Features of the Tien Shan newest orogen morphostructure

Research subject. The concept of morphostructure implies the presence of a relationship between the relief forms of segments of the Earth’s crust and their structural and material content. This article describes the geological ensembles of the Tien Shan orogen, the tectonic structure and modern relief of which differ in their parameters from the general morphostructural plan and which, therefore, belong to the category of morphostructural anomalies. Materials and methods. The data presented in the article were obtained in the course of field structural-geological and morphostructural study of key segments of the Tien Shan orogen, as well as an analysis of materials from previous research, including the results of geophysical sounding of the Earth’s crust and geodesical monitoring of relative modern movements of reference points on the surface.Results. The article demonstrates that, against the background of the general linear-wave morphostructure of the Tien Shan orogen, there are areas whose relief and tectonic structure do not agree with the general tectonic plan of the mountain. Wi thin the considered region, different types of morphostructural anomalies are identified and described, reflecting the speci fics of the evolution and geotectonic position of individual volumes of upper-crust rock complexes: zones of concentrated deformation and tectonic joining; centrally symmetric structures formed on the site of paleoatolls; neotectonic protrusions of the granite basement; trans-regional zone of the Talaso-Ferghana Fault and other structures. Conclusion. The formation of morphostructural anomalies is associated with the presence of non-trivial geodynamic environments operating against the background of the tectonic regime common to the Tien Shan. The modern morphostructure of the Tien Shan is the result of interference between various geodynamic regimes and settings: a regime common to the entire territory of the orogen and particular regimes that manifest themselves sporadically and are reflected in the modern relief.

Investigation of the Size Effects on the Elongation of Ti-2.5Al-1.5Mn Foils with Digital Image Correlation Method

The increasing demand for parts with a large specific surface area such as fuel panels has put forward higher requirements for the plasticity of foils. However, the deformation characteristics of foils is hard to be illustrated in-depth due to their very short deformation process. In this paper, the digital image correlation method was applied to investigate the influence of size effect on the elongation of Ti-2.5Al-1.5Mn foils. The results showed that the elongation of Ti-2.5Al-1.5Mn foils increased with the decrease in the ratio of thickness-to-grain diameter (t/d value). Then, the macro deformation distribution of foils was analyzed, combined with their microstructure characteristics, and it was found that the increasing influence of individual grain heterogeneity leads to the earlier formation of a concentrated deformation zone, which changes the deformation mode of foils. The concentrated deformation increases with the decrease in t/d value, thus dominating the trend of the foil elongation. Furthermore, the homogeneous deformation and concentrated deformation can be divided into two different zones by a certain critical t/d value. These results provide a basis for understanding and further exploration of the deformation behavior of titanium foils.

Manifestation of “flower structures” in geophysical models of the Central Tien Shan

Based on the analysis of deep geophysical (geoelectric and seismic) models of the Central Tien Shan, structures with the morphology resembling the crown of palm trees or the shape of a flower were identified. Geoelectric models are considered along a series of regional profiles (75º, 76º, 76º 30’). The length of the profiles intersecting all the main tectonic structures of the Tien Shan ranges from 75 to 250 km. Particular attention was paid to those zones of concentrated deformation, where the tectonic regime combines the conditions of shear and lateral compression (transpression zones). The structure of the collisional - accretionary wedge of the Atbashi zone in the distribution of electrical and velocity characteristics of the geological section is considered. Geoelectric models plotted along a series of regional profiles identify areas of increased electrical conductivity and show “flower structures”. The integral picture of the distribution and morphology of zones of increased electrical conductivity in the segments of the Earth’s crust of the Central Tien Shan may reflect a discretely localized manifestation of palm tree structures due to the evolution of transpressive suture zones during the Hercynian and Alpine tectogenesis.

Microstructural Evolution During a Solid State Tube Pinch Weld of Type 304l Stainless Steel

Microstructure development is examined for a specialized spot weld that is used as a solid-state closure process for austenitic stainless steel tubing, referred to as pinch welding. In order to elucidate the microstructural evolution of the weld, a series of test welds were made at nominal conditions using tubing and production like components. These pinch welds normally terminate after twelve cycles of a 60 Hz AC weld process. In this study, production tubes were welded from one to twelve cycles and the microstructure and weld variables after each individual weld cycle number were characterized using radiography and optical metallography. Two electrochemical etchants were used to highlight different microstructural features. The study revealed that: (1) this type pinch weld is largely complete after about six cycles of 60 Hz AC current, half the weld time utilized; (2) the resistance, deformation, and closure length approach “steady-state” conditions after six cycles; and (3) both oxalic and nitric acid electrolytic etchants are useful for highlighting specific microstructural attributes of type 304 L stainless steel. Finally, two distinct microstructural regions can be identified for these welds: the edge of the weld, which is driven by concentrated deformation, recrystallization, and grain growth, and the center region, which is more typical of forge welding and micro-asperity breakdown followed by diffusion and grain-growth.

