Sensing and Control of Thermally Induced Vibrations of Stationary Blades Using Piezoelectric Materials

Thermally induced cracks due to temperature gradient in mass concrete have adverse effects on its durability and service life. Heat released during the hydration of Portland cement in early age mass concrete can be quite excessive depending on the ambient temperature, cement content of the concrete mix and the size. Finite difference model using Crank Nicholson implicit method was developed based on the two dimensional unsteady state heat conduction. Optimized MATLAB based software was developed for simulation and data visualization. A mass concrete block cast with standard mix ratio and water cement ratio was used to verify the efficacy of the model. Type-K thermocouple and digital thermometer were used to monitor the temperature at time intervals. The temperature profile showed a hotter core and cooler surface except for the initial placement temperature, which exhibited a uniform temperature for all thermocouple locations. Peak temperature values were recorded within the first day of concrete placement. The model successfully predicted the temperature profile of the mass concrete at early ages of cement hydration. With the knowledge of the ambient temperature and the configuration of the mass concrete, the model can reliably predict the temperature profile from which potential for thermal cracks occurrence can be determined to enable suitable proactive preventive and control measures.

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Thermally Induced Errors Modeling and Control for PCMA

Chinese Optics Letters ◽

10.3788/col201412.s11203 ◽

2014 ◽

Vol 12 (s1) ◽

pp. S11203-311207

Author(s):

Wanli Liu Wanli Liu ◽

Zhankui Wang Zhankui Wang ◽

Xiaoyang Li Xiaoyang Li

Keyword(s):

Thermally Induced ◽

Modeling And Control ◽

And Control

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Control of Static Shape, Dynamic Oscillation, and Thermally Induced Vibration of Nozzles

Journal of Pressure Vessel Technology ◽

10.1115/1.2217968 ◽

2005 ◽

Vol 128 (3) ◽

pp. 357-363 ◽

Cited By ~ 3

Author(s):

D. W. Wang ◽

H. S. Tzou ◽

S. M. Arnold ◽

H.-J. Lee

Keyword(s):

Finite Element ◽

Conical Shell ◽

Shape Control ◽

Numerical Data ◽

Analysis Data ◽

Mode Shapes ◽

Thermal Excitation ◽

Thermally Induced ◽

Control Effectiveness ◽

And Control

Static shape actuation and dynamic control of nozzles can improve their performance, accuracy, reliability, etc. A new curved laminated piezothermoelastic hexahedral finite element is formulated based on the layerwise constant shear angle theory and it is used for modeling and analysis of piezothermoelastic conical shell structures subjected to control voltages for static shape actuation and dynamically and thermally induced vibration controls. Free vibration characteristics of an elastic truncated conical shell nozzle with fixed-free boundary conditions are studied using the new finite element. Both frequencies and mode shapes are accurately computed and compared favorably with available experimental and other numerical data. This study is then extended to evaluate control effectiveness of the conical shell with laminated piezoelectric layers. Static shape control is achieved by an applied electric potential. Vibration sensing and control are carried out using the negative velocity control scheme. Control of thermal excitation is also investigated. Analysis data suggest that the dynamic behavior and control characteristics of conical shells are quite complicated due to the coupled membrane and bending effects participating in the responses. To improve control effectiveness, segmentation and/or shaping of sensor and actuator layers need to be further investigated.

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Micro-Structronics and Control of Hybrid Electrostrictive/Piezoelectric Thin Shells

Aerospace ◽

10.1115/imece2003-42398 ◽

2003 ◽

Cited By ~ 1

Author(s):

W. K. Chai ◽

H. S. Tzou ◽

S. M. Arnold

Keyword(s):

Curie Point ◽

Piezoelectric Materials ◽

Constitutive Relations ◽

Ferroelectric Materials ◽

Polar Phase ◽

Free Energy Function ◽

Generic Theory ◽

And Control ◽

Electrostrictive Effect ◽

Piezoelectric Characteristics

Certain ferroelectric materials possess dual electrostrictive and piezoelectric characteristics, depending on their specific Curie temperatures. These materials exhibit piezoelectric characteristics in the ferroelectric phase when the temperature is below the Curie point. However, they become electrostrictive in the paraelectric phase (non-polar phase) as the temperature exceeds the Curie point. The (direct) electrostrictive effect is a quadratic dependence of stress or strain on applied electric field. The nonlinear electromechanical effect of electrostrictive materials provides stronger actuation performance as compared with that of piezoelectric materials. Due to the complexity of the generic ferroelectric actuators, micro-electromechanics and control characteristics of generic electrostrictive/piezoelectric dynamics system deserve an in-depth investigation. In this study, electro-mechanical dynamic system equations and generic boundary conditions of hybrid electrostrictive/piezoelectric double-curvature shell continua are derived using the energy-based Hamilton’s principle, elasticity theory, electrostrictive/piezoelectric constitutive relations, and Gibb’s free energy function. Moreover, the second converse electrostrictive effect and the direct piezoelectric effect are all considered in the generic governing equations. Simplifications of the generic theory to other common geometries or specific materials are demonstrated and their electromechanical characteristics are also evaluated.

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