Prediction method based on strain monitoring for thread root crack in high pressure hydraulic fracturing manifold

There is a high stress concentration at the connection threads of high-pressure manifolds. Under the action of internal pressure(Pint) and rapid vibration, the root of the thread is prone to fatigue cracking. To study the variation in the damage of a high-pressure manifold with connection threading, this paper first analyzed the strain of the manifold with different Pint and with or without defects at different positions on the outer wall shaft. The potential fatigue crack damage of a high-pressure manifold of a hydraulic fracturing truck was monitored and analyzed by strain testing technology. The variation of the strain signals of defected and defect-free high-pressure pipe fittings were compared. The damage stress concentration point of the connection thread of the high-pressure manifold was analyzed. When there is a crack at the root of the thread, results show that there is a large difference in strain in the axial direction of the crack compared to the strain in threading thread without a crack. Meanwhile, the strain concentration coefficients of different stress concentration points change regularly. In this paper, the damage state of the thread is analyzed by strain monitoring. The results can provide a theoretical and practical basis for the prediction of root cracks in connection threads.