Thin-walled Pipes Research Articles

Burst pressure of thin-walled pipes with arbitrarily orientated isolated surface corrosion defect

Accurate prediction of the burst pressure is essential for structural integrity assessment of pipelines. Current design codes and models for residual burst pressure assessment of pipelines with surface corrosion defects are only applicable to axially orientated defects. Theoretical and empirical models for the prediction of burst pressure of thin-walled pipes with pre-existing localised and arbitrarily oriented surface corrosion defect are proposed. The theoretical model is based on power-law hardening and J2 flow theory while the empirical model is derived from nonlinear finite element analysis results of the burst pressure. Burst pressure experiments are used to validate the model predictions. The theoretical and empirical models are found to be reliable in predicting the effect of defect width, length, and orientation on the burst pressure.

Special-Oriented Annealing-Twins-Induced Orange Peel Morphology of Heat Pipe under Bending Deformation

The thin-wall heat pipe is an efficient heat transfer component that has been widely used in the field of heat dissipation of high-power electronic equipment in recent years. In this study, the orange peel morphology defect of thin-wall heat pipes after bending deformation was analyzed both for the macro-3D profile and for the micro-formation mechanism. The morphology and crystal orientations of the grains and annealing twins were carefully characterized utilizing optical metallography and the electron backscatter diffraction technique. The results show that after high-temperature sintering treatment, the matrix grains of the heat pipe are seriously coarsened and form a strong Goss texture, while certain annealing twins with the unique copper orientation are retained. The distribution of the Schmid factor value subjected to the uniaxial stress indicates that inhomogeneity in the intergranular deformation exists among the annealing twins and matrix grains. The annealing twin exhibits a "hard-oriented" component during the deformation; thus, it plays a role as a barrier and hinders the slipping of dislocation. As the strain accumulates, part of the annealing twins may protrude from the surface of the heat pipe, forming a large-scale fluctuation of the surface as the so-called "orange peel" morphology. The 3D profile shows the bulged twins mostly perpendicular to the drawing direction, about 200-300 in width and 10-20 μm in height.

Role of welding residual stress in stainless steel piping with application of the leak-before-break technology

The predicted leakage rate of piping circumferential through-wall cracks (CTWC) under various loading levels is a critical factor for the application of leak-before-break (LBB) technology. In current engineering approaches, the effect of welding residual stress has not been carefully taken into account. In this paper, both numerical analyses and comparative verification are adopted to examine the influence of typical welding residual stress field on the crack opening displacement for austenitic stainless steel piping with representative geometric dimensions and in situ measured material performance curves. An in-depth investigation is carried out to reveal the effect of the residual stress on morphological parameters of the CTWC flow channel. In the case where the residual internal stress of welding has the greatest effect, the Henry-Fauske model is employed to analyze the flow medium passing through the CTWC and the corresponding leak rate for a typical nuclear power plant. The results indicate that the welding residual stress leads to a substantial change in the crack opening displacement and crack morphology parameters. Both the current GE/EPRI method and the NUREG/CR-6837 modification recommended by the American Electric Power Research Institute underestimate the effect of this phenomenon, resulting in a higher prediction of the medium leakage rate. A similar situation is most likely to occur for the cases of short cracks in thin-walled piping and long cracks in thick-walled piping. Additionally, the obtained results reveal that the welding residual stress causes the whole crack surface to open negatively, and the axial line of the long crack on the thick-walled piping is close to a conic curve under specific conditions.

INVESTIGATING THE STRESS-STRAIN STATE OF OBTAINING BIMETALLIC PIPES THROUGH COMPUTER MODELING

The problem is solved with dimensionless quantities. This makes it possible to obta¬in solutions from bimetallic composite pipes taking into account the real properties of any solid material, as well as bimetallic materials with different porosities. The inner tube of the bimetallic pipe is in a state of plane stress. The differential equation of the element of the conical part of the pipe and the Laplace equation of a thin-walled cylindrical pipe in a conical matrix, as well as a simplified form of the Mises plasticity condition are investigated. As a result, by integrating the obtained differential equation, formulas for determining dimensionless meridional and circumferential stresses are obtained, as well as current porosities v. In addition, to determine v, formulas from the deformation plasticity theory of porous materials are used. The outer tube of the bimetallic pipe is in a state of dimensional stress. As a result, the Laplace equation and the simplified plasticity condition change compared to the previous one. Numerical calculations of the stress-strain state of bimetallic completing pipes are carried out in the MS EXCEL software environment. In particular, computer modeling of the outer pipe is carried out by the preliminary determination of various initial values of the meridional dimensionless stress σ ̅_m0. It is shown that to the pipe extrusion process corresponds an initial stress value σ ̅_m0 at which the meridional stress σ ̅_m of the pipe upon the exiting value is zero.

