bluuebunny/crossref_metadata_2025_split huggingface dataset:
Calculation of Stress Intensity Factors for Interface Cracks Under Mixed-Mode Loading
Authors: Naik RA , Crews JH 
Published: March 2009

A simple technique was developed using conventional finite element analysis to determine stress intensity factors (K1 and K2) for interface cracks under mixed-mode loading. This technique involves the calculation of crack-tip stresses using nonsingular finite elements. These stresses are then combined and used in a linear regression procedure to calculate K1 and K2. The technique was demonstrated by calculating K1 and K2 for three different bimaterial combinations.
For the normal loading case, the calculated K1 and K2 were within 2.6% of an exact solution. The normalized K1 and K2 under shear loading were shown to be related to the normalized K1 andK2 under normal loading. Based on these relations, a simple equation was derived for calculating K1 and K2 for mixed-mode loading from a knowledge of K1 and K2 under normal loading. Thus, for a given material combination and geometry, only one solution of K1 and K2 (under normal loading) is required to determine K1 andK2 over the full range of mixed-mode loading conditions.
The equation was verified by computing K1 and K2 for a mixed-mode case with equal normal and shear loading. The correlation between the exact and the finite element values was very good with errors of less than 3.7%.
This study provides a simple procedure to compute the K2/ K1 ratio, which can be used to characterize the stress state at the crack tip for various combinations of materials and loadings. Tests conducted over a range of K2/ K1 ratios could be used to characterize fully interface fracture toughness.
A Historical Overview and Discussion of Computer-Aided Materials Testing
Authors: Braun AA 
Published: March 2009

Consistency of test data has always been a key concern in any materials testing application. Test technique or method, operator skill and experience, and capabilities of the apparatus are all parameters that affect the consistency of the desired information. The arrival of testing automation has contributed significantly to improving the consistency of materials testing apparatus, modifying existing test methods, creating new test methods due to enhanced capability, and improving the productivity of testing systems.
This paper surveys the development of computer-aided testing over the last 20 to 25 years and includes a discussion of current systems implementations and the emerging area of laboratory-wide automation. The rapid development of materials testing automation capability has generally tracked the trends in the computer industry. Advances in microprocessor hardware technology have driven testing automation by allowing for embedded intelligence in key test system components and by allowing for high-performance supervisory computer subsystems to control or supervise the overall test rig. Software technology advances in concert with expanding hardware capability have provided truly useful real-time operating environments, more efficient applications development tools, and higher productivity through more intuitive user interface technology. All together, these technology improvements have allowed for more sophisticated, consistent, and higher performance testing automation. Further improvements will be realized through the true utilization of the emerging digitally based systems architectures and emerging networking technology. This discussion concludes with a brief look at where emerging capabilities such as these will allow for new types of experiments to be performed and where information management will be enhanced, thus allowing for greater productivity in the test laboratory.
Computer Applications in Full-Scale Aircraft Fatigue Tests
Authors: Hewitt RL , Rutledge RS 
Published: March 2009

The development of computerized load processing techniques for application to a full-scale fatigue test of the aft fuselage and empennage of a Canadian Forces CT-114 (Tutor) aircraft is described. The procedures used to select significant end points from the flight loads and to eliminate nondamaging maneuvers are presented together with the development of the test actuator loads required to simulate the flight cases. The optimization procedure used to minimize the error in the applied load distribution, based on the sensitivity of stresses at critical locations to errors in the test loads, is also given.
The integration of the load control and multichannel data acquisition systems is described. By taking and automatically checking data on specific load cycles on a continuous basis throughout the test, it was possible to get immediate notification of any structural changes that occurred and check the functioning of the test system. Two examples are given that demonstrate the use of this integration.
Computer-Aided Laser Interferometry for Fracture Testing
Authors: Maji AK , Wang J 
Published: March 2009

The fracture process in quasi-brittle materials such as concrete, rocks, and ceramics is characterized by localized cracking and an R-curve type of behavior due to the fracture process zone. Accurate estimation of materials toughness can be determined only if the exact crack-tip location is known and the influence of the process zone can be measured.
In the nondestructive evaluation (NDE) of steel bridges, the location of cracks is a difficult problem, particularly due to lack of accessibility and due to the sheer size and number of the bridges that require inspection. Adequate tools for nondestructive inspection are therefore needed.
In recent years, laser interferometry techniques have proven to be major assets in accomplishing these tasks. Image analysis systems have removed the need for chemical processing, and optical data can be processed in real time by personal computers. These advances have led to new uses for laser techniques both for locating fractures and for assessing fracture parameters of materials.
A Computer-Aided Technique for the Determination of R-Curves from Center-Cracked Panels of Nonstandard Proportions
Authors: Sutton GR , Thomas CE , Wheeler C , Wilson RN 
Published: March 2009

