bluuebunny/crossref_metadata_2025 huggingface dataset:
Annealing Behavior and Tensile Properties of Elevated-Temperature PM Aluminum Alloys
Authors: Kim Y-W , Griffith WM
Published: December 2008

Two rapidly solidified powder metallurgy (PM) aluminum alloys, Al-7.4Fe-3.4Ce and Al-5.7Fe-6.1Ni, were investigated to characterize the annealing response and to relate room-temperature tensile properties with the forging reduction (up to 65%), starting from vacuum-hot-pressed material. The Al-Fe-Ce alloy is typified by a planar/dendritic microstructure having ultrafine (<200-Å) unidentified intermetallic compounds; the Al-Fe-Ni alloy exhibits a planar/coupled-eutectic/eutectic microstructure. At temperatures up to 350°C (660°F), both alloys show excellent stability, which degrades rapidly at higher temperatures. At temperatures above 350°C (660°F), the metastable dispersoids in Al-Fe-Ce transform into acicular (Al3Fe type) and spherical (Al10Fe2Ce type) compounds that grow rapidly with increasing temperature. The eutectic compounds (FeNiAl9) of Al-Fe-Ni are spheroidized before coarsening at temperatures above 350°C (660°F). The strength and elongation of both alloys are enhanced to a maximum value by increased forging reduction; however, they approach the maximum at different rates. Al-Fe-Ce attains maximum strength after 48% reduction, but the elongation continues to increase with additional reduction. In contrast, Al-Fe-Ni does not achieve maximum strength even after 65% forging, and the elongation is far below the maximum value and much lower than that of Al-Fe-Ce. These trends are explained in terms of powder particle bonding (for both alloys) and the breakup of eutectic intermetallics (for Al-Fe-Ni). The poorer properties of Al-Fe-Ni are attributed to incomplete eutectic breakup, even after 65% forging.
Effect of Compositional Variations on the Microstructure and Properties of Rapidly Solidified Al-3Li Alloys
Authors: Meschter PJ , Pao PS , Lederich RJ , O'Neal JE
Published: December 2008

The quantitative effects of stepwise additions of the precipitation-strengthening element copper, the solid-solution-strengthening element magnesium, and the substructure-refining element zirconium on the microstructures and peak-aged mechanical properties of rapid solidification processed (RSP) Al-3Li alloys have been determined. Additions of 0.2 to 0.5% zirconium by weight produce a 1.4 to 1.9-μm diameter, fully recovered subgrain structure in Al-3Li-Zr extrusions and raise the peak-aged yield stress of Al-3Li by 100 to 140 MPa. The addition of 1% magnesium raises the yield stress of Al-3Li-0.2Zr by 35 MPa, but a further addition to 2% has no effect. Additions of 1 to 2% copper to Al-3Li-0.2Zr raise the yield stress by 45 MPa per weight percent copper and render the peak-aged mechanical properties of the alloy sensitive to variations in solutiontreatment temperature and process stretch. Improvements in the properties of RSP Al-3Li-Cu-Zr alloys, in comparison with those measured by previous investigators, are related to improvements in consolidation processing and, in particular, to effective disintegration of oxide layers on the RSP particulates. Al-3Li-1Mg-0.2Zr and Al-3Li-2Cu-0.2Zr are promising substitutes for commercial 2XXX and 7XXX aluminum alloys, respectively, at 10 to 11% lower density levels.
An Evaluation of the Benefits of Utilizing Rapid Solidifcation for Development of 2XXX (Al-Cu-Mg) Alloys
Authors: Paris HG , Chellman DJ
Published: December 2008

The advantages of rapid solidification processing over ingot metallurgy processing in the development of 2XXX aluminum alloy compositions were evaluated using a similarly processed ingot metallurgy (IM) control alloy. The powder metallurgy (PM) alloy extrusions showed a reduced age-hardening response in comparison with similar IM compositions, with higher tensile properties for naturally aged extrusions but lower properties for artificially aged ones. However, the tensile properties of naturally and artificially aged PM alloy extrusions based on a version of IM 2034 alloy, but containing 0.6 weight percent zirconium, were comparable to those of the IM control extrusions and had significantly superior combinations of strength and toughness. The tensile properties of this PM alloy showed even greater advantage in 6.4-mm (0.25-in.) and 1.8-mm (0.070-in.) plate and sheet, the yield strength being about 68 MPa (10 ksi) greater than reported values for the IM 2034 alloy sheet. An artificially aged PM alloy based on 2219 alloy also showed a strength and strength-toughness combination comparable to those of the PM Al-Cu-Mg-Zr alloy, substantially outperforming the IM 2219 alloy. These results show that rapid solidification offers the flexibility needed to modify conventional IM compositions to produce new alloy compositions with superior mechanical properties.
Interpretation of In Situ Groundwater Quality from Well Samples
Authors: Metzger I
Published: December 2008

Water quality determinations made from monitoring wells may differ from actual in situ groundwater quality by virtue of construction, operation, and sampling of the well. Observations made on several groundwater studies and theoretical considerations are used to interpret the reasons for differences, and are illustrated by studies for a landfill project. These studies suggest considerable care is needed to interpret monitoring results—especially when they are compared with regulatory requirements.
Use of Detrended Correspondence Analysis in Evaluating Factors Controlling Species Composition of Periphyton
Authors: Leland HV , Carter JL
Published: December 2008

Detrended correspondence analysis (DCA) was evaluated for its usefulness in elucidating relationships among samples and among species of periphyton in an oligotrophic stream, and for its effectiveness in displaying major gradients where an experimental gradient (copper) affecting species composition was imposed. It was highly sensitive to differences among samples and consistently provided ecologically meaningful species ordinations.

