Thesis (Ph.D.)--University of Tulsa, 1994. / Includes bibliographical references (leaves 87-92).

Carbon fibre reinforced polymer, or CFRP composite materials, play an increasingly important role in modern manufacturing. They are widely used in aerospace, and their use is currently spreading to other industries where high strength-to-weight ratios are required. However, machining of composites is still a challenging task and often hampered by poor quality. Despite the extensive research that was conducted on the machining of composite materials over the last few years, mechanical drilling still suffers from delamination, fibre pull-out and poor surface finish, whereas laser cutting produces microstructured defects and a taper problem. This thesis reports on the drilling of CFRP composites by demonstrating the possibility of drilling small diameter holes (i.e. 8mm) into 25.4mm thick carbon fibre reinforced polymer composites (CFRPs) using mechanical drilling and laser drilling as stand-alone processes and as a sequential combination. The research involved four main phases of experimental testing. The first part of Phase 1 involved!preliminary experiments of drilling thick CFRP to identify the most suitable drilling strategy. Three mechanical drilling strategies conducted in the same parameter by using a 2-flute uncoated WC twist drill that was assessed with respect to feasibility of drilling thick CFRP. The results showed that the single-step strategy was the most feasible strategy to drill thick CFRP compared to 2- and 4-peck drilling strategies. The second part of Phase 1 concerned the influence of speed-feed combinations on hole quality by utilising three twist drills with different materials and geometries in both an uncoated and coated condition. The results indicated that a significant increase in peel-up delamination was found with increasing feed rate. In contrast, using a constant feed rate but increasing the spindle speed seemed to reduce peel-up delamination. Furthermore, the hole entry for 2-flute uncoated WC drill bits was an uncommon study finding because most of the previous researchers experienced more damages at the hole exit and their investigation focused on the hole exit only. Currently, implementation of laser technology in cutting and drilling composites is becoming popular as an alternative solution. Various experiments were conducted with the goal of identifying the effects of machining parameters on key output measures (i.e. heat affected zone (HAZ), hole depth and other damages) in drilling of 25.4 mm thick CFRP by using a fibre laser. Phase 2 involved a number of machining parameters selected to identify the potential of a fibre laser in drilling thick CFRP composites (i.e. laser power, scanning speed, focal point plane position (FPP), assisted-gas type and gas pressure). The results proved that a fibre laser could penetrate thick CFRP to a 22mm depth only. Moreover, the spiral trepanning strategy was able to penetrate 80% out of the total thickness of the CFRP in continuous wave (CW) mode, whereas the modulated laser beam (i.e. laser pulse mode) can penetrate 67% only. This result was a major recorded breakthrough because previous research attempts cut up to 5mm only. Laser power proved to be the most influential factor for hole depth in laser drilling of thick CFRP when the spiral trepanning strategy was applied. Machining trials were conducted in Phase 3 by using a 16kW fibre laser in modulated pulsed laser mode. In this phase, laser power of more than 1kW was attempted to cut the whole thickness of CFRP composites in CW mode, but it was unsuccessful. However, a new parameter was discovered (i.e. the cooling time between passes in modulated pulsed mode), which proved a considerable reduction of HAZ when the higher cooling time was imposed. Finally, phase 4 involved the experiments of sequential laser-mechanical drilling. A 1kW fibre laser was selected as a pre-drilling or initial step and followed by mechanical drilling as the final step. The sequential drilling method successfully reduced thrust force and torque for mechanical drilling by an overall average of 61%, resulting in high productivity and decreasing the thermal and mechanical stresses in the cutting tool and, in turn, promoting higher tool life. The highest delamination factor (Fda) ratio was experienced by the sequential laser 8mm – mechanical 8mm for both tools (i.e. 2- and 3-flute uncoated tungsten carbide) and laser pre-drilling strategies (i.e. single- and double-side). Thus, a novel laser-mechanical sequential drilling technique was developed, evaluated and tested in the drilling of thick CFRP composites; this is the first time ever in drilling thick CFRP (i.e. 25.4mm).

Orientador: Celso Kazuyuki Morooka / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica e Instituto de Geociencias / Made available in DSpace on 2018-08-12T08:27:01Z (GMT). No. of bitstreams: 1 Tavares_RogerioMartins_M.pdf: 4486428 bytes, checksum: b451b4e88fa208c51397fb1846b31ebb (MD5) Previous issue date: 2006 / Resumo: A exploração de petróleo no mar desenvolveu-se substancialmente nas últimas décadas. Ao longo desse processo, notadamente a partir da década de 80, a quantidade de informação gerada durante a perfuração aumentou dramaticamente. Se por um lado o cenário atual apresenta informação em abundância, por outro lado existe carência de ferramentas capazes de fazer uso efetivo da informação disponível. Esta dissertação apresenta procedimentos que, através da análise e interpretação de dados de perfuração, buscam melhorar o processo de construção de poços de petróleo. Três procedimentos independentes são propostos. O primeiro consiste na utilização de um sistema de visualização para acompanhamento da perfuração direcional. A aplicação desse sistema traz benefícios para a atividade de controle da trajetória do poço. O segundo procedimento trata da utilização de um sistema automático para classificar as operações realizadas durante a perfuração de um poço de petróleo. O sistema de classificação pode ser utilizado para produzir um relatório preciso e detalhado sobre as atividades realizadas durante a perfuração. O terceiro e último procedimento diz respeito à detecção precoce de problemas de perfuração. Esse procedimento consiste em reconhecer, em tempo real nos dados de perfuração, comportamentos capazes de precocemente identificar problemas de perfuração. Através desse trabalho é possível concluir que os dados de perfuração atualmente disponíveis representam uma fonte bastante rica de informações e podem ser utilizados para melhorar o processo de construção de poços de petróleo. / Abstract: The offshore petroleum exploration has substantially developed in the last decades. During this process, mostly in the 80s, the amount of information generated during the drilling operation has dramatically increased. If on one hand the existing scene presents great quantity of information, on the other hand there is a lack of tools able to make effective use of the available information. This work presents procedures that, through the analysis and interpretation of drilling data, aim to improve the construction process of petroleum wells. Three independent procedures are presented. The first one concerns the use of a visualization system for tracking the execution of directional drilling operation. The utilization of this system brings benefits to the trajectory control activity. The second procedure deals with the use of an automated system to classify the activities performed during well drilling operation. The automated classification system may be used to generate a precise and detailed report considering the executed drilling activities. The third and last procedure concerns the early detection of drilling troubles. This procedure consists of recognizing online, in the drilling data, behaviors able to identify drilling problems. Through this work it is possible to conclude that the available drilling data represent a high potential source of information and can be used to improve the petroleum well construction. / Mestrado / Explotação / Mestre em Ciências e Engenharia de Petróleo

