The effect of nickel plating in reducing the fatigue strength of carbon steels has been previously reported. The present report is made of the fatigue test that was carried out on the postnickel plating heat treatment (Baking) in order to investigate a method of level up on the reducing fatigue strength of nickel plated steel. The test specimen were made of annealed S10C, annealed and quenched-tempered S40C steel in Table I. The nickel plating were prepared from a standard Watt's solution. The average thickness of nickel plating was about 85μ. Heat treatment (Baking) after nickel plating, were carried out in air at temperature from 20°C to 550°C for 2 hours. The test results are summarized as follows; (1) Baking up to 250°C slightly increases the fatigue limit of nickel plated steel with decreased hardness of the nickel plating. (2) But the treating above 550°C causes the fatigue limit below the plated value with decreased hardness of the steel and the plated nickel.
This study was performed by measuring micro Vickers hardness, to make certain of the material changes which had occurred in 18-8 austenitic steel in the course of thermal fatigue under conditions of transient temperature gradient. The thermal fatigue and cyclic tests were carried out by means of the previously mentioned thermal fatigue testing machine of high-frequency induction-current heating and water-cooling type (average heating rate being at 200°C/sec, and the holding time at maximum temperature being 5, 10 and 20sec). After testing to a certain number of thermal cycles, the hardness changes across the cross-section of wedge-shaped specimen were measured, and the effects of cyclic thermal strain and cyclic heating on the changes of its hardness during thermal fatigue, were studied in comparison with the results of prementioned Coffin's type thermal fatigue test. The conclusion is drawn as follows. In the case of thermal fatigue originating from the transient temperature gradient (temperature variations being at 800 and 600°C, and the holding time at the maximum temperature being 5sec), the hardness change by thermal cycling or precipitation hardening showed the values of 3 to 18per cent of total hardness change during thermal fatigue, and the hardness change by thermal strain cycling or the resultant of strain hardening and its softening indicated the values of 67 to 90per cent. These hardness ratios varied as the holding time at the maximum temperature was prolonged. It was found, however, that the hardness change during thermal fatigue was, after all, as it was the case with the results of Coffin's type thermal fatigue, the consummation of these hardness changes.
The temperature dependence of Vickers hardness was obtained in the range of -196°C to 250°C for molybdenum (Mo) and -196°C to about 550°C for tungsten (W) by impressions in the central region of the specimens. On the other hand, when one makes impressions in the region near the edge of the specimen the macroscopic cracks were found on the edge side of the impressions under certain conditions. If we assume that the temperature in nearly equal zero on the apparent total length of the cracks is the boundary between the ductile zone and the transition zone, and that the temperature which is nearly constant at the upper point of the brittle zone, the results obtained in this paper can be recognized to be consistent with the ductile-brittle transition based on tensile properties of Mo and W hitherto obtained by other authors by taking account of the difference of the material conditions. By the above definition the ductile zone, the transition zone and the brittle zone are >-39°C, -39°C∼-92°C and <-92°C for Mo, and >394°C, 394°C∼-33°C and <-33°C for W, respectively. The crack formation modes of Mo were essentially of transgranular type with a few intergranular type in the temperature range investigated here, and that of W was intergranular type above about -100°C and essentially transgranular with a few intergranular type below about -100°C, which was not consistent in detail with the results obtained by Bechtold et al.
We designed the measuring instrument of thickness variation of bulged foil, and by using this apparatus, studied the configuration of bulged surface of aluminum foil. (1) The bulged surface of aluminum foil is composed by two parts; one part near the appex is spherically constant in thickness, the other part is settled inside the sphere. (2) The instable state of bulged surface of alumium foil occurs before the initiating point destructions. (3) The bulged height corresponding to the initiating instable state is detected by measuring the thickness variation.
The contact pressure of wire ropes which are wound around the sheave or that on the roller has an important effect upon the durability of wire ropes. We have carried out a series of studies on the contact pressure of the wire rope, and reported some results of them, when the wire rope was bent by a small angle by the cast iron or the lining roller. In this paper is reported the result of studies made experimentally and theoretically on the contact pressure of wire ropes which are wound around the cast iron or the lining sheave. The result can be summarized as follows: (1) The contact pressure of wire ropes on cast iron sheaves can be calculated from Q/d2-Ac/μνd2 curve. (2) With larger diameter of the sheave, the contact pressure decreases in the case of the lining sheave. (3) The contact pressure of wire ropes which are wound around the lining sheave is nearly equal to that of the wire ropes on the lining roller for the angle of the deviation 2α=6°. (4) The contact pressure of the wire ropes which are bent by a small angle by the lining roller can be obtained, if values calculated by Herz's formula are multiplied by a compensation factor based on the construction of the wire rope.
Based on the postulate of stability of materials failure criteria of macroscopically homogeneous isotropic brittle materials under combined stresses are represented by convex surfaces in the principal stress space. The failure surfaces of both high- and low-strength concretes were compared in the compression rarge as the maximum first stress invariant up to 5.2 times of the uniaxial compressive strength. The surfaces of the both concretes are almost identical when they are represented in the non-dimensional principal stress space, though their absolute values are quite different. The surfaces are convex and have the space diagonal as a threefold rotation axis. Right sections of the surfaces are slightly bulged from equilateral triangles and expand almost isotropically with a decreasing ratio as the hydrostatic pressure increases.
In order to find out the general view of mechanical properties for rigid PVC plates as a whole, the measured values of various kinds of mechanical properties have been investigated with respect to their mutual relations about ten kinds of plates. The results obtained are summarized as follows: (1) There exists a close relationship between the results of tensile tests and those of impact tests. The plate which shows more sudden necking phenomenon at its arising in the tensile test, has lower impact strength. (2) There are roughly linear relationships between any two of the Vickers, the Brinell, the Rockwell and the Shore-rebound hardnesses. The values of HV/σ1 (HV: Vickers hardness, σ1: tensile strength, i.e. yield strength) take roughly a constant value, i.e. 2.3. (3) The rigid PVC plate which shows higher modulus of elasticity, has higher yield strength (tensile strength), higher hardness, smaller elongation and lower impact strength. There are roughly linear relationships between any two of the measured values of above mentioned mechanical properties.
In this paper, the “FRP” plate is considered as continuous body having orthotropic elasticity in the region of infinitesimal deformation, and an analytical method is presented for calculating its orthotropic elastic compliance Sij. The conditions given for the calculation are the structure of the composite system and the elastic constants of the fiber and the resin. A typical example treated mainly in this paper is cloth reinforced plastic. The plate is consisted of two parts, one is the part of yarn having some resin which can be treated as an uni-directionally reinforced plastic rod, and the part of pure resin. The property of resin part is isotropic, but the yarn part has orthotropic property. It is assumed that the orthotropic property of the FRP plate has been caused by this orthotropic character of the yarn parts by the angle between the yarn axis and the direction load. The uniform deformation of all parts in the FRP plate is also assumed. Good agreement between calculated values and observed one for elastic constant has been confirmed by some experiments in which model samples made of single layer FRP plates was used.