Electrode Misalignment Research Articles

Finite element analysis for the measurement error of electrostatic accelerometer due to the electrode misalignment

Abstract The electrostatic accelerometer is the key payload of many space missions, such as satellite gravity measurements, space gravitational experiments, with a typical precision requirement from nano-g to femto-g. The measurement error model analysis is an important issue for the electrostatic accelerometer with numerous error sources. The traditional method by theoretical analysis is complicated to evaluate the complete measurement error models quantitatively especially when the machining and assembly errors of the sensor head are considered. Limited by the earth gravity and seismic noise which is much higher than the intrinsic noise, the complete error model of electrostatic accelerometers can also hardly be tested on ground. In this paper, the method by using finite element analysis of the sensor head is studied. The simulation model for an electrostatic accelerometer sensor head is built, and the multi-conductor capacitance matrix data is simulated. The accuracy of the capacitance simulation is evaluated in three ways including the convergence check of the capacitance with the mesh size, the symmetry verification, and the sensitivity comparison with the theoretical model. Finally, the accelerometer measurement model is analyzed based on the simulation data, using the case of rotating installation misalignment of the upper electrode as an example. The measurement model and error items of one horizontal axis and one rotating axis are quantitatively evaluated. The method proposed in this paper provide a new effective approach to the measurement model analysis of the electrostatic accelerometers in complex working scenarios both in orbit and on ground, which could be helpful to enhance the performance and the efficiency of application.

Detection of electrode misalignment and its effect on joint quality in resistance spot welding: a low-cost computer vision-based approach

Electrode misalignment in resistance spot welding can be caused by poor fitting or deformation of electrode with continuous usage. This leads to asymmetric weld nugget formation, porosity and expulsion. This paper presents a novel low-cost real-time inspection system for angular misalignment using an image processing approach. The proposed solution can effectively segment the electrode tips even from the image captured at noisy industrial background such as automotive assembly line, by using a regional convolutional neural network based object identification method. The trained model has a mean average precision and recall of 99.01% and 96.6%, respectively. A series of image processing tools and mathematical operations were used to identify the edge line contours of electrode tips accurately from the detection mask, and determine the angular misalignment with a maximum deviation of less than 0.06°. Experimental results showed that the weld nuggets exhibited porosity, shrinkage voids, and cracks when performed under angular misalignment conditions.

Sensitivity of Electrocardiogram on Electrode-Pair Locations for Wearable Devices: Computational Analysis of Amplitude and Waveform Distortion.

An electrocardiogram (ECG) is used to observe the electrical activity of the heart via electrodes on the body surface. Recently, an ECG with fewer electrodes, such as a bipolar ECG in which two electrodes are attached to the chest, has been employed as wearable devices. However, the effect of different geometrical factors and electrode-pair locations on the amplitude and waveform of ECG signals remains unclear. In this study, we computationally evaluated the effects of body morphology, heart size and orientation, and electrode misalignment on ECG signals for 48 scenarios using 35 bipolar electrode pairs (1680 waveforms) with a dynamic time warping (DTW) algorithm. It was observed that the physique of the human body model predominantly affected the amplitude and waveform of the ECG signals. A multivariate analysis indicated that the heart-electrode distance and the solid angle of the heart from the electrode characterized the amplitude and waveform of the ECG signals, respectively. Furthermore, the electrode locations for less individual variability and less waveform distortion were close to the location of electrodes V2 and V3 in the standard 12-lead. These findings will facilitate the placement of ECG electrodes and interpretation of the measured ECG signals for wearable devices.

