Aluminum Square Research Articles

Web crippling of aluminium tubular structural members strengthened by CFRP

Aluminium tubular structural members may experience web crippling failure due to localise concentrated loads or reactions. This paper presents a test programme on strengthening of high strength aluminium tubular structural members using externally bonded carbon fibre-reinforced polymer (CFRP). A series of tests on CFRP strengthened aluminium square and rectangular hollow sections subjected to web crippling is presented. The web crippling tests were conducted under four loading conditions of End-Two-Flange, Interior-Two-Flange, End-One-Flange and Interior-One-Flange. A total of 48 web crippling tests was conducted in this study. The investigation was mainly focussed on the effects of web slenderness of aluminium tubular sections on CFRP strengthening against web crippling. The tests were performed on eight different sizes of square and rectangular hollow sections which covered a wide range of web slenderness (flat portion of web depth-to-thickness) ratio from 6.2 to 62.2. The test specimens were fabricated by extrusion from 6061-T6 heat-treated aluminium alloys. Material properties of the aluminium sections were obtained from tensile coupon tests. Most of the strengthened specimens were failed by debonding of CFRP plate from the aluminium tubes. Three main failure modes were observed in the tests, namely the adhesion, combination of adhesion and cohesion, and interlaminar failure of CFRP plate. The failure loads, failure modes and the load-web deformation behaviour of the aluminium sections are also presented. It was found that the web crippling capacity of aluminium sections are significantly increased due to CFRP strengthening, especially for those sections with large value of web slenderness ratio.

Experimental study of impact energy absorption in aluminium square tubes with thermal triggers

This study presents an approach for the improvement of crashworthiness properties of aluminium tubular structures using initiators introduced through localized heating. The main objective of this approach is to improve the ability to absorb impact energy in a progressive and controlled manner by a local modification of material properties. Through a localized heating in areas previously chosen for initiation, associated with the softening of the aluminium alloy the deformation can be introduced precisely, forcing the tubular structure to deform in a mode of high energy absorption and reducing the maximum load in a controlled manner. This study presents the properties for an aluminium alloy 6061-T5 modified by thermal treatment by the use of a laser beam. Experimental results are presented of quasi-static and impact tests of tubular structures using the proposed approach. This concept appears as possible and effective in the experimental work presented.

Crash of automotive side member subjected to oblique loading

This paper presents the crash behavior analysis of automotive side member represented by aluminum square column subjected to oblique loading via finite element method. In crash research, energy absorption capacity is greatly affected by the deformation pattern, thus the collapse behavior and deformation pattern of this column is studied and observed. Effect of the geometrical parameters and loading angle, effect of these parameters on crashworthiness parameters that is specific energy absorption (SEA) and crush force efficiency (CFE) are explored. Observation on deformation pattern of the column shows that the bending is more apparent at the upper end for loading angle of 5 to 15° and at the bottom end for loading angle of 20 to 30°. Results also show that SEA and CFE have less effected on the variation of column width. Ultimately, an equation that is expressed as a function of length and thickness is proposed to estimate crashworthiness parameters. Key words: Column, oblique loading, crashworthiness.

Experimental, theoretical, and numerical studies on the response of square plates subjected to blast loading

This article presents the results of experimental and analytical studies on the response of steel and aluminium square plates with different thicknesses subjected to blast loading. Based on the blast wave details and the scaling law for explosions, a method of determining the blast load is proposed in which ballistic pendulums do not need to be utilized for obtaining the blast wave impulses. The loads applied to the plates are assumed to be the quasi-exponential pressure pulses, which are the same as the explosion overpressures. The theoretical solutions are presented using a rigid, perfectly plastic idealization and are exact within the context of dynamic plasticity. The dynamic energy imparted to structures can cause material failure. The presented investigation considers such a failure for fully clamped plates subjected to a blast loading idealized as an initial velocity distributed uniformly throughout the area. The predicted deflections and general failure modes of the plates are presented and compared with experimental results. Moreover, a numerical simulation is carried out by modelling an FSI (fluid–solid interaction) problem. Results are compared with each other and a better agreement between numerical results with experimental ones is observed.

