V-groove Weld Research Articles

A precise guiding technology for V-groove initial weld point based on binocular vision and structured light vision

A precise guiding technology for V-groove initial weld point based on binocular vision and structured light vision

Virtual simulation of weld morphology for V-groove multi-layer welding

In order to study the virtual simulation of weld morphology for V-groove multi-layer welding, the prediction of characteristic parameters for weld morphology was realized by constructing the neural network models between the characteristic parameters and process parameters of different layers. At the same time, the virtual models of different layers were established according to the characteristic parameters of weld morphology and the structure parameters of V-groove. Combined with the prediction model and the virtual model, the process parameters were associated with the weld morphology, and the virtual simulation of weld morphology was realized. In the process of establishing the virtual model, first of all, the virtual model of root weld is established. Then, the virtual model of filling layer is established based on the root layer, and the virtual model of weaving layer is established based on the filling layer. Finally, validation experiments were carried out to verify the accuracy of the model. Verification results show that the prediction model can effectively predict the characteristic parameters of each layer, and the average relative errors of melting depth and width were less than 8%. The virtual simulation morphology has a high consistency with the actual morphology, and the average relative error of cross section area was less than 10%.

Application research on ultrasonic phased array detection algorithm for austenitic stainless steel with V-groove weld

Conventional ultrasonic detection methods are commonly used for detecting austenitic stainless steel weld structure. The anisotropy and inhomogeneity of the weld produces a strong scattering and energy attenuation effect on the acoustic wave. Controlling the accurate focusing of synthetic beams by ultrasonic transducer with multi-array element can be challenging, and difficult in detecting internal defects. A multi-group sequence grain model was established according to the distribution of grain orientation (DGO) in the weld, and then the “Velocity Coefficient K” algorithm was explored and developed, which is capable of quickly determining the acoustic wave propagation in the austenitic stainless steel weld with V-groove weld. By establishing an acoustic ray-tracing model with its analysis, the focusing law can be obtained quickly. The experimental results showed that the proposed algorithm has great effectiveness in detecting the signal-to-noise ratio (SNR) and imaging quality of defects.

Fatigue life analysis based on the groove angle reduction in the butt welding of excavator booms

This study analyzes the effect of changes in groove angle on the fatigue strength of the V-groove butt weld joint made of SM490A steel used in excavators. Butt-type specimens with different groove angles of 40° and 30° were manufactured by CO2 welding at a speed of 300 mm/min on a 13.5 mm thick steel plate. Four-point bending fatigue tests were conducted at room temperature with a frequency of 5 Hz and stress ratio of R = 0.1, and fatigue limits were set to 2 × 106 cycles. The high-cycle fatigue life of VG40 was approximately 7% higher than that of VG30. The stress concentration coefficient calculated using the effective notch stress method was 1.62 for the VG40, and 1.78 for the VG30, with an approximate difference of 9%. This decrease in fatigue life was caused by stress concentration due to the notch effect at the weld root, which was attributed to the adjacent backplate. Although the fatigue life decreased slightly owing to the improvement angle of the welded part, no difference was observed in microstructure and hardness. Therefore, it was confirmed that a sound weld was formed. The results of this study can be used as important basic data for determining the V-groove angle.

Structural performance of cold metal transfer welding technique on cold-formed steel flare v-groove welds

The performance and feasibility of a recent welding technique called Cold Metal transfer (CMT) welding technique for Cold-Formed Steel (CFS) welded sections is presented in this paper. The study focuses on understanding the behaviour of flare v-groove welds on back-to-back connected CFS sections subjected to longitudinal shear. A total of thirty lap shear specimens were fabricated and the parameters such as length of the weld and thickness of the weld were varied and tested under longitudinal loading. The weld geometry was observed under an optical microscope after polishing and chemical etching of the weld cross-section to determine the thickness of the weld for CMT flare v-groove welds. Based on the weld cross-section profiles, a set of calibrated welding parameters for 1.5mm CFS section is presented in the paper. The lap shear specimens failed in either transverse plate tearing of the individual cross-section or fracture of the weld at the weld contours. The test results show that AISI design standard yield over-conservative strength prediction and inaccurate failure modes for longitudinal flare v-groove welds. Therefore, a limiting ratio constituting of length of the weld, outstanding flange length, ultimate strength of parent material, and ultimate strength of wire electrode is proposed in the paper to accurately predict the failure mode. Additionally, a modified and reliable design equation is recommended to determine ultimate shear strength of CMT flare v-groove welds subjected to longitudinal loading.

