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The presence of reliable techniques for predicting the stress state in composite materials is one of the most important requirements in the design of composite components and structures. An analytical model has been developed to evaluate the shear stresses at the substrate-coating interface in tensile testing of a flat specimen. The developed model has been verified by numerical simulation. The strength and mechanisms of the fracture of furan epoxy composite coatings with polyvinyl chloride and zinc oxide fillers with various concentrations were studied. The adhesion strength of furan epoxy composite coatings with metal substrate was determined by the pull-off test of cylindrical specimens and the tensile test of flat-coated specimens. The correlation between the measured values of fracture stresses for two types of tests of composite coatings was determined. It is concluded that for qualitative comparison of fracture stress in composite coatings it is possible to neglect stress concentration in the specimens. The analyzed methods of stress evaluation have the same trends in the change of the measured values for different composite coatings. However, considering the stress concentration in the specimens provides more accurate results in determining the strength characteristics. [ABSTRACT FROM AUTHOR]

The high-speed process of laser impact welding is examined. Finite element modeling of the laser impact welding technology is carried out using the Euler thermomechanical method, where the pressure in the shock wave is taken as an external effect. With the help of the developed model, the distributions of rapidly changing velocities along the length of the plates, shear stresses, plastic strains, and temperatures during the entire laser impact welding process were determined. It is shown that, during welding of this type, there is no effect of melting the plates. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering (17264073) is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

On the basis of existing experimental studies on web-opening wood composite beams, six new types of reinforcement were proposed in this study. The effects of different reinforcement measures on mechanical properties such as the load-carrying capacity, deformation capacity, internal force distribution law, and force transfer mechanism of web-opening wood composite beams were investigated. The results show that the stress distribution in the opening area is more uniform after reinforcement, and the influence of different reinforcement measures changes the damage mode of the whole beam. The setting of reinforcement measures in the opening area can effectively inhibit and slow down the generation and development of the cracks in the opening area of the web opening and reduce the negative influence of the composite beam caused by the opening. With reinforcement, the allowable and ultimate bearing capacity of wood composite beams can be increased by 3%~21% and 28%~59%; the redistribution of shear force occurs in the opening area after reinforcement, and plywood and cold-formed thin-walled section (CFTWS) help to bear 14%~76% of the value of shear force in the opening area. The most effective reinforcement measures are bolts–epoxy–CFTWS. [ABSTRACT FROM AUTHOR]

Abstract The present work investigates the combined effects of the upstream sediment mining pit and vegetation on the riverbank using emergent rigid vegetation beyond the toe on the flow structure and morphological changes due to fluvial erosion. A steep gradient of streamwise velocity and other turbulence parameters such as Reynolds shear stress (RSS), transverse RSS, and turbulent kinetic energy (TKE) at the interface of the vegetated and unvegetated part of the test segment was observed. The cross-sectional analysis showed that vegetation increased the velocity of the unvegetated main channel, and the sandpit increased even the near-bed velocity with a similar trend in its longitudinal variation at the center line of the main channel. The abrupt variation in RSS and transverse RSS at the location of the berm induces instability and erodes the berm present at the toe of the riverbank. The combination of the vegetation and sandpit led to increased TKE of the flow at the near-bed and berm locations. The morphological analysis showed complete riverbank erosion in both cases of the unvegetated riverbank, i.e., without or with an upstream pit. The installed stems of rigid vegetation on the riverbank helped decrease the fluvial erosion of the riverbank, and its profile observed minimal changes over the length of the test segment. However, the main channel erosion was amplified due to the vegetation (in no-pit case) at the beginning of the test segment, which eroded the bed of the main channel by about 67% of the bed thickness. Also, in the vegetated riverbank cases, the upstream pit caused an increase in erosion by 7.66% at the center of the main channel. The study helps establish the hypothesis of negating the effects of sediment mining on bank erosion by using the rigid vegetation on the riverbank beyond its toe location, which performed well by maintaining the riverbank profile.

The present work investigates the combined effects of the upstream sediment mining pit and vegetation on the riverbank using emergent rigid vegetation beyond the toe on the flow structure and morphological changes due to fluvial erosion. A steep gradient of streamwise velocity and other turbulence parameters such as Reynolds shear stress (RSS), transverse RSS, and turbulent kinetic energy (TKE) at the interface of the vegetated and unvegetated part of the test segment was observed. The cross-sectional analysis showed that vegetation increased the velocity of the unvegetated main channel, and the sandpit increased even the near-bed velocity with a similar trend in its longitudinal variation at the center line of the main channel. The abrupt variation in RSS and transverse RSS at the location of the berm induces instability and erodes the berm present at the toe of the riverbank. The combination of the vegetation and sandpit led to increased TKE of the flow at the near-bed and berm locations. The morphological analysis showed complete riverbank erosion in both cases of the unvegetated riverbank, i.e., without or with an upstream pit. The installed stems of rigid vegetation on the riverbank helped decrease the fluvial erosion of the riverbank, and its profile observed minimal changes over the length of the test segment. However, the main channel erosion was amplified due to the vegetation (in no-pit case) at the beginning of the test segment, which eroded the bed of the main channel by about 67% of the bed thickness. Also, in the vegetated riverbank cases, the upstream pit caused an increase in erosion by 7.66% at the center of the main channel. The study helps establish the hypothesis of negating the effects of sediment mining on bank erosion by using the rigid vegetation on the riverbank beyond its toe location, which performed well by maintaining the riverbank profile. [ABSTRACT FROM AUTHOR]

