bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance Characteristics of Four Rotary Atomizers
Authors: Derksen RC , Bode LE
Published: December 2008

A one-dimensional imaging probe was used to measure samples of the spray distribution produced by four different rotary atomizers operating at several different flow rates and rotary speeds using tap water and vegetable oil as carriers. The operating characteristics of the laser imaging probe affected the data collection results. The warm-up interval, effective sampling width, droplet velocity, and spray density were the most critical factors. Each rotary atomizer produced a range of droplet sizes for which uniformity depended on the operating conditions and liquid carrier. At water flow rates below 0.5 L/min, the Micron Micromax produced the most uniform droplet distributions. At rates above 0.5 L/min of water, the Spraying Systems RotoJet produced the most uniform droplet distributions. A larger selection of volume median diameters was produced using vegetable oil rather than water as the carrier. The uniformity of the droplet distributions is controlled better with oil. The RotoJet produced the most uniform droplet distribution with oil in comparison with the other atomizers. There was little difference between water and oil as carries in the drift potential at low rotational speeds. However, at higher operating speeds the drift potential was reduced by using oil as the liquid carrier.
Agricultural Formulation Stability Studies Using a Personal Computer
Authors: Demchak RJ , Maurer CH
Published: December 2008

Computer programs have been written which manage stability studies for agricultural formulations. The programs have been interfaced with a chromatography software package from Nelson Analytical. They are used to initiate stability studies, automatically file stability data from high-performance liquid chromatography (HPLC) equipment, and access composition and stability data for reports. In addition, they are used to search the composition data files and to update the files on auxilliary disks. A description is provided of the function of each program and how they are organized into a working system.
Determining Delivery Rates of Push-Type Granular Product Spreaders
Authors: Birthisel TD
Published: December 2008

A method for and the equipment needed for calibrating delivery rates of push-type granular product spreaders are discussed.

This method has proven to be suitable for use by product and equipment manufacturers in determining specific product spreader settings for the full range of push-type spreaders and for some small tractor-pulled models.

Experience over a wide range of materials and conditions has provided numerous insights into some underlying principles and problem areas. These are treated briefly and include the following: (a) the need for proper metering orifice calibration, (b) variation between individual spreaders of the same model and manufacturer, (c) flow variations in relation to the hopper-fill level, (d) the nonlinear relationship between the flow and the spreader setting scale, (e) problems due to spreader wear, (f) variation due to the product repose angle, and (g) variation due to particle size changes in the product.
Ball Mill and Hub Test Methods for Slurry Erosion Evaluation of Materials
Authors: William JS
Published: December 2008

Abrasive wear under wet sliding conditions can be very severe on alloy steels, not to mention expensive. Armco has developed an austenitic stainless steel called NITRONIC 30 having superior wear resistance compared to abrasion-resistant (AR) steels and most stainless steels. Two different laboratory tests were used to characterize the corrosive wear of these steels, a hub test and a ball mill test. Different corrodents of varying degrees of severity were used such as distilled water, synthetic sea water, synthetic nickel mine water, and a mixture of sodium chloride plus acetic acid. Other variables such as surface roughness and bulk hardness were also studied.
The SAR Number for Slurry Abrasion Resistance
Authors: Miller JE
Published: December 2008

With the use of the Miller Number for slurry abrasivity and its usefulness in the slurry pumping industry in predicting pump wear, it became obvious that the same test could be run in “reverse” to determine the effect of a “standard” slurry on a candidate material, thereby giving a relative measure of how a particular material would perform. In fact, about half of the 20 Miller machines in existence throughout the world are used specifically for wear or abrasion-resistance tests.

In this presentation the machine will be briefly described along with the basic procedure for determining SAR (slurry abrasion resistance) as derived from the Miller Number procedure.
A New Flow-Through Slurry Erosion Wear Test
Authors: Madsen BW , Blickensderfer R
Published: December 2008

A new flow-through slurry test developed by the Bureau of Mines significantly reduces abrasive particle degradation and contamination of wear debris in the slurry during the test. Fresh slurry is continuously fed into the test container as used slurry is discharged. Sixteen stationary specimens form the walls of the container in which the slurry is circulated by an impeller. Slurries of silica sand in water can range from 1.3 to 34 weight % solids as the sand flow ranges from 90 to 1600 g/min. An American Foundrymen's Society (AFS) 50/70 mesh test sand was used. Results of tests conducted on a variety of materials showed that the wear rate was constant with time for each material. In contrast, when no fresh slurry was added, as in a conventional slurry pot test, the wear rate decreased significantly as the test proceeded. This decrease is attributed to micropolishing of the surfaces of the abrasive particles. The relative effects of cutting wear and deformation wear during slurry erosion are described.
Hydraulic and Metallurgical Criteria in Slurry Pumping System Design
Authors: Sinha SK
Published: December 2008

