Welding in the World最新文献

The torsion test is rarely used for resistance spot-welded joints since they are not subjected to torsion in applications. Normal, shear, and/or peel loads are usually the main stresses. Extensive scientific investigations in the context of Kunsmann’s dissertation date back more than 50 years. These investigations are still the basis of ISO 17653 and the German guideline DVS 2916-1. Recent scientific investigations only use torsion tests, but do not describe the reason for its use. A decisive advantage of the torsion test over the other standardized destructive testing methods lies in the types of fracture modes that occur and the properties of the fracture surfaces. Torsional loading results in either interfacial or button-pulled fracture modes. No material residues occur on the fracture surfaces for ductile and advanced high-strength steels. Hence, the measurement of weld diameter is achievable with minimal constraints, resulting in reduced variability and facilitating objective assessments of spot welds. This article delineates these attributes through a comparative analysis of various destructive testing methods employing statistical approaches. Additionally, the article expounds on the design concept of the developed rig for conducting torsion tests on spot welds.

Reactive air brazing (RAB) is a low-cost process for joining ceramic composites in air. However, due to the comparably low strength values that can be achieved by RAB, the process is only used in special applications like solid oxide fuel cells as a sealant. The limited strength values are the result of a severe pore formation during the brazing operation that remain in the brazing fillet after the solidification of the brazing filler. In this work, the formation of the pores during RAB brazing of alumina using a paste containing Ag4CuO powder and various binders was investigated. The formation and evolution of the pores were observed and quantified in in situ X-ray measurements. It could be observed that during debinding, pores have developed in the filler metal. The pore structure depends on the binder and the heating rate in the debinding stage. With the melting of the filler metal, many pores are closed by the melt flow. But it seems that the wetting of the alumina was hindered by the pores. The change of porosity during cooling is comparatively low.

The creep rupture life of ferritic heat-resistant steel weld joints is limited by Type IV cracking that occurs in the heat-affected zone (HAZ), whose shape affects creep damage accumulation. In this study, we address the inverse problem of extending the creep rupture life of weld joints by controlling HAZ shape via welding conditions. As reported separately, we have developed a workflow that predicts weld joint creep rupture life from the predicted HAZ shape from welding conditions and have implemented it in the material design system. Using this workflow, we presented a tandem Bayesian model for predicting the creep rupture life from welding conditions via the geometric features of HAZ shapes (HAZ shape factors), which are considered to determine the creep rupture life. The prediction model of a HAZ shape factor from welding conditions was formed by Gaussian process regression. The prediction model of the creep rupture life was formed by Bayesian linear regression. These models were probabilistically connected by Bayesian statistical mathematics. An algorithm to increase the creep rupture life was developed to search for welding conditions. This method was applied to a 2 1/4Cr–1Mo heat-resistant steel weld joint simulated with a plate I-bevel three-layer gas tungsten arc welding. The number of welding conditions combination reaches ({7}^{8}=5764801). Start from 49 initial HAZ shape factors and 22 creep rupture life data, we performed forward calculations of 20 rupture lives to find welding conditions that can improve the creep rupture life by 12% over the initial data.

The use of hollow sections to form lightweight structures is widespread in common steel processing industries such as crane, commercial vehicle, steel bridge and agricultural machinery construction. The hollow sections are mainly designed as truss or frame structures, in some cases using high-strength and higher-strength steels in order to achieve optimum utilization of the component and material. A new collection of fatigue life data covering sequence effects and the accuracy of the linear damage accumulation is presented. Effects of the shape of the applied load spectra and sequence effects of different amplitudes have been investigated. This document covers tubes of 4 to 8 mm thickness made by low-carbon or mild steel S355J2H. In general, it was found that the spectrum shape and the loading sequence have an influence on the service life. Depending on the shape of the spectrum, random tests tended to lead to shorter service lives than tests with block-loading sequences. An influence of overloads was also found for the tests with interspersed overloads. Typical maximum linear damage sums taken from recommendations and codes of 0.2 or sometimes 0.5 are exceeded for all spectra investigated and in some of the cases even significantly above 1.0. Transferability of the recommendations to component-type structures like tubular joints needs revision to lift its lightweight potential. Using stress concentration factors (SCF) from finite element analysis, typical strength values for the structural and effective notch stress concepts are checked. All joints investigated show a significantly higher strength compared to the IIW recommendations using the structural stress approach or compared to the DVS 0905 with the effective notch stress approach.

Hybrid laser arc welding (HLAW) was performed in a single-pass on M250 maraging steel plates of 10-mm thickness with three modified joint designs. A Y-groove joint preparation with included angles (IA) of 16°, 24°, and 30° and root face of 2.5 mm was used. Welding was performed using M250 W2 filler wire. The heat input for welding increased as the IA increased. The composition of weld fusion zone affected the reverted austenite (RA) volume fraction formed on aging. With an increase in base metal melting, the fusion zone was enriched with solute elements such as Ni, Mo, and Ti, ultimately increasing RA after aging. The fusion zone hardness of joints 1 and 2 was in the range 500–550 HV. The fusion zone of joint 3 exhibited a lower hardness of 475–525 HV due to the increased heat input involved in making the joint. When the transverse tensile strength of all welds was comparable to that of the parent metal, a significant reduction in K_Ic fracture toughness of fusion zone (FZ) was observed as the RA increased. K_Ic fracture toughness values were in the order, base > joint 1 > joint 2 > joint 3. The space between neighboring RA pools was smaller in the laser fusion zone (LFZ) owing to its fine cell size compared to the arc fusion zone (AFZ), and the welds failed by connecting series of cavities that only arise in the RA. LFZ appears to play an important role in determining weld toughness of HLAW welds.

