Various colloidal systems including paints, printing inks, flour dough, clay paste, butters, powder bed etc. behave as substances showing very complicated mechanical properties.
Their flow is non-Newtonian. Their specific viscosity-concentration relationships do not obey the Einstein law. They show thixotropy or rheopexy. Some powder systems appear as bodies showing dilatancy. Concentrated suspensions and emulsions behave as visco-elastic.
The above-mentioned peculiar flow properties of colloidal suspensions and emulsions are characterized by various nonlinear nature and, from the structural point of view, formation of a scaffolding structure by the suspended or emulsified particles; the structure, which is formed by weak secondary bonds, is easily broken and regenerated in the field of flow.
Some schemes of studying the complicated mechanical properties of colloidal disperse systems are discussed.
One of the most classical methods of analysis is to describe their flow properties by a plastic yield value and plastic viscosity first proposed by Bingham. The concept of Bingham plasticity is conveniently applicable to the study of concentrated suspensions.
Measurement of dynamic visco-elasticity of colloidal dispersions reveals the nature and the structural aspects of many rheological peculiarities. For example, spinnability or thread-forming property of some lyophile colloidal solutions is described as the superposed phenomena of viscous flow and elastic elongation.
Description of their stress-strain-time behavior by the power law which was proposed by Nutting and Scott Blair makes an other way of studying rheology of pasty matters.
Other schemes are of experimental nature. For example, it is recommendable to study the rheological properties of suspension of particles whose surface physico-chemical nature can be controlled by chemical treatment. Various synthetic latexes and suspensions of powders of ion-exchange resins are conveniently used as the model substances for the study of complicated rheological properties of colloids. Their surfaces are well-defined and easily controlled by chemical techniques.

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The prevailing relaxation theory on the nature of the glass transition (the sharp bend occurring in specific volume vs. temperature curve measured under a constant rate of cooling) in high polymers and other glass-forming liquids is re-examined.
It is pointed out that the glass transition is essentially a non-linear relaxational phenomenon in which volume relaxation time varies steeply with temperature change, the excitation variable in this case, and that this variation is the real cause for the transition. It is therefore emphasized that elucidation of the mechanism of the transition is essentially equivalent to that of the mechanism of the precipitous change of relaxation time or viscosity near the transition temperature, as described in most cases analytically by WLF Eq. or more ultimately by Doolittle type equation in terms of the concept of free volume.
It is also pointed out that the transition manifests itself in many physical properties as sharp change of their temperature coefficients and the time-scale determining the transition temperature thus located is only the rate of cooling in any case. The transition or freezing-in of free volume occurs necessarily through a range of temperature owing to the nature of relaxational phenomenon and both ends of the range are to be determined by means of the manifestation of the transition in some appropriate physical properties. As a special example of such cases relation between viscosity and volume retardation is discussed. By using a simple kinetic equation of the first order reaction type for volume retardation and Doolittle type equation for viscosity, it is easily shown that WLF Eq. referred to some equilibrium state is derived so far as volume follows the equilibrium liquid line and further shown that viscosity begins to deviate from WLF curve in response to the commencement of volume retardation with decrease of temperature. The temperature where the deviation starts is the higher temperature end of the transition range and on the other hand the lower end can be determined as the temperature where relaxation effect becomes remarkable with increase of temperature.
The above-mentioned considerations are experimentally verified on five polymeric substances by observing viscoelastic and thermal expansion behaviors.

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In order to find out the defacement prevention effect of the material when it is used for points of the railway, the author conducted a test, using an Amsler-type abrasion testing machine, at slip velocities of 0-15cm/sec, and under contact pressures of 50-90kg/mm².
The test piece of tyre is about 0.7% C standard structure steel, and the other material of high manganese steel and chrome manganese steel are from 1050°C water-toughening.
The followings are the findings resulted from the present test:
(1) Hardness of high manganese steel goes up to a fixed extent at the beginning of its usage, however, anti-wearing charactor can not be expected to increase together with this increase of its hardness.
(2) Satisfactory effect of wear proofing can hardly be expected in sliding motion between C-steel and high manganese steel due to sliding friction.
(3) Chrome manganese steel, which somewhat covers the effects of high manganese steel, must be used carefully in some cases, because of its limited application.
(4) Test specimens, selected and prepared on the basic of field knowledge and experience so that they might be suited to actual field conditions as much as possible, were used in the laboratory experiments. And the results of this case prove to accord precisely with the data in the actual field of defacement condition.

