Automated Fiber Placement Defect Identity Cards: Cause, Anticipation, Existence, Significance, and Progression

Automated Fiber Placement (AFP), a major composite manufacturing process, can result in many defects during the layup process that often require manual corrective action to produce a part with acceptable quality. These defects are the main limitation of the technology and can be hard to categorize or define in many situations. This paper provides a thorough definition and classification of all AFP defects. This effort constitutes a comprehensive and extensive library relevant to AFP defects. The defects selected and defined in this work are based on understanding and experience from the manufacture and research of advanced composite structure. Proper classification of these defects required an in-depth literature review and consideration of various viewpoints ranging from designers, manufacturers, analysts, and inspection professionals. Collectively, these sources were utilized to develop the most accurate view of each of the individual defect types. The results are presented as identity cards for each defect type, intended to provide researchers and the manufacturing industry a clear understanding of the (1) cause, (2) anticipation, (3) existence, (4) significance, and (5) progression of the defined AFP defects. The link between AFP defects and process planning, layup strategies, and machining was also investigated. Categorization of all important automated fiber placement defects is presented

Experimental Analysis and Analytical Modeling of Bridges With and Without Diaphragms

Two prestressed concrete (P/C) I-girder bridges along the coal haul route system of Southeastern Kentucky were constructed with a 50 degree skew angle. One of the bridges has concrete intermediate diaphragms, while the other bridge has no intermediate diaphragms. Bridges of similar design along coal haul routes have experienced unusual concrete spalling at the interface of the diaphragms and the bottom flange of the girders. The purpose of this report is to identify the cause of the damage, and to evaluate the effectiveness of intermediate diaphragms. Experimental static and dynamic field testing was conducted on both bridges. All field tests were completed prior to the opening of the bridges. Once the calibration of the finite element models was completed using the test data, analyses were conducted with actual coal haul truck traffic to investigate load distribution and the cause of the spalling at the diaphragm-girder interface. Based on the results obtained in this research study, a significant advantage in structural response is generally not noted due to the presence of intermediate diaphragms. Although large differences were noted percentage wise between the responses of the two bridges, analyses suggested the bridge without intermediate diaphragms will experience displacements and stresses well within AASHTO and ACI design requirements. Finite element analyses also revealed the cause of concrete spalling witnessed in the diaphragm-girder interface region. The tendency of the girders to separate as the bridge was loaded played a large role in generating high stress concentrations in the interface region. Other mitigating factors were the presence of the diaphragm anchor bars and the fact the bridge is subjected to the overloads of coal trucks. Resolving this problem would in some measure require the removal of the concrete intermediate diaphragm. However, the total elimination of intermediate diaphragms is not recommended since they are required during construction and in the event the deck is to be replaced. The use of temporary steel diaphragms, therefore, is recommended as substitutes for the concrete intermediate diaphragms

Barge Traffic on Kentucky Rivers

Kentucky currently has the second longest navigable inland waterway system in the United States. Prior to the design of a bridge at a specific location on a river, a thorough investigation of barge traffic at that location ust be conducted. This report investigates the barge traffic on all navigable waterways in Kentucky. This report provides the data necessary to develop the risk assessment procedures for Kentucky vessel impact design problems in accordance with the AASHTO Guide Specification and Commentary for Vessel Collision Design of Highway Bridges design Method II. Method II is more rigorous to apply than Method I, but it is recommended by the guide specification for most bridges and should lead to more economical designs. A computer program was written to process the database and calculate the probability based length, width, and capacity for each barge category. Additionally, a second computer program was written to calculate the probability based number of barges in a flotilla column and row, and subsequently categorize that flotilla based upon the barge length and width categories designated by the U.S. Army Corps of Engineers. The equivalent static impact loads were then calculated using the probability based flotilla sizes and tonnages. The calculations for the Maysville, KY bridge over the Ohio River are offered as a design example

Barge Impact Loads for the Maysville Bridge

This report provides the barge equivalent static load distribution data needed to apply method II of vessel impact design for the Maysville, Kentucky bridge over the Ohio River. The information provided in this report is in accordance with the AASHTO Guide Specification and Commentary for Vessel Collision Design of Highway Bridges. A computer program was written to process the database and calculate the probability based length, width., and capacity for each barge category. Additionally, a second computer program was written to calculate the probability based number of barges in a flotilla column and row, and subsequently categorize that flotilla based upon the barge length and width categories designated by the U.S. Army Corps of Engineers. The equivalent static impact loads were then calculated using the probability based flotilla sizes and tonnages. The results indicated 12 barge categories occurring along the Maysville section of the Ohio River. The associated frequencies and impact loads are reported. The equivalent static load for the usually neglected 290 x 54 foot barge was calculated to be a maximum of 8,140 kips with a significant frequency of occurrence of 205 downbound passages per year

