Welding Pattern Research Articles

Analysis of fuel storage tanks under internal deflagrations with different venting technologies: an experimental and numerical study

This study investigates small-scale fuel storage tanks subjected to internal methane-air explosions, focusing on three depressurization technologies using roof ventilation to mitigate overpressure and damage. Tests with low methane-air concentrations were conducted to generate a pseudo-static internal pressure. This approach minimized scale effects and aligned internal pressure frequency with real-scale tank behavior during deflagrations. The first prototype features a tank with a frangible roof activated by localized brittle failure of stitch welds around the roof-to-shell junction. This confirms that stitched weld patterns ensure controlled brittle failure with activation pressure estimated by a simplified equation. The second technology employs a sequential ventilation strategy, starting with a small hinged panel followed by stitch weld failure, managing low to medium-intensity explosions with the small vent alone, and allowing rapid operational recovery. In severe explosions, the hinged door facilitates earlier activation of the frangible roof, reducing the initial pressure rise rate and controlling the roof opening direction. Lastly, the study explores tanks with commercial explosion vent panels as an alternative to traditional frangible roofs, offering a practical solution for retrofitting existing tanks. Each technology enhances safety in fuel storage facilities by effectively managing internal pressures during explosive events.

Investigation on structural feature and bonding performance of Hastelloy foil/steel explosive welding composites under different explosive loads

Hastelloy foil/steel composite is of most interest in many industrial fields, as it has competitive advantages of excellent corrosion resistance and low cost. Due to the low thermal conductivity and thermal hardening property, traditional fusion-based connection methods fail to provide high-quality Hastelloy/steel composites. Here an improved explosive welding was introduced to prepare this composite, and the effect of the explosive amount was carefully investigated. The characterizations (including optical microscopy (OM), electron backscatter diffraction (EBSD), bending, nanoindentation, and electrochemical corrosion) were conducted to understand the bonding properties, and Smoothed Particle Hydrodynamics (SPH) simulation was used to investigate transient interface behavior. It was found that the self-developed explosive welding was a suitable method to produce superior Hastelloy/steel composites. Under reasonable welding parameters, both the surfaces of Hastelloy and Hastelloy/steel interface exhibited ideal welding patterns without defects, and the composite remained intact under 90° bending loading. The explosive load is a crucial factor determining bonding properties, and the undesirable features like wrinkles and melting area were found to be positively correlated with the explosive load, which reduced the corrosion resistance. This comprehensive research enabled to provide a new perspective for Hastelloy/steel preparation and improve the understanding of explosive welding process behavior.

Determination of beam oscillating pattern for tailoring melt flow and microstructural characteristics of laser welded Ti–6Al–4V alloy

The trajectory of beam is highly correlated to the heat distribution and fluid flow within the melting pool in laser welding, which has a great impact on improving the joint microstructure. This study employs fluid simulation techniques to investigate the temperature distribution and flow behavior of Ti–6Al–4V alloy under three laser oscillation welding patterns including none oscillation, sinusoidal oscillation, and circular oscillation, and the optimal oscillating pattern was determined through an analysis of microstructure characteristics. Temperature field simulation results indicate that the oscillation of the beam is efficaciously utilized to diminish the concentrated heat distribution on the base material. Moreover, a manifest difference in energy density and the area of laser action is produced, which leads to variations in the location and depth of the distribution of keyholes. Under circular oscillation, the flow behavior is more pronounced, with peak flow velocity increasing by approximately 80 % compared to none oscillation and new vortices were created in the horizontal section at the end of an oscillation period. Furthermore, compared to none oscillation and sinusoidal oscillation, the lower cooling rate under circular oscillating pattern contributes to the formation of equiaxed grains. The fine equiaxed grains are easy to move and form an ordered lattice structure, which favors the transformation of low-angle grain boundaries and the increase in the strength of the crystal texture. Therefore, with oscillation frequency and amplitude set at 80 Hz and 0.8 mm, respectively, the use of circular oscillating pattern in laser welding results in an improvement in weld seam microstructure.

