bluuebunny/crossref_metadata_2025 huggingface dataset:
Product Form Variability in the Mechanical Behavior of Type 304 Stainless Steel at Room Temperature and 593°C (1100°F)
Authors: Swindeman RW , McAfee WJ , Sikka VK
Published: March 2009

Data are presented that describe the variability of 15 products of a reference heat of Type 304 stainless steel tested in the laboratory reannealed condition. Included in the data are chemistry, hardness, grain size, yield strength at room temperature, tensile curves at 593°C (1100°F), and creep-rupture curves to 1000 h at 593°C (1100°F). The standard deviation, representing the variation in the yield strength of the 15 products about the average, is near ±7.7 MPa at room temperature and ±6.3 MPa at 593°C (1100°F). The 1000-h rupture strength varies by 3.8 percent from the average and the stress to produce a minimum creep rate of 0.01 percent/h by 3.0 percent. Variation of strength in the primary creep range is also examined. The strength for a standard product, 25-mm plate, for which a large data base exists, is compared to the behavior of the other products, and it is observed that the 25-mm plate is fairly representative of the product average. Reasons for variability are examined, and it is thought that carbon content, nitrogen content, grain size, temperature control, and extensometer performance contribute to variability, and the extent depends on the type of test.
Variation in Mechanical Properties of Carbon Steel Plates and Wide Flange Shapes
Authors: McCune DC
Published: March 2009

This paper presents a method of analysis of the variation, relative to a standard or reference test, in the mechanical properties of carbon steel plates and shapes. Specific data from American Iron and Steel Institute Product Surveys are used to illustrate the procedure.
Use of the Short-Beam Shear Test for Quality Control of Graphite-Polyimide Laminates
Authors: Stinchcomb WW , Henneke EG , Price HL
Published: March 2009

The properties of laminated composite materials are strongly affected by many fabrication variables including temperature, time, and molding pressure. It is therefore necessary to have reliable quality control tests to check the properties of manufactured materials. The short-beam shear test is used widely by both manufacturers and researchers as a quality control test in the production of materials and development of new material systems. There are, however, several limitations to the standard test method. This paper presents the results of short-beam shear tests on graphite-polyimide laminates and reports on stiffness-strength relationships and nondestructive evaluation methods which aid in the interpretation of the test data.
Stress-Rupture Data Correlation with Generalized Regression Analysis: An Alternative to Parametric Methods
Authors: Rummler DR
Published: March 2009

The applicability of multiple regression analysis techniques to stress-rupture data correlation has been investigated. A generalized interacting variable (GIVAR) method of data correlation is proposed and evaluated. The GIVAR method is compared to 6 parametric methods of data correlation on 20 sets of data. In all cases, the GIVAR method provided the best data correlation. Application of prediction intervals is discussed. The applicability of correlating variables, such as tensile strength and elastic modulus, in addition to temperature and stress, is also discussed.
Effects of Some Variables in Specimen Selection and Procedures on the Results of Shear Tests
Authors: Kaufman JG , Davies RE
Published: March 2009

Studies of the effect of variations in test method and specimen orientation and location on the results of shear tests of aluminum alloys have shown that, in double-shear tests, (a) specimen size and lubrication—even that from the human skin—affect shear strength values by 3 to 4 percent, and (b) shear strength varies with location of shear plane through the thickness of aluminum alloy products. In blanking-shear tests, clearance between punch and dies up to 12 percent of the sheet thickness has no significant effect on test values.
Low-Temperature Rheology of Asphalt Cements—Rheological Background
Authors: Schweyer HE , Baxley RL , Burns AM
Published: March 2009

This paper, which is the first of a proposed series, reviews selected published information on the low-temperature flow properties of asphalt cements obtained by creep procedures and dynamic techniques over temperatures below 25°C (77°F) and down to −20°C (−4°F) and lower. A comprehensive summary is given with comments on the magnitudes of the reported viscoelastic parameters (elastic, stiffness, and viscosity) and relevance of the results to other test properties. It is suggested that simplifying approximations in available apparatus may be equally useful for evaluating the rheological creep behavior as obtained in constant stress test modes. These suggestions are implemented by experimental creep measurements on two paving and two roofing asphalts over temperature ranges from 150 down to −5°C (302 to 23°F). It is demonstrated that a reasonably correct fit of the data results for a Maxwell-Kelvin modified five-parameter model. It is recommended that the use of stiffness values as a function of time together with a power law relation for viscosity is a realistic approach for evaluating low-temperature properties of asphalt cements.
A Review of the Manufacture, Processing, and Use of Rail Steels in North America—A Report of AISI Technical Subcommittee on Rails and Accessories
Authors: Knupp GG , Chidley WH , Giove JL , Hartman HH , Morris GF , Taylor CW
Published: March 2009

