bluuebunny/crossref_metadata_2025 huggingface dataset:
Research to Understand the Embrittlement Behavior of Yankee/BR3 Surveillance Plate and Other Outlier RPV Steels
Authors: Fabry A , Van de Velde J , Puzzolante JL , Van Ransbeeck T , Verstrepen A , Biemller EC , Carter RG , Petrova T
Published: March 2009

The reactor pressure vessels at the Yankee Rowe and Belgian BR3 nuclear plants were constructed by Babcock & Wilcox in 1958. The plates of an open-hearth fabrication were welded using a submerged-arc process with Linde 80 flux as the filler. The original surveillance programs at the two plants were limited to representative A302B specimens; they feature similar chemistries as the ASTM reference plate, but coarser microstructure. The present testing program includes sixteen Charpy-V and four tensile specimens of the surveillance plate, irradiated at BR3 at a dose rate of ≈ 7 E10 cm−2.s−1 (>1MeV) over a period of 25 years; the investigation also addresses annealing and notch orientation effects. The new experimental results are compared to previously published data for the same and/or related melts. The Yankee/BR3 surveillance plate displays an anomalously large 41J Cv-shift as compared to the ASTM reference plate and to Regulatory predictions. Some of the Linde 80 welds investigated by the BR3 program are also found to behave as outliers. The data are evaluated in the light of state-of-the-art damage modeling and fracture micro-mechanics concepts, which are currently being incorporated into a new, consolidated strategy for improved RPV surveillance. The approach makes extensive use of the information contained in the load-deflection response of the instrumented Cv test. The implications of such analysis in terms of RPV steel embrittlement trend curve development are discussed.
Electron Microscopy and Small Angle Neutron Scattering Study of Precipitation in Low Alloy Steel Submerged-Arc Welds
Authors: Williams TJ , Phythian WJ
Published: March 2009

In previous studies, submerged-arc welds with a range of compositions were irradiated in test reactors over a range of dose and dose-rates. The effect of irradiation was measured by Charpy V-notch and hardness tests, and an irradiation response model was developed. In this paper we report the results of a combined electron m icroscopy and small angle neutron scattering (SANS) study on material from some of the Charpy specimens. The results have been interpreted in terms of the Russell and Brown modulus hardening model. In general they have confirmed the predictions of the irradiation response model, and shown that the copper precipitation contribution to the observed macroscopic hardening is strongly dependent on nickel, dose and dose-rate.
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.
Effects of Annealing Time on the Recovery of Charpy V-Notch Properties of Irradiated High-Ccopper Weld Metal
Authors: Iskander SK , Sokolov MA , Nanstad RK
Published: March 2009

Charpy Impact Response of RPV SteelsABSTRACT: One of the options to mitigate the effects of irradiation on reactor pressure vessels is to thermally anneal them to restore the toughness properties that have been degraded by neutron irradiation. An important issue to be resolved is the effect on the toughness properties of reirradiating a vessel that has been annealed. This paper describes the annealing response of irradiated high-copper submerged-arc weld HSSI 73W. For this study, the weld has been annealed at 454°C (850°F) for lengths of time varying between 1 and 14 days. The Charpy V-notch 41-J (30-ft-lb) transition temperature (TT41J) almost fully recovered for the longest period studied, but recovered to a lesser degree for the shorter periods. No significant recovery of the TT41J was observed for a 7-day anneal at 343°C (650°F). At 454°C for the durations studied, the values of the upper-shelf impact energy of irradiated and annealed weld metal exceeded the values in the unirradiated condition. Similar behavior was observed after aging the unirradiated weld metal at 460 and 490°C for 1 week.
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.
Reconstitution: Where Do We Stand?
Authors: van Walle E
Published: March 2009

A comprehensive review of the status of the reconstitution technique, as applied to reactor pressure vessel steel, is given. The reconstruction techniques in use at this moment on different small-size specimen geometries are highlighted, and the reconstitution methodology is evaluated. The advantages and limitations of reconstituted specimens are discussed, in relation to preparation and material conditions and in view of the test techniques to be used. For plant life management issues, the importance of finding an indexing parameter independent of the reconstitution process will be indicated.
Variations in Charpy Impact Data Evaluated by a Round-Robin Testing Program — A Summary
Authors: Lowe AL
Published: March 2009

A round-robin type test program was designed to quantify some of the variables associated with Charpy impact test data. Each participant tested pre-ma-chined specimens at each of six designated test temperatures. The data were evaluated using several techniques normally used to determine transition region temperatures and upper-shelf energies. These data were interpreted statistically to determine mean values and standard deviations. Variations in data appear to be more a factor of the specimen location within the material than related to test temperature. The variations in the data between the different testing participants were within the limits commonly observed. The expected erosion determining the 30 and 50 ft-lb transition temperatures and the upper-shelf energies were found to be independent of the evaluation technique used.
The Embrittlement Data Base (EDB) and Its Applications
Authors: Wang JA , Kam FBK , Stallmann FW
Published: March 2009

