Service Life Research Papers - Academia.edu (original) (raw)

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- Engineering, Architecture, Comparative Study, Building

Wood coatings are widely used for aesthetic and protective reasons. Assessment of coating performance during service life is crucial in order to establish a knowledge database for product optimization. A vast amount of techniques is available for analysis of a coating's behavior of which micro-imaging is an important tool. In addition to standard microscopy techniques, high-resolution X-ray tomography is presented as a modality offering non-destructive visualization of a coating and the substrate applied on. Combined with analysis of the 3D volumetric data, surface roughness, structure and thickness of the coating layer, penetration depth and related mechanical anchoring can be studied in relation with the underlying substrate. To provide a clear illustration of the possibilities and limitations of this technique, both an opaque solvent-borne and an opaque water-borne coating applied on two different wood types were scanned and analyzed. Clearly, three-dimensional X-ray imaging at high resolution produces valuable information merely by visualization. Moreover by proper analysis quantitative data is obtained taking into account the limitations of Xray computed tomography and of automated image processing.

- by Joris C R Van Acker
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- Materials Engineering, Materials Science, Image Processing, X-ray imaging

Thermal analysis and the ageing studies of butyl rubber (IIR) compounds have been carried out in order to assess the effect of a silane coupling agent, Bis-(3-triethoxysilylpropyl)tetra sulphide (Si-69) on thermal and thermoxidative stability of IIR. The thermal stability of the raw rubber remained uneffected on adding Si-69, whereas the thermoxidative stability was enhanced. Similar behaviour, though to a lesser extent, has been observed for compounded rubber. The ageing properties and service life are also improved with Si-69. A suitable mechanism has been proposed.

- by Rabindra Adhikari
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- Engineering, Materials Science, CHEMICAL SCIENCES, Thermal Analysis
- by Andrew Burke
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- Design, Evaluation, Performance, Technology Assessment

Battery energy storage systems, comprising lead-acid batteries, power conversion systems, and control systems, are in commercial operation around the world. They are used by three main groups: power generating utilities; power distributing utilities; and major power consumers (such as electric furnace foundries). The principal advantages of battety energy storage systems to generating utilities include: load leveling: frequency control; spinning re-.\erve; modular construction; convenient siting; no emissions; and investment deferral for new generation and transmission equipment. Power distributing utilities and major power consumers can avoid costly demand changes by discharging their batteries Lit peak periods and then recharging with lowjer cost off-peak power (say, at night). Battery energy storage systems are most cost effective when designed for discharge periods qf less than 5 I!; other systems (for example, pumped water storage) are better Juited for longer discharges. It is estimated that by the year 2000 there will be a potential need for 4000 MW of' battery c'nergy storage. New construction of five plants totaling 100 MW is presently scheduled for completion by the Puerto Rico Electric Power Authority between 1992 and 1995.

- by Max Anderson
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- Engineering, Biomedical Engineering, Technology Assessment, Puerto Rico
- by Daniel Ferreira V. Mattos
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- Structural Integrity, Structural Design, Service Life, Damage Tolerance

This study focuses on developing methodologies to predict the service life of a pavement marking material based on its retroreflectivity. Data from the 2002 National Transportation Product Evaluation Program (NTPEP) pavement marking material test deck in Mississippi are used for model development and model validation. The smoothing spline method and time series modeling are applied to estimate the service lives of different types of materials based on the assumption of a required minimum retroreflectivity value. The same models can also predict the retroreflectivity values at future times for a pavement marking product based on its retroreflectivity values in the past. The validation of the models shows satisfactory accuracy. As demonstrated in a case study, the predicted service lives of the marking materials can be used in life-cycle cost comparisons for selecting pavement marking material.

- by Dongfeng Wu
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- Methodology, Case Studies, Forecasting, Time series analysis

Hair clipper Ion nitriding PVD CVD a b s t r a c t Making the angle of a hair clipper blade edge acute improves its cutting ability but causes the edge to be susceptible to wear, resulting in decreased cutting service life. An enhancement of blade edge hardness of hair clippers by various surface modifications has been studied to increase their wear resistance. Ion nitriding method formed a thick nitrided layer on the mother material surface. PVD and CVD methods formed a fine and thin hard coating at relatively low temperatures. In this study, surface modification by ion plating and plasma CVD methods was carried out to improve the cutting edge qualities of 45 angle blades, material which is used is hardened SUS420J2Mo. The effectiveness was verified by cutting performance lifetime test using artificial hair. It enhanced the cutting performance lifetime of clipper blades more than four times.

