Fatigue strength of welded joints under repeated load must be more carefully investigated than it is done for static strength. Particularly in the welding of high tensile strength structural steel advanced technique and the utmost care are required in order to obtain as much confidence as in the welding of mild steel.
Recently, longitudinal welding joint of thin plate has been used for bridge structures on economical reasons for example box girder and steel slab, so that the authors carried out these tests to determine the fatigue strengths of longitudinal butt welds of several types.
In these tests, two types of specimens were used, one consists of two high tensile strength structural steel plates welded by the longitudinal single-V butt welds, and the other of a high tensile strength plate and a mild steel plate welded in the same way.
In each of the both types, three groups of specimens were tested, the first group specimens were welded by using D 5216 electrode, the second by D 4316 electrode, and the third by D 4301 electrode; all plates used were of 8mm thickness and the surface of the plate for all specimens were kept at the condition as they were delivered.
The fatigue tests were carried out by using the Losenhausen fatigue testing machine (UHS type), at the room temperature (approximately 18°C) and the repeated stress of the tests were taken as pulsating stress 0-+σ_max.
Some of the experimental results are as follows.
A little differences were recognized between the two types of specimen, i. e. longitudinal butt welded joint of two high tensile strength structural steel plates and that of high tensile strength steel plate and mild steel plate.
It was seen from these results that the D 4301 electrode used in these tests were sufficiently reliable for the fatigue failure.
By the inspection of the fatigue fractured surfaces, it seems to be clear that the greater part of fatigue failure started from the welding defects, blow hole, slag inclusion etc.
The fatigue failure of specimens for high tensile strength structural steel connected with mild steel were occured either in the welding part or in the mild steel part.

View full abstract

To find out of the prevention method of defacement in case of Caterpillar Mechanism in tractor, when heat-treated link and roller operat in sand and clay, I examed following condition by using Amsler-type abrasion testing machine. Namely, condition is slip velocities 0-15cm/sec and contacting pressures 50-120kg/mm².
The test piece of link at this time is 0.52%C steel, which oil heat-treated in 800°C by high frequency induction and the other roller is follow, 0.19%, 0.52% and 0.71%C steel.
The roller material is in next three cases, combined roller material and test roller with sand.
i.e. Case-1 0.19%C steel carbonized
Case-2 0.52%C steel high frequency heat-treatment
Case-3 0.71%C steel standard structure.
As a result, we confirm that in prevention of defacement case-1 was most effective, and sand caused the most severe damage of the test pieces. And the results of this case prove to accord precisely with the deta in the actual field of defacement condition.
For the purpose of bring sand and clay clored to practical condition. Its contained 30% water in weight comparison sand and clay, but it done lubricationd faculty, and became clear that the test pieces of each other is not a little defacement.

View full abstract

Inhomogeneous deformation of rolled metals with considerably large reductions has been studied by many investigators. But it appears that the study on rolled metals with small reduction such as temper rolling is very few.
This experiment was carried out to make clear the aspect of inhomogeneous deformation which might be necessary on discussing the test results on strain aging which plays a very important role in temper rolled steel sheet.
The sheet metal used in this experiment is 0.06%C steel, with 1.2mm thickness.
At first, the elongation of the sheet in rolling direction caused by temper rolling was measured. The temper rolled sheet was seemingly elongated and reduced uniformly, but distribution of Micro-Vickers hardness, residual stress and etching rate from the rolled surface to the center of thickness revealed that the material was subjected to inhomogeneous deformation.
And the condition of friction in the interface between work-roll and sheet was found to have a large effect on the deformation.
The test results are summerized as follows.
(1) The temper-rolled sheet steel is deformed inhomogeneously in its thickness direction and the inhomogeneity depends on the rolling reduction. The inhomogeneity seems to have different aspects with a border line at a reduction of some 0.25%.
(2) The change of spread of a specimen by temper-rolling is almost equal to the value calculated by E. Siebel's formula.
(3) Temper rolling is influenced considerably by frictional condition of the surfaces. If there is a slight difference of frictional conditions on the sheet surfaces, roll-working becomes limp; the surface with a larger frictional force is rolled more severely.

