bluuebunny/crossref_metadata_2025 huggingface dataset:
An Analysis of Two Casting Defects in Parts Made from ACI Type HF Heat-Resistant Stainless Steel
Authors: Bosak EM , Elmendorf R
Published: March 2009

Subsequent to the production of American Casting Institute Type HF stainless steel castings, two types of casting defects have been found: hot tearing and shrinkage. Analyses of castings with these types of defects have been conducted. The hot tears were detected by fluorescent dye penetrant inspection and were found to be confined to certain similar locations in separate castings. The shrinkage was detected by gamma radiography and was confined to the interior of one casting. The investigation of the hot tearing condition has led to a metallographic definition of carbide distributions and a tentative microchemical description of the area containing the hot tear. A metallographic and microchemical characterization of the interdendritic region near those areas displaying shrinkage and microshrinkage in a different HF stainless steel casting has also been made. In both cases, a description of the means by which the casting defects were eliminated is included. Scanning electron microscope, energy-dispersive X-ray analysis, and surface replication techniques were used, as well as routine metallographic procedures.
Effect of Nitrogen in Cast Heat-Resistant Alloys for Service in Atmospheres Containing High Sulfur at High Temperature
Authors: Finch LE
Published: March 2009

Chromium contents of at least 20 percent are necessary for long-term protection from hydrogen sulfide attack at 889 to 982°C (1650 to 1800°F) in high British thermal unit gas compositions. The cast alloys HD and HE with a chromium content range of 26 to 30 percent are duplex alloys ferrite in an austenitic matrix as normally produced. Additions of nitrogen can lower the ferrite content and increase the short-time elevated temperature properties. This report notes the rate of increase per 0.01 percent nitrogen for HD and HE at 760°C (1400°F) and HF at 704°C (1300°F).
Manufacturing and Properties of Large Castings in 13Cr-1Ni Low-Carbon Steel (ASTM A217)
Authors: Santafè C , Priante M , Amici G , Finocchio M
Published: March 2009

Previous investigations on the steel ASTM A217 (TERNI FM1M) with low carbon content have been extended by creep-rupture and stress corrosion tests. Creep test results were analyzed in order to evaluate long-term creep resistance according to the Larson-Miller method. Stress corrosion tests did not show any cracks, up to 700 h, for the applied stress of both 90 and 110 percent yield strength, but pitting phenomena were evident.

Cavitation tests were performed to evaluate the behavior of this steel for hydraulic purposes.

Results concerning the manufacture of six turbine shells for a nuclear power station, weighing about 80 metric tons at shipment, are reported.
Characterization of Lamina and Interlaminar Damage in Graphite/Epoxy Composites by the Deply Technique
Authors: Freeman SM
Published: March 2009

A unique technique is described for separating a cured graphite/epoxy composite into its individual laminae while maintaining the integrity of each lamina. The use of this technique provides information heretofore unavailable for fracture and failure analysis. Examples of damage characterization using this technique are presented for pin-loaded holes and impact areas. In the case of the pin-loaded holes the extent of fiber bundle fractures in the internal laminae are shown to be a function of increasing loads. For impact-damaged areas the delaminations between the various laminae were marked with a unique process prior to the deplying process. After the laminae were deplied, the indicated areas of delamination and the incidents of fiber fracture were measured using a digital image analyzer. Photographs of typical damage are included.
Hybrid-Fiber-Reinforced Sheet Molding Compound Composite
Authors: Chang DC
Published: March 2009

This paper presents an analytical method of determining the effective stiffness properties of hybrid-fiber sheet molding compound (SMC) composites and of tailoring desired hybrid composites for design applications. Results are presented specifically for a chopped carbon/glass hybrid-SMC that is suitable for high-volume automotive production. The stiffness properties and material costs are computed and illustrated as functions of total fiber content and percent of carbon fibers. Also presented are material costs for the complete family of carbon/glass hybrid-SMC having equal Young's modulus.
Biaxial Strength Behavior of Glass-Reinforced Polyester Resins
Authors: Owen MJ , Rice DJ
Published: March 2009

Numerous strength theories have been proposed for fiber-reinforced materials. After preliminary consideration. 14 of these have been applied to the behavior of glass fabric and woven roving fabric reinforced polyester resin under both biaxial and fatigue loading. Results from 350 tube tests reveal that the failure mode depends on the biaxial stress ratio, fatigue life, and material combination. The distinction between failure theories tends to be obscured by scatter in the results. The scatter is caused mainly by thickness variation arising from the wet lay-up technique. Accordingly strength and life results were related to a particular thickness rather than average values. The fit of failure theories to experimental data tends to deteriorate with increasing fatigue life, and only three of the theories considered offered a reasonable design basis up to 106 cycles. One of the resin systems was more flexible than the other and gave substantially enhanced static tensile strength to the laminates. This benefit was not transferred to the laminates under tension-compression conditions or under fatigue conditions.
Initiation and Accumulation of Damage in Composite Laminates
Authors: Sandhu RS , Gallo RL , Sendeckyj GP
Published: March 2009

