bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of Warm Prestress Data
Authors: Macdonald BD , Embley GT , Irizarry-Quinones H , McAfee WJ , McCabe DE , Smith PD , Wuthrich JW 
Published: March 2009

Loading a cracked structure at elevated temperature, or warm prestressing (WPS), enhances its fracture resistance at a lower temperature. Five data sets, comprising 119 unclad pressure vessel steel specimens, were combined to derive correlations for WPS-enhanced fracture toughness (KIfrac) in the absence of ductile tearing. New WPS test results for 27 surface-flawed specimens, eight subclad-flawed specimens, and five strain-aged specimens are discussed. KIfrac exceeded non-WPS fracture toughness, KIc, for all experiments. The WPS data showed that no specimens failed while K was decreasing, and that at least an additional 7% additional reloading from the minimum value of applied KI took place prior to final fracture. The data included complete and partial unloading after WPS prior to final fracture. Crack tip three-dimensional elastic-plastic finite element (3DEPFE) analysis was performed to support statistical analysis of the data. Regression models were compared with the Chell WPS model.
Crack tip 3DEPFE analysis indicated that partially unloaded and completely unloaded data should be treated separately, and that the amount of unloading is unimportant for partially unloaded data. The regression models, which use KI at WPS (KIwps) and KIc as independent variables, better represented the WPS benefit than did the more complicated Chell model. An adequate accounting was made for constraint in the WPS experiments. The subclad flaw data support the use of the partial unload regression model provided that some care is taken to represent the effect of intact cladding if present. The effect of strain aging at or below 260°C (500°F) on the WPS benefit was of no consequence for the pressure vessel steels and WPS temperatures used to derive the regression models. The presence of ductile tearing precludes the use of the regression models. The regression model for partial unloading accurately predicted the behavior of full-scale pressure vessel WPS experiments. All but one of the 174 experiments considered lie above the lower 2σ estimate of the regressions. The experiments all supported Type I WPS, i.e., there was no fracture during cooling until reloading occurred. However, the regression equations apply to the reload and are inapplicable to Type I WPS.
How Fatigue Cracks Grow, Interact with Microstructure, and Lose Similitude
Authors: Davidson DL 
Published: March 2009

This paper reviews the processes by which fatigue cracks grow and interact with applied load and microstructure. Fatigue crack growth processes are remarkably similar irrespective of microstructure, crack size, or nature of the loading. Large strains at fatigue crack tips applied over repeated cycles severely alter, or homogenize, microstructures, followed by crack advance. Microstructure affects fatigue crack growth kinetics more than growth processes. But, under marginal conditions, fatigue crack growth rates are also affected by microstructural features. Examples are small cracks growing under low stresses or large cracks growing near threshold.
The prediction of safe lifetimes for machine parts, such as gas turbine components, requires that laboratory-generated fatigue crack growth rate data be transferred to field-operating conditions. This transfer depends on the maintenance of similitude: microstructurely, mechanically, and environmentally. However, for many industrially important conditions, similitude with large fatigue crack growth is lost, partially because of changes in fatigue crack closure. The effect of closure on similitude is discussed.
New data are presented to illustrate the loss of similitude between applied loading and crack tip strain response. The resulting strain rates of material within the process zone are unexpected. Environmentally influenced fatigue crack growth rates are likely to be influenced by these strain rates.
S-N Curve for Crack Initiation and an Estimate of Fatigue Crack Nucleus Size
Authors: Yang CY , Liaw PK , Palusamy SS , Ren W 
Published: March 2009

A study of fatigue life prediction was made for ASTM A533 Grade B nuclear pressure vessel steel. The objectives of the study were to predict the S-N curve, representing crack initiation, and to estimate the average crack nucleus size using an engineering approach. The plastic replica method was used to monitor crack initiation and growth from well-polished specimens under uniaxial tension-tension stressing.
Two methods were used to estimate crack nucleus size: (1) backcalculating crack length via the da/dN versus ΔK relationship, and (2) evaluating an assumed relationship between the endurance limit and the threshold stress intensity factor range. Crack nucleus size estimated by these two methods are fairly consistent when the effects of crack closure and plastic zone correction are taken into account.
The Need for Standardization of Fire Resistance Testing of Industrial Fluids (First Keynote Address)
Authors: Brandao AV 
Published: March 2009

