Thin-walled Pipes Research Articles

Bending Failure Behavior of Thin-walled Composite Tube Structures

Abstract The bending failure, failure load and failure mode of thin-walled circular tubes made of carbon fiber reinforced resin matrix composites were investigated by experiments and numerical simulation. Three typical failure modes of circular tubes under bending load were observed in experiments, and the characteristics and mechanisms of different failure modes were analyzed. The results show that interlaminar shear induces the generation and propagation of microcracks at the interface of circular tubes, which accelerates the failure of circular tubes. In the bending failure process, because the interlayer performance of the round pipe is relatively low, it is the weak link of the structure, and the pipe wall is the first to produce interlayer delamination and splitting failure under the action of shear stress, resulting in structural instability and premature fracture failure. The lay-up and initial defects of thin-walled round pipe have great influence on the bending failure mode and failure load.

Crash resistance analysis and optimization of sponge like thin-walled pipes under multiple working conditions

The crashworthiness of bionic thin-walled structures has been the subject of considerable research interest. In this article, we emulate the bi-diagonal skeletal structure of deep-sea glass sponges and construct sponge-like multicellular thin-walled tubes (SLMTT) with a parameterized ratio of the number of two distinct single-celled organisms (CSS I and CSS II). Thin-walled sponge-like tubes of varying dimensions were manufactured using selective laser melting (SLM) technology. The crashworthiness of these structures was evaluated under axial compression, transverse compression, and three-point bending conditions through experimental and computational approaches, including parametric analyses of the inner and outer wall thicknesses. The results show that SLMTT I has better crashworthiness under the three working conditions, and the SEA of BLMESI is 40.9 and 26.13% higher than that of BLMESII. under transverse compression and three-point bending conditions, respectively. Finally, a multi-objective optimization design of SLMTT I under multiple operating conditions is carried out by the second generation of Non-dominated Sorting Genetic Algorithm (NSGA-II) with the aim of obtaining the ideal structure with maximum specific energy absorption and minimum initial peak crushing force. This study offers novel insights into the design of bionic energy-absorbing structures under diverse operational scenarios.

Microstructure and mechanical properties of thin-walled TA1 titanium pipes fabricated by high-frequency induction welding

High frequency induction welding (HFIW) was effectively employed for the high-speed fabrication of thin-walled TA1 titanium pipes (TWTPs) with a nominal wall thickness of ∼0.6 mm. The microstructure and mechanical properties of TWTPs manufactured under varying welding parameters were investigated. The weld zone (WZ) exhibits a waist shape measuring ∼622 μm in width, and the width of the heat-affected zone (HAZ) spans between 763 and 864 μm. Both the WZ and HAZ are composed of a mixture of coarse serrated α grains with fine acicular and twins, while the BM retains equiaxed grains. This unique microstructure was resulted from the thermal cycling during HFIW, contributing to a notable increase in microhardness within the WZ compared to both the HAZ and the BM. Optimal manufacturing conditions were identified at a welding power of 14.4 kW, a welding speed of 60 m/min, an opening angle of 6°, and a squeeze displacement of 0.2 mm, yielding the TWIP with a tensile strength of ∼307 MPa and tensile elongation of ∼27%. Tensile fracture analysis revealed that failure predominantly occurred within the BM, underlining a ductile fracture mode characterized by pronounced dimple formations. The enhanced mechanical performance of the weld joints can be attributed to the heterogenous microstructure in the WZ, where the presence of large serrated α-grains enhances ductility, and the fine martensite and twins contribute to the high strength.

