Strong Arc Research Articles

3D reconstruction of GMAW pool surface using composite sensor technology

Weld pool is the most direct signal to reflect welding quality, that means measurement and reconstruction of the pool surface is one of the most urgent task in industrial robotic welding. A lot of researches have been done in this area, but the strong welding arc and the violent oscillation of weld pool affect their effectiveness. To better resolve this problem, a composite vision sensing system was proposed in our previous study, which consists of an active vision part and a passive vision part. The geometric parameters of the weld cross section and the weld pool have been successfully extracted by using this system. Based on the obtained information, the dynamic relationship between the weld speed and the bead geometric parameters is established by multistep predictive model based on neural network. By using the established model and iterative algorithm, the pool tail height is estimated in this paper. A spatial vision calibration is also proposed to calculate the real geometric parameters of the weld pool. Then the 3D surface of the weld pool is also reconstructed by the means of space curved surface fitting. Finally, the verification experiment is also conducted to verify the feasibility of this method.

Application of Strong Arcs in m-Polar Fuzzy Graphs

Recently, m-polar fuzzy graph (mPF graph) becomes a growing research topic as the generalization of fuzzy graph. In this paper, at first mPF path, mPF cycle in an mPF graph are defined. The strength of connectedness of mPF path is introduced. Next, strongest and strong mPF path, mPF bridges, mPF cut nodes, mPF tree and mPF forests in an mPF graph are considered. Also, it is proved that an arc of mPF tree is strong mPF arc if and only if it is an mPF bridge. Finally, mPF end nodes in an mPF graph is defined and investigated some properties of it. An application of strongest path problem in 3-polar fuzzy graph is also given at the end.

Learning Siamese networks for laser vision seam tracking.

To design a stable laser vision seam-tracking system, an advanced weld image processing algorithm based on Siamese networks is investigated and proposed to resist the interference of arc and spatter in the welding process. This specially designed neural network, combined with powerful feature expression capabilities of deep learning, takes two welding images with different sizes as inputs and generates a target confidence map in a single forward pass by using the cross-correlation algorithm. To prevent the error accumulation and model drift, an online update strategy via local cosine similarity is developed. The use of metal inert-gas welding can realize real-time and precious tracking under the condition that the strong arc continuously shields the welding seam feature points.

A precise seam tracking method for narrow butt seams based on structured light vision sensor

At present, most popular approaches of seam detection are based on structured light vision sensors owing to features of high accuracy and robustness. However, the deformation of laser stripe is not obvious enough when it is projected onto narrow butt seam, whose width is less than 0.2 mm, so the traditional structured light vision sensor cannot detect the seam feature of narrow butt seam. In this paper, a precise seam tracking method for narrow butt seams based on structured light vision sensor is proposed. Firstly, a new structured light vision sensor with optical filters and an extra LED light is developed to filtered out most of noises from strong arc lights and acquire the image including laser stripe and narrow butt seam. In addition, an image processing method for the vision sensor is designed to obtain welding torch deviations of narrow butt seams both in horizontal and vertical directions. Based on the obtained deviations, two independent Fuzzy-PID controllers are designed to achieve seam tracking control accurately. Finally, in order to verify the effectiveness of the proposed method in this paper, a welding experimental system is setup and welding experiments are carried out. Experimental results demonstrate that this method can meet the requirement of narrow butt seams tracking accuracy.

Thermal behavior and fluid flow during humping formation in high-speed full penetration gas tungsten arc welding

An unusual type of humping defect with periodic humped region and perforated region may occur in high-speed full penetration GTAW, which deteriorates the homogeneity of weld property seriously. In this paper, the thermal behavior and fluid flow during full penetration humping (FP-humping) formation is revealed by a numerical investigation to explain the defect's physical mechanism. Self-adaptive double-ellipse distributions of arc heat flux, arc pressure, arc shear stress and electromagnetic force varying with transient free surface evolution are proposed. For the first time, the actual morphology of FP-humping in GTAW can be predicted numerically. The numerical results are well verified by experimental weld geometry and high-speed melt pool images captured by a color camera. The workpiece is melted under arc heat to form the melt pool, and its free surface is gouged significantly under strong arc forces. When the depth of gouging region approaches workpiece thickness, the bottom thin liquid layer in gouging region is easily disrupted to initiate FP-humping formation. The lateral channel becomes the only transfer channel for liquid metal backward flow. The transition region between lateral channel and rear part of melt pool will be necked, and solidified instantly without the arc heat. Both scaling model of thermal conduction and numerical results imply that the premature solidification of necked lateral channel is a predominant factor to influence the FP-humping formation.

