Two separate problems are to be investigated in this thesis. The first problem is the propagation of waves through a short rod (or slug) of viscoelastic material. The second problem is the study of impact of a short viscoelastic rod (or slug) on a stationary semi-infinite viscoelastic. rod. The viscoelastic materials are modelled as standard linear solids which involve 3 material parameters and the motion is treated. as one-dimensional. For the first study, a viscoelastic slug is placed between two semi-infinite elastic rods and a wave initiated in the first rod is transmitted through the slug into the second rod. The objective is to relate the transmitted signal to the material parameters of the slug. We solve the governing system of partial differential equations using the Laplace transform and we examine the propagating velocity discontinuity using discontinuity analysis and the limit theorem of the Laplace transform. We then approximate the solution of the propagating disturbance using the regular perturbation method. We invert the Laplace transformed solution numerically to obtain the transmitted signal for several viscosity time constants and ratios of acoustic impedances. We compare the results obtained using the above techniques. In the second problem, we first model the impact and solve the governing system of partial differential equations in the Laplace transform domain. Then we examine the propagating stress and velocity discontinuities using discontinuity analysis. We approximate the solutions of the propagating stress and velocity using the regular and multiple scales perturbation methods. In this problem, we first consider the slug is elastic and the rod is viscoelastic. Secondly, we consider the slug is viscoelastic and the rod is elastic and thirdly, we consider both materials are viscoelastic. Numerically we invert the Laplace transformed solutions for the interface stress and interface velocity for several viscosity time constants and ratios of acoustic impedances to determine whether the slug and the rod part company or remain in contact. Then we compare the results obtained using the discontinuity analysis, regular and multiple scales perturbation methods.

Oil is a very complex chemical system, as for instance, the paraffinic type which was considered as a fluid to be evaluated in this scientific paper, trough the static interfacial tension with the surfaces of the API 5L grade B conduction pipe and the EPOXY and EPOXY M resins. The paraffinic oil produced in the 7-PIR-244D-AL well, which is located in the producing field of Pilar in the state of Alagoas, presents special characteristics concerning its flow which are different from the other oils in the Sedimentary Basin of Sergipe and Alagoas. The resin used in the experiments were the EPOXY, commercially know as DGEBA, as well as EPOXY M, which was produced from the DGEBA with the addition of a substance whose objective is to reduce the deposit of organic and/or inorganic molecules in its surfaces along the oil flow. The evaluation of the static interfacial tension between this type of paraffinic oil and the surfaces of the EPOXY (37,2 mN/m), EPOXY M (14,8 mN/m) resins and the steel pipe (4.790,2 mN/m) has produced results, the performance of this fluid compared with the EPOXY M resin was better than when compared with the EPOXY and, as a consequence, better than when compared with the metallic material of the pipe. As a result of the data got through the experiments with these materials, there was a conclusion about the possibility of practical use of the EPOXY M resin as a coating in the internal surface of the pipes that carry oil with a considerable quantity of paraffin in its composition, aiming at a better performance relating to the flow of this fluid. / O petróleo é um sistema químico bastante complexo, como por exemplo, o do tipo parafínico, o qual foi considerado como o fluido para ser avaliado nesse trabalho científico, através da tensão interfacial estática com as superfícies do tubo de condução metálico API 5L grau B e das resinas EPÓXI e EPÓXI M. O óleo parafínico produzido no poço 7-PIR-244D-AL, o qual está localizado no campo produtor de Pilar no estado de Alagoas, apresenta particularidades com relação ao escoamento, diferentes dos outros petróleos na Bacia Sedimentar de Sergipe e Alagoas. As resinas utilizadas nos experimentos foram a EPÓXI comercialmente denominada DGEBA, como também a EPÓXI M que foi produzida a partir da DEGEBA com a adição de uma substância cuja finalidade é reduzir o depósito de moléculas orgânicas e/ou inorgânicas nas suas superfícies durante o escoamento do petróleo. A avaliação da tensão interfacial estática entre este tipo de petróleo parafínico e as superfícies das resinas EPÓXI (37,2 mN/m) e EPÓXI M (14,8 mN/m) como também do tubo de aço (4.790,2 mN/m), gerou resultados; onde a performance desse fluido com relação a resina EPÓXI M foi melhor quando comparada com a EPÓXI, e conseqüentemente em relação ao material metálico do tubo. Como conseqüência dos dados obtidos através dos experimentos realizados entre estes materiais, concluiu-se a possibilidade de uso prático sobre a utilização da resina EPÓXI M como revestimento junto à superfície interna de tubulações que possuam petróleo com considerável quantidade de parafina em sua composição, objetivando um melhor desempenho quanto ao escoamento desse fluido.