Gradients related to seasonality of taxa and year-to-year differences in population densities were evident in DCA ordinations if data for all sampling dates were included, and these gradients complicated interpretation of the copper gradient. Clear discontinuities between samples in control and copper-treated stream sections existed only if data for each sampling date were ordinated separately. Prior to copper exposure, stage of succession of the community was the major gradient displayed in species ordinations. During periods of exposure, sensitivity of taxa to copper was the primary factor controlling the spatial distribution of periphyton. Stage of succession was a secondary gradient during exposure and complicated interpretation of the copper gradient after a major disturbance event (flooding).
The Role of Aquatic Macrophytes in Nutrient Flow Regulation in Lotic Ecosystems
Authors: Hill BH
Published: December 2008

Aquatic macrophytes in an agricultural drainage ditch were able to accrue large amounts of nitrogen (N) and phosphorus (P) during the growing season and held these nutrients until tissue breakdown in autumn. Total nutrient accumulation by aquatic macrophytes in a 1.4 km (8612 m2) ditch was 49.0 kg N (5.65 mg N m−2) and 11.0 kg P (1.29 mg P m−2). Release of these nutrients upon tissue breakdown was rapid. Average breakdown rates, based on ash-free dry mass (AFDM) loss, for Elodea canadensis and Potamogeton nodosus were 0.0615 ± 0.0450 d−1 (r2 = 0.788) and 0.0260 ± 0.0170 d−1 (r2 = 0.688), respectively. Time required for 95% loss of plant tissue (T95 = 3/k) was 49.0 days for Elodea and 116.9 days for Potamogeton. Nitrogen and phosphorus losses from decaying plants closely followed AFDM losses. Mass balances for N and P indicated the 94% of the N and 72% of the P accumulated by aquatic macrophytes were obainted from surface sediments. Sediment N and P pools were 864 kg and 62 kg, respectively.
Dacron® Arterial Grafts: Comparative Structures and Basis for Successful Use of Current Prostheses
Authors: Sauvage LR , Smith JC , Davis CC , Rittenhouse EA , Hall DG , Mansfield PB
Published: December 2008

By the 1960s, woven and knitted Dacron® grafts were in widespread use. Currently, approximately ten different Dacron prostheses are available for clinical use and several others are being developed. The advantages and limitations of three different types of grafts are discussed: (1) tightly woven and crimped; (2) knitted, crimped, and nonsupported; and (3) knitted, noncrimped, and supported. The microanatomy of grafts from each category is presented.
Expanded Polytetrafluoroethylene (PTFE) Arterial Grafts: An Eight-Year Experience
Authors: Veith FJ , Ascer E , Gupta SK
Published: December 2008

Eight hundred twenty-two polytetrafluoroethylene (PTFE) grafts were used in arterial reconstructions for lower limb ischemia over the last eight years at Montefiore Medical Center, Albert Einstein College of Medicine. Four hundred twenty-seven femoropopliteal reconstructions with PTFE had a six-year cumulative life table patency rate of 55%, with follow-up of seventy-six grafts for more than three years and twenty-eight grafts for more than four years. Seventy-nine bypasses to an isolated popliteal segment had a six-year cumulative patency rate of 72%. There were 207 bypasses performed to the tibial, peroneal, or dorsalis pedis arteries. Life table patency rates were 55% at one year, 40% at two years, and 37% at four years. Ninety-two PTFE femorofemoral and sixty-two axillofemoral bypasses had a five-and-one-half-year cumulative life table patency rates of 83 and 75%, respectively. Axillopopliteal PTFE bypasses can salvage otherwise doomed limbs. Thirty-four such grafts had 74% one-year and 45% five-year patency rates. The overall infection rate in all 822 PTFE grafts was only 0.5%. Thus, PTFE is a promising vascular prosthetic material that can facilitate otherwise difficult or impossible limb salvage procedures.
Coronary Artery Grafts
Authors: Kantrowitz A
Published: December 2008

The problem of vascular grafts in cardiac surgery is somewhat different from the problems associated with vascular grafts involving larger vessels. Cardiac surgeons must deal with small-caliber grafts exclusively. The diameters of the coronary artery vessels that are usually involved in bypass procedures are about 1 to 2 mm, and occasionally as large as 3 mm. Coronary artery bypass procedures for the most part have been greeted with excellent success. Long-term patency rates of more than 95% using internal mammary arterial grafts and more than 85% for saphenous venous grafts are routinely reported. A prosthetic graft that would permit this order of long-term patency rates would be of enormous usefulness in the field of cardiac surgery.
Physical Properties and Test Methods for Expanded Polytetrafluoroethylene (PTFE) Grafts
Authors: McClurken ME , McHaney JM , Colone WM
Published: December 2008

