The aim of this paper is to investigate the ultimate strength of aluminium plates with flatbar stiffeners with a torsional buckling or tripping failure mode. The formulations for torsional buckling of stiffeners in steel plating are still debated. Compared with steel structures, the ultimate strength of aluminium structures is sensitive not only to residual stresses and initial deformations, but also to the deterioration of mechanical strength in heat-affected zones (HAZ). In the present paper, the ultimate strength of stiffened aluminium panels with predominantly torsional failure modes is investigated by experimental and theoretical analysis. Stiffened panels made of the aluminium alloy AA5083-H116 and AA6082-T6 are considered. Various height of flatbar and various thickness of plate and stiffener were studied. The test results are compared with numerical predictions by using the finite element code ABAQUS (ABAQUS Version 5.7 (1997)), considering the influence of initial deflections, welding residual stresses and HAZ. The influence of HAZ and residual stresses on the ultimate strength of stiffened aluminium panels with the actual failure mode is discussed in detail. The numerical predictions are also compared with strength of material formulations used in DNV Rules for Classification of High Speed and Light Craft (Rules for classification of high speed and light craft, Hull structural design (1996)), NORSOK (Design of steel structures (1998)) all for steel, using the relevant values of the modulus elasticity and yield strength of aluminium, as well as EUROCODE 9 (Eurocode 9, Part 1-1: General rules (1998)).

Ultimate strength of stiffened aluminium panels with predominantly torsional failure modes

In the present work, a set of finite element analyses (FEA) was carried out, using Abaqus to reproduce the mechanical behaviour of integrally stiffened panels when subject to longitudinal compression. Since most fabrication processes, such as welding, introduce distortions and affect the material properties, the sensitivity to these defects was assessed. Different shapes and magnitudes of the initial geometrical imperfections were tested and a high sensitivity was observed to both factors on the ultimate load. The existence of a heat affected material showed no influence on the ultimate strength of the tested panels.

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Numerical simulation of aluminium stiffened panels subjected to axial compression: Sensitivity analyses to initial geometrical imperfections and material properties

https://orbi.uliege.be/bitstream/2268/28148/1/20091110154018083.pdf

Sensitivity analysis on ultimate strength of aluminium stiffened panels

Aluminum alloys are being increasingly used in a wide range of construction applications owing to their sound mechanical properties, lightness in weight, strong corrosion resistance, abilit...

/pdf/full-range-stress-strain-curves-for-aluminum-alloys-2g7ylmagm8.pdf

Full-Range Stress–Strain Curves for Aluminum Alloys

The objective of this thesis is to develop improved reliability-based structural design methods for stiffened aluminium. panels in high-speed vessels. In recent years aluminium high-speed vessels have grown larger and are venturing into increasingly hostile operating environments. Designing such vessels requires structural prediction techniques capable of producing a light structure with high confidence in its strength and safety. However, current aluminium marine structural design methods are largely simple modifications of steel methods that do not account for all of the differences between aluminium and steel. TTds thesis presents new reliability-based design techniques for the ultimate strength and fatigue strength of aluminium stiffened panels. A review of recent aluminium high-speed vessels is made, along with their structural configuration and hydrodynamic loading. Structural reliability techniques are discussed. Existing prediction methods, including marine approaches and civil engineering design codes are compared to experimental results for the compressive collapse of aluminium plates and stiffened panels. A modified technique is proposed to model the compressive collapse of such panels. The tensile response of welded aluminium, structures is investigated, including the influence of strain concentration in the reduced-strength region around welds. Reliability formulations are presented and discussed for ultimate strength predictions. A reliability based hot-spot S-N fatigue prediction method is developed for welded connections, including an analysis of the material and prediction uncertainty values and a comparison with existing design codes. Discussion of extending the fatigue prediction techniques to include through-life initiationpropagation fatigue models are presented, along with a simple trial application to butt welds. Conclusions from the techniques investigated are presented, and potential future developments are discussed.

The strength and reliability of aluminium stiffened panels

Flatbar stiffeners are attractive in stiffened plates from a fabrication point of view. Flatbars are susceptible to torsional buckling and collapse. Current approaches to assess torsional buckling strength are uncertain. For instance, formulations for torsional buckling of stiffeners in steel panels are still debated. Compared to steel structures, the strength of aluminum structures is influenced not only by the residual stresses and initial imperfections, but also reductions in mechanical properties in heat-affected zones (HAZ). In the present paper, an experimental and numerical investigation of the torsional buckling strength of longitudinal stiffeners in aluminum (aluminum alloy 5083-H116 and 6082-T6) panels subjected to axial compression is conducted. The experimental results are presented and compared with numerical predictions by using finite element method code ABAQUS, considering the influence of the HAZ and actual initial deflections. The effect of the HAZ on the torsional buckling strength of t...

Experimental and Numerical Prediction of Collapse of Flatbar Stiffeners in Aluminum Panels

Ultimate strength of stiffened aluminium panels exhibiting primarily torsional buckling is investigated by experimental and numerical analysis. Such failure modes are of particular interest in flat bar/bulb stiffeners, which are attractive from a fabrication point of view. Current approaches to assess torsional strength are uncertain. For instance, formulations for torsional buckling of stiffeners in steel panels are still debated. In the present paper, an experimental and numerical investigation of torsional buckling strength of longitudinal flat bar stiffeners in aluminium panels subjected to axial compression is carried out. All 25 stiffened plates with various aluminium material (AA5083 Hl16 and AA6082 temper T6), web height, thickness were tested. Some test results are presented and compared with numerical calculation using ABAQUS (1998), considering initial deflection, welding residual stresses, as well as heat affected zones (HAZ). The experimental and numerical results are also compared with buckling strength formulations used in DNV Rules for Classification of High Speed and Light Craft (1996), NORSOK (1998) for steel, using the relevant values of the modulus elasticity and yield strength of aluminium, as well as the most recent Eurocode 9 (1998) for

Yufeng Zha

Papers

Ultimate strength of stiffened aluminium panels with predominantly torsional failure modes

Experimental and Numerical Prediction of Collapse of Flatbar Stiffeners in Aluminum Panels

Experimental And Numerical Study of Torsional Buckling of Stiffeners In Aluminium Panels