Bearing friction effect on cup anemometer performance modelling

In the present work, the effect of the friction forces at bearings on cup anemometer performance is studied. The study is based on the classical analytical approach to cup anemometer performance (2-cup model), used in the analysis by Schrenk (1929) and Wyngaard (1981). The friction torque dependence on temperature was modelled using exponential functions fitted to the experimental results from RISØ report #1348 by Pedersen (2003). Results indicate a logical poorer performance (in terms of a lower rotation speed at the same wind velocity), with an increase of the friction. However, this decrease of the performance is affected by the aerodynamic characteristics of the cups. More precisely, results indicate that the effect of the friction is modified depending on the ratio between the maximum value of the aerodynamic drag coefficient (at 0° yaw angle) and the minimum one (at 180° yaw angle). This reveals as a possible way to increase the efficiency of the cup anemometer rotors. Besides, if the friction torque is included in the equations, a noticeable deviation of the rotation rate (0.5-1% with regard to the expected rotation rate without considering friction) is found for low temperatures.

Study on the tribological properties and fault mechanisms of copper-based alloy journal bearing under different working conditions

This paper experimentally investigates the influence of working conditions on the friction properties, wear behaviors, and seizure limit of journal bearing friction pairs including the aluminum bronze shafts and the steel bearings. The tribological tests were conducted by the journal bearing friction and lubrication characteristic test-rig under different relative clearances, applied loads, rotational speeds, and inlet oil temperatures. The worn surfaces were measured by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and laser microscopic 3D profile device to obtain the fault mechanisms. The results showed that the seizure limit value could be improved with the increase of relative clearance. The main wear mechanism of friction pairs is adhesive wear for a small relative clearance, and the main wear mechanism is transformed into abrasive wear with the increase of the bearing relative clearance.

The Flow-Heat Coupling Study of Cooling Circulating Channel of Magnetic Drive Pump

The medium in the cooling circulation channel of the magnetic drive centrifugal pump will take away the heat generated by the magnetic eddy current and bearing friction in time to avoid the high temperature demagnetization phenomenon of the permanent magnets. Therefore, the reasonable design of the cooling circulation channel directly affects the stable operation of the magnetic drive centrifugal pump. In this paper, the heat exchange and temperature distribution in the cooling circulating channel of magnetic drive pump are studied by means of numerical calculation of fluid-heat coupling and external characteristic test. The temperature distribution and development law of the isolation sleeve clearance, the bottom of the isolation sleeve and the reflow hole are analysed emphatically, and the convection heat transfer coefficient distribution in the isolation sleeve clearance is studied.

Viscous Friction Effect During the Process of Tightening and Loosening of Bolted Joints

Bolted connection is one of the most widely used mechanical connections because of its easiness of installation and disassembly. Research of bolted joints mainly focuses on two aspects: high precision tightening and improvement of anti-loosening performance. The under-head bearing friction coefficient and the thread friction coefficient are the two most important parameters that affect the tightening result of the bolted joint. They are also the most critical parameters that affect the anti-loosening performance of the bolted joint. Coulomb friction model is a commonly used model to describe under-head bearing friction and thread friction, which considers the friction coefficient as a constant independent of normal pressure and relative sliding velocity. In this paper, the viscous effect of the under-head bearing friction and thread friction is observed by measuring the friction coefficient of bolted joints. The value of the friction coefficient increases with the increase of the relative sliding velocity and the decrease of the normal pressure. It is found that the Coulomb viscous friction model can better describe the friction coefficient of bolted joints. Taking into account the dense friction effect, the loosening prediction model of bolted joints is modified. The experimental results show that the Coulomb viscous friction model can better describe the under-head bearing friction coefficient and thread friction coefficient. The model considering the dense effect can more accurately predict the loosening characteristics of bolted joints.

