Rotating Loosening Mechanism of Nut Connecting Rotary Disc Under Rotating-Bending Force

2003 ◽  
Author(s):  
Yasuo Fujioka ◽  
Tomotsugu Sakai
Keyword(s):  
High Pressure ◽  
Contact Area ◽  
Radial Direction ◽  
Small Difference ◽  
Relative Rotation ◽  
Bearing Surface ◽  
Bending Force ◽  
Transmitted Force ◽  
Rotating Bending ◽  
Dimensional Errors

There are fastened structures composed of rotary disc and shaft, which are fastened with bolts and nuts with tapered bearing surfaces. Those are loaded with rotating-bending force. It has been difficult to explain clearly the rotating loosening mechanism of such joint’s nuts by the previously proposed mechanism. In this study, the rotating mechanism of this nut was investigated from theoretical and experimental view points. Finally two types of mechanisms were derived. One is as follows: High pressure contact area is formed by external load oriented in the radial direction of a disc. It gives very small difference of radii between the bearing surface of disc and that of nut. Then, with the revolution of the disc, it makes occurrence of two friction torques in opposite direction, which are Tw and Ts torques on bearing and on threads respectively. When revolving disc, relative rotating direction of nut is dominated by bigger torque of Tw and Ts. If Tw is bigger than Ts, the rotating direction of nut is the same as the disc revolution. If Ts is bigger than Tw, the rotating direction is opposite to disc revolving direction. Taking into consideration this mechanism, some tests were carried out by changing magnitude of the friction coefficients both of bearing surface and of threads surface with greasing and degreasing intentionally. Loosening and tightening rotations were confirmed to occur just as predicted from the above mentioned mechanism. The other is due to the eccentricities caused by dimensional errors around the bolt, the nut and the tapered bearing surface of rotary disc. In this case, the direction of the force transmitted through the high pressure contact area changes from the center of bolt axis. So, the transmitted force can cause the torque which loosens and tightens the nut during one revolution of rotary disc, therefore relative rotation of nut results in small fluctuating of loosening and tightening. Combining two types of mechanisms, repeating small angle of loosening and tightening, nuts are rotated inclined to loosening or tightening direction after many revolutions of disc.

Rotating Loosening Mechanism of a Nut Connecting a Rotary Disk Under Rotating-Bending Force

2005 ◽  
Vol 127 (6) ◽  
pp. 1191-1197 ◽  
Author(s):  
Yasuo Fujioka ◽  
Tomotsugu Sakai
Keyword(s):  
High Pressure ◽  
Contact Area ◽  
The Other ◽  
Bearing Surface ◽  
Bending Force ◽  
Rotary Disk ◽  
Rotating Bending ◽  
Dimensional Errors ◽  
The Revolution

Structures composed of a rotary disk and a shaft, which are fastened with bolts and nuts having tapered bearing surfaces, are loaded with a rotating-bending force. Upon investigation, two rotating mechanisms of the nut were derived. In one mechanism a high-pressure contact area is formed at the nearest loading point on threads and bearing surfaces. This leads to a difference in the curvature radii between the bearing surface of the disk and that of the nut. During the revolution of the disk, two friction torques occur in opposite directions on the bearing surface and the threads, respectively. The relative rotating direction of the nut is dominated by the greater torque. The other mechanism is due to the eccentricities caused by dimensional errors of the bolt, nut, and disk. By combining the two mechanisms, the rotations of the nuts either cause a loosening or tightening after many revolutions of the disk.

scholarly journals Discrete Element Analysis of High-Pressure Zones of Sea Ice on Vertical Structures

2021 ◽  
Vol 9 (3) ◽  
pp. 348
Author(s):  
Xue Long ◽  
Lu Liu ◽  
Shewen Liu ◽  
Shunying Ji
Keyword(s):  
High Pressure ◽  
Sea Ice ◽  
Failure Mode ◽  
Contact Area ◽  
Loading Rate ◽  
Discrete Element ◽  
Offshore Platforms ◽  
Marine Structures ◽  
Element Analysis ◽  
Ice Pressure

