bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Fastener Flexibility on the Prediction of Load Transfer and Fatigue Life for Multiple-Row Joints
Authors: Huth H
Published: December 2008

An improvement of the accuracy of fatigue life prediction methods used for multiple-row riveted or bolted joints can be expected only if the rivet load distribution is considered during design and fatigue analysis. To calculate the individual load transfer and the bypassing load the fastener flexibility must be taken into account. Semiempirical formulas for the calculation of fastener flexibility existing in the literature turn out to be not exact or at least not applicable for a wider range of joint geometries. This unsatisfactory situation was the reason for performing an extensive experimental investigation during which fastener flexibilities for a wide range of joints of practical interest were determined.

The effects of primary joint parameters, such as the plate material, clamping length, and diameter and material of the fastener, as well as the effects of secondary parameters, such as the clamping force, condition of the faying surfaces, and fit and type of head of the fastener, were investigated through specific variations. For this purpose load-deformation measurements under quasi-static and flight-by-flight loading conditions were performed using single- and double-shear specimens with known load transfer.

A formula for fastener flexibility, valid for riveted and bolted metallic and graphite/epoxy joints, was derived from the test results and proved to be significantly superior to those found in the literature. This formula for load transfer calculations of multiple-row fatigue loaded joints was used to predict accurately the measured values of load transfer. This improvement also leads to a better fatigue life prediction. The load transfer measurements showed a quasi-linear relationship between the applied load and the total load transfer which was little affected by fatigue loading, although the load transferred by bearing was not constant. By measuring bearing loads and local strains close to fastener holes in a multiple-row joint the author shows that with increasing friction the bearing stress and the local strains decreased. The redistribution of loads or the changes in the mechanisms of load transfer result in a relief of the fatigue critical location. Since these changes of the local stress situation cannot be predicted, the application of fatigue life prediction methods on the basis of local strains must lead to inaccurate results.
Strength and Lifetime of Bolted Laminates
Authors: Ramkumar RL , Tossavainen EW
Published: December 2008

An extensive experimental program was conducted to investigate the effects of various parameters on the strength and lifetime of bolted laminates. The tested joint specimens were composite-to-metal joints where a single fastener transferred the load from one plate to the other. The various test variables were the bolted plate geometry, laminate lay-ups, stacking sequences and thicknesses, fastener material, diameter, fastener head type (protruding or countersunk), fastener torque, joint configuration (single lap or double lap), load type (tensile or compressive under static and fatigue loading conditions), and test environment conditions (room or ambient temperature and dry; elevated temperature and wet). All the laminates were fabricated using AS1/3501-6 graphite/epoxy prepreg material.

Static tests reproduced the general trends reported in the literature for the effects of plate edge distance and plate width on the strengths of laminates and the corresponding failure modes. Constant-amplitude fatigue tests were conducted at a frequency of 10 Hz, maintaining a constant minimum-to-maximum cyclic load ratio. The effect of the maximum cyclic load amplitude, as a fraction of the corresponding static strength, on the number of cycles to failure was recorded. Hysteresis plots, hole diameter, and fastener torque loss measurements were also obtained during fatigue. The obtained results complement data available in the literature.
Fatigue of Bolted Continuous Fiber Sheet Molding Compound Composite-Metal Joints
Authors: Mallick PK , Little RE , Dunham JW
Published: December 2008

Load-controlled tension-tension cyclic tests on continuous fiber sheet molding compound (CSMC) composite-metal bolted joints have been performed. The test results show that both failure mode and stress-life data depend strongly on whether the width of the specimen is larger or smaller than the clamped area. Based on the observed failure modes in a single bolt pattern, a stress-life model is proposed. Limited data for multiple bolt patterns are reasonably consistent with the failure model.
The Development and Field Service History of Ford Automotive Aluminum Radiators
Authors: Barkley JM , Wiggle RR , Winterbottom WL
Published: December 2008

A major program was launched by Ford Motor Company in 1976 to develop lightweight and durable aluminum heat exchangers. This program resulted in the identification of two radiator designs: a brazed flat tube design for maximum efficiency and weight savings and a mechanically assembled design with superior mechanical durability at a reduced facilities investment. Both designs have plastic tanks mechanically crimped to the header and an epoxy coating added to the air side of the header to insure mechanical integrity and leak-free tube-to-header joints.

Heat exchanger development testing of both brazed and mechanically assembled aluminum radiators ranged from simple laboratory glassware tests to controlled fleet and limited production field tests. A key element of this development program was the tracking and retrieval of radiators from two large-scale field trials. Radiators from these trials were analyzed metallographically for internal and external corrosion. Only 3 of 150 mechanically assembled aluminum radiators analyzed showed significant corrosion. For these three samples, high chloride levels (>100 ppm), low glycol concentrations (<30%), and very low inhibitor levels were found. Significant internal corrosion in prototype vacuum brazed aluminum radiators was found to be related to tubes clad with AA7072 and the use of a AA6951 header material. Subsequent production level radiators with no sacrificial clad on the tube interior surfaces and a AA3005 header material showed very little corrosion. External corrosion was noted on tube surfaces for some vacuum brazed radiators retrieved from areas near the seacoast or where large amounts of deicing salts are used.

