Accuracy of Quarter-point Element in Modeling Crack-tip Fields

Accuracy of the quarter-point and transition elements is investigated on one- and two-dimensional problems with inverse square-root singularity. It is demonstrated that most coefficients of the stiffness matrix of the quarter-point element are unbounded. However, numerical integration produces finite values of these coefficients. Influence of several parameters on the error in determining the stress intensity factor is studied. Solution accuracy can be improved using special distribution of element sizes and increasing the element integration order in the radial direction

Specimen thickness effect on elastic-plastic constraint parameter A

Three-dimensional elastic-plastic problems for a power-law hardening material are solved using thefinite element method. Distributions of the J-integral and constraint parameter A along the crack front forvarying specimen thickness and crack depth are determined for edge cracked plate, center cracked plate, threepoint bend and compact tension specimens. The constraint parameter A is a measure of stress field deviationfrom the HRR field. Higher A values signify lower specimen constraint. Results of finite element analyses showthat the constraint parameter A significantly decreases when specimen thickness changes from 0.1 to 0.5 of thespecimen width. Then it has more or less stable value. Among four specimen the highest constraint is demonstrated by the compact tension specimen which has the constraint parameter A lower than its small scale yielding value

Political Marriage as a Method of Strengthening Emperor’s Power in Komnenoi’ Byzantium

В данном докладе рассматривается брачная дипломатия династии Комнинов как средство укрепления власти. Император опирался на «родственников и свойственников» — свой род и кланы, породнившиеся с правящим домом. Выявлено, что такая брачная политика была выгодна лишь в краткосрочной перспективе.This scientific report reviews the marriage diplomacy of Komnenoi as a method of strengthening power. Emperor has relied on his relatives and other families connected with the house of Komnenoi by marriage. It was found that such a policy was efficient only in a short term

X-ray computed tomography study of kink bands in unidirectional composites

An experimental study on the axial compressive failure of cylindrical unidirectional (UD) carbon fibre-epoxy rods has been performed to better understand kink bands and the relevant damage mechanisms in three dimensions (3D). Post-mortem X-ray micro-computed tomography (micro-CT) imaging has shown that fibre kink bands predominantly all lie within the same plane in a cylindrical rod sample uniaxially compressed without lateral constraint. Kink bands at different stages of development are contained in the damage volume and the geometric parameters of fully developed kink bands are consistent through the damage zone, with a kink-band width ω ≈ 20–320 μm, kink-band angle β ≈ 11–40° and fibre rotation angle Φ (φ + φo) ≈ 18–52°. Fibre failure, longitudinal splitting and matrix micro-cracks within the fibre kink zone are identified by scanning electron microscopy (SEM) and X-ray micro-CT observations. The smallest radius of curvature that corresponds to maximum amount of bending of the unbroken buckled fibres was ∼280 μm (40 fibre diameters). Kink-band boundary planes and longitudinal splitting have been extracted and visualised in 3D for the first time

Cracks, microcracks and fracture in polymer structures: Formation, detection, autonomic repair

The first author would like to acknowledge the financial support from the European Union under the FP7 COFUND Marie Curie Action. N.M.P. is supported by the European Research Council (ERC StG Ideas 2011 n. 279985 BIHSNAM, ERC PoC 2015 n. 693670 SILKENE), and by the EU under the FET Graphene Flagship (WP 14 “Polymer nano-composites” n. 696656)

The influence of the HAZ softening on the mechanical behaviour of welded joints containing cracks in the weld metal

The mechanical behaviour of welds containing cracks was analysed through the numerical simulation of the three-point bending tests of welded specimens. This paper presents the mechanical model and the methodology used for the numerical simulation of the tests. The variation in crack driving force of cracked welds is studied as a function of the strength mismatch in the heat affected zone and of the crack position relative to the weld metal/heat affected zone interface. This analysis was performed with recourse to the numerical calculation of the J integral.http://www.sciencedirect.com/science/article/B6V2R-4B0X38N-6/1/7027467d6e068a7f5c062427de733a1

Object Oriented Design of a Finite Element Code in Java

This paper presents the object oriented approach to programming the finite element method using the Java language. The developed finite element code consists of ten Java packages. Three main methods are related to generation of finite element models, solution of elastic and elastic-plastic boundary value problems, and visualization of models and solution results. Object-oriented model of the code is described. It is demonstrated that Java 1.5 new features are useful in development of the finite element code. Java 3D is used for visualization of models and results