The purpose of this research presents the research results obtained from a numerical simulation using the ABAQUS/CAE version 2019 finite element software. This study tested the shear behavior of T-beams made of reinforced concrete (RC). The structure is reinforced with a carbon fiber reinforced polymer (CFRP) bar embedded through a section (ETS). The numerical validation approach implicated using numerical analysis on the experimental data collected from twelve reinforced concrete (RC) T-beams divide into two groups each group include reference beam, the field of numerical analysis was expanded to encompass the examination of many aspects, such as the impact of the diameter of CFRP bars. The main objective of this project is to create a computational model that accurately transcribes the complex nonlinear properties inherent in beams. This work conducts a comparative investigation of computational and experimental models, with a specific focus on their load-deflection features and cracking patterns. The study found that the average ratio of ultimate load to deflections in numerical model simulations for beams was 1.011, whereas in experimental testing it was 0.928. The research findings establish a clear correlation between the diameter of CFRP bars and the stiffness of a beam, assuming a constant angle of inclination and spacing.

Rafts are frequently used to design foundations on soft soils to minimize the overall and differential settlements of structures built on them. In many cases, the raft alone can offer sufficient bearing capacity and all that is needed to restrict foundation settlements to a predetermined level with a few widely spaced piles. Granular piles (GPs) can be used due to their several advantages over steel or concrete piles. An annular raft foundation is generally provided for overhead water tanks, chimneys, etc. The provision of granular piles underneath the annular raft foundation not only increases the capacity of the foundation but also minimizes the settlement to an acceptable level. The present study deals with a rigorous analysis of annular raft foundation supported by GPs based on the continuum approach. A new numerical method is developed with geometric considerations for excluding the loaded pile portion from the region of the raft area by considering two distinct zones. This article introduces a novel approach, the annular raft over granular piles, which represents an innovative solution in geotechnical engineering. This innovation has the potential to improve the efficiency and effectiveness of foundation design in various construction projects. The response of annular raft foundation with GPs is evaluated in terms of settlement influence factor (SIF), load shared by granular piles (in %), and normalized shear stress variation along the GP–soil interface. The present study reveals that the presence of the pile influences the stress distribution locally. The stiffness of GP, relative length of GP, relative size of the raft influence the settlement and load sharing of annular raft with GPs.

Introduction. Self-compacting concrete (SCC) technologies are actively used in modern construction, which are developing in the direction of lightweight self-compacting concrete (LWSCC) technology. The main advantage of LWSCC is to reduce the weight of concrete and reinforced concrete structures while maintaining structural integrity, load-bearing capacity and high mobility. The purpose of the study is to evaluate the rheology of the flow of the studied mixtures depending on the varying factors of W/C and the concentration of plasticizer Cpl and the ratio of filler (fractionated sand and quartz flour).Materials and methods. The object of the study is concrete mixtures on hollow microspheres. The design average concrete density is 1,400 kg/m3. The following composition is presented: Portland cement, ceramic microspheres, complex silica additive, fractional sand, quartz flour, hyperplasticizer and water. The results of studies of the rheological characteristics of LWSCC were obtained. The key rheological parameters are shear stress and viscosity.Results. Reducing the W/C increases the viscosity and shear stress of the concrete mix, regardless of the Cpl. A similar dependence is observed in compositions with variable Cpl. An increase in Cpl reduces the density of the mixture, reducing viscosity and shear stress. The limiting value of Cpl is noted, when this value is overcome by rheological parameters of mixtures tend to zero as the volume of the additive increases. The evaluation of the rheology of mixtures using the Ostwald de Waele equation shows the greatest importance of the W/C ratio for density and the possibility of changing the flow pattern of mixtures from pseudoplastic to dilatant with varying studied factors. Replacing the fraction of fractionated sand with flour from 100 to 0 % increases the density of the mixture by almost three times.Conclusions. The results determining the possibility of changing the rheological nature of the LWSCC flow on hollow microspheres with varying studied factors are presented. A comparative analysis of the obtained rheological curves is performed using the Ostwald de Waele equation for heavy and light mixtures with hollow microspheres. The role of filler dispersion in controlling the rheological properties of the studied LWSCC is considered.

The present work aims to analyze the deformation and stresses of lap joints made of sisal fiber-reinforced composite joined with epoxy adhesive under a transverse load. Finite element models were created with varying numbers of layers in the adherent (two, four), and the response of each layer was identified in terms of deformations, normal stresses, and shear stresses. Additionally, the lap joint was modeled with Buckminster fullerene reinforcement, and the composite was prepared with sisal fiber composite and epoxy adhesive (S/E), sisal fiber-reinforced composite with Buckminster fullerene mixed epoxy adhesive composite (S/FMA), and sisal fiber reinforced with fullerene mixed epoxy and fullerene mixed epoxy adhesive (S/F/F/E). Comparative studies were performed to investigate the effectiveness of fullerene on the adhesive and the adherent by studying the deformations and stresses generated on each layer. The addition of fullerene to the adhesive and sisal fiber-reinforced composite reduced transverse deformation by 27.4%. Adding two more layers to the lap joint without increasing the total laminate thickness reduces stress in both the pure epoxy adhesive and fullerene mixed adhesive. This research is useful for designing lap joints reinforced with natural fibers and nano-reinforcements, while considering the influence of the number of layers in an adherend. [ABSTRACT FROM AUTHOR]

