bluuebunny/crossref_metadata_2025 huggingface dataset:
Design and Characterization of a Facility for Fast Neutron Irradiation of Semiconductors at Penn State
Authors: Petrovic B , Abou-Zaid A , Haghighat A , Daubenspeck TH
Published: April 2008

This paper describes the design and characterization of a fast neutron irradiation facility (FNI) at the Penn State Breazeale Reactor. The facility was designed to provide a hard neutron spectrum with a minimum of contamination by thermal neutrons and gamma rays, and to accommodate semiconductor wafers of up to 8 inches (∼20 cm) in diameter. The design was effected through two-step Monte Carlo simulations that included (i) core criticality simulations, and (ii) FNI shielding analysis. A rectangular FNI shape was selected to improve the neutronic coupling between the FNI and the core. Analysis was performed to determine an optimum combination of materials and their dimensions. The FNI was constructed and it has been in use for about two years now. A set of activation foils was irradiated to obtain the FNI neutron spectrum andevaluate spatial flux distribution. The neutron spectrum was unfolded using the SAND-II code. Good agreement was observed between the calculated and measured data.
Accuracy and Parallel Performance of PENTRAN™ Using the VENUS-3 Benchmark Experiment
Authors: Haghighat A , Abderrahim HA , Sjoden GE
Published: April 2008

We use the VENUS-3 experimental benchmark to examine the accuracy and parallel performance of PENTRAN™ (Parallel Environment Neutral-particle TRANsport), a three- dimensional parallel Sn code. VENUS-3 with its partial length assemblies is a 3-D benchmark with 370 measurements (58Ni(n,p), 115In(n,n'), and 27Al(n,α) dosimeters). PENTRAN results are very close to experimental results; more than 95% of the Calculated-to-experimental (C/E) values are within ±10%. The remaining 5% of the values are within ±10% and ±15%. The PENTRAN calculation (with 84748 spatial meshes, 80 directions, and 26 energy groups) is performed on an IBM SP2 parallel computer using different numbers of processors and different parallel algorithms. It is demonstrated that PENTRAN requires less than 1.4 hrs wall-clock time on32 processors, and it exhibits an excellent parallel performance with a scalability of ̃90%.
Constructing and Controlling Compaction of Earth Fills
Authors: Shanklin DW , Talbot JR , Rademacher KR
Published: April 2008

Description

This unique volume explores the use of various standardized methods for specifying and controlling the compaction of soils for engineered constructed earth fills. Topics address the historical background, current state-of-the-art practices, case histories of challenging situations, new concerns regarding appropriate design parameters for compaction control, and new methods to evaluate soil compaction and other related qualities.

Also included is a paper on the history of the development and use of the nuclear gauge in the quality control of constructed earth fills. The nuclear gauge has had the single largest impact of any technology in the last 30 years in the field of compaction control. Many of the papers in included in this volume use the nuclear gauge as the basis for comparison of the results of field density and water content measurements.

21 papers divided into 3 sections examine:

• Compaction Control Technology and Comparison of Current Methods

• Applications and Lessons Learned in the Field

• Soil Liner Construction and New Compaction Technology

For Geotechnical, Civil, and Construction Engineers
Microstructure and Properties of Zirconium Alloys in the Absence of Irradiation
Authors: Charquet D
Published: April 2008

In order to optimize zirconium-based alloys, it is usually necessary to understand the relationships and interactions between four different types of parameters: chemical composition, manufacturing process, metallurgical characteristics, and functional properties. Examples for various materials show that corrosion resistance depends on the texture and density, distribution, and composition of the precipitate particles. The precipitate composition is determined not only by the alloy chemistry, but also by other factors, such as the cooling rate from the beta phase range. It is also pointed out that some parameters can have opposite effects on nodular and uniform corrosion. Finally, the effects of some impurity elements are described, especially the effect of sulfur on creep and of chlorine on microstructure.
High-Fluence Irradiation Growth of Cold-Worked Zr-2.5Nb
Authors: Holt RA , Causey AR , Griffiths M , Ho ETC
Published: April 2008

Irradiation growth specimens manufactured from cold-worked Zr-2.5Nb pressure tube material have been irradiated in Osiris at a fast flux of ∼1.8 × 1018 n · m-2 · s-1 E > 1 MeV, at nominal temperatures of 553 and 583 K, to growth strains of 1%. The pressure tubes have a pronounced crystallographic texture, with ∼95% of the basal plane normals in the radial/transverse plane, predominantly in the transverse direction. Both longitudinal specimens, which generally exhibit positive growth strains, and transverse specimens, which generally exhibit negative strains with approximately 50% of the magnitude of the axial strains, show nonlinear growth, the rate increasing gradually with fluence up to 1.3 x 1026 n · m-2, E > 1 MeV (580 K) and 1.7 × 1026 n · m-2, E > 1 MeV (550 K).

The previously reported temperature dependence of the axial growth strains (decreasing with increasing temperature for fluences up to 4 to 5 × 1025 n · m-2, E > 1 MeV) is maintained to the higher fluences now achieved, as is the effect of Fe (axial growth strains decreasing with increased Fe concentration in the range 380–1090 ppm by wt.). The effects of temperature and Fe in the transverse direction are approximately the reverse of those in the longitudinal direction.