Case Study of Non Strong Arc in Cartesian Product of Fuzzy Graphs

Case Study of Non Strong Arc in Cartesian Product of Fuzzy Graphs

A seam tracking system based on a laser vision sensor

It is difficult to ensure robustness and accuracy when the traditional morphological method (TMM) is used to detect weld feature points, especially in an environment with a strong arc light and splash interference. In this study, a novel and robust seam tracking system based on a laser vision sensor is proposed. The feature point is obtained using the traditional morphological method before welding and can thus determine the tracked region. When the welding begins, a spatiotemporal context (STC) tracking algorithm is utilized in order to detect the weld feature points. In the welding process, the STC algorithm is adopted to determine a feature point with a strong arc light and splash interference and the morphological method is used to obtain an accurate weld feature point when the interference decays. As a result, the STC model can be updated in time, so the tracking drift problem can be solved and the robustness can be improved. A model reference adaptive control method is then adopted to improve the robustness of the robot system, which can convert the deviation between the theoretical and actual welding trajectory into a voltage to control the robot’s movement. Experimental results show that the tracking error of our seam tracking system is within 0.5 mm even when the distance between the laser stripe and the welding pool is 15 mm, which can completely satisfy the industrial requirements.

Geochemistry, age and origin of the Mons Claudianus TTG batholith (Egypt): insight into the role of Pan-African magmatism in uniting plates of Gondwana

AbstractThe tonalite–trondhjemite–granodiorite (TTG) Mons Claudianus Batholith (MCB) of Egypt is subsolvus, metaluminous to mildly peraluminous, exhibits wide ranges of SiO2, Al2O3, Sr, Rb, Zr, shows large Ba enrichment, is moderately enriched in rare earth elements (REE) and is depleted in K, Ti, Nb, Y, Hf and heavy REE (HREE), reflecting strong arc geochemical signatures. Moderate fractionation of REE and lack of Eu anomaly characterize the MCB. It is typical of high-Al TTGs of volcanic-arc affinities. U–Pb–zircon dating produced a Pan-African age of 664.12 ± 0.38 Ma. The MCB exhibits 87Sr/86Sr isotopic compositions of 0.70352–0.70626 (initial Sr ratio of 0.70259) and 143Nd/144Nd ratios of 0.51261–0.51276 (εNd; –0.5 to +2.4), suggestive of a mantle source. Anatexis of a basaltic slab under eclogitic conditions leaving garnet in the residue produces high-Al TTG rocks characterized by low Yb values (<1.8 ppm). Values (in ppm) of Yb (0.65–1.8), Y (2.2–19), Nb (1.2–6.4), and ratios of Nb/Ta (7–17), (La/Yb)N of 11.7, Sr/Y and Zr/Sm (58 and 45, respectively) are all consistent with anatexis of a basaltic slab under eclogitic conditions, leaving garnet in the residue to produce this high-Al TTG suite. The data conform to magma generation via partial melting (F = 0.25–0.50) leaving 15–25 % garnet in the residue. Voluminous synorogenic magmatic pulses, resulting from slab melting during the closure of the Mozambique Ocean via convergence of east and west Gondwana, produced the MCB and similar large batholiths forming the core of Pan-African belts. These belts welded together vestiges of fragmented Rodinia, assembling them into a united Gondwana.

