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

  • effects of nanofeatures induced by severe shot peening ssp on mechanical corrosion and cytocompatibility properties of magnesium alloy az31
    Acta Biomaterialia, 2018
    Co-Authors: Sara Bagherifard, I Fernandezpariente, Thomas J Webster, Daniel J Hickey, Stanislava Fintova, Filip Pastorek, Michele Bandini, M Guagliano
    Abstract:

    Abstract The application of biodegradable magnesium-based materials in the biomedical field is highly restricted by their low fatigue strength and high corrosion rate in biological environments. Herein, we treated the Surface of a biocompatible magnesium alloy AZ31 by severe shot peening in order to evaluate the potential of Surface Grain refinement to enhance this alloy’s functionality in a biological environment. The AZ31 samples were studied in terms of micro/nanostructural, mechanical, and chemical characteristics in addition to cytocompatibility properties. The evolution of Surface Grain structure and Surface morphology were investigated using optical, scanning and transmission electron microscopy. Surface roughness, wettability, and chemical composition, as well as in depth-microhardness and residual stress distribution, fatigue behaviour and corrosion resistance were investigated. Cytocompatibility tests with osteoblasts (bone forming cells) were performed using sample extracts. The results revealed for the first time that severe shot peening can significantly enhance mechanical properties of AZ31 without causing adverse effects on the growth of surrounding osteoblasts. The corrosion behavior, on the other hand, was not improved; nevertheless, removing the rough Surface layer with a high density of crystallographic lattice defects, without removing the entire nanocrystallized layer, provided a good potential for improving corrosion characteristics after severe shot peening and thus, this method should be studied for a wide range of orthopedic applications in which biodegradable magnesium is used. Statement of Significance A major challenge for most commonly used metals for bio-implants is their non-biodegradability that necessitates revision surgery for implant retrieval when used as fixation plates, screws, etc. Magnesium is reported among the most biocompatible metals that resorb over time without adverse tissue reactions and is indispensable for many biochemical processes in human body. However, fast and uncontrolled degradation of magnesium alloys in the physiological environment in addition to their inadequate mechanical properties especially under repeated loading have limited their application in the biomedical field. The present study provides data on the effect of a relatively simple Surface nanocrystallziation method with high potential to tailor the mechanical and chemical behavior of magnesium based material while maintaining its cytocompatibility.

  • nanoscale Surface modification of aisi 316l stainless steel by severe shot peening
    Materials & Design, 2016
    Co-Authors: Sara Bagherifard, Sebastian Slawik, I Fernandezpariente, Christoph Pauly, Frank Mucklich, M Guagliano
    Abstract:

    Abstract Surface nanocrystallization is gaining increased attention due to its high potential of enhancing mechanical functionality and modulating material's interaction with the surrounding environment. Among mechanical approaches, severe shot peening has recently shown to be a very promising technique for Surface Grain refinement, considering its efficiency, eco-friendliness, relative low cost and minimum geometrical restrictions. This study evaluates the effect of severe shot peening on microstructural and mechanical properties of 316L stainless steel, which is widely used in biomedical, food preparation, structural and marine applications. 316 L samples, shot peened with different peening parameters, were studied in terms of morphological and structural features, defect density, Grain size, phase transformation, Surface topography, Surface wettability, residual stresses and microhardness. The results indicated that severe shot peening induced near Surface Grain refinement to nano and sub-micron range and transformed the austenite phase into strain-induced α’- martensite in a layered deformation band structure. Severe shot peening also induced compressive residual stresses and work hardening in the top Surface layer. Surface roughness and Surface wettability, both of which favorably contribute to modulating the interaction of material with biological environment, were also notably enhanced by severe shot peening.

  • mesh sensitivity assessment of shot peening finite element simulation aimed at Surface Grain refinement
    Surface & Coatings Technology, 2014
    Co-Authors: Sara Bagherifard, R Ghelichi, M Guagliano
    Abstract:

    Abstract Shot peening process is widely used as a Surface treatment for metallic components to generate Surface compressive residual stresses, work harden the Surface layer of material and consequently improve the component's fatigue behavior. Numerical simulation is much helpful to limit the costly and time consuming experiments. Thus several approaches have been suggested for numerical simulation of shot peening in the recent years. However no comprehensive assessment has been yet done to perform parametric study of the process and its favorable effects. This study has focused on numerical simulation of severe shot peening, generally aimed at creating a fine Grained layer of material on Surface of the treated part. Mesh size effects have been particularly studied and analyzed, not only on residual stress computation, which has been always dealt with, but also by considering the accumulated equivalent plastic strain (PEEQ). PEEQ is recognized as a key parameter in the development of Grain refinement process. In the end, a practical method is suggested to estimate the value of PEEQ independent from element size to be employed for assessing the generation of refined Grains.

Sara Bagherifard - One of the best experts on this subject based on the ideXlab platform.

  • effects of nanofeatures induced by severe shot peening ssp on mechanical corrosion and cytocompatibility properties of magnesium alloy az31
    Acta Biomaterialia, 2018
    Co-Authors: Sara Bagherifard, I Fernandezpariente, Thomas J Webster, Daniel J Hickey, Stanislava Fintova, Filip Pastorek, Michele Bandini, M Guagliano
    Abstract:

    Abstract The application of biodegradable magnesium-based materials in the biomedical field is highly restricted by their low fatigue strength and high corrosion rate in biological environments. Herein, we treated the Surface of a biocompatible magnesium alloy AZ31 by severe shot peening in order to evaluate the potential of Surface Grain refinement to enhance this alloy’s functionality in a biological environment. The AZ31 samples were studied in terms of micro/nanostructural, mechanical, and chemical characteristics in addition to cytocompatibility properties. The evolution of Surface Grain structure and Surface morphology were investigated using optical, scanning and transmission electron microscopy. Surface roughness, wettability, and chemical composition, as well as in depth-microhardness and residual stress distribution, fatigue behaviour and corrosion resistance were investigated. Cytocompatibility tests with osteoblasts (bone forming cells) were performed using sample extracts. The results revealed for the first time that severe shot peening can significantly enhance mechanical properties of AZ31 without causing adverse effects on the growth of surrounding osteoblasts. The corrosion behavior, on the other hand, was not improved; nevertheless, removing the rough Surface layer with a high density of crystallographic lattice defects, without removing the entire nanocrystallized layer, provided a good potential for improving corrosion characteristics after severe shot peening and thus, this method should be studied for a wide range of orthopedic applications in which biodegradable magnesium is used. Statement of Significance A major challenge for most commonly used metals for bio-implants is their non-biodegradability that necessitates revision surgery for implant retrieval when used as fixation plates, screws, etc. Magnesium is reported among the most biocompatible metals that resorb over time without adverse tissue reactions and is indispensable for many biochemical processes in human body. However, fast and uncontrolled degradation of magnesium alloys in the physiological environment in addition to their inadequate mechanical properties especially under repeated loading have limited their application in the biomedical field. The present study provides data on the effect of a relatively simple Surface nanocrystallziation method with high potential to tailor the mechanical and chemical behavior of magnesium based material while maintaining its cytocompatibility.

  • nanoscale Surface modification of aisi 316l stainless steel by severe shot peening
    Materials & Design, 2016
    Co-Authors: Sara Bagherifard, Sebastian Slawik, I Fernandezpariente, Christoph Pauly, Frank Mucklich, M Guagliano
    Abstract:

    Abstract Surface nanocrystallization is gaining increased attention due to its high potential of enhancing mechanical functionality and modulating material's interaction with the surrounding environment. Among mechanical approaches, severe shot peening has recently shown to be a very promising technique for Surface Grain refinement, considering its efficiency, eco-friendliness, relative low cost and minimum geometrical restrictions. This study evaluates the effect of severe shot peening on microstructural and mechanical properties of 316L stainless steel, which is widely used in biomedical, food preparation, structural and marine applications. 316 L samples, shot peened with different peening parameters, were studied in terms of morphological and structural features, defect density, Grain size, phase transformation, Surface topography, Surface wettability, residual stresses and microhardness. The results indicated that severe shot peening induced near Surface Grain refinement to nano and sub-micron range and transformed the austenite phase into strain-induced α’- martensite in a layered deformation band structure. Severe shot peening also induced compressive residual stresses and work hardening in the top Surface layer. Surface roughness and Surface wettability, both of which favorably contribute to modulating the interaction of material with biological environment, were also notably enhanced by severe shot peening.

  • mesh sensitivity assessment of shot peening finite element simulation aimed at Surface Grain refinement
    Surface & Coatings Technology, 2014
    Co-Authors: Sara Bagherifard, R Ghelichi, M Guagliano
    Abstract:

    Abstract Shot peening process is widely used as a Surface treatment for metallic components to generate Surface compressive residual stresses, work harden the Surface layer of material and consequently improve the component's fatigue behavior. Numerical simulation is much helpful to limit the costly and time consuming experiments. Thus several approaches have been suggested for numerical simulation of shot peening in the recent years. However no comprehensive assessment has been yet done to perform parametric study of the process and its favorable effects. This study has focused on numerical simulation of severe shot peening, generally aimed at creating a fine Grained layer of material on Surface of the treated part. Mesh size effects have been particularly studied and analyzed, not only on residual stress computation, which has been always dealt with, but also by considering the accumulated equivalent plastic strain (PEEQ). PEEQ is recognized as a key parameter in the development of Grain refinement process. In the end, a practical method is suggested to estimate the value of PEEQ independent from element size to be employed for assessing the generation of refined Grains.

I Fernandezpariente - One of the best experts on this subject based on the ideXlab platform.

  • effects of nanofeatures induced by severe shot peening ssp on mechanical corrosion and cytocompatibility properties of magnesium alloy az31
    Acta Biomaterialia, 2018
    Co-Authors: Sara Bagherifard, I Fernandezpariente, Thomas J Webster, Daniel J Hickey, Stanislava Fintova, Filip Pastorek, Michele Bandini, M Guagliano
    Abstract:

    Abstract The application of biodegradable magnesium-based materials in the biomedical field is highly restricted by their low fatigue strength and high corrosion rate in biological environments. Herein, we treated the Surface of a biocompatible magnesium alloy AZ31 by severe shot peening in order to evaluate the potential of Surface Grain refinement to enhance this alloy’s functionality in a biological environment. The AZ31 samples were studied in terms of micro/nanostructural, mechanical, and chemical characteristics in addition to cytocompatibility properties. The evolution of Surface Grain structure and Surface morphology were investigated using optical, scanning and transmission electron microscopy. Surface roughness, wettability, and chemical composition, as well as in depth-microhardness and residual stress distribution, fatigue behaviour and corrosion resistance were investigated. Cytocompatibility tests with osteoblasts (bone forming cells) were performed using sample extracts. The results revealed for the first time that severe shot peening can significantly enhance mechanical properties of AZ31 without causing adverse effects on the growth of surrounding osteoblasts. The corrosion behavior, on the other hand, was not improved; nevertheless, removing the rough Surface layer with a high density of crystallographic lattice defects, without removing the entire nanocrystallized layer, provided a good potential for improving corrosion characteristics after severe shot peening and thus, this method should be studied for a wide range of orthopedic applications in which biodegradable magnesium is used. Statement of Significance A major challenge for most commonly used metals for bio-implants is their non-biodegradability that necessitates revision surgery for implant retrieval when used as fixation plates, screws, etc. Magnesium is reported among the most biocompatible metals that resorb over time without adverse tissue reactions and is indispensable for many biochemical processes in human body. However, fast and uncontrolled degradation of magnesium alloys in the physiological environment in addition to their inadequate mechanical properties especially under repeated loading have limited their application in the biomedical field. The present study provides data on the effect of a relatively simple Surface nanocrystallziation method with high potential to tailor the mechanical and chemical behavior of magnesium based material while maintaining its cytocompatibility.

  • nanoscale Surface modification of aisi 316l stainless steel by severe shot peening
    Materials & Design, 2016
    Co-Authors: Sara Bagherifard, Sebastian Slawik, I Fernandezpariente, Christoph Pauly, Frank Mucklich, M Guagliano
    Abstract:

    Abstract Surface nanocrystallization is gaining increased attention due to its high potential of enhancing mechanical functionality and modulating material's interaction with the surrounding environment. Among mechanical approaches, severe shot peening has recently shown to be a very promising technique for Surface Grain refinement, considering its efficiency, eco-friendliness, relative low cost and minimum geometrical restrictions. This study evaluates the effect of severe shot peening on microstructural and mechanical properties of 316L stainless steel, which is widely used in biomedical, food preparation, structural and marine applications. 316 L samples, shot peened with different peening parameters, were studied in terms of morphological and structural features, defect density, Grain size, phase transformation, Surface topography, Surface wettability, residual stresses and microhardness. The results indicated that severe shot peening induced near Surface Grain refinement to nano and sub-micron range and transformed the austenite phase into strain-induced α’- martensite in a layered deformation band structure. Severe shot peening also induced compressive residual stresses and work hardening in the top Surface layer. Surface roughness and Surface wettability, both of which favorably contribute to modulating the interaction of material with biological environment, were also notably enhanced by severe shot peening.

Edwin L Thomas - One of the best experts on this subject based on the ideXlab platform.

