Abstract
Post-mortem characterisation is a pivotal tool to trace back to the origin of structural failures in modern engineering analyses. This work compared both the crack propagation and rupture roughness profiles based on areal parameters for total fracture area. Notched and smooth samples made of weather-resistant structural steel (10HNAP), popular S355J2 structural steel and aluminium alloy AW-2017A under bending, torsion and combined bending–torsion were investigated. After the fatigue tests, fatigue fractures were measured with an optical profilometer, and the relevant surface parameters were critically compared. The results showed a great impact of the loading scenario on both the local profiles and total fracture areas. Both approaches (local and total fracture zones) for specimens with different geometries were investigated. For all specimens, measured texture parameters decreased in the following order: total area, rupture area and propagation area.
Highlights
Post-mortem analysis is a fundamental engineering procedure to identify the damage accumulation mechanisms associated with fatigue failure
The material grades studied in the present research were: (a) 10HNAP weather-resistant structural steel [39]; (b) S355J2 structural steel [41] and (c) AW-2017A-T4 aluminium alloy [42]
The fracture plane analysis revealed that, in S355J2 steel samples, the cracks initiated in the plane of maximum shear stresses and propagated in the plane of maximum normal stresses (Figure 6a)
Summary
Post-mortem analysis is a fundamental engineering procedure to identify the damage accumulation mechanisms associated with fatigue failure. Much research connected with surface metrology has been focused on extensive investigations in which 3D surface roughness parameters have been presented in light of the relationship between surface properties and operation properties [4,5,6,7,8]. This analysis provides useful information, post-failure fractographic surface examinations allow the cause of failure in materials to be determined [9,10,11,12]. Even though advanced methods such as optical coherence tomography [18], scanning acoustic microscopy [19] or energy response approach based on strain energy density histories during variable loading [20,21] are described in the Materials 2020, 13, 3691; doi:10.3390/ma13173691 www.mdpi.com/journal/materials
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