Blank Cross-section Research Articles

Numerical Analysis of the Die Forging of Porous Blanks in a Die with the Implementation of Active Friction Forces

This paper provides the results of simulating the hot die forging of porous powder preforms with active friction forces applied along the lateral surface of the blank under deformation due to internal cohesion in the die–material system. The study covers the evolution of the distribution of the relative density over the blank cross section at different stages of deformation, the stress-strain state, and the total strain force while varying the boundary loading conditions by changing the initial compression force applied to elastic elements that prevent the die from displacement. It is shown that the active friction forces that act on the periphery of the forged piece adjacent to the die inner side result in areas with a significantly higher deformation intensity compared to deformations in the center of the blank volume. In this case, the volume of the high deformation intensity area and the maximum values of deformation increase with a decrease in the initial compression force of the springs and, accordingly, with an increase in the die displacement value during the deformation. The automatic displacement of the die due to the internal cohesion in the die–deformed material system leads to a decrease in the total deformation force, and the deformation force increases with a decrease in the die displacement value during deformation.

Numerical analysis of porous blank die forging in the die with the implementation of active friction forces

The paper provides the results of simulating the hot die forging of porous powder preforms with active friction forces applied along the lateral surface of the deformable blank by means of internal cohesion in the die-material system. The study covers the evolution of relative density distribution over the blank cross section at different stages of deformation, stress-strain state and total strain force while varying the loading boundary conditions by changing the initial compression force applied to elastic elements that prevent the die from displacement. It is shown that active friction forces acting on the periphery of the forging adjacent to the die inner side result in areas with a significantly higher deformation intensity compared to deformations in the center of the blank volume. At the same time, the volume of the high deformation intensity area and maximum values of deformation increase with a decrease in the spring initial compression force and, accordingly, with an increase in the die displacement value during deformation. Automatic die displacement due to internal cohesion in the die-deformable material system leads to a decrease in the total deformation force, and with a decrease in the die displacement value during deformation, the deformation force increases.

Quantitative and qualitative analysis for the study of Middle Paleolithic retouched artifacts: Unit III of Teixoneres cave (Barcelona, Spain)

Retouched artifacts constitute an important part of Paleolithic lithic assemblages. Evaluating what constraints shaped morphological variability can provide data about mobility, territorial management, and even about different adaptive strategies. This study attempts to understand what factors conditioned the intensity of retouch and the morphological variability of the retouched artifacts from unit III of Teixoneres cave (Barcelona, Spain) and to ascertain whether differences in retouch intensity depend on the raw materials used and the type of site occupation. First, a qualitative and descriptive technological analysis of the retouched artifacts is undertaken. Second, an analysis of the intensity and extent of retouch is carried out in a quantitative way using reduction indexes, and then crossed with a study of technological attributes such as the stone raw material, blank cross-section, or implement type. Lastly, all these variables are crossed and compared using a cluster analysis. The results show that retouched artifacts from unit III of Teixoneres cave can be classified into clear groups that represent different lithic strategies linked to the short-term occupation patterns inferred for unit III.

Deformation Analysis of Elliptical Cross-Section Spiral Equal Channel Extrusion Technique

Abstract The simplified slice-plain-strain method and the incorporating incremental superposition theory were adopted for the cumulative effective strain (CES) of elliptical cross-section spiral equal-channel extrusion (ECSEE) process. The ECSEE deformation was divided into two basic deformation modes: round-ellipse/ellipse-round cross-section transitional channel deformation and elliptical cross-section torsion transitional channel deformation, through tracking a particle of the cross section. The change laws for the combined CES of the particle with the channel length and the combined effective strain (ES) distribution were obtained by MATLAB software programming, and the results were compared with these via Deform-3D finite element method (FEM). The results show that the ECSEE accumulation torsion strain is greater than that of other forms, and the shear deformation is dominant. The blank cross-section ES presents the gradient decreasing trend from the periphery to the center. The FEM results also verify the accuracy of analytical solution.

Modeling Analysis of the Wire-Drawing Operation Using the Weighted-Residual Finite Element Method

Numerical analysis of a wire drawing operation to compute the stress distribution along the blank cross-section is presented. The governing equation describing the wire drawing equation is weakened using the Bubnov-Galerkin finite element method to obtain the finite element model. The blank is descritized into a mesh of C0 quadratic isoparametric and C0 cubic finite elements. Stiffness matrices for all elements are obtained using the finite element model which were subsequently assembled by enforcing continuity of the nodal stress. Boundary conditions are applied and the resulting condensed system of equation solved for unknown nodal stresses using Gauss Seidel method. The relative performance of the C0 quadratic and C0 cubic elements are assessed. Parametric analysis is carried out to show the influence of drawing parameters on the stresses generated and drawing load. The analysis was carried out using a Visual Basic.Net program developed by the authors.The results are presented in both graphical and tabular forms.

Macrostresses in sintered carbides

In a carbide blank the presence of a composition gradient on its cross section sets up a gradient of its coefficient of linear expansion. The level of the residual stress σ I res is determined mainly by the extent and character of variation of the CLE over the blank cross section.