bluuebunny/crossref_metadata_2025 huggingface dataset:
Uptake, Clearance, and Bioconcentration of 14C-Sec-Butyl-4-Chlorodiphenyl Oxide in Rainbow Trout
Authors: Blanchard FA , Takahashi IT , Alexander HC , Bartlett EA
Published: March 2009

Steady state bioconcentration factors for sec-butyl-4-chlorodiphenyl oxide in rainbow trout muscle were calculated using a simple two-compartment model from radioassay data of concentrations of 14C in fish and water during an uptake and clearance (depuration) experiment. There was a relatively rapid removal with one half of the material cleared in 30 to 40 h.

Average Exposure Concentration, ppbUptake Rate, k1, ppb/ppb/hClearance Rate, k2, h−1Bioconcentration FactorClearance Half Time, hTime to 90% of Steady State, h3.626.1 ± 1.00.021 ± 0.004292 ± 7533 ± 7111 ± 220.345.3 ± 0.50.016 ± 0.002336 ± 5244 ± 5146 ± 18

A partition coefficient (octanol/water) for sec-butyl-4-chlorodiphenyl oxide of 16000 ± 4900 was measured. The regression equation relating the partition coefficient to bioconcentration factor in trout muscle predicts a bioconcentration factor of 100 to 500, in agreement with the calculated values of 292 and 336.

The two-compartment model used for analysis of the data does not distinguish between 14C activity in the form of sec-butyl-4-chlorodiphenyl oxide from that in the form of metabolic products. The reported bioconcentration factor is an overall number encompassing both the compound and its metabolites. Thin-layer chromatography analysis of tissue extracts showed polar metabolites were formed during the experiment. The calculated bioconcentration factors are somewhat larger than they would be if put on a pure compound basis. However, we believe that the reported bioconcentration factors are valid, since there is good agreement between the 14C-derived muscle bioconcentration factors and the bioconcentration factor derived from the partition coefficient equation.
A Model System to Study the Desorption and Biological Availability of PCB in Hydrosoils
Authors: Halter MT , Johnson HE
Published: March 2009

Model aquatic systems incorporating hydrosoil, water, and fish components were used to measure the dynamics of Aroclor 1254 [polychlorinated biphenyl (PCB)] under both flowing and static water conditions.

PCB desorption from hydrosoils was consistent with adsorption-desorption theory. Under static conditions, hydrosoil PCB concentrations from 10 to 500 µg/g produced equilibrium levels of 0.13 to 7.60 µg/litre PCB in water. In continuous flow tests, equilibrium PCB levels in water ranged from 0.11 to 0.54 µg/litre for hydrosoil concentrations of 100 to 500 µg/g PCB. Equilibrium PCB concentrations in water could be predicted under both static and continuous flow conditions with the distribution coefficient equation. Desorption favored the lower-chlorinated, more water-soluble components of Aroclor 1254.

Fathead minnows allowed direct contact with PCB-contaminated hydrosoils accumulated PCB residues at six times the rates of those screened from direct exposure to sediments. Fish selectively bioaccumulated the higher chlorinated components of Aroclor 1254.
Evaluation of the Significance of Waterway Sediment-Associated Contaminants on Water Quality at the Dredged Material Disposal Site
Authors: Lee GF , Mariani GM
Published: March 2009

During the past few years, considerable interest has developed concerning the significance of chemical contaminants associated with dredged sediments. Research has been done on the factors influencing the release of contaminants from waterway sediments and the toxicity of these sediments to various forms of aquatic life. This study has shown that the only two compounds which are released in potentially significant amounts to affect water quality at the disposal site are manganese and ammonia. The other compounds studied including heavy metals, chlorinated hydrocarbon pesticides, polychlorinated biphenyls (PCBs), and aquatic plant nutrients are either not released, released in insignificant amounts, or taken up as a result of mixing the sediments with the overlying waters under conditions which simulate typical dredging and dredged material disposal.

Bioassays conducted of the elutriates of the sediments with the sediments present show that, in general, large concentrations of contaminants can be present in dredged sediments which would have little or no effect on water quality at an in-water disposal site. These results show that the bulk chemical criteria that have been used frequently by pollution control agencies to establish the method of dredged material disposal are not a technically valid approach for determining the significance of contaminants associated with natural water particulate matter. In fact, in some instances, the methods of dredged material disposal which have been adopted because of excessive concentrations of contaminants based on bulk chemical criteria may have been more detrimental to environmental quality than the previously used methods of dredged material disposal.
Application of an Evaporative Loss Model to Estimate the Persistence of Contaminants in Lentic Environments
Authors: Spacie A , Hamelink JL , Waybrant RC
Published: March 2009

A simple, two-layer model for predicting evaporative losses of nonionic synthetic chemicals from water is presented. Losses from well-stirred small vessels are predicted accurately. Losses from thermally stratified bodies of water were poorly predicted because turbulent mixing processes at the interfaces were retarded.
The Effect of Subacute Parathion Exposure on the Locomotor Behavior of the Bluegill Sunfish and Largemouth Bass
Authors: Rand GM
Published: March 2009

