The Experts below are selected from a list of 171363 Experts worldwide ranked by ideXlab platform
Markus J Buehler - One of the best experts on this subject based on the ideXlab platform.
-
flaw tolerance of nuclear intermediate filament lamina under extreme Mechanical Deformation
ACS Nano, 2011Co-Authors: Zhao Qin, Markus J BuehlerAbstract:The nuclear lamina, composed of intermediate filaments, is a structural protein meshwork at the nuclear membrane that protects genetic material and regulates gene expression. Here we uncover the physical basis of the material design of nuclear lamina that enables it to withstand extreme Mechanical Deformation of >100% strain despite the presence of structural defects. Through a simple in silico model we demonstrate that this is due to nanoscale mechanisms including protein unfolding, alpha-to-beta transition, and sliding, resulting in a characteristic nonlinear force−extension curve. At the larger microscale this leads to an extreme delocalization of Mechanical energy dissipation, preventing catastrophic crack propagation. Yet, when catastrophic failure occurs under extreme loading, individual protein filaments are sacrificed rather than the entire meshwork. This mechanism is theoretically explained by a characteristic change of the tangent stress−strain hardening exponent under increasing strain. Our res...
-
flaw tolerance of nuclear intermediate filament lamina under extreme Mechanical Deformation
ACS Nano, 2011Co-Authors: Zhao Qin, Markus J BuehlerAbstract:The nuclear lamina, composed of intermediate filaments, is a structural protein meshwork at the nuclear membrane that protects genetic material and regulates gene expression. Here we uncover the physical basis of the material design of nuclear lamina that enables it to withstand extreme Mechanical Deformation of >100% strain despite the presence of structural defects. Through a simple in silico model we demonstrate that this is due to nanoscale mechanisms including protein unfolding, alpha-to-beta transition, and sliding, resulting in a characteristic nonlinear force-extension curve. At the larger microscale this leads to an extreme delocalization of Mechanical energy dissipation, preventing catastrophic crack propagation. Yet, when catastrophic failure occurs under extreme loading, individual protein filaments are sacrificed rather than the entire meshwork. This mechanism is theoretically explained by a characteristic change of the tangent stress-strain hardening exponent under increasing strain. Our results elucidate the large extensibility of the nuclear lamina within muscle or skin tissue and potentially many other protein materials that are exposed to extreme Mechanical conditions, and provide a new paradigm toward the de novo design of protein materials by engineering the nonlinear stress-strain response to facilitate flaw-tolerant behavior.
Yuris A Dzenis - One of the best experts on this subject based on the ideXlab platform.
-
Mechanical Deformation and failure of electrospun polyacrylonitrile nanofibers as a function of strain rate
Applied Physics Letters, 2007Co-Authors: Mohammad Naraghi, Ioannis Chasiotis, H Kahn, Yuris A DzenisAbstract:The Mechanical Deformation of 12μm long electrospun polyacrylonitrile (PAN) nanofibers with diameters of 300–600nm was investigated. The nanofibers were subjected to cold drawing in atmospheric conditions and at strain rates between 10−2 and 10−4s−1. The ultimate strain of the PAN nanofibers was 60%–130% varying monotonically with the strain rate. On the contrary, the fiber tensile strength, ranging between 30 and 130MPa, varied nonmonotonically with the slowest drawing rate resulting in the largest ductilities and fiber strengths. At the two faster rates, the large fiber ductilities originated in the formation of a cascade of ripples (necks), while at the slowest strain rate, the nanofibers deformed homogeneously allowing for the largest engineering strengths and extension ratios.The Mechanical Deformation of 12μm long electrospun polyacrylonitrile (PAN) nanofibers with diameters of 300–600nm was investigated. The nanofibers were subjected to cold drawing in atmospheric conditions and at strain rates between 10−2 and 10−4s−1. The ultimate strain of the PAN nanofibers was 60%–130% varying monotonically with the strain rate. On the contrary, the fiber tensile strength, ranging between 30 and 130MPa, varied nonmonotonically with the slowest drawing rate resulting in the largest ductilities and fiber strengths. At the two faster rates, the large fiber ductilities originated in the formation of a cascade of ripples (necks), while at the slowest strain rate, the nanofibers deformed homogeneously allowing for the largest engineering strengths and extension ratios.
