Search Results (584)

Dissimilar steel welding is a necessary means for engineering structures to meet complex service conditions. However, residual stress becomes a challenge for the service properties of dissimilar welded joints (DWJs), as it can reduce fatigue strength and trigger cracking in welded components. Therefore, accurately estimating the distribution of residual stress and efficiently eliminating it is of great importance. This study investigated the evolution of residual stress during the welding process of two commonly used ferritic steels through experimental and numerical analyses. The results show that different thermal cycle behaviors between DWJs have a significant impact on the formation of residual stress. Longitudinal tensile residual stress is predominant in the weld and heat-affected zone (HAZ), with higher longitudinal tensile and compressive stresses in the Q390 side than in the Q690 side, while the maximum transverse tensile stress occurs in the HAZ of the Q690 side. Hammer peening shows excellent ability to eliminate residual stress after welding, with a maximum elimination rate of approximately 62%, and converts the stress state from tensile to compressive at a certain welding depth. The analysis of process parameters reveals that peening velocity is the most influential factor. Under the present experimental configuration, the peening velocity should be set between 4.5 m/s and 5.5 m/s. Full article

Direct fusion welding of aluminum (Al) to magnesium (Mg) results in the formation of brittle intermetallic compounds (IMCs) that significantly restrict the application of these joints in structural applications. In this study, cold spray, a promising solid-state coating deposition technology, was employed to introduce a nickel (Ni) interlayer to facilitate joining of Al to Mg sheets by means of resistance spot welding (RSW). The ability of cold spraying to deposit metallic powder on the substrate without melting proves beneficial in mitigating the formation of the Al-Mg IMCs. The Ni-coated coupons were subsequently welded via resistance spot welding at optimized parameters: 27 kA for 15 cycles in two pulses with a 5-cycle inter-pulse delay. Scanning electron microscopy confirmed metallurgical bonding between the Al, Mg, and Ni coatings in the fusion zone. It is shown that the bonding between the three elements inhibits the formation of deleterious IMCs. Tensile shear testing showed joint strength exceeding 4.2 kN, highlighting the potential of the proposed cold spray RSW approach for dissimilar joining in structural applications. Full article

The use of weld bond (WB) joints in automotive manufacturing is gaining popularity for joining similar and dissimilar materials. This study investigated the effect of Sikaflex-252 (Sika Australia Pty Ltd, Perth, Australia) adhesive in DP600 similar steel joints and DP600 and AISI 316 stainless steel dissimilar steel joints. An increase in welding current from 7 kA to 10 kA increased the weld diameter and tensile shear strength in the RSW joints and the WB joints. WB joints had bigger weld diameters of 5.39 mm and 4.84 mm, higher tensile shear strengths of 12.3 kN and 6.85 kN, and higher energy absorption before failure of 32.6 J and 24.6 J at 10 kA compared to joints at 7 kA for similar and dissimilar joints, respectively. The use of adhesive increased heat generation at 10 kA welding current, due to the increase in dynamic resistance. At 7 kA welding current, the adhesive could not produce sufficient heat for spot weld development. The use of adhesive narrowed the weldability lobe in dissimilar RSW and WB joints and showed changes in failure mode. In similar RSW joints and WB joints, weldability lobe changes were not observed, and RSW and WB joints had the same fracture mode for the same welding current. WB welds have reduced stress distribution across the weld nugget compared to RSW welds because of the bigger weld diameter of 5.39 mm and lesser sheet bending of 1.13 mm. WB joint failure comprises the adhesive failure at the start and later the spot weld failure, while RSW joint failure is purely due to spot weld failure. Full article

Stainless steel welding plays a critical role in industrial manufacturing due to its superior corrosion resistance and structural reliability. The keyhole tungsten inert gas (K-TIG) welding, renowned for its high efficiency, high precision, and cost-effectiveness, demonstrates particular advantages in medium-to-thick plate joining. In order to synergistically leverage the properties of 2205 duplex stainless steel (DSS) and 316L austenitic stainless steel (ASS), we have implemented K-TIG welding with a single variable under control: a constant current and voltage travelling speeds spanning 280–360 mm/min. Defect-free dissimilar joints were consistently achieved within the 280–320 mm/min speed window. The effects of welding speed on microstructural characteristics, mechanical properties, and corrosion behavior of the weld seams were systematically investigated. The percentage of austenite in the weld zone decreases from 84.7% to 59.9% as the welding speed increases. At a welding speed of 280 mm/min, the microstructural features in the regions near the weld seam and fusion zone were investigated. All obtained joints exhibited excellent tensile properties, with their tensile strengths surpassing those of the 316L base metal. The optimal impact toughness of 142 J was achieved at a welding speed of 320 mm/min. The obtained joints exceeded the hardness of TIG joints by 19%. Notably, the grain refinement in the weld zone not only enhanced the hardness of the welded joint but also improved its corrosion resistance. This study provides valuable process references in dissimilar stainless steel K-TIG welding applications. Full article

