Behavior Of Shaft Research Articles

BACKWARD WHIRL OF UNBALANCED SHAFT AT ELASTICALLY CONSTRAINED JOURNAL BEARINGS AND FLOATING SEALS DUE TO MECHANICAL CONTACT

The paper deals with the known phenomenon which takes place at rotor-stator contact. It is backward precession (whirl) of unbalanced shaft inside rigidly constrained sleeves (journal bearings) in the range below its critical speed. The purpose of this theoretical work is to research dynamic behavior of unbalanced shaft at the elastically constrained sleeves and above-resonant range.

Bumpless Automatic Transfer for a Switched-Doubly-Fed-Machine Propulsion Drive

Variable-speed drives (VSDs) combined with doubly-fed machines (DFMs) offer interesting flexibility for power electronic drive design. These also provide opportunities for controlling interactions with an ac grid. Design options are most versatile for the VSD DFM when the machine stator can be operated from an ac or a dc source, selected as appropriate. This paper presents a silicon-controlled rectifier (SCR)-based transfer switch that can connect the stator of the DFM either to an ac source or a dc source “on-the-fly.” Current commutations of the SCRs and a “bumpless” transition in shaft behavior are both controlled from the rotor. Experimental results demonstrate wide-speed-range and four-quadrant operation of the drive achieved with a rotor converter rating that is one third of the DFM power rating.

Numerical investigation of spatial aspects of soil structure interaction for secant pile wall circular shafts

Implementation of fast and cost-effective shoring systems has become very necessary to overcome the technical challenges such as variable soil and rock profiles, high groundwater tables and limitations imposed by the built environment. Secant pile wall shoring systems allow the construction of overlapped piles in almost all subsurface conditions. They are constructed in a circular plan layout to form a vertical shaft which provides unique advantages such as compression ring behavior. This paper presents a numerical study to investigate various aspects of the behavior of circular shafts constructed using secant pile walls. The studied aspects include the identification of earth pressure distributions exerted on circular shafts, the impact of excavation of single and multiple holes on the shaft stresses, and the stresses in the shaft in the case of sloping bedrock. A three-dimensional finite element model is developed to conduct the present analyses taking into consideration the actual behavior of soils surrounding the walls. The stress concentrations calculated for circular shafts were seen to vary from the results of the infinite plate with hole solution. The sloping bedrock was also seen to result in significant deviations from the compression ring behavior. A large increase in the maximum compressive stresses and emergence of some significant tensile stress zones were observed for bedrock inclinations larger than 20°. The results presented in this study address some practical design concerns and were considered to be of interest to those involved in design and construction of vertical shafts.

Determination of the Stress Intensity Factor of an elliptical breathing crack in a rotating shaft

The failures due to the propagation of fatigue cracks are one of the most frequent problems in rotating machines. Those failures sometimes are catastrophic and are sufficient to provoke the loss of the complete machine with high risks for people and other equipments. When a cracked shaft rotates, the breathing mechanism appears. The crack passes from an open state to a close state with a transition in which a partial opening or closing of the crack is produced. In this work, a new general expression that gives the Stress Intensity Factor (SIF) along the crack front of an elliptical crack in a rotating shaft in terms of the crack depth ratio, the crack aspect ratio, the relative position on the front and the angle of rotation has been developed for linear elastic materials. By the moment, no expressions of the SIF in term of these variables have been found in the literature. To this end, a quasi-static 3D numerical model of a cracked shaft with straight and elliptical cracks subjected to rotary bending using the Finite Element Method (FEM) has been made. To simulate the rotation of the shaft, different angular positions have been considered. The SIF in mode I along the crack front has been calculated for each angular position of the cracked shaft and for different crack geometries. The expression results have been compared with solutions obtained from the literature. It has been found that they are in good agreement. The model has been applied to other crack geometries with good results. The obtained SIF expression allows studying the dynamic behavior of cracked shafts and can be used to analyze the crack propagation.

Investigation of the Effect of Fiber Orientation on FML Hollow Shaft Subjected to Static Torsion Loading

In this study, the torsional behavior of cylindrical FML hollow shafts was examined by a combined experimental and numerical approach. The FML hollow shafts with glass fibers wound on Al metallic liner at different fiber orientations were prepared using filament winding machine. To examine the effect of fiber orientation, FML hollow shafts of 0/90°, 60/30°, ± 45° and ± 55° fiber orientations were considered. Three different FRP thicknesses of 1, 2 and 3 mm were selected for all fiber orientations to study the torsional buckling and deformation behaviour of FML hollow shafts. Numerical investigation using ANSYS static and linear analysis was performed to validate the end and transition effects of torsional phenomenon. Both the experimental and numerical results showed FML hollow shafts with 0/90° fiber orientation possessed higher torsional strength as compared to FML hollow shafts with 60/30°, ± 45° and ± 55° fiber orientation.

