bluuebunny/crossref_metadata_2025 huggingface dataset:
Relevance of Impacter Shape to Nonvisible Damage and Residual Tensile Strength of a Thick Graphite/Epoxy Laminate
Authors: Poe CC
Published: March 2009

An investigation was made to determine the relevance of impacter shape to nonvisible damage and tensile residual strength of graphite/epoxy cases for the solid rocket motors of the Space Shuttle. Impacters were dropped onto 30.5-cm (12-in.)-long rings (short cylinders) that were 76.2 cm (30 in.) in diameter and 36 mm (1.4 in.) thick. The kinetic energies ranged from 17.0 to 136 J (12.5 to 100 ft∙lb). Some rings were filled with inert propellant and some were empty. A 5 kg (11 lb) impacter was used with a 12.7-mm (0.5-in.)-diameter hemisphere and a sharp corner attached. The rings were impacted numerous times around the circumference and cut into 51-mm (2-in.)-wide specimens. Because of a shortage of rings, impacts with a 6.3-mm (0.25-in.)-diameter bolt-like rod were simulated by quasi-statically pressing the rod against the face of individual specimens. All of the specimens were uniaxially loaded to failure in tension. Results from a previous impact study using a 25.4-mm (1.0-in.)-diameter hemisphere were also considered. For the range of impact energies investigated, the corner and rod always made visible damage on the surface, but the hemispheres did not. The damage on the surface consisted of a crater shaped like the indenter, and the damage below the surface consisted of broken fibers that appeared to result from shear failure of the matrix. The damage initiated when the contact pressure exceeded a critical level but did not become visible on the surface until an even higher pressure was exceeded. The contact pressures for the rod and corner exceeded the critical level to cause visible damage. The kinetic energy to initiate damage and to cause visible damage on the surface increased approximately with hemisphere diameter to the third power. For a given kinetic energy, the residual strengths did not vary significantly with indenter shape. However, the reduction in strength for nonvisible damage increased dramatically with increasing hemisphere diameter, 9 and 30% for the 12.7-mm (0.5-in.) and 25.4-mm (1.0-in.)-diameter hemispheres, respectively. Factors of safety for nonvisible damage increased with increasing kinetic energy. With the factor of safety for the filament-wound case (1.4), the maximum allowable kinetic energy was 123 J (91 ft ∙lb). The effects of hemisphere diameter on impact force, damage size, damage visibility, and residual tensile strength were predicted quite well assuming Hertzian contact and using maximum stress criteria and a surface crack analysis.
Fatigue Behavior of Continuous Carbon Fiber-Reinforced PEEK
Authors: Curtis DC , Davies M , Moore DR , Slater B
Published: March 2009

This paper examines fatigue behavior for AS4/PEEK and IM6/PEEK laminates. Tensile fatigue data in the form of stress-log n curves are shown for multiangle ply laminates at 23 and -55°C. Fatigue behavior is also examined for ±45 laminates at different cooling rates from the melt during consolidation. Compressive fatigue data are reported for 40-ply unidirectional laminates at test temperatures of 23 and 120°C. Again, the influence of cooling rate from the melt is explored. The paper also attempts to discuss an interpretation of the results in terms of the expected failure mechanisms that occur for these laminates and the chosen stress fields.
Fatigue Damage Mechanics of Notched Graphite-Epoxy Laminates
Authors: Spearing M , Beaumont PWR , Ashby MF
Published: March 2009

A modeling approach is presented that recognizes that the residual properties of composite laminates after any form of loading depend on the damage state. Therefore, in the case of cyclic loading, it is necessary to first derive a damage growth law and then relate the residual properties to the accumulated damage.

The propagation of fatigue damage in notched laminates is investigated. A power law relationship between damage growth and the strain energy release rate is developed. The material constants used in the model have been determined in independent experiments and are invariant for all the layups investigated. The strain energy release rates are calculated using a simple finite element representation of the damaged specimen. The model is used to predict the effect of tension-tension cyclic loading on laminates of the T300/914C carbon-fiber epoxy system. The extent of damage propagation is successfully predicted in a number of cross-ply laminates of the form (90i/0j)ns and the quasi-isotropic laminate (90/+45/-45/0)s. The dependence of damage on load amplitude and specimen size is also well described.

Residual strength is calculated as a function of damage dimensions for (90/0)s specimens using a stress-based failure criterion in conjunction with a Weibull dependence of the 0° ply strength on the volume under stress.
Effect of Interlaminar Normal Stresses on the Uniaxial Zero-to-Tension Fatigue Behavior of Graphite/Epoxy Tubes
Authors: Krempl E , An D
Published: March 2009

During the past several years, the Mechanics of Materials Laboratory of Rensselaer Polytechnic Institute (RPI) has developed a method of obtaining biaxial fatigue data under axial/torsion loading. A thin-walled tubular specimen can be made from prepregs by a layup procedure and tested in an MTS servohydraulic axial/torsion testing machine with computer control. We have provided completely reversed load-controlled fatigue data on graphite/epoxy materials under uniaxial and combined loadings using [± 45]s and [0, ± 45]s layups. The edgeless specimen eliminates suspected end effects and can be used for tests involving significant compressive loading.

