Papers by Keyword: Ultrasonic Wave (UW)

Abstract: The Masaryk Railway Station is the oldest still working terminal railway station in Europe. It was built in 1845 and the buildings belonged to the most splendid railway stations in that time. During the long life the part of Masaryk Station burned, it was also damaged while World Wars and finally large reconstruction started last year. The buildings have a high historical value, so the specialists from National Heritage Institute wanted all the original structural members to be preserved. The structure was constructed from two wooden species spruce and fir. Selected timber elements were tested by various non-destructive methods to assess their health. Pilodyn, a device with iron stick can assess a material quality using correlation between depth of stick indentation and material strength. Sylvatest device operates with ultrasonic waves and can determine dynamic modulus of elasticity as one of the mechanical characteristics. Dynamoe device uses an acoustic wave to assess the material quality. The aim of the paper is to present the procedure of timber testing and to discuss measured results.

Abstract: The paper presents a survey of state-of-the-art nondestructive and semi-destructive diagnostic techniques of testing timber structures and examples of their application. Nondestructive testing is a field of study which covers: identifying the mechanical and physical properties of materials and structural components, detecting material defects and discontinuities, and measuring the geometric dimensions of objects without affecting their performance. The nondestructive and semi-destructive methods are described in a systematic manner and the relevant equipment, technology and applications are discussed. The paper focuses on acoustic methods, resistance drilling techniques and radiography, which are suitable for detecting internal defects, decay and cracks, determining the location and dimensions of degraded areas and assessing the mechanical properties of structural timber members. Much attention is devoted to the techniques that are used in practice and have shown significant promise for future development. The results of several drilling resistance tests carried out on historic timber structures are presented.

Abstract: In this paper, based on the ultrasonic dispersion principle, the grafting reaction of maleic anhydride (MAH) onto solid PP in water was studied with acetone as the phase physiognomy solvent, ammonium persulfate [(NH4)2S2O8] as the initiator. The influence of specific surface area on the graft ratio was also studied. The results showed that the grafting reaction had obvious relationship with the specific surface area of original PP particles.

Abstract: The research programs and positioning methods of precise positioning technology of the Mine locomotive unmanned systems were discussed in this paper, It implements the positioning of three-dimensional spatial coordinates, and analyses the experiment of positioning calculation and positioning deviation. Experimental results show that the new technique and method can improve precision positioning accuracy above 5%, and provide reliable security protection for the Mine locomotive unmanned systems.

Abstract: Electrochemical micro-machining (EMM) has become one of the main machining methods for production of miniaturized parts and components. Utilizing the developed EMM set-up, the effects of ultrasonic wave frequency on characteristics of localized dissolution and accuracy of micro-hole in EMM are investigated and evaluated. The experiment results demonstrate that the accuracy of micro-hole and characteristics of localized dissolution can become better with the increase of ultrasonic wave frequency. The accuracy of micro-hole machined by 26KHZ can improve about 30% than that by 16KHZ. Moreover, the ability of localized dissolution by 26KHZ can be increased about 27%-30%.

Abstract: The modular design is adopted in the whole circuit. The AT89S52 single chip microcomputer (SCM) is used as the main part of the controller. The hardware circuit mainly contains ultrasonic emission-receiving module HC-SR04, temperature detecting circuit, liquid crystal display (LCD) circuit and alarm circuit. Signals of the emission probe and the receiving probe are synthetically analyzed by using SCM. The purpose of measuring the body height is realized by using the time difference between two times receiving ultrasonic wave. and it has the advantages of low cost, easily measuring, and short measuring time. The accuracy of the system can be reached to 1 cm, and the measurement range is between 0.50 m and 4.00 m, which can completely meet the design requirement of height measuring system.

Abstract: Damage detection using guided waves in the inspection of tapered sandwich structures with high density foam core (Dyvinicell HP100) is investigated. Characterisation of the fundamental symmetric and anti-symmetric Lamb wave modes is carried out in terms of their velocity and magnitude variation as they encounter a change in the thickness of a composite sandwich plate, aiming at optimising the mode selection to improve the capability and increase the sensitivity of guided waves in inspection of tapered sandwich structures. In addition, an imaging algorithm based on time reversal is developed to detect multiple debonding and artificial damage in tapered sandwich panels based guided waves from an active sensor network. The correlation coefficients between the original and reconstructed time reversal signals are calculated to define a damage index for individual sensing paths, which are used later in the fusion process, identifying the presence of damage in the monitoring area enclosed by the active sensor network. The results confirm that the incident wave signals and their reconstructed time-reversed counterparts can be used to accurately detect the debonding/damage in tapered sandwich structures.

Abstract: In this paper a new type shield cutter wear detection method based on ultrasonic thickness measurement theory was presented. Its working principle was introduced. Its hardware and software were designed. Compared with the existing detection methods, the new method is more accurate and more intuitive, and the method can also provide technical support for the project very well.

Abstract: It's very important to control the sensors of ultrasonic and Time Domain Reflectometry when study the relationship between gas hydrate saturation and acoustic parameters in sediments. We combined Ultrasonic Wave and Time Domain Reflectometry in one apparatus to study the acoustic parameters of gas hydrate-bearing sediments in different saturation. The experimental results show that the apparatus is well designed and can work smoothly. Subsequently, we compare the calculated data by time-average equation, Woods equation, Lees weighted equation and Biot-Gassmann Theory by Lee (BGTL) with the observed data in experiments. It suggests that the Lees weighted equation and BGTL are more applicable in our experiments and various sediments.

Abstract: Silver particles were synthesized by reducing silver ions with copper metal. The as-synthesized silver particles were characterized by scanning electron microscope (SEM). The effects of synthesis conditions on particle morphology were studied. The results showed that dendritic structures were readily synthesized when the silver nitrate solution kept stationary. The low concentration of silver ion was benefit to get perfect silver dendrite. The use of ammonium made the silver shape transferring from dendritic to spherical. The ultrasonic wave accelerated the diffusion of mass and produced spherical silver particles. These results indicated that dendritic silver particles were easy to obtain in non-equilibrium condition while the shape of silver rod-like or spherical was easy to get in equilibrium condition. The morphology and the size of silver particles depend on the synthesis conditions. The formation mechanism of dendritic silver particles were also deduced.