Energy absorption Research Papers - Academia.edu (original) (raw)

Selective laser melting (SLM) is an additive technology that allows for the production of precisely designed complex structures for energy absorbing applications from a wide range of metallic materials. Geometrical imperfections of the SLM fabricated lattice structures, which form one of the many thin struts, can lead to a great difference in prediction of their behavior. This article deals with the prediction of lattice structure mechanical properties under dynamic loading using finite element method (FEA) with inclusion of geometrical imperfections of the SLM process. Such properties are necessary to know especially for the application of SLM fabricated lattice structures in automotive or aerospace industries. Four types of specimens from AlSi10Mg alloy powder material were manufactured using SLM for quasi-static mechanical testing and determination of lattice structure mechanical properties for the FEA material model, for optical measurement of geometrical accuracy, and for low-v...

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- Engineering, Materials Science, Materials, Medicine
- by praveen pinnoji
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- Materials Science, Fracture and cohesive zone model, Numerical Simulation, Impact

A thesis submitted to the Faculty of Graduate Studies and Research in partial f u l f h e n t of the requirements for the degree of Master of Science in Structural Engineering Deparmient of Civil and Environmental Engineering Edmonton, Aberta Fail 1997 Acquisitions and Acquisitions et Bibliographie Services se ~i c e s bibliographiques 395 Wellington Street 395, rue Wellington ûüawaON K1AON4 Ottawa ON K I A ON4 Canada Canada The author has granted a nonexclusive licence allowing the National Library of Canada to reproduce, loan, distribute or sell copies of this thesis in rnicroform, paper or electronic formats. The author retains ownershp of the copyright in this thesis. Neither the thesis nor substantial extracts fiom it may be printed or otherwise reproduced without the author's permission. your l ue votre riifnmce Our lue Nom reMrence L'auteur a accordé une licence non exclusive permettant à la Bibliothèque nationale du Canada de reproduire, prêter, disûibuer ou vendre des copies de cette thèse sous la forme de microfiche/^, de reproduction sur papier ou sur format électronique. L'auteur conserve la propriété du droit d'auteur qui protège cette thèse. Ni la thèse ni des extraits substantiels de celle-ci ne doivent être imprimés ou autrement reproduits sans son autorisation. A bstract An experimental investigation of 15 cyciicalty loaded extended end plate connections was undertaken to determine the important design parameters. The parameters investigated were beam size, bolt layout, use of extension stineners, end plate thickness, and weldùig tefhnîque. Of the 15 test specimens, 12 were designed to confine failure to the end plate and three were designed to develop the plastic moment capacity of the beam. In addition to the experimental program, a literature survey was conducted and ten models, developed to predict the capacity of extended end plate moment connections, were evaluated. Of the beam sizes tested (W360x51, W460x97 and W610x125) the W460x97 beam connections provided the most ductiüty. The relaxed bolt configurations increased energy dissipation capacity and maximum connection rotation. The use of extension stineners increased energy dissipation capacity and raised comection yield rotation. Increased end plate thickness increased connection moment capacit y. The variation of welding techniques did not greatly affect connection performance. Bolt bending and loss of preload was cornmon. Extended end plate connections showed po tential for use in seismic zones. This project was conducted with the financial ssistance of the Structural Steel Education Foundation and the C.W. Carry Chair. The author acknowledges fuiancial support from the Structural Steel Education Foundation, the C.W. Carry Chair and the Faculty of Graduate Studies of the University of Al berta. The assistance of the technical staff at the LF. Morrison laboratory at the University of Alberta has been invaluable. 'Ihanks are extended to Waiward Steel for the donation of wo specimens and al1 of the flux cored arc welding. Mr. Clarke Bickneli's expert hand must be thanked for al1 of the shielded metal arc welding. Mr. Jeff DiBanista's assistance enabled the project to p t underway quickl y and eficiently. I would like to thank my supervisors, Dr. Gilbert Grondin for his countiess hours of assistance and Dr. J.J. Roger Cheng for the opportunity to work on this project. Finally 1 would like to thank Ann Schumacher whose encouragement uid companionship made the entire U of A experience more enjoyable.

- by Gilbert Grondin
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- Civil Engineering, Cyclic Loading, Energy absorption

In this paper the results of experimental works pertaining to the crash behaviour, collapse modes and crashworthiness characteristics of carbon fibre reinforced plastic (CFRP) tubes that were subjected to static axial compressive loading are presented in detail. The tested specimens were featured by a material combination of carbon fibres in the form of reinforcing woven fabric in thermosetting epoxy resin, and they were cut at various lengths from three CFRP tubes of the same square cross-section but different thickness, laminate stacking sequence and fibre volume content. CFRP tubes were compressed in a hydraulic press of 1000 kN loading capacity at very low-strain rate typical for static testing. The influence of the most important specimen geometric features such as the tube axial length, aspect ratio and wall thickness on the compressive response and collapse modes of the tested tubes is thoroughly analysed. In addition, the effect of the laminate material properties such as the fibre volume content and stacking sequence on the energy absorbing capability of the thin-wall tubes is also examined. Particular attention is paid on the analysis of the mechanics of the tube axial collapse modes from macroscopic and microscopic point of view, emphasizing on the mechanisms related to the crash energy absorption during the compression of the composite tubes.

