bluuebunny/crossref_metadata_2025 huggingface dataset:
Creating a Data Element Dictionary for Computer-Aided Terminology Work
Authors: Wright SE
Published: March 2009

This paper treats the development of a Data Element Dictionary within the framework of ISO Technical Committee 37, Terminology: Principles and Coordination Sub-committee 3 for Computational Aids in Terminology. The paper discusses the need for a standardized list of data element names for the purpose of data interchange among databases having different structural features and functional objectives. It lists the important steps to be followed in compiling such a data element dictionary and explains some of the specific problems that have occurred in reaching consensus on which data elements to include, how to define them, and how they may behave both in the local environments and in the interchange format. In conclusion the paper examines a single typical terminology entry and demonstrates the data element selections that should be made preparatory to expressing this terminology entry using data elements taken from ISO CD 12620: Computational Aids in Terminology — Data Element Dictionary. [ISO-1]2
Roundtable Discussion: Concerns in Terminology Harmonization
Authors: Meyer I , Strehlow RA , Wright SE
Published: March 2009

Following the presentation of symposium papers, the participants held a roundtable discussion focusing on the issues treated in the previous papers. As noted in the Overview introducing this book, the quality of comments transcribed during this exchange has led the editors to reproduce the transcript for the most part intact.
Interlaminar Fracture Toughness of Glass Fiber Laminates Additionally Reinforced with Carbon Bead
Authors: Lee J-J , Ogin SL , Smith PA
Published: March 2009

The plane-strain fracture toughnesses of two different particle-filled epoxies have been measured using compact tension specimens. Significant increases in toughness were observed (up to about 50 with 30% volume fraction of bead). In the phenolic bead-filled epoxy, the major toughening mechanism is crack pinning, while in the carbon bead-filled epoxy, localized plastic deformation associated with particle-matrix debonding and transparticle fracture lead to the toughening. The interlaminar fracture behaviors of hybrid composites, based on bead-filled epoxy matrices, have been investigated using DCB (double cantilever beam) and ENF (end notch flexure) specimens for Mode I and Mode II tests, respectively. The hybrid composite based on carbon bead shows an increase in both GIc initiation and GIIc values as compared to a GFRP laminate with unmodified epoxy matrix. The optimum bead volume fraction for the hybrid composite is about 15% by volume of the matrix. However, the unmodified epoxy glass fiber composite shows a higher GIc propagation value than that of the hybrid composites due to fiber bridging, which is less pronounced in the hybrids, as the presence of the beads results in a matrix-rich interply region. The relationship between the Mode I interlaminar fracture mechanics parameters (i.e., GIc and KIc values), obtained from DCB specimens, has been reviewed using orthotropic fracture mechanics.
Modeling of Accumulated Damage and Failure of Multidirectional Composite Plates Subjected to In-Plane Loads
Authors: Shahid I , Chang F-K
Published: March 2009

An investigation was performed to study damage accumulation in multidirectional laminated composite plates subjected to in-plane loads. Matrix cracking-induced accumulated damage in a multi-directional laminate was the primary concern. A progressive damage analysis has been developed for predicting the accumulated damage and its effect on the failure and the response of the composite plates. The development of the analysis was based on the assumption that the accumulated damage would be generated uniformly in composites under uniform in-plane loads. Hence, the free edge effect and the laminates that are prone to delamination were not considered in the analysis.

The analysis consists of three parts: constitutive modeling, damage accumulation prediction, and stress analysis. Based on the two-dimensional elasticity analysis, constitutive equations of a ply containing matrix crack-induced damage in a laminate were developed. In the failure analysis, a set of damage accumulation criteria modifying the existing failure criteria was proposed for predicting the extent of the damage in composites as a function of the applied loads. The stresses and deformations in the laminates were calculated by a nonlinear finite element method that incorporated the constitutive equations and the damage accumulation criteria.

The predictions of the model were compared with the available experimental data for laminates with and without a cutout. Overall, the predictions agreed with the data quite well.
Shear Deformation Analysis of the Energy Release Rate of Transverse Cracking in Laminated Composites
Authors: Sriram P , Armanios EA
Published: March 2009

The low transverse strength properties of laminated composites often result in matrix cracking in off-axis plies as the initial failure mode. Strength-based theories are generally inadequate for modeling such phenomena, while fracture mechanics-based approaches offer significantly better potential. The shear deformation model developed in a previous publication to predict the stiffness loss associated with matrix cracking is extended to yield the strain energy release rate and hence load versus crack spacing predictions. These predictions are shown to be in reasonable agreement with experimental data for graphite/epoxy systems also. The shear deformation model can also be applied to other laminate configurations, for example, (±25/90n)s type.
A Random-Damage Finite Element for Modeling Failure in Advanced Composite Materials
Authors: Slattery KT
Published: March 2009

