Enhancing fatigue performance of AA6063-T6 fasteners through novel electromagnetic cold expansion using a double-frequency discharge

• Published in: Engineering fracture mechanics 2024-11, Vol.310, p.110509, Article 110509
• Main Authors: Ouyang, Shaowei, Xu, Xiaofei, Geng, Huihui, Du, Limeng, Li, Changxing, Zhang, Wang, Zhu, Xinhui, Han, Xiaotao, Cao, Quanliang, Li, Liang
• Format: Article
• Language: English
• Subjects: Discharge circuit; Electromagnetic cold expansion; Fastener; Fatigue life; Lorentz force
• ISSN: 0013-7944
• DOI: 10.1016/j.engfracmech.2024.110509

•Novel EMCE using double-frequency currents is proposed to enhance fastener fatigue life.•The proposed EMCE requires only one set of power supply that is easy to implement.•Significant fatigue improvement at varying stress loads through EMCE treatment.•Fatigue behavior and strengthening mechanism of fasteners are revealed. Non-contact electromagnetic cold expansion process (EMCE) represents a highly promising way to enhance the fatigue performance of fasteners. However, within the current technological framework, the necessity for dual power supplies and an accurate discharge control system has constrained the development and application of this technique. To address this, a novel EMCE process utilizing a double-frequency discharge is proposed. This process is accompanied by the development of an electromagnetic system with only one set of power supply to generate a current composed of a gradual-ascending and rapid-descending stage. This current induces a significant radially outward Lorentz force, facilitating hole expansion and introducing residual compressive stress around the hole, thus increasing the fatigue life of the fasteners. The experimental results demonstrate a remarkable enhancement in fatigue life for samples treated with the EMCE process when compared to untreated ones, showing an impressive 6.8-fold, 4.9-fold, and 1.6-fold increase at stress loads of 120 MPa, 130 MPa, and 150 MPa, respectively. Microstructural analysis reveals that the processed components exhibit favorable surface integrity, and there is no significant grain refinement near the hole. Moreover, it is found that there existed optimal current waveform to maximize fatigue life. These findings hold significance in understanding the EMCE process and advancing its practical applicability.