bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetomechanical Damping in Thermally Sprayed Fe-Cr-X Coatings
Authors: Karimi A , Giauque PH , Martin JL
Published: March 2009

The ability of high damping capacity iron-chromium based coatings to absorb mechanical vibrations has been investigated over a wide range of frequencies varying between ∫= 10Hz to 10 kHz, and deformation amplitude between ϵ = 10-6to 10-3. The magnetomechanical hysteresis loss (Q-1) was determined based on the modal analysis technique of a flat beam and was found to be very sensitive to internal stress in the samples. Heat treatments usually enhanced the loss capability, but only high-temperature annealing of coatings restored the whole damping capacity to be comparable to that of cast alloys of same chemical composition. The variation of Q-1 versus vibration amplitude first increased rapidly, passed through a maximum, and then declined relatively slowly to its initial values. The position of the maximum damping was shifted towards lower strains with annealing time and temperature. In contrast to the strain amplitude, the vibration frequency did not influence damping behavior significantly, as expected in ferromagnetic materials. The structure of magnetic domains was observed using the magnetooptical Kerr effect Modification of structure following heat treatments was associated with different values of the damping capacity. Accordingly, the beneficial effect of annealing on damping capacity arises on the one hand from improved mobility of unpinned domain walls and on the other hand from growth of 90 deg domains, leading rather to equiaxed domain configurations. The irreversible movement of domain walls upon application of an external stress in general occurred suddenly and abruptly between two pinned positions.
Magnetoplastic Effect: Relaxation of the Dislocation Structure and Microcreep of Nonmagnetic Crystals
Authors: Alshits VI , Darinskaya EV , Kazakova OL , Mikhina EY , Petrzhik EA
Published: March 2009

A new physical phenomenon—the dislocation displacements as a result of exposing specimens to a static magnetic field (B = 0.1-27) in the absence of mechanical loading—is discovered and investigated for sodium chloride, cesium iodide, lithium fluoride, zinc, and aluminum (NaCl, Csl, LiF, Zn, and AI) single crystals. This effect is characterized by the following properties: The mean dislocation displacement or path ℓ is proportional to B2, inversely proportional to the square root of the concentration C of paramagnetic impurities, and increases linearly with time t of the magnetic treatment; there is no influence of the magnetic field on dislocation mobility in crystals with diamagnetic impurities; the effect is temperature independent in the range T = 4.2-77 K and grows only by 20% with a further increase of T up to room temperature; the saturation of ℓ(t) and ℓ(B) dependencies takes place at large values of t and B on the level corresponding to an average distance between the “forest” dislocations; an abrupt decrease of the effect is found when the frequency v of an alternating (over orientation) magnetic field exceeds some critical value vc ∝ B2, independent of T and C, but sensitive to a type of impurity, to X-ray irradiation, and different for edge and screw dislocations; a strong effect of a static electric field (E = 0.2-12 kV/m) on the mobility of charged dislocations in NaCl and LiF specimens simultaneously exposed to a static magnetic field is found (with no electric influence at B = 0); and the critical level Ec is found above which there is no saturation of dislocation displacements ℓ (B, t)—that is, the transition from a relaxation of dislocation structure to a microcreep is observed at E > Ec.

phenomenon is interpreted as a result of unlocking of dislocations from paramagnetic centers because of spin-dependent electron transitions in a dislocation-impurity system under the action of external magnetic field with further motion of dislocations in the long-range internal stress field combined with an electric driving force when an electric field is applied.
Internal Friction Spectrum Analysis for Complex Alloyed Austenitic Steels
Authors: Golovin IS , Zharkov RV , Golovin SA
Published: March 2009

At least two maxima have been defined in the relatively narrow domain (240 to 280°C, 1 Hz) on the temperature-dependent internal friction curves for the quenched and coldworked austenitic alloys with different chemical composition. The first peak is connected with reorientation of interstitial atoms couples in the applied stresses, the second with the dislocation motion. Analysis of the temperature-dependent internal friction spectrum for heat treated or mechanical treated alloys or both is considered to be difficult.

A new approach for the investigation of this complex spectrum has been developed. Computer simulation of internal friction (IF) peak splitting to a few partial peaks is suggested. The method applied for the splitting of complex IF peaks in the heat treated iron-nickel-molybdenum (Fe-Ni-Mo) alloys is based on different activation energies of diffusion for carbon and nitrogen atoms in face-centered-cubic solid solution. The optimization procedure has been carried out with the use of experiment planning and by searching for the function minimum by the method of steepest descent.

After plastic deformation the IF spectrum of the quenched specimens becomes more compli-cated. The superposition of three IF peaks Qc-1 (carbon), Qn-1 (nitrogen) and strain-induced IF peak Qp-1 takes place.

