bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Method for Calculating Strain Energy Release Rates in Preliminary Design of Composite Skin/Stringer Debonding Under Multiaxial Loading
Authors: Krueger R , Minguet PJ , O'Brien TK 
Published: April 2008

Three simple procedures were developed to determine strain energy release rates, G, in composite skin/stringer specimens for various combinations of uniaxial and biaxial (in-plane/out-of-plane) loading conditions. These procedures may be used for parametric design studies in such a way that only a few finite-element computations will be necessary for a study of many load combinations. The results were compared with mixed-mode strain energy release rates calculated directly from nonlinear two-dimensional plane-strain finite-element analyses using the virtual crack closure technique. The first procedure involved solving three unknown parameters needed to determine the energy release rates. Good agreement was obtained when the external loads were used in the expression derived. This superposition technique, however, is applicable only if the structure exhibits a linear load/deflection behavior. Consequently, a second modified technique was derived which was applicable in the case of nonlinear load/deformation behavior. The technique, however, involved calculating six unknown parameters from a set of six simultaneous linear equations with data from six nonlinear analyses to determine the energy release rates. This procedure was not time efficient, and hence, less appealing.
Finally, a third procedure was developed to calculate mixed-mode energy release rates as a function of delamination lengths. This procedure required only one nonlinear finite-element analysis of the specimen with a single delamination length to obtain a reference solution for the energy release rates and the scale factors. The delamination was subsequently extended in three separate linear models of the local area in the vicinity of the delamination subjected to unit loads to obtain the distribution of G with delamination lengths. This set of subproblems was solved using linear finite-element analyses, which resulted in a considerable reduction in CPU time compared to a series of nonlinear analyses. Although additional modeling effort is required to create the local submodel, this superposition technique is very efficient for large parametric studies, which may occur during preliminary design where multiple load combinations must be considered.
Damage-Tolerance-Based Design of Bolted Composite Joints
Authors: Qing X , Sun H-T , Dagba L , Chang F-K 
Published: April 2008

An approach based on damage tolerance is proposed for the design of bolted composite joints. The approach requires knowledge of failure processes and damage accumulation in composites under physical loading. Based on experimental observation, a progressive damage model was developed for predicting the accumulated damage and failure modes in composite joints.
In order to utilize the model for design, a computer code, 3DBOLT, has been developed. The code is based on the progressive damage model, and it interfaces with the commercial finite-element code ABAQUS to perform calculations of three-dimensional stresses, strains, and deformations of the joints for a given load. for a given joint configuration, ply orientation, and loading condition, the code can predict the response of the joint from the initial loading to final failure, estimate accumulated damage in the joint as a function of applied load, and predict the joint deformations. In order to verify the proposed damage model, the data obtained from the experiments were compared with the predictions from the 3DBOLT/ABAQUS code. Based on the code, a parametric study was performed to characterize several important factors that can significantly influence the design of bolted composite joints.
Flammability and Sensitivity of Materials in Oxygen-Enriched Atmospheres: 10th Volume
Authors: Steinberg TA , Newton BE , Beeson HD 
Published: April 2008

Description
The tenth volume in this ongoing series provides 28 peer-reviewed papers written by experts in their field. This unique publication gives you the latest information available on flammability and sensitivity of materials in oxygen-enriched atmospheres, including oxygen compatibility and risk management concepts and practices. Topics include:
Ignition and Combustion of Nonmetals covers resistance of polymers to ignition by pneumatic impact; assessment of nonmetallic materials that are used in oxygen systems with a focus on toxicity; statistical evaluation of upward flammability testing (NASA STD 6001 Test 1 ) and ignition of materials exposed to liquid oxygen by mechanical impact.
Ignition and Combustion of Metals presents work evaluating metallic filters for use in oxygen systems; a unique ultrasonic system used to measure the melting rate of the metal rods while burning in oxygen in both normal gravity and reduced gravity; stainless steel promoted ignition tests under flowing conditions; a model for the ignition of rods and tubes in flowing oxygen; microanalysis of aluminum rods that were burned in oxygen and either quenched or self-extinguished; and several ignition-combustion test programs.
Failure/Hazard Analysis and Safety focuses on the documentation of failures and their causes; and techniques being used and developed to analyze systems or components operating in oxygen-enriched atmospheres to ensure system functionality and personnel safety. Papers cover a new technique for analyzing large systems based on prioritizing system components based on operating conditions; an analysis of the space shuttle external tank pressurization system; a failure analysis of fires that have been occurring in oxygen production process valves; a review of some incidents in oxygen systems that have occurred in Australia over a 30-year period; cause and origin analyses of fires; and an electronic database being used by NASA White Sands Test Facility to perform and archive oxygen system/component hazards analyses.
The final section discusses a diverse range of topics, including a parametric model examining nonmetallic materials that are contaminated or damaged being used in oxygen environments; and optical techniques used to view oxygen system fires.
This new publication is an invaluable source of new information and is highly relevant to individuals and organizations that own, operate, or in any way interface with oxygen systems or oxygen-enriched atmospheres.
Joining and Repair of Composite Structures
Authors: Kim H , Kedward KT 
Published: April 2008

