Papers by Keyword: Strength

Abstract: The thermal stability of composite materials based on basalt fibers is determined by the strength of fibers under thermal stress. The decrease in strength occurs due to the crystallization of the original fibers and the development of microcrystalline nuclei in them during heating. Experimental studies of the influence of the processing temperature of continuous basalt fibers on their strength have been carried out. It has been established that the strength of fibers during their heat treatment up to 400^оС decreases by 25 % from the initial one. At the temperature of approximately 500^оС, the strength of the fibers is almost half. At 600^оС, the fiber strength is 20 % of the initial strength. At a processing temperature of 700^оС, the fiber is completely destroyed. The main reasons for the decrease in fiber strength are the development of microcrystalline nuclei that have formed in the fibers at the drawing stage in the crystallization zone. From above, this zone is determined by the temperature of the upper limit of melt crystallization, and from below it is limited by the glass transition temperature. The residence time of the melt in this range is the crystallization time. Calculations the speed of movement and the cooling rate of the melt stream during fiber drawing were carried out, which made it possible to determine the temperature zone and time of crystallization. The results of theoretical studies have shown that for the production of fibers used in composites, it is necessary to select such basalts and conditions for the fiber drawing, under which the values of the temperature zone and time of crystallization will be the smallest.

Abstract: Hollow glass microspheres (HGM) have been employed in a wide range of applications such as thermal insulating coatings for construction and transportation applications and for acoustic insulation coatings. As such, it is expected for the HGM to exhibit an extremely high pressure tolerance in order to endure the harsh environment. In this present study, an effort has been made to investigate the mechanical properties of hollow glass microsphere. The glass sphere with diameters between 5-30 µm, 50-90 µm and 90-125 µm were used for this investigation. This study's objectives are to investigate the strength of HGM and gain an in-depth understanding of the mechanical characteristics of the sintered spheres.

Abstract: A comparative study of the structure and properties of two biodegradable Fe – 27Mn and Fe – 27Mn – C alloys for biomedical use after equal channel angular pressing (ECAP) has been carried out. It is noted that addition of carbon in the alloy leads to a change in the mechanism of plastic deformation from the formation of martensite to deformation twinning in austenite. ECAP improves the strength characteristics of the alloys under study and the corrosion rate by refining the structure and increasing the dislocation density. The presence of a partially twinned structure in the Fe – 27Mn – C alloy results in a lower corrosion rate despite a stronger refinement of the alloy structure after ECAP.

Abstract: Austenite restoration during thermomechanical (TM) rolling of typical vanadium-microalloyed structural steels was studied to optimize strength in the as-rolled and air-cooled condition. Multi-pass plate rolling simulations were performed on V-N microalloyed and CMn steels to compare recrystallisation behaviour in various temperature regions. Included were a conventional schedule ending at high temperature and two TM schedules with mill exit temperatures in the intermediate and low austenite regions. Increasing delay periods after roughing enhance the suppression of recrystallisation after the start of finishing thereby increasing both nucleation site density and nucleation rate for ferrite formation and refinement in grain size. Good agreement was found between microstructures after industrial TM rolling and those obtained from laboratory simulations. Although precipitation of vanadium carbonitrides is an effective strengthening mechanism, appreciable gains in yield strength due to grain refinement can be achieved by rolling in the lower austenite region. Low nitrogen contents in V steels produce coarser final ferrite grain sizes and lower strengths probably due to a larger precipitate size. V-N steels display similar flow behaviour to CMn grades down to approximately 825°C at low to intermediate strain rates but may experience alternate regions of work hardening and dynamic softening at lower temperatures in austenite.

Abstract: Concrete the spirit of the infrastructures and it’s a combination of cement, water and coarse aggregate, fine aggregate and add mixtures. Sand and cement is consider as critical material in significant mix design due reality that collecting of cement and uncovering sand is impacting out. In case consider concrete the manufacturing of it release out CO₂ and other green house gases and in other hand sand expulsion furthermore is lead us to stream bed declination, so most ideal choice for the both of materials ought to be taken vital notes. Through this paper an imaginative focus on utilization of Pareva Dust as a replacement to concrete and Quartz Sand as replacement to sand at different level (5%,10%15%) is utilized and assist with getting's mom earth. Through this examination paper study is given for the mechanical and quality properties of which guide as choice in concrete.

Abstract: This study presents a set of "particular" strength criteria of the constituent elements of masonry as a composite material constituted by homogeneous fragments of heterogeneous materials (brick and mortar) and contact interface (shear and normal adhesive strength). This paper proposes the expressions for calculate the values of each particular strength criterion used for the discrete modelling of masonry. The results were obtained based on the experimental study of stresses and failure modes in masonry specimens, mortar samples and brick units. There are determined a set of 8 particular strength criteria, which correspond to the actual work of the masonry constituent elements. Their use in the structural micromodelling of masonry allows to determine the body contact interactions, track the gradual accumulation of local stresses, exclude from the calculation model the elements in which a particular strength criterion has been exceeded, and modelling the degradation process.

Abstract: The article presents the physical, mechanical (strength, density), and chemicalcharacteristics of complex M100 water-resistant mortar compositions, which include crushedlimestone (0.16–1.25 mm) and granite-crushed sand. Additionally, stone masonry mortar mixtureswith a grain size of up to 5 mm have been developed using local raw materials for the restoration ofwall constructions in building structures.The relationship between the density and chemical stabilityof the hardened samples was determined using the results of complex research on the structuringprocess of the test samples obtained with the modifiers used to improve the workability of theprocessed lime mortars.

Abstract: It was determined that the active component of modern concrete is water. Water has a variable structure, the type of which depends on the temperature at which the water was processed. The use of water in the production of concrete, which has a certain changed structure, allows influencing the rheological properties of concrete mixtures and modifying the structure of cement stone in such a way as to give concrete properties that ensure high operational reliability of structures. However, this method of increasing the strength of concrete has certain disadvantages that prevent its wide application. The purpose of the research is to determine the effect of a mixture of water of different structure on the strength of fine-grained concrete and the speed of its formation.

Abstract: One of the main active components of modern concrete is water. Water has a variable structure, the type of which depends on the water treatment technology. The use of water in the production of concrete, which has a changed structure as a result of the action of certain substances, allows influencing the rheological properties of concrete mixtures and modifying the structure of cement stone in such a way as to give concrete properties that ensure high operational reliability of structures. However, this method of increasing the strength of concrete has certain disadvantages that prevent its wide application. The purpose of the study is to determine the influence of the type of plasticizers used for water activation on the speed of structure formation and the strength of fine-grained concrete.

Abstract: The study evaluates the method for determination of the rational technical and economic indicators, namely the rational composition and flexural strength, of building materials containing ash-and-slag obtained from heat-and-electric power plant as waste from the combustion of masute and coal. Results of method application were obtained. The study is aimed on reduction of the negative technogenic impact on the lithosphere by developing an appropriate environmental protection technology for utilization of the mentioned above waste as a replacement of sand in building materials made of cement-sand mixture. The rational composition of the building materials containing ash-and-slag waste granules was selected basing on the results of two stages of experimental research – mechanical bending tests of straight two-support beams on a rupture machine. It was proposed to provide a complex index for assessment of the efficiency of ash-and-slag waste disposal in the building materials, which refers to relation of the strength limit to the density of the material per unit value. The results of calculation of the index magnitudes were obtained.