bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Laser-Induced Damage of Optical Crystals from the U.S.A. and U.S.S.R.
Authors: Soileau MJ , Wei T , Said AA , Chapliev NI , Garnov SV , Epifanov AS
Published: March 2009

In this paper we report the results of comparative measurements of laser-induced damage (LID) in optical material from the USA and the USSR. Bulk LID thresholds were measured in very pure alkali halide crystals at 1064 nm and 532 nm and surface LID thresholds in selected nonlinear optical crystals were measured at 10.6 microns. The results show that the LID thresholds of the USSR and the USA samples are approximately the same except for KCl where the USA samples have a factor of 2 higher LID threshold electric field then the Soviet sample.
Effect of Ionizing Radiations and Thermal Treatment on the Infrared Transmittance of Polycrystal CsI
Authors: Miley GH , Barnouin O , Procoli A
Published: March 2009

Alterations to the far infrared spectrum of polycrystal CsI due to nuclear irradiation or thermal treatment are studied. Pure and cerium doped crystals were used. The transmittance loss due to irradiation reaches 50% and stabilizes at that level for irradiation doses less bhan or equal to 1 Mrad. The transmittance loss is smaller for the cerium doped crystal. Heat treatment at 115°C–300°C of pre irradiated samples also causes a significant reduction of the transmittance, showing that high temperature annealing is not a useful approach to restore the transmission.
A Simple High Precision Extinction Method for Measuring Refractive Index of Transparent Materials
Authors: Nee SF , Bennett HE
Published: March 2009

Linearly polarized light remains linearly polarized after reflection from a transparent material at oblique incidence. The reflected polarization angle is determined from the extinction position of the analyzer. If the incident polarization angle is 45°, the reflected polarization angle gives the ratio of the reflected p-wave to s-wave. This value can be used to determine the index of refraction from Fresnel equations. With our instrument, the uncertainty in the deduced refractive index is ±0.0004. This method is fast, convenient and versatile enough to provide accurate results on small laboratory samples. In addition to measuring the refractive index, the method is sufficiently accurate to characterize the homogeneity of transparent materials.
Photoacoustic Characterization of Surface Absorption
Authors: Reicher DW , Wilson SR , Kranenberg CF , Raja MYA , McNeil JR , Brueck SRJ
Published: March 2009

Photoacoustic spectrososcopy is used to characterize the surface absorption of polished fused silica substrates and thin films deposited on fused silica substrates. The extreme sensitivity of this technique allows measurement of surface absorptions of a few tenths of a part per million. Characterization of samples with surfaces finished using a variety of methods is reported.
The Role of Valence-Band Excitation in Laser Ablation of KCl
Authors: Haglund RF , Tang K , Bunton PH , Wang L-J
Published: March 2009

We present recent measurements of excited-atom and ion emission from KCl surfaces illuminated by vacuum-ultraviolet synchrotron radiation (hv = 8–28 eV) and ultraviolet laser light (hv = 4 eV). At low intensities characteristic of the synchrotron experiments, excited atoms are desorbed by simple valence-band excitation process involving the metallization of the KCl surface. At the higher intensities typical of laser desorption and ablation, we observe a strong decrease in K* emission as a function of the number of laser shots, but an essentially constant yield of Cl*. K+ and Cl- emission at high intensities show similar behavior. The energetics of these desorption phenomena can be treated in a bond-orbital model which shows that creation of a single valence hole is sufficient to excite an ion to an anti-bonding state.
Multipulse Laser-Induced Failure Prediction for Mo Metal Mirrors
Authors: Becker MF , Ma C , Walser RM
Published: March 2009

In combination with known thermomechanical fatigue data for Mo, we have applied the Transient Photothermal Deflection (TPD) technique to develop a model for the N-on-1 damage of Mo mirrors to predict their multipulse lifetimes. In laser-damage experiments to verify the model, mechanically polished Mo mirrors were irradiated with 10 ns Nd:YAG laser pulses at 1064 nm at a 10 Hz rep rate. In the TPD experiments, the approximately 600 μm diameter Nd/3YAG laser spot was probed off axis by a smaller HeNe laser beam whose deflection was detected by a fast bicell photodetector and amplifier. Digitized photodetector waveforms indicated that the surface angular deflection could be converted into surface displacement. In addition, thermal modelling of the vertical heat distribution enabled the peak surface-deflection signal to be converted into peak surface temperature. The thermomechanical model was verified by both the experimental and model results.

