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A high-density polyethylene (HDPE) geogrid soil-reinforced dry-cast concrete block retaining wall 6.3-m high was designed using the K-stiffness method as part of a highway-widening project southeast of Seattle, Washington. The amount of reinforcement needed for the original wall design using the K-stiffness method was approximately 50% of that required using the AASHTO simplified method. This paper describes the construction, instrumentation program, and interpretation of the measurements. Geogrid strains were measured using strain gauges and extensometers attached to reinforcement layers. An extensive materials testing program was conducted to characterize the backfill soil properties and geogrid stiffness properties and to calibrate strain gauge readings. The reinforcement loads deduced from the measured strains are compared with Class A, B, and C1 predictions using the AASHTO simplified and K-stiffness methods. These comparisons demonstrate that the simplified method significantly overestimated reinforcement loads, whereas the K-stiffness method provided estimates that were consistent with the measured results. This paper describes lessons learned, the influence of construction activities on wall performance, and the limitations of both methods in estimating connections loads. [ABSTRACT FROM AUTHOR]

Centrifuge models of soft-clay deposits were shaken with suites of earthquake ground motions to study site response over a wide strain range. The models were constructed in an innovative hinged-plate container to effectively reproduce one-dimensional ground-response boundary conditions. Dense sensor arrays facilitate back-calculation of modulus-reduction and damping values that show modest misfits from empirical models. Low-amplitude base motions produced nearly elastic response in which ground motions were amplified through the soil column, and the fundamental site period was approximately 1.0 s. High-intensity base motions produced shear strains higher than 10%, mobilizing shear failure in clay at stresses larger than the undrained monotonic shear strength. The authors attribute these high mobilized stresses to rate effects, which should be considered in strength-parameter selection for nonlinear analysis. This nonlinear response deamplified short-period spectral accelerations and lengthened the site period to 3.0 s. The nonlinearity in spectral amplification is parameterized in a form used for site terms in ground-motion prediction equations to provide empirical constraint unavailable from ground-motion databases. [ABSTRACT FROM AUTHOR]

Accurately predicting peak penetration resistance qpeak during spudcan installation into sand overlying clay is crucial to an offshore mobile jack-up industry still suffering regular punch-through failures. This paper describes a series of spudcan penetration tests performed on medium-loose sand overlying clay and compares the response to existing centrifuge data from tests performed on dense sand overlying clay. Together these data demonstrate that punch-through is a potential problem for both dense and loose sand overlying clay soil stratigraphies. Using this experimental database, a failure-stress-dependent model has been modified to account for the embedment depth, and the depth of occurrence of qpeak is shown to be a function of the sand thickness Hs. The model then was recalibrated, taking these findings into account, for a larger range of material properties and ratios of sand thickness to spudcan diameter (Hs=D). Finally, the performance of the modified and recalibrated model is verified by comparing its predictions with those calculated using current guidelines. The comparisons show that the modified model yields more accurate predictions of qpeak over the range of Hs=D ratios of practical interest, which when used in practice will potentially mitigate the risk of unexpected punch-through on sand overlying clay stratigraphies. [ABSTRACT FROM AUTHOR]

Interpretation of experimental and field cone penetration test (CPT) data from across a broad range of stress conditions requires defining the dependence of the measurements on overburden stress and other influencing factors. This paper examines three possible methods for overburden normalization of CPT tip resistance in sand at the same state parameter or same relative state parameter. The three methods for determining state-based normalized tip resistance at a reference overburden stress of 101.3 kPa (1 atm) are evaluated against calibration chamber test data for four well-studied clean sands. The CPT data from the calibration chamber tests are corrected for chamber boundary effects using two different methods to illustrate the effect this step has on derived relationships. The CPT data are further normalized to a common lateral earth pressure coefficient to illustrate the effect of this step. The three methods for state-based overburden normalization were evaluated for bias and dispersion against the calibration chamber data, including their dependence on the applied chamber correction relationship. The dependence of state-based overburden normalized tip resistances on the crushing behavior of the clean sand was evaluated by examination of one-dimensional limiting compression curves for these four sands. Finally, correlations for estimating the state parameter or relative state parameter from the state-based overburden normalized tip resistance were developed and evaluated based on the examined data. [ABSTRACT FROM AUTHOR]

A microcavity extrinsic Fabry--Perot interferometric (EFPI) fiber-optic sensor is presented for measurement of strain. The EFPI sensor is fabricated by micromachining a cavity on the tip of a standard single-mode fiber with a femtosecond (fs) laser and is then self-enclosed by fusion splicing another piece of single-mode fiber. The fs-laser-based fabrication makes the sensor thermally stable to sustain temperatures as high as 800°C. The sensor exhibits linear performance for a range up to 3700 µε and a low temperature sensitivity of only 0.59 pm/°C through 800°C. [ABSTRACT FROM AUTHOR]