- by Dimitrios Manolakos
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- Engineering, Strain Rate, Composite structures, Energy absorption

A novel flexible tripodal ligand derived from 3-methylindole, (''InTREN" L), and its mononuclear Zn(II), Cu(II), Ni(II), Hg(II) and Pd(II) complexes are described. All compounds gave analytically pure solid samples. Characterisation of the compounds was accomplished by 1 H NMR, IR and absorption spectroscopies, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and elemental analysis and their geometry optimized using density functional theory (DFT).

Aluminum columns are used in a wide variety of automotive and aerospace applications and especially as crash absorber elements. In automotive application, metallic thin-walled structures absorb impact energy in a plasticity deformation. Thereby, they bring the passenger compartment to rest without subjecting the occupant to high decelerations. A numerical study is presented in this paper to investigate and determine the

- by Azrol Jailani
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- Energy absorption, Plastic deformation, Failure Mode

In this study, therapeutic effects of Vitamin K2, Raloxifene and their co-administration on bone, uterus, blood and weight profiles were investigated with an ovariectomized rat model. Forty Wistar rats were divided into five groups (n = 8): Raloxifene (R), Vitamin K2 (K), Raloxifene + Vitamin K2 (R + K), ovariectomized controls (OVX) and Sham-operated controls (Sham). Treatment began 3 months after ovariectomy. Vitamin K2 and Raloxifene were administered 30 and 1.5 mg/kg/day separately and in combination five times per week for 12 weeks. All treatment groups had significantly higher ultimate strength and energy absorption capacity (P < 0.05) than ovariectomized controls in both femur and tibia. Histological results showed that treatment groups had healthy lumen structure, whereas OVX had degeneration. Adverse effects which were seen in individual treatments (myometrium weakening in K, endometrium weakening in R, and ALP increase in group R) were not observed in the R + K group implying a synergistic effect of these two agents when they are co-administered. According to blood analysis, ALP values were significantly high in Raloxifene-only group (P < 0.0001). This effect is suppressed in the co-administered group. In summary, the groups R, K and R + K had significantly higher ultimate strength and less susceptibility to fracture than ovariectomized controls. In summation, Vitamin K2 treated groups (either in single or combined with Raloxifene) had considerable biomechanical performance and reproductive tissue profile indicating that this agent is prospectively effective in osteoporosis management.

- by Hasan Bilgili and +2
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- Fracture, Evaluation, Estrogen Receptor, Osteoporosis

This paper presents the energy absorption properties of hexagonal honeycomb structures of varying cellular geometries under high speed in-plane crushing. While the crushing responses in terms of energy absorption and densification strains have been extensively researched and reported, a gap is identified in the generalization of honeycombs with contr'olled and varying geometric parameters. This paper addresses this gap through a series of finite element (FE) simulations where the cell angle and the inclined wall thickness, are varied while maintaining a constant mass of the honeycomb structure. A randomly filled, nonrepeating design of experiments (DOEs) is generated to determine the effects of these geometric parameters on the output of energy absorbed and a statistical sensitivity analysis is used to determine the parameters significant for the crushing energy absorption of honeycombs. It is found that while an increase in the inclined wall thickness enhances the energy absorption of the structure, increases in either the cell angle or ratio of cell angle to inclined wall thickness have adverse effects on the output. Finally, the optimization results suggest that a cellular geometry with a positive cell angle and a high inclined wall thickness provides for maximum energy absorption, which is verified with a 6% error when compared to a FE simulation.

- by Joshua Summers
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- Mechanical Engineering, Energy absorption, Mechanical design
- by Kjeld Søballe
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- Biomedical Engineering, Hydroxyapatite, Medicine, Dogs

The paper describes the computational analysis and experimental crash tests of a new road safety barrier. The purpose of this research was to develop and evaluate a full-scale computational model of the road safety barrier for use in crash simulations and to further compare the computational results with real crash test data. The impact severity and stiffness of the new design have been evaluated with the dynamic nonlinear elasto-plastic analysis of the three-dimensional road safety barrier within the framework of the finite element method with LS-DYNA code. Comparison of computational and experimental results proved the correctness of the computational model. The tests have also shown that the new safety barrier assures controllable crash energy absorption which in turn increases the safety of vehicle occupants.

- by M. Vesenjak
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- Materials Engineering, Mechanical Engineering, Civil Engineering, Road safety

The effect of low-density metal filler, such as aluminum foam or honeycomb, is studied on the bending collapse resistance of thin-walled prismatic columns. A combination of analytical and numerical results is used to predict the initial and post collapse response of empty and filled columns. Closed-formed solutions for the bending-rotation characteristics are constructed in terms of the geometrical parameters and the filler strength. The low-density metal core retards sectional collapse of the thin-wall column, and increases bending resistance for the same rotation angle. Numerical simulations show that, in terms of achieving the highest energy absorption to weight ratio, columns with aluminum honeycomb or foam core are preferable to thickening the column wall. Moreover, the presence of adhesive improved the specific energy absorption significantly.

