bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of the Effect of Chemical Composition on the Irradiation Sensitivity of Reactor Vessel Weld Metal
Authors: Biemiller EC , Byrne ST
Published: March 2009

The effects of weld metal alloying constituents on the irradiation response of reactor vessel weld metal have been evaluated to determine why vessel welds tend to be more sensitive to irradiation damage than parent plate material. Weld data, collected from published reports, were compared on the basis of neutron radiation exposure; subsequent nil-ductility transition temperature (NDTT) shift (measured at the Charpy 30 ft∙lb energy fix); chemical composition; postweld heat treatment, and microstructure. The data comparison produced a correlation between NDTT shift with irradiation and a ratio of a weld's major alloying elements. The alloy ratio is designated A/B where the element content of the weld, by weight percent, is expressed: A/B = (Ni + Si)/(Mn + Cr + Mo). As the ratio increases for a weld, higher NDTT shifts with irradiation can be expected. Effects of postweld heat treatment and microstructure are also related to the NDTT shift-A/B correlation. The known effects of copper content on NDTT shift with irradiation have been found to be separate from the effects of the A/B ratio. Both copper and A/B effects, however, contribute to the total NDTT shift experienced by the weld with irradiation.
Structural Design of Precast Concrete Box Sections for Zero to Deep Earth Cover Conditions and Surface Wheel Loads
Authors: Heger FJ , Long KN
Published: March 2009

This paper presents the current level of development of computerized analysis and design of precast reinforced concrete box sections. The complete range of overburden depths are considered now. This paper contains a summary of the initial program, that is, for culverts with greater than 2 ft of overburden and recent modifications to the program to update its capabilities. Also presented is a detailed discussion of a recently developed extension of this program to accomplish analysis and design of shallow buried box sections where overburden cover is 2 ft or less.
Discussion and Application of CANDE Computer Program to Design of Reinforced Concrete Culverts
Authors: Katona MG
Published: March 2009

The purpose of this paper is to introduce CANDE, a new computer program for the structural design and analysis of pipe culverts, including not only reinforced concrete, but also corrugated steel, corrugated aluminum, and plastic pipe. CANDE operates either in a design or an analysis mode and offers a choice of three solution levels ranging from an elasticity solution to a general finite-element solution. The solution level concept allows the design engineer to choose a degree of rigor and cost commensurate with a particular project. Analytical modeling features include: incremental construction, nonlinear behavior of both soil and pipe, and nonlinear contact interfaces.
Evaluating Four Types of Soil-Structure Conduit Systems
Authors: Breitfuss TK
Published: March 2009

New types of concrete pipe conduit construction had been compared analytically with conventional trench-type installations and with construction with soil-cement bedding. The new conduits were of composite construction using in situ concrete bonded to various portions of thin precast cores. Considerable cost savings appeared to be obtainable with composite construction in narrow trenches.

Tests were conducted with the intention of verifying the assumptions. The removal, examination, and reevaluation of the test pipe and backfill are described, as are unexpected delayed responses in the test installation. New analyses are centered on composite and conventional conduits and on two types of concrete backfilled systems, comparing construction techniques and cost estimates. Means are proposed to obtain actual installations which duplicate theoretical conditions to obtain calculated savings.
A Study of Soil-Structure Interaction of Buried Concrete Pipe
Authors: Parmelee RA
Published: March 2009

A long-range research project was undertaken by the American Concrete Pipe Association to investigate the nature of the loading imposed on a concrete pipe when it is buried at a significant depth below the surface of the ground. The project consisted of an experimental and an analytical phase. The data from the experimental programs were used to assist in the development of a comprehensive finite-element program which can simulate the behavior of buried pipelines. This paper presents an overview of the entire project and describes in detail the structural aspects of the experimental phases of the research program.
Assessment of Soil Constitutive Models for Numerical Analysis of Buried Concrete Pipe Systems
Authors: Krizek RJ , Atmatzidis DK
Published: March 2009

Notwithstanding the limitations of analytical procedures, the greatest error in currently available techniques for the analysis and design of soil-pipe systems, as well as most other problems involving soil-structure interaction, probably lies in the specification of material properties, especially those for the soil surrounding the pipe. Based on the premise that a continuum approach, as implemented by the recent development of the finite-element method and high-speed digital computers, offers the best hope for achieving major advances in our knowledge of soil-pipe interaction phenomena, the stress-strain behavior of the soil surrounding the pipe is usually considered to be one of the most important factors that affects the response of the system. Although a large variety of models have been proposed in recent years to characterize the stress-strain behavior of soils, all have certain inherent advantages and disadvantages which depend to a large degree on their particular application. This study is directed toward assessing qualitatively and quantitatively the relative merits and limitations of several of these models within the context of their use in the numerical analysis of soil-pipe systems involving reinforced concrete pipe.
Analysis and Measurement of Soil Behavior Around Buried Concrete Pipe
Authors: Corotis RB , Krizek RJ
Published: March 2009

