Pipe Bend Research Articles

A transferred hybrid surrogate model integrating Gaussian membership virtual sample generation for small sample prediction: Applications in metal tube bending

The high-performance virtual sample generation (VSG) method has been extensively introduced to solve the problem of small sample sizes. Data distribution information is a key element of current VSG methods at the data-driven level. Herein, we propose an improved VSG method with a Gaussian distribution and explore the relationship between the Gaussian function and data expansion. To obtain more feasible virtual samples, information expanded based on the Gaussian membership function (GMIE) was established. For further improvement, a hybrid surrogate model based on transfer (THSM) is proposed, which differs from the general hybrid surrogate model (HSM) methods that only mix single models. Using a prevailing evaluation method, our proposed method, which combines a Gaussian membership function with a hybrid surrogate model, outperforms other competing approaches in 12 numerical cases owing to its feasibility and efficacy. Additionally, the proposed approach is applied to a metal tube rotary draw bending (RDB) prediction problem to illustrate its ability to support complex engineering designs.

Integrated Assessment of Discrepancy Between Tracheal Tube and Tube Exchanger as Advancement: A Manikin Simulation Study.

Advancing a tracheal tube over a tracheal tube exchanger into the trachea frequently causes difficulties because of the tube impingement on laryngeal structures. In the present study, we measured the resistance of tube advancement both objectively and subjectively with a variety of combinations of tube exchanger sizes and tracheal tubes using a manikin simulator. Lubricated 7.5 mm ID standard and Parker Flex-Tip (PFT) tracheal tubes were railroaded over the tube exchangers (OD 1-6 mm) into the trachea through the oral route in a manikin. Consequently, 12 combinations of tracheal tube-exchanger tube assemblies were evaluated. Tube advancing resistance at the laryngeal inlet was subjectively evaluated. The objective tube advancing resistance (force) at the laryngeal inlet was evaluated using a digital force gauge. The execution of each tracheal tube-exchanger trial was conducted 10 times. With a 1-mm tube exchanger, all intubation attempts with both standard and PFT tubes failed. Esophageal intubation or severe impingement at the right arytenoid accompanied with a bent tracheal tube was observed. With a 2-mm tube exchanger, during intubation with a standard tracheal tube, rotation of the tube was sometimes required; however, all other intubations were done without problems. When PFT tubes were used, all intubation attempts were performed without problems. The rest of the trials were successfully performed regardless of the combinations of tube exchangers and tracheal tubes; however, one attempt of intubation with a combination of a 5 mm tube exchanger and a standard tracheal tube required withdrawal and rotation of the tube because of impingement at the epiglottis. In cases where there was no gap resistance, which means tube advancing resistance generated by a gap between an introducer and a tracheal tube, the pressing force was approximately less than 10 N. However, in the cases requiring some interventions to overcome the gap, the pressing force reached around 15 N. When intubation failed, for example when the tube bent, or esophageal intubation, the pressing force reached around 30 N. Impingement due to the gap between the tube exchanger and the tracheal tube is thought to occur in the PFT tube less frequently. Once an impingement occurs, we can feel approximately twice the amount of resistance as usual, which may be a chance to consider taking some interventions. When the impingement is not released, regardless of interventions, excessive force may result in esophageal intubation or tracheal injury.

Exploring bundle bamboo split technique in bending dendrocalamus asper for landscape structure

Bamboo is one of the fastest-growing natural construction materials and is locally available in most developing countries, including South America, Africa, and Asia. Bamboo is a “green gold” plant in the tropical forest. It is a fast-growing monocotyledon species belonging to the Gramineae family (Bambusoideae) and requires a short time for re-production. Bamboo’s physical strength provides builders from ancient times until today an opportunity to use bamboo as a natural and sustainable construction material for building houses and structures. Due to its capability to bend, bamboo is the most preferred material in vernacular construction and lately in Southeast Asia countries which borne new trend in building design. The built-environment professionals, namely landscape architects, architects, and engineers in Malaysia, still lack knowledge of bamboo, especially on bending capabilities, as one of the sustainable construction materials. Less concern was given to researching the capabilities of bamboo’s ability to bend, even though its strength is more than steel and provides various design opportunities compared to other sustainable materials. Different types of bamboo present different strength capacities. Therefore, the aims of this research is to compare and determine their strength capacity, bending criteria and species suitability for design and construction in Malaysia. This paper collects published literature on experimental studies on the different methods of Hot and Cold Bending Methods which allow bamboo to bend to suit designer needs and concentrate on Malaysian Dendrocalamus asper (Buluh Betung), which considered as tough and durable species, as the primary construction material for landscape structures. Bundle Bamboo Split (BBS), identified as one of the bending techniques adopted for an experimental project, using BBS of 0.8m radius, produces a prototype for a landscape structure. The findings indicate observation of works by a team of craftsmen trained by an expert in bamboo construction who used to produce bamboo structures from Bali, Indonesia, highlighted tools and procedures in bamboo construction. In short, this paper will also enhance the use of bamboo as an accessible, durable, creative and sustainable construction material that represents the local identity of Tropical Malaysia Landscape Architecture.