A random-damage finite element for modeling the failure process in advanced composite materials has been developed. The random response properties of the element are determined from the results of micromechanical simulations of the degradation of a small cell of the material. The random-damage finite element replaces a finite element model consisting of thousands of degrees of freedom with a single, eight-degree-of-freedom element. This allows a typical composite specimen to be modeled and analyzed on a workstation. A special-purpose finite element code was developed to efficiently perform the nonlinear analysis. The element is used to simulate the failure of small laminates and strands of Kevlar/epoxy composite. These results are compared with experiments.
The Effect of Graphite Fiber Properties on Microcracking Due to Thermal Cycling of Epoxy-Cyanate Matrix Laminates
Authors: Knouff BJ , Tompkins SS , Jayaraman N
Published: March 2009

Graphite-fiber-reinforced polymer composite materials have become prime candidates for space structures. The high specific strengths and stiffnesses obtainable with these materials and the ability to design them with a near-zero coefficient of thermal expansion provide a flexibility that is virtually unmatched. However, microcracks resulting from thermal cycling can lead to drastic property changes of the composites. Specimens of five composite materials, each with the same epoxy-cyanate blend matrix and reinforced with different graphite fibers, were subjected to a simulated spacecraft thermal cycling environment to determine the effects of fiber physical properties on the resulting microcrack behavior. The lay-up for each material was [0/45/90/-45]s with a nominal ply thickness of 0.0125 cm (0.005 in). The specimens were cycled between -157°C (-250°F) and +121°C (+250°F) up to 500 times. They were examined at a magnification of ×400 at different thermal cycle intervals for microcracks. It was found that although the maximum crack density varied with the ply lay-up angle, it did not vary much with fiber type. However, the fiber type had a strong influence on the rate of microcrack development. This behavior was found to be best described by fitting a hyperbolic function to the microcrack density as a function of the number of thermal cycles.
Observations of the Load Redistribution in Polymeric Composite Laminates Under Tension-Tension Fatigue Loading
Authors: Connolly MP , Davidson DL
Published: March 2009

A series of detailed measurements were obtained of the edge displacements at different stages in the fatigue life of a composite laminate subject to tension-tension fatigue loading. The objective of these measurements was to understand the nature of load redistribution in a composite laminate as it accumulates damage and fails. The measurements were performed using a computer-based stereoimaging system, which provides two-dimensional displacement maps by comparing photographs of the specimens taken at different load levels. Using this approach, a record of the edge displacements within a [0/452/-452/90]s graphite-epoxy laminate, subject to tension-tension fatigue loading, was obtained as a function of the cyclic life. These maps were used to provide a chronology of the strains and displacements along the specimen edge as the specimen failed. Very early in the fatigue life, large shear deformation occurred at the interface of the 45° and -45° layers. This deformation produced a delamination that eventually resulted in separation of the laminate into three sublaminates, consisting of the two edge [0/452] layers, together with the central [-452/902/-452] layers. No load was carried by the central off-axes layers, and final failure coincided with the failure of the outer 0° layers. The strains in each of the layers were obtained at different numbers of cycles from these displacement maps, and the results showed the redistribution of strains which occurs as the laminate accumulates damage and fails. These results are discussed in light of a recent proposed model based on a damage-dependent lamination equation to predict the stiffness degradation in composite materials subject to fatigue.
A New Test for Compression Testing of Impregnated Tows
Authors: Cairns DS
Published: March 2009

In a typical new material development scenario, scaleup must occur prior to obtaining meaningful results with respect to compression. This is necessitated by the need to have enough material to manufacture the large quantities required for typical compression testing. A new test for compression testing of continuous, filamentary composites is proposed, developed, and implemented in this study. The results are compared to standard ASTM D 695 (end loaded, side supported specimens) analytically and experimentally. Both tests yield comparable means, but the tow compression test may offer advantages with respect to understanding the performance of the basic building block for filamentary composites (individual tows). The test requires less material and requires fewer steps for sample preparation compared to other unidirectional compression test configurations.
Influence of Impact Parameters on the Response of Laminated Composite Plates
Authors: Ambur DR , Starnes JH , Prasad CB
Published: March 2009

The response characteristics of quasi-isotropic laminated composite plates made of AS4/3502 graphite-epoxy and IM7/5260 graphite-bismaleimide materials and subjected to low-speed impact by airgun-propelled or dropped-weight impactors are presented. For a given impact energy level, smaller impactors with higher impact speeds produce larger response magnitudes and are likely to result in more damage to the specimen than larger mass impactors. The strain magnitudes for a dropped-weight impact event are much larger for smaller specimens than for specimens with larger area dimensions for a given impact energy level. The results for an airgun-propelled impact event indicate that there are no significant differences in response for different size specimens, suggesting that response data from coupon speimens may be useful for the design of larger structures for this type of impact event. Analytical and experimental results are presented that identify large-deformation effects for 24-, 32-, and 48-ply laminated plates with all sides simply supported and with two sides simply supported and two sides clamped. These results for increasing impact energy levels suggest that it is important to consider large-deformation effects even for 32-ply laminates impacted at energy levels as low as 4.10 J and to account for the actual boundary conditions.
Delamination in Composites with Terminating Internal Plies Under Tension Fatigue Loading
Authors: Wisnom MR , Jones MI , Cui W
Published: March 2009

