Aluminum Panels Research Articles

Structurally-integrated resonators for broadband panel vibration suppression

There is limited understanding on interaction mechanisms that govern vibration attenuation when a small coverage of lightweight resonators are applied to practical engineering structures. To shed light on the unknowns, this research investigates lightweight elastomeric half cylindrical resonators attached to an aluminum panel using a small mass ratio around 3% and only around 1.7% coverage over the panel area. Finite element modeling of the system dynamics is complemented by corresponding experimental undertaking. The eigenfrequencies and eigenmodes of the resonators are scrutinized for the respective contributions provided towards broadband panel vibration suppression. The first order eigenmodes of the resonators are found to exert great influence on the starting mode for greater vibration attenuation, which may be tuned by the Young’s modulus of the resonators. The concept of displacement polarization is established to probe how the resonator eigenmodes quantitatively contribute to attenuate the forced panel vibration. This study reveals how flexural panel vibration may be attenuated by transferring the vibration from the panel to resonators by virtue of modal interaction, and prepares a generalized analytical technique that may be used by other researchers studying multi-modal interactions between host structures and applied resonators. These findings may guide the future development of lightweight resonators with a small coverage area for vibration suppression in engineering applications.

Gold Nanoparticles Grown by Galvanic Replacement on Graphene-Coated Aluminum Panels as Large-Area Substrates for Surface-Enhanced Raman Scattering

Galvanic replacement (GR) is a widely used method to obtain substrates with nanostructure morphologies. However, substantial challenges related to the uniformity of the deposited nanostructures, th...

Modelling and Analyses of Fiber Fabric and Fabric-Reinforced Polymers under Hypervelocity Impact Using Smooth Particle Hydrodynamics

In a hypervelocity impact (HVI) event, fiber fabrics and the fabric-reinforced polymers (FRP) would undergo shock compression, large deformation and fragmentation. The smooth particle hydrodynamics (SPH) approach was applied to assess the shielding performance of the fabric and its composite structure in a Whipple shield. In the fabric model, a fiber is built by SPH particles to properly reproduce the spreading feature of fragmented fabric under HVI. The simulations display that an aluminum panel, serving as the bumper of a Whipple, has the better performance in debris spreading than fabric layers. In the stuffed layer of a Whipple, the widely used plain weave fabric has the similar performance as the 3D weave both in debris spreading and speed retarding. The fabric model is further developed and extended to FRP by building fiber and polymer materials separately based on specific geometries. The computations illustrate that the FRP/Aluminum hybrid laminate can efficiently reduce the shock peak under HVI and meanwhile produce large deformation for kinetic energy absorption, in good agreement with experimental measurements. It applies to the rear wall of a Whipple which should resist the HVI of a debris cloud, forming a high but short shock pulse. The further optimization of the hybrid laminate was made by using a corrugated aluminum plate, a gap and a Kevlar fabric layer, leading to the considerable reduction of the laminate areal mass in a prescribed thickness.

In situ wavenumber–frequency modal decomposition of acoustic emissions

A new acoustic sensing capability, consisting of a flexible high-density linear piezoelectric sensor array coupled to a high-bandwidth interrogation device, is developed and applied to in situ wavenumber–frequency modal decomposition of acoustic emissions in plates. An experimental assessment of the capability is undertaken using acoustic emissions generated by a ball-drop impact on aluminium and composite panels. A new method for acoustic source localisation based on this new sensor array is described, and it is shown to be more accurate than a conventional multilateration technique using single-point piezoelectric receivers. The potential of this new capability for acoustic emission detection, location and possible quantification is discussed.

Numerical residual strength prediction of stationary shoulder friction stir welding structures

The residual strength of a structure made of dissimilar Aluminium panels joined by a stationary shoulder friction stir welding (SSFSW) process is predicted by numerical simulation using finite elements including cohesive elements for crack propagation. The yield strength and strain hardening parameters within the stirred zone and adjacent thermo-mechanically affected and heat affected zones are derived from a tensile specimen cut out from the panel perpendicular to the weld seam. The identification is conducted by a hybrid numerical/experimental procedure with an inverse search by help of digital image correlation in order to obtain the strain field at the welded surface and to compare them to the numerical calculation. The crack propagation parameters are retrieved from specimens with crack in the stir zone and heat affected zone on either side. After this identification procedure, the fracture behaviour of a coupon specimen with a crack crossing the weld is predicted.