A piece-wise linear finite-element model of a buried concrete pipe and the surrounding soil is used to analyze the behavior of a soil-pipe system for both a trench and an embankment installation. Soil moduli for the various soils comprising each installation were determined from uniaxial strain tests, and they are considered to be functions of the major principal stress and the initial dry density. Values of Poisson's ratio were determined from triaxial tests with lateral strain measurements. Based on an extensive set of data from uniaxial strain tests on compacted and undisturbed soils, formulations are proposed to predict the constrained modulus from a knowledge of various soil index properties. Predicted soil stresses and deformations, interface stresses, and pipe deformations were compared to actual measured values from two field installations, and the results substantiate the adequacy of the approach.
Fractographic Method of Evaluation of the Cyclic Stress Amplitude in Fatigue Failure Analysis
Authors: Madeyski A , Albertin L
Published: March 2009

The first part of this paper describes laboratory work results substantiating the correlation of fatigue striation spacings with crack growth rate and with cyclic stress intensity amplitude, ΔK. The results were obtained by transmission electron microscope (TEM) replica fractography of a fracture mechanics type wedge-opening-loading (WOL) steel specimen previously tested in fatigue.

In the second part of this paper, an illustration of a practical application of this fractographic approach is described in detail. The laboratory test results from the first part are applied successfully to the service failure analysis of a crankshaft. Cyclic stresses calculated using a combined fractographic-fracture mechanics method were in good agreement with the values obtained from a theoretical and experimental stress analysis.
Fractographic Analysis of Gaseous Hydrogen Induced Cracking in 18Ni Maraging Steel
Authors: Gangloff RP , Wei RP
Published: March 2009

Fracture surfaces, produced by sustained load gaseous hydrogen assisted cracking of 18Ni maraging steel, were examined by scanning electron microscopy. Cracking developed along boundaries associated with the maraging steel microstructure. The specific crack path depended on test temperature and correlated with the influence of this variable on crack growth rates. At low temperatures, crack-growth proceeded predominantly along prior austenite grain boundaries. Increasing temperature produced a continuously increasing amount of transgranular quasicleavage associated with lath martensite boundaries. The proportions of quasicleavage fracture correlated with temperature induced reductions in the crack rate over those predicted from low temperature Arrhenius behavior. Both reduced hydrogen pressure and yield strength decreased the temperature for the onset of the transition to transgranular fracture but had no influence on the crack path. The lower strength steel fracture morphology contained an increased proportion of features typical of ductile rupture. The crack path through the microstructure was independent of the applied stress intensity factor, and hence crack growth rate, from very low values to those beyond the Stage I and Stage II transition for all temperature conditions. Comparison between fractographic observations and known sites for hydrogen segregation suggested that microstructural features play a significant role in the mechanism for gaseous hydrogen embrittlement.
Analysis of Fracture Morphology of Hydrogen-Assisted Cracking in Steel and Its Welds
Authors: Kikuta Y , Araki T , Kuroda T
Published: March 2009

The relationships between fracture morphology of hydrogen-assisted cracking, microstructure, and crystallographic orientation were investigated using the scanning electron microscope.

In the fracture morphology of hydrogen-assisted cracking, quasicleavage fracture, intergranular fracture, and dimple rupture were observed. In the quasicleavage fracture caused by hydrogen, subcracks often were observed along the boundary of martensite lath or ferrite lath, or both, and at the interface between the matrix and carbides.

The unit fracture facet for hydrogen-assisted cracking, therefore, was defined as the region between subcracks. The unit fracture facet for hydrogen-assisted cracking was smaller than that for cleavage fracture of martensite, upper bainite, and bainitic ferrite. Using the etch pit method the crystallographic orientation of the fracture morphology of hydrogen-assisted cracking was found to be the {110} plane.

The fracture morphologies of hydrogen-assisted cracking can be categorized as one of four types, each of which can be explained by the microscopic diffusion behavior of hydrogen.
Fracture of Ti-8Al-1Mo-1V Alloy Fan Blade by Stress Corrosion Cracking and Fatigue
Authors: Lee EU , Mahorter RG , Wacaser JD
Published: March 2009

Similar fractures occurred in two gas turbine engine fan blades made of Ti-8Al-1Mo-1V alloy. Their analyses and a supplementary test were performed with the aid of scanning electron microscope (SEM) and transmission electron microscope (TEM) fractography to identify the common mechanism(s).

The initial fracture surface of each fan blade exhibited an area of subcritical crack growth. The area in one fan blade contained three blue discolored zones along the crack initiation side, whereas that in the other fan blade was discolored to white-gray. Intergranular separation and transgranular cleavage were evident at the three discolored zones in one fan blade and near the crack initiation site in the other. Cleavage-like facets were predominant in the remaining area of subcritical crack growth. On some of those facets, striations were seen.

A hot salt stress corrosion cracking test of Ti-8Al-lMo-lV alloy plates resulted in discoloration, intergranular separation, and transgranular cleavage, similar to those observed in one fan blade.

