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作者: J.P. Escobedo>
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摘要: AbstractThe low-velocity impact response of closed-cell aluminium foams using various shaped indenters has been investigated. Impact tests were conducted using an instrumented drop-tower with flat, hemispherical, conical and truncated-conical indenter at impact energies ranging from 46.8 J to 105 J. The effects of variation of indenter shape and impact velocity on mechanical properties and deformation mechanisms of foam have been explicitly investigated. The results show that the mechanical resp关键词: Indentation; Closed-cell aluminium foam; Energy absorption; Collapse mechanisms; Low-velocity impact
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摘要: Abstract(#br)The mechanical properties of closed-cell aluminium foams are governed by their geometrical and topological evolution during impact. Here we non-destructively investigate the deformation mechanisms of a closed-cell aluminium foam sample at the cell scale. The sample has been compressed with 21 interrupted drop-weight impacts at a nominal strain rate of 40 s −1 and the post-impacted sample has been imaged at four pertinent strain states with high-resolution X-ray micro-computed tomogr关键词: Metal foam; X-ray computed tomography; Impact behaviour; Topology
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M.A. Kader; P.J. Hazell; A.D. Brown; M. Tahtali; S. Ahmed; J.P. Escobedo; M. Saadatfar;
Additive ManufacturingVolume 31, Issue C, 2020, PP 100976-100976
摘要: Abstract(#br)Cellular materials, such as foams, can be used as load bearing members in civil construction and as protective energy absorbing structures for personnel and equipment. In the present study, novel lightweight closed-cell structures were designed, and their mechanical properties and collapse mechanisms were investigated through a combination of experimental validation and finite element (FE) simulations. Selected porous structure designs were manufactured from acrylonitrile butadiene 关键词: Closed-cell foam; Additive manufacturing; Finite element modelling (FEM); Energy absorption; Collapse mechanisms
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摘要: Abstract(#br)The dynamic compressive response of closed-cell (CYMAT™) stabilised aluminium alloy foams (SAF) has been investigated using a modified Split Hopkinson Pressure Bar (SHPB) in conjunction with a high-speed camera. Tests have been carried out on 45 mm diameter and 23 mm thick cylindrical specimens. The elastic-plastic pore collapse mechanism has been investigated using Digital Image Correlation (DIC) and micro-computed X-ray tomography. A stress-strain relationship for individual speci
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摘要: Abstract(#br)The commercial hydrocode ANSYS AUTODYN ® was used to create a thermally dependent model of an Ultra-High Molecular Weight Polyethylene (UHMW-PE) composite under high and hypervelocity impact. In particular this model was validated against high-velocity fragment-simulating projectile (FSP) impacts and hypervelocity polycarbonate cylinder impacts at 2,100 m/s and 3,500 m/s. It appeared that despite the same material model being used for thick unidirectional Dyneema ® laminates and thi关键词: Spectra; Dyneema; Hypervelocity; Failure
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摘要: The pore collapse mechanisms of closed-cell aluminium foams during quasi-static compression have been investigated. A suite of experiments and numerical simulations were carried out to elucidate the deformation pathways of individual pores during quasi-static compressive loading. X-ray computed tomography was utilized to generate 3D views of the foams before and after deformation. The tomography based foam geometry was imported into the finite element software ABAQUS/Explicit for simulations. Th
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M.A. Kader; M.A. Islam; P.J. Hazell; J.P. Escobedo; M. Saadatfar; A.D. Brown; G.J. Appleby-Thomas;
International Journal of Impact EngineeringVolume 96, Issue , 2016, PP 78-88
摘要: Highlights•Plate impact experiments have been carried out on closed-cell aluminium foams.•A micro-computed tomography based geometry was developed for modelling studies.•Wave propagation mechanisms through the closed-cell Al foams have been investigated.•Cell collapse mechanisms have been explored during plate-impact loading.;AbstractPlate-impact experiments have been conducted to investigate the elastic–plastic behaviour of shock wave propagation and pore collapse mechanisms of closed-cell alum关键词: Shock propagation;Closed-cell aluminium foam;Plastic collapse;Micro-computed tomography;Meso-scale modelling
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摘要: Abstract(#br)This study investigates the influence of microstructure on the strength properties of individual cell walls of closed-cell stabilized aluminium foams (SAFs). Optical microscopy (OM), micro-computed X-ray tomography (µ-CT), electron backscattering diffraction (EBSD), and energy dispersive X-ray spectroscopy (EDS) analyses were conducted to examine the microstructural properties of SAF cell walls. Novel micro-tensile tests were performed to investigate the strength properties of indiv关键词: Closed-cell foams; Microstructure; Micro-tensile; Cell wall properties
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摘要: The effect of high pressure on the mechanical behavior and accompanying microstructural evolution in Ta has been investigated. Thin-foil Ta samples were deformed while being subjected to pressures in the 1–5GPa range in a modified opposed-anvil Bridgman apparatus. Examination of deformed microstructures revealed similar changes in texture in all samples, independent of pressure. However, dislocation structures are observed to change from entanglements to well-developed dislocation cells with inc关键词: High pressure;Mechanical behavior;Dislocation dynamics;Tantalum;bcc
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E.K. Cerreta; J.P. Escobedo; P.A. Rigg; C.P. Trujillo; D.W. Brown; T.A. Sisneros; B. Clausen; M.F. Lopez; T. Lookman; C.A. Bronkhorst; F.L. Addessio;
Acta MaterialiaVolume 61, Issue 20, 2013, PP 7712-7719
摘要: AbstractAt high pressures zirconium undergoes a phase transformation from the hexagonal closed packed (hcp) α-phase to the simple hexagonal ω-phase. In high purity Zr and under shock loading conditions the phase transformation has been observed to begin at approximately 7GPa [1]. Evolution of the plastic response and phase transformation during dynamic loading is not well understood and therefore the contributions of this evolution to strength and damage are not well predicted. Here, through a c关键词: Phase transformation; Zirconium; Twinning; High strain rate
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J.P. Escobedo; E.K. Cerreta; C.P. Trujillo; D.T. Martinez; R.A. Lebensohn; V.A. Webster; G.T. Gray;
Acta MaterialiaVolume 60, Issue 11, 2012, PP 4379-4392
摘要: AbstractExperiments were conducted to characterize the influence of texture and impact velocity on the dynamic, high-strain, tensile extrusion of zirconium. Bullet-shaped samples were machined from a clock-rolled, highly textured Zr plate. Specimens in two orthogonal directions were tested: the extrusion direction aligned with either the in-plane (IP) rolling or the through-thickness (TT) direction of the plate. The post-extrusion microstructure and texture evolution were examined using electron关键词: Zirconium; Extrusion; Deformation structure; Electron backscatter diffraction (EBSD); VPSC modeling
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E.K. Cerreta; J.P. Escobedo; A. Perez-Bergquist; D.D. Koller; C.P. Trujillo; G.T. Gray III; C. Brandl; T.C. Germann;
Scripta MaterialiaVolume 66, Issue 9, 2012, PP 638-641
摘要: The role of grain boundary type in the early stages of dynamic damage evolution in copper has been investigated. Through a combination of polycrystalline and large-grained specimens, it has been shown that Σ3 and low-angle boundaries are resistant to void nucleation during shock loading to peak compressive stresses between 1.5 and 2.5GPa. It is postulated that these boundaries promote slip transmission or secondary slip activation and thereby relieve the stress concentrations necessary for void 关键词: Grain boundaries; Impact behavior; Microstructure; Demage
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