In cold regions, ice pressure poses a serious threat to the safe operation of ship hulls and fixed offshore platforms. In this study, a discrete element method (DEM) with bonded particles was adapted to simulate the generation and distribution of local ice pressures during the interaction between level ice and vertical structures. The strength and failure mode of simulated sea ice under uniaxial compression were consistent with the experimental results, which verifies the accuracy of the discrete element parameters. The crushing process of sea ice acting on the vertical structure simulated by the DEM was compared with the field test. The distribution of ice pressure on the contact surface was calculated, and it was found that the local ice pressure was much greater than the global ice pressure. The high-pressure zones in sea ice are mainly caused by its simultaneous destruction, and these zones are primarily distributed near the midline of the contact area of sea ice and the structure. The contact area and loading rate are the two main factors affecting the high-pressure zones. The maximum local and global ice pressures decrease with an increase in the contact area. The influence of the loading rate on the local ice pressure is caused by the change in the sea ice failure mode. When the loading rate is low, ductile failure of sea ice occurs, and the ice pressure increases with the increase in the loading rate. When the loading rate is high, brittle failure of sea ice occurs, and the ice pressure decreases with an increase in the loading rate. This DEM study of sea ice can reasonably predict the distribution of high-pressure zones on marine structures and provide a reference for the anti-ice performance design of marine structures.

Prediction of the Leakage Threshold for Hertzian Contact Seals: An Experimental Approach

2018 ◽  
Author(s):  
Jeroen Van Wittenberghe ◽  
John Vande Voorde
Keyword(s):  
High Pressure ◽  
Contact Pressure ◽  
Contact Area ◽  
Oil And Gas ◽  
Empirical Evaluation ◽  
Evaluation Criteria ◽  
Hertzian Contact ◽  
Surface Topology ◽  
Current Form ◽  
Leak Tightness

The prediction and evaluation of leakage and leak tightness is an important issue in a multitude of high-pressure applications, such as valves, flanges and threaded pipe connections that are used under extreme service conditions that occur in oil and gas exploration and production. Using Hertzian contact theory or finite element techniques it is possible to determine the local contact conditions at the seal on a macroscopic level (to wit the extent of the contact area and the contact pressure in this area). However, the leak tightness of such a contact depends also on the surface topology, which is a microscopic characteristic. Therefore, the assessment of leak tightness requires an evaluation criterion relating both scales. Empirical evaluation criteria have been postulated in the past, each with their own application domain. More recently the Persson method has been developed that models the contact area microscopically using contact models developed in the field of tribology. However, in its current form this model is limited to flat surfaces while in many applications, such as valves, O-ring seals or metal-to-metal seals of threaded pipe connections, the contact is Hertzian and the contact pressure distribution is not uniform but parabolic. This paper provides the experimental results that will be used to validate an extension of the Persson model to Hertzian contact seals. A set of samples for leakage experiments was produced with varying surface topology. The surface roughness of these samples is measured and the leakage behaviour under high pressure is evaluated. This paper focusses on the experimental evaluation of the influence of surface topology on leakage.

Pitting of Steel Under Varying Speeds and Combined Stresses

1969 ◽  
Vol 91 (2) ◽  
pp. 282-290 ◽  
Author(s):  
C. A. Foord ◽  
C. G. Hingley ◽  
A. Cameron
Keyword(s):  
High Pressure ◽  
High Viscosity ◽  
Mathematical Treatment ◽  
Bending Stress ◽  
Bending Fatigue ◽  
Combined Stresses ◽  
Transit Times ◽  
Rotating Bending Fatigue ◽  
Rotating Bending ◽  
Theory And Experiment

A new loader is described for pitting research. It consists of a ball in a cylinder. Behind the ball is high-pressure oil which forces it against the moving counterface, which in its turn causes the ball to spin, and so remain centered in the cylinder. In the first part of the paper the effect of speed on pitting is studied using this loader. The results are correlated by a mathematical treatment of Way’s hydraulic crack-propagation hypothesis. The theory shows that high viscosity and compressibility and short transit times increase pitting life. Semiquantitative agreement is found between the new pitting theory and experiment. In the second part the action of combined stresses on pitting is investigated. The ball is loaded against a shaft mounted in a rotating-bending fatigue machine. It is found that a relatively small tensile bending stress reduces pitting life dramatically, whereas a small compressive bending stress completely inhibits pitting.

Microstructures and Mechanical Property of Ni Processed by High-Pressure Torsion and Their Evolution upon Annealing

2006 ◽  
Vol 114 ◽  
pp. 45-50 ◽  
Author(s):  
Zhi Qing Yang
Keyword(s):  
High Pressure ◽  
Grain Boundaries ◽  
Room Temperature ◽  
High Pressure Torsion ◽  
Small Difference ◽  
Dynamical Evolution ◽  
Peripheral Region ◽  
Lattice Defects ◽  
Grain Sizes ◽  
Xrd And Tem

