bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Biomechanical and Histological Examination of Different Surface Treatments of Titanium Implants for Total Joint Replacement
Authors: Saha S , Albright JA , Keating ME , Misra RP 
Published: December 2008

The objective of this study was to evaluate biomechanically and histologically the effectiveness of different surfaces—specifically, smooth, textured, and plasma-sprayed porous surfaces—on titanium implants in achieving stable fixation for total joint replacements.
Hollow cylindrical metal plugs (5 to 6 mm in diameter) with different surfaces were implanted in the femora of two dogs. After five months of implantation, pull-out tests were carried out on these cylinders. The ultimate shear strengths were 11.54 ± 2.96, 3.17 ± 0.81, and 1.04 ± 0.32 N/m2 for the plasma-sprayed, textured, and smooth surfaces, respectively. As expected, the smooth cylinders showed the minimum pull-out strengths and the porous-coated ones the maximum. Histological examination showed maximum bony ingrowth in the plasma-sprayed group and moderate growth in the textured group. Our results suggest that a textured surface or a porous coating (plasma spray) on titanium implants could significantly improve the long-term stability of uncemented total joint replacements.
Quantitation of Bone Ingrowth into Porous Implants Submitted to Pulsed Electromagnetic Fields
Authors: Dallant P , Meunier A , Christel P , Guillemin G , Sedel L 
Published: December 2008

This study has been conducted to evaluate the effect of electromagnetic fields of low frequency and low amplitude on bone growth into porous implants in order to consider a potential clinical application—that is, improvement of the anchorage in articular prostheses intended to be implanted without cement. The experiment has been conducted in vivo on sheep, using porous implants made of Ti-6Al-4V alloy implanted in the cortical bone. The electromagnetic stimulation was provided by external generators connected to Helmholtz coils placed on each side of the stimulated limb.
The results of this stimulation have been quantified by measuring the shear properties of the bone/implant interface and the bone regrowth around and into the porous implants in control and stimulated animals. These results were measured in a total of 16 animals sacrificed at three and five weeks after implantation. No improvement was shown in the mechanical properties of the bone/implant interface. On the other hand, the depth of bone tissue ingrowth and the ratio of bony ingrowth within the implant to the total new bone formation increased at five weeks (13 and 20%, respectively) when electromagnetic fields were used. However, this increase is not statistically significant.
Microstructural Aspects of Crack Propagation in Filled Polymers
Authors: Newaz GM 
Published: December 2008

A study was undertaken to evaluate the fracture behavior of sand and clay-filled polyester composites. A two-pronged effort was made (1) to characterize the fracture toughness of sand-polyester and sand-clay-polyester composites and (2) to identify the mechanisms which account for fracture resistance in these composites.
Separate laminates of sand-resin and sand-clay-resin were made using a polyester resin, sand (300-μm mesh), and clay (0.5- to 3-μm mesh) particulates. The volume fraction of the constituents were 30/70 and 23/7/70 in the laminates, respectively. Three-point bend notch tests were conducted to record the load-deflection response of the composites. Fracture energy was calculated based on linear elastic fracture mechanics. Results show that the fracture energy of the sand-polyester composite was about 25% greater than that of the sand-clay-polyester composite. Fractographic study was undertaken using a scanning electron microscope to determine the mechanisms which contribute to fracture resistance in the two composites. This evaluation was considered critical to evaluate the role of the sand and clay fillers on the overall fracture behavior.
In the sand-filled specimens, fracture steps were observed behind the particles, which are characteristic of the pinning mechanisms. These features arise from the crack front breaking away from the pinning position, that is, from the rigid sand particles. The toughening mechanism in this composite is essentially attributed to the crack-pining phenomenon and subsequent interaction of various crack fronts. In this case, the particles act as obstacles to the moving crack front, and additional energy is required to break away from the pinned positions, contributing to higher fracture energy. This increase in line energy of the crack front is analogous to the line-tension effect due to dislocation pinning in metals. However, in the sand-clay-polyester composite, the pinning mechanism appears to be absent. Rather, the fracture surface is rough and is reminiscent of quasicleavage-type damage. Fracture energy in this case may be related to the size and density of cavities. The toughening mechanism in this type of hybrid particulate-filled composite is not well understood and requires further investigation.
A Fractographic Investigation of Fatigue Damage in Carburized Steel
Authors: Newaz GM 
Published: December 2008

