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Volume 20, Issue 2
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Effects of length of reduced section and radius of fillets of test specimensShiro SATO1970 Volume 20 Issue 2 Pages 55-62
Published: February 28, 1970
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSTwo sorts of tension tests were conducted on plates of 6mm thickness of aluminum alloy designated as 5052-0.
The 1st test were to investigate the effects of the change in the length of reduced sections of the test specimens on tensile properties. Throught these tests, the ends of the specimens were maintained in the length as large as 1.4 times of the width of reduced sections and the radius were maintained in the length equal to that of the reduced sections.
The 2nd tests were to investigate the effects of the change in the radius of fillets on the deformation behavior at near the ends of reduced sections. The width and length of reduced sections of the specimens were maintained at constant during these tests.
The principal results obtained were as follows.
(1) The tensile strength was very little increased with the decrease in the value of specimens from Lc/W = 3 (in which Lc and W are the length and width of reduced sections, respectively). However, the effect was so little that the tensile strength would be unchanged unless the test specimens with very small length of reduced sections were used.
(2) The elongation percentage was slightly decreased with the decrease in the value of Lc/W.
(3) The length of the neck, ln, which had been measured along the undeformed specimen, was equal to 5√A (in which A is the cross-sectional area of the reduced section) for the material used in this experiment. It is desirable in tensile tests that the complete length of neck remains within the gauge length when the rupture occurs within the half of the gauge length (around the center of the length). Accordingly, for this purpose, it is also desirable that the gauge length, Lo, should be determined by the following formula:
L0/√A ( = 2ln/√A) ≥ 10
(4) The length of the region of shoulder constraining the strain distribution in the part near the end of the reduced section was about (0.40.2) W starting from the end of the straight section. Therefore, the value of Lc shall conform to the following formula; Lc ≥ Lc + 0.8 W for eliminating the effect of shoulder fillet radius on the results of tensile tests.View full abstractDownload PDF (704K) -
Secondary recrystallization of aluminum alloys (3rd report)Masuhiro SATO, Yoshizo NAKATANI, Kyoji SHIMIZU1970 Volume 20 Issue 2 Pages 63-68
Published: February 28, 1970
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSStatistical examinations were made on the distribution of metallographical particles dispersed at random.
As the results, a convenient method for the estimation of the particle density was proposed on the basis of Poisson's distribution function.
The relative frequency distribution of the particle separation was approximately derived from the function, as the following formula :
PU=√2α(U2•e1-u2)α/U2D2/U2D2/π
where PU: relative frequency of U
α: constant, depending on experimental conditions
D: Average particle separation
Di: Individual particle separation
U: Relative particle separation ( = Di/D)
The above formula shows the broadening tendency of the distribution of particle separation with decreasing of the particle density. Therefore, the tendency of frequency distribution would promote the abnormal grain growth.
All the discussions mentioned above were confirmed by the experiments on 5056 alloy plates.View full abstractDownload PDF (821K) -
Yuzo SAITO, Kinji SATO, Tsuneo SAGA, Makoto OGAWA, Shozo MIZUSAWA1970 Volume 20 Issue 2 Pages 69-76
Published: February 28, 1970
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSMachinability by using twist drills plays a singnificant role in manufacturing process of machine parts. Recently, the machinability of light metals such as aluminum has been an important problem in mass production of machine parts with lighter weights. However, few reports have been published concerning the general data on drilling of aluminum sheets. This paper discusses machinability in drilling of two kinds of test pieces (same sizes of 40 × 50 mm, but different in thicknesses: 0.5 and 1.0mm).
In general, the machinability in drilling is controlled by various factors such as drilling force, life of tools, finish and accuracy of holes (dimensional accuracy and out of roundness), chip figure, and removal of chips. However, in drilling of aluminum sheets, the most important factors may be height and shape of burr and dimenshional accuracy of holes rather than life of tools.
