Longitudinal Seam Research Articles

Use of the Cone Expansion Test to Assess the Potential for Longitudinal Seam Failure in Extruded AZ31 and AM30 Mg Alloy Tubes

Magnesium generally has limited ductility which, in the case of extruded tubes, may be further reduced at the extrusion seams. These are locations where the material flow separates and rejoins during extrusion and are unavoidable when a hollow profile product is continuously extruded. When this type of magnesium tube is stressed along the circumferential direction, as in hydroforming, tube ruptures consistently occur along the extrusion seams. The aim of this project was to investigate the propensity to fail at these locations by means of cone expansion tests. These were performed to failure on batches of both magnesium AZ31 and AM30 tubes, at several temperatures and compression rates. In this paper, the role that microstructural changes at the seams such as those associated with precipitate dispersions, local texture changes, grain size changes and entrained material, play in failure is discussed. The sources of these irregularities in the extrusion process are discussed and some means of removing or mitigating them are presented. The most important cause of fracture is shown to be the voids present at the interface between the slowly and rapidly flowing streams of the material within the die. The effects of the extrusion parameters on the extent of such void formation are considered.

Use of the Cone Expansion Test to Assess the Potential for Longitudinal Seam Failure in Extruded AZ31 and AM30 Mg Alloy Tubes

Use of the Cone Expansion Test to Assess the Potential for Longitudinal Seam Failure in Extruded AZ31 and AM30 Mg Alloy Tubes

Physical Simulation of Longitudinal Weld Seam Formation During Extrusion to Produce Hollow Aluminum Profiles

Uniaxial compression tests were performed to understand the solid-state bonding process that occurs in porthole dies during the manufacturing of hollow aluminum extrusions. Strain, strain rate, and temperature applied during the tests were those typically encountered during aluminum extrusion. For a good bond, strain was found to be the most influential parameter, along with bonding time. The effect of temperature on bonding depended on alloy composition. Bonding stress was less influential within the range investigated. Surface stretching was introduced to the AA6060, AA6082, and AA7020 aluminum alloys as a criterion to quantify the bonding phenomena and distinguish their bondabilities.

Three Dimensional Analysis of High Frequency Induction Welding of Steel Pipes With Impeder

High frequency induction welding is widely employed for longitudinal seam welding of small scale tubes and pipes due to its relatively high processing speed and efficiency. This research is aimed at understanding the variables that affect the quality of the high frequency induction welding. The welding variables include the welding frequency, weld speed, vee angle, and tube thickness. Temperature distribution of the tube is calculated through three dimensional coupled electromagnetic and thermal finite element analysis. The skin and proximity effects are considered in the electromagnetic analysis. The influence of the impeder is also analyzed. The effects of the operating welding variables on the temperature distribution are investigated quantitatively by exhibiting the heat affected zone. The results explain the mechanism of significant enhancement of welding efficiency when the impeder is used. Not only good weld state can be obtained but also overheated edge can be avoided by understating the effect of welding variables. Suggestions are made for the better induction welding conditions.

Displacement Field Simulation and Deformation Prediction of Longitudinal Straight Seam Welding of Thin-Wall Aluminium Alloys Cylinder

The numerical simulation calculation of longitudinal seam TIG welding of thin-wall aluminium cylinder was conducted by the FEM software, Marc. Based on the generating of analysis model, displacement field was quantitatively described. Circular profile of aluminium alloy cylinder after welding was predicted by the radial displacement. The simulation results showed that the post-weld deformation for the longitudinal seam of aluminium alloy cylinder was mainly destabilizing deformation.

Analysis of Metal Flow through a Porthole Die to Produce a Rectangular Hollow Profile with Longitudinal Weld Seams

A detailed analysis of metal flow through a porthole die to produce a rectangular hollow aluminium profile was performed by means of three-dimensional FE simulation using DEFORM 3D. It was aimed at revealing the flow patterns of a medium-strength aluminium alloy 7020 through a porthole die and gaining an insight into the formation of longitudinal weld seams inside the welding chamber during extrusion. In the case of extruding a rectangular hollow profile through a porthole die with four ports, two neighbouring ports were different from each other. Using an FE model including these two ports, different flow patterns of two individual metal streams were revealed. The 3D FE simulation also showed how two unequal metal streams contacted each other and became bonded in the welding chamber under a certain hydrostatic pressure and at a certain temperature, before the metal flew through the die bearing. The difference in velocity between the metal streams led to uneven flow at the die bearing and thus a wavy extrusion nose.