Evaluation of Stress and Fatigue of a Rail Vehicle Suspension Component

The article discusses the use of pivot bearing friction liners, made of selected materials, in railway freight wagons’ spherical centre bowls. Comparative studies on the effect of suspension dynamics on the equivalent stresses in the liner material were carried out using the finite element method and multibody simulation. The results show the magnitude and location of the highest stresses in the liner with varying input loads, friction coefficients and interacting materials. The analysis is a basis for a simulation method for predicting the fatigue life of the suspension friction liner placed in the centre bowl between the bogie frame and the vehicle body.

Analysis of Factors Affecting Horizontal Displacement of Pier Top of High-Pile and High-Pier Bridge

The excessive longitudinal horizontal displacement of pier top has become one of the common defects of high-pier bridge, which seriously affects the safety of the bridge structure. In order to determine the influencing factors of the horizontal displacement of the pier top of high-pile and high-pier bridges, this paper establishes the finite element model of the whole bridge based on the high-pile and high-pier bridge of the Qianhuang Expressway, and considers the influence of dead load, vehicle load, vehicle braking force, temperature load, bearing friction coefficient, and bearing under eccentric compression on the horizontal displacement of the pier top. By comparing and analyzing the law of various factors influence on the horizontal displacement of the pier top, the main causes of the horizontal displacement of the pier top of high-pile and high-pier bridges are summarized, which can provide reference for the analysis of pier top deviation of similar high-pile and high-pier bridges.

Analysis of Standby Losses and Charging Cycles in Flywheel Energy Storage Systems

Aerodynamic drag and bearing friction are the main sources of standby losses in the flywheel rotor part of a flywheel energy storage system (FESS). Although these losses are typically small in a well-designed system, the energy losses can become significant due to the continuous operation of the flywheel over time. For aerodynamic drag, commonly known as windage, there is scarcity of information available for loss estimation since most of the publications do not cover the partial vacuum conditions as required in the design of low loss energy storage flywheels. These conditions cause the flow regime to fall between continuum and molecular flow. Bearings may be of mechanical or magnetic type and in this paper the former is considered, typically hybridized with a passive magnetic thrust bearing. Mechanical bearing loss calculations have been extensively addressed in the open literature, including technical information from manufacturers but this has not previously been presented clearly and simply with reference to this application. The purpose of this paper is therefore to provide a loss assessment methodology for flywheel windage losses and bearing friction losses using the latest available information. An assessment of windage losses based on various flow regimes is presented with two different methods for calculation of windage losses in FESS under rarefied vacuum conditions discussed and compared. The findings of the research show that both methods closely correlate with each other for vacuum conditions typically required for flywheels. The effect of the air gap between the flywheel rotor and containment is also considered and justified for both calculation methods. Estimation of the bearing losses and considerations for selection of a low maintenance, soft mounted, bearing system is also discussed and analysed for a flywheel of realistic dimensions. The effect of the number of charging cycles on the relative importance of flywheel standby losses has also been investigated and the system total losses and efficiency have been calculated accordingly.

Triboelectric touch sensor for position mapping during total hip arthroplasty

Objective: In this research, a triboelectric nanogenerator (TENG) was utilized to determine if a pressure-based sensor could detect bearing friction in a total hip arthroplasty (THA) and detect the contact of specific areas during ROM checks. Results : The pressure-based sensor shows capability to sense bearing friction. In more detail, the TENG embedded in four different sides of the trial exhibits up to 1 V from peak-to-peak. Moreover, these flexible touch sensors with TENG describes a peak signal in output voltage which should lead to extremely sensitive detection of bearing friction induced by the THA.

Triboelectric Touch Sensor for Position Mapping During Total Hip Arthroplasty

Objective: In this research, a triboelectric nanogenerator (TENG) was utilized to determine if a pressure-based sensor could detect bearing friction in a total hip arthroplasty (THA) and detect the contact of specific areas during ROM checks. Results: The pressure-based sensor shows capability to sense bearing friction. In more detail, the TENG embedded in four different sides of the trial exhibits up to 1 V from peak-to-peak. Moreover, these flexible touch sensors with TENG describes a peak signal in output voltage which should lead to extremely sensitive detection of bearing friction induced by the THA.