The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

S R Reid - One of the best experts on this subject based on the ideXlab platform.

  • air blast response of Cellular Material with a face plate an analytical numerical approach
    International Journal of Mechanical Sciences, 2015
    Co-Authors: Majid Aleyaasin, John J Harrigan, S R Reid
    Abstract:

    Abstract The air-blast response of a sacrificial cladding consisting of a Cellular Material with a front face-plate is investigated. The Cellular Material is sandwiched between a rigid face-plate and a rigid support. The support represents the structure that is to be protected. The air blast is assumed to be an exponentially decaying pulse. The Cellular Material is idealised as rigid, perfectly-plastic, locking and the deformation is governed by the propagation of a compaction (shock) wave travelling through the Material. A second order nonlinear ordinary differential equation is derived to predict the displacement of the face-plate and the compression of the Cellular layer by coupling the reflected over-pressure with the stresses at the interface between the face-plate and the Cellular Material. The Cellular Material may attenuate or enhance the shock transmitted to the structure. Extensive simulations are carried out to define the attenuation/enhancement boundary for a range of initial peak pressures and cladding parameters. Herein, enhancement is considered to occur if the shock front reaches the support. A new method of accounting for fluid–structure interaction (FSI) is derived. The predictions are compared to those with no FSI as well as an existing model that accounts for the FSI effect, but for a free-standing plate.

  • dynamic stress strain states for metal foams using a 3d Cellular model
    Journal of The Mechanics and Physics of Solids, 2014
    Co-Authors: Zhijun Zheng, S R Reid, Changfeng Wang, John J Harrigan
    Abstract:

    Abstract Dynamic uniaxial impact behaviour of metal foams using a 3D cell-based finite element model is examined. At sufficiently high loading rates, these Materials respond by forming ‘shock or consolidation waves’ ( Tan et al., 2005a , Tan et al., 2005b ). However, the existing dynamic experimental methods have limitations in fully informing this behaviour, particularly for solving boundary/initial value problems. Recently, the problem of the shock-like response of an open-cell foam has been examined by Barnes et al. (2014) using the Hugoniot-curve representations. The present study is somewhat complementary to that approach and additionally aims to provide insight into the ‘rate sensitivity’ mechanism applicable to Cellular Materials. To assist our understanding of the ‘loading rate sensitivity’ behaviour of Cellular Materials, a virtual ‘test’ method based on the direct impact technique is explored. Following a continuum representation of the response, the strain field calculation method is employed to determine the local strains ahead of and behind the resulting ‘shock front’. The dynamic stress–strain states in the densification stage are found to be different from the quasi-static ones. It is evident that the constitutive behaviour of the Cellular Material is deformation-mode dependent. The nature of the ‘rate sensitivity’ revealed for Cellular Materials in this paper is different from the strain-rate sensitivity of dense metals. It is shown that the dynamic stress–strain states behind a shock front of the Cellular Material lie on a unique curve and each point on the curve corresponds to a particular ‘impact velocity’, referred as the velocity upstream of the shock in this study. The dynamic stress–strain curve is related to a layer-wise collapse mode, whilst the equivalent quasi-static curve is related to a random shear band collapse mode. The findings herein are aimed at improving the experimental test techniques used to characterise the rate-sensitivity behaviour of real Cellular Materials and providing data appropriate to solving dynamic loading problems in which Cellular metals are utilised.

  • the correct analysis of shocks in a Cellular Material
    International Journal of Impact Engineering, 2010
    Co-Authors: John J Harrigan, S R Reid, Seyed A Yaghoubi
    Abstract:

    Abstract Cellular Materials have applications for impact and blast protection. Under impact/impulsive loading the response of the Cellular solid can be controlled by compaction (or shock, see Tan et al. (2005) [3] , [4] ) waves. Different analytical and computational solutions have been produced to model this behaviour but these solutions provide conflicting predictions for the response of the Material in certain loading scenarios. The different analytical approaches are discussed using two simple examples for clarity. The differences between apparently similar “models” are clarified. In particular, it is argued that mass-spring models are not capable of modelling the discontinuities that exist in a compaction wave in a Cellular Material.

  • about one dimensional shock propagation in a Cellular Material
    International Journal of Impact Engineering, 2006
    Co-Authors: S R Reid
    Abstract:

    Abstract Comments and clarifications of shock wave propagation in Cellular Materials are presented in this short communication. Several problems associated with the shock propagation model proposed in [Int J Impact Eng 2004;30(4):421–445] are discussed.

Yi Min Xie - One of the best experts on this subject based on the ideXlab platform.