A progressive-ply-failure finite element program for predicting damage initiation and progression in composite structures with stress concentrators is described. The program was used to predict the damage accumulation process in double-edge notched graphite-epoxy specimens subjected to tensile loading. The predictions were found to be in good agreement with experimental data.
Failure Characterization of a Graphite/Epoxy Laminate Through Proof Testing
Authors: Hahn HT , Hwang DG
Published: March 2009

The object of the present work was to investigate the failure behavior of a [02/90/±45] AS/3501-5A graphite/epoxy laminate through proof testing. The primary emphasis was on the delineation of the effect of the proof test on the residual strength and life, the establishment of strength-life relations, and the identification of failure process. The test series consisted of static tests, tension-tension fatigue tests preceded by proof tests, and examinations of failure modes. Major findings can be summarized as follows: (1) Proof tests have little effect on the residual strength and life. (2) Strength and life are statistically interrelated so that a statically stronger specimen has a longer life. (3) A higher modulus is an indication of a higher strength and longer life. (4) The failure process of the present laminate is similar to that of the quasi-isotropic [0/90/±45]8 laminate. However, the crack multiplication in the present laminate is more extensive and faster. (5) Delamination surfaces consist of shiny and dull areas. The shiny areas have bare fibers, whereas the dull areas have fiber imprints in the epoxy.
Nondestructive Evaluation of Fiber-Reinforced Composites with Acoustic Backscattering Measurements
Authors: Bar-Cohen Y , Crane RL
Published: March 2009

Experimental studies of acoustic backscattering in the Rayleigh region (0.1 ≤ ka ≤ 1.0) from fiber-reinforced composites were conducted. A significant increase in backscattering was observed for those orientations which place the axis of the fibers or other discontinuities at normal incidence to the acoustic beam. Fiber orientations and the distribution of cracks within specific plies were easily mapped by this technique.
Strain Rate Characterization of Unidirectional Graphite/Epoxy Composite
Authors: Daniel IM , Hamilton WG , LaBedz RH
Published: March 2009

Unidirectional graphite/epoxy was characterized at various strain rates ranging from quasi-static to over 500 s−1. Properties were obtained by testing thin rings 10.16 cm (4 in.) in diameter, 2.54 cm (1 in.) wide, and 6 to 8 plies thick under internal pressure. Unidirectional 0, 90, and 10-deg off-axis rings were tested to obtain longitudinal, transverse, and in-plane shear properties. In the dynamic tests internal pressure was applied explosively through a liquid, and the pressure was measured with a calibrated steel ring. Strains in the calibration and specimen rings were recorded with a digital processing oscilloscope. The data were processed and the equation of motion solved numerically by a minicomputer attached to the oscilloscope. Results were obtained and plotted in the form of a dynamic stress-strain curve. Times to failure were as short as 30 μs. The 0-deg properties which are governed by the fibers do not vary much with strain rate with only a moderate increase in modulus. The 90-deg properties show a marked increase in modulus and strength with strain rate. In-plane shear properties follow a similar trend, although less pronounced than transverse properties. In all cases ultimate strains do not vary much with strain rate.
Use of the Lognormal Distribution for Characterizing Composite Materials
Authors: Whitney JM
Published: March 2009

In the characterization of composite materials the two-parameter lognormal distribution is shown to offer many practical advantages over the two-parameter Weibull distribution in terms of the availability of best unbiased estimators, ease of computing confidence bounds, and availability of best unbiased estimators for pooled data. The parameters of the lognormal distribution can also be put into a form which is analogous to the parameters of a Weibull distribution. Reasonable correlation to the lognormal distribution is obtained for static and fatigue data on graphite/epoxy composites.
Study of Compression Properties of Graphite/Epoxy Composites with Discontinuities
Authors: Grimes GC , Dusablon EG
Published: March 2009

This study assesses the static compression and R=10 compression-compression fatigue properties of graphite/epoxy composites with ply drop-off discontinuities under severe operating environments, including room-temperature dry and wet, −65°F wet, and 218°F dry and wet. In 30-ply [(±45)5/016/904]C laminates two 0-deg plies or four 45-deg plies are dropped off, symmetrically, in the middle one third of the specimen thickness. Static strength and moduli of elasticity are unaffected by these discontinuities; however, some proportional limit values and Poisson's ratio values are significantly changed. At 1.25 × 106 cycles of constant frequency and amplitude fatigue, the algebraic minimum endurance limit stress level is degraded 15 to 30 percent by the two 0-deg ply drop-offs, but only 0 to 13 percent by the four 45-deg ply drop-offs, or is even increased somewhat. The endurance limits of the surviving specimens are lower than their residual strengths, which vary directly with maximum applied cyclic compressive stress up to a threshold level. Detailed data tables and plots are included.
Selected Aspects of the Design of Offshore Structure for Fatigue Resistance
Authors: Hartt WH
Published: March 2009

