Connection Zone Research Articles

Research of the melting zone of the relit – cupronicel composite alloy when surfacing metallurgical equipment parts using the furnace method

With the furnace surfacing method, a composite alloy is obtained, consisting of reinforcing particles of tungsten and cupronickel carbides, which, after exposure to the melting temperature of the binder alloy, form a wear-resistant layer on the surface being hardened. It has been established that in the zone of connection of the composite alloy relit – cupronickel with the steel surface of the part, in the absence of conditions that guarantee auto-vacuum cleaning of the surface from oxides, an interlayer with an imperfect crystal structure is formed, which leads to delamination of the deposited alloy. It has been experimentally shown that the use of additional control for the gas tightness of the surfacing space makes it possible to improve the quality of the deposited surface when furnace hardening of metallurgical equipment parts with the composite alloy relit – cupronickel.

Composition, divergence and variability: A comprehensive analysis of fish trait responses to connectivity

Connectivity, a fundamental concept in ecology, refers to the extent to which different habitats or ecosystems are interconnected through the movement of organisms, nutrients, and energy. Lateral hydrological connectivity (LHC) plays an especially critical role in shaping aquatic community organization in river-floodplain systems. However, a comprehensive understanding of various trait responses to LHC remains elusive. We characterized how attributes of fish community traits, specifically composition, divergence, and temporal variability respond to LHC in the Austrian-Hungarian floodplains of the Danube River using environmental DNA (eDNA) metabarcoding. Trait composition was quantified by community-level weighted means (CWM) as the degree of changes in trait responses along the LHC gradient from isolated oxbows to the main river. Divergence was measured using Rao’s quadratic functional diversity index and a null model approach to calculate standardized effect sizes (SES), with larger SES values indicating greater divergence and smaller values indicating convergence. Temporal variability, representing the degree of instability in community traits over time, was calculated using a functional beta diversity measure for multiple communities. Our findings revealed apparent compositional changes for many trait variables, highlighting the significance of LHC in shaping community functional diversity. Divergence patterns indicated that isolated habitats foster trait convergence presumably due to habitat filtering, whereas more connected areas promote trait divergence due to higher species richness and habitat availability. Temporal variability of traits associated with flow preference exhibited a hump-shaped relationship with LHC, suggesting intermediate connectivity zones are hotspots of ecological dynamism. The study suggests that examining composition, divergence, and temporal variability together provides a more complete understanding of trait responses to connectivity, stressing the importance of maintaining diverse connectivity levels in river-floodplain systems for effective conservation and ecosystem management.

Fatigue life prediction method for bolted joints based on equivalent structural stress under tensile–compressive loading

In this study, load amplitude–life (Fa–N) curves were obtained through tensile–compressive fatigue tests of bolted joints. It was observed that the correlation coefficient squared (R2) value of the Fa–N curve with the same geometric and pre-tightening parameters was high, but the R2 value of the Fa–N curve with all the parameters was low, indicating poor correlation and inability to meet the engineering requirements. Therefore, an equivalent structural stress model for the bolted joint was first developed based on a mechanical model with a strict mathematical definition to normalize these Fa–N curves, which considered the bolted joint loads as the input conditions and integrated the geometric and pre-tightening parameters. Subsequently, a classical beam–shell equivalent finite element model of the bolted joint was constructed. The nodal loads in the bolted connection zone were coupled with the forces and moments of the beam element nodes through finite element simulation, and the equivalent structural stress (σs) of the bolted joint was then obtained based on the equivalent structural stress model. Consequently, the equivalent structural stress–life (Ss–N) curve and probabilistic stress–life (P–Ss–N) curve normalized for different Fa–N curves were obtained by fitting the data of σs and N. Lastly, the accuracy of the fatigue life prediction method based on equivalent structural stress was verified by conducting the vibration fatigue test on the bolted joint structure of the subway antenna bracket.