Carbonate Platform Development in an Intraoceanic Arc Setting: Costa Rica’s Largest Limestone Sequence - The Fila de Cal Formation (Middle Eocene to Lower Oligocene)

The limestones of the Fila de Cal Formation build the largest carbonate platform sequence of Costa Rica extending over 180 km from southern Costa Rica into the Panamanian boarder area of David. The detailed limestone microfacies analysis and micropaleontologic dating based on the contained larger foraminiferal assemblages of 22 samples selected from the most representative exposures reveal three main carbonate facies: (1) Eoannularia eocenica-bearing spiculite facies from the Middle Eocene, (2) large lepidocyclinid-nummilitid facies from the Upper Eocene lead by the Lepidocyclina chaperi-Lepidocyclina tobleri panamensis assemblage and (3) dominant Lower Oligocene Lepidocyclina yurnagunensis-Lepidocyclina undosa assemblage. These three biostratigraphically successive facies record circa 14 to 19 m.y. of continuous shallow-marine carbonate sedimentation in the Pacific frontal arc region of southern Costa Rica. During this time large communities of benthic organisms: larger foraminifera, calcareous algae, corals, bryozoans, mollusks and equinoderms rapidly grew in warm tropical waters to build the largest and long-lasting carbonate platform on the Costa Rican arc. The carbonate sedimentation ended abruptly with accumulation of thick volcaniclastic marine platform-to-slope deposits of the Térraba Formation. Tectonically, the Fila de Cal carbonate platform development coincides with rapid convergence rates of the Farallón plate beneath southern Central America leading to strong arc uplift and new widespread neritic environments. The correlation with contemporaneous carbonate arc sequences clearly indicates that primarily their proximity to the inner volcanic arc areas and strong subsidence in response to emerging volcanic edifices are probably the main factors that controlled growing and persistence of carbonate environments within the arc setting.

Real-time seam tracking control system based on line laser visions

A set of six-degree-of-freedom robotic welding automatic tracking platform was designed in this study to realize the real-time tracking of weld seams. Moreover, the feature point tracking method and the adaptive fuzzy control algorithm in the welding process were studied and analyzed. A laser vision sensor and its measuring principle were designed and studied, respectively. Before welding, the initial coordinate values of the feature points were obtained using morphological methods. After welding, the target tracking method based on Gaussian kernel was used to extract the real-time feature points of the weld. An adaptive fuzzy controller was designed to input the deviation value of the feature points and the change rate of the deviation into the controller. The quantization factors, scale factor, and weight function were adjusted in real time. The input and output domains, fuzzy rules, and membership functions were constantly updated to generate a series of smooth bias robot voltage. Three groups of experiments were conducted on different types of curve welds in a strong arc and splash noise environment using the welding current of 120 A short-circuit Metal Active Gas (MAG) Arc Welding. The tracking error was less than 0.32 mm and the sensor’s metrical frequency can be up to 20 Hz. The end of the torch run smooth during welding. Weld trajectory can be tracked accurately, thereby satisfying the requirements of welding applications.

New GTAW variant for high-throughput aluminum welding

For aluminum joining, the gas tungsten arc welding (GTAW) and the gas metal arc welding (GMAW) processes are widely used. The GTAW process is mainly used when high quality is required whereas the GMAW process allows higher throughput at a lower quality. Therefore, aluminum fabricators have to compromise between a high quality and a high productive welding process thus far. In this paper, a new GTAW welding variant is presented that operates in DCEP polarity (electrode as the anode) at high currents up to 450 A. The use of a second gas stream ensures a strong penetration and good arc stability. The welding performance of the new GTAW variant is compared to AC GTAW and pulsed GMAW. It enables high-quality welds for a wide thickness range between 2 and 10 mm at even higher welding speeds compared to GMAW.

