bluuebunny/crossref_metadata_2025 huggingface dataset:
Focused Ion Beam as New Tool for Local Investigations of the Interaction of Microcracks with Grain Boundaries
Authors: Marx M. , Schaef W. , Welsch M. , Vehoff H.
Published: March 2010

So far the interaction of microcracks with microstructural elements like grain boundaries or phase boundaries is described qualitatively well by the models of Tanaka and Navarro and De Los Rios. However, an experimentally verified quantitative description is missing due to a lack of systematic experiments. The concept by Marx and Schaef introduced a combination of a focused ion beam technique with high resolution scanning electron microscopy. It is the first method to initiate artificial microcracks with idealized crack parameters relative to selected phase and grain boundaries. This combination of characterizing and manipulating techniques on a microscale enables for the first time a systematic investigation of the interaction between short cracks and micro-structural barriers to check the models quantitatively. However, the geometry of the active slip planes in the adjacent grains, their misorientation angle, and the position of the grain boundary is a three-dimensional problem. Therefore the geometry was reconstructed after the crack propagation measurements by focused ion beam tomography to measure the inclination angles between the surface, the crack plane, and the grain boundary. The results should lead to a better understanding of the physical mechanisms of crack propagation through grain and phase boundaries, which is fundamental to explain the huge scatter in the short crack behavior and to develop materials with fatigue resistant grain boundaries.
An Examination of Fatigue Initiation Mechanisms in Thin 35Co-35Ni-20Cr-10Mo Medical Grade Wires
Authors: Schaffer Jeremy E.
Published: March 2010

Knowledge of the intrinsic defect size distribution, surface grain size distribution, and prior deformation history are important factors in determining fatigue crack initiation mechanisms and total life variability in thin, metallic, medical grade wires. The ASTM F562 alloy system is used extensively as a fine wire coil or cable in the production of cardiac rhythm management leads which require excellent fatigue life, and a good understanding of life variability. In the present investigation, samples of 0.0070 in. diameter ASTM F562, 35Co-35Ni-20Cr-10Mo wires were produced with a variety of grain sizes and strain hardening conditions. Samples were then cyclically loaded to failure in rotary beam testing and preserved for post mortem fractography using high resolution scanning electron microscopy (HR-SEM). Fatigue cracks were found to initiate from three sources: intrinsic microstructural inhomogeneities, persistent slip bands (PSBs), and extrinsic surface defects. The dominance of the various initiation mechanisms was shown to be a function of the constituent particle and grain size as well as the fatigue loading conditions and prior deformation history. In samples exhibiting a surface grain size significantly larger than the constitutive particle distribution, cracks were observed to preferentially nucleate from surface intersecting PSBs rather than near-surface-particles. Understanding of these phenomena is important in the design of robust cardiac lead systems that will outlive the patient.
Hydrogen∕Plasticity Interactions at an Axial Crack in Pipeline Steel
Authors: Dadfarnia M. , Sofronis P. , Somerday B. P. , Robertson I. M.
Published: March 2010

The technology of large scale hydrogen transmission from central production facilities to refueling stations and stationary power sites is at present undeveloped. Among the problems which confront the implementation of this technology is the deleterious effect of hydrogen on structural material properties, in particular at gas pressure of 15 MPa which is the desirable transmission pressure suggested by economic studies for efficient transport. To investigate the hydrogen embrittlement of pipelines, a hydrogen transport methodology for the calculation of hydrogen accumulation ahead of a crack tip in a pipeline steel is outlined. This work addresses the interaction of hydrogen with an axial crack on the inside surface of the pipe. The approach accounts for stress-driven transient diffusion of hydrogen and trapping at microstructural defects whose density evolves dynamically with deformation. The results address the effect of hydrostatic constraint, stress, and plastic strain on the time it takes for the steady state hydrogen profiles to be established.
Experimental Study of the Fracture Toughness Transferability to Pressurized Thermal Shock Representative Loading Conditions
Authors: Scibetta M. , Schuurmans J. , Lucon E.
Published: March 2010

Fracture toughness testing on standard specimens in the ductile to brittle transition regime is well established and was first standardized by ASTM in 1997. However, its applicability to structural components and its potential conservatism, due to the high constraint condition in standard specimens, remain a subject of concern. In this work a study of the transferability of the fracture toughness measurements from laboratory specimens to structural components is performed. The structural component of interest is the Reactor Pressure Vessel subjected to an accidental loading condition called Pressurized Thermal Shock (PTS). As the actual component cannot be reasonably tested, an original experimental set-up is developed to simulate PTS representative loading conditions. A semi-elliptical crack is introduced by fatigue in a disk shape specimen which is biaxial loaded in the ductile to brittle transition regime. The developed disk specimen is called PTS-D specimen. Master Curve tests on 15 PTS-D specimens are performed and compared to standard size specimens having deep and shallow cracks. The reference temperature obtained on PTS-D is equivalent to the one obtained on half-inch compact tension specimens. To support the experimental results, finite element calculations are performed. It turns out that, in the tested range, constraint in PTS-D specimens is high. However, loss of constraint appears earlier than in standard specimens. It is found that the Beremin approach combined with analytical tool allows rationalizing all test results.
Analysis of Crack Growth at R=−1 under Variable Amplitude Loading on a Steel for Railway Axles
Authors: Carboni M. , Beretta S. , Madia M.
Published: March 2010

