RT - Levels 1 & 2 RADIOGRAPHY/RADIOSCOPY TESTING

Preamble

This training course outline describes specific training necessary to NDT inspectors that are seeking to certification in the aerospace industry.

Concepts are redundant with COFREND general training; they nevertheless are taken again here because they are essential to the general understanding of the unit.

The training will relates to general notions such as physics of x-rays, the equipments, the shoot techniques and the practical applications on materials and the defects met in the aeronautical .

In term of general training the requirements in radioscopy are identical to those of radiography, only the X Rays detector differs. A specific chapter described the use of all detectors other than film and numerical techniques. 

General information on x-rays

Physical principles

• Nature and properties of x-rays
• Interaction x-rays/materials
• X-rays principle absorption, attenuation coefficient µ
• Radiography principle

X-rays generation

• Generation principles, spectrum of radiation
• X-rays line ≤ 420 kV
• X-rays accelerators > 420 kV

Image Quality indicators / IQI sensitivity

General principles

• Geometric unsharpness
• Elliptical projections
• Contrast: object, image, average gradient
• Radiation energy
• Scattered radiation, limitations

Penetrameters or Image Quality Indicators (IQI's)

• Types of penetrameters or IQI's
• Use rules
• Standards

Use of radiographic film

The radiographic Film

• Structure of radiographic film
• H & D density, sensitivity level, exposure chart, exposure time, exposure latitude
• Intensifying screens role and use
• Film Processing, processing, storage, archival storage.
• Artefacts

Part Setup and Exposure

• Exposure parameters determination
• RT techniques, with constant exposure
• Multi films technique
• Defects position, triangulation

Radioscopy, digidal  Radio and associated techniques

Radioscopy, digidal  radio

• Detectors: Image intensifier, flat panel display, linear detector
• Real-time control
• Advantages and limitations compared to film

Computed Tomography

• Principle and potential applications
• Industrial equipments,

Image processing

• General information about image processing and basic concepts
• Main functions for digital radioscopy

Metallic materials knowledge

Foundry / casting

• Metallurgy knowledge (steel, aluminium, magnesium, super alloy) and manufacturing techniques
• Defects met: cavities, gas holes , shrinkage, foreign material
• Application of standards (ISO, EN, ASTM, AIR 3380)
  - Casting NDT inspection
  - NDT technique instructions (to Level 1)
  - Shooting, use of the IQI and interpretation / evaluation
  - Disposition to NDT report

Assemblies, Weldings, Brazing, Riveting

• Welding Processes (TIG, Electron Beam, laser, spot welding)
• Defects met: cracks, lack of penetration or brazing, inclusions.
• Application of standards (ISO, EN, ASTM, AIR 3380)
• Welding NDT inspection
  - Examination of circumferential of pipes welding / butt welds
  - NDT technique instructions (to Level 1) - Shooting, use of the IQI and interpretation / evaluation
  - Disposition to NDT report

Composite materials NDT inspection

• Concepts of development (Carbon, Kevlar, honeycomb  and manufacturing techniques
• Defects met: cavities, delaminations
• Application of standards (ISO, EN, ASTM, AIR 3380)
• Composite NDT inspection
  - tangential shooting
  - NDT technique instructions (to Level 1)
  - Shooting, use of the IQI and interpretation / evaluation
  - Disposition to NDT report

Maintenance NDT inspection

Maintenance indications

• Defects met:
  - cracks on butt welding, brazed or riveted
  - delaminations in composite
  - corrosion

RT – Ionizing Radiation Level 3

Public concerned :

All agents of NDT concerned with the level 3 COSAC certification

Specificities of COSAC activity

The aeronautical and aerospace activity is exerted on particular domains with specif techniques.

This activity is exerted on four main fields:

- Engines,

- Structures (airframes, satellite body),

- Equipments,

- Solid Propulsion.

Preamble

In order not to repeat IR general training program which describes the laws of IR physics and their application to the NDT technique to industry in general. The program is organized around each “product” according to the phases of its development:

- Study,

- Manufacture,

- Operation,

- Follow-up of ageing,

- Maintenance.

Plan

1 Operators,

2 Equipments,

3 Object of the NDT by Ionising radiations

4 Operating procedures,

5 Image quality indicators,

6 Checking, calibration of the installations.

In each paragraph, it will be indicated the specific criteria related to the development phase and the product life.

1. Operators

- Visual and medical aptitudes compatible with dangerous environments,

- Formation to safety which implies knowledge of the controlled products risks (pyrotechnical risk. Static electricity risk),

- Formation on manufactured products: 

To act as soon as possible (on the level of the study and manufacture), so that IR controls are then realizable in good conditions.

