Torsional oscillation in liquid chlorobenzene at high molecular number densities

1977 ◽  
Vol 73 (5) ◽  
pp. 729
Author(s):  
Gareth J. Evans
Keyword(s):  
Torsional Oscillation ◽  
Molecular Number ◽  
Liquid Chlorobenzene

Fore-Aft Forces in Tire-Wheel Assemblies Generated by Unbalances and the Influence of Balancing

1991 ◽  
Vol 19 (3) ◽  
pp. 142-162 ◽  
Author(s):  
D. S. Stutts ◽  
W. Soedel ◽  
S. K. Jha
Keyword(s):  
Mathematical Model ◽  
Elastic Foundation ◽  
Torsional Oscillation ◽  
Vertical Direction ◽  
Torsional Stiffness ◽  
Rolling Motion ◽  
Vertical Force ◽  
Horizontal Force ◽  
Wheel Rim ◽  
Open Question

Abstract When measuring bearing forces of the tire-wheel assembly during drum tests, it was found that beyond certain speeds, the horizontal force variations or so-called fore-aft forces were larger than the force variations in the vertical direction. The explanation of this phenomenon is still somewhat an open question. One of the hypothetical models argues in favor of torsional oscillations caused by a changing rolling radius. But it appears that there is a simpler answer. In this paper, a mathematical model of a tire consisting of a rigid tread ring connected to a freely rotating wheel or hub through an elastic foundation which has radial and torsional stiffness was developed. This model shows that an unbalanced mass on the tread ring will cause an oscillatory rolling motion of the tread ring on the drum which is superimposed on the nominal rolling. This will indeed result in larger fore-aft than vertical force variations beyond certain speeds, which are a function of run-out. The rolling motion is in a certain sense a torsional oscillation, but postulation of a changing rolling radius is not necessary for its creation. The model also shows the limitation on balancing the tire-wheel assembly at the wheel rim if the unbalance occurs at the tread band.

Non-linear torsional oscillation of a two-degree-of-freedom system incorporating a Hooke joint

1964 ◽  
Vol 277 (1368) ◽  
pp. 92-106 ◽  
Keyword(s):  
Large Amplitude ◽  
Critical Speed ◽  
Torsional Oscillation ◽  
Degree Of Freedom ◽  
Non Linear ◽  
Two Degree Of Freedom

The non-linear torsional oscillation of the system is analyzed by means of a variant of Kryloff and Bogoliuboff’s method. It is shown that each mode of the system can perform oscillations of large amplitude in a number of critical speed ranges, and that hysteresis effects and discontinuous jumps in amplitude are to be expected in these speed ranges if the damping is light.

Torsional oscillation of rigid disk in infinite transversely isotropic elastic cylinder

2006 ◽  
Vol 27 (7) ◽  
pp. 911-917 ◽  
Author(s):  
Sakti Pada Barik ◽  
Mridula Kanoria ◽  
P. K. Chaudhuri
Keyword(s):  
Torsional Oscillation ◽  
Transversely Isotropic ◽  
Elastic Cylinder ◽  
Rigid Disk

Power transmission system modelling

1998 ◽  
Vol 212 (6) ◽  
pp. 497-505 ◽  
Author(s):  
H Bartlett ◽  
R Whalley
Keyword(s):  
Power Transmission ◽  
Dynamic Performance ◽  
Torsional Oscillation ◽  
Transmission System ◽  
System Modelling ◽  
Hybrid Modelling ◽  
Response Characteristics ◽  
Power Transmission System ◽  
Discrete Modelling ◽  
Modelling Techniques

This paper employs hybrid modelling techniques in the investigation of the dynamic performance of ‘long’ driveshafts, which include a clutch and load, for power transmission purposes. The power transmission system considered is suitable for a wide variety of applications in which the load is coupled directly to the clutch and hence to the ‘long’ driveshaft. Owing to the length of the shaft and relatively pointwise location of the clutch and load, a distributed—lumped (D—L) description of the arrangement is investigated. This enables the behaviour of the dispersed driveline shaft to be ‘adequately’ replicated along with the connecting elements. A discrete modelling approach is adopted and analysis and simulated response characteristics are presented, thereby validating the technique. Existing results on clutch judder are referred to and the interaction between judder and the driveshaft torsional oscillation is commented upon.

