bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanisms of Fatigue in the Creep Range
Authors: Wells CH , Sullivan CP , Gell M
Published: March 2009

The mechanisms of deformation and fracture in creep and fatigue are surveyed. Interactions between time- and cycle-dependent mechanisms are discussed from the standpoint of cumulative damage laws for lifetime prediction. The major roles of temperature and time in the fatigue process are shown to be an increase in the homogeneity and irreversibility of slip, cavitation of particle-matrix interfaces, and the growth of surface oxide layers to a thickness that can affect crack initiation; the principal effect of cyclic loading on creep fracture is the acceleration of crack propagation resulting from resharpening of microcracks.

One of the major areas of uncertainty in cumulative damage is concluded to be the influence—either beneficial or deleterious—of compressive loading. Cavities initially produced in tension may be sintered by diffusion or rewelding in compression; on the other hand, sharp microcracks generated in compressive creep can severely accelerate fracture. It is suggested that these effects may be understood by considering whether the deformation is planar or wavy.
Automotive Emission Research—Review of the Coordinating Research Council Program
Authors: Moser CE
Published: March 2009

The Coordinating Research Council automotive emission research program, supported by the American Petroleum Institute, the Automobile Manufacturers Association, and the National Air Pollution Control Administration, is completing its third year of work. Some thirty projects in the categories of engineering, atmospheric, and medical research are being undertaken under contract with research institutes, universities, government, and industrial laboratories. Results obtained will provide industry and government with technical information to aid in further reducing automotive emissions.
Fuel Technology Now Requires Uniform GLC Analytical Procedures
Authors: Hurn RW
Published: March 2009

Experimental work within the broad spectrum of fuels technology calls for both accurate and uniform analytical methods for fuels and combustion products. Recent experience, however, has shown wide variation in analytical results obtained by different laboratories each possessing generally high competence for petroleum analysis. Analytical capability across laboratories would be improved through use of more nearly uniform methods so that laboratories doing air pollution research would be able to separate, identify, and quantify the many fuel components and products in comparable manner. Moreover, to fully utilize the advantages of such uniform analyses, results must then be expressed in a systematic, standardized format. Improved accuracy in the analytical data is needed, but accuracy alone will not suffice and should be sought in conjunction with uniform procedures and identification format. The paper suggests a hydrocarbon identification and classification scheme to be used in reporting analyses that are obtained following uniform, standardized analytical procedures. The resulting information would be readily translatable from laboratory to laboratory.
Influence of Vehicle Emission Control Systems on the Relationship Between Gasoline and Vehicle Exhaust Hydrocarbon Composition
Authors: Morris WE , Dishart KT
Published: March 2009

Relationships have been developed that describe how vehicle exhaust hydrocarbon composition is influenced by hydrocarbon composition of the gasoline and by the use of various emission control systems which give a range of exhaust emission levels. The relationships were obtained by computer regression analysis of the detailed individual hydrocarbon compositions of 15 gasolines of varying aromatic and olefin content and the exhaust emissions from these fuels.

The gasolines, which consisted of five refinery-component blended fuels and ten matching commercial gasolines, were all leaded premium grade with similar octane quality and volatility characteristics. The aromatic and olefin contents of the blended gasolines were varied according to a statistical design that covered the usual variation found in commercial premium gasolines.

The vehicles in which these fuels were tested were equipped with several different types of emission control systems. These included no control device, conventional air injection and engine modification systems, and a duPont exhaust manifold reactor system capable of low exhaust emission levels.

With all four emission control systems, most of the hydrocarbons emitted were formed by degradation of fuel hydrocarbons. Regression analyses results indicate that ethylene was formed from saturates and olefins, propylene and isobutylene/1-butene were formed primarily from saturates, and diolefins were formed primarily from olefins. Toluene was the most important fuel hydrocarbon from the standpoint of contribution to calculated photochemical reactivity, and survived through the vehicle in larger proportion than the other principal fuel hydrocarbons. Along with the toluene that survived, additional amounts were formed from higher aromatics. Similarly, additional benzene and xylenes were formed from higher aromatics. Additional 2-methyl-2-butene was formed from fuel saturates.

Fuel effects on photochemical reactivity of the hydrocarbon emissions were quite small in relation to the effects of emission control systems. Calculated total photochemical reactivity of the exhaust from the thermal reactor car was only 2 to 3 percent of that of the cars with other control systems.
The IIEC Program—A Progress Report
Authors: Osterhout DP , Jagel KI , Koehl WJ
Published: March 2009

After nearly three years of work in the Inter-Industry Emission Control (IIEC) program, research studies in 18 projects directed at the many mechanical and chemical engineering aspects of automotive emissions have been crystallized in three concept vehicle emission control packages. This paper will: (1) outline the makeup and emission control effectiveness of these three packages, (2) review the chemical engineering aspects of their development, and (3) document some of the major problems with these concepts that must be overcome before they can be termed feasible for production.

