Investigated Process Parameters Research Articles

Development of a fs-pulsed laser pretreatment process on thin-walled nickel to improve adhesion for adhesive bonding applications

Due to its inert surface, producing adhesive bonds on nickel is challenging and requires a surface pretreatment. A laser pretreatment process on nickel is investigated using a Yb:YAG slab laser at 780 fs pulse length. The process is varied in pulse density, pulse energy, and focus position to produce various surface structures on a nanometer scale. The surface structures are categorized topologically in scanning electron microscopy (SEM). Random nanostructures, laser-induced periodic surface structures (LIPSS), and process vapor depositions are observed. To quantify the adhesion properties of the produced surfaces, peel tests are conducted using a two-component epoxy adhesive. All investigated process parameters lead to a significant increase in peel strength; however, high pulse density and high pulse energy in focus lead to the highest peel strengths. These process parameters generally produce LIPSS and process vapor depositions on the surface, which might be linked to the high peel strengths. The analysis of the fracture pattern shows an adhesion failure, and in SEM, a partial failure of adhesive and adherent is visible. The surface structures are fully wetted by the adhesive on a sub-micrometer level. Nanoparticles deposited from the process plasma are broken out of the surface during the peel tests. A general trend to high accumulated fluence for best results in peel strength is shown.

Fabrication of Spherical Colloidal Supraparticles via Membrane Emulsification.

Colloidal supraparticles are micrometer-scale assemblies of primary particles. These supraparticles have potential application in photonic materials, catalysis, gas adsorption, and drug delivery. Thus, the synthesis of colloidal supraparticles with a narrow size distribution and high yield has become essential. Here, we demonstrate membrane emulsification as a high-throughput approach for fabricating spherical supraparticles with a narrow size distribution and control over particle size and crystallinity. Spherical supraparticles with well-ordered surface structures are synthesized by generating emulsion droplets of an aqueous colloidal dispersion in fluorocarbon oil using a Shirasu porous glass membrane followed by the consolidation of particles through water removal within the emulsion. We systematically investigate process parameters, including the flow rate of the particle dispersion, the particle concentration, and the average pore diameter of the membrane, on the mean size and size distribution of the supraparticles, revealing key factors governing supraparticle properties and production throughput. A comparative evaluation with commonly employed methods highlights the advantage of membrane emulsification, which combines well-defined internal structure and controlled supraparticle sizes with comparably high yields on the order of tens of grams per day. Importantly, in contrast to widely used droplet-based microfluidics, membrane emulsification allows fabrication of supraparticles in nonfluorinated oil. Overall, membrane emulsification offers a simple yet versatile method for fabricating colloidal supraparticles with high quality and yield and may serve as a bridge between existing high-precision techniques, such as droplet-based microfluidics, and high-throughput processes with less control, such as spray-drying.

Optimization of Execution Microscopic Extrusion Parameter Characterizations for Color Polycarbonate Grading: General Trend and Box–Behnken Designs

This research article concentrates on process conditions in addition to improving color selections in polymer compounders and developing more accurate simulation models. The feed rate (FR), temperature (T) and screw speed (SS) are three processing variables that the research investigates using general trends (GTs) and Box–Behnken design (BBD) response surface methodology. The identical set of processing settings was tweaked at three separate phases independently of one another. This study uses the experimental design to investigate process parameters’ optimization while holding all other parameters constant. This design was given the name GT. To develop this design and its statistical optimization, this study used the software of the design expert method. A regression model was run in this design, which displayed collective as well as individual effects of the parameters on color images. The values of tri-stimulus color with the best optimization had the smallest proper color variance (dE*). To obtain information on pigment characteristics, an SEM image analysis was conducted, which aids in improving future designs and overcoming manufacturing issues that affect color fluctuation properties and waste reduction for various chemical grades, both of which enhance environmentally friendly processes.

