scholarly journals Characterization of Piezoelectric Wafer Active Sensors

2000 ◽  
Vol 11 (12) ◽  
pp. 959-976 ◽  
Author(s):  
Victor Giurgiutiu ◽  
Andrei N. Zagrai
Keyword(s):  
Mechanical Response ◽  
Impedance Spectrum ◽  
Calibration Procedure ◽  
Structural Vibration ◽  
Sensor Calibration ◽  
Active Sensors ◽  
One Dimensional ◽  
Active Sensor ◽  
Aluminum Plates ◽  
In The Beginning

In the beginning, the classical one-dimensional analysis of piezoelectric active sensors is reviewed. The complete derivation for a free-free sensor is then extended to cover the cases of clamped and elastically constrained sensors. An analytical model based on structural vibration theory and theory of piezoelectricity was developed and used to predict the electromechanical (E/M) impedance response, as it would be measured at the piezoelectric active sensor’s terminals. The model considers one-dimensional structures and accounts for both axial and flexural vibrations. The numerical analysis was performed and supported by experimental results. Experiments were conducted on simple beam specimens to support the theoretical investigation, and on thin gauge aluminum plates to illustrate the method’s potential. It was shown that E/M impedance spectrum recorded by the piezoelectric active sensor accurately represents the mechanical response of a structure. It was further proved that the response of the structure is not modified by the presence of the sensor, thus validating the sensor’s non-invasive characteristics. The sensor calibration procedure is outlined and statistical analysis was presented. It was found that PZT active sensors have stable and repeatable characteristics not only in as-received condition, but also while mounted on 1-D or 2-D host structure. It is shown that such sensors, of negligible mass, can be permanently applied to the structure creating a non-intrusive sensor array adequate for on-line automatic structural identification and health monitoring.

Embedded Self-Sensing Piezoelectric Active Sensors for On-Line Structural Identification

2001 ◽  
Vol 124 (1) ◽  
pp. 116-125 ◽  
Author(s):  
Victor Giurgiutiu ◽  
Andrei N. Zagrai
Keyword(s):  
Mechanical Response ◽  
Impedance Spectrum ◽  
Structural Identification ◽  
Calibration Procedure ◽  
Structural Vibration ◽  
Sensor Calibration ◽  
Ultrasonic Frequency ◽  
Active Sensors ◽  
Turbine Engine ◽  
On Line

The benefits and limitations of using embedded piezoelectric active sensors for structural identification at ultrasonic frequency are highlighted. An analytical model based on structural vibration theory and theory of piezoelectricity was developed and used to predict the electro-mechanical (E/M) impedance response, as it would be measured at the piezoelectric active sensor’s terminals. The model considers one-dimension structures and accounts for both axial and flexural vibrations. Experiments were conducted on simple specimens in support of the theoretical investigation, and on realistic turbine blade specimen to illustrate the method’s potential. It was shown that E/M impedance spectrum recorded by the piezoelectric active sensor accurately represents the mechanical response of a structure. It was further proved that the response of the structure is not modified by the presence of the sensor, thus validating the latter’s noninvasive characteristics. It is shown that such sensors, of negligible mass, can be permanently applied to the structure creating a nonintrusive sensor array adequate for on-line automatic structural identification and health monitoring. The sensor calibration procedure is outlined. Numerical estimation of the noninvasive properties of the proposed active sensors in comparison with conventional sensors is presented. Self-diagnostics capabilities of the proposed sensors were also investigated and methods for automatic self-test implementation are discussed. The paper underlines that the use of piezoelectric wafer active sensors is not only advantageous, but, in certain situations, may be the sole investigative option, as in the case of precision machinery, small but critical turbine-engine parts, and computer industry components.

Mechanical response of double-stranded DNA to dynamic excitation

2021 ◽  
pp. 107754632110458
Author(s):  
Hamze Mousavi ◽  
Moein Mirzaei ◽  
Samira Jalilvand
Keyword(s):  
Mechanical Behavior ◽  
Mechanical Response ◽  
Actual Condition ◽  
Dimensional System ◽  
One Dimensional ◽  
Linear Elastic ◽  
Dynamic Excitation ◽  
Double Stranded Dna ◽  
Elastic Forces ◽  
Mass Spring

The present work investigates the vibrational properties of a DNA-like structure by means of a harmonic Hamiltonian and the Green’s function formalism. The DNA sequence is considered as a quasi one-dimensional system in which the mass-spring pairs are randomly distributed inside each crystalline unit. The sizes of the units inside the system are increased, in a step-by-step approach, so that the actual condition of the DNA could be modeled more accurately. The linear-elastic forces mimicking the bonds between the pairs are initially considered constant along the entire length of the system. In the next step, these forces are randomly shuffled so as to take into account the inherent randomness of the DNA. The results reveal that increasing the number of mass-spring pairs in the crystalline structure decreases the influence of randomness on the mechanical behavior of the structure. This also holds true for systems with larger crystalline units. The obtained results can be used to investigate the mechanical behavior of similar macro-systems.

