Piston Vibration Research Articles

In situ monitoring of defects in steel structures using a robot‐assisted ultrasonic inspection technique

AbstractIncidents in extreme environments can bring unprecedented consequences that would endanger the lives of many humans. Real‐time and early detection of cracks and defects in the steel used for the construction of industrial sites can bring many benefits to remote operators and site managers. Although different methods and systems have been proposed in the past, they are not suitable for real‐time fault detection or long‐term operation in harsh environments. Therefore, this paper proposes a low‐power robotic platform with a magnetic actuator mechanism which is capable of wireless inspection of steel structures using the ultrasonic method. The proposed magnetic motion uses the inertia force generated by the piston vibration and the difference in frictional force during movement. The paper evaluates the performance of the steel structure defect detection system from four different perspectives: sensing principle, wireless communication network, driving part, and power supply.

Focused Shear Wave Beam Propagation in Tissue-Mimicking Phantoms.

Ultrasound transient elastography (TE) technologies for liver stiffness measurement (LSM) utilize vibration of small, flat pistons, which generate shear waves that lack directivity. The most common cause for LSM failure in practice is insufficient shear wave signal at the needed depths. We propose to increase shear wave amplitude by focusing the waves into a directional beam. Here, we demonstrate the generation and propagation of focused shear wave beams (fSWBs) in gelatin. Directional fSWBs are generated by vibration at 200-400 Hz of a concave piston embedded near the surface of gelatin phantoms and measured with high-frame-rate ultrasound imaging. Five phantoms with a range of stiffnesses are employed. Shear wave speeds assessed by fSWBs are compared with those by radiation-force-based methods (2D SWE). fSWB amplitudes are compared to predictions using an analytical model. fSWB-derived shear wave speeds are in good agreement with 2D SWE. The amplitudes of fSWBs are localized to the LSM region and are significantly greater than unfocused shear waves. Overall agreement with theory is observed, with some discrepancies in the theoretical source condition. Focusing shear waves can increase the signal in the LSM region for TE. Challenges for translation include coupling piston vibration with the patient skin and increased attenuation in vivo compared to the phantoms employed here. Fibrosis is the most predictive measure of patient outcome in non-alcoholic fatty liver disease. Increased shear wave amplitude in the LSM region can reduce fibrosis assessment failure rates by TE, thus reducing the need for invasive methods like biopsy.

Theoretical and numerical analysis on low-frequency sound transmission from façades into room

Regarding low-frequency sound transmission from building façades into room for outdoor noise, its mechanism is very complicated due to the combination of outer walls and windows, the vibration behavior of an entire building structure, and the acoustic coupling with an interior sound field. In particular, the installation of a double window system involves combined phenomena of its resonance transmission and normal modes of the room, which has not been fully understood. In order to investigate the phenomena, a theoretical examination is first conducted based on a one-dimension vibro-acoustic model assuming piston vibration of double windowpanes and air spring between them. Next, numerical simulations based on the vibro-acoustic FEM are performed for a house model that consists of outer walls and double windowpanes. The results are compared to clarify the effects of the thickness, stiffness and size of glazing and the air layer thickness for the double window, and also sound absorption of the room. Furthermore, the composite soundproofing effect of weight increasing of the outer walls and installation of the double window is examined to consider appropriate measures for low-frequency sound.

Compact aerial ultrasonic source integrating the transverse vibration part with the bolt-clamped Langevin transducer

We have previously developed a compact circular vibrating plate aerial ultrasonic source with a grooved uniform rod that can produce a large vibration displacement by using piston vibration and emit intense sound waves perpendicular to the vibration surface. In this paper, to create a compact ultrasonic source that can radiate intense aerial ultrasonic waves, we produced a compact aerial ultrasonic source integrating the transverse vibration part with a bolt-clamped Langevin transducer and we investigated the sound source characteristics. These results demonstrated that compared with a conventional source, the length of our source was shorter, the sound pressure was higher, and its structure was simpler.

