Reduced thoracolumbar fascia shear strain in human chronic low back pain

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Konofagou Elisa E

2011-09-01

Full Text Available Abstract Background The role played by the thoracolumbar fascia in chronic low back pain (LBP is poorly understood. The thoracolumbar fascia is composed of dense connective tissue layers separated by layers of loose connective tissue that normally allow the dense layers to glide past one another during trunk motion. The goal of this study was to quantify shear plane motion within the thoracolumbar fascia using ultrasound elasticity imaging in human subjects with and without chronic low back pain (LBP. Methods We tested 121 human subjects, 50 without LBP and 71 with LBP of greater than 12 months duration. In each subject, an ultrasound cine-recording was acquired on the right and left sides of the back during passive trunk flexion using a motorized articulated table with the hinge point of the table at L4-5 and the ultrasound probe located longitudinally 2 cm lateral to the midline at the level of the L2-3 interspace. Tissue displacement within the thoracolumbar fascia was calculated using cross correlation techniques and shear strain was derived from this displacement data. Additional measures included standard range of motion and physical performance evaluations as well as ultrasound measurement of perimuscular connective tissue thickness and echogenicity. Results Thoracolumbar fascia shear strain was reduced in the LBP group compared with the No-LBP group (56.4% ± 3.1% vs. 70.2% ± 3.6% respectively, p Conclusion Thoracolumbar fascia shear strain was ~20% lower in human subjects with chronic low back pain. This reduction of shear plane motion may be due to abnormal trunk movement patterns and/or intrinsic connective tissue pathology. There appears to be some sex-related differences in thoracolumbar fascia shear strain that may also play a role in altered connective tissue function.

Effects of different aging statuses and strain rate on the adiabatic shear susceptibility of 2195 aluminum–lithium alloy

International Nuclear Information System (INIS)

Yang, Y.; Tan, G.Y.; Chen, P.X.; Zhang, Q.M.

2012-01-01

The adiabatic shear susceptibility of 2195 aluminum–lithium alloy was investigated by means of split Hopkinson pressure bar. The stress collapse in true stress–true strain curves and true stress–time curves was observed. The adiabatic shear susceptibility of different aging statuses and strain rate were discussed by means of metallography observation. The critical strain, stress collapse time and formation energy of adiabatic shear bands were compared. The results show that different aging statuses and strain rate have significant influences on adiabatic shear behaviors of 2195 aluminum–lithium alloy. The peak-aged specimen has the highest adiabatic shearing susceptibility, while the under-aged specimen has the least adiabatic shear susceptibility. The susceptibility of adiabatic shearing increases with the increases of strain rate.

Effects of different aging statuses and strain rate on the adiabatic shear susceptibility of 2195 aluminum-lithium alloy

Energy Technology Data Exchange (ETDEWEB)

Yang, Y. [School of Materials Science and Engineering, Central South University, Changsha 410083, Hunan (China); State Key Laboratory of Explosion Science and Technology, Beijing 100081 (China); Tan, G.Y., E-mail: yangyanggroup@163.com [School of Materials Science and Engineering, Central South University, Changsha 410083, Hunan (China); Chen, P.X. [School of Materials Science and Engineering, Central South University, Changsha 410083, Hunan (China); Zhang, Q.M. [State Key Laboratory of Explosion Science and Technology, Beijing 100081 (China)

2012-06-01

The adiabatic shear susceptibility of 2195 aluminum-lithium alloy was investigated by means of split Hopkinson pressure bar. The stress collapse in true stress-true strain curves and true stress-time curves was observed. The adiabatic shear susceptibility of different aging statuses and strain rate were discussed by means of metallography observation. The critical strain, stress collapse time and formation energy of adiabatic shear bands were compared. The results show that different aging statuses and strain rate have significant influences on adiabatic shear behaviors of 2195 aluminum-lithium alloy. The peak-aged specimen has the highest adiabatic shearing susceptibility, while the under-aged specimen has the least adiabatic shear susceptibility. The susceptibility of adiabatic shearing increases with the increases of strain rate.

Large strain deformation behavior of polymeric gels in shear- and cavitation rheology

Science.gov (United States)

Hashemnejad, Seyed Meysam; Kundu, Santanu

Polymeric gels are used in many applications including in biomedical and in food industries. Investigation of mechanical responses of swollen polymer gels and linking that to the polymer chain dynamics are of significant interest. Here, large strain deformation behavior of two different gel systems and with different network architecture will be presented. We consider biologically relevant polysaccharide hydrogels, formed through ionic and covalent crosslinking, and physically associating triblock copolymer gels in a midblock selective solvent. Gels with similar low-strain shear modulus display distinctly different non-linear rheological behavior in large strain shear deformation. Both these gels display strain-stiffening behavior in shear-deformation prior to macroscopic fracture of the network, however, only the alginate gels display negative normal stress. The cavitation rheology data show that the critical pressure for cavitation is higher for alginate gels than that observed for triblock gels. These distinctly different large-strain deformation behavior has been related to the gel network structure, as alginate chains are much stiffer than the triblock polymer chains.

The Effects of Shear Strain, Fabric, and Porosity Evolution on Elastic and Mechanical Properties of Clay-Rich Fault Gouge

Science.gov (United States)

Kenigsberg, A.; Saffer, D. M.; Riviere, J.; Marone, C.

2017-12-01

Ultrasonic/seismic waves are widely used for probing fault zone elastic and mechanical properties (gouge composition, frictional strength, density) and elastic properties (Vp, Vs, bulk and shear moduli), as it can provide insight into key processes and fault properties during shearing. These include fabric and force chain formation, porosity evolution, and fault zone stiffness, which are in turn factors in fault slip, damage, and healing. We report on a suite of direct shear experiments on synthetic fault gouge composed of 50% smectite /50% quartz at a normal stress of 25 MPa, in which we use ultrasonic wave transmission to continuously monitor compressional and shear wave velocities (Vp, Vs) up to shear strains of 25, while simultaneously measuring friction and monitoring the evolution of density and porosity. We find that wavespeeds vary with shear strain, due to fabric development and the evolution of density and porosity. The coefficient of friction peaks at μ .47 at a shear strain of .5 - 1, decreases to a steady state value of μ .43 by shear strains of 4.5- 6 and then remains rather constant to shear strains of 6 - 25, consistent with previous work. Density increases rapidly from 1.78 g/cm3 to 1.83 g/cm3 at shear strains from 0-2 (porosity decreases from 33% to 25% over that range), and then more gradually increases to a density of 2.08 g/cm3 (porosity of 21%) at a shear strain of 25. Vp increases from 2400 m/s to 2900 m/s during the onset of shear until a shear strain of 3, and then decreases to 2400-2500 by shear strain of 7-9. At shear strains above 9, Vp slowly increases as the layer becomes denser and less porous. We interpret the co-evolving changes in friction, porosity, and elastic moduli/wavespeed to reflect fabric development and alignment of clay particles as a function of shearing. More specifically, the decrease in Vp at a shear strain of 3 reflects the clay particles gradually aligning. Once the particles are aligned, the gradual increase of

The Influence of Forming Directions and Strain Rate on Dynamic Shear Properties of Aerial Aluminum Alloy

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Ying Meng

2018-03-01

Full Text Available Dynamic shear properties under high strain rate are an important basis for studying the dynamic mechanical properties and microscopic mechanisms of materials. Dynamic impact shear tests of aerial aluminum alloy 7050-T7451 in rolling direction (RD, transverse direction (TD and normal direction (ND were performed at a range of strain rates from 2.5 × 104 s−1 to 4.5 × 104 s−1 by High Split Hopkinson Pressure Bar (SHPB. The influence of different forming directions and strain rates on the dynamic shear properties of material and the microstructure evolution under dynamic shear were emphatically analyzed. The results showed that aluminum alloy 7050-T7451 had a certain strain rate sensitivity and positive strain rate strengthening effect, and also the material had no obvious strain strengthening effect. Different forming directions had a great influence on dynamic shear properties. The shear stress in ND was the largest, followed by that in RD, and the lowest was that in TD. The microstructure observation showed that the size and orientation of the grain structure were different in three directions, which led to the preferred orientation of the material. All of those were the main reasons for the difference of dynamic shear properties of the material.

Effect of Re on stacking fault nucleation under shear strain in Ni by atomistic simulation

International Nuclear Information System (INIS)

Liu Zheng-Guang; Wang Chong-Yu; Yu Tao

2014-01-01

The effect of Re on stacking fault (SF) nucleation under shear strain in Ni is investigated using the climbing image nudged elastic band method with a Ni—Al—Re embedded-atom-method potential. A parameter (ΔE sf b ), the activation energy of SF nucleation under shear strain, is introduced to evaluate the effect of Re on SF nucleation under shear strain. Calculation results show that ΔE sf b decreases with Re addition, which means that SF nucleation under shear strain in Ni may be enhanced by Re. The atomic structure observation shows that the decrease of ΔE sf b may be due to the expansion of local structure around the Re atom when SF goes through the Re atom. (rapid communication)

Strain-induced shear instability in Liverpool Bay

Science.gov (United States)

Wihsgott, Juliane; Palmer, Matthew R.

2013-04-01

Liverpool Bay is a shallow subsection of the eastern Irish Sea with large tides (10 m), which drive strong tidal currents (1 ms-1). The Bay is heavily influenced by large freshwater inputs from several Welsh and English rivers that maintain a strong and persistent horizontal density gradient. This gradient interacts with the sheared tidal currents to strain freshwater over denser pelagic water on a semi-diurnal frequency. This Strain-Induced-Periodic-Stratification (SIPS) has important implications on vertical and horizontal mixing. The subtle interaction between stratification and turbulence in this complex environment is shown to be of critical importance to freshwater transport, and subsequently the fate of associated biogeochemical and pollutant pathways. Recent work identified an asymmetry of current ellipses due to SIPS that increases shear instability in the halocline with the potential to enhance diapycnal mixing. Here, we use data from a short, high intensity process study which reveals this mid-water mechanism maintains prolonged periods of sub-critical gradient Richardson number (Ri ≤ ¼) that suggests shear instability is likely. A time series of measurements from a microstructure profiler identifies the associated increase in turbulence is short lived and 'patchy' but sufficient to promote diapycnal mixing. The significance of this mixing process is further investigated by comparing our findings with long-term observations from the Liverpool Bay Coastal Observatory. We identify that the conditions for shear instability during SIPS are regularly met and suggest that this process contributes to the current underestimates of near coastal mixing observed in regional models. To assist our understanding of the observed processes and to test the current capability of turbulence 'closure schemes' we employ a one-dimensional numerical model to investigate the physical mechanisms driving diapycnal mixing in Liverpool Bay.

Theory and Practice of Shear/Stress Strain Gage Hygrometry

Science.gov (United States)

Shams, Qamar A.; Fenner, Ralph L.

2006-01-01

Mechanical hygrometry has progressed during the last several decades from crude hygroscopes to state-of-the art strain-gage sensors. The strain-gage devices vary from different metallic beams to strain-gage sensors using cellulose crystallite elements, held in full shear restraint. This old technique is still in use but several companies are now actively pursuing development of MEMS miniaturized humidity sensors. These new sensors use polyimide thin film for water vapor adsorption and desorption. This paper will provide overview about modern humidity sensors.

Micromechanics of soil responses in cyclic simple shear tests

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Cui Liang

2017-01-01

Full Text Available Offshore wind turbine (OWT foundations are subjected to a combination of cyclic and dynamic loading arising from wind, wave, rotor and blade shadowing. Under cyclic loading, most soils change their characteristics including stiffness, which may cause the system natural frequency to approach the loading frequency and lead to unplanned resonance and system damage or even collapse. To investigate such changes and the underlying micromechanics, a series of cyclic simple shear tests were performed on the RedHill 110 sand with different shear strain amplitudes, vertical stresses and initial relative densities of soil. The test results showed that: (a Vertical accumulated strain is proportional to the shear strain amplitude but inversely proportional to relative density of soil; (b Shear modulus increases rapidly in the initial loading cycles and then the rate of increase diminishes and the shear modulus remains below an asymptote; (c Shear modulus increases with increasing vertical stress and relative density, but decreasing with increasing strain amplitude. Coupled DEM simulations were performed using PFC2D to analyse the micromechanics underlying the cyclic behaviour of soils. Micromechanical parameters (e.g. fabric tensor, coordination number were examined to explore the reasons for the various cyclic responses to different shear strain amplitudes or vertical stresses. Both coordination number and magnitude of fabric anisotropy contribute to the increasing shear modulus.

A New Accurate yet Simple Shear Flexible Triangular Plate Element with Linear Bending Strains

DEFF Research Database (Denmark)

Damkilde, Lars; Pedersen, Ronnie

2010-01-01

The paper describes a new shear flexible triangular element. The formulation is based on displacement interpolation of the transverse displacement of the midsurface and the rotations of the cross-sections, and the element is fully compatible. The basic principle is to use a so-called balanced...... interpolation so that the part of the shear strains that relates to the transverse displacement has the same polynomial variation as the part of the shear strains that relates to the rotations of the cross-section. This balanced interpolation in combination with complete polynomial interpolations prevents shear...... are virtually the same. The slightly incompatible formulation can be implemented directly into commercial codes....

Observations of strain accumulation across the san andreas fault near palmdale, california, with a two-color geodimeter.

Science.gov (United States)

Langbein, J O; Linker, M F; McGarr, A; Slater, L E

1982-12-17

Two-color laser ranging measurements during a 15-month period over a geodetic network spanning the San Andreas fault near Palmdale, California, indicate that the crust expands and contracts aseismically in episodes as short as 2 weeks. Shear strain parallel to the fault has accumulated monotonically since November 1980, but at a variable rate. Improvements in measurement precision and temporal resolution over those of previous geodetic studies near Palmdale have resulted in the definition of a time history of crustal deformation that is much more complex than formerly realized.

Magnetic fabric of sheared till: A strain indicator for evaluating the bed deformation model of glacier flow

Science.gov (United States)

Hooyer, T.S.; Iverson, N.R.; Lagroix, F.; Thomason, J.F.

2008-01-01

Wet-based portions of ice sheets may move primarily by shearing their till beds, resting in high sediment fluxes and the development of subglacial landforms. This model of glacier movement, which requires high bed shear strains, can be tested using till microstructural characteristics that evolve during till deformation. Here we examine the development of magnetic fabric using a ring shear device to defom two Wisconsin-age basal tills to shear strains as high as 70. Hysteresis experiments and the dependence of magnetic susceptibility of these tills on temperature demonstrate that anisotropy of magnetic susceptibility (AMS) develops during shear due to the rotation of primarily magnetite particles that are silt sized or smaller. At moderate shear strains (???6-25), principal axes of maximum magnetic susceptibility develop a strong fabric (S1 eignevalues of 0.83-0.96), without further strengthening at higher strains, During deformation, directions of maximum susceptibility cluster strongly in the direction of shear and plunge 'up-glacier,' consistent with the behavior of pebbles and sand particles studied in earlier experiments. In contrast, the magnitude of AMS does not vary systematically with strain and is small relative to its variability among samples; this is because most magnetite grains are contained as inclusions in larger particles and hence do not align during shear. Although processes other than pervasive bed deformation may result in strong flow parallel fabrics, AMS fabrics provide a rapid and objective means of identifying basal tills that have not been sheared sufficiently to be compatible with the bed deformation model. Copyright 2008 by the American Geophysical Union.

Shear-coupled grain-boundary migration dependence on normal strain/stress

Science.gov (United States)

Combe, N.; Mompiou, F.; Legros, M.

2017-08-01

In specific conditions, grain-boundary (GB) migration occurs in polycrystalline materials as an alternative vector of plasticity compared to the usual dislocation activity. The shear-coupled GB migration, the expected most efficient GB based mechanism, couples the GB motion to an applied shear stress. Stresses on GB in polycrystalline materials seldom have, however, a unique pure shear component. This work investigates the influence of a normal strain on the shear coupled migration of a Σ 13 (320 )[001 ] GB in a copper bicrystal using atomistic simulations. We show that the yield shear stress inducing the GB migration strongly depends on the applied normal stress. Beyond, the application of a normal stress on this GB qualitatively modifies the GB migration: while the Σ 13 (320 )[001 ] GB shear couples following the 〈110 〉 migration mode without normal stress, we report the observation of the 〈010 〉 mode under a sufficiently high tensile normal stress. Using the nudge elastic band method, we uncover the atomistic mechanism of this 〈010 〉 migration mode and energetically characterize it.

A study of graphite-epoxy laminate failures due to high transverse shear strains using the multi-span-beam shear test procedure

Science.gov (United States)

Jegley, Dawn C.

1989-01-01

The multi-span-beam shear test procedure is used to study failure mechanisms in graphite-epoxy laminates due to high transverse shear strains induced by severe local bending deformations in test specimens. Results of a series of tests on specimens with a variety of stacking sequences, including some with adhesive interleaving, are presented. These results indicate that laminates with stacking sequences with several + or - 45 and 90 deg plies next to each other are more susceptible to failures due to high transverse shear strains than laminates with + or - 45 and 0 deg plies next to each other or with + or - 45 deg plies next to layers of adhesive interleaving. Results of these tests are compared with analytical results based on finite elements.

Shear Strains, Strain Rates and Temperature Changes in Adiabatic Shear Bands

Science.gov (United States)

1980-05-01

X14A. It has been found that when bainitic and martensitic steels are sheared adiabatically, a layer of material within ths shear zone is altezed and...Sooiety for Metals, Metals Park, Ohio, 1978, pp. 148-0. 21 TABLE II SOLID-STATE TRANSFORMATIONS IN BAINITIC STEEL TRANSFORMATION TRANSFORMATION...shear, thermoplastic, plasticity, plastic deformation, armor, steel IL AnSRACT ( -=nba asoa.tm a naeoesM iN faity by bleak n bet/2972 Experiments

High-Strain Rate Failure Modeling Incorporating Shear Banding and Fracture

Science.gov (United States)

2017-11-22

High Strain Rate Failure Modeling Incorporating Shear Banding and Fracture The views, opinions and/or findings contained in this report are those of...SECURITY CLASSIFICATION OF: 1. REPORT DATE (DD-MM-YYYY) 4. TITLE AND SUBTITLE 13. SUPPLEMENTARY NOTES 12. DISTRIBUTION AVAILIBILITY STATEMENT 6. AUTHORS...Report as of 05-Dec-2017 Agreement Number: W911NF-13-1-0238 Organization: Columbia University Title: High Strain Rate Failure Modeling Incorporating

Effect of shear strain on the deflection of a clamped magnetostrictive film-substrate system

International Nuclear Information System (INIS)

Ming Zhenghui; Ming Li; Bo Zou; Xia Luo

2011-01-01

The effect of in-plane shear strain of a clamped bimorph on the deflection produced by magnetization of the film is investigated. The deflection is found by minimizing the Gibbs free energy with respect to four parameters, strains and curvatures along x and y directions at the interface, by assuming that the curvature in the y direction varies as a function of aspect ratio w/l along x. A set of standard linear equations of four parameters are obtained and the deflection is expressed in terms of the four parameters by solving the equations using Cramer rules. The inconsistencies pointed out by previous authors are also reviewed. For actuators made of thick and short clamped film-substrate system, the in-plane shear deformation should not be omitted. The present calculation model can give a relatively simple and accurate prediction of deflection for thick and short specimens of aspect ratio w/l<10, which supports the results obtained by finite element modeling. - Highlights: → We model the deflection of a thick magnetostrictive film-substrate cantilever plate. → Total stress along z from magnetic field is not zero without external force. → Effect of in-plane shear strain in calculating deflection examined. → Analytical solution of deflection obtained by assuming a curvature function. → Shear strain for short cantilever film-substrate plate considered.

Signal-to-noise ratio, contrast-to-noise ratio and their trade-offs with resolution in axial-shear strain elastography

International Nuclear Information System (INIS)

Thitaikumar, Arun; Krouskop, Thomas A; Ophir, Jonathan

2007-01-01

In axial-shear strain elastography, the local axial-shear strain resulting from the application of quasi-static axial compression to an inhomogeneous material is imaged. In this paper, we investigated the image quality of the axial-shear strain estimates in terms of the signal-to-noise ratio (SNR asse ) and contrast-to-noise ratio (CNR asse ) using simulations and experiments. Specifically, we investigated the influence of the system parameters (beamwidth, transducer element pitch and bandwidth), signal processing parameters (correlation window length and axial window shift) and mechanical parameters (Young's modulus contrast, applied axial strain) on the SNR asse and CNR asse . The results of the study show that the CNR asse (SNR asse ) is maximum for axial-shear strain values in the range of 0.005-0.03. For the inclusion/background modulus contrast range considered in this study ( asse (SNR asse ) is maximum for applied axial compressive strain values in the range of 0.005%-0.03%. This suggests that the RF data acquired during axial elastography can be used to obtain axial-shear strain elastograms, since this range is typically used in axial elastography as well. The CNR asse (SNR asse ) remains almost constant with an increase in the beamwidth while it increases as the pitch increases. As expected, the axial shift had only a weak influence on the CNR asse (SNR asse ) of the axial-shear strain estimates. We observed that the differential estimates of the axial-shear strain involve a trade-off between the CNR asse (SNR asse ) and the spatial resolution only with respect to pitch and not with respect to signal processing parameters. Simulation studies were performed to confirm such an observation. The results demonstrate a trade-off between CNR asse and the resolution with respect to pitch

Orientations and Relative Shear-strain Response Coefficients for PBO Gladwin Tensor Strainmeters from Teleseismic Love Waves

Science.gov (United States)

Roeloffs, E. A.

2016-12-01

A Gladwin Tensor Strainmeter (GTSM) is designed to measure changes of the horizontal strain tensor, derived as linear combinations of radial elongations or contractions of the strainmeter's cylindrical housing measured at four azimuths. Each radial measurement responds to changes in the areal, horizontal shear and vertical components of the strain tensor in the surrounding formation. The elastic response coefficients to these components depend on the relative elastic moduli of the housing, formation, and cement. These coefficients must be inferred for each strainmeter after it is cemented into its borehole by analyzing the instrument response to well-characterized strain signals such as earth tides. For some GTSMs of the Earthscope Plate Boundary Observatory (PBO), however, reconciling observed earth-tide signals with modeled tidal strains requires response coefficients that differ substantially between the instrument's four gauges, and/or orientation corrections of tens of degrees. GTSM response coefficients can also be estimated from high-resolution records of teleseismic Love waves from great earthquakes around the world. Such records can be used in conjunction with apparent propagation azimuths from nearby broadband seismic stations to determine the GTSM's orientation. Knowing the orientation allows the ratios between the shear strain response coefficients of a GTSM's four gauges to be estimated. Applying this analysis to 14 PBO GTSMs confirms that orientations of some instruments differ significantly from orientations measured during installation. Orientations inferred from earth-tide response tend to agree with those inferred from Love waves for GTSMs far from tidal water bodies, but to differ for GTSMs closer to coastlines. Orientations derived from teleseismic Love waves agree with those estimated by Grant and Langston (2010) using strains from a broadband seismic array near Anza, California. PBO GTSM recordings of teleseismic Love waves show differences of

Microstructure and mechanical properties of nickel processed by accumulative roll bonding

DEFF Research Database (Denmark)

Zhang, Yubin; Mishin, Oleg; Kamikawa, N.

2013-01-01

rolling to an identical nominal strain, the microstructure after ARB is more refined and contains a greater fraction of high angle boundaries. This enhanced refinement is attributed to the geometric accumulation of shear-strain influenced volumes as a result of the ARB process and large-draught rolling...

Comparison and Combination of Strain and Shear Wave Elastography of Breast Masses for Differentiation of Benign and Malignant Lesions by Quantitative Assessment: Preliminary Study.

Science.gov (United States)

Seo, Mirinae; Ahn, Hye Shin; Park, Sung Hee; Lee, Jong Beum; Choi, Byung Ihn; Sohn, Yu-Mee; Shin, So Youn

2018-01-01

To compare the diagnostic performance of strain and shear wave elastography of breast masses for quantitative assessment in differentiating benign and malignant lesions and to evaluate the diagnostic accuracy of combined strain and shear wave elastography. Between January and February 2016, 37 women with 45 breast masses underwent both strain and shear wave ultrasound (US) elastographic examinations. The American College of Radiology Breast Imaging Reporting and Data System (BI-RADS) final assessment on B-mode US imaging was assessed. We calculated strain ratios for strain elastography and the mean elasticity value and elasticity ratio of the lesion to fat for shear wave elastography. Diagnostic performances were compared by using the area under the receiver operating characteristic curve (AUC). The 37 women had a mean age of 47.4 years (range, 20-79 years). Of the 45 lesions, 20 were malignant, and 25 were benign. The AUCs for elasticity values on strain and shear wave elastography showed no significant differences (strain ratio, 0.929; mean elasticity, 0.898; and elasticity ratio, 0.868; P > .05). After selectively downgrading BI-RADS category 4a lesions based on strain and shear wave elastographic cutoffs, the AUCs for the combined sets of B-mode US and elastography were improved (B-mode + strain, 0.940; B-mode + shear wave; 0.964; and B-mode, 0.724; P shear wave elastography showed significantly higher diagnostic accuracy than each individual elastographic modality (P = .031). These preliminary results showed that strain and shear wave elastography had similar diagnostic performance. The addition of strain and shear wave elastography to B-mode US improved diagnostic performance. The combination of strain and shear wave elastography results in a higher diagnostic yield than each individual elastographic modality. © 2017 by the American Institute of Ultrasound in Medicine.

Comparison of strain and shear wave elastography for qualitative and quantitative assessment of breast masses in the same population.

Science.gov (United States)

Kim, Hyo Jin; Kim, Sun Mi; Kim, Bohyoung; La Yun, Bo; Jang, Mijung; Ko, Yousun; Lee, Soo Hyun; Jeong, Heeyeong; Chang, Jung Min; Cho, Nariya

2018-04-18

We investigated addition of strain and shear wave elastography to conventional ultrasonography for the qualitative and quantitative assessment of breast masses; cut-off points were determined for strain ratio, elasticity ratio, and visual score for differentiating between benign and malignant masses. In all, 108 masses from 94 patients were evaluated with strain and shear wave elastography and scored for suspicion of malignancy, visual score, strain ratio, and elasticity ratio. The diagnostic performance between ultrasonography alone and ultrasonography combined with either type of elastography was compared; cut-off points were determined for strain ratio, elasticity ratio, and visual score. Of the 108 masses, 44 were malignant and 64 were benign. The areas under the curves were significantly higher for strain and shear wave elastography-supplemented ultrasonography (0.839 and 0.826, respectively; P = 0.656) than for ultrasonography alone (0.764; P = 0.018 and 0.035, respectively). The diagnostic performances of strain and elasticity ratios were similar when differentiating benign from malignant masses. Cut-off values for strain ratio, elasticity ratio, and visual scores for strain and shear wave elastography were 2.93, 4, 3, and 2, respectively. Both forms of elastography similarly improved the diagnostic performance of conventional ultrasonography in the qualitative and quantitative assessment of breast masses.

Comminution of solids caused by kinetic energy of high shear strain rate, with implications for impact, shock, and shale fracturing.

Science.gov (United States)

Bazant, Zdenek P; Caner, Ferhun C

2013-11-26

Although there exists a vast literature on the dynamic comminution or fragmentation of rocks, concrete, metals, and ceramics, none of the known models suffices for macroscopic dynamic finite element analysis. This paper outlines the basic idea of the macroscopic model. Unlike static fracture, in which the driving force is the release of strain energy, here the essential idea is that the driving force of comminution under high-rate compression is the release of the local kinetic energy of shear strain rate. The density of this energy at strain rates >1,000/s is found to exceed the maximum possible strain energy density by orders of magnitude, making the strain energy irrelevant. It is shown that particle size is proportional to the -2/3 power of the shear strain rate and the 2/3 power of the interface fracture energy or interface shear stress, and that the comminution process is macroscopically equivalent to an apparent shear viscosity that is proportional (at constant interface stress) to the -1/3 power of this rate. A dimensionless indicator of the comminution intensity is formulated. The theory was inspired by noting that the local kinetic energy of shear strain rate plays a role analogous to the local kinetic energy of eddies in turbulent flow.

Adiabatic shear bands as predictors of strain rate in high speed machining of ramax-2

International Nuclear Information System (INIS)

Zeb, M.A.; Irfan, M.A.; Velduis, A.C.

2008-01-01

Shear band formation was studied in the chips obtained by turning of stainless steel- Ramax-2 (AISI 420F). The machining was performed on a CNC lathe using a PVD (Physical Vapor Deposition) cutting tool insert. The cutting speeds ranged from 50 m/ min to 250 m/min. Dry cutting conditions were employed. At cutting speeds higher than 30 m/mill, the chip did not remain intact with the workpiece using quick stop device. It was difficult to get the chip root SEM (Scanning Electron Microscope) micrographs at further higher speeds. Therefore, the width of the shear bands was used as the predictor of the strain rates involved at various cutting speeds. The results showed that the strain rates are quite in agreement with the amount of strain rate found during machining of such types of stainless steels. It was also observed that shear band density increased with increasing cutting speed. (author)

Microstructural evolution in adiabatic shear bands of copper at high strain rates: Electron backscatter diffraction characterization

International Nuclear Information System (INIS)

Tang Lin; Chen Zhiyong; Zhan Congkun; Yang Xuyue; Liu Chuming; Cai Hongnian

2012-01-01

The microstructural evolution of adiabatic shear bands in annealed copper with different large strains at high strain rates has been investigated by electron backscatter diffraction. The results show that mechanical twinning can occur with minimal contribution to shear localization under dynamic loading. Elongated ultrafine grains with widths of 100–300 nm are observed during the evolution of the adiabatic shear bands. A rotational dynamic recrystallization mechanism is proposed to explain the formation of the elongated ultrafine grains. - Highlights: ► The microstructural evolution of ASB is studied by electron backscatter diffraction. ► Twinning can occur in ASB while the contribution to shear localization is slight. ► Elongated ultrafine grains are observed during the evolution process of ASB. ► A possible mechanism is proposed to explain the microstructure evolution of ASB.

Himalayan Strain Accumulation 100 ka Timescales

Science.gov (United States)

Cannon, J. M.; Murphy, M. A.; Liu, Y.

2015-12-01

Crustal scale fault systems and tectonostratigraphic units in the Himalaya can be traced for 2500 km along strike. However regional studies have shown that there is variability in the location and rate of strain accumulation which appears to be driven by Main Himalayan Thrust (MHT) geometry and convergence obliquity. GPS illuminates the modern interseismic strain rate and the historical record of great earthquakes elucidates variations in strain accumulation over 103 years. To connect these patterns with the 106 year structural and thermochronometric geologic record we examine normalized river channel steepness (ksn), a proxy for rock uplift rate, which develops over 104 - 105 years. Here we present a ksn map of the Himalaya and compare it with bedrock geology, precipitation, the historic earthquake record, GPS, seismicity, and seismotectonic models. Our map shows significant along strike changes in the magnitude of channel steepness, the areal extent of swaths of high ksn channels, and their location with respect to the range front. Differences include the juxtaposition of two narrow (30 - 40 km) range parallel belts of high ksn in west Nepal and Bhutan coincident with MHT duplexes and belts of microseismcity, with a single broad (70 km) swath of high ksn and microseismicity in central and eastern Nepal. Separating west and central Nepal a band of low ksn crosses the range coincident with the West Nepal Fault (WNF) and the lowest rate of microseismicity in Nepal. To the west the orogen is obliquely convergent and has less high ksn channels, while the orthogonally convergent region to the east contains the highest concentration of oversteepened channels in the Himalaya supporting the idea that the WNF is a strain partitioning boundary. The syntaxes are characterized by locally high channel steepness surrounded by low to moderate ksn channels consistent with the hypothesis that rapid exhumation within the syntaxes is sustained by an influx of lower crust.

Plastic strain accumulation during asymmetric cyclic loading of Zircaloy-2 at room temperature

International Nuclear Information System (INIS)

Rajpurohit, R.S.; Santhi Srinivas, N.C.; Singh, Vakil

2016-01-01

Asymmetric cyclic loading leads to accumulation of cyclic plastic strain and reduces the fatigue life of components. This phenomenon is known as ratcheting fatigue. Zircaloy-2 is a important structural material in nuclear reactors and used as pressure tubes and fuel cladding in pressurized light and heavy water nuclear reactors. Due to power fluctuations, these components experience plastic strain cycles in the reactor and their life is reduced due to strain cycles. Power fluctuations also cause asymmetric straining of the material and leads to accumulation of plastic strain. The present investigation deals with the effect of the magnitude of mean stress, stress amplitude and stress rate on hardening/softening behavior of Zircaloy-2 under asymmetric cyclic loading, at room temperature. It was observed that plastic strain accumulation increased with mean stress and stress amplitude; however, it decreased with stress rate. (author)

Strain on the san andreas fault near palmdale, california: rapid, aseismic change.

Science.gov (United States)

Savage, J C; Prescott, W H; Lisowski, M; King, N E

1981-01-02

Frequently repeated strain measurements near Palmdale, California, during the period from 1971 through 1980 indicate that, in addition to a uniform accumulation of right-lateral shear strain (engineering shear, 0.35 microradian per year) across the San Andreas fault, a 1-microstrain contraction perpendicular to the fault that accumulated gradually during the interval 1974 through 1978 was aseismically released between February and November 1979. Subsequently (November 1979 to March 1980), about half of the contraction was recovered. This sequence of strain changes can be explained in terms of south-southwestward migration of a slip event consisting of the south-southwestward movement of the upper crust on a horizontal detachment surface at a depth of 10 to 30 kilometers. The large strain change in 1979 corresponds to the passage of the slip event beneath the San Andreas fault.

Normal and Fibrotic Rat Livers Demonstrate Shear Strain Softening and Compression Stiffening: A Model for Soft Tissue Mechanics.

Directory of Open Access Journals (Sweden)

Maryna Perepelyuk

Full Text Available Tissues including liver stiffen and acquire more extracellular matrix with fibrosis. The relationship between matrix content and stiffness, however, is non-linear, and stiffness is only one component of tissue mechanics. The mechanical response of tissues such as liver to physiological stresses is not well described, and models of tissue mechanics are limited. To better understand the mechanics of the normal and fibrotic rat liver, we carried out a series of studies using parallel plate rheometry, measuring the response to compressive, extensional, and shear strains. We found that the shear storage and loss moduli G' and G" and the apparent Young's moduli measured by uniaxial strain orthogonal to the shear direction increased markedly with both progressive fibrosis and increasing compression, that livers shear strain softened, and that significant increases in shear modulus with compressional stress occurred within a range consistent with increased sinusoidal pressures in liver disease. Proteoglycan content and integrin-matrix interactions were significant determinants of liver mechanics, particularly in compression. We propose a new non-linear constitutive model of the liver. A key feature of this model is that, while it assumes overall liver incompressibility, it takes into account water flow and solid phase compressibility. In sum, we report a detailed study of non-linear liver mechanics under physiological strains in the normal state, early fibrosis, and late fibrosis. We propose a constitutive model that captures compression stiffening, tension softening, and shear softening, and can be understood in terms of the cellular and matrix components of the liver.

Shear banding in large strain plasticity - Influence of specimen dimensions

Science.gov (United States)

Mucha, Marzena; Wcisło, Balbina; Pamin, Jerzy

2018-01-01

The paper deals with numerical analysis of shear banding which occurs in an elongated rectangular plate for a large strain elastic-plastic material model. It is focused on the influence of plate size proportions and finite element mesh density on numerical results. The discussion is limited to isothermal conditions and ideal plasticity. First a plain strain case is computed for different lengths of the plate, then simulations are repeated for plane stress for which different thicknesses of the plate are considered. Most of the computations are performed for three finite element meshes to verify discretization sensitivity of the results. The simulations are performed using AceGen and AceFEM packages for Wolfram Mathematica.

Spectral calculations for pressure-velocity and pressure-strain correlations in homogeneous shear turbulence

Science.gov (United States)

Dutta, Kishore

2018-02-01

Theoretical analyses of pressure related turbulent statistics are vital for a reliable and accurate modeling of turbulence. In the inertial subrange of turbulent shear flow, pressure-velocity and pressure-strain correlations are affected by anisotropy imposed at large scales. Recently, Tsuji and Kaneda (2012 J. Fluid Mech. 694 50) performed a set of experiments on homogeneous shear flow, and estimated various one-dimensional pressure related spectra and the associated non-dimensional universal numbers. Here, starting from the governing Navier-Stokes dynamics for the fluctuating velocity field and assuming the anisotropy at inertial scales as a weak perturbation of an otherwise isotropic dynamics, we analytically derive the form of the pressure-velocity and pressure-strain correlations. The associated universal numbers are calculated using the well-known renormalization-group results, and are compared with the experimental estimates of Tsuji and Kaneda. Approximations involved in the perturbative calculations are discussed.

[Dynamic accumulation regulation of curcumin, demethoxycurcumin and bisdemethoxyeurcumin in three strains of curcuma longae rhizome].

Science.gov (United States)

Li, Qing-Miao; Yang, Wen-Yu; Tang, Xue-Mei; Zhang, Mei; Zhou, Xian-Jian; Shu, Guang-Ming; Zhao, Jun-Ning; Fang, Qing-Mao

2014-06-01

The paper is aimed to study the dynamic accumulation regulation of curcumin (Cur), demethoxycurcumin (DMC) and bisdemethoxyeurcumin (BDMC) in three strains of Curcuma longa, and provide scientific references for formalized cultivation, timely harvesting, quality control and breeding cultivation of C. longa. The accumulation regulation of the three curcumin derivatives was basically the same in rhizome of three strains. The relative contents decreased along with plant development growing, while the accumulation per hectare increased with plant development growing. The accumulation of curcuminoids per hectare could be taken as the assessment standard for the best harvest time of C. longa. A3 was the best strain in terms of Cur and BDMC content.

Relationship of trehalose accumulation with ethanol fermentation in industrial Saccharomyces cerevisiae yeast strains.

Science.gov (United States)

Wang, Pin-Mei; Zheng, Dao-Qiong; Chi, Xiao-Qin; Li, Ou; Qian, Chao-Dong; Liu, Tian-Zhe; Zhang, Xiao-Yang; Du, Feng-Guang; Sun, Pei-Yong; Qu, Ai-Min; Wu, Xue-Chang

2014-01-01

The protective effect and the mechanisms of trehalose accumulation in industrial Saccharomyces cerevisiae strains were investigated during ethanol fermentation. The engineered strains with more intercellular trehalose achieved significantly higher fermentation rates and ethanol yields than their wild strain ZS during very high gravity (VHG) fermentation, while their performances were not different during regular fermentation. The VHG fermentation performances of these strains were consistent with their growth capacity under osmotic stress and ethanol stress, the key stress factors during VHG fermentation. These results suggest that trehalose accumulation is more important for VHG fermentation of industrial yeast strains than regular one. The differences in membrane integrity and antioxidative capacity of these strains indicated the possible mechanisms of trehalose as a protectant under VHG condition. Therefore, trehalose metabolic engineering may be a useful strategy for improving the VHG fermentation performance of industrial yeast strains. Copyright © 2013 Elsevier Ltd. All rights reserved.

Competitive accumulation of betaines by Escherichia coli K-12 and derivative strains lacking betaine porters.

Science.gov (United States)

Randall, K; Lever, M; Peddie, B A; Chambers, S T

1995-08-17

Escherichia coli was grown in hyperosmotic media containing both glycine betaine and one other betaine. E. coli K-12 derivative WG439 (putP- proP- proU-) did not accumulate any of 15 betaines. Strains WG445 (putP- proP- proU+), WG443 (putP- proP+ proU-) and the control strains all accumulated less betaine, (CH3)3N(+)-(CH2)n-COO-, when n was greater than 1. Accumulation was not detectable when n = 5. Both L- and D-isomers of alpha-substituted betaines were accumulated by both strains WG443 and WG445, the D-isomers more slowly. Hydroxylated alpha-substituted betaines were accumulated relatively more through the osmoregulated transport protein ProU than through ProP. In actively growing cultures glycine betaine appeared to be the preferred substrate for accumulation, but the proportion of the second accumulated betaine increased as cultures approached stationary phase.

Microstructural characteristics of adiabatic shear localization in a metastable beta titanium alloy deformed at high strain rate and elevated temperatures

Energy Technology Data Exchange (ETDEWEB)

Zhan, Hongyi, E-mail: h.zhan@uq.edu.au [Centre for Advanced Materials Processing and Manufacture, School of Mechanical and Mining Engineering, The University of Queensland, St Lucia, Queensland 4072 (Australia); Zeng, Weidong [State Key Laboratory of Solidification Processing, School of Materials, Northwestern Polytechnical University, Xi' an 710072 (China); Wang, Gui [Centre for Advanced Materials Processing and Manufacture, School of Mechanical and Mining Engineering, The University of Queensland, St Lucia, Queensland 4072 (Australia); Defence Material Technology Centre, Level 2, 24 Wakefield St, Hawthorn, VIC 3122 (Australia); Kent, Damon [School of Science and Engineering, University of the Sunshine Coast, Sippy Downs, Queensland 4575 (Australia); Dargusch, Matthew [Centre for Advanced Materials Processing and Manufacture, School of Mechanical and Mining Engineering, The University of Queensland, St Lucia, Queensland 4072 (Australia); Defence Material Technology Centre, Level 2, 24 Wakefield St, Hawthorn, VIC 3122 (Australia)

2015-04-15

The microstructural evolution and grain refinement within adiabatic shear bands in the Ti6554 alloy deformed at high strain rates and elevated temperatures have been characterized using transmission electron microscopy. No stress drops were observed in the corresponding stress–strain curve, indicating that the initiation of adiabatic shear bands does not lead to the loss of load capacity for the Ti6554 alloy. The outer region of the shear bands mainly consists of cell structures bounded by dislocation clusters. Equiaxed subgrains in the core area of the shear band can be evolved from the subdivision of cell structures or reconstruction and transverse segmentation of dislocation clusters. It is proposed that dislocation activity dominates the grain refinement process. The rotational recrystallization mechanism may operate as the kinetic requirements for it are fulfilled. The coexistence of different substructures across the shear bands implies that the microstructural evolution inside the shear bands is not homogeneous and different grain refinement mechanisms may operate simultaneously to refine the structure. - Graphical abstract: Display Omitted - Highlights: • The microstructure within the adiabatic shear band was characterized by TEM. • No stress drops were observed in the corresponding stress–strain curve. • Dislocation activity dominated the grain refinement process. • The kinetic requirements for rotational recrystallization mechanism were fulfilled. • Different grain refinement mechanisms operated simultaneously to refine the structure.

Finite-strain analysis of Metavolcano-sedimentary rocks at Gabel El Mayet area, Central Eastern Desert, Egypt

Science.gov (United States)

Kassem, Osama M. K.; Abd El Rahim, Said H.

2010-09-01

Finite strain was estimated in the metavolcano-sedimentary rocks, which surround by serpentinites of Gabel El Mayet area. Finite strain shows a relationship to nappe contacts between the metavolcano-sedimentary rocks and serpentinite and sheds light on the nature of the subhorizontal foliation typical for the Gable Mayet shear zone. We used the Rf/ ϕ and Fry methods on feldspar porphyroclasts and mafic grains from 10 metasedimentary and six metavolcanic samples in Gabel El Mayet region. Our finite-strain data show that the metavolcano-sedimentary rocks were moderately deformed and axial ratios in the XZ section range from 1.9 to 3.9. The long axes of the finite-strain ellipsoids trend W/WNW in the north and W/WSW in the south of the Gabel El Mayet shear zone. Furthermore, the short axes are subvertical to a subhorizontal foliation. The strain magnitudes increase towards the tectonic contacts between the metavolcano-sedimentary rocks and serpentinite. The data indicate oblate strain symmetry in the metavolcano-sedimentary rocks. Hence, our strain data also indicate flattening strain. We assume that the metasedimentary and metavolcanics rocks have similar deformation behaviour. The fact that finite strain accumulated during the metamorphism indicates that the nappe contacts formed during the accumulation of finite strain and thus during thrusting. We conclude that the nappe contacts formed during progressive thrusting under brittle to semi-brittle deformation conditions by simple shear and involved a component of vertical shortening, which caused the subhorizontal foliation in the Gabel El Mayet shear zone.

Effects of texture on shear band formation in plane strain tension/compression and bending

DEFF Research Database (Denmark)

Kuroda, M.; Tvergaard, Viggo

2007-01-01

In this study, effects of typical texture components observed in rolled aluminum alloy sheets on shear band formation in plane strain tension/compression and bending are systematically studied. The material response is described by a generalized Taylor-type polycrystal model, in which each grain ...... shear band formation in bent specimens is compared to that in the tension/compression problem. Finally, the present results are compared to previous related studies, and the efficiency of the present method for materials design in future is discussed....

A new strain of Claviceps purpurea accumulating tetracyclic clavine alkaloids.

Science.gov (United States)

Schumann, B; Erge, D; Maier, W; Gröger, D

1982-05-01

A new strain of Claviceps was isolated from a blokked mutant of Claviceps purpurea. This strain accumulates substantial amounts of clavine alkaloids (2 g/l). The alkaloid fraction is composed of chanoclavine-I ( approximately 10%) and a mixture of agroclavine/elymoclavine (90%). Most suitable for alkaloid production in submerged culture is an ammoncitrate/sucrose medium. The genealogy of the new strain, designated Pepty 695/ch-I is the following one: Pepty 695/S (ergotoxine producer) --> Pepty 695/ch (secoergoline producer) --> Pepty 695/ch-I (tetracyclic clavine producer).

Studies of Shear Band Velocity Using Spatially and Temporally Resolved Measurements of Strain During Quasistatic Compression of Bulk Metallic Glass

Energy Technology Data Exchange (ETDEWEB)

Wright, W J; Samale, M; Hufnagel, T; LeBlanc, M; Florando, J

2009-06-15

We have made measurements of the temporal and spatial features of the evolution of strain during the serrated flow of Pd{sub 40}Ni{sub 40}P{sub 20} bulk metallic glass tested under quasistatic, room temperature, uniaxial compression. Strain and load data were acquired at rates of up to 400 kHz using strain gages affixed to all four sides of the specimen and a piezoelectric load cell located near the specimen. Calculation of the displacement rate requires an assumption about the nature of the shear displacement. If one assumes that the entire shear plane displaces simultaneously, the displacement rate is approximately 0.002 m/s. If instead one assumes that the displacement occurs as a localized propagating front, the velocity of the front is approximately 2.8 m/s. In either case, the velocity is orders of magnitude less than the shear wave speed ({approx}2000 m/s). The significance of these measurements for estimates of heating in shear bands is discussed.

Diagnosis of Fibrosis and Activity by a Combined Use of Strain and Shear Wave Imaging in Patients with Liver Disease.

Science.gov (United States)

Yada, Norihisa; Tamaki, Nobuhura; Koizumi, Yohei; Hirooka, Masashi; Nakashima, Osamu; Hiasa, Yoichi; Izumi, Namiki; Kudo, Masatoshi

2017-01-01

Performing shear wave imaging is simple, but can be difficult when inflammation, jaundice, and congestion are present. Therefore, the correct diagnosis of liver fibrosis using shear wave imaging alone might be difficult in mild-to-moderate fibrosis cases. Strain imaging can diagnose liver fibrosis without the influence of inflammation. Therefore, the combined use of strain and shear wave imaging (combinational elastography) for cases without jaundice and congestion might be useful for evaluating fibrosis and inflammation. We enrolled consecutive patients with liver disease, without jaundice or liver congestion. Strain and shear wave imaging, blood tests, and liver biopsy were performed on the same day. The liver fibrosis index (LF index) was calculated by strain imaging; real-time tissue elastography, and the shear wave velocity (Vs) was calculated by shear wave imaging. Fibrosis index (F index) and activity index (A index) were calculated as a multiple regression equation for determining hepatic fibrosis and inflammation using histopathological diagnosis as the gold standard. The diagnostic ability of F index for fibrosis and A index for inflammation were compared using LF index and Vs. The total number of enrolled cases was 388. The area under the receiver operating characteristic (AUROC) was 0.87, 0.80, 0.83, and 0.80, at diagnosis of fibrosis stage with an F index of F1 or higher, F2 or higher, F3 or higher, and F4, respectively. The AUROC was 0.94, 0.74, and 0.76 at diagnosis of activity grade with an A index of A1 or higher, A2 or higher, and A3, respectively. The diagnostic ability of F index for liver fibrosis and A index for inflammation was higher than for other conventional diagnostic values. The combined use of strain and shear wave imaging (combinational elastography) might increase the positive diagnosis of liver fibrosis and inflammation. © 2017 S. Karger AG, Basel.

Increasing Accuracy of Tissue Shear Modulus Reconstruction Using Ultrasonic Strain Tensor Measurement

Science.gov (United States)

Sumi, C.

Previously, we developed three displacement vector measurement methods, i.e., the multidimensional cross-spectrum phase gradient method (MCSPGM), the multidimensional autocorrelation method (MAM), and the multidimensional Doppler method (MDM). To increase the accuracies and stabilities of lateral and elevational displacement measurements, we also developed spatially variant, displacement component-dependent regularization. In particular, the regularization of only the lateral/elevational displacements is advantageous for the lateral unmodulated case. The demonstrated measurements of the displacement vector distributions in experiments using an inhomogeneous shear modulus agar phantom confirm that displacement-component-dependent regularization enables more stable shear modulus reconstruction. In this report, we also review our developed lateral modulation methods that use Parabolic functions, Hanning windows, and Gaussian functions in the apodization function and the optimized apodization function that realizes the designed point spread function (PSF). The modulations significantly increase the accuracy of the strain tensor measurement and shear modulus reconstruction (demonstrated using an agar phantom).

Strain accumulation in a prototypic lmfbr nozzle: Experimental and analytical correlation

International Nuclear Information System (INIS)

Woodward, W.S.; Dhalia, A.K.; Berton, P.A.

1986-01-01

At an early stage in the design of the primary inlet nozzle for the Intermediate Heat Exchanger (IHX) of the Fast Flux Test Facility (FFTF), it was predicted that the inelastic strain accumulation during elevated temperature operation (1050 0 F/566 0 C) would exceed the ASME Code design allowables. Therefore, a proof test of a prototypic FFTF IHX nozzle was performed in the Westinghouse Creep Ratcheting Test Facility (CRTF) to measure the ratchet strain increments during the most severe postulated FFTF plant thermal transients. In addition, analytical procedures similar to those used in the plant design, were used to predict strain accumulation in the CRTF nozzle. This paper describes how the proof test was successfully completed, and it shows that both the test measurements and analytical predictions confirm that the FFTF IHX nozzle, subjected to postulated thermal and mechanical loadings, complies with the ASME Code strain limits. Also, these results provide a measure of validation for the analytical procedures used in the design of FFTF as well as demonstrate the structural adequacy of the FFTF IHX primary inlet nozzle

Strain hardening in startup shear of long-chain branched polymer solutions.

Science.gov (United States)

Liu, Gengxin; Cheng, Shiwang; Lee, Hyojoon; Ma, Hongwei; Xu, Hongde; Chang, Taihyun; Quirk, Roderic P; Wang, Shi-Qing

2013-08-09

We show for the first time that entangled polymeric liquids containing long-chain branching can exhibit strain hardening upon startup shear. As the significant long-chain branching impedes chain disentanglement, Gaussian coils between entanglements can deform to reach the finite extensibility limit where the intrachain retraction force exceeds the value expected from the usual conformational entropy loss evaluated based on Gaussian chain statistics. The phenomenon is expected to lead to further theoretical understanding.

The Cora Lake Shear Zone: Strain Localization in an Ultramylonitic, Deep Crustal Shear Zone, Athabasca Granulite Terrain, Western Churchill Province, Canada

Science.gov (United States)

Regan, S.; Williams, M. L.; Mahan, K. H.; Orlandini, O. F.; Jercinovic, M. J.; Leslie, S. R.; Holland, M.

2012-12-01

Ultramylonitic shear zones typically involve intense strain localization, and when developed over large regions can introduce considerable heterogeneity into the crust. The Cora Lake shear zone (CLsz) displays several 10's to 100's of meters-wide zones of ultramylonite distributed throughout its full 3-5 km mylonitized width. Detailed mapping, petrography, thermobarometry, and in-situ monazite geochronology suggest that it formed during the waning phases of granulite grade metamorphism and deformation, within one of North America's largest exposures of polydeformed lower continental crust. Anastomosing zones of ultramylonite contain recrystallized grain-sizes approaching the micron scale and might appear to suggest lower temperature mylonitization. However, feldspar and even clinopyroxene are dynamically recrystallized, and quantitative thermobarometry of syn-deformational assemblages indicate high P and T conditions ranging from 0.9 -10.6 GPa and 775-850 °C. Even at these high T's, dynamic recovery and recrystallization were extremely limited. Rocks with low modal quartz have extremely small equilibrium volumes. This is likely the result of inefficient diffusion, which is further supported by the unannealed nature of the crystals. Local carbonate veins suggests that H2O poor, CO2 rich conditions may have aided in the preservation of fine grain sizes, and may have inhibited dynamic recovery and recrystallization. The Cora Lake shear zone is interpreted to have been relatively strong and to have hardened during progressive deformation. Garnet is commonly fractured perpendicular to host rock fabric, and statically replaced by both biotite and muscovite. Pseudotachylite, with the same sense of shear, occurs in several ultramylonitized mafic granulites. Thus, cataclasis and frictional melt are interpreted to have been produced in the lower continental crust, not during later reactivation. We suggest that strengthening of rheologically stiffer lithologies led to

Mechanical characteristics under monotonic and cyclic simple shear of spark plasma sintered ultrafine-grained nickel

International Nuclear Information System (INIS)

Dirras, G.; Bouvier, S.; Gubicza, J.; Hasni, B.; Szilagyi, T.

2009-01-01

The present work focuses on understanding the mechanical behavior of bulk ultrafine-grained nickel specimens processed by spark plasma sintering of high purity nickel nanopowder and subsequently deformed under large amplitude monotonic simple shear tests and strain-controlled cyclic simple shear tests at room temperature. During cyclic tests, the samples were deformed up to an accumulated von Mises strain of about ε VM = 0.75 (the flow stress was in the 650-700 MPa range), which is extremely high in comparison with the low tensile/compression ductility of this class of materials at quasi-static conditions. The underlying physical mechanisms were investigated by electron microscopy and X-ray diffraction profile analysis. Lattice dislocation-based plasticity leading to cell formation and dislocation interactions with twin boundaries contributed to the work-hardening of these materials. The large amount of plastic strain that has been reached during the shear tests highlights intrinsic mechanical characteristics of the ultrafine-grained nickel studied here.

Mechanical characteristics under monotonic and cyclic simple shear of spark plasma sintered ultrafine-grained nickel

Energy Technology Data Exchange (ETDEWEB)

Dirras, G., E-mail: dirras@univ-paris13.fr [LPMTM - CNRS, Institut Galilee, Universite Paris 13, 99 Avenue J.B. Clement, 93430 Villetaneuse (France); Bouvier, S. [LPMTM - CNRS, Institut Galilee, Universite Paris 13, 99 Avenue J.B. Clement, 93430 Villetaneuse (France); Gubicza, J. [Department of Materials Physics, Eoetvoes Lorand University, P.O.B. 32, Budapest H-1518 (Hungary); Hasni, B. [LPMTM - CNRS, Institut Galilee, Universite Paris 13, 99 Avenue J.B. Clement, 93430 Villetaneuse (France); Szilagyi, T. [Department of Materials Physics, Eoetvoes Lorand University, P.O.B. 32, Budapest H-1518 (Hungary)

2009-11-25

The present work focuses on understanding the mechanical behavior of bulk ultrafine-grained nickel specimens processed by spark plasma sintering of high purity nickel nanopowder and subsequently deformed under large amplitude monotonic simple shear tests and strain-controlled cyclic simple shear tests at room temperature. During cyclic tests, the samples were deformed up to an accumulated von Mises strain of about {epsilon}{sub VM} = 0.75 (the flow stress was in the 650-700 MPa range), which is extremely high in comparison with the low tensile/compression ductility of this class of materials at quasi-static conditions. The underlying physical mechanisms were investigated by electron microscopy and X-ray diffraction profile analysis. Lattice dislocation-based plasticity leading to cell formation and dislocation interactions with twin boundaries contributed to the work-hardening of these materials. The large amount of plastic strain that has been reached during the shear tests highlights intrinsic mechanical characteristics of the ultrafine-grained nickel studied here.

