Formation and rheological properties of mixed protein-polysaccharide gels (composites) was studied. The composites consisted of whey proteins gelling separately, which were surrounded by polysaccharide gel. The polysaccharide gels were obtained from κ-carrageenan and κ-carrageenan-galactomannan (guar gum and locust bean gum) mixtures. The texture of gels obtained was examined by their compression and bending test. The composite gels obtained from 14% WPI solution and the 1.5% mixture of κ-carrageenan with locust bean gum in a 1:1 ratio exhibited a higher shear stress value at fracture in comparison to WPI gels, but they were less resistant to fracture in the bending test. The texture of gels was highly influenced by pH.
analysis (DMA), three-point bendingtest, and Brinell’s hardness. The influence of poly(ester) structure on cross-linking density ( ν e ), tgδ max , tgδ max height, storage modulus ( ), hardness, flexural modulus at bending ( E mod ), deflection at
The determination of service life of concrete structural members is an important aspect of durability design. The scope of the paper is to present an effective and easy to use method for the estimation of service life of pre-cast concrete structural members. A stochastic approach using stochastic finite element method was applied during the analysis. The effect of creep, shrinkage, relaxation, carbonation induced corrosion and deterioration of cross-sectional sizes on the mean value and standard deviation of bending moment resistance, as well as the change of load effect in time were taken into account during the calculations. The results of probabilistic analysis were compared to results of bending tests that were carried out on pre-stressed concrete beams. The use of the introduced method for the purposes of service life estimation is also presented in case of a long-span, pre-cast, pre-stressed concrete beam. Initial stochastic parameters of material properties and structural geometry were derived from destructive material tests and geometry measurements on appropriate beams. Considering the same safety level and design-life as in Eurocode 2, the introduced probabilistic design method delivers about 10% higher load carrying capacity as the application of relevant Eurocode 2 standard in case of the presented beam.
The influence of the structure of succinic or glutaric anhydride modified linear unsaturated (epoxy) polyesters on the course
of the cure reaction with styrene initiated by benzoyl peroxide (BPO) or the mixture of benzoyl peroxide/tetrahydrophthalic
anhydride (BPO/THPA) or benzoyl peroxide/maleic anhydride, as well as viscoelastic properties and thermal behavior of their
styrene copolymers have been studied by DSC, DMA, and TGA analyses. Additionally, mechanical properties: flexural properties
using three-point bending test and Brinell’s hardness for studied copolymers were evaluated. It was confirmed that the structure
of used polyesters had a considerable influence on the course of the cure reaction with styrene, viscoelastic, thermal, and
mechanical properties of prepared styrene copolymers. Generally, one or two asymmetrical peaks for the cure reaction of succinic
or glutaric anhydride modified linear unsaturated epoxy polyesters with styrene were observed. They were connected with various
cure reaction, e.g., copolymerization of carbon–carbon double bonds of polyester with styrene, thermal curing of epoxy groups,
polyaddition reaction of epoxy to anhydride groups in dependence of used curing system. In addition, only one asymmetrical,
exothermic peak attributed to the copolymerization process of succinic or glutaric anhydride modified linear unsaturated polyesters
with styrene was visible. Moreover, the obtained styrene copolymers based on succinic or glutaric anhydride modified linear
unsaturated epoxy polyesters were characterized by higher values of
, Tg, E″, νe, Emod, Fmax, hardness, IDT, FDT but lower ε − Fmax compared to those values observed for styrene copolymers prepared in the presence of succinic or glutaric anhydride modified
linear unsaturated polyesters. This supported to the production of stiffer and more thermally stable polymeric structure of
copolymers based on unsaturated epoxy polyesters. Moreover, the copolymers prepared in the use of glutaric anhydride modified
linear unsaturated (epoxy) polyesters were described by lower values of
, Tg, E″, νe, Emod, Fmax, hardness, IDT, FDT but higher ε − Fmax than those based on succinic anhydride modified linear unsaturated (epoxy) polyesters. The presence of longer aliphatic chain
length in polyester’s structure leads to produce more flexible network structure of styrene copolymers based on glutaric anhydride
modified linear unsaturated (epoxy) polyesters than those based on succinic anhydride modified linear unsaturated (epoxy)
