Acoustically driven mixing of small fluid volumes is reported. Using surface acoustic waves on a mixer chip, conversion of those into bulk waves, and employing wave guiding effects enables us to distribute a set of "virtual sources" for acoustic streaming over large areas. we demonstrate the applicability of our mixing technique to micro array applications, for mixing of individual wells in a micro titer plate, and other state-of-the-art hybridization assays.
The rates of flame spread and minimum oxygen concentrations supporting flame spared over thermally thick fuel beds were determined at earth gravity and microgravity for varying concentrations of a gaseous extinguishing agent (N2, CO2, or He) added to "baseline" O 2-N2 atmospheres. Drop towers were used to obtain microgravity, and foam fuels were employed to obtain sufficiently rapid flame spread in these short-duration facilities. At earth gravity, CO2 was the most effective on a molar basis at reducing spread rate whereas at microgravity, He was the most effective at reducing spread rate and causing flame extinction. These findings are proposed to result from the transition from a high-speed blow off-type limit at earth gravity to a low-speed radiative heat loss-induced limit at microgravity. CO2 is less effective as an extinguishment agent at microgravity because it reabsorbs radiation from flame and reradiates it back to the fuel bed at microgravity, whereas with N2 and He this phenomena is not evident at microgravity because these two gases are radiatively nonparticipating. He is particularly effective at microgravity because its high thermal diffusivity leads to much larger flame thicknesses resulting in much greater volume for radiative heat losses. Radiative effects are unimportant at earth gravity because convective flow is significantly faster, leading to thinner flames with much lower ratios of radiative to conductive/convective heat transfer. These results are particularly noteworthy considering that the International Space Station employs CO2 as fire extinguishers; our results suggest that helium may be a better suppressant agent on both mass and mole bases at microgravity even though CO2 is much better on a mole basis at earth gravity.
A methodology is shown for predicting the time-dependent reliability of ceramic components against catastrophic rupture when subjected to transient thermomechanical loads (including cyclic loads). The methodology takes into account the changes in material response that can occur with temperature or time (i.e., changing fatigue and Weibull parameters with temperature or time). This capability has been added to the NASA CARES/Life (Ceramic Analysis and Reliability Evaluation of Structures/Life) code. The code has been modified to have the ability to interface with commercially available finite element analysis (FEA) codes executed for transient load histories. Examples are provided to demonstrate the features of the methodology as implemented in the CARES/Life program.
The effect of individual engine component life distributions on engine life prediction was determined. A Weibull-based life and reliability analysis of the NASA Energy Efficient Engine was conducted. The engine s life at a 95 and 99.9 percent probability of survival was determined based upon the engine manufacturer s original life calculations and assumed values of each of the component s cumulative life distributions as represented by a Weibull slope. The lives of the high-pressure turbine (HPT) disks and blades were also evaluated individually and as a system in a similar manner. Knowing the statistical cumulative distribution of each engine component with reasonable engineering certainty is a condition precedent to predicting the life and reliability of an entire engine. The life of a system at a given reliability will be less than the lowest-lived component in the system at the same reliability (probability of survival). Where Weibull slopes of all the engine components are equal, the Weibull slope had a minimal effect on engine L(sub 0.1) life prediction. However, at a probability of survival of 95 percent (L(sub 5) life), life decreased with increasing Weibull slope.
Fatigue crack growth rate testing is performed by automated data collection systems that assume straight crack growth in the plane of symmetry and use standard polynomial solutions to compute crack length and stress-intensity factors from compliance or potential drop measurements. Visual measurements used to correct the collected data typically include only the horizontal crack length, which for cracks that propagate out-of-plane, under-estimates the crack growth rates and over-estimates the stress-intensity factors. The authors have devised an approach for correcting both the crack growth rates and stress-intensity factors based on two-dimensional mixed mode-I/II finite element analysis (FEA). The approach is used to correct out-of-plane data for 7050-T7451 and 2025-T6 aluminum alloys. Results indicate the correction process works well for high DeltaK levels but fails to capture the mixed-mode effects at DeltaK levels approaching threshold (da/dN approximately 10(exp -10) meter/cycle).
As part of an multi-laboratory study on accelerated concrete microbar test for alkali-carbonate reaction, the effect of a number of variables on expansion were evaluated, including the effect of alkali content of the cement, the type and source of alkali, the aggregate particle size, and the bar size. The expansivities of various dolomitic limestones from different origins were evaluated in the concrete prism test and in the accelerated concrete microbar test. The effect of replacement of a portion of the portland cement with fly ash on the expansion of microbars containing selected dolomitic limestones and a typical alkalisilica reactive aggregate were also evaluated. The paper presents the obtained results and the correlation between expansions in the concrete prism test and the accelerated test.
For the time being, the concrete prism test (CPT) CSAA23.2-14A or ASTM C1293 remains the most reliable test method to evaluate the effectiveness of lithium nitrate against alkali-silica reaction (ASR) in concrete; however, the extended testing period of two years has often limited its acceptance by practitioners. In its actual form, the popular accelerated mortar bar test (AMBT) CSA A23.2-25A or ASTM C1260 cannot be used to predict this effectiveness, thus it needs to be modified accordingly. Part I of this study looked at the influence of a number of parameters on the effectiveness of lithium to control expansion of mortar bars incorporating a variety of reactive aggregates from Canada and the United States. The second part of this study (Part II) compares the results obtained in modified versions of the AMBT with those from the CPT performed on the same aggregates, with the objective of proposing the best accelerated test procedure for determining the minimum amount of lithium nitrate necessary to counteract ASR expansion in concrete. The results obtained in this study have shown that the effectiveness of lithium nitrate greatly varies from one reactive aggregate to another while not being correlated with the degree of reactivity or the pétrographie nature of the reactive aggregates to counteract. A safe method of predicting the effective [Li]/[Na+K] to used in concrete is proposed which uses two AMBTs, one of which involves adding lithium to both the mortar bar and the soak solution. It allows the prediction of an effective [Li]/[Na+K] for aggregates that respond relatively well to lithium. The method allows the identification of aggregates that respond particularly badly to the lithium, for which the concrete prism test Is recommended for evaluating the minimum lithium dosage to use for ASR control.
