Weld Penetration Research Articles

Artificial Neural Networks Based Prediction of Penetration in Activated Tungsten Inert Gas Welding

Using GTAW, or tungsten inert gas (TIG) welding, weld penetration is usually lesser than the other arc welding processes. ATIG (Activated-flux TIG) welding can be a good alternative to provide deep penetration, and hence, improved productivity. In this work, 304L SS plate of 8 mm thickness was used as base plate, and a flux with a mixture of SiO2, MnO2 and MoO3 was used as a ternary flux in the ratio of 1:1:2. A 2-factor 3-level response surface methodology of central composite design was considered for designing experimental runs. Back Propagation (BP) type Artificial Neural Networks (ANN) model was developed to assess penetration in ATIG welding by using heat input and pulse frequency as the two process parameters. The ANN chosen has 2-10-1 network structure. Results show that the predicted values through ANN are conforming quite well to the experimentally obtained penetration, and hence, the applicability of ANN.

Predicting weld pool metrics in laser welding of aluminum alloys using data-driven surrogate modeling: A FEA-DoE-GPRN hybrid approach

Multi-physics computational models based on finite element analysis, offer detailed insights into the dynamics and metrics in the weld pool formed by laser welding. Conversely, data-driven surrogate models provide a cost-effective means to predict desired responses. These models establish statistical or mathematical correlations with input–output data, eliminating the need for additional simulations during design optimization. This study proposes a data-driven surrogate model, employing the Gaussian process regression network (GPRN), to predict weld pool metrics, such as weld width and depth of penetration in laser welding of aluminum alloy. A 3D computational fluid dynamics-based numerical model is initially constructed and experimentally validated to predict weld pool metrics. Subsequent experimental runs, guided by the design of experiments, include various configurations of process parameter settings. The developed numerical model computes weld pool metrics for each experimental run, forming a dataset for training and testing the GPRN model. The GPRN model is evaluated against simulated data, showing adequacy with a mean square error of 1.7 µm and mean absolute percentage error of 10−7, with experimental validation further confirming its accuracy, revealing a minimum error of 1.7%, a maximum error of 8%, and an average error of 3%. The key contribution and novelty of this study lie in the development of the hybrid data-driven model, which accurately predicts weld pool metrics while minimizing experimental and computational efforts.

An improved multi-frequency eddy current array sensor for detecting micro-defects of welding seam in metal plates

This study proposes an improved multi-frequency eddy current array sensor for the accurate detection of micro-defects (under-welding, over-welding, partial welding breakage, and minute penetration holes) of welding seam in metal plates. The primary goal is to further reduce the external and internal noise of the induced coil by optimizing the composition structure of the eddy current probe, thereby improving its sensitivity and signal-to-noise ratio in micro-defect detection. In response to the issue of external noise, this research introduces a gradient differential coil model, which can compensate for initial errors based on a geometrically balanced structure. By establishing a 3D simulation model and a physical mechanical structure, the suppression effect of this structure on excitation magnetic field and external environmental interference is verified. Furthermore, for the internal noise, a mathematical model of the direct stranded litz wire is established. Theoretical calculations and experimental validation confirm that the litz wire exhibits lower eddy current loss and higher Q value compared to traditional copper conductors, thus mitigating internal noise and improving signal-to-noise ratio. On this basis, the excitation mode of the eddy current coil probe array is set to a multi-frequency excitation method based on a center frequency, greatly reducing the electromagnetic interference between channels. Experimental results demonstrate that the improved eddy current sensor can effectively recognize as low as Φ1 mm weld penetration defect at a lift-off value of 0.5 mm, achieving a remarkably high signal-to-noise ratio of approximately 17.7 dB.

Weldability and Mechanical Properties of Pure Copper Foils Welded by Blue Diode Laser.

The need to manufacture components out of copper is significantly increasing, particularly in the solar technology, semiconductor, and electric vehicle sectors. In the past few decades, infrared laser (IR) and green laser (GL) have been the primary technologies used to address this demand, especially for small or thin components. However, with the increased demand for energy saving, alternative joint techniques such as blue diode laser (BDL) are being actively explored. In this paper, bead-on-plate welding experiments on 0.2 mm thick pure copper samples employing a BDL are presented. Two sets of parameters were carefully selected in this investigation, namely Cu-1: Power (P) = 200 W; Speed (s) = 1 mm/s; and angle = 0°, and Cu-2: P = 200 W; s = 5 mm/s; and angle = 10°. The results from both sets of parameters produced defect-free full penetration welds. Hardness test results indicated relatively softer weld zones compared with the base metal. Tensile test samples fractured in the weld zones. Overall, the samples welded with Cu-1 parameters showed better mechanical properties, such as strength and elongation, than those welded with the Cu-2 parameters. The tensile strength and elongation obtained from Cu-1 were marginally lower than those of the unwelded pure copper. The outcomes from this research provide an alternative welding technique that is able to produce reliable, strong, and precise joints, particularly for small and thin components, which can be very challenging to produce.