Quantitative detection of crack depth in V-groove weld using laser-generated surface acoustic waves

Thick-walled structures are widely used in kinds of high-end equipment. As the most conventional method adopted to manufacture large-scale structures, multi-pass butt-welds are one of the most critical areas prone to defects. In this paper, we focus on the quantitative detection of crack depth in a V-groove weld using laser-generated surface acoustic waves. A two-dimensional finite-element method with Q345 steel is adopted to reveal the complicated propagation characteristics of laser-generated surface acoustic waves with surface cracks. The displacement fields are discussed to show the wave transmission, reflection, and mode-conversion phenomena. The main propagating wave modes—P, R, R′, R′r, and R′t waved—are distinguished with the help of the out-of-plane displacement under different crack depths in the time domain. It is found that R′r can be used to locate the cracks and R′t can be used to quantify the depth of the cracks.

Impact of Electrode Rotation on Aluminum GMAW Bead Shape

Aluminum gas metal arc welding (GMAW) uses inert shielding gas to minimize weld pool oxidation and reduce susceptibility to porosity and incomplete fusion defects. For aluminum shipbuilding, naval welding requirements highly recommend the use of helium-argon mixtures or pure helium shielding gas to provide a broader heat field and better weld toe fusion. Pure argon shielding gas can be used but has been susceptible to incomplete fusion and porosity defects, where argon’s lower thermal conductivity promotes a narrower arc heat field and shallow weld fusion depth. Using helium is a concern because it is a finite resource that costs approximately five times more than argon. The rotating electrode pulsed GMAW process was investigated to improve argon shielding fusion characteristics and reduce helium usage. Argon-shielded bead-on-plate tests were used to evaluate the relationship between ER5183 electrode rotation parameters and arc power on constant deposit area bead shape. These tests were compared to stringer beads (no oscillation) that were made with argon, helium, and helium-argon shielding gases. Electrode rotation improved underbead fusion depth width and toe fusion. With preferred rotation parameters, the bead width and incomplete fusion at weld toes were equivalent to helium-based welds. For weld reinforcement, electrode rotation promoted a nonsymmetric profile with deposit bias on the bead side, where rotation direction was aligned with travel direction. The bead-side deposit bias is an advantage based on preliminary horizontal V-groove welding procedures using ceramic backing. Electrode rotation can offset the effects of gravity, promoting a smoother bead and fusion profile.

Finite element analysis on the propagation characteristics of laser-generated surface acoustic wave in V-groove weld

Thick-walled structures, such as marine engineering and rail transportation, are widely used in modern society. V-groove welding is a common welding method in thick structures. At the same time, the V-groove weld is also the area of a thick-walled structure in which defects are most easily formed. Laser-generated surface acoustic waves are a promising non-destructive testing method in most fields. This study examined the propagation characteristics of laser-generated surface acoustic waves in a V-groove weld. A two-dimensional finite element model with Q345 steel was constructed. A thermoelastic mechanism was adopted to generate the wave. The temperature and displacement fields were analyzed in detail. The results showed that wave transmission, reflection, and mode conversion are generated with an R wave at the junction, and the dispersion phenomenon of the R wave occurred in the welded area.

Bending Performance of the Steel Longitudinal Joint for Quasi-Rectangular Pipe-Jacking Tunnels

Pipe jacking is a special tunneling method for installing underground pipelines or tunnels with the minimum surface disruption. Longitudinal pipe-to-pipe joints are important for tunnels with the pipe-jacking technique. The longitudinal joint generally adopts the socket type, that is, a bell-and-spigot joint, designed for use with gaskets work well for jacking. The joints should have sufficient bearing surfaces to transmit the required axial thrust and have the ability to resist lateral forces from ground movements during tunnel construction and operation. This paper focuses on the mechanical performance of the longitudinal joint of the superlarge cross section quasi-rectangular pipe-jacking tunnel under the action of local bending moments caused by lateral forces. A full-scale ultimate bending test of the local joint specimen was carried out to study its bearing mechanism, ultimate bearing capacity, and failure mode. Numerical simulations were then employed to analyze the performance of the joint specimen and were verified by the experimental results. The damage evolution process and bearing mechanism changes of the joint specimen were analyzed by numerical simulations. The results show that the bell part contributes much more to the bending of the joint than the spigot part. The bolt contributes little to the bearing capacity and stiffness of the joint but plays a role in positioning the pipe to pipe in the installation. The bending failure of the joint is characterized by weld fractures between the longitudinal rib and its flange next to the V-groove weld at the bottom of the bell part. The V-groove weld connecting the bottom of the spigot part and the bell part primarily affects the bending capacity of the joint.

