Numerical simulations of test under biaxial bending on cruciform specimen made of quasi-brittle material

Příspěvek představuje numerickou studii vlivu vybraných vstupních parametrů materiálového modelu na průběh testu ve zkušební konfiguraci biaxiálního ohybu křížového tělesa s koncentrátorem napětí i bez něj, vyrobeného z kvazikřehkého materiálu. Jde konkrétně o tzv. Gilsocarbon grafit používaný jako moderátor jaderné reakce v reaktorech jaderných elektráren ve Velké Británii.The paper is focused on a numerical study of the influence of selected input parameters of the used material model on the progress of a test in the configuration of biaxial bending of cruciform specimen with and without notch made of quasi-brittle material. In particular, the tested material is Gilsocarbon graphite that is used as a moderator of nuclear reaction in gas-cooled nuclear reactors in UK

Numerical Models of the Connection of Thin-Walled Z-Profile Roof Purlins

High thin-walled purlins of Z cross-section are important elements in steel wide-span structures. Their behaviour is influenced by many variables that need to be examined for every specific case. Their practical design thus requires extended knowledge of their behaviour for the possible configurations and dimensions. Numerical analysis verified by experimental investigation can thus enrich such knowledge. Numerical models have the advantage of repeatability and the ability to offer parametric changes. The parametric study presented shows a detailed description of a finite element model of thin-walled cross-sectional roof purlins connected to other roof elements. Models include various approaches to modelling bolt connection. Two schemes of purlins, with and without cleats, are presented. The results of different approaches in numerical modelling are compared with the results of a physical test on a real structure. The article shows a significant agreement in the case of specific approaches and points out the differences with others. The results can be helpful in terms of how to approach the modelling of thin-walled structures and the effective approach to experimental preparation

Fatigue damage analysis of a riveted steel overhead crane support truss

A method is proposed to evaluate the residual life of existing steel structures in terms of fatigue damage. The proposed method is demonstrated on the assessment of selected elements in a nearly 100-year old exterior riveted crane support truss. The Monte Carlo method is used to generate a time-dependent load based on the operation of the overhead crane, and detailed numerical modelling based on rainflow counting and the Palmgren-Miner rule to assess their fatigue resistance and estimate their residual life is evaluated and discussed. This study provides a novel approach to the reliability assessment of riveted joints stressed by cyclic loading and stochastic modelling of the load history of existing structures.Web of Science128art. no. 10519

The general procedure of numerical analysis related to a fatigue damage on the cyclically loaded construction

The paper presents a general procedure of numerical analysis of the steel structure in case of cyclic loading. The basic recommendations that can be applied to different details, are discussed. The article shows examples of the truss structure loaded with a crane track, but also applicable to other types of constructions. There are basic ideas of the whole process, which is divided into several parts. The beginning of the process is to determine the influence line from the simplified model of the whole structure. A stochastic estimation of the load effect associated with the load history in combination with the influence line is utilized. The complex 3D FEM model for estimation of residual life of the chosen detail is the main result of the analysis

The general procedure of numerical analysis related to a fatigue damage on the cyclically loaded construction

The paper presents a general procedure of numerical analysis of the steel structure in case of cyclic loading. The basic recommendations that can be applied to different details, are discussed. The article shows examples of the truss structure loaded with a crane track, but also applicable to other types of constructions. There are basic ideas of the whole process, which is divided into several parts. The beginning of the process is to determine the influence line from the simplified model of the whole structure. A stochastic estimation of the load effect associated with the load history in combination with the influence line is utilized. The complex 3D FEM model for estimation of residual life of the chosen detail is the main result of the analysis

Comparison of Patients with Reduced and Mildly Reduced Left Ventricular Ejection Fraction: Intermediate Data from the FAR NHL Registry

