Magnetic properties of ferromagnetic particles under alternating magnetic fields: Focus on particle detection sensor applications

© 2018 by the authors. Licensee MDPI, Basel, Switzerland. The electromagnetic wear particles detection sensor has been widely studied due to its ability to monitor the wear status of equipment in real time. To precisely estimate the change of the magnetic energy of the sensor coil caused by the wear particles, the magnetic property models of wear particles under the alternating magnetic field was established. The models consider the hysteresis effect and the eddy current effect of the wear particles. The analysis and experimental results show that with the increase of the effective field frequency, the change of the magnetic energy caused by the wear particles gradually decrease, which makes the induced electromotive force output by the sensor reduce with the decrease of the particle speed, so a signal compensation method is presented to obtain a unified signal when the same wear particle passing through the sensor in different speeds. The magnetic coupling effect between the two adjacent wear particles is analyzed. The result illustrates that the change of the magnetic energy caused by the dual wear particles system is larger than the sum of the energy variation caused by two independent wear particles, and with the increase of the interparticle distance, the magnetic coupling effect gradually weakens and disappears

Detailed state of the art review for the different on-line/in-line oil analysis techniques in context of wind turbine gearboxes

The main driver behind developing advanced condition monitoring (CM) systems for the wind energy industry is the delivery of improved asset management regarding the operation and maintenance of the gearbox and other wind turbine components and systems. Current gearbox CM systems mainly detect faults by identifying ferrous materials, water, and air within oil by changes in certain properties such as electrical fields. In order to detect oil degradation and identify particles, more advanced devices are required to allow a better maintenance regime to be established. Current technologies available specifically for this purpose include Fourier transform infrared (FTIR) spectroscopy and ferrography. There are also several technologies that have not yet been or have been recently applied to CM problems. After reviewing the current state of the art, it is recommended that a combination of sensors would be used that analyze different characteristics of the oil. The information individually would not be highly accurate but combined it is fully expected that greater accuracy can be obtained. The technologies that are suitable in terms of cost, size, accuracy, and development are online ferrography, selective fluorescence spectroscopy, scattering measurements, FTIR, photoacoustic spectroscopy, and solid state viscometers

Um novo modelo de conceito para implantes ortopédicos instrumentados ativos

Doutoramento em Engenharia MecânicaTotal hip replacement (THR) is one of the most performed surgical procedures around the world. Millions of THR are carried out worldwide each year. Currently, THR revision rates can be higher than 10%. A significant increase of the number of primary and revision THRs, mainly among patients less than 65 years old (including those under 45 years old) has been predicted for the forthcoming years. A worldwide increase in the use of uncemented fixation has also been reported, incidence caused mainly by the significant increase of more active and/or younger patients. Besides the significant breakthroughs for uncemented fixations, they have not been able to ensure long-term implant survival. Up to date, current implant models have shown evidences of their inability to avoid revision procedures. The performance of implants will be optimized if they are designed to perform an effective control over the osseointegration process. To pursue this goal, improved surgical techniques and rehabilitation protocols, innovative bioactive coatings (including those for controlled delivery of drugs and/or other bio-agents in the bone-implant interface), the concepts of Passive Instrumented Implant and Active Instrumented Implant have been proposed. However, there are no conclusive demonstrations of the effectiveness of such methodologies. The main goal of this thesis is to propose a new concept model for instrumented implants to optimize the bone-implant integration: the self-powered instrumented active implant with ability to deliver controlled and personalized biophysical stimuli to target tissue areas. The need of such a new model is demonstrated by optimality analyses conducted to study the performance of instrumented and non-instrumented orthopaedic implants. Promising results on the potential of a therapeutic actuation driven by cosurface-based capacitive stimulation were achieved, as well as for self-powering instrumented active implants by magnetic levitation-based electromagnetic energy harvesting.A artroplastia total da anca (THR) é um dos procedimentos cirúrgicos mais realizados à escala global. Milhões de THRs são realizadas todos os anos em todo o mundo. Atualmente, as taxas de revisão destas artroplastias podem ser superiores a 10%. O número de THRs primárias e de revisão têm aumentado e estima-se que cresçam acentuadamente nos próximos anos, principalmente em pacientes com idades inferiores a 65 anos (incluindo aqueles com menos de 45 anos). Também se tem verificado uma tendência generalizada para o uso de fixações não cimentadas, incidência principalmente causada pelo aumento significativo de pacientes mais jovens e/ou activos. Embora se tenham realizado avanços científicos no projeto de implantes não cimentados, têm-se verificado o seu insucesso a longo-prazo. Encontram-se evidências da ineficácia dos modelos de implantes que têm sido desenvolvidos para evitar procedimentos de revisão. O desempenho dos implantes será otimizado se estes foram projetados para controlarem eficazmente o processo de osseointegração. Para se alcançar este objetivo, têm sido propostas a melhoria das técnicas cirúrgicas e dos protocolos de reabilitação, a inovação dos revestimentos (onde se incluem os revestimentos ativos projetados para a libertação controlada de fármacos e/ou outros bio-agentes) e os conceitos de Implante Instrumentado Passivo e Implante Instrumentado Ativo. Contudo, não existem demonstrações conclusivas da eficácia de tais metodologias. O principal objetivo desta tese é propor um novo modelo de conceito para implantes instrumentados para se otimizar a integração osso-implante: o implante instrumentado ativo, energeticamente auto-suficiente, com capacidade de aplicar estímulos biofísicos em tecidos-alvo de forma controlada e personalizada. A necessidade de um novo modelo é demonstrada através da realização de análises de otimalidade ao desempenho dos implantes instrumentados e não-instrumentados. Foram encontrados resultados promissores para o controlo otimizado da osseointegração usando este novo modelo, através da atuação terapêutica baseada na estimulação capacitiva com arquitetura em co-superfície, assim como para fornecer energia elétrica de forma autónoma por mecanismos de transdução baseados em indução eletromagnética usando configurações baseadas na levitação magnética

