The Experts below are selected from a list of 1380 Experts worldwide ranked by ideXlab platform
Gordon G Wallace - One of the best experts on this subject based on the ideXlab platform.
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3d scaffolds of polycaprolactone copper doped bioactive glass architecture engineering with additive manufacturing and cellular assessments in a co culture of bone marrow stem cells and endothelial cells
ACS Biomaterials Science & Engineering, 2019Co-Authors: Xiaoju Wang, Binbin Zhang Molino, Sanna Pitkanen, Miina Ojansivu, Chunlin Xu, Markus Hannula, Jari Hyttinen, Susanna Miettinen, Leena Hupa, Gordon G WallaceAbstract:The local delivery of Cu2+ from copper-doped bioactive glass (Cu-BaG) was combined with 3D printing of polycaprolactone (PCL) scaffolds for its potent angiogenic effect in bone tissue engineering. PCL and Cu-BaG were respectively dissolved and dispersed in acetone to formulate a moderately homogeneous ink. The PCL/Cu-BaG scaffolds were fabricated via direct ink writing into a cold ethanol bath. The architecture of the printed scaffolds, including Strut Diameter, Strut spacing and porosity, were investigated and characterized. The PCL/Cu-BaG scaffolds showed a Cu-BaG content-dependent mechanical property, as the compressive Young’s modulus ranged from 7 to 13 MPa at an apparent porosity of 60%. The ion dissolution behavior in simulated body fluid was evaluated and the hydroxyapatite-like precipitation on the Strut surface was confirmed. Furthermore, the cytocompatibility of the PCL/Cu-BaG scaffolds was assessed in human bone marrow stem cell (hBMSC) culture and a dose-dependent cytotoxicity of Cu2+ was obs...
Xiaoju Wang - One of the best experts on this subject based on the ideXlab platform.
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3d scaffolds of polycaprolactone copper doped bioactive glass architecture engineering with additive manufacturing and cellular assessments in a co culture of bone marrow stem cells and endothelial cells
ACS Biomaterials Science & Engineering, 2019Co-Authors: Xiaoju Wang, Binbin Zhang Molino, Sanna Pitkanen, Miina Ojansivu, Chunlin Xu, Markus Hannula, Jari Hyttinen, Susanna Miettinen, Leena Hupa, Gordon G WallaceAbstract:The local delivery of Cu2+ from copper-doped bioactive glass (Cu-BaG) was combined with 3D printing of polycaprolactone (PCL) scaffolds for its potent angiogenic effect in bone tissue engineering. PCL and Cu-BaG were respectively dissolved and dispersed in acetone to formulate a moderately homogeneous ink. The PCL/Cu-BaG scaffolds were fabricated via direct ink writing into a cold ethanol bath. The architecture of the printed scaffolds, including Strut Diameter, Strut spacing and porosity, were investigated and characterized. The PCL/Cu-BaG scaffolds showed a Cu-BaG content-dependent mechanical property, as the compressive Young’s modulus ranged from 7 to 13 MPa at an apparent porosity of 60%. The ion dissolution behavior in simulated body fluid was evaluated and the hydroxyapatite-like precipitation on the Strut surface was confirmed. Furthermore, the cytocompatibility of the PCL/Cu-BaG scaffolds was assessed in human bone marrow stem cell (hBMSC) culture and a dose-dependent cytotoxicity of Cu2+ was obs...
Russell Goodall - One of the best experts on this subject based on the ideXlab platform.
