The Experts below are selected from a list of 16065 Experts worldwide ranked by ideXlab platform

Shakeel Safdar - One of the best experts on this subject based on the ideXlab platform.

  • the effect of material thickness laser power and cutting speed on cut Path Deviation in high power diode laser chip free cutting of glass
    Optics and Laser Technology, 2010
    Co-Authors: Salman Nisar, Mohammad Sheikh, Shakeel Safdar
    Abstract:

    In the laser cleaving of brittle materials, using controlled fracture technique, thermal stresses are used to induce the crack and the material is separated along the cutting Path by extending the crack. One of the problems in laser cutting of glass with this technique is the cut Path Deviation at the leading and the trailing edges of the glass sheet. Previous work has shown this Deviation to be partly due to the high magnitudes of thermal stresses generated near the edges of the sheet. This paper reports on the experimental results of the effects of glass thickness, laser power and the cutting speed on cut Path Deviation in diode laser cutting of glass. Finite element modelling of the cutting process has also been used to simulate the transient effects of the moving beam and predict thermal fields and stress distributions. These predictions are validated against the experimental data and are used to explain the process mechanisms. It is shown that an increase in the thickness of the glass sheet for the same power and cutting speed or an increase in the cutting speed with constant power and a given sheet thickness results in smaller cut Path Deviations at the leading and trailing edges of the glass sheet.

  • The Effect of Laser Beam Geometry on Cut Path Deviation in Diode Laser Chip-Free Cutting of Glass
    Journal of Manufacturing Science and Engineering, 2010
    Co-Authors: Salman Nisar, Mohammad A. Sheikh, Andrew J. Pinkerton, Lin Li, Shakeel Safdar
    Abstract:

    In laser cleaving of brittle materials using the controlled fracture technique, thermal stresses are used to induce a single crack and the material is separated along the cutting Path by extending the crack. One of the problems in laser cutting of glass with the controlled fracture technique is the cut Deviation at the leading and the trailing edges of the glass sheet. This work is about minimizing this Deviation through an optimization process, which includes laser beam geometry. It has been established that the thermal stresses generated during laser scanning are strongly dependent upon laser beam geometry. Experimental techniques are used to quantify cut Deviation for soda-lime glass sheets under a set of conditions while finite element modeling is used to optimize the process and reduce (or eliminate) cut Deviation. The experimental results of the effect of different laser beam geometries on cut Path Deviation have been presented in this study, along with the finite element modeling of the cutting process to simulate the transient effects of the moving beam and predict thermal fields and stress distribution. These predictions are compared with the experimental data. In comparison to other beam geometries, the triangular-forward beam at the leading edge and triangular-reverse and circular beam geometry at the trailing edge produces lower tensile stresses (sigma(xx)) and hence minimizes the cut Path Deviation. The work also shows that beam divergence inside the glass plays a significant role in changing the cut Path Deviation at the bottom leading and trailing edges of the glass.

  • effect of thermal stresses on chip free diode laser cutting of glass
    Optics and Laser Technology, 2009
    Co-Authors: Salman Nisar, Lin Li, Mohammad Sheikh, Shakeel Safdar
    Abstract:

    Abstract In laser cleaving of brittle materials using controlled fracture technique, thermal stresses are used to induce a crack and the material is separated along the cutting Path by extending this crack. In this study, a glass sheet is stressed thermally using a 808–940 nm diode laser radiation. One of the problems in laser cutting of glass with controlled fracture technique is the cut Deviation at the leading and the trailing edges of the glass sheet. In order to avoid this damage it is necessary to understand the stress distributions which control crack propagation. A study is conducted here to analyse the cut Deviation problem of glass by examining the stress fields during diode laser cutting of soda-lime glass sheets. Optical microscope photographs of the breaking surface are obtained to examine the surface quality and cut Path Deviation while the latter is explained from the results of the stress fields which are obtained from a finite element simulation.

Salman Nisar - One of the best experts on this subject based on the ideXlab platform.