For the time being, the only reliable test method to evaluate the effectiveness of lithium nitrate against alkali-silica reaction (ASR) in concrete is the concrete prism test (CPT) CSAA23.2-14A or ASTM C1293, extended to two years. In its actual form, the more commonly used accelerated mortar bar test (AMBT) CSA A23.2-25A or ASTM C1260 Is not able to predict this effectiveness and needs to be modified to improve it's reliability. Part I of this study, which involves a large variety of reactive aggregates from Canada and the United States, aims to evaluate the partition of various ions (OH -, Na+, K+, Li+, and silica species) between the mortar pore solution and the soak solution in the AMBT, and the effect of a number of experimental parameters on the expansion of mortar bars with/without lithium nitrate, e.g., the presence of lithium in the original mortar bars, the Li concentration in the soak solution, the concentration and the composition (NaOH versus KOH) of the soak solution, the cement alkali content, the water-to-cement ratio, and the initial 24-h soaking in pure water. The second part of this study (Part II) compares the above AMBT results with the CPT results for the same aggregates and aims to propose modifications to the AMBT when testing lithium nitrate against ASR to better correlate with the most realistic CPT results.
This project examined the wind uplift performance of adhesive applied roofing systems. Testing was done on eight mockups with steel decks, polyisocyanurate insulation, cover boards and membranes, and adhesives that varied in terms of type, quantity and application method. The mockups were subjected to both static and dynamic wind loading conditions. The test results were used to develop a numerical model and a wind design guide and standard for adhesive applied roofing systems. Dans le cadre de ce projet, on a étudié la performance en termes de résistance à l'arrachement sous l'action du vent des couvertures appliquées par adhésif. Des essais ont été réalisés sur huit (8) maquettes avec platelage en tôle, panneau isolant en polyisocyanurate, garnissage en bois et membrane, ainsi qu'avec de l'adhésif, dont les type, quantité et méthode d'application variaient. Ces maquettes ont été soumises à des conditions de charge due au vent tant statiques que dynamiques. Les résultats des essais ont servi au développement d'un modèle numérique, d'un guide de calcul des charges dues au vent pour fin de conception et d'une norme couvrant les toitures appliquées par adhésif. RES
Adiabatic compression testing of components in gaseous oxygen is a test method that is utilized worldwide and is commonly required to qualify a component for ignition tolerance under its intended service. This testing is required by many industry standards organizations
and government agencies; however, a thorough evaluation of the test parameters and test system influences on the thermal energy produced during the test has not yet been performed. This paper presents a background for adiabatic compression testing and discusses an approach to estimating potential differences in the thermal profiles produced by different test laboratories. A “Thermal Profile Test Fixture” (TPTF) is described that is capable of measuring and characterizing the thermal energy for a typical pressure shock by any test system. The test systems at Wendell Hull & Associates, Inc. (WHA) in the USA and at the BAM Federal Institute for Materials Research and Testing in Germany are compared in this manner and some of the data obtained is presented. The paper also introduces a new way of comparing the test method to idealized processes to perform system-by-system comparisons. Thus, the paper
introduces an “Idealized Severity Index” (ISI) of the thermal energy to characterize a rapid pressure surge. From the TPTF data a “Test Severity Index” (TSI) can also be calculated so that the thermal energies developed by different test systems can be compared to each other
and to the ISI for the equivalent isentropic process. Finally, a “Service Severity Index” (SSI) is introduced to characterizing the thermal energy of actual service conditions. This paper is the second in a series of publications planned on the subject of adiabatic compression testing.
Adiabatic compression testing of components in gaseous oxygen is a test method that is utilized worldwide and is commonly required to qualify a component for ignition tolerance under its intended service. This testing is required by many industry standards organizations and government agencies. This paper traces the background of adiabatic compression testing in the oxygen community and discusses the thermodynamic and fluid dynamic processes that occur during rapid pressure surges. This paper is the first of several papers by the authors on the subject of adiabatic compression testing and is presented as a non-comprehensive background and introduction.
Investigations of spectrum adjustment by unfolding techniques for different locations of critical and driven subcritical MUSE4 configurations are presented. The current analysis is based on the recent accomplishment of specific foil activation measurements and on the use of the unfolding code STAY'SL in conjunction with IRDF-90 and IRDF-2002 dosimetry libraries. Specific developments have been conducted to consider the uncertainties associated with the determination of the experimental absolute reaction rates and the initial calculated spectrum in the most realistic manner. In this context, the iterative adjustment process for the neutron spectrum is established on the basis of variance/covariance matrices defined for the three types of input parameters, i.e., the experimental reaction rates, the initial spectrum, and the dosimetry nuclear data files. The results highlight the spectral variations between different locations of the MUSE4 cores, in particular the characteristic behavior of a subcritical configuration driven by an external T(d,n)He 4 (14 MeV neutrons) source. Copyright 2006 by ASTM International.
