Fit Clearance Research Articles

Design of Window Wiper for Optical Measurement Camera Applicable in Humid Environment

Design window wiper for optical measurement camera used in humid environment with temperature variation, to realize normal operation of optical measurement camera in snow and rain, in oceans and in other humid environment. Design kinematics solution and get integral structural design of the wiper according to theory of mechanism and technical conditions in combination with practical engineering application; then design fit clearance of axle hole at hinge inside the mechanism through finite element and virtual prototyping simulation and analyze impact of clearance on mechanism kinematics, conduct modeling on the wiper and perform kinematic and dynamic simulation analysis. The result has indicated that: in case initial value of axle hole at the hinge is 0.1mm, the wiper is operating normally within required variation range of the environment temperature, and can meet engineering design requirement.

Stability Analysis of a Direct-Operated Seawater Hydraulic Relief Valve under Deep Sea

Taking into account the deformation of a designed direct-operated seawater hydraulic relief valve in deep sea, which might have a great influence on the stability of the valve, a mathematic model of the relief valve was established and stability analysis was conducted. As the fitting clearances between the damping sleeve and the damping bar play a key role in the performance of the relief valve, the fitting clearances after deformation under pressure of different ocean depths were obtained using finite element method. Applying the deformation data to the relief valve model, the stability and relative stability could be analyzed quantitatively through both the frequency domain analysis method and the time domain analysis method to detect the influence of the fitting clearance after deformation. The simulation results show that the seawater relief valve has a stable performance within 4000 meters deep under the sea.

Analysis of the axial fitting clearance between the fuel rod and the end seat in CIADS

The fuel assembly is key structure in China Initiative Accelerator Driven System, and the axial fitting clearance (AFC) for the fuel assembly design is an essential subject of study. In this paper, different methods are used to calculate critical stress in cylindrical shells. Because the thermal expansion of fuel assembly outer tube is larger than that of the cladding of fuel rod, enough space should be reserved between the upper end plug and upper seat slot. The collapse critical compressive stress of the cladding is obtained numerically through ANSYS simulation calculation. The AFC range between the fuel rod cladding and the end seat due to the displacement of thermal expansion is given by the theoretical formulas and ANSYS buckling analysis. These provide a reference for the AFC design of the reactor fuel assembly.

Simulation and analysis of a seawater hydraulic relief valve in deep-sea environment

Considering the deformation of a designed seawater direct-acting relief valve (SDARV) in deep-sea environment, which has a significant influence on the dynamic performance, the mathematic model of SDARV was established and related dynamic characteristic simulations were conducted. Since the fit clearance between damping spindle and damping bush is the key parameter affecting the dynamic characteristic of SDARV, the different fit clearances against varying depths were studied by ANSYS Workbench. The variations of seawater properties at different sea depths were also introduced to investigate the effect. From this study, the valve's dynamic performance after optimization in deep-sea environment was researched by MATLAB and the effective sea depth suiting for normal work was got. The results indicated effective dynamic performance of the SDARV within the depth of 1700m and the optimum fit clearances after deformation should be kept in the range of 0.019mm to 0.045mm in deep sea environment.

Design and Optimization of the Slide Guide System of Hydraulic Press Based on Energy Loss Analysis

The clearances in the slide guide system of a hydraulic press are one of the significant factors affecting its accuracy. These clearances also affect the energy consumption of the press. An energy loss model that considers the oil leaks and friction associated with these clearances was proposed, and the size of clearances was optimized based on the model. The maximum allowable eccentric load and the energy loss on the wedge clearance condition were calculated to ensure the slide and guide pillars function properly. The stiffness of pillars and wear of guide rails were checked under an eccentric load condition. A case for rapid sheet metal forming with a 20 MN hydraulic press was examined. For this case, the optimum fit clearances were found to be approximately 0.4 mm. The energy loss under an eccentric load condition was increased by approximately 83% compared to a non-eccentric load condition. The pillars were optimized by reducing excessive stiffness, which served to decrease the pillar weight by nearly 20%.

