bluuebunny/crossref_metadata_2025 huggingface dataset:
Hierarchical modelling of microstructural effects on mechanical properties of wood. A review COST Action E35 2004–2008: Wood machining – micromechanics and fracture
Authors: Hofstetter Karin , Gamstedt E. Kristofer
Published: December 2008

Wood exhibits a hierarchical architecture. Its macroscopic properties are determined by microstructural features at different scales of observation. Recent developments of experimental micro-characterisation techniques have delivered further insight into the appearance and the behaviour of wood at smaller length scales. The improved knowledge and the availability of increasingly powerful micromechanical modelling techniques and homogenisation methods have stimulated rather comprehensive research on multiscale modelling of wood. Linking microstructural properties to macroscopic characteristics is expected to improve the knowledge of the mechanical behaviour of wood and to serve as the basis for the development of innovative wood-based products and for biomimetic material design. Moreover, understanding fundamental aspects of wood machining requires multiscale approaches which can take into account the heterogeneity, anisotropy and hierarchies of wood and wood composites. In this review, recent developments in the field of hierarchical modelling of the hygroelastic behaviour of wood are discussed, and a short outline of the theoretical background is given. Much focus is placed on composite micromechanical models for the wood cell wall and on multiscale models for wood resting upon hierarchical finite element models and on the application of continuum micromechanics, respectively. These models generally lead to the specification of equivalent homogeneous continua with effective material properties. Finally, current deficiencies and limitations of hierarchical models are sketched and possible future research directions are specified.
Reactor Dosimetry: Methods, Applications, and Standardization
Authors: Farrar H , Lippincott EP
Published: December 2008

Description

Included are papers on applications to reactor pressure vessel surveillance; measurements to provide basic nuclear data and benchmarks for measurement standardization; calculational methods; and research on breeder and fusion environment. Section headings: LWR Pressure Vessel Surveillance Programs; Nuclear Data; Benchmarks and Standards; Fusion and Damage Analysis.
Composite Materials: Fatigue and Fracture, Second Volume
Authors: Lagace PA
Published: December 2008

Description

Important and useful information on concerning fatigue and fracture of composite materials. Majority of papers deal with composite systems of thermosetting epoxies. Some attention to more recent thermoplastic systems. Section headings: Fatigue and Damage Growth; Models and Analysis; Delamination; and Structural Aspects.
Implication of Aggregates in the Design, Construction, and Performance of Flexible Pavements
Authors: Schreuders HG , Marek CR
Published: December 2008

Description

A practical approach to road and paving problems and testing for those who must make good road surfaces with available aggregate materials. Ten papers include

• Performance of a Thin Surfaced, Crushed Stone Base Pavement

• Measuring the Susceptibility of Emulsion Based Seal Coats to Debonding

• Hot Mix Asphalt Moisture Susceptibility Problems: The Need to Test and Specify via a Common Procedure.
Oil Dispersants: New Ecological Approaches
Authors: Flaherty LM
Published: December 2008

Description

A positive and timely look at the use of dispersants to protect the environment. 23 papers include material on: dispersant testing; contingency planning for dispersant use cost effectiveness; new related products; ecological and freshwater dispersant applications; and training for dispersant applications; and training for dispersant use.
Environmental Aspects of Stabilization and Solidification of Hazardous and Radioactive Wastes
Authors: Côté P , Gilliam M
Published: December 2008

Description

STP 1033 provides a unique perspective on stabilization and solidification research as performed by the hazardous and radioactive waste communities. These papers are grouped into 4 sections: Processes; Regulatory Aspects and Testing Methods; Laboratory Evaluation; and Large Scale Evaluation or Demonstration.
Basic Approach in the Development of TURBISTAN, a Loading Standard for Fighter Aircraft Engine Disks
Authors: Breitkopf GE
Published: December 2008

The development of TURBISTAN was a joint effort by CEAT (Centre ďEssais Aeronautique de Toulouse, France); IABG (Industrieanlagen-Betriebsgesellschaft); LBF (Fraunhofer-Institut für Betriebsfestigkeit, West Germany); MTU (MTU Motoren- und Turbinen-Union Munchen GmbH, West Germany); NLR (Nationaal Lucht- en Ruimtevaartlaboratorium, The Netherlands); RAE (Royal Aircraft Establishment, Great Britain); Rolls-Royce (Great Britain) and SNECMA (Société Nationale ďEtude et de Construction de Moteurs ďAviation, France); RWTH (Rheinisch-Westfälische Technische Hochschule Aachen, West Germany); and University of Utah (United States) to derive a loading standard for fighter aircraft engine disk usage.

The sequence was designed to contain the characteristics that are determinants of cyclic fatigue in the form, frequency, and application typical of actual operations. It represents a unique standard for low cycle fatigue (LCF) and crack growth experiments, and enables quantitative insights to be gained into the sequencing effect at moderate experimental effort.