The problem of fatigue of welded steel connections in sea water is reviewed, and it is demonstrated that this failure mode is most troublesome in deep water or rough sea locations where 107 to 108 relatively low-stress range load excursions must be anticipated during a typical design life. Mechanical, material, and environmental variables which influence this fatigue are discussed; and attention is focused upon the effects of cathodic protection, where existing data appear contradictory. The appropriateness of a design procedure which integrates S-N and (da/dN)-ΔK data is discussed, and examples of its applicability to welded specimens and connections in sea water are presented.
Experimental Evaluation of Initial Flaw Criticality and Analysis Methods for Damage Tolerant Air Force Aircraft
Authors: Rudd JL , Brussat TR , Chiu ST , Creager M
Published: March 2009

This paper considers two aspects of the United States Air Force analytical and experimental damage tolerance design requirements for metallic airframes: the locations of initial damage and the accuracy of crack growth analysis. Following a summary of the requirements, an assessment is made of the validity of the initial continuing damage locations specified in the requirements. Guidelines are provided for selecting the initial primary damage location needed but not specified in the requirements. Analyses and test results are presented for typical aircraft structure (that is, chordwise splices, spanwise splices, stringer-reinforced continuous skin, 2-bay wing panels, etc.). The analytical and experimental results are correlated in order to assess the accuracy of the state-of-the-art analytical capability to satisfy the Air Force damage tolerance requirements.
An Investigation of Initial Fatigue Quality
Authors: Wang DY
Published: March 2009

This paper describes an investigation to define statistical fatigue in terms of the initial quality of fastener holes. The objective is to develop and verify equivalent initial flaw size (EIFS) concepts for fatigue durability analysis of typical production quality structures.

A special test procedure was used to obtain a statistically large sample of data under spectrum loading by testing a specimen containing 24 holes. It is possible to obtain a maximum of 96 fatigue data sets in the test of two specimens up to 100 000 flights in a reasonable time. The method involved removing the early cracked holes with a circular saw cutter and continuing the testing of the remaining holes. Marker cycles, which were designed to be an integral part of the spectrum, have served the intended purpose of identifying crack origins and microcrack growth rates using scanning electron microscope (SEM) fractography. The surface mechanical and material defects responsible for the origin of microcracks were examined quite fully.

Through quantitative analysis of a large amount of microcrack growth data and surface macrocrack growth data, many parameters affecting apparent fatigue scatter were resolved. A method was developed to define statistical fatigue quality of fastener holes in terms of EIFS distribution. The EIFS should be a function of initial surface quality and independent of other secondary variables that affect crack growth rate. The procedure involves the use of a master crack growth curve developed from the experimental data of microcrack growth ranging from initial physical flaws as small as 0.005 mm (0.0002 in.). The essential physical defects in 2024-T3 as origins of microfatigue cracking are the tool marks and inclusions.
Factors Influencing Propagation of Mode III Fatigue Cracks under Torsional Loading
Authors: Hurd NJ , Irving PE
Published: March 2009

Mode III fatigue crack growth rates have been measured in a quenched and tempered low-alloy steel heat treated to a range of strength levels. When compared with Mode I crack growth rates, it is found that Mode III rates are slower than the Mode I by a factor of between 10 and 50. ΔKT-values in Mode III are believed to be much larger than those of Mode I.

The stability of Mode III cracks compared with those in Mode I is shown to be related to applied ΔK, R-ratio, and the strength level of the steel. Mode III cracks are most stable in tests at R = −1, at high values of ΔK, and in the softest material. These conclusions are in part related to the differences between Mode III and Mode I crack growth rates. The results are considered in the light of surface hardening treatments applied to shafts loaded in torsion.
Prediction of Fatigue Crack Growth under Variable-Amplitude and Spectrum Loading Using a Closure Model
Authors: Newman JC
Published: March 2009

The present paper is concerned with the application of an analytical crack-closure model in the study of crack growth under various load histories. The model was based on a concept like the Dugdale model, but modified to leave plastically deformed material in the wake of the advancing crack tip.

