Ultrasonic Fatigue Endurance Investigation on Plastic Material Nylon 6

Ultrasonic fatigue tests were carried out on the plastic material Nylon 6. Special attention was devoted to the tempera-ture control in order to avoid physic-chemical transformation of this low melting point material. Under ultrasonic fa-tigue tests, important heat dissipation takes place at the narrow section of hourglass shape specimen leading to high temperature at this zone. The specimen was calculated to meet the resonance condition with the smallest dimensions at its narrow section, with aim to reduce the temperature gradient at this zone of this non heat conducting material. Tem-perature at narrow section was maintained lower than 45˚C using a cooling system with cooling air; under this condi-tion the ultrasonic fatigue tests were performed. Experimental tests were carried out at low loading range (9 %- 12.5% of the elastic limit of material) in order to control the highest temperature and to avoid that specimen was out of reso-nance condition. Experimental results are analyzed together with the fracture surfaces and conclusions are presented concerning the ultrasonic fatigue endurance of this polymeric material