Analisa Kekuatan Mekanik Sambungan Las Menggunakan Pola Ayunan Melingkar Dan Zig-Zag Pada Baja Karbon Sedang

Welding is one of the metal joining techniques by melting some of the parent metal and filler metal which is currently widely used with different methods and movements of welding electrodes. These methods aim to obtain flat and smooth welds and at the same time become the impetus for the compilers to conduct research entitled "analysis of the mechanical strength of welded joints using circular and zig-zag swing patterns on medium carbon steel" with the aim of knowing the effect of welding patterns on hardness test on medium carbon steel material and the effect of microstructure welding pattern on medium carbon steel material. This research was conducted in August 2020, at the Mechanical Engineering Materials and Technology Laboratory, Department of Mechanical Engineering, Faculty of Engineering, Halu Oleo University Kendari. The tools used are welding machines, grinding machines, welding goggles, pliers, masks and gloves while the materials are 0.5 cm carbon steel plate, welding electrodes, grinding wheels. The results of the first research are that for welding using a circular electrode movement pattern which shows a softer or more ductile result, while for a harder or brittle result, it is shown in the zigzag electrode movement welding process and secondly that the circular electrode movement in the welding process has an impact on the microstructure. in the HAZ area which is getting darker because the structure formed is dominated by pearlite, while in welding the zigzag electrode movement has an impact on the HAZ area which is getting brighter because it is dominated by the bainite structureKeywords: Circular Welding Pattern, Mechanical Strength, Medium Carbon Steel, Zigzag Welding Pattern,

Weld crack detection and quantification using laser thermography, mask R-CNN, and CycleGAN

Steel members are susceptible to cracking, and a number of non-destructive testing (NDT) techniques are used for crack detection. However, these NDT techniques are not only labor intensive but also time consuming. In particular, inspection of welded areas requires surface treatment, and data must be interpreted by experienced engineers to differentiate cracks from weld patterns. In this study, an automated weld crack detection and quantification system was developed by integrating laser thermography, Mask R-CNN, and CycleGAN. The developed system comprises a laser heat source, an IR camera, and a control unit. The laser applied heating to the target surface, and the resulting thermal radiation emitted from the surface was measured using an IR camera. Subsequently, the thermal images were processed for crack detection using Mask R-CNN, and for crack quantification using medial axis transform. The detection and quantification performance of the developed system were validated through laboratory and field tests.

Effect of Swing-Spiral-Trajectory on pulsed fiber laser welding stainless steel/Copper dissimilar metals

The dissimilar metal combinations of SUS303 stainless steel and C19210 pure copper with a thickness of 0.2 mm by utilizing a nanosecond pulsed fiber laser was performed in lap welding with swing-spiral-trajectory. The weld effect was evaluated by means of microstructural and mechanical examinations. The influence of pulse frequency, speed and swing frequency as well as pulse waveform on mechanical properties and microstructure was clarified. The metallurgical behavior and weld penetration inside the fusion zone were observed with microscopic inspection of the welded joints and the welded surface. Part of molten pool materials inserted into copper plate formed an intertwined nails for enhancing the interfacial bonding strength was observed in the cross-section of the weldment. Additionally, the presence of a thin intertwined transition layer with solid solutions accomplished by the copper and liquid stainless steel mutual diffusion at the fusion line, indicated that the swing spiral welding pattern can strengthen the interface fusion. Some defects, such as porosities and microcracks, were also found in the welded joints. They were mainly due to the significantly different linear expansion coefficients of copper and steel. Energy dispersive spectroscopy (EDS) analysis confirmed that the interdiffusion and dissolution of copper and stainless steel occurred inside the molten pool, and the surface composition of the weld pool was dominated by iron. The microhardness (MH) study showed that the heat-affected zone (HAZ) was harder than the fusion zone on the stainless steel side, and the fusion interface microhardness much variation indicated microstructural change alongside the weld interface. The tensile test results revealed that the fracture location was in the molten pool on the stainless steel side, the fracture was protruded and the fracture mode was intergranular brittle fracture.

A mesoscale approach to simulate residual deformations in complex laser welding processes

Laser welding can be characterized by very small radii of beam, in the order of tenths of a millimeter, and very short high power inputs (more kW in few ms), and thus, it can be certainly classified as a microscale process with a high level of physical complexity. This is clearly incompatible, due to the high computational costs, with the analysis of macroscale processes related to large geometries and non-uniform welding patterns. In order to overcome this issue, a simplified finite element method (FEM)–based thermo-elastoplastic model is presented to simulate heat transfer and residual deformations due to thermal expansion and material plasticity. The idea is to substitute the microscale analysis with a mesoscale approach that renounces to describe in detail all the physical phenomena occurring in the heated zone and focuses attention on the correct prediction of the keyhole depth and weld pool size, that are the most important parameters to describe the mechanical characteristics of the welded joint. The concept of passive element, based on the numerical adjustment of the material properties in order to take into account the orthotropic behavior during the keyhole formation, is introduced. In particular, the new approach has been tested on the pulsed laser welding process of two overlapping DC04 steel plates with thickness of 0.5 mm (so-called sandwich) and validated through experimental tests involving different input parameters, such as power, pulse duration and frequency, speed, and geometrical pattern.