The subject of the paper is the basic approach used in the development process. The paper also adds a few application notes.
Water Vapor Transmission Through Building Materials and Systems: Mechanisms and Measurement
Authors: Trechsel HR , Bomberg M
Published: December 2008

Description

Round robin data, case histories, and panel discussions on the moisture in walls and roofs. 15 peer-reviewed papers cover mechanisms, field observations, and measurement. For those engaged in research on moisture movement and concerned with material properties relating to water vapor transmission.
Damage Initiation and Growth in Notched Laminates Under Reversed Cyclic Loading
Authors: Bakis CE , Yih HR , Stinchcomb WW , Reifsnider KL
Published: December 2008

The initiation and growth of fatigue damage in notched Cycom AS4/1808 graphite/epoxy laminates were investigated experimentally. Two layups, (0/45/90/−45)s4 and (0/45/0/−45)s4, provided contrasting responses to the fully reversed fatigue loads. Full-field strains and stresses surrounding the circular notch were evaluated at several stages of fatigue life with the photoelastic coating and adiabatic thermal emission measurement techniques and were related to the corresponding damage state and residual strength, stiffness, and life.
Asphalt Concrete Mix Design: Development of More Rational Approaches
Authors: Gartner W
Published: December 2008

Description

STP 1041 offers practical applications, specific lessons learned from testing research, and conclusions that yield useful suggestions: in short, an alternative to the empirical methods currently in use which, according to Gartner, "are not adequate for today's loading conditions of alteration of material properties."
Hazardous and Industrial Solid Waste Minimization Practices
Authors: Conway RA , Warner DJ , Wiles CC , Duckett EJ , Frick JH
Published: December 2008

Description

This practical guide cites actual experiences in waste minimization, and describes to waste disposal as well as how to minimize environmental impact. 17 peer reviewed papers cover: general managerial practices; waste minimization audits; solvent recovery, used oil recovery; and miscellaneous separation and utilization practices.
Safety in Ice Hockey
Authors: Castaldi CR , Hoerner EF
Published: December 2008

Description

The first book published on the historical and scientific aspects of safety in the sport of ice hockey. Contains 25 papers covering: injury rates in amateur, college, and professional hockey; risk factors, game rules and officiating; playing equipment, skates, sticks, protective types; playing facilities (indoor and outdoor) causative factors in catastrophic injuries; the role of standards in protective equipment for the head and face, and for skate blades and their effectiveness.
Corrosion Susceptibility of Reinforced Earth Systems: Field Surveys
Authors: Whiting D
Published: December 2008

Field surveys were performed on four reinforced earth retaining walls. Concrete facing units were used on each wall. The objective of these surveys was to obtain information concerning the susceptibility to corrosion of metallic elements (both embedded in backfill and in concrete) in these soil stabilization systems. The structures surveyed represented differing environmental conditions and materials. Both marine and inland structures were included, with ages ranging from 6 to 11 years.

A variety of field tests were carried out at each site. Field tests included visual and photographic surveys, delamination detection, electrical potential surveys, measurements of concrete and soil resistivities, measurements of concrete cover, and stray current testing. Powdered and core samples of concrete were returned to the laboratory for chloride analyses and rapid chloride permeability testing. Chemical and metallographic analyses were carried out on samples of soil and earth reinforcing strips.

Results indicate that two of the four structures surveyed exhibit corrosion problems that may limit their useful life. These include a reinforced earth structure located in a tidal estuary where aluminum alloy reinforcing strips are exposed to low resistivity and high chloride conditions and an interstate highway slope stabilization structure where galvanized metal earth-reinforcing strips are exposed to a highly alkaline backfill of nonuniform composition. Other structures surveyed showed little or no evidence of corrosion.
Detection and Considerations of Corrosion Problems of Prestressed Concrete Cylinder Pipe
Authors: Rothman PS , Price RE
Published: December 2008

Prestressed concrete cylinder pipe (PCCP) is constructed by circumferentially winding a high strength steel wire, under tension, around a concrete core containing a sheet steel cylinder, which serves as a watertight membrane. The service life of such pipe is generally determined by the ability of this steel prestressing wire to retain its integrity under tension. Corrosion of the steel wire results in pitting, embrittlement, or the dissolution of the iron with a corresponding reduction in cross-sectional area. The result is degradation of the physical strength of the high tensile wire and possible failure of the prestressed concrete cylinder pipe through this mechanism. Pipe affected by this failure mode does not develop leaks as in the case of the steel pipe, but bursts catastrophically. Failure is usually attributed to “wire breaks,” not specifically to corrosion.

For concrete cylinder pipe, the components of the joint are susceptible to stray current corrosion if component low resistance continuity does not exist. This condition can be responsible for failure of the steel prestressing wires if they are not electrically continuous with the other components of the pipe (steel cylinder, bell ring, spigot ring, fittings, and so forth).

