bluuebunny/crossref_metadata_2025 huggingface dataset:
Zirconium in the Nuclear Industry: 15th International Symposium
Authors: Kammenzind Bruce , Limbäck Magnus
Published: September 2009

Description

The latest in this popular series provides 44 peer-reviewed papers on the latest international research covering all aspects of zirconium alloy properties and performance relevant to the nuclear industry.

Topics address:

• All aspects of the fuel cycle

• Basic metallurgy

• Spent fuel

• Corrosion

• Mechanical properties

• Deformations mechanisms

• Failure mechanisms

• LOCA and Transients.

These papers provide examples of studies where experimental techniques are combined with analytical tools and calculations; reflect a stronger trend towards efforts that enable fundamental in-reactor measurements, which are essential for further development of experimental techniques as well as for the possibility to enhance the development of improved alloys; and examine an increasing number of alternative alloys being developed and verified.
Part 3: Control Chart Method of Analysis and Presentation of Data
Authors: Westman AER , Dodge HF , Peterson AI , Romig HG , Simon LE
Published: September 2009

This Part 3 of the A.S.T.M. Manual on Quality Control of Materials gives formulas, tables, and examples which are useful in applying the control chart method of analysis and presentation of data. This method requires that the data be obtained from several samples or that the data be capable of subdivision into subgroups on the basis of relevant engineering information. Although the principles of this Part are applicable generally to many kinds of data, they will be discussed herein largely in terms of the quality of materials and manufactured products.
A Study of Dislocations in Thin Aluminum Foils Elongated in the Electron Microscope
Authors: Wilsdorf HGF
Published: September 2009

Tensile experiments are described which have been conducted with thin aluminum foils approximately 1000 Å thick. It was the aim of this investigation to obtain information on the origin of dislocations and their behavior in thin foils during plastic flow. The method of observation was by transmission electron microscopy, as first described by Hirsch, Horne, and Whelan (l), and by Bollmann (2).
Plasma Assisted Heat Treating Processes of Bearing Components
Authors: Beer Oskar
Published: September 2009

Plasma surface-engineering technologies show several advantages over conventional surface engineering. In this paper the basic properties of a glow discharge plasma process and the way it is used for industrial applications is demonstrated via plasma nitriding and plasma carburizing of bearing parts. Plasma nitriding was applied for duplex hardening (DH) of bearing parts made from M50 and M50 NiL material. The influence of the process parameters on hardness profile and microstructure of the diffusion layer formed during nitriding is shown. By metallurgical evaluation of many specimens, located at different positions in the furnace, the uniformity of the process is demonstrated. Results of several rig tests show the superiority of the nitrided bearings but also confirm the importance of close control of the nitriding process. Plasma carburizing processes were applied on bearing parts made from M50 NiL material. The mechanical and thermo chemical pre-treatment of the surface can be replaced by an initial sputtering which improves the reliability of the process. Hardness profiles, microstructure, and residual stress profiles of the carburized zone are comparable to those from gas carburizing.
Florida Skid Correlation Study of 1967 — Skid Testing with Trailers
Authors: Smith L. L. , Fuller S. L.
Published: September 2009

The Florida State Road Department, in cooperation with the Bureau of Public Roads, conducted a skid resistance correlation study at Dunnellon Airport in Marion County, Florida, during October and November, 1967 — Twenty different organizations participated in the testing.

The principal objective of this study was to evaluate the degree of standardization achieved by several skid test trailers constructed in accordance with the newly developed ASTM Test for Skid Resistance of Pavements Using a Two-Wheel Trai1er.

The experimental design for the trailer tests included zoning of the test pavements and randomized testing sequence to equalize the differences within a given surface and to reduce the effect of extraneous variables. The trailers were tested at 20, 40 and 60 MPH.

Results of the trailer tests indicate good reproducibiIity within the individual trailers and fair correlation between some of the trailers. However, a considerable interaction was evident between the trailers and the sites tested. Good reproducibility was obtained with trailers utilizing their self-watering systems even though large differences resulted between the trailers.

Texture measurements were also made on all surfaces using the Texas Text-Ur-Meter, the NASA Grease Test and the Bureau of Public Roads Outflow Meter. Satisfactory correlation between the coefficient of friction, speed gradients and texture measurements on the different surfaces was not achieved.
Pavement Dynamic Permeability Testing
Authors: Hutchinson J. W. , Kao T. Y. , Pendley L. C.
Published: September 2009

Skid resistance of wet pavement surfaces decreases with speed as hydrodynamic pressure builds up under vehicle tires. Porous pavements have previously been tested for their effectiveness in preventing this hydrodynamic reduction in tire-pavement friction. It is suggested that factors associated with fluid inertia and flow velocities encountered at the tire pavement interface are not accounted for in pavement static permeability tests. The difference between static and dynamic permeability is discussed and illustrated. A testing device of the type needed in predetermining pavement surface hydrodynamic drainage characteristics is described.
One System of Laboratory Testing to Appraise Serviceability of Oils in Transformers
Authors: Call R. G.
Published: September 2009

It is the practice of the American Gas and Electric Co. System periodically to conduct routine field tests on insulating oils in service for dielectric strength, neutralization value, color, power factor, and visible presence of sludge. Samples of those oils which are shown to have test values out of range of arbitrarily set limits are sent to the company's general laboratory for further examination.

