TY - JOUR
T1 - Inelastic Strain and Damage in Surface Instability Tests
AU - Kao, Chu Shu
AU - Tarokh, Ali
AU - Biolzi, Luigi
AU - Labuz, Joseph F.
N1 - Publisher Copyright:
© 2015, Springer-Verlag Wien.
PY - 2016/2/1
Y1 - 2016/2/1
N2 - Spalling near a free surface in laboratory experiments on two sandstones was characterized using acoustic emission and digital image correlation. A surface instability apparatus was used to reproduce a state of plane strain near a free surface in a modeled semi-infinite medium subjected to far-field compressive stress. Comparison between AE locations and crack trajectory mapped after the test showed good consistency. Digital image correlation was used to find the displacements in directions parallel (axial direction) and perpendicular (lateral direction) to the free surface at various stages of loading. At a load ratio, LR = current load/peak load, of approximately 30 %, elastic deformation was measured. At 70–80 % LR, the free-face effect started to appear in the displacement contours, especially for the lateral displacement measurements. As the axial compressive stress increased close to peak, extensional lateral strain started to show concentrations associated with localized damage. Continuum damage mechanics was used to describe damage evolution in the surface instability test, and it was shown that a critical value of extensional inelastic strain, on the order of −10−3 for the virgin sandstones, may provide an indicator for determining the onset of surface spalling.
AB - Spalling near a free surface in laboratory experiments on two sandstones was characterized using acoustic emission and digital image correlation. A surface instability apparatus was used to reproduce a state of plane strain near a free surface in a modeled semi-infinite medium subjected to far-field compressive stress. Comparison between AE locations and crack trajectory mapped after the test showed good consistency. Digital image correlation was used to find the displacements in directions parallel (axial direction) and perpendicular (lateral direction) to the free surface at various stages of loading. At a load ratio, LR = current load/peak load, of approximately 30 %, elastic deformation was measured. At 70–80 % LR, the free-face effect started to appear in the displacement contours, especially for the lateral displacement measurements. As the axial compressive stress increased close to peak, extensional lateral strain started to show concentrations associated with localized damage. Continuum damage mechanics was used to describe damage evolution in the surface instability test, and it was shown that a critical value of extensional inelastic strain, on the order of −10−3 for the virgin sandstones, may provide an indicator for determining the onset of surface spalling.
KW - Acoustic emission
KW - Continuum damage mechanics
KW - Digital image correlation
KW - Surface spalling
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U2 - 10.1007/s00603-015-0771-5
DO - 10.1007/s00603-015-0771-5
M3 - Article
AN - SCOPUS:84957959826
SN - 0723-2632
VL - 49
SP - 401
EP - 415
JO - Rock Mechanics and Rock Engineering
JF - Rock Mechanics and Rock Engineering
IS - 2
ER -