bluuebunny/crossref_metadata_2025_split huggingface dataset:
In-Plane Behavior of a Ribbon-Reinforced Composite
Authors: Yeow YT 
Published: March 2009

Experimental and analytical procedures are used to ascertain the inplane behavior of a class of ribbon-reinforced composites containing different combinations of ribbon width, pattern, volume fraction, and amount of ribbon overlap. The rationale and description of four types of unidirectional and cross-ply composites are also given. One of the objectives of this study is to determine whether the analytical tools, based on classical laminated plate theory, developed for filamentary composites are suitable for the characterization of unnotched ribbon-reinforced composites.
The experimental results of the principal properties of the unidirectional composites indicate that the materials are orthotropic. In the longitudinal direction, the response is not affected by the ribbon width, pattern, and amount of ribbon overlap: however, influences of these parameters are observed in the transverse and in-plane shear directions. The transverse-to-longitudinal ratios (E22/E11 and σ22/σ11, modulus and strength ratios respectively) of the laminates containing 1.27-cm ribbons were found to vary from 0.78 to 0.91 for the modulus and 0.67 to 0.78 for the strength, depending on the ribbon pattern used. Good overall correlations are observed between the off-axis results and analyses.
The axial stress-strain response of all cross-ply laminates is always between the longitudinal and transverse response curves. This averaging behavior of the cross-ply laminates is due to the substantial contribution of the 90-deg laminae to the axial response of the composite. Further in-plane studies on the cross-ply laminates indicate that the trends of the moduli and strengths, for laminates containing ribbons which are packed hexagonally, are parabolic with respect to the inclination of the 0-deg laminae and the axial load. For cross-ply laminates containing ribbons packed in a staggered manner, the properties may be assumed to be isotropic. The average axial-to-longitudinal ratios (Ex/E11 and σx/σ11) for the cross-ply laminate are 0.91 for the modulus and 0.82 for the strength. The correlations between experiment and analysis show that the predictions are generally conservative, especially in terms of strengths. This is primarily due to the presence of interlaminar reinforcing effects, which are not considered in the analysis. In addition, variations in stacking sequence do not affect the response of all the laminates tested. Based on macroscopic and microscopic observations of the fractured specimens and the results presented here, it would be conclusive to say that freeedge effects are substantially reduced when ribbon reinforcement is used.
Construction and Use of Toughness Maps in a Fracture Analysis of the Micromechanics of Composite Failure
Authors: Wells JK , Beaumont PWR 
Published: March 2009

Analytical expressions are presented that predict the debonding and pullout lengths observed in brittle fiber composites. These characteristic lengths are combined with models of four toughening mechanisms to calculate the work of fracture of a composite. The results are presented as maps showing not only contours of toughness but also the dominant toughening micromechanism. The toughness is largely determined by six material parameters, each map demonstrating the combined effect of changing two of these simultaneously.
Maps are presented for glass-fibers in epoxy and carbon-fibers in epoxy. Their use is demonstrated by showing the effects of hygrothermal aging on the toughness of the composites.
Testing: Thermal Expansion of Reinforced and Nonreinforced Urethane Materials
Authors: Heckla WE 
Published: March 2009

This paper reports factors that influence the determination of the coefficient of thermal expansion of reinforced and nonreinforced urethane materials.
The factors investigated were repeated test cycling of the specimen, additional post-curing, and preconditioning the specimens at various relative humidity levels. In addition, the results of an interlaboratory round robin program are presented to show the expected precision of the test method when the above factors are controlled.
Maintenance Scheduling Based on Accumulated Crack Growth
Authors: Berens AP , Gallagher JP 
Published: March 2009

Currently United States Air Force aircraft structures are inspected and maintained in accordance with a Force Structural Maintenance (FSM) plan. Because actual aircraft mission usage is different for each individual aircraft structure in a force of aircraft, the schedule for individual structural inspections and modifications is adjusted to account for differences in the crack growth accumulation rate. Scheduling adjustments are based on continuous direct or indirect measurements of a potential crack length through individual aircraft tracking.
The purpose of this paper is to describe (1) the logistics/maintenance environment in which the tracking program operates, (2) the crack length projection procedures embedded within the tracking program, and (3) the accuracy requirements for the procedures employed. Accuracy requirements are studied through an analysis of potential errors that are possible in the projections of calendar time to critical crack length. The analysis isolates the effect of potential errors in the estimate of current crack length and compares this component of the total error with those due to the unknown future flying rate and the unknown future stress environment severity. The method permits comparison of prediction precisions for competing tracking systems, and conversely, provides realistic accuracy goals for the development of new systems. Numerical examples are presented based on data from current tracking programs.
The Role of Servocontrolled Testing in the Development of the Theory of Viscoplasticity Based on Total Strain and Overstress
Authors: Krempl E 
Published: March 2009