We investigated the role of fatigue in muscle strain injuries using the extensor digitorum longus muscles of 48 rabbits. The muscles of the rabbits were fatigued by 25% or 50% then stretched to failure and compared with the contralateral controls. Three rates of stretch were used. The force to muscle failure was reduced in the fatigued leg in all groups (range, 93% to 97.4%

This paper describes an approximate approach to evaluating the performance, including the probability of loss-of-power (or loss-of-load, as some would have it) of stand-alone photovoltaic solar energy systems. The method treats the energy capture, storage and disbursement process as a random walk in the storage domain. To apply the technique, one must know the variance, as well as the mean, of the probability density of the daily solar insolation impinging onto the photovoltaic array. Analytical expressions are obtained for the probability of depleting the system's storage, as well as how much auxiliary energy, on the average, would be required to cover the load in that event.

- by louis bucciarelli
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- Engineering, Solar Energy, Performance Prediction, Random Walk

Carbon/epoxy square tubes and channel sections have been used in modern automotive and aircraft structures, respectively, as dedicated components designed to dissipate energy under controlled collapse. However, there are currently no specialized test methods for the characterization of Specific Energy Absorption (SEA) of composite materials. A systematic experimental investigation is conducted to evaluate the effect of geometric features on crush behavior. From a square tube, individual test segments are machined in order to isolate corner radii and flat sections of varying sizes, for a total of five different test geometries. Laminate thickness, material system, manufacturing process, and test methodology are kept constant throughout the study. For the material system and lay-up considered in this study, fiber tensile fracture and tearing at the corners is responsible for the vast percentage of the energy absorbed, while frond formation and splaying of the flat segments is responsible for a much lower percentage. An analytical expression is derived that accounts for the combined behavior of corner elements and flat segments in the crush behavior of more complex test articles, such as tubes.

- by Paolo Feraboli
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- Materials Engineering, Mechanical Engineering, Aerospace Engineering, Modeling

The paper presents the basic guidelines for the design of a landing gear adopting a crash tube as an energy absorbing device in crash conditions. In the considered landing gear layout , a light alloy thin walled tube is mounted coaxially to the shock absorber cylinder and, in severe impact condition, collapses in order to enhance the energy absorption performance of the landing system. A novel triggering mechanism, activated in crash impact conditions, has been developed in order to eliminate the initial load peak in the tube collapse process. The device allows to study the possible design solutions for an additional shock absorbing stage that can be integrated in a landing gear structure without requiring the introduction of frangible attachments. The characteristics of the triggering device are presented and the structural layout of a crashworthy landing gear adopting the developed additional energy absorbing stage is outlined. Experimental and numerical results relevant to the triggering system development are reported. The potential performances of a landing gear featured with the additional stage are analysed by means of a simplified numerical model, showing that appreciable energy absorbing capabilities and efficiencies can be obtained in crash conditions.

In the context of capacity design philosophy, where a desired failure mode exhibiting adequate levels of energy absorption capacity is envisaged, control must be exercised on the member behaviour to safeguard the achievement of the target... more

- by Rui Pinho
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- Civil Engineering, Earthquake Engineering, Energy absorption, Seismic response

Earthquakes of the past have proved beyond doubt that the loss of life and property can be minimized if the structures are designed and detailed to behave in a ductile manner. The secrete of improving the ductility factor of reinforced concrete frames lies in the increased rotational capacity of the cross sections, especially at the joint where the complex state of stress exist.
Previous research have attempted to improve the joint performance by either including fibrous concrete at the joints to improve the tensile strength of concrete or by using Self Compacting Concrete(SCC) for properly compacted concrete at the joints. However, these strategies were only individually quantified. In this work two different methodologies, namely, adopting fibrous conventional concrete in joint and fibrous SCC at joints are evaluated for their influence on the full range behavior of square RC one fourth scale frames subject to static cyclic loading.
Totally four number of specimens first one with conventional concrete for monotonic loading test, the second with conventional concrete with cyclic loading, the third one with fibrous concrete at joint subjected to cyclic loading and fourth one of SCC with Fibre subjected to cyclic loading are taken up. M40 grade of concrete is used. The behavioral parameters compared are initial stiffness, degradation of stiffness, first crack load, energy absorption, ductility factor and failure pattern of frames.
The experimental results of the monotonic tests are compared with linear and non-linear finite element analysis results using standard structural analysis software and using plastic analysis procedure. The investigation indicated that the frames with fibres added to SCC at hinges indicated relatively better performance under cyclic loading and hence is recommended for improving seismic performance of RC frames.

In this paper two types of polymeric foams, namely, cross-linked poly-vinyl chloride (PVC) and polyurethane (PUR) were examined under compression loading at different strain rates. Quasi-static compression tests were performed using a servo-hydraulic material testing system (MTS) at strain rate of 0.001, 0.01, and 0.1 s −1 . Higher strain rate compression tests were performed using a split Hopkinson pressure bar (SHPB) apparatus with polycarbonate bars at strain rate ranging from 130 to 1750 s −1 . PVC foams with three densities and two microstructures, and PUR foams with two densities were considered. All foam specimens were tested in the thickness (rise) direction and the stress-strain responses at different strain rate were established to determine the peak stress and energy absorption. Both peak stress and energy absorption were found to be dependent on foam density, foam microstructure, and strain rate. A power law relationship between the peak stress and foam density revealed that the constants were different at different strain rate. Microstructural examinations of the failed specimens showed that PUR foams disintegrated completely around 1600 s −1 whereas PVC foams densified completely like a solid material.