多孔質真円ジャーナル軸受における非定常時潤滑特性の実験的研究（ピボット支持におけるクリアランス変化をパラメータとした軸振れ挙動に関する一考察）

多孔質真円ジャーナル軸受における非定常時潤滑特性の実験的研究（ピボット支持におけるクリアランス変化をパラメータとした軸振れ挙動に関する一考察）

Analysis of Shaft Movement Using FEM Model Considering Inertia Effect of Club Head

Previous studies simulating shaft movement during a golf swing demonstrate shaft movement using a finite element method (FEM) model with the club head modelled as a concentrated mass. The objectives of this study are to simulate shaft movement while taking into account the inertia effect of the club head. A head was attached to a FEM model of the shaft as a simplified rigid model. We also compared the experimental results and simulation results of the shaft behavior. The simulated results corresponded to the experimental results and we therefore concluded that the inertia force of the club head causes deflection during the swing and torque of inertia angle of the twist during the swing.

Large diameter shafts for underground infrastructure

The technique of large diameter shafts for deep excavations was analysed in terms of its basic construction elements, reported literature cases and design methods. The effects of the construction sequence and the geological deposition on the behaviour of the shaft was analysed using 3D finite element models. Induced stresses and displacements on the soil mass were investigated. Three methods to assess the stability of the shaft lining were presented and employed as a post-processing stage of analysis of the models. The results indicated a major influence of the height of the vertical excavation stages on the shaft behaviour, markedly on the induced settlements. The lining analysis also demonstrated the effects of the vertical excavation stages and how different safety assessment methods can produce significantly different results.

Torsional behaviour of filament wound kenaf yarn fibre reinforced unsaturated polyester composite hollow shafts

Synthetic fibre is of higher strength in composites and is a low cost material, but the problem is that it does not degrade in the environment. Studies on single yarn natural fibre have been reported, especially those concerned with improving its mechanical properties. This can be used for lower end applications such as furniture and automotive dash board to reduce the utilization of synthetic fibre. Continuous yarn fibres are required to increase the strength for engineering applications and filament winding is a method to produce aligned technical composites which have high fibre content. This paper presents an experimental and simulation studies to investigate the behaviour of composite hollow shafts, with a specific focus on the maximum torsion capacity of the composite hollow shaft for different winding angles and aluminum reinforcement. The conventional filament winding machine was modified and added to a new resin bath mechanism in order to produce a new natural fibre composite hollow shaft using kenaf yarn fibre reinforced with unsaturated polyester resin. The results show that the torsion capacity is significantly affected by changing the winding angle and the presence of aluminum in the static torque test capacity properties. The maximum static torsion capacity of kenaf yarn fibre reinforces unsaturated polyester composite shaft at a winding angle of 45° was higher strength than 90° orientation while the presence of aluminum enhanced the torsion property significantly. Finite element analysis (FEA) using Abaqus software was carried out and showed a good agreement with the experimental results.

Measurement of Shaft Orbits with Photographic Images and Sub-Sampling Technique

Vibration measurement in rotating machines is an important procedure in the identification of malfunctions and in the prevention of failure. In this case, due to difficulties in mounting sensors on rotating parts, non-contacting measurement methods are usually employed (interferometry, vibrometry, proximity sensing, photogrammetry). This work focuses on the development of a low cost image acquisition system capable of measuring the dynamic behavior of a rotor shaft (lateral vibration) using photographic images (full field measurement). The proposed method is based on sub-sampling techniques (reconstruction of the vibration signal by measuring long acquisition periods), and it is suitable for structures or machines whose vibrating frequencies are known (e.g. rotating machines). After image acquisition, the vibration at specific points of interest in the shaft is obtained by adopting a suitable image processing technique. Experimental tests are performed in a rotating system with flexible shaft, driven by an electric motor controlled by a frequency inverter in the frequency range of 300 rpm (5 Hz) to 990 rpm (16.5 Hz). Shaft vibration measurements are compared to measurements obtained with proximity sensors, and good agreement is observed even for small vibration amplitudes (130 μm).