Investigations of regulatory issues, such as vessel integrity over plant life, vessel failure, and plant license renewal, can be greatly expedited by the use of a well-designed computerized data base. Also, such a data base is essential for the validation of embrittlement prediction models by researchers. The EDB is this comprehensive collection of data resulting from the merging of the Power Reactor Embrittlement Data Base (PR-EDB) and the Test Reactor Embrittlement Data Base (TR-EDB). The current version of the PR-EDB lists the test results of 98 heat-affected-zone (HAZ) materials, 105 weld materials, and 136 base materials that were irradiated in 252 capsules from 96 power reactors. The current data collection of the TR-EDB contains 1230 different irradiated sets, 797 of which are from base materials, 378 from welds materials, and 55 from HAZ materials. The data files are given in dBASE format and can be accessed with any personal computer using the DOS operating system. The different types of data that are implemented or planned for EDB are discussed. “User-friendly” utility programs have been written to investigate a variety of problems using this data base. The results of several studies, which include the parameter study of the chemistry composition effect on radiation embrittlement, the irradiation temperature effect on radiation embrittlement, vendor-specific embrittlement model, etc., are presented in this paper.
On the Effect of Flux and Composition on Irradiation Hardening at 60°C
Authors: Odette GR , Lucas GE , Klingensmith RD , Stoller RE
Published: March 2009

A large matrix of simple alloys and complex commercial type steels was irradiated over a range of fluxes at 60°C up to a fast fluence of about 3×1022 n/m2. Combined with data in the literature, these results show a negligible effect of flux on irradiation hardening in the range of 2×1013 to 5×1018 n/m2-s. This observation lends indirect support to the proposal that the accelerated embrittlement in the High Flux Isotope Reactor surveillance steels was due to an anomalously high level of damage from gamma rays. A weak dependence of hardening on a number of elements, including copper, nickel, phosphorous, molybdenum and manganese, can be described by a simple empirical chemistry factor. Particular combinations of elements resulted in hardening differences of up to about 60% in the complex commercial type steels and up to about 100% in simple model alloys. Direct effects of microstructure appear to be minimal. Hardening varies with the square root of fluence above a threshold around 4×1020 n/m2. The results suggest that low temperature hardening is dominated by local intracascade processes leading to the formation of small defect-solute clusters/complexes. The observed hardening corresponds to nominal maximum end-of-life transition temperature shifts in support structure steels of about 120°C.
The Dependence of Radiation Hardening and Embrittlement on Irradiation Temperature
Authors: Jones RB , Williams TJ
Published: March 2009

Assessments of the hardening and embrittlement of pressure vessel steels and welds as a function of neutron dose use trend curves derived from surveillance programmes and accelerated irradiation data. A temperature dependent factor is incorporated for assessing vessel locations operating at different temperatures. As hardening and embrittlement arise from the sum of matrix damage and copper impurity precipitation, the influence of irradiation temperature on each process needs to be established. For irradiations performed below ~300°C recent data shows that the dose-dependent growth of copper precipitates ceases at a mean diameter of about 2 nm that also corresponds to peak hardening and embrittlement by copper. For doses beyond this peak copper dose the property-dependence on irradiation temperature can be identified with that of matrix damage alone. An analysis of several experiments on plate steels, performed at differing irradiation temperatures, has permitted the temperature dependence of matrix hardening to be defined by the simple empirical factor FT=1.869-4.57×10-3T where T is the irradiation temperature. When a linear correlation between irradiation hardening and embrittlement is observed, then FT can be used to analyse the temperature dependence of matrix embrittlement. The validity of using FT in successfully correlating irradiation results has been demonstrated for several plate steels and welds with differing copper contents.
The Influence of Metallurgical Variables on the Temperature Dependence of Irradiation Hardening in Pressure Vessel Steels
Authors: Odette GR , Lucas GE , Klingensmith RD
Published: March 2009

Yield stress elevations (Δσy) in pressure vessel steels irradiated at intermediate flux and fluence systematically decreased with increasing temperature and decreasing copper and nickel content. Lower stress relief temperature also decreased Δσy at bulk copper concentrations greater than about 0.3%. The dependence of Δσy on irradiation temperature between 260 and 316°C increased with copper and nickel content and decreased with phosphorous content. When normalized by the average Δσy, the fractional temperature dependence correlates with a simple empirical chemistry factor of copper and phosphorous. The correlation predicts data on the irradiation temperature dependence of Δσy found in the literature within a standard error of about 0.3 MPa/°C and is consistent with current understanding of hardening mechanisms. However, questions remain about the effects at very low flux and finer scale variations over smaller temperature intervals.
Ductile Fracture Mechanisms in an A302B Modified Reactor Pressure Vessel Steel
Authors: Cuddy LJ , Manahan MP , Brauer G , Martinko J
Published: March 2009