A fatigue study was conducted to determine the performance of unnotched and notched carburized American Iron and Steel Institute (AISI) 8620H steel specimens and to evaluate the corresponding fatigue damage. Completely reversed, constant amplitude, load-controlled tests were conducted using cylindrical carburized steel specimens with stress concentrations of 1.00, 1.46, and 2.22. All tests were conducted at a frequency of 2 Hz under an ambient laboratory environment. Fatigue data plotted as stress amplitude versus mean fatigue life show that, at long life, both sets of notched specimens have similar performance. At shorter lives, the specimens with stress concentration of 1.46 exhibit superior performance compared with the specimens having a stress concentration of 2.22, as expected. The performance of smooth specimens is significantly better compared with the notched specimens at all lives.
Fractographic investigation conducted using scanning electron microscopy revealed the nature of initiation and the subsequent propagation of fatigue cracks in these specimens. At shorter lives, the crack initiation in smooth specimens was found to be surface-initiated at one or more sites on the surface, which then circumferentially converged and propagated through the carburized case into the core. The fracture surface of the case was smooth and flat, while in the core it was nonuniform and coarse. At higher lives, crack initiation in the smooth specimen originated at inclusions within the core. The subsurface crack initiation site showed convergence of radial lines toward a focal point, the site of a nonmetallic inclusion. Fractographs of notched specimens which failed at shorter lives show damage similar to that in smooth specimens. At longer lives, clear evidence of separation between the case and the core was found, with some evidence of subsurface initiation from nonmetallic silicon oxide inclusions having dimensions of 20 to 50 μm.
Fractographic Analysis of Hydrogen-Assisted Cracking in Alpha-Beta Titanium Alloys
Authors: Meyn DA , Bayles RA 
Published: December 2008

The role of hydrogen in the subcritical crack growth of titanium alloys is a subject of intense interest to those who use these alloys for structural applications. The most widely accepted theories are based on the absorption of hydrogen (in the case of environmental hydrogen-assisted cracking), its diffusion to regions of high tensile stress, and the initiation of microcracks at hydrides precipitated in such regions. One of the difficulties with such a mechanism is the paucity of observations of titanium hydrides on fracture surfaces, such as those caused by stress corrosion cracking or inert-environment sustained load cracking caused by residual hydrogen impurity. Another difficulty has been the identity in microstructural crack paths between stress corrosion cracking in hydrogen-containing (saltwater, etc.) and hydrogen-free (carbon tetrachloride) environments.
Studies reported in this paper suggest that hydrogen is not unique in its ability to cause alpha cleavage, but may be a primary cause of alpha-beta interface cracking. Alpha cleavage also occurs in sustained load cracking, but is not, in the present studies, influenced by hydrogen content. Cracking in environmental hydrogen gas is primarily distinguished by alpha-beta interface cracking. The detailed fractographic character of such interface cracking appears to show that the microstructural locus of interface cracking is at the boundary between the alpha phase and the interface phase. The existence of this phase in bulk materials has recently been called into question, and it will be one purpose of this paper to discuss the role of hydrogen content on its formation and the effects of this phase on fracture mechanisms.
Tensile Properties of Several 800 MeV Proton-Irradiated bcc Metals and Alloys
Authors: Brown RD , Wechsler MS , Tschalär C 
Published: December 2008

