Dynamic Bearing Research Articles

Dynamic Response and Energy Absorption Characteristics of a Three-Dimensional Re-Entrant Honeycomb

In this paper, we design a new three-dimensional honeycomb with a negative Poisson’s ratio. A honeycomb cell was first designed by out-of-plane stretching a re-entrant honeycomb and the honeycomb is built by spatially combining the cells. The in-plane response and energy absorption characteristics of the honeycomb are studied through the finite element method (FEM). Some important characteristics are studied and listed as follows: (1) The effects of cell angle and impact velocity on the dynamic response are tested. The results show that the honeycomb exhibits an obvious negative Poisson’s ratio and unique platform stress enhancement effect under the conditions of low and medium velocity. An obvious necking phenomenon appears when the cell angle parameter is 75°. (2) Based on the one-dimensional shock wave theory, the empirical formula of the platform stress is proposed to predict the dynamic bearing capacity of the honeycomb. (3) The energy absorption in different conditions are investigated. Results show that as the impact velocity increases, the energy absorption efficiency gradually decreases. In addition, with the increase of cell angle, the energy absorption efficiency is gradually improved. The above study shows that the honeycomb has good potential in using in vehicle industry as an energy absorption material. It also provides a new strategy for multi-objective optimization of mechanical structure design.

Modified pseudo–dynamic bearing capacity of strip footing on rock masses

In this paper, the seismic bearing capacity of a strip footing sitting on rock masses has been investigated following the upper bound theorem of limit analysis. The generalized tangential technique is used to obtain the equivalent Mohr–Coulomb parameters of the modified Hoek–Brown criterion. Considering the damping characteristics of the site as well as the dynamic characteristics of the seismic waves, the modified pseudo-dynamic (MPD) method is applied to evaluate the seismic effects. A parametric study is conducted, which shows that the seismic acceleration coefficient, the geological strength index, the material constant of the intact rock, and the normalized frequency all have a significant effect on the seismic bearing capacity. The MPD results are also compared with other methods, including the conventional pseudo-dynamic (CPD) method, spectral pseudo-dynamic method (SPD), and pseudo-static (PS) method. A high degree of agreement can be observed between the MPD results and the CPD results as the normalized frequency increases. When the normalized frequency equals 0.5 + nπ, the values of the bearing capacity factor obtained by using the MPD method and the SPD method will hit their local minima, while the CPD and PS methods will overestimate the bearing capacity factor to a large extent.

COMPARATIVE ANALYSIS OF STATIC AND DYNAMIC PILE TESTS IN DIFFICULT GROUNDS OF KAZAKHSTAN

A comparative analysis of the results of field tests to determine the bearing capacity of a pile at the facilitys in the Nur-Sultan city and Petropavlovsk city. The aim of the study was to carry out a comparative analysis of the results of dynamic and static tests in the two construction site in order to identify the difference in performance. This article provides programs and results of tests with static indentation load and dynamic load on a pile in different two of the construction site under different soil conditions. The results of the comparative analysis are the following: Dynamic tests are needed for a preliminary assessment of the dynamic bearing capacity and the possibility of driving piles in different soil conditions. The bearing capacity of the pile, determined by dynamic tests, is slightly lower than during static tests, the difference between the results is 11 and 17%.

Design of a Combined Magnetic and Gas Dynamic Bearing for High-Speed Micro-Gas Turbine Power Plants with an Axial Gap Brushless Generator