Numerical modeling of liquid metal embrittlement initiation during resistance spot welding of third generation advanced high strength steel – Effect of welding schedule and electrode alignment

Third generation (GEN3) advanced high-strength steels are increasingly used to reduce vehicle body structure weight for improved fuel economy. Zinc-induced liquid metal embrittlement (LME) has become a prevalent challenge when these steels are welded by resistance spot welding (RSW). In the literature, various numerical models have been developed to study LME during RSW of GEN3 steels. Those models tend to have a limited utility in predicting how various factors such as RSW parameters affect LME cracking. In this study, a novel LME calculation method has been developed by integrating an electro-thermo-mechanical finite element model of RSW process with an LME ratio for crack initiation established from hot tensile testing data. The onset of different types of LME cracking is tracked throughout the weld region over the entire course of RSW including the final cooling stage after electrode retraction. The model is validated using an existing set of literature data that involves different welding schedules, electrode geometries and electrode misalignments. The local temperature and stress conditions during RSW are calculated and used to understand how different welding parameters affect the severity of LME cracking. It is found that electrode misalignment exacerbates crack initiation on outer surfaces of the spot weld due to the tensile stress arisen from the off-centered squeeze force as well as the reduced surface cooling to electrodes. Initiation of cracks between the steel sheets, taking place mainly after electrode retraction, is not significantly affected by the welding schedule and the electrode tip diameter.

How to Make a Single-Layer Pouch Cell That Matches the Performance of a Commercial Li-Ion Cell

As lithium-ion batteries (LIBs) have exploded in popularity due to the consumer electronics and electric vehicle industries, many resources are poured into research. While the simplest cell format requiring the least amount of active material to make in a research laboratory to study various aspects of the cell is usually the coin cell, it is far from the most representative of commercial LIBs. Oftentimes, coin cells are made with a large negative electrode overhang to reduce the risk from positive/negative electrode misalignment, but the overhang region can cause Li+ to become effectively trapped at higher C-rates1. While this is a necessary trade-off in today’s commercial LIB manufacturing, the overhang area is normally a much smaller fraction of the total negative electrode area in a commercial cell than in a laboratory coin cell, which can lead to discrepancies in cycle testing. Moreover, during assembly of commercial stacked or wound cells, there is always a region in which one side of a double-sided coating, typically the negative, is not needed and thus a single-sided electrode should be used. However, not all manufacturers eliminate the outward-facing second side and elect to simply use double-sided coatings throughout. Therefore, studying the effects of excess electrode in single-layer pouch cells will be explored in this presentation. In this presentation, cells made in various formats (coin and stacked pouch) will be compared to single-layer pouch cells made with and without negative electrode overhang. Single-layer pouch cells are the easiest format for assembling full cells without overhang because they are neither too small nor too big for positive/negative electrode alignment to be difficult. Moreover, single-layer pouch cells made with double-sided coatings (without overhang) and cycled using Ultra-High Precision Coulometry (UHPC) will be shown to have poor cycling. This is for two reasons: 1) for a double-sided negative, the outward-facing coating of the electrode can trap Li+ just like the overhang on the inward-facing coating; and 2) the outward-facing positive can be deintercalated and provide more capacity than desired2, possibly even surpassing the negative/positive areal capacity ratio. Single-layer pouch cells with no overhang are shown in Figure 1a to outperform all other cell formats tested, retaining 90% of their original capacity after 500 cycles at C/3 and 40 °C, and have the lowest difference in capacity between typical C/3 and C/20 checkup cycles as shown in Figure 1b. The stacked pouch cells in Figure 1 are composed of 3 positive and 4 negative electrodes that are all double-sided, meaning there are two outward-facing negative electrode coatings that can trap Li+, possibly resulting in the much poorer capacity fade to 80% after 500 cycles illustrated in Figure 1a. Thus, single-layer pouch cells without overhang give the most realistic cycling results for the tested electrode materials. Figure 1. C/3 cycling of full cells of various formats denoted in the legend. Plotted in (a) is the normalized discharge capacity and (b) is the difference in areal discharge capacity between the C/20 checkup cycle and preceding C/3 cycle. REFERENCES Gyenes, B., Stevens, D.A., Chevrier, V.L., and Dahn, J.R. (2015). Understanding Anomalous Behavior in Coulombic Efficiency Measurements on Li-Ion Batteries. J Electrochem Soc 162, A278–A283. 10.1149/2.0191503jes.Smith, A., Stüble, P., Leuthner, L., Hofmann, A., Jeschull, F., and Mereacre, L. (2023). Potential and Limitations of Research Battery Cell Types for Electrochemical Data Acquisition. Batter Supercaps e202300080. doi.org/10.1002/batt.202300080. Figure 1

Diagnosis of Current Flow Patterns Inside Fault-Simulated Li-Ion Batteries via Non-Invasive, In Operando Magnetic Field Imaging.

