Axial Vibration Dynamic Responses Of The Rope

Large subsea oil and gas equipment such as subsea tree,manifold and subsea base plate is the key equipment in the efficient development of deep-sea oil and gas.As offshore oil and gas exploration and engineering development enter deeper water depth and more severe environment,the fracture caused by the axial vibration of the rope caused by hull heave movement is a problem that must be solved in the direction of modularization and integration of large underwater equipment.Paper used for lifting equipment of steel wire rope sling the or axial vibration problem of application of d 'alembert's principle of vibration mechanics,set up the steel wire rope as a mechanical model of continuous systems with infinite degrees of freedom,in rope viscous damping and structure under the effect of drag force in the sea water,considering the boundary conditions of the lower rope connection weights and fixed in the installation of rope under the heave motion of upper vessel dynamic incentive effects,deduce the axial vibration of steel wire rope partial differential equation,and through the method of separation of variables,The law of the effect of alternating load on the fatigue life of wire rope is obtained.In addition,considering installing the rope under the condition of axial vibration load and fatigue life,the quality of water depth,the diameter of the rope,and delegate object parameter sensitivity of the three factors and quantitative analysis,the analysis results show that in the depth of 1500 m,the rope diameter of 100 mm,lower the quality of equipment for 190 t,installation of the rope in the first three order resonance frequency were 4.2371 rad/s,12.7158 rad/s and 21.1936 rad/s.The safe life of the rope is 18.6 days;The maximum axial stress of the installation rope axial vibration occurs at the top of the rope and is 5.23 MN.?1 When the water depth is increased by 500 meters,the resonance base frequency of the installed rope is reduced by 8.3807%,and the fatigue life of the installed rope is reduced by 50%.?2 When the rope diameter increased by 10 mm,the resonance base frequency increased by 4.0216% and the fatigue life increased by 173.9130%.?3 When the lowering equipment mass increases by 50 t,the resonance base frequency of the installed rope decreases by 16.0487%,and the fatigue life of the installed rope decreases by 50%.It can be seen that the quality of the lowering device has the greatest influence on the resonance frequency of the installation rope.The results of this study can provide a basis for the engineering design of rope in deep water lifting environment.