Interpretation of radiograph (Part 3).

Pressure marks (crimp marks).
Produced by careless film handling – if the film is crimped or buckled either
before or after exposure crescent-shaped images in the processed radiograph
will result. Light marks indicate crimping before exposure, dark marks crimping
after exposure but before film processing.
It is usually possible to identify crimp marks by viewing the film in reflected
light. They should appear as indentations in the surface of the film. Lead
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Interpretation of Radiographs (Part 2).

Film quality.
The success of radiographic interpretation is dependent upon the quality of the
film presented. If the film does not meet the minimum applicable standards for
quality then it should be rejected and reshot. The manufacturer’s interpreter
may, for economic reasons, not be inclined to reject radiographs which do not
meet the minimum quality standards. Therefore any third party viewing the
radiographs should be extremely careful to correctly assess the quality of the
radiographs prior to endorsing the relevant report, otherwise they will be open
to criticism should the film become the subject of any subsequent legal inquiry.
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Interpretation of Radiographs (Part 1).

Interpretation of Radiographs
Interpretation of radiographs is a skill only gained through long experience.
The interpretation of a radiograph should not be confused with the acceptance
or rejection of a component. The radiograph must first be interpreted and any
defects observed assessed against the applicable standard. A weld or casting
must be accepted on its merits or rejected for its faults and should neither be
accepted nor rejected due to difficulties encountered in the interpretation of
radiographs. Any radiograph not meeting code requirements with regard to
radiographic quality must be rejected.
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The definition of the technological properties concept and the requirements for it. The technical and economic indicators of power sources. The criterion for selecting power sources for welding.

When selecting power sources for welding, take into account technological and economic indicators. The choice of sources will ultimately be based on economic calculations, but this economic calculation will be performed from the set of sources that satisfy the first two criteria. Therefore, it is necessary to know about these two criteria.

The power source is considered to be technological if it provides:

  1. the arc stability (estimated by the coefficient of stability– КУ);
  2. the arc elasticity;
  3. the minimum level of spattering of the electrode metal.

The arc elasticity is the ability of a stable arc to burn without breaks in its elongation.

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The heterogeneous nucleation.

If there are impurities in the liquid phase in the form of solid particles, then the crystallization often begins on them, as on finished substrates.

The role of such particles can play the walls of molds, non-metallic inclusions, oxides, etc. The foreign particles are active if the work of germs formation is less on them than the work of spontaneous generation of the germs. This is the case when the surface tension at the interface of the germ is an alien particle smaller than at the interface between the nucleus and the liquid phase. The interfacial energy is characterized by the wetting angle of the droplet of the mother phase on the Continue reading →

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