Strain rate sensitive hull structure collision reduced scale model construction method considering scale effect

Abstract

The invention relates to a strain rate sensitive hull structure collision reduced scale model construction method considering a scale effect, and the method comprises the steps: constructing a reduced scale model of a ship based on a preset geometric reduced scale ratio; acquiring a collision load parameter and a collision speed of the reduced scale model; and carrying out a collision test based on the collision load parameter and the collision speed by using the reduced scale model. According to the method, complex iteration and prior information are not needed, a reduced scale model meeting laboratory conditions can be designed through a known prototype structure, and the collision impact resistance of a real ship can be accurately evaluated and assessed through a model test.

Description

Technical Field

[0001] The present invention relates to the technical field of test similarity scale model correction under collision load, and in particular to a method for constructing a strain rate sensitive hull structure collision scale model considering scale effect. Background Art

[0002] Collision issues currently hold important research significance in the field of ship structure design. Ships are huge in mass and possess considerable kinetic energy during navigation, while the structure in the collision area absorbs a large amount of energy in a relatively short period of time. Therefore, it will quickly enter the plastic stage, and may even cause failures such as large deformation, buckling, and rupture. As the most direct research method, the experimental method can provide intuitive results for the collision problem. However, due to the large-scale geometric characteristics of ship structures, full-scale ship collision tests are extremely expensive and difficult to implement. Therefore, in order to study the response of ship structures during collisions, the use of scaled model test results to predict the damage and deformation of prototype structures under impact loads has become the mainstream method. However, the ship collision process is a highly nonlinear problem involving materials, geometry, contact, motion, etc. Due to the influence of factors such as strain rate effects and material damage, the classical similarity law cannot effectively complete the design of similarity models under collision loads. Summary of the Invention

[0003] The purpose of the present invention is to propose a method for constructing a scaled collision model of a strain-rate sensitive hull structure taking into account the scale effect. Without complex iteration and prior information, a scaled model that meets laboratory conditions can be designed based on a known prototype structure, and the collision impact resistance of the actual ship can be accurately evaluated and assessed through model tests.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] A method for constructing a scaled model of a strain-rate sensitive hull structure collision considering scale effect includes:

[0006] Build a scale model of the ship based on the preset geometric scale ratio;

[0007] Obtaining collision load parameters and collision speed of the scaled model;

[0008] A collision test is performed using the scaled model based on collision load parameters and collision speed.

[0009] Optionally, based on a preset geometric scale ratio, constructing a scaled model of the hull structure includes:

[0010] Determine the size parameters of the scaled model based on a preset geometric scale ratio;

[0011] A scale model was constructed using the same materials as the ship and based on the size parameters.

[0012] Optionally, the size parameters include:

[0013] The number of stiffeners of the scaled model, the length of the scaled model, the width of the scaled model, the thickness of the strip plate of the scaled model, the height of the stiffener web of the scaled model, the thickness of the stiffener web of the scaled model, the width of the stiffener strip plate of the scaled model, and the thickness of the stiffener strip plate of the scaled model.

[0014] Optionally, the collision load parameters include:

[0015] Collision position Z of the scale model system m :Z m =Z p β; where β is the scale ratio of the geometric dimensions, Z p is the collision position of the prototype structure (distance from the boundary);

[0016] Collision mass M of the scale model system Im : Among them, M Ip is the input collision mass in the prototype structural system, The quality of the prototype structure.

[0017] Optionally, obtaining the collision speed includes:

[0018] Obtaining the modified velocity factor based on the dimensional analysis method;

[0019] A collision velocity is obtained based on the modified velocity factor.

[0020] Optionally, the correction speed factor is:

[0021]

[0022] in, is the cross-sectional plastic bending moment scaling factor for the prototype and scaled model, Input collision mass scale factor for the prototype and scaled model systems.

[0023] Optionally, the collision speed is:

[0024]

[0025] Among them, v 0p is the input collision velocity in the prototype structural system, Scale factor for the input collision velocity in the prototype and scaled model systems.

