01.01.2009 - 31.12.2011
The quality of a 3D computer tomography scan depends to a large extent on the environmental conditions of the measurement and the parametrization of the 3DCT system. The three-year Bridge project "Smart CT“ with a project extent of 388.600€ is based on the idea of generating an optimal data basis for the 3D-measurement of the complete geometry of a multimaterial component. The major goal is it to make 3DCT devices capable of dimensional measurement of multi-material components and therefore to significantly extend the application areas of 3DCT.
Introduction and Motivation
The measurement of the three dimensional geometry of industrial components is an integral aspect of state of the art components development and quality assurance. To overcome the limitations of optical and tactile metrology, 3D Computer tomography (3DCT) recently gained importance. The major advantages of 3DCT are:
- Compared to conventional means of metrology and non destructive testing 3DCT is a fast method. Typical scan times are about 30 minutes. Although the evaluation of the scans is computationally expensive, typical evaluations take about 2-3 hours.
- 3DCT allows a non-touching characterization. Even flexible or soft parts can be measured.
- 3DCT non-destructively penetrates the specimen with Xrays. The X-ray attenuation is measured by a flat panel detector. If the absorption of materials differs, the materials are distinguishable.
- 3DCT is the only method, which fully characterizes a specimen including the complete outer and inner structure of a specimen. Also hidden structures (e.g., inner holes, voids or cooling channels) within the component can be measured without disassembling or destroying the specimen.
Multi-material components with high density differences are not suitable due to the limited dynamics of the X-Ray detector of 3DCT machine and due to different physical effects for 3DCT. High density and highly absorbing materials (e.g., steel) produce scattered radiation which is manifested in the reconstructed dataset.
Use and goals
The main goal of Smart CT is to develop novel methods and techniques for dimensional measurements of complex, artefact-affected multi-material components based on Dual Energy CT. By scanning a specimen twice using different energies and therefore different energy spectra of the X-ray source, it is possible to quantify the different materials of a component by combining information from both scans. The entire measurement process chain will be analyzed starting from scanning parameters, measurement procedure, positioning of the specimen to calibration, reconstruction, data fusion/recombination and surface extraction and optimized focussing on optimal geometry information of the entire component (including internal and external geometry). The main goals of SmartCT are:
- Principal purpose: Smart CT for the metrology of complex multi-component item numbers
- Characterisation and measurement of material changes and/or - boundary surfaces
- Calibration of the CT-measurements of complex multi-material parts (accuracy)
- Extraction process for the complete 3D measurement
The "SmartCT”- project is a spin off project of the FH-plus of project “Non destructive and insitu - characterisation of work pieces and materials with special consideration of fuel cells". The following activities are planned for the project runtime:
- Calibration preocedure for 3DCT-scanning
- Simulation for the 3DCT-parameter analysis
- Recombination/fusion of the CT-measurment data
- Surface extraction/enhancement of CT-results of multi-material components
- Implementation of a prototype
- Test and evaluation of the reached accuracy
- HDEMC Hessenberger Gmbh, Attnang-Puchheim
- DTECH Steyr Dynamics & Technology Services GmbH, Steyr
- TU Wien, Institut für Computer Graphik und Algorithmen
- FH OÖ Forschungs & Entwicklungs GmbH, Campus Wels
Dr. Christoph Heinzl
Prof.(FH) DI Dr. Johann Kastner