scholarly journals Single Axis Singularity Mapping for Mixed Skew Angle, Non-Redundant, Single Gimbaled CMG Systems

2020 ◽  
Author(s):  
Eryn A. Culton
Keyword(s):  
Skew Angle

Roller Cutter Forces

1970 ◽  
Vol 10 (01) ◽  
pp. 57-65 ◽  
Author(s):  
C.R. Peterson
Keyword(s):  
Normal Force ◽  
Penetration Rate ◽  
Rolling Force ◽  
Skew Angle ◽  
Average Force ◽  
Straight Line ◽  
Bearing Load ◽  
Boring Machines ◽  
Force Reduction ◽  
Cutter Head

Abstract An experimental technique is described in which three component forces are measured while a typical toothed cutter is rolled in a straight line over a rock sample. The technique includes the attainment of a steady state in which volume-averaged penetration is correlated with average force during penetration is correlated with average force during the removal of several layers from the rock surface. Simple rolling and skewed rolling forces are measured. The cutter was artificially dulled for some of the measurements. Surprisingly little variation in force requirement is noted. A qualitative explanation is suggestedThe normal force requirement is substantially reduced when the cutter is skewed. A theoretical description of the force reduction is presented, showing reasonable agreement with the observed behavior in terms of cutter radius, tooth width, penetration and skew angle. penetration and skew angle Introduction Toothed roller cutters have long been in use on tricone bits, and they are in common use on boring machines. Yet the designer of boring machines is still faced with a dearth of good design information on the performance of such cutters. For example, what are the relationships between thrust, power, and penetration rate? How are these relationships influenced by rock properties and cutter configuration?While the data presented here provide answers to more specific questions than those mentioned above, these data are necessary for arriving at solutions to the broader questions. This work is restricted to one tooth type, typical of the wedge-shaped steel teeth used on medium rock. A limited range of rock types was tested; this coupled with the extreme variation of rock drillability, renders the data of limited value in predicting penetration rate. But the designer must predicting penetration rate. But the designer must answer questions even more important than the prediction of absolute penetration rate. For example, prediction of absolute penetration rate. For example, the cutter normal force is usually known in terms of the thrust to be applied to the cutter head. What is the torque or power required to rotate the cutter head? For an answer, one need know only the ratio of normal force to the tangential or rolling force. This ratio may be estimated from the present data. Variation of this ratio is reasonably small from one rock to another so that, lacking more specific information, these data can provide at least rough design estimates for other rocks. Tricone bits for soft to medium rock usually are constructed with skewed cutter elements that provide a "gouging and scraping action". Whatever the explanation, skewed cutters do provide increased drilling rate or, for a given drilling rate, a decreased thrust requirement. To my knowledge, skewed cutter elements have not been used on boring machines. If they were, bearing load could be reduced at a given penetration rate, or, conversely, an increased penetration rate could be obtained at the same penetration rate could be obtained at the same bearing load. Of course, a side load is introduced to the cutter bearing and this must be provided for. As for the rolling force, the designer really needs only the ratio of side-to-normal load. The present data indicate that this ratio is quite independent of rock type. The magnitude of the force reduction to be expected with skewed cutters is also of interest. The present data indicate that substantial reductions might be expected. A simple analytical model predicts the observed reduction reasonably well on the basis of the limited data available. EXPERIMENTAL APPARATUS AND TECHNIQUES Forces produced by a single cutter wheel rolling in a straight line over the rock specimen were measured. This simple geometry is experimentally convenient and is thought to be reasonably representative of cutter conditions on a large boring machine. Fig 1 illustrates the "linear apparatus" on which the measurements were made. The cutter wheel was rotatably mounted in a heavy yoke. SPEJ P. 57

Assessment of Thin Heteroepitaxial Layers Using Skew Angle Asymmetrical X-Ray Double Crystal Diffraction

1988 ◽  
Vol 138 ◽  
Author(s):  
S. J. Miles ◽  
G. S. Green ◽  
B. K. Tanner ◽  
M. A. G. Halliwell ◽  
M. H. Lyons
Keyword(s):  
Skew Angle ◽  
Double Crystal ◽  
X Ray ◽  
Heteroepitaxial Layers