One of the key factors for obtaining reliable instrumented Charpy results is the calibration of the instrumented striker. An interesting alternative to the conventional static calibration recommended by the standards is the dynamic force adjustment (DFA), in which forces and displacements are iteratively adjusted until equality is achieved between absorbed energies calculated under the test record (Wt) and measured by the machine encoder (KV). In this study, the procedure has been applied to the instrumented data obtained by ten international laboratories using notched and precracked Charpy specimens, in the framework of a Coordinated Research Project (CRP8) of the International Atomic Energy Agency (IAEA). DFA is extremely effective in reducing the between-laboratory scatter for both general yield and maximum forces. The effect is less significant for dynamic reference temperatures measured from precracked Charpy specimens using the Master Curve procedure, but a moderate reduction of the standard deviation is, however, observed. It is shown that striker calibration is a prominent contribution to the interlaboratory variability of instrumented impact forces, particularly in the case of maximum forces.
Several herbicides reduce, directly or indirectly, the efficiency of photosynthesis of plants. As a consequence, the fluorescence of the chlorophyll increases. The relative increase of fluorescence [(Fm-F0)/Fm] can be used to compare the influence of formulations and adjuvants on the activity of herbicides. This procedure allows the accurate and non-destructive screening of sprayed plants in the first minutes and hours after treatment. A new development is the automated imaging and quantification of the relative increase of fluorescence at the whole plant level. Use of a robot-arm enables a laser-camera to take pictures of the chlorophyll fluorescence of different plants with short time intervals between plants. This procedure makes it possible to screen hundreds of plants simultaneously. Individual pictures can be used, or pictures can be used to compose a video demonstrating the dynamics of the herbicide action. The potency of this technology for monitoring bentazon, glufosinate and glyphosate action is demonstrated. In addition to investigating the influence of formulations and adjuvants on herbicide activity, the fluorescence imaging technology can be used to monitor phytotoxicity of formulations and spray application parameters like water volume and drop size
luorescence can be used to measure and visualize the activity of herbicides that inhibit the photosynthesis. Glyphosate, although not acting primarily on the photosystems, appears to increase fluorescence of plants. We investigated whether fluorescence technology is a useful tool to both quantify and image of the performance of different adjuvants for glyphosate. A red laser beam providing equipment is used to scan black nightshade plants at a low and high light intensity. A cooled, integrating 16 bit CCD camera is used to record the fluorescence during the low level (Fo) and high level scan (Fm). The relative increase of fluorescence expressed as [(Fm¿Fo)/Fm] 100 % is calculated and color images are produced. Glyphosate was applied at two suboptimal application rates of 16.9 and 33.8 g ae/ha at 200 L/ha. Both the influence of glyphosate rate and the influence of added adjuvants were obvious. The fluorescence data 30 h after treatment demonstrated that the adjuvants HM9121-A and HM9110 performed better than AMS, HM9541-A, HM9910, or HM2005-B. This observation was consistent over the next three observations (54, 78, and 102 h). The fluorescence data after 72 h correlated (R2=0.82; logarithmic regression) with the fresh weight reduction caused by the glyphosate treatments. The adjuvants HM 9121-A and HM9110 performed the best and the adjuvant HM9541-A had little effect on glyphosate performance. Both imaging and fresh weight data indicate that HM 9121-A performs somewhat better than HM9110.
The “classical” regulatory approach to the analysis of surveillance capsules in nuclear power plants entails an indirect estimate of the fracture toughness of the beltline materials, by inferring rather than measuring their toughness properties. Indeed, the irradiation-induced shift of the fracture toughness curve is assumed to be equal to the shift of the Charpy absorbed energy transition curve at a predefined level (41 J). An alternative surveillance approach, primarily based on direct fracture toughness measurements in the ductile-to-brittle transition region using the Master Curve procedure, has been applied to surveillance materials from several Belgian nuclear power plants in the past 15 years. This has led to the establishment of a significant database, consisting of 292 fracture toughness data points for 23 material conditions (unirradiated materials and surveillance capsules). In this study, different temperature normalization approaches are applied to the available data. The analyses show that data clearly follow the Master Curve formalism. Moreover, it is confirmed that both the static (KIc) and the dynamic (KIR) curves of the ASME Code Section XI provide an effective lower bound to the measured results, although more conservatism is evident when using RTNDT as the normalization parameter.
The so-called EURO data set is the largest set ever assembled, consisting of fracture toughness results obtained in the ductile-to-brittle transition region. It was the outcome of a large project, sponsored by the European Union, which involved ten European laboratories in the second half of the 1990s. Several post-project investigations have identified one of the blocks from which specimens were extracted (block SX9) as macroscopically inhomogeneous and significantly tougher than the remaining blocks. In this paper, the variability of block SX9 has been investigated using the conventional master curve (MC) methodology and some recent MC extensions, namely, the SINTAP (structural integrity assessment procedure) lower tail, the single point estimation, the bi-modal MC, and the multi-modal MC. The basic MC method is intended for macroscopically homogeneous ferritic steels only, and the alternative approaches have been developed for the investigation of inhomogeneous materials. Therefore, these methods can be used to study the behavior of block SX9 within the EURO data set. It has been found that the bi-modal and multi-modal MC approaches are quite effective in detecting the “anomaly” represented by block SX9 but only when analyses are performed on data sets of comparable size.
To ensure te ongoing safe operation of the Royal Australian Air Force (RAAF) P-3 Orion life-support oxygen system, a system review was completed that included a failure modes and effects analysis combined with an oxygen hazards and fire risk analysis. Though the RAAF P-3 Orion oxygen system has been operational for many years, the results of these analyses clearly identified many deficiencies in the current system configuration, thus demonstrating the value of the formal analysis approach. Design, procedural, maintenance, and material issues were all identified and addressed in the course of this process. This paper provides a brief summary of the analyses performed, the results obtained, risk tables generated, and their use leading to the recommendations for changes incorporated onto RAAF P-3 Orion aircraft that resulted from this work.
