Round Cross-section Research Articles

Wood-fibre composite connectors for roundwood trusses: structure and material

Timber structures and buildings made from sustainable forestry might be the solution for today's ecological challenges when their renewable materials are locally processed with low energy consumption in production. The current market shows a dominance of rectangular cross-sections in engineered timber solutions. Roundwood – a traditional material in the past – is no longer common due to a lack of applications in modern structures, lost knowledge in handcraft skills and the high costs of computerised numerical control-based manufacturing. However, solid timber with a round cross-section outperforms other engineered wood products, such as glued laminated products, in terms of energy consumption and environmental aspects. To overcome restrictions in joint technologies and to increase the usability of roundwood, especially in truss structures, a new type of connector was developed. The investigation was split into two research topics: the connection design in roundwood with modified bonded-in rods and the design of wood-fibre composite moulded connectors, which is described in this paper.

Influence of process layouts of multi-roll solid-liquid cast-rolling bonding process on circumferential performance uniformity during fabricating metal cladding materials

The twin-roll casting (TRC) process is typically used to fabricate laminated metal cladding strips with rectangular cross-sections, and it has the advantages of short flow, low energy consumption, green environmental protection, etc. Recently, a twin-roll solid-liquid cast-rolling bonding (TRSLCRB) process was proposed based on the TRC process to fabricate metal cladding materials with round cross-sections. However, the nonuniformity of heat transfer and mass transfer along the circumferential direction finally influences the performance uniformity. Therefore, a multi-roll solid-liquid cast-rolling bonding (MRSLCRB) process was proposed integrating cast-rolling bonding technology and multi-roll groove rolling technology. The steady-state thermal resistance network was established, and the influences of nominal roll radius, groove radius, and molten pool height on the heat transfer and mass transfer were studied systematically. 3-D steady-state thermal-fluid coupled simulation models of twin-roll, three-roll, and four-roll layouts were established. The results indicate that increasing casting roll number can improve the nominal cast-rolling velocity, service life of the casting roll, temperature uniformity, strain uniformity, and strain rate uniformity through regulating the heat transfer and mass transfer. Considering the manufacturing feasibility, the MRSLCRB equipment based on the three-roll layout was designed. Cu/steel cladding bars with uniform circumferential performance were fabricated, and the forming mechanism was revealed. The multi-field coupled analysis method provides a way to control heat and mass transfer uniformity, and the successful attempts of various typical metal cladding materials inspire exploring new forming processes.

Experimental study on the flexural behaviour of timber beams strengthened with high ductility and low cost hybrid fibre sheets

Timbers with defects are often used in historical buildings. However, the existing fibre sheet reinforcing technology for the timber beams is difficult to balance the strength, ductility and cost. This paper aims to develop novel high ductility hybrid fibre sheets for strengthening timber beams at a lower cost than available methods. First, four types of unidirectional and two types of bidirectional fibre reinforced polymer (FRP) sheets were designed and evaluated using scanning electron microscopy (SEM) and tensile tests. Then, the FRP sheets were used to make 68 timber beams with square and round cross sections for bending tests. Finally, parameter analysis was conducted to evaluate the enhancement law of specimens with different sheet layers, fibre types, reinforcement angles and interlaminar hybrid modes. The results show that the reinforcement angle of a round timber beam has a great influence on its ultimate bearing capacity, for which the recommended value range is 45°∼60°. Unidirectional fibre sheets with a fibre ratio of carbon fibre:aramid fibre:glass fibre = 2:1:1 have a positive hybrid effect on bearing capacity and can improve the ultimate deflection of timber beams by 69.2–115.4% with one layer. These research results can contribute to state-of-the-art knowledge about round and square section timber beams strengthened with hybrid fibre sheets and the conservation of timber structures.

Experimental validation of inviscid linear stability theory applied to an axisymmetric jet

We study the development of perturbations in a submerged air jet with a round cross-section and a long laminar region (five jet diameters) at a Reynolds number of 5400 by both inviscid linear stability theory and experiments. The theoretical analysis shows that there are two modes of growing axisymmetric perturbations, which are generated by three generalized inflection points of the jet's velocity profile. To validate the results of linear stability theory, we conduct experiments with controlled axisymmetric perturbations to the jet. The characteristics of growing waves are obtained by visualization, thermoanemometer measurements and correlation analysis. Experimentally measured wavelengths, growth rates and spatial distributions of velocity fluctuations for both growing modes are in good agreement with theoretical calculations. Therefore, it is demonstrated that small perturbations to the laminar jet closely follow the predictions of inviscid linear stability theory.

