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The model of elastoplastic medium is based on the concept of slip proposed by Batdorf and Budiansky. The conditions of slip on a slip plane take into account “the local loading criterion”. Under some assumptions we succeeded in integrating the plastic shears over all possible slip planes in case of arbitrary three‐dimensional stress state and obtained an expression for the plastic strain tensor increments and the closed variant of the elastoplastic model, which turns out to be a variant of the plastic flow theory. The integration method proposed can be applied for establishing the links between local conditions and macroscopic equations, and for some other slip conditions too.

THE paper by Thompson, Wadsworth and Louat on ‘The Origin of Fatigue Fracture in Copper’ contains much valuable information which, together with other recent work of the same nature, affords a basis for reviewing various theories concerning the mechanism of fatigue. In the light of recent information, it appears probable that the greatest road‐blocks in our progress toward understanding fatigue have been mental or semantic in nature. It is remarkable that a phenomenon of such importance has resisted solution for over 100 years, in spite of the tremendous amount of testing, papers and conferences that have been devoted to solving the problem.

Under this heading are published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Committee, Reports and Technical Notes of the U.S. National Advisory Committee for Aeronautics, and publications of other similar research bodies as issued

The purpose of this work is to apply a recently proposed constitutive model for mechanically induced martensitic transformations to the prediction of transformation loci. Additionally, this study aims to elucidate if a stress-assisted criterion can account for transformations in the so-called strain-induced regime.

The model is derived by generalising the stress-based criterion of Patel and Cohen (1953), relying on lattice information obtained using the Phenomenological Theory of Martensite Crystallography. Transformation multipliers (cf. plastic multipliers) are introduced, from which the martensite volume fraction evolution ensues. The associated transformation functions provide a variant selection mechanism. Austenite plasticity follows a classical single crystal formulation, to account for transformations in the strain-induced regime. The resulting model is incorporated into a fully implicit RVE-based computational homogenisation finite element code.

Results show good agreement with experimental data for a meta-stable austenitic stainless steel. In particular, the transformation locus is well reproduced, even in a material with considerable slip plasticity at the martensite onset, corroborating the hypothesis that an energy-based criterion can account for transformations in both stress-assisted and strain-induced regimes.

A recently developed constitutive model for mechanically induced martensitic transformations is further assessed and validated. Its formulation is fundamentally based on a physical metallurgical mechanism and derived in a thermodynamically consistent way, inheriting a consistent mechanical dissipation. This model draws on a reduced number of phenomenological elements and is a step towards the fully predictive modelling of materials that exhibit such phenomena.

The purpose of this paper is to formulate an algorithm for a novel damage‐coupled material law for crystalline polyethylene at finite inelastic strains followed by investigation of the influence of the aggregate representation and material parameters on the material response.

The constitutive equations are developed within the framework of continuum damage mechanics to describe crystal fragmentation caused by atomic debonding of the crystallographic planes. The material is assumed initially isotropic and homogeneous and is represented as an aggregate of randomly oriented crystals with an orthorhombic lattice. For the velocity gradient, an additive decomposition into symmetric and skew‐symmetric components is applied, where the skew‐symmetric part (spin) is decoupled from the lattice shear by means of a damage variable. Structural features such as lattice parameters and orientations, slip systems, and kinematic constraints are incorpo‐rated.

The proposed model is implemented to predict stress‐strain behaviour under uniaxial tension and damage accumulation and texture development at the different stages of deformation. In the numerical examples, the effects of the aggregate size, crystal orientations, and material parameters on the model estimates are analyzed.

The model used herein is a first attempt to analyze the influence of crystal fragmentation caused by the debonding of the crystallographic planes on the predicted mechanical behaviour and texture development of polyethylene prior to failure.

