Non-destructive Probe Research Articles

Characterisation of Microstructures, Deformation, and Fatigue Damage in Different Steels Using Magnetic Barkhausen Emission Technique

The characterization of microstructures, mechanical properties, deformation, damage initiation, and growth by Non-Destructive Evaluation (NDE) techniques is assuming a vital role in various industries because of the growing awareness of the benefits that can be derived by using NDE techniques for assessing the performance of various components. NDE is widely applied for assessment of material degradation, where investment in new plants is not cost-effective and safe operational life of existing plants needs to be extended. In recent years, various advanced NDE techniques have been successfully employed for characterization of defects and microstructural features such as grain size, texture, nucleation and growth of second phases, assessment of tensile, creep and fatigue properties, deformation, and damage. With the advent of fracture mechanics concepts, microstructure, defects as well as stresses must be quantitatively characterized to have reliable and fail-safe materials and components. Any alteration in the microstructure, which reduces the life or performance, should be predicted sufficiently in advance in order to ensure safe, reliable, and economic operation of the components. This is possible when one realizes that the interaction of the nondestructive probing medium with the material depends on the substructural/microstructural features such as point defects, dislocations, voids, micro and macro cracks, secondary phases, texture, residual stress, etc. In this paper, use of Magnetic Barkhausen Emission technique for characterization of microstructures, deformation, and fatigue damage in different steels would be discussed. When a ferromagnetic material is subjected to a varying magnetic field, the magnetic flux densidy during magnetization varies in discrete steps as the magnetic domain walls have to overcome various types of obstacles during their movement. The discrete changes in magnetization induce electric voltage pulses in pickup coil placed near the surface of ferromagnetic materials. This noise like voltage pulses were, firstly observed by Barkhausen in 1919 and this phenomenon is named as magnetic Barkhausen Noise (MBN) or magnetic Barkhausen emission (MBE). Based on the two stage magnetization process modeled by the authors, the size of the grain/lath and carbides in ferritic steels could be correlated with MBE parameters. The influence of morphology of cementite (lamellar and spheroidized) on the MBE behaviour has been understood. Various stages of tensile deformation, viz. (i) perfectly elastic, (ii) micro-plastic yielding, (iii) macroyielding, and (iv) progressive plastic deformation in ferritic steels could be identified using the MBE parameters. The hardening depth and its quality with respect to the microstructure in induction hardened specimens could also be established using the MBE technique. MBE is found to be highly sensitive in detection of stress induced martensite in stainless steels with metastable austenite phase. Different stages of fatigue damage in 9Cr-1Mo steel, viz. (i) cyclic hardening, (ii) softening, (iii) saturation, and (iv) crack initiation could be identified using the MBE parameters.

Electrochemical Porosimetry

AbstractWe have developed the electrochemical porosimetry analyzing microstructures of porous electrodes, which can give geometric information most meaningful in electrochemical systems. The methodology is based on the transmission line model with pore size distribution (TLM-PSD) that relates electrochemical impedance data with microstructural information. Pore length (lp), as well as pore size distribution, can be obtained by fitting the TLM-PSD to the experimental impedance data of a porous electrode. This geometric information was validated for the microporous, mesoporous and macroporous samples by comparing with the data obtained from conventional porosimetry. It was also shown that the electrochemical porosimetry could be used as a nondestructive probe to investigate the construction of electrochemical devices.

Surface Characterization of the TiClx/MgCl2 Model Ziegler−Natta Polymerization Catalysts: Adsorption Site Studies Using Mesitylene Thermal Desorption

Temperature-programmed desorption (TPD) of physisorbed mesitylene molecules has been used as a nondestructive surface probe to distinguish the surface adsorption sites of model Ziegler−Natta polymerization catalysts. A MgCl2-supported titanium chloride film (TiClx/MgCl2) was fabricated on an inert gold substrate by codeposition of Mg metal and TiCl4 from the gas phase. The mesitylene TPD probe revealed two types of surface adsorption sites. The dominant site was attributed to the basal plane of these halide crystallites. The minor site could be tentatively attributed to a defective structure at the basal plane boundaries or other crystal planes. Due to the chlorine termination nature of the catalyst surface, the metal ions under the chlorine layer could not be differentiated directly with the physisorbed mesitylene molecules. However, the mesitylene TPD profile was able to monitor compositional changes in the outermost chlorine layer accompanying the reaction of the catalyst film with the triethylaluminum cocatalyst, electron beam irradiation of the film surface, and diffusion of bulk chlorine to minimize the number of defect sites.