Nonlinear Vibrations of Composite Cylindrical–Cylindrical Shells with Bolt Loosening Connection

The nonlinear vibrations of composite cylindrical–cylindrical shells with bolt loosening connections are investigated. First, a theoretical model of such a combined shell is developed, with a multisegmental virtual material ring technique being adopted to replicate the partial bolt looseness in the bolted connection zone of two single shells. Furthermore, to consider the nonlinear vibration issue of such a bolted connection zone affected by external excitation amplitude, the equivalent Young’s modulus of the virtual material is defined, and the equation of motion is derived to solve nonlinear vibration parameters. Finally, three single composite cylindrical shells are connected with 12 bolts to form two combined shell specimens, and experimental tests are carried out to validate the model and examine the nonlinear vibration characteristics of such combined shells. Also, the impact of partial bolt loosening parameters on the nonlinear vibration behaviors is investigated with some important findings being summarized. The analysis methods, modeling techniques, test methods and important conclusions proposed in this study provide a useful reference for the study of the vibration issues of bolted composite shells.

Experimental behavior of connection between composite columns and reinforced concrete flat slab

The combination of concrete-filled steel tube (CFST) columns and reinforced concrete flat slabs provides a suitable structural solution that can be used to replace traditional structures in high-rise buildings. The connection between the CFST column and the RC flat slab is an important factor for this construction system to operate efficiently. In this study, a new form for the connection between the CFST column and the RC flat slab has been proposed. This connection has more constructability, where the steel tube is cut at the level of the slab to prevent the separation between the slab and the concrete inside the steel tube as the slab reinforcement is allowed to continue in the connection zone. The joint zone is strengthened with rebar rings to compensate for the loss in confinement caused by cutting the steel tube at the slab level. In addition to using longitudinal rebar in the joint zone to bear part of the vertical load and to ensure bending rigidity. The behavior of the proposed connection was investigated by testing three sets of small-sized samples. In addition, an equation based on the outcomes of the second set of tests has been carried out to determine the joint bearing capacity for the vertical load.

Metallurgical and technological features of forming the connection zone between the welded layer and base metal during repair welding of cast iron parts with carbon dioxide and oxygen

Metallurgical and technological features of forming the connection zone between the welded layer and base metal during repair welding of cast iron parts with carbon dioxide and oxygen

Experimental investigation on seismic performance of CHS T-joints in salt spray environment

This paper aims to investigate the seismic performances of circular hollow section (CHS) T-joints with different regions of corrosion damage. A total of seven CHS T-joint specimens with various corrosion degrees were applied to conduct the quasi-static tests of brace axial cyclic loading, and the effects of corrosion damage on the hysteresis behavior and failure mode were discussed. Experimental results indicated the brace corrosion only had a slight influence on the seismic performance of CHS joints, while the corrosion difference on two sides of the brace might cause an additional bending moment and damage accumulation to accelerate the plastic collapse of the connection zone. Compared with the corrosion on the brace, the resistance of CHS joints was more susceptible to the corrosion located in the chord wall, resulting in the axial cyclic carrying capacity and stiffness of CHS joints significantly decreasing with the increase of chord corrosion level. However, the increasing corrosion on the chord would affect the final fracture behavior and fracture position, so the total energy dissipation and deformation of CHS joints presented a complicated and nonlinear degradation trend. In addition, corrosion damage simultaneously had an impact on reducing the bending capacity of the chord, and this phenomenon not only caused the differences between the degradation rates of axial tensile and compressive strength of CHS joints but also affected the failure mechanism and local deformation of CHS joints under the brace axial cyclic loading.

Scale model test and numerical analysis on the anchorage zone of a cable-stayed bridge with the cross-anchor structure

In this paper, scale model test and numerical analysis are conducted to investigate the stress distribution and crack development in the anchorage zone of a cable-stayed bridge with a cross-anchor structure. Initially, scale model test is performed on the tower-crossbeam connection zone to observe the stress distribution at key positions. Then, the anchorage zone is simulated using ABUQUS, considering the material's nonlinearity. The correctness of the finite element model is verified through model test. Finally, we analyze the stress and crack development under 2.7 times the design load. Results show that cracks are prone to occur on the concrete sidewalls. Cracks appear under 1.14 times the design load, and through cracks appear under 1.56 times the design load, initially in the upper-middle part of the anchorage zone. The stress distribution in the stirrups is the most complex among the rebar stresses. After local cracks and through cracks appear in the concrete, the stress in the stirrups increases rapidly.

