The Experts below are selected from a list of 2235 Experts worldwide ranked by ideXlab platform

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

  • elastically isotropic open cell Minimal Surface shell lattices with superior stiffness via variable thickness design
    Additive manufacturing, 2021
    Co-Authors: Lei Zhang, Junhao Ding, Xu Song, Mingdong Zhou, Michael Yu Wang
    Abstract:

    Abstract Triply Periodic Minimal Surface (TPMS) shell lattices are attracting increasingly attention due to their unique combination of geometric and mechanical properties, and their open-cell topology. However, uniform thickness TPMS shell lattices are usually anisotropic in stiffness, namely having different Young’s moduli along different lattice directions. To reduce the elastic anisotropy, we propose a family of variable thickness TPMS shell lattices with isotropic stiffness designed by a strain energy-based optimization algorithm. The optimization results show that all the six selected types of TPMS lattices can be made to achieve isotropic stiffness by varying the shell thickness, among which N14 can maintain over 90% of the Hashin-Shtrikman upper bound of bulk modulus. All the optimized shell lattices exhibit superior stiffness properties and significantly outperform elastically-isotropic truss lattices of equal relative densities. Both uniform and optimized types of N14 shell lattices along [100], [110] and [111] directions are fabricated by the micro laser powder bed fusion techniques with stainless steel 316 L and tested under quasi-static compression loads. Experimental results show that the elastic anisotropy of the optimized N14 lattices is reduced compared to that of the uniform ones. Large deformation compression results reveal different failure deformation behaviors along different directions. The [100] direction shows a layer-by-layer plastic buckling failure mode, while the failures along [110] and [111] directions are related to the shear deformation. The optimized N14 lattices possess a reduced anisotropy of plateau stresses and can even attain nearly isotropic energy absorption capacity.

  • elastically isotropic open cell Minimal Surface shell lattices with superior stiffness via variable thickness design
    arXiv: Numerical Analysis, 2021
    Co-Authors: Lei Zhang, Junhao Ding, Xu Song, Mingdong Zhou, Michael Yu Wang
    Abstract:

    Triply Periodic Minimal Surface (TPMS) shell-lattices are attracting increasingly attention due to their unique combination of geometric and mechanical properties, and their open-cell topology. However, uniform thickness TPMS shell-lattices are usually anisotropic in stiffness, namely having different Young's moduli along different lattice directions. To reduce the anisotropy, we propose a family of variable thickness TPMS shell-lattices with isotropic stiffness designed by a strain energy-based optimization algorithm. The optimization results show that all the five selected types of TPMS lattices can be made to achieve isotropic stiffness by varying the shell thickness, among which N14 and OCTO can maintain over 90% of the Hashin-Shtrikman upper bound of bulk modulus. All the optimized shell-lattices exhibit superior stiffness properties and significantly outperform elastically-isotropic truss-lattices. Both uniform and optimized types of N14 shell-lattices along [100], [110] and [111] directions are fabricated by the micro laser powder bed fusion techniques with stainless steel 316L and tested under quasi-static compression loads. Experimental results show that the elastic anisotropy of the optimized N14 lattices is reduced compared to that of the uniform ones. Large deformation compression results reveal different failure deformation behaviors along different directions. The [100] direction shows a layer-by-layer plastic buckling failure mode, while the failures along [110] and [111] directions are related to the shear deformation. The optimized N14 lattices possess a reduced anisotropy of plateau stresses and can even attain nearly isotropic energy absorption capacity.

  • Hierarchical sheet triply Periodic Minimal Surface lattices: Design, geometric and mechanical performance
    'Elsevier BV', 2021
    Co-Authors: Lei Zhang, Michael Yu Wang, S Feih
    Abstract:

    Lattices with hierarchical architectures exhibit unique geometric and mechanical properties compared with single scale ones. While numerous research efforts have focused on hierarchical strut lattices, hierarchical sheet lattices have yet to be studied in detail. This paper proposes a systemic framework including geometric design, finite element modelling, additive manufacturing, and mechanical testing for hierarchical sheet triply Periodic Minimal Surface (TPMS) lattices such that the lattice walls comprise successively smaller scale TPMS architectures. Geometric properties including relative densities and volume-specific Surface areas of hierarchical lattices are analytically calculated and verified via numerical calculations. The compressive properties of 2-order sheet Gyroid lattices are investigated with finite element simulations and experimentally validated using micro-selective laser melting fabricated stainless-steel specimens. Geometric analysis shows that hierarchical sheet lattices have great potential to achieve a wide range of controllable geometric properties including hierarchical porosities, ultralow densities, and significantly enlarged Surface areas. Simulation results indicate that 2-order lattices have superior buckling strength over single scale lattices at ultralow densities. At moderate densities, 2-order lattices exhibit reduced modulus and strength, but more stable failure behaviour. With these unique combinations of geometric and mechanical properties, hierarchical sheet TPMS designs are shown to be desirable structural configurations for biomedical scaffolds

  • pseudo ductile fracture of 3d printed alumina triply Periodic Minimal Surface structures
    Journal of The European Ceramic Society, 2020
    Co-Authors: Lei Zhang, S Feih, Stephen Daynes, Shuai Chang, Michael Yu Wang, Jun Wei
    Abstract:

    Abstract Additive manufacturing enables the fabrication of Periodic ceramic lattices with controllable micro-architectures. Many studies reported their catastrophic brittle fracture behaviour. However, ceramic lattices may fail by a layer-by-layer pseudo-ductile fracture mode, by controlling micro-architectures and porosities. Moreover, their fracture behaviour can be optimised by introducing strut/wall thickness gradients. This paper investigates the fracture behaviour and the fracture mode transition of ceramic triply Periodic Minimal Surface (TPMS) structures. Alumina TPMS structures with relative densities of 0.14-0.37 are fabricated by ceramic stereolithography. Quasi-static compression tests validate a transition density range for non-graded samples: low ( 0.25) relative density samples show layer-by-layer pseudo-ductile and catastrophic brittle fracture modes, respectively. The pseudo-ductile failure mode increases the energy absorption performance, enabling load-bearing capacity for a compressive strain up to 50%. With appropriate thickness gradients, graded structures exhibit significant increase of energy absorption without a decrease of fracture strength compared to their non-graded counterparts.

  • energy absorption characteristics of metallic triply Periodic Minimal Surface sheet structures under compressive loading
    Additive manufacturing, 2018
    Co-Authors: Lei Zhang, S Feih, Stephen Daynes, Shuai Chang, Michael Yu Wang, Wen Feng Lu
    Abstract:

    Abstract Designing metallic cellular structures with triply Periodic Minimal Surface (TPMS) sheet cores is a novel approach for lightweight and multi-functional structural applications. Different from current honeycombs and lattices, TPMS sheet structures are composed of continuous and smooth shells, allowing for large Surface areas and continuous internal channels. In this paper, we investigate the mechanical properties and energy absorption abilities of three types of TPMS sheet structures (Primitive, Diamond, and Gyroid) fabricated by selective laser melting (SLM) with 316 L stainless steel under compression loading and classify their failure mechanisms and printing accuracy with the help of numerical analysis. Experimental results reveal the superior stiffness, plateau stress and energy absorption ability of TPMS sheet structures compared to body-centred cubic lattices, with Diamond-type sheet structures performing best. Nonlinear finite element simulation results also show that Diamond and Gyroid sheet structures display relatively uniform stress distributions across all lattice cells under compression, leading to stable collapse mechanisms and desired energy absorption performance. In contrast, Primitive-type structures display rapid diagonal shear band development followed by localized wall buckling. Lastly, an energy absorption diagram is developed to facilitate a systematic way to select optimal densities of TPMS structures for energy absorbing applications.

Lei Zhang - One of the best experts on this subject based on the ideXlab platform.

  • elastically isotropic open cell Minimal Surface shell lattices with superior stiffness via variable thickness design
    Additive manufacturing, 2021
    Co-Authors: Lei Zhang, Junhao Ding, Xu Song, Mingdong Zhou, Michael Yu Wang
    Abstract:

    Abstract Triply Periodic Minimal Surface (TPMS) shell lattices are attracting increasingly attention due to their unique combination of geometric and mechanical properties, and their open-cell topology. However, uniform thickness TPMS shell lattices are usually anisotropic in stiffness, namely having different Young’s moduli along different lattice directions. To reduce the elastic anisotropy, we propose a family of variable thickness TPMS shell lattices with isotropic stiffness designed by a strain energy-based optimization algorithm. The optimization results show that all the six selected types of TPMS lattices can be made to achieve isotropic stiffness by varying the shell thickness, among which N14 can maintain over 90% of the Hashin-Shtrikman upper bound of bulk modulus. All the optimized shell lattices exhibit superior stiffness properties and significantly outperform elastically-isotropic truss lattices of equal relative densities. Both uniform and optimized types of N14 shell lattices along [100], [110] and [111] directions are fabricated by the micro laser powder bed fusion techniques with stainless steel 316 L and tested under quasi-static compression loads. Experimental results show that the elastic anisotropy of the optimized N14 lattices is reduced compared to that of the uniform ones. Large deformation compression results reveal different failure deformation behaviors along different directions. The [100] direction shows a layer-by-layer plastic buckling failure mode, while the failures along [110] and [111] directions are related to the shear deformation. The optimized N14 lattices possess a reduced anisotropy of plateau stresses and can even attain nearly isotropic energy absorption capacity.

  • elastically isotropic open cell Minimal Surface shell lattices with superior stiffness via variable thickness design
    arXiv: Numerical Analysis, 2021
    Co-Authors: Lei Zhang, Junhao Ding, Xu Song, Mingdong Zhou, Michael Yu Wang
    Abstract:

    Triply Periodic Minimal Surface (TPMS) shell-lattices are attracting increasingly attention due to their unique combination of geometric and mechanical properties, and their open-cell topology. However, uniform thickness TPMS shell-lattices are usually anisotropic in stiffness, namely having different Young's moduli along different lattice directions. To reduce the anisotropy, we propose a family of variable thickness TPMS shell-lattices with isotropic stiffness designed by a strain energy-based optimization algorithm. The optimization results show that all the five selected types of TPMS lattices can be made to achieve isotropic stiffness by varying the shell thickness, among which N14 and OCTO can maintain over 90% of the Hashin-Shtrikman upper bound of bulk modulus. All the optimized shell-lattices exhibit superior stiffness properties and significantly outperform elastically-isotropic truss-lattices. Both uniform and optimized types of N14 shell-lattices along [100], [110] and [111] directions are fabricated by the micro laser powder bed fusion techniques with stainless steel 316L and tested under quasi-static compression loads. Experimental results show that the elastic anisotropy of the optimized N14 lattices is reduced compared to that of the uniform ones. Large deformation compression results reveal different failure deformation behaviors along different directions. The [100] direction shows a layer-by-layer plastic buckling failure mode, while the failures along [110] and [111] directions are related to the shear deformation. The optimized N14 lattices possess a reduced anisotropy of plateau stresses and can even attain nearly isotropic energy absorption capacity.

  • Hierarchical sheet triply Periodic Minimal Surface lattices: Design, geometric and mechanical performance
    'Elsevier BV', 2021
    Co-Authors: Lei Zhang, Michael Yu Wang, S Feih
    Abstract:

    Lattices with hierarchical architectures exhibit unique geometric and mechanical properties compared with single scale ones. While numerous research efforts have focused on hierarchical strut lattices, hierarchical sheet lattices have yet to be studied in detail. This paper proposes a systemic framework including geometric design, finite element modelling, additive manufacturing, and mechanical testing for hierarchical sheet triply Periodic Minimal Surface (TPMS) lattices such that the lattice walls comprise successively smaller scale TPMS architectures. Geometric properties including relative densities and volume-specific Surface areas of hierarchical lattices are analytically calculated and verified via numerical calculations. The compressive properties of 2-order sheet Gyroid lattices are investigated with finite element simulations and experimentally validated using micro-selective laser melting fabricated stainless-steel specimens. Geometric analysis shows that hierarchical sheet lattices have great potential to achieve a wide range of controllable geometric properties including hierarchical porosities, ultralow densities, and significantly enlarged Surface areas. Simulation results indicate that 2-order lattices have superior buckling strength over single scale lattices at ultralow densities. At moderate densities, 2-order lattices exhibit reduced modulus and strength, but more stable failure behaviour. With these unique combinations of geometric and mechanical properties, hierarchical sheet TPMS designs are shown to be desirable structural configurations for biomedical scaffolds

  • pseudo ductile fracture of 3d printed alumina triply Periodic Minimal Surface structures
    Journal of The European Ceramic Society, 2020
    Co-Authors: Lei Zhang, S Feih, Stephen Daynes, Shuai Chang, Michael Yu Wang, Jun Wei
    Abstract:

    Abstract Additive manufacturing enables the fabrication of Periodic ceramic lattices with controllable micro-architectures. Many studies reported their catastrophic brittle fracture behaviour. However, ceramic lattices may fail by a layer-by-layer pseudo-ductile fracture mode, by controlling micro-architectures and porosities. Moreover, their fracture behaviour can be optimised by introducing strut/wall thickness gradients. This paper investigates the fracture behaviour and the fracture mode transition of ceramic triply Periodic Minimal Surface (TPMS) structures. Alumina TPMS structures with relative densities of 0.14-0.37 are fabricated by ceramic stereolithography. Quasi-static compression tests validate a transition density range for non-graded samples: low ( 0.25) relative density samples show layer-by-layer pseudo-ductile and catastrophic brittle fracture modes, respectively. The pseudo-ductile failure mode increases the energy absorption performance, enabling load-bearing capacity for a compressive strain up to 50%. With appropriate thickness gradients, graded structures exhibit significant increase of energy absorption without a decrease of fracture strength compared to their non-graded counterparts.

  • energy absorption characteristics of metallic triply Periodic Minimal Surface sheet structures under compressive loading
    Additive manufacturing, 2018
    Co-Authors: Lei Zhang, S Feih, Stephen Daynes, Shuai Chang, Michael Yu Wang, Wen Feng Lu
    Abstract:

    Abstract Designing metallic cellular structures with triply Periodic Minimal Surface (TPMS) sheet cores is a novel approach for lightweight and multi-functional structural applications. Different from current honeycombs and lattices, TPMS sheet structures are composed of continuous and smooth shells, allowing for large Surface areas and continuous internal channels. In this paper, we investigate the mechanical properties and energy absorption abilities of three types of TPMS sheet structures (Primitive, Diamond, and Gyroid) fabricated by selective laser melting (SLM) with 316 L stainless steel under compression loading and classify their failure mechanisms and printing accuracy with the help of numerical analysis. Experimental results reveal the superior stiffness, plateau stress and energy absorption ability of TPMS sheet structures compared to body-centred cubic lattices, with Diamond-type sheet structures performing best. Nonlinear finite element simulation results also show that Diamond and Gyroid sheet structures display relatively uniform stress distributions across all lattice cells under compression, leading to stable collapse mechanisms and desired energy absorption performance. In contrast, Primitive-type structures display rapid diagonal shear band development followed by localized wall buckling. Lastly, an energy absorption diagram is developed to facilitate a systematic way to select optimal densities of TPMS structures for energy absorbing applications.

Lei Yang - One of the best experts on this subject based on the ideXlab platform.

  • compression compression fatigue behaviour of gyroid type triply Periodic Minimal Surface porous structures fabricated by selective laser melting
    Acta Materialia, 2019
    Co-Authors: Chunze Yan, Yusheng Shi, Lei Yang, Wenchao Cao, Zhufeng Liu, Bo Song, Shifeng Wen, Cong Zhang, Shoufeng Yang
    Abstract:

    Abstract Triply Periodic Minimal Surface (TPMS) porous structures are recognized as the most promising bionic artificial structures for tissue engineering. The fatigue properties of additive manufactured porous structures are essential for long-term use in a dynamical bio-skeletal environment. The aim of this study is to study the compression–compression fatigue behaviour and the underlying fatigue mechanism of Gyroid cellular structures (GCS), a typical TPMS porous structure. The high-cycle fatigue results show that both cyclic ratcheting and fatigue damage phenomena contribute to the failure of GCS during fatigue testing. For most fatigue loading stress, the failure samples have nearly 45° fracture bands along the diagonal Surface. The fatigue ratio of GCS reaches 0.35 for as-built samples and can be raised to 0.45 after sandblasting treatment. The fatigue ratio values are higher than most of the other bending-dominated lattice structures, suggesting superior fatigue resistance properties of GCSs due to the smooth Surface connection between struts. Besides, a systematic investigation of the crack initiation and propagation was conducted by both deformation analysis and finite element method to support experimental phenomena. The results also indicate that the fatigue resistance properties of GCSs are significantly enhanced by sandblasting post-treatment, through removing the adhered powder particles, inducing compressive residual stress on the Surface and generating a nanocrystalline zone.

  • mechanical response of a triply Periodic Minimal Surface cellular structures manufactured by selective laser melting
    International Journal of Mechanical Sciences, 2018
    Co-Authors: Lei Yang, Peng Chen, Shoufeng Yang
    Abstract:

    Abstract Cellular structures with controllable mechanical properties and porous architecture are the most promising candidates for many applications such as bone implants. Selective laser melting (SLM), one of the additive manufacturing (AM) technologies, enables manufacturing of space filling lattice structures with exceptional load bearing efficiency, customizable stiffness, controllable cell topology, cell size, and porosity. In this work, Schoen Gyroid (SG) unit cell, a triply Periodic Minimal Surface (TPMS) structure, was used to design the cellular structures. As opposed to many other types of unit cells, SG has superior characteristics of self-supporting and high manufacturability for AM technologies. The titanium alloy (Ti–6Al–4V) SG cellular structures were manufactured by SLM. Finite element (FE) method was employed to predict the elastic modulus, compressive yield strength and stress/strain distributions of the SG cellular structures, and the failure occurrence mechanisms were analyzed. The FE results were compared with the experimental data. The results show that through FE method, the mechanical responses of the SG cellular structures can be accurately described and it is possible to customize the mechanical properties of SLM-produced titanium alloy TPMS lattices.

Ahmed Hussein - One of the best experts on this subject based on the ideXlab platform.

  • microstructural and Surface modifications and hydroxyapatite coating of ti 6al 4v triply Periodic Minimal Surface lattices fabricated by selective laser melting
    Materials Science and Engineering: C, 2017
    Co-Authors: Ahmed Hussein
    Abstract:

    Abstract Ti-6Al-4V Gyroid triply Periodic Minimal Surface (TPMS) lattices were manufactured by selective laser melting (SLM). The as-built Ti-6Al-4V lattices exhibit an out-of-equilibrium microstructure with very fine α′ martensitic laths. When subjected to the heat treatment of 1050 °C for 4 h followed by furnace cooling, the lattices show a homogenous and equilibrium lamellar α + β microstructure with less dislocation and crystallographic defects compared with the as-built α′ martensite. The as-built lattices present very rough strut Surfaces bonded with plenty of partially melted metal particles. The sand blasting nearly removed all the bonded metal particles, but created many tiny cracks. The HCl etching eliminated these tiny cracks, and subsequent NaOH etching resulted in many small and shallow micro-pits and develops a sodium titanate hydrogel layer on the Surfaces of the lattices. When soaked in simulated body fluid (SBF), the Ti-6Al-4V TPMS lattices were covered with a compact and homogeneous biomimetic hydroxyapatite (HA) layer. This work proposes a new method for making Ti-6Al-4V TPMS lattices with a homogenous and equilibrium microstructure and biomimetic HA coating, which show both tough and bioactive characteristics and can be promising materials usable as bone substitutes.

  • ti 6al 4v triply Periodic Minimal Surface structures for bone implants fabricated via selective laser melting
    Journal of The Mechanical Behavior of Biomedical Materials, 2015
    Co-Authors: Ahmed Hussein, P G Young
    Abstract:

    Abstract Triply Periodic Minimal Surface (TPMS) structures have already been shown to be a versatile source of biomorphic scaffold designs. Therefore, in this work, Ti–6Al–4V Gyroid and Diamond TPMS lattices having an interconnected high porosity of 80–95% and pore sizes in the range of 560–1600 μm and 480–1450 μm respectively were manufactured by selective laser melting (SLM) for bone implants. The manufacturability, microstructure and mechanical properties of the Ti–6Al–4V TPMS lattices were evaluated. Comparison between 3D micro-CT reconstructed models and original CAD models of the Ti–6Al–4V TPMS lattices shows excellent reproduction of the designs. The as-built Ti–6Al–4V struts exhibit the microstructure of columnar grains filled with very fine and orthogonally oriented α′ martensitic laths with the width of 100–300 nm and have the microhardness of 4.01±0.34 GPa. After heat treatment at 680 °C for 4 h, the α′ martensite was converted to a mixture of α and β, in which the α phase being the dominant fraction is present as fine laths with the width of 500–800 nm and separated by a small amount of narrow, interphase regions of dark β phase. Also, the microhardness is decreased to 3.71±0.35 GPa due to the coarsening of the microstructure. The 80–95% porosity TPMS lattices exhibit a comparable porosity with trabecular bone, and the modulus is in the range of 0.12–1.25 GPa and thus can be adjusted to the modulus of trabecular bone. At the same range of porosity of 5–10%, the moduli of cortical bone and of the Ti–6Al–4V TPMS lattices are in a similar range. Therefore, the modulus and porosity of Ti–6Al–4V TPMS lattices can be tailored to the levels of human bones and thus reduce or avoid “stress shielding” and increase longevity of implants. Due to the biomorphic designs, and high interconnected porosity and stiffness comparable to human bones, SLM-made Ti–6Al–4V TPMS lattices can be a promising material for load bearing bone implants.

Shoufeng Yang - One of the best experts on this subject based on the ideXlab platform.

  • compression compression fatigue behaviour of gyroid type triply Periodic Minimal Surface porous structures fabricated by selective laser melting
    Acta Materialia, 2019
    Co-Authors: Chunze Yan, Yusheng Shi, Lei Yang, Wenchao Cao, Zhufeng Liu, Bo Song, Shifeng Wen, Cong Zhang, Shoufeng Yang
    Abstract:

    Abstract Triply Periodic Minimal Surface (TPMS) porous structures are recognized as the most promising bionic artificial structures for tissue engineering. The fatigue properties of additive manufactured porous structures are essential for long-term use in a dynamical bio-skeletal environment. The aim of this study is to study the compression–compression fatigue behaviour and the underlying fatigue mechanism of Gyroid cellular structures (GCS), a typical TPMS porous structure. The high-cycle fatigue results show that both cyclic ratcheting and fatigue damage phenomena contribute to the failure of GCS during fatigue testing. For most fatigue loading stress, the failure samples have nearly 45° fracture bands along the diagonal Surface. The fatigue ratio of GCS reaches 0.35 for as-built samples and can be raised to 0.45 after sandblasting treatment. The fatigue ratio values are higher than most of the other bending-dominated lattice structures, suggesting superior fatigue resistance properties of GCSs due to the smooth Surface connection between struts. Besides, a systematic investigation of the crack initiation and propagation was conducted by both deformation analysis and finite element method to support experimental phenomena. The results also indicate that the fatigue resistance properties of GCSs are significantly enhanced by sandblasting post-treatment, through removing the adhered powder particles, inducing compressive residual stress on the Surface and generating a nanocrystalline zone.

  • mechanical response of a triply Periodic Minimal Surface cellular structures manufactured by selective laser melting
    International Journal of Mechanical Sciences, 2018
    Co-Authors: Lei Yang, Peng Chen, Shoufeng Yang
    Abstract:

    Abstract Cellular structures with controllable mechanical properties and porous architecture are the most promising candidates for many applications such as bone implants. Selective laser melting (SLM), one of the additive manufacturing (AM) technologies, enables manufacturing of space filling lattice structures with exceptional load bearing efficiency, customizable stiffness, controllable cell topology, cell size, and porosity. In this work, Schoen Gyroid (SG) unit cell, a triply Periodic Minimal Surface (TPMS) structure, was used to design the cellular structures. As opposed to many other types of unit cells, SG has superior characteristics of self-supporting and high manufacturability for AM technologies. The titanium alloy (Ti–6Al–4V) SG cellular structures were manufactured by SLM. Finite element (FE) method was employed to predict the elastic modulus, compressive yield strength and stress/strain distributions of the SG cellular structures, and the failure occurrence mechanisms were analyzed. The FE results were compared with the experimental data. The results show that through FE method, the mechanical responses of the SG cellular structures can be accurately described and it is possible to customize the mechanical properties of SLM-produced titanium alloy TPMS lattices.