Bending Process Research Articles

Effect of bending radius on deformation behavior of H62 brass tubes in a less constrained free bending process

Effect of bending radius on deformation behavior of H62 brass tubes in a less constrained free bending process

Active laminated-plate model for spontaneous bending of Hydra tissue fragments driven by supracellular actomyosin bundles

The outstanding regeneration of Hydra’s excised tissue fragments occurs via initial spontaneous bending to some quasi-stable shape in several minutes. However, the underlying mechanism and dynamics of such initial spontaneous bending are still debated. Here, we propose that the spontaneous bending is driven mechanically by supracellular actomyosin bundles inherited from parent Hydra. Our active laminated-plate (ALP) model predicts that the equilibrium fragment shape is determined by anisotropy in contractility and elasticity. We construct a minimal dynamic ALP model including three dissipation mechanisms. By variational analysis and bead-spring simulations, we find that the bending process starts diffusively from the edges and relaxes exponentially to the equilibrium shape. The different dissipation mechanisms take place at distinct timescales: the viscous drag occurs in 0.001 seconds, while the interlayer frictional sliding and cellular dissipation take place in minutes. The ALP model could be adapted to study multi-layered viscoelastic tissues with nematic cytoskeletal structures and provides a useful framework for tissue morphogenesis and regeneration.

Curvature-dependent strain-induced photoluminescence modulations in flexible Er-doped Pb0.98La0.02Zr0.95Ti0.05O3 antiferroelectric thin films prepared by the sol-gel method

Tunable photoluminescence (PL) has wide applications in optical waveguides and communication. Since the PL intensity is strongly dependent on the crystal field symmetry, curvature-dependent strain-induced PL modulation is expected in flexible antiferroelectric (AFE) thin film materials. Here, flexible Er-doped Pb0.98La0.02Zr0.95Ti0.05O3 (PLZT) AFE thin films were prepared via the sol-gel method. A giant and reversible PL intensity modulation (482%) was achieved during the bending process. Based on density functional theory (DFT) calculations and Raman spectra measurements, the relationship amongst the curvature-dependent strains, crystal structure, and PL modulation was discussed. The induced strain leads to lattice distortion and even a phase transition, both of which contribute to the reduction in crystal symmetry and thus significantly enhance the PL intensity.

A study on the evolution mechanism of small diameter thin-walled stainless steel bellows during a bending process

In order to accurately construct the evolution mechanism of the matrix during the bending process, this paper combines finite element simulation and material characterization methods to study the evolution process of the matrix in detail. Firstly, a repeated bending model of the bellows was constructed by ABAQUS finite element software. The deformation hardening, geometry evolution, stress and strain evolution of the matrix were analyzed in depth. At the same time, by characterizing the microstructure of the trough under different bending times, the evolution of the microstructure during the fracture process was obtained. Combined with the fracture characteristics, it can be seen that the deformation hardening of the trough is significant and the stress is large, so it is most likely to become the failure zone. The waveform distortion increases the deformation inhomogeneity of the trough at different positions, resulting in local large strain accumulation and further aggravating the fracture failure of the trough. During the bending process, a large number of martensite tissue appears in the central area of the bellow wall thickness, and the dislocation gradually moves from the inner and outer surfaces to the center. The crack initiates first at the bellow outer surface and propagates along the circumference and wall thickness direction. Bending four times is the key node of crack propagation. Moreover, the crack propagation models of the trough in the wall thickness and circumferential direction are established, and the fracture failure mechanism of the trough during repeated bending is revealed.

Influencing Factors on Plasticity and Life of Hydraulic Pipelines for Logging

The bending behavior of the hydraulic pipeline on the roller of the logging winch will cause a certain plastic deformation of the hydraulic pipeline, which has a certain influence on its performance. In view of the above problems, this paper uses finite element analysis software to analyze the plastic deformation law of hydraulic pipelines under different bending radii. It can be found from the analysis results that during the bending process, the plastic deformation of the metal continuous capillary gradually increases with the neutral layer outward. In the range of the bending radius from 75 mm to 150 mm, with the increase of the bending radius, the equivalent plastic deformation decreases from 3.5×10-2 to 1.46×10-2. The changing trend of life also tends to be gentle with the increase of the bending radius, and the number of cycles increases from 25000 to 398107. The analysis of the plastic deformation law and the life of hydraulic pipelines provides a reference for designing winch drums.

