Corner Part Research Articles

Bending behavior of detachable tapered-head bolt inter-module connection of steel modular structure

The force transmission between steel module units is primarily achieved through inter-module unit connections. However, the existing connections often fail to meet the installation requirements for central connections, and some connections require on-site welding and are difficult to disassemble, with strict demands on the cross-section of beams and columns. To address the shortcomings of the current connections, a detachable tapered-head bolt inter-module connection of steel modular structure is proposed. It solves the problem of limited installation space for central connections, enabling rapid installation and disassembly with high construction efficiency. A study on the bending behavior of the connection under static load is conducted through four-point bending tests. Various mechanical characteristics, including failure mode, ductility, load-bearing capacity, and strain distribution are investigated. The results indicate that the primary failure mode for the connection under bending moment is the yielding of the bottom plate of the upper corner part, demonstrating a ductile failure mode. The results of parametric numerical simulations show that increasing the bottom plate thickness and side plate thickness of the upper corner part are effective measures to improve the connection bending performance. Furthermore, the simplified theoretical calculation model for the connection is established, and the formula for calculating the bending bearing capacity is proposed. This provide a reliable design basis and reference for the practical application of the connection in engineering projects.

Multi-Story Volumetric Blocks Buildings with Lower Frame Floors

This article presents the results of experimental studies of the stress–strain state of volumetric blocks based on the underlying frame structures. The aim of the research is to evaluate the stress–strain state and the nature of damage development as a result of an increase in the load up to a critical level. Based on the analysis of the nature of the damage, recommendations have been developed to strengthen the destruction zone. Data were collected on the redistribution of stresses and deformations, the formation of cracks and joint openings, the magnitude of horizontal displacements, and the failure mode of volumetric blocks and floor frames. Five full-scale volumetric blocks were tested under the loading of hydraulic jacks, differing in concrete type, reinforcement, presence of doors, and dimensions of the stylobate beams. When the volumetric modules were supported by a frame floor the results revealed that the maximum destructive load of 10,462 kN was observed in the first specimen; the horizontal displacements of the walls decreased by 13–18 mm, and there was a decrease in the crack opening width to 0.5 mm. The cracks decreased the strength of the walls, leading to a redistribution of the compressive stresses and their increase in the support zone. The most significant compressive strains in concrete in the corner parts of longitudinal walls were in the range of (600–620) × 10−6, and in the middle part of the walls, 370 × 10−6 were observed. Furthermore, the largest cracks caused significant horizontal displacements (deplanation) of the walls, which decreased the stiffness of the conjunction of longitudinal walls with the floor slab and created an additional eccentricity of the vertical force. Based on the findings, the correlation between the measured parameters of each specimen at all stages of vertical load increase is demonstrated and illustrated in graphs of the measured parameters. The importance of quantity compliance with the initial rigid connection between the longitudinal wall and ceiling plate has been estimated.

Defects Imaging in Corner Part with Surface Adaptive Ultrasonic and Focusing in Receiving (FiR) Strategy

Defects Imaging in Corner Part with Surface Adaptive Ultrasonic and Focusing in Receiving (FiR) Strategy

Parametric Analysis on Formability of SS304 Metal Bipolar Plate with Wave Flow Field Structure

The main production method of metal bipolar plate is stamping, and the size parameters of the flow field structure can not only change the performance of the fuel cell, but also affect the stamping quality of the metal bipolar plate. In the case of ensuring the performance of the fuel cell, it is necessary to study the stamping of the metal bipolar plate with different flow field structures. In the past, there were few studies on the wave flow field stamping forming. This paper analyzed the wave flow field, formulated several sets of bipolar plate structural dimension parameters, and evaluated the stamping forming quality of the reaction zone of SS304 metal bipolar plate through finite element simulation. By reducing the rib height ΔH=0.075mm in the corner part, the maximum thinning rate can be reduced from 34.833% to 24.689% and the thickness can reach 0.0753mm when the flow channel width S=1.0mm, the rib width W=1.5mm and the forming depth H=0.5mm. It provides some guidance for optimizing the structural dimension parameters of metal bipolar plates.