Computational analysis of the influence of the perforated plate on sandwich transducer in sound radiation performance

To improve the acoustic radiation performance of the sandwich transducer, a perforated plate is added to the radiation end of the transducer. The improved effect of the addition of a perforated plate on acoustic radiation performance of the transducer is studied. First, based on electromechanical equivalence principle, when a perforated plate is attached to a piston vibrator, the expressions of the vibration velocity of radiation surfaces, directivity index (DI) and radiated sound power are derived. Thus, the influences of the perforated plate on the sound radiation performance of the piston vibrator are analyzed. Then, the perforated plate is attached to the radiation surface of a sandwich transducer, and the electromechanical equivalent circuit of the transducer is established. Thus, the input impedance at the radiation end, vibration velocity and sound pressure level (SPL) of the transducer are derived. Further, the SPL of the transducer is calculated and the influences of the perforated plate on the transducer acoustic radiation performance with or without a matching layer are studied. And, the influences of the perforated plate on acoustic radiation performance of different operating frequency transducers are analyzed. Finally, the influences of the perforated plate structural parameters on the SPL of transducer are studied. The results show that the perforated plate with appropriate parameters could further improve the impedance matching between the input impedance and the radiation impedance at the radiation end of the transducer, thus the radiated SPL could be improved maximally. The research method is expected to applied in high-power transducer design.

High-intensity aerial ultrasonic source with sharp directivity containing a compact circular vibrating plate

An intense aerial ultrasonic source containing a compact circular vibrating plate with a uniform rod-type partially grooved source that can produce large displacement in part of the piston vibration and emit intense sound waves in a direction perpendicular to the vibration surface is investigated. Two different compact circular vibrating plates of intense aerial ultrasonic sources (square grooves and round grooves) are designed by considering the stress generated in ultrasonic sources and the sound pressure of the radiated sound waves. The vibration displacement distribution, the directivity of the emitted sound waves, and the input/output characteristics in designed ultrasonic sources are discussed. It was found that the sound waves can be emitted farther away perpendicular to the vibration surface at a very high sound pressure compared with traditional sources.

Estimation of High-Speed Liquid-Jet Velocity Using a Pyro Jet Injector

The high-speed liquid-jet velocity achieved using an injector strongly depends on the piston motion, physical property of the liquid, and container shape of the injector. Herein, we investigate the liquid ejection mechanism and a technique for estimating the ejection velocity of a high-speed liquid jet using a pyro jet injector (PJI). We apply a two-dimensional numerical simulation with an axisymmetric approximation using the commercial software ANSYS/FLUENT. To gather the input data applied during the numerical simulation, the piston motion is captured with a high-speed CMOS camera, and the velocity of the piston is measured using motion tracking software. To reproduce the piston motion during the numerical simulation, the boundary-fitted coordinates and a moving boundary method are employed. In addition, we propose a fluid dynamic model (FDM) for estimating the high-speed liquid-jet ejection velocity based on the piston velocity. Using the FDM, we consider the liquid density variation but neglect the effects of the liquid viscosity on the liquid ejection. Our results indicate that the liquid-jet ejection velocity estimated by the FDM corresponds to that predicted by ANSYS/FLUENT for several different ignition-powder weights. This clearly shows that a high-speed liquid-jet ejection velocity can be estimated using the presented FDM when considering the variation in liquid density but neglecting the liquid viscosity. In addition, some characteristics of the presented PJI are observed, namely, (1) a very rapid piston displacement within 0.1 ms after a powder explosion, (2) piston vibration only when a large amount of powder is used, and (3) a pulse jet flow with a temporal pulse width of 0.1 ms.

Hydrothermal reactor for in-situ synchrotron radiation powder diffraction at SPring-8 BL02B2 for quantitative design for nanoparticle

A hydrothermal reactor for nanoparticle synthesis was designed and constructed for in-situ synchrotron radiation powder diffraction experiment at SPring-8 BL02B2 beamline. The oscillation measurement with a piston vibrator in the system contributed to measurement of homogeneous intensity distribution of Debye Scherrer ring. In-situ powder diffraction study of CeO2 nanoparticle synthesis was described to show the performance of the reactor. Three-dimensional diagram using pressure, temperature and size of CeO2 nanoparticles was determined by the system. The pressure and temperature dependence of particle formation speeds, lattice constants, and particle sizes was clearly determined as a reproducible result. A sensitive response of the cell volume by applying additional 7 MPa pressure was observed in the supercritical condition, whereas there were almost no volume changes in the liquid phase by applying additional 10 MPa pressure. The present in-situ system will be used to optimize the synthesis condition of functional nanoparticles.

