Numerical simulation of tensile testing of pe 80 polymer specimens

The aim of this paper is to present the behaviour of specimens made of polyethylene material PE 80, subjected to tensile load until failure. Measurements of the temperature distribution have been done using the infrared thermography during specimens loading. Finite element analysis was performed in ABAQUS software, where numerical models were made based on the thermograms and force-displacement diagrams obtained from these experiments. Afterwards, results from the simulation were compared with the experimental results and it was determined in which way the model can be optimized so that these results comply at an acceptable level. Numerical model has shown that the highest values of plastic strain were located near the notch. Value of this plastic strain is several times greater than the values in the remaining parts of the specimen. The numerical analysis also determined that defining the load in displacement form was a much better solution than defining it using the force, since the results have shown much better compliance, and the calculation time was much shorter in this case

Tensile behaviour of polyethylene under different loading rates in the presence of imperfections

This paper highlights the changes of polyethylene behaviour during various loading rates. The experimental programme was carried out on samples taken from PE80 polyethylene gas pipes with simulated imperfections with bilateral V-notch, U-notch and central hole. The hybrid technique tensile test - infrared test was used for examining the fracture behaviour of PE80 thermoplastic material samples under different loading rates. Correlation between the loading rate and tensile strength of polyethylene has been established. It has been shown that tensile strength varies with loading rate according to a logarithmic law. Also, it was shown that viscoelastic-plastic character of the polymer material influences directly the specific response of material to loading rates

Tensile behaviour of polyethylene under different loading rates in the presence of imperfections

This paper highlights the changes of polyethylene behaviour during various loading rates. The experimental programme was carried out on samples taken from PE80 polyethylene gas pipes with simulated imperfections with bilateral V-notch, U-notch and central hole. The hybrid technique tensile test - infrared test was used for examining the fracture behaviour of PE80 thermoplastic material samples under different loading rates. Correlation between the loading rate and tensile strength of polyethylene has been established. It has been shown that tensile strength varies with loading rate according to a logarithmic law. Also, it was shown that viscoelastic-plastic character of the polymer material influences directly the specific response of material to loading rates

On the Particles Size Distributions of Diatomaceous Earth and Perlite Granulations

When filtering products with a high level of non-soluble solids and containing filtration-inhibiting substances, a variety of different filter aids can be used. Among others, kieselguhr and perlite are possible materials for this purpose. The selection of the granulation that should be applied depends on the filtered liquid medium and the desired retention level. While perlite is most commonly used for rough filtration, kieselguhr is also suitable for more subtile filtration. In the paper, particle size distributions of three kieselguhr granulations and a perlite granulation are analysed. Particle sizes are measured by the morphometric method commonly used in the microbiology. Basic statistic parameters are calculated for all considered samples and compared. The applicability of hyperbolic and log-hyperbolic functions, in describing the particles size distributions of these granulations is verified. Depending on the imposed filtration requirements, this approach enables simple modelling and composition of a wide variety of different granulations characterised by appropriate particle size distributions from a few available granulations

Ispitivanje mogućnosti iznalaženja optimalne koncentracije evaporiranog mlijeka radi proizvodnje mlijeka u prahu na spray postrojenju, s osvrtom na Maillard-ov tip potamnjivanja

Autori su ispitivali utjecaj koncentracije evaporiranog mlijeka na kvalitetu mlijeka u prahu i pojavu Maillardove reakcije. Na osnovu rezultata provedenih fizičko-kemijskih i organoleptičkih ispitivanja zaključuju da je optimalno sušenje evaporiranog mlijeka sa 50 % s.t. U toku uskladištenja obranog i punomasnog (25 %) mlijeka u prahu do 90 dana na sobnoj temperaturi povećava se intenzitet Maillard-ove reakcije znatno brže, nego u mlijeku skladištenom kod 4 °C

Influence of printing parameters on the eligibility of plane-strain fracture toughness results for PLA polymer

The majority of manufacturers of polymer filaments for FDM technology rely their datasheets only on tensile tests, so their documentation usually lacks any data concerning fracture mechanics parameters. Having in mind the importance of fracture mechanics parameters in material design and application e.g., plane-strain fracture toughness, and the fact that it can be measured using only standard tensile grips, or three-point bending test fixture on a regular tensile testing machine, this practice offers vital information for AM components carrying the load. Anyhow, it is not always a simple task to satisfy all requirements of the standard for plane-strain fracture toughness assessment of plastic materials (ASTM D5045-14), as in the case of FDM technology due to many printing parameters that not only influence fracture toughness results, but also can question the eligibility of test results if crack propagation deviates from the expected path or if the specimens don't meet the size criterion necessary for achieving the plane-strain condition. These problems are tackled in this research on PLA polymer, a material widely used in FDM technology. For this research SENB specimens are prepared according to ASTM D5045-14 standard and tested on tensile testing machine using three-point bending test fixtur