The intent of this, the initial paper of this publication, is generally to set the stage for the more specific and detailed state-of-the-art papers to follow. The evolution of the North American tee rail in its struggle to “keep its head” under progressively heavier and faster-moving motive power and rolling stock is traced briefly. Technological developments in rail steel and rail production designed to improve quality and enhance resistance to service developments are reviewed. This includes adaptation of various steelmaking processes and grades of steel to the production of rails, and the handling of the steel through the forming, cooling, finishing, and in some cases further treatment of the rails.
Role of Alloying and Microstructure on the Strength and Toughness of Experimental Rail Steels
Authors: Bouse GK , Bernstein IM , Stone DH
Published: March 2009

Previous studies on eutectoid steel have demonstrated that strength and toughness are essentially independently varying parameters, with the former primarily controlled by the pearlite interlamellar spacing and the latter primarily controlled by the prior austenite grain size. The work has now been extended to study the effect of modest compositional variations on strength and toughness of 17 experimental rail alloys. Carbon, manganese, and silicon levels were varied over ranges to yield eutectoid or hypoeutectoid microstructures. Vanadium was added to some of these compositions, primarily as a grain refiner. These steels were heat treated to produce varying austenite grain sizes and a reasonably constant, fine pearlite spacing. Instrumented impact tests on precracked Charpy bars were performed to determine both the dynamic fracture toughness (KId), and the Charpy transition temperature. Tensile tests were used to monitor strength and ductility. Mechanical test data were correlated with observed microstructural variations, particularly the austenite grain size and pearlite spacing as well as fractographic studies of the variation of fracture facet size with austenite grain size. These studies led to a general description of the fracture process in such steels.
Fracture Mechanics Analysis of Rails with Shell-Initiated Transverse Cracks
Authors: Besuner PM
Published: March 2009

This report develops a fracture mechanics model for railhead transverse defects, specifically detail fractures from rail shell. The model is applied to calculate the failure strength of 71 rail segments which were rejected by inspection, removed, and tested by the Association of American Railroads in three-point bending. Utilizing the defect measurements for each rail, reasonable agreement is obtained between observed failure loads and failure loads calculated from the stress and fracture mechanics analyses. The fracture mechanics analysis is then extended to obtain preliminary estimates of the fatigue performance of defective rails in service. Specifically, the crack tip stress intensity factor is calculated for transverse defects under various types of in-service loading. The fracture mechanics solutions are utilized to calculate conservatively the remaining lifetime of the rail as a function of defect size and magnitude of wheel load. Using a simplified two-dimensional stress analysis and a three-dimensional fracture mechanics analysis, it is calculated that the shear stress reversal experienced as the wheel passes from one side to the other side of a transverse crack is the dominant stress component causing fatigue crack propagation. Recommendations are made for additional analytical developments and experimental programs required to refine the fatigue life predictions and incorporate them into rail risk assessment and reliability optimization programs.
Prediction of Rail Steel Strength Requirements—A Reliability Approach
Authors: Mair RI , Groenhout R
Published: March 2009

The determination of rail yield strength levels to support increased wheel loads is usually based on empirical adjustments to the Hertzian equations for contact stresses. A formulation is given, based on reliability theory, which enables a more refined analysis to be carried out and incorporates the material property variations, provided these can be approximated as Gaussian normal distributions.

Application has been made to unit train operations and estimates made of strength levels required for mean wheel loads in excess of 150 kN. The results indicate the importance of rail/wheel tangential forces on rail damage in curves and show that, while variations in wheel loads about the mean have an influence on performance, the effects are not highly significant. Spread of steel strength also has only a marginal influence within the bounds of accepted steelmaking control.

A comparison has been made between the predicted strength level and service trials which indicates that the suggested procedure provides conservative results.
Fatigue and Fracture Behavior of Carbon-Steel Rails
Authors: Barsom JM , Imhof EJ
Published: March 2009

The Ad Hoc Committee on Rail Research, which is composed of representatives from the American Railway Engineering Association (AREA), the Association of American Railroads (AAR), and the American Iron and Steel Institute (AISI) Committee on Railroad Materials, formulated a program to investigate the effects of metallurgical properties, mechanical properties, and applied stress conditions on the service fracture behavior of carbon-steel rails. This paper presents the fatigue and fracture behavior of five rails having extremes in room-temperature tensile properties and Charpy V-notch toughness, and an analysis of the effect of this behavior on the in-service useful life of carbon-steel rails. These five rails were removed from service after 15 to 18 years of operation and were selected from a population of about 90 rails that were removed from service because they contained service-developed defects. A companion paper in this symposium describes the results of chemical analysis, hardness and tension tests, and the results of wear, deformation, metallographic, and fractographic analysis.

