The Impact of Geometric Imperfections on Metallic Stiffened Panels with Skin Bay Buckling Containment Features

2012 ◽  
Author(s):  
Graham Houston ◽  
Damian Quinn ◽  
Adrian Murphy ◽  
Christopher Glazebrook ◽  
Frederic Bron
Keyword(s):  
Geometric Imperfections ◽  
Stiffened Panels ◽  
The Impact

scholarly journals Effects of plies orientations and initial geometric imperfections on buckling strength of a composite stiffened panel

2018 ◽  
Vol 191 ◽  
pp. 00008
Author(s):  
Ikram Feddal ◽  
Abdellatif Khamlichi ◽  
Koutaiba Ameziane
Keyword(s):  
Stiffened Panel ◽  
Buckling Mode ◽  
Element Analysis ◽  
Geometric Imperfections ◽  
Stiffened Panels ◽  
Specific Strength ◽  
Euler Buckling ◽  
Buckling Behavior ◽  
Composite Stiffened Panel ◽  
Strength And Stiffness

The use of composite stiffened panels is common in several activities such as aerospace, marine and civil engineering. The biggest advantage of the composite materials is their high specific strength and stiffness ratios, coupled with weight reduction compared to conventional materials. However, any structural system may reach its limit and buckle under extreme circumstances by a progressive local failure of components. Moreover, stiffened panels are usually assembled from elementary parts. This affects the geometric as well as the material properties resulting in a considerable sensitivity to buckling phenomenon. In this work, the buckling behavior of a composite stiffened panel made from carbon Epoxy Prepregs is studied by using the finite element analysis under Abaqus software package. Different plies orientations sets were considered. The initial distributed geometric imperfections were modeled by means of the first Euler buckling mode. The nonlinear Riks method of analysis provided by Abaqus was applied. This method enables to predict more consistently unstable geometrically nonlinear induced collapse of a structure by detecting potential limit points during the loading history. It was found that plies orientations of the composite and the presence of geometric imperfections have huge influence on the strength resistance.

Comparison of Numerical Results With Experiments on the Ultimate Strength of Long Stiffened Panels

2011 ◽  
Author(s):  
Mingcai Xu ◽  
C. Guedes Soares
Keyword(s):  
Numerical Analysis ◽  
Test Results ◽  
Buckling Mode ◽  
Geometric Imperfections ◽  
Geometric Nonlinearities ◽  
Stiffened Panels ◽  
Initial Imperfections ◽  
Linear Buckling ◽  
Initial Geometric Imperfections ◽  
Collapse Behavior

The behavior of long stiffened panels are simulated numerically and compared with test results of axial compression until collapse, to investigate the influence of the stiffener’s geometry. The material and geometric nonlinearities are considered in the simulation. The initial geometric imperfections, which affect the collapse behavior of stiffened panels, are also analyzed. The initial imperfections are assumed to have the shape of the linear buckling mode. Four types of stiffeners are made of mild or high tensile steel for bar stiffeners and mild steel for ‘L’ and ‘U’ stiffeners. To produce adequate boundary conditions at the loaded edges, three bays stiffened panels were used in the tests and in the numerical analysis.

scholarly journals Stability design criteria for closely spaced built-up stainless steel columns

2021 ◽  
Vol 64 (4) ◽  
pp. 235-250
Author(s):  
Jelena Dobrić ◽  
Nina Gluhović ◽  
Zlatko Marković ◽  
Dragan Buđevac
Keyword(s):  
Stainless Steel ◽  
Shear Stiffness ◽  
Minor Axis ◽  
Structural Performance ◽  
Design Criteria ◽  
Geometric Imperfections ◽  
Steel Columns ◽  
Flexural Buckling ◽  
The University ◽  
The Impact

This paper aims to develop design recommendations for closely spaced built-up stainless steel columns, based on findings gained in performed research at the University of Belgrade. The research focuses on pin-ended built-up columns formed from two press-braked channel chords oriented back-to-back and addresses their flexural buckling capacity about the minor axis. The impact of overall and local chord slenderness, interconnection stiffness, geometric imperfections and material nonlinearity is evaluated. In order to fully exploit their structural performance, two separate approaches for the design of built-up columns with welded or bolted interconnections are defined that include different formulas for shear stiffness.

