Bottom Pivot Research Articles

Machine learning calculation model for hydrodynamic lubrication characteristics of a miter gate bottom pivot

The bottom pivot is a vital support device in the miter gate but often subject to poor lubrication and wear failures. Calculating the hydrodynamic lubrication characteristics of the bottom pivot is a complex three-dimensional (3D) problem, and most of existing models adopt simplified assumptions to reduce the calculation difficulty. To solve this issue, this work develops a 3D model to calculate the hydrodynamic lubrication characteristics of the miter gate bottom pivot. The finite difference method is used to solve the oil film thickness and pressure distribution based on the spherical coordinates Reynolds equation. The component forces in three directions are calculated from the pressure distribution and compared with the theoretical values to generate the calculation difference. Then, the genetic algorithm (GA) is used to minimize the difference to determine the optimal initial parameters for the 3D model. The analysis results show that the calculation accuracy can be significantly improved by using the optimal initial model parameters. When our initial pressure is 5.64MPa, the results meet the engineering accuracy requirements.

Study on surface wear of gate bottom pivot based on multi-notch measurement

Wear quantify is an important parameter for wear research. However, the measurement of wear is a key problem in the theoretical study of large - mass regular surface friction pairs with uneven wear. So, this paper proposes a method based on the measurement of multi-notch chord length, which realizes the indirect measurement of the surface wear of semi-spherical friction pair. The relationships among measurement error, notches number, notches distribution of the friction pair in different diameters are derived by theoretical calculation, Then the experimental results show that the measurement precision of wear increases with the increase of the number of surface notch holes, but the increment of precision decreases gradually until convergence, and the function between the optimal number of scratches and the measuring accuracy and the radius of friction pair is given. By setting the number of scratches of the calculated results in advance during the manufacturing process, and combining the corresponding calculation formula and the field measurement results, the fast measurement of the wear quantify of the hemispherical bearing is completed.

Tribological Performance of Gate Bottom Pivot Friction Pair QT600-3/40Cr and Its Wear Surface Power Spectral Density Characterization

Tribological Performance of Gate Bottom Pivot Friction Pair QT600-3/40Cr and Its Wear Surface Power Spectral Density Characterization

Study on the Miter Gate Fault Diagnosis Methods Based on Vibration Signals

This miter gates of Three Gorges Dam and Gezhou Dam open and close frequently under low speeds and heavy loading conditions. The moving componets, including hoist, door shaft, roof pivot and bottom pivot, work long-term and go wrong easily. The traditional periodic maintenance and fault overhaul are ineffective and may cause damage and waste. With the No.1 ship lock maintenance of Gezhou Dam, the top pivots poor lubrication operating mode was simulated. The vibration signal of top hub reinforcement plate was collected before and after overhaul, then several signal processing and analysis techniques were selected for research on fault diagnosis methods. The results illustrate that it is feasible to achieve miter gate faults diagnosis based on vibration signal detection technology, which has certain guiding significance on miter gate maintenance.

Study on the Miter Gate Fault Diagnosis Methods Based on Vibration Signals

The miter gates of Three Gorges Dam and Gezhou Dam open and close frequently under low speeds and heavy loading conditions. The moving componets, including hoist, door shaft, roof pivot and bottom pivot, work long-term and go wrong easily. The traditional periodic maintenance and fault overhaul are ineffective and may cause damage and waste. So the miter gate fault diagnosis methods based on vibration signal are put forward in this subject. With the No.1 ship lock maintenance of Gezhou Dam, the top pivots poor lubrication operating mode was simulated. The vibration signal of top hub reinforcement plate was collected before and after overhaul, then several signal processing and analysis techniques were selected to research the fault diagnosis methods. The results illustrate that it is feasible to achieve miter gate faults diagnosis based on vibration signal detection technology, which has some certain guiding significance on miter gate maintenance.

The Vibration Characteristics Analysis of Miter Gate Based on ANSYS Workbench and Vibration Test

The 3d model of miter gate has been set up based on skeleton model of Pro/E, and it has been imported into ANSYS Workbench module for static structure analysis and modal analysis. In the process of finite element simulation, the rotational constraints has been imposed on the top and bottom pivot according to the actual operation situation of the miter gate, and obtain the first several order frequencies and corresponding modal vibration mode of the miter gate, which can show the hydrodynamic vibration stress and strain distribution. According to the results of the finite element simulation analysis, the prototype vibration test of the miter gate has been done. The test results show that the vibration amplitude and the stress and strain distribution of each part of the miter gate are corresponding to the vibration test.

OS5-2-5 Micro scale monotonic and tension fatigue testing of spring-bridge freestanding thin films application for MEMS

An electroplating spring-bridge micro-tensile specimen is demonstrated and fabricated here. The specimen is fit into a specially designed micro-mechanical apparatus to carry out a series of tensile testing on sub-micron freestanding thin films. Freestanding thin films were then loaded by performing monotonic loading/ unloading up to 20 μm/(10^<-1>s) and tension-tension fatigue experiments at 25 Hz up to 〜10^5cycles. Loading was applied using a piezoelectric actuator with 0.1 μm resolution connected through pin hole into the test chip. Loads were measured by connected specimens through a pin connected rod using its bottom pivot to transfer loads and displacement from sample load sensing beam into a capacitor load cell. For the monotonic loading/unloading experiments, we found the modulus of copper thin films with thickness of 200 nm at ambient temperature. Displacement controlled tension-tension fatigue experiments on copper thin films have also been performed and a trend of decreasing cycles to failure with increasing mean displacement has been noted but requires further experimental exploration.

