Daraio et al., 2006b; Nesterenko, 2001) or by controlling the wave amplitude (Daraio and Nesterenko, 2006; Daraio et al., 2005 2006b). The addition of periodic heterogeneities in the chain can also be used to tailor wave properties in the chain, such as, wave speed, wave amplitude, and wave width, can be changed accordingly (Porter et al., 2008 2009). By tuning the various system parameters, the properties of the HNSWs can be controlled and designed for specific applications. Sen et al. (1998) and Hong and Xu (2002) showed the possibility of using the nonlinear solitary waves for the detection of defects and im- purities in granular media. Hong and Xu (2002) showed that the backscattered signal’s velocity and shape depend on the presence of light and heavy impurities in granular chains. Nesterenko et al. (2005) and Vergara (2005 2006) studied wave reflection and scattering from the interface of two granular media and found that the energy can be trapped and back-scattered from the interface depending on the interface properties. Job et al. (2005) studied experimentally and numerically the interaction of nonlinear media with a wall of different mechanical properties and found that the reflected waves from the interface depend on the wall’s mechanical properties. Daraio et al. (2006a) and Vergara (2006) showed the potential usefulness of these systems in energy trapping and shock disintegration works. Besides these, some of the other areas of potential application in which highlynonlinear solitary waves can be useful are sound focusing devices (tunable acoustic lenses and delay lines), sound absorption layers, and sound scramblers (Daraio et al., 2005; Herbold et al., 2006; Nesterenko et al., 2005; Spadoni and Daraio, 2010).
This thesis concentrates on research into pulse compression and metamaterials. Each has the potential for improving the quality of measurements in various materials. Chapter 2 reports the mathematical background of several kind of coded excitations, as well as algorithms to perform pulse compression technique and filtering. Moreover, numerical simulations results are shown with the aim to give a guideline on the optimal choice of a coded excitation for a specific purpose. Chapter 3 is focused on the historical and theoretical background to acoustic metamaterial and phononic crystals. Chapter 4 shows the finite element simulation results for several exotic acoustic metamaterial structures. Numerical results on the use of acoustic metamaterial for sub-wavelength acoustic imaging are also shown. Experimental results on the use of acoustic metamaterials for sub-wavelength imaging purpose are given in Chapter 5, together with a path toward the realization of a broad-band acoustic metamaterial device. Chapter 6 reports the use of coded signals and advanced signal processing techniques for the non-destructive testing of several highly attenuating materials. Furthermore, it also shows the realization of a portable device for real time pulse compression, as well as its application on the investigation of concrete structure. An advanced application of the combined use of coded signals and pulse compression for thermography is shown in Chapter 7. Finally, Chapter 8 gives overall conclusions and ideas for further work.
Linear as well as nonlinear collective processes in dusty or complex plasmas have received special attention in the past decade mainly due to the realization of their occur- rence in both the laboratory and space environments [1-3]. A dusty plasma is a normal electron-ion plasma with an additional highly charged component of small micron or sub-micron sized extremely massive charged particulates (dust grains). Wave propagation in such complex systems is therefore expected to be substantially different from the ordinary two component plasmas and the presence of charged dust can have a strong influence on the characteristics of the usual plasma wave modes, even at frequencies where the dust grains do not partici- pate in the wave motion. It has been found that the pres- ence of static charged dust grains modifies the existing plasma wave spectra. On the other hand, it has been shown that the dust dynamics introduces new eigen- modes, such as, dust-acoustic (DA) mode  (weak cou- pling regime), dust-lattice (DL) mode  (strong cou- pling regime), dust Bernstein-Greene-Kruskal (DBGK) modes [6-8], etc. Among the host of modified dusty modes discussed in the literature, the dust ion-acoustic wave (DIAW) has received wide attention as well as ex- perimental confirmation in several low-temperature dusty plasma devices [9-14]. Shukla and Silin  have first theoretically shown that due to the conservation of equi-
To find these problems, material inspection is required—however, the complex designs made possible through using AM present a challenge for standard contact-based measurement techniques. Simple visual inspection methods also do not provide sufficient information about the quality of the built part, as the key-holing phenomenon observed during manufacture (where a subsurface pore is created) would not be identified . It is possible to characterise parts through destructive testing, which would provide statistical information based on AM build parameters , however, this indirect part information is undesirable to high performance part manufacturers. Post-production inspection is also possible—X-ray computer tomography (XCT) is a widely adopted technique for this purpose . However, due to the method of manufacture, it is possible to use a surface-based non-destructiveevaluation (NDE) techniques on each top layer as a structure is built—an in-situ inspection technique could be used to collect volumetric data of a part being built. Rapid measurements could be fed back into the system for reworking or in severe cases, scrapping builds to save material and time. Current areas of focus for in-situ AM inspection includes using purely optical measurement techniques to observe the surface topography and to find large surface breaking defects , and observing the melt-pool created when the feed material is locally heated to create the build structure .