A spallation neutron source for the 600-MeV proton accelerator facility at the Swiss Institute for Nuclear Research (SIN) consists of a vertical cylinder filled with molten Pb-Bi. The proton beam enters the cylinder, passing upward through a window in contact with the Pb-Bi eutectic liquid that must retain reasonable strength and ductility upon irradiation at about 673 K to fluence of about 1 × 1025 protons/m2.
Investigations are underway at the 800-MeV proton accelerator at the Los Alamos Meson Physics Facility (LAMPF) to test the performance of candidate SIN window materials under appropriate conditions of temperature, irradiation, and environment. Based on considerations of chemical compatibility with molten Pb-Bi, as well as interest in identifying fundamental radiation damage mechanisms, Fe, Ta, Fe-2.25Cr-1Mo, and Fe-12Cr-1Mo (HT-9) were chosen as candidate materials.
Sheet tensile samples, 0.5-mm thick, of the four materials were fabricated and heat treated. The samples were sealed inside capsules containing Pb-Bi and were proton-irradiated at LAMPF to two fluences, 4.8 and 54 × 1023 p/m2. The beam current was approximately equal to the 1 mA anticipated for the upgraded SIN accelerator. The power deposited by the proton beam in the capsules was sufficient to maintain sample temperatures of about 673 K. Post-irradiation tensile tests were conducted at room temperature at a strain rate of 9 × 10−4s−1. The yield and ultimate strengths increased upon irradiation in all materials, while the ductility decreased, as indicated by the uniform strain. The pure metals, Ta and Fe, exhibited the greatest radiation hardening and embrittlement. The HT-9 alloy showed the smallest changes in strength and ductility.
The increase in strength following irradiation is discussed in terms of a dispersed-barrier hardening model, for which the barrier sizes and formation cross sections are calculated.
Comparison of Irradiation-Induced Transition Temperature Increases from Notch Ductility and Fracture Toughness Tests
Authors: Hiser AL 
Published: December 2008

Reactor pressure vessel (RPV) surveillance capsules contain Charpy-V notch ductility Cv specimens, but many do not contain fracture toughness specimens; accordingly, the radiation-induced shift (increase) in the brittle-to-ductile transition region ΔT is based upon the ΔT determined from Cv tests. Since the American Society of Mechanical Engineers (ASME) KIc and KIR reference fracture toughness curves are shifted by the ΔT from Cv, assurance that this ΔT does not underestimate ΔT associated with the actual irradiated fracture toughness is required to provide confidence that safety margins do not fall below assumed levels.
To assess this behavior, comparisons of ΔTs defined by elastic-plastic fracture toughness and Cv tests have been made using data from RPV base and weld metals in which irradiations were made under test reactor conditions. Using “as-measured” fracture toughness values KJc, average comparisons between ΔT(Cv) and ΔT(KJc) reveal that, on average, ΔT(Cv) tends to underestimate ΔT(KJc) for plates by 22°C and to overestimate ΔT(KJc) for welds by 5°C on average.
When the fracture toughness data are adjusted to account for specimen size using a “βIc correction,” the trends are the same as for KJc, with the underestimate for plates an average of 10°C and the overestimate for welds 11°C on average.
Comparison of ΔTs at various index levels implies that the Cv curve for irradiated material tends to be shallower than that for unirradiated material. However, the shape of the KJc curve for irradiated and unirradiated material is the same, but the Kβc curve for irradiated material is steeper than that for unirradiated material.
Comparison of the Effect of Power and Test Reactor Irradiations on the Fracture Properties of Submerged-Arc Welds
Authors: Lowe AL , Pavinich WA 
Published: December 2008

The Babcock & Wilcox (B&W) Owners Group Integrated Reactor Vessel Surveillance Program contained two irradiation phases in addition to the plant specific surveillance programs. One phase provided materials for a short-term (test reactor) study of the effects of neutron irradiation on high-copper low-upper-shelf weld metals as a part of the Heavy Section Steel Technology (HSST) Program. This phase was followed with an irradiation study using the long-term (power reactor) radiation source.
These studies were distinguished from other irradiation studies in that production weld metals were used. The chemical composition of the weld metals were similar except for the copper content which ranged from 0.21 to 0.42%. The specimens used for mechanical properties evaluation consisted of tension, Charpy V-notch, and compact fracture specimens.
The power reactor irradiations were conducted in B&W Owner's Group host reactors. The fluence attained in both the test and power reactors was approximately 7 × 1018 neutrons (n)/cm2. These two neutron sources provide a means for evaluating the influence of neutron environment on material damage.
The Charpy impact toughness is evaluated by the 41 J (30 ft · lb) shift and decrease in upper-shelf energy. The tension data is evaluated using the standard mechanical properties. The fracture toughness data obtained from compact fracture specimens, using J-R elastic-plastic fracture test techniques, was evaluated.
These comparisons indicate that test reactor irradiated yield strength data and fracture toughness data is equivalent to that of a power reactor. A comparison of Charpy properties indicates that the data may be sensitive to parameters other than neutron environments.
The Effect of Thermal Annealing on the Fracture Properties of a Submerged-Arc Weld Metal
Authors: Pavinich WA , Lowe AL 
Published: December 2008