The development of a technique for the measurement of fracture toughness using computer-aided data collection and analysis has greatly reduced the computation time, increased accuracy, and enabled crack resistance curves to be determined from center-cracked panels of nonstandard geometries. The effective crack length is determined from compliance measurements and a geometric correction to stress intensity factor for nonstandard geometries derived from fatigue crack growth data and from energy release-rate calculations. Fracture toughness tests have been conducted on panels up to 2 m wide with a length-to-width ratio of 0.5.
The technique is illustrated using results showing the effect of panel size and geometry for the 2024-T3 aluminum alloy.
A Computerized Variable Amplitude Fatigue Crack Growth Rate Test Control System
Authors: Joyce JA , Wright W 
Published: March 2009

The objective of this paper is to present a low cost control system for servohydraulic load frames to perform variable amplitude fatigue crack growth rate testing. The system consists of a relatively low cost personal computer equipped with two combination 12 bit A/D-D/A cards. A four channel simultaneous A/D card is used for reading load and CMOD from the specimen while a second card provides real-time function generation of the command signal. Depending on the loads and specimen size, variable amplitude loading can be applied at high speeds of up to 100 Hz, thereby minimizing the time required for threshold type testing. This system can be connected easily to existing hydraulic equipment and will provide variable amplitude capability that is both low in cost and flexible enough to perform specialized testing.
The system is capable of automatically shedding loads under both constant R-ratio and constant Kmax conditions, and could be adapted easily to other specialized types of testing. Both crack length and ΔK are calculated continuously using the compliance of the specimen. In addition, crack closure analysis is performed from the compliance data to calculate ΔKeff. The results of tests performed on high strength-low alloy structural steel used for highway bridge construction are presented to demonstrate the capabilities of the system.
Load Simulation Test System for Agricultural Tractors
Authors: Nishizaki K 
Published: March 2009

To establish an evaluation technology on the reliability for agricultural tractors, we have developed a field simulation system to evaluate the durability of agricultural tractors.
The load simulation system for the power take-off (PTO) shaft and the road (road-load) simulation system utilizing the “remote parameter control” principle are described.
First, experimental studies on the PTO load simulation system prove the possibility of laboratory simulation by using actual loads. This system includes the analysis of torque and revolution data frequency and the modification (editing) of the load pattern (actual data).
Second, experimental studies on the road-load simulation prove that with the utilization of the “remote parameter control” method it is possible to obtain excellent results when working with a servohydraulic test system. Some factors that affect the simulation processes, which are different for different tractors, are also shown.
Fatigue and Fracture Analysis of Type 316L Thin-Walled Piping for Heavy Water Reactors: Crack Growth Prediction Over 60 Years (With and Without Stratification) and Flawed Pipe Testing
Authors: Poole AB 
Published: March 2009

Thermal stresses in piping produce through-wall stress gradients that may influence crack growth in the pipe wall. In heavy water reactors (HWRs), the pressure-induced stress in piping is small due to the low pressure values. For major HWR plant transients, the thermal stresses (both wall profile and bending due to axial thermal growth) provide approximately 80% of the nominal pipe stress. Cases of local thermal stratification can provide a significant increase in the pipe stresses and the number of stress cycles applied to the piping. One focus in this paper will be to assess the impact of thermal stresses, in general, and thermal stratification, in particular, on the growth of flaws in a pipe due to fatigue loadings. The study will evaluate both the primary loop piping and the pressurizer surgeline piping. Evaluations of fatigue crack growth will be developed for both base material and weldments. The crack growth analysis for 60-year operation of a HWR plant will be reviewed. This analysis will be provided for the primary loop piping and the pressurizer surgeline piping and will establish the worst-case flaw size predicted from fatigue analysis by end of life.
Full-scale flawed pipe fracture testing has been completed at the Oak Ridge National Laboratory (ORNL) in an approach to show the improbability of an instantaneous double-ended-guillotine break (DEGB) for HWR primary piping. This testing required a major facility (Pipe Impact Test Facility, PITF) to apply all possible design loads, including an equivalent major earthquake (called the SSE earthquake). The facility was designed and built at ORNL in six months. The test article, a 6.1-m (20-ft) long, 406-mm (16-in.) diameter, Schedule 40, 316 L Type stainless steel pipe was fabricated to exacting standards and inspections following the nuclear industry standard practices. A flaw was machined and fatigued into the pipe at a butt weld as an initial condition. The flaw/crack was sized to be beyond the worst-case flaw that HWR piping could see in 60 years of service—if all leak detection systems and if all crack inspection systems failed to notice the flaw's existence.
Since October 1991, the test article was subjected to considerable overloadings. The pipe was impacted 104 times at levels equal to and well beyond the safe-shutdown earthquake (SSE) loadings. In addition, 569 751 fatigue cycles and 20 purposeful static overloads have been applied in order to extend the flaw to establish the data necessary to confirm fracture mechanics theories, and, more importantly, to simply demonstrate that an instantaneous DEGB is highly improbable for a HWR primary system at an operating pressure of 1.72 MPa and temperature of 110°C.
Prediction of the Fatigue Life of Mechanical Structures
Authors: Flavenot J-F 
Published: March 2009