Crush dynamics of rubber tube under low velocity impact

2013 ◽  
Vol 228 (3) ◽  
pp. 426-440 ◽  
Author(s):  
ZH Zhang ◽  
Y Chen ◽  
HX Hua ◽  
Y Wang
Keyword(s):  
Low Velocity Impact ◽  
Rubber Tube ◽  
Low Velocity ◽  
Geometric Imperfections ◽  
Rubber Material ◽  
Velocity Impact ◽  
Tube Cell ◽  
The Impact ◽  
Global Peak

It is proved that hyperelastic honeycomb coatings can attenuate underwater blast loads impinged on the ship hull. The crush behavior of a unit tube cell of the coating made of rubber material is investigated in this study. A series of tests are conducted to investigate the crush dynamic behavior of the tube under low velocity impact loads. Numerical analyses are carried out to explore the impact process of the rubber tube and the role of some dynamic parameters, thereby serve as a reference in the design of new coating. Some characteristics, such as the geometric imperfections, nonlinear elasticity and material viscosity, are analyzed. The results of simulation and experiments show that the geometric imperfections not only attenuate the shock force in the buckling and the force plateau stages, but also enhance the shock force in the densification stage greatly and promote the global peak force initiation, while the material viscosity enhances the force plateau and attenuates the shock force in the densification stage greatly. These effects are illustrated and quantified with the aid of experiments and numerical calculations.

scholarly journals Review of Ultimate Strength Assessment of Ageing and Damaged Ship Structures

2020 ◽  
Author(s):  
M. Tekgoz ◽  
Y. Garbatov ◽  
C. Guedes Soares
Keyword(s):  
Ultimate Strength ◽  
Load Capacity ◽  
Fatigue Cracking ◽  
Ship Hull ◽  
Structural Behaviour ◽  
Ship Structures ◽  
Strength Assessment ◽  
Stiffened Panels ◽  
The Impact ◽  
Damaged Ship

AbstractThe objective of this work is to provide an overview of the ultimate strength assessment of ageing and damaged ship structures in the last decades. Particular attention is paid to the ultimate strength of plates, stiffened panels, box girders, and entire ship hull structures subjected to corrosion degradation, fatigue cracking, and mechanical damage caused by accidental loading or impact. A discussion on the effect of the cyclic load on the plate rigidity, re-yielding, and ultimate load capacity on the ship hull girder is also part of the present study. Finally, some conclusions and discussions about potential future work are provided, identifying that more studies about the impact of corrosion degradation on the structural behaviour of the stiffened panels and the overall hull girders are needed. Studies related to the dynamic collapse behaviour of corroded and damaged ship structures under time-variant load also requires additional attention.

Passive Sensing of Sensorized Composite Panels: Support Vector Machine

2016 ◽  
Vol 713 ◽  
pp. 199-202
Author(s):  
Nan Yue ◽  
Zahra Sharif Khodaei ◽  
M.H. Ferri Aliabadi
Keyword(s):  
Least Square ◽  
Training Data ◽  
Composite Panel ◽  
Support Vector ◽  
Stiffened Panels ◽  
Passive Sensing ◽  
Vector Machines ◽  
Meta Modeling ◽  
Sensor Signals ◽  
The Impact

Strain readings recorded by surface mounted piezoelectric sensors due to impact events on composite panel are used to detect and characterize the impact. Sensor signals on a composite stiffened panels have been simulated by a valid numerical model. Applicability of least square support vector machines (LSSVM) on creating a meta-model to detect and characterize impact event has been investigated. In particular, the main advantage of LSSVM over other meta-modeling technique was found to be the smaller number of training data that is required. Experimental results on a composite panel has been used to validate the findings.