Several years ago an elementary treatise was prepared to indicate to the maintenance engineers how the analyses are interpreted by the general laboratory. The following is the original article to which several additional examples have been added.
Performance of Inhibited Transformer Oils
Authors: von Fuchs George H.
Published: September 2009

The fiftieth anniversary of the invention of the parallel connection of transformers (1) and of the transformer with closed magnetic circuit (2) was celebrated in 1935 (3). The first commercial transformer built on these principles was placed in operation in Budapest, Hungary, on May 1, 1885, by three Hungarian engineers, Zipernowsky, Déri, and Bláthy, of Ganz & Co. A. G. Budapest. The following year, George Westinghouse, who correctly anticipated the possibilities of the alternating current to be realized by the transformer, commissioned William Stanley to build and operate the first American transformer at Great Barrington, Mass.
Introductory Summary
Authors: LaQue F L
Published: September 2009

The prime purpose of the Symposium on Evaluation Tests for Stainless Steels, held under the auspices of subcommittee IV of Committee A-10 on Iron-Chromium, Iron-Chromium-Nickel and Related Alloys was to permit a critical appraisal of some of the testing methods that were in regular use for evaluating certain corrosion-resistant characteristics of these alloys. Mr. H. L. Maxwell of the duPont Company served as cochairman of the Symposium with the author of this introductory summary. Special attention was focussed on two features: first, the significance of results of the laboratory evaluation tests with relation to practical experience under diverse service conditions and, second, the effects on behavior of the alloys in test and in use of lowering carbon contents to extremely low limits.
Present Knowledge of Low-Carbon 18-8
Authors: Gillett H W
Published: September 2009

The data reported in the literature, upon austenite stability, carbide precipitation, weldability, and corrosion resistance of low-carbon 18-8, are reviewed. Not only carbon but nitrogen as well must be impractically low to make 18-8 absolutely resistant to precipitation and grain boundary corrosion under any and all conditions of sensitization and corrosion.

This absolutely resistant condition is not required under most conditions of service. Commercially obtainable low-carbon and moderate nitrogen contents appear adequate to avoid sensitization upon cooling from welding under usual conditions, but evidence on this score is chiefly indirect.

Artificial, conventional methods for evaluating sensitization and corrosion-resistance are incompetent to appraise truly the material for a given actual service. Specifications calling for such tests may discard perfectly satisfactory material.
Corrosion Resistance and Mechanical Properties of Low Carbon Austenitic Stainless Steels
Authors: Buck D C , Heger J J , Phillips F J , Queneau B R
Published: September 2009

Sixty-nine 30-ton arc-furnace heats of low-carbon (0.030 per cent max.) 18-8,2 18-8 Cb, 18-8 Mo, and 18-8 Mo Cb were made and processed and their corrosion resistance and mechanical properties were investigated.

All of the steels exhibited satisfactory corrosion resistance in a copper sulfate-sulfuric acid test after being sensitized 2 hr. at 1250 F. (675 C.), and all of the 18-8 and 18-8 Cb heats tested had satisfactory corrosion resistance in boiling 65 per cent nitric acid after being heated for 2 hr. at 1000 F. (538 C.), 1100 F. (593 C.), 1200 F. (649 C.), 1250 F. (675 C.), 1500 F. (815 C.), or 1625 F. (885 C.).

After heating for 24 hr. at 1100 F. (593 C.), none of the heats of the four grades was satisfactory in boiling 65 per cent nitric acid, and none of the 18-8 Mo or 18-8 Mo Cb heats was satisfactory after sensitizing either 2 or 24 hr. at 1250 F. (675 C.).

The room temperature tensile and elevated temperature creep strengths of these low-carbon steels were slightly lower than those of higher carbon stainless steels, and the low-temperature impact properties of the low-carbon grades were satisfactory.

The results of corrosion tests of welded samples indicated that these low-carbon grades are satisfactory substitutes for the titanium and columbium-stabilized grades for applications, such as welding, that involve short heating times.
An Appraisal of Methods for Evaluating the Corrosion Resistance of Stainless Steels
Authors: Brown M H , DeLong W B , Myers W R
Published: September 2009

The vulnerability of as-welded or improperly heat-treated unstabilized austenitic stainless steels to intergranular corrosion in certain types of corrosive media is well known. Several laboratory testing methods have been developed which have been employed for detecting susceptibility to intergranular corrosion. The use of such evaluation procedures permits prediction in advance as to whether or not the material represented by the test specimen will fail through intergranular corrosion when in service environments capable of attacking susceptible material in this manner. The three principal methods currently employed are the boiling 65 per cent nitric acid test, the acidified copper sulfate solution test, and the nitric-hydrofluoric acid test.
Some Observations on Tests for Intergranular Susceptibility of 18-8 Mo Stainless Steels
Authors: Ebling H , Scheil M A
Published: September 2009

It is the intentions of the authors of this paper to focus attention on the tests used to determine the susceptibility to intergranular attack of stainless alloys. It is pointed out that a large number of variables exist in the present testing practice and that a standard practice should be inaugurated.