  • the effect of material thickness laser power and cutting speed on cut Path Deviation in high power diode laser chip free cutting of glass
    Optics and Laser Technology, 2010
    Co-Authors: Salman Nisar, Mohammad Sheikh, Shakeel Safdar
    Abstract:

    In the laser cleaving of brittle materials, using controlled fracture technique, thermal stresses are used to induce the crack and the material is separated along the cutting Path by extending the crack. One of the problems in laser cutting of glass with this technique is the cut Path Deviation at the leading and the trailing edges of the glass sheet. Previous work has shown this Deviation to be partly due to the high magnitudes of thermal stresses generated near the edges of the sheet. This paper reports on the experimental results of the effects of glass thickness, laser power and the cutting speed on cut Path Deviation in diode laser cutting of glass. Finite element modelling of the cutting process has also been used to simulate the transient effects of the moving beam and predict thermal fields and stress distributions. These predictions are validated against the experimental data and are used to explain the process mechanisms. It is shown that an increase in the thickness of the glass sheet for the same power and cutting speed or an increase in the cutting speed with constant power and a given sheet thickness results in smaller cut Path Deviations at the leading and trailing edges of the glass sheet.

  • The Effect of Laser Beam Geometry on Cut Path Deviation in Diode Laser Chip-Free Cutting of Glass
    Journal of Manufacturing Science and Engineering, 2010
    Co-Authors: Salman Nisar, Mohammad A. Sheikh, Andrew J. Pinkerton, Lin Li, Shakeel Safdar
    Abstract:

    In laser cleaving of brittle materials using the controlled fracture technique, thermal stresses are used to induce a single crack and the material is separated along the cutting Path by extending the crack. One of the problems in laser cutting of glass with the controlled fracture technique is the cut Deviation at the leading and the trailing edges of the glass sheet. This work is about minimizing this Deviation through an optimization process, which includes laser beam geometry. It has been established that the thermal stresses generated during laser scanning are strongly dependent upon laser beam geometry. Experimental techniques are used to quantify cut Deviation for soda-lime glass sheets under a set of conditions while finite element modeling is used to optimize the process and reduce (or eliminate) cut Deviation. The experimental results of the effect of different laser beam geometries on cut Path Deviation have been presented in this study, along with the finite element modeling of the cutting process to simulate the transient effects of the moving beam and predict thermal fields and stress distribution. These predictions are compared with the experimental data. In comparison to other beam geometries, the triangular-forward beam at the leading edge and triangular-reverse and circular beam geometry at the trailing edge produces lower tensile stresses (sigma(xx)) and hence minimizes the cut Path Deviation. The work also shows that beam divergence inside the glass plays a significant role in changing the cut Path Deviation at the bottom leading and trailing edges of the glass.

  • The effect of continuous and pulsed beam modes on cut Path Deviation in diode laser cutting of glass
    International Journal of Advanced Manufacturing Technology, 2010
    Co-Authors: Salman Nisar, Mohammad A. Sheikh, Lin Li, Andrew J. Pinkerton
    Abstract:

    During laser cleaving of brittle materials, with the controlled fracture technique, thermal stresses are generated which induce the crack and extend it along the cutting Path subsequently causing material separation. One of the problems in laser cutting of glass with this technique is the cut Path Deviation at the leading and the trailing edges of the glass sheet. Previous work with a continuous beam diode laser has shown the Deviation to be partly due the high magnitudes of thermal stresses generated near the edges of the sheet. This paper reports on the effects of using a pulsed diode laser to cut soda lime glass. The effect of pulse parameters and cutting speed on the quality output variables such as cut Deviation angle and surface finish are studied. Finite element modelling is also used to simulate the effects of the moving beam on stress generations to facilitate the understanding of the process mechanisms and the results are compared with the experimental data. This work shows how to minimise the cut Path Deviation at the edges by reducing thermal stresses using optimum pulsed diode laser parameters and providing additional flexibility to the process.

