4,683 Works

Hypothetical fracture at fibber-matrix interface in Cu-SiC composite due to thermal stresses

Piotr Czarnocki, Grzegorz Krzesiński, Piotr Marek & Tomasz Zagrajek
The Copper-SiC composite was investigated with the help of FEM. The authors modeled and analyzed the effect of relaxation of thermal stresses due to seasoning at room temperature after the manufacturing process together with the effect of thermal stresses induced by reheating the material to a service temperature. Especially, hypothetical fracture at interface was of interest. It was shown that, for a fixed temperature, a single crack emanating at 0° or 45° azimuth would develop...

Dynamic stability of three-layered annular plates with viscoelastic core

Dorota Pawlus
Three-layered, annular plate with viscoelastic core is subjected to loads acting in the plane of the plate facings. One formulates the dynamic, stability problem concerning the action of time-dependent compressive stress on a plate with imperfection. This problem has been solved. One created the basic system of differential equations in which the approximation finite difference method was used for calculations. The essential analysis of the problem was concentrated on evaluation of the influence of the...

The influence of equivalent radius and thread inclination angle in a screw joint on dissipation of energy for frictional models of bolted joint

Wojciech Kaczmarek
The article presents the problem of structural friction appearing in a screw joint with frictional effects between its elements. In the article, two mathematical models of screw joint are analysed. In the first model, high stiffness of a nut is assumed. In the second model, the influence of both cooperating elements (the screw and nut) is assumed.

Research on rotary system with tilting-pad journal bearings

Vladas Vekteris & Audrius Cereska
This paper presents the results of research on self-vibrations of rotary systems with segmental tilting-pad journal bearings having different frequencies of rotor revolution. The problem of research formulated in this work concerns technical characteristics of primary elements of the investigated system and its principle of operation. The obtained results are illustrated with graphs. The paper also contains comparison of results and discussion. General conclusions are given at the end of the paper.

Kinematic model for forming dough into cylindrical shapes

Feliks Chwarścianek
This study presents a description of the mechanics of forming dough pieces into cylindrical (cylinder-like) shapes. Based on the configuration of forming, the movement of the formed piece and its surface deformations were described. Kinematic relationships concerning the dough piece material as a rheological fluid were formulated. Next, the relationships coupling the kinematic quantities present with both descriptions were determined. The components of the deformation rate tensor, presented in the assumed forming configuration (cylindrical coordinate...

The constructional increase of crumbling effectiveness

Feliks Chwarścianek
The study presents an attempt at increasing the effectiveness of the crushing process through the application of a new original crumbling system. In the process of crushing materials, friction is present in many crushers as extremely significant or even dominating factor. The proposed construction solution is characterized by the occurrence – always on one of the working surfaces – of the static friction factor, and thus a friction that is greater than the kinetic friction.

Estimation of platform spatial pose and displacement of parallel mechanism using wire-based sensors

Marta Góra, Józef Knapczyk & Michał Maniowski
This paper presents an estimation method for the spatial pose and displacement parameters of multi-rod suspension mechanism, based on measurement results by using wire sensors. Some changes of position and orientation of the platform fixed to wheel knuckle cause corresponding changes of sensors’ cable lengths. The fixation points of the cable sensors are selected with the collision-free conditions taken into account. Numerical example deals with platform poses and positioning of the sensors that satisfy the...

Stress and deformation states in single-coil inductors used for pipe calibration by means of electrodynamic method

Józef Bednarczyk
The article presents results of tests performed at the AGH-University of Science and Technology in Cracow on strength of single-coil inductors used as tools in electrodynamic machining of pipes. The character of volumetric Lorentz forces acting on coils of compressing and expanding inductors was discussed, and numerically determined distributions of stresses and displacements created in coils under the impact of these forces were presented. The problems presented are relevant when designing durable inductors intended for...

Application of differential evolution algorithm for identification of experimental data

Łukasz Maciejewski, Wojciech Myszka & Grażyna Ziętek
In the paper, the authors present the approach to modelling of austenitic steel hardening basing on the Frederick-Armstrong’s rule and Chaboche elastic-plastic material model with mixed hardening. Non-linear uniaxial constitutive equations are derived from more general relations with the assumption of an appropriate evolution of back stress. The aim of the paper is to propose a robust and efficient identification method of a well known material model. A typical LCF strain-controlled test was conducted for...