It has been demonstrated that thermal cycling of a previously quenched and tempered reactor pressure vessel (RPV) steel induces a hardness increase equivalent to an increase in flow stress of about 70 MPa. Single cycle heat treatments produce no such changes in hardness, flow stress, ductility or upper shelf energy (USE). Equivalent cycles will occur during reactor operation and may thus contribute to the observed changes during service of the properties of RPV steels. Preliminary microstructural examination offered no clear explanation for these effects, although it was observed that thermal cycling induced decomposition of retained austenite. It is demonstrated that, should the defects involved be shearable defects similar to those introduced by irradiation, they would promote ductile fracture by enhancing the growth and linking of microvoids and thus contribute to a drop in USE.

An analysis was performed which demonstrates that, of the several defects of the shearable type produced during irradiation of steels, vacancy clusters (or voids) are unstable with respect to both individual vacancies and collapsed vacancy loops. Thus, the latter defect and depleted zones would be the predominant vacancy hardening defects. Since irradiation produces both shearable (Cu/Ni/Mn rich precipitates, depleted zones, and loops) and non-shearable (Mo2C) hardening defects, it is important to resolve whether the shearable or non-shearable contribution is greater in order to be able to adequately model the effect on ductile fracture. For this purpose, a study of light water reactor (LWR) surveillance tensile data trends was performed and the results show negligible copper dependence of the yield strength change on fluence for fluences less than the boiling water reactor (BWR) end-of-license (EOL) fluence. These trends also show that the change in strain hardening behavior for U.S. steels is also negligible which indicates that shearable particles are the primary defect responsible for hardening. In addition to the Charpy curve shift, the shearable obstacles also cause a shelf drop during the strain controlled ductile fracture process. Rather than diffusing strain by slip plane hardening, as with non-deformable particles, shearable obstacles cause localization of strain in the unhardened slip plane. Strain localization in ligaments between voids leads to premature ligament failure in the irradiated material by the flow localization mechanism of void linkage.
Fracture Toughness Test Results of Thermal Aged Reactor Vessel Materials
Authors: DeVan MJ , Lowe AL , Hall JB
Published: March 2009

Thermal-aged surveillance materials consisting of SA-533, Grade B, Class 1 plate material; SA-508, Class 2 forging material; and 2 Mn-Mo-Ni/Linde 80 weld metals were removed from two commercial reactor pressure vessels. The material from the first reactor vessel received a thermal exposure of approximately 103,000 hours at 282°C (540°F), while the material from the second reactor vessel received a thermal exposure of approximately 93,000 hours at 282°C (540°F). Tensile and 1/2T compact fracture toughness specimens were fabricated from these materials and tested. In addition, to examine the effects of annealing, selected thermal-aged and unaged specimens were annealed at 454°C (850°F) and tested. Varying responses in the fracture toughness properties were observed for all materials after exposure to the thermal-aging temperature. The base metal plate had an observed decrease in J-values after its respective aging exposure, while no significant difference in the J-values were observed for the Linde 80 weld metals. No significant difference was seen in the J-data for the aged/annealed materials, but because of the small number of test specimens available, no conclusion could be determined for the response to annealing.
Influence of Thermomechanical Treatment on Irradiation Microstructures in an ODS Ferritic Steel
Authors: Little EA
Published: March 2009

The effects of thermomechanical treatment on microstructural changes and void swelling in a DT2203YO5-grade 13%Cr oxide-dispersion-strengthened (ODS) ferritic alloy have been studied following ion irradiations to a damage level of 50 dpa at 475°C with 600 appm helium gas implantation. Swelling in a solution treated and aged (STA) condition ranges from 0.07 to 0.24% due to cast-to-cast variations, whilst in a solution treated, cold-worked and aged (STCWA) condition the swelling decreases to 0.025%. Cavities are in general irregularly shaped, non-uniformly distributed and frequently attached to small yttria dispersoid particles.

The results confirm that this ODS ferritic steel exhibits low irradiation-induced swelling in the presence of high gas concentrations, as required for advanced fast and fusion reactor applications. The observed sensitivity of irradiation-induced swelling to compositional or processing variables implies that ODS ferritic alloys can be further optimized for high radiation resistance.
Effect of Boron on Post Irradiation Tensile Properties of Reduced Activation Ferritic Steel (F-82H) Irradiated in HFIR
Authors: Shiba K , Suzuki M , Hishinuma A , Pawel JE
Published: March 2009

Reduced activation ferritic / martensitic steel, F-82H (Fe-8Cr-2W-V-Ta), was irradiated in the High Flux Isotope Reactor (HFIR) to doses between 11 and 34 dpa at 400 and 500°C. Post irradiation tensile tests were performed at the nominal irradiation temperature in vacuum. Some specimens included 10 B or natural boron (nB) to estimate the helium effect on tensile properties.

