bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cracked Strip Problem Subjected to a Nonsymmetric Transverse Loading by a Stamp
Authors: Yahşi OS , Demir Y 
Published: March 2009

In this study, the problem of an infinite elastic strip that contains a crack perpendicular to its boundaries and subjected to a nonsymmetric transverse loading is considered. The problem is a coupled crack-contact problem in which the distribution of the transverse loads is not known and is dependent on the geometry of the crack as well as the stamp. The effect of friction that may exist at the punches is taken into consideration in formulating the problem by prescribing the tangential as well as the normal tractions on the boundaries.
The solution of the problem is given for two stamp geometries, namely, a rigid flat-ended stamp with sharp corners and a curved elastic stamp.
To solve the problem, the stress and displacement fields of the strip were obtained by using Fourier transforms and then crack solution was added. As a result, three singular integral equations were obtained.
These singular integral equations are solved for the discrete values of contact stresses at certain collocation points, and stress intensity factors are obtained and tabulated for various geometries and material combinations.
Environmentally Controlled Fracture of an Overstrained A723 Steel Thick-Wall Cylinder
Authors: Underwood JH , Olmstead VJ , Askew JC , Kapusta AA , Young GA 
Published: March 2009

A through-wall, 1.7-m-long crack grew suddenly from an outer diameter (OD) notch in a 285-mm-OD A723 steel overstrained tube that was undergoing plating operations with no externally applied loads. A description is given of the fracture mechanics tests and analyses and the fractography that were performed to characterize the cracking. Key material, residual stress, and environment information are: 1200 MPa yield strength; 150 MPa √m fracture toughness; composition typical of air-melt A723 steel; tensile residual stress at the OD of about 600 MPa; and electro-polishing bath of sulfuric and phosphoric acids at 54°C.
The bolt-loaded test for threshold stress intensity factor for environmentally controlled cracking described by Wei and Novak was used here with two significant modifications. Some tests included only a notch with radius matching that of the tube, and a new expression for K in terms of crack-mouth displacement was developed and used. Scanning electron microscopy (SEM) fractography and energy dispersive X-ray spectra were used to identify cracking mechanisms.
Results of the investigation include: (a) a measured threshold of hydrogen stress cracking for the material/environment below 20 MPa √m, (b) da/dt versus K behavior typical of classic environmental control, (c) an improved K/v expression for the bolt-loaded specimen and associated criteria for determining plane strain test conditions in relation to the Irwin plastic zone.
Fatigue Lifetimes for Pressurized, Eroded, Cracked, Autofrettaged Thick Cylinders
Authors: Parker AP , Plant RCA , Becker AA 
Published: March 2009

This paper summarizes Boundary Element Method Stress Intensity Factor solutions, obtained by the authors and presented elsewhere, for internally pressurized thick cylinders having a single longitudinal, semicircular erosion on the internal bore with radial straight-fronted and elliptical cracks emanating from the deepest point of the bore erosion.
A ratio of external to internal cylinder radii (R0/R1) of 2.0 is employed and a range of semicircular erosion depths varying from 0 to 40% of the wall thickness. Care is taken to determine accurate stress concentration factors for the various erosion depths in order to accurately quantify limiting values of stress intensity factor at very short crack lengths.
Employing a standard fatigue crack growth law, lifetime calculations are presented for cyclic pressurization of the bore. The results indicate that the presence of a modest semicircular erosion at the bore serves to reduce the fatigue lifetime by an order of magnitude. A similar reduction in lifetime results from the elimination of the autofrettage residual stress field.
Fatigue Crack Growth Analysis of Structures Exposed to Fluids with Oscillating Temperature Distributions
Authors: Chattopadhyay S 
Published: March 2009

This investigation considers amplitudes and frequencies of the oscillating temperature distribution as parameters for crack propagation studies. The alternating stresses produced by the temperature distribution are used to determine the ranges of stress intensity factors for a particular crack geometry using the principles of linear elastic fracture mechanics. The crack growth is then studied using a crack growth law for the material relating the crack growth per cycle to the number of cycles.
The analysis predicts that the number of cycles required to drive a crack of a specified initial size is dependent on the frequency of temperature cycling. The model also predicts that as the frequency increases, larger amplitudes of temperature variation can be permitted for the same number of cycles to failure. A design curve relating the temperature amplitude with the number of cycles to failure (a specified crack length) is obtained for various frequencies of temperature oscillations.
Effects of Sample Size and Loading Rate on the Transition Behavior of a Ductile Iron (DI) Alloy
Authors: Salzbrenner R , Crenshaw TB 
Published: March 2009

