Fatigue Behavior of PLA Material and the Effects of Mean Stress and Notch: Experiments and Modeling
Mohammed Algarni
Abstract
Additive manufacturing (AM) is a 3D printing technology that creates complex engineering parts by printing layer by layer. AM is a disruptive technology that is rapidly growing, owing to its effective features: high accuracy, fast production, and low cost. Parts made of polylactic acid (PLA) biodegradable material fused deposition modeling are being increasingly produced in the industry because of their high strength and environment-friendliness. Three-dimensionally printed parts are prone to different loading types (static, dynamic, and time-dependent loading) during in-service operations. They react differently to loadings based on their manufacturing process parameters and geometry. This research aims to study the influence of notch and mean stress on the uniaxial fatigue behavior of PLA parts. The fatigue tests were load-controlled and performed with fatigue load ratios, R = -1, 0.1, and 0.3, on three rectangular-shaped specimens with large, medium, and sharp notches. The study was conducted with 180 fatigue tests and mainly focused on the high cycle fatigue regime. The experimental results showed that the effect of notches and mean stresses were significant on the PLA fatigue life. The Kohout and Vechet model, along with the factor of stress triaxiality, was used in order to study the notch influence on PLA fatigue life. Moreover, Walker model was used to investigate the influence of mean stress on PLA fatigue life. The life prediction of the two models accurately agreed with the experimental results.