bluuebunny/crossref_metadata_2025 huggingface dataset:
Utilization of Soil Gas Monitoring to Determine Feasibility and Effectiveness of In Situ Bioventing in Hydrocarbon-Contaminated Soils
Authors: Frishmuth RA , Ratz JW , Hall JF
Published: March 2009

To determine the feasibility and effectiveness of in situ bioventing, careful monitoring of soil gas chemistry is essential. Prior to design of a bioventing system, initial soil gas surveys should be performed. Concentrations of three constituents, oxygen (O2), carbon dioxide (CO2), and total volatile hydrocarbons (TVH), are used in bioventing design. TVH are an indicator of contaminant distribution; O2 and CO2 are indicators of biodegradation activity. Analysis of soil gas data collected during pilot-scale testing is the primary design basis for full-scale remediation systems. Biodegradation rates determined from respiration tests are used to estimate the length of time that a system will have to operate to remediate the contamination. Air permeability of the soil, calculated from permeability testing, determines the number and spacing of air injection wells that will be required to ensure adequate oxygen influence through the entire contaminated area.
Microbeam Analysis of Heavy Element Phases in Polished Sections of Particulate Material — An Improved Insight into Origin and Bioavailability
Authors: Kennedy SK , Casuccio GS , Lee RJ , Slifka GA , Ruby MV
Published: March 2009

The contamination of environmental materials (soil and dust) by heavy elements is of concern in assessing environmental pollution. Characterization of samples is performed in order to provide information that can be used to assess the potential hazard of the material, to assess remediation strategies, and to determine the source of the heavy element-bearing material. This is difficult because the particles in which the element of interest occur may consist of multiple phases, some potentially hazardous and some benign. Bulk properties of samples are often determined to assess the potential risk related to such a sample. Such an assay may reveal the total content of a contaminant, and so document the maximum hazard potential, but cannot directly address important mitigating factors, including the specific phases present, their size distribution and internal particle structure.

Microbeam analysis using a scanning electron microscope (SEM) or electron microprobe on polished particle mounts allows the size, internal morphology and chemical composition to be determined on a particle-by-particle basis. Computer controlled SEM allows all factors except internal structure to be acquired in an automated fashion.

We present examples of two studies using microbeam techniques. In the first example, we illustrate how cadmium associated with sphalerite (zinc sulfide) in soils can be quantified at levels down to a few parts per million (ppm) using computer controlled SEM techniques. In the second example, we illustrate how lead in soils can be assigned to phases, phase sizes and to internal structure types using manual electron microprobe techniques.
Soil Gas Sample Analysis Method Evaluation and Comparison
Authors: Calkins CC , Gabriel CA , Banikowski JE
Published: March 2009

The quality of soil gas survey data is a function of many variables, particularly the analytical method used to analyze the collected samples. Several analytical methods are commonly employed, including direct reading photoionization detectors, portable gas chromatographs (GCs), and mobile laboratories equipped with benchtop GCs. Two analytical methods employing Hewlett-Packard (HP) 5890 Series II GCs were compared relative to their sensitivity, precision, accuracy, practicality, and productivity. The first method utilized direct injection as the method of sample introduction, and the second, a Tekmar LSC 2000/ALS 2016 purge and trap autosampler. The direct injection method provided greater accuracy, precision, and ease of use, while the purge and trap autosampler method provided increased sensitivity and higher productivity.
New Materials and Forgings Used for Pressure Vessels Operating in Hydrogen Environment
Authors: Bocquet P , Cheviet A , Coudreuse L , Dumont R
Published: March 2009

To improve the in-service behaviour of Cr Mo (V) steel grades used for the pressure vessels operating in hydrogen environment at high temperature for the oil industry, the manufacture of heavy forgings needs a high quality. Improvement of the standard and enhanced strength (ASME Case 1960) 2 l/4 Cr 1 Mo steel grades may be achieved by reducing drastically the impurities (S, P, X, etc…) to extra low level and avoiding segregates at the inner surface of the shells. For high temperature operation, new V modified steel grades are proposed (ASME case 1961, Code Case 1973 and Code Case 2098). Their conventional mechanical properties are similar to those of enhanced strength 2 1/4 Cr 1 Mo but they offer higher creep properties and improved resistance to hydrogen damage.
Improved Mechanical Properties of the A 508 Class 3 Steel for Nuclear Pressure Vessel Through Steelmaking
Authors: Kim J-T , Kwon H-K , Kim K-C , Kim J-M
Published: March 2009