The Pivot Wash in Two Impeller Modes for the Baylor/Miwatec Centrifugal Blood Pump

A centrifugal blood pump with a double pivot impeller and an eccentric inlet port is being developed as an implantable artificial heart by the Baylor College of Medicine and Miwatec Co. Ltd. Flow visualization measurements were conducted to compare the flow around the pivot for two impeller operational modes: the top and the bottom contact modes. In the top contact mode, one-way flow in the pivot gap due to the eccentric vortex was observed, and sufficient wall shear rate to prevent thrombus formation was attained around the bottom pivot for over 1,400 rpm. Computational fluid dynamic analyses confirmed that the causes of the eccentric vortex were the inlet eccentricity and the pressure imbalance in the volute.

Flow visualization in a centrifugal blood pump with an eccentric inlet port.

Flow visualization analysis was applied to the Baylor/Miwatec centrifugal artificial heart to evaluate its fluid dynamic characteristics regarding antithrombogenicity. An eccentric vortex was found both in the upper and the lower gaps of the impeller, which is supposed to be caused by the eccentric inlet port. Therefore, one-way flow toward the outlet is formed and washes the pivot. The combination of an eccentric vortex and a pivot bearing that is washed is unique to the Baylor/Miwatec pump. For the male pivots exposed to periodic wash, the minimum shear rate around the bottom pivot was estimated to be 650/s, which is higher than the threshold for thrombus formation shown by other studies. The wall shear rate at the impeller bottom surface was found to be larger in the top contact mode than in the bottom contact mode.

HYDRAULIC SUSPENSION GYRO PUMP

An impeller suspension mechanism is a major concern to avoid thrombus formation for long-term centrifugal pump application. A gyro-type centrifugal pump has been developed as permanent implantable ventricular assist device (VAD). Currently, this titanium-made gyro pump utilizes a novel hydraulic impeller suspension system. This study aims to evaluate the anti-thrombogenicity of the hydraulic suspension (HS) gyro pump. In vitro studies were conducted to examine the platelet adhesion at the bottom pivot, which is a primary lesion of white thrombus after pump implantation. For the pump hemorheology analysis, the particle tracing flow visualization was performed utilizing. In addition to these in vitro studies, current in-vivo animal studies were retrospectively examined.TableHS pumps demonstrated 50% lower platelet adhesion rate at the bottom pivot lesion compared to the control gyro pump. With the flow visualization study, continuous washout flow was created around the the center pivot behind the impeller. Total 20 pumps were implanted to 10 calves, and no thromboembolism was observed. Only one case had thrombus formation inside the right pump head due to low pump flow caused by the outflow graft kinking. This HS gyro pump is a compact, secure, and affordable VAD.

Morphological changes of the pivot bearings in the Gyro Pump C1E3 after clinical use

The Gyro Pump C1E3 incorporates a doublepivot bearing system as a completely sealless centrifugal pump. The male pivot is made of alumina ceramic, and the female is made of polyethylene. Therefore, the durability of this pump depends upon morphological changes of the female polyethylene pivots, which we examined after clinical usage in the present study. We examined 30 pumps, which were used for cardiopulmonary bypass (CPB), in terms of weight, depth, and surface roughness of the female polyethylene pivots. To determine changes caused by clinical use, we also examined 10 pumps of the same lot numbers with the pumps clinically used and stocked in the factory. There were no significant changes in weight of top and bottom pivots. Also, there was no significant difference in depth and surface roughness of the top pivots. However, there was a significant increase in depth and a decrease in surface roughness of the bottom pivots from clinical use. The results revealed that the bottom pivot, rather than the top pivot, is subject to mechanical deformation by clinical use of the Gyro Pump for CPB. Since morphological changes of the bottom pivot may result from spinning of the impeller at the bottom contact phase, the magnetic coupling distance may need to be increased to obtain more stable spinning of the impeller in a routine CPB.

Quantitative approach to control spinning stability of the impeller in the pivot bearing-supported centrifugal pump.

The Gyro C1E3 pump has been developed as a completely sealless centrifugal pump driven by a magnetic coupling system for long-term usage. The Gyro C1E3 pump is a pivot bearing-supported pump in which the impeller is supported with the top and bottom pivot bearings. In the Gyro C1E3 pump, the impeller spinning is affected by the force balance between the floating force (Ff[N]) of the hydrodynamic effect and the magnetic thrust force (Tf[N]). The authors quantitatively investigated the floating force of the impeller in vitro to determine the magnetic coupling distance (MCD[mm]) that would result in stable impeller spinning. In vitro tests were performed using a loop filled with 37% glycerin solution to obtain the relationship between the MCD and floating speed (Rf, rotational speed when the impeller starts floating [rpm]) and the relationship between the MCD and Tf. From the obtained relationships, we calculated Ff and determined the relationship between the Ff and the rotational speed (R). Furthermore, we determined the relationship between d (minimum required MCD [mm]) and R from the results of determining the relationship of the MCD and Tf and of the Ff and R. The following relationships were obtained: Rf = 6.24 x 10(4) x MCD-1.35; Tf = 5.27 x 10(3) x MCD-2.29; Ff = 4.71 x 10(-6) x RPM1.69; and d = 9.02 x RPM-0.85 where RPM is the rotational speed. It was demonstrated that the floating force of the impeller is a function only of the rotational speed in the pivot bearing-supported Gyro C1E3 pump. The floating force is estimated to be 10 N to 40 N at rotational speeds of 1,500 rpm to 3,000 rpm at which the Gyro pump may be used in most clinical situations. It would be possible to control the impeller position of the Gyro pump automatically at the stable spinning condition by controlling the adequate magnetic coupling distance based upon its relationship with the rotational speed which was obtained in this study.