Triaxial Probe Research Articles

A novel TMR based triaxial eddy current test probe for any orientation crack detection

The paper proposes the development, the analysis, and the experimental validation of a novel probe for Eddy Current (EC) Non-Destructive Testing especially thought to warrant good signal to noise ratios in the detection of thin defects when low excitation currents are adopted and whatever the orientation of the probe respect to the orientation of the defect. The probe is based on a simple double coil excitation, that generate a single direction EC flow, and adopts three magnetic sensors that form a triaxial magnetic sensor. Other main contributions of this paper are: i) performance analysis of an EC triaxial probe carried out in simulation environment that considers the measurement uncertainty of the magnetic sensors; ii) an experimental campaign that allow evaluating the performance of the realized probe; iii) a comparison between simulated and experimental results that prove the goodness of the proposed approach.

Particle-scale insight into transitional behaviour of gap-graded materials – small-strain stiffness and frequency response

This study aims to develop a fundamental understanding of the role of fine particles on the small-strain stiffness of gap-graded granular soils. Stiffness was measured using cyclic triaxial probes, which give a measure of static stiffness, and dynamic wave propagation data, from which the dynamic stiffness can be measured. Assemblies of loosely packed spherical particles were considered. In the laboratory, local deformation transducers were used to measure the static stiffness, while the dynamic stiffness was calculated from stress wave velocities, measured using planar piezoelectric elements. To relate the particle-scale responses to the overall soil stiffness, complementary discrete element method (DEM) simulations were performed in which both static and dynamic stiffnesses were measured. Both the laboratory and the DEM data indicate that at low fines contents (< 30%) the stiffness decreases with increasing fines content. When the fines content increases from 30% to 35% there is a sharp increase in stiffness with increasing fines content; this is understood to mark the transition point at which the fines start to contribute significantly to the overall behaviour. Analyses of the frequency domain response of shear wave signals revealed that the lowpass frequency increases significantly at this transition point. This observation can be used to develop experimental interpretation protocols to assess to what extent fines are contributing to the overall soil stiffness.

Radiofrequency exposure near an attocell as part of an ultra-high density access network.

In the future, wireless radiofrequency (RF) telecommunications networks will provide users with gigabit-per-second data rates. Therefore, these networks are evolving toward hybrid networks, which will include commonly used macro- and microcells in combination with local ultra-high density access networks consisting of so-called attocells. The use of attocells requires a proper compliance assessment of exposure to RF electromagnetic radiation. This paper presents, for the first time, such a compliance assessment of an attocell operating at 3.5 GHz with an input power of 1 mW, based on both root-mean-squared electric field strength (Erms ) and peak 10 g-averaged specific absorption rate (SAR10g ) values. The Erms values near the attocell were determined using finite-difference time-domain (FDTD) simulations and measurements by a tri-axial probe. They were compared to the International Commission on Non-Ionizing Radiation Protection's (ICNIRP) reference levels. All measured and simulated Erms values above the attocell were below 5.9 V/m and lower than reference levels. The SAR10g values were measured in a homogeneous phantom, which resulted in an SAR10g of 9.7 mW/kg, and used FDTD simulations, which resulted in an SAR10g of 7.2 mW/kg. FDTD simulations of realistic exposure situations were executed using a heterogeneous phantom, which yielded SAR10g values lower than 2.8 mW/kg. The studied dosimetric quantities were in compliance with ICNIRP guidelines when the attocell was fed an input power <1 mW. The deployment of attocells is thus a feasible solution for providing broadband data transmission without drastically increasing personal RF exposure. Bioelectromagnetics. 38:295-306, 2017. © 2017 Wiley Periodicals, Inc.