Domain mapping of periodically poled lithium niobate via terahertz wave form analysis

We demonstrate a nondestructive probing technique to investigate the inner crystal domain structure of ferroelectric crystals by analyzing the terahertz wave forms generated by optical rectification. Quantitative analysis of the domain structure has been performed for the domain width in periodically poled lithium niobate. Simulation results show that the terahertz wave form analysis reproduces root-mean-square domain width fluctuations.

Imaging the electron wave function in self-assembled quantum dots.

Magnetotunneling spectroscopy is used as a noninvasive and nondestructive probe to produce two-dimensional spatial images of the probability density of an electron confined in a self-assembled semiconductor quantum dot. The technique exploits the effect of the classical Lorentz force on the motion of a tunneling electron and can be regarded as the momentum (k) space analog of scanning tunneling microscopy imaging. The images reveal the elliptical symmetry of the ground state and the characteristic lobes of the higher energy states.

Using Raman spectroscopy to solve crime: inks, questioned documents and fraud.

Raman microscopy is becoming a tool of major importance in forensic analysis, particularly of drugs and explosives. It is a non-invasive, non-destructive chemical probe allowing samples to be examined in their entirety without any preparation. This paper demonstrates the use of the technique as a general tool for inks analysis. Furthermore, it addresses two important issues that historically have been extremely difficult for the professional document examiner, namely, comparison of black ballpoint inks and the chronological sequencing of crossed ink lines. We show that Raman can successfully distinguish between a representative sample of commercially available black ballpoint inks. This data has been converted into a database for future reference. A method for chronological sequencing of crossed ink lines has been developed using confocal Raman microscopy. Case study work has shown the feasibility of this approach.

A New Noncontact Probe for Thermophysical Properties of Solid Surfaces

Based on the photothermal displacement effect and the optical diffraction effect, an alternative pulsed photothermal technique has been developed. This technique overcomes some disadvantages of conventional methods and provides a sensitive, noncontact and nondestructive probe of the transient thermal and mechanical process at solid and thin film surfaces. Meanwhile, a three-dimensional theoretical model has also been presented to describe the experimental phenomena. Excellent agreement between the theory and the experiment is obtained. As an example, the technique is demonstrated by measuring the thermal diffusivity of aluminum and brass thin plates.

Reflection Anisotropy Spectroscopy An Optical Probe of Surfaces and Interfaces

Reflection anisotropy spectroscopy (RAS) is a nondestructive surface-sensitive optical probe capable of operation within a wide range of environments. RAS has been applied to semiconductor surfaces and has found use as an in situ monitor of semiconductor growth. Surface sensitivity has been demonstrated with the detection of reconstructions, dimer orientations, and adsorption. More recently, RAS has been used to probe the surface optical properties of metals. In this article, some aspects of the RAS technique are described, including an analysis of the passage of polarized light through the RA spectrometer, which results in frequency-dependent terms related to the real and imaginary RA. A short review of recent applications of RAS is given.

REFLECTION ANISOTROPY SPECTROSCOPY: AN OPTICAL PROBE OF SURFACES AND INTERFACES

Reflection anisotropy spectroscopy (RAS) is a nondestructive surface-sensitive optical probe capable of operation within a wide range of environments. RAS has been applied to semiconductor surfaces and has found use as an in situ monitor of semiconductor growth. Surface sensitivity has been demonstrated with the detection of reconstructions, dimer orientations, and adsorption. More recently, RAS has been used to probe the surface optical properties of metals. In this article, some aspects of the RAS technique are described, including an analysis of the passage of polarized light through the RA spectrometer, which results in frequency-dependent terms related to the real and imaginary RA. A short review of recent applications of RAS is given.

Phase modulation spectroscopy: a non-destructive probe of Bose-Einstein condensates

The measurement of the optical phase of far-detuned laser light by phase modulation spectroscopy is promising as a non-destructive probe of the dynamics of Bose-Einstein condensates. We have developed the experimental technique on a room-temperature Cs vapour cell, and a Cs magneto-optical trap (MOT). We measure column densities with an accuracy better than 7%. A numerical model, including Doppler broadening and transitions between all relevant hyperfine levels, accurately describes the data from the Cs cell. The same model without Doppler broadening gives quantitative agreement with measurements from the Cs MOT. We show that the conditions needed for non-destructive measurements of BEC dynamics are achievable with conventional equipment and a simple, robust experimental setup.