Although residual stress In welded structures and components has long been known to have an effect on their fatigue performance, access to reliable, spatially accurate residual stress field data has been limited. Recent advances in neutron and synchrotron X-ray diffraction allow a far more detailed picture of weld residual stress fields to be obtained that permits the development and use of predictive models that can be used for accurate design against fatigue in aircraft structures. This paper describes a fully integrated study of the three-dimensional residual stress distribution accompanying state-of-the-art fusion welds in 2024-T4 aluminum alloy, and how it is affected by subsequent machining and service loading. A particular feature of this work has been the development of techniques allowing the nondestructive evaluation of the residual stress field in the full range of specimens used to provide the design data required for welded aircraft structures and the integration of this information into all aspects of damage tolerant design.
This paper provides a review of the factors that affect joint sealant performance for airport aprons, taxiways, and parking areas for Portland cement concrete paving, defines the key elements of the specification, and highlights the benefits of a performance based specification for the selection of durable joint sealants for airports. It addresses the issue of premature failure and requirements for extending joint sealant service life.. Ce document examine les facteurs qui influent sur la performance des scellants pour joints des aires de trafic, des voies de circulation et des aires de stationnement des aéroports, pour les bétonnages en ciment Portland, définit les éléments clés de la norme, et met en lumière les avantages d'une norme axée sur la performance relativement au choix de scellants pour joints durables pour les aéroports. On y aborde la question de la défaillance prématurée des joints de scellant et des exigences visant la prolongation de leur durée de vie. RES
High-Cr ferritic/martensitic steels are being considered as structural materials for a large number of future nuclear applications, from fusion to accelerator-driven systems and GenIV reactors. Fe-Cr alloys can be used as model materials to investigate some of the mechanisms governing their microstructure evolution under irradiation and its correlation to changes in their macroscopic properties. Focusing on these alloys, we show an example of how the integration of computer simulation and theoretical models can provide keys for the interpretation of a host of relevant experimental observations. In particular we show that proper accounting for two basic features of these alloys, namely, the existence of a fairly strong attractive interaction between self-interstitials and Cr atoms and of a mixing enthalpy that changes sign from negative to positive around 8 to 10 % Cr, is a necessary and, to a certain extent, sufficient condition to rationalize and understand their behavior under irradiation. These features have been revealed by ab initio calculations, are supported by experimental evidence, and have been adequately transferred into advanced empirical interatomic potentials, which have been and are being used for the simulation of damage production, defect behavior, and phase transformation in these alloys. The results of the simulations have been and are being used to parameterize models capable of extending the description of radiation effects to scales beyond the reach of molecular dynamics. The present paper intends to highlight the most important achievements and results of this research activity.
Promoted-ignition testing of 3.2 mm diameter aluminum rods in high purity oxygen was
performed. The rod and detached drops of both self-extinguished and water quenched samples were examined using scanning electron microscopy and electron probe microanalysis to analyze the physical structure of the sample and gather compositional data. A comparison of the micrographs of self-extinguished and quenched samples reveals clear differences in the extent of melted and re-solidified (unreacted) material and the thickness of the oxide layer, highlighting the effect of cooling rate on the burning system. A qualitative physical model for the burning of bulk aluminum in gaseous oxygen is presented. The model, incorporating a molten drop growth and detachment cycle, is based on an initial heterogeneous burning phase leading to a second phase of combined heterogeneous and homogeneous burning.
No Hydration of five Roman and American natural cements was analyzed using X-ray diffraction, mercury intrusion porosimetry, and scanning electron microscopy of cement pastes. Two cements were prepared in the laboratory by burning marls from geological sources in Poland (Folwark) and Austria (Lilienfeld). The selection of raw materials and burning conditions were optimized so that the hydraulic nature and appearance of the final burnt materials matched as closely as possible historic Roman cements widely used in the 19th and the beginning of the 20th centuries in Europe to decorate buildings. Three other cements are produced commercially: quick setting Prompt cement from Vicat, France, and Rosendale cements from Edison Coatings Inc., USA. The hydration of the cements studied was shown to comprise two distinct stages. The immediate setting and early strength is due to the formation of calcium aluminum oxide carbonate (or sulfate) hydroxide hydrates. The development of long-term strength is brought about by the formation of calcium silicate hydrates. Similarities and differences between the individual cements are discussed.
This paper investigates the role of the vapor barrier in exterior wood-frame stucco walls with the help of a two-dimensional hygrothermal simulation tool, hyglRC-2D. For this purpose, the wall is subjected to the exterior weather conditions of six different North American geographic locations and three different interior climatic conditions. Seven different vapor diffusion strategies, generated by varying the water vapor permeance of the vapor barrier, installed outboard of the interior finish, have been studied to generate critical understanding on the role of vapor barrier in the wood-frame stucco walls. The outputs from the simulations have been analyzed with the help of a novel moisture response indicator called RHT index. Simulation results indicate that the vapor transmission characteristics of the vapor barrier, in terms of water vapor permeance, play a very important role in the overall moisture response of the wood-frame stucco wall. A very high or low vapor permeance of the vapor barrier does not produce the optimum moisture management strategy for the wood-frame stucco wall. Moreover, simulation results indicate that the removal of vapor barrier from the wall system can result in a heightened moisture response and a considerable accumulation of moisture in the interior gypsum board that may lead to severe consequences in particular, the premature deterioration of the interior facing gypsum board. It has also been observed from the simulation outputs that the optimum vapor diffusion strategy, that of limiting the vapor permeance of the vapor barrier, is not a function of interior climatic conditions considered in this study. It is hoped that the results reported In this paper will shed some light on a number of concerns raised In recent years on the role of vapor barrier in wood-frame stucco wall construction.
