Laser Doppler Vibration Research Articles

Non-destructive Detection of Small Blowholes in Aluminum by Using Laser Ultrasonics Technique

In this paper, blowhole defects of sub-millimeter diameter in an aluminum alloy are successfully detected by the laser ultrasonic (LU) technique. A Q-switched and pulsed Nd:YAG laser is used for ultrasonic generation, and a laser Doppler vibration meter is used for detection of ultrasound waves on the sample surface. Through adding a thin and transparent film on the sample, a bulk wave penetrating method can be used for evaluating the position and size of the blowhole defects using the LU system. And the directivities of a longitudinal wave generated by a laser at different conditions are discussed. By two-dimensional moving of the sample with a precise motorized translation platform, the ultrasonic waves can be detected at different positions of the sample for evaluating the defects. The C-scan images were obtained to analyze the blowholes’ position and size. Furthermore, a numerical simulation is also used to research the propagation properties of ultrasound in the specimen with internal holes. Results from the experiment and numerical simulation are discussed and compared to demonstrate the reliability and accuracy of the method.

In situ monitoring of dynamic bounce phenomena in RF MEMS switches

This paper presents the first ultra-low-power complementary metal–oxide–semiconductor (CMOS)-based measurement technique for monitoring the cold-switched dynamic behavior of ohmic radiofrequency microelectromechanical systems (RF MEMS) switches in real time. The circuit is capable of providing precise information about contact timing and ohmic contact events. Sampling of dynamic events at frequencies of 1 and 5 MHz shows contact timing accuracy of 99% when compared with real-time true-height information obtained from laser Doppler vibration data. The technique is validated for an ohmic RF MEMS switch with multiple bounces. The actuation voltage has also been designed to enhance bouncing behavior to more clearly study the performance and limits of the presented technique. More than 13 bounces are successfully captured by the electronic measurement technique. The weakest bounces exhibit vertical displacements of less than 20 nm as recorded by a laser Doppler vibrometer. This demonstrates the ability to capture precise timing information even for weak contacting events. A detailed discussion of how parasitics influence this technique is also presented for the first time.

Novel Applications of Laser Doppler Vibration Measurements to Medical Imaging.

Laser Doppler Vibrometry (LDV) has been widely used in engineering applications involving non-contact vibration and sound measurements. This technique has also been used in some biomedical applications including hearing research. The detectable frequencies are in the range of near-DC to 1 GHz or higher. This paper reviews applications of LDV in biomedical engineering and proposes new medical imaging applications based on measuring surface vibrations of tissues and organs. Tests were conducted on human skin using single point and scanning laser vibrometers. These tests suggest that skin vibrations due to the forcing excitation from the heart can be used in imaging of blood flow. The results of these tests illustrate the potential of such vibration measurements in a variety of diagnostic medical imaging applications including blood flow/restrictions, real-time monitoring of blood pressure variations, wound healing, muscle movements, etc. The fact that the measurements can be conducted remotely (non-contact) is an important benefit that adds to the promise of this approach.Electronic supplementary materialThe online version of this article (doi:10.1007/s11220-013-0077-1) contains supplementary material, which is available to authorized users.

Vibration Analysis of Main Shaft of Paper Advance Mechanism Based on Laser Doppler Vibrometer

Modal analysis was done to steel shaft and rubber shaft, and their top ten orders of nature frequency were obtained. The lowest nature frequency of steel shaft is 64HZ and the rubber steel’s is 2.2463HZ. Doppler vibration measurement was done to main shaft of paper advance mechanism and the time domain signal and frequency domain signal were obtained when the rotational speed is 80, 160, 240, 320, 400 Rpm. The frequency and amplitude were obtained by signal analysis. It proves that the nature frequency of steel main shaft is much higher than measuring result, but the seventh and eighth order nature frequency of rubber material is in accord with measuring result of laser doppler vibration.

The Fiber Measuring Method for Rotating Parts Comprehensive Vibration

Light propagation in the air is easily affected by the environment. Shaft bending vibration and torsional vibration are needed to be measured at the same time. The different vibration state are coupled each other. For these reasons, it is necessary to design the optical fiber laser Doppler measurement system and develop the integrated optical fiber system, which is in favor of various vibration modes decoupling and can improve the signal-to-noise ratio. The double parallel beam differential scheme is adopted in the torsional vibration measurement, which the light exposed in the air is coupled into the optical fiber. The optical fiber heterodyne Doppler interference measuring method is adopted in the bending vibration measurement. The laser Doppler vibration measurement technology is applied to a rotating shaft vibration measurement. Comprehensive measuring technology is developed, which can simultaneously measure bending vibration, torsional vibration and the rotation speed of shaft.