  • effect of thermal stresses on chip free diode laser cutting of glass
    Optics and Laser Technology, 2009
    Co-Authors: Salman Nisar, Lin Li, Mohammad Sheikh, Shakeel Safdar
    Abstract:

    Abstract In laser cleaving of brittle materials using controlled fracture technique, thermal stresses are used to induce a crack and the material is separated along the cutting Path by extending this crack. In this study, a glass sheet is stressed thermally using a 808–940 nm diode laser radiation. One of the problems in laser cutting of glass with controlled fracture technique is the cut Deviation at the leading and the trailing edges of the glass sheet. In order to avoid this damage it is necessary to understand the stress distributions which control crack propagation. A study is conducted here to analyse the cut Deviation problem of glass by examining the stress fields during diode laser cutting of soda-lime glass sheets. Optical microscope photographs of the breaking surface are obtained to examine the surface quality and cut Path Deviation while the latter is explained from the results of the stress fields which are obtained from a finite element simulation.

Lin Li - One of the best experts on this subject based on the ideXlab platform.

  • The Effect of Laser Beam Geometry on Cut Path Deviation in Diode Laser Chip-Free Cutting of Glass
    Journal of Manufacturing Science and Engineering, 2010
    Co-Authors: Salman Nisar, Mohammad A. Sheikh, Andrew J. Pinkerton, Lin Li, Shakeel Safdar
    Abstract:

    In laser cleaving of brittle materials using the controlled fracture technique, thermal stresses are used to induce a single crack and the material is separated along the cutting Path by extending the crack. One of the problems in laser cutting of glass with the controlled fracture technique is the cut Deviation at the leading and the trailing edges of the glass sheet. This work is about minimizing this Deviation through an optimization process, which includes laser beam geometry. It has been established that the thermal stresses generated during laser scanning are strongly dependent upon laser beam geometry. Experimental techniques are used to quantify cut Deviation for soda-lime glass sheets under a set of conditions while finite element modeling is used to optimize the process and reduce (or eliminate) cut Deviation. The experimental results of the effect of different laser beam geometries on cut Path Deviation have been presented in this study, along with the finite element modeling of the cutting process to simulate the transient effects of the moving beam and predict thermal fields and stress distribution. These predictions are compared with the experimental data. In comparison to other beam geometries, the triangular-forward beam at the leading edge and triangular-reverse and circular beam geometry at the trailing edge produces lower tensile stresses (sigma(xx)) and hence minimizes the cut Path Deviation. The work also shows that beam divergence inside the glass plays a significant role in changing the cut Path Deviation at the bottom leading and trailing edges of the glass.

  • The effect of continuous and pulsed beam modes on cut Path Deviation in diode laser cutting of glass
    International Journal of Advanced Manufacturing Technology, 2010
    Co-Authors: Salman Nisar, Mohammad A. Sheikh, Lin Li, Andrew J. Pinkerton
    Abstract:

    During laser cleaving of brittle materials, with the controlled fracture technique, thermal stresses are generated which induce the crack and extend it along the cutting Path subsequently causing material separation. One of the problems in laser cutting of glass with this technique is the cut Path Deviation at the leading and the trailing edges of the glass sheet. Previous work with a continuous beam diode laser has shown the Deviation to be partly due the high magnitudes of thermal stresses generated near the edges of the sheet. This paper reports on the effects of using a pulsed diode laser to cut soda lime glass. The effect of pulse parameters and cutting speed on the quality output variables such as cut Deviation angle and surface finish are studied. Finite element modelling is also used to simulate the effects of the moving beam on stress generations to facilitate the understanding of the process mechanisms and the results are compared with the experimental data. This work shows how to minimise the cut Path Deviation at the edges by reducing thermal stresses using optimum pulsed diode laser parameters and providing additional flexibility to the process.

  • effect of thermal stresses on chip free diode laser cutting of glass
    Optics and Laser Technology, 2009
    Co-Authors: Salman Nisar, Lin Li, Mohammad Sheikh, Shakeel Safdar
    Abstract:

    Abstract In laser cleaving of brittle materials using controlled fracture technique, thermal stresses are used to induce a crack and the material is separated along the cutting Path by extending this crack. In this study, a glass sheet is stressed thermally using a 808–940 nm diode laser radiation. One of the problems in laser cutting of glass with controlled fracture technique is the cut Deviation at the leading and the trailing edges of the glass sheet. In order to avoid this damage it is necessary to understand the stress distributions which control crack propagation. A study is conducted here to analyse the cut Deviation problem of glass by examining the stress fields during diode laser cutting of soda-lime glass sheets. Optical microscope photographs of the breaking surface are obtained to examine the surface quality and cut Path Deviation while the latter is explained from the results of the stress fields which are obtained from a finite element simulation.