Coaxial electrospinning of polycaprolactone – A design of experiments approach

Coaxial electrospinning is a commonly used technique in pharmaceutical sciences that allows producing polymeric nano- or microfibers with core-shell structure. In addition to process parameters such as voltage and flow rate of the polymer solutions, the properties of such fibers are influenced by solution properties including the total polymer concentration and the polymer ratio between fiber core and shell. As these parameters are typically changed empirically during development of electrospinning methods, there is a lack of structured studies that determine the optimal settings for the production of homogeneous, mechanically stable fibers. Therefore, we used a design of experiments approach to systematically address the coaxial electrospinning process of polycaprolactone, a polymer for biomaterials applied to the skin, for instance in the form of patches for wound healing or the treatment of skin cancer. We set out to investigate the influence of different process parameters on the fiber morphology (diameter and size distribution) as well as their mechanical properties as these properties are decisive determinants for handling and pharmaceutical efficacy of such patches. The investigated process parameters were the polymer concentration in the electrospinning solution and the ratio of polymer between fiber core and shell. We additionally investigated the impact of the presence of the model drug hydrocortisone in the fiber core on the electrospinning outcome and the drug release. The experiments revealed that the fiber diameter increases with increasing total polymer concentration, correlating with a narrower fiber size distribution. In addition, our results show that a higher ratio of polymer content in core and shell leads to more mechanically stable fibers (higher tensile strength, higher Young’s modulus). Taken together, the results obtained in this study contribute to a better understanding of the electrospinning process of polycaprolactone.

Improving wear and corrosion resistance through plasma oxidation in silicate-based Electrolytes for enhanced surface protection

ABSTRACT A study was conducted to enhance the resistance of Al6061 material to corrosion by utilising plasma oxidation to create an Aluminium oxide layer. The microstructure of the resulting samples was investigated using FESEM and XRD analyses, with a focus on the characteristics of wear and corrosion resistance. The formation of the oxide compound on the surface layer of the material resulted in an increase in its hardness. The study investigated process parameters such as current voltage, oxidation time, and electrolytic composition, and identified a relationship between them. The use of an electrolyte based on silicate was found to be highly effective in increasing the number of oxidation processes. The study concludes that the wear and corrosion resistance of high-strength Aluminium alloy can be improved through the process of plasma oxidation, making it a promising solution for industrial applications.

Bioprocess development for endospore production by Bacillus coagulans using an optimized chemically defined medium.

Bacillus coagulans is a promising probiotic, because it combines probiotic properties of Lactobacillus and the ability of Bacillus to form endospores. Due to this hybrid relationship, cultivation of this organism is challenging. As the probiotics market continues to grow, there is a new focus on the production of these microorganisms. In this work, a strain-specific bioprocess for B. coagulans was developed to support growth on one hand and ensure sporulation on the other hand. This circumstance is not trivial, since these two metabolic states are contrary. The developed bioprocess uses a modified chemically defined medium which was further investigated in a one-factor-at-a-time assay after adaptation. A transfer from the shake flask to the bioreactor was successfully demonstrated in the scope of this work. The investigated process parameters included temperature, agitation and pH-control. Especially the pH-control improved the sporulation in the bioreactor when compared to shake flasks. The bioprocess resulted in a sporulation efficiency of 80%-90%. This corresponds to a sevenfold increase in sporulation efficiency due to a transfer to the bioreactor with pH-control. Additionally, a design of experiment (DoE) was conducted to test the robustness of the bioprocess. This experiment validated the beforementioned sporulation efficiency for the developed bioprocess. Afterwards the bioprocess was then scaled up from a 1L scale to a 10 L bioreactor scale. A comparable sporulation efficiency of 80% as in the small scale was achieved. The developed bioprocess facilitates the upscaling and application to an industrial scale, and can thus help meet the increasing market for probiotics.

Influence of ECM process parameters on SS316 material

Electro-Chemical Machining (ECM) seems to be a hopeful technique in the production area of automobile manufacturing and other productions. In recent years, the demand for stainless steel (SS) micro products and components has evolved significantly in fields such as biotechnology, electronics, optics, medicine and so on. This stainless-steel material is ideal for hygienic environments because it is easily sterilized and corrosion resistant. The process parameters of ECM for stainless steel material are investigated experimentally in this study. The SS-316 alloy was chosen to influence the electrochemical machining process with different electrodes and to investigate process parameters using SEM analysis. The tool material has been changed to investigate the improved quality of ECM process parameters.

Study on Slag Splashing Behavior in a 120 t Converter Based on Physical and Mathematical Simulation

The service life of converter linings is crucial for efficiency and emission reduction. Slag splashing performance is essential in steelmaking. This study constructs a physical model based on a specific 120 ton converter using similarity principles. Dimensional analysis is employed to investigate process parameters and fluid properties. The influence of various process parameters on slag splashing performance is analyzed. Mathematical simulations using the volume of fluid method are conducted to quantitatively assess the volume of slag splashing, determine the optimum lance height, and examine the effects of nitrogen flow rate on the impact crater profile, splashing shape, and angle. The results demonstrate that when the fluid viscosity and surface tension meet specific conditions, the lance height in the physical model and the prototype satisfy geometric similarity. However, as no suitable fluid meeting the conditions is found, a corrective relation for the lance height between the physical model and the prototype is established to optimize the process parameters. By adjusting the lance height and bottom gas flow rate, damaged areas can be repaired, while modifying the nitrogen flow rate alters the shape of the slag splashing, resulting in uniform slag splashing.

