bluuebunny/crossref_metadata_2025 huggingface dataset:
The Initiation of Hot-Salt Stress Corrosion Cracking of Titanium Alloys
Authors: Rideout SP
Published: March 2009

The initial stages of hot-salt stress corrosion cracking of titanium alloys were studied using hot-stage microscopy and cinematography. An incubation period for cracking was observed, the duration of which depends on exposure temperature, salt composition, and alloy composition. For Ti-8Al-1Mo-1V exposed to sodium chloride (NaCl) the incubation period decreased from about 96 hr at 475 F, to 20 hr at 500 F, to 1½ hr at 650 F, to only 10 min at 850 F. This same alloy cracked severely in only 20 min at 475 F when exposed to tin chloride (SnCl2) indicating that the apparent “threshold temperature” for cracking is strongly influenced by chemical environment. At 650 F the incubation period for NaCl cracking of four alloys containing aluminum increased with decreasing aluminum content. Cracks appeared abruptly and propagated rapidly for a short distance, then apparently paused for additional corrosion-embrittlement to occur. Moisture was demonstrated to be a vital ingredient in hot-salt attack, and the presence of absorbed hydrogen in salt-corroded areas has been demonstrated using radiotracer tritium (H3). These results support the hypothesis that absorption of corrosion-produced hydrogen promotes embrittlement and crack initiation.
Effects of a 3.5 Per Cent Sodium Chloride Aqueous Saline Environment on the Fatigue Crack Propagation Characteristics of Titanium Alloys
Authors: Crooker TW , Lange EA
Published: March 2009

Fatigue crack propagation studies were conducted on Ti-6Al-4V, Ti-7Al-2Cb-1Ta, Ti-6Al-6V-2Sn-1Cu-0.5Fe, Ti-6Al-3V-1Mo, and Ti-7Al-2.5Mo alloys. These materials possess yield strengths in excess of 100 ksi, combined with favorable levels of fracture toughness, and they are currently under evaluation for application in large welded structures. Where an application involves repetitive loading, a knowledge of fatigue crack propagation characteristics is required for failure-safe design against fracture. Fabrication and nondestructive testing procedures cannot guarantee that crack-like defects which can grow to a critical size will not be present in plate-thickness sections containing welded joints. In addition, the role of an aggressive environment, such as salt water, in this failure mechanism is of the utmost importance. This paper reports on fatigue crack propagation data taken in both ambient room air and 3.5 per cent salt water environments. Surface-notched plate bend specimens were cycled in full-reverse (tension-to-compression) sinusoidal loading. The fatigue crack was observed optically, and the crack growth rate is described as an empirical power-law function of the total (elastic plus plastic) strain range. Fatigue crack growth rate relationships are first developed in an air environment and then employed as baselines for establishing the effect of the salt water environment. Comparisons are made among the fatigue crack propagation characteristics of the several titanium alloys described in this paper and among a broad spectrum of high-strength structural alloys, both ferrous and nonferrous, previously studied.
Laboratory Simulation of Seismic Activity in Saturated Sands
Authors: Schroeder WL , Schuster RL
Published: March 2009

To achieve satisfactory control of significant variables governing the response of soils to earthquake or vibratory loading it is often necessary to conduct investigations under laboratory conditions. The authors have taken this approach in an attempt to devise a testing procedure and an apparatus which permit valid conclusions to be drawn concerning earthquake effects on saturated sands. Relationships are established through the use of elastic wave propagation theory which describe the effects of passage of an earthquake disturbance through a soil deposit. These relationships form the basis for the design of a test apparatus with which simulated seismic disturbances can be applied to small saturated sand samples. The disturbances are produced by employing a device which includes, among other components, a standard triaxial cell of proper piston-sample diameter ratio and a cell pressure changing mechanism. Recorded responses of the specimens are summarized to establish the effects of several important variables on the tendency of sand for liquefaction and on observed deformations. Among the factors considered are initial void ratio and relative density and initial stress conditions. It is shown that initial shearing stresses are significant in their effect on pore pressure responses. The results are compared with those of other investigators and with observations of naturally occurring phenomena to evaluate the validity of the tests.
Nonlinear Dynamic Response of Soft Clay
Authors: Krizek RJ , Franklin AG
Published: March 2009

A series of approximately 40 controlled-deformation, torsional shear tests in sinusoidal oscillation was performed on a Georgia Kaolin clay at moisture contents ranging from slightly below to considerably above the liquid limit. The tests were done with a rotational viscometer using a cone-and-plate sample holder to provide reasonable homogeneity of strains and stresses. The results are expressed in terms of complex viscoelastic response parameters, and some aspects of the limitations and usefulness of viscoelastic relations to describe soil response are examined by (a) study of the strain dependence of the response parameters and (b) comparison of energy dissipation as calculated by viscoelastic relations with that measured directly from hysteresis loops.

