Objective To address the unclear mechanical behaviors of ultra-high-pressure (UHP) wellhead flanges under the coupled action of axial force, internal pressure and moment, a deformation-based moment calculation method is proposed, providing theoretical support for the design of non-standard flanges with a pressure rating of 175 MPa.
Method By combining finite element simulations with composite loading tests, a flange deflection angle-moment calculation model was established. Strain gauges were employed to monitor the stress distribution of the flange during loading, and comparative analysis between simulation results and experimental data was conducted to verify the accuracy and applicability of the proposed model.
Result The relative error of moment calculation for the proposed model did not exceed 15%. Under the C8 condition, the stress on the inner side of the flange midsection reached 471.69 MPa, which was 2.1 times that on the outer side but still below the material yield strength. Moreover, when the axial force increased to 18 000 kN, the elastic coefficient rose by 5.63 times.
Conclusion The proposed method enables accurate quantification of flange moment under multi-load coupling, reveals the axial force-dominated variation rules of the elastic coefficient, and provides a new approach for the safe design of UHP flanges.
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