THE ASPECTS OF ALMG6 ALUMINIUM ALLOY DEFORMATION UNDER EXPLOSIVE WELDING

The paper presents the results of a study of the features of the deformation of the main plate made of AlMg6 in the process of explosion welding (with corrosion-resistant steel 08Cr18Ni10Ti). It was found that the end and edge sections of the main plate undergo severe deformation, as evidenced by the constructed maps of the distribution of residual deformations over the plate area. With an increase in the detonation velocity, an intensification of the deformation process occurs, which leads to the appearance of cracks and local spalling of plate fragments. In addition, the results of measurements of the elongation of the main plate showed that a noticeable longitudinal deformation of the plate begins approximately at a distance equal to 2/3 of the total length of the plate. The measured value of the beginning of elongation (240 ± 10 mm) with an accuracy of 95% converges with the calculated value (229 mm).

Improving the accuracy of calculating the speed of movement at the time of an accident in collisions with incomplete overlap of a part of the car

Introduction. Driving at a speed exceeding the permitted and average speed of traffic flow often leads to a collision of vehicles with other road users or with elements of the arrangement of highways. As a result, it is necessary to establish whether the fact of this violation of the traffic rules, which led to the occurrence of an emergency-dangerous road traffic situation. The methods used to calculate the speed of vehicles based on the resulting deformations are quite accurate, but this fact is true in conditions of complete overlap (impact across the entire width of the front, rear or side parts of the body). But there is a scientific task of developing a methodology according to which an expert or investigator will be able to calculate the average statistical value of measuring the depth of deformation of a vehicle for a specific road traffic situation.Materials and methods. The paper proposes a method for evaluating the possibility of using the data available to the expert for calculation by introducing the coefficient of variation of the depth of penetration. With the help of the coefficient of variation, the specialist has a tool for selecting and ignoring individual measurements of the depth of penetration, depending on the degree of overlap and on the ‘spread’ of the deformation values.Conclusions. After studying a number of collisions with incomplete overlap and excluding the ‘extra’ values of penetration, the speed equivalent to the energy cost for the development of residual deformations and errors (the difference between the true collision speed and the established one without taking into account the ‘falling out’ values of deformations) was calculated and it was found that the use of the algorithm taking into account the coefficient of variation led to sufficiently accurate calculation results.Discussions. The proposed methodology regulates the use of the coefficient of variation as a criterion for the admissibility of the use of source data to determine the quality of the final result of the calculation. This mathematical device is applicable to all collisions, but is especially relevant when studying collisions with incomplete overlap of any part of the car body.

Layer-Specific Residual Deformations and Their Variation Along the Human Aorta

This study described the regional distribution of layer-specific residual deformations in fifteen human aortas collected during autopsy. Circumferentially- and axially-cut strips of standardized dimensions from the anterior quadrant of nine consecutive aortic levels were photographed to obtain the zero-stress state for the intact wall. The strips were then dissected into layers that were also photographed to obtain their zero-stress state. Changes in layer-specific opening angle, residual stretches, and thickness at each aortic level and direction were determined via image analysis. The circumferential and axial opening angles of the intima were ~240° and ~30°, respectively, throughout the aorta; those of the adventitia were ~150° and -20° to 70°. The opening angles of the intact wall and media were similar in either direction. The circumferential residual stretches of the intima and the axial residual stretches of the media showed high values in the aortic arch, decreasing in the descending thoracic aorta and increasing toward the iliac artery bifurcation, while the axial residual stretches of the adventitia increased distally. The remaining residual stretches did not vary significantly with aortic level, suggesting an intimal role in determining circumferential, as well as medial and adventitial roles in determining axial residual stretches. We conclude that the tensile residual stretches released in the intima and media upon separation, and the compressive residual stretches released in the adventitia may moderate the inverse transmural stress gradients under physiologic loads, resulting from the >180° circumferential opening angle of the intact wall.

STUDY OF DYNAMIC DRAG OF DISLOCATIONS IN КСl CRYSTALS WITH IMPURITIES AND DIFFERENT DISLOCATION STRUCTURE

The frequency spectra of the dislocation decrement of attenuation ∆ d(f) on KCl + Ba (10-2 wt.%) impurity single crystals with residual deformations ꜫ of 0.25; 0.45; 0.75% at T = 300 K were investigated by the pulse method in the frequency range 22.5… 232.5 MHz. In the framework of the Granato-Lucke theory, the coefficients of dynamic drag of dislocations B for crystals with different ꜫ are calculated. It is shown that neither the presence of impurities nor the change of the dislocation structure affects the level of dynamic drag of dislocations.