BIOBUTANOL ACCUMULATION USING ALTERNATIVE SUBSTRATES BY CULTIVATION OF Clostridium acetobutylicum STRAINS

Directory of Open Access Journals (Sweden)

О. О. Тigunova

2017-10-01

Full Text Available The aim of the research was to investigate the accumulation of biobutanol by strains Clostridium acetobutylicum using alternative substrates (Jerusalem artichoke juice, technical glycerol, crude glycerol, shredded biomass of soy, rape, wheat and switchgrass. In order to increase the accumulation of butanol in the process of cultivation, the cells of C. acetobutylicum were statically immobilized on carriers (belting strips, ferrite rings and Raschig rings by the method of adsorption immobilization. The cells were precipitated by centrifugation, the supernatant was distilled and then fermentation products were determined. Gas chromatography was used to determine the presence of solvents in the culture fluid. The biggest accumulation of butanol (2 g/dm3 was at concentration of crude glycerol 16 g/dm3 in the medium, and complete inhibition of culture development — at glycerol concentration 25 g/dm3. The accumulation of butanol by the strain C. acetobutylicum ІМВ В-7407 using fill and draw method depended on the amount of sequestered and infused medium. Immobilization of the culture using the Raschig rings allowed increasing the bioconversion to butanol twice. So it is shown the possibility to use non-traditional substrates for the production of biobutanol. The most accumulation of butanol was achieved using glycerol (11 g/dm3 as water-soluble substrate, and using switchgrass as lignocelluloses substrate (2,6 g/dm3. Immobilization of C. acetobutylicum culture cells on carriers increased the accumulation of butanol. The use of Raschig rings, as carriers for immobilization, allowed increasing the accumulation of butanol twice.

Mechanisms of strain accommodation in plastically-deformed zircon under simple shear deformation conditions during amphibolite-facies metamorphism

Science.gov (United States)

Kovaleva, Elizaveta; Klötzli, Urs; Wheeler, John; Habler, Gerlinde

2018-02-01

This study documents the strain accommodation mechanisms in zircon under amphibolite-facies metamorphic conditions in simple shear. Microstructural data from undeformed, fractured and crystal-plastically deformed zircon crystals are described in the context of the host shear zone, and evaluated in the light of zircon elastic anisotropy. Our work challenges the existing model of zircon evolution and shows previously undescribed rheological characteristics for this important accessory mineral. Crystal-plastically deformed zircon grains have axis oriented parallel to the foliation plane, with the majority of deformed grains having axis parallel to the lineation. Zircon accommodates strain by a network of stepped low-angle boundaries, formed by switching between tilt dislocations with the slip systems {010} and {110} and rotation axis [001], twist dislocations with the rotation axis [001], and tilt dislocations with the slip system {001} and rotation axis [010]. The slip system {110} is newly described for zircon. Most misorientation axes in plastically-deformed zircon grains are parallel to the XY plane of the sample and have [001] crystallographic direction. Such behaviour of strained zircon lattice is caused by elastic anisotropy that has a direct geometric control on the rheology, deformation mechanisms and dominant slip systems in zircon. Young's modulus and P wave velocity have highest values parallel to zircon [001] axis, indicating that zircon is elastically strong along this direction. Poisson ratio and Shear modulus demonstrate that zircon is also most resistant to shearing along [001]. Thus, [001] axis is the most common rotation axis in zircon. The described zircon behaviour is important to take into account during structural and geochronological investigations of (poly)metamorphic terrains. Geometry of dislocations in zircon may help reconstructing the geometry of the host shear zone(s), large-scale stresses in the crust, and, possibly, the timing of

Evaluating location specific strain rates, temperatures, and accumulated strains in friction welds through microstructure modeling

Directory of Open Access Journals (Sweden)

Javed Akram

2018-04-01

Full Text Available A microstructural simulation method is adopted to predict the location specific strain rates, temperatures, grain evolution, and accumulated strains in the Inconel 718 friction welds. Cellular automata based 2D microstructure model was developed for Inconel 718 alloy using theoretical aspects of dynamic recrystallization. Flow curves were simulated and compared with experimental results using hot deformation parameter obtained from literature work. Using validated model, simulations were performed for friction welds of Inconel 718 alloy generated at three rotational speed i.e., 1200, 1500, and 1500 RPM. Results showed the increase in strain rates with increasing rotational speed. These simulated strain rates were found to match with the analytical results. Temperature difference of 150 K was noticed from center to edge of the weld. At all the rotational speeds, the temperature was identical implying steady state temperature (0.89Tm attainment. Keywords: Microstructure modeling, Dynamic recrystallization, Friction welding, Inconel 718, EBSD, Hot deformation, Strain map

Yielding and flow of sheared colloidal glasses

International Nuclear Information System (INIS)

Petekidis, G; Vlassopoulos, D; Pusey, P N

2004-01-01

We have studied some of the rheological properties of suspensions of hard-sphere colloids with particular reference to behaviour near the concentration of the glass transition. First we monitored the strain on the samples during and after a transient step stress. We find that, at all values of applied step stress, colloidal glasses show a rapid, apparently elastic, recovery of strain after the stress is removed. This recovery is found even in samples which have flowed significantly during stressing. We attribute this behaviour to 'cage elasticity', the recovery of the stress-induced distorted environment of any particle to a more isotropic state when the stress is removed. Second, we monitored the stress as the strain rate dot γ of flowing samples was slowly decreased. Suspensions which are glassy at rest show a stress which becomes independent of dot γ as dot γ →0. This limiting stress can be interpreted as the yield stress of the glass and agrees well both with the yield stress deduced from the step stress and recovery measurements and that predicted by a recent mode coupling theory of sheared suspensions. Thus, the behaviours under steady shearing and transient step stress both support the idea that colloidal glasses have a finite yield stress. We note however that the samples do exhibit a slow accumulation of strain due to creep at stresses below the yield stress

Effect of shear strain on the α-ε phase transition of iron: a new approach in the rotational diamond anvil cell

International Nuclear Information System (INIS)

Ma Yanzhang; Selvi, Emre; Levitas, Valery I; Hashemi, Javad

2006-01-01

The effect of shear strain on the iron α-ε phase transformation has been studied using a rotational diamond anvil cell (RDAC). The initial transition is observed to take place at the reduced pressure of 10.8 GPa under pressure and shear operation. Complete phase transformation was observed at 15.4 GPa. The rotation of an anvil causes limited pressure elevation and makes the pressure distribution symmetric in the sample chamber before the phase transition. However, it causes a significant pressure increase at the centre of the sample and brings about a large pressure gradient during the phase transformation. The resistance to the phase interface motion is enhanced due to strain hardening during the pressure and shear operations on iron and this further increases the transition pressure. The work of macroscopic shear stress and the work of the pressure and shear stress at the defect tips account for the pressure reduction of the iron phase transition

The elastic strain energy of crystallographic shear planes in reduced tungsten trioxide

International Nuclear Information System (INIS)

Iguchi, E.; Tilley, R.J.D.

1977-01-01

Calculations of the elastic strain energy due to crystallographic shear (c.s.) planes lying upon 102, 103 and 001 planes in reduced tungsten trioxide crystals have been made. The cases analysed in detail are for both isolated c.s. planes and for pairs of c.s. planes. These results are used to determine the elastic strain energy per unit volume for crystals containing ordered arrays of c.s. planes. It was found that the magnitude of the elastic strain energy was in the sequence 001 < 102 < 103 and that at relatively small inter-c.s. spacings the curves of elastic strain energy against c.s. plane separation take the form of a series of peaks and valleys. These results are compared with experimental observations of c.s. plane spacings in substantially reduced crystals containing quasi-ordered arrays of c.s. planes and with observations of c.s. plane nucleation and growth in both slightly and more appreciably reduced crystals. It was found that the elastic strain energy plays a significant part in controlling the microstructure of c.s. plane arrays in such cases. (author)

Localization in inelastic rate dependent shearing deformations

KAUST Repository

Katsaounis, Theodoros

2016-09-18

Metals deformed at high strain rates can exhibit failure through formation of shear bands, a phenomenon often attributed to Hadamard instability and localization of the strain into an emerging coherent structure. We verify formation of shear bands for a nonlinear model exhibiting strain softening and strain rate sensitivity. The effects of strain softening and strain rate sensitivity are first assessed by linearized analysis, indicating that the combined effect leads to Turing instability. For the nonlinear model a class of self-similar solutions is constructed, that depicts a coherent localizing structure and the formation of a shear band. This solution is associated to a heteroclinic orbit of a dynamical system. The orbit is constructed numerically and yields explicit shear localizing solutions. © 2016 Elsevier Ltd

Localization in inelastic rate dependent shearing deformations

KAUST Repository

Katsaounis, Theodoros; Lee, Min-Gi; Tzavaras, Athanasios

2016-01-01

Metals deformed at high strain rates can exhibit failure through formation of shear bands, a phenomenon often attributed to Hadamard instability and localization of the strain into an emerging coherent structure. We verify formation of shear bands for a nonlinear model exhibiting strain softening and strain rate sensitivity. The effects of strain softening and strain rate sensitivity are first assessed by linearized analysis, indicating that the combined effect leads to Turing instability. For the nonlinear model a class of self-similar solutions is constructed, that depicts a coherent localizing structure and the formation of a shear band. This solution is associated to a heteroclinic orbit of a dynamical system. The orbit is constructed numerically and yields explicit shear localizing solutions. © 2016 Elsevier Ltd

InSAR velocity field across the North Anatolian Fault (eastern Turkey): Implications for the loading and release of interseismic strain accumulation

KAUST Repository

Cakir, Ziyadin

2014-10-01

We use the Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) technique with the European Space Agency\\'s Envisat and ERS SAR data acquired on three neighboring descending tracks (T350, T078, and T307) to map the interseismic strain accumulation along a ~225 km long, NW-SE trending section of the North Anatolian Fault that ruptured during the 1939, 1942, and 1943 earthquakes in eastern Turkey. We derive a line-of-sight velocity map of the region with a high spatial resolution and accuracy which, together with the maps of earthquake surface ruptures, shed light on the style of continental deformation and the relationships between the loading and release of interseismic strain along segmented continental strike-slip faults. In contrast with the geometric complexities at the ground surface that appear to control rupture propagation of the 1939 event, modeling of the high-resolution PS-InSAR velocity field reveals a fairly linear and narrow throughgoing shear zone with an overall 20 ± 3 mm/yr slip rate above an unexpectedly shallow 7 ± 2 km locking depth. Such a shallow locking depth may result from the postseismic effects following recent earthquakes or from a simplified model that assumes a uniform degree of locking with depth on the fault. A narrow throughgoing shear zone supports the thick lithosphere model in which continental strike-slip faults are thought to extend as discrete shear zones through the entire crust. Fault segmentation previously reported from coseismic surface ruptures is thus likely inherited from heterogeneities in the upper crust that either preexist and/or develop during coseismic rupture propagation. The geometrical complexities that apparently persist for long periods may guide the dynamic rupture propagation surviving thousands of earthquake cycles.

Modeling combined tension-shear failure of ductile materials

International Nuclear Information System (INIS)

Partom, Y

2014-01-01

Failure of ductile materials is usually expressed in terms of effective plastic strain. Ductile materials can fail by two different failure modes, shear failure and tensile failure. Under dynamic loading shear failure has to do with shear localization and formation of adiabatic shear bands. In these bands plastic strain rate is very high, dissipative heating is extensive, and shear strength is lost. Shear localization starts at a certain value of effective plastic strain, when thermal softening overcomes strain hardening. Shear failure is therefore represented in terms of effective plastic strain. On the other hand, tensile failure comes about by void growth under tension. For voids in a tension field there is a threshold state of the remote field for which voids grow spontaneously (cavitation), and the material there fails. Cavitation depends on the remote field stress components and on the flow stress. In this way failure in tension is related to shear strength and to failure in shear. Here we first evaluate the cavitation threshold for different remote field situations, using 2D numerical simulations with a hydro code. We then use the results to compute examples of rate dependent tension-shear failure of a ductile material.

Effect of strain and deformation route on grain boundary characteristics and recrystallization behavior of aluminum

International Nuclear Information System (INIS)

Sakai, Tetsuo; Takahashi, Yasuo; Utsunomiya, Hiroshi

2014-01-01

The effect of strain and deformation route on the recrystallization behavior of aluminum sheets has been investigated using well lubricated cold rolling and continuous equal channel angular extrusion. Three different deformation routes in plane strain corresponding to (1) simple shear, (2) compression, and (3) the combination of simple shear and compression were performed on 1100 aluminum sheet. Fixed amounts of the equivalent strain of 1.28 and 1.06 were accumulated in each route. In case of the combined deformation route, the ratio of shear strain to the total equivalent strain was varied. The recrystallized grain size was finer if the combined deformation route was employed instead of the monotonic route under the same amount of equivalent strain at either strain level. The density of high angle grain boundaries that act as nucleation sites for recrystallization was higher in materials deformed by the combined route. The orientation imaging micrographs revealed that the change in deformation route is effective for introducing a larger number of new high angle grain boundaries with relatively low misorientation angle

Effect of strain and deformation route on grain boundary characteristics and recrystallization behavior of aluminum

Science.gov (United States)

Sakai, Tetsuo; Utsunomiya, Hiroshi; Takahashi, Yasuo

2014-08-01

The effect of strain and deformation route on the recrystallization behavior of aluminum sheets has been investigated using well lubricated cold rolling and continuous equal channel angular extrusion. Three different deformation routes in plane strain corresponding to (1) simple shear, (2) compression, and (3) the combination of simple shear and compression were performed on 1100 aluminum sheet. Fixed amounts of the equivalent strain of 1.28 and 1.06 were accumulated in each route. In case of the combined deformation route, the ratio of shear strain to the total equivalent strain was varied. The recrystallized grain size was finer if the combined deformation route was employed instead of the monotonic route under the same amount of equivalent strain at either strain level. The density of high angle grain boundaries that act as nucleation sites for recrystallization was higher in materials deformed by the combined route. The orientation imaging micrographs revealed that the change in deformation route is effective for introducing a larger number of new high angle grain boundaries with relatively low misorientation angle.

Large strain variable stiffness composites for shear deformations with applications to morphing aircraft skins

Science.gov (United States)

McKnight, G. P.; Henry, C. P.

2008-03-01

Morphing or reconfigurable structures potentially allow for previously unattainable vehicle performance by permitting several optimized structures to be achieved using a single platform. The key to enabling this technology in applications such as aircraft wings, nozzles, and control surfaces, are new engineered materials which can achieve the necessary deformations but limit losses in parasitic actuation mass and structural efficiency (stiffness/weight). These materials should exhibit precise control of deformation properties and provide high stiffness when exercised through large deformations. In this work, we build upon previous efforts in segmented reinforcement variable stiffness composites employing shape memory polymers to create prototype hybrid composite materials that combine the benefits of cellular materials with those of discontinuous reinforcement composites. These composites help overcome two key challenges for shearing wing skins: the resistance to out of plane buckling from actuation induced shear deformation, and resistance to membrane deflections resulting from distributed aerodynamic pressure loading. We designed, fabricated, and tested composite materials intended for shear deformation and address out of plane deflections in variable area wing skins. Our designs are based on the kinematic engineering of reinforcement platelets such that desired microstructural kinematics is achieved through prescribed boundary conditions. We achieve this kinematic control by etching sheets of metallic reinforcement into regular patterns of platelets and connecting ligaments. This kinematic engineering allows optimization of materials properties for a known deformation pathway. We use mechanical analysis and full field photogrammetry to relate local scale kinematics and strains to global deformations for both axial tension loading and shear loading with a pinned-diamond type fixture. The Poisson ratio of the kinematically engineered composite is ~3x higher than

Magnetism and Raman Spectroscopy of Pristine and Hydrogenated TaSe2 Monolayer tuned by Tensile and Pure Shear Strain

Science.gov (United States)

Chowdhury, Sugata; Simpson, Jeffrey; Einstein, T. L.; Walker, Angela R. Hight

2D-materials with controllable optical, electronic and magnetic properties are desirable for novel nanodevices. Here we studied these properties for both pristine and hydrogenated TaSe2 (TaSe2-H) monolayer (ML) in the framework of DFT using the PAW method. We considered uniaxial and biaxial tensile strain, as well as shear strain along the basal planes in the range between 1% and 16%. Previous theoretical works (e.g.) considered only symmetrical biaxial tensile. Pristine ML is ferromagnetic for uniaxial tensile strain along ◯ or ŷ. For tensile strain in ŷ, the calculated magnetic moments of the Ta atoms are twice those for the same strain in ◯. Under pure shear strain (expansion along ŷ and compression along ◯), a pristine ML is ferromagnetic, but becomes non-magnetic when the strain directions are interchanged. Due to carrier-mediated double-exchange, the pristine ML is ferromagnetic when the Se-Ta-Se bond angle is < 82° and the ML thickness is < 3.25Å. We find that all Raman-active phonon modes show obvious red-shifting due to bond elongation and the E2 modes degeneracy is lifted as strain increases. For a TaSe2-H ML, the same trends were observed. Results show the ability to tune the properties of 2D-materials.

Shear Melting of a Colloidal Glass

Science.gov (United States)

Eisenmann, Christoph; Kim, Chanjoong; Mattsson, Johan; Weitz, David A.

2010-01-01

We use confocal microscopy to explore shear melting of colloidal glasses, which occurs at strains of ˜0.08, coinciding with a strongly non-Gaussian step size distribution. For larger strains, the particle mean square displacement increases linearly with strain and the step size distribution becomes Gaussian. The effective diffusion coefficient varies approximately linearly with shear rate, consistent with a modified Stokes-Einstein relationship in which thermal energy is replaced by shear energy and the length scale is set by the size of cooperatively moving regions consisting of ˜3 particles.

Fusarium proliferatum strains change fumonisin biosynthesis and accumulation when exposed to host plant extracts.

Science.gov (United States)

Górna, Karolina; Pawłowicz, Izabela; Waśkiewicz, Agnieszka; Stępień, Łukasz

2016-01-01

Fumonisin concentrations in mycelia and media were studied in liquid Fusarium proliferatum cultures supplemented with host plant extracts. Furthermore, the kinetics of fumonisin accumulation in media and mycelia collected before and after extract addition was analysed as well as the changes in the expression of the FUM1 gene. Fumonisin content in culture media increased in almost all F. proliferatum strains shortly after plant extracts were added. The asparagus extract induced the highest FB level increase and the garlic extract was the second most effective inducer. Fumonisin level decreased constantly until 14th day of culturing, though for some strains also at day 8th an elevated FB level was observed. Pineapple extract induced the highest increase of fum1 transcript levels as well as fumonisin synthesis in many strains, and the peas extract inhibited fungal growth and fumonisin biosynthesis. Moreover, fumonisins were accumulated in mycelia of studied strains and in the respective media. Copyright © 2016 British Mycological Society. Published by Elsevier Ltd. All rights reserved.

Experimental study of shear rate dependence in perpetually sheared granular matter

Science.gov (United States)

Liu, Sophie Yang; Guillard, François; Marks, Benjy; Rognon, Pierre; Einav, Itai

2017-06-01

We study the shear behaviour of various granular materials by conducting novel perpetual simple shear experiments over four orders of magnitude of relatively low shear rates. The newly developed experimental apparatus employed is called "3D Stadium Shear Device" which is an extended version of the 2D Stadium Shear Device [1]. This device is able to provide a non-radial dependent perpetual shear flow and a nearly linear velocity profile between two oppositely moving shear walls. Using this device, we are able to test a large variety of granular materials. Here, we demonstrate the applicability of the device on glass beads (diameter 1 mm, 3 mm, and 14 mm) and rice. We particularly focus on studying these materials at very low inertial number I ranging from 10-6 to 10-2. We find that, within this range of I, the friction coefficient μ of glass beads has no shear rate dependence. A particularly appealing observation comes from testing rice, where the attainment of critical state develops under much longer duration than in other materials. Initially during shear we find a value of μ similar to that found for glass beads, but with time this value decreases gradually towards the asymptotic critical state value. The reason, we believe, lies in the fact that rice grains are strongly elongated; hence the time to achieve the stable μ is primarily controlled by the time for particles to align themselves with respect to the shear walls. Furthermore, the initial packing conditions of samples also plays a role in the evolution of μ when the shear strain is small, but that impact will eventually be erased after sufficient shear strain.

A Constitutive Model for Strain-Controlled Strength Degradation of Rockmasses (SDR)

Science.gov (United States)

Kalos, A.; Kavvadas, M.

2017-11-01

The paper describes a continuum, rate-independent, incremental plasticity constitutive model applicable in weak rocks and heavily fractured rockmasses, where mechanical behaviour is controlled by rockmass strength rather than structural features (discontinuities). The model describes rockmass structure by a generalised Hoek-Brown Structure Envelope (SE) in the stress space. Stress paths inside the SE are nonlinear and irreversible to better simulate behaviour at strains up to peak strength and under stress reversals. Stress paths on the SE have user-controlled volume dilatancy (gradually reducing to zero at large shear strains) and can model post-peak strain softening of brittle rockmasses via a structure degradation (damage) mechanism triggered by accumulated plastic shear strains. As the SE may strain harden with plastic strains, ductile behaviour can also be modelled. The model was implemented in the Finite Element Code Simulia ABAQUS and was applied in plane strain (2D) excavation of a cylindrical cavity (tunnel) to predict convergence-confinement curves. It is shown that small-strain nonlinearity, variable volume dilatancy and post-peak hardening/softening strongly affect the predicted curves, resulting in corresponding differences of lining pressures in real tunnel excavations.

Comparison of game-farm and wild-strain mallard ducks in accumulation of methylmercury

Science.gov (United States)

Heinz, G.H.

1979-01-01

The accumulation of mercury was compared in game-farm and wild-strain mallard ducks fed a diet containing 0.5 ppm mercury in the form of methylmercury dicyandiamide. There were no significant differences between the two strains in levels of mercury that accumulated in blood, kidney, liver, breast muscle, brain, eggs, or ducklings. Mercury levels in blood were significantly correlated with levels in other tissues and eggs, as were levels in down feathers of ducklings with levels in carcasses of ducklings. The results indicate that game-farm mallards are probably suitable substitutes for wild mallards in toxicological work, that blood samples can be used to estimate levels of mercury in other tissues of adults, and that down feathers are predictive of mercury levels in duckling carcasses.

Effect of nitrogen concentration and temperature on the critical resolved shear stress and strain rate sensitivity of vanadium

International Nuclear Information System (INIS)

Rehbein, D.K.

1980-08-01

The critical resolved shear stress and strain rate sensitivity were measured over the temperature range from 77 to 400 0 K for vanadium-nitrogen alloys containing from 0.0004 to 0.184 atom percent nitrogen. These properties were found to be strongly dependent on both the nitrogen concentration and temperature. The following observations were seen in this investigation: the overall behavior of the alloys for the temperature and concentration range studied follows a form similar to that predicted; the concentration dependence of the critical resolved shear stress after subtracting the hardening due to the pure vanadium lattice obeys Labusch's c/sup 2/3/ relationship above 200 0 K and Fleischer's c/sup 1/2/ relationship below 200 0 K; the theoretical predictions of Fleischer's model for the temperature dependence of the critical resolved shear stress are in marked disagreement with the behavior found; and the strain rate sensitivity, par. delta tau/par. deltaln γ, exhibits a peak at approximately 100 0 K that decreases in height as the nitrogen concentration increases. A similar peak has been observed in niobium by other investigators but the effect of concentration on the peak height is quite different

In situ observation of shear-driven amorphization in silicon crystals

Energy Technology Data Exchange (ETDEWEB)

He, Yang; Zhong, Li; Fan, Feifei; Wang, Chongmin; Zhu, Ting; Mao, Scott X.

2016-09-19

Amorphous materials have attracted great interest in the scientific and technological fields. An amorphous solid usually forms under the externally driven conditions of melt-quenching, irradiation and severe mechanical deformation. However, its dynamic formation process remains elusive. Here we report the in situ atomic-scale observation of dynamic amorphization processes during mechanical straining of nanoscale silicon crystals by high resolution transmission electron microscopy (HRTEM). We observe the shear-driven amorphization (SDA) occurring in a dominant shear band. The SDA involves a sequence of processes starting with the shear-induced diamond-cubic to diamond-hexagonal phase transition that is followed by dislocation nucleation and accumulation in the newly formed phase, leading to the formation of amorphous silicon. The SDA formation through diamond-hexagonal phase is rationalized by its structural conformity with the order in the paracrystalline amorphous silicon, which maybe widely applied to diamond-cubic materials. Besides, the activation of SDA is orientation-dependent through the competition between full dislocation nucleation and partial gliding.

Continuous shear - a method for studying material elements passing a stationary shear plane

DEFF Research Database (Denmark)

Lindegren, Maria; Wiwe, Birgitte; Wanheim, Tarras

2003-01-01

circumferential groove. Normally shear in metal forming processes is of another nature, namely where the material elements move through a stationary shear zone, often of small width. In this paper a method enabling the simulation of this situation is presented. A tool for continuous shear has beeen manufactured...... and tested with AlMgSil and copper. The sheared material has thereafter been tested n plane strain compression with different orientation concerning the angle between the shear plane and the compression direction....

Shear localization and microstructure in coarse grained beta titanium alloy

Energy Technology Data Exchange (ETDEWEB)

Wang, Bingfeng, E-mail: biw009@ucsd.edu [State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan (China); School of Materials Science and Engineering, Central South University, Changsha, Hunan (China); Department of Mechanical and Aerospace Engineering, University of California, San Diego, United States of America (United States); Key Lab of Nonferrous Materials, Ministry of Education, Central South University, Changsha, Hunan (China); Wang, Xiaoyan [State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan (China); School of Materials Science and Engineering, Central South University, Changsha, Hunan (China); Li, Zezhou [Department of Mechanical and Aerospace Engineering, University of California, San Diego, United States of America (United States); Ma, Rui [School of Materials Science and Engineering, Central South University, Changsha, Hunan (China); Zhao, Shiteng [Department of Mechanical and Aerospace Engineering, University of California, San Diego, United States of America (United States); Xie, Fangyu [State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan (China); School of Materials Science and Engineering, Central South University, Changsha, Hunan (China); Zhang, Xiaoyong [State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan (China)

2016-01-15

Adiabatic shear localization plays an important role in the deformation and failure of the coarse grained beta titanium alloy Ti-5 Al-5 Mo-5 V-1 Cr-1 Fe with grain size about 1 mm at high strain rate deformation. Hat shaped specimens with different nominal shear strains are used to induce the formation of shear bands under the controlled shock-loading experiments. The true stress in the specimens can reach about 1040 MPa where the strain is about 1.83. The whole shear localization process lasts about 35 μs. The microstructures within the shear band are investigated by optical microscopy, scanning electron microscopy / electron backscatter diffraction, and transmission electron microscopy. The results show that the width of the shear bands decreases with increasing nominal shear strain, and the grains in the transition region near the shear band are elongated along the shear band, and the core of the shear band consists of the ultrafine deformed grains with width of 0.1 μm and heavy dislocations. With the aims of accommodating the imposed shear strain and maintaining neighboring grain compatibility, the grain subdivision continues to take place within the band. A fiber texture is formed in the core of the shear band. The calculated temperature rise in the shear band can reach about 722 K. Dynamic recovery is responsible for the formation of the microstructure in coarse grained beta titanium alloy.

Sands subjected to repetitive vertical loading under zero lateral strain: accumulation models, terminal densities, and settlement

KAUST Repository

Chong, Song Hun; Santamarina, Carlos

2016-01-01

). Repetitive vertical loading tests under zero lateral strain conditions are conducted using three different sands packed at initially low and high densities. Test results show that plastic strain accumulation for all sands and density conditions can

Experimental study of shear rate dependence in perpetually sheared granular matter

Directory of Open Access Journals (Sweden)

Liu Sophie Yang

2017-01-01

Full Text Available We study the shear behaviour of various granular materials by conducting novel perpetual simple shear experiments over four orders of magnitude of relatively low shear rates. The newly developed experimental apparatus employed is called “3D Stadium Shear Device” which is an extended version of the 2D Stadium Shear Device [1]. This device is able to provide a non-radial dependent perpetual shear flow and a nearly linear velocity profile between two oppositely moving shear walls. Using this device, we are able to test a large variety of granular materials. Here, we demonstrate the applicability of the device on glass beads (diameter 1 mm, 3 mm, and 14 mm and rice. We particularly focus on studying these materials at very low inertial number I ranging from 10−6 to 10−2. We find that, within this range of I, the friction coefficient μ of glass beads has no shear rate dependence. A particularly appealing observation comes from testing rice, where the attainment of critical state develops under much longer duration than in other materials. Initially during shear we find a value of μ similar to that found for glass beads, but with time this value decreases gradually towards the asymptotic critical state value. The reason, we believe, lies in the fact that rice grains are strongly elongated; hence the time to achieve the stable μ is primarily controlled by the time for particles to align themselves with respect to the shear walls. Furthermore, the initial packing conditions of samples also plays a role in the evolution of μ when the shear strain is small, but that impact will eventually be erased after sufficient shear strain.

Influence of Additive Manufactured Scaffold Architecture on the Distribution of Surface Strains and Fluid Flow Shear Stresses and Expected Osteochondral Cell Differentiation.

Science.gov (United States)

Hendrikson, Wim J; Deegan, Anthony J; Yang, Ying; van Blitterswijk, Clemens A; Verdonschot, Nico; Moroni, Lorenzo; Rouwkema, Jeroen

2017-01-01

Scaffolds for regenerative medicine applications should instruct cells with the appropriate signals, including biophysical stimuli such as stress and strain, to form the desired tissue. Apart from that, scaffolds, especially for load-bearing applications, should be capable of providing mechanical stability. Since both scaffold strength and stress-strain distributions throughout the scaffold depend on the scaffold's internal architecture, it is important to understand how changes in architecture influence these parameters. In this study, four scaffold designs with different architectures were produced using additive manufacturing. The designs varied in fiber orientation, while fiber diameter, spacing, and layer height remained constant. Based on micro-CT (μCT) scans, finite element models (FEMs) were derived for finite element analysis (FEA) and computational fluid dynamics (CFD). FEA of scaffold compression was validated using μCT scan data of compressed scaffolds. Results of the FEA and CFD showed a significant impact of scaffold architecture on fluid shear stress and mechanical strain distribution. The average fluid shear stress ranged from 3.6 mPa for a 0/90 architecture to 6.8 mPa for a 0/90 offset architecture, and the surface shear strain from 0.0096 for a 0/90 offset architecture to 0.0214 for a 0/90 architecture. This subsequently resulted in variations of the predicted cell differentiation stimulus values on the scaffold surface. Fluid shear stress was mainly influenced by pore shape and size, while mechanical strain distribution depended mainly on the presence or absence of supportive columns in the scaffold architecture. Together, these results corroborate that scaffold architecture can be exploited to design scaffolds with regions that guide specific tissue development under compression and perfusion. In conjunction with optimization of stimulation regimes during bioreactor cultures, scaffold architecture optimization can be used to improve

Haptic Edge Detection Through Shear

Science.gov (United States)

Platkiewicz, Jonathan; Lipson, Hod; Hayward, Vincent

2016-03-01

Most tactile sensors are based on the assumption that touch depends on measuring pressure. However, the pressure distribution at the surface of a tactile sensor cannot be acquired directly and must be inferred from the deformation field induced by the touched object in the sensor medium. Currently, there is no consensus as to which components of strain are most informative for tactile sensing. Here, we propose that shape-related tactile information is more suitably recovered from shear strain than normal strain. Based on a contact mechanics analysis, we demonstrate that the elastic behavior of a haptic probe provides a robust edge detection mechanism when shear strain is sensed. We used a jamming-based robot gripper as a tactile sensor to empirically validate that shear strain processing gives accurate edge information that is invariant to changes in pressure, as predicted by the contact mechanics study. This result has implications for the design of effective tactile sensors as well as for the understanding of the early somatosensory processing in mammals.

Problems associated with use of the logarithmic equivalent strain in high pressure torsion

International Nuclear Information System (INIS)

Jonas, J J; Aranas, C Jr

2014-01-01

The logarithmic 'equivalent' strain is frequently recommended for description of the experimental flow curves determined in high pressure torsion (HPT) tests. Some experimental results determined at -196 and 190 °C on a 2024 aluminum alloy are plotted using both the von Mises and logarithmic equivalent strains. Three types of problems associated with use of the latter are described. The first involves the lack of work conjugacy between the logarithmic and shear stress/shear strain curves, a topic that has been discussed earlier. The second concerns the problems associated with testing at constant logarithmic strain rate, a feature of particular importance when the material is rate sensitive. The third type of problem involves the 'history dependence' of this measure in that the incremental logarithmic strain depends on whether the prior strain accumulated in the sample is known or not. This is a difficulty that does not affect use of the von Mises equivalent strain. For these reasons, it is concluded that the qualifier 'equivalent' should not be used when the logarithmic strain is employed to describe HPT results

Tectonic setting and strain analysis of Halaban Area, Eastern Arabian Shield, Saudi Arabia

Science.gov (United States)

Alamri, Y. A., II; Kassem, O. M. K.

2016-12-01

Finite strain technique was applied for Abt schist, sheared granitoids and volcanosedimentary rocks exposed at Halaban area, Eastern Arabian Shield. This study aims to attempt to decipher the relationship of these lithologies to nappe contacts and to clarify the nature of subhorizontal foliation pervasively recorded in the Halaban area. The Rf/φ and Fry methods are utilized on quartz and feldspar porphyroclasts, as well as on mafic crystals, such as hornblende and biotite, in eighteen samples. The X/Z axial ratios range from 1.12 to 4.99 for Rf/φ method and from 1.65 to 4.00 for Fry method. The direction of finite strain for the long axes displays clustering along the WNW trend (occasionally N) with slight plunging. The Z axes are subvertical and associated with a subhorizontal foliation. The data reveal oblate strain symmetry (flattening) and the strain magnitudes show no considerable increase towards the tectonic contacts. The obtained finite-strain data demonstrate that the sheared granitoids are mildly to moderately deformed. It is suggested that the accumulation of finite strain was not associated with any significant volume change. The penetrative subhorizontal foliation was concurrent with thrusting and shows nearly the same attitudes of tectonic contacts with the overlying nappes. Field relations and observations, together with finite stain data, are inconsistent with the proposed idea that nappes in orogens resulted from simple-shear deformation.

Study on shear properties of coral sand under cyclic simple shear condition

Science.gov (United States)

Ji, Wendong; Zhang, Yuting; Jin, Yafei

2018-05-01

In recent years, the ocean development in our country urgently needs to be accelerated. The construction of artificial coral reefs has become an important development direction. In this paper, experimental studies of simple shear and cyclic simple shear of coral sand are carried out, and the shear properties and particle breakage of coral sand are analyzed. The results show that the coral sand samples show an overall shear failure in the simple shear test, which is more accurate and effective for studying the particle breakage. The shear displacement corresponding to the peak shear stress of the simple shear test is significantly larger than that corresponding to the peak shear stress of the direct shear test. The degree of particle breakage caused by the simple shear test is significantly related to the normal stress level. The particle breakage of coral sand after the cyclic simple shear test obviously increases compared with that of the simple shear test, and universal particle breakage occurs within the whole particle size range. The increasing of the cycle-index under cyclic simple shear test results in continuous compacting of the sample, so that the envelope curve of peak shearing force increases with the accumulated shear displacement.

Loading direction-dependent shear behavior at different temperatures of single-layer chiral graphene sheets

Science.gov (United States)

Zhao, Yang; Dong, Shuhong; Yu, Peishi; Zhao, Junhua

2018-06-01

The loading direction-dependent shear behavior of single-layer chiral graphene sheets at different temperatures is studied by molecular dynamics (MD) simulations. Our results show that the shear properties (such as shear stress-strain curves, buckling strains, and failure strains) of chiral graphene sheets strongly depend on the loading direction due to the structural asymmetry. The maximum values of both the critical buckling shear strain and the failure strain under positive shear deformation can be around 1.4 times higher than those under negative shear deformation. For a given chiral graphene sheet, both its failure strain and failure stress decrease with increasing temperature. In particular, the amplitude to wavelength ratio of wrinkles for different chiral graphene sheets under shear deformation using present MD simulations agrees well with that from the existing theory. These findings provide physical insights into the origins of the loading direction-dependent shear behavior of chiral graphene sheets and their potential applications in nanodevices.

Assessment of homogeneity of the shear-strain pattern in Al–7 wt%Si casting alloy processed by high-pressure torsion

Energy Technology Data Exchange (ETDEWEB)

Cepeda-Jiménez, C.M., E-mail: carmen.cepeda@imdea.org [Department of Physical Metallurgy, CENIM, CSIC, Av. Gregorio del Amo 8, 28040 Madrid (Spain); Orozco-Caballero, A.; García-Infanta, J.M. [Department of Physical Metallurgy, CENIM, CSIC, Av. Gregorio del Amo 8, 28040 Madrid (Spain); Zhilyaev, A.P. [Institute for Metals Superplasticity Problems, Russian Academy of Science, 39 Khalturina, 450001 Ufa (Russian Federation); Ruano, O.A.; Carreño, F. [Department of Physical Metallurgy, CENIM, CSIC, Av. Gregorio del Amo 8, 28040 Madrid (Spain)

2014-03-01

An as-cast Al–7 wt%Si alloy was subjected to processing by high-pressure torsion (HPT) at room temperature, through 1/4, 1/2, 1 and 5 turns at a pressure of 6 GPa and two rotation speeds, 0.1 and 1 rpm. Vickers microhardness was measured along diameters of HPT disk surfaces. The final hardness values were higher than in the initial as-cast condition and, unexpectedly, nearly constant under all different processing conditions, and along the disk diameter. The microstructure was characterised by optical and scanning electron microscopy. The as-cast microstructure comprises equiaxed primary α dendrite cells embedded in the Al–Si eutectic constituent. The morphology and distribution of the eutectic constituent in the HPT processed materials is used to delineate the shear strain, which was analysed in the cross-section planes of the disks. A high degree of homogeneity in the imposed shear strain throughout the samples was observed, being congruent with the ideal rigid-body torsion. In addition, the high compressive pressure applied, causing compressive strain prior to the torsional strain, is responsible for the deformation-induced precipitation of small Si particles and for the (sub)grain refinement in the primary Al constituent. The role of torsional strain is that of increasing monothonically the redistribution of the eutectic silicon and the misorientation of the (sub)grains.

Evaluation of healthy muscle tissue by strain and shear wave elastography – Dependency on depth and ROI position in relation to underlying bone

DEFF Research Database (Denmark)

Ewertsen, Caroline; Carlsen, Jonathan Frederik; Christiansen, Iben Riishede

2016-01-01

and methods: Ten healthy volunteers (five males and five females) had their biceps brachii, gastrocnemius, and quadriceps muscle examined with strain- and shear wave elastography at three different depths and in regions located above bone and beside bone. Strain ratios were averaged from cine-loops of 10 s...

Experiments on sheet metal shearing

OpenAIRE

Gustafsson, Emil

2013-01-01

Within the sheet metal industry, different shear cutting technologies are commonly used in several processing steps, e.g. in cut to length lines, slitting lines, end cropping etc. Shearing has speed and cost advantages over competing cutting methods like laser and plasma cutting, but involves large forces on the equipment and large strains in the sheet material.Numerical models to predict forces and sheared edge geometry for different sheet metal grades and different shear parameter set-ups a...

Heat transfer modeling in asymmetrical sheet rolling of aluminium alloys with ultra high shear strain

Directory of Open Access Journals (Sweden)

Pesin Alexander

2016-01-01

Full Text Available Asymmetrical sheet rolling is a method of severe plastic deformation (SPD for production of aluminium alloys with UFG structure. Prediction of sheet temperature during SPD is important. The temperature of sheet is changed due to the conversion of mechanical work into heat through sliding on contact surfaces and high shear strain. Paper presents the results of FEM simulation of the effect of contact friction, rolling speed and rolls speed ratio on the heating of aluminium sheets during asymmetrical rolling.

Study on reinforced lightweight coconut shell concrete beam behavior under shear

International Nuclear Information System (INIS)

Gunasekaran, K.; Annadurai, R.; Kumar, P.S.

2013-01-01

Highlights: • Coconut shell used as aggregate in concrete production. • Coconut shell concrete beam behavior studied under shear. • Coconut shell concrete beam behavior are compared with control concrete beams. - Abstract: Lightweight concrete has been produced using crushed coconut shell as coarse aggregate. The shear behavior of reinforced concrete beam made with coconut shell is analyzed and compared with the normal control concrete. Eight beams, four with coconut shell concrete and four with normal control concrete were fabricated and tested. Study includes the structural shear behavior, shear capacity, cracking behavior, deflection behavior, ductility, strains in concrete and in reinforcement. It was observed that the shear behavior of coconut shell concrete is comparable to that of other lightweight concretes. The results of concrete compression strain and steel tension strain showed that coconut shell concrete is able to achieve its full strain capacity under shear loadings. However, the failure zones of coconut shell concrete were larger than for control concrete beams

Stress-strain relation of bentonite at undrained shear. Laboratory tests to investigate the influence of material composition and test technique

Energy Technology Data Exchange (ETDEWEB)

Dueck, Ann; Boergesson, Lennart; Johannesson, Lars-Erik (Clay Technology AB, Lund (Sweden))

2010-12-15

This report describes a laboratory study conducted to update the material model of the buffer material used in the analyses of the effect of a rock shear through a deposition hole. The study considers some new conditions and is especially focused on the reference case with MX-80Ca developed for SR-Site (MX-80 ion exchanged to Ca). The material model is based on relations between density, swelling pressure, shear strength and rate of strain. The reference model is described by Boergesson et al. (2010). The laboratory study is focused on undrained stress-strain-strength properties, which have been studied mainly by conducting triaxial tests and unconfined compression tests. The test results are compared to the earlier measurements and models which show that the new results fit very well into the general picture and models. For the new conditions suitable values of constants included in the model are proposed

Stress-strain relation of bentonite at undrained shear. Laboratory tests to investigate the influence of material composition and test technique

International Nuclear Information System (INIS)

Dueck, Ann; Boergesson, Lennart; Johannesson, Lars-Erik

2010-12-01

This report describes a laboratory study conducted to update the material model of the buffer material used in the analyses of the effect of a rock shear through a deposition hole. The study considers some new conditions and is especially focused on the reference case with MX-80Ca developed for SR-Site (MX-80 ion exchanged to Ca). The material model is based on relations between density, swelling pressure, shear strength and rate of strain. The reference model is described by Boergesson et al. (2010). The laboratory study is focused on undrained stress-strain-strength properties, which have been studied mainly by conducting triaxial tests and unconfined compression tests. The test results are compared to the earlier measurements and models which show that the new results fit very well into the general picture and models. For the new conditions suitable values of constants included in the model are proposed

Microstructure evolution of pure copper during a single pass of simple shear extrusion (SSE): role of shear reversal

Energy Technology Data Exchange (ETDEWEB)

Bagherpour, E., E-mail: e.bagherpour@semnan.ac.ir [Faculty of Metallurgical and Materials Engineering, Semnan University, Semnan (Iran, Islamic Republic of); Department of Mechanical Engineering, Doshisha University, Kyotanabe, Kyoto 610–0394 (Japan); Qods, F., E-mail: qods@semnan.ac.ir [Faculty of Metallurgical and Materials Engineering, Semnan University, Semnan (Iran, Islamic Republic of); Ebrahimi, R., E-mail: ebrahimy@shirazu.ac.ir [Department of Materials Science and Engineering, School of Engineering, Shiraz University, Shiraz (Iran, Islamic Republic of); Miyamoto, H., E-mail: hmiyamot@mail.doshisha.ac.jp [Department of Mechanical Engineering, Doshisha University, Kyotanabe, Kyoto 610–0394 (Japan)

2016-06-01

In the present paper the role of shear reversal on microstructure, texture and mechanical properties of pure copper during a single pass of the simple shear extrusion (SSE) process was investigated. For SSE processing an appropriate die with a linear die profile was designed and constructed, which imposes forward shear in the first half and reverse shear in the second half channels. Electron back-scattering diffraction (EBSD), transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) were used to evaluate the microstructure of the deformed samples. The geometrical nature of this process imposes a distribution of strain results in the inhomogeneous microstructure and the hardness throughout the plane perpendicular to the extrusion direction. Strain reversal during the process results in a slight reduction in dislocation density, the hardness and mean disorientation angle of the samples, and an increase in the grain size. After a complete pass of SSE, dislocation density decreased by ~14% if compared to the middle of the process. This suggests that the dislocation annihilation occurred by the reversal of the shear strain. The simple shear textures were formed gradually and the strongest simple shear textures were observed on the middle of the SSE channel. The degree of the simple shear textures decreases with the distance from the middle plane where the shear is reversed, but the simple shear textures are still the major components after exit of the channel. Hardness variation was modeled by contributions from dislocation strengthening and grain boundary strengthening, where dislocation density is approximated by the misorientation angle of LAGBs which are regarded as dislocation cell boundaries. As a result, the hardness can be predicted successfully by the microstructural features, i.e. the low-angle boundaries, the mean misorientation angle and the fraction of high-angle grain boundaries.

Structural state diagram of concentrated suspensions of jammed soft particles in oscillatory shear flow

Science.gov (United States)

Khabaz, Fardin; Cloitre, Michel; Bonnecaze, Roger T.

2018-03-01

In a recent study [Khabaz et al., Phys. Rev. Fluids 2, 093301 (2017), 10.1103/PhysRevFluids.2.093301], we showed that jammed soft particle glasses (SPGs) crystallize and order in steady shear flow. Here we investigate the rheology and microstructures of these suspensions in oscillatory shear flow using particle-dynamics simulations. The microstructures in both types of flows are similar, but their evolutions are very different. In both cases the monodisperse and polydisperse suspensions form crystalline and layered structures, respectively, at high shear rates. The crystals obtained in the oscillatory shear flow show fewer defects compared to those in the steady shear. SPGs remain glassy for maximum oscillatory strains less than about the yield strain of the material. For maximum strains greater than the yield strain, microstructural and rheological transitions occur for SPGs. Polydisperse SPGs rearrange into a layered structure parallel to the flow-vorticity plane for sufficiently high maximum shear rates and maximum strains about 10 times greater than the yield strain. Monodisperse suspensions form a face-centered cubic (FCC) structure when the maximum shear rate is low and hexagonal close-packed (HCP) structure when the maximum shear rate is high. In steady shear, the transition from a glassy state to a layered one for polydisperse suspensions included a significant induction strain before the transformation. In oscillatory shear, the transformation begins to occur immediately and with different microstructural changes. A state diagram for suspensions in large amplitude oscillatory shear flow is found to be in close but not exact agreement with the state diagram for steady shear flow. For more modest amplitudes of around one to five times the yield strain, there is a transition from a glassy structure to FCC and HCP crystals, at low and high frequencies, respectively, for monodisperse suspensions. At moderate frequencies, the transition is from glassy to HCP via

Experimental Investigation of Adiabatic Shear Banding at Different Impact Velocities

Science.gov (United States)

1993-01-01

plasticity and ASB’s is the Double-notch Shear specimen, it has been decided to use this concept in shear testing at medium and high strain rates...is the Double-notch Shear specimen. it has been decided to use this concept in shear testing at medium and high strain rates. Originally, Campbell...7] C. Fressengeas, Analyse dynamique 61asto-viscoplastique de l’h6tdrogdndit6 de la ddforma- tion plastique de cisalllement, Proc. Int. Conf. on

Thermal conductivity of graphene nanoribbons under shear deformation: A molecular dynamics simulation

Science.gov (United States)

Zhang, Chao; Hao, Xiao-Li; Wang, Cui-Xia; Wei, Ning; Rabczuk, Timon

2017-01-01

Tensile strain and compress strain can greatly affect the thermal conductivity of graphene nanoribbons (GNRs). However, the effect of GNRs under shear strain, which is also one of the main strain effect, has not been studied systematically yet. In this work, we employ reverse nonequilibrium molecular dynamics (RNEMD) to the systematical study of the thermal conductivity of GNRs (with model size of 4 nm × 15 nm) under the shear strain. Our studies show that the thermal conductivity of GNRs is not sensitive to the shear strain, and the thermal conductivity decreases only 12–16% before the pristine structure is broken. Furthermore, the phonon frequency and the change of the micro-structure of GNRs, such as band angel and bond length, are analyzed to explore the tendency of thermal conductivity. The results show that the main influence of shear strain is on the in-plane phonon density of states (PDOS), whose G band (higher frequency peaks) moved to the low frequency, thus the thermal conductivity is decreased. The unique thermal properties of GNRs under shear strains suggest their great potentials for graphene nanodevices and great potentials in the thermal managements and thermoelectric applications. PMID:28120921

Earthquake induced rock shear through a deposition hole. Influence of shear plane inclination and location as well as buffer properties on the damage caused to the canister

International Nuclear Information System (INIS)

Boergesson, Lennart; Hernelind, Jan

2006-10-01

The effect on the canister of an earthquake induced 20 cm rock shear with the shear rate 1 m/s along a fracture intersecting a deposition hole in a KBS-V repository has been investigated for a number of different shear cases and for different properties of the buffer material. The scenarios have been modelled with the finite element method and calculations have been done using the code ABAQUS. D-element models of the rock, the buffer and the canister have been used. Contact elements that can model separation have been used for the interfaces between the buffer and the rock and the interfaces between the buffer and the canister. The influence of mainly the following factors has been investigated: 1. Inclination of the intersecting fracture. 2. Shear direction when the fracture is not horizontal (inclination deviates from 90 deg). 3. Location of the shear plane when the inclination is 90 deg. 4. Magnitude of the shear displacement. 5. Bentonite type. 6. Bentonite density. 7. Transformation of the buffer to illite or cemented bentonite. The results from the calculations show that all these factors have important influence on the damage of the canister but the influence is for most factors not easily described since there are mutual interferences between the different factors. Plastic strain larger than 1% was reached in the copper already at 10 cm shear in all cases with Na- and Ca- bentonite. However, for several cases of Na-bentonite and one case of Ca-bentonite such plastic strain was only reached in the lid. The plastic strain in the steel was generally smaller than in the copper mainly due to the higher yield stress in the steel. For all cases of Na-bentonite except one and for about half of the Ca-bentonite cases the plastic strain in the steel was smaller than 1% after 10 cm shear. The shear inclination 45 deg was more harmful for the copper tube than the shear inclination 90 deg when tension shear was considered. At the shear inclinations 45 deg and 22.5 deg

Earthquake induced rock shear through a deposition hole. Influence of shear plane inclination and location as well as buffer properties on the damage caused to the canister

Energy Technology Data Exchange (ETDEWEB)

Boergesson, Lennart [Clay Technology AB, Lund (Sweden); Hernelind, Jan [5T Engineering AB, Vaesteraas (Sweden)

2006-10-15

The effect on the canister of an earthquake induced 20 cm rock shear with the shear rate 1 m/s along a fracture intersecting a deposition hole in a KBS-V repository has been investigated for a number of different shear cases and for different properties of the buffer material. The scenarios have been modelled with the finite element method and calculations have been done using the code ABAQUS. D-element models of the rock, the buffer and the canister have been used. Contact elements that can model separation have been used for the interfaces between the buffer and the rock and the interfaces between the buffer and the canister. The influence of mainly the following factors has been investigated: 1. Inclination of the intersecting fracture. 2. Shear direction when the fracture is not horizontal (inclination deviates from 90 deg). 3. Location of the shear plane when the inclination is 90 deg. 4. Magnitude of the shear displacement. 5. Bentonite type. 6. Bentonite density. 7. Transformation of the buffer to illite or cemented bentonite. The results from the calculations show that all these factors have important influence on the damage of the canister but the influence is for most factors not easily described since there are mutual interferences between the different factors. Plastic strain larger than 1% was reached in the copper already at 10 cm shear in all cases with Na- and Ca- bentonite. However, for several cases of Na-bentonite and one case of Ca-bentonite such plastic strain was only reached in the lid. The plastic strain in the steel was generally smaller than in the copper mainly due to the higher yield stress in the steel. For all cases of Na-bentonite except one and for about half of the Ca-bentonite cases the plastic strain in the steel was smaller than 1% after 10 cm shear. The shear inclination 45 deg was more harmful for the copper tube than the shear inclination 90 deg when tension shear was considered. At the shear inclinations 45 deg and 22.5 deg

Dilatancy of Shear Transformations in a Colloidal Glass

Science.gov (United States)

Lu, Y. Z.; Jiang, M. Q.; Lu, X.; Qin, Z. X.; Huang, Y. J.; Shen, J.

2018-01-01

Shear transformations, as fundamental rearrangement events operating in local regions, hold the key of plastic flow of amorphous solids. Despite their importance, the dynamic features of shear transformations are far from clear, which is the focus of the present study. Here, we use a colloidal glass under shear as the prototype to directly observe the shear-transformation events in real space. By tracing the colloidal-particle rearrangements, we quantitatively determine two basic properties of shear transformations: local shear strain and dilatation (or free volume). It is revealed that the local free volume undergoes a significantly temporary increase prior to shear transformations, eventually leading to a jump of local shear strain. We clearly demonstrate that shear transformations have no memory of the initial free volume of local regions. Instead, their emergence strongly depends on the dilatancy ability of these local regions, i.e., the dynamic creation of free volume. More specifically, the particles processing the high dilatancy ability directly participate in subsequent shear transformations. These results experimentally enrich Argon's statement about the dilatancy nature of shear transformations and also shed insight into the structural origin of amorphous plasticity.

Modeling of Mesoscale Variability in Biofilm Shear Behavior.

Directory of Open Access Journals (Sweden)

Pallab Barai

Full Text Available Formation of bacterial colonies as biofilm on the surface/interface of various objects has the potential to impact not only human health and disease but also energy and environmental considerations. Biofilms can be regarded as soft materials, and comprehension of their shear response to external forces is a key element to the fundamental understanding. A mesoscale model has been presented in this article based on digitization of a biofilm microstructure. Its response under externally applied shear load is analyzed. Strain stiffening type behavior is readily observed under high strain loads due to the unfolding of chains within soft polymeric substrate. Sustained shear loading of the biofilm network results in strain localization along the diagonal direction. Rupture of the soft polymeric matrix can potentially reduce the intercellular interaction between the bacterial cells. Evolution of stiffness within the biofilm network under shear reveals two regimes: a initial increase in stiffness due to strain stiffening of polymer matrix, and b eventual reduction in stiffness because of tear in polymeric substrate.

Periodic Viscous Shear Heating Instability in Fine-Grained Shear Zones: Possible Mechanism for Intermediate Depth Earthquakes and Slow Earthquakes?

Science.gov (United States)

Kelemen, P. B.; Hirth, G.

2004-12-01

Localized ductile shear zones with widths of cm to m are observed in exposures of Earth's shallow mantle (e.g., Kelemen & Dick JGR 95; Vissers et al. Tectonophys 95) and dredged from oceanic fracture zones (e.g., Jaroslow et al. Tectonophys 96). These are mylonitic (grain size 10 to 100 microns) and record mineral cooling temperatures from 1100 to 600 C. Pseudotachylites in a mantle shear zone show that shear heating temperatures can exceed the mantle solidus (e.g., Obata & Karato Tectonophys 95). Simple shear, recrystallization, and grain boundary sliding all decrease the spacing between pyroxenes, so olivine grain growth at lower stress is inhibited; thus, once formed, these shear zones do not "heal" on geological time scales. Reasoning that grain-size sensitive creep will be localized within these shear zones, rather than host rocks (grain size 1 to 10 mm), and inspired by the work of Whitehead & Gans (GJRAS 74), we thought these might undergo repeated shear heating instabilities. In this view, as elastic stress increases, the shear zone weakens via shear heating; rapid deformation of the weak shear zone releases most stored elastic stress; lower stress and strain rate coupled with diffusion of heat into host rocks leads to cooling and strengthening, after which the cycle repeats. We constructed a simple numerical model incorporating olivine flow laws for dislocation creep, diffusion creep, grain boundary sliding, and low T plasticity. We assumed that viscous deformation remains localized in shear zones, surrounded by host rocks undergoing elastic deformation. We fixed the velocity along one side of an elastic half space, and calculated stress due to elastic strain. This stress drives viscous deformation in a shear zone of specified width. Shear heating and thermal diffusion control temperature evolution in the shear zone and host rocks. A maximum of 1400 C (where substantial melting of peridotite would occur) is imposed. Grain size evolves during dislocation

The dynamics of a shear band

Science.gov (United States)

Giarola, Diana; Capuani, Domenico; Bigoni, Davide

2018-03-01

A shear band of finite length, formed inside a ductile material at a certain stage of a continued homogeneous strain, provides a dynamic perturbation to an incident wave field, which strongly influences the dynamics of the material and affects its path to failure. The investigation of this perturbation is presented for a ductile metal, with reference to the incremental mechanics of a material obeying the J2-deformation theory of plasticity (a special form of prestressed, elastic, anisotropic, and incompressible solid). The treatment originates from the derivation of integral representations relating the incremental mechanical fields at every point of the medium to the incremental displacement jump across the shear band faces, generated by an impinging wave. The boundary integral equations (under the plane strain assumption) are numerically approached through a collocation technique, which keeps into account the singularity at the shear band tips and permits the analysis of an incident wave impinging a shear band. It is shown that the presence of the shear band induces a resonance, visible in the incremental displacement field and in the stress intensity factor at the shear band tips, which promotes shear band growth. Moreover, the waves scattered by the shear band are shown to generate a fine texture of vibrations, parallel to the shear band line and propagating at a long distance from it, but leaving a sort of conical shadow zone, which emanates from the tips of the shear band.