The major components of the three concept packages are: Package A, thermal reactor and exhaust gas recirculation (EGR) for use with leaded or unleaded gasoline; Package B, catalytic reactor for hydrocarbon and carbon monoxide control and EGR for use with low lead or unleaded gasoline; Package C, dual catalytic reactors to control hydrocarbons, carbon monoxide, oxides of nitrogen and EGR, for use with unleaded gasolines. The important chemical engineering studies embodied in the concept packages include: (1) mathematical modeling of both thermal and catalytic reactors to guide their design, (2) development of effective catalysts for use with both leaded and unleaded fuel, (3) screening of high-temperature oxidation resistant materials for thermal reactor construction, and (4) studies of interactions between EGR and fuel and lubricant compositions as they relate to engine cleanliness.
Correlation of Microfractography and Macrofractography of AISI 4340 Steel—A Report of ASTM E-24/II Task Group
Authors: Carr FL , Biehler D , Connolly A , Dragen R , Faller J , Johari O , Morais R , Parker MT , Sailors RH
Published: March 2009

A co-operative investigation was made by a task group of ASTM Committee E-24 Subcommittee II to correlate the microfractography and macrofractography of notch tension specimens of 4340 steel heat treated to 8 strength levels. Selected testing temperatures provided fractures with macroscopic topography representing the complete fracture transition of each material. The observed microscopic fracture modes were correlated with the two macroscopic zones of fracture surface configurations (fibrous and radial) and the final area of separation. Regardless of tempering temperature the fibrous zone of all materials consisted of microvoid coalescence and holes. Radial zones consisted of quasi cleavage for specimens tempered at high temperatures, and intergranular fracture with grain boundary microvoid coalescence for specimens tempered at low temperatures. Mixtures of these modes were observed in radial zones on specimens tempered at intermediate temperatures. The amount of each of these modes present in the radial zone depended on both testing and tempering temperatures.

This correlation and the strong temperature dependencies become evident by the examination of fractures representing the complete macroscopic transitional appearances of sufficient materials obtained by different tempering temperatures.
Design, Analysis, and Testing of an Advanced Composite F-111 Fuselage
Authors: Ashton JE , Burdorf ML , Olson F
Published: March 2009

The paper describes the design, analysis, and testing of a full-scale section of an F-111 aft fuselage center body made from advanced composite materials. A 160-in.-long test component was fabricated and tested to destruction. The composite material systems were graphite/epoxy, boron/ epoxy, boron/aluminum, and glass/epoxy. Maximum use of composites was maintained throughout the structure, with both skins and substructures being treated. Design concepts for the various structural elements were developed through a program of testing of subelement specimens. Test results were obtained on the strength of boron and graphite composites applied to sandwich panels, stiffened sheet panels, frames, bulkheads, and fittings.

A static test component was detail designed and fabricated. Fourteen subassemblies of frames and panels were fabricated and assembled into a 920-lb component using 460 lb of composite material. A weight saving of 18 percent of the counterpart aluminum and steel structure was obtained. Static testing of the part included loading in bending with simultaneous application of internal pressure. The component sustained 130 percent of the design ultimate load. Deflection gage and strain gage data showed excellent agreement with analytical results.
Design Philosophy for Boron/Epoxy Structures
Authors: Hadcock RN
Published: March 2009

The philosopy followed to satisfy design requirements for aircraft structures is discussed. An approach is described which has been successfully used to generate boron/epoxy design allowables data on the basis of 90 percent probability of survival with a confidence of 95 percent (MIL-HDBK-5 B basis). This approach results in design strength data which include not only the variations in material properties but also any inadequacies in theoretical methods for strength prediction. Results of tests on full scale components and subcomponents are compared with theoretical predictions using these design allowables data.
Thermal Expansion Characteristics of Graphite Reinforced Composite Materials
Authors: Freeman WT , Campbell MD
Published: March 2009

The high modulus and negative thermal expansion coefficient of graphite filaments provide the potential for fabrication of laminated composites exhibiting negligible thermal sensitivity. Advanced satellite and space antenna applications requiring structurally efficient materials that are distortion free over a wide range of thermal gradients and local thermal conditions are now practical. The paper describes an investigation to determine the thermal expansion characteristics of graphite composites. Thermal strain measurements over a wide temperature range, -320 to 550 F(-196 to 288 C), were made by General Dynamics using a modified Leitz dilatometer. The feasibility of measuring thermal strains with strain gages is discussed.