The development of flexible polymer monofilament fiber strain sensors have many applications in both wearable computing (clothing, gloves, etc.) and robotics design (large deformation control). For example, a high-stretch monofilament sensor could be integrated into robotic arm design, easily stretching over joints or along curved surfaces. As a monofilament, the sensor can be woven into or integrated with textiles for position or physiological monitoring, computer interface control, etc. Commercially available conductive polymer monofilament sensors were tested alongside monofilaments produced from carbon black (CB) mixed with a thermo-plastic elastomer (TPE) and extruded in different diameters. It was found that signal strength, drift, and precision characteristics were better with a 0.3 mm diameter CB/TPE monofilament than thick (~2 mm diameter) based on the same material or commercial monofilaments based on natural rubber or silicone elastomer (SE) matrices. [ABSTRACT FROM AUTHOR]

Conventional metallic strain sensors are flexible, but they can sustain maximum strains of only ~5%, so there is a need for sensors that can bear high strains for multifunctional applications. In this study, we report stretchable and flexible high-strain sensors that consist of entangled and randomly distributed multiwall carbon nanotubes or graphite flakes on a natural rubber substrate. Carbon nanotubes/graphite flakes were sandwiched in natural rubber to produce these high-strain sensors. Using field emission scanning electron microscopy, the morphology of the films for both the carbon nanotube and graphite sensors were assessed under different strain conditions (0% and 400% strain). As the strain was increased, the films fractured, resulting in an increase in the electrical resistance of the sensor; this change was reversible. Strains of up to 246% (graphite sensor) and 620% (carbon nanotube sensor) were measured; these values are respectively ~50 and ~120 times greater than those of conventional metallic strain sensors. [ABSTRACT FROM AUTHOR]

The Brillouin optical time-domain analysis (BOTDA)-based optical fiber method has been proposed to measure strain variations caused by corrosion expansion. Spatial resolutions of 1 m can be achieved with this kind of Brillouin sensor for detecting the distributed strain. However, when the sensing fiber is wound around the steel rebar in a number of circles in a range of several meters, this spatial resolution still has limitations for corrosion monitoring. Here, we employed a low-coherent fiber-optic strain sensor (LCFS) to survey the performance of Brillouin sensors based on the fact that the deformation measured by the LCFS equals the integral of the strains obtained from Brillouin sensors. An electrochemical accelerated corrosion experiment was carried out and the corrosion expansion was monitored by both BOTDA and the LCFS. Results demonstrated that the BOTDA can only measure the expansion strain of about 1,000 µe, which was generated by the 18 mm steel rebar corrosion, but, the LCFS had high sensitivity from the beginning of corrosion to the destruction of the structure, and no obvious difference in expansion speed was observed during the acceleration stage of the corrosion developed in the reinforced concrete (RC) specimens. These results proved that the BOTDA method could only be employed to monitor the corrosion inside the structure in the early stage. [ABSTRACT FROM AUTHOR]

The paper presents an analysis of the stress and deflections changes due to creep in statically determinate composite steel-concrete beams. The mathematical model involves the equation of equilibrium, compatibility, and constitutive relationship, that is, an elastic law for the steel part and an integral-type creep law of Boltzmann-Volterra for the concrete part. Based on the theory of the viscoelastic body of Arutyunian-Trost-Bažant for determining the redistribution of stresses in beam sections between a concrete plate and steel beam with respect to time t, two independent Volterra integral equations of the second kind have been derived. A numerical method based on linear approximation of the singular kernal function in the integral equation is presented. An example with the proposed model is investigated. The creep functions are suggested by the Gardner and Lockman model. The elastic modulus of concrete Ec(t) is assumed to be constant in time t. [ABSTRACT FROM AUTHOR]

An experimental study was performed to evaluate the applicability of ACI 318 to the Class B splice of 600 MPa (87 ksi) reinforcing bars. Twelve simply supported beams and slabs with reinforcing bar splices were tested under monotonic loading. The test parameters were the reinforcing bar diameter, concrete cover thickness, concrete strength, and stirrup spacing. Concrete strengths ranged from 24.7 to 55.3 MPa (3582 to 8021 psi). Most of the specimens were designed to satisfy the Class B splice length specified by ACI 318. The average bar stresses resulting from this test were compared with the predictions by the ACI 318 provisions. The results showed that the reinforcing bar splices gave a satisfactory performance for all D13 (diameter = 13 mm [0.51 in.]) bar splices. For D22 and D32 bars, the use of either transverse reinforcement or thick concrete cover was recommended to develop the specified yield strength of 600 MPa (87 ksi). The test results were also compared with the predictions by the ACI 408R-03 and Eurocode 2 provisions. [ABSTRACT FROM AUTHOR]

To decrease the size of portable devices, this study incorporates a stacked three-dimensional integrated circuit architecture into advanced packaging techniques. The traditional FR-4 substrate was substituted with silicon interposers. Because silicon is rigid and highly resistant to deformation, this minimizes thermal stress caused by thermal expansion mismatch in the structure. This study shows that underfill applied stress to the dies when the temperature was varied, threatening the devices. Damage was most likely to occur at the die corners. The stresses were measured in situ at different temperatures using synchrotron radiation x-ray analysis. Simulation results confirm the measured data trends. [ABSTRACT FROM AUTHOR]