Measurement of earthquake-induced shear strain in sandy gravel

International Nuclear Information System (INIS)

Ohkawa, I.; Futaki, M.; Yamanouchi, H.

1989-01-01

The nuclear power reactor buildings have been constructed on the hard rock ground formed in or before the Tertiary in Japan. This is mainly because the nuclear reactor building is much heavier than the common buildings and requires a large bearing capacity of the underlying soil deposit, and additionally the excessive deformation in soil deposit might cause damage in reactor building and subsequently cause the malfunction of the internal important facilities. Another reason is that the Quaternary soil deposit is not fully known with respect to its dynamic property. The gravel, and the sandy gravel, the representative soils of the Quaternary, have been believed to be suitable soil deposits to support the foundation of a common building, although the soils have rarely been investigated so closely on their physical properties quantitatively. In this paper, the dynamic deformability, i.e., the shear stress-strain relationship of the Quaternary diluvial soil deposit is examined through the earthquake ground motion measurement using accelerometers, pore-pressure meters, the specific devices developed in this research work. The objective soil deposit in this research is the sandy gravel of the diluvial and the alluvial

Noninvasive characterization of carotid plaque strain.

Science.gov (United States)

Khan, Amir A; Sikdar, Siddhartha; Hatsukami, Thomas; Cebral, Juan; Jones, Michael; Huston, John; Howard, George; Lal, Brajesh K

2017-06-01

Current risk stratification of internal carotid artery plaques based on diameter-reducing percentage stenosis may be unreliable because ischemic stroke results from plaque disruption with atheroembolization. Biomechanical forces acting on the plaque may render it vulnerable to rupture. The feasibility of ultrasound-based quantification of plaque displacement and strain induced by hemodynamic forces and their relationship to high-risk plaques have not been determined. We studied the feasibility and reliability of carotid plaque strain measurement from clinical B-mode ultrasound images and the relationship of strain to high-risk plaque morphology. We analyzed carotid ultrasound B-mode cine loops obtained in patients with asymptomatic ≥50% stenosis during routine clinical scanning. Optical flow methods were used to quantify plaque motion and shear strain during the cardiac cycle. The magnitude (maximum absolute shear strain rate [MASSR]) and variability (entropy of shear strain rate [ESSR] and variance of shear strain rate [VSSR]) of strain were combined into a composite shear strain index (SSI), which was assessed for interscan repeatability and correlated with plaque echolucency. Nineteen patients (mean age, 70 years) constituting 36 plaques underwent imaging; 37% of patients (n = 7) showed high strain (SSI ≥0.5; MASSR, 2.2; ESSR, 39.7; VSSR, 0.03) in their plaques; the remaining clustered into a low-strain group (SSI routine B-mode imaging using clinical ultrasound machines. High plaque strain correlates with known high-risk echolucent morphology. Strain measurement can complement identification of patients at high risk for plaque disruption and stroke. Copyright © 2017 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.

Creep Behavior in Interlaminar Shear of a SiC/SiC Ceramic Composite with a Self-healing Matrix

Science.gov (United States)

Ruggles-Wrenn, M. B.; Pope, M. T.

2014-02-01

Creep behavior in interlaminar shear of a non-oxide ceramic composite with a multilayered matrix was investigated at 1,200 °C in laboratory air and in steam environment. The composite was produced via chemical vapor infiltration (CVI). The composite had an oxidation inhibited matrix, which consisted of alternating layers of silicon carbide and boron carbide and was reinforced with laminated Hi-Nicalon™ fibers woven in a five-harness-satin weave. Fiber preforms had pyrolytic carbon fiber coating with boron carbide overlay applied. The interlaminar shear properties were measured. The creep behavior was examined for interlaminar shear stresses in the 16-22 MPa range. Primary and secondary creep regimes were observed in all tests conducted in air and in steam. In air and in steam, creep run-out defined as 100 h at creep stress was achieved at 16 MPa. Larger creep strains were accumulated in steam. However, creep strain rates and creep lifetimes were only moderately affected by the presence of steam. The retained properties of all specimens that achieved run-out were characterized. Composite microstructure, as well as damage and failure mechanisms were investigated.

The response of dense dry granular material to the shear reversal

Science.gov (United States)

Zhang, Jie; Ren, Jie; Farhadi, Somayeh; Behringer, Robert

2008-11-01

We have performed two dimensional granular experiments under pure shear using bidisperse photo-elastic disks. Starting from a stress free state, a square box filled with granular particles is subject to shear. The forward shears involved various number of steps, leading to maximum strains between 0.1 and 0.3. The area is kept constant during the shear. The network of force chains gradually built up as the strain increased, leading to increased pressure and shear stress. Reverse shear was then applied to the system. Depending on the initial packing fraction and the strain at which the shear is reversed, the force chain network built prior to the shear reversal may be destroyed completely or partially destroyed. Following the force chain weakening, when the reserve shear is continuously applied to the system, there is a force chain strengthening. Following each change of the system, contact forces of individual disks were measured by applying an inverse algorithm. We also kept track of the displacement and angle of rotation of every particle from frame to frame. We present the results for the structure failure and reconstruction during shear reversals. We also present data for stresses, contact force distributions and other statistical measures.

Beam model for seismic analysis of complex shear wall structure based on the strain energy equivalence

International Nuclear Information System (INIS)

Reddy, G.R.; Mahajan, S.C.; Suzuki, Kohei

1997-01-01

A nuclear reactor building structure consists of shear walls with complex geometry, beams and columns. The complexity of the structure is explained in the section Introduction. Seismic analysis of the complex reactor building structure using the continuum mechanics approach may produce good results but this method is very difficult to apply. Hence, the finite element approach is found to be an useful technique for solving the dynamic equations of the reactor building structure. In this approach, the model which uses finite elements such as brick, plate and shell elements may produce accurate results. However, this model also poses some difficulties which are explained in the section Modeling Techniques. Therefore, seismic analysis of complex structures is generally carried out using a lumped mass beam model. This model is preferred because of its simplicity and economy. Nevertheless, mathematical modeling of a shear wall structure as a beam requires specialized skill and a thorough understanding of the structure. For accurate seismic analysis, it is necessary to model more realistically the stiffness, mass and damping. In linear seismic analysis, modeling of the mass and damping may pose few problems compared to modeling the stiffness. When used to represent a complex structure, the stiffness of the beam is directly related to the shear wall section properties such as area, shear area and moment of inertia. Various beam models which are classified based on the method of stiffness evaluation are also explained under the section Modeling Techniques. In the section Case Studies the accuracy and simplicity of the beam models are explained. Among various beam models, the one which evaluates the stiffness using strain energy equivalence proves to be the simplest and most accurate method for modeling the complex shear wall structure. (author)

Rb-Sr dating of strain-induced mineral growth in two ductile shear zones in the western gneiss region of Nord-Troendelag, Central Norway

International Nuclear Information System (INIS)

Piasecki, M.A.; Cliff, R.A.

1988-01-01

In the Bjugn district of the northern part of the Western Gneiss Region, Nord-Troendelag, a basement gneiss-cover nappe boundary is marked by a thick zone of ductile shearing. In this zone a layer-parallel mylonitic fabric with related new mineral growth overprints and retrogresses a previous fabric associated with a granulite facies mineral assemblage. Related minor shear belts contain abundant new minerals and vein systems, including pegmatites, believed to represent strain-induced products formed at the time of the shearing movements. Central parts of two large muscovite books from such a pegmatite yielded Rb-Sr, Early to Middle Devonian ages of 389±6 Ma and 386±6 Ma, interpreted as indicating the approximate time of pegmatite formation and of the shearing. Small, matrix-size muscovite and biotite grains from the host mylonite gave ages of 378±6 Ma and 365±5 Ma, respectively, supposed to relate to post-shearing uplift and cooling

Interpretation of large-strain geophysical crosshole tests

International Nuclear Information System (INIS)

Drnevich, V.P.; Salgado, R.; Ashmawy, A.; Grant, W.P.; Vallenas, P.

1995-10-01

At sites in earthquake-prone areas, the nonlinear dynamic stress-strain behavior of soil with depth is essential for earthquake response analyses. A seismic crosshole test has been developed where large dynamic forces are applied in a borehole. These forces generate shear strains in the surrounding soil that are well into the nonlinear range. The shear strain amplitudes decrease with distance from the source. Velocity sensors located in three additional holes at various distances from the source hole measure the particle velocity and the travel time of the shear wave from the source. This paper provides an improved, systematic interpretation scheme for the data from these large-strain geophysical crosshole tests. Use is made of both the measured velocities at each sensor and the travel times. The measured velocity at each sensor location is shown to be a good measure of the soil particle velocity at that location. Travel times to specific features on the velocity time history, such as first crossover, are used to generate travel time curves for the waves which are nonlinear. At some distance the amplitudes reduce to where the stress-strain behavior is essentially linear and independent of strain amplitude. This fact is used together with the measurements at the three sensor locations in a rational approach for fitting curves of shear wave velocity versus distance from the source hole that allow the determination of the shear wave velocity and the shear strain amplitude at each of the sensor locations as well as the shear wave velocity associated with small-strain (linear) behavior. The method is automated using off-the-shelf PC-based software. The method is applied to large-strain crosshole tests performed as part of the studies for the design and construction of the proposed Multi-Function Waste Tank Facility planned for Hanford Site

Determining Recoverable and Irrecoverable Contributions to Accumulated Strain in a NiTiPd High-Temperature Shape Memory Alloy During Thermomechanical Cycling

Science.gov (United States)

Monroe, J. A.; Karaman, I.; Lagoudas, D. C.; Bigelow, G.; Noebe, R. D.; Padula, S., II

2011-01-01

When Ni(29.5)Ti(50.5)Pd30 shape memory alloy is thermally cycled under stress, significant strain can accumulate due to elasticity, remnant oriented martensite and plasticity. The strain due to remnant martensite can be recovered by further thermal cycling under 0 MPa until the original transformation-induced volume change and martensite coefficient of thermal expansion are obtained. Using this technique, it was determined that the 8.15% total accumulated strain after cycling under 200 MPa consisted of 0.38%, 3.97% and 3.87% for elasticity, remnant oriented martensite and creep/plasticity, respectively.

Material model for shear of the buffer - evaluation of laboratory test results

International Nuclear Information System (INIS)

Boergesson, Lennart; Dueck, Ann; Johannesson, Lars-Erik

2010-12-01

The report describes the material model of bentonite used for analysing a rock shear through a deposition hole. The old model used in SR-Can has been considerably changed. The new reference model that has been developed for SR-Site is described and motivated. The relevant properties of the buffer that affect the response to a rock shear are (in addition to the bentonite type) the density (which yields a swelling pressure), the shear strength, the stiffness before the maximum shear stress is reached and the shear rate, which also affects the shear strength. Since the shear caused by an earthquake is very fast and the hydraulic conductivity of the bentonite is very low there is no possibility for the pore water in the water saturated bentonite to be redistributed. Since the compressibility of water and particles are negligible, the bentonite can be modelled as a solid material that cannot change volume but only exhibit shear deformations. A proper and simple model that behaves accordingly is a model with von Mises' stress modelled as a function of the strain (stress-strain model). The model is elastic-plastic with an E-modulus that determines the behaviour until the material starts yielding whereupon the plastic strain is modelled as a function of von Mises' stress and added to the elastic strain. Included in the model is also a strain rate dependency of the stress-strain relation, which ranges between the strain rates 10 -6 1/s 3 1/s. The reference material model is derived from a large number of laboratory tests made on different bentonites at different strain rates, densities and with different techniques. Since it cannot be excluded that the exchangeable cat-ions in the Na-bentonite MX-80 is exchanged to calcium-ions the Ca-bentonite Deponit CaN is proposed to be used as reference material. The overall conclusion is that a relevant and probably also slightly conservative material model of Ca-converted MX-80 is derived, presented and well motivated

Adiabatic shear localization in ultrafine grained 6061 aluminum alloy

Energy Technology Data Exchange (ETDEWEB)

Wang, Bingfeng, E-mail: biw009@ucsd.edu [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Department of Mechanical and Aerospace Engineering, University of California, San Diego (United States); State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan (China); Key Lab of Nonferrous Materials, Ministry of Education, Central South University, Changsha 410083 (China); Ma, Rui; Zhou, Jindian [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Li, Zezhou; Zhao, Shiteng [Department of Mechanical and Aerospace Engineering, University of California, San Diego (United States); Huang, Xiaoxia [School of Materials Science and Engineering, Central South University, Changsha 410083 (China)

2016-10-15

Localized shear is an important mode of deformation; it leads to catastrophic failure with low ductility, and occurs frequently during high strain-rate deformation. The hat-shaped specimen has been successfully used to generate shear bands under controlled shock-loading tests. The microstructure in the forced shear band was characterized by optical microscopy, microhardness, and transmission electron microscopy. The true flow stress in the shear region can reach 800 MPa where the strain is about 2.2. The whole shear localization process lasts for about 100 μs. The shear band is a long and straight band distinguished from the matrix by boundaries. It can be seen that the grains in the boundary of the shear band are highly elongated along the shear direction and form the elongated cell structures (0.2 µm in width), and the core of the shear band consists of a number of recrystallized equiaxed grains with 0.2−0.3 µm in diameters, and the second phase particles distribute in the boundary of the ultrafine equiaxed new grains. The calculated temperature in the shear band can reach about 667 K. Finally, the formation of the shear band in the ultrafine grained 6061 aluminum alloy and its microstructural evolution are proposed.

Relations Between Shear and Normal Stresses in a Step-Shear Experiment

DEFF Research Database (Denmark)

Hassager, Ole; Pedersen, Sven

1978-01-01

The Lodge-Meissner step-shear relation for simple fluids is examined. It is demonstrated that the relation depends critically on two assumptions for the integral expansion of the simple fluid: First, the use of the Cauchy strain tensor as strain measure, and second, that the memory functions...... are bounded. It is pointed out that many simple differential and integral models do not satisfy these criteria and hence predict deviations from the Lodge-Meissner relation....

Numerical simulation of systems of shear bands in ductile metal with inclusions

Energy Technology Data Exchange (ETDEWEB)

Plohr, JeeYeon N., E-mail: jplohr@lanl.gov; Plohr, Bradley J. [Los Alamos National Laboratory, Theoretical Division, Los Alamos, NM 87545 (United States)

2016-02-15

We develop a method for numerical simulations of high strain-rate loading of mesoscale samples of ductile metal with inclusions. Because of its small-scale inhomogeneity, the composite material is prone to localized shear deformation (adiabatic shear bands). This method employs the Generalized Method of Cells of Paley and Aboudi [Mech. Materials, vol. 14, pp. 127–139, 1992] to ensure that the micro mechanical behavior of the metal and inclusions is reflected properly in the behavior of the composite at the mesoscale. To find the effective plastic strain rate when shear bands are present, we extend and apply the analytic and numerical analysis of shear bands of Glimm, Plohr, and Sharp [Mech. Materials, vol. 24, pp. 31–41, 1996]. Our tests of the method focus on the stress/strain response in uniaxial-strain flow, both compressive and tensile, of depleted uranium metal containing silicon carbide inclusions. We use the Preston-Tonks-Wallace viscoplasticity model [J. Appl. Phys., vol. 93, pp. 211–220, 2003], which applies to the high strain-rate regime of an isotropic viscoplastic solid. In results, we verify the elevated temperature and thermal softening at shear bands in our simulations of pure DU and DU/SiC composites. We also note that in composites, due the asymmetry caused by the inclusions, shear band form at different times in different subcells. In particular, in the subcells near inclusions, shear band form much earlier than they do in pure DU.

Numerical simulation of systems of shear bands in ductile metal with inclusions

Directory of Open Access Journals (Sweden)

JeeYeon N. Plohr

2016-02-01

Full Text Available We develop a method for numerical simulations of high strain-rate loading of mesoscale samples of ductile metal with inclusions. Because of its small-scale inhomogeneity, the composite material is prone to localized shear deformation (adiabatic shear bands. This method employs the Generalized Method of Cells of Paley and Aboudi [Mech. Materials, vol. 14, pp. 127–139, 1992] to ensure that the micro mechanical behavior of the metal and inclusions is reflected properly in the behavior of the composite at the mesoscale. To find the effective plastic strain rate when shear bands are present, we extend and apply the analytic and numerical analysis of shear bands of Glimm, Plohr, and Sharp [Mech. Materials, vol. 24, pp. 31–41, 1996]. Our tests of the method focus on the stress/strain response in uniaxial-strain flow, both compressive and tensile, of depleted uranium metal containing silicon carbide inclusions. We use the Preston-Tonks-Wallace viscoplasticity model [J. Appl. Phys., vol. 93, pp. 211–220, 2003], which applies to the high strain-rate regime of an isotropic viscoplastic solid. In results, we verify the elevated temperature and thermal softening at shear bands in our simulations of pure DU and DU/SiC composites. We also note that in composites, due the asymmetry caused by the inclusions, shear band form at different times in different subcells. In particular, in the subcells near inclusions, shear band form much earlier than they do in pure DU.

Numerical simulation of systems of shear bands in ductile metal with inclusions

Science.gov (United States)

Plohr, Jeeyeon

2017-06-01

We develop a method for numerical simulations of high strain-rate loading of mesoscale samples of ductile metal with inclusions. Because of its small-scale inhomogeneity, the composite material is prone to localized shear deformation. This method employs the Generalized Method of Cells to ensure that the micro mechanical behavior of the metal and inclusions is reflected properly in the behavior of the composite at the mesoscale. To find the effective plastic strain rate when shear bands are present, we extend and apply the analytic and numerical analysis of shear bands of Glimm, Plohr, and Sharp. Our tests of the method focus on the stress/strain response in uniaxial-strain flow, both compressive and tensile, of depleted uranium metal containing silicon carbide inclusions. In results, we verify the elevated temperature and thermal softening at shear bands in our simulations of pure DU and DU/SiC composites. We also note that in composites, due the asymmetry caused by the inclusions, shear band form at different times in different subcells. In particular, in the subcells near inclusions, shear band form much earlier than they do in pure DU.

Effects of Wheat Flour Dough’s Viscoelastic Level by Adding Glucose Oxidase on its Dynamic Shear Properties whatever the Strain Modes

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Jean Didier Koffi Kouassi

2014-05-01

Full Text Available The objective of this work was to study the effects of wheat flour dough’s viscoelastic level by adding glucose oxidase (Gox on its rheological properties at dynamic shear strain mode to predict the final product quality. Dough does display a linear viscoelastic domain. Glucose oxidase (Gox was added to dough in order to enhance its viscoelasticity and to take into account the possible effects of this viscoelasticity on the results. Whatever the types of dough strain used G’ increased, tan δ decreased and led to less sticky dough. Wheat flour dough, an increase in G’ with extension may be associated to a strain-hardening phenomenon but the role of dough viscoelasticity is discussed.

Effect of salinity on the quantity and quality of carotenoids accumulated by Dunaliella salina (strain CONC-007 and Dunaliella bardawil (strain ATCC 30861 Chlorophyta

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PATRICIA I GÓMEZ

2003-01-01

Full Text Available Dunaliella salina and D. bardawil are well-known microalgae accumulating high levels of b-carotene under growth-limiting conditions. In both taxa, this pigment is primarily composed of the isomers 9-cis and all-trans. The 9-cis b-carotene occurs only in natural sources and is the most attractive from a commercial point of view. The conditions that enhance the preferred accumulation of 9-cis b-carotene in D. salina are controversial and they have not been well established yet. This study examined the effect of salinity on the quantity and quality of total carotenoids and b-carotene isomers accumulated by D. salina (strain CONC-007 and D. bardawil (strain ATCC 30861 grown in two media with different nutritional compositions (PES and ART and at salt concentrations of 1M, 2M and 3M NaCl. Total carotenoids were determined by spectrophotometry and b-carotene isomers, by HPLC. The highest carotenoid contents per cell were obtained at 2M NaCl in both taxa. In both media, an increase of the 9-cis/all-trans b-carotene ratio was observed in D. bardawil when the salt concentration increased, with a maximum value of 2.6 (in ART medium at 3M NaCl. In D. salina this ratio did not exhibit the same pattern, and the salt concentrations for maximal ratios were different in both media. The highest ratio obtained for this strain was 4.3 (in ART medium at 2M NaCl.

The occurrence of shear banding in a millimeter scale (12-bar3)[634] grain of an Al-4.5% Mg alloy during plane strain compression

International Nuclear Information System (INIS)

Chapelle, David; Darrieulat, Michel

2003-01-01

The appearance of localization in shear bands during plane strain compression (PSC) of an Al-4.5% Mg alloy is investigated, with emphasis on a millimeter scale S-orientated grain in the longitudinal section of the specimen, upon which a gold microgrid was deposited. In order to justify this focus, attention is also paid on smaller grains of other areas. The microgrid technique allows the local strain field at various steps of deformation to be followed and in-plane components to be plotted over the selected region. Electron back scattered diffraction analysis was also used to gain an insight into the crystallography of local lattice rotations. One can then predict the potentially activated slip systems according to the Schmid law with Taylor's hypothesis, and assert the initial crystallographic feature of shear banding. This provides the opportunity to gain a more complete understanding, assuming a grain scale effect, of the mechanisms involved in the occurrence of shear banding in this alloy, and to reveal its influence on the rolling texture

Dynamic Strength and Accumulated Plastic Strain Development Laws and Models of the Remolded Red Clay under Long-Term Cyclic Loads: Laboratory Test Results

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Li Jian

2015-09-01

Full Text Available The dynamic strength and accumulated plastic strain are two important parameters for evaluating the dynamic response of soil. As a special clay, the remolded red clay is often used as the high speed railway subgrade filling, but studies on its dynamic characteristics are few. For a thorough analysis of the suitability of the remolded red clay as the subgrade filling, a series of long-term cyclic load triaxial test under different load histories are carried out. Considering the influence of compactness, confining pressure, consolidation ratio, vibration frequency and dynamic load to the remolded red clay dynamic property, the tests obtain the development curves of the dynamic strength and accumulated plastic strain under different test conditions. Then, through curve fitting method, two different hyperbolic models respectively for the dynamic strength and accumulated plastic strain are built, which can match the test datum well. By applying the dynamic strength model, the critical dynamic strength of the remolded red clay are gained. Meanwhile, for providing basic datum and reference for relevant projects, all key parameters for the dynamic strength and accumulated plastic strain of the remolded red clay are given in the paper.

Magma-assisted strain localization in an orogen-parallel transcurrent shear zone of southern Brazil

Science.gov (United States)

Tommasi, AndréA.; Vauchez, Alain; Femandes, Luis A. D.; Porcher, Carla C.

1994-04-01

In a lithospheric-scale, orogen-parallel transcurrent shear zone of the Pan-African Dom Feliciano belt of southern Brazil, two successive generations of magmas, an early calc-alkaline and a late peraluminous, have been emplaced during deformation. Microstructures show that these granitoids experienced a progressive deformation from magmatic to solid state under decreasing temperature conditions. Magmatic deformation is indicated by the coexistence of aligned K-feldspar, plagioclase, micas, and/or tourmaline with undeformed quartz. Submagmatic deformation is characterized by strain features, such as fractures, lattice bending, or replacement reactions affecting only the early crystallized phases. High-temperature solid-state deformation is characterized by extensive grain boundary migration in quartz, myrmekitic K-feldspar replacement, and dynamic recrystallization of both K-feldspar and plagioclase. Decreasing temperature during solid-state deformation is inferred from changes in quartz crystallographic fabrics, decrease in grain size of recrystallized feldspars, and lower Ti amount in recrystallized biotites. Final low-temperature deformation is characterized by feldspar replacement by micas. The geochemical evolution of the synkinematic magmatism, from calc-alkaline metaluminous granodiorites with intermediate 87Sr/86Sr initial ratio to peraluminous granites with very high 87Sr/86Sr initial ratio, suggests an early lower crustal source or a mixed mantle/crustal source, followed by a middle to upper crustal source for the melts. Shearing in lithospheric faults may induce partial melting in the lower crust by shear heating in the upper mantle, but, whatever the process initiating partial melting, lithospheric transcurrent shear zones may collect melt at different depths. Because they enhance the vertical permeability of the crust, these zones may then act as heat conductors (by advection), promoting an upward propagation of partial melting in the crust

Friction of Shear-Fracture Zones

Science.gov (United States)

Riikilä, T. I.; Pylväinen, J. I.; Åström, J.

2017-12-01

A shear fracture of brittle solids under compression undergoes a substantial evolution from the initial microcracking to a fully formed powder-filled shear zone. Experiments covering the entire process are relatively easy to conduct, but they are very difficult to investigate in detail. Numerically, the large strain limit has remained a challenge. An efficient simulation model and a custom-made experimental device are employed to test to what extent a shear fracture alone is sufficient to drive material to spontaneous self-lubrication. A "weak shear zone" is an important concept in geology, and a large number of explanations, specific for tectonic conditions, have been proposed. We demonstrate here that weak shear zones are far more general, and that their emergence only demands that a microscopic, i.e., fragment-scale, stress relaxation mechanism develops during the fracture process.

Improved failure prediction in forming simulations through pre-strain mapping

Science.gov (United States)

Upadhya, Siddharth; Staupendahl, Daniel; Heuse, Martin; Tekkaya, A. Erman

2018-05-01

The sensitivity of sheared edges of advanced high strength steel (AHSS) sheets to cracking during subsequent forming operations and the difficulty to predict this failure with any degree of accuracy using conventionally used FLC based failure criteria is a major problem plaguing the manufacturing industry. A possible method that allows for an accurate prediction of edge cracks is the simulation of the shearing operation and carryover of this model into a subsequent forming simulation. But even with an efficient combination of a solid element shearing operation and a shell element forming simulation, the need for a fine mesh, and the resulting high computation time makes this approach not viable from an industry point of view. The crack sensitivity of sheared edges is due to work hardening in the shear-affected zone (SAZ). A method to predict plastic strains induced by the shearing process is to measure the hardness after shearing and calculate the ultimate tensile strength as well as the flow stress. In combination with the flow curve, the relevant strain data can be obtained. To eliminate the time-intensive shearing simulation necessary to obtain the strain data in the SAZ, a new pre-strain mapping approach is proposed. The pre-strains to be mapped are, hereby, determined from hardness values obtained in the proximity of the sheared edge. To investigate the performance of this approach the ISO/TS 16630 hole expansion test was simulated with shell elements for different materials, whereby the pre-strains were mapped onto the edge of the hole. The hole expansion ratios obtained from such pre-strain mapped simulations are in close agreement with the experimental results. Furthermore, the simulations can be carried out with no increase in computation time, making this an interesting and viable solution for predicting edge failure due to shearing.

Strain localisation in mechanically layered rocks beneath detachment zones: insights from numerical modelling

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L. Le Pourhiet

2013-04-01

Full Text Available We have designed a series of fully dynamic numerical simulations aimed at assessing how the orientation of mechanical layering in rocks controls the orientation of shear bands and the depth of penetration of strain in the footwall of detachment zones. Two parametric studies are presented. In the first one, the influence of stratification orientation on the occurrence and mode of strain localisation is tested by varying initial dip of inherited layering in the footwall with regard to the orientation of simple shear applied at the rigid boundary simulating a rigid hanging wall, all scaling and rheological parameter kept constant. It appears that when Mohr–Coulomb plasticity is being used, shear bands are found to localise only when the layering is being stretched. This corresponds to early deformational stages for inital layering dipping in the same direction as the shear is applied, and to later stages for intial layering dipping towards the opposite direction of shear. In all the cases, localisation of the strain after only γ=1 requires plastic yielding to be activated in the strong layer. The second parametric study shows that results are length-scale independent and that orientation of shear bands is not sensitive to the viscosity contrast or the strain rate. However, decreasing or increasing strain rate is shown to reduce the capacity of the shear zone to localise strain. In the later case, the strain pattern resembles a mylonitic band but the rheology is shown to be effectively linear. Based on the results, a conceptual model for strain localisation under detachment faults is presented. In the early stages, strain localisation occurs at slow rates by viscous shear instabilities but as the layered media is exhumed, the temperature drops and the strong layers start yielding plastically, forming shear bands and localising strain at the top of the shear zone. Once strain localisation has occured, the deformation in the shear band becomes

An Experimental Investigation into Failure and Localization Phenomena in the Extension to Shear Fracture Transition in Rock

Science.gov (United States)

Choens, R. C., II; Chester, F. M.; Bauer, S. J.; Flint, G. M.

2014-12-01

Fluid-pressure assisted fracturing can produce mesh and other large, interconnected and complex networks consisting of both extension and shear fractures in various metamorphic, magmatic and tectonic systems. Presently, rock failure criteria for tensile and low-mean compressive stress conditions is poorly defined, although there is accumulating evidence that the transition from extension to shear fracture with increasing mean stress is continuous. We report on the results of experiments designed to document failure criteria, fracture mode, and localization phenomena for several rock types (sandstone, limestone, chalk and marble). Experiments were conducted in triaxial extension using a necked (dogbone) geometry to achieve mixed tension and compression stress states with local component-strain measurements in the failure region. The failure envelope for all rock types is similar, but are poorly described using Griffith or modified Griffith (Coulomb or other) failure criteria. Notably, the mode of fracture changes systematically from pure extension to shear with increase in compressive mean stress and display a continuous change in fracture orientation with respect to principal stress axes. Differential stress and inelastic strain show a systematic increase with increasing mean stress, whereas the axial stress decreases before increasing with increasing mean stress. The stress and strain data are used to analyze elastic and plastic strains leading to failure and compare the experimental results to predictions for localization using constitutive models incorporating on bifurcation theory. Although models are able to describe the stability behavior and onset of localization qualitatively, the models are unable to predict fracture type or orientation. Constitutive models using single or multiple yield surfaces are unable to predict the experimental results, reflecting the difficulty in capturing the changing micromechanisms from extension to shear failure. Sandia

Accumulation of Astaxanthin by a New Haematococcus pluvialis Strain BM1 from the White Sea Coastal Rocks (Russia

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Konstantin Chekanov

2014-08-01

Full Text Available We report on a novel arctic strain BM1 of a carotenogenic chlorophyte from a coastal habitat with harsh environmental conditions (wide variations in solar irradiance, temperature, salinity and nutrient availability identified as Haematococcus pluvialis Flotow. Increased (25‰ salinity exerted no adverse effect on the growth of the green BM1 cells. Under stressful conditions (high light, nitrogen and phosphorus deprivation, green vegetative cells of H. pluvialis BM1 grown in BG11 medium formed non-motile palmelloid cells and, eventually, hematocysts capable of a massive accumulation of the keto-carotenoid astaxanthin with a high nutraceutical and therapeutic potential. Routinely, astaxanthin was accumulated at the level of 4% of the cell dry weight (DW, reaching, under prolonged stress, 5.5% DW. Astaxanthin was predominantly accumulated in the form of mono- and diesters of fatty acids from C16 and C18 families. The palmelloids and hematocysts were characterized by the formation of red-colored cytoplasmic lipid droplets, increasingly large in size and number. The lipid droplets tended to merge and occupied almost the entire volume of the cell at the advanced stages of stress-induced carotenogenesis. The potential application of the new strain for the production of astaxanthin is discussed in comparison with the H. pluvialis strains currently employed in microalgal biotechnology.

Strain Pattern in Supercooled Liquids

Science.gov (United States)

Illing, Bernd; Fritschi, Sebastian; Hajnal, David; Klix, Christian; Keim, Peter; Fuchs, Matthias

2016-11-01

Investigations of strain correlations at the glass transition reveal unexpected phenomena. The shear strain fluctuations show an Eshelby-strain pattern [˜cos (4 θ ) /r2 ], characteristic of elastic response, even in liquids, at long times. We address this using a mode-coupling theory for the strain fluctuations in supercooled liquids and data from both video microscopy of a two-dimensional colloidal glass former and simulations of Brownian hard disks. We show that the long-ranged and long-lived strain signatures follow a scaling law valid close to the glass transition. For large enough viscosities, the Eshelby-strain pattern is visible even on time scales longer than the structural relaxation time τ and after the shear modulus has relaxed to zero.

Oil accumulation in the model green alga Chlamydomonas reinhardtii: characterization, variability between common laboratory strains and relationship with starch reserves

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Carrier Patrick

2011-01-01

Full Text Available Abstract Background When cultivated under stress conditions, many microalgae species accumulate both starch and oil (triacylglycerols. The model green microalga Chlamydomonas reinhardtii has recently emerged as a model to test genetic engineering or cultivation strategies aiming at increasing lipid yields for biodiesel production. Blocking starch synthesis has been suggested as a way to boost oil accumulation. Here, we characterize the triacylglycerol (TAG accumulation process in Chlamydomonas and quantify TAGs in various wild-type and starchless strains. Results In response to nitrogen deficiency, Chlamydomonas reinhardtii produced TAGs enriched in palmitic, oleic and linoleic acids that accumulated in oil-bodies. Oil synthesis was maximal between 2 and 3 days following nitrogen depletion and reached a plateau around day 5. In the first 48 hours of oil deposition, a ~80% reduction in the major plastidial membrane lipids occurred. Upon nitrogen re-supply, mobilization of TAGs started after starch degradation but was completed within 24 hours. Comparison of oil content in five common laboratory strains (CC124, CC125, cw15, CC1690 and 11-32A revealed a high variability, from 2 μg TAG per million cell in CC124 to 11 μg in 11-32A. Quantification of TAGs on a cell basis in three mutants affected in starch synthesis (cw15sta1-2, cw15sta6 and cw15sta7-1 showed that blocking starch synthesis did not result in TAG over-accumulation compared to their direct progenitor, the arginine auxotroph strain 330. Moreover, no significant correlation was found between cellular oil and starch levels among the twenty wild-type, mutants and complemented strains tested. By contrast, cellular oil content was found to increase steeply with salt concentration in the growth medium. At 100 mM NaCl, oil level similar to nitrogen depletion conditions could be reached in CC124 strain. Conclusion A reference basis for future genetic studies of oil metabolism in Chlamydomonas

NEW STRAIN PRODUCERS OF BIOBUTANOL. III. METHODS OF INCREASED BUTANOL ACCUMULATION FROM BIOMASS OF SWITCHGRASS Panicum virgatum L.

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Tigunova O. O.

2015-08-01

Full Text Available The aim of this work was to enlarge accumulation of butanol from switchgrass Panicum virgatum L. biomass using strains-producers obtained from grounds and silts of Kyiv lakes. The objects of the study were strains of C. acetobutylicum ІМВ B-7407 (IFBG C6H, Clostridium acetobutylicum IFBG C6H 5М and Clostridium tyrobutyricum IFBG C4B from the "Collections of microbial strains and lines of plants for food and agricultural biotechnology" of the Public Institution "Institute of Food Biotechnology and Genomics" of the National Academy of Sciences of Ukraine. Gas chromatography was used to determine the alcohol concentration at the stage of solvent synthesis. To determine the effect of butanol precursors during cultivation, butyric, lactic and acetic acids were used. Optimization of processing parameters, which was based on the needs of cultures, allowed us to increase the yield by 20 and 50% for the initial and mutant strain respectively. Using synthetic precursors (such as lactic, butyric and acetic acid during cultivation increased total concentration of butanol by 1.7 times. To optimize the process, a study was carried out using acetone- butyl grains. Using of acetone-butyl grains in concentrations up to 60% does not affect the synthesis of butanol by C. acetobutylicum IFBG C6H 5M. Increasing the concentration of grains led to decrease in accumulation of butanol. Almost double increase in accumulation of the target product (butanol was achieved using two-stage fermentation and/or precursors of synthesis. It was shown the possibility of using acetone-butyl grains in fermentation. As a result the mass fraction of the waste was reduced.

Accumulation of a Polyhydroxyalkanoate Containing Primarily 3-Hydroxydecanoate from Simple Carbohydrate Substrates by Pseudomonas sp. Strain NCIMB 40135

OpenAIRE

Haywood, Geoffrey W.; Anderson, Alistair J.; Ewing, David F.; Dawes, Edwin A.

1990-01-01

A number of Pseudomonas species have been identified which accumulate a polyhydroxyalkanoate containing mainly 3-hydroxydecanoate monomers from sodium gluconate as the sole carbon source. One of these, Pseudomonas sp. strain NCIMB 40135, was further investigated and shown to accumulate such a polyhydroxyalkanoate from a wide range of carbon sources (C2 to C6); however, when supplied with octanoic acid it produced a polyhydroxyalkanoate containing mainly 3-hydroxyoctanoate monomers. Polymer sy...

Strain Localization and Weakening Processes in Viscously Deforming Rocks: Numerical Modeling Based on Laboratory Torsion Experiments

Science.gov (United States)

Doehmann, M.; Brune, S.; Nardini, L.; Rybacki, E.; Dresen, G.

2017-12-01

Strain localization is an ubiquitous process in earth materials observed over a broad range of scales in space and time. Localized deformation and the formation of shear zones and faults typically involves material softening by various processes, like shear heating and grain size reduction. Numerical modeling enables us to study the complex physical and chemical weakening processes by separating the effect of individual parameters and boundary conditions. Using simple piece-wise linear functions for the parametrization of weakening processes allows studying a system at a chosen (lower) level of complexity (e.g. Cyprych et al., 2016). In this study, we utilize a finite element model to test two weakening laws that reduce the strength of the material depending on either the I) amount of accumulated strain or II) deformational work. Our 2D Cartesian models are benchmarked to single inclusion torsion experiments performed at elevated temperatures of 900 °C and pressures of up to 400 MPa (Rybacki et al., 2014). The experiments were performed on Carrara marble samples containing a weak Solnhofen limestone inclusion at a maximum strain rate of 2.0*10-4 s-1. Our models are designed to reproduce shear deformation of a hollow cylinder equivalent to the laboratory setup, such that material leaving one side of the model in shear direction enters again on the opposite side using periodic boundary conditions. Similar to the laboratory tests, we applied constant strain rate and constant stress boundary conditions.We use our model to investigate the time-dependent distribution of stress and strain and the effect of different parameters. For instance, inclusion rotation is shown to be strongly dependent on the viscosity ratio between matrix and inclusion and stronger ductile weakening increases the localization rate while decreasing shear zone width. The most suitable weakening law for representation of ductile rock is determined by combining the results of parameter tests with

Strain localization and elastic-plastic coupling during deformation of porous sandstone

Energy Technology Data Exchange (ETDEWEB)

Dewers, Thomas A. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States). Geomechanics Dept.; Issen, Kathleen A. [Clarkson Univ., Potsdam, NY (United States). Mechanical and Aeronautical Engineering; Holcomb, David J. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States). Geomechanics Dept.; Olsson, William A. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States). Geomechanics Dept.; Ingraham, Mathew D. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States). Geomechanics Dept.

2017-09-12

Results of axisymmetric compression tests on weak, porous Castlegate Sandstone (Cretaceous, Utah, USA), covering a range of dilational and compactional behaviors, are examined for localization behavior. Assuming isotropy, bulk and shear moduli evolve as increasing functions of mean stress and Mises equivalent shear stress respectively, and as decreasing functions of work-conjugate plastic strains. Acoustic emissions events located during testing show onset of localization and permit calculation of observed shear and low-angle compaction localization zones, or bands, as localization commences. Total strain measured experimentally partitions into: A) elastic strain with constant moduli, B) elastic strain due to stress dependence of moduli, C) elastic strain due to moduli degradation with increasing plastic strain, and D) plastic strain. The third term is the elastic-plastic coupling strain, and though often ignored, contributes significantly to pre-failure total strain for brittle and transitional tests. Constitutive parameters and localization predictions derived from experiments are compared to theoretical predictions. In the brittle regime, predictions of band angles (angle between band normal and maximum compression) demonstrate good agreement with observed shear band angles. Compaction localization was observed in the transitional regime in between shear localization and spatially pervasive compaction, over a small range of mean stresses. In contrast with predictions however, detailed acoustic emissions analyses in this regime show low angle, compaction-dominated but shear-enhanced, localization.

An evaluation of the lap-shear test for Sn-rich solder/Cu couples: Experiments and simulation

Science.gov (United States)

Chawla, N.; Shen, Y.-L.; Deng, X.; Ege, E. S.

2004-12-01

The lap-shear technique is commonly used to evaluate the shear, creep, and thermal fatigue behavior of solder joints. We have conducted a parametric experimental and modeling study, on the effect of testing and geometrical parameters on solder/copper joint response in lap-shear. It was shown that the farfield applied strain is quite different from the actual solder strain (measured optically). Subtraction of the deformation of the Cu substrate provides a reasonable approximation of the solder strain in the elastic regime, but not in the plastic regime. Solder joint thickness has a profound effect on joint response. The solder response moves progressively closer to “true” shear response with increasing joint thickness. Numerical modeling using finite-element analyses were performed to rationalize the experimental findings. The same lap-shear configuration was used in the simulation. The input response for solder was based on the experimental tensile test result on bulk specimens. The calculated shear response, using both the commonly adopted far-field measure and the actual shear strain in solder, was found to be consistent with the trends observed in the lap-shear experiments. The geometric features were further explored to provide physical insight into the problem. Deformation of the substrate was found to greatly influence the shear behavior of the solder.

Draft Genome Sequence of Bacillus aryabhattai Strain PHB10, a Poly(3-Hydroxybutyrate)-Accumulating Bacterium Isolated from Domestic Sewerage.

Science.gov (United States)

Balakrishna Pillai, Aneesh; Jaya Kumar, Arjun; Thulasi, Kavitha; Reghunathan, Dinesh; Prasannakumar, Manoj; Kumarapillai, Harikrishnan

2017-10-12

Bacillus aryabhattai PHB10 is a poly(3-hydroxybutyrate) (PHB)-accumulating bacterium isolated from domestic sewerage. Here, we report the 4.19-Mb draft genome sequence, with 4,050 protein-coding genes and a G+C content of 37.5%. This sequence will be helpful in the study of the high-level PHB accumulation mechanism of the strain. Copyright © 2017 Balakrishna Pillai et al.

Sense of shear and displacement estimates in the Abeibara-Rarhous late Pan-African shear zone, Adrar des Iforas, Mali

Science.gov (United States)

Boullier, Anne-Marie

The late Pan-African Abeibara-Rarhous shear zone in the Adrar des Iforas (Mali) is described and studied with the aim of defining the direction, sense of movement and amount of displacement along the zone. It is a strike-slip shear zone, the dextral sense of which is demonstrated at the scale of the map by the rotation of the related mylonitic foliation and at the scale of the thin section with characteristic microstructures. Preferred orientation of quartz c-axes is tentatively used; three quartz-rich samples of 35% or more quartz indicate dextral strike-slip movement, but other samples do not show preferred orientation of quartz c-axes. Strain measurements have been performed on one half of the shear zone using established techniques and a new technique using the thickness of mylonitic layering. The results vary along the length of the shear zone when using the same method and for the same cross-section when using the three methods together. A mean value of 4 km is obtained for total displacement which is low when considering the apparent width of the shear zone. This result is discussed in view of the assumptions involved in the strain estimation. The tectonic history of the Abeibara-Rarhous shear zone and its significance in the Trans-Saharan Pan-African collisional belt are discussed.

Experimental determination of the stress/strain situation in a sheared tunnel model with canister

International Nuclear Information System (INIS)

Pusch, R.

1978-03-01

A previous report concerned a technical matter which could be of great importance as regards the mechanical strength of canisters embedded in a bentonite/quartz buffer mass, i.e. the effect of a differential movement triggered by a critical deviatoric stress condition. Even if this is extremely unlikeley to occur it was considered to be of importance to verify the theoretical expressions for the maximum bending moment and maximum shear force. A special reason was to test the hypothesis that the contact pressure would soon reach a high value and then stay fairly constant when the displacement increased. The theoretical approach requires that the stress/strain properties of the fill are thoroghly investigated and described in therms of a mathematical model. Experience shows that this may be a tedions and difficult task. (L.E.)

Shear banding, discontinuous shear thickening, and rheological phase transitions in athermally sheared frictionless disks

Science.gov (United States)

Vâgberg, Daniel; Olsson, Peter; Teitel, S.

2017-05-01

We report on numerical simulations of simple models of athermal, bidisperse, soft-core, massive disks in two dimensions, as a function of packing fraction ϕ , inelasticity of collisions as measured by a parameter Q , and applied uniform shear strain rate γ ˙. Our particles have contact interactions consisting of normally directed elastic repulsion and viscous dissipation, as well as tangentially directed viscous dissipation, but no interparticle Coulombic friction. Mapping the phase diagram in the (ϕ ,Q ) plane for small γ ˙, we find a sharp first-order rheological phase transition from a region with Bagnoldian rheology to a region with Newtonian rheology, and show that the system is always Newtonian at jamming. We consider the rotational motion of particles and demonstrate the crucial importance that the coupling between rotational and translational degrees of freedom has on the phase structure at small Q (strongly inelastic collisions). At small Q , we show that, upon increasing γ ˙, the sharp Bagnoldian-to-Newtonian transition becomes a coexistence region of finite width in the (ϕ ,γ ˙) plane, with coexisting Bagnoldian and Newtonian shear bands. Crossing this coexistence region by increasing γ ˙ at fixed ϕ , we find that discontinuous shear thickening can result if γ ˙ is varied too rapidly for the system to relax to the shear-banded steady state corresponding to the instantaneous value of γ ˙.

Imaging Shear Strength Along Subduction Faults

Science.gov (United States)

Bletery, Quentin; Thomas, Amanda M.; Rempel, Alan W.; Hardebeck, Jeanne L.

2017-11-01

Subduction faults accumulate stress during long periods of time and release this stress suddenly, during earthquakes, when it reaches a threshold. This threshold, the shear strength, controls the occurrence and magnitude of earthquakes. We consider a 3-D model to derive an analytical expression for how the shear strength depends on the fault geometry, the convergence obliquity, frictional properties, and the stress field orientation. We then use estimates of these different parameters in Japan to infer the distribution of shear strength along a subduction fault. We show that the 2011 Mw9.0 Tohoku earthquake ruptured a fault portion characterized by unusually small variations in static shear strength. This observation is consistent with the hypothesis that large earthquakes preferentially rupture regions with relatively homogeneous shear strength. With increasing constraints on the different parameters at play, our approach could, in the future, help identify favorable locations for large earthquakes.

Imaging shear strength along subduction faults

Science.gov (United States)

Bletery, Quentin; Thomas, Amanda M.; Rempel, Alan W.; Hardebeck, Jeanne L.

2017-01-01

Subduction faults accumulate stress during long periods of time and release this stress suddenly, during earthquakes, when it reaches a threshold. This threshold, the shear strength, controls the occurrence and magnitude of earthquakes. We consider a 3-D model to derive an analytical expression for how the shear strength depends on the fault geometry, the convergence obliquity, frictional properties, and the stress field orientation. We then use estimates of these different parameters in Japan to infer the distribution of shear strength along a subduction fault. We show that the 2011 Mw9.0 Tohoku earthquake ruptured a fault portion characterized by unusually small variations in static shear strength. This observation is consistent with the hypothesis that large earthquakes preferentially rupture regions with relatively homogeneous shear strength. With increasing constraints on the different parameters at play, our approach could, in the future, help identify favorable locations for large earthquakes.

Inter-Rifting and Inter-Seismic Strain Accumulation in a Propagating Ridge System: A Geodetic Study from South Iceland

Science.gov (United States)

Travis, M. E.; La Femina, P. C.; Geirsson, H.

2012-12-01

The Mid-Atlantic Ridge, a slow spreading (~19 mm/yr) mid-ocean ridge boundary between the North American and Eurasian plates, is exposed subaerially in Iceland as the result of ridge-hotspot interaction. Plate spreading in Iceland is accommodated along neovolcanic zones comprised of central volcanoes and their fissure swarms. In south Iceland plate motion is partitioned between the Western Volcanic Zone (WVZ) and Eastern Volcanic Zone (EVZ). The EVZ is propagating to the southwest, while the WVZ is dying out from the northeast. Plate motion across both systems has been accommodated by repeated rifting events and fissure eruptions. In this study we investigate whether the WVZ is active and accumulating strain, and how strain is partitioned between the WVZ and EVZ. We also test how strain is accumulating along fissure swarms within the EVZ (i.e. is strain accumulation localized to one fissure swarm, or are multiple systems active?). We use GPS data and elastic block models run using the program DEFNODE to investigate these issues. GPS data are processed using the GIPSY-OASIS II software, and have been truncated to the 2000.5-2011 time period to avoid co-seismic displacement from the two June 2000 South Iceland Seismic Zone earthquakes. We also truncate the time series for sites within 20 km of Eyjafjallajökull to the beginning of 2010 to eliminate deformation associated with the March 2010 eruption of that volcano. We correct for co-seismic displacement from the two May 2008 SISZ earthquakes, inflation at Hekla volcano and the horizontal component of glacial isostatic rebound (GIA). Our best-fit model for inter-rifting and inter-seismic elastic strain accumulation suggests 80-90% of spreading is accommodated in the EVZ with the other 10-20% accommodated by the WVZ. The best-fit location of the EVZ is between Veidivotn and Lakigigar in an area of no Holocene volcanic activity. We suggest the WVZ is only active at Hengill and its associated fissure swarm. Geologic and

Strain differences of cadmium-induced hepatotoxicity in Wistar-Imamichi and Fischer 344 rats: involvement of cadmium accumulation

International Nuclear Information System (INIS)

Shimada, Hideaki; Takamure, Yasutaka; Shimada, Akinori; Yasutake, Akira; Waalkes, Michael P.; Imamura, Yorishige

2004-01-01

We previously reported that Wistar-Imamichi (WI) rats have a strong resistance to cadmium (Cd)-induced lethality compared to other strains such as Fischer 344 (Fischer) rats. The present study was designed to establish biochemical and histological differences in Cd toxicity in WI and Fischer rats, and to clarify the mechanistic basis of these strain differences. A single Cd (4.5 mg/kg, s.c.) treatment caused a significant increase in serum alanine aminotransferase activity, indicative of hepatotoxicity, in Fischer rats, but did not in WI rats. This difference in hepatotoxic response to Cd was supported by pathological analysis. After treatment with Cd at doses of 3.0, 3.5 and 4.5 mg/kg, the hepatic and renal accumulation of Cd was significantly lower in the WI rats than in the Fischer rats, indicating a kinetic mechanism for the observed strain differences in Cd toxicity. Thus, the remarkable resistance to Cd-induced hepatotoxicity in WI rats is associated, at least in part, with a lower tissue accumulation of the metal. Hepatic and renal zinc (Zn) contents after administration were similarly lower in WI than in Fischer rats. When Zn was administered in combination with Cd to Fischer rats, it decreased Cd contents in the liver and kidney, and exhibited a significant protective effect against the toxicity of Cd. We propose the possibility that Zn transporter plays an important role in the strain difference of Cd toxicity in WI and Fischer rats

Shear-induced breaking of cages in colloidal glasses: Scattering experiments and mode coupling theory

Energy Technology Data Exchange (ETDEWEB)

Amann, Christian P., E-mail: Christian.2.Amann@uni-konstanz.de; Fuchs, Matthias, E-mail: Matthias.Fuchs@uni-konstanz.de [Fachbereich Physik, Universität Konstanz, 78457 Konstanz (Germany); Denisov, Dmitry; Dang, Minh Triet; Schall, Peter [Van der Waals-Zeeman Institute, University of Amsterdam, Amsterdam (Netherlands); Struth, Bernd [Deutsches Elektronen-Synchrotron, Hamburg (Germany)

2015-07-21

We employ x-ray scattering on sheared colloidal suspensions and mode coupling theory to study structure factor distortions of glass-forming systems under shear. We find a transition from quadrupolar elastic distortion at small strains to quadrupolar and hexadecupolar modes in the stationary state. The latter are interpreted as signatures of plastic rearrangements in homogeneous, thermalized systems. From their transient evolution with strain, we identify characteristic strain and length-scale values where these plastic rearrangements dominate. This characteristic strain coincides with the maximum of the shear stress versus strain curve, indicating the proliferation of plastic flow. The hexadecupolar modes dominate at the wavevector of the principal peak of the equilibrium structure factor that is related to the cage-effect in mode coupling theory. We hence identify the structural signature of plastic flow of glasses.

Shear-induced breaking of cages in colloidal glasses: Scattering experiments and mode coupling theory

International Nuclear Information System (INIS)

Amann, Christian P.; Fuchs, Matthias; Denisov, Dmitry; Dang, Minh Triet; Schall, Peter; Struth, Bernd

2015-01-01

We employ x-ray scattering on sheared colloidal suspensions and mode coupling theory to study structure factor distortions of glass-forming systems under shear. We find a transition from quadrupolar elastic distortion at small strains to quadrupolar and hexadecupolar modes in the stationary state. The latter are interpreted as signatures of plastic rearrangements in homogeneous, thermalized systems. From their transient evolution with strain, we identify characteristic strain and length-scale values where these plastic rearrangements dominate. This characteristic strain coincides with the maximum of the shear stress versus strain curve, indicating the proliferation of plastic flow. The hexadecupolar modes dominate at the wavevector of the principal peak of the equilibrium structure factor that is related to the cage-effect in mode coupling theory. We hence identify the structural signature of plastic flow of glasses

Shear-induced breaking of cages in colloidal glasses: Scattering experiments and mode coupling theory.

Science.gov (United States)

Amann, Christian P; Denisov, Dmitry; Dang, Minh Triet; Struth, Bernd; Schall, Peter; Fuchs, Matthias

2015-07-21

We employ x-ray scattering on sheared colloidal suspensions and mode coupling theory to study structure factor distortions of glass-forming systems under shear. We find a transition from quadrupolar elastic distortion at small strains to quadrupolar and hexadecupolar modes in the stationary state. The latter are interpreted as signatures of plastic rearrangements in homogeneous, thermalized systems. From their transient evolution with strain, we identify characteristic strain and length-scale values where these plastic rearrangements dominate. This characteristic strain coincides with the maximum of the shear stress versus strain curve, indicating the proliferation of plastic flow. The hexadecupolar modes dominate at the wavevector of the principal peak of the equilibrium structure factor that is related to the cage-effect in mode coupling theory. We hence identify the structural signature of plastic flow of glasses.

Shear zone nucleation and deformation transient: effect of heterogeneities and loading conditions in experimentally deformed calcite

Science.gov (United States)

Morales, L. F. G.; Rybacki, E.; Dresen, G. H.; Kilian, R.

2015-12-01

In the Earth's middle to lower crust, strain is frequently localized along ductile shear zones, which commonly nucleate at structural and material heterogeneities. To investigate shear zone nucleation and development due to heterogeneities, we performed constant strain-rate (CSR) and constant stress (CS) simple shear (torsion) deformation experiments on Carrara marble samples containing weak (limestone) inclusions. The experiments were conducted in a Paterson-type gas deformation apparatus at 900 °C temperature and 400 MPa confining pressure and maximum bulk shear strains of 3. Peak shear stress was about 20 MPa for all the samples, followed by smooth weakening and steady state behavior. The strain is predominantly localized in the host marble within the process zone in front of the inclusion, defined by a zone of intense grain size reduction due to dynamic recrystallization. In CS tests a narrow shear zone developed in front of the inclusion, whereas in CSR experiments the deformation is more heterogeneously distributed, up to g=3.. In the later, secondary foliations oblique to the process zone and alternating thin, high-strain layers are common. In samples deformed at the same shear strain (g=1), the average recrystallized grain size in the process zone is similar for CS and CSR conditions. Crystallographic preferred orientation (CPO) measurements shows that different grain sizes have slightly different CPO patterns. CPO strength varies for different grain sizes, with a CPO strength peak between 40-50 μm, decreasing progressively within smaller grain size, but with secondary peaks for different coarse-grained sizes. Our observations suggest that the initial formation and transient deformation of shear zones is strongly affected by loading conditions.

