bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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.
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.
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.
Analysis of Morphological Alteration Accompanying Post-Irradiation Aging in Montell 1900 Ultra-High Molecular Weight Polyethylene (UHMWPE)
Authors: Bellare A , Spector M , Cohen RE 
Published: March 2009

For many years, ultra-high molecular weight polyethylene (UHMWPE) components of joint replacement prostheses have been sterilized with a 25 to 37 kilograys dose of gamma radiation in an air environment. Gamma radiation is known to cause chemical and morphological changes in polyethylene that continue to occur with both in vivo and shelf-life age. Generation of free radicals leading to predominantly crosslinking and chain scission (to a lesser extent) are immediate chemical effects. Slow oxidation of the free radicals contributes to further chain scission, thereby lowering the overall molecular weight of UHMWPE components with aging. Since lower molecular weight polyethylenes have a lower resistance to wear, oxidation-induced chain scission is believed to lower the wear resistance of UHMWPE components used in joint replacement prostheses.
We have studied mechanisms of morphological alterations in UHMWPE components (Montell 1900) that accompany radiation-induced chemical changes with shelf-life aging. Differential scanning calorimetry on aged and unirradiated Montell 1900 UHMWPE revealed that there was an increase in crystallinity in components of post-irradiation aged Montell 1900 UHMWPE, in agreement with previous studies. Small-angle X-ray scattering measurements on unirradiated Montell 1900 UHMWPE revealed that there was a low degree of morphological order. One-dimensional correlation functions obtained by Fourier transformation of the scattering curves were employed to characterize the morphology of Montell 1900. The long period or the most probable center-to-center distance between neighboring crystalline lamellae, was 940 ± 15 and 550 ± 15Å. In the case of post-irradiation aged Montell 1900 UHMWPE, a new long period of 480 ± 15 Å was present in addition to the original long period. The emergence of a new long period along with an increase in crystallinity showed that recrystallization with post-irradiation aging occurred by growth of new crystallites in the amorphous domains in-between crystallites rather than by thickening of original crystallites. Growth of new crystallites was attributed to oxidation in the amorphous domains that releases constraints on interlamellar tie molecules by chain scission, thereby allowing the chains to form new crystallites.
Test Method for Fatigue of a Modular Posterior-Stabilized Tibial Component
Authors: Anthony ME , Cooper MB , Holbrook JA 
Published: March 2009

Posterior-stabilized (P/S) total knee replacements are designed o replace the function of the knee joint in the absence of the posterior cruciate ligament. The most prevalent P/S tibial components are modular, consisting of a plastic tibial insert which is secured by the locking mechanism to a metallic tibial tray. While these tibial components offer the advantages of modularity including increased flexibility and decreased inventory, they must withstand loading that will be transferred to the tibial insert post, without excessive deformation of the post or disassociation of the tibial insert from the tibial tray. The objective of this study is to develop a test method to determine the fatigue integrity of a modular P/S tibial component under physiologic loading.
Modular P/S tibial components are subjected to a combined compressive and nteroposterior shear load transferred from the femoral component to the tibial insert post and the condylar surfaces. A test method was developed to reproduce this loading by placing a P/S implant at 30° of flexion and transferring load to the tibial component as would occur in vivo. By applying a 5 Hz, sinusoidal load in this manner for ten million cycles, the fatigue integrity of the modular component can be evaluated. Additional information may be gained by measuring the angular deformation of the tibial insert post and determining the static locking strength of the tibial construct after fatigue loading. Failure criteria for the modular component would be either disassociation of the tibial insert or gross deformation of the tibial insert post.