Fracture tests of unsaturated polyester resin on large, single-edge notched-bend specimens were conducted under static and dynamic bend tests at room temperature. The velocity of a loading point in ...the three-point bending was changed from 8.3×10-6mm/s to 7×105 times its value. The two types of fracture marks of the both-ends-closed mark (like ellipses) and the one-end-opened mark (like parabolas) were observed and they were expressed by the equation of fracture marks. A rocket mark, defined here, was also often observed in the dynamic bending test and was well-approximated by the equation. The experimental number, percentage, relative interference appearing distance and the calculated relative critical distance of the marks changed with the crack propagation distance and the testing speed. The velocity of a primary crack propagation was measured and approximated by a mixed-condition relation proposed by us. This change and the gammer-letter relation between the velocity and a dynamic stress intensity factor KD (or a dynamic strain energy release rate, SD) gives the latter (KD or SD) as a function of the crack propagation distance. This provides a good theoretical explanation of the above variations of fracture marks.
When flowing down a tapered tube, such as a narrow capillary, red blood cells (RBCs) are subject to deformation, the first event of which is folding in a pancake manner. The RBC deformability is ...reduced during cell ageing, a phenomenon that may reflect alterations in intracellular viscosity, membrane rigidity or RBC shape. Age related shape changes and their importance for increased RBC rigidity were theoretically analysed. The average empirically observed RBC profile is shown to offer little resistance to bending as compared to other, theoretically possible profiles of the same membrane area and RBC volume. Because of a decrease in projected area (diameter size), and therefore in pressure load, the pressure needed to initiate folding of an old RBC is between 20 and 55% higher than that required to fold a young one if, during RBC ageing, membrane area to cell volume ratio is constant as empirically observed. This difference exists whether the RBC is mathematically treated as a solid body or as a membrane shell.
Assessment of wood decay in small-scale unsterile soil-bed tests Machek, L; Derksen, A.M; Sierra-Alvarez, R. (Wageningen Agricultural Univ. (Netherlands). Forestry Dept.)
Document - the International Research Group on Wood Preservation (Sweden),
1997
97-20111
Conference Proceeding
PDF
