bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relations Between the Strain Energy Density Distribution and Elastic-Plastic Stress-Strain Fields Near Cracks and Notches and Fatigue Life Calculation
Authors: G Glinka 
Published: February 2009

Relations between the strain energy density distribution and the elastic-plastic strain-stress fields near notches have been analyzed. It was found that the strain energy density distribution in the plastic zone ahead of the crack or notch tip can be satisfactorily estimated on the basis of the theoretical elastic stress field. The strain energy density can be translated into the elastic-plastic strain and stress in the plastic zone if the nonlinear material stress-strain curve is known. Good agreement with finite element calculations has been achieved for cracks under plane strain conditions. It has also been shown that the equivalent strain energy approach can be useful for the notch-tip elastic-plastic strain calculation under both monotonic and cyclic loading.
Very good agreement between the experimentally measured and calculated notch-tip strains has been obtained up to general yielding. The elastic-plastic notch-tip strain histories calculated on the basis of the equivalent strain energy density concept were used for fatigue life calculation of key-hole specimens tested under SAE transmission loading history. Significant improvement of fatigue life prediction has been achieved in comparison to the calculations based on Neuber's rule.
Possible applications of the equivalent strain energy density concept for fatigue crack growth prediction are also discussed.
Evaluation of Low Cycle Creep-Fatigue Degradation for Notched Components
Authors: SN Singhal , RA Tait 
Published: February 2009

Four approaches have been examined to predict the endurance of circumferentially notched, uniaxially loaded test pieces subjected to fully reversed strain-controlled cyclic loading at elevated temperatures. Results are compared with uniaxial data derived from smooth test pieces. The strain-time waveforms include both trapezoidal and triangular shapes to distinguish between fatigue and fatigue-creep damage. The four materials investigated are HP-45 (1144 K), Incoloy 800H (1144 K), Incoloy 800 (922 K), and 1¼Cr-½Mo (811 K). The analysis has reflected the various degrees of cyclic hardening and creep deformation exhibited by these materials. The predictive approaches include Neuber notch strain analysis and finite element analyses to identify the maximum plastic strain range, the equivalent plastic strain range, and the total plastic work per cycle.
The study provides a simple, pragmatic approach to predicting whether cyclic plant operation is lifetime limiting. The primary conclusion is that the total plastic work-per-cycle approach is the preferred method for evaluation of fatigue-limited plant lifetimes.
Reconsideration of Macroscopic Low Cycle Fatigue Laws Through Observation of Microscopic Fatigue Process on a Medium Carbon Steel
Authors: S Harada , Y Murakami , Y Fukushima , T Endo 
Published: February 2009

In order to correlate macroscopic low-cycle fatigue laws such as the Manson-Coffin relation and Miner's rule with the actual microscopic fatigue process, cyclic strain-controlled lowcycle fatigue tests were conducted on a medium carbon steel under constant-, two-step-, and random-strain amplitude conditions. Through continual observation of the microscopic fatigue process of plain specimens and holed specimens with a very small hole (40 μm diameter), it was found that the total fatigue life is mostly occupied by the microcrack propagation life. Both the Manson-Coffin relation and Miner's rule are derived using the microcrack propagation law. Then, background for the applicability of Miner's rule is discussed.
The results of the random loading fatigue tests showed that microcrack propagation life can be predicted on the basis of the microcrack growth law in conjunction with the rain flow method for counting fatigue damage. Finally, the microcrack growth law-aided approach was applied to interpret anisotropy in fatigue strength of a thick forged steel plate.
Grain Boundary Oxidation and an Analysis of the Effects of Oxidation on Fatigue Crack Nucleation Life
Authors: Y Oshida , HW Liu 
Published: February 2009