The development of modern energy is moving towards distributed generation, in which numerous sources of different capacities are connected into a single network. This makes it possible to increase the reliability of the entire system, since the probability of the failure of several energy sources at the same time is small. One of the major possibilities of distributed generation is the generation of electric energy based on high-speed gas turbines. The main advantage of these sources are high specific energy indicators, which improve with increasing rotation speed. However, it is technically difficult to realize the advantages of high-speed devices. It is necessary to abandon the step-down gearbox for the generator and directly connect it to a high-speed turbine, use high-strength materials that can withstand the load from centrifugal forces, abandon traditional plain bearings, and use special supports. Installations with generators that have a radial rotor design are the most widespread. The main problem with generators of this type is that the rotor diameter is limited by the mechanical strength from centrifugal forces and the power can be increased only by increasing the axial length. At the same time, only two supports can be used for a radial structure; this leads to a decrease in the rigidity of the shaft and the occurrence of resonant frequencies during acceleration. In addition, radial generators have unreasonably large losses in the stator magnetic circuit, which increase with increasing speed and are difficult to remove from a limited volume. For this reason, radial structures have exhausted their reserves and cannot develop further in the direction of increasing the speed of rotation. This article proposes the design of a high-speed gas turbine installation based on a generator of a fundamentally different design. This is a multi-section generator with an axial air gap. The electric machine has a diamagnetic armature, which eliminates magnetic losses and allows for increased efficiency and simplification of the design. A large number of rotor sections can be used as supports for a gas-dynamic bearing, which greatly increases the rigidity of the structure and eliminates resonant frequencies during acceleration. The main structural difference from existing designs is the use of two types of bearings at the same time: magnetic bearings and gas-dynamic bearings. Magnetic bearings ensure operation at low speeds during acceleration, and gas-dynamic bearings ensure the rotation of the rotor and its rigidity at high speeds. Analysis of developments in this area shows that this solution is innovative. The proposed design required study of both the power part, including the axial inductor and the diamagnetic armature, and the combined support. This article shows the results of the development of a combined suspension and provides calculations of magnetic and gas-dynamic bearings for a gas turbine installation of 100 kW and 70,000 rpm. The results of the study can be applied to a number of gas turbine installations from 10 kW to 500 kW. The authors consider this concept to be competitive with modern analogues that have a radial generator design.

Comprehensive Evaluation of Long-term Dynamic Mechanical Behavior in a Rat MIA OA Model

Osteoarthritis (OA) is highly prevalent across the world with 30% of the US population who are 45 and older estimated to have knee osteoarthritis. The primary clinical indication of OA is pain. Mono-iodo acetate (MIA) induced osteoarthritis is commonly used to study pain in pre-clinical models. Currently mechanical allodynia and thermal hyperalgesia are used to measure the pain outcomes in most pre-clinical models however, the non-evoked dynamic weight bearing analysis provides more clinically relevant behavioral assessment of pain. The goal of the study is to comprehensively understand the changes in dynamic weight bearing behavior of rats with MIA induced OA over a period of 16 weeks. Osteoarthritis was induced in female Sprague-Dawley rats by C-arm guided injections of MIA (3 mg) into the intra-articular region of the right knee. Non-evoked dynamic weight bearing was evaluated using a pressure sensor system (Bioseb DWB 2.0), mechanical allodynia using Von Frey filaments, and transcriptional changes at the dorsal root ganglion using BioRad gene array. MIA model showed mechanical allodynia of the ipsilateral paw for over 3 months. The dynamic weight bearing parameters reveal continuous compensatory weight preference towards the uninjured limbs for the same period. Unlike Von Frey, significantly different dynamic behavioral parameters begin to appear within 24 hours post MIA injection. Moreover, parameters related to weight and area distribution showed temporal changes over the course of the study. The study shows that dynamic weight bearing assessment is an effective tool to understand the long-term progression of pain behavior in a MIA model. Grant support from NIH R01AR075143.

Research on static characteristics of elastic foil gas thrust bearing applied to aeronautical ACM

In air conditioning system for aircraft, air cycle machine (ACM) is the flimsy core component, which is impacted observably by the performance and reliability of elastic foil air-dynamic pressure bearing. It's necessary to have research on static characteristics of elastic foil air-dynamic pressure bearing. Based on finite element analysis (FEA) theory, it’s clearly obtained that discretized fluid lubrication Reynolds equation of foil dynamic pressure bearing by the weighted residual method. Coupled with the elastic deformation of foil calculated by beam element model, foil gas film thickness equation is used to work out static characteristics of elastic foil air-dynamic pressure bearing by iterative calculation. And then, it’s known how the basic parameters of the bearing impact its static characteristics. The result of the method in this paper, is verified that it’s correct by the experiment data in other relevant papers, and it’s appropriate to be used as guidance and reference for the further application of elastic foil bearing in ACM.

