Papers by Keyword: Thin-Walled Tube

Abstract: This paper focuses on the computational modeling of the crashworthiness performance of designed foam-filled thin-walled tubular structures under quasi-static compression loading. The studied foam sample is designed in SolidWorks using the ‘sphere subtraction method’ and implemented as a filler material in the thin-walled tube. The quasi-static compression was simulated by Abaqus software. The foam porosity is manipulated to enhance the crashworthiness performance of empty tubes. The deformation mode and energy absorption capability of the analyzed structures are introduced in detail. The numerical results showed that foam-filler material could change the deformation mode and improve stability during the compression process of thin-walled tubular structures. The number of lobes significantly increases when introducing the foam filler to the tube. These folds are affected by the foam porosity. Results also indicate that the total crushing load of the foam-filled tube is also a function of foam porosity, the mechanical response of the foam-filled tubes tended towards the response of the empty tube for a high porosity (P >85%), while for low porosity (P<85%) the mechanical response of the foam-filled tubes exhibits the three universal deformation characteristics of foams, namely, initial linear stage, extended plateau stage, and final densification stage. The main mechanical properties: collapse stress, plateau stress, and densification strain were obtained via the energy-efficient method for different configurations. The calculated mechanical properties exhibited a strong dependence on foam porosity. To give a quantitative description of the obtained quasi-static compressive properties, these properties are expressed as a function of foam porosity. The proposed formulas can easily recover the quasi-static compressive properties of the empty tube in the case of the absence of foam. The control of the compressive performance of foam-filled tubes as a function of porosity allows for finding an optimum geometry with a predefined foam porosity value adjusted for a given application.

Abstract: As a kind of structural and functional composite material, foam filled tubes have an application prospect in automobile industry because it meets the requirements of automobile light weight and safety performance. The traditional preparation method of foam filled tubes is ex-situ preparation and there is no metallurgical bonding between the ordered porous aluminum filler and the thin-walled tube. In this study, the in-situ ordered porous aluminum filled tubes were proposed and prepared by combining the additive manufacturing technique and infiltration casting technique. The sand preform fabricated by selective laser sintering technique was placed in the bottom of 6061 aluminum alloy thin-walled tube. ZL111 aluminum alloy was utilized to infiltrate the sand preform and expected to form a metallurgical bonding between the ordered porous aluminum filler and the thin-walled tube. The infiltration process of the in-situ ordered porous aluminum filled tube was optimized by integrated computation. The peak temperature of contact region on the thin-walled tube was obtained. The in-situ ordered porous aluminum filled tubes were successfully fabricated by utilizing the optimized parameters.

Abstract: Filling the thin-walled tubes with a foam core is a typical method to enhance the energy absorption performance and stabilize their crushing responses under impact loading. Recently, auxetic foam material with negative Poisson’s ratio has gained remarkable popularity as an effective candidate to enhance the energy absorption capability of structures. In this paper, polyurethane auxetic foam is suggested as a foam core with the negative Poisson’s ratio of-0.31. Numerical simulation was performed to quantify the crush characteristics of auxetic foam-filled square aluminum tubes for variations in initial width of tube under quasi-static axial loading using the nonlinear finite element (FE) code LS-Dyna. Based on the numerical results, the influence of tube width was quantified in terms of energy absorption (EA), specific energy absorption (SEA), initial peak force (P_max) and crush force efficiency (CFE). It is found that the progressive collapse and deformation modes of auxetic foam-filled tube (AFFT) is pronouncedly affected by varying the tube width. Furthermore, the SEA of AFFT is remarkably sensitive to the tube width variations, yet show low sensitivity to the EA of AFFT. The present study provides new design information on the crush response and energy absorption performance of auxetic foam-filled square tube with varying tube width.

Abstract: Intensive development of Russian aviation and aerospace industries put an emphasis to the problem of quality of using materials and workpieces and to the value of technical and economical indexes in the context of planned production level [1, 2]. Waste-free technologies are preferred. Cutting by torsion or cutting by shear are preferable technologies if thin-walled tube cutting is the main blanking operation. Build-up of workpiece deformation zone plays an important role in the cutting process. Deformation zone determines stability of details during further processing and exploitation. An extended research was conducted about tube separation process using torsion with an active counterpressure. Some parameters was defined in the result of research, in particular: distribution of deformation zone along length and thickness of workpiece, angular deflection and compression force and workpiece heating temperature impact on build-up of whisker disposition in the cut zone. It allows identifying optimum compression force range and temperature conditions. Compliance with recommended practices allows conducting thin-walled tube separation simultaneously with build-up on the workpieces whisker structure that is fortunate for further pressure treatment and exploitation.

