Pipeline steel ultrasonic fatigue test sample heat dissipation method
By immersing the ultrasonic fatigue test sample of low-strength pipeline steel in a flowing cooling medium, the problem of burn damage caused by heat accumulation in the sample is solved, and the accuracy and cost of the test data are reduced.
Patent Information
- Application Number
- CN202311827069.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-27
- Publication Date
- 2025-06-27
AI Technical Summary
Low-strength pipeline steel is prone to burning due to internal heat accumulation during ultrasonic fatigue testing, resulting in inaccurate test data.
Using a flowing cooling medium, such as water or deionized water, heat dissipation of the sample is achieved by immersing the ultrasonic fatigue test sample in the cooling medium, and adding corrosion inhibitors to the cooling system to inhibit corrosion.
It effectively avoids burning in the middle of the sample, ensures the accuracy of the test data, and reduces the test cost.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of ultrasonic fatigue testing, and particularly relates to a heat dissipation method for an ultrasonic fatigue test sample of pipeline steel. Background Art
[0002] The change in the performance of a material under repeated stress and strain is called fatigue. After a period of accumulation, if it causes the fracture of a component, it is called fatigue fracture. Usually, pipelines connected to air compressors or equipment generating vibration loads may experience fatigue failure due to high-frequency vibration. During service, oil and gas pipelines are subjected to various alternating stresses, and fatigue fracture is a relatively common failure mode of long-distance oil and gas pipelines. The alternating loads causing pipeline fatigue may come from the pressure fluctuations inside the pipeline or the vibration loads or fluctuating loads outside the pipeline. These factors cause fatigue cracks to initiate at the surface or internal defects of the steel pipe, eventually leading to pipeline fracture or leakage. Judging from the working conditions, this kind of fatigue of pipeline steel belongs to ultra-high cycle fatigue. Therefore, the study of the ultra-high cycle fatigue behavior of pipeline steel is the basis for the safe design of pipelines.
[0003] Since Wohler began fatigue tests in the mid-19th century, there has been a research history of more than 150 years. In the early 20th century, the highest cyclic load frequency that could be achieved using a mechanically driven testing machine was only 33 Hz. In 1911, Hopkinson invented a high-frequency electric resonance fatigue test system with a frequency of 116 Hz. Most of the fatigue data selected by the current main fatigue design codes are based on 10^7 cycle data.
[0004] However, in many industrial sectors, components often bear mechanical conditions of high frequency and low load, and the load cycles of components can reach 10^9 - 10^12 cycles, that is, fatigue of more than 1 billion cycles. Using a 20 Hz fatigue testing machine to test would take up to one and a half years or even longer. The time cost is very high, and if affected by factors such as power outage during the test, the accuracy of the test results is also restricted. This kind of ultra-high cycle fatigue test requires a fatigue testing machine with a higher frequency. In 1950, Mason applied piezoelectric crystals and electromagnetic resonance technology to achieve a vibration frequency of 20,000 Hz, opening up a new front in the field of fracture mechanics research for ultrasonic vibration technology.
[0005] Nowadays, ultrasonic fatigue testing machines have been developed. Their frequency ranges from 15 - 22 kHz. It is a fatigue testing method that can conduct fatigue tests for more than 1 billion cycles, and this fatigue testing method is relatively reliable. Compared with existing fatigue testing machines, under the same conditions, to complete a 1 billion - cycle fatigue test, an ordinary fatigue testing machine (20 Hz) takes about one and a half years, while an ultrasonic fatigue testing machine (20 kHz) only takes about 15 hours. The test time is greatly shortened and the cost is greatly reduced. The ultrasonic fatigue test technology is different from the traditional fatigue test technology. One end of the ultrasonic fatigue specimen is free, and the other end is connected to a displacement amplifier. Under the excitation of the displacement amplifier, it resonates and generates a resonant wave in the specimen. Therefore, the design of the ultrasonic fatigue specimen must meet the resonant conditions of the test system.
[0006] The ultrasonic fatigue test method has unique advantages: The test time is shortened by hundreds or even thousands of times. It is applicable to life tests with extremely high cycle numbers and studies on extremely low crack growth rates, especially for the study of fatigue limits and crack growth threshold values; The output power required for the test equipment is very low (tens of watts to hundreds of watts), which can save a large amount of energy; Saving time and energy also saves the test cost; It can perform random variable - amplitude loading, including low - level loads, thus being closer to engineering reality; When resonating, the stress level at the end of the specimen is very low, which simplifies the specimen clamping. Especially when R = - 1, only one - end clamping is required, which is very beneficial for brittle materials. However, this test technology also has its limitations: Limited by the resonant conditions, it cannot conduct full - scale component tests; It cannot perform single - cycle or low - cycle loading; The stress level needs to be measured through strain measurement and cannot be directly measured; Materials with strong internal friction heat up at high frequencies and need to be cooled.