Research on thermal stratification of surge line in the marine reactor based on fluid-solid thermal coupling model

Due to the requirements of ship movement, the power of the marine reactor is constantly changing, and the expansion and contraction of the primary coolant make the fluid flow in and out through the surge line. This paper establishes a fluid-solid thermal coupling model for the thermal stratification of a Marine reactor surge line. The low Reynolds number eddy viscosity model and the curvature modification of the bending pipe are used in this model. Qiao experiment is provided to verify the model's applicability to the thermal stratification analysis. The typical working conditions of the Marine reactor are analyzed, and the results show that: the temperature difference between the top and bottom of the pipe changes constantly with the fluctuation of the fluid, the maximum temperature difference in the horizontal section is 59.6 K, and the maximum temperature difference in the vertical area is 23.9 K. The maximum stress fluctuation of the horizontal section is 36 MPa, while that of the vertical section is 5 MPa. In the non-destructive testing, many small pits were found in the horizontal section of the pipeline, while no obvious damage was found on the surface of the vertical section, which is consistent with the results of our numerical analysis.

Mechanical properties and application of glass fiber reinforced polyurethane composites communication lattice tower

To address the deficiencies in traditional communication towers in mobile communication engineering, such as heavy weight, easy corrosion and poor durability, this study proposes replacing traditional communication towers with GFRP communication lattice towers with lightweight, high-strength and good durability. Firstly, GFRP material test and GFRP circle tube bending capacity test are conducted. The maximum bending moment that can be subjected to the anchorage end of GFRP circular tube is 18.20 kN·m. Finite element analysis of GFRP circular tubes verifies the accuracy of the bending test results. Secondly, a GFRP communication lattice tower with a height of 25 m is designed adopting GFRP circular tubes as tower columns. Through the bending test of the GFRP tower, it is verified that the connection between the columns and web members of the GFRP tower is reliable and the force pattern of the GFRP tower is reasonable. The large deflection theory can be adopted to the displacement of GFRP towers accurately. Thirdly, according to the actual engineering requirements, the finite element analysis of 25 m-high GFRP tower under the basic wind pressure of 0.45 kN/m2 is carried out by using 3D3S (a spatial structure design software). It can be obtained that the vibration mode of the GFRP communication tower shows two forms of lateral bending and axial torsion. 0° wind load direction has the greatest influence on the displacement of the GFRP tower. The stress ratio of each component in the GFRP tower is less than 1, indicating that no damage occurs in the GFRP tower. Finally, GFRP towers have good economic benefits, good environmental performance and wide range of application after comparing the GFRP tower and traditional steel tower. The demonstration project of the GFRP communication lattice tower is established in Qingyuan City, Guangdong Province, China. When subjected to a typhoon with a wind speed of 17.26 m/s, The horizontal displacement of the GFRP tower top is 10 m, which is about 2/5 of the height of GFRP tower. Although the displacement is large, the GFRP tower is still not destroyed. It can be concluded from the research in this paper that GFRP towers have low cost, good mechanical properties, good durability, and wide application range, which can promote the rapid construction of 5 G communication base stations.