Characterization of damage size in metallic plates using Lamb waves

By employing the Lamb waves for monitoring the structural integrity, a theory was proposed to approximately evaluate the damage size based on the reflection intensity information from the damage. First, to relate the wave reflection intensity to the size and shape of the damage, this theory was constructed for an arbitrary elliptical damage, which can be changed into a crack-like or a circular damage. Then, this theory was verified by employing the numerical results predicted by a powerful numerical approach for through-thickness elliptical holes in aluminum plates. Furthermore, experimental verification was also performed for through-thickness circular holes in aluminum plates. By assuming a damage of a circular shape, this theory was further extended to approximately predict the damage size using a coarse sensor/actuator network after identifying the damage location. To validate the proposed method, a four PZT transducer network was used to experimentally identify the locations and sizes of a circular hole and an elliptical hole in aluminum square plates.

Image quality assessment in digital mammography: part II. NPWE as a validated alternative for contrast detail analysis

Assessment of image quality for digital x-ray mammography systems used in European screening programs relies mainly on contrast-detail CDMAM phantom scoring and requires the acquisition and analysis of many images in order to reduce variability in threshold detectability. Part II of this study proposes an alternative method based on the detectability index (d′) calculated for a non-prewhitened model observer with an eye filter (NPWE). The detectability index was calculated from the normalized noise power spectrum and image contrast, both measured from an image of a 5 cm poly(methyl methacrylate) phantom containing a 0.2 mm thick aluminium square, and the pre-sampling modulation transfer function. This was performed as a function of air kerma at the detector for 11 different digital mammography systems. These calculated d′ values were compared against threshold gold thickness (T) results measured with the CDMAM test object and against derived theoretical relationships. A simple relationship was found between T and d′, as a function of detector air kerma; a linear relationship was found between d′ and contrast-to-noise ratio. The values of threshold thickness used to specify acceptable performance in the European Guidelines for 0.10 and 0.25 mm diameter discs were equivalent to threshold calculated detectability indices of 1.05 and 6.30, respectively. The NPWE method is a validated alternative to CDMAM scoring for use in the image quality specification, quality control and optimization of digital x-ray systems for screening mammography.

Numerical modelling of partially filled aircraft fuel tanks submitted to Hydrodynamic Ram

Hydrodynamic Ram (HRAM) is a phenomenon that occurs when a high-kinetic energy object penetrates a fluid-filled container. The projectile transfers its momentum and kinetic energy through the fluid to the surrounding structure, increasing the risk of catastrophic failure and excessive structural damage. This is of particular concern in the design of wing fuel tanks for aircraft since it has been identified as one of the important factors in aircraft vulnerability. Usually the HRAM phenomenon is analyzed considering completely filled tanks, but its effect on partially filled containers should also be taken into account due to the fact that tanks use to be impacted under these conditions. In the present paper, the commercial finite element code LS-DYNA has been used to simulate an HRAM event created by a steel spherical projectile impacting a partially water-filled aluminium square tube. The ALE formulation is employed to reproduce the event. Experimental tests which indicate the pressure at different points of the fluid, displacement of the walls and cavity evolution for different impact velocities, are compared with the numerical results in order to assess the validity and accuracy of the ALE technique in reproducing such a complex phenomenon.

Web crippling of aluminium tubes with perforated webs

Experimental and numerical investigations of aluminium alloy square hollow sections with a circular hole in the webs subjected to web crippling are presented in this paper. A total of 216 data that include 84 test results and 132 numerical results are presented. The web crippling tests were conducted under two loading conditions of end-two-flange (ETF) and interior-two-flange (ITF). The test specimens were fabricated by extrusion using a 6061-T6 heat-treated aluminum alloy. The web holes were located at the mid-depth of the webs and centred beneath the bearing plates. A non-linear finite element model is developed and verified against the experimental results. Geometric and material non-linearities were included in the finite element model. It was shown that the finite element model closely predicted the web crippling strengths and the failure modes of the tested specimens. Hence, the model was used for an extensive parametric study of the different sizes of the cross-section and circular holes in the webs. The influence of the circular web holes on the web crippling strength of aluminium square hollow sections is investigated in this study. Web crippling strength reduction factor equations are proposed for the ETF and ITF loading conditions. It is shown that the proposed strength reduction factors are generally conservative and agree well with the experimental and numerical results. Furthermore, a unified web crippling equation for the aluminium square hollow sections with circular web holes is also proposed.

