bluuebunny/crossref_metadata_2025 huggingface dataset:
Prediction of End-Use Impact Resistance of Composites
Authors: Peraro JS
Published: December 2008

The ability to predict material behavior under impact loading is very important in the design and manufacture of products. To predict product performance adequately, it is important to simulate the conditions under which the material is used.

Traditional impact tests often fail to provide the data required to evaluate and predict behavior under impact stress. An instrumented multivariable high-rate impact tester is designed to provide this information. The instrument is capable of testing materials of almost any configuration at velocities from 0.0127 to 12.7 m/s (30 to 30 000 in./min) and in environments simulating service conditions. Electronic instrumentation and a sophisticated computerized microprocessor simplifies the gathering, processing, and calculation of the impact property data. The graphic and calculated values permit a detailed analysis of impact performance.

The high-rate impact tester used at Owens-Corning Fiberglas Corp. is described, with examples of test programs in which the instrument capabilities were utilized to simulate the impact forces on boat, pipe, and tire constructions. Modifications made to the ram, or mode of operation, better simulate end-use conditions.

The results adequately predict impact behavior experienced under service conditions within a laboratory environment. This provides the scientist with a means of observing the impact phenomenon under laboratory conditions. As new materials are developed, characterization can be accomplished rapidly and at minimum cost. Screening of candidate materials can be accomplished without the time-consuming and expensive process of producing a product and conducting in-service tests.

The information developed can be invaluable for improving existing products and developing new products. By observing the test and evaluating the traces obtained, one can identify potential weaknesses in a product, which can be corrected by redesign or substitution of alternative materials.
Impact Characterization of New Composite Materials
Authors: Gause LW , Buckley LJ
Published: December 2008

Drop-weight instrumented impact tests were used in conjunction with ultrasonic C-scan inspection to characterize the impact responses of several new graphitefiber composite material systems. The AS4/Hercules 3501-6 graphite/epoxy was compared with the newer AS4/Hercules 2220-1, Celion high-strain/Narmco 5245 and IM6/Narmco 5245C systems in the 394 K (250°F) service category. The materials tested in the 450 K (350°F) service category were T300/Avco 130B, T300/Hexcel 81-5, T300/U.S. Polymeric V378A, XAS/Hysol 9101-3, and HX/Hexcel 1516 graphite/bismaleimides. A material ranking is given, along with measured impact parameters and impact energy versus damage relationships. The impact behavior of all four 394 K (250°F) systems was similar, except that IM6/5245C had the highest impact resistance. The bismaleimides had incipient damage levels similar to those of the epoxies but were more easily punctured. The impact resistance of the five 450 K (350°F) systems was similar except that T300/130B had the lowest impact resistance.
Flexed-Plate Impact Testing of Polyether Sulphone: Development of a Notched Specimen
Authors: Turner S , Reed PE
Published: December 2008

In flexed-plate impact tests at room temperature, injection-molded disks of polyether sulphone could not be broken or penetrated by an impactor with an incident energy of 238 J. A central hole 1 mm in diameter was sufficient to embrittle a high proportion of the specimens subjected to the same impact. The failures could be segregated into three classes. A few subsidiary tests on thinned specimens with no hole suggest that in this particular molded form, and under the specific test conditions used, polyether sulphone has a tough-brittle transition within the thickness range of 1.4 to 2.0 mm.
Impact Fatigue of Polymers Using an Instrumented Drop Tower Device
Authors: Adams GC
Published: December 2008

Using low and constant-impact energy, a relatively simple method of impact fatigue has been devised to provide toughness measurements on polymers. Crystalline polymers, particularly the nylons and polyacetal, appear to have better fatigue performance than noncrystalline polymers. Fatigue curves that are normalized with the fracture area can potentially detect the influence of crystalline morphology on fatigue. Using retained energy values and fracture area measurements from each impact, an estimate of the fracture energy is obtained. The higher fracture energy values obtained in fatigue, over those obtained in single-blow impacts, indicate that different energy absorption processes occur in single- and multiple-impact testing.
Assessment of Impact Characteristics for Incipient Crack Formation in Polymeric Materials
Authors: Lee WM , Rieke JK
Published: December 2008

For many material applications, the evidence of a visible flaw (for example, a crack) can be regarded as the start of failure. It is important to determine the impact conditions for which incipient crack formation occurs. From the material design standpoint, it is essential to identify the key material properties governing this crack formation process. Therefore, its assessment and characterization become indispensable to polymeric material manufacturers as well as design engineers in material selection.

