Void Growth

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Marc A. Meyers - One of the best experts on this subject based on the ideXlab platform.

  • response to shear impossibility comments on Void Growth by dislocation emission and Void Growth in metals
    Scripta Materialia, 2010
    Co-Authors: Eduardo M. Bringa, Vlado A. Lubarda, Marc A. Meyers
    Abstract:

    We thank the authors of Ref. [1] for their comments and interest in our work [2–6]. We agree that the emission of shear loops on one single shear plane cannot lead to Void Growth. However, our simulations suggest that coordinated shear on non-parallel planes can lead to Void Growth/shrinkage [3–5]. Detailed descriptions of this process are still being worked out and represent an exciting area for future research. Thus, there seem to be two separate dislocation mechanisms operating either sequentially or simultaneously: shear and prismatic loop emission. Whereas prismatic loops are well known and have been extensively documented, the postulation of “special” shear loops is novel. The authors [1] have correctly pointed out that special restrictions need to be applied to these shear loops, something not mentioned in Refs. [2–6]. On the subject of shear impossibility, the authors [1] bring some good points in their comments of our papers. Indeed, the closed loop emitted from the surface of the Void does not by itself expand the Void. This is obvious from our papers, in which we considered a Growth of a cylindrical Void by emission of an edge dislocation [2], and a collapse of the Void by an emission of an opposite-signed edge dislocation [5]. Thus, if both (positive and negative) dislocations were emitted (which is a 2-D counterpart of a dislocation loop), no net effect on the Void Growth would take place. Void Growth takes place by the outward transfer of the material, which is possible even in an incompressible case due to the outward movement of the remote boundary of the body (the plastically deformed region around the Void is surrounded by an elastically deformed region). Eq. (1) of the Comments on our papers [1] nicely states that the net amount of added material associated with the crea-

  • Response to "Shear Impossibility—Comments on 'Void Growth by Dislocation Emission' and 'Void Growth in Metals'"
    Scripta Materialia, 2010
    Co-Authors: Eduardo M. Bringa, Vlado A. Lubarda, Marc A. Meyers
    Abstract:

    We thank the authors of Ref. [1] for their comments and interest in our work [2–6]. We agree that the emission of shear loops on one single shear plane cannot lead to Void Growth. However, our simulations suggest that coordinated shear on non-parallel planes can lead to Void Growth/shrinkage [3–5]. Detailed descriptions of this process are still being worked out and represent an exciting area for future research. Thus, there seem to be two separate dislocation mechanisms operating either sequentially or simultaneously: shear and prismatic loop emission. Whereas prismatic loops are well known and have been extensively documented, the postulation of “special” shear loops is novel. The authors [1] have correctly pointed out that special restrictions need to be applied to these shear loops, something not mentioned in Refs. [2–6]. On the subject of shear impossibility, the authors [1] bring some good points in their comments of our papers. Indeed, the closed loop emitted from the surface of the Void does not by itself expand the Void. This is obvious from our papers, in which we considered a Growth of a cylindrical Void by emission of an edge dislocation [2], and a collapse of the Void by an emission of an opposite-signed edge dislocation [5]. Thus, if both (positive and negative) dislocations were emitted (which is a 2-D counterpart of a dislocation loop), no net effect on the Void Growth would take place. Void Growth takes place by the outward transfer of the material, which is possible even in an incompressible case due to the outward movement of the remote boundary of the body (the plastically deformed region around the Void is surrounded by an elastically deformed region). Eq. (1) of the Comments on our papers [1] nicely states that the net amount of added material associated with the crea-

  • Void Growth by dislocation emission
    Acta Materialia, 2004
    Co-Authors: Vlado A. Lubarda, M. S. Schneider, Daniel H. Kalantar, Bruce Remington, Marc A. Meyers
    Abstract:

    Laser shock experiments conducted at an energy density of 61 MJ/m 2 revealed Void initiation and Growth at stress application times of approximately 10 ns. It is shown that Void Growth cannot be accomplished by vacancy diffusion under these conditions, even taking into account shock heating. An alternative, dislocation-emission-based mechanism, is proposed for Void Growth. The shear stresses are highest at 45 to the Void surface and decay with increasing distance from the surface. Two mechanisms accounting for the generation of geometrically necessary dislocations required for Void Growth are proposed: prismatic and shear loops. A criterion for the emission of a dislocation from the surface of a Void under remote tension is formulated, analogous to Rice and Thomsons criterion for crack blunting by dislocation emission from the crack tip. The critical stress is calculated for the emission of a single dislocation and a dislocation pair for any size of initial Void. It is shown that the critical stress for dislocation emission decreases with increasing Void size. Dislocations with a wider core are more easily emitted than dislocations with a narrow core.

