| Budget Amount *help |
¥2,300,000 (Direct Cost: ¥2,300,000)
Fiscal Year 1994: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1993: ¥1,100,000 (Direct Cost: ¥1,100,000)
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| Research Abstract |
The structures in service conditions such as offshore structures, towers, bridges and so on are always suffered the pulsating loads by waves, current, wind or moving vehicles, etc. So, repair, reinforcement or reconstruction works by welding on these structures are done under the pulsating loads.
The weld cracking test under the pulsating loads is carried out. As the results of the experiments, the accumulation strain, epsilon_t, by which the weld metal was repeatedly applied at a short time from the liquidus to the solidus was proposed as a measure for deciding hot crack initiation under the pulsating loads. epsilon_t was expressed with the relative root gap opening displacement, DELTAdelta, which can be easily measured before welding. The practical deciding equation for hot crack initiation under the pulsating loads using DELTAdelta was derived. Applying the practical deciding equation to the results of the hot cracking test for the case that the uniform pulsating loads are applied, its validity was shown.
It is found that the hot cracks under the pulsating loads can be classified into crack of solid-liquid state and crack of solid state by conducting the high temperature tensile test on the weld metal. The former is called a solidification crack and the latter is HS (Hot Crack in Solid state) - type crack. Concerning the solidification crack initiation, the main factor was the product of DELTAdelta by the external loads and repeated number. The main factor for HS-type crack initiation was the maximum strain rate (the maximum root gap opening rate) by the external loads in a cycle.
Welding is applied to the actual work for a bridge in service and its validity demonstrated.
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