Effective mechanochemical synthesis of sulfide solid electrolyte Li3PS4 in a high energy ball mill by process investigation

Mechanochemical syntheses have a high potential as environmentally friendly and scalable processes. However, especially in case of solid electrolytes, these syntheses are reported as very time consuming with process times up to several days. In this study, the sulfide solid electrolyte Li3PS4 was successfully synthesized in less than 5 h after a systematic variation and subsequently optimization of the process parameters in a high energy ball mill. The synthesized electrolyte samples were characterized according to their composition, morphology, particle size distribution and ionic conductivity. Therefore, a better understanding of the process-structure–property relations and process efficiency was achieved. Thus, the results allow a correlation between the stressing conditions and kinetic rates. The stressing conditions are mainly affected by process parameters such as rotational speed, grinding media size and grinding media filling ratio. The kinetic of the mechanochemical process is highly dependent on the normal power input by head-on collisions, leading to a reduction of conversion time with increasing specific power input. The different sets of investigated process parameters also exhibit systematic effects on the crystallinity and particle size distribution of the solid electrolytes. As a result, a highly enhanced process with lowest specific energy demand was achieved by using the largest grinding media with highest rotational speeds at medium grinding media filling ratio.

A comparative study on the mineralization of waste butyl acetate by electrochemical oxidation via persulphate/hypochlorite and silver (II) reagents using DSA® anodes: Statistical optimization by response surface methodology

AbstractMediated electrochemical oxidation of butyl acetate (BA) in wastewater was conducted by employing two different techniques based on S2O8−2/ClO− and Ag (II) reagents using commercial Dimensionally Stable Anode (DSA)®‐O2 or DSA®‐Cl2 anodes. Response surface methodology (RSM) was also engaged to investigate process parameters impacts and their interactions on BA mineralization efficiency and energy consumption. Fourier‐transform infrared spectroscopy (FT‐IR), UV–visible, and gas chromatography (GC) analyses confirmed BA mineralization and the optimum removal conditions were then attained for both systems. Chemical oxygen demand (COD) analysis showed that electro‐oxidation by mixed persulphate/hypochlorite oxidants favours the mineralization of BA (99.7%) compared to the Ag (II) technique (96.56%). The higher removal efficiency obtained by S2O8−2/ClO− was achieved in a neutral aquatic medium using DSA®‐Cl2 at a lower current density (CD), temperature, and electrolysis time (pH: 6, CD: 0.1 kA/m2, and time: 60 min) compared to those obtained by Ag (II) ions (pH: ≤3, CD: 1.69 kA/m2, and time: 130 min). The former process occurred under the charge transfer control mechanism at low CDs, whereas at an elevated CD (about 1.0 kA/m2), mass transfer was predominant due to the parasitic oxygen evolution. On the other hand, the latter process was found charge transfer‐controlled at low BA concentrations (≤200 ppm), whereas it turned out mass transfer‐controlled at higher BA concentrations. Comparing the anode type, energy consumption for BA mineralization by S2O8−2/ClO− ions using DSA®‐Cl2 at the optimum conditions was 0.009 kW · h/dm3, which was about three times lower than that of the DSA®‐O2 anode.

Influence of TIG welding process parameters on microstructure and mechanical properties of as-cast Mg–8Li–3Al–2Zn-0.5Y alloy

In this study, the feasibility of TIG welding of as-cast Mg–8Li–3Al–2Zn-0.5Y alloys was investigated, and the quality of welded joints using different welding currents was evaluated in terms of microstructural evolution and mechanical properties. The results showed that the welding position of plates was successfully welded with good formability and no obvious welding defects at the investigated processing parameters. Significant refinement of phase size was beneficial to improve the mechanical properties of the welded joints. Under the influence of heat input, the AlLi phase in the heat-affected zone dissolved into the matrix, which improved the mechanical properties of the welded joint. The ultimate tensile strength, yield strength and elongation of the welded joint at 100 A were 224.8 MPa, 177.4 MPa and 9.9%, respectively, which is 159.5%, 159% and 43.8% of the corresponding values of the base alloy in the as-cast state. The burning loss of Li element in the welded joint was effectively controlled, which confirmed the feasibility of this welding process for welding Mg–Li alloys.

Experimental Investigation of Temperature and Contact Pressure Influence on HFI Welded Joint Properties.