Abstract—The paper presents an attempt to estimate the contribution of thermal processes in the Earth's crust to earthquake generation. As a case study, the seismically active junction zone of the Chu depression and Kyrgyz ridge of the Northern Tien Shan is considered. The analysis is based on the previously constructed models of temperature, petrophysical characteristics, and elastic moduli. The silica content model derived from seismic tomography data is used to build a lithotype model. The thermal conductivity model is constructed and used in conjunction with the temperature model to create a depth model of the heat flow density. The shear stress and thermoelastic stress models derived from density, elastic moduli, and temperature models are compared with the distribution of earthquake hypocenters in the region. The comparison suggests that on the scale of the seismically active junction zone of the Chu depression and the Kyrgyz ridge of the Northern Tien Shan, seismicity is mainly determined by thermomechanical effect induced by hot ascending flow of acid magma rising from the upper mantle beneath the Muyunkum–Narat median massif. [ABSTRACT FROM AUTHOR]

In this present study, we are interested in the use of a precise theory of shear deformation for the buckling analysis of plates with functional gradation simply supported such as the refined theory of plates with four variables. Several parameters of comparison have been used, dimensional and nondimensional. The displacement field is compatible with this study, the nonuse of shear correction factors is satisfied, and the choice of material is very precise in such a way are variable according to the thickness of the plate and on the other hand to make comparison with other researcher and confirms that this study gives precise results and converges. The transverse shear stresses vary through the thickness, the results found is also studied and discussed. [ABSTRACT FROM AUTHOR]

This study aims to compare the response of reinforced concrete (RC) T-beams strengthened with carbon fibre-reinforced polymer (CFRP) composite with that of non-strengthened control beams when subjected to monotonic two-point loading until failure for flexural once and shear again. The experimental programme tested eight RC T-beams, which included two reference beams without strengthening and six strengthened beams. The eight beams were divided into two main groups according to strengthening (flexural and shear). Experimental analysis was performed to study the effect of the CFRP laminate width in the flexural group and the spacing of CFRP U-wrap sheets in the shear group on the ultimate load capacity, load-strain relationship, and load-deflection relationship. Results show that increasing the width of the CFRP laminate in the flexural group improves the ultimate strengths to approximately 9.5%, 35%, and 41% for beams with CFRP laminate widths of 50, 100, and 150 mm, respectively, compared with the reference non-strengthened beam. The stiffness of the beams increases in direct proportion to the width of the CFRP laminate. In the meantime, decreasing the spacing of the CFRP laminate in the shear group increases the ultimate strengths to approximately 13.2%, 17.7%, and 23.5% for beams with CFRP U-wrap sheet spacings of 166, 125, and 100 mm, respectively, compared with the reference nonstrengthened beam. Therefore, the spacing of the CFRP sheet is inversely proportional to the stiffness of the beam. [ABSTRACT FROM AUTHOR]

In this research, commotional analysis based on the finite element analysis (FEA) has been performed to investigate IZOD impact test based on the ASTM D256 standard. The ANSYS model primarily employs a composite constructed of glass fiber-reinforced polyester for the boundary conditions. The CEAST 9050 instrument was used to implement the impacting technique in the experimental inquiry. By employing mathematics, we have calculated that the applied force is 9.2 N. A hammer traveling at a speed of 3.5 meters per second is used to strike the samples, and the results are recorded after each blow. The object of this study is the mechanical properties and structural integrity of the composite material composed of glass fibers and polyester when subjected to impact forces. The main hypothesis of the study encompasses the optimism that the glass fiber-reinforced polyester composite, when put through the Izod impact test in accordance with ASTM D256. Convergence between the overall deformation indicator and the numerical result has occurred. Results from the numerical analysis were examined and confirmed, and compared to those from the experiment. The specimens in this study were totally distorted at three different thicknesses (6 mm, 8 mm, and 10 mm). Deformation was found to be greatest for the thinnest value of thickness considered in the study (6 millimeters), as determined by the results of the computer analysis. This was the case even though the thickness value was not the sole criterion. This is the actual state of affairs. The specimen was subjected to a von-Mises stress at three different thicknesses of 6 mm, 8 mm, and 10 mm. The computer investigation revealed that the Von-Mises stress was highest at the thinnest possible thickness of just 6 millimeters. Internal energy, kinetic energy, and touch energy are only few of the various types of energy that have been studied in the context of energy conservation. [ABSTRACT FROM AUTHOR]

This paper presents an experimental analysis of fiber-reinforced polymer composites (CFRP) fabric to galvanized steel adhesive connection. An experimental research has been conducted on the adhesive connection between CFRP fabric and galvanized steel subjected to shear forces. The specimens were made from the steel plates overlapped on both sides with SikaWrap 230 C fabric using SikaDur 330 adhesive. Observations of natures of failure for CFRP-steel adhesive connection were conducted based on visual inspection using a scanning microscope. Mixed nature of the connection failure was specified. Moreover, an advanced numerical model has been developed and later on validated and verified on the basis of performed original laboratory tests. Ultimately, final conclusions were drawn based on the advanced numerical model that has been developed, verified and validated using laboratory tests results, as well as analytical models and nature of the connection failure was specified. [ABSTRACT FROM AUTHOR]