A study on the effects of pre-oxidation on subsequent fatigue life was conducted. The surface oxidation and grain boundary oxidation of a nickel-base superalloy (TAZ-8A) were studied at 600 to 1000°C for 10 to 1000 h in air. The surface oxides were identified and the kinetics of surface oxidation was discussed.
The grain boundary oxide penetration and morphology were studied. The pancake-type grain boundary oxide penetrates deeper and its size is larger, therefore, it is more detrimental to fatigue life than the cone-type grain boundary oxide. The oxide penetration depth, am, is related to oxidation temperature, T, and exposure time, t, by an empirical relation of the Arrhenius type. The effects of T and t on the statistical variation of am were analyzed according to the Weibull distribution function. Once the oxide is cracked, it serves as a fatigue crack nucleus. The statistical variation of the remaining fatigue life, after the formation of an oxide crack of a critical length, could be related directly to the statistical variation of grain boundary oxide penetration depth.
Compressive Properties and Laser Absorptivity of Unidirectional Metal Matrix Composites
Authors: Chang DJ , Steckel GL , Hanna WD , Izaguirre F 
Published: February 2009

Metal matrix composite (MMC) use has been impeded because there is no well qualified property data base. Elevated temperature compressive properties and laser absorptivity data are in great demand in the design, modelling, and analysis of MMC structures in elevated temperature applications and survivability assessment. Testing methods were developed for room-temperature and elevated-temperature compressive modulus and strength measurements of single-ply unidirectional graphite-aluminum (Gr/Al) and graphite-magnesium (Gr/Mg), and to generate laser absorptivity data for these two types of materials.
An effective gage length was established for valid compression tests to eliminate buckling failure. The measured failure strength values for Gr/Al and Gr/Mg are approximately 50 to 60% lower than the material tensile strength. Small gage strain gages are being used to measure the compressive modulus as a function of temperature.
The laser absorptivities of Gr/Al and Gr/Mg were measured by the use of an in-house developed differential calorimeter. The calorimeter has been used to measure total hemispherical emittance and normal laser absorptance of specimens as a function of temperature from 200 to 700°C.
Test results indicated that the laser absorptances of Gr/Al and Gr/Mg at 10.6 μm wavelength remain more or less constant over most of the temperature range tested.
Mechanical Behavior of Three-Dimensional Braided Metal Matrix Composites
Authors: Majidi AP , Yang J-M , Chou T-W 
Published: February 2009

The results of an on-going experimental study to characterize the mechanical properties and failure mechanisms of a novel 3-D braided composite of α-alumina fiber (fiber FP) in a matrix of aluminum +2.5% lithium have been presented. Quasi-static tension, compression, and shear tests have been conducted. Acoustic emission data have been collected during tension tests to provide additional information about failure. Fracture toughness and drop-weight impact characteristics have been also evaluated and compared with those of unidirectional FP/aluminum-lithium composites.
The 3-D braiding of fibers not only provides reinforcement in the thickness direction and reduces or eliminates potential for interlaminar failure, but also appears to be an effective approach to increasing the resistance of the composite to crack propagation under both static and impact conditions of loading.
Factors Affecting the Determination of Thermophysical Properties of Metal Matrix Composites
Authors: Tye RP , Smith SE 
Published: February 2009

Methods, techniques, and models available for the measurement or estimation of thermal conductivity, electrical conductivity, thermal diffusivity, thermal expansion, and heat capacity, are reviewed with respect to their applicability to metal matrix composite materials and systems.
Various factors influencing the choice of method used to obtain reliable properties information are discussed. These include: (a) application and use of the material or system; (b) continuous and discontinuous reinforcement of the matrix; (c) layered and other combination of materials; (d) size and form; (e) anisotropy; and (f) temperature and accuracy requirements.
Considering the unique problems represented by these materials and systems, recommendations are made regarding the most appropriate means currently available to obtain reliable thermal properties information. Areas are identified where further information and work are required in order to improve existing models and measurement techniques.
Minimechanics Analysis and Testing of Short Fiber Composites: Experimental Methods and Results
Authors: Awerbuch J , Goering J , Buesking K 
Published: February 2009