This paper presents the potential corrosion problems and causes associated with the metallic components of prestressed concrete cylinder pipe. The difficulties in detecting these problems, because of materials and fabrication practices are discussed, as well as methods that have been used successfully to detect corrosion in buried lines (pipe-to-soil potential profiles, cell-to-cell potential profiles).

The results of a few typical studies are presented as a suggested approach to the investigation and analysis of potential problems involving both galvanic and electrolytic (stray current) corrosion.
The Thermal Properties of Wood—Data Base
Authors: Cardenas TJ , Bible GT
Published: December 2008

A data base of steady-state thermal properties for 15 wood species representative of those used commercially in building construction has been developed from available test data. Selected mean values of conductivity, density, moisture content, and thermal resistance are tabulated for representative groups of softwoods and hardwoods. The methodology for organizing the test data incorporating ASTM standards on wood is presented, and the statistical methods utilized for the empirical analysis are discussed. A proposed table of thermal design coefficients for softwoods doubles the reliability of predicted values currently listed in the ASHRAE Handbook of Fundamentals.

All test data are documented in a format suitable to a broad range of user groups. Design professionals undertaking computer modeling of composite assemblies and systems for building energy analysis will find the data base a useful reference tool. Recommendations on the need to verify the steady-state thermal properties for wood and wood-based building materials are presented and discussed.
Asphalt Rheology to Define the Properties of Asphalt Concrete Mixtures and the Performance of Pavements
Authors: Roque R , Tia M , Ruth BE
Published: December 2008

The behavior of asphalt concrete paving mixtures at low temperatures is primarily dependent upon the rheological properties of the asphalt binder. The Schweyer Constant Stress Rheometer was used to define the low-temperature rheological properties of asphalts recovered from laboratory-compacted mixtures and field cores. Asphalt viscosity relationships with resilient modulus, mix viscosity, static modulus, stiffness, fractures strain, fracture energy, and fracture stress of the mix were established using dynamic, static, and constant stress indirect tension testing procedures.

Resilient moduli predicted from the viscosity of asphalts recovered from pavements were used in elastic layer analyses to define deflection and strain basins produced by Dynaflect or plate tests. These deflection and strain basins compared favorably with those measured on a test pit pavement and on selected in-service pavements.

Relationships between asphalt viscosity and mix parameters are presented to illustrate the importance of asphalt viscosity and to suggest their potential use in the modeling of the thermal behavior of flexible pavements. It is shown that there is no appreciable difference between resilient and status moduli when asphalt viscosity exceeds about 400 MPa·s. The importance of shear susceptibility for both asphalt and mix viscosity determinations is discussed with recommendations for use of constant power viscosity to minimize errors induced by extrapolation of viscosity at shear rates outside those obtained in the test.

Parameters for thermal and load induced fracture include stress, strain, and energy. Laboratory test results were used to develop relationships between these parameters and the constant power viscosity of the asphalt binder. Tests on pavement cores produced fracture corresponding to that obtained in the laboratory tests. Comments are provided on the reliability of these parameters in defining fracture.
Dispersants in the Freshwater Environment
Authors: Brown HM , Goodman RH
Published: December 2008

During the past four years, a research program to investigate the effect of oil and dispersant chemicals on a freshwater ecosystem has been carried out. Laboratory experiments were used to select a suitable dispersant for a field trial and to develop monitoring techniques which would be capable of detecting chronic and sublethal effects in selected species of the freshwater ecosystem. The field trial demonstrated that a spill of light oil covering 5 to 10% of the surface of a small shallow freshwater lake had no long-term measurable effects and that the application of a dispersant ameliorated some short-term effects even in this low energy system.
The Behavior of Dispersed and Nondispersed Fuels in a Sewer System
Authors: Fingas MF , Hughes KA , Bobra AM
Published: December 2008

A small-scale model sewer was constructed to determine the behavior of dispersed and nondispersed fuel flushed or spilled into sewers. The system included a headbox containing a concrete pad with a drain in the middle. The drain fed into a sewer pipe. Six vapor sensors were positioned in ports or simulated manholes at intervals along the pipe length. The vapor sensors were connected to a computer which generated a continuous data record of vapor concentrations at each port. Liquid samples were also taken at different intervals under the vapor sensor ports.

Vapors in a sewer system have two distinct origins: the first is vapor evaporating from the liquid fuel as it is transported with the water and the remainder is vapor that formed upstream and is in the process of moving downstream at a slower rate than the underlying liquid. The latter movement is caused by the pumping action of the water flow, but is slower than the liquid flow as a result of the drag of the walls and the low gas-to-liquid friction coefficient. Gasoline, whether treated with dispersant or not, produces two sharply different vapor peaks at the sensor ports because it evaporates rapidly upon entering the sewer and thus produces a slowly moving vapor cloud. Diesel fuel does not evaporate as rapidly and produces only a single vapor peak at the ports.