Railway axles are designed for infinite life, but occasional failures have been and are observed in service. The failures, which are usually due to fatigue crack propagation, are typically positioned at the press fits which correspond to the wheels, gears, brakes, or they appear at the axle body close to the notches and transitions. The way to addressing this problem is to adopt the concept of “damage tolerance” in order to determine the inspection intervals of the axle depending on the NDT method. The issue open to discussion is the choice of the correct algorithm for simulating crack growth at R=−1 at variable amplitude loading especially when considering mild steels such as A1N. The aim of the present research is to discuss the application of state-of-the-art algorithms to estimate the effect of block loading at R=−1 (derived from real load spectra experienced by the axle) upon constant crack growth rate. More specifically the current research addresses: (i) crack growth experiments at R=−1 under constant amplitude loading on two novel types of small-scale specimens; (ii) crack growth experiments under block loading on small-scale specimens; and (iii) the prediction of the experimental evidences by well-known and wide-spread analytical tools.
Mechanical Evaluation of Mixed As-Cast and Friction Stir Processed Zones in Nickel Aluminum Bronze
Authors: Nolting Allison , Cheng Leon M. , Huang James
Published: March 2010

The performance of nickel aluminum bronze (NAB) propellers can be limited by the resistance of the alloy to fatigue. Friction stir processing (FSP) is a potential method for improving the fatigue life and fracture toughness of this material through grain structure refinement. As friction stir processing is a surface treatment, as-cast, thermo-mechanically affected zone (TMAZ), and FSP zone microstructures can all occur in components with thick cross sections and when FSP is performed on only selected areas of the component surface. The boundary between modified and unmodified microstructures produced by traditional processing techniques (i.e., heat affected zones produced by welding) are often the source of in-service failures as they can contain defects, residual stresses, deleterious microstructures or any combination thereof. In this paper, the mechanical behavior of FSP nickel aluminum bronze specimens containing as-cast, TMAZ, and FSP microstructures are evaluated using monotonic tensile tests and rotating bending fatigue tests. Analysis of the fatigue specimen fracture surfaces indicate that fatigue cracks initiated and propagated through the as-cast microstructure before penetrating the TMAZ and the FSP microstructures. The tensile specimens failed in the as-cast structure away from the FSP zone and the TMAZ. These results indicate that the as-cast material is weaker than both the FSP and the TMAZ, implying that localized friction stir processing is not detrimental to the mechanical behavior of a NAB component, even in the boundary region.
Fatigue Behavior of Adhesively Bonded Aluminium Double Strap Joints
Authors: Nolting A. E. , Underhill P. R. , DuQuesnay D. L.
Published: March 2010

The fatigue life and failure mode of double strap joints constructed from bare and clad aluminum alloys were examined. Substrate failures were found to occur at lower stress levels, while the failure mode at higher stresses was debonding of the patches. The stress∕strain state at the edge of the patch was altered by changing the patch thickness, patch modulus, or by tapering the edges of the patch. The specimens were modeled using finite element analysis. The results of the finite element analysis revealed a power law relationship between fatigue life and either the peak principal strain in the adhesive for adhesive failures, or the nominal axial stress in the substrate for substrate failures. The fatigue life and failure mode of a double strap joint specimen can be determined by calculating the failure life for that specimen under adhesive and substrate failure. The failure mode with the shortest life will indicate the failure mode and fatigue life of that specimen.
A Simplified Modeling Approach for Predicting Global Distortion in Large Metallic Parts Caused by the Installation of Interference Fit Bushings
Authors: Widdle Richard D. , Firth Lee C. , Reed Paul W.
Published: March 2010

One technique for improving the fatigue life of a fastener hole in a built-up metallic structure is to use an interference fit bushing. The installation of these bushings produces residual compressive stresses around the hole that improve the fatigue life. It also causes residual strains and therefore distortion of the part. The distortion is both in-plane growth of the part and out-of-plane deflection, or cupping. The resulting distortion can cause difficulty in downstream assembly, such as misalignment of fastener holes or a misfit of mating surfaces. For small parts with only a few bushings, it is possible to predict the distortion by explicitly modeling the installation process by using a finite element approach. However, for a large part with many bushings, it is not practical to build a model with a detailed finite element representation of each bushing installation. In this work, a simplified approach is presented for predicting the global distortion of large shell-like parts that is caused by installing many interference fit bushings. The simplified approach consists of representing the bushings with equivalent springs in a shell-based finite element model of a large part. In this approach, the equivalent springs are not constructed with spring elements that are commonly found in finite element codes. Rather, the equivalent springs are constructed with a number of shell elements in two layers. The properties of the elements that make up the equivalent springs are estimated from experiments on small test coupons. The same springs, with the same calibrated parameters, are then applied to the larger part of interest. Results indicate that this approach can be used to estimate the distortion that can be expected in a large part that is cause by the installation of interference fit bushings.
A Concept for the Fatigue Life Prediction of Components from an Aluminum-Steel Compound
Authors: Lamik A. , Leitner H. , Eichlseder W. , Riemelmoser F.
Published: March 2010