The results of the fractographic investigation conducted under AAR-AISI contract that are presented in part in the companion paper showed that in-service fatigue cracks initiated from inclusions having a width of about 0.03 mm (1.25 mils). The results of the present investigation showed that fatigue crack initiation from such small discontinuities occurs when the magnitude of the stress fluctuations applied to the railhead with the passage of each wheel are equal to about the tensile strength of the steel. The cost of the steelmaking practices required to eliminate such small discontinuities is believed to be economically prohibitive. Moreover, the detection of such discontinuities is beyond the capabilities of presently available nondestructive inspection procedures. The results also showed that the fatigue crack propagation behavior of various carbon-steel rails is essentially identical and is independent of chemical composition or mechanical properties. Moreover, the dynamic fracture toughness of these rails at the minimum operating temperature of about -351°C (-30°F) was about 27.5 MPam(25 ksi in.), and a significant increase in the fracture toughness of the rail would result in a negligible increase in the useful fatigue life of the rail. Significant increase in the fatigue life of rails can be achieved by decreasing the wheel load, by maintaining the roadbed, by changes in the design of rails, and by establishing a residual compressive stress field in the upper portion of the railhead which can be accomplished, for example, by induction hardening. Consequently, it is suggested that the safety and reliability of rails can be ensured best by decreasing the magnitude and fluctuation of the stresses in the rail and by periodic nondestructive inspection of rails.
An Evaluation of the Fatigue Performance of Conventional British Rail Steels
Authors: Dabell BJ , Hill SJ , Watson P
Published: March 2009

A comprehensive evaluation of the fatigue behavior of eight conventional pearlitic rail steels is presented. The materials examined are UIC Grades A, B, and C, 1 percent chromium, BS11 Cast 1879, BS11 Cast 500, BS11 Cargo Fleet and BS11 Concast 2971. Of these, the UIC and 1 percent chromium steels are all specifically designed for wear resistance, whereas the BS11 steels are representative of the rail steels in general usage by British Rail. The investigations ranged from the endurance limit to the low cycle region, and both smooth and notched specimens were employed to provide data indicating cyclic strength and ducility, notch sensitivity, and resistance to crack initiation and early growth. In constant-amplitude, strain-controlled, smooth specimen fatigue tests, the conventional BS11 steels proved superior in the low cycle region, whereas the more highly alloyed steels were generally stronger at long lives. Where a tensile mean stress is present, the superiority of the BS11 rail steels in the short life region is reduced, and the 1 percent chromium steel exhibits a high resistance to fatigue over a large range of endurances. In the notched plate tests, the 1 percent chromium and UIC Grade B steels proved most resistant in general to fatigue crack initiation and early growth. Overall, the superior performance of the 1 percent chromium steel on the basis of both fatigue characteristics and static properties is demonstrated.
Cyclic Inelastic Deformation and Fatigue Resistance Characteristics of a Rail Steel
Authors: Leis BN
Published: March 2009

The cyclic inelastic deformation and fatigue resistance characteristics of a typical rail steel in use by American railroads have been determined. Uniaxial smooth specimens were obtained from the head of an unused section of rail and subjected to a variety of test conditions—static tension, static compression, and fully reversed constant-amplitude strain cycling. Additionally, a study of “history effects” was made. Included in this study were tests to examine the influence of orientation, mean stress, initial prestrain, and periodic overstrain, both the cyclic deformation response and the fatigue resistance being reported for each condition. Results obtained from these tests are discussed in light of predictive models for rail failure, particular attention being paid to the influence of stress state on deformation response and fatigue resistance.
Dynamic Analysis of Crack Propagation and Arrest in the Double-Cantilever-Beam Specimen
Authors: Kanninen MF , Popelar C , Gehlen PC
Published: March 2009

A simple one-dimensional analysis model was developed previously for rapid unstable crack propagation and arrest in wedge-loaded rectangular double-cantilever-beam (DCB) specimens. In this paper, the model is generalized to treat contoured specimens and machine-loading conditions. The development starts from the basic equations of the two-dimensional theory of elasticity with inertia forces included. Exploiting the beam-like geometry of the DCB specimen results in governing equations that are analogous to a variable-height Timoshenko beam partly supported by a generalized elastic foundation. These are solved by a finite-difference method. Crack propagation arrest results illustrating the effect of specimen geometry and loading conditions are described in the paper.
Preliminary Approaches to Experimental and Numerical Study on Fast Crack Propagation and Crack Arrest
Authors: Kanazawa T , Machida S , Teramoto T
Published: March 2009

Within the limit of relatively short arrested crack, static approximation by applying linear fracture mechanics has yielded useful results for theoretical interpretation and practical application of currently used brittle fracture propagation arrest test (the concept of arrest toughness). But later experimental investigations using very wide specimens (1300 to 2500-mm-wide plates) have revealed that this simple interpretation fails to have a consistency with the case of a long arrested crack. For the inadequacy of static approximation based on arrest toughness concept, the concept of an effective stress intensity factor has been introduced from a practical point of view without a clear quantitative explanation for it. In search of a more relevant theory for fast crack propagation and to see how the neglect of dynamic aspects affects the interpretation of unstable crack propagation arrest test and philosophy of crack arrest design, a dynamic fracture mechanics analysis was made with the use of the finite-difference method to solve the equation of motion for the two-dimensional elastic problem.

