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Important resolution properties of the high-resolution 3-axis neutron diffraction set-up were investigated in the frame of feasibility of its use for strain/stress measurements on bulk polycrystalline samples. The strain analysis was carried out by rocking the BPC-analyzer and the neutron signal registered by a point detector. The so-called rocking curve then provided a sample diffraction profile and could reflect the lattice or structural changes. In comparison with a conventional 2-axis set-up, this instrument alternative could be successfully applied, namely, in the strain/stress measurements in bulk samples exposed to an external load, e.g. in tension/compression rig, in aging machine etc. and provide average strain values over a large irradiated volume of the sample. [ABSTRACT FROM AUTHOR]

The study summarises the selection of dedicated techniques and procedures for measuring real stresses arising in shaft steelwork components due to car-shaft steelwork interactions as well as stresses at critical points of the car frame in the elevator installation in the Regis Shaft of the Wieliczka Salt Mine. The implemented solution and operational parameters of the hoisting installation in the Regis Shaft of the Wieliczka Salt Mine are summarised, the adopted measurement method and dedicated equipment are presented, focusing on the procedure for locating the critical points on the car frame and shaft steelwork. The purpose-built measurement set-up as well as the adopted stress measurement procedure and results are explained in detail. [ABSTRACT FROM AUTHOR]

This study investigated electrical strain gage technology, which is widely used in experimental stress measurement, on an application. Strain gages are used to precisely measure strain directly in a system. This method is carried out to verify the numerical and analytical calculations performed or to record the strain data generated during the active duty of a system and to investigate the fatigue damage. In particular, verifying numerical calculations in the strength-material recovery optimizations of mass-produced systems contributes to the development of the system. In this study, strain measurement using strain gage and strain measurement technology is presented on an application. Information was given about strain gages. A full bridge wheatstone bridge consisting of 4 linear gages was created on a prototype. The system was tested with a load cell validation. Structural finite element analysis of the prototype and analytical calculation of the fullbridge strain gage connection were performed. The results showed that the measurement with the strain gauge differed 1.20% and 1.40% from the analytical and numerical results, respectively. Thus, precision strain measurement technology was successfully presented in engineering systems. [ABSTRACT FROM AUTHOR]

One significant issue associated with in situ stress measurements is that the uncertainty of the results cannot be determined. In this study, we propose a novel analytical procedure for the anelastic strain recovery (ASR) method, an in situ stress measurement method, enabling us to conduct uncertainty quantification based on Bayesian statistical modeling (BSM). The new procedure consists of the following steps: i) measuring the ASR of a rock core with strain gauges, ii) applying a probability model based on BSM to the measured ASR data and simulating the probability densities of the elements of an in situ stress tensor and other parameters; and iii) regarding the probability densities as the results of in situ stress measurements with uncertainty. This paper presents the results obtained by applying the proposed procedure to simulated ASR data. The results show that the uncertainties of some parameters are reduced by giving the elastic moduli. Notably, the rates of uncertainty decrease vary for each parameter. To reveal the cause of these differences, we introduce the new evaluation tool, Sobol' indices, which comprise a global sensitivity analytic tool, to facilitate a quantitative discussion. [ABSTRACT FROM AUTHOR]

We propose a digital model for high quality superlattices by including fluctuations in the superlattice periods. The composition and strain profiles are assumed to be coherent and persist throughout the superlattice. Using this model, we have significantly improved the fit with experimental X-ray diffraction data recorded from the nominal InAs/GaSb superlattice. The lattice spacing of individual layers inside the superlattice and the extent of interfacial intermixing are refined by including both (002) and (004) and their satellite peaks in the fitting. For the InAs/GaSb strained layer superlattice, results show: (i) the GaSb-on-InAs interface is chemically sharper than the InAs-on-GaSb interface, (ii) the GaSb layers experience compressive strain with In incorporation, (iii) there are interfacial strain associated with InSb-like bonds in GaSb and GaAs-like bonds in InAs, (iv) Sb substitutes a significant amount of In inside InAs layer near the InAs-on-GaSb interface. For support, we show that the composition profiles determined by X-ray diffraction are in good agreement with those obtained from atom probe tomography measurement. Comparison with the kinetic growth model shows a good agreement in terms of the composition profiles of anions, while the kinetic model underestimates the intermixing of cations. [ABSTRACT FROM AUTHOR]