Description
Twelve peer-reviewed papers provide the latest information on the design, analysis, testing, and fabrication of structural joint and attachment configurations. Topics cover:
Adhesively Bonded Attachments includes two useful analysis techniques on closed-form model development and the development of a test specimen configuration suitable for the strength measurement of lap joints loaded under in plane shear. This section also investigates a new double-strap joint design configuration that makes use of extra attachments to improve significantly the joint strength; the correlation between analysis and testing of thick section thermoplastics composite-to-titanium for a marine application; and a "bondable" peel ply application for bonding fiberglass skins to a polyamide honeycomb core.
Adhesively Bonded Repair addresses the repair of new armor concepts that are to be used on advanced composite military vehicles, with particular focus on characterizing the dynamic response of the adhesive joints formed in scarf repairs; and the repair of thick steel structures used in earth excavation equipment.
Bolted Attachments discusses mechanically-fastened joints, as well as cover bolted and riveted composite joint analyses; the Strain Invariant Failure Theory (SIFTŕ bolted joint failure prediction; and the use of nonlinear finite element analyses for predicting failure in composite joints based on lamina-level failure criteria
Advances in Geosynthetic Clay Liner Technology: 2nd Symposium
Authors: Mackey RE , von Maubeuge K 
Published: April 2008

Description
Ten-peer reviewed papers give you the latest information on geosynthetic clay liner (GCL) technology. Topics address the ability of the current ASTM standards to assess GCLs, and how they can be improved to better meet the needs of the industry; compatibility and longevity testing of GCLs; and new testing methods to advance the understanding of GCLs and their components.
Sections cover:
Assessment of Clay Component—examines various aspects of testing the clay component and what knowledge these test results generate for the user.
Durability of Clay Component—provides a better understanding of liquid/soil interactions with the bentonite and their possible effects on the durability of the clay component of the GCL.
Evaluation of Current and Proposed GCL Standards—discusses ASTM standards D 5889 Practice for Quality Control of Geosynthetic Clay Liners; D 6495 Guide for Acceptance Testing of Geosynthetic Clay Liners; and D6243 Test Method for Determining the Internal and Interface Shear Resistance of Geosynthetic Clay Liner by the Direct Shear Method
Movement of Compounds through the GCLs—details investigations on the behavior of GCLs subject to thermal gradients in a containment application; effect of freeze-thaw on the permeation of arctic diesel fuel through GCLs
STP 1456 is a valuable resource for regulators, engineers, and researchers.
A Multiaxial Fatigue Analysis of Fretting Contact Taking Into Account the Size Effect
Authors: Fouvry S , Kapsa P , Vincent L 
Published: April 2008

Fretting damage that consists of cracking or wear generated by debris formation is induced by very small alternated displacements between contacting surfaces. This paper focuses on the quantification of the fretting crack nucleation. Fretting experimental results obtained with a well defined quenched aeronautical steel are analyzed by means of a multiaxial fatigue approach. The plane/sphere configuration was studied under partial slip situations. Validated for classical fatigue conditions, the Dang Van's fatigue prediction is compared to fretting cracking mechanisms. The correlation is achieved according to some conditions : - The friction coefficient operating in the annular partial slip contact has to be identified.
It permits more accurate estimation of the stress loading path. - The loading states which are computed to determine the crack nucleation risk must be averaged on an elementary volume representative of the microstructure of the steel. It allows a convenient size effect consideration regarding the very small material volume stressed below the contact.
Fretting Fatigue of 8090-T7 and 7075-T651 Aluminum Alloys in Vacuum and Air Environments
Authors: Elliott CB , Georgeson AM 
Published: April 2008