Eduardo M. Bringa - One of the best experts on this subject based on the ideXlab platform.

  • response to shear impossibility comments on Void Growth by dislocation emission and Void Growth in metals
    Scripta Materialia, 2010
    Co-Authors: Eduardo M. Bringa, Vlado A. Lubarda, Marc A. Meyers
    Abstract:

    We thank the authors of Ref. [1] for their comments and interest in our work [2–6]. We agree that the emission of shear loops on one single shear plane cannot lead to Void Growth. However, our simulations suggest that coordinated shear on non-parallel planes can lead to Void Growth/shrinkage [3–5]. Detailed descriptions of this process are still being worked out and represent an exciting area for future research. Thus, there seem to be two separate dislocation mechanisms operating either sequentially or simultaneously: shear and prismatic loop emission. Whereas prismatic loops are well known and have been extensively documented, the postulation of “special” shear loops is novel. The authors [1] have correctly pointed out that special restrictions need to be applied to these shear loops, something not mentioned in Refs. [2–6]. On the subject of shear impossibility, the authors [1] bring some good points in their comments of our papers. Indeed, the closed loop emitted from the surface of the Void does not by itself expand the Void. This is obvious from our papers, in which we considered a Growth of a cylindrical Void by emission of an edge dislocation [2], and a collapse of the Void by an emission of an opposite-signed edge dislocation [5]. Thus, if both (positive and negative) dislocations were emitted (which is a 2-D counterpart of a dislocation loop), no net effect on the Void Growth would take place. Void Growth takes place by the outward transfer of the material, which is possible even in an incompressible case due to the outward movement of the remote boundary of the body (the plastically deformed region around the Void is surrounded by an elastically deformed region). Eq. (1) of the Comments on our papers [1] nicely states that the net amount of added material associated with the crea-

  • Response to "Shear Impossibility—Comments on 'Void Growth by Dislocation Emission' and 'Void Growth in Metals'"
    Scripta Materialia, 2010
    Co-Authors: Eduardo M. Bringa, Vlado A. Lubarda, Marc A. Meyers
    Abstract:

    We thank the authors of Ref. [1] for their comments and interest in our work [2–6]. We agree that the emission of shear loops on one single shear plane cannot lead to Void Growth. However, our simulations suggest that coordinated shear on non-parallel planes can lead to Void Growth/shrinkage [3–5]. Detailed descriptions of this process are still being worked out and represent an exciting area for future research. Thus, there seem to be two separate dislocation mechanisms operating either sequentially or simultaneously: shear and prismatic loop emission. Whereas prismatic loops are well known and have been extensively documented, the postulation of “special” shear loops is novel. The authors [1] have correctly pointed out that special restrictions need to be applied to these shear loops, something not mentioned in Refs. [2–6]. On the subject of shear impossibility, the authors [1] bring some good points in their comments of our papers. Indeed, the closed loop emitted from the surface of the Void does not by itself expand the Void. This is obvious from our papers, in which we considered a Growth of a cylindrical Void by emission of an edge dislocation [2], and a collapse of the Void by an emission of an opposite-signed edge dislocation [5]. Thus, if both (positive and negative) dislocations were emitted (which is a 2-D counterpart of a dislocation loop), no net effect on the Void Growth would take place. Void Growth takes place by the outward transfer of the material, which is possible even in an incompressible case due to the outward movement of the remote boundary of the body (the plastically deformed region around the Void is surrounded by an elastically deformed region). Eq. (1) of the Comments on our papers [1] nicely states that the net amount of added material associated with the crea-

Vlado A. Lubarda - One of the best experts on this subject based on the ideXlab platform.