Conventional mechanical fatigue data for Mo were used to derive a predictive equation for the laser-accumulation lifetime of Mo mirrors. Experiments were performed with one to 104 pulses per site yielding laser-damage thresholds and accumulation curves. The accumulation behavior predicted from measurements of mechanical fatigue was in excellent agreement with the measured behavior. It is possible that data on high-cycle (>106) mechanical fatigue can be used to predict the performance of optical surfaces at equally large values of N. Furthermore, a single-pulse TPD measurement of peak deformation at a subthreshold laser fluence, in conjunction with mechanical fatigue data, may be used to estimate the safe operating fluence for a component in a multipulse laser environment.
An Understanding of the Abnormal Wavelength Effect of Overcoats
Authors: Wu ZL , Reichling M , Fan ZX , Wang ZJ
Published: March 2009

In this paper wavelength dependent damage phenomena in SiO2 overcoats on TiO2/SiO2 and ZrO2/SiO2 HR coatings are systematically investigated with the help of various techniques, including a dynamical study of the damage process by time-resolved photothermal deflection technique, microscopic analysis of the absorption sites by cw-modulated photo-thermal microscopy, and observation of the coating microstructures and damage morphology by TEM and Nomarski optical microscopy. From the data for 355 nm and 1.06 μm radiation and a theoretical calculation of the temperature distribution inside the coating, we conclude that damage occurs first either in the HR coating or in the overcoat depending on the wavelength of the incident radiation. The influence of the local absorption sites, the interface morphology, as well as the heat transfer on the damage thresholds is discussed. The interpretation is supported by additional results on samples with various coating designs including SiO2 undercoats.
Applications of Pulsed Photothermal Deflection Technique in the Study of Laser-Induced Damage in Optical Coatings
Authors: Wu ZL , Reichling M , Fan ZX , Wang ZJ
Published: March 2009

Pulsed photothermal deflection technique (pulsed-PDT) is employed to make in-situ investigations of laser-induced damage in optical coatings. Preliminary experimental results show that the technique is capable of providing a lot of new information about not only the damage thresholds but also the damage processes, of which of particular interest are the transient damage behavior and the cumulative effect.
Morphology and Laser Damage Studies by Atomic Force Microscopy of E-Beam Evaporation Deposited AR and HR Coatings
Authors: Tesar AA , Balooch M , Shotts KW , Siekhaus WJ
Published: March 2009

Atomic Force Microscopy is a powerful tool for exploring the surface morphology of dielectric thin film coatings. We have demonstrated the utility of this tool in monitoring processing defects, laser conditioning and aging, and laser damage in e-beam evaporation deposited AR and HR coatings with a resolution not previously available.
High Threshold HR Coatings at 1064 nm
Authors: Rainer F , De Marco FP , Hunt JT , Morgan AJ , Mott LP , Marcelja F , Greenberg MR
Published: March 2009

We have conducted an extensive series of laser damage measurements on highly reflective (HR) dielectric coatings which have yielded 1064-nm thresholds as high as 40 J/cm2 for 8- to 10-ns pulses at pulse-repetition frequencies (PRF) of 10 Hz. Moreover, by laser conditioning these coatings with sub-threshold pulses, the thresholds of some coatings were raised to levels exceeding 70 J/cm2. These are the highest threshold dielectric HR coatings that we have tested in this regime.

The coatings were originally developed to produce HR-overcoated metal mirrors for free-electron-laser (FED applicationsat high PRF. Our tests included coatings deposited on both dielectric substrates and molybdenum (Mo) substrates. In each category we also examined coatings with a pre-coat of Mo between the substrate and the HR stack. The improved dielectric HR stacks effectively shielded the Mo from the laser irradiation so that the thresholds of virtually all Mo samples exceeded levels of the best dielectric-enhanced and dielectric-HR-coated metal mirrors we have tested to date.

In addition to the low PRF measurements, we also conducted 1064-nm damage tests at 6-kHz PRF using 65-ns pulses from the Kilroy damage test facility. The coatings survived thermal loading of fluences ranging from 2 to 10 J/cm2 with respective small spot sizes on the order of 1.2 to 0.3 mm (1/e2 diameter).
Laser Conditioning and Electronic Defects of HfO2 and SiO2 Thin Films
Authors: Kozlowski MR , Staggs M , Rainer F , Stathis JH
Published: March 2009

Multilayer HfO2/SiO2 high reflectors (HR) and polarizers show a permanent increase in their 1064-nm damage thresholds following laser conditioning at subthreshold fluences. Threshold increases of 2–3x are typical. In an effort to better understand the conditioning effect we have made laser conditioning and electronic property measurements on single layers of these two materials. The laser damage threshold of 1-μm thick e-beam deposited SiO2 was increased by laser conditioning for wavelengths ranging from 355 to 1064 nm. The damage threshold of HfO2 single layers was not influenced by sub-threshold illumination.

