bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface Science Spectra: Practical Aspects of Applying Transformation Modeling to Analytical Data
Authors: Lee RN , Gaarenstroom SW
Published: March 2009

The new computer-based American Vacuum Society journal Surface Science Spectra is providing a unique test of the practicality of evolving analytical data standards. As with other analytical techniques, data items in surface analysis data records have proven difficult to define and classify. A major source of problems arises from the fact that different instrument design approaches to the same type of measurement lead to different parameterizations of instrument settings and specifications. Transformation modeling is a promising approach to generic data modeling in which each stage of an analytical measurement is described by a mathematical transformation. The transformation modeling formalism shows that, in principle, every analytical measurement can be modeled by a mathematical structure that specifies and organizes the information providing a complete, orthogonal description of the measurement. In practice, the feasibility of applying the formalism to a given type of measurement will depend on the availability of sufficiently accurate analytical transformations for the measurement.
The Use of SGML for Retrieval of Chemical Data
Authors: Strehlow RA , Tallant TO , Mason JD , Kienlen PL , Barry KT
Published: March 2009

The encoding of information within a document using Standard Generalized Markup Language (SGML) permits a novel approach to direct retrieval of data from documents. Although SGML is designed primarily for electronic interchange of texts, its features have been found to be useful in the management of data contained within a document. Encoding can include scientific and technical information, as well as associated and ancillary data, management data, and other metadata. This paper describes and gives examples of the use of the technique with special reference to chemical data. Examples of tags used in documents are shown. Retrieval of contained information is conventionally done by means of searches to retrieve a set of documents that have a probability of containing the desired information. The method described here uses a radically different approach to the information retrieval problem.
Visual Presentation of Numerical and Scientific Data in Printed Publications
Authors: Lawyer B , King M
Published: March 2009

The International Centre for Diffraction Data (ICDD) is a non-profit scientific organization which collects, edits, and publishes powder diffraction data. The powder diffraction data are maintained in a computer-readable database format and are known within the scientific community as the Powder Diffraction File (PDF). The database is published on a variety of media—books, microfiche, magnetic tape, and CD-ROM.

Several years ago, the ICDD investigated the potential of using desktop publishing (DTP) to design and produce publications in-house. In 1990, ICDD established a DTP department. At first, the full capabilities of this set-up and its impact on data manipulation and presentation were not fully understood. Three years later, several completed products prove the power, flexibility, and control that an in-house DTP department promotes. The variety of layouts and enhancements for readability that can be designed into a document prove that numerical scientific data can be presented in a clear and concise manner.

Today, the DTP department coordinates the design, layout, and file creation of all hard copy products. The end process of printing and production determines the development process, regardless of the size of the product or whether the product will be produced completely in-house or coordinated with outside service bureaus and printers. DTP offers greater control over the proofing process and permits cost-effective production. Shortened turn-around times for development of layouts and production of final electronic files or camera-ready copy allow additional time early in the process to experiment with layout and design of projects and to refine data presentation to improve readability.

Through this experimentation, we gained insights on the readability and visual presentation of numerical/scientific data with the end user in mind. In this paper, discussion will center on the process involved in publishing from a database, planning for a publication, and discovering design ideas to increase readability of data. Examples will include new and redeveloped publications.
Simulation and Analysis of Trucks Using the Modeling and Simulation Program BAMMS
Authors: Verheul CH , Batstra G , Jansen STH
Published: March 2009

A description is given of a general purpose, open-structured simulation tool based on the bond graph method. The method and capacities of the program are discussed. Research performed with the help of the program are discussed. Models are made of a race truck in order to study and optimize the road-handling behavior of the vehicle. The final part of the paper discusses models made of truck trailer combinations. The purpose of these simulations is to study parameter variations with respect to the stability of these vehicles. The general intention of the paper is to give an impression of the modeling and analysis approach used when working with BAMMS.
Some Factors Affecting the Design and Use of the Texas Mobile Load Simulator
Authors: Hugo F
Published: March 2009

The Texas Department of Transportation (TxDOT) is implementing a strategy for full-scale accelerated pavement testing (APT). The Texas mobile load simulator (TxMLS) is being designed and manufactured as part of this strategy. Two 1:10 scale MLS models are also being used to conduct laboratory tests to enhance the design, understanding, and use of the machine.

The expected dynamic behavior of the MLS was investigated using computer simulation. This greatly enhanced the understanding of the vehicle pavement interaction as well as the structural response of the MLS. The feasibility of the structural system was confirmed, and the need for a continuous ramp and transition zones at the junction of the circular and straight sections was demonstrated. The simulation was also used as a means of reducing unwanted dynamic effects and finding the optimal solution for the electric drive. Variable frequency drive (VFD)-induction motors were selected.