This paper will assist the Food and Drug Administration's efforts to develop rational standards for vascular grafts. Since very little technical information has been published on the physical properties of polytetrafluoroethylene (PTFE) grafts, this paper will also address the concerns of ASTM, clinicians, and graft manufacturers. Detailed descriptions are given for current test methods designed to measure physical dimensions, bulk density, porosity, water entry pressure, longitudinal tensile strength, radial tensile strength, suture retention strength, burst strength, and percent sintered. Grafts made by all three current suppliers were tested according to the described test methods. The results indicate that currently available PTFE grafts have very similar inner surfaces with widely varying outer surfaces. Though variations in design directly influence physical strength, all currently available PTFE grafts appear to possess adequate physical properties to ensure safe clinical use.
Strength and Endurance of Vascular Grafts
Authors: Snyder RW , Tenney B , Guidoin R
Published: December 2008

A review of the strength and endurance of current vascular prostheses. Data is referenced to demonstrate that endurance is a property separate from strength. Current proposed test methods are described. It is proposed that endurance is to be demonstrated by bench testing, animal studies, and carefully controlled clinical studies. Strength characteristics are then used to control the production of the product.
The Importance of Vascular Graft Surface Composition as Demonstrated by a New Gas Discharge Treatment for Small Diameter Grafts
Authors: Hoffman AS , Ratner BD , Garfinkle AM , Reynolds LO , Horbett TA , Hanson SR
Published: December 2008

Biomaterial surface chemistry can have an important influence on biologic responses. Vascular graft chemistries may be modified in a number of ways. In this paper we report on a surface treatment using a gas discharge that deposits a thin coating onto the graft surface, significantly changing its surface chemistry, but without measurable change in porosity, compliance, or surface topography. Treatments with tetrafluoroethylene (TFE) gas yield dramatic improvements in both thrombo and emboli resistance of the graft, based on in vitro and ex vivo tests.
Sterility and Pyrogenicity Issues of Synthetic Vascular Grafts
Authors: Helmus MN , Botan EA , Malone JM , Botzko KM , Reinert RL , Bevans-Lynch R , Brendel K , Duhamel RC , Snyder RW
Published: December 2008

Common sterilization techniques, validation methods, and the physical and biologic effects of sterilization on synthetic vascular graft materials are reviewed. Pyrogenicity issues are discussed. A series of endotoxin-contaminated polyester externally supported grafts were tested in a canine model to assess the clinical significance of pyrogen contamination. Systemic pyrogenicity was observed, but gross thrombus formation was unaffected. The pathogenesis of graft infections are then reviewed.
Viewpoints on Safety and Efficacy of Vascular Grafts
Authors: MacNeill CE , Sung P
Published: December 2008

Section 514 of the Food, Drug, and Cosmetic Act requires performance standards to assure reasonable safety and effectiveness. Although the procedures appear to be complex and lengthy, they are comparable to those established by national and international standards organizations. Persons most directly affected by the standard may participate in both the performance standard development and the establishment of a final regulation on the performance standard. As a part of due process, those most affected have the opportunity to request a review of any matter by an advisory committee of experts. A key element in the performance standard development procedure is the establishment of a statement of the risks associated with the use of the device and intended to be controlled by a performance standard. For vascular graft prosthesis with diameters of 6 mm and greater, the establishment of the device risks and methods of control will be the basis from which the development of a performance standard can proceed. The objective is to select a set of risks and methods of control so that the standards development procedure is manageable and results in an effective performance standard.
State of the Art: Consolidation Testing
Authors: Olson RE
Published: December 2008

The state of the art of consolidation testing is addressed except that conditions involving generalized stress states were excluded and large-strain problems were assigned to a companion paper. Terzaghi's classical theory was found to fit primary data rather well and the root time fitting method was preferred. Errors associated with boundary impedance and ring friction can be major but are generally understood and can be minimized. Existence of nonlinear stress-strain relationships can perturb the shape of S-t curves significantly and lead to problems when pore pressures are used to determine cv. Radial flow tests should be used for field problems involving horizontal flow; theories are presented to use in reducing laboratory data. Secondary effects can be addressed using linear theory and trial solutions, but such effects may be much more apparent in the laboratory than in the field. Effects of partial saturation are understood qualitatively and can influence laboratory data greatly. Continuous loading tests lead to overprediction of effective stresses but apparently to reasonable values of cv. Soil properties change significantly as a result of sampling disturbance and storage time; techniques for correcting for these effects are presented. The usefulness of laboratory data is examined using a case history.
State of the Art: Evaluation and Interpretation of Soil Consolidation Tests
Authors: Crawford CB
Published: December 2008

The consolidation characteristics of natural soils vary widely depending on their stress history, void ratio, and structure. The standard method of measuring consolidation properties involves the incremental loading of specimens of soil, but other methods using controlled loading techniques have been useful in improving the understanding of soil compressibility. The various test methods and their influence on the evaluation of consolidation properties are reviewed in the paper. The interpretation of preconsolidation pressure for some soils is greatly influenced by the rate of loading. Total consolidation settlements can be estimated reasonably well from good oedometer tests, but predictions of the rate of settlement are usually quite unreliable in the primary consolidation stage. The ability to evaluate and interpret consolidation tests has been improved where the tests have been carried out in conjunction with field observations. More research of this kind is needed to improve the usefulness of consolidation theories and testing.
Consolidation in the Intergranular Viscosity of Highly Compressible Soils
Authors: Zeevaert L
Published: December 2008

The author has been interested for several decades in finding better correlations, from the practical engineering point of view, between theory and the phenomenological behavior of highly compressible soils as observed in oedometer tests and in the field.

