Analysis of the forming characteristics for Cu/Al bimetal tubes produced by the spinning process

Tube spinning technology represents a process with high forming precision and good flexibility and is increasingly being used in the manufacture of bimetal composite tubular structures. In the present study, a forming analysis of clad tube and base tube in spinning process was conducted through numerical simulations and experiments. There was an equivalent stress transition on the interface since the stress transmission was retarded from clad tube to base tube. The yield strength became a main consideration during a design bimetal composite tube. Meanwhile, the strain distributions in axial direction, tangential direction, and radial direction were also investigated to determine the deformation characteristics of each component. As the press amount increased, the strain of clad tube changed more than base tube. As the feed rate increased, the strain decreased in axial direction and tangential direction but almost unchanged in radial direction. Simultaneously, a method for controlling the wall thickness of the clad tube and the base tube is proposed. These results to guide the design of bimetal tube composite spinning process have the certain meanings

Prevalence of cerebral palsy comorbidities in China: a systematic review and meta-analysis

ObjectivesThis systematic review aimed to comprehensively understand the comorbidity of cerebral palsy (CP) in China.MethodsWe searched through databases in both Chinese and English until December 2022 to gather cross-sectional studies on the comorbidity of CP in China. After two reviewers independently screened the articles, collected the data, and assessed the bias risk, a meta-analysis was conducted using the Stata 17.0 software.ResultsA total of 73 articles were included. Of these, 16 articles reported total comorbidity, with a prevalence of 79.7% (95% CI: 73.8–85.7%); 56 articles reported epilepsy, with a prevalence of 17.9% (95% CI: 15.4–20.4%); 48 articles reported intellectual disability, with a prevalence of 58.0% (95% CI: 51.8–64.3%); 32 articles reported speech disorders, with a prevalence of 48.0% (95% CI: 41.6–54.4%); 41 articles reported hearing disorders, with a prevalence of 17.2% (95% CI: 13.0–21.4%); and 35 articles reported vision disorders, with a prevalence of 23.1% (95% CI: 16.3–29.8%). The topographical type of CP was the primary source of heterogeneity in the prevalence of epilepsy. Diagnostic criteria for CP, clinical type of CP, GMFCS, publishing time, and topographical type of CP were the primary sources of heterogeneity in the prevalence of intellectual disability. Clinical type of CP and topographical type were the primary sources of heterogeneity in the prevalence of speech disorders. Finally, the region was the primary source of heterogeneity in the prevalence of hearing disorders.ConclusionThe prevalence of comorbidities in CP is high in China. Comorbidities are related to the characteristics, severity, and risk factors of brain insult and have a particular relationship with regional economic development and medical and health levels

Effect of Active Deflection on the Forming of Tubes Manufactured by 3D Free Bending Technology

The formed parts of tubes easily interfere with the equipment when forming complex tubes in 3D free bending forming technology. Consequently, to solve the interferential phenomenon, an active deflection method (ADM) to avoid interference was proposed to drive the deformed tube around its axis by controlling the bending die. The method extended the activity freedom of the equipment without installing the additional motion shafting. However, severe section distortion, surface scratches and other forming defects frequently occurred during the implementation of ADM, which reduced the structural strength and pressure resistance of the tubes. A mechanical model was developed to analyze the force state of the tube, and the results showed that the driving force of active deflection was mainly determined by the trajectory radius. The curve of the adopted bell-shaped transition structure was closer to the bending curvature of the tube than the rounded structure, which transformed the guider and the tube from linear contact to surface contact. The simulation and experiment results indicated that adding the trajectory radius could strengthen the rotation torque. The stress concentration in the tube was alleviated after applying the bell-shaped transition structure

Finite element modeling and experimental investigation on manufacturing TA18 alloy pipes via hot free bending forming technology: Forming characteristics and process optimization

Free bending forming (FBF) technology is widely used for manufacturing complex-shaped Ti pipes without changing the forming die. Nevertheless, the characteristics of Ti alloys, such as low ductility and high yield stress, pose challenges in achieving high-quality components at room temperature. Therefore, the hot FBF technology is used to manufacture and optimize the process parameters to produce complex-shaped TA18 pipes. Combining theoretical analysis, FE modeling, and experimentation, the forming characteristics of TA18 alloy pipes at elevated temperatures were revealed, and the process parameters were optimized. The Johnson-Cook constitutive model was established in this study and coupled with FE modeling providing accurate simulations of the hot FBF process under various conditions. The FE model of the TA18 alloy pipe was verified by comparing its results with the actual TA18 pipe trials. The hot FBF process can improve the wall thickening and cross-sectional distortion of TA18 bending components and reduce the bending radius of the pipe by weakening the dynamic rebound at the end of the bending and forming of titanium pipes. The increase in heating length is also generally conducive for forming TA18 pipe, and the component's external wall thickness reduction and cross-sectional distortion can be inhibited when the heating length is 250 mm. Moreover, the increase in axial propulsion speed improves the thickening of the inner wall thickness of the TA18 bending components but also increases the thinning of the wall thickness and the distortion of the cross-section. Finally, the process parameters were optimized, and the forming quality of the complex-shape TA18 pipe can be improved. The microstructure of the TA18 pipe hardly changes during the hot FBF process

Experimental Analysis of Electro-Assisted Warm Spin Forming of Commercial Pure Titanium Components