The full-scale prototype is expected to be completed by the summer of 1993. Tests with the model-MLS on pavements demonstrated that it could be used to conduct selective studies of wheel/pavement interaction to enhance the future use of the full-scale MLS. The first tests have focused on rutting of asphaltic concrete. The effects of accelerated aging of asphaltic concrete by heat is expected to be important in the future use of APT.
Traction Tests on an Expressway Treated with a Pavement Rejuvenator
Authors: Navin F
Published: March 2009

A rash of accidents on a major freeway immediately after it was treated with a pavement rejuvenator prompted the British Columbia Ministry of Transportation and Highways (BCMoTH) to commission a set of traction tests by the author. A series of 31 maximum braking tests were run at speeds of 50, 70, 90, and 120 km/h on wet normal and treated pavements, and two additional tests were run on dry pavements at 50 km/h.

A 1991 ABS-equipped Lincoln Town Car was outfitted with a Lamar™-5th wheel, g-ANALYST™, and two bumper guns and was driven by a police-trained driver. The tests were divided more or less equally between maximum ABS and slide-to-stop braking.

The untreated surface had an average coefficient of friction at 50 km/h of 0.71 for peak (ABS) braking and at 75 km/h of 0.61 for maximum locked wheel braking. The standard deviation in both cases was 5% of the mean value. The similar conditions for the treated surface were 0.68 for the peak ABS at 50 km/h and 0.53 for the locked wheel at 75 km/h.

An interesting outcome of this testing is in the experience with the equipment. It was difficult to determine when and where the onset of braking actually started and stopped. The devices failed to function at a rate of 6 to 12 in 100. It was found that all measuring devices were needed to provide sufficient data to confidently estimate the average coefficient of friction.
Development and Evaluation of the Ride Number Concept
Authors: Spangler EB , Kelly WJ
Published: March 2009

The statistical analysis of pavement ride quality was introduced in the United States during the 1950s at the AASHO Road Test. It was at the Road Test that Carey and Irick developed the statistical relationship between pavement surface profile and measured subjective ride quality. Interest in pavement ride quality continued in the 1960s with the development of the road meter and the inertial profilometer, which for the first time provided a fast and accurate method for measuring and recording pavement surface profile in a computer-readable format.

During the 1970s, ride quality transforms relating pavement surface profile measurements made with the inertial profilometer to measured subjective ride quality were developed at the University of Texas and at the Michigan Department of Transportation. During the 1980s, the ride number concept for estimating pavement ride quality from surface profile measurements was developed by Janoff et al. in a National Cooperative Highway research project. This paper discusses the further development of the ride number transform, its evaluation in the NCHRP and Ohio DOT research projects, and the comparison of its performance to other candidate measures of pavement ride quality including the Texas Serviceability Index, the Michigan Ride Quality Index, the Mays Road Meter Index, and the International Roughness Index.
A Geometry-Based Contact/No-Contact Simulation Model Applied to Ride Quality
Authors: Gilmore B
Published: March 2009

In this work, ride quality is considered a function of the dynamic interaction between a rider and the vehicle/seat. The seat is coupled to the human, which influences its dynamics. This coupling may introduce situations where contact between the seat and the human is lost, the seat bottoms out, etc., resulting in discomfort and/or personal injury.

This paper presents a design tool in the form of a computer simulation program for the above systems. The tool uses a mechanical model of a human to evaluate ride quality and therefore removes subjectivity from the analysis. The program predicts contact/no-contact situations and automatically reformulates the equations of motion to represent the actual system topology. Thus, the program can predict the bottoming out of a seat or a human leaving (losing contact with) the seat. Since the program uses the geometric model of the system to make decisions about contact/no-contact, the geometry of the seat and its effect on ride comfort can be predicted.
Steering and Suspension Development of Road Vehicles
Authors: Alstead CJ , Whitehead JP
Published: March 2009

The evaluation and development of a vehicle's ride and handling characteristics are still largely carried out by subjective means within the automotive industry. However, the need to reduce product development times and to “design in” acceptable handling characteristics at the prototype stage requires a more formalized approach to handling development. The use of objective measurement methods, alongside subjective techniques, in a vehicle development program is described, and it is argued that these methods allow a better understanding of vehicle characteristics and progress development more rapidly than using subjective techniques alone.

Prediction of the ride and handling characteristics of a vehicle at the design stage is only possible in very general terms, and this leads to lengthy development work being carried out on the preproduction prototype. Continuing and future research programs are expected to lead to closer correlation of subjective and objective results and the verification and refinement of a mathematical model for use as a tool for the prediction of handling behavior at the design stage.
Vehicle Noise Testing Problems Due to Vehicle/Tire/Road Interactions
Authors: Wagner P
Published: March 2009

European Community legislation will decrease the limits of drive-by noise according to ISO 362 from 77 to 74 dB(A) in 1995. In Germany, the government will also enforce a new emission-related car tax, probably in 1993.