Crushing behavior of lightmass structural member

Carbon fiber reinforced plastic (CFRP) of the advanced composite materials is widely used in lightmass structural materials of air planes, ship and automobiles because of high strength and stiffness. In this study, experimental investigation was performed for each specimen. The square section members consist of aluminum, CFRP and hybrid (aluminum/CFRP) member, and hat-shaped section members consist of CFRP and hybrid (aluminum/CFRP) members specimen. Based on the collapse characteristics of aluminum square section member, the collapse characteristics and energy absorption capability of hat-shaped section members were analyzed. The axial static collapse tests were carried out for each section member. The collapse modes and the energy absorption capability of the members were analyzed. In the lightmass design aspect, the collapse characteristics and energy absorption capability of the members were compared.

Tests and Design of Aluminum Tubular Sections Subjected to Concentrated Bearing Load

This paper presents a series of tests on high strength aluminum square hollow sections subjected to concentrated bearing load. A total of 64 web-bearing tests was conducted. The test specimens were fabricated by extrusion using 6061-T6 heat-treated aluminum alloy. The tests were carried out under end and interior loading conditions, where the specimens were seated on a fixed solid steel base plate. These tests closely simulated the support condition of the floor joist members seated on solid foundation. The test results were compared with the design strengths obtained using the American Aluminum Design Manual and European code for aluminum structures. It was shown that the design strengths predicted by these codes are either quite conservative or unconservative. Furthermore, the Australian Standard AS4100 and British Standard BS5950 Part 1 were used for aluminum square hollow section with sharp corners. The design rules of steel codes were modified to predict the web-bearing strength based on this study. ...

The piezoelectric thickness mode hydrophone using tonpilz structure for deep‐sea application.

A piezoelectric thickness mode hydrophone for deep‐sea application using tonpilz structure was designed, and its macroprototype was made as a preliminary for the micromachined version. Several types of micromachined thin‐diaphragm sensors for hydrophone application have been reported. They have two issues in deep‐sea applications. One is a sensitivity problem. To enhance the sensitivity, a cone structure for sound pressure amplification was placed between the clamped diaphragm and the piezoelectric square plate. To evaluate the effect of the cone structure on sensitivity, which was motivated by tonpilz structure, an air‐backed prototype was made using aluminum and piezoelectric ceramic square plate of 700 μm length and 400 μm thickness. A lumped parameter model was used in the design procedure. The measured sensitivity of the prototype was −249.60 dB ref. One volt per micropascal without a preamplifier, and the measured resonant frequency was 30 kHz, which agreed with the prediction. The other is an endurance problem due to high hydrostatic pressure. To develop the endurance for the high hydrostatic pressure in deep‐sea, PZT thickness mode and oil‐backing on the diaphragm backside were proposed. The comparison of oil‐backing and air‐backing is to be presented as an evaluation of the endurance development. [Research supported by MRCnd.]

Bivalve Assemblages on Living Coral Species in the Northern Red Sea, Egypt

Two stations northern Hurghada (Marine Biological Station and Ras El-Behar) were chosen during summer 2006 and winter 2007, to study and evaluate the compatibility of living bivalve assemblages on the living corals. Twenty-nine samples of hard corals contributed by living bivalves were collected using 0.25 m2 aluminum square frame and were taken during daylight using SCUBA diving equipments. A total surveyed area of 132 m2 and 534 bivalve individuals were counted from the studied sites and were associated with living corals, these individuals represented by 7 different families and 12 species. Pteriidae represented the highest individual numbers 229 (42.88%), whereas Veneridae recorded the lowest number 11 (2.06%). Electroma alacorvi recorded the highest presence 35.38% whereas Gefrarium pectinatum had the lowest value 2.06%. There was a high association and correlation between density and standard deviation of the bivalves. Mytilidae and Pteriidae have a wide and strong association with some corals (as Stylophora pistillata; Porites solida; Pocillopora verrucosa; Favites abdita; Favites fluxuosa; and Goniastrea pictinata; Acropora pharonis; Montipora venosa; Acropora humilis, Anacropora spinosa and Montipora spongiosa), whereas Pectinidae, Arcidae, and Tridacnidae have a low coral association. Electroma alacorvi recorded the highest density 6.79 individuals/0.25m2 and a standard deviation ±2.41, whereas Barbatia setigera recorded the lowest density 1.9 individuals/0.25 m2 (S.D ± 0.78). Sedimentation rate and the large coral coverage play a major role in the bivalve assemblages, density, and diversity where the highest coverage and dominance of Stylophora pistillata, Acropora spp., Porites solida, Favites spp., and Goniastrea pictinata were associated with high bivalve species density. Finally, the over-fishing activities, pollution particularly with oil and sedimentation are the major reasons for coral death causing absence of many bivalve species at Ras El-Behar.