The growing use of composites in automotive and aerospace fields highlights the need for effective joining of dissimilar materials. Adhesive bonding offers significant advantages over traditional methods. Therefore, comprehensively exploring the relationship between multiple design variables and joint strength, and subsequently achieving accurate prediction of joint strength based on this understanding, is essential for enhancing the effectiveness and efficiency of adhesive joint structural optimization. However, the joint—the critical yet weakest part—has strength governed by complex structural variables that are not fully understood, limiting optimization potential. Based on the effectiveness of finite element simulation in tensile fracture mechanics, this study developed a deep neural network (DNN). Combining the DNN model with a genetic algorithm (GA), both single-objective and multi-objective optimization were conducted. The single-objective optimization focused solely on maximizing joint strength, while the multi-objective GA further quantified the Pareto optimal trade-offs between joint strength and bond area, identifying compromise solutions. The effectiveness of the optimized parameters was validated, demonstrating higher efficiency and accuracy compared to traditional optimization methods such as response surface methodology (RSM). This integrated approach provides a robust framework for predicting joint strength and achieving effective optimization of bonded structures. Full article

Aluminium alloys are known for their high strength-to-weight-ratio offering a wide range of applications in the aerospace and automotive industries. However, challenges exist like porosity, oxidation, solidification shrinkage, hot cracking, etc., in joining aluminium alloys. To address these challenges, there is a necessity to understand the process parameters for the welding/joining of aluminium alloys. The present study aims to investigate the effect of cold metal transfer (CMT) welding process parameters (i.e., welding speed and wire feed rate) on mechanical properties for dissimilar AA6061-AA6082 alloys weld joints. Two different welding conditions viz. CMT1 (speed: 0.5 m/min with feed: 5 m/min) and CMT2 (speed: 0.3 m/min with feed: 3 m/min), were considered. The weldments were deployed for testing different mechanical properties such as tensile, impact, hardness, corrosion tests and bead profile geometries. The results reveal that CMT1 has better mechanical properties (tensile_233 MPa; impact_8 J; corrosion rate_0.01368 mm/year) than CMT2, showing the welding speed and wire feed rate play a significant role in the joint performance. The heat affected zone and fusion zone are narrow for CMT1 when compared with CMT2. The present study provides insights into the CMT process and dissimilar joining of aluminium alloys that might be helpful for additive manufacturing of dissimilar aluminium alloys as future research directions. Full article

The object of this study is welded joints of AISI 321 and Ti-6Al-4V, obtained by diffusion welding on developed conical surfaces. The problem of creating bimetallic joints of AISI 321 and Ti-6Al-4V with developed conical contact surfaces, using diffusion welding through an intermediate Electrolytic Tough Pitch Copper (Cu-ETP) copper layer, was solved. The joints were studied using micro-X-ray spectral analysis, microstructural analysis, and mechanical tests. High mutual diffusion of copper and titanium, along with increased concentrations of Cr and V in copper, was detected. The shear strength of the obtained welded joints is 250 MPa and 235 MPa at 30 min and 15 min, respectively, which is higher than the copper layer’s strength (180 MPa). The obtained results are explained by the dislocation diffusion mechanism in the volume of grains and beyond, due to thermal deformations during welding. Under operating conditions of internal pressure and cryogenic temperatures, the strength of the connection is ensured by the entire two-layer structure, and tightness is ensured by a vacuum-tight diffusion connection. The obtained strength of the connection (250 MPa) is sufficient under the specified operating conditions. Analysis of existing solutions in the literature review indicates that industrial application of technology for manufacturing bimetallic adapters from AISI 321 stainless steel and Ti-6Al-4V titanium alloy is limited to butt joints with small geometric dimensions. Studies of the transition zone structure and diffusion processes in bimetallic joints with developed conical contact surfaces enabled determination of factors affecting joint structure and diffusion coefficients. The obtained bimetallic adapters, made of Ti-6Al-4V titanium alloy and AISI 321 stainless steel, can be used to connect titanium high-pressure vessels with stainless steel pipelines. Full article