Using an acidified copper sulfate solution, a series of tests was made on type 316 heats to determine the effects of the stabilizing heat-treatment temperature (1550 and 1650 F.), stabilizing heat-treatment time and the cooling rate after the stabilizing heat treatment. It is shown that the cooling rate after stabilizing is important since it can effect sensitization of the alloy. Another series of tests was made to study the effects of sensitizing type 316 heats at 800 and 900 F. for 500 hr. after the stabilizing heat treatment. In these tests the regular type 316 alloys failed. However most of the low-carbon (0.03 per cent carbon maximum) type 316 heats sustained the sensitizing treatment at 800 and 900 F. for 500 hr. and exhibited immunity to intergranular attack.

Some tests were made on type 316 Cb2 in order that some comparison could be made with the low-carbon type 316.

In another series of tests, specimens of low-carbon type 316 and type 316 Cb were sensitized at 900 and 1020 F. for times up to 1000 hr.

The results of these tests show that the low-carbon type 316 alloy will sensitize at the low temperature if held for a sufficient length of time.
Comparison of Plant Corrosion Test Results on Austenitic Stainless Steels with Results of Huey and Strauss Tests
Authors: Teeple H O
Published: September 2009

The purpose of this paper is to present certain data on the resistance of some of the austenitic stainless steels to corrosion by media encountered in the chemical and process industries in relation to the performance of these same steels in both the Strauss and Huey tests.

The plant corrosion data obtained by exposing test specimens in many different plant corrosives are tabulated. Unwelded, as-welded, and welded and heat-treated specimens of type 304, type 347, and type 316 stainless steels were used. Also some tests were made wherein as-welded specimens of 0.03 per cent carbon maximum type 316 stainless steel were used.

Those same steels with certain heat treatments were subjected to Strauss and Huey tests in the laboratory with the results tabulated for reference with the corrosion-resisting behavior of these alloys as indicated by the tabulated plant corrosion data.

The specific compositions of the alloys used are also tabulated.
Results of some Plant Corrosion Tests of Welded Stainless Steels
Authors: Comstock G F
Published: September 2009

Corrosion tests of welded stainless steels were made in a number of chemical plants under regular operating conditions, and the results are compared with those obtained on the same steels tested by the standard boiling nitric acid procedure in the laboratory. The steel specimens included types 304, 321, and 347 sheets, welded with types 308, 321, and 347 electrodes, respectively, and tested both in the as-welded and stress-relieved conditions. The results show no correlation between the standard nitric acid test and the plant corrosion tests. In the latter there were no significant differences between the results from type 321 steel and those from type 347 steel.
Testing Multiple Specimens of Stainless Steels in a Modified Boiling Nitric Acid Test Apparatus
Authors: Long W B De
Published: September 2009

When it is desired to use the 65 per cent boiling nitric acid test as an evaluation method on a relatively large number of specimens, as in extensive research investigations or for routine inspection purposes, the amount of acid, apparatus, and laboratory space required frequently imposes a serious limitation on the number of tests that can be run in any reasonable time. This paper describes an apparatus in which a number of specimens can be exposed simultaneously, the use of which will result in appreciable savings in cost, acid, power, and laboratory space.
Sandwich Construction in the Elastic Range
Authors: March H. W.
Published: September 2009

A brief survey is made of a selected group of problems concerned with the elastic behavior of sandwich construction. These include the wrinkling of the facings under compressive load and the effect of shear deformation in the core on the deflection of uniformly loaded panels and on the buckling loads of panels subjected to edgewise compression or shear. In most of the investigations made at the Forest Products Laboratory in cooperation with the Air Force-Navy-Civil Subcommittee on Aircraft Design Criteria, the materials of the facings and core have been taken to be orthotropic. In this paper, in order to show the characteristic features of the behavior of sandwich construction in as simple form as possible, the formulas and curves are presented for constructions with isotropic facings and cores. These results are obtained directly from those for orthotropic materials. Reference is made to reports containing the corresponding more general results.
Paper Honeycomb as a Core for Structural Sandwich Construction
Authors: Kuenzi Edward W.
Published: September 2009

This paper summarizes the work done at the Forest Products Laboratory on different types of paper cores for use in aircraft and for house construction. Discussions are given of the manufacturing processes and, finally, the results of tests of core materials made from several papers containing various kinds and quantities of resin. Conclusions of a theoretical analysis are presented for predicting the compressive and shear strength of the aircraft-type paper core. Included in a discussion of core materials for housing are the results of tests of strength, thermal insulation, decay, and actual exposure to weather in a test unit.
Aluminum Honeycomb Sandwich Construction
Authors: Pajak T. P.
Published: September 2009

Aluminum honeycomb core material has outgrown the experimental stage and is used on production structures. The combination of aluminum facings, aluminum core, and a specially developed adhesive results in a structural material with desirable high strength and rigidity characteristics. The advantages of the aluminum honeycomb core material are uniform density, high specific strength, high shearing modulus, and resistance to environmental effects with constant strength under variable humidity and temperature conditions.

