Form Of Tubes Research Articles

A novel path strategy design for precise 2D and 3D laser tube forming process; experimental and numerical investigation

Laser tube forming is a flexible process in which the heat generated by the laser beam scanning on the tube surface results in bending. Unlike laser sheet forming, few studies have been carried out on laser tube forming. This originates from the complexity of this process compared to the sheet forming, as well as the limited applicability of the forming strategies. In this research, a new idea is proposed based on the circular scanning method, which is presented in the form of two step-by-step and reverse schemes. Using this new strategy, it would be easy to precisely extract the laser scanning path for all 2D and 3D shapes. Since this strategy is programmable, it can be designed and implemented in a variety of forms only by changing the input parameters. In order to form a desired 2D and 3D shapes on a tube based on this idea, the proposed strategy was verified with both finite element and experimental methods. Fiber laser was used to form the AISI 304L tubes with certain parameters to achieve a specific bend angle. The experimental results are in a very good agreement with the designed path strategy and FE simulations, which confirms the efficiency and effectiveness of the path scanning strategy proposed in this paper.

Study on multi-roller rotary feed forming mechanism of spiral tube with uniform wall thickness

The positive displacement motor is one of the most widely used downhole power drill in drilling operations. In order to solve the problem of short life of conventional positive displacement motor and the inner spiral surface of stator with equal wall thickness is difficult to process. This paper uses multi-roller rotary feed forming process to process spiral tube with uniform wall thickness. According to the indoor processing experiment of 5LZ73 spiral tube and tensile test of material, the finite element model of multi-roller rotary feed forming spiral tube was established. The forming analysis of the 5LZ73 spiral tube was simulated by finite element method and compared with the experimental results. The results verify that the numerical simulation method can accurately analyze the forming result of the spiral tube. The forming of 5LZ54 spiral tube was studied by finite element method, and the influence of forming speed, rolling surface arcs the radius, forming temperature, rolling depth, and friction coefficient on the processing of spiral tube was analyzed. The results show that when the pipe outer diameter is 56 mm, the pipe wall thickness is 5 mm, the rolling depth is 3.3 mm, the forming speed is less than 15 mm/s, the hot forming is adopted, the arc radius of the 304 stainless steel rolling surface is 6.3 mm, and the radius of the arc of the 20G rolling surface is 7.1 mm, so the formed spiral tube is of good quality. The research results have important engineering significance for improving the processing quality of the spiral tube and improving the working performance of the positive displacement motor.

Vortex dynamics mechanisms of separated boundary layer in a highly loaded low pressure turbine cascade

This paper investigates the vortex dynamics in the suction-side boundary layer on an aero-engine low pressure turbine blade at two different Reynolds numbers at which short and long laminar separation bubbles occur. Different vortical patterns are observed and investigated through large eddy simulation (LES). The results show that at the higher Reynolds number, streamwise streaks exist upstream of separation line. These streaks initiate spanwise undulation in the form of vortex tubes, which roll-up and shed from the shear layer due to the Kelvin–Helmholtz instability. The vortex tubes alternately pair together and eventually distort and break down to small-scale turbulence structures near the mean reattachment location and convect into a fully turbulent boundary layer. At the lower Reynolds number, streamwise streaks are strong and the separated flow is unable to reattach to the blade surface immediately after transition to turbulence. Therefore, bursting of short bubbles into long bubbles can occur, and vortex tubes have larger diameters and cover a part of the blade span. In this case vortex pairing does not occur and vortex shedding process is promoted mainly by flapping phenomenon. Moreover, the results of dynamic mode decomposition (DMD) analysis show a breathing motion as a source of unsteadiness in the separation location, which is accompanied by the flapping phenomenon.

Robust Perpendicular Skyrmions and Their Surface Confinement.

Magnetic skyrmions are two-dimensional magnetization swirls that stack in the form of tubes in the third dimension and which are proposed as prospective information carriers for nonvolatile memory devices due to their unique topological properties. From resonant elastic X-ray scattering measurements on Cu2OSeO3 with an in-plane magnetic field, we find that a state of perpendicularly ordered skyrmions forms, in stark contrast to the well-studied bulk state. The surface state is stable over a wide temperature range, unlike the bulk state in out-of-plane fields which is confined to a narrow region of the temperature-field phase diagram. In contrast to ordinary skyrmions found in the bulk, the surface state skyrmions result from the presence of magnetic interactions unique to the surface which stabilize them against external perturbations. The surface guiding makes the robust state particular interesting for racetracklike devices, ultimately allowing for much higher storage densities due to the smaller lateral footprint of the perpendicular skyrmions.