The fretting fatigue characteristics of 8090-T7 and 7075-T651 aluminum alloys were investigated. The purpose of this investigation was to determine the relative effects of wear and environmental degradation from laboratory air on the fretting fatigue process.
The fretting fatigue test system used in this experimentation enables testing either in air or a scanning electron microscope vacuum environment. Fretting fatigue damage in vacuum tests was considered as resulting predominantly from wear, whereas damage from tests in air results from the concurrent wear and oxidation mechanisms.
Based on this experimentation, it was concluded that: • Degradation of fatigue life in air due to fretting is caused primarily by wear mechanisms for 8090-T7 aluminum. • Fretting fatigue life in air was greater than fretting fatigue life in a vacuum for the 8090-T7 aluminum under the conditions of this experimentation. • Environmental mechanisms significantly decrease fatigue life due to fretting in air for 7075-T651 aluminum. • Fretting fatigue behavior is material dependent.
Influence of Ambient Air on Nucleation in Fretting Fatigue
Authors: Woodtli J , Trzebiatowski Ov , Roth M 
Published: April 2008

Fretting damage often participates in failures caused by multiple site damage (MSD) as a nucleation process. Fretting itself is an extremely complex degradation process consisting of a combination of mechanical and chemical attacks. In order to avoid damage it is essential to understand which dominating parameter influences the crack nucleation.
The topography of the fracture surface, as well as changes in microstructure provide information about the dominant damage mechanism. An exact differentiation of the predominant damage mechanism can be established by microscopic and metallographic investigations.
Two service failures in axles for ski lifts, which suffered from fretting fatigue, are discussed. Though the macroscopic findings are very similar, the microscopic investigation indicates a completely different crack nucleation mechanism.
Skiing Trauma and Safety: Sixteenth Volume
Authors: Johnson RJ , Shealy JE , Yamagishi T 
Published: April 2008

Description
Ten peer-reviewed papers provide the latest information on winter sports safety, by identifying and reducing the risks in these activities, as well as identifying appropriate treatment when injuries are sustained. Topics include:
• Injuries in Norwegian Ski Resorts 2002—2004
• Observations study on fall trends in snowboarding
• On piste fatalities in recreational snow sports in the U.S.
• Arthroscopic treatment of the first anterior shoulder dislocation in young skiers
• Evaluation of the protective role of helmets in snowboarding
• Functional and release characteristics of Alpine ski equipment
• And more!
The Effect of the Contact Conditions and Surface Treatments on the Fretting Fatigue Strength of Medium Carbon Steel
Authors: Kubota M , Tsutsui K , Makino T , Hirakawa K 
Published: April 2008

Fretting fatigue tests characterized with employing a contact bridge pad clamped to a fatigue specimen were conducted to find the effect of shapes of contact pads. The shapes of the contact edge of the pad used in the test were sharp and round. The relative slip amplitude during fatigue testing was measured and the effect of the location of the displacement sensor was discussed with the result of the stress analysis around the contact area. The effect of molybdenum coating on the fretting fatigue strength was also investigated.
It was found that by using the round edge pad, reproducible fretting scars could be obtained and also the round edge pad prevented the fatigue failure at the contact edge. A remarkable difference of the measured slip amplitude was found by the location of the displacement sensor. The molybdenum coating increases the fretting fatigue limit about 1.5 times that of the fretting fatigue strength of uncoated specimens. Fretting fatigue cracks always initiate at the inner site of the contact area. The results were explained from the results of contact stress analysis where the maximum shear stress occurred at the inner surface of the contact area in both types of the pad.
Integrating Ground Penetrating Radar and Falling Weight Deflectometer Technologies in Pavement Evaluation
Authors: Scullion T , Saarenketo T 
Published: April 2008

The first step in selecting the optimal rehabilitation strategy for any pavement is to identify the cause of the existing defects. In recent years nondestructive technologies such as Falling Weight Deflectometers and Ground Penetrating Radar have been used to evaluate subsurface conditions. However when used independently these technologies are not always adequate for identifying the cause of pavement deterioration. This paper will present the argument for developing an integrated approach to pavement evaluation wherein the high speed GPR survey results can be used to identify homogenous sections, locate potential subsurface defects and estimate layer thicknesses. The GPR then provides critical inputs to both the processing of the FWD data and the interpretation of the results.
In this paper a brief review will be presented on the principles of operation of both air launched and ground coupled GPR systems. Recently developed signal processing techniques for converting the GPR reflected waves into parameters of significance to highway engineers will be described. Five case studies from Texas and Finland will be included which demonstrate how both ground coupled and air launched GPR results can be effectively integrated with the FWD data to make project level decisions.
Nevada's Approach to the Backcalculation Process
Authors: Sebaaly PE , Bemanian S , Lani S 
Published: April 2008