Hydraulic transportation of slurries is being adopted for short-distance, loop-in-process industries as well as for long-distance pipeline transportation of mining ores. The presence of slurry causes excessive wear on pump components as well as on the system. Wear depends on the type of slurry to be transported by the pumping system. It is, therefore, essential to select proper metallurgy so that the life of the system is increased and so that minimum possible repair and maintenance are required. There is a need for more technological innovation to adopt a proper sealing system and to use special elastomers and other materials to increase the life of the pump components. Centrifugal pumps are used normally for the short loop system, where medium and low pressure is required. Positive displacement pumps are used for long-distance transportation with a high-pressure and low discharge requirement. Special care is required to design the hydraulic passage, depending on the size of the solid being pumped in the design of components for centrifugal pumps. Glandless pumps are also developed to avoid the complex sealing system.
Industrial Problem Solving by Microscopic Fourier Transform Infrared Spectrophotometry
Authors: Miseo EV , Guilmette LW
Published: December 2008

This paper is divided into two separate parts. The first part of the paper describes the permanent mount for an infrared microscope. The original design called for the microscope to be put in the infrared sample compartment of a Digilab FTS-15 spectrometer. Our changes allow the microscope to be permanently mounted using the original external beam configuration of the instrument with changes in the base plate optics on the microscope. The second part describes four analytical applications of the microscope showing how it can be used to substntially reduce sample preparation and allow examination of very small specimens. These four applications include identifying a lubricant in a nylon block, identifying a microcontaminant, elucidating an ink formulation, and looking at a multilayer polymer film.
Fatal Skiing Accidents in Austria—Epidemiology and Analysis
Authors: Berghold F
Published: December 2008

This study analyzes the circumstances and influences that led to fatal skiing incidents in Austria between 1983 and 1986 (268 cases). Seventy-four skiers died by injuries during on-piste skiing, 17 died during off-piste skiing, and 99 died in avalanches. So called nontraumatic fatalities, mostly cardiac arrests, have been reported in 51 cases on piste, 11 cases off piste, and 34 during cross-country skiing.

The results show that more than two thirds of all deaths caused by injuries in on-piste skiing do not actually occur on the piste itself, but suddenly after the marked paths have been left. About half of all the fatal collisions occur by crashing into trees; fatal collisions between two skiers are very rare. Fatal accidents off piste are caused by falls over rocky areas and by avalanches. Although off-piste skiers starting from cable-car stations definitely outweigh the number of ski mountaineers, mountaineers suffer avalanche deaths much more frequently than the others. Contrary to common belief, incidents caused by cardiac arrest are extremely rare for both alpine and cross-country skiing.

These results may be useful in developing detailed safety precautions for skiers.
Unilateral Fracture of the Posterior Elements of the Lumbar Spine in Alpine Skiing
Authors: Yamagishi T , Yahashi K
Published: December 2008

Three patients with unilateral fracture of the posterior elements of the lumbar spine suffered while they were alpine skiing are presented. The common mechanism of injury was hyperextension with compression. A rotational element may be implicated in single facet fractures. Unilateral fracture of the lumbar spine without dislocation can be managed conservatively, but these patients have to be followed closely. These results indicate that the lumbar neural arch, at the pars interarticularis, is vulnerable to mechanical fatigue. Attention should be given to young or adolescent skiers with acute injury of the lumbar spine.
Eyewear-Related Eye Injuries in Snow Skiing
Authors: Piziali RL
Published: December 2008

Eye injuries have historically represented a small percentage of skiing injuries. With the passage of ASTM Specification for Eye Protective Devices (F 659) in 1980 it was anticipated that broken glass-related injuries would decrease. This paper examines the history of eyewear-related eye injuries in skiing by pursuing several approaches: (1) a review of the literature, (2) a review of the injuries reported to the National Electronic Injury Surveillance System, (3) a review of the National Ski Areas Association/ASTM 3-year study, (4) a review of the 11-year Sugarbush North study, and (5) a telephone survey of 29 ski area medical facilities and nearby hospitals.

