Papers by Keyword: Deformation

Abstract: As a result of the research, the deformation properties of aluminosilicate adhesives modified with nitrate salts and intended for gluing wooden products and structures made of pine, beech and oak wood at different stages of their hardening were determined. Considering that pine is the most common wood in the manufacture of products and structures, then in order to reduce the numerical values of the elastic modulus in glued materials, it is advisable to add ammonium, lithium and sodium nitrates in an amount of 0.5%, potassium nitrate in an amount of 1% into the composition of an aluminosilicate adhesive. which will ensure the approximation of the elastic modulus values to the values of the unmodified aluminosilicate adhesive and will significantly affect the water resistance of the glue joint and the depth of penetration of the adhesive into the wood structure. For gluing beech wood products to reduce the elasticity modulus, it is advisable to introduce 0.5% ammonium and potassium nitrates and 1% lithium and sodium nitrates, which will reduce the numerical values of the elastic modulus in glued materials by 1.18 and 1.53 times compared with the values of the elastic modulus of the unmodified aluminosilicate adhesive. For gluing oak wood products to reduce the elasticity modulus, it is advisable to introduce 0.5% potassium nitrate and 1.5% sodium nitrate, which will reduce the numerical values of the elastic modulus in glued materials by 1.4 and 2.83 times compared to the values modulus of elasticity of unmodified aluminosilicate adhesive.

Abstract: The study is aimed at surface strengthening of jewelry tools. Samples in the form of a tool with a flat and curved surface profile are considered. Macrophotographs of jewelry korneisen at different stages of wear, as well as after restoration and strengthening are given. The results of the influence of chemical-thermal and thermo-friction treatments on the structure and properties of U7 and U8A steels used for jewelry tools are presented. The methodology of experimental researches is given. The equipment used for each of the hardening methods investigated in this work is considered. Auxiliary media and features of sample preparation for the experiment are also described. Photos of samples and some equipment at different stages of the study are given. Data on the distribution of microhardness, photographs of microstructures in cross section of samples after different types of hardening are presented. A comparison of the strengthening efficiency of the samples after the use of different processing methods is performed.

Abstract: Due to repeated loads, the pavement structures will experience repeated stresses and strains resulting in permanent deformation even though the working loads are still smaller than the design load. The permanent deformation will lead to cracking and fatigue failure with the life of the pavement. This phenomenon can be reduced by increasing the stiffness, flexibility, durability, stability and water absorption of the pavement. Material modification including the utilization of waste tire rubber (WTR) and natural zeolite is one of the efforts to increase those parameters in semi flexible pavement (SFP). The aim of this study therefore, to assess the deformation and fatigue failure of SFP incorporating WTR and natural zeolite under cyclic loading. The WTR was used as an additive at the level of 3% of asphalt content while natural zeolite was used as cement replacement at the 0, 5, 15 and 25% replacement levels. Permanent deformation tests were conducted by applying wheel tracking loads with the pressure of 6.4 ± 0.15 kg/cm² on the surface of the specimens with 1260 cycles per hour while fatigue tests were conducted on the simple supported beams with the span length of 30 cm by applying forth point loading at the frequency of 10 Hz. The test results showed that the best performance in sustaining cyclic loading was achieved at the zeolite content of 5%.

Abstract: The paper investigates the features of deformation and fracture of steels obtained using the technology of 3D printing by electric arc surfacing based on the registration of the acoustic emission signal. With a decrease in the test temperature of 07Cr25Ni13 steel, a decrease in the work expended in stretching the specimen is observed, both at the stage of elastic deformation and at the stage of strain hardening. It was found that the most informative characteristic parameters of the AE signal include: the pulse count rate N, the total count NΣ, and the AE signal entropy. With a decrease in the test temperature, there is a significant increase in the intensity of the AE signal, the total number of pulses at all stages of deformation and destruction of steel. The obtained regularities of changes in the characteristic parameters of the AE signal can be used as diagnostic features, both in assessing the stage of deformation and destruction of the material, and the structural state of the material. Fractographic studies have shown a significant decrease in the tough component of 08Mn2Si steel with a decrease in the test temperature. The fracture mechanisms of 07Cr25Ni13 steel change insignificantly with decreasing temperature, however, a significant decrease in the ductility of the metal is observed, as evidenced by a decrease in the size of ductile fracture cups.

