Backing Strip Research Articles

Virtual Fatigue Life Prediction of Back Strip Butt Weld Joint under Bending and Torque Load Conditions

The welding components used in automobile and aerospace industries are subjected to cyclic loading during field utilization. Understanding the behavior of the weld joints under fatigue loading is essential for designing components for optimum performance. This paper presents the study of virtual fatigue life prediction of back strip butt weld joint under bending and torque load conditions by varying weld joint parameters such as plate thickness, root gap and load. Virtual experiments are carried out on all samples by using finite element analysis (FEA) as per the concept of the design of experiment (DOE) approach. The response surface methodology, one of the DOE approaches, is used to obtain the different weld joint parameter combinations. Static structural analysis is performed to obtain the stress distribution in the weld model. Fatigue life is calculated by using the “E” Class S-N curve. The analysis of variance (ANOVA) approach is exploited to evaluate the influence of weld parameters of plate thickness, root gap and load on fatigue life.

Development of fabrication technologies for the first wall of the HCCR blanket

The helium-cooled ceramic reflector (HCCR) concept is a primary candidate among demonstration fusion power reactor (DEMO) blanket options in Korea. The HCCR blanket is composed of a first wall (FW), a breeding zone, side cover plates and a back manifold. This study focuses on fabrication technologies for the FW using laser-beam welding (LBW) and hot isostatic pressure (HIP) bonding. Permanent backing strips in the pressure boundaries of the HCCR blanket are not allowed according to regulations related to pressure vessels and nuclear pressure vessels because high-pressure helium gas at 8 MPa is used as the coolant. LBW conditions and procedures for the fabrication of a FW without backing strips were investigated using small mock-ups with an advanced reduced-activation alloy called ARAA, which was developed in Korea. The laser beam power, thickness of the cover plate, and width of the backing strips were considered as parameters. The LBW conditions and procedures were optimized to remove the backing strip and achieve uniform and continuous back beads. After LBW, the fabrication of the FW with small mock-ups was completed by joining the back plate with HIP bonding. The small mock-ups were subject to very high temperatures exceeding 1000°C during the LBW and HIP bonding processes, which led to changes in the microstructures and hardness levels. The microstructures and hardness levels were recovered through post-heat treatments performed after HIP bonding. The microstructures of the HIP bonding interface after the heat treatments were observed. A partial HIP bonding line was confirmed and transverse tensile tests were carried out to investigate the impact of the partial HIP bonding line on the mechanical properties of the HIP bonding interface. The tensile strength of the HIP bonding interface was approx. 2% lower than that of the base metal, indicating that the partial HIP bonding line caused a slight decrease in the tensile strength, but the impact on the HCCR blanket design would be negligible.

A TEST REPORT ON BLOWHOLES AND PROCESSING METHOD OF THE FULL PENETRATION BUTT WELDED JOINT OF BEAMS THAT COATED WITH STANDARD THICKNESS OF THE ANTICORROSIVE PAINT

The authors focused on blowholes caused by the anticorrosive paint for the groove. The parameters are the assembly method of the backing strip and the presence or absence of the mill scale on the surface where the backing strip and the base metal contact. As a result, many blowholes were generated depending on the assembly method of the backing strip without completely removing the mill scale. By the assembly method of the backing strip from the groove side, the blowholes were reduced to the same extent as the complete removal of the mill scale without removing the mill scale.

Fabrication and testing of small mock-ups for helium cooled ceramic reflector breeding blanket development

Korea has developed a helium cooled ceramic reflector test blanket module (TBM) for fusion reactors. An advanced reduced activation alloy has been developed as a structural material and various joining methods such as E-beam welding, tungsten inert gas (TIG) welding, laser welding, and hot isostatic pressing have been applied to establish its fabrication method and procedure. Based on the current design of the TBM and breeding blanket, TIG welding was selected as the main joining method, and the U-shaped first wall (FW) was adopted. For welding of the breeding blanket, a special joining technique without a permanent backing strip with simultaneous full penetration welding in accordance with the design rules of class N2RX of RCC-MRx is required for the pressure vessel. For the U-shaped FW, distortion of the drilled cooling hole during the bending should be limited. Three small mock-ups were fabricated in this study to investigate these issues. The joints and bending parts were visually observed after cutting, and the hydrostatic pressure test was performed for regions with low thickness. The results show that the proposed fabrication methods are applicable in the fabrication procedure development for the breeding blanket.

