Perforated Aluminum Research Articles

An Investigation of the Enhanced Fatigue Performance of Low-porosity Auxetic Metamaterials

An experimental and numerical investigation of fatigue life and crack propagation in two-dimensional perforated aluminum structures is presented. Specifically, the performance of positive Poisson’s ratio (PPR) geometries using circular holes is compared to that of auxetic stop-hole and straight-groove hole geometries. Mechanical fatigue testing shows that the considered auxetic structures have more than 20% longer life than the porous PPR structure at the same porosity and peak effective maximum stress despite having holes with larger stress concentrations. Digital image correlation is used to detect crack initiation and damage propagation much earlier than can be detected by the unaided eye. Accompanying finite element analyses reveal that auxetic structures have the advantage over their PPR counterparts by delaying crack initiation, spreading damage over a larger area, and having a stress intensity factor that decreases over a significant range of crack lengths. In addition, numerical simulations suggest that auxetic structures maintain their negative Poisson’s ratios in the presence of cracks.

Numerical investigation and design of perforated aluminium alloy SHS and RHS columns

This paper describes a numerical investigation on perforated aluminium alloy square and rectangular hollow section (SHS and RHS) columns by the finite-element analysis (FEA). The non-linear finite-element model (FEM) was developed by considering both geometric and material non-linearities. The initial local and overall geometric imperfections of aluminium alloy columns were incorporated in the FEM. The non-linear FEM was verified against the corresponding experimental results, which was further used for an extensive parametric study that consisted of 594 specimens with different cross-section dimensions, overall lengths, as well as diameters, numbers and locations of circular openings. The ultimate strengths of the columns obtained from FEA were employed to evaluate the current design specifications for aluminium alloy and cold-formed steel structures. It is demonstrated that American Specification (AA) and limit state design (LSD) in Australian/New Zealand Standard (AS/NZS) are somewhat unconservative, whereas allowable stress design (ASD) in Australian/New Zealand Standard (AS/NZS) and Chinese Code are quite conservative, while European Code (EC9) is generally appropriate for imperforated aluminium alloy columns. In addition, North American Specification (NAS) and direct strength method (DSM) for cold-formed steel structural members with openings are quite conservative for aluminium alloy columns with circular openings. The design equations proposed based on the design rules of EC9 were verified to be accurate for perforated aluminium alloy SHS and RHS columns under axial compression.

Simultaneous removal of Cd2+ and Zn2+ from aqueous solution using an upflow Al-electrocoagulation reactor: optimization by response surface methodology.

The presence of heavy metals in the environment has increased, and cadmium (Cd) and zinc (Zn) are considered to be among the most dangerous. An upflow Al-electrocoagulation reactor was used to remove Cd2+ and Zn2+ ions from aqueous media. The system consisted of perforated aluminum circular electrodes for fluid distribution with elimination of external agitation. The effect of different parameters, i.e. current intensity, electrolysis time, concentration of Cd2+ and Zn2+ ions and electrolytic support dose were optimized by response surface methodology. The results indicated that increasing the current intensity and the electrolysis time had a positive effect on the elimination efficiency of the pollutant ions. Likewise, increasing the dose of electrolytic support and decreasing the concentration of the pollutants improved the efficiency of the system. The optimal results were: current intensity of 0.4 A, electrolysis time of 40 min, ion concentration of 44.6 mg·L-1 and electrolytic support dose of 0.56 mg·L-1, with the maximum elimination percentages of 96 ± 3.8% and 96 ± 2.7% for Cd2+ and Zn2+, respectively. This study showed that the electrocoagulation process in an upflow electrocoagulation reactor could be successfully applied to remove pollutants from water.