The use of dispersants at the beginning of the sewer increases the volatilization rate of the smaller fuel molecules and thus increases the amount of vapor present in the sewer system. This occurs irrespective of the amount or brand of dispersant employed. When dispersants are applied, the vapor concentration and duration is increased at each subsequent port. An increasing amount of dispersant or dispersant/water mixture increases this effect. If dispersants are mixed with the fuel in a very vigorous manner the vapor concentration may not be increased in the first ports, but it will not be decreased and the concentrations are increased 5 min downstream. In no case is the vapor concentration at any port reduced by the use of dispersants.

The results from the small-scale model show that dispersants do not reduce the explosion risk of fuels in sewers. In fact, the use of dispersants will in most cases greatly increase the potential for explosions and their magnitude. Dispersants increase the rate of volatilization of small fuel molecules and increase the total amount of those released. This is consistent with the results obtained by other authors who have conducted static experiments of similar nature.
Effects of Hydride Morphology on Zr-2.5Nb Fracture Toughness
Authors: Wallace AC , Shek GK , Lepik OE
Published: December 2008

The effects of hydride morphology on the axial fracture toughness of cold-worked Zr-2.5Nb pressure tube material have been determined between room temperature and 240°C. Tests were performed on small compact tension specimens machined from samples of material prepared with different morphologies and hydrogen concentrations. The morphologies were characterized by a parameter referrred to as the hydride continuity coefficient (HCC), which provides a measure of the extent to which hydrides are oriented in the axial-radial plane of the pressure tube. Hydrides in this orientation are known to be detrimental to the fracture properties of the tube. Fracture toughness was characterized by a J-R curve technique, from which it is possible to estimate the maximum stable size of a through-wall axial crack for typical reactor operating conditions. Material with HCC values greater than 0.5 exhibited low toughness from room temperature to 240°C, at which temperature there was an abrupt transition to an upper shelf toughness value. As HCC decreases, the transition to upper shelf toughness occurs more gradually and is complete at a lower temperature.
Effects of Loading and Thermal Maneuvers on Delayed Hydride Cracking in Zr-2.5 Nb Alloys
Authors: Shek GK , Graham DB
Published: December 2008

Delayed hydride crack velocities in Zr-2.5 wt% Nb alloys with different ther-momechanical treatments were measured. Materials with higher strength have higher crack velocity, and the stepwise crack propagation occurred by smaller increments associated with a smaller zone of crack tip hydrides. A series of load reduction experiments were performed on specimens with an active delayed hydride crack. An incubation period was required for the specimen to resume cracking after reducing the applied K to a level still significantly above the threshold stress intensity factor K 1H. The length of the incubation period depended on the amount of K reduction, material strength, temperature, and the final K in which cracking occurred. Crack velocity increases with the amount of hydrogen in solution in the matrix. Crack velocity increased as a function of the peak temperature reached in the initial cooldown thermal cycle. There is hysteresis in hydride solubility which results in different levels of hydrogen in solution depending upon the thermal history. The implication of this in terms of crack velocity is discussed.
Microstructure and Corrosion Studies for Optimized PWR and BWR Zircaloy Cladding
Authors: Garzarolli F , Steinberg E , Weidinger HG
Published: December 2008

The increased discharge burnups envisaged today require an optimization of the Zircaloy cladding properties with regard to corrosion with different strategies for optimizing the corrosion for boiling water reactor (BWR) and pressure water reactor (PWR) applications.

A broad laboratory study showed that the influence of temperature and environmental details upon autoclave test results is rather complex. Zircaloy with fine (∼ 0.05 μm), uniformly distributed intermetallic precipitates reveals nodular corrosion in steam at 420°C or below and excessive uniform corrosion in water at 350°C, but the best nodular behavior in steam at 500#x00B0;C. However, samples with larger intermetallic precipitates (>0.2 μm) exhibit a strong tendency to nodular corrosion in 500°C steam, but good behavior in steam at 420°C or below and in water at 350°C. The tendency toward nodular corrosion in 400 to 500°C steam can be suppressed by additions of oxygen; the ranking in uniform corrosion in 350°C water can be altered by additions of hydrogen. The latter was observed on samples exposed up to 1000 days in degassed water and afterwards 1000 days in water with a hydrogen overpressure.

Similar correlations were found for in-pile exposure with some exceptions. Materials with very fine intermetallic precipitates, which show little tendency for nodular corrosion and behave well in-pile in oxygenated (mostly BWR) environments, exhibit accelerated uniform corrosion in a hydrogenated (PWR) environment with a corrosion rate that depends very little on temperature. However, in oxygenated coolant, materials with coarse precipitates indicate severe nodular corrosion, which is almost independent of the temperatures within the range of 290 and 350°C. As a result of these findings a dual strategy is technologically feasible by using different values of the accumulated annealing parameters (Σ Ai) for BWR and PWR application. For optimized BWR cladding tubes ΣAi ⩽ 10 -18 h is proposed; the best range for PWR cladding appears to be at 2 × 10-18 h ⩽ Σ Ai ⩽ 5 × 10-17 h.
Development of a Cladding Alloy for High Burnup
Authors: Sabol GP , Kilp GR , Balfour MG , Roberts E
Published: December 2008

