Erling Ringgaard - Academia.edu (original) (raw)

Papers by Erling Ringgaard

Journal of Electroceramics, 2010

Piezoelectric thin film ultrasonic transducer was realised and tested for short range distance me... more Piezoelectric thin film ultrasonic transducer was realised and tested for short range distance measurements in water. The transducer structure (154 x 154 µm 2) utilising electric field excitation in thickness and transversal direction by special electrode layout was designed. Displacement and acoustic response in air and water was modelled by FEMLab and structure was adjusted to obtain resonance frequency in 5 MHz in air and ~3 MHz in water. The transducer was fabricated on SOI wafer by chemical solution deposition (CSD) where 32 sequential layers of PZT were deposited with the total thickness of 2 µm. Subsequently, a cavity underneath the piezoelectric layer was wet etched creating a bending membrane with total thickness of ~12 µm. The ultrasonic transducer was poled with 10 V/µm electric field at 150 °C temperature obtaining an effective transversal piezoelectric coefficient of-15 C/m 2 [1]. After poling the displacement of the unimorph was measured as a function of frequency by fiber-optic laser vibrometer and admittance of the transducer was measured by network analyser in air and water. Performance improvement for conventional electrode design was estimated and modelling and measurement results were compared.

Structural Health Monitoring (SHM) is a general term for methods of detecting defects in structur... more Structural Health Monitoring (SHM) is a general term for methods of detecting defects in structures before they become fatal. The typical areas of application cover aeronautics, civil engineering (buildings, bridges etc.) and recently also the automotive industry. One of the techniques used for SHM is based on the propagation of ultrasonic waves through a structure in order to assess its structural integrity. The common solution relies on the use of piezoelectric transducers to emit and receive ultrasonic waves. However, because of the high number of echoes and possible propagation modes within the structure, those applications require very extensive signal processing. In this work we present an approach involving piezo-composite transducers dedicated to SHM in combination with specific electronics that has been developed and successfully tested for reducing the complexity of the detection schemes. This has been achieved by selecting the mode and direction of the Lamb waves. The arr...

Recent progress in development of new functional materials that are flexible and can be processed... more Recent progress in development of new functional materials that are flexible and can be processed at very low temperatures (below 100 °C) opens a new opportunity for applications, such as non-destructive evaluation (NDE), or structural health monitoring (SHM) by applying active materials directly on the structures made out of a variety of materials, e.g. metals (aluminium), plastics, and polymers, including CFRP (Carbon Fibre Reinforced Polymer). This paper presents sensor arrays based on a flexible piezoelectric material – PiezoPaintTM. The newly developed material exhibits relatively high sensitivity (d33 coefficient up to 45 pC/N), extremely low processing temperatures (< 120 °C), and high compliance in the cured state, enabling direct deposition of acoustic/vibration sensor arrays on structures to be monitored by means of screenor padprinting. The printed sensors have been applied for impact detection where four-element arrays and a fully integrated wiring system has been dep...

Ultrasonic-based SHM (Structural Health Monitoring) applications commonly rely on the use of piez... more Ultrasonic-based SHM (Structural Health Monitoring) applications commonly rely on the use of piezo-electric patches to emit and receive ultrasonic waves. The objective is to study the propagation of the waves through a structure to assess its structural integrity. Because of the elevated number of echoes and possible modes of propagation of the waves within the structure, those applications suffer from a burden of signal processing. This paper presents a composite piezo-electric patch that was designed and successfully tested for reducing the complexity of the SHM detection schemes by selecting the mode and direction of the Lamb waves received. The piezo-composite is composed of a row of eight independent ceramic pillars separated with polymer, so it is a 1-D matrix of independent piezo-patches. Used with adequate electronics and signal processing, it was shown that it allowed selecting the direction and the mode of the Lamb waves.

Journal of Physics: Materials

Journal of Physics: Energy

Piezoelectric materials are essential for the conversion between mechanical and electrical energy... more Piezoelectric materials are essential for the conversion between mechanical and electrical energy, for example in ultrasound imaging and vibrational energy harvesting. Here, we are making and exploring the effects of a new design: co-sintered multilayers with texture (grains of a preferential crystallographic direction). The motivation is the combination of increased piezoelectric response in certain crystallographic directions; multilayer structures where thick films rather than bulk materials can allow higher frequency operation and large area; and co-sintering to avoid detrimental effects from gluing layers together. Samples of the lead-free piezoelectric material Li 0.06 (K 0.52 Na 0.48) 0.94 Nb 0.71 Ta 0.29 O 3 with 0.25 mol% Mn (KNNLTM) were made by tape casting and co-sintering. NaNbO 3 platelets with (100) orientation which were used as templates to introduce texture, and polymethyl methacrylate (PMMA) was used as a pore forming agent for making porous substrates. The electrical impedances of the co-sintered samples were recorded and analyzed by equivalent electrical circuit modelling. A texture up to 85% in the [100] crystallographic direction was obtained. The samples displayed ferro-and piezoelectricity, with a maximum thickness coupling coefficient (k t =0.18) between mechanical and electrical energy in the most textured sample. This demonstrates that the introduction of texture in multilayered, co-sintered piezoelectrics shows promise for improving devices for ultrasound imaging or energy harvesting.

