scholarly journals Stick-Slip Analysis of a Drill String Subjected to Deterministic Excitation and Stochastic Excitation

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Hongyuan Qiu ◽  
Jianming Yang ◽  
Stephen Butt
Keyword(s):  
White Noise ◽  
Gaussian White Noise ◽  
Element Model ◽  
Random Excitation ◽  
Time Instant ◽  
Drill String ◽  
Stochastic Excitation ◽  
Stick Slip ◽  
Probabilistic Distribution ◽  
Noise Simulation

Using a finite element model, this paper investigates the torsional vibration of a drill string under combined deterministic excitation and random excitation. The random excitation is caused by the random friction coefficients between the drill bit and the bottom of the hole and assumed as white noise. Simulation shows that the responses under random excitation become random too, and the probabilistic distribution of the responses at each discretized time instant is obtained. The two points, entering and leaving the stick stage, are examined with special attention. The results indicate that the two points become random under random excitation, and the distributions are not normal even when the excitation is assumed as Gaussian white noise.

Stochastic and Deterministic Vibration Analysis on Drill-String With Finite Element Method

2013 ◽  
Author(s):  
Hongyuan Qiu ◽  
Jianming Yang
Keyword(s):  
Finite Element ◽  
Degrees Of Freedom ◽  
Beam Theory ◽  
Element Model ◽  
Random Excitation ◽  
Drill String ◽  
Mitigation Measures ◽  
Stick Slip ◽  
Drilling Performance ◽  
Mc Simulation

Using Euler-Bernoulli beam theory, a finite element model with six degrees of freedom per node is developed for a drill-string assembly. The drill-string is driven by a DC motor on the top and is subjected to distributed loads due to its own weight as well as bit/formation interaction. The model is axial-torsional, lateral-torsional coupled. Under deterministic excitations, the model captures stick-slip behavior in drilling operation. Analysis on its negative effect on drilling performance are made, and potential mitigation measures are also discussed. In random model, the excitations to the drill-bit are modeled as combination of deterministic and random components. Monte Carlo (MC) simulation is employed to obtain the statistics of the response. Two cases of random excitation with different intensities are investigated. The results from MC simulation are compared against that from deterministic case.

Response Statistics and Reliability Analysis of a Mistuned and Frictionally Damped Bladed Disk Assembly Subjected to White Noise Excitation

2010 ◽  
Author(s):  
Pankaj Kumar ◽  
S. Narayanan
Keyword(s):  
White Noise ◽  
Probability Density ◽  
Gaussian White Noise ◽  
Random Excitation ◽  
Forced Response ◽  
Computationally Efficient ◽  
Bladed Disk ◽  
White Noise Excitation ◽  
Bladed Disk Assembly ◽  
Mean Square Response

In the design of gas turbine engines, the analysis of nonlinear vibrations of mistuned and frictionally damped blade-disk assembly subjected to random excitation is highly complex. The transitional probability density function (PDF) for the random response of nonlinear systems under white or coloured noise excitation (delta-correlated) is governed by both the forward Fokker-Planck (FP) and backward Kolmogorov equations. This paper presents important improvement and extensions to a computationally efficient higher order, finite difference (FD) technique for the solution of higher dimensional FP equation corresponding to a two degree of freedom nonlinear system representative of vibration of tip shrouded frictionally damped bladed disk assembly subjected to Gaussian white noise excitation. Effects of friction damping on the mean square response of a blade are investigated. The friction coefficient of the damper is assumed to be a function of the sliding velocity of the contact surface. The effects of stiffness and damping mistuning on the forced response of frictionally damped bladed disk are investigated. Numerical studies are presented for a pair of mistuned blades of cyclic assemblies. The response and reliability of a blade subjected to random excitation is also obtained. With time averaged probability density as an invariant measure, the probability of large excursion in case of damping mistuning is also presented. The results of the FD method are validated by comparing with Monte Carlo Simulation (MCS) results.

scholarly journals Friction Damping of Random Vibration in Gas Turbine Engine Airfoils

1987 ◽  
Author(s):  
Alok Sinha
Keyword(s):  
White Noise ◽  
Numerical Simulations ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Random Vibration ◽  
Gaussian White Noise ◽  
Random Excitation ◽  
Equivalent Linearization ◽  
Turbine Engine ◽  
Optimal Value

The optimal value of slip load is calculated for a frictionally damped turbine blade subjected to random excitation. The nature of excitation is assumed to be Gaussian white noise and the statistics of response are obtained using equivalent linearization approach. The results from this technique are compared with those from numerical simulations.