The rate-dependent properties of AISI Type 304 stainless steel and of the high-strength Ti-7Al-2Cb-1Ta alloy obtained with tension specimens using a servocontrolled testing machine at room temperature are discussed. Tests involve strain rates between 10−8 and 10−2 s−1, strain rate changes, relaxation periods, stress rates between 10−1 and 102 MPa s−1, and creep periods.
The viscoplasticity model based on total strain and overstress is introduced and shown to qualitatively reproduce the properties observed under strain control. The theory is then examined for its qualitative prediction under stress control, and it is found that the average creep rate need not increase with an increase in stress owing to the overstress (effective stress) dependence of the creep rate. Numerical experiments illustrate this property, which is then confirmed by real experiments.
The theory has two material functions representing work hardening and rate dependence. A method of determining the function representing rate dependence from strain rate change tests is discussed. For Type 304 stainless steel this function is represented by two equivalent expressions which can be used from static (10−8 s−1) to dynamic strain rates (103 s−1). A rate sensitivity factor M (akin to the m-factor used in materials science) is introduced. It is shown to vary with overstress or strain rate.
Specimen-Test Machine Coupling and Its Implications for Plastic Deformation Models
Authors: Holbrook JH , Swearengen JC , Rohde RW 
Published: March 2009

A unified and detailed evaluation of the coupling between specimen and test machine is presented. It is demonstrated that an accurate formulation of the specimen/machine coupling relation requires exact additivity of elastic and plastic strain contributions, and that additivity is only possible with a specific set of definitions for these strains. When these definitions are implemented to ensure additivity, two strain-dependent terms in the coupling relation are identified that have been treated as constants in previous studies. One term is shown to account for the decreasing true total strain rate with increasing plastic strain at a fixed crosshead speed. The second term accounts for strain dependence of the combined specimen/machine modulus due to change in length and area of the specimen.
Several applications of the coupling relation are given that illustrate the importance of treating the specimen and test machine as a well-defined system when inferring information about plastic-deformation models from raw data. Topics covered include (1) effect of machine stiffness on work-hardening behavior, (2) variation of total and plasticstrain rate during tensile deformation, (3) effect of machine stiffness on stress relaxation behavior, (4) relationship between stress rates before and after a change in crosshead speed, and (5) deductions about mobile dislocation density from observed stress-time behavior.
Multiaxial Creep of Textured Zircaloy-4
Authors: Murty KL , Adams BL 
Published: March 2009

Extremes of anisotropic multiaxial creep behaviors were considered by analyzing the strain rate ratios versus applied stress ratio for highly cold-worked stress-relieved and partially recrystallized Zircaloy-4 tubings. Power-law creep was modeled by using the upper-bound estimate with the assumption that prism, basal, and pyramidal slip modes are possible mechanisms. Experimental strain rate ratios were compared with those calculated by statistical averaging of crystallite behavior using the crystallite orientation distribution function (CODF). The experimental data on the stress-relieved material were in excellent agreement with the model predictions based on basal slip as the dominant deformation mode. Data on partially recrystallized material were in reasonable agreement with the predictions based on a combination of basal and prism slip modes.
These results are also correlated with the Von-Mises—Hill phenomenological description with appropriate contractile strain ratios (anisotropy parameters), R and P. The parameter R is relatively insensitive to partial recrystallization and is related to the basal pole angle. The P-parameter, however, is shown to be very sensitive to fabrication procedures and is greater than unity for well-annealed material with split prism pole distributions. As the amount of cold work increased, P-parameter decreased to well below unity.
Geotechnical Properties of Calcareous Rocks of Southern Florida
Authors: Saxena SK 
Published: March 2009

This paper presents the geotechnical properties of young calcareous rocks of southern Florida. The rocks covered are Miami, Key Largo, and Fort Thompson limestones. The paper briefly details the formation and areal extent of the rocks and then evaluates several samplers for obtaining maximum recovery in a relatively undisturbed form. Evaluation of the properties is based on field and laboratory tests. The field tests included seismic refraction studies, downhole and crosshole wave velocity studies, and Menard Pressuremeter tests. The laboratory tests comprised index tests and strength and deformation evaluation tests. In addition to the usual unconfined compression tests, this investigation reports the results of the Ko-triaxial tests on the rock specimens.
The range of values for porosity, compressive strength, and modulus from various tests is presented. The discussion provides a rationale for the difference in values obtained from the tests. The suitability of various tests in providing a representative mechanical behavior is discussed.
Research and Development Efforts in Military Antifreeze Formulations
Authors: Conley JH , Jamison RG 
Published: March 2009