Typically, a Gardner impact tester has been employed to determine the first crack formed in a material. However, Gardner methods lack the capability of evaluating the crack initiation process as a function of impact speed. The Rheometrics impact tester can be used to determine the crack formation point by adjusting the ram travel distance into a test specimen short of complete penetration. Nevertheless, the large momentum of the impact ram at increasingly high speeds makes its stoppage at a preset travel distance extremely difficult. Hence, this mode of testing is limited to low impact speeds. In order to facilitate crack formation study at high speeds, the authors of this paper have developed a testing technique using a Dynatup impact tester. This technique involves the use of variable-thickness shims to raise the test specimen height from its lowest impact point, where contact between the tup and test specimen is just made. This allows us to control the distance the tup travels into the specimen.

The impact characteristics (that is, impact energy, impact force, and ram displacement) at crack formation are analyzed in connection with material selection. One of these three quantities is suggested for impact toughness evaluation, and its underlying rationale and significance are discussed. Also, the impact characteristics at crack initiation and at complete puncture are compared in relation to material design and selection.
Analysis of Force and Energy Measurements in Impact Testing
Authors: Hodgkinson JM , Williams JG
Published: December 2008

Complete velocity-time (v-t) relationships for a pendulum striker during impact testing of sharp-notched high-density polyethylene have been recorded by means of laser-Doppler velocimetry. The velocity data have been processed using a microcomputer to give force-deflection curves and hence absorbed energy. Toughness is expressed in terms of the critical strain energy release rate, Gc, and the critical stress intensity, Kc. The plane stress Gc from pendulum energy was 11.3 kJ/m2, and that from areas under force-deflection curves was 9.9 kJ/m2. The authors observed that an initiation Gc of the order 2.3 kJ/m2 might be expected for this material below its glass transition. By defining crack initiation in these room temperature tests as the point of maximum recorded force, an initiation Gc of 2.0 kJ/m2 is obtained. The critical stress intensity factor, Kc, is also defined from the maximum force, and a value of 2.1 MN/m3/2 is calculated. The elastic modulus is computed from compliance measurements to be 1.84 GN/m2, whereas from E=Kc2∕G the plane-stress modulus is 1.93 GN/m2, and the introduction of Poisson's ratio gives a plane-strain modulus of 1.69 GN/m2.
A Detailed Investigation of the Air Infiltration Characteristics of Two Houses
Authors: Nagda NL , Harrje DT , Koontz MD , Purcell GG
Published: December 2008

The relationships among energy use, air infiltration, and indoor air quality are being investigated in two detached houses identical in design and wind exposure. One of the two houses was retrofitted to reduce its infiltration rate. Fan pressurization/depressurization measurements taken over twelve months indicated that the air leakage rates for the unretrofitted control house remained unchanged. In the case of the experimental house, a 35% reduction as measured by fan pressurization/depressurization measurements was achieved by retrofitting; this reduction remained constant. The difference in air infiltration rates between the experimental and the control house was 22 to 24% as measured by tracer gas dilution. Infiltration rates were strongly affected by the seasons; infiltration rates obtained in the fall were 50% higher than rates obtained in the summer.
Measurements of Air Infiltration and Airtightness in Passive Solar Homes
Authors: Persily AK
Published: December 2008

The airtightness of 82 passive solar homes located throughout the United States was studied using tracer gas measurements of air infiltration and pressurization testing. The air infiltration measurements employed the tracer gas decay technique in a low-cost mode employing air sample bags and off-site infiltration determination. The infiltration rates measured under natural conditions ranged from about 0.05 to almost 2 air changes per hour (ACH). The pressurization test results ranged from 1 to more than 30 ACH at 50 Pa, with an average of about 10 ACH. By comparing the pressurization measurements on these homes to measurements on other homes, the passive solar homes were found to be in general no tighter than other U.S. homes. The air infiltration and pressurization measurements of the Class B homes were compared using existing infiltration models and other empirical relations.
Pressurization Testing, Infiltration Reduction, and Energy Savings
Authors: Jacobson DI , Dutt GS , Socolow RH
Published: December 2008

House tightening has become an important component of residential energy conservation programs. The technique of pressurization as a means of improving the effectiveness and labor productivity of house tightening has been increasingly used. It would be desirable if the measurements taken as part of the house pressurization activity could be used to quantify the degree of tightening actually accomplished. Such measurements were taken both immediately before and immediately after a house tightening activity carried out, as part of the Modular Retrofit Experiment (MRE), in 98 single-family houses in seven sites in New Jersey and New York. We have reduced the pressurization data from 55 homes according to two prescriptions, one rooted in the airflows actually observed at a relatively high pressure (50 Pa) and one requiring the extrapolation to a low pressure (4 Pa) by means of a curve fit through and beyond the observations. The two prescriptions turn out to give very different answers to the question: By what percent has the average air infiltration rate been reduced? In a large fraction of cases, the process of house tightening leaves a signature in the pressurization data such that the percent reduction in airflow is greater at lower pressures; as a consequence, the prescription which involves extrapolating to 4 Pa gives much larger estimates of the percent reduction in air infiltration achieved by the tightening process. In the seven sites we examined, the estimated percentage savings for the 4-Pa extrapolation was over twice as large on the average. The differences in the interpretation of pressurization data also lead to wide discrepancies in the expected reduction in naturally induced air infiltration, which was not measured in the MRE. In a subsequent experiment, known as the Dual Infiltration Reduction Experiment (DIRE), tracer gas decay measurements before and after house tightening supplement pressurization data. This experiment helps to clarify the relationship between air leakage reduction as measured by the two techniques—an area that has not been explored in past research relating natural air infiltration and leakage reduction pressurization.

