Health Monitoring of Composite Material Structures Using a Vibrometry Technique

Non-destructive evaluation (NDE) methods for quantifying and locating damage are essential for inspecting structures to ensure safety and reliability. Transmittance function monitoring is a potentially new NDE technique being tested as a tool to detect, quantify, and locate damage on flexible structures. The technique has a large spatial range that is practical for detecting damage on large composite material structures such as a reusable launch vehicle. The Transmittance Function (TF) theory is based on structural dynamics principles that define how vibration at one point in a structure is related to a force at another point. This relationship is called the Frequency Response Function (FRF). A Transmittance Function (TF) is derived as the ratio of FRFs, and can detect damage because the FRFs change due to damage. If one excitation is used for the testing, the force does not need to be measured to compute the TF. In the damage detection procedure, the structure is subjected to wide-band vibration and TFs are computed between different accelerometers to detect changes in the structure, presumably due to damage. In the first year of the project the TF method was tested on a bolted panel, a curved panel, and beams, all made of fiberglass. It was shown that damage could be detected using low frequency vibration, 250 to 1,250 Hz. The technique is sensitive to damage, but it requires storage of historical or pre-damage TFs for the healthy structure. This would become a large data storage requirement for large structures. Thus one objective for the second year of the project was to eliminate the need to store historical data. The second year report gives details of how storage of historical data was eliminated. Further results of testing panel structures are also given

Health Monitoring of Composite Material Structures using a Vibrometry Technique

Large composite material structures such as aircraft and Reusable Launch Vehicles (RLVS) operate in severe environments comprised of vehicle dynamic loads, aerodynamic loads, engine vibration, foreign object impact, lightning strikes, corrosion, and moisture absorption. These structures are susceptible to damage such as delamination, fiber breaking/pullout, matrix cracking, and hygrothermal strain. To ensure human safety and load-bearing integrity, these structures must be inspected to detect and locate often invisible damage and faults before becoming catastrophic. Moreover, nearly all future structures will need some type of in-service inspection technique to increase their useful life and reduce maintenance and overall costs. Possible techniques for monitoring the health and indicating damage on composite structures include: c-scan, thermography, acoustic emissions using piezoceramic actuators or fiber-optic wires with gratings, laser ultrasound, shearography, holography, x-ray, and others. These techniques have limitations in detecting damage that is beneath the surface of the structure, far away from a sensor location, or during operation of the vehicle. The objective of this project is to develop a more global method for damage detection that is based on structural dynamics principles, and can inspect for damage when the structure is subjected to vibratory loads to expose faults that may not be evident by static inspection. A Transmittance Function Monitoring (TFM) method is being developed in this project for ground-based inspection and operational health monitoring of large composite structures as a RLV. A comparison of the features of existing health monitoring approaches and the proposed TFM method is given

THE_PM_BOK_CODE

This paper puts forward the argument that PM is spreading because it is a well adapted collection of memes, and that the Project Management Institute (PMI®) Guide to the Project Management Body of Knowledge (PMBOK® Guide) version of project management (the PM_BOK Code) has more to do with the appearance of a capability for productivity than it does with actual productivity. It suggests that project management is evolving in a toxic manner, and that corporations will reap more benefit from it than people. The paper concludes with a call for a reformation of the PMBOK®

Walden’s New Journal! Journal of Sustainable Social Change

Walden University announces a change of name for its Journal of Social Change. The new name is the Journal of Sustainable Social Change and will focus more attention on both multi-level socio-economic and environmental systems and sustainability (defined as long-term quality of life

Integrating Animal and Human Data: A Health Based Risk Assessment for Acrylonitrile

Epidemiologic studies of workers exposed to acrylonitrile (ACN) have not found a significant increase in central nervous system (CNS) cancer mortality. In contrast, bioassays have consistently found elevated incidence of CNS cancer. A linearized multistage model for estimating excess lifetime risk from bioassay data was used to examine whether the CNS cancers predicted from a rat bioassay and the CNS cancers observed in epidemiologic studies were consistent. Several steps were performed to complete the calculation of the CNS cancers predicted from the rat bioassay in human cohorts- (1) the excess lifetime risk was adjusted for less than complete lifetime follow-up in the epidemiologic study, and applied to all cohort members and, (2) the predicted excess deaths were added to the expected background deaths for the cohort and compared to the observed. The model predicted 1.88 and 1.83 CNS cancer deaths for two large epidemiologic studies-(Collins et al, 1989, J.Occup.Med. 31, 368-371) and (Swaen et al, 1992, J.Occup.Med. 34, 801-809)-similar to the observed CNS cancer deaths, and well within the 95% CI of the observed, (0.03-5.6) and (0.6-8.8), respectively. Small numbers of excess CNS cancer deaths were predicted because of low exposure levels and large adjustments for less than complete lifetime follow-up in the epidemiologic studies.Master of Science in Public Healt

Besturen in commissie

Nederland bestuurt in commissie. Bepaald niet iedereen is daar gelukkig mee. Regelmatig klinkt de roep om het mes te zetten in het aantal commissies (zie bijvoorbeeld Duyvendak en Van de Koppel 2005).1 Commissies zouden vooral dienen als werkverschaffing voor bestuurders van weleer. Ze worden opgevat als synoniem voor alles wat stroperig is, geen resultaat oplevert en afbreuk doet aan het politieke primaat. In dat licht verzocht de Tweede Kamer al eerder per motie het aantal onderzoeks- en adviescommissies te beperken.2 De minister van Bestuurlijke Vernieuwing uit het vorige kabinet, Alexander Pechtold, liet weten ‘gek te worden van adviescommissies’ toen hij een bundel met opstellen over het verschijnsel kreeg aangeboden.3 Diverse ministers uit eerdere kabinetten hebben hun tanden er al op stukgebeten, maar een beroep doen op commissies lijkt onuitroeibaar als fenomeen. Dat vraagt om een nader onderzoek naar ‘besturen in commissie’. Want wat weten we er eigenlijk precies vanaf? Hoeveel commissies worden er ingesteld? Waarom worden ze ingesteld? Wie wil afrekenen met de veelheid aan commissies die Nederland kent, doet er goed aan zich eerst te verdiepen in de redenen die er zijn om keer op keer toch weer van hun diensten gebruik te maken