The results of computer simulation of the IF spectrum as well as the obtained data for activation energies for the heat treated and deformed iron-nickel, iron-nickel-molybdenum, iron-chromium-nickel, and iron-manganese-aluminum alloys are discussed. The influence of the degree of plastic deformation and chemical composition on the IF peak is analyzed on this basis.
Mechanism for the High Damping State in Alloys of the Fe-Al System
Authors: Udovenko VA , Chudakov IB , Polyakova NA
Published: March 2009

Magnetic and crystalline structure as well as magnetic and damping properties of binary iron-aluminum (Fe-Al) alloys in the region from 3 to 12 wt.% aluminum have been investigated by using transmission electron microscopy (TEM), X-ray scattering, neutron scattering, magnetic hysteresis loops, and magnetostriction studies.

It was found that independent of the impurity content (vacuum or air melting of alloys) the concentration dependence of damping capacity displays a pronounced maximum in the region of ̃5.5 wt.% aluminum, where the maximum value of the logarithmic decrement δ exceeds 25%. It was found that the magnetic domain structures in the bulk materials differ strongly for the alloys in the high damping state and for the alloys with the same composition after suppressing the high damping by heat treatment.

The analysis of obtained magnetic data and microstructural analysis shows that the necessary condition for the appearance of the high damping state is the formation of a special magnetic domain structure with an enhanced fraction of movable 90-deg domain walls. An additional condition is the formation of a crystalline structure which provides a moderate value of magnetic hysteresis losses and coercive force. For the Fe-Al alloys investigated, it means that the most favorable structural condition for high δ-values is an intermediate stage of short-range ordering of the D03 structure.
Young's Modulus and Mechanical Loss in PZT Ceramics Associated with Phase Transitions
Authors: Cheng BL , Gabbay M , Fantozzi G
Published: March 2009

In piezoelectric ceramic lead zirconate titanate (PZT) dielectric loss and mechanical loss are coupled. So, in PZT ceramics used as power transducers, the high mechanical lossresults in an increasing of the temperature which contributes to reducing the intensity of polarization. Moreover, Young's modulus is very sensitive to phase transitions and polarization level.

In the present report, the Young's modulus E(T) and the mechanical loss Q-1(T) are measured in order to study phase transitions and temperature-induced depolarization. The temperature range is 100 K to 700 K. Two classes of doped PZT ceramics are tested: the Navy 1 and the Navy 3. These two classes are used mainly for power transducer applications.

Two phase transitions are easily observed by two anomalies on the E(T) curves: rhombohedral to tetragonal (TR-T), and tetragonal to cubic (Tc). The tetragonal phase is located between 2S0 K and 590 K for the Navy 1 class, and located between 180 K and 520 K for the Navy 3 class. The phase transition TR-T induces a smooth decrease of mechanical loss, but a very high mechanical loss peak corresponds to the phase transition Tc.

Moreover, the E(T) and Q-1(T) curves allow the study of the influences of thermal cycles on the polarization of the material: before annealing of poled specimens, the Young's modulus is higher, and the mechanical loss is lower than those in unpoled specimens. After annealing of poled specimens, the Young's modulus is reduced and mechanical loss is increased. However, the Young's modulus of annealed specimens remains still higher than in unpoled specimens through the temperature range of both ferroelectric and paraelectric phases.
An Experimental Comparison of the In-Air and Underwater Damping Properties of Composite Cylinders
Authors: Crane RM , Ratcliffe CP
Published: March 2009

Acoustic radiation and self noise are potentially problematic in many underwater applications since both can interfere with the performance of onboard sensors. This is especially prevalent when the structural material for the pressure hull is metallic. In an effort both to reduce radiated noise and minimize structural vibrations, experiments were undertaken to investigate the use of composite materials for cylinders which would be subjected to hydrostatic pressure loading. The damping characteristics of cylinders with various designs and material combinations were obtained initially from modal analysis testing in air. This technique very quickly provides very consistent results. The results desired for this venture, however, were the damping characteristics of these cylinders underwater, which significantly is a more complex experimental configuration.

This paper presents the test procedure and results of modal analysis testing conducted in air and underwater on some composite cylinders. The experimental results, which are presented and compared herein, include the resonant frequencies, damping factors, and mode shapes at resonance. In order to ensure a valid comparison, the natural frequencies and damping factors are compared on a mode-by-mode basis, that is, the result for two cylinders are compared when the resonance has the same mode shape. Despite the increased complexity of the experiments required to obtain these underwater measurements, it is shown that the in-air and underwater levels of damping observed at relatively low frequencies are comparable.

The results show that an appropriate choice of composite materials can increase the levels of damping by at least an order of magnitude over conventional metals. The damping can be increased additionally by using a double hollow core or triple-shell configuration with reinforced polyurethane ribs. The paper discusses this new reinforced polyurethane as a structural component of the cylinder, and proposes various mechanisms of damping that this material form provides.
Anelasticity of Single and Polycrystalline Materials by the Resonant Sphere Technique (RST)
Authors: Suzuki I
Published: March 2009

The resonant sphere technique (RST) has been developed for the purpose of measuring elasticity and anelasticity of crystals. This method has various advantages, and introduction of the Fourier Transform (FT) method to RST makes data acquisition possible with a 1 K temperature interval. In the RST, anisotropic elastic moduli Cij and internal friction Qij-1 of a specimen are determined by inversion calculations for a sufficient number of spectral data of resonant peak frequency f and half-width 2δf. In single crystals of silicates and oxides, resonance peaks are very sharp and their relative half-widths 2δf/f are of the order of 10-4.