Numerical Investigations of Turbulent Flow Through A 90-Degree Pipe Bend And Honeycomb Straightener

Abstract Pipe bends are commonly used in piping systems in offshore and subsea installations. The present study explores the design considerations for the honeycomb straightener inserted downstream of a 90-degree pipe bend. The objective of the study is to evaluate the effectiveness of the honeycomb in suppressing the flow swirling for different distances from the bend outlet (Lb) and different values of the honeycomb thickness (t). The turbulent flow through the 90-degree circular pipe bend with the honeycomb straightener is investigated by carrying out numerical simulations using the Reynolds-Averaged Navier-Stokes (RANS) turbulence modeling approach. The Explicit Algebraic Reynolds Stress Model (EARSM) is adopted to resolve the Reynolds stresses. The honeycomb thickness to pipe diameter ratio (t/D) is varied between 0.1 and 1. The normalized distance from the bend outlet to the honeycomb straightener (Lb/D) is varied between 1 and 5. The disturbance in the velocity field is generated by the pipe bend with the curvature radius to pipe diameter ratio (Rc/D) of 2 and Reynolds number (Re) of 2×105. It is found that both the increase in Lb/D and t/D improves the performance of the device in removing the swirl behind the bend outlet. The best performance is observed for the honeycomb straightener with the distance Lb/D=5 and thickness t/D=0.5.

Effect of relative humidity on methane explosion characteristics of curved pipes in pipe gallery

To explore the influence of relative humidity on the explosion characteristics of methane-premixed gas in the urban underground pipe corridor. The experiment took a 30° bend pipe as an example, and the relative humidity in the pipe had been set to 50% RH, 70% RH, and 90% RH while changing the methane volume fraction to 7%, 9.5%, and 12% to study its influence on the explosion characteristics. When the methane volume fraction is 9.5%, the relative humidity under the same conditions is set in the straight pipe to compare the parameter changes of flame morphology and explosion pressure. The results show that when the methane in the bend is entirely burned, the flame propagation time is delayed by 32.64% by the influence of relative humidity, the flame is hindered by the wall of the bend, the phenomenon of multiple enhancement occurs, and the flame in the straight pipe decays monotonically with the increase of relative humidity. The relative humidity stabilizes the explosion pressure; the relative humidity of 70% RH in the bend has the best impact on suppressing the explosion pressure, and the relative humidity of 90% RH in the straight pipe dramatically reduces the explosion pressure range. In the bending pipe, the relative humidity inhibited the flame propagation velocity, and the flame propagation velocity at 70% RH and 90% RH decreased by 15.46% and 10.65%, respectively, compared with 50% RH.

Crystallographic characteristics and mechanical behavior of laser welded joints of hot roll bending parts

In this work, laser welding was performed on the hot roll bending parts obtained by local-induction-heating bending forming. The influence of the crystallographic characteristics of the phase transformation products in different regions of the laser welded joint on the mechanical properties was systematically studied, and the reasons for the performance degradation were discussed in detail. The results show that upper-critical HAZ (UCHAZ) forms coarse prior austenite grain (PAG) and bainite, resulting in the lowest dislocation density of 2.5 × 1014 m−2 and the lowest impact toughness value of 46 J/cm2. Sub-critical HAZ (SCHAZ) forms tempered martensite, causing the joint to soften and the tensile strength to decrease by 18%. The number of variants in SCHAZ is the lowest, where short laths with smaller misorientations merge into long laths, and precipitates nucleation and growth occurs. The uniform orientation of the variants in SCHAZ forms low-angle grain boundaries (LAGBs), which reduces the hindrance to crack propagation, so the mechanical properties of SCHAZ decrease. In addition, the texture analysis found that UCHAZ has the highest 〈001〉//RD orientation volume fraction, indicating that UCHAZ is most prone to rapid expansion of brittle cracks on the {001} cleavage plane, so the toughness of UCHAZ is reduced. SCHAZ has the highest {001}〈110〉 texture volume fraction and the lowest proportion of high-angle grain boundaries (HAGB), indicating that the deformed grain structure with the {001} cleavage planes distributed along the LAGB after welding heat tempering is the main reasons for the delamination of SCHAZ.

