Poor Weld Research Articles

A detection and configuration method for welding completeness in the automotive body-in-white panel based on digital twin

To address the problems of poor welding completeness and inefficient configuration for defective automotive body-in-white panels, we propose a method for detecting and configuring the welding completeness of automotive body-in-white panels based on digital twin (DT) and mixed reality (MR). The method uses DT to build an MR-oriented DT framework for the detections and configuration of body-in-white panel welding completeness. We propose a method to build a DT knowledge base for panels, a Yolov4-based welding completeness detection method, and a MR-based configuration method for the welding completeness in panels. Our team develop a panel welding completeness detection and configuration system to fully validate the effectiveness of the method.

Infrared Visual Sensing Detection of Groove Width for Swing Arc Narrow Gap Welding

To solve the current problem of poor weld formation due to groove width variation in swing arc narrow gap welding, an infrared passive visual sensing detection approach was developed in this work to measure groove width under intense welding interferences. This approach, called global pattern recognition, includes self-adaptive positioning of the ROI window, equal division thresholding and in situ dynamic clustering algorithms. Accordingly, the self-adaptive positioning method filters several of the nearest values of the arc’s highest point of the vertical coordinate and groove’s same-side edge position to determine the origin coordinates of the ROI window; the equal division thresholding algorithm then divides and processes the ROI window image to extract the groove edge and forms a raw data distribution of groove width in the data window. The in situ dynamic clustering algorithm dynamically classifies the preprocessed data in situ and finally detects the value of the groove width from the remaining true data. Experimental results show that the equal division thresholding algorithm can effectively reduce the influences of arc light and welding fume on the extraction of the groove edge. The in situ dynamic clustering algorithm can avoid disturbances from simulated welding spatters with diameters less than 2.19 mm, thus realizing the high-precision detection of the actual groove width and demonstrating stronger environmental adaptability of the proposed global pattern recognition approach.

Direct evidence of interfacial crystallization preventing weld formation during fused filament fabrication of poly(ether ether ketone)

Poly(ether ether ketone) (PEEK) is a high-performance, semicrystalline thermoplastic that has attracted significant interest for material extrusion additive manufacturing techniques such as fused filament fabrication (FFF) but remains beset by poor weld strength. Here, it is observed that under typical processing conditions that surface crystallization prevents effective weld formation between printed layers, leading to weak and brittle welds. Utilizing atomic force microscopy, differential scanning calorimetry, bulk tensile fracture testing, and mode III tear testing, appropriate processing conditions and post-print annealing conditions have been developed to improve the weld strength of FFF-PEEK. After printing PEEK in an amorphous state through careful control of the thermal gradients during printing a two-step annealing procedure yields crystalline PEEK welds that are 6–8 times stronger than welds in FFF-PEEK that crystallized during printing. • Fused filament fabrication of PEEK leads to weak and brittle welds with printed fibers. • Atomic force microscopy is used to map the weld microstructure of PEEK and is correlated with measurements of weld strength. • Interfacial crystallization between fibers inhibits weld formation, reducing the strength of fused filament fabricated PEEK. • A printing and annealing procedure reduces interfacial crystallization, improving PEEK weld strength from 7 MPa to 37 MPa.

An Incremental Grey-Box Current Regression Model for Anomaly Detection of Resistance Mash Seam Welding in Steel Mills

Annealing and galvanization production lines in steel mills run continuously to maximize production throughput. As a part of this process, individual steel coils are joined end-to-end using mash seam welding. Weld breaks result in a production loss of multiple days, so non-destructive, data-driven techniques are used to detect and replace poor quality welds in real-time. Statistical models are commonly used to address this problem as they use data readily available from the welding machine and require no specialized equipment. While successful in finding anomalies, these statistical models do not provide insight into the underlying process and are slow to adapt to changes in the machine’s or material’s behavior. We combine knowledge-based and data-driven techniques to create an incremental grey-box welding current prediction model for detecting anomalous welds, resulting in a powerful and interpretable model. In this work, we detail our approach and show evaluation results on industrial welding data collected over a period of 15 months containing behavioral shifts attributed to machine maintenance. Due to its incremental nature, our model resulted in two-thirds fewer rejected welds compared to statistical models, thus greatly reducing production overhead. Grey-box modeling can be applied to other welding features or domains and results in models that are more desirable for the industry.