Image-based measurement of one-dimensional compressibility in cement-treated soils

This paper reports an attempt to accurately quantify one-dimensional compressibility of stiff, cement-treated high-water-content clays by using a constant-rate-of-strain (CRS) oedometer equipped with an image-based strain measurement system. The errors in stiffness measurements due to imperfect specimen–platen bedding and apparatus compliances, significant factors when stiff soils are tested, were avoided by directly observing movements of the specimen's lateral surface over a transparent confining ring. The proposed system is meant to be practical, requiring only minimum alterations to existing CRS oedometers and a generally available mid-market digital camera. The effectiveness of the method is demonstrated by testing six cement-treated clay specimens with or without air-foam inclusions in one-dimensional compression and by comparing the obtained compression curves with those obtained by more conventional measuring systems. The image analysis always revealed significantly stiffer responses than observed by the conventional methods. Validity of the image-based stiffness determination at small strains was confirmed by generally good agreements of its derived stiffness values with those obtained from highly precise triaxial probes, which provided a full set of cross-anisotropic elastic parameters. Implications for field problems are discussed in relation to an offshore reclamation project, in which similar cement-treated high-water-content clays were extensively used for upper layers.

Conversion from mono-axial to isotropic measurements for assessing human exposure to electromagnetic fields of GSM/DCS/UMTS base stations

This paper proposes a way to assess total electric field strength by using mono-axial probe (instead of isotropic, tri-axial probe). When mono-axial probe is used, additional conversion factor should be applied. Consequently, the usage of mono-axial probe causes additional uncertainty in measurement results that should be taken into account. Measurement results for seven different environments show that the additional multiplicative conversion factor value of 1.95 should be applied and additional uncertainty in measurement results of 33.07 % should be taken into account.

Effects of Construction-Induced Stresses on Dynamic Soil Parameters of Bootlegger Cove Clays

This paper presents the influence of construction-induced stress changes on the dynamic soil parameters of Bootlegger Cove Formation (BCF) clays at the site of the Port of Anchorage (POA) expansion project. Results are presented based on numerical simulations of the POA wharf construction and laboratory experimentation where both free-field and postconstruction conditions are reproduced. The postconstruction stability of the foundation clay is considered under both static and dynamic loadings. For the dynamic case, a cyclic triaxial loading equivalent to the contingency-level earthquake (CLE) established for design was used, whereas for the static case, undrained triaxial compression and extension loadings to failure were employed. The results from numerical simulations and laboratory experiments are presented and compared with field measurements and performance data collected during the project construction. The results obtained from specially designed cyclic triaxial probes show the large effects that the construction-induced stresses can have on the dynamic soil parameters and illustrate the importance of adequately considering such effects. Testing protocols and procedures are proposed for quantifying postconstruction soil parameters to better reflect field values and values at small (and otherwise appropriate) strain levels.

Triaxial AFM Probes for Noncontact Trapping and Manipulation

We show that a triaxial atomic force microscopy probe creates a noncontact trap for a single particle in a fluid via negative dielectrophoresis. A zero in the electric field profile traps the particle above the probe surface, avoiding adhesion, and the repulsive region surrounding the zero pushes other particles away, preventing clustering. Triaxial probes are promising for three-dimensional assembly and for selective imaging of a particular property of a sample using interchangeable functionalized particles.

Focus on vacuum and cryogenics

Focus on vacuum and cryogenics

Complementary Peptide Sequence Coverage Using Alternative Enzymes for On-Line Digestion with a Triaxial Electrospray Probe

Using alternative enzymes for on-line digestion with a triaxial electrospray probe extends sequence coverage. This is the first report of utilization of our triaxial probe for on-line analysis with enzymes other than pepsin, suggesting potential for broader application. The probe allows access to processes occurring on a timescale and/or involving substrate conformations complementary to those for conventional (off-line) digestion. Some of the features observed in application to Abeta fibrils are suggestive of unique reactive intermediates during dissolution. Data obtained with enzyme mixtures suggest synergistic effects.

Wind Tunnel And Field Measurements Of Turbulent Flow In Forests. Part I: Uniformly Thinned Stands

