Longitudinal Tensile Stress Research Articles

Numerical simulation of thermal and stress fields for multilayer and multi-pass weaving WAAM of magnesium alloy

Purpose A 3D finite element (FE) model based on the double ellipsoidal heat source was developed to investigate the evolution of temperature and stress fields during the multilayer and multi-pass wire and arc additive manufacturing (WAAM) process. This paper aims to investigate the evolution of temperature and stress fields during the multilayer and multi-pass wire and arc additive manufacturing (WAAM) process by developing a 3D finite element (FE) model based on the double ellipsoidal heat source. Design/methodology/approach Experimental thermal cycle curves and residual stresses were obtained by thermocouples and X-ray diffraction, respectively. The validity of the model was verified by the corresponding experimental results. Findings The deposition process of the upper pass led to the partial remelting of the lower deposited pass. The thermal process of the current-deposited pass alleviated the stress concentration in the previous-formed passes. A more uniform temperature distribution could be obtained by using the reciprocating deposition path. Compared to the reciprocating deposition path, the peak values of the transverse and longitudinal tensile residual stresses of the deposited sample under the unidirectional deposition path were reduced by 15 MPa and increased by 13 MPa, respectively. The heat conduction in the deposited passes could be improved by extending the inter-pass cooling time appropriately. With an increase in the inter-pass cooling time, the longitudinal residual stress in the middle region of sample along longitudinal and transverse directions showed increase and decrease–increase trends, respectively, while the transverse residual stress exhibited decrease trend. Originality/value This study enhances the understanding of temperature and stress fields evolution during the multilayer and multi-pass cold metal transfer-WAAM processes of magnesium alloy and provides the reference for parameter optimization.

Advances in longitudinal equivalent bending stiffness analysis-novel nonlinear characteristics in the assembly process of prefabricated subway stations

The longitudinal bending stiffness of quasi-rectangular prefabricated subway stations plays a great important role in studying their mechanical behavior and conducting safety assessments. To address the issue of immature stress assumptions for existing prefabricated subway stations, three stress assumptions and five bending modes are proposed while considering the coupling effect between axial force and bending moment. The study investigates novel nonlinear characteristics in the longitudinal equivalent bending stiffness and the influencing factors during the assembly of an existing subway station. An effective method for identifying the longitudinal bending modes suitable for the prefabricated subway station is established, the proposed solution has a good agreement with measured longitudinal bending stiffness efficiency. The study demonstrates that the longitudinal bending mode of the prefabricated subway station shifts from "upward convex" to "downward concave" due to the stepwise assembly method. The longitudinal bending stiffness efficiency displays a significant hysteresis curve, eventually stabilizing at approximately 1 %. Upon completion of the monitoring ring assembly, the concrete bears both longitudinal tensile and compressive stress. When assembling 10 rings from the monitoring ring, the longitudinal reinforcing bars bear tensile stress. The longitudinal bending stiffness of the prefabricated subway station exhibits significant time-variable characteristics throughout the assembly process. The research findings can provide effective references for the analysis of longitudinal mechanics and bending performance during the assembly process.

Calving Dynamics and the Potential Impact of Mélange Buttressing at the Western Calving Front of Thwaites Glacier, West Antarctica

AbstractThe western region of the wide Thwaites Glacier terminus is characterized by a near‐vertical calving front. The grounding line at this western calving front (WCF) rests on a relatively high ridge, behind which exists a reverse‐sloping bed; retreat of the grounding line into this over‐deepening basin could therefore expose deep calving faces that may be subject to ice‐cliff failure. Here, we use the 3D Helsinki Discrete Element Model to identify the factors that control the calving dynamics in this location. We then focus on the ability of mélange to influence these dynamics given the wide embayment in which Thwaites Glacier terminates. We find that calving along the WCF is currently influenced by ice flow across the grounding line and consequent longitudinal tensile stress and rift formation. Calving is slowed in simulations that are initiated with a highly constricted mélange, with a thicker mélange suppressing calving entirely. We liken the constrained simulations to a scenario in which mélange piles behind a large grounded iceberg. In a future which may see calving become a more dominant control on the retreat of Thwaites Glacier, this type of blockage will be necessary for robust force chains to develop and transmit resistive forces to the terminus. The ability of the mélange to hinder calving at this location will be determined by the presence and rigidity of binding land‐fast sea ice and iceberg keel depths. Therefore, it is necessary to represent calving, mélange and sea ice in a single framework to predict the fate of Thwaites Glacier.