This paper presents an experimental electro-thermo-mechanical simulation of high-frequency induction (HFI) welding to investigate the effect of temperature and contact normal stress on the weld seam quality. Therefore welding experiments at different temperatures and contact pressures are performed using flat specimens of 34MnB5 steel sheet. In order to characterize the weld seam strength of the welded specimens, tensile and bending tests are performed. To obtain a relative weld seam strength, the bending specimens were additionally hardened prior to testing. With the hardened specimens, it can be shown that the weld seam strength increases with increasing temperature and contact normal stress until a kind of plateau is formed where the weld seam strength remains almost constant. In addition to mechanical testing, the influence of the investigated process parameters on the weld seam microstructure is studied metallographically using light optical microscopy, scanning electron microscopy, EBSD and hardness measurements. It is shown that the weld seam strength is related to the amount of oxides in the bonding line.

Numerical and experimental investigations on the mechanism of flow‐induced fiber orientation in short‐shot water‐assisted injection‐molded short‐glass‐fiber‐reinforced polypropylene

AbstractIt is a critical requirement to have an insight into the mechanism of flow‐induced fiber orientation in short‐shot water‐assisted injection molding (SSWAIM) of fiber‐reinforced polymer for improving the structural rigidity and service life of molded parts. However, this mechanism is still unclear, which stunts the development of SSWAIM. In this work, the mechanism of flow‐induced fiber orientation in SSWAIM parts of short‐glass‐fiber‐reinforced polypropylene (SGF/PP) was clarified through numerical research and experimental verification. The results showed that the difference of fiber orientation distribution at different positions both in the radial direction and along the flow direction between SSWAIM parts and conventional injection molding (CIM) parts was mainly due to the strong flow field caused by the high‐pressure water penetration in SSWAIM. Moreover, fiber orientation in the SSWAIM part depended not only on its position both in the radial direction and along the flow direction, but also on the processing parameters. At the front of SSWAIM part, fiber orientation changed greatly in the radial direction and presented an obvious “shell layer‐core layer‐water channel layer” hierarchical structure across the part thickness, whereas this phenomenon became more inconspicuous with increasing the distance of the selected position from the water injection inlet. Short‐shot size is the principal parameter affecting the fiber orientation, and within the range of investigated processing parameters, smaller short‐shot size, shorter water injection delay time, higher water pressure, and lower melt temperature could significantly facilitate fiber orientation across the part thickness.

Optimization of the Indirect Extrusion Process of Copper-Clad Aluminum Rods by Methods of Statistical Experimental Designs and Numerical Analyses

The success of composite extrusion is influenced by multiple process parameters. In order to investigate the significance of specific parameters during indirect extrusion of copper-clad aluminum (CCA) rods, statistical methods were applied and a central composite experimental design was implemented. The runs of the experimental design were modeled with the finite element method based software DEFORM 2D and evaluated with respect to product quality, described by four response variables. Using variance and regression analyses, as well significant linear and quadratic effects of the five investigated process parameters as interactions between them were identified. Based on a statistical model, an overall optimum setting for the process parameters was predicted utilizing the response surface methodology with a desirability approach. By applying the output of the statistical analysis to an extrusion trial, the extrusion of a high quality CCA rod was achieved. Moreover, the results of the statistical analysis could be verified by comparing predicted and experimentally determined values of the investigated quality characteristics.

Sequential Self-Folding of Shape Memory Polymer Sheets by Laser Rastering Toward Origami-Based Manufacturing

Abstract Origami-based fabrication strategies open the door for developing new manufacturing processes capable of producing complex three-dimensional (3D) geometries from two-dimensional (2D) sheets. Nevertheless, for these methods to translate into scalable manufacturing processes, rapid techniques for creating controlled folds are needed. In this work, we propose a new approach for controlled self-folding of shape memory polymer sheets based on direct laser rastering. We demonstrate that rapidly moving a CO2 laser over pre-strained polystyrene sheets results in creating controlled folds along the laser path. Laser interaction with the polymer induces localized heating above the glass transition temperature with a temperature gradient across the thickness of the thin sheets. This gradient of temperature results in a gradient of shrinkage owing to the viscoelastic relaxation of the polymer, favoring folding toward the hotter side (toward the laser source). We study the influence of laser power, rastering speed, fluence, and the number of passes on the fold angle. Moreover, we investigate process parameters that produce the highest quality folds with minimal undesired deformations. Our results show that we can create clean folds up to and exceeding 90 deg, which highlights the potential of our approach for creating lightweight 3D geometries with smooth surface finishes that are challenging to create using 3D printing methods. Hence, laser-induced self-folding of polymers is an inherently mass-customizable approach to manufacturing, especially when combined with cutting for integration of origami and kirigami.