The model was used to correlate crack growth rates under constant-amplitude loading, and to predict crack growth under variable-amplitude and aircraft-spectrum loading on 2219-T851 aluminum alloy sheet material. Predicted crack-growth lives agreed well with experimental data. For 80 crack growth tests subjected to various load histories, the ratio of predicted-to-experimental lives, NP/NT, ranged from 0.5 to 1.8. The mean value of NP/NT was 0.97 and the standard deviation was 0.27.
Application of an Improved Crack Growth Prediction Methodology on Structure Preliminary Design
Authors: Chang JB , Engle RM , Hiyama RM
Published: March 2009

An improved crack growth methodology which accounts for load interaction effects was implemented into a computer module, PREGRO, and was subsequently incorporated into an existing preliminary design analysis computer program, APAS. The procedure utilizes the equivalent damage concept, which converts the random spectrum into equivalent constant-amplitude load cycles. By using this improved crack growth prediction module, unnecessary weight penalties can be avoided in the preliminary design of primary structures. Examples are given for the application of this predictive method to wing structures for typical fighter and transport aircraft.
Fatigue Crack Growth in Stiffened Panels under Pressure Loading
Authors: Chu HP , Hauser JA , Sikora JP
Published: March 2009

An experimental study was conducted to characterize the fatigue crack growth behavior of stiffened panels under uniform lateral pressure loading. The panels were made of standard 5456 aluminum alloy and fabricated by weldbonding. Fatigue failure of the panels consisted of cracking of the stiffeners, followed by cracking of the skin. Crack growth rate data showed a maximum value in the stiffeners and a constant value in the skin before failure. A weldbonded stiffened panel could endure more fatigue cycles than a gas metal arc welded panel under similar pressure loading. The panel data were correlated with base line materials data and represented by either of two simple equations in terms of fatigue crack growth rate versus stress intensity factor range. The stress intensity analysis for the panels was made by an approximation method which considered the combined effects of tension and bending stresses. Accuracy of this method was verified by photoelastic measurements.
Deformation Modeling and the Strain Transient Dip Test
Authors: Jones WB , Rohde RW , Swearengen JC
Published: March 2009

Recent efforts in material deformation modeling reveal a trend toward unifying creep and plasticity with a single rate-dependent formulation. While such models can often describe actual material deformation with some precision, most require a number of different experiments to generate model parameter information. These experiments can be complex, time-consuming, and expensive to perform. Recently, however, a new model has been proposed which is unique in that most of the requisite constants may be found by examining creep transients brought about through abrupt changes in creep stress, namely, the so-called strain transient dip test. While the strain transient dip test is simple in concept, it is extremely difficult to perform in actuality. The critical measurement in this test is the absence of a resolvable creep rate after a stress drop. As a consequence, the result is extraordinarily sensitive to strain resolution as well as machine mechanical response. This paper presents the design of a machine in which these spurious effects have been minimized and discusses the nature of the strain transient dip test using the example of aluminum. It is concluded that the strain transient dip test is not useful as the primary test for verifying any micromechanical model of deformation. Nevertheless, if a model can be developed which is verifiable by other experiments, data from a dip test machine may be used to generate model parameters.
Strain Rate History Effects in Body-Centered-Cubic Metals
Authors: Klepaczko J , Duffy J
Published: March 2009

This paper presents a discussion of the strain rate history effects that occur during the deformation of body-centered-cubic (BCC) metals. It is divided into two parts: a brief review of previous work, which also includes some new data, followed by an analysis of material behavior based on previous and new results. The review discusses early experiments on steels and other BCC metals in which interrupted tests were performed. These tests consist of loading initially at one strain rate, unloading, and reloading at a second strain rate, either higher or lower than the first. Early experiments of this type had revealed a substantial difference in response between BCC and face-centered-cubic (FCC) metals. The review also includes results of incremental strain rate tests with large jumps in strain rate, augmented by a series of experiments designed to study strain rate history effects in steel. The latter consist of incremental tests performed on specimens of an AISI 1020 hot-rolled steel over the temperature range 83 K ≤ T ≤ 494 K. Results indicate that at temperatures near the ambient and for relatively small shear strains (up to γ ≈ 0.20) strain rate history effects play a minor role compared with strain rate effects per se. However, for low temperatures and for dynamic aging temperatures, strain rate history effects are shown to be of considerable importance. The second part of the paper concentrates on an analytical discussion of adiabatic coupling during deformation and on constitutive modeling of deformation in BCC metals.
Cyclic Stress-Strain Behavior of Inconel 718
Authors: Cook TS
Published: March 2009

An investigation of the cyclic stress-strain behavior of forged Inconel 718 is described. The study was conducted at 294, 616, and 839 K, and Rε (εmin/εmax) = 0, −1. The material showed moderate amounts of cyclic strain softening, with the extent and rate of softening increasing as the temperature increased. It was expected that the cyclic stress-strain curve defined by the amplitude of the load-displacement hysteresis loops would be independent of Rε; specimen-to-specimen scatter prevented such a conclusion, although the data tended to support it. A second cyclic stress-strain curve, defined by the locus of the tips of the hysteresis loops, incorporates the mean stress of the loop and was dependent on Rε. The presence of the mean stress in this definition of the cyclic stress-strain curve produced a curve with a hump; after reaching a maximum value at about 0.8 percent strain range, the stress decreased as strain range increased further. This hump shape is not the result of transient behavior, but represents the stable cyclic curve. The transient behavior and the stable state reached by the material during the test is discussed.
A Kinetics Approach to the Derivation and Measurement of the Constitutive Equations of Time-Dependent Deformation
Authors: Krausz AS , Faucher B
Published: March 2009