Three-dimensional analysis of the stress-strain state for straightening pipes on skew-roll straightening machines with special roll profiling

In order to increase the competitiveness of domestic metal products, in particular pipes, it is necessary to ensure their compliance with international standards in terms of the main quality indicators. The pipe straightening process provides quality indicators such as straightness and cross-sectional shape. Skew-roll pipe straightening machines are the most common and most effective for straightening pipes of small and medium diameters. The most modern are six-roll pipe straightening machines with special roll profiling, which provide straightening of two types: in the caliber of the profiled rolls and at the step between the roll clamps. But the lack of knowledge about the regularities of straightening pipes holds back the wide implementation of such machines. In the work, a finite element model was developed and with its use, a study of the influence of the straightening process parameters in profiled rolls with symmetric and asymmetric profiling of the extreme pairs of rolls on the indicators of pipe straightness and straightening force was carried out. According to the results of their implementation, it was established that straightening the pipe in gauge and pitch allows to reduce the residual curvature of the pipe by almost three times with a 2.5 times smaller overlapping of the middle rolls relative to the outer ones. At the same time, the force on the most heavily loaded middle rolls increases almost twice, which should be taken into account in view of the possibility of ovality in the section of thin-walled pipes. The use of additional asymmetric profiling of the extreme rolls with step adjustment practically does not affect the quality of straightening in the gauge, increases the quality of straightening at the step by up to 15 %, while reducing the maximum straightening force by 5—7 %. The developed finite-element model allows determining the rational values of rolls overlaps to ensure the minimum residual curvature of the pipes.

Зміцнення інструменту для холодної роликової прокатки корозійностійких труб

The work is devoted to a topical technical problem - to increase the wear resistance of pipe tools for cold roller rolling of corrosion-resistant pipes, due to its significant cost and difficult working conditions. It is proposed to improve the technology of heat treatment of rolled tools for the production of corrosion-resistant pipes (mandrels, rollers, support strips) from steels 4Х5МФ1С and 60С2ХФА. Instead of the usual technology - tempering with tempering, tempering with tempering and subsequent ionic nitriding in plasma of two-stage vacuum-arc discharge in a modified installation "Bulat-6" in the laboratory of plasma technology. The microstructure of special samples of these steels on a scanning electron microscope (SEM) at different magnifications was studied. Their microhardness was determined using a microhardness tester PMT-3. A comparison of the microhardness of the samples after traditional treatment and the proposed. The wear resistance of the actual tool (mandrels made of 60С2ХФA steel) for cold roller rolling of particularly thin-walled corrosion-resistant pipes was studied directly during industrial tests in the factory. Studies of the microstructure on the REM of the nitrided layer after ion-plasma nitriding revealed a finely dispersed very strong ε-phase. Due to its presence in the surface layer, the surface hardness of nitrided parts increases due to the formation of stable in the process of heating carbides, nitrides, carbonitrides. Steel acquires high hardness on the surface, high wear resistance, high endurance, corrosion resistance. Tests of mandrels in the factory, which were additionally subjected to ionic nitriding, showed an increase in their stability by 25-30%. Also reduced the cost of processing the manufacture of pipes and improved the quality of the inner surface of the pipes (absence of films, cuts and other defects of corrosion-resistant pipes). Replacement of steel 60С2ХФA with secondary hardening steel 4Х5MФ1С for the manufacture of rollers and support bars in addition to improving the quality of the inner surface of the pipes increased the stability of the tool by 2.7-3 times. Keywords: rollers, support laths, mandrels, cold rolling, heat treatment, ionic nitriding.

Forced vibration of sandwich pipes with zero Poisson's ratio honeycomb core under moving pressure

Based on Love shell theory and equivalent single layer theory, a new method is proposed in this paper to analyze the dynamic response of honeycomb sandwich pipe under the action of moving pressure. The results of displacement response under two boundary conditions are within 3.5% error range with the FEM results. The theoretical model takes into account the effect of thickness, and the calculation results are more accurate compared with the FSDT method, which can be used for both thin-walled and thick-walled pipes. By analyzing the effects of honeycomb structure parameters and pipe dimensions on the critical velocity and displacement response of honeycomb sandwich pipe, theoretical guidance is provided for the design of new pipeline structures.