FE analysis of metal flow and weld seam formation in a porthole die during the extrusion of a magnesium alloy into a square tube and the effect of ram speed on weld strength

The present communication concerns a detailed analysis of metal flow into a porthole extrusion die to produce a thin-walled square magnesium tube by means of three-dimensional FE simulation in both the transient state and steady state. The research was aimed to get an insight into the longitudinal weld seam formation during extrusion through porthole dies and to evaluate the factors determining the quality of the weld seams. FE simulation revealed distinctive stages at the beginning of an extrusion cycle, corresponding to the changes in extrusion pressure during the process. It showed that the commonly observed defect at the extrudate head was due to entrapped air under the bridges in the upper part of the welding chamber. The dead metal zones existed at the corners between the container and die face and between the bottom and sidewall of the welding chamber. Because of the friction at the die bearing, the metal flow through the die bearing resembled laminar flow. Only the virgin metal from the interior of the billet flowed along the bridges and formed the welding seams. As ram speed increased, the mean stresses and temperatures on the welding plane in the welding chamber increased, which was reflected in the increases in extrusion pressure and extrudate temperature, being beneficial to the solid-state bonding at the weld seams. Tensile tests confirmed that extrusion at a higher ram speed led to enhanced transverse tensile strength and strain of the extruded square tube, as a result of improved bonding at the longitudinal weld seams.

Study on inner force and dislocation of segments caused by shield machine attitude

Attitude deflection of shield machine is inevitable in process of driving forward, therefore, the tail brush, circular shape retainer and even shell of shield machine will extrude the exterior surfaces of segments. The squeezing action acting on segments causes dislocation, stress concentration and even crack in segments. Finite element code, ADINA, was used to analyze numerical tunnel model of 9 segment rings. The loads acting on different segment rings included squeezing action of tail brush under four attitude deflection, jacking forces, grouting pressure and earth pressure. The aspects of analysis included displacement feature and stress distribution. The analysis results indicate attitude deflection of shield machine causes biggish dislocation between segments, and the key segment is the most affected and weakest part in same ring which causes irregular displacement and dislocation in whole tunnel structure. In general, under squeezing action induced by shield machine, circumferential seam is much more affected than longitudinal seam. The squeezing action causes the segment dislocation exceed the limiting dislocation value which means curved bolt has extruded bolt hole and crack or breakage frequently concentrates in key segment and adjacent segment. Deflection of shield machine attitude is inevitable, but two deflection attitudes, including shield machine attitude deviates right direction and the head of shield machine goes down, should be avoided.

Numerical and experimental study on the extrusion through a porthole die to produce a hollow magnesium profile with longitudinal weld seams

In this study, the thermomechanical behaviour of a magnesium alloy AZ31B during extrusion through a porthole die to form a square tube was revealed. Three-dimensional numerical simulation demonstrated that metal flow into the portholes, welding chamber and die bearing of the porthole die corresponded to the stepped increases of extrusion pressure at the initial stages of an extrusion cycle. Experimental measurements of extrusion pressure and extrudate temperature were found to be in agreement with the predicted values. Extrusion pressure decreased continuously after the pressure peak while the workpiece temperature increased steadily, leading to gradual increases of the recrystallised grain sizes of the extrudate along its length. Expansion tests showed consistent quality of the longitudinal weld seams along the extrudate length, although the temperature on the welding plane increased and the maximum normal pressure in the welding chamber decreased during extrusion. It is thus the ratio of the maximum normal pressure in the welding chamber to the flow stress of the workpiece material on the welding plane that determines the weld seam quality.

Replacement of Imported Drawn Tubes Built in Heat Exchangers by Longitudinal Seam Pipes Produced by DUNAFERR

Diverse technologies in domestic enamelling production for machining, cutting and joining process are applied. The experiments presented in this paper focused on the opportunities of replacement of the drawn tubes built in heat exchangers longitudinal seam pipes produced by DUNAFERR Co. Ltd. The steel grade which satisfies the requirement of two-side enamelling, formability and after-fire sag resistance has been investigated. It has been shown that the coldrolled DC 04 EK-B steel grades stand all demands needed and therefore are able to replace the imported drawn tubes presently used.

Physical Simulation of Longitudinal Weld Seam Formation in Aluminium Extrusions

In the present study, a thermomechanical simulator (Gleeble 3500) was used to represent the solid–state bonding of aluminium in hollow dies during the extrusion of AA7020 alloy. The variations in strain, strain rate, temperature and pressure reflected those typically encountered during extrusion. The results showed that to form a good bond, strain was the most influential parameter, along with the time of deformation (bonding time). Temperature and pressure were found to be less influential within the parameter ranges investigated. On the basis of the results obtained, the ‘stretching’ of the interface has been proposed to be a critical parameter to quantify the solid–state bonding phenomenon.

