Deformation Behavior Of Tubes Research Articles

Systematic investigation of deformation behavior of tubes in a three-coil electromagnetic forming process

Systematic investigation of deformation behavior of tubes in a three-coil electromagnetic forming process

Investigation on the influence of mandrel on the forming quality of thin-walled tube during free bending process

The forming defects such as the cross-sectional distortion and axial instability often occur during the free bending process of thin-walled tube. To eliminate or suppress the above-mentioned forming defects, the method of inserting the mandrel inside tube was employed in this paper. First, the principle of free bending with mandrel was theoretically deduced, which was used to explain the mechanism of the supporting force provided by the mandrel on the deformation behavior of tube. Then the influence of the mandrel position, the number of core balls in mandrel and the clearance between the mandrel and tube on the free bending forming quality of thin-walled tube was analyzed and summarized by the numerical simulation method. Finally, the free bending experiment of thin-walled tube with optimized mandrel parameters was conducted to verify the reliability of the numerical simulation method and the rationality of the mandrel parameters. All of these findings advance the insight into the deformation behavior of thin-walled tube influenced by mandrel and help to improve the forming quality of thin-walled tube and facilitate the application of free bending technology in thin-walled tube.

Experimental investigation on deformation behavior and energy absorption capability of nested steel tubes under lateral loading

The energy absorption behavior of nested tubes under lateral loading conditions was investigated in this study. Nested tubes are considered as an alternative to energy absorption structures used in many industries including automotive, military, and aerospace. Steel tubes with the same wall thickness and different diameters were used in the experiments. First, experiments of single tubes were carried out, and the deformation behavior of tubes under lateral load was examined in detail. Afterward, experiments were carried out on nested tube samples in which a minimum of 2 and a maximum of 6 tubes were used together in different numbers and sequences. It was seen from the experiments that the best-nested tube configuration in terms of energy absorption capacity was the sample that contains 6 tubes with 1767 J. While this sample absorbed 5% higher energy than the sample with 5 tubes, the specific energy absorption value was calculated to be 10% lower. Additionally, the sample with 6 tubes has a value of 43% in terms of energy efficiency which is 7% lower compared to that of the sample with 5 tubes. It was determined that the sample with 5 tubes yielded the most efficient design when specific energy absorption capability, work effectiveness, and energy efficiency parameters were considered.

Effect of pulse width of middle-coil current on deformation behavior in electromagnetic tube forming under two-stage coils system

In the majority of electromagnetic tube forming system, the distribution of Lorentz force acting on tube is restricted and has poor controllability, which leads to the tube being unable to meet the requirement of manufacturing flexibly. A new electromagnetic tube-forming method based on the two-stage coils system, which consists of two coils and two independent capacitor banks, has been proposed to improve the distribution mode and controllability of Lorentz force. With higher deformation depth and less occurrence of cracking compared with the conventional one single-coil system; this method has been proved to be effective in improving the deformation behavior of tube in electromagnetic forming through experiments. However, the deformation behavior of tube in this forming method still needs further studies. In this paper, the effect of pulse width of middle-coil current on AA1060 aluminum tube deformation behavior under two-stage coil system is investigated through simulation model, which is based on the combination of current filament method and finite element method. Results show that the short pulse width of the middle-coil current can achieve larger deformation depth of tube under relatively small discharging energy, and the long pulse width of the middle-coil current has good performance in deformed profile. Moreover, the thickness reduction in the case of long pulse width of middle-coil current is less than the case of short pulse width of the middle-coil current under equal deformation depth of tube.

Improvement of deformation behavior of tube in electromagnetic forming with a triple-coil system

Improvement of deformation behavior of tube in electromagnetic forming with a triple-coil system

Deformation behavior of tube in electromagnetic forming with an external die

Deformation behavior of tube in electromagnetic forming with an external die

Simulation of Extrusion of Tubes with Outer Heavy Ends

Computer simulation of expansion of tubes by extrusion was performed. Deflected mode analysis was described. Influence of collar taper angle, radius of rounding in interface of conical and cylindrical sections of mandrel, geometry of blank on deformation behavior of tube during expansion was determined.

