A ship hull structure wave instability test device and test method

Abstract

The application discloses a hull structure wave instability test device and test method, which comprises a test pool, a ship model, a ballast assembly, a mooring assembly, a wave measuring unit, a structure motion measuring unit, a water pressure measuring unit, a structure stress measuring unit and a synchronous control unit. The ship model comprises a middle test cabin and a head and tail loading cabin, and the structural stability of the middle test cabin is lower than that of the head and tail loading cabin. The middle test cabin is formed into a predetermined bending initial state by adjusting the ballast, and regular waves are applied. The water pressure, structure stress, wave and motion posture data are uniformly triggered and time marked by the synchronous control unit, the phase is corrected according to the wave propagation time delay, the data of different sampling frequencies are matched to the common time axis, the longitudinal pressure distribution, distributed structure stress and overall bending angle under the same wave phase are obtained, and the corresponding relationship between the wave load and the structure response is analyzed, so that the local buckling and post-buckling evolution of the hull structure are identified.

Description

Technical Field

[0001] This invention relates to the field of ship and marine engineering structure testing technology, and in particular to a test device and test method for wave-induced nonlinear instability mechanism of ship hull structure based on hull pressure distribution, continuous distributed optical fiber stress and measured wavefront phase registration. Background Technology

[0002] Under longitudinal bending, the thin-walled stiffened plates of large, lightweight ships may successively experience elastic bending, near-local buckling, local buckling, and post-buckling states. After entering the nonlinear bending state, the hull's submersion state, the spatial distribution of water pressure at the bottom, the overall bending motion, and the local stress bearing path are interconnected. Measuring the overall bending moment, single-point water pressure, or a small amount of discrete stress alone is insufficient to reveal the phase correspondence between the load distribution and the local structural response.

[0003] Existing ultimate strength or successive collapse tests for ship hulls mostly employ four-point bending, end moment, or concentrated loads, which are suitable for obtaining static bearing capacity and final failure modes, but cannot directly reflect the dynamic distribution of bottom pressure along the ship's length under real regular wave action. Existing wave tank tests, even when simultaneously collecting water pressure, stress, and motion data, often struggle to reliably correlate the load distribution in the same phase with the structural response due to insufficient spatial coverage of pressure measurement points and discrete stress measurement points. Summary of the Invention

[0004] This application aims to address at least one of the technical problems existing in the prior art. The present invention aims to provide a test device and method for wave instability testing of ship hull structures, which is used to simultaneously obtain the longitudinal discrete pressure distribution of the ship bottom, the distributed stress at three cross-sectional positions, and the overall bending angle under a pre-formed nonlinear bending state, and to establish the load-structure response correspondence under the same wave phase.

[0005] According to a first aspect of the present invention, a ship hull structure wave instability testing apparatus includes: Test pool; A ship model is used to set in the test pool. The ship model includes a bow loading chamber, a mid-section test chamber, and a stern loading chamber. The bow loading chamber and the stern loading chamber are detachably installed at both ends of the mid-section test chamber. The structural stability of the mid-section test chamber is lower than that of the bow loading chamber and the stern loading chamber. A ballast assembly, the ballast assembly including at least one adjustable ballast for mounting on the bow loading compartment and the stern loading compartment; A mooring assembly for limiting the ship model to movements other than pitching and heaving; A wave measurement unit, used to collect wave data, including wave rise and wave period; A structural motion measurement unit is installed on the ship model and is used to collect the motion attitude data of the ship model. A water pressure measurement unit is installed on the wet surface of the ship model to collect water pressure data of the wet surface. The water pressure data includes the longitudinal pressure distribution of the ship model under static ballast conditions, and the longitudinal pressure distribution, pressure time history, and pressure phase change of the ship model under wave loading conditions. A structural stress measurement unit is installed on the central test chamber and is used to collect structural stress data of the central test chamber. A synchronization control unit is connected to the water pressure measurement unit, the structural stress measurement unit, the wave measurement unit, and the structural motion measurement unit. The synchronization control unit is used to output a unified acquisition trigger signal to each measurement unit and to time-mark the data output by each measurement unit according to the same clock reference, so that the water pressure data, the structural stress data, the wave data, and the motion attitude data form synchronized data with a unified time correspondence.

[0006] According to some embodiments of this application, the water pressure measurement unit includes a plurality of water pressure sensors, each of which is spaced apart along the longitudinal direction of the ship model, and the spacing between adjacent water pressure sensors located in the mid-section test chamber and its adjacent area is smaller than the spacing between adjacent water pressure sensors located in the bow loading chamber and the stern loading chamber areas.

[0007] According to some embodiments of this application, the central test chamber is provided with at least two transverse measurement sections spaced apart along the length of the ship model; the structural stress measurement unit includes a continuous distributed optical fiber, which is disposed on the transverse measurement section, and adjacent transverse measurement sections form a longitudinal measurement section.

[0008] According to some embodiments of this application, the structural motion measurement unit includes at least two inclinometers, wherein a first inclinometer is disposed on the connection structure between the bow loading chamber and the middle test chamber, and a second inclinometer is disposed on the connection structure between the tail loading chamber and the middle test chamber.

[0009] The method for testing wave instability of a ship's hull structure according to the second aspect of this application includes the following steps: A ship model was constructed comprising a bow loading compartment, a mid-section test compartment, and a stern loading compartment connected in sequence, wherein the structural stability of the mid-section test compartment is lower than that of the bow loading compartment and the stern loading compartment. A water pressure measurement unit is set on the wet surface of the ship model, a structural stress measurement unit is set on the test chamber in the middle of the ship model, a structural motion measurement unit is set on the ship model, a wave measurement unit is set in front of the bow of the ship model, and the water pressure measurement unit, structural stress measurement unit, structural motion measurement unit and wave measurement unit are respectively connected to the synchronous control unit. The ship model was placed in the test pool. In still water, the ballast components set on the bow and stern loading tanks were adjusted to bring the mid-section test tank into a predetermined initial bending state. The mooring components restrict the ship model from undergoing any motion other than pitching and heaving. Maintaining the ballast state of the ballast components, regular waves propagating along the ship's length are applied to the ship model, subjecting it to wave loads while maintaining a predetermined bending state. During wave loading, the synchronous control unit outputs a unified acquisition trigger signal to the water pressure measurement unit, structural stress measurement unit, wave measurement unit, and structural motion measurement unit, and timestamps the data output by each measurement unit according to the same clock reference, so that the water pressure data, structural stress data, wave data, and motion attitude data form synchronized data with a unified time correspondence.