The magnitude of the complex modulus was found to vary exponentially with the moisture content and to vary as the -1.3 power of the strain amplitude. The phase lag between stress and strain had no discernible dependence on the moisture content for moisture contents above the liquid limit, but was found to vary as the 0.4 power of the strain amplitude. Despite the marked nonlinearity of the material, the calculation of energy dissipation according to viscoelastic relations agrees comparatively well with the observed data.
Soil Studies for Seismic Design of San Francisco Transbay Tube
Authors: Aisiks EG , Tarshansky IW
Published: March 2009

The Transbay Tube, currently under construction, is a 3.6 mile sunken tube railroad tunnel under San Francisco Bay between San Francisco and Oakland. The Tube traverses a stratum of nonuniform silty clay with pockets of sand, shell, and organic matter, known locally as San Francisco Bay Mud.

Earthquake resistant design requirements involved investigation of dynamic soil properties in order to: (1) evaluate potential loss of soil shear strength during an earthquake and (2) determine deformations and loads imposed on the Tube by ground deformations during earthquake.

The investigation included an underwater field seismic survey, installation of an earthquake sensing and recording system in the Bay sediments, and dynamic testing of undisturbed soil samples. The dynamic tests were triaxial compression tests under alternating strains and simple shear tests under confining pressure with alternating strains. Soil properties used in analysis were derived from experimental stress-strain curves of a hysteretic type and consisted of shear moduli and viscous damping coefficients. The soil properties established in this manner were used to estimate free-field responses and soil-structure interaction.

It was concluded that in these soils significant loss of strength will not occur under earthquake strains and durations. Stresses imposed on the Tube by ground deformation are not of significant magnitude. Differential movements between the Tube and the ventilation buildings at either end required provision of a special universal sliding joint.
Stress-Strain Behavior of Clays in Dynamic Compression
Authors: Yong RN , Japp RD
Published: March 2009

Instability of earth structures and yielding and flow in soils due to earthquake loadings may be traced quite often to the problem of large displacements directly relatable to the resultant dynamic load condition occurring in the soil. This study examines the problem of large strain performance of clays under impulsive-type loadings, where the ultimate objective is to assess material behavior with a view to specification of pertinent and significant material parameters.

The formulation of a flow rule relying upon a base value at particular strains and strain-rates and additive strength performance is shown, and further study of the contribution to strength arising from increased strain-rates is examined. At the higher rates of sample straining, the significant increases in strength of the clay soils cannot be totally accounted for by linear extrapolations of rate effects and the contribution from coupled inertia terms. It is shown that these contributions, can be due to nonlinearity in rate effects at the higher end of the strain-rate spectrum, coupled with the formation of a quasi shock front. It appears that the rate of impulsive loading is higher than the ability of the specimen to deform plastically in the region adjacent to the loading front. Hence, a moving shock front is created and significant increases in strength are realized because of the change in material properties in the presence of this moving shock front.

In the problem of loading arising from impulsive mechanisms, instability in yield surfaces can be realized, and hence the problem of definition of a critical time-dependent yield surface as a function of strain-rate becomes apparent. This concept is also examined and discussed in this paper in relation to the previously described material characteristics.
Effect of Creep-Rupture Ductility and Hold Time on the 1000 F Strain-Fatigue Behavior of a 1Cr-1Mo-0.25V Steel
Authors: Krempl E , Walker CD
Published: March 2009

A single heat of wrought 1Cr-1Mo-0.25V steel was heat treated to a very low and to a higher level of creep-rupture ductility. Completely reversed, uniaxial strain-fatigue tests were run on the two materials at 1000 F with hold times of 1, 10, or 60 min used at the maximum tensile strain point of the cycle. The total strain range in the tests was either 0.5 or 1.0 percent. The cycles to failure decreased significantly as the hold time increased. The hold-time effect was more pronounced in the low than in the high creep-rupture ductility material, and was greater in the 0.5 percent than in the 1.0 percent total strain range tests. Log-log plots of cycles to failure versus hold time formed curves which tended to bend downward, showing an increased hold-time effect at the longer hold times. The fatigue cracks in both the low and the high creep-rupture ductility material tended to shift from transgranular to intergranular as the hold time increased, which indicates that creep-rupture damage occurred during the hold periods.
Resistance of Titanium-Base Alloys to Atmospheric Corrosion
Authors: Greenlee ML , Plock LF
Published: March 2009

Eight titanium alloys were included in the 1957 ASTM Committee G-1 (formerly B-3) program to determine the atmospheric corrosion behavior of nonferrous metals and alloys. Representative alloys of the alpha, alpha-beta, and beta type were evaluated. Based upon results of weight change measurements and tension tests, two- and seven-year exposures at four prominent ASTM test sites resulted in no significant corrosion. Slight staining was observed, but there was no appreciable weight change.
Computerized Long-Term Corrosion Data
Authors: Spatig DO , Ailor WH
Published: March 2009