The mechanism of initial crack growth is stress corrosion cracking at an elevated temperature in one fan blade and at ambient temperature in the other. The mechanism of subsequent subcritical crack growth is fatigue at ambient temperature in both fan blades.
Effect of the Cyclic Rate on Corrosion Fatigue and Fractography of Type 304 Stainless Steel in Boiling 42 Percent Magnesium-Chloride Solution
Authors: Hioki S , Muhai Y
Published: March 2009

Corrosion fatigue tests of Type 304 stainless steel were conducted at various cyclic rates between 0 and 104 rpm in boiling 42 percent magnesium-chloride (MgCI2) solution in rotating bending. As a result, the following conclusions were ob-tained: (a) the cyclic rate affects the failure life at the cyclic rates less than 103 rpm, (b) the rate of crack propagation, da/dn, is proportional to the maximum stress intensity factor, Kmax, that is, da/dn = C ∙ Kmaxm, where C and m depend on the cyclic rate, (c) the fracture surfaces at higher cyclic rates and static loading were mostly of the transgranular type, that is, step pattern and striation, but the intergranular type was observed partly on the fracture surfaces at lower cyclic rates. Intergranular type fracture surface was observed most frequently at 1 rpm.
Metallurgical Characterization of the Fracture of Aluminum Alloys
Authors: Bhandarkar MD , Lisagor WB
Published: March 2009

A systematic investigation was conducted to examine the fracture behavior of the structural aluminum alloys 2024, 6061, 7075, and 7178 (in selected heat treatments) tested under several controlled conditions. The investigation included both time independent (tensile, shear, and precracked notch-bend) fractures and time dependent (fatigue and stress corrosion) fractures. Specimens were obtained from both sheet and plate material and tested in longitudinal and transverse orientations. Strain rate effects on fracture morphology were examined in tension and shear tests. Fatigue fracture studies included an examination of the influence of minimum-to-maximum-load ratio on fracture morphology. Second-phase particles observed on fracture surfaces and metallographically prepared sections and corrosion products associated with stress corrosion fractures were analyzed chemically using scanning electron microscopy and energy-dispersive X-ray analysis. Fracture morphology was related to the microstructural features, the testing conditions, and the form of commercial product. The characteristic and distinguishing fracture features were reported for the different alloys. The information obtained from the systematic and controlled studies described here should prove useful in the analysis of service failures that often occur under complex service conditions.
Fractographic and Metallographic Morphology of Fatigue Initiation Sites
Authors: Eylon D , Kerr WR
Published: March 2009

An approach for analyzing fatigue failures by investigating the underlying microstructure of the fatigue crack origin sites is presented. A precision sectioning technique, developed by the authors, makes it possible to slice fatigue specimens through the crack initiation sites thus permitting concurrent fractographic and metallographic examination. This failure analysis was found useful in determining the reason for low fatigue lives of titanium alloy powder compacts; nonmetallic inclusions were found to be the prime source for early fatigue initiation. In superalloy powder compacts, residual porosity was related to the fatigue crack origins. In β-processed or cast titanium alloy products, the shear of large colonies of transformed α-platelets and fracture along grain boundary α were identified as the main initiation mechanisms. The identification and the elimination of the metallurgical crack initiating features has the potential for improving the fatigue life and reducing the scatter of the fatigue results, since the largest proportion of fatigue life is spent in crack initiation.
Examination of Fracture in a Pressure Vessel under Creep Conditions
Authors: Coleman MC
Published: March 2009

The relevance of creep crack growth data obtained from uniaxial laboratory experiments to the assessment of defects in plants is being investigated in a pressure vessel research program involving full size half-percent chromium-molybdenum-vanadium components containing machined defects. The first vessel in this program contained external circumferential notches in a large pipe and was tested at 565°C and 62.5 MN/m2 steam pressure, during which time crack growth and deformation in the vessel were monitored. Final failure occurred in an explosive manner after 1583 h. This paper concentrates on the fractographic and metallographic aspects of the failure analysis.

Examination of the vessel revealed three fracture modes across the failed ligament. Intergranular creep fracture occurred immediately ahead of the machined notch, followed by 45-deg ductile shear involving extensive deformation and finally low ductility shear fracture causing fast failure. These observations are interpreted primarily in terms of the mechanisms involved, with some consideration given to the mechanics of the fracture. The intergranular creep fracture mode is considered typical of that associated with plant failures and the significance of this in defect assessment is mentioned. The transfer to ductile shear is discussed in terms of the formation of void sheets, and net section yielding is related to uniaxial tensile data. The change in mode to fast shear fracture, attributed to gross overloading, produced an explosive failure.

