bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of Impact Stresses in Composite Plates
Authors: Kubo JT , Nelson RB 
Published: March 2009

In this paper an analytical study is presented of the two-dimensional response of an elastic laminated composite plate to an impact load applied to its surface. The surface load is arbitrarily distributed along the extent of the plate surface and varies sharply in time to model the impact loading. Each layer of the laminated plate is of arbitrary (constant) thickness with specified density and orthotropic material properties, with the material axes coincident with the plate axes.
The physical behavior of the plate is exactly represented along the extent of plate in the form of a Fourier series, and its behavior in the thickness direction is modeled by a sufficiently large number of generalized coordinates to capture quantitatively the propagation and dispersion of stress waves due to the surface impact, with emphasis directed to calculating stresses on laminate interfaces. This method of analysis results in a sequence of algebraic eigenvalue problems, the solutions of which are used to decouple the equations of motion into a large number of simple differential equations in time. This procedure is quite straightforward and computationally effective and may be used to study the impact problem for an arbitrarily laminated plate.
An isotropic plate with a specified surface impact loading is presented to indicate both the accuracy of the results obtained and the time domain for which they are valid. A two-layer boron-epoxy plate is examined in detail to indicate the quantity and quality of information which may be generated by this method for composite material structures in impact environments. The results for this problem also reveal potentially harmful effects which develop during impact.
Sufficient information is presented to permit an experimental verification of the results obtained, for regions of time where the magnitudes of the impact stresses are most critical to material integrity.
Fatigue Crack Propagation Behavior of the Ni-Ni3 Cb Eutectic Composite
Authors: Mills WJ , Hertzberg RW 
Published: March 2009

Room temperature four-point-bending fatigue studies of the unidirectionally solidified Ni-Ni3Cb eutectic composite have been conducted to better understand fatigue behavior in composite materials. Fatigue crack propagation (FCP) data for this eutectic composite alloy revealed a power relationship between the stress intensity factor range and the crack growth rate from 10-7 to 10-4 in./ cycle. This application of fracture mechanics concepts to FCP data represents the first such reported information of its kind for eutectic composites. Fatigue behavior of this eutectic alloy was found to be sensitive to solidification parameters, thermal history, and the mean stress intensity level.
Metallographic and electron fractographic examination of the fatigue fracture revealed the FCP mechanism to be a function of the prevailing stress intensity factor at the crack tip with a fatigue fracture mechanism transition occurring between 5 × 10-6 and 1.5 × 10-5 in./cycle. At low growth rates, the Ni(γ) phase exhibited faceting indicative of Stage I propagation along active slip planes, while above 5 × 10-5 in./cycle, the γ fracture surface was characterized by the presence of fatigue striations which laid parallel to the Ni-Ni3Cb interface. At both high and low growth rates, the fatigue response of the Ni-Ni3Cb composite was controlled by the γ lamellae.
Fatigue Crack Growth in Dual Hardness Steel Armor
Authors: Kula EB , Anctil AA , Johnson HH 
Published: March 2009

Crack growth tests under cyclic loading conditions were conducted on samples from different lots of dual hardness steel (DHS) armor. The results showed that the growth rate increased with stress level, and the cracks grew at a different rate in the frontal and backup layers of the armor. This difference in growth rate became progressively greater with increases in the stress level. The crack growth rate also increased with reductions in the frequency of loading and temperature increases over the range of -60 to +200°F.
Attempts are made to explain the crack growth behavior of the composite in terms of the behavior of each component. The growth rates in the composite are related to the stress intensity factor, ΔK, calculated from the surface crack length assuming that there was no interaction between the layers and the displacement in each layer was the same on the crack line. The latter procedure yielded better results and suggested that the interface plays an important role in retarding crack growth in the frontal layer of DHS.
Monitoring of Wastewater Discharges Aboard Navy Ships
Authors: Talts A , van Hees W 
Published: March 2009

The U.S. Navy has taken an early initiative in bringing about the development of shipboard wastewater treatment systems. Liquid wastes generated aboard Navy ships originate from man related activities (sanitary and “hotel” wastes) as well as industrial activities associated with the particular mission of any ship.
This paper discusses the problems encountered in the characterization of aqueous waste streams, other than bilge and ballast waters, that are generated on Navy ships. Monitoring methodology is discussed in terms of quantitative assessment of potential waste sources, the selection of flow monitoring methods, sampling procedures, shipboard constraints on analytical methods, and data collection. Waste flow profiles have been determined for major shipboard contributors. A pragmatic approach of hardware applications and survey procedures was employed under unique circumstances. These are discussed in light of the practical application of such acquired information in the development of the most practicable wastewater management systems for Navy ships.
Continuous Liquid-Liquid Extraction of Organic Pesticides from Aqueous Solutions
Authors: Wu C , Suffet IH 
Published: March 2009