3D free thermal bending of BR1500HS high-strength steel tube: Simulation and experimental investigation

Ultra-high strength steel (UHSS) pipes find widespread application in the automotive industry. To address the challenges associated with forming complex structural parts from UHSS pipes, the three-dimensional free thermal bending (3D-FTB) technology for UHSS pipes based on a robotic arm and a bending roller mold was firstly developed. A finite element simulation prediction model for accurately describing the forming process is established and discussed. In this paper, the thermal-mechanical coupling model of the material is established by Gleeble thermal tensile test and modified Arrhenius model. The effects of parameters such as current frequency, current density, axial feed rate, and quenching conditions on forming temperature and microstructure transformation are thoroughly investigated via finite element simulation analysis. The mechanical properties and potential defects of the pipe fittings after forming are analyzed and validated experimentally. The results demonstrate that the finite element simulation and analysis method based on the thermal-force coupling model of the BR1500HS UHSS pipe can accurately predict the forming process parameters. The optimal process conditions are identified as follows: current frequency of 55 kHz, current density of 650 A/mm2, and feed rate of 8 mm/s. Under these parameters, the austenite transformation rate of the pipe fittings reaches an impressive 98 % and the maximum tensile strength reaches 1540 MPa. Lastly, the overall wall thickness distortion rate of the formed pipe remains below 0.2 % and the bending rebound angle exhibits an average reduction of over 80 % compared to that under room temperature conditions.

A multi-state fusion informer integrating transfer learning for metal tube bending early wrinkling prediction

Wrinkling is one of the most fatal defects of metal tube bending, which may seriously affect the forming quality and even lead to forming failure. Traditional wrinkling prediction methods fail to provide accurate results due to the complexity of multi-die coupling in the bending process and the neglect of time-varying effects. To this end, a novel early wrinkling prediction method is proposed in this paper, distinct from conventional methods, realizing to forecast future wrinkling trends during the bending process and laying the foundation for real-time wrinkling prediction. It leverages the wrinkling factor (WrF), calculated using the energy method, as temporal data during the bending process to indirectly predict future tube wrinkling trends. Since the wrinkling occurs at the beginning of the bending process, a multi-state informer-based early prediction of tube wrinkling is put forward utilizing the limited WrF collected at the start of the bending process. To meet the demand for high accuracy and efficiency of wrinkling early prediction in a dynamic process, the model pre-trained by the multi-state fusion wrinkling data from the fully bent tube is migrated to the target model through the transfer learning approach. A stainless-steel tube bending case is conducted as the verification experiment, which is simultaneously compared with the finite element analysis (FEA) result. The results show the superior prediction accuracy and higher efficiency of the proposed method mainly compared with the traditional Informer model, Transformer model, and Long Short-Term Memory (LSTM).

Forming characteristics of thin-walled tubes manufactured by free bending process-based nontangential rotation bending die

The free-bending process of a metal tube involves a geometric relationship between the eccentricity, the rotation angle of the bending die, the deformation zone length, and the bending radius. Ideally, during the forming process, the contact position between the bending die, and the outer bend of the tube remains tangent. However, due to factors such as the clearance of the bending die and material properties, the rotation angle can be adjusted within a specific range while still ensuring smooth tube formation. The tangential state is disrupted when the rotation angle changes, resulting in overbending or underbending. Thus, in this study, a new theoretical analysis of the free bending process, accounting for clearance, was developed to analyze the material flow and changes in the bending radius during the nontangential contact between the bending die and the tube. In addition, the reasons for achieving smooth tube bending even after adjusting the rotation angle were explained, and the deformation mechanism of the tube under the combined effects of additional tangential force from the bending die and axial propulsive force was analysed. Furthermore, the impact of the rotation angle on the bending radius and the displacement of the strain neutral layer (strain NL) was determined. Afterwards, finite element (FE) modeling and forming experiments were conducted to verify the proposed theoretical analysis under different deformation zone lengths and eccentricities conditions. Besides, the distribution of the inner and outer wall thicknesses of the tube under the nontangential rotation of the bending die was further analysed. The simulation and experimental results fit well with that obtained from theoretical analysis.