The effects were studied of a 24-h exposure to a subacute concentration of parathion on the locomotor orientation of the bluegill sunfish (Lepomis macrochirus) and largemouth bass (Micropterus salmoides) in response to: a food odor in water flowing at 200 ml/min (odor/Flow I) and 400 ml/min (odor/Flow II) and water without odor flowing at these rates (Flow I and Flow II, respectively). In sunfish, prior to parathion exposure, odor/Flow II was more attractive than any other condition. Following exposure, the response to Flow II and to odor/Flow II was avoidance, that to odor/Flow I remained attractive, thus causing a parathion by flow interaction. Two weeks after exposure, the relative response to the treatments was similar to that of un-exposed fish. In bass, prior to parathion exposure, the odor/Flow II was also more attractive than any other condition but the fish were unable to discriminate between odor/Flow I and Flow I alone. Following exposure, the fish were unable to discriminate between odor/Flow II and Flow I (the control), whereas particularly odor/Flow I and, to a lesser extent. Flow II were avoided. Thus, there was a significant interaction between odor and flow. After a two-week interval, all treatments were attractive, but the most significant relative attraction was that to odor/Flow I. The general activity in all experimental conditions was also depressed following parathion exposure.
Evaluation of the Efficacy of Sulfite Pulp Mill Pollution Abatement Using Oyster Larvae
Authors: Cardwell RD , Woelke CE , Carr MI , Sanborn EW
Published: March 2009

Improvement in marine water quality due to treatment of sulfite pulp mill effluents (SPME) was assessed in two regions of Puget Sound, Washington, from 1972 to 1975. The acute toxicity of these waters to larvae of Pacific oysters was the primary criterion for assessing water quality. Incineration of sulfite waste liquor (SWL) dramatically reduced the extent and scope of receiving water toxicity to oyster larvae. For example, more than 30 km2 of receiving water near Everett, Washington, was highly toxic to oyster larvae in 1972 before incineration of SWL, but only 1 km2 was similarly toxic in 1975 after institution of this process. The results suggested that secondary treatment may not be required to eliminate receiving water toxicity from SPME to Pacific oyster larvae. However, a definitive judgement cannot be made until the effects of SPME on the life cycles of sensitive, indigenous species have been determined.
Impact Response of Graphite-Epoxy Flat Laminates Using Projectiles that Simulate Aircraft Engine Encounters
Authors: Preston JL , Cook TS
Published: March 2009

An investigation of the response of a graphite-epoxy material to foreign object impact was made by impacting spherical projectiles of gelatin, ice, and steel normally on Modmor II/PR-286 flat panels. The observed damage was classified as transverse (stress wave delamination and cracking), penetrative, or structural (gross failure): the minimum, or threshold, velocity to cause each class of damage was established as a function of projectile characteristics. Steel projectiles had the lowest transverse damage threshold (30 m/s), followed by gelatin (170 m/s) and ice (215 m/s). Making use of the threshold velocities and assuming that the normal component of velocity produces the damage in non-normal impacts, a set of impact angles and velocities was established for each projectile material which would result in damage to composite fan blades. Analysis of the operating parameters of a typical turbine fan blade shows that small steel projectiles are most likely to cause delamination and penetration damage to unprotected graphite-epoxy composite fan blades.
Residual Strength Characterization of Laminated Composites Subjected to Impact Loading
Authors: Husman GE , Whitney JM , Halpin JC
Published: March 2009

An analogy between damage inflicted by a single-point hard-particle impact and damage inflicted by inserting a flaw of known dimensions in a static tensile coupon is discussed. The results suggest that residual strength can be predicted as a function of kinetic energy of impact by executing two experiments, a static tension test on an unflawed specimen and a static tension test on a coupon previously subjected to a single-point impact. The model appears to be accurate for impact velocities which are less than the penetration velocity. For velocities above complete penetration, the residual strength is identical to the static strength of a coupon with a hole having the same diameter as the impacting particle. Comparison of various materials indicates that the impact strength of composite materials is strongly influenced by the strain energy to failure of the reinforcement.
Behavior of Laminated Composite Plates Subjected to Impact
Authors: Mortimer RW , Chou PC , Carleone J
Published: March 2009

Preliminary results from an analytical-experimental study into the response of laminated composite plates subjected to edge impacts are presented. An experimental impact facility, developed to monitor simultaneity of impact, bending due to impact, wave velocity, impact velocity, and strain histories, is shown to be satisfactory. The experimentally and analytically predicted wave velocities and strain histories are shown to be in good agreement.
Studies on the Impact Structural Damage of Composite Blades
Authors: Sun CT , Sierakowski RL
Published: March 2009

The dynamic response of jet engine fan blades subjected to foreign object impact loadings has been investigated. Two analytical methods based upon a discrete mass distribution have been used for model purposes. Numerical results for blade natural frequencies, tip displacements, and bending moments have been obtained for boron-aluminum, graphite-epoxy, titanium, and stainless steel blades. Numerical data have been discussed for the various materials considered.
Fatigue Crack Propagation in 0°/90° E-Glass/Epoxy Composites
Authors: Mandell JF , Meier U
Published: March 2009