As-deposited thin films of a-SiO2 are known to contain paramagnetic electronic defects. We have used electron paramagnetic resonance (EPR) to study the concentrations and types of defects present in single layer and multilayer films of HfO2 and SiO2. E' and oxygen hole centers with concentrations on the order of 1017/cm3 have been measured in the SiO2 layers. A previously unreported defect has been observed for HfO2. The concentration of defects was studied both before and after laser conditioning and damage with 1064-nm photons. These electronic structure measurements are discussed in relation to an electronic defect model for laser conditioning of dielectric multilayers.
Multishot Ablation of Thin Films: Sensitive Detection of Film/Substrate Transition by Shockwave Monitoring
Authors: Hunger E , Petzoldt S , Pietsch H , Reif J , Matthias E
Published: March 2009

During multishot ablation with 248 nm excimer laser pulses, for each single laser shot the shock wave emerging from the ablated material was monitored by the acoustic mirage effect. The Shockwave parameters turned out to depend sensitively on the nature of the ablated material. In particular during ablation of a polymeric film/SiO2/Si multilayer system, distinct changes in the deflection signal were found when the ablation was driven through the interface between layers. Inspection by optical microscopy and depth profiling was used as cross check.
Reactive Ion-Beam-Sputtering of Fluoride Coatings for the UV/VUV Range
Authors: Schink H , Kolbe J , Zimmermann F , Ristau D , Welling H
Published: March 2009

Fluoride coatings produced by thermal evaporation suffer from high scatter losses, ageing and cracking due to high tensile stress. These problems impose severe limitations to the production of low loss multilayer coatings for the VUV range. A key position for improved performance is the microstructure of the layers.

The aim of our investigations is to improve the microstructure of AlF3- and LaF3-films by ion-beam-sputtering. Scatter measurements of single layers revealed lower values for IBS than for boat evaporation. Unfortunately, sputtered fluoride films have high absorption losses caused by decomposition of the coating material.

By sputtering in reactive atmospheres and annealing we were able to reduce the absorption losses significantly. Antireflective as well as high reflective coatings were produced. Reflection and transmission values were obtained with a VUV-spectrophotometer. Damage tests at the 193 nm ArF laser wavelength were performed at the Laser-Laboratorium Göttingen.
Correlation of Surface Topography and Coating Damage with Changes in the Responsivity of Silicon PIN Photodiodes
Authors: Huffaker DL , Walser RM , Becker MF
Published: March 2009

Laser-induced morphological damage initiated by single 10 ns, 1.06 μm Nd:YAG laser pulses was observed on three types of EG&G silicon PIN photodiodes. When the samples were irradiated at fluences above the melting threshold, the damage morphologies were observed to vary according to the type of coating and the fluence. Nomarski microscopy at 200X was used to analyze the laser-induced topography at the damage sites. The topography was characterized generally by ripples, ridges and boiling marks in order of increasing fluence. However, all test fluence levels remained below the threshold for electrical degradation and no increase in leakage current was detected. The detector responsivity at the damage sites was mapped by means of a probe laser. The sample was translated within its plane in order to obtain a series of raster scans across each damage site. A comparison of the topographical data and responsivity data suggests that local variations in responsivity were correlated with laser-induced surface roughness and with the removal of the thin-films.
Closed-Form Onset Threshold Analysis of Defect-Driven Surface and Bulk Laser Damage
Authors: O'Connell RM
Published: March 2009

Surface and bulk laser damage probability distribution functions are derived for a Gaussian beam and a power-law defect ensemble. Closed-form solutions are derived and plotted for six and three values of the defect ensemble parameter p, respectively, in the surface and bulk damage distribution functions. The derived degenerate (p = 1) and non-degenerate (p = 0) bulk damage equations are least-squares fitted to measured laser damage statistics in PMMA. The results show that the power law defect ensemble is a reasonable description of the defects in the damage-tested PMMA and that the ensemble is more degenerate in character than uniform.
Finite Element Analysis of the Transient Behavior of Optical Components under Irradiation
Authors: Borik S , Giesen A
Published: March 2009

With increasing laser power the transient behavior of the optical components becomes more and more important, giving rise to investigations in this field, e.g. [1,2,3]. Especially the time dependence of the optical properties which influence the laser beam parameters is of interest.

In this paper the heating of optical components caused by the absorption of a small part of the laser power as well as the resulting deformation of the phase front of the laser beam have been studied with finite element analysis. For this, the spatial temperature profile, the mechanical deformation and the stress of the optical component have been calculated as a function of laser power, laser mode profile and irradiation time. Using the temperature dependence of the index of refraction, the spatially resolved optical path difference compared to the unirradiated component has been calculated with a ray tracing algorithm.