Measurements of the longitudinal and transverse dilatation of five composite systems containing high modulus and high tensile strength graphite fibers in three different resin binders are reported. Moisture content was found to have a significant effect on thermal strain versus temperature hysteresis characteristics of both neat resins and composites. Moisture removal at high temperature was manifested as a shrinkage in the material length, and the thermal expansion coefficient remained constant over a given temperature range after sufficient drying. With the exception of unidirectional composites, the thermal coefficient increased nonlinearly with temperature. The practical aspects of stress relaxation effects and hysteresis characteristics on unidirectional laminates are discussed. Data obtained on quasi-isotropic laminates, 0/± 60 and 0/±45/90, indicate that low expansion coefficients are obtainable.
Toughening Mechanisms in Continuous Filament Unidirectionally Reinforced Composites
Authors: Olster EF , Jones RC
Published: March 2009

The fracture toughness perpendicular to the reinforcement of a composite is much greater than the volume fraction average of the fracture toughnesses of its components. Several years ago Outwater and Mandell independently proposed that the high toughness of glass reinforced plastics is due to the tensile energy stored in the debonded region for the fibers in the vicinity of the fracture surface. Using appropriate modifications of Irwin's expression for the strain energy release rate, this concept is shown to be valid in other composite systems as well. Analogies also extend its use to composites with ductile fibers and elastoplastic matrices. The data imply that the toughness contribution of the fiber to the overall composite toughness is proportional to the irrecoverable energy in the fiber, that is, the elastic and plastic energy within a debonded region of the fiber or within a portion of the fiber encased by matrix material that has yielded. The results obtained here, in conjunction with the Outwater-Mandell toughening mechanism, lead to a unified concept of toughening in fiber reinforced materials.
Analysis of Short Beam Bending of Fiber Reinforced Composites
Authors: Berg CA , Tirosh J , Israeli M
Published: March 2009

The deformation of an elastoplastic fiber reinforced short beam specimen is studied numerically. The properties used in the calculation are chosen to represent measured properties of graphite fiber reinforced epoxy composites (Modmor II). The strong departures (∼100 percent) of the calculated stress from those obtained via ASTM D 2344-67 estimates suggest that the short beam shear test be used only as a screening test and that where precise measurements of shearing strength are required torsion experiments be used. The plastic zone under the contact load is found to grow linearly with applied load P per unit width of the beam. In a material of yield stress τy the plastic zone radius Rp may be approximated by the formula Rp≃12Pτy.
The Embedded Strain Gage Technique for Testing Boron/Epoxy Composites
Authors: Daniel IM , Mullineaux JL , Ahimaz FJ , Liber T
Published: March 2009

An embedded strain gage technique for measuring subsurface strains in boron/epoxy composites was successfully developed and tested. Preliminary tests to establish the feasibility of the technique demonstrated that conventional foil gages do not produce local thickening of the specimen when a patch of scrim cloth is removed, do not change the average material properties, and do not reduce the strength of the specimen. The technique was used to determine surface and subsurface strains in three-, five-, and seven-ply boron/epoxy tension coupons of three different layups. In preparing these specimens an area of scrim cloth corresponding to the gage area was removed and the gages were laid down without any adhesive. Two- and three-element rosettes were used. Ribbon leads were soldered to the gages and taken out from the sides of the specimen. The assembled specimen with the embedded gages and leads was then cured in the autoclave, tabbed, and tested to failure.

Results are presented first in the form of stress-strain curves for each ply and then as strain variations through the thickness with applied stress as a parameter. Values of modulus, Poisson's ratio, and strength were obtained from these tests. Deviations of varying degrees were observed in the strain readings through the thickness. The diagonal (45-deg) strain deviations were higher than those of the transverse strains, which in turn were higher than those of the longitudinal strains. It was also observed that deviations tended to be smaller when the gages were oriented in the direction of the fibers than when they were oriented transverse to them.
Acoustic Emission from Composite Materials
Authors: Liptai RG
Published: March 2009

A review of the application of acoustic emission analysis to the evaluation of material properties and defect structure is presented, including a brief discussion of experimental techniques. Sources of acoustic emission in composite materials under strain are discussed. Particular attention is directed toward fiber reinforced composites, and experimental results on filament wound NOL rings and vessels (glass/epoxy) are reported. It is concluded that acoustic emission data are helpful in establishing the mechanisms governing operative fracture modes and assessing structural integrity.
Impact Behavior of Unidirectional Resin Matrix Composites Tested in the Fiber Direction
Authors: Novak RC , DeCrescente MA
Published: March 2009

Charpy impact strength data are presented for unidirectional graphite/, boron/, and glass/resin composites tested in the fiber direction. The impact strength of glass/resin is significantly higher than that of either the boron or the graphite composites. The mechanisms by which resin matrix composites absorb energy are studied, and it is found that the tensile stress-strain characteristics of the fibers are of primary importance in determining the level of composite impact resistance. The toughness of the resin matrix is shown to represent a small contribution to composite impact energy. Increasing the impact strength of boron and graphite composites by the inclusion of glass fibers is discussed.
Vibration Characteristics of Unidirectional Filamentary Composite Material Panels
Authors: Clary RR
Published: March 2009

