Nondestructive Welding Testing Methods

Welding is an excellent method of joining together different metals in order to create complex items that can resist to large forces. On the other hand, this procedure can sometimes generate disasters, as you can never know whether you’ve done a solid job or not. If you cut through the welding line in order to test its strength, you won’t get anywhere, as you are going to destroy the welded part. This is why you have to make use of nondestructive welding testing methods, so that you can have the peace of mind you’ve done a great job.

Nondestructive examination is used in many industries and activities such as forensic engineering, mechanical engineering, aeronautical engineering and electrical engineering.

Methods

SONY DSC

SONY DSC

Most nondestructive welding testing methods use X-rays, ultrasounds or other types of penetrating radiation. Ultrasonic testing, for instance, works by comparing the subject of the test against a bulk sample which is known to be free from internal flaws. If the pattern is different, it means there’s a problem with the welding line or point. In addition, some methods involve the use of fluorescent or non-fluorescent liquids to emphasize fatigue cracks or other flaws.

Electrochemical methods are also very effective for detecting progressive damage via electrochemical fatigue crack sensors. This is how such cracks can be discovered long before they become dangerous.

Spectral analysis is another nondestructive method for testing metals. However, most spectrometers require a small sample to be cut from the main item and polished in a special manner, in order to provide accurate results. If cutting a sample isn’t possible, this type of analysis requires a portable spectrometer. These machines have a special mobile probe that can be used to generate an electric arc in a pure argon atmosphere. This electric discharge blasts a superficial layer of the metal, decomposing it in its elements. The sensors in the machine are able to convert each wavelength into the corresponding chemical element. This is how you can know the chemical composition of the welding material without having to destroy the part.

Consequences

It is very important to discover all such material flaws before they cause an accident. Hydroelectric plants, for instance, use huge turbines that generate electricity through their rotation movement. The turbines and the diaphragms have many small elements welded together on the main frame. If a welding line or point cracks and fails, the resulting fragments are going to be propelled at impressive speeds inside the turbine, thus causing major damage. These accidents can kill everyone around the unit, so they have to be avoided at all costs.

Nondestructive testing is implemented today in many production processes, as it increases the safety levels and it reduces the costs. It’s much cheaper to invest in good NDE equipment and technique rather than destroying the parts in order to analyze the material flaws. Sometimes, cutting the part isn’t possible without destroying it, so ultrasonic testing, spectroscopy and electrochemical methods have to be considered as the only possible methods of knowing there are no hidden flaws that could cause major damage.