Longitudinal Transducers Research Articles

Ultrasonic tooling system design and development for single point diamond turning (SPDT) of ferrous metals

In ultra-precision diamond turning, work pieces with a surface roughness of R a < 5 nm and a form accuracy of <250 nm can be machined. Materials such as alumina, copper, electroless nickel and some plastics are mainly used in this process. In conventional ultra-precision diamond turning, it is not possible to machine ferrous metals such as hardened steel. A chemical reaction between carbon of the diamond and iron of the steel takes place and increases the tool wear significantly. The method of adding ultrasonic vibrations to the cutting process was developed to reduce the contact time between tool and work piece. This method leads to a significant reduction of the chemical process and thus enables the machining of ferrous materials with diamond tools. For the realization of this method, an ultrasonic tool holder was designed and a prototype of this tool holder was elaborated. Based on a longitudinal excited transducer, a longitudinal wave is transformed through a flexural sonotrode into a transversal wave. The aim of the new development was to reach a higher operating frequency of 100 kHz and minimize disadvantageous features related to weight and geometry of such devices.

Biomechanical implications of cortical elastic properties of the macaque mandible

Knowledge of the variation in the elastic properties of mandibular cortical bone is essential for modeling bone function. Our aim was to characterize the elastic properties of rhesus macaque mandibular cortical bone and compare these to the elastic properties from mandibles of dentate humans and baboons. Thirty cylindrical samples were harvested from each of six adult female rhesus monkey mandibles. Assuming orthotropy, axes of maximum stiffness in the plane of the cortical plate were derived from ultrasound velocity measurements. Further velocity measurements with longitudinal and transverse ultrasonic transducers along with measurements of bone density were used to compute three-dimensional cortical elastic properties using equations based on Hooke’s law. Results showed regional variations in the elastic properties of macaque mandibular cortical bone that have both similarities and differences with that of humans and baboons. So far, the biological and structural basis of these differences is poorly understood.

Ultrasonic metal welding with a vibration source using longitudinal and torsional vibration transducers

Conventional ultrasonic metal welding for joining dissimilar metals uses a linear vibration locus, although this method suffers from problems such as low overall weld strength. Our previous studies have shown that ultrasonic welding with a planar vibration locus improves the weld strength. However, the vibration source in our previous studies had problems in longitudinal-torsional vibration controllability and small welding tip. Therefore, the study of the optimal shape of the vibration locus was difficult. Furthermore, improvement of weld strength cannot be expected. We have developed a new ultrasonic vibration source that can control the longitudinal-torsional vibration and can connect to a large welding tip. In this study, we clarified the longitudinal-torsional vibration controllability of the developed ultrasonic vibration source. Moreover, we clarified that using the planar locus of the developed vibration source produced a higher weld strength than our previous studies, and clarified the optimal shape of the vibration locus.

Study of guided wave propagation on a plate between two solid bodies with imperfect contact conditions

In this work, fundamental symmetric Lamb wave S0 mode is characterized in terms of its velocity variation as function of the interfacial conditions between solid bodies in contact. Imperfect contact conditions are numerically and experimentally determined by using ultrasonic Lamb wave propagation parameters. For the study, an experimental system was used, formed by two solid aluminum rods (25.4mm in diameter) axially loading a thin aluminum plate to control contact interfacial stiffness. The axially applied load on the aluminum plate was varied from 0MPa to 10MPa. Experimental Lamb wave signals were excited on the plate through two longitudinal contact transducers (1MHz of central frequency) using a pitch-catch configuration. Numerical simulations of contact conditions and Lamb wave propagation were performed through Finite Element Analysis (FEA) in commercial software, ANSYS 15®. Simulated Lamb wave signals were generated by means of a 5 cycles tone burst signals with different frequency values. Results indicate a velocity change in both, experimental and simulated Lamb wave signals as function of the applied load. Finally, a comparison between numerical results and experimental measurements was performed obtaining a good agreement.

