvinylchloride probes with a length of 110 cm and an outer diameter ranging from 10 to 30 Fr with a step of 2 Fr are used as nutrient tubes. An imitation is performed nourishment 5 times a day for 300 ml for 30 days. After simulation, the probe’s internal clearance will wash 150 ml of water with a temperature of 37 °C, dried. At the beginning and end of the experiment, weighing and measuring the length of the probe was carried out. The results and their discussion. The specialized feed caused a blockage of 10 and 12 Fr probes, which were removed by washing 150 ml of water. There was no significant change in the mass of probes after the enteric feeding, indicating minimal sediments on the inner surface. The blending caused a blockage of probes 10, 12 and 14 Fr in diameter. Probes 10 and 12 Fr in diameter could not be recovered from washing with water. The power deposition on the inner walls of the probes was visually determined. No significant changes in the length of the probes were observed during the experiment. However, the change in the mass of probes after the blender feed is statistically larger than after the specialized one (p<0.001, Mann-Whitney criterion). Conclusion. It is advisable to use gastrostomic tubes with a diameter of 14-18 Fr to feed specialized mixtures. 18-24 Fr diameter tubes should be used when using a blender supply.

The influence of the radial internal clearance on the dynamic response of self-aligning ball bearings

In this work, we present a quantitative and qualitative analysis of the dynamic response of ball bearings dependent on radial internal clearance. We measured the vibrations of a rotating system based on self-aligning ball bearings for different clearances and rotating speeds. The analysis of vibration spectra was conducted considering a set of different recurrence indicators in order to describe the response of the bearing to the optimal clearance. It comes out that indicators have different sensitivity to the changes of the internal clearance. Few quantificators, i.e. entropy, trapping time, and recurrence period density entropy demonstrate the highest sensitivity to the change of radial clearance. The proposed quantificators are useful for real-time monitoring of operating clearance.

Targeting Ocular Drug Delivery: An Examination of Local Anatomy and Current Approaches.

Ocular drug delivery remains the focus of much modern research. Primary routes of administration include the surface, the intravitreal space, the subretinal space, and the subconjunctival space, each with its own series of unique challenges, limitations, and advantages. Each of these approaches requires careful consideration of the local anatomy, physical barriers, and key cells as well as the interface between the anatomy and the drug or drug system being delivered. While least invasive, the topical route poses a challenge with the many physical barriers that prevent drug penetration into the eye; while injection into the intravitreal, subretinal, and subconjunctival spaces are direct and targeted but limited due to the many internal clearance mechanisms and potential for damage to the eye. Polymeric-based, sustained-release drug delivery systems have been identified as a potential solution to many of these challenges; however, the design and successful implementation of a sustained-release system that is well-tolerated, bioactive, biocompatible, and degradable remains, in many cases, only in the early stages. The drugs and biomaterials in question also require special attention as small chemical changes could result in vastly different outcomes. This paper explores the anatomy and key cells of these four primary drug delivery routes as well as the interface between drug and drug delivery systems and the anatomy, reviewing the recent developments and current state of research in each area. Finally, this paper also examines the frequently used drugs and biomaterials found in ocular drug delivery and summarizes the primary interactions observed.

RELIABILITY ANALYSIS OF ROLLING BALL BEARINGS CONSIDERING THE BEARING RADIAL CLEARANCE AND OPERATING TEMPERATURE

The aim of the research conducted in this particular paper was related to a comprehensive reliability analysis of SKF 626 Open Deep Groove ball bearings, conducted under controlled laboratory conditions. The experimental research consisted of: measurements of radial internal clearance (RIC) in ball bearings, measurement methods for the detection of bearing operating temperature and rolling element bearing wear, complete with the cage deformation of the the damaged bearing, the failure of which was revealed after the examination. The inspected SKF 6206 open deep groove ball bearings operating under laboratory conditions – simulated the model of dynamic behavior under real conditions by using the crankshaft of an air compressor. The results of research conducted based on the inspected samples of rolling bearings, showed that there was a significant dependence of the predictors of internal radial clearance on operating bearing temperature. Out of five test samples of rolling bearings, there was only one rolling ball bearing detected to be with failure after the bearing inspection. The examination of the damaged bearing revealed the final radial clearance value of 0.045 mm, i.e. operating temperature of 75 °C.

