Tubular Components Research Articles

Welding of Low Carbon Steel Tubes Using Magnetically Impelled Arc Butt Welding: Experimental Investigation and Characterization

Magnetically impelled arc butt (MIAB) welding is a solid-state technique of welding that utilizes the heating effect of a high-speed rotating arc for the formation of the weld. The process exhibits lower time and power consumption compared to conventional solid-state processes for tube–tube joining. However, the available research reports on MIAB welding of Mild Steel (MS)1018 are still inadequate and lack the details required for extending the applications of this process. Hence, this study was undertaken to investigate MIAB welding for MS 1018 tubes. Experimental investigations were performed on a specifically designed and newly fabricated MIAB welding machine. The experimental trials involved varying the process parameters and understanding their influence on joint strength and other weld characteristics. Microstructure of the MIAB weld consisted of acicular ferrite which differed from the microstructure of the heat-affected zone. These trials helped to arrive at the optimum parametric window that specified the ranges of key parameters viz. welding current, upset current, and welding time to yield an efficient weld. Chemical analysis of the weld indicated the absence of inter-metallics. MIAB welding of MS1018 showed greater strength and integrity at the joint when optimum ranges of the process parameters were maintained, and is feasible for deployment as economizer coils in boilers, pressure part tubes, and automobile tubular component joining applications.

Enhancing bending buckling strength of hollow tubes using concrete filling

Hollow tubular components are widely used in industries as structural elements which are subjected to bending loads. These tubes are susceptible to bending (transverse) buckling, more so in tubes with thinner cross sections. The presented work investigates the effect of adding an inexpensive core like concrete (with good compressive strength) on the bending buckling strength of thin hollow tubes. This study is based on the results obtained from three-point bend tests performed on hollow and concrete filled thin stainless-steel tubes of small diameter. The size of test specimens was chosen such that the bending buckling mode dominates over the yielding as a failure mode. The experimental results are validated by finite element-based simulations. It was observed that addition of a concrete core significantly improves the bending buckling strength of the thin hollow tubes.

Effect of heterogeneous microstructure on the mechanical properties and deformation behavior of rotating backward extruded ZK61 alloy

The rotating backward extrusion (RBE), as a novel severe plastic deformation process, has prosperous industrial application prospect. However, the capability and potential of the RBE process to prepare samples with different heterogeneous microstructures has not attracted attention. In order to explore the relationship between different microstructural compositions and mechanical properties of tubular component prepared by RBE process, the grain size distribution, grain orientation and mechanical properties of a ZK61 Mg alloy tubular component prepared by the RBE process in different regions (along the wall thickness and height directions) were investigated. The results show that the microstructure evolution in different regions is closely related to the equivalent strain distribution. The grain refinement effect is positively correlated with the equivalent strain, but a higher applied strain also leads to a strong basal orientation and high residual stress. Furthermore, the tensile deformation behavior of different samples revealed that samples with preferentially microstructural compositions (volume fraction of fine grains: 40∼60%) have better work hardening capability and strong-toughness synergy. This is mainly attributed to more effective coordinated deformation between different regions (fine grain region and coarse grain region), which can relieve local stress concentration and accommodate more dislocations. In contrast, an excessively high volume fraction of fine grains in samples limits their ability to store dislocations that saturate rapidly with increasing strain, while an excessively low volume fraction of fine grains in samples has difficulty accommodating the high density dislocations transferred from the coarse grain region, resulting in accumulation of high local stress at the interfaces of different regions (fine grain region and coarse grain region). Both of the above can deteriorate the work hardening ability and comprehensive performance, causing the sample to fail before sufficient work hardening occurs.