Effects of regenerator structure on performance of free piston stirling engine (FPSE)

This study explains the construction and use of SAGE, a commercial analysis program used in the development of Stirling engines, and describes its applications. The free piston Stirling engine (FPSE), which is a type of Stirling engine, eliminates excessive mechanical parts to solve the disadvantages of conventional Stirling engines (weight, size, and mechanical loss of connecting parts for reciprocating motion) and connecting springs to each piston vibration system. In this paper, we briefly describe the SAGE program and investigate the effect of numerical variations of the analytical elements (porosity, mesh diameter, regenerator diameter) of the regenerator on the performance of FPSE using the basic model embedded in the program. We also apply this model to future FPSE development.

Application of the Novel Test Machine, Retention and Drainage Analyzer (RDA), for Wet-end Analysis of Papermaking Process (II) : Vibratory RDA and Selection of CaCO3 Filler by Simultaneous Considering of Multiple Assessment Factors

Wet-end where the fibrous components and functional additives are applied is an essential part for determination of properties of the final product and runnability of papermaking process. However, it is difficult to anticipate physical and chemical phenomena in wet-end using some instruments for lab-scale papermaking test. In addition the performance of retention aids and fillers have to be evaluated by overall analysis of retention, drainage, and paper uniformity. With regard to renovate retention and drainage analyzer (RDA), a new analysis of retention, drainage, and paper uniformity using the RDA had been studied. In this study the RDA was modified by equipping air piston vibrator which could delay the consolidation of wet web and reduce the retention of fines. Effects of the varied kinds of fillers on wet-end of fine paper were analyzed by summation of drainage, turbidity (retention), and paper uniformity using the modified RDA. As a consequence, the selection of proper filler for the optimization of wet-end of paper making process for fine paper was made by using the modified RDA.

PhD theses completed in 2017

Christian SchleihsAcoustic Design of Hydraulic Axial Piston Swashplate MachinesRWTH Aachen University, Aachen, GermanySound and vibration issues have ever since been addressed in the research and d...

Design and Research of Deep-Sea Hydrothermal Sampler with Multi-Cavity

In this paper, on the basis of the existing hydrothermal sampling equipment has devised a new hydrothermal sampler. Using Ansys Workbench software to analyze the valve core and valve seat sealing, the valve core half cone Angle is obtained on the influence law of sealing performance. Cavity of hot fluid into the sampling moment of impact piston is analyzed, the analysis shows that the strength of the piston to meet requirements and the impact piston vibration does not affect the o-rings seal performance.

Reduction of Diesel Knock Noise by Controlling Piston Vibration Characteristics

Reduction of Diesel Knock Noise by Controlling Piston Vibration Characteristics

Investigation of the design method of an angled ultrasonic longitudinal solid horn

A solid horn is one of the key components of power ultrasonic longitudinal vibration system, and the most common horns are designed to allow the vibration travels along straight direction. However, some applications need to change the transmission direction of longitudinal vibration. The design method for angled ultrasonic longitudinal solid horns is investigated in this work. The frequency equation is established by using the continuity of displacement, force, bending moment and angle of rotation, as well as free boundary conditions at its two ends, and the method of calculation of displacement amplification factor is given. The resonant frequencies of some different fabricated angled solid horns consisted of two section bars are calculated by using the proposed frequency equation, and basically agree with the values by finite element method, and are validated by experiment with Vibpilot vibration test system. And then, connection these solid horns with a piezoelectric transducer with resonant frequency of 19.8 kHz, experimental comparison of the amplification factors and vibration modes of output port of the solid horns between the designed and fabricated angled horns validates the effectiveness of the design method. It shows that the longitudinal vibrations excited by transducer along the horizontal direction are successfully transferred to the output ports (in piston vibration) via the angled solid horns. Finally, the relationships between amplification factors of angled solid horns and their geometric dimensions are obtained through a lot of calculation.