Effects of welding angle on microstructure and mechanical properties of longitudinal weld in 6063 aluminum alloy extrusion profiles

In order to explore the effects of welding angle on microstructure and mechanical properties of longitudinal weld, a porthole die with different welding angles was designed and manufactured, by using which various extrusion experiments were carried out. The microstructure and mechanical properties of longitudinal weld were characterized, and the extrusion process was simulated. The results show that as welding angle increases, the longitudinal weld gradually transforms from a linear shape to a cross shape. A larger welding angle will not only reduce stress triaxiality and strain rate in the main welding zone, but also increase area of the dead metal zone, thus leading to poor welding quality. The crystal orientations of <100> and <111>//ED can be found in the welding zones of the profiles extruded by using the dies with different welding angles, and the texture components exhibit significant differences. There are a certain number of dislocations, a small amount of Mg2Si precipitates and insoluble iron-containing intermetallic compounds in the welding zones. By comprehensively considering the influence of welding angle on welding quality, extrusion load, effective stress and strain of the porthole die, the welding angle ranges under different welding quality requirements were determined. It is found that the welding quality is higher when the range of welding angle is 38–46°, the welding quality is lower when the range of welding angle is 54–68°. If taking in account both of welding quality and porthole die strength requirement, the preferred welding angle is recommended to be in the range of 46–54°.

Failure Investigation and Analyses of Ni-Based Super Alloy Barrel Used in Twin Screw Extruder

Barrel cooling system is very critical for the extruder application such as polymer compounding, reactive extrusion, food processing and plasticizing etc., in order to achieve the required quality of the output material. One of the typical failures of barrel cooling system is water leakage due to poor weld integrity. A few published investigations address the root cause(s) for such failure and provide robust corrective actions to enhance the durability of barrel cooling system from design and manufacturing points of view.However, water leakage from the heater hole of the Inconel 625 barrel from one of our customers has been unique. Macro- examination of the failed barrel reveals multiple cracks inside the heater hole on the barrel top, but no such cracks found on the barrel bottom. With detailed metallographic analysis we observe precipitation of Nickel-Niobium rich gamma prime phase near the heater hole causing increased hardness from 220 to 400HV0.5. Barrels of the other region conforms to precipitation free, austenitic Ni-Matrix typical of Inconel 625 solution annealed condition. Fractography analysis conducted on the cut section clearly shows crack originating from cooling hole and propagated towards the heater hole. Various aspects of the investigation findings were analyzed in detail, arrived at the comprehensive failure mechanism, and concluded that the failure is primarily due to Thermal Fatigue. Also, recommendation to prevent such failures during service has been provided as part of this analysis.

Minimization of defects generation in laser welding process of steel alloy for automotive application

Laser welding (LW) thanks to its flexibility, limited energy consumption and simple realization has a prominent role in several industrial sectors. LW process requires careful parameters’ tuning to avoid generating internal defects in the microstructure or a poor weld depth, which reduce the joining mechanical strength and result in waste. This work exploits a supervised machine learning algorithm to optimize the process parameters to minimize the generated defects, while catering for design specifications and tolerances to predict defect generation probability. The work outputs a predictive quality control model to reduce non-destructive controls in the LW of aluminum for automotive applications.

Optimization of welded K-node in offshore jacket structure including the stochastic size effect

Offshore structures are exposed to cyclic loading and thereby at risk of fatigue failure, especially at the welded joints between trusses in offshore jacket foundations. In this paper, an optimization framework for welded joints considering fatigue damages is presented. The framework can be used to optimize the orientation and location of welds connecting the joint in a welded K-node in offshore jacket structures considering fatigue damage. It is known that longer welds are at higher risk of fatigue failure compared to shorter welds. To account for this, the statistical size effect is modelled using the Karhunen-Loéve expansion which can be used to take into account the effect of longer welds in the damage assessment. The approach is included in the optimization framework and it is shown that using this method it is possible to simulate the effect of having a good welding quality and a poor welding quality using the correlation length and coefficient of variation. The proposed optimization framework is validated on a simple plate structure and the effect of the statistical input parameters in the statistical size effect is examined. The results show that the proposed optimization approach is robust in predicting the expected tendencies for a simple plate structure. Furthermore, a full-scale welded K-node in an offshore jacket structure manufactured using cast steel is optimized with respect to mass. The optimization is performed considering a good quality weld and a poor-quality weld by including the statistical size effect. The results show that using high quality welds will result in lower mass of the K-node.