Examination by transmission electron microscopy and X-ray diffraction of Zr-2.5Nb pressure tubes irradiated to 1 × 1026 n · m-2, E > 1 MeV, at 520 to 570 K in power reactors, and fracture toughness specimens machined from pressure tubes and irradiated, unstressed, in Osiris to 1.5 × 1026 n · m-2, E > 1 MeV, at 530 K, shows a multiplication of the c-component dislocations with increasing fast fluence. This contrasts with a rapid saturation of the density of a-type dislocations after about 0.1 × 1026 n · m-2, E > 1 MeV.

The multiplication of the c-component dislocations occurs mainly by nucleation of vacancy loops on screw dislocations; this mostly occurs in crystals with their c-axes close to the radial direction because they tend to contain many c-component screw dislocations. Crystals with their c-axes close to the transverse direction contain fewer screw dislocations and exhibit less dislocation multiplication over the fluence range studied. Thus, the gradual evolution of the growth rate with fluence appears to be related to the gradual increase in the c-dislocation density with time as in the case of Zircaloy-2.
Post-Irradiation Characterization of Ultra-High-Fluence Zircaloy-2 Plate
Authors: Mahmood ST , Farkas DM , Adamson RB , Etoh Y
Published: April 2008

Zircaloy-2 plate with neutron exposure more than 3 × 1026 n/m2 (E > 1 MeV) has been tested to study the effects of ultra-high neutron fluence on the mechanical and physical behavior of Zircaloy-2.

The Zircaloy-2 plate used in this study is a section of a 6.4-mm-thick control blade follower that resided in a pressurized water reactor (PWR) for 17 one-year cycles at an irradiation temperature of 563 K (290°C). The irradiation growth of the plate was 2.2%. The hydrogen content of the plate is in the range of 85 to 110 ppm. The second-phase particle (SPP) size is 0.29 μm for the unirradiated archive material and 0.23 (μm after irradiation. The archive material was characterized using optical metallography, crystallographic texture measurements, microstructural analysis using STEM, and microhardness measurements. In addition to the optical and electron microscopy for microstructural analysis of the irradiated material, post-irradiation mechanical properties have been assessed using Knoop microhardness testing at room temperature, tensile testing at 561 K (288°C), Charpy impact testing in the temperature range from 293 to 648 K (20 to 375°C), and ductile fracture toughness testing at 573 K (300°C). Delayed hydride cracking velocity (DHCV) measurements were made in the temperature range of 473 to 573 K (200 to 300°C).

Knoop microhardness and tensile test results reveal that the material hardened, strengthened, and became less ductile as a result of neutron irradiation. Charpy impact testing and fracture toughness measurements show that the material has considerable ductility at all test temperatures. Comparisons are made to smaller SPP materials tested after lower fluence [1].

The DHCV measurements showed that delayed hydride cracking occurred at temperatures equal to or less than 533 K (260°C). No DHC was observed at higher temperatures.

The implications of the observed microstructural and mechanical property changes, and the temperature dependence of delayed hydride cracking, are discussed.
Fundamental Study on the Corrosion Mechanism of Zr-0.2Fe, Zr-0.2Cr, and Zr-0.1Fe-0.1Cr Alloys
Authors: Murai T , Isobe T , Takizawa Y , Mae Y
Published: April 2008

Corrosion and hydrogen pickup properties were investigated on sheet materials of pure Zr, Zr-0.2 wt%Fe, Zr-0.2 wt%Cr, and Zr-0.1 wt%Fe-0.1 wt%Cr which were given an intermediate anneal of 853 K or 1003 K, and a final anneal at 853 K. To clarify the substantial effects of iron and chromium, impurities were minimized by using crystal bar zirconium and pure alloy additions.

Corrosion results in 633 K water showed that Zr had the lowest corrosion resistance and that Zr-0.1Fe-0.1Cr alloy heat treated at 1003 K had the highest. The alloys heat-treated at 1003 K showed higher corrosion resistance that those treated at 853 K for each composition except the Zr-0.2Fe alloy. Zr-0.2Fe alloys had higher hydrogen pickup ratios (80%) than those of Zr-0.2Cr and Zr-0.1Fe-0.1Cr alloys (10 to 20%).

TEM and HR-SEM examination of oxide cross sections was also performed. Zr-0.1Fe-0.1Cr alloy formed columnar oxide grains with few fine cracks, while Zr and Zr-0.2Cr alloys had fine-equiaxed grains. Zr-0.2Fe alloys formed columnar oxide grains and included many lateral cracks.

The corrosion mechanism of the alloys was associated with the electrochemical characteristics of the precipitates in this study.
Studies of Zirconium Alloy Corrosion and Hydrogen Uptake During Irradiation
Authors: McDougall GM , Urbanic VF , Aarrestad O
Published: April 2008

The in-reactor corrosion and hydrogen pickup of Zircaloy-2 and Zr-2.5Nb pressure tube materials are being studied in two test loops: a light water loop in the NRU research reactor, and a new heavy water loop in the Halden reactor. The complimentary test programs examine the corrosion behavior of small specimens as a function of fast neutron flux and fluence, temperature, water chemistry, and specimen pre-oxidation.