Damage in structures can be defined as changes of material and/or geometric properties in a structure that could affect the structure’s performance. [1, 25, 26].There are many ways than can be used to detect incipient damage in solid structure, a method to detect is linear analysis or non-linear analysis known as Nondestructive Test/Evaluation (NDT/NDE) methods. This measurement system evaluates a structure’s properties without causing damage. Widely used NDT techniques are dye penetration, magnetic particle, eddy-current, radiography, ultrasonic and acoustic emission. [2, 3, 22].Dye penetration, magnetic particle, eddy-current, radiography, ultrasonic can be categorized as linear test while Vibro-acoustic test is non-linear test. Linear test can be defined as the method which get the direct result after test have been carried out, while non-linear test is the process where the result can only been obtained after few procedure have been taken.
Due to misalignment the output of such analysis received high level of noise characteristic frequencies which is one of the useful and valuable parameter for finding the health of condition assessment of automobile rotating machine, whereas for weak condition/old machine sound has missing frequencies compare to the new machine. The RMS value of dB and frequency also been studied in this research but it doesn’t have direct relation with performance of rotating machine. The FFT observation table depicts the spectral mean values. These values are significant in identifying the defective non defective machine. The increase in spectral mean values is indication of initialization or occurrence of minor decay and defect in the machine.
Nonlinearacoustic shadow method that utilizes the secondary wave of parametric array is newly developed for the noninvasive detection of solid structure in water. The experiments are carried in water with and without square cylinder and the result shows that larger variation of relative signal is observed through structure in the secondary wave than the primary waves. It is also observed that the reverberation artifact is reduced and the measurement accuracy is improved in the nonlinearacoustic shadow method using the secondary wave. These results show the capability of lower artifact with higher accuracy for the target object detection by nonlinearacoustic shadow imaging using parametric array, and might lead to a wider application of ultrasound in under- water imaging.
Abstract— In this paper, we present the design and the implementation of a digital Application Specific Integrated Circuit (ASIC) for Acoustic Emission (AE) non-destructive testing. The AE non-destructive testing method is a diagnostic method used to detect faults in mechanically loaded structures and components. If a structure is subjected to mechanical load or stress, the presence of structural discontinuities releases energy in the form of acoustic emissions through the constituting material. The analysis of these acoustic emissions can be used to determine the presence of faults in several structures. The proposed circuit has been designed for IoT (Internet of Things) applications, and it can be used to simplify the existing procedures adopted for structural integrity verifications of pressurized metal tanks that, in some countries, they are based on periodic checks. The proposed ASIC is provided of Digital Signal Processing (DSP) capabilities for the extraction of the main four parameters used in the AE analysis that are the energy of the signal, the duration of the event, the number of the crossing of a certain threshold and finally the maximum value reached by the AE signal. The circuit is provided of an SPI interface capable of sending and receiving data to/from wireless transceivers to share information on the web. The DSP circuit has been coded in VHDL and synthesized in 90 nm technology using Synopsys. The circuit has been characterized in terms of area, speed, and power consumption. Experimental results show that the proposed circuit presents very low power consumption properties and low area requirements.
A method for measuring texture of metal plates or sheets usingnon-destructive ultrasonic investigation includes measuring the velocity of ultrasonic energy waves in lower order plate modes in one or more directions, and measuring phase velocity dispersion of higher order modes of the plate or sheet if needed. Texture or preferred grain orientation can be derived from these measurements with improves reliability and accuracy. The method can be utilized in production on moving metal plate or sheet.
Structural Health Monitoring (SHM) aims to give, at every moment during the life of a structure, a diagnosis of the “state” of the constituent materials, of the different parts, and of the full assembly of these parts constituting the structure as a whole. The state of the structure must remain in the domain specified in the design, although this can be altered by normal aging due to usage, by the action of the environment, and by accidental events. Thanks to the time-dimension of monitoring, which makes it possible to consider the full history database of the structure, and with the help of Usage Monitoring, it can also provide a prognosis (evolution of damage, residual life, etc.). If we consider only the first function, the diagnosis, we could estimate that Structural Health Monitoring is a new and improved way to make a Non-DestructiveEvaluation. This is partially true, but SHM is much more. It involves the integration of sensors, possibly smart materials, data transmission, computational power, and processing ability inside the structures. It makes it possible to reconsider the design of the structure and the full management of the structure itself and of the structure considered as a part of wider systems.
