低炭素鋼のクリープの形状および寸法効果

抄録

The effects of changes in shape and size of specimens on creep and rupture properties of low carbon steel were investigated on the plate specimens having various thickness (t₀), breadth (b₀) and parallel length (L₀). t₀ ranged from 2 to 30mm, b₀ from 30 to 60mm, and L₀ from 32 to 180mm. L₀/√A (A: area of cross section) varied between 2 and 13.7. Creep and rupture tests were carried out at 450°C and 550°C.
It is shown that, with increasing L₀/√A, the rupture time decreases in the case of plate specimens when L₀/√A≤6, but it is constant when L₀/√A>6. On the other hand, it increases with L₀/√A in the case of round specimens when L₀/√A≤6. With increasing L₀/√A, the minimum creep rate increases in the case of plate specimens when L₀/√A is small, but it is constant when L₀/√A>6. The changes in t₀, b₀ and L₀ of the plate specimens affect both the rupture time and the minimum creep rate little if L₀/√A is maintained constant.
In the case of short rupture time, the plate specimens with the dimensions of b₀/t₀>10 show the fracture oblique to the tensile axis across the broad sides. The angle of inclination made by the line of fracture is approximately 60°.