In NRU tests conducted over a range of reducing conditions (20 to 60 cm3 H2 · kg-1) at 568 K, Zr-2.5Nb specimens bearing “thin” prefilm oxides (⩽6 ηm) experience a reduction in oxidation rate influx. However, samples with thick prefilm oxides exhibit higher rates, suggesting that, like Zircaloy-2, rates for Zr-2.5Nb may increase as the oxide film continues to thicken.

Initial results from the Halden program (5 to 7 cm3 D2 · kg-1) show that prefilmed specimens from tubes made of β-quenched material exhibit lower oxidation and deuterium pickup rates than tubes made from non-β-quenched materials. Prefilmed tubes made from β-quenched material also pickup a lower percentage of the D generated by the corrosion reaction. At high flux levels, prefilmed specimens from tube made of both materials exhibit a narrow range of percentage pickup values (4 to 5%), irrespective of temperature. A preliminary examination of activation energies over the range 523 to 598 K suggests significant differences in the temperature dependencies for oxidation and deuterium pickup of prefilmed specimens of tubes made from β and non-β-quenched Zr-2.5Nb. The differences are correlated with fast flux level.
PENT-Universal Test for Slow Crack Growth in Plastics
Authors: Brown N , Lu X
Published: April 2008

Slow crack growth (SCG) under plane strain conditions as measured by the PENT test is governed by the stress intensity, K. The PENT test, ASTM specification F 1473, which was originally designed to measure the resistance to SCG in pipes, fittings, and resins for conveying gas, can be used to measure the resistance to SCG in all polyethylene products. The resistance to SCG as measured by the PENT test in hours has been directly correlated with the lifetime of large scale gas pipe systems and is expected to be correlated with the lifetime of all polyethylene piping systems. The PENT resistance to SCG has been measured on various polyethylene products. It is now possible to specify a resistance to SCG of a PE resin as measured by the PENT test which will satisfy the commercially desired lifetime of the product. For example, a gas pipe system that contains a polyethylene resin with a PENT value of 100 h will exhibit practically no SCG failures during its first 100 years of service. It is recommended that the PENT test replace the ESCR test, ASTM D 1693, in all the ASTM specifications and that it should be used in place of the ISO specification in ISO 138/SC4, known as the British Gas Notch Test.

It is shown how the PENT test can be applied to all polymers that exhibit SCG.
Pitfalls in Measurement of non-Newtonian Materials—“It's a Line, Not a Point!”
Authors: Whittingstall P
Published: April 2008

Isaac Newton in his “Principia” defined viscosity for simple liquids such as water and oils, which have a constant viscosity at a given temperature. As a result such liquids are labeled as “Newtonian” in his honor. Most materials of interest to the laboratory however are non-Newtonian, in that they do not have a single value for their viscosity at a given temperature. In fact, their viscosity is a function of applied shear stress or shear rate. The science of rheology examines the behavior of real, viscoelastic materials as they deform or flow under applied shear or extension, and an understanding of its concepts is necessary if complex fluids are to be successfully measured. This article highlights some of the anomalies that can be encountered when trying to measure the subtleties of such materials.
Factors Affecting the Accuracy of TMA Measurements
Authors: Foreman J , Kelsey M , Widmann G
Published: April 2008

This study investigates factors that cause differences between reported temperatures in thermomechanical analysis (TMA) instruments and actual sample temperatures. Observations of the melting of indium are made under several sets of conditions. These include varying the indium specimen size, altering the position of the thermal sensor, changing the heating rate, and placing pieces of indium atop and below glass and copper specimens of varying thickness. A TMA instrument with direct-contact thermal sensor and single differential thermal analysis capability yields better sample temperature measurements and allows direct examination of the effects of heat capacity. In a second set of experiments, the glass transition of polycarbonate film is measured in the tension mode using different forces and specimen lengths. The results of this study show that low material thermal conductivity and high specimen heat capacity cause the sample temperature to be lower than that of the surrounding atmosphere. Temperature gradients along the length of the furnace can intensify the temperature difference. Furthermore, stress applied to specimens in tension can lead to erroneous Tg values. Specimen and calibration procedural changes are recommended.
Reinforced Epoxy Resin Cure Assessment in Composite Materials: Measure and Effects
Authors: Zaffaroni G , Cappelletti C , Guerra S , Guerra S , Risetti S
Published: April 2008

The effects of three degrees of cure (low, standard and postcured) on two carbon reinforced epoxy resins are examined. The polymerization degree is tentatively assessed by thermal analysis techniques, namely by Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA). The effects on both static mechanical and fracture toughness properties have been checked. It has been found that the glass transition temperature measured by DMA is the parameter, among those studied (both thermal and mechanical), that is more sensitive to the cure degrees.
Results of the ASTM Instrumented/Miniaturized Round Robin Test Program
Authors: Manahan MP , Martin FJ , Stonesifer RB
Published: April 2008

Two related standards are currently being developed by ASTM Subcommittee E 28.07.07. The first is focused on test procedures for instrumented impact testing. It is intended that ASTM Standard E 23 will eventually reference the instrumented test standard for tests conducted using conventional Charpy V-notch (CVN) specimens. The second new standard covers miniaturized Charpy V-notch (MCVN) testing. The Instrumented/Miniaturized Charpy Round Robin Test Program was established to support development of these standards. The goal of the program is to test CVN and MCVN specimens in the transition region and in the upper-shelf region using an instrumented striker system. The test procedure for the round robin is prescribed in the draft standards. A total of six specimens are being tested in the upper-shelf region and six in the transition region for two materials.
Safety in Ice Hockey: Fourth Volume
Authors: Ashare AB , Pearsall DJ
Published: April 2008

Description

The latest volume in this ongoing series enhances your understanding of both the injuries incurred in the game of ice hockey and the techniques used to decrease the risk of these injuries.