The measurement and understanding of the fracture toughness of ductile irons (DI) are critical to the analysis of nuclear transportation casks made from these alloys. Cask containment must be assured for all loading events from normal handling to accidents during which high loads can be delivered at elevated rates. Cask walls are commonly in the range of 20 to 50 cm thick (or greater) in order to provide requisite nuclear shielding, and this requires that associated mechanical constraint effects must be considered. At elevated temperatures (that is, in the vicinity of ambient), DI behaves in an elastic-plastic manner, even for large section sizes (thickness &gt; 20 cm) and moderately high loading rates. However, as the temperature is lowered or the loading rate is increased, ferritic DI alloys exhibit a relatively sharp transition to linear elastic behavior, with a significant decrease in the fracture toughness.
The fracture toughness of a DI alloy has been measured using linear elastic and elastic-plastic experimental techniques. Measurements have been made as a function of temperature, loading rate, and section size. The loading rates span the range that a cask could experience during normal transport and handling, as well as accident events. Specifically, the stress intensity rate, K, was varied between 10-3 to &gt; 10+5 MPa m1/2/s. The range in section size that was examined was restricted to moderate thicknesses (̃1 to ̃4 cm) because of the limitations of available hydraulic test frames. For static testing rates, it was found that increasing specimen thickness appears to shift the transition behavior to slightly higher temperatures. The effect of increased specimen thickness during elevated rate testing was more pronounced. As the thickness was increased from ̃1 to ̃2 cm, the fracture toughness was decreased by roughly 25% at 25°C, and 40% at -29°C (the fracture toughnesses of both thicknesses were the same at -50°C where fracture was essentially all cleavage). Initial fractographic results show that the amount of brittle cleavage (at initiation) was larger for the thicker specimens in the ductile-brittle transition region. The decrease in fracture toughness with increasing section size (in the transition region) occurred even though all specimens met the size criteria of the ASTM Test Method for JIc, A Measure of Fracture Toughness (E 813-87). Measurements also showed that the temperature range of the transition region for this DI alloy increased with increasing loading rate and extended up to room temperature. A consistent explanation for the measured behavior seems to be that increased constraint (from increased specimen thickness) can cause an increase in cleavage if the test temperature (for a specific loading rate) is close to the transition region. The extent of this effect has an obvious impact on the analysis of the fracture resistance of transportation containers.
Chemical Stability of Polyester Fibers and Geotextiles Without and Under Stress
Authors: Netravali AN , Krstic R , Crouse JL , Richmond LE 
Published: March 2009

High tenacity industrial grade polyester fibers were aged up to three months, in various chemicals at different stress levels. The accelerated aging was done at temperatures up to 70°C, which is thought to be the maximum underground temperature for applications such as surface veneers for waste landfills. The chemicals used in the study include trichloroethylene, deionized water, sea water, and 2% solutions of sulfuric acid and sodium hydroxide. The stress values used were 0 MPa, 100 MPa, and 260 MPa. The fibers were tested for their mechanical and thermal properties as a function of aging.
The results suggest that there are no changes in the fiber strength and glass transition temperature (Tg) after aging in trichloroethylene, sea water, and deionized water under any stress level and test temperatures. However, there is a small increase in the melting temperature indicating the possibility of crystal growth, especially at 70°C, due to the annealing effect.
Significant degradation in fiber strength is seen after a week of aging in sulfuric acid solution (-1.1 pH) at room temperature and 40°C. Under the severe acidic conditions, at 70°C and higher stress levels, the fibers completely disintegrated after one week.
In the strong alkaline condition (-13.7 pH), strength decreases of 33% and more than 50% are seen under 0 and 100 MPa stress levels within the first week of aging in NaOH, at RT. All fibers, regardless of stress, did not survive one month in the highly alkaline environment.
These results suggest that 1) severe hydrolysis occurs in strong alkaline and acidic media 2) no hydrolysis occurs under more normal soil conditions (∼pH 7-8) at temperatures up to 70%C and 3) higher stress levels do not significantly affect the degradation process.
Swelling Suppression in Phosphorus-Modified Fe-Cr-Ni Alloys During Neutron Irradiation
Authors: Lee EH , Packan NH 
Published: March 2009