The goal of this research project is the development of a simulation model for lifetime estimation of components from AA6016-T4∕FeP06 material compound. Since such components are manufactured predominantly by rolling (for manufacturing of the material compound) and deep-drawing, the influence of the plastic deformations during the manufacturing process on the fatigue behavior must be investigated. In particular, the influence of the rolling reduction on the behavior of FeP06 steel has a relevant effect on the fatigue life of this aluminum-steel compound. Simulation models for fatigue life estimation of this material compound must therefore consider the influence of the elastic plastic deformation which occurs during, e.g., rolling and deep-drawing processes. For this purpose, a new model for the generation of yield curve as a function of the rolling reduction of the material FeP06 was determined. The proposed yield curve model shows good results at low and high rolling reduction compared to the models of Voce and Swift. The lifetime estimation shows a substantial improvement of accuracy (600 %) by the consideration of the influence of the rolling reduction.
Impact Fatigue Failure Investigation of HVOF Coatings
Authors: David C. N. , Athanasiou M. A. , Anthymidis K. G. , Gotsis P. K.
Published: March 2010

Dynamic impact-wear and coating fatigue at cyclic loading conditions demonstrates a very demanding failure mode, which occurs in a number of mechanical applications and it becomes very critical when the application concerns aggressive working environments. The coating impact testing is a novel experimental technique developed to investigate the fatigue behavior of coating-substrate compounds, which was not possible with the common testing methods previously available. The objective of this study is to investigate the influence of the impact load on the fatigue strength of thermal spray high velocity oxy-fuel (HVOF) coatings. Furthermore, the overall aim of the current research is to prove the reliability of the impact testing method to assess the coating lifetime against fatigue, to interpret the coating failure modes, and thereby to explore its capability, whether this nonstandard test can be used in industrial scale as a reliable technique in the development and optimization of fatigue resistant coatings. Based on the above method the current research provides experimental results concerning the coating fracture in terms of cohesive and adhesive failure modes. The fatigue strength of the tested coatings is determined in terms of fatigue-like diagrams by means of scanning electron and white light interference microscopy, as well as by electron dispersive x-ray analysis (EDX) at discrete loads and number of loading cycles. From the conducted experiments, it was shown that the optimum HVOF coating against fatigue is the WC-CoCr.
Glyphosate Weed Control Enhancement with Ammonium Sulfate and Commercial Water Conditioning Agents
Authors: Peterson Dallas E. , Thompson Curtis R.
Published: March 2010

Glyphosate herbicide labels generally recommend addition of ammonium sulfate (AMS) to the spray solution, which often improves weed control, especially when mixed with hard water. AMS in solution disassociates, and the sulfate binds with cations in the spray solution, preventing the development of glyphosate-cation complexes that tend to have lower absorption into plant leaves. In addition, the ammonium ion can associate with the glyphosate molecule, which helps facilitate glyphosate absorption into the leaf. The recommended AMS rate is 1–2 % w∕w, and AMS is available in both dry and liquid formulations. Applicators generally find AMS inconvenient to use because of the high use rate and handling issues. Several companies are marketing low-rate water conditioner products to be used as an alternative to AMS with glyphosate. Pesticide applicators like the convenience of low-rate water conditioners, but performance of these products has been inconsistent. Field experiments were conducted near Manhattan, KS, from 2005 to 2008 to compare the efficacy of glyphosate with AMS and various commercial water conditioners on velvetleaf, sorghum, corn, and sunflower. Each experiment consisted of a sublethal (0.31 or 0.43 kg ae∕ha) dose of glyphosate applied in combination with the recommended application rate of each adjuvant. Water hardness, environmental conditions, and plant growth stages varied by experiment. Control of all assay species with glyphosate was enhanced by the addition of AMS, unless control was near complete in the absence of AMS. Commercial water conditioner products that included an AMS component at the equivalent rate of 1 % w∕w gave equal or slightly better control than glyphosate plus 1 % w∕w AMS. Commercial water conditioners that did not provide an equivalent amount of AMS gave less control than glyphosate with 1 % or 2 % w∕w AMS and were often no better than glyphosate alone for the low-rate products.
The Effect of Adjuvants, Pesticide Formulation, and Spray Nozzle Tips on Spray Droplet Size
Authors: Klein Robert N. , Golus Jeffrey A. , Nelms Kelli L.
Published: March 2010

