bluuebunny/crossref_metadata_2025 huggingface dataset:
Book Reviews
Authors: Sullivan Graeme , Houghton Nicholas
Published: March 2009

Thinking Through Art: Reflections on Art as Research, Katy Macleod and Lin Holdridge (eds), (2006) London and New York: Routledge, 256 pp., ISBN 0415364779 (hbk), US$120

Hornsey 1968: The Art School Revolution, Lisa Tickner, (2008) London: Francis
Lincoln, 203 pp., ISBN 139780711228740 (pbk), 12.99
Use of a Downhole Block Sampler for Very Soft Organic Soils
Authors: Long M
Published: March 2009

Techniques required to successfully obtain downhole block samples of typical very soft high plasticity organic clay from Ireland are described. The vane shear strength of the material is as low as 4 kPa. These included using a sampler penetration rate three times faster than normally adopted. Comparisons are made between the results of laboratory tests on Sherbrooke block samples, on two fixed piston tube samplers, and on a continuous sampler. In addition idealized tube sampling strains were imposed on block sample specimens prior to shearing (ideal sampling approach). Both approaches confirmed that the material studied could not survive tube sampling undamaged, unlike the findings of a recent study in the Netherlands on Dutch organic soil. Tube sampling was found to have a more significant effect on triaxial test parameters that on those from the one-dimensional compression testing, where the behavior of the block sample specimens and those from one of the two tube samplers were similar to in situ response. Increasing levels of disturbance were associated with progressively more dilatant behavior.
Sample Preparation of Silts for Liquefaction Testing
Authors: Bradshaw A. S. , Baxter C. D. P.
Published: March 2009

One of the most important aspects of cyclic testing in the laboratory is using samples that are representative of their in-situ conditions. Since undisturbed samples of cohesionless soils are typically too difficult or costly to obtain, reconstituted samples need to be prepared using a method that most closely replicates the in-situ stress, density, and fabric. Research has clearly shown the effect of sample preparation methods on the liquefaction resistance of sands, and it is believed that wet pluviation methods most closely approximate the in-situ fabric of fluvial soils. For pure silts, however, these methods are limited because only very loose samples can be made. This paper introduces a new modified moist tamping method that can be used to reconstitute denser specimens of silt. It was found that samples tamped at an initial saturation level of about 55 % gave comparable cyclic strengths to samples prepared from a slurry and to specimens trimmed from an in-situ block sample. The method can be considered a cost-effective alternative for the liquefaction testing of silts.
Evaluation of Quasi-Elastic Properties of Gravel Using a Large-Scale True Triaxial Apparatus
Authors: AnhDan LQ , Koseki J , Sato T
Published: March 2009

In order to investigate the anisotropy in the deformation characteristics of gravel, a large-scale true triaxial apparatus that can control three principal stresses independently has been newly developed. One of the two horizontal stresses is applied by means of rigid vertical platens that confine the specimen, to induce a uniform horizontal strain over the height of the specimen in that one direction. A set of local deformation transducers and proximity transducers are used to measure strains to minimize the effects of specimen corners, bedding error, and system compliance. Specimens have a prismatic rectangular shape with dimensions of 50 cm high and 25 cm × 22 cm in cross section. Using this apparatus, a couple of tests were conducted on gravel specimens prepared by manual compaction at a water content of 5.5% to reach dry densities of 2.0 and 2.2 g/cm3. At several stress states, during isotropic compression and subsequent triaxial loading, vertical and horizontal loading cycles of a very small stress amplitude were applied to evaluate the quasi-elastic deformation properties. The test results show that the small-strain quasi-elastic Young's modulus in a given direction is essentially a unique function of the normal stress in the same direction, regardless of the density of the specimen. Although this is contrary to some of the well-established models used in practice, it is consistent with results of relevant laboratory tests by others. Small-strain quasi-elastic vertical and horizontal Young's moduli exhibited effects of inherent and stress state-induced anisotropies. Performing cyclic loading tests of successively increased the stress amplitude, strain-level dependency of the equivalent Young's modulus and hysteretic damping ratio in both the vertical and horizontal directions was obtained.
Consolidation Characteristics and Undrained Strength of Saturated Soft Clay under Repeated Impact Loading
Authors: Bai B
Published: March 2009

The consolidation characteristics of saturated soft clay under repeated impact loading are studied by laboratory tests. Particularly, the influence of drainage conditions on consolidation and reconsolidation of soft clay are analyzed in detail. The uniqueness of the relationship between pore water pressure and reconsolidation volumetric strain is described, and the methods for determining the coefficient of reconsolidation volume compressibility and the reconsolidation compression index are given. It is demonstrated that the samples undergoing several stages of impact and reconsolidation show an apparent quasi-overconsolidation state, and have an increased shear strength. Models for predicting the deformation and the undrained strength of soft clay foundation from impact loading are also suggested. In the models, the conditions of partial drainage and stages of impact are taken into account. Calculated results by the present models are in good agreement with the test data.
Design of a Miniature Piezoprobe for High Resolution Stratigraphic Profiling
Authors: DeJong Jason T. , Yafrate Nicholas J. , DeGroot Don J.
Published: March 2009

