Scientists from Tomsk Polytechnic University have created an X-ray complex which is able to detect the smallest defects in the rotors of gas turbine engines of modern civil and military aircrafts.
The X-ray complex was designed and assembled after an order by the JSC United Engine Corporation (UEC). It consists of a robotic manipulator, an X-ray machine, a linear radiation receiver and a rotating table where the objects to be tested are placed.
The X-ray complex can work with rotors up to 70cm in diameter. The radiation receiver is placed inside the rotor, while the X-ray machine stays outside. After X-ray scanning, specialists can obtain a high-resolution digital image of the weld, which displays even very small defects up to 100 microns in size.
According to Alexander Cheprasov, Doctor of Technical Sciences at the Department of Physical Methods and Devices of Quality Testing, the huge thermal and mechanical loads that an aircraft engine’s rotor is subject to means it is important to ensure the integrity of the welds.
“[The rotor] consists of disks connected by electron-beam welding. It is a high-quality technique but there may also be defects. The most dangerous are places where metal is not welded. In these places a rotor may simply breakdown thus causing an accident. In aviation any abnormal situation invites a disaster,’ he explained.
Traditionally, rotors are tested with X-ray-sensitive films. The film is used to seal welds, and radiation causes an image of the defects to be displayed on the film. This is a highly precise method, but takes a long time and is not suited for all products.
The engineers tested their new X-ray complex on a rotor that was detect using X-ray film. However, the method failed to detect some defects, and the rotor broke down at the testing stage. Cheprasov said that the use of X-ray film requires the X-ray radiation source to be place inside the product, which is not always possible due to the size of the source.
“Therefore, the customer set us the task to create an automated radiographic complex of high spatial resolution without using the X-ray film,” he said.
To solve the problem of placing a large source of radiation inside the product, the researchers applied an inverse radiation transmission scheme.
The radiographic complex will be installed at the customer enterprise in the dedicated room and staff will work in another dedicated operating room. It can operate around the clock without interruption, and can be used for non-destructive testing of any thin-walled objects up to two meters in diameter, as well as products of any arbitrary shape.
The non-destructive testing technology developed for this facility may be applied for testing significantly larger objects, such as gas turbine power plants installed on ships or on ground.