Surface Tension Estimation of Steel above Boiling Temperature

Surface tension is an important characteristic of materials. In particular at high temperatures, surface tension values are often unknown. However, for metals, these values are highly relevant in order to enable efficient industrial processing or simulation of material behavior. Plasma, electron or laser beam processes can induce such high energy inputs, which increase the metal temperatures to, and even above, boiling temperatures, e.g., during deep penetration welding or remote cutting. Unfortunately, both theoretical and experimental methods experience challenges in deriving surface tension values at high temperatures. Material models of metals have limitations in explaining complex ion interactions, and experimentally measuring temperature and surface tension at high temperatures is a challenge for methods and equipment. Therefore, surface wave analysis was conducted in this work to derive surface tension values around the boiling temperature of steel and identify trends. In addition, a simple ion interaction calculation was used to simulate the impacting parameters that define the surface tension. Since both the experimental values and simulation results indicate an increasing trend in surface tension above the boiling temperature, it is concluded that the dominating attractive forces above this temperature should increase with increasing temperature and lead to increasing surface tension forces in the surface layers of liquid metal.

Improvement in weld quality of Al and Cu joints using dual-beam laser welding

The high weld quality of dissimilar aluminum (Al)/copper (Cu) joint is essential to improve the reliability of connecting components in secondary batteries. This study was aimed at enhancing the weld quality of dissimilar AlCu joints to connect tab-to-busbar in secondary batteries. AA1050 and Ni-coated Cu (C1100) sheets were lap-welded using dual-beam laser welding with a continuous-wave (CW) laser for welding and a pulsed laser for preheating. Consequently, the weld quality was investigated by characterizing the morphology, microstructure, and mechanical and electrical properties of the joints. For comparison of the weld quality, single-beam welding was also performed. Soundly welded joints were achieved using a dual-beam at a CW laser power range of 1000–1400 W for fixed pulsed laser power and welding speed of 100 W and 80 mm/s, respectively. Microstructural analysis of the weld indicated that the upper weld metal (WM) comprised α-Al and AlCu eutectic phases, whereas the lower WM exhibited mixed morphology of different phases including Al2Cu, AlCu, Al3Cu4, and Al4Cu9. Further, the electrical resistance was linearly correlated with weld penetration depth, exhibiting a minimum of 352.3 μΩ against a penetration depth of 341.7 μm. In addition, The Vickers microhardness and lap shear tensile testing of soundly welded sample (A4) exhibited an average hardness value of 921.7 HV in the lower WM, and the average tensile load for the welded sample was 247.4 N. This study provides valuable insights for improving the weld quality of reliable AlCu dissimilar joints for connecting tab-to-busbar in secondary batteries.

Controlling the weld penetration depth of laser beam micro welding by using an iterative learning approach

AbstractIn order to meet the increasing demand for high‐speed joining processes, laser beam micro welding is used to reproducibly weld metallic joining partners such as steel. Long weld seams or high cycle speeds, however, remain a challenge to achieve a constant welding depth throughout the entire welding process without major fluctuations. This paper shows the development and evaluation of a weld penetration depth control system based on interferometric measurement of the depth of the vapor capillary. High path speeds and small weld depths are challenging for real‐time depth control. Therefore, the offline data of the interferometric measurements are used to implement an iterative learning control of the weld penetration depth. The quality of the control is verified by welding with and without spatial power modulation on 1.4301 steel while following a linear and sinusoidal trajectory.