Arhitektura palate Popović Tonkić u Leskovcu

The economic and social development of Leskovac was accompanied by intensive construction activity. The urban environment was enriched by the construction of private residential buildings, whose owners were distinguished members of the bourgeois class. The palace of industrialist Milan Popović Tonkić occupies a prominent place in the architectural heritage of Leskovac. It was built in 1937 as a monumental corner building for residential and commercial purposes. It was designed by architect Miša Manojlović, who had a private design office in Belgrade with his colleague Isak Azriel. His independent authorship is evidenced by a marble tile placed on the corner part, under the window of the former tavern. Since historical styles were preferred in the circles of clients due to the expression of social position, the author applied an academic style tempered by a personal reinterpretation of experimentation with form. Following the contemporary practice of designing residential architecture, he paid equal attention to the interior of the building, applying high-quality decorative treatment and functional disposition of the Belgrade apartment. After more then a decade since the last historiographic contributions on the history and visual identity of the building, the main goal of this research is to contextualize the Popović Tonkić palace in Leskovac with phenomenological and stylistic aspects of interwar residential architecture.

Experimental investigation on the cold-forming effect of high strength cold-formed steel sections

Many researches were carried out on the cold-forming effect of cold-formed steel sections while research on that of high strength cold-formed steel sections was quite few. Thus, an experimental investigation on the material property and residual stress of high strength cold-formed steel sections was carried out and the effect of residual stress on the overall stability bearing capacity was studied. It was found that: (1) the increase of yield strength of high strength cold-formed steel was similar to that of Q235 and Q345 cold-formed steel; (2) the residual stress at corner parts was much higher than that at flat parts and the bending residual stress of high strength cold-formed steel was much lower than that of Q235 and Q345 cold-formed steel; (3) residual stress would lead to a decline of the overall stability bearing capacity of axially loaded high strength cold-formed C-shaped steel sections and the effect became lower with the increase of strength grade.

Fasad Sculpture of Provincial Eclectics on the Example of Rostov-on-Don: Iconography, Symbols, Stylistics

The article is devoted to the study of eclectic facade sculpture in the historical center of Rostov-on-Don, considered in accordance with specific neo-styles. Sculpture plays an important compositional role in the design of the facades of Neo-Baroque monuments, emphasizing the rhythmic organization of facades, emphasizing the central and corner parts of buildings. Sculptural decor in the design of facades, designed within the neo-Greek and Neo-Renaissance, obeys the compositional rhythm set by architectural forms, is most often placed in architecturally limited fields, highlights the compositional axes of facades and more actively uses motifs of ancient origin. In general, the iconography of the sculptural decor includes plant motifs (laurel, flower, fruit garlands, flower baskets, acanthus, wreaths, rosettes), images of objects, including symbolic ones (shells, cartouches, caduceus, flowerpots, a cornucopia, a fountain, attributes of industry, trade, sciences and arts, armorial shields), zoomorphic images (mainly lion mascarons, griffins), mixanthropic and anthropomorphic images. Among the latest figurines are putti, mascarons of satyrs, Aphrodite, Hermes; belt herms of Hercules, Omphale, Deianira; sculptures of nymphs, Apollo, Ceres, goddesses of Glory; scenes from the history of Cupid and Psyche. The symbolism of the sculptural decor corresponds to the purpose of the building, expresses the ideas of prosperity and progress: Ceres, Apollo, the goddess of Glory — on the building of the City Duma; musical instruments and theatrical masks — on the theater building; plots symbolizing various types of activities — on the building of the Property Pledge Society; attributes of trade, industry, sciences, arts, mascarons of Hermes and his caduceus, cornucopia — on tenement houses; Hercules, Dejanira, Omphala, Aphrodite’s mascarons are on the mansions. There is a “universalization” of the mascarons of Hermes and his caduceus, which are used everywhere, regional motifs appear (bees, salting fish), the use of neo-style decor on the building, reproducing the type of kuren, is noted. Stylistically, the sculpture is focused mainly on classicism and the Renaissance, using the techniques of mannerism, baroque, rococo. The prototypes are the motifs of the sculptural decoration of famous buildings in St Petersburg, Vienna, Berlin, Brussels, chronologically close to the monuments under consideration.

