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D.d.l. Chung - One of the best experts on this subject based on the ideXlab platform.

  • electrical resistance based damage self sensing in carbon fiber reinforced cement
    Carbon, 2007
    Co-Authors: Sihai Wen, D.d.l. Chung
    Abstract:

    Damage self-sensing (to be distinguished from strain self-sensing) by electrical resistance measurement is effective in carbon fiber reinforced cement below the percolation threshold, as shown under uniaxial compression. Major damage that is accompanied by irreversible strain is indicated by irreversible resistivity increase ranging from 10% to 30%. Minor damage in the Elastic Regime is indicated by this increase ranging from 1% to 7%. The irreversible resistivity fractional change per unit irreversible strain is higher in the transverse direction than the longitudinal direction. The origin of the damage self-sensing ability is attributed to the fracture of fibers that bridge microcracks and the consequent resistivity increase. The fracture of a bridging fiber occurs upon microcrack opening or shear.

  • self sensing of flexural strain and damage in carbon fiber polymer matrix composite by electrical resistance measurement
    Carbon, 2006
    Co-Authors: Shoukai Wang, D.d.l. Chung
    Abstract:

    The self-sensing of flexural strain and damage has been demonstrated in carbon fiber polymer-matrix composite by measuring the DC electrical resistance. Upon strain in the Elastic Regime, the compression surface resistance decreases reversibly (due to increase in the current penetration), while the tension surface resistance increases reversibly (due to decrease in the current penetration), and the oblique resistance increases reversibly. Upon minor damage, (i) the oblique resistance after unloading decreases, (ii) the oblique resistance decreases during load increase near the start of loading, and (iii) the curve of the oblique resistance or the resistance of the tension or compression surface vs. deflection becomes nonlinear. Upon major damage, all resistances abruptly and irreversibly increase, such that the onset occurs earlier for the compression surface resistance and the oblique resistance than the tension surface resistance. The surface resistances are superior indicators of strain, whereas the oblique resistance is a superior indicator of damage.

  • defect dynamics of cement paste under repeated compression studied by electrical resistivity measurement
    Cement and Concrete Research, 2001
    Co-Authors: Sihai Wen, D.d.l. Chung
    Abstract:

    Defect dynamics, as studied by electrical resistivity measurement during repeated compression of cement paste in the Elastic Regime, are characterized by defect generation that dominates during the first loading, defect diminution that dominates during subsequent loading, and defect extension that dominates during subsequent unloading.

  • uniaxial compression in carbon fiber reinforced cement sensed by electrical resistivity measurement in longitudinal and transverse directions
    Cement and Concrete Research, 2000
    Co-Authors: Sihai Wen, D.d.l. Chung
    Abstract:

    Uniaxial compression of carbon fiber-reinforced cement pastes in the Elastic Regime caused reversible decreases in both longitudinal and transverse electrical resistivities. In contrast, uniaxial tension had been previously reported to cause reversible increases in both resistivities. The fractional change in resistivity per unit strain is higher in magnitude for carbon fiber silica fume cement paste than carbon fiber latex cement paste.

  • carbon fiber reinforced concrete as an intrinsically smart concrete for damage assessment during dynamic loading
    Journal of the American Ceramic Society, 1995
    Co-Authors: Puwoei Chen, D.d.l. Chung
    Abstract:

    Concrete containing short carbon fibers (0.2–0.5 vol%) wasfound to be an intrinsically smart concrete that can sense Elastic and inElastic deformation, as well as fracture. The signal provided is the change in electrical resistance, which is reversible for Elastic deformation and irreversible for inElastic deformation and fracture. The presence of electrically conducting short fibers is necessary for the concrete to sense Elastic or inElastic deformation, but the sensing of fracture does not require fibers. The fibers serve to bridge the cracks and provide a conduction path. The resistance increase is due to conducting fiber pullout in the Elastic Regime, conducting fiber breakage in the inElastic Regime, and crack propagation at fracture.

Prasanta Sahoo - One of the best experts on this subject based on the ideXlab platform.