These planned restrictions make it necessary to look more closely at the influence of tire/road noise in relation to the drive-by noise level during vehicle type approval. Volkswagen has built four test tracks according to ISO/DIS 10844 and compared the influence of tire/road noise on these and other tracks in relation to drive-by noise.

The main differences of noise level were measured on different road surfaces. Nearly comparable is the effect of different tires. It must be considered that tire/road noise may be much higher under accelerating conditions than under coast-by conditions. These noise levels generally do not correlate. The effect of temperature has a large influence on drive-by noise, especially when measuring in the third gear. Aging of the test track should be recognized the first year after construction. The car itself influences the sound propagation through the design of the wheelhous-ing and the floor of the car body. Tire inflation pressure and vehicle weight may influence the noise level of low-noise cars.

If these effects are not taken into account, drive-by noise may spread in the range of 3 dB(A) even on an “ISO” test track.
Road Noise Simulation Using Road Surface Weighting Functions
Authors: Voutyras MP , Thomson KR
Published: March 2009

The purposes of this study were to investigate the effects of different road surfaces on vehicle interior noise and to investigate a method of predicting road noise from multiple surfaces based on noise measurements of a single surface. The primary focus is on coarse road surfaces. However, both smooth asphalt and rough road surfaces are included in the study.

A road surface survey was conducted to determine the effect of different road surfaces on vehicle interior noise. Weighting functions were developed for the purpose of modifying the noise response from one road to match the response of other roads. The weighting functions were experimentally derived from road noise measurements of a number of vehicles driven over different surfaces. A second group of vehicles were then tested to determine if road noise due to different road surfaces could be predicted accurately based on a single surface noise measurement.

It is concluded that road surface weighting functions (RSWFs) are a useful tool for estimating the vehicle interior noise due to different surfaces and investigating differences in road surfaces and vehicle nonlinearity. The potential applications of the RSWFs include both laboratory chassis rolls and computer model simulations. The implications to computer simulations are that similar RSWFs may be used to predict the noise response from a control road profile.
The Effect of Vehicle-Road Interaction on Fuel Consumption
Authors: Gyenes L , Mitchell CGB
Published: March 2009

This is a review paper of experimental measurements of the effects of road and tire characteristics on the rolling resistance and fuel consumption of cars, goods vehicles, and buses. The rolling resistance of tires has been reduced by improved design and can be reduced in use by higher inflation pressures and, for goods vehicles, by the use of wide single tires in place of duals. For heavy vehicles, higher inflation pressures and wide single tires increase road wear.

On paved roads, rolling resistance and fuel consumption is increased separately by the surface macrotexture and the profile unevenness. These effects are additive and over the range of conditions found on European roads can each increase car fuel consumption by about 5% Unevenness can increase goods vehicle fuel consumption by up to 10% On unpaved roads in developing countries, fuel consumption of goods vehicles and buses is increased by 15 to 20% over that on paved roads. In addition, loose material on the road surface further increases fuel consumption.
The Influence of Pavement Evenness and Macrotexture on Fuel Consumption
Authors: Delanne Y
Published: March 2009

This paper is concerned with light vehicle fuel consumption on paved roads. It starts with a recall of different factors affecting car consumption and then focuses on the effect of road irregularities. Recall of results of practical tests carried out at the LCPC, on the one hand, and more recently in collaboration with a tire manufacturer (Michelin-France), on the other hand, are presented. Then, when considering effects of road irregularities on road qualities such as: riding quality, braking efficiency, inside and outside noise (tire/road interaction), and component vibrations, it appears that required specifications for low fuel consumption surfaces can be detrimental to other road qualities. Nevertheless, some new surfaces offer a very good tradeoff.
Two-Parameter Crack-Tip Field Associated with Stable Crack Growth in a Thin Plate: An Experimental Study
Authors: Dadkhah MS , Kobayashi AS
Published: March 2009

J-integral values were determined directly from the measured orthogonal displacement fields surrounding a stably growing crack in 2024-0 and 5052-H32 aluminum alloy single-edge notched (SEN) and cruciform specimens of 0.8-mm thickness. These J values were then used to compute the crack-tip displacements associated with the Hutchinson-Rice-Rosengren (HRR) field. The displacement component as a result of the difference field in the simplified two-parameter J-Q or J-T ductile fracture theories was obtained by subtracting the HRR displacement from the measured crack-tip displacement. The slope of the log-log plots of the two orthogonal, difference-field displacement components varied irregularily with radial distance with no consistent second-order strain singularity. The results suggest that further analysis is necessary before the simplified J-Q theory can be used to analyze stable crack growth in thin plates.
An Approximate Technique for Predicting Size Effects on Cleavage Fracture Toughness (Jc) Using the Elastic T Stress
Authors: Kirk MT , Dodds RH , Anderson TL
Published: March 2009