- by Tadashi Hamada
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- Materials Engineering, Surface modification, Vacuum, CVD

The electrochemical behaviour of reinforcing steel in plain and blended cement concrete specimens placed in sulphate, chloride and sulphate-chloride environments was investigated. The effect of cement composition and the exposure condition on the corrosion behaviour of reinforcing steel was evaluated by measuring corrosion potentials at periodic intervals and conducting potentio-dynamic scans after two and half years of exposure. The corrosion potential data indicated passive corrosion in plain and blended cement concrete specimens placed in the pure sulphate environment. The time to initiation of reinforcement corrosion, however, was higher in blended cements than plain cements in all chloride and chloride-sulphate environments. The concomitant presence of suphate and chloride salts did not significantly influence the time to corrosion initiation. The corrosion rate, however, was significantly influenced by the quantum of sulphate ions associated with the chloride salts. The superior performance of silica fume blended cement, in terms of longer time to corrosion initiation and lower corrosion rate, indicates its potential in enhancing the useful service life of reinforced concrete structures placed in the chloride-sulphate environments.

As well as acting as a moderator and reflector, graphite is used as a structural component in many gas-cooled fission nuclear reactors. Therefore the ability to predict the structural integrity of the many graphite components which make up a graphite reactor core is important in safety case assessments and reactor core life prediction. This involves the prediction of the service

- by Barry Marsden
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- Materials Engineering, Nuclear Materials, Structural Integrity, Stress analysis

The objective of this study is to put forward a full analysis of the impact of the difference between the Canadian and American energy realities on the life cycle of fuel cell vehicles and internal combustion engine vehicles. Electricity is a major type of energy used in the transportation sector. Electricity is needed in the production of feedstock of fuel, the production of the fuel, the production of the vehicle material and the assembly of the vehicles. Therefore, it is necessary to investigate the impact of the electricity mix difference between Canada and the United States. In the analysis, the life cycle of the fuel consists of obtaining the raw material, extracting the fuel from the raw material, transporting and storing the fuel as well as using the fuel in the vehicle. Four different methods of obtaining hydrogen were analyzed; using coal and nuclear power to produce electricity and extract hydrogen through electrolysis and via steam reforming of natural gas in a natural gas plant and in a hydrogen refueling station. It is found that fuel cell vehicle fuelled by hydrogen has lower energy consumption and greenhouse gas emissions than internal combustion engine vehicle fuelled by conventional gasoline except for hydrogen production using coal as the primary energy source in Canada and the United States. Using the Canadian electricity mix will result in lower carbon dioxide emissions and energy consumption than using the American electricity mix. For the present vehicles, using the Canadian electricity mix will save up to 215.18 GJ of energy and 20.87 t of CO2 on a per capita basis and 26.53 GJ of energy and 6.8 t of CO2 on a per vehicle basis. Similarly, for the future vehicles, using the Canadian electricity mix will lower the total carbon dioxide emissions by 21.15 t and the energy consumed is reduced by 218.49 GJ on a per capita basis and 26.53 GJ of energy and 7.22 t of CO2 on a per vehicle basis. The well-to-tank efficiencies are higher with the Canadian electricity mix.

- by Nada Zamel
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- Engineering, Transportation, Energy Consumption, Comparative Study

Fatigue analysis and consequent life prediction of turbomachine blading requires the stress load history of the blade. A blade designed for safe operation at particular constant rotor speeds may, however, incur damaging stresses during start-up and shut-down operations. During such operations the blade experiences momentary resonant stresses while passing through the criticals, which may lie in the speed range through which the rotor is accelerated. Fatigue due to these transient influences may accumulate to lead to failure. In this paper a technique for fatigue damage assessment during variable-speed operations is presented. Transient resonant stresses for a blade with nonlinear damping have been determined using a numerical procedure. A fatigue damage assessment procedure is described. The fatigue failure surface is generated on the S-N-mean stress axes and Miner’s Rule is employed to estimate the accumulation of fatigue.

- by Nalinaksh Vyas
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- Engineering, Mechanical Engineering, Aerospace Engineering, Fossil Fuels
- by Michael Galvin
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- Pest Management, Arboriculture, Case Study, Urban Trees

Aircraft structural parts are structure critical parts and they are exposed to various and tedious inspections from the design phase thru the end of their service life. During design phase, taking fatigue under dynamic and static loads, corrosion and aging effects into consideration, detailed calculations are performed on structural parts to be utilized with no problems during their service lives. The areas that are more prone to fail are the critical areas for these parts. The service life of a part is especially assigned according to the critical areas. These areas play the main role to assign the inspection period and the inspection types for the part as well. Critical areas may cause notch sensitivity and vary part to part but rivet/bolt hole edges, sharp edges, threads, necked down areas from elongation are the critical areas in general for a part.

- by Osman Çelik
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- Materials Engineering, Mechanical Engineering, Civil Engineering, Failure Analysis

To cite this Article Nguyen, Minh N. , Leicester, Robert H. , Wang, Chi-Hsiang and Foliente, Greg C.(2011) 'Corrosion effects in the structural design of metal fasteners for timber construction', Structure and Infrastructure Engineering,,

- by Greg Foliente
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- Civil Engineering, Arsenic, Engineering Design, Structural Design

In the Army mechanical fatigue subject to external and inertia transient loads in the service life of mechanical systems often leads to a structural failure due to accumulated damage. Structural durability analysis that predicts the fatigue life of mechanical components subject to dynamic stresses and strains is a compute intensive multidisciplinary simulation process, since it requires the integration of several