Twenty-three peer-reviewed papers address a diverse range of topics from the fields of sports science, sports medicine, athletic training, biomechanics, risk factor management, epidemiology, sports psychology, injury surveillance, sports equipment, physical conditioning, behavioral factors in sports, as well as case reports from individuals associated with national sports governing bodies, playing facilities, officiating, and playing rules.

Equally important, this new publication also discusses strategies of prevention, including protective equipment; different approaches to managing the conduct of players, coaches and parents, and better implementation of training and conditioning.

Four sections cover

This volume is a valuable resource for hockey equipment manufacturers, biomechanical engineers, hockey coaches and administrators, sports medicine physicians, and athletic trainers.
Parametric Study of Three-Stringer Panel Compression-After-lmpact Strength
Authors: Rousseau CQ , Baker DJ , Hethcock JD
Published: April 2008

Damage tolerance requirements for integrally stiffened composite wing skins are typically met using design allowables generated by testing impact-damaged subcomponents, such as three-stringer stiffened panels. To improve these structures, it is necessary to evaluate the critical design parameters associated with three-stringer stiffened-panel compressive behavior. During recent research and development programs, four structural parameters were identified as sources for strength variation: (a) material system, (b) stringer configuration, (c) skin layup, and (d) form of axial reinforcement (tape versus pultruded carbon rods). The relative effects of these parameters on damage resistance and damage tolerance were evaluated numerically and experimentally. Material system and geometric configuration had the largest influence on damage resistance; location and extent of the damage zone influenced the sublaminate buckling behavior, failure initiation site, and compressive ultimate strength. A practical global-local modeling technique captured observed experimental behavior and has the potential to identify critical damage sites and estimate failure loads prior to testing. More careful consideration should be given to accurate simulation of boundary conditions in numerical and experimental studies.
Development of a Test Method for Closed-Cross-Section Composite Laminates Subjected to Compression Loading
Authors: Bucinell RB , Roy B
Published: April 2008

A test method for evaluating the material properties of closed-cross-section composite laminates has been developed. A finite-element investigation of the first five eigenvalues for the specimen in buckling shows that the critical load is at least a factor of three higher than the failure load observed during testing. This same analysis shows that the highest stresses and strains occur in the gage section of the specimen.

The test specimens are 228.6 cm (9 in.) in length, 50.8 cm (2 in.) in diameter, and have fiberglass end tabs co-cured onto them. Several specimens were manufactured in a quasi-isotropic configuration ([±45/0/90]s and [±45/90/0]s) in order to experimentally evaluate the robustness of the test method, observe typical failure modes, and to catalog the accumulation of damage in the specimens up to failure. Several of these tubes were outfitted with strain gages to detect the presence of buckling and bending in the specimens. Damage was observed by loading specimens to 45%, 60%, 75%, 90%, and 95% of the mean ultimate load. At each of these load levels specimens were cut along their length, a dye penetrate was applied, and then the tubes were X-rayed. The experimental investigation shows that the specimens did not buckle and that the mode of failure is a compressive material failure in the gage section of the tube.
Tension Pull-off and Shear Test Methods to Characterize 3-D Textile Reinforced Bonded Composite Tee-Joints
Authors: Owens SD , Schmidt RP , Davis JJ
Published: April 2008

Test methods, data acquisition, and data reduction techniques used to generate design properties for skin-to-spar composite bonded joints that are reinforced using shaped 3-D textiles are presented. These methods represent the culmination of lessons learned after execution of government Small Business Innovative Research (SBIR), Contracted Research and Development (CRAD), and company Independent Research and Development (IRAD) projects. Industry recognition of the poor interlaminar properties of laminated composite materials has limited applications to structures that primarily react to in-plane loads. However, under company IRAD, CRAD, and SBIR-funded Z-fiber programs, revolutionary tension-loaded bonded joints that utilize 3-D woven textile preforms have demonstrated vastly improved strength and damage tolerance capabilities. Characterization of failure modes and the onset of permanent damage for these novel joints are described. Test procedures involving stepped and fatigue type loading have been developed in order to distinguish between ultimate failure loads that are typically reported versus the service load capability of a particular joint. Overviews of the procedures used to conduct two specific types of element tests are presented. The methods are described as (1) tension web pull-off or tee-pull, and (2) horizontal joint shear.
Applications of Fracture Mechanics in Fretting Fatigue Life Assessment
Authors: Giannakopoulos AE , Lindley TC , Suresh S
Published: April 2008

