Journal of Advanced Joining Processes最新文献

The aim of this research is to investigate the effect of different pin geometries, the ratio of shoulder diameter to pin diameter, and advancing speed on the mechanical and microstructural properties of the specimens fabricated from 6061 aluminum sheet by friction stir processing. Cylindrical, frustum and prisms with triangular section (in three sizes), square and hexagonal cross-sections pins were prepared. The diameter of the shoulder was considered 18 and the diameter of the peripheral circle of all the pins was considered 6 mm. Advancing speeds of 14, 20, and 28 mm/min and rotational speed of 1000 rpm were considered. The smallest grain size was obtained using a pin with square cross-section. As the advancing speed increased, the average grain size decreased and its lowest value was observed at the advancing speed of 28 mm/min. In addition, the best mechanical properties were observed in the specimens fabricated by square cross-section pin and frustum pin. As the advancing speed increased, the ultimate strength of all specimens and the yield stress of most specimens increased. The highest hardness was observed in the specimens fabricated by square cross-section pin and the lowest hardness was observed using cylindrical pin. Also, in specimens fabricated by triangular cross-section pins, by decreasing the ratio of the shoulder diameter to the pin diameter, the ultimate strength and hardness increased and the elongation decreased.

Ultrasonic metal welding (USMW) is an industrially widespread joining process. Low heat input and large bonding area qualify USMW for demanding applications such as electrotechnical components. Despite all efforts process and quality fluctuations occur in industrial use. Until now, there is no non-destructive testing method, which makes extensive monitoring of process input variables (work piece characteristics) necessary. USMW is particularly surface-sensitive, but to date no generally valid surface parameters are known for characterizing the weldability of parts and components. Component cleaning before the process is common, but to achieve consistent quality, the cleaning process must be adapted to the condition of the uncleaned component and to the desired surface. In industrial applications, cleaning has so far often been carried out using costly and comparatively environmentally harmful processes based on mechanical and chemical principles. Within this study we investigate prior treatment of copper workpieces for USMW by means of laser beam and compare the results with chemically and mechanically processed samples. Laser treatment of the typically bright copper surfaces (low radiation absorption in the infrared range), remaining organic residues and the new formation of oxide layers pose significant challenges developing a robust process chain. Different laser treatment strategies are compared and evaluated for different initial surface conditions. The influence on the resulting cleaned surface properties, the resulting USMW process and the joint quality thus achieved is experimentally evaluated. An analytical approach to assessing the weldability based on surface properties and surface treatment is derived. The correlation of surface properties of the materials used, the welding process and welding results is possible. The lowest surface roughness and removal of rolling grooves results in the most efficient welding process. The use of laser treatment leads to the desired alignment of different input conditions, which is also represented in the robustness of the welding result. Without adjustment of the welding parameters, the laser treatment used so far results in a reduction of the joint strength.

Laser beam butt welding is often the technique of choice for a wide range of industrial tasks. To achieve high quality welds, manufacturers often rely on heavy and expensive clamping systems to limit the sheet movement during the welding process, which can affect quality. Jiggless welding offers a cost-effective and highly flexible alternative to common clamping systems. In laser butt welding, the process-induced joint gap has to be monitored in order to counteract the effect by means of an active position control of the sheet metal. Various studies have shown that sheet metal displacement can be detected using inductive probes, allowing the prediction of weld quality by ML-based data analysis. The probes are dependent on the sheet metal geometry and are limited in their applicability to complex geometric structures. Camera systems such as long-wave infrared (LWIR) cameras can instead be mounted directly behind the laser to overcome a geometry dependent limitation of the jiggles system. In this study we will propose a deep learning approach that utilizes LWIR camera recordings to predict the remaining welding process to enable an early detection of weld interruptions. Our approach reaches 93.33% accuracy for time-wise prediction of the point of failure during the weld.