Forming limit of 6061 aluminum alloy tube at cryogenic temperatures

Cryogenic medium pressure forming has been proposed to fabricate aluminum alloy complex tubular components. It is urgently needed to evaluate and predict the cryogenic forming limit of aluminum alloy tubes for the novel process. Cryogenic bulging test using different length-diameter ratios was proposed to test the forming limit in the tension-tension zone. A modified M-K model was established to rapidly predict the cryogenic forming limit, based on the dynamic hardening with deformation. Theoretical analysis and fracture characterization were implemented to reveal the improvement mechanism of cryogenic forming limit from the macroscopic and microscopic perspectives, respectively. The forming limit of AA6061 tube at −196 °C is approximately double that at room temperature, especially in the tension-tension zone, which contributes significantly to the forming of complex features under biaxial tension. The cryogenic limiting deformation ability increases gradually as the strain state changes from plane strain to biaxial tension. Under the biaxial tension condition of λ=1.2, the limiting strain can reach 0.52 at −196 °C. The cryogenic forming limit can be successfully predicted by the modified M-K model with a prediction deviation of only 4.35% at −196 °C. The enhanced cryogenic hardening ability promotes the improvement of deformation uniformity and delays the occurrence of uncoordinated deformation. Ductile fracture is main fracture mechanism at cryogenic temperature. The significantly increased ductile fracture characteristics contribute to the improved cryogenic forming limit. This research can provide important guidance for the cryogenic forming of aluminum alloy tubular components.

Hot Spinning of Cutting Blades for Food Industry

The spinning process is a flexible incremental forming process for the manufacturing of axially-symmetric sheet metal or tubular components with functionally graded properties. It is characterized by the utilization of universal tooling geometries and quite low forming forces. The process has a high potential to reduce material waste, to extend the forming limits and to achieve more complex geometries as well as favorable part properties [1]. Current research work at the Chair of Forming Technology (LUF) is focused on innovative flow-turning processes that have a high potential for producing flat components with excellent geometrical and mechanical properties while keeping process times short [2]. In combination with process-integrated local heat treatment, the new spinning process is predestined for the efficient forming of ultra-high-strength steel or tailored materials. Due to the desired field of food industry only food-safe materials such as special stainless steels are being investigated. This paper presents an innovative machine layout as well as an adequate process design for the production of high-performance circular knives with optimized mechanical hardness. In this context, particular attention is paid to various areas of temperature control as well as process-related challenges during the process.

Numerical and Experimental Investigations on the Mechanical Properties of Milled Specimens from an AA7020 Tube

The reduction of weight is crucial in the automotive sector to reach a lower energy consumption and an increased range, especially for electrically powered vehicles. In this regard, body-in-white parts offer a high potential for the application of lightweight construction. The required weight savings can be achieved by implementing parts with a high strength-to-weight ratio. A promising approach is the combination of lightweight materials and lightweight design, which can be realized by tubular components made of high strength aluminum. Due to their structural stiffness and high crashworthiness, those structures are often used as safety-relevant car body components. However, the material characterization of tube profiles is a major challenge, which in turn impedes an accurate numerical simulation and precise process design. In contrast to flat semi-finished parts, various effects of the production process and the geometry, regarding the stress state under load, must be taken into account. For this purpose, adapted testing methods considering the geometrical and mechanical properties of the tubular parts have to be investigated, in order to generate an accurate material model and process design. Within this research work, tubular components made out of AA7020 in W-temper condition were used to analyze the mechanical properties. In this regard, several tensile specimens are milled from a tube, so they also have a curvature profile. The experimental tensile tests have been performed at different strain rates by using an universal testing machine from type Gleeble 3500. To ensure a proper measurement of the mechanical properties, the clamping jaws of the testing machine are adjusted to the curved samples. The investigated material parameters are subsequently transferred to an FE-Model with curved specimen to enable an accurate prediction of the forming behavior. In addition, an FE model of a flat tensile specimen was also created for comparison, in order to gain a profound knowledge regarding the influence of the geometric and mechanical properties of tubular components.

Investigation of the Tube Expansion Test with Elastomer Using Locally Overaged AA6063 Tubes

The definitive implementation of Aluminium alloys as the main choice for lighter structural components needs the availability of innovative manufacturing processes capable of overcoming their poor formability at room temperature. The local modifications of the material properties (by means of short-term heat treatments) have shown their effectiveness in such terms. In a previous study from the same authors, it was experimentally investigated that, if a AA6063-T6 tubular component is locally brought to the overaged condition, its strain behavior significantly changes during an expansion test with elastomer. In light of this, the equipment used for the tube expansion tests was simulated by means of a FE model created using Abaqus and properly tuned using data coming from experimental tests carried out on AA6063-T6 tubular specimens. The calibrated model could be thus used to simulate the tube expansion while considering several distributions of the material properties (obtained through different heating strategies). Numerical results confirmed the possibility to change the slope of the strain path, thus suggesting that the strain behavior of a tubular component can be tailored, according to the specific applications, by properly designing the laser heating strategy.

