A Novel Analytical Solution on the Mode I SIF for Finite Plates with Slanted Cracks

This contribution addresses a novel analytical procedure to evaluate the Stress Intensity Factors (SIF) of slant notches existing in flat plates employing the concept of the stress dead-zone. The compliance function formulation is extended to the Linear Elastic Fracture Mechanics (LEFM) to assess the fracture characterization. Therefore, the hypothesis is established for centrally oriented cracked specimens with various slant angles. To fulfil the study objectives, a hybrid experimental/computational study resorting to Digital Image Correlation (DIC) and Finite Element Method (FEM) is undertaken, aiming at the monitoring of the component deformation around the cracked region and subsequent SIF determination. A comparison is drawn on the SIF results extracted via the dead-zone concept, experimental and numerical studies to the reference solution, available in the literature. Besides, as a further investigation, the stress dead-zone region, which was analytically characterized, is also numerically verified through FEM. Encouraging results have been obtained which validate the dead-zone hypothesis for slant-cracked plates. (C) 2020 The Authors. Published by Elsevier B.V

Fracture and fatigue behaviour of a laser additive manufactured Zr-based bulk metallic glass

Laser additive manufacturing of bulk metallic glass (BMG) provides an effective bypassing of the critical casting thickness constraints that limit the size of components that can be produced; however, open questions remain regarding the resulting mechanical properties. In this work, a Zr-based BMG known as AMZ4 with composition Zr59.3Cu28.8Nb1.5Al10.4 was printed using a laser powder bed fusion (LPBF) technique. Micro X-ray computed tomography results together with electron microscopy imaging revealed porous processing defects in LPBF produced AMZ4 that led to a loss in tensile strength. Fatigue crack growth studies revealed a fatigue threshold, ΔKth., of ∼1.33 MPa√m and a Paris law exponent of m = 1.14, which are relatively low values for metallic materials. A KIC fracture toughness of 24−29 MPa√m was found for the LPBF BMG samples, which is much lower than the KQ of 97−138 MPa√m and KJIC of 158−253 MPa√m measured for the cast alloy with the same composition. The lower fracture toughness of the laser processed AMZ4 was attributed to ∼7.5× higher dissolved oxygen in the structure when compared to the cast AMZ4. Despite the higher level of oxygen, the formation of oxide nanocrystals was not observed by transmission electron microscopy. Oxygen induced toughness loss was confirmed by dissolving elevated concentrations of oxygen into cast AMZ4 rods, which led to a reduction in bending ductility and changes in the short-range order of the glass structure, as revealed by synchrotron X-ray diffraction