Purpose -This work seeks to present a systematic study that aimed to provide quantitative understanding of the fundamental factors that influence the chloride threshold of pitting corrosion of steel in concrete, by conducting a set of laboratory tests to assess the corrosion potential (E corr ) and pitting potential (E pit ) of steel coupons in simulated concrete pore solutions. Design/methodology/approach -With the aid of artificial neural network, the laboratory data were used to establish a phenomenological model correlating the influential factors (total chloride concentration, chloride binding, solution pH, and dissolved oxygen (DO) concentration) with the pitting risk (characterized by E corr 2 E pit ). Three-dimensional response surfaces were then constructed to illustrate such predicted correlations and to shed light on the complex interactions between various influential factors. Findings -The results indicate that the threshold [Cl 2 ]/[OH 2 ] of steel rebar in simulated concrete pore solutions is a function of DO concentration, pH and chloride binding, instead of a unique value. Research limitations/implications -The limitations and implications of the research findings were also discussed. Practical implications -This research could have significant practical implications in predicting the service life of new or existing reinforced concrete in chloride-laden environments. Originality/value -This study further advances the knowledge base relevant to the chloride-induced corrosion of steel rebar in concrete.

- by tuan anh Nguyen
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- Materials Engineering, Corrosion, Design Methodology, Knowledge base

In a typical power electronics package, a grease layer forms the interface between the direct bond copper (DBC) layer or a baseplate and the heat sink. This grease layer has the highest thermal resistance of any layer in the package. Reducing the thermal resistance of this thermal interface material (TIM) can help achieve the FreedomCAR partnership goals of using a glycol water mixture at 105°C or even air cooling. It is desirable to keep the maximum temperature of the conventional silicon die below 125°C, trench insulated gate bipolar transistors (IGBTs) below 150°C, and silicon carbidebased devices below 200°C. Using improved thermal interface materials enables the realization of these goals and the dissipation of high heat fluxes. The ability to dissipate high heat fluxes in turn enables a reduction in die size, cost, weight, and volume. This paper describes our progress in characterizing the thermal performance of some conventional and novel thermal interface materials. We acquired, modified, and improved an apparatus based on the ASTM D5470 test method and measured the thermal resistance of various conventional greases. We also measured the performance of select phase-change materials and thermoplastics through the ASTM steady-state and the transient laser flash approaches, and compared the two methodologies. These experimental results for thermal resistance are cast in the context of automotive power electronics cooling. Results from numerical finite element modeling indicate that the thermal resistance of the TIM layer has a dramatic effect on the maximum temperature in the IGBT package.

- by Sreekant Narumanchi
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- Engineering, Materials Science, Power Electronics, Modeling

When adequately maintained, the mechanical system of rewinders and similar machines in paper industry may have a significantly longer service life than its electrical and control systems. Over the lifetime of the facility, a rewinder may experience several major maintenance cycles, and these generally include significant upgrades to the electrical drive and control system. These upgrades present an opportunity to modify the design of the control system to eliminate some of the sensors or to provide signal redundancy by using state estimation. During such major reconstruction of a paper-board rewinder, it was noticed that the shipping-roll radius and the web tension force can be accurately estimated from the measurements available within the drive's control system. This paper presents the implementation of the two estimators on a commercial production rewinder. Test results from the equipment in service show that the measured signals can be supplemented with the estimated ones to provide an alternative in the event of sensor malfunction or to enable trending of accuracy of calibration. Both applications have an entitlement to reduce the downtime of the rewinder, as the replacement of the faulted sensor can be scheduled for the next planned idle period of the machine.

- by M. Bebic
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- Engineering, Control system, Maintenance Engineering, Mechanical systems

Sarel LAVY 1 and Igal M. SHOHET 2 1 Department of Construction Science, College of Architecture, Texas A&M University, 422A Langford, 3137 TAMU, College Station, Texas 77843-3137, USA E-mail: slavy@archmail.tamu.edu 2 Division of... more

- by Sarel Lavy
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- Facility Management, Strategic Decision Making, Life Cycle, Service Life

The installation may represent the hardest stress on a geosynthetic during its service life. Full-scale field installation tests have been performed on 38 different geotextiles and geogrids. The findings have been used to determine the corresponding reduction factor which must be taken into account to assess the long-term tensile strength of reinforcing geosynthetics. Based on the present study and full-scale field installation tests presented elsewhere, a matrix to assess the survivability of geosynthetics is proposed. In addition, parts of the geosynthetics have been submitted to a laboratory simulation of the damage during installation, which showed a reasonable correlation to the results of the field test. r

- by Rudolf Hufenus
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- Civil Engineering, Service Life, Tensile Strength

The road network in Saudi Arabia has experienced remarkable development both in length and standards to become one of the longest and most modern highway networks in the Middle East. Quality of performance of some roads, however, was below a satisfactory level. Various parameters directly and indirectly contribute to the pavement quality performance. The contributing factors are design, specifications, environment (traffic, temperature), and construction-related factors; the indirect factors are managerialrelated factors. This paper reviews the factors that contribute to the quality of pavement performance in Saudi Arabia. This review was achieved via both a comprehensive literature review and a highway contractor’s survey. The significant performance factors were arranged into three groups: (1) managerial-related factors that include qualification of owner’s inspection team, contractor experience, and capability; (2) design and specifications-related factors that include considerat...

