Figure 6.23 shows the comparison of the heating indexes calculated from the signals shown in Figure 6.22. Generally, the shape of the heating index is similar in both cases and the largest peak appears at the same time which means the same frequency in a linear sweep test. However, the velocity signal shows two peaks at 1 and 2 but the force signal shows only one peak at 1. This can be explained by a comparison of the magnitude and frequency characteristics of both signals. At the peak 1 shown in Figures 6.22(a1) and (b1), both the velocity and the force are high and more high harmonics are excited as shown in STFTs in Figures 6.22(a3) and (b3) but at the peak 2 the velocity is high but the force is small and less high harmonics are excited as shown in the STFTs. This shows that there is a resonance of the clamp and blade system. Therefore low force is required to excite it. The position of the excitation point with respect to the mode shape of the excited mode of the clamp and blade system can affect the level of response and the force input. The force depends on how close the excitation point is to a node of the excited mode. At peak 2 the excitation point seems to be close to an anti-node of the excited mode and this leads to the result that the response is high but the force is small at peak 2. This characteristic leads to the disappearance of the second peak in the heating index calculated from the force signal. In summary, the force sensor can detect the vibration achieved in the blade up to very high frequency and the velocity measured by a laser vibrometer on the blade and the force provide a similar shape of HI when the vibration has a rich frequency content. However, the force signal is not proportional to the response but it depends on the excitation position relative to the excited system mode shape. Therefore it could give a false indication of the vibration achieved in the blade, particulary when a single dominant mode is excited. It also needs improvement in fatigue strength if the idea is to be applied in practice.
The most concerning outcome of the field trial is the damage observed in one of the probe’s housing. The current housing is probably unsuitable for long term use. Each probe should ideally be robust enough to function for a long time, i.e., a year or more of continuous use. There are several possible options of improving the system’s physical robustness. Different materials could be used for the probe housing. Currently, clear perspex is used for the inner electronics housing. This material is very hard, but quite brittle, especially in locations where small cracks have developed, e.g., around screw holes. Another method of improving the robustness could be to change the way the transducer attaches to the electronics. Currently, the transducer is rigidly attached to the electronic housing. This means that the housing experiences an impulsive stress when the probe is hit into the tree. The housing could be decoupled from the transducer by separating the two using a short length of cable. When performing a measurement, the electronics housing would dangle from the cable, and would be fixed to the cable using either a crimp or a screwed locking-connector. This arrangement would also have the advantage that the operator must grab the transducer at its head when removing it from the tree. With the current system, they can easily grab at the bottom of the probe, potentially applying a damaging torque where the transducer and housing connect.
97 1 INTRODUCTION
Non-destructivetesting (NDT) is defined as the course of inspecting, testing, or evaluating materials, components or assemblies without destroying the serviceability of the part or system (Workman & O. Moore, 2012). The purpose of NDT is to determine the quality and integrity of materials, components or assemblies without affecting the ability to perform their intended functions. Non-destructiveness ought not to be confused with non-invasiveness. Testing methods that do not affect the future usefulness of a part or system are considered to be non-destructive even if they consist of invasive actions. For exam- ple, coring is a common NDT method that is em- ployed to extract and test specimens from concrete components in order to determine the properties of in-situ concrete. Coring alters the appearance of the component and marginally affects its structural in- tegrity. If done correctly, coring maintains the ser- viceability of the structural component and is thus considered to be non-destructive.
Infrared spectroscopy is based on the excitation of vibrational states of molecules via exposure of substances to infrared radiation. IR spectroscopy is considered as a key technology in the field of molecule-specific sample analysis. By analyzing changes in the spectral composition of the probing light beam, the spectra gathered via these methods provide access to detailed information on the binding characteristics of functional groups within the sample. Therefore this technique is highly important for the identification and characterization of unknown substances as well as the investigation of interactions between different compounds. Thus, this method enables a sophisticated qualitative and quantitative analysis of the chemical composition of a product in solid as well as liquid state.