Tensile properties including the 0.2% offset yield stress, the ultimate tensile strength, the uniform elongation and the total elongation were measured. The tensile properties were not depend on helium content in specimens irradiated to 34 dpa; however 10 B-doped specimens with the highset levels of hilium showed slightly higher yield strength and less ductility than boron-free specimens. Strength appears to go through a peak, and ductility through a trough at about 11 dpa. The irradiation to more than 21 dpa reduced the strength and increased the elongation to the unirradiated levels.
Irradiation Effects on Base Metal and Welds of 9Cr-1Mo (EM10) Martensitic Steel
Authors: Alamo A , Séran JL , Rabouille O , Brachet JC , Maillard A , Touron H , Royer J
Published: March 2009

The effects of fast neutron irradiation on the mechanical behaviour of base metal and welds of 9Cr-1Mo (EM10) martensitic steel have been studied. Two types of weldments have been produced by TIG and electron beam techniques. Half of samples have been post-weld heat treated to produce a stress-relieved structure. The irradiation has been conducted in the Phenix reactor to doses of 63 – 65 dpa in the temperature range 450 – 459 °C. The characterization of the welds, before and after irradiation, includes metallographic observations, hardness measurements, tensile and Charpy tests. It is shown that the mechanical properties of the welds after irradiation are in general similar to the characteristics obtained on the base metal, which is little affected by neutron irradiation.
Microstructural Evolution of Austenitic Stainless Steels Irradiated in a Fast Reactor
Authors: Borodin OV , Bryk VV , Voyevodin VN , Neklyudov IM , Shamardin VK , Neystroev VS
Published: March 2009

Analysis of the microstructure of the stainless steels 16Cr15Ni3MoNb and 18Cr10NiTi, irradiated at temperatures where changes in phase stability occur due to radiation-induced segregation, shows that the stability of second-phase particles depends on the structure of particle-matrix interface.
Irradiation Hardening and Loss of Ductility of Type 316L(N) Stainless Steel Plate Material Due to Neutron-Irradiation
Authors: Horsten MG , de Vries MI
Published: March 2009

Type 316L(N) stainless steel plate material has been irradiated up to 10 dpa at temperatures of 80, 225, 325, and 425°C in the High Flux Reactor (HFR) of Petten. Tensile tests have been performed in the temperature range from RT to 575°C at a conventional strain rate of 5×10−4 s−1. The results of the tensile tests are analyzed in terms of irradiation hardening and loss of ductility due to irradiation. Tensile properties saturate in the early stage (within 0.65 dpa) at the lowest applied irradiation temperature. It is indicated that the most severe degradation of tensile ductility occurs in the temperature range of 275 to 350°C. Comparison with literature data revealed a large scatter in irradiation hardening at irradiation temperatures above 325°C.
Fatigue Crack Propagation by Channel Fracture in Irradiated 316 Stainless Steel
Authors: Jitsukawa S , Hishinuma A , Suzuki M
Published: March 2009

Fatigue crack growth rates (da/dN)in an irradiated cold worked 316 stainless steel were obtained at temperatures of 298, 573 and 673 K. Specimens were prepared from a duct material, which irradiated at 683 K to 20 displacements per atom in an experimental fast breeder reactor.

Fatigue loading caused channel fracture to occur in the irradiated material. This was accompanied by acceleration of da/dN. Both the increment of da/dN and the fraction of channel fracture in fracture surface became larger with stress intensity factor range at temperatures of 573 and 673 K, but they were not at 298 K. Results indicate that irradiation induced channel fracture increased da/dN.
Data Collection on the Effect of Irradiation on the Mechanical Properties of Austenitic Stainless Steels and Weld Metals
Authors: Tavassoli A-A , Picker C , Wareing J
Published: March 2009

Data on the influence of low dose 400–550°C irradiation on the mechanical properties of structural steels (Types 304, 316, 316L, 316H and 316L(N) and associated weld metals) at temperatures from 20°C to 750°C, have been compiled from published literature and the results of British, Dutch, French and German laboratories. Properties evaluated include tensile, impact, creep, fatigue, and creep-fatigue. The preliminary results, which cover the dose range from 0 to 5 displacements per atom (and/or up to 9 appm helium) are presented as comparisons between irradiated and unirradiated control data, covering a range of strength and cyclic properties. The results show that low dose irradiation can have a significant influence on the properties, i.e.:• increases in tensile proof strength,• reductions in tensile ductility,• decreases in impact energy,• reductions in creep-rupture strength and ductility, and • reductions in creep-fatigue endurance.

