Papers by Keyword: Cohesive Strength

Abstract: The article presents the computer simulation results and real experiment of foam concrete cohesion with glass-composite, basalt-composite and metal fittings in bending elements. Numerical simulation of beams implemented with software package “Lira-SAPR 2013” using finite element method for modeling. For real experiment used bending beam test method according to ISO 10406-1:2015. As a result, the influence of the loading level and foam concrete density on the reinforcement slipping value and foam concrete cohesive strength with reinforcement in the bending elements. The foam concrete cohesive strength with glass-composite fittings meets the standard requirements, so it can be recommended for the foam concrete bending elements reinforcement. Verification of the computer simulation results with the real experiment data allowed to establish the efficiency of the used numerical model and revealed the need to use the cohesion parameters in the "foam concrete – reinforcement" system for foam concrete structures calculations in specialized programs.

Abstract: Plasma sprayed FeSi nanocomposite coating is used more and more widely, yet the cohesive force in nanocomposite coating on mild steel is still a problem to solve. This paper aimed to use MM simulation to estimate the cohesive strength. To simulate the interfacial binding energy in plasma sprayed FeSi nanocomposite coating on mild steel, different kinds of FeSi-Fe molecular models were built. The simulation results indicated that the mild steel supporting plasma sprayed FeSi nanocomposite coating showed a higher cohesive strength with moderate thickness and thermal treated of FeSi. In the system of FeSi-Fe, the separation will take place between FeSi and Fe layer, the best thickness of plasma sprayed FeSi nanocomposite coating is about 6μm, and thermal treated under hydrogen atmosphere is about 1400K. The results of MM simulation provide some theoretical basis for preparation of plasma sprayed FeSi nanocomposite coating on mild steel with advanced cohesive strength.

Abstract: Limit stress diagram by Pelczyński was constructed in the coordinates σ_m - σ_H (σ_m - average stress for the process, σ_H - stress according to the Huber hypothesis) based on the hypothesis Huber - de Saint Venant and is consistent connection between the two hypotheses. This diagram allows for presentation the dangerous states of stresses for arbitrary stress state so plane and space (biaxial and triaxial). It also allows for the analysis of stress states occurring in various processes of plastic forming. To determine the state stresses occurring in the technological process starts from the components of the plastic deformation. In the case of a wire drawing process with a circular section in the inlet area of the die there is equality of deformation φ₂ = φ₃ and the equality of stress σ₂ = σ₃ (which is uniform biaxial compression), while in a outlet of the die there is a uniaxial tensile σ₁, which cannot achieve a value equal to σ_p (yield strength), since in this case the wire could be deformed outside the die.The aim of this study was to construct the Pelczynski diagram in such a way to show on the example of brass wire M63, the course of the stresses in the drawing process.The research program included:- Realization of the drawing processes in order to obtain samples of varying degrees strengthening,- Determination on the basis of tensile strength the properties R_m, R_p0,2 and cohesive strength of R₀ for varying degrees of strengthening,- Determine the influence of cold deformation for the course of curve of the yield strength,- Constructing a diagram of drawing process on a background of the diagram of yield strength in this process.

Abstract: With the rapid development of reinforced earth technology, different reinforced materials are also gradually applied to Reinforced earth. In this paper, we focus on the need for the study of interface characteristics between different reinforced materials and clay, by making indoor drawing test with two kinds of reinforced materials commonly used in engineering and the same clay. The test results show that: the drawing strength between the two reinforced materials and clay both increase with the normal stress increasing, both of their strength envelopes are straight lines; In the drawing test between the warp knitted geogrid and clay, the cohesive strength is 6.65kPa, the friction angle is 21.03°; while the drawing test between the geonet and clay, the cohesive strength is 2.9kPa, the friction angle is 10.96°; The average tensile strength of warp knitted geogrid is 26.4% of genet's, while the drawing strength of warp knitted geogrid in the test is about 48.1% of genet's, so when chosing reinforced materials in some engineerings, it is an important factor that we must consider the particle size and gradation of the filled reinforced materials, selecting the most appropriate size effect.

Abstract: The interface zone in concrete is the weak link and its structures and properties are the key factors determining overall performance of concrete. In this paper, the cohesive strength on the interface zone is tested through the in- situ drawing test of the aggregate from the concretes of C15,C20, C25, C30,C35,C40. and the tensile strength and the shear strength on the interface zone are analyzed by the simple assumptions about the uniform drawing and well distributed stress on the interface. As a result, It’s showed that with the pebble size increased, normalized pull strength of low grade concrete has a tendency to increase, while high grade concrete is in the vicinity of 7% fluctuation; when pebble diameters are the same, with the concrete strength increases, the normalized pull-out strength decreases. As the particle size less than 30mm or more than 110mm, tensile strength seems to limit value. the macro pull strength is on the range of 4%—12% of concrete compressive strength.

Abstract: The mechanical performance of DLC coatings on 316L stainless steel deposited by a saddle field fast atom beam source has been evaluated using the four point bend (FPB) test. Two different deposition parameters, pressure and current were varied when depositing the films. Load-displacement measurements were carried out during the bend test to determine the load corresponding to crack initiation. This load designated as the cohesive strength of the coating which is also called the cracking resistance of coating and provides a measure of the strength of the coating. The cohesive strength of the coating was calculated based on elementary beam theory. Scanning Electron Microscopy (SEM) was used to determine the location of the crack. Finite element analysis was used to predict the stress distribution across the coating thickness. The experimental work on FPB tests has been used to support the numerical (finite element) model for the determination and prediction of film cohesive strength. It was observed that at lower deposition current, the cohesive strength increases with increased deposition pressure whereas, for higher deposition current, these values do not increase with increasing deposition pressure. The model takes into account the film’s Young’s modulus, thickness and deposition pressure and current, and has shown that it is capable of predicting film cohesive strength when combined with a theoretical formulation for brittle fracture. It has been observed that the maximum stress develops at the outer surface of the film and propagates through the film-substrate interface. This result has only been validated for films with higher Young’s modulus compared to that of the substrate material.

Abstract: Many processes in ceramic manufacturing require handling of fine powders with particle sizes down to sub-micron range. Problems that are often experienced with these powders, such as stoppages and/or surges, can be predicted and prevented by first measuring relevant flow properties of these powders, and then using these properties to design a handling system. In this paper we will review common problems with handling such powders and the relevant flow properties tests, such as permeability, compressibility, cohesive strength and friction, as well as how these properties can be used to prevent and solve problems. Issues related to handling titanium dioxide (TiO2) will be used as an illustration.

Abstract: Application of coating fragmentation test for determination of coating properties is considered. A probabilistic model of coating fragmentation under uniaxial tensile loading is applied for coating and interface property identification of thin brittle coating/polymer substrate system. A finite element model is developed to simulate the process of buckle formation in coating strips during fragmentation test. The measured buckle geometry parameters and buckle density evolution as a function of the applied strain is used to estimate the interface toughness.