Comparative study of laser swelding-brazing of aluminum alloy to galvanized steel butted joints using five different filler wires

The purpose of this paper is to provide the gist for the selection of filler wire during the laser welding-brazing of Al to steel. A comprehensive comparison of laser welding-brazing 5052 aluminum alloy to unbeveled galvanized steel using pure Al, AlSi5, AlMg5, AlCu6, and ZnAl2 filler wires were conducted with varied laser beam offset. The comparison was carried out in terms of weld formation, interfacial microstructures, and mechanical properties. The results show that the fluidity of liquid filler is Pure Al < AlSi5 < AlMg5 < AlCu6 < ZnAl2. Too small or too large fluidity will lead to poor weld formation. The interfacial intermetallic compound consisted of layered Fe2Al5 and scattered FeAl3 when pure Al, AlMg5, and AlCu6 filler wires were used. When pure Al filler wire was used, cracks were most likely to occur in the reaction layer. The other four filler wire all improved the crack resistance. The thickness of the reaction layer significantly decreased when AlSi5 filler wire was used. Si element was found as a solid solution in the reaction layer to form Fe2(Al, Si)5 and Fe(Al, Si)3. A large amount of FeZn10 was mixed between Fe2(Al, Zn)5 when using ZnAl2 filler wire. The order of maximum tensile strength of the joints using different filler wires was AlSi5 > AlMg5 > AlCu6 > ZnAl2 > pure Al. The fracture of the joints all occurred at the brittle intermetallic layers when five different filler wires were used.

Estimation of fatigue life parameters of an Alumino Thermic weld on UIC60 rail joint using LEFM

At wheel track contact point, the high stress concentration, poor weld quality, and heterogeneity of weld material are the main factors that cause fatigue crack on any rail weld. Railway network agencies are concerned about the safety of the railway track when it comes to detecting and fixing weld faults to avoid vehicle derailment and loss of lives. This study analysed a numerical simulation of fatigue crack and its evolution under loaded service condition. A 3-D CAD wheel rail weld assembly model was built to study an AT welded joint under fatigue, and for stress concentration factor (SIF) calculation. The results are found by inserting a semi elliptical crack on the rail weld head surface with ANSYS, and then numerical simulation has been performed to get the different three modes of SIF at rail weld crack. The analysis findings data was recorded with critical fracture parameters of SIFs and its number of cycles to failure using LEFM technique and respective results have been plotted. With ANSYS the stress intensity on a crack will be resulted. By using numerical method, the critical crack size and number of cycle load with fatigue life of rail would be determined. The numbers of rail weld inspection per year has been determine by using the maximum number of cycle. The aim of this paper is to develop an effective inspection and maintenance frequency based on rolling contact surfaces crack propagation analyse. This will help to prevent the occurrence of rail failure by taking the required action at the right time, and extend the rail life expectancy, reduce the rail maintenance work and its cost.

All-position welding control system based on machine vision and nonlinear regression

Aiming at the problems of poor welding quality and low degree of automatic welding on the engineering site, a welding process parameter control method based on machine vision and nonlinear regression technology is proposed. Firstly, a vision unit and a peripheral sensor unit are designed to obtain the information of each influencing factor of the welding process parameters. Secondly, a clustering algorithm is used to improve the extraction accuracy of feature point coordinates of weld images. Thirdly, a nonlinear regression fitting method is proposed to determine the mathematical relationship between welding quality at different welding positions and corresponding process parameters. Experimental results show that the control system is easy to operate, and the flexible control of welding process parameters in the whole process is realized. The weld cumulative height and width deviations are less than 0.5 and 0.3 mm, respectively. The welding surface is stable and meets welding requirements. Therefore, this method is of great practical significance in engineering field welding.

Effect of ER5356 Welding Wire on Microstructure and Mechanical Properties of 5083 Aluminum Alloy GTAW Welded Joint

Automatic gas tungsten arc welding experiments of 5083 aluminum alloy were completed, to analyze the weld microstructure and mechanical properties. The influences of welding current, travel speed, frequency, and arc length on weld forming and mechanical properties were studied. When the welding current was 160 A, the travel speed was 380 mm/min, the frequency was 100 Hz, the arc length was 4 mm, and the maximum tensile strength of the welded joint was 296.9 MPa, which was 86.8% of the base metal’s tensile strength. The fracture elongation was 7.8%. No porosity was formed in the weld, but there were poor fusion problems. ER5356 welding wire can improve the problem of poor weld fusion and accommodate Mg element vaporization losses. When the wire feeding speed was 1200 mm/min, the tensile strength of the welded joint can be improved to 315.2 MPa, which was 92.2% of the base material’s tensile strength, and the fracture elongation was 8.5%. The tensile specimens fractured in the heat-affected zone. The fracture surface was characterized as plastic fracture. Introduction Specific strength of aluminum alloy is high, so aluminum alloys reduce the weight of the structure compared with steel structures. Aluminum alloys have a broad application prospect in aerospace, automotive, and marine industries based on their good corrosion resistance, low temperature resistance, good processability, and rich alloy system (Kuk et al. 2004; Wang &amp; Zhang 2015; Canepa et al. 2018; Gaur et al. 2018; Qiang &amp; Wang 2019). In recent years, to reduce the weight of the structure such as trimaran hull and improve speed, aluminum alloys have been more and more applied in shipbuilding. But there are many problems in the welding of aluminum alloy.