Examining shear processes during magma ascent

Science.gov (United States)

Kendrick, J. E.; Wallace, P. A.; Coats, R.; Lamur, A.; Lavallée, Y.

2017-12-01

Lava dome eruptions are prone to rapid shifts from effusive to explosive behaviour which reflects the rheology of magma. Magma rheology is governed by composition, porosity and crystal content, which during ascent evolves to yield a rock-like, viscous suspension in the upper conduit. Geophysical monitoring, laboratory experiments and detailed field studies offer the opportunity to explore the complexities associated with the ascent and eruption of such magmas, which rest at a pivotal position with regard to the glass transition, allowing them to either flow or fracture. Crystal interaction during flow results in strain-partitioning and shear-thinning behaviour of the suspension. In a conduit, such characteristics favour the formation of localised shear zones as strain is concentrated along conduit margins, where magma can rupture and heal in repetitive cycles. Sheared magmas often record a history of deformation in the form of: grain size reduction; anisotropic permeable fluid pathways; mineral reactions; injection features; recrystallisation; and magnetic anomalies, providing a signature of the repetitive earthquakes often observed during lava dome eruptions. The repetitive fracture of magma at ( fixed) depth in the conduit and the fault-like products exhumed at spine surfaces indicate that the last hundreds of meters of ascent may be controlled by frictional slip. Experiments on a low-to-high velocity rotary shear apparatus indicate that shear stress on a slip plane is highly velocity dependent, and here we examine how this influences magma ascent and its characteristic geophysical signals.

Dynamic compressive constitutive relation and shearing instability of metallic neodymium

International Nuclear Information System (INIS)

Wang Huanran; Cai Canyuan; Chen Danian; Ma Dongfang; Hou Yanjun; Wu Shanxing

2011-01-01

Highlights: → Dynamic constitutive relation of Nd was determined in first compression of SHPB. → Deformation of Nd in multi-compression of SHPB were recorded by high-speed camera. → Constitutive relation of Nd was adjusted in modeling large deformation of Nd. → Results of SDDM investigation of recovered Nd specimens showed shearing fracture. → Shearing instability of Nd was estimated with constitutive relation. - Abstract: Based on static tests on MTS and dynamic tests on split Hopkinson pressure bar (SHPB) during the first loading, this study determined the dynamic compressive constitutive relation of metallic Nd. Based on large deformations of metallic Nd specimens generated by the multi-compressive loadings during SHPB tests, and recorded by a high-speed camera, the results of numerical simulations for SHPB test processes were used to extend the determined constitutive relation from small strain to large strain. The shearing instability strain in dynamic compressive deformations of metallic Nd was estimated with the extended constitutive relation according to the criterion given by Batra and Wei, and was compared with the average strain of recovered specimens.

Shear crack formation and propagation in fiber reinforced cementitious composites (FRCC)

DEFF Research Database (Denmark)

Paegle, Ieva; Fischer, Gregor

2011-01-01

Knowledge of the mechanisms controlling crack formation, propagation and failure of FRCC under shear loading is currently limited. This paper presents a study that utilized photogrammetry to monitor the shear deformations of two FRCC materials and ordinary concrete (OC). Multiple shear cracks...... and strain hardening of both FRCC materials was observed under shear loading. The influence of fibers, fiber type, including polyvinyl alcohol (PVA) and polypropylene (PP) fibers, and shear crack angle were investigated. Based upon photogrammetric results, fundamental descriptions of shear crack opening...

Shear crack formation and propagation in fiber reinforced cementitious composites (FRCC)

DEFF Research Database (Denmark)

Paegle, Ieva; Fischer, Gregor

2012-01-01

Knowledge of the mechanisms controlling crack formation, propagation and failure of FRCC under shear loading is currently limited. This paper presents a study that utilized photogrammetry to monitor the shear deformations of two FRCC materials and ordinary concrete (OC). Multiple shear cracks...... and strain hardening of both FRCC materials was observed under shear loading. The influence of fibers, fiber type, including polyvinyl alcohol (PVA) and polypropylene (PP) fibers, and shear crack angle were investigated. Based upon photogrammetric results, fundamental descriptions of shear crack opening...

Domino structures evolution in strike-slip shear zones; the importance of the cataclastic flow

Science.gov (United States)

Moreira, N.; Dias, R.

2018-05-01

The Porto-Tomar-Ferreira do Alentejo dextral Shear Zone is one of the most important structures of the Iberian Variscides. In its vicinity, close to Abrantes (Central Portugal), a localized heterogeneous strain pattern developed in a decimetric metamorphic siliceous multilayer. This complex pattern was induced by the D2 dextral shearing of the early S0//S1 foliation in brittle-ductile conditions, giving rise to three main shear zone families. One of these families, with antithetic kinematics, delimits blocks with rigid clockwise rotation surrounded by coeval cataclasites, generating a local domino structure. The proposed geometrical and kinematic analysis, coupled with statistical studies, highlights the relation between subsidiary shear zones and the main shear zone. Despite the heterogeneous strain pattern, a quantitative approach of finite strain was applied based on the restoration of the initial fracture pattern. This approach shows the importance of the cataclastic flow coupled with the translational displacement of the domino domain in solving space problems related to the rigid block rotation. Such processes are key in allowing the rigid block rotation inside shear zones whenever the simple shear component is a fundamental mechanism.

Development of a Shear Deformable Element Using the Absolute Nodal Coordinate Formulation

National Research Council Canada - National Science Library

Omar, Mohamed

2000-01-01

.... The effect of the shear deformation is accounted for without the need for introducing Timoshenko's shear coefficient By using the absolute coordinates, the nonlinear strain-displacement relationships...

Experimental study and FEM simulation of the simple shear test of cylindrical rods

Science.gov (United States)

Wirti, Pedro H. B.; Costa, André L. M.; Misiolek, Wojciech Z.; Valberg, Henry S.

2018-05-01

In the presented work an experimental simple shear device for cutting cylindrical rods was used to obtain force-displacement data for a low-carbon steel. In addition, and FEM 3D-simulation was applied to obtain internal shear stress and strain maps for this material. The experimental longitudinal grid patterns and force-displacement curve were compared with numerical simulation results. Many aspects of the elastic and plastic deformations were described. It was found that bending reduces the shear yield stress of the rod material. Shearing starts on top and bottom die-workpiece contact lines evolving in an arc-shaped area. Due to this geometry, stress concentrates on the surface of the rod until the level of damage reaches the critical value and the fracture starts here. The volume of material in the plastic zone subjected to shearing stress has a very complex shape and is function of a dimensionless geometrical parameter. Expressions to calculate the true shear stress τ and strain γ from the experimental force-displacement data were proposed. The equations' constants are determined by fitting the experimental curve with the stress τ and strain γ simulation point tracked data.

Modeling fracture in the context of a strain-limiting theory of elasticity: a single anti-plane shear crack

KAUST Repository

Rajagopal, K. R.

2011-01-06

This paper is the first part of an extended program to develop a theory of fracture in the context of strain-limiting theories of elasticity. This program exploits a novel approach to modeling the mechanical response of elastic, that is non-dissipative, materials through implicit constitutive relations. The particular class of models studied here can also be viewed as arising from an explicit theory in which the displacement gradient is specified to be a nonlinear function of stress. This modeling construct generalizes the classical Cauchy and Green theories of elasticity which are included as special cases. It was conjectured that special forms of these implicit theories that limit strains to physically realistic maximum levels even for arbitrarily large stresses would be ideal for modeling fracture by offering a modeling paradigm that avoids the crack-tip strain singularities characteristic of classical fracture theories. The simplest fracture setting in which to explore this conjecture is anti-plane shear. It is demonstrated herein that for a specific choice of strain-limiting elasticity theory, crack-tip strains do indeed remain bounded. Moreover, the theory predicts a bounded stress field in the neighborhood of a crack-tip and a cusp-shaped opening displacement. The results confirm the conjecture that use of a strain limiting explicit theory in which the displacement gradient is given as a function of stress for modeling the bulk constitutive behavior obviates the necessity of introducing ad hoc modeling constructs such as crack-tip cohesive or process zones in order to correct the unphysical stress and strain singularities predicted by classical linear elastic fracture mechanics. © 2011 Springer Science+Business Media B.V.

Laboratory studies on the effects of shear on fish: Final report

Energy Technology Data Exchange (ETDEWEB)

Neitzel, Duane A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Richmond, M. C. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Dauble, D. D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Mueller, R. P. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Moursund, R. A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Abernethy, C. S. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Guensch, G. R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Cada, G. F. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2000-09-01

The overall objective of these studies was to specify an index describing the hydraulic force that fish experience when subjected to a shear environment. Fluid shear is a phenomenon that is important to fish. However, elevated levels of shear may result in strain rates that injure or kill fish. At hydroelectric generating facilities, concerns have been expressed that strain rates associated with passage through turbines, spillways, and fish bypass systems may adversely affect migrating fish. Development of fish-friendly hydroelectric turbines requires knowledge of the physical forces (injury mechanisms) that impact entrained fish and the fish’s tolerance to these forces. It requires up-front, pre-design specifications for the environmental conditions that occur within the turbine system; in other words, determining or assuming conditions known to injure fish will assist engineers in the design of a fish-friendly turbine system. To address the development of biological specifications, this experiment designed and built a test facility where juvenile fish could be subjected to a range of shear environments and quantified their biological response. The test data reported here provide quantified strain rates and the relationship of these forces to direct and indirect biological effects on fish. The study concludes that juvenile salmonids and American shad should survive shear environments where strain rates do not exceed 500 cm/s/cm at a Dy of 1.8 cm. Additional studies are planned with a sensor fish to better link hydraulic conditions found within the laboratory and field environments.

Magma shearing and friction in the volcanic conduit: A crystal constraint

Science.gov (United States)

Wallace, P. A.; Kendrick, J. E.; Henton De Angelis, S.; Ashworth, J. D.; Coats, R.; Miwa, T.; Mariani, E.; Lavallée, Y.

2017-12-01

Magma shearing and friction processes in the shallow volcanic conduit are typical manifestations of strain localisation, which in turn can have an influential role on magma ascent dynamics. The thermal consequences of such events could drive the destabilisation of magma and thus dictate the style of activity at the surface. Shear heating and fault friction are prime candidates for the generation of significant quantities of heat. Here we use a combination of field and experimental evidence to investigate how crystals can act as sensitive recorders of both physical and chemical processes occurring in the shallow volcanic conduit. Spine extrusion during the closing of the 1991-95 eruption at Unzen volcano, Japan, provided the unique opportunity to investigate marginal shear zone formation, which preserves a relic of the deformation during magma ascent. Our results show that crystals can effectively act as a deformation marker during magma ascent through the viscous-brittle transition by accommodating strain in the form of crystal plasticity before fracturing (comminution). Electron backscatter diffraction (EBSD) reveals up to 40° lattice distortion of biotite phenocrysts in zones of high shear, with negligible plasticity further away. Plagioclase microlites display a systematic plastic response to an increase in shear intensity, as recorded by an increase in lattice distortion towards the spine margin of up to 9°. This localisation of strain within the shear zone is also accompanied by the destabilisation of hydrous mineral phases (i.e. amphibole), compaction of pores (23-13% Φ), glass devitrification and magnetic anomalies. The narrow zone of disequilibrium textures suggests the likely effect of a thermal input due to strain localisation being the contributing factor. These observations are complimented by high-temperature high-velocity rotary shear experiments which simulate the deformation evolution during shear. Hence, understanding these shallow volcanic

Predicting Shear Transformation Events in Metallic Glasses

Science.gov (United States)

Xu, Bin; Falk, Michael L.; Li, J. F.; Kong, L. T.

2018-03-01

Shear transformation is the elementary process for plastic deformation of metallic glasses, the prediction of the occurrence of the shear transformation events is therefore of vital importance to understand the mechanical behavior of metallic glasses. In this Letter, from the view of the potential energy landscape, we find that the protocol-dependent behavior of shear transformation is governed by the stress gradient along its minimum energy path and we propose a framework as well as an atomistic approach to predict the triggering strains, locations, and structural transformations of the shear transformation events under different shear protocols in metallic glasses. Verification with a model Cu64 Zr36 metallic glass reveals that the prediction agrees well with athermal quasistatic shear simulations. The proposed framework is believed to provide an important tool for developing a quantitative understanding of the deformation processes that control mechanical behavior of metallic glasses.

Relating rheology to geometry in large-scale natural shear zones

Science.gov (United States)

Platt, John

2016-04-01

The geometry and width of the ductile roots of plate boundary scale faults are very poorly understood. Some field and geophysical data suggests widths of tens of km in the lower crust, possibly more in the upper mantle. Other observations suggest they are much narrower. Dip slip shear zones may flatten out and merge into zones of subhorizontal lower crustal or asthenospheric flow. The width of a ductile shear zone is simply related to relative velocity and strain rate. Strain rate is related to stress through the constitutive relationship. Can we constrain the stress, and do we understand the rheology of materials in ductile shear zones? A lot depends on how shear zones are initiated. If they are localized by pre-existing structures, width and/or rheology may be inherited, and we have too many variables. If shear zones are localized primarily by shear heating, initial shear stress has to be very high (> 1 GPa) to overcome conductive heat loss, and very large feedbacks (both positive and negative) make the system highly unstable. Microstructural weakening requires a minimum level of stress to cause deformation and damage in surrounding rock, thereby buffering the stress. Microstructural weakening leads to grain-size sensitive creep, for which we have constitutive laws, but these are complicated by phase mixing in polyphase materials, by viscous anisotropy, by hydration, and by changes in mineral assemblage. Here are some questions that need to be addressed. (1) If grain-size reduction by dynamic recrystallization results in a switch to grain-size sensitive creep (GSSC) in a stress-buffered shear zone, does dynamic recrystallization stop? Does grain growth set in? If grain-size is still controlled by dislocation processes, then the effective stress exponent for GSSC is 4-5, even though the dominant mechanism may be diffusion and/or grain-boundary sliding (GBS). (2) Is phase mixing in ultramylonites primarily a result of GBS + neighbour switching, creep cavitation and

Damage Assessment of Heat Resistant Steels through Electron BackScatter Diffraction Strain Analysis under Creep and Creep-Fatigue Conditions

Science.gov (United States)

Fujiyama, Kazunari; Kimachi, Hirohisa; Tsuboi, Toshiki; Hagiwara, Hiroyuki; Ogino, Shotaro; Mizutani, Yoshiki

EBSD(Electron BackScatter Diffraction) analyses were conducted for studying the quantitative microstructural metrics of creep and creep-fatigue damage for austenitic SUS304HTB boiler tube steel and ferritic Mod.9Cr piping steel. KAM(Kernel Average Misorientation) maps and GOS(Grain Orientation Spread) maps were obtained for these samples and the area averaged values KAMave and GOSave were obtained. While the increasing trends of these misorientation metrics were observed for SUS304HTB steel, the decreasing trends were observed for damaged Mod.9Cr steel with extensive recovery of subgrain structure. To establish more universal parameter representing the accumulation of damage to compensate these opposite trends, the EBSD strain parameters were introduced for converting the misorientation changes into the quantities representing accumulated permanent strains during creep and creep-fatigue damage process. As KAM values were dependent on the pixel size (inversely proportional to the observation magnification) and the permanent strain could be expressed as the shear strain which was the product of dislocation density, Burgers vector and dislocation movement distance, two KAM strain parameters MεKAMnet and MεδKAMave were introduced as the sum of product of the noise subtracted KAMnet and the absolute change from initial value δKAMave with dislocation movement distance divided by pixel size. MεδKAMave parameter showed better relationship both with creep strain in creep tests and accumulated creep strain range in creep-fatigue tests. This parameter can be used as the strain-based damage evaluation and detector of final failure.

Shear behavior of reinforced Engineered Cementitious Composites (ECC) beams

DEFF Research Database (Denmark)

Paegle, Ieva; Fischer, Gregor

2010-01-01

This paper describes an experimental investigation of the shear behavior of beams consisting of steel reinforced Engineered Cementitious Composites (ECC). Based on the strain hardening and multiple cracking behavior of ECC, this study investigates the extent to which ECC can improve the shear...... capacity of beams loaded primarily in shear and if ECC can partially or fully replace the conventional transverse steel reinforcement in beams. However, there is a lack of understanding of how the fibers affect the shear carrying capacity and deformation behavior of structural members if used either...

The electronic origin of shear-induced direct to indirect gap transition and anisotropy diminution in phosphorene.

Science.gov (United States)

Sa, Baisheng; Li, Yan-Ling; Sun, Zhimei; Qi, Jingshan; Wen, Cuilian; Wu, Bo

2015-05-29

Artificial monolayer black phosphorus, so-called phosphorene, has attracted global interest with its distinguished anisotropic, optoelectronic, and electronic properties. Here, we unraveled the shear-induced direct-to-indirect gap transition and anisotropy diminution in phosphorene based on first-principles calculations. Lattice dynamic analysis demonstrates that phosphorene can sustain up to 10% applied shear strain. The bandgap of phosphorene experiences a direct-to- indirect transition when 5% shear strain is applied. The electronic origin of the direct-to-indirect gap transition from 1.54 eV at ambient conditions to 1.22 eV at 10% shear strain for phosphorene is explored. In addition, the anisotropy diminution in phosphorene is discussed by calculating the maximum sound velocities, effective mass, and decomposed charge density, which signals the undesired shear-induced direct-to-indirect gap transition in applications of phosphorene for electronics and optoelectronics. On the other hand, the shear-induced electronic anisotropy properties suggest that phosphorene can be applied as the switcher in nanoelectronic applications.

Discrete Analysis of Damage and Shear Banding in Argillaceous Rocks

Science.gov (United States)

Dinç, Özge; Scholtès, Luc

2018-05-01

A discrete approach is proposed to study damage and failure processes taking place in argillaceous rocks which present a transversely isotropic behavior. More precisely, a dedicated discrete element method is utilized to provide a micromechanical description of the mechanisms involved. The purpose of the study is twofold: (1) presenting a three-dimensional discrete element model able to simulate the anisotropic macro-mechanical behavior of the Callovo-Oxfordian claystone as a particular case of argillaceous rocks; (2) studying how progressive failure develops in such material. Material anisotropy is explicitly taken into account in the numerical model through the introduction of weakness planes distributed at the interparticle scale following predefined orientation and intensity. Simulations of compression tests under plane-strain and triaxial conditions are performed to clarify the development of damage and the appearance of shear bands through micromechanical analyses. The overall mechanical behavior and shear banding patterns predicted by the numerical model are in good agreement with respect to experimental observations. Both tensile and shear microcracks emerging from the modeling also present characteristics compatible with microstructural observations. The numerical results confirm that the global failure of argillaceous rocks is well correlated with the mechanisms taking place at the local scale. Specifically, strain localization is shown to directly result from shear microcracking developing with a preferential orientation distribution related to the orientation of the shear band. In addition, localization events presenting characteristics similar to shear bands are observed from the early stages of the loading and might thus be considered as precursors of strain localization.

Shear-driven dynamic clusters in a colloidal glass

Science.gov (United States)

Eisenmann, Christoph; Kim, Chanjoong; Mattsson, Johan; Weitz, David

2007-03-01

We investigate the effect of shear applied to a colloidal glass on a microscopic level using a shear device that can be mounted on top of a confocal microscope. We find that the glass yields at a critical strain of about 10%, independently of the shear rate. Surprisingly, the yielding is accompanied by an increase of cooperative particle movements and a formation of dynamic clusters which is in contrast to the normal glass transition where one typically finds heterogeneity increasing whilst moving towards the glass transition.

Introduction to the viewpoint set on shear bands

International Nuclear Information System (INIS)

Hutchinson, J.W.

1984-01-01

Recent work aimed at improving our understanding of shear banding and flow localization as modes of deformation and failure is summarized in the six viewpoint articles which follow. For the most part, the emphasis here is on the observation and analysis of shear banding in metals, but active efforts are also underway to understand the role of shear bands in the deformation and failure of soils and rocks. There is a tendency to regard shear bands as a failure mode, as indeed they often are. But extensive straining under highly constrained conditions such as rolling can give rise to profuse flow localization into shear bands which can be regarded as microscopic in the sense that their extent is on the scale of the grains rather than the overall dimensions of the block of material being deformed. Hatherly and Malin describe in detail the observation of such bands and emphasize that they should be considered as a mode of deformation under these circumstances. They relate the formation of the bands to microstructural aspects and discuss their role in the development of recrystallization textures. It will be clear from reading the articles in this viewpoint set that the beginnings of a quantitative theory of shear banding is in place. Continued progress will require parallel developments in constitutive theory and experimental observation. Moreover, basic questions remain to be explored related to the spatial development of the shear bands, their mutual interaction, their development into a failure mode, and how these are influenced by factors such as overall deformational constraint, rate of straining, and temperature

Shear Strength of Remoulding Clay Samples Using Different Methods of Moulding

Science.gov (United States)

Norhaliza, W.; Ismail, B.; Azhar, A. T. S.; Nurul, N. J.

2016-07-01

Shear strength for clay soil was required to determine the soil stability. Clay was known as a soil with complex natural formations and very difficult to obtain undisturbed samples at the site. The aim of this paper was to determine the unconfined shear strength of remoulded clay on different methods in moulding samples which were proctor compaction, hand operated soil compacter and miniature mould methods. All the samples were remoulded with the same optimum moisture content (OMC) and density that were 18% and 1880 kg/m3 respectively. The unconfined shear strength results of remoulding clay soils for proctor compaction method was 289.56kPa with the strain 4.8%, hand operated method was 261.66kPa with the strain 4.4% and miniature mould method was 247.52kPa with the strain 3.9%. Based on the proctor compaction method, the reduction percentage of unconfined shear strength of remoulded clay soil of hand operated method was 9.66%, and for miniature mould method was 14.52%. Thus, because there was no significant difference of reduction percentage of unconfined shear strength between three different methods, so it can be concluded that remoulding clay by hand operated method and miniature mould method were accepted and suggested to perform remoulding clay samples by other future researcher. However for comparison, the hand operated method was more suitable to form remoulded clay sample in term of easiness, saving time and less energy for unconfined shear strength determination purposes.

Microstructure and mechanical properties of commercially pure aluminum processed by accumulative back extrusion

International Nuclear Information System (INIS)

Haghdadi, N.; Zarei-Hanzaki, A.; Abou-Ras, D.

2013-01-01

Accumulative back extrusion (ABE), as a new severe plastic deformation (SPD) method, was applied on a commercially pure aluminum, resulting in an ultrafine microstructure. The grain refinement was attributed to the shearing and/or to the mechanical partitioning of the initial coarse grains as well as different dynamic recrystallization mechanisms (i.e., discontinues and continues ones). The effects of imposing several passes along with the strain reversal path method during consecutive ABE passes were discussed. Mechanical characterization revealed that the yield and ultimate strength of pure Al were significantly increased through applying ABE. This was related to grain boundary and dislocation strengthening, as well as to Orowan dislocation bowing mechanisms. The elongation, however, was deteriorated after ABE processing. This was interpreted through the lack of ability of the material to accommodate the ABE-induced strain, inhomogeneous distribution of strain across the ABE-processed workpieces, and the reduced work hardening capacity of the fine-grained aluminum. The formability index and static toughness were also considered to verify the overall mechanical performance of the ABE-processed pure Al

Effect of Different Loading Conditions on the Nucleation and Development of Shear Zones Around Material Heterogeneities

Science.gov (United States)

Rybacki, E.; Nardini, L.; Morales, L. F.; Dresen, G.

2017-12-01

Rock deformation at depths in the Earth's crust is often localized in high temperature shear zones, which occur in the field at different scales and in a variety of lithologies. The presence of material heterogeneities has long been recognized to be an important cause for shear zones evolution, but the mechanisms controlling initiation and development of localization are not fully understood, and the question of which loading conditions (constant stress or constant deformation rate) are most favourable is still open. To better understand the effect of boundary conditions on shear zone nucleation around heterogeneities, we performed a series of torsion experiments under constant twist rate (CTR) and constant torque (CT) conditions in a Paterson-type deformation apparatus. The sample assemblage consisted of copper-jacketed Carrara marble hollow cylinders with one weak inclusion of Solnhofen limestone. The CTR experiments were performed at maximum bulk strain rates of 1.8-1.9*10-4 s-1, yielding shear stresses of 19-20 MPa. CT tests were conducted at shear stresses between 18.4 and 19.8 MPa resulting in shear strain rates of 1-2*10-4 s-1. All experiments were run at 900 °C temperature and 400 MPa confining pressure. Maximum bulk shear strains (γ) were ca. 0.3 and 1. Strain localized within the host marble in front of the inclusion in an area termed process zone. Here grain size reduction is intense and local shear strain (estimated from markers on the jackets) is up to 8 times higher than the applied bulk strain, rapidly dropping to 2 times higher at larger distance from the inclusion. The evolution of key microstructural parameters such as average grain size and average grain orientation spread (GOS, a measure of lattice distortion) within the process zone, determined by electron backscatter diffraction analysis, differs significantly as a function of loading conditions. Both parameters indicate that, independent of bulk strain and distance from the inclusion, the

Shear crack formation and propagation in reinforced Engineered Cementitious Composites

DEFF Research Database (Denmark)

Paegle, Ieva; Fischer, Gregor

2011-01-01

capacity of beams loaded primarily in shear. The experimental program consists of ECC with short randomly distributed polyvinyl alcohol (PVA) fiber beams with different stirrup arrangements and conventional reinforced concrete (R/C) counterparts for comparison. The shear crack formation mechanism of ECC......This paper describes an experimental investigation of the shear behaviour of beams consisting of steel reinforced Engineered Cementitious Composites (R/ECC). Based on the strain hardening and multiple cracking behaviour of ECC, this study investigates the extent to which ECC influences the shear...

A study on plastic strain accumulation caused by traveling of temperature distribution synchronizing with temperature rise

International Nuclear Information System (INIS)

Okajima, Satoshi

2016-01-01

The prevention of excessive deformation by thermal ratcheting is important in the design of high-temperature components of fast breeder reactors (FBR). This includes evaluation methods for a new type of thermal ratcheting caused by an axial traveling of temperature distribution, which corresponds to moving-up of liquid sodium surface in startup phase. Long range traveling of the axial temperature distribution brings flat plastic deformation profile in wide range. Therefore, at the center of this range, residual stress that brings shakedown behavior does not accumulate. As a result, repeating of this temperature traveling brings continuous accumulation of the plastic strain, even if there is no primary stress. In contrast, in the case with short range traveling, residual stress is caused by constraint against elastic part, and finally it results in shakedown. Because of this mechanism, we supposed that limit for the shakedown behavior depends on distance from the elastic part (i.e. half length of region with plastic deformation). In this paper, we examined characteristics of the accumulation of the plastic strain caused by realistic heat transients, namely, traveling of temperature distribution synchronizing with temperature rise. This examination was based on finite element analyses using elastic-perfectly plastic material. As a result, we confirmed that the shakedown limit depends not on the traveling range of the temperature distribution but the plastic deformation range, which was predicted by the elastic analysis. In the actual application, we can control the plastic deformation range by changing rate of the moving-up of liquid sodium surface. (author)

Torsional shear flow of granular materials: shear localization and minimum energy principle

Science.gov (United States)

Artoni, Riccardo; Richard, Patrick

2018-01-01

The rheological properties of granular matter submitted to torsional shear are investigated numerically by means of discrete element method. The shear cell is made of a cylinder filled by grains which are sheared by a bumpy bottom and submitted to a vertical pressure which is applied at the top. Regimes differing by their strain localization features are observed. They originate from the competition between dissipation at the sidewalls and dissipation in the bulk of the system. The effects of the (i) the applied pressure, (ii) sidewall friction, and (iii) angular velocity are investigated. A model, based on the purely local μ (I)-rheology and a minimum energy principle is able to capture the effect of the two former quantities but unable to account the effect of the latter. Although, an ad hoc modification of the model allows to reproduce all the numerical results, our results point out the need for an alternative rheology.

Effect of Shear Applied During a Pharmaceutical Process on Near Infrared Spectra.

Science.gov (United States)

Hernández, Eduardo; Pawar, Pallavi; Rodriguez, Sandra; Lysenko, Sergiy; Muzzio, Fernando J; Romañach, Rodolfo J

2016-03-01

This study describes changes observed in the near-infrared (NIR) diffuse reflectance (DR) spectra of pharmaceutical tablets after these tablets were subjected to different levels of strain (exposure to shear) during the mixing process. Powder shearing is important in the mixing of powders that are cohesive. Shear stress is created in a system by moving one surface over another causing displacements in the direction of the moving surface and is part of the mixing dynamics of particulates in many industries including the pharmaceutical industry. In continuous mixing, shear strain is developed within the process when powder particles are in constant movement and can affect the quality attributes of the final product such as dissolution. These changes in the NIR spectra could affect results obtained from NIR calibration models. The aim of the study was to understand changes in the NIR diffuse reflectance spectra that can be associated with different levels of strain developed during blend shearing of laboratory samples. Shear was applied using a Couette cell and tablets were produced using a tablet press emulator. Tablets with different shear levels were measured using NIR spectroscopy in the diffuse reflectance mode. The NIR spectra were baseline corrected to maintain the scattering effect associated with the physical properties of the tablet surface. Principal component analysis was used to establish the principal sources of variation within the samples. The angular dependence of elastic light scattering shows that the shear treatment reduces the size of particles and produces their uniform and highly isotropic distribution. Tablet compaction further reduces the diffuse component of scattering due to realignment of particles. © The Author(s) 2016.

Deformation and failure response of 304L stainless steel SMAW joint under dynamic shear loading

International Nuclear Information System (INIS)

Lee, Woei-Shyan; Cheng, J.-I.; Lin, C.-F.

2004-01-01

The dynamic shear deformation behavior and fracture characteristics of 304L stainless steel shielded metal arc welding (SMAW) joint are studied experimentally with regard to the relations between mechanical properties and strain rate. Thin-wall tubular specimens are deformed at room temperature under strain rates in the range of 8 x 10 2 to 2.8 x 10 3 s -1 using a torsional split-Hopkinson bar. The results indicate that the strain rate has a significant influence on the mechanical properties and fracture response of the tested SMAW joints. It is found that the flow stress, total shear strain to failure, work hardening rate and strain rate sensitivity all increase with increasing strain rate, but that the activation volume decreases. The observed dynamic shear deformation behavior is modeled using the Kobayashi-Dodd constitutive law, and it is shown that the predicted results are in good agreement with the experimental data. Fractographic analysis using scanning electron microscopy reveals that the tested specimens all fracture within their fusion zones, and that the primary failure mechanism is one of the extensive localized shearing. The fracture surfaces are characterized by the presence of many dimples. A higher strain rate tends to reduce the size of the dimples and to increase their density. The observed fracture features are closely related to the preceding flow behavior

Strain-accelerated dynamics of soft colloidal glasses

KAUST Repository

Agarwal, Praveen

2011-04-11

We have investigated strain-accelerated dynamics of soft glasses theoretically and experimentally. Mechanical rheology measurements performed on a variety of systems reveal evidence for the speeding-up of relaxation at modest shear strains in both step and oscillatory shear flows. Using the soft glassy rheology (SGR) model framework, we show that the observed behavior is a fundamental, but heretofore unexplored attribute of soft glasses. © 2011 American Physical Society.

Evaluation of stress distribution due to shearing in non-oriented electrical steel by using synchrotron radiation

Directory of Open Access Journals (Sweden)

Yoshiaki Zaizen

2016-05-01

Full Text Available The influence of the shearing process on the iron loss of non-oriented electrical steels with grain sizes of 10 μm-150 μm was investigated. The deterioration ratio of iron loss was clearly smaller in sample with small grain sizes. The droop height, reflecting the amount of plastic deformation, displayed a good relationship with the deterioration of iron loss under the effect of the material grain size. To clarify the strain distribution around the sheared edge, the elastic strain in a sheet sample with the thickness of 0.30 mm and grain size of 10 μm was evaluated by using synchrotron radiation. The width of the region of elastic strain due to shearing was two or three times of the material thickness. The results of the plastic strain distribution obtained by the measurements were then used to estimate the iron loss deterioration rate in 5 mm width sheared samples. The estimated loss deteriotation coincided with the actual measured iron loss.

Evaluation of stress distribution due to shearing in non-oriented electrical steel by using synchrotron radiation

Energy Technology Data Exchange (ETDEWEB)

Zaizen, Yoshiaki, E-mail: y-zaizen@jfe-steel.co.jp; Omura, Takeshi; Senda, Kunihiro [Steel Research Laboratory, JFE Steel Corporation, Kawasakidori 1,Mizushima, Kurashiki,712-8511 (Japan); Fukumura, Masaru [Steel Research Laboratory, JFE Steel Corporation, Kawasaki, Kanagawa 210-0855 (Japan); Toda, Hiroaki [Steel Business Planning Dept, JFE Steel Corporation, Tokyo 100-0011 (Japan)

2016-05-15

The influence of the shearing process on the iron loss of non-oriented electrical steels with grain sizes of 10 μm-150 μm was investigated. The deterioration ratio of iron loss was clearly smaller in sample with small grain sizes. The droop height, reflecting the amount of plastic deformation, displayed a good relationship with the deterioration of iron loss under the effect of the material grain size. To clarify the strain distribution around the sheared edge, the elastic strain in a sheet sample with the thickness of 0.30 mm and grain size of 10 μm was evaluated by using synchrotron radiation. The width of the region of elastic strain due to shearing was two or three times of the material thickness. The results of the plastic strain distribution obtained by the measurements were then used to estimate the iron loss deterioration rate in 5 mm width sheared samples. The estimated loss deteriotation coincided with the actual measured iron loss.

MM98.57 Quantification of Combined Strain Paths

DEFF Research Database (Denmark)

Nielsen, Morten Sturgård; Wanheim, Tarras

1998-01-01

this curve into useful scalar relations from experimental data.The strain history for plane strain when assuming volume constancy may be plotted in a shear strain, normal strain diagram, which has the property of showing both the rotation of principal deformation axes during the deformation and the amount...... is to describe the total strain history as a curve in the 6-dimensional shear strain, normal strain space. In order to be able to use these experimental data for calculation, the development of this strain curve must be transformed into a set of scalar relations that may be used for predicting the yield surface...... at a given point in a new strain history. A simple example of this concept is to take the length of the strain curve as describing scalar relation: E.g. to use the equivalent strain as parameter for describing the yield stress. This paper focuses on the strain curve concept and the possibilities to convert...

Effect of Attachment Type on Denture Strain in Maxillary Implant Overdentures: Part 1. Overdenture with Palate.

Science.gov (United States)

Takahashi, Toshihito; Gonda, Tomoya; Maeda, Yoshinobu

This study examined the effects of attachments on strain in maxillary implant overdentures supported by two or four implants. A maxillary edentulous model with implants inserted into anterior, premolar, and molar areas was fabricated, and three types of unsplinted attachments-ball, locator, and magnet-were set on the implants distributed under various conditions. Maxillary experimental dentures were fabricated, and two strain gauges were attached at the anterior midline on the labial and palatal sides. A vertical occlusal load of 98 N was applied and shear strain of the dentures was measured. On both sides, magnet attachments resulted in the lowest shear strain, while ball attachments resulted in the highest shear strain under most conditions. However, differences in shear strain among the three attachment types were not significant when supported by four implants, especially molar implants. Shear strain of the maxillary implant overdenture was lowest when using magnet attachments. Magnet attachments mounted on four implants are recommended to prevent denture complications when using maxillary implant overdentures.

Elliptical posts allow for detailed control of non-equibiaxial straining of cell cultures

DEFF Research Database (Denmark)

Olesen, Christian Gammelgaard; Pennisi, Cristian Pablo; de Zee, Mark

2013-01-01

tissue cells in vivo are subjected to a range of mechanical deformations including shear strain caused by activities of daily living. Shear strains are suspected to play an important role in tissue necrosis. Method The Flexcell system was redesigned using a finite element model in order to obtain large...... areas of the membrane in a controlled, uniform non-equibiaxial strain state. Results The redesign was manufactured and the resulting strains were experimentally validated by means of image analysis methods. The results showed that the system could be used for experiments varying the shear strain....... Conclusion The result allows scientists and experimentalists to apply detailed control of the strain tensor applied to tissue samples in two dimensions....

Generation of lycopene-overproducing strains of the fungus Mucor circinelloides reveals important aspects of lycopene formation and accumulation.

Science.gov (United States)

Zhang, Yingtong; Chen, Haiqin; Navarro, Eusebio; López-García, Sergio; Chen, Yong Q; Zhang, Hao; Chen, Wei; Garre, Victoriano

2017-03-01

To generate lycopene-overproducing strains of the fungus Mucor circinelloides with interest for industrial production and to gain insight into the catalytic mechanism of lycopene cyclase and regulatory process during lycopene overaccumulation. Three lycopene-overproducing mutants were generated by classic mutagenesis techniques from a β-carotene-overproducing strain. They carried distinct mutations in the carRP gene encoding lycopene cyclase that produced loss of enzymatic activity to different extents. In one mutant (MU616), the lycopene cyclase was completely destroyed, and a 43.8% (1.1 mg/g dry mass) increase in lycopene production was observed in comparison to that by the previously existing lycopene overproducer. In addition, feedback regulation of the end product was suggested in lycopene-overproducing strains. A lycopene-overaccumulating strain of the fungus M. circinelloides was generated that could be an alternative for the industrial production of lycopene. Vital catalytic residues for lycopene cyclase activity and the potential mechanism of lycopene formation and accumulation were identified.

High Resolution Shear Profile Measurements in Entangled Polymers

KAUST Repository

Hayes, Keesha A.

2008-11-17

We use confocal microscopy and particle image velocimetry to visualize motion of 250-300 nm. fluorescent tracer particles in entangled polymers subject to a rectilinear shear flow. Our results show linear velocity profiles in polymer solutions spanning a wide range of molecular weights and number of entanglements (8≤Z≤56), but reveal large differences between the imposed and measured shear rates. These findings disagree with recent reports that shear banding is a characteristic flow response of entangled polymers, and instead point to interfacial slip as an important source of strain loss. © 2008 The American Physical Society.

Strain localization band width evolution by electronic speckle pattern interferometry strain rate measurement

Energy Technology Data Exchange (ETDEWEB)

Guelorget, Bruno [Institut Charles Delaunay-LASMIS, Universite de technologie de Troyes, FRE CNRS 2848, 12 rue Marie Curie, B.P. 2060, 10010 Troyes Cedex (France)], E-mail: bruno.guelorget@utt.fr; Francois, Manuel; Montay, Guillaume [Institut Charles Delaunay-LASMIS, Universite de technologie de Troyes, FRE CNRS 2848, 12 rue Marie Curie, B.P. 2060, 10010 Troyes Cedex (France)

2009-04-15

In this paper, electronic speckle pattern interferometry strain rate measurements are used to quantify the width of the strain localization band, which occurs when a sheet specimen is submitted to tension. It is shown that the width of this band decreases with increasing strain. Just before fracture, this measured width is about five times wider than the shear band and the initial sheet thickness.

Shear at Twin Domain Boundaries in YBa2Cu3O7-x

Science.gov (United States)

Caldwell, W. A.; Tamura, N.; Celestre, R. S.; MacDowell, A. A.; Padmore, H. A.; Geballe, T. H.; Koster, G.; Batterman, B. W.; Patel, J. R.

2004-05-01

The microstructure and strain state of twin domains in YBa2Cu3O7-x are discussed based upon synchrotron white-beam x-ray microdiffraction measurements. Intensity variations of the fourfold twin splitting of Laue diffraction peaks are used to determine the twin domain structure. Strain analysis shows that interfaces between neighboring twin domains are strained in shear, whereas the interior of these domains are regions of low strain. These measurements are consistent with the orientation relationships of twin boundaries within and across domains and show that basal plane shear stresses can exceed 100MPa where twin domains meet. Our results support stress field pinning of magnetic flux vortices by twin domain boundaries.

The effects of abscisic acid, salicylic acid and jasmonic acid on lipid accumulation in two freshwater Chlorella strains.

Science.gov (United States)

Wu, Guanxun; Gao, Zhengquan; Du, Huanmin; Lin, Bin; Yan, Yuchen; Li, Guoqiang; Guo, Yanyun; Fu, Shenggui; Wei, Gongxiang; Wang, Miaomiao; Cui, Meng; Meng, Chunxiao

2018-03-27

Sustainable renewable energy is being hotly debated globally because the continued use of finite fossil fuels is now widely recognized as being unsustainable. Microalgae potentially offer great opportunities for resolving this challenge. Abscisic acid (ABA), jasmonic acid (JA) and salicylic acid (SA) are involved in regulating many physiological properties and have been widely used in higher plants. To test if phytohormones have an impact on accumulating lipid for microalgae, ABA, JA and SA were used to induce two Chlorella strains in the present study. The results showed 1.0 mg/L ABA, 10 mg/L SA, and 0.5 mg/L JA, led strain C. vulgaris ZF strain to produce a 45%, 42% and 49% lipid content that was 1.8-, 1.7- and 2.0-fold that of controls, respectively. For FACHB 31 (number 31 of the Freshwater Algae Culture Collection at the Institute of Hydrobiology, Chinese Academy of Sciences), the addition of 1.0 mg/L ABA, 10 mg/L SA, and 0.5 mg/L, JA produced 33%, 30% and 38% lipid content, which was 1.8-, 1.6- and 2.1-fold that of controls, respectively. As for lipid productivity, 1.0 mg/L ABA increased the lipid productivity of C. vulgaris ZF strain and FACHB-31 by 123% and 44%; 10 mg/L SA enhanced lipid productivity by 100% and 33%; the best elicitor, 0.5 mg/L JA, augmented lipid productivity by 127% and 75% compared to that of controls, respectively. The results above suggest that the three phytohormones at physiological concentrations play crucial roles in inducing lipid accumulation in Chlorella.

Laboratory Studies on the Effects of Shear on Fish

Energy Technology Data Exchange (ETDEWEB)

Neitzel, Duane A.; Richmond, Marshall C.; Dauble, Dennis D.; Mueller, Robert P.; Moursund, Russell A.; Abernethy, Cary S.; Guensch, Greg R.

2000-09-20

The overall objective of our studies was to specify an index describing the hydraulic force that fish experience when subjected to a shear environment. Fluid shear is a phenomenon that is important to fish. However, elevated levels of shear may result in strain rates that injure or kill fish. At hydroelectric generating facilities, concerns have been expressed that strain rates associated with passage through turbines, spillways, and fish bypass systems may adversely affect migrating fish. Development of fish friendly hydroelectric turbines requires knowledge of the physical forces (injury mechanisms) that impact entrained fish and the fish's tolerance to these forces. It requires up-front, pre-design specifications for the environmental conditions that occur within the turbine system, in other words, determining or assuming that those conditions known to injure fish will provide the descriptions of conditions that engineers must consider in the design of a turbine system. These biological specifications must be carefully and thoroughly documented throughout the design of a fish friendly turbine. To address the development of biological specifications, we designed and built a test facility where juvenile fish could be subjected to a range of shear environments and quantified their biological response.

Phenomenological interpretation of the shear behavior of reinforced Engineered Cementitious Composite beams

DEFF Research Database (Denmark)

Paegle, Ieva; Fischer, Gregor

2016-01-01

This paper describes an experimental investigation of the shear behavior of beams consisting of steel Reinforced Engineered Cementitious Composites (R/ECC). This study investigates and quantifies the effect of ECC's strain hardening and multiple cracking behavior on the shear capacity of beams...

Stud-bolts strength for cell-liner design under shearing deformation

International Nuclear Information System (INIS)

Watashi, Katsumi; Nakanishi, Seiji

1991-01-01

This paper presents experimental and analytical stud-bolt strength subjected to large shearing deformation at high temperature. Tensile test result of the material, SM41B, was shown in the range of room temperature to 550degC at 10 -3 and 10 -4 m/m/s in strain rate. Shearing fracture test result of the stud-bolt is shown at room temperature and 530degC. Shearing fracture criterion was discussed based on both test results and FEM analysis result. (author)

High fluid shear strain causes injury in silver shark: Preliminary implications for Mekong hydropower turbine design

Energy Technology Data Exchange (ETDEWEB)

Baumgartner, L. J. [New South Wales Department of Primary Industries, Narrandera Fisheries Centre, Narrandera NSW Australia; Institute of Land, Water and Society, Charles Sturt University, Albury NSW Australia; Thorncraft, G. [Faculty of Agriculture, Forestry and Fisheries, National University of Laos, Vientiane Lao People’s Democratic Republic; Phonekhampheng, O. [Faculty of Agriculture, Forestry and Fisheries, National University of Laos, Vientiane Lao People’s Democratic Republic; Boys, C. [New South Wales Department of Primary Industries, Port Stephens Fisheries Institute, Nelson Bay NSW Australia; Navarro, A. [Institute of Land, Water and Society, Charles Sturt University, Albury NSW Australia; Robinson, W. [Institute of Land, Water and Society, Charles Sturt University, Albury NSW Australia; Brown, R. [Pacific Northwest National Laboratory, Richland WA USA; Deng, Z. D. [Pacific Northwest National Laboratory, Richland WA USA

2017-02-09

Fluid shear arises when two bodies of water, travelling at different velocities, intersect. Fish entrained at the interface of these two water masses will experience shear stress; which can be harmful. The stress magnitude is dependent on waterbody mass and velocity; with the fish impact largely related to body size. Elevated shear stress occurs where rapidly flowing water passes near spillways, across screens, within turbine draft tubes or other passage routes. A flume was used to determine critical tolerances of silver shark (Balantiocheilos melanopterus) to different shear stress rates generated by a high velocity jet. Fish experienced higher levels of injury and mortality as shear stress was increased. Excessive shear forces had damaging impacts on fish. Mortality occurred at shear levels higher that 600/s. It is important that developers should attempt to model potential shear profiles expected during turbine passage in selected designs. These data will be critical to determine potential impacts on fish. If the likelihood of adverse impact is high, then alternative designs which have lower shear stress could be explored.

Creep strain accumulation in a typical LMFBR piperun

International Nuclear Information System (INIS)

Johnstone, T.L.

1975-01-01

The analysis described allows the strain concentrations in typical LMFBR two anchor point uniplanar piperuns to be calculated. Account is taken of the effect of pipe elbows in attracting creep strain to themselves as well as possible movements of the thrust line due to strain redistribution. The influence of the initial load conditions is also examined. The stress relaxation analysis is facilitated by making the assumption that a cross-sectional stress distribution determined by the asymptotic fully developed state of creep exists at all times. Use is then made of Hoff(s) analogy between materials with a creep law of the Norton type and those with a corresponding non-linear elastic stress strain law, to determine complementary strain energy rates for straight pipes and bends. Ovalisation of the latter produces an increased strain energy rate which can be simply calculated by comparison with an equal length of straight pipe through employing a creep flexibility factor due to Spence. Deflection rates at any location in the pipework can then be evaluated in terms of the thermal restraint forces at that location by an application of Castigliano's principle. In particular for an anchor point the deflection rates are identically zero and this leads to the generation of 3 simultaneous differential equations determining the relaxation of the anchor reactions. Indicative results are presented for the continuous relaxation at 570 deg C of the thermally induced stress in a planar approximation to a typical LMFBR pipe run chosen to have peak elbow stresses close to the code maximum. The results indicate a ratio, after 10 5 hours, of 3 for creep strain concentration relative to initial peak strain (calculated on the assumption of fully elastic behavior) in the most severely affected elbow, when either austenitic 316 or 321 creep properties are employed

Structural mechanisms of formation of adiabatic shear bands

Directory of Open Access Journals (Sweden)

Mikhail Sokovikov

2016-10-01

Full Text Available The paper focuses on the experimental and theoretical study of plastic deformation instability and localization in materials subjected to dynamic loading and high-velocity perforation. We investigate the behavior of samples dynamically loaded during Hopkinson-Kolsky pressure bar tests in a regime close to simple shear conditions. Experiments were carried out using samples of a special shape and appropriate test rigging, which allowed us to realize a plane strain state. Also, the shear-compression specimens proposed in were investigated. The lateral surface of the samples was investigated in a real-time mode with the aid of a high-speed infra-red camera CEDIP Silver 450M. The temperature field distribution obtained at different time made it possible to trace the evolution of plastic strain localization. Use of a transmission electron microscope for studying the surface of samples showed that in the regions of strain localization there are parts taking the shape of bands and honeycomb structure in the deformed layer. The process of target perforation involving plug formation and ejection was investigated using a high-speed infra-red camera. A specially designed ballistic set-up for studying perforation was used to test samples in different impulse loading regimes followed by plastic flow instability and plug ejection. Changes in the velocity of the rear surface at different time of plug ejection were analyzed by Doppler interferometry techniques. The microstructure of tested samples was analyzed using an optical interferometer-profilometer and a scanning electron microscope. The subsequent processing of 3D deformation relief data enabled estimation of the distribution of plastic strain gradients at different time of plug formation and ejection. It has been found that in strain localization areas the subgrains are elongated taking the shape of bands and undergo fragmentation leading to the formation of super-microcrystalline structure, in which the

Strain Anomalies during an Earthquake Sequence in the South Iceland Seismic Zone

Science.gov (United States)

Arnadottir, T.; Haines, A. J.; Geirsson, H.; Hreinsdottir, S.

2017-12-01

The South Iceland Seismic Zone (SISZ) accommodates E-W translation due to oblique spreading between the North American/Hreppar microplate and Eurasian plate, in South Iceland. Strain is released in the SISZ during earthquake sequences that last days to years, at average intervals of 80-100 years. The SISZ is currently in the midst of an earthquake sequence that started with two M6.5 earthquakes in June 2000, and continued with two M6 earthquakes in May 2008. Estimates of geometric strain accumulation, and seismic strain release in these events indicate that they released at most only half of the strain accumulated since the last earthquake cycle in 1896-1912. Annual GPS campaigns and continuous measurements during 2001-2015 were used to calculate station velocities and strain rates from a new method using the vertical derivatives of horizontal stress (VDoHS). This new method allows higher resolution of strain rates than other (older) approaches, as the strain rates are estimated by integrating VDoHS rates obtained by inversion rather than differentiating interpolated GPS velocities. Estimating the strain rates for eight 1-2 year intervals indicates temporal and spatial variation of strain rates in the SISZ. In addition to earthquake faulting, the strain rates in the SISZ are influenced by anthropogenic signals due to geothermal exploitation, and magma movements in neighboring volcanoes - Hekla and Eyjafjallajökull. Subtle signals of post-seismic strain rate changes are seen following the June 2000 M6.5 main shocks, but interestingly, much larger strain rate variations are observed after the two May 2008 M6 main shocks. A prominent strain anomaly is evident in the epicentral area prior to the May 2008 earthquake sequence. The strain signal persists over at least 4 years in the epicentral area, leading up to the M6 main shocks. The strain is primarily extension in ESE-WNW direction (sub-parallel to the direction of plate spreading), but overall shear across the N

Enhancing Rotational Diffusion Using Oscillatory Shear

KAUST Repository

Leahy, Brian D.

2013-05-29

Taylor dispersion - shear-induced enhancement of translational diffusion - is an important phenomenon with applications ranging from pharmacology to geology. Through experiments and simulations, we show that rotational diffusion is also enhanced for anisotropic particles in oscillatory shear. This enhancement arises from variations in the particle\\'s rotation (Jeffery orbit) and depends on the strain amplitude, rate, and particle aspect ratio in a manner that is distinct from the translational diffusion. This separate tunability of translational and rotational diffusion opens the door to new techniques for controlling positions and orientations of suspended anisotropic colloids. © 2013 American Physical Society.

Viscosity, granular-temperature, and stress calculations for shearing assemblies of inelastic, frictional disks

International Nuclear Information System (INIS)

Walton, O.R.; Braun, R.L.

1986-01-01

Employing nonequilibrium molecular-dynamics methods the effects of two energy loss mechanisms on viscosity, stress, and granular-temperature in assemblies of nearly rigid, inelastic frictional disks undergoing steady-state shearing are calculated. Energy introduced into the system through forced shearing is dissipated by inelastic normal forces or through frictional sliding during collisions resulting in a natural steady-state kinetic energy density (granular-temperature) that depends on the density and shear rate of the assembly and on the friction and inelasticity properties of the disks. The calculations show that both the mean deviatoric particle velocity and the effective viscosity of a system of particles with fixed friction and restitution coefficients increase almost linearly with strain rate. Particles with a velocity-dependent coefficient of restitution show a less rapid increase in both deviatoric velocity and viscosity as strain rate increases. Particles with highly dissipative interactions result in anisotropic pressure and velocity distributions in the assembly, particularly at low densities. At very high densities the pressure also becomes anisotropic due to high contact forces perpendicular to the shearing direction. The mean rotational velocity of the frictional disks is nearly equal to one-half the shear rate. The calculated ratio of shear stress to normal stress varies significantly with density while the ratio of shear stress to total pressure shows much less variation. The inclusion of surface friction (and thus particle rotation) decreases shear stress at low density but increases shear stress under steady shearing at higher densities

Impedance method for measuring shear elasticity of liquids

Science.gov (United States)

Badmaev, B. B.; Dembelova, T. S.; Damdinov, B. B.; Gulgenov, Ch. Zh.

2017-11-01

Experimental results of studying low-frequency (74 kHz) shear elasticity of polymer liquids by the impedance method (analogous to the Mason method) are presented. A free-volume thick liquid layer is placed on the horizontal surface of a piezoelectric quartz crystal with dimensions 34.7 × 12 × 5.5 cm. The latter performs tangential vibrations at resonance frequency. The liquid layer experiences shear strain, and shear waves should propagate in it. From the theory of the method, it follows that, with an increase in the layer thickness, both real and imaginary resonance frequency shifts should exhibit damped oscillations and tend to limiting values. For the liquids under study, the imaginary frequency shift far exceeds the real one, which testifies to the presence of bulk shear elasticity.

Living bacteria rheology: Population growth, aggregation patterns, and collective behavior under different shear flows

Science.gov (United States)

Patrício, P.; Almeida, P. L.; Portela, R.; Sobral, R. G.; Grilo, I. R.; Cidade, T.; Leal, C. R.

2014-08-01

The activity of growing living bacteria was investigated using real-time and in situ rheology—in stationary and oscillatory shear. Two different strains of the human pathogen Staphylococcus aureus—strain COL and its isogenic cell wall autolysis mutant, RUSAL9—were considered in this work. For low bacteria density, strain COL forms small clusters, while the mutant, presenting deficient cell separation, forms irregular larger aggregates. In the early stages of growth, when subjected to a stationary shear, the viscosity of the cultures of both strains increases with the population of cells. As the bacteria reach the exponential phase of growth, the viscosity of the cultures of the two strains follows different and rich behaviors, with no counterpart in the optical density or in the population's colony-forming units measurements. While the viscosity of strain COL culture keeps increasing during the exponential phase and returns close to its initial value for the late phase of growth, where the population stabilizes, the viscosity of the mutant strain culture decreases steeply, still in the exponential phase, remains constant for some time, and increases again, reaching a constant plateau at a maximum value for the late phase of growth. These complex viscoelastic behaviors, which were observed to be shear-stress-dependent, are a consequence of two coupled effects: the cell density continuous increase and its changing interacting properties. The viscous and elastic moduli of strain COL culture, obtained with oscillatory shear, exhibit power-law behaviors whose exponents are dependent on the bacteria growth stage. The viscous and elastic moduli of the mutant culture have complex behaviors, emerging from the different relaxation times that are associated with the large molecules of the medium and the self-organized structures of bacteria. Nevertheless, these behaviors reflect the bacteria growth stage.

Finite element analyses for Seismic Shear Wall International Standard Problem

International Nuclear Information System (INIS)

Park, Y.; Hofmayer, C.; Chokshi, N.

1997-01-01

In the seismic design of shear wall structures, e.g., nuclear reactor buildings, a linear FEM analysis is frequently used to quantify the stresses under the design loading condition. The final design decisions, however, are still based on empirical design rules established over decades from accumulated laboratory test data. This paper presents an overview of the state-of-the-art on the application of nonlinear FEM analysis to reinforced concrete (RC) shear wall structures under severe earthquake loadings based on the findings obtained during the Seismic Shear Wall International Standard Problem (SSWISP) Workshop in 1996. Also, BNL's analysis results of the International Standard Problem (ISP) shear walls under monotonic static, cyclic static and dynamic loading conditions are described

Room Temperature Shear Band Development in Highly Twinned Wrought Magnesium AZ31B Sheet

Science.gov (United States)

Scott, Jon; Miles, Michael; Fullwood, David; Adams, Brent; Khosravani, Ali; Mishra, Raja K.

