Mild Steel Tubes Research Articles

Magnetic pulse cladding of aluminum alloy on mild steel tube

Bi-metal tubes, which combine the advantageous properties of two different metals, are desirable in industries where corrosion resistance is important. A new cladding method named magnetic pulse cladding (MPC) was used to form bi-metal tubes. A cladding of mild steel tube by aluminum alloy (AA3003) was achieved. The effect of the geometry of the field shaper on cladding quality was investigated as well as other main process parameters, such as, feeding size, radial gap and discharge voltage. The mechanical property was evaluated by compression-shear test and a maximum strength of 79.2MPa and an average of 29.7MPa were attained to by the following process settings: profiled field shaper, feeding size of 12mm, radial gap of 2.0mm and discharge voltage of 15kV. OM and SEM images show a smooth integral interface and a small wavy one. EDS mapping reveals the interfacial diffusion zone up to 50-μm wide. The results show that the proposed MPC process is able to form sound cladding bonds and could be applicable to a tubular clad component with a high axial length.

Empty circular metal tubes in the splitting process – theoretical and experimental studies

This article derives some theoretical relations to predict the instantaneous axial force of the circular metal tubes during the splitting process under the axial compression by the theoretical and experimental methods. A new theoretical model of splitting deformation of the circular tube as a thin-walled structure subjected to the axial loading is introduced and based on the deformation model and using the energy method, some analytical formulas are derived to estimate the instantaneous axial load, maximum splitting load, steady force and curl radius of the tubes. To verify the present theory, some aluminum, mild steel and brazen tubes with the circular cross-section and different geometrical and material characteristics were prepared and axially compressed on conical dies with the different cone angles. Comparison of the theoretical predictions and the experimental measurements shows a good correlation and it affirms verity of the new theoretical deformation model and the present theory. Also, based on the experimental results, the effects of wall thickness and inner radius of the tubes and also, number and length of initial slits and semi-angle of conical die are studied on the axial load and maximum splitting load.

BEHAVIOUR OF CFST MEMBERS UNDER COMPRESSION EXTERNALLY REINFORCED BY CFRP COMPOSITES

This research is aimed at investigating the structural improvements of concrete filled steel tubular (CFST) sections with normal strength concrete externally bonded with fibre reinforced polymer (FRP) composites. For this study, compact mild steel tubes were used with the main variable being FRP characteristics. Carbon fibre reinforced polymer (CFRP) fabrics was used as horizontal strips (lateral ties) with several other parameters such as the number of layers and spacing of strips. Among twenty one columns, eighteen were externally bonded by CFRP strips having a constant width of 50 mm with a spacing of 20 mm and 40 mm and the remaining three columns were unbounded. Experiments were undertaken until column failure to fully understand the influence of FRP characteristics on the compressive behaviour of square CFST sections including their failure modes, axial stress-strain behaviour, and enhancement in load carrying capapcity. It was found that the external bonding of CFRP strips provides external confinement pressure effectively and intended to delay the local buckling of steel tube and also to improve the load carrying capacity further.

Plastic deformation due to reflected detonation

We report the experimental conditions and results for a series of experiments involving detonation loading of steel tubes alongside computational comparisons performed using an analytic one-dimensional model and a finite element simulation. To achieve plastic deformation, thin-walled steel tubes were filled with a stoichiometric ethylene–oxygen mixture and detonated. The range of initial pressures covered the span from entirely elastic to fully plastic deformation modes. A unique mode of periodic radial deformation was discovered. A model for the pressure load on the tube wall was developed and tested against experimental measurements.Building on the experimental results, we discuss theoretical and computational models describing these experiments. The simplest model considers the oscillation of a single degree of freedom of the tube’s cross section. Using this simple model, we explain that the periodic deformation observed in the experiment is the result of interference between the reflected shock wave and the elastic oscillations set in motion by the incident detonation. To capture the effects of boundary conditions and wave propagation, we performed computations using a two-dimensional axisymmetric model of the tube wall. For the mild steel tubes this required material testing, and the resulting constitutive relation proved to be limited. As a result, fidelity with experiments was much greater in the case of the stainless steel tubes.