The thermal responses of composite box girder bridges with corrugated steel webs under solar radiation

Owing to the direct exposure to complex atmospheric environments, the temperature field of composite box girder bridge with corrugated steel webs (CBGB-CSW) is likely non-uniformly distributed. Whereas, the current researches regarding the thermal responses of CBGB-CSW are insufficient, and the thermal responses of CBGB-CSW under solar radiation are still unknown. Therefore, this paper conducted a long-term temperature experiment on a scaled model to explore the temperature distribution characteristics in CBGB-CSW. Meanwhile, a three-dimensional thermal–mechanical coupling Finite Element (FE) model is established to simulate the temperature field in the experiment girder. The accuracy and effectiveness of the developed FE model has been verified by the measured temperature data. Therewith, the thermal responses (i.e., stress and displacement) of a full-scale continuous CBGB-CSW with a span of 150 m are numerically investigated. The results indicate that the maximum stresses always occur at the midspan section (with a depth of 5 m) of the continuous CBGB-CSW, and considerable concentrations of stress are observed in the steel-concrete junction. The maximum longitudinal tensile and compressive normal stresses within 0.4 m of the upper junction can reach 5.55 MPa and −8.46 MPa respectively, and those of the lower junction can reach 6.96 MPa and −7.05 MPa respectively. Besides, owing to the impacts of vertical and horizontal temperature gradients, significant displacements of the whole bridge can also be observed. The maximum vertical displacement (5.33 mm) of the CBGB-CSW is estimated at the top plate in the midspan, while the maximum horizontal displacement (0.74 mm) is estimated at the trough of the southern corrugated steel web in the midspan. Notably, the outcomes of this paper can provide some useful references for engineers and scholars to understand the thermal responses of the CBGB-CSW.

Research on Mechanism of Non-Uniform In-Situ Stress Induced Casing Damage Based on Finite Element Analysis

Casing damage is a common problem encountered during oil and gas field development due to the complex stress state of the casing. Despite the large number of studies focusing on this problem, the mechanism of non-uniform in-situ stress-induced casing damage in a low-permeability reservoir is still unclear. In this study, casing damage due to non-uniform in-situ stress variations was investigated, and then the tectonic stress coefficients in the study area were determined by an in-situ stress inversion technique, which led to the derivation of formulas for calculating the maximum and minimum horizontal in-situ stresses. Subsequently, finite element numerical simulations were performed to assess the stress distribution during the formation of the casing cement sheath in a G155 block, a typical low-permeability reservoir. The results indicate that casing damage is caused not only by non-uniform in-situ stresses but also by various additional creep-induced loads. Subsequent finite element investigations into casing behavior under mudstone creep conditions indicated that immersion of mudstone in water instigated further shearing and deformation of the casing, culminating in premature well failure prior to water inundation. Notably, Von Mises stress levels exhibited a positive correlation with injection production ratios, with values exceeding critical thresholds leading to distinct modes of mechanical failure including shear-induced deformations, longitudinal tensile stress, and localized yielding near water wells. Maintenance of an optimal injection production ratio is identified as a key strategy for prolonging casing longevity in the region. To this end, recommendations include augmenting the casing wall thickness or enhancing the steel pressure specifications to mitigate casing damage progression, thereby extending the operational lifespan. This research serves as a pivotal theoretical framework for informing future development strategies aimed at mitigating and preempting casing failures in a low-permeability reservoir.

Unveiling the mechanisms of Moso bamboo's motor function and internal growth stress.