Many factors, including adjuvants, pesticide formulations, and nozzle tips, affect spray droplet size. It is important to understand these factors as spray droplet size affects both drift and efficacy of pesticides, which is a main concern with pesticide application. A laser particle analyzer was used to determine the spray droplet size and distributions of a range of formulations sprayed through several types of nozzle tips. Nozzles included were extended range flat fan sizes 11003 and 11005 (Spraying Systems XR), air induction flat fan sizes 11005 and 11004 (AI), air induction extended range flat fan size 11005 (AIXR), preorifice flat fan size 11005 (TT), and a second preorifice flat fan size 2.5 (TF). Several deposition∕retention adjuvants were studied, including Array, Interlock, In-Place, and Thrust. Another study looked at diflufenzopyr + dicamba (Status, BASF) in combination with several adjuvants. Also, three fungicides were evaluated at differing spray volumes. Results indicated that the droplet size of some nozzle tips is more affected than others by changes in the contents of the spray solution.
Selection of Sequestering Agents Having Affinity for Calcium Ion for Stabilization of the Emulsifiable Concentrate Formulations
Authors: Kozuki Y. , Ohtsubo T. , Sasaki M.
Published: March 2010

Emulsifiable concentrates (ECs) are often used for pesticides, which are highly soluble in a non-polar solvent. When a pesticide is hardly soluble in a normal non-polar solvent, it is difficult to prepare an EC formulation with high pesticide content. In order to overcome this difficulty, polar solvents are used to enhance the solubility of the pesticide. N-methyl-2-pyrrolidone (NMP) is well-known as one of the most preferred polar solvents. However, many agrochemical manufacturers have started research to remove this solvent from EC formulations because of recent regulations by the authorities. However, it is not easy to find alternative solvents that have both good solvency and a good safety profile. The authors selected diethyl oxalate as an alternative candidate for NMP by using the organic conceptual diagram discussed in the previous report. A pesticide in an EC formulation containing diethyl oxalate as a co-solvent was chemically stable and showed good emulsion stability even after accelerated storage. These results suggested that this solvent could be used as an alternative to NMP. However, a decrease in pH and water content were also observed, and the sample became turbid after storage. As this turbidity was confirmed to be derived from the generation of calcium oxalate, the calcium oxalate generation process was studied. As a result, it is speculated that diethyl oxalate was hydrolyzed to oxalic acid under the acidic conditions and calcium ion, derived from an anionic surfactant contained in the EC formulation, reacted with the oxalic acid to form calcium oxalate. In order to inhibit this reaction, several kinds of sequestering agents were tested. Among them, mono-alcohols were the best though they did not completely inhibit the reaction. Though the mechanism is still unclear, mono-alcohols were effective in blocking the binding of calcium ion and oxalic acid. A mono-alcohol is a structured molecule having a hydrophilic head region and a lipophilic tail region like a surfactant. If calcium ions are dissolved in the water in the EC formulations, even though the water content is low, a mono-alcohol may form something like an inverse micelle, which captures the calcium ions inside.
A Predictive Solubility Tool for Pesticide Emulsifiable Concentrate Formulations
Authors: Kozuki Y. , Ohtsubo T.
Published: March 2010

Emulsifiable concentrates (ECs) are one of the most widely used pesticide formulations because they have a lot of advantages, such as good storage stability, relatively high biological activity, easy weighing, easy production, and so on. An EC is normally prepared by dissolving a pesticide in a nonpolar solvent with surfactants. When a pesticide is hardly soluble in a common nonpolar solvent, a polar solvent is used as a co-solvent. One of the preferred polar solvents, which have been used for this purpose is N-methyl-2-pyrrolidone (NMP). However, because of its toxic profile, which has recently become apparent, the commercial use of NMP is recently restricted in many fields. Under the circumstances, it is desirable to look for an alternative solvent in the pesticide formulation area. The organic conceptual diagram was tried to search for the alternative solvents because it is a useful tool for predicting the physico-chemical properties of an organic compound. In the organic conceptual diagram, the physico-chemical properties are expressed by the combination of the organic value (OV) and the inorganic value (IV). According to the theory, organic compounds that have similar IV∕OV ratios (the inorganic organic balance = IOB) are mutually miscible in each other. In order to investigate the applicability of this concept to search for a suitable solvent for a pesticide that is hardly soluble in nonpolar solvents, the relationship of the IOB between two hardly soluble pesticides (i.e., a neonicotinoid insecticide and an herbicide) and several types of solvents was evaluated. As expected, solvents having an IOB close to the targeted pesticide showed high solvency against it, while the pesticide did not dissolve in solvents, which have an IOB farther off. It was demonstrated that the organic conceptual diagram can be a good tool for the selection of a solvent for a pesticide that is hardly soluble in the usual nonpolar solvents.
Stabilization of Suspension Concentrate Formulations via Specialized Double-Comb Polymers
Authors: Hazen James L. , Bergström Karin
Published: March 2010