Structure and Electronics of a Series of CAAC-Stabilized Diboron-Doped Acenes from 1,4-Diboranaphthalene to 6,13-Diborapentacene.

This combined experimental and theoretical study examines the influence of acene elongation, boron atom position, and acene substitution pattern on the structure and electronics of cyclic alkyl(amino)carbene (CAAC)-stabilized diboraacenes and presents the first syntheses of neutral diboranaphthalene (DBN) and diborapentacene (DBP). Whereas 2,3-diethyl-substituted 1,4-(CAAC)2-Et2DBN is isolated as a mixture of a planar (structurally characterized) NMR-active conformer and a presumably bent EPR-active conformer, 6,13-(CAAC)2-DBP resembles 9,10-(CAAC)2-DBA (DBA = diboraanthracene), with a highly puckered 6,13-DBP core and a typical biradical EPR signal. Both species are easily reduced to their puckered dianions. DFT calculations confirm that 6,13-(CAAC)2-DBP is only stable in its bent conformation, whereas 1,4-(CAAC)2-Et2DBN exists as both flat closed-shell and bent open-shell biradical conformers, which interchange by thermally activated ethyl and CAAC rotation/diboraacene bending processes. An in-depth computational study of the series of unsubstituted, CAAC-stabilized, symmetrically diboron-doped acenes from 1,4-(CAAC)2-DBN to 6,13-(CAAC)2-DBP was carried out. The results show interesting trends dependent on the position of the boron atoms within the acene framework as well as on the relative orientation of the CAAC ligands, which enable fine-tuning of the electronic and structural features.

Study of effect on parameters of bend quality for tubes

Tube bending is a metal forming process that is used to shape pipes or tubing. Bending machines take straight tube stock and create a shape involving single or multiple bends. This allows the tubing to be formed in any fashion to fit the application's specific needs. The process of tube bending involves using mechanical force to push stock material pipe or tubing against a die, forcing the pipe or tube to conform to the shape of the die. There are three basic bends that are commonly used: the 90° bend, the common offset, and the saddle. Wrinkles occur when the mandrel inside the tube is no longer able to provide enough counteractive force. Wipers are always used in combination with mandrels inserted inside the tube during bending. The mandrel's primary job is to control the shape on the outside radius of the bend. They are excessively used in everything from the automotive industry to aviation, shipbuilding, aerospace, oil and gas, etc. The automotive sector heavily relies on mandrel bending machines to minimize thin wall tubing's ovality when it's bent.

Structural analysis of customized 3D printed plate for pelvic bone by comparison with conventional plate based on bending process

Pelvic bone fracture is highly complex, and its anatomical reduction is difficult. Therefore, patient-specific customized plates have been developed using three-dimensional (3D) printing technology and are being increasingly used. In this study, the reduction status in five representative pelvic fracture models was compared between two groups: the 3D printing plate (3DP) group using a patient-specific 3D printed plate after virtual reduction and the conventional plate (CP) group using a conventional plate by manual bending. The 3DP and CP groups included 10 and 5 cases, respectively. The fractured models were reduced virtually and their non-locking metal plates were customized using 3D printing. The process of contouring the conventional plates to fit the contact surface of the bone with the bending tool was conducted by an experienced pelvic bone trauma surgeon. The reduction and fixation achieved using the two different plate groups was compared, and the significance of differences in the results was analyzed using paired t-tests, after verifying the normality of data distribution. The vertex distances between the surface of the bone and the contact surface of the plate were significantly lower in the 3DP group than in the CP group (0.407 ± 0.342 and 2.195 ± 1.643, respectively, P = 0.008). Length and angular variations, which are measurements of the reduction state, were also lower in the 3DP group than in the CP group (length variation: 3.211 ± 2.497 and 5.493 ± 3.609, respectively, P = 0.051; angular variation: 2.958 ± 1.977 and 4.352 ± 1.947, respectively, P = 0.037). The customized 3D printed plate in the virtual reduction model provided a highly accurate reduction of pelvic bone fractures, suggesting that the customized 3D printed plate may help ensure easy and accurate reduction.