- by Abdulaziz Bubshait
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- Civil Engineering, Construction, Middle East, Service Life

Installation and removal of conventional refractories and refractory ceramic fiber (RCF) in industrial furnaces may lead to occupational exposure to respirable crystalline silica (including quartz, cristobalite, and tridymite). Exposure to elevated concentrations of these materials has been linked to adverse respiratory effects, including silicosis and lung cancer. Unlike conventional refractories, RCF does not contain any of these materials as produced. However, depending upon time and temperature during the service life of the insulation, RCF may partially devitrify, creating the potential for exposure upon removal of after-service insulation. For removal of after-service RCF, exposure data collected as part of a 5-year consent agreement with EPA are presented and analyzed. Because of relatively low concentrations of these materials, limitations on the sensitivity of the analytical method, and the relatively short duration of furnace removal activities, many measurements are less than the limits of detection (LODs), creating challenges for data analysis. Several methods of analysis of censored data are illustrated and the theory of maximum likelihood estimates is generalized to cover the case of multiple LODs. Average exposures to these materials associated with removal of after-service RCF are compared to those in various industries.

- by Daniel Maxim
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- Data Analysis, Lung Cancer, Ceramics, Industry

In this report, cycling induced capacity fade of a LiFePO 4 battery was studied and cycle-life models were established. Cell life data for establishing the model were collected using a large cycle-test matrix. The test matrix included three parameters, temperature (−30 to 60 • C), depth of discharge (DOD) (90-10%), and discharge rate (C-rate, ranging from C/2 to 10C, with the 1C rate corresponding to 2A). At the low Crates , experimental results indicated that the capacity loss was strongly affected by time and temperature, while the DOD effect was less important. At the high Crates , the charge/discharge rate effects became significant. To establish a life model, we adopt a power law equation in which the capacity loss followed a power law relation with time or charge throughput while an Arrhenius correlation accounted for the temperature effect. This model, when parameters were allowed to change with Crates , was found to represent a large array of life cycle data. Finally, we discuss our attempts in establishing a generalized battery life model that accounts for Ah throughput (time), Crate , and temperature.

- by Elena Sherman
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- Engineering, Power Law, Life Cycle, Lancet

The growth of sustainability awareness has driven many industries to provide "greener" products and processes and promote new approaches to improve their environmental performances. In particular, Life Cycle Assessment (LCA) is a framework for estimating the environmental impacts of a product, a process, or a service throughout its life-cycle.

Résumé -Le système de suspension des véhicules routiers légers comprend généralement des ressorts hélicoïdaux en acier dont le rôle est de filtrer les vibrations. Leur dimensionnement revêt un caractère particulièrement important pour obtenir les caractéristiques mécaniques souhaitées tout en optimisant masse non suspendue, durée de vie et coûts. La cinématique des trains et l'implantation des ressorts impliquent, dans bon nombre de cas, un fonctionnement non axial dit « en sécateur ». Dans ces conditions, la prévision du comportement par les outils analytiques habituels apporte une solution incomplète qui nécessite souvent le passage par l'expérience et nuit à la définition optimale du ressort. Le calcul numérique par Eléments Finis offre une solution souple, fiable et complète prenant en compte les particularités de l'environnement véhicule (encombrement, cinématique des trains, raideurs parasites. . .). Cet outil permet d'optimiser le ressort en terme de contraintes supportées et d'allègement. Des résultats de simulations numériques sont présentés et discutés à la vue de résultats d'expérience. Ils démontrent les apports de l'outil numérique dans le dimensionnement de ressorts sous fonctionnements particuliers.  2001 Éditions scientifiques et médicales Elsevier SAS

- by Ouakka A
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- Kinetics, Numerical Simulation, Finite element modelling, Service Life
- by Mauricio Angeloni
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- Cast Iron, Thermal Conductivity, Service Life, Low Noise

A complex interdisciplinary approach to the reliability assessment of reinforced concrete structures is introduced and demonstrated on a real existing bridge structure. The reliability index of the structure decreases during its life cycle due to material degradation. A retrofitting to the desired reliability level should be performed. This procedure is modeled by advanced life-cycle computer simulation. The main feature of the presented approach is the nonlinear finite element analysis of the structure employed for the realistic assessment of structural behavior. A suitable technique of statistical sampling, which allows relatively small numbers of simulations, is used in this context. Different degradation scenarios are analyzed concerning their effect on the structures reliability progression. These studies give a basis for future models including analytical deterioration models combined with in situ monitoring, used to launch the degradation process. Finally the presented methodology for advanced life-cycle analysis shall be integrated in the innovative decision-making tool that supports maintenance planning of engineering structures.