Liquid-liquid extraction (LLE) is considered by most residue analysts to be the best method for quantitative recovery of organic pesticides from aqueous solutions. Continuous liquid-liquid extraction is a logical extension of the process. This paper reviews the LLE process especially the alternative of continuous LLE for the isolation of organic pesticides from aqueous solutions. Trends and user problems are noted.
A continuous liquid-liquid extraction apparatus with capabilities for continuous solvent recycling and sample enrichment is described. The principal parts of this design are a helix Teflon coil mixing chamber, a column phase-separator, and an evaporative concentrator.
Initial experiments were made to evaluate the design. Extraction efficiencies ranging from 85 to 93 percent were obtained for five organophosphate pesticides extracted from water with benzene under the optimized conditions of coil length, helix diameter, flow rate, and water to solvent ratio.
The apparatus is simple and economic to build. It is contamination-free as all parts in contact with water and solvent are made either of Teflon or glass. Complete automation of this apparatus is possible by adding liquid-level controllers, solenoid valves, and electronic relay systems.
A Model for Fatigue Crack Growth Delay Under Two-Level Block Loads
Authors: Adetifa OA , Gowda CVB , Topper TH 
Published: March 2009

After reviewing previous attempts to quantify delay, a composite stress intensity parameter, (Kℓmax/Khmax) ∙ ΔKℓ; proposed to correlate the number of delay cycles in simple two-level variable-load amplitude tests for various combinations of stress levels. Its application is restricted in the present investigation to room temperature tests in an air environment. Delay (cycles) is defined herein as the period of apparent zero crack growth after the overload, and the stress intensity factors, Kℓmax and Khmax refer to the stress intensities accompanying the lower and higher load levels, respectively. It is hypothesized on the basis of experimental observations that material under different two-level block loading sequences, but having equal values of the parameter, will experience the same delay.
Good correlations for data on aluminum alloys, titanium alloys, and carbon steel taken from the work of several investigators are obtained using the parameter. An empirical model relating the delay to a power function of the parameter is suggested. Limitations of the model are pointed out and discussed. The engineering significances of the parameter with respect to the determination of crack propagation life and crack arrest conditions are discussed.
Effect of Spectrum Type on Fatigue Crack Growth Life
Authors: Reiman JA , Landy MA , Kaplan MP 
Published: March 2009

An ever-present problem in airplane design has been the accurate prediction of fatigue crack growth rate in new (never flown) aircraft. This problem has become even more critical in light of the new U. S. Air Force Damage Tolerance Requirements (MIL-A-83444). Briefly, the purpose of this specification is to protect flight structures from potentially deleterious defects which can be introduced into the structure during processing, manufacturing, etc. One of the most important things to consider when performing a damage tolerance analysis is the type of fatigue loading spectrum to be used. The purpose of this paper is to present a method of deriving a randomized flight-by-flight loading spectrum which can be used in preliminary design, and to show the effect on crack growth life of varying certain important parameters.
The random spectrum is derived using mission profiles, MIL-A-008866A or flight recorder exceedance data, design loads, and stress data. The mission mix and actual load sequence is determined randomly. The spectrum is then analyzed using a conventional crack growth computer program which calculates crack growth (a versus N) curves, and critical crack length.
The sensitivity of fatigue crack growth life to the variation in a number of parameters was investigated. These parameters include different random sequences and cycle counting methods. Random sequence effects include randomizing the loads on a mission segment or on a flight-by-flight basis. The results of this study are compared to the results obtained when the basic exceedance data was combined into a conventional block loading sequence.
Stress Spectrums for Short-Span Steel Bridges
Authors: Klippstein KH , Schilling CG 
Published: March 2009

U. S. Steel's Research Laboratory is currently completing research on Project 12-12, sponsored by the National Cooperative Highway Research Program of the National Academy of Sciences, and entitled “Welded Steel Bridge Members Under Variable-Cycle Fatigue Loadings.” The main objectives of the program are to develop fatigue data on welded bridge members under variable-amplitude random-sequence stress cycles representative of stress spectrums such as occur in actual bridges and to develop an analytical method of predicting the fatigue behavior under variable-amplitude stress spectrums from constant-amplitude fatigue data.
This paper summarizes available field measurements of stresses in short-span bridges under traffic, and describes the stress spectrums that were developed from these measurements for use in the testing program. The available field data show that the passage of a vehicle over a bridge produces a single major stress cycle and superimposed vibrational stress cycles. In most types of bridges, the vibrational stresses are small enough to be neglected; however, the described method of deriving a simple equation for the stress spectrum is applicable to field data with or without vibrational stresses. The frequency of occurrence of stress cycles can be defined by a family of skewed Rayleigh probability-density curves; a particular curve from the family is defined by the modal value, Srm, and the dispersion, Srd. The major stress cycles (or stress ranges) are added to the dead-load stress, Smin, which remains essentially constant during the life of the bridge. In general, the stress cycles are arranged in random sequence. The stress spectrums used in the main test program, therefore, are defined by three parameters: Srm, Srd, and Smin. The fatigue-test control tapes corresponding to these spectrums record 500 individual loads that satisfy one of the family of Rayleigh probability-density curves and are arranged in a random sequence. The tape is continuously cycled throughout a fatigue test.
Fatigue Crack Growth Under Variable-Amplitude Loading in Various Bridge Steels
Authors: Barsom JM 
Published: March 2009

