A method for fast evaluation of critical stress of cylindrical shell structure under external pressure

Abstract

This application belongs to the field of stress assessment for thin-walled structures, and specifically relates to a rapid assessment method for the critical stress of a cylindrical shell structure under external pressure. The method includes: Step 1, calculating the theoretical critical pressure of the cylindrical shell under external pressure based on its geometric parameters; Step 2, obtaining the experimental critical pressure of the cylindrical shell under external pressure through experiments; Step 3, defining a stability coefficient, and fitting a stability coefficient curve based on the theoretical and experimental critical pressures; Step 4, extracting the stability coefficient from the stability coefficient curve based on the geometric parameters, and calculating the critical pressure of the cylindrical shell under external pressure based on the stability coefficient and the theoretical critical pressure. This application, combining experimental results and introducing a stability coefficient K, yields a corrected formula that approximates the experimental results. By plotting the stability coefficient curve and combining it with the geometric parameters of the cylindrical shell, the stability coefficient K can be quickly obtained, thereby rapidly determining the critical pressure of the structure.

Description

Technical Field

[0001] This application belongs to the field of stress assessment of thin-walled structures, and specifically relates to a rapid assessment method for the critical stress of a cylindrical shell structure under external pressure. Background Technology

[0002] Cylindrical shell structures are simple in structure and inexpensive, and are widely used in pipelines, pressure vessels, and other fields. External pressure is a typical load condition for cylindrical shell structures, and estimating the load-bearing capacity of a cylindrical shell is an important aspect of structural design. When a cylindrical shell becomes unstable under external pressure, several deep indentations are formed evenly distributed around its circumference, accompanied by a popping sound. Each indentation extends along the generatrix to the entire shell.

[0003] Preventing instability in cylindrical shells is a key parameter that needs to be determined at the initial design stage. Calculating the critical stress of the cylindrical shell structure can preliminarily determine its dimensional parameters. The finite element method (FEM) is currently the primary method used to calculate the critical stress of cylindrical shell structures by establishing a mechanical model. This calculation requires comprehensive consideration of simplified loading and constraint methods, and recalculation and comparison are necessary when structural parameters change to determine the optimal solution. However, the FEM is time-consuming and computationally intensive, which is not conducive to stress and weight estimation requirements in the preliminary structural design stage. Furthermore, the FEM is based on an ideal shell and does not fully account for the impact of manufacturing defects on shell stability, resulting in critical pressure values ​​that exceed actual experimental values, requiring correction based on experimental data.

[0004] Therefore, there is an urgent need for a technical solution to overcome or mitigate at least one of the aforementioned defects in the existing technology. Summary of the Invention

[0005] The purpose of this application is to provide a rapid method for evaluating the critical stress of a cylindrical shell structure under external pressure, so as to solve at least one problem existing in the prior art.

[0006] The technical solution of this application is:

[0007] The first aspect of this application provides a method for rapid assessment of the critical stress of a cylindrical shell structure under external pressure, including:

[0008] Step 1: Calculate the theoretical critical pressure of the cylindrical shell under external pressure based on its geometric parameters;

[0009] Step 2: Obtain the critical test pressure of the cylindrical shell under external pressure through experiments;

[0010] Step 3: Define the stability coefficient and fit the stability coefficient curve based on the theoretical critical pressure and the experimental critical pressure.

[0011] Step 4: Extract the stability coefficient from the stability coefficient curve based on the geometric parameters, and calculate the critical pressure of the cylindrical shell under external pressure based on the stability coefficient and the theoretical critical pressure.

[0012] In at least one embodiment of this application, the horizontal axis of the stability coefficient curve is... Where L is the length of the cylindrical shell, R is the radius of the cylindrical shell, and δ is the thickness of the cylindrical shell.

[0013] In at least one embodiment of this application, the stability coefficient curve includes a stability coefficient curve under full pressure conditions.

[0014] In at least one embodiment of this application, the stability coefficient curve includes a stability coefficient curve under lateral pressure conditions.

[0015] In at least one embodiment of this application, the critical pressure of the cylindrical shell under external pressure is:

[0016] P=KP 理

[0017] Where P is the critical pressure, K is the stability coefficient, and P 理 This is the theoretical critical pressure.

[0018] The second aspect of this application provides a rapid assessment system for the critical stress of a cylindrical shell structure under external pressure, comprising:

[0019] The theoretical critical pressure acquisition module is used to calculate the theoretical critical pressure of the cylindrical shell under external pressure based on the geometric parameters of the cylindrical shell.