Analytical relations for fields and currents in magnetic-pulsed «expansion» of tubular conductors of small diameter

Introduction. This work was initiated by the problems of cardiovascular diseases, which are one of the main causes of mortality of the population of our planet. More than ten years ago, in 2012, approximately 3.7 million people died of acute coronary syndrome worldwide. The fight against such pathologies is carried out with the help of so-called stents, the manufacture of which can be carried out by the method of magnetic pulse «expansion» from hollow metal cylinders. The limited production possibilities of magnetic pulse «expansion» were caused by the minimum cross-sectional size of the inductor-instrument, which can be practically manufactured. Other tools are required to perform this operation. Novelty. A system of magnetic-pulse expansion of thin-walled pipes of small diameter with an inductor that excites an azimuthal electromagnetic field in the case of direct current passing through the processing object and in the absence of its connection in an electric circuit with an inductor is proposed. Purpose. The main analytical dependencies for the characteristics of the electromagnetic processes taking place in the inductor systems for the expansion of cylindrical conductive pipes of small diameter when direct passage of current through the processed object and when it is not connected to an electric circuit with an inductor (insulated billet) is derived. Methods. The solution of the boundary value problem with given boundary conditions was carried out by applying Laplace transforms and integrating Maxwell’s equations. Results. Analytical expressions were obtained for the main characteristics of the processes: the intensities of the excited electromagnetic fields and currents in the system depending on the parameters of the studied systems. The analysis of possible technical schemes for solving the given problem indicated the choice of the optimal variant of an effective system of magnetic-pulse «stretching» of thin-walled cylindrical conductors of small diameter. Practical value. Based on the qualitative analysis of the obtained results, recommendations for the practical implementation of the proposed system were formulated. The obtained dependences allow us to give numerical estimates of the effectiveness of excitation of magnetic pressure forces on the object of processing and to choose directions for further improvement of the magnetic pulse technology for solving such problems. References 23, figures 2.

Enhanced elastic stress solutions for junctions in various pipe bends under internal pressure and combined loading ([formula omitted] pipe bend, U-bend, double-bend pipe)

Piping systems in nuclear power plants normally operate under high pressure and high temperature. To efficiently manage space within these systems, pipe bends are extensively used. However, the welded joints connecting these pipes may be susceptible to flaws due to weld residual stress, transient loads, and operating environments. When flaws are present in such areas, analytical evaluation of flaws is to be carried out based on fracture mechanics parameters such as stress intensity factor. To calculate the stress intensity factor, distributions of the elastic stress are required. Therefore, this paper presents closed-form approximations of elastic stress in the junction between a pipe bend and a straight pipe under internal pressure. Review of the existing elastic stress solutions for estimating the stresses in pipe bends was carried out analyzing their limitations. Based on those limitations elastic stress solutions for thick to thin wall pipe bends were proposed and were validated against finite element (FE) analysis for thick-wall to thin-wall pipe bends under internal pressure and combined loading (i.e. internal pressure, in-plane bending, out-of-plane bending inflicted simultaneously). 90° pipe bend, U-bend and double-bend pipe configurations were considered and showed good agreement with the FE results exhibiting less than 5.8 % discrepancies. The accuracy of the elastic stress solutions for pipe bends provided in the existing code are summarized and validated in the appendix as well.

Accurate backside boundary recognition of girth weld beads

Visual recognition of weld beads is essential for post-weld robotic grinding. The recognition of thin-walled weld bead boundary, especially the backside boundary, remains challenging due to the diverse features such as debris, misalignment, and deformation. Based on point cloud from a laser scanner, we present a robust and accurate backside boundary recognition method for girth weld beads of thin-walled pipes. A boundary point extraction method is designed based on an adaptive sliding window model. Without prior morphology features, the influence of misalignment and deformation on the accuracy of boundary point recognition is greatly reduced by the local model matching strategy. Leveraging the correlation among overall weld bead features, an anomalous boundary point recognition and correction method based on DBSCAN clustering is proposed to further enhance robustness. A series of validation experiments were conducted by the obtained backside point cloud data inside a girth weld pipe, and our proposed method showed a high accuracy and a high robustness to misalignment, deformation and debris features.

Study of Alternatives to Manufacturing of Long Pipes with Many Holes

Abstract In industrial manufacturing, certain long, thin-walled pipe-type parts that have many holes arranged along their longitudinal axis are required. In the automotive industry, such thin-walled long pipe parts are needed for body frames, for heavier component supports, for protection bars, etc. Frequent cases are encountered, for example, in the manufacture of modular shelves for storage. In these cases, long pipes, up to 6 meters long, with thin walls are used. Such long thin-walled pipes, which have many holes arranged along them, sometimes even equally spaced between them, are frequently made with a manufacturing technology that has several characteristic steps: 1) making holes in sheet metal strips, 2) bending the strips and welding them lengthwise, resulting in perforated pipes having a rectangular or square section. In this paper, two variants of obtaining pipes with holes arranged along the length of the pipe, but which are obtained from laminated pipes with thin walls of rectangular section, are proposed and analyzed. The characteristics of obtaining holes in these pipes are presented and the advantages and disadvantages of the proposed solutions are analyzed. The finite element method was also used for the analysis using SolidWorks software.