An atomistic model to account for the impact of stress during solid phase epitaxial regrowth (SPER) is proposed. This model is based on the lattice kinetic Monte Carlo method. It has been compared with experimental data of regrowth velocity as a function of hydrostatic and non-hydrostatic stresses. In particular, it permits to provide a physical explanation of the observations upon in-plane uniaxial stress based on the assumption that {100} events occur through a dual-timescale atomistic mechanism. Our model also catches the fact that compressive normal uniaxial stress and hydrostatic pressure result in an enhancement of the regrowth velocity with a similar activation volume. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

In this paper, a wireless sensing system for structural field evaluation and rating of bridges is presented. The system uses a wireless platform integrated with traditional analogue sensors including strain gages and accelerometers along with the operating software. A wireless vehicle position indicator is developed using a tri-axial accelerometer node that is mounted on the test vehicle, and was used for identifying the moving truck position during load testing. The developed software is capable of calculating the theoretical bridge rating factors based on AASHTO Load and Resistance Factor Rating specifications, and automatically produces the field adjustment factor through load testing data. The sensing system along with its application in bridge deck rating was successfully demonstrated on the Evansville Bridge in West Virginia. A finite element model was conducted for the test bridge, and was used to calculate the load distribution factors of the bridge deck after verifying its results using field data. A confirmation field test was conducted on the same bridge and its results varied by only 3% from the first test. The proposed wireless sensing system proved to be a reliable tool that overcomes multiple drawbacks of conventional wired sensing platforms designed for structural load evaluation of bridges. [ABSTRACT FROM AUTHOR]

In this paper, the importance of displacement history and its effects on performance limit states, the relationship between strain and displacement, and the spread of plasticity in RC structures is explored. An experimental study is underway to assess the performance of 30 circular, well-confined, bridge columns with varying lateral displacement history, transverse reinforcement detailing, axial load, aspect ratio, and longitudinal steel content. Eight of these columns, with similar geometry and detailing, were subjected to various unidirectional displacement histories including standardized laboratory reversed cyclic loading and re-creations of the displacement responses obtained from a nonlinear time-history analysis of multiple earthquakes with distinct characteristics. Longitudinal reinforcing bars were instrumented to obtain strain hysteresis, vertical strain profiles, cross section curvatures, curvature distributions, and fixed-end rotations attributable to strain penetration. Results have shown that the limit state of reinforcement bar buckling was influenced by load history, but the relationship between strain and displacement along the envelope curve was not. The main impact of load history on bar buckling is its influence on accumulated strains within the longitudinal reinforcement and transverse steel. [ABSTRACT FROM AUTHOR]

The objective of this study is to investigate the effectiveness of an alternative technique for strengthening masonry columns, based on the use of steel cords. Although fiber-reinforced polymer (FRP) strips or jackets are successfully used as strengthening elements for this kind of application, such a strengthening method represents a new opportunity to restore ambit, with considerable development in unreinforced masonry wrapping. Thus, to assess the potential of steel cord wrapping, this paper presents the results of an experimental program consisting of 48 solid-brick specimens subjected to uniaxial compression load. Different cross-section geometry (octagonal, square, and rectangular) and different amounts and different schemes for confining reinforcement were investigated. The primary experimental outcomes are presented and discussed in the paper considering the mechanical behavior of specimens and the axial stress-axial strain relationships. Test results have shown that the investigated confining systems are able to provide significant gains, both in the compressive strength and in the deformation capacity of masonry columns. [ABSTRACT FROM AUTHOR]

Given the schedule pressure of lime-stabilized soil construction, many agencies specify the use of elevated temperature (e.g., 41°C), shorter duration (e.g., 5-7 days) accelerated specimen curing for unconfined compressive strength () testing and acceptance as a proxy for of specimens normally cured under 28-day 23°C conditions. Moreover, lime and highway transportation industry associations prescribe a unique accelerated curing regime for all lime-stabilized soils (7-day, 41°C). This paper presents the results from a laboratory investigation of stress-strain-strength development of four lime-stabilized soils under 2-8 day 41°C accelerated curing and the 0-28 day 23°C normal curing regime. Specimens cured at 41°C reached values equivalent to 28-day 23°C after 1.8-5.9 days. Accordingly, 7-day 41°C curing overestimates 28-day normal cure by 13-260%. When combined with a detailed analysis of data available in the literature, the results illustrate that the prescription of a unique equivalent accelerated curing regime is oversimplified and can lead to significant overestimation of design . [ABSTRACT FROM AUTHOR]

