Support test method and device for ship oil delivery pipe

Abstract

The invention discloses a supporting test method and device for a ship oil conveying pipe. The method comprises the following steps that an oil pipe supporting test piece is installed in an experimental device; arranging a strain measuring device on the surface of the test piece and collecting strain response data; setting loading conditions, and executing static loading and fatigue loading on the test piece; and recording response data of the test piece and performing fatigue life evaluation. The device comprises an oil pipe test piece and a servo telescopic cylinder, two ends of the oil pipe test piece are respectively hinged with a floating joint of the servo telescopic cylinder and a fixed seat, a seat body of a base of the servo telescopic cylinder is fixed on a mounting seat, the tail part of the servo telescopic cylinder is hinged with the other fixed seat, the servo telescopic cylinder and the oil pipe test piece are coaxial, and the oil pipe test piece is connected with an oil path system.

Description

Technical Field

[0001] The invention relates to a support test method and device for a ship's oil pipeline. Background Art

[0002] In a ship's propulsion system, the in-shaft oil pipe carries the crucial task of transporting lubricating oil to the propeller tail shaft and its supporting bearings. Due to the complex environment in which it operates, the pipe must withstand frequent alternating loads over its long service life while also maintaining high structural strength and sealing performance. Especially during long-distance, high-speed, or frequently shifting voyages, the pipe support structure is susceptible to structural failures such as fatigue cracks and localized deformation, posing a potential threat to the safety and reliability of the entire ship's propulsion system.

[0003] Currently, fatigue life assessments of in-shaft oil pipe support structures rely heavily on finite element simulations and static strength verification, lacking a systematic physical test verification path. This makes it difficult to fully reflect the fatigue evolution of the structure under actual service conditions. Furthermore, traditional fatigue testing systems generally suffer from problems such as a single loading method, poor alignment, and low data acquisition accuracy, making it difficult to meet the engineering requirements for high-precision life assessments. Furthermore, different types of oil pipes vary significantly in structural dimensions, installation methods, and load response, making it difficult to achieve integrated verification and comparative analysis of multiple types of support structures using existing testing methods.

[0004] Therefore, it is urgent to establish an experimental method and device with high-precision loading control, stress monitoring closed-loop feedback and adaptability to multiple types of support structures, so as to realize the fatigue life assessment and failure mechanism research of the in-shaft oil pipe support structure under real working load conditions. Summary of the Invention

[0005] The purpose of the present invention is to solve the above deficiencies in the prior art and to provide a die-cutting device with an automatic calibration function.

[0006] A support test method for a ship oil pipeline comprises the following steps:

[0007] Install the tubing support test piece in the experimental device;

[0008] Arrange a strain measuring device on the surface of the test piece and collect strain response data;

[0009] Set loading conditions and perform static loading and fatigue loading on the test piece;

[0010] Record the specimen response data and perform fatigue life assessment.

[0011] Furthermore, the strain measurement device is a resistance strain gauge, which is attached to the axially symmetrical position of the test piece. After attachment, it is insulated and protected. It is connected to the acquisition system through a wire, and the conductivity and resistance value are tested to see if they meet the requirements.

[0012] Furthermore, data zeroing is performed before loading so that the strain channel output is within a preset error range under no-load conditions. Subsequently, an initial load lower than the rated load value is applied and strain response data is collected. After verifying that the acquisition system is normal, the load is unloaded. The loading parameters are set according to the structural simulation results of the test piece.

[0013] Furthermore, static loading includes incremental loading and load-maintaining operations at multiple loading levels, where the loading levels cover part or all of the rated loading value range. Each level of loading is maintained for a set duration and the strain response is collected. The target stress value is then calculated based on the strain data and the material elastic modulus. If the expected stress standard is not met, the loading parameters are adjusted until the set stress requirement is reached.

[0014] Furthermore, fatigue loading adopts a cyclic loading waveform, the loading stress is set to multiple increasing levels, the loading frequency is controlled within the set range, and multiple cycles are loaded at each level; the state of the test piece is monitored during the loading process. If damage occurs, the loading is terminated and the defect detection technology is used to confirm the damage location; after the fatigue life data is statistically analyzed, the fatigue life median and discrete index are calculated.

[0015] An experimental device applied to the experimental method described in claim 1 includes an oil pipe test piece and a servo telescopic cylinder. The two ends of the oil pipe test piece are respectively hinged to the floating joint and the fixed seat of the servo telescopic cylinder. The base of the servo telescopic cylinder is fixed on the mounting seat, and its tail is hinged to another fixed seat. The servo telescopic cylinder and the oil pipe test piece are coaxial, and the oil pipe test piece is connected to the oil circuit system.