A program has been devised which permits computer handling of all data derived from 20-year atmospheric and marine programs. This program makes feasible the routine handling of thousands of test specimens and calculations in an accurate but rapid method. Tape records from punched cards include exposure location, duration of test, mechanical properties, density, alloy type, and panel dimensions for both control and exposed specimens. These tape records are processed on an IBM 1410 computer to calculate the effects of aging and exposure. The final machine-printed report gives the corrosion rate in mdd (milligrams per square decimeter per day) and mpy (mils per year), along with per cent changes in tensile, yield, and elongation values due to corrosion for individual specimens, and also calculates average values of these properties by alloy and exposure site.
Atmospheric Corrosion of Copper Alloys
Authors: Thompson DH
Published: March 2009

Specimens of 18 copper metals were exposed outdoors in four locations for periods of two and seven years. Corrosion damage was assessed by measurement of loss in weight, loss in mechanical properties, and depth of pitting. Weight loss is shown to be the best measure of uniform corrosion. The mean corrosion rate was on the order of 0.05 mils per year (mpy) (1.3 mm/year). Greatest corrosion occurred at the industrial site followed by east coast marine, west coast marine, and the rural site. Nickel improved the atmospheric corrosion resistance of the copper alloys tested. Results are comparable to those obtained in other similar tests.
Atmospheric Exposure of Nonferrous Metals and Alloys—Aluminum: Seven-Year Data
Authors: McGeary FL , Summerson TJ , Ailor WH
Published: March 2009

This report describes the results of weathering tests on 34 wrought aluminum alloys exposed seven years at four ASTM sites in the United States. Also included, for comparison, are data on three additional aluminum alloys exposed six years at five sites in England.

The British industrial atmosphere exposures at Sheffield and London were found to produce the most corrosion, particularly on the sheltered sides of these panels which were exposed at an angle of 30 deg from the horizontal. The self-limiting corrosion characteristics were observed on weather surfaces at all test sites in both countries.

The test will be continued and again reported after twenty years, as was the case in a previous ASTM B-3 test (ASTM STP 175) on older aluminum alloys.
Copper and Copper Alloys
Authors: Mattsson E , Holm R
Published: March 2009

In 1958 exposure tests were started in Sweden to gain knowledge of the natural patination and the corrosion behavior of copper and copper alloys when used outdoors. The investigation covered 36 alloys in sheet or rod form: 5 coppers, 20 brasses, 5 phosphor bronzes, 1 silicon bronze, 1 aluminum bronze, 1 cadmium bronze, 2 nickel-silvers, and 1 free-cutting phosphor bronze. Specimens were exposed in rural, marine, and urban atmospheres. After two- and seven-years' exposure, specimens were examined.

During the first years of atmospheric exposure the copper and copper alloys acquired a dark surface coating consisting mainly of copper oxide (Cu2O). In urban and marine atmospheres, signs of green patina appeared on copper after about six to seven years; the basic copper salt causing the green color being sulfate in the urban, chloride and sulfate in the marine atmosphere. The average penetration as calculated from the weight loss during 7-years' exposure was: in rural atmosphere 0.2 to 0.6 μm per year, in marine atmosphere 0.6 to 1.1 μm per year, in urban atmosphere 0.9 to 2.2 μm per year. The corrosion rate decreased with the time of exposure. The losses in mechanical properties were in most cases of negligible importance.

The dezincification of brass was of significant degree only in β-brass and in certain (α + β)-brasses when exposed to the urban or the marine atmosphere. Dezincification was observed also in α-brass, even with as high copper content as 92 per cent, although the depth of attack was not very great. It should also be mentioned that arsenic was consistently effective as a dezincification inhibitor for α-brass only in the marine atmosphere. This indicates that the mechanism of dezincification is different in the presence and in the absence of chloride.

The tests described here are continued and further examinations will be carried out after 20 years of exposure.
Stress Intensity Factors for Internally Pressurized Thick-Wall Cylinders
Authors: Underwood JH
Published: March 2009

Selected stress intensity factor solutions from the literature are related to the problem of internally pressurized thick-wall cylinders with straight-front and curved-front cracks. The recent K solutions of Bowie and Freese and Rice and Levy are combined in an estimate of the K solution for a pressurized cylinder with a semielliptical crack originating along the inner wall. The estimate of K is compared with the available experimental and analytical K data for shallow cracks.

The estimated K solution is modified to account for various complex loadings in pressurized cylinders. Included are modifications to describe (1) lack of pressure on the crack surfaces in pressurized cylinders, (2) residual stress in the wall of pressurized cylinders, and (3) a combination of an unpressurized crack and residual stress in the wall. The effect of cyclic pressure loading on K is also discussed in relation to Throop's work on fatigue of pressurized cylinders.
Crack Shapes and Stress Intensity Factors for Edge-Cracked Specimens
Authors: Orange TW
Published: March 2009

A simple stress intensity factor expression is given for a deep edge crack in a plate in tension. The shapes of cracks opened by tension or bending are approximated by conic sections and the conic section coefficients related to plate geometry by very simple empirical equations. The magnitude of the crack displacement is a function of applied load, plate geometry, and the elastic constants of the plate material. The shape of a loaded crack in a semi-infinite plate is, approximately, a portion of an ellipse whose semimajor axis is about three times the crack length. As the crack length (relative to the plate width) increases, the crack shape becomes parabolic, then hyperbolic, the acuity of the hyperbola increasing with the relative crack length.
Extensive Study of Low Fatigue Crack Growth Rates in A533 and A508 Steels
Authors: Paris PC , Bucci RJ , Wessel ET , Clark WG , Mager TR
Published: March 2009