Thickness distribution uniformity improvement and forming pressure reduction of stepped tubular components by axial hydro-pressing method

Thickness distribution uniformity improvement and forming pressure reduction of stepped tubular components by axial hydro-pressing method

An investigation into the effect of pre-bending on the tube hydro-forging technology

THFG is an advanced technology to manufacture tubular components with complex cross-sections. Meanwhile, curved axis often exists in such components, which is formed by pre-bending steps before THFG. However, the effect of pre-bending on the subsequent THFG, especially on the critical internal pressure required to inhibit wrinkling, has not been clarified yet. Considering the difference in the cold work-hardening and the thickness distribution caused by pre-bending, the change rule between the critical internal pressure and the hoop strain was re-established based on the energy method. It is found that the cold work-hardening has a great influence on the change rule. Subsequently, by solving the three-dimensional mechanics condition of single and double curvature differential segments respectively, the distribution of hoop strain after THFG was obtained by combining pre-bending. Pointing out that the initial thickness has an obvious effect on the hoop strain distribution, while the cold work-hardening is almost negligible. The maximum hoop strain was brought into the change rule between critical internal pressure and hoop strain, then, a new analytical model between the critical internal pressure and the punch stroke considering pre-bending was built. The critical internal pressure considering pre-bending is determined by that of outer straight wall, and its value is always greater than the critical internal pressure without considering pre-bending under the same punch stroke. With the reduction of bending radius, the critical internal pressure distinction between considering and not considering pre-bending will be greater. Moreover, the smaller the friction coefficient also will lead the distinction to be more prominent. In this work, our proposed new prediction model of critical internal pressure is meticulously demonstrated, which can improve the accuracy by 74% at least when existing the pre-bending.

Numerical modelling of Direct Hot Tube Rotary Draw Bending of 22MnB5 High Strength Steel

The use of High Strength Steel (HSS) tubular components in structural frames allows a drastic increase of the stiffness-to-weight ratio and, therefore, may open new possibilities to the design lightweight components for the transport industrial sector. However, the diffusion of these elements is still limited by the lack of manufacturing technologies capable of efficiently forming and bending HSS hollow profiles. To overcome the limits of traditional room temperature processes, an innovative rotary draw bending process carried out at high temperature is proposed, in which the profile cross section is quickly heated to the target temperature and, then, bent and selectively cooled to induce controlled microstructure changes. The paper presents a fully coupled thermo-mechanical-metallurgical numerical model to support the process design, which was applied to 22MnB5 tubes. The model was used to identify the optimal thermal and mechanical parameters to increase the material formability and to obtain the target microstructure in the final part. All the process steps, namely heating, handling, forming, and cooling, were modelled, and the results were experimentally validated by industrial trials carried out on a bending pilot plant. The results prove the possibility of an accurate prediction of both the final shape and the distribution of the microstructural and mechanical properties along the bend.

Vascular and glomerular vs. proximal tubular components in calcineurin inhibitor‐related nephrotoxicity