[0026] The beneficial effects of the present invention are:

[0027] The present invention proposes a method for constructing a scaled model of a collision of a strain-rate sensitive hull structure taking into account the scale effect. First, a scaled model of a ship is constructed based on a preset geometric scale ratio; secondly, the collision load parameters and collision velocity of the scaled model are obtained; and then, a collision test is carried out using the scaled model based on the collision load parameters and collision velocity. The present invention reveals the reasons for the differences in the prediction and inversion of the dynamic responses of strain-rate sensitive prototype structures in scaled model collision tests commonly used in engineering practice, and proposes a targeted correction method. A dimensionless quantity combination including multiple geometric input physical quantities and structural dynamic flow stresses is established, and the similarity criterion for the collision scaled model test is clarified. Furthermore, the similarity criterion is applicable to complex reinforced prototype structures, and the scaled model system designed therefor can quickly and accurately predict the typical dynamic responses of strain-rate sensitive prototype structures. Compared with the traditional similarity law, the error is significantly reduced, thereby improving the reliability and accuracy of the scaled model test. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 A schematic diagram of the relationship between the prototype and scaled model collision systems of an embodiment of the present invention;

[0030] Figure 2 Schematic diagram of the prototype structure and punch of a typical side plate frame of a double-hull LNG ship according to an embodiment of the present invention; (a) is a prototype specimen of a stiffened plate, and (b) is a parabolic punch;

[0031] Figure 3 The figure is a flow chart of a method for constructing a scaled model of a strain-rate sensitive hull structure collision considering scale effect according to an embodiment of the present invention. DETAILED DESCRIPTION

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] The collision and impact damage resistance of the hull structure determines its vitality in sea transportation, so the collision and impact damage characteristics of the structure must be mastered in hull design. Experimental research on damage caused by collision and impact loads on ship structures is the most direct means, but the collision and impact experiments on real ships are expensive and difficult to implement. Using scaled models for collision and impact experiments is a widely used alternative. In order to effectively convert the results of model tests to real ships, it is necessary to design scaled models and transform responses based on collision similarity criteria. In view of this, this embodiment proposes a method for constructing a scaled model of hull structure collision that takes into account scale effects, which has high accuracy, a simple design process, and a wide range of applications. Without complex iterations and prior information, a scaled model that meets laboratory conditions can be designed based on a known prototype structure, so that the collision and impact resistance of the real ship can be accurately evaluated and assessed through model tests.

[0035] This embodiment is aimed at the prototype of complex hull reinforcement structure, focusing on typical ship-to-ship collision scenarios, and provides a method for accurately evaluating and assessing the collision resistance of real ships through model tests. Therefore, the service object of this embodiment can be described by a typical T-shaped reinforcement section with strip plates. In the scale model design method of this embodiment, the relationship between the prototype and scale model collision system is as follows: Figure 1 shown.

[0036] To represent the parameters of the prototype and scaled model, the subscript p represents the prototype parameter ( p , the subscript m represents the geometric similarity scale model parameter () m β represents the scale ratio of geometric dimensions, X represents the scale ratio of the physical quantity X, and the scale ratio calculation formula is: β X =X m / X p .

[0037] This embodiment first establishes a dimensionless combination of a scaled model of a hull structure collision and a corresponding similarity criterion, including:

[0038] In the hull side collision resistance, the focus is on the maximum deformation of the structure and the collision force, which are dimensionless quantities based on velocity (V), stress (S), and gravity (G). The physical quantities represented by each parameter are consistent with the symbol table, and the corresponding series of dimensionless quantity combinations are:

[0039] Hull structure collision similarity criterion: structural geometric similarity (L m =L p β), the collision position is similar (Z m =Z p β), collision loads are similar

[0040] Further, if Figure 3 This embodiment provides a method for constructing a scaled model of a strain-rate sensitive hull structure collision that takes into account the scale effect. After the material properties and dimensional parameters of the strain-rate sensitive prototype structure are known, the steps include:

[0041] Build a scale model of the ship based on the preset geometric scale ratio;

[0042] Obtain the collision load parameters and collision velocity of the scaled model;

[0043] Using a scaled model, a collision test is conducted based on collision load parameters and collision speed.

[0044] Specifically, in this embodiment, step 1: based on a preset geometric scale ratio, determine the size parameters of the scale model; use the same material as the ship and construct the scale model based on the size parameters.