Improving the double-exponential windowing method to identify modal frequencies and damping ratios of dynamically large structures

Dynamically large structures can have many closely spaced modes. A particular example is an extruded aluminium panel used for building high-speed trains. Such a structure may be modelled deterministically with a large number of degrees of freedom (dofs), or statistically represented as a statistical energy analysis (SEA) system having particular SEA parameters. In both cases, experimental modal parameter identification may be required. Although there are several commercial packages which can be used for modal parameter identification, alternative methods with different strengths and/or convenience are still desirable. In this paper, the double-exponential windowing method developed by the second author is revisited and improved. Improvements are achieved by taking into account the effect of the finite time duration of Fourier transforms and making use of the real parts of driving point mobilities. The method is easy to implement and the improvements make the choice of the decay rate in the exponential window much flexible: for a very lightly damped structure, it allows to use a large positive decay rate to depress measurement noise, and for a highly damped structure, it allows to use a negative decay rate to make modes more evident or to separate overlapped modes. The usefulness of the improved method are demonstrated for a 30-bladed wheel model with known modal parameters, and for an extruded aluminium panel.

Experimental and numerical analysis of solar-absorbing metallic facade panel with embedded heat-pipe-array

The integrative performance of advanced building façade is important for sustainable building development. This paper introduces two solar-absorbing curtain-wall panels with embedded straight-heat-pipe and heat-pipe-ring respectively. Taking advantage of the high thermal conductance of heat pipe, the proposed solar-absorbing aluminum panels can preheat cold water, like for the domestic hot water supply. They also reduce the solar transmission to the indoor space. In hot summer, the dual effect leads to considerable energy saving in both the hot-water and the air-conditioning systems. Comparing with the water-tubing collector panel, the heat-pipe type has wider application by eliminating the water-freezing problem. The conceptual design, prototype construction and computer-model development of these two panels are discussed in this paper. Measurements were taken with the two prototypes installed at an outdoor environmental chamber. Dynamic simulation models were then developed through the control volume finite difference method, and validated with the measured data. The simulation models can be used in advanced building simulation tools for transient thermal performance analysis. Further numerical analysis with these models showed that comparatively, the innovative heat-pipe-ring is the more promising design because of the effective increase in solar absorbing surface area. In the studied warm climate scenarios from summer to winter and from sunny to cloudy conditions, the water heat gain efficiency was estimated from 62.5% to 94.9% in all cases with the glazed panel. The estimated room heat gain/loss as well as the electricity saving performance are also attractive.

Polypyrrole Modified E-Coat Paint for Corrosion Protection of Aluminum AA1200

This article reports the potential of Polypyrrole (PPy) particles as anticorrosive additive on an epoxy water-based paint to increase the corrosion protective property of aluminum-coated panels. AA1200 aluminum panels were painted using the electrophoretic deposition method and the coatings with different concentrations of PPy particles tested. PPy particles were synthetized by oxidative polymerization of pyrrole (Py) with iron (III) chloride hexahydrate (FeCl3.6H2O) in the presence of dodecylbenzenesulfonic acid (DBSA). Electrically conducting PPy particles (6.5 S.cm-1) were obtained with a size average of 154 nm. The as-prepared PPy particles were added into a water-based epoxy paint and AA1200 panels were coated via electrophoretic deposition method. The corrosion protective properties of e-coated AA1200 panels were evaluated by means of electrochemical impedance spectroscopy over prolonged exposure time in neutral non-aerated 0.1 M NaCl electrolyte. In particular, the addition of 0.4 wt. % PPy has improved the coating corrosion protective property with respect to epoxy clearcoat and exhibited the highest value among the studied coatings.