Ethanol Antiallodynia and Reward Seeking in Mice with Spared Nerve Injury

Clinical data suggests that both men and women with chronic pain are more likely to develop alcohol use disorder, to relapse after a period of abstinence, and to report using alcohol to manage chronic pain. These data led to the hypothesis that alcohol-related behaviors are different in those experiencing chronic pain. To test this hypothesis, the analgesic effect of multiple doses of ethanol (0.5, 1, 2 g/kg i.p.) on male and female mice with spared nerve injury (SNI) was investigated using Von Frey and dynamic weight bearing assays. A conditioned place preference (CPP) paradigm was then used to model ethanol seeking after nerve injury. Findings indicate that SNI reduced mechanical thresholds, increased weight bearing on the contralateral hindpaw, and decreased paw print area on the ipsilateral hindpaw. In male SNI mice, all three doses of ethanol fully reversed mechanical hypersensitivity, while in female mice only the highest dose (2.0 g/kg) was fully antiallodynic. Additionally, the highest dose was analgesic in Sham animals in both male and female mice. In the CPP experiments, conditioning with 0.5 g/kg ethanol induced a modest CPP for the ethanol-paired chamber in SNI and Sham male mice. Further, following extinction, painful stimulation reinstated ethanol-seeking behavior only in SNI mice. These data suggest that the analgesic effects of alcohol are distinct in male and female mice and that animals in chronic pain may be more sensitive to stress-induced reinstatement when pain is the stressor. Ongoing work is focused on characterizing ethanol CPP in female mice and investigating neural correlates of ethanol analgesia and reward in mice in chronic pain.

NIH HEAL Initiative: National Institute of Neurological Disorders and Stroke Preclinical Program for Non-Addictive Pain Therapeutic Development

The National Institutes of Health Helping to End Addiction Long-term, or NIH HEAL Initiative aims to focus efforts on advancing scientific solutions to stem the opioid crisis, improving prevention and treatment of opioid misuse/addiction, and enhancing pain management. NINDS is charged with accelerating the discovery and development of new non-addictive pharmacologic and non-pharmacologic pain therapeutics as part of the HEAL Initiative. PSPP provides researchers from academia and industry, within the US and internationally, an efficient, rigorous, one-stop in vivo resource to screen and profile therapeutic candidates including small molecules, biologics, natural products, and devices for the treatment of pain. Under PSPP direction, preclinical testing is performed by a National Institute of Neurological Disorders and Stroke (NINDS) contract facility, PsychoGenics Inc., in a blinded and confidential manner at no cost to the PSPP participants. Participant assets are evaluated in a suite of in vivo pain-related models, for example, chemotherapy-induced neuropathic pain, osteoarthritis pain, and headache. In these models, PSPP uses both evoked (e.g., paw withdrawal threshold, acetone) and non-evoked (e.g., dynamic weight bearing) endpoints to rigorously assess efficacy of the asset in both male and female animals. Importantly, abuse liability is also assessed using a conditioned place preference paradigm or using intravenous self-administration. A key feature of the PSPP is the flexibility to continuously acquire and validate innovative models and endpoints that more closely represent human pain conditions. Notably, in addition to enabling evaluation of small molecules, biologics and natural products, models and endpoints can be appropriately adapted or incorporated to assess devices. We will describe the advances made to date towards establishing program goals of evaluating assets in a rigorous and reproducible manner.

Experimental study of different structural parameters on gas lubricated spiral groove thrust bearing for cryogenic turbo expander

With the development of high speed and miniaturization of turbo expander, the gas-lubricated spiral groove dynamic pressure gas bearing plays an important role. An experimental study on the gas-lubricated spiral groove gas thrust bearing is carried out to research the relationship between the bearing loading capacity and the structural parameters such as the spiral angle, the groove length ratio, the groove width ratio and the rotating speed. The contrast experiment of spiral groove structure on thrust disc and bearing end face was also carried out. The experimental results show that the optimum spiral angle is 20°, the optimum groove length ratio is 0.61∼0.68, the optimum groove width ratio is 0.5∼0.55, and the new structure of the spiral groove on the thrust disc will increase the bearing loading capacity by 7.6% than the traditional structure.

