On the Ductile Response of Stiffened Panels Subjected to Lateral Indentation: Experimental and Numerical Analysis

2010 ◽  
Author(s):  
Hagbart S. Alsos ◽  
Jo̸rgen Amdahl
Keyword(s):  
Finite Element ◽  
Plate Thickness ◽  
Offshore Structures ◽  
Instability Criterion ◽  
Potential Hazard ◽  
Explicit Finite Element ◽  
Stiffened Panels ◽  
Environmental Consequences ◽  
Structural Capacity ◽  
Indentation Tests

Reliable prediction of ductile fracture is essential in analysis of accidental response of ships and offshore structures. The consequences of fracture are significant. It may imply a significant reduction in structural capacity. It may also pose a potential hazard for human safety, as well as lead to an environmental and economical loss, e.g. caused by tanker collision or grounding. A series of five steel-plate indentation tests were conducted at the Norwegian University of Science and Technology (NTNU), Department of Mariner Technology, during late fall 2007. These are performed quasi-statically on various configurations of stiffened panels. The tests represent hull or deck plates in ships or platform structures subjected to accidental actions from ship-ship collisions, ship grounding or dropped object impacts. Various configurations of stiffened panels are tested, all laterally by a cone shaped indenter until fracture occurred. The specimen dimensions represent a 1:3 scale of the dimensions found in medium sized tankers, i.e. plate thickness of 5 mm. Naturally, because damaged hull and cargo tanks may cause severe environmental consequences, focus is on the plastic deformation and fracture resistance of the panels. The panel tests are primarily intended to serve as verification for advanced finite element simulations using a failure criterion based on instability mechanisms, i.e. local necking. This is implemented into the non linear explicit finite element code LS-DYNA and is referred to as the BWH instability criterion. In addition, the influence of the element size with respect to onset of failure is studied using three different element sizes for the various test cases. Although, attention is primarily placed on accidental scenarios, such as ship collision and grounding, the experimental results are of considerable relevance for other types of abnormal actions, e.g. dropped objects on deck and subsea structures, and stiffened panels subjected to explosion or ice actions.

Comparative Study of Hydroelastic Impact for One Free-Drop Wedge With Stiffened Panels by Experimental and Explicit Finite Element Methods

2011 ◽  
Author(s):  
Hanbing Luo ◽  
Hui Wang ◽  
C. Guedes Soares
Keyword(s):  
Finite Element ◽  
Stress Responses ◽  
Complex Structure ◽  
Water Entry ◽  
Explicit Finite Element ◽  
Stiffened Panels ◽  
Longitudinal Stiffeners ◽  
Free Drop ◽  
Good Agreement ◽  
Impact Problem

This paper studies the hydroelastic responses of a complex structure for one water entry problem. One steel wedge with complex stiffened panels was designed with a deadrise angle of 22 degrees and a series free-drop model tests were carried out. An explicit finite element code is adopted to simulate this coupled hydroelastic impact problem. The motion, stress responses on longitudinal stiffeners and transverse frames are obtained. Comparisons of the numerical and the experimental results are carried out. Good agreement is achieved. The hydroelastic effect is discussed.

scholarly journals Assessment of Buckling Behaviour on an FPSO Deck Panel

2020 ◽  
Vol 27 (3) ◽  
pp. 50-58 ◽  
Author(s):  
Ozgur Ozguc
Keyword(s):  
Finite Element ◽  
Limit State ◽  
Practical Interest ◽  
Structural Response ◽  
Ultimate Limit State ◽  
Imperfection Sensitivity ◽  
Stiffened Panels ◽  
Structural Capacity ◽  
Response Subject ◽  
Ultimate Limit

AbstractStiffened plates are the main structural building block in ship and offshore hulls and their structural response subject to loads is a topic of significant practical interest in ship and offshore structural design. To investigate the structural capacity for design and evaluation purposes, it is becoming an efficient and reliable practice to carry out non-linear finite element (FE) analysis. The present study is to assess the buckling strength of a stiffened deck panel on an FPSO vessel using the nonlinear finite element code ADVANCE ABAQUS, where imperfection sensitivity work is also accounted for. The cases studied correspond to in-plane bi-axial compression in the two orthogonal directions. The findings are compared with the DNVGL PULS (Panel Ultimate Limit State) buckling code for the stiffened panels. It is found that the strength values from the ADVANCE ABAQUS and DNVGL PULS code are very close. The results and insights developed from the present work are discussed in detail.