The mode of fatigue crack growth is described for a 0/90° E-glass/epoxy laminate under cyclic tension-tension loading. Crack growth appears to occur in a stepwise fashion with the crack remaining stationary for many cycles before each step of growth, whereupon a ligament of longitudinal ply at the crack tip is broken. A simple theory is described which assumes that the ligament at the crack tip is fatigued according to the S-N curve of the unnotched material. Using an assumed stress field and cumulative damage law, the number of cycles for initial growth from a notch and the rate of crack growth thereafter are predicted, and good agreement is demonstrated with experimental data.
Reducing the Effect of Water on the Fatigue Properties of S-Glass Epoxy Composites
Authors: Gauchel JV , Steg I , Cowling JE
Published: March 2009

An epoxy resin composed of N,N-diglycidyl tribromoaniline (DGTBA) crosslinked with metaphenyline diamine (MPDA) has proven to be far superior to standard epoxy systems in reducing the effect of long-term water immersion on the fatigue life of epoxy-S glass composites. The results of experiments indicate up to a 20 to 30 percent improvement in fatigue life retention for the DGTBA/MPDA-S glass system over conventional bisphenol-A based epoxy-S glass systems. Copolymers of DGTBA and diglycidyl ether of bisphenol-A (DGEBA) containing over 50 percent DGTBA have essentially the same fatigue properties as those with pure DGTBA matrices. Copolymer results are explained in terms of a simple relationship between matrix water absorption and composite fatigue life.
Fatigue Failure Mechanisms in a Unidirectionally Reinforced Composite Material
Authors: Dharan CKH
Published: March 2009

The fatigue failure mechanisms in a unidirectional glass fiber-epoxy material were studied. Specimens were made by filament winding the glass fiber roving and vacuum impregnating with a low viscosity room temperature curing resin. The fatigue response could be divided into three distinct life ranges. In the first region (< 200 reversals), there was a small dependence of the fatigue life on cycling. Behavior here was believed to be dependent upon the fiber mean strength and strength distribution. In the second region (200 to 106 reversals), the logarithm of the applied stress decreased almost linearly with the logarithm of the number of cycles. Fatigue failure in this region occurred by the growth of matrix microcracks, which lead to preferential fiber failure, and was followed by interfacial shear failure. In the third region (> 106 reversals), the applied stress was below the microcrack initiation stress and none of the few specimens tested failed. Unlike behavior in the first two regions, where defects were formed in the first cycle and subsequently propagated, most of the cycles in this region were used in crack nucleation.
High Strain Fatigue in a Ni(Cr)-TaC Fibrous Eutectic
Authors: Henry MF , Stoloff NS
Published: March 2009

The eutectic Ni(Cr)-TaC has been directionally solidified to yield a fibrous composite. The material was studied in strain-limited low-cycle fatigue at room temperature and 1000°C. The eutectic with brittle fibers and a ductile matrix was found to obey the Coffin-Manson law at both temperatures. The hysteresis behavior is explained and related to tensile deformation. Surface studies of highly polished cyclic-bend specimens revealed the fatigue crack nucleation and early growth characteristics. The data are compared to conventional materials, and the fatigue resistance is found to be essentially equivalent.
Fatigue Behavior of an Ag3Mg-AgMg Eutectic Composite
Authors: Kim YG , Maurer GE , Stoloff NS
Published: March 2009

The eutectic alloy Ag-32 atomic percent Mg has been directionally solidified at rates ranging from 0.8 to 27.7 cm/h to produce an aligned lamellar structure. The alloy, consisting of 40 volume percent AgMg and 60 volume percent of a solid solution of approximate composition Ag-27 atomic percent Mg, has been cycled in tension-tension loading at room temperature. Fatigue life increased sharply with both higher growth speeds and with the introduction of long range order into the Ag-27 atomic percent Mg phase by post-solidification heat treatment. Fractographic examination revealed a marked change in crack path and striation morphology as order was produced. It is concluded that improvements in fatigue life with growth speed were a consequence of decreased interlamellar spacing and the resulting rise in tensile strength of the alloy.
Flexural-Fatigue Evaluation of Aluminum-Alloy and Kraft-Paper Honeycomb-Sandwich Beams
Authors: Person NL , Bitzer TN
Published: March 2009

Flexural static and fatigue tests were conducted on 314-in.-thick honeycomb-sandwich beams having either aluminum-alloy or kraft-paper cores and identical aluminum facings. When the beams have relatively small ratios of length to thickness (short spans, thick cores), the static and fatigue strengths are determined primarily by the shear properties of the core material. In this case, the aluminum honeycomb sandwich was stronger than the kraft-paper honeycomb sandwich. With longer beams, the strengths are dependent mainly on the properties of the facing materials. Since the facings were the same for the two types of sandwiches, the respective static and fatigue properties were approximately equal.
Realism in Fatigue Testing: The Effect of Flight-by-Flight Thermal and Random Load Histories on Composite Bonded Joints
Authors: Wilkins DJ , Wolff RV , Shinozuka M , Cox EF
Published: March 2009

Current military specifications call for increased realism in fatigue testing. Criteria are discussed which recognize those portions of a spectrum that should be random and those that should be deterministic.

