Papers by Keyword: Deformation

Abstract: The article investigates the influence of ultraviolet (UV) on polyurethane foams' structural and mechanical characteristics. To assess the impact of changes and degradation of foam properties, studies were conducted for two groups of samples: those without exposure to UV and those exposed to natural UV for 3 months. According to the analysis of IR spectra, insignificant chemical changes in the structure of the outer surface of the samples were established as a result of three months of UV influence on the foam. No noticeable chemical changes were found in the inner part of such samples. Compression tests of samples of different groups were carried out under static loading to study the change in mechanical characteristics. Based on experimental tests, changes in the values of mechanical, strength, and deformation characteristics were investigated: Young's modulus, elastic strength, yield strength, and degree of deformation recovery. A conclusion was made about the resistance of polyurethane foam to ultraviolet influence for a period of up to three months.

Abstract: The deformation of semisolid slurry within a mould or die is complex in the case of semisolid forming. Understanding and improving the efficiency of such a forming process requires a systematic study of the flow of semisolid slurry under deformation. This study considers the flow characteristics of semisolid A356 alloy slurry under deformation between two parallel plates. The semisolid slurry is represented here by an apparent viscosity under deformation and cooling. The process is then modelled using momentum and energy conservation equations, comprising an analytical solution to predict related flow and deformation behaviour of the slurry. The final solution involves coupling the governing equations by developing a numerical code on the FORTRAN platform. The model then predicts the distribution of temperature, solid fraction, apparent viscosity of the semisolid slurry, and stress to deform the slurry. The deformation stress found in this study has a realistic value, which is also supported by the available research. Prediction of deformation characteristics for any semisolid slurry is possible using the present model, which is simple and appropriate. This study also found that the deformation stress increases with an increase in the plate length and decreases with an increase in the slurry deformation velocity.

Abstract: The purpose of the suppressor is to partially eliminate the sound effect after firing and to mask the muzzle flame (essential for power components). When fired, the temperature rises approximately seven to ten degrees with each shot, assuming uniform temperature conditions of 21 °C. Given this knowledge, the suppressor can reach temperatures of 150 °C to 280 °C after firing one or two 30-round magazines. Assuming active training of the force or sport shooters, the suppressor will reach temperatures of 540 °C Celsius during continuous firing in an army combat situation, with temperatures in excess of 1000 °C. Already temperatures exceeding 280 °C during firing significantly affect the degradation of the suppressor material by thermal expansion through wear and tear, clogging by sediments in the case of frequent use of suppressors, massive deterioration by high temperature pressures and a significant reduction of the effect. Thermal deformation also has a significant effect, which can cause twisting or bending of the material, which can result in contact of the projectile with the suppressor and deflection of the projectile, in the worst case resulting in rupture of the suppressor and fragmentation of the projectile. Current knowledge, studies, professional articles published by the shooting public, representing the opinions and knowledge of the force components, sport shooters as well as hunters point to the lack of functionality, durability effectiveness of suppressors and point to defects, shortcomings during active use.

Abstract: The utilization of hydrogen in the construction of a decarbonized society is expected to expand the application of austenitic stainless steels with high resistance to hydrogen embrittlement as structural materials. However, the residual stress generated during machining causes material deformation, leading to increased costs and decreased productivity. Therefore, cutting methods that can control residual stress are necessary, prompting numerous studies on residual stress. We proposed conditions to reduce deformation and clarify the relationship between the depth of cut and material deformation, as well as the relationship between residual stress and material thickness after machining. In this study, stainless steel (AISI 304) was face milled, and the relationship between the cutting temperature and material deformation after machining was evaluated, as in a previous study. In addition, electrolytic polishing was performed to measure the residual stress in the depth direction, and its relationship with material deformation was evaluated. The experimental results showed no correlation between the cutting temperature and deformation. However, the measurement of the residual stress in the depth direction suggests that the removal of the surface layer by electropolishing may affect material deformation and residual stress.

Abstract: The strain rate exerts a profound influence on the mechanical characteristics of nanomaterials. To investigate this phenomenon, the molecular dynamics approach was employed to examine the impact of uniaxial compression along the [100] crystallographic direction in monocrystalline Al. The purpose of this research was to determine the differences in reactions observed during the elastic and plastic phases. It employed the Embedded Atom Method (EAM) as well as the Modified Embedded Atom Method (MEAM) potentials at 300 K. A comparative analysis of the outcomes from these potentials demonstrated considerable disparities. The results encompassed the percentage distribution of crystal structures (fcc, hcp, bcc, and others) as well as their atomic configurations. Several analytical factors were examined, including the strain-stress curve, the radial distribution function (RDF), the common neighbor analysis (CAN). The applied MEAM potential represents a subsequent occurrence of transitions following EAM, encompassing both increasing and decreasing phase transitions.

