The Influence of Wagon Structure Part Shape Optimization on Ultimate Fatigue Strength

This study investigates how shape optimisation affects the ultimate fatigue strength of a mechanical part. The mechanical part chosen for this investigation is an axle guard of running gear elements of the Hccrrs 2x2 axle car-carrying wagon. The static and fatigue strength analysis procedure according to the UIC 517 standard and numerical methods have been applied. Material properties were determined experimentally and the necessary numerical calculations were performed by using the finite element method. The observed axle guard is exposed to low cycle fatigue. ε-N curves and material properties of the S355J2+N steel grade are obtained by combining theoretical formulae and a mathematical function. According to the obtained experimental and numerical results the number of cycles until failure for both shapes of axle guards is obtained

Elastoplastic constitutive model for granular soil based on hyperbolic failure surface

U radu se prikazuje numerički postupak za razvoj i primjenu novog elastoplastičnog konstitutivnog modela za nekoherentne zrnate materijale. Prikazani model temelji se na hiperboličnoj anvelopi sloma koja je razvijena primjenom teorije inkrementalne plastičnosti. Metoda vodećeg parametra (eng. governing parameter method - GPM) koristi se za implicitno integriranje konstitutivnih odnosa. Razvijeni algoritam unesen je u računalni program konačnih elemenata PAK koji se koristi za statičke, dinamičke, linearne i nelinearne analize. Model je verificiran i provjeren kroz numeričke simulacije troosnog pokusa i pokusa izravnog smicanja.Numerical procedure for the development and implementation of a new elastoplastic constitutive model for cohesionless granular materials is presented in the paper. The presented model is based on the hyperbolic failure envelope developed using the theory of incremental plasticity. The governing parameter method (GPM) is used for implicit integration of constitutive relations. The developed algorithm is implemented in the general-purpose finite element program PAK designed for the static, dynamic, linear and non-linear analysis. The model is calibrated and verified through numerical simulation of triaxial test and direct shear test

Microstructure evolution and phase transition in Er doped BaTiO3 ceramics

The Er doped BaTiO3 ceramics, with different Er2O3 content, ranging from 0.01 to 1.0 wt% Er, were investigated regarding their microstructural and dielectric characteristics in this paper. Doped BaTiO3 were prepared by using conventional method of solid state sintering at 1380 °C for four hours. SEM analysis of Er/BaTiO3 doped ceramics showed that in samples doped with a rareearth ions low level, the grain size ranged from 20-40 μm, while with the higher dopant concentration the abnormal grain growth is inhibited and the grain size ranged between 2-10μm. Dielectric measurements were carried out as a function of temperature up to180°C at different frequencies. The low doped samples sintered at 1380 °C, display the high value of dielectric permittivity at room temperature, 2160 for 0.01 Er/BaTiO3. A nearly flat permittivity-response was obtained in specimens with higher additive content. Using a Curie-Weiss low and modified Curie-Weiss low the Curie constant C, Curie temperature Tc and a critical exponent of nonlinearity γ were calculated. The Curie temperature of doped samples were ranged from 126 to 130 °C. The Curie constant for all series of samples decrease with increase of dopant concentration and the lowest values were mesured from samples doped with 0.01 wt% of aditive. The obtained value of γ pointed out that the specimens have almost sharp phase transition