The Bulging Behavior of Thick-Walled 6063 Aluminum Alloy Tubes Under Double-Sided Pressures

To make further exploration on the deformation behavior of tube under double-sided pressures, the thick-walled 6063 aluminum alloy tubes with an outer diameter of 65 mm and an average thickness of 7.86 mm have been used to be bulged under the combined action of internal and external pressures. In the experiment, two ends of the thick-walled tubes were fixed using the tooth and groove match. Three levels of external pressure (0 MPa, 40 MPa, and 80 MPa), in conjunction with the internal pressure, were applied on the tube outside and inside simultaneously. The effect of external pressure on the bulging behavior of the thick-walled tubes, such as the limiting expansion ratio, the bulging zone profile, and the thickness distribution, has been investigated. It is shown that the limiting expansion ratio, the bulging zone profile, and the thickness distribution in the homogeneous bulging area are all insensitive to the external pressure. However, the external pressure can make the thick-walled tube achieve a thinner wall at the fracture area. It reveals that the external pressure can only improve the fracture limit of the thick-walled 6063 tubes, but it has very little effect on their homogeneous bulging behavior. It might be because the external pressure can only increase the magnitude of the hydrostatic pressure for the tube but has no effect on the Lode parameter.

Deformation Behaviors of Tube in Hydroforming with Radical Crushing

Working principle and advantages of tube in hydroforming with radical crushing were described and introduced briefly. The research status of deformation behaviors of tube in hydroforming with radical crushing with the tube cross-section shape was made into triangle, rectangle or trapezoid were reviewed in this paper. Finally, the development trend and burning questions of tube in hydroforming with radical crushing were predicted.

Establishment of Stress-Strain Relationships of Tailor-Welded Tubes via DIC Method Based on Uniaxial Tensile Tests

Tailor-welded tubes are widespread in aircraft and automotive industries due to their advantages of low cost, reduction in part weight and flexibility in mass production. It is necessary to obtain the stress-strain relationship of tailor-welded tubes to study deformation behaviors of tubes and simulate deformation tests of tubes. Then a method via digital image correlation (DIC) method based on uniaxial tensile test (UTT) is proposed in this paper to establish stress-strain relationship of tailor-welded tubes. Material parameters of tailor-welded tubes obtained from three methods, i.e. the method based on UTT, the iso-strain method based on a rule of mixtures and the proposed method, were compared in this paper. To assess the accuracy of material parameters obtained from these three methods, UTTs were simulated, and load-displacement curves and maximal loads obtained from simulations were compared with those obtained from UTTs. In simulations of UTTs, finite element models of specimens of sole parent metal and mixed specimens were established, respectively. The results show that: When HAZ included in the specimen has large proportion of the specimen, the proposed method is more reliable than the iso-strain method based on a rule of mixtures on determining the material parameters of the weld; load-displacement curve and maximal load obtained from the proposed method are more close to those obtained from UTT than those obtained from the method based on UTT.

Deformation analysis for the shear bending process of circular tubes

In order to minimize the space of bent tubular parts, a bending technology with small bending radii has been requested recently. Tube shear bending is a suitable technology to realize a considerable small bending radius. In this paper, the procedure of tube shear bending has been introduced. Moreover, an elasto-plastic 3D finite element simulation has been conducted to analyze the forming process. Also the deformation behavior of tube has been investigated. For this purpose, tube strain distribution has been illustrated. The theoretical values of strains have been obtained and compared with the simulated results. In order to show the validity of simulation, the FEM results of tube thickness strain have been compared with the experimental ones. The results of this paper clarify the deformation characteristic of tube during shear bending process. These results demonstrate that the forming process is under a combination of shearing and bending deformations.

Deformation behavior of tubes with thickness deviation in circumferential direction during hydraulic free bulging

The influence of the initial thickness deviation of the tube wall on the deformation behavior during free hydraulic bulging was studied. The experimental study was performed with tubes that had an initial thickness deviation of approximately 1–4%. FEM simulation and theoretical speculation were also carried out in order to examine the experimental results. It was clarified that the cross sectional shape of the bulged tube maintained its circular shape until just before tube bursting. This tendency appeared independently of the amount of the initial thickness deviation. On the other hand, increase in thickness deviation during tube bulging depended on the degree of the initial thickness deviation, n-value and r-value. When the initial thickness deviation was large and n-value and r-value were small, the increase in thickness deviation was large.