Laser vision seam tracking system based on image processing and continuous convolution operator tracker

To address the problem of low welding precision caused by the poor real-time tracking performance of common welding robots, a novel seam tracking system with excellent real-time tracking performance and high accuracy is designed based on the morphological image processing method and continuous convolution operator tracker (CCOT) object tracking algorithm. The system consists of a six-axis welding robot, a line laser sensor, and an industrial computer. This work also studies the measurement principle involved in the designed system. Through the CCOT algorithm, the weld feature points are determined in real time from the noise image during the welding process, and the 3D coordinate values of these points are obtained according to the measurement principle to control the movement of the robot and the torch in real time. Experimental results show that the sensor has a frequency of 50 Hz. The welding torch runs smoothly with a strong arc light and splash interference. Tracking error can reach ±0.2 mm, and the minimal distance between the laser stripe and the welding molten pool can reach 15 mm, which can significantly fulfill actual welding requirements.

Types of domination in intuitionistic fuzzy graph by strong arc and effective ARC

Types of domination in intuitionistic fuzzy graph by strong arc and effective ARC

Domination in cartesian product of fuzzy graphs using strong ARC

Domination in cartesian product of fuzzy graphs using strong ARC

Curvature sensor based on Mach–Zehnder interferometer with vase-shaped tapers

A novel Mach–Zehnder Interferometer (MZI) formed by cascading two vase-shaped tapers in a single mode fiber (SMF) is proposed in this work. The vase-shaped taper is fabricated by fusion splicing a fiber sphere with a fiber tip by applying strong arc discharge. The curvature sensing characteristic of the proposed vase-shaped taper-based MZI is experimentally investigated, displaying that the interference spectrum has a blue shift with the increase of applied curvature. The sensor realizes a large range measurement of curvature from 0.9284m−1 to 4.0470m−1 with sensitivities of −8.41nm/m−1 and −16.72nm/m−1 in the curvature range of 0.9284m−1 to 2.4564m−1 and 2.6025m−1 to 4.0470m−1, respectively. Its temperature-curvature cross-sensitivities are −0.0021m−1/°C and −0.0011m−1/°C in the two measurement ranges, which are lower than the corresponding curvature resolutions which are 0.0024m−1 and 0.0012m−1. The proposed sensor exhibits the advantages of low cost, negligible temperature cross-sensitivity, fine curvature sensitivity and large measurement scale.

Automatic Welding Seam Tracking and Identification

In the automatic welding process on mid/thick plates, the precision of the welding position has an important effect on welding quality, which mainly relies on the identification of the welding seam. However, due to some possible disturbances in complex unstructured welding environments, e.g., strong arc lights, welding splashes, thermal-induced deformations, etc., it is a great challenge to identify the welding seam. In this paper, we propose a robust automatic welding seam identification and tracking method by utilizing structured-light vision. First, after the preprocessing of the welding image, the gray distribution of the laser stripe is tracked and the profile of the welding seam is searched in a small area by using the Kalman filter, with the aim to avoid some disturbances. Second, in order to extract the welding seam profile, a series of centroids obtained by scanning the columns in the rectangular window are fitted using the least-squares method. Third, a character string method is proposed to qualitatively describe the welding seam profile, which might consist of different segment and junction relationship elements. And then, these character strings acquired from the object image are matched with those from the model, so that the position of the welding seam can be determined. Finally, the advantages of the new algorithm are testified and compared through several experiments.

Seam tracking investigation via striped line laser sensor

PurposeThis paper aims to propose a set of six-axis robot arm welding seam tracking experiment platform based on Halcon machine vision library to resolve the curve seam tracking issue.Design/methodology/approachRobot-based and image coordinate systems are converted based on the mathematical model of the three-dimensional measurement of structured light vision and conversion relations between robot-based and camera coordinate systems. An object tracking algorithm via weighted local cosine similarity is adopted to detect the seam feature points to prevent effectively the interference from arc and spatter. This algorithm models the target state variable and corresponding observation vector within the Bayes framework and finds the optimal region with highest similarity to the image-selected modules using cosine similarity.FindingsThe paper tests the approach and the experimental results show that using metal inert-gas (MIG) welding with maximum welding current of 200A can achieve real-time accurate curve seam tracking under strong arc light and splash. Minimal distance between laser stripe and welding molten pool can reach 15 mm, and sensor sampling frequency can reach 50 Hz.Originality/valueDesigning a set of six-axis robot arm welding seam tracking experiment platform with a system of structured light sensor based on Halcon machine vision library; and adding an object tracking algorithm to seam tracking system to detect image feature points. By this technology, this system can track the curve seam while welding.