The main implication of the failure analysis is that defects in this material can be assessed using mechanics describing intergranular creep fracture. Even so, it is demonstrated that in a nominally ductile situation final failure can be rapid and catastrophic.
Comparison of the Threshold Stress Intensities and Fracture Characteristics for Temper Embrittled and Deembrittled 2¼ Cr-1M0 Steel in a Hydrogen Charging Environment
Authors: Hicho GE , Gilmore CM
Published: March 2009

Fracture toughness tests and fractographic examinations were conducted on temper embrittled and deembrittled 2¼Cr-1Mo steel using double cantilever-beam specimens. The tests were conducted in an aqueous/acetic acid solution containing hydrogen sulfide (H2S). The threshold stress intensity of the temper embrittled specimen tested in the H2S environment was lower than that of the deembrittled specimens tested in a similar environment. For the purpose of comparing fracture appearances, temper embrittled and deembrittled specimens were fractured in air.

The fracture appearances of the temper embrittled and the deembrittled specimens tested in the H2S environment and the temper embrittled specimen fractured in air were predominantly intergranular. The fracture appearance of the deembrittled specimen fractured in air exhibited a transgranular ductile mode of failure. These results indicate that the embrittling effects due to temper embrittlement and to the H2S environment act cooperatively in reducing the threshold stress intensity of 2 ¼ Cr-1Mo steel.
Fractographic Analysis of Ceramics
Authors: Mecholsky JJ , Freiman SW , Rice RW
Published: March 2009

The development of fracture surface observations into a quantitative tool for analysis of brittle fracture is reviewed. The effect of temperature, strain rate, and residual stresses on the “mirror constant,” A, is discussed through recent experimental results, as well as new analysis of established literature. The current theories of mirror formation in glasses, glass ceramics, single crystals, and polycrystalline ceramics are compared to the results of a number of investigators. The relationship of the mirror constant to fracture toughness, that is, KIc, is discussed. Methods to incorporate the effects of grain size and internal stress on fracture are demonstrated. Finally, application of fracture surface analysis to scientific and applied problems are enumerated.
Fracture Toughness Test Methods for Abrasion-Resistant White Cast Irons Using Compact Specimens
Authors: Diesburg DE
Published: March 2009

The fracture toughness of abrasion-resistant white cast irons has been measured, using precracked compact specimens. Some procedures used for precracking the brittle cast irons were outside the ASTM Test for Plane-Strain Fracture Toughness of Metallic Materials (E 399-72) requirements but still gave valid results. The excellent reproducibility, combined with a range in toughness values of 17.5 to 28.5 ksi√in. (19.2 to 31.4 MN/m3/2) for abrasion-resistant white cast irons, provided the sensitivity necessary to distinguish differences in the toughness of white cast irons resulting from variations in composition or microstructure. The fracture toughness of three commonly used irons, 27Cr, 9Cr-6Ni, and 20Cr-2Mo-1Cu, was compared in the as-cast (and stress-relieved) condition. Heat treating the 20Cr-2Mo-1Cu iron substantially increased the hardness and reduced the fracture toughness slightly.
Development of Fast Fracture in a Low Alloy Steel
Authors: Radon JC , Pollock AA
Published: March 2009

Fracture mechanics, acoustic emission, and fractography were used to study the process of crack growth in 2-in. thick double cantilever beam specimens of a low-alloy steel over a wide temperature range. KIc values ranged from 33 ksi√in. at -200°C to 240 ksi√in. at +18°C. The acoustic emission rate rose steadily with load up to fast fracture. Changes in the emission amplitude distribution were observed shortly before fracture at one of the warmer temperatures. Emission during load holds was measured and emission waveforms were photographed. Fractography showed a small region of ductile tearing prior to fast fracture at warmer temperatures. A model of the interaction of ductile tearing and cleavage fracture is proposed. Ductile tearing is seen as a process taking time and strongly dependent on temperature. Cleavage is seen as a rapid process averted by ductile flow and tearing. Emissions are believed to be produced by plastic zone growth and by cleavage. The experimental facts can be consistently interpreted through this small set of assumptions.
Acoustic Emission from 4340 Steel During Stress Corrosion Cracking
Authors: Chaskelis HH , Cullen WH , Krafft JM
Published: March 2009

A commercially available system is employed to detect and count acoustic emissions emanating from the aqueous stress corrosion crack propagation in 4340 steel. Standard ASTM E 399 compact tension specimens with short notches, a/W=0.25 versus 0.50 standard, are prepared in four tempering temperatures: 204, 316, 427, and 538°C (400, 600, 800, and 1000°F). Crack length is monitored with a notch opening clip gage. Comparisons show the time rate of emission events to increase with stress intensity in rough correspondence to, but much more rapidly than, the crack velocity. Tempering back tends to suppress the count rate as a warning of fast fracture instability. Some similarity is observed between the areal rate of acoustic emission and factors which influence degree and intensity of plastic flow instability in the fracture process zone.
Subcritical Crack Growth Under Single and Multiple Periodic Overloads in Cold-Rolled Steel
Authors: Gardner FH , Stephens RI
Published: March 2009