Fatigue is an important property from the standpoint of structural reliability. It is very complex because it is affected by several factors. Many studies focus on a specific factor affecting fatigue life; few studies consider multiple factors. This study investigated the factors influencing the fatigue life of linear friction welded (LFWed) low carbon steel SM490A. The LFWed joints were fabricated by varying the applied pressure after oscillation. Joints with higher post oscillation pressure had a longer fatigue life than those with lower applied pressure. The factors affecting fatigue were primarily residual stress, hardness distribution, microstructure, crack propagation path, and local stress concentration. The results showed that for joints with a longer fatigue life, a reduced local stress concentration had a positive effect, whereas the other factors had a negative effect. Thus, it can be concluded that the most effective way to improve the fatigue life of LFWed joints is to reduce the local stress concentration by controlling the weld toe shape. The linear friction welding (LFW) method of changing the weld toe shape by increasing the applied pressure after oscillation can produce excellent joints.

Friction stir welding (FSW) is an innovative joining technology suitable for manufacture of magnesium welded lightweight structures. This paper presents tensile and fatigue crack growth rate (FCGR) behaviors of friction stir AZ31B-H24 magnesium alloy welded joints produced using two different pins, namely cylindrical and square pins at varying tool rotation rates of 910 rpm, 1500 rpm and 2280 rpm. Experiments conducted in this study included microstructural observations, Vickers microhardness measurements, tensile tests, residual stress measurements and FCGR tests. The results showed that increasing tool rotation rate increased ultimate tensile strength (UTS) of the welded joints and the highest values of UTS were achieved at 2280 rpm giving 229.0 MPa for the cylindrical pin and 200.3 MPa for the square pin. In the middle tension M(T) fatigue specimens, FCGR of FSW joint fabricated using the square pin at 2280 rpm was lower in comparison to the weld produced by the cylindrical pin. Subsequently, in single edge crack tension (SECT) specimens, the higher FCGRs were observed as the crack propagated across heat affected zone (HAZ) followed by the crack growth retardation in the weld nugget zone (WNZ). These fatigue crack growth rate behaviors were likely dictated by the weld microstructure and residual stresses.

Corrosion-induced leakage in flanged gasketed joints is a critical issue in various industries, with implications for safety, environmental compliance, and economic sustainability. This review paper examines the mechanisms and factors contributing to corrosion-related failures in these joints, clarifying the diverse range of materials, operating conditions, and gasket types that influence their susceptibility to degradation. The paper investigates the key corrosion processes, such as pitting, crevice, and galvanic corrosion, that can initiate and propagate in the joint's critical areas. It explores the role of environmental factors, including microorganisms, temperature, flow, and chlorination, in accelerating the corrosion process. Additionally, the influence of gasket materials and design on corrosion susceptibility is investigated, highlighting the importance of selecting appropriate materials and sealing technologies. Furthermore, it reviews various corrosion monitoring techniques that can help identify corrosion early, ensuring the integrity and reliability of flanged gasketed joints.

Welding quality is a critical criterion for evaluating welding operations. Traditional evaluation methods suffer from drawbacks such as lack of objectivity, untimeliness, and high costs. Therefore, real-time monitoring and assessment of the weld pool have become the mainstream trend in welding technology. This study introduces a novel method for defining weld pool width boundaries. It utilizes an infrared (IR) camera to capture the weld pool temperature clusters and employs the Sobel operator for convolution to generate the gradient map of the weld pool temperature clusters. Through enhanced processing in the gradient map, the width boundaries of the weld pool are more effectively detected compared to previous methods. Previous studies defined weld pool width boundaries by identifying characteristic points with the most distinct temperature fluctuations, caused by the different radiative properties of the same material in different states. However, practical tests revealed susceptibility to interference from reflected arc light. The proposed method mitigates the impact of reflected arc light and is applicable to complex multilayer welding scenarios. To address the lag in quality monitoring, reduce welding costs, and achieve real-time monitoring of the weld pool process, we employed machine vision and an artificial neural network (ANN) model. This led to the development of a weld penetration assessment system based on infrared thermal images. The system successfully predicted the penetration depth for 4 mm carbon steel with an accuracy of 86.6 %. This validates the feasibility of estimating and predicting weld performance using the surface temperature characteristics of the weld pool. The newly proposed weld pool boundary definition method holds promise for real-time monitoring in more complex multilayer pipe welding scenarios. It lays the groundwork for predicting and fusing the weld depth in intricate multi-pass pipe welding.