-
Mechanical Deformation and failure of electrospun polyacrylonitrile nanofibers as a function of strain rate
Applied Physics Letters, 2007Co-Authors: Mohammad Naraghi, Ioannis Chasiotis, H Kahn, Yongkui Wen, Yuris A DzenisAbstract:The Mechanical Deformation of 12μm long electrospun polyacrylonitrile (PAN) nanofibers with diameters of 300–600nm was investigated. The nanofibers were subjected to cold drawing in atmospheric conditions and at strain rates between 10−2 and 10−4s−1. The ultimate strain of the PAN nanofibers was 60%–130% varying monotonically with the strain rate. On the contrary, the fiber tensile strength, ranging between 30 and 130MPa, varied nonmonotonically with the slowest drawing rate resulting in the largest ductilities and fiber strengths. At the two faster rates, the large fiber ductilities originated in the formation of a cascade of ripples (necks), while at the slowest strain rate, the nanofibers deformed homogeneously allowing for the largest engineering strengths and extension ratios.
Zhao Qin - One of the best experts on this subject based on the ideXlab platform.
-
flaw tolerance of nuclear intermediate filament lamina under extreme Mechanical Deformation
ACS Nano, 2011Co-Authors: Zhao Qin, Markus J BuehlerAbstract:The nuclear lamina, composed of intermediate filaments, is a structural protein meshwork at the nuclear membrane that protects genetic material and regulates gene expression. Here we uncover the physical basis of the material design of nuclear lamina that enables it to withstand extreme Mechanical Deformation of >100% strain despite the presence of structural defects. Through a simple in silico model we demonstrate that this is due to nanoscale mechanisms including protein unfolding, alpha-to-beta transition, and sliding, resulting in a characteristic nonlinear force−extension curve. At the larger microscale this leads to an extreme delocalization of Mechanical energy dissipation, preventing catastrophic crack propagation. Yet, when catastrophic failure occurs under extreme loading, individual protein filaments are sacrificed rather than the entire meshwork. This mechanism is theoretically explained by a characteristic change of the tangent stress−strain hardening exponent under increasing strain. Our res...
-
flaw tolerance of nuclear intermediate filament lamina under extreme Mechanical Deformation
ACS Nano, 2011Co-Authors: Zhao Qin, Markus J BuehlerAbstract:The nuclear lamina, composed of intermediate filaments, is a structural protein meshwork at the nuclear membrane that protects genetic material and regulates gene expression. Here we uncover the physical basis of the material design of nuclear lamina that enables it to withstand extreme Mechanical Deformation of >100% strain despite the presence of structural defects. Through a simple in silico model we demonstrate that this is due to nanoscale mechanisms including protein unfolding, alpha-to-beta transition, and sliding, resulting in a characteristic nonlinear force-extension curve. At the larger microscale this leads to an extreme delocalization of Mechanical energy dissipation, preventing catastrophic crack propagation. Yet, when catastrophic failure occurs under extreme loading, individual protein filaments are sacrificed rather than the entire meshwork. This mechanism is theoretically explained by a characteristic change of the tangent stress-strain hardening exponent under increasing strain. Our results elucidate the large extensibility of the nuclear lamina within muscle or skin tissue and potentially many other protein materials that are exposed to extreme Mechanical conditions, and provide a new paradigm toward the de novo design of protein materials by engineering the nonlinear stress-strain response to facilitate flaw-tolerant behavior.
Karsten Wedel Jacobsen - One of the best experts on this subject based on the ideXlab platform.