Results of an extensive series of repeated load triaxial tests performed on three major recycled construction and demolition (C&D) materials at various moisture contents and stress levels were analysed to ascertain their performance in pavement subbases. The development of the resulting permanent deformation that accumulates with the repeated loading and the determination of resilient modulus by two phases of the test are described. The experimental study shows that the C&D materials perform satisfactorily at a moisture content of about 70% of their optimum moisture contents. Furthermore, the C&D materials also satisfy the two-parameter and three-parameter models. The results of this study indicate that, at a density ratio of 98% compared to maximum dry density obtained in the modified proctor test and with moisture contents in the range of 65-90% of the optimum moisture content, most of the recycled C&D materials produce comparatively smaller permanent strain and greater resilient modulus than natural commonly used granular subbase materials in pavement subbase applications. [ABSTRACT FROM AUTHOR]

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This paper reports on damage morphology created in low-cycle high-load spherical indentations of feldspar porcelain and leucite glass ceramic to mimic teeth clenching or grinding. Maximum contact stresses were evaluated as functions of cycle numbers and applied loads using a Hertz model. The surface damage of the two materials after low-cycle high-load indentation testing was viewed using scanning electron microscopy to understand the relations between crack propagation and microstructures. The results indicate that the maximum contact stresses for both materials reduced significantly with the cycles (ANOVA, p < 0.05) but did not show a significant change with the applied loads (ANOVA, p > 0.05). Feldspar porcelain can endure much less maximum contact stress than leucite glass ceramic. Low-cycle high-load spherical indentations induced extensive ring cracks, wedging of crack faces by debris, fragmentation, and pulverization on feldspar porcelain surfaces. In contrast, leucite glass ceramic surfaces yielded only minimum microcracks at 500 N load and localized fractures and cracks at the higher loads of 600 and 700 N. This study shows that leucite glass ceramic had much higher resistance to low-cycle high-load fatigue impacts than feldspar porcelain and it can be a better choice for restorations under teeth clenching and grinding conditions. [ABSTRACT FROM AUTHOR]

The main purpose of the present work is to measure the stress-strain behavior under warm conditions (about 100 °C) of advanced high strength steel (AHSS) sheets up to large strains compared to uniaxial tension. The test equipment consists of two main parts, i.e., a hydraulic bulge tester and a heating device. A mechanical system is attached to the test equipment for measuring the membrane stress and thickness strain at the bulge pole. The stress-strain curves were measured for three kinds of AHSS sheets with the proposed test method for various initial temperatures (10, 50 and 100 °C). The proposed method does not provide isothermal stress-strain curves because the specimen temperature increases during the test due to the effect of deformation-induced heating. A numerical scheme using thermo-mechanical finite element (FE) simulations is suggested to deconvolute the isothermal stress-strain curves. [ABSTRACT FROM AUTHOR]

Abstract: In the paper the method of experimental temperature and stress measurement of reinforced concrete foundation slab during construction of the National Supercomputing Centre in Ostrava, Czech Republic is described. Measured results are compared with numerical analysis and time dependent development of concrete strength. Decreasing the tensile stress in concrete by use of the sliding joint was verified. [Copyright &y& Elsevier]

We discuss the design, instrumentation, and calibration of a versatile force transducer with feedback control, called the Micro-Extensional Rheometer (MER). A force range of eight decades (1-108 pN) and a displacement range of four decades (10-105 nm) with a spatial resolution of the order of nanometers are accessible with the instrument. A feedback-loop algorithm is used to control the commanded force or the extensional strain on the sample and implement different rheometric protocols such as step-strain, step-force, exponential strain, among others. The device may also be used to measure the forces exerted by active suspensions, pulling neurons, etc. [ABSTRACT FROM AUTHOR]

We report on a systematic study of the stress transferred from an electromechanical piezo-stack into GaAs wafers under a wide variety of experimental conditions. We show that the strains in the semiconductor lattice, which were monitored in situ by means of X-ray diffraction, are strongly dependent on both the wafer thickness and on the selection of the glue which is used to bond the wafer to the piezoelectric actuator. We have identified an optimal set of parameters that reproducibly transfers the largest distortions at room temperature. We have studied strains produced not only by the frequently used uniaxial piezostressors but also by the biaxial ones which replicate the routinely performed experiments using substrate-induced strains but with the advantage of a continuously tunable lattice distortion. The time evolution of the strain response and the sample tilting and/or bending are also analyzed and discussed. [ABSTRACT FROM AUTHOR]

In this article, an analytical model is developed for estimation of the maximum normal stress in a beam-column member subjected simultaneously to an axial load and bending moments. The analytical model is derived by defining the relationship between the maximum strain and average strains measured wirelessly from vibrating wire strain gages. On the basis of the experimental tests on a two-dimensional steel frame structure with beam-column members, the performance of the estimation model is evaluated by comparing the maximum strains directly obtained from electrical strain gages and the estimated maximum strains from the model. Using the model, a practical monitoring of the maximum stress in steel beam-columns is made possible by measuring three average strains at arbitrary locations. [ABSTRACT FROM AUTHOR]