The thesis is dealing with drilling deep holes. Theoretical part of thesis is focused on base knowledge of deep drilling. Experimental part deals with testing two different borers, with different cutting conditions and different purchase prize. Drilling was made into 1.2343 ESU material. Conclusion of this work is concept of purchase machinery for deep drilling.

The studies conducted on hole cleaning have been started with single phase drilling fluids for vertical holes in 1930&rsquo / s, and have reached to multiphase drilling fluids for directional and horizontal wells today. The influence of flow rate and hole inclination on cuttings transport has been well understood, and many studies have been conducted on effective hole cleaning either experimentally or theoretically. However, neither the hydraulic behavior nor the hole cleaning mechanism of gasified drilling fluids has been properly understood. The aims of this study are to investigate and analyze the hole cleaning performance of gasified drilling fluids in horizontal, directional and vertical wells experimentally, to identify the drilling parameters those have the major influence on cuttings transport, to define the flow pattern types and boundaries as well as to observe the behavior of cuttings in detail by using digital image processing techniques, and to develop a mechanistic model based on the fundamental principles of physics and mathematics with the help of the experimental observations. A mechanistic model is developed with the help of the obtained experimental data. Developed model is used for estimating optimum flow rates for liquid and gas phases for effective cuttings transport as well as for determining the total pressure losses and void fraction of each phase for a given drilling conditions. The v mechanistic model obtained using the experimental data within the scope of this study will be used to develop the hydraulic program and equipment selection to be used in the field during underbalanced drilling applications.

Thesis (M. S.)--Texas A&M University, 2004. / Vita. Abstract. "Major Subject: Petroleum Engineering" Includes bibliographical references.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

The reliability of ocean systems is dependent on organizational factors. It has been shown that low probability / high consequence system failures are overwhelmingly induced by organizational factors. However, no methodology is yet widely accepted for the evaluation of this phenomenon or its accurate quantification. A qualitative complementary approach is proposed based on the CANL (Complex Adaptive Non-Linear) model. In the first part, the understanding of organizational processes that affect reliability is sought. The approach is applied to several case studies based on published information: the "Story of a Platform Audit" (where no failure occurred) and some offshore accidents. A methodology is proposed to complement regular safety audit procedures. The approach is shown useful also to improve post-mortem investigations. In the second part, quantitative probabilistic formulations are revised, based on the understanding obtained through the previous approach. Some of the limitations of these quantitative methods are pointed out. The Reliability State of an Organization is defined and a ranking for its evaluation is proposed. Preliminary guidelines are presented for the use of this approach as a framework to identify suitable quantitative methods for a given case. The use of a qualitative approach is demonstrated. A different insight into organizational factors is achieved based on a disciplined approach that relies on experience. Significant conclusions regarding quantitative methods, their limitations and appropriate use, are obtained. / Graduation date: 1999

No description available.

The influence of three elastic contact models on the dynamics of the drilling module is studied by representing the percussive drilling process as a drifting oscillator. The Kelvin-Voigt, Hertz stiffness and nonlinear stiffness and damping models were considered. The local dynamics of the system were found to be almost identical for the three models. Hence the Kelvin-Voigt system adequately describes the local dynamics of the system. However, for larger frequency and higher damping the behaviour of the three models differed. Experimental indentation studies were carried out on sandstones samples using static and dynamic loading. A force penetration relation was obtained for the loading and unloading phases of the indentation using a conical and spherical indenter under quasi-static conditions. Conical indentation tests were carried out in dynamic conditions. Both experiments showed that the force penetration relationship that could describe the contact model were closer to that obtained for the elastic-plastic indentation of ductile materials. The dynamic model for the drilling module was developed using an elastic plastic model for conical and spherical indenter. In addition, the model’s parameters were modified to those obtained from the experiments and used for the comparison with the results obtained for the elastic plastic model. The result obtained suggested a topological similarity between the experimental and theoretical parameters. It was also noted that the results suggested that the conical indenter appeared to be more efficient of the two indenter types considered. Finally, the rock fracture as a result of its contact with the drill-bit insert was investigated. For simplicity, the inserts are considered as flat punch and the contact problem is treated as a plane strain problem. Experimental studies were also carried out to determine the crack initiation angle in sandstone.