Metallurgical Characterization of Micro Friction Stir Spot Welding (μFSSW) Parameters on Similar Materials AA1100

The Micro Friction Stir Spot Welding (μFSSW) process is a metal plate welding technique with a relatively thin plate thickness. The advantages of this welding are the higher quality of the weld and the relatively low deformation. This study aimed to determine the effect of depth of penetration, dwell time, and tool geometry on the trend of material flow on the macro-structure of the welds produced in μFSSW technique using AA1100 thin aluminum plates. In this study, the parameters that are changed are the depth of the chisel, dwell time, and tool geometry. In this study, the parameters of the penetration depth were divided into 500 microns, dwell time was split into three lengths of time (300 ms, 500 ms, and 700 ms), and tool geometry was divided into two types of tool geometries (tool-1 and tool-2). In addition, the macro test was carried out to determine the depth of the weld, contour profile, and stretch macrostructure. The results of the macro test will be used to analyze the material flow relationship in each weld zone on the welding results of all existing parameters. Based on the results of the study, the effect of depth of penetration, dwell time, and tool geometry on the weld depth and metallography (hook width, hook height, and effective top sheet thickness) of welds using AA1100 thin plates is influential along with various tool geometries and the deeper the weld penetration and the longer stirring time, although the results are not always directly proportional.

Microstructure and properties of laser welding Ni-based alloy/austenitic stainless steel with filler wire for nuclear reactor pump can end sealing

The current study investigates the microstructure and properties of laser welding involving Hastelloy C-276 and 304 stainless steel with filler wire, which is closely related to nuclear reactor pump can end sealing. The experimental results indicate the presence of an unmixed zone (UZ) and a small amount of Mo-rich secondary phase in weld seam, and microstructure of UZ is composed of austenite and ferrite phases. Laser welding enhances the ratio of low-angle misorientation and the uniformity of elements macro-distribution. The end sealing property of nuclear reactor pump can is characterized by anti-peel property of weld joints. The welded joint has local fracture and through fracture in the test of anti-peel property. The weld with local fracture exhibits superior anti-peel property. The joint crack starts at the bottom of the UZ. The anti-peel property of the welded joint is 239.6 ± 4.7 N/mm and mainly related to the weld penetration. The corrosion property of welded joints is determined by the elements of the weld, and the welded joints showcasing a better integral corrosion property than that of 304 base metals. Laser welding Ni-based alloy/austenitic stainless steel with filler wire has significant technical advantages for end sealing of nuclear reactor pump can.

Online Detection of Laser Welding Penetration Depth Based on Multi-Sensor Features.

The accurate online detection of laser welding penetration depth has been a critical problem to which the industry has paid the most attention. Aiming at the laser welding process of TC4 titanium alloy, a multi-sensor monitoring system that obtained the keyhole/molten pool images and laser-induced plasma spectrum was built. The influences of laser power on the keyhole/molten pool morphologies and plasma thermo-mechanical characteristics were investigated. The results showed that there were significant correlations among the variations of the keyhole-molten pool, plasma spectrum, and penetration depth. The image features and spectral features were extracted by image processing and dimension-reduction methods, respectively. Moreover, several penetration depth prediction models based on single-sensor features and multi-sensor features were established. The mean square error of the neural network model built by multi-sensor features was 0.0162, which was smaller than that of the model built by single-sensor features. The established high-precision model provided a theoretical basis for real-time feedback control of the penetration depth in the laser welding process.

Investigation on weld forming, microstructure and mechanical characteristics of dissimilar steel GTAW under novel composite magnetic field

During dissimilar steel welding, differences in magnetic permeability and thermophysical parameters between materials result in significant disparity in heat distribution on both sides of weld and poor weld formability. To solve the welding quality problems caused by significant disparity in heat distribution, a novel composite magnetic field consisting of longitudinal magnetic field (LMF) and cusp magnetic field (CMF) is applied to dissimilar steel welding. In this study, the influence of novel magnetic field on the mechanical characteristics, microstructure, and weld formation of dissimilar steel gas tungsten arc welding (GTAW) welds was investigated. It was found that arc deflection is influenced by both the material properties and LMF. When longitudinal exciting current (IL) was 0.5A, the weld melting zone tended to be symmetrical. On the premise that IL remained unchanged at 0.5A, as cusp exciting current (IC) increased from 0A to 5A: the weld fusion zone always remained symmetrical; The arc compression degree, weld penetration, melting area of weld and weld penetration/width ratio significantly increased, while the weld width progressively reduced; The heat-affected zone's (HAZ) width of the base metals and the mean grain size in the HAZ are significantly reduced; The mean microhardness of the weld metal (WM) and tensile properties are also significantly improved. The study results enrich the research foundation on heat input regulation in dissimilar steel GTAW, providing experimental evidence and theoretical support for resolving welding quality issues caused by welding conditions with different material properties.