This study evaluated the effect of six screw-tightening sequences and two tightening methods on the screw preload in implant-supported superstructures. The preload was measured using strain gauges following the screw tightening of a metal framework connected to four implants. The experiment included six sequences ([1] 1-2-3-4, [2] 4-2-3-1, [3] 4-3-1-2, [4] 1-4-2-3, [5] 2-3-4-1, and [6] 3-2-4-1), two methods (one-step, three-step), and five replications. Significant differences were found between tightening sequences and methods. In the three-step method, a higher total preload was found in sequences 2 (312 ± 85 N), 3 (246 ± 54 N), and 4 (310 ± 96 N). In the one-step method, a higher total preload was found in sequences 1 (286 ± 94 N), 5 (764 ± 142 N), and 6 (350 ± 69 N). It is concluded that the highest total screw preload was achieved when anterior implants of the superstructure were first tightened in one step, followed by posterior implants. [ABSTRACT FROM AUTHOR]

The growth of single layer graphene by chemical vapor deposition on polycrystalline Cu substrates induces large internal biaxial compressive strain due to thermal expansion mismatch. Raman backscattering spectroscopy and atomic force microscopy were used to study the strain relaxation during and after the transfer process from Cu foil to SiO2. Interestingly, the growth of graphene results in a pronounced ripple structure on the Cu substrate that is indicative of strain relaxation of about 0.76% during the cooling from the growth temperature. Removing graphene from the Cu substrates and transferring it to SiO2 results in a shift of the 2D phonon line by 27 cm-1 to lower frequencies. This translates into additional strain relaxation. The influence of the processing steps, used etching solution and solvents on strain, is investigated. [ABSTRACT FROM AUTHOR]

Slow earthquakes, including low-frequency earthquakes and tremor, occur in the brittle-ductile (plastic) transition zone on plate boundary faults. To understand how transitions in deformation mechanisms can influence seismic behavior, we conducted stick-slip experiments on halite gouge at normal stresses (σn) of 8 to 113 MPa. In the brittle regime (σn ≤ 18 MPa), the halite gouge showed fast and regular stick-slip associated with velocity-weakening behavior. In contrast, increasing the normal stress within the semibrittle regime (σn ≥ 27 MPa) led to a significant decrease in slip velocity and stress drop, which was associated with a transition from velocity-weakening to velocity-strengthening behavior. Local stress measurements along the simulated faults, made using strain gauges, revealed that the critical nucleation length (Lc) increased with increasing normal stress. Macrostructural and microstructural observations showed that the transition from fast dynamic slip to slow quasi-static slip could be attributed to an increasing contribution from semibrittle/plastic deformation occurring within domains that are heterogeneously distributed within the gouge layer. Our findings suggest that brittle-plastic fault heterogeneity, which may be generated by spatial variations in pore fluid pressure and/or lithology, contributes to the emergence of slow earthquakes. [ABSTRACT FROM AUTHOR]

The article focuses on Optical fiber sensor based on Sagnac interferomter. Topics include that the sensor is designed by combination of photonic crystal fiber (PCF) and fiber Bragg grating (FBG) and the device is used for measuring various physical parameters including temperature and stress by the changes of physical characteristics such as interference, diffraction, and polarization caused by light propagation in the optical fiber.

Wall shear stress and wall streamline direction measurements were conducted on a generic delta wing model to demonstrate the potential of the white-light oil-film interferometry in three-dimensional flows. With the proposed algorithm, an automatic oil-film thickness calculation is possible and yields reproducible and plausible wall shear stress distributions on the leeward side of the delta wing for various angles of attack. [ABSTRACT FROM AUTHOR]

Stress measurements are required to prevent collapse accidents of structures. Surface SH‐wave acoustoelasticity can measure principal stress difference nondestructively and easily. Currently, surface SH‐wave acoustoelasticity can measure with high precision using a T‐type surface SH‐wave sensor in ideal environments such as in the laboratory. However, in actual environments, it cannot be measured with high precision due to change in the temperature of the specimen. In this paper, temperature dependence of surface SH‐wave acoustoelastic constants was verified to investigate the influence of specimen temperature on surface SH‐wave acoustoelasticity. In addition, the measuring system of surface SH‐wave acoustoelasticity using a cross T‐type surface SH‐wave sensor to reduce the influence of specimen temperature was developed. [ABSTRACT FROM AUTHOR]

Low-acyl gellan gum fluid gels were obtained using two different gel-promoting cations under the same processing conditions, and their rheological properties were investigated. For that reason, stress and frequency sweep measurements and flow curve tests were carried out. Small amplitude oscillatory shear assays demonstrated that these materials exhibit weak gel behavior despite the shape of their mechanical spectra being similar to those obtained from strong gels. However, the existence of a weak gel structure was confirmed by the fact that the difference between the elastic and viscous components was of only one order of magnitude. In addition, a reduction in the storage and lost modules and the viscosity as a function of the applied shear was observed with increasing cation concentration. Finally, in order to produce fluid gels, a higher concentration of the monovalent cation was required than when divalent cations were employed in the low-acyl gellan gum fluid gel formulation. [ABSTRACT FROM AUTHOR]