An advanced Zircaloy cladding containing niobium has been developed and tested extensively both in long-term out-of-pile autoclave exposures and through high burnup irradiation in a pressurized water reactor (PWR) environment. Tubing of zirconium-based binary alloys containing 0.5, 1.0, and 2.5% niobium, and a quaternary composition containing tin, niobium, and iron was fabricated in such a manner that the second phase was fully precipitated, but with minimal particle growth. Autoclave testing in pure water and steam over the temperature range of 589 to 727 K indicates that all of the alloys except the 0.5% Nb have a lower post-transition corrosion rate than does Zircaloy-4, with the relative benefit increasing with temperature. Additional autoclave testing in LiOH solutions indicated a marked sensitivity of the Nb binaries to accelerated corrosion, and in these solutions only the Sn-Nb-Fe alloy was superior to Zircaloy-4. Experimental fuel assemblies with cladding of the advanced alloys were examined after one, three, and four cycles in the BR-3 reactor. Rod average burnups of up to 71 GWD/MTU were obtained with total residence times of up to 66 months. Results of post-irradiation examinations are given only for the Sn-Nb-Fe alloy as compared to Zircaloy-4. These examinations revealed that the Sn-Nb-Fe alloy showed the lowest overall corrosion, up to 50% better than Zircaloy-4 at the highest burnups, and was superior to the Zr-Nb binaries. The Sn-Nb-Fe alloy, called ZIRLO™, also displayed lower irradiation growth and creep than the others.
Influence of Chemical Composition and Manufacturing Variables on Autoclave Corrosion of the Zircaloys
Authors: Graham RA , Tosdale JP , Finden PT
Published: December 2008

Previous investigators have reported the separate influences of chemical composition and heat treatment on the nodular and uniform corrosion of zirconium-based alloys. However, many of these compositions lie outside the allowable Zircaloy ranges required by most nuclear fuel specifications. The current study shows that the corrosion performance of the Zircaloys can be optimized by adjusting chemical compositions within current ASTM ranges, and examines the influence of composition on response to heat treatment. It is believed that this approach will yield improved corrosion performance and results in a product that can be introduced for immediate nuclear service application.

To investigate the effect of tin, iron, chromium, and nickel on the nodular corrosion of Zircaloy-2, a special 5500-kg ingot was triple melted. The composition was intentionally varied within a controlled portion of the ASTM range along the ingot length. Specimens of the ingot with different compositions were hot worked and beta quenched at a common size. Strip specimens (0.67 mm thick) were fabricated using three process schedules spanning the annealing parameter (∑Ai = ∑ti, exp — QIRTi) range applicable to current production practice for either tubeshell or strip material. Corrosion weight gains were obtained from a 500°C static autoclave test. A statistically significant reduction in 500°C weight gain was found as (1) the percentage nickel and iron increased; (2) the percentage of tin decreased; and (3) the accumulated annealing parameter decreased.

A “controlled composition” is defined where nickel and iron are adjusted towards the upper ASTM composition limits and tin is adjusted towards the lower limit. The 500°C weight gain of controlled composition Zircaloy-2 is basically insensitive to accumulated annealing parameter over the range of 6.2 × 10−21 h to 1.1 × 10−17 h. The effect of beta quench rate on 500°C weight gains was also determined for Zircaloy-2 controlled composition material. Weight gains varied less than 5 mg/dm2 over a range of surface cooling rates from 18 to 36°C/s.

Analysis of the effect of beta quench rates on the uniform and nodular corrosion of Zircaloy-4 was performed. Uniform corrosion post-transition rates are not significantly affected by beta quench rate for 360, 400, and 420°C autoclave tests. During 450°C testing, unrecrystallized microstructures of Zircaloy-4 promoted retention of tight, adherent oxide layers for much longer exposures than fully recrystallized microstructures. 500°C static autoclave weight gains are inversely proportional to the logarithm of the cooling rate for Zircaloy-4.
Direct Measurement of Matrix Composition in Zircaloy-4 by Atom Probe Microanalysis
Authors: Wadman B , Andrén H-O
Published: December 2008

A method for analyzing the matrix composition of Zircaloy-4 (Zr-4) nuclear fuel cladding tubes has been developed, using atom probe analysis. This technique has a spatial resolution of about 1 nm, and makes it possible to measure matrix concentrations, between precipitates, with an accuracy of 0.01% for all elements. Two differently heat treated Zr-4 materials have been analyzed. It was found that the matrix in both materials was highly depleted with respect to iron and chromium. A difference in matrix iron content between the two materials was measured; the material with the longest intermediate annealings at higher temperatures was the least depleted of iron. This difference is explained in terms of iron diffusion to the precipitates during final annealing. The material with high iron concentration in the matrix also showed the best uniform corrosion properties, as tested in autoclave.
A Review of Pipeline Slurry Erosion Measurements and Research Recommendations
Authors: Summer RM
Published: December 2008