[0010] According to some embodiments of this application, the step of adjusting the ballast components disposed on the bow and stern loading chambers to bring the mid-section test chamber into a predetermined initial bending state includes... By symmetrically and progressively adding ballast material to the bow and stern loading chambers near their corresponding ends, the initial nonlinear state of the central test chamber is determined simultaneously using structural stress data collected by the structural stress measurement unit, thereby determining the predetermined initial bending state. The predetermined initial bending state includes at least one of the following: near-elastic bending state, local buckling critical state, local buckling initiation state, and post-buckling stable state.

[0011] According to some embodiments of this application, the wave measurement unit is located at a predetermined distance forward of the bow; Based on the distance between the wave measurement unit and the ship model reference position and the corresponding wave propagation speed, the propagation time delay of the wave from the wave measurement unit to the ship model reference position is determined; the wave crest time, wave trough time or zero crossing time after propagation time delay correction is used as the phase reference; a stable wave cycle is divided into multiple wave phases, and water pressure data, structural stress data, wave data and motion attitude data of different sampling frequencies are registered to a common time axis according to the time stamp of each measurement data, so as to extract the water pressure data, structural stress data and motion attitude data corresponding to each wave phase.

[0012] According to some embodiments of this application, the water pressure measurement unit includes multiple water pressure sensors, each water pressure sensor is spaced apart along the longitudinal centerline of the ship model, and collects water pressure data at the corresponding position; Establish longitudinal coordinates by setting the positions of each water pressure sensor along the longitudinal direction of the ship model, and form the longitudinal discrete pressure distribution of the ship model corresponding to the wave phase based on the water pressure value collected by each water pressure sensor under the same wave phase and the corresponding longitudinal coordinate.

[0013] According to some embodiments of this application, the middle test chamber is provided with at least two transverse measurement sections at intervals along the length of the ship model; the structural stress measurement unit includes a continuous distributed optical fiber, which is laid back and forth in the order from the transverse measurement section at the front end to the transverse measurement section at the end end, and the synchronous control unit continuously demodulates the same continuous distributed optical fiber. A mapping relationship is established between the fiber length coordinates, ship model spatial coordinates, and fiber local laying direction of the continuous distributed optical fiber. Based on the mapping relationship, distributed stress data of each transverse and longitudinal measurement segment are extracted from the continuous demodulation data of the continuous distributed optical fiber to obtain the transverse distributed stress and longitudinal distributed stress, respectively.

[0014] According to some embodiments of this application, the structural motion measurement unit includes at least two inclinometers, wherein the first inclinometer is disposed on the connection structure between the bow loading chamber and the middle test chamber, and the second inclinometer is disposed on the connection structure between the tail loading chamber and the middle test chamber. The overall bending angle of the central test chamber is determined based on the difference between the tilt angle data collected by the first and second tilt gauges. The longitudinal discrete pressure distribution, the transverse distributed stress, the longitudinal distributed stress, and the overall bending angle under the same wave phase are analyzed to obtain the correspondence between the spatial distribution of wave loads, the redistribution of structural stress, and the nonlinear bending response of the central test chamber. Based on the correspondence, the local buckling and post-buckling evolution states of the central test chamber are identified.

[0015] The hull structure wave instability test apparatus and test method according to the embodiments of this application have at least the following beneficial effects: The hull structure wave instability test device and test method of this application constructs a ship model with a bow loading chamber, a midships test chamber and a stern loading chamber in sequence, so that the structural strength or stiffness of the midships test chamber is lower than that of the bow loading chamber and the stern loading chamber; multiple fiber optic water pressure sensors are arranged along the longitudinal centerline of the hull bottom; and continuous distributed optical fibers are laid on the inner surface of the midships test chamber to form three transverse measurement profiles at the front, midship and stern of the midships test chamber.

[0016] In still water, the central test chamber is brought into a predetermined initial bending state by fixed end ballasts in the bow and stern loading chambers, followed by regular wave-facing. The pressure acquisition system, optical frequency domain reflection demodulation system, wave acquisition system, and tilt angle acquisition system are activated simultaneously. Each system can sample at its own sampling frequency, but all of them save the corresponding time series or sampling sequence number.

[0017] Using the measured pressure history obtained from the water pressure measurement unit at the bow as the phase reference, the time delay of wave propagation from the wave measurement position to the bow is corrected, and different sampling data are resampled to a common time axis. The measured values ​​of the pressure measurement points on the bottom of the ship are extracted according to phase and sorted by longitudinal coordinate to form a discrete pressure distribution; based on the mapping relationship between the fiber length coordinate and the spatial coordinates of the hull and the laying direction, longitudinal stress and transverse stress are extracted respectively.

[0018] A correlation is established between the longitudinal discrete pressure distribution on the ship's bottom at the same phase, the distributed stress in the three sections A, B, and C, and the difference between the readings of the two inclinometers. Qualitative comparisons can be made graphically, and the peak time delay or phase difference between the pressure and stress histories can be further calculated to analyze the correlation between the pressure peak migration and the structural stress redistribution.

[0019] The present invention has at least the following beneficial effects: First, the pressure measurement points are arranged along the longitudinal centerline of the ship's bottom and densified near the midship test chamber, which can obtain the longitudinal discrete pressure distribution of the ship's bottom that cannot be provided by traditional single-point pressure measurement; Second, the continuous distributed optical fiber includes both longitudinal and transverse sections, which can extract the continuous stress response of three profiles and the region between them according to spatial coordinates and directions; Third, synchronous start-up, time series registration, measured wavefront phase reference, and propagation delay correction improve the reliability of in-phase correspondence between different sampling systems; Fourth, the midship test chamber can be replaced and re-riveted after the rivets are removed, which facilitates the reuse of the fore and stern loading chambers and measurement systems.

