The creep tests of thick-walled cylinders subjected to internal pressure and heat flux through the wall were conducted on a low carbon steel at elevated temperature, and the results were discussed from the standpoint of multiaxial creep theory, considering the transient creep.
The conclusions obtained are as follows:
(1) The feature of creep curves for tubular specimens with temperature gradient is similar to that for the case without temperature gradient.
(2) The method of analysis employed by R.W. Bailey, L.F. Coffin, J.E. Traexler and others for the steady state creep of thick-walled tubes with radial temperature gradient was extended to the case of transient creep, by using a strain hardening type stress-strain rate equation. It was found that the analytical creep strain based on the Mises effective stress was smaller than the measured creep strain, while the Tresca effective stress gave larger deformation than the experimental one.
(3) We can take a temperature level for the test temperature of a thick-walled cylinder under internal pressure yielding the same amount of creep strain with similar cylinder subjected to the same amount of internal pressure with radial temperature gradient. It is called the equivalent temperature and can be determined by analysis for a given test condition. It enables us to predict the creep rupture life of the tube under internal pressure with radial temperature gradient, and to provide, at this temperature, the creep rupture data by using the Tresca mean effective stress.
(4) The analytical creep deformation of the cylinder under internal pressure with heat flux from inside to outside is larger than that of the cylinder with inverse heat transmission within the same temperature range.
(5) The creep activation energy of the material tested is 7×10⁴ cal·mol^-1 which was obtained from the temperature-creep rate relations for uniaxial creep tests at the stress of 12kg/mm² and the temperature 500°C. This agrees fairly well with the self diffusion energy of α-iron.

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High speed steel SKH 9 and 5%Cr hot work die steel SKD 61 are used now for elevated temperature springs. An important problem in the elevated temperature spring is creep in torsion, and there has hitherto been little published information on the creep of hardened and tempered elevated temperature spring steel. The present work was made to study the torsion creep behavior and creep strength at the temperature 300 to 550°C for quenched and tempered SKD 61 and SKH 9 steel, and the effect of nitriding treatment on the creep strength was also tested for SKD 61. The dimensions of the specimen of creep test were 5mm in diameter and 30mm in length. The machine employed in the torsion creep test was made in our laboratory.
No remarkable creep was observed at 300°C of SKD 61 under 60kg/mm² of twisting stress, nor at 400°C of SKH 9 under 65kg/mm² of stress. At 400°C of SKD 61 and 500°C of SKH 9 torsion creep increased gradually with increased stress, and at higher test temperature the creep rate rose enormously. Nitriding treatment was very effective for increasing the creep strength at 500°C of SKD 61.

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Regarding the mechanical properties of metals at low temperature the investigations have hitherto been mostly confined to the impact and tensile properties, and there have been but few works^1)∼3)on the fatigue. In this paper, the fatigue strength of the nodular cast iron and Ni-Zr cast steel for the unnotched and notched specimens at +20°C, -16°C and -78°C, were measured with the rotating cantilever Wöher-type fatigue machine at the revolution speed of 4500rpm.
The experimental results are summarized as follows:-
(1) The tensile strength of nodular cast iron decreases with lowering testing temperature from room temperature so that 61kg/mm² at room temperature becomes 58.5kg/mm² at-78°C.
(2) The fatigue endurance limit of nodular cast iron and Ni-Zr cast steel increased at lower testing temperature than that in room temperature.
In the case of unnotched specimen of nodular cast iron, the value of 22kg/mm² at room temperature increased to 25kg/mm² at -78°C. Similarly, the value of Ni-Zr cast steel rose to 29.5kg/mm² from 25kg/mm².
(3) The fatigue limit of 10kg/mm² at room temperature for the notched Ni-Zr cast steel specimen increased to 13kg/mm² at -78°C. For the notched nodular cast iron, 14kg/mm² rose to 18kg/mm².
(4) The value of fatigue notch factor β_k of the Ni-Zr cast steel decreased from about 2.45 to 2.25 as the test temperature was lowered from +20°C to -78°C. Similarly, the value of nodular cast iron decreased from 1.6 to 1.4.
(5) The value of notch sensitivity η_k decreased as the test temperature was lowered. The value of η_k of Ni-Zr cast steel keeps twice as high as that of nodular cast iron, that is, for the Ni-Zr cast steel the range from 1.5 to 1.2 at the test temperature +20°C and -78°C respectively, corresponded to 0.7 to 0.4 of the nodular cast iron.

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For the purpose of studying the progressive fatigue damage accumulation normalized V notched steel (0.36%C) specimens were subjected to experiments under the repeated stress of multifolded and multiple loading.
The mechanical properties of the material of the specimens are given as follows; tensile strength σ_B=58.0kg/mm², lower yield point σ_S=30.4kg/mm², actual breaking point σ_T=91.5kg/mm².
The first experiment consisted of test of fatigue under the stress of multifolded and multiple loading of the following patterns, and the experiment was repeated until fracture was made.
(1) σ₁→σ₂→σ₃→σ₂→σ₁→σ₂→……
(2) σ₂→σ₃→σ₂→σ₁→₂→σ₃→……
(3) σ₃→σ₂→σ₁→σ₂→σ₃→σ₂→……
where σ₁=15kg/mm², σ₂=18kg/mm², σ₃=21kg/mm².
It is found that the larger is the number of loading cycle by decreasing the frequency of repetition on each stress level the smaller the total sum of the cycle ratio will become, descending ultimately to approximately 0.6.
Furthermore, in order to investigate the above mentioned fact, fatigue tests were conducted under the same stress pattern with only one loading cycle at the beginning of the loading, followed by constant stress amplitude. It appears that the total sum of the cycle ratios is much affected by the stress change at the beginning of the loading.

