TY - JOUR
T1 - Determining the angles of squat cracks via CT scanning and metallographic observations
AU - Naeimi, Meysam
AU - Li, Zili
AU - Dollevoet, Rolf
PY - 2020
Y1 - 2020
N2 - This study investigates the angles θ1, θ2, and θ3 that squat crack faces form with respect to three orthogonal planes: the rail top, the longitudinal-vertical cross-section and the lateral-vertical cross-section. Rail samples with squats of various severities are obtained from the field. Their three-dimensional crack networks are reconstructed using CT (computed tomography) scanning and serial cutting. A 3D visualization method, together with the necessary geometric definitions, is developed for enabling effective measurement and characterization of the squat cracks. It is found that the cracks can be characterized by four orientations (T1 – T4). The variation ranges of the crack angles are determined for each orientation that satisfies 132° ≤θ1 ≤ 150°, 6° ≤θ2 ≤ 36° and 67° ≤θ3 ≤ 81°. By investigating the occurrence frequency of the orientations, it is found that T4 and T1 together form the primary V-shaped cracks of the squats, and T2 and T3 together form the secondary V-shaped cracks. A finite element modelling of the wheel-track system, in combination with contact mechanics and multi-axial fatigue analysis, successfully relates the stress state to the RCF cracks.
AB - This study investigates the angles θ1, θ2, and θ3 that squat crack faces form with respect to three orthogonal planes: the rail top, the longitudinal-vertical cross-section and the lateral-vertical cross-section. Rail samples with squats of various severities are obtained from the field. Their three-dimensional crack networks are reconstructed using CT (computed tomography) scanning and serial cutting. A 3D visualization method, together with the necessary geometric definitions, is developed for enabling effective measurement and characterization of the squat cracks. It is found that the cracks can be characterized by four orientations (T1 – T4). The variation ranges of the crack angles are determined for each orientation that satisfies 132° ≤θ1 ≤ 150°, 6° ≤θ2 ≤ 36° and 67° ≤θ3 ≤ 81°. By investigating the occurrence frequency of the orientations, it is found that T4 and T1 together form the primary V-shaped cracks of the squats, and T2 and T3 together form the secondary V-shaped cracks. A finite element modelling of the wheel-track system, in combination with contact mechanics and multi-axial fatigue analysis, successfully relates the stress state to the RCF cracks.
KW - Crack angle
KW - Crack orientation
KW - CT scan
KW - Primary crack
KW - Secondary crack
KW - Serial cutting
KW - Squat
UR - http://www.scopus.com/inward/record.url?scp=85082508965&partnerID=8YFLogxK
U2 - 10.1016/j.engfracmech.2020.107016
DO - 10.1016/j.engfracmech.2020.107016
M3 - Article
AN - SCOPUS:85082508965
SN - 0013-7944
VL - 230
JO - Engineering Fracture Mechanics
JF - Engineering Fracture Mechanics
M1 - 107016
ER -