2013-01-01

Failure mechanisms were studied in wrought AZ31B magnesium alloy after forming under different strain paths. Optical micrographs were used to observe the shear band formation and regions of high twin density in samples strained under uniaxial, biaxial, and plane strain conditions. Interrupted testing at 4 pct effective strain increments, until failure, was used to observe the evolution of the microstructure. The results showed that shear bands, with a high percentage of twinned grains, appeared early in the samples strained under biaxial or plane strain tension. These bands are similar to those seen in uniaxial tension specimens just prior to failure where the uniaxial tensile ductility was much greater than that observed for plane strain or biaxial tension conditions. A forming limit diagram for AZ31B, which was developed from the strain data, showed that plane strain and biaxial tension had very similar limit strains; this contrasts with materials like steel or aluminum alloys, which typically have greater ductility in biaxial tension compared to plane strain tension.

Microbial accumulation of uranium from nuclear liquid waste

International Nuclear Information System (INIS)

Mahmood, A.H.

1986-01-01

This investigation includes the isolation, identification and the fluctuations of the population densities of microorganisms in the nuclear liquid waste released by some laboratories of Iraqi Atomic Energy Commission. The efficiency of uranium accumulation on isolates (22 bacterial strains, 24 fungal strains and 6 yeast strains) was assessed in aqueous solution using fluorometric techniques. Two of the isolated microoganisms namely Bacillus sp. -15B and Mucor sp.16F showed exceptionally high attitude towards uranium accumulation. Optimal conditions required for efficient accumulation and recovery of uranium was then studied using the two selected isolates. 10 figs.; 162 refs.; 16 tabs

Application and Analysis of Measurement Model for Calibrating Spatial Shear Surface in Triaxial Test

Science.gov (United States)

Zhang, Zhihua; Qiu, Hongsheng; Zhang, Xiedong; Zhang, Hang

2017-12-01

Discrete element method has great advantages in simulating the contacts, fractures, large displacement and deformation between particles. In order to analyze the spatial distribution of the shear surface in the three-dimensional triaxial test, a measurement model is inserted in the numerical triaxial model which is generated by weighted average assembling method. Due to the non-visibility of internal shear surface in laboratory, it is largely insufficient to judge the trend of internal shear surface only based on the superficial cracks of sheared sample, therefore, the measurement model is introduced. The trend of the internal shear zone is analyzed according to the variations of porosity, coordination number and volumetric strain in each layer. It shows that as a case study on confining stress of 0.8 MPa, the spatial shear surface is calibrated with the results of the rotated particle distribution and the theoretical value with the specific characteristics of the increase of porosity, the decrease of coordination number, and the increase of volumetric strain, which represents the measurement model used in three-dimensional model is applicable.

Strain mapping near a triple junction in strained Ni-based alloy using EBSD and biaxial nanogauges

Energy Technology Data Exchange (ETDEWEB)

Clair, A. [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 5209 CNRS, Universite de Bourgogne, 9 Avenue Alain Savary, BP 47870, 21078 Dijon Cedex (France); Foucault, M.; Calonne, O. [Areva ANP, Centre Technique Departement Corrosion-Chimie, 30 Bd de l' industrie, BP 181, 71205 Le Creusot (France); Lacroute, Y.; Markey, L.; Salazar, M.; Vignal, V. [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 5209 CNRS, Universite de Bourgogne, 9 Avenue Alain Savary, BP 47870, 21078 Dijon Cedex (France); Finot, E., E-mail: Eric.Finot@u-bourgogne.fr [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 5209 CNRS, Universite de Bourgogne, 9 Avenue Alain Savary, BP 47870, 21078 Dijon Cedex (France)

2011-05-15

Research highlights: > Surface strains measured using nanogauge were compared to the texture obtained by EBSD. > Statistics of the principal strain discern the grains according to the Schmid factor. > Strain hotspots were localized near a triple junction of alloy 600 under tensile loading. > Asymetrical profile of the GB strains is a criterion for surface cracking initiation. - Abstract: A key element for analyzing the crack initiation in strained polycrystalline alloys is the local quantification of the surface strain distribution according to the grain texture. Using electron backscattered diffraction, the local microstructure was determined to both localize a triple junction and deduce the local Schmid factors. Kernel average misorientation (KAM) was also used to map the areas of defect concentration. The maximum principal strain and the in-plane shear strain were quantified using the biaxial nanogauge. Distortions of the array of nanodots used as spot markers were analyzed near the triple junction. The crystallographic orientation and the surface strain were then investigated both statistically for each grain and locally at the grain boundaries. The superimposition of microstructure and strain maps allows the high strain gradient (reaching 3-fold the applied strain) to be localized at preferential grain boundaries near the triple junction. The Schmid factors and the KAM were compared to the maximum principal strain and the in-plane shear strain respectively. The polycrystalline deformation was attributable first to the rotation of some grains, followed by the elongation of all grains along their preferential activated slip systems.

Strain Localization during Equal-Channel Angular Pressing Analyzed by Finite Element Simulations

Directory of Open Access Journals (Sweden)

Tobias Daniel Horn

2018-01-01

Full Text Available Equal-Channel Angular Pressing (ECAP is a method used to introduce severe plastic deformation into a metallic billet without changing its geometry. In special cases, strain localization occurs and a pattern consisting of regions with high and low deformation (so-called shear and matrix bands can emerge. This paper studies this phenomenon numerically adopting two-dimensional finite element simulations of one ECAP pass. The mechanical behavior of aluminum is modeled using phenomenological plasticity theory with isotropic or kinematic hardening. The effects of the two different strain hardening types are investigated numerically by systematic parameter studies: while isotropic hardening only causes minor fluctuations in the plastic strain fields, a material with high initial hardening rate and sufficient strain hardening capacity can exhibit pronounced localized deformation after ECAP. The corresponding finite element simulation results show a regular pattern of shear and matrix bands. This result is confirmed experimentally by ECAP-processing of AA6060 material in a severely cold worked condition, where microstructural analysis also reveals the formation of shear and matrix bands. Excellent agreement is found between the experimental and numerical results in terms of shear and matrix band width and length scale. The simulations provide additional insights regarding the evolution of the strain and stress states in shear and matrix bands.

Origins of Shear Jamming for Frictional Grains

Science.gov (United States)

Wang, Dong; Zheng, Hu; Ren, Jie; Dijksman, Joshua; Bares, Jonathan; Behringer, Robert

2016-11-01

Granular systems have been shown to be able to behave like solids, under shear, even when their densities are below the critical packing fraction for frictionless isotropic jamming. To understand such a phenomena, called shear jamming, the question we address here is: how does shear bring a system from a unjammed state to a jammed state, where the coordination number, Z, is no less than 3, the isotropic jamming point for frictional grains? Since Z can be used to distinguish jammed states from unjammed ones, it is vital to understand how shear increases Z. We here propose a set of three particles in contact, denoted as a trimer, as the basic unit to characterize the deformation of the system. Trimers, stabilized by inter-grain friction, fail under a certain amount of shear and bend to make extra contacts to regain stability. By defining a projection operator of the opening angle of the trimer to the compression direction in the shear, O, we see a systematically linear decrease of this quantity with respect to shear strain, demonstrating the bending of trimers as expected. In addition, the average change of O from one shear step to the next shows a good collapse when plotted against Z, indicating a universal behavior in the process of shear jamming. We acknowledge support from NSF DMR1206351, NASA NNX15AD38G, the William M. Keck Foundation and a RT-MRSEC Fellowship.

Adiabatic shear localization in a near beta Ti–5Al–5Mo–5 V–1Cr–1Fe alloy

Energy Technology Data Exchange (ETDEWEB)

Wang, Bingfeng, E-mail: biw009@ucsd.edu [School of Materials Science and Engineering, Central South University, Changsha 410083, Hunan (China); Key Lab of Nonferrous Materials, Ministry of Education, Central South University, Changsha 410083, Hunan (China); Department of Mechanical and Aerospace Engineering, University of California, San Diego (United States); Sun, Jieying; Wang, Xiaoyan; Fu, Ao [School of Materials Science and Engineering, Central South University, Changsha 410083, Hunan (China)

2015-07-15

Adiabatic shear localization plays an important role in the deformation and failure of near beta Ti–5Al–5Mo–5 V–1Cr–1Fe alloy used in aircraft's gear at high rate deformation. Hat shaped specimens with different nominal shear strains are used to induce the formation of an adiabatic shear band under controlled shock-loading experiments. When the nominal shear strain is about 0.68, unstable shear deformation of the alloy emerges after the true flow stress reaches 1100 MPa, the first vibration peak during the split Hopkinson pressure bar testing, and the whole process lasts about 62 μs. The microstructures within the shear band in the Ti–5Al–5Mo–5V–1Cr–1Fe alloy are investigated by means of optical microscopy, scanning electron microscopy and transmission electron microscopy. Phase transformation occurs in the shear band when the nominal shear strain increases to 0.68. A number of equiaxed grains with sizes 50–200 nm and alpha″-phase are in the center of the shear band. Kinetic calculations indicate that during the deformation process, the recrystallized nanosized grains can be formed in the shear band by way of the subgrain boundaries rotation, and the alpha″ phase transformation start after the subgrain boundaries rotated to 30°.

Mechanical properties and local mobility of atactic-polystyrene films under constant-shear deformation

NARCIS (Netherlands)

Hudzinskyy, D.; Michels, M.A.J.; Lyulin, A.V.

2012-01-01

We have performed molecular-dynamics simulations of atactic polystyrene thin films to study the effect of shear rate, pressure, and temperature on the stress-strain behaviour, the relevant energetic contributions and non-affine displacements of polymer chains during constant-shear deformation. Under

Adiabatic shear banding and scaling laws in chip formation with application to cutting of Ti-6Al-4V

Science.gov (United States)

Molinari, A.; Soldani, X.; Miguélez, M. H.

2013-11-01

The phenomenon of adiabatic shear banding is analyzed theoretically in the context of metal cutting. The mechanisms of material weakening that are accounted for are (i) thermal softening and (ii) material failure related to a critical value of the accumulated plastic strain. Orthogonal cutting is viewed as a unique configuration where adiabatic shear bands can be experimentally produced under well controlled loading conditions by individually tuning the cutting speed, the feed (uncut chip thickness) and the tool geometry. The role of cutting conditions on adiabatic shear banding and chip serration is investigated by combining finite element calculations and analytical modeling. This leads to the characterization and classification of different regimes of shear banding and the determination of scaling laws which involve dimensionless parameters representative of thermal and inertia effects. The analysis gives new insights into the physical aspects of plastic flow instability in chip formation. The originality with respect to classical works on adiabatic shear banding stems from the various facets of cutting conditions that influence shear banding and from the specific role exercised by convective flow on the evolution of shear bands. Shear bands are generated at the tool tip and propagate towards the chip free surface. They grow within the chip formation region while being convected away by chip flow. It is shown that important changes in the mechanism of shear banding take place when the characteristic time of shear band propagation becomes equal to a characteristic convection time. Application to Ti-6Al-4V titanium are considered and theoretical predictions are compared to available experimental data in a wide range of cutting speeds and feeds. The fundamental knowledge developed in this work is thought to be useful not only for the understanding of metal cutting processes but also, by analogy, to similar problems where convective flow is also interfering with

Endothelial biocompatibility and accumulation of SPION under flow conditions

International Nuclear Information System (INIS)

Matuszak, Jasmin; Zaloga, Jan; Friedrich, Ralf P.; Lyer, Stefan; Nowak, Johannes; Odenbach, Stefan; Alexiou, Christoph; Cicha, Iwona

2015-01-01

Magnetic targeting is considered a promising method to accumulate the nanoparticles at the sites of atherosclerotic lesions, but little is known about the biological effects of magnetic nanoparticles on the vascular wall. Here, we investigated endothelial cell growth and vitality upon treatment with SPION (0–60 µg/mL) using two complementing methods: real-time cell analysis and live-cell microscopy. Moreover, the uptake of circulating superparamagnetic iron oxide nanoparticles (SPIONs) was assessed in an in vitro model of arterial bifurcations. At the tested concentrations, SPIONs were well tolerated and had no major influence on endothelial cell growth. Our results further showed a uniform distribution of endothelial SPION uptake independent of channel geometry or hemodynamic conditions: In the absence of magnetic force, no increase in accumulation of SPIONs at non-uniform shear stress region at the outer walls of bifurcation was observed. Application of external magnet allowed enhanced accumulation of SPIONs at the regions of non-uniform shear stress. Increased uptake of SPIONs at non-uniform shear stress region was well tolerated by endothelial cells (ECs) and did not affect endothelial cell viability or attachment. These findings indicate that magnetic targeting can constitute a promising and safe technique for the delivery of imaging and therapeutic nanoparticles to atherosclerotic lesions

Endothelial biocompatibility and accumulation of SPION under flow conditions

Energy Technology Data Exchange (ETDEWEB)

Matuszak, Jasmin; Zaloga, Jan; Friedrich, Ralf P.; Lyer, Stefan [Section of Experimental Oncology and Nanomedicine (SEON), Else Kröner-Fresenius Stiftungsprofessur for Nanomedicine, University Hospital Erlangen, Erlangen (Germany); Nowak, Johannes; Odenbach, Stefan [Chair of Magnetofluiddynamics, Measuring and Automation Technology, Technische Universität Dresden, Dresden (Germany); Alexiou, Christoph [Section of Experimental Oncology and Nanomedicine (SEON), Else Kröner-Fresenius Stiftungsprofessur for Nanomedicine, University Hospital Erlangen, Erlangen (Germany); Cicha, Iwona, E-mail: Iwona_Cicha@yahoo.com [Section of Experimental Oncology and Nanomedicine (SEON), Else Kröner-Fresenius Stiftungsprofessur for Nanomedicine, University Hospital Erlangen, Erlangen (Germany)

2015-04-15

Magnetic targeting is considered a promising method to accumulate the nanoparticles at the sites of atherosclerotic lesions, but little is known about the biological effects of magnetic nanoparticles on the vascular wall. Here, we investigated endothelial cell growth and vitality upon treatment with SPION (0–60 µg/mL) using two complementing methods: real-time cell analysis and live-cell microscopy. Moreover, the uptake of circulating superparamagnetic iron oxide nanoparticles (SPIONs) was assessed in an in vitro model of arterial bifurcations. At the tested concentrations, SPIONs were well tolerated and had no major influence on endothelial cell growth. Our results further showed a uniform distribution of endothelial SPION uptake independent of channel geometry or hemodynamic conditions: In the absence of magnetic force, no increase in accumulation of SPIONs at non-uniform shear stress region at the outer walls of bifurcation was observed. Application of external magnet allowed enhanced accumulation of SPIONs at the regions of non-uniform shear stress. Increased uptake of SPIONs at non-uniform shear stress region was well tolerated by endothelial cells (ECs) and did not affect endothelial cell viability or attachment. These findings indicate that magnetic targeting can constitute a promising and safe technique for the delivery of imaging and therapeutic nanoparticles to atherosclerotic lesions.

Steady shear characteristic and behavior of magneto-thermo-elasticity of isotropic MR elastomers

International Nuclear Information System (INIS)

Gao, Wei; Wang, Xingzhe

2016-01-01

The magneto-thermo-elastic steady shear behaviors of isotropic smart composites of silicon rubber matrix randomly filled with ferromagnetic particles, commonly referred to as magnetorheological (MR) elastomers, are investigated experimentally and theoretically in the present study. The strip specimens of the MR elastomer composite with different ferromagnetic particle concentrations are fabricated and implemented for lap-shear tests under both magnetic and thermal fields. It is illustrated that the magneto-thermo-elastic shear modulus of the MR elastomer is markedly enhanced with the volume fraction of ferromagnetic particles and the applied external magnetic field, while the shear modulus is decreased with the environment temperature. To qualitatively elucidate the magneto-thermo-elastic shear performance of this kind of magnetic smart composites, a modified constitutive of hyperelasticity is suggested taking into account the influence of magnetic field and temperature on the magnetic potential energy and strain energy. The theoretical modeling predictions on the stress–strain behaviors for different applied magnetic fields and environment temperatures are compared to experimental observations to demonstrate a good agreement. (paper)

Stability of surface plastic flow in large strain deformation of metals

Science.gov (United States)

Viswanathan, Koushik; Udapa, Anirduh; Sagapuram, Dinakar; Mann, James; Chandrasekar, Srinivasan

We examine large-strain unconstrained simple shear deformation in metals using a model two-dimensional cutting system and high-speed in situ imaging. The nature of the deformation mode is shown to be a function of the initial microstructure state of the metal and the deformation geometry. For annealed metals, which exhibit large ductility and strain hardening capacity, the commonly assumed laminar flow mode is inherently unstable. Instead, the imposed shear is accommodated by a highly rotational flow-sinuous flow-with vortex-like components and large-amplitude folding on the mesoscale. Sinuous flow is triggered by a plastic instability on the material surface ahead of the primary region of shear. On the other hand, when the material is extensively strain-hardened prior to shear, laminar flow again becomes unstable giving way to shear banding. The existence of these flow modes is established by stability analysis of laminar flow. The role of the initial microstructure state in determining the change in stability from laminar to sinuous / shear-banded flows in metals is elucidated. The implications for cutting, forming and wear processes for metals, and to surface plasticity phenomena such as mechanochemical Rehbinder effects are discussed.

Shear wave elastography with a new reliability indicator

Directory of Open Access Journals (Sweden)

Christoph F. Dietrich

2016-09-01

Full Text Available Non-invasive methods for liver stiffness assessment have been introduced over recent years. Of these, two main methods for estimating liver fibrosis using ultrasound elastography have become established in clinical practice: shear wave elastography and quasi-static or strain elastography. Shear waves are waves with a motion perpendicular (lateral to the direction of the generating force. Shear waves travel relatively slowly (between 1 and 10 m/s. The stiffness of the liver tissue can be assessed based on shear wave velocity (the stiffness increases with the speed. The European Federation of Societies for Ultrasound in Medicine and Biology has published Guidelines and Recommendations that describe these technologies and provide recommendations for their clinical use. Most of the data available to date has been published using the Fibroscan (Echosens, France, point shear wave speed measurement using an acoustic radiation force impulse (Siemens, Germany and 2D shear wave elastography using the Aixplorer (SuperSonic Imagine, France. More recently, also other manufacturers have introduced shear wave elastography technology into the market. A comparison of data obtained using different techniques for shear wave propagation and velocity measurement is of key interest for future studies, recommendations and guidelines. Here, we present a recently introduced shear wave elastography technology from Hitachi and discuss its reproducibility and comparability to the already established technologies.

Shear wave elastography with a new reliability indicator.

Science.gov (United States)

Dietrich, Christoph F; Dong, Yi

2016-09-01

Non-invasive methods for liver stiffness assessment have been introduced over recent years. Of these, two main methods for estimating liver fibrosis using ultrasound elastography have become established in clinical practice: shear wave elastography and quasi-static or strain elastography. Shear waves are waves with a motion perpendicular (lateral) to the direction of the generating force. Shear waves travel relatively slowly (between 1 and 10 m/s). The stiffness of the liver tissue can be assessed based on shear wave velocity (the stiffness increases with the speed). The European Federation of Societies for Ultrasound in Medicine and Biology has published Guidelines and Recommendations that describe these technologies and provide recommendations for their clinical use. Most of the data available to date has been published using the Fibroscan (Echosens, France), point shear wave speed measurement using an acoustic radiation force impulse (Siemens, Germany) and 2D shear wave elastography using the Aixplorer (SuperSonic Imagine, France). More recently, also other manufacturers have introduced shear wave elastography technology into the market. A comparison of data obtained using different techniques for shear wave propagation and velocity measurement is of key interest for future studies, recommendations and guidelines. Here, we present a recently introduced shear wave elastography technology from Hitachi and discuss its reproducibility and comparability to the already established technologies.

Seismic cycle feedbacks in a mid-crustal shear zone

Science.gov (United States)

Melosh, Benjamin L.; Rowe, Christie D.; Gerbi, Christopher; Smit, Louis; Macey, Paul

2018-07-01

Mid-crustal fault rheology is controlled by alternating brittle and plastic deformation mechanisms, which cause feedback cycles that influence earthquake behavior. Detailed mapping and microstructural observations in the Pofadder Shear Zone (Namibia and South Africa) reveal a lithologically heterogeneous shear zone core with quartz-rich mylonites and ultramylonites, plastically overprinted pseudotachylyte and active shear folds. We present evidence for a positive feedback cycle in which coseismic grain size reduction facilitates active shear folding by enhancing competency contrasts and promoting crystal plastic flow. Shear folding strengthens a portion of a shear zone by limb rotation, focusing deformation and promoting plastic flow or brittle slip in resulting areas of localized high stress. Using quartz paleopiezometry, we estimate strain and slip rates consistent with other studies of exhumed shear zones and modern plate boundary faults, helping establish the Pofadder Shear Zone as an ancient analogue to modern, continental-scale, strike-slip faults. This feedback cycle influences seismicity patterns at the scale of study (10s of meters) and possibly larger scales as well, and contributes to bulk strengthening of the brittle-plastic transition on modern plate boundary faults.

Exact solutions for oscillatory shear sweep behaviors of complex fluids from the Oldroyd 8-constant framework

Science.gov (United States)

Saengow, Chaimongkol; Giacomin, A. Jeffrey

2018-03-01

In this paper, we provide a new exact framework for analyzing the most commonly measured behaviors in large-amplitude oscillatory shear flow (LAOS), a popular flow for studying the nonlinear physics of complex fluids. Specifically, the strain rate sweep (also called the strain sweep) is used routinely to identify the onset of nonlinearity. By the strain rate sweep, we mean a sequence of LAOS experiments conducted at the same frequency, performed one after another, with increasing shear rate amplitude. In this paper, we give exact expressions for the nonlinear complex viscosity and the corresponding nonlinear complex normal stress coefficients, for the Oldroyd 8-constant framework for oscillatory shear sweeps. We choose the Oldroyd 8-constant framework for its rich diversity of popular special cases (we list 18 of these). We evaluate the Fourier integrals of our previous exact solution to get exact expressions for the real and imaginary parts of the complex viscosity, and for the complex normal stress coefficients, as functions of both test frequency and shear rate amplitude. We explore the role of infinite shear rate viscosity on strain rate sweep responses for the special case of the corotational Jeffreys fluid. We find that raising η∞ raises the real part of the complex viscosity and lowers the imaginary. In our worked examples, we thus first use the corotational Jeffreys fluid, and then, for greater accuracy, we use the Johnson-Segalman fluid, to describe the strain rate sweep response of molten atactic polystyrene. For our comparisons with data, we use the Spriggs relations to generalize the Oldroyd 8-constant framework to multimode. Our generalization yields unequivocally, a longest fluid relaxation time, used to assign Weissenberg and Deborah numbers to each oscillatory shear flow experiment. We then locate each experiment in the Pipkin space.

Accumulation of metabolites during bacterial degradation of PAH-mixtures

Energy Technology Data Exchange (ETDEWEB)

Vila, J.; Lopez, Z.; Bauza, J.I. [Universitat de Barcelona (Spain). Department de Microbiologia; Minguillon, C. [Parc Cientific de Barcelona (ES). Institut de Recerca de Barcelona (IRB-PCB); Grifoll, M.

2003-07-01

In a previous work we identified a number of metabolites accumulated during growth in pyrene by Mycobacterium sp. AP1, and proposed a metabolic pathway for pyrene utilization. In order to confirm and complete this pathway we have isolated and identified the pyrene-degrading strains Mycobacterium sp. PGP2, CP1 and CP2. During growth on pyrene, strains AP1, PGP2, CP1 and CP2 accumulated 4,5-cis-pyrene-dihydrodiol, 4,5-phenanthrene dicarboxylic acid, 4-phenanthrene carboxylic acid, 3,4-dihydroxy-3-hydrophenanthrene-4-carboxylic acid, phthalic acid, and 6,6'-dihydroxy-2,2'-biphenyl dicarboxylic acid. Strains AP1, PGP2, CP1 and CP2 also grew on fluoranthene accumulating acenaphthenone, naphthalene-1,8-dicarboxylic acid, 9-fluorenone-1-carboxylic acid, Z-9-carboxymethylenefluorene-1-carboxylic acid and benzene-1,2,3-tricarboxylic acid. Similar metabolites were produced during growth onf fluoranthene by the Gram-positive strains CFt2 and CFt6, isolated by their capability of using this PAH as a sole source of carbon and energy. These fluoranthene-degrading strains also accumulated cis-1,9a-dihydroxy-1-hydrofluorene-9-one-8-carboxylic acid. In addition to pyrene and fluoranthene, all pyrene-degrading utilized phenanthrene as a sole source of carbon and energy, while the fluoranthene-degrading strains were unable to utilize pyrene or phenanthrene. Mycobacterium sp. AP1 acted on a wide range of PAHs, accumulating aromatic dicarboxylic acids, hydroxyacids, and ketones resulting from dioxygenation and ortho-cleavage, dioxygenation and meta-cleavage, and monooxygenation reactions. In cultures of strains AP1 and CP1 with a defined PAH-mixture only 20% removal of the parent compounds was observed. Analysis of acidic extracts showed the accumulation of the anticipated aromatic acids, suggesting that accumulation of acidic compounds could prevent further degradation of the mixture. Those results led us to isolation of strains DF11 and OH3, able to grow on the selected

On the use of accumulative roll bonding process to develop nanostructured aluminum alloy 5083

Energy Technology Data Exchange (ETDEWEB)

Reza Toroghinejad, Mohammad; Ashrafizadeh, Fakhreddin [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Jamaati, Roohollah, E-mail: r.jamaatikenari@ma.iut.ac.ir [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Young Researchers Club, Ayatollah Amoli Branch, Islamic Azad University, Amol (Iran, Islamic Republic of)

2013-01-20

In the present study, the effect of accumulative roll bonding (ARB) process at room temperature on the microstructure and mechanical properties of AA5083 strip was investigated. Microstructural observations were done by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Also, mechanical properties were performed by tensile, hardness, and microhardness tests. It was observed that accumulative roll bonding is a promising process for production of nanostructured (80 nm) AA5083 strips. Nano shear bands were formed in the microstructure after the fourth cycles. When the number of cycles increased, the tensile strength and hardness of the accumulatively roll bonded strips increased. However, by increasing the number of cycles, the elongation value decreased except for the last (sixth) cycle. It was found that when the number of cycles increased, the distribution of microhardness values became more uniform. After the tensile test, debonding can be observed especially in the interface formed in the last cycle. Observations revealed that the failure mode in the accumulatively roll bonded AA5083 strip was a shear ductile rupture with elongated shallow shear dimples.

Metamorphism and Shear Localization in the Oceanic and Continental Lithosphere: A Local or Lithospheric-Scale Effect?

Science.gov (United States)

Montesi, L.

2017-12-01

Ductile rheologies are characterized by strain rate hardening, which favors deformation zones that are as wide as possible, thus minimizing strain rate and stress. By contrast, plate tectonics and the observation of ductile shear zones in the exposed middle to lower crust show that deformation is often localized, that is, strain (and likely strain rate) is locally very high. This behavior is most easily explained if the material in the shear zone is intrinsically weaker than the reference material forming the wall rocks. Many origins for that weakness have been proposed. They include higher temperature (shear heating), reduced grain size, and fabric. The latter two were shown to be the most effective in the middle crust and upper mantle (given observational limits restricting heating to 50K or less) but they were not very important in the lower crust. They are not sufficient to explain the generation of narrow plate boundaries in the oceans. We evaluate here the importance of metamorphism, especially related to hydration, in weakening the lithosphere. Serpentine is a major player in the dynamics of the oceanic lithosphere. Although its ductile behavior is poorly constrained, serpentine is likely to behave in a brittle or quasi-plastic manner with a reduced coefficient of friction, replacing stronger peridotite. Serpentinization sufficiently weakens the oceanic lithosphere to explain the generation of diffuse plate boundaries and, combined with grain size reduction, the development of narrow plate boundaries. Lower crust outcrops, especially in the Bergen Arc (Norway), display eclogite shear zones hosted in metastable granulites. The introduction of water triggered locally a metamorphic reaction that reduces rock strength and resulted in a ductile shear zone. The presence of these shear zones has been used to explain the weakness of the lower crust perceived from geodesy and seismic activity. We evaluate here how much strain rate may increase as a result of

Tailoring the gradient ultrafine-grained structure in low-carbon steel during drawing with shear

Directory of Open Access Journals (Sweden)

G. I. Raab

2016-04-01

Full Text Available Conventional drawing and drawing with shear were conducted on the rods of low-carbon steel. Deformation by simple drawing forms basically a homogenous structure and leads to a uniform change in microhardness along the billet volume. A comparative analysis of the models of these processes showed that shear drawing of steel at room temperature reduces energy characteristics in half, normal forces on the die – by 1,8, and enhances the strain intensity from 0,5 to 1,6. During drawing with shear, strain-induced cementite dissolution occurs and a gradient structure is formed, which increases the microhardness of the surface layer up to values close to 7 000 MPa.

Dynamic behavior and functional integrity tests on RC shear walls

International Nuclear Information System (INIS)

Akino, Kinji; Nasuda, Toshiaki; Shibata, Akenori.

1991-01-01

A project consisting of seven subprojects has been conducted to study the dynamic behavior and functional integrity of reinforced concrete (RC) shear walls in reactor buildings. The objective of this project is to obtain the data to improve and prepare the seismic analysis code regarding the nonlinear structural behavior and integrity of reactor buildings during and after earthquakes. The project started in April, 1986, and will end in March, 1994. Seven subprojects are strain rate test, damping characteristic test, ultimate state response test and the verification test for the test of restoring force characteristics regarding dynamic restoring force characteristics and damping performance; the restoring force characteristic test on the shear walls with openings; and pull-out strength test and the test on air leakage through concrete cracks regarding the functional integrity. The objectives of respective subprojects, the test models and the interim results are reported. Three subprojects have been completed by March, 1990. The results of these projects will be used for the overall evaluation. The strain rate test showed that the ultimate strength of shear walls increased with strain rate. A formula for estimating air flow through the cracks in walls was given by the leakage test. (K.I.)

Correlation of data on strain accumulation adjacent to the San Andreas Fault with available models

Science.gov (United States)

Turcotte, Donald L.

1986-01-01

Theoretical and numerical studies of deformation on strike slip faults were performed and the results applied to geodetic observations performed in the vicinity of the San Andreas Fault in California. The initial efforts were devoted to an extensive series of finite element calculations of the deformation associated with cyclic displacements on a strike-slip fault. Measurements of strain accumulation adjacent to the San Andreas Fault indicate that the zone of strain accumulation extends only a few tens of kilometers away from the fault. There is a concern about the tendency to make geodetic observations along the line to the source. This technique has serious problems for strike slip faults since the vector velocity is also along the fault. Use of a series of stations lying perpendicular to the fault whose positions are measured relative to a reference station are suggested to correct the problem. The complexity of faulting adjacent to the San Andreas Fault indicated that the homogeneous elastic and viscoelastic approach to deformation had serious limitations. These limitation led to the proposal of an approach that assumes a fault is composed of a distribution of asperities and barriers on all scales. Thus, an earthquake on a fault is treated as a failure of a fractal tree. Work continued on the development of a fractal based model for deformation in the western United States. In order to better understand the distribution of seismicity on the San Andreas Fault system a fractal analog was developed. The fractal concept also provides a means of testing whether clustering in time or space is a scale-invariant process.

Shear strength behavior of geotextile/geomembrane interfaces

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Belén M. Bacas

2015-12-01

Full Text Available This paper aims to study the shear interaction mechanism of one of the critical geosynthetic interfaces, the geotextile/geomembrane, typically used for lined containment facilities such as landfills. A large direct shear machine is used to carry out 90 geosynthetic interface tests. The test results show a strain softening behavior with a very small dilatancy (<0.5 mm and nonlinear failure envelopes at a normal stress range of 25–450 kPa. The influences of the micro-level structure of these geosynthetics on the macro-level interface shear behavior are discussed in detail. This study has generated several practical recommendations to help professionals to choose what materials are more adequate. From the three geotextiles tested, the thermally bonded monofilament exhibits the best interface shear strength under high normal stress. For low normal stress, however, needle-punched monofilaments are recommended. For the regular textured geomembranes tested, the space between the asperities is an important factor. The closer these asperities are, the better the result achieves. For the irregular textured geomembranes tested, the nonwoven geotextiles made of monofilaments produce the largest interface shear strength.

Fifty years of shear zones

Science.gov (United States)

Graham, Rodney

2017-04-01

temperature shear zones with flaser gabbro and amphibolitization must have been developed at deeper levels in the shear zone and 'dragged upwards'. An attempt to justify these assertions will made using outcrop exsmples and some deep Seismic data John Ramsay was always cautious about up-scaling and indulging in large scale tectonic speculations, but without his geometric acumen the big scale picture would have been even less clear. Ramsay, J.G. and Graham, R.H., 1970. Strain variation in shear belts. Canadian Journal of Earth Sciences, 7(3), pp.786-813.

Effect of Asymmetric Rolling on Plastic Anisotropy of Low Carbon Steels during Simple Shear Tests

International Nuclear Information System (INIS)

Gracio, J. J.; Vincze, G.; Panigrahi, B. B.; Kim, H. J.; Barlat, F.; Rauch, E. F.; Yoon, J. W.

2010-01-01

Simple shear tests are performed on low carbon steel pre-deformed in conventional, asymmetric and orthogonal-asymmetric rolling. The simple-shear tests were carried out at 0 deg. , 45 deg. and 135 deg. with respect to the previous rolling direction. For a reduction ratio of 15%, a transient stagnation in the hardening rate is observed at reloading for all changes in strain path. The shear stress level, the hardening rate and extent of the plateau appear to be insensitive to the preliminary applied rolling conditions. After a reduction ratio of 50%, plastic instability was detected at reloading for all the changes of strain path and rolling conditions studied. A specific heat treatment was then designed allowing the material to become ductile after rolling while retaining the fine microstructure and therefore the high strength. Promising results were obtained essentially for 45 deg. shear tests.

Shear Strengthening of RC Beams Using Sprayed Glass Fiber Reinforced Polymer

Directory of Open Access Journals (Sweden)

Sayed Mohamad Soleimani

2012-01-01

Full Text Available The effectiveness of externally bonded sprayed glass fiber reinforced polymer (Sprayed GFRP in shear strengthening of RC beams under quasi-static loading is investigated. Different techniques were utilized to enhance the bond between concrete and Sprayed GFRP, involving the use of through bolts and nuts paired with concrete surface preparation through sandblasting and through the use of a pneumatic chisel prior to Sprayed GFRP application. It was found that roughening the concrete surface using a pneumatic chisel and using through bolts and nuts were the most effective techniques. Also, Sprayed GFRP applied on 3 sides (U-shaped was found to be more effective than 2-sided Sprayed GFRP in shear strengthening. Sprayed GFRP increased the shear load-carrying capacity and energy absorption capacities of RC beams. It was found that the load-carrying capacity of strengthened RC beams was related to an effective strain of applied Sprayed GFRP. This strain was related to Sprayed GFRP configuration and the technique used to enhance the concrete-FRP bond. Finally, an equation was proposed to calculate the contribution of Sprayed GFRP in the shear strength of an RC beam.

Hoof position during limb loading affects dorsoproximal bone strains on the equine proximal phalanx.

Science.gov (United States)

Singer, Ellen; Garcia, Tanya; Stover, Susan

2015-07-16

Sagittal fractures of the proximal phalanx (P1) in the racehorse appear to be associated with turf racing surfaces, which are known to restrict forward slide of the foot at impact. We hypothesized that restriction of forward foot slip would result in higher P1 bone strains during metacarpophalangeal joint (MCPJ) hyperextension. Unilateral limbs from six equine cadavers were instrumented with strain gauges and bone reference markers to measure dorsoproximal P1 bone strains and MCPJ extension, collateromotion and axial rotation during in vitro limb loading to 10,500 N. By limiting movement of the distal actuator platform, three different foot conditions (forward, free, and restricted) were applied in a randomised block design. Bone reference markers, recorded by video, were analyzed to determine motion of P1 relative to MC3. Rosette strain data were reduced to principal and shear magnitudes and directions. A mixed model ANOVA determined the effect of foot position on P1 bone strains and MCPJ angles. At 10,000 N load, the restricted condition resulted in higher P1 axial compressive (p=0.015), maximum shear (p=0.043) and engineering shear (p=0.046) strains compared to the forward condition. The restricted condition had higher compressive (p=0.025) and lower tensile (p=0.043) principal strains compared to the free condition. For the same magnitude of principal or shear strains, axial rotation and collateromotion angles were greatest for the restricted condition. Therefore, the increase in P1 principal compressive and shear bone strains associated with restricted foot slip indicate that alterations in foot:ground interaction may play a role in fracture occurrence in horses. Copyright © 2015 Elsevier Ltd. All rights reserved.

Ab initio study of Ni2MnGa under shear deformation

Directory of Open Access Journals (Sweden)

Zelený Martin

2015-01-01

Full Text Available The effect of shear deformation on Ni2MnGa magnetic shape memory alloy has been investigated using ab initio electronic structure calculations. We used the projector-augmented wave method for the calculations of total energies and stresses as functions of applied affine shear deformation. The studied nonmodulated martensite (NM phase exhibits a tetragonally distorted L21 structure with c/a > 1. A large strain corresponding to simple shears in {001}, {100} and {100} systems was applied to describe a full path between two equivalent NM lattices. We also studied {101} shear which is related to twining of NM phase. Twin reorientation in this system is possible, because applied positive shear results in path with significantly smaller energetic barrier than for negative shear and for shears in other studied systems. When the full relaxation of lattice parameters is allowed, the barriers further strongly decrease and the structures along the twinning path can be considered as orthorhombic.

Creep behavior in interlaminar shear of a Hi-Nicalon™/SiC–B4C composite at 1200 °C in air and in steam

International Nuclear Information System (INIS)

Ruggles-Wrenn, M.B.; Pope, M.T.; Zens, T.W.

2014-01-01

Creep behavior in interlaminar shear of a non-oxide ceramic composite with a multilayered matrix was investigated at 1200 °C in laboratory air and in steam environment. The composite was produced via chemical vapor infiltration (CVI). The composite had an oxidation inhibited matrix, which consisted of alternating layers of silicon carbide and boron carbide and was reinforced with laminated Hi-Nicalon™ fibers woven in a five-harness-satin weave. Fiber preforms had pyrolytic carbon fiber coating with boron carbon overlay applied. The interlaminar shear properties were measured. The creep behavior was examined for interlaminar shear stresses in the 16–22 MPa range. Primary and secondary creep regimes were observed in all tests conducted in air and in steam. In air and in steam, creep run-out defined as 100 h at creep stress was achieved at 16 MPa. Similar creep strains were accumulated in air and in steam. Furthermore, creep strain rates and creep lifetimes were only moderately affected by the presence of steam. The retained properties of all specimens that achieved run-out were characterized. Composite microstructure, as well as damage and failure mechanisms were investigated. The tested specimens were also examined using electron probe microanalysis (EPMA) with wavelength dispersive spectroscopy (WDS). Analysis of the fracture surfaces revealed significant surface oxidation, but only trace amounts of boron and carbon. Cross sectional analysis showed increasing boron concentration in the specimen interior

Microstructural evolution, mechanical properties, and strain hardening behavior of ultrafine grained commercial pure copper during the accumulative roll bonding process

Energy Technology Data Exchange (ETDEWEB)

Fattah-alhosseini, A. [Department of Materials Engineering, Bu-Ali Sina University, Hamedan 65178-38695 (Iran, Islamic Republic of); Imantalab, O., E-mail: o.imantalab@gmail.com [Department of Materials Engineering, Bu-Ali Sina University, Hamedan 65178-38695 (Iran, Islamic Republic of); Mazaheri, Y. [Department of Materials Engineering, Bu-Ali Sina University, Hamedan 65178-38695 (Iran, Islamic Republic of); Keshavarz, M.K. [Department of Engineering Physics, Polytechnique Montreal, Montreal (Canada)

2016-01-05

In this study, the microstructural evolution, mechanical properties, and strain hardening behavior of commercial pure copper processed by the accumulative roll bonding (ARB) were investigated. Transmission electron microscopy (TEM) micrographs and atomic force microscopy (AFM) images indicated that with increasing the number of ARB cycles, the grain size of samples decreased. An Ultrafine grained (UFG) structure with an average grain size of about 200 nm was achieved after four cycles of ARB. The yield and ultimate tensile strength of pure copper with the UFG microstructure was reached about 360 MPa and 396 MPa (about 400% and 100% higher than that of the annealed state), respectively. All ARB-processed copper samples showed lower strain hardening exponent in comparison with the annealed state. Moreover, the strain hardening rate increased with increasing ARB cycles up to 3 cycles and then decreased.

Microstructural evolution, mechanical properties, and strain hardening behavior of ultrafine grained commercial pure copper during the accumulative roll bonding process

International Nuclear Information System (INIS)

Fattah-alhosseini, A.; Imantalab, O.; Mazaheri, Y.; Keshavarz, M.K.

2016-01-01

In this study, the microstructural evolution, mechanical properties, and strain hardening behavior of commercial pure copper processed by the accumulative roll bonding (ARB) were investigated. Transmission electron microscopy (TEM) micrographs and atomic force microscopy (AFM) images indicated that with increasing the number of ARB cycles, the grain size of samples decreased. An Ultrafine grained (UFG) structure with an average grain size of about 200 nm was achieved after four cycles of ARB. The yield and ultimate tensile strength of pure copper with the UFG microstructure was reached about 360 MPa and 396 MPa (about 400% and 100% higher than that of the annealed state), respectively. All ARB-processed copper samples showed lower strain hardening exponent in comparison with the annealed state. Moreover, the strain hardening rate increased with increasing ARB cycles up to 3 cycles and then decreased.

Coexistence and transition between shear zones in slow granular flows.

Science.gov (United States)

Moosavi, Robabeh; Shaebani, M Reza; Maleki, Maniya; Török, János; Wolf, Dietrich E; Losert, Wolfgang

2013-10-04

We report experiments on slow granular flows in a split-bottom Couette cell that show novel strain localization features. Nontrivial flow profiles have been observed which are shown to be the consequence of simultaneous formation of shear zones in the bulk and at the boundaries. The fluctuating band model based on a minimization principle can be fitted to the experiments over a large variation of morphology and filling height with one single fit parameter, the relative friction coefficient μ(rel) between wall and bulk. The possibility of multiple shear zone formation is controlled by μ(rel). Moreover, we observe that the symmetry of an initial state, with coexisting shear zones at both side walls, breaks spontaneously below a threshold value of the shear velocity. A dynamical transition between two asymmetric flow states happens over a characteristic time scale which depends on the shear strength.

Comparison of shear wave velocity measurements assessed with two different ultrasound systems in an ex-vivo tendon strain phantom.

Science.gov (United States)

Rosskopf, Andrea B; Bachmann, Elias; Snedeker, Jess G; Pfirrmann, Christian W A; Buck, Florian M

2016-11-01

The purpose of this study is to compare the reliability of SW velocity measurements of two different ultrasound systems and their correlation with the tangent traction modulus in a non-static tendon strain model. A bovine tendon was fixed in a custom-made stretching device. Force was applied increasing from 0 up to 18 Newton. During each strain state the tangent traction modulus was determined by the stretcher device, and SW velocity (m/s) measurements using a Siemens S3000 and a Supersonic Aixplorer US machine were done for shear modulus (kPa) calculation. A strong significant positive correlation was found between SW velocity assessed by the two ultrasound systems and the tangent traction modulus (r = 0.827-0.954, p Aixplorer 0.25 ± 0.3 m/s (p = 0.034). Mean difference of SW velocity between the two US-systems was 0.37 ± 0.3 m/s (p = 0.012). In conclusion, SW velocities are highly dependent on mechanical forces in the tendon tissue, but for controlled mechanical loads appear to yield reproducible and comparable measurements using different US systems.

Increased ethanol accumulation from glucose via reduction of ATP level in a recombinant strain of Saccharomyces cerevisiae overexpressing alkaline phosphatase.

Science.gov (United States)

Semkiv, Marta V; Dmytruk, Kostyantyn V; Abbas, Charles A; Sibirny, Andriy A

2014-05-15

The production of ethyl alcohol by fermentation represents the largest scale application of Saccharomyces cerevisiae in industrial biotechnology. Increased worldwide demand for fuel bioethanol is anticipated over the next decade and will exceed 200 billion liters from further expansions. Our working hypothesis was that the drop in ATP level in S. cerevisiae cells during alcoholic fermentation should lead to an increase in ethanol production (yield and productivity) with a greater amount of the utilized glucose converted to ethanol. Our approach to achieve this goal is to decrease the intracellular ATP level via increasing the unspecific alkaline phosphatase activity. Intact and truncated versions of the S. cerevisiae PHO8 gene coding for vacuolar or cytosolic forms of alkaline phosphatase were fused with the alcohol dehydrogenase gene (ADH1) promoter. The constructed expression cassettes used for transformation vectors also contained the dominant selective marker kanMX4 and S. cerevisiae δ-sequence to facilitate multicopy integration to the genome. Laboratory and industrial ethanol producing strains BY4742 and AS400 overexpressing vacuolar form of alkaline phosphatase were characterized by a slightly lowered intracellular ATP level and biomass accumulation and by an increase in ethanol productivity (13% and 7%) when compared to the parental strains. The strains expressing truncated cytosolic form of alkaline phosphatase showed a prolonged lag-phase, reduced biomass accumulation and a strong defect in ethanol production. Overexpression of vacuolar alkaline phosphatase leads to an increased ethanol yield in S. cerevisiae.

Bolt Shear Force Sensor

Science.gov (United States)

2015-03-12

0030] FIG. 7 is an isometric view of a deformable ring of the bolt shear force sensor of the present invention with an optical Attorney Docket No...102587 9 of 19 fiber having Bragg gratings wound around the ring; [0031] FIG. 8 is an isometric view of the deformable ring with wire strain... strength . [0047] Once the joint is subjected to an external load (see force arrows “F” and “F/2”); any frictional resistance to slip is overcome and

Effect of single-particle magnetostriction on the shear modulus of compliant magnetoactive elastomers

Science.gov (United States)

Kalita, Viktor M.; Snarskii, Andrei A.; Shamonin, Mikhail; Zorinets, Denis

2017-03-01

The influence of an external magnetic field on the static shear strain and the effective shear modulus of a magnetoactive elastomer (MAE) is studied theoretically in the framework of a recently introduced approach to the single-particle magnetostriction mechanism [V. M. Kalita et al., Phys. Rev. E 93, 062503 (2016), 10.1103/PhysRevE.93.062503]. The planar problem of magnetostriction in an MAE with magnetically soft inclusions in the form of a thin disk (platelet) having the magnetic anisotropy in the plane of this disk is solved analytically. An external magnetic field acts with torques on magnetic filler particles, creates mechanical stresses in the vicinity of inclusions, induces shear strain, and increases the effective shear modulus of these composite materials. It is shown that the largest effect of the magnetic field on the effective shear modulus should be expected in MAEs with soft elastomer matrices, where the shear modulus of the matrix is less than the magnetic anisotropy constant of inclusions. It is derived that the effective shear modulus is nonlinearly dependent on the external magnetic field and approaches the saturation value in magnetic fields exceeding the field of particle anisotropy. It is shown that model calculations of the effective shear modulus correspond to a phenomenological definition of effective elastic moduli and magnetoelastic coupling constants. The obtained theoretical results compare well with known experimental data. Determination of effective elastic coefficients in MAEs and their dependence on magnetic field is discussed. The concentration dependence of the effective shear modulus at higher filler concentrations has been estimated using the method of Padé approximants, which predicts that both the absolute and relative changes of the magnetic-field-dependent effective shear modulus will significantly increase with the growing concentration of filler particles.

Microstructure and texture development during high-strain torsion of NiAl

Energy Technology Data Exchange (ETDEWEB)

Kloeden, B.

2006-07-01

In this study polycrystalline NiAl has been subjected to torsion deformation. The deformation, microstructure and texture development subject to the shear strain are studied by different techniques (Electron Back-Scatter and High Energy Synchrotron Radiation). Beside the development of microstructure and texture with shear strain, the effect of an initial texture as well as the deformation temperature on the development of texture and microstructure constitute an important part of this study. Therefore, samples with three different initial textures were deformed in the temperature range T=700 K-1300 K. The shear stress-shear strain curves are characterized by a peak at low strains, which is followed by softening and a steady state at high strains. Grain refinement takes place for all samples and the average grain size decreases with temperature. For temperatures T>1000 K, discontinuous dynamic recrystallization occurs, by which new grains form by nucleation and subsequent growth. The texture is characterized by two components, {l_brace}100{r_brace}<100> (cube,C) and {l_brace}110{r_brace}<100> (Goss,G). Torsional creep of NiAl is characterized by a stress exponent, which depends on temperature and an activation energy, which is stress dependent. The Swift effect, due to which samples change their axial dimension during torsion without applied axial stress, is observed for NiAl. (orig.)

Characterization of Shear Properties for APO/MBI Syntactic Foam

Energy Technology Data Exchange (ETDEWEB)

Reser, Patrick M. [Univ. of New Mexico, Albuquerque, NM (United States); Lewis, Matthew W. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Clark, Jarod [Univ. of New Mexico, Albuquerque, NM (United States); Ahuja, Nishant [Univ. of New Mexico, Albuquerque, NM (United States); Lenke, Lary R. [Univ. of New Mexico, Albuquerque, NM (United States)

2017-12-14

their procedures are discussed in Chapter 2. Chapter 2 contains the types of tests performed and the apparatus used for testing the material. Chapter 2 also has a brief explanation of the equipment and the procedures used for conducting the tests. In Chapter 3, the material characteristics and mechanical properties obtained from the tests are described; composite plots of deviatoric vs. mean stress and deviatoric stress vs. longitudinal strain are also included. The plots of deviatoric stress vs. mean stress clearly identify the shear envelope for the material. Chapter 4 summarizes the vital information obtained from the tests and the conclusions made. All the necessary plots and the data generated during the testing have been included in the Appendix. The information in the appendix includes plots of: Strain vs. Time, Stress vs. Time, Stress vs. Strain, Mean Stress vs. Volumetric Strain, Lateral Strain vs. Longitudinal Strain, and q vs. p. Bulk modulus, Poisson’s ratio, and Young’s modulus are displayed in the appropriate plots in each appendix.

Interseismic strain accumulation and the earthquake potential on the southern San Andreas fault system.

Science.gov (United States)

Fialko, Yuri

2006-06-22

The San Andreas fault in California is a mature continental transform fault that accommodates a significant fraction of motion between the North American and Pacific plates. The two most recent great earthquakes on this fault ruptured its northern and central sections in 1906 and 1857, respectively. The southern section of the fault, however, has not produced a great earthquake in historic times (for at least 250 years). Assuming the average slip rate of a few centimetres per year, typical of the rest of the San Andreas fault, the minimum amount of slip deficit accrued on the southern section is of the order of 7-10 metres, comparable to the maximum co-seismic offset ever documented on the fault. Here I present high-resolution measurements of interseismic deformation across the southern San Andreas fault system using a well-populated catalogue of space-borne synthetic aperture radar data. The data reveal a nearly equal partitioning of deformation between the southern San Andreas and San Jacinto faults, with a pronounced asymmetry in strain accumulation with respect to the geologically mapped fault traces. The observed strain rates confirm that the southern section of the San Andreas fault may be approaching the end of the interseismic phase of the earthquake cycle.

Molecular characteristics of stress overshoot for polymer melts under start-up shear flow.

Science.gov (United States)

Jeong, Sohdam; Kim, Jun Mo; Baig, Chunggi

2017-12-21

Stress overshoot is one of the most important nonlinear rheological phenomena exhibited by polymeric liquids undergoing start-up shear at sufficient flow strengths. Despite considerable previous research, the fundamental molecular characteristics underlying stress overshoot remain unknown. Here, we analyze the intrinsic molecular mechanisms behind the overshoot phenomenon using atomistic nonequilibrium molecular dynamics simulations of entangled linear polyethylene melts under shear flow. Through a detailed analysis of the transient rotational chain dynamics, we identify an intermolecular collision angular regime in the vicinity of the chain orientation angle θ ≈ 20° with respect to the flow direction. The shear stress overshoot occurs via strong intermolecular collisions between chains in the collision regime at θ = 15°-25°, corresponding to a peak strain of 2-4, which is an experimentally well-known value. The normal stress overshoot appears at approximately θ = 10°, at a corresponding peak strain roughly equivalent to twice that for the shear stress. We provide plausible answers to several basic questions regarding the stress overshoot, which may further help understand other nonlinear phenomena of polymeric systems.

Development of Test Method for Simple Shear and Prediction of Hardening Behavior Considering the Branchings Effect

International Nuclear Information System (INIS)

Kim, Dongwook; Bang, Sungsik; Kim, Minsoo; Lee, Hyungyil; Kim, Naksoo

2013-01-01

In this study we establish a process to predict hardening behavior considering the Branchings effect for zircaloy-4 sheets. When a metal is compressed after tension in forming, the yield strength decreases. For this reason, the Branchings effect should be considered in FE simulations of spring-back. We suggested a suitable specimen size and a method for determining the optimum tightening torque for simple shear tests. Shear stress-strain curves are obtained for five materials. We developed a method to convert the shear load-displacement curve to the effective stress-strain curve with Fea. We simulated the simple shear forward/reverse test using the combined isotropic/kinematic hardening model. We also investigated the change of the load-displacement curve by varying the hardening coefficients. We determined the hardening coefficients so that they follow the hardening behavior of zircaloy-4 in experiments

Development of Test Method for Simple Shear and Prediction of Hardening Behavior Considering the Branchings Effect

Energy Technology Data Exchange (ETDEWEB)

Kim, Dongwook; Bang, Sungsik; Kim, Minsoo; Lee, Hyungyil; Kim, Naksoo [Sogang Univ., Seoul (Korea, Republic of)

2013-10-15

In this study we establish a process to predict hardening behavior considering the Branchings effect for zircaloy-4 sheets. When a metal is compressed after tension in forming, the yield strength decreases. For this reason, the Branchings effect should be considered in FE simulations of spring-back. We suggested a suitable specimen size and a method for determining the optimum tightening torque for simple shear tests. Shear stress-strain curves are obtained for five materials. We developed a method to convert the shear load-displacement curve to the effective stress-strain curve with Fea. We simulated the simple shear forward/reverse test using the combined isotropic/kinematic hardening model. We also investigated the change of the load-displacement curve by varying the hardening coefficients. We determined the hardening coefficients so that they follow the hardening behavior of zircaloy-4 in experiments.

The effects of lower crustal strength and preexisting midcrustal shear zones on the formation of continental core complexes and low-angle normal faults

KAUST Repository

Wu, Guangliang

2016-08-22

To investigate the formation of core complexes and low-angle normal faults, we devise thermomechanical simulations on a simplified wedge-like orogenic hinterland that has initial topography, Moho relief, and a preexisting midcrustal shear zone that can accommodate shear at very low angles (<20°). We mainly vary the strength of the lower crust and the frictional strength of the preexisting midcrustal shear zone. We find that the strength of the lower crust and the existence and strength of a preexisting shear zone significantly affect the formation and evolution of core complexes. With increasing lower crustal strength, we recognize varying extensional features with decreasing exhumation rate: these are characterized by bivergent metamorphic massifs, classic Cordilleran metamorphic core complexes, multiple consecutive core complexes (or boudinage structures), and a flexural core complex underlined by a large subsurface low-angle detachment fault with a small convex curvature. Topographic loading and mantle buoyancy forces, together with divergent boundaries, drive a regional lower crustal flow that leads to the exhumation of the lower crust where intensive upper crustal faulting induces strong unloading. The detachment fault is a decoupling zone that accommodates large displacement and accumulates sustained shear strain at very low angle between upper and lower crust. Though the regional stress is largely Andersonian, we find non-Andersonian stress in regions adjacent to the preexisting shear zone and those with high topographic gradient. Our new models provide a view that is generally consistent with geological and geophysical observations on how core complexes form and evolve.

The effects of lower crustal strength and preexisting midcrustal shear zones on the formation of continental core complexes and low-angle normal faults

KAUST Repository

Wu, Guangliang; Lavier, Luc L.

