Non-destructive testing

Industrial radiography involves exposing the material to be tested to radiation. The radiation passes through the object being examined and creates an image on a recording medium placed on the opposite side of the object.

For thinner or less dense materials like aluminum, electrically generated x-ray radiation (X-rays) is commonly used. For thicker or denser materials, gamma radiation is often employed.

When a magnetic flux is applied to the inspection surface, leakage flux is generated on the discontinuities on the surface, depending on their location. If ferromagnetic powders are sprinkled on the inspection surface, these powders are attracted by the leakage fluxes and accumulate on the discontinuities. In this way, the locations of the discontinuities can be determined.

Application Areas:

It is applicable to all ferromagnetic materials.

Limitations:

It cannot be applied to non-ferromagnetic materials. Discontinuities cannot be detected if they are not positioned at an angle corresponding to the direction of the applied magnetic field. Very high magnetization currents may be required for large parts. A very rough inspection surface negatively affects the result. If there is paint or coating on the inspection surface, its thickness directly affects the inspection result. Generally, additional processes such as demagnetization and final cleaning are required after the inspection.

Essentially, the Phased Array technique operates on ultrasonic principles. However, unlike classical ultrasonic inspection techniques, instead of using single/double crystals, it utilizes multiple angles and sound beams, tailored to user needs and inspection requirements, allowing for more effective, faster, and detailed defect detection and providing clearer information about the test piece.
PAUT (Pause Testing) technique allows for three-dimensional inspection to detect internal material irregularities, providing information about the orientation and location of defects within the material in a single test.

In this method, the probe uses 8-16-32-64-128… independent elements. The firing order of the elements can be adjusted to focus them on a specific area. This method has many advantages over the traditional pulse-echo method.

Digital radiography is one of the newest forms of radiographic imaging. Since no film is required, digital radiographic images are obtained using flat panels containing special phosphor screens or micro-electronic sensors. The resulting images are digitally detailed and easily archived.

Liquid Penetrant Inspection (LPI), also called Penetrant Testing (PT), is a rapid, economical, and widely used non-destructive testing method for detecting surface discontinuities in all non-porous materials (metals, plastics, or ceramics).

Penetrant testing is based on the principles of capillary action, where a liquid penetrates a cavity.

Penetrant testing is performed by thoroughly cleaning the test surface, applying a colored or fluorescent penetrant, allowing for penetration time, removing excess penetrant, and then applying a developer (dry or liquid form).

The developer helps to draw out the penetrant that has permeated surface discontinuities.

After the developer, the test surface is examined for leakage under natural light or UV light (depending on the penetrant type). Fluorescent Penetrant Testing is the most sensitive test method.

Visual inspection is the oldest of the non-destructive testing methods. It involves directly inspecting the material to be tested using the naked eye or intermediate equipment. The most important requirement is that the amount of light is at an acceptable level. Before testing, the surface should be cleaned and inspected with sufficient light. Prior to this, information about the part's manufacturing process, operating conditions, and similar details should be reviewed.

Visual inspection is used to detect different surface discontinuities. To reach areas that cannot be directly visualized, tests are performed using devices such as baroscopes.

Many people think that visual inspection should only take place after production is complete. However, pre-welding and in-welding inspections will eliminate errors that might occur after welding and will facilitate the final production inspection process.

Non-destructive testing (NDT) uses high-frequency sound waves in the 0.2–25 MHz range to detect discontinuities in the part being tested. Here, Hertz (Hz) is the unit of frequency and is equal to the number of vibrations per second.

Ultrasonic testing is based on the principle that a sound beam propagating through a material is partially or completely reflected (echoed) as a result of a change in acoustic impedance (the resistance of a material to sound propagation).

This test method can also be used to test for discontinuities (cracks, porosity) in castings. A prerequisite for successful application of the method is that defects on the material surface are visible. Evaluation of the test surfaces is carried out under daylight conditions exceeding 500 lx on the workpiece.

The leak detection criteria for impact testing, which can be performed under practical test conditions, are approximately 10⁻⁵ to 10⁻⁴ Pa*m³/s (10⁻⁴ to 10⁻³ mbar*l/s).

In the testing methods used with our equipment, the weld or casting surface area to be examined for leaks is wetted with a foam-generating testing agent.