Abstract: Based on the assumption that bending stress is negligible in explosion disk, the author proved that the cross-sectional curvature, at explosion, depends on material only, therefore, design of explosion disk, which is a problem of large deformation in plastic region, is reduced to the calculation of the extremely simple membrane equation: δ=CPD, in which C is a constant determined on properties of material. The above formula agrees with the experimental formula recommended by 数森敏郎 in his “高压技术”. Also, some experiments, made by the author, though inadequate, agree remarkably well with the calculated results.

Key words: high efficient welding, Mild steel thick plate, One-side welding with back formation, Root/backing welding, MAG-TIG double arc tandem welding