With the growing popularity of Li-ion batteries in large-scale applications, building a safer battery has become a common goal of the battery community. Although the small errors inside the cells trigger catastrophic failures, tracing them and distinguishing cell failure modes without knowledge of cell anatomy can be challenging using conventional methods. In this study, a real-time, non-invasive magnetic field imaging (MFI) analysis that can signal the battery current-induced magnetic field and visualize the current flow within Li-ion cells is developed. A high-speed, spatially resolved MFI scan is used to derive the current distribution pattern from cells with different tab positions at a current load. Current maps are collected to determine possible cell failures using fault-simulated batteries that intentionally possess manufacturing faults such as lead-tab connection failures, electrode misalignment, and stacking faults (electrode folding). A modified MFI analysis exploiting the magnetic field interference with the countercurrent-carrying plate enables the direct identification of defect spots where abnormal current flow occurs within the pouch cells.

Li Dendrite Formation on the Side of Cu Current Collector during Charging in Misaligned Pouch-Type Lithium-Ion Batteries

Not only high-capacity electrode materials but also electrode/cell design greatly governs the electrochemical performance of LIBs. For instance, there are systematic works to unravel the effect of area or capacity ratio between anode and cathode or the electrolyte amount. [1,2,3] Especially, our research group has already reported the effect of electrode misalignment, which can frequently occur during the coin cell assembly, on the electrochemical properties, where Li dendrites formed on the coin cell bottom mainly deteriorated the cell performance. [4] However, considering the commercial cell configurations like pouch-type LIBs, which have insulating polypropylene inner layer, those negative phenomena should be evaluated in misaligned LIB cells.For this purpose, three pouch-type cells (well-aligned, slightly misaligned, and largely misaligned) using LixNi0.6Co0.2Mn0.2O2 cathode and graphite anode were fabricated in a dry room. Surprisingly, a similar misalignment effect to coin cells was also observed in the pouch-type cell, even though the inner layer of the Al-pouch is insulative. When we disassembled the misaligned cell after precycling, we could observe Li dendrites formed on the side of the Cu current collector (CC) of the anode. That is, the Li ions from the cathode are able to be plated on the metal side of Cu CC of a few micrometer thickness. Thus, even in pouch cells, the electrode misalignment can lead to Li inventory loss. To solve this problem, an insulating coating was applied to the side of the Cu CC, and as a result, the cycle performance of the misaligned cell was improved by suppressing the Li dendrite formation. In addition, the electrochemical characteristics were compared as a function of the lithiation state (SOL, x in LixNi0.6Co0.2Mn0.2O2) using EIS, DC-IR, XRD, etc.Reference B. Son, Y. M. Lee et al., J. Power Sources , 243 (2013) 641-647R. Xue et al., J. Power Sources , 55 (1995) 111-114B. R. Long, J. R. Croy et al., J. Electrochem. Soc. , 163 (2016) A2999N. Kim, Y. M. Lee et al., J. Electrochem. Soc. , 169 (2022) 023502

Effect of electrode misalignment on the quality of resistance spot welds

The quality of resistance spot welds is critical to the structural integrity of components manufactured using the process. This paper analyses the effect of electrode misalignment, referred to as electrode tilt, on the quality of resistance spot welds and their relationship. The weld quality is represented by the diameter of the weld nugget as is standard in industry. Principal Component Analysis (PCA) was used to reduce the dimensionality of the dynamic resistance signal and extract features to be used in a linear regression model for the prediction of nugget diameter. This paper found that increased misalignment of the electrodes reduced the peak resistance of the welding process resulting in smaller nugget diameters and therefore a lower weld quality.