This paper presents a comparison of two live-load tests performed on a posttensioned, box-girder bridge. The initial live-load test was performed more than 20 years before the most recent test. Strain gauges were placed at the same location for both tests. In each case, the bridge was subjected to nearly identical loads so that changes in strain could be correlated as a heavy truck drove across the instrumented bridge. A comparison of the bridge behavior based on the two load tests is presented. The changes in recorded strain were also used to validate a detailed finite-element (FE) model using primarily shell elements. From this calibrated FE model, the live-load distribution factors for moment were obtained. These factors were used to calculate both the inventory and operating rating factors of the bridge. These values were compared with those calculated in accordance to the AASHTO LRFD specifications for distribution factors. It was found that the rating factors could be increased by 26% because of the partial fixity caused by the integral abutments. [ABSTRACT FROM AUTHOR]

Experimental research on imposed deformation is generally conducted on small-scale laboratory experiments. The attractiveness of field research lies in the possibility to compare results obtained from full-scale structures to theoretical predictions. Unfortunately, measurements obtained from real structures are rarely described in literature. The structural response of integral edifices depends significantly on stiffness changes and constraints. The New Airport Terminal Barajas in Madrid, Spain provides investigators with large integral modules, partially post-tensioned concrete frames, cast monolithically over three floor levels with an overall length of approximately 80 m. The field campaign described in this article explains the instrumentation of one of these frames, focusing on the influence of imposed deformations such as creep, shrinkage, and temperature. The applied monitoring equipment included embedded strain gauges, thermocouples, hand-held mechanical strain gauge measurements, and simple displacement measurements. Data were collected throughout construction and during two years of service. A complete data range of five years is presented and analyzed. Using a simple approach, the results are compared to predict the long-term shortening of this concrete structure. Both analytical and experimental results are discussed. [ABSTRACT FROM AUTHOR]

Purpose – Safety analysis has been done for thermal non-homogeneous thick-walled circular cylinder under internal and external pressure. The paper aims to discuss these issues. Design/methodology/approach – Transition theory based on the concept of generalized principal Lebesgue strain measure has been used which simplifies the constitutive equations by prescribing a priory the order of the measure of deformation and helps to achieve better agreement between the theoretical and experimental results. Findings – From the analysis, the paper can conclude that by introducing a suitably chosen temperature gradient, non-homogeneous compressible circular cylinder with internal and external pressure for non-linear measure is on the safer side of the design as compared to the cylinder without temperature because circumferential stresses are less for cylinder with temperature as compared to cylinder without temperature. Practical implications – Introduction of temperature gradient leads to the idea of "Stress Saving" and minimizing the possibility of fracture of cylinder. Originality/value – The paper shows that circumferential stresses are less for cylinder with temperature gradient as compared to cylinder at constant temperature, which leads to the idea of "Stress Saving" and minimizing the possibility of fracture of cylinder. [ABSTRACT FROM AUTHOR]

Sn-Co alloys are promising Pb-free solders, while plating layers and substrates of Ag and Cu are commonly encountered in electronic products. This study examines the interfacial reactions between Sn-0.25 wt% Co/Ag and Sn-0.25 wt% Co/Cu at 180 and 210 °C, with and without current stressing. CoSn3 precipitates are found in the solder matrix in the as-prepared condition. In Sn-0.25 wt% Co/Ag couples, a continuous Ag3Sn reaction phase layer is observed at the interface and Ag3Sn phase particles are dispersed in the matrix, with and without current stressing. When there is a 500 A/cm2 electrical current, the growth rate of the Ag3Sn phase is not affected at either the cathode side or the anode side. However, the passage of an electrical current leads to the formation of needle-like Ag3Sn phase particles in the solder matrix. In Sn-0.25 wt% Co/Cu couples, both Cu6Sn5 and Cu3Sn reaction phases are formed at the interface, with and without current stressing. Cu6Sn5 precipitates, with a higher Co content, are found in the matrix, mostly nucleated on CoSn3 precipitates. When there is a 500 A/cm2 electrical current stressing, all the reaction phase layers are thicker and the anode interfaces are nonplanar. It is observed that there is cracking and that there are discontinuous Cu6Sn5 layers at the interface and that a significant amount of Cu6Sn5 phase in the matrix accompanies 500 A/cm2 electrical current stressing. [ABSTRACT FROM AUTHOR]

ABSTRACT A simple method to analyse the notch sensitivity of specimens in fatigue tests is presented. The parameter m, which can be used to measure the notch sensitivity, the nominal stress and the stress concentration factor ( Kt) are used to establish the method. In order to verify the feasibility of the method, notch fatigue test results from our group and literatures were collected. The results reveal that an optimal value of parameter m does exist for each material. Life predictions indicated that the model is able to describe the life evolution for notched specimens under high cycle fatigue and low cycle fatigue tests. Because the geometry effect is accounted for Kt, the method is suitable for the conditions when the notch geometries and the absolute dimensions are similar to the tested specimens. [ABSTRACT FROM AUTHOR]