Experimental study on improving the heat transfer performance of large-diameter thin flattened heat pipes

Theoretically, when flattened to the same thickness, thin flattened heat pipes made from thin-walled cylindrical heat pipes with larger diameters have better thermal performance, but the conventional wick structures cannot meet their high-performance thermal requirements. In this study, to improve the heat transfer performance of large-diameter thin flattened heat pipes, composite sintered wick structures with spiral woven mesh and different mesh sizes of orthogonal woven mesh were designed and fabricated. The sizes were 150, 200, and 250 mesh. Four types of wick structures were developed to investigated the effects of the weaving mesh size and the composite sintering of the orthogonal woven mesh on heat transfer performance. The results demonstrated that the sample with the 200-mesh orthogonal woven mesh sintered wick exhibited the most pronounced improvement in thermal performance. The maximum heat transport capacity of the sample was found to be 46 W, representing an increase of 91.67 % compared with the sample utilizing the spiral woven mesh wick. Additionally, the evaporation resistance decreased by 56.24 %, and the total thermal resistance decreased by 53.40 %. These findings are highly conducive to the economic fabrication and performance improvement of large-diameter thin flattened heat pipes.

Mechanism clarification and mitigation measures of radial deformation induced by girth welding of thin-walled pipes

Girth welding is extensively utilized in connecting pipeline structures. Excessive welding deformation may result in a decrease in ultimate bearing capacity and fatigue life. This research explores the characteristics and underlying mechanics of radial deformation in thin-walled girth welded pipes and proposes mitigation measures. Initially, several 304 stainless steel pipes were joined utilizing four distinct welding procedures. Welding deformation and residual stress distribution were measured using a 3D coordinate measuring machine (CMM) and the Cos α X-ray diffraction (XRD) method, respectively. Subsequently, numerical models were developed to simulate the welding process and verify the accuracy of the fusion zone, residual stress field, and radial deformation in the models. The mechanism of radial deformation was further elucidated based on the inherent strain method. The results show that the direction of radial deformation relies substantially on the hoop plastic strain. Hoop tensile plastic strain corresponds to radial outward deformation, while hoop shrinkage plastic strain corresponds to radial inward deformation. In addition, the influence of axial constraint on the formation process and results of hoop plastic strain, as well as the effect of heating zone width on radial deformation, was studied. Through simulation outcomes, the research suggests employing a regulated heat source method to mitigate radial deformation, which could potentially reduce deformation by 92.8%, offering considerable advantages in deformation mitigation and welding efficiency augmentation.

Optimization design of crashworthiness of polyurethane foam filled Origami thin wall square tube based on an surrogate model

Rigid polyurethane foam, due to its low density, light weight and effective energy absorption, can be used as a new filling material to improve the energy absorption capacity of pipe fittings, thus improving the overall crashworthiness of automobiles. In this paper, numerical simulations on rigid polyurethane foam-filled origami thin-walled pipe fittings are carried out. The effects of interlayer dihedral angle, number of layers of creased pipe, and filling of foam with different densities on the crashworthiness of the pipe fittings are compared and analyzed. Additionally, an surrogate model is established to predict the correlation between the above three factors and the model. Taking the specific absorption energy (SEA) and the initial peak force (PCF) as optimization objectives, the NSGA-II algorithm and the CHC algorithm were used for optimization analysis respectively. Simulation experiments were conducted to validate the accuracy of the optimized structural parameters. The results show that the CHC algorithm provides more accurate optimization results compared to the NSGA-II algorithm. The optimized optimal interlayer dihedral angle is 150°, the number of creased tube layers is 8, and the foam density is 0.3 g/cm3. Consequently, the tubing’s specific absorption energy is enhanced by 10.3 % compared to ordinary straight tubing, demonstrating the significant improvement in crashworthiness achieved through foam filling. This study proves that the filling of tubing with foam has excellent impact resistance, and the results provide a certain reference value for future research.