[0020] It should be noted that the "nonlinear instability mechanism test" referred to in this invention refers to the study of the relationship between wave load distribution and structural response under nonlinear bending state using the above-mentioned repeatable measurement and phase registration methods, and does not require a single test to directly prove that the wave induced the material yielding for the first time as a necessary condition. Attached Figure Description

[0021] The present application will be further described below with reference to the accompanying drawings and embodiments, wherein: Figure 1 This is a schematic diagram of the front view structure of an experimental device according to an embodiment of the present invention; Figure 2 This is a top view of the experimental apparatus according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of a connecting segment according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the longitudinal and transverse laying of three cross-sections of continuous OFDR distributed optical fiber according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the longitudinal arrangement of a ship bottom fiber optic water pressure sensor according to an embodiment of the present invention. Figure 6 This is a diagram showing the longitudinal stress distribution in the cross section of the bottom plate of a ship under various initial still water conditions according to an embodiment of the present invention. Figure 7 This is a schematic diagram of the selection of gauge pressure time history and stabilization period at the bow water pressure measuring point under the condition that the wave height is set to 200mm in the wave-making equipment, according to an embodiment of the present invention. Figure 8 This is a schematic diagram of the periodic phase division of a stable regular wave according to an embodiment of the present invention; Figure 9 This is a longitudinal discrete pressure distribution diagram of the ship's bottom at phases t1, t6, t11, and t16, according to an embodiment of the present invention. Figure 10 This is a schematic diagram of the pressure-stress synchronous phase registration and correlation analysis process according to an embodiment of the present invention.

[0022] Figure label: Ship model 100; bow loading compartment 110; midships test compartment 120; first transverse measurement section 121; second transverse measurement section 122; third transverse measurement section 123; bottom plate 124; bilge 125; longitudinal stiffener 126; stern loading compartment 130; connecting section 140; first mounting section 141; Wave measurement unit 200; wave height meter 210; Structural motion measurement unit 300; Inclinometer 310; Water pressure measuring unit 400; water pressure sensor 410; Structural stress measurement unit 500; Fiber optic cable 510; Test pool 1000. Detailed Implementation

[0023] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0024] In the description of this application, it should be understood that the use of terms such as "center," "middle," "longitudinal," "transverse," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," and "circumferential" to indicate orientation or positional relationships is based on the orientation or positional relationships shown in the accompanying drawings and is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, features defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0025] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0026] The following reference Figures 1 to 10 This application describes the wave instability test apparatus and test method for ship hull structure in the embodiments of this application. The directional terms "forward," "rear," "longitudinal," "lateral," and "bottom" are all based on the usual coordinate system of the ship model 100, with the longitudinal direction being the length direction of the ship model 100 and the lateral direction being the width direction of the ship model 100.

[0027] according to Figure 1 and Figure 2 As shown, an embodiment of the ship structure wave instability test device of this application includes a test pool 1000, a ship model 100, a ballast assembly (not shown), a mooring assembly (not shown), a wave measurement unit 200, a structural motion measurement unit 300, a water pressure measurement unit 400, a structural stress measurement unit 500, and a synchronization control unit (not shown).

[0028] The test pool 1000 is used to create a wave environment. A ship model 100 is placed in the test pool 1000 for testing. The ship model 100, along its length, includes a bow loading chamber 110, a midships test chamber 120, and a stern loading chamber 130. The bow and stern loading chambers 110 and 130 are used to arrange ballast, adjust the model's buoyancy, and control boundaries, transferring longitudinal bending loads to the midships test chamber 120. The midships test chamber 120 serves as the main instability observation area, characterizing the typical load-bearing configuration or equivalent instability characteristics of the dangerous area in the midship of the target hull. It simulates the nonlinear instability response of the dangerous area in the target hull under the combined action of longitudinal wave bending moment and water pressure. Typical load-bearing configurations include one or more of the following: a large-opening stiffened box girder configuration, a bottom-stiffened plate structure configuration, and a side-bottom combined plate structure configuration. By changing the plate arrangement, opening type, stiffening type, or plate thickness parameters of the midships test chamber 120, the local load-bearing characteristics and instability sensitivity characteristics of different dangerous areas of the hull can be simulated.

[0029] The ballast assembly includes at least one adjustable ballast (not shown), which is fixedly mounted on the bow loading chamber 110 and the stern loading chamber 130. By adjusting the weight of the ballast or moving its position, the central test chamber 120 is brought into a predetermined initial nonlinear state, i.e., a predetermined initial bending state. Specifically, the adjustable ballast is firmly fixed to the bow loading chamber 110 and the stern loading chamber 130 near their corresponding ends to prevent the ballast blocks from moving and changing the load boundary during the wave test. The ballast can be a counterweight, a ballast block, a ballast water bag, or an adjustable weight.

[0030] Furthermore, the structural stability of the central test chamber 120 is lower than that of the bow loading chamber 110 and the stern loading chamber 130. That is, the strength or stiffness of the bow loading chamber 110 and the stern loading chamber 130 is higher than that of the central test chamber 120, so that local buckling, post-buckling, and local plastic deformation preferentially occur in the central test chamber 120. Specifically, the strength or stiffness of the bow loading chamber 110 and the stern loading chamber 130 can be made higher than that of the central test chamber 120 by increasing plate thickness, increasing component dimensions, or adding reinforcing plates.

[0031] Furthermore, the bow loading compartment 110 and the stern loading compartment 130 are detachably mounted at both ends of the midships test compartment 120. The detachable connection structure is one of bolted connection, riveting, clamping connection, and plug-in connection, allowing the midships test compartment 120 to be removed from and replaced from the hull structure test model. Specifically, both ends of the midships test compartment 120 of the ship model 100 also include connecting sections 140, see below. Figure 3The connecting section 140 is provided with multiple first mounting parts 141. The bow loading tank 110 and the stern loading tank 130 are also provided with second mounting parts (not shown) at corresponding positions that cooperate with the first mounting parts 141. The intermediate test tank 120 is watertightly riveted to the bow loading tank 110 and the stern loading tank 130 respectively through the connecting section 140. When the intermediate test tank 120 needs to be replaced, the rivets at the connection are removed, the original intermediate test tank 120 is removed, another intermediate test tank 120 is installed, and it is re-riveted and watertightened. The detachable and replaceable intermediate test tanks facilitate comparative tests under the same loading tank, mooring boundary, and measurement system conditions.

