Research On Boom Lifting Process For Fly-Jib Working Condition Of All-Terrain Crane

All terrain crane is mostly used crane on modern construction site because of its flexibility. Its fly-jib working condition is one of commonly used working patterns. The boom lifting process for fly-jib working condition is complexity and dangerous. Boom lifting not only influence working efficiency, even do harm to human safety. Larger deformation can be produced with the consideration of nonlinear factor especially for larger length of fly jib working condition, and thereby influence the crane’s stability. So nonlinear factor needs to be considered when designing boom system.This paper mainly research on the boom lifting process of fly jib working condition of all terrain crane. Firstly, the possibility of successfully boom lifting for18-126m fly jib working condition without outside help is verified. Then optimal methods of boom lifting for each length of fly jib working condition is obtained. Finally, the influence pattern of nonlinear and linear theory on boom lifting process is derived. Specific contents about this paper as follows:(1) Based on the analysis of motion characteristics and mechanical property of each phase of boom lifting with or without assistant bracket, mechanical model of boom lifting is simplified. Then, the possibility of successfully boom lifting in every phase with or without assistant bracket is verified in case of no outsider help by the appraisal criterions of luffing cylinder force, extension cylinder force, the bending moment on main boom tip and overturning stability coefficient;(2) According to the mechanical characteristics and overturning coefficient under different boom lifting patterns, optimal boom lifting pattern for each length of fly jib working condition is derived;(3) Parameterized finite boom lifting model is established by ANSYS APDL language based on geometry nonlinear theory and method of equivalent moment of inertia. According to analysis results of linear and nonlinear theory on boom lifting process, the influence pattern with consideration of linear and nonlinear factors on boom lifting process is concluded.Achievements as follows:boom lifting with assistant bracket is more stable and mechanically reasonable than without assistant bracket. Employing LSL boom lifting pattern is more safer for the short length of fly jib working condition, while LLS boom lifting pattern takes much advantages for larger length of fly jib working condition. As mentioned above. LSL boom lifting pattern:main boom luffing-main boom extension-fly jib lifting; LLS boom lifting pattern:main boom luffing-fly jib lifting-main boom extension;Linear model can replace nonlinear model for the purpose of improving efficient when analyzing on boom lifting process for shorter length of fly jib working condition, while nonlinear factor need to be considered for larger length of fly jib on boom lifting process. The role play by assistant bracket on boom lifting process as follows:a) Keep safe distance between main boom tip and luffing link:b)Reduce the deformation and loading force in larger scale, improve the stability of whole crane, on the beginning luffing angles of fly jib lifting process.Achievements give certain guiding meanings for similar crane’s fly jib working condition such as simplify boom lifting model, the operation of site boom lifting and the design of boom system.