Assumptions for Modeling of the Hot Plate Welding Process Considering the Automatic Welding Machine Design

Drive and conveyor belts are widely used in processing and mining industries. One of their types, which are often used in light-duty applications, are the belts with round cross-section and several millimeters in diameter. They are often made of thermoplastic elastomers, in particular ofweldable polyurethane. Their production process requires to carry out the operation of joining the belt ends to obtain a closed loop. This operation is often carried out by means of butt welding utilizing the hot plate method. This process is often performed by hand using simple tools. Authors took an effort to design the automatic welding machine, which can make durable joints of this type automatically. The design works comprise control system configuration which calls for identifying the technological parameters of the process, being the reason for undertaking the research works on the hot plate welding process. The main aim of this activity was to formulate of the mathematical model of the hot plate welding of round drive belts which is necessary to identify the process parameters and the correlations between them. In the paper, the assumptions for the hot plate welding process modeling were presented. During their formulating, technical conditions were taken into consideration resulting from some of the characteristics observed in an automatic welding device prototype which had been implemented for industry production.

Shaking Table Test Study on the Earthquake Behavior of High‐Speed Railway Bridge Pier with Rounded Rectangular Cross Section

Rounded rectangular cross section piers were widely used for high‐speed railway (HSR) bridges in China. However, the performance of such piers under seismic scenarios has not been well studied. To study the earthquake behavior and damage of rounded rectangular cross section piers under different intensities of earthquake excitation, nine scaled pier specimens were constructed and tested on the shaking table. Experimental results show that the specimen remains elastic (no or slight damaged) for all experimental earthquake scenarios (from 0.45 g to 0.96 g). Finite element (FE) models were developed and validated by the experimental results. Using this FE model, the damage levels of these specimens under severe earthquake excitations (from 1.05 g to 1.95 g) were quantified. Numerical results show that the specimen in transverse direction shows no or slight damage, while repairable damage can be seen in longitudinal direction as the earthquake intensity increases from 1.05 g to 1.65 g. Repairable and unrepairable damage can be seen in transverse and longitudinal direction, respectively, as the earthquake intensity increases to 1.95 g. Researchers can make good use of these findings for better earthquake design or protection of this type of HSR piers in the future.

Impact of conductor assembly indentation on the fatigue properties of copper power cable wires

The production process of high voltage power cables includes the assembly of the conductor, which is composed of different layer of independent wires wound in helixes of opposite pitch for each subsequent layer. Each wire, which has an initial constant round cross section and is close to annealed conditions, is wound around the previous layer and the assembled layers are passed through a calibrated die which compacts the wires together. This process creates periodically spaced indents on the inner side of the wires and work hardens the material in the indented sections and their immediate proximity. Both the local and global strain distribution related to static loads as well as the fatigue properties of the wires are impacted by such process and its consequent geometrical and material inhomogeneities. In this work, strain-control fatigue results of copper conductor wire are presented. The non-uniform strain distribution caused by the inhomogeneities inferred by their manufacturing process is investigated with the means of digital image correlation. The "indentation" process is modelled with the use of explicit finite elements and the deformation of the virtual specimen obtained is compared with the experimental results.

Investigation of steel wire mechanical behavior and collaborative mechanism under high temperature

This study investigated the high-temperature mechanical properties and collaborative working mechanism of zinc-5% aluminum-mixed mischmetal alloy-coated steel strand cables (M-C cables) and internal steel wires by numerical analysis, based on the experimental data for the high-temperature mechanical properties of steel wire. The high-temperature mechanical properties of zinc-5% aluminum-mixed mischmetal alloy-coated steel (M-C steel) with round and Z-shape cross-section shapes were studied in the temperature range of 30–800 °C using the constant temperature loading test method. The two-stage Ramberg-Osgood model for M-C steel wires at elevated temperatures is proposed for modeling of the M-C steel wires. Furthermore, the equations for the reduction in the nominal yield strength, elastic modulus and ultimate strength for M-C steel wires at elevated temperatures are proposed. Numerical analysis and investigation of the high-temperature mechanical properties of normal M-C cables and locked M-C cables under eight temperature conditions are carried out. Based on the high-temperature constitutive relationship of the round and Z-shaped M-C steel wires obtained experimentally, the thermostatic drawing process is simulated at different temperatures for two types of M-C cables. The high-temperature stress-strain relationship between the two and the relevant high-temperature mechanical performance index were obtained. According to the numerical simulation results, the energy, contact stress distribution and radial displacement deformation of M-C cables under the different temperature condition were evaluated and analyzed. The collaborative working mechanism of M-C cabled affected by temperature was revealed.

