Dimensional Plasticity Research Articles

Онтогенетическая и виталитетная структура ценопопуляций Globularia bisnagarica L. в Среднем и Нижнем Поволжье

The article presents the results of studying the ontogenetic and vitality structure of 13 cenopopulations of Globularia bisnagarica from the Middle and Lower Volga region. The assessment of the ontogenetic structure was carried out by constructing and analyzing the ontogenetic spectra of each of the studied cenopopulations, as well as the basic ontogenetic spectrum, followed by determining the type of cenopopulations according to the “delta-omega” criterion. On the basis of morphometric parameters, the vitality indices of individuals and cenopopulations were determined, followed by the identification of vitality types and the calculation of the dimensional plasticity index. It has been established that the ontogenetic spectra of the majority of cenopopulations are complete, asymmetric, with peaks in several age groups. The basic ontogenetic spectrum is bimodal, asymmetrical, with a maximum on virginal and mature generative individuals. The majority of G. bisnagarica cenopopulations are young, being dominated by individuals of the pregenerative state. The Srg cenopopulation growing on the territory of the Samara region consisted mainly of individuals of the post-generative state. Four cenopopulations (Pch, Grm, Lhv, Bkm) turned out to be transitional, since they are dominated by generative individuals. According to the assessment of the vitality state, individuals of the middle class of vitality predominated in all the studied cenopopulations. At the same time, most of the studied cenopopulations are defined as prosperous. Likewise, only two cenopopulations: Grm and Lhv from the Ulyanovsk region were characterized as depressed. Thus, taking into account the features above, the general condition of the three cenopopulations: Srg, Grm and Lhv is assessed as unsatisfactory, which makes them the most vulnerable in the event of the impact of adverse environmental factors or an increase in anthropogenic pressure on their habitats.

A Three Dimensional Plasticity Model for Sands Based on State Concept

A three dimensional plasticity model for shear deformation in sand is developed based on the plane strain model of Cubrinovski and Ishihara [1]. The model uses a circular bounding surface. The model is hypoplastic in nature, rendering the principal directions of plastic strain increment different from those of the stress, and thus, allows for accumulation of plastic strain with principal stress rotation. The model uses the multi-surface based mixed hardening rule. This paper presents results from simulations under bi-directional (torsional-stress path) uniform stress cycles, as well as bi-directional stress-controlled simulation results, where two orthogonal horizontal components of a ground acceleration time series are converted to bi-directional stress history, providing a rigorous verification of the algorithm.

A three dimensional plasticity model for perpendicular to grain cohesive fracture in wood

A three dimensional cohesive zone model for perpendicular to grain wood fracture analysis is derived within the framework of plasticity theory and implemented for numerical calculations by the finite element method. The criterion used for strain instability and localization to a fracture plane is according to the orthotropic Tsai–Wu criterion accounting for all six stress components. The after localization plastic softening performance is governed by the three out-of-fracture plane stress and deformation components. The material model is applied to analyses of double cantilever beam specimens and end-notched beams. The results show in particular that stress and strength along grain may significantly affect perpendicular to grain fracture. The two dimensional development of the fracture process zone is also studied as affected by varying material principal directions.

Energy Response Spectra of Single-Mass Bi-Degrees of Freedom Systems for Hard Soil Site

The traditional energy response spectra depend on the single-directional earthquake excitations and two dimensional dynamic analyses, in which the imbalance and coupled characteristics of multi-dimensional responses of structures are not considered. So, the energy spectra of constant ductility facotors are developed by considering the single-mass bi-degrees of freedom systems subjected to perpendicular bi-directional earthquake motions. The restoring force rule of single-mass bi-degrees of freedom systems is assumed as two dimensional yield-surface plasticity function. The relative energy spectra for input energy, hysteretic energy, kinetic energy and damping energy are presented and analyzed based on 34 pair earthquake motion records of hard soil site. Analytic results show that the energy spectra for hard soil site have their own characteristics, and the spectral forms and values are affected strongly by vibration period, ductility factor and period ratio of single-mass bi-degrees of freedom systems.

Modelling the Static Recrystallisation Texture of FCC Metals Using a Phase Field Method

A three dimensional phase field model has been developed to simulate the texture formed during the static recrystallisation of FCC metals with medium or high stacking fault energy, such as aluminium, copper and nickel. Before recrystallisation the deformation texture as well as the stored energy was simulated using a three dimensional crystal plasticity finite element model. This output calculated on the distorted finite element mesh was first mapped onto the regular grid of the phase field model using a linear interpolation method and then used as initial condition for the subsequent recrystallisation texture modelling. This model has successfully predicted the typical recrystallisation texture components: cube {001}<100>, R {124}<211> in the aluminium alloy. In addition, the softening fraction and three dimensional microstructure produced during static recrystallisation have also been simulated by this model.

