Research On Structure And Load Transfer Mechanism Of Flexible Beam In Curved Pipe

The flexible beam in the pipe is a unique structure in chemical process machinery and oil drilling engineering.It is important to carry out research on the flexible beam structure and load transfer mechanism in the curved pipe,which is of great significance to the optimization of flexible beam structure design and process parameters.The equal-section beam and the pipe are selected as the research object.The double nonlinear finite element model and numerical calculation method of equal-section beam with the same section in the pipe are established by combining the contact element and geometric nonlinear beam element.The feasibility of the numerical method is verified by an example.Considering the structural characteristics of discontinuous eccentrically variable beam structure,non-full circumferential slot and eccentricity of the section,the eccentric section beam is connected with the full section beam by the rigid beam element.The beam element,the rigid beam connection element and the beam-beam contact element are combined to establish a contact nonlinear finite element model and numerical calculation method for the eccentric variable section beam in the curved pipe.Contact nonlinear mechanical analysis of eccentric variable section beam in different influencing factors(external load,annulus and radius of curvature)are carried out.The load transfer law of eccentric variable cross-section beams with different influencing factors is studied.The results show that the axial force loss rate of the eccentric variable section beam changes little with the increase of the external load.With the increase of the annulus gap,the axial force loss rate of the eccentric variable section beam increases gradually.With the increase of the radius of curvature,the axial force loss rate of the variable section beam is gradually reduced.Based on the structural characteristics of the controllable universal joint connection,it is described by a universal joint element.The mutual transition between the controllable hinge beam mechanism and the structure is achieved by the motion constraint of the universal joint element.Considering the mechanism problem of the controllable universal joint connection and the contact nonlinearity problem,the 3D beam element,the universal joint element and the beam-beam contact element are combined to establish a contact nonlinear finite element model of the controllable universal joint beam in the curved pipe.The dynamic relaxation method of beam-beam contact nonlinear analysis is proposed,which solves the problem that the system does not converge due to rigid body displacement in beam-beam contact problem.In order to verify the feasibility of the contact model and numerical calculation method of the controllable hinged beam in the curved pipe,according to the superposition principle,the equilibrium equation and the deformation coordination condition,the expressions of deflection,bending moment and contact force at the hinge are derived when lateral load is applied to the controllable hinge of the controllable universal hinge beam inside the outer beam.Comparing the numerical solution with the theoretical solution,the results agree well.According to the flexibility matching between the hinged beam and the curved pipe,the expression of the maximum single-section length and the universal joint angle corresponding to the single-section length of the hinged beam in the case where the single-section is not bent is derived.The contact nonlinear mechanical analysis of the controllable universal joint beam in the curved pipe is carried out.The influence of the single-section length of the hinged beam and the rotation limit of the universal joint on its load transfer law is studied.The results show that the torque loss rate of the hinged beam increases from 4.0% to 14.6% when the length of the hinged beam is increased from 200 mm to 700 mm.When the rotation limit dgree is increased from 3.82° to6°,the torque loss rate of the hinged beam is increased from 4.0% to 4.7%.The composite beams with complex structures and pipe are selected as the research object.Considering the controllable hinged beam mechanism and structural transition problem,beam section eccentricity and two-layer contact nonlinearity,the beam element,the universal joint element,the rigid beam element and the beam-beam contact element are combined.A two-layer contact nonlinear finite element model and numerical calculation method for multi-element combination of composite beams with complex structures in pipe are established.The feasibility of the numerical calculation method is verified by an example.The contact nonlinear mechanical analysis of the composite beams with complex structures in the pipe reveals the mechanical properties of the controllable universal joint beam,the eccentric variable section beam and the curved pipe.The results show that the contact force between the hinged beam and the eccentric variable section beam is randomly distributed.As the length increases,the torque of the hinged beam of the vertical section does not change much,and the torque of the hinged beam of the curved section gradually decreases.The contact force between the eccentric section beam and the curved pipe of the vertical section is smaller than that of the curved section.With the increase of length,the axial force of the eccentric variable section beam of the vertical section gradually increases,and the axial force of the eccentric variable section beam of the curved section gradually decreases.The results of this dissertation provide a numerical calculation method for the contactnonlinear analysis of flexible beam structures in curved pipes.The flexible beam structure and load transfer mechanism in curved pipes are revealed,which provides theoretical guidance for the structural design of flexible beams in curved pipes.