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This paper aims to measure the oil film thickness between the roller and the inner ring in roller bearings by the ultrasonic method. The oil film thickness between the roller and the inner ring in roller bearings is a key performance indicator of the bearing lubrication condition. As the oil film is very thin and the contact region is very narrow, measurement of this film thickness is very challenging. A promising ultrasonic method was used to measure this film thickness, and this method was expected to overcome some drawbacks in other methods.

A simplified roller bearing only configured one roller, and an inner ring was built up to investigate this measurement. A miniature piezoelectric element is bonded on the inner surface of the inner ring to measure the reflection coefficient from the layer of oil between the roller and the inner raceway. As the width of the line contact region is smaller than the width of the piezoelectric element, a ray model is used to calibrate the reflection coefficient measured. The quasi-static spring model is then used to calculate oil film thickness from the corrected reflection coefficient data.

The results measured by this method agree reasonably well with predictions from elastohydrodynamic lubrication (EHL) theory. Also, a dynamic displacement of the rig caused by the skid of the roller versus the inner ring was found under light-load and high-speed conditions.

This work shows that the oil film between the roller and the inner raceway in roller bearings can be measured accurately by ultrasound and shows a deal method when the contact width is smaller than the piezoelectric element width.

The use of polymer thick‐film technology for the implementation of piezoelectric sensors opens up the way towards the low‐cost production of piezoelectric sensing devices. A novel polymer thick‐film piezoelectric paste is presented and compared with other piezoelectric materials. The main advantages of these films are the low processing temperature, their flexibility and the ease of creating patterns with feature sizes as small as 200μm. Various applications are proposed demonstrating the potential of these screen printable polymer piezoelectrics.

This paper aims to present the details of isotactic polypropylene (it-PP) films with a cellular structure (air-cavities) dedicated to pressure sensors. The polymer composites (thin films enriched with 5 and 10 wt% of mineral fillers as Sillikolloid P 87 and glass beads) should exhibit suitable structural elasticity within specific stress ranges. After the deformation force is removed, the sensor material must completely restore its original shape and size.

Estimating the stiffness tensor element (C₃₃) for polymer films (nonpolar space-charge electrets) by broadband resonance ultrasound spectroscopy is a relatively simple method of determining the safe stress range generated in thin pressure sensors. Therefore, ultrasonic and piezoelectric studies were carried out on four composite it-PP films. First, the longitudinal velocity (v_L) of ultrasonic waves passing through the it-PP film in the z-direction (thickness) was evaluated from the ω-position of mechanical resonance of the so-called insertion loss function. In turn, the d₃₃ coefficient was calculated from accumulated piezoelectric charge density response to mechanical stress.

Research is at an early stage; however, it can be seen that the mechanical orientation of the it-PP film improves its piezoelectric properties. Moreover, the three-year electric charge stability of the it-PP film seems promising.

Ultrasonic spectroscopy can be successfully handled as a validation method in the small-lot production of polymer films with the air-cavities structure intended for pressure sensors. The structural repeatability of polymer films is strongly related to a homogeneous distribution of the electric charge on the electret surface.

A study has been carried out on the relationship between the composition, poling condition and piezoelectric properties of thick film layers. Pastes based on lead‐titanate‐zirconate (PZT) powders, with either PbO or a lead‐alumina‐silicate glass frit as binder, were prepared. Microstructure, electrical and mechanical properties were analysed. Processing and poling conditions modify these properties; then a wide latitude of opportunities is offered in the choice of ferroelectric/piezoelectric characteristics of the layers used as sensing elements for sensors. A pressure sensor was realised where a circular diaphragm of alumina supports two piezoelectric layers obtained by screen printing and firing a PZT/PbO‐based ferroelectric paste. The design and the performance characteristics are described.

PVDF piezo polymers are new, valuable materials for sensing and actuating applications. These materials are strong candidates for new sensors that cannot be realised with piezoceramics or single crystals. The combination of the mechanical properties of a plastic material with those of a piezoelectric material led to new sensors and transducers whose design is not easy. For this reason, the characteristics and properties of piezo polymer are described as well as basic knowledge that engineers need for technical use.