[0007] Empirically, for high - strength materials with a tensile strength above 1400 MPa during ultrasonic fatigue testing, it is not easy to generate a large amount of heat inside the sample, and air cooling can be used to control the heating of the sample. However, when the tensile strength of the sample is below 1000 MPa, it is very easy to accumulate a large amount of heat inside the sample during ultrasonic fatigue testing, and the middle part of the sample is prone to burnout. This will cause changes in the microstructure of the sample and ultimately lead to inaccurate test data.
[0008] In summary, the heat generation phenomenon of low - strength materials during ultrasonic fatigue testing due to material internal friction has become a technical difficulty in the ultra - high - cycle fatigue testing of low - strength materials. Summary of the Invention
[0009] When conducting ultrasonic fatigue tests on low-strength pipeline steel, a large amount of heat easily accumulates inside the low-strength pipeline steel sample, and the middle part of the sample is prone to burning damage, which causes changes in the microstructure of the sample and ultimately leads to inaccurate test data. The purpose of the present invention is to provide a heat dissipation method for ultrasonic fatigue test samples of pipeline steel, which overcomes the technical problem of insufficient cooling caused by using compressed air for air-cooled convection zones, resulting in sample burning damage and affecting test results.
[0010] To achieve the above object, the technical solution adopted by the present invention is as follows:
[0011] A heat dissipation method for ultrasonic fatigue test samples of pipeline steel, comprising the following steps:
[0012] Immerse the ultrasonic fatigue test sample of pipeline steel undergoing ultrasonic fatigue tests in the flowing cooling medium within the heat dissipation system for cooling.
[0013] Further, the cooling medium is water.
[0014] Further, the cooling medium is deionized water.
[0015] Further, the cooling medium is deionized water containing a corrosion inhibitor.
[0016] Further, the mass concentration of the corrosion inhibitor in the cooling medium is 0.8%.
[0017] Further, the corrosion inhibitor is a water-soluble imidazoline corrosion inhibitor.
[0018] Further, the heat dissipation system includes a cooling water tank, an upper water tank, an outlet water tank, a first plastic conduit, a second plastic conduit, and a water pump. The upper water tank is arranged at the upper end on one side of the cooling water tank, the outlet water tank is arranged at the lower end on the other side of the cooling water tank. The cooling water tank is provided with an inlet and an outlet. The upper water tank is connected to the cooling water tank, and the outlet water tank is connected to the cooling water tank.
[0019] Further, the upper water tank is connected to the cooling water tank through the first plastic conduit via the water pump, and the outlet water tank is connected to the cooling water tank through the second plastic conduit.
[0020] Further, the cooling water tank is provided with a chuck for fixing the ultrasonic fatigue sample in the cooling water tank.
[0021] Further, a temperature sensor is arranged inside the cooling water tank. When the water temperature collected by the temperature sensor exceeds 30°C, the flow rate of the cooling medium is increased.
[0022] Compared with the prior art, the beneficial effects of the present invention are:
[0023] The present invention aims at samples for ultrasonic fatigue testing, and uses a flowing cooling medium to dissipate heat from the samples. Through the flowing cooling medium, a large amount of heat that easily accumulates inside the samples during ultrasonic fatigue testing can be taken away, avoiding the problem of easy burnout in the middle of the samples, and enabling accurate test data for the microstructure of the samples.
[0024] Furthermore, water is a good cooling medium for absorbing and transferring heat. Immersing the ultrasonic fatigue test samples in water will not result in dead angles caused by air convection. In this way, the heat dissipation problem at the key parts of the ultrasonic fatigue samples of low-strength steel during the testing process can be solved.
[0025] Furthermore, if the cooling medium is deionized water, the presence of corrosive ions in the water will cause corrosion on the surface of the ultrasonic fatigue test samples. After the corrosion phenomenon occurs, corrosion defects will appear on the surface, resulting in inaccurate test results. Therefore, deionized water is used as the cooling medium.
[0026] Furthermore, if the cooling medium is flowing, if the cooling water in the cooling water tank does not flow, the water temperature will rise after a period of time. The method to solve the problem of rising water temperature is to make the water flow. In this regard, the cooling water tank is specially designed. The water inlet is close to the upper end of the cooling water tank, and the water outlet is close to the lower end of the cooling water tank. The power for making the water flow comes from the water pump and the self-gravity of the water. In this way, heat will be taken away and dissipated into the air during the process of cooling water circulation, and this process will achieve good heat dissipation of the ultrasonic fatigue samples, achieving the cooling effect.
