This experimental research was made to clarify the effects of penetration depth and bead form of fillet welding on the fatigue strength of welded joint.
Front fillet welded joint (cross type) was adopted to the specimens in this experiment, and two kinds of electrode were used to clarify the effect of penetration depth and bead form.
Steel plates were of JIS SM 41 W carbon steel of 12mm thickness, and surface of specimens were mill scale on.
The welding electrodes were high iron oxide type A, and B which had slight differences in characteristics and chemical composition, and the diamater of core wire was 6.4mm, both types can produce deep penetration weld.
The welded specimens were produced by one pass fillet weld, at room temperature. The specimens were tested in the as-welded condition (reinforcement on, not stress-relieved). Fatigue tests were conducted by the Losenhausen fatigue testing machine (UHS type) under the pulsating stresses of 0-+σ_max, and +8.5kg/mm²-+σ_max, at room temperature (appoximately 24°C).
The main experimental results of this research are as follows.
(1) The series of specimens connected by the electrode A which has medium penetration depth, that is shallower as compared with B, has higher fatigue strength than in the case of specimens connected by the electrode B.
(2) The specimens connected by electrode A fractured at the heat affected zone of mother metal, and those connected by electrode B fractured at the weld metal zone of welded joint.
(3) It seems that the fracture occurred in the mother plate was caused mainly by the rolling structure.

抄録全体を表示

Rectangular specimens and chain link plate specimens were taken from a cold rolled Cr-Mo steel plate. Various factors that affect the elongation of these specimens were investigated. These factors are as follows:
1) Quenching temperature, 2) Holding time at quenching temperature,
3) Tempering temperature, 4) Coloring temperature and time.
The elongation of specimen was measured by means of a jig boring machine having the precision of 10^-3mm. The obtained results are summarized as follows:
(1) Quenched rectangular specimen without annealing pretreatment scarcely shows any bending.
(2) Quenching temperature and the holding time have the greatest effect on the change of elongation of the rectangular specimen.
(3) The effect of tempering and coloring treatment on the elongation of the rectangular specimen is quite similar to that in the case of the annealed specimen, which was shown in the previous report.
(4) The average value of the contraction of the rectangular specimen given by the whole tratment is 2.8×10^-3mm/cm.
(5) Quenching temperature has the greatest effect on the change of the elongation of the chain like plate specimen.
(6) Tempering temperature is more sensitive to the elongation in this case than in the case of the rectangular specimen, and, therefore, the variation of tempering temperature must be kept as small as possible.
(7) The change of the condition of coloring treatment does not show any significant effect on the elongation of the specimen.
(8) Chain link plate specimen is deformed irregularly by the whole treatment.
(9) The average value of the contraction of chain like plate specimen given by the whole treatment is 2×10^-3mm/cm in the direction of the longest axis.

抄録全体を表示

Recently, not a few rupture accidents of distribution pipes of water works have occurred at some cities in our country. The pipes ruptured were of high grade cast iron and had been considered to be safe from rupture, because their construction was not very old as we might expect such accidents.
To clarify the cause of the accidents from the view point of the strength of pipe, some static and fatigue tests were made, to which were put rectangular test pieces taken out from bodies of various pipes, that is, the pieces from ruptured pipes and unused pipes manufactured in different years.
Along with those tests, determination of chemical compositions and comparison of microstructures of cast iron were made.
Some of the test results obtained are as follows:
(1) The microstructure of cast iron manufactured in 1940, 1952 and 1954 were gray cast iron. According to the classification of ASTM, all the pipes belong to the type A of graphite flake type chart, and the pipes manufactured in 1940 and 1952 belong to the size 4 of graphite flake size chart, and the pipes made in 1954 belongs to the size 5.
(2) Comparing the fatigue strength of test pieces of the pipes of the same year with each other, the damaged pipes showed a very low strength in comparison to that of the series 2 taken out from unused pipes. The same tendency was shown about the static strength of test pieces.
(3) The test pieces, series 6, were taken from the ductile pipe, and their static and fatigue strengths were higher than the others.
(4) In forming the test pieces, each of which has a rectangular section, the cast skin of the pipes was removed. These treatments must have produced conditions considerably different from the actual state of the pipes, so that the strengths obtained from the tests showed somewhat lower values.

抄録全体を表示

The Port method regarding the fatigue test of metals has pecently been appraised by many investigators. According to these results, n in Eq. 1 in this paper takes different values for different materials and no systematic arrangement has been established yet for each kind of material. Even if the numerical values of n are selected so that the experimental points may be located on a straight line, the extension of such line in most cases, deviates from a point equivallent to the Wöhler endurance limit on the abscissa. The author tried to obtain the equation of the S-N curve and the S-α curve for progressive load fatigue making use of the general idea of cumulative damage, and got the results which would explain the above experimental data and clarify the relations between the S-N curve and the S-α curve. From the above results, it might be said that caution must be exercised in determining the Wöhler fatigue limit by using the S-α diagram, because the curve plotted in this diagram does not form a straight line for what value of n, but is expected to form a complex curve as expressed by Eq. 4 in this paper.

抄録全体を表示

The objected of this experimental research was to decide the quality of several kinds of wire ropes of different sectional patterns under the static and the pulsating loads. Especially, the authors placed great emphasis on the latter case, and clarified the relations between the cycles of load repetitions and the elongation of wire ropes.
Fatigue tests were made under the pulsating tensile load of +500kg-+5000kg, using the Losenhausen fatigue testing machine Type UHS.
The wire ropes tested were of the following six kinds: Filler tpye of Hemp core (abbreviated to H.C.) and Rope Core (abbreviated to R.C.); Special Seale type of H.C. and R.C; and Warrington type of H.C. and R.C.. The Diameter of all wire ropes was 16mm in nominal size.
Measurements on the elongation of wire rope during the progress of load repetitions were taken, using the Tanabe Deflectometer, with the cyclic interval, as a rule, with 25000 cycles interval of load repetitions.
Main results obtained are as follows.
(1) The fatigue failure of wire rope occurred in the neighbourhood of the socket of alloy metal where the most remarkable twist was observed during the testing.
(2) The relation between the elongation of wire rope and the number of cycles of loading formed a line almost straight in most cases, on the semi-log graph, until the element wire failed, in which the abscissa was taken as the logarithm of the number of cycles. After the element wire failed, the elongation of the wire ropes gradually a remarkable increase, which got higher and higher showed the elongation which increased more and more until the strand failed, and they endured more than 20000 load cycles.
(3) The order of durability of the wire ropes for the repeating load of +500kg-+5000kg was as follows: Special Seale type of R.C. (the best); The same of H.C.; Filler type of R.C.; The same of H.C.; Warrington type of R.C.; The same of H.C..
(4) The rate of increment of wire rope elongation accompamying the progreass of cycles of load repetitions increased as for each wire rope in the following order: Warrington type of R.C.; Special Seale type of R.C.; Filler type of R.C.; Special Seale type of H.C.; Filler type of H.C.; Warrington type of H.C..
(5) Comparing the group R.C. with that of H.C., the durability for fatigue of R.C. group was superior to that of H.C. group. On the contrary, the rate of increment of the elongation of R.C. group was inferior to that of H.C. group.

抄録全体を表示