This presentation will address the need for global standardization of fire resistance criteria to promote free trade and to maximize the purchasing power of users facing increasingly tight budgets. The current proliferation of standards, both from various jurisdictions and specific to different industries, increases the number of overlapping tests that producers must perform to bring a new fluid to market.
Relative fire resistance is but one of the properties that must be established for any new or reformulated fluid. However, there is little agreement on test methodology among various jurisdictions and industries. This is a result of the largely empirical nature of fire research until very recent times. While still embracing much empirically-derived technology, in the past several decades fire research has increasingly made use of a more scientific approach. Developments in combustion science have led to a better understanding of the underlying phenomena. These new insights are now available to facilitate the design of tests that are more universally applicable to a wide variety of potential fire scenarios.
Fire Resistance Tests for Fluids and Lubricants — Their Limitations and Misapplication
Authors: Phillips WD 
Published: March 2009

A large number of tests are currently available for assessing the fire resistance of functional fluids and lubricants. Since it is extremely difficult to simulate fire conditions for fluids in laboratory tests, the main use for the different methods is a comparative assessment of the various fluids.
The fluids in commercial use, where fire resistance is a critical feature, can be divided into those which depend on water for their performance and non-aqueous fluids, where the fire resistance depends on the chemical composition. Ideally a fire resistance test should be capable of assessing the behaviour of all candidate fluids on an equal basis, but because the two groups of fluids behave in totally different ways comparison in most tests is not valid.
Although some tests suffer from indifferent precision or are unable to satisfactorily discriminate one type of fluid from another (within the same group), many rank the fluids in approximately the same order and therefore do not provide any additional information.
The introduction of two new spray ignition tests which enable all the different fluids to be compared under similar conditions is a major step forward. These tests, however, cannot simulate a condition where the water content of aqueous fluids can volatilise and leave behind a flammable residue. As a result, for the minimum assessment of the behaviour of both groups of fluid it is advisable to obtain both spray ignition test performance and performance in a ‘hot surface’ test.
Spray Flammability of Hydraulic Fluids
Authors: Khan MM 
Published: March 2009

The spray flammability characteristics of several hydraulic fluids, and mineral oil, methanol, ethanol, and n-heptane, sprayed vertically upward in the open through a pressure-jet hollow cone nozzle and stabilized by a propane-air ring burner, have been evaluated using the Factory Mutual Research Corporation (FMRC) Fire Products Collector. A spray flammability parameter (SFP) has been defined, which combines the combustion intensity of spray fires in terms of chemical heat release rate with the fluid volatility described by the critical heat flux for ignition. An SFP value has een identified at or below which a range of hydraulic fluids cannot be stabilized as spray flames using a standard flame stabilization test. Mineral oil, some hydraulic fluids, and highly volatile fluids such as n-heptane, methanol and ethanol, have high SFP values and are easy to stabilize as spray flames. SFP appears to be useful in discriminating between flammable and less flammable fluids.
Experimentally, it was found that the burning of multi-component fluids, such as water-in-oil emulsion and polyglycol-in-water on a wick (porous ceramic disc), does not simulate burning of such fluids in an atomized spray. Thus, a spray fire test appears to be a much better method for characterizing the flammability of all types of hydraulic fluids.
Minnesota's Quality Management Program “A Process for Continuous Improvement”
Authors: Wegman DE 
Published: March 2009

Minnesota's Quality Management Program began in 1986 when the Minnesota Department of Transportation (Mn/DOT) and the Minnesota Asphalt Pavement Association (MAPA) formed a partnership to develop a process for improving the quality of asphalt pavements within the state. A Quality Management Task Force was formed with members representing Mn/DOT Construction and Materials, Counties, Cities, Consultants, FHWA, Hot Mix Asphalt (HMA) Contractors and a Consultant hired as a technical advisor. The Task Force was charged with the goal to “Develop and Implement a Quality Management Program to Assure Construction of Quality Asphalt Pavements”. This was the beginning of a continuous evolution which has and will continue to guide the production and placement of HMA Mixtures.
Today the key components of the program are: 1. Volumetric Quality Control(QC), Quality Assurance (QA) and Independent Assurance Sampling and Testing (IAST) 2. Technical Certification 3. Plant Certification 4. Incentives/ Disincentives 5. Program Evaluation through Data Analysis 6. An Issue Resolution Policy
Design and Implementation of a Dynamic Quality Management System for HMA: A Case Study
Authors: Weigel JJ , Cominsky RJ , Moulthrop JS 
Published: March 2009

One of the items identified during the AASHO Road Test, constructed in Ottawa, Illinois in the late 1950's, was the variability of materials, the effects of this variation on material properties and, subsequently, the performance of various construction items. These activities had a marked influence on the development of assurance specifications during the last 30 years. These specifications, while recognizing variability in sampling and testing and establishing means to evaluate their effects, also clearly delineate the quality management responsibilities of the contractor during the construction process and the acceptance procedures of the agency.
The objective of this paper is to document an effective quality management system for an HMA contractor that has been used since 1989 on numerous projects and the steps taken to design and implement such a program.
This paper discusses the essential aspects of the QM Program and the actions required by the contractor's key management personnel in implementing the program. These include planning, budgeting, equipment acquisition and training. The program was intentionally designed to be dynamic so that changes that occur because of job conditions can be easily handled.
Specific attention is given to the unit costs associated with the implementation process and the elements of an effective company-wide training effort.
The Use of Falling Weight Deflectometer in Asphalt Pavement Construction Quality Control
Authors: Zaghloul SM , Saeed NA 
Published: March 2009