This paper describes a study performed to experimentally investigate the constitutive behavior of silicon carbide whisker reinforced aluminum and to provide data for a companion material modelling study. The experimental program included measurement of material stress-strain curves, assessment of the acoustic emission response of the material, and examination of the material failure surfaces.
The results of the mechanical tests showed that as the whisker content increases, stiffness, strength, and rate of strain hardening increases, whereas the strain to failure decreases. Changes in the extrusion ratio have little effect upon the composite properties although the extruded bulk aluminum was significantly different from commercial aluminum alloy 6061-T6. The acoustic emission results showed that the failure modes of the composites and unreinforced materials were similar. The scanning electron microscopy results showed that failure of the materials was due to microyielding within the aluminum. Therefore, the composite failure is believed to be caused by matrix plasticity and whisker pullout.
Nondestructive Evaluation of Fiber FP Reinforced Metal Matrix Composites
Authors: Widrig JE , McCabe DD , Conner RL 
Published: February 2009

Fiber FP is a continuous polycrystalline alumina fiber suited for reinforcement of metals, plastics, and ceramics. Fiber FP/metal composites are very attractive for weight and stiffness critical applications. In order for these materials to be accepted in the marketplace, quality control methods needed to be developed. In this study, we developed methods based on computed tomography (CT) and ultrasonic scanning to identify porosity, delamination, and other discontinuities in Fiber FP reinforced composites.
Prior to this work, Fiber FP/metal plates and coupons were inspected using a combination of X-ray and ultrasonic methods—both with significant limitations. The ultrasonic evaluation utilized a defect threshold technique with inherent sensitivity uncertainties of defects close to the threshold level. This study demonstrated that defect intensity level scanning was superior to threshold scanning for Fiber FP reinforced composites. We developed color indicators for the various intensity levels to facilitate data interpretation.
The ultrasonic technology was also limited to simple flat shapes. Fiber FP development programs have recently shifted to fabrication of more complex prototype components such as connecting rods and helicopter transmission housings. CT offers several advantages over traditional radiographic techniques. Standard radiography creates an obscure 2-D image of a 3-D body by superimposing defect indications. A CT scanner has the ability to look at 2-D slices of a 3-D component. A series of 2-D images can be taken, and then interfaced with a computer to show the 3-D nature of the object. This technique has been demonstrated for prototype connecting rods and confirmed via destructive testing.
Compressive Testing of Metal Matrix Composites
Authors: Bethoney WM , Nunes J , Kidd JA 
Published: February 2009

A newly developed direct compressive test fixture for metal matrix composites is described and evaluated in this paper. This fixture was designed to be reusable, provide accurate and reproducible data, and to eliminate premature “brooming” failures. A comparative analysis between this test method and ASTM D 3410 for compressive properties of unidirectional or cross-ply fiber-resin composites using the Illinois Institute of Technology Research Institute (IITRI) indirect compression test method was also investigated.
In utilizing the direct compressive test method, the affects of specimen size and geometry were studied on a uniaxially oriented FP-alumina fiber reinforced magnesium composite. Cylindrical specimens 6.35, 9.53, and 12.7 mm in diameter, and a 9.53-mm-square specimen were tested at a constant 1/d ratio of 2.0. The tabbed specimen size and geometry that was employed in the IITRI test method was 2.54 mm thick by 6.35 mm wide by 152.4 mm long with a 12.7 mm untabbed gage length. All IITRI test specimens were tabbed by employing an improved method for bonding the aluminum tabs to the FP-alumina/magnesium surface. This tabbing procedure was developed to overcome earlier difficulties that were encountered in obtaining sufficient tabbed bond strength.
All of the test specimens investigated were from a single plate of as-cast composite material that contained a fiber volume fraction of 55%.
Tests were conducted with the applied load parallel to the fiber axis. Each specimen was strain gaged to provide a continuous load-strain curve to failure, to determine various materials properties, and to monitor any bending of the specimen. Data obtained included the ultimate compressive strength, the tangent modulus, the apparent proportional strain, strain to failure, and Poisson's ratio. Results from both the direct and the indirect compressive test methods were statistically compared. Finally, post test metallographic and fractographic examinations were performed to determine the principal failure modes.
Final results indicate that the cylindrical specimens, regardless of their respective diameters, display the least scatter in their ultimate compressive strengths (UCS). Also, higher stress values for the cylindrical specimens was obtained; as compared to the IITRI specimens.
Short-Term High-Temperature Properties of Reinforced Metal Matrix Composites
Authors: Boland PL , DiGiovanni PR , Franceschi L 
Published: February 2009