Tension-tension fatigue tests have been undertaken on glass-fiber and carbon-fiber epoxy specimens with terminated internal plies. All specimens delaminated along the interfaces between the continuous and discontinuous plies. Delamination starts immediately, and the rate is approximately constant. Different specimens delaminate at different rates. However, when the strain-energy-release-rate amplitudes are normalized by the values for delamination under static loading, the delamination rates for all the specimens of both glass and carbon epoxy are very similar.

Terminated 0° plies are much more susceptible to delamination than ±45° plies. The number of plies terminated together has a large effect on delamination. Tapered sections with dropped plies are stronger than equivalent untapered sections with cut plies. Delamination at terminated plies can cause a significant reduction in fatigue strength, especially for carbon-fiber epoxy.
A Review of Alternative Accelerated Corrosion Testing
Authors: Singh CB , Cordo OL
Published: March 2009

Over the years, traditional methods for testing and screening materials which are prone to corrosion have suffered from chronic complaints about the lack of acceleration. Efforts to respond to this criticism have included changes in laboratory cyclic test chambers and outdoor test methods. This paper examines the performance of a specific coating system after cyclic exposure to seven different accelerated corrosion test methods, two of which are South Florida Test Service test designs.

Of the seven accelerated corrosion test methods reviewed, the ones that provided the fastest corrosion growth after a total of 4 weeks of exposure are: cyclic salt fog and cyclic salt spray. It is also possible to achieve significant corrosion growth by conducting outdoor cyclic corrosion tests in the Arizona desert.
Self-Induced and Machine-Induced Specimen Vibrations in Fretting Testing
Authors: Vingsbo O , Schon J
Published: March 2009

Vibrations are often observed overlapping unidirectional sliding in wear testing. The vibrations are either an effect of sliding at the contact interface (self-induced), or induced as a secondary effect by unavoidable vibrations in the load transfer system of the testing machine (system-induced). In the present work the effects of overlapping vibrations have been studied in an actuator for tangential vibrations. Longitudinal vibrations are generated by a giant-magnetostrictive rod, and fed, via a mechanical load transfer system, to a vibrating specimen, clamped against a stationary specimen. The actuator was designed to minimize system-induced vibrations. In particular, possible machine resonance conditions were analyzed, with the purpose of choosing unavoidable resonance frequencies as far from the applied vibrational frequencies as possible. A number of mechanical models were set up, analyzed with respect to spring and damping constants and vibrating masses, and adapted to the design of the different parts of the machine. Spring constants were controlled by the size and elastic modulus of relevant machine elements. An evaluation of the vibrator shows that system-induced vibrations can be effectively controlled within large frequency intervals. It will be demonstrated how the device makes it possible to distinguish between self-induced and machine-induced vibrations of the “stationary” specimen. A fiber optic specimen displacement transducer system is used to measure the relative specimen displacements, which are found to be considerably smaller than the displacement of the vibrating specimen, and can be measured with an accuracy of 2 nm. Tangential and normal forces are measured and recorded as functions of time, compared as to phase and amplitude. A “vibrational friction coefficient” is discussed.
Wear Reductions and Contact Interface Observations for Carbon Samples Sliding Against Wavy and Smooth Copper Surfaces
Authors: Bryant MD , Lin J-W
Published: March 2009

Wear tests are presented in which a carbon graphite slider, loaded by a constant 20 N force spring, slides against smooth and wavy copper rotors. Rotors were prepared by attaching 250 μm thick copper foil to underlying backings of steel or photoelastic polycarbonate. A “smooth” rotor surface firmly attached copper sheeting to a steel disk, machined with a flatness tolerance less than 0.051 mm around the outer circumference. Special “smooth” and “wavy” rotors were prepared by curing polycarbonate beneath 250 micron thick copper foil. Sliding tracks on “wavy” rotors possessed surface waves of tens of microns; here higher harmonic (5 and greater) surface wave components had spectral amplitudes larger than about 50 μm.

Carbon samples with various contact geometries given in table 2 were slid over the smooth and wavy rotors; wear rates (μgm/sec) were plotted versus rotor speed. Wear rates for the smooth and wavy rotors were identical at some speeds, but at other speeds the wear rates for the wavy rotors were slightly less than half those on the smooth rotors.

Friction, contact voltage drop across the sliding interface (due to a 5 volt source and 220 ohm resistor in series with the slider and rotor), and vibration amplitudes for motions of the slider perpendicular to the sliding surface were also measured versus rotor speed. On the wavy rotor the vibration amplitudes were noticeably larger (tens to hundreds of microns) at those speeds where the wear rates for the wavy rotor were most reduced. Traces of the friction coefficient were similar on the wavy and smooth rotors. The contact voltage drop never changed abruptly (from low to high), implying that the vibrations never separated the slider from the rotor.