We use the OpnFoam package to numerically study the turbulent flow over a wavy surface for various values of the amplitude and wavelength of the perturbation of the channel wall. The RANS and LES models are used to describe turbulent characteristics. The Reynolds number in the flow is 20 000. The average profiles of velocities and shear stresses on the channel wall are obtained. The values of the amplitude and phase shift for perturbations of the shear stress are calculated for various geometrical parameters of the channel. Comparison with the theoretical model and experimental results is carried out. [ABSTRACT FROM AUTHOR]

Reducing friction losses is one of the most common ways to improve fluid film bearings, whose adjustable design provides additional opportunities to improve their dynamic and tribological properties. Previous studies have shown the possibility of reducing viscous friction in actively lubricated bearings by adjusting the rotor position. This work provides a theoretical justification for the mechanism of this effect for the cases of purely laminar lubricant flows in journal bearings. The operating modes connected with the transition to turbulent phenomena and the occurrence of Taylor vortices are beyond the scope of this paper. Conditions that ensure the minimization of friction losses in hydrodynamic and hybrid bearings with hydrostatic parts are determined based on the equations describing viscous friction in a fluid film. In non-adjustable plain hydrodynamic bearings, the minimum of friction is achieved with the centered shaft position that is actually unstable due to the resulting forces configuration. In actively lubricated hybrid bearings, a further reduction in viscous friction is possible by combining film thickness and pressure distributions. Recombining them, along with adjustment of the shaft position, allows the optimization of the distribution of shear stresses in the fluid film. As a result, the shear stresses caused by the rotation of the shaft can be partially compensated by the stresses caused by the pressure gradient, reducing the torque-resisting rotation. In addition, additional benefits can be obtained in the minimum friction state by the reduced lubricant flow and power losses to its pumping. A series of numerical calculations for elliptical, 3-, and 4-lobe bearings show that non-circular bores provide additional variability in film thickness distribution and a premise for optimizing the bearing tribological parameters. Four-lobe bearing demonstrated the best ability for reducing viscous friction among the considered designs. The results obtained can be used as a basis for further optimization of the geometry of fluid film bearings of both active and passive designs by reducing power losses due to viscous friction. [ABSTRACT FROM AUTHOR]

This study focuses on the topological optimization of adhesive overlap joints for structures subjected to longitudinal mechanical loads. The aim is to reduce peak stresses at the joint interface of the elements. Peak stresses in such joints can lead to failure of both the joint and the structure itself. A new approach based on Rational Approximation of Material Properties (RAMP) and the Finite Element Method (FEM) has been proposed to minimize peak stresses in multi-layer composite joints. Using this approach, the Mises peak stresses of the optimal structural joint have been significantly reduced by up to 50% under mechanical loading in the longitudinal direction. The paper includes numerical examples of different types of structural element connections. [ABSTRACT FROM AUTHOR]

The structure of the cooling tower shell locally made of materials differing in their specifications is considered. Such structures are created as a result of cooling tower shell repairs or reinforcements. The results of an analysis of the distribution and magnitude of shear stress at the interface between layers made of different materials are presented. [ABSTRACT FROM AUTHOR]

Bar reinforced concrete structures, which include piles, in real working conditions perceive a whole range of internal force factors. Axial tension-compression forces, bending moments and shear forces are the most commonly perceived internal force factors. Of particular interest is the effect on the cross section of the shear force. If a complex curly shape is replaced by elementary form, then the calculation is not difficult. However, when calculating the composite cross section, there is no unambiguous solution. In accordance with the adopted regulatory documentation, it is necessary to accept only a main part, while discarding the surrounding areas. It is important to study the configuration of the shape of a complex section for the perception of a shear force. The purpose of the work was to refine the account of the entire complex section using numerical simulation by the finite element method, analytical calculations and small-scale experiments. Determination of further practical application of the obtained results on real structures was also the goal of the study. The parameters of the distribution of shear force between the main rib and flanges were obtained by numerical analysis and small-scale experiments. Numerical models of rectangular and tee cross sections beams have been developed. Analytical dependences were studied and full-scale tests of reinforced concrete beams of various sections were carried out. It has been established that when taking into account the work of the entire cross-section, the bearing capacity of concrete for the action of a shear force is 20% greater than when calculating only the main section without taking into account the shelves. [ABSTRACT FROM AUTHOR]

The paper presents the solution of the problem of interaction of a single reinforced concrete compressible pile with an elastoplastic single-layer soil mass. The settlement is calculated on the basis of the analytical equation in the elastic formulation. A graph-analytical method is proposed to account for the nonlinear behavior of soils, which limits the bearing capacity of the pile on the lateral surface to the strength of the adjacent soil and under the pile toe to the ultimate load determined by the Brinch Hansen formula. The novelty of this method consists in taking into account the mechanism of load redistribution on the pile, the nonlinear behavior of the soil on the lateral surface and under the pile toe, and also the possibility of detachment and slippage of the pile after reaching the ultimate strength. A comparative analysis of the graph-analytical solution with the numerical solution in the geotechnical software Plaxis 2D and with static pile tests was performed. According to the results of the performed calculations, graphs of the dependence of settlement on loads were plotted, and conclusions about the possibility of using the graph-analytical method were drawn and the prospects for further development of the graph-analytical method are proposed.