Surrogate modeling with non-stationary-noise based Gaussian process regression and K-Fold ANN for systems featuring uneven sensitivity distribution

In the realm of aircraft design, there is a prevalent need for surrogate modeling techniques capable of efficiently and accurately modeling objects with high evaluation costs and uneven sensitivity distributions, such as those encountered in the nonlinear buckling of thin-walled structures and aerodynamics at transonic speeds. However, the non-stationary Gaussian Process Regression (GPR) model requires extensive hyperparameters or judicious assumptions, limiting its applications in such tasks, and the commonly used K-Fold methodology suffers from inherent instability. Addressing these issues, this paper proposes an active learning method for surrogate modeling in systems featuring uneven sensitivity distribution, integrating non-stationary-noise GPR and K-Fold Artificial Neural Network (ANN) methodology, namely NSN-GPR-KF. Instead of relying on a non-stationary kernel function, the algorithm regards noise as a non-stationary factor within a stationary GPR framework, with noise levels estimated via the K-Fold ANN methodology, allowing GPR to efficiently adapt to non-stationary systems while avoiding the aforementioned requirements for non-stationary GPR. Case validations, performed on two test functions with pronounced uneven spatial sensitivity, demonstrate that NSN-GPR-KF outperforms commonly used stationary GPR and pure K-Fold methodology. It synthesizes the exploration capabilities of GPR with the exploitation proficiency of the K-Fold methodology, achieving comparable global accuracy with reduced sample sizes—up to 26 % and 22 % less than the other two algorithms, respectively. The algorithm was successfully applied to predict the buckling load of thin-walled pipe beams, demonstrating accelerated convergence and approximately 25 % greater accuracy compared to pure K-Fold model. These results suggest that NSN-GPR-KF can serve as an efficient and precise modeling tool for engineering tasks with high evaluation costs and complex sensitivity distributions.

Investigation of ratcheting fatigue behavior and failure mechanism of 1Cr18Ni10Ti pressure pipe under different force amplitudes and internal fluid pressure

This work reports on the development of an improved testing system to examine the effects of force amplitude and internal fluid pressure on ratcheting behavior and failure mechanism of 1Cr18Ni10Ti aero-engine pipe. Experimental results indicate that the ratcheting displacement and its rate during steady stage increase with the increasing force amplitude or internal fluid pressure, exhibiting a reverse tendency to fatigue life. Continuous cyclic softening response until fatigue fracture was observed in all conditions. Furthermore, microstructural evolution was characterized by SEM, EDS, XRD, and EBSD. The critical force amplitude to trigger noticeable dislocation accumulation and transition from austenite to ferrite phase was evaluated to be around 1900 N. The results highlight the decreased high-angle grain boundary (HAGB) and increased dislocation density causing the sample with a higher force amplitude to be more inclined to fracture. The initiation of fatigue crack was accelerated by the accumulation of dislocation within ferrite phase grains. Similar fatigue fracture morphology with ovalization phenomenon was observed in all conditions. To predict the ratcheting fatigue life of aero-engine thin wall pipes, a validated fatigue life estimation model considering steady ratcheting displacement rate based on a finite element analysis (FEA) model was conducted, and all of the fatigue data are contained in a 1.1X scatter band.