- by MD Kabir
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- Materials Engineering, Mechanical Engineering, Materials Science, Strain Rate
- by K. Spentzas and +1
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- Automotive Industry, Composite Material, Energy absorption, Crashworthiness

The energy absorption mechanism in the close near Eeld of dipole antennas is studied by numerical simulations. All computations are performed and validated applying the threedimensional multiple multipole (3DMMP) software package. The numerical model of the plane phantom is additionally checked by accurate as possible experimental measurements. For the plane phantom, the interaction mechanism can be well described by H-Eeld induced surface currents. The spatial peak specific absorption rate (SAR) can be approximated within 3 dB by a formula given here based on the incident H-field or antenna current and on the conductivity and permittivity of the tissue. It is further shown that these findings can be generalized to heterogeneous tissues and larger biological bodies of arbitrary shape for frequencies above 300 MHz. The SAR is found to be mainly proportional to the square of the incident If-Eeld, which implies that in the close near field, the spatial peak SAR is related to the antenna current and not to the input power. Another consequence of this study is that the exclusion clause of the ANSI C95.1-1982 standard for low-power communication equipment must be revised because it is in direct contradiction with the basic peak SAR limits.

- by Quirino Balzano
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- Engineering, Technology, Biomagnetism, Numerical Simulation

Closed cell aluminium foam has been examined with respect to crash protection systems, stiff and strong light weight structures and sound absorbing panels / enclosures for use in automotive systems. Monotonic compression tests revealed that the crash box made from aluminium foam-filled steel tube showed twice the energy absorption compared to empty crash box. Flexural studies on foam-filled thin walled aluminium extruded section showed higher resistance to bending (7.5 kN) against empty Al-section (5.8 kN). Differences in the mechanisms of deformation between foam filled sections and their empty counterparts were studied in compression and bend loading conditions. Acoustic behaviour was evaluated in the as-received foam and in foams post processed to increase cell interconnectivity. High sound absorption coefficients were observed in most conditions. The optimum combination of high sound absorption coefficient and frequency range occurred in a crushed foam with good cell interconnectivity.

- by Satya Sahu
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- Materials Science, Energy absorption, Metal Foam, Compression test

On railway track structures, dynamic impact loads with very high magnitude but short duration are often caused by wheel or rail abnormalities such as flat wheels and dipped rails. The possibility of the large impact loading to cause an extreme failure to an in situ concrete sleeper could be very low about once or twice in the design life cycle. However, to the current knowledge, the behaviour of the in situ prestressed concrete sleepers under the ultimate impact loading has not yet been comprehended, resulting in the design deficiency. A high-capacity drop-weight impact testing machine was thus constructed at the University of Wollongong, in order to evaluate impulsive resistance of in situ prestressed concrete sleepers under impact loads. This paper describes the detail of the high-capacity impact testing machine, as well as the instrumentation, the calibration, and the analysis of failure mode, crack propagation, flexural toughness, and energy absorption mechanisms with respect to railway prestressed concrete sleepers. The impact tests were carried out using the prestressed concrete sleepers manufactured in Australia. An in situ track test bed was simulated in laboratory and calibrated against the frequency response functions obtained from the experimental modal analysis. The experiments using the high-capacity impact testing machine to investigate the impact energy transfer mechanism of the prestressed concrete sleepers are highlighted.

- by Om Gandhi
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- Differential Equations, Polarization, Energy absorption, Bandwidth

AbstractPurpose: This study aims to determine the material integration of Islamic religious education and natural science on photosynthesis experiments. Methodology: This research is library research. Data obtained from a literature review. The analytical method used is conceptual-descriptive. Findings: The results of the study show that there are two topics of natural science material experiments closely relatedtoscientific cues on QS. Yasin verse 80, QS. Nuh verse 16, and QS. Thaha verse 53. Those topics are about light and photosynthesis. Light (an-nur) is one of the names of letters in the Qur'an. Photosynthesis experiments can explain the relationship of light interpretation materially. Sunlight is the main source of energy for the life of all living things in the world. For plants especially those with chlorophyll, sunlight greatly determines photosynthesis. Photosynthesis is a basic process in plants to produce food. The food produced will determine the availability of energy for plant growth and development. Low light intensity has three choices, namely: reduction of respiration speed, increase in leaf area to obtain a larger surface absorption of light; and increased photosynthetic velocity per unit of light energy and leaf area. Applications: This study can be used by Islamic education institution for education, research, and community services. Novelty/Originality: This study is the integration between scientific cues and natural science experiment material

- by MGES Journals
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- Photosynthesis, Natural Science, Chlorophyll, Integration

This article describes several European cooperative research examples in the field of polymer composite materials. The projects, which were carried out in collaboration between industrial and academic partners, were all supported by the European Union. They deal, e.g., with (a) the manufacturing and crash testing of thermoplastic composite structures, (b) the production of thermoplastic composite preforms, and (c) the energy absorption behavior of aluminum foams, and other interesting subjects.