The author has developed a theory on secondary compression or intergranular viscosity in the consolidation process as he has gotten more experience in the field. The theory is based on two rheological models: the Terzaghi model and the Z-unit developed by the author. The theory has been revised, and currently offers good correlations in the interpretation of the phenomenon observed in practice.

The theory calls for the ability to develop fitting methods to obtain the parameters necessary for the formulae. Two fitting methods are used to cover the consolidation curves observed in the tests performed in the oedometer with undisturbed specimens and in the range of the recompression close to the critical stress. The method proposed also may be used after the critical stress zone has been passed and the soil structure is stabilized at a new stress level. Several examples of fitting calculations are given in the paper to acquaint the reader with the method for practical use.

The author discusses problems with the oedometer conventional test, and ends with recommendations and an analysis of the material presented.
Oedometer Testing at the Norwegian Geotechnical Institute
Authors: Sandbaekken G , Berre T , Lacasse S
Published: December 2008

The paper describes the test equipment, the testing procedures, and the interpretation of the results from oedometer tests as practiced today by the Norwegian Geotechnical Institute. Both the incremental loading and the constant-rate-of-strain methods are used. The test procedures and the interpretation include steps to account for the effects of sample disturbance. A new method for determination of the coefficient of consolidation is presented.
Consolidation of Natural Clays and Laboratory Testing
Authors: Kabbaj M , Oka F , Leroueil S , Tavenas F
Published: December 2008

A numerical model has been developed, making use of a strain-rate-dependent compressibility law and a permeability-void ratio law, both experimentally established. The numerical program is used to simulate the behavior of clay specimens submitted to oedometric tests (MSL, CGT, creep, etc.). The following conclusions are drawn:

1. The effective stress-strain clay behavior depends on the type of test carried out. In particular, the preconsolidation pressure value varies from one test to another.

2. Each element throughout the specimen follows a specific stress-strain relation depending on its strain rate history. Moreover, the oedometric curve, as usually interpreted from a multiple-stage loading (MSL) test, does not agree with any of these relations, not even with the average curve followed by the whole specimen.

3. The pore pressure isochrones maintain the same shape during controlled-gradient (CGT) or creep tests, in particular when the effective stresses correspond to the preconsolidation pressure.
Brittle Behavior of a Varved Clay During Laboratory Consolidation Tests
Authors: Bemben SM
Published: December 2008

The brittle behavior aspects manifested during laboratory consolidation tests of a varved clay deposited in a glacial lake and thereafter having acquired natural cementation are presented. The effect of the quality of the test specimens on the shape of the compression curves from one-dimensional consolidation tests employing both incremental and constant rate of strain loading are presented. For good quality test specimens, the compression curves are arithmetically linear up to critical stress values at which breakage of the cement commences. A method is presented for estimating the maximum previous vertical effective stress remembered by the soil fabric of the intact natural state soil when one-dimensional test curves display brittle behavior. When the cement bonds of the natural-state soil are intact, the soil fabric can be underconsolidated or overconsolidated with respect to the existing vertical effective stress. The brittle behavior of the intact natural-state soil is attributed to the behavior of the cement bonds.
Consolidation of Sand-Clay Mixtures
Authors: Fukue M , Okusa S , Nakamura T
Published: December 2008

Consolidation properties of bentonite-sand mixtures, as reclamation materials, were investigated in the one-dimensional consolidation test. From the relationships between the void ratio of nonclay fraction and consolidation pressure was found the existence of a threshold void ratio at which the frictional resistance becomes dominant during consolidation. The threshold value is slightly greater than the maximum void ratio of sand used for the mixtures.

A new standard, which utilizes values of clay content, dry density, and threshold void ratio, is proposed to clarify the boundary between sandy and clayey soils.