To interpret IR images by having in memory the anteriority of controls carried out.

2. Equipments

IR Generators adapted to the objects size and thickness to be controlled: (from few millimetres to several meters).

-  X-ray lines from 50 to 400 Kv

- VAN DE GRAAFF Generators. 2 MV and 2,5 MV.

- Linear Accelerators 15 MeV.

- Generators with Microfocus.

Image process:

- Films, high power viewer with variable field and variable intensity,

- Paper,

- TV Radioscopy:

with solid shield,

with image intensifier.

with linear detector.

Microdensitometry of films.

Image processing.

Video backup.

Computed Tomography.

Automated installations: 

In NDT workshop.

On a production line.

To respect the regulation on the personnel protection compared to the automation and compatibility with the pyrotechnics requirements .

Masking to limit the diffusion followed automatic of profile.

Vigilance detector (in general the operator is discharged from all work of handling, writing, but it must detect the defect, it should be made sure that its attention is maintained).

assisted computed detection.

Periodic calibration of the installation under examination by specific IQI.

Particular installation

For example:

- Control in shooting to the engine test rig with solid propellant.

- Control of the test deck evolution during an engine test.

Mechanisms adapted to follow the phenomena observed.

System with large field.

System with travelling. 

Adaptation of the images receivers to the studied event dynamics.

Normal video camera: 25 images/second.

Fast video: up to 1000 images/second.

Flash Radiography.

3. Object of the NDT by IONIZING RADIATIONS

Search for defects:

- matter health: Cavities, cracks, flaky preparations, heterogeneities foreign materials

- separations, cracks.

- porosities, shrinkages, cold shots

Checking objects geometry and their assembly

example: Thicknesses measure.

4. Operating procedures:

Shooting methods:

- Radial

- Tangential

- Multifilm technique.

In control NDT workshop.

- Design of these workshops.

- IR Protection . means and staff safety; cleanliness class:

- Adaptation of the handling means to the size and the objects weight (of a few grams to several tens of tons),

- choice of the radiographic technique and the imagery system according to the cost criteria and effectiveness.

 radiography or Real time radioscopy

- Image enhancement by  image processing.

- Precautions for the film introduction into the parts to control .combustion (mechanical risk and static electricity…)

Films in paper bag,

Films in flexible box,

Films in rigid box

Films in rubber box with vacuum.

Configuration and position of objects during X-ray control.

- Choice of the object position to request the possible defects and to facilitate their detection (example: debounding).

Use of stresses to reveal the defects:

- pneumatic,

- hydraulics,

- thermics.

To facilitate the defects visibility :

For examples:

- Control  “under pressure” to simulate an ignition phase of an engine with solid propellant

* Matérialisation of a large field of examination.

* Shooting view before and after the pressurization.

* Measure of channel deformations.

Control during manufacture.

For example:

Casting.

Definition of the  on line X Rays device in workshop:

- X-ray station

- Real time X Rays,  Video backup

Follow-up of ageing

- object or complete engines are subjected to ageing, normal or accelerated .

- periodicals X-ray Control.

- Importance of the methods reproducibility,

- Comparison and appreciation of defects evolution, methods, qualitative and quantitative.

5. Penetrameter or Image Quality Indicators (IQI).

These penetrameter must be adapted to the objects:

Materials choice according to their Xrays attenuation (half value layer) :

- Magnesium,

- Vinylidene Polyfluoride,

- Titanium etc…

Various types of IQI

- IQI step AFNOR type

- IQI wire for the connections,

- IQI slits for separations,

- IQI observed in displacement for the real-time imagery,

- Manufacture of representative samples starting from composition having the same absorption coefficients to the X-ray,

- Techniques of manufacture of artificial defects and insert for the defects of health matter and connections,

- Standard Blocks adapted to the examinations:

-  radiography,

- real-time X Rays,

– Computed Tomography Scan.

6. Checking calibration of the installations.

- Checking of the radiographic films sensitivity.

- The use of the multifilms technique by coupling films of different sensitivity requires the checking of their sensitivity to the reception.

- Watching of development baths installations

- Measure of location and size of the X Rays source focus

Periodic checking of the state :

- rigid boxes

-  intensifying screens

-  IQI

-  digital device

Calibration of automatic installations:

- with representative samples.

- Personnel qualification which ensures maintenance, mainly for the automatic machines.

- Protection checking against radiation.