In order to train English talents better, in the process of English teaching in higher vocational colleges, it is necessary to reform its teaching mode constantly so as to promote the quality of English teaching. However, according to the analysis of big data, in the current situation, there are still many problems in English teaching in China, so we should make full use of the advantages of four-dimensional teaching method to improve the current difficulties in English teaching. Therefore, this article is mainly to explore four-dimensional teaching methods based on the current problems in English teaching of higher vocational education, and with a view to providing reference for the follow-up English teaching.

To confirm pipeline designs and validate the weld toughness, extensively works of Curved Wide Plate (CWP) test methods was carried out. The method of Two Clip Gauge-CTOD was firstly introduced in CWP test in this paper. The test results of CWP analyzed by Two Clip Gauge-CTOD method and Compliance—J method was compared. The CTOD-R curves achieved by these methods showed the good consistence with each other. Furthermore, the difference of the test results among SENB(single edge-notched bend), SENT(single edge-notched tensile) and CWP was discussed. It shows that the toughness obtained by SENB is relatively conservative, and CWP and SENT are recommend to be chosen for pipeline steel welds toughness test.

Tie-in is a very important step on the final stage of pipe construction. The stress of the tie-in girth weld is really one of the key roles that affect the security of the pipeline in service. In this paper, Finite Element Method (FEM) was used to determine the stress of the tie-in girth weld. The factors of stress of tie-in girth weld were analyzed. The results show that uncovered pipe length, tie-in offset and misalignment were the important factors which affect the stress of tie-in girth weld. The maximum Mises stress and axial stress at tie-in girth weld increased with the uncovered pipe length decreasing and the tie-in offset increasing. The stress also increased significantly with girth weld misalignment, especially for axial stress.

In the pipeline construction, the girth welds tend to be the weakness because of defects and microstructure. The importance of suitable assessment of various defects in the weld is not only to prevent the cracks from unstable growth to cause catastrophic accident but also can effectively reduce the weld repair to reduce construction cost. Although many welding defects assessment methods and codes are used in this field, there are many differences among them. In this paper, the welding defect assessment methods, such as API 1104 and BS7910, were studied. The results show the key factors that affect the result of these assessment methods. The application of these methods was also discussed. The results indicate that API 1104 level1 has the highest conservatism, while API 1104 level 2 is next.

Composite repair systems of buried pipeline will be affected by moisture and other factors due to anti-corrosion and construction problems. These environmental factors will reduce the service life of the composite system. In this paper, the performance of composite and interface between composite and steel under the action of water were studied. It was found that the formation of micro-cracks on the surface of composite materials and the hydrolysis of epoxy resin were the important reasons for the Performance degradation. Moreover, the aging properties of composite materials and their interfaces under water immersion were analyzed by residual strength theory, and the life prediction equation of composite materials and interfaces were obtained, which can be useful to the field application of composite repair systems.