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Erosion-corrosion tests were carried out at two regimes, non-swirling jets with swirl number (S=0), and weakly swirling jets up to reaching vortex breakdown (S=0.1, 0.2 and 0.3); the average flow velocity was adjusted at 3.2 ms−1, meanwhile the corrosive media consisted of 1 l of distilled water and 2 g/l NaCl purged with CO 2 and abrasive particles of 20 μm of aluminium oxide ( Al 2 O 3 ) suspended into test solution with a content of 11 kg m − 3 . The impinging angle was 90 ° in the near-field. Electrochemical measurements were performed using the polarization resistance technique (Rp). Furthermore, to characterize the damaged surface, optical and scanning electron microscopy (SEM) images were taken, also the corrosion products were analyzed by means of X-ray diffraction (XRD) and EDS techniques to identify the material loss mechanism. The experimental results shows that the maximum corrosion rate was observed at high swirl numbers, moreover, this swirling regime is more severe than the non-swirling condition improving the pit formation.

A fabrication process for FeAl intermetallic compound powders has been developed in the present work. The fabrication process is based on a technique employed to study the environmental embrittlement of AlFe intermetallic systems. In the present process, thin metallic ribbons were produced by rapid solidification, placed in a steel mesh inside a reactor for subsequent exposure to water vapour for their final transformation into metallic powders. The process also showed the possibility to add alloying elements in small quantities (1–4 at.-%) in order to improve FeAl ductility. The results showed that the present process has advantages in cost for industrial applications since the raw material low cost and the use of water vapour instead of employing high cost equipment. Additionally, the technique can fix some important problems in the process fabrication, which are generally presented in other powders processing techniques.

The environmental contour concept, in conjunction with the Inverse First Order Reliability Method, is often used to determine the extreme response of marine structural systems. This technique is a powerful option to determine the extreme response associated to a probability of exceedance without the need to perform a long-term analysis, where a large number of short-term simulations are needed. However, there are significant uncertainties involved in its determination, such as the uncertainties related with the probabilistic model used for the environmental variables, as well as the ones related with the threshold selection when the peaks over threshold (POT) method is applied. This paper shows the results of a comparative analysis of the extreme tension of the most loaded mooring line of an FPSO subjected to environmental conditions in deep water, derived from environmental contour lines which were defined with different probabilistic models to represent the significant wave height and different criteria to establish the threshold for the POT methodology. The results showed that the probabilistic model has an important effect on the extreme response of the FPSO and this epistemic uncertainty should be accounted for in the calibration of the design safety factors.

Marine risers are subjected to several types of excitation loads, such as motions induced by the floating production system, external hydrodynamics forces due to currents and waves and internal forces due to the internal fluid flow regularly composed by water, oil and gas. When internal flow conditions as pressure, temperature and flow rate fluctuations appear in a riser, they can induce vibration motion to the system. This paper shows a numerical algorithm to evaluate the vibrations of vertical rigid production risers under internal multiphase flow behavior. The numerical algorithm developed computes the natural frequencies of vertical risers model coupled with a hydrodynamic numerical model. The internal flow was composed of water, oil and gas and was treated as a pseudo-single phase (mixture). The numerical algorithm was developed using difference finite method. The results were compared with information available in the literature.

The proportion of Grade A ship plate steel for the construction of merchant ships is huge, however there is an increasing concern about the susceptibility of Grade A steel plate to brittle fracture. A recent ship failure [1] illustrate the importance of the concern. At low enough temperature, the fracture of structural steels is often dominated by cleavage. McMahon and Cohen [2] demonstrated that the cracking of carbide particles located at ferrite grain boundaries represents a primary initiation mechanism in mild steels. Further investigation led to the Smith model [3] which assumed that a cleavage crack could initiate when a grain boundary carbide is fractured by impingement of a dislocation pile-up, and the final fracture is controlled by the carbide-sized crack propagation into the neighbouring ferrite grain. A number of studies [4]–[8] have used notched specimens to investigate the mechanism controlling cleavage fracture and the fracture criterion. In the present work, an investigation into the micro-mechanisms for cleavage fracture has been undertaken using notched specimens. The material used for the investigation of cleavage fracture is a Grade A ship plate steel. The chemical composition is given in table 1. The microstructure reveals the ferrite matrix and bands of pearlite.