Papers by Keyword: NDE

Abstract: The paper presents the theoretical and experimental results from evaluating the early phase of material fatigue and discusses the issues concerning the example of two object classes: supporting structures and shaft working under real environmental conditions. In theoretical considerations, the Hall-Petch and Bailey-Hirsch relationships between microstructure and mechanical parameters are given. Magneto-mechanical effects and the magnetic passive observer have been used for evaluating the early phase of material fatigue. The Metal Magnetic Memory method of structural health assessment was verified and the potential for a reliable diagnosis of damage to the ferromagnetic material at the 1^st and 2^nd stage was confirmed.

Abstract: We report several radio-frequency (RF) sensors for possible use in material NDE and process control: an ultra-wide band (UWB) impulse sensor and microwave and millimeter-wave stepped-frequency sensors. The UWB sensor generates ultra-short pulses directly while the stepped-frequency sensors produce ultra-short pulses indirectly through pulse-synthesis. Ultra-short pulses possess ultra-wide bandwidths and have uniquely desirable characteristics such as fine resolution and high accuracy for material assessment. The UWB impulse sensor operates over multiple pulse durations from 450 to 1170 ps with 5.5-GHz RF bandwidth. It performs well through tests of various samples, demonstrating its usefulness for sensing. The microwave stepped-frequency sensor operates from 0.6 to 5.6 GHz and the millimeter-wave stepped-frequency sensor operates from 29.72-37.7 GHz. They have demonstrated abilities in surface and near-surface sensing of various structures. These developed compact RF sensors are attractive for NDE and process control of materials and various other sensing applications.

Abstract: Thermosonics is a rapid and potentially cost-saving non-destructive testing (NDT) screening technique that can be applied to the identification of cracks in high pressure compressor turbine blades in turbofan engines. The reliability of the thermosonic technique is not well established for inspecting these complex components; in particular the vibrational energy generated within a component during a thermosonic test is often highly non-uniform, leading to the possibility of missing critical defects. The aim of this study was to develop a methodology, using a combination of vibration measurements and finite element analysis (FEA), to model the vibrational energy within a turbine blade in a typical thermosonic inspection scenario. Using a laser vibrometer, the steady-state vibration response (i.e. frequency response) at several locations on a blade was measured and used to identify the prominent peaks in the frequency spectra. These were then used to generate an excitation function for the finite element modelling approach. Acceptable correlation between the measured and simulated vibration response at a number of specific locations on the blade allowed the forcing function to simulate the vibration response across the whole blade. Finally, the predicted displacement field was used to determine the vibrational energy at every point on the blade which was mapped onto a CAD representation of the blade, thereby highlighting areas on the blade that were below the defect detection threshold.

Abstract: The objective of this paper is to predict the flaw response in an inhomogeneous solid medium. Multi-Gaussian Beam (MGB) model is used to represent the incident ultrasonic beam. The effect of ultrasonic attenuation and phase velocity dispersion due to grain scattering is included in the predictions. The effect of variation of mean diameter of the grains on the received voltage for different domain of interest is studied through the experimental results.

Abstract: New software using VEE Pro was developed to integrate the various components of photoacoustic spectrometer through RS-232 interface and this is the first time such an effort is made not only to integrate but also to automatically acquire the data for depth profile and wave length scanning. The performance and validity was rigorously tested for repeatability and standard error for samples like air, glass and silicon wafer. As an application towards NDE, the thermal parameters obtained from photoacoustics are compared with ultrasonics and discussed.

Abstract: Ultrasonic methods are used in a wide variety of applications including medical studies, geological mapping, and nondestructive evaluation (NDE) tests. In the field of ultrasonic NDE, it is necessary to treat inverse problems of various types. The objective of this paper is to predict the flaw response in an inhomogeneous solid medium. A mathematical modelling of the testing situation is very valuable for a number of reasons. The modelling helps in developing physical intuition and in the interpretation of tests. Multi-Gaussian Beam (MGB) model is used to represent the incident ultrasonic beam. The effect of ultrasonic attenuation and phase velocity dispersion due to grain scattering is included in the predictions. The variation of received voltage is analyzed against the distance of the flaw from the transducer for different dimensions of a square cylinder void. The effect of variation of mean diameter of the grains on the received voltage for different domain of interest is also studied.

Abstract: This paper is aimed at experimentally developing an in-situ macro-fibre composite (MFC^TM) piezoelectric transducer sparse array which functions as both actuator and sensor of Lamb wave for damage detection in composite laminate. Lamb waves which have been used in non-destructive evaluation (NDE) of plate-like structures, can be used for active monitoring and interrogating the health of the structures due to their long range propagation with less attenuation. MFC acting as a powerful actuator of Lamb wave as well as a sensitive sensor is highly conformable and anisotropic in behaviour compared to monolithic piezoelectric transducer. The surface bonded MFC transducer on woven carbon fibre reinforced plastic (CFRP) laminate shows directional Lamb wave generation and reception characteristics. Pitch catch approach is used for low velocity impact damage detection. The MFC sensor shows a drastic drop in signal amplitude with the growth of the impact damage.

Abstract: Braided carbon fiber reinforced plastics (CFRP) is one of the multifunctional materials for applications to industrial products. We applied the superconducting quantum interference devise (SQUID) nondestructive evaluation (NDE) technique with high magnetic sensitivity and spatial resolution to inspect the state of the fabric in the braided CFRP. We prepared flat braided CFRP samples with nonuniform, uniform and cut-out bundles, which were fabricated with fold biaxial (±45º) tubular fabric and epoxy resin. While injecting ac current into each sample, the diagonal magnetic field gradients dBz/dx and dBz/dy above each sample were measured by the NDE system employing a SQUID gradiometer and xy-scanning stage, and then, the current flow in each sample was visualized by the field-gradient-to-current conversion method. In the measurements, it was shown that the current flowed along the continuous bundles in the cases of nonuniform and uniform samples, and it transmitted between bundles in the case of the sample with cut-out bundles. From these results, we showed the possibility that the NDE method can be applied to the nondestructive inspection of the integrity of the textile of braided CFRP.

Abstract: The infrared thermography technique is being applied in many areas. Particularly these days, non-destructive inspection and evaluation using the ultrasound-infrared thermography technique are hogging the spotlight in a wide range of study areas. The ultrasound-infrared thermography technique uses the principle that ultrasound waves projected to objects with cracks or defects at connections generate local heat from the defective surface. In this research, introduce nondestructive evaluation method for total inspection of special shoes applying Ultrasound Infrared thermography Technique. Performance of the proposed method are shown by through thermo-Image. The total inspection system using infrared thermal camera for special shoes, its applicability, and system configuration are introduced.

Abstract: The effect of Cd additions on NDE of an as-cast Mg-Cd alloy in 0.1M NaCl solution was investigated using the gas collection method, potentiostatic current decay test and in-situ Laser Raman Spectroscopy. The experimental results showed that, in the cathodic region the addition of Cd reduced the hydrogen evolution and the magnesium hydride formation; in the anodic region the addition of Cd restrained the NDE but slightly increased the anodic dissolution.