The stratigraphic features present in all natural deposits, which reflect their deposition environment, can significantly influence the response of these deposits to engineered construction. This paper presents the development of a miniature piezoprobe optimized for the continuous detection of stratigraphic features within a varved soil deposit where individual layers are less than one centimetre in thickness. The study uses previous research to identify parameters in the design of a field-deployable miniature piezoprobe and to present a framework that enables stratigraphic detection from pore pressure measurements. Laboratory experiments on the ability of fluids to saturate the filter and the influence of the fluid-filter system on piezoprobe sensitivity reveal that low to moderate viscosity immiscible fluids (e.g., 100 cS silicone oil) provide optimal performance considering practical implementation aspects. Laboratory and field studies that examine the soil deformation characteristics within the vicinity of such probes indicate that an apex filter location is preferable for stratigraphic detection and that soil deformations around the probe are primarily limited to less than one probe radii. Proof of concept results from an in situ profile obtained with the miniature piezoprobe compares well with measurements from a continuous core sample from a Connecticut Valley varved clay deposit.
An In-situ Device for Rapid Determination of Permeability for Granular Bases
Authors: White David J. , Vennapusa Pavana K. R. , Suleiman Muhannad T. , Jahren Charles T.
Published: March 2009

This paper describes a new in-situ Air Permeameter Test (APT) device developed for estimating the hydraulic conductivity of drainable granular base materials. The device is assembled from commonly available components including air flow meters and differential pressure gages. Using prescribed air flow and pressure measurements from the APT, a theoretical relationship is derived to calculate the saturated hydraulic conductivity. The geometric factors for the device, sample boundary conditions, partial saturation, compressibility and viscosity of the permeant fluid (i.e. air), and the Brooks-Corey pore size distribution index are considered in the derivation. Attempts at correlating in-situ APT calculated hydraulic conductivity values for compacted granular base materials to hydraulic conductivity values from reconstituted laboratory compaction mold permeability tests show that the in-situ values are generally higher and more variable. The in-situ variability is attributed to segregation and is shown to be spatially correlated to the fines content (passing No. 200 sieve).
Interpretation of Pressuremeter Results for Design of a Diaphragm Wall
Authors: Monnet J , Allagnat D
Published: March 2009

The usual way to use a pressuremeter device is to measure a pressuremeter modulus, which is correlated with the elastic modulus, and a limit pressure, which is used to find the bearing capacity of the foundation. We present a new interpretation of the pressuremeter test, which allows the measurement of the elastic shear modulus by the application of an unload-reload sequence in the experimental pressuremeter process and the determination of the angle of internal friction for granular soil by the application of an elasto-plastic theory. This new method is accurate and validates the use of the pressuremeter tests for the mechanical characteristics determination, for slope stability analysis, retaining wall and tunnel design. It is used in this paper for the design of a diaphragm wall of Lyon underground.
Determination of Maximum and Minimum Densities of Poorly Graded Sands Using a Simplified Method
Authors: Muszynski MR
Published: March 2009

Evaluation of maximum and minimum (limit) density values of sands is important in geotechnical engineering. Limit density values are important physical properties needed to provide a more complete description of sands, and they are required when evaluating relative density of soils. The conventional methods for determination of limit densities are generally costly, require relatively large sample volumes, and are time consuming. A simplified method for determining limit densities of clean poorly graded fine to medium sands was developed. The simplified method is easy to perform, requires less sample volume, and is faster than the conventional methods for determining these properties. Results of this study indicate that the simplified method gives limit density values comparable to those obtained using conventional methods for clean poorly graded fine to medium sands. Limitations of the simplified method are discussed.
Evaluation of Ultrasonic Testing in Rock Material Characterization
Authors: Basu A , Aydin A
Published: March 2009

Although ultrasonic testing is simple and nondestructive, its potential has not yet been fully utilized in rock material characterization because the experimental setup and the methodology adopted strongly influence the characteristics of the ultrasonic beam, and hence the resultant ultrasonic velocity of the specimen under investigation. This paper focuses on the importance of the selection and use of ultrasonic wave transducers in rock material characterization. It illustrates both theoretically and experimentally how different transducer parameters control the efficiency of ultrasonic velocity as an indicator of microfabric changes. The study reveals that the existing standards do not provide sufficient and/or practical guidelines on a number of issues, and calls for consideration of the proposed modifications.
A New Laboratory Apparatus for Grout Injection Studies
Authors: Alfred Au SK , Soga K , Yeung AT
Published: March 2009

