scholarly journals Impact-Rubbings Dynamics Behavior of Magnetic-Liquid Double Suspension Bearing in Electromagnetic Failure Model

2021 ◽  
Vol 11 (14) ◽  
pp. 6345
Author(s):  
Zhao Jianhua ◽  
Xing Lanchun ◽  
Ma Xuchao ◽  
Wang Yongqiang ◽  
Gao Dianrong ◽  
...  
Keyword(s):  
Power Amplifier ◽  
Drop Impact ◽  
Magnetic Liquid ◽  
Heavy Load ◽  
Electromagnetic System ◽  
Theoretical Simulation ◽  
Lower Unit ◽  
Failure Models ◽  
The Impact ◽  
Bearing System

Magnetic-liquid double suspension bearing (MLDSB) is a new type of suspension bearing with electromagnetic suspension as the main part and hydrostatic supporting as the auxiliary part. It can greatly improve the bearing capacity and stiffness of rotor bearing system and is suitable for medium speed, heavy load, and frequent starting occasions. The electromagnetic system adopts PD control, and hydrostatic system adopts constant pressure supply model to adjust and control the rotor’s displacement in real time. Once bearing electromagnetic system fails, the “dropping-collision” phenomenon of the rotor will be triggered in operation process, leading to cracking and shedding of magnetic sleeve plating and magnetic pole plating. Then the operational reliability and stability of MLDSB will be greatly reduced. So in this paper, Firstly, the drop impact-rubbing equation of the single DOF bearing system under four failure models (upper unit failure, lower unit failure, bilateral failure, and power amplifier failure) is established. Secondly, the paper simulates influence laws of different structure and operation parameters (plating/liquid film thickness and oil pocket pressure, bias current) on falling rotor impact-rubbings behavior. The results show that: (1) the degree of “dropping-collision” of the rotor under the four failure models is successively as follows: power amplifier failure > upper unit failure > bilateral failure > lower unit failure. (2) Due to the impact-rubbing damping effect of hydraulic oil, it plays a certain inhibitory and buffering role on the phenomenon of “drop-collision”. The degree and probability of “dropping-collision” of rotor can be effectively reduced by increasing the pressure of oil chamber appropriately. (3) The rotor drop impact-rubbing behavior obtained from the test is basically consistent with the theoretical simulation, and the correctness of the theoretical simulation can be effectively verified. The research provides a theoretical basis for fault prevention and diagnosis of MLDSB.

scholarly journals Impact-Rubbing Dynamic Behavior of Magnetic-Liquid Double Suspension Bearing under Different Protective Bearing Forms

Processes ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 1105
Author(s):  
Jianhua Zhao ◽  
Lanchun Xing ◽  
Sheng Li ◽  
Weidong Yan ◽  
Dianrong Gao ◽  
...  
Keyword(s):  
Dynamic Behavior ◽  
Ball Bearing ◽  
Magnetic Liquid ◽  
Electromagnetic System ◽  
Fixed Ring ◽  
Deep Groove ◽  
Deep Groove Ball Bearing ◽  
Protection Devices ◽  
Hydrostatic System ◽  
The Impact

The magnetic-liquid double suspension bearing (MLDSB) is a new type of suspension bearing, with electromagnetic suspension as the main part and hydrostatic supports as the auxiliary part. It can greatly improve the bearing capacity and stiffness of rotor-bearing systems and is suitable for a medium speed, heavy load, and frequent starting occasions. Compared with the active electromagnetic bearing system, the traditional protective bearing device is replaced by the hydrostatic system in MLDSB, and the impact-rubbing phenomenon can be restrained and buffered. Thus, the probability and degree of friction and wear between the rotor and the magnetic pole are reduced drastically when the electromagnetic system fails. In order to explore the difference in the dynamic behavior law of the impact-rubbing phenomenon between the traditional protection device and hydrostatic system, the dynamic equations of the rotor impact-rubbing in three kinds of protection devices (fixed ring/deep groove ball bearing/hydrostatic system) under electromagnetic failure mode are established, and the axial trajectory and motion law of the rotor are numerically simulated. Finally, the dynamic behavior characteristics of the rotor are compared and analyzed. The results show that: Among the three kinds of protection devices (fixed ring/deep groove ball bearing/hydrostatic system), the hydrostatic system has the least influence on bouncing time, impact-rubbing force, and impact-rubbing degree, and the maximum impact-rubbing force of MLDSB is greatly reduced. Therefore, the protective bear is not required to be installed in the MLDSB. This study provides the basis for the theory of the “gap impact-rubbing” of MLDSB under electromagnetic failure, and helps to identify electromagnetic faults.

