Buckling Strength Analysis of Stiffened Panels of Ship Structures Using Non-linear FEM

论文摘要

加筋板是钢板或者铝合金板板结构中基本的强度单元。船舶和海洋结构物都是由加筋板组成的。加筋的板和壳体单元多年来一直应用于多种工程结构中。在造船工程领域中，加筋板用于船体的建造，而在航空航天领域中，加筋板用于飞机的机身和机翼的建造。所以加筋板的屈曲对整个结构的强度至关重要。船体结构的屈曲和极限强度近年来被广泛研究，主要通过理论分析方法，实船实验，经验公式和非线性有限元计算。理论分析方法采用第一准则并且十分精确，许多的研究已经完成。由于课题的复杂性，理论研究的办法主要处理简单的情况。由于建模和计算的耗时耗力等原因，对于设计要求来说加筋板的非线性有限元计算并不切合实际。在上一个十年中，由于计算机计算能力的提升和技术的普及，能给出特殊载荷下结构准确的力学行为且不受弹性范围的限制的非线性有限元分析变得尤为重要起来。目前研究工作旨在利用现有的有限元软件ANSYS完成对加筋板和平板结构的非线性屈曲分析，并且比较理论分析结果和线性屈曲分析结果。分析计算采用两种方法，一种是基于结构强度理论，一种是船级社的设计规范，如ABS,CSR,等等。非线性屈曲分析可以通过ANSYS软件完成。模型的生成和整个分析过程完全采用APDL （ANSYS参数化语言设计）完成。这种方法的优势在于模型的生成和分析过程更加灵活。并且在改变模型参数需要多次迭代计算的情况下能节省大量时间。分析不同的载况并且最后的结果与其他有名望的研究人的理论分析和有限元分析结构相比较，来检验分析结果的准确性。整个过程证明非线性有限元对于了解结构在不同载况下的屈曲行为非常重要。另外，开发一种新的单元初步应用于半解析有限元技术——理想结构单元法。基于理想结构单元理论，用MATLAB编写了能实现几何非线性平板分析的程序。

论文目录

• 摘要
• ABSTRACT
• CHAPTER 1 INTRODUCTION
• 1.1 Stiffened Plate and Panels
• 1.2 Use of Stiffened Panels In Engineering Structures
• 1.3 Buckling And Ultimate Strength
• 1.3.1 Buckling
• 1.3.2 Buckling in Stiffened panels of Ships
• 1.4 Buckling Strength Analysis Techniques
• 1.4.1 Analytical Methods
• 1.4.2 Experimental Tests
• 1.4.3 Empirical Approaches
• 1.4.4 Nonlinear Finite Element Methods
• 1.4.5 Idealized Structural Unit Method （ISUM）
• 1.5 Historical Background
• 1.6 Objectives and Scope of Current Work
• 1.7 Organization Of The Thesis Report
• CHAPTER 2 STIFFENED PLATE AND PANEL ANALYSIS TECHNIQUES
• 2.1 Introduction
• 2.2 Buckling Analysis of Stiffened Panels
• 2.2.1 Plates And Stiffened Panels in offshore structures
• 2.2.2 Structural Buckling
• 2.3 Different Analysis Techniques
• 2.3.1 Analytical method
• 2.3.2 Rules laid down by classification societies
• 2.3.3 Finite element Analysis （FEA）
• 2.3.4 Types of Finite Element Analysis
• 2.3.5 Idealized Structural Unit Method （ISUM）
• CHAPTER 3 THEORETICAL BACKGROUND OF BUCKLING STRENGTH EVALUATION
• 3.1 Introduction
• 3.2 Description of the Chosen Panel
• 3.2.1 Geometrical properties
• 3.2.2 Material Properties
• 3.2.3 Loading conditions
• 3.3 Theoretical And Empirical Formulations For Buckling Strength Evaluation of plate panel
• 3.3.1 Plate Dimensions
• 3.3.2 Plate Loading conditions
• 3.3.3 Boundary Conditions
• 3.3.4 Elastic buckling of plate under single type of load
• 3.3.5 Elastic buckling of plate under two load components （Biaxial compression）
• 3.3.6 Lateral pressure loading in addition to biaxial compression
• 3.3.7 Elastic-plastic Buckling of plates
• 3.4 Plate panel Buckling strength Parameters
• 3.5 Theoretical And Empirical Formulations For Buckling Strength Evaluation of Stiffened Panel
• 3.5.1 Stiffened Panel Loading conditions
• 3.5.2 Boundary Conditions for panel
• 3.5.3 Elastic buckling of Panel under Longitudinal Axial compressive load
• 3.5.4 Elastic Local Buckling of Plate
• 3.5.5 Elastic Local Buckling of Stiffener Web
• 3.5.6 Elastic Local Buckling of Stiffener Flange
• 3.6 Buckling Analysis Using FEM Techniques
• 3.7 Buckling Analysis Using ANSYS
• 3.7.1 GUI Method
• 3.7.2 Using APDL
• 3.8 Linear Buckling Analysis
• 3.8.1 Procedure to perform the Linear Buckling analysis in ANSYS
• 3.9 Non-Linear Buckling Analysis
• 3.9.1 Procedure to perform the Non-Linear Buckling analysis in ANSYS
• CHAPTER 4 LINEAR AND NONLINEAR BUCKLING ANALYSIS & RESULTS
• 4.1 Introduction
• 4.2 Specifications of the Stiffened Panel and Plate Panel
• 4.3 Initial Imperfections
• 4.4 Linear （Eigenvalue） analysis of Plate Panel:
• 4.4.1 Pre-processing
• 4.4.2 Solution Phase
• 4.4.3 Post-Processing
• 4.5 Nonlinear analysis of Plate Panel
• 4.6 Generation of imperfections for nonlinear analysis
• 4.7 Running the Nonlinear Buckling Analysis
• 4.8 Buckling strength under longitudinal stress with lateral pressure
• 4.8.1 Buckling strength of plate panel under biaxial loading
• 4.9 Linear （Eigenvalue） analysis of stiffened Panel
• 4.9.1 Finite Element Model Details
• 4.10 Discussion on Results
• CHAPTER 5 DEVELOPMENT OF ISUM UNIT
• 5.1 The background
• 5.1.1 Types of Nonlinearities
• 5.2 Idealized structural unit method （ISUM）
• 5.3 Modelling strategies for steel plated structures using ISUM
• 5.4 Procedure for development of ISUM units
• 5.5 Development of the ISUM rectangular plate unit for analysis of ultimate strength
• 5.6 Theoretical background
• 5.7 Strain-displacement relationship
• 5.8 The Elastic tangent stiffness matrix [K]E
• 5.9 Total lagrangian approach
• 5.10 The Updated Lagrangian Approach
• 5.11 Formulation For the ISUM Unit
• 5.11.1 Shape Function
• 5.11.2 Derivation of strain-displacement matrix Bp and Bb
• 5.11.3 Solution of the Nonlinear set of equations:
• 5.12 Discussion on Improvement of Element
• CONCLUDING REMARKS AND FUTURE RECOMMENDATIONS
• Concluding Remarks
• Recommendations for Future Work
• REFERENCES
• ACKNOWLEDGEMENTS