Results of a numerical experiment are presented, and experimental results for polymethylmethacrylate specimen and structural steels are discussed in terms of dynamic fracture mechanics analysis with a focus on energetic aspect of the crack propagation processes.
Dynamic Finite Element and Dynamic Photoelastic Analyses of Crack Arrest in Homalite-100 Plates
Authors: Kobayashi AS , Emery AF , Mall S
Published: March 2009

A dynamic finite element code, HONDO, was used to analyze four dynamic photoelastic experiments in which the propagating crack arrested. The time-averaged crack-tip velocity in the finite element model was matched with the measured crack-tip velocity in the dynamic photoelastic experiments. Dynamic energy release rates were computed by a procedure similar to that used in computing strain energy release rate in static finite element analysis. These directly computed dynamic energy release rates at crack arrest agreed reasonably well with those computed from the dynamic stress intensity factors determined photoelastically. The energy release rates at crack arrest in the four Homalite-100 plates were approximately 50 percent of the critical strain energy release rate, ςC, and were approximately 80 percent of the corresponding static strain energy release rates.
Singularity-Element Simulation of Crack Propagation
Authors: Aberson JA , Anderson JM , King WW
Published: March 2009

Finite-element simulations of rapid crack propagation are presented. An earlier analysis of a crack extending in an infinite body is reviewed, and an unsuccessful attempt to take advantage of a crack-tip singularity element is discussed. Plausible stress-intensity factors are obtained for both constant speed and accelerating cracks in finite sheets; the results are compared to those obtained by other investigators.
Dynamic Finite Difference Analysis of an Axially Cracked Pressurized Pipe Undergoing Large Deformations
Authors: Emery AF , Love WJ , Kobayashi AS
Published: March 2009

An axial through crack was suddenly introduced into the wall of a pipe which was pressurized by either hot water or air. The crack tip was assumed to advance along the pipe according to a fracture criterion based upon the character of the deformation. For brittle elastic failure a maximum stress intensity factor was utilized, while for a plastic stress field, a maximum strain criterion was used. The fluid pressure in the pipe was calculated by a finite difference method in which the effect of the outflow through the crack was taken into consideration.
Measurements of Dynamic Stress Intensity Factors for Fast Running and Arresting Cracks in Double-Cantilever-Beam Specimens
Authors: Kalthoff JF , Beinert J , Winkler S
Published: March 2009

The influence of dynamic effects on the crack arrest process is investigated. For propagating and subsequently arresting cracks, actual dynamic stress intensity factors were measured applying a shadow optical technique in combination with a Cranz Schardin high-speed camera. The experiments were performed in wedge-loaded double-cantilever-beam (DCB) specimens machined from an epoxy resin (Araldite B). In the initial phase of crack propagation the measured dynamic stress intensity factors were found smaller; in the arresting phase, however, they were larger than the corresponding static values. After arrest the dynamic stress intensity factor oscillates with decreasing amplitude around the static stress intensity factor at arrest. Crack arrest toughness values determined according to a static analysis showed a dependence on the crack velocity prior to arrest, but the dynamic crack arrest toughness yielded a single value only, indicating that this quantity represents a true material property.
Crack Propagation with Crack-Tip Critical Bending Moments in Double-Cantilever-Beam Specimens
Authors: Burns SJ , Chow CL
Published: March 2009

Rapidly wedged, double-cantilever-beam (DCB) specimens have a critical bending moment as a propagating fracture criterion in the limit of the Bernoulli-Euler beam theory. The magnitude of the critical bending moment is calculated from a fully dynamic analysis of crack propagation. The shear force in the beam at the constant displacement rate end of the DCB specimen, multiplied by the square root of the loading time, is related to the critical bending moment. Experimental measurements of the time dependence of the shear force have been used to calculate the specific fracture surface energy versus crack velocity. The crack velocity in a single specimen decreases with increasing time, it varies by a factor of five and is typically 0.01 of √E/ρ. Details of the experimental measurements for brittle and ductile fractures, including stress intensity values versus crack velocity, are described.
Computation of Crack Propagation and Arrest by Simulating Microfracturing at the Crack Tip
Authors: Shockey DA , Seaman L , Curran DR
Published: March 2009

This paper describes the initial development stages of a computational capability for fast fracture and arrest, based on treatment of plastic flow and microfracturing at the crack tip. The approach is to model the events occurring within the process zone, compute the associated energies, and thereby determine the fracture toughnesses of propagating and arresting cracks.

The model treats crack propagation as occurring by the nucleation, growth, and coalescence of microfractures in the plastically deforming material at the crack tip. It uses as input actual measurements from specimens fractured under stress wave loads. The dynamic stress history experienced by this material is calculated by a two-dimensional wave propagation code.