Interlaminar normal stresses were thought to influence fatigue performance by enhancing delamination. To check on this hypothesis, zero-to-tension fatigue tests were run on graphite/epoxy [± 45]s tubes with and without internal pressurization. The pressure levels were chosen so as to compensate the suspected interlaminar tensile stresses. Fatigue test results in the range from 104 to 106 cycles with and without pressurization were within the same reasonable scatter band. In the course of testing, it was discovered that performance could be considerably improved by providing a restraint in the hoop direction by either inserting a mandrel or by including a 90° layer on the inside and outside. Fatigue tests with [90,±45]s specimens under zero-to-tension loading showed a significantly improved fatigue performance.
Effects of Notch Geometry and Moisture on Fracture Strength of Carbon/Epoxy and Carbon/Bismaleimide Laminates
Authors: Underwood JH , Burch IA , Bandyopadhyay S
Published: March 2009

Composite panels of various ply orientations and 1 to 2 mm thickness were tested in tension with a center notch to determine the translaminar fracture toughness and in bending with no notch to determine the bulk flexural strength and modulus. Carbon/epoxy panels with a variety of notch lengths and widths were subjected to laboratory air conditions before testing. Carbon/bismaleimide panels with one basic notch configuration were tested in three pretest exposure conditions: laboratory air, a 400-h exposure in a controlled moisture chamber, and a 4000 h exposure in a natural tropical environment.

The tests were performed to investigate the following effects on fracture and mechanical properties and on micro and macrofailure mechanisms of the laminates.

(a) Effects of notch width and length and ply orientation on translaminar fracture toughness were studied in 0/90 and 0/±60 carbon/epoxy laminates, including effects of notches produced by ballistic penetration.

(b) Effects of extended exposure to moisture and sunlight on fracture and mechanical properties were studied in various 0/90 layups of carbon/bismaleimide laminates. A direct comparison of controlled chamber and natural tropical moisture effects was made for two materials.

(c) The load-deflection macrobehavior of notched panels was noted and analyzed. Linear-elastic and J-integral analyses were used to determine critical values of stress intensity factor, K, at the onset of self-similar translaminar fracture. A simple splitting model was used to describe the interlaminar failure that competed with and often prevented the translaminar fracture.

(d) Scanning electron microscope fractography was used to investigate and contrast the microfailure mechanisms of the laminates. The differences in micromechanisms between carbon/epoxy and carbon/bismaleimide were related to differences in the macrofracture behavior of the materials.

Analysis was performed of the test procedures for determination of fracture toughness and flexural strength and modulus. The method used for fracture toughness and associated K, J, and displacement expressions were proposed for more general use in measuring translaminar fracture toughness of composites. Use of the four-point bending test for flexural strength and modulus revealed an error that can occur in this type of test that is not fully addressed in ASTM Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials (D 790-86).
Fracture of Fibrous Metal Matrix Composites Containing Discontinuities
Authors: Bahei-El-Din YA
Published: March 2009

The work of Dvorak et al. and Bahei-El-Din et al. on fracture of unidirectionally reinforced boron/aluminum specimens with a center notch is extended here for specimens with other types of discontinuities. The experimental results indicate that long, discrete plastic shear zones similar to those found at the notch tip are present in all specimens. The plastic zones grow from the discontinuity in the fiber direction. The measured fracture strength was not affected by geometry of the notch, it is only a function of the notch width/specimen width ratio. Finite element analysis of the specimens with center square hole provided the plastic zone length and the local stresses. The results verified that the criterion controlling fracture in center-notched specimens is applicable to other notch geometries. Namely, failure is controlled by a critical ratio of the largest principal stress to off-axis unnotched strength in the principal direction, in a small representative volume in the vicinity of the notch.
Fatigue Crack Growth in a Unidirectional SCS-6/Ti-15-3 Composite
Authors: Kantzos P , Telesman J , Ghosn L
Published: March 2009

An investigation was conducted to characterize and model the fatigue crack growth (FCG) behavior of a SCS-6/Ti-15-3 metal matrix composite. Part of the study was conducted using a fatigue loading stage mounted inside a scanning electron microscope (SEM). This unique facility allowed high magnification viewing of the composite fatigue processes and measurement of the near crack tip displacements. The unidirectional composite was tested in the [0]8 (that is, longitudinal) and [90]8 (that is, transverse) orientations. For comparison purposes, unreinforced matrix material produced by the identical process as the reinforced material was also tested.

The results of the study reveal that the fatigue crack growth behavior of the composite is a function of specimen geometry, fiber orientation, and the interaction of local stress fields with the highly anisotropic composite. In the case of [0]8 oriented single edge notch (SEN) specimens and [90]8 oriented compact tension (CT) specimens, the crack growth was normal to the loading direction. However, for the [0]8 CT specimens, the crack grew mostly parallel to the loading and the fiber direction.

