Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10140204 | Engineering Fracture Mechanics | 2018 | 10 Pages |
Abstract
Crack arrest testing of micro-sized cantilever beams (â8â¯Ãâ¯4â¯Ãâ¯6â¯Î¼m, length, width and height, respectively) was conducted in order to evaluate the suitability of a new method to quantify local crack arrest properties. Chevron notched cantilevers were milled to match the (1â¯0â¯0)[0â¯1¯â¯1] crack system in α-iron, where earlier attempts to obtain brittle or rapidly propagating fracture proved difficult. Brittle crack initiation and propagation was achieved by means of the deposition of a layer of SiOX on the surface, acting as a brittle starter. All tests were performed at â75â¯Â°C, using an in-house designed cooling system. The cracks arrested after propagation into the iron cantilever. A finite element model was developed to determine the appropriate dimensionless shape factor and provide a rigorous computer analysis of these complexly shaped cantilevers. KQC and KQa, at initiation and arrest respectively, were determined and evaluated. The cantilevers were later displaced further at 40â¯K to allow evaluation of crack jump lengths and to obtain a more complete analysis of the fracture surfaces. The average fracture toughness was determined to be 3.89â¯Â±â¯1.00â¯MPam, and the average arrest toughness to be 2.6â¯Â±â¯0.86â¯MPam. The finite element model highlights the effect of small variations in geometry which was larger than anticipated and strongly affects the shape factor, up to a 25% difference in f(a/W). As small variations in geometry are inevitable when milling with FIB, the need for individual models tailored to every cantilever is discussed.
Related Topics
Physical Sciences and Engineering
Engineering
Mechanical Engineering
Authors
Brage Dahl Snartland, Antonio Alvaro, Vidar Osen, Christian Thaulow,