The design, fabrication, and assembly of a new laboratory apparatus for the investigation of fundamental behavior of compaction grouting and fracture grouting are presented in this paper. Clayey soil specimens of different overconsolidation ratios can be prepared to study the grout deformation pattern, fracture pattern, and consolidation behavior of soil induced by grout injection as a function of operating parameters. Ideal compacting grouting is replicated by expanding a latex balloon placed within the soil specimen and fracture grouting by injecting epoxy resin or high water content cement bentonite grout into the soil specimen. Moreover, the apparatus can accommodate multiple-point grout injection experiments to examine the behavior of grout interactions. Illustrative results are also presented in the paper.
Centrifuge Seismic Modeling of Pile-Supported Wharves
Authors: McCullough Nason J. , Dickenson Stephen E. , Schlechter Scott M. , Boland Jonathan C.
Published: March 2009

Five pile-supported wharf models were dynamically tested in a large-scale geotechnical centrifuge at UC Davis, California. Models representing pile-supported wharf configurations common in the United States were subjected to recorded acceleration time histories. Model variations included single-lift, multi-lift, and cut-slope rock dike configurations with foundation layers of loose liquefiable sand, marine clay, or dense sand, or a combination thereof. In addition, zones of soil were placed to model soil improvement. Structural elements representing pile-supported wharf geometries were placed within the models; some models included all vertical piles, while two of the models included batter piles. In addition, single piles were placed in two of the models and subjected to static cyclic lateral load tests. All models were extensively instrumented with nearly 100 instruments recording accelerations, pore pressures, linear deformations, and pile strains. This paper summarizes the design, construction, and testing of these complex models, and includes a brief summary of the results and recommendations for future modeling.
Shear Strength of Degraded Reconsitituted Municipal Solid Waste
Authors: Harris JM , Shafer AL , DeGroff W , Hater GR , Gabr M , Barlaz MA
Published: March 2009

Relative changes in Waste shear strength parameters as a function of strain level and stress path are investigated based on the results of 16 direct simple shear (DSS) tests, one direct shear (DS) test with four stages, and three triaxial tests. The magnitudes of shear strength parameters obtained from drained DSS tests and undrained DSS tests with pore water pressure measurement were comparable. This was the case even though the effective stress path in both approaches was different. Data indicated the dependency of the mobilized strength parameters on strain, or deformation level. Generally, stress-deformation response increased monotonically with no well defined peak or ultimate stress levels. The results of the DSS and DS tests show no dependency of the strength parameters on the stress level. Results from DSS and DS indicated a range of effective strength parameters of 9 to 14 kPa for cohesion and 23°–29° for friction angle. Data from the triaxial testing showed dependency of the shear strength parameters on the initial compression stress level. Given the number of potentially confounding issues associated with the measurement of shear strength, it is rather important to also report information on sample collection methods, sample age and chemical composition, sample processing, sample composition, the size of testing equipment and level of strain (instead of ultimate or peak) at which the strength parameters are evaluated.
Development of TDR Penetrometer Through Theoretical and Laboratory Investigations: 1. Measurement of Soil Dielectric Permittivity
Authors: Lin CP , Tang SH , Chung CC
Published: March 2009

To better characterize a bulk soil electrically, both the electrical conductivity and dielectric permittivity should be measured. This study developed a time domain reflectometry (TDR) penetrometer to allow simultaneous measurements of dielectric permittivity and electrical conductivity during cone penetration. A TDR penetrometer is formed by placing a multiple-conductor waveguide around a nonconducting shaft. Probe design considerations and calibration methods for measuring dielectric constant were first theoretically discussed and then evaluated through laboratory investigations. A prototype TDR penetrometer was fabricated and used to perform simulated penetration tests in a calibration chamber. The effect of penetration disturbance on dielectric constant is quantitatively reported and explained. The implications of the data that can be measured by the TDR penetrometer are also discussed.
The Filter Paper Method Revisited
Authors: Marinho FAM , Oliveira OM
Published: March 2009

The calibration curve for any device or method to infer suction is the most important characteristic to evaluate for reliable measurement to be obtained. Some published literature (e.g. Houston et al. 1994; Bulut et al. 2001; Leong et al. 2002) have presented results in which the calibration for the filter paper method is not unique in relation to the type of suction (i.e., total or matric). A review of the data from the literature is presented, together with data showing the reason that justifies a unique calibration curve for the filter paper. It is also shown that it is necessary to check the calibration curve by performing a quick calibration check. A procedure for calibrating the filter paper for this check is given. Fundamental matters necessary for understanding the concept on which the filter paper method is based are also presented.
Selection and Use of Engine Coolants and Cooling System Chemicals
Authors: Committee D-15
Published: March 2009

Description

The purpose of this publication is to provide practical information and advice on engine coolants as well as cooling system chemicals, such as cleaning compounds, antirusts, and stop-leaks. The references to cooling system services are confined to the practices directly affecting coolants, since the subject of general cooling system maintenance is already covered in published automotive literature.
Some Aspects of Quantitative Surface Analysis by Electron Spectroscopy for Chemical Analysis
Authors: Phillips LV , Salvati L , Carter WJ , Hercules DM
Published: March 2009

Application of surface-sensitive spectroscopic techniques to quantitative surface analysis requires consideration of the distribution of species on the surface, as well as the characteristics of the technique. For electron spectroscopy for chemical analysis (ESCA), these problems are considered for the following situations: material adsorbed on a surface at less than monolayer coverage, a thin film of surface species overlaying the bulk, a sample distributed throughout the bulk in an inhomogeneous fashion, and a multilayered system.