  • response to shear impossibility comments on Void Growth by dislocation emission and Void Growth in metals
    Scripta Materialia, 2010
    Co-Authors: Eduardo M. Bringa, Vlado A. Lubarda, Marc A. Meyers
    Abstract:

    We thank the authors of Ref. [1] for their comments and interest in our work [2–6]. We agree that the emission of shear loops on one single shear plane cannot lead to Void Growth. However, our simulations suggest that coordinated shear on non-parallel planes can lead to Void Growth/shrinkage [3–5]. Detailed descriptions of this process are still being worked out and represent an exciting area for future research. Thus, there seem to be two separate dislocation mechanisms operating either sequentially or simultaneously: shear and prismatic loop emission. Whereas prismatic loops are well known and have been extensively documented, the postulation of “special” shear loops is novel. The authors [1] have correctly pointed out that special restrictions need to be applied to these shear loops, something not mentioned in Refs. [2–6]. On the subject of shear impossibility, the authors [1] bring some good points in their comments of our papers. Indeed, the closed loop emitted from the surface of the Void does not by itself expand the Void. This is obvious from our papers, in which we considered a Growth of a cylindrical Void by emission of an edge dislocation [2], and a collapse of the Void by an emission of an opposite-signed edge dislocation [5]. Thus, if both (positive and negative) dislocations were emitted (which is a 2-D counterpart of a dislocation loop), no net effect on the Void Growth would take place. Void Growth takes place by the outward transfer of the material, which is possible even in an incompressible case due to the outward movement of the remote boundary of the body (the plastically deformed region around the Void is surrounded by an elastically deformed region). Eq. (1) of the Comments on our papers [1] nicely states that the net amount of added material associated with the crea-

  • Response to "Shear Impossibility—Comments on 'Void Growth by Dislocation Emission' and 'Void Growth in Metals'"
    Scripta Materialia, 2010
    Co-Authors: Eduardo M. Bringa, Vlado A. Lubarda, Marc A. Meyers
    Abstract:

    We thank the authors of Ref. [1] for their comments and interest in our work [2–6]. We agree that the emission of shear loops on one single shear plane cannot lead to Void Growth. However, our simulations suggest that coordinated shear on non-parallel planes can lead to Void Growth/shrinkage [3–5]. Detailed descriptions of this process are still being worked out and represent an exciting area for future research. Thus, there seem to be two separate dislocation mechanisms operating either sequentially or simultaneously: shear and prismatic loop emission. Whereas prismatic loops are well known and have been extensively documented, the postulation of “special” shear loops is novel. The authors [1] have correctly pointed out that special restrictions need to be applied to these shear loops, something not mentioned in Refs. [2–6]. On the subject of shear impossibility, the authors [1] bring some good points in their comments of our papers. Indeed, the closed loop emitted from the surface of the Void does not by itself expand the Void. This is obvious from our papers, in which we considered a Growth of a cylindrical Void by emission of an edge dislocation [2], and a collapse of the Void by an emission of an opposite-signed edge dislocation [5]. Thus, if both (positive and negative) dislocations were emitted (which is a 2-D counterpart of a dislocation loop), no net effect on the Void Growth would take place. Void Growth takes place by the outward transfer of the material, which is possible even in an incompressible case due to the outward movement of the remote boundary of the body (the plastically deformed region around the Void is surrounded by an elastically deformed region). Eq. (1) of the Comments on our papers [1] nicely states that the net amount of added material associated with the crea-

  • Void Growth by dislocation emission
    Acta Materialia, 2004
    Co-Authors: Vlado A. Lubarda, M. S. Schneider, Daniel H. Kalantar, Bruce Remington, Marc A. Meyers
    Abstract:

    Laser shock experiments conducted at an energy density of 61 MJ/m 2 revealed Void initiation and Growth at stress application times of approximately 10 ns. It is shown that Void Growth cannot be accomplished by vacancy diffusion under these conditions, even taking into account shock heating. An alternative, dislocation-emission-based mechanism, is proposed for Void Growth. The shear stresses are highest at 45 to the Void surface and decay with increasing distance from the surface. Two mechanisms accounting for the generation of geometrically necessary dislocations required for Void Growth are proposed: prismatic and shear loops. A criterion for the emission of a dislocation from the surface of a Void under remote tension is formulated, analogous to Rice and Thomsons criterion for crack blunting by dislocation emission from the crack tip. The critical stress is calculated for the emission of a single dislocation and a dislocation pair for any size of initial Void. It is shown that the critical stress for dislocation emission decreases with increasing Void size. Dislocations with a wider core are more easily emitted than dislocations with a narrow core.