The U.S. Army was convinced as early as 1941 that a composition type antifreeze was desirable. The Army's needs are much more complex and operating conditions more severe than the individual automobile owner's. Army vehicles must be in the best possible operating condition at all time. These vehicles may be sent to almost any part of the world, and have to be combat ready on short notice. Operating conditions can be severe, requiring both highway and off-highway operation. Heat loads on the vehicle's cooling system vary depending upon the loads being carried and the terrain over which they are required to travel.
Indiscriminate use of commercial antifreeze coolants could result in cooling system failure. Mixtures of two good antifreeze formulations could have a direct effect on the corrosion protection of cooling system metals. In combat situations this could be disasterous.
Use of Electrochemical Techniques for Corrosion Testing of Antifreezes
Authors: O'Brien EF , Hirozawa ST , Wilson JC 
Published: March 2009

Two electrochemical techniques were used for corrosion testing of antifreezes. The first method, the galvanic test procedure, evaluates corrosion in galvanic bimetallic couples commonly found in automotive cooling systems. It identifies the anode (major corroding metal) in the couple, gives useful corrosion rates in as little as 24 h, and can generate corrosion rates as a function of time. Thus, more detailed data can be obtained more rapidly than with the standard glassware corrosion test, which gives only a weight loss measurement after two weeks of testing. Test results were compared for a number of antifreezes obtained with this electrochemical method and with ASTM Corrosion Test for Engine Coolants in Glassware (D 1384-70) and ASTM Simulated Service Corrosion Testing of Engine Coolants (D 2570-73). These results show good correlation between the methods but also point out some areas where the electrochemical method can give misleading data.
The second method, the resistance polarization method, determines the corrosion rate on a freely corroding metal and is thus used to evaluate corrosion of a metal not galvanically coupled to another metal. An example is shown in which this method was used in combination with the galvanic method to obtain information on a corrosion mechanism; that is, the effect of localized corrosion of one metal on the corrosion losses in a galvanic couple. An antifreeze was selected for which the corrosion losses from the ASTM D 1384 method did not correlate with the corrosion rate measured by the galvanic method. The corrosion rate determined by resistance polarization correlated much better with these weight loss results. This indicates that the mechanism is predominantly controlled by local corrosion processes, which account for the major portion of weight losses seen in the ASTM D 1384 method.
The patented corrosion cell used with the electrochemical methods was developed in the BASF Wyandotte laboratory and is designed to be versatile, rugged, and simple. It duplicates the anodic polarization curve for 430 stainless steel in 1.0 N H2SO4 obtained in the ASTM Standard Reference Method for Making Potentiostatic and Potentiodynamic Anodic Polarization Measurements (G 5–72).
A discussion on the usefulness of the electrochemical methods for testing antifreezes concludes the paper.
Limiting Factors in the Spectrophotometric Analysis of Minor Components of Blended Metal Powders
Authors: Javier-Son AC , Kachelmeier EJ , Reynolds GH 
Published: March 2009

The accuracy of chemical analysis of minor components of blended metal powders is dependent on good mixing conditions, representative sampling, complete sample dissolution, and sensitivity of measurement system.
An accurate, precise, and sensitive analytical procedure has been developed which facilitates the use of large sample sizes of blended metal powders and overcomes the difficulties of sample dissolution. The technique involves homogenization of the metal blends by arc melting in an inert atmosphere and analysis of the resulting arc-melted button and slag by atomic absorption spectrophotometry. Methods of eliminating interferences in atomic absorption determinations are discussed. Mathematicial correction can be applied in lieu of slag analysis which cuts down the analysis time by 50 percent. A mechanism for slag formation is proposed.
Contamination Control in Trace Element Analysis
Authors: Zief M 
Published: March 2009

Contamination problems inherent in analysis at the ultratrace (&lt;1 µg/g) element level are reviewed. Suggestions for controlling systematic errors in the following parameters are offered: the sample, the laboratory, containers, and reagents.
The addition of the blanks contributed from each of these sources comprises the total analytical blank in an analysis. Inasmuch as high blanks invalidate most ultratrace analyses, reduction in the size and variability of the blank components is a major step in attaining higher accuracy.
The Quality of Analysis Depends on Written Procedures
Authors: Rowe WA 
Published: March 2009