The basic factors which determine the ability of a slurry to abrade or erode its conduit are the properties of the slurry itself, the properties of the pipe material, and the nature of the flow. The Miller number currently used to predict sliding wear in pumps may be useful to predict relative wear resistance of pipelines until standardized pipeline tests are developed. Values of the hardness parameter of slurry and pipe material show a strong correlation with erosion capability of a slurry, although the derived empirical relationships are only valid for the specific system under study. Future abrasion studies should include: (1) standardization of slurry and pipe material properties and flow characteristics for laboratory and field investigations; (2) determination of the relationship between commonly used abrasion indices and pipeline service life; and (3) continued development of methods for measuring absolute abrasion rates.
Experimental Prospective Skiing Injury Study
Authors: Hauser W
Published: December 2008

A two-year comprehensive prospective experimental skiing injury study is presented. All skiers of two randomly chosen groups registered data of every skier day including injuries, inadvertent releases, hours of skiing, and falls.

The main objective of this study was to estimate the risk difference in skiers with a correct binding setting compared to the average binding setting in a normal skiing population. Also, the risk difference between normal ski poles with a special grip design regarding injury risk to the skier's thumb was investigated.

Nearly 18 000 skier/days were registered. Risk data regarding severe injuries show a similar range as in controlled clinical studies. In this prospective study, however, the bypass effect of unreported injuries can be avoided. Therefore, the overall injury rate including those injuries perceived by the skier as being nonsevere skiing injuries is distinctly higher. Among such injuries is the “skier's thumb” rupture of the ulnar collateral ligament of the metacarpophalangeal joint. Analyzing the injury pattern of this study shows that the most frequent injury is the “skier's thumb.”

Furthermore, many aspects of skier behavior can be shown with this study. The number of falls related to skiing ability and skiing performance and the rate of injuries per falls are reported.

The experimental design can show a distinctly lower risk of injury to skiers with proper binding settings compared to the control group. The risk of lower extremity equipment-related (LEER) injuries is about 3.5-fold lower with the properly adjusted ski bindings compared to the average binding setting we find today on ski slopes. The difference in the risk is caused by a distinct reduction of knee injuries.
Cruciate Ligament Injuries in Female Alpine Ski Racers
Authors: Ellman BR , Holmes EM , Jordan J , McCarty P
Published: December 2008

In recent years, more and more articles in the literature have documented female athletic injuries, especially knee injuries and, in particular, injuries to the anterior cruciate ligament. It has become obvious that this injury is a particularly serious one. A number of explanations have been given for this increased incidence. One obvious difference in recent years has been the more aggressive approach to athletics by the female participant.

To see whether female alpine ski racers were having a greater percentage of anterior cruciate ligament injuries, a study was developed in conjunction with the Vermont Alpine Racing Association (VARA). A questionnaire was sent to all VARA alpine racers during the summer of 1985, asking for information about ski injuries, training, mechanism of injuries, and treatment. The questionnaire included a release from the skier for information from treating physicians. In addition, coaches were sent printouts of responses, so that further responses and information could be obtained.

Out of approximately 600 racers, 196 Vermont alpine ski racers responded to the questionnaire. Of these, 135 respondees were male and 61 were female. Thirty-three male racers (twenty-five percent) reported knee injuries, but only four (three percent) reported cruciate ligament injuries. This correlated fairly closely with the percentages that have been reported for male basketball players. Twenty-three female racers (thirty-eight percent) reported knee injuries. This was not a remarkable difference from the male racers' percentage of knee injuries. Significantly, however, eleven (18%) of the females responding had cruciate ligament injuries, which was six times the incidence of their male counterparts. Almost one out of every five serious alpine female ski racers were reporting serious knee injuries that included anterior cruciate ligament tears!

This study has revealed a significantly higher incidence of serious knee injuries in female versus male ski racers. Because this fairly large group of skiers is well controlled as far as site of skiing (Vermont), level of expertise (all expert skiers), and equipment (essentially all have state-of-the art skis, bindings and boots), this observation appears to be significant. The most serious of the knee injuries is the anterior cruciate tear, and this was prevalent in females to males in a 6:1 ratio. Further study would seem to be merited to discover the cause of this difference, whether it be muscle strength, knee geometry, or equipment. Certainly, the concept of preventive bracing must be considered if this incidence of serious knee injuries continues or increases.
Concepts of Underground Corrosion
Authors: Escalante E
Published: December 2008

Corrosion in soil is a complex phenomenon, but there are some basic concepts that are useful in understanding the process. Underground corrosion is electrochemical in character, and this fact is used to describe the corrosion process in terms of an ordinary dry cell. The differences between corrosion in disturbed and undisturbed soil are discussed, and data are presented to emphasize these differences.

