Weld Seam Width Research Articles

Influence of Deck Butt Weld Seams on Fatigue Life of Steel Bridge Decks Pavement: Parameter Optimization

Abstract The butt weld at the connection between orthotropic steel bridge decks (OSBDs) can potentially pose a hazard to the fatigue endurance of the steel bridge deck pavement. This study aims to optimize the parameters of the butt weld seam using finite element (FE) analysis. The optimized parameters will provide valuable guidance for the design of pavements with a focus on antifatigue properties. Initially, the dynamic modulus of the epoxy asphalt mixture (EAM) was determined through laboratory experimentation at various frequencies and temperatures. These material parameters were then used to compute the pavement’s fatigue life. Additionally, a well-established FE model was employed to analyze the deformation and fatigue life of the pavement structure. The validity of the model was verified by the theoretical calculation results. Various factors were considered, including vehicle velocities, pavement temperatures, and weld seam misalignments as well as weld seam dimensions such as height and width. The analysis was conducted using a three-dimensional steel bridge model. The results showed that decreasing pavement temperature, weld seam height, and misalignment led to an increase in pavement fatigue life. Conversely, reducing the weld seam width resulted in a decrease in fatigue life. Furthermore, the study investigated the coupling effect of different weld seam heights and widths on the fatigue life of the pavement. Contour figures were used to establish the parameter relationship formula for weld seam height and width. These findings are significant for pavement and deck designers because they enhance the understanding of the sensitivity of weld seams as design variables affecting the fatigue characteristics of pavement structures. Moreover, special attention should be given to the impact of welding parameters on the fatigue design of steel bridge deck pavement under high-temperature conditions of pavement structures.

Welding of thin stainless-steel sheets using a QCW green laser source

Bipolar plates are structured thin metal sheets and are, next to the membrane electrode assembly (MEA), one of the main components of polymer electrolyte membrane fuel cells. One of the production steps of such bipolar plates is the joining process of its two halves. Laser welding is a suitable method for such an application since it is fast, non-contact, automatable, and scalable. Particularly important aspects of the weld seam are the weld seam width and depth. In this paper, welding of stainless-steel material analogous to materials used in bipolar plates is examined. For this purpose, a newly developed quasi continuous wave (QCW) green laser source with higher beam quality is employed to assess the effect of the wavelength and the spot diameter on the welding of stainless-steel material. By using various focusing lens, different sized beam diameters below 20 µm are achieved and their influence on the final welding result—specifically concerning the seam width—are analyzed. With welding speeds starting at 500 mm/s, reduced weld seam widths (≤ 100 µm) are realized, particularly with a focusing lens of 200 mm focal distance. The suitability of such a process for thin channels of under 75 µm width is examined.

Impact of fume on two-channel-pyrometric temperature measurements and process stability during Laser Powder Bed Fusion

State of research indicates that two-channel-pyrometry based temperatures measurements during laser powder bed fusion are influenced by the amount of fume in the process zone. Different absorption coefficients of the fume in relation to the two pyrometer measurement wavelengths can lead to deviating temperature measurements. Further, fume can partially absorb and scatter the process laser, which reduces the effective laser power in the process zone or leads to defocusing effects. Up until now, the individual impact of these influencing factors on the measured temperatures is unknown. This study investigates the influence of fume during laser powder bed fusion on the two-channel-pyrometric measurement and the process itself individually. This is done by implementing a tungsten lamp into the setup to independently analyze the influence of fume on the pyrometric measurement, while the influence of fume on the laser and hence the process itself is analyzed based on the weld seam width and process temperature. It could be shown that predominantly the process is influenced by fume.

Study on the mechanism of Ni-26W-6Cr alloy solidification cracking: Effect of laser welding heat input

The segregation of P, S, Al, Si and Mo at solidification grain boundary (SGB) results in the formation of the low-melting-point liquid film. As heat input (HI) increases from 76.9 to 214.3 J/mm, upper weld seam width increases by 63 % and lower seam width decreases by 29.3 %. High welding HI generates lower temperature gradient, which could reduce thermal stress. The average hardness of weld metal (WM) drops from 273 to 235 HV and there is a 90 % reduction in the total length of welding solidification crack (WSC). The lower hardness under high HI facilitates the release of thermal stress, which permits the WM to accommodate the tensile stress generated during the solidification phase. Reduced thermal stress decreases the driving force of the formation of WSC.