The electrochemical approach to corrosion problems has been stressed before, but here the author dwells more on the thermodynamic aspects since comparatively small changes in energy, and hence in chemical activity, which are caused by stress may result in very marked changes in the damaging effects of corrosion. Part 1 of the article opens with a thermodynamic approach covering borderline corrosion and the corrosion of crystals, and then deals with the effect of stress on chemical attack. Following this is a comprehensive survey of types of metal deformation (e.g. slip, cleavage and grain boundary movement) and concludes with data regarding the properties of grain boundaries and the effect of temperature and rate of loading. Stress corrosion is the major subject to be covered next month.

Under this heading will be published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Committee, Reports and Technical Notes of the U.S. National Advisory Committee for Aeronautics, and publications of other similar research bodies as issued.—Ed,

The purpose of this paper is to provide a computational procedure for a novel damage‐coupled material law for semicrystalline polyethylene. Using a damage mechanics approach, the model seeks to gain insight into the mechanical behaviour of polyethylene considering the microstructure and degradation processes occurring under uniaxial tension.

The material morphology is modelled as a collection of inclusions. Each inclusion consists of crystalline material lying in a thin lamella attached to an amorphous layer. The interface region interconnecting the two phases is the plane through which loads are carried and transferred by the tie molecules. It is assumed that the constitutive model contains complete information about the mechanical behaviour and degradation processes of each constituent. After modelling the two phases independently, the inclusion behaviour is found by applying some compatibility and equilibrium restrictions along the interface plane.

The model provides a rational representation of the damage process of the intermolecular bonds holding crystals and of the tie‐molecules connecting neighbouring crystallites. The model is also used to analyze the degree of relationship between some of the material properties and the mechanical responses.

In practice, the numerical model clearly helps to understand the influence of the different microstructure properties on the tensile mechanical behaviour of semicrystalline polyethylene – an issue of particular interest in improving material processability and product performance.

To the authors’ knowledge, a phenomenon such as microstructural degradation of polyethylene has not received much attention in the literature. The proposed model successfully captures aspects of the material behaviour considering crystal fragmentation and tie‐molecule rupture.

The purpose of this study to analyze the plastic anisotropy of 6061 aluminum alloy with finite deformation using crystal plasticity finite element method.

A representative volume element (RVE) model was constructed by Voronoi tessellation. In this model, grain shapes, grain orientations and distribution of grains were involved. The mechanical response of the component under composite loading was tested using specify cruciform specimen. Moreover, different stress and strain states in the specific central region were analyzed to reveal the effects of complex loading.

We calculated the influence of misorientation of adjacent grains as well as the evolution of the micro structure’s plastic deformation on the macroscopic deformation of the structure. Geometry design for the cruciform specimen helps obtain a homogenous distribution of the stress and strain at the specimen center. In this process, the initial grain orientation is also an important factor, and the larger misorientations between special grains may cause greater stress concentration.

The influence of micro-scale factors on macro-scale plastic anisotropy of AA6061 is analyzed using RVE model and cruciform specimen, and they offer a reference for related research.

The purpose of this paper is to analyse of structures made in rock mass with multiple intersecting discrete discontinuities such as joint, fault, shear plane.

In this study, a numerical method is proposed for analyzing multiple intersecting joints with varying dip angles, spacing and roughness in eXtended Finite Element Method platform. A procedure is also outlined to treat excavated enhanced (jointed) elements for analysing the effect of excavation sequences.

The proposed method is compared with the existing interface element methods (Phase-2 model) by considering the stress and displacement distributions of a multiple intersecting jointed rock sample under uniaxial loading conditions. A circular tunnel in rock mass having intersecting joints is also analyzed for the distribution of mobilised friction angle of joints and results are compared with a derived analytical solution.

Nucleation and propagation of cracks should be incorporated into the proposed framework in future studies.

The proposed method is a useful tool for rock mechanics and geotechnical engineering problems to analyse strength and deformability of jointed rock masses.

The paper enumerates concepts and detail implementation procedures of the proposed method in three-noded triangular elements. The intersection of joints is formulated in such a way that no additional (junction) enrichment is required in model. The method has been improved for inclusion of Dirichlet and Neumann boundary conditions to be applied in the enhanced part of a problem domain.