Escape depth of photoelectrons becomes a particularly important parameter when comparing results of ESCA with those obtained by other techniques, such as Auger electron spectroscopy (AES). Different atomic ratios can be obtained from the same sample depending on the energies of electrons used.

ESCA can be used for trace analysis by preconcentrating metal ions on surface. The effectiveness of this technique depends on the equilibrium between the surface and solution. The form of the calibration curve obtained is influenced by “saturation” effects. The kinetics of the surface-solution equilibrium are also important.
Quantitative Comparison of the Doubly Integrated KLL Auger Spectra of Magnesium, Aluminum, and Silicon with Their Oxides
Authors: Springer RW , Haas TW , Grant JT
Published: March 2009

Integrals, over selected electron energies, E, of magnesium, aluminum, and silicon KLL Auger spectra of magnesium, aluminum, silicon, and their oxides have been measured directly using tailored modulation techniques. The ratios of Auger currents, I(E), measured in this way from the metals and their respective oxides have been determined and are compared with the corresponding atomic densities of magnesium, aluminum, and silicon in the metals and their oxides. It has been found that, if the I(E) are measured over only the quasi-elastic KL2,3L2,3 Auger peaks, the ratios obtained agree quite well with the atomic densities, whereas, if the I(E) are measured over larger energy ranges, thereby encompassing peaks due to plasmon losses, the agreement is rather poor. This poor agreement is probably due to the quite different inelastic loss mechanisms that occur for the metals and their oxides.
In Situ Auger Electron Spectroscopy Tensile Fracture Study of Nickel Alloys
Authors: Walsh JM , Gumz KP , Anderson NP
Published: March 2009

An elevated temperature tensile fracture device has been built for in situ Auger electron spectroscopy studies that permits characterization of grain boundary chemistry of high-temperature structural materials. The system has been applied to a series of commercial nickel-base superalloys doped with impurities known to have deleterious effects on the mechanical properties. Clear grain boundary segregation of the elements bismuth, tellurium, lead, and sulfur has been observed confirming that the elements most harmful to the mechanical properties of superalloys are also those that are grain boundary active. The additive hafnium was found to be effective in restricting the grain boundary segregation of sulfur by combining with sulfur to form a stable carbosulfide compound.
Electron Spectroscopy for Chemical Analysis Examination of Rare Earth and Near Rare Earth Species
Authors: Barr TL
Published: March 2009

A detailed electron spectroscopy for chemical analysis (ESCA) examination has been performed on a series of very pure rare earth foils, powders, and a sputter-deposited thin film consisting of yttria doped ceria. The foils were studied with their natural passivation layer intact and also sputter etched to provide approximate chemical profiles. The metals examined were cerium, lanthanum, and yttrium. The ESCA spectra of all of the passivated metals experienced charge shifts. Treatment of those shifts with an electron flood gun is an integral part of this study.

A semiquantitative analysis of the passivation layer of cerium establishes that the outer mantle is a mixed oxide-hydroxide Ce(IV) system, whereas the inner layers of the oxidative growth are initially mixed oxide-hydroxide Ce(III) systems and finally (close to the virgin metal) a substance believed to be Ce(III)2O3 is exposed. This is the first ESCA spectral analysis of the sesquioxide. Interestingly, sputter etching the ceric oxide/yttrium oxide (CeO2/Y2O3 film results in a nearly identical chemical development, indicating that some of these results may occur because of sputter reduction. The lanthanum and yttrium systems also display evidence of hydroxide formation on their outer (passivation) surfaces. A unique species which may be La(II)O is detected after sputtering into the passivation layer of lanthanum. The yttrium spectra for the CeO2/Y2O3 film exhibit superior resolution compared to that for the yttrium foil. A discussion of the satellite structure of these spectra is included.
Quantitative Analysis of Alloys and Thin Films Using Ion Scattering Spectroscopy
Authors: Baun WL
Published: March 2009

Some problems concerning the quantitative analysis of surfaces originate with the surface itself due to chemical inhomogeneity, roughness, selective diffusion, and grain boundary segregation. Therefore, it is difficult to prepare surface standards. Two choices exist. Either well-characterized bulk standards are used or analysis is done only using elemental standards. Many problems also exist with the various methods of surface analysis such as selective sputtering, surface decomposition, changing ion or electron yields and variable or unknown sampling depths. Ion scattering spectroscopy (ISS) appears to require fewer corrections than most techniques because of its high sensitivity and selectivity to surface species. ISS used with either elemental or alloy standards and the equilibrium sputtered surface concept provides a rapid and reproducible method for surface analysis.
Surface Analysis of Polymer and Glass
Authors: Sparrow GR , Mismash HE
Published: March 2009

The unique physical nature of glass results in numerous surface phenomena which have long been unexplained due to difficulties experienced by analytical chemists undertaking their study. Modern, sophisticated surface analysis instrumentation now permits analysis of surfaces from the top monolayer into the bulk material.

