| 1. |
- Blanchard, Sebastien, et al.
(författare)
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Late Triassic volcanic activity in South-East Asia: New stratigraphical, geochronological and paleontological evidence from the Luang Prabang Basin (Laos)
- 2013
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Ingår i: Journal of Asian Earth Sciences. - : Elsevier BV. - 1367-9120. ; 70-71, s. 8-26
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Tidskriftsartikel (refereegranskat)abstract
- In South-East Asia, sedimentary basins displaying continental Permian and Triassic deposits have been poorly studied. Among these, the Luang Prabang Basin (North Laos) represents a potential key target to constrain the stratigraphic and structural evolutions of South-East Asia. A combined approach involving sedimentology, palaeontology, geochronology and structural analysis, was thus implemented to study the basin. It resulted in a new geological map, in defining new formations, and in proposing a complete revision of the Late Permian to Triassic stratigraphic succession as well as of the structural organization of the basin. Radiometric ages are used to discuss the synchronism of volcanic activity and sedimentation. The Luang Prabang Basin consists of an asymmetric NE-SW syncline with NE-SW thrusts, located at the contact between Late Permian and Late Triassic deposits. The potential stratigraphic gap at the Permian-Triassic boundary is therefore masked by deformation in the basin. The Late Triassic volcaniclastic continental deposits are representative of alluvial plain and fluvial environments. The basin was fed by several sources, varying from volcanic, carbonated to silicic (non-volcanic). U-Pb dating of euhedral zircon grains provided maximum sedimentation ages. The stratigraphic vertical succession of these ages, from ca. 225, ca. 220 to ca. 216 Ma, indicates that a long lasting volcanism was active during sedimentation and illustrates significant variations in sediment preservation rates in continental environments (from similar to 100 m/Ma to similar to 3 m/Ma). Anhedral inherited zircon grains gave older ages. A large number of them, at ca. 1870 Ma, imply the reworking of a Proterozoic basement and/or of sediments containing fragments of such a basement. In addition, the Late Triassic (Carnian to Norian) sediments yielded to a new dicynodont skull, attributed to the Kannemeyeriiform group family, from layers dated in between similar to 225 and similar to 221 Ma (Carnian). (C) 2013 Elsevier Ltd. All rights reserved.
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| 2. |
- Larsson, Per-Lennart, et al.
(författare)
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On the correlation between residual stresses and global indentation quantities : Numerical results for general biaxial stress fields
- 2012
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Ingår i: Materials and Design. - : Elsevier BV. - 0261-3069. ; 37, s. 435-442
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Tidskriftsartikel (refereegranskat)abstract
- The correlation between residual stresses and the global properties from an indentation test, i.e. hardness and size of the contact area, has been studied frequently in recent years. The investigations presented have been based on experimental, theoretical and numerical methods and as a result, the basic features of the problem are fairly well understood in the case of residual equi-biaxial surface stresses. The more general case, when the principal surface stresses are not necessarily equi-biaxial, has received much less attention and it is therefore the aim of the present study to remedy this shortcoming. In doing so, qualitative results are of immediate interest in this initial study but possible ways of quantitative descriptions are also discussed for future purposes. The present analysis is based on numerical methods and in particular the finite element method (FEM) is relied upon. Classical Mises elastoplastic material behavior is assumed throughout the investigation.
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| 3. |
- Larsson, Per-Lennart, et al.
(författare)
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On the invariance of hardness at sharp indention of materials with general biaxial residual stress fields
- 2013
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Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197 .- 0261-3069. ; 52, s. 602-608
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Tidskriftsartikel (refereegranskat)abstract
- In recent years, the influence from residual surface stresses on the global indentation properties, i.e. hardness and size of the contact area, have been studied quite frequently. The investigations presented have been based on experimental, theoretical and numerical methods and for one thing, the invariance of hardness in the case of residual equi-biaxial surface stresses, has been well-established. In the more general case, when the principal surface stresses are not necessarily equi-biaxial, corresponding results are more scattered and it is therefore the aim of the present study to remedy this shortcoming. In doing so, the problem is presently attacked using numerical methods and in particular the finite element method (FEM) is relied upon. Classical Mises elastoplastic material behavior is assumed throughout the investigation which is restricted, for clarity but not for necessity, to sharp cone indentation. The results confirm the invariance of hardness also for general stress fields when the deformation in the contact region is dominated by plastic deformation.
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