Response Analysis of Discretized Plates Under In-Plane and External Nonstationary Random Excitations

1993 ◽  
Author(s):  
C. W. S. To ◽  
B. Wang
Keyword(s):  
Finite Elements ◽  
White Noise ◽  
Gaussian White Noise ◽  
Random Processes ◽  
Random Excitation ◽  
Computational Time ◽  
Response Analysis ◽  
Plate Element ◽  
Aerospace Systems ◽  
Modulating Functions

Abstract Responses of panel structures on board ships and aerospace systems under point and in-plane intensive transient excitations, originating, primarily, from near-mixed explosion and impact upon the ships are investigated and presented in this paper. The panel structures are idealized by finite elements while the intensive transient in-plane and point loads are modelled as nonstationary random processes. The latter are treated as products of modulating functions and Gaussian white noise processes. The focus of the paper is the comparison of results obtained by employing the three nodes, eighteen degree-of-freedoms (DOF) triangular bending plate element (the explicit element stiffness, mass and stability matrices of which have been derived by the authors) and the four nodes, twelve DOF Melosh-Zienkiewicz-Cheung (MZC) rectangular bending plate element. The isssues addressed are: (a) convergence and reduction of computational time by applying the eighteen DOF plate element in comparison to the MZC element, (b) the contribution of the in-plane nonstationary random excitation on the response of the discretized structures, and (c) the influence of the number of modes included in the response computation.

scholarly journals Kinematics and dynamics analysis of new rotary-percussive PDM drilling tool

2021 ◽  
pp. 146134842198915
Author(s):  
Jialin Tian ◽  
Xuehua Hu ◽  
Liming Dai ◽  
Lin Yang ◽  
Yi Yang ◽  
...  
Keyword(s):  
Drill String ◽  
Structure Design ◽  
Drilling Process ◽  
Analysis Model ◽  
Drilling Tool ◽  
Stick Slip ◽  
Rate Of Penetration ◽  
Bottom Hole ◽  
Bottom Hole Assembly ◽  
The Impact

This paper presents a new drilling tool with multidirectional and controllable vibrations for enhancing the drilling rate of penetration and reducing the wellbore friction in complex well structure. Based on the structure design, the working mechanism is analyzed in downhole conditions. Then, combined with the impact theory and the drilling process, the theoretical models including the various impact forces are established. Also, to study the downhole performance, the bottom hole assembly dynamics characteristics in new condition are discussed. Moreover, to study the influence of key parameters on the impact force, the parabolic effect of the tool and the rebound of the drill string were considered, and the kinematics and mechanical properties of the new tool under working conditions were calculated. For the importance of the roller as a vibration generator, the displacement trajectory of the roller under different rotating speed and weight on bit was compared and analyzed. The reliable and accuracy of the theoretical model were verified by comparing the calculation results and experimental test results. The results show that the new design can produce a continuous and stable periodic impact. By adjusting the design parameter matching to the working condition, the bottom hole assembly with the new tool can improve the rate of penetration and reduce the wellbore friction or drilling stick-slip with benign vibration. The analysis model can also be used for a similar method or design just by changing the relative parameters. The research and results can provide references for enhancing drilling efficiency and safe production.

scholarly journals Stochastic P-bifurcation in a bistable Van der Pol oscillator with fractional time-delay feedback under Gaussian white noise excitation

2019 ◽  
Vol 2019 (1) ◽  
Author(s):  
Yajie Li ◽  
Zhiqiang Wu ◽  
Guoqi Zhang ◽  
Feng Wang ◽  
Yuancen Wang
Keyword(s):  
Time Delay ◽  
White Noise ◽  
Gaussian White Noise ◽  
Singularity Theory ◽  
Van Der Pol Oscillator ◽  
Order System ◽  
Damping Force ◽  
Van Der Pol ◽  
Restoring Force ◽  
White Noise Excitation

Abstract The stochastic P-bifurcation behavior of a bistable Van der Pol system with fractional time-delay feedback under Gaussian white noise excitation is studied. Firstly, based on the minimal mean square error principle, the fractional derivative term is found to be equivalent to the linear combination of damping force and restoring force, and the original system is further simplified to an equivalent integer order system. Secondly, the stationary Probability Density Function (PDF) of system amplitude is obtained by stochastic averaging, and the critical parametric conditions for stochastic P-bifurcation of system amplitude are determined according to the singularity theory. Finally, the types of stationary PDF curves of system amplitude are qualitatively analyzed by choosing the corresponding parameters in each area divided by the transition set curves. The consistency between the analytical solutions and Monte Carlo simulation results verifies the theoretical analysis in this paper.

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