Static and Fatigue Behaviors of Polyamide 12 Hinge Joint Manufactured by Multi-Jet Fusion

Polyamide is a light weight and high strength polymer material and it has been widely used in light equipments as hinge joint. The reliability and service life of polyamide hinge joint are crucial for its application. This paper investigates the static and fatigue behaviors of polyamide 12 hinge joint. The polyamide 12 hinge joint specimens were manufactured using multi-jet fusion (MJF). The fatigue experiments of polyamide joint under different stress levels were conducted, and the fatigue life S-N curve of the joint specimens was obtained. The structural stress of the joint was also analyzed by finite element method. The results indicated that the fatigue fractures of polyamide hinge joints occur at the side of the hole in the transverse direction. The ultimate tensile and fatigue strengths of the polyamide hinge joints are 41 MPa and 11.4 MPa, respectively. The fatigue striations are observed on the fracture surface, and the fatigue initiation starts from microvoids. The fatigue cracks tend to occur in sintered interfaces, where the crosslinked molecular chains are easily broken. This paper provides support for the design and application of polyamide hinge joint manufactured using MJF.