  • water responsive rapid recovery of natural Cellular Material
    Journal of The Mechanical Behavior of Biomedical Materials, 2014
    Co-Authors: Jianhu Shen, Xiaodong Huang, Yi Min Xie, Shiwei Zhou, Dong Ruan
    Abstract:

    Insight into the stimuli-responsive behaviour of biological Materials with hierarchical microstructures is essential for designing new sustainable Materials and structures. Shape memory, self-healing and self-repairing will become valuable characteristics of advanced Materials. Here we report the water-triggered shape recovery of a natural biological Material, the luffa sponge. The longitudinally crushed luffa sponge column can recover up to 98% of its original shape after it is immersed in water. The mechanical properties of the luffa sponge can also be recovered, to a large extent, after a subsequent drying process. The effects of strain rate, crushing strains, loading cycles, and temperature/duration of water treatment of the drying process on the shape recovery ratio and the energy dissipation recovery ratio have been investigated. The results from this study have demonstrated that the luffa sponge Material possesses remarkable shape memory effects and mechanical recovery features which could be exploited or biomimicked for the design of water-responsive smart Materials undergoing large deformations.

  • topological design of microstructures of Cellular Materials for maximum bulk or shear modulus
    Computational Materials Science, 2011
    Co-Authors: Xiaodong Huang, A. Radman, Yi Min Xie
    Abstract:

    This paper presents a new approach to designing periodic microstructures of Cellular Materials. The method is based on the bidirectional evolutionary structural optimization (BESO) technique. The optimization problem is formulated as finding a micro-structural topology with the maximum bulk or shear modulus under a prescribed volume constraint. Using the homogenization theory and finite element analysis within a periodic base cell (PBC), elemental sensitivity numbers are established for gradually removing and adding elements in PBC. Numerical examples in 2D and 3D demonstrate the effectiveness of the proposed method for achieving convergent microstructures of Cellular Materials with maximum bulk or shear modulus. Some interesting topological patterns have been found for guiding the Cellular Material design.

John J Harrigan - One of the best experts on this subject based on the ideXlab platform.

  • air blast response of Cellular Material with a face plate an analytical numerical approach
    International Journal of Mechanical Sciences, 2015
    Co-Authors: Majid Aleyaasin, John J Harrigan, S R Reid
    Abstract:

    Abstract The air-blast response of a sacrificial cladding consisting of a Cellular Material with a front face-plate is investigated. The Cellular Material is sandwiched between a rigid face-plate and a rigid support. The support represents the structure that is to be protected. The air blast is assumed to be an exponentially decaying pulse. The Cellular Material is idealised as rigid, perfectly-plastic, locking and the deformation is governed by the propagation of a compaction (shock) wave travelling through the Material. A second order nonlinear ordinary differential equation is derived to predict the displacement of the face-plate and the compression of the Cellular layer by coupling the reflected over-pressure with the stresses at the interface between the face-plate and the Cellular Material. The Cellular Material may attenuate or enhance the shock transmitted to the structure. Extensive simulations are carried out to define the attenuation/enhancement boundary for a range of initial peak pressures and cladding parameters. Herein, enhancement is considered to occur if the shock front reaches the support. A new method of accounting for fluid–structure interaction (FSI) is derived. The predictions are compared to those with no FSI as well as an existing model that accounts for the FSI effect, but for a free-standing plate.

  • dynamic stress strain states for metal foams using a 3d Cellular model
    Journal of The Mechanics and Physics of Solids, 2014
    Co-Authors: Zhijun Zheng, S R Reid, Changfeng Wang, John J Harrigan
    Abstract:

    Abstract Dynamic uniaxial impact behaviour of metal foams using a 3D cell-based finite element model is examined. At sufficiently high loading rates, these Materials respond by forming ‘shock or consolidation waves’ ( Tan et al., 2005a , Tan et al., 2005b ). However, the existing dynamic experimental methods have limitations in fully informing this behaviour, particularly for solving boundary/initial value problems. Recently, the problem of the shock-like response of an open-cell foam has been examined by Barnes et al. (2014) using the Hugoniot-curve representations. The present study is somewhat complementary to that approach and additionally aims to provide insight into the ‘rate sensitivity’ mechanism applicable to Cellular Materials. To assist our understanding of the ‘loading rate sensitivity’ behaviour of Cellular Materials, a virtual ‘test’ method based on the direct impact technique is explored. Following a continuum representation of the response, the strain field calculation method is employed to determine the local strains ahead of and behind the resulting ‘shock front’. The dynamic stress–strain states in the densification stage are found to be different from the quasi-static ones. It is evident that the constitutive behaviour of the Cellular Material is deformation-mode dependent. The nature of the ‘rate sensitivity’ revealed for Cellular Materials in this paper is different from the strain-rate sensitivity of dense metals. It is shown that the dynamic stress–strain states behind a shock front of the Cellular Material lie on a unique curve and each point on the curve corresponds to a particular ‘impact velocity’, referred as the velocity upstream of the shock in this study. The dynamic stress–strain curve is related to a layer-wise collapse mode, whilst the equivalent quasi-static curve is related to a random shear band collapse mode. The findings herein are aimed at improving the experimental test techniques used to characterise the rate-sensitivity behaviour of real Cellular Materials and providing data appropriate to solving dynamic loading problems in which Cellular metals are utilised.

