Search results

The drill string vibrations can create harmful effects on drilling performance because they generate the stick-slip phenomenon which reduces the quality of drilling and decreases the penetration rate and may affect the robustness of the designed controller. For this reason, it is necessary to carefully test the different rock-bit contact models and analyze their influences on system stability in order to mitigate the vibrations. The purpose of this paper is to investigate the effects of rock-bit interaction on high-frequency stick-slip vibration severity in rotary drilling systems.

The main objective of this study is an overview of the influence of the rock-bit interaction models on the bit dynamics. A total of three models have been considered, and the drilling parameters have been varied in order to study the reliability of the models. Moreover, a comparison between these models has allowed the determination of the most reliable function for stick-slip phenomenon.

The torsional model with three degrees of freedom has been considered in order to highlight the effectiveness of the comparative study. Based on the obtained results, it has been concluded that the rock-bit interaction model has big influences on the response of the rotary drilling system. Therefore, it is recommended to consider the results of this study in order to design and implement a robust control system to mitigate harmful vibrations; the practical implementation of this model can be advantageous in designing a smart rotary drilling system.

Many rock-bit functions have been proposed in the literature, but no study has been dedicated to compare them; this is the main contribution of this study. Moreover, a case study of harmonic torsional vibrations analysis has been carried out in well-A, which is located in an Algerian hydrocarbons field, the indices of vibrations detection are given with their preventions.

During drilling in coal mines, sticking of drill rod (referred to as SDR in this work) is a potential threat to underground safety. However, no practical measures to deter SDR have been developed yet. The purpose of this study is to develop an anti-SDR strategy using proportional-integral-derivative (PID) and compliance control (PIDC). The proposed strategy is compatible with the drilling process currently used in underground coal mines using drill rigs. Therefore, this study aims to contribute to the PIDC strategy for solving SDR.

A hydraulic circuit to reduce SDR was built based on a load-independent flow distribution system, a PID controller was designed to control the inlet hydraulic pressure of the rotation motor and a typical compliance control approach was adopted to control the feed force and displacement. Moreover, the weight and optimal combination of the alternative admittance control parameters for the feed cylinder were obtained by adopting the orthogonal experiment approach. Furthermore, a fuzzy admittance control approach was proposed to control the feed displacement. Experiments were conducted to test the effectiveness of the proposed method.

The experimental results indicated that the PIDC strategy was appropriate and effective for controlling the rotation motor and feed cylinder; thus, the proposed method significantly reduces the SDR during drilling operations in underground coal mines.

As the PIDC strategy solves the SDR problem in underground coal mines, it greatly improves the safety of coal mine operation and decreases the power cost. Consequently, it brings the considerable benefits of coal mine production and vast application prospects in other corresponding fields. Actual drilling conditions are difficult to accurately simulate in a laboratory; thus, for future work, drilling experiments can be conducted in actual underground coal mines.

The PIDC-based anti-SDR strategy proposed in this study satisfactorily controls the rotation motor and feed cylinder and facilitates the feed and rotation movements. Furthermore, the tangible novelty of this study results is that it improves the frequency response of the entire drilling system. The drilling process with PIDC decreased the occurrence of SDR by 50%; therefore, the anti-SDR strategy can significantly improve the safety and efficiency of underground coal mining.

The purpose of this paper is to present the development of a simulator of oil well drilling processes.

The simulator incorporates the main variables that are used by drilling engineers in the definition of the drilling processes. The code is useful a priori, in the design of a drilling process, as a tool for comparing different design options and predicting their results and a posteriori of a failure to understand its genesis and therefore provide know-why to improve the drilling techniques.

The developed finite element simulator uses a co-rotational Bernoulli beam element, an explicit time integration scheme and an explicit contact algorithm. The numerical results show that the simulator is stable and provides consistent solutions.

During the drilling of oil wells, the fatigue damage and wear of the drilling column is of utmost concern. To determine the mechanical behavior of the drilling column standard simplified analyses are usually performed using commercially available codes; however, those standard analyses do not include a transient dynamic simulation of the process; hence, it is necessary to develop a specific tool for the detailed dynamic simulation of drilling processes.