This paper documents the procedures and experiences of the Nevada Department of Transportation (NDOT) with the use of falling weight deflectometer (FWD) testing and backcalculation techniques. NDOT has been actively using these technologies for the past several years. As a result of their active involvement NDOT's pavement engineers have established a great amount of knowledge regarding the collection and analysis processes of FWD data. The paper presents standard field testing protocols and data analyses procedures that have been developed by NDOT's engineers to guide the design and analysis processes.
In addition to the traditional use of FWD data, NDOT has experimented with the application of FWD testing and backcalculation technique in other specialized area such as the assessment of fractured portland cement concrete (PCC) pavements and cold in place recycled (CIR) pavements. The NDOT's experience indicated that even though the FWD technology may not be fully successful in directly assessing the in situ properties of such materials, the technology can be successfully used to evaluate the structural coefficient of these layers. The paper presents the process used to establish these coefficients and documents the values currently used by NDOT.
Seasonal Trends and Causes in Pavement Structural Properties
Authors: Ali H , Selezneva O 
Published: April 2008

The seasonal monitoring program (SMP) of the long term pavement performance (LTPP) program provides an excellent opportunity to study the seasonal trends in pavement response. In 64 pavement sections in the United States and Canada, FWD testing is performed monthly every other year, subsurface temperature is measured hourly, subsurface moisture and freezing conditions are measured monthly, and climatic factors such as ambient air temperature, solar radiation, wind speed, and precipitation are collected continuously.
In this study, a number of SMP sections were used to establish some general and statistically significant trends. The relationship between the elastic modulus of the AC layer and the temperature gradient within the layer was investigated. The relationship between the frost penetration in unbound layers and their backcalculated modulus was studied. Modeling such variability using linear and nonlinear formulations was attempted, and the practical implications of such effects on the data collection practice are discussed.
The results of the analysis showed that the AC layer temperature gradient appears to influence the layer modulus. An exponential model was developed to quantify that effect and adjust the backcalculated modulus to the temperature gradient. Analysis of frost penetration trends showed that surface deflection and the backcalculated subgrade modulus are very sensitive to the existence and extent of a frozen layer within the subgrade. As expected, the thicker the frozen layer, the larger the subgrade modulus, and the further the layer, the lower the subgrade modulus. Exponential models were used to characterize this effect.
Development of a Laser-Based High Speed Deflectograph
Authors: Hildebrand G , Rasmussen S , Andrés R 
Published: April 2008

Today's heavily congested highways provide a difficult setting for bearing capacity measurements using stationary equipment like the FWD resulting in a situation which is dangerous to both drivers and FWD operator. Furthermore, techniques like the FWD method only provide information in discrete points that are often separated several hundred metres apart. To overcome these deficiencies a laser-based high speed deflectograph is being developed which can perform continuous bearing capacity measurements at all driving speeds in the range 20–70 km/h.
The unique concept of the high speed deflectograph utilizes laser Doppler sensors to provide the deflection speed of the pavement surface. By using this technique the deflection speed is determined in one operation as opposed to the more commonly used distance laser sensor method which determines the deflection as the difference between vertical deformation in two different points. The laser Doppler system has been found capable of determining deflection speeds within the desired range of driving speeds with an accuracy of 0.14 mm/sec, which has been shown to correspond to an accuracy of the deflection of 5 μm.
While it is important to measure deflection speeds correctly, it is equally important to continuously register and control the position of the laser sensors using secondary measuring systems like servo systems and inertial units.
The high speed deflectograph consists of a towing truck and a trailer on which the laser sensors are mounted. The trailer is equipped with a system, which allows variations of the applied load.
In parallel with the development of the physical measuring device a study is carried out concerning the interpretation of results from the high speed deflectograph. Results from work carried out to establish a coupling between deflection speeds and absolute deflections, of which the latter can be compared to FWD results, are presented.
Comparative Studies of Backcalculated Results from FWDs with Different Loading Duration
Authors: Matsui K , Kikuta Y , Nishizawa T , Kasahara A 
Published: April 2008

The falling weight deflectometer (FWD) test applies an impulsive force on the surface of pavement and measures surface deflections at several locations. Although the test is dynamic, static backcalculation is commonly conducted to estimate pavement layer moduli using peak values of the impulsive force and surface deflections. However, falling weight defiectometers produced by the different manufacturers often differs in loading duration. The difference may affect backcalculation results, because the FWD test is dynamic in nature.The key issue of this paper is to investigate the effect of the difference on backcalculated layer moduli. First, the difference is numerically studied by conducting static backcalculation on the peak deflection data generated from dynamic analysis with three different loading durations. Secondly, both static and dynamic backcalculations are carried out on the sets of deflections measured by three FWDs with different loading duration. Although the difference between static and dynamic backcalculation results are conspicuous in the case of numerical simulation, but the difference is not significant when actual data are used.