The results reveal that soil composition is less important than soil resistivity, but both are subordinate in importance to oxygen availability. Thus, corrosion is negligible in undisturbed soils where oxygen concentration is low.
Backcalculation of Pavement Layer Properties
Authors: Lytton RL
Published: December 2008

This was prepared for the symposium as a state-of-the-art paper. The paper summarizes the history and present use of nondestructive testing (NDT) and speculates on future developments and uses of NDT in backcalculating pavement layer properties. The paper concentrates on the backcalculation of the elastic stiffness of pavement layers.

Measurement methods include a variety of methods of applying loads to the pavement and a number of sensors of the pavement response. Loading methods include static or slowly moving loads, vibration, near field impulse, and wave propagation which applies to far field measurements. A fundamental distinction is drawn between near field impulse loads which closely simulate traffic loads and far field impulse loads, the results of which must be corrected substantially to provide realistic pavement layer moduli.

Analysis methods are surveyed, including some historical methods, microcomputer methods, impulse and response analysis methods, and systems identification methods. The historical methods include two-layer closed form and graphical methods, equivalent layer methods, and a closed-form multilayered method that searches for the best set of moduli to satisfy a leastsquares criterion. Microcomputer methods are described generically, noting all of their common features, including methods of dealing with both random and systematic errors in measuring and computing layer moduli. Random errors can be reduced by repeating the measurements. Systematic errors include the assumptions used in the backcalculation process, including nonlinearity. The results of an exercise conducted to estimate the size of systematic errors is reported. Impulse and response methods analyze the complete signals to determine a “transfer function” of the pavement from which the complex moduli of the layers can be backcalculated. Some speculation is offered on how this information may be used to determine fatigue and permanent deformation properties of pavement layers. A systems identification method of analyzing far field measurements is illustrated.

Uses of nondestructive testing in the future are envisioned to include layer thickness, asphalt or water content, density, elastic stiffness, creep compliance, fracture, and permanent deformation properties. A strategic objective of NDT methods is for them to become the primary method of measuring pavement material properties.
The Multidepth Deflectometer (MDD) System for Determining the Effective Elastic Moduli of Pavement Layers
Authors: De Beer M , Horak E , Visser AT
Published: December 2008

This paper describes a nondestructive pavement testing system called the multidepth deflectometer (MDD), which is used to measure depth deflection profiles of pavements. Effective elastic moduli of multilayered pavement structures can be backcalculated from these measurements. This system was developed in South Africa during the late 1970s to enhance the extensive program of full-scale accelerated testing with the aid of the heavy vehicle simulator (HVS).

The MDD consists of a series of up to six linear voltage differential transducers (LVDTs) installed vertically into the pavement at preselected depths in a relatively small-diameter hole. Normally the MDDs are anchored at a depth of approximately 2 m below the surface of the pavement. Resilient depth deflections are measured with the MDD in association with a moving load.

Case studies of measured deflections and backcalculated effective elastic moduli are given for tests on an asphalt base, a granular base, a cemented base, and a concrete base pavement section. The results are interpreted and discussed in terms of the behavioral characteristics and pavement responses, including permanent deformations. It was found that: 1. Asphalt bases may become granular after extensive accelerated testing. 2. Crushed stone bases may become stronger as a result of trafficking. 3. Lightly cemented bases crush near the surface, thus weakening the layer. 4. One concrete pavement debonded from its subbase after 190 000 load repetitions.
Application of Ground-Penetrating Radar and Infrared Thermography to Pavement Evaluation
Authors: Holt FB , Eckrose RA
Published: December 2008

New technologies have enabled the pavement engineer to develop a better picture of the pavement structure. Two of these new technologies are ground-penetrating radar and infrared thermography. Each of these techniques allows the pavement engineer to nondestructively evaluate subsurface defects within and under the pavement. Infrared thermography is now widely used to determine the location of delaminations within the pavement.

In the case of delaminations or debonded sections of pavement, the thin delaminated area will heat faster than the adjacent thicker section, and the infrared scanner will detect temperature differences between the two areas. This process is widely used to inspect bridge decks. It is used to determine the extent of deterioration beneath asphalt overlays on the deck and thus save the costs of removal of the asphalt and any waterproofing membrane.

Ground-penetrating radar can be used to determine a number of characteristics useful to the pavement engineer in developing a rehabilitation scheme. Radar is used to determine the condition of joints in concrete pavement, to locate and size voids beneath the pavement, to determine the thickness of pavement, and to determine the composition of the pavement structure.

Case histories are presented to discuss each of these technologies and their applications. These technologies are presently being written into ASTM standards for particular applications, including determination of delamination using infrared thermography and determination of pavement layer thickness using ground-penetrating radar. Limitations in the use of the techniques are also discussed.
Deflection Reading Accuracy and Layer Thickness Accuracy in Backcalculation of Pavement Layer Moduli
Authors: Irwin LH , Yang WS , Stubstad RN
Published: December 2008

Accurate deflection readings must be obtained when using NDT devices in order to obtain correct backcalculated layer moduli. This paper provides an analysis of the sources of deflection errors and illustrates through a series of examples how random deflection errors and random pavement thickness errors affect backcalculated moduli.