By considering the influence of irradiation temperature and dose level, the results are rationalised in terms of irradiation hardening and grain boundary embrittlement mechanisms.
Bubble Microstructure Evolution and Helium Behavior in He+ Implanted Ni-Base Alloys
Authors: Kalin BA , Chernov II , Kalashnikov AN , Solovyev BG
Published: March 2009

Behavior of ion-implanted helium in Ni as a function of alloying element concentration (Al or Ti) and irradiation conditions (at 20 or 750°C) have been investigated by means of thermal desorption spectrometry (TDS) and transmission electron microscopy (TEM).

Substitution elements in solid solution were demonstrated to have substantial influence on the evolution of implanted helium, shifting the TDS spectrum peaks to higher temperature region and increasing the quantity of helium remaining in the samples after long-time postirradiation annealing. TEM investigations showed that in the case of postirradiation annealing, helium bubbles are formed earlier in quenched alloys than in those annealed. In the high-temperature irradiated alloys, the bubbles formed are smaller in size and higher in density than in the case of postirradiation annealed samples irradiated at room temperature. Alloying elements reduce bubble diameter and increase bubble number density. This is especially typical for concentrations of alloying elements that exceed the ultimate solubility in nickel.
Swelling and Structure of Vanadium-Base Alloys Irradiated in the Dynamic Helium Charging Experiment
Authors: Chung HM , Loomis BA , Smith DL
Published: March 2009

Combined effects of dynamically charged helium and neutron damage on density change, void distribution, and microstructural evolution of V and V-4Cr-4Ti alloys have been determined after irradiation to 18–31 dpa at 425–600°C in the Dynamic Helium Charging Experiment (DHCE). The results were compared with those from a non-DHCE in which helium generation was negligible. For V-4Cr-4Ti specimens irradiated to ≈18–31 dpa at 425, 500, or 600°C with a helium generation rate of 0.4–4.2 appm helium/dpa, only limited number of helium bubbles were observed either at some Ti(O,N,C) precipitate interfaces, in localized regions of grains, or near grain boundaries. Neither extensive coalescences of helium bubbles on grain boundaries, typical of some alloys irradiated in tritium-trick experiments, nor dense helium bubbles within grains, typical of unalloyed V or alloys not containing Ti, were observed. Under the conditions of DHCE, most of dynamically produced helium atoms seem to be trapped by irradiation-induced defects and defect clusters within grains or fine Ti5Si3 precipitates, which prevents significant bubble nucleation or growth. Density changes measured on specimens irradiated in DHCE or non-DHCE were low (<0.5%) for all the irradiation conditions investigated (425–600°C, 18–34 dpa, and <4.2 appm He/dpa).
Corrosion Response of Pre-Irradiated Zr-2.5Nb Pressure Tube Material
Authors: Urbanic VF , Griffiths M
Published: March 2009

Out reactor corrosion testing of Zr-2.5Nb pressure tubes in moist air at 573 K has shown that the pre-irradiated samples, i.e. those fabricated from tubes removed from power reactors, were more corrosion resistant than their unirradiated counterparts. The pre-irradiated materials had lower pre-transition corrosion rates, longer times to transition and lower post-transition rates than unirradiated material. As the samples were prepared equally in each case by polishing to bare metal, it is clear that the microstructural changes produced during irradiation are responsible for the improved corrosion response. For this reason X-ray diffraction (XRD) and analytical electron microscopy (AEM) have been used to characterise microstructural and microchemical changes produced by neutron irradiation of Zr-2.5Nb pressure tubes during service.

There is a positive effect of irradiation in improving the corrosion response down to fluences of at least 1×1025 n/m2 (E>1 MeV). However, despite the reduction in corrosion, the amount of deuterium absorbed, as a fraction of the total deuterium generated by the corrosion process, was about ten times higher for the irradiated material than for the unirradiated material.