An experimental and analytical study of the vibration characteristics of a series of boron/epoxy composite panels with all layers having the same filament orientation has been conducted. Nodal patterns and natural frequencies are found to be highly dependent on the filament angle. Frequencies change by as much as 90 percent with a 30-deg change in the filament angle. Measured damping coefficients are only moderately higher than those of comparative aluminum panels. There is no strong correlation between the filament angle and the amount of damping. In general, calculations based on a finite element mathematical model are in good agreement with the experimental data.
Analysis of an Improved Boron/Aluminum Composite
Authors: Jones RC , Christian JL
Published: March 2009

Improvements in the mechanical properties of a boron/aluminum composite material have been achieved through thermal treatments and the addition of small amounts of high strength stainless steel wires perpendicular to the boron. This study provides an analysis of these improved composite materials, utilizing scanning electron microscopy and X-ray radiography to examine the micromechanics of the composites and their fiber and matrix components. Phenomena analyzed and discussed are matrix-matrix bonding, filament-matrix bonding, matrix failure, filament damage, and fracture initiation and propagation.
Creep Behavior of Elastic Fiber/Epoxy Matrix Composite Materials
Authors: Koeneman JB , Kicher TP
Published: March 2009

Creep tests were run on glass fiber and Thornel fiber/epoxy matrix composites. Composite creep rates depend on specimen geometry, which can be explained by considering the average deviatoric and equivalent stress states that exist in the matrix. Tests indicate that the matrix is in the bulk plastic region considerably before failure. The stress dependence of the creep rate is used to determine the yield stress of the pure epoxy and the stress level at which the matrix of a composite becomes fully plastic.
Required Critical Aspect Ratio of Fibers Intended for Stress Rupture Applications
Authors: Jech RW
Published: March 2009

The observed critical aspect ratio for pullout specimens of tungsten wire in a copper matrix tested in stress rupture at 649 and 816 C was slightly greater than for tension tests at the same temperature. Time for failure of the stress rupture specimens was controlled by the properties of the fiber (tungsten) at aspect ratios greater than the critical aspect ratio and by the properties of the matrix (copper) at aspect ratios less than the critical ratio.
Filament Misalignment and Composite Strength
Authors: Claus WD
Published: March 2009

The effect of random filament misalignment on the strength of a unidirectionally reinforced composite is investigated. The bundle strength theory of parallel, noninteracting filaments, which many composite tensile strength theories incorporate as a starting point, is reviewed. The bundle strength theory is then extended to include random filament misalignment. The tensile strength of a unidirectional composite with misaligned filaments is discussed. It is concluded that filament misalignment, at least to that degree which may reasonably arise during composite fabrication, is much less detrimental to composite tensile strength than a distribution of filament breaking strains. Application of random filament misalignment to composite shear strength is discussed and forms a basis for a partial explanation of the observed higher shear strengths of composites made from graphite tow rather than graphite yarn.
Tensile Behavior of Bead Filled Composites
Authors: Nicolais L , Narkis M , Lavengood RE
Published: March 2009

The tensile behavior of styrene acrylonitrile composites filled with glass beads is investigated from room temperature to 30 deg above the glass transition temperature. A linearizing transformation is developed for stress relaxation data taken above the glass transition temperature, and a technique is presented which permits shifting of stress-strain curves so that a master curve independent of filler content is formed. In the glassy region, annealing alters the shape of the stress-strain curve, although the yield stress of these systems is unaffected. A model is presented to account for the effect of filler content on yield stress below Tg, and an equation is developed which shows the functional relationship between yield stress, filler content, strain rate, and temperature.
Symposium on Bituminous Waterproofing and Roofing Materials
Authors: Committee D-8
Published: March 2009

Description

This symposium stimulates the interest of those concerned with waterproofing and roofing bituminous. Eight papers are included
Chapter 7—The Utility Industry and Reactor Surveillance
Authors: Jenkins RB
Published: March 2009

Every commercial nuclear power reactor pressure vessel (RPV) is required to have a reactor vessel surveillance program at the time of plant licensing. The program is part of a continuing structural integrity assessment of the RPV. As such, the surveillance program supplements Section III of the American Society of Mechanical Engineers (ASME) Code [1],1 which is the design basis for nuclear power plant component pressure boundaries. The Code assumes that the materials of construction are ductile in the evaluation and design of all components. The surveillance program for each RPV is intended to provide assurance of continued applicability of the ASME Code, Appendix G, assessment of that RPV's operating limits. This assessment ensures that the RPV is always in a condition which precludes the unstable propagation of flaws in the vessel wall material.
Symposium on Fire Test Methods
Authors: ASTM Committee E-5
Published: March 2009

Description

This volume contains four papers related to procedures for conducting fire tests of material used in building construction; a comprehensive survey of testing methods.
A Fractographic Analysis of the Relationships Between Fracture Toughness and Surface Topography in Ultrahigh-Strength Steels
Authors: Spitzig WA , Pellissier GE , Beachem CD , Brothers AJ , Hill M , Warke WR
Published: March 2009

Fracture surfaces of fatigue precracked, notched tension test specimens of experimental oil quenched and tempered (800 F)0.45C-Ni-Cr-Mo steels of different residual sulfur contents, and of two 18Ni maraging steels (250 and 300 grades) were investigated, using electron fractography, by a task group composed of various members of Subcommittee II on Fractography of ASTM Committee E-24 on Fracture Testing of Metals. Sulfur levels of 0.008, 0.016, 0.025, and 0.049 weight per cent in the 0.45C-Ni-Cr-Mo steels corresponded to fracture toughness values (K1c) of 65.3, 55.6, 51.0, and 42.8 ksi√in., respectively. The 250- and 300-grade maraging steels exhibited K1c values of 68 and 42 ksi√in., respectively. The investigation was carried out to determine whether the differences in fracture toughness could be related to changes in fracture surface topography.