  • the correct analysis of shocks in a Cellular Material
    International Journal of Impact Engineering, 2010
    Co-Authors: John J Harrigan, S R Reid, Seyed A Yaghoubi
    Abstract:

    Abstract Cellular Materials have applications for impact and blast protection. Under impact/impulsive loading the response of the Cellular solid can be controlled by compaction (or shock, see Tan et al. (2005) [3] , [4] ) waves. Different analytical and computational solutions have been produced to model this behaviour but these solutions provide conflicting predictions for the response of the Material in certain loading scenarios. The different analytical approaches are discussed using two simple examples for clarity. The differences between apparently similar “models” are clarified. In particular, it is argued that mass-spring models are not capable of modelling the discontinuities that exist in a compaction wave in a Cellular Material.

Xiaodong Huang - One of the best experts on this subject based on the ideXlab platform.

  • water responsive rapid recovery of natural Cellular Material
    Journal of The Mechanical Behavior of Biomedical Materials, 2014
    Co-Authors: Jianhu Shen, Xiaodong Huang, Yi Min Xie, Shiwei Zhou, Dong Ruan
    Abstract:

    Insight into the stimuli-responsive behaviour of biological Materials with hierarchical microstructures is essential for designing new sustainable Materials and structures. Shape memory, self-healing and self-repairing will become valuable characteristics of advanced Materials. Here we report the water-triggered shape recovery of a natural biological Material, the luffa sponge. The longitudinally crushed luffa sponge column can recover up to 98% of its original shape after it is immersed in water. The mechanical properties of the luffa sponge can also be recovered, to a large extent, after a subsequent drying process. The effects of strain rate, crushing strains, loading cycles, and temperature/duration of water treatment of the drying process on the shape recovery ratio and the energy dissipation recovery ratio have been investigated. The results from this study have demonstrated that the luffa sponge Material possesses remarkable shape memory effects and mechanical recovery features which could be exploited or biomimicked for the design of water-responsive smart Materials undergoing large deformations.

  • topological design of microstructures of Cellular Materials for maximum bulk or shear modulus
    Computational Materials Science, 2011
    Co-Authors: Xiaodong Huang, A. Radman, Yi Min Xie
    Abstract:

    This paper presents a new approach to designing periodic microstructures of Cellular Materials. The method is based on the bidirectional evolutionary structural optimization (BESO) technique. The optimization problem is formulated as finding a micro-structural topology with the maximum bulk or shear modulus under a prescribed volume constraint. Using the homogenization theory and finite element analysis within a periodic base cell (PBC), elemental sensitivity numbers are established for gradually removing and adding elements in PBC. Numerical examples in 2D and 3D demonstrate the effectiveness of the proposed method for achieving convergent microstructures of Cellular Materials with maximum bulk or shear modulus. Some interesting topological patterns have been found for guiding the Cellular Material design.

Carl R Larsen - One of the best experts on this subject based on the ideXlab platform.

  • regression of large pelvic desmoid tumor by tamoxifen and sulindac
    Urology, 1996
    Co-Authors: Joseph K Izes, Leonard Zinman, Carl R Larsen
    Abstract:

    A 54-year-old man was evaluated for symptoms of bladder outlet obstruction. Evaluation revealed a 10 by 9.8-cm tumor composed of bland, fibroblastic, poorly Cellular Material adjacent to the prostate. Administration of a course of antiestrogen (tamoxifen) and a nonsteroidal anti-inflammatory agent (sulindac) resulted in prompt relief of symptoms and a slow decrease in the size of the tumor as measured by computed tomography. After 54 months of therapy, the tumor was undetectable clinically and dramatically reduced in size as seen on computed tomography. Data on the natural history of desmoid tumors and the efficacy of various therapeutic strategies are reviewed.