Analysis On Mechanical Properties Of Double Donkey Head Pumping Unit Considering Welding Residual Stress

Double horsehead pumping unit is a new type of energy-saving pumping unit which is widely used in oil fields in China.However,it often causes tearing cracks at the connecting hole between horsehead and beam,which leads to damage.It is found that this is not only the fatigue damage caused by the alternating stress in the long-term movement of the pumping unit,but also the welding residual stress in the joint between the donkey head and the beam.Therefore,aiming at this problem,the mechanical simulation analysis is carried out on the key part of the connection between the rear donkey head and the traveling beam,and the corresponding results are obtained,which lays the foundation for the structural optimization of the double donkey head pumping unit in the future.In this paper,the welding residual stress at the joint of rear donkey head and traveling beam is simulated firstly.According to the welding data and parameters provided in the field,the simplified model of rear donkey head is used for finite element simulation analysis,and the temperature field distribution results of the model are obtained by the birth death element method,and the welding residual stress size and distribution law are obtained by the coupling method.Taking CYJS10-5-37 HB pumping unit as the prototype,aiming at the variable four-bar mechanism of double horsehead pumping unit,a virtual prototype of double horsehead pumping unit is constructed by using ADAMS.Taking the rear horsehead as the flexible body,the whole rigid flexible coupling model is established for dynamic simulation,and the alternating load parameters of the connection between the rear horsehead and the beam during the pumping unit movement are obtained.On the basis of the above research,using the two-way interface of ANSYS and ADAMS software,the stress simulation of the flexible body behind the double horsehead pumping unit is carried out again in ANSYS,and the alternating stress value and the change rule curve of the connection place are obtained.The simulation results are compared with the dynamic stress test results of the rear horsehead in the field,and the reliability of the simulation results is verified.Finally,combined with the characteristics of welding residual stress and working alternating stress,a coupling analysis method is put forward.The welding residual stress is superposed on the calculated alternating stress,and the stress change and its characteristics after superposing are analyzed.The analysis of the coupling results shows that the stress concentration degree increases after the superposition of the two,and the reason of the joint cracking is the result of the joint action of the two,in which the welding residual stress is the main reason.In this paper,the mechanical properties of the connection between the rear donkey head and the beam are analyzed.The research methods and conclusions can provide theoretical basis and scientific basis for the crack and damage of the connection hole between the reardonkey head and the beam,and provide guidance for the improvement and optimization of the double donkey head pumping unit.