[0016] Furthermore, a first connecting piece and a second connecting piece are provided at both ends of the experimental oil pipe, the first connecting piece includes a first connecting cover, a first connecting ear, and a second connecting ear is provided on the fixed seat, the second connecting piece includes a second connecting cover, a first connecting ear, and a third connecting ear is provided on the floating joint of the servo telescopic cylinder, and the first connecting ear and the third connecting ear of the second connecting piece and the first connecting ear and the second connecting ear of the first connecting piece are hinged by passing a rotating pin shaft, and an oil inlet hole and an oil outlet hole are provided on the surface of the second connecting cover, the oil inlet hole and the oil outlet hole are connected to the control valve, and the control valve is connected to the oil source.

[0017] Furthermore, the first connecting cover and the second connecting cover are threadedly connected to both ends of the oil pipe test piece.

[0018] Furthermore, the mounting seat includes a lower seat and an upper pressure plate, the upper pressure plate is located above the lower seat, the base of the servo telescopic cylinder is located between the upper pressure plate and the lower seat, at least two screws are passed between the lower seat and the upper pressure plate, the screws are distributed on both sides of the base, and nuts are provided at both ends of the screws for locking.

[0019] Furthermore, the servo telescopic cylinder base is provided with a first connecting seat and a second connecting seat at both ends of the base body, the first connecting seat is placed on the mounting seat, and a fourth connecting ear is provided at the tail of the second connecting seat. The fourth connecting ear and the second connecting ear on the fixed seat are hinged by passing a rotating pin shaft, and the first connecting seat and the second connecting seat are connected by at least four connecting rods.

[0020] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0021] By constructing an axis-aligned loading system, a realistic simulation of the forces acting on the tubing support structure during the test was achieved, effectively avoiding stress deviations caused by centering errors in traditional tests and improving loading accuracy and consistency with test data. Secondly, the device employs a servo control system and closed-loop feedback mechanism, using strain gauges to monitor stress states in real time and reversely correct loading parameters. This allows for precise control of the loading waveform, loading frequency, and stress ratio, ensuring the stability and reliability of the test process.

[0022] In terms of data acquisition and lifespan analysis, this invention introduces a high-precision strain acquisition system, combined with staged loading and real-time data recording. This not only accurately records the structural stress response but also identifies key strain trends before initial structural damage, providing a technical basis for early assessment of fatigue processes. Furthermore, the fatigue test utilizes a three-stage loading scheme (1.1x, 1.5x, and 1.9x rated load), which not only ensures test safety but also enhances the lifespan assessment coverage, helping to fully understand the fatigue behavior of the tubing support structure under different stress levels.

[0023] The test system also boasts excellent modularity and adaptability. Through the design of standardized fixtures and connecting components, different types of tubing can be quickly replaced and installed, significantly improving test efficiency and device versatility. Furthermore, the device is easy to maintain and expand, adapting to future life verification requirements under different load spectra or structural configurations. The data processing phase incorporates the logarithmic life median method and standard deviation assessment mechanism, making the life statistics more scientific and engineering-oriented, providing a solid data foundation for structural design optimization and service life management.

[0024] In summary, the present invention not only improves the accuracy and efficiency of fatigue life verification of oil pipe support structures, but also achieves systematic technical optimization in key links such as loading control, structural docking, data acquisition and life assessment. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a flow chart of the experimental method;

[0026] Figure 2 is a schematic diagram of the experimental setup;

[0027] In the figure, 1, fixed seat, 2, second connecting ear, 3, first connecting seat, 4, connecting rod, 5, base, 6, upper pressure plate, 7, second connecting seat, 8, lower seat, 9, floating joint, 10, first connecting ear, 11, second connecting cover, 12, oil pipe test piece, 13, first connecting cover. DETAILED DESCRIPTION

[0028] In order to deepen the understanding of the present invention, the present invention will be further described in detail below with reference to embodiments and drawings. The embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0029] Example 1: Experimental method

[0030] A method for verifying the fatigue life of an in-shaft oil pipe support structure comprises the following steps: test piece preparation and installation; strain measurement system layout; data zeroing and system verification; simulation load setting and preloading; static loading confirmation; fatigue loading test; failure detection and life determination; and life assessment and data analysis.