钢包下渣检测方法展望

Several ladle slag detection methods of casting lines in the metallurgical industry are described,and the advantages and disadvantages of several detection methods are compared.The laser Doppler vibration technique is a promising detection method,and its feasibility is analysised.It is also pointed out that the technology introduced to the ladle slag detection can greatly reduce production costs,and can greatly enhance the labor productivity.

From the big bang to cleaner teeth — doppler shift — a practical engineering tool

Many basic engineering techniques rely on fundamental science that is so well embedded and accepted, that it becomes effectively ‘invisible’ to the average user. Doppler Shift is one such physical phenomenon that is widely used throughout science and engineering, but often without being noticed.Probably the most familiar scientific application of Doppler is the measurement of the speed of stars, to identify the expansion of the Universe since the ‘Big Bang’. But in engineering and R&D, it can and is being used as a powerful vibration measurement tool. Using laser-based interferometric techniques, with Doppler Frequency Shifting in one path of the interferometer, velocities and displacements as subtle as those of the hearing mechanisms of flies and as fierce as the motion of Formula 1 engines valves can be measuredThis paper describes the basics of Doppler Shift and its use within Laser Doppler Vibration and Velocity measurement instruments. It will cover the extremely wide performance capabilities of the technique and the practical advantages of such instruments, with some practical examples of how and where they are currently being used. Of these examples, many are unique and would not be practical or even feasible without the availability of such tools

Viration transfer process at thermosonic flip chip bond interface

A laser Doppler vibration (LDV) measurement system was setup to monitor the real time vibration of bonding tool and flip chip in thermosonic flip chip bonding. By analyzing the vibration of chip and comparing with the vibration of tool tip, the "stall" phenomena of chip is elucidate, which is significant critical phenomena indicating bonding states changing during bonding process. Stall means that the initial bonding strength is formed at the bonding interface. The chip was vibrated with tool tip before "stall" . After "stall" , relative movement produced between them, a part of tool energy is propagated to the bonding interface via chip and formed bonding strength, and a part of energy is consumed at the tool/chip interface friction, which caused damage to bonding strength and bonding interface structure, caused damage on the surface of chip and tool. Finally, a novel bonding parameter apply method is developed to reduce the friction and to enhance the bonding strength.

2306 進行波型圧電ポンプの研究 : 振動板の挙動(機械設計と機構,一般講演)

This study is about a novel small piezoelectric pump. The pump utilizes a thin vibration plate on which bimorph type piezoelectric actuators generate progressive wave. Characteristics of the pump are investigated by experiments. It is observed that direction of flow depends on driving frequency and the direction does not always agree with phase of driving voltage signals applied to the piezoelectric elements. Behaviors of several part of the vibration plate in the pump case filled or not filled with water are investigated with laser Doppler vibration sensor. It is clarified that phase of sinusoidal vibration of the each part does not agree with the phase of driving signal. Interaction between vibration plate and water may cause the phenomenon.

新型声光通信激光多普勒信号的鉴频电路

新型声光通信激光多普勒信号的鉴频电路

Analysis of digital spectral processing of laser Doppler vibration meter signals

A digital spectral method of the maximum harmonic for processing laser Doppler vibration meter signals from a surface vibrating according to a harmonic rule is analyzed. A digital model for this signal in the presence of additive and multiplicative noises is suggested. Examples are given for the effect of signal discretization frequency on the error of determining vibration amplitude.

Flextensional ultrasonic motor using the contour mode of a square piezoelectric plate.

This paper presents the design, fabrication, and characterization of a new type of standing wave piezoelectric ultrasonic motor. The motor uses a metallic flextensional amplifier, or cymbal, to convert the contour mode vibrations of a square piezoelectric ceramic plate into flexural oscillations, which are further converted to produce rotary actuation by means of an elastic-fin friction drive. The motor operates on a single-phase electrical supply. A beryllium copper rotor design with three-fin configuration was adopted, and the geometry was varied to include different material thicknesses, fin lengths, and inclinations. The best stall torque and no load speed for a 25-mm square motor were 0.72 Nmm and 895 r/minute, respectively. The behavior of the stator structure was analyzed by ANSYS finite element software using harmonic and modal analyses. The vibration mode estimated by finite element modeling (FEM) was confirmed by laser Doppler vibration measurements.

Vibration measurements on blades of a naval propeller rotating in water with tracking laser vibrometer

The application of laser Doppler vibration measurements is a powerful technique for monitoring and analysing mechanical systems. Frequently experiments in operative conditions may be a useful tool for analysing the real behaviour of an object. However, in several applications we may find that the object is rotating during its work and in these conditions the measurement with traditional techniques becomes difficult. For these reasons a system for the tracking of rotating objects has been developed in order to perform vibration measurements. In the present work the application of the tracking laser scanning vibrometer on an operative condition problem is shown. A tracking laser scanning vibrometer has been used for measuring the vibration of a map of points on the object surface during a complete circular motion. The analysed object was a model of a naval propeller working in water. A comparison has been found with the static analysis, in water and air, of the same propeller. Some results are shown.