The approach is based on a model that is an intermediate between the specific micromechanics models of the structural theory of plasticity and the phenomenological continuum-mechanics models of anelasticity. It is considered that the fundamental physical processes, producing the deformation of any solid, are the breaking and mending of atomic bonds, and that plastic flow occurs by the movement of flow units that very often have to overcome a series of energy barriers. Therefore the constitutive relations are derived from the kinetics analysis of the energy barriers and the deformation rate is determined from rate theory. The constitutive equations obtained in the study are in the form of ordinary differential equations and are based on a rigorously defined physical model. Numerical solutions of the equations applied to a system of two consecutive energy barriers show excellent agreement with experimental results obtained under various testing conditions. Furthermore, calculations show that the stiffness of the testing machine can have a considerable influence on the observed behavior during stress relaxation experiments.
The Role of Long-Range Internal Back Stresses in Creep of Metals
Authors: Nix WD , Gibeling JC , Fuchs KP
Published: March 2009

The use of back stress terms in constitutive equations implies the existence of inhomogeneous stresses within the solid. We suggest that such inhomogeneities arise naturally from dislocation processes and are associated with the development of hard and soft regions within the substructure. We point out that back stresses act in the soft parts of the substructure and that constitutive equations containing back stresses should be based on flow mechanisms in these regions. Constitutive equations based on flow in the hard parts of the substructure should contain forward internal stresses. We envision flow in the hard regions to be controlled by recovery and to dominate at high temperatures, while flow in the soft regions involves other kinds of thermally activated dislocation motion and is most important at low temperatures. Power law breakdown is explained with a composite model as a natural consequence of the transition from high temperature to low temperature deformation.
Inferring Microscopic Deformation Behavior from the Form of Constitutive Equations for Low-Carbon Steel and 5182-0 Aluminum
Authors: Stevenson R
Published: March 2009

Earlier work has demonstrated that the formability of a low-carbon sheet steel can be improved by deforming at temperatures below room temperature. In this work the tensile properties of a 5182-0 aluminum alloy were determined at low temperatures, and a significant increase in work-hardening rate resulted. The forms of the constitutive equations which best fitted the deformation behaviors of low-carbon steel and 5182-0 aluminum were completely different and could be rationalized in terms of the operative microscopic deformation mode. It appears that it may be possible to infer the operative microscopic deformation mechanism from the form of the constitutive equation.
Comparison of Predictions of Work-Hardening Theories for Two-Phase Alloys in Terms of Stored Energy: Eutectic Alloys Al-Al3Fe and Al-Al6Fe
Authors: Wolfenden A
Published: March 2009

Two theories [Brown and Clarke (B-C) and Tanaka and Mori (T-M)] that treat work hardening in two-phase alloys take into account the effects of precipitate shape, elastic inhomogeneity, and deformation mode. Both theories calculate the initial work hardening rate (θ), but in addition the T-M theory estimates the strain dependence of the stored energy, and the ratio of stored to expended energy. The experimental data of Adam and Wolfenden, which include values of stress, strain (ε), stored energy (Es), and expended energy (Ew) for unidirectionally solidified eutectic alloys Al-Al3Fe and Al-Al6Fe, are used for comparing the abilities of the two theories to fit the data. The comparison shows that the parameters in both theories may be adjusted to give good values for θ, and that T-M theory yields excellent agreement for Es/Ew for both alloys and for Es/ε2 for the Al-Al6Fe alloy.
Determination of Calcium Carbonate Content in Soils
Authors: Chaney RC , Slonim SM , Slonim SS
Published: March 2009

A survey of laboratory methods is presented for the determination of the calcium carbonate content of soils. The survey looks at (1) the accuracy obtained, (2) operator skill required, and (3) relative equipment costs, in addition to other variables. In addition, a summary of marine carbonate materials is also presented which illustrates their various sizes, shapes, locations, porosities, and chemical constituents. The conclusion from this survey is that the pressure calcimeter method (“Karbonat-Bombe”) is the best method suited for geotechnical engineering applications.
Calcareous Sands of the Israeli Coastal Plain
Authors: Frydman S
Published: March 2009

A large portion of the Mediterranean coastal plain of Israel is overlain by thick deposits of calcareous sands, sometimes cemented to varying degrees and forming a cemented sand known locally as kurkar. The paper presents a review of the geotechnical properties of these deposits, and methods used to evaluate them. Parameters so obtained have been used for the design and analysis of building foundations, cliff slope stability analyses, and liquefaction studies. It is found that in many cases considerable breakdown of calcareous cementing bonds occurs under conditions of high stress, with the result that the soil behaves as an essentially cohesionless material, sometimes having an extremely high compressibility.
Strength of Compacted Specimens of a Calcareous Playa Lake Clay
Authors: Olsen JM , Leonard BD
Published: March 2009

This paper presents the results of a series of tests run on specimens of a low-plasticity clay (LL = 34, PI = 12) with a calcite content of approximately 25 percent by weight. The naturally occurring clay tested is from playa lake deposits in southern Idaho. This test program investigated the strength of labratory compacted specimens as a function of time and curing conditions.

