Search results for " Plasticity"
showing 10 items of 494 documents
Infrared thermography-based evaluation of the elastic-plastic J-integral to correlate fatigue crack growth data of a stainless steel
2019
Abstract The elastic-plastic J-integral is adopted to correlate fatigue crack growth data of ductile metals. An analytical link is known to exist between the J-integral and the strain energy density averaged in a control volume embracing the crack tip. On the other hand, the strain energy fluctuation is the source of temperature variations close to a fatigue crack tip of a metal material; hence the possibility to measure the J-integral from infrared thermographic scanning at the crack tip is envisaged and it is the focus of this paper. It is proposed that the elastic component of the J-integral is derived from a thermoelastic stress analysis, while the plastic component of the J-integral is…
Cohesive–frictional interface constitutive model
2009
AbstractIn the framework of numerical analysis of joined bodies, the present paper is devoted to the constitutive modeling, via an interface kinematic formulation, of mechanical behaviour of internal adhesive layers. The proposed interface constitutive model couples a cohesive behaviour, based on the damage mechanics theory, with a frictional one, defined in a non-associative plasticity framework. Namely, the interface formulation follows the transition of the adhesive material from the sound elastic condition to the fully cracked one. This formulation is able to model, by means of a specific interpretation of the damage variable and in a relevant mathematical setting, the interface interme…
A grain boundary formulation for crystal plasticity
2016
Abstract A three-dimensional grain-boundary formulation for small strains crystal plasticity is presented for the first time. The method is developed and implemented for both single grains and polycrystalline aggregates and it is based on the use of a suitable set of boundary integral equations for modelling the individual grains, which are represented as anisotropic elasto-plastic domains. In the boundary integral framework, crystal plasticity is modelled resorting to an initial strains approach and specific aspects, related to the integration of strongly singular volume integrals in the anisotropic elasto-plastic grain-boundary equations, are discussed and suitably addressed for the first…
Interfacial energy effects within the framework of strain gradient plasticity
2009
AbstractIn the framework of strain gradient plasticity, a solid body with boundary surface playing the role of a dissipative boundary layer endowed with surface tension and surface energy, is addressed. Using the so-called residual-based gradient plasticity theory, the state equations and the higher order boundary conditions are derived quite naturally for both the bulk material and the boundary layer. A phenomenological constitutive model is envisioned, in which the bulk material and the boundary layer obey (rate independent associative) coupled plasticity evolution laws, with kinematic hardening laws of differential nature for the bulk material, but of nondifferential nature for the layer…
Boundary Element Crystal Plasticity Method
2017
A three-dimensional (3D) boundary element method for small strains crystal plasticity is described. The method, developed for polycrystalline aggregates, makes use of a set of boundary integral equations for modeling the individual grains, which are represented as anisotropic elasto-plastic domains. Crystal plasticity is modeled using an initial strains boundary integral approach. The integration of strongly singular volume integrals in the anisotropic elasto-plastic grain-boundary equations are discussed. Voronoi-tessellation micro-morphologies are discretized using nonstructured boundary and volume meshes. A grain-boundary incremental/iterative algorithm, with rate-dependent flow and har…
A thermodynamic approach to nonlocal plasticity and related variational principles
1999
Elastic-plastic rate-independent materials with isotropic hardening/softening of nonlocal nature are considered in the context of small displacements and strains. A suitable thermodynamic framework is envisaged as a basis of a nonlocal associative plasticity theory in which the plastic yielding laws comply with a (nonlocal) maximum intrinsic dissipation theorem. Additionally, the rate response problem for a (continuous) set of (macroscopic) material particles, subjected to a given total strain rate field, is discussed and shown to be characterized by a minimum principle in terms of plastic coefficient. This coefficient and the relevant continuum tangent stiffness matrix are shown to admit, …
What do leaf anatomy and micromorphology tell us about the psammophilous Pancratium maritimum (Amaryllidaceae) in response to sand dune conditions?
2015
Abstract The present study aimed at verifying the morphological variation in leaf traits among different populations of Pancratium maritimum (sea daffodil) and the correlation between leaf diversity and climate conditions at different sites. Eleven populations of P. maritimum from Mediterranean coastal sand dunes were investigated with respect to leaf surface micro-morphology, leaf anatomy, and vascular pattern. Morphometric analysis was based on 29 quantitative foliar parameters. One-way analysis of variance (ANOVA), principal component analysis (PCA), discriminant function analysis (DFA), and clustering by Ward’s method were used for the statistical evaluation. Results revealed a rather u…
Synaptic Scaling Enables Dynamically Distinct Short- and Long-Term Memory Formation
2013
Memory storage in the brain relies on mechanisms acting on time scales from minutes, for long-term synaptic potentiation, to days, for memory consolidation. During such processes, neural circuits distinguish synapses relevant for forming a long-term storage, which are consolidated, from synapses of short-term storage, which fade. How time scale integration and synaptic differentiation is simultaneously achieved remains unclear. Here we show that synaptic scaling – a slow process usually associated with the maintenance of activity homeostasis – combined with synaptic plasticity may simultaneously achieve both, thereby providing a natural separation of short- from long-term storage. The inter…
Morphology, Plasticity, and Transformation between Philosophy and Biology
2020
In biology, interest in form was the prerogative of developmental biology, while it was practically neglected by evolutionary biology. This situation has changed a lot in recent decades and has led to a reinterpretation of the concept of evolution and evolutionism focusing more on the problem of form and morphology. In Italy, especially Alessandro Minelli, one of the editors of this issue, has dedicated his studies to the need to communicate form to structure, to reconnect morphology and evolution. This theme is a highly relevant one for philosophy, inasmuch as the question of form and morphology, since the days of Goethe and Bergson, has always been considered as the starting point for a p…
Editors��� Introduction: Morphology, Organism, Evolution
2021
In biology, interest in form was the prerogative of developmental biology, while it was practically neglected by evolutionary biology. This situation has changed a lot in recent decades and has led to a reinterpretation of the concept of evolution and evolutionism focusing more on the problem of form and morphology. In Italy, especially Alessandro Minelli, one of the editors of this issue, has dedicated his studies to the need to communicate form to structure, to reconnect morphology and evolution. This theme is a highly relevant one for philosophy, inasmuch as the question of form and morphology, since the days of Goethe and Bergson, has always been considered as the starting point for a p…