Experimental and numerical tests of cold-formed square and rectangular hollow columns

This paper summarizes the results of experimental tests and finite element simulations aimed at investigating the buckling response of cold-formed square and rectangular hollow columns. The material stress–strain curves of the tested columns have been derived from testing 83 coupons sampled from the flat and corner parts of the cross-sections, along with coupons containing the weld in both longitudinal and perpendicular directions. The experimental stress–strain parameters have been statistically processed to calibrate the parameters of Ramberg-Osgood and Giuffrè-Menegotto-Pinto material models. The cross-sectional geometry and geometric imperfections have been also measured for all tested profiles. The buckling resistance of 21 different pin-ended columns has been experimentally measured in order to examine the influence of the steel grade (both S275 and S355), the normalized slenderness and the shape of cross-section. Finite element simulations of the tested members have been carried out to investigate the influence of residual stresses and out-of-straightness imperfections on the buckling resistance of hollow profiles. The buckling resistance evaluated on the basis of current EN1993-1–1 and the measured properties of the members are in very good agreement with the tested buckling resistances, even though slightly underestimating the resistance of stocky columns. The partial safety factor for flexural buckling has been evaluated using the method given by Annex D of EN 1990 and the results show that the computed average partial safety factor of curve “c” of EN1993-1–1 for cold-formed square and rectangular hollow columns is 0.92.

Tracking consolidation of out-of-autoclave prepreg corners using pressure sensors

A total of eight corner pieces with the four different thickness-to-radius ratio, one set using external and one set using internal tooling, were made to identify how unidirectional carbon-epoxy prepreg layers consolidate during lay-up and oven vacuum bag moulding. Flexible thin-film pressure sensors were introduced to both internal and external corner mould surfaces and pressure measurements were taken during hand lay-up. A second sensor was added to monitor how the pressure gradient changes during oven vacuum bag moulding. Time-lapsed pressure measurements found that the geometry-induced excess pressure on the external corners decreases during moulding, leading to some corner thinning but this effect is small. Meanwhile, internal corner parts saw significant ply-bridging in high thickness-to-radius conditions that could not be resolved during consolidation, resulting in corner thickening and voids. The flexible sensors are a viable option for in-situ pressure monitoring for potential meso-structural defects during composite product development or manufacture.

Study of the factors influencing load displacement curve of energy absorbing device by area division simulation

A pre folded energy absorbing device, which is the key device of energy absorption anti impact for roadway support, is tested by quasi-static compression and simulated. The energy absorbing device is divided into zones, and the influence of the area on the load displacement curve of the energy absorbing device is studied according to the area. It is found that the error of numerical simulation is within 5%, indicating that the finite element modeling procedure is appropriate for the problem analyzed here. The device crushes following the pre folded origami pattern in a stable progressive. The device was divided into four areas: the upper and lower opening region of the concave surface four corner parts; the other areas of opening regions; the middle fold edge; the surrounding four sides edge. Each area has effect on the first drop stage and the second rise stage of the load displacement curve. The middle fold edge area has an effect on the peak load value of load displacement curve. Four indicators of peak load, average load, load efficiency, and specific energy absorption were generated from the results of numerical simulation. The strength enhancement of corner region can ensure the energy absorbing device with low peak load and high mean crushing load. The other areas of opening regions affect the first descending and second ascending of the curve. The first rising stage bears the load from the middle edge.

