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Nina Orlovskaya - One of the best experts on this subject based on the ideXlab platform.

  • measurement of scratch Induced Residual Stress within sic grains in zrb2 sic composite using micro raman spectroscopy
    Acta Materialia, 2008
    Co-Authors: Dipankar Ghosh, Ghatu Subhash, Nina Orlovskaya
    Abstract:

    An analytical framework for determination of scratch-Induced Residual Stress within SiC grains of ZrB2–SiC composite is developed. Using a ‘‘secular equation” that relates strain to Raman-peak shift for zinc-blende structures and the concept of sliding blister field model for scratch-Induced Residual Stress, explicit expressions are derived for Residual Stress calculation in terms of phonon deformation potentials and Raman peak shift. It is determined that, in the as-processed composite, thermal expansion coefficient mismatch between ZrB2 and SiC induces compressive Residual Stress of 1.731 GPa within the SiC grains and a tensile tangential Stress of 1.126 GPa at the ZrB2– SiC interfaces. With increasing scratch loads, the Residual Stress within the SiC grains becomes tensile and increases in magnitude with scratch load. At a scratch load of 250 mN, the calculated Residual Stress in SiC was 2.6 GPa. Despite this high value, no fracture was observed in SiC grains, which has been rationalized based on fracture strength calculations from Griffith theory.

  • Measurement of scratch-Induced Residual Stress within SiC grains in ZrB2–SiC composite using micro-Raman spectroscopy
    Acta Materialia, 2008
    Co-Authors: Dipankar Ghosh, Ghatu Subhash, Nina Orlovskaya
    Abstract:

    An analytical framework for determination of scratch-Induced Residual Stress within SiC grains of ZrB2–SiC composite is developed. Using a ‘‘secular equation” that relates strain to Raman-peak shift for zinc-blende structures and the concept of sliding blister field model for scratch-Induced Residual Stress, explicit expressions are derived for Residual Stress calculation in terms of phonon deformation potentials and Raman peak shift. It is determined that, in the as-processed composite, thermal expansion coefficient mismatch between ZrB2 and SiC induces compressive Residual Stress of 1.731 GPa within the SiC grains and a tensile tangential Stress of 1.126 GPa at the ZrB2– SiC interfaces. With increasing scratch loads, the Residual Stress within the SiC grains becomes tensile and increases in magnitude with scratch load. At a scratch load of 250 mN, the calculated Residual Stress in SiC was 2.6 GPa. Despite this high value, no fracture was observed in SiC grains, which has been rationalized based on fracture strength calculations from Griffith theory.

Dipankar Ghosh - One of the best experts on this subject based on the ideXlab platform.

  • measurement of scratch Induced Residual Stress within sic grains in zrb2 sic composite using micro raman spectroscopy
    Acta Materialia, 2008
    Co-Authors: Dipankar Ghosh, Ghatu Subhash, Nina Orlovskaya
    Abstract:

    An analytical framework for determination of scratch-Induced Residual Stress within SiC grains of ZrB2–SiC composite is developed. Using a ‘‘secular equation” that relates strain to Raman-peak shift for zinc-blende structures and the concept of sliding blister field model for scratch-Induced Residual Stress, explicit expressions are derived for Residual Stress calculation in terms of phonon deformation potentials and Raman peak shift. It is determined that, in the as-processed composite, thermal expansion coefficient mismatch between ZrB2 and SiC induces compressive Residual Stress of 1.731 GPa within the SiC grains and a tensile tangential Stress of 1.126 GPa at the ZrB2– SiC interfaces. With increasing scratch loads, the Residual Stress within the SiC grains becomes tensile and increases in magnitude with scratch load. At a scratch load of 250 mN, the calculated Residual Stress in SiC was 2.6 GPa. Despite this high value, no fracture was observed in SiC grains, which has been rationalized based on fracture strength calculations from Griffith theory.

  • Measurement of scratch-Induced Residual Stress within SiC grains in ZrB2–SiC composite using micro-Raman spectroscopy
    Acta Materialia, 2008
    Co-Authors: Dipankar Ghosh, Ghatu Subhash, Nina Orlovskaya
    Abstract:

    An analytical framework for determination of scratch-Induced Residual Stress within SiC grains of ZrB2–SiC composite is developed. Using a ‘‘secular equation” that relates strain to Raman-peak shift for zinc-blende structures and the concept of sliding blister field model for scratch-Induced Residual Stress, explicit expressions are derived for Residual Stress calculation in terms of phonon deformation potentials and Raman peak shift. It is determined that, in the as-processed composite, thermal expansion coefficient mismatch between ZrB2 and SiC induces compressive Residual Stress of 1.731 GPa within the SiC grains and a tensile tangential Stress of 1.126 GPa at the ZrB2– SiC interfaces. With increasing scratch loads, the Residual Stress within the SiC grains becomes tensile and increases in magnitude with scratch load. At a scratch load of 250 mN, the calculated Residual Stress in SiC was 2.6 GPa. Despite this high value, no fracture was observed in SiC grains, which has been rationalized based on fracture strength calculations from Griffith theory.

