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Volume 41, Issue 4
Displaying 1-10 of 10 articles from this issue
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Isao Masumoto, Takeshi Shinoda1972 Volume 41 Issue 4 Pages 354-367
Published: 1972
Released on J-STAGE: August 05, 2011
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Yugoro Ishii1972 Volume 41 Issue 4 Pages 368-378
Published: 1972
Released on J-STAGE: August 05, 2011
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Isao Masumoto, Ryuichiro Ebara1972 Volume 41 Issue 4 Pages 379-384
Published: 1972
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSIt was experimentally confirmed that the fatigue crack propagation rate of steels is promoted by oxygen and/or humidity in air. And the improvement of fatigue strength of welded joints by epoxy-resin coating was attributed to its protective effect against air and humidity. It was also reported in the previous experiment that fatigue strength of 18-8 stainless steel was not improved by the epoxy-resin coating, because fatigue strength of'this steel .was not affected by oxygen and/or humidity at room temperature. The effects of atmospheres and the various coatings on the fatigue strength of aluminum alloy is studied in this. report. The results obtained are as follows.
1) Fatigue strength of Al-4.5% Mg alloy is affected by oxygen and/or humidity in air. Humidity affects more detrimental on the fatigue strength of aluminum alloy than oxygen.
2) The fatigue strength of Al-4.5% Mg alloy can also be improved by epoxy-resin coating. The larger the stress concentration factor and the thicker the coating, the more the coating is effective.View full abstractDownload PDF (1766K) -
Kunihiko Satoh, Kenji Seo1972 Volume 41 Issue 4 Pages 385-393
Published: 1972
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSIn the previous report, the effect of contour of fillet weld on the mechanical behaviour and strength of fillet welded joint was explained. The present report explains the effect of fillet size and depth of penetration on them. A model specimen, having a profile of cruciform fillet welded joint, is used for the experiments. Strain distributions in fillet weld are measured by using the Moire method. Experiments are performed in the range from 5 mm to 30 mm leg length and from -2 mm to 20 mm depth of penetration. The results obtained are as follows;
1) The yield strength of fillet welded joint is not affected by fillet size but the maximum strength decreases with incresae of fillet sixze.
2) The yield strength and the maximum sterngth of fillet welded joint are represented as a function of the penertation angle θp, and they increase with increase of the penetration angle θp.View full abstractDownload PDF (3404K) -
Hiroshi Ikawa, Shigeo Shin, Masaki Morikawa1972 Volume 41 Issue 4 Pages 394-402
Published: 1972
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSThe continuous cooling transformation diagrams of Ti-Cr, Ti-Mn, Ti-V and Ti-Mo alloys were plotted for investigations of ω phase in the cooling process of binary α+β and metastable β titanium alloys.
The supersaturated β phase decomposes with following processes for changing solute concentration and cooling rates, β0→βi+α'+ω(ω'), β0→βi+ω(ω'), β0→βi+α, where β0 represents β phase as solution treated, βi represents nonequilibrium β phase whose solute concentration changes with progress of decomposition and represents a pre-precipitation of ω phase.
The precipitation temperature of ω phase decreases with increace of cooling rates.
At the slower cooling rates α phase precipitates directly from β phase without precipitation of ω phase.
The range for precipitation of ω phase in the cooling process of binary α+β and metastable β titanium alloys by the electron concentration and cooling rates can be represented as a simple diagram. In conditions excluding this area it is possible to prevent precipitation of ω phase in the welded titanium alloys.View full abstractDownload PDF (8983K) -
Kunihiko Satoh, Kenji Seo1972 Volume 41 Issue 4 Pages 403-414
Published: 1972
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSThe present paper deals with the strength of fillet welded joint. Theoretical evaluation of the strength based on the theory of localized necking is presented and compared with the experimental results. In the theoretical analysis, Mises plastic potential and Henckys stress-strain relation are adopted. The theoretical results agree well with the test results.
The results obtained are as follows.
1) The yield strength of fillet welded joint can be evaluated with no regard for workhardcning of materials, but the maximum strength is affected by the rate of workhardening.
2) The yield strength is not affected by the size of the fillet weld, but the maximum strength decreases with an incresae of fillet size.
3) The yield strength and the maximum strength incresae with an increase of the fillet angle θf
4) The yield strength and the maximum strength are represented as a function of the penetration angle θp, and they increase with an increase of the penetration anlge θp.View full abstractDownload PDF (763K) -
Welding in air atmosphereTakuro Kobayashi, Takeshi Kuwana, Ryuji Kiguchi1972 Volume 41 Issue 4 Pages 415-424
Published: 1972
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSUsing ten series of alloy steel electrode wires, mild steel was welded in an air atmosphere.
The individual influence of the alloying elements, C, Si, Mn, Nb, Mo, V, Co, Ta, W and Cu in the electrode wires on the nitrogen content of weld metals deposited at three current levels was systematically studied.
The results are summarized as follows;
1) The alloying elements in steel electrodes can be divided into the following three groups by the type of their influences on the nitrogen content of weld metals obtained in an air atmosphere;
(I) Nb, V, Ta, Mn, Al, Ti, Zr
(II) C, Si,
(III) Cu, Co, Mo, W
2) The elements in group (I) alloyed up to a certain amount reduce the nitrogen content of weld metals and an excess amount of them again increases the nitrogen content, at low welding currents. At high currents, the elements in group (I) generally increase the nitrogen content of weld metals.