Bamboo, a renewable resource with rapid growth and an impressive height-to-diameter ratio, faces mechanical instability due to its slender structure. Despite this, bamboo maintains its posture without breaking in its battle against environmental and gravitational forces. But what drives this motor function in bamboo? This study subjected Moso bamboo (Phyllostachys edulis) to gravitational stimulation, compelling it to grow at a 45° angle instead of upright. Remarkably, the artificially inclined bamboo exhibited astonishing shape control and adjustment capabilities. The growth strain was detected at both macroscopic and microscopic levels, providing evidence for the presence of internal stress, namely growth stress. The high longitudinal tensile stress on the upper side, along with a significant asymmetry in stress distribution in tilted bamboo, plays a pivotal role in maintaining its mechanical stability. Drawing upon experimental findings, it can be deduced that the growth stress primarily originates from the broad layers of fiber cells. Bamboo could potentially regulate the magnitude of growth stress by modifying the number of fiber cell layers during its maturation process. Additionally, the microfibril angle and lignin disposition may decisively influence the generation of growth stress.

Synchrotron diffraction residual stresses studies of electron beam welded high strength structural steels

In recent years, there's been a strong focus on enhancing high-strength structural steels (HSSSs), making them tougher, stronger, lighter, and more weldable. However, these steels face challenges like cold cracking sensitivity (CCS) and reduced toughness with higher heat input. Therefore, exploring HSSSs with advanced welding techniques like electron beam welding (EBW) is crucial. EBW known for its innovation and precision, is gaining popularity in HSSSs applications for vehicles, construction industries etc. offering advantages like narrow welds, reduced heat-affected zone (HAZ) and low distortion. It is essential to understand the influence of residual stresses (RS) in HSSSs which ultimately affect structural integrity and fatigue life. Using EBW on HSSSs, coupled with synchrotron XRD for residual stress studies, has great potential to advance this research significantly. In this work, a 15-mm-thick EB-welded joint of S960QL and S960 M steels was used to study the RS. At an energy level of 20 keV, RS data from the synchrotron XRD method and its result on the top of welded joints for both types of steel were compared. S960 M steel showed a longitudinal tensile stress of 250 MPa at the weld toe, approximately 1.8 times higher than the 138 MPa observed in S960QL steel under similar conditions. In transverse stress, S960QL exhibits a higher stress of 279 MPa compared to S960 M 46 MPa at the weld toe, approximately 83% lower. The synchrotron method measured 76% lower LRS for S960QL compared to conventional XRD, while S960 M exhibited 55% lower LRS using the same approach.

The analysis and design of jointed plain concrete pavements with wider slabs

Despite the cost-effective nature of asphalt pavements, concrete pavements are preferred for their superior serviceability. Many agencies use Jointed Plain Concrete Pavement (JPCP) designs with a standard slab size of 3.5 × 4.5 m, focusing on transverse cracking. However, night-time Longitudinal Top-Down Cracking (LTDC) can occur in widened slabs due to tandem and tridem axles. This study employs a Finite Element (FE) approach to assess wider slabs under various loads. Longitudinal tensile stresses at critical points were found to increase with the slab width. Therefore, the study emphasizes the need for a design approach addressing transverse and longitudinal cracking. The design of the wider slabs (4.5 × 4.5 and 5.0 × 4.5 m) is demonstrated using a case study. If the longitudinal joint in a 9.0 m slab is placed at 5.0 m from the edge, the pavement could perform better than other slab sizes. However, it is necessary to design the pavement considering both longitudinal and transverse cracking.

Study on the permanent deformation of asphalt mixtures based on the modified Burgers model

Based on the confined test results and the viscoelastic constitutive model of asphalt mixtures, a three-dimensional finite element model of an asphalt pavement was established to study the effect of different working conditions on asphalt pavement. With the actual pavement structure response, a comparative analysis was conducted to assess the stress and strain experienced by the asphalt pavement under various working conditions. The results show that the asphalt pavement structure model can reflect the effect of different working conditions on asphalt pavement; the transverse stress and strain of asphalt pavement are most significantly affected by the working conditions during cornering, and the position of the maximum value is concentrated on the outer edge line of the wheel and a distance away from it; however, the longitudinal tensile stress and strain of the asphalt pavement are most significantly impacted by the working conditions of driving and braking, and the position of the maximum value is mainly distributed in the center line of the single wheel. The research results can provide a reference for the design of asphalt pavement structures.