Specimens of 33.3 mm (1.3 in.) diameter were prepared using the Harvard miniature kneading compaction device. Specimens for strength testing were prepared with water contents at optimum (16.5 percent) and 4.5 percent dry of optimum (12 percent). The latter value is approximately the water content of the material as-sampled. After compaction, specimens were allowed to cure under either air-dry or moist conditions prior to strength testing. The unconfined strength [ASTM Tests for Unconfined Compressive Strength of Cohesive Soil (D 2166-66)] of replicated specimens was measured at times ranging from several minutes to three months after compaction.

The results of these tests showed substantial strength gain with loss of moisture. Most of the increase in strength was experienced within the first 8 h of air-drying while the increase was more gradual for the moist cured specimens. The specimens compacted at optimum water content exhibited higher strengths than those compacted dry of optimum after curing. In the as-molded condition, however, the dry-of-optimum specimens were stronger.
Elastic and Strength Properties of Calcareous Rocks of Dade County, Florida
Authors: Prieto-Portar LA
Published: March 2009

This paper contains the findings of an extensive subsurface investigation for the Metropolitan Dade County's Rapid Rail Transit System. The first 35 km (21 miles) of the system have been studied in depth with the view of providing foundation design parameters for an entirely aerial dual-rail guideway. This guideway is commonly supported by single piers founded on shallow spread footings. Closely controlled rail and vehicle to platform tolerances demand accurate prediction of the surficial calcareous strata performance. A major portion of the transit alignment is underlain by a porous oolitic limestone, generally encountered near the ground surface and ranging in thickness from 3 to 12 m (10 to 39 ft). The shallow footings bear upon the upper surface of this calcareous formation. There is much local variability in the thickness and quality of the soil/rock. Four types of deposition modes have been identified (transverse glades and marine tidal shoals, cross-bedded marine oolites, freshwater deposits, and thin weathered uncemented limestones), and are important strength determinants. The elastic properties of the Miami calcareous formations were obtained from extensive laboratory tests on 10-cm (4 in.) inside-diameter cores. These tests included unconfined compression tests, modulus of elasticity, direct uniaxial tension tests, splitting cylinder (diametral compression tests), modulus of rupture (tensile failure stress in bending), shear strength, and punching shear strength (resistance to diagonal tension failure). These tests are shown in tables that include variability with depth. Permeability and electrical resistivity results are also included.
Simulated Service Tests for Evaluation of Engine Coolants
Authors: Schulmeister R , Speckhardt H
Published: March 2009

In order to predict coolant additive performance in actual engine service by means of short-time laboratory tests, test procedures for coolant additives which include simulated service, corrosion, and vibratory tests have been developed. By choosing suitable test conditions it is possible to gain reliable predictions, determine the weak points of the products, and eliminate additives that are not suited for their purpose.
How Good is the ASTM Simulated Service Corrosion Testing of Engine Coolants?
Authors: Choinski JV , Maxwell JF
Published: March 2009

The ASTM Simulated Service Corrison Testing of Engine Coolants (D 2570–73) was developed to evaluate coolant performance. The method has been plagued by lack of adequate reproducibility which is making the credibility of the method questionable. Several interlaboratory tests and reproducibility studies have been conducted, but no significant progress has been made to improve the reproducibility. A questionnaire was sent to ASTM Committee D15 on Engine Coolants for an opinion of the overall value of the method. Most agree that this test is excellent for development and screening, but its use as a qualifying tool is limited due to the lack of reproducibility. A statistical analysis was performed on the interlaboratory data to obtain the quantitative estimates of reproducibility and repeatability as follows: Y ± 140/60 percent and Y ± 60 percent, respectively, where Y is the value of the corrosion weight losses. These results show that reproducibility is not adequate enough to use the method as a qualifying tool, and repeatability is in a range where it can be used effectively for development, but there is room for improvement of the repeatability also.
The Analytical Chemist: His Own Worst Enemy
Authors: Byrne FP
Published: March 2009

An analytical chemist becomes his own worst enemy when he subconsciously forgets his objectivity by not taking into account the limitations of his tools. This can show up in weighing in gravimetric analysis, in reading the burette in volumetric analysis, and by taking samples that are too small. This can also appear in atomic absorption analysis when he forgets the limitations of the atomic absorption spectrophotometer. Statistics is a tool which can also be misused. Its use will not convert bad data to good data nor decide if the outlier is the only correct answer or a wrong answer. Misuse can lead to an unsound method, as in the determination of iron in uranium. By forgetting his pride, the analytical chemist can find a statistician of key help in finding the pertinent variables to control in converting a research method into a control method as in the determination of antimony in steel.
Automated Data Acquisition and Analysis for the Instrumented Impact Test
Authors: Wogulis SG , Whitney BW , Ireland DR
Published: March 2009