This paper documents a research program which included spectrum development, test facility setup, and a limited test series. The spectrum was a flight-by-flight random load history including realistic mission temperature exposures. The test facility utilized a small digital computer for closed-loop control of load and temperature.

Results of tests on three sets of five boron-epoxy-to-titanium bonded joints are discussed, and the effects of temperature exposure and time acceleration are investigated.
Structure-Sensitive Properties of Materials Disclosed by a Combination of X-Ray Topography X-Ray Diffraction Analysis, and Electron Microscopy Methods
Authors: Weissman S
Published: March 2009

To establish a significant correlation between lattice defects and structure-sensitive properties it is frequently desirable to combine various methods of structural analysis which provide supplementary information and have a synergistic effect on the course of study. Such combination methods have been developed in this laboratory. They comprise: (a) selected area X-ray topography, (b) X-ray line profile analysis, (c) anomalous X-ray transmission topography, (d) X-ray double-crystal diffractometry, (e) analysis of plastic and elastic strain distribution by disturbance of X-ray pendellösung fringes (PF), (f) transmission electron microscopy (TEM) of dislocation structure in selected areas of the specimen, and (g) scanning electron microscopy (SEM) of the specimen. Examples of the application of these combination methods are presented that include the tensile and compressive deformation of beryllium crystals, the deformation and fracture of germanium and silicon crystals, and the elucidation of the distribution of microplastic and elastic strains in crack propagation.
The Use of Hot-Stage Microscopy in the Study of Phase Transformations
Authors: Bramfitt BL , Benscoter AO , Kilpatrick JR , Marder AR
Published: March 2009

This paper summarizes the experimental techniques used in hot-stage light microscopy and the application of these techniques to ferrous transformations. In the hot-stage microscopy examples, particular emphasis is given on results of the martensite, pearlite, and ferrite transformations studied in this laboratory. Reference is also made to the results of many other investigators who have used the hot-stage microscope as a tool to study kinetics and morphology of ferrous transformations during both heating and cooling conditions.
High Voltage Electron Metallography — Achievements and Prospects
Authors: Szirmae A , Fisher RM
Published: March 2009

Electron metallography in its various forms has now reached the point where it can be used to characterize nearly all of the microstructural features which occur in materials including grain and subgrain size and shape; dislocation density and configuration; precipitate size, shape, and coherency strain; antiphase domains in ordering alloys; and magnetic structure in ferromagnetic alloys, as well as chemical composition changes on a very fine scale. Transmission electron microscopy (TEM) provides the most complete information about internal structures and is especially effective when used in conjunction with scanning microscopy of the same specimen. Development of high voltage instruments capable of operating at 1 mV or more has broadened the scope of application of electron metallography particularly because of the ability to penetrate significantly thicker specimens than with conventional 100 kV instruments. Other important characteristics of high voltage electron metallography (HVEM) such as greater accuracy in selected area diffraction, reduced chromatic aberration of thick specimens, and a unique critical voltage effect are discussed. Typical applications such as studies of recrystallization, deformation, recovery, precipitation, and ordering are described, as well as quantitative three-dimensional (stereo) analysis of dislocation distributions and electron radiation damage.
Microstructure Approach to Property Optimization in Wrought Superalloys
Authors: Muzyka DR , Maniar GN
Published: March 2009

The effects of structure control available from the precipitating phases in wrought superalloys were demonstrated in a recent review. It was shown that criteria for selection of superalloys should be reviewed periodically to establish that they reflect the state of the art. For example, expensive materials may have been specified where lower cost alloys could do a job equally well. This is especially true for superalloys in applications where properties up to about 1200°F are critical.

This paper reviews some results of the continuing study by superalloy metallurgists to reveal means of “retrograding” elevated temperature requirements to lower cost compositions that, combined with proper processing, will meet property requirements. It is shown that microstructure studies, combined with knowledge of phase relationships, prove to be an invaluable tool. Recent examples of improved hot-work behavior, heat-treat response, and property development are reviewed. Effects of thermomechanical processing are also discussed.
Specification and Implementation of Digital Control Algorithms in Chemistry Automation
Authors: Brubaker TA
Published: March 2009

In this paper an overview of control system design is presented to provide the chemist with some background on the topic. This background is necessary when writing specifications for a chemistry control system. Then procedures for characterizing and specifying error due to roundoff in digital control algorithms are discussed.
Documentation of Computerized Laboratory Systems: System Definition at the Management Level
Authors: Kunz FW , Eichen E , Schisa W
Published: March 2009

A set of guidelines for documenting computerized laboratory systems at the management level is presented. The guidelines detail the various documentation that may be required by companies which utilize financial factors to determine project feasibility. The guidelines are divided into five arbitrarily defined phases which are: (1) project initiation, (2) project development, (3) feasibility study, (4) preparation of the computer proposal, and (5) project approval. The project initiation phase includes establishing the need for computerization, determining laboratory structure and functions, conducting the laboratory evaluation, developing a proposed scope, and establishing the financial budget. The project development phase includes how to prepare a computerization objective and the assignment of personnel to the project. Included in the feasibility study are preparation of specifications, vendor contact, environmental considerations, determination of project costs, and initiating changes to the budget. Details are also presented for the preparation of the computer proposal and final approval factors.
Minicomputer Automation of Multi-Instrument Physical Chemistry Laboratory I: Management Science Methodology Used in System Definition, Specification, and Functional Design
Authors: Haeske DC , Provder T
Published: March 2009