Pulsation parameters of new and used milking liners with round cross section

Abstract. Milking machines equipped with new and used milking liners with a round cross section were studied. The used milking membranes were operated for 3 months on a farm for rearing 60 cows (Holstein cattle) with double milking per day. The experiment involved recording the standard pulsation phases “a”, “b”, “c” and “d” (in absolute units) in the frequency range from 1 Hz to 2.5 Hz, in a vacuum mode of 40 kPa and 50 kPa and at a pulsation ratio of 50/50%. It was found that the transients (phase “a” and phase “c”) are faster and the established phases (phase “b” and phase “d”) are longer in milking units equipped with used milking liners. The conclusions are related to the service life of the milking liners.

Pulsation parameters of new and used milking liners with round cross section

Pulsation parameters of new and used milking liners with round cross section

Process design and finite element analysis of multi-station two-roller cassette hot rolling for aluminum alloy 6061 wire

In this paper, a round-oval-round roller cassette wire rolling process of the aluminum alloy 6061 was studied for the process and the roller design evaluation. The elliptic groove of roller was designed for the stand of oval cross-sectional profiles. The billet diameter for this 10- stand rolling process simulation is 20mm. The diameters for the round cross-section profile stands are 16mm,12.8mm,10.2mm,8.2mm, and 6mm, respectively. The forming conditions for the CAE simulation is 400 °C for billet temperature, 0.45 for the constant shear friction factor, 20mm/s for the initial rolling speed. The CAE (Computer Aided Engineering, CAE) results had shown the maximum dimension deviation of the billet is less than 0.25 mm at the location of the roller gap and almost perfect match at the other locations. The maximum principal stress distribution on the cross section had shown a two third area was deformed under the rolling process. The CAE results had demonstrated the proposed process and die design was able to make the smaller wire with good geometrical accuracy without breaking the wire during the rolling process because of the more uniform stress distribution at the cross section of wire.

Active elements in the form of thin rods of square cross section for multichannel laser amplifiers

We study thermally induced phase distortions of laser radiation in active elements in the form of thin rods of square cross section. The absence of aberrations and beam quality deterioration is demonstrated for these elements, due to which they can be used along with rods having a round cross section, differing from the latter by much higher technological efficiency of fabrication and mounting in the cooling system. A concept of compact and reliable multichannel solid-state amplifier based on such active elements is proposed, which allows one to use a multichannel fibre laser as a master system.

Shear Bond Strength of Four Types of Orthodontic Retainers after Thermocycling and Cyclic Loading.

Objectives This study assessed the shear bond strength (SBS) of four types of orthodontic retainers after thermocycling and cyclic loading. Materials and Methods This in vitro, experimental study evaluated 120 extracted mandibular central and lateral incisors. The teeth were mounted in acrylic resin blocks in sets of three, such that the interdental contacts and positioning of the teeth resembled the dental arch. The acrylic blocks were divided into four groups (n = 10) for the use of 0.016 × 0.022-inch Bond-A-Braid® wire, 0.0195-inch twisted wire, 0.0175-inch coaxial wire, and 0.038 × 0.016-inch Ortho-Flex Tech® wire, as retainers. The retainers were bonded to the lingual surface of the teeth with Transbond XT adhesive in all groups, and the specimens underwent thermocycling and cyclic loading (125,000 load cycles applied to the incisal edge of the incisor tooth in the middle, simulating 6 months of clinical service). Any fracture in the process of aging was recorded. The teeth were then subjected to vertical loads applied along their occlusoapical axis in a universal testing machine to determine the SBS in Newtons. The adhesive remnant index (ARI) scores were also determined. Data were analyzed using ANOVA, the Monte Carlo chi-square test, and the Kruskal–Wallis test. Results Thermocycling and cyclic loading did not cause degradation or fracture of the retainers. The SBS and ARI scores of the four groups were not significantly different (P > 0.05). Conclusion The SBS of retainers with flat rectangular-shaped cross-section was similar to that of retainers with a round cross-section; thus, they have no superiority over each other in this respect.