Nonlinear static behavior analysis of single/double-layer frame tunnels with mortise and tenon joint

Prefabricated tunnels are composed of prefabricated components through joints, and the joints are of weaker stiffness than other parts. The static behavior of a tunnel shows nonlinear characteristics. This study analyzes the nonlinear static behavior of single/double-layer frame tunnels with mortise and tenon joint. The mechanical properties of mortise and tenon joint are studied by large-scale model tests. A finite element model of a prefabricated frame tunnel is established, the nonlinear static behavior of prefabricated frame single/double-layer tunnels is studied, and the mechanical properties of a prefabricated joint tunnel and a wet joint tunnel are compared and discussed. The results show that the deflection and opening values of the mortise and tenon joint show a three-stage nonlinear change during the compression bending process. The single/double-layer tunnels with mortise and tenon joint exhibit a stiffness recovery phenomenon under a static load. The deformation characteristics of the single/double-layer tunnels show obvious differences due to their different structural forms. Overall, the anti-deformationcapability of the prefabricated frame tunnel with mortise and tenon joint is weaker than that with the wet joint. The structural integrity and stability of the prefabricated tunnel are worse than those of the wet joint tunnel, and its stiffness changes greatly.

Analysis of the roll bending process of profile

Analysis of the roll bending process of profile

One-Step Hybrid Bending/Diffusion Bonding Process and Analysis of the Bonding Characteristics of Titanium Alloy Sheets.

A one-step hybrid bending/diffusion bonding process (HB/DBP) was developed for application to Ti-6Al-4V sheets to effectively improve buy-to-fly (BTF) ratio of aircraft parts, integrating sequential diffusion bonding followed by a bending process. The resulting bonding characteristics of these titanium alloy sheets were analyzed. Microstructural analysis and mechanical lap shear tests were performed to estimate the bonding quality. Additionally, bonding ratio, thickness strain, and shear strength were evaluated in relation to pressure under increasing temperature. When the applied pressure was lower than 0.5 MPa, early failure occurred at the joint of the specimens. However, when high pressure was applied, early failure occurred near the joint. To discuss the phenomenon, time-dependent viscoplastic material properties were characterized, and a numerical simulation analysis was performed. Viscoplastic deformation was observed around the bending area, which caused weakness around the bond under high-pressure conditions. A prototype of a Y-shaped heat shield was manufactured and the buy-to-fly ratio was effectively improved using the newly developed process. This study demonstrates the potential of applying the developed process for producing aircraft parts and the importance of viscoplastic behavior for the analysis of final product reliability.

Validation of applicability of induction bending process to P91 piping of prototype Gen-IV sodium-cooled fast reactor (PGSFR)

The application of the induction bending process to pipe systems in various industrial fields is increasing. Recently, efforts have also been made to apply this bending process to nuclear power plants because it can innovatively reduce welded parts of the curved pipes, such as elbows. However, there have been no cases of the application of induction bending to the piping of nuclear power plants.In this study, the applicability of the P91 induction bending piping for the sodium-cooled fast reactor PGSFR was validated through high temperature low cycle fatigue tests and creep tests using P91 induction bending pipe specimens. The tests confirmed that the materials sufficiently satisfied the fatigue life and the creep rupture life requirements for P91 steel at 550 °C in the ASME B&PV Code, Sec. III, Div. 5. The results show that the effects of heating and bending by the induction bending process on the material properties were not significant and the induction bending process could be applicable to piping system of PGSFR well.

Numerical modelling of the process chain for aluminium Tailored Heat-Treated Profiles

Lightweight construction in modern car design leads to an increased usage of various aluminium semi-finished products. Besides sheet material, aluminium extrusion profiles are frequently used due to their high stiffness and variety of possible cross-sections. However, similar to sheet material, aluminium profiles exhibit limited formability in comparison to mild steel materials. One possibility to increase the forming limits of precipitation hardened aluminium alloys is the so-called Tailored Heat Treatment technology. By a local short-term heat treatment, the material is softened and the material flow can be controlled to reduce stresses in critical forming zones. The purposeful definition of the heat treatment zones is mandatory to improve the forming results. Therefore, numerical methods are necessary. In this investigation, a numerical process chain is presented. It combines the thermo-mechanical simulation of a local laser heat treatment with a subsequent bending process of the heat-treated profile using the alloy EN AW-6082. The temperature distribution, mechanical properties, and finally, the bending result of the numerical model are validated by experimental tests.