The effects of auto-tempering martensite on mechanical strength of a microalloyed steel containing boron and titanium

Oil Country Tubular Goods (OCTG) steels are used in the form of tubes in the casing column of the oil well walls and exhibit tempered martensitic structure after quenching and tempering. In these steels, due to the high cost of chromium, nickel and molybdenum, an alternative is the replacement of these elements by boron, which increases the hardenability. In order to maintain the efficiency of boron in solution during the quenching, it is necessary to add titanium to form titanium nitrides (TiN), which inhibit austenitic grain growth and avoid the formation of boron nitride. Another factor is to evaluate the effect of heat treatment on the mechanical properties of this steel. In the present study were evaluated the microstructure, hardness and tensile properties of a microalloyed hot rolled steel containing boron and titanium after heat treatments. Samples of a coil were quenched at 850 and 1050°C and then tempered at 200 and 600°C. The results show that the hardness, yield stress and tensile strength after austenitization temperature at 1050°C are smaller, due to the formation of auto-tempering martensite in the quenching.

ПРИМЕНЕНИЕ ВЫСОКОТЕХНОЛОГИЧНОГО СПЛАВА В-1341 СИСТЕМЫ Al–Mg–Si ДЛЯ ТРУБОПРОВОДОВ ИЗДЕЛИЙ АВИАЦИОННОЙ ТЕХНИКИ

In this paper a task in developing of industrial production of cold-worked thin-walled tubes from high-tech aluminum alloy V-1341 of Al–Mg–Si system was accomplished. Tubes are purposed for application in hydraulic and air conditioning systems of aircraft products. Results of investigation of the structure and mechanical properties of tubes during their technological process and heat treatment are presented. Forming of tubes was performed and construction elements of pipelines were produced, which are identical to pipelines of commercial airplanes.

Flaring Forming of Small Tube Based on Electromagnetic Attraction

Electromagnetic forming (EMF) is a kind of high-energy-rate forming technology which uses pulsed electromagnetic forces to achieve rapid plastic deformation of workpieces. It can significantly improve the forming limit and formability of light-weight alloys and has been widely used in the field of tube forming. However, in the existing tube forming systems, the electromagnetic force between the tube and the coil is mainly dominated by a repulsive force. When flaring the tube, the coil must be placed inside the tube, which is not suitable for the forming of small tubes. In order to solve this problem, a method of flaring small tube with an outer coil is developed, where the coil current is generated by a dual-power supply system and a significant attractive electromagnetic force between the coil and the tube is produced for flaring forming. The feasibility of the method has been demonstrated by both numerical simulations and experiments. It has been shown that the flaring of an A1060-O aluminum alloy tube with diameter of 20 mm can be successfully realized, and the maximum radial deformation is about 4.88 mm. Meanwhile, it has been pointed out that the performance of tube flaring can be further improved by changing the relative position of tube and coil and the discharge voltage value of the dual-power supply system. The obtained results provide a new flaring tool for small tubes and expand the application of electromagnetic forming technology in tube processing.

Locally heat-assisted torsion forming of metal tubes for improvement of mechanical properties based on microstructure control

A locally heat-assisted torsion forming process for metal tubes is proposed and integrated in the conventional dieless drawing process. The part of the tube heated by a laser is subjected to torsion deformation due to the difference in the rotation speed of chucks. Pure aluminum tubes A1050 are used in the experiments, and excessive torsional deformation causes unstable deformation. The microstructure is controlled by the amount of torsion. The strength, ductility, and Lankford value are enhanced by the microstructure control in the proposed process. The process can be applied to the continuous mass manufacturing of metal tubes with high performance.

A short review of pyroducts (lava tubes)

Lava tubes and caves, when accessible for man, are very common in volcanic environments and poorly known to non-specialists. This short overview presents the distribution and forms of lava tubes, their speleothems and mineralogy and modes of formation. Studies of lava caves outside of Earth currently are a topic of great interest, as they may be potential locations for some life forms and future bases in space exploration. Basic features of lava tubes are illustrated with reference to the longest lava cave in the world, Kazumura Cave, in Hawaii.