The Charpy test plays a fundamental role in the nuclear field for evaluating the neutron embrittlement of the reactor pressure vessel, specifically in the framework of the so-called Enhanced Surveillance Approach, developed at SCK•CEN and aimed at extracting as much information as possible from Charpy impact tests performed with an instrumented striker. Careful analysis of the instrumented force/deflection traces allows defining important parameters which can help investigating material characteristics such as flow properties, microcleavage fracture stress, crack arrest behaviour and alternative characteristic (index) temperatures. For this advanced approach to be successfully applied, confidence on the quality of instrumented force values must be high; as a consequence, extensive research has been performed in order to establish an optimal procedure for the verification of instrumented Charpy strikers. Various approaches will be described in this paper and their applicability and effectiveness discussed. A procedure based on the comparison between yield stresses measured from tensile tests and calculated from instrumented Charpy curves has recently been adopted at SCK•CEN as the recommended in-house procedure for verifying instrumented strikers. This method has shown that for all strikers investigated, the so-called “dynamic” calibration (based on the equalization of dial and calculated energies) yields the most accurate results.
Crack arrest is an important concept that can be useful to guarantee the safety of reactor pressure vessels. In case of a pressurized thermal shock, a postulated crack can initiate and arrest due to a decrease in driving force combined with an increase in material toughness due to the thermal and neutron embrittlement gradient along the thickness. Due to the size of the specimen and the difficulty in obtaining valid results according to the ASTM E1221-06 standard, “Standard Test Method for Determining Plane-Strain Crack-Arrest Fracture Toughness, KIa, of Ferritic Steels,” current efforts to develop this technique for irradiated materials are very limited. However, advances in dynamic fracture modeling and elastic-plastic fracture mechanics open the possibility of using miniature crack arrest specimens. We have developed a stiff setup to perform crack arrest tests on precracked Charpy PCCv specimens. Different strategies were evaluated to provide enough reduction in driving force to produce arrest. Special attention is given to the starter notch and different starter notch preparations are investigated: precracking, chevron, and brittle weld. Testing configurations were found that guarantee crack arrest with sufficient remaining ligament.
For fracture toughness tests in the ductile-to-brittle transition region, ASTM E1921-05 requires specimens to be loaded using a loading rate dK/dt between 0.1 and 2 MPaVm/s during the initial elastic portion. It has been proposed that the standard allow testing at higher loading rates, including precracked Charpy specimens tested on an instrumented pendulum machine (impact toughness tests). The revised standard would require test results (KJc or To) to be reported along with the relevant loading rate, and should therefore provide guidance on how to assess the value of dK/dt in a relatively simple but reliable manner. Various options for measuring the loading rate have been investigated in this paper for several fracture toughness tests performed at different loading rates (quasi-static, dynamic, and impact). For each loading rate, three different toughness levels have been considered: low, medium, and high. Three considerably different materials have been selected: two RPV steels (JRQ, JSPS) and a ferritic/martensitic 9 % chromium steel (EUROFER97). It is found that the preferable option is given by the ratio between KJc and time at the onset of cleavage, whereas the elastic value Kel/tel or the average dK/dt can be used whenpartial unloadings are performed.
The detailing of wall-window interfaces and the consequences of defective installation of windows are an on-going concern in North America. This paper concerns laboratory evaluation of the water leakage performance of a select set of window-wall interface details. The details were for windows with mounting flanges installed in wood-frame walls sheathed with rigid extruded polystyrene foam. The tests were performed on a single full-scale test assembly in which two identical windows were installed by two similar but nonetheless different means. Each detail included a sill pan intended to collect water that gained entry into the assembly and thus was designed to be robust (tolerant of flaws). Tests were performed over a series of different water loading (spray) rates and over a series of different air pressure differentials at each spray rate. Air leakage rates through the window opening were monitored; they were controlled by a unique methodology. Leakage paths were introduced in the window frames, and these paths were alternatively blocked or opened to permit evaluation of the performance of the installation details under two different assumed conditions of window leakage. Air pressure distribution within the assemblies was monitored during spray testing. The wall assembly was designed to permit observation of water entry in it and to allow measurement of water entry to, or drainage from, various locations within the assembly. Results on water entry and management for the two wall-window interface configurations are given, and effectiveness of the details is discussed.
When assessing a wall assembly's ability to manage rainwater and control rain penetration, the two key climatic elements to consider are wind speed and rainfall intensity. However, of significance to rain penetration is the effect of wind-driven rain on the building cladding - that is wind coincident with rainfall. When water is present at openings in the cladding, water is driven into the layers of the assembly by the action of wind. Paths providing a direct line from openings in the cladding to inside the assembly offer particularly vulnerable points for water entry. Performance testing helps determine the location of vulnerable locations in a wall assembly and the test loads at which penetration occurs, and it possibly relates the amount of entry to specific details and simulated climate effects. Undertaking watertightness performance tests requires knowledge of extremes in wind-driven rain or specifically the occurrence and level of extreme rainfall events for locations of interest. A review of climate information on wind-driven rain is provided, and its relevance to assessing the watertightness performance of walls, windows, and wall-window interfaces is discussed. Values of rainfall intensity, duration, and frequency or occurrence are given, emphasizing the level of significance of these variables to different North American climates.