Models based on fracture mechanics are developed in order to describe crack growth in fretting fatigue. Particular attention is given to a recently developed model, the ‘Crack Analogue’ in which certain aspects of equivalence are recognized between contact mechanics and fracture mechanics. Here, an analogy is invoked between the sharp edged contact region between two contacting surfaces and the geometry of the near-tip regions of a double edge-cracked plate. Based on this approach, a new life prediction methodology is developed for fretting fatigue.
The Effects of Contact Stress and Slip Distance on Fretting Fatigue Damage in Ti-6Al-4V/17-4PH Contacts
Authors: Anton DL , Lutian MJ , Favrow LH , Logan D , Annigeri B
Published: April 2008

A comprehensive evaluation of fretting fatigue variables was conducted on shot-peened Ti-6A1-4V forging material in the β-STOA condition in contact with 17-4PH pins, a material couple representative of helicopter dynamic component interfaces. Utilizing test equipment incorporating independent fatigue stress and fretting slip displacement control (as described elsewhere in this symposium), a test matrix spanning slip distances, δ, of 25 ⩽ δ ⩽ 75 μm and contact stresses, σf, of 70 ⩽ σf ⩽ 200 MPa. Fatigue stresses were used which resulted in cycle lives ranging from run out, >107 to 103. A flat against flat contact geometry was used with the contact area covering ~10 mm2. Representative fretting scars through out the test matrix were examined via serial section analysis and the crack number, density, location, length and flank angle noted through the scar volume. A fretting fatigue endurance map of contact stress vs. slip distance shows that slip amplitude dominates mean fretting fatigue strength at 107 cycles under the tested conditions with contact stress playing only a moderate role. The fretting surface could be characterized as moderately pitted with dense third body debris. The debris was determined to be TiO2. Critical cracks formed through a linking of smaller cracks across the fretting scar as evidenced by a number of nucleation sites on the fracture surface. The coefficient of friction, COF, was observed to increase from its initial value of 0.15 to a stable ̃0.75 through the first 103–104 cycles.
An Investigation of Friction Force in Fretting Fatigue
Authors: Switek W
Published: April 2008

Fretting fatigue limit of mechanical joints is effected by various parameters but most important of them are friction force, relative slip, and clamping pressure which appear in the area of contacting surfaces. Unfortunately these three parameters are mutually influencing each other and their individual effect is not easy to be established. In this paper a stress model of fretting fatigue is presented according to which the fretting fatigue limit depends only on the stress distribution around the fatigue cracks developing in fretting fatigue process. That hypothesis has been proved by investigations carried out on carbon steel in ambient conditions and in an oxygen-free environment. For the last research, a special chamber has been designed and built in which the fretting junction has been investigated in an argon environment. The friction force and the relative slip between the specimen and the fretting pads have been measured by means of strain gauges. The results of the investigation are in good agreement with the theoretical formula developed by the author in previous works and prove predominant influence of friction force on the fretting fatigue limit of a mechanical joint.
An Experimental Investigation of Fretting Fatigue with Spherical Contact in 7075-T6 Aluminum Alloy
Authors: Wittkowsky BU , Birch PR , Domínguez J , Suresh S
Published: April 2008

A new fretting fatigue loading system which facilitates continuous monitoring and control of such parameters as normal and tangential contact loads, and cyclic displacements in addition to the specimen fatigue loading parameters has been designed and built. Systematic and controlled experiments have been carried out with a spherical-tip contact pad fretting against a flat surface. The pad and specimen materials were both 7075-T6 aluminum alloy. For this pad geometry, an analysis of the mechanics of the fretting test has been carried out. In addition, the influence of a number of fretting parameters on the fatigue lifetime has been experimentally investigated. The geometry of fretting scars and the stick-slip annuli has been established for the different contact conditions employed. An approach has been developed to determine the eccentricity produced by the axial load on the stick zone, which correlates very well with the experimental results. Metallographic and fractographic examinations have also been performed on the fretted specimens.
Crack Behavior in the Early Stage of Fretting Fatigue Fracture
Authors: Kondoh K , Mutoh Y
Published: April 2008

The initial stage of fretting fatigue crack growth is significantly influenced by tangential force induced by fretting action along the contact surface, where both mix-mode crack growth and short crack problems are involved. A finite element procedure for the determination of the stress field near the contact surface with friction and of stress intensity factors for fretting fatigue cracks has been introduced. Fretting fatigue tests at the stress amplitude lower than the fretting fatigue limit and mix-mode crack growth tests have been carried out. The influence of Mode II component of stress intensity factor, which accelerates the fatigue crack growth rate, is more significant for shorter and inclined cracks. The fretting fatigue cracks observed at the fretting fatigue limit conventionally defined at 107 cycles were not arrested but continued propagating. Non-propagating cracks were observed at stress amplitudes much lower than the conventional fretting fatigue limit.
Influence of Microstructure on Fretting Fatigue Behavior of a Near-alpha Titanium Alloy
Authors: Satoh T
Published: April 2008