The present work is concerned with the steelmaking practices which improve the mechanical properties of the A 508 class 3 steel for reactor pressure vessel. Three kinds of steelmaking practices were applied to manufacture the forged heavy wall shell for reactor pressure vessel, that is, the vacuum carbon deoxidation(VCD), modified VCD containing aluminum and silicon-killing. The segregation of the chemical elements through the thickness was quite small so that the variations of the tensile properties at room temperature were small and the anisotropy of the impact properties was hardly observed regardless of the steelmaking practices. The Charpy V-notch impact properties and the reference nil-ductile transition temperature by drop weight test were significantly improved by the modified VCD and silicon-killing as compared with those of the steel by VCD. Moreover, the plane strain fracture toughness values of the materials by modified VCD and silicon-killing practices was much higher than those of the steel by VCD. These were resulted from the fining of austenite grain size. It was observed that the grain size was below 20μm (ASTM No. 8.5) when using the modified VCD and silicon-killing,compared to 50μm (ASTM No. 7.0)when using VCD.
Effects of Composition and Heat Treatment on the Toughness of ASTM A508 Grade 3 Class 1 Material for Pressure Vessels
Authors: Lin M , Hansen SS , Nelson TD , Focht RB
Published: March 2009

A laboratory study was conducted to evaluate the effects of composition and heat treatment on the toughness of ASTM A508 Grade 3 Class 1 material for pressure vessels. Five steels were vacuum induction melted and cast as ingots in the laboratory. These heats included a base steel representing the specification mid-range analysis, a steel containing higher levels of Si, Ni, and Cr (high-side composition) as compared to the base steel, and three steels derived from the high-side composition by adding Al, Al/N, and Nb, respectively. The ingots were rolled to plate, heat treated, and evaluated. Among these steels, the high-side composition with additions of Al and N displays the best strength/toughness combination. For example, a 75 mm-thick plate of this steel has acceptable strength and a reference nil ductility transition temperature (RTNDT) of ≤ -29‡C after austenitizing at 875‡C, air cooling, and tempering at 660‡C for up to 20 hours. Upper-nose temper embrittlement (UNTE) occurs in all these steels. This UNTE is attributed to the precipitation of needle-like Mo-rich carbides during tempering, and is significantly reduced by increasing the cooling rate after austenitizing.
Forging Technology Adapted to the Manufacture of Nuclear PWR Austenitic Primary Piping
Authors: Morin F , Bocquet P , Cheviet A
Published: March 2009

In order to reduce the number of welds (in service inspection costs), to improve the thermal ageing resistance and the internal soundness of components, Electricité de France decided to develop a solution for forged austenitic stainless steel in place of castings to manufacture the straight parts and the elbows of the primary piping of PWR power plants. The paper presents the interest of such solution and the manufacture conditions of such for-gings applied, first, to a cold leg for the Civaux 1 unit and, second, to a complete loop for the Civaux 2 unit.
Developments in Forging Ingot Production at Bethforge Inc.
Authors: Fielding JE , Focht RB , Reppert KF , Tihansky EL
Published: March 2009

BethForge manufactures precision custom forgings for diverse applications including turbine and generator rotors, components for nuclear reactors and other pressure vessels, and rolls for steel and aluminum rolling mills. This paper will discuss the production of forging ingots for BethForge at the modernized steel making facility in Steelton, PA. The facility is operated as part of a joint effort with Pennsylvania Steel Technologies, Inc. (also a wholly owned subsidiary of Bethlehem Steel) and consists of a 150 ton (136 metric ton) DC electric arc furnace, a ladle refining station including a ladle furnace and ladle degasser, and teeming facilities which include bottom pouring and vacuum stream degassing. Steel is produced for BethForge ingots as well as continuously cast for the Pennsylvania Steel Technologies product lines. Forging, heat treating and machining operations remain at Bethlehem, PA and ingots as large as 130 inches diameter (3300 mm) and 290 tons (263 metric tons) are hot transported the 90 mile (145 km) distance from Steelton to Bethlehem in specially constructed insulated railcars. In addition to describing the facilities and operations, the presentation will focus on solutions to several of the unique engineering and technical challenges realized in successfully bringing this operation on line.
Manufacture and Properties of Continuous Grain Flow Crankshafts for Locomotive and Power Generation Diesel Engines
Authors: Antos DJ , Nisbett EG
Published: March 2009

The bulk of the large crankshaft production volume is associated with the medium speed diesel engine market These engines have seen intense development to sustain higher power outputs without change in the physical size of the crankshaft and at the same time there has been continuing pressure to reduce costs. Fatigue and bearing journal wear are the major technical hurdles that threaten the crankshaft life, and measures for dealing with these issues are described. Continuous grain flow (CGF) crankshafts are responsible for the continued integrity of these enhanced power output engines and the production of these crankshafts is described. Comparisons are made with the older slab forging crankshaft production method. The demand for the medium speed diesel engine and its natural gas derivative is strong and supports an aggressive engine building industry serving locomotive, marine and power generation markets. This demand in turn relies on practical national standards that serve the needs of the engine builder, material supplier and the end user
Reducing Stress Related Problems in Steel Forgings Using Sub-Harmonic Vibrational Energy
Authors: Hebel TE
Published: March 2009

There are predominantly three residual stress related problems plaguing steel forgings. They are 1) distortion following machining, 2) delayed distortion, and 3) premature cracking tendencies. The major source of these problems is the stress caused by a sharp temperature drop from hot forging or welding.