The residual stress distributions for plate T butt welds were determined from a detailed finite element analysis of the welding process and they were compared with those of the measured data for validation. The residual stress distributions from the analyses and measurements were shown to be in similar shape. The distributions were found to be below the master curve for the residual stresses that were previously determined from a statistical analysis for a range of weld geometries and materials. A failure assessment for the T butt weld with cracks under residual stress distributions has been carried out. The conservatism in the current life assessment procedures regarding the residual stresses were quantified based on the stress intensity factor SIF calculations for the T butt weld. It was shown that the master curve profile provides more realistic values for the SIFs with reasonable conservatism than the profiles recommended in the existing assessment procedures
Fracture toughness testing on standard specimens in the ductile to brittle transition regime is well established and standardized by the ASTM since 1997. However, its applicability to structural components and its potential conservatism remain a subject of concern. In structural integrity assessment of reactor pressure vessels submitted to an accidental loading condition called pressurized thermal shock, the cladding is generally considered not to play any role and is neglected. However, cladding has the ability to restrain the crack from opening due to its good ductility. To investigate the potential safety margin, a semielliptical crack introduced by fatigue is covered by a stainless steel cladding and specimens are tested under biaxial conditions in the ductile to brittle transition regime. Test results shows that cladding plays a significant role and contributes to an additional safety margin. In addition, cladding increases the potential for crack arrest.
The research focused on three engineering properties: (1) dimensional stability, (2) thermal resistance, and (3) compressive strength. Preliminary results from this study reveal many unknown phenomena, particularly regarding the dimensional stability and compressive strength of ISO boards. Ce document présente les résultats expérimentaux d'un projet pilote de recherche ayant pour but l'évaluation critique des exigences de la norme ASTM C 1289-02 liées aux panneaux d'isolation en polyisocyanurate alvéolaire rigides et revêtus qui sont couramment utilisés pour l'isolation thermique dans les toitures-terrasses plates. Cette recherche vise trois (3) propriétés d'ingénierie : 1) la stabilité dimensionnelle; 2) la résistance thermique; et 3 ) la résistance à la compression. Les résultats préliminaires de cette étude révèlent de nombreux phénomènes inconnus, plus particulièrement en ce qui concerne la stabilité dimensionnelle et la résistance à la compression de ces types de panneaux . RES
Broken Charpy specimens from the surveillance program of a Belgian nuclear power plant are used to obtain the fracture toughness in the transition regime using the master curve concept. Two approaches are used. The first one is based on the reconstitution of Charpy specimens that are subsequently precracked and tested in three-point bending. The second approach is an innovative one that makes use of miniature Compact Tension specimens, which are machined from the broken pieces of the original Charpy specimens. Both approaches lead to consistent results. The recently developed miniature Compact Tension design has the advantage to use less material and is less costly in terms of machining operation. For the material investigated in this research, the current regulation, based on a semi-empirical approach to obtain the lower bound fracture toughness, is demonstrated to be conservative as compared to the direct fracture toughness determination.
The ability of a wall assembly to manage rainwater and control rain penetration depends on the assembly configuration, including interface details for penetrations, and on the rain loads to which the wall is subjected. There are a variety different protocols for evaluating the ability wall systems to resist water intrusion. Generally they involve spraying varying amounts of water while maintaining a pressure difference across the specimen. Across the conterminous United States hourly weather data for extended periods (climatic data) is available for many locations. From this climatic data estimates of wind-driven rain loads can be determined. We answer the question of how often these combinations of rainfall intensities and pressure are likely to present a problem with respect to moisture management of the assembly and how often these are likely to occur over the expected life of the wall assembly. Climate information related to rainfall and wind-driven rain for Boston, Miami, Minneapolis, Philadelphia, and Seattle are provided. A methodology for generating rates of water spray impinging on and pressure differences acting across the wall assembly is also developed. Although the methodology was primarily developed to select the proper testing criteria and test conditions to mimic real events, it can also be used by designers and practitioners to: (i) determine the response of the wall assembly to the effects of wind-driven rain; (ii) estimate design loads below which adverse effects on the assembly are minimized; (iii) assess the likelihood and degree of dam-age to the assembly when design loads are exceeded; (iv) estimate the long-term performance of the wall assembly based on watertightness and moisture management the wall assembly.
Promoted-ignition testing on carbon steel rods of varying cross-sectional area and shape was performed in high pressure oxygen to assess the effect of sample geometry on the regression rate of the melting interface. Cylindrical and rectangular geometries and three different cross sections were tested and the regression rates of the cylinders were compared to the regression rates of the rectangular samples at test pressures around 6.9 MPa. Tests were recorded and video analysis used to determine the regression rate of the melting interface by a new method based on a drop cycle which was found to provide a good basis for statistical analysis and provide excellent agreement to the standard averaging methods used. Both geometries tested showed the typical trend of decreasing regression rate of the melting interface with increasing cross-sectional area; however, it was shown that the effect of geometry is more significant as the sample's cross sections become larger. Discussion is provided regarding the use of 3.2-mm square rods rather than 3.2-mm cylindrical rods within the standard ASTM test and any effect this may have on the observed regression rate of the melting interface.