The approach was demonstrated by performing a computational simulation of a Battelle double-cantilever-beam crack arrest experiment and calculating the energies absorbed in plastic flow and microfracturing. Plastic work accounted for about 95 percent of the fracture toughness, but microfracture activity controls the amount of plastic work that is done and hence governs the toughness. Agreement between computed and observed crack velocity and arrest length is not yet satisfactory but should improve when a finer computational grid is used.

The approach offers an avenue for understanding fracture toughness on a micro-level by linking micromechanical material response to continuum toughness parameters.
Effects of Grain Size and Temperature on Flat Fracture Propagation and Arrest in Mild Steel
Authors: Bullock G , Smith E
Published: March 2009

The paper presents results from an experimental program whose objective is the determination of the effects of grain size and temperature on flat fracture propagation and arrest in mild steel. Small laboratory test specimens, containing nitrided notches and surfaces so as to eliminate respectively the initiation barrier and shear lip formation, have been deformed by four-point bending. The onset of crack arrest has been correlated with the applied loading, and the fracture surface appearance during both propagation and arrest has been studied in detail; cleavage rather than ductile fracture is the predominent failure mechanism for a wide range of testing conditions. The results are discussed in relation to theoretical models describing the micromechanics of flat fracture propagation and arrest.
Fracture Initiation in Metals Under Stress Wave Loading Conditions
Authors: Costin LS , Duffy J , Freund LB
Published: March 2009

An experimental procedure is described for accurately establishing the dynamic fracture initiation properties of structural metals at extremely high loading rates. The apparatus is an adaptation of the Kolsky pressure bar (split-Hopkinson bar) in which a 1-in.-diameter round bar specimen with a prefatigued circumferential notch is loaded to failure by the rapidly rising tensile pulse resulting from an explosive detonation. Using the standard Kolsky technique, the average stress at the fracture site is measured as a function of time. Crack opening displacement is measured by optical means, as a function of time, thus yielding a complete load-displacement record for each test. From the data the critical value of the crack-tip stress intensity factor, K1c, at loading rates, ˙K1 in excess of 109 psi √in./s may be obtained. This is nearly two orders of magnitude faster than has been achieved by other standard techniques. Results are presented for dynamic tests conducted on SAE 4340 steel and 1020 cold-rolled steel, and these are compared to results from static tests performed on specimens of similar shape.
Towards Development of a Standard Test for Measuring KIa
Authors: Crosley PB , Ripling EJ
Published: March 2009

Measurement of KIa requires the production of a run-arrest segment of crack extension in a laboratory specimen and evaluation of the stress intensity factor a short time after the crack has arrested. The crack should propagate under conditions which simulate propagation in a thick section. Progress towards meeting these requirements with tests on tapered-double-cantilever-beam specimens is described. Aspects which require further clarification are discussed.
Influence of the Geometry on Unstable Crack Extension and Determination of Dynamic Fracture Mechanics Parameters
Authors: Angelino GC
Published: March 2009

The dynamic fracture toughness of the high-strength steel VCN-100 (UNI 38 NiCrMo4) is derived from tests on TPB 9 (three-point-bend) specimens. A wide range of crack velocities was obtained by changing the ER (energy ratio) of the specimen at crack instability; the crack velocity was evaluated from load versus time records during crack propagation. The results show a dependence of KID on crack velocity in good agreement with literature data.
Program Definition and Preliminary Results of a Long-Term Evaluation Program of Advanced Composites for Supersonic Cruise Aircraft Applications
Authors: Kerr JR , Haskins JF , Stein BA
Published: March 2009

Advanced composites will play a key role in the development of the technology required for the design and fabrication of future supersonic vehicles. However, implementation of the material into vehicle usage is contingent upon accelerating the demonstration of service capacity and design technology. Because of the added material complexity and lack of extensive service data, laboratory replication of the flight service will provide the most rapid method of documenting the airworthiness of advanced composite systems. A program is in progress to determine the time-temperature-stress capabilities of several high-temperature composite materials. Tests included in this study are thermal aging, ambient aging, fatigue, creep, fracture, tensile, and real-time flight simulation exposure. The program has two parts. The first includes all the material property determinations and aging and simulation exposures up through 10 000 h. The second continues these tests up to 50 000 cumulative h. The program is currently in the midst of the 10 000-h phase of the study. Some of the results obtained to date and the status of the various tests are discussed in this and a following paper.
Effects of Graphite/Epoxy Composite Materials on the Corrosion Behavior of Aircraft Alloys
Authors: Fischer P , DeLuccia JJ
Published: March 2009

A study was made to evaluate the potential galvanic corrosion problem when graphite-epoxy composite materials are coupled to naval aircraft alloys in the naval air-sea environment. Electrochemical measurements (open circuit potential) showed a relatively large potential difference, approximately 1 V, between the composite and the aluminum alloys 7075-T6, 7075-T651, and 5052-H38. This difference provides the driving force for the corrosion of aluminum as an anode and is cause for concern. Corrosion current data (zero impedance technique) show that these aluminum alloys and cadmium-plated steel are much more reactive than Ti-6A1-4V when coupled to graphite-epoxy (15 versus 0.002 μA/cm2). This technique provides a means of ranking the corrosion problem when graphite-epoxy is coupled to various aircraft alloys.