- by Michael Maier
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- Materials Science, European Union, Composite Material, Energy absorption

In this paper, the signal-to-noise ratio (S/N) of resistive Cd10x x xZnx x xTe semiconductor detectors, at different directions of irradiation, within the X-ray diagnostic energy range, has been experimentally studied. In addition, the dependence of the spatial resolution of a planar Cd10x x xZnx x xTe substrate both on the applied bias voltage and thickness has been experimentally determined. The detection efficiency of semiconductor detectors depend upon the energy absorption efficiency as well as the collection efficiency. This study suggests that high signal-to-noise ratios can be obtained by optimally choosing which polarizing electrode is directly exposed to the incident X-ray beam, as well as on both the detector thickness and applied bias voltage. In addition, the experimental results on the temporal system MTF indicate a spatial resolution of > > >6 cy/mm. Besides the intrinsic charge transport characteristics of the semiconductor sample, by decreasing the collector size and optimizing the Xray digital system geometry and temporal response, the temporal system MTF can be improved significantly. The research imaging detector system allows one to investigate methods to improve the detection and imaging performance parameters as part of the development of a digital radiographic system.

- by Robert J. Endorf and +1
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- Instrumentation, X Rays, Digital Radiography, Digital Systems

The crush ing be hav ior of com pos ite tubes in ax ial im pact load ing is in ves ti gated. Tubes of cir cu lar and rect angu lar cross sec tion are sim u lated us ing an LS-DYNA soft ware. The ef fect of fi ber ori en ta tion on the en ergy ab sorbed in lam i nated com pos ite tubes is also stud ied. The re sults ob tained show that rect an gu lar tubes absorb less en ergy than cir cu lar ones, and their max i mum crush ing load is also lower. The com pos ite tubes with a [+ -q q] lay-up con fig u ra tion ab sorb a min i mum amount of en ergy at q = 15°. The sim u la tion re sults for a rect an gu lar com pos ite tube with a [+30/-30] lay-up con fig u ra tion are com pared with avail able ex per i men tal data. Cy lin dri cal com pos ite tubes fab ri cated from wo ven glass/poly es ter com pos ites with dif fer ent lay-ups were also tested us ing a drop-weight im pact tester, and very good agree ment be tween ex per i men tal and numer i cal re sults is achieved.

- by Mahmood Shokrieh
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- Energy absorption, Cross Section, Dynamic Loading, Experimental Data

The aim of this study was to calculate the magnitude of the instantaneous muscular power output at the hip, knee and ankle joints during ergometer cycling. Six healthy subjects pedalled a weight-braked bicycle ergometer at 120 watts (W) and 60 revolutions per minute (rpm). The subjects were filmed with a cine camera, and pedal reaction forces were recorded from a force transducer mounted in the pedal. The muscular work at the hip, knee and ankle joint was calculated using a model based upon dynamic mechanics described elsewhere. The mean peak concentric power output was, for the hip extensors, 74.4 W, hip flexors, 18.0 W, knee extensors, 110.1 W, knee flexors, 30.0 W and ankle plantar flexors, 59.4 W. At the ankle joint, energy absorption through eccentric plantar flexor action was observed, with a mean peak power of 11.4 W and negative work of 3.4 J for each limb and complete pedal revolution. The energy production relationships between the different major muscle groups were computed and the contributions to the total positive work were: hip extensors, 27%; hip flexors, 4%; knee extensors, 39%; knee flexors, 10%; and ankle plantar flexors 20%.

- by Ralph Nisell
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- Mathematics, Energy Metabolism, Muscles, Energy absorption

The gamma ray energy absorption ( EABF) and exposure buildup factors ( EBF) have been calculated for some essential amino acids, fatty acids and carbohydrates in the energy region 0.015-15 MeV up to a penetration depth of 40 mfp (mean free path). The five parameter geometric progression (G-P) fitting approximation has been used to calculate both EABF and EBF. Variations of EABF and EBF with incident photon energy, penetration depth and weight fraction of elements have been studied. While the significant variations in EABF and EBF for amino acids and fatty acids have been observed at the intermediate energy region where Compton scattering is the main photon interaction process, the values of EABF and EBF appear to be almost the same for all carbohydrates in the continuous energy region. It has been observed that the fatty acids have the largest EABF and EBF at 0.08 and 0.1 MeV, respectively, whereas the maximum values of EABF and EBF have been observed for aminoacids and carbohydrates at 0.1 MeV. At the fixed energy of 1.5 MeV, the variation of EABF with penetration depth appears to be independent of the variations in chemical composition of the amino acids, fatty acids and carbohydrates. Significant variations were also observed between EABF and EBF which may be due to the variations in chemical composition of the given materials.