The consequence of these errors is most pronounced in the backcalculated modulus of the surface course. The moduli of the base and subbase layers are also affected, and the subgrade moduli are only slightly affected by these errors. To some degree this outcome may be due to the bottom-to-top approach used by the backcalculation program MODCOMP 2.

The consequence of the variability of the backcalculated moduli on the required pavement overlay thicknesses was found to be minimal. This was due to the fact that, generally speaking, data errors which cause an overestimate of the base course modulus also cause an approximately equally significant, but opposite, underestimation of the surface course modulus. Thus, the needed overlay requirement remains nearly the same.

The paper shows how certain FWD calibration and testing procedures can be used to minimize deflection measurement errors. The accuracy of backcalculated moduli is shown to be determinable from the RMS error of the deflection fit. The examples provide an impression of the extent to which random layer thickness errors and deflection measurement errors will influence the ability to discern point-to-point variability of layer moduli for the specific pavement structure considered in this investigation. This provides a perspective from which the practical accuracy of the backcalculation approach can be judged.
ILLI-SLAB and FWD Deflection Basins for Characterization of Rigid Pavements
Authors: Foxworthy PT , Darter MI
Published: December 2008

Deflection-based nondestructive evaluation methods for highway and airfield pavements rely wholly on mechanistic models of pavement behavior under load to characterize certain fundamental properties of individual pavement features (pavement section of similar thickness, construction history, and traffic). Once these key pavement parameters are quantified, areas of immediate concern can be identified for maintenance or rehabilitation, and an evaluation of the future performance of the entire feature can be made. The procedure sounds simple enough, until one tries to accomplish the task for an entire airfield which might contain well in excess of 200 distinct features. This paper details how the deflection basin created at the center of a rigid pavement slab under loads produced by the falling weight deflectometer (FWD) can be used in conjunction with the ILLI-SLAB finite-element model to backcalculate the two key parameters needed to characterize a classical Westergaard rigid pavement, a dynamic Young's Modulis (E) of the concrete surface, and a composite dynamic modulus of subgrade reaction (k) for the supporting layers of the system. The deflection basin is described in terms of two independent variables, the maximum deflection under the center of the FWD loading plate (D0) and the cross sectional “area” of the basin. The independent nature of these two variables is critical to the uniqueness of the backcalculated parameters. Using the ILLI-SLAB model, ranges of dynamic E and k that bound the actual field values are input to the computer, along with the actual FWD load, to produce a graphical solution. An iterative computer solution is then outlined that makes the task of backcalculating dynamic E and k for several hundred features more manageable. A correlation is presented that relates dynamic k values to traditional static k values determined from plate-bearing tests. Finally, comparisons between measured deflections in the field and predicted deflections using backcalculated parameters on the computer are made at center slab to verify the accuracy and repeatability of the technique for a wide variety of temperatures and thicknesses. It is only after the validity of the technique is established that confidence can be placed in the calculated stresses due to actual loads and, therefore, the evaluation itself.
A Simple Method of Measuring Pavement Rebound Deflection Bowl Data and Calculating Moduli
Authors: Rajagopal AS , Justo CEG
Published: December 2008

A simple instrument was developed by modifying the Benkelman beam so that the ordinates of the rebound deflection bowl could be measured at five points at 75-mm intervals from the center of dual wheel load, using four additional sets of auxiliary levers and dial gauges. This instrument was used to measure the ordinates of rebound deflection bowls on selected test stretches of flexible pavements in the southern region of India. As most of these pavements consist of granular layers in the subbase and base course with a thin bituminous surface course, the rebound deflection bowls were found to be deep and narrow. The rebound deflection bowl data collected were utilized for the back calculation of E values of pavement layers by finite-element method using the computer program FEAP. The paper presents the details of the simple instrument, developed at a low cost to measure the rebound deflection bowl and a methodology for the back calculation of E values of pavement layers using the rebound deflection bowl data.
A Performance Comparison of Selected Backcalculation Computer Programs
Authors: Mahoney JP , Coetzee NF , Stubstad RN , Lee SW
Published: December 2008

This paper provides an overview of six different techniques which were used to estimate the “elastic modulus” of five pavement sites located in Washington State. Five of the techniques were backcalculation computer programs and the remaining one was laboratory-determined moduli (diametral and triaxial). Further, these sets of derived moduli were used to assess the needed overlay thickness (for a fixed traffic level) for each technique.

A comparison of the moduli results revealed more “agreement” than “disagreement.” Overall, the overlay thicknesses were, in general, quite similar with a few exceptions. Further, a number of factors were presented which may have contributed to some of the differences.