Material Flow Behavior in Dissimilar Friction Stir Welds of AA2024 and AA5086 Aluminum Alloys

This research aims to investigate the material flow behaviour and microstructure evolution in friction stir welded joints of dissimilar aluminium alloys AA2024/AA5086. AA2024 plate was placed on re- treating side; welded using threaded conical flat shoulder tool rotating at 635 rpm and moving along the joint line with a speed of 75mm/min. Mixing of both the material was clearly visible in stir zone and resulted in features typical to dissimilar friction stir welding and solid state flow patterns beside different zones. Onion rings, laminar flow, vertex flow was main flow features observed in the stir zone. Non- uniform mixing of different chemical composition base material is behind the formation of these flow features and inclusive chemical mixing may abolish solid state flow features.

Behavior of steel I-beams reinforced while under load

Steel I-beams often require reinforcing while they are under load. A common method for strengthening steel beams is by welding steel cover plates to the bottom flanges of the existing members. Very limited research has been conducted on the behavior of I-beams reinforced under load. This paper presents a finite element (FE) based study on steel I-beams welded with steel cover plates while under load. A series of simply supported steel I-beams reinforced with cover plates welded at the bottom flanges are analysed. FE analysis shows that with increased preload, the capacity of the I-beam reinforced under load reduces when the failure mode of the beam is lateral-torsional buckling (LTB). On the other hand, the variation of the preload has an insignificant effect on the behavior and ultimate strength of the reinforced beam when the reinforced beam fails in flexural yielding. Also, effects of different parameters, such as residual stress patterns in the I-beam and cover plate, welding residual stress, type of welding patterns, the difference in steel grades between I-beam and reinforcing plate, on the behavior of the steel I-beams reinforced while under load are investigated numerically. Finally, the flexural capacities of reinforced I-beams with welded cover plates obtained from FE analyses are compared with the capacities predicted by the American (AISC 360-16) and Canadian (CAN/CSA-S16-19) steel design standards. FE analysis shows that AISC 360-16, when the effect of loading height is considered, can reasonably predict the capacity of I-beam reinforced with welded cover plate at the bottom flange.

Experimental study on bond strength failure of GFRP lap joints

Bonding has many advantages such as high adhesive strength, peel resistance, good toughness, shrinkage and corrosion-resistance, compared with bolting, welding and other connection patterns, which is the basic connection of the composite materials. The mechanical properties of the bond depend on the type and geometric parameters of the bond. In this paper, experiments were conducted to study the bond strength failure of GFRP single and double lap joints and explore related influencing factors. The variable factors of test specimens include bond type, length and thickness. The quasi-static tensile test was carried out at room temperature to analyze multiple influencing factors of lap joints and characteristic of GFRP bond failure strength. The results showed that the failure of the bond usually occurred at the interface of bond, and bond types, length and thickness have significant effects on the failure of bond. Failure strength increased firstly and then decreased with the increase of adhesive thickness. With the increase of bonding length, the failure mode of the double-lap joint become complex failure mode, which is accompanied by GFRP delamination near the surface of fiber of the bonding.

Effect of Beam Oscillation Patterns on the Electrochemical Corrosion Behavior of Electron Beam Welded Ti-5Al-2.5Sn Alloy in Simulated Marine Environment

Ti-5Al-2.5Sn alloy plates of 1.6 mm thickness were EB welded using four weld patterns (rectangular, elliptical, concentric circles and arrow). The fusion zone of all the patterns with variable amount had α´ martensite and acicular α with prior β at grain boundaries which resultantly affected the corrosion resistance. Several electrochemical techniques indicated that the elliptical pattern showed better passivation and film stability as compared to other patterns. The arrow pattern experienced more pitting due to the higher proportion of α´ martensite in its FZ. The EIS data indicated that the elliptical pattern had a stable uniform layer formation on the surface with low passivation resistance. In case of BM, uniform passivation layer of oxides was formed, without any sensitization.

Optimization of the tensile-shear strength of laser-welded lap joints of ultra-high strength abrasion resistance steel

The tensile-shear strength of laser-welded lap joints developed in abrasion resistance ultra-high strength ARS-600 steel was optimized by evaluating the joints achieved with different welding parameters and various configurations of weld patterns, including multiple continuous longitudinal and transverse weldments. The microstructural evolution of the fusion zone was characterized by electron backscatter diffraction (EBSD) after welding with different values of energy input (60–320 J/mm). Furthermore, in order to better comprehend the shear response of different weld patterns, stress analysis of various longitudinal and transverse lap joints was conducted by the finite element method (FEM).

