Determination of the strength parameters of intact rock samples is an important requirement in rock engineering. On the other hand, proposing a simple method as an index to estimating the strength ...parameters is one of the tasks of engineering geology. The conventional triaxial test (CTT) is one approach used to determine shear strength parameters (φ and c) that requires standard core cylindrical samples. As it is not possible to prepare standard core samples or collect rock block samples to prepare standard cores under all conditions, the shear strength parameters should be determined using samples having non-standard geometry and dimensions. For this purpose, a miniature triaxial test (MTT) device is introduced and used as an index test to apply triaxial loading on small cubic rock samples in order to estimate their shear strength parameters. The repeatability of the MTT results was determined by performing 27 MTT on 6 × 6 × 6 mm3 polymethyl methacrylate (PMMA) cubic samples. The results showed that the values measured by the device were repeatable with over 97% similarity. The internal friction angles (φ) of the mortar samples obtained from the CTT on cylindrical samples and MTT on the 6 × 6 × 6 mm3 samples are similar. However, the cohesion (c) value measured from the MTT test is nearly double the value obtained from the CTT test. The shear strength parameters of 12 different intact limestone samples from the Asmari Formation located in the Siyakouh section were obtained by performing CTT on standard NX core samples and MTT on the 6 × 6 × 6 mm3 samples. The correlation between the φ and c from the CTT and MTT had coefficients of determination (R2) of 0.92 and 0.88, respectively. The precision of the empirical relation for the CTT-MTT correlation was evaluated and showed that shear strength values estimated by the MTT had about 90% similarity with the measured shear strength values from the CTT.
•Designee and manufacture Miniature triaxial test (MTT) device.•Determining friction of angle (φ) and cohesion (C) of small cubic rock samples by MTT.•The results of MTT are reproducible.•Correlations between the φ and C from the conventional triaxial test (CTT) and MTT.
This work aims to evaluate the use of miniaturized tensile specimen (MTS) to characterise the mechanical properties of alloys developed through rapid alloy prototyping (RAP), where high throughput ...tests are required on relatively small amounts of material. Tensile tests were conducted at a variety of strain rates and with increasingly smaller specimen sizes, ranging from larger specimens conforming to ASTM/ISO standards, down to small non-standard specimens. The gauge lengths of the specimens ranged from 50 to 80 mm for the standard specimens down to 5–10 mm for the non-standard specimens. To generalize the non-standard MTS designs, three alloys, DP800, DP600 and 316L stainless steel, were adopted. The results obtained from non-standard designs were compared with those from standard designs. The results show that non-standard designs can give repeatable results for yield strength (YS), ultimate tensile strength (UTS) and uniform elongation (eU). The maximum result differences of YS, UTS and eU are 7.37%, 7.71% and 11.9%, respectively, for DP alloys comparing standard and non-standard dimensions. These values are 13.56%, 14.03% and 19.5%, respectively 316L steel. The total elongation (ef) increases as the specimen dimension decreases. The geometrically dependent constants (n) are 0.2, 0.31 and 0.11 for DP800, DP600 and 316L, respectively. However, the Young's modulus is hard to determine precisely from the miniaturized designs. The conclusion from this work is that miniaturized tensile testing can be used with confidence as a high throughput means of predicting standard mechanical properties across a range of steels.
Nonalcoholic fatty liver disease (NAFLD) is currently one of the most common chronic liver diseases, especially in developed countries. One group of substances with a potential use in the treatment ...of NAFLD are plant polyphenols, represented by resveratrol. The aim of this study was to evaluate the effect of resveratrol on steatosis and oxidative stress in HepG2 cells. The steatosis of cells was carried out using free fatty acids: oleic or palmitic acid and their mixtures. Steatosis was visualized using the intracellular lipid staining by Nile Red dye with a fluorescence microscope. This study also determined the viability of cells and mitochondrial membrane potential. The current study showed that fatty acids and their mixtures induced fat overloading in HepG2 cells. In the group of cells incubated with oleic acid (OA), observed changes were moderate with prevailing micro-vesicular steatosis. In case of cells incubated with palmitic acid (PA) and the mixtures of fatty acids, micro- and macro-vacuolar steatosis occurred in most of the cells. Resveratrol decreased steatosis in HepG2 cells induced by OA, PA, as well as their mixtures, and in most of experimental groups did not reduce cells viability. Resveratrol reduced the oxidative stress in HepG2 cells treated with fatty acids mixtures.
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