  • lamellar diblock copolymer Grain boundary morphology 3 helicoid section twist boundary energy
    Macromolecules, 1997
    Co-Authors: Samuel P Gido, Edwin L Thomas
    Abstract:

    The helicoid section morphology allows a diblock copolymer lamellar phase to maintain microphase separation across a twist Grain boundary. The interface between the two microphases in the Grain boundary region approximates a stack of sections of the helicoid minimal Surface. Grain boundary energies were calculated for the helicoid section morphology both as a function of diblock chain characteristics and as a function of Grain boundary twist angle. The basic approach to Grain boundary energy calculation is to formulate a general expression for local free energy density as a function both of chain characteristics and of the local curvature of the interface. The local energy density is then integrated over the mathematical model for the Scherk Grain boundary. Two general methods of calculation were used, and the results where then compared. First, a self-consistent field model was formulated in which average energies per chain were calculated for all the possible interfacial curvature environments encounter...

  • lamellar diblock copolymer Grain boundary morphology 1 twist boundary characterization
    Macromolecules, 1993
    Co-Authors: Samuel P Gido, Edwin L Thomas, Janelle Gunther, David Hoffman
    Abstract:

    Grain boundary morphologies in poly(styrene-b-butadiene) lamellar diblock copolymers were characterized using transmission electron microscopy (TEM). Two types of twist Grain boundaries were observed in which microphase separation of the two blocks was maintained in the Grain boundary region by intermaterial dividing Surfaces that approximate classically known minimal Surfaces. The geometry of these interfaces was demonstrated by comparing experimental TEM images with ray tracing computer simulations of the model Surfaces as the projection direction was systematically varied in both the experimental and simulated images. The two morphologies observed were found to have intermaterial dividing Surfaces that approximate either Scherk's first (doubly periodic) Surface or a section of the right helicoid. The helicoid section boundary was observed at low twist angles, less than or equal to about 15. The Scherk Surface family of boundary morphologies, which consists of a doubly periodic array of saddle Surfaces, was found over the entire twist range from 0 to 90[degree]. As the twist angle approaches 0[degree] the Scherk Surface Grain boundary morphology is transformed into a single screw dislocation that has an intermaterial dividing Surface with the geometry of a single helicoid. Direct TEM imaging of the detailed core structure of this screw dislocation is presented.more » These images demonstrate that in the lamellar diblock copolymer the screw dislocation core is nonsingular. This nonsingular core structure represents a radical departure from the singular core structures observed in classical studies of dislocations in atomic crystals.« less

Samuel P Gido - One of the best experts on this subject based on the ideXlab platform.

  • lamellar diblock copolymer Grain boundary morphology 3 helicoid section twist boundary energy
    Macromolecules, 1997
    Co-Authors: Samuel P Gido, Edwin L Thomas
    Abstract:

    The helicoid section morphology allows a diblock copolymer lamellar phase to maintain microphase separation across a twist Grain boundary. The interface between the two microphases in the Grain boundary region approximates a stack of sections of the helicoid minimal Surface. Grain boundary energies were calculated for the helicoid section morphology both as a function of diblock chain characteristics and as a function of Grain boundary twist angle. The basic approach to Grain boundary energy calculation is to formulate a general expression for local free energy density as a function both of chain characteristics and of the local curvature of the interface. The local energy density is then integrated over the mathematical model for the Scherk Grain boundary. Two general methods of calculation were used, and the results where then compared. First, a self-consistent field model was formulated in which average energies per chain were calculated for all the possible interfacial curvature environments encounter...

  • lamellar diblock copolymer Grain boundary morphology 1 twist boundary characterization
    Macromolecules, 1993
    Co-Authors: Samuel P Gido, Edwin L Thomas, Janelle Gunther, David Hoffman
    Abstract:

    Grain boundary morphologies in poly(styrene-b-butadiene) lamellar diblock copolymers were characterized using transmission electron microscopy (TEM). Two types of twist Grain boundaries were observed in which microphase separation of the two blocks was maintained in the Grain boundary region by intermaterial dividing Surfaces that approximate classically known minimal Surfaces. The geometry of these interfaces was demonstrated by comparing experimental TEM images with ray tracing computer simulations of the model Surfaces as the projection direction was systematically varied in both the experimental and simulated images. The two morphologies observed were found to have intermaterial dividing Surfaces that approximate either Scherk's first (doubly periodic) Surface or a section of the right helicoid. The helicoid section boundary was observed at low twist angles, less than or equal to about 15. The Scherk Surface family of boundary morphologies, which consists of a doubly periodic array of saddle Surfaces, was found over the entire twist range from 0 to 90[degree]. As the twist angle approaches 0[degree] the Scherk Surface Grain boundary morphology is transformed into a single screw dislocation that has an intermaterial dividing Surface with the geometry of a single helicoid. Direct TEM imaging of the detailed core structure of this screw dislocation is presented.more » These images demonstrate that in the lamellar diblock copolymer the screw dislocation core is nonsingular. This nonsingular core structure represents a radical departure from the singular core structures observed in classical studies of dislocations in atomic crystals.« less