STUDIES ON PREVENTION OF END CRACKING IN ONE SIDE AUTOMATIC WELDING (REPORT #2)

Recently one sided automatic welding has widely been used in the assembly stage of Japanese shipyards. As one of the problems of welding procedure, as well as any other welding techniques, cracking which sometimes occurs near the end of weld, has become an important problem. The authors have proposed a calculation technique in seam welding. The most significant feature of the method differing from the ordinary welding thermal stress analysis is that the conditions of calculation are simulated to be those of more realistic welding procedures. Then, the following assumptions are imposed in order to calculate stress and strain during welding. (1) Before welding, specimens are connected by tack welds and prepared edges are free boundaries. (2) Molten region containing arc tip is free from stress. (3) After the arc passed by, the plates are connected by solidifying of the molten pool, that is, free prepared edges are changed to supported ones as temperature is cooled down. (4) When the arc passed through a tack weld, is should be melted away and free from stress. In order to calculate the thermal stress during welding, firstly we solved un-stationary heat conduction problems and obtained temperature distributions during welding. Based on the calculated temperature distribution, we analysed uncoupled thermal stress problems by using the finite element method, and conclusively showed that one of the main causes of end cracking is the transient tensile stresses generated near the end part of the weldment when the stress re-distribution has taken place due to the melting of the last tack weld. To endorse the numerical calculation by the proposed method, experiments are carried out and it is confirmed that the method could be applicable to this kind of transient welding stress-strain state with time depending varying boundary conditions.

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  • Corporate Authors:

    Society of Naval Architects of Japan

    23 Shiba-kotohiracho, Minato-ku
    Tokyo 135,   Japan 

    Society of Naval Architects of Japan

    15-16, Toranomon, 1-chome, Minato-ku
    Tokyo,   Japan 
  • Authors:
    • Fujita, Y
    • Terai, K
    • Matsumura, H
    • NOMOTO, T
  • Publication Date: 1974-6

Language

  • Japanese

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Filing Info

  • Accession Number: 00071563
  • Record Type: Publication
  • Source Agency: Society of Naval Architects of Japan
  • Files: TRIS
  • Created Date: Nov 12 1974 12:00AM