Multichannel fiber laser acoustic emission sensor system for crack detection and location in accelerated fatigue testing of aluminum panels

Detection and location of the source of acoustic emission in a thin aluminum panel is demonstrated using a multichannel fiber laser sensor system. Acoustic emission generated by a crack in an aluminum panel used as a test coupon in an accelerated fatigue experiment is detected and the location of the crack identified. Acoustic emission is detected over a bandwidth of around 0.5 MHz from a serially multiplexed array of four laser sensors and compared with measurements taken from four piezo-electric sensors co-located with the fiber laser sensors. The location of the crack is determined by first estimating time difference of arrival of signals at each sensor using a novel algorithm based on the cumulative distribution transform method with hyperbolic positioning. The fiber laser sensor is shown to match the signal-to-noise ratio of the industry standard (Mistras S9225) piezo-electric acoustic emission sensor.

Strength assessment of aluminium and steel stiffened panels with openings on longitudinal girders

The ultimate compressive strength of equivalent stiffened panels made of aluminium and steel is analysed numerically and compared. This equivalence is established based on the design formulations as defined by the Classification Society Rules. Novel web girders, with openings for passing pipes and cables, are designed, and their importance on the ultimate strength of stiffened plates is assessed. This type of structural configuration is often applied in the design of the ship decks and superstructures. A series of finite element analyses are performed in order to evaluate the ultimate compressive strength of the equivalent aluminium and steel stiffened panels employing different design solutions. The welded heat-affected zone of aluminium structures and different boundary conditions in finite element analyses are considered. The results have shown that the equivalent stiffened panels yield at the same compressive load, but the aluminium panels have higher ultimate strength than the steel panels. Finally, the effect of the openings on web girders, heat-affected zone and boundary conditions are discussed.

UPAYA PENINGKATAN PRODUKTIVITAS TERKAIT MOTIVASI DAN DISIPLIN KERJA KARYAWAN PT. KARINDO PERSADA

PT. Karindo Persada is a general contracting company in the service and production of aluminum and composite panels that is growing rapidly in Bekasi. Delays in the delivery of goods and work systems implemented by the company where employees are fully responsible for the delivery of goods if there is damage to goods in the shipping process. This is allegedly due to lack of employee welfare and lack of employee work discipline very influential on the survival of the company. After analyzing using the IFAS (Internal Factor Analysis System) and EFAS (External Factor Analysis System) matrix, it is known that the company's internal strategic factors which consist of strengths and weaknesses show a weighted score of 2.09. and the company's external strategic factors consisting of opportunities and threats show a weighted score of 2.38. The results of the study of factors that hinder or challenges in increasing employee work productivity: initial selection and training. Knowledge training is needed for employees to increase their motivation and work discipline, this is done to increase employee knowledge so that even though the education level of employees is weak, employees get knowledge from the company. The knowledge provided can be directed in accordance with the objectives to be achieved by the company. This will have an impact on increasing productivity.

To the Issue of Strengthening the Monolithic Reinforced Concrete Slab with Carbon Canvases

The main issue of the study is the modern ways to improve the bearing capacity of building structures. As one of these methods may be strengthening composite materials. Structural degradation of reinforced concrete structures is largely due to their composite base. The aim of the study is a systematic integrated approach to solving the problem of improving the reliability of structures through the use of composite materials. The main advantages and disadvantages of composites are considered. Their classification by type of reinforcing element is given. The main areas of application of composites in construction – in the composition of plastics, concrete, aluminum panels. Approbation of methodical provisions is carried out by calculation of a reinforced concrete plate (δ=0,3 m) in the program complex of the SCAD PC. The gain calculation was performed by the finite element method. The purpose of the calculation was to observe the stress-strain state of the plate before and after its strengthening, to check the correctness of the external composite reinforcement. The calculation results showed that in the case of composite reinforcement in the plate there is a decrease in vertical deformations (about 1.1%) and tensile stresses (1.5%). Conclusions: the results show the feasibility of using composite materials to improve the bearing capacity of building structures.

Evaluation of recycled Al–LDPE–Al sandwich panels as ballistic protection material

Metal–polymer–metal hybrid sandwich panels are gaining importance in civil, automotive and aerospace applications due to their light weight and damping properties. Compared with composite materials, hybrid materials consisting of separate metal and thermoplastic parts can be recycled much more easily. Besides their applications as covering material on buildings as well as general insulation material, recycled aluminum (Al)–low-density polyethylene (LDPE)–aluminum hybrid panels yield a potential usage of light ballistic protection. In this study, a standard hybrid panel of 3·2 mm polyethylene filling and two 0·4 mm aluminum metal sheets was experimentally tested under ballistic impact. A finite-element model was used with a commercial software program and validated against the experimental results. The finite-element results show that stacking of multiple layers of panels absorbs more energy than an equivalent single-layer panel. Six layers of stacked hybrid aluminum–LDPE–aluminum panels are capable of absorbing the impact energy of a 9 mm pistol projectile, and they can be utilized as recyclable inexpensive ballistic protection materials.