The impact-echo methods of the University of Stuttgart (IE-USt) [7, 8] and BAM (IE-BAM-1 und IE-BAM-2) [9, 10] work with an electric controlled impactor. This testingmethod can be operated as a single point measurement as well as automated by measurements using a scanner. The data measured by USt were analysed with the LabView based software IEDA. Ultrasonics, radar and impact-echo measurements at BAM were accomplished by a scanner for construction sites . For the ultrasonic method of BAM a dry coupled double transducer probe for shear waves was used (ACSYS A1220) . Also a 3D-reconstruction analysis was applied . The measured value for ultrasonic time of flight is the value between maximum of initial pulse to maximum received pulse regarding the delay.
Non-DestructiveTesting (NDT) is the term used in connection to represent the techniques that are based on the application of physical principles employed for the purpose of determining the characteristics of materials or system and for detecting and assessing the in homogeneities and harmful defects without impairing the usefulness of such materials or components or systems.An NDT method ranges from the simple to the intricate. Visual inspection is simplest of all. Surface imperfection in visible to the eye may be revealed by penetrant or magnetic methods. If serious surface defects are found, there are often little points in proceeding further to more complicated examination of the interior by other methods like ultrasonic or radiography. The principle optical methods are visual or optical inspection, dye penetrant testing, magnetic particle testing, eddy current testing, radiography testing, and ultrasonic testing.
This is used to estimate the area percentage of different phase’s composition of material. In phase analysis thresholding images can be done by different color. It is calculated area% and area of selected Phase in different colors. Single Phase can be done by simply clicking on particular portion and it can be reset or deleted. It allows user to acquire, process, and analyze the images of the polished sections when it is necessary to estimate the area percentage of different phases. If the image is color or b/w (depending on the image) the program starts its processing. The phases for (e.g. different minerals, inclusions in the metals, etc.) are threshold. For phase thresholding the B/W or Color manual thresholding method is used. If you are not satisfied with their thresholding there is an ability to adjust it by moving the graphical sliders. The phase analyses ASTM
tire (by wt.) were produced in the shape of 5cm 3 cubes. After this, all the concrete was cured for 28 days.
Densities and open porosities were determined by the Archimedes principle, according to the ASTM C642 test standard. A compressive test (ASTM C109/C109M), which is a destructive test method, the Schmidt method, which is the most common method used for non-de- structive testing of concrete (ASTM C805), and a UPV test, which is another non-destructive test method (ASTM C597), were performed.
The membrane resonance method is similar to the mechanical impedance method except that it specifically measures local resonant vibration, and the excitation source is non- contact. It works on the principle that collectively the layers above a delamination constitute a membrane constrained at the perimeter of the delamination. It follows that the thickness of the membrane is the same as the depth of the delamination and that this together with the composite properties and the membrane equivalent diameter determine the frequency at which the membrane resonates. Therefore at frequencies around the membrane resonance, the vibration response for a given input force amplitude will be greater near the delamination than in a sound region. The difference in dynamic impedance between a good region and a defective region is significantly greater for the membrane resonance method than observed for the mechanical impedance method. Consequently it is not necessary to place such stringent controls on the input force making it a potentially simpler method. The probe is scanned over the surface, and to ensure that the membrane resonance is found at each location, the input signal is generally broadband. One way of achieving this is by applying white noise in the frequency range 0.5 to 10kHz using piezoelectric material for both transmitter and receiver. The ratio between the transmitted and received energy is displayed on a meter. This is the principle of the Fokker type I bond tester.
Following the determination of the configuration, the analyzer then determines the conductor resistance values at three different constant current levels, 0.1, 0.5, and 0.8 amperes, using Four Wire Kelvin measurements. In addition, subsequent conductor resistance measurements were made at current levels of 1.0, 2.0, and 2.5 amperes using the two-wire method. The purpose of these measurements was to isolate conductors that exhibited significant differences in resistance values at the various loads. The variation of measurements may be indicative of several types of faults including broken conductors, corrosion at terminals or in the conductor at insulation breaches, loose terminations, cold solder joints, and improper crimps. For the two-wire testing, two wiring specimens from the DC-9 (2) tested higher than the expected 3.0 ohms and both of
Core drilling method is the most direct way of measuring the actual strength of concrete in the structure. It mostly involves proper selection of location and number of samples to be obtained. Core should be taken so as to avoid the reinforcement. If avoidance of secondary reinforcement or surface reinforcement is inescapable, strength of Core can be taken as 10% less than measured strength. Cylindrical specimen of 100mm or 150mm diameter are common; other sizes may also be permitted but the least lateral dimension should not be less than 3 times the maximum size of the aggregates used. The core specimen to be tested should preferably have height of specimen as twice the diameter. If there are difficulties of obtaining samples of such size, the length to diameter ratio is permitted to be lower, but in no case lower than 0.95. The samples are to be stored in water for two days prior to testing and are to be tested in moist condition. The ends of specimens are trimmed and flatten and capped with molten sulphur or high alumina cement or some other permissible capping material to obtain a true flat surface. The specimen is then tested in compression.
desalination equipment, and wastewater treatment facilities.
