Modern applications require a special treatment when the conventional specimen size is much larger than the component size. Additional to that, high sophisticated materials are used for highly loaded ...components. Often the conventional fatigue limit is exceeded and loads are applied in the VHCF regime. Focus was put on the lifetime calculation and the implementation of investigated fatigue data of a X5CrNiCuNb-16-4 type steel. Two specimen geometries with diameters D
7.5
=7.5 mm and D
2.5
=2.5 mm were tested at R=-1, at room temperature and up to 10
9
cycles to failure. The application of different software tools (FEMFAT, fe-safe) showed several issues based on the current results. Results showed a change of crack initiation mechanism to subsurface crack initiation at approx. 2x10
6
cycles to failure. The gradient based correction of the reference fatigue data showed a good applicability up to 2x10
6
cylces. The application of fe-safe allows the flexible modification of S/N parameters over the whole cycle range. The usage of the actual material configuration introduced several important questions regarding the fatigue data and the implementation into lifetime calculation tools.
Nowadays lifetime calculation in the high cycle fatigue region is commonly based on S/N curves which are modified by different influences to ensure accurate results. Especially the application of ...these models is important when small components with complex stress distributions are used. The influence of the stress distribution was considered by the stress gradient approach which is implemented in the lifetime tool FEMFAT. Specimens with diameters of D4mm and D7.5mm were used to examine the effect of the calculation modified by the stress gradient. On the one hand regarding different types of this approach it can be shown that the results fit very well compared to the testing results but on the other hand a big difference was observed when the gradient increases by smaller specimen sizes.
Modern applications require a special treatment when the conventional specimen size is much larger than the component size. Additional to that, high sophisticated materials are used for highly loaded ...components. Often the conventional fatigue limit is exceeded and loads are applied in the VHCF regime. Focus was put on the lifetime calculation and the implementation of investigated fatigue data of a X5CrNiCuNb-16-4 type steel. Two specimen geometries with diameters D
7.5
=7.5 mm and D
2.5
=2.5 mm were tested at R=-1, at room temperature and up to 10
9
cycles to failure. The application of different software tools (FEMFAT, fe-safe) showed several issues based on the current results. Results showed a change of crack initiation mechanism to subsurface crack initiation at approx. 2x10
6
cycles to failure. The gradient based correction of the reference fatigue data showed a good applicability up to 2x10
6
cylces. The application of fe-safe allows the flexible modification of S/N parameters over the whole cycle range. The usage of the actual material configuration introduced several important questions regarding the fatigue data and the implementation into lifetime calculation tools.
Nowadays technical applications require very small components which leads to the question of how to handle fatigue strength data gained from tests carried out on specimen which are even larger than ...the component itself. Previous high-cycle-fatigue (HCF) tests have outlined the negative influence of increasing “risk volumes” due to enlargement of the specimen size. Additional to the effect of “risk volumes” the influence of stress gradient may not be neglected as the gradient changes as well due to the enlargement of the specimen size. Especially thin profiles could be affected by high stress gradients which results in high and low stress loaded profile areas. The fatigue strength of an hourglass shaped specimen with a standardized diameter of 7.5 mm tends to have higher fatigue strength than a specimen with a larger diameter. In this work rotating bending tests were carried out on specimens with a diameter of 4 and 7.5 mm. Lifetime simulations with different specimen diameters (D2.5, D4 and D7.5) were carried out by a common simulation tool FEMFAT and simultaneous testing of D4 and D7.5 specimens was performed to compare the results. An outlook is given on how such influences can be estimated and an appropriate method can be derived for damage calculations.
U radu je istražen odnos između rezidualne vrijednosti i vijeka trajanja strojeva. Rezultat istraživanja je kreiranje nekoliko modela primjenom simboličke regresije u kojoj je zavisna varijabla ...rezidualna vrijednost, nezavisne varijable su modeli strojeva, kalendarska starost stroja, kumulativni broj radnih sati stroja i indeks inflacije. Procjena rezidualne vrijednosti je ključna za donošenje investicijskih odluka. Istraživanje je pokazalo da postoji mogućnost razvijanja okvirnog prognostičkog matematičkog modela rezidualne vrijednosti građevinske mehanizacije koristeći simboličku analizu dostupnog seta podataka koji čine 61 153 stroja.
Small bowel obstruction (SBO) is a common entity encountered in surgical patients. The most common causes of the SBO range from postoperative adhesions to cancer. We present the case of a 55-year-old ...male who underwent a laparoscopic left radical nephrectomy and presented with an early SBO. An imaging study revealed an obstructive pattern with proximal dilated jejunum with decompressed distal small bowel. The patient underwent an exploratory laparotomy with extensive lysis of adhesions and release/resection of a long segment of incarcerated jejunum from an 8-cm retroperitoneal hernia in the left renal fossa. The patient was discharged home, and at 3-month follow-up no bowel complaints were reported.
This article presents a process of evaluation and selection of the most favourable location for a sanitary landfill facility from three alternative locations, by applying a multi-criteria ...decision-making (MCDM) method. An incorrect choice of location for a landfill facility can have a significant negative economic and environmental impact, such as the pollution of air, ground and surface waters. The aim of this article is to present several improvements in the practical process of landfill site selection using the VIKOR MCDM compromise ranking method integrated with a fuzzy analytic hierarchy process approach for determining the evaluation criteria weighing coefficients. The VIKOR method focuses on ranking and selecting from a set of alternatives in the presence of conflicting and non-commensurable (different units) criteria, and on proposing a compromise solution that is closest to the ideal solution. The work shows that valuable site ranking lists can be obtained using the VIKOR method, which is a suitable choice when there is a large number of relevant input parameters.
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