Mechanical Behavior of Hollow Shaft and Sleeve with Interference Fit and Axial Tensile Load in Textile Machinery

Mechanical Behavior of Hollow Shaft and Sleeve with Interference Fit and Axial Tensile Load in Textile Machinery

Effect of torsional strain-rate and lay-up sequences on the performance of hybrid composite shafts

In this study, the torsional behavior of hybrid composite shafts was examined by a combined experimental and numerical approach. Glass and carbon fiber reinforced hybrid shafts with three lay-up sequences were manufactured using filament winding technique. All three shafts had same amount of glass and carbon fiber. Angular velocities of 0.1°/min and 5°/min were used as torsion test speeds. The effect of torsional strain-rate and lay-up sequences on the response of hybrid shafts was studied. Torque–twisting angle changes were recorded. Test results revealed that changing angular velocities did not affect the torsional behavior of composite shafts significantly. However, three different lay-up sequences resulted in remarkably different torsional behavior.Torsional behavior of composite shafts was simulated using Finite Element (FE) software, Abaqus. The elastic orthotropic composite model was used for simulations. FE models were validated using experimental test results. Numerically and experimentally obtained results exhibited quite similar torsional behavior.

Finite element analysis of functionally hybridized carbon/glass composite shafts

External torque on circular composite shafts produces linearly decreasing shear stresses along radial direction. The inner layers never stressed as much as outmost layer. Accommodating fiber stiffness of each layer based on these linearly decreasing stresses may be advantageous. To reduce the cost of carbon fiber-reinforced composite drive shaft, inner layers of shaft can be reinforced by hybrid fiber systems with less stiffness. To achieve that, while the top layer is still reinforced with carbon fiber, inner layers can be reinforced with the mixture of glass and carbon fiber. Without changing the fiber volume fractions, replacement of some carbon fiber with glass fiber will reduce the overall stiffness of fiber system. Mixture ratio or hybrid ratio can be calculated using linearly decreasing stress levels and the rule of mixture. These hybrid composite shafts can be manufactured by filament winding technique. During filament winding, composite shafts are wound layer by layer and filament type can be changed between the layers. The proper mixing ratio can be achieved by arranging the fiber count in each filament bundle. The relation between geometrical parameters and hybrid fiber volume fractions of composite shaft was derived. Finite element analysis on carbon fiber and functionally hybridized glass/carbon fiber shafts with same geometry was conducted. Stress, strain, and moment behavior of both shafts were compared. The possible advantages and disadvantages of hybridization were discussed.

Axial Non-linear Dynamic Soil-Pile Interaction - Keynote

This keynote lecture describes recent analytical and numerical advances in the modeling of the axial nonlinear dynamic interaction between a single pile and its embedding soil. On one hand, analytical solutions are developed for assessing the nonlinear axial dynamic response of the shaft of a pile subjected to dynamic loads, and in particular to vibratory loads. Radial inhomogeneity arising from shear modulus degradation is evaluated over a range of parameters and compared with those obtained by other authors and by a numerical radial discrete model simulating the pile and soil movements from integration of the laws of motion. New approximate non linear solutions for axial pile shaft behaviour developed from general elastodynamic equations are presented and compared to existing linear solutions. The soil non linear behaviour and its ability to dissipate mechanical energy upon cyclic loading are shown to have a significant influence on the mechanical impedance provided by the surrounding soil against pile shaft movement. The limitations of over-simplified modelling of pile response are highlighted.

Proposed point bearing load transfer function in jointed rock-socketed drilled shafts

The point bearing behavior of rock-socketed drilled shafts under axial loading is investigated by numerical analysis and a load transfer approach (q–w). A numerical analysis using the distinct element method (DEM) is carried out to investigate the effects of pile diameter and the elastic modulus, discontinuity spacing and the inclination of rock mass on the point bearing behavior. The emphasis is quantifying the point bearing mechanism by taking rock discontinuity into consideration based on field loading tests performed on 39 instrumented piles. A new hyperbolic q–w function is proposed considering the point bearing resistance influence factors, including rock mass discontinuity. Through comparisons with other field data, the proposed q–w function represents a significant improvement in the prediction of the point bearing load transfer characteristics of jointed rock-socketed drilled shafts.