Methods for analyzing service time histories and simulating fatigue conditions are now well known and incorporated into application software. However, they carry a risk, if used routinely, that the effects of interaction of the material, the fatigue loading conditions, and the structural design are often too complex for correct evaluation using a single method of approach.
The first part of this paper presents the different phases that must be included in the methodology for predicting service fatigue life and recommends any steps in which the analysis parameters (significant amplitude level of maximum cycles or nondamaging cycles, choice of low- and high-truncation levels of the spectrum, choice of counting method, etc.) may be in contradiction with the real damage process of the material.
After determining the correct loading history, different ways of predicting fatigue life using two methods are presented, namely, 1. the use of damage laws for predicting the crack initiation life (or the damage tolerance approach with modeling of crack propagation), and 2. simulation of the loading history on a fatigue machine. The methodology used in this approach is presented together with precautions to be taken. These two methods are explained, along with the importance of the interaction of the material properties, the fatigue loading, and the design.
Fatigue Testing and Life Prediction for Notched Specimens of 2024 and 7010 Alloys Subjected to Aeronautical Spectra
Authors: Bleuzen C , Chaudonneret M , Farcy L , Flavenot J-F , Ranganathan N 
Published: March 2009

Tension compression fatigue tests were carried out on notched specimens made of aluminum Alloys 2024 and 7010. For Alloy 2024, the specimens were submitted to an aeronautical spectrum developed from a transport aircraft spectrum using different percentages of low-level cycle omission (omission of cycles as a function of the mean stress). For Alloy 7010, a landing gear load spectrum was used. Other tests were carried out with simplified loading sequences in order to study the influence of under- or over-stressing on the fatigue damage. The experimental fatigue life up to crack initiation was measured using the electrical potential drop method (crack initiation on the order of 0.1 to 0.4 mm). Tests were also carried out in order to determine the fatigue properties of the materials tested.
Three methods of fatigue life prediction were tested. In the first method, developed by Office National d'Etudes et de Recherches Açrospataics (ONERA), the notch effect was taken into account using the Neuber calculation and the fatigue damage was calculated using a nonlinear damage accumulation law (Lemaitre-Chaboche). The two other methods consist of using the local strain life approach with Fatimas software or Glinka's method that takes the notch aspect into account using the Neuber calculation and the fatigue damage calculation using Miner's law.
A comparison of the results obtained using these three methods of fatigue life prediction shows that a better prediction is obtained when a nonlinear damage accumulation law is used. Nevertheless, it can be noted that the three different methods used in the study often give a nonconservative prediction of the fatigue life.
The Relation Between Rheology, Artificial Weathering, and Urethane Sealant Performance
Authors: Leonard NE , Malik TM 
Published: March 2009

There has been vigorous debate on the ability of urethane sealants to withstand the conditions found in high-performance construction applications. A number of studies have suggested that multicomponent urethanes, as a generic technology, are unable to endure the high heat, humidity and ultraviolet light found in some parts of the world.
This paper argues that it is incorrect to make blanket statements about the performance characteristics of any sealant technology, whether it is silicone or organic. The focus is, however, on multicomponent urethanes. Results of standard ASTM xenon and QUV tests are discussed. Several novel test regimens, including the “frog pond test” and sophisticated Theological techniques, are also reviewed. To gather as much data as possible, samples were run through these procedures for as long as 7000 hours.
This paper outlines several important conclusions. First, silicones actually have a higher modulus at cold temperatures (below -35°C) than the multicomponent urethanes examined. Second, the wide range of performance results in the urethanes tested highlights the fallacy of blanket statements about these sealants. Some were clearly unable to endure the conditions to which they were exposed. Other multicomponents, however, did not degrade. Rheological techniques are used to augment the data provided by the traditional QUV and xenon procedures.
Performance of Bridge Deck Concrete Overlays
Authors: Babaei K , Hawkins NM 
Published: March 2009

