Resonance transducers have been widely developed and studied, as they can be profitably used in many application
such as liquid atomizing and sonar technology. The active element of these devices can be a giant magnetostrictive
material (GMM) that is known to have significant energy density and good performance at high frequencies. The
paper introduces an analytical model of GMM transducers to describe their dynamics in different working
conditions and to predict any change in their performance. The knowledge of the transducer behavior, especially in
operating conditions different from the ideal ones, is helpful in the design and fabrication of highly efficient devices.
This transducer is design to properly work in its second mode of vibration and its working frequency is around 8000
Hz. Most interesting parameters of the device, such as quality factor, bandwidth and output strain are obtained from
In this research, a new method is presented for eliciting the proper features for recognizing and classifying the kinds of the defects by guided ultrasonic waves. After applying suitable preprocessing, the suggested method extracts the base frequency band from the received signals by discrete wavelet transform and discrete Fourier transform. This frequency band can be used as a distinctive feature of ultrasonic signals in different defects. Principal Component Analysis with improving this feature and decreasing extra data managed to improve classification. In this study, ultrasonic test with A0 mode lamb wave is used and is appropriated to reduce the difficulties around the problem. The defects under analysis included corrosion, crack and local thickness reduction. The last defect is caused by electro discharge machining (EDM). The results of the classification by optimized Neural Network depicts that the presented method can differentiate different defects with 95% precision and thus, it is a strong and efficient method. Moreover, comparing the elicited features for corrosion and local thickness reduction and also the results of the two’s classification clarifies that modeling the corrosion procedure by local thickness reduction which was previously common, is not an appropriate method and the signals received from the two defects are different from each other.
Performance and efficiency of magnetostrictive transducer are highly dependent on working conditions. Magnetic bias field and pre-stress of the magnetostrictive rod are two of the main factors affecting the transducer behavior. Unexpected changes may cause unpredictable behavior of the transducer and a dramatic loss of performances. This paper experimentally investigates the effect of different working conditions on quality factor, bandwidth, resonance of a Terfenol-D resonance transducer that works in its first mode of vibration. For this purpose, an experimental setup consisting of laser Doppler, power amplifier and current transducer has been used. A Terfenol-D resonance transducer that is capable of changing magnetic bias field and mechanical pre-stress has been designed and fabricated. Working frequency of the transducer is between 5000 Hz to 7000 Hz. Output parameters of the transducer are experimentally calculated using an equivalent electrical circuit model. Results of the study improves the knowledge in the field and gives suggestions to the design of resonance transducers.
This paper presents a new method to eliminate deviation in positioning caused by coil’s heat generation in magnetostrictive actuators. The advantages of the proposed system are compactness, high controllability and high reliability. The actuator package consists of Galfenol as active element and a magnification mechanism combined with a Peltier element or thermoelectric cooler (TEC). By using the temperature sensor, a thermoelectric cooler (TEC) is activated to reduce the temperature of the coil. However, the reduction of temperature by TEC alone is not enough to eliminate the error and controlling of applied voltage is also required. A simple PI controller for coil’s current is combined with TEC and by reducing the temperature and current simultaneously, the positioning error is vanished completely.
Liquid atomization has many applications such as car fuel injector, heat dissipation, coating, medical use, etc.
The most common way in atomization is to exploit high frequency and high vibration amplitudes of
piezoelectric devices. This paper investigates the effectiveness of a giant magnetostrictive transducer for
atomizing liquids. Effect of vibration amplitudes on output parameters such as atomization size and output
Dubai have been investigated so as the frequency response of the transducer when plunged into the water.
Droplet size particles have been measured through high speed camera. Results show that using giant
magnetostrictive transducer leads to uniformity that is considered a key factor in many applications. Results
demonstrates that sonic transducers based on giant magnetostrictive material can be profitably used as liquid
Proc. SPIE. 9799, Active and Passive Smart Structures and Integrated Systems 2016
KEYWORDS: Mathematical modeling, Actuators, Data modeling, Sensors, Manufacturing, Magnetism, Amplifiers, Data acquisition, Signal processing, Thermoelectric materials, Analog electronics, Physical sciences, Optimization (mathematics), Control systems design, Systems modeling, Temperature metrology
Feedback control strategies are desirable for disturbance rejection of human-induced vibrations in civil engineering structures as human walking forces cannot easily be measured. In relation to human-induced vibration control studies, most past researches have focused on floors and footbridges and the widely used linear controller implemented in the trials has been the direct velocity feedback (DVF) scheme. With appropriate compensation to enhance its robustness, it has been shown to be effective at damping out the problematic modes of vibration of the structures in which the active vibration control systems have been implemented. The work presented here introduces a disturbance observer (DOB) that is used with an outer-loop DVF controller. Results of analytical studies presented in this work based on the dynamic properties of a walkway bridge structure demonstrate the potential of this approach for enhancing the vibration mitigation performance offered by a purely DVF controller. For example, estimates of controlled frequency response functions indicate improved attenuation of vibration around the dominant frequency of the walkway bridge structure as well as at higher resonant frequencies. Controlled responses from three synthesized walking excitation forces on a walkway bridge structure model show that the inclusion of the disturbance observer with an outer loop DVF has potential to improve on the vibration mitigation performance by about 3.5% at resonance and 6-10% off-resonance. These are realised with hard constraints being imposed on the low frequency actuator displacements.
Terfenol-D resonant transducers have some advantages, such as high energy density and high vibrational amplitude, that make them suitable for working in a wide range of application. On the contrary, the main drawback is that operating frequency is fixed and correspond to the resonance frequency of the device itself. If working frequency is far away from the resonance, efficiency of the transducer decreases suddenly. In this paper, an attempt to design and simulation of a multi-resonance sonic transducer is presented. The idea is to increase the range of operating frequencies of about 1.5 kHz. This can be obtained by exploiting ΔE effect in Terfenol-D in response to changes in mechanical preload and magnetic bias. Design procedure is validated by a finite element commercial software and effects of changing resonance frequency in vibrational mode shape of the transducer are presented. The magnetic circuit of the transducer is designed to minimize flux leakage and it is simulated with ANSYS12.
Results of this paper can help to design the more flexible transducer in operating frequency and modal shape.
Terfenol-D resonance transducer has high energy-density and high vibration amplitude. These features make them good selection for using in different applications such as liquid atomizers and sonar transducers. Operating mode of the Terfenol- D transducer plays an important role in efficiency of it. It can also change some parameters of the transducer such as quality factor. In this paper, experimental comparative study between first and second longitudinal modes of vibration in the Terfenol-D transducer is presented. It contains the mechanical quality factor, band with frequency and also effect of changing Young modulus in resonance frequency and mode shape. For this purpose, a resonance transducer for working in 3 kHz in first mode and 8.25 kHz in second mode has been designed and fabricated. In design procedure, preload mechanism location is considered as nodes. Quality factor and bandwidth is calculated experimentally and resonance frequency and mode shape has been calculated both with analytical method and ANSYS12 FEM commercial software. Results show that higher quality factor in the second mode shape and this mode shows lower sensitivity with Young modulus .