Abstract: This work presents simplified models for strain and temperature measurement during orthogonal cutting process applying Ernst-Merchant theory and considering a 2-D steady state heat conduction problem. In order to validate the thermal model experiments with high speed imaging and with Infrared imaging were performed. The results of the infrared thermal measurements were compared with the outputs of the temperature model, considering the average temperature on the shear plane and temperature distribution. Also video analysis technique was developed to obtain shear strain in a precise way compared with Ernst-Merchant classical analysis. Experiments were conducted in a specially adapted milling machine for different low cutting velocities and feedrates. [Copyright &y& Elsevier]

In situ neutron diffraction lattice strain measurements have been made during compressive loading tests on Zircaloy-2 at different temperatures. The experimental results show changes of the relative contributions of different deformation modes with increasing temperature. Among the operating deformation modes, basal slip is found to operate at a higher applied stress than prism slip at ambient conditions, but at a similar applied stress at elevated temperatures. Twinning is found to be present at 573 K (300 °C), but is not observed at a temperature of 773 K (500 °C) at the loading rate used. [ABSTRACT FROM AUTHOR]

In this study, a generalized equivalent Stress Block Model has been proposed that is applicable to all types of concrete, including lightweight and high-strength concrete (HSC). First, available stress-strain models for concrete were verified through an extensive database. Then, the coefficients used in the proposed stress blocks were formulated based on a nonlinear regression analysis of the values determined from the layer-by-layer integral evaluation approach. The hypothesis underlying this integral approach is that the magnitude and location of the resultant force in the equivalent stress distribution are the same as those in the actual distribution. The extreme compressive fiber strain of 0.003 and the factor of 0.85 used to compensate for the difference between the in-place strength and the cylinder strength were assumed, as was done for normalweight and/or normal-strength concrete (NSC). The reliability and safety of the proposed stress blocks were confirmed through comparisons with the flexural capacities measured from approximately 175 normalweight and 80 lightweight concrete (LWC) beams, and approximately 100 normalweight concrete (NWC) columns. [ABSTRACT FROM AUTHOR]

To replace a traditional steel bogie with a composite one, this study designed and manufactured a composite bogie frame made of glass fiber-reinforced plastics to be applied to the bogie of an urban subway train. To evaluate its structural behavior, the composite bogie frame was tested under critical load conditions encompassing vertical loads and a twisting load. The test revealed that the maximum strain measured under the vertical load corresponded to 16.3% of the failure strain of the GEP224 glass fabric/epoxy sample. According to a durability evaluation using Goodman diagrams, both the measured and the calculated stress data were within the endurance limit. Therefore, the composite bogie frame satisfied the structural safety requirements. The evaluation of the contribution of each load case clearly showed that the vertical and braking loads were the most critical load cases. Adding the braking load cases led to movement of the critical point from the inner joint to the outer joint due to the increased torsion. [ABSTRACT FROM AUTHOR]

Strain-induced abnormal grain growth was observed along the gage length during high-temperature uniaxial tensile testing of rolled Mg-Al-Zn (AZ31) sheet. Effective strain and strain rates in biaxial forming of AZ31 sheets also affected the nature of grain growth in the formed sheet. For the uniaxial testing done at 400 °C and a strain rate of 10-1s-1, abnormal grain growth was prevalent in the gage sections that experienced true strain values between 0.2 and 1.0. Biaxial forming of AZ31 at 5 × 10-1s-1 and 400 °C also exhibited abnormal grain growth at the cross sections which experienced a true strain of 1.7. Uniaxially tested sample at 400 °C and a strain rate of 10-3s-1, however, showed no abnormal grain growth in the gage sections which experienced true local strain values ranging from 1.0 to 2.3. The normalized flow stress versus temperature and grain size compensated strain rate plot showed that the deformation kinetics of the current AZ31 alloy was similar to that reported in the literature for AZ31 alloys. Orientation image microscopy (OIM) was used to study the texture evolution, grain size, and grain boundary misorientation during uniaxial and biaxial forming. Influence of deformation parameters, namely strain rate, strain, and temperature on grain growth and refinement were discussed with the help of OIM results. [ABSTRACT FROM AUTHOR]

To study the mechanical behavior of concrete filled steel tube columns subjected to compression- bending-torsion combined load, based on the general finite element program ABAQUS, the suitable material constitutive equations including concrete damage plastic model and steel perfect elastic-plastic model, boundary conditions and combined load conditions were chosen and applied, then the "shell-solid" refined model of concrete filled steel tube columns was established. A good agreement could be observed between the predicted results and test results, and both the stress-strain state of the steel and concrete and the global torsion moment versus rotation angle relations could be obtained, showing that the "shell-solid" refined model had high precisions, and the comprehensive results of concrete filled steel tubes subjected to torsion could be obtained. [ABSTRACT FROM AUTHOR]