Axial behaviour of HSS tubular sections strengthened by CFRP strips: an experimental investigation

AbstractThe main objective of this investigation is to assess the feasibility of strengthening square hollow steel tubular sections subjected to compression and to develop or predict the suitable wrapping scheme of fibre reinforced polymer (FRP) to enhance the structural behaviour of it. For this study, compact mild steel tubes were used with the main variable being FRP characteristics. Carbon fibre has been considered and used as strips with several other parameters such as the number of layers, width and spacing of strips, the sectional area of strips, and wrapping scheme. Experiments were undertaken until column failure to fully understand the influence of FRP characteristics on the compressive behaviour of square hollow steel tubes including their failure modes, stress-strain behaviour, enhancement in load carrying capacity and effect of distribution of CFRP layers. The behaviour of externally bonded hollow steel tubular sections was compared with one another and also with the control specimen. From the test results, it was found that CFRP strengthening significantly increases the load carrying capacity and ductility of the hollow steel tubular members further.

Effect of length on crashworthiness parameters and failure modes of steel and hybrid tube made by steel and GFRP under low velocity impact

The use of tubes as energy absorption structures has been prevalent for many decades and numerous studies have been done on metal and composite tubes of varying thickness, length and section geometry. This paper extends the work to hybrid tubes and presents the results of experimental work pertaining to the collapse modes and crashworthiness characteristics of hybrid tubes that were subjected to quasi-static axial compressive loading. The hybrid specimens were featured by inner mild steel tube wrapped by a material combination of glass fibres in the form of reinforcing direct roving fabric in thermosetting polyester resin. Tubes were cut at different lengths of the same circular cross-section that encompassed both classical progressive buckling and the global bending modes of failure. Particular attention was paid to the investigate effect of tube length on crashworthiness parameters and critical length to avoid global bending during quasi-static crushing of thin-walled tubes. At first, similar work was done on steel tubes to compare results obtained by hybrid tubes with plain counterparts.

The Response of Sandwich Panels Made of Thin-Walled Tubes Subjected to Axial Load

This paper presents the results of experimental and numerical work on the response of sandwich panels made of thin-walled tubes and mild steel plates to axial loading. The core of the sandwich panels consists of mild-steel square tubes, 20×20×0.9 mm in cross-section, in three different layouts comprising of four or five or nine tubes, (panels A, B and C respectively). Three tube configurations are investigated, as–received tubes, tubes with circular cut-out on opposite sides, and tubes with dents on opposite sides. The imperfections are located at the mid-section of the tube. The outer skin of the sandwich panel is 150×150×10 mm in cross-section and non-deformable. Quasi-static tests carried out on two and three tubes laid out in parallel between the skin indicate that the axial forces is a multiple of the axial force of a single tube, as expected. Consequently, the sandwich panel with the nine tubes deforms less than the sandwich panels with five and four tubes when subjected to similar impact energy. Triggers in the tubes improve the collapse mode of the sandwich panels. The Finite Element package ABAQUS/Explicit v6.7 is used to construct a ¼ symmetry model using shell elements to simulate the response of the sandwich panels to dynamic axial load. The Finite element simulations, validated using high speed photography footage, show good correlations with experiments.

Experimental study on CFST members strengthened by CFRP composites under compression

The concrete filled steel tubular (CFST) members become very popular in the construction industry and, at the same time, aging of structures and member deterioration are often reported. The actions like implementation of new materials and strengthening techniques become essential to combat this problem. This research work aimed to investigate the structural improvements of CFST sections with normal strength concrete externally bonded with fibre reinforced polymer (FRP) composites. For this study, compact mild steel tubes were used with the main variable being FRP characteristics. Carbon fibre reinforced polymer (CFRP) fabrics were used as horizontal strips (lateral ties) with several other parameters such as the number of layers, width and spacing of strips. Among thirty specimens, twenty seven were externally bonded with 50mm width of CFRP strips with a spacing of 20mm, 30mm and 40mm and the remaining three specimens were unbonded. Experiments were undertaken until column failure to fully understand the influence of FRP characteristics on the compressive behaviour of square CFST sections including their failure modes, axial stress–strain behaviour, and load carrying capapcity. From the test results, it was found that the external bonding of CFRP strips provides external confinement pressure effectively and delays the local buckling of steel tube and also improves the load carrying capacity further. Finally, an analytical model was proposed herein for predicting the axial load carrying capacity of strengthened CFST sections under compression.

