Fracture failure analysis and structure improvement on thread joint of turbine shaft. (September 2020) - Liu, Yang
Highlights: Did the testing of composition and mechanical properties about material. The largest stress of the thread joint was brought about by a larger torque. Carried out the three-dimension simulation of 4 1/2 in. REG. Mechanical strength analysis and structural improvement of thread. Abstract: Macroscopic and microscopic analysis of the fracture of turbine shaft joint was carried out in this paper. A number of groups of tensile and impact tests have been done after fracture sampling, the stress-strain curve and impact toughness curves of fracture materials are obtained, and the mechanical properties of turbine shaft materials are further tested. The microscopic analysis shows that the fracture surface is mainly distributed with a lot of quasi-cleavages, indicating that the material of turbine shaft is mainly brittle. In addition, establish a full-structure finite element analysis model of three-dimensional of thread joint to fit the various load conditions in the borehole accurately. In order to improve its torsion, tension and bending resistance, this paper improves the conventional American Petroleum Institute standard thread and proposes a double-shoulder structure thread. It is also found that the maximum stress value of double-shoulder thread is lower than that before the improvement. Comprehensive analysis shows that fracture of turbine shaft joint caused by structural design and material defects.