Determining Particle Size and Position in a Coplanar Electrode Setup Using Measured Opacity for Microfluidic Cytometry

Microfluidic impedance flow cytometers enable high-throughput, non-invasive, and label-free detection of single-cells. Cytometers with coplanar electrodes are easy and cheap to fabricate, but are sensitive to positional differences of passing particles, owing to the inhomogeneous electric field. We present a novel particle height compensation method, which employs the dependence of measured electrical opacity on particle height. The measured electrical opacity correlates with the particle height as a result of the constant electrical double layer series capacitance of the electrodes. As an alternative to existing compensation methods, we use only two coplanar electrodes and multi-frequency analysis to determine the particle size of a mixture of 5, 6, and 7 µm polystyrene beads with an accuracy (CV) of 5.8%, 4.0%, and 2.9%, respectively. Additionally, we can predict the bead height with an accuracy of 1.5 µm (8% of channel height) using the measured opacity and we demonstrate its application in flow cytometry with yeast. The use of only two electrodes is of special interest for simplified, easy-to-use chips with a minimum amount of instrumentation and of limited size.

Bead Geometry Prediction Model for 9% Nickel Laser Weldment, Part 1: Global Regression Model vs. Modified Regression Model

Due to its excellent toughness and stiffness in cryogenic conditions, 9% nickel steel is applied to LNG storage facilities, and its usage is increasing as a result of changes in environmental regulations. A study was conducted on the development of a predictive model to optimize the laser welding process of 9% nickel steel, and two prediction models were developed using one hundred data points obtained through experiments. A global regression model used as a general prediction model and a modified regression model using the p-value of the analysis of variance were developed, and their prediction performance was compared. It was found that the modified regression model was superior to the global regression model in terms of predicting the bead shape, including parameters such as penetration depth, bead height, and area ratio.

Multi response optimization of Inconel 625 wire arc deposition for development of additive manufactured components using Grey relational analysis (GRA)

The paper investigates the multi response optimization of single bead deposition characteristics which affects the additive manufactured structures in later stages of multi layered depositions. Inconel 625 single beads were deposited using the cold metal transfer (CMT) based on Wire Arc Additive Manufacturing (WAAM). The bead width, bead height, penetration depth as well as microhardness of the fusion region are considered for the decision criteria models. Grey relational analysis (GRA) is used to solve the multi criteria optimization problem. Analysis of variance has been performed to quantify the parameters effects on grey relational grade (GRG). From the GRA, it is observed that at parameter setting of 110 Amps current, 0.4 mm/sec weld speed, and 4 mm standoff distance gives minimum bead width, minimum bead height, maximum penetration depth, and maximum microhardness.

Prediction of mild Steel weld properties using artificial neural network and regression analysis

Safety hazards resulting from structural material failure occur mostly in less developed countries where material standard specifications are not strictly adhered to, due to failure of government policy implementation. These hazards often result in loss of life. Failures tend to occur at welded joints, and various research institutions are making attempts to prevent such failures by developing new methods that could predict and improve welded joint qualities. The concern goes beyond safety, but also encompasses economic and other similar long term considerations. In this study, experimental methods were used to obtain the Bead Height (BH), Ultimate Tensile Strength (UTS) and Brinell Hardness Number (BHN) of mild steel welded joints. Thereafter, the artificial neural network (ANN), and Regression analysis methods were applied to predict the corresponding values of the BH, UTS, and BHN. The resulting performance of these two predictive methods was compared side by side to determine which one of the two methods better predicted these quality properties. This comparative analysis was carried out by comparing the percentage error of ANN to that of the Regression analysis. From the results obtained, it was found that for the bead height, Regression analysis method produced a total of 1.72% error. For UTS, ANN method produced a total of 63.31% error whereas Regression analysis produced a total of 0.39% and for BHN, ANN method produced a total of 353.86% error whereas, Regression analysis method produced a total of 2.58% error. The results shows that overall, regression analysis method predicted the properties better. Also, the effect of the process parameters on the weld properties were investigated. In this study, a step by step method is applied.

Comparative Enhancement of Mild Steel Weld Mechanical Properties for Better Performance Using COPRAS–ARAS Method

Some machine part failures have often occurred in areas of components where the strength was lowest, especially at its weld region. Presence of voids in weldments or weld joints greatly reduces the quality of the weldment. To prevent these defects, a proper optimum selection of process parameters is highly encouraged to achieve an acceptable weld mechanical property. The Complex Proportional Assessment (COPRAS) method was applied to determine the relative significance of each alternative and the quantitative utility for each alternative. The Addition Ratio Assessment (ARAS) method was applied to optimize these parameters by utilizing the weights generated using COPRAS method. In this study, the COPRAS-ARAS method which is a multi-criteria decision making tools was applied to determine the optimum process parameters to improve the mechanical properties of the weldment. From applying these methods, it was found that weldments 7, possess the optimum input process parameters. The corresponding mechanical properties of ultimate tensile strength (UTS) of 395MPa, absorbed impact strength (CVN) of 250J, Bead height (BH) of 1.98mm and Bead width (BW) of 4.82mm was found to possess the best mechanical properties.