- by Murat Kurudirek
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- Geochemistry, Exposure, Energy absorption, Fatty Acid

The interesting properties of metal foams as light weight, good energy absorption, low thermal conductivity, recyclability have spurred new process developments with the goal to obtain materials with a good relation between properties and... more

- by Rossella Surace
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- Powder Metallurgy, Statistical Analysis, Materials Design, Design of experiment

The basic concepts of radiation dosimetry are reviewed on basis of ICRU reports and text books. The radiation field is described with, among others, the particle fluence. Cross sections for indirectly ionizing radiation are defined and indicated is how they are related to the mass energy transfer and mass energy absorption coefficients. Definitions of total and restricted mass stopping powers of directly ionizing radiation are given. The dosimetric quantities, kerma, absorbed dose and exposure together with the relations between them are discussed in depth. Finally it is indicated how the absorbed dose can be measured with a calorimeter by measuring the temperature increase and with an ionisation chamber measuring the charge produced by the ionizing radiation and making use of the Bragg-Gray relation.

- by Adrie J.J. Bos
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- Radiation Dosimetry, Field emission, Exposure Assessment, Phase transition

1. Introduction Concrete is the most frequently used human-made material in the world. It is durable, inexpensive, read-ily moulded into complicated shapes and has ad-equate compressive strength and stiffness. However, concrete has low... more

- by Abdul-hamid Zureick
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- Engineering, Materials Science, FIBRE REINFORCED CONCRETE, Polypropylene

By carrying out finite element simulation, energy absorption values of thin-walled tubes with different geometric dimensions were investigated. Square, circular, and elliptic tubes of steel and aluminum were used to compare energy absorption. The experimental results of load-displacement used for verification in the square steel tubes showed good agreement. Three-dimensional simulation was accomplished with a finite element method while the impactor collided with one side of tube and the other side was kept rigid. Square tubes for 2 specified widths with 2 different thicknesses were also compared. In addition, 2 other cross sections including circle and ellipse with the same area were studied for comparison in a loaddisplacement curve. The results show that the ellipse cross section had more energy absorption than the 2 others. Moreover, the amount of energy absorption will be greater with increasing thickness for smaller section tubes.

- by Aznil Nawawa
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- Mechanical Engineering, Structural Engineering, Finite element method, Impact

A solar assisted absorption refrigeration system (SAARS) was designed for acclimatizing of villas in Mardin which is located in Turkey and the performance of the system under different temperatures was analyzed by using MATLAB. Hourly cooling load calculation of the villas was done between 15th of May and 15th of September by considering the season for the cooling. Cooling capacity

- by Derya Burcu Özkan
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- Engineering, Mechanical Engineering, Chemistry, Energy

The deformation mechanisms and energy absorption capability of polystyrene foams and polycarbonate shells for protective helmets are experimentally studied with the aim of developing a comprehensive constitutive law to be implemented into FEM codes for impact analysis. Expanded polystyrene (EPS) of different densities are considered. Tensile and bending tests on both EPS and PC are performed. Static and dynamic compression tests on EPS are performed as well, according to both variable-and fixed-volume methods. Falling weight tests are performed on both plane PC and sandwich PC/EPS at different energy contents to investigate possible couplings. EPS dynamic-mechanical tests are also carried out at different frequencies to evaluate temperature and strain rate influence on material stiffness. The extensive scanning electron microscopy analysis allows the investigation of strain mechanisms responsible for energy absorption as well as the validation of existing theoretical models. It is demonstrated that the energy absorption capability of these materials can be controlled at two different stages: at the macroscopic scale, by choosing the foam density able to minimise the transferred load and the acceleration value in relation to the available absorbing volume; at the microscopic scale, by modifying EPS internal structure in terms of hollow bead dimensions and walls thickness. 

An investigation is described concerning the interaction of propagating interlaminar cracks with embedded strips of interleaved materials in E-glass fibre reinforced epoxy composites. The approach deploys interlayer strips of a thermoplastic film, thermoplastic particles, chopped fibres, glass/epoxy prepreg, thermoset adhesive film and thermoset adhesive particles ahead of the crack path on mid-plane of Double Cantilever Beam (DCB) specimens. During these mode I tests, the interlayers were observed to confer an apparent increase in the toughness of the host material. The crack arrest performance of individual inclusion types are discussed and the underlying mechanisms for energy absorption and the behaviour of the crack at the interaction point of the interleave edge were analysed using scanning electron microscopy.

Stirred mills are becoming increasingly used for fine and ultra-fine grinding. This technology is still poorly understood when used in the mineral processing context. This makes process optimisation of such devices problematic. 3D DEM simulations of the flow of grinding media in pilot scale tower mills and pin mills are carried out in order to investigate the relative performance of these stirred mills. Media flow patterns and energy absorption rates and distributions are analysed here. In the second part of this paper, coherent flow structures, equipment wear and mixing and transport efficiency are analysed.

- by Matt Sinnott
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- Chemical Engineering, Mineralogy, Energy Consumption, Minerals Engineering

Shape memory alloys (SMAs) exhibit peculiar thermomechanical, thermoelectrical and thermochemical behaviors under mechanical, thermal, electrical and chemical conditions. Examples of these materials are Cu-based SMAs, NiTi SMAs, ferrous SMAs, shape memory ceramics and shape memory polymers. NiTi SMAs in particular, have unique thermomechanical behaviors such as shape memory effect and pseudoelasticity, which have made them attractive candidates for structural vibration control applications. Numerous studies have been conducted in modeling and applications of NiTi SMAs in structural vibration control. Several active, passive and hybrid energy absorption and vibration isolation devices have been developed utilizing NiTi SMAs. In this paper we present an overview of NiTi behaviors, modeling and applications as well as their limitations for structural vibration control and seismic isolation.

