Papers by Keyword: Stress Tensor

Abstract: This article is devoted to the study of the filtration coefficient depending on the loads applied to the material. In filtration theory, it is classical to solve problems with a constant filtration coefficient. Moreover, due to the conditionality of the filtration coefficient value by various physical and chemical processes, both in the solid fraction and in the liquid, its value is usually determined empirically. However, it is obvious that depending on the loads applied to the material, the pore space and filtration coefficient will change. This is especially true when using various filter materials, such as concrete. The latter, depending on the brand, can absorb the liquid quite well. Therefore, assuming that the pore space is a collection of capillary tubes, the paper shows the relationship between the filtration coefficient and the average pore diameter of the material. The dependence of the material filtration coefficient on the first invariant of the stress tensor arising in the medium is found. The change in the filtration coefficient of a concrete slab at different points is shown when a force load is applied to its upper surface.

Abstract: An innovative X-ray diffractometer especially designed for residual stress measurements was deployed at the Institute of Physical Metallurgy, Metalforming and Nanotechnology of the University of Miskolc. The advantages of the equipment over the traditional X-ray diffraction stress measuring methods are presented through our experiences on industrial components with varying sizes, geometries and measurement requirements. The microstructural limitations of the X-ray diffraction based residual stress measurement method are also discussed.

Abstract: In this paper, we investigate the stress distribution on a two phase problem in micro-extrusion. Molten polymer is compressed from a vessel and the extruded fluid is being solidified through the heat exchange with the solid polymer and the ambient environment resulting in a two phase/moving boundary problem. The temperature profile of such problem has analytically been determined and the present author, Chan further investigates the fluid flow of the molten polymer embedded inside the condensed outer-shell. In this paper, we investigate the stress distribution induced by the fluid flow, which is driven by the incoming fluid and the moving boundary. We find that when x’>>H (see Fig. 1), shear stress dominates whereas the principal stress dominates when x’<<H. When x’ approximates H, both the shear and principal stresses coexist.

Abstract: An innovative X-ray diffractometer was used to measure the residual stress being the source of a typical deformation failure called ovality on bearing rings. The equipment performs the measurements without sample cutting making it possible to measure the stress state of the same rings after each processing step. Thus, the stress state evolution during the complete manufacturing scenario was monitored on the same rings and the manufacturing process was revised.

Abstract: Control of microstructure in single phase alloys are relatively limited and less way of expedient are available compared to multiphase alloys. Authors have attempted microstructural control of single phase alloy by formation of distribution of plastic strain and residual stresses. In this paper, residual stress distribution of 1070 single phase aluminium with RBT (Rotary Bending and Tensile) loading have been measured by 2D-XRD method. After suitable heat treatment, the alloy show spatial grain size distribution of 30-150μm. Measured stress tensor enabled by 2D-XRD method clealy show distribution of stress components of residual stress tensors and principal stresses. Direction of the principal stresses gradually rotate depending on position from center to radial direction. Even after annealing, the direction of principal axis agree with that of torsion during the RBT treatment. This results show possibility of control of microstructure in single phase material accomplished by introduction of gradual distribution of residual stresses.

Abstract: We study the chemical bonds of small Al clusters (Al_n, n=2-8) and hydrogenated Al clusters (Al_nH_m , n=1-8 and m=1,2) using electronic stress tensor. We calculate the bond order based on energy density for these clusters. We also study the electronic structure under the presence of electronic current by the electronic stress tensor for AlH₃ molecule.

Abstract: By associating texture determinations and strains measurements by neutron diffraction, the elastoplastic behaviours of families of crystallites with the same crystallographic orientations were characterized in situ in a brass and a bronze alloys under uniaxial loading. The polycrystalline orientation analysis method proposed here allows an intermediate approach between a “local” (intragranular) and a “global” characterization, within the bulk of massive samples.