This study describes the methodology used in the conceptualization, design, and implementation of a minicomputer system to automate data acquisition, reduction, and analysis from a multi-instrument facility at Glidden-Durkee's Dwight P. Joyce Research Center. The instruments to be automated consist of gas chromatographs, gel permeation chromatographs, a disk centrifuge photosedimentometer, a light-scattering photometer, an autoviscometer, a torsional pendulum, an ultraviolet visible spectrophotometer, and a liquid chromatograph. Both the existing and the desired methods for servicing these instruments are described and then used in showing how management science was used to specify the minicomputer system objectives in terms of system hardware/software characteristics. The steps taken in matching the system characteristics with vendors' stated capabilities are discussed and include designing and using a benchmark to simulate the system and evaluate vendor service and software/hardware functioning, detailing of the functional software requirements, and programming/testing of the system. Recommendations are provided, based on these experiences, for the attainment of system objectives within the constraints of in-house and vendor resources. Finally, an up-to-date evaluation is included of system performance with regard to the original specifications.
An Assessment of Automatic Sewer Flow Samplers
Authors: Shelley PE , Kirkpatrick GA
Published: March 2009

A brief review of the characteristics of storm and combined sewer flows is given, followed by a general discussion of the purposes for and requirements of a sampling program. The desirable characteristics of automatic sampling equipment are set forth, and problem areas are outlined. A discussion of various commercially available and custom designed automatic samplers is given with brief descriptions and characterizations of some units presented along with comments on their suitability for a storm or combined sewer application or both. A review of some field experience with automatic sampling equipment is given covering problems encountered and lessons learned. A technical assessment of the state of the art in automatic sampler technology is presented, and design guides for development of a new, improved automatic sampler for use in storm and combined sewers are given.
Industrial Experience with On-Line Instrumentation for Water Pollution Monitoring
Authors: Sugar JW , Brubaker JH
Published: March 2009

On-line instrumentation has performed a significant role in helping Union Carbide protect public waterways from excessive or abnormal pollutant discharges. Instrumentation has been successfully applied to the surveillance of cooling water and process water sewers and to the control of pollution abatement facilities. Although current instrumentation (total carbon analyzer, specific organics analyzer, automatic titrator, foam detectors, etc.) is being successfully applied to a variety of monitoring problems, there are still improvements that are required in the areas of sensitivity, specificity, and reliability. Support hardware (sampling pumps, transfer lines, sample conditioning hardware, and telementry) is also continuing to be improved. While present instrumentation is meeting the needs of today, instrumentation based on new measurement principles (liquid chromatography, biological activity monitors, turbidimeters, etc.) is being currently developed to meet the environmental measurement needs of tomorrow.
Fatigue Crack Growth with Negative Stress Ratio Following Single Overloads in 2024-T3 and 7075-T6 Aluminum Alloys
Authors: Stephens RI , Chen DK , Hom BW
Published: March 2009

Modified pre-cracked compact specimens of 2024-T3 and 7075-T6 aluminum alloys were subjected to four different overload patterns followed by subsequent constant-amplitude steady-state loading with R=Pℓmin/ℓmax equal to 0, -1/2, -1, and -2. The overload patterns were tension, compression-tension, tension-compression, and compression. Cyclic loading with negative stress ratio, R, drastically reduced crack-growth retardation. The higher the negative R ratio the greater the reduction in retardation. Overload ratios, OLR =Phmax/Pℓmax, ranging from 2.0 to 3.0 were used. For compression overloads, the OLR ranged from -2.0 to -4.0. High compression overloading was detrimental and dependent upon subsequent R ratio loading. Substantial fracture surface abrasion near the mid-thickness occurred for higher negative R ratios. Striations were not readily found in this region, however, they were quite evident near the edges, which indicated crack closure was greater near the mid-thickness. The 2024-T3 gave better crack growth life than 7075-T6 in some loading conditions, while the opposite was true for other loadings. The results indicate negative R ratio must be considered in retardation models and that retardation life cannot be modeled based solely on overload plastic zone sizes.
Effect of Single Overload/Underload Cycles on Fatigue Crack Propagation
Authors: Alzos WX , Skat AC , Hillberry BM
Published: March 2009