Jihui Wang - One of the best experts on this subject based on the ideXlab platform.

  • process Induced Residual Stress of variable stiffness composite laminates during cure
    Composite Structures, 2018
    Co-Authors: Guiming Zhang, Jihui Wang
    Abstract:

    Abstract One of the most important issues for designing variable-stiffness composite structures reflects on determination of the steered fiber paths. In this paper a linear variation of steered fiber curves and the change rule of the fiber angles were presented to create the mathematical model of variable-stiffness composite laminates. Compared to the straight-fiber laminate, the reference path with linearly changed angles leads to higher mechanical strength and more design freedoms. A novel methodology was developed to predict the distributions of process-Induced Residual Stresses during cure. A three-dimensional (3D) thermochemical model of the curing process was established and the mechanical responses during cure were evaluated coupled with the results of thermochemical analyses. The distributions of the temperature and the degree of cure were obtained. The process-Induced Residual Stresses were calculated using ABAQUS. The resin modulus was determined using the cure hardening instantaneous linear elastic (CHILE) model. The cure kinetic process was simulated using Kamal model for AS4/3501-6 prepregs. The results show that the process-Induced Residual Stresses of variable-stiffness composite panels are reduced with increasing the end angle of the present fiber path during cure.

  • a three dimensional thermo viscoelastic analysis of process Induced Residual Stress in composite laminates
    Composite Structures, 2015
    Co-Authors: Anxin Ding, Jihui Wang
    Abstract:

    Abstract A three-dimensional thermo-viscoelastic model to simulate the Residual Stress in composite laminates during curing was proposed using the differential constitutive law. Based on a generalized Maxwell model with n Maxwell elements, a three-dimensional differential thermo-viscoelastic constitutive law was developed and corresponding differential finite element codes were incorporated into commercial software ABAQUS with an UMAT subroutine. In the present thermo-viscoelastic model the changes in thermal expansion, chemical shrinkage and Stress relaxation were taken into account. The differential thermo-viscoelastic model and its finite element analysis were numerically validated in comparison to those presented by White and Kim (1998). Furthermore, the influence of aluminum skins on Residual Stress development for autoclaved composite laminates was evaluated with the present differential thermo-viscoelastic model. The results indicate that the aluminum skins have negligible effects on the cure of composite laminates and significant effects on the Residual Stress development during curing.

Ghatu Subhash - One of the best experts on this subject based on the ideXlab platform.

  • measurement of scratch Induced Residual Stress within sic grains in zrb2 sic composite using micro raman spectroscopy
    Acta Materialia, 2008
    Co-Authors: Dipankar Ghosh, Ghatu Subhash, Nina Orlovskaya
    Abstract:

    An analytical framework for determination of scratch-Induced Residual Stress within SiC grains of ZrB2–SiC composite is developed. Using a ‘‘secular equation” that relates strain to Raman-peak shift for zinc-blende structures and the concept of sliding blister field model for scratch-Induced Residual Stress, explicit expressions are derived for Residual Stress calculation in terms of phonon deformation potentials and Raman peak shift. It is determined that, in the as-processed composite, thermal expansion coefficient mismatch between ZrB2 and SiC induces compressive Residual Stress of 1.731 GPa within the SiC grains and a tensile tangential Stress of 1.126 GPa at the ZrB2– SiC interfaces. With increasing scratch loads, the Residual Stress within the SiC grains becomes tensile and increases in magnitude with scratch load. At a scratch load of 250 mN, the calculated Residual Stress in SiC was 2.6 GPa. Despite this high value, no fracture was observed in SiC grains, which has been rationalized based on fracture strength calculations from Griffith theory.