Gas metal arc (GMA) welding requires improved process stability, higher quality and efficiency, and quantitative control of the heat input and deposition. These requirements can be achieved by appropriately controlling the metal transfer phenomenon. However, this control method has primarily been applied to short-circuit transfer, and very few examples of its application to free-flight transfer exist. Therefore, the effect of wire feed control on free-flight transfer remains unclear. In this study, the influence of wire feed control on the free-flight transfer phenomenon in the GMA welding process using an aluminum wire electrode was investigated through experimental observations, and free-flight transfer control was attempted.

It was observed the free-flight transfer phenomenon, particularly globular transfer, under low-current conditions with controlled wire feeding under various feed conditions, using wire feed–retract speeds and cycles as parameters. The observation results revealed two patterns with different timings of droplet detachment under long- and short-period conditions. Furthermore, the observation of the droplet detachment motions revealed that the inertia caused by the acceleration or deceleration of the feed speed acts on the droplet. Moreover, the difference between the two transfer patterns is primarily caused by the inertia acting on the droplet before and after switching the wire feed–retract direction and the size of the droplet at that time. Based on this, free-flight transfer can be stabilized by reconfiguring the feed conditions.

Bead-on-plate welding of pure copper with a blue-IR hybrid laser was conducted to achieve a spatter suppression in deep penetration welding of pure copper for the performance improvement of battery and power device of e-mobility. This hybrid laser combines an infrared (IR) laser and a blue diode laser as the welding source and preheating source, respectively. Preheating increases the light absorptivity of pure copper in the IR region. A 1.5-kW blue diode laser was employed to increase the light absorptivity by changing the phase of the preheated area from solid phase to liquid and gas phase. By experimentally investigating the influence of the blue diode laser intensity, the phase effects of the preheated area on pure copper welding with a blue-IR hybrid laser are elucidated. As a result, it was found that a liquid preheated area minimizes spatter during deep penetration welding.

The creep rupture life of weld joints decreases to values from half to one-tenth of that of the base metal in Cr–Mo heat-resistant steels. It is industrially very important to understand the creep performance of weld joints and to minimize the reduction in the creep performance of weld joints relative to the base metal. In this study, a consistent prediction computational workflow was developed for practical three-layer cladding welds that connect two modules. These are the weld heat transfer analysis module, which predicts the heat-affected zone (HAZ) shape from welding conditions, and the creep damage analysis module, which calculates the creep rupture life from the predicted shape of the HAZ. Using this workflow, we examined the effects of welding conditions on creep rupture life of 2.25Cr-1Mo steel. Welding conditions were selected on the basis of the design of experiment method, and the correlation between each factor and creep rupture life was evaluated by factorial effect analysis. The results clarify that the creep rupture life changed significantly depending on the control of welding heat input under conditions that simulate practical welding. This suggests that there is an appropriate welding heat input to bring the creep rupture life of weld joints close to that of the base metal. Although previous studies of creep rupture life with relatively simple HAZ geometries have indicated the correlation with the width and angle of HAZ, it was newly discovered that these indices cannot simply explain the creep rupture life of the weld joints with complex HAZ geometries that appear in practical welding. The effect of HAZ shape on creep rupture life is more complicated than previously reported, suggesting that more appropriate HAZ shape factors should be considered.

Given the tremendous growth of the microelectronics industry in recent years, soldering efficiency is more crucial than ever. Despite the great importance of the solder joints, these interconnections happen to be the weakest link in electronic packaging. Many surveys have been carried out in order to investigate their thermomechanical reliability but still incomplete since the electro-thermomechanical reliability is the one encountered in real operational services. A thorough insight into the multiphysics behavior of Pb-free solder joints is fundamental to enhancing the operational efficiency since the extent of their deterioration is a significant function of their compositions. This article investigates the response of various solder alloys (Sn63Pb37, SAC105, SAC305, SAC405, and InnoLot) to electrothermal loadings. The study explores their performance under different temperature conditions and examines factors such as melting temperature variations, residual stresses, and the impact of the IMC layer. The results highlight the superior reliability of SAC405, particularly regarding inelastic strain and premature damage. The study underscores the significance of mitigating these factors during electronics design and manufacturing to enhance solder joint lifetime. The findings contribute to advancing solder alloy reliability and improving electronic system performance.

This paper analyses the applicability of a modified strain approach to predict the fatigue life of HFMI-treated transverse stiffeners under variable amplitude loading (VAL) with random load sequences of a p(1/3) and linear shaped spectrum. Local stresses are determined using linear-elastic finite element analyses. The measured weld geometry and component imperfections are considered. From the hardness of the HFMI-treated zone and the base material, the elastic–plastic material behaviour and Coffin-Manson parameters to describe the damage parameter Woehler curve are estimated. Based on a hysteresis counting method (HCM), the damage for each closed hysteresis is calculated. The applied notch strain approach includes the impact of residual stresses and the influence of surface roughness. Thus far, the application of similar approaches has only been validated for welded components with comparatively low residual stresses and HFMI-treated welds subjected to constant amplitude loading. To validate the accuracy of the approach for HFMI-treated welds under variable amplitude loading, the approximated fatigue life is compared to the number of cycles derived from experimental investigations. In this study, it is shown in conjunction with experimental results that it is essential to consider the strength of the base material near the weld when assessing the service life. This area can be more critical than the HFMI-treated weld toe.