The differences in fracture toughness among the quenched-and-tempered 0.45 carbon alloy steels of different residual sulfur contents could be accounted for by differences in the frequency (or spacing) of the sulfide inclusions. These particles seemed to have nucleated microvoids in advance of the crack tip, which coalesced and resulted in dimple rupture. The particle spacing in each steel was equivalent to a process zone size based on the Krafft model. A similar correlation was not found for the two grades of 18Ni maraging steel having different toughness levels, possibly because the mechanism of fracture is more complex than for the 0.45 carbon alloy steels. Another fractographic feature, namely, the extent of a “stretched” zone between the fatigue-cracked and overload regions of the fractures, did appear to show some correlation with the KIc levels for both classes of steels, and may be related to the size of the process or plastic zone at the crack tip. This feature, and its significance in terms of planestrain fracture toughness, is being more extensively investigated by Subcommittee II of E-24.
Environmental Effects on Fracture Morphology
Authors: Nielsen NA
Published: March 2009

The utility of fractography can be greatly increased if the technique can be applied on a broader basis to provide unambiguous interpretation of fracture surface morphology (and thereby, identification of the fracture mode) resulting from specific environmental exposure of stressed metals and alloys.

This paper reviews the present status of electron fractography in this area of expanded application. High-strength steels, martensitic and austenitic alloys, and titanium and zirconium alloys are considered with respect to the effects chemical environment, including high energy irradiation, induces in the fracture characteristics of the alloys.
Effects of the Deep-Sea Environment on Battery Materials and Characteristics
Authors: Work GW
Published: March 2009

Battery materials are subjected to strong acid or alkali and oil in addition to the environmental factors which act on any material immersed in the sea. Glass reinforced epoxy has particular merit as a battery box material. Evaluation of materials for cell cases, compensating oil, and electrolyte de-entrainment devices are discussed and a deep-sea simulating test facility described. Data on deep-sea silver-zinc batteries show that power efficiency increases with pressure, charge acceptance is reduced at lower temperatures, and batteries may be operated satisfactorily to any depth in the sea without a pressure enclosure.
Effects of Hydrostatic Pressures on Electrolytic Hydrogen in Iron
Authors: Nanis L , DeLuccia JJ
Published: March 2009

The permeation of hydrogen in iron under high hydrostatic pressures has been studied using an electrochemical source and sink for hydrogen in a pressurized cell. The drumhead arrangement of the electrochemical cell marks a breakthrough in techniques for the study of corrosion mechanisms under high pressures. Studies on pure iron at 21 C clearly indicate a positive deviation from Sieverts' square root relationship between pressure and hydrogen solubility.

Hydrogen solubility and diffusion coefficient in iron have been determined at pressures up to 8250 psig (18,400 ft depth) in an overall study of hydrogen embrittlement.

The nature of permeation and related electrochemical factors (cathodic overpotential) are considered in terms of anticipated deep submergence corrosion problems.
Effects of Marine Environment on High-Strength Steels
Authors: Wacker GA
Published: March 2009

This investigation summarizes the general and stress-corrosion cracking behavior of several classes of high-strength steels in the marine environment. Eleven experimental heats of maraging steel were evaluated for resistance to stress-corrosion cracking in seawater. Those alloys containing 10 and 12 percent nickel were found to be susceptible to pitting attack and stress-corrosion cracking, while 18 percent nickel maraging steels were found to be highly resistant to pitting attack.

The corrosion characteristics of 5Ni-Cr-Mo-V HY-130 steel were also investigated in natural seawater. The stress corrosion threshold stress for HY-130 was determined utilizing the criteria of no failure after six months of exposure in natural seawater under sustained stress in the precracked cantilever test. A major portion of the investigative work was concentrated on answering the question of whether long-term continuous cathodic protection of HY-130 in natural seawater will lead to eventual problems associated with hydrogen embrittlement. Preliminary work utilized precracked cantilever specimens, which were precharged with hydrogen at several high-current density levels and then step loaded to failure while still being cathodically protected. Cathodic protection tests were also carried out utilizing two-point loaded bent-beam specimens stressed to 90 percent of the 0.2 percent yield strength which were cathodically protected at 13 and 130 mA/ft2 current densities for one year in low-velocity flowing seawater. The effect of cathodic protection on the low-cycle corrosion fatigue behavior of HY-130 was also determined.
Aluminaut — Three Years Later
Authors: Lindberg RI
Published: March 2009