Simulation of Crack Tip Plasticity Using 3D Crystal Plasticity Theory

To investigate the plasticity distribution of microstructurally small crack tip in FCC crystals, the crack tip opening displacment(CTOD), crack tip plastic zone and maximum plastic work for stationary microstructurally small cracks were calculated with the three dimensional crystal plasticity finite element theory, which was implemented in the finite element code ABAQUS with the rate dependent crystal plasticity theory code as user material subroutine. Results show that crystallographic orientation has significant influence on CTOD and maximum plastic work. The CTOD and maximum plastic work in hard orientation are larger than that in soft orientaion under the displacement controlled boundary condition, which means that crack in hard orientation is more likely to extend than that in soft orientaion. The high-angle grain boundary shows a tendency to reduce crack extension, and the dislocation ahead of the crack tip becomes blocked by high-angle grain boundary.

A simple method for non-linear analysis of steel fiber reinforced concrete

This paper proposes a physical non-linear formulation to deal with steel fiber reinforced concrete by the finite element method. The proposed formulation allows the consideration of short or long fibers placed arbitrarily inside a continuum domain (matrix). The most important feature of the formulation is that no additional degree of freedom is introduced in the pre-existent finite element numerical system to consider any distribution or quantity of fiber inclusions. In other words, the size of the system of equations used to solve a non-reinforced medium is the same as the one used to solve the reinforced counterpart. Another important characteristic of the formulation is the reduced work required by the user to introduce reinforcements, avoiding "rebar" elements, node by node geometrical definitions or even complex mesh generation. Bounded connection between long fibers and continuum is considered, for short fibers a simplified approach is proposed to consider splitting. Non-associative plasticity is adopted for the continuum and one dimensional plasticity is adopted to model fibers. Examples are presented in order to show the capabilities of the formulation.

On nonlocal regularization in one dimensional finite strain elasticity and plasticity

The purpose of this article is to explore in details the theoretical and numerical aspects of the behavior of spatial trusses, undergoing large elastic and/or elastoplastic strains. Two nonlocal formulations are proposed in order to regularize the problem, avoiding the mesh dependence of the numerical response. The classical example of a simple bar in tension is chosen to explore the various features of the proposed models and to highlight the interplay between material and geometrical nonlinearity in the localization.

Regularity of solutions to a one dimensional plasticity model

On etudie un modele uni-dimensionnel quasi-statique de plasticite base sur une loi cinematique multi-lineaire, et formule comme un systeme d'inegalites variationnelles. On montre la regularite H 2 dans la variable d'espace pour la deformation, et la regularite H 1 pour la contrainte.

On the numerical evaluation of the singular integral equations used in two and three — dimensional plasticity problems

On the numerical evaluation of the singular integral equations used in two and three — dimensional plasticity problems

Sheet Metal Die Forming Using Closed-Loop Shape Control

The shape of compound curvature sheet metal parts is determined primarily by the geometry of forming dies and secondarily by interfacial and other forming environment conditions. Consequently the die geometry design step is critical to successful part manufacture. Existing analytical techniques do not permit sufficiently accurate prediction of die shape because of the inherent complexity of the three dimensional plasticity problem, the difficulty of characterizing interface forces and the need to continuously recalibrate the model as material properties vary. In this paper the use of a variable configuration, discrete element die in a closed-loop shape control system is proposed as a solution to this problem. The system forms a workpiece by an iterative procedure involving forming, measuring, and die shape change until shape convergence occurs. A critical experiment was performed on such a system that confirmed the validity of this concept.

Casa para la playa, New Jersey

The McMullan house, built on the beach, has been designed to be inhabited all the year round. Basically this building is a rectangular block, lifted above the dunes on a framework of timber columns and beams. The ground floor contains the entrance hall, the guest room or servant's quarters, including a bath room, and a shower room which can be reached separately from the beach. The second floor is taken up with the main living quarters, and the second floor contains the bedrooms. The northern and southern sides have few windows, whilst the eastern and western sides have balconies protected with sliding and Venetian blinds, which in addition to supplying an effective protection against the sun, give the house a pleasant sense of secluded intimacy. The blinds are made of wood, and are painted dark brown. Doors and windows are also made of wood, but painted white. This beautiful house on the New Jersey coast exhibits in a marked degree the sculptural quality of architecture, a three dimensional plasticity, which is often neglected in many buildings of the more simple kind. Marcel Breuer has succeeded in making each of the facades of this elementary boxlike design have an interest of its own, by playing with their colour, light and shade effects, texture and combination of materials.