Authors:László Kátai, Péter Szendrő, and Péter Gárdonyi
The V-belt drive is a rather popular, widely used form of power transmission in agricultural and food industry engineering. At the same time, its stability, the lifetime of V-belt is influenced by several environmental factors, namely in the food industry by the contamination affecting the belt sides, the ambient temperature, humidity and the occasionally aggressive (acidic, alkaline air, air saturated with gases, etc.) medium. In the case of agricultural machinery, the vibration caused by uncertainly oriented pulleys with bearing in different plate structures (often being shaken in the fields) as well as alignment adjustment inaccuracies jeopardize the reliability of the parameters of the drive. Furthermore, the efficiency is determined by several factors together: the slippage occurring during drive transmission, the hysteresis loss resulting from the external and internal friction occurring with the belt entering and exiting the pulley. Experimental equipment and calculation methods were developed to determine the dynamics of temperature increase generated by the belt and pulley relationship. The temperature generated in the V-belt was measured as a function of pretension, pulley diameter and bending frequency. The so-called damping factor characterizing the contact with the pulley (the external friction when entering and exiting the groove) and the hysteresis loss (inner friction) are also determined. On the basis of the damping factor (ζ ≈ 400 Ns/m2) of the V-belt involved in the experiments the other losses (Poth) occurring from the pulley—V-belt contact and internal friction may be estimated. The drive parameters may be optimized with the mathematical model describing the effect of the pulley diameter and belt frequency on the increase in temperature.
A standardized calculation method as well as design factors valid for the properly adjusted drive and normal operating conditions determined through empirical and laboratory experiments are used for the sizing of V-belt drives. The lifetime of V-belt drives designed in this way, used in extreme conditions typical of agricultural machinery will not be appropriate and will not provide clear, predictable information for maintenance planning. In such cases the results of our own many lifetime tests conducted in the given circumstances can be safely relied on.
The agricultural harvesting machines are large plate-body self-propelled structures on which most of the power supply of the (threshing, cleaning, moving, etc.) machine units handling the crop is realized via belt drives. The distance and angular displacement of the axes involved in the drive can vary within wide limits. The misalignment and angular displacement of the pulleys can be the result of installation instability — due to the plate structure — and the deformation of the plate structure occurring during the operation as well. V-belt drives operate satisfactorily under such conditions as well, however these faults are unfavourable in terms of belt lifetime and result in the reduction of drive efficiency.
A further aim of our research is to examine through experiments the lifetime and efficiency of V-belts used in agricultural machines as a function of drive adjustment errors. According to the results of the measurements of the geometrical adjustment errors of V-belt drives performed in the field, the pulleys of agricultural equipment are not always positioned in the medium plane of the drive. In our experiments these data served as independent variables. Figure 1 shows the arrangement of a V-belt drive in a grain harvester with the laser pulley alignment measuring instrument installed as an accessory. In the case of many machine types in 80% of the tested drives three times the permissible error was measured, and because of off-road use, due to dynamic load these errors further increased as a result of the frame deformation.
The results of both the belt bending testing and the geometrical adjustment testing of the drive offer great help in the design of belt drives. At the same time they can be the source of lifetime and efficiency forecasts.
Authors:Martin Vavruš, Peter Koteš, František Bahleda, and Jozef Jošt
.50 22350,19 2223.31 22627.68 22492.17 f c (MN m −2 ) 43.617 39.942 40.277 52.296 47.874 47.994 Average values f c (MN m −2 ) 41.278 49.388 Realization of the 3-point bendingtests was executed according to the EN 14651 standard [ 17 ]. An axial distance
Authors:Haroune Rachid Ben Zine, Filiz Cinar Sahin, Zsolt E. Horváth, Zsolt Czigány, Ákos Horváth, Katalin Balázsi, and Csaba Balázsi
sintering are shown in Figure 3 .
In the case of 316L/0.33 wt. % Si 3 N 4 (Figures 3 a and b), the analysis of the resulting fractured surface after three points bendingtest by SEM revealed the dominance of the transgranular fracturing behavior