Ultrasonic zeppelin-shape transducer for algae oil extraction

Energy consumption worldwide is increasing each year. Alternative energy sources supplement these energy demands. Algae are one of such alternative energy sources. As oil needs to be extracted from the ground, algae are needed to be prepared for bio-fuel production. There are a few methods that are used for algae to crack open: chemical and mechanical. Among mechanical methods, the one that is suitable for that purpose is ultrasonication.The current paper presents an ultrasonic cylinder-shape transducer designed for that purpose. Commercial piezo-mechanical systems for algae processing are mostly ordinary longitudinal transducers. The efficiency of such systems is based on irradiation surface, which is normally about 1000mm2. In our system, we propose a different approach to increase the vibration area that produces a cavitation field needed to crack the cell wall of algae. Normally, the active end of transducers is immersed into a reservoir filled with algae-liquid mixture. We propose to create a vibrating reservoir as a part of transducer, thus enlarging the area of acoustic irradiation. Excitation is produced by two full-wave longitudinal transducers orientated opposite to each other and connected to a specifically designed resonant chamber.Experiments have been carried out using two colonial algae species, namely Scenedesmus acutus Meyen and single-cell Monoraphidium griffithii. Comparative experiments have been performed using the standard commercial ultrasonic system for algae processing and the proposed system. The key parameters obtained from the experiments include power consumption and destruction rate.

Ultrasound attenuation and phase velocity of micrometer-sized particle suspensions with viscous and thermal losses

The attenuation coefficient and the phase velocity of micrometer-sized polydivinylbenzene particles in water were investigated by ultrasound spectroscopy equipped with 10–30MHz longitudinal wave transducers. While the surrounding liquid could be assumed to be inviscid for large particles with the size comparable to the wavelength of longitudinal ultrasound, the viscous and thermal waves were considered to have important roles with decreasing the particle size because the particle size becomes comparable with those wavelengths. In this study, these contributions were systematically investigated by changing the particle-size.

Equivalent homogeneous model of D31-mode longitudinal piezoelectric transducers

This article focuses on modelling of D31-mode longitudinal piezoelectric transducers. A simple equivalent one-dimensional homogeneous model of D31-mode longitudinal piezoelectric transducers is proposed in this article. Homogeneous properties of the model are derived by a simple analytical mixing method based on the operation principle of D31-mode longitudinal piezoelectric transducers. Compared with other models in the literature, the proposed homogeneous model can consider passive layers in D31-mode longitudinal piezoelectric transducers for more accurate predictions in either static or dynamic behaviour. The proposed model is validated by a three-dimensional finite element model. Besides, based on the homogeneous model and borrowing the network theory, an exact equivalent circuit is formulated. A more straightforward form of the equivalent circuit can further facilitate analysis and modelling of D31-mode longitudinal piezoelectric transducers. Also, the proposed homogeneous model is wrapped into a transfer matrix form. The formulated transfer matrix of D31-mode longitudinal piezoelectric transducers can be used with the transfer matrix method to facilitate the calculations, when D31-mode longitudinal piezoelectric transducers are connected with numerous mediums in the operation direction. The effectiveness of the equivalent circuit and the transfer matrix is also verified.

An I-shape linear piezoelectric actuator using resonant type longitudinal vibration transducers

Resonant type longitudinal vibration transducers are used in this work to construct a linear piezoelectric actuator with four driving feet. Totally three longitudinal transducers are integrated in I-shape to form the proposed actuator, which contains one vertical transducer and two horizontal transducers. These three transducers vibrate under longitudinal modes with certain temporal sequence, whose vibrations are superimposed in the actuator to generate elliptical motions on the four driving feet. The three transducers are tuned to be suitable dimensions, under which they have very close 1st longitudinal resonance frequencies; the working frequency of the piezoelectric actuator is designed to be about 31.3kHz. The vibration coupling problem between the longitudinal transducers are studied by calculating the motion trajectories of the four feet. It is found that the temporal shift of the longitudinal vibrations can be used to tune the movement trajectories; the four feet can get nearly the same vertical displacements under a phase shift of 105°. At last, the vibration characteristics and mechanical output performances of a prototype are measured. The working frequency of the prototype, the maximum speed, and the maximum thrust force are measured to be 33.15kHz, 1563mm/s, and 158.2N, respectively.