This investigation examines the ability of an elastic T-stress analysis coupled with a modified boundary layer (MBL) solution to predict stresses ahead of a crack tip in a variety of planar geometries. The approximate stresses are used as input to estimate the effective driving force for cleavage fracture (J0) using the micromechanically based approach introduced by Dodds and Anderson. Finite-element analyses for a wide variety of planar-cracked geometries are conducted that have elastic biaxiality parameters (β) ranging from -0.99 (very low constraint) to +2.96 (very high constraint). The magnitude and sign of β indicate the rate at which crack-tip constraint changes with increasing applied load. All results pertain to a moderately strain-hardening material (strain-hardening exponent (n) of 10). These analyses suggest that β is an effective indicator of both the accuracy of T-MBL estimates of J0 and of applicability limits on evolving fracture analysis methods (that is, T-MBL, J-Q, and J/J0). Specifically, when ∣β∣ >0.4 these analyses show that the T-MBL approximation of J0 is accurate to within 25% of a detailed finite-element analysis. As “structural-type” configurations, that is, shallow cracks in tension, generally have ∣β∣ >0.4, it appears that only an elastic analysis may be needed to determine reasonably accurate J0 values for structural conditions.
A Void Growth Model Relating Fracture Toughness and Constraint
Authors: Miller TC , Anderson TL
Published: March 2009

Loading of a metal results in the nucleation of voids around particles. Further deformation results in void growth and coalescence. This work combines mathematical models for void nucleation, growth, and coalescence into a simulation of a ductile fracture to examine the effects of stress triaxiality and constraint loss on ductile fracture.

Nucleation of voids from the particles is assumed to depend on the particle-matrix interface strength; subsequent void growth occurs according to equations developed by Rice and Tracey. The coalescence criterion involves a consideration of microstructural geometry.

Two types of loading are considered: proportional loading and near crack tip loading. In the latter case, a near crack tip region with a relatively large plastic zone and with significant constraint loss is considered. Results include a two-parameter failure locus for initiation of ductile fracture, which predicts the effect of constraint on ductile initiation.
Crack Depth Effects Measured by Dynamic Fracture Toughness Tests
Authors: Nevalainen M , Wallin K , Rintamaa R
Published: March 2009

Dynamic fracture toughness tests with an instrumented inverse geometry impact hammer have been made on small, side-grooved, prefatigued Charpy-type specimens (10 by 10 by 55 mm) with varying crack depth. The a/W was approximately 0.05, 0.1, 0.3, and 0.5. Prefatiguing was performed with wider specimens after which the specimens were machined to achieve identical sharp cracks of specified length.

Impact tests were performed at a temperature corresponding to the transition region of the material's ductile to brittle transition curve. Load and energy were measured as a function of specimen displacement. Fracture toughness, Jc, at cleavage crack initiation was calculated as a result of the test.

The test results were used for determining the applicability of parameters like T stress, Q parameter, and small-scale yielding correction (SSYC) for in-plane constraint correction. It was concluded that the small-scale yielding procedure corrects the effect of constraint effectively. T stress and Q as indexing parameters were not suitable for a quantitative constraint correction.

The SSYC was also applied to some results from the literature. The effect of SSYC improved as the width of the specimen decreased from 200 to 50 mm. The results imply that although SSYC is highly promising, more FEM-analysis is needed before it can be used as a standard procedure.
Application of J-Q Fracture Methodology to the Analysis of Pressurized Thermal Shock in Reactor Pressure Vessels
Authors: Shum DKM , Theiss TJ , Rolfe ST
Published: March 2009

Detailed two-dimensional plane strain analysis results for a reactor pressure vessel (RPV) with a shallow inner-surface axial flaw subject to a postulated pressurized thermal shock (PTS) transient are presented. The PTS transient simulates the pressure-fluid temperature history of an RPV in a pressurized water reactor (PWR) under postulated “small break loss of coolant accident” (SBLOCA) conditions. Analysis results appear to support the utility of the J-Q approach and interpretation method to characterize the crack-tip fields in an RPV under PTS conditions. Specifically, the (Q-stress parameter can be defined, for the assumed RPV and flaw geometries and transient conditions, up to maximum loading as characterized by the value of the J-integral during the transient. A method that incorporates small-specimen Jc(Q, T) toughness locus data in the safety-margin assessment of an RPV is presented. Analysis results suggest that the predicted margin of safety in RPVs under PTS conditions is greater based on the J-Q approach than that based on the conventional single-parameter J approach.
Single-Specimen Test Analysis to Determine Lower-Bound Toughness in the Transition
Authors: Landes JD , Zerbst U , Heerens J , Petrovski B , Schwalbe K-H
Published: March 2009