Smart Adhesive Joint with High-Definition Fiber-Optic Sensing for Automotive Applications.

Structural health monitoring of fiber-reinforced composite-based joints for automotive applications during their manufacturing and on-demand assessment for its durability in working environments is critically needed. High-definition fiber-optic sensing is an effective method to measure internal strain/stress development using minimally invasive continuous sensors. The sensing fiber diameters are in the same order of magnitude when compared to reinforcement (glass, basalt, or carbon fibers) used in polymer composites. They also offer a unique ability to monitor the evolution of residual stresses after repeated thermal exposure with varying temperatures for automotive components/joints during painting using an electrophoretic painting process. In this paper, a high-definition fiber-optic sensor utilizing Rayleigh scattering is embedded within an adhesive joint between a carbon fiber-reinforced thermoset composite panel and an aluminum panel to measure spatially resolved strain development, residual strain, and thermal expansion properties during the electrophoretic paint process-simulated conditions. The strain measured by the continuous fiber-optic sensor was compared with an alternate technique using thermal digital image correlation. The fiber-optic sensor was able to identify the spatial variation of residual strains for a discontinuous carbon fiber-reinforced composite with varying local fiber orientations and resin content.

Application of Prefabricated Curtain Wall Sectors in Special-shaped Stadium Projects

Due to complex shape and irregularity, projects of special-shaped buildings and venues are always limited by low construction efficiency and uncontrollable quality. The main form of the Application of Curtain Wall Prefabrication Scheme in Phoenix Mountain Sports Center is perforated aluminum panel curtain wall, which connects the stadium and gym through gradually varied curves, and creates the varied facade texture through metal panels of two colors (dark and light). The facade of the perforated aluminum panel curtain wall is streamlined, the overall shape is complex, with gradually varied and irregular shapes in horizontal and vertical directions, the aluminum panels are arranged in staggered seams, and the theoretical positions of the four corners are not coplanar. The number of aluminum panels is about 6000, and the number of assembled aluminum panels with different size is about 60,000. Conventional construction measures cannot meet the requirements of construction period and benefit. This paper aims to explore the application of prefabrication schemes in special-shaped curtain walls and provide relevant experience for other similar projects by studying the process of implementing the curtain wall prefabrication scheme in Phoenix Mountain Sports Center. A series of practices have proven that a large stadium can be constructed according to the integral hoisting scheme of sectors. Studies on how to design overall hoisting system for steel joist of large volume unit, how to install the steel joist of large volume unit, how to install non-coplanar special-shaped curtain wall and how to implement integral hoisting of metal roofing purlin may help to solve difficulties such as difficult construction, high cost and uncontrollable quality of large volume non-coplanar special-shaped curtain wall. Especially, studies on prefabrication construction techniques may help to simplify complex traditional bulk construction procedures, save time, improve work efficiency and reduce construction costs.

Experimental study on aluminium based sandwich composite with polypropylene foam sheet

Sandwich structures have been widely employed to build lightweight components having good mechanical properties and energy absorbing capacity. Aluminum-foam sandwich structures have been increasingly used in a wide range of applications. This work aims in improving the strength and mechanical properties of aluminum materials by the inclusion of polypropylene foam sheets. This paper studies the various characteristics of the Aluminum/PP/Aluminum sandwich composite which is made by compressive moulding. Tensile test, bending test and microhardness tests were carried out to investigate the characteristics of the sandwich composite. Thermal analysis of sandwich composite is carried out and is compared with aluminium panel