Fatigue crack growth retardation, delayed retardation, initial acceleration, and optimum fatigue crack growth life under single, single periodic, and multiple periodic tensile overloads were investigated in cyclic strain softening AISI 1020 cold-rolled steel using compact type specimens. Macroscopic delayed crack growth retardation was observed following both single and multiple periodic overloads and was best observed at high overload ratios and larger crack lengths. Initial crack growth acceleration at the beginning of an overload interval was not quantitatively evident, however initial acceleration could have occurred before the crack extended to the least measurable scale division. Under constant load range testing, multiple periodic overloads of about 10 to 30 gave optimum or maximum fatigue life in most cases, however values of 1 gave maximum life in some cases. The largest increase in fatigue life was 453 percent. Maximum or optimum fatigue life obtained from multiple periodic overloads was always greater than that obtained from a single overload. In general, the results suggested maximum fatigue life can be obtained by applying a few multiple tensile overloads at high overload ratios only when accelerated crack growth begins following low load crack retardation.
Effect of Mean Stress Intensity on Fatigue Crack Growth in a 5456-H117 Aluminum Alloy
Authors: Chu HP
Published: March 2009

Fatigue crack growth data on a 5456-H117 aluminum alloy have been obtained by testing compact tension and contoured double cantilever beam specimens. The effect of tensile mean stress on crack growth rate is found to reach a maximum when stress ratio R ⩾ 0.25. The crack propagation laws are discussed and two new equations are developed. It is shown that the new equations can represent the entire range of fatigue crack growth rate versus applied stress intensity for different R values from fatigue threshold to unstable crack propagation.
Effects of R-Factor and Crack Closure on Fatigue Crack Growth for Aluminum and Titanium Alloys
Authors: Katcher M , Kaplan M
Published: March 2009

Following the crack closure studies of Elber, experiments were performed which appear to corroborate the link between the load required to open a crack at its tip and the shift in crack growth rate curves with stress ratio. Measurements of fatigue crack growth rates and closure loads were made on compact tension specimens for positive stress ratios of R=0.08 to R=0.8 and at rates between 10-7 and 10-5 in./cycle. An Rcut exists for 2219-T851 and recrystallization annealed Ti-6A1-4V wherein da/dN versus ΔK data does not shift to faster rates with increasing stress ratios above R=0.32 and R=0.35, respectively. The physical basis for the Rcut can be adequately explained in terms of crack tip closure. Fatigue S-N data also exhibited an Rcut when replotted as ΔS-N.
Proposed Fracture Mechanics Criteria to Select Mechanical Fasteners for Long Service Lives
Authors: Grandt AF , Gallagher JP
Published: March 2009

It is proposed that long service lives may be attained by selecting a fastener system which keeps the stress intensity range during service below the threshold stress intensity range. Using this criterion one may specify the maximum flaw size (from prior damage or initiated by fretting) which will be permanently retained by the residual stress field surrounding the fastener.

An analytical procedure which can be employed to obtain stress intensity factors for practical fastener crack configurations is demonstrated with results for open holes, cold-worked holes, interference fit fasteners, and pinloaded holes. In addition, threshold stress intensity factor data are taken from the literature and presented in a form convenient for use by the design engineer.
Wear Testing Objectives and Approaches
Authors: Peterson MB
Published: March 2009

Wear tests are performed for a variety of reasons: to gain an understanding of the wear process, to determine the effects of variables, to characterize materials, and to select materials for specific applications. Selection of test rigs and procedures is only difficult where simulation of an application is necessary. Under these circumstances it is necessary to consider the important variables which affect the wear process; primary consideration should be given to the surface temperature. Many types of test rigs are available to make such evaluations. The development of a standard wear test is considered to be urgently needed.
Testing for Adhesive Wear
Authors: Mecklenburg KR , Benzing RJ
Published: March 2009

This paper presents a technical definition of adhesive wear, comparing adhesive wear to abrasive, erosive, corrosive, fretting, and other forms of wear. The effects of various material factors and test parameters on adhesive wear are described. How to select materials and test conditions to produce the maximum adhesive wear are outlined. Test repeatability and accuracy are included.
Testing for Abrasive Wear
Authors: Borik F
Published: March 2009

The abrasive wear of machine components used in mining, mineral dressing, and earth moving machinery has long been recognized as a major problem in material design. This problem has been studied on a laboratory scale using four types of tests which simulate abrasion conditions ranging from severe gouging wear to low-stress erosion. These tests, namely, the jaw crusher test, the pin test, the rubber wheel abrasion test, and the impeller test, are described; the data obtained from the tests are interpreted in terms of the effects of those metallurgical variables that influence the abrasion resistance of an alloy. The results demonstrate the usefulness of the tests in assessing the magnitude of the metallurgical effects and the usefulness of the data for the design of better abrasion-resistant alloys.
Low Stress Abrasive and Adhesive Wear Testing
Authors: Tucker RC , Miller AE
Published: March 2009