The unusual fatigue behavior of the [0]8 CT specimens was attributed to the specimen geometry and the associated high tensile bending stresses perpendicular to the fiber direction. These stresses resulted in preferential cracking in the weak interface region perpendicular to the fiber direction. The interface region, and in particular the carbon coating surrounding the fiber, proved to be the composite's weakest link.

In the [0]8 SEN, the crack growth was confined to the matrix, leaving behind unbroken fibers that bridged the cracked surfaces. As the crack grew longer, more fibers bridged the crack resulting in a progressive decrease in the crack growth rates and eventual crack arrest. The actual near-crack-tip displacement measurements were used in a proposed formulation for a bridging-corrected effective crack driving force, ΔKeff. This parameter was able to account for most of the experienced bridging and correlated the [0]8 SEN fatigue crack growth data reasonably well.
Observations of Fatigue Crack Initiation and Damage Growth in Notched Titanium Matrix Composites
Authors: Naik RA , Johnson WS
Published: March 2009

The purpose of this study was to characterize crack initiation and growth in notched titanium matrix composites at room temperature. Double-edge-notched or center-open-hole SCS-6/Ti-15-3 specimens containing 0° or both 0° and 90° plies were fatigued. The specimens were tested in the as-fabricated (ASF) and in heat-treated conditions. A local strain criterion using unnotched specimen fatigue data was used to estimate fatigue crack initiation with varying success. The initiation stress level was accurately predicted for both a double edge notched unidirectional specimen and a cross-plied center-hole specimen. The fatigue produced long multiple cracks growing from the notches. These fatigue cracks were only in the matrix material and did not break the fibers in their path. The combination of matrix cracking and fiber/matrix debonding appears to greatly reduce the stress concentration around the notches. The laminates that were heat treated showed a different crack growth pattern. In the ASF specimens, matrix cracks had a more tortuous path and showed considerably more crack branching. For the same specimen geometry and cyclic stress, the [0/90/0] laminate with a hole had far superior fatigue resistance than the matrix-only specimen with a hole.
Damage and Performance Characterization of ARALL Laminates Subjected to Tensile Cyclic Loading
Authors: Osiroff R , Stinchcomb WW , Reifsnider KL
Published: March 2009

The behavior of ARALL (ARamid ALuminum Laminates) subjected to tension-tension cyclic loading was experimentally investigated as a first step towards the understanding of the long-term behavior of ARALL laminates. Specifically, this work addresses fatigue damage mechanisms and relationships between damage and stiffness change, remaining strength, and life. The quasi-static and dynamic material response of unnotched ARALL-2 coupons were measured at normalized maximum stress levels (5) ranging from 0.4 to 0.9 of the ultimate tensile strength. The damage mechanisms and failure modes changed over this range of cyclic stresses. while at low cyclic stress levels, the fatigue properties of the fiber-reinforced plies are key factors; at high cyclic stress levels, the laminate's response is governed by the aluminum plies. Five distinct stages were recognized in the damage sequence. A shear lag analysis is presented to model the regular spacing of cracks called the characteristic damage state. Appropriate modifications were made to accommodate for the hybrid nature of the laminate.
An Investigation of the Effects of Temperature on the Impact Behavior and Residual Tensile Strength of an ARamid Aluminum Laminate (ARALL-2 Laminate)
Authors: Lee TC , Wilson DA
Published: March 2009

The main objective of this investigation was to determine the effects of temperature on the impact behavior of ARALL-2 laminate. Post-impact studies included the assessment of localized damage and the determination of residual tensile strength. Longitudinal specimens (0° fiber orientation) were subjected to impact damage at temperatures of -29, 24, 66, 93, 121, and 138°C (-20, 75, 150, 200, 250, and 280°F) using an instrumented pendulum impact testing system and then loaded in tension to failure. Damage assessment included ultrasonic C-scanning of the impact areas and a scanning electron microscope (SEM) analysis.

The effects of temperature on the impact response of ARALL-2 were made apparent through the behavior of the aluminum layers. Impact damage and, consequently, residual tensile strength were found to vary considerably with temperature. The 24°C (75°F) impacts produced the least amount of internal damage, displayed the longest backsurface cracks, and absorbed the greatest amount of energy. As the impact temperature increased, the internal damage area increased and the energy absorbed decreased. Backsurface cracks decreased with increasing temperature, disappearing altogether at 93°C (200°F) and above.

A maximum tensile strength reduction of 41% occurred for the specimens impacted at 24°C (75°F). Accordingly, the residual tensile strength increased with increasing impact temperature. Since the tensile load was carried primarily by the fibers, this indicated that as temperature increased, fewer fibers experienced breakage. The -29°C (-20°F) impact specimens deviated from these trends. This was attributed to the behavior of the metal adhesive. Less localized deformation occurred, and more unbroken fibers remained to bridge the crack, thus contributing to the residual tensile strength.
Flame Penetration Test for Protective Clothing in Oxygen
Authors: Sanders J , Currie JL
Published: March 2009

There are a plethora of test methods for assessing the flammability of flame resistant fabric materials. However, there is no suitable test method to assess the relative levels of protection provided by flame resistant clothing materials to personnel who may be subjected to the effects of an ignition in an oxygen system or equipment. BOC Limited has developed a flame penetration test which simulates the severe conditions that exist during an ignition event in oxygen. The test has been used to rank candidate materials in order of their resistance to flame and metal impingement.