The results for various optical components (mirrors, windows; coated and uncoated) are given and compared to experimental investigations.
Thermal Analysis of Multifacet-Mirror Ring Resonator for XUV Free-Electron Lasers
Authors: McVey BD , Goldstein JC , McFarland RD , Newnam BE
Published: March 2009

XUV (10 nm ⩽ λ ⩽ 100 nm) free-electron lasers (FELs) are potentially important light sources for advanced lithography and materials applications. The average power of an XUV FEL oscillator may be limited by thermal loading of the resonator mirrors. We analyze the requirements for the thermal performance of the mirrors of a metal, multifacet-mirror ring resonator for use at 12 nm. We use analytical methods and numerical approaches which include simulations with the 3-D FEL code FELEX. Thermal distortion of mirror surfaces leads to optical wavefront aberrations which reduce the focusability of the light beam in the gain medium (wiggler/electron beam) and limit the laser performance.
Determination of SBS Induced Damage Limits in Large Fused Silica Optics for Intense, Time-Varying Laser Pulses
Authors: Kyrazis DT , Weiland TL
Published: March 2009

The propagation of intense 3rd harmonic light (0.351 μm) through large optical components of the Nova laser results in fracture damage of the center of the component. This damage is caused by an intense acoustical wave brought to focus in the center by reflecting off the circular edge of the optic. The source of this wave is light generated by transverse stimulated Brillouin scattering (SBS). By taking into account the transient gain characteristics of the SBS, we can correctly predict the pulse energy that would cause damage for any time variation in intensity in the pump beam, and predict the relative intensity of the Brillouin light. Our model is based on the transient behavior of a first order linear system.
Correlation Between the Laser-Induced Breakdown Threshold in Solids, Liquids, and Gases
Authors: Bettis JR
Published: March 2009

A simple theoretical expression is developed which allows correlation between laser-induced breakdown threshold in solids, liquids, and gases. It is shown that the breakdown threshold for single-layer thin films, surfaces of dielectrics, the bulk of solid dielectrics, linear liquids, and gases all follow a linear fit to the expression N2/3/(n2-1), where N is the atomic number density and n is the refractive index. The threshold for sol-gels is compared with conventional thin film thresholds and is shown to agree reasonably well with the relative threshold predicted by the simple expression. The gas breakdown threshold vs pressure is compared with the predicted dependence. Finally, maximum values for solid, liquid and gas thresholds are plotted against the expression and are seen to fall on a single straight line across three decades of physical constants.
Excimer Laser Optics
Authors: Morozov NV , Sagitov SI , Sergeyev PB
Published: March 2009

For optical materials, mirrors and antireflection coatings the laser damage resistance results for XeCl, KrF, ArF excimer laser wavelengths are presented.
Experimental Determination of Fracture Parameters in Three-Dimensional Problems
Authors: Smith CW
Published: March 2009

Two established optical methods are described briefly with refinements to allow accurate near-tip measurements for three-dimensional cracked body problems. Several illustrations of their use are presented and compared with numerical results.
ASTM E 1304, The New Standard Test for Plane-Strain (Chevron-Notched) Fracture Toughness: Usage of Test Results
Authors: Barker LM
Published: March 2009

The origins and rationale for the three plane-strain fracture toughnesses defined by the new ASTM Test Method for Plane-Strain (Chevron-Notch) Fracture Toughness of Metallic Materials (E 1304-89) are reviewed. KIvM represents the toughness measured in a greatly simplified test, but it can be less accurate than KIv and KIvj. The test for KIv is complete with all the procedures and validity criteria necessary to assure accurate measurements of plane-strain critical stress-intensity factors. When a material exhibits a crack-jump behavior, the KIv procedure must be modified, and the toughness is called KIvj. This paper suggests that ASTM E 1304-89 toughness measurements can be used for the full range of applications appropriate to KIc values measured by the ASTM Test Method for Plane-Strain Fracture Toughness of Metallic Materials (E 399-83). However, a material-dependent constant, equal to about three times the ctack-tip plastic zone radius, should be added to the preexisting flaw size in calculations of crack stability.
Three-Dimensional Elastic-Plastic Analysis of Small Circumferential Surface Cracks in Pipes Subjected to Bending Load
Authors: Franco C , Gilles P
Published: March 2009

This study presents the elastic-plastic behavior of a circumferentially surfacecracked pipe using the finite element method based on a three-dimensional model.

The action of a pure bending load on the pipe is analyzed for three crack depths with a/t equal to 0.25, 0.5, and 0.75, and their eccentricities, a/c, being 0.2, 0.4, and 0.6, respectively.