FE Analysis of Effect of Variation in Coil length and Coil-tube Relative Positions on Establishment of Magnetic Fields and Distribution of Velocities in Electromagnetic Forming of Muffler Tube

The electromagnetic forming (EMF) process is a high energy rate process that uses magnetic forces to deform the metal workpieces. It also involves high velocities and high strain rates. It is tough to find out these process parameters experimentally, which proposes the need for numerical models. The EMF of muffler tube is a novel technique of manufacturing a single piece of component of the desired shape, which eliminates the disadvantages of conventional manufacturing techniques. This paper presents an FE model to observe the distribution of the magnetic field and velocities that drives the muffler tube. The coil-tube axial position is significant in the EMF process as the magnetic field produced is not uniform along the length of the coil. In the analysis of EMF processes, it is essential to able to estimate the magnetic field generated along the length of the coil. The presented coupled FE model can estimate the magnetic field and impact velocity generated during different coil-tube positions and discharge energies. The developed model is validated with deformation obtained in experimental runs. The simulation results show that to deform the aluminium tube minimum of 3 T magnetic field or a minimum of 87 m/s velocity is required. It is found that the coil having 100 mm length is giving more uniform pressure compare to other lengths. It is also observed that with the use of 100 mm length coil and amongst all coil-tube positions when offset between coil and tube relative position is zero, it develops the uniform distribution of magnetic field and velocities at a required area which results in maximum deformation compared to other positions. The development of such an FEA model helps to eliminate empirical investigation to discover the magnetic field and velocities involved in the process.

The application of the elastic tube with the specific cross section form in the linear peristaltic pump

The article presents a study of the tube form influence on performance of the peristaltic pump with the linearly placed tube and several pushers squeezing it in the transverse direction. The coupled numerical simulation of fluid flow and solid domain deformation was carried out using the software, based on the finite volume method. The cross sections with surface protrusions of two different types are considered for numerical simulation. The simulation results have shown that protrusions without a smooth transition at the tube walls reduce the compression ratio of the tube and therefore yield the flow rate reduce. Protrusions with s smooth transition at the tube walls on the contrary increase the flow rate in a high pressure range. Higher flow rate and pressure values achieved in the case of surface protrusions placed in the first compression region of the tube only. Comparison of pump characteristic curves shows that the use of tube surface protrusions can significantly increase the energy efficiency of the pump.

Three-dimensional finite element modeling of rotary-draw bending of copper-titanium composite tube

The copper-titanium bimetallic composite bent tube, which could integrate the advantages of physical, chemical, and mechanical properties of two materials, shows an urgent application demand prospect in mechanical manufacturing, marine operations, and other industrial fields. This paper develops a research on the modeling of rotary-draw bending of copper-titanium composite tube by using two kinds of grid elements S4R and C3D8R, respectively. The contact problem of base tube and covered tube is set as coulomb friction contact mode, whose optimal friction coefficient is obtained by pressure-shearing experiment and its simulation. The springback model is established by considering the contact action of the two tubes. Finally, the S4R shell FE model is compared with the C3D8R solid FE model from the two aspects of section deformation and springback. It is found that the shell element model is accurate in predicting the springback and section deformation, while the solid element model has a large deviation from the experimental results in predicting the section deformation. In order to gain a deeper understanding of the plastic deformation behavior of the bimetallic composite tube, the tangential stress, equivalent stress, equivalent strain, and damage values have been studied. Results show that (1) there is no significant uneven deformation between the base tube and the covered tube, which will not produce obvious wrinkling and section distortion even without the filling of the mandrel dies. (2) Sliding and stratification are existing between the base tube and the covered tube in the bending process. (3) The force of the dies on the base tube is transmitted through the side surface contact between the base tube and the covered tube. (4) The maximum damage value of the covered tube is larger than that of the base tube. This research will promote the development of precise plastic processing technology and play a role in the research of secondary plastic forming of metal composite tubes.