In the present time, thermal transportation in the colloidal suspensions under various scenario becomes an influential research direction due to their extensive applications. Therefore, investigation of thermal transport over a rotating disk under the impacts of thermal and velocity slip, imposed Lorentz forces and thermal radiation is conducted for multiple shape effects of the nanomaterial. The nanofluid model suspended by Al2O3, TiO2 and Cu nanomaterial is reduced in dimensionless version via similarity variables. After that, RK scheme is implemented and handle the model effectively. The outcomes of various parameters for the velocity, thermal transport, skin friction and local heat transport are sketched and explained broadly. It is examined that the heat transport for the nanofluids becomes dominant throughout the analysis in comparison with conventional liquid. The temperature of the nanofluids significantly enhances due to the velocity slip effects. Moreover, thermal radiation and the volumetric fraction of the nanomaterials favor the local heat transfer rate.

While silicon carbide (SiC) has been predicted to undergo pressure-induced amorphization, the microstructural evidence of such a drastic phase change is absent as its brittleness usually prevents its successful recovery from high-pressure experiments. Here we report on the observation of amorphous SiC recovered from laser-ablation-driven shock compression with a peak stress of approximately 50 GPa. Transmission electron microscopy reveals that the amorphous regions are extremely localized, forming bands as narrow as a few nanometers. In addition to these amorphous bands, planar stacking faults are observed. Large-scale non-equilibrium molecular dynamic simulations elucidate the process and suggest that the planar stacking faults serve as the precursors to amorphization. Our results suggest that the amorphous phase produced is a high-density form, which enhances its thermodynamical stability under the high pressures combined with the shear stresses generated by the uniaxial strain state in shock compression.

In this manuscript, off-set strip fin structures are presented which are adapted to the possibilities of additive manufacturing. For this purpose, the geometric parameters, including fin height, fin spacing, fin length, and fin longitudinal displacement, are varied, and the Colburn j-factor and the Fanning friction factor are numerically calculated in the Reynolds number range of 80–920. The structures are classified with respect to their entropy production number according to Bejan. This method is compared with the results from partial differential equations for the calculation of the irreversible entropy production rate due to shear stresses and heat conduction. This study reveals that the chosen temperature difference leads to deviation in terms of entropy production due to heat conduction, whereas the dissipation by shear stresses shows only small deviations of less than 2%. It is further shown that the variation in fin height and fin spacing has only a small influence on heat transfer and pressure drop, while a variation in fin length and fin longitudinal displacement shows a larger influence. With respect to the entropy production number, short and long fins, as well as large fin spacing and fin longitudinal displacement, are shown to be beneficial. A detailed examination of a single structure shows that the entropy production rate due to heat conduction is dominated by the entropy production rate in the wall, while the fluid has only a minor influence. [ABSTRACT FROM AUTHOR]

When testing piles, the distance between the main pile and the anchor piles has a large effect on the test cost. Lower distance between piles results in lower test cost. However, codes usually set a lower limit for this distance between piles. This work presents a numerical study to determine the relationship between the distances of the piles in a static pile load test with the rise in shear stresses around the main pile. Finite element method is used for this purpose, which was verified by comparison with field full sized experimental tests. Finite element captured the pile settlement behavior successfully. After that, finite element was used to conduct a parametric study to find a relationship between piles spacing and stresses around the main pile. Parametric studies included piles spacing, piles diameter, piles number, and soil elasticity modulus. A non-linear equation was proposed to relate the pile spacing to the rise in shear stress around the main pile. This can help designers and engineers in determining the optimum distance of reaction piles in a static pile load test. [ABSTRACT FROM AUTHOR]

This paper aims to examine the heat and mass characteristics for thermally stratified chemically heated, dissipative flow under the cross-diffusion and imposed Lorentz forces. A self-similar model is obtained employing suitable similarity transformations. Then, the RK technique is used for mathematical analysis. The stimulations of pertinent physical quantities in the flow regimes, shear stresses, and the Nusselt number were examined graphically. It is noted that more radiative flow favors the thermal behavior of the fluid and increases in the Prandtl number causes the decrease in thermal characteristics. Moreover, decreases in mass characteristics were examined by the fluctuating chemical reaction and Schmidt parameters. Lastly, key outcomes of the work are pinpointed.