A Novel Design Method of Heat Sink with Conjugate Heat Transfer by Free-Shape Channel Modeling

Heat sink is an indispensable and even hard-core device which ensures the reliability and lifespan of most electronic equipment. Geometry factor plays a crucial role in the heat sink design. This paper proposes a novel geometric modeling method for heat sink with conjugate heat transfer properties, which involves parametric design of the flow passage patterns and cross-sections. Two assumed serpentine cooling plates with round and quadrilateral cross-sections are utilized to validate the proposed method respectively. During modeling, the fixed geometry dimensions are divided into several degrees of freedom to promote the flexibility of geometry factor with regard to heat sink design. The Bernstein-Bézier function is utilized to define these degrees of freedom. The numerical simulations based on the orthogonal experimental design are carried out, and then the results are analyzed and compared. The experimental results revealed that the optimised design can be obtained by adjusting the relevant control coefficients, which further improves the performance of cooling plate effectively. This paper guides the heat sink design and provides an insight into the structure problems from the perspective of geometry parameterization.

Multi-Objective Optimization of Efficiency and Pressure Fluctuation for Vertical Inline Pump

Vertical inline pump is a single-stage single-suction centrifugal pump. In order to save the installation space, there is a bent pipe before the impeller. In this paper, to achieve efficient and stable operation of the pump, a multi-objective optimization of efficiency and pressure fluctuation on the inlet pipe of vertical inline pump was proposed based on Latin Hypercube Sampling. The geometric shape of an inlet pipe is controlled by the mid curve and the shape of cross section. The fifth-order Bezier curve was adopted to fit the mid curve and a round cross section was set. Totally 7 design parameters of the inlet pipe were selected as design variables, and the pump efficiency and the pressure fluctuation amplitude at the tongue were set as the optimization objectives. 36 groups of sample points were obtained from Latin hypercube sampling (LHS). The results showed that at design flow rate, the efficiency increased from 77.60% to 79.33%. Comparing with prototype, the pressure fluctuation amplitudes of main frequency at two monitoring points were decreased by 0.89% and 9.15%. It was observed that the profile of inlet pipe has an obvious influence on the pump performance and unsteady flow characteristics. Therefore, the profile of inlet pipe will be the key component for the optimization of vertical inline pump, and this study can provide theoretical guidance for researching the hydraulic efficiency and unsteady pressure fluctuation.

Cross-section Effect on Mechanical Properties of Al A356 Alloy Tensile Specimens

Tensile testing is an effective method to evaluate the mechanical property of aluminum alloys. In the present work, two types of standard tensile specimens with round (RD) and rectangular (RT) cross-sections were cast in the same permanent die and their solidification characteristics, microstructures, and mechanical performances were studied. The equilibrium solidification and Scheil solidification models of the studied A350 alloy were calculated by Pandat software. The experimental solidification and cooling temperature analysis revealed that the solidification platform and supercooling of the RD sample were 3 seconds wider and 1.2 °C bigger than those of the RT one. The microstructural analysis expressed that the mean grain diameter and secondary dendrite space of RD were 1.52 and 0.75 um smaller than those of RT; hence, the strength and elongation of RD were better than those of RT. Brinell hardness tests and differential scanning calorimetry were also carried out. According to the obtained data, the round specimen was selected for tensile test because of its superior performance.

Preparation and Characterization of Carbon Fibers from Lyocell Precursors Grafted with Polyacrylamide via Electron-Beam Irradiation.

Carbon fibers, which act as reinforcements in many applications, are often obtained from polyacrylonitrile (PAN). However, their production is expensive and results in waste problems. Therefore, we focused on producing carbon fibers from lyocell, a cellulose-based material, and analyzed the effects of the process parameters on their mechanical properties and carbon yields. Lyocell was initially grafted with polyacrylamide (PAM) via electron-beam irradiation (EBI) and was subsequently stabilized and carbonized. Thermal analysis showed that PAM grafting increased the carbon yields to 20% at 1000 °C when compared to that of raw lyocell, which degraded completely at about 600 °C. Stabilization further increased this yield to 55%. The morphology of the produced carbon fibers was highly dependent on PAM concentration, with fibers obtained at concentrations ≤0.5 wt.% exhibiting clear, rigid, and round cross-sections with smooth surfaces, whereas fibers obtained from 2 and 4 wt.% showed peeling surfaces and attachment between individual fibers due to high viscosity of PAM. These features affected the mechanical properties of the fibers. In this study, carbon fibers of the highest tensile strength (1.39 GPa) were produced with 0.5 wt.% PAM, thereby establishing the feasibility of using EBI-induced PAM grafting on lyocell fabrics to produce high-performance carbon fibers with good yields.

