Stick slip

The phenomenon of stick-slip vibration is widespread in the exploration of deep and ultra-deep wells. It causes the reduction of the mechanical drilling rate and wastes the driving energy. Besides, it also accelerates the aging and failure of the drill strings and threatens the safety of drilling seriously. In order to effectively control the stick-slip vibration of the drill string, a new type of torsional vibration tool is proposed in this paper firstly. Then, the theoretical model of the drill string system based on the tool is established. And then, the viscosity reduction characteristics of the new torsional vibration tool are studied by the PID control method. Finally, field tests were carried out in comparison with simulation. The results show that the new torsional vibration tool can reduce the stick-slip vibration. And the two PID control equations can both control the drill bit speed in real time through changing the turntable speed. The results also have important reference significance for reducing and controlling the stick-slip vibration of the drill string and improving the rock-breaking efficiency.

A key problem in drill string dynamics is the stick-slip in deep and large displacement horizontal wells that may lead to the decline in drilling performance or cause tool failure, which may eventually cause underground accidents. Therefore, the research on the production safety, ROP, and increased efficiency in relation to stick-slip theory and practical stick-slip reduction is highly relevant, especially in complex drilling conditions. On this basis, this study takes the new constant torque tool as the engineering background and establishes the working mechanism analytical model of stick-slip reduction and torque constant. A helical dynamic model is established to solve the core problem of the constant torque tool. Then, the differential equation of the helical spline drive motion is deduced. The motion of the helical spline mandrel is calculated, and its analytical results are compared with simulation results. Findings show that the laws of angular displacement, angular velocity, axial displacement, and axial velocity are consistent with the simulation results when the helical spline mandrel moves up or down. The established theoretical model can promote the development of drill string dynamics in new drilling conditions. Moreover, the proposed designing methods can provide new ideas for the development of a stick-slip reduction tool. The results can be further used as reference for key parameter determination and stick-slip reduction technology optimization.

Inherent to any heavy-duty hydraulic machine operation with a large number of interconnected components are nonidealities such as gear backlash, friction and leakage. The swing motion of the operator’s cabin in an excavator is a typical example. In this paper we conduct a study comprising experimental, mathematical and simulation components to determine the degree to which these nonlinearities affect the performance of such machines. The inclusion of the conventional model of backlash in the simulation of the excavator swing motion is shown to be inefficient and unnecessary in terms of computation time and the final results. A new model which combines the fluid-flow and the gear train dynamics is developed. The study of contact and non-contact cases brings about proper sets of static and dynamic equations which efficiently simulate this phenomenon for the class of excavator machines under consideration. The inclusion of stick-slip friction model in the simulation shows two effects. ...

Ashless antiwear additives have begun to find applications in automotive and heavy industry applications as sludge formation is reduced leading to improved efficiency. In this study, six different ashless antiwear agents, including an ashless neutral dialkyl dithiophosphate (DDP-1), an acidic dialkyl dithiophosphate (DDP-2), an alkylated triphenyl phosphorothionate (A-TPPT), a butylated triphenyl phosphorothionate (B-TPPT), a triphenyl phosphorothionate (H-TPPT), and an amine

Abstract: In manufacturing by machining, thermal loads on cutting tools can have a major influence on tool wear and hence process cost, especially at higher cutting speeds. An investi-gation has been undertaken to determine heat partition into the cutting tool for high-speed machining ...

This paper investigates a damping strategy for integrally bladed disks (blisks) based on the use of friction rings. The steady-state forced response of the blisk with friction rings is derived using the so-called dynamic Lagrangian frequency-time method adapted to cyclic structures with rotating excitations. In addition, an original approach for optimal determination of the number of Fourier harmonics is proposed. In numerical applications, a representative compressor blisk featuring several rings is considered. Each substructure is modeled using finite-elements and a reduced-order modeling technique is used for the blisk. The efficiency of this damping technology is investigated, and friction dissipation phenomena are interpreted with respect to frequency responses. It is shown that the friction damping effectiveness depends mainly on the level of dynamic coupling between blades and disk, and on whether the dynamics features significant alternating stick/slip phases. Through parame...

This paper investigates a damping strategy for integrally bladed disks (blisks) based on the use of friction rings. The steady-state forced response of the blisk with friction rings is derived using the so-called dynamic Lagrangian frequency-time method adapted to cyclic structures ...

A driven wedge test is used to characterize the mode I fracture resistance of adhesively bonded composite beam specimens over a range of crosshead rates up to 1 m/s. The shorter moment arms (between wedge contact and crack tip) significantly reduce inertial ...

Understanding the frictional behavior between glass and metals at elevated temperatures is necessary for accurate modeling and simulation of the precision glass molding (PGM) process, and can help in determining the required geometry of molds, inserts, and dies to produce various optical components. In this research, the frictional behavior of N-BK7, an oxide glass, at elevated temperatures in contact with plain steel has been studied. The results show two important phenomena related to temperature. First, the stick-slip phenomenon is more pronounced at higher temperatures close to the glass transition temperature. This is expected since relaxation and creep of glass occur by molecular diffusion, which becomes more rapid as temperature increases. Second, when the temperature is above the glass transition temperature and the glass begins to behave viscoelastically, the stick-slip friction behavior shows an exponential increase in friction force prior to the onset of sliding that is c...

Abstract We develop a relationship to describe the effect of surface roughness on the stick-slip transition for linear polymers. Using the Brochard–de Gennes slip model and including molecular chain dynamics at the wall, we develop an expression for the critical shear stress for the onset of wall slip as a function of the wettability of the polymer on the die surface or, more precisely, as a function of the apparent contact angle between polymer and die surface. The surface roughness can be also accounted for using additional parameters.

In manufacturing by machining, thermal loads on cutting tools can have a major influence on tool wear and hence process cost, especially at higher cutting speeds. An investigation has been undertaken to determine heat partition into the cutting tool for high-speed machining of AISI/SAE 4140 high-strength alloy steel with uncoated and TiN-coated tools. The cutting tests have been performed at cutting speeds ranging between 100 and 880 m/min with a feed rate of 0.1 mm/rev and a constant depth of cut of 2.5 mm. Cutting temperatures are measured experimentally using an infrared thermal imaging camera. The sticking and sliding regions are investigated from an examination of the tool—chip contact region using a scanning electron microscope (SEM). In addition, non-uniform heat intensity is modelled according to the contact phenomena. In this work, evaluation of the fraction of heat flowing into the cutting tool is carried out by iteratively reducing the available heat flux until the finite...

The Stability of machining process depends on the dynamics of the machine tool, among other things. However, the dynamics of the machine tool changes when the tool is changed. To avoid the need for repeating the measurements, sub-structuring analysis may be used to couple ...

Many powders show a characteristic behavior when sheared, known as stick-slip. For such powders, when sheared under a normal load, once the peak shear point has been reached, the shear stress values start oscillating. The causes of stick-slip at particle level and the factors affecting this behavior are not well understood. In the present work, the stick-slip behavior of three