scholarly journals Double Closed-Loop Compound Control Strategy for Magnetic Liquid Double Suspension Bearing

Processes ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 1195
Author(s):  
Jianhua Zhao ◽  
Yongqiang Wang ◽  
Xuchao Ma ◽  
Sheng Li ◽  
Dianrong Gao ◽  
...  
Keyword(s):  
Control Strategy ◽  
Electromagnetic Force ◽  
Closed Loop ◽  
Static Characteristic ◽  
Magnetic Liquid ◽  
Initial Current ◽  
Electromagnetic System ◽  
Initial Flow ◽  
Hydrostatic Force ◽  
Position Feedback

As a new type of suspension bearing, the magnetic liquid double suspension bearing (MLDSB) is mainly supported by electromagnetic suspension and supplemented by hydrostatic support. At present, the MLDSB adopts the regulation strategy of “electromagnetic-position feedback closed-loop, hydrostatic constant-flow supply” (referred to as CFC mode). In the equilibrium position, the external load is carried by the electromagnetic system, and the hydrostatic system produces no supporting force. Thus, the carrying capacity and supporting stiffness of the MLDSB can be reduced. To solve this problem, the double closed-loop control strategy of “electromagnetic system-force feedback inner loop and hydrostatic-position feedback outer loop” (referred to as DCL mode) was proposed to improve the bearing performance and operation stability of the MLDSB. First, the mathematical models of CFC mode and DCL mode of the single DOF supporting system were established. Second, the real-time variation laws of rotor displacement, flow/hydrostatic force, and regulating current/electromagnetic force in the two control modes were plotted, compared, and analyzed. Finally, the influence law of initial current, flow, and controller parameters on the dynamic and static characteristic index were analyzed in detail. The results show that compared with that in CFC mode, the displacement in DCL mode is smaller, and the adjustment time is shorter. The hydrostatic force is equal to the electromagnetic force in DCL mode when the rotor returns to the balance position. Moreover, the system in DCL mode has better robustness, and the initial flow has a more obvious influence on the dynamic and static characteristic indexes. This study provides a theoretical basis for stable suspension control and the safe and reliable operation of the MLDSB.

scholarly journals Development and Prospect of UAV-Based Aerial Electrostatic Spray Technology in China

2021 ◽  
Vol 11 (9) ◽  
pp. 4071
Author(s):  
Yali Zhang ◽  
Xinrong Huang ◽  
Yubin Lan ◽  
Linlin Wang ◽  
Xiaoyang Lu ◽  
...  
Keyword(s):  
Plant Protection ◽  
Structure Design ◽  
Research Progress ◽  
Theoretical Simulation ◽  
Spray System ◽  
Charged Droplets ◽  
Agricultural Use ◽  
Field Efficiency ◽  
The Impact ◽  
Electrostatic Spray

Aerial electrostatic spray technology for agriculture is the integration of precision agricultural aviation and electrostatic spray technology. It is one of the research topics that have been paid close attention to by scholars in the field of agricultural aviation. This study summarizes the development of airborne electrostatic spray technology for agricultural use in China, including the early research and exploration of Chinese institutions and researchers in the aspects of nozzle structure design optimization and theoretical simulation. The research progress of UAV-based aerial electrostatic spray technology for agricultural use in China was expounded from the aspects of nozzle modification, technical feasibility study, influencing mechanism of various factors, and field efficiency tests. According to the current development of agricultural UAVs and the characteristics of the farmland environment in China, the UAV-based aerial electrostatic spray technology, which carries the airborne electrostatic spray system on the plant protection UAVs, has a wide potential in the future. At present, the application of UAV-based aerial electrostatic spray technology has yet to be further improved due to several factors, such as the optimization of the test technology for charged droplets, the impact of UAV rotor wind field, comparison study on charging modes, and the lack of technical accumulation in the research of aerial electrostatic spray technology. With the continuous improvement of the research system of agricultural aviation electrostatic spray technology, UAV-based electrostatic spray technology will give play to the advantages in increasing the droplets deposition on the target and reducing environmental pollution from the application of pesticides. This study is capable of providing a reference for the development of the UAV-based agricultural electrostatic spray technology and the spray equipment.