Mitigating the influence of industrially relevant disturbances on LME severity of dissimilar resistance spot welded advanced high-strength steels

The third generation of advanced high-strength steels (3G-AHSS) has been developed to provide high strength and high ductility, which attract automakers. To protect these materials from corrosion during service, these materials are typically coated with zinc. During resistance spot welding (RSW), the zinc coating can melt, allowing it to penetrate into the grain boundaries (GBs), and lead to liquid metal embrittlement (LME) phenomena. Concerns regarding LME susceptibility have impacted the industrial application of 3G-AHSS; therefore, its mitigation has become a top focus for automakers. Several possible strategies for lowering LME severity by altering welding parameters have been proposed to mitigate LME in similar spot weld joints. However, these strategies were not tested on a dissimilar spot weld joint. Therefore, in this work, 1.4 mm gauge thickness galvanized (GI-coated) 3G-980 AHSS was joined with 0.6 mm thick Interstitial Free (IF) steel. In this work, current pulsation and ultra-short hold time were proposed to minimize LME severity. The robustness of the developed welding schedule was then tested on welds made with industrial disturbance factors such as pre-strained sheets (between 0 to 80% of 3G-980 material yield strength) and electrode misalignment (between 0° to 10° misalignment) compared to baseline parameters. In severe circumstances of disturbance factors, the resulting optimized welding schedule decreased LME cracking and showed improved resistance to LME, lowering LME severity by 41% for the extreme pre-strain condition and 27% for the extreme misalignment angle.

Systematic study on Li dendrite growth and suppression in pouch-type lithium-ion batteries with misaligned electrode pairs

Among the various latent defects in pouch-type lithium-ion batteries (LIBs), electrode misalignment can occur during cell assembly or due to external impacts during actual operation. However, the effects of electrode misalignment on the electrochemical characteristics have not been sufficiently investigated, especially in pouch-type LIBs. Thus, we systematically design three pouch-type LIBs with different degrees of electrode misalignment (well-aligned, slightly misaligned, and largely misaligned configurations). As the degree of misalignment increases, not only the initial Coulombic efficiency but also the reversible discharge capacity decrease because of Li dendritic growth on the side of the Cu current collector (CC) that overlaps with the misaligned cathode. To address this unavoidable latent defect, we suggest a new strategy to block the side of the Cu CC through application of an insulating layer. This insulating layer can successfully improve both the initial Coulombic efficiency and reversible discharge capacity by efficiently suppressing Li dendritic growth. Thus, this simple idea is an excellent option for ensuring the safety of LIBs with misaligned electrode pairs.

Monopolar and bipolar electrooculography signal characteristics due to target displacements—have we seen the whole picture?

The development of electrooculography (EOG)-based human-computer interface systems is generally based on the processing of the commonly referred to horizontal and vertical bipolar EOG channels, which are computed from a horizontally-aligned and another vertically-aligned pair of electrodes, respectively. Horizontal (vertical) target displacements are assumed to result in changes in the horizontal (vertical) EOG channel only, and any cross-talk between the bipolar channels is often neglected or incorrectly attributed solely to electrode misalignment with respect to the ocular rotation axes. Objective. The aim of this work is to demonstrate that such cross-talk is intrinsic to the geometric relationship between the orientation of the verging ocular globes and the planar displacement of the gaze target with respect to the primary gaze position. Approach. Since it is difficult to record actual EOG data with electrodes which are perfectly-aligned with the ocular rotation axes, this is studied by simulating the EOG potential values for various horizontally- and vertically-displacing targets using a dipole model of the eye. Main results. We show that cross-talk between the horizontal and vertical bipolar EOG channels is manifested even if the electrodes are aligned with the ocular rotation axes. Specifically, for a horizontally- (vertically-)displaced target, while the monopolar EOG signals obtained from the horizontally- (vertically-)aligned electrodes exhibit an expected predominant potential displacement, a smaller displacement is also exhibited in the monopolar EOG signals obtained from the vertically- (horizontally-)aligned electrodes. These unexpected displacements in the vertically- (horizontally-)aligned monopolar channels may have different magnitudes, resulting in an effective potential displacement in the vertical (horizontal) bipolar EOG channel. Significance. This is significant as it shows that, unlike in many works published so far for EOG-based ocular pose estimation, it is not sufficient to only use the horizontal (vertical) bipolar EOG channel to estimate the horizontal (vertical) displacement of the ocular pose.

Real-Time Condition Monitoring System for Electrode Alignment in Resistance Welding Electrodes.