A Novel Ceramic Backing Strip from Metakaolin-Based Geopolymer with Gas Flow Holes for Welding Application

This research is firstly presented the thermal resistance of a ceramic backing made from metakaolin-based geopolymer for stainless steel welding. The general problems such as lack of fusion, hydrogen inclusion, porosity and corrosions of stainless steel welded specimens were found because, largely, stainless steel presents an affinity to gases as oxidation. Therefore, during welding, if these gases do not escape from the weld pool before solidification of weld metal, it results in porosities or hydrogen inclusions. In this case, it can be solved by properly using inert gas backing. The welder usually uses the steel backing plate with a gas release hole to support weld root and gas transmission for completed weld penetration and superior weld quality. Since the geopolymer shows a good property of thermal resistance, researchers are interested in using the ceramic backing made from geopolymer instead of the commercial ceramic backing. The ceramic backings from the geopolymer were designed merely in 3 types as follows: Narrow curved groove without gas release hole, narrow curved groove with gas release holes and wide curved groove with gas release holes. Consequently, two pieces of stainless steel were welded by gas tungsten arc welding and then the weld quality such as defects, porosity and root penetration of welded specimens was inspected. Moreover, the surface failure of ceramic backing after the welding process was also considered. The results revealed that ceramic backing from a geopolymer with wide curved groove and gas release holes gave completed penetration at the root when inspecting with non-destructive testing such as visual test, penetration test, and radiography test. It was concluded that the geopolymer could be used as ceramic backing in stainless steel welding by gas tungsten arc welding. Moreover, it could be used as backing for aluminum and steel welding as well.

Miniaturized conductor‐backed CPW high‐pass filter for C‐band satellite applications

AbstractA miniaturized conductor‐backed coplanar waveguide high‐pass filter for C‐band satellite applications is presented in this article. It consists of high impedance line and hexagonal resonator with interdigital coupling implemented in coplanar by etching square ring metallic pattern at the ground plane of the substrate. The necessary transmission zero is obtained by the shunt connected square ring pattern. The hexagonal resonator arrangement is used to produce band pass characteristics and the back side strip introduces capacitance effect thereby improving the rejection level. Hence, the filter behaves as high‐pass filter. Design, simulation, and fabrication of Satellite C‐band high‐pass filter characteristics are investigated. The proposed filter yields excellent band width starts from 2 to 8 GHz at 10 dB. Hence, the proposed filter will be best suitable for Satellite C‐band applications. The overall size of filter is achieved to be 39 mm × 8 mm × 1.6 mm on accounting all the features. The fractional band width of the filter is calculated from bandwidth to center frequency ratio and it is found 120%. S‐parameter results of high‐pass filter are return loss (RL) S11 is about −30 dB and insertion loss (IL) S21 is −0.98 dB are obtained in simulation. Whereas in the measurement, the RL is nearly −25 dB and IL is −2 dB.

Influence of weld details on fracture behavior of connections using high-strength steel

Based on post-earthquake research, brittle fracture of steel structures typically occurs near connection weld seams. The study proposes a new welded structure to improve the fracture resistance of connections. The fracture toughness of steel may decrease with increases in steel strength, and thus the fracture behavior of connections using high strength steel (HSS) was studied. Local welded specimens with different design details were tested under quasi-static loads, a finite element model was established, and initial cracks were assumed to analyze the fracture behavior of three types of local welded structures. Based on fracture mechanics, mode I elastic stress intensity factor (KI) and inelastic J-integral (JI) at the crack tip were calculated to predict the failure modes of HSS connections with different local welded structures. The experimental results were consistent with the expected results predicted via fracture mechanics, and the fracture of the specimen with the new design detail involving a backing strip welded at both sides occurred at a location away from the weld seam. The results indicated that the new design detail of local welded structure improves the fracture behavior of HSS connections.

One improved burial history recovery method and computer model establishment

This paper which depended on the foundation of back strip method has established mathematic model to simulate stratum burial history, which considered the computation of stratum skeleton depth based on max depth and the equation-depth point on the procedure to recover stratum by stripping each layer, and put forward the enhanced restoration method taking layers group as studying object. Finally, the method has been applied to build the computer model and program automatic back strip algorithm successfully. Experiments have proved that the method is accurate, applicable, and extensible under the conditions of various complex strata.

Reduction in through put time of drum shell manufacturing by single-V welding configuration

The present work highlights the outcomes of the case study that investigate the reduction in through put time of drum shell manufacturing, which earlier employed a double-V butt welding configuration for joining the ends of the plates after rolling the plates into cylindrical form, while the proposed method makes use of single-V type configuration to fabricate the drum shells with ceramic backing strip arrangement. The proposed work eliminates some redundant operations like inside welding, back grinding and other side edge preparations thereby reducing the production time of drum shell manufacturing. 38% improvement in production rate of drum shells was observed by proposed method compared to the earlier method.

