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Time-triggered smart transducer networks  [PDF]
Wilfried Elmenreich
Computer Science , 2015, DOI: 10.1109/TII.2006.873991
Abstract: The time-triggered approach is a well-suited approach for building distributed hard real-time systems. Since many applications of transducer networks have real-time requirements, a time-triggered communication interface for smart transducers is desirable, however such a time-triggered interface must still support features for monitoring, maintenance, plug-and-play, etc. The approach of the OMG Smart Transducer Interface consists of clusters of time-triggered smart transducer nodes that contain special interfaces supporting configuration, diagnostics, and maintenance without affecting the deterministic real-time communication. This paper discusses the applicability of the time-triggered approach for smart transducer networks and presents a case study application of a time-triggered smart transducer network.
Defect Inspection of Flip Chip Solder Bumps Using an Ultrasonic Transducer  [PDF]
Lei Su,Tielin Shi,Zhensong Xu,Xiangning Lu,Guanglan Liao
Sensors , 2013, DOI: 10.3390/s131216281
Abstract: Surface mount technology has spurred a rapid decrease in the size of electronic packages, where solder bump inspection of surface mount packages is crucial in the electronics manufacturing industry. In this study we demonstrate the feasibility of using a 230 MHz ultrasonic transducer for nondestructive flip chip testing. The reflected time domain signal was captured when the transducer scanning the flip chip, and the image of the flip chip was generated by scanning acoustic microscopy. Normalized cross-correlation was used to locate the center of solder bumps for segmenting the flip chip image. Then five features were extracted from the signals and images. The support vector machine was adopted to process the five features for classification and recognition. The results show the feasibility of this approach with high recognition rate, proving that defect inspection of flip chip solder bumps using the ultrasonic transducer has high potential in microelectronics packaging.
Piezoelectric transducer parameter selection for exciting a single mode from multiple modes of Lamb waves

Zhang Hai-Yan,Yu Jian-Bo,

中国物理 B , 2011,
Abstract: Excitation and propagation of Lamb waves by using rectangular and circular piezoelectric transducers surface-bonded to an isotropic plate are investigated in this work. Analytical stain wave solutions are derived for the two transducer shapes, giving the responses of these transducers in Lamb wave fields. The analytical study is supported by a numerical simulation using the finite element method. Symmetric and antisymmetric components in the wave propagation responses are inspected in detail with respect to test parameters such as the transducer geometry, the length and the excitation frequency. By placing only one piezoelectric transducer on the top or the bottom surface of the plate and weakening the strength of one mode while enhancing the strength of the other modes to find the centre frequency, with which the peak wave amplitude ratio between the S0 and A0 modes is maximum, a single mode excitation from the multiple modes of the Lamb waves can be achieved approximately. Experimental data are presented to show the validity of the analyses. The results are used to optimize the Lamb wave detection system.
Online Fabric Defect Inspection Using Smart Visual Sensors  [PDF]
Yundong Li,Jingxuan Ai,Changqing Sun
Sensors , 2013, DOI: 10.3390/s130404659
Abstract: Fabric defect inspection is necessary and essential for quality control in the textile industry. Traditionally, fabric inspection to assure textile quality is done by humans, however, in the past years, researchers have paid attention to PC-based automatic inspection systems to improve the detection efficiency. This paper proposes a novel automatic inspection scheme for the warp knitting machine using smart visual sensors. The proposed system consists of multiple smart visual sensors and a controller. Each sensor can scan 800 mm width of web, and can work independently. The following are considered in dealing with broken-end defects caused by a single yarn: first, a smart visual sensor is composed of a powerful DSP processor and a 2-megapixel high definition image sensor. Second, a wavelet transform is used to decompose fabric images, and an improved direct thresholding method based on high frequency coefficients is proposed. Third, a proper template is chosen in a mathematical morphology filter to remove noise. Fourth, a defect detection algorithm is optimized to meet real-time demands. The proposed scheme has been running for six months on a warp knitting machine in a textile factory. The actual operation shows that the system is effective, and its detection rate reaches 98%.
Design of a Smart Ultrasonic Transducer for Interconnecting Machine Applications  [PDF]
Tian-Hong Yan,Wei Wang,Xue-Dong Chen,Qing Li,Chang Xu
Sensors , 2009, DOI: 10.3390/s90604986
Abstract: A high-frequency ultrasonic transducer for copper or gold wire bonding has been designed, analyzed, prototyped and tested. Modeling techniques were used in the design phase and a practical design procedure was established and used. The transducer was decomposed into its elementary components. For each component, an initial design was obtained with simulations using a finite elements model (FEM). Simulated ultrasonic modules were built and characterized experimentally through the Laser Doppler Vibrometer (LDV) and electrical resonance spectra. Compared with experimental data, the FEM could be iteratively adjusted and updated. Having achieved a remarkably highly-predictive FEM of the whole transducer, the design parameters could be tuned for the desired applications, then the transducer is fixed on the wire bonder with a complete holder clamping was calculated by the FEM. The approach to mount ultrasonic transducers on wire bonding machines also is of major importance for wire bonding in modern electronic packaging. The presented method can lead to obtaining a nearly complete decoupling clamper design of the transducer to the wire bonder.
Actuating frequency selection of single mode Lamb waves using single piezoelectric transducer