The natural air infiltration reduction can be interpreted directly in terms of energy savings. For the MRE houses, the air infiltration energy savings component is computed from estimates of natural air infiltration reduction. This component is compared woth total savings in space heating energy use where available utility billing data permit the latter to be calculated.
Building Site Measurements for Predicting Air Infiltration Rates
Authors: Bassett MR
Published: December 2008

This paper examines the sensitivity of the predicted air infiltration rate to measured building airtightness data and the wind exposure index determined from site inspection. Results of airtightness tests in New Zealand houses are presented to indicate the range of leakage resistance for components (windows, doors, and chimneys, etc.), for solid materials (such as wall and ceiling lining materials), and for cracks separating major components such as the floor and walls. The distribution of leakage opening is discussed in relation to the driving forces of wind- and stack-induced airflows and also in relation to New Zealand styles of house building.

The building site exposure class must be determined in order that standard wind engineering formula can be used to calculate site wind speeds from meteorological weather data recorded some distance away. In the New Zealand situation, with high wind speeds and modest indoor-outdoor temperature differences, predicted natural air infiltration rates are particularly sensitive to site exposure details. Examples of measured and predicted air change rates are given for a number of houses together with comment on the sensitivity to experimental error.
A Review of European Research into Airtightness and Air Infiltration Measurement Techniques
Authors: Liddament MW
Published: December 2008

An important function of the Air Infiltration Centre, Bracknell, Berkshire, Great Britain, is to keep research organizations informed of on-going research into air infiltration in buildings. To fulfill this need, the Centre regularly undertakes a worldwide survey of current research. In this report, the results of the Centre's most recent survey, completed in 1983, are used to provide a background to present European airtightness and air infiltration measurement practices. A wide range of research activities are summarized involving the use of both pressurization and tracer gas techniques. In addition, the increasing effort being devoted to the measurement of air infiltration in nondomestic buildings is emphasized. Other topics covered include ventilation efficiency measurements and multitracer air movement studies.
Dynamic Delamination Crack Propagation in a Graphite/Epoxy Laminate
Authors: Grady JE , Sun CT
Published: December 2008

Ballistic impact tests of [90/0]5s T-300/934 graphite/epoxy laminates of beam-like dimension with embedded delamination cracks were conducted. High speed photography (16 000 frames/second) was used to record the impact response and subsequent crack propagation. From the photographic data, impact characteristics such as the contact duration and the dynamic response of the impact specimen were measured. In addition, the time of initiation of delamination propagation and measurements of the subsequent delamination length versus time were obtained. By changing the location of the embedded delamination in the specimens relative to the impact point, additional results were obtained on the variation of the threshold impact velocity necessary to cause crack propagation in the different specimen configurations. These data, together with the photographic results, suggest that the mode of crack propagation is dependent on the specimen geometry as well as the loading condition. The time dependent nature of the crack velocity and its variation with impact conditions was investigated.

A finite element program was used to calculate the dynamic strain energy release rate before the onset of crack propagation. This strain energy release rate was used to gage the instability of the delamination crack during impact.
Probabilistic Fracture Kinetics of “Natural” Composites
Authors: Krausz AS , Krausz K , Necsulescu DS
Published: December 2008

The behavior of crack propagation in “natural” composite materials (eutectics) was investigated. It was shown that the conditions of failure should be described by a probabilistic analysis that represents correctly the physical properties, rather than by the usual deterministic approach. It is considered that the method is applicable for the failure analysis of “artificial” composite materials as well.

The environment-enhanced subcritical crack velocity, v, is represented by the appropriate kinetics combination of the elementary rate constants, ƙ, as v = f(ƙ). The rate constants are described explicitly as ƙ=kThexp(−ΔGkT)withΔG=ΔG≠−W(K) where k is the Boltzmann constant, h is Planck's constant, T is the absolute temperature, ΔG≠ is the appropriate atomic bond energy of the low- and high-strength components encountered, respectively, as the crack tip moves into the corresponding zone, W is the mechanical work in the corresponding zone, and K is the stress intensity factor.