Charpy impact and compact fracture specimens were tested to determine the response of actual reactor vessel weld metals to the in-situ annealing cycle (454°C for 168 h) suggested by the Electric Power Research Institute (EPRI). This annealing cycle was developed to recover fracture properties lost as a result of radiation damage. The Linde 80 submerged-arc weld metals from the Babcock and Wilcox (B&W) Owners Group Integrated Reactor Vessel Material Surveillance Program were irradiated in power reactors. Resultant data are compared with the data from the EPRI sponsored in-situ annealing program. Comparison of the power reactor and test reactor data show similar responses to annealing. One-hundred percent recovery of the upper shelf and transition temperature was achieved after annealing for both reactor types. The EPRI J-R data showed only partial recovery with annealing. However, the B&W submerged-arc weld metals exhibited four responses to annealing: 1) complete recovery, 2) partial recovery, 3) negligible effect of either irradiation or annealing on the J-R fracture toughness, and 4) an increase in J-R fracture toughness to greater than the unirradiated value.
These varied responses indicate that the mechanism(s) of annealing recovery may be more complex than heretofore believed. A qualitative rationale, based on a defect cluster mechanism and a copper precipitation mechanism, is employed to explain the various annealing responses.
Field Measurements for Air Quality in Office Buildings: A Three-Phased Approach to Diagnosing Building Performance Problems
Authors: Sterling EM , McIntyre ED , Collett CW , Meredith J , Sterling TD 
Published: December 2008

This paper reports on a phased system of integrated measurements of ventilation and occupant complaints that is relatively inexpensive yet may lead to effective diagnosis of a building's indoor air quality (IAQ) problems.
1. Physical inspection of the building, surroundings, and ventilation system.
2. Use of standardized questionnaire to (1) compare distribution of responses to those obtained from buildings without increased occupant complaints, (2) determine major types of complaints, (3) inspect distribution of complaints by location in building, and (4) check for specific complaints that may indicate special sources of contaminants.
3. Use carbon dioxide (CO2) concentrations as an index of overall ventilation adequacy.
4. Use carbon monoxide (CO) distribution as an index for overall infiltration pattern of combustion byproducts.
5. Measure fresh air supply by location, during variation of mechanical system operation, using tracer gases, smoke pencils, and tests of actual functioning of the mechanical system.
6. Compare design specification of mechanical system with all observations.
Specific measurement techniques are illustrated through a case study.
Analysis of Asphalt-Containing Mixtures by Nuclear Magnetic Resonance
Authors: Irwin WP 
Published: December 2008

An instrumental method using continuous-wave nuclear magnetic resonance (NMR) has been developed to determine, quickly and accurately, the asphalt content of asphalt-containing mixtures. The resonance signal of the asphalt, which is proportional to the total hydrogen content, through calibration, can be directly related to the asphalt content of asphalt-containing mixtures such as stabilized coating and asphalt-containing products such as saturated felt.
The NMR method has been compared with specific gravity, calcination, and extraction methods. The NMR method has been found to provide the most accurate measurement of stabilizer content and an equivalent measurement of the percent saturation of saturated felt. The typical analysis time is 5 to 15 min.
Performance Testing of Fully Adhered, Polymer-Modified, Bituminous Roofing Membranes
Authors: Burnett EFP , Howson C 
Published: December 2008