Tests, represented in a three-dimensional matrix, were performed to investigate the effects of a single overload/underload sequence on the fatigue crack-growth rate in 2024-T3 aluminum alloy. Three different stress intensity ratios were studied to investigate the delay phenomenon: (1) overload level to maximum cyclic level, Kol/Kmax; (2) underload level to overload level, Kul/Kol; and (3) minimum cyclic level to overload level, Kmin/Kol. These ratios ranged from 1.6 to 3.0, -1.0 to +0.3, and 0.11 to 0.3, respectively. All tests had the same overload stress intensity level. Sufficient data were recorded to accurately determine the crack-growth rate through the overload affected zone. The crack length versus number of cycles data for each test were represented by a spline function which was then analytically differentiated to obtain the growth rate. The number of delay cycles was found to be directly related to the minimum growth rate following the overload/underload sequence. The ratios Kol/Kmax and Kul/Kol were shown to be of particular significance to the delay while the ratio Kmin/Kol was shown to be of less significance. The results were correlated with an extended crack closure concept. From this the maximum value of the opening stress intensity level following the overload/underload sequence can be determined and used to predict the number of delay cycles.
Effects of Rest Time on Fatigue Crack Retardation and Observations of Crack Closure
Authors: Sharpe WN , Corbly DM , Grandt AF
Published: March 2009

Fatigue cracks grown in compact tension specimens of 2024-T851 aluminum at ΔK = 6.93 MN/m3/2 (R =0.1) were subjected to single-peak overloads of 17.31 MN/m3/2. After the overload, the specimens were held at zero load for periods of 3 min, 1 h, and 20 or more hours before recycling at ΔK = 6.93 MN/m3/2. Increasing the rest time had the effect of slightly reducing the crack retardation as measured on the specimen surface.

The load at which the fatigue crack faces fully separate was measured on the specimen surface by laser interferometric techniques and in the specimen interior by through-transmission ultrasonic methods. Crack opening loads measured on the specimen surface were found to increase with application of an overload and then decrease to the original value when the specimen was allowed to rest at zero load, while opening loads measured through the sample by the ultrasonic method did not vary significantly with peak loads or rest times. Varying specimen thickness between 0.64 and 2.54 cm had little effect on surface measured retardation or opening loads. The relationship between applied load and crack surface displacement as measured by ultrasonics varied significantly with specimen thickness.
Spike Overload and Humidity Effects on Fatigue Crack Delay in Al 7075-T651
Authors: Buck O , Frandsen JD , Marcus HL
Published: March 2009

This paper describes experiments on fatigue crack growth, Δa/ΔN, in part-through crack specimens of 7075-T651 aluminum alloy. The effects of dry and humid environment in combination with single-spike overloads on Δa/ΔN, the crack growth delay, ND, and the “effective” stress intensity range, ΔKeff, are discussed. Using an acoustic monitoring technique, it was observed that the crack closure not only reflects the influence of the environment, but also of the spike overload on the plastic deformation at the crack tip and therefore on Δa/ΔN. The relationship Δa/ΔN = A (ΔKeff)n describes both environmental and spike overload effects, uniquely. Delay is more pronounced in a dry environment and increases strongly with increasing overload ratio.
Mathematical Modeling of Crack Growth Interaction Effects
Authors: Bell PD , Wolfman A
Published: March 2009

A combined analytical and experimental program was performed to obtain additional insight into the growth of cracks subjected to simple variable-amplitude loading. The experimental results were used to examine methods of mathematically modeling crack propagation behavior to enhance predictive capability for arbitrary spectrum loading.

The mathematical modeling consisted, primarily, of using the crack closure concept to correlate predicted crack propagation behavior with observed behavior for various simple loading spectra. Two analytical schemes were developed, one of which calculated the crack opening load based on residual forces acting on the crack surface, and another where empirical relationships between loading sequences and crack opening behavior were utilized. Difficulties with the Residual Force Model in correctly representing some of the experimentally observed crack opening and closing effects led to emphasizing the development of the more empirical Crack Closure Model.

The test program encompassed constant-amplitude tension loads, single and multiple tensile overloads, compression spikes, and simplified variable-amplitude load sequences applied to 2219-T851 aluminum and Ti-6Al-4V annealed titanium alloy specimens. Detailed crack-growth and crack closure measurements were obtained. These measurements were used to quantify crack closure behavior as a function of stress ratio, including negative values, and various loading sequences.
Structural Reliability Prediction Method Considering Crack Growth and Residual Strength
Authors: Varanasi SR , Whittaker IC
Published: March 2009

An analysis method to estimate structural reliability based on crack growth and residual strength of aircraft structures is presented. The method is based on linear elastic fracture mechanics theory and allows for the variability of crack initiation and growth found in the experimental data of various metals. At a reference stress intensity factor, the central tendency and the variance values of material crack-growth parameters are determined. Combinations of these parameters are selected by Monte Carlo simulation techniques, and are used to describe the characteristically stochastic behavior of crack growth in a material. This description of material crack-growth behavior is then applied to the typical case of the built-up skin-stringer configuration of fail-safe type airplane structures to predict the number and size of cracks in a fleet at any time during its life. Thus, inspection routines may be established based on realistic fleet performance, to provide suitable levels of structural reliability for a fleet of airplanes during its operational lifetime.
Spectrum Fatigue Crack Growth in Lugs
Authors: Impellizzeri LF , Rich DL
Published: March 2009

Analytical and experimental investigations were conducted to determine the crack growth behavior in lug joints subjected to a randomized flight-by flight spectrum. Specific objectives were to evaluate capabilities for analyzing spectrum crack growth in lugs and to assess the effects on crack growth of KIc and cold working the material surrounding the lug holes. Stress intensity solutions were developed for cracks radiating from lug holes using Bueckner's weight function approach for various stress distributions surrounding the lug hole. The stress distributions were determined using an elastic/plastic finite element analysis. Included in these analyses were residual stress distributions following either large lug loads or mandrel hole enlargement. Spectrum crack growth calculations were made using the resulting stress intensity values and the Wheeler retardation crack growth model.