In general, projections made on the basis of the retrieval studies indicated that the aluminum radiators have comparable or better durability than current production copper/brass radiators. Copper/brass radiators appear to be more susceptible to field performance degradation because of external fin-to-tube solder corrosion after several years in service. Although material and design improvements have led to a marked improvement in the corrosion resistance of both copper/brass and aluminum radiators, further effort is required to attain a “corrosion proof” system. Current investigations involve improving clad/core alloys, external coatings, gasket materials, header designs, and braze processes.
Inhibitors and Coolant Corrosivity
Authors: Vukasovich MS , Sullivan FJ
Published: December 2008

Today's automotive engine coolants must give corrosion protection in both the standard cast-iron and brass and the newer aluminum cooling systems. The formulation of coolants for this dual protection was studied by investigating the effects of various corrosion inhibitors, pH, and coolant silicate depletion on cooling system corrosion. Laboratory glassware and simulated service corrosion tests were used for the study. It was found that inhibitors for some metals can be corrosive to others, but good aggregate protection for both types of cooling systems can be obtained by using some combinations of common coolant corrosion inhibitors. Low coolant pH is to be preferred over high pH for cooling systems containing aluminum. Coolant depleted of silicate is dependent on the remaining inhibitors for ongoing aluminum protection, and little or no accrued protection results from the prior contact by silicate. Several coolant formulations are described that give good aggregate protection without resort to phosphate or silicate.
Testing of Engine Coolant Inhibitors by an Electrochemical Method in the Laboratory and in Vehicles
Authors: Fiaud C , Netter P , Tadjamoli M , Tzinmann M
Published: December 2008

An electrochemical test based on the measurement of galvanic currents has been developed for water-glycol solutions on five different metallic materials. An acidity function is first defined for ethylene glycol, propylene glycol, and water glycols, which allows comparisons to be made of their aggressiveness towards metals. Different combinations of inhibitors are tested by using the method. It is shown that the method is particularly suitable for testing aluminum: the effects of inhibitors on the behavior of the oxide layer, on pitting tendency, and on general dissolution of the metal are easily detected. The corrosion parameters may be continuously monitored by inserting the electrochemical cell into the cooling system of a car.
Test Methods for the Development of Supplemental Additives for Heavy-Duty Diesel Engine Coolants
Authors: Hudgens RD , Hercamp RD
Published: December 2008

This paper deals with the use of supplemental coolant additives (SCAs) for the protection of heavy-duty diesel cooling systems. The unique needs of heavy-duty diesel are discussed as well as the special demands made upon the coolant by heavy-duty service. Developmental considerations for heavy-duty SCAs are given and new and modified test methods are proposed for their evaluation.
A Review of Factors Influencing Coolant-Metal Interfaces in Engines
Authors: O'Callaghan TM
Published: December 2008

The importance of the cooling system is often not recognized in an engine development program and the coolant used is not always compatible for good cooling system operation. The main crux in any engine cooling system is good heat transfer from metal to coolant and, therefore, it follows that the hot engine metal to coolant interface surfaces should be kept clean. A review is made of the factors affecting heat transfer and the part the antifreeze/inhibitors play in preventing any heat barrier.
U.S. Army Antifreeze after 50 Years
Authors: Jordan CB
Published: December 2008

In the early 1930s, the U.S. Army became involved in the research and development of automotive antifreeze/coolants. This effort was justified because military requirements for antifreeze/coolants are more severe than those usually encountered in normal civilian operation. The tactical and operational deployment of military vehicles results in exposure to extreme climatic operating conditions and unusual storage situations. Nearly every conceivable cooling system design is utilized in military vehicles. Because of the need for antifreeze/coolants that will perform in all of these environments, the development of Army antifreeze specifications through the years centered around a single universal material that would be compatible with all situations. The aim for maximum efficiency, simplified logistics, and safety has been maintained.

Technical activities for the past 50 years demonstrate the Army's willingness and ability to assume its share of responsibility for coolants. Army contributions and expertise are recognized by associates in government and industry. This paper highlights stages of technological progress made toward the development of coolants through the years.
Use of the Disk Bend Test to Assess Irradiation Performance of Structural Alloys
Authors: Hamilton ML , Huang FH
Published: December 2008

The disk bend test has been a valuable technique for rapid evaluation of the ductility of a large number of alloys under consideration for use as structural materials in the breeder and fusion reactor programs. The test employs the 3-mm-diameter, 0.3-mm-thick microscopy and density disk specimen, conserving valuable experimental volume in the limited reactor space available.

The test involves bending the disk symmetrically about the center, producing a simple, axisymmetric stress state. Experimental results are in agreement with a theoretical analysis of the bend configuration. The advantages and limitations of the technique are discussed.