Calculation of the stress-strain state of layers of cross-ply laminate based on an experimental stress-strain curves under uniaxial tension

A method for calculating the stress-strain state of layers of cross-ply laminate based on an experimental deformation diagram under uniaxial tension is proposed. The essence of the method consists in solving a system of two equations describing the experimental curves σx = f(εx) and σx = f(εy), which allows determination of two unknown parameters related to the secant elastic characteristics of the material layers. The law of change in the remaining unknown parameters is set by assumptions regarding deformation of the polymer matrix composite and its layers during loading. To carry out the calculation, it is necessary to set the initial values of the elastic properties of the unidirectional material of the layers, which should be well consistent with the initial values of the elastic properties of the structure under study determined from the experiment. According to the developed algorithm, calculated dependences between average stresses, deformations and secant elastic properties of the layers of the structure are obtained (0°/90°/90°/0°) made of fiberglass E-Glass/MY750 using experimental data from the literature. Calculations carried out for three sets of initial values of the elastic properties of the material under study showed qualitatively identical results. The transverse tensile stress in the 90° layer reaches a maximum in the first half of the stress-strain diagram, and then decreases to zero. A similar stress in the 0° layer reaches a maximum at the failure point of the structure under study. It is revealed that the maximum calculated values of transverse stresses acting in layers 0° and 90° noticeably exceed the transverse tensile strength of the material specified in the literature. The longitudinal tensile stress in the 0° layer reaches a maximum at the failure point and corresponds to 95% of the value of the longitudinal tensile strength of the material. The longitudinal compressive stress in the 90° layer is at a low level throughout the deformation process of the structure under study. The results of this study can be recommended for developing models of the behavior of layers with cracks in the matrix when loading a polymer matrix composite.

Effect of Residual Stress on the Ultimate Bearing Capacity of Titanium Alloy Pressure Spherical–Cylindrical-Combined Shells

Titanium alloy pressure spherical–cylindrical shells enable the effective utilization of the strength of spherical and cylindrical pressure-resistant shell components. In this study, a numerical simulation of the residual stress of a titanium alloy butt-welding plate was conducted by employing sequential coupling and a temperature heat source model. The results of welding residual stress analysis agreed well with the experimental results reported in the literature. Subsequently, the welding residual stress of a titanium alloy pressure spherical–cylindrical shell was calculated and analyzed using the same method. Finally, the influence of residual stress on the ultimate bearing capacity of the shell was assessed. On the inner surface of the shell, the horizontal welding residual tensile stress, perpendicular to the weld path, exhibited a bimodal distribution. The longitudinal welding residual tensile stresses were higher than the horizontal welding residual stress. Near the weld on the outer shell surface, higher longitudinal welding residual tensile stresses existed, whereas the horizontal welding residual stress was compressive. Both the inner and outer shell surfaces exhibited significant longitudinal residual tensile stresses along the weld path, though residual compressive stresses existed on both surfaces. The influence of welding residual stress on the ultimate load-bearing capacity of the shell was minimal.

Analysis of Residual Stresses in Curved Cutouts of Steel Box Girder Transverse Diaphragms

In order to analyze the characteristics of cutting residual stress distribution at the arc‐shaped cutout of steel box girder diaphragm and to study its fatigue cracking mechanism. Taking Xia Zhang Bridge as the engineering background, this paper proposes a systematic method for calculating the residual stress field at the arc‐shaped cutout of the diaphragm. First, a mathematical model of the cutting heat source was established for predicting the temperature field changes during the cutting process of the diaphragm. Then, a 3D thermoelastic‐plastic finite element model was established using Abaqus to parametrically analysis the residual stresses during the fabrication of the transverse spacer. The results show that the cutting heat source creates a “thermal stagnation” effect at the curved notch, which leads to the local metallurgical transformation of the metal surface layer, which is unfavorable to its fatigue performance. The residual stresses are mainly concentrated near the cutting line, and the transverse residual stresses are lower at the free edge of the cutting line, which is easy to crack, and higher in the middle of the arc section of the arc notch. Inside the transverse bulkhead, at 14.5 mm from the free edge of the cut, in addition to the existence of high longitudinal residual tensile stress, its transverse residual tensile stress is also high, with a peak value of 199.3 MPa. Thermal cutting produces high residual tensile stress at the free edge, and the tensile stress cycle formed under the combined effect of wheel load is one of the reasons for the formation of initial fatigue cracks.

