Present investigation has been carried out to improve the mechanical properties of carbon steel by quenching. As the quenching was taken place from the temperatures below the A₁ point, it may be called “Low-Temperature Queuching”
The specimens quellched from 450-700°C displayed the excellent fatigue strength and wear resistance retaining their original ductility and toughness.
In the fatigue test, the specimens quenched from below about 500°C became harder by repeated loading. However, it was observed that the hardness of specimens quenched from a temperature just below the A₁ point decreased during fatigue test, that is, the specimens was actually strain softened. This softening phenomena may attributed to ageing.
It seems that the low-temperature quenching is one of the beneficial treatment as well as shot-peening, carburizing etc. for carbon steel which will be applied for shaft, leaf-spring and other machine elements.

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In order to study the scale effects in the notch sensitivity of mild steel, we have performed slow bending test of mild steel specmens having geometrically similar shape.
We have found that, as the specimen size becomes larger, the absorbed energy per unit volume and the modulus of rupture (maximum nominal fiber stress) under constant temperature decrease to the lower values, and the transition temperature attains to the higher value.
We can conclude from these facts that mild steel has a tendency to become more brittle in the larger specimen than in the smaller one.

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Torsional fatigue deformation of steel under pulsating torsion was measured about the specimens pre-stressed to various degrees. The pre-stress was applied by torsional cold working such as setting used on springs.
Summary of the results is as follows:
(1) Torsional working is of great use to decrease the torsional fatigue deformation.
(2) To prevent the fatigue deformation the pre-stress must be chosen about 20% over the repeated stress.

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This paper deals with the experimental research on the effects of wire drawing conditions, mainly the shape of drawing surface of die and reduction of diameter, on the fatigue strength of drawn wire.
Using a Haigh-Robertson type fatigue testing machine we tried to investigate the endurance limit of 0.10% carbon steel wires drawn under several kinds of drawing conditions.
As the results, we have made it clear that:
(1) the endurance limit of the wire drawn with a die of larger radius of curvature of drawing surface was higher than that of smaller radius.
(2) the endurance limit increased sharply with the increase of the reduction of diameter in the range of low reduction, tending to a constant value when the reduction of diameter was more than 10%.

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In this paper, we explain the newly devised method to measure the soil strength necessary for calculation of the cutting resistance acting on a tool. This method is, by measuring the over-turning moment of a steel plate inserted vertically in the soil around the fixed hinge set on the soil surface and the inserted depth of the plate, to calculate the indices of the strength of the soil using these two values.
As the indices of the strength of soils obtained with this method have a certain relation to their cutting resistance, these indices can be used as the characteristic values for cutting strength of soils, as if cohesion and angle of internal friction are used for shearing strength.
With these indices, we can estimate the digging character of the machine for various soils.

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