Investigation of the effective parameters on welding residual stress in GTAW of aluminum cylindrical shell

77-86The present work aims to study the influence of different geometrical, technological, and material parameters on residual stress in tungsten inert gas butt-welded aluminum cylinder. In order to present a simple analytical model to estimate the welding residual stress, the Taguchi L18 array has been employed with one 6-level factor and four 3-level factors. A 3D coupled thermo-mechanical finite element model considering temperature-dependent material properties has been developed to determine the welding residual stress in all experiments. The numerical model has been validated using the hole-drilling method. Using statistical analysis, the order of factors based on their effect on residual stress has been determined as yield strength, length, thickness, heat input, and finally diameter. The residual stress increases with an increase in yield strength, diameter, and heat input, while decreases with an increase in thickness. Contribution of each parameter on residual stress has been specified using variance analysis; yield strength with 99.6% contribution is the most significant factor, while diameter has insignificant impact. Finally, high accuracy equations have been proposed to calculate the welding residual stress

Charpy Impact Response of the Cracked Aluminum Plates Repaired with FML Patches using the Response Surface Methodology

Here, the effect of fiber metal laminate (FMLs) patches was studied for repairing of single-sided cracked aluminum plates experimentally to see their response to Charpy impact tests. The main desired parameters were composite patch lay-up, crack length, and crack angle each one in three levels. All experimental attempts generated and followed based on the design of experiments method by using of response surface methodology. The predicted energy absorption values obtained from the model were in good agreement with the experimental results. No matter the specimens were repaired or not, as the crack length was increased the energy absorption of the structure was decreased. The experimental results also showed that for lengthen cracks, increasing of the crack angle had more effect on energy absorption. Also it was observed that the patch lay-up effective on the impact response of the specimens. The more the metal layer was departed from the aluminum plate and the FML patches interfacial surface, the less energy was absorbed in the structure

Investigation of the effective parameters on welding residual stress in GTAW of aluminum cylindrical shell

The present work aims to study the influence of different geometrical, technological, and material parameters on residualstress in tungsten inert gas butt-welded aluminum cylinder. In order to present a simple analytical model to estimate thewelding residual stress, the Taguchi L18 array has been employed with one 6-level factor and four 3-level factors. A 3Dcoupled thermo-mechanical finite element model considering temperature-dependent material properties has been developedto determine the welding residual stress in all experiments. The numerical model has been validated using the hole-drillingmethod. Using statistical analysis, the order of factors based on their effect on residual stress has been determined as yieldstrength, length, thickness, heat input, and finally diameter. The residual stress increases with an increase in yield strength,diameter, and heat input, while decreases with an increase in thickness. Contribution of each parameter on residual stress hasbeen specified using variance analysis; yield strength with 99.6% contribution is the most significant factor, while diameterhas insignificant impact. Finally, high accuracy equations have been proposed to calculate the welding residual stress

Unsupervised Learning for Subterranean Junction Recognition Based on 2D Point Cloud

This article proposes a novel unsupervised learning framework for detecting the number of tunnel junctions in subterranean environments based on acquired 2D point clouds. The implementation of the framework provides valuable information for high level mission planners to navigate an aerial platform in unknown areas or robot homing missions. The framework utilizes spectral clustering, which is capable of uncovering hidden structures from connected data points lying on non-linear manifolds. The spectral clustering algorithm computes a spectral embedding of the original 2D point cloud by utilizing the eigen decomposition of a matrix that is derived from the pairwise similarities of these points. We validate the developed framework using multiple data-sets, collected from multiple realistic simulations, as well as from real flights in underground environments, demonstrating the performance and merits of the proposed methodology

Unsupervised Learning for Subterranean Junction Recognition Based on 2D Point Cloud

This article proposes a novel unsupervised learning framework for detecting the number of tunnel junctions in subterranean environments based on acquired 2D point clouds. The implementation of the framework provides valuable information for high level mission planners to navigate an aerial platform in unknown areas or robot homing missions. The framework utilizes spectral clustering, which is capable of uncovering hidden structures from connected data points lying on non-linear manifolds. The spectral clustering algorithm computes a spectral embedding of the original 2D point cloud by utilizing the eigen decomposition of a matrix that is derived from the pairwise similarities of these points. We validate the developed framework using multiple data-sets, collected from multiple realistic simulations, as well as from real flights in underground environments, demonstrating the performance and merits of the proposed methodology

Comparative study of the effective parameters on residual stress relaxation in welded aluminum plates under cyclic loading

The prediction of residual stress relaxation is essential to assess the safety of welded components. This paper aims to study the influence of various effective parameters on residual stress relaxation under cyclic loading. In this regard, a 3D finite element modeling is performed to determine the residual stress in welded aluminum plates. The accuracy of this analysis is verified through experiment. To study the plasticity effect on stress relaxation, two plasticity models are implemented: perfect plasticity and combined isotropic-kinematic hardening. Hence, cyclic plasticity characterization of the material is specified by low cycle fatigue tests. It is found that the perfect plasticity leads to greater stress relaxation. In order to propose an accurate model to compute the residual stress relaxation, the Taguchi L18 array with four 3-level factors and one 6-level is employed. Using statistical analysis, the order of factors based on their effect on stress relaxation is determined as mean stress, stress amplitude, initial residual stress, and number of cycles. In addition, the stress relaxation increases with an increase in mean stress and stress amplitude

An experimental study on the tensile behavior of the cracked aluminum plates repaired by fiber metal laminate (FML) patches

Fiber metal laminates (FMLs) are widely used in aerospace industries nowadays. Repairing of the cracks in these advanced materials was first done by some aeronautical laboratories in early 1970s. In this study, experimental investigations were done on the effect of repairing the center-cracked aluminum plates using the FML patches. The repairing processes were conducted to characterize the response of the repaired structures to tensile tests. The composite patches were made of one aluminum layer and two woven glass-epoxy composite layers. Three different crack lengths in three crack angles and different patch lay-ups were examined. It was observed that no matter what the crack length was, the more the crack angle is larger, the more ultimate tensile strength of the structure became. It was also indicated that the patch lay-up had an important effect on the tensile response of the repaired specimens. When the aluminum layer of the patches was farther from the repair zone, the ultimate tensile strength reached to its maximum value