On the bead design in LFT structures: the influence of manufacturing-induced residual stresses

In the design of long fibre reinforced thermoplastic (LFT) structures, there is a direct dependency on the manufacturing. Therefore, it is indispensable to integrate the manufacturing influences into the design process. This not only offers new opportunities for material- and load-adapted designs, but also reduces cost-intensive modifications in later stages. The goal of this contribution is to make the complexity manageable by presenting a method which couples LFT manufacturing and structural simulations in an automated optimization loop. Herein, the influence of linear-elastic, local anisotropic material properties as well as residual stresses resulting from the compression molding of LFT on the stiffness-optimized design of beaded plates is investigated. Based on the simulation studies in this contribution, it can be summarized that the resulting bead height and flank angle, considering anisotropies and residual stresses, are smaller compared to isotropic modelling. As a conclusion, the strength constraint limits the maximum bead height and the flank angle needs to be additionally chosen as a consequence of the local fibre orientations and residual stresses resulting from manufacturing. Optimized bead cross sections are only valid for a specific system under investigation, as they depend on the defined boundary conditions (load case, initial charge geometry and position, fibre orientations, etc.).

Stamp Forming: A Comparison in the Use of Draw Beads and Blank Holder Force for Producing Aluminum Panels

An investigation was performed examining the effects of draw beads and blank holder forces on local forces in various regions of a stamp forming process that produced oval aluminum panels. The results showed that provided there was sufficient blank holder forces to prevent wrinkling, the regions with draw beads were affected more by draw bead height than by blank holder force. However, at the die ends, away from the draw beads, blank holder force had more of an effect than the draw beads did with respect to local forces. Additionally, the draw bead height effects at the die end were not directly related but had to be interpreted based upon the effect on strains within the flange region at the die ends. This study may be especially useful for researchers in the automotive sector who are particularly interested in aluminum panel forming.

EVALUATION OF OVERHANG ANGLE IN TIG WELDING-BASED WIRE ARC ADDITIVE MANUFACTURING PROCESS

Wire Arc Additive Manufacturing (WAAM) is a relatively new manufacturing method. It is a novel technique to build net-shaped or near-net-shaped metal components in a layer-by-layer manner via applying metal wire and selection of a heat source such as laser beam, electron beam, or electric arc. WAAM process is preferable as an alternative to traditional manufacturing methods especially for complex featured and large scale solid parts manufacturing and it is particularly used for aerospace structural components, manufacturing and repairing of dies/molds. TIG welding-based WAAM method is implemented by depositing continuous wire melted via heat. In this study, the overhang (self-supporting) angle in TIG welding-based wire arc additive manufacturing process is investigated. The overhang angles are the angles at which a 3D printer can build tapered (overhang) surfaces without the need to supporting material below the printing layer. The material, bead height, TIG weld parameters and the environment temperature (cooling rate of printed layer) are the parameters which affect the overhang angle. The results show that the maximum overhang angle is also dependent on the temperature of the previous layer. For the selected set of process parameters, the maximum overhang angle is found as 28o, if the temperature of the previous layer is cooled to 150oC before the subsequent layer is deposited.

Prediction of welding bead geometry for wire arc additive manufacturing of SS308l walls using response surface methodology

In the wire arc additive manufacturing (WAAM) process, the geometry of single welding beads has significant effects on the stability process and the final quality and shape of manufactured parts. In this paper, the geometry of single welding beads of 308L stainless steel was predicted as functions of process parameters (i.e. welding current I, voltage U, and travel speed v) by using the response surface methodology (RSM). A set of experimental runs was carried out by using the Box-Behnken design method. The adequacy of the developed models was assessed by using an analysis of variance (ANOVA). The results indicate that the RSM allows the predictive models of bead width (BW) and bead height (BH) to be developed with a high accuracy: R2-values of BW and BH are 99.01% and 99.61%, respectively. The errors between the predicted and experimental values for the confirmatory experiments are also lower than 5% that again confirms the adequacy of the developed models. These developed models can efficiently be used to predict the desirable geometry of welding beads for the adaptive slicing principle in WAAM.

Analysis and Characterization of the Weld Pool and Bead Geometry of Inconel 625 Super-TIG Welds

The welding market is changing globally, becoming eco-friendly, robotized and automated. The tungsten inert gas welding (TIG) process is indispensable in industries that require high-quality welds with the absence of spatter and fumes. However, the production rate of TIG welding is very low, which limits its many applications. The present study introduces a novel TIG welding method called super-TIG welding. Super-TIG welding is able to produce a high production rate of welds compared to other fusion welding methods. In super-TIG welding, the novel C-type filler is used, which is different from the conventional TIG welding of circular wire. The relations of the heat input ratio in super-TIG welding to weld pool length and weld bead geometry were measured using the Inconel 625 C-filler. Two types of deposition techniques were used for a bead-on-plate welds, such as stringer beads and oscillation beads. The weld pool and bead geometry measurements are found to be different between stringer beads and oscillation bead techniques. The length of the molten pool and bead size were higher for oscillation beads over the stringer beads. These changes were associated with the difference in heat transfer contact area and bead height.