Several approaches towards lead-free ceramic PM have been reported, such as piezoelectric single crystals (langasite), and ferroelectric ceramics with a perovskite structure and bismuth layer-structured ferroelectrics (BLSF), which have been extensively researched. This resulted in the development of PZT-polymer composites, and the feasible integration of functional PM composites on large scale, by simple thermal welding or by conforming processes. However, promising is the integration of ceramic disks into industrial appliances moulded from plastic. Furthermore, they show low Curie temperature, leading to constraints in terms of applications in harsh environmental conditions. In addition polymers also exhibit high strength, high impact resistance, low dielectric constant, low elastic stiffness, and low density, thereby a high voltage sensitivity which is a desirable characteristic along with low acoustic and mechanical impedance useful for medical and underwater applications.Īmong PMs, PZT ceramics are popular as they have a high sensitivity, a high g 33 value. Moreover, piezoelectric polymeric sensors and actuators, due to their processing flexibility, can be readily manufactured into large areas, and cut into a variety of shapes. Piezoelectric polymers (PVDF, 240 mV-m/N) possess higher piezoelectric stress constants ( g 33), an important parameter in sensors, than ceramics (PZT, 11 mV-m/N), which show that they can be better sensors than ceramics. Organic polymer PMs, such as PVDF, have low Young's modulus compared to inorganic PMs. Inorganic ceramic PMs offer advantages over single crystals, including ease of fabrication into a variety of shapes and sizes not constrained crystallographic directions. Semiconducting PMs offer features such as compatibility with integrated circuits and semiconductor devices. Gallium nitride and zinc oxide can also be regarded as a ceramic due to their relatively wide band gaps. The most commonly produced piezoelectric ceramics are lead zirconate titanate (PZT), barium titanate, and lead titanate. Piezoelectric materials (PMs) can be broadly classified as either crystalline, ceramic, or polymeric. doi: 10.This page lists properties of several commonly used piezoelectric materials. Zhang J, Drinkwater BW, Dwyer-Joyce RS (2005) Calibration of the ultrasonic lubricant-film thickness measurement technique. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 220(6):619–628. Tribol Lett 17(2):1216ĭrinkwater BW, Pritchard J, Harper P, Dwyer-Joyce RS (2006) Oil film measurement in polytetrafluoroethylene-faced thrust pad bearings for hydrogenerator applications. ![]() doi: 10.1016/s1350-4789(06)71260-0ĭwyer-Joyce RS, Harper P, Drinkwater BW (2004) A method for the measurement of hydrodynamic oil films using ultrasonic reflection. Reddyhoff T, Dwyer-Joyce R, Harper P (2006) Ultrasonic measurement of film thickness in mechanical seals. Li M, Liu H, Xu C, Jing M, Xin W (2015) Ultrasonic measurement of cylindrical roller bearing lubrication using high pulse repletion rates. Li M, Jing M, Chen Z, Liu H (2014) An improved ultrasonic method for lubricant-film thickness measurement in cylindrical roller bearings under light radial load. Ultrasonics 32(6):431–440ĭwyer-Joyce RS, Reddyhoff T, Drinkwater BW (2004) Operating limits for acoustic measurement of rolling bearing oil film thickness. Pialucha T, Guyott CCH, Cawley P (1989) Amplitude spectrum method for the measurement of phase velocity. Hunter A, Dwyer-Joyce R, Harper P (2012) Calibration and validation of ultrasonic reflection methods for thin-film measurement in tribology. In: World Tribology Congress III, Washington, D.C., USA, 2005. doi: 10.1098/rspa.2002.1018ĭwyer-Joyce RS, Reddyhoff T Ultrasonic phase and amplitude and the measurement of oil film thickness. ![]() ![]() Ultrasonics 32(6):431–440ĭwyer-Joyce RS, Drinkwater BW, CJ D (2003) The measurement of lubricant-film thickness using ultrasound. Pialucha T, Cawley P (1994) The detection of thin embedded layers using normal incidence ultrasound normal incidence ultrasound. Johnston GJWR, Spikes HA (1991) The measurement and study of very thin lubricant films in concentrated contacts. Gohar RCA (1963) Optical measurement of oil film thickness under elasto-hydrodynamic lubrication. Philos Trans R Soc A Math Phys Eng Sci 250(981):387–409. Aircraft Engineering and Aerospace Technology 19(9):294–297. Br J Appl Phys 3(10):315–318īrix VH (1947) An electrical study of boundary lubrication: further Rolls-Royce investigations tending to confirm deductions from previous tests. Lane TB, Hughes JR (1952) A study of the oil-film formation in gears by electrical resistance measurements.
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