The test is comparatively simple. The test apparatus consists of a horizontally mounted oxygen-acetylene welding torch. The torch is mounted in front of the textile specimen which is vertically mounted in a metal frame. Between the specimen and torch is a sheet of mild steel which is used to provide molten metal splashes. Several flame retardant materials were evaluated by the test including FirotexR, NomexR, PanotexR, FlamretR, KermelR, and ProbanR. ProbanR had the highest ranking in the test. Other parameters evaluated were the effect of washing the material and ageing of the material to assess their effects on test results. Further development of the test method will be undertaken in particular on repeatability and reproducibility of results.
Recommended Changes in ASTM Test Methods D2512-82 and G86-84 for Oxygen-Compatibility Mechanical Impact Tests on Metals
Authors: McColskey JD , Reed RP , Simon NJ , Bransford JW
Published: March 2009

A cooperative test program to assess the oxygen compatibility of aluminum-lithium alloys with NASA White Sands Test Facility (WSTF), NASA Marshall Space Flight Center (MSFC), and the National Institute of Standards and Technology (NIST) led to the assessment of the mechanical impact test by NIST. There were substantially different variations in test parameters between the test laboratories; some of these led to significant variability in the actual energy absorbed by the specimens. Therefore, test results varied widely.

To reduce the large disparities in interlaboratory test results, a number of changes are recommended in the current ASTM test standards.
Laser Resistant Endotracheal Tubes -- Protection Against Oxygen-Enriched Airway Fires During Surgery?
Authors: de Richemond AL
Published: March 2009

The risk of an oxygen enriched airway fire during oropharyngeal surgery with a laser is supposedly minimized by the use of a laser-ignition-resistant endotraoheal tube such as those made by Bivona, Mallinckrodt, Baxter Norton, Sheridan, or Xomed; or Merocel, a tube wrap marketed as laser resistant; or 3M copper, 3M aluminum, or Radio Shack sensing metallic tapes which are commonly used to protect standard tubes. We exposed these devices to CO2, Nd:YAG, and KTP laser energy in various oxygen-nitrogen and oxygen-helium atmospheres. Only the Baxter Norton tube and the 3M copper taped tubes did not burn under any test conditions. Other tubes were ignition resistant under some conditions, and the Sheridan and Xomed tubes burned under most test conditions.
Endotracheal Tube Fires: A Flame Spread Phenomenon
Authors: Sidebotham GW , Wolf GL , Stern J , Aftel R
Published: March 2009

Three flame types can result when an ignition source is applied to a tube of a combustible material through which an oxidizer flows. If the oxygen concentration inside the tube is greater than the tube material's limiting oxygen index (LOI), an opposed flow flame can spread along the inner surface of the tube (primary intraluminal flame). This flame, which requires a forced flow, consumes the supplied oxygen (fully or in part) and produces combustible, toxic gases which emerge from the free end (and ignition hole where applicable). These gases can then react with the oxygen in the ambient environment and thereby support the second flame type (secondary jet diffusion flame). If the LOI is exceeded outside the tube, an extraluminal flame (the third flame type) can occur, and be supported by natural convection.
Effects of Oxygen Concentration, Diluents, and Pressure on Ignition and Flame-Spread Rates of Nonmetals: A Review Paper
Authors: Hirsch DB , Bunker RL , Janoff D
Published: March 2009

The literature reviewed indicates that oxygen concentration, diluents, and pressure in combustion-test environments can influence the ignition and flame-spread rates of nonmetals. Increased oxygen concentrations result in easier ignition and higher flame-spread rates. The flame-spread rate is generally a non-linear function of oxygen concentration, indicating that different processes are controlling combustion at different oxygen concentrations. The effect of oxygen concentration is higher at the minimum conditions required for ignition and at near-extinction conditions. Diluents affect the ignition and flame-spread rates in oxygen/diluent mixtures due to their effects on the thermal conductivity, specific heat, and diffusivity of the mixtures. Helium, which has a higher thermal conductivity than nitrogen, was shown to be a better inhibitor of ignition processes. Nitrogen/oxygen environments, which have higher heat capacity and lower diffusivity than helium/oxygen mixtures, generally result in lower flame-spread rates. The data also indicates that increased test pressures generally result in easier ignition and higher flame-spread rates. However, higher pressures can affect ignition and flamespread in opposing ways by affecting the gas-phase kinetics of the combustion process. The effects of test pressure are more pronounced at minimum conditions for ignition or at near-extinction conditions.
Iron Combustion in Microgravity
Authors: Steinberg TA , Benz FJ
Published: March 2009