Abstract: Thin-walled spatial bending tube can not only provide engineering design with higher flexibility and lighter structure, but also enhance the construction of space saving and aerodynamics improvement. Based on rotary draw bending technique, a new method for spatial consecutive bending with no straight line for thin-walled tube was put forward. Firstly, a new bionic elastic mandrel was developed by analyzing the structural characteristics of the squilla. It mainly consisted of bowl-shaped mandrel balls, an elastomer and a mandrel shank. The bowl-shaped mandrel balls, nested matching one another, generated a non-smooth surface which can provide continuous support for internal surface of the tube wall. It could also achieve small bending radius. The elastomer featured of certain bending stiffness and enough tensile strength. Secondly, a curved clamping die was advanced to clamp the spatial consecutive bending tube with no straight line effectively. Based on the shape of the bending tube after the former bending forming process, the curved clamping dies which can match the shape of the former bending tube were designed for the later bending. Lastly, bending experiments was performed. A thin-walled tube made of Q235 with two passes, one bending angle 90° and the other 180° was taken for example and the spatial consecutive bending tube with no straight line was successfully obtained. It is of significant importance in enriching the spatial bending tube technique and achieving the small bending radius.

Abstract: Welding temperature is the main factor that influences welding quality in high frequency induction welding process of composite aluminum alloy thin-walled tube. The finite element analysis software ANSYS is used to simulate temperature field. One complete penetration of thin-walled tube and boundary conditions of thermal calculation are taken into account. Then a linear thermal model is used to load and calculate to draw temperature distribution and thermal cycle curves of welding process. Research results provide corresponding theoretical basis for further analysis of welding stress and strain.

Abstract: Copper Oxide (CuO) microfibers with different morphologies were prepared by the electrospinning and calcination process. The formation process of CuO microfibers was analyzed by thermogravimetry and their microstructures were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed the spinnability and electrical conductivity of the polymer solution are affected by the concentration of acetic acid solution. The morphologies of CuO are closely related to the calcination temperature. The thin-walled tubulous microfibers can be obtained by calcination of the electrospun precursor with 8 wt.% acetic acid at 500 ^○C for 2 h.

Abstract: Thin-walled tubes have always considered as energy absorption systems by researchers. This paper presents a new technique for energy absorption system which is simpler than other designs in production. This novel model is a thin-walled tube with perforation. During manufacturing process, equal numbers of holes are created in rows and columns in order to increase the energy absorption ability. In this article two different workpieces with the same geometry, one with holes and the other one with grooves, are compared to validate the model in accordance with other presented ones. For this purpose, specimens were modeled in finite element software ABAQUS with the same conditions and the amount of energy absorption, the initial decay, and the weight ratio of energy absorption (SEA) were evaluated. Then results which obtained from simulation are compared with experimental ones. Results confirmed that specimens with perforation have better decay symmetry rather than ones with grooves. In addition, force absorption in workpieces with hole is as twice as ones with grooves. The amounts of absorbed energy and SEA in workpieces with perforation are 56% and 46% more than workpieces with grooves, respectively.

Abstract: In order to realize the objective of lightweight manufacturing, the forming methods of thin-walled tubes are studied in this paper. Liquid impact forming, a compound forming technique of thin-walled tube using stamping and hydroforming processes, is presented in order to reduce the forming difficulty and increase the forming efficiency. A simple experimental tooling, including stamping device and tube hydroforming apparatus is developed. Forming experiments of stamping and liquid impact forming processes in rectangular cross-section dies are performed for 304 stainless steel tubes. The results of experiments show that the liquid impact forming technology is feasible, and it will be widely applied in the future.

Abstract: As there was no precise theoretical model for predicting the stress of deformation zone while straightening thin-walled tube, some technological parameters depended mostly on the experience of workers and on the results of trials, therefore by means of the membrane shell theory the equilibrium differential equations of stress is obtained firstly, then we analyze the strain of deformation zone, finally lead to a new theoretical model for predicting the stress in the elastic and plastic zone. Subsequently the simulated experiments have been done, the results show that the theoretical calculations coincide well with the simulated results, the errors are within 1％of the calculations, it is testified that the model is correct and efficient for the thin-walled tube straightening.