While stress is a widely utilized concept, no direct methods facilitating its measurement are currently available. In our previous work we proposed stress entropic load (SEL) as a potential new marker of stress response in the human body. However, at that time no method for SEL measurement existed. In this pilot study we devised and then tested methodology for SEL measurement. Healthy male participants were monitored by indirect calorimetry and thermography while resting and subsequently while under prolonged mental effort. The acquired data was then used to calculate the temporal development of SEL for each participant. Our results show that SEL production increased significantly in participants subjected to prolonged mental effort. Furthermore, we observed that the calculated development of SEL over time may be used to accurately determine the time point at which participants started performing stressful tasks. [ABSTRACT FROM AUTHOR]

Due to the weak interface in shape memory alloy wire–reinforced composites, the influence of interphase on the mechanical properties and stress distribution of hybrid composites is of considerable importance. In this article, a three-cylinder axisymmetric model using a pull-out test is developed to predict stress transfer and interfacial behavior between shape memory alloy wire, interphase, and matrix. In this article, only superelasticity behavior of the shape memory alloy wire is considered. Based on the stress function method and the principle of minimum complementary energy, stress distribution is derived for three different cases in terms of loading and boundary conditions (thermal loading model, intact model, and partially debonded model). Inhomogeneous interphase and different radial and hoop stress components in each phase are considered to achieve deeper physical understanding. Finite element analysis also performed to simulate stress transfer from the wire to the matrix through the interphase. To evaluate the accuracy of this model, the results of the work are compared with the results of the two-cylinder model proposed by Wang et al. and finite element results. [ABSTRACT FROM AUTHOR]

The equipment used in stress- and pressure-related non-destructive testing (NDT) experiments tends to have single functionality and a low degree of automation. There are also safety risks inherent in existing pressure testing methods. This paper develops a remote online NDT comprehensive experimental device. It uses a high degree of automation to remotely monitor changes in a pressure vessel’s prefabricated defects during pressure tests. Safety is guaranteed, as the operator is located remotely. The experimental pressure vessel employs a split structure connected by a quick-release system using flange-type U-slot bolt holes. Pressure vessel defects can be prefabricated in different forms, and the vessels can be disassembled and changed easily. This process reduces the experiment materials needed, lowers costs, and saves experimental time. The device can be used for various experiments, such as acoustic emission monitoring of the pressure-bearing and load-holding capacities of pressure vessels, measurement of pressurized vessel strain, and pressure vessel NDT (magnetic powder inspection, ultrasonic flaw detection, magnetic flux leakage testing, magnetic memory testing). Operators can obtain experimental data and conduct analyses simply by controlling the computer. The device can enrich the content of undergraduate experiments and solve the single-functionality problem of existing experimental equipment. With this device, the acoustic emission online monitoring experiment of pressure vessel and the stress measurement of pressure vessel are carried out. Which verify the diversity of function and reliability of the test. [ABSTRACT FROM AUTHOR]

Stress-birefringence measurement is critical in optical glass materials. A laser self-mixing interference (SMI) stress measurement system with a measuring range of 1 deg to 179 deg is presented. The light source of the system is a He-Ne laser with a variable frequency difference. Birefringent external cavity SMI experiments are conducted with the laser with different frequency differences. Experimental results show that a large frequency difference decreases the cross-saturation effect between the two laser eigenstates, and alternate oscillations are more likely to occur, which directly improves the sensitivity and expands the measuring range of the system. A piece of neodymium glass is tested with the system and the results are given, proving that the large frequency difference laser SMI system provides a simple, low-cost, and high-sensitivity stress measurement method. [ABSTRACT FROM AUTHOR]

As a part of the DECID2 French National Project (2008–2012), construction of a large platform entirely made of smart composites was carried out and two demonstrators were installed. During a previous study, an ABAQUS model of smart composite platform was set up to perform numerical simulations that predict the mechanical behaviour of bolt-fastened platform under static three-point bending load, and a stress concentration is observed around the bolt holes. Unidirectional composites are subjected to delamination at very low stress, and this cannot be tolerated because most of the applications of pultruded structures are in civil engineering, which involves human safety. Therefore, it is essential to study the correlation of delamination onset and find a technology to enhance delamination strength. In this study, a numerical analysis was carried out to enhance the delamination strength around the bolt holes. Bidirectional fiberglass cloths were wrapped around unidirectional pultruded beams to reinforce the structure and to prevent delamination. Due to the high cost of these cloths, a study was also carried out to select an appropriate cloth material by taking into account two aspects: density and number of layers of cloths. The selected cloth was compared with conventional continuous fibreglass mat, and it was found that bidirectional fibreglass cloth material performs well in preventing delamination, even though it is expensive. [ABSTRACT FROM AUTHOR]

