Research On Vibration Fatigue Life Of Rotary Drilling Rig Mast Based On Power Spectrum Density

As the key structure of support and force of rotary drilling rig,drilling mast has an important influence on the overall service life of rotary drilling rig.In this paper,the vibration fatigue life of drilling mast structure is studied by combining power spectral density theory and fatigue life theory,including the following contents:Firstly,the load of drilling mast structure under two typical working conditions: drilling and lifting.A finite element model of drilling mast structure is established in workbench software by force analysis,and static strength and static stiffness are checked for two ultimate working conditions.The results show that the design requirements are met,and the dangerous position of mast structure prone to fatigue damage is preliminarily determined.Secondly,the dynamic characteristics of drilling mast structure are studied in three aspects.The first aspect is to carry out modal analysis,study the natural frequency and modal mode of drilling mast structure,and judge that the main excitation source will not lead to resonance phenomenon of mast.The second aspect is the harmonic response analysis,which studies the dynamic characteristics of the drilling mast under the action of the engine excitation force.Through the frequency response analysis of the dangerous position,it is judged that the drilling mast structure can withstand the simple harmonic load of the engine acting on the drilling mast.The third aspect is to carry on the random vibration analysis,to carry on the test collection to the dangerous position acceleration signal,after the frequency domain conversion takes the acceleration load spectrum as the excitation,simulates the drilling mast structure under the vibration load dynamic response.After that,the dynamic analysis results are introduced into the n Code fatigue simulation software,and the fatigue life value of the mast structure under vibration load is solved.Finally,the response information obtained from the dynamic characteristic analysis is combined with the power spectral density theory,the Dirlik method is used to calculate the parameters in the fatigue life formula to obtain the life value of the mast structure.Comparing with the calculation result of n Code proves that the calculation is correct.After that,the fatigue life analysis can be carried out by using white noise spectrum to approximate the response spectrum of alternative structure.The results calculated by Dirlik method are consistent with the finite element simulation results,indicating that the method is not problematic.On this basis,the influence of white noise with different bandwidth and frequency on the fatigue life of the structure is further analyzed.