The results of the analyses indicate that improvements in corrosion behaviour may be linked with decreases in the Nb concentration in the α-Zr matrix due to Nb precipitation during irradiation. However there is no clear indication as to the cause of the increased deuterium uptake.
Environmental Stress Cracking and Solvent Effects in High-Performance Polymeric Composites
Authors: Parvatareddy H , Heithoff C , Clifton AP , Dillard DA , Kander RG
Published: March 2009

The environmental stress cracking (ESC) behavior of three carbon fiber-reinforced high-performance thermoplastic composite systems and a thermoplastic toughened thermoset composite system, in the presence of organic solvents, was investigated. Three-point bending/ flexure tests were conducted on [90°]4s (unidirectional) composite coupons. Results from the flexure tests showed a 10 to 30% drop in the bending strength of the composite specimens when solvents were applied just prior to the testing. Scanning electron micrographs of the fracture surfaces show differences in the failure modes as well as the microstructure. ESC was observed in the cross-ply specimens after solvent exposures from an hour up to a day, in the absence of external mechanical loads due to residual stresses. The effect of different solvents on the polymers and the resulting ESC phenomena could partially be explained by the differences in the solubility parameters of the concerned solvents and polymers.
Damage Mechanics on Hydrothermal-Aged Fiber-Reinforced Plastics (FRP)
Authors: Hamada H , Maekawa Z-i , Morii T , Tanimoto T , Yokoyama A
Published: March 2009

The elastic modulus of randomly oriented, glass fiber mat reinforced plastics after hydrothermal aging was estimated introducing finite element analyses and the damage mechanics. The debonding between fiber and matrix of the hydrothermal aged fiber-reinforced plastics (FRPs) was dealt with as the internal damage, and the damage mechanics were introduced to the finite element analyses. The damage angle around the fiber greatly affected the modulus reduction of the aged FRPs independent of the damage thickness. The internal damage of the aged FRPs was determined quantitatively by the weight loss due to water immersion, and the modulus of the aged FRPs was calculated by the finite element analysis introducing the damage parameter. The calculated results corresponded well to the experimental results, and it was analytically clarified that the modulus reduction of the aged FRPs was caused by the occurrence of the debonding between fiber and matrix.
Characterization of Localized Failure Modes in Honeycomb Sandwich Panels Using Indentation
Authors: Tsotsis TK , Lee SM
Published: March 2009

The indentation behavior of aircraft floor panels (honeycomb sandwich structures) was investigated from the viewpoints of test methodology, effects of panel construction, and failure mechanisms. An indentation test method using a simply-supported plate was developed to replicate observed in-use failure modes. The localization and type of damage induced with this test method correlated extremely well with damage present in panels returned from airlines suggesting that highly-concentrated loads, such as from high heels, cause most panel damage. Furthermore, damage appeared to spread due to an accumulation of multiple damage events more so than propagating from only a few. Both aramid- and aluminum-cored panels showed failures that occurred just below the resin fillet on the top skin. Aramid failed in brittle compression and post-buckling whereas aluminum failed due to ductile buckling. These results strongly indicate that near-surface properties dominate indentation behavior in contrast to the core-dominated stabilized core compression test as well as the skin-dominated failure criteria used in ASTM-type impact tests. Indentation tests using various skin and core constructions demonstrated the influence of changing core density, core material, and skin construction as well as the synergistic effect of skin and core on indentation damage resistance. Several analytical models were examined to aid in understanding the failure mechanisms due to indentation. These suggest that large local skin deflections are important in local load redistribution leading to core failure.
Effect of Preform Architecture on Modulus and Strength of Two-Dimensional, Triaxially Braided, Textile Composite Materials
Authors: Masters JE , Minguet PJ
Published: March 2009

This paper investigates the mechanical response of two-dimensional, triaxially braided, textile composites from an experimental viewpoint. The specific objective of this study was to empirically define the role of the braid architecture in determining laminate mechanical properties. Three primary braiding parameters, that is, braid angle, 0° yarn content, and yarn size, were identified. A number of reinforcing fiber architectures were designed to provide a direct comparison of the effects of these parameters on mechanical performance. These parameters were varied over a wide range to establish data that reflect the full spectrum of viable braid architectures. Braid angle varied from 45° to 70°, 0° yarn content ranged from 12 to 46%, and yarn bundle size ranged from 6 thousand fibers per bundle to 75 thousand fibers per bundle. The laminates studied featured AS4 graphite fibers in Shell's 1895 epoxy matrix.

In addition, two secondary braiding parameters, 0° yarn spacing and yarn crimp, were also investigated. A set of laminates was designed to isolate the effects of these two parameters.