고주파 유도용접 현상의 3차원 해석

High frequency induction welding is widely employed for longitudinal seam welding of small scale tubes and pipes because of its relatively high processing speed and efficiency. This research is aimed at understanding the variables that affect the quality of the high frequency induction welding. The welding variables include the welding frequency, weld speed, V-angle and tube thickness. Temperature distribution of the tube is calculated through three dimensional coupled electromagnetic and thermal FE analysis. The skin and proximity effects are considered in the electromagnetic analysis. The influence of the impeder is also analyzed. The effects of the operating welding variables on the temperature distribution are investigated quantitatively by exhibiting the heat affected zone (HAZ). The results explain the mechanism of significant enhancement of welding efficiency when the impeder is used. The proper welding conditions without the overheated edge are obtained through FE analysis.

The Influence of the Solid-State Bonding Process on the Mechanical Integrity of Longitudinal Weld Seams

For production of complex hollow 6xxx series aluminium extrusions, porthole dies are the predominant tooling set up. In porthole dies, the billet is divided into multiple metal streams, which are rejoined in the weld chamber to form ‘longitudinal weld seams’. Fundamental understanding of the solid state bonding process, as well as the ability to detect a well bonded (or a defective) weld seam are important for the production of high quality structural hollow extrusions. A study is being conducted to investigate the solid state bonding and weld seam formation processes during extrusion. The method chosen was to use a thermo-mechanical simulator (Gleeble 3500), thereby having the ability to vary process parameters such as strain, strain rate and temperature. The alloy investigated was primary and remelt AA6082. It was determined that the key parameter for bonding is surface stretching (creation of new surface at the interface) and bonding time.

AWB-06: The Influence of the Solid-State Bonding Process on the Mechanical Integrity of Longitudinal Weld Seams(AWB-I: ADVANCED WELDING AND BONDING, NDE)

AWB-06: The Influence of the Solid-State Bonding Process on the Mechanical Integrity of Longitudinal Weld Seams(AWB-I: ADVANCED WELDING AND BONDING, NDE)

Buckling of cylindrical shells under transverse shear

This work concerns with experimental studies on buckling of thin-walled circular cylindrical shells under transverse shear. The buckling loads are also obtained from finite element models, empirical formulae and codes and are compared. Experiments are conducted on 12 models made of stainless steel by rolling and longitudinal seam welding. In situ initial geometric imperfection surveys are carried out. The tests are conducted with and without axial constraint at the point diametrically opposite the loading. Theoretical analyses are carried out using ABAQUS finite element code. Two finite element models considered are: (i) geometry with real imperfection (FES-I) and (ii) critical mode imperfect geometry (FES-II). In the former, the imperfections are imposed at all nodes and in the latter, the imperfection is imposed by renormalizing the eigen mode, using the maximum measured imperfection. General nonlinear option is employed in both the cases for estimating the buckling load. Galletly and Blachut’s expressions, design guidelines of Japan for LMFBR main vessel expressions (empirical formulae), ASME and aerospace structural design codes are used for comparing with experimental loads. The comparisons of experimental, numerical and analytical buckling loads reveal the following. The numerical results are always higher than the experimental values; the percentage difference depends on the wall thickness. FES-II predicts somewhat a lower load than that of the FES-I. The Japanese guidelines predict the lowest load, which is conservative. Experimental loads are lower than that predicted by both ASME and aerospace structural design codes.

Influence of the Textile Structure on the Degradation of Explanted Aortic Endoprostheses

Objectives. To investigate mechanisms of textile failure in explanted human aortic endoprostheses. Materials and methods. Endoprostheses ( n=31) underwent optical and scanning electron microscopy, filament dynamometry, and saturation index measurement. Results. The macroscopic lesions observed in the Stentor and Vanguard devices were holes at the extremities of the stents and slipping of the warp yarns at the level of sutures or of the longitudinal seams. The macroscopic lesions observed in AneurX endoprostheses were holes, slipping of the warp yarns and ruptures of the ligatures. The macroscopic lesions observed in the two Talent endoprostheses were sections of fibers at the level of the suture holes and few areas lesions of wear, with sometimes holes at the contact of the stent extremities. Stentor, Vanguard and AneurX all demonstrated low saturation indexes of the fabric (44–59%) with an important anisotropy. Whereas the Talent endograft demonstrated a high index of saturation (124–131%) with a low anisotropy. We did not demonstrate significant polymer degradation in any of the endoprostheses. Conclusions. It is essential to take into account the saturation index to optimally choose a woven textile for the construction of an endoprosthesis since this property of the textile may contribute to explain the macroscopic lesions observed. We did not observe significant polymer degradation by filament dynamometry but further studies are needed to confirm these data.

