舶用ディーゼル機関用チェーンの安全性評価法に関する一考案 A Consideration for the Security Evaluation Method of the chain in the Marine Diesel Engines
The chains for the 2nd order moment compensator in the marine diesel engines are designed usually to have extremly large safty margin. However, in a certain ship with the relatively large counter weight to reduce the hull vibration, it is possible to occur the non-linear vibration of the chain by the two node torsional vibration of the crank shaft.<BR>For this problem, the non-linear vibration analysis of the chain was carried out with the measured spring characteristics by means of the chain tightener mechanism, which was represented by the form of T<I><SUB>q</SUB></I>=k<SUB>1</SUB>⋅θ+k<SUB>3</SUB>⋅θ<SUP>3</SUP>.<BR>In order to avoid such a non-linear vibration of the chain, it is important to increase the socalled ith order critical speed n<I><SUB>c</SUB></I>= (60/2π) √k<SUB>1</SUB>/I/i of the chain, which is related to the linear part of the chain spring characteristic k<SUB>1</SUB>, comparing with the rated engine speed n<I><SUB>MCR</SUB></I>. This can be obtained by increasing k<SUB>1</SUB> or decreasing the moment of inertia I of the counter weight. Also, the increase of k<SUB>1</SUB> is able to be realized by increase of the initial chain tension F<SUB>0</SUB> or by stepping up the size of the chain and etc.<BR>From this point of view, in this paper, a security evaluation method for the chain was considered in relation to the value of n<I><SUB>c</SUB></I>/n<I><SUB>MCR</SUB></I>, on the basis of the reaults of the non-linear vibration analysis of the chain.
日本舶用機関学会誌 31(9), 661-669, 1996-09-01
The Japan Institute of Marine Engineering