The following observations are made: (1) eye injuries in skiing where eyewear is mentioned are generally minor and infrequent, approximately 18 per year in the United States and (2) injuries as a result of broken lens glass are extremely rare and appear to be almost nonexistent since the passage of the eyewear standards.
Acute Arterial Occlusion Caused by High Ski Boots Treated with Low-Dose Streptokinase
Authors: Essinger A
Published: December 2008

In the past 15 years ski boot design has changed drastically and, even though it has been improved notably, boots are still the most potentially neuralgic part of the equipment. The unusual case of a 45-year-old woman who suffered thrombosis of the 3 arteries of the leg, approximately 10 cm above the ankle joint, is reported. Treatment consisted in low-dose thrombolysis and resulted after 3 days in recanalization. Venous occlusion and embolism as well as neurologic lesions as a result of the tourniquet effect of modern ski boots have already been reported in the literature, but this seems to be the first reported case of an acute arterial occlusion caused by a ski boot.
A New Lower Leg Prosthesis with Simulation Device for the Achilles Tendon
Authors: Menke W , Bodem F , Casel J , Volkert R
Published: December 2008

In former investigations it could be shown that binding release by active plantar flexion of the ankle joint has to be considered a regular heel release mechanism that occurs, in particular, in slow frontal ski falls. Based on these findings it seemed necessary to design a new lower leg prosthesis for testing ski boot design and skier/ski boot/ski binding interactions. This new lower leg prosthesis is presented in the following, and preliminary results of some pilot tests with the new prosthesis are demonstrated.
Measurement of Boot Loads Using a Second-Generation Microcomputer-Controlled Snow Ski Binding System
Authors: Wunderly GS , Hull ML , Maxwell SM
Published: December 2008

In the study of sports biomechanics, alpine skiing injuries have always demanded significant attention. To aid in understanding the loading phenomena associated with alpine skiing, a new research binding system has been designed, which enables both the recording of boot loading data and actively controlled release of the skier's boot from the ski. The new research binding system consists of three hardware components: a dynamometer, which senses all six load components at the boot/ski interface; an electromechanical device capable of releasing the boot from the ski; and a new general purpose microprocessor-based data acquisition and release control module. Constructed integrally with the dynamometer, the release mechanism is activated by electrical command from the control module. The mechanical and electrical design features of the dynamometer/release mechanism as well as important features of the hardware and software of the data acquisition and control module are discussed briefly. The system has been tested both in the laboratory and on the ski slopes. The emphasis of this paper is on the boot loading data acquired through field testing and observations on the loading environment during common recreational skiing maneuvers. Through analysis of the data, insight into both the style and safety aspects of alpine skiing is gained.
Elevated Racer Binding Settings and Inadvertent Releases
Authors: Young LR
Published: December 2008

Alpine ski racers generally set their ski bindings higher than binding manufacturers and ASTM/IAS (International Association for Safety and Skiing) recommendations for expert skiers. Racer binding settings among two groups of recreational racers were investigated and correlated with incidences of inadvertent binding releases during racing. Preliminary findings confirmed higher settings among both 13-year-old children racers (median 1 scale indicator above S recommendation) and among adult Masters recreational skiers (median 2 scale settings above recommendation for the toe and 2.5 above recommendation for the heel).

Reliable reports of inadvertent release incidents during races were investigated. In addition to the lateral release at the toe, which constituted almost all slalom inadvertent releases, associated with rapid onset of torque at a gate, the common giant slalom inadvertent heel release was documented. This latter event can occur when the ski is pressed down into a trough well below a giant slalom gate, with skier weight far forward and deceleration of the weighted ski, and is not prevented by high heel release settings. This common heel “prerelease” corresponds to the new inadvertent heel release mechanism (“Brown's Bow”) identified by Brown and Ettlinger (ASTM STP 860, 1985, pp. 224–237). A related heel inadvertent release upon sudden unweighting is also suspected.
Modeling Forces on the Anterior Cruciate Knee Ligament During Backward Falls While Skiing
Authors: Bally A , Boreiko M , Bonjour F , Brown CA
Published: December 2008

In recent years a dramatic increase has been observed in isolated anterior cruciate knee ligament (ACL) lesions and in knee sprains where the principle injury has been to the ACL. Traditional mechanisms for this type of injury are not, in general, consistent with the type of fall nor do they explain why there should be such an increase in ACL injuries. One new mechanism that has been proposed is the boot-induced anterior drawer. In a fall involving this mechanism, a skier is off-balance posteriorly such that loads are applied to the tail of the ski tending to push it forward and rotate the tip down. The loads are transmitted to the skier through the boot which pushes the tibia anteriorly relative to the femur, thus stressing the ACL. In this work, the loads on the ACL have been modeled during a boot-induced anterior drawer incident. These loads have been shown to increase in the impact phase with increased slope and in the impact and rotation phases with increased boot stiffness in backward lean.
Skier's Thumb: Continuing Biomechanical Analysis
Authors: Lamont MK
Published: December 2008