Detailed studies of glass surfaces provide the information necessary to understand how common cleaning, polishing, etching, and heat treatments affect the chemistry and properties of glass. Similar information obtained from studies of the first 30Å of treated polymers contributes to the understanding and explanation of their properties such as those related to oxidation, degradation, reflectance, hardness, and especially adhesion. The primary objective achieved through detailed surface analysis of the treated polymers was the knowledge necessary to develop better adhesion to polymers.

Problems inherent in surface analysis of glass and polymers relate to their physical nature. Their surfaces are highly subject to ion migrations which are disconcerting to the analyst. The nonconductive or electrical insulating property defeats many instrumental methods of analysis. Combined high-performance ion scattering spectrometer (ISS), utilizing a recently developed cylindrical mirror analyzer (CMA), and a secondary ion mass spectrometer (SIMS) were used in these studies. The system was also equipped with a charge neutralization system and an automatic high-speed data processing device. Common soda lime glass was subjected to treatment by chromic acid, alcoholic potassium hydroxide (KOH), hydrogen fluoride (HF) vapor, and HF bath, and studied from the top monolayer to several hundred angstroms. Zirconium polished glass and various heat-treated glasses were studied similarly. Results were compared to analysis of the surface and bulk of untreated glass. A commercial polyimide, Kapton, cleaned by acid, base, solvents, and various drying techniques was surface analyzed. Surface information was correlated with original and residual contaminants and thin film bondability.

Results indicated that most glasses are normally surface rich in sodium from 0 to about 30Å, but chemical cleaning by chromic acid, KOH, and HF vapor removes surface sodium, leaving a surface of primarily silica only. Heat treatment caused extensive concentration changes to several thousand Å. The surface carbon, nitrogen, and oxygen concentrations of a polyimide were substantially altered by simple cleaning treatments to about 30Å. However, the surface exhibiting greatest bondability of coated aluminum showed minimum contaminations due to metal such as sodium, magnesium, aluminum, silicon, potassium, calcium, and fluorine. The combined results illustrate that the extensive surface information available through modern analytical instrumentation contributes substantially toward understanding and controlling surface phenomenon not previously explained.
Secondary Ion Mass Spectrometry and Auger Electron Spectroscopy Semiquantitative Analysis of Metal Alloys
Authors: Davis LE , Gerlach RL
Published: March 2009

Secondary ion mass spectroscopy (SIMS) and Auger electron spectroscopy (AES) data were obtained for metal alloys of known bulk composition. The measurements were made from the same surface regions of the alloys and then compared to measurements of elemental standards to facilitate quantitative analysis. The SIMS data were obtained with and without a residual oxygen base pressure to investigate the role of oxygen enhancement in determining surface composition. Compositions of a nimonic and lead-bronze alloy as determined by AES and SIMS were compared and the differences discussed in terms of secondary ion yields and sputtering effects.
Development of High Fracture Toughness Titanium Alloys
Authors: Williams JC , Froes FH , Chesnutt JC , Rhodes CG , Berryman RG
Published: March 2009

This paper describes the relationship between composition, processing history, and microstructure of a series of α + β and metastable β titanium alloys. The relation between a wide range of microstructures and the resulting properties of these alloys has been investigated by making extensive use of electron fractography and metallographic fracture path determinations. These results were obtained in connection with an alloy development program in which two alloy compositions ultimately were selected: Ti-5Mo-4.5A1-1.5Cr and Ti-8Mo-2.5A1-4.5Cr. These alloys were processed according to various schedules in order to achieve microstructures which produce good strength-toughness combinations. In the α + β alloy (Ti-5Mo-4.5A1-1.5Cr), the optimum property combinations were achieved in β-processed material which has an acicular microstructure and α-phase at prior β-grain boundaries, although excellent properties also were obtained in equiaxed α + β processed material. In the metastable β-alloy (Ti-8Mo-2.5A1-4.5Cr), significantly better strength-toughness combinations were achieved in α + β processed material which contains globular primary α, compared to β-processed material which contains grain boundary α. The metastable β-alloy exhibits a significant degree of directionality of properties in all microstructural conditions. It is suggested that such directionality is due to the elongated β-grain structure which causes more crack branching when the crack is propagating in the transverse direction compared to the longitudinal direction. Finally, a model is presented to account for the effect of grain boundary α on fracture toughness of α + β and metastable β alloy.
Relationship of Fracture Toughness and Ductility to Microstructure and Fractographic Features in Advanced Deep Hardenable Titanium Alloys
Authors: Froes FH , Chesnutt JC , Rhodes CG , Williams JC
Published: March 2009