Compressive strength properties of hyper-compacted concrete

The most important property of a concrete mix is concrete workability, i.e., the ability of the mixture to spread and take a given form while maintaining solidity and uniformity. The main influence on the workability of the concrete mixture is exerted by water consumption and, in part, cement consumption. Workability is determined by the mobility of the concrete mixture at the time of filling the mold and plasticity, i.e., the ability to deform without breaking the continuity. In the process of vibrating and pressing the concrete mixture placed in the mold, the total volume of the mixture changes until the pressure is balanced by the resistance forces. Deformation of concrete mix or, more precisely, freshly laid concrete with any compaction methods, including vibration compaction, is divided into elastic (reversible) and residual (irreversible). Residual deformations during vibration compaction occur as a result of water squeezing out and redistribution of aggregate fractions. Permanent deformation is part of the total. Its value at the same composition of the concrete mixture depends on the shape and size of the pressed sample. At the same time, it is noteworthy that after reaching a certain pressure, only elastic deformations will be characteristic of the freshly laid concrete mixture. So, A.D. Nikitin, in the course of the experiments, found that at a pressure of 2.2 MPa, the elastic moduli of the components of the concrete mixture have the following values: for cement paste - 0.16 · 104 MPa, aggregate - 4.5 · 104 MPa and air - 3 MPa ... After reaching a static pressure of 2.2 MPa, the compressible mixture showed only elastic deformation. This indicates that by the time the specified pressure was reached, the relative movement of the aggregates had ended, i.e., they are located most compactly.

Seismic assessment of tall RC frames with hybrid friction damper and SMA designed by PBPD method

In this study, a new lateral load resisting system for high-rise (Reinforced Concrete) RC frames is proposed, which includes friction damper-superelastic SMA wires. The proposed SMA-friction damper can not only regulate the mechanism of frictional energy dissipation components with its self-centering SMA wires according to the design method based on the proposed performance, which is able to provide a hysteretic behavior and high self-centering capacity with the lowest SMA consumption but also has some advantages such as simple configuration and economic application. In this paper, two high-rise 18 and 22-story RC frames were designed in two design modes of common and with the proposed damper. The nonlinear time history analysis subjected to 10 far-field earthquakes performed in Opensees software. The results of the analyses showed that using the proposed SMA-friction damper, in addition to the effective increase in ductility, lateral stiffness and lateral strength, provided an excellent self-centering capacity, which resulted to the significant reduction in the maximum drift and the residual deformations in the structure.

Investigation on the reasonable area of energy-dissipation bars for hybrid rocking columns

<p>In recent years, hybrid rocking columns have drawn more and more interests from researchers, due to their self-centering capacity. The energy-dissipation bars, which are generally applied at the rocking joints of hybrid rocking columns, could improve their energy dissipation capacities. Thus, the reasonable reinforcement ratio of energy-dissipation bars is much required for engineering applications. To determine the reasonable reinforcement ratio of energy-dissipation bars, a numerical investigation is conducted in this paper based on nonlinear time-history analysis. The analysis results show that a reasonable reinforcement ratio of energy-dissipation bars can effectively reduce seismic displacements of the hybrid rocking columns, without excessive residual deformations. Further, the reasonable reinforcement ratio of energy-dissipation bars for hybrid rocking columns with different periods is proposed in this paper.</p>

Investigation of residual deformations in innovative methods of combined mandrel drilling

Investigated the influence of the nature and microgeometrical parameters influencing surface work tool, as well as the technological lubricant to remain-wide deformation of the hollow cylindrical specimen of a brass brand of LS 59-1.

Strong-axis response of steel I-sections subjected to close-in detonations

The analysis of structural members subjected to close-in detonations involves a complicated dynamic scenario. Since the charge is very close to the structural member, the reflected pressure distribution on the member surface is highly non-uniform. In addition, the level of damage to the structural member may be high because of the large magnitude of the load. Due to these phenomena, the response of a structural member to close-in detonation cannot be accurately modelled by relatively simple methods like single-degree of freedom models, and more complicated models are required. Such models need to include numerical simulation of the detonation process, which produces a non-uniform pressure environment, allowing the pressure to reflect and flow around the member section. The local damage and flow around the section are especially of interest in I-shaped, or wide-flange-section members. Herein, the response of such sections is modelled by numerical simulations using a novel technique, which overcomes the difficulty of computation time, and is validated through various calculations. The model is used to perform a parametric study to investigate the response of I-sections subjected to close-in detonations, in terms of local damage and global behaviour, with scaled distances of 0.15–0.29 m/kg1/3 and loading causing flexure about the strong axis. Various aspects that affect the performance are studied, such as: the effect of scaled distance, the addition of welded stiffening plates between the flanges and web, the effect of boundary conditions and the effect of charge shape. Resulting local damage and residual deformations are assessed for the cases studied.