- by I. Bar-on and +1
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- Engineering, Vibration Control, Smart Materials, Behavior Modeling

The present work focuses on the development, implementation, and verification of a plane-stress continuum damage mechanics (CDM) based model for composite materials. A physical treatment of damage growth based on the extensive body of experimental literature on the subject is combined with the mathematical rigour of a CDM description to form the foundation of the model. The model has been implemented in the commercial finite element code, LS-DYNA and the results of the application of the model to the prediction of impact damage growth and its effects on the impact force histories in carbon fibre reinforced plastic laminates are shown to be physically meaningful and accurate. Furthermore, it is demonstrated that the material characterization parameters can be extracted from the results of standard test methodologies for which a large body of published data already exists for many composite materials. commonly used strain equivalence approach, a material containing damage, subjected to a strain, e, and under a state of stress, r, can be represented as an equivalent undamaged material subject to the same strain, e, but under an effective stress state,r r. This can be expressed mathematically by the relation:

- by Vamsi Aluru
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- Materials Science, Composites, Impact, Continuum Damage Mechanics

Ebook ini boleh dijadikan acuan/ditaruh di situs lain, namun berdasarkan etika harus mencantumkan link balik ke situs Gainscope.com selaku penulis panduan ini Panduan di Ebook ini Harap Dipelajari DENGAN SEKSAMA agar Anda dapat mengetahui... more

- by santosa santosa
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- Engineering, Numerical Simulation, Energy absorption

A synergistic algorithm for producing global leaf area index and fraction of absorbed photosynthetically active radiation fields from canopy reflectance data measured by MODIS (moderate resolution imaging spectroradiometer) and MISR (multiangle imaging spectroradiometer) instruments aboard the EOS-AM 1 platform is described here. The proposed algorithm is based on a three-dimensional formulation of the radiative transfer process in vegetation canopies. It allows the use of information provided by MODIS (single angle and up to 7 shortwave spectral bands) and MISR (nine angles and four shortwave spectral bands) instruments within one algorithm. By accounting features specific to the problem of radiative transfer in plant canopies, powerful techniques developed in reactor theory and atmospheric physics are adapted to split a complicated three-dimensional radiative transfer problem into two independent, simpler subproblems, the solutions of which are stored in the form of a look-up table. The theoretical background required for the design of the synergistic algorithm is discussed.

- by Steven Running
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- Climate Change, Multidisciplinary, Product Model, Look up Table

Concentric bracings composed of three members arranged in y shaped geometry have been traditionally used to provide openings in braced bays. However, simultanous occurance of compression in three braces leads to instability and out of plane buckling of braces accompanied by low hysteretic energy absorption. In order to study the behavior of y-braced frames, a research program including experimental tests was conducted at BHRC† structural engineering laboratory. Quasi-static cyclic loading was applied to specimens including four full-scale two-bay frames with y-bracings of different cross sections and connection types. The bays are braced symmetrically to have a combination of tensile and compressive braces at all loading stages. The results show that out-of-plane buckling with single curvature in braces can be substituted by in plane, double curvature buckling through appropriate detailing of cross sections and connections. Thus, hysteretic energy dissipation of y-bracing is remarkably improved due to spreading of plastic strains in braces. In this paper, seismic performance of y-braced frame specimens and a reference X-braced frame are also assessed by capacity spectrum method.

- by sohail majid zamani
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- Civil Engineering, Structural Engineering, Steel Structures, Cyclic Loading

This paper is devoted to study and verify the suitability of the expanded polypropylene (EPP) foam as a liner for motorcycle helmet and to perform helmet design optimization. This EPP foam has a multi-impact protection performance and also has a potential for ventilation system improvement due to its resiliency. This resiliency allows for the ease of ventilation holes and channels molding without the foam breakage at the stage of mold extraction. The large scale, non-linear, dynamic finite element package LS-DYNA3D is used as a verification tool for motorcycle helmet design. Then the simulation work is carried further to provide data for helmet design analysis and optimization using the response surface methodology (RSM). The foam thickness, the foam density, and shell thickness being selected as the design factors for the response surface generation and design optimization. The results showed that the EPP satisfies the 300g headform center of gravity acceleration limit required by most of the international standards. The extended simulation output data is then used to create the response surface and determine the optimum design points. Therefore, two main contributions on motorcycle helmet design are achieved. The first is on the use of the EPP as a helmet energy absorption liner for the motorcycle helmet application, and the second is that by combining the simulation output with the design of experiment (DOE) method to study the effects of the various factors on helmet design optimization.