A method is proposed for determining a lower-bound fracture toughness value from the result of a single test in the transition region for steels. The method is based on the size criterion of Iwadate et al. for determining the number of tests needed to characterize toughness adequately at a given condition and a Weibull statistical distribution. The method was evaluated by determining a lower-bound toughness value for 68 sets of data, which include over 700 fracture toughness values in the transition. The lower-bound estimate was judged to be conservative if all of the lower-bound estimates were lower than the lowest toughness value in the set. The method was conservative for more than 60% of the data sets and for more than 95% of the individual toughness values. In addition, the method was evaluated by comparing it with 4 methods that used multiple specimens for determining a lower-bound toughness. The single-specimen method gave essentially the same lower-bound estimates as the other multiple-specimen methods.
A Perspective on Transition Temperature and KJc Data Characterization
Authors: McCabe DE , Merkle JG , Nanstad RK
Published: March 2009

Proper identification of the transition temperature and the shape of the lower-bound (KIc) fracture toughness curve in the transition range has been a long-term objective of work at Oak Ridge National Laboratory. A past practice has been to test a large number of specimens of varying sizes, from 1/2 to 8T compacts, in expectation that size effects and statistical variability of KJc could be resolved empirically. Recently, statistical and constraint-based models have been developed that purport to explain much of what has been seen. Weakest-link theory has been successfully used to predict specimen size effects for the lower part of the transition curve. Constraint-based models of βc - βIc and Jssy (small-scale yield) also can model size effects, but these tend to conflict among themselves with regard to the prediction of full constraint KJc. All lack potential for defining the absolute lower bound of fracture toughness. Statistically based models have the benefit of quantifying data scatter characteristics and provide a basis for making lower-bound toughness estimates with assigned error estimates. The appropriate characterization of transition temperature is of value in industrial problems and is of particular importance to the nuclear industry where safety issues are involved. Here the KJc data are obtained from small specimens, the size of which is dictated by volume limitations of surveillance capsule size. A basis has been explored for establishing a lower-envelope curve from such data.
A Statistical Study on the Effect of Local Brittle Zones (LBZs) on the Fracture Toughness (Crack Tip Opening Displacement) of Multipass Welded Joints
Authors: Machida S , Yoshinari H , Suzuki Y
Published: March 2009

The paper presents the experimental heat-affected zone (HAZ) crack tip opening displacement (CTOD) test data in terms of the size and number of local brittle zones (LBZ) hit by fatigue precrack which were carried out by the Fracture Toughness of Weldments (FTW) Committee of the Japan Welding Engineering Society (JWES). The data plots of the critical CTOD versus LBZ size lead to the observation that the so-called “LBZs,” which include grain-coarsened HAZ, have fracture toughness values (δc) with large scatter, but the mean value δc seems to be represented by a function of LBZ size.

A probabilistic model is proposed that consists of ¯δc, the average value of δc versus LBZ size, the Weibull distribution δc for a given ¯δc, the experimentally determined size distribution of individual LBZ, and the distribution of a number of LBZs hit by fatigue precrack in CTOD specimens. In the model, it is assumed that the smallest δc for individual LBZ hit by a fatigue precrack controls the overall CTOD fracture toughness of a HAZ CTOD specimen (weakest link concept).

Numerical simulations based on this model compared well with the experimental results. The American Petroleum Institute (API) requirement to HAZ CTOD testing is discussed on the basis of numerical simulations. The plate thickness effect is predicted by taking mechanical and metallurgical effects into account.
Results of MPC/JSPS Cooperative Testing Program in the Brittle-to-Ductile Transition Region
Authors: Van Der Sluys WA , Miglin MT
Published: March 2009

This paper describes the activities and test results of the Material Properties Council (MPC) working group on fracture toughness testing in the brittle-to-ductile transition region, a cooperative testing program. The MPC working group was organized in 1987 with the objective to study the problem of data scatter in the transition region and to develop the materials information needed to support the development of test procedures and testing philosophies or both. The MPC group was invited by the Japan Society for the Promotion of Science (JSPS) to coordinate a cooperative testing program in the United States and elsewhere.

A total of 18 laboratories participated in the test program with approximately 150 1T compact fracture toughness specimens being tested. The tests were conducted at three test temperatures in the ductile-to-brittle transition region. This paper presents an overview of the test program, details about the material, overall test matrix, test plan, and summary of the results.

