| Portal cranes(hereinafter referred to as "door machines")are typical rotary cranes widely used in ports,shipyards,etc.,mainly for loading and unloading and handling of cargo.At present,the port loading and unloading machinery and equipment is developing toward large-scale,continuous,high-speed and automation,and the high-speed is achieved by increasing the operating speed of each mechanism in actual operations,which makes the dynamic load of the crane structural members become larger.Dynamic performance has higher requirements.Due to the large inertia of the rotary part of the door machine and the flank clearance between the large ring gear and the small gear,the slewing mechanism will experience the impact vibration during normal operation.This phenomenon is particularly obvious when braking,and gear failures often occur..A survey of some coastal ports in China found that before a design life is reached,the large ring gear of a large type of door machine has a broken tooth fault,and the breaking rate is as high as 30%,resulting in slewing failure,maintenance cost and economic loss.Huge,the main parameters of this type of door machine are: rated lifting capacity of 40~60t,maximum range of 38~45m,lifting height of more than 40 m.GB/T 17495-2009 "Port Door Crane" stipulates that after the installation of the slewing bearing of the door machine is completed,the meshing side gap between the large ring gear and the driving pinion gear should be 0.5mm~1.6mm.When the manufacturer manufactures such a door machine,the meshing side gap under no-load conditions satisfies the standard.The study found that in the state of the load,the pinion will produce a relative displacement,which will cause the pinion and the axis of the slewing ring to be non-parallel,so that the meshing side gap exceeds the national standard,and the gear pair stress concentration is formed.As a result,the large ring gear is broken and the service life is much lower than the design life.Therefore,the dynamic analysis of large-scale door slewing bearing based on this positional accuracy error,as well as life estimation,is of great significance.In this paper,the MQ4040 door machine is taken as the research object,and the position precision error generated by the slewing pinion and the large ring gear under actual working conditions is calculated.The dynamic analysis and simulation verification of the contact and meshing condition of the slewing bearing sub-point during the turning process are carried out.Based on this,the fatigue life estimation of the large gantry slewing gear is carried out.Mainly completed the following aspects of work:(1)According to the relevant parameters of the model door machine,the three-dimensional model of the inner and outer rings,rolling elements,cylinders and turntables of the slewing ring is established by means of SolidWorks software,and the loading calculation is carried out in the ANSYS workbench according to the actual load condition of the slewing bearing.The parallelism error of its axis;(2)Establish a dynamic model of the movement of the swing mechanism of the door machine,and analyze the dynamic load and other calculation parameters when the swing mechanism is started.Analyze the dynamic response of the slewing gear pair during the starting process of the slewing structure when the door machine is under the maximum working range and full load condition;(3)The assembly model of the slewing bearing of the door machine under the position accuracy error is established by the 3D modeling software SolidWorks.The load and the constraint are added into the ANSYS/LS-DYNA to obtain the dynamics of the slewing ring gear during the starting process of the slewing mechanism.Tooth surface contact stress and contact force.According to the principle of gear tooth surface strength evaluation,the strength of the large ring gear tooth surface during the starting process of the slewing mechanism was analyzed and evaluated.(4)According to the fatigue analysis theory,the SN curve of the material is modified,and the Fatigue fatigue analysis module in ANSYS Workbench/Transient Structural software is used to fatigue the slewing ring gear under three typical working conditions during the starting process of the slewing mechanism.Life analysis,compared with design life and survey statistical life,find the minimum point of fatigue life,analyze its relationship with position accuracy error,and provide optimization goals for the optimization scheme.(5)With the aim of reducing the relative displacement generated between the teeth,the cylindrical plate thickness and height are used as design variables to improve the rigidity of the cylindrical structure.After verifying the improved fatigue life of the slewing ring gear teeth,it is found that the improved fatigue life results can achieve the design life of the slewing ring. |
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