Effect of welding mode and filler metal on microstructure and mechanical properties of dissimilar joints of S900MC thermomechanical steel to St52 carbon steel welded by gas tungsten arc welding

In this research, S900MC thermomechanical steel was jointed to St52 carbon steel through a gas tungsten arc welding process in the continuous and pulsed modes. The welding was performed in two different weld designs of V-groove and close square, with and without using an ER70S filler metal, respectively. Furthermore, the microstructure, hardness, and tensile strength of the joints were investigated. A bainitic microstructure was observed in the weld metal of the samples jointed in the continuous mode. While the weld metal microstructure of the pulsed joints was changed from a ferritic microstructure to a tempered martensitic microstructure by implementing filler metal in the V-groove weld design. In all joints, the heat-affected zone was narrower at the S900M side and had a fine bainitic microstructure. Among all joints, the maximum hardness of 389 HV was achieved for the weld metal of V-groove joints welded in the pulsed mode. At a normal strain rate, there was no considerable contrast between the yield and tensile strength of all joints, however, the elongation of the continuous joints was better than that of the pulsed joints. Increasing the strain rate led to the drastic improvement of yield and tensile strength of the joint welded in the continuous mode without using filler metal.

Multiple weld seam laser vision recognition method based on the IPCE algorithm

Robotic weldingis a critical technology in manufacturing. Vision sensor is critical for increasing the flexibility and adaptability of robot welding, and the line-structured laser(LSL) visionsensor, in particular, is a long-standing research hotspot in robot intelligent welding.The key technology of the LSL vision sensor used in robot welding is the weld seam recognition algorithm.However, the common weld seam recognition algorithm is hampered by heavyarc and spatter noise during welding. Furthermore, many common weld seam recognition methods can only recognize specifictypes of weld seams and have limitations in terms of flexibility and robustness. To overcome thesechallenges,in this paper, we present a fast, accurate, and robustmultiple-type weld seam recognition algorithm.The algorithm consists primarily of our proposed dynamic ROI method, local adaptive threshold method, internal propulsioncenter extracting(IPCE)algorithm, a weld seam edge point detection operator, and a center analyzing method. Experiment results show that the proposed algorithm can recognize multiple types of weld seams, including I-groove butt weld seams, V-groove butt weld seams, single bevel groove butt weld seams, lap weld joints, etc., even in the presence of heavy arc and spatter noise.

Effect of Transverse Restraint on Welding Residual Stress in V-Groove Butt Welding

When evaluating the safety of steel structures, welding residual stress is used as the secondary load and if there is any restraint, the yield stress of the base material is used for secondary load, regardless of the size of the restraint. Of late, as the yield stress of members is increasing with the increase in the use of high-strength steels, the proportion of the residual welding stress in the total load during the evaluation of the safety of structures is increasing. Therefore, it is necessary to investigate the effect of the size of the restraint on the residual welding stress, determine reasonable residual stress according to the size of the restraint, and apply the residual stress as a secondary load. To investigate the effect of constraint conditions on residual welding stress, thermoelastic–plastic analysis was performed for different member thicknesses, yield stresses, and constraint sizes. The restraint did not affect the residual stress in the direction of the weld line but did affect the residual stress in the direction perpendicular to the weld line. The restraint moved the tensile stress to the compression stress in the direction perpendicular to the weld line at the first layer of the weld and moved the compression stress to the tensile stress at the middle and final layers of the weld. The change in residual stress was the largest in the middle of the weld.

Research on the deviation sensing of V-groove weld seam based on a novel two channel acoustic sensor

It is essential to sense the deviation of weld seam real timely in robotic welding process. However, welding process always accompanied with high temperature, strong arc light, and background noises, which significantly affects the application of sensors. In this study, a novel acoustic sensor was developed. This sensor consists of two microphones. Based on the sound signals collected by these two microphones, the deviation of weld seam was detected. The frequency response of the developed acoustic sensor was studied through simulation method firstly, and then, the sensing performance of it was analyzed with experiments. The experimental results show that the developed acoustic sensor has a linear property for the deviation detection of V-groove weld seam. This research provides a novel method for weld seam tracking.