  • dynamic analysis of non uniform taper bars in post Elastic Regime under body force loading
    Applied Mathematical Modelling, 2009
    Co-Authors: Debabrata Das, Prasanta Sahoo
    Abstract:

    This paper presents a simulation study of the free flexural vibration behavior of non-uniform taper bars of circular and rectangular cross-section under body force loading due to gravity. The loading is controlled statically to take the bar to its post-Elastic state so as to predict its dynamic behavior in the presence of plastic deformation. Hence the analysis is carried out in two parts; first the static problem under axial gravity loading is solved, then the dynamic problem is solved in this loaded condition. Appropriate variational method is employed to derive the set of governing equations for both the problems. The formulation is based on unknown displacement field which is approximated by finite linear combinations of orthogonal admissible functions. The present method is validated successfully with a well-known finite element package. Results are presented to investigate the effect of shape and size on the dynamic behavior of non-uniform taper bars. The study can be extended to study the post-Elastic dynamic behavior of other related problems such as rotating beams and rotating disks.

  • out of plane free vibration analysis of rotating tapered beams in post Elastic Regime
    Materials & Design, 2009
    Co-Authors: Debabrata Das, Prasanta Sahoo
    Abstract:

    Abstract Free vibration dynamic behaviour of rotating tapered beams in Elastic and post-Elastic Regimes is presented in the paper. The entire analysis is carried out in two parts. First the analysis of the rotating beam under static centrifugal loading is performed and then it is followed by the dynamic analysis using the solution parameters of the static analysis. The governing equations are obtained by the application of suitable variational principles. The displacement fields are assumed using the linear combinations of admissible orthogonal functions which are generated numerically using Gram–Schmidt schemes. Elastic and post-Elastic dynamic behaviour of rotating tapered beams are presented through suitable normalized parameters of the beam geometries and rotational speeds. The results would serve as benchmarks for both Elastic and post-Elastic dynamic problems of rotating tapered beams.

  • dynamic analysis of non uniform taper bars in post Elastic Regime under uniform axial loading
    Materials & Design, 2009
    Co-Authors: Debabrata Das, Prasanta Sahoo, Kashinath Saha
    Abstract:

    Abstract The present paper investigates the dynamic behavior of non-uniform taper bars under uniform axial loading in post-Elastic Regime. A variational principle is used for problem formulation and the system governing equation is solved by Galerkin’s principle. First the static axial loading problem is solved and with the known displacement field the subsequent eigen value problem is solved for dynamic analysis. It is observed that some portion of the bar attains a different tangent modulus value which becomes critical in defining its dynamic response. In post-Elastic part some typical patterns of change in natural frequencies are seen.

Debabrata Das - One of the best experts on this subject based on the ideXlab platform.

  • dynamic analysis of non uniform taper bars in post Elastic Regime under body force loading
    Applied Mathematical Modelling, 2009
    Co-Authors: Debabrata Das, Prasanta Sahoo
    Abstract:

    This paper presents a simulation study of the free flexural vibration behavior of non-uniform taper bars of circular and rectangular cross-section under body force loading due to gravity. The loading is controlled statically to take the bar to its post-Elastic state so as to predict its dynamic behavior in the presence of plastic deformation. Hence the analysis is carried out in two parts; first the static problem under axial gravity loading is solved, then the dynamic problem is solved in this loaded condition. Appropriate variational method is employed to derive the set of governing equations for both the problems. The formulation is based on unknown displacement field which is approximated by finite linear combinations of orthogonal admissible functions. The present method is validated successfully with a well-known finite element package. Results are presented to investigate the effect of shape and size on the dynamic behavior of non-uniform taper bars. The study can be extended to study the post-Elastic dynamic behavior of other related problems such as rotating beams and rotating disks.

