RCAAP Repository

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Universidade Federal de Uberlândia

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Conselho Nacional de Desenvolvimento Científico e Tecnológico

The flexible pipes are used extensively as a means of conducting crude oil, gas and water between the wellheads and oil platform. These pipes are made of layers of polymeric materials, interspersed with steel straps, forming a composite that combines high corrosion resistance and flexibility of movements. They absorb the changes imposed by water currents, but can wear the outer polymeric layer. In order to simulate this tribossistema, the Laboratório de Tecnologia em Atrito e Desgaste designed and built a tribometer able to reproduce middle-scale conditions similar to the wear that occurs on the field. The developed device consists of a system capable of alternating vertical movements in underwater environment, and applied on the samples tested loads normal to its surface, whose values can reach 1000 kN. The automation control and monitoring of process variables is essential for the correct operation of the equipment. In this dissertation is describes the instrumentation developed for this tribometer, with preliminary testing of the sensors and the analysis of mechanical performance and data obtained from the sensors to each subsystem. Finally, after complete assembly and testing of the tribometer, we could verify that the performance of mechanical and instrumentation system oscillation attend the function for which the system was designed. Furthermore, it was observed that the proportional valve control hydraulic pressure of the compression system is inadequate to sample the range of applied forces, and must be replaced. After the tube change the system retested. The force sensors of the compression system are adequate. The sensors, in principle, would measure the wear of the samples showed shifts in the alternation of the direction of movement of the flexible duct, and low resolution. Setting up these sensors will be used only to limit the maximum wear of the samples. The wear characteristics of the samples need to be analyzed out of the tribometer, with more precise tools. Vibration levels for loads tested were too low, not acting for the equipment problem.

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Wave loads introduce significant dynamic stresses on welded connections of offshore structures, leading to fatigue crack growth. Innovations in repair techniques are being pursued to perform these repairs without the need of shutdown of FPSOs (Floating Production Storage and Offloading). While common repair techniques are based on fusion welding process, solid state welding technique such as friction welding has always being sought as an alternative method for repair. The Friction Hydro Pillar Processing (FHPP) technique can be described as a fill and drill process, where a consumable rod is rotated, then entered co-axially into a cavity. Since the repair occurs below the melting point of the material, the process does not suffer from the common welding problems such as cracking, porosity, gas adsorption, atmospheric contamination and hydrogen embrittlement. Looking forward to applying this technology, the company Petrobras signed an agreement with the Federal University of Uberlandia - Brazil, and a FHPP equipment was developed. It was used to optimize the parameters and geometries for the new technique. Later, studies for field application began towards designing a portable friction welding head, which is the mechanical part that applies axial load and rotation to the consumable rod. In the present work, a portable friction welding head was conceived, designed and assembled for operations of 40 kN of axial load and 5.000 rpm. A 15 kg welding head was connected to the equipment. FHPP and FPPW (Friction Pull Plug Welding) tests were performed. Specific chucks and clamping systems for pipes and flat surfaces were developed and tested. The weld head was portablelized and demonstrated itself capable to perform field operations.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

The increased in the demand for plastic products and the need for reduction manufacturing times, and the growing dependence of man on the computer in present day, especially in manufacturing activities, has resulted in constant research of technological developments in order to supply these needs. In dies and molds manufacturing industry for plastic injection requiring machining operations such as (milling, drilling and polishing, among others), is increasing dependence by computer systems, such as CAD/CAM. This technology helps in the manufacturing steps, provides fast and high accuracy in the manufacturing of complex geometries. Therefore, to understand and to use efficiently these resources that aided in manufacturing are of enormous importance for the optimization of a production process. In this context, this work presents a study on the use of resources programming CAD/CAM in milling operation of cavities steel VP50 with inserts cemented carbide with ball nose. The influence of two types of interpolation (linear and circular) and tolerances bands (0.05 mm and 0.1 mm) that define the tool path for machining of a cavity that has a similar form the a mold of a battery cover cell phone. As output variables evaluated were machining time, the number of lines of the program, the parameters of surface roughness (Ra, Rq, Rz) of parts, the radius of curvature, form deviation of any line profile and the tool wear. The results showed that, from the statistical point of view (ANOVA), none of the conditions of interpolation and tolerance employed significantly influenced the values of surface roughness in form deviation of any line and tool wear. Linear interpolation with tolerance of 0.1 mm was most viable for the production of such cavity in the conditions investigated because the produced good finish, low tool wear and machining time is shorter.

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

Numerical simulations of two-phase ow require high accuracy in order to obtain detailed information of the ow. Low computational cost is also very important, because in general, numerical simulation require a high grid renement, which makes them onerous. Thus, in the present work the authors propose the use of Fourier pseudo-spectral method to solve multiphase ow problems. This method presents high order numerical convergence and low computational cost, due to the algorithm called FFT (Fast Fourier Transform). In addition, when this method is applied to solve the Navier-Stokes equations, decouples the pressure and velocity through the projection method, without the need to solve the pressure Poisson equation. To handle the two-phase ow with moving and deformable geometries, Fourier pseudo-spectral method coupled with the hybrid method Front-Tracking/ Front-Capturing. This hybrid method works with two elds, one Eulerian, where the Navier-Stokes and continuity equations are solved for the uid and the Lagrangean equations are solved for interfaces. For this method, both domains are coupled by interpolation and distribution process. Nevertheless, the lagrangean interface are transported through the Eulerian domain. The verication and validation is presented using manufactured solution. Spurious currents and vortex ow were simulated and good results were obtained. The results for the rise of a single bubble are presented and compared with experimental data Clift, Grace e Weber (1978).

Conselho Nacional de Desenvolvimento Científico e Tecnológico

This work presents the results for the instrumentation, control and operation of a friction hidro pillar processing unit with an axial load capacity of 500 kN. In this case, a pin is rotated and pressed against a block with a hole. The relative motion between the surfaces creates a metallurgical bond between the pin and block material. After its instrumentation and control, tests were carried out to evaluate the functionality of the equipment and identify the limits of its operating parameters. The following parameters were controlled: axial force, rotational speed and burn-of-length. In addition to these parameters was acquired the torque, thus allowing the calculation of heat input in the operation. Welding parameter matrices were evaluated making it possible to identify the unit operating ranges as well as the effects of the input energy on the final microstructure and mechanical properties. Moreover, it was observed that using a two-stage cycle may be an important strategy to overcome some difficulties during friction hidro pillar processing.

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior