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Terence G Langdon - One of the best experts on this subject based on the ideXlab platform.

  • the evolution of damage in Perfect Plastic and strain hardening materials processed by equal channel angular pressing
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2009
    Co-Authors: Roberto B Figueiredo, Paulo Roberto Cetlin, Terence G Langdon
    Abstract:

    The evolution of damage was investigated for an aluminum alloy processed by equal-channel angular pressing. The investigation was performed for two different structural states: an annealed condition where there is strain hardening and a processed condition where the strain hardening capability is essentially exhausted and there is a near Perfect-Plastic behavior. Finite element modeling (FEM) was used with experimental data obtained from tension and compression testing at room temperature. The results show that high levels of damage may be accumulated in the material exhibiting strain hardening behavior and this may lead to billet segmentation whereas in the near Perfect-Plastic condition cracking occurs only on the upper surfaces of the billets and these cracks are reasonably stable.

Aly El Domiaty - One of the best experts on this subject based on the ideXlab platform.

  • bending of tube and section made of strain hardening materials
    Journal of Materials Processing Technology, 2008
    Co-Authors: El A Megharbel, G El A Nasser, Aly El Domiaty
    Abstract:

    Abstract The objective of the present work is to introduce a theoretical analysis of the elastic–Plastic bending of tubes and sections with different shapes. Analytical methods are given in the form of equations to provide a quantitative method for predicting the moment for forming the section of the tube to a specific radius of curvature. The springback and the residual stress distributions are determined. The results of tube bending of the strain hardening material which has a constitutive equation in the form σ = Cɛn were compared with the results obtained by Al-Qureshi [Al-Qureshi, H.A., 1999. Elastic–Plastic analysis of tube bending. Int. J. Mach. Tools Manuf. 39, 87–104] for Perfect Plastic material. The results obtained show that the present analysis is more realistic to represent the material behavior since the applied constitutive equation is in the form of power law equation σ = Cɛn.

Min Hong Seo - One of the best experts on this subject based on the ideXlab platform.

  • effects of strain hardenability and strain rate sensitivity on the Plastic flow and deformation homogeneity during equal channel angular pressing
    Journal of Materials Research, 2001
    Co-Authors: Hyoung Seop Kim, Sun Ig Hong, Min Hong Seo
    Abstract:

    The effects of strain hardenability and strain rate sensitivity on the Plastic flow and deformation inhomogeneity during equal channel angular pressing were studied using a finite element method analysis. In this study, Perfect Plastic nonhardening and rate-insensitive materials, and rate-sensitive materials were considered. In case of the nonhardening and rate-insensitive materials, the deformed geometry was predicted to be quite uniform and homogeneous. Deformation inhomogeneity developed, however, in materials with finite work-hardening exponent and strain-rate sensitivity. The corner gap formed in strain-hardening materials whereas the upper and lower channel gaps formed in strain-rate-sensitive materials. The deformation inhomogeneity was strongly dependent on the relative effects of strain-hardening exponent and strain-rate sensitivity. The predictions on the deformation inhomogeneity and the formation of corner and channel gaps were compatible with the experimental data published in the literature.

Roberto B Figueiredo - One of the best experts on this subject based on the ideXlab platform.

  • the evolution of damage in Perfect Plastic and strain hardening materials processed by equal channel angular pressing
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2009
    Co-Authors: Roberto B Figueiredo, Paulo Roberto Cetlin, Terence G Langdon
    Abstract:

    The evolution of damage was investigated for an aluminum alloy processed by equal-channel angular pressing. The investigation was performed for two different structural states: an annealed condition where there is strain hardening and a processed condition where the strain hardening capability is essentially exhausted and there is a near Perfect-Plastic behavior. Finite element modeling (FEM) was used with experimental data obtained from tension and compression testing at room temperature. The results show that high levels of damage may be accumulated in the material exhibiting strain hardening behavior and this may lead to billet segmentation whereas in the near Perfect-Plastic condition cracking occurs only on the upper surfaces of the billets and these cracks are reasonably stable.

Aaron M. Forster - One of the best experts on this subject based on the ideXlab platform.