A three-dimensional failure criterion model considering the effects of fiber misalignment on longitudinal tensile failure

This paper proposes a three-dimensional failure criterion model for unidirectional fiber-reinforced composites. In contrast to previous models that only accounted for the effect of fiber misalignment in the presence of longitudinal compressive stress, the proposed failure criterion model comprehensively considers the effect of localized misaligned regions on the failure under any stress state. Another key contribution of this study is the introduction of the effective misalignment angle. Considering effective misalignment angles, the proposed failure criterion model can reasonably reveal the effect of localized misaligned regions on the failure behavior under different stress states. The agreement between the predicted results and the experimental data proves that the proposed model has good applicability. Furthermore, the influence of initial misalignment angles on failure is analyzed under varying stress conditions. The results indicate that even under longitudinal tensile stress, the initial misalignment angle still plays an important role in the failure behavior of materials.

Mechanical properties and moisture diffusion in hot-pressed jute fiber composite subjected to hygrothermal ageing

Jute fiber is one of the most extensively used eco-friendly natural fibers that are hydrophilic. The performance of natural fiber-reinforced composites is affected by the diffusion of heat and moisture from the environment in addition to the exposure time. In the present investigation, the ultimate tensile strength, displacement at fracture, and energy at yield of the jute fiber-reinforced composite under different hygrothermal (temperature and relative humidity) conditions are investigated. The samples were prepared by hand lay-up technique and the laminates were hot pressed on a hydraulic press apparatus. The specimens were further exposed to a hygrothermal environment using a humidity cabinet (with an inbuilt thermometer and hygrometer) for varied intervals of time of 4, 16, and 64 h. The longitudinal tensile stress ( σ) increased at lower hot-pressing temperatures and minimum hygrothermal ageing and it decreased at a higher temperature. Upon increase in hygrothermal ageing, σ decreased at all temperatures. The energy at yield point ( E) decreased significantly at lower temperatures and minimum hygrothermal ageing while minimum changes were observed at a higher hot-pressing temperature. The diffusion of moisture as a function of time and temperature explained using Fickian law. The initial region showed nearly linear variation. With continuous hygrothermal ageing, the equilibrium, considering partial pressure, was achieved between the environment and moisture inside the sample. The microstructure of the sample processed at lower hot-pressing temperatures followed by hygrothermal ageing of 16 h showed diffusion and fiber pull-out. However, at a higher temperature, matrix cracking was also observed.

Rewelding Residual Stress of Fatigue Crack at U-Rib-to-Deck of an Orthotropic Steel Deck

The orthotropic steel deck is a prevalent stiffening girder structure utilized in long-span cable-stayed bridges and suspension bridges. Nonetheless, the issue of fatigue cracking has persisted in in-service orthotropic steel decks, significantly impacting the longevity of bridges. This study examines the analysis of the distribution of residual stress during the rewelding process of a fatigue crack at the U-rib-to-deck-plate joint of an orthotropic steel bridge deck. Additionally, the impact of the initial welding and the stiffness of the boundary constraint on the residual stress field during rewelding is discussed. The findings indicate that the removal of the fatigue crack prior to rewelding alleviates the transverse residual stress caused by the initial welding. After undergoing the rewelding procedure, both the transverse residual stress and the longitudinal residual stress exhibited a significant stress peak. More precisely, the transverse tensile stress underwent a rise from 21 MPa to 385 MPa, while the longitudinal tensile stress experienced an increase from 345 MPa to 525 MPa. Furthermore, the range of tensile stress within the longitudinal residual distribution expanded by 88%. Moreover, the stress redistribution during the rewelding of the local fatigue crack varied depending on the constraints imposed on the steel bridge deck. Notably, the transverse residual stress increases by 40.6% when compared to the absence of constraints. The findings of this research offer valuable insights for the implementation of rewelding repair techniques on steel bridge decks, emphasizing the significance of considering the effects of residual stresses induced during the rewelding process.