The system logic employed in developing an automated instrumented impact system, the rationale for data analysis, and comparison of the operation of this system with that of other methods for the instrumented impact test are presented. The system is used with a wide variety of impact machines and consists of the following major components: instrumented tup (load sensing transducer), velocity measuring/trigger unit, microprocessor, printer/plotter, and floppy disk drive. System operation minimizes operator interaction and requirements for knowledge of electronics or the intricacies of data analysis for the instrumented impact test. Test results are provided as graphical (20 cm2) and tabular listing of key test and data parameters. The software is applicable to any type of impact test. Data acquisition and analysis is performed using consistent procedures and complex in-depth analyses are possible on a routine basis.
CAUS-1 (Computer-Aided Ultrasonic System)
Authors: Doherty JE , LaGrotta JM , Burr RJ , Wheeler E
Published: March 2009

This paper reports on the construction of a computer aided ultrasonic inspection system (CAUS-1) which does not require inspection shapes to have premachined rectilinear surfaces nor the large material overstock needed by conventional inspection methods.

The main features of CAUS-1 include a contour sensing-following system, computer controlled ultrasonic instrumentation, and flexible software package. The contour following system maintains the inspection beam normal to the inspection surface and enables dimensional measurement of the shape simultaneously with ultrasonic inspection. The ultrasonic instrumentation can resolve a number one flat bottom hole (FBH) 2 mm from the front surface and through 35 mm of material using a single instrument setting. The instrument has a special defect gate that reports the magnitude and position of the two largest indications detected by each ultrasonic pulse. A knowledge of computer programming is not needed in order to use CAUS-1, because inspection procedures are developed interactively using English language. The software contains data analysis features for process control inputs, inspection data archival storage, dimensional inspection, and a method of inputting shape data into a computer aided machining system (CAM).

CAUS-1 is a fully integrated inspection system that can inspect near-net shapes for material defects and dimensional tolerance in a quarter of the time it takes to inspect a disk for material defects alone using conventional inspection methods.
Thermal Performance of Buildings and Building Envelope Systems: An Annotated Bibliography
Authors: Carroll WL
Published: March 2009

A bibliography of published papers describing models, measurement techniques, apparatus, and data for the thermal performance of whole buildings and building envelope systems has been collected (aggregate energy consumption of whole buildings; performance of heating, ventilating, and air-conditioning equipment; and solar technologies are not included). Summary descriptions of the content of each citation are provided. Measurements on whole buildings or on systems other than walls are sparse. However, new and recently completed measurement facilities are increasing these capabilities. Measurements under dynamic conditions are difficult to accomplish and few reliable data exist. Some analogs have been explored experimentally and analytically. Citations on analytical models are selective and concentrate on methodology that forms the basis of computer programs for whole-building energy analysis. Interesting future directions include new approaches to dynamic measurements, both in the laboratory and in the field, for envelope systems and for whole buildings.
Air Intrusion Effects on the Performance of Permeable Insulation Systems
Authors: Berlad AL , Tutu N , Yeh Y-J , Jaung R , Krajewski R , Hoppe R , Salzano FJ
Published: March 2009

The R-values of permeable insulation systems are generally determined in test apparatuses designed to assure one-dimensional heat transfer and to assure no air intrusion effects. Such classical R-values are then calculationally employed to help describe in situ heat-transfer rates through insulation systems.

The research reported herein reexamines the applicability of these classical R-values to commonly encountered insulation systems where air intrusion is physically possible. Several kinds of findings are reported: (a) Laboratory-determined R-values for several types and thicknesses of permeable insulators, under conditions of no externally imposed flows. (b) Laboratory-determined heat-transfer rates for several permeable insulators under conditions of externally imposed flows (air intrusion). (c) Theoretically calculated heat-transfer rates for permeable insulation systems which sustain infiltrative-exfiltrative air intrusion effects.