The combustion of iron at high oxygen pressure in normal gravity and microgravity was investigated. Cylindrical rods 3.81- to 11.43-cm long, with diameters of 0.10, 0.20, and 0.32 cm, were burned in 100% gaseous oxygen, in normal gravity and microgravity, and the results were compared and contrasted. Two types of tests were conducted: 1) gravitational gradient tests and 2) microgravity combustion tests. The gravitational gradient test results showed that burning iron rods do not extinguish with a reduction in the gravity level, and may, in view of an observed increase in the consumption rate of the rod, have combustion enhanced in microgravity environments. The microgravity tests showed that the same dependency exists between rod diameter, oxygen pressure, and regression of the melting interface in normal gravity as in the microgravity combustion of iron rods: as the oxygen pressure is decreased, or the rod diameter increased, the regression of the melting interface decreased. The dominant processes in the combustion of metal rods are circulation of the metal, oxygen, and combustion products in the molten ball, and heat transfer to the solid rod. This circulation in the molten ball is not controlled by buoyancy, but is believed to be produced primarily due to differences in surface tension.
The Analysis of Metals Combustion Using a Real-Time Gravimetric Technique
Authors: Sircar S , Gabel H , Stoltzfus J , Benz F
Published: March 2009

The current view is that metallic materials burn in either the liquid or vapor phase. Evidence for this has been offered experimentally by the visual behavior of the combustion process and theoretically by the criterion proposed by Glassman, which is based on the boiling points and combustion temperatures of metallic materials and their oxides. However, results reported by Sato, et al. with aluminum, and recent tests at the NASA White Sands Test Facility with titanium and aluminum, suggest that metallic materials may undergo transitions and burn in both phases. These results have important implications on how we view the overall combustion mechanism of metallic materials, and are important in the development of burn-resistant alloys. An apparatus that monitors the sample weight change during combustion was used to study the burning phase of metallic materials. Materials that burn in the liquid phase were expected to gain weight while the molten, burning droplets were attached to the samples, whereas metals that burn in the vapor phase were expected to lose weight. Experiments were conducted with titanium and aluminum in oxygen at pressures ranging from 0.07 to 0.55 MPa (10 to 80 psia). The titanium sample burned quiescently and there was a consistent increase in the test sample weight during the growth of the burning droplet, indicating that it burns in the liquid phase. These data are consistent with the Glassman criterion. For aluminum, however, the sample alternated between quiescent and turbulent burning, and the sample weight sometimes increased, sometimes decreased, and sometimes remained constant. This indicates that the phase of combustion was erratic and inconsistent with the Glassman criterion, which indicates that aluminum should burn in the vapor phase. Visual techniques are not sufficient to distinguish between vapor-phase and liquid-phase combustion. The gravimetric technique used in this work provides an important additional means of making this distinction.
Oxygen Compatibility of High-Surface-Area Materials
Authors: Dunbobbin BR , Hansel JG , Werley BL
Published: March 2009

High-surface-area metallic structured packings are finding increasing use in the cryogenic distillation of air. An experimental program was performed to determine the oxygen compatibility of selected metals under the high-surface-area-to-volume ratios and adiabatic conditions encountered in commercial use.

Under some conditions brass packing unexpectedly had a higher relative flammability than aluminum, which is contrary to reported test results using metal rods and strips. This is due, we believe, to the specific geometric and adiabatic configuration of the packing material which appears to enhance the propagation of combustion in brass. Aluminum flammability in gaseous oxygen has been shown to be very dependent upon argon dilution and, in the presence of liquid oxygen, strong energy releases have been observed, similar to those experienced with aluminum powder and liquid oxygen. Copper was found to be nonpropagating in all tested oxygen purities.

These findings suggest that results from oxygen compatibility tests on rods and strips cannot be used reliably for ranking the suitability of materials in high-surface-area-to-volume ratio and adiabatic configurations.
Influence of Specimen-Absorbed Energy in Lox Mechanical-Impact Tests
Authors: Reed RP , Simon NJ , Berger JR , McColskey JD
Published: March 2009

In mechanical-impact tests, the potential energy of the plummet is divided between energy absorbed by the specimen, the plummet's kinetic energy of rebound, and various losses in the test machine. Thus, all of the potential (or drop height) energy is not transferred to the specimen. The fracture and deformation characteristics and the reactability of metal specimens are dependent on the amount of energy that the specimen absorbs. The absorbed energy may be calculated either from knowledge of the potential energy and rebound height (assuming losses are negligible), or from the depth of striker-pin penetration into the specimen. The depth measurement gives an estimate of specimen strain; an estimate of force exerted on the specimen during deformation allows calculation of the work of deformation. The effects of the absorbed energy on fracture and deformation characteristics and on reactions in Al-Li alloys and alloy 2219 are discussed.
Use of Computer Analysis to Predict and Reduce Liquid Hammer Forces in High Pressure, High Flow Liquid Oxygen Systems
Authors: deQuay L , Scheuermann PE
Published: March 2009

During the advanced and final development phases of rocket engine component and subsystem testing failures are very likely to occur from time to time. To minimize or prevent damage or destruction to the components and to the test facility itself, high pressure oxygen supplied must be cut off rapidly on the order of 100 to 400 milliseconds. However, rapid cutoff of liquid oxygen, as well as, other liquids and high pressure gases can impart large pressure surges and hammer forces. For liquid and gaseous oxygen this phenomenon can initiate ignition and subsequent destruction of test articles as well as facility piping systems.