The test has shown that commercial precipitation-strengthened alloys and the Path B alloys of the U.S. Fusion Program exhibit unacceptably low ductilities following irradiation. This was demonstrated for a number of alloys, in a variety of thermomechanical conditions, including cold worked, cold worked and aged, and solution treated and aged.
Shear Punch and Microhardness Tests for Strength and Ductility Measurements
Authors: Lucas GE , Odette GR , Sheckherd JW
Published: December 2008

In response to the requirements of the fusion reactor materials development program for small-scale mechanical property tests, two techniques have been developed, namely ball microhardness and shear punch tests. The ball microhardness test is based on the repeated measurement at increasing loads of the chordal diameter of an impression made by a spherical penetrator. A correlation has been developed to predict the constitutive relation of the test material from these data. In addition, the indentation pile-up geometry can be analyzed to provide information on the homogeneity of plastic flow in the test material. The shear punch test complements the microhardness test. It is based on blanking a circular disk from a fixed sheet metal specimen. The test is instrumented to provide punch load-displacement data, and these data can be used to determine flow properties of the test material such as yield stress, ultimate tensile strength, work-hardening exponent, and reduction of area.
Effects of Specimen Thickness and Grain Size on the Mechanical Properties of Types 304 and 316 Austenitic Stainless Steel
Authors: Igata N , Miyahara K , Uda T , Asada S
Published: December 2008

The mechanical properties of thin foil specimens of Types 304 and 316 austenitic stainless steels (thickness: 18 to 350 µm) have been investigated at room temperature. The 0.2% proof stress, ultimate tensile strength, work hardening exponent, and total elongation generally decrease with decreasing specimen thickness at a constant grain size. The effect of grain size on the 0.2% proof stress of the 316 stainless steel is smaller than that of the 304 stainless steel. The fracture mode of the specimens is ductile fracture and does not depend on the specimen thickness.
Failure Strain for Irradiated Zircaloy Based on Subsized Specimen Testing and Analysis
Authors: Adamson RB , Wisner SB , Tucker RP , Rand RA
Published: December 2008

This paper describes specimen geometries that have proven useful in characterizing the mechanical behavior of irradiated Zircaloy components. In many cases, small plane strain-type specimens obtained from the component of interest have been chosen. Specimen fabrication techniques are discussed. Failure strains for the various types of specimens are compared and analyzed in terms of the microdeformation mechanisms that occur in irradiated Zircaloy. Finite element analyses of specimens are conducted to determine details of the strain distribution just before the initiation of plastic instability. Results of these analyses are used to determine the maximum principal plastic strain at the failure initiation point.
Comparison of Mechanical Properties in Thin Specimens of Stainless Steel with Bulk Material Behavior
Authors: Rickerby DG , Fenici P , Jung P , Piatti G , Schiller P
Published: December 2008

Simulation of neutron damage by means of light ions produced by a charged particle accelerator requires the use of specimens having a relatively small irradiated area in order to obtain a high displacement damage rate. The irradiated zone must also be thin (∼ 20 to 200 µm typically) to ensure homogeneity of the damage and to avoid excessive specimen heating due to absorption of beam energy.

To gauge the effect of very thin specimens on the mechanical behavior of Type 316 stainless steel, three series of comparative tests have been performed: tension tests on miniature specimens of 2 mm width, thermal creep tests using this same type of specimen, and fatigue crack growth measurements in 8-mm-wide notched specimens. Experimental results for thin, reduced-size specimens have been compared both with those for rather thicker specimens of the same design and with published data for specimens of standard dimensions.

Tension tests on the miniaturized specimens in the temperature range of 297 to 1123 K indicated little dependence of the yield stress and the ultimate tensile stress on thickness, while elongation to fracture tended to decrease with decreasing thickness. A negligible influence of thickness on thermal creep behavior was observed for tests carried out in vacuo. Fatigue crack growth rate and number of cycles to crack initiation were found to be similar in both thin and thick specimens.
A Miniaturized Mechanical Testing System for Small-Scale Specimen Testing
Authors: Hannula S-P , Wanagel J , Li C-Y
Published: December 2008

In this paper a miniaturized mechanical testing system designed for multiple testing modes is described. The main testing modes include (1) constant displacement rate testing in uniaxial tensile, compressive, and cyclic loading; (2) load relaxation testing; and (3) indentation hardness testing with a controlled displacement rate or displacement (load relaxation) with an indentation probe size as small as a few micrometers in diameter. The system, originally developed for testing materials and interconnecting structures for microelectronic components, is designed so that tests in different modes can be performed with only minor modifications. For room temperature testing, the temperature stability of the system is better than 0.1°C. The maximum loading capacity and displacement range are ∼ 100 N and 5 cm, respectively, and the smallest displacements that can be controlled are ∼ 0.01 µm.

