抄録
The relaxation characteristics of high strength bolt under high temperatures and the correlation between creep and relaxation are discussed in this paper. In this relaxation test, two types of specimens of the same ones as used in the case of creep test described in Part 1 were used. The property of bolt was F 10 T, and the initial strain was of 3000μ, 4000μand 5000μ corresponding to the range of the initial tension of high strength bolts. Under the conditions that the heating temperatures ranged from 300℃ to 500℃ with pitches of 50℃, and the measuring time was 6 hours. As a result, it was found that an exponential approximate expression in which temperature, stress and time are variables was used as the experimental equation concerning the relaxation. This expression was confirmed that it can agree with the experimental values with considerably good accuracy. The correlation between creep and relaxation was examined. When estimating the value of relaxation by using the creep experimental equation, both the stain hardening theory and the time hardening theory were examined as the creep law with the results that it was found the former could provide better agreement.