[0027] Furthermore, adding a corrosion inhibitor to the deionized water can inhibit the corrosion of the oxygen in the deionized water on the ultrasonic fatigue samples of low-strength steel, so as to better protect the samples from corrosion while achieving good cooling effects. Description of the Drawings
[0028] Figure 1 is a schematic structural diagram of the heat dissipation system adopted by the present invention;
[0029] Figure 2 is the fracture morphology of the sample in Example 1. Among them, (a) is the fracture with air cooling by compressed air, and (b) is the fracture after water cooling.
[0030] In the figure, 1 is the cooling water tank, 2 is the upper water tank, 3 is the water outlet tank, 4 is the first plastic conduit, 5 is the second plastic conduit, 6 is the water pump, 7 is the chuck, and 8 is the ultrasonic fatigue sample. Detailed Embodiments
[0031] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. The preferred embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present invention more thorough and comprehensive.
[0032] To solve the heat dissipation problem of the key parts during the ultrasonic fatigue test of low-carbon pipeline steel samples, a heat dissipation method for ultrasonic fatigue test samples of pipeline steel according to the present invention includes the following steps:
[0033] (1) Using water as the cooling medium, during the ultrasonic fatigue test, the ultrasonic fatigue test sample is immersed in water at room temperature for cooling.
[0034] Water is a good cooling medium for absorbing and transferring heat. Immersing the ultrasonic fatigue test sample in water can achieve the cooling effect of the sample. At the same time, the key parts of the sample are completely immersed in water, and there will be no dead angles caused by air convection. In this way, the heat dissipation problem of the key parts of the low-strength steel ultrasonic fatigue sample during the test can be solved. Using water medium as the cooling medium, the heat dissipation system used for dissipating heat from the ultrasonic fatigue sample is as Figure 1 shown. The heat dissipation system is composed of five main parts: a cooling water tank 1, an upper water tank 2, a water outlet tank 3, a first plastic conduit 4, a second plastic conduit 5, and a water pump 6. The ultrasonic fatigue sample 8 is arranged in the cooling water tank 1 through a chuck 7. The upper water tank 2 is arranged on one side of the cooling water tank 1, and the water outlet tank 3 is arranged on the other side of the cooling water tank 1. The cooling water tank 1 is provided with a water inlet and a water outlet. The upper water tank 2 is connected to the cooling water tank 1 through the first plastic conduit 4 by means of the water pump 6, and the water outlet tank 3 is connected to the cooling water tank 1 through the second plastic conduit 5.
[0035] Preferably, a temperature sensor is arranged in the cooling water tank 1. When the water temperature collected by the temperature sensor exceeds 20°C, the water flow rate is increased to make the water temperature not higher than 20°C.
[0036] The cooling system structure in the present invention is very simple, is very easy to be integrated into the ultrasonic fatigue testing machine, and the operation is also very simple. This is conducive to ensuring the experimental accuracy and better serving the ultrasonic fatigue test of low-strength pipeline steel. This cooling method is also pollution-free, the cooling medium can be recycled, and the cost is very low. It will not bring additional financial expenditure to the ultrasonic fatigue test.
[0037] The water used in the cooling system should be deionized water. If there are corrosive ions in the water, it will cause corrosion on the surface of the ultrasonic fatigue test sample. After the corrosion phenomenon occurs, corrosion defects will be generated on the surface, resulting in inaccurate test results. The method to solve this problem is to remove the ions in the water, that is, using deionized water as the cooling medium.
[0038] The cooling medium should flow. If the cooling water in the cooling water tank 1 does not flow, the water temperature will rise after a period of time. The way to solve the problem of rising water temperature is to make the water flow. For this problem, a special design is carried out for the cooling water tank 1. The water inlet is close to the upper end of the cooling water tank 1, and the water outlet is close to the lower end of the cooling water tank 1, as Figure 1 shown. The power to make the water flow comes from the water pump 6 and the self-gravity of the water. In this way, heat is taken away and dissipated into the air during the process of cooling water circulation. This process can achieve good heat dissipation of the ultrasonic fatigue sample and achieve the cooling effect.
[0039] (2) Prepare the cooling medium by mixing an inhibitor and deionized water to inhibit the corrosion of the ultrasonic fatigue sample of low-strength steel.
[0040] Using deionized water as the cooling medium can solve the corrosion problem of the ultrasonic fatigue sample of low-strength steel caused by ions in the water. However, in addition to ions, oxygen is also an influencing factor for the corrosion of low-strength steel. Therefore, an inhibitor needs to be added to the cooling medium. The corrosion process of metals is usually an electrochemical reaction process, which consists of two main reactions, the cathode reaction and the anode reaction. According to the basic principles of electrochemistry, controlling one of the reaction processes can achieve the inhibition of metal corrosion. Here, an inhibitor is used to inhibit the cathode reaction of low-strength pipeline steel to achieve the effect of inhibiting its corrosion, so as to better protect the sample and avoid corrosion while achieving a good cooling effect.