To investigate the effect of microstructure on the fretting fatigue behavior of a near-α titanium alloy, fretting fatigue tests were carried out using DAT54, which is used in compressor blades and disks in aircraft gas turbine engines. Two kinds of microstructure in DAT54 were prepared using different solution heat treatment temperatures: one is the equiaxed α + α lath microstructure and the other is the transformed β structure. The plain and fretting fatigue strengths for the equiaxed α + α lath microstructure are higher than for the transformed β structure. Fretting reduced fatigue strengths by a factor of three for both materials. Sensitivity to microstructure in fretting fatigue is relatively low compared with plain fatigue. Shot peening improved fretting fatigue life, because of lower tangential force between the specimen and the contact pad and because of residual stress in compression induced by shot peening treatment.
An Analysis of Rotating Bending Fretting Fatigue Tests Using Bridge Specimens
Authors: Ciavarella M , Demelio G , HillsD A
Published: April 2008

The rotating-bending type of fretting fatigue apparatus is analyzed by treating the ‘feet’ of the bridge as flat pads with rounded corners. This permits a closed-form solution for the contact pressure—indeed, even more complex geometries could be considered, providing the corners are not sharp-and stick/slip zones to be found, allowing for: (a) shearing force, (b) tension within the specimen and (c) tilting of the specimen with respect to the bridge. Example solutions for each of these separate effects are displayed, together with certain combinations of effects.
Comparison of the Dynamic Cone Penetrometer with Other Tests During Subgrade and Granular Base Characterization in Minnesota
Authors: Siekmeier JA , Young D , Beberg D
Published: April 2008

During the 1998 construction season, the dynamic cone penetrometer (DCP), Loadman portable falling weight deflectometer (PFWD), and Humboldt soil stiffness gauge (SSG) were used to characterize the subgrade and granular base for several projects in Minnesota. The DCP penetration index (DPI) was converted to modulus using previously established correlations between the DPI, California bearing ratio (CBR), and modulus. Standard FWD tests were also performed at some locations and the moduli backcalculated using EVERCALC. The moduli were then compared to determine the ability of each device to accurately measure in situ stiffness. Finally, thin-wall and bag samples were collected from some locations for laboratory resilient modulus testing and the results compared to the field-derived moduli.

The results show the stress dependent nature of the materials tested and that a strong correlation exists between the instruments that are designed to measure modulus. The results also show a weaker, yet still useful, correlation between the strength, as measured with the DCP, and the elastic deformation modulus, measured using the PFWD and SSG.
Dynamic Analysis of FWD Test Results for Rigid Pavements
Authors: Khazanovich L
Published: April 2008

This paper investigates the importance of accounting for the dynamic behavior of the rigid pavement system during falling weight deflectometer (FWD) testing. An analytical closed-form solution for dynamic loading of a plate on the Winkler foundation is derived and, using this solution, FWD sensor deflections are simulated and compared with the measured deflections. The lag between the peak of the applied FWD load and sensor deflections can be explained by the effects of pavement inertia and subgrade dumping. Nondimensional parameters that govern the dynamic behavior of a rigid pavement system are also identified.
The Certification of Protective Equipment for Ice Hockey in the United States
Authors: Morehouse CA
Published: April 2008

The three essential phases for certification of protective equipment for ice hockey in the United States are described in this article. The initial phase includes the necessary prerequisites for the development of objective scientific standards based on physical tests consistent with current engineering technology. The features of the Hockey Equipment Certification Council (HECC) including the principal responsibilities of a third party validator for the certification of products to available standards are outlined in the second phase. The final phase consists of the communication and cooperation of rules-making organizations necessary for proper compliance and the ultimate safety of hockey players. Finally, the benefits of certified equipment to players, coaches, parents of players and manufacturers are presented. The certification of ice hockey equipment can be very effective in reducing injuries, if a program is properly organized and administered.
Concussions in Youth Ice Hockey Players
Authors: Bednarz RL
Published: April 2008

A study on youth ice hockey players was conducted during the 1995-1996 hockey season to obtain data on the occurrence, severity and causes of cerebral concussions as well as to identify the injury response systems and decision processes that coaches use for players injured with concussions. Twenty-eight of 83 teams in the Michigan National Hockey League (MNHL) with approximately 500 hockey players, aged 8 through 17 years, were included in the study. An occurrence rate of 1 concussion in 20 players, or 5%, per season was determined. Most of the head-injuries (64%) were identified as “bell-ringer” concussions. The largest number of concussions were reported for the peewee minor level (28%) followed by the midget major level (24%). Most of the concussions occurred in league games during the first-half of the season. Forwards (wings and centers) had the highest number of recorded concussions. The majority of concussions were caused by collisions between players (56%) or with the boards (28%). The coach or team ”trainer“ was the first to aid the injured player in most of the reported cases. Nearly 90% of the players with concussions returned to play either in the same game or the next scheduled game and less than 30% of the head-injured players were seen by medical doctors for follow-up evaluation and treatment. Training and guidelines for the management of concussion in youth ice hockey players are needed for coaches, assistants, and other non-medical as well as medical personnel who assist the injured player and decide if, and when, the player will return to competition. A national data record and reporting system for head injuries in youth ice hockey players is recommended to fully understand the scope of the problem.
Position of the Cervical Vertebrae During Helmet Removal and Cervical Collar Application in Ice Hockey
Authors: Prinsen RKE , Syrotuik DG , Reid DC
Published: April 2008

There is lack of consensus among prehospital personnel (athletic therapists, paramedics, sport physiotherapists) concerning specific aspects of initial care and assessment of injured athletes presenting signs and symptoms of a cervical spine injury (CSI). In instances of serious injury involving the head and/or spine, complicated by altered levels of consciousness, protective equipment such as helmets and shoulder pads may provide a hindrance to prompt, safe and efficient management. Specifically, there is disagreement concerning the need or advisability of removing protective head gear, as in the case of hockey athletes.