[0032] In some embodiments, the model material of the ship model 100 may be aluminum alloy, steel, plexiglass or other model materials that meet the requirements of similar tests, and its elastic modulus, Poisson's ratio, density and yield strength are determined by material tensile tests.

[0033] In some embodiments, see Figure 2 and Figure 4 The midships test chamber 120 includes a bottom plate 124, side plates (not shown), and a deck (not shown). The bottom plate 124 has bilges 125, longitudinal stiffeners 126, and transverse frames (not shown). The longitudinal stiffeners 126 are spaced along the length of the ship on the bottom plate 124, forming a compression grid between adjacent longitudinal stiffeners 126. The transverse frames are spaced along the length of the ship and connect to the bottom plate 124, side plates, and deck to provide transverse boundary constraints for the midships test chamber 120. Furthermore, the midships test chamber 120 has a large opening (not shown) in its midsection, extending along the length of the ship model 100. This large opening is located in the midsection of the deck or upper frame and can be rectangular, rounded rectangular, elliptical, or other opening forms suitable for simulating the weakening effect of large hatches on the hull. This large midsection opening reduces the local stiffness of the midships test chamber 120, creating a local buckling-sensitive area. The edge of the large opening is provided with at least one of a coffered plate, an edge reinforcing rib, and a reinforcing elbow plate to form a local boundary reinforcement structure for the hull opening area.

[0034] The mooring assembly, used to restrict the ship model 100 from movements other than pitch and heel, includes at least four flexible mooring lines (not shown) connected to the bow and stern. Specifically, the ship model 100 is moored at the bow and stern using four flexible mooring lines. The mooring arrangement restricts non-target movements such as pitch, sway, roll, and bow roll, allowing the model to primarily retain pitch and heel degrees of freedom in this experiment. Mooring force, stiffness, and preload are not measured in this embodiment and therefore are not considered to limit the invention based on their specific values.

[0035] See back Figure 2The wave measurement unit 200 is used to collect wave data, including wave rise, wave crest, and wave period. Specifically, the wave measurement unit 200 is set at a preset distance in front of or near the bow of the ship model 100. The wave measurement unit 200 is a wave height meter 210, and the preset distance can be 0m to 1m, preferably 0.5m, to obtain the wave rise time history.

[0036] See Figure 1 and Figure 2 A structural motion measurement unit 300 is mounted on the ship model 100 to collect motion attitude data of the ship model 100. Specifically, the structural motion measurement unit 300 includes at least two inclinometers 310. The first inclinometer 310 is mounted on the connection section 140 between the bow loading chamber 110 and the mid-section test chamber 120, and the second inclinometer 310 is mounted on the connection section 140 between the stern loading chamber 130 and the mid-section test chamber 120. The difference between the readings of the first inclinometer 310 and the second inclinometer 310, Δθ = θ_forward - θ_backward, is used to characterize the overall bending angle of the mid-section test chamber 120.

[0037] See Figure 1 and Figure 2 A water pressure measurement unit 400 is installed on the wetted surface of the ship model 100 to collect water pressure data from the wetted surface. The water pressure data includes the longitudinal pressure distribution of the ship model 100 under static ballast conditions, and the longitudinal pressure distribution, pressure time history, and pressure phase changes of the ship model 100 under wave loading conditions. Specifically, the water pressure measurement unit 400 includes multiple fiber optic water pressure sensors 410, which are spaced apart along the longitudinal centerline of the ship's bottom. The spacing between adjacent water pressure sensors 410 located in the mid-section of the test chamber 120 and its adjacent area is smaller than the spacing between adjacent water pressure sensors 410 located in the bow loading chamber 110 and the stern loading chamber 130, i.e., see [reference needed]. Figure 7 The density of water pressure sensors 410 located in the central test chamber 120 and its adjacent areas is greater than the density of water pressure sensors 410 located in the bow loading chamber 110 and the stern loading chamber 130.

[0038] See Figure 1 , Figure 2 and Figure 5The structural stress measurement unit 500 is installed on the mid-section test chamber 120 to collect structural stress data of the mid-section test chamber 120 and capture stress abrupt changes, stress concentration transfer, plate buckling, and local yielding development. Specifically, the mid-section test chamber 120 has at least two transverse measurement sections (not shown) spaced apart along the length of the ship model 100; the structural stress measurement unit 500 includes a continuous distributed optical fiber 510, which is installed on the transverse measurement sections, and adjacent transverse measurement sections form longitudinal measurement sections, thereby obtaining longitudinal and transverse distributed stresses. Further, the continuous distributed optical fiber 510 is installed on the bottom plate frame, bilge 125, longitudinal stiffening members, transverse members, or local buckling sensitive areas of the mid-section test chamber 120.

[0039] In some embodiments, the continuous distributed optical fiber 510 can be replaced by an optical fiber 510 grating stress array.

[0040] In some embodiments, see Figure 4 and Figure 5 The central test chamber 120 is provided with three transverse measurement sections at intervals along the length of the ship model 100, including a first transverse measurement section 121, a second transverse measurement section 122, and a third transverse measurement section 123 arranged sequentially from the front end to the rear end of the ship model 100. Continuous distributed optical fiber 510 is laid back and forth in the order of the first transverse measurement section 121, the second transverse measurement section 122, and the third transverse measurement section 123. The optical fiber 510 contains transverse measurement sections at three cross sections and also contains longitudinal measurement sections between adjacent transverse measurement sections, thereby obtaining longitudinal distributed stress and transverse distributed stress.

[0041] The synchronization control unit is connected to the water pressure measurement unit 400, the structural stress measurement unit 500, the wave measurement unit 200 and the structural motion measurement unit 300 respectively. The synchronization control unit is used to output a unified acquisition trigger signal to each measurement unit and to time-mark the data output by each measurement unit according to the same clock reference, so that the water pressure data, structural stress data, wave data and motion attitude data form synchronized data with a unified time correspondence.