Effect of pulse frequency on droplet transfer and weld formation in local dry underwater welding

This paper presents the effect of pulse frequency on the droplet transfer behavior and weld formation in local dry underwater welding (LDUW) based on micro-drainage device. Three different droplet transfer modes: projected transfer, globular transfer and spherical repelled transfer, were observed in the LDUW at the pulse current frequency of 25 Hz to 200 Hz. With the increase of pulse frequency from 100 Hz to 150 Hz, the direction of electromagnetic force changes, and the projected transfer becomes the globular transfer. With the increase of pulse frequency from 150 Hz to 200 Hz, the droplet transfer changes from the globular transfer to the spherical repelled transfer. The droplet transfer frequency decreases with the increase of pulse frequency. The weld formation with no obvious defects and relatedly deeper weld penetration were obtained in the mode of projected transfer, while in the mode of globular transfer, it is opposite. It is necessary to avoid the globular transfer, which would lead to the poor weld formation and minimum weld penetration.

Improving the Mechanical properties of 6061 and 5083 welded joint using Friction stir lap welding

Joining of metal is very important operation in every manufacturing activity. Conventional welding of Al alloys by Tungsten inert gas welding, Metal inert gas welding and Resistance spot welding was reported to produce poor quality weld joints, as the inherent characteristics of the base metal affected the weld properties. Friction stir welding, identified as one of the best alternative is employed to join Al 5083 and Al 6061 in this study. Aluminum alloys, Al 5083 and Al 6061 are welded in lap joint configuration, with SiC nano particles interlayer. The process parameters such as welding speed tool, rotational speed and volume percentage of Nano-powder were optimized by utilizing Response surface methodology, RSM. The joints welded without the SiC nano particle interlayer were observed to possess low mechanical strength at the best welding conditions determined by the RSM.

A comparison of laser-metal inert gas hybrid welding and metal inert gas welding of high-nitrogen austenitic stainless steel

Abstract High-nitrogen austenitic stainless steel (HNASS) has many excellent properties, such as high strength and toughness, high strain-hardening ability, strong corrosion resistance and low magnetization compared with the traditional widely used Ni–Cr austenitic stainless steel. The high nitrogen content in HNASS leads to the welded joint in the risk of many problems, such as nitrogen escape and loss, nitride precipitation, formation of pores and thermal cracks, resulting in the poor welding performance. The HNASS joints without obvious defects were obtained by metal inert gas (MIG) welding and laser-MIG hybrid welding, separately. The microstructures and properties of welded joints were compared. The nitrogen content in fusion zones of the two joints was tested by an oxygen, nitrogen and hydrogen analyzer. The tensile strength and the impact absorption energy of laser-MIG hybrid welded joint were about 27% and 20% higher than those of MIG welded joint, respectively. It could be attributed to the stronger solid solution strengthening effect resulted by the high nitrogen content of laser-MIG hybrid welded joint. The finer grains and the reduction of ferrite and precipitation phase in the microstructure of laser-MIG hybrid welded joint contributed to the improvement of toughness.

Evaluation of the Creep Strength of 9Cr-1Mo-V and 1Cr-1Mo-1/4V Castings and Weldments Using Accelerated Creep Testing

Abstract The traditional method to generate creep data requires several long term tests; in some cases upward of 100,000 h. These tests are often time and cost prohibitive to perform. Creep data in literature are limited to commonly available materials in set processing conditions. This speaks very little to the properties for new materials, alternate processing of existing materials, as well as properties for weldments and heat affected zones (HAZ) that occur in the fabrication of large equipment. Due to this, several methods have been developed for accelerated creep testing. The stress relaxation test (SRT) is one such method and is discussed as the means to evaluate two different materials and their weldments used in the manufacturing of steam turbine casings. Cast 9Cr-1Mo-V material from two different foundries as well as their weldments and HAZ were tested at temperatures between 550 °C and 700 °C. The SRT generated data closely match that given in literature. In a nearly identical test program, cast 1Cr1Mo¼V steel showed anomalies in the weld and HAZ behavior. Further investigation showed that the incorrect weld metal was used, and in a second attempt, poor welding practice lead to premature specimen failure due to Type IV cracking. These two case studies illustrate the ability of the SRT method to accurately predict creep properties and its sensitivity to detect variations in properties, which can make it useful for rapid verification of casting suppliers and welding procedures for high temperature applications.