Monomorphs, bimorphs, and multimorphs from polar polymer electrets

Mono-, bi-, and multimorphs are poled electrets with +/0, +/-, and more complicated alternating-polarity dipole-orientation patterns, respectively. Because of their unusual macroscopic piezo- and pyroelectrical as well as nonlinear optical properties, such structures are of particular interest for special transducer and optical waveguide applications. In this contribution, the preparation of such dipole-polarization patterns in ferroelectric and amorphous polymer electrets and their nondestructive probing by means of thermal and acoustical techniques are reviewed.

Three-dimensional finite element analysis of nondestructive testing of metallic tubular product

This paper presents the analysis of the remote field eddy current phenomenon for the nondestructive testing of metallic tubular products. A finite element code using linear tetrahedral edge elements is used for the analysis. The calculated results for different frequencies of exciting coil are evaluated. In the model without a hole in the pipe, the absolute value of the phase of the remote field depends on the frequency of the exciting coil. The phase varies around the hole and the phase difference compared with the case without hole also depends on the frequency. The calculated results and the developed code can be used for the design of the remote field nondestructive testing probe.

Phonon signatures of spontaneous CuPt ordering in Ga0.47In0.53As/InP

Polarized Raman scattering spectra of spontaneously ordered Ga0.47In0.53As alloys, combined with low-temperature photoluminescence and transmission electron microscopy, are used to find a unique phonon signature of CuPtB-type ordering. In the Raman spectra of ordered alloys, a new phonon peak that is absent in the spectrum of the random alloy appears at 181 cm−1. The intensity of this peak correlates with the degree of ordering inferred from electron diffraction measurements. We propose that Raman scattering measurements can be used as a nondestructive probe to detect spontaneous ordering in this alloy.

Muscle colour development in Arctic charr, Salvelinus alpinus (L.), monitored by fibre-optics and electrical impedance

Farmed Arctic charr, Salvelinus alpinus (L.), (n 5 270) with a wide range of carotenoid muscle pigmentation were produced by feeding astaxanthin at different levels (0‐120 mg kg ‐1 feed). Steaks were scored subjectively for pigment concentration (dark 5 high score). Internal reflectance spectra were measured with a relatively non-destructive 1mm-diameter fibre-optic probe. Colour scores were only moderately correlated with reflectance (R 5 0.66 and P , 0.01, using data at 500, 610 and 520 nm) because the small-diameter probe had a short light-path through the tissue and was highly responsive to scattering. However, in fish without astaxanthin in their diet, this sensitivity to microstructural causes of scattering revealed that fibre-optic reflectance increased (P , 0.01) with age from 400 nm (r 5 0.68) to 440 nm (r 5 0.40), and from 530 nm (r 5 0.30) to 700 nm (r 5 0.56). In agreement with these results, colour scores decreased with age (r 5 ‐0.52; P , 0.001; n 5 85), as did electrical resistance 24 h post-mortem (r 5 ‐ 0.42 at 120 Hz, r 5 ‐0.39 at 1 kHz and r 5 ‐0.54 at 10 kHz; P , 0.001). Resistance was correlated with colour score (r 5 0.40 and P , 0.001 for resistance at 10 kHz) and with fibre-optic reflectance (R 5 0.42 and P , 0.01 for resistance at 120 Hz and 1 kHz versus reflectance from 420 to 680 nm). Thus, without astaxanthin in the diet, muscle colour and tissue integrity at 24 h deteriorated with the age of the fish.

Positron annihilation induced Auger electron spectroscopy with an intense slow-positron beam

The apparatus for positron annihilation induced Auger electron spectroscopy (PAES) has been constructed at an intense slow-positron beam line of the Electrotechnical Laboratory. Experimental results with this apparatus show that PAES is a sensitive and non-destructive probe for adsorbates on surfaces.

Readout of Magnetic Film-Based Memories by Nonlinear-Optical Magnetic Kerr Effect

AbstractMagnetic field induced second harmonic generation (MSHG) is suggested as a nonlinear-optical readout for magnetic film-based memories: Systematic studies of the nonlinear-optical magnetic Kerr effect and MSHG interferometry are carried out for (i) magnetic rare-earth iron garnet films, (ii) Gd-containing Langmuir-Blodgett films and (iii) CoxCu1-x granular films. The magneto-induced nonlinear-optical properties of thin films being used for recording the information can be easily distinguished by the MSHG nondestructive probe. An estimation of the signal-to-noise ratio (readout error) shows an acceptable value of the magnetic contrast for this potential readout.

