Micro-damage Modeling And Dynamic Analysis Of Derrick

The large steel structure is widely used in the fields of construction,electric power,machinery and energy.As the main equipment in the field of petroleum production,the derrick steel structure will gradually expand the small defects contained in the components and connecting parts during the service throughout the year,forming local damage,which may lead to rapid expansion of damage in the process of continuous use,thus forming major accidents such as overall failure of steel structure.In order to prevent the influence of micro damage on derrick and other steel structures,the micro damage at the local level of the structure and even at the member level is studied,and the early detection and real-time early warning of micro damage are provided.Based on the establishment of the finite element model of micro damage of derrick steel structure,this paper discusses the modeling method of multiple structural element fusion models,analyzes the mechanical characteristics of the micro damage model,and describes the different characteristics of the micro damage derrick steel structure with multiple indexes,which provides a theoretical basis for the damage identification of the micro damage derrick structure.Firstly,by using the sub model technology,the member model of shell element with geometric micro damage is "embedded" into the derrick model of beam element,and the derrick model of "beam shell" element is constructed.The mechanical properties of the fusion model are compared with those of the original beam element model,which shows the rationality of the model and provides another idea for the modeling of derrick damaged structure.Then,the mechanical analysis of derrick model with micro damage is carried out,and the influence of different damage conditions on the static mechanical performance of derrick structure is compared;the constraint modal analysis,prestressed modal analysis and harmonic response analysis are carried out for derrick under different conditions,and the influence of micro damage under different conditions on the dynamic performance of derrick structure is qualitatively examined.Finally,through the derrick micro damage model,the quantitative effects of micro damage on the modal frequency,modal mode shape,modal curvature and modal strain energy of derrick structure are discussed.The displacement of mode shape,the change of curvature and the change of energy stiffness ratio are derived,which are parameters sensitive to micro damage.With the help of derrick models under different working conditions,the corresponding indexes of derrick under different working conditions are calculated through simulation test,and the identification ability of derrick under different working conditions is verified.