MiR‐106b‐25 Dysregulation in Complex Regional Pain Syndrome Contributes to T Cell Dysfunction

BackgroundComplex regional pain syndrome (CRPS) is a debilitating chronic pain disorder with no effective treatments. Growing evidence implicates aberrant immune regulation in the skin and T cell dysfunction in CRPS pathology. MicroRNA (miRNA) show promise in identifying biomarkers and disease mechanisms. miRNA cluster miR‐106b‐25 is dysregulated in CRPS patient whole blood and serum derived small extracellular vesicles (sEVs) compared to healthy controls. miR‐106b‐25 members are predicted to target several immune genes related to T cell function including CD69. We hypothesize that miR‐106b‐25 cluster plays a role in T‐cell dysfunction by regulating members of CD69 signaling pathway. Here we examine miR‐106b‐25 mediated signaling in sEVs, whole blood, and skin from the tibia fracture model (TFM) of CRPS.MethodsMouse TFM was generated, and pain hypersensitivity was confirmed by von Frey and dynamic weight bearing. Serum, whole blood, and hind limb skin were collected from TFM and control mice. sEVs were isolated by differential centrifugation and characterized using nanoparticle tracking analysis, transmission electron microscopy and western blotting. miRNA from sEVs were assessed through HTG EdgeSeq. T cells were isolated from single cell suspensions of hind limb skin. Whole blood samples were obtained from CRPS patients or healthy controls. miRNA and gene expression changes in blood and T cells were assessed by qPCR. Luciferase reporter assay was used to confirm miR‐25 binding to CD69. Jurkat cells were transfected with miR‐25 mimic or inhibitor to assess regulation of gene expression by qPCR and flow cytometry. T cell phenotypes and expression of CD69 and other residency markers were determined by flow cytometry.ResultsCharacterization of sEVs showed no difference between TFM and control mice. miRNA analysis of TFM sEVs confirmed dysregulation of 30 miRNA previously associated with CRPS patients including miR‐106b‐25. There was an inverse correlation of miR‐25 and CD69 in blood samples from CRPS patients compared to controls. Reporter assay confirmed miR‐25 binding to CD69. miR‐25 nucleofection in Jurkat cells downregulated CD69 as measured by flow cytometry. Analysis of miR‐106b‐25 and target gene expression in TFM whole blood and skin T cells and T cell flow cytometry experiments are ongoing.ConclusionsmiRNA signatures in CRPS patients and TFM mice show common alterations including miR‐106b‐25. miR‐25 can regulate CD69 expression in vitro. miR‐25 may contribute to localized T cell dysfunction in the skin in CRPS.

Horizontal Vibration Characteristics of a Tapered Pile in Arbitrarily Layered Soil

A tapered pile (TP) is a new type of pile with a good bearing capacity, and scholars have conducted in-depth research on its static bearing characteristics. However, there is relatively little research on its dynamic bearing characteristics. In this paper, the horizontal vibration behavior of a tapered pile in arbitrarily layered soil is studied. Utilizing the Winkler foundation model and Timoshenko beam model to simulate pile-surrounding soil (PSS) and a tapered pile, respectively, the horizontal vibration model of a tapered pile embedded in layered soil was built. The analytical solutions for the horizontal displacement (HD), bending moment (BM), and shear force (SF) of a tapered pile were derived, and then the solutions for the horizontal dynamic impedance (HDI), rocking dynamic impedance (RDI), and horizontal-rocking coupling dynamic impedance (HRDI) of pile head were obtained. Using the present solutions, the effects of soil and pile properties on the horizontal vibration characteristics of a tapered pile were systemically studied. The ability of a tapered pile–soil system to resist horizontal vibration can be improved by strengthening the upper soil, but this ability cannot be further improved by increasing the thickness of the strengthened upper soil if its thickness is greater than the critical influence thickness.