Ultrasonic wire bonding is a process of connecting two or more surfaces using a metal wire. In battery manufacturing heavy wire bonding is used to connect battery cells with each other or more commonly with printed circuit board or metal (aluminum, plated or bare copper) busbar by means of metal (aluminum, copper) wire with diameters ranging 100–500 µm. Single sided battery cell bonding means that connections are made from one side on both positive (cap) and negative (crimp) battery terminals. The main advantages of this method are easy process automation, low production time, easier recyclability, self-fusing properties of the wire and high process flexibility allowing for more space efficient battery holder design and different material thermal expansions (in comparison with direct busbar to cell joining using resistance or laser welding). This study is focused on analysis of selected properties of 400 µm aluminum wire ultrasonic wedge heavy wire bonding on 18,650 Lithium-Ion cylindrical battery cells. Bonding process was conducted using a RBK03 bond head equipped on a Hesse Bondjet BJ985 CNC wire bonder. As part of the work, the transversal and the longitudinal cross-section profile of the weld, the microstructure of the weld and the heat-affected zones of the dissimilar joint were described using electron and optical microscopy, the microhardness distribution in the joint was characterized and the joint sheer tests were performed according to DVS-2811. Materials of the aluminum bonding wire and the battery cell cylinder used for joining were also characterized. Bonding process on the machine used in this study is controlled by its duration, wire deformation or both of these parameters and consist of wire touch down and several (usually 2 or 3) bonding phases. Parameters of each bonding phase consist of bonding force, bonding force ramp, ultrasonic generator current/voltage, ultrasonic generator current/voltage ramp and bonding time. Each wire has at least 2 bonds connected by wire loop and is ended with wire pre-cut and tear off.

The objective of this study concerns simulation of Laser welding process, in a context of thin austenitic steel structures assembly.

Experiments and numerical simulations have been performed in order to predict, in a robust way, distortions induced by the Laser welding. A comparison between experiments and simulations is performed, considering thermal and mechanical approaches.

The experimental part of this work was based on instrumented tests. The in-situ measurements were carried out on sheets of 1 mm thickness. Macrographic observations in transverse section of the weld seam were performed in order to identify an equivalent heat source for butt welding configuration with filler metal.

The identified heat source was then implemented into a thermo-mechanical model taking into account thermal, elastic and plastic strains. For this, two different behavior laws were tested for the computations, namely bilinear isotropic strain hardening model, and Johnson–Cook model (neglecting the strain rate effect).

The keyhole depth is a key measurement characteristic in the laser welding of busbar to battery tabs in battery packs for electric vehicles (EV), as it directly affects the quality of the weld. In this work, experiments are carried out with controlled and adjusted laser power and feed rate parameters to investigate the influence on the keyhole width, keyhole depth and porosities. A 3D numerical model of laser keyhole welding of an aluminum alloy (A1050) has been developed to describe the porosity formation and the keyhole depth variation. A new integration model of the recoil pressure and the rate of evaporation model is implemented which is closer to the natural phenomena as compared to the conventional methods. Additionally, major physical forces are employed including plume formation, upward vapor pressure and multiple reflection in the keyhole. The results show that keyhole depth is lower at higher feed rate, while lower feed rates result in increased keyhole depth. This study reveals that low energy densities result in an unstable keyhole with high spattering, exacerbated by increased laser power. Mitigating incomplete fusion is achieved by elevating laser energy density. The findings emphasize the critical role of keyhole depth in optimizing laser welding processes for applications like busbar-to-battery tab welding.