Self-enhancement pressure optimization and residual stress field life evaluation of high-power fracturing pump hydraulic cylinder

YAO Kong

doi:10.16579/j.issn.1001.9669.2026.08.014

Abstract：[Objective]To enhance the fatigue life of high-power fracturing pump hydraulic cylinders under ultra-high alternating pulse loads,a quantitative correlation analysis method between autofrettage residual stress and hydraulic cylinder fatigue life was established based on the thick-walled cylinder autofrettage mechanism.[Methods]Firstly,six pressure levels of autofrettage process parameters were designed by taking the minimum allowable maximum autofrettage pressure,and a three-dimensional model of the 5 000 HP type fracturing pump hydraulic cylinder was established to provide a geometric basis for subsequent finite element simulation analysis.Secondly,a finite element model of the hydraulic cylinder was developed,and the distribution patterns of residual stress under different autofrettage pressures and the superposition effects of working loads were simulated by combining Ansys software and Miner's linear cumulative damage rule,with the fatigue life safety factor calculated accordingly.Then,the residual stress and superimposed stress were measured using X-ray diffraction method and strain gauge method,respectively,to verify the effectiveness of the simulation results.Finally,the fatigue life of the hydraulic cylinder before and after autofrettage treatment was compared through field fracturing operation tests.[Results]The results show that the optimal autofrettage performance is achieved at an autofrettage pressure of 430 MPa.The simulated residual compressive stress on the inner wall of the hydraulic cylinder reaches 723 MPa,the maximum combined stress on the inner wall under working conditions is reduced by 51％,and the fatigue life safety factor is increased to 2.05 times that before autofrettage.The optimal residual stress measured in the test is 732.1 MPa,and the optimal superimposed working stress is 335.5 MPa.The field operation tests verify that the fatigue life of the hydraulic cylinder after autofrettage treatment is extended by 2.4 times compared with that of the untreated one.