Source Zones, Recurrence Rates, and Time Histories for Earthquakes Affecting Kentucky

Time histories of hypothetical earthquakes, along with their peak-particle accelerations, and 0 and 5 percent damped response spectra are developed as guidelines for the seismic design of highway structures and bridges within Kentucky. The time histories are derived through the use of random vibration analyses, and take into consideration the probability of earthquakes from nearby seismic zones, the attenuation of ground motions with distance in the Central United States, and the possibility of a random event occurring outside of the generally recognized zones of seismicity in the area. Suggested peak-particle accelerations, time histories, and response spectra are intended for use at sites where the structure is assumed to be situated at the top of a bedrock foundation. For sites underlain by soils, and in particular for those sites underlain by poorly consolidated soils, it is recommended that site specific investigations be conducted by qualified professionals in order to determine the possibilities of frequency-dependent amplification (including resonance), damping, and soil failure when subjected to the suggested time histories. It should be noted that the seismic data is generated at the county seat and not at the county centroid

Digging into acceptor splice site prediction : an iterative feature selection approach

Feature selection techniques are often used to reduce data dimensionality, increase classification performance, and gain insight into the processes that generated the data. In this paper, we describe an iterative procedure of feature selection and feature construction steps, improving the classification of acceptor splice sites, an important subtask of gene prediction. We show that acceptor prediction can benefit from feature selection, and describe how feature selection techniques can be used to gain new insights in the classification of acceptor sites. This is illustrated by the identification of a new, biologically motivated feature: the AG-scanning feature. The results described in this paper contribute both to the domain of gene prediction, and to research in feature selection techniques, describing a new wrapper based feature weighting method that aids in knowledge discovery when dealing with complex datasets

The International Space Station Solar Alpha Rotary Joint Anomaly Investigation

The Solar Alpha Rotary Joint (SARJ) is a single-axis pointing mechanism used to orient the solar power generating arrays relative to the sun for the International Space Station (ISS). Approximately 83 days after its on-orbit installation, one of the two SARJ mechanisms aboard the ISS began to exhibit high drive motor current draw. Increased structural vibrations near the joint were also observed. Subsequent inspections via Extravehicular Activity (EVA) discovered that the nitrided case hardened steel bearing race on the outboard side of the joint had extensive damage to one of its three rolling surfaces. A far-reaching investigation of the anomaly was undertaken. The investigation included metallurgical inspections, coupon tests, traction kinematics tests, detailed bearing measurements, and thermal and structural analyses. The results of the investigation showed that anomaly had most probably been caused by high bearing edge stresses that resulted from inadequate lubrication of the rolling contact. The profile of the roller bearings and the metallurgical properties of the race ring were also found to be significant contributing factors. To mitigate the impact of the damage astronauts cleaned and lubricated the race ring surface with grease. This corrective action led to significantly improved performance of the mechanism both in terms of drive motor current and induced structural vibration

Religious Fundamentalism as an Obstacle to Peace in the Middle East: Under What Conditions Might Pragmatism Prevail?

Religious fundamentalists have in several instances served as barriers to the peaceful conclusion of disputes in the Middle East, especially in the framework of the peace process in the Israeli-Palestinian conflict. As a consequence and irrespective of the specific definition of fundamentalism, these groups can constitute in various countries a substantial hurdle for any arms control initiative such as the upcoming Middle East Conference (MEC). This gathering is to deal with the establishment of a zone free of all kinds of weapons of mass destruction (WMD) and their delivery vehicles (DVs). Achieving a successful and sustainable outcome at the MEC could be hampered by a host of problems, one of which is the diffi cult role that religious fundamentalism could possibly play in undermining this initiative. Hence, this POLICY BRIEF provides decision makers and practitioners with information on these presumably ‘negative’ actors, drawn from case studies covering various fundamentalist groups within the Middle East and beyond. These recommendations are based on the key finding that, contrary to mainstream expectations, the major players can behave pragmatically, provided they are acting in favorable circumstances