Numerical Description of Acoustic Vibrations of a Vapor–Gas–Droplet Mixture in a Closed Channel Based on a One-Velocity, One-Temperature Model

The paper describes a mathematical model and the results of numerical calculations of resonance acoustic vibrations of a vapor–gas–droplet mixture in a closed volume under the action of periodic acoustic waves generated by a harmonically vibrating piston. The numerical method of solving the equations of the model is based on MacCormack′s scheme. The model of equilibrium phase transitions used in the numerical scheme has allowed a chart of regimes of the vapor–gas–droplet mixture vibrations to be constructed depending on the initial vapor content. In accordance with the piston vibration amplitude, the limit of the critical vapor content below which vapor condensation is impossible has been found.

Diesel Combustion Noise Reduction by Controlling Piston Vibration

Diesel Combustion Noise Reduction by Controlling Piston Vibration

Ultra low frequency electromagnetic underwater sound source

A detail analysis is presented of one ultra low frequency sound source which is smaller and lighter than conventional piezoelectric ultra low frequency sound source. This sound source is single piston vibration using the electromagnetic principle. The radiation characteristic of sound source is researched by single piston radiation model in low frequency. The dynamic characteristic such as resonant frequency, vibrant displacement of sound source is researched by analytic method and finite element method. In analytic method, the electricity-magnetism, magnetism-force, and force-vibration conversion models of sound source are established by differential equations in different coupling physical fields, and the dynamic characteristics based on the conversion models are simulated by combining and solving differential equations using the Matlab/Simulink. In finite element method, using transient solver of electromagnetic analysis finite element software Ansoft, the dynamic characteristics of sound source are solved. Optimizing the dynamic characteristic of sound source by adjusting magnetic circuit, drive coil, and elastic component parameters, the resonant frequency and radiated sound power of sound source are determined. One prototype sound source design, in which the source level is 184 dB in frequency 73 Hz by calibration, is fabricated that demonstrated proof-of-concept.

Hydraulic Vibration Exciter and Hydraulic Circuit Design Research

Pressure of the liquid is used as power source of hydraulic vibration exciter. Rotary directional control valve is the realization of oiling-way veversing components . The piston is reciprocated under the influence of the change of the hydraulic. The reciprocating movement of the piston is a result of fluid pressure.Working area of the piston multiplied by the pressure of the liquid is equal to the thrust of the piston.Displacement response of the vibration exciter can be simplified to the second-order vibration systems.Elastic beam is used as limit components of piston of vibration exciter,the piston vibration waveform is a sine wave .The volume of elastic beam is smaller than the volume of fluid elastic element . The hydraulic circuit is a dual pump fuel supply circuits.Pumps are used to supply rotary valve and hydraulic cylinder .Dual pumps fuel supply system is conducive to control fluid pressure and flow of the rotary valve and vibration piston.

Behavior of Ultrasonically Levitated Object above Reflector Hole

Using an axis-symmetric model comprising a flat reflector with a hole and a piston vibrator, we simulate the radiation force acting on a small object levitated near the hole, and predict that the position of the object shifts from the center line of the hole. We also experimentally investigate the behavior of a levitated polystyrene sphere approaching the hole. As predicted, the sphere avoids approaching the hole with some distance, depending on the reflector/vibrator interval and the hole diameter. We believe that this effect is useful in discriminating the droplets to be dispensed from those that should not be dispensed.

Perturbation methods for the spectral analysis of a weakly nonlinear acoustic field generated by a transient insonation

In this study an infinite plane piston is considered which oscillates with finite amplitude in unbounded homogeneous fluid. To illustrate the shape of the weakly nonlinear acoustic field generated by a transient insonation, the function defined by Funch/Muller representing a damped sinusoid is used to simulate the temporal waveform of the piston vibration. The acoustic transient wave generates harmonic components as result of nonlinearities in the material properties of the fluid and in the convective terms of the propagation equation. The mathematical approach is based upon the generalized Burgers’ equation, which is a good approximation of the exact equation for the nonlinear propagation when diffraction effects are assumed to be negligible. The pressure amplitude of the fundamental is considered large enough to produce the second harmonic wave. Under the quasi-linear approximation, an analytical description of the fundamental and the second harmonic waves is elaborated. To simulate the spectrum of the weakly nonlinear acoustic field, the pressure field is written in a perturbation series where the first term is the linear acoustic field that results from an infinitesimal oscillation of the piston and the second term contains the first nonlinear contribution to the acoustic field due to the finite amplitude effects.