The effects of fiber architecture on the mechanical performance are thus further defined in the investigation. Experimental results will include measures of the materials' longitudinal and transverse tensile moduli, their Poisson's ratios, and their shear moduli. In addition, the effects of the textile preforms' architecture on laminate tensile strength will also be reviewed.
In-Phase Thermomechanical Fatigue of Metal Matrix Composites: Deformation Response and Progressive Damage Mechanisms
Authors: Newaz GM , Majumdar BS
Published: March 2009

An investigation was undertaken to characterize the deformation response of unidirectional SCS-6/Ti 15-3 metal matrix composite (MMC) lamina subjected to in-phase thermomechanical fatigue (TMF) loading. Evaluations were done in an inert atmosphere to avoid oxidation effects. It was found that the dominant effect on deformation was due to strain ratchetting. Distributed fiber cracking was found to be the primary damage mode in in-phase TMF. The early part of strain ratchetting was identified to be due to the viscoplastic response of the composite as fewer fiber cracks were found to develop at this stage in the MMC specimens. Early fiber cracks were found to occur near molybdenum (Mo) ribbon sites. The fiber-cracking process was determined to be progressive in nature. On qualitative grounds, the concept of fiber ineffective length and the zone of stress intensification at the neighboring fiber at temperature, as in the case of in-phase TMF, was consistent with the observation of progressive fiber cracking in the MMCs.
Constitutive Response and Deformation Mechanisms in Unidirectional Metal Matrix Composites Under Compression
Authors: Newaz GM
Published: March 2009

An investigation was undertaken to evaluate the constitutive response and in-elastic deformation characteristics in titanium-based metal matrix composites (MMC) with two types of ceramic fibers, namely, SCS-6 and Sigma. The titanium matrix was Beta 21S, currently named TIMETAL-21S. Monotonic tests were conducted at room temperature (RT) and between 483 and 815°C. The inelastic deformation in the [0]8 lamina under compression was controlled primarily by matrix plasticity, although some evidence of fiber-matrix debonding was observed. The inelastic deformation mechanisms under compression in [90]8 lamina were primarily due to radial fiber cracking from the core for the SCS-6 fiber and fiber-matrix debonding. However, for the Sigma fiber, radial cracking was absent. The effect of temperature on degradation of mechanical properties such as modulus and yield strength for the composites with two different fibers were compared.
Analysis of the Short-Beam Shear Test for Unidirectional Composites
Authors: Chatterjee SN
Published: March 2009

The stress field in the short-beam shear test specimen is very complex. Failure of the short beam (and every other shear specimen used to date) occurs due to a combination of multiple failure mechanisms, since a state of pure shear can not be achieved. However, test results for brittle unidirectional composites reported in the literature indicate that development of transverse (interlaminar) shear cracks cause specimen failure for a wide range of span-to-depth ratios. In this study, stress analyses have been performed for graphite and glass fiber-reinforced beams for various span-to-depth ratios. The results are correlated with test data reported in the literature, and it is shown that the failure loads for small span-to-depth ratios can be predicted based on the maximum shear stress at failure that may sometimes differ significantly from the apparent interlaminar shear strength obtained from beam theory. In addition, high transverse compressive stresses at critical locations, which provide frictional resistance to sliding, may increase the failure load resulting in a higher apparent shear strength. For larger span-to-depth ratios, a subcritical yield phenomenon due to compressive flexural stress may increase the maximum shear stresses and yield lower apparent shear strengths.
Design Allowables from Regression Models Using Data from Several Batches
Authors: Vangel MG
Published: March 2009

Regression analysis is useful when limited data on a material is obtained under various experimental conditions, and design allowables are required for certain (perhaps different) conditions. Since composite material properties typically exhibit considerable variability, and since composite material testing is expensive, the use of regression methodology for the efficient analysis of experimental data is even more important than for metals. However, test data for composites often come from several batches, with nonnegligible between-batch variability. The usual approach when confronted with such data is to combine all batches at each test condition, and then to use conventional regression methodology to determine allowables. This approach does not take the variability between batches into account, and, consequently, the allowables can be nonconservative. New methodology has been developed for regression allowables in the presence of between-batch variability that overcomes this limitation for a wide class of practical situations. This article discusses the interpretation of statistically-based design allowables, particularly for realistic situations where the data come from several batches over a test matrix of fixed conditions. A computer program (available from the author), which is an implementation of the new methodology, is used to analyze a set of graphite/epoxy compressive strength data.
A Systematic Approach to Representative Sampling in the Environment
Authors: Chai EY
Published: March 2009

In environmental sampling, samples are taken for the purpose of solving a problem in a target population. The problem may not be correctly solved if bias is present in the samples, in the measurement of the samples, and/or in the use of the sample data to make conclusions about the population. This paper discusses a systematic approach which considers all these potential sources of bias when attempting to obtain a representative set of samples for making inference about the population.
Worker Exposure During Environmental Sampling: The Hazards Involved
Authors: Lyons TJ , Knapik JP
Published: March 2009