Seven points were selected to measure in situ stress, and the simulation software ANSYS was used to introduce a 3D geological model of Licun colliery, which has a thick coal seam and large mining height. A BP neural network was applied to the inversion of in situ stress, and distributions of σ1, σ2, and σ3 were achieved. This proved that a BP neural network can be applied to the inversion analysis of the colliery’s in situ stress. Furthermore, different angles α between the maximum principal stress and roadway axial were simulated. The results showed that as α increases, the shallow maximum principal stress varies from symmetric distribution to asymmetrical distribution. Finally, this becomes a symmetric distribution as the concentrated contours vary from the roof to two sides at the same time. The maximum tensile stress of the roof and α were positively correlated, and the depth of the maximum tensile stress and α were negatively correlated. The tensile stress of the roof surrounding shallow rock increases as α increases, and the roof tends to cause tensile failure. Thus, the roadway axial and the maximum principal stress should be laid out in parallel as much as possible, and angle α should be less than 30º in the Licun colliery. [ABSTRACT FROM AUTHOR]

This article examines the structural behaviour of six structural units composed of single, simply paired and paired-interconnected bending-active members, coupled with a single cable element. The form-found curvilinear shape of the members is achieved through fastening by contracting auxiliary elements, as well as through further deformation by decreasing the cable’s length. The overall structural behaviour of the units is investigated based on a step-by-step finite-element analysis. All units are evaluated with regard to the components’ stresses and deformations developed during the form-finding process and subsequent external vertical loading, for different possible section thickness values of the elastic members. [ABSTRACT FROM AUTHOR]

Based on critical refraction longitudinal wave (Lcr wave) acoustoelastic theory, correction method for grain size effect on surface stress measurement was discussed in this paper. Two fixed distance Lcr wave transducers were used to collect Lcr wave, and difference in time of flight between Lcr waves was calculated with cross-correlation coefficient function, at last relationship of Lcr wave acoustoelastic coefficient and grain size was obtained. Results show that as grain size increases, propagation velocity of Lcr wave decreases, one cycle is optimal step length for calculating difference in time of flight between Lcr wave. When stress value is within stress turning point, relationship of difference in time of flight between Lcr wave and stress is basically consistent with Lcr wave acoustoelastic theory, while there is a deviation and it is higher gradually as stress increasing. Inhomogeneous elastic plastic deformation because of inhomogeneous microstructure and average value of surface stress in a fixed distance measured with Lcr wave were considered as the two main reasons for above results. As grain size increasing, Lcr wave acoustoelastic coefficient decreases in the form of power function, then correction method for grain size effect on surface stress measurement was proposed. Finally, theoretical discussion was verified by fracture morphology observation. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of FME Transactions is the property of University of Belgrade, Faculty of Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of FME Transactions is the property of University of Belgrade, Faculty of Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: In this paper, an analytical study is carried out on the work‐hardening, elastic‐plastic stress distributions in a cracked body under antiplane shear deformation. A modified Ramberg‐Osgood law is introduced to describe the material behaviour, and stress and strain fields are derived in closed form. Compared with the conventional Ramberg‐Osgood formulation, the new law includes the effect of a new parameter, κ, which allows the transition from the ideally elastic behaviour (low stress regime) to the power law behaviour (large stress regime) to be controlled, thus providing 1 more degree of freedom to better fit the actual behaviour of engineering materials. A discussion is carried out on the features of stresses and strains close to and far away from the crack tip. [ABSTRACT FROM AUTHOR]

A new methodology for the estimation of tyre-contact forces is presented. The new procedure is an evolution of a previous method based on harmonic elimination techniques developed with the aim of producing low cost dynamometric wheels. While the original method required stress measurement in many rim radial lines and the fulfillment of some rigid conditions of symmetry, the new methodology described in this article significantly reduces the number of required measurement points and greatly relaxes symmetry constraints. This can be done without compromising the estimation error level. The reduction of the number of measuring radial lines increases the ripple of demodulated signals due to non-eliminated higher order harmonics. Therefore, it is necessary to adapt the calibration procedure to this new scenario. A new calibration procedure that takes into account angular position of the wheel is completely described. This new methodology is tested on a standard commercial five-spoke car wheel. Obtained results are qualitatively compared to those derived from the application of former methodology leading to the conclusion that the new method is both simpler and more robust due to the reduction in the number of measuring points, while contact forces’ estimation error remains at an acceptable level. [ABSTRACT FROM AUTHOR]