Many forest management methods alterstand density uniformly. The effectsof such a change on the wind andturbulence regimes in the forest arecritical to a number of processes governingthe stability of the stand and itsmicroclimate. We measured wind speed andturbulence statistics with a Dantec tri-axialhot-film probe in model forests of variousdensities (31–333 trees m-2), created byremoving whole trees in a regular pattern in awind tunnel, and compared them with similarmeasurements made with propeller anemometers insimilarly thinned plots (156–625 trees ha-1)within a Sitka spruce stand in Scotland. The results agree well, in general, with measurements made inother such studies with diverse canopy types.The systematic variations with density and verticalleaf-area distribution (which differed betweenwind-tunnel and field trees) in our work can explainmuch of the variability shown in scaled profiles ofbasic turbulence statistics reported in theliterature. The wind tunnel and field results are shown to be in good agreement overalldespite the difference in vertical leaf-areadistribution. Within-canopy and isolated-treedrag coefficients in the wind tunnel showthat tree-scale shelter effects increase astree density increases. The measurements indicatethat turbulence in the canopy is dominated bylarge-scale structures with dimensions of the sameorder as the height of the canopy as found inother studies but suggest that inter-tree spacing also modulates the size of these structures. These structures are associated with the sweeps that dominatemomentum exchange in the canopy and it is thisfact that allows the tri-axial probe to operate sowell despite the relatively narrow range of anglesin which the wind vector is correctly measured. Theratio of streamwise periodicity of these structuresto vorticity thickness varies systematically withtree density in the range 2.7–5.1, which spans theexpected range of 3.5–5 found in a laboratorymixing-layer, suggesting that tree spacing imposes another relevant length scale. This test andothers show that the results are in agreement withthe idea that canopy turbulence resembles that of a mixing layer even though they disagree with, and challenge the linear relationship between, streamwise periodicity andshear length scale presented recently in theliterature. The measurements are also in goodoverall agreement with simple drag models presented recently by other researchers.

Capillary electrophoresis with detection by inverse UV spectroscopy and electrospray mass spectrometry for the examination of quaternary ammonium herbicides

The value of capillary electrophoresis (CE) and combined capillary electrophoresis-electrospray mass spectrometry (CE-ES-MS) for the analysis of simple quaternary ammonium ions, including herbicides, has been assessed. Choline, chlormequat, known contaminants of their formulation products, and some other small ammonium cations have been examined. Lacking a chromophore, the cations were detected by inverse UV absorption utilizing a buffer containing creatinine as visualization agent. In this way, all six cations could be resolved, detected and quantified within 8 min. To confirm the identities of the ammonium ions, coupled ES-MS provided mass measurement on all migrating cations. The triaxial probe proved to be an efficient interface for examining the small cations ( m/ z 60–124) by CE-ES-MS. Results on three formulation products containing chlormequat have been obtained by CE and CE-ES-MS, and compared with quantitative data from analysis by ion chromatography.

The generalized plane strain problem and its application in three-dimensional stress measurement

This paper proposes a complete definition of the plane strain problem. It consists of five subtypes: the classical one and four subtypes of the generalized plane strain problem. Among them the axial strain is a compatible condition. Following that definition, for problems which are not more complex than that, the axial load as well as axial strain are linear functions of x, y, and the problems can be solved as a plane strain problem. Their solutions are found by simply superposing the solutions of three of the fundamental equations. According to the fourth subtype of the generalized plane strain problem mentioned, the solutions of a hollow inclusion adhered inside a round hole in an infinite object are given, by which the six stress components of virgin stresses in a rock mass stress measurement using CSIR or CSIRO triaxial probes can be fixed. Comparing the calculated results by the method proposed in this paper with the existing methods, utilizing the data of some authors, it is noticed that the axial stress component calculated by the former method is reduced and that the principal stresses and their directions are altered, which may directly explain the discovery by some authors that the axial stress analyzed by the existing methods tends to a higher value.

Characteristics of the Near Wake of a Compressor of a Fan Rotor Blade

Research reported in this paper covers an experimental investigation of the rotor wake. The experimental investigation included a study of the mean velocity, turbulence intensity, and Reynolds stress variations across the wake of a lightly loaded rotor blade at various axial and radial locations. Only the mean velocity data and their interpretation are presented in this paper. Measurements were carried out with a triaxial probe, rotating with the rotor and stationary behind the rotor. Also, measurements were made with a spherical head static pressure probe rotating with the rotor. Wakes were measured at various incidences to discern the effect of blade loading on the rotor wake. The wake is found to be three-dimensional in nature with appreciable radial velocity. The measurements close to the blade trailing edge indicate that the decay of the wake is rapid in this region. The wake data are correlated to derive expressions for the profile and decay of all the components.