  • rheological characterization of next generation ballistic witness materials for body armor testing
    Polymers, 2019
    Co-Authors: Ran Tao, Kirk D. Rice, Anicet S. Djakeu, Randy A. Mrozek, Shawn T. Cole, Reygan M. Freeney, Aaron M. Forster
    Abstract:

    Roma Plastilina No. 1 (RP1), an artist modeling clay that has been used as a ballistic clay, is essential for evaluation and certification in standards-based ballistic resistance testing of body armor. It serves as a ballistic witness material (BWM) behind the armor, where the magnitude of the Plastic deformation in the clay after a ballistic impact is the figure of merit (known as “backface signature”). RP1 is known to exhibit complex thermomechanical behavior that requires temperature conditioning and frequent performance-based evaluations to verify that its deformation response satisfies requirements. A less complex BWM formulation that allows for room-temperature storage and use as well as a more consistent thermomechanical behavior than RP1 is desired, but a validation based only on ballistic performance would be extensive and expensive to accommodate the different ballistic threats. A framework of lab-scale metrologies for measuring the effects of strain, strain rate, and temperature dependence on mechanical properties are needed to guide BWM development. The current work deals with rheological characterization of a candidate BWM, i.e., silicone composite backing material (SCBM), to understand the fundamental structure–property relationships in comparison to those of RP1. Small-amplitude oscillatory shear frequency sweep experiments were performed at temperatures that ranged from 20 °C to 50 °C to map elastic and damping contributions in the linear elastic regime. Large amplitude oscillatory shear (LAOS) experiments were conducted in the non-linear region and the material response was analyzed in the form of Lissajous curve representations with the values of Perfect Plastic dissipation ratio reported to identify the degree of Plasticity. The results show that the SCBM exhibits dynamic properties that are similar in magnitude to those of temperature-conditioned RP1, but with minimal temperature sensitivity and weaker frequency dependence than RP1. Both SCBM and RP1 are identified as elastoviscoPlastic materials, which is particularly important for accurate determination of backface signature in body armor evaluation. The mechanical properties of SCBM show some degree of aging and work history effects. The results from this work demonstrate that the rheological properties of SCBM, at small and large strains, are similar to RP1 with substantial improvements in BWM performance requirements in terms of temperature sensitivity and thixotropy.

  • Rheological Characterization of Next-Generation Ballistic Witness Materials for Body Armor Testing
    MDPI AG, 2019
    Co-Authors: Ran Tao, Kirk D. Rice, Anicet S. Djakeu, Randy A. Mrozek, Shawn T. Cole, Reygan M. Freeney, Aaron M. Forster
    Abstract:

    Roma Plastilina No. 1 (RP1), an artist modeling clay that has been used as a ballistic clay, is essential for evaluation and certification in standards-based ballistic resistance testing of body armor. It serves as a ballistic witness material (BWM) behind the armor, where the magnitude of the Plastic deformation in the clay after a ballistic impact is the figure of merit (known as “backface signature”). RP1 is known to exhibit complex thermomechanical behavior that requires temperature conditioning and frequent performance-based evaluations to verify that its deformation response satisfies requirements. A less complex BWM formulation that allows for room-temperature storage and use as well as a more consistent thermomechanical behavior than RP1 is desired, but a validation based only on ballistic performance would be extensive and expensive to accommodate the different ballistic threats. A framework of lab-scale metrologies for measuring the effects of strain, strain rate, and temperature dependence on mechanical properties are needed to guide BWM development. The current work deals with rheological characterization of a candidate BWM, i.e., silicone composite backing material (SCBM), to understand the fundamental structure–property relationships in comparison to those of RP1. Small-amplitude oscillatory shear frequency sweep experiments were performed at temperatures that ranged from 20 °C to 50 °C to map elastic and damping contributions in the linear elastic regime. Large amplitude oscillatory shear (LAOS) experiments were conducted in the non-linear region and the material response was analyzed in the form of Lissajous curve representations with the values of Perfect Plastic dissipation ratio reported to identify the degree of Plasticity. The results show that the SCBM exhibits dynamic properties that are similar in magnitude to those of temperature-conditioned RP1, but with minimal temperature sensitivity and weaker frequency dependence than RP1. Both SCBM and RP1 are identified as elastoviscoPlastic materials, which is particularly important for accurate determination of backface signature in body armor evaluation. The mechanical properties of SCBM show some degree of aging and work history effects. The results from this work demonstrate that the rheological properties of SCBM, at small and large strains, are similar to RP1 with substantial improvements in BWM performance requirements in terms of temperature sensitivity and thixotropy