Analysis of Axially Magnetized Permanent Magnet Bearing Characteristics

The use of permanent magnets as bearings has gained attention of researchers nowadays. The characteristics of forces and moments have to be analysed thoroughly for the proper design of permanent magnet bearings. This paper presents a mathematical model of an axially magnetized permanent magnet bearing (ring magnets) using Coulombian model and a vector approach to estimate the force, moment and stiffness. A MATLAB code is developed for evaluating the parameters. Furthermore, it is extended to analyse stacked ring magnets with alternate axial polarization. The proposed model is validated with the available literature. Comparison of force and stiffness results of the present model with the results of three dimensional (3D) finite element analysis using ANSYS shows good agreement. Finally, the cross coupled stiffness values in addition to the principal stiffness values are presented for elementary structures and also for stacked structures with three ring permanent magnet

Load Bearing Characteristics Of Implants For Osteochondral Defect Repair

Objective: To measure changes in joint contact mechanics, during simulated gait, in the presence of a medial femoral osteochondral defect and after filling the defect using two different polyvinyl alcohol implant configurations. Methods: Seven human cadaveric knees were tested under simulated gait, while the contact stresses on the tibial plateau were recorded using an electronic sensor. Each knee was tested using the following conditions: intact, defect, and after the defect has been filled with either 10% PVA, 20% PVA, 10% PVA + a porous titanium base, or 20% PVA + porous titanium base. Changes in contact area, total force, weight center of contact, and stress pattern differences were measured for each knee. Results: At 14% of the gait cycle, there were no changes in contact area observed between conditions. At 45% of the gait cycle, differences were seen in the meniscal-cartilage contact area with increases in contact area between the intact and 10% PVA as well as 20% PVA scaffolds. At 14% of gait, there was a significant increase in total force between intact and defect conditions and between defect and 20% PVA + pTi in the menical-cartilage region with forces of 179 ± 113 N, 278 ± 113 N, and 193 ± 96 N for the intact, defect, and 20% PVA + pTi respectively. At 45% of gait, there was a significant difference in total force between intact condition and the defect condition in the meniscal-cartilage contact area with average total force of 90 ± 73 N and 148 ± 75 N respectively. Differences were found in the cartilage-cartilage total force at 45% of gait between intact and all other conditions and between defect and 20% PVA + pTi. The total forces were 486 ± 134 N for the intact, 360 ± 158 N for the defect, and 431 ± 177 for the 20% PVA + pTi, and the remaining implants tested having total force values below 412 N. Conclusions: The presence of an osteochondral defect causes an increase in loading on the meniscus. Implants in the range of tissue engineered constructs can partially restore joint loading but cause alterations in contact stress patterns

Study on Bearing Characteristics of Reciprocating Compressor for Refrigerator

In recent years, in order to reduce the energy consumption of refrigerators through reduction of input power and improved refrigeration capacity, reciprocating compressors are gradually converted to inverter type. Correspondingly, we have studied the sliding bearing characteristics of the crankshaft journal at variable speed which is the key to improving the efficiency of reciprocating compressor. Generally, the characteristics of a sliding bearing are explained with a Stribeck curve. In the fluid lubrication regime, there is sufficient lubricant between metal surfaces. As the rotational speed decreases, the viscous resistance is reduced and it will result in the reduction of friction coefficient. Conversely, it is widely known that further reduction of rotational speed will shift to boundary lubrication regime where the friction coefficient increases due to metal to metal contact. In the inverter reciprocating compressor, it is presumed that the sliding of crankshaft on bearing at high rotational speed is in fluid lubrication regime. The input power can be reduced with gradual decrease of friction coefficient by lowering rotational speed, but then the sliding characteristic of the crankshaft at each rotational speed was unclear such that when the speed is too low it will progress into the boundary lubrication regime. This paper explains our experimental study to obtain a Stribeck curve at low load, low speed, and low viscosity oil in inverter operation using a bearing tester that estimate sliding crankshaft on bearing. The results obtained enable the prediction of sliding characteristic of crankshaft and optimization of the bearing property in reciprocating compressor

The performance and application of high speed long life LH2 hybrid bearings for reusable rocket engine turbomachinery

Data are presented for two different experimental programs which were conducted to investigate the characteristics of a hybrid (hydrostatic/ball) bearing operating in liquid hydrogen. The same bearing design was used in both programs. Analytical predictions were made of the bearing characteristics and are compared with the experimental results when possible. The first program used a bearing tester to determine the steady state, transient, and cyclic life characteristics of the bearing over a wide range of operating conditions. The second program demonstrated the feasibility of applying hybrid bearings to an actual high speed turbopump by retrofitting and then testing an existing liquid hydrogen turbopump with the bearings

An experimental study of the viscoseal bearing Interim report

Viscoseal bearing experimental analysis of bearing characteristics and sealing performanc

Lateral load bearing characteristics of light gauge steel and lightweight concrete shear walls

In China, there is a new structural system named light gauge steel and lightweight concrete (LSLC) structure, which used lightweight concrete as structural material in composite way with cold-formed steel. Here, the shear walls are the main structural members for the LSLC structure, which are assembled with the light gauge steel lattice columns and horizontal braces, and filled with lightweight concrete. In this study, the LSLC shear walls are experimentally investigated to evaluate their failure mechanism and lateral load bearing capacity. For this purpose, several specimens with different shear span ratio are designed and tested under static cyclic loading. This paper presents the damage state and hysteresis loops of the specimens detailly. Then, the lateral load bearing characteristics of the LSLC shear walls are discussed according to the failure mechanism, such as shear and flexural failure. Finally, the calculation methods of lateral strength for the LSLC shear walls are proposed based on the diagonal strut mechanism and sectional force equilibrium

Розробка та дослідження прецизійної сферичної опори ковзання

Наведена інформація про розроблену прецизійну опору ковзання. Викладені результати досліджень характеристик опори, зокрема визначені динамічні моменти опору при поперечно-кутових переміщеннях опори та частотні характеристики опор по моменту опору. The information about developed high-precision sliding bearing is given. The results of investigation of bearing characteristics are given. In particular, dynamic resistance moments by cross-angular travels of bearing and frequency characteristics of bearing by resistance moment are determined

Cantilever mounted resilient pad gas bearing

A gas-lubricated bearing is described, employing at least one pad mounted on a rectangular cantilever beam to produce a lubricating wedge between the face of the pad and a moving surface. The load-carrying and stiffness characteristics of the pad are related to the dimensions and modulus of elasticity of the beam. The bearing is applicable to a wide variety of types of hydrodynamic bearings

Titanium reinforced boron polyimide composite

Program involves development of process technique for boron-polyimide prepeg, lay-up and curing procedures for prepegs when processed under vacuum bag pressure, and development and evaluation of titanium hard points for smooth transition of loads from titanium attach points into boron reinforced body of structure