strength

RESEARCH OF MODIFIED GYPSUM BINDERS PROPERTIES

In the article the analysis of literary sources concerning methods of gypsum binders modification is shown. It is shown that today more and more attention is paid on the ecology of production and the maximum efficiency of the use of natural resources, therefore the development of non-klinker binders, such as anhydrite and gypsum, is relevant.

INFLUENCE OF ELEVATED TEMPERATURES ON THE PERFORMANCE OF NANOMODIFIED FIBER-REINFORCED CONCRETES

Exposure to elevated temperatures has detrimental effects on the properties of concretes based on the Portland cement, leading to irreversible changes, up to total failure. One of solutions to improve resistance of structures after exposure to high temperatures may be the use of cement-based materials modified at the nanoscale.

ROAD CEMENT CONCRETES BASED ON MODIFIED ADDITIVES OF NEW GENERATION

The modified concrete mixes design and cement concrete with the given operational parameters was developed. During the experiment, cement concrete was obtained from concrete mixtures of various compositions with modifying additives of a new generation containing a superplasticizer based on polycarboxylates and an air-absorbent additive. Superplasticizer was injected into a concrete mix with water in a quantity of 0,6; 0,8 and 1,0 % of the mass of cement, and the additive-aeration – in the amount of 0,1 % of the mass of cement in all the components of concrete.

EFFECT OF COMPONENT COMPOSITION ON PROPERTIES OF ENGINEERED CEMENTITIOUS COMPOSITES

The application of engineering cementitious composites (ECC) – a specially developed class of cement-based material reinforced with fibers – allows to enhance the loading capacity, stability under static and dynamic influences, as well as durability of building structures due to controlled cracking process. The design of engineering cementitious composites is based on the concept of micromechanics, which includes the strength and energy criteria of deformation strengthening throughout the wide range from the macro- to the nanostructural level.

INFLUENCE OF DEFECTS OF THE WORKING REBAR ON THE BEARING CAPACITY OF THE REINFORCED CONCRETE BEAMS

Every construction is influenced by different factors during operation. As a result, there are various defects and damage of these elements, which affects their operating condition. One of such defects is the corrosion of the working rebar. Investigation of samples with corrosion is a complicated and labor-intensive process. Instead of corrosive effects, we perform controlled valves of damaged. In this way, we obtained experimental samples with a fixed value of reducing the diameter of the valve.

Іnfluence of fatigue crack growth resistance characteristics of wheel steels with nitride strengthening on their damage resistance under contact fatigue

The relationship between spalling formation on model wheels tread surface and cyclic fracture toughness of steels with nitride strengthening is study. It is shown that the nitride strengthening of wheel steels has a positive influence on damage resistance of surface rolling of model wheels. To improve the serviceability of wheel steels with nitride strengthening indicated the need to optimize their chemical composition providing content of carbon in the range of 0.50...0.55%, vanadium – 0.08...0.12% and nitrogen – 0,008...0,015%.

Interrelated processes of local electric field amplification in solid dielectrics, contributing to their degradation

The complex processes of local disturbance of an electric field, as well as the amplification of electrical strength and mechanical and thermal intensities in the solid dielectric, depending on the configuration of its conducting micro-inclusions are described.

Investigation of the Influence of Machining Factors on the Workpiece Deformation Mode in the Chip-forming Zone by the Finite Element Method

The results of studies of the impact strength, temperature factors and parameters of cutting tool geometry on the formation of the stress-strain and thermodynamic state of surfaces with different types of engineering materials in the cutting process are described in the article. Analysis of simulation modeling of power, temperature and deformation parameters is the basis for making of forecasting models of influence of the structure and process parameters on the formation of complex operational properties of the product.

The increase of the strength of the tooth - rolling cutter joint

There have been investigated the strength of the tooth-rolling cutter joining which greatly affects the durability of the drilling bit. The increase of interference during the compression results to the increase of the stress concentration in the tight coupling tooth rolling cutter body. It has been shown that for the assembly with the maximal interference the contact pressure exceed the permissible, which is unacceptable. To avoid this the selective assembly of the tooth-rolling cutter body press-joint is proposed.