SORPTION OF MERCURY(II) AS A COMPLEX WITH KARMOAZIN ON ANIONITE AV-17-8 IN DYNAMIC MODE

In present paper, the kinetic features of mercury(II) adsorption from dilute aqueous solutions in a dynamic mode was studied. Using dynamic and kinetic curves that take into account the change in the rate coefficient of the sorption process versus its duration, the mechanism of the formation of adsorption layers in the sorption column during the sorption of mercury (II) in the form of its complex with 4-sulfo-2-(4′-sulfonaphthalene-1′ -azo)naphthol-1 (Carmoasine) which formed after coresponding redox-reaction by surface of the organopolymer anion exchanger AV-17-8 in dynamic mode. Azo dye carmoazine, which is a selective reagent for mercury(II), was used for its preliminary binding to a strong complex prior to sorption removal. The main process that determines the adsorption interaction in the studied system is the electrostatic attraction of the anionic complex to the positively charged surface of the anionite and the formation of a strong monolayer. The additional fixation of complex is due to the hydrophobic interactions between its molecules and the phenyl radicals of the AV-17-8 matrix. Based on the calculated mass transfer coefficients of the sorption process and the corresponding sorption isotherm, the optimal conditions for the extraction of the complex are established, namely: the volumetric rate of transmission of the sorbate through the sorption column is at least - 2 cm3/min; column diameter - 10.0 mm; the minimum weight of the sorbent is 0.05 g; the diameter of the ionite grains is 0.43 ÷ 0.50 mm. Based on the complex of the experimental results obtained and their interpretation, taking into account the known provisions, a mechanism of sorption in the dynamic mode and the formation of adsorption layers in the studied system was proposed. The data obtained can then be used to develop a test system in the form of an indicator tubes and as well as for quantitative sorption-spectroscopic determination of mercury(II) in various categories of waters.

Heat engineering properties of energy-efficient material based on plant additives (dried hogweed)

Introduction. The articlecompares the heat engineering properties of construction materials: high-strength concrete, ordinary concrete, and two concrete samples containing a vegetable additive, dried stem fragments of hogweed (Heracleum sosnowskyi). The first sample contains the additive in the crushed form, while the second contains the additive in the form of tubes. The research to estimate heat conduction in the four samples under unsteady conditions.
 Materials and methods. The thermal diffusivity of two samples with plant additive is determined using a comparative physical experiment. When determining the thermal properties, the accumulating component of the enclosure is taken into account what leads to a long delay in the temperature variation over time. DS18B20 digital temperature sensors connected to an Arduino Uno board were used to measure the temperature. The experiment was carried out in the Challenge 250 chamber at an initial temperature of 20 ºС. Then the chamber temperature was lowered to 0 ºС within 30 minutes. In the next period, the temperature dropped from 0 ºС to –10 ºС. The data obtained are of interest for improving the energy efficiency of buildings.
 Results. The experiments showed that the tubular-hogweed sample is close to high-strength concrete by its heat engineering properties. The material thermal diffusivity affects the amplitude of temperature fluctuations and the accumulating capacity of the wall.
 Conclusions. It is established experimentally that at lower thermal diffusivity of a hogweed-containing sample, the amplitude of temperature fluctuations increases. This indicates a greater time lag, just as in the case of a high-strength concrete sample. When using the hogweed as an additive, we obtain a heat-resistant minimum-cost material for enclosures. Considering an issue of the energy efficiency in construction and existing additives to concrete, the researchers have reached the conclusion that it is efficient to use the dried hogweed as the plant additive.

Research progress of steel tube rubber concrete

As a new form of concrete-filled steel tube, this paper focuses on the experimental research of the axial pressure performance of steel tube rubber concrete members in recent years, explains and summarizes related research results of hysteresis behaviors and seismic performance. Then further work to be carried out is listed. Finally, the possibility and development trend of its application in practical engineering is discussed.

Investigation of the electromagnetic attractive forming utilizing a dual-coil system for tube bulging

The electromagnetic force between the tube and the coil is generally dominated by repulsive Lorentz force in the existing electromagnetic tube forming systems. In these cases, the coil has to be placed inside the tube for tube bulging, which makes it difficult to achieve when the inner space of the tube is not large enough to accommodate the coil. To solve this problem, a new electromagnetic tube bulging process with an external dual-coil system was developed in this work. According to both numerical and experimental studies, it has been demonstrated that the AA6061-O aluminum alloy tube with a diameter of 33 mm and a thickness of 1 mm can be attracted toward the coil, and the maximum deformation is more than 4 mm after a single discharge. Meanwhile, the tube deformation can be significantly increased by multiple discharges using the attractive forming process. Furthermore, a series of simulations and experiments were carried out to systematically investigate the attractive forming behavior of the tube under different discharge conditions, showing that the discharge voltages of the two coils and the current waveform controlled by a crowbar circuit have a great impact on the tube forming.