This paper presents a proposed qualitative framework to discuss the heterogeneous burning of metallic materials, through parameters and factors that influence the melting rate of the solid metallic fuel (either in a standard test or in service). During burning, the melting rate is related to the burning rate and is therefore an important parameter for describing and understanding the burning process, especially since the melting rate is commonly recorded during standard flammability testing for metallic materials and is incorporated into many relative flammability ranking schemes. However, whilst the factors that influence melting rate (such as oxygen pressure or specimen diameter) have been well characterized, there is a need for an improved understanding of how these parameters interact as part of
the overall melting and burning of the system. Proposed here is the ‘Melting Rate Triangle’, which aims to provide this focus through a conceptual framework for understanding how the melting rate (of solid fuel) is determined and regulated during heterogeneous burning. In the paper, the proposed conceptual model is shown to be both (a) consistent with known trends and previously observed results, and (b)capable of being expanded to incorporate new data. Also shown are examples of how the Melting Rate
Triangle can improve the interpretation of flammability test results. Slusser and Miller previously published an ‘Extended Fire Triangle’ as a useful conceptual model of ignition and the factors affecting ignition, providing industry with a framework for discussion. In this paper it is shown that a ‘Melting Rate Triangle’ provides a similar qualitative framework for burning, leading to an improved
understanding of the factors affecting fire propagation and extinguishment.
This paper presents the findings of an investigation into the rate-limiting mechanism for the heterogeneous burning in oxygen under normal gravity and microgravity of cylindrical iron rods. The original objective of the work was to determine why the observed melting rate for burning 3.2-mm diameter iron rods is significantly higher in microgravity than in normal gravity. This work, however,
also provided fundamental insight into the rate-limiting mechanism for heterogeneous burning. The paper includes a summary of normal-gravity and microgravity experimental results, heat transfer analysis and post-test microanalysis of quenched samples. These results are then used to show that heat transfer across the solid/liquid interface is the rate-limiting mechanism for melting and burning, limited by the interfacial surface area between the molten drop and solid rod. In normal gravity, the work improves the
understanding of trends reported during standard flammability testing for metallic materials, such as
variations in melting rates between test specimens with the same cross-sectional area but different crosssectional
shape. The work also provides insight into the effects of configuration and orientation, leading to an improved application of standard test results in the design of oxygen system components. For microgravity applications, the work enables the development of improved methods for lower cost metallic material flammability testing programs. In these ways, the work provides fundamental insight
into the heterogeneous burning process and contributes to improved fire safety for oxygen systems in applications involving both normal-gravity and microgravity environments.
The effect of sample geometry on the melting rates of burning iron rods was assessed. Promoted-ignition tests were conducted with rods having cylindrical, rectangular, and triangular crosssectional shapes over a range of cross-sectional areas. The regression rate of the melting interface (RRMI) was assessed using a statistical approach which enabled the quantification of confidence levels for the observed differences in RRMI. Statistically significant differences in RRMI were observed for rods with the same cross-sectional area but different cross-sectional shape. The magnitude of the proportional difference in RRMI increased with the cross-sectional area. Triangular rods had the highest RRMI, followed by rectangular rods, and then cylindrical rods. The dependence of RRMI on rod shape is shown to relate to the action of molten metal at corners. The corners of the rectangular and triangular rods melted faster than the faces due to their locally higher surface area to volume ratios. This phenomenon altered the attachment geometry between liquid and solid phases, increasing the surface area available for heat transfer, causing faster melting. Findings relating to the application of standard flammability test results in industrial situations are also presented.
no Marls were identified from a range of European sources and assessed for their Cementation Index, as proposed by Eckel. Two were selected for calcination in a laboratory kiln; one from Folwark in Poland (CI 1.75) and one from Lillienfeld in Austria (CI 2.03). Analysis of historical documents, while not revealing precise kiln conditions, does suggest that they were such as not to yield complete decarbonation of the calcite. Consequently, a series of calcinations was undertaken in which the peak temperature control of the kiln was set in the range 730°C to 1100°C, with residence times in the range 150 to 1250 min. The airflow through the kiln was sufficient to maintain a minimum oxygen content of at least 12 %. The resulting clinker was ground to comply with the 19th century Austrian Norme. Pastes were produced at w/c = 0.65 and assessed for setting time and strength development (6 h to 1 year). Both parameters were highly dependent upon calcination conditions with both “low” and “high” calcinations producing slower setting and slower strength development than intermediate conditions. Two strength development profiles were identified; one being the expected continuous increase of strength, albeit with a declining rate of increase with time, while the other showed a three-step sequence of high initial strength, a dormant period which could last for many weeks and a final increase in strength to an age of one year. The cements were compared using X-ray diffraction (XRD). Considerable variation in the composition was noted and related to the calcination conditions. Of particular interest is the formation of both α'-belite and β-belite under differing calcination conditions. Clinker particles were also compared using the SEM in back-scattered electron imaging mode and the development of morphology observed.
To investigate the feasibility of the production of sub-size Charpy reference test pieces, tests were performed on sub-size samples (3 × 4 × 27 mm³) carefully machined from full-size (10 × 10 × 55 mm³) Charpy V-notch certified reference test pieces. The measured absorbed energy (KV) values indicate a highly satisfactory homogeneity of the sub-size specimens. Sub-size specimens were prepared from full-size reference test pieces of 30, 60, 80, 120, and 150 J nominal absorbed energy; and values between 2 J and 7.2 J were obtained, covering almost fully the range of interest for sub-size Charpy tests. A linear relationship is observed between the KV values of sub-size and full-size samples of the same material.