Thermal stress analysis of spiral laser-welded tube

Laser welding of mild steel tube was carried out under the nitrogen assisting gas ambient. Finite element method (FEM) was used to predict the temperature and stress fields in a laser spirally welded tube with 1.6 mm wall thickness and 75 mm diameter. Temperature-dependent thermal and mechanical properties of steel were incorporated in the model. Laser was modeled as a 3D volumetric moving heat source. The residual stresses produced after the completion of the laser welding process were investigated. Moreover, the effect of welding speed on the level of residual stress was studied. It was found that von Mises stress attained high values in the cooling cycle after the solidification of the molten zones. The residual stress developed in the welding region was measured using the XRD technique and results were compared with the predictions. Optical microscopy and SEM were used for metallurgical examination of the welding sites. The numerically predicted residual stress was in good agreement with the XRD results. Increasing the welding speed with constant power resulted in reduction of the width of the high stress zone.

Flexural Waves in Fluid-Filled Tubes Subject to Axial Impact

We experimentally studied the propagation of coupled fluid stress waves and tube flexural waves generated through projectile impact along the axis of a water-filled tube. We tested mild steel tubes, 38–40 mm inner diameter and wall thicknesses of 0.8 mm, 6.4 mm, and 12.7 mm. A steel impactor was accelerated using an air cannon and struck a polycarbonate buffer placed on top of the water surface within the tube. Elastic flexural waves were observed for impact speeds of 5–10 m/s and plastic waves appeared for impact speeds approaching 20 m/s for a 0.8 mm thickness tube. We observed primary wave speeds of 1100 m/s in a 0.8 mm thickness tube, increasing to the water sound speed with 6.4 mm and 12.7 mm thickness tubes. Comparison of our measurements in the 0.8 mm thickness tube with Skalak’s water hammer theory indicates reasonable agreement between the predicted and measured peak strains as a function of the impact buffer speed (1956, “An Extension to the Theory of Water Hammer,” Trans. ASME, 78, pp. 105–116). For thick-walled tubes, the correlation between the experimentally determined peak pressures and strains reveals the importance of corrections for the through-wall stress distribution.

Experimental and numerical analysis of tube-core claddings under blast loads

An investigation into the response of a sandwich cladding panel under blast loading is presented. The sandwich cores are composed of square thin-walled metallic tubes. Three primary panel layouts are identified, consisting of panels with four, five and nine tubes within the core. Annealed mild steel and 6063-T6 aluminium alloy tubes are selected as the core material. Hemispherical indentation triggers are used to induce progressive, symmetric buckling. A series of experimental blast tests are conducted on the proposed panels. A ballistic pendulum is used to measure the impulse transferred to the panel. At smaller blast impulses, irregular buckling modes are observed for both the steel and aluminium tube-core panels primarily due to variable trigger performance. For blasts which utilize the full stroke of the tubes, symmetric buckling modes are observed. In all cases panel crush distance increases with increasing impulse and decreases with an increasing number of tubes in the panel core. Further to this, at equal charge mass, the aluminium tube cores show significantly higher crush distance than identical steel tube panels. Analytical predictions of panel response give satisfactory agreement with experimental and finite-element results provided the response is within the pre-compaction regime. Finite-element results using ABAQUS/Explicit also show satisfactory correlation with experimentally obtained global response. Numerical analysis shows that energy absorption is primarily confined to the core tubes with only minimal plastic strains developing in the top plate. A numerical parametric study is conducted to determine influence of load uniformity on panel response. Energy absorption efficiency is found to be highly sensitive to the uniformity of the load, primarily in panels with fewer core tubes and thinner top plates.

