Loading Rate Effects for Flaws Undergoing Mixed-Mode I/III Fracture

• Published in: Experimental mechanics Vol. 61; no. 8; pp. 1291 - 1307
• Main Authors: Fahem, A., Kidane, A., Sutton, M.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.10.2021; Springer Nature B.V
• Subjects: Aluminum; Biomedical Engineering and Bioengineering; Characterization and Evaluation of Materials; Control; Crack initiation; Digital imaging; Dynamical Systems; Engineering; Finite element method; Fracture mechanics; Fracture toughness; Lasers; Loading rate; Material properties; Optical Devices; Optics; Parameters; Photonics; Research Paper; Solid Mechanics; Stress intensity factors; Vibration; Dynamic Mixed-mode I/III; Stereo DIC; MOD; Spiral Notch; Torsional Split Hopkinson Bar; Loading Rate
• ISSN: 0014-4851; 1741-2765
• DOI: 10.1007/s11340-021-00739-0

Background The effect of loading rate on the fracture properties of materials had been the subject of interest for more than four decades. However, the effect of loading rates on Mixed-mode fracture, involving Modes I and III, is known little due to the complexity of loading conditions and the inertia effect at a high loading rate. Objective The main objective is to develop a framework to investigate the relationship between loading rate and fracture parameter under Mixed-mode (I/III) loading conditions using a novel laboratory setup. Methods Experimentally, a modified spiral Notched specimen, stereo-digital image correlation, and a torsional Hopkinson bar apparatus are employed to characterize the dynamic fracture response of materials subjected to a combined torsion and tension loading. Specimens with different gauge lengths were used to generate low, intermediate, and high loading rates associated with Mixed-mode (I/III) notch tip conditions. Numerically, finite element analyses were performed to calculate the dynamic stress intensity factor using the dynamic interaction integral approach. Results The fracture initiation time was seen to be related to the spiral angle. It was found that the Mixed-mode fracture initiation toughness increase with the loading rate. For Aluminum 2024-T3, the dynamic fracture initiation toughness under Mode-III is threefold smaller than the Mode-I condition. Conclusions The proposed approach, dynamic tension–torsion loading of a spirally notched specimen, successfully generates a range of loading rates on Mixed-mode fracture involving Modes I and III conditions. The dynamic integral method was effectively used to extract fracture parameters at different loading rates and conditions. Therefore, the proposed approach is a promising method for investigating the dynamic Mixed-mode fracture of materials involving Mode I and III conditions.