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To address the challenges posed by the complex shapes of hollow parts, this study examined the ultrasonic-assisted granular medium hydroforming (UGMF) process for tubular components. The dynamics of the deformation behavior and deformation control during 6063-T5 aluminum alloy tube free forming by UGMF were studied via simulations and experiments. Based on the ABAQUS software platform, a coupled method based on finite element (FE) simulation analysis and discrete element (DE) analysis for the UGMF free forming process was used. The results showed that ultrasonic vibration (UV) could reduce the forming force required for expansion and promote the flow of material at the end to the forming area as well as inhibit the decrease in the wall thickness. The accuracy of the FE-DE coupled simulation model and a parabolic geometric model was verified by testing. The results found that UV enhances material flow, decreases the forming force needed, and minimizes damage to the granular surface. [ABSTRACT FROM AUTHOR]

The present study employed the ABAQUS numerical simulation method to analyze the forward flow forming of 7075 aluminum alloy tubes using power staggered spinning compression materials. Subsequently, a power staggered spinning experiment was conducted to analyze the microstructure and mechanical properties. The simulation results revealed that increasing the spinning temperature led to a decrease in the limit thickness reduction per pass while increasing range, as well as enhanced deformation along the wall thickness direction. At 400 ℃, favorable forming properties were observed with minimal plastic strain occurring in the inner layer when thickness reduction is below 10%. These findings indicate that an escalation in total thickness reduction resulted in refined and uniform grain distribution along the wall thickness direction, accompanied by improved hardness (up to 178.6 HV) due to synergistic effects from fine grain strengthening, strain strengthening, and dispersion strengthening induced by second particles. [ABSTRACT FROM AUTHOR]

The explosive formability of common age-hardenable Al alloys (2024-T4, 2024-T6, 6061-T4, 6061-T6, 7075-T4, and 7075-T6) is investigated experimentally. Manufacturers utilize explosive forming to produce parts having large and complex geometries in a single operation. To investigate the explosive formability of the most common Al alloys used in the aerospace/aircraft industry, an experimental die design is constructed. Tensile tests are carried out to determine the mechanical behavior of the alloys at low strain rates. Charpy V-notch tests are used as input values to determine the fracture toughness and fracture energy. The strain rate considering the expansion angle is calculated through the analytical formula of the Gurney metal velocity. The strain rates obtained by explosive forming conducted in air are calculated roughly as s , which is an extreme rate. The experimental results reveal that the 6061-T4 Al alloy could be explosively formed to the demanded geometry without any hollows, cracks, tearing, and fractured regions. It is clear that the T6 temper condition significantly improves the strength of the tested alloys, accompanied by reduction of ductility and crack initiation potential. Except for the 6061-T4 Al alloy, all of the tested alloys are fractured during explosive forming tests. Stereo microscopy and scanning electron microscopy investigations reveal transgranular fracture and cleavage facets resulting from brittle fracture initiated by high strain rates, which occurs in the peak-strength temper condition-T6 of the tested Al alloys. [ABSTRACT FROM AUTHOR]

Cylinder TNT-RDX explosives were wrapped by a spiral aluminum tube that stored high-pressure active gases (H 2 , O 2 , or CO 2) to improve the detonation performance. Their detonation performance was investigated by underwater explosion and air explosion systems. The underwater explosion results show that hydrogen participating in the detonation reaction of explosives mainly improves the peak overpressure, and simultaneous fragmentation and combustion of the spiral aluminum tube mainly contribute to the improvement of energy parameters. In the air explosion, the hydrogen utilizes ambient oxygen to further improve the peak overpressure of composite explosives. The increase amplitude of energy parameters in the air explosion is much lower than that in the underwater explosion due to the air explosion with a higher attenuation speed of shock waves and detonation temperature. The increase amplitude of oxygen to the peak overpressure (6.429%) is less than that of hydrogen to the peak overpressure (8.066%). The energy improvement of oxygen on composite explosives is best due to changing the object that reacts with the aluminum fragments. The average fragment length of aluminum tube calculated by the Grady model and the Goloveshkin model indicates that aluminum fragments formed by the aluminum tube increase the characteristic length of aluminum that can participate in the reaction. • Cylinder TNT-RDX explosives were wrapped by a spiral aluminum tube that stored high-pressure active gases (H 2 , O 2 , or CO 2). • Hydrogen and aluminum tube enhance different detonation parameters, respectively. • The effect of active gas type on the detonation performance of composite explosives were investigated. • Aluminum fragments increase the characteristic length of aluminum that can participate in the reaction. [ABSTRACT FROM AUTHOR]