This paper documents performance of twelve concrete bridge decks in Washington State that were rehabilitated and/or protected with latex-modified concrete and low-slump dense concrete overlays in order to prevent further deicing salt penetration and concrete deterioration caused by reinforcing steel corrosion. An evaluation is made of the factors that have affected the serviceability of those overlaid bridge decks, and recommendations are made based on that evaluation for the design and construction of concrete overlays in order to improve bridge deck performance and to extend bridge deck service life. The factors evaluated are overlay freeze-thaw scaling, surface wear and skid resistance, surface cracking, bond with the underlying deck, chloride and water intrusion, and finally the concrete overlay's ability to retard continued reinforcing steel corrosion and corresponding concrete deterioration.
The results of the evaluation indicate that, regardless of concrete deterioration caused by reinforcing steel corrosion, concrete overlaid bridge decks will require resurfacing after about 25 years of service. That maintenance will be needed as a result of traffic action and weathering. Typical forms of distress are freeze-thaw scaling, extensive wear in wheel lines, lack of skid resistance, and the loss of overlay bond. Concrete overlays are resistant but not impermeable to chloride infiltration. Further contamination of the underlying deck occurs in time depending on the rate of salt application. There are indications that the continued corrosion of reinforcing steel in the salt-contaminated underlying deck is less extensive in the absence of overlay surface cracking. There are numerous reasons for concrete overlays cracking during construction and service, and those reasons and their relation to the performance of bridge decks is discussed.
Orthotropic Steel Plates for Bridge Deck Replacement
Authors: Stahl FL 
Published: March 2009

A large number of our nation's bridges have reached the age where serious deterioration requires replacement of the roadway deck. Where first cost is the determining factor, replacement in kind—usually reinforced concrete—is the normally accepted method. However, where life cycle costs are considered, or where availability of traffic capacity during commuting hours is important, orthotropic steel deck construction offers a practical solution.
Orthotropic deck construction consists of a steel plate stiffened by single web (open) or double web (closed) ribs and paved—usually prior to installation—with a layer of asphalt. In a typical application, a section of the old deck is cut and removed during low-density traffic hours and immediately replaced by a modular section of new orthotropic deck. As soon as this section is connected to the supporting framework, it can be opened to traffic without restrictions. Several such decks have been installed recently on major bridge structures, similar in principle but quite different in details and execution.
Analysis of Additive Metals in Lubricating Oils
Authors: Mackey JR , Watt ST , Cardy CA , Smith SI , Meunier CA 
Published: March 2009

Additive elements such as Ba, Ca, Zn, Cu, Cl, P and Mg are added to lubricating oils for improved engine performance. Although necessary, additive concentrates are very expensive and it is important that refineries blend within the required specifications using reliable and accurate analytical techniques to measure the metal concentrations.
This paper is an overview of additive element analysis in lubricating oils at the Esso Petroleum Canada Research Centre. A comparison of the two current techniques, wavelength dispersive X-ray fluorescence (WXRF) and simultaneous inductively coupled plasma emission spectroscopy (ICPES), will be described.
We will give a brief summary on the scope, theory, and methodology of each technique plus the strengths and weaknesses of each method as they relate to fresh and used oils. A comparison of the precision between WXRF and ICPES will be examined as well as the use of robotics to improve precision and turnaround time with the ICPES method.
Our hope is to give the nonexpert a better understanding of the advantages and disadvantages of WXRF versus ICPES when choosing instrumentation or methodology for analyzing additive elements in fresh and used lubricating oils.
Analysis of Lubricant Additive Elements by X-Ray Fluorescence and Supporting Methods
Authors: Sieber JR , Salmon SG , Williams MC 
Published: March 2009

At Texaco's Research Center, X-ray Fluorescence (XRF) is our workhorse method for the determination of additive elements in lubricating materials. Other analysis techniques are used to assist in method development by confirming compositions of standards and quality control samples, or by verifying analysis results from newly developed XRF methods.
Often it is impractical to make a determination of all analytes in a sample by XRF due to inherent limitations of X-ray fluorescence measurements and the complexity of calibrating for many analytes in a single method. Analyses of high volumes of samples can be made more efficient by omitting difficult or infrequently encountered elements. When a unique sample comes along, alternative analytical techniques are used to determine elements for which the X-ray spectrometer is not sensitive or not calibrated. These concentrations can be combined with theoretical influence coefficients to correct existing XRF calibrations for the effects of unanalyzed elements. A working example, sodium in research samples, is given. Another example, barium in oils, shows the serious shortcomings of this approach. Alternative techniques such as inductively coupled plasma atomic emission spectroscopy, atomic absorption spectrometry, sulfur determination by high temperature combustion with infrared detection, and wet chemical methods can be used to complete an analysis or to confirm the accuracy of XRF methods for determinations of additive elements in lubricants. Examples of our elemental analysis methods, how they relate to ASTM procedures, and how we use our techniques are described.