For two heats of ASTM A533 Grade B Class 1 pressure vessel steel and an ASTM A508 Class 2 forged steel, an extensive study of fatigue crack growth rate characteristics was conducted within the framework of linear elastic fracture mechanics. Experimental data obtained covered a wide variation in cyclic growth rates ranging from those associated with fatigue threshold (order of 10-9 in./cycle) up to rapid fracture. The bulk of experimental information obtained was at very low cracking rates, usually 10-6 in./cycle and below. Considered in the investigation were: (1) an evaluation of the effect of stress ratio, R = σmin/σmax, on verv slow rates of fatigue crack extension; (2) an evaluation of temperature (75 to 650 F) on very slow rates of fatigue cracking; (3) an examination of the combined effects of temperature and stress ratio and their influence on fatigue crack extension; (4) an evaluation of the effect of a distilled water environment on fatigue crack propagation rates; (5) an examination of the effects of specimen thickness; and (6) a comparison of results for two separate heats of the same alloy.
Fatigue Crack Propagation of D6ac Steel in Air and Distilled Water
Authors: Paris PC , Bucci RJ , Little CD
Published: March 2009

Fatigue crack propagation studies were conducted on a D6ac steel. The tests were performed in room air and distilled water environments all at room temperature. Fatigue crack propagation rates were enhanced in the water environment with results being strongly dependent upon test frequency, the lower test frequencies exhibiting the higher crack growth rates. A simple superposition technique, which qualitatively accounts for the observed frequency trends was examined.
Delay Effects in Fatigue Crack Propagation
Authors: von Euw EFJ , Hertzberg RW , Roberts R
Published: March 2009

The fatigue crack propagation behavior resulting from variations in load is examined for 2024-T3 aluminum alloy, from both a macroscopic and a fractographic point of view. A peak load is found to cause retardation of the crack growth rate, which becomes more pronounced as the percentage overload or baseline stress intensity level or both is increased. The delaying effect of the overload is observed to exist for a calculated crack length increment equivalent to the plastic zone size formed during the peak load. Multiple overloads and high-low block loading sequences are found to result in additional retardation. For a given ΔK and percentage overload it is noted that the greatest retardation occurs when λ equals 1 (λ = Kmax/ΔK).

It is observed that the macroscopic fracture surface appearance (that is, transition to plane stress) is a function of the crack growth rate. From fractographic examination it is found that the initiation of microvoid coalescence during fatigue occurs when plane stress conditions are achieved; this limits the extent of the stretch zone associated with an overload cycle. As a result, the stretch zone is found to be followed by striations in plane strain and by dimples under plane stress conditions. The size of the stretch band is observed to depend on the stress intensity level during the overload cycle.

The usefulness of closure concepts in aiding the understanding of fatigue crack propagation under uniform and nonuniform loading conditions is considered. Evidence is given to demonstrate the general applicability of closure concepts for analysis of macroscopic and fractographic fatigue crack propagation results.
Fatigue Crack Growth Analysis of Pressurized Water Reactor Vessels
Authors: Riccardella PC , Mager TR
Published: March 2009

The concepts of linear elastic fracture mechanics are applied to perform a fatigue evaluation of a pressurized water reactor vessel. The results of this work indicate that, for the types of flaws which could exist in a reactor vessel, fatigue crack growth due to normal operating conditions during the design life of the vessel is negligible. We have previously presented a simplified technique to approximate the potential for fatigue crack growth in the beltline region of a typical pressurized water reactor vessel during the forty-year design life of the vessel. The beltline region is the most critical from the standpoint of irradiation embrittlement of the material, and thus was the first to be considered. However, there are several areas in a reactor vessel which are more critically stressed during operation than the beltline region, and the crack growth in these regions must be considered before any general conclusions are drawn concerning the vessel.

In this paper, the following four regions of the reactor vessel are considered separately: (1) the closure head, (2) the nozzle shell course, (3) the beltline region, and (4) the lower head. A fatigue crack growth analysis is performed on the most critically stressed location in each region. Initial flaw sizes are assumed which are conservative upper bounds of the types of flaws which could exist in the hardware. Crack tip stress intensity factors are estimated using continuous surface flaw expressions, after linearizing the thermal and pressure stress distributions through the thickness of the vessel. An estimate of the degree of conservatism introduced by these two major approximations is included. Fatigue crack growth data from various sources were used. The sensitivity of the data to such variables as temperature, irradiation, and biaxiality is discussed.
Rayleigh Waves for Continuous Monitoring of a Propagating Crack Front
Authors: Buck O , Ho CL , Marcus HL , Thompson RB
Published: March 2009

A simple ultrasonic system which uses Rayleigh (surface) waves is briefly described. Applied to a part-through crack (PTC) specimen the wave is attenuated according to the crack depth. Functional relations of the crack depth and hence the stress intensity factor versus the number of load cycles N or the crack growth rate da/dN versus the cyclic stress intensity range ΔK are therfore easily obtained by continuously monitoring such a surface wave.