View full abstract

Rectangular specimens were machined from a Cr-Mo steel plate which was cold rolled with subsequent full annealing at 850°C. Various factors that affect the elongation of the specimen were investigated. These factors were as follows:
1) decarburized surface layer, 2) quenching temperature,
3) holding time at quenching temperature, 4) temperature of the quenching oil,
5) tempering temperature, 6) coloring temperature and time.
The elongation of specimen was measured by using of a pench micrometer or a jig boring machine both having the precision of 10^-3mm. The obtained results were summerized as follows:
(1) The decarburized surface layer has a great influence on the elongation of specimen after quenching. The decarburized specimen has the tendency to contract by quenching treatment while the nondecarburized specimen to expand.
(2) The specimen shows the larger elongation (4.5-5.7)×10^-3mm/cm by heating at a higher temperature and keeping shorter time at the same temperature, and it shows the shorter elongation (1.1-2.5)×10^-3mm/cm by heating at a lower temperature and keeping longer time at the same temperature.
(3) Retained austenite seems to be almost zero in the quenched structure.
(4) The quenched specimen shows the contraction by tempering treatment, and its value (7.9×10^-3mm/cm) is almost constant and is independent of the existence or nonexistence of the decarburized layer.
(5) The tempered specimen shows the contraction by coloring treatment, but its absolute value is very small when compared with that of the changes by quenching or tempering.
(6) The average value of the contraction of specimen by the whole treatments is 4.4×10^-3 mm/cm.
(7) Quite the same tendency was observed concerning the elongation of specimen either by using a pench micrometer or by a jig boring machine.

View full abstract

Using a Green type viscometer the change of viscosity with time under constant shearing force was observed for the purpose of measureing the extent thixotropic break down of the clay suspensions.
The results may be summarized as follows:
(1) When the amount of electrolyte (sodium silicate) is less than 2 milli equivalents/100g clay the viscosity increase with time. The addition of a little more electrolyte, i.e. 3m. eq/100g clay., affects the progress in such a way that the viscosity decreases at the beginning until it reaches the minimum, from then gradually increases with time. With the addition of more than 5m. eq./100g clay the viscosity decreases linearly with time and the slip shows thixotropy.
(2) Clay slip containing NaO·SiO₂ or NH₄OH shows the thixotropic breakdown to a small extent, which increases remarkably by the additional of sodium carbonate (0, 25g/100g clay).
The authors have reached to the conclusion that a clay slip suitable for solid casting may be prepared by adding sodium silicate for decreasing the viscosity and also sodium carbonate in order to give the thixotropic property.

View full abstract

The influences of current density, temperature, and acidity of electrolyte on the swelling and the corrosion of anode graphite which was anodically attacked by sulphate ions, were studied. The corrosion of graphite caused by swelling was found to be minimum at the following conditions; 3 to 5amp./dm²., above 50°C, and acidity of the electrolyte below 1N.
From the above results, it was confirmed that the corrosion of anode graphite in electrolysis of sodium chloride solution on the amalgam process was not caused by the swelling due to the sulphate ions contained as impurities in electrolyte, but to the anodic oxidation.

View full abstract

Tensile tests of rimmed steels with specimens having brittle pre-cracks of various length at their one side were performed at temperature ranges of 10°C and -50°C.
The size of test specimens were 70mm width and 500mm length, and the length of pre-crack varied between 0.5mm and 25mm.
The preparation of specimens were done in the following way. First, large size specimens of about 100mm width with a machined notch at their one side were prepared. Then, inserting a spltting wedge at the machined notch, a small hammering to the wedge was given to produce a brittle crack at sufficient low temperature by immersing the specimen in liquid oxygen. Any desired length of brittle crack was obtained by controlling the intensity of hammering and by trimming off the marginal side of specimen having pre-crack.
The test results show that the breaking stress under constant temperature were inversery proportional to the square root of the initial crack length approximately, and the length of short fibrous crack formed at the tip of the brittle pre-crack decreased as the test temperature lowered.
A new theory on the mechanism of brittle fracture propagation is proposed, using the yielding stress curve, the brittle fracture stress curve, and the fibrous fracture stress curve of the material, and satisfactory coincidence is found between the proposed theory and experimental results.

View full abstract