A new technology of local electrically assisted necking and thickening forming of 5A02 aluminum alloy tube is developed, to enhance the quality of tube necking and thickening and increase the thickness of the tube wall in thickening area. Advantages of the electroplasticity of pulse current are utilized to guarantee the forming quality of tube necking and thickening. Process parameters such as thickness of the guide block, contact mode of the upper electrode, and the cooling method were studied. The results indicate that the thicker the guide block, the less prone to premature bending and instability in the forming process. The integral electrode is the most stable and the best heat dissipation effect, which avoids the tube from internal buckling. With the increase of the cooling capacity, the average wall thickness increases first and then decreases. According to these results, a process scheme is designed, with which successful experiments have been performed. And the microstructures of the necking and thickening areas were studied by optical microscope. Local electrically assisted necking and thickening technology shows great benefits in tube extrusion forming. [ABSTRACT FROM AUTHOR]

Recent years have witnessed the rapid development of electromagnetic flanging of tubes, which uses coils to generate electromagnetic forces to achieve the deformation with high speed but without contact. However, the electromagnetic force decays dramatically with the increase of distance, resulting in strict requirements of geometrical matching between the coils and the tubes. Usually, new coils should be fabricated for tubes with new sizes, which is inconvenient and uneconomical. Therefore, a more flexible and economical method is proposed in this paper, which introduces a solenoid field shaper into the existing electromagnetic flanging system. By adjusting the structure and the position of the field shaper, the distribution of electromagnetic forces can be reshaped to form tubes with various sizes, without changing the coil, whose cost is much higher than a field shaper. The principle of this method is introduced in detail. Then, an electromagnetic-structure coupled finite element simulation model is established to calculate the forming process. The results show that when forming an A6063-T83 aluminum alloy tube with an inner diameter of 110mm, the discharge voltage can be tuned down from 5.3kV, without field shaper, to 4.6kV, with field shaper. That means the energy consumption of the system can be saved by 25%, and the manufacturing process of the field shaper is simpler than that of the forming coil. What's more, when forming tubes with different sizes, the new method shows higher effectiveness, greater flexibility, and lower cost than the traditional way. [ABSTRACT FROM AUTHOR]

Aluminum honeycombs are widely applied in weight sensitive applications, increasing their specific strength and energy absorption capacity are rather important. Thin-walled metallic tube was used to enhance the mechanical properties of aluminum honeycomb and formed a novel tube-reinforced honeycomb structure. Its compressive and three-point bending performances were studied experimentally and numerically. Due to tube filling, the specific compressive strength, elastic modulus and energy absorption have been increased by 16%, 26% and 73%, and the specific bending load and stiffness increased by 42% and 62% respectively. The strengthen mechanism study indicated that the sum of tube and honeycomb caused the increase of compressive properties, and aluminum tube filling changed the stress distribution and expanded the stress concentration region which led to a transformation of bending failure mode. The present reinforcement method will make honeycomb more competitive in light-weight structure applications. [ABSTRACT FROM AUTHOR]