Structural Health Monitoring With Piezoelectric Active Sensors

2000 ◽  
Author(s):  
Howard A. Winston ◽  
Fanping Sun ◽  
Balkrishna S. Annigeri
Keyword(s):  
Structural Health Monitoring ◽  
Health Monitoring ◽  
Structural Damage ◽  
Electromechanical Coupling ◽  
Low Cost ◽  
Piezoelectric Element ◽  
Impedance Spectrum ◽  
Active Sensors ◽  
Electromechanical Impedance ◽  
Structural Health

A technology for non-intrusive real-time structural health monitoring using piezoelectric active sensors is presented. The approach is based on monitoring variations of the coupled electromechanical impedance of piezoelectric patches bonded to metallic structures in high-frequency bands. In each of these applications, a single piezoelectric element is used as both an actuator and a sensor. The resulting electromechanical coupling makes the frequency-dependent electric impedance spectrum of the PZT sensor a good mapping of the underlying structure’s acoustic signature. Moreover, incipient structural damage can be indicated by deviations of this signature from its original baseline pattern. Unique features of this technology include its high sensitivity to structural damage, non-intrusiveness to the host structure, and low cost of implementation. These features have potential for enabling on-board damage monitoring of critical or inaccessible aerospace structures and components, such as aircraft wing joints, and both internal and external jet engine components. Several exploratory applications will be discussed.

Backfill of Radioactive Waste Disposal: Feasibility Study of Argillite/Bentonite (COx/MX80) Pellets

2021 ◽  
Author(s):  
Danai Tyri ◽  
Bui Quoc Huy Ly ◽  
François Nader ◽  
Irini Djeran-Maigre ◽  
Jean-Claude Robinet ◽  
...  
Keyword(s):  
Radioactive Waste ◽  
Mechanical Response ◽  
Raw Materials ◽  
Radioactive Waste Disposal ◽  
Maximum Diameter ◽  
Optimal Conditions ◽  
Swelling Potential ◽  
Deep Geological Disposal ◽  
In The Beginning ◽  
Influential Parameters

Abstract A pelletized solution composed of COx argillite and MX80 bentonite is examined as backfill for the deep geological disposal of radioactive waste (Cigeo project). The implementation is studied in terms of installation and hydration conditions as well as their influence on the hydro-mechanical behavior of the mixture. In the beginning, the optimum grain size distribution (GSD) of pellets assembly is determined to minimize initial voids. A series of DEM simulations on ternary samples made of spheres is carried out, investigating the optimal conditions in terms of sizes and proportions. Density maximization occurs when maximum diameter is the dominant size, while minimum and medium diameters are following. As optimum GSD, sizes of 16 mm, 10 mm and 4 mm in 60%, 10% and 30% respectively are chosen. The pelletization of the selected sizes is optimized using an adapted tablet machine to carry out the pellet fabrication. A detailed analysis of influential parameters related to the machine accessories and the inserted raw materials is presented. After modifications, quasi-spherical pellets presenting density of at least 1.95 Mg/m3 are produced. COx/MX80 pellets hydro-mechanical response is indirectly assessed by studying the swelling potential of COx/MX80 powdered mixtures at equivalent emplaced densities. The influence of density, stress and MX80 content on swelling is obtained.

Uncertainty Evaluation on Multi-Hole Aerodynamic Pressure Probes

2020 ◽  
Author(s):  
Andrea Notaristefano ◽  
Paolo Gaetani ◽  
Vincenzo Dossena ◽  
Alberto Fusetti
Keyword(s):  
Uncertainty Analysis ◽  
Evaluation Method ◽  
Experimental Testing ◽  
Uncertainty Propagation ◽  
Calibration Procedure ◽  
Fast Response ◽  
Uncertainty Evaluation ◽  
Sensor Calibration ◽  
Pressure Probe ◽  
Aerodynamic Pressure