[0020] The critical pressure acquisition module is used to obtain the critical pressure of a cylindrical shell under external pressure through experiments.

[0021] The stability coefficient curve acquisition module is used to define the stability coefficient and fit the stability coefficient curve based on the theoretical critical pressure and the experimental critical pressure.

[0022] The critical stress rapid assessment module is used to extract the stability coefficient from the stability coefficient curve based on the geometric parameters, and to calculate the critical pressure of the cylindrical shell under external pressure based on the stability coefficient and the theoretical critical pressure.

[0023] The invention has at least the following beneficial technical effects:

[0024] The present application presents a rapid assessment method for the critical stress of a cylindrical shell structure under external pressure. The method is simple, easy to use, and highly operable. During the design phase of a cylindrical shell structure, it can be used to assess the structural bearing capacity, estimate weight, and preliminarily determine structural parameters. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a cylindrical shell under full pressure conditions according to one embodiment of this application;

[0026] Figure 2 This is a schematic diagram of a cylindrical shell under lateral pressure conditions according to one embodiment of this application;

[0027] Figure 3 This is a stability coefficient curve of one embodiment of this application. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are some, but not all, embodiments of this application. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application. The embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0029] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do 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. Therefore, they should not be construed as limiting the scope of protection of this application.

[0030] The following is in conjunction with the appendix Figures 1 to 3 This application will be described in further detail.

[0031] The first aspect of this application provides a method for rapid assessment of the critical stress of a cylindrical shell structure under external pressure, comprising the following steps:

[0032] Step 1: Calculate the theoretical critical pressure of the cylindrical shell under external pressure based on its geometric parameters;

[0033] Step 2: Obtain the critical test pressure of the cylindrical shell under external pressure through experiments;

[0034] Step 3: Define the stability coefficient and fit the stability coefficient curve based on the theoretical critical pressure and the experimental critical pressure.

[0035] Step 4: Extract the stability coefficient from the stability coefficient curve based on the geometric parameters, and calculate the critical pressure of the cylindrical shell under external pressure based on the stability coefficient and the theoretical critical pressure.

[0036] The method for rapid assessment of the critical stress of a cylindrical shell structure under external pressure in this application first calculates the theoretical critical pressure P of the cylindrical shell under external pressure based on the geometric parameters such as the length, radius, and thickness of the cylindrical shell. 理 , Where E is the elastic modulus of the cylindrical shell material, L is the length of the cylindrical shell, R is the radius of the cylindrical shell, and δ is the thickness of the cylindrical shell.

[0037] Secondly, the critical pressure P of the cylindrical shell under external pressure was obtained through experiments. 试 .

[0038] Then, define the stability coefficient K based on the theoretical critical pressure P. 理 and the test critical pressure P 试 The stability coefficient curve was fitted, P 试 =KP 理 The horizontal axis of the stability coefficient curve is .

[0039] In a preferred embodiment of this application, the stability coefficient curve includes a stability coefficient curve under full pressure and a stability coefficient curve under lateral pressure. Uniformly distributed external pressure acts on the cylindrical shell in two ways: full pressure and lateral pressure, such as... Figure 1 , Figure 2 As shown. The correction formulas for the two types of external pressure can be unified, although the stability coefficient K takes different values ​​for the two, such as... Figure 3 As shown.

[0040] Finally, during the rapid assessment of critical stress, the abscissa value was calculated based on the geometric parameters of the cylindrical shell. Extract the corresponding stability coefficient K from the stability coefficient curve, and then apply the formula P=KP. 理 =K The critical pressure P of the cylindrical shell under external pressure was calculated.

[0041] Analysis of numerous experimental results shows that the critical pressure at which a cylindrical shell becomes unstable under external pressure is approximately 70% of the theoretical value for an ideal shell. When there are large initial shape defects exceeding the wall thickness, the critical pressure is 40-60%. As the shell length increases, the difference between the experimental critical pressure and the theoretical critical pressure gradually decreases.

[0042] The present application proposes a method for rapid assessment of the critical stress of a cylindrical shell structure under external pressure. By combining experimental results and introducing a stability coefficient K, a corrected formula that approximates the experimental results can be obtained. By plotting the stability coefficient curve and combining it with the geometric parameters of the cylindrical shell, the stability coefficient K can be obtained quickly, thereby enabling rapid determination of the critical pressure of the structure.