Development of an improved limit pressure equation for structurally distorted thin-walled pressurized 90 degree pipe bends

PurposeThis paper aims to present the approximate limit pressure solutions for thin-walled shape-imperfect 90° pipe bends. Limit pressure was determined by finite element (FE) limit analysis with the consideration of small geometry change effects.Design/methodology/approachThe limit pressure of 90° pipe bends with ovality and thinning has been evaluated by geometric linear FE approach. Internal pressure was applied to the inner surface of the FE pipe bend models. When von-Mises stress equals or just exceeds the yield strength of the material, the corresponding pressure was considered as the limit pressure for all models. The current FE methodology was evaluated by the theoretical solution which has been published in the literature.FindingsOvality and thinning produced a significant effect on thin-walled pipe bends. The ovality weakened pipe bend performance at any constant thinning, while thinning improved the performance of the bend portion at any constant ovality. The limit pressure of pipe bends under internal pressure increased with an increase in the bend ratio and decreased with an increase in the pipe ratio. With a simultaneous increment in bend radius and reduction in wall thickness, there was a reduction in limit pressure. A new closed-form empirical solution was proposed to evaluate limit pressure, which was validated with published experimental data.Originality/valueThe influences of structural deformation (ovality and thinning) in the limit pressure analysis of 90° pipe bends have not been investigated and reported.

The effect of porosity on strain evolution and failure of soldered, small-diameter, thin-walled metallic pipes

Small-diameter, thin-walled pipes have applications in a wide range of industries including high-energy physics, heat transfer, nuclear, medical and communications. There are no standards that exist for welds less than 0.5 mm in width, and as such it is difficult to determine the likely performance of a thin-walled pipe weld. Porosity is largely inevitable in fusion welded joints and is a determining factor in the performance of a connection.This study focused on characterisation of the evolution of strains in soldered welds less than 0.5 mm in width, by incrementally tensile loading samples and studying them in-situ with Synchrotron X-Ray Computed Tomography and X-Ray Diffraction. Two sample geometries were studied, and porosity defects were present in both, although the levels of porosity size, number and area varied dramatically between the two samples.Lattice strain interpretation showed that crack propagation for such samples is not driven by porosity but that crack evolution occurs at the same location and load levels irrespective of the presence of pores. Residual stresses of up to 0.3% from the fusion welding process were seen in both samples and appear to have a greater impact on locations of failure than porosity. Porosity does cause differences in strains across directions, however high strains alone did not appear to cause premature failure. Hence, efforts to improve weld strength should in future focus more on reducing residual stresses than reducing porosity.

Lightweight cost-effective hybrid materials for energy absorption applications

The present paper experimentally explores the influence of the fiber hybridization and layering sequence on crashworthiness behavior and deformation history of polymer/metal thin-walled pipes. Jute (J)/glass (G) reinforced epoxy over wrapped aluminum (Al) pipes were prepared via hand wet wrapping then subjected to axial quasi-static compressive loads. The load versus displacement plots and crashing indicators, i.e. peak crushing load ({mathrm{F}}_{mathrm{ip}}), mean crushing load ({mathrm{F}}_{mathrm{m}}), total energy absorption (mathrm{U}), specific energy absorption left(mathrm{SEA}right), and crush force efficiency left(mathrm{CFE}right) were determined. Experimental results revealed that the maximum left(mathrm{SEA}right) was recorded for Al/2J/4G/2J pipe with a value of about 42.92 kJ/g, with an enhancement of 20.56% in left(mathrm{SEA}right) compared with pure Al-pipes. Al/2J/4G/2J specimens display the maximum (mathrm{U}), left(mathrm{SEA}right), and left(mathrm{CFE}right) and could be employed as energy absorbing members in automobiles.

Buckling initiation and propagation in pipes under external pressure

A universal plastic ring-beam model is presented considering the longitudinal stretching effect in the transition zone based on the pipes' deformation mode analysis. An improved ring model is applied to the pipe's propagation pressure problem. The closed-form solutions are significantly improved compared to previous studies and are much closer to the FEM or experimental results, especially for medium-thick or thin-walled pipes. The proportion of longitudinal stretching effect in propagation pressure decreases with the increase of diameter-thick-ratio, accounting for 20%–30% of thin wall pipes (25≤ D/t ≤ 40), and 30%–40% for medium-thick-walled pipe (15≤ D/t ≤ 25). Buckling triggers simultaneously in the multiple equal ovalities along the pipe's axial direction. Oval defect deviation angle leads to generating torsional moments in the propagation buckling process, which in turn produces a flip phenomenon, propagation flip-flop mode occurs when the defect deviation angle is a right angle. Whether multipoint trigger mode, flip-flop mode or other axial factors of oval defects in pipes affect buckling initial pressure to different degrees but seem to have no effect on the propagation pressure.