- by Konrad Pakuła
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- Civil Engineering, Decision Making, Structure, Structural Reliability

Incidents of failure due to corrosion/stress corrosion cracking of high-pressure gas pipelines in Pakistan have been observed to occur after about 15-20 years of service. The present paper constitutes the failure analysis of an 18-inch diameter electric resistance-welded gas pipeline. The failure was characterized, on the basis of all the available evidence and the metallurgical examination carried out on the ruptured pipe, as a stress corrosion failure that had initiated at a longitudinal 'stress raiser'. This stress raiser, which was essentially a manufacturing defect, constituted a longitudinal 'step' on the pipe surface that had resulted from the faulty trimming/shaving of the weld flash. The findings of this study, thus, emphasize the need for the care that must be taken during the shaving-off of the weld flash.

- by Faiz Hasan
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- Materials Engineering, Mechanical Engineering, Civil Engineering, Ergonomics

Purpose There is no clear guidance for responsible food service operations to reduce their environmental footprint, so the efforts put forth by a restaurant may not have the environmental impact intended. As a result, Green Seal conducted life cycle assessment research on restaurants and food service operations to define priorities for environmental improvement. This information was then used to develop a sustainability standard and certification (i.e., ecolabel) program.

- by Nana Wilberforce
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- Environmental Engineering, Climate Change, Life Cycle Assessment, Fossil Fuels

An experimental program was conducted to determine the effects of geosynthetic reinforcement on mitigating reflection cracking in asphalt overlays. The objectives of this study were to asses the effects of geosynthetics inclusion and its placement location on the accumulation of permanent deformation. This study revealed that geosynthetic reinforced specimens improved resistance to reflection cracking. Placing the geogrid at the one third depth of overlay thickness from bottom had the maximum service life. Results indicate a significant reduction in the rate of crack propagation and rutting in reinforced samples compared to unreinforced samples.

- by Fereidoon Moghadas Nejad
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- Civil Engineering, Asphalt, Crack propagation, Deformation

A total of 349 residential building audits were performed in seven European countries to collect data on the degradation of building elements (architectural and installations). The buildings cover typical architectural typologies, sizes, constructions and installations, at different states of deterioration. The data was collected based on a standardized methodology for building audits. Follow up analysis revealed the most important influencing factors on the deterioration of existing residential buildings throughout Europe and estimated service lives of various building architectural elements and electromechanical installations. #

- by Popi Droutsa and +1
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- Engineering, Energy, Energy Efficiency Buildings, Service Life

The application of concrete is rapidly increasing worldwide and therefore the development of sustainable concrete is urgently needed for environmental reasons. As presently about 7% of the total anthropogenic atmospheric CO 2 emission is due to cement production, mechanisms that would contribute to a longer service life of concrete structures would make the material not only more durable but also more sustainable. One such mechanism that receives increasing attention in recent years is the ability for self-repair, i.e. the autonomous healing of cracks in concrete. In this study we investigated the potential of bacteria to act as self-healing agent in concrete, i.e. their ability to repair occurring cracks. A specific group of alkali-resistant spore-forming bacteria related to the genus Bacillus was selected for this purpose. Bacterial spores directly added to the cement paste mixture remained viable for a period up to 4 months. A continuous decrease in pore size diameter during cement stone setting probably limited life span of spores as pore widths decreased below 1 m, the typical size of Bacillus spores. However, as bacterial cement stone specimens appeared to produce substantially more crack-plugging minerals than control specimens, the potential application of bacterial spores as self-healing agent appears promising.

- by bindu balu
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- Engineering, Ecological Engineering, Earth Sciences, Environmental Sciences

- by Max Anderson
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- Biomedical Engineering, Technology Assessment, Puerto Rico, Power Plant

Increasing needs of very high resistance to cosmetic corrosion, of more extended service life and reduced maintenance costs for infrastructures, civil and industrial buildings open new fields of application for coil coated stainless steel. This paper describes the adhesion and corrosion properties ol new coil coated staìnless steel materials produced in industrial coil coating lines. The use of an electrochemical test (electrochemical impedance spectroscopy) can give detailed information on the reactivity of the system and allow the performance of different substrates (AISI 409, 430, 316 and 304) coated with different polymers (polyvinylidene and polyester) to be compared. The results obtained show the interesting properties ol this new class of coil coated products. The materials were tested for a long time (about 200 days) in an aggressive environmenf (3.5o/o sodium chloride solution) also in the presence of macrodefects. In particular, VIVINOX 430,304 and 316 revealed no reactivity, corrosion or disbonding, thus supporting the expectancy of very long trouble free exposure also in very aggressive natural environments. (VIVINOX is the brand name of the AST (Acciali Speciali Terni) line of coil coated stainless steel.)

- by pier luigi Bonora
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- Materials Engineering, Mechanical Engineering, Stainless Steel, Service Life

Nitriding of complex-shaped extrusion dies may result in non-uniform nitride layers and hence a required hardness may not be achieved in some regions of the bearing area. The present study is carried out to assess the effect of extrusion die profile on the characteristics and growth behavior of nitride layers so that the critical die design feature can be identified to enhance the uniformity of the nitride layer. For this purpose, AISI H13 steel samples have been manufactured with profiles similar to those of hot extrusion dies. The samples were then gas nitrided under controlled nitriding potential. The uniformity and depth of nitride layers have been investigated in terms of compound layer and total nitride case depth for selected die features. The results of this study indicated the need to include the effect of profile on the nitride layer for the optimal die design with improved service life.