Development of a performance booster for the evaporator of window-type air conditioners

This study investigated the effect of a performance booster (PB) on the performance of a window-type air conditioner (WAC). The PB was fabricated using perforated aluminum plates with different pore size configurations according to the return air distribution of evaporator. The WAC was tested under various outdoor air conditions, and the performance of the WAC before and after PB installation was compared. Results showed that the PB effectively improved the performance of the WAC. The PB with three pore sizes improved the WAC performance more than the PB with two pore sizes. The maximum improvements in the WAC’s cooling capacity, dehumidification capacity, and energy efficiency ratio (EER) under the configuration with three pore sizes were 13.70 %, 59.63 % and 14.37 %, respectively, compared with the original WAC at an outdoor dry-bulb temperature of 30 °C.

Tests of perforated aluminium alloy SHSs and RHSs under axial compression

This paper presents an experimental investigation on a wide range of aluminium alloy stub, intermediate and slender columns containing multiple circular openings. Three series of compression tests including six different cross-section dimensions of columns with different lengths were conducted by applying uniform axial load to the pin-ended specimens, which were fabricated by extrusion of square and rectangular hollow sections (SHS and RHS) using 6061-T6 and 6063-T5 heat-treated aluminium alloys. In test series I, the specimens were fabricated by welding aluminium alloy plates at both ends of the columns for pin-ended compression tests. In test series II, the specimens were further reinforced by carbon fiber-reinforced polymer (CFRP) at the heat-affected zone resulted from the welding. In test series III, the special aluminium alloy sleeves were designed instead of welding at both ends of the columns to preclude the form of the heat-affected zone. The column strengths, failure modes, load versus axial shortening curves, and strain distributions along the circular openings of test specimens were all obtained from the experimental investigation. In addition, the test strengths of aluminium alloy SHS and RHS columns with or without openings were compared with the design strengths calculated using the design rules given in the current design guidelines. It is shown from the comparison that the first design method proposed by Zhu and Young for aluminium alloy SHS and RHS welded columns is comparatively appropriate for the design of aluminium alloy SHSs and RHSs under axial compression. Whereas, the current design rules for cold-formed steel structural members with openings may be inapplicable to the design of perforated aluminium alloy SHSs and RHSs under axial compression.

A novel MEMS capacitive microphone using spring-type diaphragm

In this paper, we present a new design of diaphragm that supported by frog arms for MEMS capacitive microphone structure. The proposed diaphragm reduces the air damping and diaphragm stiffness to improve the microphone sensitivity. The behaviour of the microphones with clamped and supported diaphragm by frog arms are analysed and simulated using finite element method (FEM). The structure has a perforated aluminium diaphragm with a thickness of 3 µm, a diaphragm size of 0.5 mm × 0.5 mm, and an air gap of 1 µm. According to the results, the mechanical sensitivity of the new microphone is 9.893 nm/Pa and pull-in voltage is 2.25 V whereas the clamped one with same diaphragm size has a mechanical sensitivity of 0.309 nm/Pa and pull-in voltage of 44.6 V. By introducing the frog arms around the diaphragm, the mechanical sensitivity increased 32 times. The results also yield a capacitance sensitivity of 0.15 fF/Pa for clamped microphone and 27.45 fF/Pa for supported one with frog arms. The pull-in voltage of the supported microphone by frog arms has decreased about 95% compared with clamped one.

Experimental investigation of the failure modes of in-plane loaded inserts in CFRP sandwich panels

The aim of this paper is the experimental determination and investigation of the different failure modes of various insert types under inplane load in sandwich materials with CFRP face sheets and a perforated aluminum honeycomb core. In addition, also insert under an out-of-plane load are tested. In total three different kind of inserts are investigated: blind inserts, trough-the-thickness inserts and special inserts which are developed within the iBOSS research project. The inserts are tested until failure and monitored with the digital image correlation system Aramis. This test monitoring is intended to determine the first failure mode. It is shown that this works well for out-of-plane loaded insert connections and the special inserts under in-plane load. However, this does not work so well with in-plane loaded standard inserts. In further investigations, a failure of the adhesive shortly before failure of the top layers can be shown.