Laboratory testing procedures used to evaluate materials for their resistance to adhesive wear and dry abrasion under low stress conditions are presented. The abrasion test described utilizes a gravity-fed silica sand stream conveyed between the specimen and a rotating rubber wheel to produce the wear. The adhesive wear test uses a block-on-ring machine, and wear and friction under dry or boundary lubrication are evaluated. The effects of test variables on the reproducibility of the results and the determination of the wear rate are discussed.
Wear Testing for Office and Data Processing Equipment
Authors: Bayer RG , Trivedi AK
Published: March 2009

The metallic wear situations frequently encountered in office and data processing equipment are reviewed. Motions producing the wear and the nature of the interfaces are discussed. The reasons for wear testing for these applications are identified and a test methodology is discussed. The more frequently encountered wear tests (for example, ball-plane, pin-on-disk, and block-ring tests) are evaluated in terms of this background. An overview is established based on these considerations.
Use of Fracture Mechanics Concepts in Testing of Film Adhesion
Authors: Bascom WD , Becher PF , Bitner JL , Murday JS
Published: March 2009

The constant-compliance and applied-moment double-cantilever beam tests for adhesive fracture energy have been adapted to the measurement of the adhesion of thick-film metallizations on alumina substrates. The thick-film tests involve beams soldered to metallization strips and measure the strain energy release rate, Gc The fracture results are compared with peel strengths from solder-wire peel tests of the same metallizations. Both the fracture and peel tests indicate failure in the thick films but near the film/alumina boundary. The constant-compliance and the peel test data exhibit a bimodal distribution. The magnitude of the fracture energies indicate that failure usually occurs in the glass phase of the film but that film adherence is greatly enhanced by interlocking between the metal and glass phases. This interlocking and thus the film adhesion are strongly dependent on firing time and temperature.
Techniques for Measuring Adhesive Energies in Metal/Ceramic Systems
Authors: Murr LE
Published: March 2009

The adhesive energies of nickel on thorium dioxide (ThO2), nickel/chromium (80/20) on ThO2, and iron/nickel/chromium (304 stainless steel) on aluminum oxide (Al2O3) were determined at temperatures ranging from roughly 200°C (360°F) below the melting point of the metallic component to approximately 50°C (90°F) above. The technique involves the measurement of the average surface free energy for the solid metals and liquid metal drops utilizing the zero-creep and sessiledrop shape concepts, respectively. Measurements of equilibrium energetics and associated geometries as well as the contact angles at metallic particles in contact with the ceramic substrates are described using the techniques of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Measurements of surface free energy of nickel/chromium and stainless steel drops equilibrated at temperatures below the melting point and utilizing the sessile-drop method are compared with those determined by the zero-creep method. The results of this investigation represent the first systematic study of the variation of adhesive energy of a metal/ceramic system with temperature, and the comparison of surface free energies determined from equilibrium particle shapes with zero-creep measurements of wires of the same material in the solid state.
Electromagnetic Tensile Adhesion Test Method
Authors: Krongelb S
Published: March 2009

A method is described for applying a known tensile stress to a thin-film structure without requiring any mechanical attachment to the film. The stress is developed by the interaction of an external magnetic field with an electric current through a suitably patterned specimen of the film to be evaluated. An apparatus for producing the required magnetic fields and electric currents is described, and procedures are given for preparing suitable test specimens using conventional electronic device fabrication technology. Results showing the use of this technique for measuring the adhesion of evaporated copper on thermally oxidized silicon are presented. The maximum stress which can be produced is limited by the available magnetic field, the fabrication of the test structure, and the heating effect of the current through this structure. These factors are discussed, and it is shown that useful stresses of at least 24 000 psi (165 600 kPa) are practical by the electromagnetic method.
Hardness and Adhesion of Filmed Structures as Determined by the Scratch Technique
Authors: Ahn J , Mittal KL , MacQueen RH
Published: March 2009

In the first part we discussed the evolution of the scratch technique for measuring adhesion of thin films and the associated difficulties involved in the interpretation of the results. Subsequently, results on scratch hardness and adhesion of multilayered structures as determined by a single point loaded scratch tester are presented. The controlled scratches produced by the tester were examined by a very sensitive surface profilemeter and by scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDX) for their scratch topography, modes of film deformation, and the mechanisms for film material removal. It is found that (a) the mechanism of film failure depends on whether the film is ductile or brittle; (b) there may not always be a clear channel formation, that is, complete removal of the film; and (c) scratch depth increases linearly with increasing load, which provides a means to determine scratch hardness for various layers.
Adhesion of Granular Thin Films
Authors: Faure R
Published: March 2009

With a view to measuring the adhesion of the microscopic metallic grains which constitute granular thin films, we have perfected a dynamic method. Very high accelerations (107 m/s2) are obtained by means of ultrasonic vibration amplifiers.

Investigation of the adhesion of granular silver films deposited on carbon provided very interesting results: the presence of a coalescence phenomenon shows that there are interactions between grains. The adhesion varies according to the size of the grains, and is very low (150 N/m2) compared with that of thick films (5.0 × 106 N/m2).