The material obeys a Ramberg-Osgood power law. The goals are to determine the stressstrain fields and the values of J on the crack front, to define the different plastic deformation stages reached as the load on the crack is increased, and to validate the Central Electricity Generating Board (U.K.) (CEGB) two-criteria rule for circumferential surface flaws on the basis of the J results.
Elastic-Plastic Crack-Tip Fields Under History-Dependent Loading
Authors: Brust FW , Ahmad J , Naboulsi S
Published: March 2009

Elastic-plastic behavior of a cracked structure subjected to cyclic loading is evaluated through a series of finite element analyses of a test specimen geometry. A specimen of an extremely ductile material (Type 304 stainless steel) is loaded to just below the Ji value at crack initiation, then unloaded and reloaded using R-ratios of 0.0, -0.5, and - 1.0 including the effects of crack face contact. The crack-tip asymptotic fields, tensile and compressive plastic zones, and crack-tip parameters such as crack-tip-opening displacement and the J- and T*-integrals are evaluated and discussed in the context of cyclic loading for a stationary crack.
Advanced Fracture Mechanics Analyses of the Service Performance of Polyethylene Gas Distribution Piping Systems
Authors: O'Donoghue PE , Kanninen MF , Popelar CF , Popelar CH
Published: March 2009

Most of the plastic gas distribution pipe now in service is polyethylene (PE). While this material has an excellent safety record, due to a variety of abnormal loadings that can arise in long-time service, some slow crack growth (SCG) related field failures have occurred. Accelerated test procedures to accurately predict the long-term performance of PE gas pipes are therefore required for the evaluation of existing gas piping systems and to qualify new pipe materials prior to installation. In addition, particularly as interest in the use of larger diameter and higher pressure polyethylene pipes increases, rapid crack propagation (RCP) can occur in a gas piping system at the site of an SCG failure, or as a result of third party damage, or by other similarly unforeseeable mechanisms, attention must be given to the possibility of RCP. Accordingly, dynamic fracture mechanics research aimed at preventing RCP in PE gas distribution pipelines has also been carried out. This paper reviews current advanced fracture mechanisms research on PE gas pipe materials that investigates both SCG and RCP events.
Three-Dimensional Analysis of Thermoelastic Fracture Problems
Authors: Chen W-H , Huang C-C
Published: March 2009

This paper deals with three-dimensional thermoelastic fracture problems using both analytical and numerical results. The analytical temperature distribution of an infinite solid with an embedded elliptical insulated crack subjected to an uniform heat flow solved by the authors is first described briefly to provide a verification for the three-dimensional finite element model with collapsed quarter-point singular elements around the crack front. To determine the thermal stress-intensity factors, the three-dimensional path-independent integrals that are physically the energy release rates per unit area of crack extension along respective directions of crack growth are employed and computed for three-dimensional realistic thermoelastic fracture problems.

To evaluate the influence of geometry and Poisson's ratio on the computation of temperature distributions and thermal stress-intensity factors for various thermal conditions, several representative examples are presented. The variations of pure and mixed-mode thermal stressintensity factors along the crack front are also studied for both through and part-through cracks in finite elastic solids.

Good agreements between the computed results and referenced solutions show the validity and accuracy of the present analysis.
Traction Boundary Integral Equation (BIE) Formulations and Applications to Nonplanar and Multiple Cracks
Authors: Cruse TA , Novati G
Published: March 2009

The hypersingular Somigliana identity for the stress tensor is used as the basis for a traction boundary integral equation (BIE) suitable for numerical application to nonplanar cracks and to multiple cracks. The variety of derivations of hypersingular traction BIE formulations is reviewed and extended for this problem class. Numerical implementation is accomplished for piecewise-flat models of curved cracks, using local coordinate system integrations. A nonconforming, triangular boundary element implementation of the integral equations is given. Demonstration problems include several three-dimensional approximations to planestrain fracture mechanics problems, for which exact or highly accurate numerical solutions exist. In all cases, the use of a piecewise-flat traction BIE implementation is shown to give excellent results.
Dynamic Stress-Intensity Factors for Interface Cracks in Layered Media
Authors: Bouden M , Datta SK
Published: March 2009

The scattering of elastic waves by interfacial cracks in layered media has been investigated in this paper. A hybrid numerical method is employed for obtaining the solution. This method combines the finite element equations and the Green's function boundary integral representation. Numerical results are presented for the crack opening displacements (COD) and the Mode I and Mode II stress-intensity factors (SIF) as functions of nondimensional frequency when normal and tangential time harmonic line loads are applied on the free surface of the layered medium.
Probabilistic Fracture Models for Predicting the Strength of Notched Composites
Authors: Cheng MC , Lin KY
Published: March 2009

This paper presents two probabilistic fracture models for predicting the tensile strength of filamentary composites containing geometric discontinuities such as holes or cracks. The statistical fracture model considers the case of a constant load while the stochastic model deals with monotonically increasing loads. Both models use the Weibull distribution of fiber strength and elastic fiber/matrix properties to calculate the number of broken fibers near the crack tip in the 0-plies as a function of applied loads for different probability levels. Using the probabilistic models, the notched strength of (±45/02)s boron/aluminum composites with various crack sizes have been predicted. These results agree well with existing experimental data. In addition, the relationship between fracture stress and notch size is found to be governed by a power law, as previously suggested by Mar and Lin using a deterministic approach.
The Needs of Users and Their Response to Materials Databanks
Authors: Hossain K , Barry T
Published: March 2009

The commercial and design requirements for data at the conception of a product and at each stage of its design for processing, use and ultimate disposal place great demands on materials information. The breadth and depth of need are examined in relation to the ways in which they influence the choice of sources and types of data. It can be seen from this approach that those with the ability to draw on and make use of data from a wide range of sources have an obvious advantage in product innovation. A survey in the UK of the response of potential users of materials information systems is reviewed and possible solutions to user resistance examined.