Electromagnetic attractive forming is meaningful for expanding the applications of electromagnetic forming, but it has been a challenge due to the fact that electromagnetic repulsive forces always dominate during the forming process with conventional RLC circuits. To solve this problem, a new discharge circuit topology is proposed in this work to generate a dual-frequency current for significantly increasing electromagnetic attractive forces, where only a single coil and a single power supply are required. Both numerical and experimental results demonstrate that the proposed method is more beneficial for attractive forming compared to the existing methods. Furthermore, it is shown that the developed forming system with the new circuit can be applied to achieve attractive forming of AA6061-O aluminum alloy tubes with a diameter of 33 mm both in the absence and presence of an inner solid die, where the generated attractive force can be larger than the repulsive force. Meanwhile, an interesting observation is the promotion of material flow due to the axial compressive force in the proposed attractive forming process, thus improving the forming ability and inhibiting the thinning. At the end, as an example, the developed circuit for attractive forming is further applied to the tube joint disassembly. These results could have great significance in understanding electromagnetic attractive forming process and promote its practicality. [Display omitted] • A new circuit is proposed to achieve attractive forming of small-diameter tubes. • The circuit can produce an attractive force that is larger than the repulsive force. • The attractive forming behavior and mechanism of tubes are revealed. • The axial compressive force can promote material flow and improve tube forming limit. • The developed attractive forming method can achieve the disassembly of tube joints. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Tube cryogenic bulging method was proposed to test the cryogenic forming limit in the tension-tension zone. • The established modified M-K model can predict the cryogenic forming limit with high accuracy. • Dramatically improved forming limit can be obtained at cryogenic temperature, facilitating the forming of complex components. • Improvement mechanism of cryogenic forming limit was revealed by theoretical analysis and fracture characterization. [ABSTRACT FROM AUTHOR]

• An enhanced constitutive model was proposed based on the Yld2000–2d model. • The enhanced model improves the model applicability and accuracy for introduction of an additional term. • The yield and plastic flow behaviors of anisotropic tubes in both biaxial tension and pure shear stress states can be considered simultaneously. • The yield loci and plastic flow directions of the tubes in both biaxial tension and pure shear stress states can be accurately predicted by the enhanced model. • The enhanced model is validated to be efficient and accurate in simulation of tube hydroforming. In forming of complex thin-walled tubular parts, such as tube hydroforming with axial feeding, both biaxial tension and one axial tension & one axial compression (around the pure shear stress state) deformations are involved. The deformations under both biaxial tension and pure shear stress conditions cannot be accurately modeled and described with the symmetrical constitutive models based on the tensile properties. It is due to the fact that the anisotropic yielding and plastic flow behaviors of tubes are not well articulated over the entire range of stress states. To address this issue, an enhanced constitutive model was proposed based on the Yld2000–2d model (Barlat et al., 2003). The enhanced model improves the applicability of the Yld2000–2d by introducing an additional term, which can flexibly describe the change of the curvature of yield locus around the pure shear stress state. The yielding and plastic flow characteristics of the tubes under both biaxial tension and pure shear stress conditions can be well considered by the enhanced model and the model convexity can be strictly guaranteed. Moreover, the predictability of the proposed model for the deformation behaviors under these states was analyzed and compared with the quoted anisotropic constitutive models. The accuracy and efficiency were also verified and corroborated with the forming of AA6061-O tubes. It showed that the enhanced constitutive model can accurately predict the experimental yield loci and the plastic flow directions of the AA6061-O tube under both biaxial tension and pure shear stress deformations. The in-depth comparisons with the three benchmarked models and experiments were also conducted in terms of the predicted profile and wall thickness distribution of tube hydroforming, in such a way to further validate the enhanced model in terms of the efficiently and accurately modeling of the forming of complex tubes. [ABSTRACT FROM AUTHOR]