The strength of aluminum honeycomb core varies directly with the density of the core regardless of the various combinations of cell sizes and foil thicknesses. Standardization of cell size has resulted in volume production of core material and increased applications. Proper design and fabrication process control are required to achieve satisfactory results. An impressive variety of aircraft parts has been made of aluminum core and recent trends indicate that an increasing percentage of new airframe designs are utilizing aluminum honeycomb sandwich construction.
Some Developments in Structural Sandwich Building Panels Having Inorganic Cores
Authors: Rapp G. M.
Published: September 2009

The past decade has produced a new technology in sandwich constructions. The wartime needs for more effective use of materials and for higher strength-weight ratios directed first practical developments to military airframes. The plywood-balsa sandwich monocoque fuselage of the Mosquito Bomber is the classic example of this kind of pioneer application. Later in the war, drastic increases in air speeds and the concomitant requirement for aerodynamically smoother surfaces added interest. Finally, the sharp growth after 1945 in size of both commercial and military planes—which tended at first to outpace power developments—spurred the efforts to reduce airframe weight and intensified the work on sandwich materials. Thus, the aircraft industry has set the pattern for this new technology.
Fabrication Techniques for Structural Sandwich Constructions
Authors: Heebink Bruce G.
Published: September 2009

The concept of sandwich-type construction is daily being applied to an ever-increasing list of products that affect individual lives and, perhaps more important at present, the life of the nation.
On the Statistical Nature of Fatigue
Authors: Stulen Foster B.
Published: September 2009

Usually conventional fatigue tests are not designed to evaluate the character and dispersion of the fatigue life and endurance limit of a material, and as a result little is known about these important characteristics of materials. Several methods are proposed in this paper for the determination of these characteristics, and the results of tests utilizing these techniques as well as methods of graphically representing the data are given.

The elementary theory of extreme values as related to the size effect is given in this paper. Explanations of the understressing effect and of the variation in notch sensitivity between different materials are proposed.

Tests have also been conducted which show that the material near the surfaces and edges of the specimens appears to have lower endurance limits than the material in the interior of the specimens. This is in agreement with observations recently made by several other investigators.
Gaseous Insulation: Its Importance and Need for Test Methods
Authors: Manning M. L.
Published: September 2009

The range of equipment applications for gaseous dielectrics, including transformers, circuit breakers, airborne electronics, and radar, has been broadened because of the development of new electronegative gases. These gases have higher breakdown voltage characteristics than air or nitrogen. This permits the design of smaller and lighter equipment, while maintaining high standards of reliability and performance.

ASTM Committee D-27 on Electrical Insulating Liquids and Gases investigated the uses of the test cell reported by Manning in 1959 and two other cells for evaluating the dielectric strength of gases. Interlaboratory tests were conducted with these cells to establish a procedure and explore the probable precision.

This paper discusses many questions in the applications of test methods that would evaluate the use of gases as insulation in electrical equipment. A general review of the literature is given regarding test methods, electrode systems, and results of test.
The Use of Sulfur Hexafluoride as a Gaseous Dielectric
Authors: Brown J. A.
Published: September 2009

Sulfur hexafluoride, probably the first electronegative gas to warrant detailed study for use in electrical equipment, has many of the properties necessary for successful application. The chemical and physical properties of the gas and the effect of electrical arcing on these properties are discussed. The effect of contaminents such as air and moisture on these properties and also on the dielectric strength of the gas is presented. Many of these properties allow greater design latitude in electrical equipment. The electrical properties of the gas are also discussed, including behavior and dielectric properties in uniform and nonuniform fields and under corona and arcing conditions.
Studies on the Determination of Stable Oxides in Low-Alloy Steels Using a Combination of Chemical Separations
Authors: McKaveney J. P. , Raber W. J. , Vassilaros G. L. , Snook J. M.
Published: September 2009