Turbidity and oil removal from oilfield produced water, middle oil company by electrocoagulation technique

Huge quantity of produced water is salty water trapped in the oil wells rock and brought up along with oil or gas during production. It usually contains hydrocarbons as oil and suspended solids or turbidity. Therefore the aim of this study is to treat produced water before being discharge to surface water or re injected in oil wells. In this paper experimental results were investigated on treating produced water (which is obtained from Middle Oil Company-Iraq), through electrocoagulation (EC). The performance of EC was investigated for reduction of turbidity and oil content up to allowable limit. Effect of different parameters were studied; (pH, current density, distance between two electrodes, and electrolysis time). The experimental runs carried out by an electrocoagulation unit was assembled and installed in the lab and the reactor was made of a material Perspex, with a capacity of approximately 2.5 liters and dimensions were 20 cm in length, 14 cm in width and 16 cm height. The electrodes employed were made of commercial materials. The anode was a perforated aluminum rectangular plate with a thickness of 1.72 mm, a height of 60 mm and length of 140 mm and the cathode was a mesh iron. The current was used in the unit with different densities to test the turbidity removing efficiency (0.0025, 0.00633, 0.01266 and 0.0253 A/cm2).The experiment showed that the best turbidity removing was (10, 9.7, 9.2, 18 NTU) respectively. The distance between the electrodes of the unit was 3cm. The present turbidity removing was 92.33%. A slight improvement of turbidity removing was shown when the distance between the electrodes was changed from 0.5 to 3 cm with fixation of current density. The best turbidity removing was 93.5% , (7.79 NTU) when the distance between the electrodes were 1 cm. The experimental results found that concentration of oil had decreased to (10.7, 11.2, 11.7, 12.3) mg/l when different current densities (0.00253, 0.00633, 0.01266, 0.0253) A/cm2 were used, respectively with the distance between the electrodes was 3 cm. The best result of oil content decreasing was 10.7 mg/l with current density 0.0253 A/cm2. These results are within allowable limit to provide the possibility of reuse the water and can be injected in oil wells

Aluminium plates with pre-formed slits subjected to blast loading

The dynamic response of thin, perforated aluminium plates subjected to blast loading was studied both experimentally and numerically. Two different blast intensities were used and the plates were pre-cut with four horizontal and vertical slits prior to testing. The applied AA6016-T4 plates had an exposed area of 0.3 m x 0.3 m and a thickness of 1.5 mm. Special focus was placed on the dynamic response and failure characteristics of the plates. Uniaxial tensile tests were conducted in three different directions to determine the material behaviour and material parameters were found by inverse modelling using the optimization tool LSOPT. Finally, numerical simulations were performed in the finite element code Abaqus/Explicit where the plates were uniformly loaded with time-dependent pressure histories from similar tests on massive plates. The material behaviour was assumed to follow the J2 flow theory of plasticity and an uncoupled damage model was used in combination with element erosion to predict material failure. The numerical results were in good agreement with the experimental observations and predicted both the dynamic response and the complete tearing of the centre part of the plates.

Accuracy-enhanced constitutive parameter identification using virtual fields method and special stereo-digital image correlation

The virtual fields method (VFM) is generally used with two-dimensional digital image correlation (2D-DIC) or grid method (GM) for identifying constitutive parameters. However, when small out-of-plane translation/rotation occurs to the test specimen, 2D-DIC and GM are prone to yield inaccurate measurements, which further lessen the accuracy of the parameter identification using VFM. In this work, an easy-to-implement but effective “special” stereo-DIC (SS-DIC) method is proposed for accuracy-enhanced VFM identification. The SS-DIC can not only deliver accurate deformation measurement without being affected by unavoidable out-of-plane movement/rotation of a test specimen, but can also ensure evenly distributed calculation data in space, which leads to simple data processing. Based on the accurate kinematics fields with evenly distributed measured points determined by SS-DIC method, constitutive parameters can be identified by VFM with enhanced accuracy. Uniaxial tensile tests of a perforated aluminum plate and pure shear tests of a prismatic aluminum specimen verified the effectiveness and accuracy of the proposed method. Experimental results show that the constitutive parameters identified by VFM using SS-DIC are more accurate and stable than those identified by VFM using 2D-DIC. It is suggested that the proposed SS-DIC can be used as a standard measuring tool for mechanical identification using VFM.