Study on defects repairing using Friction Stir technologies

Abstract Defects are usual in most of the manufacturing processes, including in welding. But the welding defects are described as abnormalities that occur in the given weld metal due to improper welding patterns or incorrect welding, etc. Each inappropriate divergence from technological and design specifications concerning welding is known as welding defects. Mainly, welding defects are resulted due to the inappropriate weld parameters along with the wrong electrode, improper job preparation, and inaccurate process condition, etc. Friction Stir (FS) technologies have gained significant consideration to address these issues as Friction Stir Welding (FSW) is one of the most viable methods of joining. This review article focuses on the credibility of the FS technologies in the repairing process and studies the FS technologies effect on microstructural, tensile, hardness, and corrosion properties. The article ends with the conclusions drawn from the literature study.

Analysis of the residual stresses and deformations during the autogenous GTAW process

PurposeThe gas tungsten arc welding (GTAW) process is a widely used process that produces quality weldments. But the high heat generation from the GTAW arc can cause extreme temperatures as high as 20,000°C. The residual stresses and deformations are high accordingly. One of the methods for decreasing residual stresses and deformations is to change the welding pattern. In the literature, there are not so many examples of modeling dealing with welding patterns. This paper aims to investigate the influence of welding patterns on the deformations.Design/methodology/approachIn this work, back-stepping patterns and partitioning of the weld line were investigated and the distortions and residual stresses were calculated. By doing this, temperature-dependent thermophysical and thermo-mechanical material properties were used. The temperature distribution and deformation from experiments with the same welding conditions were used for validation purposes.FindingsSeven different welding patterns were analyzed. There is only one pattern with a single partition. There are three patterns investigated for both two and three partitioned weldings. The minimum deformation and the optimum residual stress combination is obtained for the last pattern, which is a three partitioned and diverging pattern.Originality/valueThe most important aspect of this paper is that it deals with welding patterns, which is not much studied beforehand. The other important thing is that the structural part and the thermal part of the simulation were coupled mutually and validated according to experiments.

Effect of welding pattern during repair and maintenance of Francis runner on sediment erosion: An experimental investigation using RDA

In Nepal, sediment erosion is a major cause of hydro-turbine failure. Every year turbine parts expose to water got eroded and failed ultimately resulting in loss of efficiency as well as increase in the repair cost. For repair of these eroded surfaces welding is quit famous in Nepal due to low cost to build up the eroded surface however specific welding pattern on the eroded surfaces has not been used which results low strength in repaired equipment. In this paper, the study of the relation of the welding pattern on the erosion rate had carried out taking the Francis turbine blade of Dhamile Khola (14 kW) as reference. Experimental analysis was adopted for studying the effect of welding pattern on erosion rate through laboratory tests. Four different welding patterns on four different specimens were developed and accelerated tests were carried out in the Rotating Disc Apparatus (RDA) at Turbine Testing Lab (TTL), Kathmandu University. Furthermore, erosion pattern on forged blades were compared with the CFD analysis carried out on same blade which is similar. After an operation time of 1050 minutes, the extent of wear was found significantly less in the test specimen with right inclined welding pattern taking material loss as a basis for comparison. The aim of this paper is to provide a specific welding pattern with relatively less erosion rate during the repair and maintenance of the sediment eroded surface of the runners.

Influence of electron beam oscillation patterns on the microstructure, texture, residual stress and mechanical properties of Ti-5Al-2.5Sn alloy weldments

Vacuum electron beam welding is widely employed for the welding of titanium alloys using different beam oscillation patterns. Since these patterns influence the physical phenomenon in the weld pool, its effect on the microstructure, texture, mechanical properties and residual stresses is of prime interest. In order to understand this influence, electron beam welding was used to prepare Ti-5Al-2.5Sn weldments using beam oscillations of triangular and rectangular waveform. It was observed that a change of welding pattern had a strong influence on the residual stresses, impact properties and texture of weld zone while tensile properties were not significantly affected. A partial martensitic transformation was observed in both the triangular and rectangular waveform of oscillations. An increase in alpha lathe width was observed in the fusion zone and similar strength of the rectangular pattern as compared to triangular pattern. Despite of this, the observed higher Vickers hardness of the fusion zone of rectangular pattern as compared to triangular and no-oscillation was attributed to texture strengthening using rectangular waveform.