Numerical Simulation and Experimental Measurement of a Printed Circuit Board Subjected to Drop Test

2009 ◽  
Vol 419-420 ◽  
pp. 37-40
Author(s):  
Shiuh Chuan Her ◽  
Shien Chin Lan ◽  
Chun Yen Liu ◽  
Bo Ren Yao
Keyword(s):  
Finite Element ◽  
Experimental Measurement ◽  
Test Specimen ◽  
Printed Circuit Board ◽  
Drop Impact ◽  
Simulation Technique ◽  
Drop Test ◽  
Circuit Board ◽  
Printed Circuit ◽  
The Impact

Drop test is one of the common methods for determining the reliability of electronic products under actual transportation conditions. The aim of this study is to develop a reliable drop impact simulation technique. The test specimen of a printed circuit board is clamped at two edges on a test fixture and mounted on the drop test machine platform. The drop table is raised at the height of 50mm and dropped with free fall to impinge four half-spheres of Teflon. One accelerometer is mounted on the center of the specimen to measure the impact pulse. The commercial finite element software ANSYS/LS-DYNA is applied to compute the impact acceleration and dynamic strain on the test specimen during the drop impact. The finite element results are compared to the experimental measurement of acceleration with good correlation between simulation and drop testing. With the accurate simulation technique, one is capable of predicting the impact response and characterizing the failure mode prior to real reliability test.

The Influence of Lubricant Supply Conditions and Bearing Configuration on the Performance of (Semi) Floating Ring Bearing Systems for Turbochargers

2017 ◽  
Author(s):  
Luis San Andrés ◽  
Feng Yu ◽  
Kostandin Gjika
Keyword(s):  
Heat Flow ◽  
Thermal Energy ◽  
Operating Conditions ◽  
Temperature Fields ◽  
Engine Oil ◽  
Large Temperature ◽  
Oil Viscosity ◽  
Supply Pressure ◽  
The Impact ◽  
Bearing System

Engine oil lubricated (semi) floating ring bearing (S)FRB systems in passenger vehicle turbochargers (TC) operate at temperatures well above ambient and must withstand large temperature gradients that can lead to severe thermo-mechanical induced stresses. Physical modeling of the thermal energy flow paths and an effective thermal management strategy are paramount to determine safe operating conditions ensuring the TC component mechanical integrity and the robustness of its bearing system. On occasion, the selection of one particular bearing parameter to improve a certain performance characteristic could be detrimental to other performance characteristics of a TC system. The paper details a thermohydrodynamic model to predict the hydrodynamic pressure and temperature fields and the distribution of thermal energy flows in the bearing system. The impact of the lubricant supply conditions (pressure and temperature), bearing film clearances, oil supply grooves on the ring ID surface are quantified. Lubricating a (S)FRB with either a low oil temperature or a high supply pressure increases (shear induced) heat flow. A lube high supply pressure or a large clearance allow for more flow through the inner film working towards drawing more heat flow from the hot journal, yet raises the shear drag power as the oil viscosity remains high. Nonetheless, the peak temperature of the inner film is not influenced much by the changes on the way the oil is supplied into the film as the thermal energy displaced from the hot shaft into the film is overwhelming. Adding axial grooves on the inner side of the (S)FRB improves its dynamic stability, albeit increasing the drawn oil flow as well as the drag power and heat flow from the shaft. The predictive model allows to identify a compromise between different parameters of groove designs thus enabling a bearing system with a low power consumption.

Mechanical Event Simulation of Drop Testing for Toy Product

2006 ◽  
Vol 532-533 ◽  
pp. 993-996
Author(s):  
Anthony Yee Kai Yam ◽  
Kai Leung Yung ◽  
Chi Wo Lam
Keyword(s):  
Material Properties ◽  
Impact Analysis ◽  
Plastic Material ◽  
Free Fall ◽  
Drop Impact ◽  
Local Analysis ◽  
Element Analysis ◽  
Event Simulation ◽  
Long Time ◽  
The Impact

Toys that are free from drop failures normally take a long time to develop. It is often time and cost consuming after the production tooling is built to detect drop test failure. This paper introduces a new drop testing analysis method for Toys. The method uses a simple approach with a local analysis that based on the linear and non linear finite element analysis. Modeling and transient drop analysis of a pre-school toy is used as a case study to demonstrate the method. The impact analysis of the product hitting the solid concrete floor after a free fall is presented. The analysis focuses on the deformation of the housing for a product with electronic circuit and mechanical mechanism inside. Experimental data has been obtained for drop simulation of the housing and its correlation with the plastic material properties. The stress and strain of the housing during drop impact tests are noted. The effects of the material properties to the housing deflection under drop/impact shock have been investigated. Numerical results are compared with experimental results to validate the method.