[0043] This application presents a rapid assessment method for the critical stress of a cylindrical shell structure under external pressure. Based on finite element calculations and experimental verification, it summarizes the relationship between the critical stress of the cylindrical shell and structural parameters, plots a stability coefficient curve, and allows designers to quickly query and obtain the critical stress. This enables rapid assessment of critical pressure, estimation of structural weight, and subsequent optimization of the structural configuration.

[0044] This application presents a rapid assessment method for the critical stress of cylindrical shell structures under external pressure. The method is conceptually clear, highly accurate, and easy to use, requiring no computer or related software and applicable in simple environments such as fieldwork. In the preliminary structural design stage, this method can conveniently and quickly estimate the critical external pressure for different structural options, estimate the structural load-bearing capacity and weight, and accurately determine the compliance with design requirements. Furthermore, this method is based on experimental verification, giving it high reliability and widespread application value in engineering practice.

[0045] Based on the above-mentioned rapid assessment method for the critical stress of a cylindrical shell structure under external pressure, a second aspect of this application provides a rapid assessment system for the critical stress of a cylindrical shell structure under external pressure, comprising:

[0046] The theoretical critical pressure acquisition module is used to calculate the theoretical critical pressure of the cylindrical shell under external pressure based on the geometric parameters of the cylindrical shell.

[0047] The critical pressure acquisition module is used to obtain the critical pressure of a cylindrical shell under external pressure through experiments.

[0048] The stability coefficient curve acquisition module is used to define the stability coefficient and fit the stability coefficient curve based on the theoretical critical pressure and the experimental critical pressure.

[0049] The critical stress rapid assessment module is used to extract the stability coefficient from the stability coefficient curve based on geometric parameters, and to calculate the critical pressure of the cylindrical shell under external pressure based on the stability coefficient and the theoretical critical pressure.

[0050] The design details of each module of the rapid assessment system for critical stress of cylindrical shell structure under external pressure in this application are based on the rapid assessment method for critical stress of cylindrical shell structure under external pressure, and will not be repeated here.

[0051] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for rapid assessment of the critical stress of a cylindrical shell structure under external pressure, characterized in that, include: Step 1: Calculate the theoretical critical pressure of the cylindrical shell under external pressure based on its geometric parameters; Step 2: Obtain the critical test pressure of the cylindrical shell under external pressure through experiments; Step 3: Define the stability coefficient and fit the stability coefficient curve based on the theoretical critical pressure and the experimental critical pressure. Step 4: Extract the stability coefficient from the stability coefficient curve based on the geometric parameters, and calculate the critical pressure of the cylindrical shell under external pressure based on the stability coefficient and the theoretical critical pressure.

2. The method for rapid assessment of critical stress of cylindrical shell structure under external pressure according to claim 1, characterized in that, The horizontal axis of the stability coefficient curve is Where L is the length of the cylindrical shell, R is the radius of the cylindrical shell, and δ is the thickness of the cylindrical shell.

3. The method for rapid assessment of critical stress of cylindrical shell structure under external pressure according to claim 2, characterized in that, The stability coefficient curve includes the stability coefficient curve under full pressure conditions.

4. The method for rapid assessment of critical stress of cylindrical shell structure under external pressure according to claim 3, characterized in that, The stability coefficient curve includes the stability coefficient curve under lateral pressure conditions.

5. The method for rapid assessment of critical stress of cylindrical shell structure under external pressure according to claim 4, characterized in that, The critical pressure of a cylindrical shell under external pressure is: P=KP 理 Where P is the critical pressure, K is the stability coefficient, and P 理 This is the theoretical critical pressure.

6. A rapid assessment system for the critical stress of a cylindrical shell structure under external pressure, characterized in that, include: The theoretical critical pressure acquisition module is used to calculate the theoretical critical pressure of the cylindrical shell under external pressure based on the geometric parameters of the cylindrical shell. The critical pressure acquisition module is used to obtain the critical pressure of a cylindrical shell under external pressure through experiments. The stability coefficient curve acquisition module is used to define the stability coefficient and fit the stability coefficient curve based on the theoretical critical pressure and the experimental critical pressure. The critical stress rapid assessment module is used to extract the stability coefficient from the stability coefficient curve based on the geometric parameters, and to calculate the critical pressure of the cylindrical shell under external pressure based on the stability coefficient and the theoretical critical pressure.

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