Experimental investigation of aluminum square and rectangular beams with circular perforations

Both three-point and four-point bending tests were conducted on aluminum square and rectangular beams with circular perforations. Test specimens consist of 9 perforated and 4 imperforated beams subjected to gradient and constant bending moment. The extrusion of 6061-T6 and 6063-T5 heat-treated aluminum alloys were used to manufacture square and rectangular hollow sections (SHS and RHS), respectively. The evaluation of the strength and behavior of aluminum square and rectangular beams focuses on the effects of the aspect ratio, the ratio of plate width, the ratio of plate slenderness, the ratio of perforation dimension and the number of perforations. Test results including the ultimate strengths, failure modes of local and flexural buckling failure, bending moment versus curvature curves and strain distributions along the circular perforations are all reported, which were employed to assess the suitability of the current design specifications. The comparison of test strengths with design strengths shows that the modified DSM for aluminum structural members is somewhat conservative with the lowest value of COV, whereas other design specifications for cold-formed steel and aluminum structural members are quite conservative with comparatively high value of COV. It is also demonstrated from the comparison that the perforated sections close to the mid-span of the beams are the critical section under gradient and constant bending moment. In addition, the comparison of test strengths with design strengths also reveals that the current design rules for perforated cold-formed steel and aluminum structural members are all conservative, in which North American Specifications (NAS) for perforated cold-formed steel structural members are generally appropriate with the lowest value of COV.

22.02: The music square canopy: An outdoor stage for Amager Kulturpunkt

ABSTRACTMusiktorvet, or “The Music Square” is the connecting element for a number of local cultural institutions, like music venues, a scenographic art institution, a children's theater and children's day care institutions. The music square is their collective outdoor stage, marked by a recently completed canopy.The canopy provides shelter and functional space, setting the stage for concerts, circus, markets, theatre, etc. Provisions are made to allow both spontaneous and planned events, for example by a number of fixed light setups for various stage positions, whilst fixing points are provided in the roof for the attachment of audio and lighting racks.The 500m2 canopy is formed by a grillage of welded steel box beams, supported by five slender columns, placed around the perimeter of the roof. The 70 tons roof was produced in 8 pieces which were assembled at the production facility, using the final bolted connections, before welding. This was done to ensure that all parts would fit perfectly together for the on‐site assembly. After the roof was assembled on the ground, the whole roof was lifted into place in one lifting operation.The top of the roof is covered with triangular ETFE foil cushions, whilst a ceiling of reflective, perforated aluminum panels allows a large amount of sunlight to penetrate the roof structure. A special feature of the canopy is the steel mesh curtains that can be drawn around the perimeter of the canopy to create a more sheltered space, to match the type of event taking place. The installation of the mesh curtains required a consideration of the various wind loading conditions for open, closed and semi‐closed conditions.This paper describes the design process and the chosen solutions with their argumentation, as well as the production and erection process.

High-transmission acoustic self-focusing and directional cloaking in a graded perforated metal slab

A design strategy and its modeling for high-transmission acoustic self-focusing and directional cloaking in a two-dimensional (2D) and an axisymmetric three-dimensional (3D) gradient-index phononic crystal (GRIN-PC) are reported in this paper. A gradient perforated aluminum slab sandwiched by water is considered. A low-loss directional cloaking device is achieved by controlling the matching coefficient between the slab and the water. The anisotropy coefficient that affects the scattering properties is also introduced. Furthermore, the phase discontinuity for directional cloaking inside and outside the slab is overcome by introducing a non-gradient slab having a lower group velocity behind the GRIN slab as an acoustic delay device. In addition, an axisymmetric 3D directional cloaking structure is obtained by rotating the corresponding 2D structure around the slab axis.