The salt infiltration into the mixtures causes a rapid settlement but greatly reduces the swelling in unloading stage. As long as the void ratio of nonclay fraction is less than the threshold value, however, the influence of salt disappears.
A Comparative Laboratory Evaluation of Band-Shaped Prefabricated Drains
Authors: Guido VA , Ludewig NM
Published: December 2008

Theoretical studies pertaining to the design and application of vertical drainage systems, and recommendations for the selection of design spacing for band-shaped prefabricated (wick) drains, were examined. It was the intent of this study to examine the effects of band-shaped prefabricated drains on the consolidation characteristics of a clay soil, and in addition to evaluate and contrast the efficiency of the prefabricated drains in a laboratory experiment in a way that would guide the engineering application of prefabricated drains in the field. An apparatus referred to as a “wick drain consolidometer” was designed and constructed to fulfill the above-stated intent of study. Five different prefabricated drains were tested: Castleboard, Franki-Kjellman, Mebradrain, Geodrain, and Alidrain. All wick drains with a central core and loosely fitted filter jacket performed better than the Franki-Kjellman wick, which had the filter glued to the core. Based on compression versus time data, the Alidrain wick performed the best, with Castleboard, Mebradrain, and Geodrain all performing approximately the same.
Consolidation Testing—A Comparative Study
Authors: Bauer GE , El-Hakim AZ
Published: December 2008

The knowledge of the preconsolidation pressure, p′e, of an overconsolidated clay is of vital importance in the settlement analysis of structures. It has been found that the semigraphical methods to determine p′e proposed by Casagrande, Burmister, and Schmertmann are not completely satisfactory for sensitive clays. Also, the standard oedometer test is not adequate to fully describe the strain-effective stress behavior of such clays. Renewed interest in this topic by several investigators has shown that the magnitude of the preconsolidation pressure is greatly affected by the rate of loading, type of loading, specimen size, and type of testing apparatus used.

This paper reports on the results of a comparative study of consolidation behavior using two types of clays and four different testing techniques. The first series of tests was carried out on undisturbed specimens of soft Leda (Champlain Sea) clay cut from block samples and the second series was performed on prepared and consolidated kaolin specimens. For each series, four different consolidation apparatuses were used: a standard oedometer, a modified Rowe cell, an Anteus apparatus, and triaxial K0 tests. Both Leda clay and kaolin specimens were tested in parallel. Several sizes (diameters) of specimens and different loading techniques were used. Based on these test results, it was shown that the controlled gradient consolidation test using the Rowe cell with a softer membrane was the most suitable technique to establish a well-defined effective stress-strain curve. The controlled gradient test using the Anteus apparatus also gave a well-defined stress-strain relationship, but the operational procedures were found quite cumbersome. The K0-triaxial test was quite time-consuming and an elaborate recording of data was required. The results from standard oedometer tests, even using a modified loading, did not yield continuous effective stress-strain plots and p′e was difficult to determine. Also, a comparison of the coefficients of consolidation was made for the two clays and the various testing techniques employed.
An Evaluation of Fracture Analysis Methods
Authors: Newman JC
Published: December 2008

This paper presents the results of an experimental and predictive round robin conducted by the American Society for Testing and Materials (ASTM) Task Group E24.06.02 on Application of Fracture Analysis Methods. The objective of the round robin was to verify whether fracture analysis methods currently used can or cannot predict failure loads on complex structural components containing cracks. Fracture results from tests on compact specimens were used to make these predictions. Results of fracture tests conducted on various-size compact specimens made of 7075-T651 aluminum alloy, 2024-T351 aluminum alloy, and 304 stainless steel were supplied as baseline data to 18 participants. These participants used 13 different fracture analysis methods to predict failure loads on other compact specimens, middle-crack tension (formerly center-crack tension) specimens, and structurally configured specimens. The structurally configured specimen, containing three circular holes with a crack emanating from one of the holes, was subjected to tensile loading.

The accuracy of the prediction methods was judged by the variations in the ratio of predicted-to-experimental failure loads, and the prediction methods were ranked in order of minimum standard error. The range of applicability of the prediction methods was also considered in assessing their usefulness. For 7075-T651 aluminum alloy, the best methods (predictions within ±20% of experimental failure loads) were: the effective KR-curve, the critical crack-tip-opening displacement (CTOD) criterion using a finite-element analysis, and the KR-curve with the Dugdale model. For the 2024-T351 aluminum alloy, the best methods were: the Two-Parameter Fracture Criterion (TPFC), the CTOD criterion using the finite-element analysis, the KR-curve with the Dugdale model, the Deformation Plasticity Failure Assessment Diagram (DPFAD), and the effective KR-curve with a limit-load condition. For 304 stainless steel, the best methods were: limit-load (or plastic collapse) analyses, the CTOD criterion using the finite-element analysis, the TPFC, and the DPFAD. The failure loads were unknown to all participants except the author, who used both the TPFC and the CTOD criterion (finite-element analysis).
Predictions of Instability Using the Modified J, JM-Resistance Curve Approach
Authors: Ernst HA , Landes JD
Published: December 2008

This paper presents a method for predicting the behavior of an untested structure using the modified J, JM-resistance curve approach. The method combines the JM-R curve, calibration functions, and the expression for JM for the untested geometry to provide the load-load point displacement characteristics and the JM-TM diagram of the structure. These two records contain all the information needed to assess structural behavior, maximum load, the tendency for instability, and the load-point displacement at every point.
Prediction of Stable Crack Growth and Instability Using the VR-Curve Method
Authors: Newman JC
Published: December 2008

This paper presents a methodology for predicting stable crack growth and instability of cracked structural components from results of laboratory tests on metallic materials under plane-stress conditions. The methodology is based on the displacement (VR) at the tip of a stably tearing crack. Basically, the VR-curve method is a resistance curve approach, such as KR and JR, except that the “crack drive” is written in terms of crack-tip displacement instead of K or J. The relationship between crack-tip-opening displacement, crack length, specimen type, and tensile properties is derived from the Dugdale model for the cracked structure of interest.