Classification of Weld Seam Width Based on Detrended Fluctuation Analysis, t-Distributed Stochastic Neighbor Embedding, and Support Vector Machine

Classification of Weld Seam Width Based on Detrended Fluctuation Analysis, t-Distributed Stochastic Neighbor Embedding, and Support Vector Machine

Parametric Study of Laser Welding on Polyamide using Design of Experiments

Laser welding was primarily employed for metals but recent developments in laser technology have enabled its applications in the polymers field. Laser transmission welding or joining of two polymers and metal-polymer has become feasible. The study was mainly aimed to investigate the influence of laser power, speed of welding, and number of passes based on Taguchi orthogonal array on responses by using continuous mode high power diode fiber laser on polyamide. The weld quality was assessed by measuring the strength of weld and width of the weld seam. Initial study on diode fiber laser welding machine and the parameters associated with it was essential to design the experimental layout. Polyamide, which is widely used in the automotive industry was selected as the material and the influence of various parameters on the laser welds were studied using design of experiments. The experimental studies were performed based on orthogonal array method. The responses of the weld were measured using an optical metallurgical microscope. The ideal parameters for maximum joint strength and minimum weld width are investigated using Taguchi method. The multi-objective optimization has been done by applying grey relational analysis to identify the levels of factors that result in the maximum strength and minimum weld seam width.

Denoising and feature extraction of weld seam profiles by stacked denoising autoencoder

Active vision sensing is widely used in intelligent robotic welding for bead detection and tracking. Disturbed by welding noise such as arc light and spatter, it is a hard work to extract the laser stripe and feature values. This paper presents a method for denoising and feature extraction of weld seam profiles with strong welding noise in gas metal arc welding (GMAW) process by using stacked denoising autoencoder (SDAE). This algorithm encodes the images of various butt joints with strong welding noise to several useful intermediate representations, which can be decoded to the image of pure laser stripe in 1-pixel width. The results show little deviations when there are large spatters across the laser stripe. A back propagation neural network (BPNN) is developed to verify the reliability of the intermediate representations gotten from the encoder, in which the intermediate representations are input neurons and the weld seam width is output neuron. The average width error in training dataset and testing dataset is 0.042 mm and 0.061 mm. The results show that this algorithm can extract the weld seam profiles with strong welding noise and extract feature values accurately.

Laser Welding of Grey Cast Iron with Spheroidal Graphite-Influence of Process Parameters on Crack Formation and Hardness

In the investigation at hand, sheets of ferritic and pearlitic grey cast iron with spheroidal graphite are welded using a fiber-laser. The influence of varying laser power and welding speed on the macroscopic characteristics of the weld seam and crack formation are analyzed and discussed. Substantial crack formation with crack densities of up to 2.93 cm−1 are found. Furthermore, hardness measurements are conducted to evaluate the formation of brittle phases within the weld metal and heat-affected zone. Peak hardness values of up to 860 HV0.3 and 975 HV0.3 are identified in EN-GJS-400-15 and EN-GJS-700-2, respectively. Subsequently, a proposition on the dependence of crack formation on weld seam width is given. Furthermore, the influence of nickel-containing filler material on the microstructure, crack formation and hardness is studied. It can be derived from the results that laser-beam welding of grey cast iron with spheroidal graphite requires further research in order to achieve crack-free weld seams and hinder the formation of undesirable, brittle phases.

OCT Capillary Depth Measurement in Copper Micro Welding Using Green Lasers

The transition of the powertrain from combustion to electric systems increases the demand for reliable copper connections. For such applications, laser welding has become a key technology. Due to the complexity of laser welding, especially at micro welding with small weld seam dimensions and short process times, reliable in-line process monitoring has proven to be difficult. By using a green laser with a wavelength of λ=515 nm, the welding process of copper benefits from an increased absorption, resulting in a shallow and stable deep penetration welding process. This opens up new possibilities for the process monitoring. In this contribution, the monitoring of the capillary depth in micro copper welding, with welding depth of up to 1 mm, was performed coaxially using an optical coherence tomography (OCT) system. By comparing the measured capillary depth and the actual welding depth, a good correlation between two measured values could be shown independently of the investigated process parameters and stability. Measuring the capillary depth allows a direct determination of the present aspect ratio in the welding process. For deep penetration welding, aspect ratios as low as 0.35 could be shown. By using an additional scanning system to superimpose the welding motion with a spacial oscillating of the OCT beam perpendicular to the welding motion, multiple information about the process could be determined. Using this method, several process information can be measured simultaneously and is shown for the weld seam width exemplarily.