Good quality control (QC) practices are essential to obtain satisfactory pavements. Typical QC tests for asphalt pavements include: asphalt content, mixture properties of laboratory samples, density, …, etc. Results of these tests are used to ensure that the constructed pavements comply to specifications. However, quality of compliance to specifications and quality performance are two different things and are not always directly related to each other. The ultimate goal of QC is to have high quality of performance. However, efforts are made to achieve this goal by using laboratory based specifications, which are empirically related to field performance.
Current specifications are based on standard conditions which can be easily controlled in the laboratory but never exist in the field. Also, laboratory tests are run on samples representing individual layers (such as surface, base, etc.). In real life, a pavement structure performs as one unit and failure in one layer could happen because of another layer. Therefore, a performance-based specification that describes how a pavement must perform under the actual field conditions should be considered.
A study is underway in the Dubai Municipality (DM), U.A.E., to develop a procedure in which the falling weight deflectometer (FWD) is used to evaluate the in situ structural capacity of new pavements. FWD testing is conducted on each layer before constructing the next layer. Comparisons between the FWD test results and target deflection values are made to evaluate the construction quality of layers, as well as to identify weak spots. In this paper, the outline of this procedure is presented. Also, the results of a pilot study conducted to evaluate the procedure are presented.
Effects of Loading Rate on Creep Crack Growth During the Succeeding Load-Hold Period Under Trapezoidal Fatigue Waveshapes
Authors: Yoon KB , Baek UB , Suh CM 
Published: March 2009

When turbines are started up in power plants, the procedures recommended by the manufacturer should be carefully followed. However, many utilities often start turbines so fast that they accelerate the crack growth of existing cracks. Hence, in order to accurately predict the crack growth life of a turbine rotor, a crack growth prediction model is needed in which the effects of load increase time on the crack growth rate during the succeeding load hold period are considered.
In this study, creep-fatigue crack growth tests were performed at 538°C using C(T) specimens of 1Cr-1Mo-0.25V rotor steel. Triangular and trapezoidal fatigue waveshapes with 0.5, 1, 10, and 100-s load rise times and 100-s load hold times were employed. The time-dependent crack growth rate during the load hold period, (da/dt)avg, was correlated with estimated (Ct)avg. Large data scatter was observed due to the effect of various load increase rates reaching the hold load. A new Ct, estimation equation was proposed in which the effects of load increase rate are considered. The effectiveness of the proposed equation is argued by showing that the scatter of the measured (da/dt)avg data was reduced when the new equation was adopted. Also, characteristics of the initial transient crack growth behavior are studied and show that the cause is the oxidation-dominated crack growth mechanism during the transient period.
Thermal Fatigue Testing System for the Study of Gamma Titanium Aluminides in Gaseous Environments
Authors: Gao M , Dunfee W , Miller C , Wei RP , Wei W 
Published: March 2009

To critically assess the thermal fatigue resistance of γ-titanium aluminides in hydrogen and other gases, a thermal fatigue test system and associated procedures were developed. The test equipment consisted of an environmental chamber, a rigid test fixture with fixed grips, and a thermal controller. Direct electrical resistance heating was used to heat the specimen, and cooling was accomplished by a chilled gas jet. Characterization of the thermal-mechanical features of the equipment showed that the system allows for rapid heating and cooling rates with acceptable control of the thermal stresses and has excellent repeatability between cycles.
Proof tests were performed on a Ti-48Al-2Cr alloy in helium, hydrogen, and air, with temperature cycling between 25 and 900°C and a preload equal to 50% of the material's yield strength. The results showed that the equipment and test method developed here are an effective tool for material evaluation, specifically for the critical assessment of materials for high temperature applications in hydrogen and hydrogenous gases.
The B&W Owners Group Program for Microstructural Characterization and Radiation Embrittlement Modelling of Linde 80 Reactor Vessel Welds
Authors: Pavinich WA , Harbison LS 
Published: March 2009

