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Deformation and failure laws and acoustic emission characteristics of low‑strength molybdenum ore

100%

Zhao K. , Yang J. , Song Y. , Wang Q. , Zhao K. , Ji Y.

tom Vol. 23, no. 2

art. no. e74, 2023

Uniaxial compression acoustic emission (AE) tests were conducted on low-strength molybdenum ore (LSMO) to investigate its deformation and failure laws and AE characteristics. The stress-strain curve and AE parameter data of LSMOs were obtained by uniaxial compression AE test, and the relationships of stress, AE parameter, amplitude fractal dimension, and AE b value with loading time were analyzed accordingly to obtain the general law of their deformation and failure and a series of AE characteristics. The research shows that under the action of uniaxial stress, the failure mode of LSMOs mainly shows brittle failure, and the failure form mainly shows monoclinic shear failure. The stress-strain curve shows obvious plastic-elastic deformation, the plastic deformation time is long, and the division of each stage of deformation failure is not obvious. The simultaneous occurrence of large surges in ringing count and energy to higher orders of magnitude can be used as precursor information for failure destabilization of LSMOs. The evolution process of AE parameters of LSMO corresponds well with its deformation and failure process, and the variation pattern of ringing counts and energy shows a high consistency. With increasing stress, the amplitude correlation dimension and b value are mainly in the form of "falling-rising-falling-fluctuating". The results of the study can provide some theoretical basis for the assessment of the stability of the mine surrounding rock and the determination of a reasonable and effective reinforcement plan.

The impact of technology on Poisson's ratio of auxetic polyurethane foams

80%

Lisiecki J. , Nowakowski D.

tom Vol. 41, Issue 1

119--140; 141--160

The article presents a method for measuring Poisson’s ratio of the polyurethane foam, including shapes of the auxetic foam. The impact of technology applied in Air Force Institute of Technology, that is a method for processing the selected polyurethane foams, on the value of Poisson’s ratio of the auxetic foam shape was presented. In order to manufacture the auxetic foam shapes, two methods; mechanical-thermal and mechanical-chemical-thermal, were applied.

W artykule przedstawiono sposób pomiaru współczynnika Poissona próbek pianki poliuretanowej, w tym kształtek pianki auksetycznej. Przedstawiono wpływ technologii zastosowanej w ITWL, tzn. sposobu przetwarzania wybranych pianek poliuretanowych na wartość współczynnika Poissona kształtki pianki auksetycznej. Do wytwarzania kształtek pianki auksetycznej zastosowano dwie metody: mechaniczno-termiczną oraz mechaniczno-chemiczno-termiczną.

Auxetic polyurethane foams – method for determining a softening point

70%

Lisiecki J.

tom Vol. 40, Issue 2

5--21; 22--38

The article described selected methods for determining a softening point of plastics (polymers). The way of determining a softening point of polyurethane foams was suggested. Moreover, the influence of annealing temperature of an auxetic polyurethane foam on its volume was presented.