Calcineurin inhibitors (CNI) are widely in use for immunosuppression in transplant recipients, but their nephrotoxicity may cause or aggravate renal disease. CNI pathology includes vascular and tubulointerstitial alterations.We have compared the effects of cyclosporine A (CsA) and tacrolimus (Tac) upon chronic administration in a rat model. We have tested whether Tac caused less damage than CsA. To this end, functional as well as glomerular and tubulointerstitial parameters were compared.Adult Wistar rats received CsA (25 mg/kg/d), Tac (2 mg/kg/d), or vehicle via subcutaneously implanted minipumps. After four weeks, rats were sacrificed and organs removed for protein analysis or perfusion‐fixed and kidneys analyzed for histopathology. NRK cells were treated with graded concentrations of CNI for 24h. For evaluation, confocal immunohistochemistry, EM nanotomy, EM immunostaining, Western blot, and clinical chemistry methods were applied.In rats, CsA and Tac produced distinct alterations in the tubulointerstitium. With CsA, dysmorphic lysosomes with peripheral LAMP1 signal, autophagic and mitophagic vacuoles caused epithelial decay of the initial proximal tubule, while glomerular changes were less pronounced. With Tac, glomerulosclerosis and damage encroachment to proximal tubule were more prominent. Both drugs induced fibrotic upregulation of alpha‐smooth muscle actin in the interstitium. Alterations in unfolded protein response (UPR) parameters included rises in p‐eIF2α, p‐PERK, p‐IRE1, sXBP1, CHOP in CsA‐, but not in Tac‐treated rats. Epithelial TUNEL signal was stronger in the CsA than in the Tac groups. Results were verified in NRK cells using graded caspase‐3 and lysosome formation criteria.Data revealed distinct nephrotoxicity patterns in the two examined immunosuppressive medications. While CsA seems to be primarily tubulotoxic, a stronger glomerular component was detected with Tac. Results may serve to better adjust treatment combinations in transplant patients.

Cryogenic deformation behavior of 6061 aluminum alloy tube under biaxial tension condition

Cryogenic forming has been proposed for the fabrication of complex aluminum alloys tubular components to overcome the shortcomings of traditional forming processes. It is difficult to evaluate the cryogenic biaxial deformation behavior. In this study, a novel cryogenic hydro-bulging device was established to evaluate cryogenic deformation behavior and verify the feasibility of the new forming process. The cryogenic biaxial stress-strain relations were determined using a new analytical model to quantitatively characterize the hardening behavior. The cryogenic deformation mechanism was revealed by microstructure characterization. It is found that the maximum expansion rate of 6061 aluminum alloy tube at − 196 ℃ increases to 34.0% ± 0.6%, being 99.8% higher than that at room temperature. The obtained cryogenic biaxial flow curve exhibits the significantly improved plasticity and hardening ability with a strain hardening exponent of 0.43 at − 196 ℃. The high cryogenic strain hardening rate contributes to the stable uniform deformation. The improved cryogenic plasticity is associated with the diminished dislocations accumulation at grain boundaries. The enhanced cryogenic hardening ability is attributed to the impeded movable dislocations slip. The research demonstrates that cryogenic medium pressure forming has great potential for the fabrication of complex aluminum alloy tubular components. • A novel cryogenic hydro-bulging device was established for evaluating the cryogenic biaxial deformation behavior oftubes. • The cryogenic biaxial mechanical properties and hardening behavior were quantitatively evaluated by a new analytical model. • Excellent cryogenic biaxial formability can be obtained, contributing to the fabrication of complex tubular parts. • Microstructure was characterized to reveal the cryogenic deformation mechanism.

Characterization of Surface-Breaking Cracks on Tubular Structures Using Ultrasonic Phased Array with Rayleigh Waves

Surface-breaking cracks are typical defects in tubular structures. Compared with other types of defects such as internal voids, surface cracks often impose more serious threats to structural integrity. This study presents an approach to detect and characterize surface-breaking cracks on tubular samples through the use of ultrasonic phased array technology with surface acoustic waves (SAWs). A Rayleigh type surface wave is selected in our work as it is nondispersive and highly sensitive to surface and subsurface defects. Finite element (FE) analysis is used to simulate the interaction between Rayleigh waves and surface-breaking cracks with varying depths, inclined angles and profiles. The reflection coefficient of Rayleigh waves is calculated based on simulation results and fitted to a proper model. Crack depths and inclined angles can be evaluated from the fitted curves. Furthermore, a full matrix capture (FMC) data acquisition strategy is simulated in FE models with phased array to collect pulse-echo signals of Rayleigh waves. An array imaging algorithm is applied to FMC data and adapted to curved surface. The profile and location of surface cracks are reconstructed from imaging results. The configuration of phased array is optimized to increase the resolution of the method. The proposed approach is validated numerically and provides an efficient way to measure the length, depth and inclined angle of surface-breaking cracks on tubular component.