Vibration analysis of a 3-phase model transformer core

Noise generated by a transformer core has been reduced by improving material and design, but further reduction is still required. To obtain the reduction, the comprehension of noise generating mechanism is important. It is achieved by detailed investigation of core vibration. A vibration measuring system utilizing a laser Doppler vibration meter was developed, and the vibration of a 3-phase 3-limb transformer core was measured. The following results were obtained. The vibration on the front and back of the core was two or three times higher than the other surfaces. The vibration occurred mainly in the limbs of the core, and the vibration direction was perpendicular to the core surface. The vibration waveforms were out of phase between the center limb and both of the side limbs. These results reveal that the principal cause of the vibration on the core was resonance. On the upper surface of the yoke, the vibration was higher in the right and left part and the middle. It is likely that the vibration on the right and left parts is derived from the magnetostriction of the side limbs. The vibration in the middle was considered to be generated by the magnetostriction under the rotational magnetization which occurs in the T-joint area of a 3-phase transformer core. © 1997 Scripta Technica, Inc. Electr Eng Jpn 119(1): 1–8, 1997

3相モデル変圧器鉄心の振動解析

Noise generated by a transformer core has been reduced by improving material and design, but further reduction is still required. To obtain the reduction, the comprehension of noise generating mechanism is important. It is achieved by detailed investigation of core vibration. A vibration measuring system utilizing a laser Doppler vibration meter was developed, and the vibration of a 3-phase 3-limb transformer core was measured. The following results were obtained. The vibration on the front and back of the core was two or three times higher than the other surfaces. The vibration occurred mainly in the limbs of the core, and the vibration direction was perpendicular to the core surface. The vibration waveforms were out of phase between the center limb and both of the side limbs. These results reveal that the principal cause of the vibration on the core was resonance. On the upper surface of the yoke, the vibration was higher in the right and left part and the middle. It is likely that the vibration on the right and left parts is derived from the magnetostriction of the side limbs. The vibration in the middle was considered to be generated by the magnetostriction under the rotational magnetization which occurs in the T-joint area of a 3-phase transformer core. © 1997 Scripta Technica, Inc. Electr Eng Jpn 119(1): 1–8, 1997

Laser Doppler vibration measurement using a polarisation-based device : Pleydell, M.E. Measurement, Vol. 6, No. 1, pp. 10–18 (Jan./Mar. 1988)

Laser Doppler vibration measurement using a polarisation-based device : Pleydell, M.E. Measurement, Vol. 6, No. 1, pp. 10–18 (Jan./Mar. 1988)

On Laser Vibrometry of Rotating Targets: Effects of Torsional and In-Plane Vibration

Vibration measurements on rotating surfaces are often referred to in the commercial literature as a major application of laser Doppler vibration transducers. This paper examines such use of these instruments and shows how the presence of a velocity component due to the rotation itself leads to spurious measurement dependence on both torsional vibration and motion perpendicular to the line of incidence of the laser beam. In addition, the scale of this dependence increases with both rotation speed and perpendicular distance between the line of incidence and a parallel line through the centre of rotation. These phenomena are investigated theoretically and excellent agreement is found when compared with experimental data. Two solutions are suggested; the first involves careful alignment of the laser beam whereas the second requires two simultaneous, orthogonal measurements to be made. If neither method is adopted it is entirely conceivable that the intended solid body vibration measurement may be masked at many frequencies of interest.

Analysis of the accuracy of a laser Doppler vibration meter

Analysis of the accuracy of a laser Doppler vibration meter

Laser Doppler vibration measurement using a polarisation-based device

A non-contacting laser-based displacement and vibration measuring device is presented. It is based on the coherent detection of the Doppler shift introduced into light scattered by an optically rough target object. Geometric manipulation of the beams within the system compensates for the speckle in the scattered light. The sense of the target motion is derived using a passive technique based on controlled polarisation of the reference beam.In its simplest mode of operation it has a resolution of half of the laser wavelength, but this may be increased by a factor of four. Continuous measurements of displacement of up to 10 cm have been made with an experimental system, with less than 1% error; vibrations of smaller amplitude have been measured with greater accuracy. In the existing configuration the maximum target velocity in the direction of the measuring beam is limited by the 100 kHz analogue signal processing roll-off to 32 mm/s; however, this may easily be extended by using more sophisticated electronics.

Laser Doppler vibration amplitude measurement with optical fiber probe.

Laser Doppler vibration amplitude measurement with optical fiber probe.