The terms “Gamekeeper's thumb” (chronic joint trauma) and “Skier's thumb” (acute rupture of the ulnar collateral ligament) are not synonymous terms. Skier's thumb can be classified into three grades which are indicative of the mechanism of injury. Because of the predominence of ligament failures (as against avulsion fractures), it is clear rotational forces are responsible for the injury. The rotary force required to rupture the ligament is about half that required to cause damage in pure abduction. The injury could be totally prevented by providing a shield on the front of all ski poles.
A Technique for Analyzing the Thermal Resistance of Ski Gloves
Authors: Roberts CC
Published: December 2008

The thermal resistance of ski gloves is an important design characteristic when evaluating ski glove performance. Classical experimental techniques involve a copper “hand” that is instrumented and heated. The hand is of a particular size that may not fit gloves from many manufacturers. A new technique is proposed using a flexible bladder shaped to simulate a hand. The bladder is attached to a chamber containing a working fluid. By heating the chamber, vapor is generated from the liquid, which pressurizes the bladder to a given pressure. This allows the bladder to fit consistently several different sizes of gloves. The liquid inside the chamber generates vapor that travels to the bladder and condenses in a fashion similar to that of a thermosiphon. This results in nearly isothermal condensation on the bladder wall. When an infrared scanner is used to acquire a thermogram of the glove, various regions of surface temperature are recorded. This can be reduced to temperature difference across the glove material that is proportional to the thermal resistance of a glove. Comparative thermal resistance tests are presented. More quantitative thermal resistance tests are proposed by using heat flow as well as temperature difference to calculate thermal resistance. The expandible bladder and infrared imager offer a new and more flexible way to assess ski glove thermal resistance.
Ratios of Ideals—A New Twist to an Old Idea
Authors: Cooper HR , Earle MD , Triggs CM
Published: December 2008

Consumer estimations of “ideal” product attributes have been used for many years to guide product development. Massey University work has studied consumer ideals calculated as absolute, interval and ratio scores. Ideal absolute and ideal interval scores, because of context effects, have proved of limited value in long-term projects. Ideal ratio scores indicating percentage change needed to make an attribute “ideal” have proved more useful.

Both “fixed” and “floating” ideals are useful in product development; “floating” ideals in the early stages of product concept development and the later stages of product testing; “fixed” ideals in the laboratory development of the product. Multivariate analysis of data containing ideals is useful in understanding the “ideal” in terms of other products and their attributes. Ideal ratio scores are needed to give specific information to guide product development. It is recommended that both ideal ratio scores and multivariate analysis of data be used.
A Simplified System for Doing ICP Analysis on Radioactive Samples
Authors: McCown JJ
Published: December 2008

A sequential inductively coupled plasma atomic emission spectrometer (ICP-AES) was procured in 1983 for use on solutions from leach tests of fully loaded spent fuel and glass. The instrument was set up by Westinghouse Hanford Co. in a 3 by 6-m (10 by 20-ft) laboratory room in a radiochemistry building at the Hanford Engineering Development Laboratory.

The installation was designed to be as simple as possible, making full use of the building's exhaust and filtration capabilities. Previous experience in using a standard flame photometer and an atomic absorption spectrometer had shown that total enclosure of the plasma section should not be required.

This rather simple installation has been used for over two years without contamination of the ICP-AES or the laboratory work areas. Details of the installation, operation, and types of materials analyzed are presented.
Use of an Inductively Coupled Plasma Emission Spectrometer System in a Separations Process Plant Laboratory
Authors: Hiller JM , Lawry DH
Published: December 2008

A commercially available inductively coupled plasma (ICP) emission spectrometry system has been modified and placed into operation for the analysis of radioactive samples in support of a separations process plant. The modifications consisted of building a ported hood around the standard torch box, modifying the gas and electrical connections in and to the torch box, providing an off-gas purification system and providing a shielded drain system. The ICP system, its modifications, support equipment, sample preparation, and two years of working experience are described.
Adaptation of a Beckman Spectraspan VI Spectrometer to a Plutonium Glove Box
Authors: Lovell AP , Glenn GE , Marshall TK , Hahn TR
Published: December 2008

The analytical chemistry group of the Los Alamos National Laboratory has modified a Spectraspan VI D-C plasma emission spectrometer for the analysis of nuclear material by adapting it to a plutonium glove box. The plasma source compartment of the spectrometer was enclosed in a specially designed glove box end plate on the end of a two-station containment box assembly.

Very little modification of the spectrometer was necessary to mount the torch on the glove box wall. A quartz window was inserted in the glove box wall to provide an optical interface between the spectrometer and the source. There was no further modification of the optical path. To maintain optimum instrument performance, the distance between the plasma and the entrance slit was designed to remain the same as it was originally.