All relevant international standards for determining if a metallic rod is flammable in oxygen utilize some form of “promoted ignition” test. In this test, for a given pressure, an overwhelming ignition source is coupled to the end of the test sample and the designation flammable or nonflammable is based upon the amount burned, that is, a burn criteria. It is documented that (1) the initial temperature of the test sample affects the burning of the test sample both (a) in regards to the pressure at which the sample will support burning (threshold pressure) and (b) the rate at which the sample is melted (regression rate of the melting interface); and, (2) the igniter used affects the test sample by heating it adjacent to the igniter as ignition occurs. Together, these facts make it necessary to ensure, if a metallic material is to be considered flammable at the conditions tested, that the burn criteria will exclude any region of the test sample that may have undergone preheating during the ignition process. A two-dimensional theoretical model was developed to describe the transient heat transfer occurring and resultant temperatures produced within this system. Several metals (copper, aluminum, iron, and stainless steel) and ignition promoters (magnesium, aluminum, and Pyrofuze®) were evaluated for a range of oxygen pressures between 0.69 MPa (100 psia) and 34.5 MPa (5,000 psia). A MATLAB® program was utilized to solve the developed model that was validated against (1) a published solution for a similar system and (2) against experimental data obtained
during actual tests at the National Aeronautics and Space Administration White Sands Test Facility. The validated model successfully predicts temperatures within the test samples with agreement between model and experiment increasing as test pressure increases and/or distance from the promoter increases. Oxygen pressure and test sample thermal diffusivity were shown to have the largest effect on the results. In all cases evaluated, there is no significant preheating (above about 38°C/100°F) occurring at distances greater than 30 mm (1.18 in.) during the time the ignition source is attached to the test sample. This
validates a distance of 30 mm (1.18 in.) above the ignition promoter as a burn length upon which a definition of flammable can be based for inclusion in relevant international standards (that is, burning past this length will always be independent of the ignition event for the ignition promoters considered here.
KEYWORDS: promoted ignition, metal combustion, heat conduction, thin fin, promoted combustion,
burn length, burn criteria, flammability, igniter effects, heat affected zone.
This research examined the field performance of low-sloped roofs based on the effects of three important parameters: corner wind suction, parapets and internal pressure. The paper presents scientific documentation for each parameter and discusses how field observations reflect fundamental principles. It presents correlations developed for roof wind design, compares calculations of North American codes of practice for wind design data to show the impact of science and field observation on durable roof design, and provides recommendations for improving roof design for hurricane prone regions. Dans le cadre de cette recherche, on examine la performance in situ de toitures-terrasses plates, en se fondant sur les incidences qu'ont trois (3) paramètres importants : l'action aspirante du vent aux angles; les parapets; et la pression interne. Ce document présente de la documentation scientifique pour chaque paramètre et décrit comment les observations sur le terrain font ressortir des principes fondamentaux. On expose également des corrélations développées pour le calcul du vent pour les toitures, on compare des calculs des codes de bonne pratique nord-américains afin que les données de calcul du vent révèlent l'incidence sur la durabilité des conceptions de toiture qu'ont les observations scientifiques et les observations sur le terrain, et enfin, on fournit des recommandations en vue d'améliorer les conceptions de toiture pour les régions sujettes aux ouragans. RES
The knowledge of dynamic mechanical properties is useful in all cases where the strain rate sensitivity of metallic materials is an issue, and whenever the actual loading conditions for a structure either in normal operation or under accidental circumstances are different from static. Furthermore, in some investigations, increasing the loading rate in a mechanical test is used to simulate other embrittling mechanisms such as thermal aging or neutron exposure. Precracked Charpy-type PCVN specimens, tested under impact loading rates using an instrumented pendulum, have been used for more than 30 years to measure dynamic fracture toughness; the experimental procedure and the analysis methodology are fairly well established, despite the lack of an ASTM or ISO official test standard. This paper addresses the applicability of fatigue precracked miniature Charpy specimens of KLST type (PKLST-B = 3 mm, W = 4 mm and L = 27 mm) for impact toughness measurements in the ductile-to-brittle transition regime and in fully ductile (upper shelf) conditions. In the transition region, tests have been analyzed using the Master Curve approach; the multiple-specimen (low-blow) method has been applied in the upper shelf regime.
Surface coatings are increasingly used to improve the tribological performance of advanced products. The novel coating deposition techniques offer numerous possibilities for tailoring surfaces with different materials and structures. The tribological contact of loaded surfaces is, however, a complicated system itself, and further complexity is introduced when functionally graded coating structures are considered or improvement of specific micro-and nanostructural features is pursued. Furthermore, the mechanisms of damage in such a system are from a modeling standpoint highly complex and to great extent remain an active and open field of study. The focus of the current work is in the numerical modeling of graded thin hard coatings on a plastically deforming metallic substrate when loaded by contact that is typically exhibited during a scratch test. A finite element approach is implemented wherein a coating crack initiation and propagation are modeled using cohesive zone formalism. The cracks are considered to initiate and propagate within the coating and also within the coating to substrate interface. The results demonstrate how an optimization of the coating structure can enhance and exceed the performance of simplistic traditional coated systems. The material parameters of the problem and their significance in terms of fracture and failure behavior are discussed. The results are compared to fracture mechanical analyses and experimental information regarding the problem under study.
In the nuclear field, the importance of direct fracture toughness measurements on RPV materials has been nowadays widely recognized, as opposed to Charpy-based estimations. However, sample dimensions have to be kept small in order to optimize the use of available material (often in the form of previously broken Charpy specimens) or, in the case of new irradiations, make effective use of the limited space available inside irradiation facilities. One of the most appealing geometries for fracture toughness measurements is the miniature Compact Tension specimen, MC(T), which has the following dimensions: B = 4.15 mm, W = 8.3 mm, cross section 10 × 10 mm². Four MC(T) specimens can be machined out of a broken half Charpy, and in the case of irradiation ten MC(T) samples occupy approximately the same volume as a full-size Charpy specimen. A comprehensive investigation is presented in this paper, aimed at assessing the applicability of MC(T) specimens to measure fracture toughness in fully ductile (upper shelf) conditions. In this study, 18 1TC(T) and 20 MC(T) specimens have been tested at different temperatures from three RPV steels and one low-alloy C-Mn steel.