[0045] in:

[0046] Number of ribs in scaled model (N s ):N m =N p ;

[0047] The length of the scale model (L m ):L m =L p β;

[0048] Width of scale model (B m ):B m =B p β;

[0049] The thickness of the plate of the scaled model (h p ):h m =h p β;

[0050] Height of stiffener web of scaled model (h w ) m ):(h w ) m =(h w ) p β;

[0051] The thickness of the stiffener web of the scaled model ((t w ) m ):(t w ) m =(t w ) p β;

[0052] The width of the stiffener strip plate of the scaled model (b f ) m ):(bf ) m =(b f ) p β;

[0053] Thickness of the stiffener strip plate of the scaled model (t f ) m ):(t f ) m =(t f ) p β.

[0054] Step 2: After knowing the material properties and dimensional parameters of the scaled model, preliminarily determine some collision load parameters of the scaled model, where:

[0055] Collision position of the scale model system (Z m ): Z m =Z p β;

[0056] Collision mass of the scale model system (M Im ):

[0057] Step 3: Obtain a modified velocity factor based on a dimensional analysis method; and obtain the collision velocity based on the modified velocity factor.

[0058] Specifically, with the goal of achieving similar structural strain rate levels in the scaled model collision system, a calculation formula for the collision load in the scaled model system is derived, where:

[0059] The collision velocity of the scale model system (v 0m ):

[0060] In order to address the distortion effect caused by the dissimilar strain rate levels of the structure due to the change in the scale of the scaled model, this embodiment proposes that the velocity load in the scaled model collision system needs to be corrected for different strain rate levels. The corrected velocity factor derived by the dimensional analysis method should be calculated using the following formula:

[0061] Below, this embodiment takes a double-hull LNG ship as an example to illustrate the scaled design process of this embodiment and gives the experimental verification results. In order to facilitate the explanation of the scaled process, the plate frame near the waterline that is susceptible to collision loads is used as the prototype structure, and its geometric parameters are as follows: Figure 2 As shown. As shown, Figure 2 (a) is the prototype specimen of the stiffened plate. Figure 2 (b) is a parabolic punch; the base plate is 1800×1800×12mm, the number of reinforcing ribs is 3, and the size is With reference to the actual collision scenario, the collision load of the prototype panel is taken as the collision speed of 4.49m / s, the collision mass of 2.11t, the collision position of the panel center, and Z p =900. It is worth noting that to meet the test conditions, the prototype plate frame specimen was welded with surrounding plates and had bolt holes drilled to achieve clamped boundary conditions. The plate frame was made of strain-rate-sensitive marine steel, and its detailed material parameters are shown in Table 1.

[0062] Table 1 Material parameters of a typical side plate prototype of a double-hull LNG ship

[0063]

[0064] To compare the similarity effects of this embodiment, scaled model systems RPmodel-A and RPmodel-B were established, respectively, based on the traditional similarity law and the similarity design method proposed in this embodiment. First, the scaled model system RPmodel-A was established based on the traditional similarity law. The geometric scale factor between the scaled model system and the prototype structure remained consistent with the scale ratio (β) 1 / 3, and the materials and processing techniques remained consistent with the prototype structure. The collision position was set at the center of the panel frame, the collision velocity was consistent with the prototype structure, and the collision mass was scaled according to the scale factor.

[0065] Secondly, the scaled model system RPmodel-B is established according to the similar design process proposed in this embodiment. The geometric scale factor between it and the prototype structure is kept consistent with the scale ratio (β) 1 / 3, and the materials and processing technology are kept consistent with the prototype structure. According to step 1, the number of stiffeners of the scaled model of the scaled model system RPmodel-B can be determined to be 3. The length, width, and thickness of the scaled model can all be calculated: the bottom plate size is 600×600×4mm, and the stiffener web size is According to step 2, its collision position is Z m =300 (center of the frame), the collision mass is 0.077t. According to step 3, the corresponding correction speed factor is 1.047, that is, the correction speed should be 4.70m / s.

[0066] According to the method proposed in this example, the dimensional parameters and load parameters of the prototype and two sets of scaled models are shown in Table 2. Crash tests were conducted on the prototype and two sets of scaled models based on the design loads, and the test dynamic response results were obtained. The collision force and maximum deformation during collision are important guiding parameters for considering the crashworthiness level. Therefore, Table 3 summarizes the maximum plastic deformation and maximum collision force results corresponding to each set of tests.

