| The hydraulic power tong is a special tool for the quick shackle operation of the string.It has the advantages of simple structure,convenient operation,reliable performance,long service life,wide application range,large output torque and so on.It can be improved that the working efficiency of workers and reduce labor intensity greatly.Hydraulic power tongs in the completion of the shackle operation require shift reversal frequently,due to torque and speed and other external excitation changes will inevitably produce impact in the gear transmission system in the transmission process.Shock load is much larger than normal working load,while the conventional fatigue life prediction is based on the load spectrum under normal operating conditions,therefore,predictions and actual working conditions there is a difference,in order to make the prediction results closer to the actual conditions,the use of impact load spectrum for fatigue life prediction is more research significance.This paper based on the multibody dynamics,theory of impact dynamics and fatigue life,according to the actual working condition of hydraulic power tongs.Studied the opening gear that is the important parts of hydraulic power tongs.Finished the following works:Analyzed the working parameters and the basic principle of hydraulic power tong.modeling the 3d model and assembly of the hydraulic power tong gear transmission system by three-dimensional modeling software.Finally,simplified model according to the needs of finite element analysis.Modelled the virtual prototype model of hydraulic power tongs gear transmission system with ADAMS.Have completed the analysis of multi-body dynamics in hydraulic power tongs gear transmission system working with screw and unscrew,have analyzed the kinematic and dynamic characteristics in hydraulic power tongs gear transmission system with two kinds of working conditions.Deduced the gear dynamic contact dynamics differential equation based on the Hamilton vibrational principle.Have solved the elastic dynamics differential equation by Newmark direct integral method,and correction.The Newmark method has been chosen as the final solution of gear dynamic contact calculation method.Have calculated the impact velocity and load of hydraulic power tongs starting in low twist at high speed,high torque at low speed,low in high-grade,high-grade gear down,single and double gear alternation.The impact load is largest when high-grade gear down.Lastly,learned the basic processes and theory of fatigue life prediction.The finite element analysis was carried out on the gear to confirm the critical locations of the open gear.The fatigue load spectrum of the open gear is calculated by the rain flow cycle counting method.The fatigue characteristic curve of the material was plotted in consideration of the survival rate of the material,the Goodman method is used to correct the average stress.Finally,the fatigue life of the open gear under the impact load and the normal working condition is predicted by the fatigue analysis module.For a tooth,the normal operating conditions can be completed on the number of shackle operations for 7.63×105 times,while 2.83×105 times in the position of the the single and double gear alternate,but under the impact load only 50848 times.It can be seen that impact load had a great influence on life of gear. |
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