The physical process is controlled by thermal activation; the consequence of this is that crack growth in a probabilistic process is controlled by the instantaneous state of the load-material-crack system. It is recognized that on the atomic scale, bond breaking as well as healing occurs—the equivalent of the birth-death Markovian processes of probability mathematics. The analysis defines the crack size distribution as a function of time: The expectation value of the probability distribution is the experimentally measurable average; the spread of the probability density function defines the failure time probability of the composite material. It is concluded that the probabilistic physical process leads to a significantly different, and often more dangerous, failure occurrence than what is expected from the usual deterministic analysis.
Fracture of Thick Graphite/Epoxy Laminates with Part-Through Surface Flaws
Authors: Harris CE , Morris DH
Published: December 2008

An experimental investigation of the fracture behavior of tension specimens containing part-through semi-elliptic surface flaws was conducted utilizing T300/5208 graphite/epoxy laminates with a [0/±45/90]10s stacking sequence. The notched strength of the specimens was found to be influenced by the flaw aspect ratio as well as flaw depth. Using a value of fracture toughness previously obtained for this material system, linear elastic isotropic fracture mechanics predicted the influence of the flaw shape and size on the notched strength.
Damage Mechanics Analysis of Matrix Effects in Notched Laminates
Authors: Aronsson C-G , Bäcklund J
Published: December 2008

The main objective of this study was to investigate the matrix influence on the fracture behavior of carbon/epoxy three-point bend specimens. The matrices investigated were a brittle Fiberite 1034 and a more ductile Fiberdux 914C epoxy matrix. For the analysis of strength and load versus displacement behavior of the specimens, a damage zone model (DZM) was used. The damage is represented by a Dugdale/Barenblatt cohesive zone, where the cohesive stresses are assumed to decrease linearly with an increased crack opening.

Excellent agreement is obtained between predicted and measured fracture loads of the specimens. Also the nonlinear load versus displacement curves are accurately reproduced by the analysis. The present model is compared with previous models, such as the inherent flaw and the point stress criteria. The damage zone extension in the brittle and ductile matrix specimens was studied and compared with the DZM calculations, as an attempt to explain the difference in fracture behavior between the brittle and ductile matrix specimens.
Tire Wet-Pavement Traction Measurement: A State-of-the-Art Review
Authors: Henry JJ
Published: December 2008

In this paper, methods currently in use to measure tire-pavement friction are reviewed. The emphasis is on full-scale measurement systems operated at highway speeds, including systems that measure brake force coefficients (under slip or lockedwheel conditions or both) and side-force coefficients. A comparison is made of the data and information produced by each of these measurement methods. Attempts to relate the data produced by each of these methods are reviewed, and the reasons for their lack of agreement are discussed. In addition to direct traction measurement methods, texture measurements are discussed, and the reliability of texture-friction relationships is reviewed. The influence of texture on each of the full-scale measurement methods is investigated as a means of explaining the lack of agreement of the data produced by these methods.

Tire-pavement traction measurements are used for evaluating pavement safety and for predicting vehicle performance. The procedures for characterizing tire-pavement friction for these two applications usually differ. In the United States, pavements are monitored in annual inventories by a single measurement of skid resistance at a single speed with a standard ribbed test tire. Additional tests at multiple speeds or tests with a blank test tire or both may be conducted at accident sites. In some European countries, side-force coefficients or slip tests, both of which have the advantage of providing continuous measurements, are used to monitor pavement networks. These measurements are generally used in conjunction with a minimum texture depth requirement. A comparison of these approaches with U.S. practice is discussed. In conclusion, the status of consensus standards within ASTM and the International Standards Organization (ISO) is summarized, and recommendations are made for future standards development.
Effects of Tire Structure and Operating Conditions on the Distribution of Stress Between the Tread and the Road
Authors: Lippmann SA
Published: December 2008

Between the tread of the tire and the road there are distributions of interfacial pressure and horizontal stresses that affect many of the important operating properties of pneumatic tires. Among these are traction, treadwear, steering forces, noise generation, power loss, and envelopment properties. These distributions of pressure and stress are determined by the internal structure of the tire, the inflation, the load, and the operating conditions. The paper describes some of the relationships obtained from experimental studies. These same distributions also serve as clues of mechanical processes that take place within the structure of the tire. From these data we observe such matters as (1) the relationship of the lateral gradient of the interfacial pressure to the overturning moment and to the lateral walkout of the tire; (2) the mechanics of the rib to rib offset of the fore and aft shears in free rolling and steered tires; (3) the lateral stress distribution as affected by crown structure, the compressive spreading effects and the sidewall structure; (4) the dependence of the lateral pressure gradients on the characteristics of the sidewall; and (5) the effects of the above on the traction ratios (regional slip zones).
Aircraft Tire Footprint Forces
Authors: Howell WE , Perez SE , Vogler WA
Published: December 2008