Electrode misalignment, produced by mechanical fatigue or bad adjustments of the welding gun, leads to an increase in expulsions, deformations and quality problems of the welding joints. Different studies have focused on evaluations of the influence of a misalignment of the electrodes and the final quality of the weld nugget. However, few studies have focused on determining a misalignment of the electrodes to avoid problems caused by this defect, especially in industrial environments. In this paper, a method for performing the condition monitoring of electrode alignment degradation was developed following previous research, which has shown the relationship between the misalignment of short-circuited electrodes and the magnetic field generated by them. This method was carried out by means of a device capable of measuring the magnetic field. Finally, an integral system for the detection of misalignments in real production lines is presented. This system set behavior thresholds based on the experimentation, allowing the condition monitoring of the alignment after each welding cycle.

New hybrid multiplanar cone beam computed tomography-laser-fluoroscopic-guided approach in cochlear implant surgery

PurposeCochlea implant surgery with proper positioning of the cochlear electrode can be challenging. Intraoperative real-time hybrid laser-fluoroscopic-guided navigation based on a multiplanar cone beam computed tomography (CBCT) dataset opens up the opportunity to immediate radiological control of primary electrode misalignments and offering new insights into the cochlea electrode insertion routes and favorable cochlear implant-insertion angle.MethodsIn this retrospective study, 50 cases (29 males, 18 females) of conventional electrode implantation (without intraoperative image control; group A) and nine cases (7 males, 2 females) of CBCT-laser-fluoroscopic-guided surgery (group B) were included in the present study. CBCT-laser-guided surgery under real-time fluoroscopic control was conducted using an intraoperative C-arm CBCT. All patients received preoperative cross-sectional imaging (CT and MRI), in which cochlear malformation could be excluded. Postoperatively, we looked for electrode misplacements.ResultsIn group A, electrode misalignment was detected postoperatively in 14 of 50 cases (28.0%). In group B, primary electrode misalignment was detected intraoperatively in two patients (22.2%). In both patients, the misalignments were corrected in the same session. The comparison of cochlear insertion angles showed significant differences. Group A: 47.5 ± 2.6° (actual conventional surgery) vs 17.6 ± 2.8° (theoretical CBCT-laser-fluoroscopic-guided surgery) P < 0.001. Group A vs group B: 47.5 ± 2.6° (actual conventional surgery; Group A) vs 17.9 ± 2.5° (actual CBCT-laser-fluoroscopic-guided surgery; Group B) P < 0.001.ConclusionWe consider that an intraoperative hybrid CBCT-laser-fluoroscopic-controlled approach in cochlear implant surgery using a C-arm CT can be beneficial, because electrode misalignments can be reduced and if it does occur, remedied in the same surgical session.

Deconvoluting CO2 Electroreduction Membrane-Electrode-Assembly Performance Via Five-Electrode Setup