Mogućnost upotrebe kozjeg mesa u proizvodnji tradicionalnog sudžuka

Two variants of sucuk were made: one of beef meat and beef tail fat and another of goat meat and goat tail fat with meat/fat ratio of 75/25 and the same ingredients. After filling, the sausages were hung to dry in a traditional smoking house (without the possibility to control the temperature or humidity). Weight loss, pH, non-protein nitrogen content, basic chemical composition, instrumental colour measurement and sensory evaluation were done for both variants. Both variants had an almost identical weight loss (36.98 beef sucuk and 36.25 goat sucuk). Changes in pH value and non-protein nitrogen content had the same tendency and end values did not differ. The basic chemical composition at the end of production indicates that both variants were of very good quality. L*and b*values did not differ, but there was a significant difference in a*value (11.72 beef and 14.15 goat). In terms of appearance, texture and taste, assessors gave poorer grades to goat sucuk, but these grades do not indicate that the product is unacceptable (they were more than 5). It is possible to replace goat tail fat with beef fat to appease the specific flavour of the product and to make it more acceptable to consumers who may not be used to such flavour.U Srbiji, sudžuk se tradicionalno proizvodi u planinskom delu, uglavnom u malim pogonima ili domaćinstvima, u jesenjem i zimskom periodu, kada to klimatski uslovi (temperatura i relativna vlažnost) dozvoljavaju. U ovom ogledu napravljene su dve varijante sudžuka: prva od goveđeg mesa i masnog tkiva sa repa goveda i druga od kozjeg mesa i masnog tkiva sa repa koza. Kod obe grupe kobasica je odnos meso/masno tkivo bio 75/25 i korišćeni su isti začini i aditivi. Nakon punjenja, kobasice su sušene u tradicionalnoj pušnici. Kod obe varijante kobasica određen je: gubitak mase tokom sušenja, pH, neproteinski azot, osnovni hemijski sastav i izvršeno je instrumentalno merenje boje i senzorska ocena. Obe grupe kobasice su imale skoro identičan gubitak mase tokom sušenja (36,98 kod goveđeg i 36,25 kod kozjeg sudžuka). Promene pH vrednosti i neproteinskog azota tokom zrenja su imale istu tendenciju i njihove krajnje vrednosti se nisu značajno razlikovale. Na osnovu podataka za osnovni hemijski sastav na kraju procesa proizvodnje, zaključeno je da su obe grupe kobasica bile veoma dobrog kvaliteta. L*i b* vrednosti se nisu značajno razlikovale, dok je statistički značajna razlika između grupa utvrđena za vrednost a*(11,72 kod goveđih i 14,15 kod kozjih kobasica). U pogledu senzornih karakteristika: spoljnog izgleda, teksture i ukusa, kozji sudžuk je ocenjen nešto slabije, međutim, takav proizvod je i dalje bio veoma prihvatljiv (sve ocene su bile iznad 5). Jedan od načina da se smanji specifična aroma sudžuka napravljenog od kozjeg mesa, što bi ga učinilo prihvatlivijim za širu grupu potrošača, jeste zamena kozjeg loja sa goveđim

Models and Guidelines for Dimensioning Private Clouds

It is a real challenge for cloud providers to offer cloud resources that are 'virtually unlimited and can be appropriated in any quantity at any time' in a cost-effective way. In this paper, we propose quantitative models that enable cloud providers to make an informed trade-off between cost and quality. Distinguishing between public and private cloud environments we consider infinite and finite source models respectively. In both cases either homogeneous or heterogeneous cloud resource requests are considered. These models can be applied to cloud dimensioning based on request blocking probability, an important SLA parameter. We derive a novel, insightful method that makes it possible to compute resource requirements in private clouds with heterogeneous resource requests. We show the importance of applying finite source models in the context of private clouds. We also use the proposed models to quantify the benefits of cloud federations.</p

Ho2O3 additive effects on BaTiO3 ceramics microstructure and dielectric properties

Doped BaTiO3-ceramics is very interesting for their application as PTCR resistors, multilayer ceramic capacitors, thermal sensors etc. Ho doped BaTiO3 ceramics, with different Ho2O3 content, ranging from 0.01 to 1.0 wt% Ho, were investigated regarding their microstructural and dielectric characteristics. The samples were prepared by the conventional solid state reaction and sintered at 1320° and 1380°C in an air atmosphere for 4 hours. The grain size and microstructure characteristics for various samples and their phase composition was carried out using a scanning electron microscope (SEM) equipped with EDS system. SEM analysis of Ho/BaTiO3 doped ceramics showed that in samples doped with a rare-earth ions low level, the grain size ranged from 20-30μm, while with the higher dopant concentration the abnormal grain growth is inhibited and the grain size ranged between 2- 10μm. Dielectric measurements were carried out as a function of temperature up to 180°C. The low doped samples sintered at 1380°C, display the high value of dielectric permittivity at room temperature, 2400 for 0.01Ho/BaTiO3. A nearly flat permittivity-response was obtained in specimens with higher additive content. Using a Curie-Weiss low and modified Curie-Weiss low the Curie constant (C), Curie temperature (Tc) and a critical exponent of nonlinearity (γ) were calculated. The obtained value of γ pointed out that the specimens have almost sharp phase transition. [Projekat Ministarstva nauke Republike Srbije, br. 172057: Directed synthesis, structure and properties of multifunctional materials