The photoelastic behavior of polycarbonate backed rotors permitted visual observation and direct measurement of the real contact areaswithin the contact interface between the opaque copper rotor and the carbon sample. Phenomena such as friction and wear could be correlated with changes in real contact area. At higher speeds where wear rates on the smooth and wavy rotors were most different, photoelastic images revealed concentrated contact on the smooth polycarbonate rotor, but little or none on the wavy polycarbonate rotor.

Spectral analysis of slider motions measured perpendicular to the sliding surface show enhancement of vibration amplitudes on the wavy rotor at those speeds where the wear rates were most reduced. Calculations of resonant frequency suggest that certain waviness harmonics passed beneath the slider at rotor speeds that excited natural frequencies of the slider-spring-rotor dynamic system.

This study suggests that appreciable reductions (up to 50%) in wear rates can be achieved by designing small surface waves on a rotor, and running the rotor such that the surface waves cause the slider-spring-rotor system to resonate. Although these waves apparently alter the interfacial physics, friction and contact integrity appear unaffected.
Vibration Monitoring in Wear Testing of Orthopaedic Biomaterials
Authors: Waldman SD , Cornwall GB , Kiss R , Moore TN , Bowe AJ
Published: March 2009

Wear of orthopaedic bearing materials, especially the ultra high molecular weight polyethylene (UHMWPe) component, is a leading clinical concern. The reported wear rates of typical bearing materials are subject to extreme variability due to various factors including the operating environment, measuring technique, testing protocol, and machine characteristics such as mechanical stiffness and vibration. Also, a lack of standardization in reporting pertinent information confounds this variability.

This investigation characterized the performance of a wear testing device. Through vibrational analysis, an attempt was made to identify possible reasons for discrepancies in the reported wear testing results for orthopaedic biomaterials.

Wear result variability was probably a combination of the vibration characteristics of the individual tester and uncertainties introduced by the wear measurements themselves. The effect of superimposed base vibrations on the pins was investigated. Characteristic frequencies of pin vibrations were linked to the dominant wear mechanisms in the orthopaedic tribological system.
The Effect of Tool Vibration on Tool Wear in Ultrasonic Vibration Cutting
Authors: Li X
Published: March 2009

Theoretical and experimental studies on the effect of tool vibration on tool wear in ultrasonic vibration cutting are presented. Analyses are given on the mechanics of ultrasonic vibration cutting, from which the relationships between the vibration and machining parameters are described. The special mechanisms of tool wear in ultrasonic vibration cutting are discussed using the analyses. Experimental tests for tool wear in cutting with and without the vibration at various cutting conditions are conducted based on the analyses. Compared to conventional cutting, it is found that in ultrasonic vibration cutting the tool crater wear is much less, but the tool flank wear is larger. The effect of tool ultrasonic vibration on tool wear is more significant when a water-based coolant is applied to the cutting region.
Preload Optimization: A High Efficiency Design Solution for Grinding Machines Main Spindles
Authors: Hagiu GD , Gafiţanu MD
Published: March 2009

Some theoretical and experimental research was developed to determine the bearing preload that can ensure, in imposed functioning conditions, a high service life for grinding machine main spindles. The static rigidity, bearing service life, and dynamic stability were considered the main parameters defining the main spindle reliability. From the results, the optimum bearing preload for a main spindle of special construction was determined. At the same time, an optimization methodology of the bearing preload for grinding machine main spindles is given.
Numerical Simulation of Stable Crack Growth in Fracture Mechanics Specimens
Authors: Klingbeil D , Zadeh GM , Eberle A , Fricke S , Brocks W
Published: March 2009

Stable crack growth in fracture mechanics specimens, i.e. side-grooved compact tension C(T), side-grooved middle tension M(T) and side-grooved part-through surface tension PS(T) specimens, is experimentally performed and numerically analysed by finite element calculations using the node shift node release technique. The crack propagation is either controlled by J-resistance curves for the C(T) and M(T) specimens, which are modelled two-dimensionally assuming plane strain conditions, or by local CMOD-resistance curves for the PS(T) specimen, which is modelled three-dimensionally. The triaxiality, i. e. the ratio of the hydrostatic part of the stress tensor to its deviatoric part, is introduced as the quantity characterizing the stress state at the crack tip.