Free Vibration of Orthotropic Skew Plates

1999 ◽  
Vol 122 (3) ◽  
pp. 313-317 ◽  
Author(s):  
A. M. Farag ◽  
A. S. Ashour
Keyword(s):  
Boundary Conditions ◽  
Transition Matrix ◽  
Longitudinal Direction ◽  
Displacement Function ◽  
Characteristic Matrix ◽  
Skew Angle ◽  
Kantorovich Method ◽  
Vibration Effect ◽  
Finite Strip Method ◽  
Semianalytical Method

The main purpose of this paper is to develop a fast converging semianalytical method for assessing the vibration effect on thin orthotropic skew (or parallelogram/oblique) plates. Since the geometry of the skew plate is not helpful in the mathematical treatments, the analysis is often performed by more complicated and laborious methods. A successive conjunction of the Kantorovich method and the transition matrix is exploited herein to develop a new modification of the finite strip method to reduce the complexity of the problem. The displacement function is expressed as the product of a basic trigonometric series function in the longitudinal direction and an unknown function that has to be determined in the other direction. Using the new transition matrix, after necessary simplification and the satisfaction of the boundary conditions, yields a set of simultaneous equations that leads to the characteristic matrix of vibration. The influence of the skew angle, the aspect ratio, the properties of orthotropy, and the prescribed boundary conditions are investigated. Convergence of the solution is investigated and the accuracy of the results is compared with that available from other numerical methods. The numerical results show that the convergence is rapidly deduced and the comparisons agree very well with known results. [S0739-3717(00)00202-6]

Skew angle and off-track capability of near contact recording systems

1996 ◽  
Vol 32 (5) ◽  
pp. 3866-3868 ◽  
Author(s):  
Sheng-Bin Hu ◽  
Bo Liu ◽  
Teck-Seng Low
Keyword(s):  
Skew Angle ◽  
Contact Recording

scholarly journals Study on the additional support length requirements of single-span bridges due to skew using a simplified method

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Suiwen Wu ◽  
Junfeng Jia ◽  
Chiyu Jiao ◽  
Junfei Huang ◽  
Jianzhong Li
Keyword(s):  
Aspect Ratio ◽  
Response Spectrum ◽  
Skew Angle ◽  
Empirical Formulas ◽  
Design Response Spectrum ◽  
Skew Bridges ◽  
Simplified Method ◽  
Additional Support ◽  
Linear Manner ◽  
Support Length

AbstractSkew bridges with seat-type abutments are frequently unseated in earthquakes due to large transverse displacements at their acute corners. It is believed these large displacements are due to in-plane rotation of the superstructure. Lack of detailed guidelines for modeling of skew bridges, many current design codes give empirical expressions rather than theoretical solutions for the additional support length required in skew bridges to prevent unseating. In this paper, a parametric study has been carried out to study the influence of skew angle, aspect ratio and fundamental periods of bridges on the additional support length requirements of single-span bridges due to skew using a shake table experiment validated Simplified Method, which is capable of simulating gap closure based on response spectrum analysis. This method is developed based on the premise that the obtuse corner of the superstructure engages the adjacent back wall during lateral loading and rotates about this corner until the loading reverses direction. A design response spectrum specified in AASHTO LRFD Specifications was employed to represent the design-level earthquakes. The results show the additional length required to prevent unseating due to skew increases with the skew angle in an approximately linear manner when the angle is less than a critical value and decreases for angles above this value. This critical skew angle increases with the aspect ratio approximately in a linear manner and shows negligible dependence on the fundamental periods of the bridges, and combination of span length and width. In addition, the critical skew angle varies between 58° and 66°, when the aspect ratio is varied from 3.0 to 5.0. The results also show that the empirical formulas for minimum support length requirements of skew bridges in current codes and specifications can not accurately reflect the influence of skew.