The quality of chemical analysis is seriously impeded when no written procedures are available. There is a gap in the traceability of the results between specimen submitted and results reported. Documentation of the analysis is incomplete. The recipient of the results, who must draw conclusions about his materials from those results, relies solely on the reputation of the laboratory or the analyst who made the analyses in judging the quality of the results. Written procedures close the quality gap by revealing the method by which the results were obtained.
In order to become accredited by an official agency, a laboratory must prove its ability to provide quality analyses. Proof includes qualified personnel, calibrated equipment, a system of records, and written procedures. Examples of accredited laboratories are those clinical laboratories licensed by the Center for Disease Control to accept human specimens through interstate commerce.
Useful written procedures include certain topics; among these are the scope or applicability and limitations, a list of materials, sampling practice, step-wise procedures, interpretations of results, and special forms to record the analysis. Each of these topics will be discussed.
Systems for Laboratory Automation
Authors: Wonsiewicz BC , Storm AR , Sieber JD 
Published: March 2009

The use of computers to control experiments, acquire and analyze data, and maintain permanent test records has advanced significantly in recent years. This paper outlines two methods which have been used in automating materials testing. One consists of a stand-alone machine controlling testing or processing, another consists of a network of microcomputers each of which controls one or more experiments and is connected to a larger central processor. The latter approach is shown to be particularly attractive when more than a few experiments are automated.
Regardless of the configuration, automation is facilitated by: standardized hardware and interfaces, high-level programming languages, modularized software, and the presence of good tools for building programs, maintaining data archives, and analyzing or plotting results.
Design, Implementation, and Control of a Computerized Tension Testing Station
Authors: Emery RR 
Published: March 2009

This paper is based on the author's recent experience with the development of computer software for a dual unit tensile acceptance test station controlled by two minicomputers in a graphite production facility. Specific examples from that experience are used as illustrations in a more general discussion. Major items that must be considered in the design, development, and implementation of a real-time software system are control, operator, and equipment interfaces, data acquisition and analysis, and software verification and change control.
In addition to actual movement of the test machine crosshead, control aspects include consideration of methods to determine the condition of the machine by way of calibration and load rate checks, and control of the specimen testing sequence. Operator and machine interfaces should be designed in such a way that the operator does not feel impeded in the performance of his work by the computer. Control panels should indicate the progress of the computer during testing so that the operator does not panic during computer delays.
The software must be designed to have a high probability of acquiring all of the digitized stress-strain points without placing a disproportionate load on the computing system. Data analysis programs should be designed to compute values for comparison with acceptance specifications and to assist in analyzing unusual data. Orderly verification of the software by an outside person provides added insurance that the final system will perform the activities specified in the original program specifications. Any changes to verified software should be fully documented, authorized, and, if required, reverified before implementation.
This paper describes how the general requirements outlined above were implemented in a production testing system.
Computerized Methods for JIc Determination Using Unloading Compliance Techniques
Authors: Clarke GA , Brown GM 
Published: March 2009

A computerized test system used for the determination of the ductile fracture toughness value JIc is described. The system is comprised of a Westinghouse 2500 computer coupled to a servohydraulic test machine by a 12-bit data acquisition system. A considerable savings in time has been realized in the data reduction and plotting of the data using this system.
The possible bounds on the accuracy of the overall testing system is discussed along with the effects on the calculated JIc value due to these inaccuracies. Examples of test data on ASTM Quenched and Tempered Vacuum-Treated Carbon and Alloy Steel Forgings for Pressure Vessels (A 508-77) and HY-130 high-strength structural steel is shown along with graphic plots of the JIc results.
It is expected that a fully computer controlled test will result from this initial test program.
An Assessment of Thermal Insulation Materials for Building Applications
Authors: Tye RP , Ashare E , Guyer EC , Sharon AC 
Published: March 2009

A comprehensive assessment has been made of thermal insulation materials currently available for use in the building envelope. Information was obtained from four major sources: 1. manufacturers' literature, 2. open literature, 3. results of questionnaires, and 4. knowledgable experts in the field.
Information on a particular generic material or product was reviewed in relation to the major factors that influence thermal and physical performance, fire characteristics, and chemical properties. Areas in which insufficient information is available are identified.
The assessed information is reported as a series of data sheets such that the reported values for generic materials are consistent with present basic principles and this can be accepted as a reliable guide for current use. The assessment provides an authoritative collection of state-of-the-art information for government policymakers, regulatory bodies, manufacturers, installers, users, and consumers. Recommendations are made for further work on the development of properties of thermal insulation materials and on test methods for determining these properties.