To determine the shear-resistance performance and deformability of 290 mm-width fully grouted reinforced concrete masonry (FGRM) shear walls under different failure modes, ten full-scale walls were tested firstly under low cyclic reversed lateral loads simulated by a 1 000 kN jack providing constant axial load and a 630 kN servo controlled hydraulic actuator producing low cyclic reversed lateral loads. The seismic performance of walls bearing compress, shear and flexure is studied. Meanwhile, the skeleton curves of FGRM shear walls based on the data recorded in the tests are investigated considering different factors including the axial compressive stress, the horizontal reinforcement, the vertical reinforcement, et al. It is demonstrated that, firstly, both the shear and deformation capacity can be improved as the axial compressive stress increases within a certain range. Secondly, the impact of horizontal reinforcement on the shear-resistant performance of walls is related to failure modes of the wall. Compared with the flexural failure mode, a much higher shear capacity but a worse ductility is derived in a shear failure mode when the walls are confirmed with higher horizontal reinforcement. Finally, the wall shear capacity is influenced significantly by the vertical reinforcement whose effects on ductility are associated with the applied axial stress. [ABSTRACT FROM AUTHOR]

In this study, we advance the classic implicit moment method (IMM) particle simulation approach for the coupled Vlasov-Ampère system. We extend the IMM concept by (1) enforcing discrete consistency between the moment and kinetic system by introducing the concept of discrete consistency term and (2) efficiently converging the moment and kinetic system within a time step using a density normalized stress tensor. The new approach is energy conserving and is second-order accurate in time. The advantageous accuracy properties of the scheme are demonstrated with several numerical experiments including the challenging case of an ion acoustic shockwave problem. [ABSTRACT FROM AUTHOR]

This paper discusses the issue of isolating the strain from the temperature measurement using the Brillouin technique. Temperature sensing using a Brillouin distributed fibre optic sensor is influenced by the induced stress/strain. In order to isolate the stress/strain on the distributed fibre sensor, it is encased in a stainless steel (SS) tube. For this, a cantilever structure is used to introduce strain in the deployed optical fibre sensor. Using this implemented method, the bare fibre strain is determined. Also, it was found that the SS tube- encased fibre does not respond to strain. The comparison has been carried out to study the sensitivity of the SS tube-encased fibre and that of the bare fibre under various temperature conditions. [ABSTRACT FROM AUTHOR]

We report for the first time on the thorough experimental and theoretical assessment of the noise limit of mechanical stress and temperature measurements with micro-Raman spectroscopy. A comprehensive study has been performed in which, for different incident laser light intensities and acquisition times, 1000 Raman spectra of mono-crystalline silicon were acquired per setting. Curve fitting was employed to obtain the peak positions of all the spectra, from which the standard deviations of the measured peak positions were obtained versus the total accumulated amount of laser light incident on the sample during one measurement. It has been found that the noise in the obtained peak position decreases as 1/sqrt(n) over more than three decades of the incident amount of laser light. At very low light conditions, the noise decreases as 1/n. By comparing the experimental results obtained to recent theoretical work, we show that the acquisition is limited by photon shot noise over most of the range and is limited by electronic detector noise at very low light conditions only. Pixelation errors do not play a role. It is concluded that the low electronic noise of typical Raman spectroscope detectors is overkill for the investigation of mechanical stress and temperature in silicon and other materials with comparable peaks, as it has absolutely no influence on the noise level of such an experiment. Maximum Raman signal intensity on the detector and high quantum efficiency detection are more important. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper presents new data and a summarization of earlier work, especially by the authors, regarding the large strain deformation (generally severe plastic deformation) of pure zirconium, generally at elevated temperatures (300-800 °C range). It appears clear, now, that Zr deforms by classic five-power-law creep. Large strain deformation revealed recovery controlled mechanisms with grain refinement occurring by geometric necessary boundaries and/or the recovery-based mechanism of geometric dynamic recrystallization depending on the amount of grain elongation that occurs. No discontinuous dynamic recrystallization or grain growth was observed in the authors' tension and rolling studies. The refined ultra-fine grained substructure showed dramatically improved tensile properties over conventionally processed Zr. [ABSTRACT FROM AUTHOR]

Model validation remains a serious problem within the field of computational granular materials research. In all cases the rigor of the validation process is entirely dependent on the quality and depth of the experimental data that forms the point of comparison. Neutron and X-ray diffraction methods offer the only quantitative non-contact method for determining the spatially resolved triaxial stress field within granular materials under load. Measurements such as this can provide an unprecedented level of detail that will be invaluable in validating many models. In this paper the theoretical foundation underpinning diffraction-based strain measurements, their conversion to local stress in the particles and ultimately into the bulk stress field is developed. Effects such as elastic anisotropy within the particles of the granular material, particle plasticity and locally inhomogeneous stress distribution are shown to not offer any obstacles to the method and a detailed treatment of the calculation of the bulk stresses from the particle stresses is given. [ABSTRACT FROM AUTHOR]

When transverse strain is much larger than the longitudinal one, conventional fiber Bragg grating measurement model presents significant errors in the longitudinal strain measurement. The present authors presented a fiber Bragg grating measurement model to consider transverse strain effects and numerically demonstrated the effectiveness of the model. This article experimentally validates the fiber Bragg grating measurement model by measuring thermal expansion of anisotropic composite specimens and an isotropic invar specimen. The longitudinal thermal expansion of the specimens is measured by using fiber Bragg grating sensors and compared with a reference measurement result using an optical interferometer. The proposed fiber Bragg grating model shows good agreement with the reference measurement for the longitudinal strain while large discrepancy (~22%) is observed according to the conventional one-dimensional fiber Bragg grating model. [ABSTRACT FROM PUBLISHER]