CHARACTERIZATION OF WELD HEAT INPUT EFFECTS ON MECHANICAL PROPERTIES OF Cr-Mo STEEL BAR USING TIG WELDING PROCESS

Welding as an energy-consuming process is inevitable as-welded joint can be subject to various loads without failure. Therefore, this paper presents the welding thermal cycle of Cr-Mo steel bar (ASTM A304) of dimensions 100 by 50 and various thicknesses of 5, 10- and 15-mm. Pure tungsten with 2% thoriated TIG electrodes sizes 1.6 mm X 175 mm, 2.4 mm X 175 mm, and 3.2 mm X 175 were used without filler materials for the welding process. A double V-groove weld joint, with a moving heat source, was employed to determine the temperature fields and transformation in the single-pass butt-welded joint. A calibration process was attached at each point of interest using a datalogger type K-type thermocouple 3-channel–LU-MTM-380SD during the welding process on the Cr-Mo steel bar. The results showed that the welding temperature became higher at the welding centreline and decreased towards the edges of the bar. An indication that a weld thermal cycle is a veritable tool, a function of heat input to access likely consequence of the welding process at both welded and parent metal portions of steel bar. Design of Experiment using Taguchi L9 orthogonal array matrix L9(3^4), Factors:4 and Runs:18 in Minitab 17 Taguchi Design Method that suited the experimental method used. Taguchi’s L9 orthogonal array to restrict the number of experimental runs was used for the design of the experiment (DOE). Mechanical and Microstructure tests were carried out on the samples to investigate the effect of weld heat input. The hardness test result showed that samples C15 and D15 have the highest hardness values 165.0HV and 164.0HV respectively at Base metal (BM) 20mm away from weld centreline and it was also observed that samples C15 and D15 have the highest impact values 48.53J and 48.7J respectively. The microstructure of the C15 at the weld zone WZ, which consists majorly of pearlite and less ferrite, BM shows the appearance of alpha ferrite and pearlite and heat-affected zone HAZ consists majorly of pearlite and a very small proportion of ferrite resulted in increased hardness and impact values at the HAZ.

Welding-induced Residual Stresses in U-Ribs of a Steel Bridge Deck

To calculate the welding-induced residual stresses in U-ribs of the steel deck plate and conduct quantitative analysis of influential factors, the U-ribs of steel deck plate of Xinghai Bay Bridge was taken as the research object. In the ABAQUS finite element software, the local models of U-ribs of steel deck plate were established. Nodal body force loads, i.e., heat generation rate, of the double ellipsoidal heat source models were applied via the compiled subsidiary Dflux program. The welding process of the v-groove welds was simulated, to obtain the residual stresses distribution in the top plate and U-rib plates. The influence of thickness of top plate and angle of welding groove on the residual stresses in the U-ribs were studied. The results show that the welding-induced residual stresses calculated by the numerical method proposed in this paper agree well with the experimental data. The maximum residual stresses in the top plates and the U-rib plates all occur near the welds, which exceeds the yielding limitation of the material. As the thickness of top plate increases, the maximum values of residual stresses in the top plates and U-ribs increase. However, with the increase of groove angle, the maximum values of residual stresses in the top plates and U-rib plates decrease.

Influence of thermo-mechanical material properties on the structural response of a welded butt-joint by FEM simulation and experimental tests

This paper deals with the development of a Finite Element (FE) model for the simulation of a two-passes V-groove butt weld joint. Specifically, in order to reduce the computational costs and the efforts aimed to the numerical evaluation of residual stresses distribution in welded joints, a sensitivity analysis has been performed to quantify the level of accuracy provided by the model when the strict dependence of some material properties on the temperature is neglected. Before proceeding with the sensitivity analysis, the reliability of the proposed FE model was assessed against an experimental test; a good agreement between numerical and experiment results has been achieved.In detail, the material properties involved in this sensitivity analysis are: thermal conductivity, specific heat, Young's modulus and thermal expansion coefficient; the investigated outputs are: temperatures, residual stresses, displacements and angular distortion. Several test cases have been simulated by considering all of these material properties as constant, one at a time or all together. The results analysis showed that the levels of accuracy provided by the different simplifications depend on the selected output. Among the most relevant results, it has been found out that the predicted temperatures distributions are not significantly influenced by the considered material simplifications. The effects on the residual stresses in considering the thermal conductivity and the specific heat as constant are negligible. The hypothesis of a constant thermal expansion coefficient provides an acceptable level of accuracy only in proximity of the weld seam. Finally, concerning the displacements field and the angular distortion of the welded plates, by considering the thermal conductivity and Young's modulus as constant, the effectiveness of the model appears to be compromised.