Microstructure, mechanical properties, residual stresses and texture analysis of Ti-5Al-2.5Sn alloy weldments obtained using electron beam of different oscillation patterns

Electron beam welding was used for welding of Ti-5Al-2.5Sn alloy using three types of beam oscillation patterns, i.e. elliptical, concentric circles and arrow shape waveform. The influence of these patterns on microstructure, mechanical properties and residual stresses was investigated using optical microscopy, electron back scattered diffraction, scanning electron microscopy, microhardness measurement, residual stress measurement, impact testing, smooth and notch tensile testing. A partial martensitic transformation was observed in the fusion zone of all the three welding patterns. The fusion zone of arrow pattern weldment exhibited approximately 16% and 1.2% higher hardness than elliptical and concentric circles patterns, respectively. Owing to an improved texture of the basal and prismatic planes in the cross-weld direction, the arrow pattern showed improved strength, reduced tensile residual stresses than elliptical and concentric circles pattern. Elliptical pattern showed superior elongation characteristics as well as increased impact strength as compared to the arrow and concentric circle patterns.

SELECTION OF WELDING CONDITIONS FOR MINIMIZING THE RESIDUAL STRESSES AND DEFORMATIONS DURING HARD-FACING OF MILD STEEL

Hard-facing process is widely used for improving the wear resistance of mild steel. During the application of hard-facing, due to high temperatures, residual stresses and deformations may occur. The tensile residual stresses may cause crack propagation on the hard-faced part. The purpose of this study is to utilise minimum computer work for minimizing these residual stresses and deformations during the hard-facing of mild steel. The fully coupled transient heat transfer and structural analysis was performed for calculations. The double-ellipsoidal moving heat source was utilised to simulate the heat input from the gas metal arc welding (GMAW). Only eight numerical simulations were performed to minimize the computer work; the grey relational analysis was used for minimizing both the residual stresses and deformations. Welding speed, welding current, and welding pattern were considered as changing parameters. At the end of the numerical and statistical solutions, it is observed that heat input should be kept minimum to minimize the stresses and deformations. But it is obvious that the heat input must provide a temperature greater than the melding point. Straight patterns always produce better results for minimizing stresses and deformations. Transverse stress at the beginning and end of the longitudinal path gets higher significantly after cooling. Cooling does not affect the total deformation.

Seismic Performance of Precast Concrete Columns with Improved U-type Reinforcement Ferrule Connections

This paper proposes a new kind of U-type reinforcement ferrule (URF) connection for the assembly of precast concrete (PC) components, which has a good fault-tolerance ability and low cost of construction with a simple post-grouting process. The modified connection features welded U ferrules, which can increase the bonding mechanism and internal stress transmission in the spliced region. A series of quasi-static cyclic tests were performed on URF-connected PC columns with different welding patterns. Comprehensive comparisons were performed on the load-bearing capacity, the plastic energy dissipation ability, the internal force transmission, the column ductility and the stiffness. The results indicated that PC columns with welded URF connections can ensure better lateral resistance than the cast-in-place concrete column. The weld type and length influence the connection performance, and the 15d-welded and full-length welded URF connections presented better connection performance and were suggested for the assembly of PC columns. Then, finite element analyses were performed to further reveal the working and failure mechanisms and the affecting mechanism of some working parameters. Parametric simulations indicated that the increase in the axial load ratio and the concrete strength in the postcast region had a slight but limited effect on improving the lateral resistance of the column connection.

Rapid welding technology for polyethylene gas pipes at temperatures below standard

Rapid polyethylene pipes welding technology at temperatures below standard is proposed. This technology consists of preheating, equalization to acceptable temperature, reflow in regulated mode, and cooling under heat insulation layer or in heat-insulating chamber. Additional welding parameters, including heating and temperature equalization duration, heat-insulating layer thickness or heat-insulating chamber dimensions, are calculated from condition of ensuring heat process flow according to welding pattern at acceptable temperature. For mathematical model adequacy to actual heat welding process, it is proposed to consider polyethylene phase transformation heat in temperature range. When solving problem using end-to-end counting method, effective heat capacity coefficient is introduced, which is determined using temperature dependence of polymer material crystallinity degree. Crystallinity degree in welding process is determined by differential scanning calorimeter. Results of calculating cooling rates for polyethylene pipes electrofusion welding at various temperatures are given. Significant increase of cooling rate in heat-affected zone during welding at low temperatures, at which fine-crystalline structure is formed, which causes weld material plasticity, is shown. It is shown that when welding polyethylene pipes in low ambient temperatures, preheating, temperature equalization and cooling with thermal insulation with calculated parameters lead to thermal process in heat-affected zone according to welding patterns at acceptable temperature.