An additional concern is the use of liquid oxygen pressure and flow control valves required to operate these type of facilities. Pressure differentials across valves and induced turbulence and flow separation must be understood and analyzed during facility design.
An Assessment of the Metals Flammability Hazard in the Kennedy Space Center Oxygen Systems
Authors: Bryan CJ , Stoltzfus JM , Gunaji MV
Published: March 2009

Eight different metals are used in the gaseous oxygen systems at the John F. Kennedy Space Center in support of Shuttle launch operations. In 1985, a recommendation was proposed that the maximum operating gaseous oxygen system pressure be reduced to 20.6 MPa (3000 psi) from the original design operating pressure of 41.2 MPa (6000 psi). To evaluate this recommendation, a study of the burn propagation and ignition characteristics of the metals in the systems was performed by the NASA White Sands Test Facility (WSTF). The tests selected for this evaluation were the promoted propagation, particle impact, and frictional heating tests. The results of this evaluation indicated that it would be more hazardous to operate at an increased flow rate of oxygen at a lower pressure because of the increase in the possibility of an ignition due to particle impact.
Oxygen Compatibility of Materials and Equipment for the Vulcain European Rocket Engine
Authors: de Monicault J-M , Garceau P , Vagnard G
Published: March 2009

Under the aegis of the European Space Agency (ESA) and under the responsibility of the French Centre National d'Etudes Spatiales (CNES), the “Société Européenne de Propulsion” (S.E.P.) has developed systems including the engines of the three stages of the Ariane European launchers for twenty years. Several engine simplement a large use of cryogenic propellants, including liquid an gaseous oxygen.

The selection of materials for propulsion components operating in an oxygen environment — valves, pumps, transducers, etc. — requires a strict methodology.

On Vulcain, the main engine of Ariane V launcher for the Hermes space shuttle, SEP, as prime contractor, has developed a working method in coordination with its 27 European project partners to select and test materials.

We will present the application of this method for the gas generator valves of the Vulcain engine: • material choice according to foreseen risks, • laboratory choice and testing procedure (L'AIR LIQUIDE), • results and conclusions.(1) Manager, Raw Materials and Process Research Société Européenne de Propulsion - Materials and Testing Laboratory VERNON, FRANCE (2) Leader Engineer, Vulcain gas generator valves Société Européenne de Propulsion - Design Department VERNON, FRANCE (3) L'Air Liquide - Manager Center - Operational Development Division - Technology and Testing Center - LE BLANC MESNIL, FRANCE
Ignition of Materials in Oxygen Atmospheres: Comparison of Different Testing Methods for Ranking Materials
Authors: Barthélémy H , Delode G , Vagnard G
Published: March 2009

This document concerns testing methods used at L'AIR LIQUIDE Centre de Technologie et d'Expertises — Le Blanc Mesnil (France) and already described in another paper, i.e. “bomb test” (autogenous temperature determination), adiabatic compression test, oxygen index test (OI test) and impact test in LOX. We have, in particular, compared the so-called “bomb test” results with those given by the adiabatic compression test (used for ranking materials in BAM — FRG). These results appear to agree well. The bomb test results are also compared to the impact test results in LOX ; a certain correlation between these two methods has also been found. It appears that to be able to withstand the impact test in LOX, materials need to have a rather high auto-ignition temperature in oxygen ; however, this is a necessary, but insufficient condition. When comparing OI test results with bomb test results, it was not possible to draw any correlation. This could be explained by the fact that OI test allows conditions of ignition propagation to be investigated, whereas other tests give information on ignition initiation.
Test Experience with a High-Pressure Oxygen Turbopump and Heat Exchanger
Authors: Schoenman L , Sabiers RL , McIlwain MC
Published: March 2009

Test results of a 97 KW (130 hp) Monel turbopump assembly driven by 300 K (540 R), 27.6 MPa (4000 psi) oxygen at a speed of 62,000 rpm while supported on oxygen-pressurized hydrostatic bearings is presented, along with test results for a 27.6 MPa (4000 psi), 644 K (1159 R) oxygen/hydrogen heat exchanger. These new rocket components incorporate design and material selection criteria which have evolved from NASA and ASTM G-4 standards and test methods. Both components employ alloys that have low heats of combustion and high thermal diffusivity as a means of meeting a self-extinguishing safety criteria.
Federal Highway Administration — Current PMS Requirements
Authors: Papet LM
Published: March 2009

On January 13, 1989, the Federal Highway Administration (FHWA) published its Pavement Policy. One of the most important parts of that policy is a mandate that every State develop and implement a Pavement Management System (PMS) within 4 years after that publishing date. All States have been attempting to meet that deadline and FHWA has been monitoring their progress. To provide guidance on the Policy, FHWA followed with an FHPM (6-2-4-1) in which the major elements that need to be included for a system to be judged acceptable were explained. The figures chosen depict the progress being made by number of States in each of the major elements of a PMS. The comments on each give one a feel for what FHWA thinks is needed in a PMS to meet minimum criteria for acceptability.
Pavement Condition Index — Remaining Service Life
Authors: Baladi GY , Novak EC , Kuo WH
Published: March 2009