By the present paper, an analytical model was developed to study the cracked FRP-strengthened reinforced concrete beams subjected to fatigue loading. In order to follow the distribution of interfacial shear stresses causing the debonding phenomenon, a new analytical model based on the cohesive zone (CZ) approach was developed. The present model has the possibility to describe the evolution of the shear stress in the three zones (elastic, microcrack and debonding) and the bearing capacity of the repaired structure. Interface damage scenarios were evaluated for a fatigue load estimated to 90% of the elastic load and another at 60% of the ultimate load Pu. Results obtained are in good agreement with those given by the literature. The results showed that the shear strength developed by the repaired beam is sensitive to the variation of the mechanical properties (Concrete, FRP and Adhesive layer), the fatigue load ratio and the number of cycles. These parameters can be considered as indicators of damage affecting the health status of the structure repaired during fatigue. The debonding at the FRP-concrete interface noticeably reduced the strength and lifespan of the repaired structure. [ABSTRACT FROM AUTHOR]

This paper reports the construction of a durability model of basic structures, which takes into consideration the complex stressed state under the cyclic action of the complex load. The models that take into consideration this factor are categorized on the basis of equivalent for a certain indicator of the stressed-strained state. The equivalence models based on the tangent stresses and strains have been recognized as the most effective ones. However, they hold when the ratio of the limits of fatigue under tangent and normal stresses exceeds 0.5. In addition, determining the latter requires specific testing equipment. The concept of basic bearing structures for industrial equipment has been formulated. The issue related to the multi-axis fatigue of basic structures was considered from the standpoint of combining the reliability indicators of systems. The durability model has been derived from the rule of combining resource safety indices. The load is represented as a combination of individual subprocesses of simple types of deformation with their amplitudes and asymmetries. A model of durability with multi-axis fatigue has been built, which takes into consideration the parameters of the form of the strain cycle, and the type of process (synphase, disproportionate, unchanging static stress). The possibility of obtaining parameters for the multi-axis fatigue model during tests for three-point bending under conditions of varying the multiplicity of the span has been confirmed. According to this scheme, fatigue tests of prismatic samples of the steels 09G2 and 40H were carried out. For them, the parameters of fatigue resistance were found; additionally, the ratio of the fatigue limit for tangent stresses of displacement and fatigue limits for normal bending stresses, which is equal to 0.385, was established. A test procedure has been devised to determine the initial data for the multi-axle fatigue model, which is suitable for conventional test machines and simple-shape samples. The latter advantage is important precisely for basic structures, from fragments of which it is difficult to fabricate a sample of a complex shape. [ABSTRACT FROM AUTHOR]

Copyright of Polimery is the property of Industrial Chemistry Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The article considers the challenge of studying the mechanical properties of composite sandwich constructions at the interface between the base layers and the lightweight core. The results of strength tests are presented for specimens of sandwich-core panels with coats made of high-strength carbon fiber-reinforced plastics (CFRP) and polymer honeycomb core considering various loading conditions. It is noted that a discrepancy in the values of shear stresses occurs in four-point bending and shear tests due to the complex stress-strain state of the specimens during bending. In order to interpret the experimental data, numerical analysis of the area of contact interaction between the coats and the filler of the sandwich-core composite structures is carried out. It is noted that in the presence of significant normal stresses in the adhesive coat the base layers separate from the core during shear tests and there is underestimation of the values of shear stresses by about 20%. Recommendations for the assignment of ultimate shear stresses for the use in practical design of sandwich-core composite constructions are put forward.

Introduction: Surgically treated acute type A aortic dissection (ATAAD) patients are often restricted from physical exercise due to a lack of knowledge about safe blood pressure (BP) ranges. The aim of this study was to describe the evolution of early postoperative cardiac rehabilitation (CR) for patients with ATAAD. Methods: This is a retrospective study of 73 patients with ATAAD who were referred to the CR department after surgery. An incremental symptom-limited exercise stress test (ExT) on a cyclo-ergometer was performed before and after CR, which included continuous training and segmental muscle strengthening (five sessions/week). Systolic and diastolic blood pressure (SBP and DBP) were monitored before and after all exercise sessions. Results: The patients (78.1% male; 62.2 ± 12.7 years old; 54.8% hypertensive) started CR 26.2 ± 17.3 days after surgery. During 30.4 ±11.6 days, they underwent 14.5 ± 4.7 sessions of endurance cycling training, and 11.8 ± 4.3 sessions of segmental muscle strengthening. At the end of CR, the gain of workload during endurance training and functional capacity during ExT were 19.6 ± 10.2 watts and 1.2 ± 0.6 METs, respectively. The maximal BP reached during endurance training was 143 ± 14/88 ± 14 mmHg. The heart rate (HR) reserve improved from 20.2 ± 13.9 bpm to 33.2 ± 16.8 bpm while the resting HR decreased from 86.1 ± 17.4 bpm to 76.4 ± 13.3 bpm. Conclusion: Early post-operative exercise-based CR is feasible and safe in patients with surgically treated ATAAD. The CR effect is remarkable, but it requires a close BP monitoring and supervision by a cardiologist and physical therapist during training. [ABSTRACT FROM AUTHOR]

The article concerns modern, flexible adhesive joints, which might be used in timber construction. The article discusses the test results carried out for timber elements joints using polymeric adhesives produced by Sika®. The scope of the tests includes the analysis of strength criteria, tests of polymer adhesion to the timber with a pull-off method, tests of polymer layer shearing between timber elements as well as examination of bending of timber elements joined with polymer. The conclusions indicate the types of these polymers which are recommended for the creation of polymeric joints of timber-polymeric type in timber constructions.

This study focuses on the topological optimization of adhesive overlap joints for structures subjected to longitudinal mechanical loads. The aim is to reduce peak stresses at the joint interface of the elements. Peak stresses in such joints can lead to failure of both the joint and the structure itself. A new approach based on Rational Approximation of Material Properties (RAMP) and the Finite Element Method (FEM) has been proposed to minimize peak stresses in multi-layer composite joints. Using this approach, the Mises peak stresses of the optimal structural joint have been significantly reduced by up to 50% under mechanical loading in the longitudinal direction. The paper includes numerical examples of different types of structural element connections.