Abstract: This paper provides a comparative assessment of the results of modeling the processes of deformation and destruction of objects under uniaxial tension in the MSC.Marc and DEFORM software packages and in a full-scale experiment, as well as a study of the influence of the form factor of these objects and the form of unit cells on the fracture parameters in modeling and experiment.

Abstract: Thin-walled hollow mini-spheres several millimeters in diameter have promising applications as components for the absorption of sound, pressure pulses and mechanical vibrations, as well as heat transfer elements. In this paper, an assessment of some physical and mechanical properties, including the strength and elasticity of metallic mini spheres, is given. To a great extent, the properties are determined by the wall material, however, can be modified by the coating as well.

Abstract: The engineering field's main issues are often identified to be estimating the deformation and the strain measurements of the working material. Gauging displacements until the fracture more accurately is crucial in experimental procedures for assessing the chosen material properties. This research paper investigates the commercial magnesium alloy (AZ31B) material using digital images, often called Digital Image Correlation (DIC), which provides complete displacement and strain data information at each timestep rather than utilizing an extensometer. This method provides images taken during the deformation, and subsequently, the material properties computed using correlation software for tested samples. The plastic anisotropy coefficients are computed for test samples that cut down at angles of 0, 45, and 90 to the rolling direction. Also, the tensile test finite element model until the necking region was used to verify the fitted models such as Hollomon power-law and Ramberg–Osgood relationships to define the non-linear relationship between stress and strain. Hence, real models and numerical simulations of incremental forming are created to depict this research work's usefulness to the forming applications.

Abstract: It is possible to explain the phenomenon of fatigue destruction and the patterns that are observed only in the deep study of the processes taking place in the material under conditions of repeated-variable loading, i.e. in the development of the physical theory of metal fatigue. Despite the large number of work on this issue, there is currently no single interpretation of the process of fatigue destruction of metals, which is primarily due to the exceptional complexity of the problem. The purpose of the study is to study low-cycle corrosion fatigue of steel using the example of A 414 Grade A steel. The work solved problems, such as research of kinetics of crack development in conditions of low-cycle loading of metal structure made of carbon structural steel A 414 Grade A. Regression analysis has also been applied to predict a change in the thermodynamic stability of the metal during cyclic loading. Analysis of fatigue crack development at alternating loading cycle was carried out. The results of calculations based on the proposed model of elastoplastic deformation near the top of the crack at the sign-alternating loading cycle can be described by non-linear dependence. The regression analysis revealed that the correlation coefficient of the selected model is-0.93, which indicates a relatively strong relationship between the variables. In experimental way it has been proved that reduction of thermodynamic stability of metal in corrosive medium is connected with increase of number of loading cycles, which leads to accumulation of fatigue damages.

Abstract: The change in ultrasound rate in the plastic deformation of high-chromium X39Cr13 stainless steel with ferrite–carbide structure (initially), martensite structure (after quenching), and sorbite structure (after high tempering) is investigated. The loading curve is different for each state. In the initial state, the loading curve is practically parabolic. In the martensitic state, linear strain hardening is the only stage. In the sorbitic state, a three-stage curve is observed. The structure of the steel after different types of heat treatment is studied by optical and scanning probe microscopy. In parallel with the recording of the loading curve, the change in properties of the ultrasound surface waves (the Rayleigh waves) in the steel under tension is measured. The structure of the steel determines not only the type of deformation curve in uniaxial extension but also the dependence of the ultrasound rate on the strain.

Abstract: The influence of various factors on the efficiency of microstructure refinement in two-phase titanium alloys with respect to a well-known Ti-6Al-4V alloy was discussed. The kinetics of microstructure evolution in titanium alloys with a lamellar type α/β microstructure during large plastic deformation depends mainly on temperature and strain rate, type of the initial microstructure, thickness of the α lamellae, path of deformation and chemical composition. Each parameter should be controlled to provide the most efficient microstructure refinement during conventional metalforming methods.