【文章內(nèi)容簡介】 hniques such as braze welding, fe welding, gas welding, resistance welding, induction welding, arc welding, and special welding. Considering the features of shipbuilding, the welding process used in the shipyard is the arc welding process. Arc welding is a process in which coalescence is obtained by heat produced from an electric arc between the work and an electrode [8]. Arc welding is classified into several types, according to the welding mechanisms such as shield metal arc welding (SMAW), flux cored arc welding (FCAW), submerged arc welding (SAW), and electrogas arc welding (EGW). SMAW is one of the oldest, simplest, and most versatile joining processes. Currently, about 50% of most industrial and maintenance welding is performed by this process, but this process is used approximately less than 5% at most large shipyards. In FCAW, an electrode that is tubular in shape is used, and if necessary, the welding area is shielded by carbon dioxide. In SAW, the weld arc is shielded by granular flux, consisting of lime, silica, manganese oxide, calcium fluoride, and other materials. The flux is fed into the weld zone by gravity flow through a nozzle. EGW is used primarily for welding the edges of sections vertically in one pass, with the pieces placed edge to edge (butt type) [9]. To build the knowledge base for the determination of welding methods, knowledge is aquired from welding handbooks and experts. Input information of this module is geometrical information that is provided from CAD system and the welding posture determined by welding posture determination module. The knowledge is represented by rules. The examples of the rule for the determination of welding methods are as follows: (1) IF (Connection Type=0) (Groove=none) (Welding Posture=O) (6≤ Thickness≤ 50) THEN (Welding Method=SMAWMANUAL BUTT) (2) IF (Connection Type=1) (Leg Length≥ ) (Welding Posture=O, H, V) THEN (Welding Method=FCAWFILLET) . Determination of welding equipment This module selects the appropriate welding equipment by rulebased reasoning based on information about welding postures and welding methods. Table 4 shows the relationship between welding methods and welding equipment. After determining welding methods, welding equipment is automatically selected by using the information contained in Table 4. . Determination of welding materials This module determines the most proper welding materials by rulebased reasoning, based on information about welding postures, methods, and equipment. In general, steels used for block assembly are mild steels and high tensile steels. Mild steel is a rolled plate, the tensile strength of which is less than 50 kg f/mm2. High tensile steel is a lowcarbon alloy steel, the tensile strength of which is more than 50 kg f/mm2 with a yield strength of more than 30 kg f/mm2. Mild steel has four grades: A, B, D, and E. High tensile steel has three grades: AH, DH, and EH [9]. The following are examples of rules to determine welding materials. (1) IF (Welding Posture=D) (Welding Methods=FCAW FILLET) (Welding Equipment=LN7 or LN9) (Steel Grade=(Mild Steel A,B,D,E) Hightensile Steel AH,DH) THEN (Welding Material=MX200H) (2) (Welding Posture=D) (Welding Methods=SAW Bothside BUTT) (Welding Equipment=SW41) (Steel Grade=Mild Steel A,B,D,E) THEN (Welding Material=L8xs707EF H14XS705EF L8XNSH52) 3. System implementation and discussions In order to demonstrate and to verify the automated welding operation planning system for block assembly, a block located at the upper deck part of crude oil carrier is examined. Fig. 5 shows the structure of an example block and Fig. 6 represents its hierarchical