  • out of plane free vibration analysis of rotating tapered beams in post Elastic Regime
    Materials & Design, 2009
    Co-Authors: Debabrata Das, Prasanta Sahoo
    Abstract:

    Abstract Free vibration dynamic behaviour of rotating tapered beams in Elastic and post-Elastic Regimes is presented in the paper. The entire analysis is carried out in two parts. First the analysis of the rotating beam under static centrifugal loading is performed and then it is followed by the dynamic analysis using the solution parameters of the static analysis. The governing equations are obtained by the application of suitable variational principles. The displacement fields are assumed using the linear combinations of admissible orthogonal functions which are generated numerically using Gram–Schmidt schemes. Elastic and post-Elastic dynamic behaviour of rotating tapered beams are presented through suitable normalized parameters of the beam geometries and rotational speeds. The results would serve as benchmarks for both Elastic and post-Elastic dynamic problems of rotating tapered beams.

  • dynamic analysis of non uniform taper bars in post Elastic Regime under uniform axial loading
    Materials & Design, 2009
    Co-Authors: Debabrata Das, Prasanta Sahoo, Kashinath Saha
    Abstract:

    Abstract The present paper investigates the dynamic behavior of non-uniform taper bars under uniform axial loading in post-Elastic Regime. A variational principle is used for problem formulation and the system governing equation is solved by Galerkin’s principle. First the static axial loading problem is solved and with the known displacement field the subsequent eigen value problem is solved for dynamic analysis. It is observed that some portion of the bar attains a different tangent modulus value which becomes critical in defining its dynamic response. In post-Elastic part some typical patterns of change in natural frequencies are seen.

J Eckert - One of the best experts on this subject based on the ideXlab platform.

  • molecular dynamic simulation study of the structural anisotropy in cu50zr50 and cu64 5zr35 5 metallic glasses induced by static uniaxial loading within the Elastic Regime
    Journal of Alloys and Compounds, 2011
    Co-Authors: Y. Zhang, Norbert Mattern, J Eckert
    Abstract:

    Abstract The structural anisotropy in both Cu 50 Zr 50 and Cu 64.5 Zr 35.5 metallic glasses induced by various static uniaxial loads within the Elastic Regime was studied by molecular dynamic simulations. Constant tensile and compressive loads from zero up to 200 MPa below the flow stress were applied in the simulation. The degree of anisotropy was characterized using a second order contact fabric tensor. It is found that the degree of anisotropy within the Elastic Regime increases with the applied load following an exponential growth function. The most part of the structural anisotropy can be attributed to the Zr–Cu atomic pairs in Cu 64.5 Zr 35.5 and Zr–Cu, Cu–Cu atomic pairs in Cu 50 Zr 50 . The evolution of the structural anisotropy associated with the Zr–Zr and Cu–Cu pairs exhibits complex behavior, which implies that the deformation mechanism and the dynamics of Cu 50 Zr 50 and Cu 64.5 Zr 35.5 metallic glasses under compressive loads may be quite different from those under tensile loads.

  • effect of uniaxial loading on the structural anisotropy and the dynamics of atoms of cu50zr50 metallic glasses within the Elastic Regime studied by molecular dynamics simulation
    Acta Materialia, 2011
    Co-Authors: Y. Zhang, Norbert Mattern, J Eckert
    Abstract:

    Abstract The changes in the structure and dynamics of atoms and the stress-induced structural anisotropy of a Cu 50 Zr 50 metallic glass upon the application of uniaxial compressive and tensile stresses within the Elastic Regime during the loading and unloading processes have been studied using molecular dynamics simulation. The structural change is found to be more significant under tension than under compression, which is accompanied with the destruction of the full icosahedra clusters into distorted ones. Permanent structural change is found at the applied tensile stress of 1000 MPa but is still within the Elastic Regime. The fabric tensor and bond number analysis reveals that the structural anisotropy increases monotonously with the applied stress, being more pronounced along the loading direction than in the other two free directions. The results of the mean square displacement, the non-Gaussian parameter and the mobile atom analysis suggest that the dynamics of the atoms are distinctly different under uniaxial stresses above 800 MPa. The α- relaxation occurs more easily under tension than under compression as the applied stresses exceed 800 MPa. The permanent change in the structure and structural anisotropy could be correlated with the change in the dynamics of the atoms.

Sihai Wen - One of the best experts on this subject based on the ideXlab platform.