Experimental and Numerical Study on Rapid Evacuation Characteristics of Staircases in Campus Buildings

In this work, we conducted downward evacuation experiments in four types of staircases under various smoke visibility conditions of the naked eye, wearing sunglass and wearing eyeshades. Ten male and ten female college students were recruited to conduct the evacuation as a single male, single female, two males supporting one another, two females supporting one another and one male carrying another on his back. The evacuation time on each floor was recorded. The corresponding evacuation models were established by Pathfinder and verified against the test data. The effects of evacuation crowd density and response time considering gender factors on the evacuation time were simulated using the models. The results show that under the experimental condition of low visibility, the curve of evacuation time presents a stable state, whose change with the increase in the floors is not obvious. The increase in the evacuation time under different visibility indicates that males have better adaptability to the environment than females. The curves of SSP (straight running stairs with platform) and DSS (double split parallel stairs) are smoother than those of DPS (double running parallel stairs) and CS (corner stairs), indicating less pressure and less congestion during evacuation. During the emergency evacuation, the crowd pressure on the platform of the staircases is small. The front section of the flight and the corner part of the staircases are prone to congestion during evacuation. Under the influence of gender factors, since the response time of males is longer than that of females, the smaller the proportion of males, the smaller the time growth rate considering the reaction time. With the increase in crowd density, the effect of response time on total evacuation time becomes smaller.

Texture evolution in a CrMnFeCoNi high-entropy alloy manufactured by laser powder bed fusion

Additive manufacturing (AM) techniques including laser powder bed fusion have been widely used to produce metallic components with microstructures and mechanical properties distinctly different from the conventionally manufactured counterparts. Understanding how AM parameters affect the evolution of microstructure, including texture, of these AM metallic components is critical for appropriate manipulation of their processing and therefore their mechanical properties. Here we conducted a systematic investigation of texture evolution of a face-centred cubic CrMnFeCoNi high-entropy alloy cuboid fabricated using laser powder bed fusion. Our results showed that the texture evolutions along the build direction were different between the corner and central parts of the sample. Detailed analysis suggested that the texture evolution is closely related to local thermal gradient, which is a property that can be manipulated through changing AM parameters. The different textures lead to the significant variations of mechanical properties within the sample.

Kinetics‐Controlled Synthesis of {100}‐Facet‐Enclosed Gold Quasi‐Square Nanosheets with Curved Edges

AbstractWe report the preparation of gold (Au) nanosheets with a quasi‐square morphology and curved edges (Au QSNSs). The atomic packing on the edge, corner, and central part of an individual Au QSNS is carefully observed via spherical aberration corrected high‐resolution transmission electron microscopy, and the atomic‐resolution images confirm the dominant presence of {100} facets on all these regions. Such type of two‐dimensional nanostructure is of great interest, as conventional gold nanoplates/nanoprisms are mainly enclosed with {111} facets on upper/bottom faces. The use of glutathione and octadecyltrimethylammonium chloride as the shape‐directing agent and the capping agent, respectively, at appropriate amounts, together with a dropwise addition of Au precursor at controlled rate, have been validated to be crucial for the formation of such a unique two‐dimensional nanostructure. When acting as electrocatalysts for the methanol oxidation reaction in alkaline medium, the Au QSNSs/C exhibited noticeable enhancement, compared to spherical counterparts, in terms of mass activity, reaction kinetics, and long‐term durability, demonstrating their structural advantage.