For all specimens, the relation between the triaxiality and the slope of the J-resistance curves is shown and analysed, indicating that a decreasing triaxiality results in an increasing slope for the global J-resistance curves concerning the C(T) and M(T) specimens as well as for the local J-resistance curves regarding the PS(T) specimen.
Numerical Modeling of Ductile Tearing Effects on Cleavage Fracture Toughness
Authors: Dodds RH , Tang M , Anderson TL
Published: March 2009

Experimental studies demonstrate a significant effect of specimen size, a/W ratio and prior ductile tearing on cleavage fracture toughness values (Jc) measured in the ductile-to-brittle transition region of ferritic materials. In the lower-transition region, cleavage fracture often occurs under conditions of large-scale yielding but without prior ductile crack extension. The increased toughness develops when plastic zones formed at the crack tip interact with nearby specimen surfaces which relaxes crack-tip constraint (stress triaxiality). In the mid-to-upper transition region, small amounts of ductile crack extension (often < 1–2 mm) routinely precede termination of the J-Δa curve by brittle fracture. Large-scale yielding, coupled with small amounts of ductile tearing, magnifies the impact of small variations in microscale material properties on the macroscopic fracture toughness which contributes to the large amount scatter observed in measured Jc-values.

Previous work by the authors described a micromechanics fracture model to correct measured Jc-values for the mechanistic effects of large-scale yielding. This new work extends the model to also include the influence of ductile crack extension prior to cleavage. Ductile crack extensions of 10–15 · the crack-tip opening displacement at initiation are considered in plane-strain, finite element computations. The finite element results demonstrate a significant elevation in crack-tip constraint due to macroscopic “sharpening” of the extending tip relative to the blunt tip at initiation of growth. However, this effect is offset partially by the additional plastic deformation associated with the increased applied J required to grow the crack. The initial a/W ratio, tearing modulus, strain hardening exponent and specimen size interact in a complex manner to define the evolving near-tip conditions for cleavage fracture. The paper explores development of the new model, provides necessary graphs and procedures for its application and demonstrates the effects of the model on fracture data sets for two pressure vessel steels (A533B and A515).
Application of the Gurson Model to Ductile Tearing Resistance
Authors: Brocks W , Klingbeil D , Künecke G , Sun D-Z
Published: March 2009

Compared with conventional fracture mechanics concepts, constitutive equations which account for local damage of the material have the advantage that the corresponding material parameters for ductile fracture can be transferred between different specimen geometries. They will hence be able to describe the physical effect of constraint on the tearing resistance in a natural way. The paper shows the capabilities of the GURSON model in predicting JR-curves for different specimen geometries under static and dynamic loading with one set of material parameters. It is shown how these parameters can be determined from the numerical simulation of simple tensile tests. Problems and open questions are discussed and perspectives for future applications are given.
Fracture Toughness Measurements Using Small Cracked Round Bars
Authors: Giovanola JH , Homma H , Lichtenberger M , Crocker JE , Klopp RW
Published: March 2009

This study investigated using small precracked round bars (CRBs) for measuring fracture toughness values representative of material fracture resistance in large, thick components (so-called plane strain fracture toughness). The three alloys tested with CRBs (titanium-10V-2Fe-3Al, HY-130 steel, and A508 class 2A steel) cover a broad range of fracture behaviors. K or J values at crack initiation were calculated using the experimental load and displacement records. The fracture tests were complemented with scanning electron microscope observations and finite element analyses of round bars with different ratios of crack depth to bar diameter.

The CRB data were compared with independently measured toughness data obtained with larger bend specimens. In two cases, toughness values measured with precracked round rs for a given material and mode of fracture were in good agreement with those measured with larger standard fracture mechanics specimens; the exception was A508 steel at 204°C, and the lower values in this case may have occurred because the microstructural features influencing fracture were large in relation to the uncracked ligament size of the CRB. Finite element simulations of the CRB indicate that in the fully plastic regime the constraint factor Q is low (-0.75 to -0.85) for shallow crack specimens but increases with deformation (from -0.6 to -0.1) for deeply cracked bars. Experimentally, this difference in onstraint was evidenced by a transition from ductile to cleavage fracture mode in (embrittled) HY-130 steel specimens with shallow and deep cracks, respectively.

This limited feasibility study showed the potential of small CRB specimens for measuring representative plane strain fracture toughness. More work is needed to optimize specimen size and precracking methods and to improve and validate test evaluation methods.
Constraint Effects in Testing Different Curved Geometries of Zr-2.5Nb Pressure Tube Material
Authors: Davies PH , Shewfelt RSW , Järvine AK
Published: March 2009

Constraint effects in testing different curved geometries of Zr-2.5Nb pressure tube material have been studied with the aim of understanding discrepancies between toughness (critical crack length) values obtained from small specimens and burst tests. Crack growth resistance or deformation J-R curves were obtained on unirradiated pressure tube material at room temperature using small 17 and 34 mm wide curved compact specimens, 60 mm wide curved centre cracked specimens and burst test specimens.