Design guidelines for suppressing distortion and buckling in metallic thin-wall structures built by powder-bed fusion additive manufacturing

Controlling distortion in laser powder-bed fusion additive manufacturing is of critical importance especially for thin-wall structures, which typically experience significant deformation and buckling during the build process. We examine this issue from the perspective of design by systematically performing numerical simulations of the additive process of tubular components as a function of part design, including fillet radius, wall thickness, tube width and height. It is found that round corners, as opposed to sharp corners, suppress distortion even at small wall thickness (400 µm), while part width has a greater impact on distortion than part height. The buckling behavior of such structures is numerically investigated and analysis results show that for designs most prone to distortion, a critical height exists below which the component is distortion-free. The modeling was experimentally validated by manufacturing thin-wall components of IN718 alloy using the EOS M290 printer. The findings provide practical guidelines to manufacture metallic thin-wall tubular components with minimal to no distortion using powder-bed fusion additive manufacturing.

Carbon-based nanocoating for extended lifetime of conventional scale inhibitor squeeze treatment in sandstone reservoirs

Scale inhibition squeeze treatment is a common practice to prevent scale deposition within the downhole utilities, valve applications, and tubular components of the oil and gas producing wells. The conventional squeeze treatment has a short lifetime due to the reservoir rocks' limited adsorption of scale inhibitors and the quick desorption rate. As a result, this process has to be repeated multiple times per year, leading to massive increases in operational costs. Carbon-based nanomaterials are known for their high specific surface area, making them an attractive coating agent to enhance the capability of rocks’ surfaces to adsorb chemicals such as scale inhibitors. In this paper, carbon-based nanomaterials of graphene nanoplatelet (GNPs) and three different types of carbon nanotubes (CNTs) are proposed as novel nanocoating to extend the lifetime of the conventional scale inhibitor squeeze treatment. A natural polymer of Gum Arab (GA) was used to graft the nanomaterials surfaces to ensure a homogeneous and stabilized coating solution. The adsorption of diethylenetriamine penta (methylene phosphonic acid) (DTPMP) scale inhibitor into GNPs and CNTs was investigated using a UV–Vis spectrophotometer. Various characterization techniques such as FTIR, Raman spectroscopy, and XPS were performed to evaluate the interaction between DTPMP and the proposed nanocoating (GNPs/CNTs). Based on UV–Vis results, GNPs was found to be the optimal coating agent with an adsorption capacity of 135 mg/g at ambient temperature and 114 mg/g at 96 °C. Its coating gets saturated with DTPMP within 1 h of interaction. Increasing the initial scale inhibitor concentration was found to increase the adsorption capacity of GNPs. Based on the core flooding conducted on Berea sandstone, the injection of nanocoating into the core sample reduces the permeability by only 12%. Finally, the injected nanomaterial was safely transported through the core, and the primary retention mechanism was adsorption rather than physical filtration/plugging.

Results concerning manufacturing of tubular car components using hydroforming and hydroperforation processes

The purpose of the paper is to highlight the advantages that the automotive industry gains by using hydroforming and hydroperforation processes in automobile manufacturing. In recent years, progress has been made concerning the equipment and tools needed to carry out the hydroforming and hydroperforation processes. As these machines and tools have been perfected and produced on a large scale, becoming cheaper and more cost-effective were main scopes of the development, increasing the mass production, supporting the automotive industry, as well, is another goal. The improvement of the tools used and the equipment determined that these processes have to be extended for a quite large number of components of the vehicle, in the production of large series. A comparative analysis and advantages of the technology are presented regarding the impact on the environment of these processing, hydroforming, and hydroperforation processes, in relation to other traditional processing processes

Process optimization for hot forging of difficult parts by computer experiments and response surface analysis

Closed die hot forging of 304L stainless steel is difficult compared to carbon and micro-alloyed steels in terms of higher forming force and defects. An appropriate combination of design and process factors including cross-section diameter, initial billet temperature, and flash land thickness is crucial to minimize the forming force without causing any under-filling or folding defects. This paper aims to develop an optimized closed-die hot forging process for long, thin, and tubular rail body components used in gasoline direct injection systems. The effects on the forging load are investigated using computer experiments containing the finite element method under a full factorial array of three factors at three levels to obtain the main and interaction effects. Linear and quadratic surface response analyses are performed to define the relation between forging load and input factors, and finally, the simulations are validated with some limited experiments. The simulation results that fit the nonlinear regression model were in close agreement with the experiments, and an optimal set of parameters is conveniently proposed for industrial production.