- by Abul Arif
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- Materials Engineering, Service Life

In this paper, an integrated approach for gear health prognostics using particle filters is presented. The presented method effectively addresses the issues in applying particle filters to gear health prognostics by integrating several new components into a particle filter: (1) data mining based techniques to effectively define the degradation state transition and measurement functions using a one-dimensional health index obtained by whitening transform; (2) an unbiased l-step ahead RUL estimator updated with measurement errors. The feasibility of the presented prognostics method is validated using data from a spiral bevel gear case study.

- by Eric Bechhoefer
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- Mechanical Engineering, Data Mining, Systems Integration, Mathematical Models

Brittleness of materials-whether it occurs naturally or with aging-affects significantly performance and manifests itself in various properties. In the past, brittleness was defined qualitatively, but now a definition of brittleness for viscoelastic materials exists, enabling analysis of all types of polymer-based materials. The quantity brittleness, B, has been evaluated for neat thermoplastics, but here composites and metal alloys are also assessed. The physical significance of brittleness is connected to the dimensional stability of materials. The connections of brittleness to tensile elongation and to fatigue are explored while its relationship to surface propertiesspecifically wear by repetitive scratching-is examined more closely. The economic impact of wear results in monetary loss associated with failure and reduced service life of plastic parts-thus its connection to brittleness finds use across a broad spectrum of industrial applications which utilize plastics for manufacturing, processing, etc. We also demonstrate a correspondence between impact strength (Charpy or Izod) and brittleness of polymers. It is shown that the assumption hardness is equivalent to brittleness is inaccurate; this fact has important implications for interpreting the results of mechanical testing of viscoelastic materials.

- by Witold Brostow
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- Engineering, Materials Science, Economic Impact, Industrial Application

The paper deals with the modelling of riveted joints in aircraft structures with Finite Element Method. Presented works were carried out within Eureka project No. E!3496 called IMPERJA. The goal of the IMPERJA project is to increase the fatigue life of riveted joints, which will lead to an increase of the aircraft service life, a smaller number of inspections and lower operation costs of an aircraft. The project assumed FEM modelling of the operating aircraft 's structure at three different complexity levels, namely considering the complete structure, a structural detail and a single riveted joint. The paper presents analyses of various rivet models and calculations of a structure and a riveted joint. In the first part examples of various models, at global and local level, were presented and usefulness of them was discussed, influence of the following simplification was analysed; • neglection of rivets in a model (elements are jointed continuously) • rivet as a rigid element (MPC) • neglection of contact phenomenon • neglection of secondary bending • neglection of residual stresses after riveting process The basis of the analysis was the asymmetric butt joint model with 14 rivets. The model which took into account secondary bending and contact phenomenon was analysed as well. The method of modelling residual stresses with temperature and thermal coefficient was used. In the second part, the example of analysis of riveted joint was demonstrated for a wing of PZL M28 Skytruck aircraft. It 's is a twin-engine, high-wing, cantilever monoplane of all-metal structure with maximum take-off and landing weight 7500 kg. A submodeling technique was used there. At first, part of the wing model, based on a CAD model, was built. It includes 7 ribs and 6 bulkheads between them. Dimensions of the model eliminate stress perturbation, connected with boundary conditions, in the area near the middle rib. It was a shell model. The boundary conditions were taken on a basis of operation data. Presence of rivets wasn't taken into account. Instead of this, parts were connected continuously (nodes were merged). The Linear model of material was used. The purpose of the part of the wing model was to gain accurate boundary conditions for next model of riveted joint on the middle rib. The behaviour of whole model is correct but stress distribution around rivets is not correct. A shell model of riveted joint was build. A boundary conditions were set on a basis of result from previous analysis. Forces, instead of displacements, were used, as boundary conditions, on account of a large stiffness difference between part models (part of wing and riveted joint model). The nonlinear model of material was used. A contact effect and secondary bending were taken into account. Thanks to that, phenomena around rivets were represented considerably better. Results from this analysis could be used as boundary conditions in a detailed calculation of one or few rivets with solid elements. Such a model was considered as well. The presented method allows to analyse phenomena that appear around a rivet in a real structure, during operation. Analyses were performed with MSC PATRAN, NASTRAN and MARC software.

- by Jerzy Jachimowicz
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- Finite element method, Linear Model, Service Life, Residual Stress

This paper is focused on the estimation of durability and service life of reinforced concrete structures. Assuming that the chloride ion in concrete can be absorbed on tricalcium aluminate, calcium silicate hydrate, and by other constituents of hardened cement paste, hydrated or not, the exact analytical solution of the governing partial differential equation together with its boundary and initial conditions can be obtained through nondimensional parameters and Laplace's transform. When the results of an exact analytical solution using suitable parameters were compared with the results of previous experimental work, the differences were found to be very small. This suggests that the absorption model is of considerable value. The exact analytical solution with the saturation parameter and time and diffusion coefficients under different effective electrical potential could be used to predict both the experimental results and the service life of reinforced concrete structures.