The system is sufficiently sensitive to actually show an “apparent” crack depth change during a single load cycle: at a low load level, the crack depth seems to be smaller than at high load level. This indicates that at low load levels internal compressive stresses at the crack tip resist crack opening. At high load levels, however, these internal stresses are overcome and the crack opens up to its actual size. This observation should be useful for interpretations of crack closure behaviors, crack retardation effects during spike loading, and other plasticity effects in the vicinity of the crack tip.
Fracture Mechanics Consideration of Hydrogen Sulfide Cracking in High Strength Steels
Authors: Bucci RJ , Paris PC , Loushin LL , Johnson HH
Published: March 2009

Hydrogen sulfide (H2S) stress corrosion cracking studies were conducted within the framework of fracture mechanics for several high strength steels (AISI 4340, 4140, HY-80, and HY-130). For all the steels and strength levels investigated (σys = 80 to 150 ksi), H2S stress corrosion cracking was found to exist. For each of the alloys investigated, a valid plane strain KIscc (which indicates the demarcation between detectable rates of crack extension, Δa/Δt ⩾ 10-5 in./min and those below these rates) was measured and found to depend significantly on yield stress with decreasing KIscc values reported for increasing yield stress.

A limited investigation of crack growth kinetics found crack growth rates to accelerate most rapidly from presharpened fatigue cracks when loaded to K levels just beyond the KIscc threshold. In several instances, especially with the highest strength alloys, stress corrosion crack velocities attained peak values before being “damped” to some steady state velocity at increased K levels. The crack velocity damping might in part be attributed to crack division or plasticity effects associated with increasing plastic zone size to thickness ratio at higher K levels.
Hearing
Authors: Silbiger HR
Published: March 2009

Sound is the perception by humans of vibrations in some physical medium, usually air. These physical vibrations of the air are evidenced by alternating rarefractions and compressions. Man's primary sense organ for the sound stimulus is the ear (Fig. 1). The external ear consists of the pinna or auricle. From this a canal, the auditory meatus, leads into the skull. This canal terminates at the eardrum, or tympanic membrane. A small muscle, the tensor tympani, regulates the tension of the tympanic membrane.
Texture
Authors: Kramer A
Published: March 2009

Texture deals with the sense of feel and consequently the term “Kinesthetic,” the muscle sense, has been used as a synonym. Another term closely related to the characteristic of texture is “tact,” that is, the sense of touch. The adjective tactile refers to something perceptible to touch and tactual something produced by the sensation of touch.
Methods for Measuring Degree of Subjective Response
Authors: Doehlert DH
Published: March 2009

Most data in engineering and science can be called objective data. That is, the data are obtained from physical instruments that measure characteristics of the phenomenon being observed. However, there are many instances for which it is necessary to rely upon the reactions of people rather than on the reactions of instruments. Such reactions are called subjective responses.
An Investigation of Fatigue Life Performance in Lap-Type Solder Joints
Authors: Coombs VD
Published: March 2009

The reliable operation of data processing equipment depends upon the mechanical integrity of many thousands of solder joints, particularly upon the resistance of the joints to strain-cycle fatigue fractures resulting from component temperature (and thermal expansion) excursions. In an attempt to develop life prediction techniques for solder joint fatigue fracture, two test programs were conducted—torsion fatigue tests of pure tin, pure lead, tin-lead eutectic solder, and tin-lead-indium solder, and shear-fatigue tests of lap-type solder joints employing tin-lead eutectic solder. Although solder joints are operated in an “elevated temperature” range (0 to 100 C) for these metals, no significant temperature effect was discovered in the fatigue life behavior of eutectic tin-lead solder. It was observed that increasing temperature enhanced the fatigue life of pure lead (for the cyclic strain rates employed). The fatigue behavior curves provided a design aid for conservative estimates of solder joint lives.
The Evaluation of Creep Damage in a Cr-Mo-V Steel
Authors: Goldhoff RM , Woodford DA
Published: March 2009

An attempt has been made to determine and quantify the accumulation of creep damage in Cr-Mo-V steel. Damage is defined in terms of post exposure rupture data and hardness measurements which are shown to be interrelated. Correlation between the post exposure rupture life and the initial exposure parameters are achieved by simple parametric techniques which then form the basis for graphical representation of damage accumulation as a function of exposure time, stress, and temperature.