The capabilities of the testing system in different testing modes are demonstrated. Tensile and load relaxation test results of thin wires (<0.1 mm in diameter) with an accuracy comparable to bulk specimen results are presented. Also reported are results from indentation load relaxation tests with indentation depths applicable to irradiated material testing. Correlations between the mechanical properties of miniaturized specimens and bulk properties are discussed.
Post-Irradiation Creep Properties of Cold-Worked 316 Stainless Steel As Measured with Small Creep Specimens
Authors: Vandermeulen W , Snykers M , Van Asbroeck P
Published: December 2008

Small specimens (4 mm gage length, 1.3 mm diameter) of AISI 20% coldworked (CW) 316 stainless steel have been irradiated at 700°C up to 2 × 1022 n/cm2. Ageing at 650°C as well as irradiation caused a reduction in creep life and an increase in minimum creep rate as compared with as-received specimens. An investigation of a possible size effect indicated no difference between creep results obtained on these small specimens and on larger ones.
Use of Subsize Fatigue Specimens for Reactor Irradiation Testing
Authors: Liu KC , Grossbeck ML
Published: December 2008

This paper demonstrates use of subsize fatigue specimens for testing highly irradiated specimens to generate reliable information for alloy development and structural design applications. Essential specimen design features needed to accomplish irradiation and stable cyclic fatigue loading at elevated temperature and in high vacuum are discussed in detail.

As examples, test results are presented for Type 316 stainless steel tested at 430 and 550°C. Comparisons are made between data generated from full-size and subsize specimens tested at 430°C with total strain ranges as high as 2% without buckling; results indicated a good reliability of the specimens and testing methods.
Experience in Subsized Specimen Testing
Authors: McConnell P , Sheckherd JW , Perrin JS , Wullaert RA
Published: December 2008

Several techniques are reviewed for obtaining fracture toughness, impact energy, or flow data from subsized specimens. These specimens are useful when there is insufficient material or space (e.g., reactor vessel surveillance programs) for larger, more conventionally sized specimens. Such specimens are useful in other situations where, because of the structural configuration, it is appropriate to use small specimens (e.g., fusion first wall structures). The data obtained from these specimens may be (1) correlated with actual structural response or the response of larger specimens, (2) compared with test results on similar sized specimens (useful in tracking shifts in material behavior), or (3) used to provide input to fracture models.

Techniques for testing specimens of compact-tension, Charpy V-notch, and compression specimen geometries are described. Comparison is made with results from larger specimens in terms of ASTM validity criteria where possible.

Some of the specimens had been machined to substandard size from an ample amount of source material. For example, compact-tension specimens as small as 3 mm thick tested with valid fracture toughness results are discussed. Miniature Charpy specimens of similar size are also reviewed.

Other standard size specimens have been constructed from very small pieces of a limited volume of material. This approach may be useful to nuclear reactor surveillance programs. Rebuilt Charpy specimens consist of a crack tip region comprised of the original specimen to which two end tabs have been attached. The crack tip region of a compact-tension specimen is constructed from broken Charpy bars which are press-fit into a second piece of material with compact-tension shaped geometry. Results of testing these specimens are compared with those obtained from the original specimens of similar size.
Characterization of Rapidly Solidified Materials
Authors: Sater JM , Sanders TH , Garrett RK
Published: December 2008

A current topic of concern in the investigation of dispersion-hardened, rapidly solidified aluminum/transition metal alloys, both in their as-cast and wrought forms, is the development of new or improved combinations of properties through the use of extended alloys and novel processing techniques. Microstructures of materials produced by spray, chill, or weld methods generally contain the features of conventional casting, although on a finer scale. The models by Jones and by Garrett and Sanders for the classification and formation of the solidification structures are described, and a variety of as-cast structures and fracture surface are presented. Several consolidated/fabricated microstructures are also presented. Some interrelationships between processing variables, product microstructures, and mechanical properties such as notched tensile strength and yield strength are clarified. Fracture surfaces of these fabricated materials are described, as well as the effect of microvoids on fracture.
Rapid Solidification of Highly Undercooled Aluminum Powders
Authors: Perepezko JH , LeBeau SE , Mueller BA , Hildeman GJ
Published: December 2008

The amount of liquid undercooling attained during rapid solidification processing (RSP) is an important factor in determining microstructural development. An effective experimental method that may be applied in assessing undercooling potential involves the examination of a dispersion of stabilized, fine (5 to 20-µm) liquid droplets. Substantial undercoolings (ΔT ≥ 160°C) have been measured by differential thermal analysis for slowly cooled (30°C/min) droplet emulsions of aluminum alloys. Results from Al-Si and Al-Fe alloys indicate that undercooling is a function of droplet size, melt super-heating, and material composition. Comparison studies have also been conducted relating the amount of undercooling to microstructural refinement in alloys prepared as droplet emulsions and by air atomization. The results indicate that at large undercooling (ΔT > 260°C) droplet solidification can yield a microstructure similar to that formed in atomized powder. Microstructural variations with powder size are related not only to a changing cooling rate but also to a modified undercooling behavior. These observations highlight the role of undercooling in RSP and indicate that the droplet approach can be effective in examining potential aluminum powder metal alloys and in optimizing processing procedures for rapid quenching treatments.
Al3Li Precipitate Modification in an Al-Li-Zr Alloy
Authors: Gayle FW , Vander Sande JB
Published: December 2008