Advances in understanding the cooling rates and bending of needle ice: Photogrammetric and thermal observations leading to the spatial distribution of needle ice creep

AbstractThe freeze–thaw cycles are a process that dominate entire landscapes with different intensity and magnitudes that are strongly changing in the current climate change conditions. In particular, the diurnal frost heave (FH) and needle ice creep (NIC) are two poorly studied processes, especially in the field, despite their effects on the sediment transportation and vegetation colonization on Alpine slopes. In a site of the Central Alps, we applied photogrammetry, thermal imaging, manual measurements and thermistors logging to improve the knowledge of the driving parameter for the formation and accretion of needle ice, of the relations of their spatial distribution with cooling rates and the frost creep modelling change in the presence of the bending process. Among the driving factors, we demonstrate that very local conditions govern the development of the needle ice, like the air cooling rates, the deepening of the freezing front and the surficial cooling rates. Especially low cooling rates are necessary for an intense process. Also the grain size influences the development of the needle ice with higher needle ice development under fine sediment than under small clasts due to a differential thermal conductivity. Moreover, the bending of needle ice has proved to be dependent on its length, age and type of heaved sediment. Therefore, potential frost creep formulas needed to be ameliorated considering the bending angle. Subsequently, a question about the role of slope gradient in NIC is treated.

Insight into the deformation transition effect in free bending of tubes

The deformation transition has a significant impact on the forming accuracy in tube free bending. In this paper, the formation mechanism of deformation transition in free bending is analytically revealed. Considering the bending angle and the length of forming area in the transition segment, a modified relationship between the bending die deviation U and the bending radius R is proposed by introducing a new correction factor k. The developed correction method is carefully verified by free bending experiments and simulations using AA5052 tubes, and further, the influence mechanism of the deformation transition in free bending is clarified. This study provides new insights into the understanding of deformation transition in free bending, providing an effective way to design more accurate and robust bending processes for improving product quality.

Investigation on the wall thickness variation of an eccentric tube in the rotary draw bending process

PurposeWhen bending a large diameter thin-walled tube, the thickn ess of outer side wall will reduce greatly, which leads to a decrease of structural strength of the tube. To solve this problem, this paper investigated the deformation principles of an eccentric tube in the rotary draw bending process, trying to find a way to reduce the wall thickness difference between inner and outer diameters.Design/methodology/approachAn finite element model is established for analyzing the deformation of an eccentric tube in rotary draw bending process. The wall thickness distribution of the formed pipe was analyzed along the axis and diameter, respectively.FindingsIt is found that there exists an optimal eccentricity between the inner and outer circle center of the tube cross-section. If the eccentricity of the tube is chosen properly, it is possible to get a bent tube with equal thickness of inner and outer side walls. In addition, it is also found the optimal eccentricity on the cross-section can be influenced by bending radius, wall thickness, diameter and bending angle. The optimal eccentricity increases greatly with the decreasing of bending radius, the increase of outer diameter and the increase of wall thickness. The influence of bending angle on the optimal eccentricity can be divided into two situations. When the bending angle is small, the optimal eccentricity increases with the increase of bending angle. When the bending angle exceeds a certain value, the pipe enters a stable forming state. The optimal eccentricity of the stable forming region does not change with the bending angle.Originality/valueSuch a research is beneficial for reducing the thickness difference between inner and outer side walls in the rotary draw bending process.

Finite element simulation prediction of repeated bending failure zone of roll-welded bellows based on an equivalent welding model

In this paper, an equivalent welding model is proposed that takes the tensile stress and strain parameters of the axial weld area of the roll-welded bellows as the material properties to replace welding simulation. The integrated finite element method is used to simulate the following two model forming processes for the roll-welded bellows: (i) welding-bulging-repeated bending model, and (ii) equivalent welding-bulging-repeated bending model. The stress and strain distributions of the two models are compared and analyzed, and the main failure areas of the roll-welded bellows in the repeated bending process are predicted. At the same time, the accuracy of the model prediction is verified by the limited repeated bending test of the roll-welded bellows, and the failure mechanism of the roll-welded bellows is revealed. The results indicate that the stress and strain distributions of the two models are essentially the same, thus verifying the feasibility of the equivalent welding model. When the cyclic deformation reaches the limit, the predicted stress failure risk zone is located at the base metal position of the first wave-like trough of the bellows near the heat affected zone at the fixed end, which is consistent with the experimental results. This indicates that the equivalent welding-bulging-repeated bending model can accurately predict the position of the repeated bending fatigue failure of the bellows, thus laying a foundation for the optimization of the roll-welded bellows.

