Pasaulyje plačiai naudojamos kompozitinės plieno-betono konstrukcijos, o jų darbo ypatumai yra sudėtingi ir nėra iki galo ištirti. Baigiamajame magistro darbe nagrinėjama plieninio pluošto ir jungių, išdėstytų skirtingu atstumu, įtaka kompozitinių plieno-betono konstrukcijų mechaninėms savybėms. Siekiant nustatyti plieninių jungių ir metalinio pluošto įtaką kompozitinės sijos bendram darbui, bei betono mechaninėms savybėms, atlikti analitiniai skaičiavimai ir eksperimentinis tyrimas. Darbą sudaro trys dalys. Pirmoje dalyje aptariama tokių konstrukcijų darbo problematika. Antroje dalyje pristatomas eksperimentinis tyrimas, jo darbo eiga bei gauti rezultatai. Trečioje dalyje atliekami analitiniai skaičiavimai ir gauti rezultatai lyginami su eksperimentiniais. / In the world composite steel-concrete structures are widely used, and their features are complex and not fully investigated. At the final master work the steel fiber and connectors, placed in different distance, influence to composite steel-concrete structures mechanical properties are analized. To determine the steel joint and a steel-fiber influence to composite's overall work, and mechanical properties of concrete, was performed out analytical calculations and experimental. The work consists of three parts. The first part deals with the problems of construction work. The second part presents the experimental study, its process and the obtained results. The third part presents analytical calculations and obtained results are compared with experimental results.

The aim of the dissertation is to investigate the dependencies of the structure of polyester multifilament yarn fabrics and their permeability to air on the fabric structure factors and to develop methods for designing air permeable fabrics.

Aim and tasks of the work. The aim of this work is to investigate insufficiently analyzed variants of the electrodynamic super-wide-band slow-wave structures, create their models, improve methods of analysis, analyze properties of the systems and reveal potentiality of the traveling-wave cathode-ray tubes, slow-wave structures. In order to achieve the aim it is necessary: 1. To improve method for evaluation of non-linear distortions in the traveling-wave cathode-ray tubes and reveal possibilities of reduction of non-linear distortions. 2. To create models of the insufficiently analyzed variants of slow-wave structures and reveal properties of the slow-wave structures. 3. To reveal influence of periodical non-homogeneities on properties of slow-wave structures, simulate and reveal influence of transitions to properties of slow-wave structures and traveling-wav cathode-ray tubes. 4. To make investigation of potentiality of slow-wave structures and traveling-wave cathode-ray tubes and select variants of slow-wave structures that can guarantee wide band and high operating speed of the traveling-wave cathode-ray tubes. Scientific novelty and practical value. Models of insufficiently simulated slow-wave structures were created and their properties were analyzed. According to analysis and modeling results, variants of systems were selected that can guarantee the wide pass-band and high operating speed of the traveling-wave cathode-ray tubes. Using finite element method calculation... [to full text]

Tyrimo tikslas – įvertinti skirtingo natūralaus pluošto įtaką kompozicinės medžiagos polietilenas – pluoštas“ mechaninėms savybėms. Bandinių gamyba bei medžiagų mechaninių savybių tyrimai atlikti 2013/2014 m. Aleksandro Stulginskio universitete, Jėgos ir transporto mašinų inžinerijos instituto ir Žemės ūkio inžinerijos ir saugos instituto laboratorijose. Tyrinėjami kompozitai armuoti trimis skirtingai natūraliais pluoštais: kanapių, dilgėlių ir linų. Polietileno klijų kompozitas armuojamas keturiais kiekiais pluošto: 5 %,7 %, 10 % ir12 %. Tempimo ir lenkimo bandymai atlikti „Instron“ medžiagų savybių tyrimo stendu, nustatyta apkrova, kurią atlaiko bandinys ir deformacija. Atlikus lenkimo ir tempimo tyrimus nustatyta, kad geriausia armuojanti medžiaga yra kanapių pluoštas. Tempiant atlaikė didžiausią apkrovą – 753,7 N ir deformavosi 4 mm. Lenkiant kanapių pluoštu armuotas bandinys atlaikė 24,3 N apkrovą ir deformavosi 11,6 mm. / The aim - to evaluate the influence of different natural fiber composite polyethylene - fibers' mechanical properties. Specimen fabrication and mechanical properties of the materials were tested in 2013/2014 year. Alexander Stulginskio University, Power and Transport Machine Engineering and the Institute of Agricultural Engineering and Safety Institute laboratories. Reinforced composites are studied in three different natural fibers: hemp, ramie and flax. Polyethylene adhesive composite reinforced with four volumes of fiber: 5%, 7%, 10%, and 12%. Tensile and flexural tests were examined by using "Instron" material properties testing machine down load the sample and can withstand deformation. After bending and tensile tests showed that the best reinforcement material is hemp. Tensile withstood the maximum load - 753.7 N and deformed 4 mm. bending of hemp fiber reinforced sample withstood 24.3 N load and 11.6 mm.