Numerical Analysis of Distribution Characteristics of Jacking Force in Thin-Walled Pipe Groups

Numerical Analysis of Distribution Characteristics of Jacking Force in Thin-Walled Pipe Groups

Full-scale experimental investigation into stability of segment-SCC-steel tube lining under external pressure

To investigate the mechanical deformation characteristics of the ‘Segment-SCC-Steel Tube’ combined bearing lining structure under internal and external pressure, the loading device and monitoring system for the stability analysis of the full-scale lining were proposed. The effect of cracked encased concrete and local external pressure on the instability mode of thin-walled steel pipes was explored by full-scale model experiment and three-dimensional FEM numerical simulation. The influence of SCC (Self-Compacting Concrete) and stiffening rings on the stability of steel pipes subjected to external pressure was discussed. The results show that SCC cracks occur and intensify with increasing internal pressure. The external water acts directly on the steel tube through cracking, resulting in wavy deformation, and the gap between the SCC and steel tube further increases. When calculating the critical external pressure for the steel pipe, the constraint of encased concrete can be ignored, and only the constraint effect of the stiffening ring can be considered. Therefore, the Von Mises formula was used to predict the critical external pressure between the stiffening rings with high accuracy. In addition, the stiffening ring can mitigate the crack propagation of nearby SCC. The steel tube remained in the elastic stage under internal pressure. In the full-scale experiment, the external pressure could not continue to rise after reaching 0.65 MPa. Nevertheless, the amplitude of the buckling wave continued to increase. It is considered that the steel pipe is in an unstable state, and the failure mode is dominated by single-lobe buckling.

EDDY CURRENT QUALITY CONTROL OF THIN-WALLED REFRACTORY ALLOY PIPES

The experience of non-destructive quality control of thin-walled pipes of small diameter from a refractory non-magnetic alloy based on eddy current and X-ray television methods is considered. An analysis of the signal of an eddy current differential transducer during scanning of defects of various types was performed. The possibility of detecting and classifying such pipe defects as cracks, pores, local wall thinning, and ferromagnetic inclusions is shown.

A theoretical model for roller-shape design of three-roller continuous and synchronous calibration process of ovality and straightness for large thin-walled pipes

Large thin-walled pipes are particularly suitable for oil and gas transport and auxiliary pipes in cold areas or deep sea-beds. At present, the rounding and straightening processes are completed independently, and the theoretical model for roller-shape design is analyzed only in a single direction. To solve this problem, a theoretical model for roller-shape design of three-roller continuous and synchronous adjusting straightness and ovality process for large thin-walled pipes is established. The established model is verified by numerical simulation and experimental research using 304 stainless steel pipes. The results show that the three roller-shape design schemes, including three-section, four-section and five-section, proposed based on the theoretical model, can obtain qualified formed pipes. Based on the model, the residual ovality, residual straightness and maximum residual stress of the three roller-shape schemes are discussed. The residual straightness can reach within 0.2%, and the residual ovality can reach within 1%. It verifies the applicability of the model and the feasibility of the process. The model can provide a theoretical basis for presetting the process parameters and optimizing the roller-shape.

Development of a novel fabricating thin-walled TA2 titanium tube via high-frequency induction welding

Due to the problems of low welding efficiency, large heat-affected zone, and poor welding quality in the process of welding thin-walled titanium tubes by argon arc welding, there are few studies on the use of high-frequency induction welding (HFIW) of thin-walled titanium alloy tubes. The evolution law of weld microstructure and mechanical properties of the thin-walled titanium tube needs to be further studied because of rapid welding speed and the small heat-affected zone of HFIW. Therefore, a novel manufacturing method via high-frequency induction welding is proposed in this paper to solve the existing problems. With an industrial-grade titanium TA2 tube (wall's thickness is 0.5 ​mm) as the research object, a comparative study is conducted in this research to examine the morphology, microstructure, microhardness, and tensile characteristics of welded joints at different welding power. The findings demonstrated a significant efficacy of HFIW in resolving these challenges. The mechanical properties and microstructue of heat-affected zone (HAZ) were characterized. The lowest hardness is measured at 202 HV, while the base material was recorded as 184 HV, when the welding speed of HFIW is set at 50 ​m/min. Meanwhile, the heat-affected zone has the highest hardness at 224 HV, a tensile strength of 446.8 ​MPa and a post-fracture elongation of 16%. The results showed that HFIW can not only greatly improve the welding efficiency, significantly improve the microstructure of weld joint and HAZ, and improve the mechanical properties of thin-walled titanium pipe, but also provide a highly feasible welding method for welding ultra-thin-walled pipes.