MODELLING OF THE MANDREL-FREE COIL DRAWING PROCESS OF PIPES FROM STEEL 12Х18Н10Т

The metallurgical industry of Russia faces the task of joining the country with the world leaders in the production of liquefied natural gas (LNG). This task involves reducing the dependence of the level of imports, since today the dependence on imports in the LNG production industry is about 95 %. The main equipment for LNG production is a spiral heat exchanger. The purpose of this work was to study the thin-walled long-length pipes used in its construction. According to the requirements for the specified heat exchange equipment, the components of its cold-deformed pipes must have a length of at least 50 m. For the production of such pipes, it is recommended to apply the mandrel-free coil drawing process. The article presents the results of a theoretical study of the mandrel-free coil drawing process of pipes from steel AISI 321 (grade Cr18Ni10Ti). Predicting the technological feasibility of manufacturing pipes in coils can reduce the costs for subsequent organization of industrial production. Using the finite element method implemented in the “Deform-2D” software package, the boundary value problem was solved to carry out the process of mandrel-free coil drawing of pipes and the process of their winding on a drum. The simulation was carried out for the technology of manufacturing seamless cold-deformed pipes in accordance with the principal scheme of coil production ensuring its rational organization, which was developed by the research & production teams of the TMK Group. The possibility of manufacturing pipes in coils with dimensions of 10×1.0 mm from steel grade AISI 321 (grade Cr18Ni10Ti) has been theoretically justified. It is recommended to use the simulation results for the subsequent implementation of the technology.

MINIMIZATION OF DEFECT IN THE FORM OF LONGITUDINAL FOLDS AT THE END SECTIONS OF THIN-WALLED SEAMLESS PIPES DURING ROLLING AT AUTOMATIC MILL

During rolling of thin-walled seamless pipes at the rear ends, a defect in the form of end folds occurs, which leads to an increase in the consumption coefficient of the metal. To identify the causes of the formation of this defect, the mathematical modeling of rolling processes in the QForm VX software was carried out. The simulation results showed that the main factor in the formation of end folds at the rear ends of the pipe billets is an increased relative compression along the wall of the pipe billet in the first pass, which leads to flattening of the rear end of the pipe billet and formation of longitudinal folds. To prevent the formation of end folds, it is proposed to install an additional sleeve with a mandrel. As a result of the research, the values of relative compressions were determined, at which a defect is formed for rolling with a new mandrel installation option. It was found that with relative compression along the wall in the first passage from 30.0 %, a defect in the form of folds (“fins”) at the rear end of the pipe billet is formed. With a relative compression of the wall in the first passage up to 39.4 %, the installation of sleeves reduces the formation of “fin” defects at the rear end of the pipe billet; with a relative compression from 39.4 % to 41.8 %, its installation does not prevent the formation of these defects. The optimal distance between the mandrel of the automatic mill and the sleeve is 20–30 mm

Homotopy solution for nonlinear vibration analysis of multilayer graphene platelets-reinforced thin-walled pipes conveying fluid with rectangular cross-section

Homotopy solution for nonlinear vibration analysis of multilayer graphene platelets-reinforced thin-walled pipes conveying fluid with rectangular cross-section

Application of CFRP Wrap for Reinforcing Undamaged Thin-Walled Pipe Bends under Thermal Expansion Loads

Application of CFRP Wrap for Reinforcing Undamaged Thin-Walled Pipe Bends under Thermal Expansion Loads

Soil Resistance during Driving of Offshore Large-Diameter Open-Ended Thin-Wall Pipe Piles Driven into Clay by Impact Hammers

To investigate soil resistance during driving (SRD) of large-diameter open-ended thin-walled piles (LOTPs) installed in clay by impact drivers, a finite element method (FEM) analysis incorporating the dynamic remeshing and interpolation technique with small strain (RITSS) was conducted. This method was verified using a field case, and its SRD was compared with that of the empirical driving formulas. The dynamic penetrations of LOTPs with three pile inner diameters (2, 4, and 6 m), and three ratios of wall thickness to pile inner diameter (1%, 1.5%, and 2%) were then numerically analyzed. The pile load-bearing performance had a significant dimensional effect, which is characterized that an increase in diameter resulting in a decrease in SRD. The LOTP shaft frictional resistances during driving was generally held in the range of around 0.3–0.5 times the undrained shear strength of the soil (Su), and it was about 6 - 8 times for the pile end resistances. The prediction equation was proposed for SRD behavior with depth, which considered the pile diameter. Then, the curves of the equation were compared with the numerical results. This study can serve as a reference for the dynamic penetration analyses of piles, including the SRD and pile-soil interaction.