This paper describes a self‐test procedure for a micromachined silicon accelerometer realized using a commercially available microprocessor. The accelerometer is fabricated using a combination of thick‐film printing and silicon micromachining. It consists of a silicon structure with thick‐film piezoelectric elements that act as sensors, detecting the deflections of the inertial mass, and also as actuators capable of performing a self‐test routine. The self‐test procedure must be performed at resonance and the microprocessor is used to identify the individual resonant frequency of each device and confirm the operation of the PZT elements. This work has successfully demonstrated the feasibility of a microprocessor implemented procedure and has highlighted some interesting behavioral characteristics of the accelerometer. The microprocessor could also be used in the future to fully test and calibrate the device thereby ensuring correct and accurate operation.

A study of the effect of poling conditions on screen‐printed piezoceramics was undertaken. Printable pastes were produced, using a commercially available lead zirconate titanate (PZT) powder, mixed with two types of binder, lead (II) oxide and a lead borosilicate glass. Sample devices were fabricated using the two paste types and processed, using standard thick film techniques, before being poled under varying conditions. Samples were compared by measurement of piezoelectric charge constant, d₃₃ and using scanning electron microscopy techniques. Temperature and time are shown to increase poling efficiency, while poling field reaches an optimum at 2‐3 MV m^‐1. The PZT layers start to fail through a process of dielectric breakdown at fields of 3.5 MV m^‐1 and above.

This paper aims to present a prototype of the diagnostic system for the examination of the distribution of the force applied by foot to substrate during usual human moving. Presented system is competitive to other currently available devices, thanks to sensors reliability, user-friendly operation manner and design based on cheap parts. The results of examinations are transmitted by radiomodem. Its recording and visualization are possible on either personal or mobile computers.

During selection of the sensors substrate, many polymeric electrets were examined. Polyvinylidene fluoride films were selected, because they have good charge uniformity across the surface, wide range of acceptable temperatures, linear relation between mechanical stress and output signal and high resistance for squeezing. The system measures the charge generated in film.

The pressures are recorded in relation to maximum value; therefore, measuring system does not require calibration. The simultaneous recording of data from all eight sensors allows tracking the signal without distortion.

An array of sensors is installed in the shoe insole. The measuring device is fixed to the outer surface of the shoe. Its weight is 75 g. The range of transmission is suitable for examination in the natural environment, outside traditional consulting room. Software is dedicated for analysis of the pressure distribution in every moment of the foot movement. The system is suitable for examination of flat feet, diabetic foot and recovery progress after injures.

Two members of ISHM‐Hungary, Professor Zsolt Illyefalvi‐Vitéz, ELC representative, and Professor Gábor Harsányi, president and TPC representative, attended the NATO Advanced Research Workshop on MCM‐C/Mixed Technologies in Florida, USA, in May co‐sponsored by ISHM‐US and organised by:

In this contribution, the design and integration of a piezoelectric vibrating device into low-temperature, co-fired ceramic (LTCC) structures are presented and discussed. The mechanical vibration of the diaphragm was stimulated with a piezoelectric actuator, which was integrated onto the diaphragm. Three different methods for the integration were designed, fabricated and evaluated.

The vibrating devices were designed as an edge-clamped diaphragm with an integrated piezoelectric actuator at its centre, whose role is to stimulate the vibration of the diaphragm via the converse piezoelectric effect. The design and feasibility study of the vibrating devices was supported by analytical methods and finite-element analyses.

The benchmarking of the ceramic vibrating devices showed that the thick-film piezoelectric actuator responds weakly in comparison with both the bulk actuators. On the other hand, the thick-film actuator has the lowest dissipation factor and it generates the largest displacement of the diaphragm with the lowest driving voltage. The resonance frequency of the vibrating device with the thick-film actuator is the most sensitive for an applied load (i.e. mass or pressure).

Research activity includes the design and the fabrication of a piezoelectric vibrating device in the LTCC structure. The research work on the piezoelectric properties of integrated piezoelectric actuators was limited.

Piezoelectric vibrating devices were used as pressure sensors.

Piezoelectric vibrating devices could be used not only for pressure sensors but also for other type of sensors and detectors and for microbalances.