[0031] The method first installs a tubing support structure with threaded connections as a test piece on a test platform. A servo actuator is then used to construct an axis-aligned loading system, effectively simulating the stress environment under actual working conditions. The strain measurement system is configured by installing resistance strain gauges at multiple symmetrical locations along the tubing support structure's axial direction. These are connected to a strain acquisition system via wires to enable real-time monitoring of axial and circumferential stresses. Zeroing the system under zero load ensures initial data accuracy, and simulated response acquisition under a 0.2 MPa load verifies the reliability of the acquisition system.

[0032] During the simulation load setting phase, multi-level preloads were established based on the finite element simulation results of the tubing support structure to gradually activate the material stress response and ensure structural adaptability. Strain data were collected during the preloading process, and data credibility was enhanced through specimen condition inspections and image recording. Static loading tests were then conducted using a 10-level incremental loading method. The loading scheme was validated when the axial stress reached 16.5 MPa and the circumferential stress reached 33.6 MPa. Otherwise, the loading parameters were adjusted until the standards were met.

[0033] During the fatigue loading phase, a sinusoidal dynamic loading scheme was employed, with a stress ratio of 0.1 and a frequency of 1 Hz, to simulate the alternating stress state experienced by the tubing during service. A total of 15 million fatigue loading cycles were applied at three different levels of overrated load. The system continuously collected strain data to observe the cumulative fatigue evolution. The test was immediately terminated if cracks, damage, or fractures were detected. Dye flaw detection was used to determine the damage location and failure mode, while the number of load cycles was recorded.

[0034] In the final life assessment stage, statistical methods are used to process the fatigue life data of different test pieces, and the logarithmic life median method is used to calculate the life value N50 with a 50% failure probability, and its standard deviation S is calculated to establish a life prediction model and support design improvements.

[0035] This method ensures that the stress state of the oil pipe support structure in the experiment is consistent with the actual use conditions by constructing a loading structure that highly restores the real working conditions, which significantly improves the authenticity and practicality of the fatigue life data. The high accuracy and reliability of data acquisition are guaranteed by the precise strain measurement system and system calibration. The multi-stage preloading and static confirmation steps effectively improve the consistency and safety of the test. The fatigue loading scheme comprehensively covers the fatigue performance under different stress levels, which helps to fully understand the fatigue characteristics of the structure. Failure detection and life statistical analysis ensure the scientific nature of life assessment and the stability of the results, providing a strong basis for product design optimization. The overall method is highly operational and repeatable, which is convenient for promotion and use in actual engineering.

[0036] Example 2: Experimental device

[0037] An experimental device applied to the experimental method in Example 1 includes an oil pipe test piece 12 and a servo telescopic cylinder. The two ends of the oil pipe test piece 12 are respectively hinged to the floating joint 9 and the fixed seat 1 of the servo telescopic cylinder. The body of the base 5 of the servo telescopic cylinder is fixed to the mounting seat, and its tail is hinged to another fixed seat 1. The servo telescopic cylinder and the oil pipe test piece 12 are coaxial, and the oil pipe test piece 12 is connected to the oil circuit system.

[0038] This device utilizes an axially aligned servo telescopic cylinder loading system. The tubing test specimen 12 is hingedly connected to the fixed base 1 via a floating joint 9, ensuring force stability and flexible displacement during loading. The telescopic cylinder base 5 is fixed to the mounting base, forming a closed force transmission structure and achieving a loading path that matches the fatigue loading requirements of the test method. The test specimen is connected via an oil circuit system, enabling hydraulic loading control.

[0039] The device features a compact structure and uniform force lines, making it suitable for high-precision loading conditions and significantly improving the reliability and consistency of test data. Its modular connection structure also facilitates maintenance and reuse, reducing experimental costs.

[0040] In a possible embodiment, the experimental device as described in claim 6, the experimental oil pipe is provided with a first connecting member and a second connecting member at both ends, the first connecting member includes a first connecting cover 13 and a first connecting ear 10, the fixed seat 1 is provided with a second connecting ear 2, the second connecting member includes a second connecting cover 11 and a first connecting ear 10, and the floating joint 9 of the servo telescopic cylinder is provided with a third connecting ear, and the first connecting ear 10 and the third connecting ear of the second connecting member and the first connecting ear 10 and the second connecting ear 2 of the first connecting member are hinged by passing a rotating pin shaft, and an oil inlet hole and an oil outlet hole are provided on the surface of the second connecting cover 11, the oil inlet hole and the oil outlet hole are connected to the control valve, and the control valve is connected to the oil source.