  • Measurement of scratch-Induced Residual Stress within SiC grains in ZrB2–SiC composite using micro-Raman spectroscopy
    Acta Materialia, 2008
    Co-Authors: Dipankar Ghosh, Ghatu Subhash, Nina Orlovskaya
    Abstract:

    An analytical framework for determination of scratch-Induced Residual Stress within SiC grains of ZrB2–SiC composite is developed. Using a ‘‘secular equation” that relates strain to Raman-peak shift for zinc-blende structures and the concept of sliding blister field model for scratch-Induced Residual Stress, explicit expressions are derived for Residual Stress calculation in terms of phonon deformation potentials and Raman peak shift. It is determined that, in the as-processed composite, thermal expansion coefficient mismatch between ZrB2 and SiC induces compressive Residual Stress of 1.731 GPa within the SiC grains and a tensile tangential Stress of 1.126 GPa at the ZrB2– SiC interfaces. With increasing scratch loads, the Residual Stress within the SiC grains becomes tensile and increases in magnitude with scratch load. At a scratch load of 250 mN, the calculated Residual Stress in SiC was 2.6 GPa. Despite this high value, no fracture was observed in SiC grains, which has been rationalized based on fracture strength calculations from Griffith theory.

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

  • Nonlinear collapse analysis of stiffened plates considering welding-Induced Residual Stress and distortion
    Ships and Offshore Structures, 2015
    Co-Authors: Liam Gannon, Yi Liu, Neil Pegg, Malcolm J. Smith
    Abstract:

    Numerical simulation based on finite element modelling is used to study the influence of Residual Stress and distortion on the behaviour of tee- and angle-stiffened plates under axial compression. Residual Stress and distortion due to welding of the stiffener to the plate are calculated by three-dimensioanl thermo-elasto-plastic finite element analysis. The behaviour of 14 stiffened plates under compressive axial loads is evaluated both with and without welding-Induced Residual Stress and the results are compared with classification society design equations. The results show that the ultimate strength of angle- and tee-stiffened plates may be reduced by as much as 12.5% due to the presence of welding-Induced Residual Stress. Comparison of load-shortening curves generated by finite element analysis with those derived from International Association of Classification Societies (IACS) design equations for both types of stiffener shows that for ultimate strength, the two methods compare well. In the post-ultim...

  • effect of welding Induced Residual Stress and distortion on ship hull girder ultimate strength
    Marine Structures, 2012
    Co-Authors: Liam Gannon, Neil Pegg, Malcolm J. Smith
    Abstract:

    Abstract Nonlinear finite element analysis is used to simulate welding of stiffened plates, giving the three-dimensional distribution of welding-Induced Residual Stress and distortion. Load-shortening curves are generated for the welded stiffened plates under axial compression. These curves are then used as input in a hull girder ultimate strength analysis using Smith's method. Results are compared with those of an ultimate strength analysis using load-shortening curves derived from the IACS Common Structural Rules and with published experimental data. The ultimate strength predicted using IACS curves was significantly higher than the experimental result, whereas that determined using load-shortening curves from finite element analysis agreed well with the measured value.

  • effect of welding Induced Residual Stress and distortion on ship hull girder ultimate strength
    Marine Structures, 2012
    Co-Authors: Liam Gannon, Yi Liu, Neil Pegg, Malcolm J. Smith
    Abstract:

    ► Finite element welding simulation predicts Residual Stress and distortion. ► Reduction in Residual Stress and distortion due to applied loads. ► Strength of a box girder simulating a ship hull girder was predicted accurately. ► The IACS Rules may lead to over-predictions of hull ultimate strength. ► Welding-Induced Residual Stresses decrease hull girder ultimate strength by 3.3%.

  • Effect of three-dimensional welding-Induced Residual Stress and distortion fields on strength and behaviour of flat-bar stiffened panels
    Ships and Offshore Structures, 2012
    Co-Authors: Liam Gannon, Yi Liu, Neil Pegg, Malcolm J. Smith
    Abstract:

    The influence of welding-Induced Residual Stress and distortion on the behaviour of welded, flat-bar stiffened plates under uniaxial compression is examined, using finite-element simulation techniques. Residual Stresses and distortions due to welding are simulated by three-dimensional thermo-elasto-plastic finite-element analysis, and the behaviour of stiffened plates under compressive axial loads is evaluated considering various stiffened plate geometries. Welding-Induced Residual Stress and distortion distributions are examined, and the behaviour of stiffened plates under compressive axial loads with and without welding-Induced Residual Stress is compared with International Association of Classification Societies design formulae. Results of the numerical analyses reveal that welding-Induced Residual Stresses reduce the ultimate strength of flat-bar stiffened plates by as much as 18%. Load shortening curves generated by finite-element analysis are compared with curves derived from design formulae, showin...