The engineering changes to the jet assembly and glove box, the health and safety issues considered, and air flows through critical areas of the glove box are described.
The Los Alamos Facility for Inductively Coupled Plasma Atomic Emission Spectrometric Analysis of Radioactive Solutions
Authors: Apel CT , Beugelsdijk T , Gallimore D , Myers WH , Faires L
Published: December 2008

This report discusses the selection and installation of an inductively coupled plasma atomic emission spectrometer for the analysis of radioactive solutions. An Applied Research Laboratories Model 3580 inductively coupled plasma atomic emission combination polychromator and sequential scanning monochromator was selected. The instrument performance, dry box design, interfaces, proposed separation schemes, and laboratory layout are discussed.
Development and Layout of an ICP Excitation Unit in a Hot Cell
Authors: Mainka E , Müller HG , Neuber J
Published: December 2008

The layout of an inductively coupled plasma (ICP) excitation unit in a hot cell is described. The system has been built to process highly radioactive samples by an analytical technique based on emission spectroscopy after plasma excitation. Many years of experience with an alpha tight glove box had provided the basis for the system to be set up. The assembly of the components used, including the torch, nebulizer, and high-frequency coil with an impedance unit, is described in detail. The criteria for selection of the components were their ease of handling and ruggedness. These are properties that should not be underestimated, considering the aggravated conditions of work connected with remote handling.
Environmental Characteristics Controlling the Soil Corrosion of Ferrous Piping
Authors: Palmer JD
Published: December 2008

The characteristics of soils controlling the external corrosion of ferrous piping materials are examined with particular reference to an American Water Works Association (AWWA) rating formula. The relationship and reliability of the following characteristics as corrosion predictors are examined: resistivity, pH, redox potential sulfides, moisture, and chlorides. Metallurgical test results illustrating the mechanism of attack on cast iron and ductile iron are presented and the apparently different performance of the two materials is reviewed. Mitigative and preventive measures are mentioned and the organization of a corrosion control program outlined.
Statistical Analysis of Soil Characteristics to Predict Mean Time to Corrosion Failure of Underground Metallic Structures
Authors: Bushman JB , Mehalick TE
Published: December 2008

In past years, the corrosion engineer has not been able to assess the influences of various soil characteristics on the rate of corrosion of buried ferrous metal structures. In 1979, the application of multivariate statistical analysis techniques to evaluate a broad range of measurements of soil and structure data was first used successfully to predict a mean time to corrosion failure (MTCF) for underground storage tank systems (USTSs). More recently, similar procedures have been developed to determine the MTCF for discrete sections of cast iron water pipelines (CIWPs). This paper will summarize the methodologies used to predict MTCF of both USTSs and CIWPs. It is anticipated that these methodologies may be more broadly applied to other buried metal structures, including oil and gas transmission and distribution systems, steel-reinforced concrete pipelines, etc.
Comparison of Two Falling Weight Deflectometer Devices, Dynatest 8000 and KUAB 2M-FWD
Authors: Crovetti JA , Shahin MY , Touma BE
Published: December 2008

This paper presents the results of a detailed comparison conducted by the authors between two falling weight deflectometers, the Dynatest Model 8000 and the KUAB two-mass falling weight deflectometer (2M-FWD). The Dynatest Model FWD has been operating in the United States for several years. It is based upon the principal of dropping a mass on a single buffer system connected to a rigid plate resting on the pavement surface. The 2M-FWD is a newly improved version of the KUAB falling weight deflectometer which recently has been introduced into the United States. It is based upon the principal of dropping a mass on a double buffer system separated by a second mass which is connected to a segmented plate resting on the pavement surface. The addition of the second mass and buffer results in a consistent half sine curve shaped load pulse with a longer duration of loading. The two devices also differ in the type of sensor used to measure the surface deflection during loading. The Dynatest device uses geophones which measure deflection up to 2 mm, while the 2M-FWD uses LVDTs which are capable of measuring surface deflections up to 5 mm. Other hardware differences between the two devices also are discussed in the paper.

A testing program was initiated to obtain comparative deflection data from a variety of pavement types including flexible and rigid pavements over weak and strong foundations. In addition to the comparison of actual deflection data, layer moduli are computed and compared for each device. Cores from representative test locations were obtained to verify in-field pavement thicknesses.
USAF Wave Propagation NDT Method
Authors: Wang MC , Schauz W , Amend J , Greene JL
Published: December 2008

This paper reviews U.S. Air Force efforts to find a nondestructive testing (NDT) method for evaluating airfield pavement load-carrying capabilities. The paper concentrates its discussion on the wave propagation nondestructive testing method for evaluation of airfield pavements. The method was used by the Air Force from 1983 to 1985. The information given for the wave propagation method includes the theoretical background, test equipment and procedures, methods of test data analysis, and pavement analysis procedures. Also presented are: comparisons of results between the wave propagation NDT and destructive evaluation methods; reasons for the Air Force moving away from the wave propagation method; ongoing research; and possible future use of the wave propagation method.

