1983 年 49 巻 12 号 p. 1663-1668
On an application of staircase method with small number of sample to the thread-loosening test which is characterized by a three-level judgment, a theoretical study and an experimental examination are made. The purpose of this paper is to aim at an improvement of the evaluation method of the locking performances of test specimens. Analyzing the distributions, the biases and the variances on the estimated values of locking performances, the features of this method are made clear and a working guide of test is induced concerning the starting value and the step width of the evaluation factor and the sample size. On the case of the transverse vibration type thread-loosening test, one rule of the judgments on loosening is suggested and the usefullness of this method is shown through the experiments. Besides, the influences of test conditions, especially the running speed and the lubricant, being examined to a certain extent, some matters to be taken notice are pointed out.