Bar reinforced concrete structures, which include piles, in real working conditions perceive a whole range of internal force factors. Axial tension-compression forces, bending moments and shear forces are the most commonly perceived internal force factors. Of particular interest is the effect on the cross section of the shear force. If a complex curly shape is replaced by elementary form, then the calculation is not difficult. However, when calculating the composite cross section, there is no unambiguous solution. In accordance with the adopted regulatory documentation, it is necessary to accept only a main part, while discarding the surrounding areas. It is important to study the configuration of the shape of a complex section for the perception of a shear force. The purpose of the work was to refine the account of the entire complex section using numerical simulation by the finite element method, analytical calculations and small-scale experiments. Determination of further practical application of the obtained results on real structures was also the goal of the study. The parameters of the distribution of shear force between the main rib and flanges were obtained by numerical analysis and small-scale experiments. Numerical models of rectangular and tee cross sections beams have been developed. Analytical dependences were studied and full-scale tests of reinforced concrete beams of various sections were carried out. It has been established that when taking into account the work of the entire cross-section, the bearing capacity of concrete for the action of a shear force is 20% greater than when calculating only the main section without taking into account the shelves.

The practice of construction and operation of railroads in the Arctic zone shows that the greatest share of track deformations occurs in the summer period during the transition of soils of the subgrade from the frozen state to the thawed state. Wetting, freezing-thawing, and vibrodynamic effects of trains have the greatest influence on the properties of clay soils composing the railroad bed. A model of a sub-tie base stabilized by geosynthetic materials is given. The influence of geosynthetic material on redistribution of stresses during thawing and change of shear deformation character is shown.

In this manuscript, off-set strip fin structures are presented which are adapted to the possibilities of additive manufacturing. For this purpose, the geometric parameters, including fin height, fin spacing, fin length, and fin longitudinal displacement, are varied, and the Colburn j-factor and the Fanning friction factor are numerically calculated in the Reynolds number range of 80–920. The structures are classified with respect to their entropy production number according to Bejan. This method is compared with the results from partial differential equations for the calculation of the irreversible entropy production rate due to shear stresses and heat conduction. This study reveals that the chosen temperature difference leads to deviation in terms of entropy production due to heat conduction, whereas the dissipation by shear stresses shows only small deviations of less than 2%. It is further shown that the variation in fin height and fin spacing has only a small influence on heat transfer and pressure drop, while a variation in fin length and fin longitudinal displacement shows a larger influence. With respect to the entropy production number, short and long fins, as well as large fin spacing and fin longitudinal displacement, are shown to be beneficial. A detailed examination of a single structure shows that the entropy production rate due to heat conduction is dominated by the entropy production rate in the wall, while the fluid has only a minor influence.

The authors have performed 3D numerical investigations into the velocity field behind a 3D thin plate by the LES method. The plate was located at a height of 0.002 m in a turbulent boundary layer formed in a water channel. The chord length of the plate and its spanwise size were equal to 0.01 m and 0.024 m respectively. The Reynolds number calculated from the half-width of the channel and the velocity on its axis was equal to 7500. It has been shown that under the impact of the wake of the plate, the longitudinal velocity normalized to the stagnation velocity grew in the logarithmic region at a distance to x/δ = 3.8, and pulsations of all the velocity components decreased in the buffer region to the distance x/δ = 0.8. As the lower shear layer of the wake approached the surface, longitudinal pulsations reached their minima at the wall at x/δ = 1.8, whereas vertical and transverse pulsations became higher than those in an unperturbed boundary layer. The calculated characteristics of the velocity field satisfactorily correlated with the relevant characteristics obtained in experimental investigation with similar initial and boundary conditions. An analysis of the velocity fi eld has revealed the mechanism of impact of the wake on the structural change of wall flow. The involvement of the wall medium in the lower shear layer generated the outflow of the medium from the channel wall, and the involvement in the upper shear layer formed the inflow of a high-speed medium to the buffer region. The medium′soutflow from the wall led to a reduction in the velocity gradient at the surface. Shear stresses decreased at a distance of four thicknesses of the boundary layer, and their local reduction amounted to as much as ~30%. Trailing vortices descending from the plate′s side edges created a nonuniform transverse-velocity distribution. This nonuniformity caused the vorticity to form in the buffer region. The arising system of small-size vortices blocked the feed of the high-speed medium to the wall, retarding the growth in the shear stresses on the surface in the interval 1.4 ≤ x/δ ≤ 2.6. The vortex system degenerated upon the stabilization of the transverse velocity and shear flow on the surface was restored. [ABSTRACT FROM AUTHOR]

In this study, a novel method for determining stresses in the torsion problems of laminated composite trimetallic and bimetallic bars was developed and evaluated via experimental and numerical analyses. The objective of this method is to transform a real transversal section of a model for a laminated composite bar into a hypothetical virtual section that is homogenous and isotropic. An analogy with the transformed-section method for solving composite beams under flexion was conducted. The shear stresses (maximum on external surfaces and interfaces) in laminated composite bars were undergoing torsion. Isotropic symmetric and asymmetric laminated composite bars were examined analytically, and the results of their respective experimental and numerical tests were analyzed. The proposed method exhibits differences between 2 % and 12 % compared with the experimental results and between 2 % and 10 % compared with the results obtained using the finite element method. [ABSTRACT FROM AUTHOR]