The J-R curves from the burst tests were in excellent agreement with those from the curved compact specimens at short crack extensions (up to 2 mm per crack tip). However, at larger crack extensions the burst test J-R curves deviated from the small specimen results, being higher than those from the 17 mm specimen but only slightly lower (about 10%) than those from the 34 mm specimen up to 6 mm crack growth; i.e. the onset of instability at maximum pressure. In comparison, the J-R curves from the centre cracked specimens were well above those of the curved compact and burst test specimens at all crack extensions. The results suggest that the crack tip constraint of the burst test is most similar to that of a compact specimen, the centre cracked specimen having a much lower crack tip constraint. Fractographic studies confirmed the experimental results.
Size and Deformation Limits to Maintain Constraint in KIc and Jc Testing of Bend Specimens
Authors: Koppenhoefer KC , Kirk MT , Dodds RH
Published: March 2009

The ASTM Standard Test Method for Plane-Strain Fracture Toughness of Metallic Materials (E399-90) restricts test specimen dimensions to insure the measurement of highly constrained fracture toughness values (KIc). These requirements insure small-scale yielding (SSY) conditions at fracture, and thereby the validity of linear elastic fracture mechanics.

Recently, Dodds and Anderson have proposed a less restrictive size requirement for cleavage fracture toughness measured in terms of the J-integral (Jc), as given by a,b,B ≥ 200 Jc/σ0. The size requirement proposed by Dodds and Anderson increases the applicability of fracture toughness experiments by expanding the range of conditions over which fracture toughness data meeting SSY conditions can be reliably measured. This investigation compares the proposed size requirement with that of ASTM Standard Test Method E399 and, by comparison with published experimental data for various alloys, provides validation of the new requirements.
Constraint and Statistical Adjustment Models Applied to Transition Fracture Toughness Data
Authors: Landes JD
Published: March 2009

Constraint and statistical models were applied to fracture toughness data in the transition for steels to determine to what extent either or both are required to deal with size and geometry effects in the transition. A Weibull model was used for statistical adjustment to try to remove size effects from the data. The small-scale yield model was used as a constraint adjustment model to try to do the same. Results showed that no single adjustment worked in every case. To remove size effects a Weibull statistical adjustment taken alone worked best. However, statistical adjustment has not been used to remove geometry effects. To insure accurate transferability of fracture toughness data from one geometry to the next a constraint based model is needed. For this the model based on the J-Q two parameter crack tip stress field characterization was used. Fracture toughness measured on a compact specimen was used to predict the fracture toughness of center cracked and double-edge cracked tension geometries. These predictions were compared with actual data. The results showed that the model was able to predict the fracture behavior of the double-edge cracked geometry but was nonconservative for the center-cracked geometry. These results show that both statistical and constraint models are necessary for dealing with transition fracture toughness data.
Miniaturized Notch Test Specimen and Test Machine Design
Authors: Manahan MP , Stonesifer RB , Soong Y , Burger JM
Published: March 2009

Charpy V-notch specimens are widely used within the nuclear industry to monitor the effects of neutron damage to the reactor pressure vessel (RPV) beltline region. There is an ever-increasing need to obtain more notched bar impact data as plants age. Many plants will require more specimens for surveillance during the license renewal period. Other plants have experienced more embrittlement than originally anticipated, and it will be necessary to develop plant-specific Charpy shift trend curve models to ensure continued safe operation. Since physically based trend curves have not yet been validated, the use of plant-specific data will save the utilities operations costs since overly (arbitrarily) conservative models are no longer needed. Miniature specimens have also been used to characterize the material condition after vessel annealing. The use of miniaturized specimens which can be fabricated from previously tested full sized specimens offers one solution to this need for more fracture data.

Experiments performed using side-grooved miniaturized notch test (MNT) specimens have demonstrated that 1/16 scale miniature specimens can be designed to yield transitional fracture behavior and that the fracture appearance and energy-temperature curves can be quantitatively related to the conventional ASTM E23 specimen data. This paper presents the results of a study focused on designing an optimized MNT specimen and test machine. A combination of literature review, metallurgical analysis, and finite element analysis was used to consider such design parameters as minimum specimen cross-section, specimen length, notch acuity, the use of side grooves, side groove geometry, support span, and striker geometry. Two dimensional and three dimensional, elastic-plastic, large deformation, finite element analyses were used to compare stress/strain fields for standard and miniaturized specimens. Specimen and test machine geometries have been developed to ensure continuum requirements are met, the MNT specimen stress fields simulate those of the conventional specimen, and scatter for the miniature data is minimized.
Striker Geometry and Its Effect on Absorbed Energy
Authors: Ruth EA
Published: March 2009

ASTM Standard Test Methods for Notched Bar Impact Testing of Metallic Materials (E 23) requires the face of the striker to have an 8 mm radius and to be 4 mm wide. At the corners where the 8 mm radius meets the sides of the striker, E 23 calls for a radius of 0.25 mm ± 0.05 mm. This 0.25 mm radius causes a problem, as it can be worn out of tolerance quickly during normal testing. This paper presents data which exhibits the effects on absorbed energy when the corner radius is enlarged. Data is also presented which compares absorbed energy obtained using an ASTM E 23, 8 mm striker with absorbed energy obtained using an ISO 2 mm striker.
Proposed Changes to Charpy V-Notch Machine Certification Requirements
Authors: Splett JD , Wang JC-M
Published: March 2009