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Experimental investigation on multiaxial thermal fatigue was performed by using solid spherical and cylindrical specimens of low carbon steel. The specimens were subjected to cyclic multiaxial thermal stresses introduced by repeated heating and cooling processes. The uniaxial thermal cycling tests and mechanical strain cycling tests at elevated temperature were also conducted on the same material, and the relationship between the strength of material under three types of cycling were studied.
The thermal strain range containing plastic strain of multiaxial thermal fatigue has been analyzed by means of successive approximation. Taking account of the fact that the cracks nucleate and propagate on the surface of the specimen, Mises' equivalent total strain on the surface is considered to be the strain range that determines the lifetime of the material subjected to the multiaxial thermal stress cyclings. For the purpose of elucidating the relationship between these three types of strength, the basis for the criterion of lifetime in terms of the number of cycles to crack initiation, constraint of thermal strain and equivalent steady temperature has been established as variables. The comparison between the three types of test results are made by using these common bases.
From the fact that the results of multiaxial thermal fatigue tests by the use of both solid spherical and cylindrical specimens are in good correlation with the uniaxial thermal and mechanical fatigue test results, the following conclusion has been made. The strength of the material subjected to multiaxial thermal stress cycling can be predicted from the information of conventional tests, namely, the uniaxial thermal fatigue test under the same constraint of thermal strain as that of the multiaxial thermal cycling, or the uniaxial mechanical fatigue test at equivalent steady temperature.

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Up to the present, the investigations on the thermal fatigue have been carried out mainly under conditions of cyclic uniform heating and cooling in the cross-section of specimen, but in practice we meet with many cases in which the cross-section of materials are subjected to various transient temperature gradients, while studies in these cases have not been made sufficiently.
Therefore, in order to investigate these problems we have constructed a new type of thermal fatigue testing machine. With this testing machine the wedge-shaped specimen was rapidly heated by high-frequency-induction, and then cooled in water reciprocally, so as to make transient temperature gradient in its cross-section. By this method, in the specimen the bending and the axial thermal strains were introduced. In our machine, the bending strain was restricted and the axial thermal strain was freely released. The average heating rate at heating surface may change from 50°C/sec to 300°C/sec, and in the range of 10mm along gage length of specimen the same temperature distribution is obtained.
Some experimental results of 13Cr steel and 18-8 steel showed that our machine was suitable to the thermal fatigue testing under conditions of transient temperature gradient in cross-section.

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In case of practising X-ray stress measurement through a diffractometer, the Geiger tube slit must be moved from its normal position to the goniometer center by a displacement r,
r=R{1-cos(φ+η)/cos(φ-η)}
R: The goniometer radius
φ: The angle between the specimen surface and a reflecting plane
η: 90°-θ, θ: Bragg angle,
to complete a focusing condition for any θ and φ.
By means of our automatic focusing apparatus made up of a set of simple link mechanism the Geiger tube slit could follow the newly made focusing circles for a half fixed angle φ and a variable Bragg angle θ, and so all the points on the diffraction profile obtained could satisfy the focusing condition like a normal diffractometer. To test the accuracy of this method the macroscopic stress measurements were performed for various powder patterns, and satisfactory results were obtained.

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The famous Terzaghi's theory on the consolidation of clay is based on the assumption that the flow of the pore water is vertically one-dimensional under isotropic pressure. The settlement of a clay layer actually occurs in general under the condition of no lateral strain, the lateral pressure decreasing gradually with the progress of consolidation. This is recognized in the consolidation test made with a triaxial apparatus. Thus the shear stress arises within a clay sample because of the decrease in lateral pressure in spite of constant vertical pressure. This shear stress may be considered to affect the secondary compression to a great extent. In order to investigate the character of secondary compression, therefore, we have to study the behaviors of clay from the view-point not only of the deformation, but of the actually working stress.
This paper treats the results of the one-dimensional consolidation tests performed for a long term on a fully-saturated clay in the triaxial apparatus under various conditions, from the point of view that the intergranular displacement causes a creep by the occurence of shear stress during the one-dimensional consolidation.
The conclusions obtained from a series of experiments are as follows:
(1) The lateral stress σ₃ decreases with the dissipation of pore pressure from the initial value σ₁ up to the final value about 0.5σ₁. This variation in the lateral stress should be taken into consideration in the discussion of the secondary compression.
(2) The principal stress ratio K=σ₃/σ₁ decreases in proportion to the degree of consolidation. It may be considered, therefore, that the gradient of the secondary compression-time curve is a linear function of the K-value.
(3) During the secondary compression, excess pore pressure appears to keep the value of 0.01-0.02kg/cm².
(4) In the case where specimens are laterally confined with a rigid metal ring, the secondary compression ratio increases with the decrease in the thickness of specimens. Therefore, one tends to over-estimate the amount of the secondary compression, unless the sufficient thickness of specimens is taken.
(5) There exists no significant difference in the test results between the two cases of lateral drainage and vertical drainage. The secondary compression ratio can be assumed as about 10-15% of the total compression for the ordinary alluvial marine clay.

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