A simulator able to perform a description of the drilling process in the time range will be an important contribution to the tools used by drilling engineers.

The author compares the results of a series of tests on BQ wireline and TBW mining bits containing 30/40 US mesh De Beers SDA100 diamond abrasive at 60 concentration when drilling Cornish grey granite at constant penetration rate or constant thrust loads. The results confirmed earlier findings that, by setting the penetration rate of impregnated drill bits, efficient drilling can be maintained throughout the life of the bit.

Reviews piling methods and their possible effects, mainly during construction, on adjacent structures, noting that piling falls into two basic types: displacement, where the material is forced into the ground, and replacement, where the ground is removed and replaced with concrete or grout. Examines the merits and demerits of their various applications.

Numerous finite elements are proposed based on analytical solutions. However, it is difficult to find the solutions for complicated governing equations. This paper aims to present a novel formulation in the framework of assumed stress quasi-conforming method for the static and free vibration analysis of anisotropic and symmetric laminated plates.

Firstly, an initial stress approximation ruled by 17 parameters, which satisfies the equilibrium equations is derived to improve the performance of the constructed element. Then the stress matrix is treated as the weighted function to weaken the strain-displacement equations. Finally, the Timoshenko’s laminated composite beam functions are adopted as boundary string-net functions for strain integration.

Several numerical examples are presented to show the performance of the new element, and the results obtained are compared with other available ones. Numerical results have proved that the new element is free from shear locking and possesses high accuracy for the analysis of anisotropic and symmetric laminated plates.

This paper proposes a new QC element for the static and free vibration analysis of anisotropic and symmetric laminated plates. In contrast with the complicated analytical solutions of the equilibrium equations, an initial stress approximation ruled by 17 parameters is adopted here. The Timoshenkos laminated composite beam functions are introduced as boundary string-net functions for strain integration. Numerical results demonstrate the new element is free from shear locking and possesses high accuracy for the analysis of anisotropic and symmetric laminated plates.

THE two previous articles in this series have dealt respectively with a metal fabric‐covered aeroplane and a metal stressed‐skin machine, so that the Oxford, as an example of modern woodworking practice, forms a subject for direct comparison of the three main materials available. It will be remembered that the Air Council's policy of insisting upon all‐metal aeroplanes for military purposes was subjected to considerable criticism at the time of its inception some ten or twelve years ago. When the R.A.F. expansion was started the regulations were relaxed in regard to training machines and one general service type, which has resulted in the standardization of the Airspeed Oxford, de Havilland Tiger Moth, Miles Magister and Master I and the Avro Anson. All these types are built on well‐tried straightforward principles and they allow for the use of both material and labour upon which there is now comparatively little demand. Those firms which are producing wooden aeroplanes do, in fact, have far fewer delays caused by non‐delivery of parts and scarcity of labour—their rate of production is actually governed to a great extent by the delivery of metal parts and fittings—than do the producers of metal airframes.

This book contains the subject matter taught by the author at the École Nationale Supérieure de l'Aéronautique and at the École Nationale Supérieure des Mines in Paris. It is thus not primarily intended for professional mathematicians, but a rigour worthy of them is maintained throughout. In particular, the ideas of mathematical analysis are freely used and the small quantity ∈ is frequently mentioned. The production of such a comprehensive work in the 916 pages is in itself a remarkable achievement, but in the reviewer's opinion very few British engineers, unless they have an unusually strong mathematical bent, will find that they can derive much profit from it.

MORE cheering news about work study. In the Daily Express the following appeared: ‘Inflation has hit the State‐aided Remploy factories manned by wore than 6,000 disabled workers. But the workers of the 91 factories have wiped out—by increased efficiency—£124,000 of £271,000 rise in costs in the financial year up to the end of March.’

THE potentialities of television in industry were referred to by this journal (March, 1954) when we reported on the Pye TV unit which had been installed in the National College of Rubber Technology, enabling shop floor demonstrations to be seen in detail by large numbers of students in the lecture theatre some way off.