Journal of the European …, 2007

... Commercial piezoceramics, with highest d 33 values in the range of 400600 pC N −1 for soft P... more ... Commercial piezoceramics, with highest d 33 values in the range of 400600 pC N −1 for soft PZT (donor doping), operate at maximum temperatures of 200250 °C. 3 Promising results have been also obtained for single crystals of other systems with MPBs, such as Pb(In 1/2 ...

IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control

2016 IEEE International Ultrasonics Symposium (IUS), 2016

2012 Ieee International Ultrasonics Symposium, Oct 1, 2012

Detection of high-order nonlinear components issued from microbubbles has emerged as a sensitive ... more Detection of high-order nonlinear components issued from microbubbles has emerged as a sensitive method for contrast agent imaging. Nevertheless, the detection of these high-frequency components, including the third, fourth, and fifth harmonics, remains challenging because of the lack of transducer sensitivity and bandwidth. In this context, we propose a new design of imaging transducer based on a simple fabrication process for high-frequency nonlinear imaging. The transducer is composed of two elements: the outer low-frequency (LF) element was centered at 4 MHz and used in transmit mode, whereas the inner high-frequency (HF) element centered at 14 MHz was used in receive mode. The center element was pad-printed using a lead zirconate titanate (PZT) paste. The outer element was molded using a commercial PZT, and curved porous unpoled PZT was used as backing. Each piezoelectric element was characterized to determine the electromechanical performance with thickness coupling factor around 45%. After the assembly of the two transducer elements, hydrophone measurements (electroacoustic responses and radiation patterns) were carried out and demonstrated a large bandwidth (70% at -3 dB) of the HF transducer. Finally, the transducer was evaluated for contrast agent imaging using contrast agent microbubbles. The results showed that harmonic components (up to the sixth harmonic) of the microbubbles were successfully detected. Moreover, images from a flow phantom were acquired and demonstrated the potential of the transducer for high-frequency nonlinear contrast imaging.

Http Dx Doi Org 10 1080 00150190590965497, Mar 9, 2011

Materials, 2015

The use of porosity to modify the functional properties of piezoelectric ceramics is well known i... more The use of porosity to modify the functional properties of piezoelectric ceramics is well known in the scientific literature as well as by the industry, and porous ceramic can be seen as a 2-phase composite. In the present work, examples are given of applications where controlled porosity is exploited in order to optimise the dielectric, piezoelectric and acoustic properties of the piezoceramics. For the optimisation efforts it is important to note that the thickness coupling coefficient k t will be maximised for some non-zero value of the porosity that could be above 20%. On the other hand, with a good approximation, the acoustic velocity decreases linearly with increasing porosity, which is obviously also the case for the density. Consequently, the acoustic impedance shows a rather strong decrease with porosity, and in practice a reduction of more than 50% may be obtained for an engineered porous ceramic. The significance of the acoustic impedance is associated with the transmission of acoustic signals through the interface between the piezoceramic and some medium of propagation, but when the porous ceramic is used as a substrate for a piezoceramic thick film, the attenuation may be equally important. In the case of open porosity it is possible to introduce a liquid into the pores, and examples of modifying the properties in this way are given.

2015 IEEE International Ultrasonics Symposium (IUS), 2015

The use of piezoelectric materials for actuator applications has been steadily increasing in rece... more The use of piezoelectric materials for actuator applications has been steadily increasing in recent years and for the design of devices there is a need for the knowledge of relevant properties at working conditions. Piezoelectric actuators are usually operated at high electrical field and in the present work, various high-field properties have been measured for a range of commercial materials, soft-or harddoped PZT and electrostrictive PMN-PT. For the soft and electrostrictive materials, both the real and the imaginary parts of the permittivity show a linear dependence on the electric field, as predicted by the Rayleigh law. The hard PZT materials do not obey the Rayleigh law, however. For the soft materials, also the piezoelectric d 33 coefficient increases linearly with the field, but not for the hard ones.

The use of piezoelectric actuators has been steadily increasing in recent years. Piezoelectric ac... more The use of piezoelectric actuators has been steadily increasing in recent years. Piezoelectric actuators are now used in very diverse applications, e.g. fuel injection, printing, active noise and vibration control, piezo motors, piezo valves etc. Today, piezoelectric actuators are mainly manufactured by the multilayer approach, which has several advantages over the stacked type actuators, the most important being low voltage, high strain and low cost. Most suppliers of piezoelectric actuators offer high-d 33 soft-doped PZT versions only. However, for some applications actuators based on other piezoelectric or electrostrictive materials are advantageous. A comparison of actuator performances has been carried out in order to provide data for a more appropriate selection of materials for piezoelectric actuators.