Numerical modeling of the edentulous mandible with a complete denture using multiblock method

In this paper, finite element model of edentulous lower jaw (mandible) is generated, as well as the model of support layer and complete denture using various software. The aim of this study was to produce 3D digital mandibular complete denture, mucosa, and supporting bone models using reverse engineering and evaluate effect of mucosa thickness and resiliency on stress distribution of complete denture. In this study we used a model of mandibular complete denture and 5 mm thickness of mucosa (which represent the resiliences soft). The influence of resilient mucous membranes layer thickness is analysed by assigning loads to simulate the force due to chewing on the lower right and left central incisor and lower right and left first molar. Based on the numerical results, we conclude that the maximum stress values were concentrated in cortical bone

Interaction of biomaterial containing calcium hydroxyapatite/poly-l-lactide with simulated body fluid

The purpose of biomaterials is to replace a part or a function of the body in a safe, physiologically and economically acceptable way. The process of the reconstruction of bone defects has always been a big problem in orthopedics and maxillofacial surgery. Since hydroxyapatite (HAp) was detected as a component, the predominant constituent and the integral element of Mammalian bones, the development of the phospate ceramics as potential materials for implantation was enabled. This study investigated whether and in which way biomaterial calcium hydroxyapatite/poly-L-lactide (HAp/PLLA) interacts with the ionic composition of the human plasma. The simulated body fluid (SBF) is an artificial fluid that has the ionic composition and ionic concentration similar to the human blood plasma. HAp/PLLA was incubated for 1, 2, 3 and 5 weeks in SBF. The surfaces of both treated and untreated materials were analyzed on a scanning electron microscopy (SEM), and were also exposed to the energy dispersive X-ray spectroscopy (EDS), while SBF was submitted to the measuring of pH and electrical conductivity. However, our results indicate that the degradational changes of the material HAp/PLLA in SBF start from the surface of the treated material and that observed changes are the consequence of dissolution of its polymer component and the precipitation of the material similar to hydroxyapatite on its surface. This material shows good characteristics that place it among good candidates for the application in orthopedics and maxillofacial surgery

Etiology and mechanisms of ulnar and median forearm nerve injuries

© 2015, Institut za Vojnomedicinske Naucne Informacije/Documentaciju. All rights reserved. Bacgraund/Aim. Most often injuries of brachial plexus and its branches disable the injured from using their arms and/or hands. The aim of this study was to investigate the etiology and mechanisms of median and ulnar forearm nerves injuries. Methods. This retrospective cohort study included 99 patients surgically treated in the Clinic of Neurosurgery, Clinical Center of Serbia, from January 1st, 2000 to December 31st, 2010. All data are obtained from the patients' histories. Results. The majority of the injured patients were male, 81 (81.8%), while only 18 (18.2%) were females, both mainly with nerve injuries of the distal forearm – 75 (75.6%). Two injury mechanisms were present, transection in 85 patients and traction and contusion in 14 of the patients. The most frequent etiological factor of nerve injuries was cutting, in 61 of the patients. Nerve injuries are often associated with other injuries. In the studied patients there were 22 vascular injuries, 33 muscle and tendon injuries and 20 bone fractures. Conclusion. The majority of those patients with peripheral nerve injuries are represented in the working age population, which is a major socioeconomic problem. In our study 66 out of 99 patients were between 17 and 40 years old, in the most productive age. The fact that the majority of patients had nerve injuries of the distal forearm and that they are operated within the first 6 months after injury, promises them good functional prognosis