In this report, the method of measurement of the residual stress quenched or tempered plate, acting symetrically with respect to the neutral plan, is explained, which consists of the removal of the surface layer of plate from both sides by corrosion and the measurement of the resultant change of the specific volume. Let 0σx and 0σy be the residual principal stress components acting on the cross section normal to the axes x, y in the plate, and εv the resultant change of the volume strain in the remaining portion after the removal of outer layer up to thickness 2z. 0σx=0σy=-E/2(1-2ν)(εv+zdεv/dz) εv=2(1-2ν)/3(1-ν)v-v0/v0 E: Young's modulus, ν: Poisson's ratio, v0, v is the specific volume before and after removal of layer. The principle and the actual data of measurement are explained.
Several kinds of solution and aging treatments were given in combination to 17-10P stainless steel (17Cr, 10Ni, 0.25P and 0.12C), to investigate its tensile strength (at 600°C) and stress rupture strength (at 600°C), both for smooth and notched specimens. With increasing solution temperature from 1000°C to 1260°C, the tensile strength at 600°C (for both smooth and notched specimens) increased and approached certain values, but the stress rupture time (for smooth specimens) showed a maximum at about 1080°C and then decreased rapidly. The stress rupture time for notched specimens was somewhat different; the higher the ductility the greater the notch-strengthening tendency.
We carried on the rotating bending fatigue test of steel specimens with two holes and over. Specimens tested have radial holes drilled under the different conditions reciprocally, in parts of A and B types. Every specimen of A type has each hole axis on the same longitudinal section. Every specimen of B type has each hole axis on the same cross section. We investigated the effects that the conditions of drilled holes and the interference of mutual holes had on the fatigue strength. The results obtained are as follow; (1) In A type, the fatigue limits are raised slowly with the increase of the number of holes up to six holes in each pitch of holes 2mm, because of stress relaxation caused by the interference of mutual holes. (2) In the hole pitches of 2mm and of 6mm, the fatigue limit for 2mm is higher than that for a single hole, but the fatigue limit for 6mm comes almost to the same value as that for a single hole. In the pitch of 6mm, the stress relaxation is not caused by the mutual holes. (3) In B type, the fatigue limits are reduced with the increase of maximum stress caused at holes under repeated load. In the same value of maximum stress, the time strengths by overstress are reduced with the increase of the number of holes. (4) In comparison of the mechanical properties of various specimens subjected to repeated load and those of each virgin specimens, we obtained the effects of conditions of drilled holes upon the degree of fatigue progress.
Fatigue tests in torsion were conducted under completely reversed strain amplitude in order to investigate the influence of strain wave forms on fatigue strength. The changes of stress amplitude were measured during the fatigue test. And approximate hysteresis loops were assumed. The test results are 1) the hysteresis energy of the secondary wave must be larger than limiting value to cause fatigue damage, 2) twin waves are more liable to cause hardening than sinusoidal wave, 3) at the higher plastic strain range (or hysteresis energy range), the twin waves which are equal in total plastic strain (or total hysteresis energy) in one cycle, show the same fatigue live, but at the lower plastic strain range (or hysteresis energy range), the more φ increases, the more the fatigue live increases and 4) the law of linear cumulative damage makes it possible to predict fatigue lives fairly accurately through the use of plastic strain or hysteresis energy.
Coiled springs are used in many kinds of automatic or semi-automatic product machines. If the fatigue deformation takes place in these springs, even if fatigue failure may not occur, the capacity and the accuracy of these machines may be affected adversely. Investigations on the fatigue deformation of the coiled spring have not Been conducted extensively so far. In this report the fatigue deformation limit diagram is studied experimentally on the three kinds of the coiled spring of steel wire, that is untreated, heated and setting. The results obtained are as follows: (1) The effect of secular change on the fatigue defomation of coiled spring is negligiby small but the effct of elastic-after effect can not be neglected on the untreated coiled spring. Therefore, the fatigue deformation is necessary to be measured as soon as possible after unloading. (2) The fatigue deformatiom limit of the untreated coiled spring is the lowest, but by heating these, the limit increases remarkably. It seemes that such an increase of the fatigue deformation limit by heating is mainly due to age-hardening. (3) The fatigue deformation limit diagram of the coiled spring used in this experiment is curved above the staight line of 45 degrees with the axis of abscissa (mean stress axis).
We have investigated on a rapid method of estimating the life of anode graphite at the amalgam process chlorine-caustic cell, by electrolysis of sodium sulphate solution and by electrolysis of sodium chloride solution containing sulphate. This method is based on our researches about the mechanism of corrosion of anode graphite described in the previous papers. That is to say, the corrosion in electrolysis of sodium sulphate solution under conditions of above 40°C, acidity of below 1N, and anode current density of above 5amp/dm2, and that at the amalgam process chlorine-caustic cell were of just the same mechanism, namely, the pure chemical oxidation consumption from surface of graphite crystal. The following methods were found preferable: (1) The sodium sulphate solution electrolysis method for the domestic anode graphite: The corrosion rates in mg/Ah unit of anode graphites treated for 3 hours under electrolytic conditions of sulphate concentration of Na2SO4·10H2O 100g/l, 60°C, anode current density of 10amp/dm2 are compared with each other. This method was found to be better than the other method for the domestic anode graphite. (2) The rapid method, combining electrolysis of sodium sulphate solution with electrolysis of sodium chloride solution containing sulphate, for domestic and A cheson's anode graphites: The anode graphites were treated preliminarily by the above-mentioned sulphate solution electrolysis, and then treated intermediately for 2 hours under conditions of 60°C, acidity of pH 2 to 3, and anodic current density of 50amp/dm2 with sodium chloride solution of concentration of NaCl 260g/l contained sulphate of Na2SO4 25g is one liter of brine. In the last formal electrolysis, the samples are treated for 4 hours under the same condition as intermediate treatment, and the corrosion rates which were measured as difference of weight in this formal electrolysis are compared with each other. This method resulted in the best coincidence with the order obtained in long time test by amalgam process chlorine-caustic cell as for the domestic and Acheson's anode graphites.