Finally, our measurement of the adhesion of thick films revealed that the break occurs in the silver very near the silver/carbon interface, and subsequent studies of the growth of silver/carbon show that the grains form on one or several monolayers of silver.
Adhesion Measurements on Thick-Film Conductors
Authors: Hitch TT
Published: March 2009

The paper briefly reviews the measurement of adhesion of conductor film materials and describes in particular the requirements of thick-film technology. The test methods used to measure thick-film adhesion strength, which have been previously described by other workers, are treated from a fundamental basis and are discussed with reference to the usefulness and practicability of the test both for research and for more routine purposes.

The second part of the paper reviews two thick-film adhesion tests and their use at RCA Laboratories over the past several years. The first test is the thermocompression bonded peel test, which has been used for the adhesion strength measurement of gold-and silver-based conductor films. This test was developed at RCA and has proved useful for films of a wide range of adhesion strengths.

The second test description reviews RCA Laboratories' use of the soldered-wire, peel test. It also treats our progress in eliminating subjectivity from this test by limiting the use of hand operations and by controlling time-temperature cycles required in the assembly of test specimens. For both these tests, more than one failure mode has been observed. The meanings ascribed both to the failure modes and to test data, which are taken when the modes occur, are treated.

Data illustrating the variation in adhesion strength with firing temperature and film thickness are shown for several ink types. These data are correlated with the composition of the inks by grouping the gold and silver inks into three bonding classifications—fritbonded, reactively bonded, and mixed-bonded.
Effect of Aspect Ratio on Tensile Bond Strength for Butt Joint of Internal Fracture—Theoretical and Experimental Analysis
Authors: Masuoka M , Nakao K
Published: March 2009

A general formula for the tensile bond strength of a butt joint in the case of internal fracture is given in terms of a simplified model constructed from measurable parameters. The stress distribution under large plastic deformation is obtained from the stress equilibrium on the horizontal symmetry plane of the adhesive film. The yield condition of Mises or Tresca was employed. The theoretical formula shows good agreement with experimental results. The contraction ratio of lateral contractive strain to longitudinal tensile strain at yielding of the adhesive is given as a function of the aspect ratio and is independent of the adhesive materials used. The empirical relation between the bond strength and the contraction ratio is expressed by a single curve and also is independent of the adhesive materials used. The theoretical and empirical equations obtained indicate that the bond strength for the butt joint of internal fracture depends on both the yield strength and the aspect ratio of the adhesive.
Notched C-Ring Test
Authors: Jankowsky EJ
Published: March 2009

High-strength steel notched C-rings have proven to be useful specimens for studying the effects of hydrogen embrittlement, as well as screening plating processes, cleaning, and paint removal materials for use on naval aircraft parts. The specimen and some of its uses are described.
Stressed O-Ring Test
Authors: Hyter WH
Published: March 2009

A stressed steel O-ring is used by the Douglas Aircraft Company to determine the hydrogen embrittling tendency of various processes. The use of the Douglas stress ring is described for testing processes, such as plating, cleaning, deoxidizing, and paint stripping. The method of selecting the hydrogen sensitivity of the steel used to make the ring is included.
Notched Test Strips
Authors: Jones WC
Published: March 2009

This paper describes a practical test that enables the metal finisher to detect changes in a standardized plating and baking procedure. Low-cost test strips are processed with the work through the complete cycle. Changes in their median time to fracture measures the degree of hydrogen embrittlement. A simple timing device is described that will automatically record the median breaking time for a set of five specimen. Median fracture times can be correlated to the hydrogen content of the strip.
An Ultrasensitive Hydrogen Detector
Authors: Das KB
Published: March 2009

An ultrasensitive hydrogen detector is described which has a detection sensitivity of a few parts per billion in the gas stream. The detector's performance, range, and accuracy were evaluated by analyzing titanium standards from the National Bureau of Standards containing known amounts of hydrogen at the following levels: 32 ± 2 ppm, 98 ± 5 ppm, 215 ± 6 ppm. The fractional random error in the mean value of these standards at 95 percent confidence level was found to be ±5.01 percent, ±1.67 percent, and ±1.08 percent, respectively. Preliminary results of the hydrogen analysis of cadmium plated steel specimens heat treated to 260 to 280 ksi strength level when compared with the notched tension testing (failure) data show that the safe limit for (total or bulk) hydrogen concentration as measured by this technique is about 1 ppm. Results on forged steel specimens heat treated to 170 to 195 ksi level indicate that here the embrittlement failure can occur at levels exceeding 2 to 2.5 ppm. Testing costs are much lower compared to notched tension tests, and the results are reliable. The objective of this paper is to expose the readers to a new hydrogen detection system and (among its other applications) its use for studying the hydrogen embrittlement problem in high-strength structural materials.
Neodymium Detection System
Authors: Toy SM
Published: March 2009