On Buckling and Ultimate Strength of Perforated Plate Panels under Axial Compression: Experimental and Numerical Investigations with Design Formulations

2008 ◽  
Author(s):  
Ul-Nyeon Kim ◽  
Ick-Heung Choe ◽  
Jeom Kee Paik
Keyword(s):  
Finite Element ◽  
Ultimate Strength ◽  
Steel Plate ◽  
Slenderness Ratio ◽  
Plate Thickness ◽  
Shipbuilding Industry ◽  
Perforated Plates ◽  
Stiffened Panels ◽  
Buckling Strength ◽  
Plate Panels

It has been recognized that the current shipbuilding industry design practice for perforated plates is not relevant with relatively large opening size and/or with large plate thickness, and it is believed that this problem has caused structural damage accidents in actual ship structures with opening. The motive of the present study was initiated to resolve this issue by introducing a new design formulation of the critical buckling strength for perforated plates which is now pertinent to the structural design application at a safety side. For this purpose, a series of experimental and numerical studies are undertaken on buckling and ultimate strength of plates and stiffened panels with an opening and under axial compressive actions. A total of 90 perforated plates and also a total of 9 stiffened panels with an opening are tested until and after the ultimate strength is reached, where important parameters of influence such as the plate aspect ratio, the plate slenderness ratio, the opening size and shape, and the opening location are varied. Elastic-plastic large deflection finite element analyses are performed on the test structures. Existing and newly-derived design formula solutions of buckling and ultimate strength on the test plate panels are compared with experimental results and nonlinear finite element computations, indicating that the critical buckling strength formulation developed in the present study as well as an existing ultimate strength formula is useful for design and strength assessment of steel plate panels with an opening. The experimental database on buckling collapse of steel plate panels with an opening will be very useful for future use. Details of experiments and numerical computations together with insights developed from the present study are documented.

Effect of Pressure on Collapse Behaviour of Stiffened Panel

2014 ◽  
Author(s):  
Lei Jiang ◽  
Shengming Zhang
Keyword(s):  
Finite Element ◽  
Failure Modes ◽  
Lateral Pressure ◽  
Initial Pressure ◽  
Offshore Structures ◽  
Numerical Results ◽  
Stiffened Panel ◽  
Longitudinal Stress ◽  
Stiffened Panels ◽  
Hull Girder

During normal operations, ship and offshore structures, are subjected to combined lateral pressure and in-plane stresses. The effect of the lateral pressure is often ignored in hull girder ultimate assessments. This paper investigates the influence of the lateral pressures on the nonlinear collapse behavior of stiffened panels subjected to in-plane longitudinal stress. In this study, nonlinear finite element analyses were first conducted for the desired pressure alone; the longitudinal stress was then applied up to and beyond the collapse of the structures. Four representative stiffened panels taken from the bottoms of different double hull oil tankers were considered. The nonlinear analyses were performed using LR’s in-house finite element program VAST and following the procedure for nonlinear collapse analysis developed by LR. The numerical results indicated that the application of the initial pressure loads not only reduced the ultimate load carrying capacity of the panels significantly, but also changed the failure modes of the structures. The sensitivity of the ultimate strength to lateral pressure was dependent upon the panel geometry and whether the pressure was applied on the plate or the stiffener side. The numerical results and findings from this study are presented in this paper.

Computer-Aided Design of Protective Structures: Numerical Simulations and Experimental Validation

2011 ◽  
Vol 82 ◽  
pp. 686-691 ◽  
Author(s):  
Sumita Dey ◽  
Tore Børvik ◽  
Odd Sture Hopperstad
Keyword(s):  
Finite Element ◽  
Computer Aided Design ◽  
Experimental Validation ◽  
Plate Thickness ◽  
Experimental Tests ◽  
Layered Plates ◽  
Explicit Finite Element ◽  
Ballistic Protection ◽  
Computer Aided ◽  
Aided Design

This paper aims through several numerical studies to highlight some effects of layering plates in ballistic protection. The possible increase in perforation resistance by varying the material properties of the plates, the individual plate thickness (the total plate thickness is constant) and the stacking of individual plates in a double-layered target when struck by blunt and ogival nose projectiles has been investigated. This was done by conducting non-linear finite element simulations of the perforation process using an experimentally validated numerical model and an explicit finite element code. These studies are difficult to carry out experimentally due to the many materials and thicknesses involved and computer-aided design is thus an attractive approach. The numerical design indicates that it is possible to considerably increase the overall ballistic protection level by using double-layered plates and a proper design. Some of the most promising designs were then selected for experimental validation. The experimental tests gave completely opposite results than the computer-aided design, and the reasons for this will be discussed in some detail.