Wrinkling prediction of aluminum alloy tubes during reduced diameter compression forming

Wrinkling is a significant challenge associated with the forming of tubes via diameter reduction. The work reported herein employed elastoplastic principles to assess the external pressure diameter reduction forming process by generating a strain diagram showing the occurrence of critical instability. This diagram can be used to effectively predict the appearance of wrinkling defects during forming. The Donnell linear buckling theory together with a bilinear material model was used to derive an expression for the critical external pressure leading to wrinkling instability, employing constant tube end conditions and a uniform external pressure, and the effects of forming conditions and material parameters on wrinkling were explored. During experimental trials, AA6061 tubes were formed via diameter reduction in conjunction with varying heat treatment conditions using the solid granule medium forming process. A Vialux portable mesh strain tester was employed to collect relevant data to verify the critical instability points, and the effects of various factors on resistance to wrinkling were investigated. An analysis of the experimental results demonstrates that the conclusions of the theoretical analysis are correct.

Experimental investigation into the electropulsing assisted pulsating gas forming of CP-Ti tubes

Abstract A novel electropulsing assisted pulsating gas forming (EAPGF) process of commercial pure titanium (CP-Ti) tubes by using pressurized argon filled into a sealed tube was developed to optimize the process scheme and reduce the cost of die heating. The formability of CP-Ti tubes was tested on the self-designed innovative gas forming platform by applying three different frequencies of electropulsing. Based on the uniaxial tensile tests assisted by the electropulsing, the principle of EAPGF was modeled and interpreted by the generalized Johnson-Cook model. At first, the temperature variation of the experimental tubes assisted by electropulsing of three frequencies was measured and analyzed. High-frequency electropulsing will make the temperature rise steadily. Low-frequency electropulsing will cause a serration-shaped growth of the temperature. Moreover, the influences of the pulse duration and frequency on the forming pressure, the relative load, the expansion ratio, the shape deviation and the thickness distribution in the middle section were investigated. The relative load fluctuates periodically with an oscillation of temperature as well as internal pressure induced by electropulsing. In terms of the three frequencies, the higher bulging limit and more uniform deformation were observed in the condition of low frequency. From the result of microstructure analysis through EBSD, the low-angle grain boundaries (LAGBs) exhibit a strenuous increase attributed to the deformation assisted by electropulsing, with the higher increment at a lower frequency. Obvious dynamic recrystallization was observed at the electropulsing frequency of 1/20 Hz from the KAM distribution in the specimens. Finally, a modified EAPGF was suggested by adjusting pulsating hydroforming parameters by regulating the parameters of electropulsing. The relative load was adjusted to pulsate around 0.0577, and a typical adjustable CP-Ti tube with 60 % expansion ratio was successfully fabricated.

Development of a simulation model for the automatic optimization of tools for multi‐dimensional tube forming

AbstractThe increasing number of vehicle components and the advancing lightweight construction in manufacturing processes increasingly require a more flexible design of the exhaust tube geometry. The use of process supplementary simulations is necessary, in order to meet these increasing requirements in the future.The aim of this study is the development of a software tool for the simulation of multi‐dimensional tube forming processes by tube bending and tube embossing. Therefore, a graphical user interface was developed to build‐up and simulate the tube forming processes. The required material parameters for the numerical modeling were determined by means of tensile tests. The simulation models were successfully validated by comparing the numerical results with the experimental results. The influence of the workpiece and the forming tools were numerically investigated on the basis of the validated simulation models. Batch‐related tolerances could be identified as a serious source of deviations. Furthermore, experimental forming errors could be numerically reproduced and corrected by modifying the parameter settings. The tool variation increased the process knowledge and provided the basis for a subsequent optimization. The embossing structure could be optimized satisfactorily by specifying user‐defined requirements.

Converting circular tubes into square cross-sectional parts using incremental forming process

Abstract Incremental forming process is recently developed to form tubular parts. The fabrication cost and accuracy could be optimized if the effects of process parameters and the optimum values are specified. The aim of this research is using incremental forming of copper tubes to convert a circular tube into a square cross-sectional part. An experimental setup, consisting of a spherical forming punch and a fixture for clamping the tube is designed. The forming punch movement is controlled by a CNC machine. Full factorial design of experiments is carried out in order to determine the effects of process parameters including linear velocity, radial feed, and axial feed of the tool on the thinning ratio and the maximum outer diameter of the square cross-sectional parts. Results show that the radial feed has the major influence on the thinning ratio, while the axial feed plays the major role for the final profile. Increase of radial feed results in higher thinning ratio, and decrease of axial feed results in better shape conformity. Linear velocity does not have a significant effect on thinning ratio. Regression models are also given for predicting the determined responses.