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Introduction to Computed

Tomography

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Normally it is difficult to get dimensionalmeasurements of defect or depth informationusing radiography very accurately

Various parameters control the quality of aradiograph:Source energyFocal spotExposure geometryDetector characteristicsProcessing conditions

What is Radiography

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What is tomography

Industrial computed tomography (CT)scanning is a process which uses X-ray equipment to produce three-dimensional

representations of components both externallyand internally.Industrial CT scanning has been used in many

areas of industry for internal inspection of components.

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What is tomography

Tomography is a non-destructive technique toreconstruct an image of a cross sectional planethrough an object.

It is also known as Computed Tomography orComputer Aided Tomography.In case of X-rays or gamma ray based

tomography the cross sectional image isbasically a map of the approximate linearcoefficients at each point in the plane.

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What is tomography

By means of the computed tomography (CT)it is possible to generate cross sections thatshow the internal structures without any

overlay.In order to accomplish the calculations forthe cross sections, it is essential to have X-rayimages from all directions.For this purpose, the object is rotated aroundan axis by 360 degree in total.

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Tomography modalities

Transmission Tomography:Radiation source is present outside theobject and transmitted data through theobject is collected which is used forreconstruction of cross sectional image.Emission Tomography:Radiation source is present inside the object

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Setup of Industrial CT

A Tomography System based gamma or X-rays comprises of:

A source of penetrating radiation A radiation detector or an array of detectors A computer system Software for data processing, data handling and

visualisation

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Setup Industrial CT

FrontendX-Ray sourceX-Ray detector

Manipulation systemSafety cabin

BackendMeasurement system

Storage systemReconstruction clusterVisualization system

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CT inspection of the half-axle of maneuverableaircrafts stabilizer

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Fields of application

Analysis of imperfections Characterisation of cavities, pores, inclusions of impurities, crack configurations.

Integrity analysis. Assessment of material transitions and combinations.Measurements Wall-thickness measurement. Nominal/actual value comparison.

Reverse engineering Reverting dimensions of real components to CAD-data.