Well-conceived procedures used to study the safety and reliability of structures recognize that the performance of a structure or a structural component is governed not only by material properties but also by the design, fabrication, inspection, erection, and use of the structure. These parameters govern the initiation of subcritical cracks and their propagation to critical dimensions, and therefore, determine the useful fatigue life of structural components subjected to load fluctuations.
This paper presents the results of the first phase of an investigation sponsored by the National Cooperative Highway Research Program, Project 12-14, to study “Subcritical Crack Growth in Steel Bridge Members.”
The paper describes the fatigue-crack-growth behavior of various bridge steels (A36, A588-A, A588-B, A514-B, A514-E, and A514-F) under variable-amplitude random-sequence stress spectra such as occur in actual bridges. The fatigue crack growth-rate data were obtained by using wedge-opening-loading specimens tested under variable-amplitude random-sequence load spectra that are represented by a Rayleigh distribution function.
The data obtained for these steels showed that the average fatigue crack growth rates, da/dN, under variable-amplitude random-sequence load fluctuation and under constant-amplitude load fluctuation agreed closely when da/dN was plotted as a function of the root-mean-square stress intensity factor range, ΔKrms. Thus, within the limits of the present investigation, the average fatigue crack-growth rates, da/dN, of various bridge steels subjected to variable-amplitude random-sequence load fluctuations, such as occur in actual bridges and to constant-amplitude load fluctuations, can be represented by the equation dadN=A(ΔKrms)n where ΔKrms is the root-mean-square stress intensity factor fluctuation, and A and n are material constants.
Demonstration of Systems for the Recovery of Materials and Energy from Solid Wastes
Authors: Skinner JH 
Published: March 2009

This paper reviews the U.S. Environmental Protection Agency program to demonstrate new and innovative systems to recover materials and energy from municipal solid waste. The following resource recovery projects are described: (a) the use of shredded solid waste as a coal substitute, (b) the wet pulping of solid waste for materials recovery, (c) the pyrolysis of solid waste to produce a fuel oil, (d) the pyrolysis of solid waste for steam generation, (e) recovery of materials from incinerator residue, and (f) the use of shredded solid waste as a fuel in an oil-fired boiler.
The extent to which this program has been successful in promoting the implementation of resource recovery systems by state and local governments and by the private sector is discussed.
Use of Aluminum Recovered from Municipal Solid Waste
Authors: Abbate ST 
Published: March 2009

Recycling of aluminum from municipal refuse makes economic good sense and will be increasingly so due to the need to utilize resources and energy to the fullest.
The currect work of building a broad base of specifications, utilizing sample evaluations from many sources, will provide the municipal refuse processors with the technical criteria necessary to produce a product that is marketable.
Continued growth of the aluminum industry is contingent on metal supply from both primary and reclamation sources.
The durability of aluminum in its various produce forms, coupled with the growth factor, point to a strong demand on all of the suppliers of this metal. The reclamation industry, with its lower capital requirements per annual ton of output, relative to virgin aluminum, is a vital segment in the maintenance of an adequate supply of aluminum to the market. Two of the fastest growing aluminum markets today, containers and consumer products, can readily use the aluminum now being recovered and can potentially keep ahead of the supply. This helps assure market stability, and all that it means to the new industry of municipal refuse processing.
Neutron Radiography to Detect Residual Core in Investment Cast Turbine Airfoils
Authors: Edenborough NB 
Published: March 2009

Turbine engine blades and vanes for high-temperature applications are generally cooled by internal passages formed by the investment casting process. The cooling efficiency of the airfoil greatly depends on the removal of the ceramic core used to form the cooling passages. The detection of residual core in blades and vanes for operations above 2000 °F is difficult with standard visual and X-ray techniques because of the complexity of the cooling passages.
A technique using neutron radiography for improved residual core detection has been developed. The contrast is enhanced by “salting” the ceramic core base material with a 3 percent concentration of gadolinium oxide. Commercial reactors on the west coast are used for this production inspection. Turnaround time is approximately four days. Special fixtures were designed for both shipping and inspection.
Neutron radiography is now a standard production technique for high-temperature engines at Detroit Diesel Allison. Recently this inspection has been made a part of the vendor requirements.
Neutron Radiography of Nuclear Fuels at the Battelle Research Reactor
Authors: Kok KD 
Published: March 2009