For CO2 electrolysis, a zero-gap or membrane-electrode-assembly (MEA) configuration is desirable for lowering internal resistances and enabling the use of dilute supporting electrolytes for operation at industrially relevant current densities (>100 mA cm-2). However, to rationally optimize individual electrolyzer components, the contributions that cell components (cathode, anode, and membrane) have on the total cell voltage and internal resistance need to be deconvoluted. Moreover, deconvolution techniques can provide operando snapshots of electrode dynamics and component potentials to help assess component degradation for accelerated stability testing protocols1.In this work, we present a technique for the complete deconvolution of the cell voltage and internal resistances through a five-electrode setup. Unlike similar methods1-3, three additional reference electrodes are introduced: two quasi-reference electrodes on each side of the MEA and one fritted reference electrode in the supporting electrolyte, fed to the anode, for validation of quasi-reference electrode potentials before and after testing. Furthermore, the technique presented in this work was optimized for ease of implementation for a standard test setup for laboratory-scale CO2 electrolysis without requiring modifications to the electrochemical cell endplates or a multi-channel potentiostat.Using this five-electrode setup, a significant membrane impedance at both high and low frequencies is identified for a CO2 reduction MEA employing an anion exchange membrane. As shown via electrochemical impedance spectroscopy (EIS) (Fig. 1b), the membrane accounts for about 40% of the total cell impedance at high frequencies. Notably, the membrane also exhibits a low-frequency impedance attributed to concentration gradients across the membrane4. As an initial validation check, the individual EIS spectra of each component were summed to obtain the measured full cell EIS spectra, albeit with an introduction of measurement noise (Fig. 1b, d).To further validate the setup, the corners of the cathode and anode electrodes were cut asymmetrically to assess sensitivity towards edge effects from electrode misalignment reported for a similar technique (Fig. 1a,c)2. We demonstrate that the membrane impedance can be reversed by deliberately introducing this edge effect (Fig. 1b,d). In this reversed configuration, the measured membrane impedance is flipped due to the apparent reference electrode positions being swapped. Moreover, in this configuration the user inadvertently measures the cathode and anode through the membrane, thereby convoluting the signal. This is of significant concern for directly measuring the cathode mass transport dynamics measured at low frequency (<100 Hz) as the membrane has its own characteristic low-frequency impedance. We will present these results and discuss the application of this method towards catalyst layer optimization, diagnosing a working CO2 reduction MEA employing a cation exchange membrane and comparing the performance of zero-gap and hot-pressed MEA configurations.References O. Sorsa, J. Nieminen, P. Kauranen, and T. Kallio, J. Electrochem. Soc., 166, F1326–F1336 (2019) https://iopscience.iop.org/article/10.1149/2.0461916jes.R. Zeng, R. C. T. Slade, and J. R. Varcoe, Electrochim. Acta, 56, 607–619 (2010) http://dx.doi.org/10.1016/j.electacta.2010.08.032.D. Salvatore and C. P. Berlinguette, ACS Energy Lett., 5, 215–220 (2020) https://pubs.acs.org/doi/10.1021/acsenergylett.9b02356.A. Kozmai et al., Membranes (Basel)., 11, 1–17 (2021). AcknowledgementThis work was supported by the U.S. Department of Energy, Office of Energy Efficiency & Renewable Energy under award no. DE-EE0009287.0001 Figure 1

Robustness and reliability assessment of Single-Sided Spot Welding as a process for sheet to closed profile joining for Body in White vehicle structures

The application of high performance steels in combination with rolled profiles, hydro-formed or tailored tubes (TT) can create a stiffer and safer vehicle structure. However, it presents some challenges regarding the joining process, once accessibility to both sides of the surface to be joined is limited. The Single-Sided Spot Welding (SSSW) is an alternative to Resistance Spot Welding (RSW), as it only requires access to just one side of the joint to weld it. In order to validate SSSW as a robust and reliable welding process for automotive manufacturing, this work encompassed experiments comparing SSSW and RSW under manufacturing conditions and tolerance problems, such as sheets and electrode misalignment, gaps or shunt current conditions, using DX54D steel sheets, and steel profiles made of press-hardened 22MnB5 and S355J2 + N. The experimental parameters in this study were current, electrode force, geometry and misalignment angle. The performed tests were lap shear tensile strength, analyses of weld nugget quality and the measurement of spot diameters by chisel testing. The obtained results show that SSSW can meet RSW requirements regarding mechanical properties and quality standards, overcoming the set manufacturing tolerance issues, without reducing the spot diameter and with similar mechanical properties of RSW joints.

Rationally segmented triboelectric nanogenerator with a constant direct-current output and low crest factor

A multi-phase TENG (MP-TENG) was constructed only through a simple method involving electrode misalignment and circuit connection to generate a constant direct-current output with an ultra-low crest factor (1.05), which has widespread application prospects in the field of energy harvesting.

Designing Splicing Digital Microfluidics Chips Based on Polytetrafluoroethylene Membrane.

