Mandrel Speed Research Articles

Flow-forming optimization based on hardness of flow-formed AISI321 tube using response surface method

Flow forming is an advanced locally plastic deformation applied to manufacture seamless tubes with thin walls and high precision dimension. One of the important mechanical properties of flow-formed tubes is hardness. In this study, after preliminary experiments for definition of effective parameters, design of experiments (DOE) is utilized to determine the influence of the parameters such as rotational speed of mandrel, feed rate, and wall thickness reduction on the hardness of flow-formed AISI 321 steel tube. Under experimental results, a mathematical model comprising effective parameters is developed to predict the optimum hardness, using response surface methodology (RSM). RSM’s Box–Behnken design is employed to specify the optimum condition caused to a minimum hardness at high optimum confidence level. The analyzed model revealed that the hardness increases with increasing of the mandrel speed and the depth of cut, and it decreases with decreasing of the feed rate. The new point of view is related to the fact that the high level of thickness reduction covers the efficiency of mandrel speed.

Prediction of the surface roughness of AA6082 flow-formed tubes by design of experiments

Flow forming is a modern, chipless metal forming process that is employed for the production of thin-walled seamless tubes. Experiments are conducted on AA6082 alloy pre-forms to flow form into thin-walled tubes on a CNC flow-forming machine with a single roller. Design of experiments is used to predict the surface roughness of flow-formed tubes. The process parameters selected for this study are the roller axial feed, mandrel speed, and roller radius. A standard response surface methodology (RSM) called the Box-Behnken design is used to perform the experimental runs. The regression model developed by RSM successfully predicts the surface roughness of AA6082 flow-formed tubes within the range of the selected process parameters.

Finite element modeling of mandrel speed in cold expansion process

PurposeThe bodies of aircraft structures have a lot of fastener holes and under different situations these holes bear external forces, which cause a tensile stress on the surface that leads to the failure of materials. Cold expansion process is one of the widely‐used methods to improve the fatigue behavior of materials used in aerospace industry, and such improvement is due to the compressive residual stress around cold expanded hole. The induced residual stress distribution around cold expanded hole is affected by several parameters such as, diametrical interfaces, surface finish of fastener holes, temperature, mandrel speed, i.e. the speed of inserting mandrel into the hole, and so on. In previous studies, most of effective parameters were investigated, whereas, the effect of mandrel speed on the residual stress distribution has not been considered. The present study, seeks to simulate cold expansion process on aluminum alloy 2A12TA using ABAQUS finite element (FE) package and to consider the effect of different mandrel speeds on residual stress distribution around cold expanded hole. It aims to verify the results of FE simulation by experimental data.Design/methodology/approachThere are two kinds of data in this paper; experimental and FE results. The experimental results for cold expansion process have been extracted from the literature and ABAQUS finite element package was employed in order to simulate the above‐mentioned process. Moreover, FE results were validated by the experiments.FindingsThe results presented here show the influence of mandrel speed on residual stress distribution around cold expanded hole using a new analytical‐numerical method. The results gained by FE simulation show relative differences between the diagrams of residual stress distribution corresponding different mandrel speeds. It is shown in the paper; the residual stress around cold expanded hole rises by the increase of mandrel speed and consequently the improvement of fatigue life will be achieved.Originality/valueThe present study is part of Abbas Hosseini's MSc. dissertation, an original research work.

Experimental studies on the characteristics of AA6082 flow formed tubes

Flow-forming is an innovative, chip less metal forming process used to manufacture thin walled seamless tubes and other axi-symmetric components. Experiments were conducted to form annealed AA6082 alloy tubular pre-forms into thin walled seamless tubes on CNC flow forming machine with a single roller. The process parameters selected for the present investigation are roller radius, mandrel speed, roller feed, thickness reduction, etc. The characteristics of flow formed tube chosen are ovality, mean diameter, thickness variation, surface finish, etc. The effects of these process parameters on the dimensional characteristics and surface quality of flow formed tubes have been studied. The optimum process parameters are proposed to manufacture the tubes with good dimensional characteristics and sound surface quality. It has been found that, roller radius of 4 to 8 mm, thickness reduction ranging from 30 to 35%, mandrel speed of 150 rpm and roller feed in the range of 100 to 130 mm/min formed the tubes with sound characteristics. Key words: Flow-forming, AA6082 alloy, ovality, mean diameter, surface quality.