Effectiveness and acceptability of a virtual environment for assessing human–robot collaboration in manufacturing

A highly immersive and interactive virtual environment was constructed as an experimentation platform for human–robot collaboration in constricting panels from preimpregnated carbon fibre fabrics. The application involves highly collaborative tasks such as handover, removal of adhesive backing strip and fabric layup in a mould. Furthermore, the user is expected to be most of the time within the robot’s workspace, jointly working as teammates on collaborative manufacturing tasks. The environment embeds two interaction metaphors for complex tasks and advocates use of cognitive aids to cultivate proactive behaviour of the user, thus promoting situation awareness, danger perception and enrichment of communication between human and robot. The application was put under test by a group of users. Their experience was registered scholarly through questionnaires and objective observation and is reported in the paper to explore the effectiveness and acceptability of such an environment. Overall, the application was judged positively, especially the use of cognitive aids which, under circumstances turned into alarms and readily provided mental association of collision danger to its cause. Furthermore, some deficiencies were identified pertaining to lack of hand-tracking performance and need to improve the layup metaphor.

Interpretacja niezgodności spawalniczych w złączu T-joint z podkładką podczas badań ultradźwiękowych

Jedną z najczęściej stosowanych metod oceny poprawności wykonania złączy spawanych jest nieniszcząca metoda wykorzystująca fale ultradźwiękowe. Praktyka pokazuje, że pomimo wymagań stawianych personelowi wykonującemu badania, w wielu przypadkach niezgodności w spoinach czołowych w połączeniach typu T-joint z podkładką stalową są błędnie interpretowane, a w konsekwencji prowadzą do zbędnej i kosztownej naprawy złączy. W pracy zaprezentowano wyniki badań przeprowadzonych na próbkach kontrolnych, w których w rzeczywistości nie występują niezgodności spawalnicze, ale powstające wskazania na ekranie defektoskopu mogą świadczyć o występowaniu niezgodności w postaci wady pozornej.

High heat flux testing of ITER ICH&CD antenna beryllium faraday screen bars mock-ups

The Faraday Screen (FS) is the plasma facing component of ITER ion cyclotron heating antennas shielding. The requirement for the high heat exhaust, and the limitation of the temperatures to minimize strain and thus offer sufficient resistance to fatigue, imply the need for high conductivity materials and a high cooling flow rate. The FS bars are constructed by a hipping process involving beryllium tiles, a pure copper layer, a copper chrome zirconium alloy for the cooling channel and a stainless steel backing strip. Two FS bars small scale mock-ups were manufactured and tested under high heat flux. They endured 15,000 heating cycles without degradation under nominal heat flux, and revealed growing flaws when the heat flux was progressively augmented beyond. In this case, the ultrasonic test confirms a strong delamination of the Be tiles.

Effect of a Gap between Elements Being Joined on the Fatigue Service Life of Joints Welded on a Steel Backing Strip

Effect of a Gap between Elements Being Joined on the Fatigue Service Life of Joints Welded on a Steel Backing Strip

Study on fatigue experiment for transverse butt weldsunder 2G and 3G weld positions

Although the transverse butt weld method with ceramic backing strip has been widely used in various industrial fields for its fabricational convenience, it is rarely used in offshore industries since the fatigue strength of the weld joint has not been proved sufficiently. This study conducted fatigue tests for series of butt weld specimens with horizontal (2G) and vertical (3G) welding positions in order to verify the fatigue strength compared to S-N curve by DNV (Det Norske Veritas), IIW (International Institute of Welding) and Eurocode 3. The difference of the 2G specimens and the 3G specimens are investigated in terms of angular distortion and the effect on the fatigue strength are analyzed.

420 粒子法を用いたAl-Cu接合のFSWシミュレーション(OS4-(5),OS4 オーガナイズドセッション≪材料・組織と加工≫)

In FSW, unconjugated material undergoing stirring with heat generated by the rotation of the tool it is difficult to observe the state of plastic flow directly. In this study, it was visualized by particle method simulating the flow properties and the temperature distribution of the material at the time of Al-Cu bonding by the metal during processing is regarded as a highly viscous fluid by using a particle method. Also, when comparing the results with and without cooling due to backing strip, defects and burrs at the bonded compared to none in the case of cooling there will be less revealed. Therefore, potential cooling effect by backing gold is large and involved parameters to joining by FSW have been suggested.