Numerical modelling of the hydrodynamic ram phenomenon

Hydrodynamic ram (HRAM) is a phenomenon that occurs when a high-kinetic energy object penetrates a fluid-filled container. The projectile transfers its momentum and kinetic energy through the fluid to the surrounding structure, increasing the risk of catastrophic failure and excessive structural damage. This is of particular concern in the design of wing fuel tanks for aircraft since it has been identified as one of the important factors in aircraft vulnerability. In the present paper, the commercial finite-element code LS-DYNA has been used to simulate an HRAM event created by a steel spherical projectile impacting a water-filled aluminium square tube. Two different formulations (ALE and SPH) are employed to reproduce the event. Experimental tests which indicate the pressure at different points of the fluid, displacement of the walls and cavity evolution for different impact velocities are compared with the numerical results in order to assess the validity and accuracy of both ALE and SPH techniques in reproducing such a complex phenomenon.

Dependence of Particle Number on Density of States of an Aluminum Nanocluster

On basis of the Hubbard model density of states of the 2D square nanosystem by size of N × N aluminum atoms with N = 3÷30, and also density of states of the 2D aluminum square nanocluster, where one of the aluminum atom is changed by oxygen atom, is calculated. It is shown that the local density of state depends on the total number of atoms in the cluster, and also on the location of atom in a lattice and the atom sort in a lattice site.

Experimental analysis of fluid-filled aluminium tubes subjected to high-velocity impact

Abstract Hydrodynamic ram (HRAM) is a phenomenon that occurs when a high-energy object penetrates a fluid-filled container. The projectile transfers its momentum and kinetic energy through the fluid to the surrounding structure increasing the risk of catastrophic failure and excessive structural damage. It is of particular concern in the design of wing fuel tanks for aircraft since it has been identified as one of the important factors in aircraft vulnerability. For the present work, water-filled aluminium square tubes (6063-T5) were subjected to impact by steel spherical projectiles (12.5 mm diameter) at impact velocities of 600–900 m/s. The aluminium tubes were filled at different volumes to study how an air layer inside the tank might influence the impact behaviour. The test boxes were instrumented with five strain gauges and two pressure transducers. The formation process of the cavity was recorded with a high-speed camera. This work presents the results of these tests.

Behaviour and design of aluminium hollow sections subjected to transverse blast loads

Experimental and analytical investigations of metal beams subjected to transverse blast loads have predominantly focused on solid metal cross-sections. In applications such as the secondary structural members used in facade structures the cross-sections consist of thin-walled aluminium hollow profiles. This paper presents an experimental study of 73 aluminium square hollow sections subjected to transverse blast loads by application of explosives. Four different section slenderness values and three different lengths were investigated, resulting in a wide range of length/depth ratios typical to facade structures. A semi-empirical analytical solution is presented whereby existing theory developed by others for solid metal sections is modified to account for local section deformations that occur in blast-loaded hollow sections. The technique considers both the energy dissipated in local deformations and the resulting reduction in the section-bending modulus, and furnishes a solution that bounds the experimental results with reasonable accuracy. A general design procedure is outlined that may be based on a final permanent deformation or a failure load, and the limitations of such a procedure are discussed.

Aluminum tubular sections subjected to web crippling—Part II: Proposed design equations

The web crippling design rules in the current American Aluminum Design Manual, Australian/New Zealand Standard, and European code for aluminum structures are assessed. Test strengths of aluminum square and rectangular hollow sections under end-two-flange (ETF) and interior-two-flange (ITF) loading conditions are compared with the design strengths (capacities) obtained using the aforementioned specifications. Furthermore, the test strengths are also compared with the design strengths obtained using the unified web crippling equation as specified in the North American Specification for cold-formed steel structural members. It is shown that the design strengths predicted by the aforementioned specifications are either quite conservative or unconservative, but in general the predictions are unreliable resulting from reliability analysis. Hence, two different unified web crippling equations for aluminum square and rectangular hollow sections under ETF and ITF loading conditions are proposed. The proposed unified design equation (A) uses the same technique as the North American Specification for the unified web crippling equation with new coefficients of C, C N and C h determined based on the test results obtained in this study. The proposed unified design equation (B) is similar to the unified web crippling equation in the NAS Specification, and the effect of the ratio N/h is also considered, where N is bearing length and h is the depth of the flat portion of web. Generally, it is shown that the proposed unified web crippling equation (B) compares well with the test results.

