The overall structural state of a ship is a very complicated process. The following is my collection of papers on ultimate strength analysis of ship and ocean engineering structures, hoping to help you!
Abstract: When the ship is subjected to external impact load, the overall structure of the ship will be deformed. When this deformation reaches the maximum limit state, the limit state at this time is called the ultimate bending moment. Ultimate strength is the strongest ability of the whole ship frame to bear all resistance. In this paper, the ultimate strength of ship structure is analyzed. The finite element analysis method is put forward to analyze its strength and limit.
Key words: ultimate strength, ship, structure, ship and ocean engineering
With the continuous progress of science and technology, the ship structure and materials used in ships have made great progress. The overall structure and material of ship hull have become the main object of social research. With the maturity of computer technology, the overall structure and bearing capacity of the hull. The yield force can be calculated quickly and accurately through software simulation.
1. Introduction
The overall structure and bearing capacity of the hull is an important guarantee to ensure the safety of the ship, which is related to whether the ship can sail safely and return safely. With the progress of advanced design technology, computer-related design software has appeared. Design the whole structure, and simulate and test the whole hull structure. The analysis of hull structure and total strength is a complex nonlinear process, which must be divided reasonably and accurate values can be obtained by using good analysis methods. The continuous emergence of new materials makes the consumption of hull materials more economical and reasonable, and the yield strength of hull structure is becoming more and more ideal.
When analyzing the deformation and ultimate strength of the whole ship structure, most of the problems we study are linear weak deformation problems. In weakly integrated structures, displacement and strain can be linearized, which is equivalent to a proportional relationship. But in practice, the stress and strain of irregular objects are not linear, such as the bending of cantilever beam and the deformation of U-shaped beam.
2. Overall structural status
The overall structural state of a ship is a very complicated process. The collapse of the whole structure is a very common phenomenon in the past few years. It is the influence on the hull structure that exceeds the limit of the material itself. At this time, the supporting beam cannot support the whole structure of the hull. The above situation is not surprising, and similar situations often occur on the outer bodies of aircraft and submarines. At present, compared with foreign developed countries, the research of hull analysis technology in China is still in its infancy. There is still a big gap from the advanced level. In order to further research and analysis, China has invested money and manpower to establish a relatively complete hull analysis system in practical engineering, including the research on the speed control system of prime mover, the synchronous hull structure system and the management related technologies of ship control system. A series of key technologies that are easy to control the hull structure under various harsh conditions are tested and studied, and the feasibility is analyzed. Ships play a very important role, especially in hull division. The yield strength analysis shows that ship safety is the lifeline of ships. Power and structure form a complete ship system, which is the development of ultimate strength analysis of hull structure. Pointed the way.
3. Ultimate strength analysis method
How to analyze the ultimate strength of ship structure is a complex and meaningful process. There is no accurate analysis method to analyze this complex hull structure. When analyzing ultimate strength, we usually simplify complex problems, combine linear and nonlinear methods, and combine finite element analysis with boundary element analysis.
3. 1 progressive failure analysis method
At the end of last century, American physicists put forward a progressive failure analysis method based on the research results of cantilever beam and stiffened plate structure failure under axial compression load. The damage of hull structure is not a rapid change process, but a gradual process. At the same time, it will not exceed the yield limit at once, but will gradually increase with the increase of stress. In the failure analysis, the curve relationship between yield stress and displacement is established at first.
3.2 Nonlinear analysis method
The linear analysis method must be. When using modular analysis to analyze the hull, we must fully consider how to segment it, and then do nonlinear analysis by segments. In this project, the structure of a segment is different, and linear analysis and nonlinear analysis are carried out for different structures. Each segment contains all the main components within a skeleton interval. By selecting or using the principle of maximum collapse probability, the segmented skeleton is comprehensively analyzed and simulated. This analysis method needs to establish a model for each market segment and then analyze a model. Different bending and yielding capacities of hull structures lead to different analysis results.
3.3 finite element analysis method
Finite element analysis is a simple structural analysis method, which can simplify complex problems and analyze the nodes and grids of the whole structure. In finite element analysis, the hull structure is usually divided into grids, and then constraints are imposed on the grids, and variables are imposed on the uniform grids. Stimulate and observe the reaction of the whole structure. This method can simulate the boundary conditions and overall constraints of the hull. Comprehensive consideration of finite element analysis method. The shape and material of the hull are different, so we can analyze the structural limit (including the maximum stress and the maximum yield limit) through the constraints of different loads. In recent years, there are many cases in which the finite element analysis method is applied to the overall analysis and local structure analysis of ships. This analysis method has two disadvantages. One is. It can't simulate the real environment well and can't consider the influence of the surrounding environment on the deformation of the whole structure. Secondly, for components with complex structures, the finite element analysis method is not practical for complex structures, and it takes too long to set relevant algorithms to complete tasks in an effective time. The advantages of this analysis method are as follows:
The modeling method of (1) hull is intuitive and clear. When analyzing the structure, we can use linear partition and nonlinear partition grid. All models and simulations of dynamic structures can be completely analyzed by related software. Using the visual modeling window of finite element analysis module, the block diagram and model of dynamic structure can be quickly established and simulated. Users need to select the appropriate module (corresponding sub-module program module) from the component library, then change the required form, drag and drop it into the new modeling window, and click or draw lines with the mouse to connect, so as to build a very impressive structural model. His standard library has more than 150 modules, which can be used to build and simulate various dynamic structures. Module package. Includes input signal source submodule, dynamic component submodule, algebraic function and nonlinear function submodule, data display submodule, etc. Modules can be set as trigger ports and enable ports to simulate the behavior of submodels with conditional effects in large model structures.