Indepth Investigations into the Capability of Plazma Arc Cutting of Mild Steel Tubes

Indepth Investigations into the Capability of Plazma Arc Cutting of Mild Steel Tubes

The Energy Absorption Characteristics of Square Mild Steel Tubes With Multiple Induced Circular Hole Discontinuities—Part I: Experiments

This two-part article reports the results of experimental and numerical works conducted on the energy absorption characteristics of thin-walled square tubes with multiple circular hole discontinuities. Part I presents the experimental tests in which dynamic and quasistatic axial crushings are performed. The mild steel tubes are 350 mm in length, 50 mm wide, and 1.5 mm thick. Circular hole discontinuities, 17 mm in diameter, are laterally drilled on two or all four opposing walls of the tube to form opposing hole pairs. The total number of holes varies from 2 to 10. The results indicate that the introduction of holes decreases the initial peak force but an increase in the number of holes beyond 2 holes per side does not further significantly decrease the initial peak force. The findings show that strategic positioning of holes triggers progressive collapse hence improving energy absorption. The results also indicate that the presence of holes may at times disrupt the formation of lobes thus compromising the energy absorption capacity of the tube. In Part II, the finite element package ABAQUS/EXPLICIT version 6.4–6 is used to model the dynamic axial crushing of the tubes and to investigate the action of the holes during dynamic loading at an impact velocity of 8 m/s.

The Energy Absorption Characteristics of Square Mild Steel Tubes With Multiple Induced Circular Hole Discontinuities—Part II: Numerical Simulations

This paper is Part II of a two-part article and presents the results of numerical simulations conducted to investigate the energy absorption characteristics of square tubes subjected to dynamic axial loading. Part I reports the experimental results of both quasistatic and dynamic tests. The validated model is used to study the crushing characteristics of tubes with multiple induced circular hole discontinuities using the finite element package ABAQUS/EXPLICIT version 6.4-6. Holes of diameter 17 mm are used as crush initiators, which are laterally drilled into the tube wall to form opposing hole pairs. Holes of diameters 12.5 mm and 25 mm are also used to assess the effects of hole diameter on energy absorption. Two hole spacing configurations are investigated, one in which the hole pairs are placed at regular intervals of 50 mm along the tube wall and another in which the hole pairs are spaced symmetrically along the tube length. Holes are also drilled on either two or all four opposing tube walls. The number of holes is varied from 2 to 10. The results indicate that the introduction of the holes decreases the initial peak force. However, an increase in the number of holes, beyond two holes, does not further significantly decrease the initial peak force. A study of the crushing history of the tubes reveals that crushing is initiated at the location of the holes. The results also indicate that the type of hole spacing determines how crushing is initiated at the hole locations. The model satisfactorily predicts the resultant collapse shapes but overpredicts the crushed distance.

The effect of stand-off distance on the failure of fully clamped circular mild steel plates subjected to blast loads

The effect of stand-off distance and charge mass on the response of fully clamped circular mild steel plates, of radius 53 mm, subjected to blast loads travelling along tubular structures is reported. The procedure consists of creating a blast load using plastic explosive mounted onto the end of mild steel tubes. The stand-off distance is varied, from 13 to 300 mm, using different tube lengths. The plate responses range from large inelastic deformation to complete tearing at the boundary. Different loading regimes are observed, depending on the stand-off distance between the explosive charge and the plate, and are classified according to the plate response. At stand-off distances less than the plate radius (13–40 mm), the blast load is considered to be focused (localized). For stand-off distances greater than the plate radius (100–300 mm), the loading is considered uniformly distributed over the entire plate area. Theoretical and empirical analyses are performed, to enable predictions of the mid-point deflection. Appropriate modifications are introduced to account for the effect of stand-off distance on plate deformation. The modified analyses show satisfactory correlation with experimental results.

Mechanism of improvement of formability in pulsating hydroforming of tubes

The mechanism of improvement of formability by the oscillation of internal pressure in a pulsating hydroforming process of tubes was examined. Free bulging hydroforming experiments of mild steel tubes under oscillating and constant inner pressures were performed. For a high constant pressure, a round bulge with local thinning was observed, whereas wrinkling occurred for a low constant pressure. The occurrence of these defects was prevented by oscillating the internal pressure in the pulsating hydroforming. In the pulsating hydroforming, a uniform expansion in the bulging region was obtained, and thus the formability was improved by preventing the local thinning. It was found from an observation of deformation behaviour, using a video camera, that the tube is uniformly expanded by repeating the appearance and disappearance of small wrinkling. The cause of the uniform expansion for the pulsating hydroforming was also interpreted from the variation of stress components. In addition, a similar deference in deformation behaviour between the oscillating and constant inner pressures was also obtained in finite element simulation.