2016-01-01

To investigate the formation of core complexes and low-angle normal faults, we devise thermomechanical simulations on a simplified wedge-like orogenic hinterland that has initial topography, Moho relief, and a preexisting midcrustal shear zone that can accommodate shear at very low angles (<20°). We mainly vary the strength of the lower crust and the frictional strength of the preexisting midcrustal shear zone. We find that the strength of the lower crust and the existence and strength of a preexisting shear zone significantly affect the formation and evolution of core complexes. With increasing lower crustal strength, we recognize varying extensional features with decreasing exhumation rate: these are characterized by bivergent metamorphic massifs, classic Cordilleran metamorphic core complexes, multiple consecutive core complexes (or boudinage structures), and a flexural core complex underlined by a large subsurface low-angle detachment fault with a small convex curvature. Topographic loading and mantle buoyancy forces, together with divergent boundaries, drive a regional lower crustal flow that leads to the exhumation of the lower crust where intensive upper crustal faulting induces strong unloading. The detachment fault is a decoupling zone that accommodates large displacement and accumulates sustained shear strain at very low angle between upper and lower crust. Though the regional stress is largely Andersonian, we find non-Andersonian stress in regions adjacent to the preexisting shear zone and those with high topographic gradient. Our new models provide a view that is generally consistent with geological and geophysical observations on how core complexes form and evolve.

On transformation shear of precipitated zirconia particles

International Nuclear Information System (INIS)

Zhang, J.M.; Lam, K.Y.

1993-01-01

A model is proposed to investigate the transformation shear of the precipitated zirconia particles which undergo a stress-induced lattice transformation from tetragonal to monoclinic symmetry. Kinematically admissible twinning planes and the corresponding twinning elements are determined according to the continuum theory of dispacive phase transformation. It is postulated that only one twinning mode prevails in each transformed particle and that the minimization of elastic strain energy change dictates the morphology of the transformed variants. The transformation shear is determined by the twinning mode and the volume fraction of the corresponding variant. Numerical calculations show that each of the six kinematically admissible twinning modes may be kinematically favorable and therefore operate in constrained particle. The actual transformation shear in a transformed particle is shown to be dependent on the transformation stress, on the particle shape as well as on the lattice orientation relative to the principal axes of the ellipsoidal particle

Model shear tests of canisters with smectite clay envelopes in deposition holes

International Nuclear Information System (INIS)

Boergesson, L.

1986-01-01

The consequences of rock displacement across a deposition hole has been investigated by some model tests. The model was scaled 1:10 to a real deposition hole. It was filled with a canister made of solid copper surrounded by highly compacted water saturated MX-80 bentonite. Before shear the swelling pressure was measured by six transducers in order to follow the water uptake process. During shear, pressure, strain, force and deformation were measured in altogether 18 points. The shearing was made at different rates in the various tests. An extensive sampling after shear was made through which the density, water content, degree of saturation, homogenization and the effect of shear on the bentonite and canister could be studied. One important conlusion from these tests was that the rate dependence is about 10% increased shear resistance per decade increased rate of shear. This resulted also in a very clear increase in strain in the canister with increased rate. The results also showed that the saturated bentonite has excellent stress distributing properties and that there is no risk of destroying the canister if the rock displacement is smaller than the thickness of the bentonite cover. The high density of the clay makes the bentonite produce such a high swelling pressure that the material will be very stiff. In the case of a larger shear deformation corresponding to ≅ 50% of the bentonite thickness the result will be a rather large deformation of the canister. A lower density would be preferable if it can be accepted with respect to other required isolating properties. The results also showed that three-dimensional FEM calculation using non-linear material properties is necessary to simulate the shear process. The rate dependence may be taken into account by adapting the properties to the actual rate of shear but might in a later stage be included in the model by giving the material viscous properties. (orig./HP)

A new dedicated finite element for push-over analysis of reinforced concrete shear wall systems

Directory of Open Access Journals (Sweden)

Delal Doğru ORMANCI

2016-06-01

Full Text Available In this study, a finite element which has been analyzed based on anisotropic behavior of reinforced shear walls is developed. Element stiffness matrices were varied based on whether the element is in the tension or the compression zone of the cross-section. Nonlinear behavior of reinforced shear wall model is investigated under horizontal loads. This behavior is defined with a similar approach to plastic hinge assumption in frame structures that the finite element behaves lineer elastic between joints and plastic deformations are concentrated on joints as vertical plastic displacements. According to this acceptance, plastic behavior of reinforced shear wall occurs when the vertical strain reaches elastic strain limit. In the definition of finite element, displacement functions are chosen considering that the partition of shear walls just at floor levels, are enough for solution. Results of this study are compared with the solution obtained from a different computer programme and experimental results.

Significant strain accumulation between the deformation front and landward out-of-sequence thrusts in accretionary wedge of SW Taiwan revealed by cGPS and SAR interferometry

Science.gov (United States)

Tsai, M. C.

2017-12-01

High strain accumulation across the fold-and-thrust belt in Southwestern Taiwan are revealed by the Continuous GPS (cGPS) and SAR interferometry. This high strain is generally accommodated by the major active structures in fold-and-thrust belt of western Foothills in SW Taiwan connected to the accretionary wedge in the incipient are-continent collision zone. The active structures across the high strain accumulation include the deformation front around the Tainan Tableland, the Hochiali, Hsiaokangshan, Fangshan and Chishan faults. Among these active structures, the deformation pattern revealed from cGPS and SAR interferometry suggest that the Fangshan transfer fault may be a left-lateral fault zone with thrust component accommodating the westward differential motion of thrust sheets on both side of the fault. In addition, the Chishan fault connected to the splay fault bordering the lower-slope and upper-slope of the accretionary wedge which could be the major seismogenic fault and an out-of-sequence thrust fault in SW Taiwan. The big earthquakes resulted from the reactivation of out-of-sequence thrusts have been observed along the Nankai accretionary wedge, thus the assessment of the major seismogenic structures by strain accumulation between the frontal décollement and out-of-sequence thrusts is a crucial topic. According to the background seismicity, the low seismicity and mid-crust to mantle events are observed inland and the lower- and upper- slope domain offshore SW Taiwan, which rheologically implies the upper crust of the accretionary wedge is more or less aseimic. This result may suggest that the excess fluid pressure from the accretionary wedge not only has significantly weakened the prism materials as well as major fault zone, but also makes the accretionary wedge landward extension, which is why the low seismicity is observed in SW Taiwan area. Key words: Continuous GPS, SAR interferometry, strain rate, out-of-sequence thrust.

Displacement-length scaling of brittle faults in ductile shear.

Science.gov (United States)

Grasemann, Bernhard; Exner, Ulrike; Tschegg, Cornelius

2011-11-01

Within a low-grade ductile shear zone, we investigated exceptionally well exposed brittle faults, which accumulated antithetic slip and rotated into the shearing direction. The foliation planes of the mylonitic host rock intersect the faults approximately at their centre and exhibit ductile reverse drag. Three types of brittle faults can be distinguished: (i) Faults developing on pre-existing K-feldspar/mica veins that are oblique to the shear direction. These faults have triclinic flanking structures. (ii) Wing cracks opening as mode I fractures at the tips of the triclinic flanking structures, perpendicular to the shear direction. These cracks are reactivated as faults with antithetic shear, extend from the parent K-feldspar/mica veins and form a complex linked flanking structure system. (iii) Joints forming perpendicular to the shearing direction are deformed to form monoclinic flanking structures. Triclinic and monoclinic flanking structures record elliptical displacement-distance profiles with steep displacement gradients at the fault tips by ductile flow in the host rocks, resulting in reverse drag of the foliation planes. These structures record one of the greatest maximum displacement/length ratios reported from natural fault structures. These exceptionally high ratios can be explained by localized antithetic displacement along brittle slip surfaces, which did not propagate during their rotation during surrounding ductile flow.

Displacement–length scaling of brittle faults in ductile shear

Science.gov (United States)

Grasemann, Bernhard; Exner, Ulrike; Tschegg, Cornelius

2011-01-01

Within a low-grade ductile shear zone, we investigated exceptionally well exposed brittle faults, which accumulated antithetic slip and rotated into the shearing direction. The foliation planes of the mylonitic host rock intersect the faults approximately at their centre and exhibit ductile reverse drag. Three types of brittle faults can be distinguished: (i) Faults developing on pre-existing K-feldspar/mica veins that are oblique to the shear direction. These faults have triclinic flanking structures. (ii) Wing cracks opening as mode I fractures at the tips of the triclinic flanking structures, perpendicular to the shear direction. These cracks are reactivated as faults with antithetic shear, extend from the parent K-feldspar/mica veins and form a complex linked flanking structure system. (iii) Joints forming perpendicular to the shearing direction are deformed to form monoclinic flanking structures. Triclinic and monoclinic flanking structures record elliptical displacement–distance profiles with steep displacement gradients at the fault tips by ductile flow in the host rocks, resulting in reverse drag of the foliation planes. These structures record one of the greatest maximum displacement/length ratios reported from natural fault structures. These exceptionally high ratios can be explained by localized antithetic displacement along brittle slip surfaces, which did not propagate during their rotation during surrounding ductile flow. PMID:26806996

Shearing single crystal magnesium in the close-packed basal plane at different temperatures

Science.gov (United States)

Han, Ming; Li, Lili; Zhao, Guangming

2018-05-01

Shear behaviors of single crystal magnesium (Mg) in close-packed (0001) basal plane along the [ 1 bar 2 1 bar 0 ], [ 1 2 bar 10 ], [ 10 1 bar 0 ] and [ 1 bar 010 ] directions were studied using molecular dynamics simulations via EAM potential. The results show that both shear stress-strain curves along the four directions and the motion path of free atoms during shearing behave periodic characteristics. It reveals that the periodic shear displacement is inherently related to the crystallographic orientation in single crystal Mg. Moreover, different temperatures in a range from 10 to 750 K were considered, demonstrating that shear modulus decreases with increasing temperatures. The results agree well with the MTS model. It is manifested that the modulus is independent with the shear direction and the size of the atomic model. This work also demonstrates that the classical description of shear modulus is still effective at the nanoscale.

Shear strength characteristics of mechanically biologically treated municipal solid waste (MBT-MSW) from Bangalore

International Nuclear Information System (INIS)

Sivakumar Babu, G.L.; Lakshmikanthan, P.; Santhosh, L.G.

2015-01-01

Highlights: • Shear strength properties of mechanically biologically treated municipal solid waste. • Effect of unit weight and particle size on the shear strength of waste. • Effect of particle size on the strength properties. • Stiffness ratio and the strength ratio of MSW. - Abstract: Strength and stiffness properties of municipal solid waste (MSW) are important in landfill design. This paper presents the results of comprehensive testing of shear strength properties of mechanically biologically treated municipal solid waste (MBT-MSW) in laboratory. Changes in shear strength of MSW as a function of unit weight and particle size were investigated by performing laboratory studies on the MSW collected from Mavallipura landfill site in Bangalore. Direct shear tests, small scale and large scale consolidated undrained and drained triaxial tests were conducted on reconstituted compost reject MSW samples. The triaxial test results showed that the MSW samples exhibited a strain-hardening behaviour and the strength of MSW increased with increase in unit weight. Consolidated drained tests showed that the mobilized shear strength of the MSW increased by 40% for a unit weight increase from 7.3 kN/m 3 to 10.3 kN/m 3 at 20% strain levels. The mobilized cohesion and friction angle ranged from 5 to 9 kPa and 8° to 33° corresponding to a strain level of 20%. The consolidated undrained tests exhibited reduced friction angle values compared to the consolidated drained tests. The friction angle increased with increase in the unit weight from 8° to 55° in the consolidated undrained tests. Minor variations were found in the cohesion values. Relationships for strength and stiffness of MSW in terms of strength and stiffness ratios are developed and discussed. The stiffness ratio and the strength ratio of MSW were found to be 10 and 0.43

Shear strength characteristics of mechanically biologically treated municipal solid waste (MBT-MSW) from Bangalore

Energy Technology Data Exchange (ETDEWEB)

Sivakumar Babu, G.L., E-mail: gls@civil.iisc.ernet.in [Department of Civil Engineering, Indian Institute of Science, Bangalore 560012 (India); Lakshmikanthan, P., E-mail: lakshmikanthancp@gmail.com [Centre for Sustainable Technologies (CST), Indian Institute of Science, Bangalore 560012 (India); Santhosh, L.G., E-mail: lgsanthu2006@gmail.com [Centre for Sustainable Technologies (CST), Indian Institute of Science, Bangalore 560012 (India)

2015-05-15

Highlights: • Shear strength properties of mechanically biologically treated municipal solid waste. • Effect of unit weight and particle size on the shear strength of waste. • Effect of particle size on the strength properties. • Stiffness ratio and the strength ratio of MSW. - Abstract: Strength and stiffness properties of municipal solid waste (MSW) are important in landfill design. This paper presents the results of comprehensive testing of shear strength properties of mechanically biologically treated municipal solid waste (MBT-MSW) in laboratory. Changes in shear strength of MSW as a function of unit weight and particle size were investigated by performing laboratory studies on the MSW collected from Mavallipura landfill site in Bangalore. Direct shear tests, small scale and large scale consolidated undrained and drained triaxial tests were conducted on reconstituted compost reject MSW samples. The triaxial test results showed that the MSW samples exhibited a strain-hardening behaviour and the strength of MSW increased with increase in unit weight. Consolidated drained tests showed that the mobilized shear strength of the MSW increased by 40% for a unit weight increase from 7.3 kN/m{sup 3} to 10.3 kN/m{sup 3} at 20% strain levels. The mobilized cohesion and friction angle ranged from 5 to 9 kPa and 8° to 33° corresponding to a strain level of 20%. The consolidated undrained tests exhibited reduced friction angle values compared to the consolidated drained tests. The friction angle increased with increase in the unit weight from 8° to 55° in the consolidated undrained tests. Minor variations were found in the cohesion values. Relationships for strength and stiffness of MSW in terms of strength and stiffness ratios are developed and discussed. The stiffness ratio and the strength ratio of MSW were found to be 10 and 0.43.

Internal shear cracking in bulk metal forming

DEFF Research Database (Denmark)

Christiansen, Peter; Nielsen, Chris Valentin; Bay, Niels Oluf

2017-01-01

This paper presents an uncoupled ductile damage criterion for modelling the opening and propagation of internal shear cracks in bulk metal forming. The criterion is built upon the original work on the motion of a hole subjected to shear with superimposed tensile stress triaxiality and its overall...... performance is evaluated by means of side-pressing formability tests in Aluminium AA2007-T6 subjected to different levels of pre-strain. Results show that the new proposed criterionis able to combine simplicity with efficiency for predicting the onset of fracture and the crack propagation path for the entire...... cracking to internal cracks formed undert hree-dimensional states of stress that are typical of bulk metal forming....

Characterization of a Bacillus amyloliquefaciens strain for reduction of citrulline accumulation during soy sauce fermentation.

Science.gov (United States)

Zhang, Jiran; Du, Guocheng; Chen, Jian; Fang, Fang

2016-10-01

To reduce the amount of citrulline produced by arginine-consuming bacteria in the moromi mash during soy sauce production. Bacillus amyloliquefaciens JY06, a salt-tolerant strain with high arginine consumption ability and low citrulline accumulation capacity, was isolated from moromi mash. The concentration of citrulline was decreased from 26.8 to 5.1 mM and ethyl carbamate in soy sauce, after sterilization, decreased from 97 to 17 μg kg(-1) when B. amyloliquefaciens JY06 was added during fermentation. The aroma of the sauce was improved by increasing the ester content. B. amyloliquefaciens JY06 is a beneficial bacterium that can be used in soy sauce fermentation to eliminate ethyl carbonate and enhance the flavor of the sauce.

Air bubbles induce a critical continuous stress to prevent marine biofouling accumulation

Science.gov (United States)

Belden, Jesse; Menesses, Mark; Dickenson, Natasha; Bird, James

2017-11-01

Significant shear stresses are needed to remove established hard fouling organisms from a ship hull. Given that there is a link between the amount of time that fouling accumulates and the stress required to remove it, it is not surprising that more frequent grooming requires less shear stress. One approach to mitigate marine biofouling is to continuously introduce a curtain of air bubbles under a submerged surface; it is believed that this aeration exploits the small stresses induced by rising bubbles to continuously prevent accumulation. Although curtains of rising bubbles have successfully prevented biofouling accumulation, it is unclear if a single stream of bubbles could maintain a clean surface. In this talk, we show that single bubble stream aeration can prevent biofouling accumulation in regions for which the average wall stress exceeds approximately 0.01 Pa. This value is arrived at by comparing observations of biofouling growth and prevention from field studies with laboratory measurements that probe the associated flow fields. We also relate the spatial and temporal characteristics of the flow to the size and frequency of the rising bubbles, which informs the basic operating conditions required for aeration to continuously prevent biofouling accumulation.

Squatting-Related Tibiofemoral Shear Reaction Forces and a Biomechanical Rationale for Femoral Component Loosening

Directory of Open Access Journals (Sweden)

Ashvin Thambyah

2014-01-01

Full Text Available Previous gait studies on squatting have described a rapid reversal in the direction of the tibiofemoral joint shear reaction force when going into a full weight-bearing deep knee flexion squat. The effects of such a shear reversal have not been considered with regard to the loading demand on knee implants in patients whose activities of daily living require frequent squatting. In this paper, the shear reversal effect is discussed and simulated in a finite element knee implant-bone model, to evaluate the possible biomechanical significance of this effect on femoral component loosening of high flexion implants as reported in the literature. The analysis shows that one of the effects of the shear reversal was a switch between large compressive and large tensile principal strains, from knee extension to flexion, respectively, in the region of the anterior flange of the femoral component. Together with the known material limits of cement and bone, this large mismatch in strains as a function of knee position provides new insight into how and why knee implants may fail in patients who perform frequent squatting.

Microstructural and Mechanical Property Characterization of Shear Formed Aerospace Aluminum Alloys

Science.gov (United States)

Troeger, Lillianne P.; Domack, Marcia S.; Wagner, John A.

2000-01-01

Advanced manufacturing processes such as near-net-shape forming can reduce production costs and increase the reliability of launch vehicle and airframe structural components through the reduction of material scrap and part count and the minimization of joints. The current research is an investigation of the processing-microstructure-property relationships for shear formed cylinders of the Al-Cu-Li-Mg-Ag alloy 2195 for space applications and the Al-Cu-Mg-Ag alloy C415 for airframe applications. Cylinders which had undergone various amounts of shear-forming strain were studied to correlate the grain structure, texture, and mechanical properties developed during and after shear forming.

3D finite element analysis of stress distributions and strain energy release rates for adhesive bonded flat composite lap shear joints having pre-existing delaminations

Energy Technology Data Exchange (ETDEWEB)

Parida, S. K.; Pradhan, A. K. [Indian Institute of Technology, Bhubaneswar (India)

2014-02-15

The rate of propagation of embedded delamination in the strap adherend of lap shear joint (LSJ) made of carbon/epoxy composites has been evaluated employing three-dimensional non-linear finite elements. The delamination has been presumed to pre-exist in the thin resin layer between the first and second plies of the strap adherend. The inter-laminar peel and shear stress distributions have been studied in details and are seen to be predominantly three-dimensional in nature. The components of strain energy release rate (SERR) corresponding to the opening, sliding and cross sliding modes of delamination are significantly different at the two fronts of the embedded delamination. The sequential release of multi-point constraint (MPC) finite elements in the vicinity of the delamination fronts enables to simulate the growth of the delamination at either ends. This simulation procedure can be utilized effectively for evaluation of the status of the structural integrity of the bonded joints.

Piezoelectric energy harvesting through shear mode operation

International Nuclear Information System (INIS)

Malakooti, Mohammad H; Sodano, Henry A

2015-01-01

Piezoelectric materials are excellent candidates for use in energy harvesting applications due to their high electromechanical coupling properties that enable them to convert input mechanical energy into useful electric power. The electromechanical coupling coefficient of the piezoelectric material is one of the most significant parameters affecting energy conversion and is dependent on the piezoelectric mode of operation. In most piezoceramics, the d 15 piezoelectric shear coefficient is the highest coefficient compared to the commonly used axial and transverse modes that utilize the d 33 and the d 31 piezoelectric strain coefficients. However, complicated electroding methods and challenges in evaluating the performance of energy harvesting devices operating in the shear mode have slowed research in this area. The shear deformation of a piezoelectric layer can be induced in a vibrating sandwich beam with a piezoelectric core. Here, a model based on Timoshenko beam theory is developed to predict the electric power output from a cantilever piezoelectric sandwich beam under base excitations. It is shown that the energy harvester operating in the shear mode is able to generate ∼50% more power compared to the transverse mode for a numerical case study. Reduced models of both shear and transverse energy harvesters are obtained to determine the optimal load resistance in the system and perform an efficiency comparison between two models with fixed and adaptive resistances. (paper)

"Virtual shear box" experiments of stress and slip cycling within a subduction interface mélange

Science.gov (United States)

Webber, Sam; Ellis, Susan; Fagereng, Åke

2018-04-01

What role does the progressive geometric evolution of subduction-related mélange shear zones play in the development of strain transients? We use a "virtual shear box" experiment, based on outcrop-scale observations from an ancient exhumed subduction interface - the Chrystalls Beach Complex (CBC), New Zealand - to constrain numerical models of slip processes within a meters-thick shear zone. The CBC is dominated by large, competent clasts surrounded by interconnected weak matrix. Under constant slip velocity boundary conditions, models of the CBC produce stress cycling behavior, accompanied by mixed brittle-viscous deformation. This occurs as a consequence of the reorganization of competent clasts, and the progressive development and breakdown of stress bridges as clasts mutually obstruct one another. Under constant shear stress boundary conditions, the models show periods of relative inactivity punctuated by aseismic episodic slip at rapid rates (meters per year). Such a process may contribute to the development of strain transients such as slow slip.

Experimental study of the vortex-induced vibration of drilling risers under the shear flow with the same shear parameter at the different Reynolds numbers.

Science.gov (United States)

Liangjie, Mao; Qingyou, Liu; Shouwei, Zhou

2014-01-01

A considerable number of studies for VIV under the uniform flow have been performed. However, research on VIV under shear flow is scarce. An experiment for VIV under the shear flow with the same shear parameter at the two different Reynolds numbers was conducted in a deep-water offshore basin. Various measurements were obtained by the fiber bragg grating strain sensors. Experimental data were analyzed by modal analysis method. Results show several valuable features. First, the corresponding maximum order mode of the natural frequency for shedding frequency is the maximum dominant vibration mode and multi-modal phenomenon is appeared in VIV under the shear flow, and multi-modal phenomenon is more apparent at the same shear parameter with an increasing Reynolds number under the shear flow effect. Secondly, the riser vibrates at the natural frequency and the dominant vibration frequency increases for the effect of the real-time tension amplitude under the shear flow and the IL vibration frequency is the similar with the CF vibration frequency at the Reynolds number of 1105 in our experimental condition and the IL dominant frequency is twice the CF dominant frequency with an increasing Reynolds number. In addition, the displacement trajectories at the different locations of the riser appear the same shape and the shape is changed at the same shear parameter with an increasing Reynolds number under the shear flow. The diagonal displacement trajectories are observed at the low Reynolds number and the crescent-shaped displacement trajectories appear with an increasing Reynolds number under shear flow in the experiment.

Experimental study of the vortex-induced vibration of drilling risers under the shear flow with the same shear parameter at the different Reynolds numbers.

Directory of Open Access Journals (Sweden)

Mao Liangjie

Full Text Available A considerable number of studies for VIV under the uniform flow have been performed. However, research on VIV under shear flow is scarce. An experiment for VIV under the shear flow with the same shear parameter at the two different Reynolds numbers was conducted in a deep-water offshore basin. Various measurements were obtained by the fiber bragg grating strain sensors. Experimental data were analyzed by modal analysis method. Results show several valuable features. First, the corresponding maximum order mode of the natural frequency for shedding frequency is the maximum dominant vibration mode and multi-modal phenomenon is appeared in VIV under the shear flow, and multi-modal phenomenon is more apparent at the same shear parameter with an increasing Reynolds number under the shear flow effect. Secondly, the riser vibrates at the natural frequency and the dominant vibration frequency increases for the effect of the real-time tension amplitude under the shear flow and the IL vibration frequency is the similar with the CF vibration frequency at the Reynolds number of 1105 in our experimental condition and the IL dominant frequency is twice the CF dominant frequency with an increasing Reynolds number. In addition, the displacement trajectories at the different locations of the riser appear the same shape and the shape is changed at the same shear parameter with an increasing Reynolds number under the shear flow. The diagonal displacement trajectories are observed at the low Reynolds number and the crescent-shaped displacement trajectories appear with an increasing Reynolds number under shear flow in the experiment.

Accumulation of a Polyhydroxyalkanoate Containing Primarily 3-Hydroxydecanoate from Simple Carbohydrate Substrates by Pseudomonas sp. Strain NCIMB 40135.

Science.gov (United States)

Haywood, G W; Anderson, A J; Ewing, D F; Dawes, E A

1990-11-01

A number of Pseudomonas species have been identified which accumulate a polyhydroxyalkanoate containing mainly 3-hydroxydecanoate monomers from sodium gluconate as the sole carbon source. One of these, Pseudomonas sp. strain NCIMB 40135, was further investigated and shown to accumulate such a polyhydroxyalkanoate from a wide range of carbon sources (C(2) to C(6)); however, when supplied with octanoic acid it produced a polyhydroxyalkanoate containing mainly 3-hydroxyoctanoate monomers. Polymer synthesis occurred in batch culture after cessation of growth due to exhaustion of nitrogen. In continuous culture under nitrogen limitation up to 16.9% (wt/wt) polyhydroxyalkanoate was synthesized from glucose as the carbon source. The monomer units are mainly of the R-(-) configuration. Nuclear magnetic resonance studies confirmed the composition of the polymer. Differential scanning calorimetry suggested that the solvent-extracted polymer contained a significant proportion of crystalline material. The weight-average molecular weight of the polymer from glucose-grown cells was 143,000.

Modeling of Metallic Glass Matrix Composites Under Compression: Microstructure Effect on Shear Band Evolution

Science.gov (United States)

Jiang, Yunpeng; Qiu, Kun; Sun, Longgang; Wu, Qingqing

2018-01-01

The relationship among processing, microstructure, and mechanical performance is the most important for metallic glass matrix composites (MGCs). Numerical modeling was performed on the shear banding in MGCs, and the impacts of particle concentration, morphology, agglomerate, size, and thermal residual stress were revealed. Based on the shear damage criterion, the equivalent plastic strain acted as an internal state variable to depict the nucleation, growth, and coalescence of shear bands. The element deletion technique was employed to describe the process of transformation from shear band to micro-crack. The impedance effect of particle morphology on the propagation of shear bands was discussed, whereby the toughening mechanism was clearly interpreted. The present work contributes to the subsequent strengthening and toughening design of MGCs.

Shear melting and high temperature embrittlement: theory and application to machining titanium.

Science.gov (United States)

Healy, Con; Koch, Sascha; Siemers, Carsten; Mukherji, Debashis; Ackland, Graeme J

2015-04-24

We describe a dynamical phase transition occurring within a shear band at high temperature and under extremely high shear rates. With increasing temperature, dislocation deformation and grain boundary sliding are supplanted by amorphization in a highly localized nanoscale band, which allows for massive strain and fracture. The mechanism is similar to shear melting and leads to liquid metal embrittlement at high temperature. From simulation, we find that the necessary conditions are lack of dislocation slip systems, low thermal conduction, and temperature near the melting point. The first two are exhibited by bcc titanium alloys, and we show that the final one can be achieved experimentally by adding low-melting-point elements: specifically, we use insoluble rare earth metals (REMs). Under high shear, the REM becomes mixed with the titanium, lowering the melting point within the shear band and triggering the shear-melting transition. This in turn generates heat which remains localized in the shear band due to poor heat conduction. The material fractures along the shear band. We show how to utilize this transition in the creation of new titanium-based alloys with improved machinability.

Mechanical loading by fluid shear stress of myotube glycocalyx stimulates growth factor expression and nitric oxide production

NARCIS (Netherlands)

Juffer, P.; Bakker, A.D.; Klein-Nulend, J.; Jaspers, R.T.

2014-01-01

Skeletal muscle fibers have the ability to increase their size in response to a mechanical overload. Finite element modeling data suggest that mechanically loaded muscles in vivo may experience not only tensile strain but also shear stress. However, whether shear stress affects biological pathways

Effect of mid-thickness rebar mesh on the behavior and punching shear strength of interior slab–column connection

Directory of Open Access Journals (Sweden)

Ahmed Ibrahim

2016-12-01

The obtained results indicate that, the proposed shear reinforcement system has a positive effect in the enhancement of both the punching shear capacity and the strain energy of interior slab–column connection of both normal and high strength concrete. The general finite element software ANSYS can be used successfully to simulate the punching shear behavior of reinforced concrete flat plates.

Strain rate measurement by Electronic Speckle Pattern Interferometry: A new look at the strain localization onset

International Nuclear Information System (INIS)

Guelorget, Bruno; Francois, Manuel; Vial-Edwards, Cristian; Montay, Guillaume; Daniel, Laurent; Lu, Jian

2006-01-01

In-plane Electronic Speckle Pattern Interferometry has been successfully used during tensile testing of semi-hard copper sheets in order to measure the strain rate. On one hand, heterogeneity in strain rate field has been found before the maximum of the tensile force (ε t ≅ 19.4 and 25.4%, respectively). Thus, a localization phenomenon occurs before the classic Considere's criterion (dF = 0) for the diffuse neck initiation. On the other hand, strain rate measurement before fracture shows the moment where one of the two slip band systems becomes predominant, then strain concentrates in a small area, the shear band. Uncertainty evaluation has been carried out, which shows a very good accuracy of the total strain and the strain rate measurements

Strain rate measurement by Electronic Speckle Pattern Interferometry: A new look at the strain localization onset

Energy Technology Data Exchange (ETDEWEB)

Guelorget, Bruno [Universite de Technologie de Troyes (UTT), Laboratoire des Systemes Mecaniques et d' ingenierie Simultanee (LASMIS, CNRS FRE 2719), 12 rue Marie Curie, B.P. 2060, 10010 Troyes Cedex (France)]. E-mail: bruno.guelorget@utt.fr; Francois, Manuel [Universite de Technologie de Troyes (UTT), Laboratoire des Systemes Mecaniques et d' ingenierie Simultanee (LASMIS, CNRS FRE 2719), 12 rue Marie Curie, B.P. 2060, 10010 Troyes Cedex (France); Vial-Edwards, Cristian [Departemento de Ingenieria Mecanica y Metalurgica, Pontificia Universidad Catolica de Chile, Vicuna Mackenna 4860, 6904411 Santiago (Chile); Montay, Guillaume [Universite de Technologie de Troyes (UTT), Laboratoire des Systemes Mecaniques et d' ingenierie Simultanee (LASMIS, CNRS FRE 2719), 12 rue Marie Curie, B.P. 2060, 10010 Troyes Cedex (France); Daniel, Laurent [Universite de Technologie de Troyes (UTT), Laboratoire des Systemes Mecaniques et d' ingenierie Simultanee (LASMIS, CNRS FRE 2719), 12 rue Marie Curie, B.P. 2060, 10010 Troyes Cedex (France); Lu, Jian [Universite de Technologie de Troyes (UTT), Laboratoire des Systemes Mecaniques et d' ingenierie Simultanee (LASMIS, CNRS FRE 2719), 12 rue Marie Curie, B.P. 2060, 10010 Troyes Cedex (France)

2006-01-15

In-plane Electronic Speckle Pattern Interferometry has been successfully used during tensile testing of semi-hard copper sheets in order to measure the strain rate. On one hand, heterogeneity in strain rate field has been found before the maximum of the tensile force ({epsilon} {sup t} {approx_equal} 19.4 and 25.4%, respectively). Thus, a localization phenomenon occurs before the classic Considere's criterion (dF = 0) for the diffuse neck initiation. On the other hand, strain rate measurement before fracture shows the moment where one of the two slip band systems becomes predominant, then strain concentrates in a small area, the shear band. Uncertainty evaluation has been carried out, which shows a very good accuracy of the total strain and the strain rate measurements.

Brittle-ductile gliding shear zone and its dynamic metallization in uranium deposit No. 3110

International Nuclear Information System (INIS)

Fang Shiyi.

1990-01-01

A preliminary study on the macroscopic geological structure, microstructures of plastic deformation rotary strain, structural geochemistry and zoning regularity of a brittle-ductile gliding shear zone in uranium deposit No. 3110 is made. Structural dynamic metallization of uranium caused by the strong shearing stress is discussed. It is pointed out that great attention must be paid to in further exploration

Dynamic Shear Deformation and Failure of Ti-6Al-4V and Ti-5Al-5Mo-5V-1Cr-1Fe Alloys.

Science.gov (United States)

Ran, Chun; Chen, Pengwan

2018-01-05

To study the dynamic shear deformation and failure properties of Ti-6Al-4V (Ti-64) alloy and Ti-5Al-5Mo-5V-1Cr-1Fe (Ti-55511) alloy, a series of forced shear tests on flat hat shaped (FHS) specimens for the two investigated materials was performed using a split Hopkinson pressure bar setup. The evolution of shear deformation was monitored by an ultra-high-speed camera (Kirana-05M). Localized shear band is induced in the two investigated materials under forced shear tests. Our results indicate that severe strain localization (adiabatic shear) is accompanied by a loss in the load carrying capacity, i.e., by a sudden drop in loading. Three distinct stages can be identified using a digital image correlation technique for accurate shear strain measurement. The microstructural analysis reveals that the dynamic failure mechanisms for Ti-64 and Ti-55511 alloys within the shear band are of a cohesive and adhesive nature, respectively.

Strain-induced structural changes and chemical reactions. 1: Thermomechanical and kinetic models

International Nuclear Information System (INIS)

Levitas, V.I.; Nesterenko, V.F.; Meyers, M.A.

1998-01-01

Strain-induced chemical reactions were observed recently (Nesterenko et al) in experiments in the shear band in both Ti-Si and Nb-Si mixtures. Reactions can start in the solid state or after melting of at least one component. One of the aims is to find theoretically whether there are possible macroscopic mechanisms of mechanical intensification of the above and other chemical reactions due to plastic shear in the solid state. Continuum thermodynamical theory of structural changes with an athermal kinetics, which includes martensitic phase transformations, plastic strain-induced chemical reactions and polymorphic transformations, is developed at finite strains. The theory includes kinematics, criterion of structural change and extremum principle for determination of all unknown variable parameters for the case with neglected elastic strains. Thermodynamically consistent kinetic theory of thermally activated structural changes is suggested. The concept of the effective temperature is introduced which takes into account that temperature can vary significantly (on 1,000 K) during the chemical reactions under consideration. The theory will be applied in Part 2 of the paper for the description of chemical reactions in the shear band

Structure-rheology relationship in a sheared lamellar fluid.

Science.gov (United States)

Jaju, S J; Kumaran, V

2016-03-01

The structure-rheology relationship in the shear alignment of a lamellar fluid is studied using a mesoscale model which provides access to the lamellar configurations and the rheology. Based on the equations and free energy functional, the complete set of dimensionless groups that characterize the system are the Reynolds number (ργL(2)/μ), the Schmidt number (μ/ρD), the Ericksen number (μγ/B), the interface sharpness parameter r, the ratio of the viscosities of the hydrophilic and hydrophobic parts μ(r), and the ratio of the system size and layer spacing (L/λ). Here, ρ and μ are the fluid density and average viscosity, γ is the applied strain rate, D is the coefficient of diffusion, B is the compression modulus, μ(r) is the maximum difference in the viscosity of the hydrophilic and hydrophobic parts divided by the average viscosity, and L is the system size in the cross-stream direction. The lattice Boltzmann method is used to solve the concentration and momentum equations for a two dimensional system of moderate size (L/λ=32) and for a low Reynolds number, and the other parameters are systematically varied to examine the qualitative features of the structure and viscosity evolution in different regimes. At low Schmidt numbers where mass diffusion is faster than momentum diffusion, there is fast local formation of randomly aligned domains with "grain boundaries," which are rotated by the shear flow to align along the extensional axis as time increases. This configuration offers a high resistance to flow, and the layers do not align in the flow direction even after 1000 strain units, resulting in a viscosity higher than that for an aligned lamellar phase. At high Schmidt numbers where momentum diffusion is fast, the shear flow disrupts layers before they are fully formed by diffusion, and alignment takes place by the breakage and reformation of layers by shear, resulting in defects (edge dislocations) embedded in a background of nearly aligned layers

Shear Elasticity and Shear Viscosity Imaging in Soft Tissue

Science.gov (United States)

Yang, Yiqun

In this thesis, a new approach is introduced that provides estimates of shear elasticity and shear viscosity using time-domain measurements of shear waves in viscoelastic media. Simulations of shear wave particle displacements induced by an acoustic radiation force are accelerated significantly by a GPU. The acoustic radiation force is first calculated using the fast near field method (FNM) and the angular spectrum approach (ASA). The shear waves induced by the acoustic radiation force are then simulated in elastic and viscoelastic media using Green's functions. A parallel algorithm is developed to perform these calculations on a GPU, where the shear wave particle displacements at different observation points are calculated in parallel. The resulting speed increase enables rapid evaluation of shear waves at discrete points, in 2D planes, and for push beams with different spatial samplings and for different values of the f-number (f/#). The results of these simulations show that push beams with smaller f/# require a higher spatial sampling rate. The significant amount of acceleration achieved by this approach suggests that shear wave simulations with the Green's function approach are ideally suited for high-performance GPUs. Shear wave elasticity imaging determines the mechanical parameters of soft tissue by analyzing measured shear waves induced by an acoustic radiation force. To estimate the shear elasticity value, the widely used time-of-flight method calculates the correlation between shear wave particle velocities at adjacent lateral observation points. Although this method provides accurate estimates of the shear elasticity in purely elastic media, our experience suggests that the time-of-flight (TOF) method consistently overestimates the shear elasticity values in viscoelastic media because the combined effects of diffraction, attenuation, and dispersion are not considered. To address this problem, we have developed an approach that directly accounts for all

Shear machines

International Nuclear Information System (INIS)

Astill, M.; Sunderland, A.; Waine, M.G.

1980-01-01

A shear machine for irradiated nuclear fuel elements has a replaceable shear assembly comprising a fuel element support block, a shear blade support and a clamp assembly which hold the fuel element to be sheared in contact with the support block. A first clamp member contacts the fuel element remote from the shear blade and a second clamp member contacts the fuel element adjacent the shear blade and is advanced towards the support block during shearing to compensate for any compression of the fuel element caused by the shear blade (U.K.)

The Cyclic Stress-Strain Curve of Polycrystals

DEFF Research Database (Denmark)

Pedersen, Ole Bøcker; Rasmussen, K. V.; Winter, A. T.

1982-01-01

The internal stresses implied by the Sachs model are estimated for individual PSBs at low plastic strain amplitudes and for homogeneously sheared grains at higher plastic strain amplitudes. The analysis shows that the Sachs model can account semi-quantitatively for experimentally measured cyclic...... stress-strain curves for copper. A similar approximative analysis of the Taylor model cannot account for the data. An interesting feature of the Sachs model is that, although it is assumed that the flow condition is entirely controlled by the PSBs. the predicted cyclic stress-strain curve displays...

A theoretical insight into H accumulation and bubble formation by applying isotropic strain on the W-H system under a fusion environment

Science.gov (United States)

Han, Quan-Fu; Liu, Yue-Lin; Zhang, Ying; Ding, Fang; Lu, Guang-Hong

2018-04-01

The solubility and bubble formation of hydrogen (H) in tungsten (W) are crucial factors for the application of W as a plasma-facing component under a fusion environment, but the data and mechanism are presently scattered, indicating some important factors might be neglected. High-energy neutron-irradiated W inevitably causes a local strain, which may change the solubility of H in W. Here, we performed first-principles calculations to predict the H solution behaviors under isotropic strain combined with temperature effect in W and found that the H solubility in interstitial lattice can be promoted/impeded by isotropic tensile/compressive strain over the temperature range 300-1800 K. The calculated H solubility presents good agreement with the experiment. Together, our previous results of anisotropic strain, except for isotropic compression, both isotropic tension and anisotropic tension/compression enhance H solution so as to reveal an important physical implication for H accumulation and bubble formation in W: strain can enhance H solubility, resulting in the preliminary nucleation of H bubble that further causes the local strain of W lattice around H bubble, which in turn improves the H solubility at the strained region that promotes continuous growth of the H bubble via a chain-reaction effect in W. This result can also interpret the H bubble formation even if no radiation damage is produced in W exposed to low-energy H plasma.

estimation of shear strength parameters of lateritic soils using

African Journals Online (AJOL)

user

... a tool to estimate the. Nigerian Journal of Technology (NIJOTECH). Vol. ... modeling tools for the prediction of shear strength parameters for lateritic ... 2.2 Geotechnical Analysis of the Soils ... The back propagation learning algorithm is the most popular and ..... [10] Alsaleh, M. I., Numerical modeling for strain localization in ...

Measuring a critical stress for continuous prevention of marine biofouling accumulation with aeration.

Science.gov (United States)

Menesses, Mark; Belden, Jesse; Dickenson, Natasha; Bird, James

2017-10-01

When cleaning the hull of a ship, significant shear stresses are needed to remove established biofouling organisms. Given that there exists a link between the amount of time that fouling accumulates and the stress required to remove it, it is not surprising that more frequent grooming requires less shear stress. Yet, it is unclear if there is a minimum stress needed to prevent the growth of macrofouling in the limit of continuous grooming. This manuscript shows that single bubble stream aeration provides continuous grooming and prevents biofouling accumulation in regions where the average wall stress exceeds ~0.01 Pa. This value was found by comparing observations of biofouling growth from field studies with complementary laboratory measurements that probe the associated flow fields. These results suggest that aeration and other continuous grooming systems must exceed a wall stress of 0.01 Pa to prevent macrofouling accumulation.

Shear of ordinary and elongated granular mixtures

Science.gov (United States)

Hensley, Alexander; Kern, Matthew; Marschall, Theodore; Teitel, Stephen; Franklin, Scott

2015-03-01

We present an experimental and computational study of a mixture of discs and moderate aspect-ratio ellipses under two-dimensional annular planar Couette shear. Experimental particles are cut from acrylic sheet, are essentially incompressible, and constrained in the thin gap between two concentric cylinders. The annular radius of curvature is much larger than the particles, and so the experiment is quasi-2d and allows for arbitrarily large pure-shear strains. Synchronized video cameras and software identify all particles and track them as they move from the field of view of one camera to another. We are particularly interested in the global and local properties as the mixture ratio of discs to ellipses varies. Global quantities include average shear rate and distribution of particle species as functions of height, while locally we investigate the orientation of the ellipses and non-affine events that can be characterized as shear transformational zones or possess a quadrupole signature observed previously in systems of purely circular particles. Discrete Element Method simulations on mixtures of circles and spherocylinders extend the study to the dynamics of the force network and energy dissipated as the system evolves. Supported by NSF CBET #1243571 and PRF #51438-UR10.

MM98.83 Quantification of Combined Strain Paths

DEFF Research Database (Denmark)

Nielsen, Morten Sturgård; Lindegren, Maria; Wanheim, Tarras

1998-01-01

When working with processes where large plastic deformation occurs, a way of desribing the deformation process is to view the whole deformation history as a curve in the 6-dimensional shear strain normal strain space, henceforth called a strain history curve (SHC). This paper focuses on the SHC...... 3D-plasticity. Adirect use of the SHC, is to measure the yield surface at different points at a SHC, thus establishing data describing the importance of strain rotations or even strain reversals within a process. Two subcases for displaying SHC will be mentioned:The plane strain case and the single...

Strain localisation in granular media

OpenAIRE

Desrues , Jacques

1984-01-01

This study is devoted to strain localisation in Granular materials. Both experimental and theoretical results have been obtained.The first part of the thesis is a review of the methods and theories about rupture in sols mechanics and more generally, in solid mechanics. The classical framework of Shear Band analysis is presented, and the main results available for different classes of materials are discussed.The second part describes an experimental study of strain localisation in sand specime...

Effects of shear flow on phase nucleation and crystallization.

Science.gov (United States)

Mura, Federica; Zaccone, Alessio

2016-04-01

Classical nucleation theory offers a good framework for understanding the common features of new phase formation processes in metastable homogeneous media at rest. However, nucleation processes in liquids are ubiquitously affected by hydrodynamic flow, and there is no satisfactory understanding of whether shear promotes or slows down the nucleation process. We developed a classical nucleation theory for sheared systems starting from the molecular level of the Becker-Doering master kinetic equation and we analytically derived a closed-form expression for the nucleation rate. The theory accounts for the effect of flow-mediated transport of molecules to the nucleus of the new phase, as well as for the mechanical deformation imparted to the nucleus by the flow field. The competition between flow-induced molecular transport, which accelerates nucleation, and flow-induced nucleus straining, which lowers the nucleation rate by increasing the nucleation energy barrier, gives rise to a marked nonmonotonic dependence of the nucleation rate on the shear rate. The theory predicts an optimal shear rate at which the nucleation rate is one order of magnitude larger than in the absence of flow.

Clarification of strain limits considering the ratcheting fatigue strength of 316FR steel

International Nuclear Information System (INIS)

Isobe, Nobuhiro; Sukekawa, Masayuki; Nakayama, Yasunari; Date, Shingo; Ohtani, Tomomi; Takahashi, Yukio; Kasahara, Naoto; Shibamoto, Hiroshi; Nagashima, Hideaki; Inoue, Kazuhiko

2008-01-01

The effect of ratcheting on fatigue strength was investigated in order to rationalize the strain limit as a design criterion of commercialized fast reactor systems. Ratcheting fatigue tests were conducted at 550 deg. Duration of the ratchet straining was set for a certain number of strain cycles taking the loading condition of fast reactors into account, and the number of cycles for strain accumulation was defined as the ratchet-expired cycle. Fatigue lives decrease as the accumulated strain by ratcheting increases. Mean stress increased during the ratcheting cycle and its maximum value depended on the accumulated strain and the ratchet-expired cycle. Fatigue life reduction was negligible when the maximum mean stress was less than 25 MPa, corresponding to an accumulated strain of 2.2%. Accumulated strain is limited to 2% in the present design guidelines and this strain limit is considered effective to avoid reducing fatigue life by ratcheting. Microcrack growth behaviors were also investigated in these tests in order to discuss the life reduction mechanisms in ratcheting conditions

Structural analysis and magmatism characterization of the Major Gercino shear zone, Santa Catarina State, Brazil

International Nuclear Information System (INIS)

Passarelli, Claudia Regina

1996-01-01

This work describes the geometric and kinematic characteristics of the Major Gercino Shear Zone (MGSZ) in the Canelinha-Garcia area. This shear zone is one of the major lineaments that affect all southern Brazilian precambrian terrains. In Santa Catarina State, it separates, along its whole extension, the supracrustal rocks of the Brusque belt (northern part) from the Granitoid belt (southern). This zone is characterized by a regional NE trend and a dextral sense of movement where ductile-brittle structures predominate. The MGSZ is composed of two mylonitic belts separated by granitoid rocks probably associated to the development of the shear zone. Both shear zones show cataclastic to ultra mylonitic rocks, but mylonites and protomylonites conditions at high strain rate. The calc-alkaline granitoids present in the area can be grouped in two granitoid associations with meta to peraluminous affinities. The Rolador Granitoid Association is characterized by grayish porphyritic biotite-monzogranites and the Fernandes Granitoid Association by coarsed-grained to porphyritic pinkish amphibole-syenogranites. The U-Pb and Rb-Sr ages range from 670 to 590 Ma with the Sr 87 / Sr 86 initial ratios suggesting a crustal contribution in the generation of these rocks. The importance of the pure shear component is also emphasized by the results of the Fry method. Many z axes of the strain ellipses are at high angle to the shear foliation. Symmetric porphyroclasts also corroborate this hypothesis. The micaceous minerals formed during the shear development indicate K-Ar ages around 555 ± 15 Ma. Brittle reactivations of the shear zone have been placed by K-Ar in fine-fraction materials at Triassic time (215 ± 15 Ma.)

Atomistic simulation study of the shear-band deformation mechanism in Mg-Cu metallic glasses

DEFF Research Database (Denmark)

Bailey, Nicholas; Schiøtz, Jakob; Jacobsen, Karsten Wedel

2006-01-01

We have simulated plastic deformation of a model Mg-Cu metallic glass in order to study shear banding. In uniaxial tension, we find a necking instability occurs rather than shear banding. We can force the latter to occur by deforming in plane strain, forbidding the change of length in one...... of the transverse directions. Furthermore, in most of the simulations a notch is used to initiate shear bands, which lie at a 45 degrees angle to the tensile loading direction. The shear bands are characterized by the Falk and Langer local measure of plastic deformation D-min(2), averaged here over volumes...... observe a slight decrease in density, up to 1%, within the shear band, which is consistent with notions of increased free volume or disorder within a plastically deforming amorphous material....

A state-of-the-art anisotropic rock deformation model incorporating the development of mobilised shear strength

Science.gov (United States)

Noor, M. J. Md; Jobli, A. F.

2018-04-01

Currently rock deformation is estimated using the relationship between the deformation modulus Em and the stress-strain curve. There have been many studies conducted to estimate the value of Em. This Em is basically derived from conducting unconfined compression test, UCS. However, the actual stress condition of the rock in the ground is anisotropic stress condition where the rock mass is subjected to different confining and vertical pressures. In addition, there is still no empirical or semi-empirical framework that has been developed for the prediction of rock stress-strain response under anisotropic stress condition. Arock triaxial machine GCTS Triaxial RTX-3000 has been deployed to obtain the anisotropic stress-strain relationship for weathered granite grade II from Rawang, Selangor sampled at depth of 20 m and subjected to confining pressure of 2 MPa, 7.5 MPa and 14 MPa. The developed mobilised shear strength envelope within the specimen of 50 mm diameter and 100 mm height during the application of the deviator stress is interpreted from the stress-strain curves. These mobilised shear strength envelopes at various axial strains are the intrinsic property and unique for the rock. Once this property has been established then it is being used to predict the stress-strain relationship at any confining pressure. The predicted stress-strain curves are compared against the curves obtained from the tests. A very close prediction is achieved to substantiate the applicability of this rock deformation model. This is a state-of-the art rock deformation theory which characterise the deformation base on the applied load and the developed mobilised shear strength within the rock body.

Localization and Instability in Sheared Granular Materials: Role of Pore Fluids and Non-monotonic Rate Dependent Rheology

Science.gov (United States)

Ma, X.; Elbanna, A. E.; Kothari, K.

2017-12-01

Fault zone dynamics hold the key to resolving many outstanding geophysical problems including the heat flow paradox, discrepancy between fault static and dynamic strength, and energy partitioning. Most fault zones that generate tectonic events are gouge filled and fluid saturated posing the need for formulating gouge-specific constitutive models that capture spatially heterogeneous compaction and dilation, non-monotonic rate dependence, and transition between localized and distributed deformation. In this presentation, we focus primarily on elucidating microscopic underpinnings for shear banding and stick-slip instabilities in sheared saturated granular materials and explore their implications for earthquake dynamics. We use a non-equilibrium thermodynamics model, the Shear Transformation Zone theory, to investigate the dynamics of strain localization and its connection to stability of sliding in the presence and absence of pore fluids. We also consider the possible influence of self-induced mechanical vibrations as well as the role of external acoustic vibrations as analogue for triggering by a distant event. For the dry case, our results suggest that at low and intermediate strain rates, persistent shear bands develop only in the absence of vibrations. Vibrations tend to fluidize the granular network and de-localize slip at these rates. Stick-slip is only observed for rough grains and it is confined to the shear band. At high strain rates, stick-slip disappears and the different systems exhibit similar stress-slip response. Changing the vibration intensity, duration or time of application alters the system response and may cause long-lasting rheological changes. The presence of pore fluids modifies the stick slip pattern and may lead to both loss and development of slip instability depending on the value of the confining pressure, imposed strain rate and hydraulic parameters. We analyze these observations in terms of possible transitions between rate

Earthquake induced rock shear through a deposition hole - modelling of three scale tests for validation of models

International Nuclear Information System (INIS)

Boergesson, Lennart; Hernelind, Jan

2012-01-01

Document available in extended abstract form only. Three model shear tests of very high quality simulating a horizontal rock shear through a KBS-3V deposition hole in the centre of a canister were performed 1986. The tests simulated a deposition hole in the scale 1:10 with reference density of the buffer, very stiff confinement simulating the rock, and a solid bar of copper simulating the canister. The three tests were almost identical with exception of the rate of shear, which was varied between 0.031 and 160 mm/s, i.e. with a factor of more than 5000, and the density of the bentonite, which differed slightly. The tests were very well documented. Shear force, shear rate, total stress in the bentonite, strain in the copper and the movement of the top of the simulated canister were measured continuously during the shear. After finished shear the equipment was dismantled and careful sampling of the bentonite with measurement of water ratio and density were made. The deformed copper 'canister' was also carefully measured after the test. The tests have been modelled with the finite element code Abaqus with the same models and techniques that were used for the full scale cases in the Swedish safety assessment SR-Site. The results have been compared with the measured results, which has yielded very valuable information about the relevancy of the material models and the modelling technique. An elastic-plastic material model was used for the bentonite where the stress-strain relations have been derived from laboratory tests. The material model is also described in another article to this conference. The material model is made a function of both the density and the strain rate at shear. Since the shear is fast and takes place under undrained conditions, the density is not changed during the tests. However, strain rate varies largely with both the location of the elements and time. This can be taken into account in Abaqus by making the material model a function of the strain

The effects of buoyancy on shear-induced melt bands in a compacting porous medium

Science.gov (United States)

Butler, S. L.

2009-03-01

It has recently been shown [Holtzman, B., Groebner, N., Zimmerman, M., Ginsberg, S., Kohlstedt, D., 2003. Stress-driven melt segregation in partially molten rocks. Geochem. Geophys. Geosyst. 4, Art. No. 8607; Holtzman, B.K., Kohlstedt, D.L., 2007. Stress-driven melt segregation and strain partitioning in partially molten rocks: effects of stress and strain. J. Petrol. 48, 2379-2406] that when partially molten rock is subjected to simple shear, bands of high and low porosity are formed at a particular angle to the direction of instantaneous maximum extension. These have been modeled numerically and it has been speculated that high porosity bands may form an interconnected network with a bulk, effective permeability that is enhanced in a direction parallel to the bands. As a result, the bands may act to focus mantle melt towards the axis of mid-ocean ridges [Katz, R.F., Spiegelman, M., Holtzman, B., 2006. The dynamics of melt and shear localization in partially molten aggregates. Nature 442, 676-679]. In this contribution, we examine the combined effects of buoyancy and matrix shear on a deforming porous layer. The linear theory of Spiegelman [Spiegelman, M., 1993. Flow in deformable porous media. Part 1. Simple analysis. J. Fluid Mech. 247, 17-38; Spiegelman, M., 2003. Linear analysis of melt band formation by simple shear. Geochem. Geophys. Geosyst. 4, doi:10.1029/2002GC000499, Article 8615] and Katz et al. [Katz, R.F., Spiegelman, M., Holtzman, B., 2006. The dynamics of melt and shear localization in partially molten aggregates. Nature 442, 676-679] is generalized to include both the effects of buoyancy and matrix shear on a deformable porous layer with strain-rate dependent rheology. The predictions of linear theory are compared with the early time evolution of our 2D numerical model and they are found to be in excellent agreement. For conditions similar to the upper mantle, buoyancy forces can be similar to or much greater than matrix shear-induced forces. The

Shear Behavior of Corrugated Steel Webs in H Shape Bridge Girders

Directory of Open Access Journals (Sweden)

Qi Cao

2015-01-01

Full Text Available In bridge engineering, girders with corrugated steel webs have shown good mechanical properties. With the promotion of composite bridge with corrugated steel webs, in particular steel-concrete composite girder bridge with corrugated steel webs, it is necessary to study the shear performance and buckling of the corrugated webs. In this research, by conducting experiment incorporated with finite element analysis, the stability of H shape beam welded with corrugated webs was tested and three failure modes were observed. Structural data including load-deflection, load-strain, and shear capacity of tested beam specimens were collected and compared with FEM analytical results by ANSYS software. The effects of web thickness, corrugation, and stiffening on shear capacity of corrugated webs were further discussed.

Quantifying the Variation in Shear Zone Character with Depth: a Case Study from the Simplon Shear Zone, Central Alps

Science.gov (United States)

Cawood, T. K.; Platt, J. P.