(2) A dynamic structural model can be established. The model of the movable structure can be modified and simulated. Finite element analysis can also be used as a graphical and digital simulation tool to study and formulate the establishment and operation of dynamic structural models.
(3) Add and customize module components and user codes. Users can modify the icons of existing modules and reset the dialog box. Users can directly implant their own C code, FORTRAN code and Ada code into the model. In addition, module libraries and library functions are both. It is customizable and can be extended to accommodate user-defined structural link modules. .
(4) Fast and accurate design of ship structure model. He has excellent integral and differential algorithms, which brings great convenience to nonlinear structural simulation and relatively high calculation accuracy. Advanced ordinary differential equation solvers and partial differential equation solvers can be selected, which can also be used to solve mechanical rigid and non-rigid structures, and can also be used to solve logical structures with event triggering, structures with discontinuous state variables and structures with algebraic rings and parameter rings. The solver of the software can ensure the high-speed and accurate simulation of continuous structures or discrete structures.
(5) Complex structures can be expressed in different levels. According to individual needs, several substructures can be organized through various modules. Build the whole structural model from top to bottom (from component to structure) or from bottom to top (from every detail to the whole structure). This hierarchical modeling ability can make it easy to build a model with rich code, huge volume and very complicated structure. The hierarchical number of structural submodels and submodules depends entirely on the constructed structure, and the software itself will not be limited to the constructed model. The finite element method also provides models and submodels. Module structure browsing function. This is more convenient for the operation of large complex structures.
(6) Interactive simulation analysis. The oscilloscope displayed by software can be displayed in the form of graphics and animation, and the data can also be displayed in the form of action. Parametric models can be adjusted during what-if analysis operations, and simulation results can be monitored during simulation operations. It can help users quickly evaluate different algorithms and optimization parameters.
Because all the finite element modules are integrated into the finite element, all the calculation results under the finite element module can be completely saved in the finite element soft workspace, so many finite element analysis, visualization and toolbox tools can be used to manipulate the data.
4. Military development of ships.
Military application: In the 1990s, the navies of various countries led by the United States vigorously developed the performance optimization of naval vessels, and the overall structure and performance were optimized. 1993, the project plan of advanced machinery for surface ships (ASMP advanced ocean surface plan) was put forward.
The purpose of the United States is to establish the most advanced ship propulsion system, which can achieve long-range combat and high impact resistance. The US Navy adopts advanced intelligent equipment, as well as electrical control and mechanical control systems. While meeting the specified performance, the investment in ultimate strength analysis is increased and the investment in other aspects of military ships is greatly reduced. With the in-depth study of ASMP project, power integration and modularization methods have been used to study the generation, transmission, conversion and distribution of ship power. Use * * * to enjoy the propulsion device and the power supply used by the navy for daily use. The US Navy attaches great importance to the application of electric power in ships, which are integrated power systems composed of various weapons and equipment transmission, power generation and distribution systems.
Our navy is not inferior in this respect, and there are advanced design theories and analysis methods in China. The bearing capacity and impact capacity of the ship are analyzed experimentally.
summary
This paper introduces and compares three different methods of ship structure limit analysis. Finally, it is concluded that the finite element analysis method takes a long time, but it can analyze and simulate the structural limit of ships at a high level.
refer to
Qi, Peng Xingning. Ultimate strength analysis of asymmetric bending of damaged hull. Proceedings of the 1st Symposium on Structural Mechanics of Ship and Ocean Engineering, Jiujiang, Jiangxi: 1999+036- 143.
Xu Xiangdong, Cui Weicheng, et al. Experimental and theoretical study on ultimate bearing capacity of box girder. Ship mechanics, 2000,4 (5): 36-43.
Zhu, Chen Qingqiang. Study on calculation method of longitudinal strength of large container ship. Ship mechanics, 200 1, 5 (2): 34-42
Guo, Tang, Zhou Binghuan. Ultimate strength analysis and reliability evaluation of damaged hull. China Ship, 1998 (4): 49-56.
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