Zhang Hai-Yan,Cao Ya-Ping,Yu Jian-Bo,Chen Xian-Hua,

物理学报 , 2011,
Abstract: Considering the interaction between the piezoelectric transducer (PZT) and the plate, a frequency adjusting method of generating single mode Lamb waves using single piezoelectric transducer is presented in theory. The application of mode selection in Lamb wave structural health monitoring is experimentally given. The theory has the ability to predict the amplitude of each Lamb wave mode as a function of frequency for given plate material and thickness, and specific PZT size. Optimal actuating frequency can be identified at which the wave amplitude for a particular mode is maximized while the wave amplitudes for other modes are relatively minimized. Numerical results are presented to validate the theory and show the capability of single mode Lamb wave selection. Different frequencies that correspond to a preferential A0 mode, a preferential S0 mode, and both the A0 and the S0 modes are excited for damage imaging, respectively. The results show that the single Lamb wave mode detection can locate the damage more accurately, demonstrating the importance of the mode selection in Lamb wave structural health monitoring.
Numerical Time-Domain Modeling of Lamb Wave Propagation Using Elastodynamic Finite Integration Technique  [PDF]
Hussein Rappel,Aghil Yousefi-Koma,Jalil Jamali,Ako Bahari
Shock and Vibration , 2014, DOI: 10.1155/2014/434187
Abstract: This paper presents a numerical model of lamb wave propagation in a homogenous steel plate using elastodynamic finite integration technique (EFIT) as well as its validation with analytical results. Lamb wave method is a long range inspection technique which is considered to have unique future in the field of structural health monitoring. One of the main problems facing the lamb wave method is how to choose the most appropriate frequency to generate the waves for adequate transmission capable of properly propagating in the material, interfering with defects/damages, and being received in good conditions. Modern simulation tools based on numerical methods such as finite integration technique (FIT), finite element method (FEM), and boundary element method (BEM) may be used for modeling. In this paper, two sets of simulation are performed. In the first set, group velocities of lamb wave in a steel plate are obtained numerically. Results are then compared with analytical results to validate the simulation. In the second set, EFIT is employed to study fundamental symmetric mode interaction with a surface braking defect. 1. Introduction Lamb wave testing technique is increasingly used for assessing defects in thin-wall structures like plate and pipes [1–3]. Lamb waves are elastic waves whose wavelength is in the same order as thickness of the structure [4]. One of the main advantages of lamb wave technique is that it allows long-range inspection in contrast to traditional ultrasonic testing, where the coverage is limited to a small area in vicinity of each transducer. Lamb waves were first described theoretically by Horace Lamb in 1917 [5]. These waves arise from coupling between shear and longitudinal waves reflected at the top and bottom edges of a thin wall structure [6]. Lamb wave theory can be found in a number of text books [7]. Defects such as corrosion and fatigue cracks cause changes in effective thickness and local material properties and therefore measurement of variations in lamb wave propagation can be used to assess the integrity of plate [1]. Successful usage of lamb waves in an inspection system needs to understand its schemes of propagation in a waveguide and its scattering at defects. Thus, there is an increasing demand for powerful, flexible, and accurate simulation techniques. First works on numerical simulation of ultrasonic waves were done by Harumi (1986) and Yamawaki and Saito (1992) who calculated and visualized bulk wave propagation [8]. Now, numerical simulation of lamb waves is possible. Common techniques which are used to simulate
Structural damage imaging based on time-reversal theory for focusing of Lamb waves