Aircraft manufacturers continue to use larger quantities of titanium components to increase strength and reduce weight. While various forming processes can be used, spin forming is particularly well suited for economically producing small and large quantities of axisymmetric parts. However, due to its limited formability at room temperature, titanium is typically warm formed. In the study, a new type of electro-assisted warm spin forming method based on the electroplasticity effect is presented. Experimental results show that electro-assisted forming technology can significantly improve forming quality of titanium parts. Advantages of the method include short forming times, uniform temperature distribution, simple operation, and convenient control. The influence of process parameters, including current intensity, feed rate, spindle speed, and lubrication, on the formability of commercial pure titanium sheets was systematically analyzed using an industrial spinning machine. It was found that deformation is mainly concentrated in the arc phase of the curved generatrix. Finally, components were subjected to uniaxial tensile stress and biaxial compressive stress based on previously defined forming limit curves. The technology is feasible and easy to control and has the potential for application to other rotary sheet forming technologies

Effect of Active Deflection on the Forming of Tubes Manufactured by 3D Free Bending Technology

The formed parts of tubes easily interfere with the equipment when forming complex tubes in 3D free bending forming technology. Consequently, to solve the interferential phenomenon, an active deflection method (ADM) to avoid interference was proposed to drive the deformed tube around its axis by controlling the bending die. The method extended the activity freedom of the equipment without installing the additional motion shafting. However, severe section distortion, surface scratches and other forming defects frequently occurred during the implementation of ADM, which reduced the structural strength and pressure resistance of the tubes. A mechanical model was developed to analyze the force state of the tube, and the results showed that the driving force of active deflection was mainly determined by the trajectory radius. The curve of the adopted bell-shaped transition structure was closer to the bending curvature of the tube than the rounded structure, which transformed the guider and the tube from linear contact to surface contact. The simulation and experiment results indicated that adding the trajectory radius could strengthen the rotation torque. The stress concentration in the tube was alleviated after applying the bell-shaped transition structure

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

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

Strengthening mechanisms, deformation behavior, and anisotropic mechanical properties of Al-Li alloys: A review

Al-Li alloys are attractive for military and aerospace applications because their properties are superior to those of conventional Al alloys. Their exceptional properties are attributed to the addition of Li into the Al matrix, and the technical reasons for adding Li to the Al matrix are presented. The developmental history and applications of Al-Li alloys over the last few years are reviewed. The main issue of Al-Li alloys is anisotropic behavior, and the main reasons for the anisotropic tensile properties and practical methods to reduce it are also introduced. Additionally, the strengthening mechanisms and deformation behavior of Al-Li alloys are surveyed with reference to the composition, processing, and microstructure interactions. Additionally, the methods for improving the formability, strength, and fracture toughness of Al-Li alloys are investigated. These practical methods have significantly reduced the anisotropic tensile properties and improved the formability, strength, and fracture toughness of Al-Li alloys. However, additional endeavours are required to further enhance the crystallographic texture, control the anisotropic behavior, and improve the formability and damage tolerance of Al-Li alloys

Influence of particles size and concentration of carbonyl iron powder on magnetorheological properties of silicone rubber-based magnetorheological elastomer

In this study, the anisotropic magnetorheological elastomer(MRE) was prepared by mixing two-component room temperature vulcanized(RTV) silicone rubber, carbonyl iron powder particles and dimethyl silicone oil uniformly, then heated and solidified under 500 mT magnetic field intensity. Five types of magnetic particles with different concentrations of 20%, 30%, 40%, 50%, 60% and five different sizes of 1.7, 2.8, 3.9, 4.6, 7.2 μ m, were used to investigate the effects of the concentrations and sizes of the magnetic particles on the microstructure, mechanical properties and the magnetorheological effect (MR-effect) of anisotropic MREs. The results obtained from this study showed that the MR-effect has a significant dependence on the concentrations and particle sizes of the magnetic particles. It increased with the increase of the particle concentrations, and the high particle concentration makes the MRE have a high magnetostrictive modulus and MR-effect. Nevertheless, with the increase of the particle sizes, the MR-effect showed a trend of strengthening firstly and then weakening, there is an optimal particle size of 4.6 μ m, at this size, the MR-effect is the most significant

A review on flexibility of free bending forming technology for manufacturing thin-walled complex-shaped metallic tubes

Free bending forming (FBF) is a flexible forming technology that gained significant attention recently because of its broad applications in critical industries such as the automotive, aerospace, and nuclear industries. Thus, this paper aims to present a comprehensive review of FBF technology and its flexibility in manufacturing thin-walled complex-shaped metallic tubes with variable curvatures. First, the historical development and state of the art of FBF technology were reviewed and discussed its importance in tube forming recently. Then, the fundamental principles, theoretical modelling, deformation mechanisms during complex bending, critical process parameters, and forming defects with a discussion of the recent research and technological developments of FBF technology under three-, five- and six-axis processes were explained. After that, the system dies and tools design of the FBF machines and the trajectory control of the bending die were presented. Afterwards, the mechanisms of manufacturing spiral and involute hollow metallic tubes and outstanding solutions for critical issues during tube manufacturing, such as springback, cross-section deformation, over-thinning (even cracking), and wrinkling instability were introduced. Finally, the paper is concluded by providing the discussions on the system, die and tool design methodology, and outlook of the FBF technology