Phosphorus-containing austenitic alloys in the solution annealed condition were irradiated at 745 to 760 K (470 to 485°C) in the Fast Flux Test Facility (FFTF) reactor to doses ranging from 0.1 to 10 dpa. The alloys were variations on Fe-13Cr-15Ni-0.05P with respective additions of 0.8 silicon, 0.2 titanium, or 0.8 silicon plus 0.2 titanium; also included were low (0.01) and zero phosphorus compositions (all values in wt %). This alloy set was studied previously using heavy ion irradiations.
The reference ternary and the two phosphorus-only variations contained little precipitation and numerous voids and swelled rapidly, while the three variants containing phosphorus with silicon or titanium or both showed little or no void formation and profuse phosphide precipitation. These results indicate that phosphorus in solution alone does not have a major influence on void swelling, whereas fine-scale phosphide precipitation is quite effective at suppressing void formation. The possible contributing role of impurity oxygen to void formation is considered, but this role is found to be secondary to the principal mechanism restricting swelling, which is the effect of the dense precipitate microstructure. These precipitates foster profuse cavity nucleation that in turn dilutes the helium accumulation per site. The cavities together thereby require more total helium atoms (and more time) in order for individual cavities to surpass their critical size and number of gas atoms necessary for subsequent growth as voids.
Computer Simulation of Stress Corrosion Cracking Behavior of Reactor Pressure Vessel (RPV) Steels in Light Water Reactor (LWR) Environments in Slow Strain Rate Tests (SSRT)
Authors: Shoji T , Moriya S , Yoshida K 
Published: March 2009

Based upon a slip dissolution model, crack initiation and growth behavior of stress corrosion cracking of reactor pressure vessel steels, in pressurized high temperature water, was simulated by FEM (finite element method), with a combination of nodal force release techniques, simulating the crack growth by dissolution.
Results obtained from the computer simulation for this materials/environment combination agree well with experiments in overall load/displacement curves of the tests and also can simulate crack initiation and propagation behavior. This computer simulation of slow strain rate ( SSR ) tests also focused on the significance of the multiple crack problems in SSR tests, particularly for smooth specimens, in relation to an evaluation of an actual crack tip strain rate. It was also found that crack growth rates, under such a multiple crack situation, can be uniquely plotted as a function of crack tip strain rates when evaluated correctly.
The Use of Computer Modeling in the Interpretation of Filming Inhibitor Mechanisms
Authors: Palus AF , Nienart CA 
Published: March 2009

The computer has made the collection and interpretation of data easier. The advent of computer controlled instrumentation made it possible to easily acquire electrochemical impedance data; unfortunately the complex nature of the data made it difficult to interpret. One classical approach to interpretation is to hypothesize an equivalent circuit to model the electrochemical system. Since the equations and algorithms of electrical circuits are well defined, a computer program can do an excellent job of modeling these equivalent circuits. We will discuss how the use of a commercially available impedance modeling program can be used in the interpretation of real impedance data.
Cinnamaldehyde is known to act as an inhibitor to steel corrosion in hydrochloric acid. The mechanism for protection is assumed to be twofold. The chemisorption of trans-cinnamaldehyde (TCA) is usually proposed as the major contributor to inhibition. A secondary, but significant, contribution is caused by the polymerization of the TCA to form a film. Growcock and Lopp [ 1 ] have studied the nature of these two mechanisms. They showed through corrosion rate studies, organic analysis, NMR, FT-IR and GC/MS the nature and function of the organic film formed by TCA.
We have studied the film formation of TCA on 1018 steel in HCL solutions using electrochemical impedance spectroscopy. Experiments were run to try to distinguish the difference between the two major inhibition mechanisms. The impedance spectrum of an adsorbed TCA diffusion barrier should differ from the spectrum of either a polymer film or a combination polymer film and diffusion barrier. The Equivalent Circuit modeling program of Boukamp [15] was used to assist in interpretation.
Some Observations in Fracture Toughness and Fatigue Testing with Chevron-Notched Specimens
Authors: Salem JA , Shannon JL , Jenkins MG 
Published: March 2009

Chevron-notched specimens were used to test metallic and ceramic materials over a range of temperatures and testing conditions. The materials tested were M-50 bearing steel, alumina, silicon carbide, monolithic silicon nitride, and in situ toughened silicon nitride. Results were compared to measurements performed with compact-tension specimens, singleedge notched beam specimens, or single-edge precracked beam specimens.
Measured properties included fracture toughness, crack growth resistance, and fatigue crack growth rate. For materials with rising R-curves, the fracture toughness measured with chevron-notched specimens was dependent on specimen proportions and notch geometry, as related to the amount of crack extension to the measurement point. For materials with flat R-curves, the chevron-notch test is independent of notch geometry and specimen proportions.
Short Bar Chevron-Notch Fracture Toughness of Bone Cement
Authors: Bhambri SK , Gilbertson LN 
Published: March 2009