Optimization Design for Detonation Powerplant Based on LS-DYNA Simulation

To ensure the accuracy of the work capacity of the detonation powerplant, the explosive and shock process of detonation powerplants was simulated with LS-DYNA. Many maximum rising displacements of the cartridge indicating the work capacity of the device were obtained, under different fit clearances of the device. It was proved that fit clearances were the key factors affecting the work capacity of the device, and reasonable range for fit clearances was found. Besides, the objective function, constraint condition, and optimization design variables of the Genetic Algorithm were determined according to the design indicators of the detonation powerplant. The theoretical values of fit clearances of the optimization design of detonation powerplants were obtained. At last, the tests of the work capacity of the detonation powerplant and LS-DYNA simulation proved the rationality of the theoretical values from the Genetic Algorithm, providing an experimental proof for the accuracy design, which could control the service door movement accurately.

Mechanical performance analysis of hollow cylindrical roller bearing of cone bit by FEM

Abstract Bearings are key components of cone bit, thus its rapid failure is a major cause of leading to lower life of the bit. To improve the bearing performance and prolong working life, contact mechanics of hollow cylindrical roller bearing of cone bit was simulated. Effects of hollow size, drilling pressure, friction coefficient and fitting clearance on mechanics performance of the bearing were studied. The results show that the maximum equivalent stress of the hollow cylindrical roller bearing appears on the claw journal, and the maximum contact stress appears on the contact pair of the hollow roller. Besides, hollow sizes have a greater impact on the equivalent stress and contact stress of the cylindrical roller, while the influence on the stress of the cone and claw journal is relatively small. With the increasing of the drilling pressure and fitting clearance, equivalent stress and contact stress of bearing parts increase. The friction coefficient has little impact on mechanical performance of the bearing. As the 121/4SWPI517 type hollow cylindrical roller bearing of cone bit an example, the optimal hollow size is 55%, the drilling pressure is 140 kN and the fitting clearance is 0–0.02 mm.

Numerical simulation and experimental study of heat-fluid-solid coupling of double flapper-nozzle servo valve

The double flapper-nozzle servo valve is widely used to launch and guide the equipment. Due to the large instantaneous flow rate of servo valve working under specific operating conditions, the temperature of servo valve would reach 120°C and the valve core and valve sleeve deform in a short amount of time. So the control precision of servo valve significantly decreases and the clamping stagnation phenomenon of valve core appears. In order to solve the problem of degraded control accuracy and clamping stagnation of servo valve under large temperature difference circumstance, the numerical simulation of heat-fluid-solid coupling by using finite element method is done. The simulation result shows that zero position leakage of servo valve is basically impacted by oil temperature and change of fit clearance. The clamping stagnation is caused by warpage-deformation and fit clearance reduction of the valve core and valve sleeve. The distribution rules of the temperature and thermal-deformation of shell, valve core and valve sleeve and the pressure, velocity and temperature field of flow channel are also analyzed. Zero position leakage and electromagnet’s current when valve core moves in full-stroke are tested using Electro-hydraulic Servo-valve Characteristic Test-bed of an aerospace sciences and technology corporation. The experimental results show that the change law of experimental current at different oil temperatures is roughly identical to simulation current. The current curve of the electromagnet is smooth when oil temperature is below 80°C, but the amplitude of current significantly increases and the hairy appears when oil temperature is above 80°C. The current becomes smooth again after the warped valve core and valve sleeve are reground. It indicates that clamping stagnation is caused by warpage-deformation and fit clearance reduction of valve core and valve sleeve. This paper simulates and tests the heat-fluid-solid coupling of double flapper-nozzle servo valve, and the obtained results provide the reference value for the design of double flapper-nozzle force feedback servo valve.

Calculation and Analysis of the Turbocharger Assembly Errors

Turbocharger assembly process has two assembly dimension chain, the assembly dimension chain between the shell, and the assembly dimension chain of the parts of the impeller shaft. Between them are interrelated, eventually formed with the gap between the impeller and the casing. The impeller is rotationed by exhaust gas flowed through the impeller chamber through the nozzle ring promote. It will result in the loss of the exhaust gas flow if the fit clearance between the impeller and the casing is greater than the design value, the impeller speed can not meet the design requirements Resulting in turbocharger boost the value below standard,and the boost the value of turbocharger can not meet the requirements