Testing of thin-walled cylindrical shells made of steel 45 in solving the problem of stability

The theory of shell stability beyond the elastic limit is considered when studying the issue of testing, diagnostics and quality control of materials made of steel shells of round cylindrical cross-section. Since, depending on the history of the loading process of an elastic-plastic system, its final deformation corresponding to the same external load is different, by studying the inelastic stability problems should proceed from the analysis of simple combined loading processes that lead to different critical deformations. Not only the question of the loading history, which leads to the minimum value of critical loads, but also the question of choosing and implementing such a loading history of a given system, which gives it the maximum value of the stability limit and the load-bearing capacity of the material, is solved. Innovative methods are proposed for solving the problem of shell stability in tests of complex loading of steel cylindrical shells by internal pressure, compression and torsion in the direction of structural mechanics and mechanics of deformable solids, implemented on an experimental complex. The obtained results allow us to determine the loss of stability of the material beyond the elastic limit with a sufficient degree of accuracy for a given cross-section and the loading trajectory of a cylindrical thin-walled shell made of steel 45, while the correctness of the obtained results is justified experimentally.

COMPREHENSIVE FILTRATION SYSTEM FOR CLOSED HYDROSYSTEMS OF AGRICULTURAL EQUIPMENT

The article the issue of increasing the durability and reliability of units of closed hydraulic systems of agricultural equipment by ensuring the purity of the working fluid is considered. The analysis of existing systems of filtration of working liquid for the closed hydraulic systems of the agricultural equipment is resulted. It is noted that the basis of the created and implemented filtration systems are filtration installations in pressure mains, including with automatic washing, which provide filtration fineness up to 50 μm, filter elements which have high strength, reliability and are capable of countercurrent washing at working pressure of hydraulic system. The complex system of filtration of working liquid for the closed hydraulic systems of the agricultural equipment is offered. The filtration system of the working fluid provides for the use of filters with backwash and filtration elements with a slit-like brass wire of round cross section. The total length of the filtration gap of one filtration element with a width of 0.05 mm is 40 m The filter provides passive cleaning technology - countercurrent flushing, as the simplest in design, easy to manufacture and sufficiently efficient and cheap. Feature of the filtration installation is a possibility of washing of its filtration elements by a countercurrent of working liquid. The signal for flushing is the occurrence of a pressure drop on the filter, which can be used to judge the degree of contamination and the readings of manometers installed at the inlet and outlet of a closed hydraulic system of agricultural equipment. It is noted that the developed complex filtration system for closed hydraulic systems of agricultural equipment will increase the reliability of control hydraulics at least twice and reduce costly downtime of agricultural machinery due to failure of sealed elements of hydraulic equipment.

Plastic Joints in Bridge Columns of Atypical Cross-Sections with Smooth Reinforcement without Seismic Details

In seismically active areas, knowledge of the actual behavior of bridges under seismic load is extremely important, as they are crucial elements of the transport infrastructure. To assess their seismic resistance, it is necessary to know the key indicators of their seismic response. Bridges built before the adoption of standards for seismic detailing may still contain structural reserves due to the properties of the used materials and construction approach. For example, smooth reinforcement which is found in older bridges due to the material properties, detailing principles, and lower bond strength compared to ribbed reinforcement, allows for greater deformations. In bridges, columns are vital elements employed in the dissipation of seismic energy. Their cross-sections often deviate from the regular square, rectangular, or round cross-sections, which are typically found in building. Based on the behavior of the columns in the vicinity of potential plastic joints, we can determine their deformability. This paper presents an experimental study of seismic resistance indicators around a potential plastic joint for a column with an atypical cross-section, without seismic details and with smooth reinforcement. The experimental results are compared with the numerical and analytical, but also with the experimental results on samples with ribbed reinforcement. Conclusions are made about the behavior of such column elements and their seismic resistance indicators, allowing for the application of an analytical or numerical method with realistic material and element properties and derivation of correction factors due to the effect of the smooth-reinforcement slippage from the anchorage area.