Effect of high-power ultrasonic vibration on the flexible bending process of thin-walled circular tubes: Numerical and experimental research

Thin-walled bent tubes are a significant component utilized in the aerospace, shipbuilding, and chemical industries, as well as considering that they are employed as fluid and gas transporters, the quality of their manufacturing and production is critical. In recent years, new technologies for the manufacture of these structures have been developed, the most promising of which is the flexible bending process. Nevertheless, during tube bending, defects like an increase in contact stress and friction force in the bending area, thinning of the bent tube in the extrados zone, ovalization, and spring-back are some of the issues that arise. So, based on the softening and surface effects induced by ultrasonic energy in metal forming, this paper is suggested a novel method to fabricate the bent components by adding ultrasonic vibrations into the static motion of the tube. Therefore, experimental tests and finite element (FE) simulations are employed to assess the impact of ultrasonic vibrations on the forming quality of the bent tubes. Initially, an experimental setup was designed and built to guarantee the transmission of ultrasonic vibrations with a frequency of 20 kHz to the bending area. Afterward, based on the experimental test and its geometrical parameters, a 3D finite element model of the ultrasonic-assisted flexible bending (UAFB) process was developed and validated. According to the findings, forming forces were significantly reduced when the ultrasonic energy was superimposed, and thickness distribution in the extrados zone was significantly enhanced as a result of the acoustoplastic effect. In the meantime, the UV field’s application effectively diminishes the contact stress between the bending die and tube, as well as greatly reduces the material flow stress. In the end, it was found that applying UV at the appropriate vibration amplitude can effectively improve ovalization and spring-back. The current study will assist researchers in better understanding the role of ultrasonic vibrations in performing the flexible bending process and achieving improved tube formability.

Interfacial Modification and Bending Performance of 3D Orthogonal Woven Composites with Basalt Filament Yarns.

To improve their interfacial properties, 3D orthogonal woven fabrics with basalt filament yarns were modified with functionalized carboxylated carbon nanotubes (KH570-MWCNTs) and polydopamine (PDA). Fourier infrared spectroscopy (FT-IR) analysis and scanning electron microscopy (SEM) testing were used. It was demonstrated that both methods could successfully modify basalt fiber (BF) 3D woven fabrics. The 3D orthogonal woven composites (3DOWC) were produced with epoxy resin and 3D orthogonal woven fabrics as raw material by the VARTM molding process. The bending properties of the 3DOWC were tested and analyzed by experimental and finite element analysis methods. The results showed that the bending properties of the 3DOWC modified by KH570-MWCNTs and PDA were significantly improved, and the maximum bending loads were increased by 31.5% and 31.0%. The findings of the finite element simulation and the experiment results were in good agreement, and the simulation error value was 3.37%. The correctness of the finite element simulation results and the model's validity further reveal the material's damage situation and damage mechanism in the bending process.

Research on the Role of Surface Treatment of the Metal Surface on the Strength of the Metal-Ceramic Bond.

The aim of the present study is to investigate the metal-ceramic bond strength as a result of three different surface treatment methods: (1) oxidation, (2) oxidation and sandblasting, and (3) double oxidation on the metal substrate. A total of 72 metal substrates were made from two different types of metal-ceramic alloys (n = 36): group I, Ni-Cr and group II, Co-Cr alloys. Each group was further divided and subjected to three different surface treatments (n = 12): (1) oxidation in accordance with the manufacturer's instructions; (2) oxidation according to the manufacturer's instructions and then sandblasting with Al2O3, with a grain size of 110 μm, a pressure of 75 psi for 10 sec with a distance of 5 cm and steam cleaning; and (3) double oxidation. The bond strength of the specimens was evaluated with the three-point bending process. The data were recorded, tabulated, and statistically analyzed. For group I, the materials with oxidation based on the specifications, show mean value of 64.02 Nt. The oxidation and sandblasting materials have mean 55.92 Nt. The double oxidation materials have mean 55.47. For group II, the materials with oxidation based on the specifications, show mean value of 58.46 Nt. The oxidation and sandblasting materials have a mean value of 42.56 Nt. The double oxidation materials have mean 42.96 Nt. The best method of treatment of the metal substrate is specification oxidation, in terms of the strength of the metal-ceramic bond. Further treatment of the metal substrate reduces the strength of the metal-ceramic bond. A prerequisite for clinical success of metal-ceramic prosthetic restorations is the increased strength of the bond between ceramic material and metal substrate. With that in mind, the present research gives important insight into best practices for prosthetic restorations.