An Al-2.34Li-1.07Zr (weight percent) alloy was produced using rapid solidification processing in an attempt to modify the δ′ (Al3Li) precipitate found in the Al-Li binary system to a complex Al3(Li,Zr) phase. Such a modification is expected to increase fracture toughness and ductility by decreasing shear localization, which is a major drawback in Al-Li alloys. A novel microstructure is presented in which a zirconium-rich phase present as fine spheres or discontinuously precipitated rods (with diameters of 6 to 20 nm) is subsequently enveloped by δ′ during aging at 190°C.

Electron diffraction effects, energy-dispersive X-ray analysis in scanning transmission electron microscopy, and preliminary electron energy loss spectroscopy results indicate that the precipitate phase stable at 500°C is Al3(Lix,Zr1−x), where x appears to be 0.45 to 0.8. This is in contrast to the Al-Li and Al-Zr binary systems, in which the equilibrium phases at 500°C for these solute levels are aluminum solid solution and Al3Zr in an aluminum matrix, respectively. The alloy shows longitudinal strength-ductility combinations which are significantly better than those of a low-zirconium control alloy and which compare quite favorably with those of other Al-Li alloys.
A Comparative Evaluation of Aluminum Alloy Powders Used for Fabricating High-Strength Powder Metallurgy Extrusions
Authors: Bohlen JW , Kar RJ , Chanani GR
Published: December 2008

In this investigation, the characteristics of two sets of rapidly solidified aluminum alloy powders were compared, and correlations between powder characteristics and mechanical properties of extrusions fabricated from the powders were examined. Rapidly solidified 7091 and PM64 aluminum alloy powders were characterized in terms of powder morphologies, powder sizes and size distributions, dendritic cell sizes, thicknesses of surface oxide films, and oxygen contents. The analytical techniques used for powder characterization consisted of automated image analysis, scanning electron microscopy, optical metallography, Auger electron spectroscopy, and neutron activation analysis. It was determined that Alloy 7091 powders (atomized in air) and Alloy PM64 powders (atomized in nitrogen-oxygen environments) had similar powder characteristics, such as powder surface morphologies, size distributions, and microstructures. However, these two types of atomization produced differences in surface oxide chemistry and oxygen content. Extrusions fabricated from coarse powders had properties equivalent to those of extrusions from finer powders. No other correlations were observed between mechanical properties and powder characteristics.
Physical Metallurgy and Mechanical Properties of Aluminum Alloys Containing Eight to Twelve Weight Percent Iron
Authors: Skinner DJ , Okazaki K , Adam CM
Published: December 2008

New aluminum alloys with improved temperature capability have been under development during the last decade for a variety of aerospace applications. Prolonged aerodynamic heating of unprotected aluminum surfaces at relative velocities greater than Mach 2.0 produces fast degradation in the mechanical properties of currently available aluminum precipitation-hardened alloys. One alloy system which demonstrates improved 600 K strength properties and has received considerable attention is that based on Al-8(weight percent)Fe alloy (Al-8Fe) with various ternary additions. This paper reviews the physical metallurgy of aluminum-iron alloys, particularly the effect of increasing solidification rate on the crystallography of the metastable phases, and, finally, the effect of “rapid” solidification at cooling rates of ≈ 106 K/s. The current pilot production methods used for producing these alloys, in engineering quantities, include air atomization, inert gas atomization, and chill-block planar flow casting—all processes having somewhat unique characteristics and producing unique microstructures in the compositional range of 8 to 12% iron, by weight, with ternary additions. Aspects of the differences in these processes in relation to the physical metallurgy of the alloy systems are discussed. In this paper the consolidation of rapidly solidified powders is discussed, demonstrating the relationship between consolidation parameters and the evolution of acceptable mechanical properties for engineering use.
Effective Method for Degassing Evaluation of Aluminum PM Alloys
Authors: Kirchoff SD , Adkins JY , Griffith WM , Martorell IA
Published: December 2008

Current U.S. Air Force programs are using aluminum powder metallurgy (PM) to extend the use of aluminum in both airframe and engine applications. The benefits of aluminum PM over conventional ingot metallurgy (IM) processing include enhanced mechanical properties resulting from a very homogeneous microstructure, extension of solid solubility limits, formation of metastable phases, and decreased grain size. During processing of the aluminum powder into a final product or into a workable preform, degassing is desirable to facilitate the breakup of the oxide skin and to disperse it. Also, the undesirable hydroxides that form must be removed to optimize mechanical properties. Although degassing has been frequently studied, evaluation techniques for degassing efficiency have been neglected.