Effect of cold-form and tensile strain rate on mechanical properties of Q345 steel at elevated temperatures

In recent years, cold-formed steel has been extensively used, and the mechanical properties of cold-formed steel at elevated temperatures have been received considerable attention. However, little research on mechanical properties of the corner parts at elevated temperatures has been published. Meanwhile, the tensile strain rates adapted in the previous research on cold-formed steel are different, and the effect of this factor on mechanical properties was rarely investigated. In order to get a deeper understanding of the mechanical properties of cold-formed Q345 steel at elevated temperatures, an experimental investigation on flat and corner parts in cold-formed Q345 sections with two nominal thickness of 1.5 mm and 2.5 mm under three different tensile rates, 0.06/min, 0.6/min and 1.2/min, was carried out at elevated temperatures ranging from 20 °C to 800 °C. The effects of tension strain rate, cold-forming and thickness on mechanical properties of Q345 steel were systematically studied. Then the test results were compared with the prediction results provided by the current design standards and the other researchers. Furthermore, prediction equations were proposed to determine the mechanical properties of cold-formed Q345 steel.

Failure behaviors of 3D braided composites with defects in different locations under low-velocity impact compression

This paper aims to investigate the effects of the impurity defects in different locations on the transverse compressive behaviors of three-dimensional (3D) braided carbon fiber/epoxy composites under low-velocity impact. The composites with defects in different locations were prepared by placing polytetrafluoroethylene particles at the bottom surface, corner and center parts, respectively. The compression test was implemented with the drop-weight impact method. The failure morphologies were characterized using high-speed photography and micro computed tomography (Micro-CT). A mesoscale finite element model considering the defect was developed to enhance the physical understanding of the compression process. It is found that defects located at the corner zone and the central zone have a greater impact on the compression behavior of the 3D braided composite than the defect located at the bottom surface part. The defects at the corner and center zones reduce the compressive strength of the composite, increase the failure area, and cause severe damage to both the yarn and resin. In addition, the defect causes local stress concentration on the surrounding yarns. The defects in different locations cannot change the main shear failure mode of the 3D braided composite. It is shown that great attention should be given during the manufacturing or detection process to avoid such a deterioration effect of defects located in those zones on composite strength.

Ray tracing method for ultrasonic array imaging of CFRP corner part using homogenization method

A reliable nondestructive evaluation technique that can effectively detect and quantify the internal defects of corner parts in complex-shaped carbon fiber reinforced plastic (CFRP) structures is highly demanded for assuring safety and reliability of safety-critical structures. The conventional methods generally utilize normal incidence ultrasound and suffer from poor image quality due to the unfocused beam. To produce a fully focused image of the CFRP corner part, the delay-and-sum total focusing method (TFM) is preferred. The prerequisite for TFM imaging is to calculate ultrasonic ray paths, which is challenged by the curved shape, elastic anisotropy and multilayered microstructure. In this paper, the complex ultrasonic ray paths transmitting through the corner parts of CFRP structures from the concave side are calculated for ultrasonic array imaging. A ray theory-based homogenization method is firstly proposed to describe the wave velocity distribution of corner parts, which is critically important to the subsequent ray tracing calculation. A ray tracing method based on Dijkstra's algorithm is further developed for rapid calculation of multiple ray paths between two specified points when the ultrasound is incident from the corner's concave surface. To demonstrate the validity of ray tracing method, the TFM images of an CFRP corner part with side drilled holes (SDH) at different depths obtained using three different types of ray paths, are compared and analyzed. Results show that TFM images using ray paths with the minimum or maximum ultrasonic travel time present unsatisfactory image quality due to the obvious structural noises from ply reflections. In contrast, the signal to noise ratio of the image is significantly improved when TFM uses the ray paths with the weakest refraction, and all SDHs are detected and accurately positioned. This paper proves that the proposed ray tracing method is an effective method for imaging the corner parts of CFRP structures.