2017-12-01

A widely-accepted model for the rheology of crustal-scale shear zones states that they comprise distributed strain at depth, in wide, high-temperature shear zones, which narrow to more localized, high-strain zones at lower temperature and shallower crustal levels. We test and quantify this model by investigating how the width, stress, temperature and deformation mechanisms change with depth in the Simplon Shear Zone (SSZ). The SSZ marks a major tectonic boundary in the central Alps, where normal-sense motion and rapid exhumation of the footwall have preserved evidence of older, deeper deformation in rocks progressively further into the currently-exposed footwall. As such, microstructures further from the brittle fault (which represents the most localized, most recently-active part of the SSZ) represent earlier, higher- temperature deformation from deeper crustal levels, while rocks closer to the fault have been overprinted by successively later, cooler deformation at shallower depths. This study uses field mapping and microstructural studies to identify zones representing deformation at various crustal levels, and characterize each in terms of zone width (representing width of the shear zone at that time and depth) and dominant deformation mechanism. In addition, quartz- (by Electron Backscatter Diffraction, EBSD) and feldspar grain size (measured optically) piezometry are used to calculate the flow stress for each zone, while the Ti-in-quartz thermometer (TitaniQ) is used to calculate the corresponding temperature of deformation. We document the presence of a broad zone in which quartz is recrystallized by the Grain Boundary Migration (GBM) mechanism and feldspar by Subgrain Rotation (SGR), which represents the broad, deep zone of deformation occurring at relatively high temperatures and low stresses. In map view, this transitions to successively narrower zones, respectively characterized by quartz SGR and feldspar Bulge Nucleation (BLG); quartz BLG and brittle

Oscillatory shear response of moisture barrier coatings containing clay of different shape factor.

Science.gov (United States)

Kugge, C; Vanderhoek, N; Bousfield, D W

2011-06-01

Oscillatory shear rheology of barrier coatings based on dispersed styrene-butadiene latex and clay of various shape factors or aspect ratio has been explored. Barrier performance of these coatings when applied to paperboard has been assessed in terms of water vapour transmission rates and the results related to shape factor, dewatering and critical strain. It has been shown that a system based on clay with high shape factor gives a lower critical strain, dewatering and water vapour transmission rate compared with clays of lower shape factor. The dissipated energy, as calculated from an amplitude sweep, indicated no attractive interaction between clay and latex implying a critical strain that appears to be solely dependent on the shape factor at a constant volume fraction. Particle size distribution was shown to have no effect on the critical strain while coatings of high elasticity exhibited high yield strains as expected. The loss modulus demonstrated strain hardening before the elastic to viscous transition. The loss modulus peak was identified by a maximum strain which was significantly lower for a coating based on clay with a high shape factor. The characteristic elastic time was found to vary between 0.6 and 1.3s. The zero shear viscosity of barrier dispersion coatings were estimated from the characteristic elastic time and the characteristic modulus to be of the order of 25-100 Pa s. Copyright © 2011 Elsevier Inc. All rights reserved.

Compressive strain-dependent bending strength property of Al2O3-ZrO2 (1.5 mol% Y2O3) composites performance by HIP

International Nuclear Information System (INIS)

Reyes-Rojas, A.; Esparza-Ponce, H.; De la Torre, S.D.; Torres-Moye, E.

2009-01-01

Nanometric powders and sintered ceramics of Al 2 O 3 -ZrO 2 (1.5 mol% Y 2 O 3 ) prepared by hot isostatic pressing HIP have been studied. A detailed crystallographic study has been performed through X-ray diffraction, Williamson-Hall method, Rietveld method and high-resolution electron microscopy HREM analysis. The crystallographic structure data, such as domain size, lattice parameters, wt% phase, and micro-strain direction have been obtained using Rietveld refinement and Williamson-Hall methods. The results revealed that the compressive strain (ε) increased from 0.56 to 1.18 (10 -3 ) as the t-ZrO 2 content increased too. The HREM interface study conducted along the [0 0 0 1]Al 2 O 3 ||[0 0 1]ZrO 2 zone axis revealed a micro-strain lattice distortion accumulated at the grain boundary due to the ZrO 2 martensitic phase transformation on cooling, t-ZrO 2 grains coalescence and to the grain growth of α-Al 2 O 3 which cause elongated tetragonal crystals. Micro-strain lattice distortion is adjusted by the shear displacements of the planes (1 1 0) and (11-bar0) along [1-bar10] and [1-bar1-bar0] crystallographic directions, respectively; these planes are arrested by the (101-bar0) alumina plane. In this case, semi-coherent interfaces were observed along the grain boundary. It is verified that the bending strength increased in connection with the strain accumulation and amount of tetragonal structure

Third harmonic generation of shear horizontal guided waves propagation in plate-like structures

Energy Technology Data Exchange (ETDEWEB)

Li, Wei Bin [School of Aerospace Engineering, Xiamen University, Xiamen (China); Xu, Chun Guang [School of Mechanical Engineering, Beijing Institute of Technology, Beijing (China); Cho, Youn Ho [School of Mechanical Engineering, Pusan National University, Busan (Korea, Republic of)

2016-04-15

The use of nonlinear ultrasonics wave has been accepted as a promising tool for monitoring material states related to microstructural changes, as it has improved sensitivity compared to conventional non-destructive testing approaches. In this paper, third harmonic generation of shear horizontal guided waves propagating in an isotropic plate is investigated using the perturbation method and modal analysis approach. An experimental procedure is proposed to detect the third harmonics of shear horizontal guided waves by electromagnetic transducers. The strongly nonlinear response of shear horizontal guided waves is measured. The accumulative growth of relative acoustic nonlinear response with an increase of propagation distance is detected in this investigation. The experimental results agree with the theoretical prediction, and thus providing another indication of the feasibility of using higher harmonic generation of electromagnetic shear horizontal guided waves for material characterization.

Investigation of Rheological Properties of Blended Cement Pastes Using Rotational Viscometer and Dynamic Shear Rheometer

Directory of Open Access Journals (Sweden)

Yoo Jae Kim

2018-01-01

Full Text Available To successfully process concrete, it is necessary to predict and control its flow behavior. However, the workability of concrete is not completely measured or specified by current standard tests. Furthermore, it is only with a clear picture of cement hydration and setting that full prediction and control of concrete performance can be generalized. In order to investigate the rheological properties of blended cement pastes, a rotational viscometer (RV was used to determine the flow characteristics of ordinary and blended pastes to provide assurance that it can be pumped and handled. Additionally, a dynamic shear rheometer (DSR was used to characterize both the viscous and elastic components of pastes. Ordinary Portland cement paste and blended pastes (slag, fly ash, and silica fume were investigated in this study. The stress and strain of the blended specimens were measured by the DSR, which characterizes both viscous and elastic behaviors by measuring the complex shear modulus (the ratio of total shear stress to total shear strain and phase angle (an indicator of the relative amounts of recoverable and nonrecoverable deformation of materials. Cement pastes generally exhibit different rheological behaviors with respect to age, mineral admixture type, and cement replacement level.

Ideal shear strength and deformation behaviours of L10 TiAl from ...

Indian Academy of Sciences (India)

Guangxi Teachers Education University, Nanning 530023, China. MS received 18 October 2014; accepted 11 April 2016. Abstract. The stress–strain relationships for four different shear processes of L10 TiAl have been .... aThis work; bRef.

A Monte Carlo-shear lag simulation of tensile fracture behaviour of Bi2223 filament

International Nuclear Information System (INIS)

Ochiai, S; Ishida, T; Doko, D; Morishita, K; Okuda, H; Oh, S S; Ha, D W; Hojo, M; Tanaka, M; Sugano, M; Osamura, K

2005-01-01

The damage evolution in Bi2223 filaments and its influence on critical current was described by a Monte Carlo-shear lag simulation method. The experimentally observed zigzag crack propagation across aligned Bi2223 grains under tensile strain was effectively modelled by including transverse and longitudinal failure modes for individual grains. From the simulated stress-strain curve, the survival parameter (slope of the stress-strain curve normalized with respect to the original Young's modulus) was estimated with increasing applied strain. With this parameter combined with the strain sensitivity of the critical current, the measured change of critical current of the composite tape with applied strain could be described well

Influence of Palatal Coverage and Implant Distribution on Denture Strain in Maxillary Implant Overdentures.

Science.gov (United States)

Takahashi, Toshihito; Gonda, Tomoya; Tomita, Akiko; Mizuno, Yoko; Maeda, Yoshinobu

2016-01-01

As maxillary implant overdentures are being increasingly used in clinical practice, prosthodontic complications related to these dentures are also reported more often. The purpose of this study was to examine the influence of palatal coverage and implant distribution on the shear strain of maxillary implant overdentures. A maxillary edentulous model with implants inserted in the anterior, premolar, and molar areas was fabricated. Two kinds of experimental overdentures, with and without palatal coverage, were also fabricated, and two strain gauges were attached at the midline of the labial and palatal sides. A vertical occlusal load of 98 N was applied through a mandibular complete denture, and the shear strain in each denture was compared by analysis of variance (P = .05). In all situations, the shear strain in palateless dentures was significantly higher than in dentures with palate on both sides (P overdentures exhibited much higher strain than overdentures with palate regardless of the implant distribution; this may cause more prosthodontic and implant complications. The most favorable configuration to prevent complications in maxillary implant overdentures was palatal coverage that was supported by more than four widely distributed implants.

Effect of microstructure on the nucleation and initiation of adiabatic shear bands (ASBs) during impact

Energy Technology Data Exchange (ETDEWEB)

Boakye Yiadom, Solomon, E-mail: boakyeys@cc.umanitoba.ca; Khaliq Khan, Abdul, E-mail: abdulkhaliq.khan@umanitoba.ca; Bassim, Nabil, E-mail: nabil.bassim@ad.umanitoba.ca

2014-10-06

While instability may occur homogenously during plastic deformation, the formation of adiabatic shear band (ASBs) does not follow a homogenous instability during impact. Geometrical stress concentration sites and/or microstructural inhomogeneities result in the nucleation and initiation of shear strain localization. In this study, initial microstructural inhomogeneity was found to produce nucleation sites for the initiation of ASBs. It was observed that double misfit interfaces and boundary layers with random arrangement of atomic columns are formed around precipitated carbides and they increase the volume fraction of dislocation sources within the specimens. The AISI 4340 steel specimens which were tempered at the lowest temperature had smaller precipitated carbides with high aspect ratios densely distributed within the matrix and were easily susceptible to the formation of ASBs. As the tempering temperature increased, the relative sizes of the carbides increased with a corresponding reduction in their aspect ratios and their distribution density within the matrix and thus were more resistant to the formation of ASBs. In this study, it is demonstrated that the intersection of an activated dislocation source with the direction of maximum shear (regions of stress concentrations) within the specimens during impact, is a necessary condition for the point of intersection to act as a possible site for the nucleation of ASBs, depending on the rate of dislocation generation, local strain and strain rate. At a constant carbide volume fraction, the higher susceptibility of the tempered specimens to the initiation of ASBs is attributed to the volume fraction of the points of intersection between activated dislocation sources and direction of maximum shear during impact. Additionally, the smaller carbides, with their higher aspect ratios and distribution densities, accentuate the effect of strain gradients and the microstructural inhomogeneities associated with the tempered

Scalar evolution equations for shear waves in incompressible solids: a simple derivation of the Z, ZK, KZK and KP equations

KAUST Repository

Destrade, M.

2010-12-08

We study the propagation of two-dimensional finite-amplitude shear waves in a nonlinear pre-strained incompressible solid, and derive several asymptotic amplitude equations in a simple, consistent and rigorous manner. The scalar Zabolotskaya (Z) equation is shown to be the asymptotic limit of the equations of motion for all elastic generalized neo-Hookean solids (with strain energy depending only on the first principal invariant of Cauchy-Green strain). However, we show that the Z equation cannot be a scalar equation for the propagation of two-dimensional shear waves in general elastic materials (with strain energy depending on the first and second principal invariants of strain). Then, we introduce dispersive and dissipative terms to deduce the scalar Kadomtsev-Petviashvili (KP), Zabolotskaya-Khokhlov (ZK) and Khokhlov- Zabolotskaya-Kuznetsov (KZK) equations of incompressible solid mechanics. © 2010 The Royal Society.

Scalar evolution equations for shear waves in incompressible solids: a simple derivation of the Z, ZK, KZK and KP equations

KAUST Repository

Destrade, M.; Goriely, A.; Saccomandi, G.

2010-01-01

We study the propagation of two-dimensional finite-amplitude shear waves in a nonlinear pre-strained incompressible solid, and derive several asymptotic amplitude equations in a simple, consistent and rigorous manner. The scalar Zabolotskaya (Z) equation is shown to be the asymptotic limit of the equations of motion for all elastic generalized neo-Hookean solids (with strain energy depending only on the first principal invariant of Cauchy-Green strain). However, we show that the Z equation cannot be a scalar equation for the propagation of two-dimensional shear waves in general elastic materials (with strain energy depending on the first and second principal invariants of strain). Then, we introduce dispersive and dissipative terms to deduce the scalar Kadomtsev-Petviashvili (KP), Zabolotskaya-Khokhlov (ZK) and Khokhlov- Zabolotskaya-Kuznetsov (KZK) equations of incompressible solid mechanics. © 2010 The Royal Society.

Shear deformation-induced anisotropic thermal conductivity of graphene.

Science.gov (United States)

Cui, Liu; Shi, Sanqiang; Wei, Gaosheng; Du, Xiaoze

2018-01-03

Graphene-based materials exhibit intriguing phononic and thermal properties. In this paper, we have investigated the heat conductance in graphene sheets under shear-strain-induced wrinkling deformation, using equilibrium molecular dynamics simulations. A significant orientation dependence of the thermal conductivity of graphene wrinkles (GWs) is observed. The directional dependence of the thermal conductivity of GWs stems from the anisotropy of phonon group velocities as revealed by the G-band broadening of the phonon density of states (DOS), the anisotropy of thermal resistance as evidenced by the G-band peak mismatch of the phonon DOS, and the anisotropy of phonon relaxation times as a direct result of the double-exponential-fitting of the heat current autocorrelation function. By analyzing the relative contributions of different lattice vibrations to the heat flux, we have shown that the contributions of different lattice vibrations to the heat flux of GWs are sensitive to the heat flux direction, which further indicates the orientation-dependent thermal conductivity of GWs. Moreover, we have found that, in the strain range of 0-0.1, the anisotropy ratio of GWs increases monotonously with increasing shear strain. This is induced by the change in the number of wrinkles, which is more influential in the direction perpendicular to the wrinkle texture. The findings elucidated here emphasize the utility of wrinkle engineering for manipulation of nanoscale heat transport, which offers opportunities for the development of thermal channeling devices.

Hydride redistribution and crack growth in Zr-2.5 wt.% Nb stressed in torsion

International Nuclear Information System (INIS)

Puls, M.P.; Rogowski, A.J.

1980-11-01

The effect of applied shear stresses on zirconium hydride solubility in a zirconium alloy was investigated. Recent studies have shown that zirconium hydride precipiates probably nucleate and grow by means of a shear transformation mechanism. It is postulated that these transformation shear strains can interact with applied shear stress gradients in the same way that the dilatational strains can interact with a dilatational stress gradient, providing a driving force for hydride accumulation, hydride embrittlement and crack propagation. To test this proposition, crack growth experiments were carried out under torsional loading conditions on hydrided, round notched bar specimens of cold-worked Zr-2.5 wt.% Nb cut from Pickering-type pressure tube material. Postmortem metallographic examination of the hydride distribution in these samples showed that, in many cases, the hydrides appeared to have reoriented in response to the applied shear stress and that hydride accumulation at the notch tip had occurred. However, except in a few cases, the rate of accumulation of reoriented hydrides at the notch tip due to applied shear stresses was much less than the rate due to corresponding applied uniaxial stresss. Moreover, the process in shear appears to be more sensitive to the inital hydride size. Attempts to elucidate the fracture mechanism by fractographic examination using scanning and replica transmission electron microscopy proved to be inconclusive because of smearing of the fracture face. (auth)

Stress accumulation and release at complex transform plate boundaries

Energy Technology Data Exchange (ETDEWEB)

Verdonck, D.; Furlong, K.P. (Pennsylvania State Univ., University Park (United States))

1992-10-01

Finite element methods are used to model the dynamics of deformation along complex transform plate boundaries, specifically the San Andreas fault system, California. Effects of mantle rheology and fault geometry on the stress buildup and release are investigated. No prior knowledge of the earthquake cycle time or amount of fault slip is assumed that the results suggest that the San Andreas fault slips at low shear stress (about 15 MPa). Although the maximum stress on the fault is 15 MPa, models with an upper mantle shear zone deforming entirely by dislocation creep accumulate stresses that exceed 100 MPa, a stress level high enough to drive localized dynamic recrystallization and a shift in dominant deformation mechanism to diffusion creep. Models in which the mantle shear zone deform locally by diffusion creep reach a dynamic steady state where lithospheric shear stresses never exceed the specified fault stress anywhere in the model and indicate that the strength of the upper mantle is an important parameter in the dynamics of plate boundary deformation. 17 refs.

Shear punch tests performed using a new low compliance test fixture

International Nuclear Information System (INIS)

Toloczko, M.B.; Kurtz, R.J.; Hasegawa, A.; Abe, K.

2002-01-01

Based on a recent finite element analysis (FEA) study performed on the shear punch test technique, it was suggested that compliance in a test frame and fixturing which is quite acceptable for uniaxial tensile tests, is much too large for shear punch tests. The FEA study suggested that this relatively large compliance was masking both the true yield point and the shape of the load versus displacement trace obtained in shear punch tests. The knowledge gained from the FEA study was used to design a new shear punch test fixture which more directly measures punch tip displacement. The design of this fixture, the traces obtained from this fixture, and the correlation between uniaxial yield stress and shear yield stress obtained using this fixture are presented here. In general, traces obtained from the new fixture contain much less compliance resulting in a trace shape which is more similar in appearance to a corresponding uniaxial tensile trace. Due to the more direct measurement of displacement, it was possible to measure yield stress at an offset shear strain in a manner analogous to yield stress measurement in a uniaxial tensile test. The correlation between shear yield and uniaxial yield was altered by this new yield measurement technique, but the new correlation was not as greatly improved as was suggested would occur from the FEA study

Experimental Characterization of Stress- and Strain-Dependent Stiffness in Grouted Rock Masses.

Science.gov (United States)

Kim, Ji-Won; Chong, Song-Hun; Cho, Gye-Chun

2018-03-29

Grouting of fractured rock mass prior to excavation results in grout-filled discontinuities that govern the deformation characteristics of a site. The influence of joint characteristics on the properties of grouted rocks is important in assessing the effects of grouting on jointed rock mass. However, grouting remains a predominantly empirical practice and the effects of grouting on rock joint behavior and material properties have yet to be accurately assessed. Granular materials, including jointed rocks, typically display nonlinear strain-dependent responses that can be characterized by the shear modulus degradation curve. In this study, the effects of grouting on the strain-dependent shear stiffness of jointed rock mass were investigated at the small-strain (below 10 -5 ) and mid-strain (10 -5 to 10 -3 ) ranges using the quasi-static resonant column test and rock mass dynamic test devices. The effects of curing time, axial stress, initial joint roughness, and grouted joint thickness were examined. The results show that (1) grouting of rock joints leads to decreased stress sensitivity and increased small-strain shear stiffness for all tested samples; (2) the grouted rock samples display similar modulus degradation characteristics as the applied grout material; (3) the initial joint roughness determines the stress-dependent behaviors and general stiffness range of the jointed and grouted rocks, but the strain-dependent behaviors are dependent on the properties of the grout material; (4) increased grouted joint thickness results in larger contribution of the grout properties in the overall grouted rock mass.

Rock mechanics observations pertinent to the rheology of the continental lithosphere and the localization of strain along shear zones

Science.gov (United States)

Kirby, S.H.

1985-01-01

the general phenomenon of ductile faulting in which ductile strains are localized into shear zones. Ductile faults have been produced in experiments of five different rock types and is generally expressed as strain softening in constant-strain-rate tests or as an accelerating-creep-rate stage at constant differential stress. A number of physical mechanisms have been identified that may be responsible for ductile faulting, including the onset of dynamic recrystallization, phase changes, hydrothermal alteration and hydrolytic weakening. Microscopic evidence for these processes as well as larger-scale geological and geophysical observations suggest that ductile faulting in the middle to lower crust and upper mantle may greatly influence the distribution and magnitudes of differential stresses and the style of deformation in the overlying upper continental lithosphere. ?? 1985.

Dynamic deformation and failure characteristic of rock foundation by means of effect of cyclic shear loading

International Nuclear Information System (INIS)

Fujiwara, Yoshikazu; Hibino, Satoshi; Kanagawa, Tadashi; Komada, Hiroya; Nakagawa, Kameichiro

1984-01-01

The main structures of nuclear power plants are built on hard and soft rocks. The rock-dynamic properties used for investigating the stability of the structures have been determined so far by laboratory tests for soft rocks. In hard rocks, however, joints and cracks exist, and the test including these effects is not able to be performed in laboratories at present. Therefore, a dynamic repeating shearing test equipment to be used under the condition including the joints and cracks of actual ground has been made for a base rock of tuff breccia. In this paper, the test results are reported as follows. The geological features of the testing site and the arrangement of tested rocks, the preparation for tests, test equipment, loading method, measuring method, analysis, and the result and the examination. The results of dynamic deformation and failure characteristics were as follows: (1) the dynamic shear-elasticity-modulus Gd of the base rock showed greater values as the normal stress increased, while Gd decreased and showed the strain dependence as the dynamic shear strain amplitude γ increased; (2) the relationship between Gd and γ was well represented with the equation proposed by Hardin-Drnevich; (3) damping ratio increased as γ increased, and decreased as normal stress increased; (4) When a specimen was about to break, γ suddenly increased, and the dynamic shear strain amplitude at yield point was in the range of approximately (3.4 to 4.1) x 10 -3 . (Wakatsuki, Y.)

Shear Behavior Models of Steel Fiber Reinforced Concrete Beams Modifying Softened Truss Model Approaches.

Science.gov (United States)

Hwang, Jin-Ha; Lee, Deuck Hang; Ju, Hyunjin; Kim, Kang Su; Seo, Soo-Yeon; Kang, Joo-Won

2013-10-23

Recognizing that steel fibers can supplement the brittle tensile characteristics of concrete, many studies have been conducted on the shear performance of steel fiber reinforced concrete (SFRC) members. However, previous studies were mostly focused on the shear strength and proposed empirical shear strength equations based on their experimental results. Thus, this study attempts to estimate the strains and stresses in steel fibers by considering the detailed characteristics of steel fibers in SFRC members, from which more accurate estimation on the shear behavior and strength of SFRC members is possible, and the failure mode of steel fibers can be also identified. Four shear behavior models for SFRC members have been proposed, which have been modified from the softened truss models for reinforced concrete members, and they can estimate the contribution of steel fibers to the total shear strength of the SFRC member. The performances of all the models proposed in this study were also evaluated by a large number of test results. The contribution of steel fibers to the shear strength varied from 5% to 50% according to their amount, and the most optimized volume fraction of steel fibers was estimated as 1%-1.5%, in terms of shear performance.

Apparent interfacial shear strength of short-flax-fiber/starch acetate composites

DEFF Research Database (Denmark)

Andersons, J.; Modniks, J.; Joffe, R.

2016-01-01

The paper deals with an indirect industry-friendly method for identification of the interfacial shear strength (IFSS) in a fully bio-based composite. The IFSS of flax fiber/starch acetate is evaluated by a modified Bowyer and Bader method based on an analysis of the stress-strain curve of a short......-fiber-reinforced composite in tension. A shear lag model is developed for the tensile stress-strain response of short-fiber-reinforced composites allowing for an elastic-perfectly plastic stress transfer. Composites with different fiber volume fractions and a variable content of plasticizer have been analyzed. The apparent...... IFSS of flax/starch acetate is within the range of 5.5-20.5 MPa, depending on composition of the material. The IFSS is found to be greater for composites with a higher fiber loading and to decrease with increasing content of plasticizer. The IFSS is equal or greater than the yield strength of the neat...

Constitutive Behavior of Reinforced Concrete Membrane Elements under Tri-directional Shear

Science.gov (United States)

Labib, Moheb

The two-dimensional behavior of typical reinforced concrete (RC) structures has been extensively studied in the past several decades by investigating the constitutive behavior of full-scale reinforced concrete elements subjected to a bi-axial state of stress. In order to understand the true behavior of many large complex structures, the goal of this investigation is to develop new constitutive relationships for RC elements subjected to tri-directional shear stresses. Recently, additional out-of-plane jacks were installed on the panel tester at University of Houston so that concrete elements could be subjected to tri-directional shear stresses. This upgrade makes the panel tester the only one of its kind in the US that is capable of applying such combinations of stresses on full-scale reinforced concrete elements. This dissertation presents the details of the mounting and installation of the additional hydraulic jacks on the universal panel tester. The experimental program includes a series of seven reinforced concrete elements subjected to different combinations of in-plane and out-of-plane shear stresses. Increasing the applied out-of-plane shear stresses reduced the membrane shear strength of the elements. The effect of applying out-of-plane shear stresses on the in-plane shear strength was represented by modifying the softening coefficient in the compression stress strain curve of concrete struts. The modified model was able to capture the behavior and the ultimate capacity of the tested elements. The effect of the in-plane shear reinforcement ratio on the interaction between in-plane and out-of-plane shear stresses was evaluated. The model was implemented in the Finite Element package FEAP and was used to predict the ultimate capacity of many structures subjected to a combination of in-plane and out-of-plane shear stresses. The results of the analytical model were used to develop simplified design equations for members subjected to bi-directional shear loads

Microstructural and Mechanical Characterization of Shear Formed Aluminum Alloys for Airframe and Space Applications

Science.gov (United States)

Troeger, L. P.; Domack, M. S.; Wagner, J. A.

1998-01-01

Advanced manufacturing processes such as near-net-shape forming can reduce production costs and increase the reliability of launch vehicle and airframe structural components through the reduction of material scrap and part count and the minimization of joints. The current research is an investigation of the processing-microstructure-property relationship for shear formed cylinders of the Al-Cu-Li-Mg-Ag alloy 2195 for space applications and the Al-Cu-Mg-Ag alloy C415 for airframe applications. Cylinders which have undergone various amounts of shear-forming strain have been studied to assess the microstructure and mechanical properties developed during and after shear forming.

Effects of strain on the Schwinger pair creation in graphene

International Nuclear Information System (INIS)

Fanbanrai, P.; Hutem, A.; Boonchui, S.

2015-01-01

The effects of strain on mechanically deformed graphene are determined by looking at how the strain affects the amplitude of the Schwinger two particle pair state. The influences of the lattice distortions, such as isotropic tensile strain ϵ is , shear strain ϵ ss , uniaxial armchair strain ϵ as , and zigzag strain ϵ zs , on the photon emission spectrum have been analyzed. We find that the intensities of the emission increases or decreases when compared to those of the unstrained graphene, depending on the type of strain applied. Thus the structure of energy band, the frequencies of the photons and the emission spectrum can be controlled by use of the different strains

Strain gradient effects on cyclic plasticity

DEFF Research Database (Denmark)

Niordson, Christian Frithiof; Legarth, Brian Nyvang

2010-01-01

Size effects on the cyclic shear response are studied numerically using a recent higher order strain gradient visco-plasticity theory accounting for both dissipative and energetic gradient hardening. Numerical investigations of the response under cyclic pure shear and shear of a finite slab between...... rigid platens have been carried out, using the finite element method. It is shown for elastic–perfectly plastic solids how dissipative gradient effects lead to increased yield strength, whereas energetic gradient contributions lead to increased hardening as well as a Bauschinger effect. For linearly...... hardening materials it is quantified how dissipative and energetic gradient effects promote hardening above that of conventional predictions. Usually, increased hardening is attributed to energetic gradient effects, but here it is found that also dissipative gradient effects lead to additional hardening...

Shear Resistance Variations in Experimentally Sheared Mudstone Granules: A Possible Shear-Thinning and Thixotropic Mechanism

Science.gov (United States)

Hu, Wei; Xu, Qiang; Wang, Gonghui; Scaringi, Gianvito; Mcsaveney, Mauri; Hicher, Pierre-Yves

2017-11-01

We present results of ring shear frictional resistance for mudstone granules of different size obtained from a landslide shear zone. Little rate dependency of shear resistance was observed in sand-sized granules in any wet or dry test, while saturated gravel-sized granules exhibited significant and abrupt reversible rate-weakening (from μ = 0.6 to 0.05) at about 2 mm/s. Repeating resistance variations occurred also under constant shear displacement rate. Mudstone granules generate mud as they are crushed and softened. Shear-thinning and thixotropic behavior of the mud can explain the observed behavior: with the viscosity decreasing, the mud can flow through the coarser soil pores and migrate out from the shear zone. This brings new granules into contact which produces new mud. Thus, the process can start over. Similarities between experimental shear zones and those of some landslides in mudstone suggest that the observed behavior may play a role in some landslide kinematics.

Coulomb Stress Accumulation along the San Andreas Fault System

Science.gov (United States)

Smith, Bridget; Sandwell, David

2003-01-01

Stress accumulation rates along the primary segments of the San Andreas Fault system are computed using a three-dimensional (3-D) elastic half-space model with realistic fault geometry. The model is developed in the Fourier domain by solving for the response of an elastic half-space due to a point vector body force and analytically integrating the force from a locking depth to infinite depth. This approach is then applied to the San Andreas Fault system using published slip rates along 18 major fault strands of the fault zone. GPS-derived horizontal velocity measurements spanning the entire 1700 x 200 km region are then used to solve for apparent locking depth along each primary fault segment. This simple model fits remarkably well (2.43 mm/yr RMS misfit), although some discrepancies occur in the Eastern California Shear Zone. The model also predicts vertical uplift and subsidence rates that are in agreement with independent geologic and geodetic estimates. In addition, shear and normal stresses along the major fault strands are used to compute Coulomb stress accumulation rate. As a result, we find earthquake recurrence intervals along the San Andreas Fault system to be inversely proportional to Coulomb stress accumulation rate, in agreement with typical coseismic stress drops of 1 - 10 MPa. This 3-D deformation model can ultimately be extended to include both time-dependent forcing and viscoelastic response.

The Bibenzyl Canniprene Inhibits the Production of Pro-Inflammatory Eicosanoids and Selectively Accumulates in Some Cannabis sativa Strains.

Science.gov (United States)

Allegrone, Gianna; Pollastro, Federica; Magagnini, Gianmaria; Taglialatela-Scafati, Orazio; Seegers, Julia; Koeberle, Andreas; Werz, Oliver; Appendino, Giovanni

2017-03-24

Canniprene (1), an isoprenylated bibenzyl unique to Cannabis sativa, can be vaporized and therefore potentially inhaled from marijuana. Canniprene (1) potently inhibited the production of inflammatory eicosanoids via the 5-lipoxygenase pathway (IC 50 0.4 μM) and also affected the generation of prostaglandins via the cyclooxygenase/microsomal prostaglandin E 2 synthase pathway (IC 50 10 μM), while the related spiranoid bibenzyls cannabispiranol (2) and cannabispirenone (3) were almost inactive in these bioassays. The concentration of canniprene (1) was investigated in the leaves of 160 strains of C. sativa, showing wide variations, from traces to >0.2%, but no correlation was found between its accumulation and a specific phytocannabinoid profile.

Effect of pre-existing shear bands on the tensile mechanical properties of a bulk metallic glass

International Nuclear Information System (INIS)

Cao, Q.P.; Liu, J.W.; Yang, K.J.; Xu, F.; Yao, Z.Q.; Minkow, A.; Fecht, H.J.; Ivanisenko, J.; Chen, L.Y.; Wang, X.D.; Qu, S.X.; Jiang, J.Z.

2010-01-01

Bulk Zr 64.13 Cu 15.75 Ni 10.12 Al 10 metallic glass has been rolled at room temperature in two different directions, and the dependences of microstructure and tensile mechanical property on the degree of deformation and rolling directions have been investigated. No deformation-induced crystallization occurs except for shear bands. Shear band formation in conjugated directions is achieved in the specimen rolled in two directions, while rolling in one direction induces shear band formation only in a single direction. Pre-existing properly spaced soft inhomogeneities can stabilize shear bands and lead to tensile plastic strain, and the efficient intersection of shear bands in conjugated directions results in work-hardening behavior, which is further confirmed by in situ tensile scanning electron microscopic observation. Based on the experimental results obtained in two different specimen geometries and finite element analysis, it is deduced that a normal-stress-modified maximum shear stress criterion rather than a shear plane criterion can describe the conditions for the formation of shear bands in uniaxial tension.

Characterization of cadmium-resistant bacteria and their potential for reducing accumulation of cadmium in rice grains

International Nuclear Information System (INIS)

Lin, Xiaoyan; Mou, Renxiang; Cao, Zhaoyun; Xu, Ping; Wu, Xiaoliang; Zhu, Zhiwei; Chen, Mingxue

2016-01-01

Cadmium (Cd) pollution is a serious widespread environmental problem that not only destroys the microbial ecology of soil and decreases crop production, but also poses a serious risk to human health. Many methods have been used for the remediation of Cd pollution but none of these is totally satisfactory. Microbial remediation strategies have attracted increasing interest since they are environmentally friendly and cost-effective. In the present study, three Cd-resistant bacteria were isolated and evaluated for potential application in Cd bioremediation. Based on their morphological, physiological and biochemical characteristics, together with 16S rDNA gene sequence analyses, bacteria were identified as Stenotrophomonas acidaminiphila (2#), Pseudomonas aeruginosa (9#) and Delftia tsuruhatensis (12#). Pseudomonas aeruginosa showed very high tolerance to metals, especially Cd (2200 mg/L), Zn (1800 mg/L) and Pb (1200 mg/L), and is thought to be a multi-metal-resistant bacterium. Pseudomonas aeruginosa was also sensitive to 13 different antibiotics. The effects of the bacterial strains on the growth of rice plants and their ability to reduce Cd accumulation from Cd-contaminated soils in pot experiments were also evaluated. For Oryza sativa L. A grown in contaminated soil (3 mg/kg Cd), the accumulation of Cd was decreased by 31.2 and 25.5% in brown rice and polished rice, respectively, by strain 9#; Pseudomonas aeruginosa was more effective in reducing Cd accumulation in rice grains than a mixture of strains. For Oryza sativa L. B, a mixture of strains acting synergistically was more effective than a single strain in reducing Cd accumulation; treatment with mixed strains (strains + 3 mg/kg Cd) resulted in 41.3, 35.9, and 32.6% reductions in Cd accumulation in unhulled rice, brown rice and polished rice, respectively. Although different results were obtained for two rice varieties, it can still be concluded that Cd-resistant bacteria are suitable for reducing Cd

Characterization of cadmium-resistant bacteria and their potential for reducing accumulation of cadmium in rice grains

Energy Technology Data Exchange (ETDEWEB)

Lin, Xiaoyan; Mou, Renxiang; Cao, Zhaoyun; Xu, Ping; Wu, Xiaoliang; Zhu, Zhiwei; Chen, Mingxue, E-mail: cmingxue@126.com

2016-11-01

Cadmium (Cd) pollution is a serious widespread environmental problem that not only destroys the microbial ecology of soil and decreases crop production, but also poses a serious risk to human health. Many methods have been used for the remediation of Cd pollution but none of these is totally satisfactory. Microbial remediation strategies have attracted increasing interest since they are environmentally friendly and cost-effective. In the present study, three Cd-resistant bacteria were isolated and evaluated for potential application in Cd bioremediation. Based on their morphological, physiological and biochemical characteristics, together with 16S rDNA gene sequence analyses, bacteria were identified as Stenotrophomonas acidaminiphila (2#), Pseudomonas aeruginosa (9#) and Delftia tsuruhatensis (12#). Pseudomonas aeruginosa showed very high tolerance to metals, especially Cd (2200 mg/L), Zn (1800 mg/L) and Pb (1200 mg/L), and is thought to be a multi-metal-resistant bacterium. Pseudomonas aeruginosa was also sensitive to 13 different antibiotics. The effects of the bacterial strains on the growth of rice plants and their ability to reduce Cd accumulation from Cd-contaminated soils in pot experiments were also evaluated. For Oryza sativa L. A grown in contaminated soil (3 mg/kg Cd), the accumulation of Cd was decreased by 31.2 and 25.5% in brown rice and polished rice, respectively, by strain 9#; Pseudomonas aeruginosa was more effective in reducing Cd accumulation in rice grains than a mixture of strains. For Oryza sativa L. B, a mixture of strains acting synergistically was more effective than a single strain in reducing Cd accumulation; treatment with mixed strains (strains + 3 mg/kg Cd) resulted in 41.3, 35.9, and 32.6% reductions in Cd accumulation in unhulled rice, brown rice and polished rice, respectively. Although different results were obtained for two rice varieties, it can still be concluded that Cd-resistant bacteria are suitable for reducing Cd

Strain and strain-release engineering at epitaxial SiGe islands on Si(0 0 1) for microelectronic applications

International Nuclear Information System (INIS)

Vastola, G.; Marzegalli, A.; Montalenti, F.; Miglio, Leo

2009-01-01

We report original finite element method simulations of the strain components at nanometric GeSi island on Si(0 0 1), for realistic shape, sizes and average composition, discussing the main mechanisms acting in the misfit strain relaxation. The tensile strain induced in a 30 nm Si capping layer and the one upon removing the island, after fixing the top part of the Si layer, is discussed in view of application as a field effect transistor channel, with high career mobility induced by the lattice deformation. The large shear components obtained for steeper island morphologies are predicted to be particularly performing, especially in comparison to one another strained-silicon configuration (totally top-down originated), recently developed by IBM corporation.

Unexpected earthquake hazard revealed by Holocene rupture on the Kenchreai Fault (central Greece): Implications for weak sub-fault shear zones

Science.gov (United States)

Copley, Alex; Grützner, Christoph; Howell, Andy; Jackson, James; Penney, Camilla; Wimpenny, Sam

2018-03-01

High-resolution elevation models, palaeoseismic trenching, and Quaternary dating demonstrate that the Kenchreai Fault in the eastern Gulf of Corinth (Greece) has ruptured in the Holocene. Along with the adjacent Pisia and Heraion Faults (which ruptured in 1981), our results indicate the presence of closely-spaced and parallel normal faults that are simultaneously active, but at different rates. Such a configuration allows us to address one of the major questions in understanding the earthquake cycle, specifically what controls the distribution of interseismic strain accumulation? Our results imply that the interseismic loading and subsequent earthquakes on these faults are governed by weak shear zones in the underlying ductile crust. In addition, the identification of significant earthquake slip on a fault that does not dominate the late Quaternary geomorphology or vertical coastal motions in the region provides an important lesson in earthquake hazard assessment.

A Leonard-Sanders-Budiansky-Koiter-Type Nonlinear Shell Theory with a Hierarchy of Transverse-Shearing Deformations

Science.gov (United States)

Nemeth, Michael P.

2013-01-01

A detailed exposition on a refined nonlinear shell theory suitable for nonlinear buckling analyses of laminated-composite shell structures is presented. This shell theory includes the classical nonlinear shell theory attributed to Leonard, Sanders, Koiter, and Budiansky as an explicit proper subset. This approach is used in order to leverage the exisiting experience base and to make the theory attractive to industry. In addition, the formalism of general tensors is avoided in order to expose the details needed to fully understand and use the theory. The shell theory is based on "small" strains and "moderate" rotations, and no shell-thinness approximations are used. As a result, the strain-displacement relations are exact within the presumptions of "small" strains and "moderate" rotations. The effects of transverse-shearing deformations are included in the theory by using analyst-defined functions to describe the through-the-thickness distributions of transverse-shearing strains. Constitutive equations for laminated-composite shells are derived without using any shell-thinness approximations, and simplified forms and special cases are presented.

Broiler genetic strain and sex effects on meat characteristics.

Science.gov (United States)

López, K P; Schilling, M W; Corzo, A

2011-05-01

A randomized complete block design within a factorial arrangement of treatments was used to evaluate the effect of strain and sex on carcass characteristics, meat quality, and sensory acceptability. Two broiler strains were reared: a commercially available strain (strain A) and a strain currently in the test phase (strain B) that has been genetically selected to maximize breast yield. Broilers were harvested in a pilot scale processing plant using commercial prototype equipment at 42 d of age. Carcasses were deboned at 4 h postmortem. The left half of each breast was evaluated for pH, color, cooking loss, shear force, and proximate analysis. The right side of each breast was used for consumer acceptability testing. Thigh meat was evaluated for proximate composition. No interactions were observed throughout the study. Male broilers had a higher (P dressing percentage and breast meat yield when compared with females. Broilers from strain B presented a higher (P dressing percentage than those broilers corresponding to the commercially available broiler strain. At 24 h postmortem, female broilers presented a lower ultimate pH and higher Commission internationale de l'éclairage yellowness values (ventral side of the pectoralis major) when compared with male broilers. On average, no differences existed (P > 0.05) among treatments with respect to pH decline, cooking loss, shear values, and proximate composition. In addition, no differences (P > 0.05) existed among breast meat from the different strains with respect to consumer acceptability of appearance, texture, flavor, and overall acceptability, but breast meat from strain B was slightly preferred (P < 0.05) over that of strain A with respect to aroma. However, breast meat from both strains received scores in the range of "like slightly to like moderately." Overall data suggest that all treatments yielded high quality breast and thigh meat and strain cross did not present variability in terms of consumer acceptability.

Experiments and FE-simulations of stretch flanging of DP-steels with different shear cut edge quality

Science.gov (United States)

Sigvant, M.; Falk, J.; Pilthammar, J.

2017-09-01

Dual-Phase (DP) steels are today used in the automotive industry due to its large strength to weight ratio. However, the high strength of DP-steel does have a negative impact on the general formability in sheet metal forming. Unfavourable process conditions in the press shop will, on top of this, reduce the formability of DP-steels even more. This paper addresses the problem of edge fracture in stretch flanges in sheet metal parts made of DP-steel. The experimental part involves tests of ten different DP590 and DP780 steel grades with three different shear cut qualities. The influence on the fracture strain of the sample orientation of the shear cut are also studied by facing the burr away or towards the punch and testing samples with the cut edge parallel with the rolling direction and the transverse direction. The strains are measured with an ARAMIS system in each test, together with punch displacement and punch force. All tests are then simulated with AutoFormplus R7 and the results from these simulations are compared with the experimental results in order to find the appropriate failure strain for each combination of supplier, coating, thickness and shear cut quality.

Formation mechanisms of the powder porosity generated in the neighborhood of the shear plane

International Nuclear Information System (INIS)

Makino, K.; Kuramitsu, K.; Hoshikawa, H.; Mori, H.

1988-01-01

In recent years, the sophisticated technology on the process of powder feeding, packing, mixing, and compacting, by which homogeneous powder products can be manufactured in fine ceramics and electronics industries, is being established. And, in order to develop the technology, it is necessary to make clear the formation mechanism of powder porosity in the neighborhood of shear plane generated in the powder bed. However, this has not yet been sufficiently elucidated. In this paper, a single-plane shear tester which can simultaneously measure three quantities of stress, strain, and the powder porosity in the neighborhood of shear plane, was devised by using an X-ray radiograph system, and these three quantities were systematically measured under various shearing conditions. Next, a formation model of the powder porosity in the neighborhood of shear plane, composed of powder yield locus, critical state line, and Mohr stress semi, was experimentally checked by the three measured quantities mentioned above

Microstructural Origins of Nonlinear Response in Associating Polymers under Oscillatory Shear

Directory of Open Access Journals (Sweden)

Mark A. Wilson

2017-10-01

Full Text Available The response of associating polymers with oscillatory shear is studied through large-scale simulations. A hybrid molecular dynamics (MD, Monte Carlo (MC algorithm is employed. Polymer chains are modeled as a coarse-grained bead-spring system. Functionalized end groups, at both ends of the polymer chains, can form reversible bonds according to MC rules. Stress-strain curves show nonlinearities indicated by a non-ellipsoidal shape. We consider two types of nonlinearities. Type I occurs at a strain amplitude much larger than one, type II at a frequency at which the elastic storage modulus dominates the viscous loss modulus. In this last case, the network topology resembles that of the system at rest. The reversible bonds are broken and chains stretch when the system moves away from the zero-strain position. For type I, the chains relax and the number of reversible bonds peaks when the system is near an extreme of the motion. During the movement to the other extreme of the cycle, first a stress overshoot occurs, then a yield accompanied by shear-banding. Finally, the network restructures. Interestingly, the system periodically restores bonds between the same associating groups. Even though major restructuring occurs, the system remembers previous network topologies.

Cyclic Behavior of Low Rise Concrete Shear Walls Containing Recycled Coarse and Fine Aggregates.

Science.gov (United States)

Qiao, Qiyun; Cao, Wanlin; Qian, Zhiwei; Li, Xiangyu; Zhang, Wenwen; Liu, Wenchao

2017-12-07

In this study, the cyclic behaviors of low rise concrete shear walls using recycled coarse or fine aggregates were investigated. Eight low rise Recycled Aggregates Concrete (RAC) shear wall specimens were designed and tested under a cyclic loading. The following parameters were varied: replacement percentages of recycled coarse or fine aggregates, reinforcement ratio, axial force ratio and X-shaped rebars brace. The failure characteristics, hysteretic behavior, strength and deformation capacity, strain characteristics and stiffness were studied. Test results showed that the using of the Recycled Coarse Aggregates (RCA) and its replacement ratio had almost no influence on the mechanical behavior of the shear wall; however, the using of Recycled Fine Aggregates (RFA) had a certain influence on the ductility of the shear wall. When the reinforcement ratio increased, the strength and ductility also increased. By increasing the axial force ratio, the strength increased but the ductility decreased significantly. The encased brace had a significant effect on enhancing the RAC shear walls. The experimental maximum strengths were evaluated with existing design codes, it was indicated that the strength evaluation of the low rise RAC shear walls can follow the existing design codes of the conventional concrete shear walls.

Dynamic Response and Failure Mechanism of Brittle Rocks Under Combined Compression-Shear Loading Experiments

Science.gov (United States)

Xu, Yuan; Dai, Feng

2018-03-01

A novel method is developed for characterizing the mechanical response and failure mechanism of brittle rocks under dynamic compression-shear loading: an inclined cylinder specimen using a modified split Hopkinson pressure bar (SHPB) system. With the specimen axis inclining to the loading direction of SHPB, a shear component can be introduced into the specimen. Both static and dynamic experiments are conducted on sandstone specimens. Given carefully pulse shaping, the dynamic equilibrium of the inclined specimens can be satisfied, and thus the quasi-static data reduction is employed. The normal and shear stress-strain relationships of specimens are subsequently established. The progressive failure process of the specimen illustrated via high-speed photographs manifests a mixed failure mode accommodating both the shear-dominated failure and the localized tensile damage. The elastic and shear moduli exhibit certain loading-path dependence under quasi-static loading but loading-path insensitivity under high loading rates. Loading rate dependence is evidently demonstrated through the failure characteristics involving fragmentation, compression and shear strength and failure surfaces based on Drucker-Prager criterion. Our proposed method is convenient and reliable to study the dynamic response and failure mechanism of rocks under combined compression-shear loading.

Experimental Characterization of Stress- and Strain-Dependent Stiffness in Grouted Rock Masses

Directory of Open Access Journals (Sweden)

Ji-Won Kim

2018-03-01

Full Text Available Grouting of fractured rock mass prior to excavation results in grout-filled discontinuities that govern the deformation characteristics of a site. The influence of joint characteristics on the properties of grouted rocks is important in assessing the effects of grouting on jointed rock mass. However, grouting remains a predominantly empirical practice and the effects of grouting on rock joint behavior and material properties have yet to be accurately assessed. Granular materials, including jointed rocks, typically display nonlinear strain-dependent responses that can be characterized by the shear modulus degradation curve. In this study, the effects of grouting on the strain-dependent shear stiffness of jointed rock mass were investigated at the small-strain (below 10−5 and mid-strain (10−5 to 10−3 ranges using the quasi-static resonant column test and rock mass dynamic test devices. The effects of curing time, axial stress, initial joint roughness, and grouted joint thickness were examined. The results show that (1 grouting of rock joints leads to decreased stress sensitivity and increased small-strain shear stiffness for all tested samples; (2 the grouted rock samples display similar modulus degradation characteristics as the applied grout material; (3 the initial joint roughness determines the stress-dependent behaviors and general stiffness range of the jointed and grouted rocks, but the strain-dependent behaviors are dependent on the properties of the grout material; (4 increased grouted joint thickness results in larger contribution of the grout properties in the overall grouted rock mass.

Normalized Rotational Multiple Yield Surface Framework (NRMYSF) stress-strain curve prediction method based on small strain triaxial test data on undisturbed Auckland residual clay soils

Science.gov (United States)

Noor, M. J. Md; Ibrahim, A.; Rahman, A. S. A.

2018-04-01

Small strain triaxial test measurement is considered to be significantly accurate compared to the external strain measurement using conventional method due to systematic errors normally associated with the test. Three submersible miniature linear variable differential transducer (LVDT) mounted on yokes which clamped directly onto the soil sample at equally 120° from the others. The device setup using 0.4 N resolution load cell and 16 bit AD converter was capable of consistently resolving displacement of less than 1µm and measuring axial strains ranging from less than 0.001% to 2.5%. Further analysis of small strain local measurement data was performed using new Normalized Multiple Yield Surface Framework (NRMYSF) method and compared with existing Rotational Multiple Yield Surface Framework (RMYSF) prediction method. The prediction of shear strength based on combined intrinsic curvilinear shear strength envelope using small strain triaxial test data confirmed the significant improvement and reliability of the measurement and analysis methods. Moreover, the NRMYSF method shows an excellent data prediction and significant improvement toward more reliable prediction of soil strength that can reduce the cost and time of experimental laboratory test.

Vibration Analysis of Steel-Concrete Composite Box Beams considering Shear Lag and Slip

Directory of Open Access Journals (Sweden)

Zhou Wangbao

2015-01-01

Full Text Available In order to investigate dynamic characteristics of steel-concrete composite box beams, a longitudinal warping function of beam section considering self-balancing of axial forces is established. On the basis of Hamilton principle, governing differential equations of vibration and displacement boundary conditions are deduced by taking into account coupled influencing of shear lag, interface slip, and shear deformation. The proposed method shows an improvement over previous calculations. The central difference method is applied to solve the differential equations to obtain dynamic responses of composite beams subjected to arbitrarily distributed loads. The results from the proposed method are found to be in good agreement with those from ANSYS through numerical studies. Its validity is thus verified and meaningful conclusions for engineering design can be drawn as follows. There are obvious shear lag effects in the top concrete slab and bottom plate of steel beams under dynamic excitation. This shear lag increases with the increasing degree of shear connections. However, it has little impact on the period and deflection amplitude of vibration of composite box beams. The amplitude of deflection and strains in concrete slab reduce as the degree of shear connections increases. Nevertheless, the influence of shear connections on the period of vibration is not distinct.

Arsenic accumulation by the aquatic fern Azolla: Comparison of arsenate uptake, speciation and efflux by A. caroliniana and A. filiculoides

Energy Technology Data Exchange (ETDEWEB)

Zhang Xin [State Key Lab of Urban and ONAL Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, 18 Shuangqing Road, Beijing 100085 (China); Lin Aijun [Department of Environmental Science and Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Zhao Fangjie [Soil Science Department, Rothamsted Research, Hertfordshire AL5 2JQ (United Kingdom); Xu Guozhong [Agricultural Ecology Institute, Fujian Academy of Agricultural Sciences, Fuzhou 350013 (China); Duan Guilan [State Key Lab of Urban and ONAL Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, 18 Shuangqing Road, Beijing 100085 (China); Zhu Yongguan [State Key Lab of Urban and ONAL Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, 18 Shuangqing Road, Beijing 100085 (China); Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361003 (China)], E-mail: ygzhu@rcees.ac.cn

2008-12-15

This study investigates As accumulation and tolerance of the aquatic fern Azolla. Fifty strains of Azolla showed a large variation in As accumulation. The highest- and lowest-accumulating ferns among the 50 strains were chosen for further investigations. Azolla caroliniana accumulated two times more As than Azolla filiculoides owing to a higher influx velocity for arsenate. A. filiculoides was more resistant to external arsenate due to a lower uptake. Both strains showed a similar degree of tolerance to internal As. Arsenate and arsenite were the dominant As species in both Azolla strains, with methlyated As species accounting for <5% of the total As. A. filiculoides had a higher proportion of arsenite than A. caroliniana. Both strains effluxed more arsenate than arsenite, and the amount of As efflux was proportional to the amount of As accumulation. The potential of growing Azolla in paddy fields to reduce As transfer from soil and water to rice should be further evaluated. - Arsenic accumulation and efflux differ between strains of the aquatic fern Azolla.

Arsenic accumulation by the aquatic fern Azolla: Comparison of arsenate uptake, speciation and efflux by A. caroliniana and A. filiculoides

International Nuclear Information System (INIS)

Zhang Xin; Lin Aijun; Zhao Fangjie; Xu Guozhong; Duan Guilan; Zhu Yongguan

2008-01-01

This study investigates As accumulation and tolerance of the aquatic fern Azolla. Fifty strains of Azolla showed a large variation in As accumulation. The highest- and lowest-accumulating ferns among the 50 strains were chosen for further investigations. Azolla caroliniana accumulated two times more As than Azolla filiculoides owing to a higher influx velocity for arsenate. A. filiculoides was more resistant to external arsenate due to a lower uptake. Both strains showed a similar degree of tolerance to internal As. Arsenate and arsenite were the dominant As species in both Azolla strains, with methlyated As species accounting for <5% of the total As. A. filiculoides had a higher proportion of arsenite than A. caroliniana. Both strains effluxed more arsenate than arsenite, and the amount of As efflux was proportional to the amount of As accumulation. The potential of growing Azolla in paddy fields to reduce As transfer from soil and water to rice should be further evaluated. - Arsenic accumulation and efflux differ between strains of the aquatic fern Azolla

Numerical study on shear resisting mechanism for corroded RC box culverts

International Nuclear Information System (INIS)

Matsuo, Toyofumi; Matsumura, Takuro; Iwamori, Akiyuki

2013-01-01

This paper discusses the effects of reinforcing steel corrosion on the shear resisting mechanism of RC box culverts and the applicability of the material degradation model in a finite element method. First, in FEM analyses, loss of reinforcement section area and initial tension strain due to reinforcement corrosion, and deteriorated bond characteristics between reinforcement and concrete, were considered. Second, cyclic loading tests using full-scale corroded specimens were numerically analyzed. The analyzed crack patterns and load-displacement relationships up to the maximum load were observed to be in close agreement with the experiment results within the average corrosion ratio of 10% of primary reinforcement. The fact that corrosion cracks can importantly affect the progression of shear cracks and shear strength of RC beams was also found. On the other hand, we established that RC box culverts being statically indeterminate structures, sectional forces are redistributed after cracking damage, and local material deterioration has a minor effect on shear capacity. Furthermore, a parametric study was carried out for corroded RC box culverts using parameters such as size, steel corrosion location, and corrosion level. (author)

Shear Behavior Models of Steel Fiber Reinforced Concrete Beams Modifying Softened Truss Model Approaches

Directory of Open Access Journals (Sweden)

Joo-Won Kang

2013-10-01

Full Text Available Recognizing that steel fibers can supplement the brittle tensile characteristics of concrete, many studies have been conducted on the shear performance of steel fiber reinforced concrete (SFRC members. However, previous studies were mostly focused on the shear strength and proposed empirical shear strength equations based on their experimental results. Thus, this study attempts to estimate the strains and stresses in steel fibers by considering the detailed characteristics of steel fibers in SFRC members, from which more accurate estimation on the shear behavior and strength of SFRC members is possible, and the failure mode of steel fibers can be also identified. Four shear behavior models for SFRC members have been proposed, which have been modified from the softened truss models for reinforced concrete members, and they can estimate the contribution of steel fibers to the total shear strength of the SFRC member. The performances of all the models proposed in this study were also evaluated by a large number of test results. The contribution of steel fibers to the shear strength varied from 5% to 50% according to their amount, and the most optimized volume fraction of steel fibers was estimated as 1%–1.5%, in terms of shear performance.

An alternative treatment of phenomenological higher-order strain-gradient plasticity theory

DEFF Research Database (Denmark)

Kuroda, Mitsutoshi; Tvergaard, Viggo

2010-01-01

strain is discussed, applying a dislocation theory-based consideration. Then, a differential equation for the equivalent plastic strain-gradient is introduced as an additional governing equation. Its weak form makes it possible to deduce and impose extra boundary conditions for the equivalent plastic...... strain. A connection between the present treatment and strain-gradient theories based on an extended virtual work principle is discussed. Furthermore, a numerical implementation and analysis of constrained simple shear of a thin strip are presented....