This report describes the laboratory test procedure and calculations used to obtain the VR resistance curve from fracture tests of compact or of middle-crack tension (formally center-crack) specimens. The analysis procedure used to predict stable crack growth and instability of any through-the-thickness crack configuration made of the same material and thickness, and tested under the same environmental conditions, is presented. The various limitations of the present VR-curve method are given. Four example calculations and predictions are shown.
Characterization of T300/V-378A Graphite/Bismaleimide for Structural Applications
Authors: Ramkumar RL , Grimes GC , Kong SJ
Published: December 2008

This paper discusses the potential of T300/V-378A graphite/bismaleimide for use in aircraft structures that are likely to be exposed to service temperatures in the 120 to 204°C (250 to 400°F) range. The microstructure of cured T300/V-378A laminates was examined to detect the presence of any process-induced defects; moisture absorption studies were conducted to characterize the hygroscopic behavior of the material; and its basic properties were generated through static tests on [0]16T, [90]16T, and [±45]4s laminates. These were followed by static tests on plain [0/±45/90]2s T300/V-378A specimens and specimens with unloaded (open and filled) and loaded holes. Tests were conducted under room temperature, dry (RTD) and elevated temperature, wet (ETW) conditions. Plain specimens and specimens with open holes were also subjected to constant-amplitude fatigue tests at minimum-to-maximum cyclic stress ratios (R) of 0.05 and −1.0.

Subsequently, the tolerance of [0/±45/90]4s T300/V-378 laminates to low-velocity impact damage by a hard object was evaluated by measuring impact energy levels corresponding to incipient (not necessarily visible) damage and through-penetration. Specimens from impact-damaged panels were then tested to obtain residual static compression strengths. Finally, multibay, hat-stiffened, flat shear panels were fabricated using the T300/V-378A material system, and were subjected to pure-shear static and fatigue tests under RTD and ETW conditions.

Results were compared with available data on T300/5208 and AS/3501-6 graphite/epoxy laminates to assess the relative merits of the T300/V-378A graphite/bismaleimide material system. In general, the RTD matrix-dominated response of T300/V-378A laminates is inferior to that of AS1/3501-6 laminates. But, the T300/V-378A laminates retain most of their RTD strengths under 177°CW (350°FW) (wet) conditions, where conventional epoxy-matrix materials suffer property losses that occur at the glass transition temperature. The V-378A bismaleimide material, therefore, provides a viable alternative to conventional epoxy-matrix materials, for applications in components that experience humid conditions and temperatures in the 120 to 205°C (250° to 400°F) range.
Compression Failure Mechanisms in Unidirectional Composites
Authors: Hahn HT , Williams JG
Published: December 2008

The present paper examines compression failure mechanisms in unidirectional composites. Possible failure modes of constituent materials are summarized and analytical models for fiber microbuckling are reviewed from a unified viewpoint. Due to deficiencies in available models, a failure model based on nonlinear material properties and initial fiber curvature is proposed.

The effect of constituent properties on composite compression behavior was experimentally investigated using two different graphite fibers and four different epoxy resins. The predominant macroscopic-scale failure mode was found to be shear crippling. In a soft resin, shear crippling was in the form of buckling of fibers on a microscopic scale. However, for stiff resins, failure was characterized by the formation of a kink band. For unidirectional laminates, compressive strength, and compressive modulus to a lesser extent, were found to increase with increasing magnitude of resin modulus. The change in compressive strength with resin modulus was predicted using the proposed nonlinear model.
Effect of Laminate Thickness and Specimen Configuration on the Fracture of Laminated Composites
Authors: Harris CE , Morris DH
Published: December 2008

The effect of laminate thickness on the fracture behavior of laminated graphite/epoxy (T300/5208) composites has been studied. The predominantly experimental research program included the study of the [0/±45/90]ns and [0/90]ns laminates with thicknesses of 8, 32, 64, 96, and 120 plies and the [0/±45]ns laminate with thickness of 6, 30, 60, 90, and 120 plies. The research concentrated on the measurement of fracture toughness utilizing the center-cracked tension, compact tension, and three-point bend specimens. The development of crack-tip damage prior to fracture was also studied.