Using the technique of fluoroscopy, the cervical spine displacement of ten male hockey athletes was determined while wearing protective shoulder pads and protective head equipment during the following conditions: 1) helmet removal, 2) cervical collar application, and 3) as the helmetless head was allowed to rest. Subsequent frame by frame video arthokinematic analysis, using computer assisted digitization, revealed significant alterations in the position of adjacent cervical vertebrae during helmet removal, cervical collar application and head rest.

Results suggest that stabilization and transportation of hockey athletes with suspected CSI in their respective protective equipment is recommended in order to reduce the risk of further trauma by unnecessary cervical spine motion.
Thermo-mechanical and Isothermal Fatigue of a Coated Columnar-Grained Directionally Solidified Nickel-Base Superalloy
Authors: Kowalewski R , Mughrabi H
Published: April 2008

The isothermal low-cycle fatigue (LCF) and the out-of-phase thermomechanical fatigue (TMF) behaviours of the directionally solidified nickel-base superalloy DS CM 247 LC, coated with a plasma-sprayed NiCrAlY-coating (PCA-1), were studied in detail. The investigations were performed on the uncoated, the coated substrate material and also on the pure coating material, in contrast to most existing work. The results of the isothermal LCF tests show that the fatigue life of the substrate/coating-composite is governed by the fatigue behaviour of the bulk coating material. The out-of-phase TMF cyclic deformation behaviour of the substrate/coating-composite reflects that of the components and is well described by an isostrain composite model. When the mechanical strain amplitudes experienced by the coating material are plotted against the fatigue life, the data on the coated material in isothermal LCF tests at the upper and lower temperatures of the TMF cycle, respectively, and in the TMF tests coincide. This gives further evidence that the behaviour of the coating materials governs that of the coated composite.
Thermal-mechanical Fatigue and the Modelling of Materials Behaviour Under Thermal Transients
Authors: Rémy L , Koster A , Chataigner E , Bickard A
Published: April 2008

Thermal-mechanical fatigue is addressed using the following methodology: volume element tests are used to check constitutive models as well as to investigate synergy effects and damage models. Structure tests as in thermal shock are used to validate models. This methodology is applied to two gas turbine materials: a wrought polycrystalline alloy, Superwaspaloy, for moderate temperature use, and aluminized single crystal AMI superalloy for blades. The capabilities of viscoplastic constitutive models with internal variables are illustrated. A damage model is shown which describes the synergy between oxidation, creep and fatigue. Detrimental effects of aluminide coating for specific thermal mechanical loading paths are tentatively rationalized.
New Testing Facility and Concept for Life Prediction of TBC Turbine Engine Components
Authors: Marci G , Mull KM , Sick C , Bartsch M
Published: April 2008

A thermo-mechanical test facility is presented which enables testing of a cylindrical specimen under thermal and mechanical loading conditions which closely simulate the conditions in an aircraft engine. The principal features of the test facility are described. They include thermal shock during start-up and shut-down of an engine and cyclic loads comprising holdtimes simulating the loading conditions during a usual flight of an aircraft. For such conditions, the life of physical vapor deposit (PVD) thermal barrier coatings (TBC) should be determined. A concept for life predictions for TBCs based on some minimum test results is presented.
The Effect of Nonlinear Viscoelasticity on Interfacial Shear Strength Measurements
Authors: Holmes GA , Peterson RC , Hunston DL , McDonough WG , Schutte CL
Published: April 2008

Experimental evidence demonstrates that diglycidyl ether of bisphenol-A (DGEBA)/meta phenylenediamine (m-PDA) epoxy resin matrix used in the single fiber fragmentation tests exhibits nonlinear stress strain behavior in the region where E-glass fiber fracture occurs. In addition, strain hardening after the onset of yield is observed. Therefore, linear elastic shear-lag models and the Kelly-Tyson model are inappropriate for the determination of the interfacial shear strength for this epoxy resin system. Using a strain-dependent secant modulus in the Cox model, the calculated interfacial shear strength is shown to be relatively lower by at least 15% than the value determined using a linear elastic modulus. This decrease is consistent with numerical simulations which show the linear elastic approximation over predicts the number of fragments in the fragmentation test. In addition, the value obtained by the strain-dependent secant modulus is approximately 300% relatively higher than the value predicted by the Kelly-Tyson model.
Aging During Elevated Temperature Stress Relaxation of IM7/K3B Composite
Authors: Gates TS , Brinson LC , Whitley KS , Bai T
Published: April 2008

An experimental and analytical study was performed on the use of tension stress relaxation to characterize the effects of elevated temperature and physical aging on the linear viscoelastic behavior of IM7/K3B. Isothermal stress relaxation tests on a [±45]2s laminate were run over a range of sub-glass transition (Tg) temperatures. The sequenced test method most commonly employed for creep was successfully adapted to the stress relaxation test and from those sequenced tests, material parameters such as aging shift rates and momentary master curve coefficients were developed for use in the analytical model.