Alkyl naphthalene sulfonate condensates, lignosulfonates, block copolymers, and alkoxylated polyarylphenol derivatives are used as dispersants in pesticide suspension concentrate (SC) and suspoemulsion formulations. Typically, a pesticide formulation could contain either type of dispersant, with the final selection being driven by the active ingredient and the desired performance characteristics of the final formulation. Until now, little attention has been focused to the use of stabilizing polymers to improve the quality and shelf life of these formulations. Comparative data were generated on selected aqueous SC formulations to better understand the particle stabilization effects of a specialized double-comb polymer. Significant improvement of suspension stability is possible over the standard formulations.
Antifoaming and Defoaming in Agricultural Tank Mixes: Revisiting, Revising, and Reviving a Method
Authors: O'Connell Todd J. , Ruscko Lisa
Published: March 2010

The foam that is generated in agricultural tank mixes is of great concern because this foam can cause problems such as slow mixing and worker exposure. Antifoaming and defoaming agents are used to control this foam. Developing a reproducible test that accurately predicts the real world performance of these products has been difficult. Several methods are briefly reviewed. An ASTM method has been developed and established. However, this method intuitively is difficult to translate into real world performance. An older possible method has been shown to have obvious and significant problems. Several new modifications to this older method are proposed as a means of overcoming the problems and measuring the performance of products. The proposed method involves a large, polypropylene beaker that is charged with a foaming solution. The solution is stirred and foam is generated using an air sparge and a sparge stone defined in another current ASTM method. Defoamer is added to the foam and the time required for the foam to collapse and to reform is measured separately. The way the foam disintegrates and redevelops can also be observed and recorded or described. Statistical data indicate that, using this method, differences between the performances of various defoaming∕antifoaming agents can be determined. The differences are reproducible enough to identify performance differences that will be appreciable in the field. As a result, quantitative and qualitative data may be generated using the proposed method. Also significant is that the method separates antifoaming and defoaming into discrete measurements. This separation of the two measurements provides a better measurement for how a product will perform in the field relative to other products. Calculations resulting in new terms are proposed as a means to create a scale that will allow direct comparison of the performance of various antifoams∕defoamers.
Evaluation of a Proposed Drift Reduction Technology High-Speed Wind Tunnel Testing Protocol
Authors: Hoffmann W. Clint , Fritz Bradley K. , Lan Y.
Published: March 2010

The U.S. Environmental Protection Agency (EPA) has initiated the development of protocols for for measuring spray drift reduction technologies (DRTs) related to the application of agricultural protection chemicals. The DRT Program is an EPA-led initiative program to “achieve improved environmental and human health protection through drift reduction by accelerating the acceptance and use of improved and cost-effective application technologies.” The first step in implementing the DRT program is to develop a set of protocols, standard operating procedures, and data quality assurance steps so that the results from any trials or research conducted are scientifically valid and repeatable. A protocol for measuring spray droplet spectra via laser diffraction equipment in a high speed wind tunnel (air velocities >160 kph (100 mph)) was tested. Following the proposed protocol, five reference nozzles were evaluated with spray solutions of deionized water, water + 9 % isopropanol, and water + 0.25 % of a nonionic surfactant. Each of the nozzle and spray solution combinations were evaluated in 160, 193, and 225 kph (100, 120, and 140 mph) airstreams, as well as under static (0 kph) conditions. The results of these atomization studies showed that there were significant differences in droplet spectra between the spray solutions and from the different air velocities. Based on the time to complete the tests, the author suggest using a ±5 % standard deviation values as criteria for accepting atomization tests results.
Promoted Ignition-Combustion behavior of Cobalt and Nickel Alloys in Oxygen-Enriched Atmospheres
Authors: Million Joseph F. , Samant Anand V. , Zawierucha Robert
Published: March 2010

Promoted ignition-combustion behavior has been used to describe a situation in which a substance with low oxygen compatibility ignites and supports the combustion of a more combustion-resistant material. Previous work has been reported on the investigation of this phenomenon as it relates to carbon steel, stainless steels, and a number of significant engineering alloys in the nickel, cobalt, and copper families. Reported in this paper are the results of promoted ignition-combustion tests of three cobalt based alloys in oxygen-enriched atmospheres at pressures ranging from 2.86 to 34.5 MPa. Included in the test program were Stellite 6, a commonly used hard facing alloy and two high strength cobalt alloys—MP35N and Elgiloy. Also reported in this paper are the results of promoted ignition-combustion tests of four nickel based alloys in oxygen-enriched atmospheres at pressures up to 34.5 MPa. Nickel alloys evaluated in the program included Hastelloys B-3 and W, RA 330, and a cast variant of the Hastelloy C type, CW6M. Hastelloy B-3 and CW6M are used in chemical process industry applications where corrosion is of concern. RA 330 is a significant elevated temperature alloy. Hastelloy W is a filler metal used for dissimilar metal welds.
Determination of Burn Criterion for Promoted Combustion Testing
Authors: Sparks Kyle M. , Stoltzfus Joel M. , Steinberg Theodore A. , Lynn David
Published: March 2010

