| In oil and gas drilling production,the solid-liquid coupling due to discontinuous fluid pressurization often causes high-pressure tubes vibrations that will bring the tubes about sufferring complex loads and stress concentration,meanwhile,in the condition of high-speed liquid carrying sand erosion wearing,high-pressure tubes are prone to occurring stress corrosion cracking,erosion failure,puncture leakage and other damage.Therefore,it is of great importance to carry out studying on the safety inspection and evaluation of high-pressure tubes as well as the characteristics of the tube-fluid-solid coupling vibration.Based on the ANSYS software,this paper simulated and analyzed the characteristics of the solid-liquid coupling vibration of the high-pressure tubes,also provided theoretical basis and magnetic memory testing standards for the erosion damage of high-pressure tubes in service.(1)By bringing to bear on continuous pulse pressure at the inlets of the pipes,the vibration displacement characteristics,the vibration velocity characteristics and the mechanical characteristics of the straight pipe section,the elbow pipe section and the precast erosion damage elbow pipe section of high-pressure tubes were simulated and calculated.By means of comparing the calculation results of the solid-liquid coupling vibration of the three simulation models,the influence of different pipe structures on the effect of the solid-liquid coupling and the impact of the mechanical properties which the solid-liquid coupling led to on the equivalent stress distribution state of the pipe were researched.The results of the study showed that:The fluid solid coupling produced by the hydraulic pressure at the turn of bend had great influence on the dynamic characteristics of the tube vibration.At the same time,the continuous pulse water pressure had great influence on the average velocity of fluid solid coupling vibration in the joint part,but had little effect on the velocity amplitude.When the elbow section containing erosion damage was subjected to hydraulic pressure,the phenomenon of equivalent stress concentration occurred at erosion damage.(2)The erosion test of 35 CrMo steel commonly used for manifolds was carried out by the method of injection flow carrying with sand,and the relationships between erosion loss weigh by weight loss method of 35 CrMo steel samples and erosion angle,erosion velocity were studied respectively,and the microstructure of the erosion zone was observed to reveal the erosion mechanism by scanning electron microscope,a formula for assessing the erosion degree of the samples was also proposed.The results of the study showed that: The weight loss of 35 CrMo steel increased with the increase of impact velocity and particle size,and reached the maximum when the impact angle was 30 degrees.When the impact angle was low,the cutting effect of sand was the main cause of material loss.When the impact angle was high,the material was mainly damaged by the extrusion deformation of sand.The cutting weight loss and total weight loss of 35 CrMo steel were sensitive to the change of impact angle and impact speed,and the change trends were very similar.(3)Using metal magnetic memory testing technology,the quantitative relationship between the characteristic parameters of high-pressure tubes' magnetic memory signal and wall thickness,wall thickness variation were studied respectively.By designing the wall thickness of high-pressure tubes as two forms of equal increment and unequal increment.,then the quantitative relationships between the characteristic parameters of magnetic memory testing signal and wall thickness,wall thickness variation could be fitted.The experiment results showed that the relationship between the signal gradient value and wall thickness was found as linear increasing,the signal gradient wave peak value and signal gradient peak width took respectively on a linear increasing relationship with wall thickness variation.(4)The study of magnetic memory detection for erosion and wear state of 35 CrMo steel commonly used for high-pressure tubes.The erosion test equipment and surface topography scanning device were used for studying the change of magnetic memory phenomenon of 35 CrMo steel with different erosion speed as well as tensile load under the condition of hydraulic fracturing,and the relationships between magnetic memory phenomenon and surface morphology,erosion rate,etc.The results of study showed that: The intersection distance and the peak value of gradient reflected the width of erosion damage,the peak value of gradient and the gradient peak-peak value reflected the depth of erosion damage and the erosion wear quality,the peak value of gradient reflected the stress concentration of erosion damage,the increment of gradient peak-peak value reflected the change rate of weight loss.Under the condition of low speed and light load of solid-liquid erosion,the intersection distance?the peak value of gradient?the gradient peak-peak value and the erosion wear quality of 35 CrMo steel's erosion surface all increased with the increase of impact velocity and tensile load.By means of fitting test variables and signal parameters,this paper established the relationship between erosion performance of high-pressure tubes and external environment parameters,also expanded the application of magnetic memory testing technology in the detection of high-pressure tubes' erosion damage,at the same time,based on the ANSYS software,the vibration characteristics of tubes caused by solid-liquid coupling were simulated and studied,it provided theoretical basis and standard for studying erosion damage and vibration failure of in-service high-pressure tubes.The research findings can effectively reduce the risk of high-pressure tubes' accident such as washout,cracking and leakage caused by erosion failure and tubes' structure destruction as results of tube vibration. |
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