Numerical Computing Research on Tunnel Structure Cracking Risk under the Influence of Multiple Factors in Urban Deep Aquifer Zones

During the operation period of tunnels in urban deep aquifer zones, the geological environment around the tunnel is complex and the surrounding strata are rich in groundwater, which often poses a risk of structure cracking and groundwater leakage, seriously threatening the tunnel’s safety. To reduce the risk of tunnel cracking, a theoretical calculation model and a three-dimensional concrete–soil interaction thermo-mechanical coupling numerical computing model was established to analyze the tunnel structure cracking risk under the influence of multiple factors in urban deep aquifer zones. The response mechanism of structural stress and deformation under the influence of the grade of rock and soil mass, overburden thickness, temperature difference, structure’s length–height ratio, structure’s thickness, and structure’s elastic modulus was investigated, and the stress and deformation response characteristics of the structure with deformation joints were explored. The results show that the maximum longitudinal tensile stress of the structure increases with the increase in the grade of rock and soil mass, overburden thickness, temperature difference, structure’s length–height ratio, and elastic modulus. The temperature difference has the most significant impact on the longitudinal tensile stress of the structure, with the maximum tensile stress of the structure increasing by 2.8 times. The tunnel deformation joints can effectively reduce the longitudinal tensile stress of the structure, and the reduction magnitude of the tensile stress is the largest at the deformation joints, which is 64.7%.

Mechanical Characteristics and Correlation Analysis of Crack Propagation and Slip Cracking in Asphalt Pavement Surface Layer

With the rapid development in the field of road traffic, the problems of slip cracking and U-shaped cracks on the surface of asphalt pavement are becoming more and more prominent, which seriously affect the safety and service life of roads. In order to solve this problem, a reliable asphalt pavement model is established in this study by combining the joint simulation and secondary development of experimental test parameters. The model can accurately simulate the slip cracking of asphalt pavements under different conditions and provide detailed parametric analysis of the factors affecting crack development. The results show that the inter-ply bond damage no longer deteriorates when the inter-ply strength is 0.3 MPa, indicating that the form of inter-ply contact plays a role in controlling the development of slip cracks. In addition, the maximum interlayer shear stress increased by 21.1% during the increase of vehicle axle load from 100 kN to 200 kN on the asphalt pavement, which led to an increase in the length of slip cracks. Meanwhile, the maximum longitudinal tensile stress in the asphalt pavement surface layer increased by 10.2% and the maximum shear stress increased by 18.3% when the elastic modulus of the asphalt pavement surface layer was increased from 7500 MPa to 14500 MPa.

Fracture Zones of the Doldrams Megatrasform System (Equatorial Atlantic)

This article presents results of the structural and morphological analysis of the fracture zones which are part of Doldrums Megatransform System (MTS), located in the northern part of the Equatorial Atlantic (6.5°–9° N) that include Vernadskiy and Bogdanov transform faults and the Doldrums and Pushcharovskiy megatransforms. Bathymetric map, based on the multibeam echo sounding data, collected during 45 cruise of the R/V Akademik Nikolaj Strakhov was used for this analysis. It was established that large-scale variations in the width of fracture zone valleys are determined by the distribution of stresses perpendicular to the fracture zone. In the areas with compressive stresses, the fracture zone valleys are narrower, and the in extension areas are wider. The difference in geodynamic settings within the MTS is due to the difference in spreading directions, which change from \(\perp \)89° to \(\perp \)93° when moving from south to north. The depth of fracture zone valleys consistently increases from the periphery of the MTS (Bogdanov and Doldrums faults) to the center (Pushcharovskiy fracture zone) in accordance with a decrease in the upper mantle temperature. In each fracture zone, the valley depth decreases from the rift- fracture zone intersections towards the center of the active part to a certain background depth. It is assumed that this phenomenon is the result of the uplift of the valley bottom, which occurred due to the decompaction of the lithosphere, caused by the serpentinization of ultramafic rocks. The violation of the revealed variations in the width and depth of fracture zone valley patterns occurs as a result of various ridges and uplifts formation in the fracture zone. In the axial zones of the active parts of the fracture zone valleys median ridges are widespread, extending parallel to the fracture zone and representing serpentinite diapirs squeezed out above the bottom surface. Transversal ridges which were formed 10‒11 million years ago as a result of the lithospheric plate edge flexural bending under extensional conditions are now located in the western passive parts on the southern sides of the of Doldrums and Pushcharovskiy fracture zone valleys. The transverse ridge on the northern side of the Vernadskiy fracture zone, which includes Mount Peyve, was formed between 3.65‒2.4 Ma. Due to the frequent jumps of the spreading axis in this region, it was divided into three segments. There are interfracture zone ridges in megatransforms, which in the active part consist of two fracture zone valleys. Time of their formation: in Pushcharovskiy megatransform ‒ 30‒32 million years ago and in Doldrums megatransform ‒ about 4 million years ago. Due to the curvilinearity of the outlines and under the pressure of moving lithospheric plates, the interfracture zone ridges experience longitudinal (along the fault) compressive and tensile stresses, which are compensated by vertical uplifts of their separate blocks and the formation of depressions, pull apart depressions, and spreading centers (the latter are only in Pushcharovskiy megatransform). Structure-forming processes that determine pattern and morphology of the fracture zones as a part of the MTS are related by their origin to the spreading and transform geodynamic systems.