While the Department of Defense initiated Metal Matrix Composite Information Analysis Center (MMCIAC) has been charged with providing centralized information dealing with metal matrix composites (MMCs), test procedures for obtaining primary MMC properties have evolved from ASTM standards. These standards in turn have evolved from polymeric matrix composite (PMC) test procedures and have not yet been established as appropriate for MMC applications. Methods for obtaining short-term high-temperature tensile, flexural, and pin bearing data for reinforced MMC are presented. In addition, coupon design and fabrication, instrumentation, measurement techniques, and some lessons learned are discussed.
Rapid heating, typical of tactical missile aerodynamic heating, can be suitably simulated using infrared quartz lamps. In fact, this type of furnace facilitates longer term baseline testing since temperatures can be reached more quickly, and test fixtures and equipment can be easily cooled. For short-term high-temperature strain measurements, extensometers were utilized. A computerized, digital data acquisition and control system is necessary to maximize data retrieval and minimize test errors during rapidly changing test conditions. Results show that while tensile strength of MMCs subjected to rapid heating greatly exceed those strengths obtained for long-term heating, flexure and pin bearing strength exhibit only moderate increases. Furthermore, differences are observed for specimens fabricated from thin versus thick panels.
Estimation of Reservoir Submerging Losses Using CIR Aerial Photographs: Example of the Ertan Hydropower Station on the Yalong River in Southwest China
Authors: Lin H 
Published: February 2009

A geotechnical project, which used remotely sensed and other spatial data to estimate reservoir submergence losses, was carried out in 1982 at the Ertan hydropower station on the Yalong River in Sichuan province, southwest China. To meet the needs for use of data from spaceborne remote sensing to estimate the losses, color-infrared (CIR) aerial photographs were used as the first step in a series of experiments.
An orthophotomap and a land-cover and land-use map of the submerged region have been completed using 1:45 000 and 1:24 000-scale CIR aerial photographs taken in the winter and spring of 1981. After some typical on-site sampling in the region to be submerged, as well as synthetic analysis on the aerial photographs, a three-level classification system has been developed, with 25 categories of potentially submerged objects classified by use of the maps. Each level of the classification system is decided by the needs of the project design for investigating submergence losses, the resolution of the aerial photographs, and the minimum size of the mapping unit. The length or area of each category on the land-cover and land-use map (1:20 000-scale) is measured using a manual tracking digitizer.
The root-mean-square (rms) accuracy standard was adopted to check the accuracy of the estimate. The accuracy includes the classification and position accuracy of the land-cover and land-use map, and the measuring accuracy of the polygons on the maps. Among the 25 classification categories, the difference between the statistical acreage of cultivated land determined from the estimation method using CIR aerial photographs and from the conventional method of on-site investigation by surveyors was only 3.1%. This project has provided not only the data needed for the design of the hydropower station, but also a data base for use in future experiments using Landsat data.
Application of Spatial Statistics to Analyzing Multiple Remote Sensing Data Sets
Authors: Glass CE , Carr JR , Yang H-M , Myers DE 
Published: February 2009

