Effect of the stress concentration factor on the final fracture zone of aluminium AW 6063 T6 for rotating bending specimens

• Published in: Materials today communications 2022-06, Vol.31, p.103766, Article 103766
• Main Authors: Strzelecki, Przemysław, Wachowski, Marcin
• Format: Article
• Language: English
• Subjects: Aluminium alloy; Fatigue fractography; High-cycle fatigue; Stress concentration factor
• ISSN: 2352-4928; 2352-4928
• DOI: 10.1016/j.mtcomm.2022.103766

The paper presents fracture surfaces of the polycrystalline material - AW 6063 T6 aluminium alloy - under a rotating bending load. The fatigue fracture surfaces were analysed for high-cycle fatigue at approximately 1 × 105, 8 × 105 cycles and stress amplitude level equal to 140 MPa. The specimens with four different stress concentration factors Kt (with values ~1, 1.4, 2 and 2.6) were made from a drawn bar. The fatigue tests were performed by rotating bending stand with a frequency of 50 Hz. Thirty (30) tests were carried out for each geometry of the specimen. Final fracture zones for unnotched specimens were 39.9%, 35.8% and 43.3% of the total cross-sectional area for 1 × 105, 8 × 105 cycles and 140 MPa stress amplitude, respectively, However, the final fracture zone for the notched specimen with Kt equal to 2.6 was less and had a value of 13.7%, 13.8% and 18.8% of the total cross-sectional area for 1 × 105, 8 × 105 cycles and 140 MPa stress amplitude, respectively. The research aimed to compare the ratio of the area of the final fracture zone to the total cross-sectional area. The authors have found a relationship that could be used to estimate the stress concentration factor based on the area of the final fracture zone. Based on this, the stress concentration factor can be determined. The estimates calculated using the equation and the test results show a good correlation between the stress concentration factor and the ratio of the area of the final fracture zone to the total cross-sectional area. The proposed method of determining the stress concentration factor can be used to verify different manufacturing processes (e.g. surface finish, notch radius) and the loading history (e.g. existing overload conditions). [Display omitted] •The final fracture zone depends on the stress concentration factor.•Smooth specimens under rotating bending can have two origins cracks.•It is possible to estimate the stress concentration factor based on the final fracture zone.