The worldwide industries use the sub-resonant vibration stress relief and welding conditioning since beginning of nineties. In the last years, with the searching of new alternatives process aiming energy economy with consequently the Global Heating reduce, the use of this technique can be very interesting. Moreover, the time reduction between vibration and thermal stress relief processes is around 80%, allowing a faster repairing pieces, which is prime factor to make a maintenance stop in a short time. Meanwhile, the scientific literature is rare about the use and the efficacy of this system This work has the propose of comparing the results of sub-harmonic stress relief process with conventional thermal process and correlate them to the decrease of the resonance peak frequencies, before and after treatments. These researches were done through an association between Santa Cecilia University, Minas Gerais Federal University - UFMG, FEI University Center and Engebasa - Mecanica e Usinagem Ltda, that have Meta-lax equipment. All of them in Brazil. This book should be especially useful for researchers and companies that perform stress relieving in metal parts manufacturing processes.