The way in which these curves may be used to predict failure under nonsteady conditions of stress and temperature is described. In general the linear life fraction cumulative damage rule is unrealistic for this material, although under certain restricted conditions it may give a reasonable prediction of life. Apart from the measured nonlinearity with time of damage accumulation, the present results confirm that the common assumption of a unique failure criterion independent of the test conditions cannot be justified.
Verification of Structural Integrity of Pressure Vessels by Acoustic Emission and Periodic Proof Testing
Authors: Harris DO , Dunegan HL
Published: March 2009

The application of acoustic emission monitoring of periodic proof tests to the detection of structural degradation of pressure vessels is demonstrated. Test results of welded steel and aluminum vessels are presented which show that structural degradation and impending failure due to fatigue crack growth can be detected by this technique. Subcritical crack growth due to stress corrosion or hydrogen embrittlement could be detected with equal ease. Hence, emission monitoring of a periodic proof test can provide a powerful tool for the verification of the structural integrity of pressure vessels, as well as a wide variety of other structures.
Predictive Testing of Aircraft Structures
Authors: Rosenfeld MS
Published: March 2009

The historic development of airframe structural testing is reviewed and the role played by structural testing in the development of reliable airframe structures is discussed. The threefold safety-factor, safe-life, and fail-safe design approach provides reliable airframe structures when complemented by an effective laboratory test program that includes static, dynamic, and fatigue tests.

Using an iterative analytical and test approach, the operational strength limits of an airframe can be predicted fairly accurately from the static test results. However, predictions of the safe service life from fatigue test data alone leaves much to be desired because of the large variations in service usage. Nevertheless, the alarming cost of modifying aircraft in service has forced an almost complete acceptance of laboratory structural fatigue testing as an economical way of doing business.

The ability to predict the lives (actually the lives remaining) of individual aircraft depends upon the development of an instrument that would measure the fatigue damage actually incurred. Until that time, frequent and rigidly controlled periodic inspections must be performed on all aircraft, and an elaborate scheme of progressive preventive maintenance is mandatory.
Stress Corrosion Cracking of a High Strength Steel
Authors: Sheinker AA , Wood JD
Published: March 2009

Stress corrosion crack growth rates (dA/dT) as a function of stress intensity factor (K) were determined over a wide range of electrode potentials for AISI 4340 steel (200-ksi yield strength level) in deaerated 3.5 percent sodium chloride solution buffered to pH 3.8. Particular emphasis was placed on conducting the stress corrosion tests under well defined electrochemical and mechanical conditions. At intermediate K levels, dA/dT was essentially independent of K, suggesting that crack growth is limited by mass transport. Crack growth is apparently dominated by localized mechanical rupturing at high K levels where dA/dT increased rapidly with increasing K. Except at a very cathodic potential, dA/dT at intermediate K levels was also independent of potential, implying that the electrochemical conditions at the tip of the stress corrosion crack are not the same as those outside the crack. The tendency for the stress corrosion cracks to branch was found to be electrochemically, as well as mechanically, controlled.
Stress Corrosion Crack Protection from Coatings on High Strength H-11 Steel Aerospace Bolts
Authors: Taylor E
Published: March 2009

Stress corrosion cracking of high strength aerospace bolts is mostly limited to alloy steels, whose susceptibility to pitting corrosion is generally a secondary requirement compared to the outstanding tensile and fatigue properties needed. In order to provide environmental resistance for the bolt, a coating or plating is usually applied, which protects the underlying metal. In many cases, the coating chosen has proven to be inadequate. Therefore, a program was initiated to perfect a test method and gather reliable results from which predictable performance data could be obtained.

Many coatings were ultimately evaluated by a simple laboratory test method in which the coated bolt was statically stressed and exposed to a corrosive medium until failure occurred. The test is capable of evaluating a wide variety of coatings in periods from a few hundred to several thousand hours.
Corrosion Fatigue at High Frequencies and High Hydrostatic Pressures
Authors: Thiruvengadam A
Published: March 2009

The high frequency fatigue technique originated independently by Mason and Neppiras was used to study the influence of corrosive environment on the fatigue of SAE 1020 steel. With this technique, uniaxial tensile and compressive stresses are produced at the node of a “tuned” test specimen vibrating at its resonant frequency. Tests were conducted at two frequencies, namely 14 000 and 20 000 Hz. At these frequencies the reduction in fatigue strength and fatigue life in corrosive environment was comparable to the value obtained in the more familiar low frequency fatigue tests. The fatigue strength is reduced by 50 percent in 5 h at high frequency, whereas the same reduction in strength requires about 300 h at low frequency. Furthermore, the corrosion fatigue life is reduced two orders of magnitude by the superposition of a hydrostatic pressure of 1000 psig. The high frequency fatigue data in noncorrosive environment support the two distribution interpretation of Swanson; however, the value of the Weibull shape parameter increases considerably in the corrosive environment and tends to become unique. This change in probability distribution of fatigue life is brought about in less than 5 min of exposure to the environment. The mean life is reduced from 2 × 108 cycles to 5 × 106 cycles in such a short exposure time. Internal friction is affected significantly in a relatively short exposure to corrosion fatigue. The frequency at which the maximum damping is produced also changes after exposure to corrosion fatigue, These results emphasize the importance of the microstructural aspects in the mechanism of corrosion fatigue.
Resistance of High Strength Structural Steel to Environmental Stress Corrosion Cracking
Authors: Townsend HE
Published: March 2009