Pore defects are one of the most common defects in the aluminum alloy electron beam welding process. In this paper, research on the pore defects and related mechanisms of the electron beam welding of dissimilar aluminum alloys was carried out with 1060 and 2A12 aluminum alloys. Under the test conditions, the pore defects of the aluminum alloy joint were related to the penetration status, the porosity of the critically penetrated joint was low, and the porosity of the beam joint increased when it was slightly penetrated. When the welding speed changed from 300 mm/min to 1200 mm/min, the porosity in the critically penetrated joint first increased and then decreased. When the welding speed was set to 300 mm/min and the beam current was set to 26 mA, the porosity of the joints reached its minimum value at 0.23%. Based on the actual process of electron beam welding, a flow simulation model was established to study the aluminum alloy welding process. The stability of the keyhole was related to the electron beam energy density reaching the inner keyhole, so increasing the electron beam for the fully penetrated joints was advantageous for reducing the pore defects. Full article

This study develops an optimized femtosecond laser welding process for joining quartz glass and TC4 titanium alloy (Ti-6Al-4V) under non-optical contact conditions, specifically addressing the manufacturing needs of specialized photoelectric effect research containers. The joint primarily consists of parallel laser-welded zones (WZ) interspersed with base material. The defocus distance of the femtosecond laser predominantly influences the depth and phase composition of the WZ, while the weld spacing influences the crack distribution in the joint region. The maximum shear strength of 14.4 MPa was achieved at a defocusing distance of +0.1 mm (below the interface) and a weld spacing of 40 μm. The XRD stress measurements indicate that the defocusing distance mainly affects the stress along the direction of laser impact (DLI), whereas the weld spacing primarily influences the stress along the direction of spacing (DS). GPA results demonstrate that when the spacing is less than 30 μm, the non-uniform shrinkage inside the WZ induces tensile stress in the joint, leading to significant fluctuations in DS residual stress and consequently affecting the joint’s shear strength. This study investigates the effects of process parameters on the mechanical properties of dissimilar joints and, for the first time, analyzes the relationship between joint residual strain and femtosecond laser weld spacing, providing valuable insights for optimizing femtosecond laser welding processes. Full article

An ultra-high-strength press-hardening steel (PHS) and a high-strength dual-phase steel (DP) were butt-joined by the gas metal arc welding (GMAW) process, aiming to assess the effects of a high heat input welding process on the structure-property relationship and residual stress. The post-weld microstructure, the microhardness profile, the tensile behavior, and the experimentally obtained residual stresses (by x-ray diffraction) of the steels in dissimilar (PHS-DP) and similar (PHS-PHS, DP-DP) pair combinations have been analyzed. Results indicated that the ultimate tensile strength (UTS) of the dissimilar pair PHS-DP achieves a similar strength to the DP-DP joint, whereas the elongation was similar to that of the PHS-PHS weldment. The failure location of the tensile specimens was expected and systematically observed at the tempered and softer sub-critical heat-affected zone (SC-HAZ) in all welded conditions. Compressive residual stresses were consistently observed along the weldments in all specimens; the more accentuated negative RS were measured in the PHS joint attributed to the higher volume fraction of martensite; furthermore, the negative RS measured in the fusion zone (FZ) could be well correlated to weld restraint due to the sheet anchoring during the welding procedure, despite the presence of predominant ferrite and pearlite microstructures. Full article

Conventional adhesively bonded joints, such as single-lap, curved-lap, wavy-lap, double-lap, stepped-lap, and scarf joints, are widely used for aerospace, automotive, and medical applications. These adhesively bonded joints exhibit different load transfer mechanisms and stress distributions within adhesive layers, which depend primarily on their geometries and mechanical properties of bonded materials. As such, joint geometry and material properties play a critical role in determining the capability of the joints to withstand high loads, resist fatigue, and absorb energy under impact loading. This paper investigates the effects of geometry and material dissimilarity on the performance of both conventional bonded and interlocking joints under tensile loading based on the information available in the literature. In addition, bonding and load transfer mechanisms were analysed in detail. It was found that stress concentration often occurs at free edges of the adhesive layer due to geometric discontinuities, while most of the load is carried by these regions rather than its centre. Sharp corners further intensify resulting stresses, thereby increasing the risk of joint failure. Adhesives typically resist shear loads better than peel loads, and stiffness mismatches between adherents induce an asymmetric stress distribution. Nonetheless, similar materials promote symmetric load sharing. Among conventional joints, scarf joints provide the most uniform load distribution. In interlocking joints such as dovetail, T-slot, gooseneck, and elliptical types, the outward bending of the female component under tension can lead to mechanical failure. Full article

