An Investigation of Radial Basis Function Method for Strain Reconstruction by Energy-Resolved Neutron Imaging

The main objective of the current work is to determine meshless methods using the radial basis function (rbf) approach to estimate the elastic strain field from energy-resolved neutron imaging. To this end, we first discretize the longitudinal ray transformation with rbf methods to give us an unconstrained optimization problem. This discretization is then transformed into a constrained optimization problem by adding equilibrium conditions to ensure uniqueness. The efficiency and accuracy of this approach are investigated for the situation of 2d plane stress. In addition, comparisons are made between the results obtained with rbf collocation, finite-element (fem) and analytical solution methods for test problems. The method is then applied to experimentally measured continuous and discontinuous strain fields using steel samples for an offset ring-and-plug and crushed ring, respectively.

Die Design Architecture for Enhancing Tool Life Via Manipulation of the Elastic Strain Field of the Dies During Extrusion Processes

Forging and extrusion tools are often subjected to a combination of cyclic thermo-mechanical, chemical, and tribological loads. Strategies for minimizing these loads are critical for preventing premature tool failure and increasing productivity. A die design architecture for extrusion that minimizes the residual contact pressure at the die-workpiece interface during the ejection stroke is proposed. The underlying principle of this die design is that during the extrusion stroke, a tapered die can move in the direction of the extrusion load, thus inducing negative radial elastic strain on the die. When the extrusion load is removed, the elastic strain energy stored in the die is released, thus repositioning the die to its initial state. With this design architecture, the workpiece can be ejected at no load. The process was validated using finite element (FE) warm forging/extrusion simulations for a constant velocity (CV) joint and pinion gear shaft. These simulations showed that in addition to reducing residual contact pressure, which enhances tribological conditions, the new die design can easily lower die stresses, thus increasing die fatigue life. The FE simulations for CV joint and pinion gear shaft demonstrated residual pressure in certain locations of the die ranging from 30% to 100% of the pressure induced during the extrusion stroke. The case studies simulated showed that a total energy saving of up to 15% can be achieved with the proposed die setup.

Investigation of Crystallographic Aspects of Subsurface Damage Induced by Grinding Using Micro-Raman Tomographic Imaging

The objective of this study is to propose and develop an evaluation method on the process damages of sapphire wafers, regarding crystallographic aspects of the damages by use of tomographic imaging techniques with laser Raman microscopy (called as micro Raman tomographic imaging: mRTI). In this paper, tomographic images with the peak width and the shift of the peak position were observed with mRTI, on c-plane cut sapphire wafers along a-plane, with micro fractures induced by brittle-mode grinding. Fractures along m-plane from the surface to 2–7 microns-depth, and fractures along r-plane from the bottom end of the m-plane fracture to 14 microns-depth, subsequently induced elastic strain field around the fractures, could be visualized without destructions of the wafers.

Аналитическое выражение для распределения упругой деформации, создаваемой включением в форме многогранника с произвольной собственной деформацией

Analytical expressions for the displacement vector, stain tensor, and Eshelby tensor have been obtained in the case where an inclusion in an elastically isotropic infinite medium has a polyhedral shape. The eigenstrain (e.g., the lattice mismatch) is assumed to be constant inside the inclusion but not obligatorily hydrostatic. The obtained expressions describe the strain both inside the inclusion and in its environment. It has been shown that a complex three-dimensional configuration of the elastic strain field (as well as of the displacement vector field) is reduced to a combination of simple functions having an illustrative physical and geometrical interpretation.