[0042] In one specific embodiment, the ship model 100 adopts a three-section thin-walled stiffened box girder structure. The model material is 3105-O aluminum alloy with an elastic modulus of 69 GPa, a Poisson's ratio of 0.33, a density of 2700 kg / m³, and a yield strength of 100 MPa. The ship model 100 has a total length of approximately 6750 mm, a width of approximately 1000 mm, and a height of approximately 300 mm. The thickness of the bottom plate 124 of the mid-section test compartment 120 is approximately 1.5 mm. The thickness of the plates of the bow loading compartment 110 and the stern loading compartment 130 is approximately 3.0 mm. The midships test chamber 120 is a stiffened plate frame structure, including a bottom plate 124, side plates, deck, longitudinal stiffeners 126, and transverse frames. The bottom plate 124 and side plates form the main load-bearing plate frame. Longitudinal stiffeners 126 are installed along the length of the ship on both the bottom plate 124 and side plates to form the stiffened plate frame. The transverse frames are spaced along the width of the ship to simulate the boundary constraint effect of the hull's transverse frames on the stiffened plate frame. The longitudinal stiffeners 126 and the transverse frames form a compression grid. The spacing between the transverse frames is approximately 750 mm; the spacing between the bottom longitudinal stiffeners 126 is approximately 250 mm; the side longitudinal stiffeners are located approximately 150 mm from the baseline. The web height of the transverse frames is approximately 50 mm. The web height of the longitudinal stiffeners 126 is approximately 20 mm. A large opening is provided in the central region of the midships test chamber 120. This rectangular opening is approximately 2250 mm long and 1000 mm wide, located on the deck or upper deck area and arranged along the ship's length direction, with its length and width aligned with the ship's beam direction. The opening edges are fitted with cofferdams, edge stiffeners, and reinforcing elbows to simulate the localized reinforcement characteristics of a large hatch opening boundary. Through the aforementioned plate thickness, stiffening arrangement, and opening configuration, the midships test chamber 120 is designed to preferentially experience local buckling, post-buckling, or localized nonlinear instability under overall bending. The dimensions described above are for illustrative purposes only and do not constitute a limitation of the invention.

[0043] The hull structure wave instability test apparatus of the first embodiment of this application can adopt the hull structure wave instability test method in the following embodiments.

[0044] according to Figures 1 to 10 As shown, the hull structure wave instability test method of the second aspect of this application can be applied to the hull structure wave instability test device in the above embodiment, and includes the following steps.

[0045] S100. Construct a ship model 100 comprising a bow loading compartment 110, a mid-section test compartment 120, and a stern loading compartment 130 connected in sequence, wherein the structural stability of the mid-section test compartment 120 is lower than that of the bow loading compartment 110 and the stern loading compartment 130.

[0046] S200. A water pressure measuring unit 400 is installed on the wet surface of the ship model 100, a structural stress measuring unit 500 is installed on the test chamber 120 in the middle of the ship model 100, a structural motion measuring unit 300 is installed on the ship model 100, and a wave measuring unit 200 is installed in front of the bow of the ship model 100. The water pressure measuring unit 400, the structural stress measuring unit 500, the structural motion measuring unit 300 and the wave measuring unit 200 are respectively connected to the synchronous control unit.

[0047] S300. Place the ship model 100 in the test pool 1000. In still water, adjust the ballast components set on the bow loading tank 110 and the stern loading tank 130 to bring the mid-section test tank 120 into a predetermined initial bending state.

[0048] S400. The mooring components restrict the ship model 100 from moving except for pitching and heaving.

[0049] S500. Maintain the ballast state of the ballast components, apply regular waves propagating along the ship's length direction through the ship model 100, so that the ship model 100 is subjected to wave load based on a predetermined bending state; during the wave loading process, the synchronous control unit outputs a unified acquisition trigger signal to the water pressure measurement unit 400, the structural stress measurement unit 500, the wave measurement unit 200 and the structural motion measurement unit 300, and timestamps the data output by each measurement unit according to the same clock reference, so that the water pressure data, structural stress data, wave data and motion attitude data form synchronous data with a unified time correspondence.

[0050] The hydraulic pressure data includes pressure distribution along the ship's length, pressure distribution curve shape, pressure peak, pressure peak location, pressure peak region, pressure trough, pressure amplitude, pressure amplitude variation, and pressure distribution migration. Structural stress data includes stress growth, stress concentration, stress concentration region, stress sign variation, stress distribution and stress contour map, stress peak, stress amplitude, stress amplitude variation, and stress concentration region migration. Wave data includes wave rise history, stable wave period, wave height, wave rise, wave crest location, characteristic wave phase, wave phase difference, wavelength, wave direction, and wave speed. Motion attitude data includes inclination angle data.

[0051] Specifically, the wave instability test method for ship hull structure in some embodiments of this application includes the following specific steps.

[0052] S100. Construct a ship model 100 comprising a bow loading compartment 110, a midships test compartment 120, and a stern loading compartment 130 connected in sequence. The structural stability of the midships test compartment 120 is lower than that of the bow loading compartment 110 and the stern loading compartment 130. Based on the hazardous areas of the target hull under longitudinal wave bending, construct a hull structure test model, so that the midships test compartment 120 characterizes the typical load-bearing configuration, plate arrangement, opening characteristics, or equivalent instability characteristics of the hazardous areas within the ship.

[0053] S200. Multiple fiber optic water pressure sensors 410 are spaced apart along the longitudinal centerline on the bottom of the ship model 100, and the density of water pressure sensors 410 in the middle test chamber 120 and its adjacent area is greater than the density of water pressure sensors 410 in the bow loading chamber 110 and the stern loading chamber 130.

[0054] The central test chamber 120 is provided with three transverse measurement sections at intervals along the length of the ship model 100, including a first transverse measurement section 121, a second transverse measurement section 122, and a third transverse measurement section 123 arranged sequentially from the front end to the rear end of the ship model 100. Continuous distributed optical fibers 510 are laid back and forth in the order of the first transverse measurement section 121, the second transverse measurement section 122, and the third transverse measurement section 123. The optical fibers 510 contain transverse measurement sections in three sections, and also contain longitudinal measurement sections between adjacent transverse measurement sections.