[0041] The connection structure utilizes a multi-stage trunnion pinning system. The ends of the oil pipe are pivotally connected to the fixed base 1 and floating joint 9 via the first and second connecting lugs 2, ensuring angular adaptability and uniform force transmission during test loading. The second connecting cap 11 features oil inlet and outlet ports, which are connected to the control valve and oil source, forming a closed-loop hydraulic system to support high-frequency loading requirements.

[0042] The hinged structure improves connection flexibility, avoids stress concentration caused by rigid connections during loading, and improves the fatigue life of the test piece. At the same time, the control valve system improves loading control accuracy and enhances the overall system response capability.

[0043] In a possible implementation, in the experimental device as claimed in claim 7 , the first connecting cover 13 and the second connecting cover 11 are threadedly connected to both ends of the oil pipe test piece 12 .

[0044] The connection cap is threaded onto the end of the tubing test piece 12, ensuring connection strength and hydraulic tightness. This structure allows for quick connection during test piece replacement or removal, while maintaining good axis alignment and ensuring stable hydraulic loading during testing.

[0045] The standardized threaded connection method has high assembly efficiency and strong repeatability, which helps to improve the adaptability and portability of the overall experimental device and reduce maintenance costs.

[0046] In a possible embodiment, the experimental device as described in claim 6, the mounting seat includes a lower seat 8 and an upper pressure plate 6, the upper pressure plate 6 is located above the lower seat 8, the base 5 of the servo telescopic cylinder is located between the upper pressure plate 6 and the lower seat 8, and at least two screws are passed between the lower seat 8 and the upper pressure plate 6. The screws are distributed on both sides of the base 5, and nuts are provided at both ends of the screws for locking.

[0047] The mounting seat structure consists of a lower seat 8 and an upper pressure plate 6. The servo cylinder base 5 is clamped by a double-layer structure. The screw is used for vertical clamping and is locked by a nut to form a pre-tightening force, realizing the dual functions of installation and stress release, and adapting to loading conditions of different intensities and frequencies.

[0048] This structure facilitates quick installation and fine-tuning of the fixing force, has strong adaptability and stiffness adjustment capabilities, and enhances the versatility and safety of the device under different test conditions.

[0049] In a possible embodiment, in the experimental device as described in claim 9, a first connecting seat 3 and a second connecting seat 7 are respectively provided at both ends of the base body of the servo telescopic cylinder base 5, the first connecting seat 3 is placed on the mounting seat, and a fourth connecting ear is provided at the tail of the second connecting seat 7. The fourth connecting ear is hinged to the second connecting ear 2 on the fixed seat 1 by passing a rotating pin, and the first connecting seat 3 and the second connecting seat 7 are connected by at least four connecting rods 4.

[0050] The servo cylinder base 5 is equipped with connecting bases at both ends. The connecting lugs are pivotally connected to the fixed base 1, enabling flexible force transmission and axis tracking, improving loading stability. A connecting rod 4 connects the two bases to ensure uniform force distribution and structural rigidity, forming a stable loading support system.

[0051] The structure effectively resists lateral disturbances and stress concentration while maintaining precise control of the servo cylinder axis during loading. Connecting rod 4 enhances the overall stability of the system and provides a solid structural foundation for high-frequency fatigue loading.

[0052] Principle: By simulating the typical alternating loads experienced by tubing support structures during shipboard operation, a high-precision, multi-degree-of-freedom loading and monitoring platform was constructed to enable life assessment of multiple models of in-service and optimized tubing support components. The system consists of a tubing test specimen (12), a servo-telescopic cylinder loading system, a strain acquisition unit, an oil circuit control system, and structural connection components. It utilizes servo-controlled hydraulic loading combined with a strain feedback mechanism to achieve dynamic loading.

[0053] During the test preparation phase, the test specimen was threadedly connected to the fixture. A coaxial load-bearing structure was constructed with a floating joint 9 and a fixed base 1 to ensure proper alignment of the structural loading path. Multiple sets of resistance strain gauges were placed axially symmetrically along the tubing and connected to a strain gauge via dedicated wires, forming a real-time strain response monitoring system. Before loading the system, a zero calibration was performed under zero load to ensure the consistency of the acquisition baseline across all channels. An initial small load (0.2 MPa) was then applied to verify the stability and accuracy of the data from each channel.