The Aluminaut used aluminum alloy 7079 forgings, although this alloy is not particularly corrosion resistant. Corrosion control utilized a combination of protective coating and cathodic protection. The coating used was a four-coat polyurethane system applied over metal that was sandblasted and given a chromate conversion coating. Cathodic protection was obtained from the use of aluminum alloy 606 anodes. The exo-structure is free flooding and made of light gage 5083 alloy. Several areas of this noncritical structure have been bared, without corrosion occurring; indeed, so successful has the anode system been that all additional metal, such as light booms and camera mounts, are being left bare.
Influence of a Synthetic Seawater Environment on the Fracture Behavior of HP 9-4-25 and HP 9-4-20 Alloy Steels
Authors: Clark WG , Wessel ET
Published: March 2009

The influence of a synthetic seawater environment upon the crack-notch fracture characteristics of 180-ksi yield strength HP 9-4-25 and HP 9-4-20 alloy steels was investigated and the results presented in terms of the stress intensity fracture toughness parameter. Data were generated in both air and seawater under rising-load tension, short-time (½ h) sustained tension, and tension-tension cyclic loading conditions with 2-in.-thick wedge-opening-loading crack toughness specimens. Results show that a synthetic seawater environment does not influence the rising-load or short-time sustained loading fracture characteristics of either alloy. In addition, no significant difference in fatigue crack growth rate was observed for the HP 9-4-25 alloy tested in air and seawater. Limited data for the HP 9-4-20 alloy indicate that the fatigue crack growth rate in seawater exceeds that in air. However, the fatigue crack growth rate for HP 9-4-20 in seawater was equivalent to that observed for HP 9-4-25 in air. In view of the higher toughness and comparable resistance to fatigue crack growth, HP 9-4-20 steel appears more attractive than HP 9-4-25 for hydrospace structures.
Aluminum Alloys After Five Years in Seawater
Authors: Ailor WH
Published: March 2009

Eight aluminum alloys and panels of high-purity aluminum were exposed for five years in seawater at Harbor Island, N. C. Replicate 4 by 12-in. panels of each material were exposed in half-tide immersion and full immersion. Removals in triplicate were made at the end of one-, two-, and five-year exposures.

Other than the 1199 aluminum (99.99 percent purity), seven aluminum-magnesium alloys (5000 series) and one aluminum-zinc-magnesium-copper alloy 7079 were tested. Panels were degreased prior to exposure and were cleaned ultrasonically in a chromic-phosphoric acid solution after exposure. After depth of pitting was measured, tension specimens were cut from each panel, and the ultimate tensile and yield strengths and elongations were determined. All panels were heavily fouled with barnacles and other marine growth for all exposure periods. The fouling apparently had some effect on the pitting depth of the aluminum in tidal immersion.

Little change in tensile properties after five-years' exposure was noted for the 1199, 5083-O, 5086-O, or 5454-H32. Tensile losses were recorded for several alloys as follows: 5086-H112 (4.8%), 5154-H38 (6.2%), and 5457-H34 (4.3%). The high-purity 1199 and alloys 5154-H38, 5086-H112, and 5456-H321 showed losses of 6 to 10 percent in elongation while the change in elongation for the 5457-H34 was a decrease of about 16 percent.

The 7079-T6, which can only be used in seawater when protected, had severe exfoliation corrosion. Confirming other work, we found the corrosion rates to be greater for the full-seawater immersion than for the tidal immersion. The lowest five-year corrosion rate in the half-tide location was 0.07 mdd (milligrams per square decimeter per day) for the 5083-O, and the highest rate for the aluminum-magnesium 5000 series was 0.11 mdd for the 5454-H32 alloy. In full-immersion tests the lowest rate was 0.12. For comparison, the rates for the 7079-T6 alloy were 0.79 mdd in tidal and 3.4 mdd in full immersion. Corrosion weight losses and depth of pitting had reduced rates of growth over the interval between two years and five years. Maximum depth of pitting for an alloy was generally at least four times the magnitude of the average of the twenty deepest pits.