Theoretical and experimental studies for wind turbine’s shrink disk

With the wide application of multi-layer interference fit in many engineering fields, as for key component in the wind turbine generator, wind turbine’s shrink disk uses interference fit to transmit rated torque and axial force. In order to ensure the work reliability of shrink disk during the actual operation, the paper presents a more precise method on the design calculation of contact pressure on the mating surfaces with interference fit. In accordance with the order from the inside to the outside, the contact pressure of spindle-to-sleeve surface can be calculated based on the rated load required to transmit. Combining with Thick-wall Cylinder Theory and Lame Equation, taking into account the impact of fit clearance, the checking method of the bushing was used to calculate the contact pressure on mating surface of bushing-to-inner ring; and the stress analysis of the inner ring was used to calculate the contact pressure on mating surface of inner ring-to-outer ring. At the same time, the effects of frictional coefficient, fit clearance, and other design parameters on theoretical results were also analyzed. The pressure distribution of each mating surface was obtained by Abaqus software simulation, which showed that the results from improved method was closer to simulation results and had higher accuracy than traditional method by comparing the results with three different methods. Finally, the test was designed to verify whether the shrink disk could bear the load or not on the test platform of shrink disk, and the results indicated that it could meet the requirements of given loadcase.

Dynamic performance of self-operated three-way valve used in a hybrid air conditioner

A hybrid air conditioner combining a thermosyphon cycle with a vapor compression refrigeration cycle has a large energy saving potential compared with a common air conditioner for spaces requiring year-round cooling. The performance of the switch between the vapor compression mode and the thermosyphon mode largely impacts the safety and reliability of hybrid air conditioners. Therefore, a self-operated three-way valve is proposed. A thermodynamic model and a kinetic model are developed in this paper to evaluate the dynamic performance of the switch valve. The effects of the spring force constant, compressor discharging volume, fit clearance and piston length on the dynamic performance of the switch valve are analyzed. In conclusion, the proposed self-operated three-way valve can realize the switch operation accurately.

皮卫星及其星箭分离机构的热-结构耦合与间隙设计

The thermal-structure coupling for a pico-satellite and its separation mechanism was analyzed to guide a rational design of the fit clearance value between the satellite and guide rail and to ensure safe and reliable satellite separation.On the basis of the geometry relations of the satellite,the earth,and the sun in the process of launching,the internal and external heat flows absorbed by the pico-satellite and its separation mechanism were analyzed.The temperature field and thermal deformation in satellite launching were obtained by finite element analysis.The clearance fit value between the satellite and guide rail was designed on the basis of above analysis.The analysis results show that the maximum deformation occurs on the shady side because of the cold dark environment and conduction heat,and the pico-satellite shell and its guide rail surface are not distorted and deformed seriously.The amount of maximum deformation is 62.3μm when the preload force is 600N and that is 63μm when the preload force is 300N.Based on above analysis results,the fit clearance was selected.These results demonstrate that the pico-satellite and its separation mechanism can separate normally under the high and low temperature tests.The on-orbit separation attitude is in agreement with simulation results well.All of these verify that the fit clearance between the satellite and its guide rail is reasonable and it can be used in the structural design and thermal control design of pico-satellite separation mechanisms.

Engine fault detection using angle domain signal envelope algorithm

Vibration signals from internal combustion engines contain strong noise and nonstationary characteristics in the time domain, which cause difficulties when attempting to detect and diagnose incipient faults in engines using signal features. In order to improve the success rate and broaden the applicability of engine incipient fault detection, a new concept of angle domain signal envelope analysis is proposed. The new method uses an encoder to acquire an engine rotational vibration signal using equal angle sampling. Angle domain synchronous averaging is used to denoise the original signal, and engine incipient fault features are extracted by the angle domain signal envelope algorithm. Experimental results using signals recorded from an engine with a connecting rod bearing with improper fit clearance have shown that the angle domain signal envelope algorithm can extract useful features from the vibration signal. The effectiveness of the new detection algorithm was verified. The engine fault detection method based on an angle domain signal envelope algorithm provides a new way to detect and diagnose engine incipient faults.

Research on Temperature and Deformation Distributions of Scroll Compressor Plates

When scroll compressors are operated, the heat and force loads acting on scroll plates result in the deformation of them. The temperature distribution and deformations of scroll plates were researched in this paper. The simulation results show that the maximum temperatures of scroll plates are at the center of scroll profiles. And there are the maximum axial deformation values at the center of scroll profiles. The maximum radial and axial fit clearances of compressor are 59.5μm and 38.8μm respectively.