Reducing Low-Pressure Turbine Stage Blade Count Using Vortex Generator Jet Separation Control

2002 ◽  
Author(s):  
Rolf Sondergaard ◽  
Jeffrey P. Bons ◽  
Matthew Sucher ◽  
Richard B. Rivir
Keyword(s):  
Boundary Layer ◽  
Vortex Generator ◽  
Separation Control ◽  
Surface Boundary ◽  
Freestream Turbulence ◽  
Skew Angle ◽  
Suction Surface ◽  
Simple Boundary ◽  
Design Value ◽  
Vortex Generator Jets

An experimental investigation has been conducted into the feasibility of increasing blade spacing (pitch) at constant chord in a linear turbine cascade. Vortex generator jets (VGJs) located on the suction surface of each blade in the cascade are employed to maintain attached boundary layers despite the increasing tendency to separate due to the increased uncovered turning. Tests were performed at low Mach numbers and at blade Reynolds numbers between 25,000 and 75,000 (based on axial chord and inlet velocity). The vortex generator jets (30 degree injection angle and 90 degree skew angle) were operated with steady flow with momentum blowing ratios between zero and five, and from two spanwise rows of holes located at 45% and 63% axial chord. In the absence of control, pitch-averaged wake losses increase up to 600% as the blade pitch is increased from its design value to twice the design value. With the application of VGJs, these losses were driven down to or below the losses at the design pitch. The effectiveness of VGJs was found to increase modestly with increasing Reynolds number up to the highest value tested, Re = 75,000. The fluid phenomenon responsible for this remarkable range of effectiveness is clearly more than a simple boundary layer transition effect, as boundary layer trips installed on the same blades without VGJ blowing had no beneficial effect on blade losses. Also, tests conducted at elevated levels of freestream turbulence (4% at the cascade inlet) where the suction surface boundary layer is generally turbulent, showed wake loss reduction comparable to tests conducted at the nominal 1% freestream turbulence. For all configurations, blowing from the upstream row had the greatest wake influence. These findings open the possibility that future LPT designs could take advantage of active separation control using integrated VGJs to reduce the turbine part count and stage weight without significant increase in pressure losses.

Influence of skew angle on live load moments in steel girder bridges

2011 ◽  
Vol 7 (4) ◽  
pp. 151-163 ◽  
Author(s):  
Firas Bou Diab ◽  
Mounir Mabsout ◽  
Kassim Tarhini
Keyword(s):  
Live Load ◽  
Skew Angle ◽  
Steel Girder ◽  
Girder Bridges ◽  
Steel Girder Bridges

scholarly journals Nose-Angle Bridge Piers as Alternative Countermeasures for Local Scour Reduction

2018 ◽  
Vol 13 (2) ◽  
pp. 110-120 ◽  
Author(s):  
Ibtesam Abudallah Habib ◽  
Wan Hanna Melini Wan Mohtar ◽  
Atef Elsaiad ◽  
Ahmed El-Shafie
Keyword(s):  
Froude Number ◽  
Local Scour ◽  
Bridge Piers ◽  
Scour Depth ◽  
Skew Angle ◽  
Flow Angle ◽  
Sediment Size ◽  
Low Froude Number ◽  
Skew Angles ◽  
Depth Reduction

This study investigates the performance nose-angle piers as countermeasures for local scour reduction around piers. Four nose angles were studied, i.e., 90°, 70°, 60° and 45° and tested in a laboratory. The sediment size was fixed at 0.39 mm whereas the flow angle of attack (or skew angle) was varied at four angles, i.e., skew angles, i.e., 0°, 10°, 20° and 30°. Scour reduction was clear when decreasing nose angles and reached maximum when the nose angle is 45°. Increasing the flow velocity and skew angle was subsequently increasing the scour profile, both in vertical and transversal directions. However, the efficiency of nose angle piers was only high at low Froude number less than 0.40 where higher Froude number gives minimal changes in the maximum scour depth reduction. At a higher skew angle, although showed promising maximum scour depth reduction, the increasing pier projected width resulted in the increase of transversal lengths.

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