This paper will detail SUB-harmonic vibrational technology as an effective stress relief solution to reducing these problems. Also, this paper will outline the three step approach for using the sub-harmonic energy process during welding. When used during welding additional benefits of reducing weld distortion and cracking will be achieved.

Data collected from seven Test Cases will be presented including reduced machine distortion (43–76%) from forged cannon barrels and aerospace components. Reducing premature cracking will be demonstrated using examples of longer fatigue life (200–400%) from components such as forged crankshafts and connecting rods used in racing engines. Data from the U.S. Department of Energy sponsored study on this technology will be presented. This report concluded that there is evidence that the Sub-harmonic treated and thermal stressed relieved specimens are “comparable.”
The Chemistry Modifications to ASTM A707 for Offshore Structural Integrity
Authors: Walsh MA , Price S
Published: March 2009

The development of low alloy steels for offshore applications has generally led to the selection of increasingly “leaner” chemistries which are tailored to meet specific design requirements. Low carbon, low alloy, copper bearing steels based on the ASTM A707 grade system have attracted considerable interest for applications combining high strength and toughness with good weldability. Forgemasters Steel and Engineering has been intimately involved in the development of A707 variants which has led to contracts for the production of forged components for the Auger and Mars platforms. A thorough review of structure property relationships with regard to the role of copper precipitation during ageing, has been undertaken. Comparisons have been drawn with conventional low carbon, low alloy steels where similar properties are achieved with tempered bainitic microstructures.
Ultrasonic Signal Processing Using Indication Sets for Detection and Characterization
Authors: Viertl JRM
Published: March 2009

The potential for discontinuities in turbine and generator rotors must be dealt with in the manufacture of these components. In recent years it has become practical to acquire and analyze large quantities of ultrasonic data obtained from testing solid rotor forgings.

This paper describes an ultrasonic system for testing solid rotors, and discusses the detection, characterization, and imaging capability developed for evaluating rotor indications.

For detection of rotor indications, the ultrasonic signal path is divided into range windows. The signals within each window are compressed and stored for detection and characterization algorithms. Detection is performed by associating echoes from one ultrasonic path with the data from neighboring paths. These associations are constructed with respect to the cylindrical coordinate system used during the process.

Characterization is performed using the indication data sets constructed during the detection process. The final results determined by these automatic data processing algorithms are presented to the user as potential indication lists which can be correlated to images constructed from the original data.
Application of Fem-Based Modeling of Open-Die Forging to Product and Process Development at Bethforge, Inc.
Authors: Reese W , Ronemus DC , Huang K , Zimmers EW , Veerabadran T
Published: March 2009

This paper describes a FEM-based computer system implemented by BethForge to model the open-Die forging process and its application to product and process development. A brief overview of BethForge, the markets it serves, and the typical product development cycle is given. Alternative methods for modeling open-Die forging are discussed and the advantages offered by FEM techniques due to recent advances in computer hardware and software are presented. The FEM-based modeling system that BethForge has developed in partnership with the Lehigh University Computer Integrated Manufacturing Laboratory (LU-CIM) and UES, Inc. is described along with the associated modeling methodologies. Several case studies are presented including 2D-axisymmetric simulation of head-forming, punch-forming, upsetting, and back extrusion, and the 3D simulation of ingot cogging.
A Rare Type of Flake-Like Forging Burst in Heavy Forgings
Authors: Steiner JE , Murphy EL
Published: March 2009

Forging bursts are infrequently reported in the published literature. One type of forging burst, which has been observed only on four occasions in the combined experience of the authors, is described. The similarity of this defect with hydrogen-caused thermal flakes is remarkable. It is characterized by a fracture appearance similar to that of flaking when broken open, by orientation and distribution similar to flaking, but within a specific section of a large forging, generally in ultrasonic test response and by its good response to healing during reforging, as with flaking.

Case histories of two 3.5Ni-Cr-Mo-V forgings, one 1cr-1Mo-0.25v forging and one martensitic stainless steel forging are presented, and processing factors related to these bursts and means for avoidance of the problem are discussed. A fifth case of possible misidentification of this phenomenon as hydrogen flakes in a small gear component forging is discussed. Approaches to differentiation of this defect from flaking are discussed.
Martensitic 11% CrMoNiNb Steel for Turbine Rotors in Geothermal Power Stations
Authors: Schonfeld KH , Levacher R , Manning MP , Murley PF
Published: March 2009

Turbine rotors in a geothermal power station were required in high alloyed 12% Cr steel. After some preliminary investigations it was found that a modified 11% CrMoNiNb steel will fulfil the required mechanical properties as well as a sufficient resistance to corrosion.

Two LP rotors with appr. 1 295 mm (51 in.) premachined diameter and ungashed weight of appr. 31 mt were manufactured. The steel was melted in a 125 mt electric arc furnace and subsequently remelted into a 113 mt ESR ingot with 2 300 mm (90 in.) diameter. After forging and preliminary heat treatment the rotors were quality heat treated to a yield strength (0.2% and 0.02%) of appr. 600 MPa (87 ksi) and appr. 550 MPa (80 ksi) respectively and tensile strength of appr. 780 MPa (113 ksi). This resulted in a FATT of appr. 16‡C (60‡F). Low hardness is important to susceptibility to stress corrosion. It was achieved to appr. 20 HRC.

