Papers by Keyword: Welding

Abstract: Heat pumps are rapidly emerging as a crucial solution in the pursuit of decarbonization, offering significant advantages over traditional boilers due to their superior energy efficiency. The outdoor unit of a heat pump consists of around twenty key components, including a complex network of copper pipes and sheets welded to valves, connectors, and other fittings. With over thirty welded joints, there is substantial potential to reduce manufacturing time through process optimization. Copper, known for its excellent thermal and electrical conductivity, is essential in many applications. However, these same properties make welding copper particularly challenging, especially when automating industrial processes. This study explores the ultrasonic welding of copper, aiming to determine the optimal parameters for maximizing the mechanical strength of overlapping sheet joints. The optimal parameters identified for the welding process are as follows: a welding time of 3 seconds, a pressure of 6 bar, a retention time of 0.62 seconds, an initial pressure of 2 bar, a retention pressure of 2 bar, and a rising pressure for the sonotrode of 3 bar.

Abstract: This article provides an overview of Direct Energy Deposition – Arc technology (DED-Arc), also known as Wire Arc Additive Manufacturing (WAAM), which involves the deposition of metal wire using an arc power source and a CNC or robotic manipulator. The high deposition rate of WAAM justifies its use for the manufacturing of small to large-size components with lower resolution and less complex geometry. However, the use of wire as feedstock in the WAAM process has certain advantages and disadvantages, which are explained in detail. The WAAM specialties are in-situ alloying and the production of functionally graded materials (FGMs). Various sensors, path planning, process control, and FEM simulation from WAAM are used to reduce material and energy consumption and make the process more sustainable. Post-processing techniques are also discussed as a method of improving the quality of the final product. Finally, the prospects of the WAAM process are presented.

Abstract: Inland waterway shipbuilding plays a pivotal role in facilitating the transportation of goods and passengers in numerous regions worldwide. To meet the ever-evolving demands of efficiency, safety, and sustainability, shipbuilders constantly seek to enhance the quality and performance of their vessels. Welding, a critical component of shipbuilding, has garnered significant attention due to its potential to introduce deformations and residual stresses, which can adversely affect structural integrity and long-term performance. This study presents preliminary research aimed at comprehensively understanding the influence of deformations and residual stresses after the welding process in inland waterway shipbuilding. The preliminary findings of this research highlight the significant influence of welding parameters, material properties, and welding sequences on the magnitude and distribution of deformations and residual stresses in inland waterway shipbuilding. These findings have implications for ship design, fabrication, and inspection procedures. By mitigating deformation and residual stress-related issues, shipbuilders can enhance the structural integrity, safety, and operational efficiency of their vessels.

Abstract: Ti-6Al-4V, renowned for its high strength and corrosion resistance, is a preferred material in aerospace and marine applications for lightweight structures due to its durability in challenging environments. Typically, GTAW welding is used for it’s fabrication. The residual tensile stresses produced after welding are known to worsen the corrosion and mechanical properties of welds. However, these properties can be improved by introducing near surface residual compressive stress by shot peening. When compared to the traditional shot peening treatment, the surface roughness that results from multiple shot peening with varying ball sizes and intensities can be significantly reduced. In the present work, Ti-6Al-4V plates were welded using conventional GTAW technique. Six different combinations of multiple shot peening treatments were applied to the welded specimens. Surface morphology and surface roughness were analysed. Surface residual stresses measurement were performed using by X-ray stress analyzer. Domain size and microstrain were measured using X-ray diffraction technique. Micro-hardness measurements were made along the weld thickness. Corrosion studies were carried out using potentiodynamic polarization test in 3.5% NaCl solution. The SP4 parameter comes out to have the best combination among all the multiple shot peened samples. It results in lowered surface roughness, higher compressive residual stress, better grain refinement, increased surface hardness, and enhanced corrosion resistance.

Abstract: The structural integrity and safety of the vessels depends significantly on the quality of their welded joints, particularly at specific nodes where high-stress concentrations are common. This research leverages computer-aided design, artificial intelligence and materials science advancements to develop an innovative software tool that integrates expert knowledge, and best practices, for inland vessel welding. The proposed expert software system offers several key features, including the visualization of specific ship nodes, their parameters, as well as the residual stresses and strains that are specific to each node. By integrating these functionalities, the software aims to minimize human error, reduce inspection time, and ultimately improve the overall structural reliability of inland vessels.

Abstract: The role of welding in fracture mechanics development is considered from historical point of view. Starting point was analysis of Schenectady ship failure during the II World War, leading to development of linear elastic, as well as elastic-plastic fracture mechanics, soon afterwards. Two case studies are described to illustrate weldment fracture mechanics and structural integrity assessment.

Abstract: Designing and manufacturing a new mold is laborious work and requires well-trained human resources but also considerable material investments. The achizition and implementation the CAD/CAM softwares, three and five-axis machining centers, cutting tools with high performance are necessary to processing a mold. That is why it is frequently used to repair used molds. This repair is done by welding and then manufacturing on machines with numerical control. The present paper presents these stages of corrective maintenance of a mold. Starting from a concrete case, the solutions for remediation of the used mold are presented. The two basic operations in retrofitting, welding and computer-assisted processing on CNC machines are also analyzed.

Abstract: This paper presents a finite element modeling procedure to determine of crack growth behaviour of butt welded joints under the subject of load for mode I. This paper presents a computation procedure to determine the ratio of fatigue crack growth in butt welded plates for mode I fracture mechanics loading conditions. The presence of residual stresses in welded structures can significantly affect the material’s resistance to fatigue under cyclic loading. The presence of tensile residual stresses adversely affects the fatigue crack growth rate increased it. Change of microstructure and hardening material as a result of the welding process also has a negative impact on the growth of the crack. Accurate prediction and reliable assessment of the residual stress are important for the structural integrity and residual life assessment of welded parts design. Although there are several techniques for the determination of residual stresses, the finite element method (FEM) is one of the most convenient and useful. This paper presents a finite element modeling procedure to determine of crack growth behaviour of butt welded joints under tensile load for mode I. Keywords: Welding, Residual stress, Residual life, Crack growth, FEM, Butt welded joint

Abstract: Achieving dependable connections in open construction settings presents challenges or renders the use of stationary machines and equipment complicated, if not impossible. Therefore, there is a particular focus on the requirements for welding processes. Of particular interest is ensuring the strength and reliability of welded joints, especially through processes developed subsequent to the solidification of the weld at the weld zone. The extent of the thermal influence zone is contingent upon the welding conditions and the properties of the metal being welded. Hence, research into the impact of welding conditions on the formation of the structure of the welded zone and the thermal influence zone remains pertinent.

Abstract: The aim of this work was to study the microstructure evolution of simulated heat affected zone in mild steel using thermal cycle simulation and it was compared to the heat affected zone in the real welded joint. The optical microscopy, micro-hardness measurements, X-ray diffraction were used as characterization techniques. The microstructures and mechanical properties of the simulated heat affected zone were also determined. The use of the thermal cycle simulation technique revealed in detail the different microstructures in the heat affected zone (HAZ) of the welded joint. Some similarities were observed between the heat affected zone obtained by the thermal cycle simulation technique and the heat affected zone observed in the real welded joint. The thermal cycle simulation technique revealed more details about the microstructure and mechanical behavior of the heat-affected zone. The HAZ microhardness values were lowest hardness in the welded joint. Moreover, the lowest hardness value is obtained for the HAZ simulated at 850°C.