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

  • The Effect of Laser Beam Geometry on Cut Path Deviation in Diode Laser Chip-Free Cutting of Glass
    Journal of Manufacturing Science and Engineering, 2010
    Co-Authors: Salman Nisar, Mohammad A. Sheikh, Andrew J. Pinkerton, Lin Li, Shakeel Safdar
    Abstract:

    In laser cleaving of brittle materials using the controlled fracture technique, thermal stresses are used to induce a single crack and the material is separated along the cutting Path by extending the crack. One of the problems in laser cutting of glass with the controlled fracture technique is the cut Deviation at the leading and the trailing edges of the glass sheet. This work is about minimizing this Deviation through an optimization process, which includes laser beam geometry. It has been established that the thermal stresses generated during laser scanning are strongly dependent upon laser beam geometry. Experimental techniques are used to quantify cut Deviation for soda-lime glass sheets under a set of conditions while finite element modeling is used to optimize the process and reduce (or eliminate) cut Deviation. The experimental results of the effect of different laser beam geometries on cut Path Deviation have been presented in this study, along with the finite element modeling of the cutting process to simulate the transient effects of the moving beam and predict thermal fields and stress distribution. These predictions are compared with the experimental data. In comparison to other beam geometries, the triangular-forward beam at the leading edge and triangular-reverse and circular beam geometry at the trailing edge produces lower tensile stresses (sigma(xx)) and hence minimizes the cut Path Deviation. The work also shows that beam divergence inside the glass plays a significant role in changing the cut Path Deviation at the bottom leading and trailing edges of the glass.

  • The effect of continuous and pulsed beam modes on cut Path Deviation in diode laser cutting of glass
    International Journal of Advanced Manufacturing Technology, 2010
    Co-Authors: Salman Nisar, Mohammad A. Sheikh, Lin Li, Andrew J. Pinkerton
    Abstract:

    During laser cleaving of brittle materials, with the controlled fracture technique, thermal stresses are generated which induce the crack and extend it along the cutting Path subsequently causing material separation. One of the problems in laser cutting of glass with this technique is the cut Path Deviation at the leading and the trailing edges of the glass sheet. Previous work with a continuous beam diode laser has shown the Deviation to be partly due the high magnitudes of thermal stresses generated near the edges of the sheet. This paper reports on the effects of using a pulsed diode laser to cut soda lime glass. The effect of pulse parameters and cutting speed on the quality output variables such as cut Deviation angle and surface finish are studied. Finite element modelling is also used to simulate the effects of the moving beam on stress generations to facilitate the understanding of the process mechanisms and the results are compared with the experimental data. This work shows how to minimise the cut Path Deviation at the edges by reducing thermal stresses using optimum pulsed diode laser parameters and providing additional flexibility to the process.

Daniel Nelias - One of the best experts on this subject based on the ideXlab platform.

  • velocity correlated crack front and surface marks in single crystalline silicon
    Nature Communications, 2018
    Co-Authors: Lv Zhao, Didier Bardel, Anne Maynadier, Daniel Nelias
    Abstract:

    Single crystalline silicon fractures on low-energy cleavage planes such as (111) and (110). The crack propagation cannot accurately be predicted by linear elastic fracture mechanics since it does not account for small scale and inelastic phenomena such as atomic lattice trapping. Here we show that, under pure bending load, (110) cleavage in silicon single crystal rapidly accelerates to 3700 m/s without crack Path Deviation or crack branching, contrasting previous observations. We highlight that the crack front shape involves strong velocity dependence and presents a curvature jump during very high-speed crack growth. In addition, we observe special marks—a kind of periodic surface undulation—that exclusively arise on the rapid fracture surfaces, and we suggest that they are front wave traces resulting from an intrinsic local velocity fluctuation. This finding gives insight to the wavy nature of the crack front in the absence of material asperity.