The results have met the assumption with respect to this steel for application as rotor material for geothermal power stations.
Historical Overview of Improving Cleanliness of Rotor Steels for Electric Utility Applications
Authors: Viswanathan R
Published: March 2009

Abstract Improved cleanliness is perhaps the only approach that results in simultaneous improvement in strength and ductility at elevated temperatures as well as toughness at low temperatures of steels. In addition, superclean steels in which manganese and silicon have also been reduced, provide greater resistance to stress corrosion cracking than conventional steels. Major projects are underway worldwide to promote the use of clean/superclean steel rotor and disk forgings, both for low temperature and for high temperature applications in steam and combustion turbines. An international workshop sponsored by EPRI was held in 1995 in London, at which turbine manufacturers and steelmakers discussed ongoing activities with respect to clean steels. This paper summarises EPRI sponsored research on rotor steel chemistries and provide an overview of developments over the last 15 years.
Manufacturing and Properties of Newly Developed 9%CrMoVNiNbN High-Pressure Low-Pressure Rotor Shaft Forging
Authors: Azuma T , Tanaka Y , Ishiguro T , Yoshida H , Ikeda Y
Published: March 2009

In order to obtain the improved strength and toughness for high-pressure low-pressure rotor shaft forging, fundamental studies using laboratory heats were performed on the 9CrMoV base materials, and effects of chemistry on toughness and creep rupture strength were investigated. From the investigation, it is showed that the superclean 9CrMoVNiNbN steel with reduced Si and Mn contents and Ni addition provides a superior strength versus toughness balance. Based on these fundamental studies, a trial high-pressure low-pressure rotor shaft forging with diameter of low-pressure section of 1750 mm and diameter of high-pressure section of 1200 mm was successfully manufactured from the diameter of 1800 mm, and the weight of 65 ton ESR ingot. From the evaluation test results of this trial rotor forging, homogeneous distribution of chemistry was confirmed and low impurity contents was observed in the whole forging. The superior strength and toughness were confirmed with good creep rupture strength. The FATT at the center of low-pressure section was −3‡C with the tensile strength level of 870 MPa. From the results of fracture toughness test, low cycle fatigue test, and isothermal aging test, superior mechanical properties were demonstrated. Thus, the superclean 9CrMoVNiNbN steel with reduced Si and Mn contents and Ni addition, is particularly suitable to the high-pressure low-pressure rotor material for advanced combined cycle power plants.
Modeling the Measured Time to Corrosion Cracking
Authors: Newhouse CD , Weyers RE
Published: March 2009

The deterioration models for reinforced concrete structures include a period for time to corrosion cracking: time from initiation of corrosion to first cracking. Theoretical equations for determining the time to corrosion cracking have been presented but never validated. This paper reports on a study which was initiated to validate or modify a set of theoretical equations for field linear polarization, unguarded and guarded, corrosion rate devices. The test variables included six corrosion rates, two concrete cover depths, two reinforcing steel bar diameters and spacings, two exposure conditions (indoors and outdoors), and one design concrete strength (water to cement ratio). Influence of temperature and chloride content on the measured corrosion rates are presented. Corrosion rates increase with increasing chloride content and corrosion rates vary significantly with annual changes in temperature, highest in the spring and lowest in the winter. Measured metal loss measurements were compared with the calculated metal loss based on monthly corrosion rate measurements for both devices. The 3LP device significantly over-estimated the amount of metal loss and the Geocor 3 device significantly under-estimated the amount of metal loss based on average monthly measurements. The theoretical time to corrosion cracking equations significantly under-estimated the time to corrosion cracking using a uniform corrosion rate based on the measured metal loss.
Progress on Design and Residual Life Calculation with Regard to Rebar Corrosion of Reinforced Concrete
Authors: Andrade C , Alonso C
Published: March 2009

The increasing amount of structures presenting distress due to reinforcement corrosion is urging the establishment of more accurate calculation methods for the service life of concrete structures. In the present paper, a summary of the different approaches is presented that are able to calculate the expected life of new structures, in certain aggressive environments or the residual life of already corroding structures. The methods are based on the proper calculation of the carbonation front or chloride penetration and on the steel corrosion rate.
Computer Modeling of Effect of Corrosion Macrocells on Measurement of Corrosion Rate of Reinforcing Steel in Concrete
Authors: Sagüés AA , Kranc SC
Published: March 2009

The corrosion rate of steel in concrete can be significantly underestimated if corrosion is non-uniform, because of short-range uneven distribution of the excitation current during polarization measurements. This effect occurs in addition to large scale current distribution problems originating from the use of small counter electrodes or similar causes. Short range macrocells create zones that at low frequencies have much smaller interfacial impedance than the remainder of the steel. However, the impedance is small and uniform at high frequencies due to the presence of interfacial capacitance. The resulting variation of current distribution pattern with frequency prevents correct application of solution resistance compensation techniques. Finite difference computation of current distribution are combined with matrix analysisof the a.c. current distribution to illustrate this behavior. Calculations of the degree to which corrosion is underestimated as a function of system parameters are presented.
Field Measurement of the Corrosion Rate of Steel in Concrete using a Microprocessor Controlled Unit with a Monitored Guard Ring for Signal Confinement
Authors: Broomfield JP
Published: March 2009

The principle of corrosion rate measurement by the linear polarisation resistance method is simple. The equipment measures the half cell potential, applies a small current and measures the change in potential. The corrosion rate is proportional to the applied current divided by the potential shift.