Efficient propagation modelling for open‐confined mixed space using a hybrid ray‐tracing/waveguide theory method

AbstractThe accurate prediction of radio wave propagation along highways plays an important role in the design of high‐speed highway communication systems. The open‐confined mixed space is a connection zone between the open space and confined tunnel along the highway. A hybrid propagation model is presented based on ray‐tracing (RT) and waveguide theory, for the efficient modelling of open‐confined mixed space. The proposed model employs RT to predict radio waves emitted by sources with arbitrary radiation patterns in open space sections, and utilises the waveguide theory approach to accelerate the prediction process in the confined tunnel sections. Both two‐ray and six‐ray RT models are included to take into account the suburban and urban environments. Numerical results are compared with simulated results generated by RT as well as experimental measurements. The validity and usefulness of the proposed model are demonstrated in an actual open‐confined mixed space environment.

A functional connectivity approach for exploring interactions of multiple ecosystem services in the context of agricultural landscapes in the Canadian prairies

Land-use and land-cover patterns, including their spatial heterogeneity and configuration, are fundamental in shaping landscape-level ecological processes, functions, and services. Despite growing recognition of the importance of these patterns, gaps remain in our understanding of how they influence the functional connectivity of ecosystem services (ES)—a crucial aspect for ecosystem resilience and sustainability. This research aims to bridge this gap by investigating the functional connectivity among multiple ES, such as pollination, carbon storage, soil erosion control, wetland-based ES such as habitat provisioning and water storage capacity from marshes, swamps, and open water wetlands, and agricultural food production within a complex landscape. We define functional connectivity as the extent to which the landscape facilitates or impedes the interactions and interdependencies of ecological processes that combine to create distinct ecosystem services. This definition encompasses the dynamics within a spatially interconnected mosaic of land use and land cover, exemplified by connections such as those from pollination provisioning areas to croplands. The primary goal of this research is to develop an empirical framework that encapsulates ‘network topological’ interactions— essentially, the complex interplay among various components of the ecosystem — specific to agricultural landscapes and then to apply this framework to the Canadian prairies. Our methodology uses the spatial tools including InVEST, ARIES, and GIS to map diverse ES. An ecological network is then constructed for these ES at the landscape scale, designating network nodes based on high-value ES provisioning areas and defining links between pairs of ES according to their functional connections (overlapping and proximal in physical space). These functional connections effectively delineate areas of the landscape where the majority of ES flows occur. Mapping ES connectivity and network building revealed that around 29% of the studied landscape lies within functional connectivity zones for the selected ES, representing hotspots of significant ES interactions. Our findings reveal that although soil erosion-control spans just 1.36% of the total area, a substantial 72.59% of its spatial extent was identified as functionally connected. Land cover analysis in functional connectivity zones revealed that natural habitats such as shrublands, broadleaf forests, wetlands, and grasslands are vital mediators of ES. The variability in ES interconnectivity in the landscape was evident both in the intensity of interactions and observed connections. Our findings, informed by Ecological Network Analysis (ENA), emphasize the need for integrating connectivity and systems thinking in conservation sciences to achieve sustainability and ecosystem resilience. The insights offer a foundation to explore optimal ES provisioning scenarios at the landscape scale.