Promoted ignition testing [1–3] is used to determine the relative flammability of metal rods in oxygen-enriched atmospheres. In these tests, a promoter is used to ignite each metal rod to start the sample burning. Experiments were performed to better understand the promoted ignition test by obtaining insight into the effect a burning promoter has on the preheating of a test sample. Test samples of several metallic materials were prepared and coupled to fast-responding thermocouples along their length. Various ignition promoters were used to ignite the test samples. The thermocouple measurements and test video were synchronized to determine temperature increase with respect to time and length along each test sample. A recommended length of test sample that must be consumed to be considered a flammable material was determined based on the preheated zone measured from these tests. This length was determined to be 30 mm (1.18 in.). Validation of this length and its rationale are presented.
Ignition Sensitivity of Nonmetallic Materials in Oxygen-Enriched Air (NITROX): A Never Ending Story in SCUBA Diving?
Authors: Binder Chr. , Brock T. , Hesse O. , Lehné S. , Tillack T.
Published: March 2010

Self-contained underwater breathing apparatus (SCUBA) divers use different mixtures of nitrogen and oxygen as breathing gas. The socalled NITROX mixture often contains more oxygen than is contained in air and may increase the fire hazard in diving equipment. The SCUBA diving community, however, still differentiates between NITROX mixtures that contain more than 40 % oxygen or less. They consider a mixture with up to 40 % oxygen often as regular air. In filling operations of SCUBA cylinders, gas flows from high pressure to low pressure. Because of compressive heating, a sudden temperature rise in the gas occurs and nonmetallic materials, e.g., seals may ignite. BAM has used the pneumatic impact test to investigate the ignition sensitivity of ethylene propylene diene monomer (EPDM), fluorelastomer (FPM), polytetrafluorethylene (PTFE), polyetheretherketone (PEEK), and nylon (PA 6.6) to gaseous impacts in synthetic air, in various NITROX mixtures, and in pure oxygen. The test results clearly show that for nonmetallic materials, the maximum pressure of nonreaction in NITROX mixtures decreases at a content of 29 % oxygen in comparison to those in air. In addition, autoignition temperatures of the nonmetallic materials were also determined. The findings of this investigation support very well the results of other publications on oxygen enrichment. As a consequence of this study, in SCUBA diving, the same safety requirements for NITROX mixtures with more than 21 % oxygen should be applied as for pure oxygen in the industry.
The Importance of Quality Assurance and Batch Testing on Nonmetallic Materials Used for Oxygen Service
Authors: Binder Chr. , Arlt K. , Brock T. , Hartwig P. , Hesse O. , Tillack T.
Published: March 2010

In oxygen components, even for high pressure oxygen service, it is possible to use organic seals, lubricants, or filling liquids, provided their oxygen compatibility has been checked. However, fire incidents in oxygen systems still occur because these materials ignite and burn. There are many reasons, such as incorrect design, contamination, faulty operation, unsuitable materials, etc., why this happens. Another cause that is overseen very often is proper maintenance on the user's side. It is very important to replace in a component a worn out seal by the same one with identical oxygen compatibility properties. On the part of the producer or distributor of materials, batch testing and also a quality assurance system play a key role in the safety of an oxygen component. Any change in the manufacturing process of a material, or in its composition, and even its further processing may have an impact on its oxygen compatibility and finally on the component in which it is used. Numerous investigations by BAM over decades reveal the influence of minor constituents and fillers on a material's oxygen compatibility. The test results in this paper show how important it is to regularly perform batch testing on nonmetallic materials used for oxygen service and to have a quality assurance system that helps minimize incidents where unsuitable materials are chosen by accident.
Identification and Quantification of Combustion Products Released by Non-Metallic Materials Used for Medical Oxygen Equipment
Authors: Carré M. , Barthélémy H. , Bruat J. , Lombard S. , Longuet O. , Schaaff J. P.
Published: March 2010