Water contents of clinopyroxenes from sub‐arc mantle peridotites

AbstractOne poorly constrained reservoir of the Earth's water budget is that of clinopyroxene in metasomatised, mantle peridotites. This study presents reconnaissance Sensitive High‐Resolution, Ion Microprobe–Stable Isotope (SHRIMP–SI) determinations of the H2O contents of (dominantly) clinopyroxenes in rare mantle xenoliths from four different subduction zones, i.e. Mexico, Kamchatka, Philippines, and New Britain (Tabar‐Feni island chain) as well as one intra‐plate setting (western Victoria). All of the sub‐arc xenoliths have been metasomatised and carry strong arc trace element signatures. Average measured H2O contents of the pyroxenes range from 70 ppm to 510 ppm whereas calculated bulk H2O contents range from 88 ppm to 3 737 ppm if the variable presence of amphibole is taken into account. In contrast, the intra‐plate, continental mantle xenolith from western Victoria has higher water contents (3 447 ppm) but was metasomatised by alkali and/or carbonatitic melts and does not carry a subduction‐related signature. Material similar to the sub‐arc peridotites can either be accreted to the base of the lithosphere or potentially be transported by convection deeper into the mantle where it will lose water due to amphibole breakdown.

Dual manipulator system of the field hot-line working robot in 110-kV substations

PurposeThe purpose of this paper is to present a dual manipulator system for aloft hot-line assembly tasks of connection fittings in 110-kv intelligent substation, which is significant to the research on hot-line working robots.Design/methodology/approachThis paper addresses the challenges of the task and presents a dual manipulator system which can overcome these challenges to realize the robotic assembly of connection fittings in narrow space without impacting the safe distance of both phase to phase and phase to ground. Two manipulators share a same global reference coordinate. The mission of Manipulator 1 is to position the fixed part of connection fittings and screw the bolts on it. Visual computing provides the approximately position for the end-effector of Manipulator 2, after which The Manipulator 2 carries the removable part of connection fittings to this position. Then, the assembly task could be completed with the posture of the Manipulator 2 adjusted following the guidance by force-position control.FindingsThe dual manipulator system can position the target under different illumination conditions and complete fast assembly of connect fittings in 110-kV substation. No strong arc discharge or surface erosion phenomenon has been observed.Practical implicationsThis dual manipulator system will be particularly useful for the hot-line assembly of connection fittings in 110-kv intelligent substation, as well as some assembly tasks where uncertain target position and complex contact surface such as cylindrical hole is involved.Originality/valueThis study presents a dual manipulator system used by a field robot working in 110-kv intelligent substation. The system is able to achieve the connection fittings assembly task under energized simulation experimental system. Unlike other peg-in-hole assembly strategy, it does not require high stability of manipulator or plane contact surface around the hole.

Visual sensing of the weld pool geometry from the topside view in keyhole plasma arc welding

Weld pool and keyhole behaviors are the key factors to determine the process stability and weld joint quality in keyhole plasma arc welding. In this study visual sensing of the topside weld pool based on a low-cost CCD camera was realized. A visual sensing system with special dimmer glass and bandpass filtering was developed for solving the problems like strong arc disturbances and large radiation intensity gradient. Boundaries of the complete topside weld pool were acquired through image processing of the captured raw images. Weld pool dimensions were then calculated and calibrated. The relationships between the dimensions and welding current, welding speed and plasma gas flow rate were investigated. Three stages, including blind keyhole, unsteady keyhole and steady keyhole, were defined to describe the weld pool behaviors along with the keyhole’s evolution. The variation trends of weld pool shapes were discussed to study the possible mechanism of the complex physical processes. For keyhole plasma arc welding, this provides the industry a prospective low-cost way to predict the penetrations by sensing weld pool and keyhole from topside.