[0055] A first inclinometer 310 is installed on the connecting section 140 between the bow loading chamber 110 and the middle test chamber 120, and a second inclinometer 310 is installed on the connecting section 140 between the stern loading chamber 130 and the middle test chamber 120.

[0056] A wave height meter 210 is installed at a preset distance in front of the bow of the ship model 100.

[0057] The water pressure measurement unit 400, the structural stress measurement unit 500, the structural motion measurement unit 300, and the wave measurement unit 200 are respectively connected to the synchronous control unit.

[0058] The water pressure measurement unit 400 and the structural stress measurement unit 500 are connected to the fiber optic demodulation module in the synchronous control unit. It is understood that connecting the water pressure measurement unit 400 and the structural stress measurement unit 500 to the same fiber optic demodulation module enables millisecond-level synchronous acquisition, synchronously acquiring pressure and stress data using a unified time base, and outputting pressure and stress data according to the same sampling time base. The fiber optic demodulation module is used to establish pressure-stress coupling indices, including the phase difference between pressure peaks and stress peaks, the spatial correspondence between pressure peak regions and stress concentration regions, the response relationship between pressure amplitude changes and stress amplitude changes, and the correspondence between pressure distribution migration and stress concentration region migration. This eliminates timing errors, solves the problem of timing misalignment of multiple parameters, and accurately matches dynamic water pressure with local structural response, which helps improve the accuracy of the correspondence between wet surface pressure and structural response.

[0059] S300. The ship model 100 is placed in the test pool 1000. Under still water conditions, ballast is added symmetrically and in stages near the corresponding ends of the bow loading tank 110 and the stern loading tank 130. Simultaneously, the initial nonlinear state of the mid-section test tank 120 is determined using structural stress data collected by continuously distributed optical fibers 510, thereby determining a predetermined initial bending state. The predetermined initial bending state includes at least one of the following: near-elastic bending state, local buckling critical state, local buckling initiation state, and post-buckling stable state. See also Figure 6 The figure shows the longitudinal stress distribution in the cross section of the bottom plate 124 of the ship under various initial still water conditions.

[0060] Furthermore, after each stage of still water ballast conditions stabilizes, the first pressure data under still water conditions is acquired through the water pressure measurement unit 400, and the first stress data of the ship model 100 under still water conditions is acquired through the structural stress measurement unit 500. The first stress data is used to determine whether the midship test chamber 120 has entered the predetermined initial state. The first pressure data includes pressure distribution along the ship's length, pressure distribution curve shape, pressure peak, pressure peak location, pressure peak region, pressure valley, pressure amplitude, pressure amplitude change, and pressure distribution migration. The first stress data includes stress growth, stress concentration, stress concentration region, stress sign change, stress distribution, stress peak, stress amplitude, stress amplitude change, and stress concentration region migration. Based on stress growth, stress concentration, stress sign change, the first local morphology of the midship test chamber 120 and its local out-of-plane deformation direction change, and the material yield threshold, the state of the midship test chamber 120 is determined.

[0061] S400. Moor four flexible mooring lines to the bow and stern to restrict the ship model 100 from moving except for pitching and heaving.

[0062] S500. Maintain the adjustable ballast arrangement to keep the midships test chamber 120 in a predetermined initial bending state. Activate the wave-generating equipment in the test pool 1000 to apply regular waves propagating along the ship's length direction to the ship model 100, subjecting the ship model 100 to wave loads based on the predetermined bending state.

[0063] During the experiment, based on the propagation distance between the wave measurement unit 200 and the reference position of the ship model 100, and the wave propagation speed under the corresponding wave conditions, the propagation time delay required for the wave to propagate from the wave measurement unit 200 to the reference position of the ship model 100 was determined. This propagation time delay was then used to correct the wave rise time history, thus using the corrected wave crest, trough, or zero-crossing time as the phase reference when the ship model 100 is actually subjected to wave action. After obtaining a stable wave period, one stable wave period was divided into multiple wave phases (at least 20). Based on the time stamp configured for each measurement data by the synchronization control unit, the water pressure data, structural stress data, wave data, and motion attitude data were registered to a common time axis according to their respective sampling times, thereby obtaining multi-source synchronous experimental data corresponding to each wave phase. For details, see [link to relevant documentation]. Figure 7 The figure shows the time history curve and stabilization period of the measuring point of the bow water pressure sensor 410 under a wave height of 200mm; see also... Figure 8 The stable wave cycle is divided into 21 wave phases, t1 to t21.

[0064] Synchronously, each fiber optic water pressure sensor 410 collects water pressure time history data at its designated location, and establishes the location of each water pressure sensor 410 along the longitudinal direction of the ship model 100 as a longitudinal coordinate. For any wave phase, the corresponding water pressure value is extracted from the water pressure time history data of each water pressure sensor 410 according to the time corresponding to that wave phase, and the water pressure values ​​are arranged according to the longitudinal coordinate of each water pressure sensor 410, thereby forming a discrete pressure distribution of the ship model 100 along the longitudinal direction under that wave phase. See details below. Figure 9 The figure shows the water pressure distribution along the length of the ship at times t1, t6, t11, and t16.

[0065] Synchronously, the continuous distributed optical fiber 510 sequentially passes through the first transverse measurement segment 121, the second transverse measurement segment 122, and the third transverse measurement segment 123, forming a longitudinal measurement segment extending along the longitudinal direction of the ship model 100 between adjacent transverse measurement segments. The continuous distributed optical fiber 510 is connected to the optical fiber demodulation module in the synchronous control unit. The optical fiber demodulation module performs continuous demodulation along the same continuous distributed optical fiber 510 to obtain continuous stress data corresponding to the length position of the optical fiber 510. At the same time, it establishes a mapping relationship between the length coordinates of the continuous distributed optical fiber 510, the spatial coordinates of the ship model 100, and the local laying direction of the optical fiber 510. Through the mapping relationship, the continuous stress data along the length direction of the optical fiber 510 is converted into stress data corresponding to the spatial position, and the transverse distributed stress of each transverse measurement segment and the longitudinal distributed stress of each longitudinal measurement segment are extracted from it. Specifically, see Figure 10 The figure shows the longitudinal stress distribution at each transverse measurement segment at times t1, t6, t11, and t16.