Analysis of Radial Strain Distribution in the Metal Spinning Process by Taguchi Approach

The paper presents the results of radial strain distribution measurement throughout the part after multi-pass conventional metal spinning by the circle grid analysis method. The influence of the mandrel speed, workpiece geometry and planar anisotropy of material on the radial strain was studied. For experiment design, an orthogonal array L27 was used and ANOVA (Analysis of Variance) was carried out. Based on the results it is determined that the sequence of factors affecting radial strain corresponds to geometry of spun part, mandrel speed, planar anisotropy of the sheet. In particular, it is found that the workpiece geometry (specific areas of spun part: mandrel/workpiece radius, conical area, cylindrical area) is the most important factor which influences the radial strain of the spun part.

3D-FE modeling for power spinning of large ellipsoidal heads with variable thicknesses

A finite element (FE) model is urgently needed to settle unqualified wall thicknesses, poor fitability and low surface profiles and thereby improve the forming qualities obtained during the power spinning of large ellipsoidal heads with variable thicknesses (LEHVTs). Thus, based on a comprehensive understanding of the characteristics of LEHVT power spinning, an accurate and efficient three-dimensional (3D) FE model was developed and validated by comparing simulation and experimental results. The following technological strategies were addressed: (1) a method for determining the roller trajectory was developed to accurately control the movement of rollers; (2) a similarity theory for reducing the size of the FE model was introduced to save computational time; (3) a constant roller feed ratio and spinning linear speed was implemented by changing the roller feed rate and the mandrel speed, respectively, which improved the stability and efficiency of the FE model; and (4) the different degrees of reduction deformation at different LEHVT zones were considered, and variable mesh densities were adopted to improve computational efficiency. Based on this model, the distributions of stress, strain and wall thickness during this process were obtained. Unfitability and radial runout after unloading were also analyzed.

Electrospinning of Biosyn®-based tubular conduits: Structural, morphological, and mechanical characterizations

Electrospinning has garnered special attention recently due to its flexibility in producing extracellular matrix-like non-woven fibers on the nano-/microscale and its ability to easily fabricate seamless three-dimensional tubular conduits. Biosyn®, a bioabsorbable co-polymer of glycolide, dioxanone, and trimethylene carbonate, was successfully electrospun into tubular conduits for the first time for soft tissue applications. At an electric field strength of 1 kV cm −1 over a distance of 22 cm (between the Taylor cone and the collector) and at a flow rate of 1.5 ml h −1 different concentrations of Biosyn/HFP solutions (5–20%) were spun into nanofibers and collected on a rotating mandrel (diameter 4 mm) at 300 and 3125 r.p.m. Scaffolds were characterized for structural and morphological properties by differential scanning calorimetry and scanning electron microscopy and for mechanical properties by uniaxial tensile testing (in both the circumferential and longitudinal directions). Biosyn® tubular scaffolds (internal diameter 4 mm) have been shown to exhibit a highly porous structure (60–70%) with a randomly oriented nanofibrous morphology. The polymer solution concentration directly affects spinnability and fiber diameter. At very low concentrations (⩽5%) droplets were formed due to electrospraying. However, as the concentration increased the solution viscosity increased and a “bead-on-string” morphology was observed at 10%. A further increase in concentration to 13% resulted in “bead-free” nanofibers with diameters in the range 500–700 nm. Higher concentrations (⩾20%) resulted in the formation of microfibers (1–1.4 μm diameter) due to increased solution viscosity. It has also been noted that increasing the mandrel speed from 300 to 3125 r.p.m. produced a reduction in the fiber size. Uniaxial tensile testing of the scaffolds revealed the mechanical properties to be attractive for soft tissue applications. As the fiber diameters of the scaffold decrease the tensile strength and modulus increase. There is no drastic change in tensile properties of the scaffolds tested under hydrated and dry conditions. However, a detailed study on the biodegradation and biomechanics of electrospun Biosyn conduits under physiological pressure conditions is required to ensure potential application as a vascular graft.

The Effect of Mandrel Speed upon the Residual Stress Distribution around Cold Expanded Hole

In this paper, cold expansion process on aluminum alloy 2A12TA was simulated using ABAQUS finite element package and the effect of different mandrel speeds upon residual stress distribution around cold expanded hole was considered. The results gained by simulation show major difference between the diagrams of residual stress distribution corresponding different mandrel speeds. The results of FE simulation in slowly loaded process was verified by experimental data. As can be seen, when mandrel speed increases the residual stress around cold expanded hole increases as well and this is caused the fatigue life improvement of fasten holes.

