Study On Fatigue Strength Of Jack-up Drilling Platform's Cantilever Beam

The cantilever beam is an important structure for the drilling operation of the jack-up drilling platform.With the arrival of the pl atform aging,the structural safety of the cantilever beam is a problem that needs to be considered in the field of Engineering.At present,there are two m ain methods to es timate the fatigue life of ship and ocean engineering.One is based on the S-N curve and Miner linear cumulative damage theory,and the other is Fracture mechanics method based on the linear elasticity.The S-N curve method assumes that the material is free of defects,while the actual material generally has cracks or defects.So the S-N curve method is used to estimate the whole life of the structure,and the fracture mechanics method is used to calculate the remaining life of the structure.(1)The X-Y cantilever beam form a shipyard is used as the research object,and the finite element model of the cantile ver beam is built by us ing MSC.Patran software.And then according to the actual load tes t conditions,the finite element model of the cantilever beam is numerically simulated,which lays th e foundation for the research of the fatigue strength.According to the actual w orking conditions of the cantilever beam,three typical cases are selected to an alyze and check the strength.At the sam e time,the influence of different wind directions on the cantilever beam is analyzed,which lays the foundation for the subsequent fatigue analysis.(2)The m ethod of obtaining the load spectr um and the data processing m ethod are analyzed,and the load spectrum of the cantile ver beam is deduced ac cording to the load spectrum of the land drilling plat form.On this basis,The data is processed to obtain the program load spectrum,and the S-N curve for the cantilever beam is selected in th e DNV specification,at the same tim e the S-N curve is modified by using th e thickness correction formula.The load spectrum and S-N curve are loaded into the software,and the life span of the cantilever beam is estimated by the software 's full life m odule.At the same time,the effects of different parameters on the fatigue life of the cantilever beam are compared.(3)Preliminary study on the fatigue life of cantilever beam with defects.Firstly,the fatigue fracture parameters are defined,incl uding the determination of the fracture m ode,the establishment of the crack s tress intensity factor model,the initial crack size and the critical crack size,as w ell as the determination of some fatigue parameters of the material.Finally,the crack propagation life of the cantilever beam with defects is estimated by using MSC.Fatigue's Growth module,which takes into account the different crack shape ratio and the initial crack.