Abstract In the frame of a continuous improvement of the performance and accuracy in the experimental testing of turbomachines, the uncertainty analysis on measurements instrumentation and techniques is of paramount importance. For this reason, since the beginning of the experimental activities at the Laboratory of Fluid Machines (LFM) located at Politecnico di Milano (Italy), this issue has been addressed and different methodologies have been applied. This paper proposes a comparison of the results collected applying two methods for the measurement uncertainty quantification to two different aerodynamic pressure probes: sensor calibration, aerodynamic calibration and probe application are considered. The first uncertainty evaluation method is the so called “Uncertainty Propagation” method (UPM); the second is based on the “Monte Carlo” method (MCM). Two miniaturized pressure probes have been selected for this investigation: a pneumatic 5-hole probe and a spherical fast response aerodynamic pressure probe (sFRAPP), the latter applied as a virtual 4-hole probe. Since the sFRAPP is equipped with two miniaturized pressure transducers installed inside the probe head, a specific calibration procedure and a dedicated uncertainty analysis are required.

Thermal-Mechanical Response of Non-Uniformly Heated LEU Foil Based Target

2011 ◽  
Author(s):  
Kyler K. Turner ◽  
Gary L. Solbrekken ◽  
Charlie W. Allen
Keyword(s):  
Mechanical Response ◽  
Metal Foil ◽  
Transfer Coefficients ◽  
Technetium 99M ◽  
Heat Transfer Coefficients ◽  
Plate Design ◽  
Enriched Uranium ◽  
Aluminum Plates ◽  
Sandwiched Structure ◽  
Global Threat

Technetium-99m is a diagnostic radiopharmaceutical that is currently used in 80% of the global nuclear diagnostic imaging procedures. The parent isotope for technetium-99m is molybdenum-99, most commonly obtained through the irradiation of high enriched uranium (HEU) targets. In accordance with the Department of Energy’s Global Threat Reduction Initiative (GTRI) an effort is underway to develop a process to produce molybdenum-99 using low enriched uranium (LEU) targets to maintain production yield relative to HEU targets. Conversion of targets to LEU material effectively mandates that the most efficient process is to cast LEU in the form of a metal foil as opposed to current powder based dispersion designs for HEU. Using a foil requires a significant modification to the current target design. One design concept uses an LEU foil sandwiched between two nominally flat aluminum plates. The LEU is enclosed in the sandwiched structure by welding the aluminum plates together about their edges. The plate design is inspired by high density monolithic LEU fuel plates with the exception that the LEU is not bonded to the aluminum plates nor is it necessary to clamp the plate edges to prevent lateral translation. The lack of bonding between the LEU foil and the plates allows the edges of the plate to be cut off so the foil can be removed after irradiation to be chemically processed. The un-heated edges of the plate target produce 3-D temperature gradients that induce plate deformations. This paper will review thermal mechanical response of an LEU foil based molybdenum-99 plate target geometry. This study describes the effect of various edge holding conditions, thermal loads, and heat transfer coefficients on the thermal-induced deflection and stress in the plates.

Thermal-Mechanical Response of Non-Uniformly Heated Nominally Flat and Curved LEU Foil Based Target

2012 ◽  
Author(s):  
Kyler K. Turner ◽  
Gary L. Solbrekken ◽  
Charlie W. Allen
Keyword(s):  
Mechanical Response ◽  
Three Dimensional ◽  
Department Of Energy ◽  
Transfer Coefficients ◽  
Technetium 99M ◽  
Plate Design ◽  
Enriched Uranium ◽  
Aluminum Plates ◽  
Sandwiched Structure ◽  
Global Threat

Technetium-99m is a radiopharmaceutical currently used in 85% of all diagnostic imaging procedures. The relative long lived parent isotope of technetium-99m is molybdenum-99, which is commonly produced by irradiating highly enriched uranium. In accordance with the Department of Energy: National Nuclear Security Administration’s Global Threat Reduction Initiative an effort is underway to develop low enriched uranium based molybdenum-99 production concepts. Achieving comparable molybdenum-99 yields in a low enriched uranium target effectively mandates the use of a high density metal low enriched uranium foil. Using a foil requires a significant modification to the current highly enriched uranium dispersion target designs. One design concept uses a low enriched uranium foil sandwiched between either two flat or curved aluminum plates. The low enriched uranium is enclosed in the sandwiched structure by welding the aluminum plates together about their edges. The plate design is inspired by low enriched uranium fuel plates with the exception that the low enriched uranium is not bonded to the aluminum plates nor is it necessary to clamp the plate edges to prevent lateral translation. The lack of bonding between the low enriched uranium foil and the plates allows easy removal of the foil after irradiation for chemically processing and separation. The un-heated edges of the plate target produce three-dimensional temperature gradients inducing deformations and stress. This paper will review the thermal mechanical response of a low enriched uranium foil based molybdenum-99 production target. This study describes the effect of various curvatures, thermal loads, and heat transfer coefficients on the thermal-induced deflection and stress.