XRD, TEM, microhardness and thermal analysis were carried out on a series of Ni samples produced by high-pressure torsion (HPT). The evolution of microstructures and their inhomogeneity were investigated. The local microstrain showed dynamical oscillations as a function of the HPT rotations, demonstrating dynamical evolution of lattice defects during the procedure. Both XRD and TEM showed that a small difference in grain sizes remains even after 5 revolutions of HPT with smaller grain sizes at the peripheral region of the sample. The higher microhardness at the peripheral region is the result of the smaller grain sizes and the higher density of lattice defects, compared with the central region. Thermal treatment at a heating rate of 20K/min from room temperature to 473K did not result in decreased microhardness, but increased by about 10% for samples treated with not more than 3 rotations of HPT. The increase in microhardness was attributed to further grain refinement, the formation of a larger fraction of high-angle grain boundaries and grain boundaries being closer to equilibrium after recovery.

An Experimental Investigation on Frictional Properties of Bolted Joints

2002 ◽  
Author(s):  
Yanyao Jiang ◽  
Ming Zhang ◽  
Tae-Won Park ◽  
Chu-Hwa Lee
Keyword(s):  
Experimental Investigation ◽  
Contact Area ◽  
Direct Determination ◽  
Organic Coating ◽  
Bolted Joints ◽  
Marginal Effect ◽  
Bolted Joint ◽  
Bearing Surface ◽  
Frictional Properties ◽  
Bearing Friction

By using an approach developed to determining the torque-tension relationship for bolted joints, frictional properties of several typical bolted joints were studied experimentally. The approach allows for the direct determination of the thread friction and the bearing friction between the nut and its bearing surface independently. Detailed studies were made on the influences of the size and shape of the hole, the use of a slot in a bolted joint, contact area and position, and other factors such as turning speed, coating, and the use of wax on the bearing surface. The contact area and position of the washer have a marginal effect on the bearing friction. The organic coating on the nuts reduces the bearing friction significantly. Nuts with organic coating over a washer with zinc finish provide the smallest and the most consistent bearing friction. Experiments on thread friction shows that prevailing torque nuts with distorted threads and nylon inserts provided trivial benefits for preventing “self-loosening” of the nut. Repeated tightening-loosening generally increases frictions in a bolted joint. It was noted that the data scatter of the experimental results of frictions in a bolted joint may overshadow the influence of size, speed, and contact positions. The results from the experimental investigation will help to better design bolted joints.

Development and Experimental Verification of an Innovative Non-Contact Liquid Bearing Utilizing Traveling Waves

2014 ◽  
Vol 800-801 ◽  
pp. 564-568
Author(s):  
Ying Jie Li ◽  
Ming Zhou ◽  
Eiji Shamoto
Keyword(s):  
Liquid Film ◽  
Traveling Waves ◽  
Experimental Verification ◽  
Radial Direction ◽  
Piezoelectric Actuators ◽  
Rigid Support ◽  
Bearing Surface ◽  
Support Plate ◽  
Contact Liquid

A new non-contact liquid bearing, which utilizing traveling waves, is developed in this paper. The developed bearing is designed in an octagon shape where series of piezoelectric actuators are placed between a rigid support plate and the elastic thin bearing surface around the circumference and in the radial direction. The driving apparatus for the developed bearing is implemented based on DSP and voltage amplifiers. The liquid film force induced by traveling waves is confirmed by experiments which prove the feasibility of the developed bearing.

Leak Tightness Based Design Procedure for Gasketed Pipe Flange Connections

2011 ◽  
Author(s):  
Toshiyuki Sawa ◽  
Takashi Kobayashi ◽  
Hirokazu Tsuji ◽  
Satoshi Nagata
Keyword(s):  
High Pressure ◽  
Stress Distribution ◽  
Internal Pressure ◽  
Radial Direction ◽  
Design Procedure ◽  
Flange Connection ◽  
Flexibility Analysis ◽  
Bolt Preload ◽  
Leak Tightness ◽  
Institute Of Technology

A design procedure for bolted gasketed pipe flange connections has been developed by the Sealing Technology Of Pressure-equipments (STOP) Committee organized in the High Pressure Institute of Technology Japan. This paper explains not only the design procedure itself but also the technical background of the leak tightness of gasket basis for the procedure. The point to be highlighted is that the design procedure has adopted a flexibility analysis of the flange connection based on the Oyama method, which is the modification of the Koumura method calculating the interaction among pipe, hub and flange ring including gasket stiffness, in order to determine the required bolt preload achieving the specified leak tightness. The Oyama method can calculate the variations of axial bolt force, the flange rotation, and the gasket stress distribution in the radial direction due to internal pressure using relatively simple formulas.

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