Engineering Diffraction

From DANSE

Introduction

Engineering diffraction refers to a sub-field of neutron scattering which investigates microstructural features that influence the mechanical properties of materials. These include: 1) lattice strain, a measure of distortion in crystals, 2) texture, a measure of grain orientations, 3) dislocation density, a measure of the microstructure, and 4) grain morphology.

The field of engineering diffraction has experienced tremendous growth during the past two decades. Using TOF powder diffractometers such as NPD (at LANSCE), GPPD (http://www.pns.anl.gov/instruments/gppd/) (at IPNS) and ENGIN (at ISIS), numerous studies were performed that can be classified as: (i) Residual stress measurements; (ii) deformation studies; (iii) texture analysis; (iv) phase transformations.

Recently, dedicated engineering instruments such as SMARTS (http://lansce.lanl.gov/lujan/ER1ER2/SMARTs/index.html) at LANSCE and ENGIN-X (http://www.isis.rl.ac.uk/engineering/) at ISIS have been constructed, adding unprecedented capabilities. It is now possible to perform detailed investigations under a variety of conditions: applied stresses in excess of 3 GPa, temperatures above 1500C, data acquisition times in minutes, and sampling volumes as small as 1 mm^3. The planned engineering diffractometer at the SNS, VULCAN (http://www.sns.gov/users/instrument_systems/instruments/elastic/vulcan.shtml), will be a third-generation instrument that will offer even more impressive capabilities owing to improved flux and detector efficiency. It will permit detailed stress mapping, and parametric studies of both component fabrication and operating conditions. VULCAN will be ideal for studies of texture, kinetics of phase transformations and in-situ monitoring of processing. However, the engineering diffraction community cannot adequately use these new capabilities without new software for experiment planning, data acquisition, and analysis. The main objective of the engineering diffraction sub-project of DANSE is to develop software components that will not only allow a more effective use of the new engineering diffractometers but will also enable new engineering research. Below is an example that illustrates how a common finite element analysis package has been integrated into the DANSE framework permitting an efficient integration of neutron diffraction data and mechanics model predictions.

--Ersan 11:18, 21 Feb 2005 (PST)


Integration of Finite Element Analysis to DANSE Architecture

The major mechanical simulation tools that accompany an engineering neutron diffraction experiment are self-consistent modelling and finite element analysis (FEA). The following section details a proposed PYRE package that incorporates the latter:

The currently proposed package incorporates the ABAQUS software. Please follow this link (http://clue.eng.iastate.edu/~aydiner/Report_PyreABAQUS/) to reach the documentation. The structure of the package and PYRE-related decisions are explained in fair detail.

--Aydiner 14:32, 13 Sep 2004 (PDT)

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