Abstract: In order to get the insights about microstructural changes that occurs under the thermo-mechanical processing conditions, the physics based modelling approach is very useful. Therefore, the flow curves of alloy 718 are theoretical simulated using a dislocation density dependent constitutive model for different conditions. Presented model considers the microstructural ingredients that are immobile dislocation density, effective grain size and dislocation cell size as the variables to address the creep. The simulated flow curves show a good agreement with the experimental flow curves. The magnitude of immobile dislocation density and dislocation cell size in between 3.87× 10¹⁴ - 3.87× 10^14­ m^-2 and 8.29-8.45 μm, respectively, at the completion of the simulation. Furthermore, this approach also provides the possibility to quantify and depict the variation in each strengthening contributions.

Abstract: The methods of influence on the material using different energy sources are considered. The role of friction in several technological processes is emphasized. The technological process of heat treatment is proposed, which allowed to restore the properties of rolled rolls that were lost due to incorrect grinding conditions. Application of the proposed technological process has shown that: 40X steel can be hardened to martensite in oil, water, and in a 10 % aqueous solution of NaCI salt, but with different results (i); the most effective hardening mode for 40X steel rolls is quenching with cooling in a 10 % aqueous solution of NaCI salt and subsequent high-temperature tempering, which is necessary to remove dangerous residual stresses (ii); the structure of the surface working layer of 40X steel rolls, after the selected optimal heat treatment regime, consists of fine-needle martensite and a small amount of Cr carbides (iii); closer to the core of the rolls, in addition to martensite, there are areas of troostite-bainite structure (iv); the resulting structure of the rolled rolls is capable of ensuring their efficient and long-term operation, but under optimal conditions, when the rolls' heating temperatures do not exceed 200 °C, and the proposed temperature conditions are recommended for both operation and routine maintenance associated with periodic restorative grinding of the working surfaces of the rolled rolls (v).

Abstract: Grinding is a widely used process in many industries due to the precise geometric tolerances and excellent surface finishes it can offer, which makes it very useful when high quality parts have to be manufactured. Due to the wear that the grinding wheel suffers, a process known as dressing is periodically carried out to recover the cutting ability of the wheel. Dressing is an extremely important part of the grinding process, as it can alter and improve the cutting conditions of the wheel.During the dressing of vitrified bonded CBN wheels, the real dressing depth of cut is significantly lower than the theoretical depth of cut, leading to dimensional errors in the dressed grinding wheel, which consequently translate into the ground part. However, while deformations during grinding have been widely studied, this phenomenon has not been yet analyzed during dressing. Therefore, the main objective of this work is to determine the influence of the dressing parameters on the real depth of cut. Also, the effect of dresser wear and the deformations has been determined separately.To this end, a new methodology has been developed to measure the real depth of cut using a laser displacement sensor. Moreover, experimental tests have been carried out to characterize the influence that the dressing speed ratio (q_d) and set depth of cut (a_{d_set}) have on the actual depth of cut (a_{d_real}). It has been seen that the use of negative q_d results in a more accurate real depth of cut, and therefore a more efficient dressing process. While the error using negative q_d is about 10 %, using positive q_d is about 25 %.

Abstract: DP600 steels are high strength steels used in structural elements of vehicles. However, they can be used in other sectors, but this requires a study in different working conditions, with the help of tools that facilitate the realization of predictions about the mechanical properties of these materials.The "Design Expert" software was used during this research. In it, the combinable input variables are introduced, which in this case are only the size of the pin and the folding angle of the sheet, so that employing simple combinatorial operations tells us how many and which experiments we will have to perform to cover the different possibilities.Simulations have been carried out with the Deform-2D software, applying the finite element method, to know in advance what is going to be the behavior of the metal sheets interacting with the rotating pin, in processes like drawing.

Abstract: The research on tolerance stress in aluminum alloys is focused on examining the mechanical behavior of τ₄-Al₃FeSi₂ and τ₁₂-Al₃Fe₂Si phases during [001] compression and their structural evolution. The use of MD computational bond length measurements allows for a comparison to be made with previous studies on tensile deformation. The simulations were performed at a constant strain rate of 21×10¹⁰ s^-1, using NPT conditions (isothermal-isobaric), with approximately 20,000 atoms, 1 atmosphere of pressure, and 300 K temperature, using a Nosé-Hoover thermostat. Under periodic boundary conditions, the Modified Embedded Atoms Method (MEAM) potential was applied to all 3D faces, and the average bond length behavior between Al, Fe, and Si was calculated. A comprehensive investigation is carried out to explore the properties of these phases, including a detailed structural analysis at the atomic scale. This paper presents a comprehensive analysis of how changes in compound concentration affect mechanical behavior during compression. The average bond length varies depending on the applied stress axis, and it demonstrates good agreement with literature data. The mechanical deformations alter the behavior of atomic phases, as discussed in detail in the conclusion.