A simple relationship of log Q-1 = a — bv2 seems to hold between elasticity and internal friction, where a and b are constants and v2 = M/ρ,M is elastic modulus, and ρ is density. This may be applicable even to anisotropic elasticity Cij and internal friction in Qij-1. This relationship is phenomenologically understood by a thermal activation process.
A Comparison of Injuries That Occur During Collegiate Fall and Spring Football Using the NCAA Injury Surveillance System
Authors: Dick RW
Published: March 2009

The collegiate spring football season, which currently consists of five noncontact and ten contact practices, has been associated with a high incidence of injury. This study uses NCAA Injury Surveillance System (ISS) data to compare injury patterns in collegiate fall (FF) and spring (SF) football over the past four seasons. A reportable injury was defined as restricting the athlete's participating for at least one day. An athlete-exposure (A–E) was recorded for each individual participating in each practice or game. Results showed that the four-year practice injury rate for SF (9.0 injuries/1000 A–E) was more than double that of FF (4.0 injuries/1000 A–E). The top three types of injuries (knee, ankle, and shoulder) were identical in SF and FF with similar percentages of all reported injuries. Specific analysis of injury severity (time loss and required surgery), concussions, and new injuries also showed a higher rate in spring practice. There was little difference in the types of injuries that occurred in SF and FF: the SF injury incidence was just greater. Variables such as training, intensity, and recovery time may be factors in the increased SF injury rates. Reducing the number of contact practices in the spring may be one way of normalizing injury rates.
Coaches Safety Orientation and Training Skills Program
Authors: Lucenko LK
Published: March 2009

Coaching is one of the crucial elements in the conduct of safe play in football at every level. The coach can have the greatest impact on safety and must be educated to make safety a priority in team management.

There is a trend in the professional education of coaches to reduce the professional preparation course work and to hire coaches with minimal education and training. On the recreational level, coaching credentials are minimal at best.

This paper explores the problems encountered in the coaching environment relating to football safety and the steps being taken to improve coaching education. The model used, herein, is the New Jersey State Legislation regarding the requirement for a program of “Safety and Skills Orientation” for volunteer coaches. It further proposes and recommends additional education and training for football coaches on all levels of play.
Catastrophic Football Injuries and Tackling Techniques
Authors: Drake GA
Published: March 2009

The objective was to identify tackling techniques that contribute to cervical spinal cord injuries. First, the 19 tackles in the Prevent Paralysis II VHS documentary resulting in quadriplegia were analyzed for location, that is, above, at, or below the waist, direction, and head position, up or down. Second, records were kept for the same information on 3046 high school, college, and professional tackles during the 1993 season. Essentially, all tackles in the Prevent Paralysis II series were head down and resulted in quadriplegia. More than twice as many were below the waist rather than above the waist. Of the tackles below the waist, 83% were frontal and lateral at the level of the pelvis, thigh, or knee. Analysis of the 3046 tackles showed those below the waist were three times as likely to be head down, compared with tackles above the waist. Of the head down tackles below the waist, 83% were frontal or lateral at the level of the pelvis, thigh, or knee. It was concluded that head down tackling predisposes to cervical spine fracture/dislocations and spinal cord injury. The injury is most likely to occur when tackles are frontal and lateral at the level of the pelvis, thigh, and knee. Suggestions are to enforce penalties for head first contact and to establish rules that make tackling below the waist illegal except from behind, below the knee, and on initial contact in the existing 6 by 8 yd free blocking zone.
Guidelines for Return to Contact Sports After Transient Quadriplegia
Authors: Cantu RC
Published: March 2009

Three cases seen by the author will be presented that illustrate acceptable circumstances, as well as relative and absolute contraindications for athletes to return to contact/ collision sports after an incident of transient quadriplegia. Return is deemed acceptable if the athlete has complete resolution of symptoms, full range of motion, and normal curvature of the cervical spine, as well as no evidence of spinal stenosis on magnetic resonance (MR) imaging, contrast enhanced computerized tomography (CT), or myelography. Relative contraindications, as seen in Case 2, involve a mild intervertebral disc bulge that does not obliterate the reserve of cerebrospinal fluid (CSF) around the cord and transient quadriplegia caused by minimal contact. In Case 3, true spinal stenosis documented by MR imaging illustrates an absolute contraindication for return to contact/collision sports after an episode of transient quadriplegia and what can happen if return is allowed. The author realizes that these guidelines would be difficult to prove in a scientific fashion, and that the legal and moral consequences of a controlled trial would be too serious to allow it to be done.
Enhancing Safety with an Improved Cervical Test Device
Authors: Kleinberger M , Eppinger R , Haffner M , Beebe M
Published: March 2009

The cervical spine serves two primary functions: (1) as a mechanical linkage that allows a large controlled range of head motions and (2) as a protective structure for the spinal cord that passes through the spinal canals of the vertebrae. Cervical injuries involving fracture or dislocation of the vertebrae often involve the spinal cord, leading to paralysis or even death. Although serious neck injuries have become relatively rare in American football since the adoption of new spearing rules and tackling procedures, the development of cervical protective equipment should further reduce both the severity and the frequency of neck injuries.