- by HAERYONG JUNG
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- Civil Engineering, Chemistry, Building, PARTIAL DIFFERENTIAL EQUATION

A simulation of the degradation of high-impact polystyrene (HIPS), occurring during service life and mechanical recycling, was performed by multiple processing and thermo-oxidative ageing. All samples were characterized by differential scanning calorimetry (DSC), melt mass-flow rate (MFR) measurements, tensile testing and infrared spectroscopy (FTIR). Multiple processing and thermo-oxidative ageing clearly alter the oxidative stability and the elongation at break of the materials. These changes observed at a macroscopic scale have been related to chemical alterations in the structure of HIPS. The polybutadiene phase was demonstrated to be the initiation point of the degradative processes induced by processing, service life and mechanical recycling. Thermo-oxidative degradation affects more severely the degree of degradation of the material, so it may be deduced that the changes occurring during service life of HIPS are the part of the life cycle that mostly affects its further recycling possibilities and performance in second-market applications.

This review critically discusses the environmental and resource implications for the design of sustainable biocomposites. Sustainable biocomposites should satisfy several requirements: (i) renewable and/or recycled resources should be utilized for their manufacture; (ii) the synthetic, modification, and processing operations should be benign and energy effective; (iii) no hazardous environmental or toxicological effects should arise during any stage of their life cycle; and (iv) their waste management options should be implemented. The future integration of biorefineries and green chemistry will guarantee the availability of a wide range of raw materials for their preparation. The emission of volatile organic compounds and the release of nanoparticles should be evaluated from a toxicological and environmental point of view. Finally, the susceptibility of sustainable biocomposites towards degradation, including abiotic effects (water absorption, thermo-and photo-oxidation) and biofilm formation and biodegradation, must be considered, to guarantee their structural and functional stability during service life, and to ensure their biodegradability and assimilation during composting.

Radiant tubes of an ethane pyrolysis furnace at a petrochemical plant failed after a fraction of service life. The tubes developed longitudinal cracks that in extreme cases penetrated the entire tube thickness. The tubes were manufactured from HP 45 heat-resistant steel casting. Scanning electron microscopy and energy dispersive X-ray spectroscopy were used to characterize the microstructure and chemical composition of the tube \samples. Microhardness testing was used to evaluate the mechanical strength while structural analysis was conducted in an X-ray diffractometer. The experimental results showed that the mode of tube failure was a combination of high temperature carburization attack and creep damage leading to intergranular cracking. The cause of failure was overheating likely during decoking operations. Better control of furnace temperature was recommended in order to avoid overheating. However, if the furnace temperature exceeds 900°C during operation, alloy replacement must be considered. In this case, steel casting material more resistant to carburization and creep damage such as the HP + W grade was suggested as an alternative.

Because of the existence of infrastructures all around the world, the use of fossil resources as raw materials for hydrogen production can be a midterm solution in the implementation of hydrogen as a transport fuel. Therefore, the fuel processing technology used for the production of hydrogen should produce the lowest amount of greenhouse gases, with the highest energy efficiency and the lowest environmental impact. In this work, several options for hydrogen production from fossil fuels are evaluated: steam reforming, autothermal reforming of hydrocarbons, coal gasification, and methane decomposition. A system for the capture of CO 2 is supposed to be integrated in the reforming and gasification processes. This study evaluates the overall life cycle greenhouse gas emissions, the fossil energy consumption, and the environmental impact for the current and future energy scenarios. The autothermal reforming, decomposition of natural gas, and coal gasification are the best options from all of the points of view, while extrapolations to future scenarios predict very similar impacts. The economic analysis of methane decomposition processes reveals that the carbon selling price and the conversion of methane are the main factors influencing the cost-efficiency of produced hydrogen.

- by Antonio González
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- Engineering, Energy, Energy Policy, Decomposition

The latest findings regarding the long-term performance and service life of HDPE geomembrane (GM) samples exposed to air, water and leachate are presented based on data from samples that have been ageing for 8-10 years. Some of the GM samples are in Stage II, some in Stage III and some have completed all three stages of the service life. The paper provides: (1) improved data on antioxidant depletion rates for GMs immersed in air, water and leachate; (2) estimates of antioxidant depletion time (Stage I) at typical liner temperatures in air, water and leachate and, based on this data, an estimate for a composite liner at typical liner temperatures; (3) data regarding the changes in the physical and mechanical properties of the GM samples with time; (4) a surface analysis of virgin and aged GMs; (5) an initial estimate of the induction time (Stage II) and polymer degradation time (Stage III) and service lives of GM in laboratory immersion tests; and (6) predictions of the service life of leachate immersed GM at typical landfill temperatures. Based on these predictions, it appears likely that the service life of the specific GM tested immersed in leachate is likely to exceed 700 years and will probably be of the order of 1000 years (or longer) at 20 C, more than 150 years and likely 225-375 years at 35 C and more than 40 years and likely 50-90 years at 50 C. The service life in a liner configuration may be expected to be longer than predicted here for immersion in leachate.