A chemical process was developed for treating inclusions electrolytically separated from silicon or aluminum deoxidized steels, so that stable oxides were isolated for analysis. The electrolysis, a Klinger and Koch type modified by substituting ammonium salts for the sodium salts in the electrolyte, was followed by methanolic bromination of the centrifuged residue. Use of ammonium salts prevented sodium oxide chemisorption. If the residue contained carbides, nitrides, or sulfides, which are stable to bromine, the residue from the methanolic bromination was treated with a dilute mixture of nitric and hydrochloric acid. The residue from the acid treatment was then ignited and fused with Na2B4O7. The melt was leached with 10 per cent citric acid, which contained cobalt as an internal standard, and analyzed spectrochemically using a rotating disk solution technique. Proper specimen preparation is required. Argon atmosphere austenitizing is recommended rather than salt bath austenitizing as the latter can lead to considerable spinel formation. Data are presented for analyses of low-alloy steels ranging from 0.03 to 0.34 carbon, and up to 0.78 manganese, 0.20 silicon, and 0.05 aluminum as well as for medium alloy steels ranging from 0.20 to 0.40 carbon, and up to 0.75 manganese, 0.30 silicon, 1.75 nickel, 1.60 chromium, and 1.15 aluminum. A refractory type of aluminum nitride has been found in high-aluminum (1.15 aluminum) steels, which can lead to errors in alumina values. Contrary to a previous German report, this nitride is completely unaffected by metallurgical treatment of the specimen.
Isolation of Oxide Inclusions from Carbon Steels Using Bromine-Methyl Acetate
Authors: Raybeck R. M. , Pasztor L. C.
Published: September 2009

Oxides of aluminum, boron, chromium, calcium, iron, magnesium, manganese, and silicon in carbon steels can be isolated quantitatively by selectively dissolving the iron matrix, phosphides, carbides, and sulfides in a 1:3 mixture of anhydrous bromine-methyl acetate. The insoluble residue can then be filtered, ignited, and analyzed chemically or spectrochemically. Nitrides interefere in this determination, but the only one commonly encountered in plain carbon steels, aluminum nitride, can be eliminated by washing the residue on the filter paper with six per cent sodium carbonate (Na2CO3). Tests were run on the National Bureau of Standards 1040 series steel oxygen standards and on a rimmed steel specimen. Test results were in better agreement with certified vacuum fusion oxygen values and were more reproducible than those in which aqueous iodine or iodine-anhydrous methyl alcohol isolation procedures were used.
Interfacial Bonding in Graphite Fiber-Resin Composites
Authors: Goan J C , Prosen S P
Published: September 2009

Interlaminar shear strength values of 4000 psi, typical of graphite fiber-epoxy composites, are so low as to hinder more widespread use of such materials. Possible reasons for the apparently weak interfacial bonding between the fiber and the resin have been advanced, but none of these has been fully satisfactory. Attacks on the problem have been mostly empirical, but some have achieved considerable success. A study of composites made from graphite fibers in which silicon carbide whiskers were grown has demonstrated dramatic improvements in interlaminar shear strength and in transverse properties. Another approach has involved chemical activation of the fiber surface by oxidizing systems; this also has provided substantial improvement in composite shear strengths. A number of other surface treatment methods which are being investigated in various laboratories are reviewed here.
The Importance of Coatings in the Preparation of Al2O3 Filament/Metal-Matrix Composites
Authors: Noone M J , Feingold E , Sutton W H
Published: September 2009

The strength of composite materials formed by incorporating aligned brittle filamentary reinforcement into a metal matrix is dependent primarily on the strength of the filaments and on how effectively the matrix is able to transfer externally applied loads to the filaments. The interfacial zone between filament and matrix must satisfy several mechanical and chemical requirements if a useful composite is to be obtained: there must be (1) intimate contact between filament and matrix, (2) adequate bonding between filament and matrix, and (3) no chemical attack of the filament by the matrix which would be detrimental to the strength of the filament or to the bonding.

Al2O3 (sapphire) whiskers offer several advantages for use as reinforcement since they may be grown readily with high aspect ratio (l/d), have high strength and elastic modulus, have relatively low density, and are creep resistant at elevated temperature. However, Al2O3 is not wetted by many metals or alloys, and this causes difficulties in composite fabrication. One of the most practical solutions to this problem has been the application (by sputtering) of thin, metallic coatings to the filaments to enhance wetting and improve bonding to the matrix. In matrices designed for high-temperature applications, corrosive reactions at the filament surface become of critical importance in the development of a serviceable composite. Coatings have been used also to protect the surface of the filaments from degradation by matrix interactions.

This paper discusses the functions and types of coatings that have been used in the preparation of Al2O3 filament/metal-matrix composites and the importance of the coatings in promoting wetting and bonding and in preventing filament surface degradation during the composite fabrication process.
Role of the Interface in the Fracture of Fiber-Composite Materials
Authors: Cooper G A , Kelly A
Published: September 2009

The mechanical properties of a fiber-reinforced material are governed in part by the transfer of stress between fiber and matrix. This transfer occurs across the interface between the components, and the properties of this interface, therefore, will affect the properties of the composite. In this paper we consider some of the composite properties which are affected by the mechanical strength of the interface, both in tension and in shear.

The strength of the interface in tension governs the transverse strength of the composite. Properties dependent on this include the longitudinal compressive strength and the resistance of the material to the presence of notches. Theories of the transverse strength of a composite are examined and compared.

