The general methods of test for bulk specific gravity of aggregates, such as the suspension method for coarse aggregate and the pycnometer method for fine aggregate may not be applied to uneven, unsystematic and higher absorbing aggregate, especially light-weight aggregate without verification. The author established the improved methods of test for determining bulk specific gravity and absorption of almost all kind of coarse and light-weight aggregates with high accuracy.
Moreover, the method of test for surface moisture in both coarse and fine aggregates by displacement in water and kerosine was determined. By this method we can obtained directly the surface moisture in aggregate independent of the bulk specific gravity of the material.

抄録全体を表示

The porosity of a brick is calculated by comparison of apparent volume and its real volume of the brick. Therefore the porosity determined by this method shows the mean value of the sample, not that of each point.
As according to the result we obtained the stress distributions in compressed powder is very complex, it is thought that the porosity in a powdered material will be very different at each point.
As the porosity has relations between the resistance of spalling, crrosion and other properties of a brick, it will be difficult to exhibit the hole ability of the brick, if there is any point of high porosity, in spite of the mean low porosity.
Accordingly, it is desirable to know the distribution of porosity rather than to discuss about the mean value of the brick. The investigations to know the porosity by measurement of principal strain in a compressed powder, and the verification of this method, and the explanation on the distribution of the porosity on several cases are written on this report.

抄録全体を表示

Quench-age-hardening, blue shortness, strain-age-hardening after cold-working and cold brittleness have been tested on the remelted electrolytric iron deoxidized by silicon and aluminum. As the increase of dexodizers, in these materials, the values of age-hardening after quenching from the temperatures just below A₁ point have decreased, and the increases of the tensile strength in the blue heat range, have become little. Moreover, the transition temperature of cold-brittleness have lowered. Hardening values of strain-age-hardening, however, have not been changed so much after cold working. From the results of the investigation of quench-agehardening or blue shortness, non-ageing iron have been observed on the contents of deoxidizer, 0.08% aluminum.

抄録全体を表示

Metals deform plastically by the repetitions of stress of comparatively small magnitude. The yield limit under repeated stress may be determined by the same condition as that of yielding under static stress. However, the investigation concerned is scarecely found. The present study has been made for clarifying the yielding phenomena of metals under repeated stress. Results obtained are as follows;
(1) The fatigue deformation, which appears in repeated bending or torsion test, enhances rapidly soon after the start of test, and then increases slowly with repetition of stress. When stress applied is over the endurance limit, the increase of deformation continues till fracture, while deformation ceases to increase after experiencing some stress cycles, provided the stress applied is less than the endurance limit.
(2) For materials with apparent yield point in static test, the fatigue yield limit agrees with static one, while for other materials both yield limit are not the same, the former being considerably less than the latter. For the latter materials, therefore, the safety range in the endurance limit diagram hitherto used must be revided, that is the yield limit must be correctly lowered.
(3) Prestressing due to cold working is effective for descending the fatigue deformation.

抄録全体を表示

In the preceeding report, the authors explained the fatigue deformation of various kinds of steels. In the present report, the authors intend to explain how the fatigue deformation should be treated analytically in view of distribution of stress within the specimen.
Results obtained are as follows:
(1) A useful equation was introduced for expressing the magnitude of fatigue deformation under uniform distribution of stress. Two constants, included in this equation, may be determined from the fatigue test and take the same values in both cases of normal and shear stresses.
(2) It was cleared that the mean stress distribution within the specimen after fatigue deformation under uneven stress distribution can be obtained by calculation by using the above equation. By this treatment, the magnitude of fatigue deformation in this case can be also determined.
(3) Analytical treatment to obtain the magnitude of fatigue deformation was introduced for the specimens having residual stress or being work-hardened by prestressing.
(4) Analytical results have shown favorably agreement with the experimental ones for every cases of performed experiments.

抄録全体を表示