Eddy Current testing is one of the most widely used NDT Inspection method for metal tubular products. It is relatively easy to use, works within a wide range of production speeds, and has a relatively low cost of operation. However, Duplex and Super-duplex Stainless Steel tubes by definition contain about 50% ferrite in their microstructure which results in permeability variations within the grain boundaries of the microstructure of the Duplex Stainless product. These permeability variations present a problem for eddy current testing in that they act to shield or prevent the penetration of the eddy current field from sufficiently entering the metal and thereby yield poor test results 2 . The use of an Eddy Current encircling coil coupled with a saturation coil suppresses the effects of permeability variations which appear as “noise” within the test results.
The following theoretical and practical results were obtained in the paper : 1) A unified observation system for alternating electromagnetic and seismic fields using a local excitation source has been developed and tested. The choice of the type of excitation source was determined by the following: a) a uniform geometry of the normal field, b) the absence of one or several components in the measured field in the case of a quasi-layered medium. Such properties in the case of the electromagnetic field have a vertical magnetic dipole, in the case of a seis- mic field—a vertically acting force. The presence of a local source of excitation allows regularly for a given network of observations to realize overlaps at differ- ent angles of visibility (the source of excitation towards the heterogeneity). Three components of the magnetic field and three components of the field of elastic displacements as functions of spatial coordinates and time are used as input data for interpretation. For ground-based observations, the data are rec- orded on the day surface for a set of distances between the source and receiver as a function of time. Analysis of the solution of direct problems for seismic and electromagnetic cases, showed   that a single computational approach can be realized when interpreted after a preliminary transfer of electromagnetic data to the real axis, and seismic to an imaginary axis of the complex frequency plane. In this case, the whole further process of interpretation must be con- ducted on this plane, without going back to the time domain.
In order to reduce the run time in obtaining valid solutions to such problems, several researchers have developed approximate numerical schemes to treat the situation. Weight has offered a model based on geometrical acoustic considerations to describe pulse propagation in terms of direct longitudinal, edge longitudinal and shear waves  . This model incorporates an empirical extension of the impulse- response method developed for fluids [8, 9] . Lhemery refined Weight’s results by introducing an approximate integral formula for transient elastic waves which is closely related to the exact Rayleigh integral [7-9] for ultrasonic radiation into the fluid. Gridin and Fradkin used a high-frequency asymptotic approximation to obtain a time-harmonic solution and then performed harmonic synthesis to obtain information on the pulse using a fast Fourier transform [2, 4] . Jian et al have combined analytical solutions and numerical integrals to calculate the ultrasonic field due to the Lorentz force in metals, induced by an Electromagnetic Acoustical Transducer (EMAT)  . The force can be of arbitrary spatial distribution in the metal.
This is the first presentation of a framework for shape optimisation that includes NDT consid- erations. There are several limitations and potential extensions to the presented method. The forward modelling approach uses an analytical model for the transmission and reception of laser induced ultrasound [3, 29, 44]. This model is a first-order scattering approximation (waves are reflected only once by a scatterer), and therefore does not consider any boundary reflections. Ray tracing algorithms that account for reflections (e.g., Bai et al. ) or numerical simulation of wave propagation [30, 33] could be implemented to include second order scattering better representing the physics of wave propagation in practice. In addition to this, the optimisation only considers the propagation of compressional (or longitudinal) waves (Equations (3) and (5)). A weighted combination of compressional and transverse wave components  could be included in a future implementation.
