For an efficient joint, it is essential that the molten metal spreads sufficiently covering the surfaces of the metals to be joined. This is the reason why in the research work conducted on low temperature brazing, it is of special importance that a study is made on the wetting point and wettability of the brazing material. For this purpose an electrical measuring equipment was devised as shown in Fig. 1. This study is based on various data obtained on the wettability of different brazing materials such as silver, brass, German silver and G 185(Eutectic Co. U. S. A.) brazing alloys which were tested on this equipment. The results obtained were as follows: 1. It has been definitely determined that the electro-resistance method can be used for measuring the wetting point of brazing materials. 2. This electro-resistancc method is suitable for checking the quality of brazing materials and fluxes. 3. The silver brazing material was found most suitable for low temperature furnace brazing. 4. following points were determined regarding the wetting temperature during brazing: a. When the flow points of flux is lower than that of the brazing material, the wetting point will be above the melting point of the brazing material. b. When the flow point of flux is higher than that of the brazing material, the wetting point will be 10°C above the flow point of flux.
The research reported herein is an investigation of the scale effects on notch brittleness of mild steel specimens having a geometrically similar shape. The specimens were machined from the same rimmed steel, whose roll thickness was 45mm. The shape of specimens is shown in Fig. 1. The cross section of the smallest size specimen is 10 mm × 10 mm; notch depth is 2 mm ; notch shape is 45°V ; and notch radii are 0.05, 0.1, 0.2, 0.4, 0.8 and 1.6 mm respectively. The middle size specimen is 21 × 21 mm in cross section, and the largest one in 42 mm × 42 mm in cross section. The test was made by slow bending, under the condition of same strain rate. The transition temperatures are shown in Fig. 8. The smallest one has a relatively low transition temperature, but for the specimens above the 21 mm size the transition temperatures are nearly equal. The scale effects on the maximum breaking stress (nominal) and yield stress are shown in Fig. 11. As shown in the figure the maximum breaking stress gradually decreases with increase of specimen.size, but the yield stress remains nearly constant. The absorbed energy in relation to the specimen size is shown in Fig. 13; the absorbed energy in shear fracture increases with specimen size in cubic proportion, while the energy in brittle fracture is proportional to the 2.5 power. The adsorbed energy per unit volume of specimen is shown in Fig. 14. In this figure the energy in brittle fracture gradually dereses with increase of specimen size.
The mathematical study of temperature distribution of welded plates was carried out for recent years by many engineers, but most of them are trying to solve the quasi-stationary state problem during the long time welding. For the first time, the unstationary problem of the two dimensional temperature distribution of welded plates was solved by Dr. Naka, proffessor of Tokyo University. In this paper the most general case, the unstationary state of the welded moderate thickness plates was studied for three dimensional problem. And then, nondimensional expression of temperature distribution and the asymptotic expansion of the temperature distribution function associated with the infinite series of incomplete I'-function were introduced.
In the previous report, the authors confirmed in a laboratory research with small test pieces that the peak of the residual stress near the welded joint could be relieved to considerable extent, by cold peening operation on the last layer of the deposit metal and parent metal near the welded line. In this report same results are given which were obtained with comparatively large scale test pieces from the shop.