Energy efficient electrocoagulation using a new flow column reactor to remove nitrate from drinking water – Experimental, statistical, and economic approach

In this investigation, a new bench-scale electrocoagulation reactor (FCER) has been applied for drinking water denitrification. FCER utilises the concepts of flow column to mix and aerate the water. The water being treated flows through the perforated aluminium disks electrodes, thereby efficiently mixing and aerating the water. As a result, FCER reduces the need for external stirring and aerating devices, which until now have been widely used in the electrocoagulation reactors. Therefore, FCER could be a promising cost-effective alternative to the traditional lab-scale EC reactors.A comprehensive study has been commenced to investigate the performance of the new reactor. This includes the application of FCER to remove nitrate from drinking water. Estimation of the produced amount of H2 gas and the yieldable energy from it, an estimation of its preliminary operating cost, and a SEM (scanning electron microscope) investigation of the influence of the EC process on the morphology of the surface of electrodes. Additionally, an empirical model was developed to reproduce the nitrate removal performance of the FCER.The results obtained indicated that the FCER reduced the nitrate concentration from 100 to 15 mg/L (World Health Organization limitations for infants) after 55 min of electrolysing at initial pH of 7, GBE of 5 mm, CD of 2 mA/cm2, and at operating cost of 0.455 US $/m3. Additionally, it was found that FCER emits H2 gas enough to generate a power of 1.36 kW/m3. Statistically, the relationship between the operating parameters and nitrate removal could be modelled with R2 of 0.848. The obtained SEM images showed a large number dents on anode's surface due to the production of aluminium hydroxides.

Increasing photovoltaic panel power through water cooling technique

This paper presents the development of a cooling apparatus using water in a commercial photovoltaic panel in order to analyze the increased efficiency through decreased operating temperature. The system enables the application of reuse water flow, at ambient temperature, on the front surface of PV panel and is composed of an inclined plane support, a perforated aluminum profile and a water gutter. A luminaire was specially developed to simulate the solar radiation over the module under test in a closed room, free from the influence of external climatic conditions, to carry out the repetition of the experiment in controlled situations. The panel was submitted to different rates of water flow. The best water flow rate was of 0.6 L/min and net energy of 77.41Wh. Gain of 22.69% compared to the panel without the cooling system.

Wear Characterization of High Temperature Oxidized Ni Based Superalloys

Objectives: This work presents a study of the effect of membrane surface with dimples on the heat transfer in vacuum membrane distillation (VMD). Methods/Statistical Analysis: Polyvinylidene fluoride (PVDF) membrane and distilled water as feed solutions are tested in a laboratory-scale cross-flow flat-sheet membrane module with membrane area of 72.4 cm2. A perforated aluminum support embedded in the permeate compartment is used to support the membrane during the VMD process. Findings: The results show that the dimples stamped on the membrane surface by the perforated support having the diameter and depth approximately 5 and 1 mm, respectively. The permeability of the membrane with dimples increases by 3 - 20% at the corresponding feed temperature of 75 - 95°C. The deviations between the heat transfer coefficients predicted by a Nusselt correlation with dimpled effect and the experimental values are less than 10%. Application/Improvements: These findings are significant to reveal the influence of membrane deformation effect on the heat transfer correlation which is used to predict the VMD flux.

Effects of early diagenesis on molecular distributions and carbon isotopic compositions of leaf wax long chain biomarker n-alkanes: Comparison of two one-year-long burial experiments

Two burial experiments were performed to compare and contrast the effects of degradation and early diagenesis on the molecular distributions and compound specific carbon isotope compositions of leaf wax n-alkanes under different conditions. Leaves of the bamboo Neosinocalamus affinis and the shrub Osmanthus fragrans were packaged in perforated aluminum packets and buried in soil at two different subtropical locations in China. The packets were recovered after successive intervals totaling ∼1year, and the n-alkane properties of their leaves compared to those of the fresh leaves and the surrounding soil. Concentrations of total leaf n-alkanes decreased in both experiments. The waxes of N. affinis exhibited a fairly rapid decrease in their proportions of C23–C27n-alkanes and increases of less than 1‰ in n-alkane δ13C values during the burial time. In contrast, the leaves of O. fragrans showed little change in either their molecular distributions or isotopic compositions during burial. The results of the two experiments indicate that early diagenesis can lead to losses of leaf wax biomarker n-alkanes during burial in soil but has little to no effect on their stable carbon isotopic signatures, validating the reliability of compound specific n-alkane δ13C values as proxies for paleoecological and paleoenvironmental reconstructions.