This program deals with the development of an effective and rapid method of evaluating degassing in aluminum products. Several methods, including ultrasonic inspection, density measurements, mass spectroscopy, and optical metallography, have been studied and evaluated using 7091 alloy small laboratory compacts. The times and temperatures of degassing were varied in such a way as to ensure that both adequate and poor degassing conditions were obtained. Each method of evaluation is discussed.
Techniques for Assessing the Corrosion Properties of Aluminum Powder Metallurgy Alloys
Authors: Pickens JR
Published: December 2008

The test techniques that have been used to assess the corrosion behavior of aluminum powder metallurgy (PM) alloys are described. Standard ASTM tests have been used to measure general and pitting corrosion, exfoliation corrosion, and stress-corrosion cracking (SCC) susceptibilities of these alloys. However, the drive to measure subtle but important improvements in SCC behavior at higher strength levels and the desire to understand the complex SCC mechanisms in aluminum PM alloys have led to the use of extremely innovative test techniques. These techniques—the slow strain rate, loading mode, breaking load, bolt-loaded double cantilever beam, and shadow-optical-caustic tests—are described. Examples are presented comparing the susceptibilities of PM alloys to the various types of corrosion with the susceptibilities of conventional ingot alloys.
Development of Dispersion-Strengthened aluminum Alloys
Authors: Langenbeck SL , Griffith WM , Hildeman GJ , Simon JW
Published: December 2008

Dispersion-strengthened powder metallurgy aluminum alloys are being developed for structural applications up to 616 K (650°F). This research is being conducted under Air Force Wright Aeronautical Laboratories/Materials Laboratory Contract No. F33615-81-C-5096. The Lockheed-California Co. is the prime contractor with the Aluminum Company of America (Alcoa) and Pratt and Whitney Aircraft participating as subcontractors. The current alloy development has been directed towards the goal of producing high-strength/high-stiffness alloys with properties competitive to those of Ti-6Al-4V on a density-compensated basis. Alcoa has been developing the Al-Fe-Ce alloy system and Pratt and Whitney the Al-Fe-Mo alloy system. The second iteration of alloy development is presented. Mechanical property behavior of each rectangular extruded alloy was evaluated. The testing included room-temperature and elevated-temperature tension, fracture toughness, creep, and elevated-temperature stability tests. The Al-Fe-Ce alloys met or exceeded most of the program goals, while the Al-Fe-Mo alloys nearly achieved all of the goals. Achievement of the target properties provides a 15% weight savings for airframe structures and up to 35% weight savings for engine components.
Engineering Property Comparisons of PM and IM Aluminum Alloy Forgings
Authors: Wanhill RJH , Schra L
Published: December 2008

Engineering properties of the aluminum powder metallurgy (PM) alloy 7091-T7E69 and the ingot metallurgy (IM) alloys 7075-T73, 7175-T736, 7010-T736, and 7050-T736 were compared. The properties considered were strength, fracture toughness, fatigue strength, fatigue crack propagation resistance under constant amplitude and spectrum loading, stress-corrosion crack initiation and propagation resistance, and exfoliation corrosion. The PM alloy had a substantially better combination of strength and resistance to stress corrosion and exfoliation and also greater notched fatigue strength at low mean stress levels and long lives. However, its fracture toughness was lower than (in the longitudinal-long transverse orientation) or similar to (in the long transverse-longitudinal orientation) that of the IM alloys, and its resistance to fatigue crack propagation under spectrum loading was greatly inferior. There were only minor differences in properties between the IM alloys.
Aquatic Monitoring: A Rationale for Obtaining and Interpreting Aquatic Ecosystem Chemical Exposure Data
Authors: Adams WJ , Hoogheem TJ , Michael PR
Published: December 2008

Aquatic hazard evaluation of chemicals requires sound data on both exposure and toxicity so that judgment can be made on the adequacy of the margin of environmental safety. Experience obtained through three years of national aquatic monitoring indicates that chemical monitoring programs need to include the following basic components if the data are to be credible, useful, and consistent with the state-of-the-art results: (1) a rationale for site selection; (2) a logical set of criteria for selection of sample types—that is, water, sediment or biota—based upon the physical-chemical and toxicological properties of the chemical of interest; (3) an appropriate cost-effective statistical design; (4) a team with a demonstrated capability for obtaining noncontaminated samples; (5) a top-notch analytical laboratory with experienced personnel, appropriate instrumentation, and fully validated and tested methods; (6) exacting quality-assurance and quality-control measures in all aspects of the program, including sample collection, sample storage, and analyte determination; (7) an analytical limit of detection for environmental samples low enough to provide meaningful comparisons of biological effects and environmental exposure data; and (8) the capability to assess the monitoring data consistent with state-of-the-art aquatic hazard assessment techniques.

