This work addresses the crucial challenges of simulating ultrasonic inspections in welded parts. We focus on the simulation of radiated ultrasonic fields in welded materials, incorporating spatially ...varying anisotropy and damping properties. Using macroscale descriptions to capture variations in weld properties as a function of grain orientation, two simulation methods are evaluated: a ray method and a hybrid finite element solution within the CIVA software. Simple simulations validate both models, but complexities emerge in real-world scenarios, notably caustic phenomena and beam splitting due to specific grain orientations. The proposed hybrid FE model can therefore provide reliable reference solutions, even for 3D configurations, allowing the biases arising from radius approximations to be quantified.
The fatigue life of welded steel components is usually determined by the weldment; in these cases, fracture mechanical approaches are widely used for their prediction. Ferritic steels are known to ...have a fatigue strength that is dependent on temperature. Therefore, this study evaluates fatigue tests of cruciform joints and transverse stiffeners at different sub-zero temperature levels regarding fatigue life. Simultaneously, the stress intensity factors over the crack length are calculated for the individual experiments using analytical solutions. Then, using the Paris–Erdogan relation with temperature- and material-specific C and m parameters as well as tabular values, the fatigue lives are calculated with analytical solutions and compared with the experimental results. It is shown that the prediction accuracy is significantly increased for the sub-zero temperature range by using temperature-adjusted Paris–Erdogan parameters, as long as the temperature is above the fatigue transition temperature.
•Experiments above fatigue transition temperature show an increasing fatigue strength of welded joints with decreasing temperature.•Paris–Erdogan parameters derived at room temperature leads to conservative results at sub-zero temperatures.•By using Paris parameters adapted to the sub-zero temperature, an increase in fatigue life accuracy could be achieved.
Aiming at the defects of inaccurate weld extraction and high matching error rate in automatic welding system of large weldments currently. We propose a multi task detection model based on CNN ...architecture, which integrates the semantic segmentation technology required for weldment merging as well as the edge detection technology needed for weld matching. In particular, for the purpose of predicting smoother edges and welds, we carefully construct a new segment head, which adopts the sub-pixel convolution technology for up-sampling. Furthermore, a joint optimization loss function is explored to alleviate the imbalance of category distribution in large-scale weldment datasets. To verify the effectiveness of the model, abundant groups of data are collected for training and testing. The experimental results indicate that the proposed method has achieved the optimal trade-off between detection accuracy (83.35% mIoU, 95.15% F-score of welds and edges) as well as speed (74FPS) on a 2080Ti GPU compared with other state-of-the-arts, which greatly improves the robustness of the automatic welding system for large weldments.
The article deals with the possibility of a tight permanent joint of X5CrNi 18–10 austenitic steel and UNS N50400 titanium. The nuclear and chemical industries are in particular interested in solving ...this problem. The joining by means of fusion welding has come up against unreliability due to the formation of brittle intermetallic compounds between titanium and iron. The article deals with joining of these two heterogeneous materials by an innovative CMT welding method. CuSi3 soldering electrode was chosen as the additional material. Protective atmosphere consisting of clean argon has been chosen due to the undesirable gas absorption by titanium at temperatures over 600 °C. The results will compare different welding parameters and their impact on the quality of the weld joint. The quality of the created welds will be verified on the basis of the tensile test and the results will be graphically visualized. The microhardness in the weld and its surroundings will be measured. The microhardness measurement results will be graphically displayed. The experimental results will be supplemented by macrostructure snapshots and metallographic analysis snapshots.
Nitride precipitation during isothermal heating after rapidly cooled from the ferrite phase enriched temperature in duplex stainless steel was investigated to clarify the effect of nitrogen in steel ...as an alloying element and austenite phase growth. Nitride precipitation is frequently harmful for the properties such as toughness or corrosion resistance in duplex stainless steels. The heat affected zone (HAZ) in the vicinity of fusion boundary in weldments tends to have more remarkable nitride precipitation because of rapid cooling from the ferrite phase enriched temperature. During cooling process the growth of austenite phase occur resulting in the prevention of nitride precipitation.Employing 25%Cr duplex stainless steels containing various level of nitrogen of 0.1% to 0.3%, the measurement and observation of nitride precipitation were conducted in the specimens isothermally heated at 873 K to 1073 K after rapidly cooled from 1653 K. As results the low nitrogen containing steel had relatively much nitride precipitation than the higher nitrogen containing one because of the less increase in the fraction of austenite phase growth with larger nitrogen solubility. This result can be explained by the decease of oversaturation of nitrogen in ferrite phase by contribution of austenite phase growth during thermal cycle.
The stress and strain fields formed in the heat-affected zone (HAZ) of the weldment involved in pipes in thermal power plant have recently attracted attention as key plant management issue. The ...microstructure in the HAZ changes locally as a result of the thermal history imposed by the welding procedure. Hence, these changes manifest in time-dependent deformation, unlike those of the base material. In this study, the creep parameter involved in the constitutive equations of Norton’s law was identified for the base metal, HAZ, and weld metal in the weldment of a high-Cr ferritic heat-resistance steel by conducting a high temperature indentation creep test, which is useful for the in-situ identification of the creep parameter of aged components on site. The steel, which was treated here, is known to be a candidate material for the steam generating tube of the supercritical boiler. Finite element (FE) analysis was used to analyze some important engineering problems, such as the welded plate and tube subjected to creep loading by using the estimated creep parameter. As a result, the FE analysis results from the welded plate revealed that the creep strain localized at the HAZ relaxed as the angle between the weld line and loading direction increased, which indicated that the groove shape of the weld part should be sharp. From the results of the welded tube, the maximum stress component is occurred at the interface between base metal and HAZ and hydrostatic stress is also occurred at the interface in the HAZ at a deep position far from the surface of the pipe, which means that the creep void initiates in the HAZ and then grows near the interface between HAZ and base metal.
This study explores the novel design of geometric rubbing profiles on rotary friction welding for enhanced mechanical clamping in joining dissimilar alloys such as copper and stainless steel 316L. ...The clamping behavior of rubbing profiles could hold the yielding of the weld joint to a maximum level. An innovative approach to effective mixing of the weldment zone could be achieved through the definition of rubbing profiles. The effective dispersion of dissimilar metallic phases could be governed by the geometrical profile in achieving the intermetallic SS-Cu phase. Variations were made in welding parameters like tool rotational speed, upset pressure, upset time, friction pressure, and friction time to find the appropriate process for the four different rubbing profiles, namely helical fluke, plus, cylindrical, and flat to achieve a reduction in micro and macro-structural defects with strong weld nugget. Results show that helical fluke rubbing profiles were seen to have explicit values like ultimate tensile strength of 217 MPa (upset pressure), elongation of 9.8 % (upset pressure), and average hardness of 125 HV (friction pressure) at the weld nugget. Microstructural characteristics prove that the formation of IMCs through grain size reduction such as cementite increases the Vickers hardness of the weldment.
PDF