Flatwise tension test data indicated significant strength losses when graphite-epoxy sandwich specimens, composite facings bonded to aluminum honeycomb, are exposed to salt spray and synthetic seawater plus sulfur dioxide (SO2) spray environments. The strength loss is not entirely due to the galvanic effect.

Data show that galvanic coupling of the composite to 7075-T651 aluminum alloy has no discernible effect on the stress corrosion cracking behavior of the alloy but does increase its general corrosion.
Influence of Outdoor Weathering on Dynamic Mechanical Properties of Glass/Epoxy Laminate
Authors: Roylance D , Roylance M
Published: March 2009

A commercially obtained glass/epoxy composite material has been exposed to a wide variety of actual outdoor and accelerated climates at different test sites around the world. Portions of this sample population are returned at various intervals for an extensive laboratory characterization aimed at determining the effect of exposure on engineering properties and elucidating the nature of the deterioration mechanism as well. In spite of clear visual and chemical evidence of severe photolytic degradation of the resin surface layers, test values of tensile and flexural strength do not show a clearly defined correlation with this deterioration. Reasoning that the structural effect of photolytic molecular scission might be to interrupt the three-dimensional network of resin bonds and increase the effective molecular weight between crosslinks, the glass transition temperature of the laminates has been determined by torsional pendulum analysis as a function of exposure time. The molecular weight between crosslinks, as determined from these data, is then shown to correlate strongly with laser pyrolysis observations of chemical degradation.
Flexible Rubberized Asphalt Membranes for Inverted Roofing Systems
Authors: Reid WJ
Published: March 2009

A laboratory test method, based on the “toughness” value of the material, has been developed to distinguish between high- and low-performance rubberized asphalt membranes used in inverted (protected-membrane) roofing systems.

Rubberized asphalts with a high toughness level have been shown, under laboratory conditions, to be capable of bridging structural cracks in concrete decks at temperatures as low as -18°C (0°F). When the temperature is raised, the membrane remains as an undeformed continuous film. On the other hand, membranes with a lower toughness level were shown to fail at high strain rates, while at lower strain rates they sag irreversibly after such a temperature cycle. During application of the membrane, such temperatures may be experienced for short periods of time before the insulation is placed on top of the membrane or before the building is heated.

Field experience in waterproofing applications, including bridge decks, underground parking garages, and plazas as well as roofs, has shown that the toughness level, combined with other properties such as low temperature flexibility, resistance to flow, and penetration, correlate well with actual performance.
Moisture Content in Protected Membrane Roof Insulations—Effect of Design Features
Authors: Hedlin CP
Published: March 2009

In protected membrane roofs, the thermal insulation is placed above the main waterproof membrane where it is exposed to precipitation. The severity of the wetting problem can be reduced by protective measures.

Fibrous and closed cell plastic insulations, ranging from 150 to 610 mm square and 51 mm thick, were placed on experimental roofs. They were weighed periodically over periods of up to five years.

The results indicate that moisture gains are reduced by increasing deck slope. Sealing the bottom surface significantly reduced moisture gain in a bead polystyrene, but improvement was offset by placing paving stones directly on its upper surface. Slotting the lower insulation surface on a 100-mm-square grid was not found to reduce moisture uptake. Moisture content of some fibrous specimens sealed on the bottom surface and edges remained at less than 4 percent by volume. Others similarly sealed, but with paving stone cover flashed to divert water away from the upper surface, remained at less than 1.5 percent. In most cases, when specimens were placed wet on the roof in winter, significant drying occurred over a period of several months.
Fire Performance of New Roof Covering Materials and Systems and Weathered Asphalt Shingles
Authors: Donahue RL , Castino GT
Published: March 2009

Fire tests are used to classify built-up and prepared roof covering materials and systems based on their ability to resist the growth and penetration of fires of varying degrees of severity. Spread of flame tests are used to determine the flaming fire growth characteristics on the surface of materials and systems, while intermittent flame and burning wood brand tests measure fire penetration resistance by establishing the capability of a roof covering material or system to protect combustible decking from ignition.

The fire test performances of spray-applied foam systems, asphalt glass mat shingles, and aluminum shingles with various underlayment systems, as well as weathered asphalt organic-felt shingles, a:e examined.