Using the technique in the field on reinforced concrete structures is complicated because the area of measurement must be defined and readings fluctuate with the weather conditions.

This paper describes the use of a corrosion rate device in Europe and the USA on bridges, buildings and other structures. Its application for measuring the effectiveness of chloride removal and other rehabilitation techniques is discussed.
Tests for Evaluation of the Effectiveness of Penetrating Sealers in Reducing Penetration of Chlorides into Concrete
Authors: Whiting D , Nagi MA
Published: March 2009

A pair of rapid tests for evaluation of the effectiveness of penetrating sealers in preventing corrosive chloride ions from penetrating concrete have been developed. The tests are designed to yield an indication of the relative performance of a sealer as compared with unsealed concrete. The first test is based on measurement of electrical resistance between two small electrodes created on a concrete surface by use of a highly conductive spray-applied coating. A criterion of 200 k-ohms after 4 minutes of test was selected for differentiating between effective and ineffective sealers. The second test is based on absorption of water into the concrete surface over a four minute period. Development and field trials of the two tests are described. The tests are applicable to both horizontal and vertical surfaces. Applications for the tests include quality control of sealer application, qualification of sealers under field conditions, and monitoring of sealer performance over time in a nondestructive manner.
Combined Bulk and Interfacial Studies of the Cement/Steel System by Impedance Spectroscopy
Authors: Ford SJ , Mason TO
Published: March 2009

Three arcs, corresponding to the bulk, interfacial, and electrode responses, are apparent in the impedance spectrum of cement paste / reinforcing steel systems. The 3-point impedance technique, without potentiostat, is capable of simultaneously and continuously monitoring these three responses over several orders of frequency (MHz-mHz). The high frequency (MHz) bulk arc provides such parameters as diffusivity and permeability of the paste, which in turn have implications for the ingress of corrosive species, such as chloride ions, known to greatly affect the corrosion rate of reinforcing steels. The double layer arc (Hz) provides insight into the nature of the near interfacial zone of the paste/ steel system, where the higher degree of porosity may affect corrosive behavior. The low frequency (mHz) electrode arc is related to the passive nature of the steel. Oxide film thickness can be inferred, as well as corrosion rates in active, passive, and pitting regimes.
Preliminary Corrosion Investigation of Prestressed Concrete Piles in a Marine Environment: Deerfield Beach Fishing Pier
Authors: Krauss PD , Nmai CK
Published: March 2009

Between the Fall of 1991 and Spring of 1992, a new fishing pier was constructed in Deerfield Beach, Florida, to replace a badly deteriorated pier that was demolished. The precast, prestressed concrete piles used in the construction of the new pier contained a water-based organic corrosion inhibitor consisting of amines and fatty acid esters. This inhibitor offers corrosion protection by reducing chloride ingress and by forming a protective film at the surface of embedded steel. In the Fall of 1993, a preliminary corrosion investigation of the piles was performed to assess the performance of the concrete used in the construction of the pier and to establish baseline values for future investigations. The techniques used included visual and half-cell potential surveys, and determination of chloride ion contents. Chloride ion contents at the reinforcing steel level were found to be well below that which would induce corrosion. Other types of testing and analytical techniques that may be used in future investigations to assess the performance of the piles and to predict their useful service life are also discussed.
Field Experience with Rebar Probes to Monitor Performance of Sprayed Zinc Galvanic Anodes on Concrete
Authors: Sagüés AA , Powers RG
Published: March 2009

Sprayed zinc galvanic anodes have shown promise as low-cost alternatives to simple gunite repair or even impressed current systems for corrosion-damaged marine substructure of bridges. Because the anodes are permanently connected to the rebar assembly at many points, it is not normally possible to deenergize the anode for measurement of steel polarization and current delivery. Field performance of these systems has been monitored with short embedded rebar probes fitted with external switchable connections. This has allowed for current density, depolarization decay, and polarized potential measurements as a function of time. The anode current delivery has also been measured with isolated cutout anode regions “windows”, and in one case with a specially designed, fully disconnectable anode. The results of the different means of evaluating system performance over several years are compared for various field installations in Florida. The relative merits of the monitoring methods and the information they provide on the corrosion condition of the steel are analyzed.
A Case Study: Assessment of Ice Rink Refrigerant Tubing Corrosion using Half Cell Techniques
Authors: Brickey WJ
Published: March 2009

This paper describes a corrosion study performed on an ice rink. The purpose of the study was to evaluate the extent and increase in corrosion of low carbon steel refrigeration tubes and the reinforcing steel embedded in a concrete slab-on-grade. A copper-copper sulfate half cell was used in the assessment. Chemical analyses, microscopic examinations and destructive examinations were used to supplement and confirm the results of the half cell testing.