Experimental and numerical investigations on thermoforming of thermoplastic prepregs of glass fiber reinforced nylon 6

To study the effect of non-uniform temperature decreases of the charge caused by charge transfer and press fast closing processes on the fiber orientation and warpage of the thermoformed part, a co-simulation method combing LS-DYNA and Moldex3D is proposed to model thermoforming of a seatback outer part from thermoplastic prepregs, which includes transfer of the prepreg charge from heating oven to tools, gravity loading, thermoforming as well as cooling. The seatback outer part was physically thermoformed, and X-ray computed tomography scans and 3D scans were carried out to verify the simulation accuracy in terms of predicting fiber orientation and warpage of the part, respectively. It is found that fiber re-orientation mainly occurred in central layers of the formed part, while the fiber orientations in the layers closest to the surfaces remained nearly unchanged. The maximum warpage of the formed part varies nearly linearly with the temperature difference between the edge and the center of the charge. The steps of the charge transfer and press fast closing, which were ignored in numerical simulation in literatures, have a significant impact on the warpage and fiber orientation of the formed part. In addition, parametric study reveals that tool temperature exhibits the most significant effect on the warpage and residual stresses of the part over other investigated process parameters including initial charge temperature, closing rate, holding time, and holding force. It is suggested to minimize tool temperature while ensuring complete filling.

Statistical analysis and multi-objective process optimization of laser cladding TiC-Inconel718 composite coating

Laser cladding is an effective method of surface strengthening. Reasonable selection of laser cladding process parameters is critical to the clad geometry and mechanical characteristics of the coating. In this research, to investigate process parameters and properties of laser cladded TiC-Inconel718 composite coating, a statistical relationship between processing parameters (laser power, scanning speed and powder feeding rate) and responses (including dilution rate, microhardness, the ratio of layer width to height) was established using an experimental approach with response surface method and analysis of variance. The analysis of variance showed that the scanning speed was the most significant factor on the ratio of layer width to height, dilution rate and microhardness of the coating. In addition, in terms of microstructure, with the increase of laser power and the decrease of scanning speed, the distance between primary dendrite arm spacing increased. On the contrary, the microhardness of the coating decreased. Then, the desirability optimization method was employed to obtain the desired coating. Finally, validation experiments under optimal conditions showed that the predicted results agreed well with the experimental results and the errors were less than 10%. This research provides guidance for the multi-objective process optimization of laser cladding composite coatings.

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.

Effect of welding speed, pulse frequency, and pulse width on the weld shape and temperature distribution in dissimilar laser welding of stainless steel 308 and brass alloy

Laser welding of brass and stainless steel alloys is of special importance due to its wide application in the industries related to energy production. In this study, laser welding of heterogeneous metals was performed in a laboratory. Measurements of the temperature around the molten pool showed changes in the welding conditions. By changing different parameters such as welding speed, frequency, and pulse width, different thermal gradients were obtained. The results showed that the formation of the molten pool was asymmetric, and it was mostly done by melting the brass alloy. Due to the lower melting temperature and the high heat transfer rate of the brass alloy, the measured temperature and the molten volume of this alloy were higher. The microstructure of the molten pool also included intermetallic compounds. Increasing the dimensions of the molten pool (width and depth) by raising the peak power and reducing the welding speed was more effective than other parameters. The microhardness results also indicated the higher weld strength of the brass alloy with stainless steel rather than pure copper. At the range of the investigated process parameters, the adjacent temperature near the molten pool was about 20% (30 °C) higher for the brass alloy, in comparison to stainless steel, when the pulse frequency and pulse width were changed.

Effect of Springback on A6061 Sheet Metal Bending: A Review

Springback is defined as undesirable shape change that occurs after forming process upon unloading due to the occurrence of elastic recovery of the part. Aluminum alloy with high content of magnesium such as A6061 is preferred for high formability limit to be used in automotive industry. However, generally springback turns out to be a drawback. Many researchers have examined the springback of A6061 by considering parameters such as bent angle, die shoulder radius, blank holder force, sheet thickness, punch thickness, modulus young, yield strength, Poisson’s ratio, annealing temperature, applied load and bending operations such as V bending, deep drawing, tube bending, 3 point bending, U bending, and wipe bending. In this research, a comprehensive review is carried out to investigate process parameters and bending operations having critical impact on springback of A6061 and publications in the literature based on springback effect for A6061 studied in order to observe the number of publications by authors and the number of publications by affiliation. It is observed that sheet thickness and bent angle parameters have substantial effect on the springback. V bending and deep drawing are the commonly used bending processes. In addition, a critical contribution is presented by considering process parameters and analysis methods in order to provide a guidance for researchers for further research studies.