Test results showed fracture toughness to be a function of laminate thickness. The fracture toughness of the [0/±45/90]ns and [0/90]ns centercracked laminates decreased with increasing thickness and asymptotically approached lower bound values of 1043 MPa √mm (30 ksi √in.) and 869 MPa √mm (25 ksi √in.), respectively. The fracture toughness of the [0/±45]ns center-cracked laminate increased with increasing thickness but reached an upper plateau value of 1390 MPa √mm (40 ksi √in.). The fracture toughness of all laminates was independent of crack size except the [0/90]2s laminate that split extensively. The fracture surface of all thick laminates was uniform in the interior and self-similar with the starter notch. With the exception of the [0/±45]ns laminate, the fracture toughness of the thicker laminates was relatively independent of specimen configuration.
Effect of Impact and Fatigue Loads on the Strength of Graphite/Epoxy Composites
Authors: Avva VS , Vala JR , Jeyaseelan M
Published: December 2008

An extensive experimental investigation on a graphite/epoxy (T300/934) composite laminate having an orientation and a stacking sequence of (±45,0,90)2s was conducted to study the behavior of the composite material subjected to several combinations of low-velocity projectile impact and tension-tension fatigue loads. The sequence of loading (impact/cycle or cycle/impact) was changed to study its effect on the strength or the life of the composite materials. The experimental data in impact tests were compared with the corresponding results obtained by using a theoretical model.
Dynamic Stress Analysis of Smooth and Notched Fiber Composite Flexural Specimens
Authors: Murthy PLN , Chamis CC
Published: December 2008

A detailed analysis of the dynamic stress field in smooth and notched fiber composite (Charpy-type) specimens is reported in this paper. The analysis is performed with the aid of the direct transient response analysis solution sequence of MSC/NASTRAN. Three unidirectional composites were chosen for the study. They are S-glass/epoxy, Kevlar/epoxy, and T-300/epoxy composite systems. The specimens are subjected to an impact load that is modeled as a triangular impulse with a maximum of 8960 N (2000 lb) and a duration of 1 ms. The results are compared with those of static analysis of the specimens subjected to a peak load of 8960 N (2000 lb). For the geometry and type of materials studied, the static analysis results gave close conservative estimates for the dynamic stresses.
Manufacture and Characteristics of Portland Blast-Furnace Slag Cements
Authors: Frigione G
Published: December 2008

The paper gives an account of the results collected through a wide laboratory and industrial investigation carried out in order to show in which way the compressive strength and the heat of hydration are controlled by a large number of manufacture parameters, such as glass content of the slag, grinding fineness, and gypsum amount of the blended cement. Besides, the results show that the resistance to sulfates and to alkali-aggregate reaction remain very strong, if the slag percentages in the cement is high, irrespective of gypsum content and grinding fineness of the blended cement as well as of the glass amount of the slag.
Chemical Shrinkage and Differential Sorptions in Mixtures of Portland Cement and Blast-Furnace Slag
Authors: Mills RH
Published: December 2008

The relationship between chemical shrinkage, expressed as volume per unit mass of anhydrous cementing material, and chemically bound water varies over a narrow range with the ratio of portland cement (PC) to blast-furnace slag (BFS). Chemical shrinkage is easily measured and affords an easily executed nondestructive measure of quality for cements made with mixtures of PC and BFS.

The difference between the pore space occupied by water and by kerosene expressed as a fraction of water-filled space is a measure of the volume proportion of hydrate material and is related to relative shrinkage and creep.
Permeability and Pore Structure of Cement Pastes Containing Fly Ash, Slag, and Silica Fume
Authors: Hooton RD
Published: December 2008

As part of research to develop a highly durable concrete container for radioactive waste disposal in chloride and sulfate bearing granite groundwaters, a variety of cement pastes were studied. A sulfate resisting portland cement was used with various replacement levels of Class F fly ash and pelletized blast furnace slag at a water to solids ratio (W/S) = 0.36. Blends with fly ash, slag, and silica fume were also combined with a super water reducer at W/S = 0.25. Results are presented for strength development, permeability to water, and pore size distribution after 7, 28, 91, and 182 days moist curing. As a direct measure of durability, after 91 days moist curing, paste prisms were immersed in both de-ionized water and a synthetic chloride and sulfate bearing groundwater at 70°C.

While all three supplementary cementing materials (mineral admixtures) reduced ultimate permeabilities, silica fume was more effective in reducing permeability at early ages. Silica fume was also the most effective in reducing calcium hydroxide contents of the pastes while slag was the least effective; only reducing calcium hydroxide levels by dilution of the portland cement. From preliminary analysis, there does not appear to be a way of accurately predicting permeability from porosity or pore size parameters alone.
Consolidation of Soils: Testing and Evaluation
Authors: Yong RN , Townsend FC
Published: December 2008

Description

A comprehensive treatment of consolidation testing and evaluation, including infinitesimal and large strain. Paper examine two decades of advances in

• equipment and instrument capabilities

• test methodologies and data gathering and control systems,

• methods for data handling and analysis
Elastic-Plastic Fracture Mechanics Technology
Authors: Newman JC , Loss FJ
Published: December 2008

Description

Divided into two sections:

• the results of an experimental and predictive round robin designed to evaluate current EPFM methods

• the presentation of four EPFM methods, including the steps required for application, and sample calculation.
Flammability and Sensitivity of Materials in Oxygen-Enriched Atmospheres: Second Volume
Authors: Benning MA
Published: December 2008

Description

A source book on a subject not widely addressed in the available literature. Builds upon ASTM STP 812 and examines the design and operation of oxygen systems, aspects of the ignition of materials – both metallic and nonmetallic, flammability of metals in pure and dilute oxygen, and cleanliness and contamination.
Alkalies In Concrete
Authors: Dodson VH
Published: December 2008