-
atomic scale simulations of the Mechanical Deformation of nanocrystalline metals
Physical Review B, 1999Co-Authors: Jakob Schiotz, Tejs Vegge, F D Di Tolla, Karsten Wedel JacobsenAbstract:simulations of the plastic behavior of nanocrystalline copper. The simulations show that the main Deformation mode is sliding in the grain boundaries through a large number of uncorrelated events, where a few atoms ~or a few tens of atoms! slide with respect to each other. Little dislocation activity is seen in the grain interiors. The localization of the Deformation to the grain boundaries leads to a hardening as the grain size is increased ~reverse Hall-Petch effect!, implying a maximum in hardness for a grain size above the ones studied here. We investigate the effects of varying temperature, strain rate, and porosity, and discuss the relation to recent experiments. At increasing temperatures the material becomes softer in both the plastic and elastic regime. Porosity in the samples result in a softening of the material; this may be a significant effect in many experiments. @S0163-1829~99!05941-X# I. INTRODUCTION The modeling of the Mechanical properties of everyday materials is a very challenging problem. The main difficulty is the vastly different length and time scales at which the various processes occur during Deformation—ranging from
-
Mechanical Deformation of atomic scale metallic contacts structure and mechanisms
Physical Review B, 1998Co-Authors: Mads Reinholdt Sorensen, Mads Brandbyge, Karsten Wedel JacobsenAbstract:We have simulated the Mechanical Deformation of atomic-scale metallic contacts under tensile strain using molecular dynamics and effective medium theory potentials. The evolution of the structure of the contacts and the underlying Deformation mechanisms are described along with the calculated electronic conductance. Various defects such as intersecting stacking faults, local disorder, and vacancies are created during the Deformation. Disordered regions act as weak spots that reduce the strength of the contacts. The disorder tends to anneal out again during the subsequent atomic rearrangements, but vacancies can be permanently present. The transition states and energies for slip mechanisms have been determined using the nudged elastic band method, and we find a size-dependent crossover from a dislocation-mediated slip to a homogeneous slip when the contact diameter becomes less than a few nm. We show that the results measured in a nanocontact experiment depend significantly on the elastic stiffness of the experimental apparatus. For a soft setup, some of the atomic rearrangements might not be detected, whereas others are amplified.
Mohammad Naraghi - One of the best experts on this subject based on the ideXlab platform.
-
Mechanical Deformation and failure of electrospun polyacrylonitrile nanofibers as a function of strain rate
Applied Physics Letters, 2007Co-Authors: Mohammad Naraghi, Ioannis Chasiotis, H Kahn, Yuris A DzenisAbstract:The Mechanical Deformation of 12μm long electrospun polyacrylonitrile (PAN) nanofibers with diameters of 300–600nm was investigated. The nanofibers were subjected to cold drawing in atmospheric conditions and at strain rates between 10−2 and 10−4s−1. The ultimate strain of the PAN nanofibers was 60%–130% varying monotonically with the strain rate. On the contrary, the fiber tensile strength, ranging between 30 and 130MPa, varied nonmonotonically with the slowest drawing rate resulting in the largest ductilities and fiber strengths. At the two faster rates, the large fiber ductilities originated in the formation of a cascade of ripples (necks), while at the slowest strain rate, the nanofibers deformed homogeneously allowing for the largest engineering strengths and extension ratios.The Mechanical Deformation of 12μm long electrospun polyacrylonitrile (PAN) nanofibers with diameters of 300–600nm was investigated. The nanofibers were subjected to cold drawing in atmospheric conditions and at strain rates between 10−2 and 10−4s−1. The ultimate strain of the PAN nanofibers was 60%–130% varying monotonically with the strain rate. On the contrary, the fiber tensile strength, ranging between 30 and 130MPa, varied nonmonotonically with the slowest drawing rate resulting in the largest ductilities and fiber strengths. At the two faster rates, the large fiber ductilities originated in the formation of a cascade of ripples (necks), while at the slowest strain rate, the nanofibers deformed homogeneously allowing for the largest engineering strengths and extension ratios.
-
Mechanical Deformation and failure of electrospun polyacrylonitrile nanofibers as a function of strain rate
Applied Physics Letters, 2007Co-Authors: Mohammad Naraghi, Ioannis Chasiotis, H Kahn, Yongkui Wen, Yuris A DzenisAbstract:The Mechanical Deformation of 12μm long electrospun polyacrylonitrile (PAN) nanofibers with diameters of 300–600nm was investigated. The nanofibers were subjected to cold drawing in atmospheric conditions and at strain rates between 10−2 and 10−4s−1. The ultimate strain of the PAN nanofibers was 60%–130% varying monotonically with the strain rate. On the contrary, the fiber tensile strength, ranging between 30 and 130MPa, varied nonmonotonically with the slowest drawing rate resulting in the largest ductilities and fiber strengths. At the two faster rates, the large fiber ductilities originated in the formation of a cascade of ripples (necks), while at the slowest strain rate, the nanofibers deformed homogeneously allowing for the largest engineering strengths and extension ratios.