Many developers of cervical protective devices use anthropomorphic test devices, or ATDs, as physical surrogates for the athlete. Currently available ATDs are of limited biofidelity and ability to predict neck injuries under conditions involving head impact. This paper discusses the ongoing development of a new cervical test device with improved biofidelity in the frontal, lateral, and axial directions. A new transducer is proposed to measure dynamically the three dimensional curvature along the length of the neck.
Standard Test Methods and Performance Standards for Synthetic Turf Playing Surfaces and Materials
Authors: Breland RD
Published: March 2009

Synthetic turf playing surfaces have been in use for over 25 years. A set of standard test methods and performance standards have evolved and are in widespread use to characterize synthetic playing surfaces and materials. A standard guide is being published that establishes a recommended list of test methods to be used for characterization of physical properties and comparison of performance properties of synthetic turf components and systems for athletic or recreational use.

A set of ASTM testing methods and various technical properties are described in compiling a complete synthetic turf system. Some values for required performance levels and typical measured values for synthetic turf components and systems are described. The typical values are subject to normal variation both in production control and in testing, especially when different testing laboratories or testing methods are involved.

Laboratory testing conditions are controlled at 65 ± 2% relative humidity and 21 ± 1°C (70 ± 2°F) unless otherwise noted in the standard test method. Testing in laboratories under markedly different conditions and techniques will give different test results in most cases.

The objective of this paper is to present Standard Test Methods and Performance Standards adopted for physical property characterizion of synthetic turf system components, artificial turf and synthetic turf systems.
The Envelope System—Performance and Experience in the United Kingdom
Authors: Dury D , Craggs JS
Published: March 2009

The patented envelope system consists of a layer of specially selected sand or stone wrapped in a strong but highly porous membrane. This prevents erosion but allows moisture to pass through at a very high rate.

A high drainage rate has two major benefits. First, standing water is not a problem provided the surfacing material is porous to allow water into the base. Second, as little water remains within the base, the effects of frost heave are minimized.

The material in the envelope is selected so that particle size, shape, and distribution do not allow over compaction or settling out. As a result, the playing characteristics and drainage capabilities are maintained over a long period. Since 1981, experience in the United Kingdom has shown that the system matures the longer it has been down.

The special geotextile “Nottsfilm” that encases the sand or stone, has been especially developed to allow for high porosity and enable particulate material to be retained. It is a resin-bonded, needle-punched, polyester fabric only 1 to 2 mm thick yet its load-bearing capabilities are so good that only one layer is normally required. The pore spaces in the material are evenly distributed, thus, giving consistent drainage throughout the material.

By using natural paniculate materials as the base, construction is similar to a natural turf pitch with a synthetic turf surface. This combination results in playing characteristics close to those of natural turf being achieved on an installation with the usage capabilities of synthetic turf. Tests carried out in United Kingdom meet the requirements of the Winterbottom report for soccer pitches.

Injuries associated with synthetic turf areas consist primarily of either stress-related injuries to the limbs or friction burns. On conventionally constructed engineered bases, it is very difficult to eliminate these factors, as solid base construction contributes to both injuries. The envelope system is better on both counts. First, the natural impact absorption properties mean that the stresses caused by interactions with the surface are similar to those exhibited by natural turf pitches. Second, the possibility and degree of friction burns are reduced because much of the energy is dissipated into the air spaces between the materials in the base leaving less energy available to be turned into heat.
Actual Field Performance of Synthetic Turf as Measured over a Thirty Year Period
Authors: Gorham PM , Orofino TA
Published: March 2009

Over the past 30 years, AstroTurf® Manufacturing, Inc. has performed field inspections of various synthetic turf fields throughout the U.S. Testing included turf color retention, fiber wear, turf performance, padding system performance, pavement performance, as well as the subbases. To date, over 250 fields have been tested. Testing has been performed at various times of the year with recorded weather conditions, i.e., temperature, humidity, and rainfall.

Along with the visual inspections, various physical properties of the turf system have been tested by trained technicians. Pile height retention, shoe traction, turf friction, and Gmax were made. This paper will focus on the Gmax testing (ASTM Test Method for Shock-Absorbing Properties of Play Surface and Materials F 355, Procedure A) over this 30 year period. This field test data will be compared with “laboratory accelerated wear” testing performed on turf and pad. This will also illustrate the correlation between accelerated lab testing of turf products to “real live” testing.