Integrated one-dimensional dynamic analysis methodology for space launch vehicles reflecting liquid components

2017 ◽  
Vol 121 (1243) ◽  
pp. 1217-1238 ◽  
Author(s):  
J.B. Kim ◽  
J.S. Sim ◽  
S.G. Lee ◽  
S.J. Shin ◽  
J.H. Park ◽  
...  
Keyword(s):  
Dynamic Analysis ◽  
Longitudinal Direction ◽  
Structural Vibration ◽  
Launch Vehicles ◽  
Structural Modelling ◽  
Liquid Propellant ◽  
One Dimensional ◽  
Complete Vehicle ◽  
Reference Vehicle ◽  
Propellant Tank

ABSTRACTIn this paper, structural modelling and dynamic analysis methods reflecting the characteristics of a liquid propellant were developed for a pogo analysis. The pogo phenomenon results from the complex interaction between the vehicle structural vibration in the longitudinal direction and the propulsion system. Thus, for an accurate vibration analysis of a liquid propellant launch vehicle, both the consumption of the liquid propellant and the change in the stiffness reflecting the nonlinear hydroelastic effect were simultaneously considered. A complete vehicle structure, including the liquid propellant tanks, was analytically modelled while focusing on pogo. In addition, a feasible liquid propellant tank modelling method was established to obtain an one-dimensional complete vehicle model. With these methods, comparative studies of the hydroelastic effect were conducted. Evaluations of the dynamic analysis of a reference vehicle were also conducted during the first burning stage. The numerical results obtained with the present orthotropic model and the dynamic analysis method were found to be in good agreement with the natural vibration characteristics according to previous analyses and experiments. Additionally, the reference vehicle showed the estimated occurrence of pogo in the first structural mode when compared with the frequencies of the propellant feeding system. In conclusion, the present structural modelling and modal analysis procedures can be effectively used to analyse dynamic characteristics of liquid propellant launch vehicles. These techniques are also capable of identifying the occurrence of pogo and providing design criteria related to pogo instability.

Investigations of Flutter and Aerodynamic Damping of a Turbine Blade: Experimental Characterization

2017 ◽  
Vol 139 (8) ◽  
Author(s):  
Charles E. Seeley ◽  
Christian Wakelam ◽  
Xuefeng Zhang ◽  
Douglas Hofer ◽  
Wei-Min Ren
Keyword(s):  
Mechanical Response ◽  
Numerical Models ◽  
Structural Vibration ◽  
Aerodynamic Damping ◽  
Actuation System ◽  
Electromagnetic Actuation System ◽  
Wide Range ◽  
Large Motion ◽  
Damping Effects ◽  
Numerical Approaches

Flutter is a self-excited and self-sustained aero-elastic instability, caused by the positive feedback between structural vibration and aerodynamic forces. A two-passage linear turbine cascade was designed, built, and tested to better understand the phenomena and collect data to validate numerical models. The cascade featured a center airfoil that had its pitch axis as a degree-of-freedom to enable coupling between the air flow and mechanical response in a controlled manner. The airfoil was designed to be excited about its pitch axis using an electromagnetic actuation system over a range of frequencies and amplitudes. The excitation force was measured with load cells, and the airfoil motion was measured with accelerometers. Extraordinary effort was taken to minimize the mechanical damping so that the damping effects of the airflow over the airfoil, that were of primary interest, would be observable. Assembling the cascade required specialized alignment procedures due to the tight clearances and large motion. The aerodynamic damping effects were determined by observing changes in the mechanical frequency response of the system. Detailed aerodynamic and mechanical measurements were conducted within a wide range of Mach numbers (Ma) from Ma = 0.10 to 1.20. Experimental results indicated that the aerodynamic damping increased from Ma = 0.10 to 0.65, dropped suddenly, and was then constant from Ma = 0.80 to 1.20. A flutter condition was identified in the interval between Ma = 0.65 and Ma = 0.80. The aerodynamic damping was also found to be independent of displacement amplitude within the tested range, giving credence to linear numerical approaches.

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