Fire danger analysis of seismic expansion joints

Aim of the research. Investigation of fire danger of seismic expansion joints, which have recently become almost the main component of seismic protection of buildings and structures. Identify the degree of fire danger of the building structure. Develop preventive measures to ensure fire safety of buildings and structures where seismic expansion joints are used. The relevance of this problem lies in the fact that the destruction of deformation seismic joints in seismic conditions for the spread of combustion (usually secondary occur in earthquakes) from one compartment of the building to another (protected by partitions, fire compartments, locks). That is, combustion opens the possibility to bypass special protections put in its way, in order to avoid its spread. Methods. Antiseismic deformation joints have been studied from the point of view of fire safety. The work mainly deals with the expansion joints used in the installation of aluminum panels for the design of buildings and structures. The connection of fire danger of antiseismic joints combined with technological and operational errors of performers is shown. Tests of various seismic protection joints for fire danger have been carried out. Results. It is concluded that it is necessary to develop a special regulatory documentation that introduces specific rules for the execution of expansion joints, especially designed to improve the seismic safety of buildings and structures.

Towards hybridization of composite patch in repair of cracked Aluminum panel

Purpose The maintenance of aircraft structure with lower cost is one of the prime concerns to regulatory authorities. The carbon fiber-reinforced polymer (CFRP) patches are widely used to repair the cracked structure. The demands and application of CFRP compel its price to increase in the near future. A distinct perspective of repairing the cracked aluminum panel with the hybrid composite patch is presented in this paper. The purpose of this paper is to propose an alternative patch material in the form of a hybrid composite patch which can provide economical repair solution. Design/methodology/approach The patch hybridization is performed by preparing the hybrid composite from tows of carbon fiber and glass fiber. Rule of hybrid mixture and modified Halpin–Tsai’s equation are used to evaluate the elastic constant. The stress intensity factor and interfacial stresses are determined using finite element analysis. The debonding initiation load is evaluated after testing under mode-I loading condition. Findings The hybrid composite patch has rendered the adequate performance for reduction of stress intensity in the cracked panel and control of interfacial stresses in the adhesive layer. The repair efficiency and repair durability of the composite patch repair was ensured by incorporation of the hybrid composite patch. Originality/value The studies involving patch hybridization for the application of composite patch repair are presently lacking. The influence of the patch stiffness, methodology to prepare the hybrid composite patch and effects of hybridization on the performance of composite patch repair is presented in this paper.

Stress Relaxation Aging Behavior and Constitutive Modelling of AA7150-T7751 under Different Temperatures, Initial Stress Levels and Pre-Strains

Age forming is an advanced manufacture technology for forming large aluminum panels. Temperature, initial stress level and pre-strains have a great effect on the formability and performance. The stress relaxation aging behavior of AA7150-T7751 under different temperatures, initial stress levels and pre-strains was studied through stress relaxation tests, tensile tests and TEM observations. The results show that the formability can be improved with the increase of temperature, initial stress levels and pre-strains. Deformation mechanisms during stress relaxation of the material were analyzed on the basis of creep stress exponent and apparent activation energy. The aging precipitates of the studied alloy were not sensitive to the age forming conditions, but drastically coarsened at over aging temperature, which decreased the mechanical properties. In addition, the relationship between stress relaxation behavior and aging strengthening is discussed. Based on the dislocation theory and the modified Arrhenius equation, a stress relaxation constitutive equation considering the initial mobile dislocation density and temperature dependent activation energy was established. This model can predict very well the stress relaxation behavior under various temperature, stress level and pre-strain conditions, with an average error of 2%.

Similitudes for the structural response and radiated sound power of simply supported plates

This communication investigates exact and distorted similitudes and the related scaling laws for the analysis of both dynamic response and radiated power of rectangular plates. The response of a given panel in similitude from another one is determined from a generalization of the modal approach, allowing the use of mode shapes, natural frequencies and finally radiation functions in order to establish appropriate scaling laws. Analytical models of simply supported rectangular plates are used to produce both original and replica model responses under point mechanical excitation. Emphasis is then especially put on laboratory experiments which are performed on baed simply supported aluminum panels under mechanical excitations. All the six possible scaling directions, i.e., predicting a plate vibroacoustic reponse from another plate, are reported. All obtained results show that structural response or radiated sound power of a given plate can be both recovered with satisfactory accuracy by using the related scaling laws, even if parent models are used.