Non-metallic materials (plastics, elastomers, and lubricants) are known to be the most critical ones in terms of safety in high pressure oxygen distribution systems. When proper oxygen system design guidelines are not followed, the risk of accidental ignition in service arises and has been known for many years. It has been observed that if sufficient mass was available when ignited, concentrations of species could arise in a level that could be considered toxic. This is a concern in particular for those non-metallic parts containing halogens. This risk shall especially be addressed for medical equipment and for any high pressure breathing gas system. International standards (ISO 15001 or EIGA 73∕08) recommend how to address this toxicity risk. They give specific recommendations such as minimising non-metallic materials in design of equipment and use of non-metallic materials whose thermal decomposition and∕or combustion in oxygen produce less toxic products (with lethal concentration LC50>5,000 ppm). They also present a list of theoretical potential combustion products but no quantitative values of real combustion by-products from which a toxicity risk assessment can be achieved. Then, in order to evaluate the toxicity risk for medical oxygen and breathing gas applications, it is necessary not only to identify but to quantify compounds generated by combustion. In this paper, an analytical procedure used to identify and quantify the released products will be described. The target is to analyze these compounds with the shortest delay after combustion promoted by adiabatic compression with oxygen at 200 bars (20,000 kPa). The analysis of combustion by-products must be done in the few minutes following the combustion. Therefore direct analytical techniques, like Fourier transformed infrared spectrometry and mass spectrometry, were used to identify and quantify the generated species and sample extraction was taken on the closest emission point to the combustion on the installation. All such precautions were intended for avoiding modification or subsequent reaction of compounds due to sample preparation steps or delays in analysis. Comparisons were made for several plastics materials and elastomers. The list of quantified combustion by-products will be presented for polytetrafluoroethylene and polychlorotrifluoroethylene. The quantification data obtained during this study is proposed for use in a toxicity risk assessment. Then a global risk evaluation can be done including this toxicity risk assessment and an ignition risk assessment. Based on this global risk evaluation, practical recommendations could be provided.
High Pressure Quick Disconnect Particle Impact Tests
Authors: Rosales Keisa R. , Stoltzfus Joel M.
Published: March 2010

National Aeronautics and Space Administration (NASA) Johnson Space Center White Sands Test Facility (WSTF) performed particle impact testing to determine whether there is a particle impact ignition hazard in the quick disconnects (QDs) in the environmental control and life support system (ECLSS) on the International Space Station (ISS). Testing included standard supersonic and subsonic particle impact tests on 15-5 PH stainless steel, as well as tests performed on a QD simulator. This paper summarizes the particle impact tests completed at WSTF. Although there was an ignition in test series 4, it was determined that the ignition was caused by the presence of a machining imperfection. The sum of all the test results and analysis enabled NASA to conclude that the risk of particle impact ignition hazard in the ISS ECLSS QDs was acceptable.
Advanced Crew Escape Suits (ACES) Particle Impact Test
Authors: Rosales Keisa R. , Stoltzfus Joel M.
Published: March 2010

NASA Johnson Space Center requested NASA JSC White Sands Test Facility to assist in determining the effects of impaired anodization on aluminum parts in advanced crew escape suits (ACES). Initial investigation indicated poor anodization could lead to an increased risk of particle impact ignition, and a lack of data was prevalent for particle impact of bare (unanodized) aluminum; therefore, particle impact tests were performed. A total of 179 subsonic (Test Series 1–3) and 60 supersonic (Test Series 6) tests were performed with no ignition of the aluminum targets. Based on the resulting test data and analysis, WSTF found no increased particle impact hazard was present in the ACES equipment.
Oxygen Fire Hazards in Valve-Integrated Pressure Regulators for Medical Oxygen
Authors: Forsyth Elliot T. , Newton Barry E. , Chiffoleau Gwenael J. A. , Forsyth Brad
Published: March 2010

In recent years, medical oxygen regulators that incorporate a cylinder isolation valve have increased in popularity. These devices, often called valve-integrated pressure regulators (VIPRs), essentially combine several components into one highly compact manifold design, typically including a fill valve, shut-off valve, residual pressure valve, regulator, and relief valve. Combining these components into a single manifold block presents unique oxygen fire hazards that can differ greatly from those found in the stand-alone versions of the components. In order to avoid fires, these hazards must be understood and addressed in the design of the VIPR. This paper presents the most common oxygen fire hazards found in VIPR devices as well as the ASTM analysis and testing methods used to qualify a new design, specifically considering oxygen compatibility of materials, toxicity of combustion products, ignition mechanisms, and reaction effects of a fire.
Vacuum Superinsulated Liquid Oxygen Piping and Vessels
Authors: Colson Alain , Werlen Etienne , Barthélémy Hervé
Published: March 2010

Vacuum superinsulation is commonly used in industrial applications for liquid oxygen transfer piping and liquid oxygen vessels as an alternative to other solid insulation materials such as perlite or Foamglass®, which have lower thermal performances. Tests have been conducted on insulation materials according to ASTM D2512 (equivalent to ISO 11114-3, EN 1797) in LOX as well as according to ASTM G72 (equivalent to EN 1797) in GOX. The superinsulation materials that have been tested are a number of layers of aluminum foils of various thicknesses each being separated by intermediate nonmetallic layers of various nature. Based on experience and incidents in the industry, this paper is intended to discuss the recent test results in pure oxygen and the possible ignition of superinsulation material in the interspace and mechanism of propagation as well as the consequences of a fire. Recommendations regarding material selection for vacuum superinsulation materials in LOX applications are also provided.
Adiabatic Compression Testing—Part I: Historical Development and Evaluation of Fluid Dynamic Processes Including Shock-Wave Considerations
Authors: Newton Barry E. , Steinberg Ted
Published: March 2010