FEA of SAW penetration of Ramor 500 steel

Abstract Ramor 500 steel plates are used as a ballistic material due to their greater hardness and strength properties. This steel can be produced with a 2-30 mm thickness sheet which may attain 505-590 HV hardness. In the present work, Ramor 500 steel pairs are joined using a submerged arc welding (SAW) process and taking various parameters into consideration. An austenitic additional wire is used for the welding process which contains Cr, Ni, and Mn. The source model prototype was developed using ANSYS software and considering a time-dependent three dimensional thermal model with source cooling. The highest tensile stress voltage value was determined in the sample applying a constant current of 250 A, 25 V and 30 cm × min-1welding speed. It was observed that the welding seam width increases as welding tension grows and that welding height and depth increase and decrease more or less in tandem. A ANSYS thermal cooling analysis revealed that welding tension grows with heat transfer which increases 15 mm from the main center of the welding area.

FEA of SAW penetration of Ramor 500 steel

Abstract Ramor 500 steel plates are used as a ballistic material due to their greater hardness and strength properties. This steel can be produced with a 2-30 mm thickness sheet which may attain 505-590 HV hardness. In the present work, Ramor 500 steel pairs are joined using a submerged arc welding (SAW) process and taking various parameters into consideration. An austenitic additional wire is used for the welding process which contains Cr, Ni, and Mn. The source model prototype was developed using ANSYS software and considering a time-dependent three dimensional thermal model with source cooling. The highest tensile stress voltage value was determined in the sample applying a constant current of 250 A, 25 V and 30 cm × min-1welding speed. It was observed that the welding seam width increases as welding tension grows and that welding height and depth increase and decrease more or less in tandem. A ANSYS thermal cooling analysis revealed that welding tension grows with heat transfer which increases 15 mm from the main center of the welding area.

Fiber laser welding of AA 5754 in the double lap-joint configuration: process development, mechanical characterization, and monitoring

Aluminum alloys are widely spread in many industrial sectors due to their desirable characteristics as low density, good formability, high specific strength, and good resistance to corrosion. Autogenous laser welding is a technology that enables the use of these materials in the industrial process due to its high repeatability, reliability, and ease of automatization. In particular, in automotive applications, Al-alloys are welded in lap-joint configurations with more than 2 layers of material. The welding condition should be monitored in order to detect the complete penetration, hence guaranteeing the appropriate weld resistance. The use of non-invasive and coaxial monitoring solutions is highly desirable for the identification of weld defects during the process. This study investigates an autogenous laser welding process and monitoring in the double lap-joint configuration of sheets of AA 5754. First, the process parameters are investigated to identify the geometrical and mechanical characteristics of the resultant welding seams at different process conditions. The employed high-brilliance 3 kW fiber laser provided the possibility of reading the back-reflected light signal from an internal photodiode. The capability of this signal to be used as a non-invasive, coaxial, and remote monitoring system in order to predict the process outcome was tested. In the experiments the back-reflected light intensity could be correlated to the weld seam width at the second interface, as well as the strength of the joint to shear. Finally, the monitoring signal behavior was demonstrated under simulated weld defect conditions. The results show that weld anomalies such as lack of penetration, misalignment, and gap formation can be sensed through the monitoring approach.

Determination of notch factors for welded butt joints based on numerical analysis and metamodeling

Fatigue evaluation based on the effective notch stress approach requires stress concentration factors for idealized notch geometries. In this paper, stress concentration factors are calculated numerically for different idealizations of the weld geometry. The joints covered here are one-sided Y-butt joints and two-sided DY-butt joints, each with partial and full penetration. The variable parameters of the finite element models are the weld flank angle, the notch radius, the sheet thickness, the ratio of weld seam width to sheet thickness, and the ratio of height of non-fused root face to sheet thickness. Existing estimation formulae for stress concentration factors will be compared with new methods for stress concentration factor estimation: (a) polynomial regression using mixed terms and (b) artificial neural networks. These two methods show similar or superior quality compared with the existing estimations which is expressed through lower estimation errors with respect to the numerically calculated stress concentration factors. The database for the regression analysis using methods (a) and (b) consists of a total of 11,871 design alternatives obtained by finite element analysis. In addition to the improved quality of prognosis, the range of allowable geometrical parameters is significantly increased compared with the existing formulae. The methods (a) and (b) provide a possibility to a fast estimation of stress concentration factors of sufficient quality for a large range of geometrical weld seam parameters. The presented formulae could also be part of a programmed solution.