High strength structural steel, ASTM A 514/517, Type J, was evaluated for susceptibility to environmental stress corrosion cracking. Precracked cantilever beam specimens, prepared from 1-in. plate and loaded up to 90 percent of the air determined critical stress intensity, withstood 1000 h exposure to 3.5 w/o NaCl without failure. At loads greater than 90 percent of the load required to cause failure in air, fracture occurs without evidence of stress corrosion cracking. Additional specimens prepared from butt-welded plate and subjected to sustained loads beyond yielding in 4 point bending were alternately immersed in 3.5 w/o NaCl solution and dried in air for 10 000 h without cracking. These results indicate virtual immunity to environmental stress corrosion cracking for both base plate and weldments of this quenched and tempered steel.
Heat of Combustion and Oxygen Compatibility
Authors: Lowrie R
Published: March 2009

Calorimetry and its variations for difficultly combustible materials are reviewed. Relationships between heat of combustion and compatibility in oxygen atmospheres are discussed. A compilation of heat of combustion data is given for materials used in oxygen systems, and the application of these data in selecting materials is illustrated.
Techniques Employed by the NASA White Sands Test Facility to Ensure Oxygen System Component Safety
Authors: Stradling JS , Pippen DL , Frye GW
Published: March 2009

Methods of ascertaining the safety and suitability of a variety of oxygen system components are discussed. Additionally, qualification and batch control requirements for soft goods in oxygen systems are presented. Current oxygen system component qualification test activities in progress at White Sands Test Facility are described.
Application of Correlation Analysis to Acoustic Emission
Authors: Ono K , Stern R , Long M
Published: March 2009

Correlation analysis techniques have been used to characterize acoustic emission pulses from metals. A brief description of correlation functions and the method of their determination is presented. The time varying spectra of a magnesium sample have been obtained using the present techniques, and then compared with the more common methods of measuring acoustic emission. Other uses of correlation analysis in acoustic emission studies are included.
Use of Acoustic Emission for the Detection of Weld and Stress Corrosion Cracking
Authors: Hartbower CE , Reuter WG , Morais CF , Crimmins PP
Published: March 2009

This paper describes the utility of acoustic emission for the detection of weld and stress corrosion cracking. It includes a brief review of the history of acoustic emission, a selected bibliography, and the findings of two researches. It was found that a 100-ksi yield strength constructional alloy weldment produced bursts of acoustic emission for over 400 h after welding. This acoustic emission was correlated with the amount of cracking as determined by metallographic examination. With acoustic emission instrumentation, a convervative threshhold stress intensity for stress corrosion cracking was determined, based on crack propagation rather than on time to failure. A linear relationship is shown between acoustic emission count and stress intensity factor.
Detecting Acoustic Emission in Large Liquid Metal Cooled Fast Breeder Reactors
Authors: Anderson TT , Gavin AP , Karvinen JR , Price CC , Reimann KJ
Published: March 2009

Research at Argonne National Laboratory on acoustic emission and closely related areas is oriented to goals of the liquid metal cooled fast breeder reactor (LMFBR) program. These goals include acoustic monitoring of reactor core and power plant components, acoustic detection of boiling in liquid sodium, and acoustic emission testing of materials at elevated temperatures. For monitoring of sodium-filled components, several types of acoustic emission sensors are being developed for operation in sodium at temperatures to 650 C. These sensors contain the high temperature, radiation resistant, piezoelectric material, lithium niobate which is clamped or bonded to the sensor housing.

Reactor components have been monitored acoustically with both high temperature (620 C rating) accelerometers and with standard accelerometers. The acoustic surveillance tests have shown: (1) flowrate-dependent noise in a sodium-cooled nuclear reactor (EBR-II) and in a sodium component test facility (CCTL); (2) sodium-oxide binding within an EBR-II primary pump; and (3) a loose drain tube in the EBR-II primary sodium to secondary sodium intermediate heat exchanger.
New Method for the Statistical Evaluation of Constant Stress Amplitude Fatigue-Test Results
Authors: Bastenaire FA
Published: March 2009

Using the experimental and theoretical results of previous research work, the author presents a probabilistic description of constant stress amplitude fatigue-test results. This description includes the S-N curves (or equiprobability of fracture curves), P-S curves (or stress-response curves), P-N curves (cumulative distribution functions of fatigue endurances), and accounts for the occurrence of runouts.