The drilling of aluminum sheets was considered to consist of two processes; cutting and punching processes, both of which were much complicated each other. After the completion of drilling, burr was generated on the opposite side of drilling surface. The drilling was made by the type of constant feeding speed.
The experiments were made by using five kinds of tools (different in diameters: 1.0, 1.5, 3, 6 and 10mm φ). Then, drilling force was measured and cutting process and burr generation were observed.
The conclusions drawn were as follows.
(1) Thrust increased with feeding speed, but was independent of number of revolutions except for extremely low revolving rate.
(2) Torque decreased with the increase of number of revolutions, but increased with feeding speed.
(3) Hole accuracy in thin sheets was not satisfactory and the holes were similar in profile to polygons with odd vertexes.
(4) There were two types of burrs in their shape. The height of burr increased with feeding speed.View full abstractDownload PDF (1814K) -
Studies on weld cracking of AI-Zn-Mg alloys (2nd report)Takakazu TANAKA, Susumu YOSHIDA1970 Volume 20 Issue 2 Pages 77-87
Published: February 28, 1970
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSThis paper describes the effects of additional Fe and Si on hot-cracking of Al-Zn-Mg alloys containing Zr or Ti + B, or not.
The susceptibility to hot-cracking was evaluated by Fisco type weld cracking test and ring cast cracking test.
The results obrained were as follows:
(1) Addition of Fe had a little effect on the reduction of susceptibility to hot-cracking of Al-Zn-Mg alloys.
(2) However, when Fe was added to Al-Zn-Mg alloys containing Zr, the effect of cracking resistance of Zr was markedly decreased, which made the susceptibility to cracking larger. The rate of decrease was higher with the increase of additional Fe. Whereas, the addition of Fe to the alloys containing Ti + B had little effect on cracking resistance.
(3) The addition of Si had remarkable effect on the reduction of susceptibility to hot-cracking of Al-Zn-Mg alloys containing Zr or Ti + B, or not.View full abstractDownload PDF (2980K) -
Kenjiro GOTO, Goro ITO, Yoshihiko SHIMIZU1970 Volume 20 Issue 2 Pages 88-94
Published: February 28, 1970
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSThree kinds of dissolved agents are considered to be indispensable for occurrence and propagation of pitting corrosion of aluminum in water. That is, the 1st one is a corrosion inhibitor which reacts with aluminum surface and inhibits the corrosion over the whole surface, the 2nd one is an activator which locally destroys inhibitive action of the 1st one, and the last one is an oxidizing agent which depolarizes cathode and promotes cathodic reaction.
In the present study, the effects of oxidizing agents (such as dissolved oxygen, H2O2, free chlorine, K2Cr2O7, and KMnO4) on occurrence and propagation of pitting corrosion of aluminum were investigated for the specimen placed in neutral water containing sulfate or phosphate ions as inhibitors and chloride ions as activators.
The results obtained were summarized as follows:
(1) In water containing 5ppm of sulfate ions as Na2SO4 and 5ppm of chloride ions as NaCl, the pitting corrosion was not observed for less than 80ppm of dissolved oxygen, but it was distinctly observed at that amount of 150ppm. When the oxygen content was more higher, corrosion occurred over the whole surface to form a boehmite film and no pitting corrosion was observed.
(2) The addition of an oxidizing agent such as H2O2 and freechlorine to the water, containing a certain amount of corrosion inhibitors and chloride ions, promoted the occurrence of pitting corrosion of aluminum immersed in the solution. However, the oxidizing agent such as K2Cr2O7 acted as a passivator, by which pitting corrosion was not.
(3) Among the corrosion inhibitors, phosphate ion was more active than sulfate ion in provoking and propagating pitting corrosion of aluminum in water containing oxidizing agents. Whereas, fluoride ion had noability for provoking pitting corrosion.
(4) These phenomena were discussed in connection with the results of potentiostatic polarization measurements.View full abstractDownload PDF (1433K) -
[in Japanese]1970 Volume 20 Issue 2 Pages 95-102
Published: February 28, 1970
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSDownload PDF (1154K)
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