Hydrodynamics in falling liquid films on surfaces with complex geometry

These studies include investigation of the character of liquid spreading over the surfaces with complex geometry, the effect of microstructure, corrugation angle, and perforation on the wave film flow. The paper present the results of experimental studies on dynamics of the film flow of cryogenic liquid over the complex surfaces: vertical plane and ribbed aluminum plates with/without wave microtexture. Experimental results were obtained at the flow of liquid nitrogen.According to results of experiments on the ribbed structured perforated aluminum surfaces with the use of highly wetting low-viscous liquids, the film flow character depends significantly on the irrigation rate. The direction and parameters of microstructure, the angle of inclination of the main fins, position and diameter of holes effect significantly the zones of liquid spreading and its distribution over the surface of the ribbed structured plates, especially, within the range of low liquid flow rates. According to high-speed video recording, in case of horizontal microstructure the wave dynamics influences considerably liquid redistribution in transverse direction. This is caused by the fact that liquid flows intensively at propagation of secondary waves along the channels of horizontal microstructure.Experimental results on dependence of the relative portion of liquid, held in a single irrigated channel of the corrugated plates with different thicknesses, on the irrigation degree are presented.

Deformation of Perforated Aluminium Plates under In-Plane Compressive Loading

Aluminium plates containing a single hole or multiple holes in a row are recently becoming very popular among architects and consultant engineers in many constructional applications, due to their reduced weight, as well as facilitating ventilation and light penetration of the buildings. However, there are still uncertainties concerning their structural behaviour, preventing them from wider utilization. In the present paper, local buckling phenomenon of perforated aluminium plates has been studied using the finite element method. For the purposes of the research work, plates with simply supported edges in the out-of-plane direction and subjected to uniaxial compression are examined. In view of perforations, circular cut-outs and the total cut-out size has been varied between 5 and 40% of the total plate area. Moreover, different perforation patterns have been investigated, from a single, central cut-out to a more refined pattern consisting of up to 25 holes equally distributed over the plate. Regarding the material characteristics, several aluminium alloys are considered and compared to steel grade A36 on plates of different slenderness. For each case the critical (Euler) buckling load and the ultimate resistance has been determined.A study into the boundary conditions of the plate showed that the restrictions at the edges parallel to the load direction have a large influence on the critical buckling load. Restraining the top or bottom edge does not significantly influence the resistance of the plate.The results showed that the ultimate resistance of aluminium plates containing multiple holes occurs at considerably larger out-of-plane displacement as that of full plates. For very large total cut-out, a plate containing a central hole has a larger resistance than a plate with equal cut-out percentage but with multiple holes. The strength and deformation in the post-critical regime, i.e. the difference between the critical buckling load and the ultimate resistance, differs significantly for different number of holes and cut-out percentage.

Forming Behaviour of Micro-Structured Aluminium Sheets

For a deeper understanding of the forming behaviour of perforated aluminium sheets (Al99.5) in micro deep drawing processes, tensile and stretch forming tests are performed at forming speeds of 0.1 mm/s and 0.25 mm/s. The sheets have thicknesses of 100 µm and 200 µm, a perforated rectangular hole geometry of 300 µm x 300 µm and a bar width of 40 µm. During stretch-forming tests the flow characteristics and failure mechanisms within the mesh structure are determined. An isotropic forming behaviour with low ductility is observed. The maximum stretch-forming depth is increased at increasing perforated area. The mesh structure failure is peripherally obtained due to notch effects, friction and micro related size effects within the mesh structure. Moreover, the results show that cracks and necking within the mesh structure occur only tangentially to the punch movement due to high uniaxial stresses caused by the forming process.