The shear strength of the interface affects primarily the load transfer length of the fiber-matrix system. It thus affects the strength of composites reinforced by discontinuous fibers, and the work of fracture under conditions of fiber pullout. It is also an important parameter in determining creep and fatigue properties and in determining notch resistance.
Fracture in Laminated Materials
Authors: Almond E A , Embury J D , Wright E S
Published: September 2009

The effects of weak interfaces in laminated materials are examined in terms of the triaxial tensions operative at a crack tip. Depending on the orientation of the interface relative to the crack, the triaxial tensions may cause distinct types of delamination during crack propagation. The crack may be arrested by delamination and may have to be re-initiated under conditions of uniaxial tension. Alternatively the crack may be divided by delamination into a series of parallel cracks travelling independently in several layers. If these layers are sufficiently thin, a triaxial stress system cannot be supported, and the cleavage mode of fracture may be suppressed. These two basic laminate geometries are discussed with reference to the mode of crack propagation in structural steels and high-strength composites with a variety of bond strengths.

The principles of laminar composites can be applied also to materials that are inherently brittle, for example, those which do not possess a sufficient number of independent slip systems to exhibit ductile behavior. Results of work on zinc aluminum laminates are used to illustrate this effect where potential stress concentrations in the hexagonal-close-packed layers can be relieved in the face-centered-cubic layers because of the abundance of slip systems. The authors describe techniques that have been used to examine the fracture properties of laminates, and finally examples of natural laminates are reviewed where fracture resistance is increased due to decohesion of the interphase interfaces in the fracture path.
Interfacial Stability of Silicon Carbide Coated Boron Filament Reinforced Metals
Authors: Basche M
Published: September 2009

The degradation of boron filament reinforced aluminum composites at temperatures over 400 C severely limits this material to relatively low-temperature applications. In order to extend the elevated temperature usefulness of such composites boron filament was coated with a diffusion and oxidation inhibiting coating of β-silicon carbide. The coating was applied by thermally decomposing a halogenated silane compound on the surface of previously prepared boron filaments. Electron microprobe analysis showed that the boron had diffused part way through the silicon carbide layer during the deposition process at approximately 1200 C. The ultimate tensile strengths of the coated fibers, however, were found to be approximately the same as the uncoated fibers, namely, 450,000 to 550,000 psi.

The stability of the silicon carbide coated filaments in air was studied to determine the extent of oxidation inhibition of the silicon carbide layer. Test specimens of uncoated and silicon carbide coated boron filament were taken from previously evaluated control fiber and heated at several temperatures up to 600 C, for various times up to 5000 h in air. The room-temperature tensile properties of these heat treated specimens indicate that silicon carbide coated boron fibers retain most of their strength after heating to 600 C in air for 5000 h, whereas uncoated boron fibers degrade after only 1 h at 500 C or at lower temperatures for longer periods of time. It appears that the degradation in tensile properties is controlled by the rate of boron diffusion through the silicon carbide layer and, therefore, is dependent on the thickness of the coating.

To study the interfacial stability of the coated filaments in metals, test specimens of coated and uncoated fibers were packed into aluminum alloy (2024) and titanium powders, heated at several temperatures up to 600 C for various times up to 1000 h, cooled, extracted with acid, and their ultimate tensile strength measured. The aluminum powder specimens were heated in air and the titanium specimens heated in argon to prevent oxidation of the titanium. The results of the tension tests indicate that uncoated boron fibers in contact with aluminum or titanium degrade at temperatures as low as 200 C with long time exposure and degradation is very rapid at temperatures over 400 C. Silicon carbide coated fibers on the other hand had approximately the same room-temperature strength after 1000 h at 400 C and retained a room-temperature tensile strength of over 300,000 psi after 1000 h at 600 C. The results of the metal matrix studies also indicate that the boron diffusion rate through the silicon carbide layer is the controlling step in the fiber degradation process.
Effect of Water on Glass Fiber-Resin Bonds
Authors: Eakins W J
Published: September 2009

The strength realized in a composite depends in part on its ability to arrest its nascent flaws and cracks. A theory for glass fiber-resin bonding is developed based on a restrained resin layer in the interphase region, an interfacial mechanism for resistance to crack penetration through the glass surface, and the segregation of resin-glass bonds of a strong, hydrolysis-resistant type to the alkali-free, silica “islands” on the glass surface.