As a laboratory-on-a-chip application tool, digital microfluidics (DMF) technology is widely used in DNA-based applications, clinical diagnosis, chemical synthesis, and other fields. Additional components (such as heaters, centrifuges, mixers, etc.) are required in practical applications on DMF devices. In this paper, a DMF chip interconnection method based on electrowetting-on-dielectric (EWOD) was proposed. An open modified slippery liquid-infused porous surface (SLIPS) membrane was used as the dielectric-hydrophobic layer material, which consisted of polytetrafluoroethylene (PTFE) membrane and silicone oil. Indium tin oxide (ITO) glass was used to manufacture the DMF chip. In order to test the relationship between the splicing gap and droplet moving, the effect of the different electrodes on/off time on the minimum driving voltage when the droplet crossed a splicing gap was investigated. Then, the effects of splicing gaps of different widths, splicing heights, and electrode misalignments were investigated, respectively. The experimental results showed that a driving voltage of 119 V was required for a droplet to cross a splicing gap width of 300 μm when the droplet volume was 10 μL and the electrode on/off time was 600 ms. At the same time, the droplet could climb a height difference of 150 μm with 145 V, and 141 V was required when the electrode misalignment was 1000 μm. Finally, the minimum voltage was not obviously changed, when the same volume droplet with different aqueous solutions crossed the splicing gap, and the droplet could cross different chip types. These splicing solutions show high potential for simultaneous detection of multiple components in human body fluids.

Occurrence of sub-critical heat affected zone liquid metal embrittlement in joining of advanced high strength steel

Advanced high strength steels (AHSS) used in automotive structural components are commonly protected using zinc coatings. However, the steel/zinc system creates the potential for liquid metal embrittlement (LME) cracking during welding. In this study, the effect of angular welding electrode misalignment as recommended by industry was investigated and resulted in LME cracking in the sub-critical heat affected zone (SCHAZ) which is a region where LME has not been previously observed. The largest misalignment case of 6° resulted in bending of the work piece and an angled weld nugget/heat affected zone (HAZ), causing LME cracks in the lower temperature HAZ regions. SEM and EBSD analysis characterized the LME crack area as the SCHAZ and below the Ac 1 transformation temperature. Furthermore, dilatometry analysis showed the Ac 1 temperature to be approximately 660 °C, meaning LME occurred below the traditional 700 °C minimum threshold. In addition to this novel observation of LME before transformation and at low temperature, it was also noted that only misalignment beyond 2° promoted LME cracking. The low angle 2° case was observed to be statistically the same using a Student’s t -test (α = 0.05) on 6 welded samples for LME crack severity compared to a standard 0° case.

Effect of Severe Welding Conditions on Liquid Metal Embrittlement of a 3rd-Generation Advanced High-Strength Steel

The occurrence of liquid metal embrittlement (LME) during the resistance spot-welding of a zinc-coated Advanced High-Strength Steel (TRIP-aided AHSS) is investigated in this work. Welds are generated using controlled degradation of the welding conditions to favor the occurrence of LME cracks in a two-sheets homogeneous configuration. Detailed inspection of the welds shows that electrode misalignment, short holding time, low electrode force and long welding time constitute a propitious environment for both inner and outer LME cracks. A statistical analysis allows weighting and interpreting of the significance of the welding parameters. Electrode misalignment and reduced holding time appear as the most influential parameters in the design of experiment. Moreover, it is worth noting that standard ISO welding conditions are prone to avoid any LME cracks in the investigated two-sheets homogeneous configuration.

An electrode misalignment inspection system based on image processing technology for use in resistance spot welding

Weld quality in resistance spot welding (RSW) is greatly affected by any misalignment of the upper and lower electrodes. This work presents a non-contacting system for measuring electrode misalignment. It uses two industrial CCD cameras, oriented perpendicular to one another in the same plane. The electrode cap images taken by the CCD cameras are sent to a computer through an Ethernet switch. The original red, green and blue (RGB) images are converted to greyscale images. The left and right edge points of the cap images are determined by computing the first derivative of the grey level gradient of the images; the edge points are the locations of local maxima in the horizontal direction. Using the edge points, linear boundaries are fitted via the least squares method, and the noise points are eliminated. The axes of the electrode caps are calculated from the left and right linear boundaries of the images, and then the spatial and angular offsets of the two electrode axes can be determined by the two axis functions. The results of comparison experiments indicate that the abovementioned system can rapidly and accurately measure the misalignment of electrodes during the process of RSW. The measurement results will provide critical input for equipment adjustment and maintenance.