The future of the automotive industry appears to hinge on the integration of dissimilar materials, such as aluminum alloys and carbon steel. However, this combination can lead to galvanic corrosion, compromising the structural integrity. In this study, laser-welded joints of 6013-T4 aluminum alloy and DP980 steel were evaluated for their morphology, microhardness, and corrosion resistance. Corrosion resistance was assessed using the electrochemical noise technique over time in 0.1 M Na₂SO₄ and 3.5% NaCl solutions. The wavelet function was applied to remove the DC trend, and energy diagrams were generated to identify the type of corrosive process occurring on the electrodes. Corrosion on the electrodes was also monitored using photomicrographic images. Analysis revealed an aluminum–steel mixture in the melting zone, along with the presence of AlFe, AlFe₃, and AlI₃Fe₄ intermetallic compounds. The highest Vickers microhardness was observed in the heat-affected zone, adjacent to the melt zone, where a martensitic microstructure was identified. The 6013-T4 aluminum alloy demonstrated the highest corrosion resistance in both media. Conversely, the electrochemical noise resistance was similar for the DP980 steel and the weld bead, indicating that the laser welding process does not significantly impact this property. The energy diagrams showed that localized pitting corrosion was the predominant form of corrosion. However, generalized and mixed corrosion were also observed, which corroborated the macroscopic analysis of the electrodes. Full article

Monopile foundation is an important foundation form for offshore wind turbines, and the stability of the seabed around it is affected by the combined effects of wave and pile vibration. Based on the Biot consolidation theory and elastoplastic constitutive model, a multi-physical field coupling model of wave–vibration–seabed–monopile is constructed, and the dynamic characteristics of seabed pore pressure around the monopile under the joint action of wave–vibration are systematically investigated, and the influences of waves, vibrations, and seabed parameters on the distribution of pore pressure amplitude are analysed in depth. The results show that the increase in wave incident energy will increase the seabed wave pressure, and the suction and pressure generated by pile vibration will change the soil force state; the coupling of waves and vibrations results in pile displacement difference, causing the seabed pore pressure dissipation depth dissimilarity, and the peak relative amplitude of pore pressure and the peak of vibration displacement are in a linear relationship; the wave parameters and seabed characteristics have a significant effect on the change in pore pressure amplitude distribution. Full article

Friction stir welding (FSW) is a novel welding technique that produces a solid-state weld by generating frictional heat and plastic deformation at the weld spot with a revolving, non-consumable welding tool. Despite processing a wide range of industrial materials, FSW has concentrated on welding aluminum and its alloys because of its high strength-to-weight ratio and uses in the shipbuilding, aerospace, and other fabrication industries. Important FSW process factors that determine the mechanical qualities of the weldment are the tool tilt angle, tool traverse feed, tool pin profile, tool rotational speed (TRS), tool traverse speed (TTS), tool pin profile (TPP), and shoulder plunge depth. Variations in the required process parameters cause defects, which lower the weld quality of FSWed aluminum alloys (AA). Therefore, keeping an eye on and managing the FSW process is crucial to preserving the caliber of the weld joints. The current study aims to investigate the changes in the mechanical characteristics and microstructure of the FSWed AA5052-H111 and AA6061-T6 joints. To perform the FSW experiments, we varied TRS, TTS, and TPP on plates that were 5 mm thick and had a butt joint structure. Following welding, the microstructure of the weld zones was examined to observe how the grains had changed. The joint’s tensile strength reached a maximum of 227 MPa for the square-shaped TPP, and the micro-Vickers hardness test results showed a maximum of 102 HV at the weld nugget zone (WNZ). Full article

This paper delves incto the tungsten inert gas (TIG) welding process, renowned for its efficacy in creating robust metal joints and widely employed in diverse industries for fusing similar or dissimilar materials. The focus of this study is the welding of mild steel with stainless steel, showcasing the method’s ability to amalgamate exceptionally sturdy metals and alloys. The resultant welded joints exhibit a meticulously refined microstructure and an impressive strength-to-weight ratio. The primary aim is to scrutinize TIG-welded joints, specifically those connecting mild steel with stainless steel, to elucidate their metallurgical and mechanical attributes. Notably, joints formed between distinct materials, such as mild steel and stainless steel, manifest commendable mechanical and metallurgical properties. This paper extensively investigates the metallurgical microstructures and tensile characteristics of both comparable and dissimilar metal junctions, contributing valuable insights to the field. Full article