The prestress loss is one of the main factors affecting the safety of prestressed concrete structure. While the detecting signals like sound and light are difficult to spread in steel strands, there is no effective method for prestress detection of the bonded prestressed steel strands in existing structures yet. In this paper, taking into consideration that the electromagnetic oscillation characteristic can make the signal propagate effectively on the bonded prestressed steel strands, a nondestructive prestress detection method based on the electromagnetic effect to detect oscillation frequency is proposed. In a detection circuit, the steel strands are simulated as an inductance component, in which an induced electromagnetic signal passes through the steel strands to form resonance. And then, a frequency meter is used to detect the oscillation frequency of the resonant circuit. The oscillation frequency is supposed to have relationship with the prestress loading on the steel strands. A section of steel strands with a length of 1.2 m is adopted to test the correlation of stress and oscillation frequency. Both the theoretical and experimental results show that the resonant frequency of the circuit decreases with the increase of the stress of the strand and is linear in a certain range. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Machine Construction & Maintenance is the property of Institute for Sustainable Technologies - National Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Austenitic stainless steel (ASS) grade 304 is being extensively used in various high-temperature applications, which makes it important to study their properties at elevated temperatures, especially the flow stress behavior. The literature reveals flow stress of the material depends on influence of various input parameters, the important ones being the strain, strain rate and temperature. It is often noticed that these process parameters are determined by trial-and-error approach, which results in increased material failure and power losses. Constitutive models have also been developed to find the relationships between them, but these models have computational limitations and cannot capture the true stress behavior at elevated temperatures. Therefore, there is a need for formulation of a generalized explicit model/expression that can predict accurately the behavior ASS 304 at elevated temperatures. Therefore, this work proposed a new variant of genetic programming, gene expression programming (GEP), to formulate a model for true stress of ASS 304. True stress model formulated based on M-MGGP methodology has outperformed the GEP approach. Further investigation is carried out by sensitivity and parametric analyses to determine the relationships between process parameters, and it was found that the temperature has highest impact on the true stress of ASS 304 steel. [ABSTRACT FROM AUTHOR]

It is desirable to combine the stress measurement data produced by different methods to obtain a more reliable estimation of in situ stress. We present a regional case study of integrated in situ stress estimation by hydraulic fracturing, observations of borehole breakouts and drilling-induced fractures, and numerical modeling of a 1 km-deep borehole (EXP-1) in Pohang, South Korea. Prior to measuring the stress, World Stress Map (WSM) and modern field data in the Korean Peninsula are used to construct a best estimate stress model in this area. Then, new stress data from hydraulic fracturing and borehole observations is added to determine magnitude and orientation of horizontal stresses. Minimum horizontal principal stress is estimated from the shut-in pressure of the hydraulic fracturing measurement at a depth of about 700 m. The horizontal stress ratios ( S / S ) derived from hydraulic fracturing, borehole breakout, and drilling-induced fractures are 1.4, 1.2, and 1.1-1.4, respectively, and the average orientations of the maximum horizontal stresses derived by field methods are N138°E, N122°E, and N136°E, respectively. The results of hydraulic fracturing and borehole observations are integrated with a result of numerical modeling to produce a final rock stress model. The results of the integration give in situ stress ratios of 1.3/1.0/0.8 ( S / S / S ) with an average azimuth of S in the orientation range of N130°E-N136°E. It is found that the orientation of S is deviated by more than 40° clockwise compared to directions reported for the WSM in southeastern Korean peninsula. [ABSTRACT FROM AUTHOR]

The direct stress measurement is critical for the constitutive law investigation of concrete materials and dynamic behavior study of concrete structures under strong dynamic loadings where the strain-rate effect and the plastic behavior should be considered. In this article, an embedded dynamic internal normal stress sensor for concrete by employing piezoelectric lead-zirconate-titanate (PZT) patch as a sensing element is developed. After being calibrated under sinusoidal loadings with different frequencies, periodical square loadings, and random loadings, the developed dynamic internal normal stress sensor is further calibrated with a unique self-developed free-falling drop hammer with different impact velocities. The sensitivity of the developed normal stress sensor is determined accordingly. Finally, the developed sensors are employed to monitor the dynamic normal stress time history at different locations of concrete cylinder specimens under impacts with different velocities using a large-scale drop hammer test facility. The dynamic increase factors of concrete strength under impact are determined and compared with the values determined by the ComitéEuro-International du Béton code. The experimental results indicate that the PZT-based embedded dynamic internal normal stress sensor provides a novel way for the direct dynamic normal stress measurement of concrete specimens under impact loadings. [ABSTRACT FROM AUTHOR]