Poly(methylmethacrylate) is used as a grouting agent in total joint arthroplasty. Fracture toughness of the relatively brittle bone cement is an important property determining the reliability and defect tolerance capability of the material. In the present study, fracture toughness of bone cement and commercial PMMA has been determined using a short bar chevron-notch test method. Chevron-notched short bar specimens were prepared with a notch molded-in during the polymerization process or by machining techniques. Specimen size and other test parameters were varied to determine variability of the results. In addition, parameters were also varied to simulate clinical practices.
A peak load test method following ASTM E 1304-89 was used to estimate fracture toughness. The load-displacement curves obtained were independent of the displacement rates within the recommended peak load time range. Wide variation of displacement rates had no effect on the fracture toughness values. No plasticity-induced effects on fracture toughness were evident in the slow rate regime up to a peak load time of 300 s for 12.7-mm-thick short bar specimens. The results of this study indicate that the ASTM Test Method E 1304-89 can be successfully used in determining fracture toughness of bone cements.
Analysis of Radiation Embrittlement Results from a French Forging Examined in the Second Phase of an IAEA-Coordinated Research Program
Authors: Soulat PE , Houssin B , Bocquet P , Bethmont M 
Published: March 2009

Test blocks of a manganese-nickel-molybdenum (Mn-Ni-Mo) low-alloy steel, machined from a nozzle cut-out of a 230-mm-thick forging shell, were provided by France in 1978 to be investigated in the second phase of an IAEA-coordinated research program on the behavior of advanced pressure vessel steels under neutron irradiation.
The results obtained by different laboratories exhibit a great deal of scatter in Charpy-V transition temperatures, both in the initial condition and after neutron irradiation. Therefore, the shifts in Charpy-V transition curves induced by neutron irradiation at similar fluences of about 3 × 1023 n ∙ m-2 (E ⩾ 1 MeV) cover a wide temperature range from 0 up to 110°C.
A more detailed investigation of these results was undertaken, and additional Charpy tests were conducted to clarify the considerable uncertainty about the sensitivity of this forging to radiation embrittlement. The differences in results were found to be due to the various orientations and locations of the Charpy-V specimens extracted by the different laboratories, in some cases to insufficient test data in the transition region of the Charpy curve, and to the detrimental effect on Charpy-V properties of segregated zones (ghost lines) found in specific locations of large forgings.
Neutron Fluence Management to Optimize Pressure Vessel Lifetime
Authors: Lefebvre JC , Leroy P , Rieg C , Schaeffer H , Nimal JC , Lloret R 
Published: March 2009

Pressure vessel steel embrittlement management is needed to predict the tearing resistance at end of life, but also to update these predictions taking into account the evolution of the principal parameters, such as fuel management, thermohydraulics of the primary coolant circuit, and lifetime extension capability.
French 900-MW units are characterized by a high neutron fluence on the inner face of the pressure vessel at the predicted end of life. Electricité de France's (EDF) purpose is to establish the appropriate knowledge and software to predict the pressure vessel embrittlement during operation.
This work is in progress in two ways. First, appropriate existing software is being used to calculate the consequences in terms of neutron flux, on the inner face of the pressure vessel, of various operating conditions and fuel patterns, and to be able to select the best of these. Second, specific software is being developed to calculate the maximum neutron flux on the inner face of the pressure vessel, according to the contribution of the major fuel elements so we can appreciate the fluence level of each refueling pattern and choose the one that is less severe. These results have shown that a benefit of about 30% can be obtained by optimized patterns with high discharge burn-up.
Neutron fluence management can be successfully integrated in the core refueling calculation procedure, but further progress is necessary for complete validation and background to optimize the steel surveillance program.
Continuous and Sequential Multiaxial Low-Cycle Fatigue Damage in 316 Stainless Steel
Authors: Weiss J , Pineau A 
Published: March 2009

Tension and torsion low-cycle fatigue tests were carried out on thin tubular specimens of 316 stainless steel, tested at both room temperature and 600°C. Two types of experiments were performed: (1) conventional continuous isothermal tests, and (2) isothermal sequential tests with different sequences of tension/compression and torsional loading. Most of these tests were carried out under air environment at the equivalent total strain amplitude of Δεt/2 = ±0.80% in tension or Δγt/2 = ±0.80 √3% in torsion. Optical and scanning electron microscopy were used to analyze the failure modes, the orientation of microcracks and macrocracks which lead to failure, and crack density.
Continuous tests show two main results: (1) it is confirmed that, for the same equivalent von Misès strain, the fatigue lives in torsion are larger than those observed in tension; (2) detailed examinations of the microcracks' orientation showed that Stage I initiation followed by Stage II growth occurs only at room temperature or at elevated temperature under vacuum. At 600°C, however, Stage I crack initiation is bypassed due to the formation of external hematite (Fe2O3) and internal (Fe-Cr rich) oxides.
These results are used to explain qualitatively the significant deviations observed in the sequential tests from the Miner linear cumulative damage rule. A quantitative model based on a Monte Carlo simulation is developed to account for the results of sequential tests in which crack initiation and crack growth were coplanar. This model includes three fatigue damage laws: (1) a nucleation rate equation; (2) a push/pull or torsion crack growth law; and, (3) a criterion for crack coalescence. It is shown that this model is able to reproduce with good accuracy the results of sequential push/pull → torsion tests carried out at 600°C.