This paper describes the results of a program conducted to develop a metastable β titanium alloy with deep hardening characteristics and with a yield strength of 1165 MPa (170 ksi), a fracture toughness of 66 MPam (60 ksiin), and tensile ductility of 12 percent elongation and 18 percent reduction of area. After a screening study, three compositions were chosen: Ti-10Mo-6Cr-2.5A1 (Alloy 334), Ti-7Mo-4Cr-2.5A1 (Alloy 227), and Ti-10Mo-8V-2.5A1 (Alloy 253). Both β-working and β followed by α-β working were investigated as means of controlling the primary α distribution. Three distinct microstructures were subjected to extensive testing together with microstructural and fractographic analysis. It was found that grain boundary α was detrimental to properties in most cases. Stringered α, resulting from β-working, caused a directionality in mechanical properties with longitudinal values being higher than those in the transverse direction. Lenticular primary α was generally beneficial to toughness, whereas equiaxed or globular primary α was beneficial to tensile ductility. The predominant role of secondary (aged) α was in influencing strength level. The causes for these property variations with α phase morphology were analyzed using metallographic fracture face profiling and scanning electron fractography. It was found that the α-β interfaces initiate fracture and thus have a large influence on fracture related properties. Finally, the properties of the three metastable β alloys were compared to those of high strength, deep hardening α/β alloys. More attractive strength-toughness combinations are achievable in the metastable β alloys. The tensile ductilities of the α-β alloys were somewhat higher than those of the metastable β alloys. However, ductilities of the latter class of alloys were acceptable.
Analysis of Local Stresses and Strains in Ti-6A1-4V Widmanstätten α + β Microstructures
Authors: Smelser RE , Swedlow JL , Williams JC
Published: March 2009

The application of continuum mechanics to the analysis of fracture in structural materials has been helpful in understanding macroscopic behavior in these materials. However, in many classes of structural material, among these titanium alloys, microstructure has been shown to have an effect on fracture even under circumstances of constant yield stress. In such instances, macroscopic continuum mechanics are of limited value since no microstructural scale variations in stress and strain are considered. In the present study we have used finite element analysis to calculate variations in local stress and strain distributions on a scale comparable to that of the microstructural features. This paper describes the methods used to make these calculations, illustrates some of the results for one microstructure, and suggests how these results influence our understanding of fracture in two phase microstructures such as those observed in α ∔ β alloys.
Effect of Specimen Width on Fracture Toughness of Ti-6A1-4V Plate
Authors: Hall GS , Seagle SR , Bomberger HB
Published: March 2009

From a group of 96 specimens ranging in thickness from 15 to 38 mm (0.60 to 1.50 in.), a regression equation was obtained for Ti-6A1-4V plate relating the fracture toughness, KQ, of 205-mm (8-in.) wide specimens to the variables of specimen thickness and fracture toughness, KQ, for 76-mm (3-in.) width. The fracture toughness value of Ti-6A1-4V plate can be increased appreciably in thin specimens by using an oversized width specimen. The magnitude of this toughness increase diminishes as the thickness increases and approaches 38-mm (1.5-in.). Oversizing the specimen results in a significant reduction in the stress at instability at 2 percent crack extension. The specimen strength ratio, Rsc, essentially remains the same while Kmax and the Pmax/PQ ratio increase.

Crack-growth-resistance curves constructed from load versus crack-opening-displacement curves for the two different width specimens are similar. This indicates the fracture behavior is the same and not altered with increased specimen width. Furthermore, K values for oversized specimens can be calculated from the loads at the appropriate crack extension in smaller standard size specimens, and vice versa.
Fracture Resistance Characterization of Graphite/Epoxy Composites
Authors: Morris DH , Hahn HT
Published: March 2009

The resistance method has been applied to graphite/epoxy composites. The method is based on the assumption that the damage growth at the crack tip can be modeled as a self-similar crack extension through compliance matching. Experimental data for center-cracked tension specimens reveal a linear relationship between crack-growth resistance and initial crack length. For the [0/±45]s laminate, the effective increment of crack length at fracture and the corresponding crack-growth resistance essentially are independent of initial crack length. The average amount of this crack extension in the [0/±45]2s and [0/±45]s laminates is higher than the values obtained from a best fit of fracture strength data reported in the literature. However, the present method results in an improved prediction of fracture strength for the [0/90/ ±45]s laminate.
An Experimental Study of the Fracture Behavior of Laminated Graphite/Epoxy Composites
Authors: Brinson HF , Yeow YT
Published: March 2009

The results of an experimental investigation on the fracture behavior of unidirectional and multidirectional laminated graphite/epoxy composites is reported. Critical tensile fracture stresses for constant head rate uniaxial specimens containing single-edge notches, double-edge notches, and centrally located circular holes are presented. Results are reported for loads and notches at various angles to the fiber direction(s). Evidence of notch sensitivity and stable crack growth is presented. Self-similar crack growth is shown to occur for only a limited set of circumstances.