Study on the Nonlinear Behavior and Factors Influencing the Axial Compression of High-Durability Fibrous Concrete Wrapped Steel Tube Composite Members.

Thin-walled steel pipe concrete has better economic performance, but the problem of local buckling is more prominent with a thin-walled steel pipe; meanwhile, thin-walled steel pipe is more sensitive to the environment and the influence of rusting is more prominent. To solve the above problems, this paper proposes new spiral stiffened rib thin-walled steel pipe concrete laminated members to obtain better force and economic performance. Based on axial compression tests on five forms of composite members, this paper studies the nonlinear behavior of the axial compression of this new type of laminated member and the factors influencing it. The following conclusions are obtained. Under the constraint of the spiral ribs, the new composite member has good integrity and each part can ensure cooperative stress; the buckling of the steel pipe is well limited and the mechanical performance is significantly improved. Compared with ordinary thin-walled concrete-filled steel tubular members, the bearing capacity is increased by about 20% and the deformation ability is increased by more than 30%. The nonlinear behavior of the member in compression can be better achieved through finite element analysis. The parametric analysis shows that the pitch and the steel tube width-to-thickness ratio greatly influence the force behavior of the member. In contrast, the spiral rib width-to-thickness ratio and the external reinforcement only need to meet the structural requirements. Finally, based on the superposition theory, the proposed method of calculating the member's axial compressive load-bearing capacity is given and design suggestions are made. The results of this paper can provide some basis for the engineering application of this new combination member.

Optimization of Residual Stress Field and Improvement of Fatigue Properties of Thin-Walled Pipes by Filling Laser Shock Peening

In the present work, a filling and laser shock peening (LSP) method is put forward and applied to a thin-walled pipe. Specimens were experimentally and numerically investigated to identify the residual stress field and fatigue properties of a pipe with and without LSP treatment. The numerical simulation indicated that the residual compressive stress first increased and subsequently dropped as the laser power density increased, and the extent of influence of the stretching wave, reflected from the lower surface on the unloaded area, increased with the spot diameter, causing surface tensile stress in the unloaded area. By filling the pipe with the guided-wave material, the residual stress field of the pipe that was treated with LSP was optimized, and the influence of the stress wave reflection on the residual stress field was effectively decreased. The surface residual stress of the filled guided wave material was −326 MPa, improving it by 57.6% compared with the pipe not filled with guided wave materials. The fatigue life of the pipe with the filled waveguide material that was treated by LSP was extended by 48.9%, compared with the untreated pipe.

Investigation of hydraulic resistance and heat transfer in the flow of HE-XE mixture with a small Prandtl number in a quasi-triangular pipe

In this work, the process of heat transfer during the flow of gas mixtures (He-Xe) in a thin-walled quasi-triangular pipe is considered experimentally and numerically. The pipe cross-section corresponds to the shape of the channel formed by the dense packing of reactor rods for generating heat at the power plant. A helium-xenon mixture with a Prandtl number of 0.23 is used as the working fluid. Temperature distributions of the heated wall are obtained in the range of Reynolds numbers from 2860 to 39,800. The influence of the laminar-turbulent transition at the initial section of the pipe and high-velocity turbulent flow at the outlet on the wall temperature distribution along the channel is analyzed. The simulation data on heat transfer are generalized using the mass-average reduction temperature as the determining temperature, which allows correct consideration of gas compressibility at high flow velocities.

Analysis of the impact factor of burst capacity models for defect-free pipelines

The research on the failure pressure of perfect pipeline is the basis of evaluating the bearing capacity of defective pipeline. The applicability of impact factor of theoretical and empirical failure pressure prediction models for thin-walled pipes are evaluated with 77 full-scale burst test data. Impact factors analyzed in this study include diameter D, strain hardening exponent n, flow stress and yield criterion. The diameter D and strain hardening exponent n have less effect on the prediction of failure pressure of defect-free pipeline, while the flow stress and yield criterion have significant influence on the prediction of failure pressure. For the failure pressure assessment of defect-free pipelines, average shear stress yield (ASSY) criterion is the best applicable criterion, followed by Tresca and von Mises yield criterion. 1.0σu is the most accurate calculation method of flow stress for failure pressure of defect-free pipeline.