Search results for "plasticity"

A thermodynamically consistent formulation of nonlocal and gradient plasticity

1998

Surface effects, boundary conditions and evolution laws within second strain gradient plasticity

2014

Abstract The principle of the virtual power (PVP) is used in conjunction with the concepts of “energy residual” and “insulation condition” to address second strain gradient plasticity. The energy residual with its typical divergence format is an extra stress power playing the role of basic state variable to describe the gradient effects, whereas the insulation condition constitutes a global energy characterization of the body as part of the body/environment system. The microstructure of a second strain gradient material (but not of a first strain gradient one) is shown to exhibit surface effects with the formation of a thin boundary layer. This boundary layer is in local (and global) equili…

INVESTIGATIONS OF STRAIN AND STRESS STATE AND CAPACITY IN SHORT CYLINDRICAL SHELLS UNDER INTERNAL PRESSURE

1989

In the paper it has been assumed that a triaxial stress and strain state occurs in a shell. The finite element method was used and owing to that digitization of the problem was possible. Such digitization was necessary for a numerical analysis of the moment stress state in the shell. On the ground of physical relations of the Prandtl-Reuss plastic flow theory an algorithm was formulated. The algorithm was a basis of calculating strains and stresses and determining capacity in a short cylindrical shell with rigid bottoms. The shell was subject to internal pressure. Experiments were carried out, as well. The results obtained with: equations of the membraneous shell theory, using plastic flow …

On the Conditions to Prevent Plastic Shakedown of Structures: Part I—Theory

1993

For a structure of elastic perfectly plastic material subjected to a given cyclic (mechanical and/or kinematical) load and to a steady (mechanical) load, the conditions are established in which plastic shakedown cannot occur whatever the steady load, and thus the structure is safe against the alternating plasticity collapse. Static and kinematic theorems, analogous to those of classical shakedown theory, are presented.

A Study on Plastic Shakedown of Structures: Part I—Basic Properties

1993

For a continuous elastic-perfectly plastic solid body subjected to a combination of cyclic (mechanical and/or kinematical) load and of a steady (mechanical) load such as to produce plastic shakedown (i.e., alternating plasticity), a number of characterizing properties are established and discussed. The conditions for the body’s transition from plastic shakedown to ratchetting are also addressed.

On the Conditions to Prevent Plastic Shakedown of Structures: Part II—The Plastic Shakedown Limit Load

1993

Following the results of a companion paper, the concept of plastic shakedown limit load is introduced for an elastic-perfectly plastic material structure subjected to combined cyclic (mechanical and/or kinematical) loads and steady (mechanical) load. Static and kinematic approaches are available for the computation of this load, in perfect analogy with the classic (elastic) shakedown limit load. The plastic shakedown limit state of the structure being in an impending alternating plasticity collapse is studied and a number of interesting features of it are pointed out.

FEM analysis of push-out test response of Hybrid Steel Trussed Concrete Beams (HSTCBs)

2015

Abstract Aiming to investigate the steel truss–concrete stress transfer mechanism in Hybrid Steel Trussed–Concrete Beams (HSTCBs), a three-dimensional (3D) nonlinear Finite Element (FE) model is developed. The constitutive relationship of the steel composing the plates and the rebars is modeled by means of a quadri-linear law, while the concrete behavior is defined by means of a Concrete Damaged Plasticity (CDP) model, suitable for modeling concrete and brittle materials. Two main failure mechanisms are considered, namely the tensile cracking and the compressive crushing. In order to accurately grasp the complicate dowel and bond phenomena arising at the steel–concrete interface, a 3D solid…

RETA A TU MENTE, DESAFÍA A TU CEREBRO: COMPLEJIDAD AMBIENTAL Y SALUD CEREBRAL

2016

Abstract.According to the World Health Organization, it is estimated that more than 30 million people suffer from Alzheimer’s disease in the world. Currently, there is great interest in developing strategies to counteract the cognitive decline that accompanies aging and, to a greater extent, neurodegenerative diseases. The aim of the current study is to analyze the experimental evidence supporting the hypothesis that interventions based on novelty and complexity are more effective in order to achieve successful aging. In animal models it has shown that enriched environments and performing voluntary exercise can improve performance in learning and memory tasks, decrease anxiety response and …

Effect of the host plant on the immunity of a phytophagous insect : influence of grape variety on the ability of the European grapevine moth to defen…

2013

In tritrophic interactions involving phytophagous insects, host plants and natural enemies, trophic levels are highly dependent on each other. Host plant may strongly affect directly phytophagous insect and indirectly natural enemies growing on these phytophagous insects. When a natural enemy attacks a phytophagous insect, the host immune system constitutes the last chance for the host to survive to an infection. A great variation of insect immune system is generally found in populations for susceptibility to pathogens, suggesting that variable selection pressures may have shaped and driven adaptation of immune traits. This project aims to determine the influence of both host plant and natu…

Role of Diffusion in Superplasticity and Brittleness of Fine-Grained Binary Eutectics

2005

Mechanical properties of interphase boundaries (IB), stability of defects and microstructure in heavily deformed binary eutectics (Al-Sn, Zn-Sn, Pb-Sn, Cd-Sn, Bi-Sn) have been investigated at room temperature. Experiments were carried out on atomically clean surfaces of alloys and on bimetallic joints with clean interface. It has been shown that after severe deformation the phases are strengthened and relaxation processes occur mainly on the boundaries in all eutectics. For superplastic eutectics with low interphase boundary energy the intensive development of the diffusion – controlled processes of self- healing, sintering, segregation and enveloping were observed. These diffusion processe…