Consider a dense plasma consisting of electrons, positrons and positive-ions. Also, suppose that the elec- trons and positrons follow the zero-temperature Fermi- gas statistics, while, ions behave as classical fluid. In such plasma electrons and positrons may be considered collision-less due to Fermi-blocking process caused by pauli exclusion principle. Therefore, the semi-classical de- scription of nonlinear dynamics and interaction of waves in such plasma can be studied in the framework of conven- tional hydrodynamics model. The basic normalized equa- tions describing plasma dynamical state may be written as
We used immersion technique for ultrasonic measurement. Two types of ultrasonic measuring devices, FLEXSCAN SYSTEM (INSIGHT KK) and robot arm type ultrasonic measuring system (developed by NDIC), were used. The former device is appropriate to simple scanning and the later device was developed for making complex motion. We select these devices by the test conditions. Figure 2 shows a schematic illustration of the experimental setup.
Worldwide, segmented or integral gamma-scanning as well as active or passive neutron counting is used as the standard non-destructive measurement methods for the radiological characterization and quality assurance of radioactive waste packages . These techniques determine the isotope-specific activities of radionuclides in waste packages, but they cannot detect non-radioactive yet hazardous substances within the waste packages. In addition to these methods, radiography or tomography of waste packages using a radioactive gamma-source or X-ray is particularly useful to investigate the contents of heterogenous waste drums. However, these imaging methods only show the attenuation of intense radiation and do not allow a direct identification of substances. Existing imaging procedures allow to distinguish between metal, organic compounds and concrete, but they are not able to distinguish between materials of similar densities, for example between cadmium and copper. Since the chemotoxic potentials of these elements differ a lot and cannot be determined by state-of-the-art non-destructive technology, there is a need for improvement in NDA techniques for waste characterization.
In the present work, we have shown that the nonlinear evolu- tion of two-dimensional electron acousticwaves can be mod- elled by the Davey-Stewartson-I equations. These equations admit dromion solutions which are generalizations of soliton solutions to two dimensions and exhibit exponential spatial decay in both directions. Since experimentally observed po- tential structures in the PCBL region appear to have a dis- tinctly two-dimensional structure, it would be meaningful to characterize them in terms of such two-dimensional nonlin- ear entities. The basis for the present description rests on the primary assumption of the excitation and sustenance of electron acousticwaves in the PCBL region. Such a proposi- tion for one-dimensional wave has been investigated by many authors (Buti, 1980; Dubuloz et al., 1991a,b; Singh et al., 2001). Using high resolution data of FAST, Pottelette et al. (2001) presented evidence for the presence of nonlinear elec- tron acousticwaves in the auroral kilometric radiation source region. Experimental evidence pointing to the existence of energetic ions (T i > T e ) in the PCBL region (Tsurutani et al.,
Based on measurements of nonlinear second sound waves in a high-quality res- onator, we observed formation of a steady-state wave-energy cascade in He II in- volving a flux of energy through the spectral range towards high frequencies. Initial results of the studies were published in Ref. . Since then, we have found that, under some circumstances, wave energy in the acousticsystem can also flow in the reverse direction. Below we discuss these observations in more detail.
Whilst being a high technology concept, evolution of the equipment has made it robust enough for application in any industrial environment at any stage of manufacture - from steelmaking to site inspection of components already in service. A certain degree of skill is required to apply the techniques properly in order to obtain the maximum amount of information concerning the product, with consequent feed back to the production facility. Non-destructive Testing is not just a method for rejecting substandard material. The technique uses a variety of principles. On-destructive Testing is one part of the function of Quality Control and is complementary to other long established methods. By definition non-destructive testing is the testing of materials, for surface or internal flaws or metallurgical condition, without interfering in any way with the integrity of the material or its suitability for service.
Figure 1 shows the variation of Sagdeev potential V (φ) with normalized potential φ for the above mentioned pa- rameters for various values of soliton Mach number M in- dicated on the curves. It is interesting to point out that for Maxwellian electrons (α = 0), the numerical results show that soliton solution exists for 0.76 < M < 1.106. However, for α = 0.1, soliton solutions exist for 0.9 < M < 1.525 and for α = 0.2, the range of Mach numbers for which soliton solution exists is 1.07 < M < 2.172 for the above mentioned parameters. This implies that the Mach number regime in which soltions can exist gets modified with the inclusion of non-thermal electron distribution. In the presence of non- thermal electron population, the soliton can exist for larger soliton speeds or Mach numbers.
pavement thickness measurement. In the Impact-echo (IE) method, a source and a receiver are located adjacent on the material surface. Figure 4 shows the configuration of the equipment. The impactor used in the seismic reflection technique is also used for this method which is a 6mm ball bearing. The impact of the ball produces a pressure wave (p- wave) which propagate down through the material and reflects from media interface. The difference in density and velocity between the top and the successive layer cause the reflection to rise. In the case of the pavement system, this difference does not always be sufficient, due to the similarities of the asphalt layer's properties and the subbase layer. However, the bounding limitation of the pavement and the base layer is almost always enough to generate a discontinuity that can give a clear reflection.