Metallurgical and mechanical properties evaluation of the activated flux tungsten inert gas weldments

The activated flux tungsten inert gas welding process is an attractive joining technique to increase the depth of penetration in a single pass. In the last two decades, the research on activated flux tungsten inert gas welding increased drastically. Despite enhanced weld penetration, activated flux tungsten inert gas is not frequently implemented in industries because of a lack of information about the process. However, research on activated flux tungsten inert gas welding has significantly increased in the last decade due to the widespread information related to the advancements in weld penetration and mechanical properties of the activated flux tungsten inert gas process. The activated flux tungsten inert gas welding process provides a high single pass depth of penetration along with good mechanical properties compared to the tungsten inert gas welding process. The current work offers an in-depth analysis of the activated flux tungsten inert gas welding process mechanism, advancement in activated flux tungsten inert gas methodology to improve weld bead geometry, and mechanical and corrosion behaviour of the weldments. The current work also highlights recent progress made in the field of dissimilar metal joining using the activated flux tungsten inert gas welding process.

Optimization and GRA prediction of Al–Cu pulsed laser welding process based on RSM

In this paper, the process parameters of pulsed laser welding of Al–Cu are studied using response surface methodology (RSM) and grey relation analysis (GRA) to propose optimal directions for lap-shear strength of the joints. A single-factor experiment was conducted to find the suitable process parameter windows. The RSM models were established and analyzed with laser power, welding speed, pulse width, and frequency as inputs and joint lap shear, interfacial weld width, and weld-penetration-depth as outputs. With the use of GRA of interfacial weld width and weld penetration depth with the lap-shear force of joints, the improved direction for the lap-shear force of joints can be proposed.

Methods to Increase Fatigue Life at Rib to Deck Connection in Orthotropic Steel Bridge Decks

Orthotropic steel bridge decks (OSDs) are very popular all over the world because of the low dead load, high stiffness in the longitudinal direction, high strength ratio to weight, and can be used in various types of bridges. The life of these bridges is affected by fatigue cracks in different portions. One of major areas where the fatigue cracks appear in these bridges is rib-to-deck connection. In this research finite element analysis is carried out by using ABAQUS/CAE 2022 software to determine the ways to increase the fatigue life at rib to deck connection in OSDs. In the first part, smaller models are simulated; stress concentration is analyzed and hot spot stress (HSS) is calculated according to International Institute of Welding (IIW) and Det Norske Veritas (DNV) recommendations. In the second part, a parametric analysis is carried out to analyze the effect of weld penetration, thickness of deck, thickness of rib and rib to deck connection type. In the third part, simulation of models similar to the real field is carried out to determine whether the double welded connections are better than single welded connections. Different models are analyzed for different load cases like single wheel load, double wheel load and also the position of the wheels is changed. The boundary conditions are changed to analyze whether the boundary condition has any significant effect on the result obtained. It is found that thicker decks, thinner ribs, and low penetrated welded connections reduce the stress concentrations at rib to deck connections which ultimately increase fatigue life. Among the parameters examined, deck thickness is the most important parameter. It is found that the percentage of stress increase with percentage decrease in deck thickness follows a power relation. The overall fatigue life of double welded connection is excepted to be lower since the stress concentration is maximum at the weld toe at deck on the outer side of the closed stiffener; however, if the cracks initiate on the inner side of closed stiffener, the cracks at the weld root of single welded connection can propagate much rapidly than the cracks initiating on the inner side of the closed stiffener at the weld toe, thereby reducing the fatigue life of the single-welded specimen significantly.

Fatigue behaviour of root crack in stiffener-to-deck plate weld at crossbeam of orthotropic bridge decks

Steel Orthotropic Bridge Decks (OBDs) are widely used in long-span and movable bridges. Fatigue resistance analysis plays an important role in the design or assessment of OBDs. One possible fatigue failure is the crack initiating from the weld root of stiffener-to-deck plate connections at crossbeams. A full-scale experimental investigation in this study using a 20 mm thick deck plate with a dimension of 9.4 m × 5.1 m, including three crossbeams, represents the modern designed OBDs. The experiments show an arrest of crack propagation with a final crack depth of approximately 75% of the deck plate thickness. On the contrary, through thickness cracks develop in deck plates of 10 or 12 mm. Hot spot stress based fatigue detail categories (DC) using various failure criteria derived from the tests. Analysis with the effective notch stress shows that the DC has low sensitivity to the amount of weld penetration. The results of analyses with the eXtended Finite Element Method (XFEM), employed to analyse the fatigue crack propagation path and crack arrest, are in line with the experimental study.