Adiabatic compression testing of components in gaseous oxygen is a test method that is utilized worldwide and is commonly required to qualify a component for ignition tolerance under its intended service. This testing is required by many industry standards organizations and government agencies. This paper traces the background of adiabatic compression testing in the oxygen community and discusses the thermodynamic and fluid dynamic processes that occur during rapid pressure surges. This paper is the first of several papers by the authors on the subject of adiabatic compression testing and is presented as a non-comprehensive background and introduction.
Adiabatic Compression Testing—Part II: Background and Approach to Estimating Severity of Test Methodology
Authors: Newton Barry E. , Chiffoleau Gwenael J. A. , Steinberg Ted , Binder Christian
Published: March 2010

Adiabatic compression testing of components in gaseous oxygen is a test method that is utilized worldwide and is commonly required to qualify a component for ignition tolerance under its intended service. This testing is required by many industry standards organizations and government agencies; however, a thorough evaluation of the test parameters and test system influences on the thermal energy produced during the test has not yet been performed. This paper presents a background for adiabatic compression testing and discusses an approach to estimating potential differences in the thermal profiles produced by different test laboratories. A “thermal profile test fixture” (TPTF) is described that is capable of measuring and characterizing the thermal energy for a typical pressure shock by any test system. The test systems at Wendell Hull and Associates, Inc., in the United States and at the BAM Federal Institute for Materials Research and Testing in Germany are compared in this manner and some of the data obtained are presented. The paper also introduces a new way of comparing the test method to idealized processes to perform system-by-system comparisons. Thus, the paper introduces an “idealized severity index” (ISI) of the thermal energy to characterize a rapid pressure surge. From the TPTF data a “test severity index” can also be calculated so that the thermal energies developed by different test systems can be compared to each other and to the ISI for the equivalent isentropic process. Finally, a “service severity index” is introduced to characterize the thermal energy of actual service conditions. This paper is the second in a series of publications planned on the subject of adiabatic compression testing.
A Synthesis of the World Literature of Ice Hockey Injuries: Epidemiologic Principles and Future Directions
Authors: Stuart M. J. , Dajani K. A. , Crawford B. J. , Gill M. L. , Link A. A. , Smith A. M.
Published: March 2010

Ice hockey is a fast-paced, aggressive sport whose participants are subject to relatively high rates of injury. Although there is a growing emphasis on the epidemiology of ice hockey research and its application towards reducing injuries, the literature has never been organized into an accessible database. Ice hockey is played in North America, Europe, Scandinavia, the U.K., and several other non-English speaking countries, yet injury reports not written in English are often ignored in review articles. The purpose of this project was to synthesize the existing world literature on ice hockey injuries into a framework of epidemiologic criteria, accessible in an organized, retrievable library. An extensive search of the following databases was done: MEDLINE, BIOSIS, EMBASE, NTIS, CURRENT CONTENTS, DISSERTATION ABSTRACTS, SPORT DISCUS, CINAHL, and WEB OF SCIENCE. Key words used were “ice hockey” and “injuries,” and the search range was 1966 to July 2007. Endnote X (Thompson Corp., Stamford, CT) was used for reference compilation. Eight hundred sixty seven documents were catalogued, from 27 countries in 8 languages. Documents were first categorized by type, including injury (226), equipment (45), case reports (94), review articles (294), editorials (39), or as focusing on the physiological, psychological, or medical aspects of ice hockey (169). Documents were then subdivided by study type and whether they were prospective (117) or retrospective (109). Further subdivisions beyond these levels were based on the inclusion of certain critical epidemiological criteria, including exposure time, a clear definition of “injury,” and the level of play, among others. This comprehensive database should make future ice hockey research more efficient, as well as promote sound epidemiology and a more global perspective.
Acute Care in Cervical Spinal Cord Trauma with Long-Term Benefit: A Review
Authors: Ashare Alan B. , Lyckman Alvin W.
Published: March 2010

Spinal cord injury involves three phases. In the first, trauma events deliver direct pressure to the cervical spine, which may compress, dislocate, or fracture the spine, and in turn compress, crush, or transect the spinal cord. In the process, local neurons are destroyed and sensory and motor pathways can be severed. In the second phase, acute tissue responses, bleeding, and inflammation rapidly and radically change the physical and chemical conditions at the wound site. Finally, days, weeks, and months after the initial trauma, chronic post-injury processes reform the wound site into a lasting scar that impedes regeneration of spinal cord pathways. A major goal of current spinal cord injury research should be rapid and lasting inhibition of acute and chronic tissue reactions in the spinal cord wound that lead to a growth-inhibiting environment and diverting these reactions toward conditions that favor regeneration of severed spinal pathways. Here, we consider experimental strategies that could form the basis for treatments that can be rapidly administered after trauma and provides lasting benefit to spinal cord regeneration and rehabilitation.