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INTRODUCTIONThis paper presents the results of the experimental and the theoretical investigation of the dynamic behavior and the tension of a mooring chain oscillating at various frequencies of the wide range in water. The movements of a mooring chain, when forced to oscillate vertically or horizontally at its upper end, are observed by means of cinematography and the dynamic tensions induced are measured simultaneously.The results of those experiments reveal that the chain oscillates in one of the following four conditions as the frequency increases, namely, [I] Quasistatic condition, [II] Harmonic oscillate condition, [m] Snap condition and [lIT] Free-fall condition. The maximum amplitude of dynamic tension occurs in condition em] or [lIT] and can not be neglected in comparison with the magnitude of the initial tension of chain. The results of the experiments are compared with the theoretical ones and the following conclusions are obtained. 1. The tension amplitudes depend on the amplitudes and the accelerations of oscillation, D value (D = WXO/THO' W = weight per unit length of chain in water, Xo = horizontal length of catenary, THO = horizontal component of initial tension) and the drag and added mass coefficients of chain in water. In the conditions [I] and [II], the tension computed with a theoretical method assuming a mode shape and an amplitude of motion shows good agreements. This approximate calculation method is of practical use to estimate the dynamic tension of chain.3. Results calculated by the lumped mass method also coincide with those experiments fairly well.References and illustrations at end of paper. 415The reliability of a ocean structure moored in the severe ocean environment depends upon the reliability of its mooring system. Therefore, it is very important that the performance of mooring lines subject to the severe environment in the ocean can be accurately predicted. Recent investigations 1~9 on the mooring line performance have shown that the magnitude of dynamic tension of an oscillating mooring line can not be neglected in comparison with 'the magnitude of its initial tension.The dynamics of oscillating chain in the various frequencies of the wide range have not been clarified yet. In this report, these problems are investigated experimentally and theoretically in the case that a mooring chain is forced to oscillate both vertically and horizontally at its upper end in relatively slack conditions in water.The movement of mooring chain is observed by cinematography and the induced dynamic tensions are measured by load cells simultaneously. The results of those experiments reveal that the chain oscillates in one of the following four conditions as the frequency increases, namely, [I] Quasi-static condition, [II] Harmonic oscillate condition, em] Snap condition and [lIT] Free-fall condition. At the conditions [II], [m] and [lIT], the dynamic tensions of chain can not be neglected in comparison with the initial tensions and they become maximum in the condition [m] or [lIT]. The calculated...

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The coating method and the characteristics of wire explosion spraying, as developed in our laboratory, are described. A study of the mechanism of adhesion between the coating and substrate in two metal systems, W-mild steel and W-Cu which differ in mutual solubility, is discussed. Metallographic observations using electron probe and soft x ray confirmed the presence of a solid solution boundary layer in the case of the mild steel substrate, with a critical shearing stress of adhesion measured by our method ranging from 20 to 26 kg/mm 2 , which is nearly equal to the shearing strength of the tungsten coating itself of 24 kg/mm 2 ; fracture propagated within the coating itself. In the case of the copper substrate the critical shearing stress of adhesion was from 9 to 13 kg/mm 2 which is much weaker than the shearing strength of copper, 28 kg/mm 2 ; the fracture propagated along the boundary between the coating and substrate. Theoretical considerations attempt to explain the mechanisms of formation of the structures and the adhesion properties. It is concluded that the high adhesion strengths obtained by this method are attributable to the characteristics of the particles sprayed by wire explosion, i.e., the small size (average 5 µ), the high temperature (near the boiling point of materials), the high impinging velocity (500-600 m/sec), and furthermore, the uniformity of the size, velocity and temperature of the sprayed particles.

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