Pore-Scale Investigation of Microscopic Remaining Oil Variation Characteristic in Different Flow Rates Using Micro-CT

The main means of secondary oil recovery is water flooding, which has been widely used in various oilfields. Different flow rates have a great impact on the recovery ratio and the occurrence of remaining oil. Scholars have carried out extensive research on it, but mostly on the macro scale, and research on the three-dimensional micro scale is also limited by accuracy and a lack of accurate understanding. In this paper, micro-CT and core displacement experiments are used to intuitively show the occurrence state of remaining oil under different flow rates. Through a series of quantitative image processing methods and remaining oil classification methods, the occurrence characteristics of remaining oil under different flow rates are systematically evaluated and studied. The results show that: (1) As the displacement rate increases, the remaining oil saturation decreases (61%; 35%; 23%), but the remaining oil is more evenly distributed along the slice; (2) Two lower displacement speeds (0.003 mL/min; 0.03 mL/min) can reduce the volume of huge oil clusters under oil-saturated conditions, and the highest displacement speed (0.3 mL/min) can completely break up large oil clusters into small oil droplets. At the same time, the shape factor of the oil clusters also gradually increases; (3) The proportion of continuous remaining oil volume decreases, and the proportion of discontinuous remaining oil increases. Discontinuous remaining oil is the main production target of EOR; (4) After water flooding, the microscopic remaining oil is more inclined to the middle and corner parts of the larger pores.

Impact fracture energies of cold-formed steel square hollow section in and after fire

Charpy impact tests were performed on a cold-formed steel square hollow section at high temperatures and the ambient temperature after heating and cooling processes. The specimens were quarried from the flat and corner parts of the cross-section, respectively. High-temperature tests were conducted at 100–600 °C to verify the Charpy impact energies, including the blue-brittleness temperatures region (100–300 °C). In the ambient-temperature tests after the heating and cooling processes, the specimens were subjected to three heating and cooling methods: air cooling in a furnace from 600 to 900 °C (slow cooling process from the high temperature), quenching with water from 600 to 900 °C (fast cooling process from the high temperature), and air cooling outside of the furnace from 200 to 400 °C (slow cooling process from the medium temperature). The test results confirmed that the Charpy impact energy was not reduced after the slow cooling from the high temperature. However, the specimens subjected to either the quenching process from the high temperature or the slow cooling process from the medium temperature exhibited low Charpy impact energies.

Theoretical development and numerical analysis on the energy absorption of tapered multi-cell automotive structures under oblique impacts

In this paper, the crashworthiness characteristics of tapered structures with the uniform cells in cross-section subjected to oblique impacts are theoretically and numerically investigated. Benefiting from tapered structure simplifications into the corner, crisscross and T-shape parts in non-tapered structures, an engineering formula is proposed to estimate the mean crush load during structure deformations. In order to represent the behavior of the structures subjected to oblique impacts with regard to energy absorption, an oblique impact coefficient extracted from a comprehensive parametric study on the responses of the structures is considered in the formulation. In order to conduct the parametric study, a finite element model for the crumpling processes of different tapered and non-tapered structures with the uniform cells in the cross-section under axial and oblique impacts is prepared. The contributions of cell-number in the cross-section, taper angle, wall thickness, aspect ratio and impact angel on the peak crush load, mean crush load, specific energy absorption, crush force efficiency, transition thickness and transition impact angle in the crushing processes of the tapered structures with uniform cells in cross-section subjected to oblique impacts are presented and discussed. In particular case, the predicted structural energy absorption by the numerical model is compared with those experimental results that are available in the literature, indicating a good agreement.

Effect of Stagger Angle on the Three-Dimensional Separation Around a NACA65 Blade in a Decelerating Flow

In order to examine the fundamental characteristics of a corner separation in a decelerating cascade flow, an experimental apparatus was made and the three-dimensional separation around a NACA65 blade in a decelerating channel flow was investigated experimentally. Effect of stagger angle of 14 deg. and 10 deg. on the channel flow was focused on. The experimental investigation by the five-hole probe showed that the accumulations of the low energy fluid was seen around the corner part and the overturning flow due to the secondary flow existed for 14 deg. of stagger angle, whereas the accumulations of the low energy fluid were seen at around midspan for 10 deg. of stagger angle. PIV measurement showed that various focus-type separations were seen in the flow for 10 deg. of stagger angle and three-dimensional vortex structure was considered by using a vortex filament.