Lug specimens were fabricated from two heats of 6Al-4V mill annealed titanium representative of material having low and high fracture toughness levels. Basic mechanical properties including ultimate and yield strength, percent elongation, and reduction in area and fracture characteristics, including KIc and constant-amplitude crack growth rates, were determined for each heat of material. EDM cuts in the lug specimens were used as points of stress concentration where precracks were developed by low-level constant-amplitude fatigue loading. The lug holes of selected specimens were cold worked to determine the effect of compressive residual stresses on the crack growth rate. Plots of crack growth versus spectrum hours were obtained for each specimen by post-failure examination of the fracture surfaces using the scanning electron microscope.
Low-Cycle Fatigue and Cyclic Deformation Behavior of Type 16-8-2 Weld Metal at Elevated Temperature
Authors: Raske DT
Published: March 2009

The low-cycle fatigue behavior of Type 16-8-2 stainless steel weld metal deposited by the automatic submerged-arc process at 593 ° was investigated, and the results are compared with existing data for Type 316 stainless steel base metal. Tests were conducted under axial strain control and at a constant axial strain rate of 4 x 10−3 s−1 for continuous cyclic loadings as well as hold times at peak tensile strain. Uniform-gage specimens were machined longitudinally from the surface and root areas of a 25.4-mm-thick welded plate and tested in the as-welded condition. Results indicate that the low-cycle fatigue resistance of this weld metal is somewhat better than that of the base metal for continuous-cycling conditions and significantly better for tension hold-time tests. This is attributed to the fine duplex delta ferrite-austenite microstructure in the weld metal. The initial monotonic tensile properties and the cyclic stress-strain behavior of this material were also determined. Because the cyclic changes in mechanical properties are strain-history dependent, a unique cyclic stress-strain curve does not exist for this material.
Fatigue of Weldments—Tests, Design, and Service
Authors: Munse WH
Published: March 2009

For many years the fatigue behavior of welds and weldments has been studied in terms of the geometry of the members, the stresses to which they are subjected, and the materials of which they are fabricated. Numerous laboratory tests have been conducted and have served as a basis for the development of current fatigue design specifications. More recently, research on crack initiation and propagation, expanded data on loadings, and the development of new concepts of structural reliability have provided information that should help to make possible in the future greatly improved fatigue design specifications for welded structures. However, to achieve this goal, extensive further detailed research and study are necessary.
Estimating the Fatigue Crack Initiation Life of Welds
Authors: Lawrence FV , Burk JD , Mattos RJ , Higashida Y
Published: March 2009

The fatigue crack initiation life (cycles to obtain a 0.25-mm fatigue crack) was estimated for butt welds using strain-controlled fatigue concepts. Key developments which facilitated these estimates were the assumption of ??(Kf)max conditions (the largest value of ??Kf possible for a given weld shape), the use of computer simulation methods which modeled cyclic hardening and softening as well as mean stress relaxation effects, and the use of the fatigue properties of the actual weld zone in which the initial notch was located. The initiation life was found to be very sensitive to changes in ??Kf, but rather insensitive to strength level. The importance of residual stresses and mean stress varied with material as did the fraction of total life devoted to crack initiation. Mild steel (ASTM Specification for Structural Steel (A 36)) high strength, low alloy (ASTM Specification for High-Yield Strength, Quenched and Tempered Alloy Steel Plate, Suitable for Welding (A 514)) steel and aluminum alloy welds were considered.
Fatigue Crack Propagation in Aluminum-Zinc-Magnesium Alloy Fillet-Welded Joints
Authors: Maddox SJ , Webber D
Published: March 2009

The fatigue behavior of aluminum-zinc-magnesium (Al-Zn-Mg) alloy fillet-welded joints was analyzed in fracture mechanics terms. Basic crack propagation data were obtained with −2 ⩽ R ⩽ + 0.5 and correlated using formulas in the literature and, more successfully, in terms of ΔKeff, based on the results of crack closure experiments. The form of the da/dN versus ΔK relationship was influenced by the specimen geometry. A fracture mechanics analysis of the fatigue life of Al-Zn-Mg alloy fillet welds based on the da/dN versus ΔKeff relationship indicated that the weld toe was less severe from the fatigue viewpoint than the same region in a steel fillet weld. This was compatible with the fact that metallurgical examination of Al-Zn-Mg alloy fillet welds has failed to reveal toe defects similar in magnitude to those which act as fatigue crack initiators at the toes of steel fillet welds. The analysis showed that the fatigue life obtained from the Al-Zn-Mg alloy weld could be predicted on the basis that defects only one tenth the size of those observed in steel were present. Fatigue failure from the weld root in a cruciform joint was also analyzed and the optimum weld design, which gives an equal chance of failure from the root and toe, was determined. The analysis was supported by fatigue test results. Comparison with results obtained for steel added confirmation to the finding that if toe defects are present in Al-Zn-Mg alloy welds, they are smaller than those in steel.
A Study of Fatigue Striations in Weld Toe Cracks
Authors: Albrecht P
Published: March 2009