Removal Method of Core Shaft of Primary Mirror

The structure of core shaft combined with mercury belt is widely used as the primary mirror supporting structure of 1 meter class and 2 meter class large aperture telescope currently. In order to reduce the structure jitter of primary mirror, the fitting clearance between core shaft and shaft sleeve is very small, so clamping stagnation occurs during installation and disassembling process of core shaft. The removal method of clamping stagnation of core shaft is introduced. Mechanical analysis of core shaft and primary mirror is applied to make sure that the primary mirror is safe. Some tools are designed specially, and the process and the attention points to remove core shaft are introduced. In this way, the clamping stagnation of core shaft can be removed easily. The core shaft of 1 m class primary mirror was removed by the method and the primary mirror was excellent without damage.

Integrating cylindricity error into tolerance analysis of precision rotary assemblies using Jacobian–Torsor model

In this study, the cylindricity error was integrated into the tolerance analysis of precision rotary assemblies using Jacobian–Torsor model. The contact method was developed to rapidly determine the actual fitting clearance through the virtual assembling of the mating cylindrical parts using Monte Carlo simulation. By modifying the expressions of small displacement torsors of the cylinder pairs, the actual fitting clearance between the bore and the shaft was taken into account, which overcame the shortage of Jacobian–Torsor model that the form error cannot be processed. The effects of the cylindricity error and the number of lobes on the actual fitting clearance and the functional requirements were analyzed in detail. The results show that the cylindricity error has significant influence on the actual fitting clearance and the final functional requirements, and it should not be ignored in the tolerance analysis for precision rotary assemblies.

Experimental research on the surface strengthening technology of roller cone bit bearing based on the failure analysis

The roller cone bit is one of the most important rock breaking tools used in the oil–gas drilling industry. Its performance directly influences the drilling quality, efficiency and cost. As the world’s oil–gas resource exploration continuously developed, the drilling speed accelerated, accelerating the failure speed of the bearing. The roller cone bit’s service life was almost directly dependent on that of the bearing. In this paper, a bearing failure analysis, and an experimental research on the surface strengthening technology of the bearing with field applications etc. were carried out. The results showed that the bearing’s main failure modes included fracture, plastic deformation and wear. The main reasons were overload and uneven distribution of the load; elevated temperature due to friction caused property and structure change in material; wear increased the fit clearance between the bearing and the cone, increasing dynamic impact load etc. The bearing surface strengthening technology, employing plasma-arc surfacing DH-60 wear resistance alloy, could prolong the service life of the bearing. Experimental research and field tests showed that the wear and impact resistance of the enhanced bearing increased by 30% with an increased service life of 12% on average.

Wear Life Prediction for a Large Diameter Spool Valve

Life prediction for a component can’t instead of its life tests, even so it has a very important guiding significance for the optimization design and material selection of the component, and it can decrease great loss caused by design mistakes, also possibly avoid detours, especially on initial development stage. It also is an important stage of the lifecycle design of a component. According to a certain working condition, this paper predicts the wear life of a large diameter hydraulic directional spool valve with 2-position 4-way for the hydraulic system of a high speed winch, combined with the surface micro-topography of the valve body and spool, and influence factors to the fit clearance changing caused by wear, such as shaping form errors, lateral force, matching materials, hydraulic medium and so on. The result shows that the wear life of the large diameter spool valve is more than 10 million times. The prediction provides a theoretical basis for the independent development of this valve, and has a certain reference for the design of this kind of components.

Fit Clearance of Impeller to Turbocharger Performance Influence with Mechanics Properties

The fit clearance between the impeller and the impeller shell directly affect the characteristics of the turbocharger. Assembly dimension chain is the basis of the design and analysis of workpiece size.Reducing the fit clearance of the impeller and the impeller shell can improve the booster effect. The impeller of the small inertia is beneficial to increase the rotation speed of the impeller and the impeller rotation stability requirements.The turbocharger of installation small inertia impeller is characterized by small size. Followed by its supercharged performance

Effect and Analysis of Fit Clearance between Mandrel and Workpiece on the Spinning Stability of Barrel with Extra Thin-Wall and Height Diameter/Thickness Ratio

After 4 times thinning spinning, the C-276 tube with 2mm thickness and 561.5mm diameter was thinned to 0.42mm, the length was extended from 300mm to 1200mm. Discuss the problem of drum instability during the process of spinning, as well as the effect of fit clearance between mandrel and workpiece on the spinning stability. Applied the large-scale finite element software MSC.MARC to carry on the simulation analysis of the drum instability phenomena of loading workpiece under the condition of different fit clearance, put forwards measures to control the instability, so as to provide theory instruction for producing barrel with extra thin-wall and height diameter/thickness ratio which can fit the precision requirement.