Welding penetration monitoring for pulsed GTAW using visual sensor based on AAM and random forests

Abstract On-line welding penetration state monitoring based on passive visual sensing technology in pulsed gas tungsten arc welding (GTAW) has been a hot research topic in industry and academia. Passive vision sensing technology has some disadvantages. It is easy to be affected by some common disturbance during pulsed GTAW, like spattering, the change of arc intensity, the slightly change of focal length and viewing angle of visual sensor, etc. This paper proposed an intelligent penetration monitoring methodology for GTAW by combining pattern-based visual feature extraction method and supervised machine learning method. The proposed methodology mainly includes two parts: (a) visual features extraction for weld pool images based on active appearance model (AAM); (b) the implementation of penetration monitoring based on supervised machine learning method, random forests (RF). The extracted weld pool visual features include width, length and area size of weld pool. Then the extracted features are utilized to train RF model. Further, the trained RF model can implement the evaluation of penetration states and backside weld seam width. The experiments verify that the proposed method is effective with high accuracy and robustness, which also lays the foundation for online welding penetration control.

Induction Weld Seam Characterization of Continuously Roll Formed TRIP690 Tubes

The weld seam characteristics of continuously roll formed and induction seam welded TRIP690 tubes were examined in this work. These tube are subsequently used in automotive hydroforming applications, where the weld seam characteristics are critical. The induction seam welds are created through a solid-state welding process and it was shown that by increasing the induction frequency by 26%, the weld seam width within the heat affected zone (HAZ) reduced due to a plateau in the hardness distribution which was a result of a delay in the transformation of martensite. 2D hardness distribution contours were also created to show that some of the weld conditions examined in this work resulted in a strong asymmetric hardness distribution throughout the weld, which may be undesirable from a performance perspective. An increase in the pressure roll force was also examined and revealed that a wider total weld seam width was produced likely due to an increase in temperature which resulted in more austenitization of the sheet edge prior to welding. The ring hoop tension test (RHTT) was applied to the tube sections created in this work. A Tensile and Notch style ring specimen were tested and revealed excellent performance for these welds due to high peak loads (~17.2 kN) for the Notch specimens (force deformation within weld) and lower peak loads (~15.2 kN) for the Tensile specimens for which fracture occurred in the base metal.

Reduction of friction stir welding setup loadability, process forces and weld seam width by tool scaling

Friction stir welding is an increasingly used method to join similar and dissimilar materials with excellent mechanical weld seam properties. However, in certain cases, friction stir welding is restricted by high mechanical loads as a result of high forces and torques during the welding process. This relates in particular stiffness-reduced machine concepts which may cause path deviations, massive vibrations and insufficient tool plunging. Against this background, this investigation demonstrates a method to reduce forces and torques by tool scaling. Due to the stepwise diameter reduction of shoulder and probe and a simultaneous adjustment of the process parameters, a significant force and spindle torque reduction was achieved. Furthermore, it could be shown that tool scaling does not affect the mechanical strength properties. The experimental investigations were carried out with EN AW 5754 H11 with a sheet thickness of 8 mm. The weld seams were performed on a robotized friction stir welding setup (KUKA KR500) with a maximum axial force of 10 kN. Based on a 26-mm shoulder and a 10-mm pin diameter, it could be demonstrated that the general weldability of 8 mm EN AW 5754 H11 is restricted (incomplete tool plunge) by the maximum axial force of the robotized friction stir welding setup (10 kN). Due to the stepwise reduction of the shoulder and probe diameter from 26 mm to 20.8 mm and 10 mm to 8 mm, respectively, a general weldability and weld seams without irregularities could be achieved by the equal robotized friction stir welding setup. Furthermore, it could be shown that an axial force and spindle torque reduction from 10 kN to 4 kN and 29 Nm to 10 Nm, respectively, was obtained due to further reduction of the tool diameters.

Flux-Free Diffusion Joining of SiCp/6063 Al Matrix Composites Using Liquid Gallium with Nano-Copper Particles in Atmosphere Environment.