A problem not exclusive to computer based systems of materials information lies in the near certainty that they contain errors and gaps in the data and have limited ranges of application. Moreover, if they are knowledge based or offer powerful facilities for predicting materials properties using models, due care has to be taken to ensure that they are not misused, leading to users obtaining erroneous solutions. For these reasons materials databases should provide traceability not only to data sources and software but also to user input.
Terminology Standards for Materials Databases
Authors: Westbrook JH , Grattidge W
Published: March 2009

The reasons for the importance of terminological standardization in computerized information systems are discussed as well as the special aspects pertinent to materials databases. Current terminological activities in the materials field are reviewed and progress and difficulties noted. In order to demonstrate the need for standardization or harmonization of materials terminology, several very common terms from each of eight term classes were chosen for study. Definitions for each term were sought in the ASTM Compilation of Standard Definitions, in the CEC Common Reference Vocabulary, and in appropriate specialized glossaries. Comparisons of the extracted definitions are made and discussed. The results highlight the nature of the problems which must be overcome. For this small set, examples are given of harmonized definitions which might be suitable for use in computerized systems, and recommendations are made as to how a cooperative effort for further standardization might achieve the desired goal.
The Step Model of Materials Information
Authors: Rumble J
Published: March 2009

An information model of materials and their properties has been developed to support an international standard on product model data. Under the auspices of ISO, the Standard for the Exchange of Product Model Data (STEP) is being developed to support data exchange between software that performs all the engineering functions associated with manufactured products. Materials information is very important for STEP and the modeling effort has two goals: to provide a general framework for the description of a material, its properties, and the environment in which those properties are meaningful; and to support the use of materials information in product-related applications. The modeling effort has built upon work of several groups, especially ASTM Committee E49. The model has been developed using a data modeling language and its associated graphical representation.
Neutral Exchange Format for Materials Databanks, Based on Z 99-001 AFNOR Standard
Authors: Vinard DR , Pelleing C , Dereims M
Published: March 2009

SAINT-GOBAIN has developed a materials database SG-PROMAT, describing the various materials (Glass, Refractories, Ceramics, Cement, Cast Iron, and Cellulose) used or produced by its 281 affiliates through the world. The format used is QUESTEL+(Telesystemes Questel). Factual documents can be searched on either a ASCII or VIDEOTEX (Minitel) terminal. Selections can be made in particular for numerical values of the material properties and behaviour. The NFZ 99-100 (AFNOR) standard has been developed to be used as a world exchange standard for components in CAD/CAM libraries. It is based on SQL tables enabling the definition of the structure of the information to be transmitted and 2) the implementation of a dictionary of the parameters in their different languages. Other SQL tables are used to contain the data themselves. The use of this neutral format will enable SAINT-GOBAIN to transfer the information to the QUESTEL base, and also to transfer the information to its world-wide customers and licensees, who will themselves convert the information for integration into their own data systems.
Materials Information and Conceptual Data Modeling
Authors: Sargent P , Subrahmanian E , Downs M , Greene R , Rishel D
Published: March 2009

We have been developing a novel method for systematizing the concepts behind the information stored in many disparate databases containing materials test data. The conceptual structure produced will be used as a basis for the development of software systems which integrate engineers' access to many different databases. The major problems and the reason why the meanings of the concepts require explicit structuring are that (a) the everyday vocabulary used is ambiguous, (b) the same data item will have many valid names, (c) similar information is obtained by different laboratories using different methods and different scientific conceptual structures. There are also many organizational problems concerning responsibility, authority and maintenance. The complexity of the relationships between concepts requires a new technique of unusual sophistication in its handling of defaults and inheritance.
Development of Diagnostic Expert System for Environmentally Assisted Cracking (EXENAC) and Importance Evaluation of Rules in Inference
Authors: Komai K , Minoshima K , Koyama M
Published: March 2009