Evaluation of Loads During a Free-Fall Lifeboat Drop

2013 ◽  
Author(s):  
Andrea Califano ◽  
Kristoffer Brinchmann
Keyword(s):  
Finite Element ◽  
Structural Integrity ◽  
Early Stage ◽  
Free Fall ◽  
Element Model ◽  
Emergency Evacuation ◽  
Offshore Structures ◽  
Element Analysis ◽  
Safety Requirements ◽  
Structural Capacity

A new Offshore Standard (DNV-OS-E406) [1] has been developed for the design of Free Fall Lifeboats (FFLB) used for emergency evacuation from offshore structures. This standard aims at ensuring safe evacuation, focusing on the design at an early stage. Load (CFD) and structural (FE) analyses are used to assist in determining whether or not the free fall lifeboats comply with the Target Safety requirements as set forth by the Standard. The present paper describes the methodology used when assessing the structural capacity of FFLB. The structural integrity is established throughout every phase of a lifeboat drop, linking computational fluid dynamics (CFD) and finite element analysis (FEA). Loads computed from CFD on a finite volume mesh are interpolated to a finite element model where the structural analysis can be performed in order to obtain stresses, strains and deflections, and finally assess the structural capacity of the lifeboat. Emphasis in this work is given to the hydrodynamic model and loads, while structural analyses are discussed more in depth by Brinchmann et al. [2].

Prediction of Tread Pattern Wear by an Explicit Finite Element Model3

2007 ◽  
Vol 35 (4) ◽  
pp. 276-299 ◽  
Author(s):  
J. C. Cho ◽  
B. C. Jung
Keyword(s):  
Finite Element ◽  
Wear Rate ◽  
Tangential Stress ◽  
Rate Equation ◽  
Constitutive Equations ◽  
Slip Velocity ◽  
Test Results ◽  
Explicit Finite Element ◽  
Driving Condition ◽  
Driving Conditions

Abstract Tread pattern wear is predicted by using an explicit finite element model (FEM) and compared with the indoor drum test results under a set of actual driving conditions. One pattern is used to determine the wear rate equation, which is composed of slip velocity and tangential stress under a single driving condition. Two other patterns with the same size (225/45ZR17) and profile are used to be simulated and compared with the indoor wear test results under the actual driving conditions. As a study on the rubber wear rate equation, trial wear rates are assumed by several constitutive equations and each trial wear rate is integrated along time to yield the total accumulated wear under a selected single cornering condition. The trial constitutive equations are defined by independently varying each exponent of slip velocity and tangential stress. The integrated results are compared with the indoor test results, and the best matching constitutive equation for wear is selected for the following wear simulation of two other patterns under actual driving conditions. Tens of thousands of driving conditions of a tire are categorized into a small number of simplified conditions by a suggested simplification procedure which considers the driving condition frequency and weighting function. Both of these simplified conditions and the original actual conditions are tested on the indoor drum test machines. The two results can be regarded to be in good agreement if the deviation that exists in the data is mainly due to the difference in the test velocity. Therefore, the simplification procedure is justified. By applying the selected wear rate equation and the simplified driving conditions to the explicit FEM simulation, the simulated wear results for the two patterns show good match with the actual indoor wear results.

Tire Cornering Simulation Using an Explicit Finite Element Analysis Code

1998 ◽  
Vol 26 (2) ◽  
pp. 109-119 ◽  
Author(s):  
M. Koishi ◽  
K. Kabe ◽  
M. Shiratori
Keyword(s):  
Finite Element Method ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Test System ◽  
Experimental Results ◽  
The Finite Element Method ◽  
Element Analysis ◽  
Explicit Finite Element ◽  
Explicit Finite Element Analysis ◽  
Element Method

Abstract The finite element method has been used widely in tire engineering. Most tire simulations using the finite element method are static analyses, because tires are very complex nonlinear structures. Recently, transient phenomena have been studied with explicit finite element analysis codes. In this paper, the authors demonstrate the feasibility of tire cornering simulation using an explicit finite element code, PAM-SHOCK. First, we propose the cornering simulation using the explicit finite element analysis code. To demonstrate the efficiency of the proposed simulation, computed cornering forces for a 175SR14 tire are compared with experimental results from an MTS Flat-Trac Tire Test System. The computed cornering forces agree well with experimental results. After that, parametric studies are conducted by using the proposed simulation.

The Study on Crashworthiness Performance of Thin-Walled Structures and the Effect of Welding Performance on it

2011 ◽  
Vol 63-64 ◽  
pp. 655-658
Author(s):  
Qi Hao ◽  
Sheng Jun Wu
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Welded Joints ◽  
Impact Force ◽  
Deformation Energy ◽  
Optimal Shape ◽  
Explicit Finite Element Method ◽  
Explicit Finite Element ◽  
Thin Walled Structures ◽  
Thin Walled

Explicit finite element method is adopted to simulate the crashworthiness performance of four types of typical thin—walled structures used in vehicle by software LS-DYNA. The structures with the same material、area and length are crash by a rigid body with 40km/h in10ms, The crash processes and crashworthiness characters are analyzed by a series crash parameters: deformation energy with unit displacement, impact force and deceleration to look for the optimal shape with crashworthiness. With comparing, the double caps section has ascendant performance than the others. The simulating methods of welded-joints are discussed to analysis their effects on crashworthiness simulation.

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