The National Tire Modeling Program is a joint National Aeronautics and Space Administration (NASA) - industry effort to improve the understanding of tire mechanics and develop accurate analytical design tools. This effort includes fundamental analytical and experimental research on the structural mechanics of tires. As an integral part of this program, local footprint forces in the normal, lateral, and longitudinal directions were measured with the use of a footprint force transducer. Measurements of forces in the footprint were obtained by positioning the transducer at specified locations within the footprint and externally loading the tire. Data obtained for various inflation pressures and external loads are presented for an aircraft tire. The tire that was tested is representative of those used on the main landing gear of B-737 and DC-9 commercial transport airplanes.
A Review of Tire/Pavement Interaction Induced Noise and Vibration
Authors: Pottinger MG , Marshall KD , Lawther JM , Thrasher DB
Published: December 2008

The tire/pavement interface zone is the origin of a major portion of the ride vibration, ride noise, and environmental noise disturbances associated with road vehicles. It is appropriate to view these separate problems as one comprehensive systems problem involving the road, the tire, the vehicle, and human response to noise and vibration stimuli. A flow chart is used to discuss the general systems problem. Main branches of the flow chart are examined based on a thorough review of the pertinent literature. Relevant and previously unpublished information is included in the paper.
Use of the Inertial Profilometer in the Ohio DOT Pavement Management System
Authors: McQuirt JE , Spangler EB , Kelly WJ
Published: December 2008

Pavement roughness and ride quality information, for the Ohio Department of Transportation (DOT) Pavement Management System, can be accurately computed directly from highway pavement profiles measured with the Ohio DOT inertial profilometer. The pavement ride quality information includes the present serviceability index (PSI) and PSI trigger values for nonroutine maintenance.

Pavement profiles measured with the Ohio DOT inertial profilometer have also been used to calibrate the Ohio DOT Mays ride meter system, to analyze the Mays Ride meter system performance, and to provide a link between that system and pavement roughness and ride quality information obtained from the Ohio DOT inertial profilometer.
Performance Tests for Graffiti Removers
Authors: Clifton JR , Godette M
Published: December 2008

The defacing of the surfaces of masonry buildings with graffiti has increased substantially during the past decade, with removal cost exceeding several hundred million dollars annually. An assortment of materials have been used to remove graffiti with varying success. This report discusses performance tests developed to form a technical basis for selecting effective graffiti removers. Important considerations in developing the tests and criteria for graffiti removers were effectiveness in removing marks and effects on the appearance of masonry substrates.

In developing performance criteria, “standard graffiti” were produced by applying aerosol paints, crayons, lipstick, and felt-tip pens and markers to the surfaces of brick, sandstone, limestone, and aluminum specimens. The effectiveness of removers and their compatibility with masonry substrates was determined by comparing the color changes of unmarked, marked, and remover-treated masonry surfaces. Test methods were also developed to determine the ability of removers to migrate into masonry.
Designing and Building with Rehabilitation in Mind
Authors: Farbstein JD , Archea J , Kantrowitz M , Shibley RG , Wineman J , Zimring CM
Published: December 2008

Rehabilitation is viewed as a series of modifications that enhance a building. In this sense, rehabilitation can occur at any point in the building's life, even during construction. These modifications will inevitably occur as total building performance is better understood and as the performance objectives for a building change over its useful life. Design and construction should, therefore, provide for this inevitable rehabilitation. However, it is rare that a client requests a study of total building performance before the building is built.

The state of Florida has recently commissioned a diverse team to investigate its building delivery process. The study is focused upon Florida A & M University's new school of architecture, with less detailed examinations of five other new buildings of varied functions.

The key features of our study include a number of tasks: first, tracking the construction process of the six buildings (analysis of program and design decisions, modeling of the state's building delivery process, assessing change orders); second, monitoring the movein process and premove adaptations; third, carrying out postoccupancy evaluations of the six buildings. These will be comprehensive evaluations, looking at user response to the designed environment as well as technical performance in terms of energy, maintenance, and repairs. This paper describes in more detail the methods used for each task.

The significance of the study lies in its comprehensive, integrative approach, where information from each task will be weighed in light of the concerns and findings from the other tasks. We will try to answer questions about the appropriateness of the programming, design, construction, and management processes used. Technical and functional performance also will be compared. Overall performance will be judged in the light of the multifaceted points of view of the various interested parties. It is hoped that, as a result of this study, rehabilitative modifications during initial construction will be reduced on future projects.
Potential Hazards Resulting from the Misapplication of Energy Conservation Measures in Existing Religious Buildings
Authors: Chick WS
Published: December 2008

The development of a practical information data base covering a wide cross section of religious buildings is essential to determine the most effective approach in reducing their demand for energy without creating negative side effects.

