Friction Stitch Welding Unit Forming Process Research

With the development of economy, the use of oil and gas is increasing that leads to increase the intensity of the exploitation of offshore petroleum resources, the depth of mining is also increasing year by year. Different from terrestrial environment, the harsh environment of deep-water seriously affects the connection and repair to the equipment of exploration and development, these problems have been paid more and more attention. Friction stitch welding technology is a new-style solid welding connecting technique for deep-water steel structure repair technology. The related research results will provide the necessary technical reserves for the strategic goal of China’s offshore oil and gas development from shallow to deep water.The research work of this paper is depended on the support of "National Natural Science Foundation--Marine structures Friction Stitch Welding unit forming process research". The work is based on the research work that was carried out by predecessors. Research of welding unit forming process on Q345steel has been carried through, transfer of plastic material and the characteristics of acoustic emission problems in the process of FHPP have been conducted a preliminary study. The main purpose of the study is to fully understand the influence of relevant factors in welding unit forming process, and ultimately to provide theoretical guidance and basis for improving the welding quality of friction stitch welding.The marker insert technique is based on the use of a marker material that is embedded in the center position of stud bottom. After welding, the specimens was polished and corroded in longitudinal different horizontal location near weld area, which can fully reflect plastic deformation and migration of the base metal in FHPP. In addition, with enough parallel cross section images, the3d reconstruction technology is used to reconstruct3d model of the marking material, the result can be more intuitive to reflect the material deformation and the change rule of migration.In this paper, acoustic emission detection means was introduced to monitor the process of the FHPP for the first time. Through detecting acoustic emission signal, extracting characteristic signal and establishing the acoustic emission reference model in different welding craft conditions, the purpose is to real-time monitor and predict welding quality in the welding process.The innovations of this paper can be seen as bellows. First, at present, the mark insert technique is more used in friction stir welding, the3d reconstruction technique is in the majority in the field of medicine application, but the3d reconstruction of the tracer material in the process of FHPP has not been reported, so the research results of this part will play an important theoretical significance and value to improve the welding joint quality to our subsequent research. Second, there is no application of acoustic emission technology to monitor the process of forming of FHPP both at home and abroad, therefore, the study results of the series will fill the blank of this field.