The expert system, that diagnoses the sensitivity of environmentally assisted cracking (EXENAC; EXpert system for ENvironmentally Assisted Cracking), has been developed using the 0PS83 programming language. This system is composed of three independent subsystems, which respectively diagnose the sensitivity of i) stress corrosion cracking of austenitic stainless steels in a low- or high-concentration chloride solution and/or high-temperature water, ii) hydrogen embrittlement of high-strength steels in various aqueous solutions and gaseous environments, and iii) hydrogen attack of steels in high-temperature high-pressure hydrogen gases. The knowledge base covers the rules relating to environments, materials, loading conditions, heat treatments, material processing including welding and their interaction as well as fracture surface morphologies. The knowledge base consists of production rules, which have certainty factors to represent the uncertainty (contribution) of each rule to environmentally assisted cracking. The adoption of certainty factors enabled the uncertain but widely applicable knowledge to be built in a knowledge base, which in turn raised the flexibility of diagnoses made by the expert system. Applying the developed expert system to the case histories the diagnoses were accurately made. We discussed the characteristics of the individual knowledge base, related diagnosis results, and the suitable knowledge base structures for diagnoses in the area of environmentally assisted cracking. It is desirable that the inference is made through the plural affirmative and negative rules being executed. We also proposed the quantitative measure to evaluate the importance of each rule in the diagnosis. By this measure, not only the importance of knowledge in the diagnoses of the environmentally assisted cracking which occurs in service operation is evaluated but also the lack of knowledge can be made clear, which points out which field of investigation is necessary in the future.
Issues in the Development of an Advanced Ceramic Materials Selector Expert System
Authors: Begley EF , Munro RG
Published: March 2009

A materials selector expert system for advanced ceramics is being designed to assist users in identifying candidate materials for gas-fueled heat exchangers and other applications which may involve processing parameters, environmental conditions, and physical constraints. The selection process will require an appropriate and relevant knowledge base of materials properties as well as applicable rules and heuristics. The NIST Structural Ceramics Database (SCD) provides the cornerstone for the materials selector expert system and supplies critical microstructural and property measurement data. The anticipated evolution of the SCD to a knowledge-based system is discussed with an emphasis on relevant development issues.
Data for the Stepwise Simulation of Heat Exchanger Performance
Authors: Ilten DF
Published: March 2009

Fouling can cause significant problems in heat transfer equipment but is in many cases intractable theoretically and experimentally. As an aid in studying the effects of fouling and ultimately in preventing it, results of stepwise checkrating simulation calculations for case studies of a typical shell and tube heat exchanger are presented. These give information on subsections of the equipment, as well as details of its overall capabilities. In order to carry out these calculations accurate physical property data at the temperature, pressure and composition conditions actually existing at desired geometric points in the heat exchanger are required. These data can be provided in part by an internationally developed extensive collection of physical property data.
In-Service Structural Integrity Assessment Using Computerized Materials Models and Data
Authors: Jeffery CM , Bullough CK
Published: March 2009

Many large-scale engineering structures, such as steam generation plant and petro-chemical plant, operate under conditions in which the key materials properties diminish with time. Detailed understanding of this degradation is essential for structural integrity assessments, and computerization of the collection and analysis of these materials data can realise significant savings in the cost of structural integrity assessment. The authors give examples of the various methods used to obtain data and to extrapolate rates of material degradation in order to predict failure. It is shown that, from the design stage, certain assumptions, some necessary, some dubious, are incorporated into standard materials property data. Such simplification may be necessary during design but represents a challenge for in-service assessment, when a statistical or stochastic approach is required. In addition, it is noted that hardly any publicly-available computerized materials databases contain the properties of alloys following service exposure. A natural extension of computerized assessment of data is to monitor the consumption of life during service. A continuous monitoring system is described which will take advantage of material degradation models to provide real-time analysis of plant integrity.
Information Engineering: Adding Value to Data
Authors: Swindells N , Heine G
Published: March 2009

One of the important conclusions from the Materials Database Demonstrator Programme of the Commission of the European Communities was that the data available from the first generation of on-line databases in the Programme was regarded, by evaluation panels with a broad range of material interests, as having low value. If a self-sustaining market in materials information in the European Communities is to be established, then the data available should have a recognised value as being what the customer needs and can use. Information destined for the market should therefore be engineered for its intended purpose and its value ensured by this process. This concept is the basis of proposals for a new programme for materials information within the European Communities and the background to the concept of information of value and an outline of the proposals for the new programme is given.
Analysis and Evaluation of Data for Advanced Composite Materials
Authors: Newton CH , Brady PM , Volk DL
Published: March 2009

Advanced composite materials are used to replace more traditional metals and alloys in structural applications. Material property data for these composite materials are necessary for their use. The analysis and evaluation of these data, prior to their inclusion in a materials properties database, is essential due to variability that may result from test methodology, processing, and other factors. The systematic evaluation of these data requires consideration of the initial treatment of the data, statistical analysis, technical evaluation of the data, and assessment of the test procedure and other documentation. The information is presented at the review level since the details of each step in the process, particularly the statistical analysis and the theoretical predictions of properties, are clearly beyond the scope of the paper. References are provided for more detailed information.
Materials Selection: Object-Oriented Structures for Factoring Polymer Information
Authors: Demaid A , Ogden S , Zucker J
Published: March 2009