Very little information is available on religious building profiles which is of use in determining the potential hazards resulting from the misapplication of various measures.

Applying energy conservation measures to religious buildings presents unique problems. For instance, attempting to apply cost-saving energy conservation measures with an unqualified committee working in its spare time with limited funds often results in structural damage, safety problems, and fire hazards to existing structures; examination of several hundred religious buildings in the province of Ontario has confirmed the existence of many problems.

The most common problem is the improper application of thermal insulation to the roof and walls of buildings. This has resulted in the loss of structural integrity due to dry rot caused by inadequate moisture control. The accelerated deterioration of a building can result in prohibitive maintenance and repair costs to many heritage edifices.

The various effects of insulation on fire safety are also a major concern. For instance, when insulation is applied around heat-producing devices such as lighting fixtures, lack of adequate ventilation can result in dangerous levels of heat accumulation to adjacent combustible materials. Insulation applied to linings under 5 mm (for example, plywood) can accelerate ignition when exposed to an ignition source.

The presence of plastic foam insulating materials is also a major concern due to the potential for vertical spread of fire in cavity walls. Materials such as urea-formaldehyde foam insulation can cause eye and nose irritations in some people and is linked to other health risks.

In geographic areas experiencing heavy snowfalls, the snow loads on roofs can cause failure due to heavy accumulations resulting from the improper use of insulation. Serious wetting occurs inside buildings from infiltration of blowing snow where gaps in insulation exist and where moisture barriers are installed in a faulty manner.

Most of these potential hazards can be significantly reduced or entirely eliminated by obtaining competent technical advice and by the adoption of proper installation and construction practices.

Hundreds of questionnaires, in addition to visits to examine a wide variety of religious buildings, have revealed the existence of many of the anticipated problems.

Documentation of these problems should provide a useful resource base of information for those involved in the operation, maintenance, and retrofitting of these important community buildings.
Technology of Preserving Wood Structures
Authors: Sherwood GE
Published: December 2008

For the past 75 years, the Forest Products Laboratory has conducted research on topics ranging from wood anatomy to performance of entire buildings to development of construction guidelines. This paper presents research results applicable to extending the service life of wood structures. It includes information on fundamental properties of wood and on factors that influence serviceability, such as loading, temperature, moisture, chemicals, and weathering. The author summarizes state-of-the-art methods and practices for extending the life of wood structures and includes an extensive list of references.

This overview of technology for preservation and rehabilitation of wood structures should be useful to designers, builders, and regulatory bodies involved in building preservation and rehabilitation.
Lessons Learned from Investigations of Over 500 Distressed Masonry and Stone Facades
Authors: Kellermeyer KB , Chin IR
Published: December 2008

The authors and their colleagues have investigated over 500 buildings with distressed masonry and stone facades in the last five years. This work has included investigations of distressed conditions in building facades made of brick, concrete block, terracotta, granite, limestone, and marble.

Masonry and stone facades are frequently chosen by designers and building owners for their inherent durability to resist weathering and for their inherent low maintenance costs. When properly designed in accordance with available standards, their performance is normally excellent. However, their performance can be affected by insufficient care in the design of joints and by insufficient care in the design of attachment and flashing systems.

Based upon architectural design principles, knowledge of masonry and stone materials, and experience gained from investigating numerous masonry and stone facade failures, the authors discuss design factors and details that could help designers avoid failures in new masonry and stone facades. The authors also present information that can assist architects, engineers, and building owners rehabilitate and preserve existing facades on buildings.
Irradiation Effects in Reactor Pressure Vessel Steels: A Nuclear Regulatory Commission Perspective
Authors: Serpan CZ , Randall PN
Published: December 2008

The embrittling effect of neutron irradiation on reactor pressure vessel steel and welds has a significant impact on the regulation of reactors by the U.S. Nuclear Regulatory Commission (NRC). Because the NRC is concerned with the continuing integrity and safety of the reactor's primary system, the neutron-irradiation-induced loss of fracture toughness and ductility must be carefully documented, understood, and controlled to assure that despite such loss, there is always a sufficient reserve of toughness and ductility to preclude crack initiation and uncontrolled propagation in the unlikely event of an accident. Aspects of embrittlement important to the NRC, which are discussed herein, include prediction of the transition temperature and upper-shelf-energy levels at critical vessel locations for the setting of pressure-temperature limits, for analysis of accident loadings such as pressurized thermal shock, and for evaluation of flaws found in inspection. Also discussed are the use of embrittlement-related neutron dosimetry and evaluation of vessel annealing.
Surveillance Programs and Irradiation Embrittlement Research of the Loviisa Nuclear Power Plant
Authors: Ahlstrand R , Törrönen K , Valo M , Bärs B
Published: December 2008

The surveillance programs of Loviisa 1 and 2 nuclear power plants consist of irradiations of Charpy V-notch, Charpy-size three-point bend, and tensile specimens. The specimens are located outside the core barrel. The program consists of six sets of irradiation capsules that are taken out according to a special schedule.