The deepest pit found for any alloy after five years was 33.0 mils for 5456-H321 in half-tide immersion and 38.0 mils for the same alloy in full immersion. Least pitting depth occurred in 5457-H34 (less than 4.5 mils for both exposures).
Microbes and Microorganics in Water—A Review
Authors: Tallon GR
Published: March 2009

Biological degradation in a stream is a highly complex, “assembly-line” process. Most water-borne organics are consumed by microbes, but some substances may persist for long periods. Sources of refractory compounds may be industrial wastes, sewage plant discharges, land drainage, and even metabolic residues from microbial degradation of pollutants. Separation and identification of trace organics is an extremely difficult process requiring the most refined and sophisticated analytical methods. Increasing reuse of surface waters will require more surveillance and new approaches in water management.
Analysis for Organic Pesticides in Aquatic Environments
Authors: Faust SD , Suffet IH
Published: March 2009

The detection of organic pesticides in aquatic environments represents an unique analytical problem. It is unique in the context that specificity is required under extremely sensitive conditions as opposed to gross analysis for trace organics in water. First, there is the problem of pesticide identity. Second, direct measurement is not feasible because of sensitivity and specificity requirements. Extraction, concentration, and cleanup techniques must be employed prior to qualitative analysis and quantification. Third, natural waters may contain such organic interferences as aromatic and aliphatic compounds from industrial waste waters, and naturally occurring colored compounds. These impurities are often present in concentrations greater than the pesticide.

Two objectives are offered herein: (1) a brief critique of extraction, cleanup, identification, and quantification techniques is given in order to highlight limitations fallacies, and pitfalls, and (2) a model system for the recovery, separation, and confirmation of organophosphate pesticides, oxons, and their hydrolysis products. This model system provides the basic needs of pesticide methodology; namely, simplicity and minimum sample handling. The problems of recovery from water by liquid-liquid extraction, separation by gas-liquid chromatography, and subsequent confirmation by micro-ultraviolet absorption spectrophotometry are discussed.
Freeze Concentration of Microorganics in Water
Authors: Baker RA
Published: March 2009

Organic contaminants at concentrations of parts per billion or less may modify water quality significantly. However, even the most sensitive of the available analytical procedures are not capable of quantitative identification at these trace levels. Thus, the organics must be concentrated prior to analyses. Freezing was evaluated as a concentration technique. As solute-containing aqueous solutions are frozen, the ice which crystallizes initially is very pure. The solutes are rejected into the unfrozen liquid. If the process is interrupted prior to complete solidification, the residual liquid will be considerably enriched.

Recovery of micrograms per liter and milligrams per liter concentrations of various organics from aqueous solutions was studied. In the absence of dissolved inorganic salts mixing rate is not a factor. Organic dissociation potential; molecular size and weight; and nature, location, and number of substituent groups have no effect. However, dissolved salts impair organic solute rejection and in this case higher mixing rates promote recovery. An interrelationship between total dissolved salt content, mixing rate, and efficiency of organic solute recovery was demonstrated. Most important, for the systems studied, it was shown that although complete organic recovery was not achieved, all components of complex mixtures were recovered with equal efficiency. Thus, an analytical procedure making use of additions of known organic materials to serve as internal standards is suggested.
Noncombustibility: A Marine View
Authors: McDaniel DE
Published: March 2009

The concept of a suitable test procedure for noncombustible materials has long been an elusive one. It appears that a universal consensus of what such a test procedure should accomplish has not yet been achieved. Drawing from a historical base, this paper discusses the characteristics a procedure should embody to be considered suitable for testing shipboard construction materials. Results of recent experiments with various noncombustibility test procedures are discussed and limitations of current procedures are explored. Some criticisms of the concept of noncombustibility are examined and suggestions made for reconciling differences among specific procedures.
The Belgian Point of View on Testing Reaction to Fire of Building Materials
Authors: Minne R
Published: March 2009

Methods standardized in some countries have not withstood critical comparative testing by an international body. After explaining what reaction to fire of a building material really means, the proposed test method is discussed. The necessary equipment as well as the test methodology are described. The necessity for introduction of a reaction to fire index, in which the majority of relevant material properties are included, is explained. Calculation of test data is defined and the reaction to fire indices of a series of materials are given. Reproducibility of the test method seems to be good.
The Crucible Test Method for Defining Noncombustible Materials
Authors: Bellisson G
Published: March 2009

It is observed that in many construction projects, both marine and land based, it has been advantageous to use materials of low combustible content. A modified oxygen bomb calorimetric test method is considered to define the total heat release content of the material. Such a method though suffers by the imposition of combustion processes quite unlike those during a real fire. It is suggested that a test method which only assesses the heat produced by combustion of volatiles can better assess the fire hazards associated with construction materials. The crucible test method for measuring heat content of volatile gases is described and the results of its application to a variety of materials is explored. It is shown that for a variety of mineral and glass wool insulation materials formed with a single binding agent that the heat release per unit weight is linearly related to the loss of weight on heating. For cellulosic materials both in the form of woods and fabrics the volatile heating power is significantly lower than the heat of combustion. Fire retardant treatment of these materials results in a further significant reduction (about 50 percent) in the volatile heating power. A brief exploration of limitations and performance characteristics of the test method are presented. A brief concluding discussion is presented in which it is reported that in France consideration is being given to a limit of 800 J/g as suitable for defining the line of demarcation between combustible materials and those considered noncombustible.
Noncombustibility—Its Definition, Measurement, and Applications
Authors: Herpol GA
Published: March 2009