The Babcock and Wilcox Owners Group (B&WOG) is sponsoring an on-going study to develop an understanding of radiation embrittlement of Linde 80 reactor vessel welds from a micro-mechanical viewpoint. Previous work that focused on characterizing the large microstructural features indicated that a large portion of the bulk copper content is in precipitate/inclusion/carbide form. This result indicates that copper in solid solution is considerably less than the bulk composition. Field-ion microscope atom probe investigations on unirradiated weld metals with bulk copper contents ranging from 0.22 to 0.38 wt%, also indicate significant amount of copper are tied up in precipitate/inclusion/carbide form. This results is significant since the bulk copper content (which includes both copper in solid solution and copper contained in precipitates, inclusions, and carbides) is used in Regulatory Guide 1.99, Revision 2 to determine radiation damage. This paper reviews these results.
Existing radiation embrittlement models superpose the changes in yield strength due to defect clusters and copper-rich precipitates induced by neutron irradiation. Low-copper Linde 80 welds display little or no increase in the 41 joule (30 ft-lb) transition temperature as a result of neutron irradiation which indicates that precipitation is the dominant component of radiation embrittlement for Linde 80 welds. Future work will include further microstructural characterizations of Linde 80 reactor vessel welds and applying the existing radiation embrittlement models to Linde 80 welds. This paper describes the detailed plans for future work.
The Modelling of Irradiation Embrittlement in Submerged-Arc Welds
Authors: Bolton CJ , Buswell JT , Jones RB , Moskovic R , Priest RH 
Published: March 2009

Until very recently, the irradiation embrittlement behaviour of submerged-arc welds has been interpreted in terms of two mechanisms, namely a matrix damage component and an additional component due to the irradiation-enhanced production of copper-rich precipitates.
However, some of the weld specimens from a recent accelerated re-irradiation experiment have shown high Charpy shifts which exceeded the values expected from the measured shift in yield stress. Microstructural examination has revealed the occurrence of intergranular fracture (IGF) in these specimens, accompanied by grain boundary segregation of phosphorus.
Theoretical models were developed to predict the parametric dependence of irradiation-enhanced phosphorus segregation on experimental variables. Using these parametric forms, along with the concept of a critical level of segregation for the onset of IGF instead of cleavage, a three mechanism trend curve has been developed. The form of this trend curve, taking into account IGF as well as matrix and copper embrittlement, is thus mechanistically based. The constants in the equation, however, are obtained by a statistical fit to the actual Charpy shift database.
A Microstructural Study of Phosphorus Segregation and Intergranular Fracture in Neutron Irradiated Submerged-Arc Welds
Authors: Bischler PJE , Wild RK 
Published: March 2009

Accelerated irradiation experiments have been carried out on submerged-arc welds to obtain validation of trend curves built up from surveillance results. This was done by withdrawing surveillance specimens and re-irradiating them in higher flux positions. One batch, from weld HS, showed a significantly higher increase in the Charpy ΔT40J value than that for weld LS at a similar dose. Work done to explain this difference is described in this paper.
Selected Charpy specimens were examined using a shielded scanning electron microscope to determine the fracture modes present. Regions of mixed cleavage, micro-void coalescence (MVC) and intergranular failure (IGF) were found on HS weld specimens fractured in the transition region. The IGF was confined to certain regions within each weld bead. Significantly less IGF was found on LS weld specimens. Upper shelf specimens from both welds showed a fully ductile MVC fracture structure.
Sub-fracture surface ‘matchstick’ specimens were removed from embrittled regions and fractured within a scanning Auger microscope. IGF occurred in these specimens, and phosphorus was found to be the main grain boundary segregant. The levels of phosphorus increased with increasing neutron dose. No other embrittling element was consistently found at any significant level, but carbon was also found on grain boundary surfaces in some cases. The grain boundary coverage of phosphorus was determined for each weld at several neutron dose levels. These results have been compared with previous data obtained from surveillance dose specimens and some start-of-life data.
Uncertainty Evaluation in Transition Temperature Measurements
Authors: Brillaud C , Augendre H , Bethmont M 
Published: March 2009

The pressure vessel surveillance program is mainly based on the transition temperature change assessment, a change which is induced by neutron irradiation. Uncertainties in Charpy test measurements are well known; however, we are less familiar with uncertainties due to general procedures governing experiments, which can be significant and therefore must be taken into account. In fact, procedures specify neither the number of specimens needed to obtain a transition curve, nor the choice of test temperatures, nor the fitting method for the transition curve.
A study has been conducted to determine the influence of the experimental procedure on the accuracy of transition temperature determination, and the initial results are presented in this paper. Two EDF laboratories performed Charpy tests on the surveillance program reference metal, using 8, 16, 24, 32 and 64 specimens to evaluate how the number of specimens affects the transition temperature. The influence of the scatter of mechanical properties has also been studied at two levels of irradiation. We have evaluated the effect of different sampling strategies and investigated a new fitting method, which is based on a simultaneous fitting of all curves with common constraints on parameters.