The analytical viscoelastic model was based on classical lamination theory, the hereditary integral formulation type constitutive law, and effective time theory. Time-aging time super-position, effective time theory, and viscoelasticity were used to determine the physical aging related material parameters from the relaxation tests. Results were compared to previously measured isothermal creep compliance results via known relationships for the convolution of compliance to modulus. Time-temperature superposition was also used to evaluate master curves and related shift factors. All of the results illustrated that the relative influence of temperature and aging must be considered when assessing long-term performance and that the loading mode may have to be considered when accurate predictions of viscoelastic behavior are required.
Nonlinear Multiaxial Behavior and Failure of Fiber-Reinforced Composites
Authors: Hung S-C , Liechti KM
Published: April 2008

The objective of this study was to examine the nonlinear, three-dimensional behavior of a fiber-reinforced polymer. The material that was considered for this study was the carbon fiber composite, AS4/PEEK, graphite fibers in a semi-crystalline thermoplastic matrix. Arcan specimens were chosen for this study because the specimens are compact and biaxial stress states can be easily obtained. Strains were measured using geometric moiré, and specimens were subjected to shear and biaxial loading up to failure. The nonlinear behavior was examined in both the longitudinal and transverse planes of the composite. The effects of shear on the axial stress-strain behavior were obtained, as well as the effects of axial stress on the shear stress-strain behavior.

A one-parameter plasticity model was used to characterize the obtained nonlinear stress-strain curves. The original model was unable to characterize the nonlinear behavior. The effect of two-dimensional mean stress on the shear yield surface was then added to the model and a significant improvement was achieved. The work potential model with only one internal state variable was also used for characterizing the nonlinear behavior. It could not predict the observed difference of the nonlinear behavior of the composite under shear plus tension and shear plus compression.
A Viscoplasticity Model for Characterizing Loading and Unloading Behavior of Polymeric Composites
Authors: Zhu C , Sun C-T
Published: April 2008

An overstress viscoplasticity model is proposed to describe the rate-dependent behavior of a polymeric composite during loading and unloading. In the model, a three-parameter function is used to describe viscoplastic strain rate. In the loading stage, the equilibrium stress is determined using a multi-step relaxation test performed during loading. During the initial unloading stage, owing to the fact that the viscoplastic strain rate is still positive, the material still experiences “loading,” and the corresponding equilibrium stress is the equilibrium stress-strain curve for loading. In the second unloading stage, the viscoplastic strain rate becomes negative, and the material is in a true unloading mode for which the equilibrium stress is determined again using the multi-step “relaxation” test. The viscoplasticity model is found to be capable of capturing the characteristics of the rate-dependent loading and unloading behavior.
Microstructure and Phase Control in Zr-Fe-Cr-Ni Alloys: Thermodynamic and Kinetic Aspects
Authors: Barberis P , Dupin N , Lemaignan C , Pasturel A , Grange JM
Published: April 2008

TEM investigations in Zr-Fe and Zr-Fe-Ni, Zr-Ni-Cr and Zr-Cr-Fe systems were performed to assess the second particles present in these alloys, either in quasi equilibrium conditions, or after quenching and annealing experiments.

At equilibrium, Zr3Fe was found to dissolve Ni up to 12 at%. Ab initio computations provided formation enthalpies for several Zr-Fe compounds and showed that the Zr2Fe is metastable at low temperature. All of these data allowed us to extend the thermodynamic database ZIRCOBASE; very good agreement between the thermodynamic computations and the experimental evidences was obtained.

Quenching and annealing experiments showed that Zr2Fe is formed for low quenching rates, while Zr3Fe is formed for higher quenching rates.

Last, corrosion results in various conditions show that the influence of second phase particles volume fraction depends on the corroding atmosphere.
Comparison of the High Burn-Up Corrosion on M5 and Low Tin Zircaloy-4
Authors: Bossis P , Pêcheur D , Hanifi K , Thomazet J , Blat M
Published: April 2008

The corrosion and hydriding behavior of M5 and low tin Zircaloy-4 in PWR have been compared at high burn-ups (>70 GWd/t). Whereas low tin Zircaloy-4 reached about 90 µm in oxide thickness and is subjected to significant precipitation of hydride rims at the metal/oxide interface, the oxide layer on M5 remains below 20 µm, and a hydrogen content remains below 100 ppm. Owing to the modification of the oxide structure and hydrogen localization observed, it is proposed that, concerning the high burn-up corrosion acceleration of Zircaloy-4, the tin content is the parameter governing the onset of the high burn-up corrosion acceleration, which is further accelerated by hydride precipitation at the metal/oxide interface and dissolution of precipitates. On M5, since no significant evolution of the oxide structure was observed, and none of the parameters identified as contributors to acceleration are present, no acceleration of corrosion kinetics is expected at higher burn-ups.