A test method for assessing hydrogen embrittlement of high-strength steel parts in the field is described. It is applicable to both ferrous and nonferrous metals which evolve hydrogen when heated. The assessment of the hydrogen embrittlement of steel or other metal parts is dependent on the determination of the local hydrogen content and the stresses required to fracture them and the determination of the hydrogen pick-up rate by the metal part in the environment which it is exposed to. Local hydrogen analysis in the field is based on the application of a flexible neodymium hydrogen detection tape.
Various Mechanical Tests Used to Determine the Susceptibility of Metals to High-Pressure Hydrogen
Authors: Harris JA , VanWanderham MC
Published: March 2009

The use of hydrogen as a rocket fuel has been successfully established; however, it has also been established that many metals are degraded in one or more of their properties by environmental gaseous hydrogen. The degree of degradation may range from slight to extreme, depending on the metal being analyzed and the type of test or tests used. Many important variables, such as environment, stress, temperature, and time must be considered in selecting the test to be used to determine the susceptibility to gaseous hydrogen. This report will discuss several different types of tests, such as: (1) tensile (smooth and notched), (2) strain-controlled, low-cycle fatigue, (3) high-cycle fatigue, (4) creep-rupture, and (5) fracture toughness, used to determine degradation of specific material properties and enable general observations in regard to the susceptibility of various materials to hydrogen degradation.
Disk Pressure Testing of Hydrogen Environment Embrittlement
Authors: Fidelle J-P , Bernardi R , Broudeur R , Roux C , Rapin M
Published: March 2009

The rapture appearances and pressures are compared for clamped disks, biaxially stressed to rupture under upward increasing pressures of helium or of an embrittling fluid such as gaseous hydrogen isotopes. Usually the downward surface is available for observation during the test in progress, but it can be exposed to a second embrittling medium. Factors studied include: (a) for the materials; chemistry (aluminum, cobalt, chromium, copper, iron, nickel, platinum, titanium, uranium, zirconium, etc., base), surface condition, thermomechanical processing, welding, etc., (b) for the testing conditions (- 196 to - 450°C), H2 pressure, purity, pressure increase rate, etc. Low-cycle fatigue and delayed failure tests can also be conducted and discontinuous cracking monitored by various techniques, especially permeation.

The disk pressure test (DPT) can be used for selection and quality control of bulk materials, protective coatings against hydrogen environment embrittlement (HEE), and their processing. Materials selection is made according to screening tests of increasing severity. The DPT shows evidence of other causes of embrittlement and their synergistic effects with HEE, which is quite important. Other advantages of DPT, such as sensitivity, versatility, rapidity, simplicity of operation and maintenance, safety, low cost of specimens and equipment, etc., are outlined and compared to other methods.
Closing Commentary—IHE-HEE: Are They the Same?
Authors: Fidelle J-P
Published: March 2009

I certainly agree that internal hydrogen embrittlement (IHE) and hydrogen environment embrittlement (HEE) are the same on an atomic scale, HEE being caused by hydrogen absorption. This has been demonstrated by a number of investigators in the case of steels [1–4], we have also seen this for pure nickel and titanium alloys [2]. I wish to point up that the relatively large hydrogen pickups (up to 2.5 ppm) observed after short tests at room temperature are not consistent with room temperature diffusivities and have to be explained by hydrogen being drawn inwards by dislocations [5] generated either at the surface (Fisher's sources) or near the surface (Sumino's sources). Disputation of this point [4] cannot be accepted because these authors failed to consider that the dragging efficiency of a dislocation is strain rate dependent. Direct evidence of the role of dislocations in the transport of hydrogen has been supplied [6].
The Influence of State of Stress on Low-Cycle Fatigue of Structural Materials. A Literature Survey and Interpretive Report
Authors: Krempl E
Published: March 2009

A literature survey was made on the influence of state of stress on the deformation and fracture behavior during low-cycle fatigue. Only the phenomenological aspects of fracture and deformation in the low-cycle range (< 105 cycles) are considered. Most of the materials investigated are shown or are assumed to have isotropic fatigue properties so that anisotropy was generally not considered.

For the isotropic case correlation formulas between uniaxial and multiaxial states of stress (strain) are stated in Appendix 1. Individual papers are reviewed to see which formula can best correlate uniaxial and multiaxial data. No single criterion was found which consistently correlates the data. Of all the correlation formulas the von Mises or distortion energy or octahedral shear stress criterion showed the highest degree of acceptance. However, some papers show no good correlation on the basis of this criterion and serious objections are voiced against this criterion on principal grounds. The von Mises criterion gives the same value for two states of stress which differ only by a hydrostatic pressure, it is pressure insensitive. Fatigue fracture is shown to be affected by the superposition of a hydrostatic pressure and therefore a pressure sensitive criterion should be used for correlation.

In future work a clear distinction of the influence of multiaxial states of stress (strain) on crack initiation and crack growth is necessary. Crack initiation and propagation studies are urgently needed. For isotropic fatigue properties pressure sensitive criteria should be incorporated into the constants of a generalized Coffin-Manson law. In the case of anisotropic fatigue properties, new correlation procedures have to be developed.