The development and use of neutron radiography at the Battelle Research Reactor (BRR) are described. Neutron radiography was conducted in the reactor pool and in a facility located outside the reactor pool. Neutron radiographs were obtained by both the direct and transfer techniques. In general, indium conversion screens were perferred. The handling techniques included still and scanning methods. The problems encountered while working in water are also described.
The uses of neutron radiographs of nuclear fuel materials include determination of the physical condition of the material, dimensional data, enrichment, and burn-up. Neutron radiographs were used to determine the location of PuO2 particles, less than 50 μm in size, in a UO2-PuO2 fuel material. Dimensions were determined to ± 50 μ when measurements were made. Neutron radiography was a useful tool in nuclear fuel development work at the BRR.
Application of the J-Integral to the Initiation of Crack Extension in a Titanium 6Al-4V Alloy
Authors: Yoder GR , Griffis CA 
Published: March 2009

Tests were conducted to determine JIc from resistance curves of J versus crack extension, obtained from fatigue-precracked specimens of a titanium 6Al-4V alloy. Specimens of various geometries were employed, all in three-point bending. Crack extensions were delineated by heat tinting.
Results obtained with J computed from the equation, J = 2A/Bb, are compared to those obtained with the compliance technique, using the plane-stress solutions of Bucci et al. JIc results are compared with a valid KIc value for this material.
The range of ratios of crack length to specimen width (a/W) is explored over which the equation J = 2A/Bb applies. The decrease in crack extension at experimental limit load (Δapmax →Δac) is examined as the ratio of specimen thickness to uncracked ligament (B/b) is increased. Variation in JIc from specimens cut from different positions through the plate thickness is also examined.
Effect of Specimen Size on Fracture Toughness of a Titanium Alloy
Authors: Munz D , Galda KH , Link F 
Published: March 2009

This paper describes the effect of specimen size on slow crack growth and fracture toughness of the titanium alloy Ti-6A1-4V. The load versus crack opening displacement curve rises steeply after reaching the end of the linear part. Stable crack extension starts within the linear part of the P-v-curve. The crack growth resistance curve is independent of thickness B until KQ in the range 2 &lt; B &lt; 20 mm, leading to the conclusion that slow crack growth can occur in plane strain.
The secant method, leading to KQ at 2 percent crack extension, yields a specimen geometry dependent fracture toughness. KQ increases with width, W and is only slightly dependent on thickness, B.
The consequences of this behavior for fracture toughness determination in connection with the ASTM recommendation are discussed.
Cyclic Crack Growth Analysis for Notched Structures at Elevated Temperatures
Authors: Gamble RM , Paris PC 
Published: March 2009

Linear elastic fracture mechanics analysis in conjunction with the appropriate experimental crack growth data were used to predict allowable thermal fatigue crack growth rates in gas turbine disks. The crack growth predictions made for the turbine disks compared favorably with subsequent service data.
Further studies were undertaken to determine the effect of geometric stress concentration on crack initiation and crack propagation. A general method of analysis was developed to provide simple approximations of the crack growth rates for cracks initiating at notches. The crack growth rates predicted by this method are in good agreement with both experimental laboratory specimen data and field service turbine disk data.
Water Vapor Diffusion and Frost in Porous Materials
Authors: Auracher H 
Published: March 2009

It is well known that in porous materials moisture condensation occurs under certain physical conditions as a result of water vapor diffusion. In the temperature range below 0°C, ice crystals grow in the pores of the material generating a frost structure.
In pores of variable cross-sectional areas, frost growth is nonuniform. Therefore, a graphical procedure is developed with which the mass and location of frost growth in pores with any cross-sectional function can be determined. By this graphical procedure it is also possible to develop some general statements about the frost density distribution in pores at greater frost contents. It is shown, assuming a time-constant temperature function, that at the beginning of frost growth the diffusion flux in any cross section of the pore has a maximum value, and that it decreases continuously with increasing frost growth.
The results developed by means of the graphical procedure are confirmed by measurements made on capillaries with alternating cross-sectional areas. Afterwards, the diffusion and frost growth in pore-models of ordered sphere-packings are then investigated theoretically by the use of the same graphical procedure. It is shown, above all, that normally the frost growth does not begin at the smallest cross-sectional areas of the pores.
Finally, employing the graphical results, a method is developed through which the diffusion resistance factor of a porous material can be approximately calculated as a function of frost density.