The Effect of Mandrel Speed upon the Residual Stress Distribution around Cold Expanded Hole

In this paper, cold expansion process on aluminum alloy 2A12TA was simulated using ABAQUS finite element package and the effect of different mandrel speeds upon residual stress distribution around cold expanded hole was considered. The results gained by simulation show major difference between the diagrams of residual stress distribution corresponding different mandrel speeds. The results of FE simulation in slowly loaded process was verified by experimental data. As can be seen, when mandrel speed increases the residual stress around cold expanded hole increases as well and this is caused the fatigue life improvement of fasten holes.

Ratio of the pipe and mandrel speeds for deformation in a nondriven three-roller groove

To intensify helical reduction using a nondriven three-roller cell, it is important to investigate the relation between the speeds of the front and rear ends of the pipe and the mandrel. The existing formula takes no account of the deformation-source geometry in the nondriven cell [1]; it also neglects the kinematic and force conditions in helical reduction [2]. Therefore, more adequate formulas must be derived for helical reduction. In investigating helical reduction, we make the following assumptions: the blank with the inserted mandrel is supplied to the rollers at a speed v b , which is less than the pipe speed during reduction and the speed of the final pipe; on account of the frictional forces in the deformation source, the mandrel takes on a speed of v m and moves at this speed until it begins to leave the deformation source. Beginning with the calibration section x 3 (Fig. 1), the mandrel speed will be equal to the speed of the final pipe. The motion of the mandrel and final pipe beyond the rollers may be regarded as the motion of a nonhollow blank at the supply rate ensured by the drive of the helical-reduction mill. For steady reduction, the mandrel speed cannot be greater than the speed v p at which the pipe leaves the deformation source or less than the speed at which it enters the deformation source. Since the speed of the metal increases in the deformation source, there is obviously a cross section with coordinate x 0 at which the axial speeds of the pipe and mandrel are the same. Hence, in the section from entry in the deformation

Technology of electrostatic spinning for the production of polyurethane tissue engineering scaffolds

AbstractElectrostatic spinning was investigated as an alternative to electrospinning to establish the potential of the technique for the production of a range of microfibrous polyurethane scaffolds with a variety of structures and properties related to the fabrication conditions. Tecoflex® SG‐80A polyurethane was spun, systematically altering the spinning parameters, and the resulting scaffolds were characterised using scanning electron microscopy. Inter‐fibre separation was significantly affected by flow rate, spray distance and grid and mandrel voltages; fibre diameter by flow rate and mandrel voltage; void fraction by flow rate; fibre orientation by traverse speed and mandrel speed; and thickness by flow rate. Thus, scaffold (three‐dimensional) architecture may be controlled through manipulation of the electric fields and the fibre deposition (spinning parameters of flow rate and grid and mandrel voltages); and by spray movement and direction (spinning parameters of relative spray height, spray distance, traverse speed and mandrel speed). There were significant differences between the internal and external scaffold surfaces, due in part to the manner in which the surface of the mandrels was prepared. We conclude that the process may be used to produce a range of polyurethane scaffolds for use in many tissue engineering applications. Copyright © 2007 Society of Chemical Industry

Design and fabrication of low cost filament winding machine

In general, the composite pipes are fabricated using glass fiber and polyester resin matrix by hand lay-up and also by 2-axis filament winding machine. In this work, a filament winding machine was designed and developed for the fabrication of pipes and round shape specimens. A lathe-type machine and a wet winding method were used in the design of the machine. It provides a capability for producing pipe specimens with an internal diameter up to 100 mm and lengths up to 1000 mm. The range of the winding angle, or the fiber orientation angle, starts from 20° to 90° depending on the mandrel diameter used. Mandrel speed is kept constant as 13.6 revolutions per minute (rpm) while the speed of screw of delivery unit varies from 0 rpm to a maximum of 250 rpm. In the filament winding process used, a single glass roving is drawn through a bath of pre-catalyzed resin which is mounted on the lead screw by the rotating mandrel. A control unit was used to control the whole process and achieve regular winding and good surface finish. Tube samples and other circular specimens of different dimensions were produced using this machine for the different mechanical tests and applications.

Rotary splitting — a novel sheet metal forming technique

A first attempt is given to analyse and describe Skinner's rotary splitting technique theoretically. It is found that this technique is of high kinematical complexity and quite sensitive to changes in process parameters. Neglecting elastical deformation effects a plastomechanical theory is presented to predict the deformation force, depending on tool geometry, workpiece properties, feed rate and mandrel speed. Results achieved by this theory are compared to those obtained by experimental work. A large difference between experimental and theoretical values is found and attributed to neglecting elastical effects. Therefore, in the next step of investigation the author intends to improve his theory and completes it by these effects. Additionally friction and work hardening effects shall be considered in future, too.