Takashi Kunimoto

On the Compressive Buckling of Sandwick Panels Having Honeycomb Cores

Elastic contants of honeycomb-cored sandwich panels were calculated theoretically. Using these constants, theoretical solutions were derived for the buckling in uniform axial compression of simply supported sandwich panels. The theoretical formulas were compared with experiments and are found to be usuable for practical applications.

ON THE DISCOLOURATION OF ALUMINIUM SURFACE IN BOILING WATER (PRAT 2)

In the Part 1 of this report, we discussed about the conditions in which the discolouration occurres and summarized them in three simple items. In this part, we intended to solve this phenomenon by comparing the sample which is boiled in distillated water (not discoloured) with that boiled in well water (discoloured).The analyses of well-water indicate that PH is 7.5, alkalinity is 301.24ppm, acidity is 17.2apm and iron ion is 0.17ppm. In comparison with this data, the analyses of service-water of Sakai City show that PH is 7.1, alkalinity is 50ppm, acidity is 3.0ppm and iron ion is 0.05ppm.Photo. 2 are the electron diffraction photographs of the surface of aluminum. No. 1 shows the photo. of the bare aluminum before boiling. No. 2 shows the photo. of the bare aluminum which was polished and etched in 20%HNO3. No. 3 shows the photo. of the surface of aluminum after boiling in the well-water. No. 4 shows that after boiling in the distillated water. In comparison No. 3 with No. 4, we found the remarkable difference, but from this photographs we could find no clew of discolouration. We detected, however, that the crystalline alumina was formed on the sarface of aluminum which was boiled in the distillated water.From the results of the Part 1 and the analyses of well-water, the factor of discolouration seemed to be the iron ion included in the well-water. Then, we examined the discolouration of the samples that was boiled in the distillated water in which the small amount of FeSO4 or FeSO3 was contained. The results was negative as shown in Photo. 3. Namely, no discolouration was occurred before the concentration of iron ion reached to 1, 000mg/l. As the concentration of iron ion is 0.17mg/l in the well-water, however, the discolouration seemes to be not the simple action of iron ion as above experimeht, as if iron ion may be the factor of discolouration.Moreover, the next experiment certainly indicates that the mechanism of the discolouration is not the simple substitution of iron ion for aluminum ion. The experiment included that two aluminum samples were immersed in the well-water and conected to the each pole of the D. C. source (1V and 2V) and then boiled for 1 hour. For the results, the anode aluminum is more blackened than cathode one as shown in the Photo. 4. From this results, the discolouration seems to occur rather by adsorption than by substitution.We measured the single electrode potential of samples refered to Pt and solutional current in boiling distillated water and well-water, etc. Fig. 1-4 shows the results. From this curve also, we could not yet point out the factor of this phenomenon.Finally, we examined the corrosion resistance of the samples which were boild in the distillated water and well-water. Thee results are shown in Fig. 5-7. From this results, it seems to be say that the sample boiled in the distillated water is most resistant to any corrosive solution but the discoloured sample boiled in the well-watter is more resistant to the alukali solution than the bare aluminum, although it has the lowest resistance to the acid solution and 3%NaCl solution. From these facts, again, it seems to be reasonable to suppose that the blackning factor may be the iron ion.

STUDIES ON ADSORPTIVE POWER AND LUSTRE OF OXIDE COATINGS ON ALUMINUM (PART 2)

The effects of electrolytical condition include those of anodizing voltage, time and kind of electric current.If the temperature of bath is constant, the higher the voltage and concentration of sulphuric acid are, the poorer the lustre is, but the other hand, the stronger the adsorptive power is. (See Fig. 11-13)If the temperature and the concentration are constant, the longer the anodizing time is, the poorer the lustre is, but the stronger the adsorptive power is. Fig. 14-16 are the results when direct current is used and Fig. 17-19 are the results when alternative current is used. Regarding to lustre, D. C. is superior to A. C., but as for adsorptive power, A. C. is better.If the current is changed A. C. for D. C. or D. C. for A. C. in some period during anodizing, lustre varies as shown in Fig. 22. This figure illustrates that the A. C.→D. C. change gives good results for lustre and adsorptive power.

SOME INVESTIGATIONS ON THE STRENGTH OF CATHODE PLATE USED IN ELECTROLITIC REFINING PROCESS OF ZINC

It seems necessary to examine if the cathode plate which is used today is the best one in respect to its strength, its corrosion-resistance and its efficiency. Therefore, we examined some problmes on the strength of one of the cathode plate used to-day.1) The strength of aluminum reduces according to its purity and especially this inclination is more remarkable when the purity rises above 99.5%. In the view point of strength, therefore, it is better than 99.0-99.3% aluminum is used for the material of the cathode plate. But this reduces its electro-conductivity and its corrosion-resistance.2) As for the relation between the rolling process and the electrc-conductivity, when the annealing temperature during the cold rolling is held at 275°C., the electro-conductivity is 2% better than annealing at usual temperature.3) As for the shapes of bar, one having T-type section is the best in the view point of strength. But this type of section is not always available if theother bath-equipment is not fitted.4) From the stress-strain curves of this material and the stress which is imposed on the bar of this cathode plate, it may be proved that the repeated stress as strong as about elastic limit are imposed on this bar. On the other hand, corrosion weakens the strength of this bar. From two reasons mentioned above, it may be surmised that such bar as examined in this experiment willbe deformed during the repeated using.In designing such bar, therefore, the utmost care must be given to its shape and the protection of corrosion.