The wave propagation method used by the Air Force was composed of: a hardware for field testing, data reduction, and analysis; and software for evaluation of allowable gross loads (AGL) through a computer analysis. The test equipment was composed of an impact loader and a data acquisition system, both housed in a self-propelled van.

The impact loader could be operated both by program control and manually. The pavement response to the impact loading was monitored with accelerometers which were mounted on the pavement surface at various distances from the loading plate. A computer was used to perform fast Fourier transform (FFT) of the test data. From the results of the FFT analysis, graphs relating phase angle with frequency, and wave velocity with wave length (dispersion curves), were obtained. From these graphs, appropriate wave velocity values were selected for determination of the elastic modulus of each pavement constituent layer. These elastic modulus values were then used to analyze the critical pavement response to a desired aircraft loading by means of a computer program named AIRPAVE. Based on these critical response data, together with the evaluation criteria, the number of aircraft operations that could be supported by the pavement were determined.

Using the wave propagation NDT method, a number of airfield pavements were evaluated between 1983 and 1985. Results of the NDT evaluations were compared and correlated with the results of destructive testing methods. A good correlation, with a small percent of difference in AGLs between the two methods, was shown. However, because of a number of advantages associated with the falling weight deflectometer (FWD) over the wave propagation method, the Air Force has adopted the FWD as its primary evaluation method.
Back-Analyzed Elastic Stiffnesses: Comparison Between Different Evaluation Procedures
Authors: Tam WS , Brown SF
Published: December 2008

The PADAL computer program was developed to back-analyze deflection bowls from pavement testing with the falling weight deflectometer. A validation exercise was carried out to check the prediction accuracy of the PADAL computer program in practical applications. The study compared laboratory elastic stiffnesses with the back-analyzed values from PADAL and showed that the best correlation was found for the asphaltic material, with an accuracy of around 20% above measured values. The correlation for granular subbases and clay subgrades was less good. Previous studies comparing in situ stresses and strains confirmed that the nonlinear elastic characterization in the subgrade layer gave significant improvement in the accuracy of prediction compared with a linear representation.

Comparison of dynamic analysis taking account of inertia effects with the static PADAL analysis showed the latter to be quite adequate for use with the falling weight deflectometer.

A simplified back-analysis procedure using the ELMOD computer program was extensively evaluated. It was concluded that this program is best used in predicting stiffnesses of two layered structures consisting of bound asphaltic material overlying the subgrade. In cases of three-layered structures, the prediction of stiffnesses for granular layers was found to be unrealistically large.
A Data Base Method for Backcalculation of Composite Pavement Layer Moduli
Authors: Anderson M
Published: December 2008

A program called COMDEF has been written for use in nondestructive evaluation of composite pavements. The program uses a new data base technique to speed program execution. COMDEF, like most backcalculation algorithms, compares measured deflections with theoretical solutions. However, the COMDEF approach applies interpolating functions to a data base of precalculated solutions, so that the comparison basins are calculated quickly with reasonable accuracy. A description and flowchart of the method used by COMDEF is included.

This paper discusses the role of nondestructive testing in pavement evaluation and the particular problems in evaluating composite pavements. Lack of knowledge about the degree of cracking in the rigid layer is a major problem, and backcalculated modulus is presented as a way to assess the degree of cracking in the rigid layer. The use of a representative basin is discussed, and data are presented which indicate that this approach should not be used for composite pavements. A sensitivity study is presented which includes solutions using COMDEF and a general purpose backcalculation program. COMDEF consistently outperformed the general purpose program in both speed and accuracy. Laboratory modulus tests were performed on samples taken from three verification sites. Agreement between laboratory modulus tests on field samples and backcalculated moduli from COMDEF was excellent.
General Procedure for Backcalculating Layer Moduli
Authors: Uzan J , Lytton RL , Germann FP
Published: December 2008

An efficient microcomputer program for backcalculating moduli from nondestructive testing results is described. Its use is illustrated by analyzing a typical section where several deflection bowls were measured at the same location.

Sources of errors in the testing and backcalculating are presented and discussed. The error source is taken into consideration in the formulation of the objective function, the relative squared error between measured and computed deflections.

The Hooke-Jeeves' pattern search algorithm was selected for minimizing the objective function. The direct computation of the deflection at each move of the pattern search was replaced by the three-point Lagrange interpolation, using a data base generated ahead of time. The pattern search and interpolation were included in a microcomputer program named MODULUS, capable of performing and backcalculation in 1 to 2 min per deflection bowl. It is highly efficient where several deflection bowls are measured along the pavement section or at the same location.