Bidirectional-Reinforced Carbon Fiber/Polyether-Ether-Ketone Composite Thin-Walled Pipes via Pultrusion-Winding for On-Orbit Additive Manufacturing.

Benefitting from lightweight, high strength, long life, and green recyclability, continuous fiber reinforced thermoplastic composite (CFTPC) pipes have attracted extensive interest, especially in the on-orbit additive manufacturing of structural components. However, the preparation of CFTPC pipes remains challenging due to the on-orbit limited space and high processing temperature of thermoplastic resin. Here, we report an effective approach for high performance carbon fiber/polyether-ether-ketone (CF/PEEK) thin-walled pipes via bidirectional reinforcement using the pultrusion-winding technique. The continuous fabrication of thin-walled pipes can be achieved, but the limitation by the size of core mold is also broken. The compressive and shear performance of CF/PEEK pipes with different layer designs have been studied based on experiments and simulations. With the increase in axial prepreg tape layer, the resultant CF/PEEK pipes exhibit greatly improved axial compression strength. The finite element analysis indicates that the maximum axial stress is decreased due to the axial enhancement. The flexural strength is greatly proved with pultrusion-winding cycles. The simulation confirms that the circumferential strain is effectively reduced. The high performance of bidirectional reinforced CF/PEEK pipes and the facile controllability of this approach highlight their suitability for utilization in on-orbit manufacturing of large-scale structures.

Study on Fatigue Performance of Pulsed Tungsten Inert Gas Welding Joint of Duplex Stainless Steel Thin Tube.

To solve the shortage of austenite phase precipitation caused by nitrogen loss in the welding process of UNS S2205 duplex stainless steel (DSS), shielding gas nitriding was investigated by adding different N2 contents in Ar shielding gas during the welding process. A good thin-walled pipe butt joint was formed using the pulsed tungsten inert gas (P-TIG) welding method with Ar-N2 shielding gas. High cycle fatigue tests of the weld joints were conducted to study the effect of shielding gas nitriding on the fatigue properties. Fatigue tests at three stress levels of 225 MPa, 270 MPa, and 360 MPa were carried out on the weld joints with different N2 contents, and the fatigue samples were all fractured in the high temperature heat-affected zone (H-HAZ). Within the current process parameters, the fatigue life of the 4 vol.% N2 welded joints was optimal. Fatigue striations appeared in the fatigue crack propagation zone, and the transient fracture zone was similar to the tensile fracture. Under the low-stress level, the area of the crack propagation zone under 4 vol.% N2 was the highest, the tear ridges all expanded around the crack source area, and the fatigue crack propagation zone presented a radial distribution. The proliferation and expansion of dislocations were mainly carried out in the austenite grains, and the dislocation density of the fatigue specimens under 4 vol.% N2 was smaller than that of the Ar specimens. Shielding gas nitriding effectively improved the balance of the two-phase ratio and the hardness of austenite phase, optimized the internal slip system, inhibited the proliferation of dislocations in the austenite phase, and improved the fatigue life of weld joints.

Soil–Structure Interaction Analysis Using the Finite Element Method in Thin-Walled Steel Pipes Buried under Haul Roads

This paper addresses the challenges associated with steel pipes used for transporting liquid fluids within buried sections of mining facilities, specifically in areas with heavy mining vehicles. While existing design standards, such as AW-WA M11, and manufacturer recommendations largely consider loads from vehicles like the AASHTO HS20 or Cooper E-80, both weighing below 35 tons, these guidelines inadequately represent the actual loads experienced on certain mining roads, notably those accommodating heavy vehicles, like haul roads. The research presented here focuses on the interaction between soil and buried steel pipes under the substantial loads exerted by mining vehicles with a maximum gross load of up to 612 tons, inclusive of hauled material weight. Utilizing a parametric study with the finite element method, the paper identifies critical variables influencing efforts and deflections calculations in these facilities. The analysis of 108 models, varying parameters related to trench pipe installation conditions, offers insights that empower designers to refine soil trench parameters in mining facilities, mitigating pipe failures and optimizing installation costs. Ultimately, the key influential variables affecting pipe deflection and stress are identified as the trench backfill height and the elasticity modulus of the trench lateral fill.