Investigating ovality and wall-thinning behaviors in free-form bending of thin pipe bends with varying guider length and roller die diameter

Investigating ovality and wall-thinning behaviors in free-form bending of thin pipe bends with varying guider length and roller die diameter

Heat Transfer Characteristics of Turbulent Flow in Double-90°-Bend Pipes

This study evaluates the heat dissipation and Nusselt number for an S-shaped double-bend pipe, for which an experimental evaluation is lacking. In terms of the velocity field, the mean velocity and turbulent kinetic energy were measured through particle image velocimetry. Heat transfer characteristics were evaluated in validated conjugate heat transfer simulations, and a k-ω SST turbulence model was used for flow simulation inside the pipe. Heat transfer enhancement was observed at the first bend, as observed in previous studies on single-bend and U-shaped bends, whereas no heat transfer enhancement was observed at the second bend. This result was due to higher turbulent heat flux at the first bend because of higher eddy diffusion on the outside of the bend, whereas eddy diffusion was lower on the outside of the second bend owing to the history of the first bend. The heat transfer characteristics of the S-shaped double-bend pipe elucidated in this study provide valuable insight for devising strategies to reduce heat loss in automotive exhaust pipes with multiple bends. Furthermore, the conjugate heat transfer simulation model used in this study provides a benchmark for heat transfer calculations for multi-bend pipes.

Experimental investigation and numerical simulation of the effect of type of bending die on the quality of tube forming in rotary draw bending process

This study introduces a new rotary draw bending method that utilizes a variable curvature bending die. Unlike traditional methods that bend tubes with a fixed radius, this method gradually deforms the tube from a large to a small radius. The curvature of the bending die is determined by using an involute curve as the equation for the geometric location of the variable curvature. Hydroforming technology, utilizing fluid under pressure, replaces the mandrel in the rotational tensile bending process. The research was conducted using a thin-walled AA6063 tube with a 13.88 diameter-to-thickness ratio. The bending process was examined at critical bending ratios of 1 and 1.6 times the diameter, with a 90° bending angle. The maximum pressure that can be applied in any bend radius ratio was predicted using the necking criterion. The simulation and experimental tests analyzed the effects of internal fluid pressure and bend die curvature on defects such as wall thinning in the outer curvature of the bend, thickening of the wall in the inner curvature of the bend, and cross-section non-roundness. The results indicate that, at constant pressure, the amount of thinning and thickening of the bent tube is significantly improved when using the variable radius bending die compared to the fixed radius die.

Two-phase flow and wear of 90° bend pipes by normally distributed particles

Wear is a key cause of pipe failure in pipeline conveying systems. Solid-phase particles can lead to wall wear, which reduces the reliability of the conveying system. In this study, a numerical simulation of 1–3 mm particles with a normal distribution in a 90° bend section was performed based on a coupled computational method of computational fluid dynamics and discrete unit method. The results revealed that a protective layer of particles is formed near the outer wall of the bend, which reduces the direct collision of particles during the flow and protects the surface of the bend. Comparative analysis revealed that the maximum wear area of the bend is in the range 75°–90° in the middle of the bend section.

Tensile deformation behavior of high-strength TA18 titanium alloy tube under warm forming conditions and constitutive model based on dislocation density

Understanding the deformation behavior of high-strength TA18 titanium alloy tube (HS-TA18 tube) under warm forming conditions and the accurate description of flow stress is the basis of tube bending forming research. To this end, in this study, the HS-TA18 tube of 18 mm × 1.5 mm (out diameter × wall thickness) as the objective, uniaxial tensile tests were conducted under a wide temperature range (25 ℃−500 ℃). Then the macroscopic mechanical behavior and microstructure evolution were analyzed. The results show that the flow stress decreases with the increase of temperature. In the temperature range of 200–450 ℃, the degree of decline slows down. Moreover, the effect of strain rate on flow stress is not obvious, which indicates that dynamic strain aging (DSA) occurs in this region. Dislocation slip is the dominant mechanism of plastic deformation in the studied temperature range. Although dynamic recrystallization at 500 ℃ leads to softening trend of flow stress, dynamic recovery (DRV) is still the main softening mechanism during deformation. Then, a constitutive model based on dislocation density is established, which includes common thermal and athermal stresses. In addition, back stresses associated with geometrically necessary dislocations (GNDs) and additional stress caused by DSA are also taken into account. The model is used to predict the flow stress of the HS-TA18 tube under warm forming conditions. The prediction results are in good agreement with the experimental results, indicating that the established model has excellent prediction ability.