Powertrain hybridization as well as electrical energy management are imposing new requirements on electrical storage systems in vehicles. This paper characterizes the associated vehicle attributes and, in particular, the various levels of hybrids. New requirements for the electrical storage system are derived, including: shallow-cycle life, high dynamic charge acceptance particularly for regenerative braking and robust service life in sustained partial-state-of-charge usage. Lead/acid, either with liquid or absorptive glass-fibre mat electrolyte, is expected to remain the predominant battery technology for 14 V systems, including micro-hybrids, and with a cost-effective battery monitoring system for demanding applications. Advanced AGM batteries may be considered for mild or even medium hybrids once they have proven robustness under real-world conditions, particularly with respect to cycle life at partial-states-of-charge and dynamic charge acceptance. For the foreseeable future, NiMH and Li-ion are the dominating current and potential battery technologies for higher-functionality HEVs. Li-ion, currently at development and demonstration stages, offers attractive opportunities for improvements in performance and cost. Supercapacitors may be considered for pulse power applications. Aside from cell technologies, attention to the issue of system integration of the battery into the powertrain and vehicle is growing. Opportunities and challenges for potential "battery pack" system suppliers are discussed.

- by Ted Miller
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- Engineering, System Integration, Energy Management, Power

A passive thermal management system is evaluated for high-power Li-ion packs under stressful or abusive conditions, and compared with a purely air-cooling mode under normal and abuse conditions. A compact and properly designed passive thermal management system utilizing phase change material (PCM) provides faster heat dissipation than active cooling during high pulse power discharges while preserving sufficiently uniform cell temperature to ensure the desirable cycle life for the pack. This study investigates how passive cooling with PCM contributes to preventing the propagation of thermal runaway in a single cell or adjacent cells due to a cell catastrophic failure. Its effectiveness is compared with that of active cooling by forced air flow or natural convection using the same compact module and pack configuration corresponding to the PCM matrix technology. The effects of nickel tabs and spacing between the cells were also studied.

- by S. al-Hallaj
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- Engineering, Air flow, Natural Convection, Thermal runaway

The technical performance and energy requirements for production and transportation of a stand alone photovoltaic (PV)-battery system at different operating conditions are presented. Eight battery technologies are evaluated: lithium-ion (Li-ion), sodium-sulphur (NaS), nickel-cadmium (NiCd), nickel-metal hydride (NiMH), lead-acid (PbA), vanadium-redox (VRB), zinc-bromine (ZnBr) and polysulfide-bromide (PSB). In the reference case, the energy requirements for production and transport of PV-battery systems that use the different battery technologies differ by up to a factor of three. Production and transport of batteries contribute 24-70% to the energy requirements, and the PV array contributes 26-68%. The contribution from other system components is less than 10%. The contribution of transport to energy requirements is 1-9% for transportation by truck, but may be up to 73% for air transportation. The energy requirement for battery production and transport is dominant for systems based on NiCd, NiMH and PbA batteries. The energy requirements for these systems are, therefore, sensitive to changes in battery service life and gravimetric energy density. For systems with batteries with relatively low energy requirement for production and transportation (Li-ion, NaS, VRB, ZnBr, PSB), the battery charge-discharge efficiency has a larger impact. In Part II, the data presented here are used to calculate energy payback times and overall battery efficiencies of the PV-battery systems.

not a rigorous social science theory. In this article, I argue just the opposite, and any attempt to speculate on the future direction of mass communication theory must seriously include the uses and gratifications approach. In this article, I assert that the emergence of computer-mediated communication has revived the significance of uses and gratifications. In fact, uses and gratifications has always provided a cutting-edge theoretical approach in the initial stages of each new mass communications medium: newspapers, radio and television, and now the Internet. Although scientists are likely to continue using traditional tools and typologies to answer questions about media use, we must also be prepared to expand our current theoretical models of uses and gratifications. Contemporary and future models must include concepts such as interactivity, demassification, hypertextuality, and asynchroneity. Researchers must also be willing to explore interpersonal and qualitative aspects of mediated communication in a more holistic methodology.

- by Suleiman Ibrahim
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- Service Life

The aim of this study was to revise the factors influencing the service life of galvanic coupling between carbon steel and stainless steel reinforcements in simulated concrete pore solution, simulating the condition of a damaged structure repaired with stainless steel reinforcing bars. Numerous investigations have reported that austenitic stainless steel rebar, compared to carbon steel, when embedded in concrete, offer superior corrosion resistance in aggressive environments, especially chloride contaminated concrete. In concrete, contact with other metals should be avoided because of the risk of galvanic corrosion. When passive, both carbon steel and stainless steel have comparable corrosion potentials and the coupling of the two materials is of little effect on the corrosion behavior of either material. Galvanic current values measured between carbon and stainless steel are negligible.

- by Joel Quiroz
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- Civil Engineering, Stainless Steel, Service Life, Austenitic stainless steel