Microstructural Evolution During a Solid State Tube Pinch Weld

Microstructure development is examined for a specialized spot weld that is used as a solid-state closure process for stainless steel tubing, referred to as pinch welding. In order to elucidate the microstructural evolution of the weld, a series of test welds were made at nominal conditions using both tubes, used in test articles and production like components. These pinch welds normally terminate after twelve cycles of a 60 Hz AC weld process. In this study, tubes with different thermal processing history were welded from one to twelve cycles and the microstructure and weld variables after each individual weld cycle number were characterized using radiography and optical metallography. Two etchants were used that highlighted different microstructural features. The study revealed that: (1) this type pinch weld is largely complete after about six cycles of 60 Hz AC current, half the weld time utilized; (2) the resistance, deformation, and closure length approach “steady state” conditions after six cycles; and (3) both oxalic and nitric acid electrolytic etchants are useful for highlighting specific microstructural attributes of type 304L stainless steel. Finally, two distinct microstructural regions can be identified for these welds: the edge of the weld which is driven by concentrated deformation, recrystallization and grain growth and the center region which is more typical of forge welding and micro-asperity breakdown followed by diffusion and grain-growth. The bond line of annealed tubes exhibits fewer indications and less contamination than that of the partially annealed and as-received cold worked tubes.

Dynamic characteristic of partially debonded sandwich of ferry ro-ro’s car deck: a numerical modeling

The dynamic behavior of a partially debonded Ferry Ro-Ro’s sandwich car deck is investigated by using commercial finite element software ABAQUS. Debonding in the car deck model is estimated by comparing the dynamic responses of the fully intact and damaged model of the bonding condition. The influence of the debonding ratio is investigated by free vibration analysis using Lanczos iteration method. The dynamic response of the car deck model is loaded with harmonic excitation and is examined in detail. The transverse displacements, velocities, accelerations, longitudinal strains, and phase portraits are investigated in the central point of the damaged area. To evaluate the effect of inserting the spring contact element during the dynamic analysis, both debonded models with and without spring contact elements are examined. From the report, it can be concluded that the dynamic analysis which relies on the modal analysis can be used to diagnose the possibility of debonding problem in the car deck structure. The natural frequencies of the debonded model decrease due to the presence of discontinuity in the debonded region. Further, the discontinuity also creates locally concentrated deformation and significantly affects the short-term time response.

RESEARCH OF DEFORMATIONS AND OPTIMIZATION OF PARAMETERS OF DEGASATION WELLS

Purpose. Investigation of deformation of the mouth of the degassing well depending on the deformation of the rocks around the preparatory work Methodology. The deformation of the mouth of the degassing well as a function of deformations of the roof rocks of the preparatory workings from which the well was drilled is considered. The dependence of the required depth of well sealing on the level of methane leakage and roof deformation is established. Results. It is experimentally proved that in the zone of active shifts behind the operating lava, where the main amount of explosive methane is released from the massif, the mouths of degassing wells change and the main types of irreversible deformations take place. With the distance from the contour of the preparatory production, the distance between adjacent concentrated deformations of the wellbore increases according to the logarithmic dependence, and these deformations are distributed according to the normal law. The average value of the concentrated deformation of the degassing well is in logarithmic dependence on the displacements on the contour of the preparatory work. The tensile deformation of the degassing well axis decreases with distance from the production contour into the array. Stratification of rocks leads to gas leakage and air suction, which reduces the efficiency of degassing. Permissible concentrated deformations of the degassing wellbore should not exceed its radius. Originality. The empirical power dependence of the required length of sealing of the degassing well on the allowable leaks and displacements of the roof of the preparatory workings from which the well was drilled is established. Practical value. Methods for calculating the required sealing depth of the degassing well have been developed and measures have been proposed to increase its stability, which increase the reliability of the degassing system as a whole and help increase the safety of underground coal mining.

Zones of concentrated deformation (flower structures): field observations and modeling data

Our study was focused on narrow linear zones that penetrate to different depths the crust and have complex infrastructure. Rocks in such zones are more intensively tectonically altered in comparison with the background. ‘Flower structures’ and ‘zones of concentrated deformation’ (ZCD) are the terms to describe these zones. The field study results combined with the data of tectonophysical and computational modeling data and supplemented by the literature analysis gave grounds for the following conclusions. In the experiments, as well as in nature, ZCDs show similar and, in some cases, identical morphological and infrastructural features and have similar stages of their evolution. A ZCD is mainly a reflection of the transpression setting. Its formation is accompanied by 3D plastic shear flow of matter and dilatancy of the deformed volume. A ZCD may be associated with the development of the ‘basement – cover’ system. It may also occur due to the intra-cover tectogenesis that does not influence the basement. Locations of ZCDs are spatially regular and predetermine the tectonic divisibility of the crust and lithosphere.