ИССЛЕДОВАНИЕ СТРУКТУРЫ И НАПРЯЖЕННО-ДЕФОРМИРОВАННОГО СОСТОЯНИЯ СВАРЕННОГО ВЗРЫВОМ ПЯТИСЛОЙНОГО ТИТАНО-СТАЛЬНОГО КОМПОЗИТА ПОСЛЕ ГОРЯЧЕЙ ПРОКАТКИ

The results of studies of the structure of a five-layer titanium-steel composite VT1-0-08X18H10T, welded by explosion, after hot rolling at a temperature of 850 °C are presented. An analysis was carried out of the diffusion interaction in the zones of connection of the composite and the stress-strain state.

Experimental response of semi-rigid reinforced concrete beam-column joints with bolted angle dissipating connections

Accelerated building construction is a challenge and opportunity for modern construction techniques such as prefabricated building. However, insufficient connection detail for precast structures resulted in serious damages (even collapse) in past earthquake, which significantly hit the further development of prefabricated building. With satisfactory seismic performance and minimal residual displacement, self-centering joint is an excellent alternative with respect to traditional prefabricated joint. In self-centering system, bolted connections are sufficiently utilized as energy dissipation system. However, the information about connection details is quite limited. Thus, a comprehensive experimental study was conducted to characterize the seismic behavior of semi-rigid reinforced concrete (RC) beam-column joints with bolted angle dissipating connections, namely, semi-rigid joints. Ten full-scale semi-rigid joints were tested under cyclic loading, taking the connection detail as variable. The main configurations of semi-rigid joints based on Eurocode 3 were angle thickness, angle stiffener, bolt diameter, column bolt gauge, rows of beam bolts, and grouting of beam bolts. The test results showed that, by adopting the ductile connection concept, it was possible to produce high ductility and abundant energy dissipation, control damages within the connection zone, and even achieve equivalent monolithic behavior through mobilizing a sufficient rigidity. Feasibility of replacing the damaged connection with a new one with the identical or higher capacity thus obtaining the equivalent or better performance with respect to the original tested joint is also evaluated. Finally, a theoretical model was proposed to evaluate the initial stiffness and bearing capacity of the joints. A good correlation was achieved as comparing to the test results. This research provides significant insight into the performance of precast semi-rigid joints and offers essential data for further investigation of developing design-oriented procedures.

A 0D parallel transport model for varying density regimes for use in 2D drift‐fluid turbulence codes

AbstractIn this paper, a new model of the parallel transport in 2D drift‐fluid turbulence codes is formulated as a 3‐point model and benchmarked against SOLPS‐ITER. The model allows for the existence of parallel temperature gradients and local recycling near the target. To realize this, the volume of the flux tube is split into two zones: (1) a connection zone extending from the outer midplane to the ionization zone entrance and (2) an ionization zone covering the remaining space until the sheath edge. By assuming a linear increase of the parallel particle and conductive heat fluxes in the connection zone, and assuming an ad‐hoc relation for the electron pressure evolution, expressions for the plasma fields at the entrance of the ionization zone are obtained. The evaluation of the integral balances over the ionization zone leads to an implicit system in terms of the parallel fluxes. To benchmark the model, we compare with reference data from density, current and recycling scans for a flux tube with SOLPS‐ITER. From these scans, one observes that the model predicts well the parallel particle flux in the density and recycling scans. Discrepancies that arise at higher densities for both the conductive heat fluxes and the required floating upstream potential are analyzed and partly explained by the superlinear evolution of the heat fluxes in the SOLPS‐ITER simulations. It is concluded that the model can be used to construct the effective volumetric sink terms in 2D drift‐fluid turbulence models.

Влияние геометрии инструмента на формирование сварного соединения при сварке трением с перемешиванием алюминиевого сплава АМг5