Zhang Hai-Yan,Sun Xiu-Li,Cao Ya-Ping,Chen Xian-Hua,Yu Jian-Bo,

物理学报 , 2010,
Abstract: This study presents a theoretical and experimental investigation of the application of the time-reversed concept to dispersive and multimode Lamb waves for health monitoring of plate-like structures. When a Lamb wave signal is excited in a plate-like structure with damage,the damage will serve as a passive wave source. With the transfer function,the focusing in the time-reversal field composed of distributed transducer network is analyzed by deducing the amplitude expression of the time reversal Lamb wave signals. The result demonstrates that time-reversal signal reaches the maximum amplitude when the observation point is located at the damage location. To validate the focusing effect of the time-reversal method,an efficient imaging method suitable for distributed actuator/sensor networks is adopted for locating and approximate sizing of structural damages. Experimental results combined with finite element simulation illustrate that the inspection energy can be focalized on the damage. It indicates that the time-reversal method is an effective way for identifying and locating damage for Lamb wave inspection.
A Pipe Inspection Using a Circumferential SH-Mode Plate Wave Generated in a Pipe by an Electromagnetic Acoustic Transducer (EMAT)  [PDF]
Riichi Murayama, Hideo Nishino
World Journal of Engineering and Technology (WJET) , 2018, DOI: 10.4236/wjet.2018.63043
Abstract: Inspection of a pipeline is essential for the safe use of such facilities. A trial sensor using an electromagnetic acoustic transducer (EMAT), which can generate the SH-mode plate wave propagating in the circumferential direction, has been developed to realize this objective. It consists of a circulating electromagnetic induction coil around the pipe and many permanent magnets arranged on the surface of the pipe in the circumferential direction. It is postulated that the intensity of the SH-mode plate wave propagating in the circumferential direction is dependent on any defects in the circumferential direction. A resonance method was then utilized to obtain a stronger received signal. As a result, it was confirmed that the resonance status can be detected. The relationship between the signal intensity and the pipe thickness was then evaluated. It was confirmed that the wall thickness of about 20% can be detected under a static condition. Finally, a moving test has been executed by using an axially traveling device manufactured by trial. The test pipes with different sizes of drilled holes were prepared. The change in the received signal intensity according to different sizes of the drilled holes was successfully detected.
Experimental Research of Lamb Wave Tuning in Model Control

WU Bin,LIU Qi,JIAO Jing-pin,HE Cun-fu,

实验力学 , 2011,
Abstract: Lamb wave mode tuning refers to a single-mode Lamb wave testing method via frequency selection under the condition of piezoelectric transducer with certain size. The excitation and control of single-mode Lamb wave was implemented by zuthors based on the theory of Lamb wave tuning. At the same time, the effect of adhesive property and bonding position on transducer on the Lamb wave tuning controlling was experimentally studied. Results show that for different kinds of adhesive, after solidified, the stiffer the adhesive layer is, the better coherence between the experimental and the theoretical is. While for the same adhesive, the bonding at the edge of piezoelectric transducer may produce certain effect on lamb wave mode tuning due to the asymmetric mode stress amplitude increasing.
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