In 1989 the administration of the Charpy V-Notch Certification Program was assumed by the National Institute of Standards and Technology. The United States Army originated the program to insure the measurement integrity of Charpy V-notch machines across the country. The program has been operated for many years using candidate machine acceptance limits which can possibly be traced to a 1955 paper by Driscoll, however, the original statistical justification for using these acceptance criteria has been lost or never existed. A statistical analysis of recent certification program data indicates that the existing candidate machine acceptance limits should be modified. In this paper, we will discuss and justify potential changes to candidate machine acceptance limits.
Presentation of the French Supply of Charpy V Reference Test Pieces
Authors: Galban G , Le Muet I , Mougin D , Revise G , Roche R , Roesch L
Published: March 2009

Charpy V reference test pieces are required by standards EN 10045-2 and ISO DIS 442 for the indirect verification of pendulum impact testing machines. Based on an agreement between Aubert & Duval, LNE, ETCA and FFA, production of such test pieces has begun in France. A preliminary study, made with an experimental batch, has shown that these test pieces are equivalent to the BCR test pieces. This trial production allowed us to define the manufacturing and calibration conditions for the industrial production of Charpy V reference test pieces. Three levels of impact energy are available. The main features of this production are presented.
Low Cost Lower Bound Toughness Measurements
Authors: McCowan CN , Dally JW , Vigliotti DP , Lee OS
Published: March 2009

A method is proposed for determining the lower bound toughness of engineering steels based on impact loading of a modified Charpy specimen in a standard Charpy machine. The modified Charpy specimen employed here is nearly the same as the over-sized specimen studied previously by Bonenberger et al. The primary difference is that a sharp notch is employed to initiate the crack instead of pre-compression. A master curve is developed to relate the stress intensity developed at the tip of the notch to the time of crack initiation. An instrumented tup is then employed to give a force-time trace that can be interpreted to estimate the crack initiation time. Results are presented for the lower bound toughness of ASTM A 533, Type B, Class 1 steel over the temperature range from 0 to 40°C. These results are higher than the results reported by Bonenberger et al. for the same steel. The differences are attributed to the different techniques used to develop the starter crack in the modified Charpy specimen.
Instrumented Impact Testing of Polymeric Materials
Authors: Kalthoff JF , Wilde G
Published: March 2009

Measuring techniques and evaluation procedures for determining impact energies of polymeric specimens in instrumented impact tests are discussed. In particular, high sensitivity striker tups capable of measuring small loads with high accuracy are introduced and the importance of sufficiently fast electronic measuring systems for obtaining true load traces are illustrated. But even when determined with appropriate test techniques the measured impact energy might not in all cases represent the true fracture energy for breaking of the specimen. Kinematographic recordings of the movement of the broken specimen halves after the impact process show that a considerable portion of the measured impact energy is transferred into kinetic energy of the moving specimen halves. The difference of the conventionally measured impact energy and the kinetic energy of the moving specimen halves is introduced as the true impact fracture energy.
The Measurement of Regular and Irregular Surface Cracks Using the Alternating Current Potential Difference Technique
Authors: Connolly MP
Published: March 2009

The alternating current (AC) potential difference technique for measuring the growth of regular and irregular surface cracks is described. This technique is based on injecting high frequency alternating current into the metal specimen and measuring the change in voltage on the surface produced by the presence of a crack. The high frequency current tends to flow in a thin layer of the metal surface; therefore, low currents are required to produce measurable voltages on the specimen surface. Although AC techniques are increasingly employed for the measurement of surface cracks, one of the difficulties with the approach is the problem of interpreting the measured data in terms of crack shape and size. The objective of this paper is to present an inversion algorithm that can be used to determine the shape and size of surface cracks from measurements of the surfaces' voltage. This inversion algorithm is based on a model of the electromagnetic field problem, and the algorithm enables the voltage data obtained from measurements in the crack region to be interpreted directly in terms of the crack shape and size. Examples of the application of the inversion algorithm to the interpretation of voltage measurements obtained from a single semielliptical and two semielliptical intersecting surface cracks are described.
Measurement of Multiple-Site Cracking in Simulated Aircraft Panels Using AC Potential Drop
Authors: Jablonski DA
Published: March 2009

The characterization of multiple-site damage by use of laboratory test specimens is an important precursor to the understanding of multiple-site damage in aging aircraft. As the number of damage sites in the laboratory specimen increases, it becomes more time-consuming to measure crack initiation and growth from the various sites. Typically the crack initiation and crack growth would be measured either visually or with a low-power microscope. This technique is accurate, but it is labor-intensive. To decrease the time necessary to obtain multiple-site crack growth rate data, an automated crack length measuring technique, AC potential drop, was investigated.

