Search results for "plasticity"

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…

Atmosphere-induced change of microhardness and plasticity of C60 single crystals and polycrystalline films

1998

Abstract The effect of air exposure and visible light illumination on the microhardness, plasticity and dislocation mobility in the C60 single crystals was investigated. Microhardness values for defined structural states of the fullerene (pristine, oxygen-intercalated, photo-oxidized) are reported. It has been shown that oxygen intercalation in the fullerene lattice during air-aging in the dark results in the suppression of dislocation mobility. However, only a slight increase in the hardness of oxygenated samples was observed. A remarkable increase in the hardness and decrease in the plasticity of the C60 crystals under illumination-assisted air exposure was noted. Photochemical transforma…

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…

Response of Cross-Ply Composite to Off-Axis Loading

2002

Polymer composites are known to exhibit nonlinear stress–strain response due to nonlinearly elastic or plastic deformation of the matrix and damage accumulation. Mechanistic modeling of material response explicitly accounting for these interacting factors often leads to complex theories. Plasticity theory formalism provides an alternative for nonlinear deformation description of composite material. We examine the applicability of an orthotropic plasticity model, developed by Sun et al. for unidirectionally reinforced composite, to composite laminate. The response of a symmetric and balanced cross-ply glass/epoxy laminate is studied under uniaxial tensile loading at different angles to the …

Some comments on the paper “Microplane constitutive model and metal plasticity” (Brocca M and Bazˇant ZP, 2000, Appl Mech Rev53(10) 265–281)

2002

Beta-forging of Ti6Al4V titanium alloy powders consolidated by HIP: Plastic flow and strain-rate relation

2014

Ti6Al4V is probably the best known and studied titanium alloy, not only for aerospace applications. Nevertheless the deformation behavior still represents a challenge if any modification in the deformation process is required or introduced. This work deals with deformation behavior description of Ti6Al4V HIPped powders during high temperature deformation tests carried on in the Beta-region. Laboratory compression and tensile tests have been coupled with relaxation tests in order to achieve robust data about strain rate sensibility m-coefficient and activation energy Q. These results have been fitted for the assessment of a more general exponential deformation law. The final result is a “Dor…

Radiation effects on stress evolution and dimensional stability of large fusion energy structures

2021

Abstract We assess the effects of neutron irradiation on the deformation and stress evolution of large-scale fusion energy structures. This is accomplished through non-linear finite element structural analysis of the coupled thermal and mechanical fields at the Beginning-Of-Life (BOL), at 45 dpa, and at 90 dpa. Radiation effects include volumetric swelling and the influence of radiation on the mechanical properties. The system studied here is a large section of a full inboard module of an integrated structure comprising the First Wall and Blanket (FW/B) of a Dual Cooled Lithium-Lead (DCLL) energy conversion unit in the Fusion Nuclear Science Facility (FNSF). The structural material is the f…

Corrosion Behaviour of Ti6Al4V and TiMo10Zr4 Alloys in the Ringer’s Solution: Effect of pH and Plastic Strain

2015

The corrosion behaviour of titanium alloys is not well understood – especially the role of the microstructure and plastic strain. In this paper, the influence of the microstructure and plastic strain on the corrosion resistance of TiMo10Zr4 and Ti6Al4V alloys was studied in the Ringer’s solution at 37 °C. Measurements were performed for different pH values and in aerated and de-aerated solutions using potentiodynamic polarization techniques. Results obtained on the two alloys were compared. It was shown that in the absence of plastic strain TiMo10Zr4 shows better corrosion resistance than Ti6Al4V (especially for pH = 8). By contrast, the current density in the passive range measured after 8…

Mapping the 3D-surface strain field of patterned tensile stainless steels using atomic force microscopy.

2005

Abstract The quantification of microstructural strains at the surface of materials is of major importance for understanding the reactivity of solids. The present paper aims at demonstrating the potentialities of the atomic force microscopy (AFM) for mapping the three-dimensional surface strain field on patterned tensile specimens. Electron beam (e-beam) lithography has been used to deposit 16×16 arrays of gold-squared pads. Monitoring the evolution of such a pattern under applied strain allows to quantify the triaxial strains both at the micro-(plastic) domain and nanoscale (elastic) domain vs. applied strain. The proposed method was applied to stainless steels after 4.5% plastic strain.

Interface Models for the Analysis of Time-Dependent Effects in Masonry Structures

2001

The present paper is devoted to the theoretical formulation and numerical implementation of an interface model suitable to simulate the behavior of cementitious joints at long term. The interface laws are formulated in the framework of viscoplasticity for non standard materials in order to simulate the time-dependent softening response which occurs along the decohesion process in presence of shear and tension tractions. The interface model parameters identification is discussed on the base of experimental data reported in the literature. The optimization problem related to the parameters evaluation is approached by a heuristic algorithm. Finally some examples show the capabilities of the pr…