Thermal Analysis of Cylindrical Roller Bearing Considering Thermo-Mechanical Coupling

Thermal characteristic is important performance of the bearing, which reflects the friction characteristics of bearing. Thermal characteristics of bearing will change along with internal behavior when the bearing fails. There is a very complex coupling relationship. It is an important implication for the thermal analysis cylindrical roller bearing considering thermo-mechanical coupling. A model of heat generation for cylindrical roller bearing considering thermo-mechanical coupling is established based on the method of quasi-static and thermal network of bearing to solve the complex thermo-mechanical coupling of bearing. And then, the variation of complex thermal-mechanical characteristics such as friction torque, contact force and temperature for cylindrical roller bearing with wear failure is analyzed. The results show that the heat generation characteristics of the bearing are strongly coupled with the internal contact force and clearance. And the decrease of bearing clearance and the increment of contact force and friction torque, even rotor binding.with the increasing of wear degree.

Evaluating load distribution at the bearing-housing interface using thin film pressure sensors

The objective of this investigation was to utilize thin film pressure sensors to evaluate the pressure distribution between rolling element bearings and a housing. A test rig was constructed to place thin film sensors around the perimeter of a test bearing inside of a housing. High precision drive shafts were manufactured that produce a light and heavy interference fit with each of the test bearings. Pressure map results are used to evaluate the effect of internal clearance on the load distribution of different bearing types. The thin film sensor system was also used to investigate the circumferential load distribution on the housing. The presented apparatus and test method could be used to validate bearing fit selection and housing design.

Effect of substrate surface roughness on the wear of molybdenum disulphate coated rolling contact bearings

Abstract The objective of the present experimental work is to investigate the influence of subsurface roughness on the friction and wear performance of high-temperature ball bearing. Bearings, which are used in high-temperature applications, are affected by several operating conditions. Some factors under high-temperature conditions such as short grease life, thin-film thickness at low speed, and insufficient internal clearance can drastically reduce bearing service life due to an increase in surface friction. For this reason, rolling contact bearings are coated with molybdenum disulfide. Before the molybdenum disulfide (MoS2) coating, phosphatization is applied to the bearings. Because the phosphate layer is micro-porous, it assures that molybdenum disulfide is entrapped in the interstitials between the phosphates. Also, phosphate coating provides a much larger surface area for the lubricant to attach to. In this study, several process steps, sandblasting, manganese phosphate coating, molybdenum disulfide coating, friction moment testing, wear testing, wear depth measurement, SEM, and XRD analyses were carried out. Wear tests and friction moment tests were applied to the rings of bearings of varied raceway roughness. This process ultimately provides molybdenum disulfide coated bearings optimum raceway roughness parameters for good wear resistance and optimum boundary lubrication.

Vibration characteristics and condition monitoring of internal radial clearance within a ball bearing in a gear-shaft-bearing system

Internal radial clearance is a key factor influencing bearing fatigue life. Moreover, bearings inevitably suffer from various wears and tears, which result in gradual increase of clearance and shorten bearing life. Monitoring bearing clearance changes using vibration can effectively indicate the bearing wear and provide good leading time to perform maintenances. Previous studies show that vibration at ball pass frequency on outer race (BPFO) can be based for clearance monitoring. However, such clearance induced vibration has not been well understood, especially under complicated dynamic interactions such as in a gearbox system. To fill this gap, this paper presents a nonlinear gear-shaft-bearing-housing vibration model with fourteen degree of freedom (DOF) to investigate the vibration responses under the dynamic gear meshing force and progressively changed radial clearances at first. Then, the model was verified through a two-stage spur gearbox. Furthermore, bearing characteristics with different radial clearances under the influence of gear are revealed and indicator based on modulation signal bispectrum-sideband estimator (MSB-SE) was proposed. Finally, vibration data from a run-to-failure gearbox test rig was utilized to verify the effectiveness of the MSB-SE indicator for bearing clearances monitoring. Simulation results show that BPFO is modulated on gear meshing frequency (GMF) and BPFO amplitude from envelope spectrum increases with bearing clearances under the influence of gear meshing. Indicator based on MSB-SE, possessing the capability of purifying the interferences of gear meshing and strong noises, is effective to capture the variance of bearing clearances. The experiment based on a run-to-failure gearbox test rig provided evidence for the effectiveness of the proposed indicator, which is more accurate than BPFO amplitude from conventional envelope analysis and time-domain indicators, such as RMS and kurtosis. These findings are of significance for bearing fault diagnosis and maintenance.