CN-121994629-A - Fatigue test device and method for simulating underwater wave current scouring

CN121994629ACN 121994629 ACN121994629 ACN 121994629ACN-121994629-A

Abstract

The invention discloses a fatigue test device and method for simulating underwater wave current scouring. The device comprises a flushing system and a fatigue system, wherein the flushing system comprises a box body, an upper fixing plate, a lower fixing plate, a vertical rod group, a fluid monitoring probe, a fluid data acquisition system, a medium mixing tank, a proportioning pump and a flowmeter, and the fatigue system comprises a fatigue testing machine. The using method is that after the yield strength of the sample is tested by the tensile test of the static force, the sample is arranged on a fatigue tester, the seawater with the target silt content is conveyed to the box body at a certain flow rate, and the fatigue performance of the sample is measured by adopting a lifting method until the sample breaks. The device can test the fatigue performance of the metal material, the arc additive manufacturing structural member or the welding joint in the wave flow scouring environment of the simulated marine platform vertical pipe system, truly and accurately simulates the service environment of the marine platform vertical pipe system, and the obtained fatigue performance result can evaluate the safety of the structural member.

Inventors

AI FANGFANG
CHEN YIQING
WANG JIAJI
ZHONG BIN
HU FENGYA
GAO PENG
LI LIN
WANG CHU

Assignees

鞍钢股份有限公司

Dates

Publication Date: 20260508
Application Date: 20250122

Claims (10)

1. A fatigue test device for simulating underwater wave flow flushing is characterized by comprising a flushing system and a fatigue system, wherein the flushing system simulates a wave flow flushing environment to construct horseshoe-shaped vortex and denuded vortex, a fatigue performance test is conducted on a sample in the wave flow flushing corrosion process, the flushing system comprises a box body (1), an upper fixing plate (2), a lower fixing plate (3), a vertical rod (4) group, a fluid monitoring probe (5), a fluid data acquisition system (6), a medium mixing tank (9), a proportioning pump (10) and a flowmeter (11), the fatigue system comprises a fatigue test machine (7), the box body (1) is provided with the upper fixing plate (2) and the lower fixing plate (3) up and down, a space formed by the upper fixing plate (2) and the lower fixing plate (3) is a wave flow flushing space, the upper fixing plate (2), the lower fixing plate (3) are symmetrically provided with a mounting hole I (12) and a plurality of mounting holes II (13), the sample (8) penetrates through the mounting hole I (12) to be connected with the fatigue test machine (7) through threads, the vertical rod (4) is mounted between the upper fixing plate (2) and the lower fixing plate (3) and the fluid monitoring probe (5) through the mounting hole II (13), the fluid monitoring probe (5) is connected with the fluid monitoring system (5) in a circumferential direction, and the fluid monitoring system is connected with the fluid monitoring system (5) The proportioning pump (10), the flowmeter (11) and the box body (1) are sequentially connected through pipelines to form a loop.
2. The fatigue test device for simulating underwater wave flow flushing according to claim 1, wherein the number of standing bars (4) is not less than 14.
3. The fatigue test device for simulating underwater wave flow flushing according to claim 2, wherein the vertical and horizontal distances between adjacent vertical bars (4) are equal.
4. The fatigue test device for simulating underwater wave flow scouring according to claim 1, wherein the vertical rod (4) is a cylinder, polytetrafluoroethylene or organic glass material is adopted, and the diameter of the vertical rod (4) is 1-3 times of the diameter of the clamping section of the sample (8).
5. The fatigue test device for simulating underwater wave flow scouring according to claim 1, wherein the sample (8) is a circular sample with a surface roughness of less than 0.8 μm.
6. The fatigue test device for simulating underwater wave flow flushing according to claim 1, wherein the wave flow flushing space height in the flushing system box body (1) is larger than the sum of the transition section and the parallel section length of the sample (8), and the distance between the outer vertical rod (4) and the box body wall is more than or equal to 0.7m.
7. The fatigue test device for simulating underwater wave flow flushing according to claim 1, wherein the horizontal position set by the fluid monitoring probes (5) is the midpoint position of the sample (8), and the number of the vertical rods (4) and the number of the fluid monitoring probes (5) in the circumferential direction is more than or equal to 4.
8. A method of using the fatigue test device for simulating underwater wave flow scouring according to any one of claims 1 to 7, wherein, Step one, adjusting the distance between vertical rods (4), and enabling fluid to enter a flow speed test parameter of a box body (1) so as to simulate a target wave flow form; step two, carrying out tensile test through a static test to determine the yield strength of the sample (8); Step three, conveying a fluid medium into a box body (1) at the flow rate determined in the step one, mounting a sample (8) on a fatigue testing machine (7), carrying out an axial fatigue test on the sample (8) under preset stress, stress ratio and loading frequency, measuring the fatigue performance of the sample (8) by adopting a lifting method, wherein each test is carried out until the sample (8) breaks, and the cycle corresponding to the breaking is taken as the fatigue life of the sample (8) under the corresponding test condition, and the fatigue cycle number of the sample (8) exceeds 10 7 ; And step four, after the fatigue test is finished, derusting the working section of the sample (8) by using a derusting liquid, washing with deionized water, and drying for subsequent observation.
9. The method for using the fatigue test device for simulating underwater wave flow flushing according to claim 8, wherein the method for determining the space between the vertical rods (4) and the flow rate test parameters of the fluid entering the box body (1) is characterized in that a proportioning pump (8) is used for conveying the uniformly mixed simulated fluid medium into the box body (1), a fluid monitoring probe (5) is used for monitoring the flow rate and the flow direction of the fluid, data are collected every 15 minutes, a fluid waveform chart is obtained through a fluid data collecting system (6), whether the fluid forms horseshoe-shaped vortex and the denuded vortex is judged, if not, the space between the vertical rods (4) and the flow rate of the fluid entering the box body (1) are continuously adjusted until the form of the target wave flow is formed.
10. The method for using a fatigue test device for simulating underwater wave flow flushing according to claim 9, wherein the stress ratio R is-1 to 0.5, the loading frequency is 1 to 60hz, the loading stress is 0.1R el ～0.3R el , and the loading waveform is a sine wave.