Erdaoya tunnel in the highway connecting Shiyan (Hubei province) and Manchuan, (Shanxi province) was studied in the study. Various problems occurred in the construction of the tunnel, including large deformation of surrounding rocks, cracks of preliminary supports and secondary linings as well as creeping down and collapse of surrounding rock masses along schistosity planes. In which, the most serious problem was large deformation of surrounding rocks, which not only dramatically delayed the normal construction progress of the tunnel, but also brought a huge challenge for the safety of builders. In order to solve this problem, detailed investigations were made on site in the study to reveal the regional geological, engineering geological and hydrogeological conditions of the tunnel. By conducting geo-stress measurement on site, the characteristics of geo-stress field of Erdaoya tunnel were analyzed from four aspects, including magnitudes of stress, coefficient of lateral pressure, orientation of stress and the relationship between magnitudes of geo-stresses and depths. By applying the DIPS software for interactively analyzing geological locator data, structure characteristics of rock masses were analyzed for preferred structural planes and schistosity planes in the tunnel site. Furthermore, the authors tested the physical and hydrological properties of the rock specimens collected on-site. So various physical properties (density, void fraction, and wave velocity) and water absorption hydrological property of schist were obtained, which provide underlying parameters support for the deformation and support of surrounding rocks of the tunnel. [ABSTRACT FROM AUTHOR]

We use a relatively simple analytic model incorporating two primary geomechanical factors-in situ stress and frictional coefficient of discontinuity-to assess the critical pore pressure increase associated with CO geological storage that initiates shear activation of pre-existing fractures and faults. Shear activation of fractures/faults can break the sealing integrity along the discontinuities, providing possible CO leakage channels. With an example of Gyeongsang Basin, Korea, which is considered a potential onshore geological storage site, the available in situ stress measurement data are analyzed to infer the stress states at an assumed storage depth of 1 km. The stress magnitudes in the basin are characterized by their spatial heterogeneity, implying that the critical pore pressure may vary depending on locations. As another primary factor for the analysis, frictional coefficient is shown to be possibly correlated with clay content in the host rocks encompassing the discontinuities, and in the infillings within the discontinuities, which demonstrates the possibility of estimating the frictional property from the clay content measurable using borehole geophysical logs. Based on the in situ stress conditions coupled with pore pressure change and assumed frictional coefficient of 0.6, the critical pore pressure is estimated, which would induce shear activation along well-orientated discontinuities for slip under the given stress states and consequently provide potential CO leakage pathways. The estimated critical pore pressure as an upper bound of allowable pore pressure is 4-8 MPa above the hydrostatic pore pressure in most of the basin, whereas the same is 0-4 MPa in the southern part of the basin. These results may be useful in the site selection stage for CO geological storage project. [ABSTRACT FROM AUTHOR]

Numerical and experimental studies of the transit of a mode-2 internal solitary wave over an isolated ridge are presented. All studies used a quasi-two-layer fluid with a pycnocline centred at the middepth. The wave amplitude and total fluid depth were both varied, while the topography remained fixed. The strength of the interaction between the internal solitary waves and the hill was found to be characterized by three regimes: weak, moderate, and strong interactions. The weak interaction exhibited negligible wave modulation and bottom surface stress. The moderate interaction generated weak and persistent vorticity in the lower layer, in addition to negligible wave modulation. The strong interaction clearly showed material from the trapped core of the mode-2 wave extracted in the form of a thin filament while generating a strong vortex at the hill. A criterion for the strength of the interaction was found by non-dimensionalizing the wave amplitude by the lower layer depth, a/ℓ. A passive tracer was used to measure the conditions for resuspension of boundary material due to the interaction. The speed and prevalence of cross boundary layer transport increased with a/ℓ. [ABSTRACT FROM AUTHOR]

The liquid jet impact onto a clamped elastic plate is investigated. The two-dimensional jet of constant thickness and with flat vertical front is initially advancing towards the elastic plate along a flat, rigid, and horizontal plane at a constant uniform speed. The elastic plate of variable thickness is mounted perpendicular to the rigid plane. The maximum stress during the early impact stage is estimated for a given retardation time and a given relaxation time of the plate material. The stresses during the initial impact stage are compared with the static stresses in the plate placed in an equivalent uniform flow. It is shown that the static stresses are always smaller than the bending stresses during the early stage of impact for a given speed and thickness of the jet. This implies that if the stresses in the plate are smaller than the yield stress of the plate material with no plastic deformations in the plate occurring during the unsteady impact stage, then the plate behaves elastically after the impact and plastic deformations are not achieved. Approaching the plastic deformations is treated here as a damage to the plate. The maximum stress increases with an increase in jet thickness. A critical value of the jet velocity, below which the plate is not damaged by the jet impact, is obtained for given characteristics of the plate. [ABSTRACT FROM AUTHOR]