An Innovative Approach of Using Engineering Modelling to Improve Drilling Dynamics in Western Rajasthan, India

2021 ◽  
Author(s):  
Shailesh Prakash ◽  
Mohammad Zayyan ◽  
Ole Gjertsen ◽  
Manuel Centeno Acuna ◽  
Piyush Kumar Kulshrestha ◽  
...  
Keyword(s):  
Torsional Oscillation ◽  
Predictive Modelling ◽  
Integrated Approach ◽  
Vibration Monitoring ◽  
Hole Drilling ◽  
Volcanic Complex ◽  
Gas Field ◽  
Stick Slip ◽  
Unique Type ◽  
Barmer Basin

Abstract Raageshwari Deep Gas (RDG) field is a major gas field in the Barmer Basin of Rajasthan, India which comprises of a tight gas-condensate reservoir within the underlying thick Volcanic Complex. The Volcanic Complex comprises two major units – upper Prithvi Member (Basalt) and lower Agni Member (Felsics interbedded with older basalt). The production zone is drilled in 6" and has historically seen high level of shock & vibrations (S&V) and stick-slip (S&S) leading to multiple downhole tool failures and poor rate of penetration (ROP). Individual changes in Bit and bottom hole drilling assembly (BHA) design were not able to give satisfactory results and hence an integrated approach in terms of in-depth formation analysis, downhole vibration monitoring, correct predictive modelling, bit and BHA design was required. A proprietary formation analysis software was used to map the entire RDG field to understand the variation in terms of formation compactness, abrasiveness and impact (Figure 1,2,3 & 4). The resulting comprehensive field map thus enabled us to accurately identify wells that would be drilling through more of problematic Felsics and where higher S&V and S&S should be expected. To better understand the vibrations at the point of creation, i.e., bit, a downhole vibration recording tool was used to record vibration & stick-slip data at a frequency of 1024Hz. This tool picked up indication of a unique type of vibration occurring downhole known as High Frequency Torsional Oscillation (HFTO), that was quite detrimental to the health of bit and downhole tools. A proprietary predictive modelling software was used to optimize the bit-BHA combination to give least amount of S&V and S&S. Data from the downhole vibration recording tool, formation mapping software and offset bit designs was used to design a new bit with ridged diamond element cutters and conical diamond element cutters to drill through the highly compressive and hard basalt. The predictive modelling software identified a motorized Rotary steerable assembly (RSS) to give the best drilling dynamics with the newly designed bit. The software predicted much lower S&V and S&S with higher downhole RPM which was possible with the help of motorized RSS. Implementing the above recommendations from the various teams involved in the project, drilling dynamics was vastly improved and ROP improvement of about 45% was seen in the field. This combination was also able to drill the longest section of Felsics (826m) with unconfined compressive strengths as high as 50,000 psi in a single run with excellent dull condition of 0-1-CT-TD This paper will discuss in detail the engineering analyses done for improving drilling dynamics in field along with how HFTO was identified in field and what steps were taken to mitigate it.

Torsional oscillation of a homogeneous elastic spheroid

1962 ◽  
Vol 52 (3) ◽  
pp. 469-484 ◽  
Author(s):  
Tatsuo Usami ◽  
Yasuo Satô
Keyword(s):  
Fundamental Mode ◽  
Free Oscillation ◽  
Torsional Oscillation ◽  
Numerical Calculations ◽  
Higher Harmonics ◽  
Oblate Spheroidal ◽  
The Earth ◽  
Spectral Peaks ◽  
The Difference ◽  
Spheroidal Coordinates

abstract There are several causes for the observations of splitting of the spectral peaks determined from the free oscillation of the earth. In this paper, the splitting due to the ellipticity is studied assuming a homogeneous earth described by oblate spheroidal coordinates. Ellipticity causes the iTn mode to split into (n + 1) modes, while the earth's rotation causes it to split into (2n + 1) modes. 1/297.0 is adopted as the ellipticity of the earth. Numerical calculations are carried out for the fundamental mode (n = 2, 3, 4) and for the first higher harmonics (n = 1). The difference between the extreme frequencies for each value of n is 0.7% (n = 2), 0.5% (n = 3), and 0.4% (n = 4).

Mechanisms and Mitigation of 3D Coupled Vibrations in Drilling with PDC Bits

2021 ◽  
Author(s):  
Shilin Chen ◽  
Chris Propes ◽  
Curtis Lanning ◽  
Brad Dunbar
Keyword(s):  
Torsional Oscillation ◽  
Excitation Frequency ◽  
Low Frequency ◽  
Coupled Vibration ◽  
Stick Slip ◽  
Rock Interaction ◽  
Bottom Hole ◽  
New Type ◽  
Design Characteristics ◽  
Axial Resonance

Abstract In this paper we present a new type of vibration related to PDC bits in drilling and its mitigation: a vibration coupled in axial, lateral and torsional directions at a high common frequency (3D coupled vibration). The coupled frequency is as high as 400Hz. 3D coupled vibration is a new dysfunction in drilling operation. This type of vibration occurred more often than stick-slip vibration. Evidences reveal that the coupled frequency is an excitation frequency coming from the bottom hole pattern formed in bit/rock interaction. This excitation frequency and its higher order harmonics may excite axial resonance and/or torsional resonance of a BHA. The nature of 3D coupled vibration is more harmful than low frequency stick-slip vibration and high frequency torsional oscillation (HFTO). The correlation between the occurrence of 3D coupled vibration and bit design characteristics is studied. Being different from prior publications, we found the excitation frequency is dependent on bit design and the occurrence of 3D coupled vibration is correlated with bit design characteristics. New design guidlines have been proposed to reduce or to mitigate 3D coupled vibration.

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