A finite element approach to renew underwater shell plate of a dumb barge sans dry docking: an innovative and cost-effective model

Sagar Shakti, a million litre/day desalination dumb barge belonging to the National Institute of Ocean Technology (NIOT), was damaged on its underwater hull during deployment of a mooring buoy at 1000 m depth. The shell plate had several perceptible wide punctures leading to rapid seepage of sea water into void spaces. Shipyards on the east coast of India expressed inability to renew the shell plate and insisted on dry docking as the only possible way. Owing to financial and time constraints combined with severe monsoon conditions, the barge could not be towed. A suitable water-tight chamber was designed and fabricated to use it as a cofferdam with ceramic back strip welding. Finite element analysis on the water-tight chamber showed that the design was optimum. Welding was done inside the hull; molten metal fills the gap between two plates of butt joint, thereby eliminating external welding. Non-destructive tests including radiography showed the perfection of the weld joint. It was a successful work after which the barge was put into operation to demonstrate a desalination plant. This kind of underwater shell plate renewal without dry docking was done for the first time in India under class approval, thereby saving the huge cost of dry docking, and provided an innovative idea to the industry.

Low‐profile multiband planar hybrid antenna design for mobile handset applications

AbstractA compact size planar microstrip‐fed monopole antenna designed for mobile handset applications is proposed. To operate at global system for mobile communication (GSM)/global positioning system/digital communication system/personal communication system/universal mobile telecommunications system and 2.4‐GHz wireless local‐area network bands, a hybrid technique of joining the horizontal section of a T‐monopole to an open‐loop back coupling strip and loading a pair of monopole slot into the ground plane is used. Two operating bands are observed (along 3:1 VSWR) with the lower band covering only the GSM application, while the wide upper operating band covers the remaining applications. The effects on the antenna performances by tuning the various vital parameters have also been studied. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:910–915, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25889

Back Bead Characteristics during Butt Welding of a Thick Plate for Various Backing Conditions

In a welded structure, thick plates are joined by multi-pass welding in the butt joint. During the first pass of multi-pass welding, burn-through, lack of fusion, and incomplete penetration were readily found as weld defects. Accordingly, the backing condition should be carefully selected in welding of a thick plate, because improper backing conditions lead to weld defects. In the job site, a steel backing strip is usually adopted, although it reduces the fatigue strength. No backing conditions or removable backing is recommended to increase the fatigue strength, but selection of the proper backing and welding conditions is complicated. In this study, several backing methods, such as ceramic backing, water-cooled copper backing, and even the use of no backing, were investigated during GMA (Gas Metal Arc) welding of a thick steel plate. The gas metal arc welding conditions were established for each backing method, and the bead shape and mechanical properties were examined after welding.

Fatigue assessment of welded trapezoidal joints of a very fast ferry subjected to combined load

This work deals with the fatigue assessment of a very fast ferry, describing several steps of the calculation. Considering the analysis of wave and cargo induced loads, the ship’s hull structure is evaluated on both global and local levels. The local structure is represented by a longitudinal stiffener with a trapezoidal transverse section. The critical point of concern is located at the middle of the span between two transverse frames where the longitudinal trapezoidal stiffener is connected by a backing strip plate. A detailed finite element analysis determines the critical hotspots and the stress distributions. The stiffener is considered to be subjected to axial forces due to the ship’s hull girder vertical bending moments and by additional transverse force due to the presence of a truck load. Finally the fatigue damage assessment of the considered hotspot is analyzed accounting for the combination of low- and high-frequency induced loading.

Thermomechanical finite element analysis and experimental investigation of single-pass single-sided submerged arc welding of C—Mn steel plates

Determination of distortions are important while designing the arc-welded joints. These distortions occur in a varied way in almost every type of welded joint, depending on several parameters, i.e. welding speed, plate thickness, welding current and voltage, restraints applied to the job while welding, thermal history, etc. In the present work a numerical model based on the finite element package ANSYS was developed for single-pass single-sided submerged arc welding of square butt joints. Suitable macros were developed to simulate the situation of a moving distributed heat source, metal deposition to account for top and bottom reinforcements, a time step, and a meshing scheme. In this model the effect of bead geometry was incorporated. The effect of filler metal deposition was taken into account by implementing the element birth and death technique. Submerged arc welding (SAW) can be conveniently used to weld a range of plate thicknesses in a single run using a suitable backing strip achieving adequate top and bottom reinforcements. The welding methodology established in the present work resulted in minimizing angular distortions in butt welds. The numerical model yielded results comparing well with those of the experimental ones.