Purpose: Cardiovascular engineering includes flows with fluid-dynamical stresses as a parameter of interest. Mechanical stresses are high-risk factors for blood damage and can be assessed by computational fluid dynamics. By now, it is not described how to calculate an adequate scalar stress out of turbulent flow regimes when the whole share of turbulence is not resolved by the simulation method and how this impacts the stress calculation. Methods: We conducted direct numerical simulations (DNS) of test cases (a turbulent channel flow and the FDA nozzle) in order to access all scales of flow movement. After validation of both DNS with literature und experimental data using magnetic resonance imaging, the mechanical stress is calculated as a baseline. Afterwards, same flows are calculated using state-of-the-art turbulence models. The stresses are computed for every result using our definition of an equivalent scalar stress, which includes the influence from respective turbulence model, by using the parameter dissipation. Afterwards, the results are compared with the baseline data. Results: The results show a good agreement regarding the computed stress. Even when no turbulence is resolved by the simulation method, the results agree well with DNS data. When the influence of non-resolved motion is neglected in the stress calculation, it is underpredicted in all cases. Conclusion: With the used scalar stress formulation, it is possible to include information about the turbulence of the flow into the mechanical stress calculation even when the used simulation method does not resolve any turbulence. [ABSTRACT FROM AUTHOR]

Over the last two decades, the role of vegetation in the environmental and ecological restoration of surface water bodies has received much attention. In this context, the momentum exchange between the flow through the main channel and the riparian zone is a key mechanism. The primary goal of this study is to investigate the role of bank vegetation density on flow dynamics across the whole channel. This experimental study presents the major findings from a series of flow measurements across a channel having a sloping bank with vegetation at varying densities. The experiments are conducted under the same, uniform flow and fixed bed conditions, for a range of six linear and rectilinear arrangements of incremental streambank vegetation densities. A set of ten velocity profiles is obtained across the test cross-section of the channel, including the riverbank, for each vegetation density. These flow measurements are analyzed to derive roughness coefficients, which are related to the bulk flow velocities through the main channel and the riverbank and discuss the redistribution of flow velocities. An approximate doubling for the estimates of time-averaged boundary shear stress at the main channel, is observed for the case of no to dense vegetation, which enable further discussing implications for the stability of bed surface material. It is found that the vegetation arrangement, in addition to vegetation density, can have a strong impact in modifying the mean flow velocity at the main channel, for low riparian densities (φ < 0.6%). Highlights: Flow dynamics are measured across the whole channel, including the vegetated riverbank. As stem density increases, mean flow velocity in the main channel increases while mean flow at the riverbank decreases. The arrangement of riparian vegetation can be as important as that of the density, in modifying the mean flow field of the main channel, for low riparian densities. Bed shear stresses at the main channel are estimated to increase with riverbank vegetation, reducing the stability of the stream's bed surface. [ABSTRACT FROM AUTHOR]

An accurate means of predicting erosion rates is essential to improve the predictive capability of breach models. During breach growth, erosion rates are often determined with empirical equations. The predictive capability of empirical equations is governed by the range for which they have been validated and the accuracy with which empirical coefficients can be established. Most empirical equations thereby do not account for the impact of material texture, moisture content, and compaction energy on the erosion rates. The method presented in this paper acknowledges the impact of these parameters by accounting for the process of dilation during erosion. The paper shows how, given high surface shear stresses, the erosion rate can be quantified by applying the principles of soil mechanics. Key is thereby to identify that stress balance situation for which the dilatency induced inflow gives a maximum averaged shear resistance. The effectiveness of the model in predicting erosion rates is indicated by means of three validation test cases. A sensitivity analysis of the method is also provided to show that the predictions lie within the range of inaccuracy of the input parameters. [ABSTRACT FROM AUTHOR]

We study the influence of temperature, stresses, and resistivity of a foam masses on the intensity of moisture removal. We select three zones of changes in the electric resistivity. The distribution of the pressure field is connected with the filtration of moisture in capillary-porous materials. For the insufficient structural strength of interporous partitions and sharp changes in temperature, we observe the phenomenon of subsidence of the foam masses. We analyze the character of changes in membranes for the maximum possible increase in the volume of the pore and evaluate the volume of refractory component, which forms the shells of pores (cells). The filtration of liquid in the analyzed foam mass under the action of pressure gradient is characterized by its viscosity and the geometric parameters of the capillary-porous body. In the case of self-compaction of the foam system, the process of mass transfer becomes more complicated due to the changes in the filtration characteristics of the matrix. In order to exclude the stressed state in the adobe body after electric heating, the body should be gradually cooled down to a temperature safe for its structure. [ABSTRACT FROM AUTHOR]

The specified formula for determining the heat ratio due to the deformation in the shear plane enter ing chippings is got. The obtained results of the heat - sharing ratio calculation for the case of machining 12 Х 18 Н 10 Т heat - resistant steel by ВК 8 alloy are in satisfactory agreements with the literature data.