Fill Time Optimization Analysis In Flow Simulation Of Injection Molding Using Response Surface Method

This study focuses on the analysis of fill time by optimizing the injection molding parameters to reduce the defects that are always found on the plastics part such as poor weld line and part not completely filling which can contribute to mechanical properties of the plastic part. The parameters selected for this study are melting temperature, mold temperature, injection time, and the number of gate positions. Response Surface Method (RSM) was used to determine the most significant and optimum parameters on the fill time. From the result analysis, it is found that the injection time is the most significant parameter that affected the fill time with a 99% contribution. The result shows that there is no interaction between process parameters toward fill time which the injection time is the only major factor that affects the fill time. The improvement increases by 0.07% after the optimization process from 4.278s to 4.281s. The most optimum parameters to longer the injection time are mold temperature at 60°C, injection time at 4s, and the number of the gate with two gates position. Thus, the longer the injection time, it can reduce the defect of molded part in the injection molding process.

Friction stir welding of novel T-phase strengthened Zn-modified Al–Mg alloy

Friction stir welding is extensively used in aluminum alloys for advanced engineering applications. A current challenge for 5 × × × series alloys is their poor welding strength due to the lack of hardening precipitates. Here we report Zn-modified novel Al–Mg alloys with Zn/Mg ratio below 1.0. Compared with 5 × × × series alloys, the strength of the welded alloy can be increased by 100 MPa owing to the distribution of T-Mg32(AlZn)49 hardening precipitates during friction stir welding and the subsequent heat treatment after welding. Fine spherical T″ precipitates and coarsening polygonal T′ precipitates are both observed at the thermo-mechanically affected zone. The bimodal distribution of the precipitates and the widest precipitate-free zone weakened the strength of this region, and thus the welded alloys are fractured at this area. The novel alloy with T precipitates is expected to further stimulate the researchers to improve the properties of traditional 5 × × × series alloy.

Fatigue Fracture of Pie Channel Weld of Sinter Screen: A Metallurgical Insight

Sintering is an agglomeration process to convert iron ore fines into a larger mass suitable to be charged directly into the blast furnaces. A screen separates the incoming iron ore raw materials based on their size fraction. These screens are supported by pie channels. One of these channels failed during operation that led to unwarranted interruption in production. Owing to the criticality of the matter, detailed failure investigation was conducted. It involved visual observations, micro- and macro-fractography to determine the mode of fracture, chemical analysis and microstructure examination using optical and scanning electron microscopes aided with energy-dispersive x-ray spectroscopy and electron probe microanalyzer. The analysis revealed incompatible austenitic stainless-steel filler metal was used for welding mild steel material along with poor welding workmanship as suggested by underfilling and presence of thick layer of welding slag. There was formation of un-tempered martensite in dilution zone (the interface layer between heat-affected zone/fusion zone). The formation of undesirable martensite in the dilution zone is correlated with the time–temperature transformation diagram where the nose of the C-curve got significantly shifted toward the right due to enrichment with chromium and nickel as revealed by electron probe microanalysis. It was concluded that the failure occurred in fatigue mode due to deficiencies in welding and recommendations to prevent failures are also provided.

Effect of beam oscillation on microstructure and properties of laser-TIG hybrid welding of D406A ultra-high strength steel

30Si2MnCrMoVE (referred to as D406A) has not only ultra-high strength but also good toughness, which is the most critical material for solid rocket engine shell. But current methods are low efficient and poor welding quality. In this paper, a laser-TIG hybrid welding with beam oscillation was employed to join 2 mm-thick D406A steel in butt joint. Two beam oscillation modes that are continuous and pulse circular were investigated. It was found that the beam oscillation refined the dendrite structure and was beneficial to the formation of equiaxed grains in the fusion zone, and turned the columnar grains into different orientations and homogenized structures. The continuous circular oscillation had the best stirring effect on the molten pool, and the weld had the finest grain and the most amount of equiaxed grains. As a result, the transverse residual stress obtained using continuous circular oscillating of the weld was the lowest (422 MPa) and the most uniform, 40.6 % lower than the weld without oscillating. Besides, the beam oscillation had little effect on the tensile strength of the weld, but improved the ductility obviously. The strain with continuous circular oscillation was up to 5.9 %, 18 % higher than that of the pure TIG weld.