Critical stresses are compared to the theories of Waddoups et al and Whitney et al. These comparisons are presented using isotropic and orthotropic stress concentration factors together with a finite width correction factor. The results tend to show that use of only isotropic correction factors allow good correlation between theory and experiment.
Delamination in Quasi-Isotropic Graphite-Epoxy Laminates
Authors: Reifsnider KL , Henneke EG , Stinchcomb WW
Published: March 2009

The results of a study of delamination in two quasi-isotropic graphite-epoxy laminates are reported. Experimental observations are compared with predictions of laminate theory using the approach of Pagano and Pipes. The influence of stacking sequence is discussed. The relationship of delamination to other damage development is described, and the influence of gripping methods is indicated.
Evaluation of Selected High-Temperature Thermoplastic Polymers for Advanced Composite and Adhesive Applications
Authors: Maximovich MG
Published: March 2009

Commercially available polyethersulfone (PES) and polyphenylquinoxaline (PPQ) resins were evaluated as high-temperature thermoplastics for advanced composite and adhesive applications. Continuous graphite reinforced laminates up to 400 plies thick were fabricated successfully from both systems, once processing parameters were defined. Structural as well as hemispherical shapes were postformed from consolidated flat laminates. Poor-quality panels were reprocessed to high-quality parts, using the thermoplasticity of the matrix resins.

The PES exhibited sensitivity to moisture as shown in the testing of both the neat resins and advanced composites. Adhesive bonds were also fabricated on 6A1-4V titanium adherends, using PPQ and thermoplastic processing techniques. The performance of the adhesive was improved significantly by the use of woven graphite scrim cloth. It is postulated that this scrim cloth results in significantly reduced residual stress in the bond line.
Development of Multidirectional Fiber-Reinforced Plastics
Authors: Suezawa Y , Takemoto M , Takahashi S
Published: March 2009

Multidirectional (M-D) fiber-reinforced plastics (FRP) of isotropic strength have been developed utilizing a fluidized bed. Tension, compression, and bending tests were carried out on these M-D FRP, and their fracture modes also were examined paying special attention to the surface of crack initiation. Based upon the results obtained, an improvement of the strength of these composite materials was tried by retreatment of the cut end-surface of strands and use of appropriate ductile matrix. Thus we obtained an object of considerable satisfying strength.
Longitudinal Residual Stresses in Boron Fibers
Authors: Behrendt DR
Published: March 2009

A method of measuring the longitudinal residual stress distribution in boron fibers is presented. The residual stresses in commercial chemical vapor deposited boron on tungsten fibers of 102, 142, and 203 µm (4, 5.6, and 8 mil) diameters were determined. Results for the three sizes show a compressive stress at the surface, [−800 to −1400 MN/m2 (−120 to −200 ksi)], changing monotonically to a region of tensile stress within the boron. At ∼25 percent of the original radius, this tensile stress reaches a maximum [600 to 1000 MN/m2 (90 to 150 ksi)], and then decreases and becomes compressive near the tungsten-boride core. The core itself is under a compressive stress of ∼−1300 MN/m2 (−190 ksi). The effects of surface removal on core residual stress and core-initiated fracture are discussed.
An Analysis Model for Spatially Oriented Fiber Composites
Authors: Rosen BW , Chatterjee SN , Kibler JJ
Published: March 2009

This paper describes a material model for evaluation of the thermoelastic properties of fiber composite materials having a spatial distribution of fiber orientations. The approach is to construct a material model having a finite number of fiber orientations in a repeating unit cell. The basic material model is a minimechanical model based on the concept that a material system can be regarded as an assemblage of unit cells.

The unit cell models are constructed from impregnated yarn bundles and interstitial matrix regions. The predicted properties of these unit cells are those required for use in thermostructural analysis computer codes. The model treats anisotropic constituents, dispersed voids, temperature-dependent constituent properties, and fiber bundles oriented in many different directions.
Empirical Crippling Analysis of Graphite/Epoxy Laminated Plates
Authors: Spier EE , Klouman FL
Published: March 2009

This paper is concerned with developing empirical crippling curves for A-S/3501 graphite/epoxy laminated plates to use in analyzing the buckling behavior of stiffened plates. The cross sections of the stiffeners are restricted to flat plate elements, where either both unloaded edges are simply supported or one of the unloaded edges is simply supported and the other edge is free. Laminates tested are of the type [±45A/0B/∓45A]T for B/A ratios of 2, 4, and 6, which include the spectrum of most stiffener designs. Evidence shows that the laminates selected are superior to laminates of the type [0B/2/±45A]S. Crippling curves are presented in nondimensional form, which are particularly useful for estimating crippling strengths of similar graphite/epoxy systems. Corresponding buckling curves plotted along with the crippling curves show that theoretical elastic buckling theory is not adequate for predicting the ultimate compressive strength of composite laminated plates. Ultimate compression tests were performed to establish upper limit cutoff stresses for the crippling curves.
Reliability Prediction for Composites Under Periodic Proof Tests in Service
Authors: Yang JN
Published: March 2009

