Papers by Keyword: Shear Wave

Abstract: The defect detection in composite material is important for its quality control where the hidden defect such as crack, corrosion, notch, holes, void and porosity can develop. In this paper, the ultrasonic bulk wave measurements of longitudinal and shear waves are used to identify defect in the multilayered composite material. This study employs pulse echo technique and utilized angle beam transducer. The composite material model investigated in this contribution are made of 24 mm and 12 mm thick Aluminium plates with a width of 100 mm and a length of 203 mm which are separated with an approximately 1 mm thick oil layer. A simulated defect is created in the composite test material by drilling a hole with 2.5 mm diameter and 3 mm depth on the bottom surface of the third layer material. Finding indicates that the defect is located at 53.39 mm from transducer and the percentage difference of the defect location compared to the calculation method is 7%. It indicates that the proposed method can be use to detect defect in multilayered composite material within 10% accuracy compared to the calculation method.

Abstract: The process of shock disturbances in incompressible nonlinear elastic medium is considered. For the case of one-dimensional deformation the two types of plane shock waves are shown, which carry shift deformations in the medium. The properties of these waves are described, their propagation velocities are calculated. The solution of the boundary problem of the interaction of two plane waves with different shear polarization is presented to demonstrate ways of using the obtained results.

Abstract: Surface-wave dispersion analysis is widely used in civil engineering to infer a shear wave velocity model of the subsoil for a wide variety of applications. Combining with a example, multi-channel analysis of surface waves method (MASW) was discussed in this paper. The entire MASW's procedure of three steps: acquiring ground roll data in the field, processing the data to determine dispersion curve, and back calculation of the geologic parameters for different depths. Based upon all the research results by far, MASW method is an efficient methods because of its high accuracy that is achieved by both special field technique and data processing technique.

Abstract: This paper use FLAC3D method to analyze the dynamic response of some levee that has a cavity in it under the condition of no damping. The results show that there are good corresponding relationships between the shear wave spread characteristics, the horizontal position and depth of the hole, and the specific location of the holes in the levee can be determined. The results can provide references to the test of holes in levee.

Abstract: Local shear wave velocity measurements are effective to obtain tissue elasticity map. We have proposed novel wave number spectrum based shear wave velocity measurement system. However, the accuracy and resolution of this technique should be optimized and sophisticated in future clinical application for breast cancer diagnosis. We propose a simulator of RF signal in shear wave velocity measurement system which can consider arbitrary shear wave propagation. We demonstrate the usefulness of this simulator by experimental result. Moreover, accuracy and resolution of small object is discussed for breast cancer application.

Abstract: Owing to the advantages associated with their very large strength-to-weight and stiffnessto- weight ratios, composite materials are attractive for a wide range of applications. Increasingly, high performance engineering structures are being built with critical structural components made from composite materials. In particular, the importance of carbon-fiber reinforced plastics (CFRP) has been generally recognized in both space and civil aircraft industries, and CFRP composite laminates are widely used. It is very important to detect fiber orientation error in orthotropic composite laminates because the layup of a CFRP composite laminates affects the properties of the laminate, including stiffness, strength and thermal behavior. In this study, a new approach was investigated on detection of fiber orientation with using two longitudinal and a shear wave ultrasonic transducers for the orthotropic composite laminates. During testing, the most significant problem is that the couplant conditions do not remain the same because of changing the viscosity of the couplant. Therefore, making a design for generating shear wave with longitudinal transducers would greatly aid in alleviating the couplant problem. A pyramid with an isosceles triangle was made of aluminum in order to generate shear waves using two longitudinal transducers based on ultrasonic-polarized mechanism. It is found that the shear wave was very sensitive to fiber of CFRP composite. Finally, a CFRP composite material was nondestructively characterized in order to measure fiber orientation error area using automated data acquisition C-scan system.

Abstract: It is very important to detect fiber orientation error in orthotropic composite laminates because the layup of a CFRP (carbon-fiber reinforced plastics) composite laminates affects the properties of the laminate, including stiffness, strength and thermal behavior. In this study, an investigation of shear wave ultrasonic technique was carried out in order to detect stacking orientation error for the orthotropic composite laminates. During testing, the most significant problem is that the couplant conditions do not remain the same because of changing the viscosity of the couplant. Therefore, the design and use of a shear wave transducers would greatly aid in alleviating the couplant problem. A pyramid with an isosceles triangle with two 45o was made of aluminum to generate shear waves using two longitudinal transducers based on ultrasonicpolarized mechanism. Also, the signal splitter was connected to the pulser jack on the pulser/receiver and to the longitudinal transducers which were mounted with mineral oil. The shear transducer was mounted on the bottom as a receiver with burnt honey. It is found that the shear wave was generated at a maximum and a minimum based on the ultrasonic-polarized mechanism. Finally, test results with model data were compared for a fiber orientation of the laminates.

Abstract: Sedimentation is one of the most basic processes in the formation of a soil structure in nature. Many studies have been performed to describe the characteristics of clay sedimentation, based on settlement and water content measurement. In addition, there have been some attempts in numerical modeling to describe soil structure formation as a whole. However, these effects still fall short in explaining the overall process of soil structure formation because some relevant properties are measured after a self-weight consolidation is completed. Furthermore some measurement techniques significantly alter soil structure. Thus, a non-destructive evaluation is necessary for the effective description of soil characteristics during the sedimentation process. In this study, a testing device is designed that continuously monitors the self-weight consolidation process of sedimentation with shear waves. Piezoelectric bender elements are installed into a testing cell to generate and receive shear waves in a small strain regime. Slurries are prepared with kaolinite-type clay and placed in the cell. Shear wave velocities are continuously measured as a function of time during the whole process of the self weight consolidation. The experimental results suggest that as clay sediment is subjected to a certain loading, the shear wave velocity increases as time increases, showing an abrupt change in log time. This abrupt change is relevant to the formation of a stable soil skeleton. It is concluded that the time-dependent variations in shear wave velocity reflect sedimentation and self weight consolidation behavior and the evolution of the effective stress increment.

Abstract: When a material is under mechanical load, the stresses modify the velocity of acoustic waves. This consists in acoustoelastic effect. This property can be exploited for stress measurement in the material itself when the stress concerns the surface of the material, or in the bulk material, as in bolts. The ultrasonic bolt tightening control allows knowledge of preload stress in screws. The accuracy is much better than in the case of torque wrench. In fact, the use of this mechanical-based measurement equipment leads to uncertainties due to random resistant torques, induced by mechanical manufacturing tolerances. The ultrasonic measurement of the pre-load gives the information about the tension inside of the bolt, independently of mechanical uncertainties. This consists in an in-situ measurement. More, in some cases, the ultrasonic method allows knowledge of the preload on bolts already tightened, without untightening. This method is called bi-wave method, and has many connections with birefringent method. Examples of application of the method are presented about the differential mode case, which is largely known and industrialized, and in the case of bi-wave method, which lead to several on site applications, performed by CETIM with a prototype equipment.