Analyses on load stress and strain of oil tube in pupming well

In order to measure the load,stress and strain of oil tube,a device for measuring the load was developed,and a test bench for simulating the operation situation of tube was set up.Based on the experimental data,the stress and strain of oil tube were calculated by means of the finite element software ANSYS.The results show that the tube in pumping well is subjected to tensile-tensile fatigue load and situated in the condition of forced vibration with damping,which may be the basic factors resulting in the fatigue fracture of tube.The most dangerous point is at the root of the first engaged tooth of a joint.Generally,the biggest values of stress and strain may exceed the yield limit.Though the stress and strain values are high,the elastic stress and strain amplitudes at the most dangerous points are low,so as the oil tube can go into service for a long time.When non-normal conditions appear,the biggest stress and strain would get into the strengthened phase,and the larger plastic strain amplitude will be produced under the action of a circulating load,which results in the fatigue fracture of oil tube.