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In this report, the fatigue deformation of carbon steel as heat treated and the same followed by plastic twisting or torsional stress-aging were investigated and the effect of micro-structure on the fatigue deformation was studied.
The results obtained are summarized as follows:
(1) Static yield strength is nearly proportional to the fatigue yield strength, therefore, the former may be used as a measure of the latter.
(2) The static yield strength, that is, the fatigue yield strength of the heat treated steel may be affected by the strength of ferrite itself, the magnitude of the mean ferrite path and the magnitude of the resistance against slip of ferrite caused by pre-straining or stress-aging. Hence, the effect of heat treatment, pre-straining and aging on the fatigue deformation may be explained in relation to the three factors mentioned above.
(3) For heat treated steel, the torsional stress-aging is more useful for the prevention of fatigue deformation than cold-working.
(4) In plastically twisted and torsional stress-aged steels the fatigue yield strength is smaller than the yield strength in static tests and the fatigue deformation increases as the mean stress decreases.

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The authors equipped the fatigue testing machine for gear previously reported with an automatic pressure controller, and by through the use of this testing machine carried out fatigue bending tests of gear teeth of various materials.
These results were studied in comparison with static bending strength, impact strength and proportional limit.
In consequence, we got the following results.
(1) The stress concentration decreases as the radius of curvature on fillet curve, in particular at the weakest section, is enlarged.
(2) It is important to take sufficiently deep hardened layer along root fillet of surface hardened gear, from the viewpoint of increasing fatigue strength.
(3) We must take care of cut-scars, in particular, those which are left in the direction of tooth width, because fatigue strength decreases by those scars.
(4) It would seem that fatigue strength have a relation with proportional limit.

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The authors have carried out an experimental study on bending strength of non-metallic material and the fatigue tests of non-metallic gear teeth, and found some facts about the relation of fatigue strength with static strength.
In consequence, we got the following results.
(1) The bending fracture of non-metallic gear tooth is not caused by the maximum local stress, but, rather by the mean stress.
(2) The value of fatigue notch factor at root fillet of gear tooth is considerably smaller than the value of stress concentration factor.
(3) For the laminate gear of canvas No. 11 base which is generally used, we can consider that the value of fatigue strength is equal to about a half of the value of static bending strength.

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In the present paper, the normalized low carbon steel has been subjected to the fatigue stressing under rotating-beam bending with the constant-and double-amplitude in order to investigate the effect of reversed pre-understressing on the endurance limit and the fatigue life for the overstress, and the same material has been submitted to the fatigue-and-hardness test, in which the fatigue machine was stopped several times during the fatigue stressing, and the MicroVickers hardness was measured at the ferrite matrix of the surface of the specimen to study the effect of reversed pre-understressing on the hardness of the test piece. The followings are the conclusions obtained from the experiments:
(1) The endurance limit, the fatigue life for the overstress, and the hardness of the material tested in the present study are all increased comparing with those of the virgin material due to reversed pre-understressing.
(2) The increasing rates of the fatigue life and the hardness do not depend upon the level of the primary understress.
(3) The higher the level of the primary understress, the less number of stress cycles are necessary to start increasing of the endurance limit and of the fatigue life.
(4) The endurance limit and the hardness increase due to reversed understressing, but both are gradually saturated with the increase of the number of stress cycles. The maximum hardness is obtained at the number of cycles of about 10⁷ and the maximum endurance limit will be attained at a greater number of stress cycles.
(5) The fatigue life for the overstress also increases due to reversed pre-understressing. In the case of the higher secondary overstress, the increasing rate of the life drops after the number of stress cycles of about 5×10⁶. At the lower secondary overstress, the fatigue life extremely increases with the increase of the number of cycles of the pre-understress.

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Fatigue tests were made on aluminized steel in air and then in the presence of salt water, under constant stress amplitude and repeated loads of two steps. Aluminized specimens were employed in the Schenck's plane bending fatigue machine to investigate the protective action of aluminium against the corrosion fatigue of steel. The machine was operated at 1700rpm and the tests were extended to ten million cycles. The results of the test on these specimens were as follows:
(1) In air, the endurance limit (on ten million stress cycles basis) of uncoated steel was 20.2kg/mm² and that of aluminized steel was 19.4kg/mm². In the presence of salt water, the corresponding values fell down to 9.6kg/mm² and 18.1kg/mm². The decrease in corrosion fatigue limit of steel was very large and corrosion fatigue strength of aluminized steel was little changed. Under corrosion conditions, it has been proved that it has afforded an efficient protection. The experiment showed that the decrease in endurance limit of aluminized specimen as compared with uncoated specimen was caused by the presence of intermetallic compound Fe_m Al_n.
(2) When the stress amplitude of the second stage is larger than that of 1st stage, the value of ∑n/N is larger than 1. When the stress amplitude of the second stage is smaller than that of 1st stage, the value of ∑n/N is smaller than 1.

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