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the effect of defects on the mechanical response of ti 6al 4v cubic lattice structures fabricated by electron beam melting
Acta Materialia, 2016Co-Authors: Everth Hernandeznava, P J Withers, Christopher Smith, F Derguti, S Tammaswilliams, Fabien Leonard, I Todd, Russell GoodallAbstract:Electron Beam Melting (EBM) as a means of Additive Manufacturing (AM), is of interest for the fabrication of intricate geometries for cellular materials in areas where complex architectures are needed, e.g. biomedical implants. Most studies have focused on specific geometries and so the effect of the structure on mechanical performance is not well understood. Many kinds of micro- and macro-scale defects can arise in additively manufactured components, so assessment of their influence on properties is needed. In this work, lattices of Ti-6Al-4V having a cubic structure have been manufactured by EBM, and the effect of heat treatments above and below the β-transus temperature on microstructure and compression response have been investigated. The former modifies only slightly the α + β structure and mechanical performance whereas the latter leads to coarse alternating α and β lamellae packets and α at the prior grain boundaries with a 10% loss in yield strength. The variation in the compressive yield stress with Strut Diameter is in good accord with simple models based on compressive deformation rather than shearing or buckling. Internal pores for Struts aligned with the build direction are found around the edges of the solid form, in regions which seem to be associated with the EB scan pattern. Struts normal to the build direction show more significant defects but their redundancy means that they do not compromise the compressive performance in the build direction. Using a particle size in the range 45–100 μm minimum weld-track sizes were experimentally and numerically identified to be 176 and 148 μm in depth respectively with a depth-to-width ratio of 0.55. This produced a beam pass of the order of 300 μm oversizing small features (Struts of 0.4 and 0.6 mm nominal Diameter) when a contour around the Strut periphery was applied.
P J Withers - One of the best experts on this subject based on the ideXlab platform.
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the effect of defects on the mechanical response of ti 6al 4v cubic lattice structures fabricated by electron beam melting
Acta Materialia, 2016Co-Authors: Everth Hernandeznava, P J Withers, Christopher Smith, F Derguti, S Tammaswilliams, Fabien Leonard, I Todd, Russell GoodallAbstract:Electron Beam Melting (EBM) as a means of Additive Manufacturing (AM), is of interest for the fabrication of intricate geometries for cellular materials in areas where complex architectures are needed, e.g. biomedical implants. Most studies have focused on specific geometries and so the effect of the structure on mechanical performance is not well understood. Many kinds of micro- and macro-scale defects can arise in additively manufactured components, so assessment of their influence on properties is needed. In this work, lattices of Ti-6Al-4V having a cubic structure have been manufactured by EBM, and the effect of heat treatments above and below the β-transus temperature on microstructure and compression response have been investigated. The former modifies only slightly the α + β structure and mechanical performance whereas the latter leads to coarse alternating α and β lamellae packets and α at the prior grain boundaries with a 10% loss in yield strength. The variation in the compressive yield stress with Strut Diameter is in good accord with simple models based on compressive deformation rather than shearing or buckling. Internal pores for Struts aligned with the build direction are found around the edges of the solid form, in regions which seem to be associated with the EB scan pattern. Struts normal to the build direction show more significant defects but their redundancy means that they do not compromise the compressive performance in the build direction. Using a particle size in the range 45–100 μm minimum weld-track sizes were experimentally and numerically identified to be 176 and 148 μm in depth respectively with a depth-to-width ratio of 0.55. This produced a beam pass of the order of 300 μm oversizing small features (Struts of 0.4 and 0.6 mm nominal Diameter) when a contour around the Strut periphery was applied.
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influence of processing conditions on Strut structure and compressive properties of cellular lattice structures fabricated by selective laser melting
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2015Co-Authors: Chunlei Qiu, Sheng Yue, P D Lee, Nicholas J E Adkins, Mark Ward, Hany Hassanin, P J Withers, Moataz M AttallahAbstract:Abstract AlSi10Mg cellular lattice structures have been fabricated by selective laser melting (SLM) using a range of laser scanning speeds and powers. The as-fabricated Strut size, morphology and internal porosity were investigated using optical microscopy (OM), scanning electron microscopy (SEM) and X-ray microtomography (micro-CT) and correlated to the compressive properties of the structure. Strut Diameter was found to increase monotonically with laser power while the porosity was largest at intermediate powers. Laser scanning speed was found to thicken the Struts only at slow rates while the porosity was largest at intermediate speeds. High speed imaging showed the melt pool to be larger at high laser powers. Further the melt pool shape was found to vary cyclically over time, steadily growing before becoming increasingly instable and irregularly shaped before abruptly falling in size due to splashing of molten materials and the process repeating. Upon compressive loading, lattice deformation was homogeneous prior to the peak stress before falling sharply due to the creation of a (one Strut wide) shear band at around 45° to the compression axis. The specific yield strength expressed as the yield stress/(yield stress of the aluminium × relative density) is not independent of processing conditions, suggesting that further improvements in properties can be achieved by process optimisation. Lattice Struts failed near nodes by a mixture of ductile and brittle fracture.
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influence of processing conditions on Strut structure and compressive properties of cellular lattice structures fabricated by selective laser melting
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2015Co-Authors: Chunlei Qiu, Sheng Yue, P D Lee, Nicholas J E Adkins, Mark Ward, Hany Hassanin, P J Withers, Moataz M AttallahAbstract:Abstract AlSi10Mg cellular lattice structures have been fabricated by selective laser melting (SLM) using a range of laser scanning speeds and powers. The as-fabricated Strut size, morphology and internal porosity were investigated using optical microscopy (OM), scanning electron microscopy (SEM) and X-ray microtomography (micro-CT) and correlated to the compressive properties of the structure. Strut Diameter was found to increase monotonically with laser power while the porosity was largest at intermediate powers. Laser scanning speed was found to thicken the Struts only at slow rates while the porosity was largest at intermediate speeds. High speed imaging showed the melt pool to be larger at high laser powers. Further the melt pool shape was found to vary cyclically over time, steadily growing before becoming increasingly instable and irregularly shaped before abruptly falling in size due to splashing of molten materials and the process repeating. Upon compressive loading, lattice deformation was homogeneous prior to the peak stress before falling sharply due to the creation of a (one Strut wide) shear band at around 45° to the compression axis. The specific yield strength expressed as the yield stress/(yield stress of the aluminium × relative density) is not independent of processing conditions, suggesting that further improvements in properties can be achieved by process optimisation. Lattice Struts failed near nodes by a mixture of ductile and brittle fracture.
Denis P Dowling - One of the best experts on this subject based on the ideXlab platform.
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influence of process parameters on the correlation between in situ process monitoring data and the mechanical properties of ti 6al 4v non stochastic cellular structures
Additive manufacturing, 2019Co-Authors: Darragh S Egan, Denis P DowlingAbstract:Abstract Selective Laser Melting (SLM) facilitates the formation of complex, stochastic or non-stochastic, metallic cellular structures. There is a high level of interest in these structures recently, particularly due to their high strength to weight ratios and osteoconductive properties. While the ability to in-situ monitor the SLM process is of key importance for future quality control methods. In this work lattice structures were fabricated, using the single exposure scanning strategy, on a Renishaw 500M SLM machine. The build process was also monitored using a co-axial in-situ process monitoring system. It was found that by increasing the energy input, through increasing the laser power and/or exposure time, the lattice Strut Diameters, within the 1.5 mm diamond unit cells, increased from 119 to 293 μm, resulting in the major pore Diameter decreasing from 1106 to 932 μm. The effect of systematically altering the laser beam spot size on the cellular structures was also evaluated. It was observed that by doubling the laser beam spot size, that there was a 17% reduction in Strut Diameter and a 22% reduction in mechanical strength of the structures. It was also observed that at constant energy input levels, the lattice structures created using a focused laser exhibited an 81% lower mechanical strength than the structures created using a de-focused laser. Thus, demonstrating that the mode of energy input is critical to achieving the desired strength in these structures. Based on the outputs from the in-situ monitoring system, a broadly linear correlation was obtained between the laser input energy, the associated process monitoring data generated and the mechanical strength of the lattice structures.
