Wind energy, one of the most sustainable renewable energy sources, has been extensively developed worldwide. However, owing to the strong regional and seasonal differences, it is necessary to first evaluate wind energy resources in detail. In this study, the offshore wind characteristics and wind energy potential of Bohai Bay (38.7° N, 118.7° E), China, were statistically analyzed using two-year offshore wind data with a time interval of one second. Furthermore, Nakagami and Rician distributions were used for wind energy resource assessment. The results show that the main wind direction in Bohai Bay is from the east (−15°–45°), with a speed below 12 m/s, mainly ranging from 4 to 8 m/s. The main wind speed ranges in April and October are higher than those in August and December. The night wind speed is generally higher than that in the daytime. The Nakagami and Rician distributions performed reasonably in calculating the wind speed distributions and potential assessments. However, Nakagami distribution provided better wind resource assessment in this region. The wind potential assessment results suggest that Bohai Bay could be considered as a wind class I region, with east as the dominant wind direction.

With the development of modern industrial technology, there is an increasingly urgent need for the preparation of high-strength and high-performance coatings on the surface of traditional metal materials

The objective of this study was to investigate the performance of pipelines repaired with carbon-fibre-reinforced polymer (CFRP) under external pressure. The repaired pipeline experienced defects in terms of thinning of its local inner wall. The three-dimensional finite element method was used to analyse the collapse pressure of repaired pipes with internal corrosion defects. The traction–separation law and interlaminar damage criterion were applied to simulate the collapse process of repaired pipes. The results show that the collapse pressure of the composite-repaired pipe increased and the CFRP significantly reduced the strain in the defect region. It was observed that the ovality of the corrosion defect region was reduced and that the repair effectiveness mainly depended on the length, thickness, and interlayer cohesion.

In this paper, the effects of different loading paths of axial tension and external pressure on the collapse pressure of sandwich tubes are studied by experiments and finite element models. The difference of the two loading paths is investigated. Eight experiments were carried out to study the influence of different loading paths on pipeline collapse pressure under the same geometric and material parameters. Parameterization studies have been carried out, and the results are in good agreement with the experimental results. The test and finite element results show that the loading path of external pressure first and then the axial tension (P→T) is more dangerous; the collapse pressure of the sandwich pipe is smaller than the other. Through parametric analysis, the influence of the axial tension and the diameter-to-thickness ratio of the inner and outer pipe on the collapse pressure under different loading paths are studied.

In this study, a new multi-use offshore tension leg platform (TLP) was designed for wave energy production through an embedded wave energy converter (EWEC) system. The proposed EWEC system consists of four built-in tuned liquid column dampers for absorbing the hull motion energy and eight Wells turbines as the power take-off devices. A multifold nonlinear analytical model of this multibody system was developed considering the hydrodynamics of the TLP-EWEC system during large motions and the aerohydrodynamics of the chamber-turbine groups. A comprehensive assessment, including an evaluation of motion responses and preliminary generating capacity, was performed for different wave-load directions using the numerical time integration method. The results indicated that the multi-use platform can generate a considerable amount of turbine power for the offshore platform energy mix as well as serve for offshore oil and gas production in the target oil fields. Such additional benefits and profitability were proven effective and worthy for further exploration and practical application.

A modified method for predicting the wear coefficient of reciprocating sliding wear was proposed in this study, which is less time-consuming. Based on this method, reciprocating sliding wear tests of three chain alloys (CM490, SS316, and TC4) under different loadings were conducted and the friction coefficient, wear coefficient, and wear morphology were obtained and compared. The results indicated that the time-variant coefficient of friction (CoF) could be used as an indicator for the stable wear state; moreover, it also changes periodically with the wear direction. Statistical analysis of friction coefficient indicated that it follows bimodal distribution or multimodal distribution. The friction and wear behaviors of CM490 and SS316 were different from those of TC4, and a detailed micro-morphological analysis indicated that the discrepancy is caused by the difference in the quantity and size of the wear debris. Furthermore, an upper limit of the contact stress-dependent wear coefficient was also observed, and the variability of the wear coefficient was also analyzed.