The experiments were conducted between the temperature regions where the ASTM Test Methods for Plane-Strain Fracture Toughness of Metallic Materials and JIc Measure of Fracture Toughness (E 399 and E 813), respectively, are usually applied. The tests were conducted following the ASTM Test Method E 399 testing procedure except that the fracture toughness was determined using the equations in ASTM Test Method E 813 for the calculation of J at the point in the load displacement curve at which the specimen failed. The J values measured by using this procedure were converted to the units of K. Some of the laboratories used the unloading compliance procedure during the experiments to monitor the amount of crack extension prior to the cleavage failure.

A number of different procedures were used in the test program to estimate the lower bound fracture toughness values. The two and three parameter Weibull fits appear to be the best of the procedures used. The results from this cooperative test program should be of great value to researchers in this field as a data set useful for making decisive studies.
Determination of Lower-Bound Fracture Toughness for Heavy-Section Ductile Cast Iron (DCI) and Estimation by Small Specimen Tests
Authors: Arai T , Saegusa T , Yagawa G , Urabe N , Nickell RE
Published: March 2009

Spent nuclear fuel transport and/or storage casks (100-ton class) must maintain their structural integrity even when subjected to hypothetical transportation or handling accidents at storage facilities. For ductile cast iron (DCI) to be used as a cask containment boundary material, adequate fracture toughness and associated ductile behavior must be demonstrated at service temperatures and impact loading conditions of concern.

Six- and 8-in. (150- and 200-mm) thick compact tension (6TC[T] and 8TC[T]) specimens were extracted from three prototypic and two model casks and were tested. The results obtained in this study and the data obtained from another prototypic cask and six other model casks were analyzed statistically. The lower-bound fracture toughness trend curves for heavy-section DCI were finally established as a function of temperature.

Small specimens (for example, 1TC[T]), notched round bar tension, and U-notched Charpy specimens) were machined from the fractured halves of the 6TC(T) and 8TC(T) specimens and were tested under similar temperature and loading rate conditions. The relationship between the results from small specimens and those defining the lower-bound trend curves is also discussed. Fracture toughness prediction methods based on small specimen tests at specified temperature are proposed.
Crack-Face Interaction: Protrusion Interference in Brittle Materials
Authors: Boulet JAM
Published: March 2009

In the classical analysis of Griffith (line) cracks, the crack faces do not interact with each other. But for real cracks, various kinds of mechanical crack face interaction can occur. In particular, protrusion interference during biaxial loading of a bumpy Griffith crack is discussed. The influence of this interference on the stress required to produce fast fracture in a brittle material is analyzed using the Griffith fracture criterion for biaxial stress. The dependence of the fracture stress on the orientation, magnitude and biaxiality of the remote stress is described quantitatively. It is shown that the stress required to produce fracture is slightly altered by a single interference site, but significantly altered when many sites are present. It is also shown that for all cracks whose length is less than about one-tenth of a millimeter in silicon carbide or 1 mm in silicon nitride, any interference that exists influences fracture.
Elastic-Plastic Mode II Fracture in an Aluminum Beam
Authors: Cordes J , Yazici R
Published: March 2009

This paper describes an experimental and analytic study of Mode II fracture in a ductile aluminum beam. Mode II fracture is characterized by an in-plane sliding of crack surfaces relative to one another. For ductile materials such as aluminum, failure is preceded by yielding near the crack tip. In this paper, a Mode II fracture anaylsis technique that includes yielding near the crack tip is presented. Unlike other methods, the analysis presented in this paper (1) provides a simple method for modeling stable and unstable crack growth; (2) can be implemented with a general purpose finite-element package; (3) predicts the maximum load at failure and the nature of the failure, either unstable crack growth or yield; (4) includes interface elements to prevent overlap of the crack surfaces; and (5) includes directly the R-curve values. The finite-element modeling technique provided a reasonable, qualitative approximation of experimental behavior.
Weight Functions for Eccentric Cracks
Authors: Chen X , Albrecht P
Published: March 2009

The authors have developed weight functions for an eccentric crack in a finite-width plate based on an assumed crack-opening displacement (COD) expression and Isida's stress intensity factor solution for a cracked finite-width plate under tension.

The unknown coefficient in the assumed COD expression was obtained from the energy balance condition. The accuracy of the weight functions was checked with self-consistency and symmetry conditions. Comparisons with results for special cases with known solutions further validated the accuracy of the weight functions. After verifying the accuracy, the application of the weight function method (WFM) was illustrated for three basic loading conditions as well as residual welding stresses and thermal shock stresses.