This is a brief comment to highlight and discuss issues with regards to the high resolution, cross correlation-based, electron backscatter diffraction (HR-EBSD) results presented within the work of He et al. (2016) Advanced Engineering Materials. In this comment, two specific concerns are raised: one, the stress measurements, reported to be as high as 20 GPa, are unreasonable and due to a known artefact in the form of HR-EBSD analysis, which has been corrected in state-of-the-art measurements by patterning remapping; and two, the GND field measurements are incorrectly calculated and show the variations in lattice rotation and are no derived from the gradient of the lattice rotation field, as required when following Nye's analysis. An example of reasonable data is presented to highlight how these artefacts can be avoided in practice using more appropriate analysis techniques. [ABSTRACT FROM AUTHOR]

A computationally efficient surrogate model was developed based on artificial neural networks (ANN) to investigate the effect of the new generation of wide-base tires on pavement responses. Non-uniform tire contact stress measurements were obtained using a stress-in-motion instrument. The measured 3-D contact stresses were applied on two extreme 3-D flexible pavement finite element models representing low-volume (thin) and high-volume (thick) roads. Eleven critical pavement responses were modeled at two different material properties input levels-detailed and simplified-depending on data availability. The results rendered by the ANN surrogate models were highly accurate with average prediction error less than 5 % and R-square values higher than 0.95. In addition, two sensitivity analyses were performed to investigate the variables effect on pavement responses. It was found that the type of tire (wide-base vs. dual tire assembly) is more influential than the inflation pressure on pavement responses. However, the tire inflation pressure seemed to have a significant effect on near-surface responses. The developed models were incorporated into a tool to assist designers and engineers in investigating the effect of the pavement responses of wide-base versus dual tire assembly under typical loading conditions and pavement structures. [ABSTRACT FROM AUTHOR]

Robot-assisted therapy can provide effective rehabilitation training for stroke patients. The interfacial stress between the manipulator and the grasped patient's body is very important for a rehabilitation therapy robot. This paper presents a measurement method, which is able to decouple the measurement of the three-dimensional (3-D) interfacial stress components. To implement the method, interfacial stress sensors were fabricated based on plate capacitance and a superelastic material, while a high-resolution microcapacitance measurement circuit was developed based on a minimal system microprocessor and a programmable controller, and experiments are carried out by using a 3-D stress simulation equipment. The results show that the measurement circuit is capable of measuring a range of 1 fF–30 pF capacitance with a resolution better than 1 fF, and the sensor is capable of measuring Z-direction normal compressive stress at a range of \text0-3.0 \textkgf/\textcm^2 with a sensitivity of \text101 \textfF/\textkgf/\textcm^2 and X - and Y-direction shear stress at a range of 0-1.0 \textkgf/\textcm^2 with a sensitivity of \text118 \textfF/\textkgf/\textcm^2. This method can be applied to rehabilitation therapy robots to decouple the measurement of the 3-D interfacial stress components. [ABSTRACT FROM PUBLISHER]

Fusion welding is a joining process widely used in the industry. However, undesired residual stresses are produced once the welding process is completed. Post-weld heat-treatment (PWHT) is extensively employed in order to relieve the welding residual stresses. In this study, effect of PWHT time and temperature on the residual stresses of a ferritic stainless steel is investigated. Residual stress distributions in eight welded specimens were measured by using an ultrasonic method. Ultrasonic stress measurement is a nondestructive method based on acoustoelasticity law, which correlates mechanical stresses with velocity of an ultrasonic wave propagating within the subject material. The ultrasonic wave employed could be longitudinal or shear wave produced by the longitudinal (normal) or transverse (shear) transducers, respectively. Ultrasonic stress measurements based on longitudinal waves use longitudinal critically refracted (LCR) waves in this direction, while shear wave methods use an ultrasonic birefringence phenomenon. The results show that the effect of PWHT can be successfully inferred by both longitudinal and shear wave methods, but the former is found to be more sensitive to stress variation. Furthermore, the distribution of subsurface residual stresses is found to be more distinguishable when theLCRmethod is employed. [ABSTRACT FROM PUBLISHER]