The results from the first surveillance tests from Loviisa 1 showed that the shift in transition temperature (both Charpy-V and crack-opening displacement) was higher than expected. These results introduced a modification to the original withdrawal schedule of the surveillance capsules. The subsequent test results confirmed the shift in transition temperature.

In addition to the normal surveillance program, new surveillance capsules have been placed into both reactors before and after the core modification including round compact tension (CT) specimens. Parallel programs to validate the reliable use of small specimens for fracture toughness measurements and a special instrumented impact tester have been conducted.

The accuracy of the fluence measurements has been improved by the implementation of some novel procedures.

To study the amelioration of radiation embrittlement, an annealing study was carried out using the broken halves of the Charpy bars from surveillance testing.
Boiling Water Reactor (BWR) Pressure Vessel Surveillance Program
Authors: Sivaramakrishnan KS , Chatterjee S , Anantharaman S , Balakrishnan KS , Viswanathan UK , Roy PR
Published: December 2008

A302 B steel cladded with stainless steel is used as the pressure vessel material for the two 210 MW(e) boiling water reactors commissioned during 1968. Fabricated surveillance specimens, representative of the pressure vessel steel, were kept in the reactor at wall, shroud, core, and steam dryer locations of the reactor. Charpy V-notch impact and tension specimens from base, weld, and heat affected zone (HAZ) from these locations, except at the core, were tested in the hot cell.

It has been found that maximum shift corresponding to Charpy 41-J index temperature was observed for the base material at the shroud location and the estimated value was 38°C. The corresponding index temperature was 18°C. The irradiation capsules had iron, copper, and nickel flux monitors. These were analyzed for estimating the fluences (> 1 MeV), which were found to be (2.2 ± 0.4) × 1018 n/cm2 for wall and (1.5 ± 0.3) × 1019 n/cm2 for the shroud locations.

The shift in index temperatures was compared with the trend curves of Regulatory Guide 1.99.1.
Static Fracture Criteria Evaluation Using Small Specimens
Authors: Gillemot F , Havas I , Szabó L
Published: December 2008

The evaluation of valid static fracture criteria in radiation embrittlement research and surveillance measurement is always difficult due to the limited size of the specimens. Test series have been performed to evaluate the optimum side-grooving of the Charpy-size three-point bend (TPB) specimens and a method has been elaborated for using the remnants of broken Charpy specimens for measurements of energy criteria, Absorbed Specific Fracture until Energy (ASFE).
Effect of Various Metallurgical Microstructures on the Response of the Nickel-Molybdenum-Chromium BH 70 Steel to Neutron Irradiation at 285°C
Authors: Vacek M
Published: December 2008

Radiation hardening and embrittlement of the BH 70 steel heat treated to different microstructures (tempered martensite, tempered bainite, and tempered mixed ferrite-perlite, bainite, and martensite after neutron irradiation about 7 × 1023 n/m2 > 1 MeV at 285°C) were compared with commercial heat treatment conditions. Only moderate radiation hardening, with small differences for individual conditions, was measured in all four heat treatment conditions (by 29 to 48%). Roughly the same radiation embrittlement ΔTT4IJ = 137 to 148°C) was found in all heat treatment conditions used. The initial (unirradiated) and resultant (irradiated) Charpy-V 41-J transition temperature of the BH 70 steel, however, can be altered appreciably through heat treatment practices, resulting in different microstructure. Initial transition temperatures (TT4IJ) of individual heat treatments were found in the range from −73 to −143°C.
The Sea Urchin: Bioassay for the Assessment of Damage from Environmental Contaminants
Authors: Pagano G , Cipollaro M , Corsale G , Esposito A , Ragucci E , Giordano GG , Trieff NM
Published: December 2008

The sea urchin test system has been determined in our laboratory to be an extremely informative bioassay for pollutants, occurring as individual or as mixtures of xenobiotics. Harmful agents may be identified and characterized biologically to give an integrated set of data dealing with several key events, such as fertilization, mitotic activity, and embryogenesis. Therefore this bioassay may contribute to the assessment of the environmental impact of pollutants, by focusing on several important toxicological aspects.