Using the above-mentioned components of an aquatic monitoring program, cumylphenyl diphenyl phosphate (CPDPP), a component of an industrial hydraulic fluid, was monitored in 1982 at 24 sites located across the continental United States. Assessment of the hazard of CPDPP for sites where detectable levels were observed was performed by calculating the margin of safety between environmental water concentration and acute and chronic toxicological effects for aquatic organisms inhabiting the water column and sediments. A new approach for assessing chemical concentrations on sediment is proposed. The technique consists of calculating sediment interstitial water concentration of CPDPP and comparing these values with toxicological effect concentrations observed in the laboratory for sediment-dwelling organisms.

Concentrations of CPDPP in the environment ranged from < 0.1 to 0.2 μg/L in surface water and from < 100 to 200 μg/kg in sediment. Positive identification of CPDPP occurred in only 12 out of 85 surface water samples and 3 out of 53 sediment samples. CPDPP safety margins were determined to be typically a factor of 10 or greater for the most sensitive water column organism (lake trout) and 390 or greater for a typical sediment dwelling organism. These margins of safety provide evidence that CPDPP at its current use level has a low potential to affect aquatic organisms.
Rationale and Sampling Designs for Freshwater Mussels Unionidae in Streams, Large Rivers, Impoundments, and Lakes
Authors: Isom BG , Gooch C
Published: December 2008

Historically, the rationale for sampling freshwater mussels was almost entirely for purposes of taxonomy, natural history surveys, and conservation and propagation efforts following a decline of the pearl button industry in the early 1900s.

The concept of quantitative sampling of freshwater mussels is almost unknown in historical literature. Except for some proprietary or unpublished quantitative studies, the first study designed primarily to quantitatively sample freshwater mussels was by Scruggs [1] followed by Isom [2], Bates [3], Isom [4], and Dennis and Bates [5]. An earlier concept paper on “Quantitative sampling of mollusks and crustaceans” can be found in Wurtz [6].

This paper describes quantitative sampling methods for freshwater mussels within the context of varied study objectives, for example water pollution surveys. An example of a quantitative site-specific mussel study on the Cumberland River, Tennessee, is included. Difficulties with this study's design and application are discussed in some detail, along with site-specific studies on Kentucky Reservoir, Tennessee River, and Clinch River, Tennessee.
A Conceptual Framework to Guide Aquatic Monitoring Program Design for Thermal Electric Power Plants
Authors: Horner RR , Richey JS , Thomas GL
Published: December 2008

Thermal electric generating stations have a potential to alter the biotic and abiotic conditions in adjacent water bodies. Federal regulations require electrical utilities to monitor for such changes as insurance against deterioration of aquatic ecosystems. The cost of many monitoring efforts could be reduced by more precise applications of the scientific method (hypothesis testing), improved statistical design, and a focus on measures of cost-effectiveness. A multidisciplinary team of scientists and engineers from the University of Washington has developed such a conceptual framework to guide the design of power plant aquatic monitoring programs. This framework is organized into four hierarchical levels to accommodate the quality of information in a user's possession. Algorithms within the hierarchy help the monitoring program designer identify and prioritize mechanisms likely to cause ecological change, ecosystem components that might demonstrate a response, hypotheses of impact, and an appropriate sampling design for hypothesis testing. The entire framework has been programmed for interactive computer application.
Sampling and Interpretation of Algal Patterns for Water Quality Assessments
Authors: Jan Stevenson R , Lowe RL
Published: December 2008

Algal studies are valuable in water quality assessment because of their importance in aquatic ecosystems and sensitivity to changes in habitat conditions. Recent advances in algal ecology and sample analysis enable the designing of research that more directly reveals patterns of algal community structure and function that are pertinent to different kinds of environmental perturbations. In addition, advances in quantitative algal ecology enable more accurate interpretation of the importance of environmental perturbations on algal community structure and function. This paper incorporates recent advances in algal ecology into suggestions on how to design algal research for water quality assessment and methods for sample analysis, presents statistical techniques which can be useful for analyzing results, and reviews interpretations of the results.
Leaf Processing in a Reservoir: An Experimental Approach
Authors: Hendricks AC
Published: December 2008

The classical laboratory design of an experiment involves the utilization of a proper control and establishing various test treatments while holding conditions as close to those of the control as possible. In field work an experimental design such as that used in the laboratory is impossible to generate; however, field experimental work can be performed by controlling one parameter at a time and allowing this to serve as a treatment. The control in this case attempts to emulate the ecological system as close as possible. An experimental approach was utilized to determine how leaves were processed in a reservoir. Maple (Acer Spp.) leaf packets were placed in the reservoir utilizing the following experimental design: (1) Packets were placed in plastic trays and left open. These served as the controls. (2) Packets were placed in enclosures so that fish and other larger animals might not have access to the leaves. (3) Packets were placed in enclosures and a bluegill sunfish (Lepomis macrochirus) was added to each enclosure. Results from the experiments showed no significant differences between the leaf processing in the enclosure with and without fish. However, there were significant differences in leaf processing between open and enclosed leaf packets. At one time it took less than a month for this difference to occur; at another time it took from two to three months.
Fabrication and Testing of Polyester Arterial Grafts
Authors: Hoffman HL
Published: December 2008