As a result of the expansion of environmental site assessment (ESA) practice, there has developed a potential for field investigators to put themselves at risk from the materials being sampled or the site being investigated. The authors propose the development of a supporting standard to define the measures necessary to recognize, evaluate and control hazards which environmental professionals may encounter during investigative activities. Existing standards addressing environmental investigations and remediation work peripherally cite the importance of safe work practices while mandating procedures which may result in unnecessary or unknowing exposures. Federal and State regulations define what work is to be completed, and what goals are to be met but do not provide specific information on hazards to the workers involved. The authors illustrate this need through citation of various ASTM Standards, presentation of case studies and a recommended outline for development of a standard site safety and health plan.
Airborne Remote Sensing as a Tool for Monitoring Landfill Sites Within an Urban Environment
Authors: Hedges PD , Ellis RJ , Elgy J
Published: March 2009

The use of remote sensing imagery to facilitate the management of landfill sites in urban areas has, to date, been primarily confined to the use of conventional aerial photography. The potential of airborne video thermography, and the high resolution and the range of spectral bands offered by the Airborne Thematic Mapper (ATM) for monitoring landfill sites are under evaluation, with the ultimate aim of establishing an economic methodology that can be employed for rapidly surveying landfill sites within a large urban area. Detailed investigations of one urban landfill site in the West Midlands of the UK have been undertaken using ATM imagery and aerial photography obtained in 1992, and ATM imagery and thermography acquired in 1994. This work has enabled recommendations to be made regarding the techniques employed in monitoring by remote sensing which revolve around the use of the thermal infra-red band.
Investigating the Presence of Hazardous Materials in Buildings
Authors: Gustitus DA , Blaisdell PM
Published: March 2009

Environmental hazards in buildings can be found in the air, on exposed surfaces, or hidden in roofs, walls, and systems. They can exist in buildings in solid, liquid, and gaseous states. A sound methodology for investigating the presence of environmental hazards in buildings should include several components. The first step in planning an investigation of environmental hazards in buildings is to ascertain why the investigation is to be performed. Research should be performed to review available documentation on the building. Next, a visual inspection of the building should be performed to identify and document^ existing conditions, and all suspect materials containing environmental hazards. Lastly, samples of suspect materials should be collected for testing. It is important to sample appropriate materials, based on the information obtained during the previous steps of the investigation. It is also important to collect the samples using standard procedures.
ASTM Sampling Methods and Analytical Validation for Lead in Paint, Dust, Soil, and Air
Authors: Ashley K , Schlecht PC , Song R , Feng A , Dewalt G , McKnight ME
Published: March 2009

ASTM Subcommittee E06.23 on Abatement/Mitigation of Lead Hazards has developed a number of standards that are concerned with the sampling of lead in environmental media, namely paint, dust, soil and airborne particulate. An ASTM practice for the collection of airborne particulate lead in the workplace has been published. New ASTM standards for the collection of dry paint film samples, surface soil samples, and surface dust wipe samples for subsequent lead analysis have also been promulgated. Other draft standards pertinent to lead sampling are under development. The ASTM standards concerned with lead sample collection are accompanied by separate sample preparation standard practices and a standard analysis method. Sample preparation and analytical methods have been evaluated by interlaboratory testing; such analyses may be used to assess the efficacy of sampling protocols.
Municipal Solid Waste Sampling and Characterization
Authors: Brokaw WS , Hornberger GS
Published: March 2009

The character and composition of solid wastes need to be determined for a variety of objectives. These objectives include developing design criteria for resource recovery facilities, determining performance efficiency, and evaluating source reduction initiatives (e.g. recycling).

The techniques described in this paper are for the collection and characterization of municipal solid waste and can be employed at resource recovery facilities, transfer stations and sanitary landfills. The results have been used in conjunction with emissions testing and ash analyses to calculate a mass balance for an incinerator at a resource recovery facility.

The technique utilized is an adaptation of several related ASTM methodologies developed for sampling and analyzing refuse derived fuel. Representative waste samples are manually collected from trash collection vehicles (rolloff containers, compactor trucks, etc.) as they unload. The discrete samples are collected and composited during a predetermined period. Each composite sample is mixed and characterized on-site and a portion recovered and prepared for laboratory analyses.

A significant amount of data can be generated from the sampling such as the mass and percent of recyclable materials, heating value, and elemental composition (proximate and ultimate parameters). The sampling technique can be readily modified to obtain the desired data.
Use of Petrographic Analysis in Environmental Site Investigations: A Case Study
Authors: Mason JM , Gabriel WJ
Published: March 2009

Geologists conducting environmental site investigations in compliance with Federal and State regulations are often forced to rely on limited site and/or region specific geologic and hydrogeologic data. These sites are often located in industrial areas where surficial geologic features are obscured. The purpose of this paper is to describe the use of a simple, economical petrographic analysis method performed in conjunction with an environmental site investigation to better characterize subtle changes in subsurface geology. The method differentiates changes in rock type, classifies the rock samples, and provides detailed geologic descriptions for stratigraphic correlation. The results of the analyses were instrumental to understanding the site geology and ground water transport mechanisms.