Axial bearing behavior of super-long piles in deep soft clay over stiff layers

In order to find out the bearing behavior of super-long piles located in deep soft clay over stiff layers around Dongting Lake, China, a test pile was first designed with the field loading test finished afterward. Based on the measured test results, load transfer mechanism and bearing behavior of the pile shaft were discussed in detail. Then, by introducing a bi-linear model for shaft friction and the tri-linear model for pile tip resistance, respectively, the governing differential equation of pile-soil system was set up by the load transfer method with the analytical solutions derived as well, taking into account the effect by stratified feature and various bearing conditions of subsoil, material nonlinearity, and the sediment under pile tip. Furthermore, formulas to determine the axial capacity of super-long piles by the pile top settlement were advised and applied to analyze the test pile. Good agreement between the predicted load-settlement variations and the measured data is obtained to verify the validity of the present method. The results also show that, the axial bearing capacity of super-long piles should be controlled by the allowable pile top settlement, and buckling stability of the pile shaft should be paid attention as well.

Instrumented Static Load Test on Rock-Socketed Micropile

AbstractRock-socketed piles are often used to transfer heavy loads from a superstructure to competent underlying rock layers. The loads are transferred by the pile to the surrounding rock mass through shaft and base resistance. Several researchers have investigated the behavior of rock-socketed drilled shafts and related the uniaxial compressive strength of intact rock to pile-shaft resistance. However, the load-transfer behavior and load-settlement response of micropiles are different from those of drilled shafts because of the large slenderness ratio (pile length/pile diameter) of micropiles. This study presents results from a fully instrumented field-scale load test on a 0.2-m-diameter micropile socketed 4.2 m into limestone layers (2.7 m into weathered limestone and 1.5 m into hard limestone). The results show that practically no base resistance is mobilized until the pile-head settlement reaches approximately 7% of the diameter of the test micropile. The measured limit shaft resistance values are com...

Nonlinear Dynamic Behavior of a Flexible Shaft Supported by Smart Hydrostatic Squeeze Film Dampers

The aim of this research is to study the nonlinear dynamic behavior of a flexible shaft supported by smart hydrostatic squeeze film dampers, which are filled with a negative electrorheological fluid (NERF). A nonlinear model of the hydrostatic squeeze film damper has been developed in order to study the effect of the electrorheological fluid on the dynamic behavior of a flexible shaft. The results obtained are discussed and compared with the linear model, which is restricted to only small vibrations around the equilibrium position. A new smart hydrostatic squeeze film damper is proposed to reduce the transient response of the shaft and transmitted forces by applying an electric field to the NER fluid, which results in modifying its viscosity. The results show that it is possible to effectively monitor the electric field and the viscosity of the fluid inside the hydrostatic squeeze film dampers (HSFD) for a better control of flexible shaft vibration and bearing transmitted forces.

Tribological behavior of sugar mill roller shaft in laboratory simulated conditions

Wear is often observed on top roll shaft journal surface. Sugar mill roller shafts are made up of carbon steel EN8. The friction and wear behavior of carbon steel EN8 was investigated under dry, lubricated, and contaminated sliding conditions. Sugar cane juice, bagasse, and water were used to simulate the contaminated service conditions. A reciprocating pin on disk tester was used to carry out friction and wear tests. EN8 was flat surface whereas E52100 bearing ball was counterface. The friction characteristics were examined at a constant applied load and sliding speed. It was observed that the coefficient of friction and wear volume increased when the shaft material was slid in contaminated test conditions. The volumetric wear was determined to analyze the wear resistance of the shaft material in the extreme service environment. Optical and scanning electron microscopy study showed sever wear in dry and contaminated test conditions. It was observed that the cracks initiated on the surface are consequences from the tribological phenomenon at the sliding interface.

Experimental Study on the Lubrication Characteristics of Porous Journal Bearings with Hydrodynamic Shape Forming at Annular Surface under Shaft Unsteady Condition (Examination into the Whirling Behavior of Shaft at Pivot Supported Condition by Analyzing the Frequency Spectrum of Time History Waveform with Parameter of Gradient on Starting Revolution Speed Changes)

Experimental Study on the Lubrication Characteristics of Porous Journal Bearings with Hydrodynamic Shape Forming at Annular Surface under Shaft Unsteady Condition (Examination into the Whirling Behavior of Shaft at Pivot Supported Condition by Analyzing the Frequency Spectrum of Time History Waveform with Parameter of Gradient on Starting Revolution Speed Changes)