An increase in corrosion activity was determined by comparing the results of half cell surveys conducted in 1989 and 1990. The cause of the corrosion activity was determined from chemical analyses, microscopic examinations and destructive techniques.
Behavior and Design of a Single Wythe Concrete Masonry Residence in a Southern, Humid Climate
Authors: Stokoe ML
Published: March 2009

An objective recanting of the construction practices, materials, and wall design of a 3300 sq. ft. (floor space) concrete masonry structure built with standard gray units. Over 20 years in which this residence has been lived in and monitored give a good look at how total masonry homes might perform in a southern humid climate, using vertical grouted cells, internal bond beams and horizontal joint reinforcement. The study shows how a total masonry residence has performed successfully in a hot humid climate, what the problems have been and suggested solutions.
Characteristics of Concrete Masonry Architecture and Construction in Colombia
Authors: Madrid GG , Pelaez LG
Published: March 2009

Concrete masonry has developed in Colombia with very special architectural and technical characteristics, due to the restrictions of a developing economy (quality and availability of materials; training necessities; scale of application and cost relative to other technically equivalent alternatives). But those aspects have not stopped it from creating a very distinctive and high-quality image through clearly defined building categories: One and two-floor houses, low-rise apartment buildings, high-rise apartment and office buildings, churches, sport and social clubs, educational and industrial buildings, etc.; and, in a very special way, in institutional architecture, providing a distinctive image to buildings from supermarkets to designer's stores, including car dealers, gasoline stations, savings corporations, etc. The natural resources of the material, together with the ingenuity of Colombian architects and designers, are opening a great avenue for concrete masonry in this country, something that could be duplicated in many others with similar conditions.
Development of Specifications for Mortar Cement
Authors: Melander JM , Ghosh SK
Published: March 2009

A specification for mortar cement was incorporated into the Uniform Building Code (UBC) Standards by the International Conference of Building Officials (ICBO) in 1991. This action was taken on the basis of recommendations made by the Masonry Industry Code Committee (MICC), a volunteer committee of producers, general interest, and user individuals, which coordinates masonry industry input with respect to the UBC and UBC Standards. The UBC Mortar Cement Standard represents the culmination of research and standards development effort that was coordinated by the MICC. More recently, ASTM Subcommittee C01.11 on Masonry Cement has undertaken action to develop an ASTM consensus standard for mortar cement.

This paper examines the research, rationale, and events that led to the development of the UBC mortar cement standard, explains how mortar cement differs from masonry cement in use and requirements, and discusses key issues being considered in the development of an ASTM Standard Specification for Mortar Cement.
An Evaluation of Bond Wrench Testing Apparatuses
Authors: McGinley WM
Published: March 2009

Summarized are results of a combined testing and analytical investigation of four different bond wrench testing systems. The testing program involved placing a calibration block within each testing apparatus and applying a range of loads to the block. This calibration device was designed to simulate a standard brick couplet specimen and was instrumented with linear strain gauges which were monitored and recorded during loading. The results of these tests were compared and discussed in an effort to determine what attributes of the testing apparatuses can significantly affect the stress distribution in masonry couplet specimens. Evaluation of the bond wrench testing system was also performed using a finite element analysis.

Finally, in an effort to extend the scope of C 1072 -92 to include hollow masonry assemblies, an analytical evaluation of hollow couplet specimens was made. The results of these finite element analyses are presented and discussed.
Water Penetration Testing of Single Wythe Residential Load-Bearing Clay Masonry Wall Systems
Authors: McGinley WM , Brosnan DA
Published: March 2009

Summarized are the results of an investigation designed to evaluate the water penetration resistance of a variety of residential single wythe load bearing clay masonry exterior wall systems. A total of eighteen wall specimens were tested using the apparatus and procedures outlined in ASTM E 514. Six different wall configurations were evaluated, including variations in insulation, tie connectors, and moisture barriers. Also discussed are some of the construction procedures critical in the wall system performance, recommendations for detailing the system for optimum water resistance and the impact of these recommendations on the thermal and vapor resistance of the wall system.
Interfacial Mechanics and Macroscopic Failure in Titanium-Based Composites
Authors: Clyne TW , Feillard P , Kalton AF
Published: March 2009

Results are presented for Ti-6Al-4V containing silicon carbide (SiC) monofil-aments having duplex (carbon plus TiB2) coatings. Single fiber pushout testing has been used to study the debonding and frictional sliding characteristics under shear loading, with and without the residual radial compressive stress being reduced by applied in-plane tension. It is shown by finite element method (FEM) modeling that it is important to take account of thermal residual stresses when interpreting data from these tests. Prior heat treatments causing interfacial reaction tend to raise the resistance of the interface to debonding and sliding. This is correlated with data from tension testing of composites under axial and transverse loading, with continuous Poisson's ratio monitoring. The behavior under transverse loading is particularly sensitive to the mechanical response of the interface. The presence of interfacial reaction layers tends to inhibit the development of interfacial debonding and void formation under transverse loading, but causes embrittlement and leads to a reduced strain to failure.