Kyung H. Ahn - One of the best experts on this subject based on the ideXlab platform.

  • Modeling of Void Growth in Partial Frame Process
    Journal of Reinforced Plastics and Composites, 1998
    Co-Authors: Dong-hak Kim, Kyung H. Ahn
    Abstract:

    Modeling of the Void Growth in Partial Frame Process (PFP) was carried out by assuming that the shrinkage due to temperature difference is compensated by the Growth of Void, and the results will be presented in the talk. By comparing the results with the experimental data, basic assumptions will be justified and the mechanism of the Void Growth will be explained in terms of the process parameters. Experimental study has also been carried out based on the design of experiments (DOE) to see the effects of the process parameters on the Void Growth length.

  • Mechanism of Void Growth in the partial frame process
    Polymer Engineering & Science, 1998
    Co-Authors: Kyung H. Ahn, Dong-hak Kim
    Abstract:

    The Partial Frame Process (PFP) is a kind of gas-assisted injection molding, in which the Void core is generated by imposing low pressure air into the molded part just after the resin is completely filled, after which the Void grows as it compensates the volume shrinkage of resin. It resembles a secondary gas penetration step of gas-assisted injection molding, but has more advantages, such as its simplicity, design flexibility, ease of control, and cheap utilities. In this study, modeling of the Void Growth in PFP was carried out. By comparing the results with the experimental data, basic assumptions have been justified and the mechanism of the Void Growth could be explained in terms of the process parameters such as mold temperature, melt temperature, and the channel size. An experimental approach was also taken. As there are many factors affecting the process, the method of design of experiments was adopted, and the effects of the process parameters on the Void Growth length and the mechanism of the Void Growth were investigated. The results are expected to help in mold design and the determination of the operating conditions, as well as our understanding of this new process.

Dong-hak Kim - One of the best experts on this subject based on the ideXlab platform.

  • Modeling of Void Growth in Partial Frame Process
    Journal of Reinforced Plastics and Composites, 1998
    Co-Authors: Dong-hak Kim, Kyung H. Ahn
    Abstract:

    Modeling of the Void Growth in Partial Frame Process (PFP) was carried out by assuming that the shrinkage due to temperature difference is compensated by the Growth of Void, and the results will be presented in the talk. By comparing the results with the experimental data, basic assumptions will be justified and the mechanism of the Void Growth will be explained in terms of the process parameters. Experimental study has also been carried out based on the design of experiments (DOE) to see the effects of the process parameters on the Void Growth length.

  • Mechanism of Void Growth in the partial frame process
    Polymer Engineering & Science, 1998
    Co-Authors: Kyung H. Ahn, Dong-hak Kim
    Abstract:

    The Partial Frame Process (PFP) is a kind of gas-assisted injection molding, in which the Void core is generated by imposing low pressure air into the molded part just after the resin is completely filled, after which the Void grows as it compensates the volume shrinkage of resin. It resembles a secondary gas penetration step of gas-assisted injection molding, but has more advantages, such as its simplicity, design flexibility, ease of control, and cheap utilities. In this study, modeling of the Void Growth in PFP was carried out. By comparing the results with the experimental data, basic assumptions have been justified and the mechanism of the Void Growth could be explained in terms of the process parameters such as mold temperature, melt temperature, and the channel size. An experimental approach was also taken. As there are many factors affecting the process, the method of design of experiments was adopted, and the effects of the process parameters on the Void Growth length and the mechanism of the Void Growth were investigated. The results are expected to help in mold design and the determination of the operating conditions, as well as our understanding of this new process.