A new method for flux-free diffusion joining of aluminum matrix composites reinforced with SiC particles (SiCp/Al MMCs) in atmosphere environment has been developed. Liquid gallium and nano-copper particles were employed as filler metal under joining temperatures ranging between 400 °C to 480 °C, with a holding time of 2 h and pressure of 3 MPa. The results showed that 65 vol.% SiCp/6063 Al MMCs were successfully joined together. X-ray diffraction (XRD) analysis confirmed the presence of Ga2O3 at the fracture. Meanwhile, neither copper oxide nor aluminum oxide was detected. The formation of Ga2O3 can protect nano-copper particles and SiCp/6063 Al MMCs from oxidation. The width of weld seam tended to be narrowed from 40 μm to 14 μm gradually with increasing temperature from 400 °C to 480 °C. The maximum shear strength level of 41.2 MPa was achieved with a bonding temperature of 450 °C. The change of the strength was due to the adequate elements’ mutual diffusion and solution, as well as the change of the quantity and morphology of intermetallic compounds in the weld seam, such as Al2Cu and Cu3Ga. When the diffusion joining temperature reached 440 °C or above, the leak rate of the specimen remained under 10−10 Pa·m3/s.

Laser transmission welding of thermoplastic with beam wobbling technique using particle swarm optimization

Laser transmission welding is growing day by day with an increase of the uses of thermoplastic materials. This article presents the effect of various process parameters on weld strength and weld seam width obtained. The transparent polycarbonate and black carbon filled PMMA, each of 2.8 mm thickness have been joined by using low power laser. Here, effect of wobble frequency and wobble width are studied along with other process parameters. It is observed that weld seam width much depends upon the wobble width and the effect of wobble frequency is minimum. It has been observed that laser beam wobbling provides the greater weld strength by enlargement of joint area. Moreover, Beam wobbling plays a significant role to achieve better weld strength and weld width. Response surface methodology has been used to model the laser welding process parameters and responses of welding through regression analysis. The results of ANOVA reveal that the models formed appropriately predict the responses within the range of process parameters. A confirmation experiment has also been conducted to validate the results. A multi objective optimization has been used to find the optimum solution by Particle swarm optimization technique.

Fabrication of bi-layer PMMA and aluminum 6061-T6 laminates by laser transmission welding: Performance prediction and optimization

Laser transmission welding can be effectively used in fabrication of laminated parts. In the present work an attempt was made to fabricate a polymeric laminate structure made of polymathic methacrylate (PMMA) and aluminum 6061-T6 by laser transmission welding process. A series of laser welding experiment has been carried out to analyze effect of laser power, welding speed, focal position and axial pressure on lap shear force and weld seam width. Response surface methodology including regression analysis, analysis of variances and desirability approach function has been utilized here to analyze the processing data. It is found from the results that focal position has greatest influence on both the lap shear force and weld bead width. Optimization is also carried out in two different criteria for achieving desired welding performance. The optimization results obtained by this approach are consistent well with the results measured through confirmatory experiments.

Characteristics of an Implantable Blood Pressure Sensor Packaged by Ultrafast Laser Microwelding.

We propose a new packaging process for an implantable blood pressure sensor using ultrafast laser micro-welding. The sensor is a membrane type, passive device that uses the change in the capacitance caused by the membrane deformation due to applied pressure. Components of the sensor such as inductors and capacitors were fabricated on two glass (quartz) wafers and the two wafers were bonded into a single package. Conventional bonding methods such as adhesive bonding, thermal bonding, and anodic bonding require considerable effort and cost. Therefore CO2 laser cutting was used due to its fast and easy operation providing melting and bonding of the interface at the same time. However, a severe heat process leading to a large temperature gradient by rapid heating and quenching at the interface causes microcracks in brittle glass and results in low durability and production yield. In this paper, we introduce an ultrafast laser process for glass bonding because it can optimize the heat accumulation inside the glass by a short pulse width within a few picoseconds and a high pulse repetition rate. As a result, the ultrafast laser welding provides microscale bonding for glass pressure sensor packaging. The packaging process was performed with a minimized welding seam width of 100 μm with a minute. The minimized welding seam allows a drastic reduction of the sensor size, which is a significant benefit for implantable sensors. The fabricated pressure sensor was operated with resonance frequencies corresponding to applied pressures and there was no air leakage through the welded interface. In addition, in vitro cytotoxicity tests with the sensor showed that there was no elution of inner components and the ultrafast laser packaged sensor is non-toxic. The ultrafast laser welding provides a fast and robust glass chip packaging, which has advantages in hermeticity, bio-compatibility, and cost-effectiveness in the manufacturing of compact implantable sensors.