[0066] Simultaneously, the first inclinometer 310 and the second inclinometer 310 respectively acquire the inclinometer data of the connecting sections 140 at both ends of the central test chamber 120. Based on the difference between the inclinometer data of the first inclinometer 310 and the second inclinometer 310, the overall bending angle of the central test chamber 120 under the corresponding wave phase is obtained.

[0067] Furthermore, for the same wave phase, the obtained longitudinal discrete pressure distribution, transverse distributed stress, longitudinal distributed stress, and overall bending angle are analyzed accordingly. By comparing the changes in peak pressure and pressure distribution pattern, spatial distribution of transverse and longitudinal stress, and overall bending angle under different wave phases, the correspondence between the spatial distribution of wave load, stress redistribution of the central test chamber 120 structure, and nonlinear bending response of the central test chamber 120 is determined. When the pressure distribution undergoes significant migration, localized stress concentration intensification, or abrupt stress distribution changes, accompanied by nonlinear changes in the overall bending angle response, the evolution process of the central test chamber 120 from the initial bending state to the local buckling and post-buckling states can be identified by combining the local out-of-plane deformation of the central test chamber 120.

[0068] Furthermore, by comparing the local morphological deformation of the central test chamber 120 before the test, after static ballast loading, and after wave loading, the instability region obtained from the pressure-stress synchronous analysis can be further verified. The local nonlinear instability state is determined jointly by the structural stress response anomalies and local morphological deformations of the central test chamber 120. Structural stress response anomalies include sudden increases in stress peak values, stress phase lag, and increased stress gradients between adjacent measuring points. Local morphological deformations include deformation at the opening edges, plate indentation, and stiffening plate instability.

[0069] Furthermore, after completing a wave instability test of a hull structure, the midship test chamber 120 can be replaced and the above process repeated. One or more of the plate frame arrangement, opening type, stiffening type, and plate thickness parameters of the midship test chamber 120 can be changed to characterize the local load-bearing characteristics, equivalent instability characteristics, or instability sensitivity characteristics of different dangerous areas of the hull. Under the same bow and stern boundaries and measurement system conditions, the effects of different plate thicknesses, plate frame arrangements, stiffening types, opening types, initial defects, and material parameters on the instability mechanism can be compared to improve the reusability of the device.

[0070] The wave instability testing device for ship structures disclosed in this application firstly utilizes a combined structure of a bow loading chamber 110, a midships testing chamber 120, and a stern loading chamber 130. The bow and stern loading chambers 130 perform ballast loading, buoyancy regulation, and boundary control functions, while the midships testing chamber 120 performs directional instability control. Through staged static ballast loading, the midships testing chamber 120 is brought into a controllable nonlinear, pre-bending, and preferentially deformable state, solving the problem that conventional water tank wave capabilities are insufficient to directly instably instably model models. Secondly, the interchangeable configuration of the midships testing chamber 120 allows for comparison of the effects of different plate thicknesses, stiffening methods, opening types, initial defects, or material parameters on the instability mechanism under the same bow and stern boundaries and measurement system conditions.

[0071] The wave instability testing apparatus and method for ship structures in this application identify the wave-induced nonlinear instability mechanism of ship structures by establishing a coupled analysis mechanism of "ship structure deformation wave motion - water pressure field - structural stress field - local nonlinear instability state". Local instability characteristics include pressure distribution, stress distribution, tilt angle, and the local morphology of the midship test chamber 120. Wave phase changes cause changes in the water pressure distribution on the wetted surface of the hull, which induces a redistribution of the stress field in the midship test chamber 120. The local nonlinear instability state further alters the structural load-bearing path, manifesting as the migration of stress concentration areas, stress phase lag, and residual strain accumulation. This application, through wave phase division and in-phase data extraction, compares the pressure peak position, pressure distribution curve morphology, stress concentration region, stress sign change, local buckling region or local yielding region under different phases. It can identify the coupling mechanism between hull structure deformation, changes in water entry state, wet surface pressure redistribution and pressure peak migration, stress concentration transfer and structural stress redistribution, local buckling or local yielding, and thus identify the formation, development and evolution mechanism of wave-induced nonlinear instability of hull structure.

[0072] Specifically, the wave cycle is divided into multiple phase moments of at least 20, and local instability features such as pressure distribution along the ship's length direction, stress distribution in the mid-section, stress cloud map of the intermediate measurement area, inclination angle, and local morphology of the mid-test chamber 120 are extracted under each phase to establish a coupled analysis mechanism of "ship structure deformation wave motion - water pressure field - structural stress field - local nonlinear instability state".

[0073] In the description of this specification, the use of terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," and "some examples" indicates that the specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0074] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A test device for wave instability of ship hull structure, characterized in that, include: Test pool; A ship model is used to set in the test pool. The ship model includes a bow loading chamber, a mid-section test chamber, and a stern loading chamber. The bow loading chamber and the stern loading chamber are detachably installed at both ends of the mid-section test chamber. The structural stability of the mid-section test chamber is lower than that of the bow loading chamber and the stern loading chamber. A ballast assembly, the ballast assembly including at least one adjustable ballast for mounting on the bow loading compartment and the stern loading compartment; A mooring assembly for limiting the ship model to movements other than pitching and heaving; A wave measurement unit, used to collect wave data, including wave rise and wave period; A structural motion measurement unit is installed on the ship model and is used to collect the motion attitude data of the ship model. A water pressure measurement unit is installed on the wet surface of the ship model to collect water pressure data of the wet surface. The water pressure data includes the longitudinal pressure distribution of the ship model under static ballast conditions, and the longitudinal pressure distribution, pressure time history, and pressure phase change of the ship model under wave loading conditions. A structural stress measurement unit is installed on the central test chamber and is used to collect structural stress data of the central test chamber. A synchronization control unit is connected to the water pressure measurement unit, the structural stress measurement unit, the wave measurement unit, and the structural motion measurement unit. The synchronization control unit is used to output a unified acquisition trigger signal to each measurement unit and to time-mark the data output by each measurement unit according to the same clock reference, so that the water pressure data, the structural stress data, the wave data, and the motion attitude data form synchronized data with a unified time correspondence.