The issues and the setting of common engineering criteria to establish threshold values for a better calculation of the pavement distress indices and Remaining Service Life (RSL) are presented. Benefits derived from the use of RSL such as simplifying the Pavement Management System (PMS), computational procedures, improving communication between the various PMS users, and increasing the PMS capability are also included. Within the framework of a PMS, most State Highway Agencies (SHAs) collect pavement condition data to calculate pavement distress indices. Because pavement condition data is the basis for all PMS analysis, the values of the pavement indices are typically prioritized and the highest priority is placed on eliminating most deficiencies. Examination of this effort has indicated that the method is deficient and that the RSL is a better pavement condition index.

Common pavement distress indices deficiencies were found to be related to basing the indices on a single variable (pavement condition at the time of the survey). The rate of the pavement deterioration is not included in the calculation of the indices. In order to eliminate the common deficiencies, it was found that the pavement indices must be based on pavement performance which consists of two variables, surface condition and the rate of deterioration.
Airport Pavement Management: The Port of New York and New Jersey Experience
Authors: Murrell SD , Rada GR , Schwartz CW
Published: March 2009

The Port Authority of New York and New Jersey (PANY/NJ) operates John F. Kennedy International, LaGuardia, and Newark International airports, which collectively represent the largest and busiest air transport complex in the world. To provide effective maintenance and management of the extensive network of airfield pavements at these airports, data display concepts from the field of geographic information systems were coupled with established pavement analysis techniques to create a network-level planning tool: the Integrated Airport Pavement Management System, IAPMS. This paper describes the IAPMS program and summarizes the implementation experiences at the three PANY/NJ airports.
Status of PAVER Implementation within the U.S. Air Force
Authors: Kim YR , Eaddy DL
Published: March 2009

This paper describes a survey designed to estimate the present status of implementation of the pavement management system, PAVER, within the U.S. Air Force. The research described in this paper is based on a 100 percent population survey of over 100 USAF civil engineering organizations, located throughout the U.S., Europe, and the Pacific, as potential users of PAVER. This work estimates and validates not only the present extent of several pre-identified problem areas in PAVER implementation, namely, training, manpower, equipment, and top management support, but also the current extent of PAVER's use and application. In addition, multiple regression is used to determine the existence of relationships between those variables which may influence the acceptance and active use of PAVER, such as training, manpower, equipment and diffusion-of-innovation variables, and those variables which may indicate PAVER's degree of use and acceptance, such as accuracy of data input into PAVER and the extent of a pavements network input into the system.
Development of the Delaware Pavement Management System
Authors: Matsen DW , Smith HA , Rada GR
Published: March 2009

The Delaware Department of Transportation is responsible for the operation of 4,765 miles of roadways under its jurisdiction ranging from Interstate highways to local roads. The preservation and management of these facilities is vital to the economy of the state and a key responsibility of the Department. A systematic approach to the management of pavements is needed to provide the engineering and economic analysis tools to assist decisionmakers in making cost-effective selections of maintenance and rehabilitation strategies for their preservation at desired performance levels. Such an approach has come to be known as a Pavement Management System (PMS). The overall objective of the current effort is to provide the Delaware Department of Transportation with an implemented state-of-the-art set of tools for cost-effective management of the entire network of paved roads and streets under its jurisdiction. Ancillary objectives include (1) evaluations of equipment and procedures for data collection, (2) determination of pavement maintenance, rehabilitation, and reconstruction strategies applicable in Delaware, (3) selection of report types and formats required by decision makers for cost-effective management of Delaware roads & streets, and (4) preparation and demonstration of training activities for use in implementation of the Delaware PMS.
Toward Standardization of a PMS Analysis Method
Authors: Novak EC , Kuo W-H , Baladi G-Y
Published: March 2009

Determining if a PMS meets federal requirements for pavement management is a difficult, inconsistent, and subjective process. The reason is, a PMS and its analysis method are considered to be agency specific. This paper examines the needs and wants of PMS users and transforms them into non agency specific PMS requirements. These requirements, in combination with the flow of processed PMS information from condition summary up to MR&R programs is counter to many agencies desired flow of policy and MR&R decisions. This indicates PMS analysis methods should be a separate planning decision making process that precede operational development of MR&R programs. The AASHTO guidelines indicate the generic analytical nature of PMS analysis and the prerequisites for standardization. The need for ASTM to standardize a PMS analysis method comes from both the historic inability of highways agencies to communicate between technical and decision making activities, and from the confusion that is created when agencies attempt to insert PMS methodology into their operational MR&R program development procedures. The authors believe a standardized PMS analysis is realistic, would do much to break down barriers, and advance the FHWA's objectives for a PMS. This paper proposes a baseline methodology from which the ASTM may be able to further evaluate the possibilities and merits of standardizing a generic analytical PMS analysis method.
Rheological Properties of Polymer-Modified Emulsion Residue
Authors: Anderson DA , Christensen DW , Roque R , Robyak RA
Published: March 2009