Ultrasonic metal welding by longitudinal-torsional vibration source consisting of two transducers

We study ultrasonic metal welding of dissimilar metals by using planar vibration locus. The planar vibration locus consists of the longitudinal vibration and the torsional vibration. In a previous study, we used an ultrasonic vibration source that contained a vibration converter comprising diagonal slits. The vibration source with diagonal slits was driven two frequencies in order to obtain a planar vibration locus. However, it was difficult to control individual vibration when using the vibration source with diagonal slits. In order to solve this problem, we have developed an ultrasonic longitudinal-torsional vibration source consisting of two transducers in which the longitudinal-torsional vibration can be controlled. The developed vibration source is consists of a longitudinal transducer and a torsional transducer attached to the both ends of a stepped horn with the length of two wavelength of the propagating vibration. This vibration source can generate planar vibration locus of substantially square. In this study, ultrasonic metal welding of dissimilar metals was studied by using the vibration source consisting of two transducers. As a result, high weld strength was obtained in the case of welding of the planar locus than welding of only longitudinal or torsional vibration loci.

Ultrasound frequency analysis for identification of aggregates and cement paste in concrete

The aim of the present study was to identify specific frequencies related to aggregates and cement paste during concrete hydration, by performing a Fourier analysis of the ultrasonic response of concrete specimens to different excitation frequencies. This identification will reduce the high influence of aggregates in the ultrasound signal analysis, enabling a better assessment of changes occurring in the cement paste. Thirty-five cylindrical specimens with a diameter of 100mm and a length of 200mm were cast with a water to cement ratio=0.60. Thirty specimens were destructively tested at 1, 3, 5, 7, 14 and 28days for their compressive strength. The remaining five specimens were non-destructively tested at 1, 3, 5, 7, 14, 28 and 56days using longitudinal and transversal ultrasonic wave transducers with frequencies from 50kHz to 500kHz. Analysis of the evolution in frequency observed in the specimens identified variations related to progressive hydration of the cement paste, in contrast with the invariant behavior of the inert aggregates. Results show that it is possible to distinguish the behavior of cement paste and aggregates in the frequency domain. As a consequence, it should be possible in future research to evaluate more efficiently different phenomena that affect only the cement paste.

Longitudinal–torsional vibration source consisting of two transducers with different vibration modes

The planar vibration locus is applicable to, for example, ultrasonic welding, ultrasonic machining, and ultrasonic polishing. In a previous study, we obtained the planar locus using an ultrasonic longitudinal–torsional vibration source that contained a vibration converter comprising diagonal slits to drive two frequencies. It was difficult to obtain only longitudinal or torsional vibration when using an ultrasonic complex vibration source with diagonal slits. Therefore, the versatility of the ultrasonic complex vibration source with diagonal slits was low. We have developed an ultrasonic longitudinal–torsional vibration source in which the longitudinal–torsional vibration can be controlled. The requirements for an ultrasonic vibration source were longitudinal–torsional vibration control and that the source has a planar locus. In this paper, we investigate a new type of vibration source that satisfies these requirements. It consists of two transducers, a longitudinal transducer and a torsional transducer, attached to the ends of a uniform rod with a length of one wavelength of the propagating vibration.

A Longitudinal Mode Electromagnetic Acoustic Transducer (EMAT) Based on a Permanent Magnet Chain for Pipe Inspection.

A new electromagnetic acoustic transducer (EMAT) design, employing a special structure of the permanent magnet chain, is proposed to generate and receive longitudinal guided waves for pipe inspection based on the magnetostriction mechanism. Firstly, a quantitative analysis of the excitation forces shows the influence of the radial component can be ignored. Furthermore, as the axial component of the static magnetic field is dominant, a method of solenoid testing coils connected in series is adopted to increase the signal amplitude. Then, two EMAT configurations are developed to generate and receive the L(0,2) guided wave mode. The experimental results show the circumferential notch can be identified and located successfully. Finally, a detailed investigation of the performance of the proposed EMATs is given. Compared to the conventional EMAT configuration, the proposed configurations have the advantages of small volume, light weight, easy installation and portability, which is helpful to improve inspection efficiency.