A method of estimation of the model coefficients which uses the information provided by all the specimens tested (broken or unbroken) is also presented. The application of this method is demonstrated through five examples for each of which several hundred test results are available.
Application of the Monte Carlo Technique to Fatigue-Failure Analysis under Random Loading
Authors: Itagaki H , Shinozuka M
Published: March 2009

Analyzing the fatigue damage of a notched specimen subjected to a random-stress history of narrow-band characteristics, the crack propagation factor is treated as a homogeneous random process reflecting statistical variations of material property within the specimen. On the basis of the proposed statistical-mechanical model of fatigue failure, into which a crack propagation model and a fracture criterion are incorporated, statistical distribution of fatigue life is predicted with the aid of the Monte Carlo technique by digitally simulating the stress history and the crack propagation factor as random processes. The results indicate that the spacial randomness in material property can, and in fact should be considered in order to account for the larger scatter of fatigue life observed in the experiment performed under the conditions compatible with the assumptions used in the analysis.
Design of Modern Image Measurement Systems
Authors: Morton RRA
Published: March 2009

This paper is intended to provide practicing metallurgists with some understanding of the image measurement instrumentation available today. The history of image measurement is briefly traced through a discussion of the instruments which have been or are presently commercially available. Instruments are classified according to the mode of scanning employed and some of the design factors involved in an image scanning instrument are discussed. The various measurements and counts currently available are described and their applications are considered.
Color and Light
Authors: Hammond HK , Keane TJ
Published: March 2009

Man's ability to discriminate colors increases both his enjoyment and appreciation of the world around him. Because color is such a significant factor in the appearance of an object, it is an important characteristic of any paint. Appearance is one quality of a product that every customer can judge for himself. No matter how good the physical properties of a paint, if the color does not meet the expectation of the customer, he will think the finished product unsatisfactory. Color is often thought to be a property of the paint itself, and, to a degree, it is. Actually it is more complex than that for color of a paint depends on three things: (1) the spectral reflectance of the paint, (2) the spectral composition of the light in which the paint is viewed, and (3) the spectral sensitivity of the eye of the observer. For these reasons matching the color of a paint or other material requires considering all three and not merely the spectral characteristic of the material.
Gloss
Authors: Hammond HK
Published: March 2009

Gloss is often described as the attribute responsible for the shiny or lustrous appearance of an object. A more formal definition is given by the CIE [1].
Driers and Metallic Soaps
Authors: Sward GG
Published: March 2009

Metallic soaps are compounds of alkaline earth metals or heavy metals and monobasic carboxylic acids of 7 to 22 carbon atoms. It is usually convenient to include resinates (usually from rosin) and naphthenates in a discussion of metallic soaps. Their water insolubility differentiates metallic soaps from ordinary soaps. Their solubility or solvation in organic solvents accounts for their use in paints. Commercial metallic soaps are made and used in solid, paste, and liquid forms. The form depends on the metal and its amount, the nature of the organic acid, and the presence or absence of solvents or additives during manufacture. Metals of low atomic weight usually form soaps of high melting points. Long, straight chain, or saturated fatty acids form soaps of higher melting points than do short or branched chains, or unsaturated acids. Soaps made by precipitation are likely to be light fluffy powders. Soaps made by fusion are hard dense solids. Liquid and paste forms are solutions or suspensions in petroleum or other solvents.
Synthetic Resins
Authors: Swann MH
Published: March 2009

This chapter gives references and procedures for the identification and analysis of commercially important coating resins. Complete treatment is not attempted. Readily available procedures, such as ASTM methods, are referenced and discussed. Procedures for the analysis of blends and mixtures that may be encountered in finished coating materials are included so far as possible. Where muhiple methods are available for the same purpose, as in some qualitative applications, an effort is made to select the most reliable.
Plasticizers
Authors: Riley HE
Published: March 2009

Several thousand high boiling solvents that impart permanent flexibility to otherwise rigid plastics have been created in recent decades to supplement to relative few available in the twenties. The appearance of new types of plastics and their adaptation to new uses requiring flexibility has prompted this search. The utility of a plasticizer is judged by the performance characteristics of the resin or plastic to which it has been added. This indirect test on the plasticizer implies that its properties are uniform. In fact, producers place great emphasis on quality, and the properties determined and methods used are of equal importance to his customer.
Density, Specific Gravity, and Bulking Values
Authors: Sward GG
Published: March 2009

Technologists of the paint industry fully appreciate the role played by the relationship between weight and volume of materials. Whether or not a paint ingredient or the paint itself is traded on a weight basis, the product is used largely on a volume basis. Even putty and caulking compounds occupy space, and conversion to a volume basis is made, perhaps unconsciously, in many cases.
Viscosity and Consistency
Authors: McGuian JP
Published: March 2009

Viscosity or consistency is an extremely significant property that is included routinely in specifications and is an important factor in the purchase and use of not only formulated paint products but also the countless raw materials used in the industry.
Particle Size Measurement
Authors: Sward GG , Jacobsen AE
Published: March 2009

In coatings and similar prcxiucts, the criteria for best performance of particulate ingredients—inorganic, organic, extender, and metallic flake pigments, and the dispersed phase of latexes—depends in large measure on the size and shape of the particles composing the particulate materials. Examples of these relationships appear in other parts of this book. The importance of particle size measurement including the amount of coarse oversize particles is evident. In this book it is practical to cover in detail the many procedures employed in the measurements, but the brief descriptions are supported by references to the literature. Also cited are textbooks for the reader who desires to acquaint himself with general theory [1–8]. The recent book by Allen [8] can be particularly helpful.