Creep crack growth behavior of p91 steel weldments

The steels operating at elevated temperatures are well known to be exposed to premature failure due to cracking caused by constant thermal stress, i. e. secondary creep process. Therefore, creep crack growth tests were carried out on compact tension specimens machined from P91 weld joint at 600 degrees C to determine its behavior in realistic conditions. At the same time, numerical method for predicting the creep crack growth in compact tension specimens by a series of incremental steady-state finite element analysis were performed using Norton's law to represent creep behavior. Verification of the finite element predictions were obtained for weld metal and heat affected zone by comparison with experimental results, indicating at the same time that creep crack growth rates are significantly higher for weld metal than for base metal

Creep crack growth behavior of p91 steel weldments

The steels operating at elevated temperatures are well known to be exposed to premature failure due to cracking caused by constant thermal stress, i. e. secondary creep process. Therefore, creep crack growth tests were carried out on compact tension specimens machined from P91 weld joint at 600 degrees C to determine its behavior in realistic conditions. At the same time, numerical method for predicting the creep crack growth in compact tension specimens by a series of incremental steady-state finite element analysis were performed using Norton's law to represent creep behavior. Verification of the finite element predictions were obtained for weld metal and heat affected zone by comparison with experimental results, indicating at the same time that creep crack growth rates are significantly higher for weld metal than for base metal

One-dimensional diffusion equation for the particle size distribution of perlite filter granulation

Mnoštvo pročistačkih sustava do sada je načinjeno s uporabom različitih granulacija perlita. Raspodjela veličina čestica perlita izravno utječe na svojstva retencije pročistačkih medija. Informacije o raspodjeli veličine granulacija perlita, koji se koriste u svakom konkretnom postupku dead-end filtracije (filtracija koja se odvija u pravcu okomitom na ravninu pročistača), od presudne je važnosti za odgovarajuću tvorbu pročistaćkog medija. Kako bi se olakšala tvorba pročistaćkog medija koji posjeduje pročistaćke sposobnosti ove vrste, novi i specifični matematički model je razvijen za ovo istraživanje. Temelji se na odgovarajućoj parcijalnoj diferencijalnoj jednadžbi i dodanim matematičkim uvjetima, čije rješenje je eksponencijalna funkcija koja opisuje vjerojatnost raspodjele gustoće različitih veličina čestica perlita. Formulirani model eksperimentalno je potvrđen mjerenjem veličine čestica perlita pomoću morfometrijske metode, koja se temelji na primjeni standardnog svjetlosnog mikroskopa i softvera za digitalnu analizu slika. Postupak pronalaženja najtočnije funkcije za rezultate istraživanja ostvaruje zadovoljavajuću točnost - visoki R2 čimbenik (R2 = 0,905) i mala vrijednost srednje kvadratne pogreše (MSE = 0,490).Many filtration systems employing perlite granulations have been designed so far. Size distribution of perlite particles directly influences the retention properties of filter media. The information on the size distribution of perlite particles, used in each specific dead-end filtration process (the flow of fluid being filtered is perpendicular to the surface of filter medium), is crucial for the adequate design of filter medium. In order to facilitate the design of filter systems possessing filter media of this kind, a new and particular mathematical model has been developed for this present study. It is based on an appropriate partial differential equation and additional mathematical conditions, whose solution is an exponential function describing the probability density distribution of perlite particle sizes. The formulated model was experimentally verified by measuring the particle sizes of a perlite granulation using the morphometric method, based on the application of a standard light microscope and digital image analysis software. The fitting procedure of experimental data gave acceptable values of accuracy parameters - high R-square factor (R2 = 0,905) and small value of the root-mean square error (MSE = 0,490)

Antioxidant biomarker profile of chironomid larvae from carp ponds: Evaluation of the effects of different fish feeding patterns

A 102-day feeding trial was conducted to evaluate the effects of four different fish feeding patterns on carp pond water quality and antioxidant biomarkers [superoxide dismutase (SOD), Catalase (CAT), Glutathione peroxidase (GPx), Glutathione reductase (GR), Glutathione S-transferase (GST) and Thiol groups (SH)], protein content and biomass of the midge Chironomus plumosus. Farmed fish were fed two commercial diets: Soprofish 25/7 Standard (containing 25% protein and 7 % fat) and Soprofish 32/7 Profi Effect (containing 32 % protein and 7 % fat). These feeds were combined during a feeding trial in four different feeding patterns, designated as A, B, C and D. In feeding pattern A, the fish received Soprofish 25/7 Standard throughout the experiment and in feeding pattern D, Soprofish 32/7 Profi Effect. During feeding patterns B and C, a mixed feeding pattern was used, alternating between lower and higher protein diets. The study revealed no significant effects (P > 0.05) of the feeding regimens on water quality, so their effects on C. plumosus larvae can be evaluated independently. The activities of the chironomid enzymes CAT and GR showed a clear statistically significant dependence on the feeding pattern (P 0.05). Overall, our results suggest that long-term supplementation with a highly concentrated protein diet may have preventive effects against oxidative stress and support the use of C. plumosus as a model for assessing the effects of organic pollution on pond zoobenthic fauna. © 202