• Manufactured seamless Fibre Metal Laminate (FML) tubes for crashworthiness study. • The tubes could avoid catastrophic failure on composite tubes. • The tubes have great energy absorption capability compared to an individual composite or aluminium tube. • By using a validated numerical model, various configurations of FML can be proposed. This study aims to evaluate the crushing behaviour of aluminium-glass fibre reinforced plastic (GFRP) with different layer configurations known as fibre metal laminate (FML) subject to dynamic loading conditions. The tubes were assembled to form 2/1 and 3/2 layout configurations. Resin and braided fiberglass sleeve were introduced as composite layer and sandwiched with two layers of aluminium tubes in forming 2/1 lay-up structure while a layer of composite and aluminium tube is added up alternately for 3/2 lay-up structure. These tubes were tested to evaluate the impact characteristics under low-speed axial impact loading. A finite element (FE) model was also developed and validated against the experimental results. In the numerical evaluation using a validated FE model, the internal energy of an aluminium tube was higher than the internal energy of a GFRP tube when the FML tube was progressively crushed. A series of parametric studies have shown that the increase in aluminium and GFRP wall thickness resulted higher specific energy absorption (SEA). The FML tube fold similar to the crush mode of outer tube material as when it is in its single tube form. All tube configurations were progressively crushed and unlikely to fail under catastrophic failure. FE model founds the aluminium tube layer is more dominant in energy absorption mechanism of the FML tube and increasing the number of tube layers improved crashworthiness significantly. From this discovery, a FML tube could be considered as a suitable lightweight candidate for energy absorbing applications with considerable crashworthiness capability. [ABSTRACT FROM AUTHOR]

Flow forming technology is widely used in the production of the axisymmetric industrial parts. The advantage of flow forming process over other manufacturing methods such as press forming is use of simple tooling, reduced forming loads due to localized deformation, and enhanced mechanical and surface quality of finished parts. In this study, the effects of thickness reduction on the mechanical properties and spinning accuracy are experimentally investigated on 7075-O aluminum tube. A prototype spinning machine has been designed and manufactured. The effects of spinning accuracy, surface roughness, percentage of elongation, yield strength, and the ultimate strength as a function of thickness reduction are experimentally examined. The experimental results show that with increment of thickness reduction, the yield strength, ultimate strength, surface hardness, and crystal refining increase, and on the other hand, it has adverse effect on diameter growth, geometrical accuracy, surface roughness, and percentage elongation of spun tube. [ABSTRACT FROM AUTHOR]

The present study deals with the numerical simulation of the dynamic response of the pure aluminum AA1050 tube under internal gas mixture detonation loading. This practical topic involves structural large plastic deformation, fluid motion, and chemical reaction, and detonation wave/structure interaction. Therefore, the Fluid-Structure Interaction (FSI) with finite-rate chemistry in compressible Conservation Element/Solution Element (CESE) solver with the Immersed Boundary Method (IBM) was used to model the real situation of the whole forming process. The numerical model was verified with existing experimental data for aluminum tubes under internal gas detonation of H 2 +O 2 in terms of the pressure-time history and deformation pattern. Moreover, the simulation results were also compared to those numerical ones in the open literature. It is found that the current numerical modelling approach reproduces the experimental observations very well, and it has a more accurate prediction capability in comparison to the reported study. Hence, the present numerical approach can be used for the design of pressure vessels and piping systems subjected to internal gas detonation loading and also further studies on hazard analysis of pipeline explosion accidents. Moreover, the effect of ignition point location, double ignition points, initial pressure, and repeated loading on the response was investigated. The results show that an experimental setup with double ignition points gives a uniform distribution for plastic deformation in the longitudinal direction of the tube while the ignition point is located at a distance of 1/6 length of the tube from both ends. Furthermore, the double gas detonation loading at the low initial pressure of 0.85 MPa gives the same result obtained for single loading at the moderate initial pressure of 1.2 MPa. • The dynamic response of pure aluminum tubes under internal gas mixture detonation loading was investigated. • FSI with finite-rate chemistry in the CESE solver with the IBM method was used for numerical simulations. • The numerical model was verified with existing experimental data for aluminum tubes under internal gas detonation of H 2 +O 2. • The effect of ignition point location, double ignition points, initial pressure, and repeated loading on the response was further studied. [ABSTRACT FROM AUTHOR]