[0054] The subsequent loading phase sets the target stress values ​​for static and fatigue loading based on the finite element simulation results of the oil pipe structure. Static loads are gradually applied to 100% of the rated value through graded loading, and strain data is collected and the status is confirmed after each level of loading. When the axial stress and circumferential stress reach 16.5MPa and 33.6MPa, respectively, they serve as the standard benchmark for subsequent fatigue tests. During the fatigue test, the system uses sinusoidal wave loading, sets the stress ratio to 0.1, and the loading frequency to 1Hz. It then performs three-stage loading at 1.1 times, 1.5 times, and 1.9 times the rated load, with each stage loading 5 million times and the total number of loading times not exceeding 15 million times. Strain data is continuously recorded during the test.

[0055] If a specimen shows signs of cracking, damage, or fracture, loading is immediately terminated and a color flaw detection test is performed to confirm the damage location and record the cumulative number of loading cycles. Specimens that have not failed are then loaded again until the test is complete. Ultimately, all test data is incorporated into a life assessment system. Using the logarithmic life median method (N50) and statistical methods using standard deviation S, fatigue life distribution parameters for various tubing types are derived, providing a quantitative basis for design optimization and service life prediction.

[0056] Through this structured test platform and control strategy, the invention simulates the realistic fatigue response of the tubing support structure under complex stress conditions within the shaft. This method, with high precision, repeatability, and operability, is suitable for life verification and comparative studies of multiple tubing support models. The overall test principle is scientific and rational, providing effective support for the design verification and life assessment of in-shaft support structures in the marine equipment industry.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A support test method for a ship oil pipeline, characterized in that: The following steps are involved: Install the tubing support test piece in the experimental device; Arrange a strain measuring device on the surface of the test piece and collect strain response data; Set loading conditions and perform static loading and fatigue loading on the test piece; Record the specimen response data and perform fatigue life assessment.

2. The method according to claim 1, characterized in that The strain measurement device is a resistance strain gauge, which is attached to the axially symmetrical position of the test piece. After attachment, it is insulated and protected. It is connected to the acquisition system through a wire and detects whether the conductivity and resistance value meet the requirements.

3. The method according to claim 2, characterized in that Before loading, perform data zeroing to ensure that the strain channel output is within the preset error range under no-load conditions. Then, apply an initial load lower than the rated load value and collect strain response data. After verifying that the acquisition system is normal, unload the system. The loading parameters are set according to the structural simulation results of the test piece.

4. The method according to claim 3, characterized in that Static loading includes incremental loading and load maintenance operations at multiple loading levels. The loading levels cover part or all of the rated load value range. Each loading level is maintained for a set time and the strain response is collected. The target stress value is then calculated based on the strain data and the material elastic modulus. If the expected stress standard is not met, the loading parameters are adjusted until the set stress requirement is achieved.

5. The method according to claim 4, characterized in that Fatigue loading uses a cyclic loading waveform, with the loading stress set to multiple increasing levels. The loading frequency is controlled within the set range, and multiple cycles are performed at each level. The state of the test piece is monitored during loading. If damage occurs, loading is terminated and defect detection technology is used to confirm the damage location. After the fatigue life data is statistically analyzed, the fatigue life median and discrete index are calculated.

6. An experimental device applied to the experimental method according to claim 1, characterized in that: It includes an oil pipe test piece and a servo telescopic cylinder. The two ends of the oil pipe test piece are respectively hinged to the floating joint and the fixed seat of the servo telescopic cylinder. The base body of the servo telescopic cylinder is fixed on the mounting seat, and its tail is hinged to another fixed seat. The servo telescopic cylinder is coaxial with the oil pipe test piece, and the oil pipe test piece is connected to the oil circuit system.

7. The experimental device according to claim 6, characterized in that The mounting seat includes a lower seat and an upper pressure plate. The upper pressure plate is located above the lower seat. The base of the servo telescopic cylinder is located between the upper pressure plate and the lower seat. At least two screws are passed between the lower seat and the upper pressure plate. The screws are distributed on both sides of the base, and nuts are provided at both ends of the screws for locking.

8. The experimental device according to claim 7, characterized in that: The servo telescopic cylinder base is provided with a first connecting seat and a second connecting seat at both ends of the base body, the first connecting seat is placed on the mounting seat, and a fourth connecting ear is provided at the tail of the second connecting seat. The fourth connecting ear is hinged to the second connecting ear on the fixed seat by passing a rotating pin shaft, and the first connecting seat and the second connecting seat are connected by at least four connecting rods.

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