The development of a high-speed miniature pump with dynamic bearing

Abstract A high-speed miniature pump is proposed for the application in aerospace area, where high efficiency and reliability are expected for the pump under the microgravity operation condition. In this paper, a miniature centrifugal pump with dynamic bearing is selected as the objective for the performance development. The prototype of the miniature pump is manufactured and tested by experiments at the rotational speed of 10,000r/min. The comparison of hydraulic performance near the design operation shows good agreement between the numerical results and experimental data. In order to improve hydraulic performance of the pump, the effects of splitter blades, number of blades, and wrap angle of blades are analyzed numerically. For each operating condition, in order to compare the influence of splitter blades on the performance and the internal flow, the impellers with and without splitter blades are designed respectively. In addition, for the splitter blades, the influence of the splitter blade position and the splitter blade thickness are also investigated. The numerical result shows that the highest efficiency among all the impellers is achieved with the blade number of 5, wrap angle of 160° and with no splitter blades. Moreover, for the impellers with the splitter blades, hydraulic performance of the pump is mainly decided by the main blades, while the splitter blades hardly help to improve the efficiency of the pump. The study is helpful for the further application of the high-speed miniature pump in various societies.

Summary of Research on Oil Film Temperature Characteristic of Hydrostatic and Hydrodynamic Thrust Bearings

Background: This study was conducted to explore the temperature rise and distribution of the micro-gap lubricating oil film of the hydrostatic and hydrodynamic thrust bearing, solve the problem of thermal deformation of the friction pair of the hydrostatic and hydrodynamic support, and improve the operation accuracy and stability of the hydrostatic and hydrodynamic thrust bearing. Objective: Combined with the theory of dynamic and static pressure bearings, the problem of lubricating oil film temperature rise is analyzed, and specific research directions are proposed. It is hoped that it will be helpful to improve the research of bearing stability and provide a theoretical basis for the structural design and operational reliability of heavy hydrostatic bearings. Methods: This article summarizes the research status of the oil film temperature rise of hydrostatic and hydrodynamic thrust bearings, especially focusing on the influence of hot oil carrying on the temperature rise of the lubricating oil film, and finally, the specific research directions and methods of the oil film temperature rise are prospected. Methods: Current and future developments of the oil film temperature rise of hydrostatic and hydrodynamic thrust bearings are finally provided and discussed. It provides theoretical support for the thermal deformation control of the bearing friction pair, and provides a basis for the highprecision and stable operation of the bearing. Conclusion: Aiming at the research hotspots of lubricating oil film temperature rise and distribution, based on the analysis of the principle of hydrostatic and dynamic pressure bearings, the domestic and foreign literature on the influence of the micro-gap lubricating oil film temperature rise and distribution of hydrostatic and hydrodynamic thrust bearings is collected and analyzed. The research shows that although some research results have been made in this area, current research methods and angle analysis still have certain limitations, so the study of the oil film temperature rise is not comprehensive, and further detailed discussion and analysis are still needed.

Effect of Preload on the Vibrations of EHL Angular Contact Ball Bearings: Theoretical and Experimental Results

The vibrations of a shaft in rotary mechanical systems supported by angular contact ball bearings are investigated theoretically and experimentally for various preloads in this paper. In the theoretical part of the study, a dynamic bearing model is presented, a rigid shaft supported by EHL angular contact bearing has been modelled as 5 DoF. Non-linear equations of motion are solved numerically by the Runge–Kutta method. In the second part of the study, an experimental setup that enables performing different operating cases has been designed to validate the theoretical results. Theoretical and experimental data are investigated and compared in both time and frequency domains and the results are compared. It is observed from both the theoretical and experimental studies that preload has a significant effect on the vibration behaviour. Results show that the increase in preload reduces the amplitude of the variable compliance frequencies of bearing, the natural frequency of system is shifted to a higher value, and using signal processing with an envelope spectrum gives better results in spectral analysis; small deviations occur between the theoretical and the experimental data due to modulation and noise from machine elements such as gear, motor, misalignment, waviness, etc. Therefore, the presented dynamic bearing model can be used with a reasonable accuracy to examine effect of preload on the vibration of shaft-bearing system.

Walk-IT: An Open-Source Modular Low-Cost Smart Rollator.