[0041] The inhibitor in the present invention uses a water-soluble imidazoline inhibitor with excellent corrosion inhibition performance for pipeline steel, and its mass fraction in water is 0.8%.
[0042] Example 1
[0043] (1) Prepare an ultrasonic fatigue test sample of low-carbon pipeline steel;
[0044] (2) Install the sample on the chuck of the ultrasonic fatigue testing machine.
[0045] (3) Inject 3L of deionized water into the upper water tank.
[0046] (4) Add an inhibitor to the upper water tank so that the mass concentration of the inhibitor is 0.8%, and use a glass rod to stir the inhibitor evenly.
[0047] (5) Start the water pump to inject cooling water into the cooling water tank until the key test part of the ultrasonic fatigue sample is completely immersed in the cooling water.
[0048] (6) Set the parameters on the ultrasonic fatigue testing machine, the load is 380 MPa, the frequency is 20 kHz, the interval time is 1500 ms, and start the ultrasonic fatigue testing machine to start the test.
[0049] (7) Open the drain valve to make the water flow system flow automatically until the test is completed.
[0050] (8) After the sample breaks, turn off the water pump and take out the sample; the sample number is 1#-1;
[0051] Repeat the process of Example 1 twice, and the obtained sample numbers are 1#-2 and 1#-3. Record the test results, see Table 1.
[0052] Table 1 Ultra-fatigue test data and results of water-cooled pipeline steel
[0053]
[0054] (9) After the test, the fracture morphology of the sample in Example 1 is as Figure 2 shown in (a) and (b).
[0055] From Figure 2 it can be seen that the fracture is damaged by air-cooling with compressed air, and the fracture is not damaged after water-cooling.
[0056] The above is only an illustration of the best embodiment of the present invention, but it should not be construed as a limitation to the claims. The present invention is not limited to the above embodiments, and its specific structure is allowed to vary. Any changes made within the protection scope of the independent claims of the present invention are within the protection scope of the present invention.
Claims
1. A heat dissipation method for an ultrasonic fatigue test sample of pipeline steel, characterized in that, It includes the following steps: Immerse the ultrasonic fatigue test sample of pipeline steel for ultrasonic fatigue test in the flowing cooling medium in the heat dissipation system for cooling.
2. The heat dissipation method of the ultrasonic fatigue test sample of the pipeline steel according to claim 1, characterized in that The cooling medium is water.
3. The heat dissipation method of the ultrasonic fatigue test sample of the pipeline steel according to claim 1, characterized in that, The cooling medium is deionized water.
4. The heat dissipation method of the ultrasonic fatigue test sample for pipeline steel according to claim 1, wherein, The cooling medium is deionized water containing an inhibitor.
5. The heat dissipation method of the ultrasonic fatigue test sample for pipeline steel according to claim 4, characterized in that, The mass concentration of the inhibitor in the cooling medium is 0.8%.
6. The heat dissipation method of the ultrasonic fatigue test sample for pipeline steel according to claim 4, characterized in that The inhibitor is a water-soluble imidazoline inhibitor.
7. The heat dissipation method of the ultrasonic fatigue test sample of the pipeline steel according to claim 1, wherein, The heat dissipation system includes a cooling water tank (1), an upper water tank (2), an outlet water tank (3), a first plastic conduit (4), a second plastic conduit (5) and a water pump (6). The upper water tank (2) is arranged at the upper end on one side of the cooling water tank (1), and the outlet water tank (3) is arranged at the lower end on the other side of the cooling water tank (1). The cooling water tank (1) is provided with an inlet and an outlet. The upper water tank (2) is connected to the cooling water tank (1), and the outlet water tank (3) is connected to the cooling water tank (1).
8. The heat dissipation method of the ultrasonic fatigue test sample for pipeline steel according to claim 7, characterized in that, The upper water tank (2) is connected to the cooling water tank (1) through the first plastic conduit (4) via the water pump (6), and the outlet water tank (3) is connected to the cooling water tank (1) through the second plastic conduit (5).
9. The heat dissipation method of the ultrasonic fatigue test sample for pipeline steel according to claim 7, wherein The cooling water tank (1) is provided with a chuck (7) for fixing the ultrasonic fatigue sample (8) in the cooling water tank (1).
10. The heat dissipation method of the ultrasonic fatigue test sample of the pipeline steel according to claim 7, wherein, A temperature sensor is arranged in the cooling water tank (1). When the water temperature collected by the temperature sensor exceeds 30 °C, the flow rate of the cooling medium is increased.