Methods and proceeding

High-frequency hammering method

High-frequency hammering methods are very effective to increase fatigue strength. The methods High Frequency Impact Treatment (HiFIT) and Ultrasonic Impact Treatment (UIT) will be analyzed and optimized regarding their effectiveness.

In application, hardened pins hammer the weld seam transition section with frequencies between 150Hz and 200Hz, so that plastic dents are created. Due to the plastification the sharpness of grooves is reduced and the material’s resistance is increased.

The HiFIT method is a hand-held unit of the size of about 15cm which is operated by pressurized air. The hammer head is a single steel pin with a diameter of 3-4mm, depending on the application, meaning local geometry and strength in the transmission section. The hammering frequency is in between 150Hz and 200Hz.

Different to the HiFIT method the excitation of the UIT method results of a magnetostrictive ultrasonic converter. The device is about 40cm big with a diameter of about 5cm. Depending on the application three to four simultaneously hammering pins with diameters from 3 to 5mm are used with a frequency of 200Hz.