Buckling and post-buckling study of open section cylindrical shells subjected to constrained torsion

Tomasz Kopecki & Hubert Dębski
The work concerns numerical – experimental studies on pre- and post-buckling of thin-walled, steel, cylindrical shells, with the open section, subjected to constrained torsion. Two geometrically varied structures are considered: an open section cylindrical shell without stiffeners and one that is reinforced by closed section stringers. The shells have five different length to diameter ratios. Numerical simulations were carried out and the neuralgic zone stress distributions in pre- and post-buckling responses, were determined. Torsion experiments...

Computer simulation of transient processes in a turbojet engine, with special attention to amplitudes of thermal shocks in some selected fault modes of operations

Wojciech Pawlak
Results of mathematical modelling and computer simulation of transient processes in the turbine jet engine SO-3 have been presented. The transient processes result from two different fault conditions. In the first case, the transient process has been induced with a rapid fuel shut-off. In the second case, the transient process follows some failure to the shaft that connects the turbine rotor to that of the compressor. The failure occurred in the area of the middle...

Undeformed chip sizes in grinding process of regular surface texture generation

Piotr Stępień
The paper presents theoretical analysis and simulation results of the process of regular surface texture generation by grinding with the wheel shaped in a special way. Simple variant of the method consists in grinding with the wheel having single helical groove. Non-uniform load of abrasive grains located in different zones of the wheel circumference was described. Two models (deterministic and probabilistic) of the wheel active surface were developed, assuming different grain arrangement. Results of two...

Optimum control of selected vibration forms in mechanical systems

Edmund Wittbrodt & Rafał Hein
In the paper, the authors describe and solve the problem of optimum control of selected vibration forms in mechanical systems. Two illustrative examples have been used to present the procedure for determination of the optimum controller coefficients. In the first example, a simplified mechanical system is considered, while in the second one – a rotor with magnetic bearing. In both cases, the integral performance indices have been defined in order to minimize the vibration level...

Diagnostics of ballistic resistance of multi-layered shields

Zdzisław Zatorski
In the presented work, the author describes a new diagnostic method of ballistic resistance of multi– layered shields. The proper ballistic energy absorbed by the shield is introduced in the form V2BL[R] according to Recht’s and Ipson’s method, and V2BL[Z] according to author’s method. The kinetic energy of the bullet mp · V2p/2 and the momentum of force I are transferred to the shield and the dynamometer of ballistic pendulum. They are used to determine...

Instytucjonalne aspekty ocenyskuteczności terytorialnej polityki rozwoju w kontekście strategii rozwoju województwa

Aleksander Noworól
Biuletyn Komitetu Przestrzennego Zagospodarowania Kraju PAN (Biuletyn KPZK) to najstarsze wydawnictwo Komitetu ukazujące się nieprzerwanie od 1960 roku. Do końca 2018 roku wydane zostały 272 numery regularne, 7 numerów poufnych (seria A) oraz jedna publikacja jako numer specjalny. Biuletyn KPZK PAN od początku swego istnienia był czasopismem publikującym: ekspertyzy, dyskusje, artykuły naukowe dotyczące przeglądu aktualnych problemów związanych z problematyką planowania zagospodarowania przestrzennego oraz regionalistyki. Każdy z tomów biuletynu poświęcony jest odrębnemu zagadnieniu i opatrzony tytułem...

Warm winter and cold summer spells in Spitsbergen and their circulation conditions

(:Unav)
The quarterly Polish Polar Research edited by the Committee on Polar Research of the Polish Academy of Sciences is an international journal publishing original research articles presenting the results of studies carried out in polar regions. All papers are peer-reviewed and published in English. The Editorial Advisory Board includes renowned scientist from Poland and from abroad. Polish Polar Research is indexed in Science Citation Index Expanded, Journal Citation Reports/Science Edition, Biological Abstracts, BIOSIS Previews, Cold...

Importance of snow as component of surface mass balance of Arctic glacier (Hansbreen, southern Spitsbergen)

(:Unav)
The quarterly Polish Polar Research edited by the Committee on Polar Research of the Polish Academy of Sciences is an international journal publishing original research articles presenting the results of studies carried out in polar regions. All papers are peer-reviewed and published in English. The Editorial Advisory Board includes renowned scientist from Poland and from abroad. Polish Polar Research is indexed in Science Citation Index Expanded, Journal Citation Reports/Science Edition, Biological Abstracts, BIOSIS Previews, Cold...