This study was carried out on some inorganic pollutants [Cd(II), Cu(II), Zn(II), and Se(IV)] and their mixtures. Sublethal pH changes were taken into account as an additional stressor, capable of influencing the toxicities of tested agents. The experiments were performed on Paracentrotus lividus sperm and embryos, and on Echinus esculentus sperm. The results showed distinct patterns of embryotoxicity for the agents tested, which resulted in developmental defects as relatively high levels (>10−5 kmol/m3) for Cd(II) and Se(IV), whereas the embryotoxic effects of Cu(II) and Zn(II) were exerted at lower concentrations (5 × 10−7 kmol/m3) close to their natural seawater levels. Cytogenetic analysis of exposed embryos failed to reveal any morphological or quantitative changes in mitotic activity, at embryotoxic levels of all tested contaminants. The fertilization success of exposed sperm showed peculiar dose-response changes, as a result of the specific contaminant levels and of the simultaneous presence of other contaminants. Specifically, slight increases in Cd(II) or Cu(II) levels enhanced fertilization success, up to critical levels (10−7 to 10−6 kmol/m3); however, further increases in these metal ion concentrations led to a drop in fertilization success. The simultaneous presence of Zn(II) or Se(IV) dramatically changed the dose-response patterns, depending on the different mixtures and the test species.

The results may represent an example of the need to account for the simultaneous presence of several pollutants, whose combined impacts may be substantially different from those of the individual toxins. Moreover, the results attest to the high sensitivity of the sea urchin bioassay, which responds to very slight increases in microelements or contaminant levels above their natural concentrations.
Evaluation of Simple Generic Aquatic Ecosystem Tests to Screen the Ecological Impacts of Pesticides
Authors: Sheehan PJ , Axler RP , Newhook RC
Published: December 2008

Simple laboratory aquatic ecosystem models composed of naturally coadapted communities of phytoplankton, bacteria, zooplankton, and small benthic invertebrates were developed and evaluated for their effectiveness and consistency in screening the ecological impacts of pesticides on community functions. These generic microcosm toxicity tests were used to rank the potential hazard of pesticides on community metabolic processes. The reproducibility of hazard rankings was evaluated in sequential experiments with the same microcosm inoculum, and in simultaneous experiments using two sets of microcosms with taxonomically different community inocula, but the same major functional groups present (i.e., primary producers, grazers, detritivores, and decomposers). Based on an integrated measure of system response, relative impact, which accounts for both the magnitude and duration of displacement of defined treatment effects from the normal range of control system functions, these generic test systems were remarkably consistent in ranking pesticide impacts on community metabolic activities.
Population and Guild Analysis for Interpretation of Heavy Metal Pollution in Streams
Authors: Petersen RC
Published: December 2008

The analysis of several closely related species, a guild, may be a practical and informative technique for studying the ecological effects of toxic substances. The five criteria of taxonomic simplicity, commonness, sensitivity, available literature, and laboratory practicality define guilds appropriate for community toxicity testing. As an example, the benthic macroinvertebrate community and a guild of three coexisting species of the caddisfly larva, Hydropsyche, were analyzed along a Swedish river, Kolbäcksån, with a history of heavy metal pollution. There was an increase in the relative proportion of early instar H. siltalai within the guild with increasing heavy metal pollution. The increase in early instar H. siltalai was correlated with a decrease in later instar H. pellucidula. More severe disturbance resulted in the removal of H. pellucidula and a reduction in H. siltalai density, while the more tolerant species, H. angustipennis, remained unchanged. Analysis of the guild leads to the conclusion that metal pollution not only eliminates species and reduces population density but changes interspecific interactions among members of the guild.
Impact of Drilling Fluids on Seagrasses: An Experimental Community Approach
Authors: Morton RD , Duke TW , Macauley JM , Clark JR , Price WA , Hendricks SJ , Owsley-Montgomery SL , Plaia GR
Published: December 2008

Effects of a used drilling fluid on an experimental seagrass community (Thalassia testudinum Konig et Sims) were measured by exposing the community to the suspended particulate phase (SPP) in laboratory microcosms. Structure of the macroinvertebrate assemblage, growth and chlorophyll content of grass and associated epiphytes, and rates of decomposition as indicated by weight loss of grass leaves in treated and untreated microcosms were compared. Health of the plants and structure of the macroinvertebrate assemblage maintained in the laboratory were compared periodically with the seagrass community from which the plants and attendant sediment were taken.

Treated microcosms were exposed to either 190 parts per million (ppm), volume to volume, of SPP or an equivalent amount of montmorillonite clay. Untreated microcosms received only flowing water from Santa Rosa Sound. Sixteen replicates were provided for each treated and untreated set.

There were statistically significant differences in community structure and function among untreated microcosms and those receiving the clay and drilling fluid. For example, drilling fluid and clay caused a significant decrease in the numbers of the ten most numerically abundant (dominant) macroinvertebrates, and drilling fluid decreased the rate at which Thalassia leaves decomposed.