scholarly journals The Impact of Heavy Load Carrying on Musculoskeletal Pain and Disability Among Women in Shinyanga Region, Tanzania

2020 ◽  
Vol 86 (1) ◽  
pp. 17
Author(s):  
Jillian L. Kadota ◽  
Sandra I. McCoy ◽  
Michael N. Bates ◽  
Agatha Mnyippembe ◽  
Prosper F. Njau ◽  
...  
Keyword(s):  
Musculoskeletal Pain ◽  
Heavy Load ◽  
Load Carrying ◽  
The Impact

scholarly journals Experimental Study of Drop Impact on Deep-Water Surface in the Presence of Wind

2018 ◽  
Vol 48 (2) ◽  
pp. 329-341 ◽  
Author(s):  
Xinan Liu
Keyword(s):  
Deep Water ◽  
Water Surface ◽  
Water Drop ◽  
Threshold Value ◽  
Impact Angle ◽  
Drop Impact ◽  
Wind Speeds ◽  
Secondary Droplets ◽  
Low Wind Speeds ◽  
The Impact

AbstractThe effects of wind on the impact of a single water drop on a deep-water surface are studied experimentally in a wind tunnel. Experiments are performed by varying impacting drop diameters, ranging from 2.5 to 4.1 mm and wind speeds up to 6.7 m s−1. The sequence of splashing events that occurred during drop impacts is recorded with a backlit, cinematic shadowgraph technique. The experimental results show that for low wind speeds, an asymmetrical crown forms on the leeward of the periphery of the colliding region after the drop hits the water surface, while a wave swell forms on the windward. Secondary droplets are generated from the crown rim. For high wind speeds with large drop diameters, ligaments are generated from the crown rim on the leeward of the drop impact site. The ligaments grow, coalesce, and fragment into secondary droplets. It is found that both the drag force and surface tension play important roles in the evolution process of the ligaments. The nondimensional K number (K = WeOh−0.4, where We is the Webber number and Oh is the Ohnesorge number) is used to describe the splashing-deposition limit of drop impact. The threshold value of this K number changes with the wind velocity and/or drop impact angle.

Influence of Liquid Properties on Energy Conversion During Crown Evolution Following Drop Impact Upon Films

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Yujia Zhang ◽  
Peiqing Liu ◽  
Qiulin Qu ◽  
Fanglin Liu ◽  
Ramesh K. Agarwal
Keyword(s):  
Reynolds Number ◽  
Energy Conversion ◽  
Weber Number ◽  
Stokes Equations ◽  
Drop Impact ◽  
Navier Stokes ◽  
Impact Process ◽  
Vof Model ◽  
The Moment ◽  
The Impact

Abstract The energy conversion is proposed to analyze the effects of liquid properties on the formation of an ejecta sheet, prompt splashing, and crown evolution. The incompressible laminar Navier–Stokes equations coupled with the volume-of-fluid (VOF) model are solved numerically in an axisymmetric frame to simulate the impact process. Based on the energy conversion curves and liquid–gas interface shapes, the Weber number is shown to be the main dimensionless quantity controlling the impact process, especially with regard to crown evolution. However, the Reynolds number does have some influence on the drop impact process, especially during the stage of ejecta sheet formation and prompt splashing. By studying energy conversion during the impact process, the crown evolution is shown to be accelerated significantly with decreasing Weber number, but is hardly affected by the Reynolds number. A linear relation is found between the time to the moment of crown stabilization (when the crown height reaches its maximum value) and the square root of the Weber number. The relationship between the Weber number and the energy distribution at the moment of crown stabilization is also studied.

Clearance Effects on the Impact Behavior of Large Aspect Ratio Silicon Journal Microbearings

2010 ◽  
Author(s):  
S. Demiri ◽  
S. Boedo
Keyword(s):  
Wear Behavior ◽  
Coefficient Of Restitution ◽  
Journal Bearings ◽  
Impact Behavior ◽  
Radial Clearance ◽  
Test Apparatus ◽  
Rotor Speed ◽  
Dynamic Impact ◽  
The Impact ◽  
Bearing System

This paper investigates the effect of bearing clearance on the impact behavior of microfabricated silicon journal bearings. The design of a novel test apparatus to assess microbearing wear behavior is presented. Microbearing designs, microfabrication processes, and metrology characterization techniques are discussed. A dynamic impact model of the bearing system based on classical impulse-momentum relations is formulated in order to assess the effect of clearance on rotor speed. Coefficient of restitution values obtained over the range of kinematically allowable radial clearance specifications are found to agree well with previously published results for polysilicon microstructures.

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