The results obtained show that the thermal insulation provided by a permeable insulation system may differ substantially from that which is predicted by simple application of classical R-values.
Thermal Research Facility—A Large Calibrated Hot Box for Horizontal Building Elements
Authors: Mumaw JR
Published: March 2009

A large multipurpose facility utilizing existing calibrated hot-box technology was designed and constructed to perform research on the heat flow mechanisms of horizontal building elements. The Thermal Research Facility incorporates a 4.3 by 6-m (14 by 20 ft) opening calibrated hot-box metering pit with a 10.7 by 21.3 by 7.6 m (35 by 70 by 25 ft) primary chamber to permit measurements on both horizontal building elements, such as floors, ceilings and roofs, and complex building elements such as a one-room house or a small manufactured house. This paper describes the design considerations and construction details required to build the facility using state-of-the-art technology for measurements and control.
Low-Temperature Properties of Expanded Polyurethane and Polystyrene
Authors: Sparks LL
Published: March 2009

Two materials being used extensively as cryogenic insulations are the expanded plastics polyurethane (PU) and polystyrene (PS). These cellular plastics are excellent thermal insulators with measured values of apparent thermal conductivity at a mean temperature of 112 K being 0.013 to 0.016 W/m·K. The effect of aging and conditions of aging are critical factors in determining the ultimate conductivity. The major component of the overall conductivity, gas conductivity, is affected by permeation of gases through the cell walls. The reasonably high strength-to-density ratio for PU and PS at room temperature, 8 to 9 kPa/kg/m3 compared with ∼50 for aluminum alloys and ∼25 for stainless steels, allows these insulations to be self-supporting and to lend structural support to the system. The thermal, elastic, and mechanical properties are functions of several nonindependent parameters such as density, cell size, composition, and method of processing. The properties of these expanded plastics are also anisotropic. The large variations found in existing data reflect these complex dependencies. Expected behavior and experimentally determined data are discussed for the following properties: tensile, compressive, and shear strengths and the associated moduli, thermal conductivity, linear thermal expansion, specific heat, and thermal diffusivity. Temperatures below 300 K are considered.
Environmental Effects on Graphite Fiber Reinforced PMR-15 Polyimide
Authors: Serafini TT , Hanson MP
Published: March 2009

Studies were conducted to establish the effects of thermo-oxidative and hydrothermal exposure on the mechanical properties of T300 graphite fabric reinforced PMR-15 composites. The effects of hydrothermal exposure on the mechanical properties of HTS-2 continuous graphite fiber composites were also investigated. The thermo-oxidative stability characteristics of T300 fabric and T300 fabric/PMR-15 composites were determined. Flexural strengths of specimens from composites in the as-fabricated and environmentally exposed conditions were determined. The useful lifetime of T300 fabric/PMR-15 composites in air at 316°C was found to be about 100 h. The useful lifetimes in air at 228 and 260°C were determined to be 500 and 1000 h, respectively. Absorbed moisture was found to reduce the elevated temperature properties of both the T300 fabric and HTS-2 continuous fiber composites. The moisture effect was found to be reversible.
Thermomechanical Characterization of Graphite/Polyimide Composites
Authors: Kunz SC
Published: March 2009

The stiffness, strength, and shear properties of three polyimide resins (NR-150B2, PMR-15, and CPI-2237) combined with three different moduli graphite fibers (C-6000, F-5A, and GY-70) have been determined in the temperature range 20 to 371°C (68 to 700°F). Flexural test results from the various unidirectional composites show that stiffness retention with increasing temperature is affected only by the thermal integrity of the polyimide matrix. No loss in modulus occurs up to 316°C (600°F) for the PMR-15 and CPI-2237 based composites [Tg ≃ 377°C (710°F)] or to 260°C (500°F) for the NR-150B2 based material [Tg ≃ 349°C (660°F)], with any of the three fibers. In contrast, both flexure and shear strengths show fiber-dependent behavior, irrespective of the matrix resin, with increasing temperature. The higher modulus fiber composites (F-5A, GY-70) undergo little strength change up to 343°C (650°F). Composite strengths of the lower modulus fibers (C-6000), however, degrade by as much as 50 percent over the same temperature range. Thermal-oxidative stability of the various graphite fibers, and its effect on interfacial strength degradation, are considered primary causes for the fiber-type dominated strength behavior. In general, strength retention appears directly related to degree of graphitization (modulus) of the fibers. The accumulated mechanical property data, some previously unknown, are correlated with microstructural features such as fiber-matrix adhesion, porosity, and processing defects. This study of a family of graphite/polyimide composites provides a basis for selecting a high temperature, structural weight-saving material.
Thermophysical Properties Data on Graphite/Polyimide Composite Materials
Authors: Campbell MD , Burleigh DD
Published: March 2009

Measurements of the thermal properties of HTS/NR 150B2 and HTS/PMR 15 laminates were made over the temperature range 116 to 588 K(−250 to 600°F). Properties investigated included thermal conductivity, thermal expansion, specific heat, and emittance. Layups of [0]n and [0, 45, 90, 135]n were measured in two directions for both materials. The quality of both composite systems was relatively poor. This was typical of polyimide composites at the time. It was expected that, for a given layup and direction, results would be comparable for the two materials. This was the case, with some differences attributable to laminate quality rather than differences in basic materials properties. Erratic variations in thermal expansion measurements from the same specimen were observed at times. Although these were tentatively attributed to laminate quality, additional work is necessary to fully understand this behavior.