The bending stress of wire rope and the contact pressure between the wire rope and the cast iron roller have an important effect upon the durability of the wire rope. There have, however, been few studies made on the contact pressure beyond a series of studies by Th. Wyss. Furthermore, Th. Wyss' studies seem to have some doubtful points, so the authors developed some experimental investigation on the contact pressure of a wire rope in order to solve these problems and tried to make the matter clear theoretically by attempting to extend Hertz's stress theory into the plastic region. We have obtained some satisfactory results on the contact pressure, and succeeded in inducling a practical formula for calculating the bending stress based on the experiment; 1) The maximum bending stress of a wire rope on the cast iron roller can be estimated by the fomula σb=(1∼1.2)EbQd/4√EIS 2) The contact pressure between the wire rope and the cast iron roller can be calculated by using P/dr2-Aμνdr2 curve, and the maximum value of the contact pressure can properly be taken as 180kg/mm2.
In this report the authors studied how far the bending stress of wire ropes and the contact pressure between the roller and the wire rope could be reduced when the roller was lined with rubber or synthetic resins, in comparison with those when the unlined cast iron roller was used. From the experimental results, the following facts were found. 1) The maximum bending stress of the wire rope on the lined roller is about three-fourth of that on the unlined cast iron roller. 2) The maximum contact pressure σ0max between the rubber-lined roller and the wire rope is 1.7kg/mm2. σ0max between the rubber-and BANCOLLAN-lined roller and the wire rope is 1.8 kg/mm2, and σ0max between the BANCOLLAN-lined roller and the wire rope is 2.1kg/mm2. These respective values are not exceeded.
In order to investigate the behavior of wire rope under the dynamic load, we experimented with a drop hammer type impact tester, which was of our own design, and discussion was made on the impact breaking strength and the absorption of energy of wire ropes, comparing with those obtained by static tests. In this paper we report how the breaking strength and absorption of energy are influenced by the impact speed and the length of wire rope. The results can be summarized as follows: Under the test conditions: Length of wire rope varying from 500mm to 2000mm, Impact speed varying from 3.8m/s to 6.9m/s, 1) As the impact speed is increased or as the specimen becomes shorter, the breaking strength increases. 2) As the impact speed is increased or as the specimen becomes shorter, the inclination of stress-strain diagram augments, and absorption of energy decreases. 3) Absorption of energy is not so markedly influenced by the impact speed within the range of this experiments, but when the rope is extremely short, then it decreases very rapidly.
An investigation of the size effect on fatigue strength under bending and on damage properties of hard drawn steel wire has been carried out on 0.4%C (σB=130kg/mm2) and 0.6%C (σB=165 kg/mm2) wires ranging in size from 1.2 to 3.3mm in diameter. The principal results of this investigation can be summarized as follows: (1) Fatigue strength of hard drawn steel wires having the same tensile strength decreases with the increase of diameter. Fatigue limit of 1.5mm wire is 6∼8% higher than that of 3mm wire, and the size effect on fatigue limit is more remarkable at 0.4%C wire than 0.6%C wire. (2) For the size effect on fatigue limit under rotating bending of hard drawn steel wire, we present the following experimental equation σWd'=σW3'+m·log3/d where σWd' and σW3' are respectively fatigue limit of any diameter d and 3mm diameter wire. m is materialial constant. (3) Fatigue damage by overstressing is difficult to occur as the wire becomes finer, so the size effect can also be recognized on fatigue damage.
In order to determine some characteristics of the impact strength of small-diametral and thin-walled steel tubes in the longitudinal direction, we have performed the notched tube impact bending test of cold-drawn, seamless steel tubes. And in this test we have investigated the effects upon the impact strength of cold-drawn steel tubes, of the class of the steel in question (whether rimmed or killed steel) the dimensions of the tube (25φ×1.5t and 2t), the reduction rate of area by drawing (10, 20 and 30%), aging after cold-drawing (100°C×7hr, 200°C×15min and 200°C×2.5hr heating) and the impact test temperature (100∼-190°C). The results obtained are outlined as follows. (1) With larger reduction rate of area by drawing, the notched tube impact bending strength decreases in every tube, and the transition temperature rises that moves from the ductile fracture to a brittle one. (2) The impact strength is of almost constant value between 100°C and -60°C in every tube, but gets rapidly smaller below -100°C, and all steel tubes get perfectly brittle fractures at -190°C. (3) The effect of aging after cold-drawing on the impact strength was scarcely recognized in this test. (4) The thicker the wall of the tube, the greater is the energy absorbed in the fracture of the impact test. But the effect of various factors on the impact strength tends to be similar in both the instances of thick tubes and thin ones.
It is known that the ultrasonic attenuation changes by microstructure and grain size of polycrystalline metals. Generally, it is considered that the mechanisms that cause loss in metals are mainly elastic hysteresis, forced motion of dislocations and scattering by the grains. Several authors have reported that ultrasonic attenuation of polycrystalline metals is fit by the equation α=A1f+A2f2+A4f4 Here α is ultrasonic attenuation, f is ultrasonic frequency, A1, A2 and A4 are the coefficients. The component proportional to the fequency shows the presence of elastic hysteresis (including motion of magnetic domain wall in ferromagnetic metals). The second term proportional to the second power of frequency is indicative of the motion of dislocation (in this study, the term is negligibly small). The last term proportional to the fourth power of frequency is Rayleigh scattering loss. The theory of Mason and McSkimin gives the follwing form for A4 on longitudinal wave when α is neper/cm: A4=2π3T/v4<(ΔK/K)2>Av. where T=volume of grain, v=velocity of the ultrasonic wave, K=average effective elastic modulus over all directions for propagating the ultrasonic wave in a given direction in a crystallite, ΔK=difference of the effective elastic modulus from its average as function of direction and <(ΔK/K)2>Av=average of the fraction over all directions in the crystallite (ΔK/K)2. Lifshits, Parkhomovskii and other authors also give the same form as above for A4 which is proportional to the third power of grain diameter D. Therefore, we prepared five samples of armco iron with different ferrite grain size. Transducer was X-cut quartz disk 2cm in diameter for longitudinal wave measurement. The attenuation was mesured at the 1, 3 and 5 megacycles per second. Theoretical and experimental results were compared with respect to the attenuation of Rayleigh scatter in specimens.
On the basis of Maxwell element, whose elastic and viscous elemlnt can produce the birefringence proportional to their strains, the complex modulus of elasticity E*, the complex strain-optical coefficient K* and the complex stress-optical coefficient M* as well as three kinds of loss tangent can be derived. These quantities can also be generalized by employing a concept of the so-called continuous distribution of relaxation times. Lissajous' figures obtained by means of the apparatus reported in the previous paper at 1.5cycles/sec have been analyzed in order to evaluate E*, K*, M* and the loss tangent for vulcanized Hevea rubber, low density polyethylene and polypropylene films at 30°C. The order of phase of the stress, strain and birefringence in these materials are quite different from each other. In the case of rubber, the stress and birefringence are almost in phase with each other, and only the strain lags far behind them in the phase. For polyethylene, on the other hand, the strain lags behind the stress and the birefringence behind the strain. Polypropylene shows negative strain-optical coefficient and the order of phase is the stress, birefringence and strain. These differences in the phase relations probably indicate that molecular mechanisms of deformation from which the birefringence originates are quite diffrent for each material.