Field assessment of oxidative aging in asphalt concrete pavements with unknown acoustic properties

Because in the field asphalt concrete acoustic properties (i.e., velocities and corresponding attenuations) are unknown, a modified version of the non-collinear wave mixing method is proposed to evaluate oxidative aging levels. Longitudinal transducers mounted on angle wedges are employed to launch subsurface dilatational waves to allow evaluation when there is only access to one side of the asphalt concrete pavement. For the mixture used, one fixed incident angle was found, which is suitable for the range of oven-aged asphalt concrete specimens, i.e., 0–36h. Theoretical explanation and experimental evidence supporting the validity of the proposed approach is presented.

Measurement of mechanical quality factors of polymers in flexural vibration for high-power ultrasonic application

A method for measuring the mechanical quality factor (Q factor) of materials in large-amplitude flexural vibrations was devised on the basis of the original definition of the Q factor. The Q factor, the ratio of the reactive energy to the dissipated energy, was calculated from the vibration velocity distribution. The bar thickness was selected considering the effect of the thickness on the estimation error. In the experimental setup, a 1-mm-thick polymer-based bar was used as a sample and fixed on the top of a longitudinal transducer. Using transducers of different lengths, flexural waves in the frequency range of 20–90kHz were generated on the bar. The vibration strain in the experiment reached 0.06%. According to the Bernoulli–Euler model, the reactive energy and dissipated energy were estimated from the vertical velocity distribution on the bar, and the Q factors were measured as the driving frequency and strain were varied. The experimental results showed that the Q factors decrease as the driving frequencies and strains increase. At a frequency of 28.30kHz, the Q factor of poly(phenylene sulfide) (PPS) reached approximately 460 when the strain was smaller than 0.005%. PPS exhibited a much higher Q factor than the other tested polymers, which implies that it is a potentially applicable material as the elastomer for high-power ultrasonic devices.

Multimode Wave Propagation in Immersed Pipes

In recent years, the guided waves proved their potential use in Nondestructive Testing (NDT) due to their capability to travel relatively long distances in pipes and inspecting the whole cross-section of the waveguide. This is particularly important in industries requiring risk management, such as petrochemical, nuclear and aeronautical industries. The theoretical, numerical and experimental study of guided waves is in progress in the last decades. The authors of the present paper have focused in the last years on theoretical, numerical and experimental validation of several classes of problems encountered in pipe NDT using guided waves. The present work is comparing numerical and experimental results on a water immersed pipe. The experimental setup consists of a longitudinal wave transducer placed at one end of a pipe. Several guided modes are generated. In the received signal is identified the L(0,2) mode, with highest amplitude.

Design and Fabrication of a Skew-Typed Longitudinal-Torsional Composite Ultrasonic Vibrator for Titanium Wire Drawing

In this paper, a new longitudinal-torsional (L&T) hybrid vibrator driven by two longitudinal ultrasonic transducers is proposed for ultrasonic-assisted wire drawing. The two identical transducers were vertically installed on the two side surfaces of a transformer, however, with an offset distance (Δx) and stagger angle (α) between their axes. Therefore, the transformer could synthesize and amplify the vibration of the two transducers to produce an L&T composite vibration. Harmonic and transient simulations were performed in ANSYS to investigate the dynamic characteristics and frequency-dependent sensitivity of the vibrator. Δx and α between the transducers were subsequently optimized to maximize the output amplitude. Based on the finite element analysis (FEA) results, a prototype was manufactured with an electrical circuit developed for impedance matching. The vibrator generates an L&T composite vibration with a measured longitudinal amplitude of about 20 μm when driven by a voltage of 400 Vp-p, 19.597 kHz. The result is consistent with the FEA prediction, which indicates a new method of combining two different forms of ultrasonic vibration.