The just mentioned systems and materials perform similarly to the more traditional classified systems.
Density of Mineral Stabilizers in Asphalt Roofing Coatings
Authors: Smith DJ
Published: March 2009

This study was undertaken to assess the value of high-density rock as a mineral stabilizer for the asphalt coatings used in the manufacture of prepared roofings. The hope was that more mineral stabilizers could be used in the roofings than was the usual practice, thus saving on the high-energy, higher-priced asphalt. This is possible and desirable, but it entails increasing the current specification limits for the use of mineral stabilizers. Physical properties of coatings varied according to their volume proportions of mineral, irrespective of the mineral identity; these properties were modified in minor degree by the proportion of “fines” in the mineral. Accelerated weathering test results were influenced more by the kind of mineral and its particle size distribution than by the proportion of the mineral stabilizer. Indications are that a volume percent of 35 to 40 will prove to be the maximum practical proportion of mineral in either soft or standard asphalts. Two roofing mill trials showed the feasibility of these concepts, including also the maintenance of heat balances on the machine.
Effect of Moisture on the Strength Characteristics of Built-Up Roofing Felts
Authors: Laaly HO
Published: March 2009

Stress-strain properties of Type 15 asphalt-saturated, organic, and asbestos felts are compared at room temperature and 50 percent relative humidity. The rate of water sorption by asphalt-saturated organic felt immersed for 520 h in distilled water at room temperature and the effect of moisture on its strength characteristics are assessed. The structure of unsaturated organic felt and the inter-locking characteristics of the fibers were examined by a scanning electron miscroscope.
Relationship Between the Fracture Toughness and the Crack Tip Radius
Authors: Taggart R , Wahi KK , Beeuwkes R
Published: March 2009

The conditions that surround the tip of a sharp crack in a ductile metallic material dictate the onset of plastic flow and crack extension. The problem of predicting the onset of unstable fracture is related directly to the difficulty of measuring or calculating the actual stresses and strains within the plastic enclave that encompasses the crack tip. Beeuwkes has obtained an approximate solution for the elastic-plastic state in the vicinity of the crack tip and concludes that the crack tip radius after deformation together with the fracture strength at nil ductility of the material form the basis for a fracture criterion.

In this study measurements have been made of the crack opening of fatigue cracked double cantilever beam specimens of 6061-T6 and annealed 4340VM steel. The crack opening measurements have been used to compute the crack tip radius at different loads by fitting the experimental data with an nth order polynomial (n = 2, 4, 6, and 8). The polynomial for which the average deviation in the computed values is a minimum with respect to the measured values was chosen to represent the crack geometry. The values of the crack tip radius as given by this polynomial were plotted against the stress intensity factor.

It has been found for both the selected materials that the stress intensity factor and the crack tip radius follow a linear relation when plotted on a log-log basis. The stress intensity factor and the ratio of the crack tip radius to a critical crack tip radius also plot as a straight line on a log-log basis.

It is concluded that the concept of a critical crack tip radius is consistent with a crack extension model that depends on void coalescence and growth. The data also support the fracture criterion based on the elastic-plastic analysis proposed by Beeuwkes.
Fracture Analysis of Various Cracked Configurations in Sheet and Plate Materials
Authors: Newman JC
Published: March 2009

A two-parameter fracture criterion has been derived which relates the linear-elastic stress-intensity factor at failure, the elastic nominal failure stress, and two material parameters. The fracture criterion was used previously to analyze fracture data for surface- and through-cracked sheet and plate specimens under tensile loading. In the present paper the fracture criterion was applied to center-crack tension, compact, and notch-bend fracture specimens made of steel, titanium, or aluminum alloy materials tested at room temperature. The fracture data included a wide range of crack lengths, specimen widths, and thicknesses. The materials analyzed had a wide range of tensile properties. Failure stresses calculated using the criterion agreed well (± 10 percent) with experimental failure stresses. The criterion was also found to correlate fracture data from different specimen types (such as center-crack tension and compact specimens), within ± 10 percent for the same material, thickness, and test temperature.
Biotic Monitoring
Authors: Mount DI
Published: March 2009

Past water pollution regulatory actions have dealt largely with eliminating existing unacceptable conditions from surface waters. Since the beginning of this decade, increased attention has been focused on preventing such conditions from developing. The shift has changed the informational need from one of assessing field conditions to one of predicting effects before they occur. A concomitant increased need from bioassays as predictive tools has occurred. Furthermore, analytical methods have not been developed to measure biologically active forms, and often they are not sensitive enough to measure concentrations at this “no effect” level. In addition, the composition of wastes from today's industrial society are complex and variable and often contain many unidentified components. Therefore, aquatic bioassays are an essential tool for today's problems of aquatic environmental regulation.
Evaluation of an Automated Biological Monitoring System at an Industrial Site
Authors: Westlake GF , van der Schalie WH
Published: March 2009