The WFM developed in this study is an important step toward solving more complex engineering crack problems such as two-tip eccentric cracks in the web or flange of steel bridge girders and a three-tip crack extending across flange and into the web.
Fracture Mode Evaluation of Flawed Piping Under Dynamic Loading
Authors: Nickell RE , Quiňones DF
Published: March 2009

A recent series of large-scale, high-energy dynamic degraded piping experiments, conducted for the International Piping Integrity Research Group (IPIRG), are evaluated to determine the ability of modern structural and fracture analysis computational tools to predict the dynamic response and failure mode of prototypical piping systems with degraded sections. Results are also useful in confirming leak-before-break principles. This paper assesses the IPIRG 1.3 test series failure mode(s) for austenitic and ferritic base and weld metal test sections under severe dynamic loading conditions. Small-scale test specimen data are used to perform limit load, ductile tearing, and low-cycle fatigue calculations at 288°C, and calculated results are compared to data from five large-scale pressurized piping system experiments with circumferential interior flaws. Experimental behavior and fractographic evidence are also described.

The dominant prepenetration failure mechanism for the IPIRG 1.3 experiments was not lowcycle flaw growth, but another mechanism such as ductile tearing followed by instability.
Methodology for Predicting Canopy Fracturing Patterns During Ejection
Authors: Arnold RR , Collins PS , Ayoub PS , Tung R
Published: March 2009

A computer program for the prediction of crack propagation in aircraft transpar encies is described. The program, PACE (program for automated crack extension), provides an analyst with an automated means to update continually an initial finite element model to account for the propagation and branching of cracks resulting from the use of detonating cord and mechanical breakers to fragilize the transparency. The time frames of action for both the exploding detonating cord and fast fracture of the polymer transparency are short with respect to any gross movement of the canopy; hence, the primary focus of the research is the determination of the initial fracture or breakout pattern of the canopy. Relatively simple fracture mechanics expressions are used to estimate crack propagation direction and the number of branches. Experimental work and correlations to predictions made by PACE are described. An overview of the computational process is provided.
Calculation of Stress Intensity Factors for Interface Cracks Under Mixed-Mode Loading
Authors: Naik RA , Crews JH
Published: March 2009

A simple technique was developed using conventional finite element analysis to determine stress intensity factors (K1 and K2) for interface cracks under mixed-mode loading. This technique involves the calculation of crack-tip stresses using nonsingular finite elements. These stresses are then combined and used in a linear regression procedure to calculate K1 and K2. The technique was demonstrated by calculating K1 and K2 for three different bimaterial combinations.

For the normal loading case, the calculated K1 and K2 were within 2.6% of an exact solution. The normalized K1 and K2 under shear loading were shown to be related to the normalized K1 andK2 under normal loading. Based on these relations, a simple equation was derived for calculating K1 and K2 for mixed-mode loading from a knowledge of K1 and K2 under normal loading. Thus, for a given material combination and geometry, only one solution of K1 and K2 (under normal loading) is required to determine K1 andK2 over the full range of mixed-mode loading conditions.

The equation was verified by computing K1 and K2 for a mixed-mode case with equal normal and shear loading. The correlation between the exact and the finite element values was very good with errors of less than 3.7%.

This study provides a simple procedure to compute the K2/ K1 ratio, which can be used to characterize the stress state at the crack tip for various combinations of materials and loadings. Tests conducted over a range of K2/ K1 ratios could be used to characterize fully interface fracture toughness.
Impact Testing of Al2O3 and SiCw/Al2O3 Ceramics
Authors: Deobald LR , Kobayashi AS
Published: March 2009

A bar impact test procedure was used to study spallation of Al2O3 bars and dynamic fracture of Al2O3 and SiCw/Al2O3 bars. Fractography analysis of the spalled surface showed extensive intergranular fracture (90 to 95% area). Dynamic fracture studies of precracked Al2O3 and SiCw/Al2O3 bars showed that the dynamic initiation fracture toughness, KId, and the crack branching stress intensity factor, KIb, remained constant with increased impact velocity, that is, impact stress. Despite the increase in static fracture toughness, KIc with the addition of SiC whiskers in A12O3 matrix, KIds and KIbs of Al2O3 and SiCw/Al2O3 were about the same, suggesting that the SiC whiskers are not effective in dynamic fracture.
A Historical Overview and Discussion of Computer-Aided Materials Testing
Authors: Braun AA
Published: March 2009

Consistency of test data has always been a key concern in any materials testing application. Test technique or method, operator skill and experience, and capabilities of the apparatus are all parameters that affect the consistency of the desired information. The arrival of testing automation has contributed significantly to improving the consistency of materials testing apparatus, modifying existing test methods, creating new test methods due to enhanced capability, and improving the productivity of testing systems.