One of the important parameters influencing the formation of a weld during friction stir welding is the tool geometry, which affects the processes of heat generation and stirring of metals in their connection zone. These processes influence the formation of a high quality and strength welded joint without continuity defects. In this regard, it is relevant to analyze the influence of tool geometry on the welding mode parameters, at which the welded joint is formed without continuity defects, as well as on the welded joint strength under static tension. The work considers the influence of the cylindrical and conical shapes of the tool pin, as well as the conical shape of the pin with a thread on its outer surface and a spiral groove on the end surface of the tool shoulder on the welding mode parameters, at which the welded joint is formed without continuity defects. The study shows that changing the shape of the pin working surface from cylindrical to a conical one had no effect on the range of welding mode parameters, at which the welded joint is formed without continuity defects. It has been found that the presence of a thread on the pin outer surface and a groove on the end surface of a tool shoulder allows producing welded joints without continuity defects in a wider range of welding mode parameters compared to a simpler tool geometry. The macrostructure of the resulting welded joints was considered. It has been found that the studied tool geometry has almost no influence on the maximum strength values of welded joints produced by friction stir welding and reaches 95 % of the strength of the base metal.

The Effects of Corrosion and Fire Damage on the Steel-Bolted T-Section Connections Used in the Steel Construction.

The most common type of connection in steel structures is the T-section connection. Steel structures can be damaged due to environmental effects such as earthquakes, fires, corrosion, etc., in real applications used in industry. Therefore, in this study, the corrosion and fire condition effects that occur in the T-section connection on the behavior of the connection zone were investigated. The study was carried out with 18 T-section connections with various corrosion (hydrochloric acid and sulfuric acid) in different layers at 5, 10, 15, and 20% corrosion levels, and fire (ISO834) conditions after corrosion have been evaluated and compared. T-section-bolted joints examined in the study were produced using IPE300 standard profiles. In the first part of the study, the behavior of the 18 T-section connections under an axial tensile load has been determined experimentally. The second part created a finite element model with the ABAQUS program for all models. It was seen that the finite element model analysis results converged with the results obtained as a result of the experimental study. As a result, compared to H2SO4 corrosion, HCl corrosion has little effect on the load-deformation characteristics of the connections. Also, if corrosion specimens are exposed to fire, then the connections will change from semirigid to hinged.

Efficiency of Flange-Bonded CFRP Sheets in Relocation of Plastic Hinge in RC Beam–Column Joints

Beam–column connection zones are high regions of interest in reinforced concrete (RC) structures, which are expected to respond elastically to seismic loads. Using carbon fiber-reinforced polymers (CFRP) to improve these connections, performance is critical in retrofitting deficient RC frames because existing slabs may pose numerous limitations in the design and wrapping of CFRP sheets in joints. The main aim of this research is to develop a new design for flange-bonded CFRP retrofit of frames, including slabs, for the relocation of plastic hinges of the connection area toward the beam and to develop beam–column joint capacity and building stability in cases of subjection to dynamic loads. The performance of these proposed retrofittings was explored both experimentally and numerically. Two full-scale fabricated interior RC joints of a real moment-resisting frame with moderate ductility were subjected to monotonic loads before and after retrofitting, and the results were used to detail the numerical progress and verify of the beam–column connection. Moreover, a parametric study was conducted on CFRP sheets’ optimal thickness to examine its influence on plastic hinge relocation in the connection region. Results show that the retrofitting method can efficiently relocate the plastic hinge to the mid-span of the beam, which, in turn, leads to improved capacity and achievement of the RC frame and guarantees better structural safety a lower cost.

Differences in the Occurrence of Cell Wall Components between Distinct Cell Types in Glands of Drosophyllum lusitanicum.