Previous research on the feasibility of using biodegradable magnesium alloys for bone implant applications mainly focused on biocompatibility and corrosion resistance. However, successful clinical employment of endosseous implants is largely dependent on biological fixation and anchorage in host bone to withstand functional loading. In the present study, we therefore aimed to investigate whether boneimplant interface strength and osseointegration of a novel biodegradable magnesium alloy (Mg-Y-Nd-HRE, based on WE43) is comparable to that of a titanium control (Ti-6Al-7Nb) currently in clinical use. Biomechanical push-out testing, microfocus computed tomography and scanning electron microscopy were performed in 72 Sprague-Dawley rats 4, 12 and 24 weeks after implantation to address this question. Additionally, blood smears were obtained from each rat at sacrifice to detect potential systemic inflammatory reactions. Push-out testing revealed highly significantly greater maximum push-out force, ultimate shear strength and energy absorption to failure in magnesium alloy rods than in titanium controls after each implantation period. Microfocus computed tomography showed significantly higher bone-implant contact and bone volume per tissue volume in magnesium alloy implants as well. Direct bone-implant contact was verified by histological examination. In addition, no systemic inflammatory reactions were observed in any of the animals. We conclude that the tested biodegradable implant is superior to the titanium control with respect to both bone-implant interface strength and osseointegration. These results suggest that the investigated biodegradable magnesium alloy not only achieves enhanced bone response but also excellent interfacial strength and thus fulfils two critical requirements for bone implant applications.

- by Richard Lindtner
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- Computed Tomography, Osseointegration, Scanning Electron Microscopy, Titanium

Weight savings in vehicles enhances fuel efficiency and decreases maintenance costs, especially in mass transit systems. Lightweight composite materials, such as glass fiber reinforced polymers, have been used to replace traditional steel and aluminum components. In this paper, a mass transit bus side body panel was designed, analyzed, and manufactured using thermoplastic composite materials. The design featured a sandwich composite with E-glass fiber/polypropylene (glass/PP) face sheets and PP honeycomb core as constituents that provide low weight, high strength and energy absorption benefits. The panel was designed and analyzed using Pro/Engineer 2001 (Pro/E), Altair Ò Hypermesh Ò 6.0 (Hypermesh) and ANSYS 7.0 (ANSYS). A single diaphragm forming process was used to manufacture the glass/PP face sheets. This process provides excellent consolidation, which was confirmed by microstructural analysis of the face sheets. The face sheets and core material were adhesively bonded and tested to validate the model. The failure of the body panel occurred by adhesive failure when the load reached 11.7 kN. The static loading requirements of the American Public Transportation Association (APTA) for the body panel were met. The thermoplastic composite body panel exhibited excellent weight saving of more than 55% compared to a conventional bus with aluminum skin and supporting steel bars.

- by Gregg M Janowski
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- Engineering, Public Transport, Polypropylene, Composite Material

This paper presents the results of a series of experiments conducted to investigate the e ectiveness of ÿbre inclusion in the improvement of mechanical performance of concrete with regard to concrete type and specimen size. Lightweight aggregate concrete and limestone aggregate concrete with and without steel ÿbres were used in the study. The compressive strength of the concrete mixes varied between 90 and 115 MPa and the ÿbre content was 1% by volume. Splitting tests on prisms and three-point bending test on notched beams were carried out on specimens of varying sizes to examine the size e ect on splitting strength, exural strength and toughness.

- by Abid Nadeem
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- Lightweight Concrete, Size Effects, High Strength Concrete, Energy absorption

This paper investigates the effect of polyurethane foam-filler on the lateral plastic deformation in the circular tubes under radial quasi-static loading, experimentally. For this purpose, the specimens were prepared with five different diameters and thicknesses. For each constant diameter of specimens, several tubes with different lengths were prepared. All geometrical groups of specimens in the lateral compression tests (flattening) were used in empty and polyurethane foam-filled conditions. The effect of length, diameter and wall thickness of tubes on the lateral load, energy absorption and the specific absorbed energy were studied. The experimental results show that the polyurethane foam-filler increase the energy absorption capability of tubes and furthermore the increment of the energy absorption in thinner tubes is more than thicker specimens. Results show that using the polyurethane foam in the circular tubes under the lateral compression works as an excellent filler.

- by Seyed Ahmad Elahi
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- Materials Design, Energy absorption, Plastic deformation, Compression test
- by Aidy Ali
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- Environmental Effect, Relative Humidity, Energy absorption, Fiber Reinforcement

A series of tests was conducted to investigate the blast resistances of slabs constructed with both plain ultra-high performance fibre concrete (UHPFC) and reinforced ultra-high performance fibre concrete (RUHPFC), and slabs reinforced with externally bonded (EB) fibre reinforced polymer (FRP) plates. Normal reinforced concrete (NRC) slabs were tested as control specimens. LVDTs and pressure transducers were used to record deflection histories, and pressure sensors located at the centre and one edge of the slabs measured airblast pressure histories. The measured pressures at the centre and edge of the slabs were significantly different from those estimated using traditional procedures such as those in TM5-1300. Tests indicated that the plain UHPFC slab had a similar blast resistance to the NRC slab and that the RUHPFC slab was superior to both. The addition of EB carbon FRP plates to the compression face of a reinforced concrete slab increased its ductility and blast resistance. Test results were compared with the maximum energy absorptions predicted from layered capacity analyses of the NRC, retrofitted, plain UHPFC, and RUHPFC specimens.

- by Richard Trask and +1
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- Materials Engineering, Mechanical Engineering, Aerospace Engineering, Scanning Electron Microscopy