The analysis of the typical section shows clearly that the measurement errors can be quite large. Averaging deflection measurements at each sensor cancels out some of the random errors and generally leads to acceptable values of the backcalculated moduli. The program MODULUS is especially suited toward these cases where multiple deflection basins are available for the same pavement geometry.
In Situ Material Properties from Dynamic Deflection Equipment
Authors: Uddin W , McCullough BF
Published: December 2008

Dynamic deflection equipment presents a very practical and cost-effective approach for nondestructive testing and evaluation of pavement-subgrade systems. The in situ Young's moduli are calculated by the inverse application of layered elastic theory to the measured dynamic deflection data. This paper discusses some of the fallacies associated with this iterative approach. The calculated moduli are user dependent and nonunique if the user inputs the initial set of moduli to start iteratives. A proven methodology to ensure uniqueness of the moduli is the generation of seed moduli as the function of measured deflections and radial distances of the sensors. The FPEDD1 (for pavements with asphalt concrete surfacings) and RPEDD1 (for rigid pavements) computer programs incorporate this methodology. The predictive equations used to generate seed moduli are based on numerous layered theory solutions and are therefore applicable to any region and soil condition.

This paper describes the approaches used in these programs to estimate nonlinear moduli for granular layers and subgrade soil, and considers rock layers. Examples are presented for in situ material properties from dynamic deflection data measured on a variety of pavementsubgrade systems. It is shown that an appropriate analysis technique yields comparable pavement moduli from the dynamic deflection data measured by vibratory or impulse loading equipment.
Development of the DBCONPAS Computer Program for Estimation of Concrete Pavement Parameters from FWD Data
Authors: Tia M , Eom K-S , Ruth BE
Published: December 2008

One of the major problems in the evaluation of concrete pavement systems is the accurate determination of pavement parameters such as elastic modulus of concrete, subgrade modulus, and edge and joint stiffnesses. One of the ways to determine these parameters is by matching a measured deflection basin caused by a falling weight deflectometer (FWD) to an analytical deflection basin computed by using a set of estimated parameters. This could be a very time-consuming and costly process. In response to this need, the user-friendly and flexible computer program DBCONPAS (Data Base for CONcrete PAvement Systems) was developed. The DBCONPAS program uses a data base of analytical results generated by the FEACONS (Finite Element Analysis of CONcrete Slabs) program. The data base can be expanded and updated easily. The program is adaptable to computers of various sizes, such as micro, mini, and mainframe computers. This paper describes the program structure, the program algorithm, the basic information in the data base, and the prediction equations used. DBCONPAS was used also to analyze FWD data obtained from several concrete pavement test sites in Florida. DBCONPAS was demonstrated to be an effective tool for analysis of concrete pavements.
Parameter Estimates of Pavement Structure Layers and Uniqueness of the Solution
Authors: Stolle D , Hein D
Published: December 2008

The question of uniqueness of backcalculated moduli of a pavement structure subjected to axisymmetric loading is addressed. Two simple examples are presented to demonstrate common difficulties associated with backcalculation, in particular problem conditioning. The sensitivity of the backcalculated solution to layer thickness, assumed Poisson's ratios, and seed moduli is examined for a two-layered problem. It is shown that it may be possible to use adjusted measured falling weight deflectometer (FWD) data together with static analysis to effect backcalculated moduli for the subgrade. However, it is concluded that the calculation of the pavement moduli from surface displacement data may not yield representative in situ pseudoelastic moduli because of the nature of multilayered stress analysis and problem conditioning.
FWD Backcalculated Moduli Compared with Pavement Pressuremeter Moduli and Cyclic Triaxial Moduli
Authors: Cosentino PJ , Briaud J-L
Published: December 2008

A relatively new in situ testing device, the pavement pressuremeter (PPMT), was used on three airport pavement subgrades in order to evaluate its usefulness in pavement design and evaluation. Four models which predict the modulus for various stress levels, various strain levels, various loading rates or creep, and repetitive loading were chosen since these loads are all encountered on airport pavements. An airport PPMT test was developed which enabled all four models to be evaluated. The PPMT moduli from the four models were compared with moduli from cyclic triaxial (CT) tests and moduli backcalculated from falling weight deflectometer (FWD) tests. The moduli comparison indicated that the pavement pressuremeter was capable of yielding moduli similar to both the cyclic triaxial and falling weight deflectometer tests. FWD deflections were compared with deflections predicted by inputting PPMT moduli and CT moduli into the finite-element program ILLI-PAVE. The PPMT-predicted deflections compared well with FWD deflections when the model 1/E = α + bϵ was used for clays and the model E = K1(ϴ/pa)K2 was used for sands.
A Mechanistic Method for Evaluation of Layer Moduli and Overlay Design
Authors: Khosla NP , Ali NA
Published: December 2008