[0067] Table 2 System input parameters of prototype and scaled model of a typical side plate frame of a double-hull LNG ship

[0068]

[0069] The test results show that although the scaled model RPmodel-A was designed using the traditional similarity law, its predicted plastic deformation was too small and its peak impact force response was too large. However, the scaled model RPmodel-B, designed using the similarity law proposed in this example, showed a significantly lower prediction error in its impact response compared to the traditional similarity law, and was more similar to the prototype.

[0070] Table 3. Collision response and comparison of prototype and scale model systems

[0071]

[0072] The material strain rate effect under collision loads introduces distortion effects in scaled model systems, hindering the accurate inversion of the dynamic characteristics of full-scale structures through scaled model testing. Due to the strong nonlinear effects during collisions, this example, based on dimensional analysis and taking into account the strain rate effect of the structure, provides a process for constructing similar scaled models of complex hull stiffeners under transverse collision loads. This process can help correct collision loads in scaled model systems and facilitate the inversion of the dynamic characteristics of full-scale models through transverse collision scaled model testing.

[0073] This example reveals the reasons for discrepancies in the prediction and inversion of the dynamic response of strain-rate-sensitive prototype structures from scaled-model collision tests, commonly used in engineering practice. A targeted correction method is proposed, along with a dimensionless combination of multiple geometric input physical quantities and structural dynamic flow stresses. This similarity criterion is also clarified for scaled-model collision tests. Furthermore, this similarity criterion is applicable to complex reinforced prototype structures. The scaled-model system designed with this method is capable of quickly and accurately predicting the typical dynamic response of strain-rate-sensitive prototype structures, significantly reducing errors compared to traditional similarity laws and improving the reliability and accuracy of scaled-model tests.

[0074] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for constructing a scaled model of a strain-rate sensitive hull structure collision considering scale effect, characterized in that: include: Build a scale model of the ship based on the preset geometric scale ratio; Obtaining collision load parameters and collision speed of the scaled model; A collision test is performed using the scaled model based on collision load parameters and collision speed.

2. The method for constructing a strain rate sensitive hull structure collision scale model considering scale effect according to claim 1 is characterized in that: Based on the preset geometric scale ratio, the scale model of the hull structure is constructed, including: Determine the size parameters of the scaled model based on a preset geometric scale ratio; A scale model was constructed using the same materials as the ship and based on the size parameters.

3. The method for constructing a strain rate sensitive hull structure collision scale model considering scale effect according to claim 2 is characterized in that: The size parameters include: The number of stiffeners of the scaled model, the length of the scaled model, the width of the scaled model, the thickness of the strip plate of the scaled model, the height of the stiffener web of the scaled model, the thickness of the stiffener web of the scaled model, the width of the stiffener strip plate of the scaled model, and the thickness of the stiffener strip plate of the scaled model.

4. The method for constructing a strain rate sensitive hull structure collision scale model considering scale effect according to claim 1 is characterized in that: The collision load parameters include: Collision position Z of the scale model system m :Z m =Z p β; where β is the scale ratio of the geometric dimensions, Z p is the collision position of the prototype structure; Collision mass M of the scale model system Im : Among them, M Ip is the input collision mass in the prototype structural system, The quality of the prototype structure.

5. The method for constructing a strain rate sensitive hull structure collision scale model considering scale effect according to claim 1 is characterized in that: Obtaining the collision velocity includes: Obtaining the modified velocity factor based on the dimensional analysis method; A collision velocity is obtained based on the modified velocity factor.

6. The method for constructing a strain rate sensitive hull structure collision scale model considering scale effect according to claim 5 is characterized in that: The correction speed factor is: in, is the cross-sectional plastic bending moment scaling factor for the prototype and scaled model, Input collision mass scale factor for the prototype and scaled model systems.

7. The method for constructing a strain rate sensitive hull structure collision scale model considering scale effect according to claim 5, characterized in that: The collision speed is: Among them, v 0p is the input collision velocity in the prototype structural system, Scale factor for the input collision velocity in the prototype and scaled model systems.

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