This paper surveys the development of computer-aided testing over the last 20 to 25 years and includes a discussion of current systems implementations and the emerging area of laboratory-wide automation. The rapid development of materials testing automation capability has generally tracked the trends in the computer industry. Advances in microprocessor hardware technology have driven testing automation by allowing for embedded intelligence in key test system components and by allowing for high-performance supervisory computer subsystems to control or supervise the overall test rig. Software technology advances in concert with expanding hardware capability have provided truly useful real-time operating environments, more efficient applications development tools, and higher productivity through more intuitive user interface technology. All together, these technology improvements have allowed for more sophisticated, consistent, and higher performance testing automation. Further improvements will be realized through the true utilization of the emerging digitally based systems architectures and emerging networking technology. This discussion concludes with a brief look at where emerging capabilities such as these will allow for new types of experiments to be performed and where information management will be enhanced, thus allowing for greater productivity in the test laboratory.
Computer Applications in Full-Scale Aircraft Fatigue Tests
Authors: Hewitt RL , Rutledge RS
Published: March 2009

The development of computerized load processing techniques for application to a full-scale fatigue test of the aft fuselage and empennage of a Canadian Forces CT-114 (Tutor) aircraft is described. The procedures used to select significant end points from the flight loads and to eliminate nondamaging maneuvers are presented together with the development of the test actuator loads required to simulate the flight cases. The optimization procedure used to minimize the error in the applied load distribution, based on the sensitivity of stresses at critical locations to errors in the test loads, is also given.

The integration of the load control and multichannel data acquisition systems is described. By taking and automatically checking data on specific load cycles on a continuous basis throughout the test, it was possible to get immediate notification of any structural changes that occurred and check the functioning of the test system. Two examples are given that demonstrate the use of this integration.
Microprocessor-Based Controller for Actuators in Structural Testing
Authors: Sunder R , Venkatesh CS
Published: March 2009

A dedicated microprocessor-based controller was developed for low-speed multichannel structural testing. The controller was designed to be mounted on the actuator and for remote calibration, tuning, and programming. It includes electronics for signal conditioning and servoloop control, programmable waveform generation, and data acquisition, as well as handshake lines for synchronous operation with other actuators. Computer-controller communication is through a serial daisy-chained interface that permits multiactuator programming through a single communication port on the host computer system.
Computer-Aided Laser Interferometry for Fracture Testing
Authors: Maji AK , Wang J
Published: March 2009

The fracture process in quasi-brittle materials such as concrete, rocks, and ceramics is characterized by localized cracking and an R-curve type of behavior due to the fracture process zone. Accurate estimation of materials toughness can be determined only if the exact crack-tip location is known and the influence of the process zone can be measured.

In the nondestructive evaluation (NDE) of steel bridges, the location of cracks is a difficult problem, particularly due to lack of accessibility and due to the sheer size and number of the bridges that require inspection. Adequate tools for nondestructive inspection are therefore needed.

In recent years, laser interferometry techniques have proven to be major assets in accomplishing these tasks. Image analysis systems have removed the need for chemical processing, and optical data can be processed in real time by personal computers. These advances have led to new uses for laser techniques both for locating fractures and for assessing fracture parameters of materials.
Sampling Rate Effects in Automated Fatigue Crack Growth Rate Testing
Authors: Donald JK
Published: March 2009

With the advent of ASTM Test Method for Measurement of Fatigue Crack Growth Rates (E 647-91) and the associated annexes for nonvisual methods of monitoring crack length, there exists a need to address many aspects of the role that automation plays in generating fatigue crack growth rate data. The current ASTM standard provides primary guidance for visual methods of monitoring crack length and manual control of the test. The associated annexes provide guidance for two common nonvisual methods of monitoring crack length. Although they are good guides for both manual and automated control, they lack detail on many important considerations related to stress intensity (K) control, crack length precision, and load precision. This paper will emphasize the effect of sampling rate and resolution on crack length precision, dynamic load precision, and control. The issues will include analog-to-digital conversion resolution, digital filtering, peak reading, and multichannel phase considerations.
Procedure for Automated Tests of Fatigue Crack Propagation
Authors: Bachmann V , Marci G , Sengebusch P
Published: March 2009

This paper describes a computer program and its periphery that allows the determination of da/dN - ΔK curves: fatigue crack propagation threshold, ΔKth: and the crack opening stress intensity factor, Kop. The main requirement on the computer program is that no a priori knowledge about the material or the test procedure is required of the operating personnel.
A Computer-Aided Technique for the Determination of R-Curves from Center-Cracked Panels of Nonstandard Proportions
Authors: Sutton GR , Thomas CE , Wheeler C , Wilson RN
Published: March 2009

The development of a technique for the measurement of fracture toughness using computer-aided data collection and analysis has greatly reduced the computation time, increased accuracy, and enabled crack resistance curves to be determined from center-cracked panels of nonstandard geometries. The effective crack length is determined from compliance measurements and a geometric correction to stress intensity factor for nonstandard geometries derived from fatigue crack growth data and from energy release-rate calculations. Fracture toughness tests have been conducted on panels up to 2 m wide with a length-to-width ratio of 0.5.

The technique is illustrated using results showing the effect of panel size and geometry for the 2024-T3 aluminum alloy.