Carnivorous plants are mixotrophs that have developed the ability to lure, trap, and digest small organisms and utilize components of the digested bodies. Leaves of Drosophyllum lusitanicum have two kinds of glands (emergences): stalked mucilage glands and sessile digestive glands. The stalked mucilage glands perform the primary role in prey lure and trapping. Apart from their role in carnivory, they absorb water condensed from oceanic fog; thus, plants can survive in arid conditions. To better understand the function of carnivorous plant emergences, the molecular composition of their cell walls was investigated using immunocytochemical methods. In this research, Drosophyllum lusitanicum was used as a study system to determine whether cell wall immunocytochemistry differs between the mucilage and digestive glands of other carnivorous plant species. Light and electron microscopy were used to observe gland structure. Fluorescence microscopy revealed the localization of carbohydrate epitopes associated with the major cell wall polysaccharides and glycoproteins. The mucilage gland (emergence) consists of a glandular head, a connecting neck zone, and stalk. The gland head is formed by an outer and inner layer of glandular (secretory) cells and supported by a layer of endodermoid (barrier) cells. The endodermoid cells have contact with a core of spongy tracheids with spiral-shaped thickenings. Lateral tracheids are surrounded by epidermal and parenchymal neck cells. Different patterns of cell wall components were found in the various cell types of the glands. Cell walls of glandular cells generally are poor in both low and highly esterified homogalacturonans (HGs) but enriched with hemicelluloses. Cell walls of inner glandular cells are especially rich in arabinogalactan proteins (AGPs). The cell wall ingrowths in glandular cells are significantly enriched with hemicelluloses and AGPs. In the case of cell wall components, the glandular cells of Drosophyllum lusitanicum mucilage glands are similar to the glandular cells of the digestive glands of Aldrovanda vesiculosa and Dionaea muscipula.

Investigation of the influence of bed joint steel reinforcement on the load‐bearing capacity and deformability of walls made of AAC (subjected to vertical compression). Part 2 test of the wall connection zone

AbstractThis paper presents results from testing full‐scale walls made of autoclaved aerated concrete (AAC). A new type of reinforcement—steel mesh reinforcement protected against corrosion, was used in these tests. This paper is a second part of the paper and a continuation of previous tests. It presents the effect of reinforcement on the connection zone of perpendicular walls. The analysis was performed for load‐bearing capacity and crack resistance of the connection of perpendicular walls subjected to non‐uniform loading. The results were compared with the results from previous tests. The results were also analyzed and rules for using reinforcement in the connection zone of perpendicular walls were established.

Nonlinear dynamics of bolted joined conical-cylindrical shells considering displacement-dependent characteristics

This paper investigates the nonlinear dynamic characteristics of joined conical-cylindrical shells (JCCSs) with bolt connection for the first time. In the process of developing mechanical model of the bolt connection, the displacement-dependent stiffness and damping are taken into account, which could simulate the change of the contact state at the connection interface under different excitations. Both theoretical and experimental studies are performed to illustrate the nonlinear vibration behaviors of the bolted JCCSs. Successive uniform distributed artificial springs between the conical and cylindrical shells are adopted to simulate the rigid joint of the two shells. Donnell's shell theory is employed in theoretical modeling, and the governing equation is obtained by the Lagrange equation. The displacement admissible function applied in the research is Chebyshev polynomial. By comparison with existing literature and experimental data, the accuracy of present theoretical model is validated. It is found that both theory and experiment show a dynamic softening phenomenon with the increase of excitation level. Taking the displacement-dependent characteristics in bolt connection zone into consideration can effectively illustrate this soft phenomenon. The established model is capable of predicting the nonlinear vibration characteristics of JCCSs with bolt connection.

Numerical parametric evaluation of ultimate resistance of high-strength bolts

High strength bolts are widely used in the engineering field due to their good compressive properties. Accurate assessment of the ultimate capacity performance of high strength bolts under combined loading is essential to ensure the safety of steel structures in the connection zone. Existing studies are not sufficiently clear on the economic and condition-specific limits on the effects of various factors on high-strength bolts under complex stress conditions. In response to these problems, the aim of this paper is to analyse the effects of different factors on the load-bearing performance of high-strength bolts on the basis of numerical simulations. The mesoscale critical plastic strain (MCEPS) method was used on the model fracture and the accuracy of the model evaluation was verified. The effects of grade, type, diameter and bolt hole clearance on the ductile fracture behaviour of high-strength bolts were investigated. It was found that fully threaded bolts and through-hole clearances can mainly affect the load-bearing properties of high-strength bolts and increase the bolt's fracture-deformation capacity. The load-bearing performance of high-strength bolts under the influence of different factors was also compared with the Eurocode design (EC3) predictions.