A series of triaxial creep tests were conducted on warm frozen silts extracted from Qinghai-Tibet Plateau at temperature of −1.5 °C under confining pressures of 0.5, 1.0, and 2.0 MPa, respectively. The applied test stress levels were 30, 50, 60, and 70% of triaxial shear strength, respectively. The test results indicate that the creep strain increases with the increase in applied stress level and there is a stress threshold, based on which the test results can be classified into two types of creep strain curves. The creep strain curve only includes primary and secondary creep stages when the stress level is less than the threshold value. When the stress level exceeds the threshold value, the creep strain velocity gradually increases and the specimen quickly fails in tertiary creep stage. Based on the creep test results, a fractional order rheological element model is established for warm frozen silt, which is also generalized from uniaxial stress state to the three-dimensional stress state. From the analysis on the features of the stress threshold, a creep strength criterion is also proposed simultaneously. Comparing the calculated results of the warm frozen silt with the tested ones, it is found that the predicted results of the proposed model are in good agreement with the test results. In the proposed fractional order model, the relationship between the damage factor and time is established to describe the damage degree of the specimen. Compared with the existing creep constitutive model of frozen soil, the proposed fractional order model has advantages of fewer model parameters, higher simulation precision and wider applicability in analyzing the mechanical properties of warm frozen silt. [ABSTRACT FROM AUTHOR]

This paper reports a novel process to fabricate low cost dummy wafers with stress and temperature sensors for wafer level packaging. The polysilicon piezoresistors and Pt resistors are fabricated in 4-in. wafers with the same pad layout as the actual wafers used in wafer level packaging. Further, the sensors are diced and attached in a face-to-face manner at the test points of the large-size dummy wafers by using benzocyclobutene films. After etching away the substrate material, the sensors are transferred to the dummy wafers, and these wafers are then ready for residual stress measurement in wafer level packaging. The polysilicon stress sensors and Pt resistors are fabricated and transferred, and the longitudinal gauge factors before and after the transfer are measured to be 34.2 and 33.0, respectively. The deviation of the longitudinal gauge factors between pre and post transfer is less than −3.5 %, indicating a sufficient level of accuracy of the transferred sensors for stress measurement. The transverse gauge factors are measured to be much lower than the longitudinal gauge factors and can be neglected. The temperature coefficient of the Pt sensor is measured to be 1.73 × 10/°C. [ABSTRACT FROM AUTHOR]

The constitutive models based on grain size effect are crucial for analyzing the deformation of metal foils. Previous investigations on the constitutive models concentrate on the foils whose thickness/average grain diameter ( T/ D) ratios are more than 3. In this study, the commercial pure titanium foils with thickness of 0.1 and 0.2 mm were employed as the experimental materials. The mechanical properties of foils with dimensions of nine different T/ D ratios categorized into three ranges ( T/ D < 1, 1 ≤ T/ D < 3, T/ D ≥ 3)were tested. Meanwhile, the fracture behaviors and fracture mechanisms of the samples with different T/ D ratios were compared and analyzed. Besides, three constitutive models incorporating the surface layer effect and grain boundary strengthening effect were established for the three T/ D ratio ranges correspondingly. In these models, the thickness of the surface layers is set T for T/ D < 1 foils, D for T/ D > 3, and increases with D linearly in 1 ≤ T/ D < 3. The results calculated by the three models were compared. The experiments indicate that those models are all in good agreement. [ABSTRACT FROM AUTHOR]

This paper presents a back analysis procedure for identification of the elastic parameters of transversely isotropic rock cores, containing an overcoring triaxial strain probe, from the strains measured during a biaxial test. A three-dimensional finite element model was developed to simulate the biaxial test on the overcored rock specimen and to compute the strains at the location of the strain gauges. Different optimisation algorithms were tested and the most suitable one was selected. The back analysis procedure was tested for identification of the five elastic parameters and the two orientation angles that characterise a transversely isotropic rock core. Despite that, with the developed methodology, convergence was reached and all those parameters could be identified, sensitivity analyses demonstrated that the results obtained were not stable, and therefore, they were not reliable. By introducing constrains based on common practice and previous experience, a stable and robust methodology was achieved: the three elastic parameters, E , E and ν , are reliably identified using the value of G calculated with Saint-Venant expression and a fixed value of ν , while the orientation parameters are obtained from observation of overcored rock. Analysis of the results shows that application of this methodology represents an enormous step forward when compared with the traditional use of isotropy. Besides, the methodology is general and can also be used with other types of overcoring equipment. The five elastic parameters and the two orientation angles obtained can then be used, together with the overcoring strains, to compute the complete in situ state of stress. [ABSTRACT FROM AUTHOR]

Neutron diffraction was used to describe the residual stress distributions in self-piercing riveted (SPR) joints. The sheet material displayed a compressive residual stress near the joint, and the stress gradually became tensile in the sheet material far away from the joint. The stress in the rivet leg was lower in the thick joint of the softer steel sheet than in the thin joint of the harder steel sheet. This lower magnitude was attributed to the lower force gradient during the rivet flaring stage of the SPR process curve. This study shows how the residual stress results may be related to the physical occurrences that happened during joining, using the characteristics curve. The study also shows that neutron diffraction technique enabled a crack in the rivet tip to be detected which was not apparent from a cross-section. [ABSTRACT FROM AUTHOR]