Time-dependent springback of high strength titanium tubular materials: Experiment and modeling

• Residual stress and dislocation evolution of HSTT during bending and springback comprehensively obtained. • Compression-tension uneven axial residual stress-driven creep mechanism of time-dependent springback for HSTT revealed. • Viscoelasticity-Kelvin constitutive model considering stress attenuation developed for modeling time-dependent springback. • Combining Viscoelasticity-Kelvin with SIM and Chord modulus models for accurate prediction of time-dependent springback. • Deformation-history dependent effects of time-dependent springback for spatial multi-bending tubes clarified. Although time-dependent springback is minor compared with instantaneous springback, its deformation-history dependent effects may deteriorates the compactness of parts assembly and poses potential hazards to the safety and stability of the equipment systems especially under harsh service conditions. However, time-dependent springback still has not been paid enough attention, and how to accurately predict this phenomenon is still a challenge needed to be solved urgently. In this work, taking high-strength Ti-3Al-2.5V titanium tubular materials (HSTT) upon bending as a case, the experimental exploration of the physical mechanisms and the prediction modeling for time-dependent springback of the HSTT were conducted. First, the residual stress and dislocation evolution of HSTT during bending, instantaneous springback and time-dependent springback are comprehensively experimentally obtained, and the compression-tension uneven residual stress-driven creep deformation mechanism of time-dependent springback for HSTT was revealed. Then, considering stress attenuation, a Viscoelastic-Kelvin constitutive model for time-dependent springback was developed and combined with the stress invariant-based model (SIM) and Chord modulus model to accurately predict the whole process of bending, instantaneous springback and time-dependent springback of the HSTT. Finally, the verified model is employed to explore the evolution rules of time-dependent springback and residual stress of HSTT upon bending, and the deformation-history dependent effects of time-dependent springback for spatial multi-bending component are clarified. The findings and methods of this study could aid in achieving higher precision manufacturing of high performance tubular components.

Research on Magnetic Memory Detection and Compensation Method for Early Damage of Tubular Components

Research on Magnetic Memory Detection and Compensation Method for Early Damage of Tubular Components

Analysing the Interaction between Microscopic Deformation, Microstructure and Void Evolution of Near-α Titanium Alloys during Non-Superplastic Hot Deformation by an Integrated Crystal Plasticity Finite Element Model.

High-efficiency and low-cost hot forming technologies for titanium alloys have been developed for producing complex-shaped, thin-walled tubular components under non-superplastic forming conditions. Under these forming conditions, there exist complex and highly integrated material evolution processes including microscopic heterogeneous deformation, microstructure evolution and damage behaviour. This paper presents an integrated crystal plasticity finite element model of near-α titanium alloys during non-superplastic hot deformation conditions considering grain boundary sliding (GBS), dynamic recrystallisation (DRX), as well as void evolution. The polycrystalline model of a near-α TA15 titanium alloy was established, containing α phase, β phase and grain boundary (GB) regions, in which the GB region was a visualised representation of GBS. The quantitative strength ratio between the GB regions and α phase was calculated according to the Zener–Holloman parameter Z and grain size, which determined the microscopic deformation behaviour. There were found to be two high microscopic strain regions in the α phase: intragranular deformation bands through the most favourable slipping and near the GBs through multiple slipping, which promoted continuous and discontinuous DRX, respectively. With the decrease in parameter Z or grain size, the activated dislocations accommodating GBS were found to no longer pile up inside the grain, but instead travel across the grain interior. Finally, methods to improve the macroscopic plastic formability were proposed for the difficult-to-form titanium alloys experiencing non-superplastic hot deformation.