Striation spacing in weld toe cracks due to constant amplitude stress cycling was found to correlate with Bates' empirical equation. Adding closely spaced periodic overloads to the constant amplitude load history increases the striation spacing. Evidence of a decrease of striation spacing for widely spaced overloads, due to crack growth delay, could not be uncovered. About ten percent of the fatigue crack surface was striated, the remaining area being occupied by quasistriations and featureless regions. The lowest spacing detected in the direct surface scanning mode of electron microscopy was 3.3 x 10−8 m/cycle at a maximum magnification of X70 000. At that growth rate, about 80 percent of the crack propagation life had already expired. The microscopic striation spacings observed in this study, employing welded specimens fabricated from A588 structural steel, did not provide reliable indications of the average crack growth rate.
Elevated Temperature Fatigue Characterization of Transition Joint Weld Metal and Heat Affected Zone in Support of Breeder Steam Generator Development
Authors: Brinkman CR , Strizak JP , King JF
Published: March 2009

Piping systems in breeder reactor plants will require transition joint weldments between austenitic and ferritic materials. Specifically, annealed 2¼Cr-1Mo steel will be welded with ERNiCr-3 using the hot wire automatic gas tungsten-arc process. These weldments may see elevated temperature service for periods of up to 30 years, and, accordingly, prototypic weldments will require extensive mechanical property characterization. It was the objective of this effort to define the strain controlled low cycle fatigue behavior of as-deposited and stress-relieved ERNiCr-3 weld metal and to develop test methods for establishing the cyclic behavior of heat-affected-zone (HAZ) material. Low cycle fatigue and cyclic stress-strain response for ERNiCr-3 were established over the temperature range of 295 to 866 K. A number of low cycle fatigue test results are reported for hourglass-shaped specimens that demonstrated that the low cycle fatigue behavior of HAZ material adjacent to the fusion line could be characterized.
Effect of Residual Stress from Welding on the Fatigue Strength of Notched 347 Austenitic Stainless Steel
Authors: Albertin L , Eiffler EE
Published: March 2009

The fatigue strength of Type 347 stainless steel forging prepared according to ASTM Specification for Forged or Rolled Alloy-Steel Pipe Flanges, Forged Fittings, and Valves and Parts for High Temperature Service (A 182) was investigated in the notch-free and notched condition including a residual stress from an arc strike simulating a local weld. The notched specimens were 22.2 and 50.8 mm (0.875 and 2 in.) in diameter with a stress concentration factor, Kt, of 5.3. The notch-free specimens were standard R. R. Moore types. In the notch-free condition, the fatigue strength at 106 cycles was found to be 234.4 MPa (34 ksi). For the 22.2 and 50.8-mm (0.875 and 2-in.) diameter notched specimens, the fatigue strength was 124 MPa (18 ksi). In the case of 50.8-mm (2-in.) diameter notch specimens subjected to the heat of an arc strike, the endurance strength was 83 MPa (12 ksi). Thus, the endurance strength of heated specimens was reduced to two thirds that of unheated notched specimens. While the notch sensitivity index was 0.20 for the unheated specimens, it was 0.43 for the notched specimens containing a residual stress from the heat of an arc strike.
Fatigue Crack Growth in Low Alloy Steel Submerged Arc Weld Metals
Authors: Seeley RR , Katz L , Smith JR M
Published: March 2009

Fatigue crack growth experiments were conducted on low alloy steel submerged arc weld metals representative of those used in the fabrication of pressure vessels. Variations of wire composition, flux type, and postweld heat treatments were used to produce weld deposits of different microstructures and tensile and toughness properties. Fatigue crack growth experiments were conducted on 25.4-mm (1-in.) thick modified wedge opening loaded (WOL) specimens at room temperature and 288 °C (550°F). A compliance calibration curve was developed at room temperature and adjusted for use with elevated temperature compliance measurements. Results of these experiments indicate: (a) a slight effect of flux type on crack growth rates, (b) incomplete tempering or relief of residual welding stress, or both, has an appreciable effect on crack growth behavior, (c) comparable or lower crack growth rates at 288°C (550°F) compared to room temperature, (d) comparable or lower crack growth rates than those predicted in Section XI of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, and (e) variations in crack growth rates due to wire, flux, and postweld heat treatment were less pronounced than the variations in toughness and tensile properties.
Materials Recovery and Utilization
Authors: Estes EM
Published: March 2009

Some raw materials are in scarce supply, and the cost of others have risen sharply. This has started the United States into a transition period, from being a “disposable” society into an era of widespread recovery, reclamation, and reuse of materials. The working of free market forces, rather than arbitrarily imposed incentive/disincentive plans, should determine how long the transition takes. It could be speeded, however, if several present disincentives to materials recovery and reuse were removed.