X-Ray Fluorescence Microtomography on a SiC Nuclear Fuel Shell

ABSTRACTTRISO fuel particles contain a small kernel of nuclear fuel encapsulated by alternating layers of C and a barrier layer of SiC. The TRISO fuel particle is used in an advanced nuclear fuel where the SiC shell provides the primary barrier for radioactive elements in the kernel. The performance of this barrier is key to containment. We have used x-ray fluorescence microtomography to measure the trace element distribution in a SiC shell. Prior to our measurements the nuclear fuel and C layers were leached from the particle. The shell was then encapsulated by kapton tape to simplify handling. The shell was mounted on a glass fiber and measurements were made with an ∼1 x3 ωm2 x-ray probe on beamline 2-ID at the APS. The distribution of trace elements in the SIC shell was reconstructed after correcting the data for artifacts arising from absorption and scattering off the kapton tape. The observed trace elements are distributed in small <1ωm regions through the SiC shell. The trace elements can be attributed to radiation enhanced diffusion of elements in the kernel or to trace elements introduced during fabrication. X-ray fluorescence microtomography is an ideal tool for this work because it is a penetrating nondestructive probe sensitive to trace elements in a low Z matrix and because it provides a picture of the elemental distribution in the shell.

Neutron diffraction in the materials science toolbox

Neutron diffraction provides information on residual stress, crystallographic texture, composition and phase transformation in engineered components. The unique power of this analysis tool is provided by the ability of neutrons to penetrate deeply inside most materials. Three dimensional maps of the residual stresses within intact components and true bulk-averaging of material properties are readily achieved by this non-destructive probe. In this paper, two examples of the use of neutron diffraction as a tool in the development of mathematical models of industrial metallurgical processes are presented: (1) the measurement of residual stresses generated by forced convective quenching of steel bars and (2) the measurement of texture evolution during recrystallization of hot rolled aluminum.

High energy X-ray diffraction measurement of the superstructure reflection (100) for a creep deformed AM1 single crystal superalloy specimen

Due to its importance for industrial applications, the microstructural behavior of single crystal nickel base superalloys as a function of the thermo-mechanical history of the material is the subject of many studies. However, some controversies remain concerning parameters which are driving the coarsening of {gamma}{prime} precipitates. In particular the role of the lattice parameter mismatch between the {gamma} and {gamma}{prime} phases (usually defined as {Delta}d/d = (a{gamma}{prime} {minus} a{gamma})/ where a{gamma}{prime} and a{gamma} represent respectively the lattice parameter value of the {gamma}{prime} and {gamma} phases) and of the internal stresses at the interfaces has to be clarified. An experiment was performed on a creep deformed sample using high energy synchrotron radiation and a Triple Crystal Diffractometer set-up (TCD) which allow nondestructive measurements and probe the bulk of the sample. With this method the superstructure reflection (100) was measured with a good accuracy and a reasonable statistics.

Study of Diagnosis Criteria for Pathological Tissues by Laser-Induced Fluorescence

It has been confirmed that the differences in fluorescence spectra of normal and pathological biotissues can be used as a sensitive and nondestructive diagnostic probe. However, experiments show that not only are the fluorescence spectral features of different tissues very different but the features of the same tissue under different detection conditions are different too. Therefore, the diagnosis criteria of pathological tissues must be changed in accordance with different spectral features. In this paper, several diagnosis methods using native fluorescence characteristics of biotissues given in existing reports are analyzed. With the fourth harmonic at 266 nm of a Q-switched YAG laser as an excitation source, laser-induced fluorescence (LIF) spectra of native human normal and pathological breast and blood vessel tissues in vitro were measured and studied. According to their spectral characteristics, two diagnosis criteria are suggested: by the fluorescence intensity ratios at several specific wavelengths, cancerous (with p < 0.001) and benign tumor ( p < 0.005) can be distinguished from the normal tissue; by the fluorescence intensity ratios of the two main peaks, atherosclerotic plague and thrombus (both with p < 0.005) can be distinguished from normal blood vessel. In order to make comparisons with the results from human cancerous breast tissues, spectra of a model mouse were also observed.