Nondestructive testing (NDT) has long been used to evaluate flexible pavement structures. The increasing popularity of nondestructive pavement evaluation methods, based on interpretation of surface deflection, has promoted the development of several types of NDT devices. One such device is the falling weight deflectometer (FWD), which is used for the purpose of pavement evaluation in North Carolina. This paper presents a methodology for the testing, evaluation, and determination of overlay thickness required for a given pavement section and subgrade condition. The overlay design procedure presented makes use of some of the recent developments for analysis and design of asphaltic concrete overlays. The evaluation of in-service pavements includes the use of the deflection parameters developed by testing of the existing pavements with known geometry for determining the moduli of various pavement layers and the required overlay thickness. The method utilizes empirical values and the VESYS structural subsystem as an integral approach complementary to each other.

Six pavement sections across the state of North Carolina were selected for deflection testing. Deflection parameters were developed to characterize the deflection data from these pavement sections. In addition, the VESYS structural system was used to develop nomographs for the interpretation of the measured deflection basin parameters. These nomographs were used to backcalculate layer moduli from deflection parameters and known layer thicknesses using iterative solutions. The backcalculated layer moduli from these nomographs correspond to the climate conditions that happen to exist during the time of testing and must therefore be adjusted to other climatic conditions. A procedure for such an adjustment is also included in the design procedure.
Evaluation of Moduli Backcalculation Programs for Low-Volume Roads
Authors: Chua KM
Published: December 2008

At the present time, numerous computer programs are available for backcalculating layer elastic moduli using deflection basins obtained by nondestructive testing. These programs usually utilize both a forward calculation and a backcalculation scheme. This paper presents the results of a study made of several of these computer codes with deflection basins obtained from several low-volume (surface-treated) road sections using a falling weight deflectometer (FWD). A nonlinear finite-element program (ILLIPAVE) was first used to backcalculate the layer moduli of the surface-treated pavement sections using FWD deflection basins by the trial-and-error approach. A pavement dynamic cone penetrometer (PDCP) was also used (in situ) to measure the layer moduli. Several backcalculation programs, namely, BISDEF, CHEVDEF, ELSDEF, ISSEM4, MODCOMP2, LOADRATE, and MODULUS then were used to backcalculate the layer moduli. The forward calculation schemes considered include: BISAR, CHEVRON, ELSYM5, NELAPAV, and ELMOD was well as ILLIPAVE. All of these programs, including ILLIPAVE, are microcomputer based. The paper also includes an example problem which involves backcalculating the layer moduli of a 30.48-m (100-ft) stretch of a typical farm-to-market road in which deflection basins were taken at one-foot spacings.
The Use of Falling Weight Deflectometer Data in Monitoring Flexible Pavement Systems
Authors: Newcomb DE , Lee SW , Mahoney JP , Jackson NC
Published: December 2008

Pavement performance studies are being conducted in the states of Nevada and Washington for the purpose of developing mechanistically based pavement design procedures for highways. A critical element of each of these studies is the statewide characterization of the pavement materials. The materials characterization process has included laboratory and field testing for 16 sites in Washington and 27 sites in Nevada.

This paper presents the general approach used by these states in the development of mechanistic design methods and how resilient moduli inferred from falling weight deflectometer (FWD) data have been used in the process. The FWD has been used to monitor the variability of roadway materials and to ascertain the seasonal changes in material properties. Comparisons of laboratory-determined and field-estimated resilient moduli are discussed. It was found that there is generally excellent agreement between the laboratory and field results on subgrade modulus. The accuracy of granular base course modulus estimates primarily depends upon the thickness of the base course and the thickness of the asphalt concrete surface. Backcalculated asphalt concrete modulus values can differ significantly from laboratory values. However, if care is taken to account for the effects of temperature and rate of loading, the agreement for uncracked asphalt concrete can be good.

One of the important assets of the FWD is that it allows the evaluation of in-place materials variations. Thus, it is possible to realistically sample and test materials for design purposes. This, in turn, means that material properties can be treated more realistically than they have been in the past.

In the development of a mechanistically based pavement design procedure, it is necessary to account for seasonal variations in material properties. The FWD can be used for the purpose of monitoring how materials change with the environment. This information can be used to develop algorithms which describe these changes. Washington State has accumulated over two years of data regarding seasonal changes, and Nevada has just begun to gather these data.

This paper presents the approaches used by these two states in the development of pavement design procedures. It is hoped that the information contained herein will be of use to others considering similar efforts.