The Gmax values will be broken down further into various subcategories: (A) Gmax values versus the life of fields. This will show the progression or loss of shock absorbency of the total field as the years of wear and use occur. (B) Gmax values versus padding systems. This will show the evolution of pad systems. Improved performance and longevity, as well as player comfort of pad systems after years of development and testing indication. (C) Gmax progression (increase) of specific fields. This will chart how individual field Gmax values progress over time. Several fields will be examined, and a relationship drawn between life of the field and amount of usage versus Gmax values.
Enhancing Participant Safety in Natural Turfgrass Surfaces Including Use of Interlocking Mesh Element Matrices
Authors: Sifers SI , Beard JB
Published: March 2009

Injuries on football fields can be grouped into different categories as related to the type of athlete movement and to the relative resiliency—softness of the surface. Many injuries are related to varying degrees of surface hardness. Turfgrasses offer the least hard surface in comparison to other alternatives available for sports activities. This is due to the biomass of the turf plus the associated root zone that provides a unique resilient characteristic or cushion.

Sports participant safety on turfgrasses is maximized by a dense biomass of turfgrass leaves and stems. It is important to select turfgrass species, cultivars, and cultural practices that have the capability of sustaining the highest possible biomass. Considerations in this regard include adaptation, wear tolerance, pest resistance, environmental stress tolerance, and the ability to recover from injury during the time of year when intense use occurs. Proper turf mowing, fertilization, irrigation, and cultivation practices also aid in maximizing the biomass cushion.

The second major dimension is the associated turfgrass root zone. High-sand/soil root zones of the proper particle size distribution are less prone to compaction and resultant hardness, plus the internal environment is more favorable for turfgrass root growth. The high-sand/soil root zones for sports use tend to be somewhat loose and thus benefit from stabilization, such as by the three dimensional, randomly oriented, interlocking 50 by 100 mm mesh elements. This mesh matrice also possesses a flexing action under traffic pressure that results in a self cultivation effect that further improves the environment for root growth by enhanced drainage and aeration.
Safety in Football—Risk Avoidance and Risk Management: An Attorney's Perspective
Authors: Granger MS
Published: March 2009

The litigation explosion in this country and the ever increasing refusal to accept personal responsibility for ones' own actions has resulted in an increased number of law suits in the sports arena. In addition to manufacturers of football equipment, schools, coaches, and leagues are now being sued. Everyone involved with the sport is exposed. Reduction of injury potential and severity is both good practice and good management in this litigation prone era. The paper discusses ways to reduce injuries and exposure including: better coaching, comprehensive reviews of facilities and programs, proper training of coaches and staff, better and stricter officiating, and proper protective gear, and warnings and instructions. The need for proper and consumer oriented information on the risk of a particular sport to the athlete and his or her family is also stressed. Finally, the role of the technical community in reporting on and reducing sports injuries is analyzed.
Effect of Moisture Content on Free Swell of the Clay Component of Geosynthetic Clay Liners
Authors: Narejo DB , Zhou Y
Published: March 2009

This paper discusses the effect of initial moisture content on free swell of the clay component of Geosynthetic Clay Liners (GCLs). Geosynthetic Research Institute (GRI) test method GCL-1 was used to perform all free swell tests included in this paper. Three commercially available GCLs were used in the study. For each GCL, free swell tests were performed at various initial moisture contents. For two GCLs, the free swell was seen to decrease linearly with an increase in the initial moisture content of the test specimens. For the third GCL, the free swell was found to decrease non-linearly with an increase in the initial moisture content. A procedure for correcting the free swell for the initial moisture content of GCLs is suggested. Using this procedure, the free swell of the clay component of a GCL test specimen at a desired initial moisture content can be calculated from the experimentally determined free swell at a different initial moisture content.
A Comparison of Sample Preparation Methodology in the Evaluation of Geosynthetic Clay Liner (GCL) Hydraulic Conductivity
Authors: Siebken JR , Lucas S
Published: March 2009

The method of preparing a single needle-punched GCL product for evaluation of hydraulic conductivity in a flexible wall permeameter was examined. The test protocol utilized for this evaluation was GRI Test Method GCL-2 Permeability of GCLs. The GCL product consisted of bentonite clay material supported by a woven and a non-woven geotextile on either side. The method preparation focused on the procedure for separating the test specimen from the larger sample and whether these methods produced difficulty in generating reliable test data. The methods examined included cutting with a razor knife, scissors, and a circular die with the perimeter of the test area under wet and dry conditions. In order to generate as much data as possible, tests were kept brief. Flow was monitored only long enough to determine whether or not preferential flow paths appeared to be present. The results appear to indicate that any of the methods involved will work. Difficulties arose not from the development of preferential flow paths around the edges of the specimens, but from the loss of bentonite from the edges during handling.
Geosynthetic Clay Liners in Alkaline Environments
Authors: McKelvey JA
Published: March 2009