The construction of highway embankments in urban areas often interferes with existing underground facilities such as sewer lines and other buried conduits. In many instances, the extra loads imposed by embankment construction on buried conduits would be unacceptably high. Severe consequences of overstressing an underground utility conduit include damage and interruption of services for both the utility and highway. Typical alternatives considered to address this problem include: relocation of utility lines; embankment load reduction using lightweight fill; at-grade pile cap bridging; at-grade geogrids-reinforced bridging; and induced (imperfect) trenches. The relocation, lightweight fill and pile cap alternatives are usually cost prohibitive. A full-scale instrumented test embankment is constructed by Ontario Ministry of Transportation to study the effects of embankment construction on the underground utilities. The test embankment comprised four sections, which facilitated the evaluation of four configurations including the conventional backfill, induced trenching and two at-grade geogrid-reinforcing bridging with different spans. Each configuration consisted of a 3 m deep trench overlain by a 10 m wide, 10 m long and 6 m high embankment section. Earth load cells were installed to monitor stresses at the fill/ground interface and at depths of 1.5 and 3 m. The numerical models of the test embankment are generated using the finite difference program FLAC. This paper presents the results of stress measurements in the 3 m wide trench under embankment loads and the results of numerical varification analyses. The results showed that the use of induced trench method (ITM) resulted in substantial reduction in vertical stresses relative to positive projection method case. It was also observed that horizontal stresses increased when ITM is employed. [ABSTRACT FROM AUTHOR]

We present a new full-field strain measurement method based on diffusing-wave spectroscopy. Our technique makes it possible to measure strains in the vicinity of the surface of highly light-scattering materials. Its main feature is an extreme sensitivity: the range of deformations measured is 10−5-10−3. To validate the measurements, experimental results from several plane stress configurations are compared with theoretical and numerical calculations. Furthermore, we propose an extension of the method for non-scattering materials. [ABSTRACT FROM AUTHOR]

We developed a simultaneous strain measurement and damage detection technique using a pair of surface-mounted piezoelectric transducers and a fiber connecting them. This is a novel sensor configuration of the fiber acoustic wave (FAW) piezoelectric transducer. In this study, lead-zirconate-titanate (PZT) transducers are installed conventionally on a plate's surface, which is a technique used in many structural health monitoring studies. However, our PZTs are also connected with an optical fiber. A FAW and Lamb wave are simultaneously guided in the optical fiber and the structure, respectively. The dependency of the time-of-flight of the FAW on the applied strain is quantified for strain sensing. In our experimental results, the FAW exhibited excellent linear behavior and no hysteresis with respect to the change in strain. On the other hand, the well-known damage detection function of the surface-mounted PZT transducers was still available by monitoring the waveform change in the conventional Lamb wave ultrasonic path. [ABSTRACT FROM AUTHOR]

An important requirement for developing an understanding of wood bending mechanics is to determine the mechanical response of softened wood during bending. This involves experimentally measuring wood's deformation or strain. Many wood bending studies have been conducted over the past 80 years to increase the understanding and investigate methods of ultimately improving the wood bending operation. The majority of these studies investigated the particular type of method of softening, using minimum bending radius and quality as a measured response. However, there is sparse literature in the public domain that offers a means of gaining an understanding of the mechanics of a wood specimen during a bending operation. This paper introduces a low-cost optical-based method for measuring engineering strain in softened wood. The method requires minimal specialised equipment and has been successfully used to determine the engineering strain response of Eucalyptus regnans during the bending process. [ABSTRACT FROM AUTHOR]

An innovative means of measuring the end-forces in a softened wood specimen during a bending process has been developed, incorporating a resultant end-force sensor. The impact of end-forces on wood deformation and associated bending performance has been investigated, and a correlation was found to exist between end-force and bending performance. The technique enables the systematic control of axial compression end-forces so that bending induced wood failure, as measured by longitudinal strain at the convex edge, can be minimised. While incorporating traditional manual end-force adjustment, it is envisaged that that this technique could facilitate automation of the bending process. Friction was identified as a significant impediment to the establishment of a reliable relationship between end-force and wood strain during bending. [ABSTRACT FROM AUTHOR]

A model was established to analyze and predict effectively the wear life of rod. It is considered in this model: the two main reasons for partial-wear: borehole curving and rod blending under pressure in the down stroke. A calculating formula suggested by ???????? was used to evaluate the increase of abrasion thickness of rod with time, and the failure position and time were estimated in accordance with the increase of stress with the decrease of residual cross-section area at the point where the wear was worst. The comparison between the model result and the spot data was used to prove the reliability of this model. The principle that the revolving wellhead could retard the progress of wear was interpreted through the calculating result made by this model [ABSTRACT FROM AUTHOR]