ABSTRACT
Root damages due to mechanical impacts result in deterioration in commercial sugar beet quality. In order to determine the mechanical characteristics of roots, a stand equipped with a pendulum enabling impact investigations of whole beets was used. The roots were stored in a monitored environment for up to 5 days (temperature 15 ± 2 °C, 40 ± 2%). During the tests, the beets were struck against a flat steel resistant surface with the velocities Vimp = 0.5, 1.0 and 1.5 m·s-1. The measurements of local root curvatures in three chosen impact areas and the deformation (dmax) allowed modelling of the volume of contact (CV) by means of the ellipsoid cap. These investigations enabled the determination of the relations between the maximal impact force, Fmax, the impact energy, Eimp, and the absorbed energy, Eabs, as well as the contact volume and impact velocity, taking into account the root storage time, St. It was found that the maximal impact force increased with increasing impact velocity and decreased with the storage time for each group of roots. With increasing velocity, there were also increases in the following: impact energy, absorbed energy, contact volume and maximal deformation, as well as absorbed energy, referred to as the mass Eabs-v from Vimp. The mean values of the stresses (σmax), being the quotients of the impact force (Fmax) and the surface area of the ellipsoid cap base (ABE), were 0.81-1.17 MPa, 1.064-1.59 MPa and 1.45-1.77 MPa for the velocities of 0.5, 1.0 and 1.5 m·s-1, respectively. It was confirmed that the statistical significance of the mentioned parameters changes depending on the impact velocity.
ABSTRACT
Compression tests of cylindrical samples were carried out using two 'Rubin' and 'Red Jonaprince' apple cultivars with flesh firmness differing in a statistically significant way. The tests were conducted under both the quasi-static and impact loading conditions, which required the use of two test stands. For this purpose, an impact measuring stand was designed and built. The tests proved that the firmness of the apple flesh influenced the mechanical response under both the quasi-static and impact loading conditions. The elasticity modulus had much higher values under the impact than quasi-static loading conditions. This indicates that the stiffness of the apple tissue was larger during the impact than at the low-speed compression. Different failure mechanisms of cylindrical apple flesh samples were found depending on the loading conditions. Under the quasi-static loading conditions, the apples of both cultivars were damaged at the same strain value. However, during the impact, apples were apt to damage at a constant stress value regardless of the firmness of the tested cultivar. The toughness of the apple tissue depended on firmness and was larger under the quasi-static loading conditions for the apples with larger firmness. However, under the impact loading conditions, the toughness was greater for the apples with smaller firmness.
ABSTRACT
The research subject was the analysis of the microstructure, barrier properties, and mechanical resistance of the psyllium husk (PH)-modified thermoplastic starch films. The tensile tests under various static loading conditions were not performed by researchers for this type of material before and are essential for a more precise assessment of the material's behavior under the conditions of its subsequent use. The film samples were manufactured by the casting method. PH addition improved starch gelatinization and caused a decrease in failure strain by 86% and an increase in failure stress by 48% compared to pure films. Fourier transform infrared spectroscopy results showed the formation of additional hydrogen bonds between polysaccharides in starch and PH. An increase in the number of hydrophilic groups in the modified films resulted in a faster contact angle decrease (27.4% compared to 12.8% for pure ones within the first 5 s); however, it increased the energy of water binding and surface complexity. The modified films showed the opacity at 600 nm, 43% higher than in the pure starch film, and lower transmittance, suggesting effectively improving barrier properties to UV light, a potent lipid-oxidizing agent in food systems.
ABSTRACT
Non-thermal endovenous ablations, due to the lowest probability of complications, are the new method of treating chronic venous insufficiency-one of the most common diseases globally. The Flebogrif system (Balton Sp. z o.o., Warsaw, Poland) is a new mechano-chemical ablation system causing the mechanical damage of endothelium that allows for better sclerosant penetration into its wall. The purpose of the article is to provide mechanical characteristics in the form of force-displacement dependence for a single cutting element, and a bundle of cutting elements of Flebogrif as a whole for different levels of protrusion of the bundle of cutting elements. A TA.HD plus (Stable Micro Systems, Godalming, UK) analyzer equipped with special handles, was used for characteristics testing. The head movement speed used was 5 mm·s-1. The Flebogrif system was tested for three cutting element protrusion levels: L = Lmax, L = 0.9·Lmax, and L = 0.8·Lmax. Before testing, geometric measurement of the spacing of the cutting elements for three proposed protrusions was performed. It was established that decreasing the working length of the cutting elements will increase their rigidity, and, as a result, increase the force exerted on the internal surface of the vein wall. The obtained characteristics will allow for specifying contact force variability ranges and the corresponding diameter ranges of operated veins.