An exploratory reliability analysis of composites under periodic proof tests in service is presented. The ultimate strength of composites is a random variable. A residual strength degradation model for composites under service loads is employed. Failure occurs as soon as the residual strength of composites is exceeded by statistical service loads, for example, gust turbulence and maneuver loads. Meanwhile, the composites are subjected to periodic proof tests in order to eliminate weak components and ensure an acceptable level of reliability. When a component fails under the proof test, a new component is manufactured and proof-tested for replacement, so that the strength of composites is renewed. Taking into account the statistical strengths, strength degradation characteristics, statistical service loads, design stresses, periodic proof tests, and renewal processes due to replacement, the probability of composite failure in service is derived. Two numerical examples, a boron/titanium bonded joint of a fighter aircraft and a glass/epoxy component of a transport-type aircraft, are worked. It is demonstrated that significant fatigue reliability improvement for composites can be achieved by the application of periodic proof tests.
Tensile and Compressive Behavior of Borsic/Aluminum
Authors: Herakovich CT , Davis JG , Viswanathan CN
Published: March 2009

The results of an experimental investigation of the mechanical behavior of Borsic/aluminum are presented. Composite laminates were tested in tension and compression for monotonically increasing load and also for variable loading cycles in which the maximum load was increased in each successive cycle. It is shown that significant strain-hardening, and corresponding increase in yield stress, is exhibited by the metal matrix laminates. For matrix dominated laminates ([90], [±45]), the current yield stress is essentially identical to the previous maximum stress, and unloading is essentially linear with large permanent strains after unloading. For laminates with fiber dominated behavior ([0], [±30], [0/90], [0/±45]), the yield stress increases with increase in the previous maximum stress, but the increase in yield stress does not keep pace with the previous maximum stress. These fiber dominated laminates exhibit smaller nonlinear strains, reversed nonlinear behavior during unloading, and smaller permanent strains after unloading.

Compression results from sandwich beams and flat coupons are shown to differ considerably. Results from beam specimens tend to exhibit higher values for modulus, yield stress, and strength.
Charpy Impact of Unidirectional Graphite/Aramid/Epoxy Hybrid Composites
Authors: Helfinstine JD
Published: March 2009

This report discusses the impact properties of interply hybrids of Kevlar 49 aramid fibers and Thornel 300 graphite fibers in Narmco 5208 epoxy resin. The instrumented Charpy was used to characterize 20-ply unidirectional composites with nine fiber ratios and three stacking sequences. It was observed that the maximum total energy per cross sectional area occurred in a symmetrically interleaved ten-ply Thornel/ten-ply Kevlar composite. However, the maximum crack initiation energy per area occurred in a three-ply Kevlar/fourteen-ply Thornel/three-ply Kevlar composite. There was no single hybrid system that was best in all categories discussed.
Impact Damage in Graphite-Fiber-Reinforced Composites
Authors: Greszczuk LB , Chao H
Published: March 2009

Theoretical and experimental studies are presented on the failure modes in graphite-fiber-reinforced composite plates subjected to low-velocity impact. Influence of the following parameters is studied theoretically or experimentally or both: fiber and matrix properties, fiber orientation, stacking sequence, and laminate thickness. A quasi-dynamic approach is used to predict theoretically the influence of the noted parameters on the impact response of composite plates. A previously developed approach is used and extended to predict the time-dependent surface pressure and its distribution in a generally orthotropic target impacted by a body of revolution. The triaxial stress state in the composite target (assumed to be generally orthotropic) is determined using a finite-element computer program. These stresses are used with failure criteria for generally orthotropic solids to determine the extent of impact damage. To verify predictions of the impact-induced failure modes, ball-drop tests are conducted on circular composite plates incorporating different fiber-resin combinations, fiber layups, and stacking sequences. Types of graphite fibers used in the experimental program include Thornel 300, Modmor II, and Celion GY-70. Fiber layups investigated include unidirectional, 2:1 bidirectional, 1:1 bidirectional, and tridirectional (pseudo-isotropic).
Impact Response of Polymer-Matrix Composite Materials
Authors: Adams DF
Published: March 2009

The more significant of the many prior investigations of the title problem have been organized into a brief summary of past achievements and an appraisal of the current state of the art with emphasis on the impact of beam specimens such as those used in the Charpy test. An extensive list of references are catagorized into general directions that prior research has taken with representative experimental results being included to emphasize the conclusions presented. These form the basis for suggestions for additional research, both experimental and analytical.
An Analytical Method for Evaluation of Impact Damage Energy of Laminated Composites
Authors: Sun CT
Published: March 2009

A higher order beam finite element is developed for computing the dynamic response of laminated beams subjected to impact of a hard object. The contact force as well as the indentation are obtained by using the Hertzian contact law. By assuming a certain unloading path, the total energy imparted from the projectile to the beam and the damage energy that causes permanent indentations are computed. Laminated cantilever beams of a glass-epoxy composite impacted by a steel ball are investigated. Part of the analytical results is in good agreement with existing experimental data.