The long history of the application of the concept “noncombustibility” in the building field was sufficient to justify drafting a recommendation for a noncombustibility test that would serve to define and measure the lack of “reaction to fire” of construction materials. A short description of the ISO noncombustibility test (R 1182) is provided, as well as a critical analysis which discusses its main features in terms of their weaknesses and advantages.
Mechanics of Materials in Low Cycle Fatigue Testing
Authors: Raske DT , Morrow J
Published: March 2009

The purpose of this paper is to outline a method for evaluating the low cycle fatigue resistance of a metal from the mechanics of materials viewpoint. This includes a discussion of the fatigue properties and the effect of repeated plastic straining on the mechanical properties of metals. The cyclic stress-strain curve is defined as the locus of tips of several stable hysteresis loops obtained at different cyclic strain ranges. An expression is presented for mathematically representing the locus of their tips, and a number of experimental methods are discussed for determining the stable cyclic stress-strain properties.

Experimental techniques for low cycle fatigue testing and methods of interpreting results are presented. The equations which relate the elastic and plastic components of cyclic strain amplitude to fatigue life are developed. A means of approximating the strain-life curve using these relations is presented.
Basic Research on the Cyclic Deformation and Fracture Behavior of Materials
Authors: Feltner CE , Mitchell MR
Published: March 2009

This paper describes the experimental methods that we employ for low cycle fatigue studies. Techniques associated with two test systems, an MTS system and an Instron machine, are described. In particular, the following subjects are treated: principles underlying low cycle fatigue testing; load frames, load cells, and load applying devices; design of specimens; specimen gripping methods; measurement of strain; selection of test program; strain control during a test; recording of data; determination of failure; analysis, reduction, and presentation of test results; and metallographic techniques associated with low cycle fatigue testing.
Engineering Materials Evaluation by Reversed Bending
Authors: Gross MR
Published: March 2009

A method for conducting low cycle fatigue tests by reversed bending is described. The advantages of bend (flexure) testing lie in its simplicity, specimen stability at high strain levels, and minimal equipment costs. Description of the method includes (1) types of specimens, (2) equipment construction and operation, (3) stress and strain measurements, and (4) data output, presentation, and analysis.
Sources of Fracture Toughness: The Relation Between KIc and the Ordinary Tensile Properties of Metals
Authors: Hahn GT , Rosenfield AR
Published: March 2009

This paper examines crack extension from a metallurgical standpoint. Stress and strain intensification at the crack tip and the basic flow and fracture properties of the material are considered. Insights derived from etchpitting experiments are reviewed. These reveal the two characteristic types of local yielding: (1) plane strain or “hinge-type” relaxation and (2) plane stress or through-the-thickness relaxation. Two simplified elastic-plastic treatments that model plane strain and plane stress are identified. They offer approximate equations connecting K (the stress intensity parameter) with the plastic zone size and the crack-tip displacement, which are in good accord with experiment. They also help to define limiting conditions for plane strain and plane stress. A method of relating the crack-tip displacement to the peak strain is described, and this is combined with a critical strain criterion for ductile fracture. In this way, the plane strain fracture toughness parameter KIc is formulated in terms of ordinary tensile properties: KIc≈23EYn2ϵ¯* (E is the modulus, Y the yield stress, n the strain hardening exponent, and ε-* the true strain at fracture of a smooth tensile bar). This expression is shown to be in good accord with available data on a variety of titanium, aluminum, and steel alloys. Since the influence of composition and heat treatment on tensile properties is already established in many cases, the tensile properties can now serve as a link between fracture toughness and the backlog of metallurgical experience. This possibility is demonstrated for Type 4340 steel heat treated to different strength levels.
A Review of Factors Influencing the Crack Tolerance of Titanium Alloys
Authors: Shannon JL , Brown WF
Published: March 2009

The paper reviews a number of factors which influence the crack tolerance of titanium alloys, particularly those which are generally encountered in the application of titanium alloys to aerospace hardware. Among these factors are cryogenic temperatures, heat treatment, interstitial element content, elevated temperature exposure, cold working, and aggressive environments. In addition a discussion of plane strain fracture toughness data for titanium alloys is given.
Toughness of Two-Phase 6Al-4V Titanium Microstructures
Authors: Gerberich WW , Baker GS
Published: March 2009

A duplex heat treatment which provides different shapes, sizes, and volume fractions of alpha platelets in 6Al-4V titanium is presented. It is shown that a 40 per cent increase in fracture toughness may be attained without any significant decrease in yield or ultimate strength. With respect to toughness, critical aspects of both the interstitial oxygen content and the shape, size, and spacing of the alpha phase are discussed. Metallographic and fractographic evidence supports the contention that the second-phase alpha in platelet form acts as a crack arrestor and causes a deviation in the crack path, resulting in additional energy absorption. A tentative hypothesis for fracture in two-phase microstructures is presented based upon the theoretical crack tip displacement. Preliminary evidence indicated that the critical toughness, size, and spacing of the second phase may all be related to the crack tip displacement concept.