In well-bonded glass fiber-resin composites, the initial effects of water are to stiffen the interphase resin layer and to create a pressure at the interface through the formation of water pockets on the glass surface. Stiffening the resin interphase layer weakens its ability to absorb the stress of a crack tip penetrating from the resin to the interface, thereby lowering composite strength resistance. The long term effect of the water layer is twofold. It creates a pressure tending to pry off the resin layer from the silica islands. It also furnishes a reservoir for the solution of aqueously soluble ions, that is, it acts to dissolve certain of the silicate areas and undermine the silica islands and thereby break the glass-resin bonds from the glass filament mass.
Interfacial Stability of Eutectic Composites
Authors: Salkind M J
Published: September 2009

Composites formed by unidirectional solidification of eutectic alloys usually exhibit a preferred crystallography of both phases and low-energy interfaces. Because of this, eutectic composites have been found to exhibit excellent microstructural stability and property retention after elevated temperature exposure. Some coarsening occurs at very high temperature without changing the basic aligned composite microstructure. The rate of coarsening is greater in finer microstructures and is related to the amount of interfacial area and the specific interfacial energy between phases.
Wetting, Adsorption, and Bonding at Glass Fiber-Coupling Agent-Resin Interfaces
Authors: Johannson O K , Stark F O , Vogel G E , Lacefield R M , Baney R H , Flaningam O L
Published: September 2009

The concepts of equilibrium free surface energies are presented and discussed in reference to the interfaces occurring between glass fibers, coupling agent, and resin matrix. Data from which the nature of the film of coupling agent on the fibers can be elucidated are presented. The conditions under which silanols and hydrolyzable silanes react with glass surfaces are given. Evidence is presented for chemical bonding between the hydrolyzate of γ-(methacryloxypropyl)trimethoxysilane on glass and a polyester.
Trends in High Temperature Structural Integrity Assessment
Authors: Webster George A.
Published: September 2009

Failure in components that may contain defects and that operate at elevated temperatures can occur by creep, fatigue, or fast fracture, or some combination of these processes. Frequently, these components include welds and repairs to welds. Codes and standards are available for assessing the structural integrity of these types of components. This paper addresses the main issues of concern in making safety assessments and reliable lifetime predictions for situations where creep processes dominate. Emphasis is placed on the creep component of cracking. Initially, models of crack initiation and growth are reviewed. The creep fracture mechanics parameter C* is used to make predictions. The influence of constraint on the mechanisms responsible for void nucleation and growth is considered and creep crack growth rate laws derived. Methods of calculating C* in components from the plastic fracture mechanics parameter J or, approximately, from stress intensity factor K and limit analysis using reference stress concepts are described. A procedure for making remaining life assessments for cracking into progressively deteriorating material is considered. Techniques for dealing with an initial transient phase, or incubation period, during which damage builds up at a crack tip are presented. An indication of the scatter to be expected in creep crack growth data, for use in sensitivity studies, is provided. The role of residual stress on the early stages of cracking and subsequent crack propagation is discussed.
European Code of Practice for Creep Crack Initiation and Growth Testing of Industrially Relevant Specimens
Authors: Dogan B. , Ceyhan U. , Nikbin K. M. , Petrovski B. , Dean D. W.
Published: September 2009

The integrity and residual life assessment of high temperature components require information obtained from the material's mechanical, uniaxial creep, creep crack initiation (CCI), and growth (CCG) properties. The information derived from these material tests needs to be validated and harmonized following a Code of Practice (CoP) so that variability in data as well as in the analysis can be optimized between different institutions. The paper describes a CoP for creep crack growth testing of industrially relevant specimens, which was developed within the framework of the partially European Commission (EC) funded project called “CRETE.” Novel aspects of the CoP include advice for testing different specimen geometries, which differ from the standard Compact Tension (C(T)) specimen proposed in the only available CCG testing standard ASTM E 1457. Recommendations for required number of tests, techniques for testing, treatment of test records, reduction of test data, and data analysis are presented. Associated specimen selection guidelines for industrial creep crack initiation and growth testing are also described. Validation tests carried out within the project on Type 316H steel at 550°C and a C-Mn steel at 400°C using relevant specimen geometries are also briefly described. The CoP contains recommended K and C* solutions, Yfunctions, and ɳ factors, which are used to determine values of the fracture parameters K and C* for the specimen geometries considered, and these are summarized in this paper. Information from these new tests, together with a review of previous creep crack growth tests on nonstandard geometries, have been used in recommending the best method of analysis for the creep crack initiation (CCI) and creep crack growth (CCG) data for a range of creep brittle to creep ductile materials.
Application of the Normalization Method to Dynamic Fracture Toughness Testing of Alloy 718
Authors: Graham Stephen M.
Published: September 2009

The fracture toughness and tensile properties of Alloy 718 were measured at quasi-static and dynamic loading rates for two different heat treatments and two product forms. Two different methods for conducting the dynamic tests were investigated; one involving interrupted tests and the other utilizing a single impact. The interrupted test method used multiple impacts with displacement limits to enable measurement of crack lengths at intermediate points. The normalization method was used to generate tearing resistance curves for the dynamic tests following the guidelines in ASTM Standard Test Method for measurement of Fracture Toughness (E 1820). The analysis pointed out the importance of obtaining a good measurement of load, displacement, and crack length at the point of maximum displacement (the anchor point). As the amount of ductile crack extension increased, the uncertainty in the plasticity function fit also increased. Methods to improve the fit were investigated, including the addition of anchor points from multiple tests, and use of a tangency point to estimate initiation. The resulting curves are compared to ascertain the variability obtained from nominally identical specimens, and to evaluate the effect of loading rate on the plasticity function. The normalization tearing resistance curves are compared with curves generated from the interrupted tests using compliance measurements during unloads to determine crack extension. Good agreement was obtained between the two methods of measuring tearing resistance, thereby validating the normalization analysis. The tests showed that multiple impacts drive down the tearing resistance, which may be significant in applications where a dynamic event causes load fluctuation.
In-Reactor Deformation of Zirconium Alloy Components
Authors: Holt R. A.
Published: September 2009