Polymeric Microsensors for Intraoperative Contact Pressure Measurement

Biocompatible sensors have been demonstrated using traditional microfabrication techniques modified for polymer substrates and utilize only materials suitable for implantation or bodily contact. Sensor arrays for the measurement of the load condition of polyethylene spacers in the total knee arthroplasty (TKA) prosthesis have been developed. Arrays of capacitive sensors are used to determine the three-dimensional strain within the polyethylene prosthesis component. Data from these sensors can be used to give researchers a better understanding of component motion, loading, and wear phenomena for a large range of activities. This dissertation demonstrates both analytically and experimentally the fabrication of these sensor arrays using biocompatible polymer substrates and dielectrics while preserving industry-standard microfabrication processing for micron-level resolution. An array of sensors for real-time measurement of pressure profiles is the long-term goal of this research. A custom design using capacitive-based sensors is an excellent selection for such measurement, giving high spatial resolution across the sensing surface and high load resolution for pressures applied normal to that surface while operating at low power

A WIRELESS SENSOR SYSTEM WITH DIGITALLY CONTROLLED SIGNAL CONDITIONING CIRCUIT FOR FORCE MONITORING AT BONE FIXATION PLATES

Post-rehabilitation of orthopedic surgery is critical for bone fracture treatments. Current protocols are not based on quantitative assessments of the patient condition but they are conservative estimations mostly based on prior experience and physician’s opinions. While there are quantitative methods for assessing the recovery of orthopedic surgery, they are typically very expensive and provide only snapshots during the healing process. A standalone, reconfigurable, embedded wireless sensor system with digitally controlled signal conditioning system capable of providing continuous monitoring of bone healing is developed. Strain sensor measurements were validated against a commercial mechanical loading instrument for relevant loads that an animal (ovine) would experience during in vivo testing (up to 250 N). The loader was configured to apply a maximum force of 250 N to the bone fixation plate at a rate of 1000 N/min. Cyclic testing of the system showed optimal stability and no observable drift in the sensor. The sensor was also implemented in a rodent model for monitoring force loading at an internal bone fixation plate. The platform’s small, robust, and low power nature is usefulness for continuous wireless monitoring and actuation in many biomedical applications

Cryostatless high temperature supercurrent bearings for rocket engine turbopumps

The rocket engine systems examined include SSME, ALS, and CTV systems. The liquid hydrogen turbopumps in the SSME and ALS vehicle systems are identified as potentially attractive candidates for development of Supercurrent Bearings since the temperatures around the bearings is about 30 K, which is considerably lower than the 95 K transition temperatures of HTS materials. At these temperatures, the current HTS materials are shown to be capable of developing significantly higher current densities. This higher current density capability makes the development of supercurrent bearings for rocket engines an attractive proposition. These supercurrent bearings are also shown to offer significant advantages over conventional bearings used in rocket engines. They can increase the life and reliability over rolling element bearings because of noncontact operation. They offer lower power loss over conventional fluid film bearings. Compared to conventional magnetic bearings, they can reduce the weight of controllers significantly, and require lower power because of the use of persistent currents. In addition, four technology areas that require further attention have been identified. These are: Supercurrent Bearing Conceptual Design Verification; HTS Magnet Fabrication and Testing; Cryosensors and Controller Development; and Rocket Engine Environmental Compatibility Testing

Cardiovascular instrumentation for spaceflight

The observation mechanisms dealing with pressure, flow, morphology, temperature, etc. are discussed. The approach taken in the performance of this study was to (1) review ground and space-flight data on cardiovascular function, including earlier related ground-based and space-flight animal studies, Mercury, Gemini, Apollo, Skylab, and recent bed-rest studies, (2) review cardiovascular measurement parameters required to assess individual performance and physiological alternations during space flight, (3) perform an instrumentation survey including a literature search as well as personal contact with the applicable investigators, (4) assess instrumentation applicability with respect to the established criteria, and (5) recommend future research and development activity. It is concluded that, for the most part, the required instrumentation technology is available but that mission-peculiar criteria will require modifications to adapt the applicable instrumentation to a space-flight configuration

Detection, Diagnosis and Prognosis: Contribution to the energy challenge: Proceedings of the Meeting of the Mechanical Failures Prevention Group

The contribution of failure detection, diagnosis and prognosis to the energy challenge is discussed. Areas of special emphasis included energy management, techniques for failure detection in energy related systems, improved prognostic techniques for energy related systems and opportunities for detection, diagnosis and prognosis in the energy field

NASA patent abstracts bibliography: A continuing bibliography. Section 1: Abstracts (supplement 14)

Abstracts are cited for 213 patents and applications for patent introduced into the NASA scientific and technical information system during the period of July 1978 through December 1978. Each entry consists of a citation, an abstract, and in most cases, a key illustration selected from the patent or application for patent