Efficient and Accurate Start Point Guiding and Seam Tracking Method for Curve Weld Based on Structure Light

Start point guiding and seam tracking are important parts of the robot’s intelligent welding process. However, some start point guiding methods have a large amount of calculation and low accuracy. In addition, due to the large curvature of the curved weld, the problem of visual advance in seam tracking should be solved. Therefore, an efficient and accurate start point guiding and seam tracking method for curve weld is proposed in this article. First, according to the characteristics of structural light of different welds, more efficient and accurate start point detection algorithms are proposed for curve v-groove welds and curve lap welds. The extraction of key characteristic points and the judgment of the relationship between them could achieve efficient weld start point detection, and the reasonable robot speed planning during the start point searching process could improve the accuracy of the start point guiding. Besides, a sliding data queue method with cubic B-spline fitting is proposed to overcome the visual advance problem and achieve accurate seam tracking of curve welds. The sliding data queue method can plan the data queue automatically, and improve the computational efficiency by reducing the amount of data to be processed. Cubic B-spline fitting can reduce the measurement error and eliminate the data fluctuation, so as to obtain a smooth welding trajectory. The experimental results show that the proposed method could achieve efficient and accurate start point guiding and seam tracking of curve v-groove weld and lap weld.

Investigation of feed-forward back propagation ANN using voltage signals for the early prediction of the welding defect

The research paper investigates the prediction capability of the artificial neural network for weld quality assessment from the captured voltage signals in a gas metal arc welding process. The bead-on-plate welds and v-groove welds were made on SA 516 grade 70 material by altering different parameters such as stickout distance, gas flow rate and travel speed. The voltage signals of each weld were captured using a data acquisition system having 8000 Hz data acquisition rate. The descriptive statistics of the voltage data such as mean, standard error, median, mode, standard deviation, sample variance, kurtosis, skewness, minimum and maximum corresponding to bead-on-plate welds and v-groove welds were used for training and testing the neural network respectively. The quality of the weld was assessed by the visual inspection, and from control charts plotted using voltage data. Overall classification accuracy of 94.7% was achieved in the training process. The feed-forward back propagation neural network predicted the quality of test v-groove welds accurately with a 90.9% prediction rate. The results proved that the developed method is promising for the immediate and early prediction of the weld quality.

Algorithms of mathematical models for fast multi-pass weld-bead drawing technique in V-groove welding

This study proposes an algorithm by using bead sequences and drawing techniques for multi-pass V-groove welding. Several points were prepared to form the weld bead shape. Then, a spline method called piecewise cubic Hermite interpolation was applied to describe the smooth curve shape of the multi-pass weld beads in Cartesian coordinates. This study simply considers the physical behavior of weld pool, such as surface tension, to describe the bead shapes differently along the layer position bead sequence. These techniques are useful to improve the welding procedure specification and thus reduce the time consumed in drawing the bead shapes to 1 s for thick-plate welding process.

A strain-controlled fracture assessment for submarine thin-walled pipes with V-groove welds and circumferential embedded cracks

Abstract In the offshore industry, oil and gas are commonly transported with thin-walled clad pipes. Reel-lay is a widely used method to install clad pipes. During the installation and service process, engineering critical assessment (ECA) is usually required to guarantee safety. Most of the ECA methods pertain to surface cracks. The DNV-RP-F108 standard indicates that an embedded crack can be transformed into a surface crack in evaluation, and the result is still conservative. However, the evaluation can be over-conservative at times, meanwhile, the effect of the weld material as well as groove shape is not considered. In this work, a more direct assessment of welded clad pipes with a circumferential embedded crack is proposed based on a modified reference strain approach. A strain-controlled boundary condition is applied, and various pipe and weld geometrical shapes are considered in the analysis matrix. Two plugins based on Python script are developed to circularly create a lot of numerical models. Hundreds of regression analyses based on the linear relationship between normalized J integral and nominal strain are implemented. An analytical solution of the peak J integral of the embedded crack is proposed, and the solution is proved to be close to FEA.