Aluminum tubular sections subjected to web crippling—Part I:: Tests and finite element analysis

A series of tests on aluminum square and rectangular hollow sections subjected to web crippling is presented. A total of 150 web crippling tests were conducted. The web crippling tests were conducted under two loading conditions of end-two-flange (ETF) and interior-two-flange (ITF). The concentrated load was applied by means of bearing plates, which act across the full flange width of the specimen sections. Different bearing lengths were investigated. The test specimens were fabricated by extrusion using 6063-T5 and 6061-T6 heat-treated aluminum alloys. The test specimens consisted of normal strength material (T5) with the 0.2% tensile proof stress (yield stress) ranging from 185 to 196 MPa, and high-strength material (T6) with the 0.2% tensile proof stress ranging from 226 to 317 MPa. The measured web slenderness value of the tubular sections ranged from comparatively stocky webs of 6.3 to relatively more slender webs of 74.5. The effect of the 0.2% proof stress and bearing length on the web crippling strength (capacity) of aluminum tubular sections was investigated. In the literature, little test data are available on aluminum members subjected to web crippling. The web crippling test results obtained from this study are valuable for the development of design rules. A non-linear finite element model (FEM) is developed and verified against the test results. The geometric and material non-linearities were considered in the FEM. It is shown that the FEM closely predicted the web crippling strengths and failure modes of the tested specimens.

Crashworthiness optimization of empty and filled aluminum crash boxes

Dynamic crash tests on empty, honeycomb-filled and foam-filled square aluminum tubes have been performed. Furthermore, in order to find more details about crash processes, finite element simulations of the experiments have been done. In terms of finding more efficient and lighter crash absorbers and achieving maximum energy absorption, Multi design optimization (MDO) technique has been applied for optimizing the square and circular tubes. Based on practical requirements the optimum tube geometry which absorbs maximum energy and has a minimum weight has been determined. The results of simulations of filled identical tubes with honeycomb and foam with the same density showed that the foam behaves better than honeycomb. Results of previous work indicated that using high density honeycomb for filling the tubes will result in more energy absorption but the weight efficiency has been lost (H R Zarei, M Kröger M and K Popp, ‘Experimental and numerical quasi static crash investigation in empty and honeycomb filled aluminum square tubes’, Int J Crashworthiness, May 2005, submitted). Therefore, a comprehensive study has been performed in order to find out the crash behavior of tubes filled with foam with different densities. The MDO procedure has been implemented to find an optimum filled tube that absorbed the same energy as an optimum empty tube can absorb.

Comparison of the load/displacement and energy absorption performance of round and square AA6061-T6 extrusions under a cutting deformation mode

Quasi-static compressive testing of extruded aluminum alloy AA6061-T6 round and square cross-sectional tubular specimens was completed to investigate the crush characteristics of these structural members under a cutting deformation mode by using a specially designed cutting tool. Results from the experimental tests showed that the cutting deformation mode of the round and square tubes exhibited high crush force efficiencies (CFE) of 0.95 and 0.81 respectively. In comparison, CFE of round specimens that experienced progressive folding and global bending deformation modes were observed to be 0.66 and 0.20 respectively and CFE of square specimens that underwent global bending were found to be 0.22. An almost constant cutting force was observed for the round tubes in the cutting deformation mode, while a slight increase in the cutting force was observed for the square tubes under the same deformation mode. The increase in cutting force for the square tubes was observed to occur primarily due to contact arising between the cutting tool and tube sidewalls and to a lesser extent due to bending of the petalled side walls. For the round tubes, contact between the cutting tool and sidewalls as well as bending of the petalled side walls was not as significant and resulted in a more consistent cutting force. For both the 200 mm and 300 mm length tubes the total energy absorption for the round and square tubes was observed to be 6.11 kJ and 4.31 kJ respectively. The energy absorption was observed to be independent of tube length.