This paper discusses the fundamental issues involved in creating a taxonomy of engineering polymers capable of being implemented in class-instance, object-oriented programming languages. It reports the authors' experience of creating this taxonomy in POISE, our object-oriented database management system implemented in Smalltalk-80™ [1]. Our account is centred on the issues involved in a strict factoring of the domain of polymers according to chemical composition, molecular scale and molecular arrangement, where these produce similar effects. Knowledge representation of materials information in our taxonomy is implicit and potentially far-reaching when rules of composition and scale are adhered to, rather than explicit and restricting when pragmatic groupings are created for particular purposes.

Knowledge representation of the relatively large scale micro-structures which create reinforced plastics pose particularly difficult issues which are discussed in detail. We find that the usual high-level, factoring of the materials domain into metals, ceramics, plastics and composites or into polymers and reinforced polymers is inappropriate for a taxonomy designed to represent plastics knowledge in a robust way independently of a user's particular purposes. This finding complements the authors' work [2] on the importance of separating perspectives for representing engineering design knowledge. A strict regime of independent perspectives is seen to be desirable at all levels of knowledge representation. This argues against the generality, or extensibility, of mixed taxonomies that are commonly seen to arise from a representation of materials information in a particular context, for a particular purpose.

POISE allows complex entities such as polypropylene, polyolefin, crystalline thermoplastic, and thermoplastic, which represent a line of direct ancestry in our taxonomy, to be stored and processed as largely independent computing objects. This accords nicely with the intuition that in deciding whether to make a washing-up bowl from polypropylene or polyethylene an engineer will have an idea of the generic properties of the two plastics and that this process is ill-served by a database model which searches through many individual grades of these polymers.

We comment on the principled support of independent browsing facilities which our taxonomy supports and argue for the nature and benefits of an object-oriented model of materials information which allows complex computing representations to evolve rather than to be designed, and which allows a representation of the structure of polymer knowledge to exist in a useful form independently of a program which provides particular services over the knowledge base.
The Importance of Carbon Monoxide in the Toxicity of Fire Atmospheres
Authors: Debanne SM , Hirschler MM , Nelson GL
Published: March 2009

This paper addresses the issue of determining toxic fire hazard in a manner that is relevant to the large-scale fire scenarios that cause most lethalities, ventilation controlled flashover fires.

The work involves (a) a literature study of background information on the toxicity of carbon monoxide (CO) to humans, (b) two very extensive forensic studies (with 2 241 and 2 673 cases, respectively) on human lethality involving CO in fires and non-fires, (c) statistical analyses of the forensic data, to ensure full separation of variables, and (d) an analysis of the literature on the effects of different parameters in fire atmospheres and in small-scale tests.

This work addresses five issues essential to fire hazard assessment: (1) Relative role of toxicants other than CO in causing fire fatalities and critical carboxyhemoglobin (COHb) values representing lethality. (2) Differences in populations between fire victims and those dying in other CO-containing atmospheres. (3) Comparison of modern fire atmospheres, containing smoke from man-made materials, with traditional fire atmospheres. (4) CO yields in flashover fires and effects of fuel chemistry. (5) CO yields in small-scale toxicity tests and fuel effects.

The work has shown that: (1) The toxicity of fire atmospheres is determined almost exclusively by the amount of CO. The lethal CO threshold level depends on the physical condition of the victim, but COHb values > 20% can produce lethality with no other apparent cause. (2) Fire and non-fire CO victim populations are very different: fire victims are much older or much younger and more infirm, and thus more sensitive to CO than those in nonfire exposures. (3) Replacing large amounts of natural and traditionally used materials by man-made materials has made no difference to fire atmosphere toxicity. (4) CO concentrations in large-scale flashover fire atmospheres are determined by oxygen availability and such variables, but are little affected by chemical composition of fuels. (6) Small-scale tests give excessively low CO yields so that they cannot be used to predict toxic fire hazard for ventilation controlled flashover fires, although post computational CO concentration corrections can make these tests useful as part of fire hazard assessment calculations.
Evaluating the Hazards of Large Petrochemical Fires
Authors: Keltner NR , Acton RU , Gill W
Published: March 2009

Fire testing and fire research would be aided by the standardization of the fire environment, test articles, sensors, and procedures for the sake of reproducibility and interlaboratory comparisons. Current and proposed fire standards dictate control by either “fire temperature” or by “fire heat flux”. This equivocation can lead to confusion. This article discusses the circumstances under which temperature may be the more important control parameter and when heat flux may be the more important control parameter. Examples are given.