Rollators are widely used in clinical rehabilitation for gait assessment, but gait analysis usually requires a great deal of expertise and focus from medical staff. Smart rollators can capture gait parameters autonomously while avoiding complex setups. However, commercial smart rollators, as closed systems, can not be modified; plus, they are often expensive and not widely available. This work presents a low cost open-source modular rollator for monitorization of gait parameters and support. The whole system is based on commercial components and its software architecture runs over ROS2 to allow further customization and expansion. This paper describes the overall software and hardware architecture and, as an example of extended capabilities, modules for monitoring dynamic partial weight bearing and for estimation of spatiotemporal gait parameters of clinical interest. All presented tests are coherent from a clinical point of view and consistent with input data.

Experimental Research on the Seismic Characteristics of a Precast Frame Structure with a Viscous Damper

ABSTRACT Precast structures have become increasingly popular in recent years. However, the low seismic capacity of prefabricated structures is still a fraught issue in high seismic intensity regions. This paper aims to improve the structural seismic capacity of a precast concrete frame by employing a viscous damper. Two precast concrete frame specimens, with and without viscous dampers (PCFV and PCF), were produced and subjected to dynamic reversed cyclic loading tests. The experimental results showed that the viscous damper could improve the dynamic bearing capacity of the frames.

Study on Characteristics of Motion of a Centrifugal Impeller Supported by Dynamic Pressure Bearings in a Right Heart Ventricular Assist Device

Study on Characteristics of Motion of a Centrifugal Impeller Supported by Dynamic Pressure Bearings in a Right Heart Ventricular Assist Device

Dynamic bearing capacity of point fixed corrugated metal profile sheets subjected to blast loading

Blast loading scenarios and the corresponding hazards have to be evaluated for infrastructure elements and buildings especially at industrial sites for safety and security issues. Point fixed corrugated metal sheets are often applied as façade elements and can become a hazard for humans if they are pulled off. This paper investigates the dynamic bearing capacity of such structural members in terms of their general bending behavior in the middle of the span and pull-out behaviors at the fixing points. The elements are fixed at two sides and the load transfer is uniaxial. An experimental series with static and dynamic tests forms the basis to identify the predominant failure modes and to quantify the maximum stress values that can be absorbed until the investigated structural members fail. The experimental findings are applied to create and to optimize an engineering model for the fast and effective assessment of the structural response. The aim is the derivation of a validated model which is capable to predict the blast loading behavior of metal sheets including arbitrary dimensions, material properties, and screw connections. Results of this study can be integrated into a systematic risk and resilience management process to assess expected damage effects and the evaluation of robustness.

Dynamic crushing behaviors and enhanced energy absorption of bio-inspired hierarchical honeycombs with different topologies

In order to pursue good crushing load uniformity and enchance energy absorption efficiency of conventional honeycombs, a kind of bio-inspired hierarchical honeycomb model is proposed by mimicking the arched crab shell structures. Three bio-inspired hierarchical honeycombs (BHHs) with different topologies are designed by replacing each vertex of square honeycombs with smaller arc-shaped structures. The effects of hierarchical topologies and multi-material layout on in-plane dynamic crushings and absorbed-energy capacities of the BHHs are explored based on the explicit finite element (FE) analysis. Different deformation modes can be observed from the BHHs, which mainly depend upon hierarchical topologies and impact velocities. According to energy efficiency method and one-dimensional (1D) shock theory, calculation formulas of densification strains and plateau stresses for the BHHs are derived to characterize the dynamic bearing capacity, which is consistent well with FE results. Compared with conventional honeycombs, the crushing load efficiency and energy absorption capacity of the BHHs can be improved by changing the proper hierarchical topology and multi-material layout. These researches will provide theoretical guidance for innovative design and dynamic response performance controllability of honeycombs.

Weight bearing as a measure of disease progression in experimental autoimmune encephalomyelitis

Motor disability in multiple sclerosis is often modeled using experimental autoimmune encephalomyelitis (EAE) and assessed using the clinical score (CS), an observer-dependent tool that can lead to potential bias. The Advanced Dynamic Weight Bearing (ADWB) system was evaluated as an observer-independent measurement of EAE symptoms. ADWB detected weight shifts onto the front paws as mice develop hindlimb motor disability. CS and ADWB were strongly correlated, indicated that these measures are comparable and suggesting that ADWB may be an appropriate observer-independent tool for the assessment of EAE progression.