Reliability Analysis of Buckling Limit State for Friction Stir Welded Aircraft Stiffened Panels

2015 ◽  
Vol 640 ◽  
pp. 35-42 ◽  
Author(s):  
Mouhat Ouadia ◽  
Abdellatif Khamlichi ◽  
Ali Limam
Keyword(s):  
Limit State ◽  
Weld Zone ◽  
Stiffened Panel ◽  
Material Strength ◽  
Heat Affect Zone ◽  
Material Degradation ◽  
Geometric Imperfections ◽  
Stiffened Panels ◽  
Friction Stir ◽  
Initial Geometric Imperfections

Buckling of stiffened panels is strongly affected by initial geometric imperfections. The panel assembling technique used can influence both the initial geometric imperfections pattern and material inohomogeneities. It was recognized for the particular case of stir friction welded stiffened panels that the presence of a weld can decrease significantly buckling strength. This is mainly due to the reduction in material strength in the weld zone. In this work, stir friction welded stiffened panels are modeled by using the finite element method. The modelling takes into account distributed and localized initial geometric imperfections as well as material degradation that are generated in the heat affect zone by this process. A parametric study was conducted on the effects of magnitude of geometric distributed imperfections; position, length and depth of a localized depression; as well as material degradation occurring near the weld stripe. Artificial neural network models were built by using the results of various simulations performed according to full factorial design of experiment tables. This has enabled to assess reliability of design of a stiffened panel with regards to the buckling limit state by means of Monte Carlo approach.

Ultimate Strength of Damaged Stiffened Panels Subjected to Uniaxial Compressive Loads Accounting for Impact Induced Residual Stress and Deformation

2015 ◽  
Author(s):  
Jie Cai ◽  
Xiaoli Jiang ◽  
Gabriel Lodewijks
Keyword(s):  
Residual Stress ◽  
Ultimate Strength ◽  
Carrying Capacity ◽  
Stiffened Panel ◽  
Load Carrying Capacity ◽  
Stiffened Panels ◽  
Load Carrying ◽  
Stress And Deformation ◽  
The Impact ◽  
Residual Stress And Deformation

In case of ship accidents, the ship’s hull will inevitably suffer from damages such as holes, cracks, dent etc., which will threaten the structural safety of ship. It is essential to study the ultimate strength of damaged ships in order to facilitate the decision-making process of ship salvage. There are considerable publications on the subject, however, the impact of the induced residual stress and deformation are normally excluded in those studies. This paper therefore aims at investigating the effect of the impact induced residual stress and deformation on the ultimate strength of a stiffened panel through application of a nonlinear Finite Element Analysis (FEA) method. Firstly, a literature review on ultimate strength of damaged ships is presented. Secondly, a nonlinear numerical simulation is adopted to investigate the ultimate strength of stiffened panels accounting for residual stress and deformation. this procedure consists of two stages: the impact stage and the static stage. The results of the numerical simulation of both stages are validated through the results of experiments and simulations available in literature. Afterwards, a series of case studies are performed deploying the validated numerical method. Finally, a closed form expression to predict the ultimate strength accounting for impact induced residual stress and deformation is proposed based on direct simulation. Results show that the combined effect of impact induced residual stress and deformation can significantly reduce structures’ load carrying capacity. The maximum reduction ratio reaches 37% in local stiffened panel. The method of removal of all the plastic deformation area is generally too conservative to predict the ultimate strength of a damaged local stiffened panel, which will underestimate the residual load carrying capacity of ships considerably.

Formation of Lunar Craters and Bright Rays as a Result of Meteorite Impacts

1962 ◽  
Vol 14 ◽  
pp. 415-418
Author(s):  
K. P. Stanyukovich ◽  
V. A. Bronshten
Keyword(s):  
Explosive Charge ◽  
The Moon ◽  
Meteorite Impacts ◽  
The Earth ◽  
Lunar Craters ◽  
The Impact

The phenomena accompanying the impact of large meteorites on the surface of the Moon or of the Earth can be examined on the basis of the theory of explosive phenomena if we assume that, instead of an exploding meteorite moving inside the rock, we have an explosive charge (equivalent in energy), situated at a certain distance under the surface.

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