Description

Fatigue test device and method for simulating underwater wave current scouring Technical Field The invention relates to the field of metal materials, in particular to a fatigue test device and method for simulating underwater wave current scouring. Background Ocean platforms are key equipment for offshore oil development and mainly consist of a foundation part, a riser system, an upper structure and a fixing system. Wherein the riser system is responsible for bearing the weight of the superstructure, is affected by ocean wave current scouring and load changes, is severely serviced, and the combined action of these factors threatens the riser system to be functionally degraded. The marine platform riser system consists of a riser, a horizontal pipe and a jacket pile, wherein the riser and the horizontal pipe are supported by adopting metal materials and are connected and assembled through a welding process. But with the rapid development of the arc additive manufacturing technology, the arc additive manufacturing technology has the advantages of high material utilization efficiency, low cost, high generation efficiency and the like, is particularly suitable for manufacturing marine platform risers, horizontal pipes and supporting structures, and has wide application prospect. The process parameters of arc additive manufacturing, such as current, voltage, welding speed, etc., have a significant impact on the fatigue performance of the structure, and internal defects, such as pinholes, inclusions, unfused, etc., may be generated during the manufacturing process, which have an adverse impact on the fatigue performance of the structure. Therefore, the metal materials in the riser system are prone to corrosion loss, scouring loss and fatigue crack in the long-term service process, so that the bearing capacity of the platform structural member and the whole is reduced, and the service safety of the structure is seriously affected. Through research, the original ocean current state of the area is changed by the establishment of the platform vertical pipe system, so that the surrounding water flow condition is very complex. The secondary flow is formed in front of the vertical pipe system, and a vortex is formed around the secondary flow, so that the scouring strength is increased, the vertical pipe system is subjected to scouring corrosion, the stress state of the pile top is changed due to scouring, the length of the equivalent pile is increased, the lateral rigidity and the internal force of the structure are influenced, and the stability of the platform is further influenced. Corrosion fatigue is the process of brittle fracture of a metallic material under the combined action of a load and a corrosive medium, periodically or aperiodically alternating. In the service process, the platform riser system is subjected to repeated actions of environmental loads such as sea waves, ocean currents and the like besides facing complex wave current scouring corrosion in the sea water, and continuously changing stress is generated in the structure. Defects in the structural member are very likely to be a source of cracks in corrosion fatigue, resulting in a decrease in fatigue toughness. Therefore, the fatigue performance test under the flushing of the service wave flow is necessary for the ocean platform structure. The invention discloses an intelligent acceleration dynamic water flushing and dynamic load fatigue loading composite tester and a method (publication No. CN 117451557A), which belong to the pavement material testing technology and are used for testing the service performance and durability of a large-gap asphalt mixture in a complex environment, wherein the related dynamic water flushing refers to a water film covering pavement, the related fatigue refers to repeated rolling of vehicle load, and the problem of sea water wave flushing and the fatigue of hydrogen environment are not related. The utility model discloses a concrete scouring test device under the coupling effect of load and environment (publication No. CN 216386650U), which relates to a scouring fatigue test of a concrete engineering structure in a simulated sea wave environment, and does not relate to wave flow scouring and fatigue performance problems. The invention discloses an experimental device for simulating scour fatigue (publication number CN 107202740B), which is applied to scour fatigue tests of high-speed rotating parts such as engine compressor blades and wind driven generator blades, and does not relate to the problems of scouring and fatigue of metal structures and wave currents in marine environments. In summary, the above-described published patent is not directed to testing the performance of a marine platform riser system under the combined effects of wave flow flushing and fatigue, and does not build the wave flow patterns of the marine platform riser environment. Therefore, the test device and the test method for testing the fati