Spatter reduction in deep penetration welding of pure copper using blue-IR hybrid laser

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.

Publisher Correction: Process comparison of laser deep penetration welding in pure nickel using blue and infrared wavelengths

Publisher Correction: Process comparison of laser deep penetration welding in pure nickel using blue and infrared wavelengths

Effect of pulse gas tungsten arc welding on the metallurgical characteristics & microstructural evolution in AZ31B magnesium alloy welds

This work assessed the effects of frequency & the pulse duration ratios on the weldability & structure-property relationships for the magnesium alloy AZ31B. In addition, AC/DC pulse welding with different pulse duration ratios was explored, to assess controlled repair welding on magnesium alloy castings. Complete penetration welds can be produced with conventional GTA welding using a heat input of ∼500 J/mm without the need for an active flux. However, the weld metal has a coarse grain structure and micro cracks, suggesting the need for an even better control of heat input for achieving defect free welds. Pulse GTA welding with at lower frequencies give relatively deeper penetration joints at different pulse duration ratios (1:1, 1:2 and 1:4). However, the full penetration welds are possible only with pulse duration ratio of 1:1. All the welds produced under pulsed GTA welding conditions were defect free. The grain sizes of the weld metals were much finer than for conventional GTA welding conditions and have a higher hardness compared to conventional GTA weld & also the parent alloy. Use of AC/DC mix for pulse welding, with the peak current being AC and the base current as DC, yields shallow penetration welds with no defects. The resultant weld metal microstructures are of finer grain size, and with finely distributed β-phase particles. This welding technique can be exploited for repair welding of magnesium alloy castings that have near-surface defects.

Monitoring Welding Torch Position and Posture Using Reversed Electrode Images – Part I: Establishment of the REI-TPA Model

Sensing, modeling, and control are the key technologies of intelligent welding manufacturing. The position and attitude of the welding torch relative to the weld seam affects the quality of the produced weld directly, which is the basis of control and offline programming of the welding robot. Based on the existing research of reversed electrode image (REI) on monitoring of weld pool surface and penetration state, this work focused on the application of REI on monitoring of welding torch position and attitude (TPA). In this paper, a REI-TPA model was established to quantitively relate REI to TPA by considering the surface of the weld pool as a spherical mirror. With the REI-TPA model, the offset distance and deflection angle of the welding torch relative to the correct position and attitude can be calculated. The calculation is based on the measurement of the relative distance between the tip of REI and the electrode in a passive visual image of the weld pool, arc length, and weld pool geometry. This model can be applied to the real-time control of TPA, which is a supplement to the application of welding passive visual image and an extension to multi-information acquisition and processing methods in the robotic welding process.

EXPERIMENTAL EVALUATION OF THE STRUCTURAL INTEGRITY OF VERTICAL CYLINDRICAL STORAGE TANK SHELL-TO-BOTTOM JOINTS OF VARIOUS DESIGNS

Bottom-to-shell joint is one of the most critical areas in vertical cylindrical storage tanks, both in terms of the number of detected flaws and the causes of failures. The primary factors contributing to the present state include the structural peculiarities of the shell-to-bottom joint, leading to incomplete fusion in the middle between the double filletgroove welds (double fillet welds) and, consequently, low inspectability. This results in a complex stress-strain state with maximum stress levels in the area of the shell-to-bottom joint. Thus, improving the existing design of the bottom-to-shell joint is relevant.This article presents the results of comparative resource evaluation tests conducted on the typical design of the shell-to-bottom joint and two prospective designs: one with complete penetration weld and another with a T-section. The tests were conducted using prototypes that replicate the necessary structural properties of the shell-to-bottom joint and the stress distribution diagram, allowing testing on standard servo-hydraulic machines. The results obtained indicate that all considered designs of shell-to-bottom joints, when free from flaws, exhibit high reliability, ensuring safe operation even under double the operational stresses for a minimum of 50 years. Considering the improved inspectability and feasibility of manufacturing these prospective shell-to-bottom joint designs, along with their comparable production costs, they can be recommended for practical applications.