The paper presents the measurement method and results as well as the results of comparative calculations aimed at determination of material data for the package of ferromagnetic sheets insulated with epoxy lacquer. During the test, the package of sheets was treated as a 3D orthotropic material. The values of Young’s and Kirchhoff’s moduli for a pre-compressed package of sheets, in accordance with the used manufacturing technology of the medium and high power electric motors’ rotors, were detennined. The carried out FEM comparative calculations confirmed that the determined mechanical parameters of the package of sheets as a 3D orthotropic material, i.e. Young’s and Kirchhoff’s moduli, for the compressive stress range of 1.0÷2.5 MPa, are included in the linear range. It was assumed that the determined mechanical properties of the package of sheets are necessary at the design stage for FEM simulation calculations of the electric motors’ vibration and strength properties. As a result of the tests, it was found that they should be repeated in order to determine the properties of other sheets or those coated with different insulating lacquer.
This article contains information on the technological process involved in the production of a composite structure with carbon-epoxy prepregs including critical parameters of the process. The information in the publication shows respectively:
1. Using composite components for constructing the airframe,
2. ways of storing and preserving carbon prepregs on a matrix of thermosetting resins,
3. specific types of varying weave fabrics used in the prepregs,
4. way of preparing material for the process,
5. cutting tools,
6. preparing swage,
7. list of the most popular materials, their characteristics, pros and cons of their applications,
8. issues related to types of release agent,
9. parameters of selecting release agents in the process of manufacturing structures with carbon prepregs,
10. process of laying plies in a layered structure,
11. defects which result from improper material laying in swage,
12. preparing the structure for heating and technical parameters of the process.
The paper includes a description of the composite material used in the aviation industry. It presents the technological development of composites in terms of their use in the most important elements of the aircraft structures, such as a spar and aircraft wing sheathing, which are subjected to high loads during operation. The type of the material implemented for production was listed and the most commonly occurred incompatibilities during the carbon pre-impregnate manufacture and transport were described.
The manufacture diagram of composite elements with a polymer matrix was presented and the quality control system carried out at each mentioned stage (material storage, defrosting, cutting of dies, structure forming, polymerisation) was discussed.
The methods of non-destructive tests of carbon laminates in a polymer matrix were also listed, describing the most effective of them, i.e. a method of ultrasonic tests.
The conclusions were drawn and the development possibilities of ultrasonic tests both in terms of quality improvement and reduction of time for detecting incompatibilities in composite structures were described.
Marcelina Bobrowska, Michał Barcikowski and Radosław Rybczyński
This paper explores the effect of tow width on the damage area produced by high velocity impacts on glass fiber/epoxy composite structures made by filament winding. The subject of the research were a four-layered composite tubes that have been designed using matrix method. The method was used to select mosaic patterns with different rest of the winding stroke and number of interlaces, which are places of stress concentration and which affect the strength of the composite. The narrowest (5 mm) and the widest (17 mm) tow width available was chosen. Composite filament-wound structures were subjected to a high velocity impact by a 2.0 g spherical hardened steel impactor propelled to a velocity of 140 ÷ 170 m/s using a gas gun. It was observed that dependence of the damage area on tow width on filament-wound composite tubes is possible.
Inconel 718 alloy was tested. A new type of specimens of variable cross-sectional area measuring part was used for the tests. This provided a continuous distribution of plastic strain in that part of the sample. The proposed method enables to replace a series of specimens by one specimen. The degradation of the material was obtained by static tensile test and the creep test. The permanent deformation that varies along the specimen axis allows for an analysis of damage induced by a plastic deformation. The degradation of the alloy corresponds with the changes of acoustics properties of the material - attenuation of ultrasonic waves. It allows to detennine the degree of damage to the material using a non-invasive - ultrasonic method. Using the damage parameter proposed by Johnson allows to obtain correlation between the non-destructive results and a damage degree of the material. The presented testing method delivers information about changes in the material structure caused by permanent deformation.