2. The hull structure wave instability test device as described in claim 1, characterized in that, The water pressure measurement unit includes multiple water pressure sensors, which are spaced apart along the longitudinal direction of the ship model. The spacing between adjacent water pressure sensors located in the mid-section test chamber and its adjacent area is smaller than the spacing between adjacent water pressure sensors located in the bow loading chamber and the stern loading chamber areas.

3. The hull structure wave instability test apparatus as described in claim 1 or 2, characterized in that, The central test chamber is provided with at least two transverse measurement sections spaced apart along the length of the ship model; the structural stress measurement unit includes a continuous distributed optical fiber, which is disposed on the transverse measurement section, and adjacent transverse measurement sections form a longitudinal measurement section.

4. The hull structure wave instability test device as described in claim 1, characterized in that, The structural motion measurement unit includes at least two inclinometers, wherein the first inclinometer is installed on the connection structure between the bow loading chamber and the middle test chamber, and the second inclinometer is installed on the connection structure between the tail loading chamber and the middle test chamber.

5. A method for testing wave instability of a ship's hull structure, characterized in that, Including the following steps: A ship model was constructed comprising a bow loading compartment, a mid-section test compartment, and a stern loading compartment connected in sequence, wherein the structural stability of the mid-section test compartment is lower than that of the bow loading compartment and the stern loading compartment. A water pressure measurement unit is set on the wet surface of the ship model, a structural stress measurement unit is set on the test chamber in the middle of the ship model, a structural motion measurement unit is set on the ship model, a wave measurement unit is set in front of the bow of the ship model, and the water pressure measurement unit, structural stress measurement unit, structural motion measurement unit and wave measurement unit are respectively connected to the synchronous control unit. The ship model was placed in the test pool. In still water, the ballast components set on the bow and stern loading tanks were adjusted to bring the mid-section test tank into a predetermined initial bending state. The mooring components restrict the ship model from undergoing any motion other than pitching and heaving. Maintaining the ballast state of the ballast components, regular waves propagating along the ship's length are applied to the ship model, subjecting it to wave loads while maintaining a predetermined bending state. During wave loading, the synchronous control unit outputs a unified acquisition trigger signal to the water pressure measurement unit, structural stress measurement unit, wave measurement unit, and structural motion measurement unit, and timestamps the data output by each measurement unit according to the same clock reference, so that the water pressure data, structural stress data, wave data, and motion attitude data form synchronized data with a unified time correspondence.

6. The method for wave instability testing of ship hull structures as described in claim 5, characterized in that, The step of adjusting the ballast components installed on the bow and stern loading chambers to bring the middle test chamber into a predetermined initial bending state includes... By symmetrically and progressively adding ballast material to the bow and stern loading chambers near their corresponding ends, the initial nonlinear state of the central test chamber is determined simultaneously using structural stress data collected by the structural stress measurement unit, thereby determining the predetermined initial bending state. The predetermined initial bending state includes at least one of the following: near-elastic bending state, local buckling critical state, local buckling initiation state, and post-buckling stable state.

7. The method for wave instability testing of ship hull structures as described in claim 5 or 6, characterized in that, The wave measurement unit is located at a preset distance forward of the bow; Based on the distance between the wave measurement unit and the ship model reference position and the corresponding wave propagation speed, the propagation time delay of the wave from the wave measurement unit to the ship model reference position is determined; the wave crest time, wave trough time or zero crossing time after propagation time delay correction is used as the phase reference; a stable wave cycle is divided into multiple wave phases, and water pressure data, structural stress data, wave data and motion attitude data of different sampling frequencies are registered to a common time axis according to the time stamp of each measurement data, so as to extract the water pressure data, structural stress data and motion attitude data corresponding to each wave phase.

8. The method for wave instability testing of ship hull structures as described in claim 7, characterized in that, The water pressure measurement unit includes multiple water pressure sensors, which are spaced apart along the longitudinal centerline of the ship model and collect water pressure data at the corresponding locations. Establish longitudinal coordinates by setting the positions of each water pressure sensor along the longitudinal direction of the ship model, and form the longitudinal discrete pressure distribution of the ship model corresponding to the wave phase based on the water pressure value collected by each water pressure sensor under the same wave phase and the corresponding longitudinal coordinate.

9. The method for testing wave instability of a ship's hull structure as described in claim 8, characterized in that, The central test chamber is equipped with at least two transverse measurement sections spaced at intervals along the length of the ship model; The structural stress measurement unit includes a continuous distributed optical fiber, which is laid back and forth in the order of the transverse measurement section at the front end to the transverse measurement section at the end. The synchronous control unit continuously demodulates the same continuous distributed optical fiber. A mapping relationship is established between the fiber length coordinates, ship model spatial coordinates, and fiber local laying direction of the continuous distributed optical fiber. Based on the mapping relationship, distributed stress data of each transverse and longitudinal measurement segment are extracted from the continuous demodulation data of the continuous distributed optical fiber to obtain the transverse distributed stress and longitudinal distributed stress, respectively.

10. The method for testing wave instability of a ship's hull structure as described in claim 9, characterized in that, The structural motion measurement unit includes at least two inclinometers, wherein the first inclinometer is installed on the connection structure between the bow loading chamber and the middle test chamber, and the second inclinometer is installed on the connection structure between the tail loading chamber and the middle test chamber. The overall bending angle of the central test chamber is determined based on the difference between the tilt angle data collected by the first and second tilt gauges. The longitudinal discrete pressure distribution, the transverse distributed stress, the longitudinal distributed stress, and the overall bending angle under the same wave phase are analyzed to obtain the correspondence between the spatial distribution of wave loads, the redistribution of structural stress, and the nonlinear bending response of the central test chamber. Based on the correspondence, the local buckling and post-buckling evolution states of the central test chamber are identified.

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