Collapse of square metal tubes in splitting and curling mode

This paper presents a further investigation into the energy absorbing behaviour of axially splitting and curling square mild steel and aluminium tubes. Both quasi-static and dynamic tests were conducted. A simple quasi-static kinematic model is developed which describes all the main features of the deformation process. It is assumed in this model that cracks start from the four corners and propagate along the axial direction due to continuous fracture/tearing. The free side plates so formed by cracks roll up into four curls with a constant radius. Formulas for the average crush force, curl radius, and the energy absorption are achieved by analysing the ‘far-field’ and ‘near-tip’ deformation events and the bending moment at the crack tip. This quasi-static model is also extended and used for dynamic cases to explore strain-rate effects in splitting square metal tubes. Solutions are presented and detailed comparisons are made between theoretical predictions and experimental results.

Study of lateral compression of round metallic tubes

A detailed experimental and computational investigation of round metallic tubes subjected to quasi-static loading is presented. Experiments were conducted wherein round aluminium and mild steel tubes of different diameter to thickness ratios were subjected to lateral compression in an Instron machine. Their deformation histories and load–compression curves were obtained. The deformation of the tubes has also been studied and analysed with the help of the finite element code FORGE2. Contours of nodal velocity, equivalent strain rate and equivalent strain at different stages of compression are presented and discussed. Experimental and computed results are compared. Basic mechanism of their deformation and the effects of process parameters on deformation behaviour of the tubes are presented and discussed.

Quasi-static and dynamic axial crushing of thin-walled circular stainless steel, mild steel and aluminium alloy tubes

Quasi-static and dynamic axial crushing tests have been performed on circular thin-walled sections made of three materials: 304 stainless steel, aluminium alloy 6063-T6, and mild steel. The tests were arranged to investigate the mode transitions during the impact crushing of thin-walled tubes and the three materials were chosen for their distinctive individual characteristics, such as strain rate sensitive properties, pronounced strain hardening, etc. The stainless steel, aluminium alloy and mild steel shells have moderate diameter-to-thickness ratios, 2R/H, of 22, 33 and 26, respectively, and were examined over a range of different axial lengths that encompassed both classical progressive buckling and the global bending modes of failure. The tests were conducted at a standardised energy of 9 kJ, approximately, with a few tests repeated at a higher energy of 18 kJ. The shells were impacted at velocities up to 13.4 m/s with masses up to 502 kg. Standard collapse modes developed in the tubes and the associated energy absorbing characteristics have been examined and compared with previous studies on mild steel. Quasi-static and dynamic tensile test results on the materials are also reported and the critical slenderness ratios at the transition between the two principal modes of failure are identified. The effects of strain hardening, strain rate as well as inertia effects due to the individual characteristics of the three materials are explored.

Method for determining reaction rate of mild steel containers during melting of magnesium-aluminium alloys and effect of aluminium content on directionally solidified microstructures

A magnesium alloy of eutectic composition (33 wt-%Al) was directionally solidified in mild steel tubes at two growth rates, 32 and 580 μm s−1 in a temperature gradient between 10 and 20 K mm−1. After directional solidification, the composition of each specimen varied dramatically, from 32%Al in the region that had remained solid to 18%Al (32 fim s−1 specimen) and 13%Al (580 (μm s−1 specimen) at the plane that had been quenched from the eutectic temperature. As the aluminium content decreased, the microstructure contained an increasing volume fraction of primary magnesium dendrites and the eutectic morphology gradually changed from lamellar to partially divorced. The reduction in aluminium content was caused by the growth of an Al-Fe phase ahead of the Mg-Al growth front. Most of the growth of the Al-Fe phase occurred during the remelting period before directional solidification. The thickness of the Al-Fe phase increased with increased temperature and time of contact with the molten Mg-Al alloy. IJCMR/455