The use of geosynthetic clay liners (GCLs) as secondary barrier layers in environmental applications such as landfills and other impoundment facilities is becoming increasingly more popular among the engineering community, particularly at project sites where earthen materials suitable for barrier layers may not be locally available. Design engineers for these environmental applications are becoming well versed at performing equivalency calculations comparing the performance of geosynthetic materials to their earthen counterparts. For barrier layers, these equivalency calculations would normally compare the mechanical and hydraulic properties of the GCL to a compacted clay liner. Of these properties, the ability of the hydraulic properties to withstand degradation due to permeation of contained leachates is of prominent concern. Such is the case in alkaline environments. The leachate may adversely affect the GCL by minimizing swelling, decreasing adsorption capacity and increasing the permeability of the material. If the effect on the material is significant, the usefulness of this product is diminished, possibly voiding any equivalency comparison to compacted clay liner performance. The design engineer must fully understand what effect, if any, specific leachates will have on the GCL being considered. Accordingly, appropriate performance testing with the leachate in question must be performed during the design phase and confirmed during construction through quality assurance testing.

This paper will present the design considerations, required laboratory testing and onformance tests for a recent project that contained an alkaline leachate. Through appropriate testing, a contaminant resistant GCL was shown to possess desired hydraulic properties in the presence of the alkaline leachate.
First-Exposure Performance of the Bentonite Component of a GCL in a Low-pH, Calcium-Enriched Environment
Authors: Quaranta JD , Gabr MA , Bowders JJ
Published: March 2009

Testing was conducted on the bentonite portion of a Geosynthetic Clay Liner (GCL) for application to an environment characterized as having high concentrations of dissolved calcium ions. This environment presents conditions that might affect the long-term hydraulic function of the GCL as a component in a barrier system. Experiments were conducted to investigate first-exposure compatibility of a sodium bentonite GCL subject to the affects of acidic groundwater and second from the combined affects of acidic groundwater enriched with calcium. Relationships between the ionic exchange of sodium, potassium, magnesium and calcium species in the bentonite, and changes in hydraulic conductivity and electrical conductance are reported and discussed.
A Design Perspective on Shear Strength Testing of Geosynthetic Clay Liners
Authors: Cowland JW
Published: March 2009

Geosynthetic Clay Liners (GCLs) are being used on increasingly steep and high landfill slopes, which requires careful determination of the appropriate shear strength to be used in design. This paper reviews shear strength testing of GCLs, and the subsequent use of the strength data, from a design viewpoint.
Effect of High Strain Rate on the Tensile Behavior of Nicalon™/Cas Continuous-Fiber Ceramic Composites.
Authors: Sánchez JM , Puente I , Elizalde R , Martín A , Martínez JM , Daniel AM , Fuentes M , Beesley CP
Published: March 2009

The tensile properties of CAS/SiC [(0/90)3]s ceramic matrix composites have been measured as a function of strain rate up to 100 s-1. Novel test methods, including the use of piezoelectric transducers as load cells, strain gauges, and high sampling rate data acquisition systems, were set up to ensure accurate measurement of load and strain. Dynamic effects were taken into account when analyzing the stress-strain raw data. It has been observed that the average fracture strength and the average strain energy density are higher with increasing strain rate. This trend is related to the mode of fracture and the damage observed in the composite at different strain rates.
The Effect of Hold Times on the Fatigue Behavior of an Oxide/Oxide Ceramic Matrix Composite
Authors: Zawada LP , Lee SS
Published: March 2009

Ceramic matrix composites (CMCs) consisting of an oxide matrix, no fiber-matrix interphase, and an oxide fiber are attractive for high-temperature structural applications because of their inherent resistance to oxidation. Such a system has recently been evaluated using tension, tensile fatigue, and tensile creep rupture. The CMC system consists of an aluminosilicate matrix reinforced with Nextel 610 fibers. The Nextel 610 fibers were in the form of an 8HSW. Results from the mechanical behavior studies showed this CMC to perform extremely well in fatigue at both room temperature and 1000°C. However, the system experienced significant creep strain under sustained loading because of creep deformation that occurs in the oxide fiber. To study the interaction between fatigue and creep, fatigue tests with hold times were conducted at a temperature of 1000°C. For all tests, the maximum fatigue stress was 75 MPa and the load ratio was 0.01. Hold times of 1, 10, and 100 s were applied at maximum load to develop the creep deformation fully. Hold times of 10 seconds were also applied at both maximum and minimum load to study creep recovery. The effect of frequency was also characterized using frequencies of 1, 0.5, and 0.1 Hz. In all tests, the measured strain accumulation was found to be linear with time with no evidence of tertiary creep behavior. The CMC exhibited increased rates of strain accumulation with decrease in frequency and increase in hold times.
Creep-Rupture Behavior of a Nicalon/SiC Composite
Authors: Verrilli MJ , Calomino AM , Brewer DN
Published: March 2009