The purpose of this paper is to present results from preliminary research using image spatial statistics to improve the resolution of low-resolution digital images. Improvement is needed whenever images from different sensors, and often when images from different spectral bands within the same sensor, are collected for geotechnical interpretation.
The experimental procedure involves degrading one of two digital images in adjacent spectral bands to simulate a low-resolution image. New samples within the sparse, low-resolution image are subsequently estimated using the spatial characteristics displayed in a variogram function and an estimation process known as co-kriging or co-estimation. The resulting high-resolution estimation image is compared with the original undegraded image as a check on estimation accuracy. Reconstruction accuracy, as judged by mean square error (MSE), improved from MSE = 826 for sample replication to 56 for co-kriging.
For cases where geotechnical decisions rely on accurate knowledge of image amplitudes, this research suggests that co-kriging provides an accurate and flexible estimation technique. Moreover, co-kriging appears to be a promising technique for future automated image interpretation and feature extraction algorithms.
Review of Corrosion Studies of Metal Containers Using Synthetic Media
Authors: Murphy TP , Pape GA 
Published: February 2009

Corrosion phenomena in metal containers differ from those encountered in, for example, pipeline or bridge construction, in that they can be apparent at very low corrosion rates. Thus, contamination of the contents of the package can occur with relatively low metal uptakes, rendering them unsuitable for use. Dissolution of tin or iron from tinplate and of aluminium from body or end stock are examples of this contamination. Sulphide stains may be unsightly, but are not harmful. Perforation of the container may allow the product to escape, leading to secondary corrosion or contamination, and associated losses; or to the ingress of contaminants, leading to flavor changes or microbial spoilage. In practice, the incidence of problems is very low.
Corrosion testing frequently uses the actual products to be packed; this is the ultimate test. Synthetic systems have been used to simulate complex natural food in particular, but also to clarify the behavior of formulated products. Test methods involve electrochemical studies, coupon testing, and test packing. The behavior of coatings for cans may also be studied in this way. Performance is assessed by considering metal pick-up and incidence of swelling or perforation. Controlled-environment chambers are used in accelerated testing.
Characterization of materials also involves using synthetic media in laboratory testing, e.g., measurement of tin oxide levels in tinplate. The properties of containers and components may be checked using synthetic or, occasionally, natural materials.
While such procedures are helpful in clarifying corrosion processes and studying components or materials, they have limitations. Ideally, the test procedure should correspond to the products to be packed under anticipated conditions of use. Nevertheless, the use of synthetic systems contributes to the optimization of the final container/product combination.
Pitting of AISI 410 Stainless Steel in CO2-Saturated Synthetic Seawater and Condensate
Authors: McIntyre DR 
Published: February 2009

Specimens of American Iron and Steel Institute (AISI) Type 410 stainless steel were exposed to aerated and deaerated solutions of artificial seawater and distilled water, with and without quaternary amine additions, with a CO2 atmosphere. Pitting rates were determined from autoclave exposures, and electrochemical parameters were obtained from potentiodynamic polarization curves.
The studies showed that in deaerated solutions, the amine additions had a mild inhibiting effect on liquid phase pitting in both seawater and distilled water. The amine additions increased the rate of attack in aerated solutions of distilled water. Correlation between electrochemical test methods, laboratory autoclave tests, and field experience is good.
Analytical and Experimental Investigation of the Notched Strength of Thick Laminates with Surface Notches
Authors: Harris CE , Morris DH , Nottorf EW 
Published: February 2009

Experimental and analytical investigations of the fracture of a [0/± 45/90]10s graphite/epoxy laminate with part-through semi-elliptic surface notches have been conducted. Experimental values of notched strength were determined for a variety of notch aspect ratios and notch depths. Analytical predictions of laminate failure were obtained from three different models. One model was based on fracture mechanics concepts while the other two models were based on strength-of-materials concepts with a linear and quadratic strain distribution through the laminate thickness at the notch. The kinematic strain assumptions were in part based on results of a moiré interferometry investigation of the strain field at the notch.
The three models were equally successful in predicting the fracture of laminates with deep notches. The experimental results of laminates with shallow notches indicated more notch sensitivity (that is, greater strength reduction) than did the analytical models.