Journal of Advanced Joining Processes最新文献

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.

In this study, different techniques are applied to measure diffusion coefficient D of three cold-rolled Advanced High-Strength Steels (AHSS): CR700Y-980T-DH, CR780Y980T-CH, and DR700Y980T-DP, and their laser-welded counterparts. By thermal desorption analysis (TDA) the hydrogen transport at elevated temperatures is investigated. This method allows the measurement of hydrogen quantities at different trapping sites and enables the determination of activation energies E_a and pre-exponential diffusion coefficients D₀. The analysis is conducted under various temperature regimes using different heating rates $\phi$. Additionally, the corresponding diffusion coefficients for the examined states are determined by electrochemical permeation (ECP) at room temperature. The findings indicate an increase in D after laser welding, with differences in microstructure and material chemistry being identified as the reasons behind this phenomenon. This study demonstrates that the employed method, along with the chosen sample geometries, holds significant potential for enhancing our understanding of hydrogen kinetics in AHSS and the effects of thermal heat treatments, such as laser-welding.

This paper investigates the low-transformation-temperature (LTT) effect in austenitic high alloy stainless steel and its influence on strain evolution of laser beam welded specimen. Due to the local heat input high temperature gradients occur between weld seam and base material, which lead to thermal and transformation induced strains. With targeted alloying in the weld seam the martensitic phase transformation can be shifted to lower temperatures resulting in the so-called Low Transformation Temperature (LTT) effect. This effect uses the volume expansion during the martensitic phase transformation. The delayed volume expansion during martensite phase transformation introduces continuous compressive strains until room temperature is reached and represents a mechanism that can serve to counteract the tensile strains caused by thermal shrinkage. The martensitic microstructure is achieved by dissimilar welding, combining an austenitic stainless steel base material with low alloyed filler wire. With this, the chemical composition of chromium and nickel is diluted, and a martensitic phase transformation occurs. As comparison, similar material combinations of stainless steel base material and conventional welding consumable are performed. In this work, in situ energy-dispersive x-ray diffraction (EDXRD) measurements in the beamline P61A at DESY are performed to investigate the expansion behaviour of martensite based on spectral data. Nine measuring positions are recorded and the strain evolution during welding and cooling of the samples are analysed. It is shown that the martensitic phase transformation changes the strain behaviour and implements compressive strain depending on the distance to the laser spot. It is found that the effect is orientation-dependent and that the highest strain influence is present in welding direction.

This work utilized a gradient method of joining plain carbon steel to stainless steel 316 L and then to Inconel 625 using wire arc additive manufacturing. The research investigated the quality of Functionally Graded Materials (FGM) structure, continuity, defect formation, microstructure, and mechanical properties of gradient regions. The investigation showed a strong, defect-free metallurgical bond between plain carbon steel and stainless steel 316 L and stainless steel 316 L and Inconel 625. The microstructure of stainless steel 316 L resulted from the solid-state transformation of ferrite-austenite (FA), with a significant presence of delta ferrite in the austenite matrix. In Inconel 625, the Laves intermetallic phase formed discontinuously between dendritic arms due to the microsegregation of alloy elements like niobium and molybdenum during solidification. The hardness values of Inconel 625, stainless steel 316 L, and plain carbon steel were 194–257 HV, 171–178 HV, and 159–170 HV, respectively. The ultimate tensile strength, yield strength, and elongation were achieved at 487 ± 10 MPa, 300 ± 6 MPa, and 40 % ± 0.15, respectively. The tensile test samples failed on the plain carbon steel side, indicating higher tensile strength at the interface and a well-bonded joint between the two alloys. Small, homogeneous dimples on the fracture surface confirmed the ductile fracture mode. The research demonstrates the use of wire-arc additive manufacturing (WAAM) to fabricate gradient materials with the required properties.

Recently, the automotive and aerospace industries have witnessed increased usage of titanium alloys. Nevertheless, the fabrication of titanium parts using conventional fabrication techniques is challenging owing to their low thermal conductivity, high affinity for oxygen, high melting temperature, high strength, and poor machinability. Advancements in welding technologies have resulted in the development of safe, efficient, and cost-effective joining techniques capable of overcoming the aforementioned challenges and enhancing titanium weld quality. The traditional approach and equipment used for welding aluminium and stainless steel had been utilized for joining titanium and its alloys but with limited success compared to the laser welding technique. Laser welding is the preferred method of welding because of its excellent qualities and great reliability, particularly for titanium alloy connections, which are frequently used in aerospace and aircraft structures. This work reviews recent works and progress recorded in laser welding of similar and dissimilar titanium alloy joints under varying processing parameters. The essential findings highlighting the impact of laser processing variables on the evolution of microstructural features, mechanical characteristics, and variations in corrosion resistance associated with laser-welded titanium joints in different environments are extensively highlighted. Finally, insightful information and prospects on laser welding of similar and dissimilar titanium alloy joints are provided.