A study of the high temperature tensile creep rupture behavior of a commercially available woven [0/90] Nicalon/SiC composite was performed. Tests were performed at temperatures of 500 to 1149°C. At a creep stress of 83 MPa, lives of less than 40 hours for temperatures above 600°C in air were obtained. At the reduced stress level of 69 MPa, lives were twice as long. However, a test conducted at 83 MPa and temperature of 982°C in vacuum yielded a run-out life of more than 1000 hours. Also, the tests performed in air have significantly shorter lives than those reported by the composite manufacturer. Post test investigations focused on identifying the mechanisms responsible for the unexpected difference in life and results are presented. Analytical modeling and supplemental testing revealed an unexpected environmentally assisted material degradation at an intermediate temperature range of 700 to 800°C. Microscopic and chemical analyses indicate that a combination of applied stress and temperature produces an oxidation-embrittlement damage mechanism. The role of the selected specimen geometry and testing conditions, which was instrumental in the detection of this failure mechanism, is thoroughly discussed.
Retained Tensile Properties and Performance of an Oxide-Matrix Continuous-Fiber Ceramic Composite After Elevated-Temperature Exposure in Ambient Air
Authors: Munson KL , Jenkins MG
Published: March 2009

An oxide-matrix continuous-fiber ceramic composite (CFCC) reinforced with Si-C-O (Nicalon™) fibers coated with an oxidation-resistant SiC/BN interphase was investigated for its resistance to elevated-temperature degradation. Tensile specimens at zero load were exposed to ambient air environments at 800 and 1000°C for 1, 24, and 100 h. Room-temperature tension tests of the exposed specimens were conducted per ASTM Test Method for Monotonic Tensile Strength Testing of Continuous Fiber-Reinforced Advanced Ceramics with Solid Rectangular Cross Section Specimens at Ambient Temperatures (C 1275) at 0.003 mm/s to ascertain retained mechanical properties. While elastic constants and strengths decreased on the order of 10 to 55%, the modulus of toughness, a direct measure of the inherent damage tolerance of CFCCs, decreased 90%. For example, elastic modulus decreased with exposure temperature and time from 150 GPa in the as-received condition to ∼135 GPa after exposure at 1000°C. Proportional limit stress decreased from 42 MPa in the as-received condition to 22 MPa after exposure to 1000°C. Ultimate tensile strength decreased from 244 MPa in the as-received condition to 107 MPa after exposure to 1000°C. Finally, modulus of toughness decreased from 1062 kJ/m3 in the as-received condition to 113 kJ/m3 after exposure to 1000°C. The Nicalon™ fibers showed some degradation effects of elevated-temperature exposure. Fractography revealed damage to both the fibers and matrix. Brittle fracture (accompanied by minimal fiber pullout) was the dominant failure mode at after exposure to all elevated temperatures.
Infrared-Based NDE Methods for Determining Thermal Properties and Defects in Ceramic Composites
Authors: Ahuja S , Ellingson WA , Steckenrider JS , Koch SJ
Published: March 2009

Continuous-fiber ceramic matrix composites are currently being developed for various high temperature applications, including use in advanced heat engines. In the material classes of interest for such applications, i.e., silicon carbide (SiC)-fiber-reinforced SiC (SiC(f)/SiC), AI2O3/Al2O3, etc., the condition of the interface between the fibers and matrix is critical to the mechanical and thermal behavior of each component. A nondestructive evaluation method developed at Argonne National Laboratory (ANL) uses infrared thermal imaging to provide “single-shot” full-field measurement of the distribution of thermal diffusivity in large components. By applying digital filtering, interpolation, and least-squares-estimation techniques for noise reduction, we have achieved acquisition and analysis times of minutes or less with submillimeter spatial resolution. The system has been used to examine the effects of thermal shock, oxidation treatment, and variations in density and fiber coatings in a full array of test specimens.
Measurement of Orthotropic Elastic Constants of Ceramic Matrix Composites from Impact Sound
Authors: Sakata M , Ohnabe H
Published: March 2009

The isotropic and/or orthotropic elastic constants of ceramic matrix composites are measured from the impact sound of a small rectangular bar specimen which is suspended by thin ceramic threads in a furnace. The natural frequencies at high temperatures of the flexural and torsional vibration modes are measured from the impact sound using a fast Fourier transform analyzer and elastic constants are computed from these frequencies using Timoshenko's beam theory and Saint-Venant's torsion theory. The natural frequencies of a rectangular silicon carbide/silicon carbide (SiC/SiC) plate are also measured at high temperatures and its elastic constants are determined using an iteration technique employing a finite element method. This technique is extended to measure the natural frequencies of a jet engine nozzle flap made of SiC/SiC composite panel from the impact sound before and after engine operation, and thus the damage of the flap is evaluated as the reduction of the Young's modulus of the material.
A Model for the Creep Response of Oxide-Oxide Ceramic Matrix Composites
Authors: Zuiker JR
Published: March 2009