The behavior under transverse load has also been studied with superimposed thermal cycling between 400 and 700⪤gC. Strain histories have been monitored using scanning laser extensometry. Under these conditions, thermal stresses have a pronounced influence on the behavior. Many of the steady-state creep characteristics can be successfully modeled on the basis of matrix creep being controlled by volume-averaged stresses (predicted using the Eshelby method), with stress relaxation processes simulated via a variable stress-free temperature. However, the behavior tends to be influenced from a relatively early stage by interfacial damage development. Interfacial debonding and damage, promoted by a combination of opening mode stress from the applied load and shear stress from differential thermal contraction (particularly towards the specimen edges), soon starts to influence the strain history and has a strong influence on the rupture strain. In sharp contrast to the room temperature behavior, the heavily reacted specimens exhibited delayed onset of interfacial damage and a much longer lifetime, although the final strains to failure were similar. These results are considered in terms of stress fields and interfacial properties.
Modeling and Prediction of Crack Arrest in Fiber-Reinforced Composites
Authors: Cardona DC , Barney C , Bowen P
Published: March 2009

This paper addresses the modeling of crack growth resistance of titanium-based metal matrix composites under cyclic loading by considering the conditions necessary to promote the crack arrest of dominant cracks that are often observed in these materials. The presence of dominant cracks facilitates the application of fracture mechanics parameters such as the stress intensity factor, K, and the stress intensity factor range, ΔK, to describe crack growth resistance under monotonic and cyclic loading, respectively. Using such fracture mechanics parameters, weight function methods have been used to model, assess, and predict the onset of crack arrest for cracks growing in both uniform and nonuniform stress fields. The model requires the experimental determination of crack arrest conditions for a particular testpiece geometry, for a given loading condition, and where the specific number of intact bridging fibers is also determined. It can then be used to predict the influence of crack shape and crack size for a variety of testpiece geometries and loading conditions. It is clear that corner cracks and semi-elliptical cracks are potentially more damaging than equivalent through-thickness cracks. Particular attention has also been taken to model the behavior of cracks growing in selectively reinforced composites, and the importance of the thickness of any unreinforced cladding is considered.
Time-Dependent Deformation of Titanium Metal Matrix Composites
Authors: Bigelow CA , Bahei-El-Din YA , Mirdamadi M
Published: March 2009

A three-dimensional finite element program called VISCOPAC was developed and used to conduct a micromechanics analysis of titanium metal matrix composites. The VISCOPAC program uses a modified Eisenberg-Yen thermo-viscoplastic constitutive model to predict matrix behavior under thermomechanical fatigue loading. The analysis incorporated temperature-dependent elastic properties in the fiber and temperature-dependent viscoplastic properties in the matrix. The material model was described and the necessary material constants were determined experimentally. Fiber-matrix interfacial behavior was analyzed using a discrete fiber-matrix model. The thermal residual stresses due to the fabrication cycle were predicted with a failed interface. The failed interface resulted in lower thermal residual stresses in the matrix and fiber. Stresses due to a uniform transverse load were calculated at two temperatures, room temperature and an elevated temperature of 650°C. At both temperatures, a large stress concentration was calculated when the interface had failed. The results indicate the importance of accurately accounting for fiber-matrix interface failure and the need for a micromechanics-based analytical technique to understand and predict the behavior of titanium metal matrix composites.
A Comparison of Analysis Tools for Predicting the Inelastic Cyclic Response of Cross-Ply Titanium Matrix Composites
Authors: Kroupa JL , Neu RW , Nicholas T , Coker D , Robertson DD , Mall S
Published: March 2009

Several micromechanical models that are currently being used for predicting the thermal and mechanical behavior of a cross-ply, [0/90], titanium matrix composite are evaluated. Six computer programs or methods are compared: (1) VISCOPLY; (2) METCAN; (3) FIDEP, an enhanced concentric cylinder model; (4) LISOL, a modified method of cells approach; (5) an elementary approach where the [90] ply is assumed to have the same properties as the matrix; and (6) a finite element method. Comparisons are made for the thermal residual stresses at room temperature resulting from processing, as well as for stresses and strains in two isothermal and two thermomechanical fatigue test cases. For each case, the laminate response of the models is compared to experimental behavior, while the responses of the constituents are compared among the models. The capability of each model to predict frequency effects, inelastic cyclic strain (hysteresis) behavior, and strain ratchetting with cycling is shown. The basis of formulation for the micromechanical models, the constitutive relationships used for the matrix and fiber, and the modeling technique of the [90] ply are all found to be important factors for determining the accurate behavior of the [0/90] composite.
Modeling of Thermomechanical Fatigue in (0/±45/90)s Sigma/TIMETAL 21S Laminates
Authors: Bahei-El-Din YA , Dvorak GJ , Nigam H , Wafa AM
Published: March 2009