Geodesic equations for guided wave helical path separation for a pipe bend

The sections of pipe bends are susceptible to wall thinning by flow-accelerated corrosion due to the sudden change in the fluid flow direction and velocity. Compared to existing screening approaches, Guided Wave Tomography (GWT) has been demonstrated to provide more accurate information about the defect. In GWT an inversion problem is solved, in which a forward model is used to predict a synthetic dataset for a given physical model. Two-dimensional (2D) forward models are preferred for the inversion scheme due to the feasibility of combining these with tomographic algorithms. Since 2D models resemble the GW propagation of a plate, they do not consider the cyclic nature of the pipe. To overcome this limitation, a robust helical path separation was introduced in Huthwaite and Seher (2015) for a straight pipe. However, it relies on time-reversing the measured wave field ϕ(t) as a function of the propagation distance xs,r from the source to the receiver. Although ray-tracing and grid-based methods are capable of computing the distance xs,r for complex geometries such as the pipe bend, they are complex and time-consuming. Hence, in this paper a straight forward approach is proposed to compute xs,r based on the pipe geometry and the geodesic equations of a torus. Then the computed distance xs,r is used for removing the helical path trajectories. Compared to the distance obtained by using the Hilbert envelope, the results show that the geodesic distances preserve the information of the wavefront of interest, including the focusing effect and the scattered wave field from a Hann-shaped defect. The technique is applied to experimental data and demonstrated to separate the wavefront of interest.

Numerical investigation of blind-tee effect on flow mixing in double-bend combinations

Blind tees are commonly used in offshore production systems for the flow mixing and measurement of oil and gas products. Since subsea pipelines usually consist of multiple bends, the blind-tee effects on bend combinations should be thoroughly investigated. In this paper, numerical simulations have been conducted to investigate the effects of blind tees on the flow physics in double-bend combinations. First, three-dimensional flow characteristics are analyzed to illustrate the blind-tee effects on double-bend pipes. Then, the absolute helicity density is introduced to quantitively evaluate the mixing capacity along the bend pipes with and without blind tees. Significant differences in flow behaviours and mixing qualities are observed in different bend configurations. If a blind tee is arranged in the first bend, strong vortices are generated, and the mixing conditions are significantly improved. However, when the blind tee is in the second bend, its internal flow is negatively influenced by the upstream elbow, resulting in a poor mixing condition. Besides, the effects of the structural parameters of double-bend combinations on the flow behaviours and mixing conditions have been systematically investigated. The analysis and results of this study can provide guidance for the application of blind tees in complex piping systems.

Improvement of turbulent flow in a bend using rotational guide vane: A shape optimization

The present study aims to minimize velocity disruption using rotational guide vane (RGV) before the 90° pipe bend where the curvature ratio is r/D = 1.0 at Re = 3 × 104. The combination of computational fluid dynamics and genetic algorithm is used as a tool for the geometric optimization of RGV. The SST k–ω turbulence model was preferred in flow analysis. The number of blade, the blade angle, and the location of RGV are the geometric parameters to be optimized. A new evaluation method of the velocity distribution after the bend is proposed. The objective function is defined as velocity distribution mean squared error that is based on the comparison of the velocity distribution on the cross section after the bend with the fully developed flow in a straight pipe under the same conditions. As a result of a series of optimization processes, velocity distribution at the 90° bend exit is compared between optimized RGV and without guide vane. The results show that the optimized RGV improves velocity distribution at the bend exit. Compared to the without guide vane case, the optimized RGV has delayed flow separation from α = 37° to 56°, and the flow reattachment point moves from x/D = 0.5 to 0 at the bend exit. Thanks to optimized RGV, the counter-rotating Dean vortices merged to form a single vortex at the center of the pipe. In addition, significant reduction in turbulent kinetic energy was observed, approximately 50% when using the optimized RGV compared to the without guide vane case.

A Telescopic Tendon-Driven Needle Robot for Minimally Invasive Neurosurgery.

This paper presents the design, characterization, and testing of a steerable needle robot for minimally invasive neurosurgery. The robot consists of a rigid outer tube and two telescopic tendon-driven steerable tubes. Through the rotation, translation, and bending of individual tubes, this telescopic tendon-driven needle robot can perform dexterous motion and follow the path of the tip. We presented the design of the needle robot and its actuation system, modeling of the robotic kinematics, characterization of the robot motion, results of the open-loop kinematic control, and demonstration of the follow-the-leader motion. The position error of the robot tip is 0.92 mm, and follow-the-leader motion error is 1.1 mm. Due to its small footprint and unique motion ability, the robot has the potential to be manipulated inside human brain and used for minimally invasive neurosurgery.