A numerical model has been developed to predict the creep response of ceramic matrix composites (CMCs) to understand better the sustained load behavior of an eight-harness satin-weave Nextel™ 6102 /aluminosilicate CMC. A two-phase system in which each phase exhibits significant creep is considered. Mori-Tanaka estimates of the overall elastic response are used in conjunction with transformation field analysis to predict the inelastic deformation in each phase and evaluate the overall CMC response. Good correlation between the model and experimental data is obtained over a wide range of temperature and stress conditions when micromechanical estimates of the matrix elastic stiffness are used. The correlation is sensitive to the matrix elastic properties and, thus, provides a method to determine in-situ matrix properties when conventional methods fail, as in this case.
Secondary Processing Effects and Damage Mechanisms in Continuous-Fiber Ceramic Composites
Authors: Ramulu M , Eswara Prasad N , Malakondaiah G , Guo Z
Published: March 2009

Continuous-fiber ceramic composites (CFCC) are a relatively new area of composite materials in research. Therefore, the feasibility of using abrasive waterjets (AWJ) as a secondary CFCC process was explored. Continuous fiber-reinforced advanced ceramic composite materials have been machined with the AWJ piercing and cutting process. The topography and morphology of the machined surfaces were evaluated with surface profilometry and scanning electron microscopy (SEM). The surface characteristics, in terms of roughness and the micro-mechanisms of material removal, were evaluated. The AWJ surface characteristics and associated damage to the CFCC were compared with that of a conventional diamond saw cut surface. The AWJ generated surface was found to be significantly different from that of the diamond saw machining surface and the micromechanical behavior of the material removal was strongly dependent on the fiber orientation.
Design, Fabrication, and Burner Rig Testing of Three-Dimensional Woven Ceramic Matrix Composite Flanged Hoop Subelements
Authors: Wildman WD , Khandelwal P
Published: March 2009

Ceramic matrix composites (CMCs) have been identified as a key material system for improving the thrust-to-weight ratio of high-performance aircraft engines. An interturbine flow-path duct for a high-performance engine has been identified as a component with the potential for 100% reduction in active cooling air and 80% reduction in weight through the use of CMC material systems. To reduce risk prior to incorporating the interturbine duct in a high-performance engine, a CMC subelement design was conducted, parts were fabricated from two potential CMC material systems, and tests were conducted in a National Aeronautics and Space Administration (NASA) high-temperature, high-pressure burner rig with parameters representative of the high-performance engine environment. The burner rig testing verified the mechanical attachment and flow path sealing techniques as well as distinguished the oxidative stability of the two CMC material systems tested. After the burner rig testing was completed, the successful subelements were laser cut into three continuous hoop configurations and tested at room temperature for hoop retained tensile strength. The retained strength test results as well as fractography work indicated the need for regional architecture modifications as well as improved methods of infiltrating the fiber tows with oxidation inhibitors.
The Lubricant Film-Forming Properties of Modern Fire Resistant Hydraulic Fluids
Authors: Ratoi-Salagean M , Spikes HA
Published: March 2009

Fire resistant hydraulic fluids tend to show significantly poorer ribological performance in hydraulic systems than conventional mineral oil-based fluids. There have recently been performance problems associated with increases of operating temperatures of mining hydraulics. This paper describes measurements of the elastohydrodynamic and boundary film-forming properties of a range of different hydraulic fluid types at temperatures up to 80°C. These are compared with friction and wear results obtained using the same fluids.
Tribological Testing with Hydraulic Pumps: A Review and Critique
Authors: Bishop RJ , Totten GE
Published: March 2009

Hydraulic fluids serve two functions in the hydraulic system; to transfer energy and to lubricate the system. The energy transfer role is relatively well understood while lubrication assessment has been hindered by inability to adequately model hydraulic systems in general by small-scale pump prototypes or by bench testing. In general, most conventional bench tests do not adequately model wear which may accompany hydraulic fluid use in various hydraulic pump designs. Therefore, this has necessitated the use of hydraulic pumps as tribological test stands. The objectives of this paper are to: 1) review common failure modes of different types of hydraulic pumps, 2) provide an overview of the deficiencies of bench testing of hydraulic fluids, 3) review the tribological criterion for successful lubrication of vane, piston and gear pump testing, 4) review the most common pump tests reported to date, and 5) critique the quality of these tests relative to their ability to provide the required data.
Review of ASTM D 2882 and Current Possibilities
Authors: Gent GM
Published: March 2009

In April of 1995, various laboratories in the United States and U.K. were contacted regarding, problems encountered, solutions and their current practice using the ASTM test method D 2882 (Standard Test Method for Indicating the Wear Characteristics of Petroleum and Non-Petroleum Hydraulic Fluids in a Constant Volume Vane Pump). Participants were sent the collected comments and techniques which had been shared by ASTM D-2 submittee N07 members over the last fifteen years. Participants were asked to review the document and add their own comments. The purpose was to collect and compare all available information about the test in an effort to resolve the operational problems associated with this test method. The objective of this paper is to present the results of this survey and to describe the engineering research performed by Conestoga to identify and remedy the operational problems associated with this method.