In the present paper, the relations between wear resistance of steels and their high temperature hardness have investigated with the wear tests under dry condition and the measurments of high temperature hardness in a vacuum. The wear tests have been carried out under various sliding speeds. The wear resistance of steels, that is a reciprocal of steady wear rate, is found to be affected by the surface hardness attained during the abrading. Hence, there have been observed close relations between wear resistance and high temperature hardness. Especially for low carbon steel, specimen with larger size of ferrite grain shows lower wear resistance than the one with smaller size of ferrite grain within a lower range of sliding speed, but at higher speed the reverse is obtained. This relation of wear resistance is compatible with that of high temperature hardness, and it is considered that the grain boundary plays considerable roles in wear. For high carbon steel of pearlite structures, wear resistance depends also on high temperature hardness up to certain sliding speed, but at the higher speed, the wear resistance tends to be extremely high because the rubbing surface is hardened due to structural change.
This investigation has been conducted to make clear the effect of strain rates on the internal structure and the mechanical properties of rapidly stretched stainless steels. The 18%Cr-8%Ni stainless steel and 17%Cr-4%Ni PH stainless steel specimens have been used in this study. The main results obtained are as follows: (1) The yield strength and the tensile strength of these stainless steels in rapid tensile testing are larger than those in static tensile testing. The strain rate gives a remarkable effect on the resistance in deformation of these stainless steels. (2) The yield strength, the tensile strength and the hardness of rapidly pre-stretched 18%Cr-8%Ni stainless steel are larger than those of statically pre-stretched sort. It was recognized that this fact is mainly due more to the promoting martensite transformation by rapid pre-stretching than by static one. (3) The yield strength, the tensile strength and the hardness of statically pre-stretched 17%Cr-4%Ni PH stainless steel are larger than those of rapidly pre-stretched sort. It seems that this fact is mainly due more to the promoting aging by static pre-stretching than by rapid one. (4) From the above mentioned results, it is recognized that the mechanical properties of prestretched stainless steels are remarkably affected by the internal structure caused by the strain rate in pre-stretching.
The study was carried out on the variation of the mechanical properties due to the treatment by cold-drawing and precipitation hardening process on the specimens of beryllium-copper alloy wire. The specimens (diameter 1mmφ) were straightened after cold drawing. The results obtained are as follows. (1) The use of the straightener to straighten the beryllium-copper alloy wire has deteriorated the mechanical properties of the wire. (2) The cold-drawing has caused the beryllium-copper alloy wire an increase in tensile strength, yield strength, spring limit, hardness, and fatigue strength, but has caused it a decrease in modulas of elasticity, elongation, and number of torsion. (3) Precipitation treatment improves static properties such as spring limit, yield strength, tensile strength, and hardness considerably, but it improves fatigue strength but slightly. (4) Such static properties in the beryllium copper alloy wire as tensile strength, yield strength, spring limit and Vickers hardness have rectilineal correlation with one another whatever the manufacturing condition is. Therefore the measurement of any one of these properties will give a clue to that of any others.
Studies have been mede on the influence of no stress time, varying stress time and maximum stress time in 1 cycle on low cycle corrosion fatigue strength of Al alloy. The electrode potential of the specimens has been measured against the saturated calomel electrode during the cycles and the fatigue cracks have been observed through a microscope. The following facts have been made clear. (1) When the cycle frequency is constant, varying stress time (ta) and maximum stress time (tm) have destructive effects which will increase the corrosion fatigue damage. The effect of ta is greater than the effect of tm. This results are due to the difference of recovery of the corrosion potential on the specimen surface. (2) When the cycle frequency gets slower owing to the increase of varying stress time (ta), destructive effects appear. When the cycle frequency gets slower by the increase of no stress time (t0) or maximum stress time (tm), protective effects appear which decrease the corrosion fatigue damage. The protective effects are due to the recovery of the corrosion potential in the crack initiation period. In the crack propagation period the effects are due to the decrease of crack propagation rate caused by the lowering of stress concentration according to the branching or the thickening of the crack tip, or to the pit formation from the cracks.