Experimental Modal Analysis Of A Water-filledCircular Cylindrical Tank

Experimental modal analysis has been performed on an empty and water-filled, circular cylindrical tank horizontally suspended. The tank is composed of a circular cylindrical shell with a longitudinal butt seam welding and two end annular plates. A rubber disk was glued to each annular plate to close the tank. The boundary conditions imposed to the circular cylindrical shell by the thin end plates can be considered very close to simply supports. Two little pipe fittings, used for supplying water, were welded to one of the end plates in such a position that they do not affect shell vibrations. The tank was hung to a truss with its axis kept horizontal by a compliant suspension, by using cables connected to the end plates. The Frequency Response Functions (FRFs) between 100 response points and one single excitation point (SIMO test) have been measured. Burst random has been used as excitation input. Natural frequencies and mode shapes are in very good agreement with theoretical data computed using the Fliigge theory of shells and potential and incompressible fluid model.

Production of NbTi CICC's for SST-1 project at IPR

A total of 24 pieces of NbTi CICC with outer dimension of 14.8 mm/spl times/14.8 mm and a piece length of 600 m each have been successfully fabricated for building TF and PF coils. The CICC is made through the roll forming and welding process. The insert cable with a scheme of 3/spl times/3/spl times/3/spl times/5 is made from 0.86 mm diameter multifilamentary NbTi/Cu strand with 10 /spl mu/m diameter NbTi filaments embedded in Cu matrix at a Cu ratio of 4.9. No treatment is applied to the strand surface. A 0.025 mm thick SS304 tape is wrapped on the finished fourth stage cable. A 15 mm thick SS304L strip is then roll formed around the wrapped fourth stage cable and TIG welding 6 applied continuously at the top longitudinal seam. The welded conduit is finished to the final square dimension, by passing it through sizing rolls and turks head rolls set at the end of the jacketing line. The critical current for a CICC, estimated through multiplying an average I/sub c/ (without self-field correction) for the 10 extracted strands by the number of strands of 135 in a CICC, is approximately 38 kA at 5 T, 4.2 K. This means that there is: no significant degradation of I/sub c/'s for the strands due to the cabling and jacketing process. It is confirmed that the finished CICC pieces of 600 m each show a He leakage level well below 0.2/spl times/10/sup -3/ Toll 1/s.

Influence of mis-match of weld and base material creep properties on elevated temperature design of pressure vessels and piping

The stress and strain concentrations developed at the weldments during the long time operation of pressure vessels and piping at high temperature due to the mis-match in the creep properties of weldment constituents (weld, heat affected zone and base metal) are estimated using detailed finite element analysis. Three materials, viz. 2.25Cr 1Mo, SS 316 LN and modified 9Cr 1 Mo which are the most commonly used materials in the nuclear and thermal power plants are considered. A longitudinal seam weld with single and double V (X) configurations are analysed. Parametric studies have been done on weld angle and stresses. Based on the analysis, critical locations and the maximum stress concentration factors in the weldments for the above materials are identified. The weld design procedures of the currently used pressure vessel and piping codes are commented. The importance of ductility based failure criteria is emphasised.

Damage Tolerance and Assessment of Foam-Inflated Aerospace Structures

Design and operational issues with respect to the use of inflatable-deployable foam-rigidized components in aerospace structures are investigated in this paper. The sample structures used in this study are fabricated from flexible Kapton film formed into a cylindrical shell by bonding a flat sheet along a longitudinal seam. This tubular shell is injected with a hardening urethane foam to form a composite strut coupon. As with all structures touted for aerospace use, the survivability of foam-rigidized structures when subjected to a micrometeor flux is of interest. This issue is investigated in this paper by performing two controlled experiments: (1) Foam-rigidized test coupons were evaluated in their pristine state to determine structural properties, severely damaged in a controlled fashion, and then evaluated again to compare the undamaged to damaged behavior; and (2) a single specimen was repeatedly tested and then slightly damaged to examine how structural behavior evolves as damage accumulates. The results of these experiments are then used to draw conclusions about the utility of foam-rigidized structures in space applications, including an evaluation of appropriate structural health monitoring strategies.