| 1. |
- Sørensen, Bent F., et al.
(författare)
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Micromechanical analysis of damage mechanisms in ceramic-matrix composites during mechanical and thermal cycling
- 1993
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Ingår i: Composites. - 2222-1018. ; 24:2, s. 129-140
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Tidskriftsartikel (refereegranskat)abstract
- This work presents a micromechanical study of the cyclic response of a undirectionally reinforced ceramic-matrix composite under time-varying load, parallel to fibres, and under thermal cycling. The analysis was based on the finite element method. The overall response was deduced from the response of a representative volume element consisting of concentrically placed cylinders of fibre and surrounding matrix, bounded axially by a matrix crack and a symmetry plane. The interface between the fibre and the matrix was assumed to be a frictional sliding contact (Coulomb friction). The results of this study indicated that the interfacial sliding stress τs may be assumed to be constant over the sliding distance, whereas its variation with the remote applied stress is important. It was also found that the overall stress/strain behaviour is non-linear when the state of interfacial sliding is changing, while a linear response results for a fully sliding interface. In the latter case, the tangential modulus in loading differs from that in unloading. For thermal cycling, the analysis showed that, due to insignificant interfacial sliding, the thermal expansion coefficients in the damaged state are practically the same as in the undamaged state.
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| 2. |
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| 3. |
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| 4. |
- Bak, Søren Alex, et al.
(författare)
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Quantification of four ionophores in soil, sediment and manure using pressurised liquid extraction
- 2013
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Ingår i: Journal of Chromatography A. - 0021-9673 .- 1873-3778. ; 1307:September, s. 27-33
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Tidskriftsartikel (refereegranskat)abstract
- A multi-residue pressurised liquid extraction (PLE) methodology has been established for the determination of the four ionophores: lasalocid, monensin, salinomycin and narasin in solid environmental matrices. The PLE methodology is combined with solid phase extraction as clean-up using liquid chromatography coupled to tandem mass spectrometry applying electrospray ionisation for detection. The samples were freeze-dried prior to extraction. The absolute recoveries for soil and sediment ranged from 71 to 123% (relative standard deviation (RSDs) below 16%) and in the range 94–133% (RSDs 9–35%) for poultry manure. The final method allowed for the detection of four ionophores down to a few hundred ng kg−1 in natural solid matrices with limit of quantifications (LOQs) being 0.96, 0.87, 0.98, and 0.64 μg kg−1 in soil for lasalocid, monensin, salinomycin, and narasin, respectively. Corresponding LOQs in sediment were 1.28, 1.34, 1.39, and 0.78 μg kg−1 for the respective ionophores, while in manure the LOQs were 0.98, 1.01, 1.45, and 1.01 μg kg−1.
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| 5. |
- Bak, Søren Alex, et al.
(författare)
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Quantification of four ionophores in soil, sediment and manure using pressurised liquid extraction
- 2013
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Ingår i: Journal of Chromatography A. - : Elsevier. - 0021-9673 .- 1873-3778. ; 1307:September, s. 27-33
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Tidskriftsartikel (refereegranskat)abstract
- A multi-residue pressurised liquid extraction (PLE) methodology has been established for the determination of the four ionophores: lasalocid, monensin, salinomycin and narasin in solid environmental matrices. The PLE methodology is combined with solid phase extraction as clean-up using liquid chromatography coupled to tandem mass spectrometry applying electrospray ionisation for detection. The samples were freeze-dried prior to extraction. The absolute recoveries for soil and sediment ranged from 71 to 123% (relative standard deviation (RSDs) below 16%) and in the range 94–133% (RSDs 9–35%) for poultry manure. The final method allowed for the detection of four ionophores down to a few hundred ng kg−1 in natural solid matrices with limit of quantifications (LOQs) being 0.96, 0.87, 0.98, and 0.64 μg kg−1 in soil for lasalocid, monensin, salinomycin, and narasin, respectively. Corresponding LOQs in sediment were 1.28, 1.34, 1.39, and 0.78 μg kg−1 for the respective ionophores, while in manure the LOQs were 0.98,1.01, 1.45, and 1.01 μg kg−1.
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| 6. |
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| 7. |
- Butler, Nick, et al.
(författare)
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Work, play and boredom : editorial
- 2011
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Ingår i: Ephemera. - 2052-1499 .- 1473-2866. ; 11:4, s. 329-335
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 8. |
- Butler, Nick, et al.
(författare)
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Work, play and boredom
- 2011
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Ingår i: Ephemera: Theory and Politics in Organization. - 1473-2866. ; 11:4, s. 329-335
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 9. |
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| 10. |
- Graciani, Enrique
(författare)
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Numerical analysis of the single fiber fragmentation test including the effect of interfacial friction
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A numerical analysis of the single fiber fragmentation test is presented in this thesis. The aim of the numerical study is elucidating the influence of friction in the growth of the debond cracks along the fiber-matrix interface. Two distinct approaches and numerical techniques have been employed in the analysis. Firstly, debond growth is studied using Linear Elastic Fracture Mechanics for interface cracks. Thus, an accurate solution of the near-tip stresses and displacements is needed, which is obtained using a self-developed numerical tool, based on the Boundary Element Method. Energy Release Rate associated to debond growth is evaluated using a modified version of Irwin's Virtual Crack Closure Technique, which takes into account the presence of frictional stresses along the crack faces. Numerical results show that friction opposes to debond growth and, consequently, it has to be taken into account if quantitative values of the interfacial fracture toughness are going to be derived from test results. In the abovementioned approach, numerical solutions are obtained neglecting the influence of load history on the frictional contact solution. For that reason, a second approach has been employed in which debond onset and growth is simulated using cohesive elements, thus following the actual load history of the sample. A commercial Finite Elements code has been employed for the numerical simulation in this approach, since there is no need for such a high refinement in the mesh as in the previous analyses. Numerical results confirm that the influence of load history is negligible in the analysis, since analogous results are obtained with both approaches.
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