The rheological properties of four polymer modified emulsions and a control (AC-10) emulsion were characterized using both routine test methods, such as penetration and softening point, and more rigorous methods, which included low temperature stiffness measurements using a bending beam rheometer, and dynamic mechanical analysis over a wide range of temperatures and frequencies. It was found that addition of the polymer modifiers had little effect on the low temperature stiffness of the emulsion residue. Evaluation of limiting stiffness temperatures determined from experimental data and as estimated from various versions of Van der Poel's nomograph showed that the nomographs in general gave significantly lower values than those found from the experimental data. This indicates that Van der Poel's nomograph should not be used in estimating low temperature properties for either neat or modified emulsion residue. Some of the modifiers did slightly increase the consistency of the residue at high temperatures, which could reduce flushing and bleeding in surface treatments constructed with polymer modified emulsions.
Influence of Binder Rheology on Rut Resistance of Polymer Modified and Unmodified Hot Mix Asphalt
Authors: Bouldin MG , Collins JH
Published: March 2009

Wheel tracking experiments were carried out on dense graded mixes containing a commercial aggregate. The binders used in these experiments consisted of a straight AR1000 and three blends of polymer modified asphalt. In all cases the AR1000 was used as base asphalt and three different polymer types were compared. These mixes showed various propencities for resistance to permanent deformation. The results correlated well with the fundamental rheological properties of the binders.
Laboratory and Field Studies of Polyolefin and Latex Modifiers for Asphalt Mixtures
Authors: Newcomb DE , Stroup-Gardiner M , Epps JA
Published: March 2009

A five-year study was performed to investigate the behavior of asphalt mixtures containing plastic and latex modifiers. The plastics were functionalized polyolefins; high meltflow index acrylic acid copolymers that were used in a pelletized form. The styrene-butadiene rubber latex was supplied as an emulsion. These materials were used separately and in combinations with each other to change the characteristics of asphalt mixtures. The research included laboratory experiments to characterize the materials and field projects in five locations to ascertain their performance. Field projects of flexible pavement overlays were constructed in Alabama, Maine, Michigan, Idaho, and Texas. This paper presents some of the significant findings made during the course of the five-year effort.

Mixture variables which were examined in the laboratory included asphalt grade, modifier type, and modifier concentration. Mixture preparation was investigated with respect to the order of addition of the components and compaction temperature. Laboratory results showed that the effectiveness of these modifiers was very dependent upon the source of the asphalt used in the mixtures. The order of addition of ingredients was found to be important for latex modified mixtures, and was not as significant in mixtures containing latex and polyolefins. The concentration of modifier changed the mixture behavior only up to levels of about 10 percent by weight of total binder. Compaction temperature had a profound effect on the resilient modulus of the mixtures.

The field projects were built in climates ranging from hot and wet in Alabama to cold and dry in Idaho. Control sections of conventional mixtures were placed along with sections of modified mixtures. The mixtures containing latex only as a modifier showed problems during construction. These problems were confined to the mixtures sticking in the dump trucks and the workability through the paver. There were considerable differences noted between the results from behind-the-paver construction samples and test results from the inplace materials. The modifiers seemed to provide more mixture stiffness at higher temperatures which possibly indicated a greater resistance to permanent deformation, while maintaining about the same characteristics as conventional mixtures at low temperatures.
Polymer Modified Hot Mix Asphalt — Oregon Experience
Authors: Rogge DF , Terrel RL , George AJ
Published: March 2009

The Oregon Department of Transportation (ODOT) has undertaken research into polymer modified asphalt binders in hot mix asphalt (HMA) with the expectation that such binders have the potential to provide more cost-effective, long-lasting asphalt concrete pavement. The research has involved three field installations with control sections of conventional asphalt and a laboratory study. Modifiers used in field installations were ethylene-vinyl-acetate (EVA), styrene-butadiene (SB), and styrene-butadiene-rubber (SBR). This paper discusses ODOT's research efforts with polymer modified HMA, and summarizes the findings of this research. ODOT's adoption of the Pacific Coast Conference on Asphalt Specifications' “Performance Based Asphalt Cement Specifications” is the next logical step based on knowledge gained from these research efforts.
Performance of Polymer Modified Asphalt Mixes in Kentucky
Authors: Fleckenstein LJ , Mahboub K , Allen DL
Published: March 2009

Historically, Kentucky has been synonymous with coal. This is because Kentucky produces 160 million tons of coal per year. This translates into relatively heavy volumes of coal-haul truck traffic moving on public highways. Excessive load and tire pressure are common problems in Kentucky.

In response to these severe truck traffic conditions, the Kentucky Department of Highways in conjunction with the Kentucky Transportation Center developed an experimental program to evaluate effectiveness of modified asphalt systems that are available in the market. This paper deals with two projects that were designed to study polymer modified asphalts.

Polymer modified asphalts are claimed to: (a) reduce thermal cracking, usually associated with low temperatures and (b) reduce rutting, usually associated with high temperatures and heavy loads. Kentucky's unique environment conditions provided the opportunity to test these claims.