ABSTRACT

To establish practical operation and apply Laser-Arc Hybrid Welding (LAHW) to shipbuilding, processing tests were performed in a variety of edge preparation methods, fixturing methods of plates, and chemical compositions of materials. As a result, satisfactory quality of LAHW joints was achieved without any additional operation work, equipment and material specification to common shipbuilding procedures. In this investigation, an experimental formula to estimate accurate fracture toughness of welding joints was proposed which correct results of Charpy V notch impact test by results of Deep Notch fracture test. Furthermore, the effectiveness of LAHW to reduce welding deformation was verified by experiments and numerical simulations.

INTRODUCTION

Laser and Laser-Arc Hybrid Welding moved in application to shipbuilding by European shipyards in the 1990s under the approval of European classification societies. Generally Laser and Laser-Arc Hybrid Welding is very sensitive to fairness of plate edge, tolerance of joint fit-up, or chemical composition of materials, and such characteristics require heavy special equipment when they are applied. Therefore, they have not been so popularized to other shipyards due to a large amount of investment which is a kind of bottleneck for introduction. This study present a new developed LAHW procedure, which is applicable to common shipbuilding procedure without any such special equipment or special works. This study also propose an evaluation method for fracture toughness of LAHW joints, which was developed in order to cover the problems found in usual Charpy V notch impact tests. Furthermore availability of the main target of LAHW to reduce welding deformation of structures was quantitatively studied by means of some experiments and numerical simulations.

CURRENT APPLICATION IN EUROPEAN SHIPBUILDING

Gerritsen and Howarth (2005) introduced that some European shipyards have employed LAHW to actual production such as Meyer Werft of Papenburg, Germany, Odense Steel Shipyard, Denmark, Blohm+Voss, Germany, etc.

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