| According to data collection of oil field, Fatigue Fracture is the main reason to failures of Sucker rod. It is agreed that the life of a Sucker rod relates to fatigue crack life which initiate as surface crack. Therefore, it is very important to study the propagation of surface crack.On the background of engineering application of30Mn2SiV sucker rod, this paper studied the residual life of fatigue crack expanded time by experimental method and numerical analysis.Firstly, tested by three-point bending test the crack propagation law of30Mn2SiV sucker rod. Based on the a-N data fitting obtained the material constants C, m.Secondly, based on three-point bending test use of the relationship of crack growth rate and stress-intensity factor range.Obtained approximate expression of the stress intensity factor by James-Anderson method.In this paper, straight edge surface crack under cyclic tensile loading the crack shape evolution were discussed.Based on the experimental results adove, using the finite element method to calculate the three-dimensional surface crack under tensile loading in the stress-intensity factor.By calculation, this paper gives the deepest point of surface cracks and surface point variation of stress-intensity factor. In addition, the initial crack for the linear and circular cracks were calculated, the deepest point of the crack front line obtained the stress intensity factor is greater than the surface.The stress-intensity factor, while the opposite circular crack.After comparing with the experimental results, we can see the validity of this method.In this paper, the shape changes of crack propagation has been predicted by numerical simulation method. Obtained the stress amplitude has little effect on the crack morphology; Initial crack depth have a significant impact on crack morphology such influence will increase as the crack depth gradually weakened; Any initial crack in the crack under cyclic tensile load will rapidly oval shape, elliptic curvature will show from small to big in the smaller of the feature, the maximum curvature occurs near0.8.Finally, based on the finite element calculated stress intensity factors calculated the remaining life of30Mn2SiV sucker rods. This paper identifies a variety of conditions in the initial crack length of remaining life. This result is the possibility of using residual life of sucker rods to provide a basis. |
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