Normal force of magnetorheological fluids with foam metal under oscillatory shear modes

Energy Technology Data Exchange (ETDEWEB)

Yao, Xingyan, E-mail: yaoxingyan-jsj@163.com [Research Center of System Health Maintenance, Chongqing Technology and Business University, Chongqing 400067 (China); Chongqing Engineering Laboratory for Detection Control and Integrated System, Chongqing 400067 (China); Liu, Chuanwen; Liang, Huang; Qin, Huafeng [Chongqing Engineering Laboratory for Detection Control and Integrated System, Chongqing 400067 (China); Yu, Qibing; Li, Chuan [Research Center of System Health Maintenance, Chongqing Technology and Business University, Chongqing 400067 (China); Chongqing Engineering Laboratory for Detection Control and Integrated System, Chongqing 400067 (China)

2016-04-01

The normal force of magnetorheological (MR) fluids in porous foam metal was investigated in this paper. The dynamic repulsive normal force was studied using an advanced commercial rheometer under oscillatory shear modes. In the presence of magnetic fields, the influences of time, strain amplitude, frequency and shear rate on the normal force of MR fluids drawn from the porous foam metal were systematically analysed. The experimental results indicated that the magnetic field had the greatest effect on the normal force, and the effect increased incrementally with the magnetic field. Increasing the magnetic field produced a step-wise increase in the shear gap. However, other factors in the presence of a constant magnetic field only had weak effects on the normal force. This behaviour can be regarded as a magnetic field-enhanced normal force, as increases in the magnetic field resulted in more MR fluids being released from the porous foam metal, and the chain-like magnetic particles in the MR fluids becoming more elongated with aggregates spanning the gap between the shear plates. - Highlights: • Normal force of MR fluids with metal foam under oscillatory shear modes was studied. • The shear gap was step-wise increased with magnetic fields. • The magnetic field has a greater impact on the normal force.

Normal force of magnetorheological fluids with foam metal under oscillatory shear modes

International Nuclear Information System (INIS)

Yao, Xingyan; Liu, Chuanwen; Liang, Huang; Qin, Huafeng; Yu, Qibing; Li, Chuan

2016-01-01

The normal force of magnetorheological (MR) fluids in porous foam metal was investigated in this paper. The dynamic repulsive normal force was studied using an advanced commercial rheometer under oscillatory shear modes. In the presence of magnetic fields, the influences of time, strain amplitude, frequency and shear rate on the normal force of MR fluids drawn from the porous foam metal were systematically analysed. The experimental results indicated that the magnetic field had the greatest effect on the normal force, and the effect increased incrementally with the magnetic field. Increasing the magnetic field produced a step-wise increase in the shear gap. However, other factors in the presence of a constant magnetic field only had weak effects on the normal force. This behaviour can be regarded as a magnetic field-enhanced normal force, as increases in the magnetic field resulted in more MR fluids being released from the porous foam metal, and the chain-like magnetic particles in the MR fluids becoming more elongated with aggregates spanning the gap between the shear plates. - Highlights: • Normal force of MR fluids with metal foam under oscillatory shear modes was studied. • The shear gap was step-wise increased with magnetic fields. • The magnetic field has a greater impact on the normal force.

Multiscale mechanical integrity of human supraspinatus tendon in shear after elastin depletion.

Science.gov (United States)

Fang, Fei; Lake, Spencer P

2016-10-01

Human supraspinatus tendon (SST) exhibits region-specific nonlinear mechanical properties under tension, which have been attributed to its complex multiaxial physiological loading environment. However, the mechanical response and underlying multiscale mechanism regulating SST behavior under other loading scenarios are poorly understood. Furthermore, little is known about the contribution of elastin to tendon mechanics. We hypothesized that (1) SST exhibits region-specific shear mechanical properties, (2) fiber sliding is the predominant mode of local matrix deformation in SST in shear, and (3) elastin helps maintain SST mechanical integrity by facilitating force transfer among collagen fibers. Through the use of biomechanical testing and multiphoton microscopy, we measured the multiscale mechanical behavior of human SST in shear before and after elastase treatment. Three distinct SST regions showed similar stresses and microscale deformation. Collagen fiber reorganization and sliding were physical mechanisms observed as the SST response to shear loading. Measures of microscale deformation were highly variable, likely due to a high degree of extracellular matrix heterogeneity. After elastase treatment, tendon exhibited significantly decreased stresses under shear loading, particularly at low strains. These results show that elastin contributes to tendon mechanics in shear, further complementing our understanding of multiscale tendon structure-function relationships. Copyright © 2016 Elsevier Ltd. All rights reserved.

Influence of particle size on the low and high strain rate behavior of dense colloidal dispersions of nanosilica

Energy Technology Data Exchange (ETDEWEB)

Asija, Neelanchali; Chouhan, Hemant; Gebremeskel, Shishay Amare; Bhatnagar, Naresh, E-mail: nareshb@mech.iitd.ac.in [Indian Institute of Technology Delhi, Mechanical Engineering Department (India)

2017-01-15

Shear thickening is a non-Newtonian flow behavior characterized by the increase in apparent viscosity with the increase in applied shear rate, particularly when the shear rate exceeds a critical value termed as the critical shear rate (CSR). Due to this remarkable property of shear-thickening fluids (STFs), they are extensively used in hip protection pads, protective gear for athletes, and more recently in body armor. The use of STFs in body armor has led to the development of the concept of liquid body armor. In this study, the effect of particle size is explored on the low and high strain rate behavior of nanosilica dispersions, so as to predict the efficacy of STF-aided personal protection systems (PPS), specifically for ballistic applications. The low strain rate study was conducted on cone and plate rheometer, whereas the high strain rate characterization of STF was conducted on in-house fabricated split Hopkinson pressure bar (SHPB) system. Spherical nanosilica particles of three different sizes (100, 300, and 500 nm) as well as fumed silica particles of four different specific surface areas (Aerosil A-90, A-130, A-150, and A-200), respectively, were used in this study. The test samples were prepared by dispersing nanosilica particles in polypropylene glycol (PPG) using ultrasonic homogenization method. The low strain rate studies aided in determining the CSR of the synthesized STF dispersions, whereas the high strain rate studies explored the impact-resisting ability of STFs in terms of the impact toughness and the peak stress attained during the impact loading of STF in SHPB testing.

Impact of organic nutrient load on biomass accumulation, feed channel pressure drop increase and permeate flux decline in membrane systems

KAUST Repository

Bucs, Szilard; Valladares Linares, Rodrigo; van Loosdrecht, Mark C.M.; Kruithof, Joop C.; Vrouwenvelder, Johannes S.

2014-01-01

organic carbon (TOC).Our studies showed that the organic nutrient load determined the accumulated amount of biomass. The same amount of accumulated biomass was found at constant nutrient load irrespective of linear flow velocity, shear, and/or feed spacer

Interseismic Strain Accumulation of the Gazikoy-Saros segment (Ganos fault) of the North Anatolian Fault Zone

Science.gov (United States)

Havazli, E.; Wdowinski, S.; Amelung, F.

2017-12-01

The North Anatolian Fault Zone (NAFZ) is one of the most active continental transform faults in the world. A westward migrating earthquake sequence has started in 1939 in Erzincan and the last two events of this sequence occurred in 1999 in Izmit and Duzce manifesting the importance of NAFZ on the seismic hazard potential of the region. NAFZ exhibits slip rates ranging from 14-30 mm/yr along its 1500 km length with a right lateral strike slip characteristic. In the East of the Marmara Sea, the NAFZ splits into two branches. The Gazikoy-Saros segment (Ganos Fault) is the westernmost and onshore segment of the northern branch. The ENE-WSW oriented Ganos Fault is seismically active. It produced a Ms 7.2 earthquake in 1912, which was followed by several large aftershocks, including Ms 6.3 and Ms 6.9 events. Since 1912, the Ganos Fault did not produce any significant earthquakes (> M 5), in contrast to its adjacent segments, which produced 20 M>5 earthquakes, including a M 6.7 event, offshore in Gulf of Saros. Interseismic strain accumulation along the Ganos Fault was assessed from sparse GPS measurements along a single transect located perpendicular to the fault zone, suggesting strain accumulation rate of 20-25 mm/yr. Insofar, InSAR studies, based on C-band data, didn't produce conclusive results due to low coherence over the fault zone area, which is highly vegetated. In this study, we present a detailed interseismic velocity map of the Ganos Fault zone derived from L-band InSAR observations. We use 21 ALOS PALSAR scenes acquired over a 5-year period, from 2007 to 2011. We processed the ALOS data using the PySAR software, which is the University of Miami version of the Small Baseline (SB) method. The L-band observations enabled us to overcome the coherence issue in the study area. Our initial results indicate a maximum velocity of 15 mm/yr across the fault zone. The high spatial resolution of the InSAR-based interseismic velocity map will enable us to better to

Analytical solution for shear bands in cold-rolled 1018 steel

Science.gov (United States)

Voyiadjis, George Z.; Almasri, Amin H.; Faghihi, Danial; Palazotto, Anthony N.

2012-06-01

Cold-rolled 1018 (CR-1018) carbon steel has been well known for its susceptibility to adiabatic shear banding under dynamic loadings. Analysis of these localizations highly depends on the selection of the constitutive model. To deal with this issue, a constitutive model that takes temperature and strain rate effect into account is proposed. The model is motivated by two physical-based models: the Zerilli and Armstrong and the Voyiadjis and Abed models. This material model, however, incorporates a simple softening term that is capable of simulating the softening behavior of CR-1018 steel. Instability, localization, and evolution of adiabatic shear bands are discussed and presented graphically. In addition, the effect of hydrostatic pressure is illustrated.

Strain gradient crystal plasticity effects on flow localization

DEFF Research Database (Denmark)

Borg, Ulrik

2007-01-01

for metals described by the reformulated Fleck-Hutchinson strain gradient plasticity theory. The theory is implemented numerically within a finite element framework using slip rate increments and displacement increments as state variables. The formulation reduces to the classical crystal plasticity theory...... in the absence of strain gradients. The model is used to study the effect of an internal material length scale on the localization of plastic flow in shear bands in a single crystal under plane strain tension. It is shown that the mesh sensitivity is removed when using the nonlocal material model considered...

Shear strength of non-shear reinforced concrete elements

DEFF Research Database (Denmark)

Hoang, Cao linh

1997-01-01

The paper deals with the plastic shear strength of non shear reinforced T-beams.The influence of an un-reinforced flange on the shear capacity is investigated by considering a failure mechanism involving crack sliding in the web and a kind of membrane action over an effective width of the flange...

Adiabatic shear behaviors in rolled and annealed pure titanium subjected to dynamic impact loading

Energy Technology Data Exchange (ETDEWEB)

Kuang, Lianjun; Chen, Zhiyong, E-mail: czysh@netease.com; Jiang, Yanghui; Wang, Zhiming; Wang, Renke; Liu, Chuming

2017-02-08

The hat-shaped samples cut from rolled and annealed titanium plates were prepared to explore the adiabatic shear behaviors subjected to high-strain-rate deformation operated via Split Hopkinson Pressure Bar. The dynamic shear response calculation reveals that dynamic deformation processes of both state samples can be divided in similar three stages but rolled sample shows a higher susceptibility of adiabatic shear localization compared with the annealed one. Optical microscopy and electronic backscatter diffraction technique (EBSD) were used to systematically analyze the microstructure and texture characteristics. The results show that adiabatic shear bands form in both state samples and rotational dynamic recrystallization (RDRX) occurs within shear area and results in the formation of ultrafine equiaxed grains. Furthermore, ultrafine equiaxed grains within adiabatic shear bands have the same texture feature that <11–20> direction and {10-10} plane parallel to macro local shear direction and shear plane respectively. In the deformation region around the shear band, {10–12} <–1011> tensile and {11–22} <11-2-3> compressive two types twins are observed in both state samples and {10–12} <–1011> tensile twins are more frequently observed in rolled sample. In the rolled sample, {10–12} <–1011> tensile twins are more likely to happen in the hat-brim side than the hat-body side due to the difference of stress state in two sides.

Impact of magnetic shear modification on confinement and turbulent fluctuations in LHD plasmas

International Nuclear Information System (INIS)

Fukuda, T.; Tamura, N.; Ida, K.

2008-10-01

For the comprehensive understandings of transport phenomena in toroidal confinement systems and improvement of the predictive capability of burning plasmas in ITER, the impact of magnetic shear has been extensively investigated in the Large Helical Device (LHD) for comparison with tokamaks. Consequently, it was heuristically documented that the pronounced effect of magnetic shear, which has been hitherto considered to be ubiquitous and strongly impacts the core transport in the tokamak experiments, is not quite obvious. Namely, the kinetic profiles respond little under extensive modification of the magnetic shear in the core, although the local transport analysis indicates the sign of improvement in confinement transiently when the magnetic shear is reduced. It was thereby concluded that the magnetic shear in the core strongly influences the MHD activity, but it may only be one of the necessary conditions for the transport reduction, and some other crucial knobs, such as the density gradient or T e /T i ratio, would have to be simultaneously controlled. The low wavenumber turbulence seems to be suppressed under the weak shear, and the turbulent fluctuation intensity behaves in a consistent manner as a whole, following the conventional paradigm accumulated in the negative shear experiments in tokamaks. However, vigorous dynamics of turbulent fluctuations have occasionally been observed under the magnetic shear modification, which respond in much faster time scale than the characteristic time scale for either the magnetic diffusion or the profile evolution. (author)

Effects of tire inclination (turning traffic and dynamic loading on the pavement stress–strain responses using 3-D finite element modeling

Directory of Open Access Journals (Sweden)

Xiaodi Hu

2017-07-01

Full Text Available In this study, ABAQUS finite element (FE modeling in three-dimensional (3-D loading mode was utilized to analytically investigate and quantify the effects of tire inclination and dynamic loading on the stress–strain responses of a pavement structure under varying loading and environmental conditions. The input variables for modeling consisted of actual laboratory and field data obtained from an in-service highway US 59 and included the in-situ pavement structure, material properties (i.e., modulus and shear strength, traffic, and climatic (i.e., temperature data. Computational modeling and sensitivity analyses were conducted through variation of the following two input variables with a focus on the top surfacing hot-mix asphalt (HMA layer: a tire inclination angle to simulate turning traffic, and, b dynamic loading to simulate accelerating, steady rolling, and decelerating (braking traffic. The generated maximum shear stress and vertical strain responses were then analyzed and correlated to the HMA material strength and the actual measured/observed field rutting performance data. The corresponding results indicated that inclined tires (simulating turning traffic and decelerating (braking vehicles induced the most severe shear stresses and vertical strains on the pavement structure in terms of magnitude (i.e., increased; exceeding the HMA material strength in some cases. Thus, for pavement design and structural analysis purposes, the following critical highway areas that may be subjected to extreme stresses and strains due to turning and stopping (braking traffic, particularly in high temperature environments, should be given more attention with respect to material strength characterization to mitigate potential shear/rutting failures: intersections, junctions; urban stop–go sections, and curves. Keywords: 3-D FE stress–strain modeling, Rutting, Shear deformation, Shear stress, Vertical strains

Computation of shear-induced collective-diffusivity in emulsions

Science.gov (United States)

Malipeddi, Abhilash Reddy; Sarkar, Kausik

2017-11-01

The shear-induced collective-diffusivity of drops in an emulsion is calculated through simulation. A front-tracking finite difference method is used to integrate the Navier-Stokes equations. When a cloud of drops is subjected to shear flow, after a certain time, the width of the cloud increases with the 1/3 power of time. This scaling of drop-cloud-width with time is characteristic of (sub-)diffusion that arises from irreversible two-drop interactions. The collective diffusivity is calculated from this relationship. A feature of the procedure adopted here is the modest computational requirement, wherein, a few drops ( 70) in shear for short time ( 70 strain) is found to be sufficient to get a good estimate. As far as we know, collective-diffusivity has not been calculated for drops through simulation till now. The computed values match with experimental measurements reported in the literature. The diffusivity in emulsions is calculated for a range of Capillary (Ca) and Reynolds (Re) numbers. It is found to be a unimodal function of Ca , similar to self-diffusivity. A sub-linear increase of the diffusivity with Re is seen for Re < 5 . This work has been limited to a viscosity matched case.

Application of kinematic vorticity and gold mineralization for the wall rock alterations of shear zone at Dungash gold mining, Central Eastern Desert, Egypt

Science.gov (United States)

Kassem, Osama M. K.; Abd El Rahim, Said H.; El Nashar, EL Said R.; AL Kahtany, Kaled M.

2016-11-01

The use of porphyroclasts rotating in a flowing matrix to estimate mean kinematic vorticity number (Wm) is important for quantifying the relative contributions of pure and simple shear in wall rocks alterations of shear zone at Dungash gold mine. Furthermore, it shows the relationship between the gold mineralization and deformation and also detects the orientation of rigid objects during progressive deformation. The Dungash gold mine area is situated in an EW-trending quartz vein along a shear zone in metavolcanic and metasedimentary host rocks in the Eastern Desert of Egypt. These rocks are associated with the major geologic structures which are attributed to various deformational stages of the Neoproterozoic basement rocks. We conclude that finite strain in the deformed rocks is of the same order of magnitude for all units of metavolcano-sedimentary rocks. The kinematic vorticity number for the metavolcanic and metasedimentary samples in the Dungash area range from 0.80 to 0.92, and together with the strain data suggest deviations from simple shear. It is concluded that nappe stacking occurred early during the underthrusting event probably by brittle imbrication and that ductile strain was superimposed on the nappe structure during thrusting. Furthermore, we conclude that disseminated mineralization, chloritization, carbonatization and silicification of the wall rocks are associated with fluids migrating along shearing, fracturing and foliation of the metamorphosed wall rocks.

Shearing-induced asymmetry in entorhinal grid cells.

Science.gov (United States)

Stensola, Tor; Stensola, Hanne; Moser, May-Britt; Moser, Edvard I

2015-02-12

Grid cells are neurons with periodic spatial receptive fields (grids) that tile two-dimensional space in a hexagonal pattern. To provide useful information about location, grids must be stably anchored to an external reference frame. The mechanisms underlying this anchoring process have remained elusive. Here we show in differently sized familiar square enclosures that the axes of the grids are offset from the walls by an angle that minimizes symmetry with the borders of the environment. This rotational offset is invariably accompanied by an elliptic distortion of the grid pattern. Reversing the ellipticity analytically by a shearing transformation removes the angular offset. This, together with the near-absence of rotation in novel environments, suggests that the rotation emerges through non-coaxial strain as a function of experience. The systematic relationship between rotation and distortion of the grid pattern points to shear forces arising from anchoring to specific geometric reference points as key elements of the mechanism for alignment of grid patterns to the external world.

Exercise-induced heat stress disrupts the shear-dilatory relationship.

Science.gov (United States)

Ives, Stephen J; Lefferts, Wesley K; Wharton, Margret; Fehling, Patricia C; Smith, Denise L

2016-12-01

What is the central question of this study? Although heat stress is known to increase cardiovascular strain, no study, to date, had explored the potential impact of exercise-induced heat stress on vascular function. What is the main finding and its importance? We found that acute exercise tended to reduce flow-mediated dilatation (FMD), owing in part to reduced reactive hyperaemia/shear stimulus; thus, when FMD is normalized to shear no postexercise deficit exists. Exercise-induced heat stress increased reactive hyperaemia, shear rate, coupled with a sustained FMD postexercise, suggests that exercise-induced heat stress increases the amount of shear stimulus to elicit a similar response, indicating reduced vascular responsiveness, or reserve, which might increase cardiovascular susceptibility. Heat stress increases cardiovascular strain and is of particular concern in occupations, such as firefighting, in which individuals are required to perform strenuous work while wearing personal protective equipment. Sudden cardiac events are associated with strenuous activity and are the leading cause of duty-related death among firefighters, accounting for ∼50% of duty-related fatalities per year. Understanding the acute effects of exercise-induced heat stress (EIHS) on vascular endothelial function may provide insight into the mechanisms precipitating acute coronary events in firefighters. The purpose of this study, therefore, was to determine the effects of EIHS on vascular endothelial function. Using a balanced crossover design, 12 healthy men performed 100 min of moderate-intensity, intermittent exercise with and without EIHS (personal protective equipment or cooling vest, respectively). Measurements of flow-mediated dilatation (FMD), reactive hyperaemia and shear rate area under the curve (SR AUC ) were performed pre- and postexercise. During EIHS, core temperature was significantly higher (38 ± 0.1 versus 37 ± 0.1°C). Postexercise FMD tended to be suppressed

Incipient Evolution of the Eastern California Shear Zone through a Transpressional Zone along the San Andreas Fault in the San Bernardino Mountains, California

Science.gov (United States)

Cochran, W. J.; Spotila, J. A.

2017-12-01

Measuring long-term accumulation of strike-slip displacements and transpressional uplift is difficult where strain is accommodated across wide shear zones, as opposed to a single major fault. The Eastern California Shear Zone (ECSZ) in southern California accommodates dextral shear across several strike-slip faults, and is potentially migrating and cutting through a formerly convergent zone of the San Bernardino Mountains (SBM). The advection of crust along the San Andreas fault to the SE has forced these two tectonic regimes into creating a nexus of interacting strike-slip faults north of San Gorgonio Pass. These elements make this region ideal for studying complex fault interactions, evolving fault geometries, and deformational overprinting within a wide shear zone. Using high-resolution topography and field mapping, this study aims to test whether diffuse, poorly formed strike-slip faults within the uplifted SBM block are nascent elements of the ECSZ. Topographic resolution of ≤ 1m was achieved using both lidar and UAV surveys along two Quaternary strike-slip faults, namely the Lake Peak fault and Lone Valley faults. Although the Lone Valley fault cuts across Quaternary alluvium, the geomorphic expression is obscured, and may be the result of slow slip rates. In contrast, the Lake Peak fault is located high elevations north of San Gorgonio Peak in the SBM, and displaces Quaternary glacial deposits. The deposition of large boulders along the escarpment also obscures the apparent magnitude of slip along the fault. Although determining fault offset is difficult, the Lake Peak fault does display evidence for minor right-lateral displacement, where the magnitude of slip would be consistent with individual faults within the ECSZ (i.e. ≤ 1 mm/yr). Compared to the preservation of displacement along strike-slip faults located within the Mojave Desert, the upland region of the SBM adds complexity for measuring fault offset. The distribution of strain across the entire

Evaluation of Intrinsic Shear Piezoelectric Coefficient d15 of c-Axis Oriented Pb(Zr,Ti)O3 Films

Science.gov (United States)

Kanno, Isaku; Akama, Kenji; Wasa, Kiyotaka; Kotera, Hidetoshi

2009-09-01

Piezoelectric shear strain was measured for c-axis oriented epitaxial Pb(Zr,Ti)O3 (PZT) thin films. The PZT films, with a composition near the morphotropic phase boundary (MPB), were epitaxially grown on (001) MgO substrates and then microfabricated into a rectangular shape by wet etching of the films. Lateral electrodes were deposited on both sides of the PZT films, to apply an external electric field perpendicular to the polarization. A sinusoidal input voltage of 100 kHz was applied between the lateral electrodes, and in-plane shear vibration was measured by a laser Doppler vibrometer. In-plane displacement due to shear mode piezoelectric vibration was clearly observed and increased proportionally with the voltage. Finite element method (FEM) analysis was conducted to determine the horizontal electric field in the PZT film, and the piezoelectric coefficient d15 was calculated to be 440×10-12 m/V. The d15 of the PZT film represents the intrinsic shear piezoelectric effect, which is slightly smaller than that of bulk PZT, due to the absence of extrinsic effects such as longitudinal and transverse piezoelectric strain or domain rotation.

Nucleation and evolution of strain-induced martensitic (b.c.c.) embryos and substructure in stainless steel: a transmission electron microscope study

International Nuclear Information System (INIS)

Staudhammer, K.P.; Hecker, S.S.; Murr, L.E.

1983-01-01

The deformation of type 304 stainless steel produces a preponderance of strain-induced /chi/ (b.c.c.) martensite, which nucleates as stable embryos at micro-shear band or twin-fault intersections as proposed by Olson and Cohen. The two intersecting micro-shear bands must have a specific defect (fault-displacement) structure, and for stable martensite embryos to form requires a minimal micro-shear band thickness ranging from 50-70 A. The critical nature of nucleation is influenced by the local temperature and strain. The structure, geometry, and morphology of strain-induced martensite embryos is essentially invariant regardless of the strain rate, strain state or temperature. Larger volume fractions of martensite evolve at large strains (greater than or equal to 20%) as a result of embryo coalescence to produce a blocky-type morphology. Martensite embryos and coalesced volume elements of /chi/ are frequently characterized by an irregular non-homogeneous distribution of smaller b.c.c. regimes which result from the irregular satisfaction of the necessary and specific fault-displacement requirements within a larger intersection volume

Cyclic Behavior of Low Rise Concrete Shear Walls Containing Recycled Coarse and Fine Aggregates

Directory of Open Access Journals (Sweden)

Qiyun Qiao

2017-12-01

Full Text Available In this study, the cyclic behaviors of low rise concrete shear walls using recycled coarse or fine aggregates were investigated. Eight low rise Recycled Aggregates Concrete (RAC shear wall specimens were designed and tested under a cyclic loading. The following parameters were varied: replacement percentages of recycled coarse or fine aggregates, reinforcement ratio, axial force ratio and X-shaped rebars brace. The failure characteristics, hysteretic behavior, strength and deformation capacity, strain characteristics and stiffness were studied. Test results showed that the using of the Recycled Coarse Aggregates (RCA and its replacement ratio had almost no influence on the mechanical behavior of the shear wall; however, the using of Recycled Fine Aggregates (RFA had a certain influence on the ductility of the shear wall. When the reinforcement ratio increased, the strength and ductility also increased. By increasing the axial force ratio, the strength increased but the ductility decreased significantly. The encased brace had a significant effect on enhancing the RAC shear walls. The experimental maximum strengths were evaluated with existing design codes, it was indicated that the strength evaluation of the low rise RAC shear walls can follow the existing design codes of the conventional concrete shear walls.

Experimental report of precast prestressed concrete shear wall. Precast prestressed concrete taishinheki no jikken hokoku

Energy Technology Data Exchange (ETDEWEB)

Takada, K.; Komura, M.; Sakata, H.; Senoo, M. (Fudo Building Research Co. Ltd., Tokyo (Japan))

1993-07-30

The present report outlines the multi-story precast prestressed concrete earthquake-proof wall (PC shear wall system). The PC shear wall is a precast wall which internally contains the columns and beams as a unit. Therefore, the present system integrates the walls, columns and beams without beam-framing installation for the intermediate stories. It can simplify the concreting in site and ease the construction of building. For the system development, experiment was made on the deformation, sliding, yield strength and destruction state of the shear wall. Used were four types of test unit which are different in both reinforcement and connection methods. The test force was given by a hydraulically drawing jack. In the experiment, the four types were compared in destruction state, relation between load and deformation, yield strength, and strain of main column reinforcing bars and wall connection reinforcing bars. PC shear wall system-based design was studied from the experimental result. The shear wall in which there occurred both bending and shearing deformations was modeled by changing to a brace unit. Divided into bending deformation and shearing deformation, the deformation was calculated, which concluded that the shearing deformation dominates in the present system. 15 figs., 4 tabs.

Quasi-static and dynamic forced shear deformation behaviors of Ti-5Mo-5V-8Cr-3Al alloy

Energy Technology Data Exchange (ETDEWEB)

Wang, Zhiming; Chen, Zhiyong, E-mail: czysh@netease.com; Zhan, Congkun; Kuang, Lianjun; Shao, Jianbo; Wang, Renke; Liu, Chuming

2017-04-13

The mechanical behavior and microstructure characteristics of Ti-5Mo-5V-8Cr-3Al alloy were investigated with hat-shaped samples compressed under quasi-static and dynamic loading. Compared with the quasi-static loading, a higher shear stress peak and a shear instability stage were observed during the dynamic shear response. The results showed that an adiabatic shear band consisting of ultrafine equiaxed grains was only developed in the dynamic specimen, while a wider shear region was formed in the quasi-static specimen. The microhardness measurements revealed that shear region in the quasi-static specimen and adiabatic shear band in the dynamic specimen exhibited higher hardness than that of adjacent regions due to the strain hardening and grain refining, respectively. A stable orientation, in which the crystallographic {110} planes and <111> directions were respectively parallel to the shear plane and shear direction, developed in both specimens. And the microtexture of the adiabatic shear band was more well-defined than that of the shear region in the quasi-static specimen. Rotational dynamic recrystallization mechanism was suggested to explain the formation of ultrafine equiaxed grains within the adiabatic shear band by thermodynamic and kinetic calculations.

Comparison of Shear Strength Properties for Undisturbed and Reconstituted Parit Nipah Peat, Johor

Science.gov (United States)

Azhar, A. T. S.; Norhaliza, W.; Ismail, B.; Abdullah, M. E.; Zakaria, M. N.

2016-11-01

Shear strength of soil is required to determine the soil stability and design the foundations. Peat is known as a soil with complex natural formations which also contributes problems to the researchers, developers, engineers and contractors in constructions and infrastructures. Most researchers conducted experiment and investigation of shear strength on peat using shear box test and simple shear test, but only a few had discovered the behavior of peat using triaxial consolidated undrained test. The aim of this paper is to determine the undrained shear strength properties of reconstituted peat and undisturbed peat of Parit Nipah, Johor for comparison purposes. All the reconstituted peat samples were formed with the size that passed opening sieve 3.35 mm and preconsolidation pressure at 100 kPa. The result of undrained shear strength of reconstituted peat was 21kPa for cohesion with the angle of friction, 41° compare to the undisturbed peat with cohesion 10 kPa and angle of friction, 16°. The undrained shear strength properties result obtained shows that the reconstituted peat has higher strength than undisturbed peat. For relationship deviator stress-strain, σd max and excess pore pressure, Δu, it shows that both of undisturbed and reconstituted gradually increased when σ’ increased, but at the end of the test, the values are slightly dropped. The physical properties of undisturbed and reconstituted peat were also investigated to correlate with the undrained shear strength results.

Discrete element simulation studies of angles of repose and shear flow of wet, flexible fibers.

Science.gov (United States)

Guo, Y; Wassgren, C; Ketterhagen, W; Hancock, B; Curtis, J

2018-04-18

A discrete element method (DEM) model is developed to simulate the dynamics of wet, flexible fibers. The angles of repose of dry and wet fibers are simulated, and the simulation results are in good agreement with experimental results, validating the wet, flexible fiber model. To study wet fiber flow behavior, the model is used to simulate shear flows of wet fibers in a periodic domain under Lees-Edwards boundary conditions. Significant agglomeration is observed in dilute shear flows of wet fibers. The size of the largest agglomerate in the flow is found to depend on a Bond number, which is proportional to liquid surface tension and inversely proportional to the square of the shear strain rate. This Bond number reflects the relative importance of the liquid-bridge force to the particle's inertial force, with a larger Bond number leading to a larger agglomerate. As the fiber aspect ratio (AR) increases, the size of the largest agglomerate increases, while the coordination number in the largest agglomerate initially decreases and then increases when the AR is greater than four. A larger agglomerate with a larger coordination number is more likely to form for more flexible fibers with a smaller bond elastic modulus due to better connectivity between the more flexible fibers. Liquid viscous force resists pulling of liquid bridges and separation of contacting fibers, and therefore it facilitates larger agglomerate formation. The effect of liquid viscous force is more significant at larger shear strain rates. The solid-phase shear stress is increased due to the presence of liquid bridges in moderately dense flows. As the solid volume fraction increases, the effect of fiber-fiber friction coefficient increases sharply. When the solid volume fraction approaches the maximum packing density, the fiber-fiber friction coefficient can be a more dominant factor than the liquid bridge force in determining the solid-phase shear stress.

Strength and behavior in shear of reinforced concrete deep beams under dynamic loading conditions

Energy Technology Data Exchange (ETDEWEB)

Adhikary, Satadru Das [School of Civil and Environmental Engineering, Nanyang Technological University, 639798 (Singapore); Li, Bing, E-mail: cbli@ntu.edu.sg [School of Civil and Environmental Engineering, Nanyang Technological University, 639798 (Singapore); Fujikake, Kazunori [Department of Civil and Environmental Engineering, National Defense Academy, Yokosuka 239 8686 (Japan)

2013-06-15

Highlights: ► Effects of wider range of loading rates on dynamic shear behavior of RC deep beams. ► Experimental investigation of RC deep beam with and without shear reinforcements. ► Verification of experimental results with truss model and FE simulation results. ► Empirical equations are proposed to predict the dynamic increase factor of maximum resistance. -- Abstract: Research on reinforced concrete (RC) deep beams has seen considerable headway over the past three decades; however, information on the dynamic shear strength and behavior of RC deep beams under varying rates of loads remains limited. This paper describes the experimental results of 24 RC deep beams with and without shear reinforcements under varying rates of concentrated loading. Results obtained serve as useful data on shear resistance, failure patterns and strain rates corresponding to varying loading rates. An analytical truss model approach proves its efficacy in predicting the dynamic shear resistance under varying loading rates. Furthermore, three-dimensional nonlinear finite element (FE) model is described and the simulation results are verified with the experimental results. A parametric study is then conducted to investigate the influence of longitudinal reinforcement ratio, transverse reinforcement ratio and shear span to effective depth ratio on shear behavior. Subsequently, two empirical equations were proposed by integrating the various parameters to assess the dynamic increase factor (DIF) of maximum resistance under varying rates of concentrated loading.

Improving the durability of the optical fiber sensor based on strain transfer analysis

Science.gov (United States)

Wang, Huaping; Jiang, Lizhong; Xiang, Ping

2018-05-01

To realize the reliable and long-term strain detection, the durability of optical fiber sensors has attracted more and more attention. The packaging technique has been considered as an effective method, which can enhance the survival ratios of optical fiber sensors to resist the harsh construction and service environment in civil engineering. To monitor the internal strain of structures, the embedded installation is adopted. Due to the different material properties between host material and the protective layer, the monitored structure embedded with sensors can be regarded as a typical model containing inclusions. Interfacial characteristic between the sensor and host material exists obviously, and the contacted interface is prone to debonding failure induced by the large interfacial shear stress. To recognize the local interfacial debonding damage and extend the effective life cycle of the embedded sensor, strain transfer analysis of a general three-layered sensing model is conducted to investigate the failure mechanism. The perturbation of the embedded sensor on the local strain field of host material is discussed. Based on the theoretical analysis, the distribution of the interfacial shear stress along the sensing length is characterized and adopted for the diagnosis of local interfacial debonding, and the sensitive parameters influencing the interfacial shear stress are also investigated. The research in this paper explores the interfacial debonding failure mechanism of embedded sensors based on the strain transfer analysis and provides theoretical basis for enhancing the interfacial bonding properties and improving the durability of embedded optical fiber sensors.

Total lipid accumulation and fatty acid profiles of microalga Spirulina ...

African Journals Online (AJOL)

Nutrient limitation in terms of nitrogen and phosphorus increased lipid accumulation under depleted growth in Spirulina strains. Nitrogen limitation was found more effective than phosphorus in accumulating lipid. The fatty acid profile was variable: palmitic (48%), linolenic (21%) and linoleic acids (15%) were the most ...

Effect of strain path on microstructure, deformation texture and mechanical properties of nano/ultrafine grained AA1050 processed by accumulative roll bonding (ARB)

Energy Technology Data Exchange (ETDEWEB)

Naseri, M.; Reihanian, M. [Department of Materials Science and Engineering, Faculty of Engineering, Shahid Chamran University of Ahvaz, Ahvaz (Iran, Islamic Republic of); Borhani, E., E-mail: e.borhani@semnan.ac.ir [Department of Nano Technology, Nano Materials Group, Semnan University, Semnan (Iran, Islamic Republic of)

2016-09-15

Commercial pure Al sheets were severe plastically deformed at room temperature by accumulative roll bonding (ARB) and cross accumulative roll bonding (CARB). Change in strain path was imposed during CARB by rotating the sheets with 90° around the normal direction axis between each cycle. Microstructural evolution of processed sheets was studied by electron back scattered diffraction (EBSD) analysis and revealed that nano/ultrafine grains (NG/UFG) with the average grain size of 380 nm and 155 nm were formed by both processing routes after eight cycles, respectively. The fraction of high angle grain boundaries and mean misorientation angle of the boundaries in the CARB were 49% and 40.20°, respectively, in comparison to that of ARB sample (41% and 37.37°). Deformation texture evolution demonstrated that the change in strain path leads to the formation of strong orientation along the β-fiber. The major texture components for ARB specimens were Brass {011}<211> and S {123}<634> while those for CARB were Brass {011}<211> and Goss {011}<100>. The CARB processed specimen exhibited the tensile strength, microhardness and elongation of about 230 MPa, 92 HV and 13% compared with ARB sample (180 MPa, 80 HV and 10.5%) after eight cycles. Scanning electron microscopy (SEM) observations of tensile fracture surface of specimens revealed ductile type fracture.

DOMESTIC BUTANOL-PRODUCING STRAINS OF THE Clostridium GENUS

Directory of Open Access Journals (Sweden)

O. O. Tigunova

2017-02-01

Full Text Available The aim of the work was to summarize the results of own research concerning obtaining butanol producing strains of Clostridium genus, to identify them by physiological, morphological and genetic methods. Further study of characteristics and biological features of the strains, and various approaches in biotechnological process of butanol production are discussed. The work includes methods to increase butanol accumulation by producer strains. Perspectives of using chemical mutagenesis in Clostridia as a method of increasing butanol production are considered. The feasibility of using non-food raw material as a substrate for fermentation is discussed. Different methods of pretreatment and their impact on the accumulation of butanol in the liquid medium are compared. Butanol accumulation is shown to increase significantly if the synthesis precursors are added as components of enzymatic medium, and the “reverse bard” is used to reduce waste production without affecting the level of butanol synthesis. The problem of conservation of producing strains is given, and protective medium for microorganisms during the freeze-drying is defined.

Mechanical strength model for plastic bonded granular materials at high strain rates and large strains

International Nuclear Information System (INIS)

Browning, R.V.; Scammon, R.J.

1998-01-01

Modeling impact events on systems containing plastic bonded explosive materials requires accurate models for stress evolution at high strain rates out to large strains. For example, in the Steven test geometry reactions occur after strains of 0.5 or more are reached for PBX-9501. The morphology of this class of materials and properties of the constituents are briefly described. We then review the viscoelastic behavior observed at small strains for this class of material, and evaluate large strain models used for granular materials such as cap models. Dilatation under shearing deformations of the PBX is experimentally observed and is one of the key features modeled in cap style plasticity theories, together with bulk plastic flow at high pressures. We propose a model that combines viscoelastic behavior at small strains but adds intergranular stresses at larger strains. A procedure using numerical simulations and comparisons with results from flyer plate tests and low rate uniaxial stress tests is used to develop a rough set of constants for PBX-9501. Comparisons with the high rate flyer plate tests demonstrate that the observed characteristic behavior is captured by this viscoelastic based model. copyright 1998 American Institute of Physics

Refined shear correction factor for very thick simply supported and uniformly loaded isosceles right triangular auxetic plates

International Nuclear Information System (INIS)

Lim, Teik-Cheng

2016-01-01

For moderately thick plates, the use of First order Shear Deformation Theory (FSDT) with a constant shear correction factor of 5/6 is sufficient to take into account the plate deflection arising from transverse shear deformation. For very thick plates, the use of Third order Shear Deformation Theory (TSDT) is preferred as it allows the shear strain distribution to be varied through the plate thickness. Therefore no correction factor is required in TSDT, unlike FSDT. Due to the complexity involved in TSDT, this paper obtains a more accurate shear correction factor for use in FSDT of very thick simply supported and uniformly loaded isosceles right triangular plates based on the TSDT. By matching the maximum deflections for this plate according to FSDT and TSDT, a variable shear correction factor is obtained. Results show that the shear correction factor for the simplified TSDT, i.e. 14/17, is least accurate. The commonly adopted shear correction factor of 5/6 in FSDT is valid only for very thin or highly auxetic plates. This paper provides a variable shear correction for FSDT deflection that matches the plate deflection by TSDT. This variable shear correction factor allows designers to justify the use of a commonly adopted shear correction factor of 5/6 even for very thick plates as long as the Poisson’s ratio of the plate material is sufficiently negative. (paper)

By activating matrix metalloproteinase-7, shear stress promotes chondrosarcoma cell motility, invasion and lung colonization.

Science.gov (United States)

Guan, Pei-Pei; Yu, Xin; Guo, Jian-Jun; Wang, Yue; Wang, Tao; Li, Jia-Yi; Konstantopoulos, Konstantinos; Wang, Zhan-You; Wang, Pu

2015-04-20

Interstitial fluid flow and associated shear stress are relevant mechanical signals in cartilage and bone (patho)physiology. However, their effects on chondrosarcoma cell motility, invasion and metastasis have yet to be delineated. Using human SW1353, HS.819.T and CH2879 chondrosarcoma cell lines as model systems, we found that fluid shear stress induces the accumulation of cyclic AMP (cAMP) and interleukin-1β (IL-1β), which in turn markedly enhance chondrosarcoma cell motility and invasion via the induction of matrix metalloproteinase-7 (MMP-7). Specifically, shear-induced cAMP and IL-1β activate PI3-K, ERK1/2 and p38 signaling pathways, which lead to the synthesis of MMP-7 via transactivating NF-κB and c-Jun in human chondrosarcoma cells. Importantly, MMP-7 upregulation in response to shear stress exposure has the ability to promote lung colonization of chondrosarcomas in vivo. These findings offer a better understanding of the mechanisms underlying MMP-7 activation in shear-stimulated chondrosarcoma cells, and provide insights on designing new therapeutic strategies to interfere with chondrosarcoma invasion and metastasis.

Shear crack propagation in MBC strengthened concrete beams”

DEFF Research Database (Denmark)

Täljsten, Björn; Blanksvärd, Thomas; Carolin, Anders

2008-01-01

thermal compatibility to the base concrete and are often sensitive to the surface nature and surrounding temperature. By using mineral based composites (MBC) some of these challenges can be overcome. MBC refers here to a cementitious bonding agent and a carbon FRP grid. This paper is a part of an ongoing......Repair and upgrading existing concrete structures using FRPs and an epoxy adhesive as the bonding agent has some disadvantages when it comes to compatibility to the base concrete. Epoxies are often restricted by regulations of use, have low permeability which may create freeze/thaw problems, poor...... study of MBC systems. Emphasis is placed on the cracking behavior of the MBC system used for shear strengthening of RC beams. Traditional foil strain gauges and photometric measurements have been used for monitoring of the cracking behavior. In this study it is shown that the use of mineral based shear...

Accumulation of intra-cellular polyphosphate in Chlorella vulgaris cells is related to indole-3-acetic acid produced by Azospirillum brasilense.

Science.gov (United States)

Meza, Beatriz; de-Bashan, Luz E; Hernandez, Juan-Pablo; Bashan, Yoav

2015-06-01

Accumulation of intra-cellular phosphate, as polyphosphate, was measured when the microalga Chlorella vulgaris was immobilized in alginate with either of two wild-type strains of the microalgae growth-promoting bacterium Azospirillum brasilense or their corresponding IAA-attenuated mutants. Wild type strains of A. brasilense induced higher amounts of intra-cellular phosphate in Chlorella than their respective mutants. Calculations comparing intra-cellular phosphate accumulation by culture or net accumulation by the cell and the amount of IAA that was produced by each of these strains revealed that higher IAA was linked to higher accumulations of intra-cellular phosphate. Application of four levels of exogenous IAA reported for A. brasilense and their IAA-attenuated mutants to cultures of C. vulgaris enhanced accumulation of intra-cellular phosphate; the higher the content of IAA per culture or per single cell, the higher was the amount of accumulated phosphate. When an IAA-attenuated mutant was complemented with exogenous IAA, accumulation of intra-cellular phosphate at the culture level was even higher than phosphate accumulation with the respective wild type strains. When calculating the net accumulation of intra-cellular phosphate in the complementation experiment, net intra-cellular phosphate induced by the IAA-attenuated mutant was completely restored and was similar to the wild strains. We propose that IAA produced by A. brasilense is linked to polyphosphate accumulation in C. vulgaris. Copyright © 2015 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.

A new model for fatigue damage accumulation of austenitic stainless steel under variable amplitude loading

International Nuclear Information System (INIS)

Taheri, S.; Vincent, L.; Le-Roux, J.C.

2013-01-01

The application of Miner's rule using a loading issued from a mock-up of a RHR system (removal heat system) of PWR plant, made of 304 steel gives a very important non-conservative fatigue life in strain control when strain fatigue curve is used. This result is due to the absence of sequence effect in Miner's rule. Many non linear damage accumulation models have been proposed to get a sequence effect. Shortcomings of some non linear damage accumulation models are discussed. So Smith-Watson-Topper and Fatemi-Socie criterions with a linear damage accumulation rule are then applied to experimental data. A major issue is the need for an elastic-plastic constitutive law which is difficult to propose in the presence of high cycle secondary hardening observed in austenitic stainless steels. A conservative model for fatigue damage accumulation under variable amplitude loading is then proposed for austenitic stainless steels in strain control, which does not need a constitutive law, but takes into account plasticity through cyclic strain stress curve. The model uses a linear damage accumulation rule. This model is based on the fact that for stainless steels, pre-hardening is detrimental for fatigue life in strain control, while it is beneficial in stress control. In the presence of low mean stress, the model is approved based on a large number of tests. Moreover the model allows to explain the larger detrimental effect of a tension mean stress in strain control tests than in stress control tests. (authors)

The influence of the anisotropic stress state on the intermediate strain properties of granular material

KAUST Repository

Goudarzy, M.

2017-07-20

This paper shows the effect of anisotropic stress state on intermediate strain properties of cylindrical samples containing spherical glass particles. Tests were carried out with the modified resonant column device available at Ruhr-Universität Bochum. Dry samples were subjected to two anisotropic stress states: (a) cell pressure, σ′h, constant and vertical stress, σ′v, increased (stress state GB-I) and (b) σ′v/σ′h equal to 2 (stress state GB-II). The experimental results revealed that the effect of stress state GB-II on the modulus and damping ratio was more significant and obvious than stress state GB-I. The effect of the anisotropic stress state was explained through the impact of confining pressure and anisotropic stress components on the stiffness and damping ratio. The results showed that: (a) G(γ) increased, η(γ) decreased and their strain non-linearity decreased with an increase in the confining pressure component σ′vσ′h; (b) G(γ) decreased, η(γ) increased and their strain non-linearity increased with an increase in the anisotropic stress component, σ′v/σ′h. The analysis of results revealed that reference shear strain was also affected by anisotropic stress state. Therefore, an empirical relationship was developed to predict the reference shear strain, as a function of confining pressure and anisotropic stress components. Additionally, the damping ratio was written as a function of the minimum damping ratio and the reference shear strain.

Fungal accumulation of metals from building materials during brown rot wood decay.

Science.gov (United States)

Hastrup, Anne Christine Steenkjær; Jensen, Bo; Jellison, Jody

2014-08-01

This study analyzes the accumulation and translocation of metal ions in wood during the degradation performed by one strain of each of the three brown rot fungi; Serpula lacrymans, Meruliporia incrassata and Coniophora puteana. These fungi species are inhabitants of the built environment where the prevention and understanding of fungal decay is of high priority. This study focuses on the influence of various building materials in relation to fungal growth and metal uptake. Changes in the concentration of iron, manganese, calcium and copper ions in the decayed wood were analyzed by induced coupled plasma spectroscopy and related to wood weight loss and oxalic acid accumulation. Metal transport into the fungal inoculated wood was found to be dependent on the individual strain/species. The S. lacrymans strain caused a significant increase in total iron whereas the concentration of copper ions in the wood appeared decreased after 10 weeks of decay. Wood inoculated with the M. incrassata isolate showed the contrary tendency with high copper accumulation and low iron increase despite similar weight losses for the two strains. However, significantly lower oxalic acid accumulation was recorded in M. incrassata degraded wood. The addition of a building material resulted in increased weight loss in wood degraded by C. puteana in the soil-block test; however, this could not be directly linked specifically to the accumulation of any of the four metals recorded. The accumulation of oxalic acid seemed to influence the iron uptake. The study assessing the influence of the presence of soil and glass in the soil-block test revealed that soil contributed the majority of the metals for uptake by the fungi and contributed to increased weight loss. The varying uptake observed among the three brown rot fungi strains toward the four metals analyzed may be related to the specific non-enzymatic and enzymatic properties including bio-chelators employed by each of the species during wood

The disconnection mechanism of coupled migration and shear at grain boundaries

International Nuclear Information System (INIS)

Khater, H.A.; Serra, A.; Pond, R.C.; Hirth, J.P.

2012-01-01

The mechanism of coupled migration and shear is studied in a range of [0 0 0 1] tilt boundaries in hexagonal close-packed metal using atomic-scale computer simulation. Symmetrical tilt boundaries spanning the low- and high-angle regimes and comprising regular arrays of grain boundary dislocations are simulated. For each misorientation, θ, the perfect boundary (pristine) is investigated as well as one containing a disconnection. Both types of structures are subjected to incremental applied strains to determine the stress that produces coupled migration and shear. The stress for motion in the pristine case, entailing nucleation, is higher than the Peierls stress for motion when disconnections are present. We conclude that the applied stresses in our simulations exert a Peach–Koehler force on pre-existing disconnections, thereby providing a feasible mechanism with a well-defined driving force that produces coupled migration and shear. This mechanism is feasible for the lower-angle boundaries studied, and facile for the high-angle cases.

Oligomerized backbone pilin helps piliated Lactococcus lactis to withstand shear flow.

Science.gov (United States)

Castelain, Mickaël; Duviau, Marie-Pierre; Oxaran, Virginie; Schmitz, Philippe; Cocaign-Bousquet, Muriel; Loubière, Pascal; Piard, Jean-Christophe; Mercier-Bonin, Muriel

2016-09-01

The present work focuses on the role of pili present at the cell surface of Lactococcus lactis in bacterial adhesion to abiotic (hydrophobic polystyrene) and biotic (mucin-coated polystyrene) surfaces. Native pili-displaying strains and isogenic derivatives in which pilins or sortase C structural genes had been modified were used. Surface physico-chemistry, morphology and shear-flow-induced detachment of lactococcal cells were evaluated. The involvement of pili in L. lactis adhesion was clearly demonstrated, irrespective of the surface characteristics (hydrophobic/hydrophilic, presence or not of specific binding sites). The accessory pilin, PilC, and the backbone pilin, PilB, were revealed to play a major role in adhesion, provided that the PilB was present in its polymerized form. Within the population fraction that remained attached to the surface under increasing shear flow, different association behaviors were observed, showing that pili could serve as anchoring sites thus hampering the effect of shear flow on cell orientation and detachment.

Arsenic accumulation by the aquatic fern Azolla: comparison of arsenate uptake, speciation and efflux by A. caroliniana and A. filiculoides.

Science.gov (United States)

Zhang, Xin; Lin, Ai-Jun; Zhao, Fang-Jie; Xu, Guo-Zhong; Duan, Gui-Lan; Zhu, Yong-Guan

2008-12-01

This study investigates As accumulation and tolerance of the aquatic fern Azolla. Fifty strains of Azolla showed a large variation in As accumulation. The highest- and lowest-accumulating ferns among the 50 strains were chosen for further investigations. Azolla caroliniana accumulated two times more As than Azolla filiculoides owing to a higher influx velocity for arsenate. A. filiculoides was more resistant to external arsenate due to a lower uptake. Both strains showed a similar degree of tolerance to internal As. Arsenate and arsenite were the dominant As species in both Azolla strains, with methylated As species accounting for Azolla in paddy fields to reduce As transfer from soil and water to rice should be further evaluated.

Shear-induced partial translational ordering of a colloidal solid

Science.gov (United States)

Ackerson, B. J.; Clark, N. A.

1984-08-01

Highly charged submicrometer plastic spheres suspended in water at low ionic strength will order spontaneously into bcc crystals or polycrystals. A simple linear shear orients and disorders these crystals by forcing (110) planes to stack normal to the shear gradient and to slide relative to each other with a direction parallel to the solvent flow. In this paper we analyze in detail the disordering and flow processes occurring beyond the intrinsic elastic limit of the bcc crystal. We are led to a model in which the flow of a colloidal crystal is interpreted as a fundamentally different process from that found in atomic crystals. In the colloidal crystal the coupling of particle motion to the background fluid forces a homogeneous flow, where every layer is in motion relative to its neighboring layers. In contrast, the plastic flow in an atomic solid is defect mediated flow. At the lowest applied stress, the local bcc order in the colloidal crystal exhibits shear strains both parallel and perpendicular to the direction of the applied stress. The magnitude of these deformations is estimated using the configurational energy for bcc and distorted bcc crystals, assuming a screened Coulomb pair interaction between colloidal particles. As the applied stress is increased, the intrinsic elastic limit of the crystal is exceeded and the crystal begins to flow with adjacent layers executing an oscillatory path governed by the balance of viscous and screened Coulomb forces. The path takes the structure from the bcc1 and bcc2 twins observed at zero shear to a distorted two-dimensional hcp structure at moderate shear rates, with a loss of interlayer registration as the shear is increased. This theoretical model is consistent with other experimental observations, as well.

Analyzing shear band formation with high resolution X-ray diffraction

Energy Technology Data Exchange (ETDEWEB)

Pagan, Darren C.; Obstalecki, Mark; Park, Jun-Sang; Miller, Matthew P.

2018-04-01

Localization of crystallographic slip into shear bands during uniaxial compression of a copper single crystal is studied using very far-field high-energy diffraction microscopy (vff-HEDM). Diffracted intensity was collected in-situ as the crystal deformed using a unique mobile detector stage that provided access to multiple diffraction peaks with high-angular resolution. From the diffraction data, single crystal orientation pole figures (SCPFs) were generated and are used to track the evolution of the distribution of lattice orientation that develops as slip localizes. To aid the identification of 'signatures' of shear band formation and analyze the SCPF data, a model of slip-driven lattice reorientation within shear bands is introduced. Confidence is built in conclusions drawn from the SCPF data about the character of internal slip localization through comparisons with strain fields on the sample surface measured simultaneously using digital image correlation. From the diffraction data, we find that the active slip direction and slip plane are not directly aligned with the orientation of the shear bands that formed. In fact, by extracting the underlying slip system activity from the SCPF data, we show that intersecting shear bands measured on the surface of the sample arise from slip primarily on the same underlying single slip system. These new vff-HEDM results raise significant questions on the use of surface measurements for slip system activity estimation. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Effect of ratchet strain on fatigue and creep–fatigue strength of Mod.9Cr–1Mo steel

International Nuclear Information System (INIS)

Ando, Masanori; Isobe, Nobuhiro; Kikuchi, Koichi; Enuma, Yasuhiro

2012-01-01

Highlights: ► Uniaxial fatigue and creep–fatigue tests with superimposed strain were performed. ► Variety of superimposed strain were applied as ratchet strain in the tests. ► Effect of superimposed strain on fatigue and creep–fatigue life is negligible. ► A cyclic softening character reducing the effect of superimposed strain. - Abstract: The effect of ratcheting deformation on fatigue and creep–fatigue life in Mod.9Cr–1Mo steel was investigated. Uniaxial fatigue and creep–fatigue testing with superimposed strain were performed to evaluate the effect of ratcheting deformation on the failure cycle. In a series of tests, a specific amount of superimposed strain was accumulated in each cycle. The accumulated strain as ratcheting deformation, cycles to reach the accumulated strain, and test temperatures were varied in the tests. In the fatigue tests with superimposed strain at 550 °C, slight reductions of failure lives were observed. All of the numbers of cycles to failure in the fatigue tests with superimposed strain were within a factor of 1.5 of that of the fatigue test without superimposed strain at 550 °C. The apparent relationship between failure cycles and testing parameters was not observed. In fatigue tests with superimposed strain at 550 °C, maximum mean stress was insignificant and generated in early cycles because Mod.9Cr–1Mo steel exhibits cyclic softening characteristics. It was assumed that suppression of mean stress generation by cyclic softening reduces the effect of ratcheting strain. Conversely, failure lives were increased by accumulated strain in the test conducted at 450 °C because of stress–strain hysteresis loop shrinkage caused by cyclic softening induced by the accumulated strain. In the creep–fatigue tests with superimposed strain, test results indicated that the accumulated stain was negligible. It was concluded that the effect of ratcheting deformation on fatigue and creep–fatigue life is negligible as long

Nucleation and thickening of shear bands in nano-scale twin/matrix lamellae of a Cu-Al alloy processed by dynamic plastic deformation

DEFF Research Database (Denmark)