Effects of In-Plane and Out-of-Plane Constraint on Fracture Toughness in Austenitic Stainless Steel

An improved understanding of the failure behaviour of safety critical component could result in substantial benefits for industry; these include a reduction in design constraints resulting in optimised and cheaper designs, reduced risk and therefore cost. Yet surprisingly, there is little information in design and assessment codes on the behaviour of thin sections. The aim of this paper is to investigate the fracture of thin sections, with reduced out-of-plane plastic constraint, by using a unified measure of constraint. A range of single edge notched bend specimen made of stainless steel 316L were tested. The specimens had a combination of in-plane and out-of-plane constraint levels achieved through different crack lengths and thicknesses. FEA simulations of the tested specimens were conducted to estimate the crack tip stress and strain fields for each, in order to determine Rice and Tracey contour values. Using critical values of Rice and Tracey parameter and a critical area (normalised by thickness) enclosed by this parameter, toughness scaling values for low constraint specimens are calculated.

Comparative Evaluation of Analytical Methods for the Determination of Coefficients of Friction and Stresses when Wire Rod Drawing

The article discusses the process of wire drawing of circular cross-section. The study of stresses of wire drawing in conditions of plane plastic flow was held. As theoretical framework the study was adopted the method of characteristics, a special case, having the definitive decision. Stresses during wire drawing are defined by decomposing the decision into two components of plane strain and the superposition of these decisions. The results of theoretical solution of the problem of wire drawing were used to determine the coefficients of friction on the surface of contact of the tool and the work piece during the deformation of steel with a diameter of 5.5 mm. It is recommended to use two-dimensional methods of solution in the analysis of the process of wire drawing in conditions with a high hearth of plastic deformation (with the relative height of the hearth of plastic deformation 2 and bigger). The theoretical dependences between the friction coefficients at the contact surface of the work piece and the tool was obtained. The obtained values of coefficients of friction can be used over solving the task of the wire drawing in conditions with a high hearth of plastic deformation.

Failures and Prediction Methods of Lateral Buckling Strength of H-Shaped Beams Connected by Flush End Plates

This paper presents boundary conditions for lateral buckling of the H-shaped beams connected to columns by flush end plates which fall into the lateral buckling following the out of plane plastic deformations of the flush end plates. The study is conducted by the following procedure: First, the behavior of the connection is researched by the no buckling experiment under the cyclic loading. As a result, it is found that the relationship between the out of plane plastic deformations of the endplates and the bending moment at the beam end can be predicted. Next, the FEM analyses of the rigid-frame structures consist of the slender beams having flush end plates connection and the structures consist of the beams having rigid connection are conducted to research the stress conditions in the tension flanges and the compression flanges of the beams during falling into lateral buckling. As a result, it is found that the rigid connection is restraining warping of the beam more tightly than the flush end plates connection, then the maximum bending moment strength against lateral buckling of the beams connected by rigid connections is higher than those of the beams connected by flush endplate. We recommend that the boundary conditions for the lateral buckling of the beams connected by flush end plates should be regarded to be different from those of the beams connected by the rigid connections.

Twinning Behavior in AZ31-B Polycrystal Texture Subjected to In-Situ Bending Test

A commercial Mg alloy, AZ31B, has been used widely. In the texture of AZ31B sheet, each grain has its c-axis almost parallel to the sheet normal. Therefore, at the bending process of the sheet, basal slip system can not accommodate an in-plane plastic strain which is perpendicular to the c-axis of each grain. It is known that {10―,12} twin can be formed by applying an extension strain parallel to the c-axis, which is equivalent to the a-axis compression strain. So in the bending deformation of the AZ31B sheet with a texture microstructure, it is expected that {10―,12} twinning occurs. In this study, an in-situ bending test of AZ31B sheet with a texture was conducted under a confocal scanning laser microscope to observe twinning by applying compression stress along a direction almost perpendicular to the c-axis of grains. In addition, EBSD techniques were used for the analysis of crystal orientations. The process of twin development observed by the in-situ bending test can be summarized as follows; with the increase of the deformation strain, the total area of twins increases. However, it is noted that the growth of twins is apparent while the number of twins is almost constant during plastic bending deformmation. EBSD analysis suggested that twinning behavior obey Schmid’s law even in the polycrystal.