Micromechanical modeling is employed to evaluate the stresses and strains in laminated composite plates reinforced by elastic fibers in a thermo-viscoplastic matrix. Loading is limited to uniform in-plane stresses and to uniform changes in temperature. The local fields and macroscopic response of the plies are estimated with the transformation field analysis method that utilizes overall elastic properties and transformation influence coefficients derived from the Mori-Tanaka model. Fiber debonding and sliding are modeled by modifying certain fiber elastic moduli. This methodology, incorporated in a finite element scheme, is applied in simulations of hot isostatic pressing and subsequent loading of a (0/±45/90)s Sigma/TIMETAL 21S laminate. Axial tension/tension stress cycles are applied at constant temperature and in-phase cyclic temperature changes. The results show that the inelastic deformation of the matrix, assisted by extensive fiber debonding in the off-axis plies, promotes stress transfer to the fibers in the 0° plies. Under repeated loads, the fiber stress increases gradually at a certain rate and the laminate fails when the fiber ultimate strength is exceeded.
Fatigue Damage Evolution and Degradation of Mechanical Properties in Silicon-Carbide (SiC) Fiber-Reinforced Titanium Matrix Composites
Authors: Jeng SM , Wang PC , Yang J-M
Published: March 2009

Fatigue damage accumulation and failure modes of several unidirectional and angle-ply SCS-6 fiber-reinforced titanium matrix composites are reviewed. The fatigue damage characteristics of the notched and unnotched composites were classified using several schematic diagrams based upon the constituent's properties and loading conditions. Quantitative relationships between the microstructural damage and stiffness reduction were also established. A shear-lag model incorporating a damage function (which involved the cracking density and length, fiber/matrix frictional stress, and debonding length) was also used to predict residual stiffness of the composites.
Characterization of Crack Growth Resistance Under Cyclic Loading in the Presence of an Unbridged Defect in Fiber-Reinforced Titanium Metal Matrix Composites
Authors: Bowen P
Published: March 2009

This paper considers the experimental characterization of crack growth from unbridged defects in fiber-reinforced titanium metal matrix composites subjected to cyclic loading by the use of fracture mechanics parameters. The conditions under which parameters such as the nominal applied stress intensity range, ΔKapp, the nominal maximum stress intensity factor, Kmax, and the effective stress intensity range, ΔKeff, are of use, and their experimental measurement are considered. Effects of fiber fracture, stress intensity factor range, mean stress, loading configuration (bending versus tension), test temperature, crack size, crack shape, and fiber-matrix interfacial strength on fatigue crack growth resistance are highlighted. The experimental determination of crack arrest in such composites is outlined.
A Hot-Spot Thermal Fatigue Test of a Titanium Matrix Composite
Authors: Wright PK
Published: March 2009

A thermal fatigue test was designed and executed based on heating and cooling of a local spot in a thin titanium matrix composite (TMC) sheet by quartz lamps. This approach offers two features not offered by the load-controlled testing of standard coupons: (1) the stress state is biaxial instead of uniaxial, and (2) the mean stress is primarly compressive instead of tensile. A test rig was constructed to subject a small spot in the center of a 51-by 51-mm sheet of TMC to alternate heating and cooling between room temperature (RT) and 615°C. A specimen of unidirectionally reinforced SCS-6/Ti-6-2-4-2 was subjected to cycling with intermittent inspection for damage. Minimal cracking was observed in this test even after 10 000 cycles. Load-controlled low cyclic fatigue (LCF) and thermomechanical fatigue (TMF) tests were also performed on this material. The observed life in the hot-spot test was significantly greater than uniaxial transverse tensile fatigue load-controlled data would suggest based on a thermal stress analysis of the test panel. However, it was in reasonably good agreement with longitudinal, uniaxial load-controlled out-of-phase TMF data.
A Methodology to Predict Damage Initiation, Damage Growth, and Residual Strength in Titanium Matrix Composites
Authors: Bakuckas JG , Johnson WS
Published: March 2009

In this research, a methodology to predict damage initiation, damage growth, fatigue life, and residual strength in titanium matrix composites (TMC) is outlined. Emphasis was placed on micromechanics-based engineering approaches. Damage initiation was predicted using a local effective strain approach. A finite element analysis verified the prevailing assumptions made in the formulation of this model. Damage growth, namely, fiber-bridged matrix crack growth, was evaluated using a fiber bridging (FB) model that accounts for thermal residual stresses. This model combines continuum fracture mechanics and micromechanics analyses yielding stress-intensity factor solutions for fiber-bridged matrix cracks. In the FB model, fibers in the wake of the matrix crack are idealized as a closure pressure, and an unknown constant frictional shear stress is assumed to act along the debond length of the bridging fibers. This frictional shear stress was used as a curve-fitting parameter to the available experimental data. Figure life and post-fatigue residual strength were predicted based on the axial stress in the first intact 0° fiber calculated using the FB model and a three-dimensional finite element analysis.