It is well known that pitting has often occurred on the water side of water cooled diesel cylinder liners. There has been but scanty record of studies made of the interrelations of cavitation erosion, the microstructure of cast iron, the hardness of chromium films plated on cast iron and the hardness of base metals studied. The present study was made with the aim to prevent pitting and to make clear the mechanism of cavitation erosion of cast iron and such chromium films. The magnetostrictive cavitation tests were carried out on specimens that are chromium films with various hardness plated on cast iron, various heat treated cast iron, chromium films with same hardness plated on various heat treated cast iron, carbon steel and chromium films plated on carbon steel. The results obtained are as follows (1) The high cavitation erosion resistance was obtained with plated chromium films of hardness between 850 and 900 Vickers hardness on specimens of chromium films with various hardness plated on cast iron. (2) The cavitation erosion resistance of cast iron increased with increasing hardness of cast iron. It seems that at first the cavitation erosion in the portion with graphite structure was caused by impact stress when cavities collapse, secondly the cracks grew up between graphite and graphite, and finally the destruction occurred. (3) The cavitation erosion resistance increased with increasing hardness of cast iron for specimens of chromium film with 874 Vickers hardness plated on various heat treated cast iron. (4) The high cavitation erosion resistance was obtained on specimens of chromium film plating on carbon steel.
A series of experiments were performed with leaded brass rods of nearly equal chemical composition with a view to finding out the effect of different sorts of casting process on their machinability in terms of cutting resistance, surface roughness and chip formation. Four billets were chosen for the specimens variously processed, namely by the continuously casting method, by the metal moulding method, by the shell moulding method, and by the bran moulding method respectively. These specimens were subjected to cutting on the lathe, drilling and reaming. The specimens were, so far as their hardness was concerned, all of no perceptible variance, but in the size of their crystallized grains were in the ascending grade from the specimen with the finest grains processed by the continuously casting method, through that processed by the metal moulding method, and further through that processed by the shell moulding method, in the end to that processed by the bran moulding method. The grains in the last mentioned two sorts were found to be of considerable size. So also in the ascending grade the specimens appeared to be in the size of the ingredient lead particles scattered in the whole structure of the specimens from the specimen with the finest ingredient lead particles processed by the continuously casting method, through that processed by the metal moulding method, and further through that processed by the shell moulding method, in the end to that processed by the bran moulding method. The result of the experiment by subjecting the speimens to cutting on the lathe shows that there is remarkable effect of the different sorts of casting process on their machinability. Here cutting resistance shows the specimens in the ascending grade from the minimum of resistance to the specimen processed by the continuously casting method, through the resistance to that processed by the metal moulding method, and further through the resistance to that processed by the shell moulding method, in the end to the resistance to that processed by the bran moulding method. Chip formation also shows the specimens of different sorts of casting process in the ascending grede corresponding to the above, while surface roughness shows no variation in the specimens of whatever casting pattern. The experiment by subjecting the specimens to reaming shows the same result as above. The experiment by subjecting the specimens to drilling shows a little variation. Here the cutting resistance to the specimens variously processed in casting shows the specimens in the ascending grade from the minimum of the cutting resistance to the specimen processed by the shell moulding method to the resistance to that processed by the continuously casting method and that processed by the bran moulding method. The surface finishing shows smooth-rough grade in the specimens variously processed in casting in favour of the specimen processed by the bran moulding method before that processed by the continuously casting method and that processed by the shell moulding method.
It is a prevalent idea that dislocations move to-and-fro during the fatigue of metals and that cracks are originated from intrusions which are produced as a result of slip movements. We made studies on the slip movements during the fatigue process, and have found that the slip lines that the dislocation made on the surface will not reverse their way when the stress is reversed. There is even an intrusion extrusion model suggested which does not contradict the above-mentioned discussions.
Polyester resin laminates reinforced with glass fibers have recently been put to good use for industrial purposes, for instance to form mechanical members of electric apparatuses and automobiles, to substitute metals. Although the mechanical properties of the laminates have often been reported, few are really the results of experiments based on studied method and design. Our investigation was carried out using the orthogonal array table type L16. Eight factors were chosen and examined with reference to the two levels: (A) The kind of resin, (B) The style of weaving the glass fabric, (C) Whether finishing touches to be given to the glass fabric or not. (D) The molding method, (E) The hardening velocity, (F) Whether to use the filler or not to, (G) Whether to cure the laminate or not to, (H) Whether the dipping of the laminates in the sea water to be processed or not. The tests were carried out in the atmosphere of 20±1°C, 65±3%RH. The main results obtained are as follows: 1) Isophthalic acid polyester produces favorable effect on bent members, especially so under repeated stress. 2) Satin-like style of weaving produces better effect than plain style of weaving. 3) The volan finishing touches given to the glass fibers show better effect than in the case of no finishing touches ever being given them. 4) The laminates containing the filler fare worse than those without the filler. 5) The effect of interaction A×C and of that F×D is large on breaking stress. 6) The effect of interaction A×E is large on fatigue strength. 7) The effect of interaction A×D is large on moduli. 8) No effect of either G or H is recognized either on breaking stress or on moduli.