STUDY OF THE ROLLING PROCESS WITH TECHNOLOGICAL LUBRICANT AT SINGLE-ZONE SLIPPING METAL IN THE ZONE OF DEFORMATION

One of the controversial provisions the rolling theory is the question of the possibility the stable process of cold rolling with lubrication at a complete lag of the strip’s metal in the deformation zone, i.e. in conditions of negative advancing.
 The equilibrium state in the zone of deformation with negative advance can be maintained due to the change in the thickness of the lubricating film. This is evidenced by experimental data from the study of the dependence of the advancing and the thickness of the lubricant layer on the grip angle during cold rolling with castor oil the copper samples in sizes 5x60 mm. Rolling was carried out on a duo 180 laboratory mill in steel rolls with a diameter of 190 mm. The rolling speed was 0.35 m/s.
 Then stress state modeling is used to theoretically substantiate the possibility of a stable process with single-zone sliding of metal in rolls during cold rolling with effective technological lubricants. According to Newton's law, the frictional forces acting in the zone of deformation depend on the sliding speed of the metal on the rolls and on the thickness of the lubricating film.
 Substituting the chooses model of specific friction forces into T. Karman's differential equation of equilibrium and solving it under known boundary conditions, expressions for the distribution of contact stresses were obtained.
 The results of calculations in the conditions of contact-hydrodynamic friction prove that the maximum of normal pressure shifts closer to the entrance to the deformation zone. In the case of rolling with a negative advancing, the longitudinal normal tensile stresses occur near the cross-section at the exit of the metal from the rolls. The average pressure in the deformation zone is always greater than the forced yield strength for the rolling strip.
 With an increase in the lag of the metal from the rolls at the exit from the zone of deformation, the average pressure decreases. Rolling with single-zone strip sliding is an energy-efficient process.

Giant Magnetoimpedance Effect of Multilayered Thin Film Meanders Formed on Flexible Substrates.

The giant magnetoimpedance effect of multilayered thin films under stress has great application prospects in magnetic sensing, but related studies are rarely reported. Therefore, the giant magnetoimpedance effects in multilayered thin film meanders under different stresses were thoroughly investigated. Firstly, multilayered FeNi/Cu/FeNi thin film meanders with the same thickness were manufactured on polyimide (PI) and polyester (PET) substrates by DC magnetron sputtering and MEMS technology. The characterization of meanders was analyzed by SEM, AFM, XRD, and VSM. The results show that multilayered thin film meanders on flexible substrates also have the advantages of good density, high crystallinity, and excellent soft magnetic properties. Then, we observed the giant magnetoimpedance effect under tensile and compressive stresses. The results show that the application of longitudinal compressive stress increases the transverse anisotropy and enhances the GMI effect of multilayered thin film meanders, while the application of longitudinal tensile stress yields the opposite result. The results provide novel solutions for the fabrication of more stable and flexible giant magnetoimpedance sensors, as well as for the development of stress sensors.