During their operation, modern aircraft engine components are subjected to increasingly demanding operating conditions, especially the high pressure turbine (HPT) blades. Such conditions cause these parts to undergo different types of time-dependent degradation, one of which is creep. A model using the finite element method (FEM) was developed, in order to be able to predict the creep behaviour of HPT blades. Flight data records (FDR) for a specific aircraft, provided by a commercial aviation company, were used to obtain thermal and mechanical data for three different flight cycles. In order to create the 3D model needed for the FEM analysis, a HPT blade scrap was scanned, and its chemical composition and material properties were obtained. The data that was gathered was fed into the FEM model and different simulations were run, first with a simplified 3D rectangular block shape, in order to better establish the model, and then with the real 3D mesh obtained from the blade scrap. The overall expected behaviour in terms of displacement was observed, in particular at the trailing edge of the blade. Therefore such a model can be useful in the goal of predicting turbine blade life, given a set of FDR data.
Abstract: Belgian Defense would like to use military thermal imagers to implement nondestructivetesting by thermography for airplanes and helicopters composite parts. The choice of this camera is warranted by the analyse of parameters like NETD and MRTD and comparison with the same parameters for a popular civil camera.
Ultrasonic pulse velocity is a nondestructive test which saves the time and is easier when compared to other methods of testing. In Ultrasonic testing, an ultrasound transducer is connected to a diagnostic machine and is passed over the specimen being tested. In this testing there are two methods of receiving the ultrasound waveform: Reflection and Attenuation. In reflection mode, the transducer performs the sending and receiving of pulsed waves. In attenuation mode, the transducer sends the ultrasound through one surface and a separate receiver detects the amount that has reached it on another surface after passing through the specimen.
The principal of using airborne ultrasound for nondestructive testing seems, in the first instance, to be ideal for a variety of non-contacting applications. This technique has, however one major flaw, namely that of transmitting ultrasound across the interface between the air and the sample under test. Because of the very large acoustic impedance mismatch between most solids and air, only a very small proportion of the ultrasonic energy is transmitted across this boundary. This is compounded when testing materials with the transducer acting as both transmitter and receiver, as the ultrasonic signal needs to cross the boundary between air and the sample twice, introducing significant losses, often prohibitively, into the received signal. Because of these massive losses, most samples cannot currently be tested in such a way. However, experiments have shown that nondestructive testing with airborne ultrasound can now be usefully employed in three situations; Firstly if another method (for example a laser) is used to generate the ultrasound (removing the losses encountered at one interface)13. Secondly, when materials with low acoustic impedances (such as paper and wood) are tested. Thirdly where the air is under high pressure
Case Study: Bridge
Nondestructive testing can be an effective tool in the inspection and condition assessment of bridge structures. It can provide knowledge that may not be possible to deduce from visual observation alone. The integration of both visual and nondestructive inspection methods is key to complete bridge condition assessment and management. Some simple nondestructive techniques, such as hammer sounding, rebound hammer testing, dye penetration, and mag- netic particle testing, can be easily integrated into visual inspections. The results of these integrated inspections will improve bridge data files, and will yield more technically based recommendations for further inspection and maintenance, and more accurate estimations of remaining service life. Once a full representation of the overall bridge condition is determined, appropriate and economical decisions regarding the possible rehabilitation or replacement of bridge members or the entire structure can be made. In the case of concrete bridge the decks consist of a concrete slab covered by an asphalt coating. The concrete slabs generally have a thickness of approximately 25 cm and contain two mats of steel rebar reinforcements. The most serious form of deterioration in concrete bridge decks is the corrosion of steel re- bars caused by the excessive use of chloride deicing salts during winter for the maintenance of the structures. As the reinforcement steel corrodes, it expands and creates a cracks or surface fracture plane in the concrete at, or just above, the level of the reinforcement. The fracture plane, or delamination, may be localized or may extend over a substantial area. Recent advances in NDE techniques have improved the functional characteristics of many NDE methods and have led to systems that are more reliable. Increased use of NDE meth- ods will depend on several factors including the ability of the systems to accurately detect deteriorated conditions, the ease of use and field portability of the systems, and the total cost of completing the NDE based inspections. Since bridges are build in almost hundreds of different kind of types and using so many different materials of supporting components, so that it is not possible to use just one NDT method for all tasks. For instants, microwave or ground penetrating radar (GPR) may be used for reinforced concrete decks but is not suitable for weld testing of steel members. Also there are many tasks which need further research to make NDT methods suitable. A lot of application reports of NDT methods for bridge testing are there. Several methods are available, some are in research and some are used for further inspection after regularly inspections indicates their needs.