This paper briefly reviews work by the author identifying and describing in-reactor deformation mechanisms of materials and structures used in nuclear reactors, in particular, Zircaloy-2, Zircaloy-4, and Zr-2.5Nb, and the CANDU fuel channel (comprising Zr alloy pressure tubes, calandria tubes, and spacers). The discussion is set in the context of contemporary findings of other workers in the international community. The following themes are highlighted: The contributions of creep and growth to deformation; c-component dislocations and the fluence dependence of irradiation growth; anisotropy of irradiation growth; deformation equations and pressure tube-to-calandria tube contact in CANDU reactors; low temperature flux (damage rate) dependence of deformation rates. The first developments were reported in 1976 at the third conference in this series and there are ongoing developments in all areas. The linear low temperature flux dependence of creep and growth rates is yet to be satisfactorily explained.
Microstructure Evolution in Zr Alloys during Irradiation: Dose, Dose Rate, and Impurity Dependence
Authors: Griffiths M.
Published: September 2009

The performance of zirconium alloys in BWR, PWR, and PHWR nuclear reactors is dependent on the microstructure. Accordingly, the characterization of the microstructure is an integral part of any study conducted to develop models for in-reactor performance. Although the as-fabricated microstructure (texture, grain size, dislocation density, and phase or precipitate distribution) determines the basic physical properties of a given component, there are changes that occur during irradiation that can have a significant effect on these properties. Microstructures that illustrate specific features of the radiation damage that forms in Zr alloys will be illustrated and discussed in terms of the dose, dose rate, and impurity factors that are applicable.
Characterization of Zirconium Hydrides and Phase Field Approach to a Mesoscopic-Scale Modeling of Their Precipitation
Authors: Zhao Z. , Blat-Yrieix M. , Morniroli J. -P. , Legris A. , Thuinet L. , Kihn Y. , Ambard A. , Legras L.
Published: September 2009

Zirconium alloys are currently used in nuclear power plants where they are submitted to hydrogen pick-up. Hydrogen in solid solution or hydride precipitation can affect the behavior of zirconium alloys during service but also in long term storage and in accidental conditions. Numerical modeling at mesoscopic scale using a “phase field” approach has been launched to describe hydride precipitation and its consequences on the mechanical properties of zirconium alloys. To obtain realistic results, it should take into account an accurate kinetic, thermodynamic, and structural database in order to properly describe hydride nucleation, growth, and coalescence as well as hydride interaction with external stresses. Therefore, an accurate structural characterization was performed on Zircaloy-4 plates and it allowed us to identify a new zirconium hydride phase called ζ. The ζ phase has a trigonal symmetry and is fully coherent with hcp αZr. The consequences of this new zirconium hydride phase on hydride transformation process and stress-reorientation phenomenon are discussed. A first attempt to numerically model the precipitation of this new zirconium hydride phase has been undertaken using the phase field approach.
Influence of Structure Changes in E110 Alloy Claddings on Ductility Loss under LOCA Conditions
Authors: Nikulin S. A. , Rozhnov A. B. , Belov V. A. , Lyaschenko N. V. , Nikulina A. V. , Mal'gin A. G.
Published: September 2009

Microstructural changes are analyzed in specimens of E110 cladding tubes that have varying total impurity contents and differing residual ductility after interaction with steam at 1100 and 1200°C to 10–18 % ECR. It is shown that characteristics of the microstructure and the fracture behavior of tube specimens substantially depend on attendant impurities (C, Si, Ni, P, Cl, etc.). The total content of impurities available in the E110 alloy tubes varied from 35 to 140 ppm. With an increase in steam temperature from 1100 to 1200°C the influence of impurities on ductility of the tubes becomes weaker. The results of X-ray spectral examinations of niobium and oxygen distributions and microhardness measurements within the cladding wall after high temperature oxidation are presented. Methods of optical and electron microscopy were used to quantitatively analyze the interrelation between microstructural changes and fractures characteristics as a result of interaction with the high temperature steam environment. This work has suggested the likely reason for the losses of ductility in the studied specimens is the different contents of impurities that govern the types of microstructures formed as a result of the β →α transformation in the prior-β region of the specimens. The primary microstructural characteristics that govern the residual ductility of the E110 specimens is the morphology of the α phase platelets in the prior-β region (parallel plate or basket weave), and the quantity and brittleness of a second “dark” phase precipitate in the prior-β region.