In cold climates, roofing membranes are subjected to at least two forms of critical loading:
1. In a fully adhered system, significant forces and deformations can be induced in the membrane by thermal deformation and movement at the joint in the substrate.
2. In severe climates, ice can form and bond to the top of the membrane. When the ice cracks, significant forces can be induced in the membrane.
The tension test is currently used as the standard test for the strength and elongation properties of most roof membrane materials. For fully adhered systems, such as modified bituminous membranes, the tension test is of only limited use since it does not simulate the actual in-place performance of the membrane or the constituent materials, especially for the load cases noted.
An alternative to the tension test is considered. A joint-bridging test procedure is developed that more closely models the loading to which a fully adhered roof system could be subjected.
The test specimen consists of a section of the roof system or membrane material that is fully adhered to a substrate. The substrate is separated into two sections. Each substrate section is gripped in the test machine jaw and these are separated at a constant rate. The force required to separate the substrate sections and the width of the joint opening between substrate sections are continuously measured.
It is evident that the joint-bridging test provides a better basis for understanding the behavior of fully adhered roof systems than does the tension test. The joint-bridging test simulates a realistic situation and it permits the study of reinforcement considerations.
Cold-Laid, Exposed, Two-Ply Modified Bitumen Roofing Systems
Authors: Schumacher W , Scherp E 
Published: December 2008

Cold-applied glue shows convincing results of having long-term qualities for use in modified bitumen roofing systems. The product's most important features include the following advantages:
1. When using cold-applied glue, there is no heating-up time. Work can begin immediately, even under poor weather conditions.
2. Thanks to the strip application, there is a reduction of up to 70% in the amount of bonding material to be transported and used, in comparison with hot bitumen. Instead of 1.5 kg/m2, only 300 to 500 g/m2 is required and the uplift resistance is even higher than that for the 1.5 kg/m2 of hot bitumen.
3. Cold-applied glue eliminates the fire risk during application and, because of the small quantities employed, reduces the amount of combustible material. In the case of an interior fire, it does not form burning droplets.
4. Cold applied glue also bonds securely to cold, damp surfaces.
A self-adhesive, high-performance cap sheet represents a logical and consistent development of the cold-applied roofing system. The authors' company introduced this product onto the market in 1975 after exhaustive development work and tests. These roof sealing sheets are made of modified polymer bitumen with a solvent-free, cold, self-adhesive bonding layer covered with a removable siliconized protective foil. The roof cap sheet is made of bitumen sheeting, modified with styrol-butadiene-styrol (SBS) thermoplastic rubber. This fulfills the requirements of German Standard DIN 52132 for modified polymer bitumen roofing sheets.
Also made of a modified bitumen mass, the adhesive coating is matched to the modified top layer of the roof sealing sheet. It contains adhesive components and is absolutely free of solvents.
At the same time that the self-adhesive sheeting is rolled out, the protective foil is pulled off and the sheeting is pressed down in place. The nongranulated sticky edges at the side of the top of the sheet ensure a perfect seam.
In the case of renovation work or new construction, a roof system can be installed with one or two layers. Over the past ten years, this system of cold glue (roll-form) insulation and a cold self-adhesive cap sheet has continued to demonstrate its economy, secureness, and ease of use in an increasing number of installations in many countries throughout the world.
Wafer Fab Automation, an Integral Part of the CAM Environment
Authors: Fiorletta CA , Lennard R , Harper JG 
Published: December 2008

A flexible/wafer fab automation system has been developed to perform three basic functions; real time inventory control, material distribution throughout the fab; and automated loading of cassette-to-cassette process machines. This System consists of Automated Guided Vehicles (AGV's) for material transport, intelligent inventory control stations for management of material in queue, and a central computer control for System management and communications to the factory's CAM system.
The wafer fab of the future must have real time control of the manufacturing environment. This includes planning and scheduling of Work In Process, dynamic monitoring of material movement, interactive communications with the process machines and control of the automation system. This interaction permits Just In Time delivery of material to process equipment, and constant monitoring of lots in process. The benefits of an integrated system are lower manufacturing costs, lower inventory levels, shorter cycle time and higher yields.