Description

Proposed mechanisms for the alkali-silica, alkali-silicate and alkali-carbonate reactions, and the sources of alkali in concrete. How to predict, minimize, control, and eliminate the causes o the alkali-aggregate problem.
State Criminals and the Limits of Extra-Communitarian Criminal Justice
Authors: Goti Jaime Malamud
Published: December 2008

The article argues against the new trends toward international criminal jurisdiction in what I narrowly construe as "domestic" violations of human rights. The argument is largely based on a particular role of punishment which it links to the notion of community. The former consists in viewing the criminal sanction as a means of equalizing perpetrators and their victims to whom punishment restores dignity and self-respect. This process, the article claims, can only be fully achieved through minimally authoritative courts whose judges belong to the community where the crimes were committed.
Enemy Combatants Versus Enemy Criminal Law: An Introduction to the European Debate Regarding Enemy Criminal Law and Its Relevance to the Anglo-American Discussion on the Legal Status of Unlawful Enemy Combatants
Authors: Díez Carlos Gómez-Jara
Published: December 2008

At the beginning of the twenty-first century two legal concepts linking citizen/enemy status with criminal law have provoked heated discussion both in Europe and in the United States. The American concept, i.e., Enemy Combatants, has been basically developed by the U.S. Supreme Court and more recently by the Bush administration. The European term, Feindstrafrecht/Enemy Criminal Law, has been fundamentally coined and explained by leading German academic Professor Günther Jakobs.

Though born and raised by different parents, the two concepts have numerous aspects in common, or at least this will be argued throughout the paper. The most important common ground is that both concepts, with similar terminology, try to address the problem of what to do with individuals who are viewed as sources of extreme dangerousness. Put differently, they both tackle the question of whether citizenship-in a broad sense-concedes certain rights but imposes a fundamental duty: to have a minimum of law-abiding behavior. If the duty is not fulfilled, then the rights are not acknowledged and the individual is treated as an enemy, not as a citizen.

The underlying reasoning oozes social contract theory. This is not by chance, as great philosophers (Rousseau, Fichte, Hobbes, Kant) have employed similar arguments that are briefly sketched in the essay. There are also references to the legal theory behind the scenes predicating that in order for legal constructions to exist (rights, the State), they need to be followed by most people. Hence such a duty to comply, in general terms, with the law is imposed upon all persons. If not, law would be just daydreaming.

Strong and consistent as all these arguments sound, the basic problem with this type of reasoning is that it is hard for the legal system to follow without entering into self-contradiction. In this light, criticism will be brought by one of the most prominent social theories of the time, i.e., systems theory, arguing that law-abiding behavior is a precondition for legal institutions to exist, yes, but it cannot be secured by law itself. It is a precondition that has to be presupposed by the legal system. Moreover, using this kind of necessity rule, i.e., the State and the Law need to secure the preconditions of their own existence (self-preservation), entails a diabolic logic as it may lead to the destruction of the system itself. To this extent, self-preservation against external threats (terrorist attacks) and internal threats (curtailment of civil liberties) seems equally important. The essay finishes with some proposals for resolving this delicate matter, trying to reflect a keen sense of balance and forward-looking thinking.
The Wrongfulness of Crimes of Unlawful Association
Authors: Meliá Manuel Cancio
Published: December 2008

Though always present in penal codes, offenses based on belonging to a criminal organization occupy a vanguard position in today's evolution of penal law systems: organized crime is located at one of the most prominent places in the criminal policy agenda. Nevertheless, neither criminal law theory nor the actual content of criminal provisions nor the putting of theory into practice enables an adequate restriction of the interpretation of the laws against criminal organizations. Therefore we need to investigate the wrongfulness at the base of this offense. European legal scholarship has proposed two basic approaches: to consider that this offense anticipates the possibility of punishing and prosecuting such behavior (anticipation theory) or to consider that it harms a collective interest ("public security," "public peace"). From our perspective, it is necessary to underline the collective wrongfulness embedded in a criminal organization and that, beyond the actual crimes committed, it questions the monopoly of violence exercised by the state. It represents the constitution of a violent organization that counters the basis of state political organization (arrogation of political organization). This approach opens a possibility to adequately define the offense of belonging to a criminal organization.
Duress and the Antcolony's Ethic: Reflections on the Foundations of the Defense and its Limits
Authors: Gómez Daniel Varona
Published: December 2008

Duress is probably the most controversial defense in criminal law theory. Neither its foundation nor its nature as a justification or mere excuse nor its limits achieves any consensus among criminal law academics. In this paper a foundation of the duress defense is presented that considers that its importance lies in the fact that it allows us to appeal to considerations of justice and fairness that can explain the decision to forgo punishment in circumstances when the conduct performed by the actor cannot be considered socially beneficial or correct according to an objective (impartial) assessment of the act. The proposed account of the defense will also help us understand why duress represents instances of excuse rather than of justification. Finally, a brief discussion of the differences between the necessity and duress defenses will be provided, as well as an analysis of the proper limits of the duress defense.