Introduction: We present the results of a study by the Pharmacology and NeuroHumoral Activation Registry (FAR NHL), which collects data on patients with chronic heart failure. The register contains 1088 patients from three workplaces in the Czech Republic which specialize in the care of patients with heart failure. Objectives: The aim was to obtain a comparison of pharmacotherapy and the incidence of comorbidities in patients with reduced ejection fraction (HFrEF) versus patients with mid-range (or newly mildly reduced) ejection fraction (HFmrEF). Methods: Patients with a baseline left ventricular ejection fraction below 50% were included and divided into HFrEF with EF below 40% and HFmrEF with EF 40–49%, according to the 2016 ESC Guidelines. In addition to the clinical condition, we also monitored laboratory parameters, comorbidities and pharmacotherapy in the patients. Results: Patients with HFrEF versus HFmrEF are more likely to be male (p < 0.008), younger (p < 0.001), have lower systolic blood pressure and are less likely to have ischemic etiology of heart failure (p < 0.001). There were no differences between the groups in the proportion of comorbidities: hypertension, diabetes mellitus, dyslipidemia, ischemic lower limb disease or chronic obstructive pulmonary disease. There were no differences in the proportion of smokers and non-smokers between the groups. Patients with HFrEF have a higher class of New York Heart Association (NYHA), a level of N-terminal fraction of natriuretic peptide B (NT-proBNP), and a higher level of urea and uric acid. They are more often treated with loop diuretics or mineral corticosteroid receptor (MRA) blockers and less often with thiazides (p < 0.001), and also have a worse two-year prognosis. Conclusion: Compared to patients with HFmrEF, patients with HFrEF have more severe heart failure, more pronounced neurohumoral activation and a worse prognosis. They do not differ in the presence of comorbidities

Numerical modeling of steel fillet welded joint

The paper is focused on the numerical modeling of steel bearing elements and their verification using experiment. Currently, for the stress-strain analysis of the elements supporting structures it is possible to use many commercial software systems, based on the finite element method - FEM. It is important to to check and compare the results of FEM analysis with the results of physical verification test, in which the real behavior of the bearing element can be observed. The results of the comparison can be used for calibration of the computational model.The article deals with the physical test of steel supporting elements, whose main purpose is obtaining of material, geometry and strength characteristics of the fillet welds. The main aim was defining of tested samples numerical models for using FEM analysis and for the commercial software ANSYS. The pressure test was performed during the experiment, wherein the total load value and the corresponding deformation of the specimens under the load was monitored. The measurements were carried out for a more detailed analysis of stresses and deformations in welds samples using a strain-gauge and a Q100 laser device for measuring the 3D deformation and infrared thermographic non-destructive testing.Obtained data were used for the calibration of numerical models of test samples and they are necessary for further strain analysis of steel supporting elements.Web of Science117695

Relation between Mid-Regional Pro-Adrenomedullin in Patients with Chronic Heart Failure and the Dose of Diuretics in 2-Year Follow-Up—Data from FAR NHL Registry

Background and Objectives: The aim of this paper is to evaluate the impact of humoral substance mid-regional pro-adrenomedullin (MR-proADM) on the two-year survival of patients with chronic heart failure and relate it to the dosage of furosemide. Materials and Methods: The data is taken from the stable systolic heart failure (EF < 50%) FAR NHL registry (FARmacology and NeuroHumoraL activation). The primary endpoint at two-year follow-up was death, heart transplantation, or LVAD implantation. Results: A total of 1088 patients were enrolled in the FAR NHL registry; MR-proADM levels were available for 569 of them. The mean age was 65 years, and 81% were male. The aetiology of HF was ischemic heart disease in 53% and dilated cardiomyopathy in 41% of patients. The mean EF was 31 ± 9%. Statistically significant differences (p < 0.001) were obtained in several parameters: patients with higher MR-proADM levels were older, rated higher in NYHA class, suffered more often from lower limb oedema, and had more comorbidities such as hypertension, atrial fibrillation, diabetes, and renal impairment. MR-proADM level was related to furosemide dose. Patients taking higher doses of diuretics had higher MR-proADM levels. The mean MR-proADM level without furosemide (n = 122) was 0.62 (±0.55) nmol/L, with low dose (n = 113) 1–39 mg/day was 0.67 (±0.30) nmol/L, with mid dose (n = 202) 40–79 mg/day was 0.72 (±0.34) nmol/L, with high dose (n = 58) 80–119 mg/day was 0.85 (±0.40) nmol/L, and with maximum dose (n = 74) ≥120 mg/day was 1.07 (±0.76) nmol/L, p < 0.001. Patients with higher MR-proADM levels were more likely to achieve the primary endpoint at a two-year follow-up (p < 0.001) according to multivariant analysis. Conclusions: Elevated plasma MR-proADM levels in patients with chronic heart failure are associated with an increased risk of death and hospitalization. Higher MR-proADM levels in combination with increased use of loop diuretics reflect residual congestion and are associated with a higher risk of severe disease progression