This AC potential drop technique was applied to aluminum test specimens under fatigue cycling conditions as well as monotonic R-curve testing. Aluminum ALCLAD 2024 test specimens of three different specimen geometries were examined. Specimens with a single-hole were used to examine the effects of lead placement on the sensitivity of AC potential drop. Three-hole specimens were used to simulate multiple-site cracking from several holes. Riveted specimens containing one row of three rivets were used to examine multiple-site cracking from fasteners. Optimum current and potential lead geometries were determined for each specimen geometry. Relationships between the AC potential and crack length were determined for AC current frequencies of 3, 10, and 30 kHz. The sensitivity of AC potential drop in measuring crack initiation was investigated. The sensitivity was found to increase substantially with increasing AC current frequency.
The Influence of Crack Deflection and Bifurcation on DC Potential Drop Calibration
Authors: McKeighan PC , Tabrett CP , Smith DJ
Published: March 2009

Finite element and analog techniques are used to assess the influence of abnormal crack morphologies on the potential drop (PD) response of an M(T) specimen. All crack geometries considered, including simply deflected, bifurcated, and periodic sawtooth morphologies, result in higher potentials than observed for an undeflected crack. The greatest influence was observed with a bifurcated crack even with relatively short branch segment lengths. The potential drop responses are assessed in terms of the overestimates of stress intensity factor which result if a standard, undeflected crack PD calibration is applied to the PD response of the deflected geometry. The overestimate of stress intensity factor generally increases as deflection angle or crack length increases. Furthermore the PD response measured from a single probe set configuration is slightly less influenced by crack deflection than a dual probe configuration. This influence is also minimized by increasing the probe gage length and sacrificing overall sensitivity. Provided the deflection geometry of a given crack is constant, an effective probe gage length can be determined and used with the standard undeflected crack calibration to approximate closely the PD response of the deflected geometry.
Ultrasonic Size Determination of Cracks with Large Closure Regions
Authors: Rehbein DK , Thompson RB , Buck O
Published: March 2009

A number of investigators have developed acoustic methods for measurement and determination of crack length. These methods have generally fallen into one of three categories, determination of crack area, time of flight to determine crack length, or recognition of the crack tip by changes in the signal response. These methods have been successful in location of the crack tip to within ± 0.5 mm. In all cases, however, it was necessary for the crack length or the crack-tip position to be determined with the crack in a fully open state in order to remove the effects of crack closure. Recent work has developed acoustic scanning techniques and subsequent analysis to the point where the same accuracy of ± 0.5 mm is now possible through scanning of the crack in an unloaded condition with closure accounted for. A review of the previous methods will be given together with an explanation of the advances in scanning technique and analysis that have allowed this simplification to occur.
Changes in Airtightness Levels of Six Office Buildings
Authors: Shaw CY , Reardon JT
Published: March 2009

This paper reports the changes in the overall airtightness values of six tall Canadian office buildings. These buildings, which are 10 to 25 stories high, were built between 1964 and 1974 and were previously tested shortly after their construction. The results indicate that as a result of various retrofit measures applied, except for one building, the building envelopes are more airtight now than 20 years ago. The improvement in the overall airtightness value at 50 Pa ranges from 0 to 43% of its original value. Details are discussed in the paper.
Whole House Fenestration Energy Consumption as a Function of Variable Window Air Leakage Rates
Authors: Kehrli D
Published: March 2009

Residential building energy consumption is dependent on many variables. The heat loss or gain attributable to fenestration products can be a significant portion of the whole building load. The fenestration industry is currently developing and implementing new test methods and rating procedures to more accurately account for fenestration energy transfer. One of the tools being developed by the National Fenestration Rating Council (NFRC) is a PC-based program called Residential Fenestration (RESFEN) heating and cooling load use and costs.

This paper will provide a review of the energy and cost impacts that variable air leakage rates of several types of window products can have on overall window energy usage as modeled in four typical building designs located in the United States. The analysis was performed with the RESFEN software as part of an NFRC sensitivity study on this issue.
Acid Deposition Effects on Materials: Evaluation of Electric Contact Materials after 4 Years of Exposure
Authors: Tidblad J , Leygraf C , Kucera V
Published: March 2009

In 1987 a co-operative field exposure program within the UN Economic Commission for Europe was initiated. The aim of the program is to evaluate the effect of sulfur pollutants in combination with NOx and other pollutants on the atmospheric corrosion of important materials. This work presents results from the evaluation of the electric contact materials nickel, copper, silver and tin after 4 years of exposure.

Dry deposition of SO2 dominates the corrosion of nickel, which forms amorphous and crystalline basic nickel sulfate, whereas both O3 and NO2 accelerate the dry deposition of SO2 on copper. Silver forms Ag2S as the dominating corrosion product. Since H2S is not measured within the program it has not been possible to estimate its contribution. The formation of oxides with different stoichiometries dominates the corrosion of tin and no equation has been found that relates the weight increase of tin to environmental data. Particulate ammonium sulfate contributes to the weight increase of all metals.