The feasibility of using biological monitoring of industrial point sources as a tool for river management has been demonstrated by a number of laboratory simulations. However, it is another task entirely to move these techniques to an industrial setting. The necessary modifications of a computerized biological monitoring system to install it in the Celanese Corporation Plant on the New River in Virginia are described. The system employs the respiration rates of bluegills (Lepomis macrochirus) as an indicator of abnormal variations in the effluent.
Rotatory-Flow Technique for Testing Fitness of Fish
Authors: Lindahl PE , Olofsson S , Schwanbom E
Published: March 2009

An improved version of rotatory-flow apparatus, which allows tests of fitness with fish of different size at constant temperature, is described. Optimal experimental conditions have been investigated with cod. The method has been applied to the study of the influence of temperature on the effect of ethanol in cod and to comparison of the fitness of cod from an inconsiderably contaminated and a polluted area.
An Automatic System for Rapid Detection of Acute High Concentrations of Toxic Substances in Surface Water Using Trout
Authors: Poels CLM
Published: March 2009

Trout normally possess a positive rheotactic behavior, and this behavior is often lost in response to toxic conditions. A continuous automated monitoring system was developed incorporating photoelectric cells and mild electric shock. When a trout no longer displayed positive rheotaxis and moved downstream in the test tank, a series of photoelectric cells were interrupted. This, in turn, caused a mild electric shock to be applied to the downstream portion of the test tank. This electric irritation continued until the fish moved back upstream away from the photocells. A second series of photoelectric cells indicate when the fish remain in the downstream area regardless of the applied electrical impulses. An alarm switch will operate when at least two of the three fish in the same 15-min period pass the photoelectric cells more often than normal or when two fish remain in the extreme downstream portion of the monitoring tank for longer than 5 min. Practical experiences on Rhine water and experiments with toxic substances suggest that this flow-through system is suited for practical application.
Some Monitoring and Analytical Techniques for the Study of Locomotor Responses of Fish to Environmental Variables
Authors: Kleerekoper H
Published: March 2009

The adaptive significance of locomotor, specifically orientation responses in fishes to environmental stimuli, is emphasized. General locomotor behavior is usually extremely variable over time whereas the responses mentioned are, most frequently, very subtle.

Techniques are described to detect and quantify these responses by comparing locomotion before stimulation with that during exposure to the environmental variable(s) under study. Models for such comparison are based on time series analysis of relevant locomotor variables, such as frequency and size of turns, length and orientation of steps, velocity, and others. Two techniques for data acquisition of these variables, by means of electronic monitoring of locomotion under controlled physical and chemical conditions, are described in some detail.

Attention is called to the possible interaction of environmental conditions and the behavioral responses of fish, an aspect which, hitherto, has received too little consideration in studies on biological effects of environmental variables.
Biological Monitoring in Activated Sludge Treatment Process
Authors: Stover EL , Woldman ML , Marks PJ
Published: March 2009

The objective of the activated sludge process, as with other biological treatment processes, is the removal of organic and select inorganic compounds from wastewaters. With ever-increasing treatment requirements, it will become necessary for treatment facilities to be operated more effectively to meet the stringent effluent quality while continuing to treat varying wastewater flows and contaminant loads. Biological systems should be monitored continuously be analytical measurements, visual observations, and operational tests, and proper responses should be made to maximize the performance of the systems to achieve the required effluent quality.
Research Related to Biological Evaluation of Complex Wastes
Authors: Horning WB
Published: March 2009

The main thrust of a research program being undertaken is the development, testing, and field verification of a battery of tests for measuring the environmental impact of effluents of variable and unknown composition, especially those meeting the effluent guidelines. These include short lethal tests, short nonlethal tests, tests that will estimate safe concentrations, behavioral tests, tainting tests, and measurements of chemical groups relatable to residue formation and toxicity. These tests will be available for use by dischargers to monitor their effluents and for use as discharge permit requirements. Some of the major problems involved in biologically evaluating complex effluents are duscussed as well as areas for additional research.
Some Methods for Hypothesis Testing and Analysis with Biological Monitoring Data
Authors: Green RH
Published: March 2009

The problem considered here is whether a specified environmental change does, or does not, affect a biological community. Commonly used procedures are often inappropriate for the data or for the questions asked. Such procedures, as well as an appropriate one, are discussed and illustrated using a set of artificial data with properties similar to those of a real benthic community. Ninety-two stations on a kilometre grid are sampled for abundances of six benthic species and four environmental variables, before and after an increased inflow of dissolved salts.

A multiple regression model which assumes that species abundances are related to environmental variables in a linear additive manner yields inefficient and misleading results. Cluster analysis methods efficiently describe natural spatial patterns, but temporal changes are swamped by the spatial patterns and are not detected. A linear additive model which relates changes in species abundances to changes in environmental variables removes the variation due to spatial pattern from the analysis and clearly shows that biological changes related to increased salt concentration have occurred. Methods for describing the changes and testing related hypotheses are presented.