Effects of fuel spills on Arctic soil, 32 years later (Hornsund, Svalbard)

(:Unav)
The quarterly Polish Polar Research edited by the Committee on Polar Research of the Polish Academy of Sciences is an international journal publishing original research articles presenting the results of studies carried out in polar regions. All papers are peer-reviewed and published in English. The Editorial Advisory Board includes renowned scientist from Poland and from abroad. Polish Polar Research is indexed in Science Citation Index Expanded, Journal Citation Reports/Science Edition, Biological Abstracts, BIOSIS Previews, Cold...

Anatomical variations of Deschampsia antarctica É. Desv.plants from distant Antarctic regions, in vitro culture, and in relations to Deschampsia caespitosa (L.) P. Beauv.

(:Unav)
The quarterly Polish Polar Research edited by the Committee on Polar Research of the Polish Academy of Sciences is an international journal publishing original research articles presenting the results of studies carried out in polar regions. All papers are peer-reviewed and published in English. The Editorial Advisory Board includes renowned scientist from Poland and from abroad. Polish Polar Research is indexed in Science Citation Index Expanded, Journal Citation Reports/Science Edition, Biological Abstracts, BIOSIS Previews, Cold...

Methods of DC/DC converter transfer function measurements, based on data acquired in the time domain

(:Unav)

Numerical simulation of deformation and fragmentation of fractal-like nanoaggregates

Łukasz Żywczyk, Arkadiusz Moskal & Rafał Przekop
Aflexible fractal-like aggregate modelwas used to study deformation and fragmentation of the structure of fractal-like aggregates via their impaction with rigid rough surface.Aggregateswere conveyed one at the time towards a surface under vacuum conditions. The number of primary particles remaining in each fragment, ratio of average fragment radius of gyration after impaction to the average fragment initial radius of gyration and ratio of average coordination number to the initial coordination number were monitored for each...

Manufacturing of substitutes for spongy bone with increased absorbability

Monika Budnicka, Agnieszka Gadomska-Gajadhur & Paweł Ruśkowski
Composite scaffolds with increased hydrophilicity were prepared for cancellous bone regeneration by the freeze-extraction method. As a construction material, a poly–L–lactide (PLLA) was applied. As a hydrophilic, modifying agent a methacrylic acid copolymer, trade name Eudragit®, was used. Apreliminary investigation and optimization of the processwere performed. For the obtained scaffolds, regression equations determining the effect of: Eudragit®E100/PLLA weight ratio; volume ratio of methanol (porophore)/PLLA solution in dioxane on interconnected porosity and mass absorbability of obtained...

Application of turbiscan lab to study the effect of emulsifier content on the stability of plant origin dispersion

Anna Zalewska, Joanna Kowalik & Ireneusz Grubecki
The effect of emulsifier volume on emulsion system stability of plant origin being the basis of diet supplements for animals in winter season was analyzed. For this purpose, measurements of the backscattered light intensity as the function of the measuring cell height were conducted with a Turbiscan LAB optical analyzer. System stability was analyzed on the basis of Turbiscan Stability Index values. A Helos laser analyzer and a Nikon Eclipse E400 POL optical microscope were...

Graphene oxide-based nano-materials as catalysts for oxygen reduction reaction

Zuzanna Bojarska, Marta Mazurkiewicz-Pawlicka & Łukasz Makowski
The aim of the presented research was to test different carbon supports, such as graphene oxide (GO), graphene oxide modified with ammonia (N-GO), and reduced graphene oxide (rGO) for catalysts used in a low-temperature fuel cell, specifically a proton exchange membrane fuel cell (PEMFC). Modification of the carbon supports should lead to different catalytic activity in the fuel cell. Reduction of GO leads to partial removal of oxygen groups from GO, forming rGO. Modification of...

Impact of carrageenan addition on rheological characteri-sation of some hydrocolloid aqueous solutions during long-lasting agitating with rotational speed changes

Krzysztof Neupauer & Maciej Kabziński
The paper presents the impact of carrageenan addition on rheological characterisation of some hydrocolloid aqueous solutions during stirring with rotational speed changes. Carboxymethyl cellulose, guar gum and xanthan gum were used. Measurements were conducted in a vessel equipped with an anchor stirrer under rotational speed increase and decrease conditions, equivalent to a hysteresis loop rheological test. Rheological parameters were calculated using the power-law equation. It was found that a carrageenan addition generally causes a reduction...

Registration Year

  • 2017
    7
  • 2018
    2,552
  • 2019
    2,050
  • 2020
    66

Resource Types

  • Text
    3,977
  • Other
    706