Comparison Between Using Longitudinal and Shear Waves in Ultrasonic Stress Measurement to Investigate the Effect of Post-Weld Heat-Treatment on Welding Residual Stresses

ABSTARCTFusion welding is a joining process widely used in the industry. However, undesired residual stresses are produced once the welding process is completed. Post-weld heat-treatment (PWHT) is extensively employed in order to relieve the welding residual stresses. In this study, effect of PWHT time and temperature on the residual stresses of a ferritic stainless steel is investigated. Residual stress distributions in eight welded specimens were measured by using an ultrasonic method. Ultrasonic stress measurement is a nondestructive method based on acoustoelasticity law, which correlates mechanical stresses with velocity of an ultrasonic wave propagating within the subject material. The ultrasonic wave employed could be longitudinal or shear wave produced by the longitudinal (normal) or transverse (shear) transducers, respectively. Ultrasonic stress measurements based on longitudinal waves use longitudinal critically refracted (LCR) waves in this direction, while shear wave methods use an ultrasonic birefringence phenomenon. The results show that the effect of PWHT can be successfully inferred by both longitudinal and shear wave methods, but the former is found to be more sensitive to stress variation. Furthermore, the distribution of subsurface residual stresses is found to be more distinguishable when the LCR method is employed.

Longitudinal mode magnetostrictive patch transducer array employing a multi-splitting meander coil for pipe inspection

Recently, a magnetostrictive patch transducer (MPT) by means of the highly magnetostrictive (such as nickel or iron–cobalt alloy) patch attached on the specimen has been applied in nondestructive ultrasonic testing in waveguides. In the study, we proposed a new MPTs array employing a multi-splitting meander coil (MSMC) for generating and receiving longitudinal guided waves in pipes. In the suggested configuration, the directions of the static magnetic field produced by the permanent magnets and the dynamic magnetic field produced by the MSMC are in the axial direction of the pipe. Two finite element models were established to simulate the distribution of the static and dynamic magnetic fields in the patch, respectively. The proposed MSMC was made of flexible printed circuit (FPC), so it could be easily installed on pipe surface. The performance of the proposed MPTs array was experimentally studied. Firstly, it was experimentally verified that the axisymmetric longitudinal guided wave mode, L(0,2), could be effectively generated and received in pipes with the developed MSMC-MPTs array. Secondly, the frequency response characteristics of the developed MSMC-MPTs array were related to D (the distance between adjacent belts of the MSMC). Thirdly, we demonstrated the ability of the developed MSMC-MPTs array for the identification and location of a crack defect in pipes. Finally, we compared the performances of the MSMC-MPTs array and conventional meander coil-MPTs and proved that the signals of the longitudinal guided wave mode could be enhanced by using the developed MSMC-MPTs array.

Stress evaluation of laser cladding coating with critically refracted longitudinal wave based on cross correlation function

Research on stress evaluation of laser cladding coating with critically refracted longitudinal wave was introduced in this paper. Two critically refracted longitudinal wave transducers with 5MHz frequency, spacing between which was constant, were employed as signal emitter and receiver. Based on acoustoelastic equation deduction, relationship between the difference in time of flight and tensile stress is obtained. Combing with cross correlation theory, the difference in time of flight between stressed and unstressed critically refracted longitudinal signals was calculated. Results show that stress evaluation is affected by layer interface and anisotropic microstructure of laser cladding coating, precision of stress evaluation of laser cladding coating increases as step length increases until it attains one cycle. In addition, influence of waveform distortion caused by microstructure of laser cladding coating on stress evaluation is discussed. At last, verification test is carried out and the experimental result is well consistent with theoretical result.

Investigation of a rotary ultrasonic motor using a longitudinal vibrator and spiral fin rotor

A Langevin transducer can provide longitudinal vibration with larger amplitude while also possessing a greater fatigue life than other types of piezoelectric vibrators. A novel rotary Ultrasonic Motor (USM) was proposed based on the use of a longitudinal transducer (acting as the stator) and a spiral fin rotor: the front cover of the Langevin transducer was designed as a double-layer cup-shaped structure, with the rotor sustained by the inner-layer, and the bearing cover fixed to the outer-layer; the rotor consisted of a shaft and spiral fins which acted as the elastic coupler. It is different from a traditional traveling USM, because the stator provides longitudinal vibration and the rotor generates the elliptical motion. This paper analyzed the motion locus equation of the fin contact points. Additionally, a theoretical analysis was performed in regards to the mechanism and the motor’s rotor motion characteristics, which demonstrates the relationships among the motor’s driving force, the torque, the revolution speed, and the motor structure parameters. A motor prototype has been manufactured and surveyed to demonstrate the motor performance. The relationships between the amplitude and the preload on the rotor, the free revolution speed, and the torque of the motor have also been studied.