The experience of researchers has shown that many material properties, including chemical and mechanical factors as well as biological response, influence the selection of synthetic fibers for use in vascular graft production. Based on accepted safety and efficacy criteria, commercial polyester fibers have become well-established as construction materials for vascular grafts. The production procedures for polyester vascular grafts show basic resemblance to those used for manufacturing knitted and woven fabrics, with every step of the process having a potentially significant effect on the properties of the finished product. Important production steps and their effects on the properties of finished vascular grafts are reviewed in detail.
Procedures in the Retrieval and Evaluation of Vascular Grafts
Authors: Anderson JM
Published: December 2008

The methods for vascular graft preservation and evaluation techniques are summarized. No single preservation technique permits the complete spectrum of evaluation procedures to be used in characterizing retrieved vascular grafts. The positive and negative aspects of the different methods for vascular graft preservation are given.
Species Selection for Vascular Graft Evaluation
Authors: Didisheim P
Published: December 2008

Similarities and differences between human and several other mammalian species are reviewed with respect to hematologic parameters and the histologic response to implanted prosthetic vascular grafts. No species is clearly more similar to man than any other with regard to all aspects reviewed. For this reason it is suggested that species selection for vascular graft evaluation be based on practical considerations such as ease of handling and of surgical and anesthetic technique and the cost of purchase and maintenance of the animal. Based on these criteria, the dog appears to be the species of choice.

In vitro tests of platelet deposition and fibrinogen adsorption to expanded polytetrafluoroethylene (EPTFE) and woven Dacron® during simulated arterial flow was predictive of results reported following implantation of these materials as small diameter vascular grafts in animals and man. These methods may therefore be useful as in vitro screens of new prosthetic vascular materials.

With five materials tested, ranking of the intensity of the blood-material response in vitro was the same or similar among three species—human, canine, and porcine—despite the major pathophysiological differences among these species. These observations suggest that, for in vitro hemocompatibility testing, species selection based on apparent similarity to man is neither necessary nor likely to yield more clinically relevant data. There is no compelling evidence at present that data derived from vascular implant studies with the baboon are more relevant to human use than data obtained from studies with the dog.

Following vascular graft implantation, thromboembolism was seen more often in the dog while calcification was observed with greater frequency in the pig. Because of such species specificities in the nature of the response, it may be advisable to evaluate grafts in more than one species, specifically the dog and pig. It may also be useful to study the effect on vascular graft patency and other responses, of diseases in the host that simulate those that commonly exist in human candidates for graft implantation.
Vascular Prostheses: The Need for Standards—Historical and Surgical Perspectives
Authors: Wesolow A
Published: December 2008

The historical and surgical perspectives with respect to standards for vascular prostheses are summarized under three headings: (1) device legislation tracing the activities of the Food and Drug Administration (FDA), ASTM, and International Organization for Standardization (ISO) from 1964 culminating in the present Medical Device Legislation as signed in 1976; (2) scientific community involvement via the media of ASTM, American Society for Artificial Internal Organs (ASAIO), Association for the Advancement of Medical Instrumentation (AAMI), and ISO; and (3) research observations focusing upon the causes of failure of vascular prostheses. Failures fall into six classes containing multiple specific causes. The conclusion is that the time is ripe for the establishment of performance standards and specifications for vascular prostheses from the aspects of political and governmental climate, scientific community awareness, willingness and expertise, and technical knowledge for the development of methods of testing and evaluation to minimize the risk of failure of vascular prosthetic devices and of the patients bearing these same implants.
Vascular Grafts: Applicability
Authors: Mortensen JD
Published: December 2008

This article focuses the attention of vascular graft developers and users on the subject of vascular graft applicability. It raises several issues that must be addressed by anyone developing standards of performance for vascular grafts.
Report on Laboratory Tests for Consolidation Behavior
Authors: Drnevich VP
Published: December 2008

Eight papers are covered in this report. The authors and titles are listed in Table 1. All papers focus on laboratory testing or theory related directly to laboratory texting. Some include field experimental results and field applications. A directory to topics covered in the papers also is given in Table 1.
Report on Theory and Laboratory Testing Requirements: Comparisons
Authors: Silvestri V
Published: December 2008

The consolidation test provides basic information on the compressibility characteristics of soft soils needed to estimate the magnitude and rate of settlements resulting from one-dimensional straining. For the past 40 years, extensive use has been made of the conventional consolidation test in which samples are subjected to increasingly large increments of load, and the resulting time/deformation curves are used to obtain the various compressibility parameters. About 20 years ago, several investigators [1–3] found that the experimental results obtained were not unique, rather they were functions of the loading sequence used and the time allowed for each load increment. In other words, as in the case of other geotechnical tests, it was realized that the conventional test was by no means a “standard” test.