Heroiu Marcel Ionescu, Sebastian Ioan Burduja and Florentina Alina Burlacu
This report’s main aim is to propose a methodology for assessing state-budget-funded projects based on a rigorous selection model, including clear and effective prioritization criteria. This report first argues that project prioritization and selection should be optimized against four dimensions: absorption, impact, legitimacy, and capacity. Second, it provides a diagnostic of the National Program for Local Development (PNDL), managed by the Ministry of Regional Development and Public Administration (MRDPA), as the most significant source of state-budget funding for local infrastructure projects. The PNDL’s current design and implementation leaves room for improvement, as reflected by the lack of strategic direction in allocating funds and the continued rise in the number of projects that get started without a feasible timeline for their completion. Further, this report makes recommendations for improvement of project evaluation and selection procedures for local infrastructure development projects, with a special focus on prioritization criteria and viable funding sources for each type of investment. The practical purpose is to enhance the efficiency and effectiveness of proposed investments, maximizing impact in the context of inherently limited available financial resources. A complementary focus is on opportunities for harmonizing and better coordinating investments across various sources of funding, in the context of nearly EUR 40 billion available to Romania from the EU for the 2014-2020 programming period.
Arch bridges were the first constructions with considerable spans built by man, due to the materials and technologies available at that time. Afterwards, these works of art have diversified and are now solutions used in countless situations, especially when crossing deep valleys.
Both their economic and architectonic aspects are hard to combat and have led to selecting this type of structure for more and more locations.
The paper will contain a brief presentation of some aspects regarding upper path concrete arch bridges composition and design methods. Also, it will have a case study regarding structural stresses over the different construction stages, and for several support hypotheses.
The case study will reflect the Crivadia viaduct, situated on DN 66, at km 150+672. The bridge has a main span of 59.20m and an overall height of 15.00m, serving a 7.80m wide carriageway and two 2.20m wide footways. It has a total length of 107.60m.
Based on the results of the case study, conclusions will be drawn regarding stress variation over the construction stages and under different support hypothesis, comparing these with the initial results.
Cable-stayed bridges are complex structures and for their design, the traditional calculation methods are hard, even impossible to use for a global analysis. Separate analyses for the each component of the bridge in a simplified manner can be conducted, but in this case the concurrence of the elements into the structure is not taken into account, leading to errors in estimating the structural response. For these structures, the construction method and the presence of the stays, which are elements having a nonlinear behaviour, implies to consider a nonlinear staged analysis including the second order effects in order to transmit form one stage to the other the stress-strain state.
In the present time, thanks to the evolution and development of the calculation methods and computer analysis, cable-stayed bridges can be accurate analysed so that the obtained response is close to the behaviour of the structure during erection and later, in service.
The aim of this paper is to present the results obtained using one of the finite element models and nonlinear staged analysis of the bridge at km 0+540 over Danube-Black Sea Canal near Agigea. Inside the paper, results related to the evolution of stress-strain state in principal structural elements of the bridge - pylons, stays and deck - during the execution and in final stage, in service are to be presented.
The characterization of the material through laboratory tests performed on asphalt mixtures offers significant performance predictions for asphalt pavements only when the material temperature is correctly taken into consideration. This paper presents an analytical pattern which, based on the thermo-physical characteristics, can predict correctly the distribution of temperatures in the mass of asphalt mixtures.
The paper also presents the organizational structure of laboratory testing, designed to validate the model for temperature determination. The temperature measurements are realized on a range of cylindrical samples at different moments in time, after submitting the sample from a low balance condition to a high balance condition by placing it in the environment precinct, according to the future test.
In conclusion, the paper aims at realizing and developing a model as a practical instrument able to offer a reliable assessment concerning the time required in order to reach the testing temperature specified for the samples of asphalt mixtures for different laboratory trials.
The natural soil used in filling the embankment of the road communications is characterized by the following factors: humidity, porosity, toughness. For certain factor values that describe the soil state is distinguished a certain soil behavior under the influence of the external forces applied through static or dynamic mechanical means.
In this study are presented the numeric simulation results of the soil-compactor interaction based on the complex and nonlinear rheological model proposed by the author in the result of the elaborated doctorate thesis, that follows the real soil characteristics (elastic, dissipative and plastic) on those of the compaction equipment (with a single vibrating roll). The model was harmonised and granted in accordance with the results obtained from the processing of the experimental data. For the simulation model was used the specialized software package Matlab (Simulink, SimMechanics). The obtained results revealed the real behavior of the equipment and its action on the compacted soil.