3) The elements in group (II) reduce the nitrogen content of weld metals both at low and high currents.
4) The elements in group (III) have no important influence upon the nitrogen content.
5) The individual influence of the element can be explained satisfactorily with its affinity to oxygen and its influence on the solubility of nitrogen in molten iron.View full abstractDownload PDF (657K) -
Heat Processing by CO2 laserYoshiaki Arata, Isamu Miyamoto1972 Volume 41 Issue 4 Pages 425-435
Published: 1972
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSThe CO2 laser was applied to a heat source for processing various materials such as welding, cutting and chilling.
Conclusions obtained are summarized as follows;
(1) Excellent fusion welding with narrow bead width and sufficient mechanical strength was performed by the CO2 laser in case of a thin metal. The surface treatment, which enhanced the CO2 laser beam absorptance of the metal, had no bad effect on the weld.
(2) New cutting technique, "laser gas cutting", of which the cutting energy consisted of laser beam energy, chemical reaction energy such as an oxidation energy and dynamic energy of gas jet, was developed, and fine cutting with narrow kerf width and heat affected thin layer was accomplished.
(3) Non-metallic material was easily heated by CO2 laser beam because of its high beam absorptance and poor thermal conductivity. In case of an easily evaporizing material such as acryl, a deep hole with a small diameter could be obtained by using the self-focusing effect of the beam. In case of a brittle material such as glass, a fine crack formed ahead of the beam spot facillitated the cutting.View full abstractDownload PDF (10426K) -
The dynamic characteristics of H.F. W-W arcKimiyuki Nishiguchi, Takayoshi Ohji1972 Volume 41 Issue 4 Pages 436-445
Published: 1972
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSThe high frequency (3kHz) arc characteristics using W-W electrodes were studied experimentally and theoretically comparing with those of 60Hz and D.C. arcs.
As the result of experimental research, it is recognized that the polarity exchange which is an undesirable property of A.C. welding arc is very easy, i.e. restriking voltage seems not to be necessary for high frequency arc in W-W electrodes and electrical dynamic characteristics of high frequency arc is resistive over all the current range of this experiment. (Fig. 5, 6 & 7)
The resistive characteristics of 3kHz arc suggests that the temperature of arc column is held constant, since the resistance of arc column directly depends on the instantaneous temperature distribution in it.
The radiation from 3Hz arc column is intensive even in the period of current zero and the phase of the small perturbation of radiation lags by about 1/4 cycle from that of the electric power input, while at 60Hz it is in the same phase as that of the instantaneous input. (Fig. 8, 9 & 10)
Such optical data mean that dynamic A.C. arc characteristics is affected remarkably by the thermal inertia of arc column.
In the second part of this paper, the thermal energy balance at A.C. arc column is discussed.
The experimental data are found quantitatively close to the results of theoretical analysis at 3kHz, qualitatively even at 60Hz.
From such a theoretical treatment, it is concluded that temperature change of A.C. arc column depends on current frequency ω, effective electric power and mean thermal energy of arc column as follows:
If ω»ω0(ω0=3e0i0/8M0Cp0T0), the dynamic characteristics of A.C. arc column becomes resistive, i.e. at a high frequency arc, the arc column can not respond to the instantaneous current, but is sustained nearly constant.
Accordingly, in arc with W-W electrodes, the polarity exchange becomes very easy at high frequency arc due to the residual plasma at current zero.
Thus, a high frequency arc has excellent characteristics for arc stability.View full abstractDownload PDF (5872K) -
Tadao Onzawa, Yugoro Ishii1972 Volume 41 Issue 4 Pages 446-455
Published: 1972
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSThe interface between explosively bonded metals exhibits a wave-like form, but the theory of formation of wave has not been fully studied. In this paper the relation between wavelength and collision angle was investigated by using the semi-cylinder method and angular method, and an attempt to explain the mechanism of wave formation was made. The results obtained are as follows.
1. The wavelength increased continuously with the collision angle until a critical angle, beyond which the wave-like profile vanished and a linear interface was observed. For a given value of collision angle, the wavelength increased with the plate thickness. However the collision velocity at the critical angle was constant independently of plate thickness.
In angular method, the wave tended to grow in the direction of bonding and none was observed for the distance of 20-30 mm from starting to bond.
2. The wave amplitude increased with the collision angle but the ratio of amplitude to wavelength was constant.
3. The material near the interface suffered extreme plastic deformation and the folw configuration, in particular wave-like profile, resembled the stream pattern in a fluid having a Karman vortex street, so the authors considered that a wavy interface resulting from Kármán vortex street occurred in the vicinity of collision point and they tried to calculate the wavelength λ. The following equation was used.
For a symmetric collision shown in Fig. 12 (a) : collision angle 2γ, λ=20h (1-cosγ)
For an asymmetric collision shown in Fig. 12 (b) : collision angle γ, λ=10h (1-cosγ) where h: the thickness of flyer plate.
The values calculated by using these equations agreed generally with measured values.
4. An increase in hardness at interface, when the collision velocity exceeded 1800 m/sec, was observed in bonding an iron flyer plate to a mild steel semi-cylinder. This fact might be attributed to martensite marking of the pressure-induced tranformation that appeared at a pressure more than 130 Kbar in iron.View full abstractDownload PDF (7717K)
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